JP2003149944A - Developing device, image forming device, and image forming process unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce toner scatter even under conditions in which the linear velocity of a developer carrier is large and to prevent image quality deterioration such as void on a trailing end even two-component developer comprising spherical magnetic toner is used. SOLUTION: The developer contains at least magnetic toner (A) and magnetic carrier (B) which have a magnetic substance. The average circularity of the magnetic toner (A) is equal to or greater than 0.93. The extinction ratio of magnetic flux density in the direction of a normal line which generates outside the surface of a developer carrier in a developer region is 50% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a fax machine, a developer used in the apparatus, a developing apparatus and an image forming process unit, and more specifically, a non-magnetic non-magnetic material capable of being rotated. Toner and magnetic particles are deposited on the developer bearing member and the developing region facing the latent image bearing member (region where a developable electric field is secured between the developer bearing member and the image bearing member). The present invention relates to a developing device including a magnetic field generating unit that generates a magnetic field that causes the developer to rise, an image forming apparatus including the developing device, an image forming process unit, and a developer used therefor.

[0002]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus such as a copying machine, a printer or a facsimile, an electrostatic latent image corresponding to image information is formed on a latent image carrier composed of a photosensitive drum and a photosensitive belt. Is formed, the developing operation is executed by the developing device, and a visible image is obtained. In such an electrophotographic system, conventionally, a one-component developing system using a one-component developing agent containing only toner and a two-component developing system using a two-component developing agent containing toner and magnetic particles are known.

In the two-component developer used in the two-component developing system, minute toner particles are held on the surface of a relatively large particle by the electric force generated by the friction between the two particles, so that they are close to the electrostatic latent image. Then, the attraction force in the latent image direction on the toner particles due to the electric field formed by the electrostatic latent image overcomes the binding force between the toner particles and the carrier particles, and the toner particles are attracted and adhered onto the electrostatic latent image to be statically attached. The latent image is visualized. Then, the developer is repeatedly used while replenishing the toner consumed by the development.

Therefore, in this two-component developing system, it is necessary to keep the mixture ratio (toner density) of carrier and toner constant in order to obtain a stable image density, and it is necessary to mount a toner replenishing mechanism and a toner density sensor for that purpose. Therefore, there is a drawback that the developing device becomes large and the operating mechanism thereof becomes complicated.

On the other hand, unlike the two-component developing system, the one-component developing system develops by an electric force generated by friction between the toner and the developing sleeve or a magnetic force between the toner containing a magnetic material and the developing sleeve containing a magnet. When the toner is held on the sleeve and approaches the electrostatic latent image, the attraction force in the latent image direction to the toner particles by the electric field formed in the electrostatic latent image overcomes the binding force between the toner particles and the developing sleeve, The toner particles are attracted and adhered onto the electrostatic latent image to visualize the electrostatic latent image.

Therefore, the one-component developing system has an advantage that the developing device can be downsized because it is not necessary to control the toner density, but the number of toner particles in the developing area is smaller than that of the two-component developing system. Therefore, the amount of toner developed on the photoconductor is not sufficient, and it is difficult to support a high-speed copying machine.

[0007]

In the above-described two-component developing method, the closer the distance between the latent image bearing member and the developer bearing member is in the developing area where the development is performed, the easier it is to obtain a high image density and the edge. It is known to have little effect. For this reason, it is desirable to bring the latent image carrier and the developer carrier closer to each other, but when both are brought close to each other, the trailing edge of the black solid image or the halftone solid image is white, so-called "rear edge blank". Image quality deterioration, which is called

The phenomenon of "white trailing edge" is considered to occur by the following mechanism. FIG. 9 shows an example of a developing unit in a developing device that performs negative-positive development by a two-component developing method. In FIG. 9, a small circle indicates toner 3
The large circle a represents a magnetic carrier (magnetic particle) 3b. Further, for convenience of illustration, only one magnetic brush in the developing area is shown by a solid line, the other magnetic brushes are shown by broken lines, and toner is omitted. Further, it is assumed that the non-image area A on the photosensitive drum 1 is negatively charged.

In FIG. 9, the developer carried on the developing sleeve 4 as the developer carrying member is carried to the vicinity of the developing area facing the photosensitive drum 1 by the movement of the developing sleeve 4 in the direction of arrow D. . In the developer, the magnetic carrier 3b stands up due to the magnetic force of the developing magnetic pole in the vicinity of the developing area to form the magnetic brush MB. On the other hand, the photosensitive drum 1 is rotating in the direction of arrow C while holding the electrostatic latent image on its surface. In the developing area, the magnetic brush MB rubs the latent image on the photosensitive drum 1 due to the linear velocity difference between the photosensitive drum 1 and the developing sleeve 4 (photoconductor linear velocity <developing sleeve linear velocity), and the developing electric field causes The toner 3a adheres to the image area B. As a result, a toner image is formed on the image portion B of the latent image on the photosensitive drum 1 on the downstream side of the developing area in the moving direction of the developing sleeve. The linear velocity of the developing sleeve is generally set higher than the linear velocity of the photosensitive member in order to secure a predetermined image density.

In such a two-component developing system developing device, it is considered that the trailing edge white spots occur due to the mechanism shown in FIG. 10A to 10C are all enlarged explanatory views in the vicinity of the opposing portion of the photosensitive drum 1 and the developing sleeve 4 in FIG. 9, and the tip of the right magnetic brush MB approaches the left photosensitive drum 1. The movement of the coming magnetic brush is displayed in time series of FIGS. 10a, 10b, 10c. In FIG. 10, the opposing portion of the photosensitive drum 1 and the developing sleeve 4 is in the state where the boundary between the non-image portion and the black solid image is being developed, that is, the state where "white trailing edge" occurs, A toner image just developed is formed on the downstream side in the rotation direction. One magnetic brush MB 1 on the developing sleeve 4 approaches the photosensitive drum 1 in this state. Here, the photosensitive drum 1 is actually rotating clockwise in the figure, but as described above, the developing sleeve 4
Is moving faster than the photosensitive drum 1, the magnetic brush MB overtakes the photosensitive drum 1. Therefore, in FIGS. 10A to 10C, the model is simplified assuming that the photosensitive drum 1 is stationary.

In FIG. 10A, the magnetic brush MB approaching the photoconductor drum 1 moves to face the non-image portion before reaching the rear end position A of the image portion to be developed. During this movement, the repulsive force B between the negative charges causes the toner 3a to gradually separate from the photosensitive drum 1 and move toward the surface of the developing sleeve (hereinafter, this toner movement is referred to as "toner drift"). As a result of this toner drift, FIG.
As shown in 0b, when the magnetic brush MB reaches the rear end position A of the image portion, the magnetic brush near the photoconductor drum 1 is exposed to the positively charged magnetic carrier 3b. Therefore, there is no toner on the surface of the magnetic carrier facing the trailing edge position A of the image portion of the latent image, and the trailing edge position A of the image portion is not present.
Therefore, there is no toner transfer from the magnetic brush MB to the photosensitive drum 1. Further, when the magnetic brush MB reaches the rear end portion C of the image portion slightly inside the image portion from the rear end position A of the image portion in FIG. 10c, when the adhesion between the toner 3a and the photosensitive drum 1 is weak, The toner 3a once attached to the photoconductor drum 1 may reattach to the magnetic carrier due to electrostatic force. As a result, development may not be performed at the trailing edge portion of the image portion, which is close to the non-image portion of the image portion, and this is considered to be the cause of "white trailing edge portion".

In the above description of the mechanism of occurrence of "rear edge white spots", the cross section perpendicular to the rotation center axis of the developing sleeve 4 has been illustrated and described, but along the longitudinal direction of the developing sleeve (rotation center axis direction). Observing, the length of each magnetic brush is not constant, but varies in the longitudinal position. FIG. 11 schematically shows the state of this magnetic brush.
11a shows a state of the magnetic brush MB spreading in the longitudinal direction, and FIG. 11b shows a cross-sectional view when the magnetic brush MB shown in FIG. 11a is cut along a plane AA perpendicular to the longitudinal direction. In order to understand the relationship with other figures,
1b schematically shows the positional relationship with the photosensitive drum 1. As shown in FIGS. 11a and 12a, the magnetic brush M
The height of B varies greatly in the longitudinal direction. For this reason,
The position of contact with the photoconductor varies irregularly along the longitudinal direction. As a result, the degree of the toner drift also varies in the longitudinal direction, and the degree of occurrence of "white trailing edge" is not constant in the longitudinal direction. Therefore, as shown in FIG. 12b, a "rear edge whiteout" having a jagged shape in the longitudinal direction occurs.

By the same mechanism, the "horizontal line thinning" phenomenon in which the horizontal thin line extending in the direction of the rotation axis of the developing sleeve 4 becomes thinner than the vertical thin line orthogonal thereto, and the formation of isolated dots becomes unstable. A phenomenon also occurs, which hinders the improvement in image quality of the two-component developing method.

Therefore, the applicant of the present invention has proposed the above-mentioned "rear end blank area".
In order to prevent the occurrence of such problems as described above, by defining the magnetic flux density distribution in the normal direction on the developing sleeve, the width of the developing area in the rotating direction of the developing sleeve (developing nip width) is narrowed, and the magnetic brush developing in the developing area is performed. A developing device having an increased agent density has been proposed (for example, Japanese Patent Laid-Open No. 2000-30536).
No. 0).

On the other hand, when a non-magnetic toner is used as the toner contained in the developer and the developing sleeve is rotated as described above, the toner is scattered by the centrifugal force acting on the toner in the developer carried on the developing sleeve. However, there is a problem that is likely to occur. In order to suppress this toner scattering, it is possible to use a magnetic toner.

However, when the magnetic toner is used as the toner of the developer, in addition to the usual electrostatic attraction force between the toner and the magnetic carrier, the magnetic force in the direction in which the toner separates from the photosensitive drum side is obtained. Since the force is generated, the above-mentioned "rear end blank area" is likely to occur.

In particular, when a spherical magnetic toner is used, the surface energy of the toner is small, so that it easily moves on the carrier surface, and as shown in FIG. 13, the surface of the photosensitive drum 1 contacts the tip of the magnetic brush MB. Part, toner 3a
Adheres in an annular shape to the surface of the magnetic carrier 3b, and the exposed magnetic carrier surface of the tip of the magnetic brush MB faces the photoconductor drum 1, resulting in "rear end blank area" due to the toner drift. Is more likely to occur. Further, due to the same mechanism, a phenomenon of "horizontal line thinning" in which a horizontal thin line becomes thinner than a vertical thin line and a phenomenon in which the formation of isolated dots becomes unstable are more likely to occur, which hinders the improvement of image quality.

Further, a developer regulating member for regulating the amount of the developer carried on the developer carrying member and conveyed toward the developing region, and the developer regulating member for regulating the carrying toward the developing region. And a toner accommodating portion having a toner supply opening facing the surface of the developer carrier at a position adjacent to the developer accommodating portion from the upstream side in the developer conveying direction. A developing device of a type in which the toner in the toner containing portion is taken into the developer according to the toner concentration of the developer on the developer carrying body by the movement of the developer accompanying the transport of the developer on the developer carrying body. In case of poor fluidity of the developer, the toner cannot be taken in efficiently, and repeated copying of an image consuming a large amount of toner tends to cause a decrease in image density or partial uneven density, resulting in high image quality. Hinders It had.

Further, it is located between the toner replenishing opening of the toner accommodating portion facing the surface of the developer carrying member and the developer accommodating portion, and the developer accommodating portion extends from the toner replenishing opening of the toner accommodating portion. A second developer regulating member that regulates the amount of the developer on the developer carrying body carried toward and toward the developing means, and the developing process is performed as the toner concentration of the developer on the developer carrying body increases. In a developing device in which the gap between the second developer regulating member and the surface of the developer carrying member is set so that the regulated amount of the developer increases, if the fluidity of the developer is poor, the toner can be taken in efficiently. However, if an image that consumes a large amount of toner is repeatedly copied, the image density is likely to drop and partial density unevenness easily occurs, which hinders the achievement of high image quality.

By the way, in recent years, a toner manufactured by a polymerization method has been used. This is because it is essential to reduce the particle size of the toner in order to meet the demand for higher image quality, but since the shape is closer to a sphere and the particle size distribution can be narrowed compared to the conventional grinding method. In addition to high yield and cost reduction, energy consumption in the manufacturing process is small and environmental load is small, so it is attracting attention as a corporate attitude.

The present invention has been made under the background described above, and an object thereof is a condition that the linear velocity of the developer carrier is high even when a two-component developer using spherical magnetic toner is used. (EN) Provided are a developing device capable of suppressing toner scattering below and preventing deterioration of image quality such as trailing edge blank areas, an image forming apparatus and an image forming process unit including the developing device.

[0022]

In order to achieve the above-mentioned object, the present invention provides a non-magnetic developer carrier which can be rotationally driven, and a developer carrying member on the above-mentioned developer carrier in a developing area facing the latent image carrier. And a brush-shaped developer carried on the surface of the developer carrying member in the developing area in the same direction as the moving direction of the surface of the latent image carrying member. In the developing device for developing the latent image on the latent image bearing member by moving the toner at a higher speed than the surface of the latent image bearing member and contacting the latent image bearing member with the magnetic toner (A) having a magnetic substance. The magnetic toner (A) contains at least the magnetic carrier (B), and the average circularity of the magnetic toner (A) is 0.93.
The above is characterized in that the attenuation rate of the magnetic flux density in the normal direction generated outside the surface of the developer carrier in the developing region is 50% or more.

Here, the "developing area" in the contact-type developing system using a two-component developer means that the brush-like developer formed by erected on the developer carrying member comes into contact with the latent image carrying member,
This is an area where the latent image on the latent image carrier can be developed with the toner in the developer. The “circularity” can be measured by various methods.

"Attenuation rate of magnetic flux density in the normal direction" means
The peak value of the magnetic flux density in the normal direction generated on the surface of the developer carrying member by the developing magnetic pole is X, and the peak value of the magnetic flux density in the normal direction at a position 1 mm away from the surface of the developer carrying member in the radial direction is Y. Then, the value is calculated by the following formula: Attenuation rate [%] = {(X−Y) / X} × 100 ... [Formula 1]

In the developing device of the present invention, since the toner is attracted to the magnetic carrier by the magnetic force by using the magnetic toner, the toner scattering hardly occurs even when the linear velocity of the developer carrying member is increased. Then, by setting the attenuation rate of the magnetic flux density in the normal direction generated outside the surface of the developer carrier in the developing region to 50% or more, the width of the developing region in the moving direction of the surface of the developer carrier is narrowed, and the spherical shape Even when the above magnetic toner is used, the toner drift from the latent image carrier toward the developer carrier at the rear end of the image portion does not occur. Furthermore, the length of brush-like developer that is erected in the developing area is short and the density is high, and even when the above magnetic toner is used, the brush-like developer does not adhere to the surface of the latent image carrier in the developing area. Thus, they come into contact with and separate from each other uniformly over the entire rotation center axis direction of the developer carrying member. This effect is large especially under the condition that the linear velocity of the developer carrier is high, and the average circularity is 0.9
By setting it to 3 or more, it is possible to simultaneously prevent the occurrence of "rear end white spots" due to toner scattering and toner drift.

Another aspect of the present invention is to provide a non-magnetic developer carrier which can be rotationally driven, and a magnetic field which causes the developer to stand on the developer carrier in a developing region facing the latent image carrier. A magnetic field generating means for generating a brush-shaped developer carried on the surface of the developer carrying member in the developing area, in the same direction as the moving direction of the surface of the latent image carrying member and from the surface of the latent image carrying member. In a developing device for developing a latent image on the latent image carrier by moving the toner at high speed to bring it into contact with the latent image carrier, the developer contains at least a magnetic toner (A) having a magnetic substance and a magnetic carrier (B). However, the average circularity of the magnetic toner (A) is 0.93 or more, and the magnetic flux density in the normal direction generated on the outer peripheral surface of the developer carrier in the developing region is from the rotation center axis of the developer carrier. Seen in the moving direction of the surface of the developer carrier Kicking 0mT inflection point between the angle width, 4
It is characterized in that it is 0 ° or less.

Here, the "0 mT inflection point" means the point where the value of the magnetic flux density in the normal direction becomes 0 mT when moving away from the center of the developing magnetic pole in the moving direction of the surface of the developer carrier, that is, the magnetic flux density in the normal direction. This is the point where the direction of is reversed.

In the developing device of this aspect, since the toner is attracted to the magnetic particles by the magnetic force by using the spherical magnetic toner, the toner scattering does not easily occur even when the linear velocity of the developer carrier is increased. . Then, the angular width between the 0 mT inflection points of the magnetic flux density in the normal direction is set to 4
By setting the angle to 0 ° or less, the width of the developing region in the moving direction of the surface of the developer bearing member becomes narrow and the length of the brush-shaped developer that stands up in the developing region becomes small even when the spherical magnetic toner is used. Short and dense.
This effect is particularly large under the condition that the linear velocity of the developer carrier is high, and the average circularity is set to 0.93 or more, so that the "white trailing edge" due to toner scattering and toner drift occurs.
It is possible to prevent the occurrence of both.

Still another aspect of the present invention is to provide a non-magnetic developer carrier which can be rotationally driven, and a magnetic field which causes the developer to stand on the developer carrier in a developing area facing the latent image carrier. A brush-shaped developer carried on the surface of the developer carrier in the developing region in the same direction as the moving direction of the surface of the latent image carrier, and more than the surface of the latent image carrier. In a developing device for developing a latent image on the latent image carrier by moving the toner at a high speed to bring it into contact, the developer contains at least a magnetic toner (A) having a magnetic substance and a magnetic carrier (B). The magnetic toner (A) has an average circularity of 0.93 or more, and has a magnetic flux density in the normal direction which is generated on the outer peripheral surface of the developer carrier in the developing region, and the central axis of rotation of the developer carrier. The direction of movement of the surface of the developer bearing member as seen Definitive half-value angle width, 20 °
It is characterized by the following.

In the developing device of this aspect, since the toner is attracted to the magnetic particles by the magnetic force by using the magnetic toner, the toner scattering does not easily occur even when the linear velocity of the developer carrier is increased. By setting the half-value angle width of the magnetic flux density in the normal direction to 20 ° or less, the width of the developing area in the moving direction of the surface of the developer carrier is narrowed and the developing area in the developing area is reduced even when the magnetic toner is used. The length of the brush-like developer that has become ears is short and the density is high. This effect is particularly great under the condition that the linear velocity of the developer carrier is high, and by setting the average circularity to 0.93 or more, it is possible to prevent the occurrence of "white trailing edge" due to toner scattering and toner drift. .

Further, in the above-described developing device, a developer regulating member for regulating the amount of the developer carried on the developer carrying member and conveyed toward the developing region, and the developing region by the developer regulating member. A developer accommodating portion for accommodating the developer whose conveyance toward the developer is restricted, and a toner replenishing opening facing the surface of the developer carrier at a position adjacent to the developer accommodating portion from the upstream side in the developer conveying direction. And a toner accommodating portion having the toner accommodating portion, and the developer in the toner accommodating portion is developed in accordance with the toner concentration of the developer on the developer bearing member by the movement of the developer accompanying the transport of the developer on the developer bearing member. It is preferred if it is adapted to be incorporated into the agent.

In the developing device having such a configuration, the toner in contact with the carried developer carried and carried on the developer carrying body at the position facing the toner replenishment opening is the carried developer and the developer accommodating portion. Are taken into the developer so as to be drawn from the interface with the contained developer housed in. And
When the toner concentration of the developer on the developer carrier increases, the bulk of the developer increases, so that the contained developer contained in the developer accommodating portion extends to cover the toner replenishment opening, and To prevent toner from being taken into the developer on the developer carrier from the toner storage portion in the supply opening. As a result, the toner concentration of the developer can be controlled within a certain range without the toner replenishment mechanism and the toner concentration sensor, so that a small-sized and inexpensive image forming apparatus can be provided. In particular, since the average circularity of the magnetic toner is 0.93 or more, the fluidity is improved and the developer can efficiently take in the toner when taking in the toner, so that even if an image that consumes a large amount of toner is repeatedly copied. It is possible to prevent a decrease in image density. Further, due to the magnetic binding force in the direction of the developer carrying member due to the magnetization of the toner itself, it is possible to effectively prevent the toner scattering due to the rotation of the developer carrying member and the toner development on the background portion.

Further, it is located between the toner replenishing opening of the toner accommodating portion facing the surface of the developer carrying member and the developer accommodating portion, and from the toner replenishing opening of the toner accommodating portion to the developer accommodating portion. A second developer regulating member that regulates the amount of the developer on the developer carrying body carried toward and toward the developing means, and the developing process is performed as the toner concentration of the developer on the developer carrying body increases. It is more preferable if the gap between the second developer regulating member and the surface of the developer carrying member is set so that the regulated amount of the developer increases.

In such a developing device, when the toner concentration of the developer on the developer carrier increases, the layer thickness of the developer increases, and the increased passage of the developer is regulated by the second developer regulating member. It The regulated developer covers the toner replenishing opening adjacent to the second developer regulating member from the upstream side in the developer conveying direction, and is carried and conveyed from the toner containing portion onto the developer carrier. To prevent toner from being taken in. As a result, the toner concentration of the developer can be controlled within a certain range without the toner replenishment mechanism and the toner concentration sensor, so that a small-sized and inexpensive image forming apparatus can be provided. In particular, since the average circularity of the magnetic toner is 0.93 or more, the fluidity is improved, and the developer can efficiently take in the toner at the time of taking in the toner, so that an image that consumes a large amount of toner is repeatedly copied. Can prevent a decrease in image density. Further, due to the magnetic binding force in the direction of the developer carrying member due to the magnetization of the toner itself, it is possible to effectively prevent the toner scattering due to the rotation of the developer carrying member and the toner development on the background portion.

The present invention also relates to a latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a developing device for developing the latent image on the latent image carrier to obtain a toner image. And a transfer device for transferring the toner image on the latent image carrier to a transfer material, wherein the developing device according to the present invention is used as the developing device. It is what

In the image forming apparatus of the present invention, by using the developing device described above, it is possible to suppress the toner scattering even when the linear velocity of the developer carrying member is increased, and to deteriorate the image quality such as trailing edge blank areas. Images can be formed on the transfer material.

The present invention further includes a latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a developing device for developing the latent image on the latent image carrier to obtain a toner image. An intermediate transfer member on which the toner image on the latent image carrier is transferred, a primary transfer device for transferring the toner image on the latent image carrier to the intermediate transfer member, and a toner on the intermediate transfer member. An image forming apparatus provided with a secondary transfer device for transferring an image onto a transfer material, wherein the developing device according to the present invention as described above is used as the developing device.

Even in the image forming apparatus having such a structure, even if the linear velocity of the developer carrying member is increased, toner scattering can be suppressed, and an image having no image deterioration such as trailing edge white spots It can be formed on a transfer material via a transfer body.

The present invention also provides at least one of a latent image carrier, a charging device for uniformly charging the surface of the latent image carrier, and a cleaning device for cleaning the surface of the latent image carrier, and the latent image carrier. An image forming process unit in which a developing device that develops a latent image on a body into a toner image is detachably attached to the main body of the image forming device as an integrated structure, and has been described above as the developing device. The developing device according to the present invention is used.

In this image forming process unit, the image forming process unit having the above-mentioned developing device is used by being mounted on the main body of the image forming device, so that toner scattering is suppressed even when the linear velocity of the developer carrying member is increased. In addition, it is possible to form an image without deterioration in image quality such as trailing edge blank areas.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, an example in which the present invention is applied to a developing device of a laser printer (hereinafter referred to as "printer") which is an electrophotographic image forming apparatus will be described. Although this printer is a monochrome type, it can be applied to a color type as a matter of course.

In FIG. 2, the photosensitive drum 1 serving as a latent image carrier is uniformly driven by a charging roller 50 that contacts the photosensitive drum 1 and charges its surface while being rotationally driven in the direction of arrow A in the figure. After being charged, the optical writing unit 51 performs scanning exposure based on image information to form an electrostatic latent image on the surface. In the present embodiment, the charging roller 5
0 and the optical writing unit 51 constitute a latent image forming means, but a charging device or an exposure device of another type may be used. The electrostatic latent image formed on the photosensitive drum 1 is developed by the developing device 2 described later, and a toner image is formed on the photosensitive drum 1. This toner image is transferred from a paper feed cassette 54 via a paper feed roller 55 and a registration roller pair 56 by a transfer unit having a transfer roller 53 as a transfer device.
2 is transferred onto. After the transfer is completed, the toner image is fixed on the paper 52 by the fixing unit 57, and the paper is ejected to the outside of the machine.
The residual toner on the photosensitive drum 1 that has not been transferred is removed from the photosensitive drum 1 by the cleaning unit 58. In addition, the residual charge on the photosensitive drum 1 is removed by the static elimination lamp 59.

Next, the overall structure of the developing device according to this embodiment will be described. FIG. 1 is a schematic configuration diagram of the entire developing device 2. The developing device 2 is disposed on the side of the photosensitive drum 1 and has a two-component developer (hereinafter referred to as “developer”) 3 including magnetic toner 3a and magnetic particles (hereinafter referred to as “magnetic carrier”) 3b as a surface. A non-magnetic developing sleeve 4 is provided as a developer carrying member for carrying the developer. The developing sleeve 4 is attached so as to be partially exposed from an opening formed on the side of the photosensitive drum 1 of the casing 2a, and a developing device in a developing area D facing the photosensitive drum 1 is driven by a driving device (not shown). Can be rotationally driven in a direction of moving the lower part (direction of arrow B in the figure). Further, inside the developing sleeve 4, a magnet roller 5 composed of a fixed magnet group as a magnetic field generating means is fixedly arranged.

The present developing device also includes a doctor 6 as a developer regulating member for regulating the amount of the developer carried on the developing sleeve 4 and conveyed toward the developing area D, and the doctor 6 upstream of the developer conveying direction. Also provided is a developer storage case 7 provided so as to form a developer storage S between the surface of the developing sleeve 4 and the doctor 6, and a toner hopper 8 as a toner storage. The toner hopper 8 has an opening 8a for toner replenishment (hereinafter referred to as "toner replenishment port") 8a which is on the upstream side of the developer accommodating portion S in the developer conveying direction on the developing sleeve 4 and faces the surface of the developing sleeve. Inside the toner hopper 8, there is provided a toner agitator 9 as a toner stirring member that rotates the toner hopper 8 in the direction indicated by the arrow C and sends the magnetic toner 3a toward the toner supply port 8a while stirring.

The developing sleeve 4 of the developer accommodating case 7
The front end portion (eave portion) close to is a pre-doctor 7a as a second developer regulating member that regulates the amount of the developer to which the magnetic toner is replenished from the toner hopper 8 and advances toward the inside of the developer accommodating portion S. It is used. Further, the developer containing portion S formed by the developer containing case 7 or the like contains the developer which is not supplied to the developing area facing the photosensitive drum 1 and whose progress is blocked by the doctor 6.

A plurality of magnets are provided on the surface of the magnet roller 5 so that a plurality of magnetic poles extending in the direction along the rotation center axis of the roller are formed radially outward. There is. Specifically, a developing magnetic pole P1 (N pole) is formed at a position opposed to the developing region D for developing by making the developer bristles, and the half-value angle width of the magnetic flux density distribution in the normal direction by the developing magnetic pole. In order to narrow the developing magnetic pole P1, auxiliary magnetic poles P1a (S pole) and P1b (S pole) having polarities opposite to those of the developing magnetic pole are provided at positions adjacent to the developing magnetic pole P1 on the upstream side and the downstream side in the developing sleeve rotation direction. Have
Further, a magnetic pole P4 (N pole) is provided between the position facing the predoctor 7a and the developing area so that the magnetic force of the magnetic field is applied to the developer accommodating portion S. Further, on the surface of the magnet roller 5, similarly to a general developing device, carrying magnetic poles P2 (N pole) and P3 (S pole) for carrying the developer while continuously carrying the developer on the developing sleeve 4 are provided. Have A dotted curve around the developing sleeve 4 in FIG. 1 indicates a normal-direction magnetic flux density distribution on the surface of the developing sleeve 4 at the central portion in the axial direction of the developing sleeve 4, which is formed by each magnetic pole.

The magnet roller 5 is formed with 6 magnetic poles, and the auxiliary magnetic pole P1b to the auxiliary magnetic pole P1 are formed.
The number of magnetic poles may be further increased until reaching a, and a magnet roller having 8 poles or 10 poles may be used.

The developing magnetic pole P of the magnet roller 5
The magnet No. 1 is composed of a magnet having a small area (hereinafter referred to as "cross-sectional area") in a cross section perpendicular to the rotation center axis. If this cross-sectional area becomes smaller, the magnetic force generally becomes weaker. However, if the magnetic force on the surface of the developing sleeve becomes too small, the force for holding the magnetic carrier becomes insufficient, so that the magnetic carrier may adhere to the photosensitive drum 1. Therefore, the magnet for the developing magnetic pole P1 is made of a rare earth metal alloy magnet having a strong magnetic force. Among rare earth metal alloy magnets, a typical iron neodymium boron alloy magnet has a maximum energy product of 358 kJ / m ³ , and an iron neodymium boron alloy bonded magnet has a maximum energy product of around 80 kJ / m ³ . Thus, typically conventionally used, since the maximum energy product becomes possible to secure a strong magnetic force than 36 kJ / m ³ before and after 20 kJ / m ³ ferrite magnet is around a ferrite bond magnet or the like, cross-sectional area It is now possible to secure the magnetic force on the surface of the developing sleeve even if a small magnet is used. To secure the magnetic force,
In addition to this, a samarium cobalt metal alloy magnet or the like may be used.

In the developing device of this embodiment, during development, a developing bias power source 10 as a developing bias applying means applies a vibration bias voltage, which is a DC bias with an AC voltage superimposed, as a developing bias VB to the developing sleeve 4. Has been done. The background portion potential (background portion potential) VD and the image portion potential VL are located between the maximum value and the minimum value of the vibration bias voltage VB. By applying the vibration bias voltage, an alternating electric field whose direction is alternately changed is formed in the developing region D. In this alternating electric field, the toner 3a of the developer and the magnetic carrier 3b violently vibrate, and the magnetic toner 3a overcomes the electrostatic binding force and the magnetic binding force to the developing sleeve 4 and the magnetic carrier 3b, and the photoconductor drum 1
Selectively adheres to the electrostatic latent image formed on the surface of the.

The difference (peak-to-peak voltage) between the maximum value and the minimum value of the developing bias VB composed of the above-mentioned vibration bias voltage is 0.5.
.About.5 kV is preferable, and the frequency is preferably 1 to 10 kHz. A rectangular wave, a sine wave, a triangular wave, or the like can be used as the waveform of the vibration bias voltage. The DC voltage component of the vibration bias is a value between the background portion potential VD and the image portion potential VL, but a value closer to the background portion potential VD than the image portion potential VL is fog to the background portion potential region. It is preferable for preventing the adhesion of toner.

When the waveform of the vibration bias voltage is a rectangular wave, the duty ratio is preferably 50% or less. Here, the "duty ratio" is the ratio of the time during which the toner tries to move toward the photosensitive drum 1 in one cycle of the vibration bias voltage. By setting this duty ratio, it is possible to increase the difference between the peak value at which the toner tends toward the photoconductor drum 1 and the time average value of the developing bias. It adheres to the potential distribution of the electrostatic latent image faithfully, improving the developing ability, and further improving the feeling of roughness and resolution. Further, since the difference between the peak value of the magnetic carrier 3b having a charge opposite to that of the toner 3a toward the photoconductor drum 1 and the time average value of the developing bias can be reduced, the movement of the magnetic carrier 3a can be reduced. Can be calmed down. As a result, the disturbance of the toner at the trailing edge of the image is prevented, and the trailing edge blank areas, fine line reproducibility, and isolated dot reproducibility are improved. Further, it also has an effect of significantly reducing the probability that the magnetic carrier adheres to the background portion of the electrostatic latent image.

Next, the developing operation of the developing device having the above construction will be described with reference to FIG. The developer 3 on the developing sleeve 4 is conveyed as the sleeve 4 rotates in the direction of the arrow B, and is regulated by the doctor 6 to form a thin layer. The thinned developer 3 is conveyed to the development area D facing the photoconductor drum 1 rotating in the direction of arrow A. In this developing area D, magnetic toner is supplied to the electrostatic latent image formed on the photosensitive drum 1, and the electrostatic latent image is visualized.
The developer on the developing sleeve 4 that has passed through the developing area D is further conveyed as the developing sleeve rotates, and the toner supply port 8a
Reach a position opposite. The magnetic toner 3a in the toner hopper 8 is fed into the toner supply port 8a by the agitator 9a.
And is retained so as to come into contact with the developer on the developing sleeve 4. After the new magnetic toner 3a is taken in through the toner supply port 8a, the process returns to the developer accommodating portion S. And
The internal pressure of the developer 3 containing the new magnetic toner 3a increases at the regulating portion by the doctor 6. In the developer whose internal pressure is increased, the toner is charged by frictional charging with the magnetic carrier. On the other hand, a part of the developer 3 which is not supplied to the developing area and is prevented from advancing by the doctor 6 moves so as to circulate in the developer accommodating portion S.

Next, the self toner concentration control during the developing operation in the present developing device will be described with reference to FIGS. 3A and 3B. The two-dot chain line in FIG. 3 indicates the interface between the developers that behave differently.

First, when a developer having a predetermined toner concentration and weight is set as an initial agent in the developing device and the developing sleeve 4 is rotationally driven, the developer 3 is conveyed to the developer 3-1.
And the contained developer 3-2 are divided into two parts. The carried developer 3-1 is a developer carried on the surface of the developing sleeve 4 by a magnetic force and carried so as to follow the surface. The stored developer 3-2 is a developer that is stored in the developer storage unit S and circulates in the developer storage unit S as the transport developer 3-1 moves. In the developer container S, four developer streams F1 and F2 are generated as shown in FIG. 3a. The first developer flow F1 is a flow of the transported developer 3-1 that flows so as to pass between the developing sleeve 4 and the peeling roller 11. The second developer flow F2 is a circulating flow of the stored developer 3c generated in the space between the doctor 6 and the peeling roller 11 as the developer rises on the back surface of the doctor 6 at the doctor 6.

Next, when the magnetic toner 3a is set in the toner hopper 8 while the developer flows F1 and F2 are generated in the developer accommodating portion S, the toner is carried on the developing sleeve 4 through the toner supply port 8a. The magnetic toner 3a is supplied to the conveyed developer 3-1. The developer on the developing sleeve 4 to which the magnetic toner has been supplied is conveyed to the developer container S together with the magnetic toner. Then, during the transportation, the transported developer 3-1
The magnetic toner supplied to the toner slightly enters the axial direction of the developing sleeve 4. Conveying developer 3 supplied with magnetic toner
-1 is after passing the regulation position by the predoctor 7a,
Part of it is mixed with the contained developer 3-2. By mixing the developers, the two developers are replaced with each other, the toner is dispersed and agitated in the developers to make them uniform, and the toner is charged by frictional charging between the magnetic toner and the magnetic carrier.

Next, when the toner concentration in the developer 3 is gradually increased by the replenishment of the magnetic toner, the bulk of the conveyed developer 3-1 is increased, so that the toner replenishing port 8 is formed.
The layer thickness of the conveyed developer 3-1 on the developing sleeve 4 increases in a section from the position facing a to the position regulated by the doctor 6. At the same time, the ratio of the magnetic carriers in the transported developer 3-1 on the developing sleeve 4 decreases, and the magnetic force to the transported developer 3-1 becomes weaker. Therefore, the moving speed of the transported developer 3-1. Becomes smaller, and the layer thickness of the conveyed developer 3-1 on the developing sleeve 4 in the above section becomes thicker and thicker. The transported developer 3-1 with the increased layer thickness is strongly subjected to the force (brake force) in the direction to prevent the transport received from the doctor 6, and the transported developer 3-1 moves at a higher speed. It will decrease.

Then, the upper layer portion of the conveyed developer 3-1 having the thickened layer at the position facing the toner supply port 8a is scraped off by the predoctor 7a, and the developer of the predoctor 7a is removed as shown in FIG. 3a. It accumulates on the upstream side in the transport direction. Hereinafter, the retained developer is referred to as "retained developer" 3-3. The staying developer 3-3 makes a circulating motion with the movement of the transported developer 3-1 in contact with the staying developer 3-3. The magnetic toner 3a sent to the toner supply port 8a is attracted to the exposed portion of the conveyed developer 3-1 and
The transported developer 3-1 and the staying developer 3-3 are taken into the developer so as to be drawn in from the confluence point P.

As the toner concentration of the developer 3 further increases, the amount of the staying developer 3-3 at the toner supply port 8a increases as shown in FIG. 3b, and the staying developer 3-3 contacts the magnetic toner. The exposed surface of the carried developer 3-1 is closed, and the confluence point P of both the developers also moves to the upstream end of the toner replenishing port 8a in the developer carrying direction. At the same time, the toner supply port 8
The circulating movement speed of the retained developer 3-3 of a also decreases.
At this point, the incorporation of the magnetic toner into the developer is almost completed, and the toner concentration does not rise any further.

The magnetic toner is taken into the predoctor 7
Part (upper layer portion) of the conveyed developer 3-1 that has passed through the gap between the a and the developing sleeve 4 is mixed and stirred with the stored developer 3-1 and a part of it is carried on the developing sleeve 4 again. To be done. The conveyed developer 3-1 having passed through the gap between the developing sleeve 4 and the doctor 6 is conveyed to the developing area D facing the photoconductor drum 1. In the developing area D, magnetic toner is supplied to the electrostatic latent image formed on the photosensitive drum 1 and used for developing the electrostatic latent image.

When the magnetic toner on the developing sleeve 4 is consumed by the development of the electrostatic latent image on the photosensitive drum 1, the toner density in this portion is reduced, and the conveying force acting on the developer by the developing sleeve 4 is reduced. With the increase, the bulk of the developer in this portion also decreases. Then, the layer thickness of the transported developer 3-1 regulated by the tip portion of the predoctor 7a is reduced, the amount of the retained developer 3-3 accumulated near the toner replenishing port 8a is reduced, and the retained developer 3 is reduced. -3 circulation speed will also increase. Then, at the toner supply port 8a, the conveyed developer 3-1 conveyed by the developing sleeve 4 comes into contact with the magnetic toner 3a from the inside of the toner hopper 8, and the magnetic toner is taken in again and the developer as described above. 3 toner density increases.

As described above, the conveyed developer 3 on the developing sleeve 4 is changed according to the change of the toner density on the developing sleeve 4.
The regulation state of -1 by the predoctor 7a is changed, and the toner concentration of the developer in the portion where the magnetic toner is consumed is self-controlled so as to fall within a predetermined concentration range. As a result, the toner concentration of the transported developer 3-1 on the developing sleeve 4 is always kept in a substantially constant concentration range. For this reason, a complicated toner concentration control mechanism such as a toner concentration sensor and a toner replenishing member becomes unnecessary.

The developer 3 carried on the developing sleeve 4 is
1 is peeled off and the stored developer 3 in the developer storage portion S is
A peeling member for mixing with 2 may be provided in the developer accommodating portion S so as to face the surface of the developing roller 4. When such a peeling member is provided, replacement of the conveyed developer 3-1 with the contained developer 3-2 is promoted, so that the developer 3 can be early charged due to a decrease in charging ability of the magnetic carrier in the developer 3. It is possible to prevent deterioration. Further, the above-mentioned transported developer 3-1
And the contained developer 3-2, the toner of the developer is dispersed and agitated, and the toner density is made uniform in the image width direction orthogonal to the developer transport direction. Therefore, good development without uneven development density is performed. be able to.

Next, the developer used in this embodiment will be described. The “circularity” used in the present application can be measured by various methods as described above.
It was determined using a flow-type particle image analyzer FPIA-1000.

The magnetic toner used in the present invention is 100
Magnetization in a magnetic field of 0 Oe is 10 to 30 [emu / g],
It is preferably 15 to 25 [emu / g]. 10 [e
If it is less than 30 [mu / g], the magnetic bias effect of the toner becomes small, so that toner scattering or background stain occurs. If it is more than 30 [emu / g], the magnetic bias effect of the toner becomes large, Image density is low.

Further, the magnetic material of the magnetic toner used in the present invention has an FeO content of 10 to 25 wt%, preferably 1
It is preferable that the specific surface area is 5 to 25 wt% and the specific surface area is 1 to 60 m ² / g, preferably 3 to 20 m ² / g. By setting the FeO content and the specific surface area within this range, it is possible to achieve both toner resistance and chargeability, and it is possible to obtain an image with high image density and without background stains.

As the toner used in the present invention, those manufactured by the conventional known method can be used. In particular,
Binder resin, magnetic substance, polarity control agent, after melt-kneading a mixture consisting of any additives as necessary, with a hot roll mill,
It can be obtained by cooling and solidifying, pulverizing and classifying the mixture, and optionally mixing an external additive.

As the binder resin, all known resins can be used. For example, polystyrene, poly-p-chlorostyrene, homopolymers of styrene such as polyvinyltoluene and substituted products thereof; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers. , Styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer,
Styrene-α-chloromethacrylate copolymer, stalene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Styrene-based copolymers such as polymers, styrene-isoprene copolymers, styrene-acrylonitrile-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, natural modified phenolic resins, natural resin modified Maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, rosin, modified rosin, terpene resin, coumaroinde Resins, aliphatic or aliphatic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin wax, alone or in admixture may be used.

Particularly in the heat and pressure fixing method, the use of the polyester resin as the binder resin makes it possible to obtain a toner having excellent vinyl chloride mat fusion resistance and offset resistance to the heat roll. When the pressure fixing method is used, for example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer. Polymer, linear saturated polyester, paraffin, etc.

For the toner, the charge control agent is preferably added internally to the toner particles or externally added to the toner particles.
The charge control agent makes it possible to control the optimum charge amount according to the developing system. In particular, the present invention is effective when used in the developing method in which the toner concentration is not controlled by using the charge control agent.

The polarity controlling agent used in the toner may be a conventionally known one, and the positive polarity controlling agent may be a modified product of nigrosine and a fatty acid metal salt; tributylbenzylammonium-1-hydroxy-4-naphthosulfonic acid. Salt, quaternary ammonium salt such as tetrabutylammonium tetrafluoroborate; diorganotin oxide such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; diorganotin borate such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate alone Or in combination of two or more. Among these, polar control agents such as nigrosine compounds and organic quaternary ammonium salts are particularly preferably used.

As the negative polarity controlling agent, for example, organic metal compounds and chelate compounds are effective. Examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and chromium 3,5-di-sali-butyl-salicylate. Particularly, acetylacetone metal complex, monoazo metal complex, naphthoic acid or salicylic acid metal complex or A salt is preferable, and a salicylic acid metal complex, a monoazo metal complex or a salicylic acid metal salt is particularly preferable.

The above polarity control agent is preferably used in the form of fine particles, and specifically, the number average particle diameter of 3 μm or less is preferable. The amount of the polarity control agent used in the toner is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner manufacturing method including the dispersion method, and is uniquely limited. However, it is preferably used in the range of 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the binder.
If the amount is less than 0.1 parts by weight, the amount of charge of the toner is insufficient, which is not practical. On the other hand, when the amount exceeds 20 parts by weight, the amount of charge of the toner is too large and the electrostatic attraction with the carrier increases, resulting in a decrease in the fluidity of the developer and a decrease in the image density.

The magnetic material used in the magnetic toner of the present invention includes magnetic iron oxides such as magnetite, hematite and ferrite, magnetic metals such as iron, cobalt and nickel; iron oxide or magnetic metals and cobalt, tin and titanium. copper,
Complex metal oxide alloys or mixtures with metals such as lead, zinc, magnesium, manganese, aluminum, silicon are used. Further, these surfaces may be coated with a coloring agent such as carbon black using a silane coupling agent as a binder.

The amount of the silane coupling agent is 0.3 to 3.0% by weight, preferably 0.3 to 3.0% by weight based on the magnetic iron oxide particles.
Used at 1.5% by weight. If the amount is less than 0.3% by weight, the coloring agent does not adhere strongly to the magnetic iron oxide particles, so that the coloring agent on the surface of the magnetic material is detached in the step of dispersing the magnetic material during toner production, causing a problem such as fogging. . Also,
If it exceeds 3% by weight, the coating layer of the coloring agent on the surface of the iron oxide particles becomes non-uniform, and the dispersibility in the toner is deteriorated.
When it becomes extreme, the composite iron oxide particles themselves are granulated, which is a problem.

Further, the amount of the coloring agent is 3 to 20% by weight, preferably 5 to 15% by weight, based on the magnetic iron oxide particles. 5
When the content is less than wt%, the coloring degree of the magnetic material itself is poor, so that the density of the output image is low. Also, 2
If it exceeds 0% by weight, the fluidity of the magnetic material is lowered, resulting in poor dispersibility of the magnetic material during toner production. Further, carbon black is easily desorbed from the magnetic material, resulting in abnormal images such as background fog. Become.

The coating of the particle surface of the magnetic iron oxide particles with the silane coupling agent may be carried out by mixing and stirring while spraying the solution of the silane coupling agent onto the magnetic iron oxide particles. The silane coupling agent used in the binder, for example, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, Benzylmethylchlorosilane, prommethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane methylcaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane , Dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetrame Tildisiloxane,
1,3-diphenyltetramethyldisiloxane may be mentioned.

As the magnetic material used in the present invention, magnetite which is magnetic iron oxide is particularly preferable, and it is produced by a known production method. For example, an iron sulfate aqueous solution is neutralized with an alkaline aqueous solution to obtain iron hydroxide. After that, the iron hydroxide suspension whose pH is adjusted to 10 or more is oxidized with a gas containing oxygen to obtain a magnetite slurry. Then, the slurry is washed with water, filtered, dried and crushed to obtain magnetite particles.

A preferred embodiment of these ferromagnetic materials is a spherical magnetic material containing substantially no silicon and having an average particle size of 0.2 to 0.4 μm, preferably 0.2 to 0.3 μm.
m is better. The amount contained in the magnetic toner is preferably 5 to 80 wt% with respect to the toner, and particularly preferably 10 to 30 wt% with respect to the toner.

The shape of the particles of the magnetic substance is octahedron, 6
There are a face piece, a spherical shape, a needle shape, and a scaly shape, but a spherical shape with little anisotropy is preferable. Further, it is possible to use a toner produced by a conventional known method by a polymerization method. For example, spherical toner particles can be obtained by suspending and polymerizing a monomer composition obtained by adding a colorant and a polarity control agent to a monomer used in the polymerization method in an aqueous medium. The production method is not limited to the above-mentioned method, and it may be produced by an emulsion polymerization method or the like, and may contain other additives.

Additives are preferably used in the toner of the present invention in order to improve charge stability, developability, fluidity and durability. Examples of these additives include metal oxides such as cerium oxide, zirconium oxide, silicon oxide, titanium oxide, aluminum oxide, zinc oxide, antimony oxide, and tin oxide, and improvement in fluidity of fine powders such as silicon carbide and silicon nitride. Agents, for example, resin fine particles such as fluorine resin fine particles, silicone resin fine particles, acrylic resin fine particles, and cleaning aids such as metal soap lubricants such as zinc stearate, calcium stearate, aluminum stearate, and magnesium stearate. To be Among these, silicon oxide and titanium oxide are particularly preferable as the fluidity improver, and zinc stearate is preferable as the cleaning aid.

The fluidity improver used in the present invention is a silicone varnish, various modified silicone varnishes, and
It is preferably treated with a silicone oil, various modified silicone oils, a silane coupling agent, a silane coupling agent having a functional group, another organic silicon compound or other treating agent, or various treating agents in combination.

The toner of the present invention may contain a releasing agent for the purpose of improving the releasing property at the time of fixing. Known release agents can be used, for example, low molecular weight polyethylene,
Low molecular weight polypropylene, microcrystalline wax, Fischer-Tropsch wax, carnauba wax, sazol wax, paraffin wax, etc. and their derivatives are 0.1 to 100% by weight of binder resin.
It is preferable to add 10% by weight to the magnetic toner.

As an example of the method for producing the two-component developer according to the present invention, first, the binder resin, the pigment or dye as the colorant, the charge control agent, the lubricant, and other additives are added to the Henschel mixer. After thoroughly mixing with a mixer such as, a batch type two-roll, Banbury mixer or continuous type twin-screw extruder, for example, KTK twin-screw extruder manufactured by Kobe Steel, TEM twin-screw manufactured by Toshiba Machine Co., Ltd. Extruder, K
CK's twin-screw extruder, Ikegai Iron Works 'PCM twin-screw extruder, Kurimoto Iron Works' KEX twin-screw extruder, continuous single-screw kneader, such as Bus Co's kneader The constituent materials are well kneaded using a kneader, cooled, and then coarsely crushed using a hammer mill or the like. In the case of color toner,
For the purpose of improving the dispersion of the pigment, it is general to use a masterbatch obtained by previously melt-kneading a part of the binder resin and the pigment as a colorant. Further, these coarsely pulverized products are finely pulverized using a fine pulverizer using a jet stream or a mechanical pulverizer alone or in combination. Next, the obtained finely divided particles are classified into a predetermined particle size by a classifier using a swirling airflow or a classifier using the Coanda effect. In order to obtain the toner having the predetermined particle size distribution of the present invention, a classifier utilizing the Coanda effect is preferably used. Further, the fluidity-imparting agent is thoroughly mixed with a mixer such as a Henschel mixer and passed through a sieve of 250 mesh or more to remove coarse particles and agglomerated particles.

In the present invention, the carrier constituting the developer has a saturation magnetization of 30 to 120 [emu / g], preferably 40 to 10 in a magnetic field of 1000 [Oe].
By setting it to 0 [emu / g], the magnetic binding force of the developer to the developing sleeve in the developing area becomes large, so that the development of the carrier on the photoreceptor is effectively prevented and a good image is obtained. You can

When the carrier constituting the developer in the present invention has a weight average particle diameter of 20 to 100 μm, preferably 20 to 80 μm, the toner concentration of the developer layer in the developing region can be increased, It is possible to obtain a good image having a high image density even under the developing conditions with a high-speed machine.

In the present invention, the core particles of the carrier constituting the developer may be known ones, for example, ferromagnetic metals such as iron, cobalt and nickel; alloys and compounds such as magnetite, hematite and ferrite; Examples thereof include a complex of body particles and a resin.

The carrier used in the present invention is preferably coated on its surface with a resin for the purpose of prolonging its durability. Examples of the resin forming the coating layer include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene;
Polyvinyl and polyvinylidene resins such as polystyrene, acrylic (for example, polymethylmethacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinylcarbazole, polyvinyl ether, polyvinylketone; vinyl chloride-vinyl acetate copolymer A silicone resin having an organosiloxane bond or a modified product thereof (eg, an alkyd resin, a polyester resin, an epoxy resin, a modified product of polyurethane, etc.); polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene Fluorine resin such as; polyamide; polyester; polyurethane; polycarbonate; amino resin such as urea-formaldehyde resin; epoxy resin . Of these, silicone resins or modified products thereof, and fluororesins, particularly silicone resins or modified products thereof, are preferable from the viewpoint of preventing toner spent.

The silicone resin may be any conventionally known silicone resin, and is modified with straight silicones having only the organosiloxane bond represented by the formula (1) and alkyds, polyesters, epoxies, urethanes and the like. Examples of the silicone resin include:

[0089]

[Chemical 1]

In the above formula, R ₁ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, R ₂ and R ₃ are hydrogen groups, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, a carbon group. Alikenyl group having 2 to 4 atoms, 2 to 2 carbon atoms
4 is an alkenyloxy group, a hydroxy group, a carboxyl group, an ethylene oxide group, a glycidyl group or a group represented by the formula (2).

[0091]

[Chemical 2]

In the above formulas (1) and (2), R ₄ and R ₅ are a hydroxy group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and 2 to 2 carbon atoms.
4 alkenyl group, alkenyloxy group having 2 to 4 carbon atoms, phenyl group, phenoxy group, subscripts k, l, m,
n, o, and p are integers of 1 or more.

Each of the above-mentioned substituents has a substituent such as an amino group, a hydroxy group, a carboxyl group, a mercapto group, an alkyl group, a phenyl group, an ethylene oxide group, a glycidyl group and a halogen atom, in addition to an unsubstituted group. May be.

The carrier used in the present invention may have a conductivity-imparting material dispersed in the coating layer in order to control its volume resistivity. Application of the conductive material to be dispersed may be conventionally known, and examples thereof include metals such as iron, gold and copper; iron oxides such as ferrite and magnetite; and pigments such as carbon black. Among them, particularly by using a mixture of furnace black and acetylene black, which is one of carbon black, it is possible to effectively adjust the conductivity by adding a small amount of conductive fine powder, and further to the abrasion resistance of the coating layer. It is possible to obtain an excellent carrier. These conductive fine powders preferably have a particle size of about 0.01 to 10 μm, and are preferably added in an amount of 2 to 30 parts by weight, more preferably 5 to 20 parts by weight, relative to 100 parts by weight of the coating resin. .

Further, a silane coupling agent, a titanium coupling agent or the like may be added to the carrier coating layer for the purpose of improving the adhesiveness with the core particles and the dispersibility of the conductivity-imparting agent. . The silane coupling agent used in the present invention is a compound represented by the following general formula (3).

[0096]

[Chemical 3]

In the above formula, X is a hydrolyzable group bonded to a silicon atom, for example, a chloro group, an alkoxy group, an acetoxy group, an alkylamino group, a propenoxy group, and Y is an organic functional group which reacts with an organic matrix. , For example vinyl groups,
Examples thereof include a methacryl group, an epoxy group, a glycidoxy group, an amino group and a mercapto group. R has 1 to 2 carbon atoms
0 is an alkyl group or an alkylene group.

Among the above silane coupling agents, an aminosilane coupling agent having an amino group in Y is preferable for obtaining a developer having a negative charging property, and an epoxy is used for Y in order to obtain a developer having a positive charging property. Epoxy silane coupling agents having groups are preferred.

As a method for forming the coating layer, the coating liquid for forming the coating layer may be applied to the surface of the carrier core particles by a method such as a spraying method or a dipping method as in the conventional method. The thickness of the coating layer is 0.1-2
0 μm is preferable.

The present invention will be specifically described below with reference to toner production examples, carrier production examples, and embodiments. [Toner Production Example 1] Polyester resin 100 parts by weight Carbon black 5 parts by weight Chromium-containing azo dye 3 parts by weight Magnetite fine particles 70 parts by weight (average particle size: 0.20 μm, FeO content: 20 wt%, specific surface area: 8.0 m ² / g , Magnetization: 61 emu / g)

The mixture having the above formulation was mixed in a Henschel mixer, kneaded by a kneading extruder set at 140 ° C., cooled and solidified, coarsely crushed by a cutter mill, and then a mechanical crusher was used. The finely pulverized product was finely pulverized, and the resulting finely pulverized product was pulverized by a jet mill using a multi-division classifier utilizing the Coanda effect and classified to obtain base particles having an average of 7.0 μm. With respect to 100 parts by weight of the base particles,
Hydrophobized colloidal silica (0.6 parts by weight) and hydrophobized titanium oxide (0.3 parts by weight) were added and mixed in a Henschel mixer to obtain toner particles a. The saturation magnetization of this toner in a magnetic field of 1000 Oe is 24 emu.
/ G, the circularity was 0.943.

[Toner Production Examples 2 to 8] In the same manner as in Production Example 1, in the process of producing the toner by the conventionally known method and producing the toner particles a, the pulverization conditions were changed and the following Table 1 was used. The toner particles b to h having the characteristics shown in Table 1 were obtained.

[0103]

[Table 1]

Next, an example of manufacturing the carrier is shown below. 2 parts by weight of polyvinyl alcohol and 60 parts by weight of water were placed in a ball mill with respect to 100 parts by weight of magnetite prepared by a wet method, and mixed for 12 hours to prepare a magnetite slurry. This slurry was spray-granulated with a spray dryer to obtain spherical particles having an average particle size of 54 μm. The particles were fired in a nitrogen atmosphere at a temperature of 1000 ° C. for 3 hours and then cooled to obtain core particles 1. On the other hand, silicone resin solution 100 parts by weight toluene 100 parts by weight γ-aminopropyltrimethoxysilane 6 parts by weight carbon black 10 parts by weight The above mixture was dispersed for 20 minutes with a homomixer to prepare a coating layer forming liquid 1. The coating layer forming liquid 1 is coated on the surface of 1000 parts by weight of the core particles 1 using a fluidized bed type coating device to obtain a silicone resin coated carrier A.
Got The characteristics of this carrier particle were as follows:
Average particle diameter: 58 μm, saturation magnetization: 65 emu / g.

[Manufacturing Example of Developer] 100 parts by weight of the carrier A prepared in the manufacturing example of carrier is mixed with the toner a:
10 parts by weight were added and mixed with a Turbula mixer to obtain a developer 1 (Developer Production Example 1). Similarly to this, a developer was prepared with the combination of the toner and the carrier shown in Table 2.

[0106]

[Table 2]

FIG. 4 shows the photosensitive drum 1 and the magnetic toner 3a.
3 shows the force generated between the magnetic carrier 3b and the magnetic carrier 3b.
The magnetic toner 3a has a force Fe caused by the electric field between itself and the photosensitive drum 1, and an electrostatic force Fs between it and the magnetic carrier 3b.
And the magnetic force Fb attracted to the developing sleeve 4 side act in the directions of the arrows. The force due to the toner drift described above can be considered as an increase amount (α) of the electrostatic force Fs, and in the state where the toner drift is generated, Fs becomes Fs + α and is easily pulled back by the magnetic carrier 3b. Further, the closer the toner shape is to the spherical shape, the easier the toner moves on the carrier, and the toner drift easily occurs. In the case of non-magnetic toner, there is no magnetic force Fb. Therefore, since the spherical magnetic toner has a magnetic force Fb as compared with the non-magnetic toner, as described above, the reproducibility of the trailing end portion of the solid image or the halftone image, the thin line, and the isolated dot is improved. Be at a disadvantage.

Therefore, in the present embodiment, the attenuation rate of the peak value of the magnetic flux density in the normal direction generated on the outside of the developing sleeve by the developing magnetic pole P1 is set to 50% or more, and the width of the developing area D in the moving direction of the developing sleeve surface ( The developing nip width) is narrowed, and α that is an increase in Fs due to toner drift is set to 0 (zero) or considerably small. Further, the density of the magnetic brush in the developing area D can be increased, and as shown in FIG. 5A, the developer can be uniformly sprouted over the entire rotation center axis direction of the developing sleeve to be brought into contact with or separated from the surface of the photosensitive drum 1. did it. As a result, as shown in FIG. 5B, a solid image without trailing edge white spots can be formed, and the image quality can be improved when the magnetic toner is used.
The line E in FIG. 5b is the rear end of the image portion.

FIG. 6 is a diagram for explaining the mechanism for improving the image quality by enlarging the vicinity of the developing area of the photosensitive drum 1 and the developing sleeve 4 in the present embodiment. The movement of the magnetic brush MB of which the tip of the magnetic brush MB is approaching is displayed. As shown in FIG. 6a, in the present embodiment, the time during which the magnetic brush rubs against the photosensitive drum 1 is short, so the toner drift in which the toner 3a moves from the tip of the magnetic brush to the surface side of the developing sleeve is reduced. Due to this reduction in toner drift, toner is present even at the position A facing the rear end of the image portion as shown in FIG. 6B, and the surface of the magnetic carrier at the front end of the magnetic brush is not exposed. Therefore, as shown in FIG. 6c, since the surface of the magnetic carrier at the tip of the magnetic brush is not exposed, the toner once attached to the image portion on the photoconductor drum 1 may reattach to the magnetic carrier at the tip of the magnetic brush. Therefore, it is possible to reduce image quality deterioration such as trailing edge blank areas, horizontal line thinning, and variations in isolated dot shape.

Instead of defining the attenuation rate of the magnetic flux density in the normal direction, the developing sleeve 4 is controlled by the developing magnetic pole P1.
An angular width θ1 between 0 mT inflection points of the normal magnetic flux density Bn generated above (see FIG. 7a) and a half value of the normal magnetic flux density Bn generated on the developing sleeve 4 by the developing magnetic pole P1 in the moving direction of the developing sleeve surface. By defining the angular width θ2 (see FIG. 7b), the toner drift may be reduced and the image quality deterioration such as trailing edge blank may be prevented. Specifically, the angular width between the 0 mT inflection points θ1
Is set to 40 ° or less, or the half-value angle width θ2 is set to 20
° or less.

[0111]

EXAMPLES Next, examples using the developing device having the above-described structure will be described. [Example 1] The experimental conditions in this example are set as shown in Table 3. Here, the measuring devices used for measuring the magnetic flux density were a Gauss meter (HGM 8300) manufactured by ADS and an A1 type axial probe manufactured by ADS, which were recorded by a pie chart recorder. The following experimental examples were also conducted under similar experimental conditions.

[0112]

[Table 3]

Under the conditions of Table 3, using the developers 1 to 8 (Table 2), the attenuation rate [% of the peak value of the normal-direction magnetic flux density Bn generated outside the developing sleeve by the above-mentioned developing magnetic pole P1 is used. ], And the trailing edge whiteout amount and line width aspect ratio of the halftone solid image were measured. Here, the case where the trailing edge whiteout amount is 0 to 0.4 mm is defined as a good range (⊚ to
○). Moreover, 0.8 mm or more was marked with x and the middle thereof was marked with Δ.

Further, the line width aspect ratio is the width of the line image in the vertical direction (developing sleeve surface moving direction) in the output image when the image formation is performed on the horizontal and vertical line images of the same width on the original. Direction divided by the width of the line image in the direction (direction of the rotation axis of the developing sleeve). The larger this value, the greater the degree of "horizontal line thinning", and normally at 1 ± 0.2, the difference between the vertical and horizontal line widths cannot be visually recognized (⊚ to ○). 1.2 to 1.25 (or 0.75 to 0.80) was evaluated as Δ, and 1.26 or more (or 0.74 or less) was evaluated as x.

As for the image density controllability, the document area ratio is 10
20 copies of 0% solid image were continuously copied and the change in image density was evaluated. The evaluation criteria are as follows. ⊚: Image density difference is less than 0.1 ○: Image density difference is 0.1 or more and less than 0.2 Δ: Image density difference is 0.2 or more and less than 0.5 ×: Image density difference is 0.5 or more

The density unevenness was measured by using a Macbeth reflection densitometer at the image density at three positions from the upper, middle and lower parts of the image, and the difference between the maximum value and the minimum value was defined as the density unevenness. . The evaluation criteria are as follows. ⊚: Image density difference is less than 0.1 ○: Image density difference is 0.1 or more and less than 0.2 Δ: Image density difference is 0.2 or more and less than 0.5 ×: Image density difference is 0.5 or more

Table 4 shows the experimental results in this example.

[Table 4]

From this result, when the magnetic toner having the circularity of 0.93 or more is used, the amount of trailing edge white spots is reduced by setting the attenuation rate of the peak value of the magnetic flux density Bn in the normal direction to 50% or more. Further, it is understood that the degree of thinning of the horizontal line is small, and the image quality is excellent in image density controllability and density unevenness.

Example 2 Under the conditions shown in Table 3, the angle width θ1 between 0 mT inflection points was changed using the developer 1, and the trailing edge whiteout amount and line width aspect ratio of a solid image were evaluated. The results are shown in Table 5.

[0120]

[Table 5]

From this result, when the magnetic toner having the circularity of 0.93 or more is used, the magnetic flux density in the normal direction is 0 m.
It can be seen that when the angle width θ1 between the T inflection points is set to 40% or less, the amount of trailing white spots and the degree of horizontal line thinning are small, and good image quality can be obtained.

Example 3 Under the conditions shown in Table 3, using developers 1 to 8, the half-value angle width θ2 of the magnetic flux density distribution in the normal direction by the developing magnetic pole was changed, and the trailing edge whiteout amount of the solid image was obtained. And the line width aspect ratio was evaluated. The results are shown in Table 6.

[0123]

[Table 6]

From this result, when the magnetic toner having the circularity of 0.93 or more is used, the half-value angle width θ2 of the magnetic flux density in the normal direction is set to 20% or less, and the trailing edge whiteout amount and It can be seen that good image quality can be obtained with a small degree of horizontal line thinning.

In the printer of the above embodiment, the photosensitive drum 1, the charging roller 50 and the cleaning device 5
At least one of the printers 8 and the developing device 2 may be configured as an integral structure that is attachable to and detachable from the printer main body to form an image forming process unit (process cartridge). FIG. 8 shows an example of the structure of the process cartridge 60. The photosensitive drum 1, the charging roller 50, the cleaning device 58, and the developing device 2 are all configured as an integrated structure that can be attached to and detached from the printer body. .

In the above embodiment, the case where the toner image formed on the photoconductor is directly transferred to the transfer paper has been described. However, in the present invention, the toner image on the photoconductor is once transferred to the intermediate transfer body, and thereafter, The present invention can also be applied to an image forming apparatus that transfers a toner image on the intermediate transfer member onto a transfer sheet and a developing apparatus used therefor. For example, a toner image of each color is sequentially formed on one photoconductor, and the toner images of the respective colors on the photoconductor are transferred by superimposing them on an intermediate transfer belt as an intermediate transfer member by a primary transfer device. It can also be applied to a color image forming apparatus for collectively transferring the upper superimposed toner image onto a transfer sheet by a secondary transfer apparatus and a developing apparatus used in the apparatus.

Further, for example, a plurality of image forming process units including photoconductors are arranged side by side along a linear moving path portion of an intermediate transfer belt as an intermediate transfer member, and the image forming process units of the respective image forming process units are arranged on each other. Toner images of different colors are formed, the toner images on the respective photoconductors are superposed and transferred on the intermediate transfer belt by a primary transfer device, and the superposed toner images on the intermediate transfer belt are transferred by a secondary transfer device. The present invention can also be applied to a tandem type color image forming apparatus for collectively transferring to and a developing device used in the apparatus.

Further, in the above-mentioned embodiment, the case of the printer and the developing device used therefor has been described, but the present invention can be applied to other image forming apparatuses such as a copying machine and a FAX and the developing device used therefor.

[0129]

According to the present invention, even when a two-component developer using spherical magnetic toner is used, the toner scattering is suppressed and the trailing edge white is suppressed under the condition that the linear velocity of the developer carrier is high. Image quality deterioration such as omission can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a printer including the developing device of FIG.

3A and 3B are explanatory views of a self-toner control mechanism in the developing device of FIG.

FIG. 4 is an explanatory diagram of a force that acts on toner at the tip of the magnetic brush.

FIG. 5A is an explanatory diagram of a magnetic brush distribution in the developing sleeve in the developing sleeve axial direction, and FIG. 5B is an explanatory diagram of a solid image output by the printer of the present embodiment.

6A and 6B are explanatory views of a mechanism for reducing trailing edge blank areas.

FIG. 7A is a magnetic flux density Bn in the normal direction due to a developing magnetic pole.
Is an explanatory view of the angular width θ1 between the 0 mT inflection points, and (b) is an explanatory view of the half-value angular width θ2 in the moving direction of the developing sleeve surface of the magnetic flux density Bn in the normal direction by the developing magnetic pole.

FIG. 8 is a schematic configuration diagram of a process cartridge.

FIG. 9 is an explanatory diagram of a developing unit in a developing device that performs negative / positive development by a two-component developing method.

10A to 10C are explanatory diagrams of a mechanism of occurrence of trailing edge blank areas.

11A is an explanatory view of a magnetic brush distribution in the developing sleeve axial direction in a developing area of a developing device according to a conventional example, and FIG. 11B is a magnetic brush distribution in a developing sleeve surface moving direction in the developing area. It is a figure.

FIG. 12A is an explanatory diagram of a magnetic brush distribution in the developing sleeve axial direction in a developing region of a developing device according to a conventional example, and FIG. 12B is an explanatory diagram of a solid image in which trailing edge white spots occur.

FIG. 13 is an explanatory diagram of the distribution of magnetic toner at the tip of the magnetic brush.

[Explanation of symbols]

1 photoconductor drum 2 Development device 2a casing 3 developer 3a Magnetic toner 3b Magnetic carrier 3-1 Transport developer 3-2 Stored developer 3-3 Staying developer 4 Development sleeve 5 magnet roller 6 Doctor 7 developer storage case 7a Predoctor 8 toner hopper 8a Toner supply port 9 Toner agitator 10 Development bias power supply 50 charging roller 51 optical writing unit 52 sheets 53 Transfer roller S developer container D development area

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/16 G03G 15/08 507E 103 21/00 312 21/10 9/08 101 (72) Inventor Higuchi Hiroto, Tokyo, Ota-ku, 1-3-3 Nakamagome, Ricoh Co., Ltd. (72) Inventor, Maiko Kondo, 1-3, Nakamagome, 1-3, Nakamagome, Ota-ku, Tokyo (72) Inventor, Hisao Koike Tokyo 1-3-6 Nakamagome Ota-ku, Ricoh Co., Ltd. (72) Inventor Atsaya Daiji Atsaya 1-3-6 Nakamagome, Ota-ku, Tokyo (72) Inventor Junichi Sano Nakata, Ota-ku, Tokyo Masachiro Yamane (72) Inventor, Kunihiro Oyama (72) Inventor, Ricoh Co., Ltd., 1-3-6, Magome Masachiro Yamane, 1-3, Nakamagome, 1-3, Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (72) Inventor Atsushi Sanpe 1-3-6 Nakamagome Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H005 AA02 AA15 FA02 2H031 AA01 AA11 AC08 AC18 AC19 AC20 AC30 AC33 AC34 AD03 BA06 BA09 FA05 2H077 AA12 AA14 AA16 AB04 AB13 AB15 AC03 AD02 AD06 AD13 AD16 AD17 AD18 BA02 BA08 BA09 DA10 DA43 DB14 EA01 FA19 2H134 GA01 GB02 GA02 FA02 K02 K01 K02 K02H01 KG03H01 KG03H01 KG03H01 KG03H01 KG03H01 HA28 HB12 JA01 JC01

Claims (8)

[Claims] 1. A non-magnetic developer carrying member which can be rotationally driven, and a magnetic field generating means for generating a magnetic field for causing the developer to stand on the developer carrying member in a developing region facing the latent image carrying member. In a developing device for developing a latent image on a latent image carrier using a brush-shaped developer carried on the surface of the developer carrier in the developing area, the developer contains at least a magnetic toner and a magnetic carrier. However, the average circularity of the magnetic toner is 0.93 or more,
A developing device, wherein the attenuation rate of the magnetic flux density in the normal direction generated outside the surface of the developer carrier in the developing area is 50% or more. 2. A non-magnetic developer carrier which can be rotationally driven, and a magnetic field generating means for generating a magnetic field for causing the developer to stand on the developer carrier in a developing region facing the latent image carrier. In a developing device for developing a latent image on a latent image carrier using a brush-shaped developer carried on the surface of the developer carrier in the developing area, the developer contains at least a magnetic toner and a magnetic carrier. However, the average circularity of the magnetic toner is 0.93 or more,
The angular width between the 0 mT inflection points of the magnetic flux density in the normal direction generated on the outer peripheral surface of the developer carrier in the developing area in the moving direction of the developer carrier as viewed from the rotation center axis of the developer carrier is 40 ° or less. Is a developing device. 3. A non-magnetic developer carrier that can be rotationally driven, and a magnetic field generating unit that generates a magnetic field that causes the developer to stand on the developer carrier in a developing region facing the latent image carrier. In a developing device for developing a latent image on a latent image carrier using a brush-shaped developer carried on the surface of the developer carrier in the developing area, the developer contains at least a magnetic toner and a magnetic carrier. However, the average circularity of the magnetic toner is 0.93 or more,
The half value angle width of the magnetic flux density in the normal direction generated on the outer peripheral surface of the developer carrier in the developing region is 20 ° or less in the developer carrier surface moving direction as seen from the rotation center axis of the developer carrier. Characteristic developing device. 4. A developer regulating member for regulating the amount of the developer carried by the developer carrying member and conveyed toward the developing area,
A developer containing portion containing a developer whose conveyance toward the developing area is regulated by the developer regulating member, and a developer carrying body at a position adjacent to the developer containing portion from the upstream side in the developer conveying direction. A toner storage portion having a toner supply opening facing the surface is provided, and the toner is stored according to the toner concentration of the developer on the developer carrier by the movement of the developer accompanying the transport of the developer on the developer carrier. The developing device according to any one of claims 1 to 3, wherein the toner in the unit is incorporated in the developer. 5. The toner carrying opening is located between the toner replenishing opening facing the surface of the developer carrying member of the toner containing section and the developer containing section, and is carried and conveyed from the toner replenishing opening of the toner containing section toward the developer containing section. A second developer regulating member that regulates the amount of the developer on the developer carrier, and the regulated amount of the developer increases as the toner concentration of the developer on the developer carrier increases. The developing device according to claim 4, wherein a gap is set between the second developer regulating member and the surface of the developer carrying member. 6. A latent image carrier, a latent image forming means for forming a latent image on the latent image carrier, a developing device for developing the latent image on the latent image carrier into a toner image, An image forming apparatus comprising a transfer device for transferring a toner image on a latent image carrier onto a transfer material, wherein the developing device according to any one of claims 1 to 5 is used as the developing device. An image forming apparatus characterized by the above. 7. A latent image carrier, a latent image forming means for forming a latent image on the latent image carrier, a developing device for developing the latent image on the latent image carrier into a toner image, An intermediate transfer member to which the toner image on the latent image carrier is transferred, a primary transfer device that transfers the toner image on the latent image carrier to the intermediate transfer member, and a toner image on the intermediate transfer member. An image forming apparatus comprising a secondary transfer device for transferring to a material, wherein the developing device according to any one of claims 1 to 5 is used as the developing device. . 8. A latent image carrier, at least one of a charging device for uniformly charging the surface of the latent image carrier, and a cleaning device for cleaning the surface of the latent image carrier; and a latent image carrier on the latent image carrier. An image forming process unit in which a developing device that develops a latent image into a toner image is detachably attached to the main body of the image forming device as an integrated structure. An image forming process unit comprising the developing device according to claim 1.