JP2005062658A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make formation of a high-grade image possible even when toner containing a release agent is used and to suppress the carrier adhesion and the like which occur when a small grain size carrier is used for further enhancement of image quality. <P>SOLUTION: The toner T is separated from the surface of the magnetic carrier CC in accordance with the mutual displacement of the magnetic carrier CC caused when the magnetic carrier rises as napping along magnetic flux from a state where the magnetic carrier CC holds the toner T and forms the state of aggregation, and the separated free toner T' is used to make an electrostatic latent image a visible image, by which the formation of the high-grade image is made possible even when the release agent-containing toner is used. Further, the following carrier is used for the magnetic carrier: The weight average grain size of the magnetic carrier is ≥20 to ≤60 [μm]. The saturation magnetization in a magnetic field of 1 kOe is ≥66 to ≤100 [emu/g], and the static resistance when a bias of 1,000 [V] is applied to the carrier is ≥10<SP>9</SP>to ≤10<SP>14</SP>[Ω cm]. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device applicable to an electrostatic image forming process, such as a copying machine, a color copying machine, a facsimile machine, and a printer, and an image forming apparatus using the developing device.

  Currently, a developer carrying member (hereinafter referred to as “developing sleeve”) having a magnet inside is disposed opposite to an image bearing member (hereinafter referred to as “photosensitive member”) provided with a photosensitive layer on the surface thereof. A two-component developer (hereinafter simply referred to as “developer”) including a toner containing a release agent and a magnetic carrier for holding the toner is carried on the developing sleeve and passed through the developing region. Sometimes, the electrostatic latent image on the photoconductor is visualized with the toner by utilizing the state of a magnetic brush formed by the developer gathering along the magnetic field lines of the magnet in the developing region. A developing device is known. Such a developing device is applied to an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and stores a two-component developer and is disposed to face a photosensitive member.

  The developer is triboelectrically charged by stirring and mixing in the developing device, and the electrostatic charge is used to electrostatically adhere the toner to the surface of the magnetic carrier. The magnetic carrier to which the toner is attached is attracted by a magnetic force to the surface of the developing sleeve in which a magnet is disposed, and is conveyed on the rotating developing sleeve. A magnet for developing (hereinafter referred to as “developing main magnet”) is disposed inside the developing sleeve at a position where the developing sleeve is closest to the photosensitive member. As the developer to be conveyed approaches the developing main magnet, a large number of magnetic carriers (hereinafter simply referred to as “carriers”) in the developer gather along the magnetic field lines of the developing main magnet to gather the spikes or chains. Form. Since many of these ears look like brushes, they are generally called magnetic brushes. A developing system that uses the state of the magnetic brushes is called magnetic brush development.

  In this magnetic brush development, it is considered that the carrier, which is a dielectric, increases the electric field strength between the photoconductor and the developing sleeve, so that the toner is developed from the surface of the carrier at the tip of the magnetic brush ear. . Therefore, until now, the portion without the magnetic brush formed by the spikes in which the carriers are gathered has not been used for developing the toner. For this reason, since the region where the toner can be developed is a limited region, it is very difficult to increase the amount of toner to be developed under other conditions. However, a developing method for obtaining a high-density image in this limited region has been proposed. For example, Patent Document 1 states that “the toner particles are carried on the magnetic particle spikes and the developer carrier, and the toner particles on the developer carrier fly between the image carrier and the developer carrier to the image carrier. By developing an electric field to be developed, an electrostatic image is developed with the toner held on the ears of the magnetic particles and the toner carried on the developer carrier, and a developing method using an alternating electric field at that time is proposed. Yes.

  In image formation by an electrostatic image forming process in an electrophotographic system, a latent image is formed on a photosensitive member such as a photoconductive substance, and charged toner particles are attached to the electrostatic latent image. After forming a visible image, the toner image is transferred to a recording medium such as recording paper and fixed to obtain an output image. In recent years, an image forming technique using an electrophotographic method has been rapidly developed from monochrome to full color, and the full color market tends to expand. In general, as a method for fixing a dry toner image on a recording medium, a contact heating fixing method in which a roller or belt having a smooth surface is heated to press the toner is often used. This contact heating fixing method has high thermal efficiency and enables high-speed fixing, and has the advantage of giving gloss and transparency to the color toner, but on the other hand, the surface of the heating fixing member and the molten toner are under pressure. Since the toner image is peeled after being brought into contact, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the fixing roller and is transferred onto another image. In order to prevent this offset phenomenon, a method is generally adopted in which the fixing roller surface is formed of silicone rubber or fluororesin with excellent releasability, and then a release oil such as silicone oil is applied to the fixing roller surface. It had been.

  This release oil application method is extremely effective in preventing toner offset, but requires a device for supplying the release oil, which increases the size and cost of the fixing device. For this reason, in monochromatic toner, viscoelasticity at the time of melting of the toner is improved by adjusting the molecular weight distribution of the binder resin so that the melted toner does not break internally, and a release agent such as wax is further included in the toner. Therefore, there is a tendency to adopt a method in which the release oil is not applied to the fixing roller or the amount of oil applied is very small. In addition, when a release agent is contained in the toner, the adhesion of the toner is increased, transferability to a transfer paper as a recording medium is lowered, and the release agent in the toner contaminates a friction charging member such as a carrier. As a result, there is a problem that the durability is lowered by lowering the chargeability.

  Under such circumstances, Patent Document 2 proposes a toner using a linear polyester resin having a softening point of 90 [° C.] to 120 [° C.] and carnauba wax. Patent Document 3 proposes a toner composed of a resin and a wax having different softening points that are compatible with each other. Patent Document 4 proposes a toner that defines the melt viscosity of polyester resin and wax. Patent Document 5 proposes a toner containing a polyester resin having a softening point of 90 [° C.] to 120 [° C.], rice wax, carnauba wax, and silicone oil. Patent Document 6 proposes a wax-encapsulated polymerization toner.

The conventional magnetic brush development method is an area where magnetic particles from an established magnetic brush are rubbed against the photoreceptor, and development is performed with toner particles held on the carrier ears in this area and toner particles on the developing sleeve. It is difficult to obtain a sufficiently high density image. In addition, since there are few carrier ears, it is difficult to obtain a smooth, high-quality image in which a solid portion, that is, a so-called solid portion is well-filled due to the electrode effect. Furthermore, since the release agent-containing toner has a relatively high degree of aggregation, a decrease in developing ability and poor dot reproduction, it is difficult to obtain a high-quality image.
In addition, in the conventional release agent-containing toner, the wax is exposed on the surface of the release agent-containing toner in order to ensure the anti-offset to fixing, and compared with the release agent-containing toner not containing wax. High degree. Generally, additives are added to the toner due to chargeability, transferability, background stains, toner scattering, carrier surface contamination (spent), etc., but in toners containing a release agent, the same amount of additive is added. Even if it is added, the effect is difficult to obtain.
The configuration in which the release oil application device is removed from the fixing device is advantageous in terms of cost and configuration. However, in the conventional magnetic brush development method using the conventional release material-containing toner, the developing ability is reduced or the dots are reduced. Due to poor reproduction, it is difficult to obtain a high-quality image.

  In Patent Document 7, in view of the above background, even when a release agent-containing toner is used, a developing device capable of forming a high-quality image such as a high image density, good solid filling, and excellent dot reproducibility. Is disclosed. Specifically, for example, the toner is removed from the surface of the carrier according to the mutual displacement of the carrier that occurs when the carrier rises as a spike along the magnetic field lines of the magnet inside the developing sleeve from a state in which the carrier holds the toner. There has been disclosed a developing device for separating and making the electrostatic latent image on the photosensitive member visible with the detached free toner. In addition, for example, the carrier rises as a spike that follows the magnetic field lines of the magnet inside the developing sleeve, and contacts the photoconductor in the development region, thereby removing the toner from the surface of the carrier and using the released free toner on the photoconductor. There is also disclosed a developing device that scatters and visualizes the electrostatic latent image. According to these developing devices, it is possible to form the high-quality image even when a release agent-containing toner is used.

Japanese Patent No. 2668781 JP-A-8-220808 Japanese Patent Laid-Open No. 9-106105 JP-A-9-304964 Japanese Patent Laid-Open No. 10-293425 JP-A-5-61242 JP 2003-202755 A

  However, although the developing device disclosed in Patent Document 7 has made it possible to form a high-quality image, there is a tendency to reduce the toner particle size along with the demand for higher image quality. The carrier also tends to have a smaller particle size. The smaller the particle size of the carrier, the smaller the magnetization and the easier the carrier adheres to the photoreceptor. Further, along with the recent demand for miniaturization of machines, there is a tendency to reduce the drum diameter of the photoreceptor and the sleeve diameter of the developing sleeve. As the drum diameter and sleeve diameter are reduced, the magnetic binding force on the carrier of the magnetic brush tip downstream of the development region (exit side) becomes smaller, and carrier adhesion is likely to occur. The occurrence of such carrier adhesion promotes deterioration of the photoconductor, the photoconductor cleaning blade, the intermediate transfer body, and the like, and white spots due to carrier adhesion occur on the image.

  As a method for improving such carrier adhesion, it is conceivable to increase the saturation magnetization of the carrier to some extent. By increasing the saturation magnetization, the magnetic binding force on the carrier of the magnetic brush tip can be maintained to some extent even with a small particle size. The saturation magnetization of the carrier has a certain relationship with the resistance of the carrier. When the saturation magnetization is increased, the resistance is lowered, and conversely, when the saturation magnetization is lowered, the resistance tends to be increased. However, there is no strict correlation. Here, the resistance is a value obtained by converting a resistance value measured after elapse of a certain time after applying a predetermined bias to a resistance measurement parallel electrode and applying a predetermined bias into volume resistivity, and is called static resistance. It is what. When the carrier resistance is lowered, the counter charge remaining on the carrier after the solid portion development is easily dissipated, and the carrier adhesion to the edge portion due to the counter charge is reduced. FIG. 5 is a schematic diagram showing the state of the electric field in the image area and the non-image area. In the image portion, an electric field is formed in which the toner is transferred from the surface of the developing sleeve to the photosensitive drum side. In the non-image area, there is no electric field at which the toner is transferred to the photoreceptor side. At the edge portion E, which is the boundary between the image portion and the non-image portion, an edge electric field that is an electric field where the carrier adheres to the photosensitive drum side is formed. The strength of the edge electric field increases as the carrier resistance increases, and decreases as the carrier resistance decreases. When the carrier resistance is lowered, the carrier adhesion is reduced. On the other hand, charges are liable to leak. In addition, when a superimposed bias obtained by superimposing an AC bias on a DC bias is applied as a developing bias, a high voltage is instantaneously applied by the AC bias, so that leakage easily occurs. When these conditions overlap, a leak occurs between the photosensitive member and the developing sleeve through the carrier, and the latent image on the photosensitive drum is disturbed. For this reason, there is a case where a so-called blurred image is generated in which the image is blurred.

In order to prevent such a blurred image, the resistance of the magnetic carrier may be set higher to some extent so that it does not become so low that the blurred image is generated. However, if the carrier resistance is increased to such an extent that the blurred image can be prevented together with the carrier adhesion, a new side effect may occur. It is a missing character edge caused by an increase in the edge effect.
In a developing device using a two-component developer, a magnetic brush can be regarded as a close counter electrode, so that a sneak electric field can be suppressed and an edge effect can be reduced. As another method for creating a state similar to that in which the counter electrode is brought close, there are methods for reducing carrier resistance and narrowing the development gap. Therefore, increasing the carrier resistance as described above results in a state similar to the case of distant the counter electrode, and the edge effect is increased, so that the character periphery is likely to be lost.

  As described above, it has been found that other side effects such as a blurred image and missing characters may occur when preventing carrier adhesion caused by the reduction in particle size of the magnetic carrier. Therefore, in the developing device disclosed in Patent Document 7 capable of forming a high-quality image, when a small particle size carrier is used in order to further improve the image quality, the adhesion of the carrier is suppressed and the above-described side effects are caused. Is also required to be within a certain allowable range.

  The present invention has been made in view of the above background, and the object thereof is related to the improvement of the developing device disclosed in Patent Document 7, and more specifically, a small particle size carrier is used to improve image quality. It is an object of the present invention to provide a developing device and an image forming apparatus that can realize suppression of carrier adhesion even when used, while suppressing both a blurred image and a character peripheral missing within an allowable range.

In order to achieve the above object, the invention of claim 1 comprises a developer carrying member having a magnet inside and an image carrying member having a photosensitive layer provided on the surface thereof to constitute a developing region, wherein toner and When a two-component developer containing a magnetic carrier for holding toner is carried on the developer carrier and passed through the development region, the two-component developer gathers along the magnetic field lines of the magnet in the development region. In the developing device that visualizes the electrostatic latent image on the image carrier with the toner using the state of the magnetic brush formed in this way, the weight average particle diameter of the magnetic carrier is 20 [μm] or more. 60 [μm] or less, similarly, the saturation magnetization of the magnetic carrier in a 1 × 10 ⁶ / 4π [A / m] magnetic field is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [ Wb · m / kg] and below to the above magnetic carrier 100 The static resistance of the magnetic carrier when a bias of 0 [V] is applied is not less than 10 ⁹ [Ω · cm] and not more than 10 ¹⁴ [Ω · cm], and the magnetic carrier holds the toner and exhibits an aggregate state. The toner is released from the surface of the magnetic carrier in accordance with the mutual displacement of the magnetic carrier that occurs when the head rises from the state where the magnetic field lines of the magnet rise, and the electrostatic latent image of the electrostatic latent image is released with the released free toner. It is used for visualization.
According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein the magnetic carrier holds the toner and forms a collective state and moves together with the developer carrying member toward the developing region. The above-mentioned free toner is generated in the initial stage.
According to a third aspect of the present invention, there is provided a developer carrier having a magnet therein and an image carrier having a photosensitive layer provided on the surface thereof to constitute a development region, and a toner and a magnetic carrier for holding the toner. When the two-component developer containing the two-component developer is carried on the developer carrier and passed through the development region, the two-component developer is gathered and formed along the magnetic field lines of the magnet in the development region. In the developing device that visualizes the electrostatic latent image on the image carrier with the toner using the state of the brush, the weight average particle diameter of the magnetic carrier is 20 [μm] or more and 60 [μm] or less, Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Hereinafter, a bias of 1000 [V] is applied to the magnetic carrier. When the static resistance of the magnetic carrier when applied is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less and the magnetic carrier rises as a spike along the magnetic field lines of the magnet, The toner is released from the surface of the magnetic carrier by being brought into contact with the image carrier, and the released free toner is sprayed on the image carrier to be used for visualizing the electrostatic latent image. It is characterized by.
According to a fourth aspect of the present invention, there is provided a developer carrier having a magnet therein and an image carrier having a photosensitive layer provided on the surface thereof to constitute a development region, and a toner and a magnetic carrier for holding the toner. When the two-component developer containing the two-component developer is carried on the developer carrier and passed through the development region, the two-component developer is gathered and formed along the magnetic field lines of the magnet in the development region. In the developing device that visualizes the electrostatic latent image on the image carrier with the toner using the state of the brush, the weight average particle diameter of the magnetic carrier is 20 [μm] or more and 60 [μm] or less, Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Hereinafter, a bias of 1000 [V] is applied to the magnetic carrier. The static resistance of the magnetic carrier when applied is not less than 10 ⁹ [Ω · cm] and not more than 10 ¹⁴ [Ω · cm], and the tip of the ear where the magnetic carrier rises as a spike along the magnetic field lines of the magnet Is moved in contact with the image carrier, so that the electric field between the image carrier and the developer carrier and the image carrier and the magnetic carrier for the image portion constituting the electrostatic latent image And developing the non-image portion while pulling back the toner already adhering to the image carrier from the image carrier to the magnetic carrier constituting the spike. To do.
Further, the invention according to claim 5 is that convex-shaped curved surfaces formed by disposing a drum-shaped developer bearing member having a magnet inside facing a drum-shaped image bearing member provided with a photosensitive layer on the surface. A developing region is formed between the adjacent opposing surfaces of the toner, and a two-component developer including a toner and a magnetic carrier for holding the toner is supported on the developer carrier, and the image carrier is rotated along with the rotation of the image carrier. When passing through the development area, the electrostatic latent image on the image carrier is formed using the state of the magnetic brush formed by the two-component developer gathering along the magnetic field lines of the magnet in the development area. In the developing device for visualizing with the toner, the weight average particle size of the magnetic carrier is 20 [μm] or more and 60 [μm] or less, and the magnetic carrier is also in a magnetic field of 1 × 10 ⁶ / 4π [A / m]. the saturation magnetization is 66 × 10 ^-7 × 4π Wb · m / kg] or ^{100 × 10 -7 × 4π [Wb} · m / kg] or less, the static resistance of the magnetic carrier upon application of a bias of 1000 [V] to the magnetic carrier is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less, and the area where the opposing surfaces are closest to each other and the vicinity thereof are defined as a developing middle area, and the moving direction of the image carrier is higher than this developing middle area. When the development area on the upstream side is a pre-development area, and the development area on the downstream side in the moving direction of the image carrier from the development middle area is the post-development area, The toner is detached from the surface of the magnetic carrier according to the mutual displacement of the magnetic carrier that occurs when the magnetic carrier rises as a spike along the magnetic field lines of the magnet from the state in which the toner is held and gathers, and the toner is separated. With the free toner In the development mode used for visualizing the latent image, and in the pre-development area, the magnetic carrier rises as a spike along the magnetic field lines of the magnet, and the development middle area strongly contacts the image carrier. The toner is released from the surface of the magnetic carrier, the released free toner is dispersed on the image carrier, and thus has a developing mode for use in visualizing the electrostatic latent image. In the post-development area, the image portion constituting the electrostatic latent image is generated by an electric field between the image carrier and the developer carrier and an electric field generated between the image carrier and the magnetic carrier. The non-image portion is developed, and the toner already attached on the image carrier is developed while being pulled back from the image carrier to the magnetic carrier constituting the spike.
According to a sixth aspect of the present invention, in the developing device according to the fifth aspect, in the pre-development area, the spike in which the magnetic carrier rises as a spike along the magnetic field line of the magnet is Instead of making strong contact with the body, development is performed with the free toner generated by the mutual displacement of the magnetic carrier that is displaced in the non-contact state in the non-contact state with respect to the image carrier after the middle development area. It is what.
According to a seventh aspect of the present invention, in the developing device of the first, second, third, fourth, fifth or sixth aspect, in the developing area, the toner held by the free toner or the magnetic carrier is placed on the image carrier side. An electric field to be moved is formed in advance, and this toner is used to move toward the image carrier side.
The invention of claim 8 is the developing device of claim 7, wherein the electric field is a direct current electric field.
The invention of claim 9 is the developing device of claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the toner uses a polyester resin or a polyol resin as a binder resin. It is characterized by.
According to a tenth aspect of the present invention, in the developing device according to the first, second, third, fourth, fifth, sixth, seventh, eighth, or ninth aspect, the toner contains a release agent, and the content of the release agent. Is not less than 2 parts by weight and not more than 10 parts by weight with respect to 100 parts by weight of the binder resin of the toner.
The invention of claim 11 is characterized in that, in the developing device of claim 10, carnauba wax or synthetic ester wax is used as the releasing agent.
According to a twelfth aspect of the present invention, in the developing device according to the tenth or eleventh aspect, the toner is a toner containing an additive, and the content of the additive is 1 with respect to 100 parts by weight of the toner base particles. 0.0 parts by weight or more and 3.6 parts by weight or less.
The invention of claim 13 is characterized in that, in the developing device of claim 12, the particle diameter of the additive is 0.02 [μm] or more and 0.2 [μm] or less in terms of an average primary particle diameter. To do.
The invention of claim 14 is characterized in that, in the developing device of claim 12 or 13, any one or more of silica, titania and alumina are used as the additive.
The invention according to claim 15 is the developing apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, wherein the two-component developer is constituted. The coverage of the toner with respect to the magnetic carrier is 35 [%] or more and 75 [%] or less.
According to a sixteenth aspect of the present invention, a drum-shaped developer bearing member having a magnet inside is disposed so as to face a drum-shaped image bearing member having a photosensitive layer provided on the surface, and a convex formed by this arrangement. A developing region is formed by the adjacent opposing surfaces of the curved surfaces, and a two-component developer including a release agent-containing toner and a magnetic carrier for holding the toner is carried on the developer carrier, and the image is obtained. When passing through the development area along with the rotation of the carrier, the two-component developer gathers along the magnetic field lines of the magnet in the development area and utilizes the state of the magnetic brush formed on the image carrier. In the developing device for visualizing the electrostatic latent image of the toner with the toner, the magnetic carrier has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less, which is also 1 × 10 ⁶ / 4π [A / M] saturation magnetization in a magnetic field ^{6 × 10 -7 × 4π [Wb} · m / kg] or ^{100 × 10 -7 × 4π [Wb} · m / kg] or less, the magnetic carrier upon application of a bias of 1000 [V] to the magnetic carrier The static resistance is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less, and the region where the opposing surfaces are closest to each other and the vicinity thereof are defined as a development middle region, which is more than the development middle region. When the development area on the upstream side in the moving direction of the image carrier is the pre-development area, and the development area on the downstream side in the movement direction of the image carrier from the development middle area is the post-development area. From the surface of the magnetic carrier according to the mutual displacement of the magnetic carrier that occurs when the magnetic carrier rises as a spike along the magnetic field lines of the magnet from the state in which the magnetic carrier holds the toner and forms a gathered state in the pre-development region. The toner is released and the released free toner Thus, the electrostatic latent image is visualized, and the magnetic carrier rises as a spike along the magnetic field lines of the magnet at the developing middle region, and the image carrier in the developing region strongly adheres to the image carrier. By contacting, the toner is released from the surface of the magnetic carrier, and the released free toner is sprayed on the image carrier, so that the electrostatic latent image is visualized. The image area constituting the electrostatic latent image is developed by the electric field between the image carrier and the developer carrier and the electric field generated between the image carrier and the magnetic carrier from the rear region to the rear region. The non-image portion is characterized in that the toner already adhered on the image carrier is developed while being pulled back from the image carrier to the magnetic carrier constituting the spike.
The invention according to claim 17 is the developing device according to claim 16, wherein the magnetic carrier rises as a spike along the magnetic field lines of the magnet in the pre-development area and the image after the development middle area. Instead of being brought into contact with the carrier, non-contacting is performed, and development is performed in close proximity.
The invention according to claim 18 is the developing apparatus according to claim 16 or 17, wherein the development main magnetic force distribution P1 formed around the developer carrier is a magnetic force in the normal direction on the developer carrier. The peak position M1 is shifted by 0 [°] or more and 30 [°] or less from the closest approach position M0 between the image carrier and the developer carrier to the downstream side in the moving direction of the image carrier. To do.
According to a nineteenth aspect of the present invention, after developing an electrostatic latent image on an image carrier having a photosensitive layer provided on the surface with a developing device using a two-component developer, the visible image is transferred to a sheet-like medium. In the image forming apparatus which obtains an image by heating and pressing and fixing, the developing device is defined by claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18 developing devices are used.
According to a twentieth aspect of the present invention, in the image forming apparatus of the nineteenth aspect, the image carrier is a single layer type in which a charge transport layer in which a charge generating material is dispersed is provided on a conductive support, or a conductive layer. And a laminated photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support.

19. A developing device according to claim 1 and an image forming device according to claim 19 and 20, wherein a two-component developer containing toner and a magnetic carrier for holding the toner is changed to a magnetic brush in the developing region. Develop the electrostatic latent image above. As the magnetic carrier in the two-component developer, one having a small particle diameter having a weight average particle diameter of 60 [μm] or less is used. As a result, it is possible to prevent the head traces and halftone image from being roughened by the magnetic carrier, that is, the deterioration of the graininess, and the image quality can be improved. Further, the lower limit of the weight average particle diameter of the magnetic carrier is set to 20 [μm]. This prevents fluidity and stress on the developer from becoming too bad. From the above, the weight average particle size of the magnetic carrier is set in the range of 20 [μm] to 60 [μm].
And the carrier adhesion which is easy to generate | occur | produce when using the said magnetic carrier of the said small particle size is suppressed as follows.
First, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] (1 k [Oe]) is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] (66 [emu / g]). That's it. The saturation magnetization is increased, and the magnetic binding force of the magnetic brush by the magnetic field generating means is strengthened to make it difficult for the carrier to be separated from the tip of the magnetic brush. This creates a situation where carrier adhesion to the image carrier can be suppressed. In addition, the saturation magnetization of the magnetic carrier in a 1 × 10 ⁶ / 4π [A / m] magnetic field is set to 100 × 10 ⁻⁷ × 4π [Wb · m / kg] (100 [emu / g]) or less. This prevents the ears of the magnetic brush from becoming too hard and the traces of the ears appearing on the image. Further, it is possible to avoid the occurrence of image density unevenness due to the occurrence of toner density unevenness on the developing sleeve due to poor developer separation and change of developer on the developing sleeve.
Furthermore, the static resistance of the magnetic carrier is set to a range of 10 ⁹ [Ω · cm] to 10 ¹⁴ [Ω · cm], which is somewhat lower. As described above, there is a certain correlation between the static resistance and the saturation magnetization of the magnetic carrier. When the saturation magnetization is increased, the static resistance tends to decrease. However, if the static resistance is lowered, the charge is likely to leak, and this causes a blurred image. Therefore, the lower limit of the static resistance is set to 10 ⁹ [Ω · cm] so that this can be avoided. On the other hand, even if the saturation magnetization of the magnetic carrier is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more, the static resistance may be relatively high. As a result of investigations by the present inventors, it was found that when the static resistance exceeds 10 ¹⁴ [Ω · cm] as shown in Table 1 later, the missing characters are worsened and exceed the allowable range. Therefore, the static resistance of the magnetic carrier is set to 10 ¹⁴ [Ω · cm] or less, and omissions in the character periphery are suppressed within an allowable range.
Further, the developing electric field generated by the developing electric field generating means is only DC bias. This is because the static resistance is set to be somewhat low as described above, so that the AC bias that causes the leak is not applied to the magnetic carrier that is likely to cause a leak, and the development bias is not likely to leak. Make a situation.

  As described above, in the inventions of claims 1 to 20, a small particle size carrier is used to improve the image quality, and the carrier saturation magnetization is increased to some extent in order to prevent carrier adhesion that tends to occur due to the use of the small particle size carrier. Set to. Furthermore, in order to suppress the image blur and character margin missing that are likely to occur due to the increase in saturation magnetization within the allowable range, the range of the static resistance of the magnetic carrier and the developing bias component are limited to the above ranges. Therefore, in the inventions of claims 1 to 20, by limiting the plurality of conditions in a composite manner as described above, suppression of carrier adhesion that tends to occur when a small particle size carrier is used can be reduced. Such an excellent effect that it can be carried out while keeping the side effects within the allowable range.

Hereinafter, an embodiment in which the present invention is applied to an image forming apparatus such as a copying machine, a facsimile, or a printer will be described.
In the image forming apparatus according to the present embodiment, a charging device, an exposure device, a developing device, a transfer device, a cleaning device, and the like are sequentially arranged around a photoconductor as an image carrier. In addition, a paper feeding / conveying device that feeds the transfer paper from the paper feeding tray and a fixing device that fixes the toner onto the transfer paper after the transfer paper on which the toner image has been transferred are separated from the photoreceptor. In the image forming apparatus configured as described above, the surface of the rotating photoconductor is uniformly charged by the charging device and then irradiated with the laser beam of the exposure device based on the image information to form a latent image on the photoconductor. Form. A toner image is formed by attaching toner charged by a developing device to the electrostatic latent image formed on the photoreceptor. On the other hand, the transfer paper is fed from a paper feed tray by a paper feed / conveying device, and then transported to a transfer portion where the photoconductor and the transfer device face each other. Then, the transfer device applies a charge having a polarity opposite to that of the toner image on the photoconductor to the transfer paper, thereby transferring the toner image formed on the photoconductor to the transfer paper. Next, the transfer paper is separated from the photoconductor, sent to a fixing device, and an image is obtained by fixing toner on the transfer paper.

  In FIG. 1, a charging device 101 for charging the surface of the photosensitive member 100 is provided around a photosensitive member 100 having a photosensitive layer provided on the surface and having a drum shape. The photoconductor 100 is rotated in the counterclockwise direction indicated by an arrow in FIG. A developing sleeve 111c in the form of a drum having a magnet inside is disposed so as to face the photoreceptor 100 and have a predetermined developing gap. The case 115 contains a two-component developer including a release agent-containing toner (hereinafter simply referred to as “toner”) containing a release agent and a carrier, and is stirred by the rotation of the stirring screws 112 and 113. And supplied to the developing sleeve 111c. The upper portion of the case 115 has a component as toner supply means, and a toner storage portion 116 is provided so that an appropriate amount corresponding to the consumed toner is replenished in the case 115.

  A position of the photosensitive member 100 that is irradiated with a laser beam Lb for forming an electrostatic latent image on a charging processing surface that is uniformly charged in advance by the charging device 101 in a downstream portion of the charging device 101 in the rotation direction. An electrostatic latent image is formed by irradiation of the laser structure at this position. The photosensitive member on which the electrostatic latent image is formed reaches a developing region facing the developing sleeve 111c, and charged toner adheres to the electrostatic latent image to form a toner image. In FIG. 1, a transfer device for transferring a toner image on the photoconductor 100 to a recording sheet, a cleaning device for removing residual toner on the photoconductor 100, and a residual potential on the photoconductor 100 are removed. The static eliminator and the like are omitted.

  In such a configuration, the toner image on the photoconductor 100 is transferred from the surface of the photoconductor 100 to a recording sheet conveyed from a paper feed tray (not shown) by a transfer device including a transfer belt (not shown). The recording paper electrostatically attached to the photoconductor 100 during the transfer is separated from the photoconductor 100, and the release agent-containing toner image on the unfixed recording paper is fixed to the recording paper by a fixing device (not shown). . On the other hand, toner remaining on the photoreceptor 100 without being transferred is removed and collected by a cleaning device. The photoconductor 100 from which the residual toner has been removed is initialized by a static elimination lamp and used for the next image forming process.

  In FIG. 2 showing the structure of the developing roller, the developing roller 111 has a fixed shaft 111a fixed to a case 115 which is a stationary member, a columnar magnet support 111b integrated with the fixed shaft 111a, and a magnet support. A drum-shaped developing sleeve 111c covering the periphery of 111b via a gap, a rotating member 111d integrated with the developing sleeve 111c, and the like. The rotating member 111d is rotatable with respect to the fixed shaft 111a via a bearing 111e, and the rotating shaft 111d is driven to rotate by receiving power from a rotation driving means (not shown). As shown in FIG. 3, a plurality of magnets MG are fixed radially at predetermined intervals on the outer periphery of the magnet support 111b. The developing sleeve 111c is rotated around these fixed magnets MG.

  As the developing sleeve 111c, a non-magnetic material such as aluminum, brass, stainless steel, or conductive resin is used. The cylindrical developing sleeve 111c is rotated around the magnet MG by a rotation driving mechanism (not shown) in FIGS. In the example, it is rotated in the clockwise direction. These magnets MG are for forming a magnetic field so as to cause the developer to rise on the peripheral surface of the developing sleeve 111c. A spike is formed by the carrier of the developer so as to follow the normal magnetic field lines emitted from these magnets MG, and a charged toner is attached to the carrier CC forming the spike to constitute a magnetic brush. The developing sleeve 111c is disposed so as to be close to the photoconductor 100, and a developing area is formed as an area where development is performed between both opposing surfaces. Since both the photoconductor 100 and the developing sleeve 111c are in the form of a drum, the developing region constituted by the adjacent opposing surfaces of the convex curved surfaces gradually becomes closer to the both sides with the closest portion therebetween. It constitutes a facing surface with a wider spacing. The magnetic brush is conveyed in the same direction as the developing sleeve 111c by the rotation of the developing sleeve 111c. In other words, the magnetic brush gradually moves from the facing space with a large interval to the space with a narrow interval, and eventually moves through the closest space and through the opposing space with a large interval.

In FIG. 1, a magnetic distribution P3 for pumping up the developer onto the developing sleeve 111c, magnetic distributions P4 and P5 for conveying the pumped developer to the developing area, and a developing main magnetic distribution P1 for causing the developer to stand up in the developing area. The magnetic force distribution P2 for transporting the developer in the developed area is due to each magnet MG. Each magnet MG corresponding to each magnetic force distribution is arranged in the radial direction of the developing sleeve 111c. In particular, the magnet constituting the main magnetic force distribution P1 forming the developing main pole is composed of a magnet having a small cross section, but a samarium alloy magnet, particularly a samarium cobalt alloy magnet can also be used. Among rare earth metal alloy magnets, a typical iron neodymium boron alloy magnet has a maximum energy product of 358 k [J / m ³ ], and an iron neodymium boron alloy bonded magnet has a maximum energy product of around 80 k [J / m ³ ]. . Unlike a conventional magnet, such a magnet can secure the necessary magnetic force on the surface of the developing sleeve 111c even if the size is considerably reduced. In such conventional ferrite magnets or ferrite bond magnets maximum energy product 36k [J / m ^3] before and after, 20k [J / m ^3] is around. If it is acceptable to increase the sleeve diameter, it is possible to narrow the half-value central angle by using a ferrite magnet or ferrite bonded magnet to increase the shape, or by forming the tip of the magnet facing the sleeve side finely. Is possible.

The developer will be described in detail later, but the outline is as follows.
Carriers include metals such as iron, nickel and cobalt or alloys of these and other metals, magnetite, γ-hematite, chromium dioxide, copper zinc ferrite, manganese zinc ferrite and other oxides, manganese-copper-aluminum Heusler, etc. Ferromagnetic particles such as alloys can be used. Further, the ferromagnetic particles may be coated with a resin such as styrene-acrylic, silicone, or fluorine. These can be appropriately selected in consideration of chargeability with the toner. Moreover, you may add a charge control agent, an electroconductive substance, etc. to resin which coat | covers a magnetic body particle. Moreover, what disperse | distributed these magnetic body particles in resin, such as a styrene-acrylic type and a polyester type, may be used.
The strength of saturation magnetization of a ferromagnetic material is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × in a 1 × 10 ⁶ / 4π [A / m] magnetic field in the case of a small particle size carrier. 10 ⁻⁷ × 4π [Wb · m / kg] or less (66 [emu / g] or more and 100 [emu / g] or less) is preferable. If it is less than 66 × 10 ⁻⁷ × 4π [Wb · m / kg], the strength of saturation magnetization is low, so that the transportability is lowered and the carrier adheres to the photoreceptor 100 increases. If it exceeds 100 × 10 ⁻⁷ × 4π [Wb · m / kg], the strength of saturation magnetization is high, so the magnetic brush becomes strong, the scavenging effect is strong, and scavenging marks are generated in the halftone area, resulting in image quality. Reduce.

  In FIG. 1, a layer that regulates the height of the developer chain spike, that is, the thickness of the developer layer on the development sleeve 111c, is located upstream of the development region in the developer transport direction (clockwise direction in the figure). A doctor blade 114 as a thickness regulating member is provided, and development is performed with the developer after being adjusted to a certain amount by being regulated by the doctor blade 114. In particular, the doctor blade 114 is aimed at setting the head height condition and the like to a certain condition.

  As shown in FIG. 3, a grounded bias power source VP is connected to the fixed shaft 111a. The voltage of the power source VP connected to the fixed shaft 111 is applied to the developing sleeve 111c through the conductive bearing 111e and the conductive rotating member 111d. On the other hand, the lowermost conductive support 31 constituting the photoconductor 100 is grounded. In this way, an electric field for moving the toner toward the photoconductor 100 is formed in the development area, and the toner is moved toward the photoconductor 100.

Next, a developing method using the developing device will be described.
In the following, in FIG. 4, the vicinity of the region where the opposed surfaces are closest to each other and the upstream side in the moving direction of the developing sleeve 111c are defined as the developing middle region B, and the developing sleeve 111c is located more than the developing middle region B. The development area on the upstream side in the movement direction will be referred to as a pre-development area A, and the development area on the downstream side in the movement direction of the development sleeve 111c from the middle development area will be referred to as a post-development area C.

[Development method with free toner using mutual displacement between carriers]
This section mainly corresponds to claims 1, 2, 7, and 8. The developing method described here causes the toner to be detached from the surface of the carrier in accordance with the mutual displacement of the carrier that occurs when the carrier rises as a spike along the magnetic field lines from the state in which the carrier holds the toner and forms an aggregate state, In this developing method, the released free toner is used to visualize the electrostatic latent image.

  This developing method can be performed by utilizing the phenomenon appearing in the development front area A in FIG. This development method is a development method in which the toner T is detached from the ears where the carrier CC having the toner T gathers in the development region, and development is performed with the detached free toner T. In the following, although the toner and the free toner are the same, the toner is separated from the carrier CC. Therefore, for easy understanding, the toner T is denoted by “′” and is indicated as the free toner T ′.

  The development will be described with reference to FIG. 5, which is a schematic view schematically showing the state of the two-component developer in the pre-development area. Here, in another expression of the development region, in the region facing the photoconductor 100 and the development sleeve 111c, the ears on which the carriers CC gather form a magnetic brush or a thin developer on the development sleeve 111c. Regardless of whether or not a layer is formed, it refers to a region where the toner T in the developer is developed toward the photoreceptor 100. The development area front area can be defined as the upstream side of the development middle area B. However, if the phenomenon is defined differently, the carrier CC in the developer approaching the vicinity of the development main magnetic force distribution P1 is It can also be said that the plurality of carriers CC gather together to form spikes while having the toner T, and the spikes of the carrier CC start rising along the magnetic lines of force.

  As already described in FIG. 3, a plurality of magnets MG are provided in the developing sleeve 111c. The development main magnetic force distribution P1 is formed to form the magnetic brush of the two-component developer at approximately the center where the photoconductor 100 and the development sleeve 111c face each other, and the magnetic force distribution is that the developer is pumped onto the development sleeve 111c. P3, the magnetic developer P4 and P5 transport the pumped developer to the development area, and the magnetic distribution P2 collects the developer in the case 115 in the post-development area. These are due to each magnet MG. is there.

  In FIG. 5, FIG. 1 and FIG. 3 schematically showing the situation where the spikes of the carrier CC rise in the pre-development area A, the magnets correspond to the magnetic force distributions P1 to P5 formed by the arrangement of the magnets NG rising. Regardless of the polarity, a magnetic brush is formed, and a thin layer is formed between the magnetic force distributions. As shown in FIG. 5, since the carriers CC that have been confined in the developer layer, which is a group of carriers CC, have a magnetic force with each other, between the magnetic force distribution and the magnetic force distribution, for example, FIG. However, between the magnetic force distribution P5 and the magnetic force distribution P1, the magnetic field lines in the normal direction are small, but the polarities of the magnets adjacent to each other are opposite, so that the magnetic field lines in the circumferential direction of the developing sleeve 111c become large. This is the force between the magnetic force distribution P5 and the magnetic force distribution P1 to form a developer layer, which is a thin group of carriers CC, compared to that on the magnetic force distribution, and the carriers CC are in the group of developer layers. It is in a state that has been kept. When this developer layer approaches the developing main magnet P1 together with the rotation of the developing sleeve 111c, several carriers CC gather together to form spikes and rise. The number of carriers CC that gather to form these spikes is generally determined by the amount of developer that passes through the developer regulating member 114, but in addition to this, the magnetic properties of the carrier CC and the development main magnetic force distribution P1. Is determined by the magnitude of the magnetic field lines, the shape of the magnet MG forming the development main magnetic force distribution P1, and the magnitude and inclination of the magnetic field lines depending on the arrangement.

  The magnet MG forming the development main magnetic force distribution is fixed to the magnet support 111b. However, since the development sleeve 111c is rotating, the angle and size of the magnetic lines of force at the position of the spike that starts rising also change. At this time, since there is a delay in the magnetic responsiveness of the carrier CC, the magnetic brush does not immediately align with the shape along the magnetic field lines. In addition, the spikes in which a large number of carriers CC have gathered escape from the restraining force from the group and rise, but a large magnetic field of the development main magnetic force distribution P1 acts, and the magnetic polarities of all the carriers CC are directed in the same direction. And repulsive forces are acting on each other. For these reasons, the developer layer of the carrier CC is suddenly broken, and the ears of the carrier C rise as magnetic brushes. Thus, the carrier CC forms a spike and rises, so that the group of the carrier CC in which the toner T is confined is spatially released, and the toner T adsorbed on the surface of the carrier CC is greatly centrifuged. By the action of the force, the toner T is detached from the surface of the carrier CC and released into the development space, and becomes a free toner T ′ released into the space.

  In the present invention, the generation process of the free toner T ′ generated in this way is expressed as releasing the toner from the surface of the carrier in accordance with the mutual displacement of the carrier CC that occurs when the carrier CC rises as a spike along the magnetic field lines. . Thus, the free toner T ′ detached from the surface of the carrier CC can be easily moved by a developing electric field or the like because no electrostatic or physical adhesion force acts on the carrier CC.

FIG. 6 is a diagram schematically showing a developing state when a DC power source is used as the power source VP in FIG. 3 and a DC electric field is applied in the reversal development method. In the photoreceptor 100 using an organic pigment as a carrier generating material, in general, a negative charge is often applied to form an image with a negative toner, and this example is also based on this. However, in the developing system, the polarity of the charged charge placed on the photoconductor 100 is not a big problem.
When writing with the laser beam Lb, the character portion is exposed to reduce the writing amount, and the charged charge in this portion is neutralized by the holes generated from the carrier generating material, and as shown in FIG. The image portion potential, which is the potential of the portion (character portion), decreases. By applying a DC voltage biased to the negative side by the power source VP connected to the developing sleeve 111c in FIG. 3 to the image portion having the reduced potential, the negative free toner T is directed to the image portion from the developing sleeve 111c side. The vector acts and is developed. In FIG. 6, in the non-image portion, the toner T is not actually present in the non-image portion on the photoconductor 100, but even if it exists, a vector from the non-image portion side to the developing sleeve 111 c side is present. By acting, it is surely separated from the non-image area, and background stains are prevented.

  The present invention relates to the carrier CC based on the powder characteristics such as the particle size of the carrier CC, the magnetic characteristics such as the saturation magnetization, the magnetic characteristics such as the saturation magnetization of the development main magnetic force distribution, and the morphological characteristics such as the width and shape. By controlling the force acting on the toner T on the surface, free toner T ′ can be generated. Furthermore, by forming a magnetic brush having this free toner T ′, the amount of toner T attached to the latent image L on the photoreceptor 100 can be increased, and a so-called highly developable developing method can be obtained. .

  In this developing apparatus, in the first pre-development area A of the developing area, a free toner T ′ that can be developed even with a low developing bias electric field is generated, so that a developing method having a high developability can be applied to toner containing developer. Can be obtained. In this example, by generating the free toner T ′ at the initial stage of entering the development region, there is also a role of strengthening the development after the development middle region, which contributes to further improvement in development performance.

  The behavior of the carrier CC and the toner T in the pre-development area A as described above is obtained using a stereo microscope (Olympus: SZH10) and a high speed camera (Photolon: FASTCAM-ULtima-12). Thus, it is confirmed by an image shot at a shooting speed of 9000 [frames / second] to 40500 [frames / second]. The same is confirmed for the middle development area B and the development rear area C described below.

[Development method in which ears are brought into contact with a photoconductor to spray free toner]
This section mainly corresponds to claim 3. In this developing method, the carrier rises as a spike along the magnetic field lines of the magnet and is brought into contact with the image carrier in the development region, whereby the toner is released from the surface of the carrier, and the released free toner is applied to the image carrier. This is a developing method for spraying and thus making the electrostatic latent image visible. This mode of contact includes a mode of strong or collision. This development mode is also a development method in which the spike rising in the pre-development area A is performed as a subsequent state.

  In this developing method, as shown in FIG. 4, the toner T is dispersed on the photosensitive member 100 from the carrier CC having the toner T on the surface in the middle development area B and developed. The scattering of the toner T on the photoreceptor 100 is caused by the strong contact of the ears of the magnetic brush with the photoreceptor 100.

FIG. 7 is a schematic diagram showing a situation in which the spikes of the carrier CC are in strong contact with the photoconductor 100 in the developing middle area B in the developing device.
On the developing sleeve 111c, the size, particularly the height, of the spike formed by the gathering of the carrier CC in the developing middle region B is, as described above, the powder characteristics such as the particle size of the carrier CC, the saturation magnetization, and the like. The magnetic characteristics such as the strength of the magnetic field, the magnetic characteristics such as the strength of the saturation magnetization of the development main magnetic force distribution P1, and the morphological characteristics such as the width and shape. For this reason, in the developing middle region B, the spikes of the carrier CC on the developing sleeve 111c move at substantially the same speed as the developing sleeve 111c except when slipping on the developing sleeve 111c. For this reason, when the height of the spike of the carrier CC is higher than the distance between the developing sleeve 111c and the photosensitive member 100, both the rising speed along the magnetic line of the developing main magnetic force distribution P1 and the peripheral speed of the developing sleeve 111c are both. It comes into strong contact with the photoconductor 100 from the direction indicated by the symbol F with speed.

Even if the ears of the carrier CC have risen completely before making strong contact with the photoconductor 100 in this way, the distance between the developing sleeve 111c and the central portion of the developing area of the photoconductor 100 is the narrowest. Since the ears of the carrier CC move in a gradually narrowing direction, if the height of the ears of the carrier CC is larger than the closest part between the developing sleeve 111c and the photoconductor 100, the carrier CC The ears strongly contact the photoconductor 100 at a speed obtained by offsetting the peripheral speed of the photoconductor 100 from the peripheral speed of the developing sleeve 111c. That is, the situation where the height of the spike of the carrier CC is higher than the distance between the developing sleeve 111c and the photosensitive member 100 is the case in the developing middle region B where the curved surfaces curved in a convex shape are formed facing the convex side. This is inevitably performed by the movement of the magnetic brush according to the rotation of the developing sleeve 111c. When this strong contact occurs, the toner T electrostatically adhering on the carrier CC is detached from the surface of the carrier CC by an impact, and due to the inertial force of the movement due to the centrifugal force, the electrostatic latent image on the surface of the photoreceptor 100. Due to the electric field and the developing bias electric field applied between the developing sleeve 111c and the photoconductor 100, the photoconductor 100 moves in the direction indicated by the arrow F1 and is developed on the photoconductor 100. The method for applying the bias electric field in this development may be a direct current or a voltage in which an alternating current is superimposed on the direct current, but the manner of development is in accordance with FIG.
Thus, high-performance development can be performed with the release agent toner T released from the carrier CC using an external force other than electrostatic force such as a developing bias.

As for the development mode in the middle development area B, the next development is also performed as a series of development modes following the development in the pre-development area A. That is, in the pre-development area A, the carrier CC gathers and forms a spike, and when it rises, the toner T is detached from the carrier CC to generate free toner T ′. By applying an electric field for development thereto, the free toner T ′ was directly developed toward the photoreceptor 100 and developed. Further, in the middle development area B following the pre-development area A, the ears of the carrier CC are further in contact with the photoconductor 100, so that the toner T on the carrier CC is dispersed on the photoconductor 100 and the photoconductor 100. The electrostatic latent image was developed. Further, due to this contact, the toner T on the photoconductor 100 previously developed is collected again on the carrier CC. As a result, the toner T developed in the non-image area or the low-potential image area by the development in the pre-development area A and the development middle area B is pulled back, so that a high-quality image free from background stain is obtained.
In addition, since the carrier CC on the developing sleeve 111c is a dielectric, in the ear where the photoconductor 100 and the carrier CC are gathered, an electric field that further emphasizes the electric field is generated, so that the toner adhered on the carrier CC. T is developed into an electrostatic latent image on the photoreceptor 100.

[Developing method in which the tip of the ear is rubbed against the photoreceptor]
This section mainly corresponds to claim 4. In this developing method, the tip of the spike that rises as a spike along the magnetic field lines of the magnet is brought into contact with the photoreceptor 100 and moved so that the image portion constituting the electrostatic latent image is the same as the photoreceptor 100. Development is performed by an electric field between the developing sleeve 111c and an electric field generated between the developing sleeve 111c and the carrier CC, and for the non-image portions, the above-described spikes are formed from above the photosensitive member 100 with toner already attached on the photosensitive member 100. This is a development method in which development is performed while pulling back the carrier CC.

  This development method is performed mainly in the post-development area C in FIG. Therefore, in the post-development area C, the magnetic brush of the carrier CC is set so as to be rubbed against the photoconductor 100 and conveyed on the developing sleeve 111c.

  FIG. 8 is a diagram schematically showing a state where the toner T is developed in this developing method in the rear area C of the developing area. In FIG. 8, an electric field for developing the toner T is normally applied between the developing sleeve 111c and the photosensitive member 100 (FIGS. 3 and 6). As already described, in the pre-development area A and the development middle area B, the toner T present on the surface is reduced because the development is performed away from the carrier CC constituting the magnetic brush. For this reason, the carrier CC having an excessive charge amount moves (slids) while contacting the photoconductor 100, and catches up with the toner T developed earlier. And it contacts strongly. The toner T developed earlier is attracted to the surface of the carrier CC by the impact force and the electrostatic Coulomb force generated by charging with opposite polarities, and is separated from the photoreceptor 100. In this case, mainly in the non-image area on the photoconductor 100, since the electrostatic charge by the charging device 101 is small, the electric field for adsorbing the toner T to the photoconductor 100 is small. Often disengaged. As a result, scumming in the non-image area is improved and prevented, and a high-quality image can be obtained. Therefore, in this development mode, the toner T is not positively adhered, but is collected from the non-image portion or the like, thereby obtaining a high image quality without background stains.

[Developing apparatus that performs through development methods in each of the pre-development area, the development middle area, and the post-development area]
This section mainly corresponds to claims 5 and 16. In the above-mentioned “development method using the free toner utilizing the mutual displacement of the carrier” in the development method in the pre-development area A, and in the above “development method in which free toner is sprayed by bringing the ears into contact with the photoreceptor” The development method in the development middle region B described above, and the development method in the development rear region C described in the above-mentioned “development method performed by rubbing the tip of the ear against the photoreceptor” are shown in FIGS. In the embodiment using the apparatus as shown, it is carried out as a series of development methods. Therefore, in this developing method, in the pre-development region A, the carrier CC is generated according to the mutual displacement of the carrier that occurs when the carrier CC rises as a spike along the magnetic field lines from the state in which the carrier CC holds the toner T. In the development mode in which the toner is released from the surface of the toner and the electrostatic toner image is visualized with the released free toner, and in the pre-development area A, the carrier CC follows the magnetic field lines of the magnet. As a result, the toner particles are released from the surface of the carrier CC, and the released free toner is sprayed on the photoconductor 100. It has a developing mode for making a latent image visible, and in the post-development area C, the electric field between the developing sleeve 111c and the photoconductor 100 and the photoconductor 100 and the image portion constituting the electrostatic latent image Cat A developing method in which development is performed by an electric field generated between the toner and the non-image portion, and the toner already attached to the photoconductor 100 is developed while being pulled back from the photoconductor 100 to a carrier constituting a spike. Therefore, it is possible to obtain high image quality with high image density, good solid filling, excellent dot reproducibility, and no background contamination.

[Example of changing the peak position of magnetic force]
This section mainly corresponds to claim 18. The downstream magnetic force distribution P2 that forms the magnetic force distribution for developer conveyance has a function of assisting the formation of the main magnetic force distribution P1, and if it is too small, carrier adhesion occurs. The magnetic brush is transferred in the same direction as the developing sleeve 111c, that is, in the clockwise direction by the rotation of the developing sleeve 111c.

  As shown in FIG. 9, the peak position M1 of the magnetic force in the normal direction on the developing sleeve 111c of the developing main magnetic force distribution P1 is the moving direction of the photosensitive member 100 from the closest position M0 between the photosensitive member 100 and the developing sleeve 111c. The magnets MG of the magnet support 111b are arranged so as to be on the downstream side in the (counterclockwise direction). In other words, the angle θ formed by the peak position M1 of the magnetic force appearing around the developing sleeve 111c with respect to the closest position M0 indicated by the line connecting the center of the photoreceptor 100 and the center of the developing sleeve 111c is 0 [°. ] Is shifted to the downstream side in the moving direction of the photosensitive member by an angle of 30 [°] or less. As a result, the generation site of the free toner T in the initial stage when the magnetic brush is formed is shifted to the developing middle region including the closest portion where the free toner T ′ is likely to move to the electrostatic latent image ML on the photoreceptor 100. Therefore, development with the free toner T ′ is promoted. That is, the generation site of the free toner T ′ in the development area front area A described in the above examples is opposed to the closest position M0.

  The polar angle between the magnet MG forming the magnetic force distribution P1 and the magnet MG forming the magnetic force distribution P5 is 60 [°], and the point where the magnetic force becomes 0 between the two magnets is 30 [°]. In other words, the magnetic brush rises at or near the closest position M0, or the skirt portion of the developing main magnetic force distribution P1 on the upstream side in the moving direction of the photoconductor 100 is positioned at or near the closest position M0. It is what you do.

[Example of First Development]
Using an image forming apparatus described later, development was performed under the development apparatus having the above-described configuration and the following conditions were set.

(I) Mechanical Conditions The developing device in the image forming apparatus of this example is based on the configuration described so far. Therefore, the following description will be given using the members having the structures described above. First, in consideration of the powder characteristics and magnetic characteristics of the carrier CC and the magnetic characteristics and shape characteristics of the main magnet for forming the development main magnetic force distribution P1, the carrier CC starts from the carrier CC. The toner T is set to be removed.
In this example, the photoreceptor diameter of the photoreceptor 100 is 60 [mm], the linear speed of the photoreceptor 100 is 350 [mm / sec], the diameter of the developing sleeve 111c is 25 [mm], and the linear speed of the developing sleeve 111c is 700 [mm / sec. ] Was set. Therefore, the ratio of the sleeve linear velocity to the photosensitive member linear velocity is 2.0. In this example, even if the ratio (Vs / Vp) of the linear velocity of the developing sleeve 111c to the linear velocity of the photosensitive member 100 is reduced to a minimum of 0.9, the necessary image density can still be obtained.
The development gap, which is the distance between the photoreceptor 100 and the development sleeve 111c, was set to 0.3 [mm]. The development gap is desirably set to 0.455 [mm] or less when the carrier particle size is 35 [μm], in other words, 13 times or less the diameter of the carrier CC. If the development gap is too narrow, the magnetic brush comes into contact with the photoconductor 100 in a wide range, and direction dependency such as thinning of the horizontal line and whiteout at the rear end is likely to occur. Conversely, if the development gap is too wide, a sufficient electric field cannot be obtained, and image defects such as unevenness occur in isolated dots and solid portions. In order to maintain the electric field strength, it is possible to increase the voltage to be applied, but abnormal images such as white images of solid portions called so-called white spots are likely to occur due to discharge.
The doctor gap, which is the distance between the doctor blade and the developing sleeve 111c, is set to 0.50 [mm]. Conventionally, a plate blade made of only a non-magnetic material has been used as the doctor blade, but the doctor blade in this embodiment has a configuration in which a plate made of a magnetic material is joined to a conventional non-magnetic plate. ing. By using a magnetic material, as will be described later, magnetic spikes with uniform head height are easily formed.
A stirring screw for pumping up the developer in the developing casing to the developing sleeve 111c while stirring the developer in the developing sleeve 111c is provided in a region opposite to the photosensitive member 100 of the developing sleeve 111c.
The developer in the developing casing is a developer composed of toner T and carrier CC. The developer is mixed and stirred by a stirring screw rotating at a rotational speed of 500 [rpm] by a driving means (not shown), and the toner T is frictionally charged. Is done. The toner charge amount (q / m) at this time is −5 [μC / g] or more and −60 [μC / g] or less, and preferably −10 [μC / g] or more and −30 [μC / g] or less. Good.

(Ii) Two-component developer As the two-component developer, one according to the following production example was used.
<Example of toner production>
Binder resin: Polyester resin (terephthalic acid, fumaric acid, polyoxypropylene- (2,2) -2,2-bis (4-hydroxyphenyl) propane, polyester resin synthesized from trimellitic acid, Tg: 62 [ ° C.], softening point: 106 [° C.] 100 parts Colorant: Yellow toner pigment (disazo yellow pigment: CI Pigment Yellow 17) 7.0 parts, Magenta toner pigment (quinacridone magenta pigment: CI Pigment Red 122) 7.0 parts, cyan toner pigment (copper phthalocyanine blue pigment: CI Pigment Blue 15: 3) 3.5 parts, black toner pigment (carbon black: CI Pigment Black 7) 6.0 parts Agent: Salicylic acid derivative zinc salt 2.5 parts Mold release agent: Carna Bawakkusu (mp: 85 ° C.) 5 parts

The raw materials were mixed with a Henschel mixer and then melt-kneaded with a biaxial kneader set at 110 [° C.]. The kneaded product was cooled with water, coarsely pulverized with a cutter mill, pulverized with a fine pulverizer using a jet stream, and mother particles were obtained using an air classifier.
Furthermore, 100 parts of the base particles, silica (hexamethyldisilazane surface-treated product, average primary particle size: 0.01 [μm]) 0.8 parts as an additive, titania (isobutyltrimethoxysilane surface-treated product, 1.0 part of the average primary particle size: 0.015 [μm]) is mixed with a Henschel mixer, and then air-screened with a sieve having an opening of 100 [μm]. Diameter: 6.8 [μm]) was obtained.
Here, the particle size distribution of the toner can be measured by various methods. In this example, the particle size distribution was performed using a Coulter Multisizer. That is, Coulter Multisizer IIe type (manufactured by Coulter Inc.) is used as a measuring device, interface Nikkaiki Co., Ltd. and a personal computer that outputs the number distribution and volume distribution are connected, and the electrolyte is first grade sodium chloride. 1 [%] NaCl aqueous solution was prepared.

  As a measurement method, 0.1 to 5 [ml] of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 [ml] of the above electrolytic aqueous solution, and a measurement sample is further added to 2 to 20 [mg]. In addition, the dispersion process was performed for about 1 to 3 minutes with an ultrasonic disperser. Further, 100 to 200 [ml] of the electrolytic aqueous solution is put into another beaker, and the sample dispersion is added therein to a predetermined concentration, and the 100 [μm] aperture is used as an aperture by the Coulter Multisizer IIe type. , By measuring the average of 50000 particles.

<Example of carrier production>
Core material: 5000 parts of Cu—Zn ferrite particles (weight average diameter: 45 [μm]) Coating material: 450 parts of toluene 450 parts of silicone resin SR2400 (made by Toray Dow Corning Silicone, nonvolatile content 50 [%]), aminosilane SH6020 10 parts (made by Toray Dow Corning Silicone), 10 parts carbon black

The coating material is dispersed with a stirrer for 10 minutes to prepare a coating solution, and the coating solution and the core material are coated in a fluidized bed while forming a swirling flow with a rotating bottom plate disk and stirring blades. The coating solution was applied on the core material.
Furthermore, the obtained carrier was baked at 250 [° C.] for 2 hours in an electric furnace to obtain a carrier (film thickness: 0.5 [μm]) of a production example.

<Manufacturing example of developer>
7 parts of the toner of the above production example and 93 parts of the carrier of the above production example were mixed with a tumbler mixer to obtain a two-component developer.

(Iii) Development Mode Under such conditions, here, the development situation under the case where the peak position of the magnetic force is changed will be described with reference to FIG.
Most of the cloud-like or smoke-like free toner T ′ generated in the pre-development area A where the magnetic brush is formed is easily moved to the image portion of the photoreceptor 100 by the developing electric field. FIG. 10 illustrates the development state with the free toner T ′ in a stepwise manner.

First, as shown in FIG. 10A, in the pre-development area A where the magnetic brush is formed, that is, at a position where the magnetic brush rises from a state where it is pressed against the developing sleeve 111c, by an impact force, a centrifugal force, or the like. A space in which the toner T can move is formed, and the toner T on the carrier CC and the toner T sandwiched between the ears where the carrier CC gathers are separated. As a result, a large number of free toners T ′ are generated in the form of cloud or smoke.
As shown in FIG. 10B, the free toner T ′ group is attracted to the electrostatic latent image ML of the photoconductor 100 by the developing electric field and developed. In the non-image portion, the electric field is directed toward the developing sleeve 111c, and the free toner T ′ returns to the carrier CC or moves onto the developing sleeve 111c. As a result, the usage efficiency of the toner T can be improved, and contamination in the apparatus due to toner scattering can be prevented. In this example, a DC electric field is applied by a DC power source according to FIG. 5 at a portion where the photoconductor 100 and the developing sleeve 111c face each other.
Further, in this example, since the magnetic brush is in contact with the photoconductor 100 in the development middle region B and the post-development region C, the carrier CC (carrier close to the photoconductor 100) at the tip of the magnetic brush and the photoconductor 100 The electrode effect acts in between, making the image portion toner layer more uniform and efficiently scavenging the non-image portion ground toner T. Further, in contrast to the conventional two-component contact development method, since the time during which the magnetic brush is in contact with the photosensitive member is short, there is no direction dependency such as thinning of the horizontal line and whiteout at the rear end.

The average particle size of the carrier CC used in this example is 50 [μm], the magnetization strength is 60 × 10 ⁻⁷ × 4π [Wb · m / kg], the average particle size of the toner T is 7 [μm], and the toner The density was 7 [wt%] and the toner charge amount was −25.5 [μC / g]. The linear speed ratio of the developing sleeve 111c to the photosensitive member was set to 1.4. The developing conditions were a charging potential of −700 [V], an image portion potential of −100 [V], and a non-image portion potential of −650 [V]. As a result, it was found that there was no roughness in the halftone part, a solid density in the solid part was high, and a high image quality with excellent line and character sharpness was obtained.

[Developing apparatus that performs the tip of the ear in a non-contact manner with the photoreceptor in each of the pre-development area, the development middle area, and the post-development area]
This section mainly corresponds to claims 6 and 17. As described above, in this developing apparatus, instead of bringing the spikes in which the carrier CC rises as the spikes along the magnetic field lines of the magnet in the pre-development area A, in the development middle area B, strongly contact the photoconductor 100. After the middle development area B, the photosensitive member 100 is not contacted, and development is performed with free toner generated by the mutual displacement of the carriers that are displaced in this non-contact state. That is, the tip of the spike is performed in a non-contact manner with the photoreceptor in each of the pre-development area, the development middle area, and the post-development area. For example, this can be achieved by adjusting the development gap, which is the closest distance between the developing sleeve 111c and the photosensitive member 100, or by adjusting the strength of the development main magnetic force distribution P1.

  The development mode in the pre-development area A conforms to the above-described content. In the middle development area B and the rear development area C, since the developing sleeve 111c rotates, the magnetic poles P1 to P6 do not move, so that the carrier CC is displaced. In order to develop further due to the generation of the free toner T ′ and the carrier CC on the developing sleeve 111c is a dielectric, an electric field that further emphasizes the electric field is generated in the ear where the photoconductor 100 and the carrier CC gather. Thus, the fact that the toner T adhering to the carrier CC is developed into an electrostatic latent image on the photoconductor 100 is utilized.

In this way, by maintaining the magnetic brush head on the developing sleeve 111c in a non-contact state where it does not come into contact with the photoconductor 100, the pre-development area A is developed with the free toner T detached from the surface of the carrier CC. After that, while the magnetic brush is transported through the developing sleeve 111c in the process from the middle developing area B to the developed rear area C, the toner T on the carrier CC is brought close to the photosensitive member 100 while the magnetic brush is transported through the developing sleeve 111c. Is developed.
Further, while the magnetic brush is transported through the developing sleeve 111c, the tip of the magnetic brush is not in contact with the photoconductor 100, so that the toner T that has already been developed in contact with the photoconductor 100 is removed even if it is brought close to the magnetic brush. In other words, the toner adhesion amount in the pre-development area A or the like is not lowered, and the image quality is not lowered.

[Example of changing the peak position of magnetic force]
This section mainly corresponds to claim 18. Also in this example, the peak position of the magnetic force can be changed according to the configuration described above.

[Example of Second Development]
Here, the same image forming apparatus as that in the first development example described above was used. However, in order to maintain the non-contact state of the magnetic brush with the photoreceptor 100, the development gap was set to 0.8 [mm] and the DC component in the development electric field was set to −630 [V] among the development conditions. Other conditions are the same as those in the first development example.

  FIG. 11 is a schematic diagram illustrating a situation in which the latent image L is developed with the toner T in the development region in the development method according to the second embodiment. Most of the cloud-like or smoke-like free toner T generated in the pre-development area A where the magnetic brush is formed is easily moved to the image portion of the photoreceptor 100 by the developing electric field. FIG. 11 is a step-by-step description of the development status with the free toner T.

  First, as shown in FIG. 11 (a), in the pre-development area A where the magnetic brush is formed, that is, at a position where the magnetic brush rises from a state where it is pressed against the developing sleeve 111c, by an impact force, a centrifugal force, or the like. A space in which the toner T can move is formed, and the toner T on the carrier CC and the toner T sandwiched between the ears where the carrier CC gathers are separated. As a result, a large number of free toners T 'are generated in the form of cloud or smoke. As shown in FIG. 11B, the free toner T ′ group is attracted to the electrostatic latent image ML of the photoconductor 100 by the developing electric field and developed. In the non-image portion, the electric field is directed toward the developing sleeve 111c, and the free toner T ′ returns to the carrier C or moves onto the developing sleeve 111c. As a result, the usage efficiency of the toner T can be improved, and contamination in the apparatus due to toner scattering can be prevented. In this example, a DC electric field is applied by a DC power source according to FIG. 5 at a portion where the photoconductor 100 and the developing sleeve 111c face each other.

[Two-component developer]
<Toner composition and production example>
This section mainly corresponds to claims 9 to 15. The following describes toners suitable for use in the present invention.
In the present invention, the content of the releasing agent in the toner T is 1 part by weight or more and 15 parts by weight or less, preferably 2 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the binder resin. If the amount is less than 1 part by weight, the effect of preventing the offset to the fixing roller is insufficient. By setting it to 2 parts by weight or more and 10 parts by weight or less, it is possible to obtain a high-quality image with high image density in the solid part, solid filling, and good dot reproducibility.

  Here, as the release agent, conventionally known ones can be used, for example, low molecular weight polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, dense wax, carnauba. Natural waxes such as wax, candelilla wax, rice wax and montan wax, petroleum waxes such as paraffin wax and microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid and myristic acid and metal salts of higher fatty acids, higher fatty acids Examples thereof include amides, synthetic ester waxes, and various modified waxes thereof. These mold release agents can be used alone or in combination of two or more kinds. Good release properties can be obtained particularly by using carnauba wax and synthetic ester wax.

  The additive amount of the toner T in the present invention is preferably 0.6 parts by weight or more and 4.0 parts by weight or less, particularly preferably 1.0 part by weight or more with respect to 100 parts by weight of the base particles. 3.6 parts by weight or less. When the amount of the additive is less than 0.6 parts by weight, the fluidity of the toner decreases and the degree of aggregation between the toners increases, so that contact with the carrier is insufficient and sufficient chargeability is obtained. In addition, transferability and heat-resistant storage stability are insufficient, and it is also likely to cause background contamination and toner scattering. On the other hand, if the amount exceeds 4.0 parts by weight, the fluidity is improved, but the cleaning of the photoconductor such as chatter and blade turning, and the filming on the photoconductor due to the additive released from the toner are likely to occur. And durability of the photosensitive member and the like are lowered, and the fixing property is also deteriorated. The above problems can be eliminated, the image density in the solid part is high, and the solid state is not less than 0.6 parts by weight and not more than 4.0 parts by weight, particularly preferably not less than 1.0 part by weight and not more than 3.6 parts by weight. It is possible to obtain a high-quality image that is buried and has good dot reproducibility.

As the additive, conventionally known ones can be used. For example, Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu And oxides such as Ag, V, and Zr, composite oxides, and the like. In particular, one or more of silica, titania, and alumina, which are oxides of Si, Ti, and Al, are preferably used.
Here, there are various methods for measuring the content of the additive, but it is generally determined by fluorescent X-ray analysis. That is, a calibration curve is prepared by fluorescent X-ray analysis for a toner whose content of the additive is known, and the content of the additive can be obtained using this calibration curve.

  Furthermore, it is preferable that the additive is subjected to a surface treatment for the purpose of hydrophobizing, improving fluidity, controlling chargeability, and the like, if necessary. The treating agent used for the surface treatment is preferably an organic silane compound, for example, alkylchlorosilanes such as methyltrichlorosilane, octyltrichlorosilane, and dimethyldichlorosilane, and alkylmethoxysilanes such as dimethyldimethoxysilane and octyltrimethoxysilane. , Hexamethyldisilazane, silicone oil and the like. Examples of the treatment method include a method of immersing an additive in a solution containing an organosilane compound and drying, a method of spraying and drying a solution containing an organosilane compound on the additive, etc. Either method can be suitably used.

  Further, the particle diameter of the additive added to the base particles is preferably 0.002 [μm] or more and 0.2 [μm] or less in terms of average primary particle diameter, from the viewpoint of imparting fluidity. Is 0.005 [μm] or more and 0.05 [μm] or less. Additives having an average primary particle size smaller than 0.002 [μm] are likely to be embedded in the surface of the base particles, so that aggregation tends to occur and fluidity cannot be sufficiently obtained. Furthermore, filming on the photoconductor and the like is likely to occur, and these tendencies are particularly remarkable under high temperature and high humidity. In addition, if the average primary particle size is smaller than 0.002 [μm], the additives tend to aggregate each other, so that it becomes difficult to obtain sufficient fluidity. Additives having an average primary particle size larger than 0.2 [μm] decrease the fluidity of the toner, so that sufficient chargeability cannot be obtained, and it is likely to cause background staining and toner scattering. Additives having an average primary particle size larger than 0.1 [μm] are liable to damage the surface of the photoreceptor and cause filming and the like. The particle size of the additive can be determined by measuring with a transmission electron microscope.

The toner is obtained by externally adding additives such as those described above to base particles containing a binder resin and other materials such as a colorant, a charge control agent, and a release agent as described above. Become.
As the binder resin used in the toner, conventionally known resins can be used. For example, polystyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid. Acid ester copolymer, acrylic resin, polyester resin, epoxy resin, polyol resin, rosin-modified maleic acid resin, phenol resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate Examples thereof include polymers, polybutyral, silicone resins and the like, and these can be used alone or in combination of two or more, and polyester resins and polyol resins are particularly preferable.
By using a polyester resin or a polyol resin as the binder resin, it becomes difficult to be offset with respect to the fixing device, that is, offset, and in addition to being excellent in transferability and charging safety, there is little aggregate toner, and the aggregate toner There is an advantage that abnormal images due to missing transfer are reduced.

（３）３価以上の多価カルボン酸ならびにその低級アルキルエステル及び酸無水物、及び、３価以上の多価アルコールのいずれかから選ばれる少なくとも一種、
上記（１）、（２）及び（３）とを反応させてなるポリエステル樹脂であることが好ましい。 Here, various types of polyester resins can be used,
(1) at least one selected from any of divalent carboxylic acids and lower alkyl esters and acid anhydrides thereof,
(2) A diol component represented by the general formula shown in the following chemical formula 1 (wherein R1 and R2 may be the same or different and are alkylene groups having 2 to 4 carbon atoms, and x and y are repeated) The number of units, each greater than or equal to 1 and x + y = 2-16.)

(3) at least one selected from any of trivalent or higher polyvalent carboxylic acids and lower alkyl esters and acid anhydrides thereof, and trivalent or higher polyhydric alcohols;
A polyester resin obtained by reacting the above (1), (2) and (3) is preferable.

  Here, examples of the divalent carboxylic acid (1) and the lower alkyl ester and acid anhydride thereof include terephthalic acid, isophthalic acid, sebacic acid, isodecylsuccinic acid, maleic acid, fumaric acid and monomethyl thereof. There are monoethyl, dimethyl and diethyl esters, phthalic anhydride, maleic anhydride and the like, and terephthalic acid, isophthalic acid and these dimethyl esters are particularly preferred in terms of blocking resistance and cost. These divalent carboxylic acids and their lower alkyl esters and acid anhydrides greatly affect the fixing properties and blocking resistance of the toner. That is, although depending on the degree of condensation, if a large amount of aromatic terephthalic acid, isophthalic acid or the like is used, the blocking resistance is improved, but the fixing property is lowered. Conversely, if a large amount of sebacic acid, isodecyl succinic acid, maleic acid, fumaric acid or the like is used, the fixing property is improved, but the blocking resistance is lowered. Accordingly, these divalent carboxylic acids are appropriately selected according to the other monomer composition, ratio and degree of condensation, and used alone or in combination.

  As an example of the diol component represented by the general formula (1) in the above (2), polyoxypropylene- (n) -polyoxyethylene- (n ′)-2,2-bis (4-hydroxyphenyl) propane , Polyoxypropylene- (n) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (n) -2,2-bis (4-hydroxyphenyl) propane and the like, 2.1 <= n <= 2.5 polyoxypropylene- (n) -2,2-bis (4-hydroxyphenyl) propane and 2.0 <= n <= 2.5 polyoxyethylene- (n) -2,2-bis (4-hydroxyphenyl) propane is preferred. Such a diol component has the advantage of improving the glass transition temperature and making it easier to control the reaction. In addition, it is also possible to use aliphatic diols such as ethylene glycol, diethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, propylene glycol as the diol component. is there.

Examples of the trivalent or higher polyvalent carboxylic acid (3) and its lower alkyl ester and acid anhydride include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,3,5-benzenetricarboxylic acid. Acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthylenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexa Tricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxy) methane, 1,2,7,8-octanetetracarboxylic acid, emporic trimer acid and their monomethyl, Examples include monoethyl, dimethyl, and diethyl ester.
Examples of the trihydric or higher polyhydric alcohol (3) are sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose. 1,2,4-butanetriol, 1,2,5-pentatriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane 1,3,5-trihydroxymethylbenzene and the like.
Here, the blending ratio of the trivalent or higher polyvalent monomer is suitably about 1 [mol%] to 30 [mol%] of the whole monomer composition. When the amount is less than 1 [mol%], the offset resistance of the toner is lowered, and the durability is easily deteriorated. On the other hand, if it exceeds 30 [mol%], the toner fixability tends to deteriorate.
Of these trivalent or higher polyvalent monomers, benzenetricarboxylic acids such as benzenetricarboxylic acid and anhydrides or esters of these acids are particularly preferable. That is, by using benzenetricarboxylic acids, both fixability and offset resistance can be achieved.

  Various types of polyol resins can be used. In particular, (1) epoxy resins, (2) alkylene oxide adducts of dihydric phenols or glycidyl ethers thereof, and (3) activity of reacting with epoxy groups. It is preferable to use a polyol resin obtained by reacting a compound having one hydrogen in the molecule with (4) a compound having two or more active hydrogens in the molecule that reacts with an epoxy group.

  The epoxy resin (1) is preferably obtained by bonding bisphenol such as bisphenol A or bisphenol F and epichlorohydrin. In particular, the epoxy resin is at least two or more bisphenol A type epoxy resins having different number average molecular weights in order to obtain stable fixing characteristics and gloss, and the number average molecular weight of the low molecular weight component is 360 to 2000, and the high molecular weight component The number average molecular weight is preferably 3000 to 10,000. Further, the low molecular weight component is preferably 20 to 50% by weight, and the high molecular weight component is preferably 5 to 40% by weight. When there are too many low molecular weight components, or when the molecular weight is lower than 360, there is a possibility that the gloss will be too high or the storage stability may be deteriorated. When the amount of the high molecular weight component is too large, or when the molecular weight is higher than 10,000, the gloss may be insufficient or the fixability may be deteriorated.

Examples of the bivalent phenol alkylene oxide adduct as the compound (2) include the following. That is, reaction products of ethylene oxide, propylene oxide, butylene oxide and mixtures thereof with bisphenols such as bisphenol A and bisphenol F can be mentioned. The resulting adduct may be used after glycidylation with epichlorohydrin, β-methylepichlorohydrin, or the like. In particular, diglycidyl ether of an alkylene oxide adduct of bisphenol A represented by the formula shown in Chemical Formula 2 below is preferred. In the formula shown below, R is a —CH 2 —CH 2 —, —CH 2 —CHCH 3 — or —CH 2 —CH 2 —CH 2 — group, and n and m are the number of repeating units, It is above and it is n + m = 2-6.

  The alkylene oxide adduct of dihydric phenol or its glycidyl ether is preferably contained in an amount of 10 to 40% by weight based on the polyol resin. If the amount is small, problems such as an increase in curl occur, and if n + m is 7 or more, or if the amount is too large, there is a possibility of excessive glossiness and deterioration of storage stability.

  Examples of the compound having one active hydrogen that reacts with the epoxy group (3) in the molecule include monohydric phenols, secondary amines, and carboxylic acids. The following are illustrated as monohydric phenols. That is, phenol, cresol, isopropylphenol, aminophenol, nonylphenol, dodecylphenol, xylenol, p-cumylphenol and the like can be mentioned. Secondary amines include diethylamine, dipropylamine, dibutylamine, N-methyl (ethyl) piperazine, piperidine and the like. Examples of carboxylic acids include propionic acid and caproic acid.

  Examples of the compound (2) having two or more active hydrogens that react with the epoxy group in the molecule include dihydric phenols, polyhydric phenols, and polycarboxylic acids. Bivalent phenols include bisphenols such as bisphenol A and bisphenol F. Examples of polyhydric phenols include orthocresol novolaks, phenol novolacs, tris (4-hydroxyphenyl) methane, and 1- [α-methyl-α- (4-hydroxyphenyl) ethyl] benzene. Examples of the polyvalent carboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, terephthalic acid, trimellitic acid, and trimellitic anhydride.

These polyester resins and polyol resins are preferably non-crosslinked or weakly crosslinked (THF insoluble content is 5% or less) because it is difficult to obtain transparency and gloss when having a high crosslinking density. preferable.
The method for producing these binder resins is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization and the like can be used.

  Next, conventionally known dyes and pigments can be used as the colorant used in the toner. Examples of the yellow colorant include naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow, (GR, A, RN, R), Pigment Yellow L, Benzidine Yellow (G, GR), Permanent Yellow (NCG), Vulcan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Examples thereof include benzimidazolone yellow and isoindolinone yellow.

  Examples of red colorants include bengara, red lead, red lead, cadmium red, cadmium mercury red, antimony red, permanent red 4R, para red, fire red, parachloro ortho nitroaniline red, and risol fast scarlet. G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red (F5R, FBB), Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroo Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Examples include orange and oil orange.

  Examples of blue colorants include cobalt blue, cerulean blue, alkali blue rake, peacock blue rake, Victoria blue rake, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue, indanthrene blue (RS, BC), indigo , Ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridiane, emerald green, pigment green B, naphthol green B, Examples include green gold, acid green lake, malachite green lake, phthalocyanine green, and anthraquinone green.

  Examples of black colorants include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. . Examples of other colorants include titania, zinc white, litbon, nigrosine dye, and iron black.

  These colorants can be used alone or in combination of two or more kinds, and the content is usually 1 to 30 parts by weight, preferably 3 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

If necessary, other materials such as a charge control agent can be added to the toner used in the present invention.
Here, as the charge control agent, conventionally known ones can be used, and examples thereof include nigrosine dyes, chromium-containing complexes, quaternary ammonium salts, and the like, which are properly used depending on the polarity of the toner particles. In particular, in the case of a color toner, a colorless or light-colored toner that does not affect the color tone of the toner is preferable, and examples thereof include a salicylic acid metal salt or a metal salt of a salicylic acid derivative (Bontron E84, manufactured by Orient). These charge control agents can be used alone or in combination of two or more, and the content thereof is usually 0.5 to 8 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the binder resin. is there.

Next, an example of toner production will be described below.
(1) The above-described binder resin, colorant, or, if necessary, a charge control agent, a release agent, a magnetic material, etc. are sufficiently mixed by a mixer such as a Henschel mixer.
(2) Batch type two rolls, Banbury mixer and continuous twin screw extruder, for example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd., twin screw manufactured by KCK Using a heat kneader such as an extruder, a PCM type twin screw extruder manufactured by Ikekai Tekko Co., Ltd., a KEX type twin screw extruder manufactured by Kurimoto Iron Works Co., Ltd., and a continuous type single screw kneader, for example, a co-kneader manufactured by Buss. Thoroughly knead the constituent materials.
(3) After cooling the kneaded product, it is coarsely pulverized using a hammer mill or the like, and further pulverized by a fine pulverizer or mechanical pulverizer using a jet stream, and a classifier using a swirling air stream or the Coanda effect is used. Classifying to a predetermined particle size with a conventional classifier to obtain base particles. As other production methods, a polymerization method, a capsule method, or the like can be used. An outline of these production methods is described below.

[Polymerization method]
(1) A polymerizable monomer and, if necessary, a polymerization initiator, a colorant and the like are granulated in an aqueous dispersion medium.
(2) The granulated monomer composition particles are classified to an appropriate particle size.
(3) The monomer composition particles having a prescribed inner particle diameter obtained by the classification are polymerized.
(4) After removing the dispersant by appropriate treatment, the polymerization product obtained above is filtered, washed with water and dried to obtain base particles.

[Capsule method]
(1) A resin and, if necessary, a colorant are kneaded with a kneader or the like to obtain a molten toner core material.
(2) The toner core material is placed in water and stirred vigorously to form a fine particle core material.
(3) The above core material fine particles are put in a shell material solution, and a poor solvent is dropped while stirring, and encapsulated by covering the surface of the core material with a shell material.
(4) The capsule obtained as described above is filtered and dried to obtain base particles.

Next, the base particles and additives are sufficiently mixed by a mixer such as a Henschel mixer (made by Mitsui Miike), a mechanofusion system (made by Hosokawa Micron), a mechanomill (made by Okada Seiko Co., Ltd.), and, if necessary, 150 It passes through a sieve having an opening of about [μm] or less to remove aggregates and coarse particles.
In addition to the above-mentioned additives, other additives can be added to the toner used in the present invention. Examples of such additives include Teflon (registered trademark), zinc stearate and polyvinylidene fluoride as a lubricant, and cerium oxide, silicon carbide, strontium titanate, and the like as an abrasive. Zinc oxide, antimony oxide, tin oxide and the like can be mentioned respectively.

  The particle size of the toner used in the present invention is preferably 4 [μm] or more and 9 [μm] or less, and particularly preferably 5 [μm] or more and 8 [μm] or less in terms of weight average diameter. Here, when the particle diameter is smaller than 4 [μm], background stains, toner scattering, and the like may occur during development, or fluidity may be deteriorated and toner replenishment and cleaning properties may be hindered. Further, when the particle diameter is larger than 8 [μm], dust in the image, deterioration of resolution, or the like may be a problem. Particularly, in the case of a color image, the influence is large.

  Here, as the carrier, conventionally known ones can be used, and examples thereof include magnetic powders such as iron powder, ferrite powder, nickel powder, and glass beads. It is preferable to coat with. In this case, examples of the resin used include polyfluorinated carbon, polyvinyl chloride, polyvinylidene chloride, phenol resin, polyvinyl acetal, acrylic resin, and silicone resin. As a method for forming this resin layer, a resin may be applied to the surface of the carrier by means of a spraying method, a dipping method or the like, as in the past. As a usage-amount of resin, 1-10 weight part is preferable normally with respect to 100 weight part of carriers. The film thickness of the resin is preferably 0.02 [μm] or more and 2 [μm] or less, particularly preferably 0.05 [μm] or more and 1 [μm] or less, more preferably 0.1 [μm]. ] When the film thickness is thick, the fluidity of the carrier and the developer tends to decrease, and when the film thickness is thin, the film tends to be easily affected by film scraping over time. .

  Here, the average particle diameter of these carriers is usually 10 [μm] or more and 100 [μm] or less, but in the present embodiment, it is 20 [μm] or more and 60 [μm] or less. In general, the mixing ratio of the toner and the carrier is suitably about 0.5 to 10.0 parts by weight of the toner with respect to 100 parts by weight of the carrier.

The coverage of the toner with respect to the carrier, calculated by the following equation (1), is suitably from 35 [%] to 70 [%].

  If the coverage is less than 35%, the amount of toner present on the surface of the carrier is small, the desired developing ability cannot be obtained, the image density is lowered, and the halftone tone is blurred, resulting in high quality. I cannot get an image. Further, the electric field strength to the carrier is increased, and the carrier may adhere to the photoreceptor 100. When the coverage exceeds 70 [%], the amount of the carrier surface is increased, the electrostatic adhesion between the toner and the carrier is reduced, the toner is separated (scattered) from the carrier, and the periphery of the developing device is stained. Cause a malfunction. By setting the coverage to 35 [%] or more and 70 [%] or less, the above problems can be solved, development characteristics faithful to the electrostatic latent image can be obtained, and a high-quality image can be obtained.

[Photoconductor]
This section mainly corresponds to claim 20. The photoreceptor 100 used in the present invention will be described with reference to the drawings. FIG. 12A is a cross-sectional view showing a photoconductor having a two-layer structure. A single-layer photoconductive layer 33 mainly composed of a charge generating material and a charge transporting material is provided on a conductive support 31. . In this case, at least the photosensitive layer surface contains a filler. FIG. 12B shows a structure in which a charge generation layer 35 mainly composed of a charge generation material and a charge transport layer 37 mainly composed of a charge transport material are laminated on a conductive support 31. ing. In this case, at least the surface of the charge transport layer 37 contains a filler. FIG. 12C shows a filler-reinforced charge transport layer in which a single-layer photosensitive layer 33 mainly composed of a charge generation material and a charge transport material is provided on a conductive support 31, and the surface of the photosensitive layer further contains a filler. 39 is provided. FIG. 12D shows a configuration in which a charge generation layer 35 mainly composed of a charge generation material and a charge transport layer 37 mainly composed of a charge transport material are laminated on a conductive support 31. Further, a filler-reinforced charge transport layer 39 containing a filler is provided on the charge transport layer 37.

The conductive support 31 has a conductivity of 10 ¹⁰ [Ω · cm] or less, such as a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, oxidation, etc. Metal oxide such as indium by vapor deposition or sputtering, film or cylindrical plastic, paper coated, or aluminum, aluminum alloy, nickel, stainless steel plates, etc. and methods such as extrusion and drawing After forming the tube, it is possible to use a tube subjected to surface treatment such as cutting, superfinishing or polishing. Further, an endless nickel belt or an endless stainless steel belt disclosed in Japanese Patent Application Laid-Open No. 52-36016 can also be used as the conductive support 31.

  In addition, a material obtained by dispersing conductive powder in an appropriate binder resin and coating it on the support can also be used as the conductive support 31 of the present invention. Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, silver, and metal oxide powder such as conductive tin oxide. The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin. Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.

Furthermore, it is electrically conductive by a heat shrinkable tube containing the above conductive powder in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer can also be used favorably as the conductive support 31 of the present invention.
The photosensitive layer in the present invention may be a single layer type in which a charge generation material is dispersed in a charge transport layer or a laminate type in which a charge generation layer and a charge transport layer are sequentially laminated. First, a laminated photoreceptor in which the charge generation layer 35 and the charge transport layer 37 are sequentially laminated will be described.

The charge generation layer 35 is a layer mainly composed of a charge generation material, and a binder resin may be used as necessary. As the charge generation material, inorganic materials and organic materials can be used.
Inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon. In amorphous silicon, dangling bonds that are terminated with hydrogen atoms or halogen atoms, or those that are doped with boron atoms, phosphorus atoms, or the like are preferably used.
On the other hand, a known material can be used as the organic material. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzo An azo pigment having a thiophene skeleton, an azo pigment having a fluorenone skeleton, an azo pigment having an oxadiazol skeleton, an azo pigment having a bisstilbene skeleton, an azo pigment having a distyryl oxadiazol skeleton, and a distyrylcarbazole skeleton Azo pigments, perylene pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Jigoido pigments, bisbenzimidazo - such as Le based pigments. These charge generation materials can be used alone or as a mixture of two or more.

  Binder resins used as necessary for the charge generation layer 35 are polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl. Formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, polyacrylamide and the like are used. These binder resins can be used alone or as a mixture of two or more. In addition, a polymer charge transport material can be used as the binder resin of the charge generation layer 35. Furthermore, you may add a low molecular charge transport material as needed.

The charge transport materials that can be used in combination with the charge generation layer 35 include an electron transport material and a hole transport material, and these include a low molecular charge transport material and a high molecular charge transport material. Hereinafter, the polymer type charge transport material is referred to as a polymer charge transport material in the present invention.
Examples of the electron transporting material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.
Examples of the hole transporting material include the electron donating materials shown below and are used favorably. For example, oxazol derivatives, oxadiazol derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene , Styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazol derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials can be used alone or as a mixture of two or more.
Moreover, the polymeric charge transport material represented below can be used. For example, a polymer having a carbazole ring such as poly-N-vinylcarbazole, a polymer having a hydrazone structure exemplified in JP-A-57-78402, etc., exemplified in JP-A-63-285552, etc. And a polysilylene polymer, a polymer having a triarylamine structure exemplified in JP-A-7-325409, and the like. These polymer charge transport materials can be used alone or as a mixture of two or more.

The charge generation layer 35 includes a charge generation material, a solvent, and a binder resin as main components, and includes any additive such as a sensitizer, a dispersant, a surfactant, and silicone oil. Also good.
As a method for forming the charge generation layer 35, a vacuum thin film manufacturing method and a casting method from a solution dispersion system can be largely mentioned. As the former method, a vacuum deposition method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD method, or the like is used, and the above-described inorganic materials and organic materials can be satisfactorily formed. . Further, in order to provide the charge generation layer 35 by the casting method, a ball mill using the above-described inorganic or organic charge generation material together with a binder resin, if necessary, using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, or butanone. It can be formed by dispersing with an attritor, a sand mill or the like, and applying the solution after diluting the dispersion appropriately. The coating can be performed using a dip coating method, a spray coating method, a bead coating method, or the like. The film thickness of the charge generation layer 35 provided as described above is suitably about 0.01 [μm] to 5 [μm], preferably 0.05 [μm] to 2 [μm]. .

Next, the charge transport layer 37 will be described.
The charge transport layer 37 can be formed by dissolving or dispersing a mixture or copolymer containing a charge transport component and a binder component as main components in an appropriate solvent, and applying and drying the mixture. The film thickness of the charge transport layer 37 is suitably about 10 [μm] or more and 100 [μm] or less, and when resolving power is required, it is suitably about 10 [μm] or more and 30 [μm] or less. In the present invention, examples of the polymer compound that can be used as the binder component include polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, polyester, polyvinyl chloride, Vinyl chloride / vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, fluorine resin, epoxy resin And thermoplastic or thermosetting resins such as melamine resin, urethane resin, phenol resin, alkyd resin, etc., but are not limited thereto. These polymer compounds can be used singly or as a mixture of two or more kinds, or can be copolymerized with a charge transport material.

Examples of the material that can be used as the charge transport material include the above-described low molecular weight electron transport materials, hole transport materials, and polymer charge transport materials. When a low molecular charge transport material is used, the amount used is 20 to 200 parts by weight, preferably about 50 to 100 parts by weight per 100 parts by weight of the polymer compound. When a polymer charge transport material is used, a material in which the resin component is copolymerized at a ratio of about 0 to 500 parts by weight with respect to 100 parts by weight of the charge transport component is preferably used.
Examples of the dispersion solvent that can be used in preparing the charge transport layer coating solution include ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone, ethers such as dioxane, tetrahydrofuran, and ethyl cellosolve, toluene, xylene, and the like. Examples include aromatics, halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate.
When the charge transport layer 37 is not provided with a filler reinforced charge transport layer 39 to be described later, it is necessary to add a filler material at least on the surface portion of the charge transport layer 37 for the purpose of improving the wear resistance. Examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, a-carbon powder, etc., and inorganic filler materials include copper, tin, aluminum, Metal powder such as indium, silica, tin oxide, zinc oxide, titanium oxide, alumina, indium oxide, antimony oxide, bismuth oxide, calcium oxide, tin oxide doped with antimony, tin oxide doped indium oxide, etc. Examples thereof include metal oxides, metal fluorides such as tin fluoride, calcium fluoride, and aluminum fluoride, and inorganic materials such as potassium titanate and boron nitride. Among these fillers, it is advantageous to use an inorganic material from the viewpoint of the hardness of the filler to improve the wear resistance. In particular, silica, titanium oxide, and alumina can be used effectively. These filler materials may be used alone or in combination of two or more. These fillers may be subjected to modification of the filler surface with a surface treatment agent for the purpose of improving dispersibility in the coating liquid and coating film. These filler materials can be dispersed by using an appropriate disperser together with a charge transport material, a binder resin, a solvent and the like. The average primary particle size of the filler is preferably 0.01 [μm] or more and 0.8 [μm] or less from the viewpoint of the transmittance and wear resistance of the charge transport layer. In addition, these fillers can be contained in the entire charge transport layer. However, since the exposed portion potential may be increased, the outermost surface side of the charge transport layer has the highest filler concentration and the support side has a lower value. It is preferable to provide a configuration in which a filler concentration gradient is provided, or a plurality of charge transport layers are provided so that the filler concentration is sequentially increased from the support side to the surface side. The film thickness (depth from the surface) of the inorganic filler layer contained on the surface side of the charge transport layer 37 is preferably 0.5 [μm] or more, more preferably 2 [μm] or more.

  When the filler-reinforced charge transport layer 39 is provided, the charge transport layer 37 is prepared by dissolving or dispersing a mixture or copolymer mainly composed of a charge transport component and a binder component in an appropriate solvent, and applying and drying the mixture. Can be formed. The thickness of the charge transport layer is suitably about 10 [μm] or more and 100 [μm] or less, and about 10 [μm] or more and 30 [μm] or less is appropriate when resolution is required. Examples of the binder component that can be used for the charge transport layer 37 in this case include the above-described thermoplastic or thermosetting resins. These polymer compounds can be used singly or as a mixture of two or more kinds, or copolymerized with a charge transport material. Examples of the material that can be used as the charge transport material include the above-described low molecular type electron transport materials, hole transport materials, and polymer charge transport materials. If necessary, a low molecular compound such as an appropriate antioxidant, plasticizer, lubricant, ultraviolet absorber, and low molecular charge transport material and a leveling agent may be added. These compounds can be used alone or as a mixture of two or more. The amount of the low molecular compound used is 0.1 to 200 parts by weight, preferably 0.1 to 30 parts by weight based on 100 parts by weight of the polymer compound, and the amount of the leveling agent used is 100 parts by weight of the polymer compound. On the other hand, about 0.001 to 5 parts by weight is appropriate.

Next, the filler reinforced charge transport layer 39 will be described.
The filler-reinforced charge transport layer 39 in the present invention refers to a functional layer that includes at least a charge transport component, a binder resin component, and a filler, and has both charge transport properties and mechanical resistance. The filler-reinforced charge transport layer 39 has a characteristic of exhibiting high charge mobility comparable to that of a conventional charge transport layer, which is distinguished from the surface protective layer. The filler-reinforced charge transport layer is used as a surface layer obtained by functionally separating the charge transport layer in the multilayer photoreceptor into two or more layers. That is, this layer is used in a laminate with a charge transport layer not containing a filler, and is not used alone. For this reason, it is distinguished from a single layer of the charge transport layer when the filler is dispersed in the charge transport layer as an additive.

As the filler material used for the filler-reinforced charge transport layer 39, as mentioned in the explanation of the charge transport layer 37, inorganic materials, particularly silica, titanium oxide, and alumina can be used effectively. These filler materials may be used alone or in combination of two or more. For the purpose of improving dispersibility in the coating liquid and coating film, these fillers may be subjected to modification of the filler surface with a surface treatment agent as described above. These filler materials can be dispersed by using an appropriate disperser together with a charge transport material, a binder resin, a solvent and the like. The average primary particle size of the filler is preferably 0.01 [μm] or more and 0.8 [μm] or less from the viewpoint of the transmittance and wear resistance of the charge transport layer.
As the coating method, a dipping method, a spray coating method, a ring coating method, a roll coater method, a gravure coating method, a nozzle coating method, a screen printing method, or the like is employed. The film thickness of the filler-reinforced charge transport layer is preferably 0.5 [μm] or more, more preferably 2 [μm] or more.

Next, the case where the photosensitive layer has a single layer structure 33 will be described.
The single-layer photosensitive layer can be formed by dissolving or dispersing a charge generating substance, a charge transporting substance, and a binder resin in a suitable solvent, and applying and drying them. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.
As the binder resin, in addition to the binder resin previously mentioned in the charge transport layer 37, the binder resin mentioned in the charge generation layer 35 may be mixed and used. Of course, the polymer charge transport materials mentioned above can also be used favorably. The amount of the charge generating material with respect to 100 parts by weight of the binder resin is preferably 5 to 40 parts by weight, and the amount of the charge transporting material is preferably 0 to 190 parts by weight, and more preferably 50 to 150 parts by weight. The single-layer photosensitive layer is formed by dip coating, spray coating, or beading a coating solution in which a charge generating material and a binder resin are dispersed together with a charge transporting material using a solvent such as tetrahydrofuran, dioxane, dichloroethane, and cyclohexane. It can be formed by coating with a coat. The film thickness of the single-layer photosensitive layer is suitably about 5 [μm] or more and 25 [μm] or less.
In a configuration in which the photosensitive layer is the outermost surface layer, it is necessary to contain a filler at least on the surface of the photosensitive layer. Also in this case, as in the case of the charge transport layer, the entire photosensitive layer can contain a filler, but a filler concentration gradient is provided, or a structure of a plurality of photosensitive layers is formed, and the filler concentration is sequentially changed. To do is an effective means.

In the photoreceptor 100 of the present invention, an undercoat layer can be provided between the conductive support 31 and the photosensitive layer. In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is coated with a solvent on these resins, it may be a resin having a high solvent resistance with respect to a general organic solvent. desirable. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin. In addition, a fine powder pigment of a metal oxide which can be exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the undercoat layer in order to prevent moire and reduce residual potential. These undercoat layers can be formed using an appropriate solvent and a coating method like the above-mentioned photosensitive layer. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer of the present invention. In addition, in the undercoat layer of the present invention, Al ₂ O ₃ is provided by anodic oxidation, organic substances such as polyparaxylylene (parylene), SiO ₂ , SnO ₂ , TiO ₂ , ITO, CeO ₂ A material provided with an inorganic material such as a vacuum thin film can also be used favorably. In addition, known ones can be used. The thickness of the undercoat layer is suitably more than 0 [μm] and 20 [μm] or less, preferably 1 [μm] or more and 10 [μm] or less.

In the present invention, in order to improve environmental resistance, in order to prevent a decrease in sensitivity and an increase in residual potential, oxidation is performed on each layer such as a charge generation layer, a charge transport layer, an undercoat layer, a protective layer, and an intermediate layer. Inhibitors, plasticizers, lubricants, UV absorbers, low molecular charge transport materials and leveling agents can be added.
Representative materials of these compounds are described below. Examples of the antioxidant that can be added to each layer include, but are not limited to, the following.
(A) Phenolic compounds 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, n-octadecyl -3- (4'-hydroxy-3 ', 5'-di-tert-butylphenol), 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2'- Methylene-bis- (4-ethyl-6-tert-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis- (3-methyl) -6-tert-butylphenol), 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6- Tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, te Lakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3′-t) -Butylphenyl) butyric acid] cricol ester, tocopherols and the like.
(B) Paraphenylenediamines N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylene Diamine, N, N′-di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine and the like.
(C) Hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2 -(2-octadecenyl) -5-methylhydroquinone and the like.
(D) Organic sulfur compounds Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate and the like.
(E) Organic phosphorus compounds Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.

Examples of the plasticizer that can be added to each layer include, but are not limited to, the following.
(A) Phosphate ester plasticizer Triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichloroethyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, Triphenyl phosphate etc.
(B) Phthalate ester plasticizers Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, phthalate Dinonyl acid, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, butyl lauryl phthalate, methyl oleyl phthalate, octyl decyl phthalate, dibutyl fumarate, dioctyl fumarate Such.
(C) Aromatic carboxylic acid ester plasticizers Trioctyl trimellitic acid, tri-n-octyl trimellitic acid, octyl oxybenzoate, and the like.
(D) Aliphatic dibasic ester plasticizer dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-octyl adipate, adipic acid n-octyl-n-decyl , Diisodecyl adipate, dicapryl adipate, di-2-ethylhexyl azelate, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, di-n-octyl sebacate, di-2-ethylhexyl sebacate, di-2 sebacate -Ethoxyethyl, dioctyl succinate, diisodecyl succinate, dioctyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate and the like.
(E) Fatty acid ester derivatives butyl oleate, glycerin monooleate, methyl acetylricinoleate, pentaerythritol ester, dipentaerythritol hexaester, triacetin, tributyrin and the like.
(F) Oxyacid ester plasticizers Methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, tributyl acetyl citrate and the like.
(G) Epoxy plasticizer Epoxidized soybean oil, epoxidized linseed oil, epoxy butyl stearate, decyl epoxy stearate, octyl epoxy stearate, benzyl epoxy stearate, dioctyl epoxy hexahydrophthalate, didecyl epoxy hexahydrophthalate, etc. .
(H) Dihydric alcohol ester plasticizers such as diethylene glycol dibenzoate and triethylene glycol di-2-ethylbutyrate.
(I) Chlorine-containing plasticizer Chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, methoxychlorinated fatty acid methyl and the like.
(J) Polyester plasticizer Polypropylene adipate, polypropylene sebacate, polyester, acetylated polyester and the like.
(K) Sulfonic acid derivatives p-toluenesulfonamide, o-toluenesulfonamide, p-toluenesulfoneethylamide, o-toluenesulfoneethylamide, toluenesulfone-N-ethylamide, p-toluenesulfone-N-cyclohexylamide and the like.
(L) Citric acid derivatives Triethyl citrate, triethyl acetyl citrate, tributyl citrate, tributyl acetyl citrate, tri-2-ethylhexyl acetyl citrate, n-octyl decyl acetyl citrate and the like.
(M) Others Terphenyl, partially hydrogenated terphenyl, camphor, 2-nitrodiphenyl, dinonylnaphthalene, methyl abietate and the like.

Examples of the lubricant that can be added to each layer include, but are not limited to, the following.
(A) Hydrocarbon compound Liquid paraffin, paraffin wax, microwax, low-polymerized polyethylene and the like.
(B) Fatty acid compounds Lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and the like.
(C) Fatty acid amide compounds Stearylamide, palmitylamide, oleinamide, methylenebisstearamide, ethylenebisstearamide and the like.
(D) Ester compounds Lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, fatty acid polyglycol esters, and the like.
(E) Alcohol compounds Cetyl alcohol, stearyl alcohol, ethylene glycol, polyethylene glycol, polyglycerol and the like.
(F) Metal soap Lead stearate, cadmium stearate, barium stearate, calcium stearate, zinc stearate, magnesium stearate and the like.
(G) Natural wax Carnauba wax, candelilla wax, beeswax, whale wax, ibotarou, montan wax and the like.
(H) Others Silicone compounds, fluorine compounds, etc.

Examples of the ultraviolet absorber that can be added to each layer include, but are not limited to, the following.
(A) Benzophenone series 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ', 4-trihydroxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4- Such as methoxybenzophenone.
(B) Salsylate type Phenyl salsylate, 2,4 di-t-butylphenyl 3,5-di-t-butyl 4-hydroxybenzoate, and the like.
(C) Benzotriazole series (2′-hydroxyphenyl) benzotriazole, (2′-hydroxy5′-methylphenyl) benzotriazole, (2′-hydroxy5′-methylphenyl) benzotriazole, (2′-hydroxy3) '-Tertiarybutyl 5'-methylphenyl) 5-chlorobenzotriazole (d) cyanoacrylate type ethyl-2-cyano-3,3-diphenyl acrylate, methyl 2-carbomethoxy 3 (paramethoxy) acrylate, and the like.
(E) Quencher (metal complex)
Nickel (2,2′thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyldithiocarbamate, nickel dibutyldithiocarbamate, cobalt dicyclohexyldithiophosphate and the like.
(F) HALS (hindered amine)
Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6 6-tetramethylpyridine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4-benzoyloxy- 2,2,6,6-tetramethylpiperidine and the like.

In order to realize further higher image quality, in the present embodiment, as described above, a carrier having a weight average particle diameter of 20 [μm] or more and 60 [μm] or less is used. The carrier has a small particle diameter of 60 [μm] or less, and it is possible to prevent grain marks and halftone images from being rough due to the magnetic carrier, that is, deterioration of graininess, thereby improving the image quality. Further, the magnetic carrier is made to have a particle size of 20 [μm] or more so that the fluidity and the stress on the developer are not deteriorated too much. From the above, the magnetic carrier having a weight average particle diameter of 20 [μm] or more and 60 [μm] or less is used.
However, the smaller the particle size of the magnetic carrier, the smaller the magnetization and the easier the carrier adheres to the photoreceptor. Further, in accordance with the recent demand for miniaturization of machines, in this embodiment, a photosensitive member having a diameter of 60 [mm] or less and a developing sleeve 7 having a diameter of 30 [mm] or less are used. As the photosensitive member diameter and sleeve diameter are reduced, the magnetic binding force on the carrier of the magnetic brush tip downstream of the developing region (exit side) becomes smaller, and carrier adhesion is likely to occur. Due to the occurrence of carrier adhesion, deterioration of members such as the photoconductor 100 and a cleaning blade (not shown) that are in contact with the photoconductor is promoted, and white spots due to carrier adhesion occur on the image. In view of this, the image forming apparatus using the small particle size carrier according to the present embodiment suppresses carrier adhesion, and also suppresses side effects that may occur when trying to prevent carrier adhesion within a certain allowable range. Hereinafter, this point will be described in detail.

In this embodiment, as described above, the saturation magnetization in a 1 × 10 ⁶ / 4π [A / m] magnetic field is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [ Wb · m / kg] or less and a carrier having a static resistance of 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less when a bias of 1000 [V] is applied is used. Further, the carrier has a coating film having at least a binder resin and particles, and the relationship between the particle diameter (D) of the magnetic carrier and the binder resin film thickness (h) is 1 <[D / h] <10. It is.

By setting the saturation magnetization of the magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] to a high value of 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or higher, it is possible to use the magnet inside the developing sleeve 111c. Strengthens the magnetic binding force on the developing sleeve surface of the magnetic brush. This makes it possible to prevent the carrier from being separated from the tip of the magnetic brush and to suppress the carrier adhesion to the photoconductor 100. Further, the saturation magnetization of the magnetic carrier in a 1 × 10 ⁶ / 4π [A / m] magnetic field is set to 100 × 10 ⁻⁷ × 4π [Wb · m / kg] or less. This prevents the ears of the magnetic brush from becoming too hard and leaving traces on the image. Further, it is possible to avoid the occurrence of image density unevenness due to the occurrence of toner density unevenness on the developing sleeve due to poor developer separation and change of developer on the developing sleeve.
Furthermore, the static resistance of the magnetic carrier is set to a range of 10 ⁹ [Ω · cm] to 10 ¹⁴ [Ω · cm], which is somewhat lower. There is a certain degree of correlation between the static resistance and the saturation magnetization of the magnetic carrier, and the static resistance tends to decrease when the saturation magnetization is increased. However, if the static resistance is too low, the charges are likely to leak, and this causes a blurred image. Therefore, the lower limit of the static resistance is set to 10 ⁹ [Ω · cm] so that this can be avoided. Even if the saturation magnetization of the magnetic carrier is set to 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more, the static resistance may be relatively high. The present inventors have found that the allowable range may be exceeded. Therefore, in the present embodiment, the static resistance of the magnetic carrier is set to 10 ¹⁴ [Ω · cm] or less, and a situation is created in which the missing characters are kept within an allowable range.
Further, in the present embodiment, a DC power source is connected to the developing sleeve 7 and the developing electric field is a DC electric field. This is because the static resistance is set to be somewhat low as described above, so that an AC bias that causes leaks is not applied to magnetic carriers that are likely to cause leaks, creating a situation in which leaks are less likely to occur. Because.
As described above, in this embodiment, a small particle size carrier is used to improve the image quality, and the saturation magnetization of the carrier is increased to some extent to prevent carrier adhesion that tends to occur due to the use of the small particle size carrier. Set. Further, in order to avoid the image blur and character margin missing that are likely to occur due to high saturation magnetization exceeding the allowable range, the range of the static resistance of the magnetic carrier and the developing bias component are limited.

In the following, what effects can be obtained in the case of having the characteristics relating to the present invention will be described below by giving a plurality of examples that satisfy the above-described configuration requirements and a plurality of comparative examples that are not. However, the present invention is not limited to the examples given here.
First, various setting conditions of a full-color printer which is an image forming apparatus used in Examples and Comparative Examples described later are as follows.

<Example Printer Setting Conditions>
Photoconductor linear velocity: 350 [mm / sec]
Photoconductor diameter: 60 [mm]
Development sleeve / photoconductor linear speed ratio: 2
Pumping amount: 50 [mg / cm ² ]
Developing sleeve diameter: Φ25 [mm]
Main pole angle: 6 [°]
Main pole magnetic flux density (P1): 120 [mT]
Main pole downstream pole magnetic flux density (P2): 110 [mT]
Charging potential VD: −600 [V]
Post-exposure potential VL: −60 [V]
Development bias Vb: -430 [V]
<Comparative example printer setting conditions>
Photoconductor linear velocity: 350 [mm / sec]
Photoconductor diameter: 60 [mm]
Development sleeve / photoconductor linear speed ratio: 2
Pumping amount: 50 [mg / cm ² ]
Developing sleeve diameter: Φ25 [mm]
Main pole angle: 6 [°]
Main pole magnetic flux density (P1): 120 [mT]
Main pole downstream pole magnetic flux density (P2): 110 [mT]
Charging potential VD: −420 [V]
Post-exposure potential VL: −60 [V]
Development bias Vb: −250 [V]

In addition, the magnetic flux density was measured by a sleeve abutting method using a magnetic force distribution measuring device (a three-dimensional magnetic measuring device manufactured by Excel System Product Co., Ltd.) and a gauss meter (manufactured by ADS Co., Ltd.). .
The developing sleeve 111c is V-grooved. The doctor 114 is a material having rigidity and magnetism. The doctor 114 is not limited to a metal material such as iron or stainless steel, but can be composed of a resin material in which magnetic particles such as ferrite and magnetite are blended. Furthermore, it is good also as a structure which fixes another member, such as a metal plate comprised with the magnetic material, directly or indirectly to the doctor 114, without comprising the doctor itself with a magnetic material.

The magnetic carriers used in the examples and comparative examples are as follows.
<Example magnetic carrier>
Acrylic resin solution (solid content 50 [wt%]) 56.0 parts, guanamine solution (solid content 77 [wt%]) 15.6 parts, alumina particles (0.3 [μm], specific resistance 10 ¹⁴ [Ω · cm]) 160.0 parts, 900 parts of toluene, 900 parts of butyl cellosolve are dispersed with a homomixer for 10 minutes to prepare a coating film forming solution, and a sintered ferrite powder having a predetermined average particle diameter is used as a core material. It was applied by a Spira coater (manufactured by Okada Seiko Co., Ltd.) to a thickness of 0.15 [μm] and dried. The obtained carrier was baked in an electric furnace at 150 [° C.] for 1 hour. After cooling, the ferrite powder bulk was crushed using a sieve having an opening of 100 [μm] to obtain a carrier.
The ratio D / h of the particle diameter D = 0.3 [μm] of the particles contained in the coating film of the magnetic carrier of Example and the binder resin film thickness h = 0.15 [μm] is 2.
<Comparative magnetic carrier>
Acrylic resin solution (solid content 50 [wt%]) 56.0 parts, guanamine solution (solid content 77 [wt%]) 15.6 parts, toluene 900 parts, butyl cellosolve 900 parts were dispersed with a homomixer for 10 minutes. A coating film forming solution was prepared, and a fired ferrite powder having a predetermined average particle diameter was used as a core material. The obtained carrier was baked in an electric furnace at 150 [° C.] for 1 hour. After cooling, the ferrite powder bulk was crushed using a sieve having an opening of 100 [μm] to obtain a carrier.
Moreover, since the coating film covering the carrier surface can be observed by observing the cross section of the carrier with a transmission electron microscope, the measurement of the binder resin film thickness can be performed with the average value of the film thicknesses. It was.
The coating film of the comparative carrier does not contain particles. Therefore, the ratio D / h of the particle diameter D of the particles contained in the coat film shown in the example magnetic carrier and the binder resin film thickness h cannot be applied to the comparative example carrier.

Images were formed under the above printer setting conditions and various condition patterns of Examples 1 to 5 and Comparative Examples 1 to 17 shown in Table 1. Table 1 also shows the results of evaluating the image from four viewpoints: a blurred image, missing characters, graininess, and carrier adhesion. A bias of “DC” is obtained by applying only a DC electric field as a developing electric field, and “AC” is obtained by superposing an AC bias on a DC bias. The AC bias has a frequency: 4.5 [kHz], Vpp: 0.9 [kV], and Duty: 35.
The saturation magnetization of the magnetic carrier is measured by the following method. As a measuring device, a BHU-60 type magnetization measuring device (manufactured by Riken Measurement) is used. About 1.0 g of a measurement sample is weighed and packed in a cell having an inner diameter of 7 [mm] φ and a height of 10 [mm] and set in this apparatus. Measurement was varied to gradually added applied magnetic field ^{1 × 10 6 / 4π [A} / m], obtaining the magnetization in ^{1 × 10 6 / 4π [A} / m] in a magnetic field.
In the evaluation results, “◎” indicates that the evaluation is very good, “◯” indicates that the evaluation is good, “Δ” indicates that the evaluation is bad, and “×” indicates that the evaluation is very poor. Of Table 1, Examples 1 to 5 and Comparative Example 10 fall within the scope of application of the present invention. However, Comparative Example 10 is described as a comparative example without being an example. Comparative Examples 1 to 17 including Comparative Example 10 are comparative examples for the examples.

From the results in Table 1, the following can be understood. Carrier adhesion is easily affected by the saturation magnetization of the magnetic carrier, and occurs in Comparative Examples 6, 9, 12, and 15 where the saturation magnetization is less than 66. In addition, it occurs in Comparative Examples 11 and 17 having a low static resistance of 10 ⁸ [Ω · cm]. It can be seen that whether or not carrier adhesion occurs is affected by saturation magnetization and, in some cases, static resistance.

The blur is likely to occur when an AC bias is applied as the developing bias, and is generated in Comparative Examples 1 to 5 using the superimposed bias. However, even if the superimposed bias is used, it does not occur in Comparative Examples 12 and 15 where the saturation magnetization of the magnetic carrier is low. These two comparative examples are not preferable because carrier adhesion occurs as described above. In addition, the occurrence of the blur is easily affected by the static resistance of the magnetic carrier, and in Comparative Examples 11 and 17 where the static resistance is low 10 ⁸ [Ω · cm], only the DC bias is used as the developing bias. Despite this, there is a rash.
FIG. 13 shows A when the saturation magnetization of the magnetic carrier is increased to 70 × 10 ⁻⁷ × 4π [Wb · m / kg] to prevent carrier adhesion, and 60 × 10 ⁻⁷ × lower than in the conventional case. It is a graph which shows the result of having investigated the difference in the generation | occurrence | production state of a blurred image by B when it is set to 4 (pi) [Wb * m / kg]. In each graph, a superimposed bias is applied, and the actual resistance is taken for each applied bias 200 [V]. The actual resistance was measured as follows. FIG. 14 is a schematic configuration diagram of an actual resistance measuring device. As shown in the figure, a bias is applied from the power source to the developing sleeve 111c to form a magnetic brush. A jig photoconductor (aluminum) 100 ′ is used as a photoconductor facing the developing sleeve, and the distance between the developing sleeve 111c and the jig photoconductor 100 ′ is 0.35 [mm]. To do. The developing sleeve 111c is rotated and a DC bias is applied to the developing sleeve. Then, the current flowing into the jig photoconductor 100 ′ is measured by a multimeter and converted into a resistance value. Table 2 shows the measurement results of FIG.

  From the results shown in Table 2 and FIG. 13, the actual resistance when a bias is applied differs depending on the saturation magnetization height of the magnetic carrier. A in which the saturation magnetization was higher was in a state in which measurement could not be performed with a lower applied voltage than B in which saturation magnetization was lower, that is, breakdown. Here, breakdown means that a large current flows so that the actual resistance becomes too low to be measured. Further, it was confirmed by visual observation that when the saturation magnetization was increased, each magnetic brush became thicker and shorter. From this, it has been found that when the saturation magnetization is high, carriers are gathered densely to form a magnetic brush, so that the actual resistance in the developing region is lowered, the electric charge is liable to leak, and the blur occurs.

Since the cause of the vomit is also related to the fact that the static resistance of the carrier is too low, it is conceivable to increase the static resistance with a coating layer of a magnetic carrier. It is possible to prevent leakage even with an AC bias. However, if the static resistance is too high, missing characters may worsen. Here, the static resistance is a resistance value measured in a packed state in the cell. Then, a magnetic carrier is inserted between resistance measurement parallel electrodes: electrodes having a gap of 2 [mm], a DC bias is applied, and a resistance value after 30 [sec] is measured by a high resist meter and converted into a volume resistivity. It is. In Comparative Examples 7 and 13, the static resistance when 1000 [V] is applied is 10 ¹⁵ [Ω · cm], and in both cases, the missing characters are “x”. On the other hand, in each of Comparative Examples 3 and 6 having a static resistance of 10 ¹⁴ [Ω · cm] when 1000 [V] is applied, the character peripheral omission is “◯”. Accordingly, it is desirable that the static resistance of the carrier is not too high in order to suppress the missing characters around the margin. There may be a difference between the static resistance and the actual resistance. The static resistance is the resistance in the packing state, and the actual resistance is the resistance in the magnetic brush state.

  As described above, if the static resistance of the magnetic carrier is too low, there is a risk of the occurrence of vomit, and the carrier adhesion due to charge injection may also occur. On the other hand, if it is too high, abnormal images such as missing characters may be deteriorated, and the image quality should be as low as possible. Further, when an AC bias is applied to the developing bias, the applied voltage is large, and therefore the lower limit of the static resistance value setting range must be increased as compared with only the DC bias. Therefore, it is possible to set the static resistance to a lower value as compared with the case where the AC bias is applied by setting the development bias only to the DC bias, and abnormal images such as missing characters in the peripheral area do not exceed the allowable range. It becomes possible to set the resistance.

  Next, a configuration and an example for improving graininess, which is another viewpoint of a high-quality image, will be described. The development gap GP, which is one of the conditions affecting the graininess, is set as follows. If the developing gap PG is too wide, the developing electric field does not reach from the developing sleeve 7 toward the photoconductor 8, and a wraparound electric field that returns to the developing sleeve surface is likely to occur. In addition, the toner does not adhere uniformly to the image area, and in particular, unevenness occurs in the halftone image and the graininess deteriorates. Therefore, in order to improve the graininess, the development gap PG is set to be relatively narrow 0.4 [mm] or less. If the development gap PG is narrowed, there is an effect of improving character margin missing and solid / line adhesion amount ratio (ratio of toner adhesion amount to solid patch portion and line portion adhesion amount, closer to 1 is better). Is known. However, if the developing gap PG is made too small, the developing sleeve 7 and the photosensitive member 8 come into contact with each other with the developer sandwiched due to slight fluctuations in the gap, or the toner is sandwiched between them to form a packing state, and the developing sleeve 7 is filled with toner. There is a risk of sticking. The lower limit of the development gap is 0.2 [mm], which is a lower limit of a general development gap.

  In Comparative Examples 10 and 16, the development gap PG is as wide as 0.5 [mm], and the graininess is “x”. In addition, the graininess is also deteriorated when there is basically a roughness. On the other hand, in each of Examples 1 to 5, the development gap PG is set to 0.2 [mm] or more and 0.4 [mm] or less, and the development electric field reaches the image portion of the photoreceptor 8 uniformly. Graininess is improved. The graininess is also related to the particle size of the magnetic carrier and the toner, and the graininess is further improved in the configuration using the small particle diameter toner as in the present embodiment.

Further, a magnetic carrier having a coating film having at least a binder resin and particles and having a particle diameter D and a binder resin film thickness h in a range of 1 <[D / h] <10 was used. When a magnetic carrier having a high saturation magnetization is used, the developer holding amount on the upstream side (upstream side in the sleeve rotation direction) of the doctor increases, and a very high stress is applied to the developer. For this reason, the developer life (carrier film scraping, carrier surface contamination due to toner fusion to the carrier surface, etc.) is shortened. However, in the present invention, the carrier having the above-described relationship between the particle diameter D and the binder resin film thickness h is used, and the improvement effect is prominent with respect to the long life of the carrier.
In this magnetic carrier, the particles are more convex than in the coating film, and therefore, the agitation for frictionally charging the developer causes a strong impact on the binder resin due to friction with the toner or friction between the carriers. Contact can be mitigated. As a result, it is possible to prevent the carrier resin from being scraped by the binder resin, which is a charging occurrence point, and to cause carrier contamination due to toner fusion, and to greatly improve the carrier life. When [D / h] is 1 or less, the particles are buried in the binder resin, so that the meaning of adding the particles is lost and the effect is remarkably lowered. When [D / h] is 10 or more, the contact area between the particles and the binder resin is small, so that a sufficient restraining force cannot be obtained, and the particles are easily detached, which is not preferable. Further, when a rigid and magnetic doctor or the like is used in order to improve the charge start-up property of the toner, the improvement effect is further remarkable. This is because when the magnetic doctor is used, the amount of developer retained in the doctor portion is further increased, and the stress becomes very large. Here, the magnetic doctor is not limited to one made of a metal material such as iron or stainless steel, but may be composed of a resin material containing magnetic particles such as ferrite or magnetite. Further, the same effect can be obtained by adopting a configuration in which another member such as a metal plate made of a magnetic material is directly or indirectly fixed to the doctor without forming the doctor itself with a magnetic material.
FIG. 15 shows the charge amount at the beginning of the change in charge amount during running for each of the carrier C1 and the comparative example carrier C2 where 1 <[D / h] <10 used in the present embodiment. It is the result shown by the ratio when it is set to 1. The decrease in the charge amount is caused by toner spent on the carrier during running. When the charge amount is 0.8 or less of the initial charge amount, that is, when the decrease rate exceeds 20%, an image problem occurs. From FIG. 15, in the carrier C1 where 1 <[D / h] <10, the charge amount exceeded the initial 0.8 even when the running number was 100K. On the other hand, in the carrier C2, the charge amount became 0.8 or less at the beginning before the running number reached 100K. As a result, the carrier of this example having a coating film having at least a binder resin and particles, in which the particle diameter (D) and the binder resin film thickness (h) are 1 <[D / h] <10, The resulting decrease in charge amount can be suppressed. The upper limit of the value of D / h is more preferably 5 from the viewpoint of avoiding particle detachment.

In Examples 1 to 5, the weight average particle diameter of the magnetic carrier is 20 [μm] to 60 [μm] and the saturation magnetization is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] to 100 × 10 ^−7. × 4π [Wb · m / kg] or less, and static resistance when 1000 [V] is applied is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less. As a result, it is possible to suppress carrier adhesion while using a small particle size carrier for high image quality, while suppressing both the blurred image and missing characters in the allowable range. In the present embodiment, the main pole magnetic flux density (P1) is 120 [mT], and the main pole downstream pole magnetic flux density (P2) is 110 [mT]. However, the present invention is not limited to this value, and the effect of the present invention can be obtained as long as the magnetic flux density is higher than any magnetic pole.

As described above, the image forming apparatus according to the present embodiment develops the electrostatic latent image on the photosensitive member 100 as the image carrier having the photosensitive layer on the surface with the developing device using the developer, and then converts the visible image into the visible image. After transfer to a sheet-like medium, the image is obtained by heat and pressure fixing. In this developing device, a developing sleeve 111c as a developer carrying member having a magnet inside is arranged opposite to the photosensitive member 100 to form a developing region, and a developing including a toner T and a magnetic carrier CC holding the toner. When the developer is carried on the developing sleeve and passed through the developing area, the static on the photoreceptor 100 is utilized by utilizing the state of the magnetic brush formed by the developer gathering along the magnetic field lines of the magnet in the developing area. The electrostatic latent image is visualized with toner T. In this embodiment, the magnetic carrier CC has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less, and a saturation magnetization in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ^−7. × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg] or less, static resistance when a bias of 1000 [V] is applied is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less is used. Thereby, as described above, it is possible to suppress carrier adhesion that tends to occur when a small particle size carrier is used, while keeping side effects such as missing images and missing characters around within an allowable range. Moreover, the toner is released from the surface of the magnetic carrier according to the mutual displacement of the magnetic carrier that occurs when the magnetic carrier CC rises as a spike along the magnetic field lines of the magnet from the state in which the toner T holds the toner T. The electrostatic latent image is visualized with the released free toner T ′. The free toner T ′ can be easily moved by a developing electric field or the like because no electrostatic or physical adhesion force acts on the magnetic carrier CC. Therefore, even when a release agent-containing toner is used, it is possible to form a high quality image having a high image density, good solid filling, and excellent dot reproducibility. In particular, in this embodiment, as described above, the magnetic carrier CC holds the toner T and moves to the developing area together with the developing sleeve 111c in a collective state, and in the initial stage of the developing area, the free toner Since T ′ is generated, it also has a role of strengthening development after the development middle region and contributes to further improvement in development performance.
Further, in the present embodiment, as described above, the toner T is detached from the surface of the magnetic carrier by bringing the ears of the magnetic carrier CC rising as the ears along the magnetic field lines of the magnet into contact with the photoconductor 100 in the development region. The detached free toner T ′ is scattered on the photosensitive member 100, and the electrostatic latent image is visualized. Thus, high-performance development can be performed with the toner T ′ released from the magnetic carrier CC using an external force other than electrostatic force such as a developing bias.
Further, in the present embodiment, as described above, the electrostatic carrier CC moves by bringing the tip of the spike rising as a spike along the magnetic field lines of the magnet into contact with the photoconductor 100 and moving it. The image portion constituting the latent image is developed by the electric field between the photoconductor 100 and the developing sleeve 111c and the electric field generated between the photoconductor 100 and the magnetic carrier CC, and the non-image portion is already described above. The toner adhering to the photoconductor 100 is developed while being pulled back from the photoconductor 100 to the magnetic carrier constituting the ear. Thereby, it is possible to obtain a high image quality without any background contamination.
In the present embodiment, as described above, the drum-shaped developing sleeve 111c is disposed so as to be opposed to the drum-shaped photoconductor 100, so that the convex curved surfaces formed between each other are close to each other. A development area is formed. The area where the opposing surfaces are closest to each other and the vicinity thereof are set as a developing middle area, and the developing area upstream of the developing direction of the photoconductor 100 from the developing middle area is defined as a pre-developing area. When the development area downstream in the moving direction of the photoconductor 100 from the middle development area is the post development area, the magnetic carrier CC holds the toner T and gathers in the pre-development area. The toner T is detached from the surface of the magnetic carrier CC according to the mutual displacement of the magnetic carrier that occurs when the magnetic carrier CC rises from the state where the magnetic field rises along the magnetic field lines of the magnet, and with the separated free toner T ′. In the development mode for making the electrostatic latent image visible, and in the pre-development region, the magnetic carrier CC rises as a spike along the magnetic field lines of the magnet. Make strong contact with Thus, the toner T is released from the surface of the magnetic carrier, and the released free toner T ′ is sprayed on the photosensitive member 100, whereby the electrostatic latent image is visualized. At least in the post-development area, the image portion constituting the electrostatic latent image has an electric field between the photoconductor 100 and the development printing portion 111c and between the photoconductor 100 and the magnetic carrier CC. The non-image portion is developed while pulling back the toner T already adhered on the photoconductor 100 from the photoconductor 100 to the magnetic carrier constituting the spike. Therefore, it is possible to obtain a high image density with high image density, good solid filling, excellent dot reproducibility, and no background stains. In particular, in the present embodiment, as described above, in the pre-development area portion, the magnetic carrier CC rises as a spike along the magnetic field lines of the magnet, and strongly contacts the photoconductor 100 in the development middle area portion. Instead of this, after the middle development area, the photosensitive member 100 is not contacted, and development is performed with the free toner T ′ generated by the mutual displacement of the magnetic carriers that are displaced in this non-contact state. Therefore, high image quality can be obtained without reducing the amount of the release agent-containing toner that has been developed at the initial stage of the development region.
In the present embodiment, as described above, an electric field for moving the free toner T ′ or the toner T held on the magnetic carrier CC toward the photoconductor 100 is formed in the development region. These toners are moved toward the photoreceptor 100 side. Thereby, the release agent-containing toner can be attached to the electrostatic latent image by the action of the electric field. In particular, in the present embodiment, as described above, since the electric field is a DC electric field, a situation in which leakage is unlikely to occur by creating an AC bias that causes leakage is generated, and generation of a blurred image is suppressed. be able to.
In this embodiment, the toner T uses a polyester resin or a polyol resin as a binder resin. In this embodiment, the toner T contains a release agent, and the content of the release agent is 2 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the binder resin of the toner. In addition, carnauba wax or synthetic ester wax is used as the release agent. The toner T is a toner containing an additive, and the content of the additive is 1.0 part by weight or more and 3.6 parts by weight or less with respect to 100 parts by weight of the toner base particles. The additive has a mean primary particle size of 0.02 [μm] or more and 0.2 [μm] or less. Moreover, any one or more of silica, titania and alumina are used as the additive. Further, the coverage of the toner T with respect to the magnetic carrier is set to 35 [%] to 75 [%]. By using such a developer, it is suitable for the development method of the present invention that enables formation of a high-quality image having releasability, high image density, good solid filling, and excellent dot reproducibility. A developer can be obtained.
Further, in the present embodiment, as described above, the drum-shaped developing sleeve 111c is disposed so as to face the drum-shaped photosensitive member 100, and the convex surfaces formed by this arrangement are located between the adjacent facing surfaces. This constitutes the development area. The area where the facing surfaces are closest to each other and the vicinity thereof are set as a developing middle area, and the developing area upstream of the developing medium in the moving direction of the photosensitive member 100 is defined as a pre-developing area. When the development area downstream in the moving direction of the photoconductor 100 from the middle area is set as the post-development area, the magnetic carrier CC holds the toner T in the pre-development area and the aggregated state is obtained. The toner T is detached from the surface of the magnetic carrier CC in accordance with the mutual displacement of the magnetic carrier that occurs when it rises as a spike along the magnetic field lines of the magnet from the state where it has been left, and the static toner is released with the released free toner T ′. The electrostatic latent image is visualized, and in the middle region of development, the magnetic carrier CC rises as a spike along the magnetic field lines of the magnet so as to make strong contact with the photoconductor 100 in the development region. (A) The toner T is separated from the surface of the CC, and the separated free toner T ′ is sprayed on the photosensitive member 100, whereby the electrostatic latent image is visualized, and the development middle region to the rear region Then, the image portion constituting the electrostatic latent image is developed by an electric field between the photosensitive member 100 and the developing sleeve 111c and an electric field generated between the photosensitive member 100 and the magnetic carrier CC. The toner T that has already adhered on the photoconductor 100 is developed while being pulled back from the photoconductor 100 to the magnetic carrier constituting the spike. As a result, the image density is high, the solid image is well filled, the dot reproducibility is excellent, and a high image quality without background stains can be obtained. In particular, in the present embodiment, in the pre-development area, the spikes in which the magnetic carrier CC rises as spikes along the magnetic field lines of the magnet are brought into contact with the photoconductor 100 after the development middle area. Instead, development is performed in a non-contact manner and in close proximity, so that high image quality can be obtained without reducing the amount of release agent-containing toner developed in the initial stage of the development area.
In the present embodiment, as described above, the peak position M1 of the magnetic force in the normal direction on the developing sleeve 111c of the developing main magnetic force distribution P1 formed around the developing sleeve 111c is the photoreceptor 100. And the developing sleeve 111c are shifted by 0 [°] or more and 30 [°] or less on the downstream side in the moving direction of the photoconductor 100 from the closest approach position M0. As a result, a large amount of free toner T ′ is generated in the vicinity of the re-approaching site, and development with the free toner T ′ is promoted.
In addition, the photoreceptor 100 of this embodiment is a single layer type in which a charge transport layer in which a charge generation material is dispersed is provided on a conductive support, or a charge generation layer and a charge transport layer on a conductive support. Are stacked in order. Therefore, it is possible to obtain an image carrier suitable for a developing device that can form a high-quality image having releasability, high image density, good solid filling, and excellent dot reproducibility.

Sectional drawing explaining the structure of the image development apparatus. It is sectional drawing of a developing roller. The figure explaining the bias voltage application means of the developing device. The figure which showed typically the state of the developer in a development area. The figure which showed typically the state of the developer in a development front area part. FIG. 3 is a diagram schematically showing an electrostatic force acting on toner on a photoreceptor. FIG. 3 is a schematic diagram showing a situation where a carrier ear is in strong contact with an image carrier in a developing middle region. 1 is a front view illustrating a configuration of a main part of an image forming apparatus. The figure which showed typically the image development aspect when shifting the peak position M1 of magnetic force from the closest approach position M0. (A) thru | or (c) is the figure which explained step by step schematically showing a mode that a magnetic brush might be in contact with a photoconductor in a development area. (A) thru | or (c) is the figure which explained the step by step schematically showing a magnetic brush being developed in non-contact with a photoconductor in a development area. 2A and 2B are diagrams illustrating a configuration of a photoreceptor having two layers, (b) and (c) having three layers, and (d) having four layers. The graph which shows the result of having investigated the relationship between the saturation magnetization of a magnetic carrier, and the generation | occurrence | production state of a blurred image. The schematic block diagram of an actual resistance measuring apparatus. The graph which showed the change of the charge amount at the time of running about each of Example carrier C1 and Comparative example carrier C2.

Explanation of symbols

100 Photoconductor 111c Development Sleeve T Release Agent-Containing Toner T 'Free Toner CC Magnetic Carrier

Claims (20)

A developer carrying body having a magnet inside is disposed opposite to an image carrying body provided with a photosensitive layer on the surface to form a development region, and a two-component developer containing toner and a magnetic carrier for holding the toner is When the developer carrying member is carried and passed through the development area, the image is obtained using the state of a magnetic brush formed by the two-component developer gathering along the magnetic field lines of the magnet in the development area. In the developing device that visualizes the electrostatic latent image on the carrier with the toner,
The magnetic carrier has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less,
Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Less than,
The static resistance of the magnetic carrier when a bias of 1000 [V] is applied to the magnetic carrier is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less,
The toner is detached from the surface of the magnetic carrier in accordance with the mutual displacement of the magnetic carrier that occurs when the magnetic carrier rises as a spike along the magnetic field lines of the magnet from the state in which the toner is held and gathers. A developing device characterized in that the electrostatic latent image is visualized with the free toner. The developing device according to claim 1.
Development wherein the magnetic carrier holds the toner and forms an aggregated state, moves together with the developer carrier toward the development area, and generates the free toner at an early stage of the development area. apparatus. A developer carrying body having a magnet inside is disposed opposite to an image carrying body provided with a photosensitive layer on the surface to form a development region, and a two-component developer containing toner and a magnetic carrier for holding the toner is When the developer carrying member is carried and passed through the development area, the image is obtained using the state of a magnetic brush formed by the two-component developer gathering along the magnetic field lines of the magnet in the development area. In the developing device that visualizes the electrostatic latent image on the carrier with the toner,
The magnetic carrier has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less,
Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Less than,
The static resistance of the magnetic carrier when a bias of 1000 [V] is applied to the magnetic carrier is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less,
The magnetic carrier comes into contact with the image carrier in the development area with a spike that rises as a spike along the magnetic field lines of the magnet, thereby releasing the toner from the surface of the magnetic carrier, and the released free toner is removed from the image carrier. And developing the electrostatic latent image into a visible image. A developer carrying body having a magnet inside is disposed opposite to an image carrying body provided with a photosensitive layer on the surface to form a development region, and a two-component developer containing toner and a magnetic carrier for holding the toner is When the developer carrying member is carried and passed through the development area, the image is obtained using the state of a magnetic brush formed by the two-component developer gathering along the magnetic field lines of the magnet in the development area. In the developing device that visualizes the electrostatic latent image on the carrier with the toner,
The magnetic carrier has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less,
Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Less than,
The static resistance of the magnetic carrier when a bias of 1000 [V] is applied to the magnetic carrier is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less,
When the magnetic carrier rises as a spike along the magnetic field lines of the magnet and moves the tip of the spike in contact with the image carrier, the image carrier for the image portion constituting the electrostatic latent image And the image bearing member and the magnetic carrier, and the non-image portion is treated with the toner already adhered on the image bearing member. A developing device for developing while pulling back from a carrier onto a magnetic carrier constituting the ear. A drum-shaped developer bearing member having a magnet inside is disposed between opposed surfaces of convex surfaces formed by disposing the drum-shaped developer bearing member facing the drum-shaped image bearing member provided on the surface. A two-component developer including a toner and a magnetic carrier for holding the toner is carried on the developer carrying member and passed through the developing region along with the rotation of the image carrier. Development in which the electrostatic latent image on the image carrier is visualized with the toner using the state of a magnetic brush formed by the two-component developer gathering along the magnetic field lines of the magnet in the development area. In the device
The magnetic carrier has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less,
Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Less than,
The static resistance of the magnetic carrier when a bias of 1000 [V] is applied to the magnetic carrier is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less,
The area where the facing surfaces are closest to each other and the vicinity thereof are set as a developing middle area, and the developing area upstream of the developing medium in the moving direction of the image carrier is the pre-developing area. When the development area downstream in the moving direction of the image carrier from the middle area is the post-development area, the magnetic carrier holds the toner and forms an aggregated state in the pre-development area. The toner is detached from the surface of the magnetic carrier in accordance with the mutual displacement of the magnetic carrier that occurs when the head rises from the magnetic field to the magnetic field lines of the magnet, and the electrostatic latent image is visible with the detached free toner. In the development mode used for imaging, and in the pre-development region, the magnetic carrier rises as a spike along the magnetic field lines of the magnet, so that the magnetic carrier is brought into strong contact with the image carrier in the development middle region The surface of the carrier The toner is released, and the released free toner is sprayed on the image carrier so that the electrostatic latent image is visualized. At least in the post-development area, the static image is developed. The image portion constituting the electrostatic latent image is developed by the electric field between the image carrier and the developer carrier and the electric field generated between the image carrier and the magnetic carrier, and the non-image portion has already been developed. A developing device, wherein the toner attached on the image carrier is developed while being pulled back from the image carrier to a magnetic carrier constituting the ear. The developing device according to claim 5.
Instead of making the magnetic carrier stand up as a spike along the magnetic field lines of the magnet in the pre-development area, instead of making the image carrier strongly contact the development medium area, after the development middle area A developing apparatus characterized in that development is performed with free toner generated by displacement between magnetic carriers that are displaced in a non-contact state with respect to the image carrier. The developing device according to claim 1, 2, 3, 4, 5 or 6.
An electric field for moving the free toner or the toner held on the magnetic carrier to the image carrier side is formed in the development area, and the toner is moved toward the image carrier side. A developing device. The developing device according to claim 7.
A developing device characterized in that the electric field is a DC electric field. The developing device according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
The developing device according to claim 1, wherein the toner uses a polyester resin or a polyol resin as a binder resin. The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9.
The above-mentioned toner contains a release agent, and the content of the release agent is 2 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the binder resin of the toner. The developing device according to claim 10.
A developing apparatus using carnauba wax or synthetic ester wax as the release agent. The developing device according to claim 10 or 11,
The toner is a toner containing an additive, and the content of the additive is 1.0 part by weight or more and 3.6 parts by weight or less with respect to 100 parts by weight of the toner base particles. apparatus. The developing device according to claim 12, wherein
The developing device, wherein the additive has a mean primary particle size of 0.02 [μm] or more and 0.2 [μm] or less. The developing device according to claim 12 or 13,
One or more of silica, titania, and alumina is used as the additive. In the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14.
A developing device characterized in that the coverage of the toner with respect to the magnetic carrier constituting the two-component developer is 35% or more and 75% or less. A drum-shaped developer carrying member having a magnet inside is arranged so as to face a drum-shaped image carrying member provided with a photosensitive layer on the surface, and between adjacent opposed surfaces of convex curved surfaces formed by this arrangement. Thus, a development area is formed, and a two-component developer containing a release agent-containing toner and a magnetic carrier for holding the toner is supported on the developer carrier, and the development area is rotated with the rotation of the image carrier. When passing, the electrostatic latent image on the image carrier is formed with the toner by utilizing the state of a magnetic brush formed by the two-component developer gathering along the magnetic field lines of the magnet in the developing region. In the developing device for visualizing the image,
The magnetic carrier has a weight average particle diameter of 20 [μm] or more and 60 [μm] or less,
Similarly, the saturation magnetization of a magnetic carrier in a magnetic field of 1 × 10 ⁶ / 4π [A / m] is 66 × 10 ⁻⁷ × 4π [Wb · m / kg] or more and 100 × 10 ⁻⁷ × 4π [Wb · m / kg]. Less than,
The static resistance of the magnetic carrier when a bias of 1000 [V] is applied to the magnetic carrier is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less,
The area where the facing surfaces are closest to each other and the vicinity thereof are set as a developing middle area, and the developing area upstream of the developing medium in the moving direction of the image carrier is the pre-developing area. When the development area downstream in the moving direction of the image carrier from the middle area is the post-development area, the magnetic carrier holds the toner and forms an aggregated state in the pre-development area. The toner is detached from the surface of the magnetic carrier in accordance with the mutual displacement of the magnetic carrier that occurs when the head rises from the magnetic field to the magnetic field lines of the magnet, and the electrostatic latent image is visible with the detached free toner. For imaging, in the middle area of the development, the magnetic carrier rises as a spike along the magnetic field lines of the magnet, and the toner is removed from the surface of the magnetic carrier by strongly contacting the image carrier in the development area. Withdrawn The released free toner is sprayed on the image carrier, so that the electrostatic latent image is visualized, and the electrostatic latent image is formed from the developing middle region to the rear region. The image portion is developed by the electric field between the image carrier and the developer carrier and the electric field generated between the image carrier and the magnetic carrier, and the non-image portion is already on the image carrier. A developing device for developing while adhering toner adhering back to the magnetic carrier constituting the ear from the image carrier. The developing device according to claim 16, wherein
In the pre-development area, the magnetic carrier rises as a spike along the magnetic field lines of the magnet. A developing device characterized in that the developing is performed. The developing device according to claim 16 or 17,
The peak position M1 of the magnetic force in the normal direction on the developer carrier of the development main magnetic force distribution P1 formed around the developer carrier is closest to the image carrier and the developer carrier. A developing device characterized by being shifted from the position M0 to the downstream side in the moving direction of the image carrier by 0 [°] or more and 30 [°] or less. After developing the electrostatic latent image on the image bearing member provided with the photosensitive layer on the developing device using a two-component developer, the visible image is transferred to a sheet-like medium, and then heated and pressed to fix the image. In the obtained image forming apparatus,
The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 is used as the developing device. An image forming apparatus. The image forming apparatus according to claim 19.
The image carrier may be a single layer type in which a charge transport layer in which a charge generation material is dispersed is provided on a conductive support, or a charge generation layer and a charge transport layer are sequentially laminated on a conductive support. An image forming apparatus having a laminated photosensitive layer.

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