JP2000258992A - Method and device for image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method and an image forming device by which the image of an excellent quality is formed by preventing the lowering of an M/S quantity on a developing sleeve by suppressing the occurrence of the soiling of the developing sleeve by a two-component system magnetic brush developing system using the polymerized toner of a small particle size having lubricant. SOLUTION: As for the image forming method developing an electrostatic latent image formed on a latent image forming medium by a developing device having a rotatable developer carrier having a magnetic field generating means fixed at inside and carrying and feeding two-component system developer having non-magnetic polymerized toner incorporating a lubricant component and a magnetic carrier to a developing area, the nonmagnetic toner whose weight average particle size is 4-9 μm and whose shape coefficient SF-1 is set to be in the range of 100-140 and whose shape coefficient SF-2 is set to be in the range of 100-120, and also a blast-processed developer carrier having surface roughness satisfying 2.0 μm<Rz<4.5 μm is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copier, a printer, and a recorded image display for developing a visible image by developing an electrostatic latent image formed on an image carrier by an electrophotographic method, an electrostatic recording method, or the like. The present invention relates to an image forming apparatus such as a facsimile apparatus and an image forming method.

[0002]

2. Description of the Related Art Conventionally, a dry developer as a developing agent is carried on the surface of a developer carrying member, and the surface of a latent image forming medium (hereinafter, referred to as an image carrying member) carrying an electrostatic latent image thereon. It is well known that a developer is conveyed and supplied, and an electrostatic latent image is developed and visualized while an alternating (alternating) electric field is applied between the image carrier and the developer carrier. . The developer carrier is generally referred to as a "development sleeve" in the following description because a development sleeve is generally used in many cases.Also, the image carrier is generally used in a photoconductor drum in many cases. Will be referred to as "photosensitive drum".

[0003] As the developing method, for example,
A magnetic brush is formed on the surface of a developing sleeve in which a magnet is arranged by a developer (two-component developer) composed of a two-component system (a mixture of carrier particles and toner particles),
The photoconductor drums facing each other with a small development gap
The magnetic brush is rubbed or approached, and an alternating electric field is continuously applied between the developing sleeve and the photosensitive drum (hereinafter, referred to as a section between SD), so that toner particles are moved from the developing sleeve side to the photosensitive drum side. A so-called magnetic brush developing method in which development is performed by repeatedly performing dislocations and reverse dislocations is known (see, for example, JP-A-55-32060 and JP-A-59-165082). A non-contact type alternating electric field developing method using a two-component developer for simple color development or multiple development is also known (for example, JP-A-56-14268 and JP-A-58-16858). -68051, JP-A-56-144452 and JP-A-59-144452.
181362, JP-A-60-176069).

In recent years, for the purpose of further improving transferability and image quality, a method for producing toner particles having a substantially spherical shape using a polymerization method has been developed. The toner composed of such toner particles has good releasability from the photosensitive drum due to the shape factor of the toner particles, and as a result, high transfer efficiency can be obtained. It has the advantage of being dignified.

On the other hand, when two-component development is performed using the above-described toner, the friction coefficient μ between the developing sleeve and the developer decreases because the shape of the toner particles is nearly spherical. Things happen. For this reason, a process for roughening the surface of the developing sleeve is usually performed by a method such as sandblasting. When the surface roughness Rz is small, the friction coefficient μ is small, so that the developer is not stably conveyed. On the other hand, when the Rz is large, it is difficult to maintain the uniformity of Rz over the entire developing sleeve, The developer may not be transported uniformly. Therefore, when a desired developing sleeve is coated with a developer, it is difficult to coat the weight of the developer per unit area (hereinafter, referred to as M / S amount) stably and uniformly. . The M / S amount on the developing sleeve is closely related to image quality, and obtaining a desired M / S amount stably for a long period of time is an important requirement for maintaining high image quality in durability. . This problem has been conventionally solved by making the surface roughness on the developing sleeve an appropriate size. Specifically, when the surface roughness is Rz, the surface roughness is set within a range of 2 μm <Rz <30 μm. The solution is being pursued. As a result, when the developer having the above-described polymerized toner is used, a desired M / S amount can be stably and uniformly coated on the developing sleeve.

[0006]

As described above, in two-component development using a polymerized toner composed of spherical particles, the surface roughness Rz of the developing sleeve is set to 2 μm <Rz <3.
By setting the thickness to 0 μm, the transportability of the developer can be stabilized. However, with the recent increase in image quality, the use of toner particles having a smaller particle size has been required, and in the surface treatment of the developing sleeve by sandblasting or the like having large abrasive grains, the shape of the particles used in the blasting process has been increased. Since it is an irregular shape having protrusions and the like, Rz increases, and the peak-to-peak average interval (Sm)
Has become narrower, which causes the following problems.

That is, according to the study of the present inventors, a wax component or the like is contained in the toner itself in order to enable oil-less fixing and simplify the device configuration. In this case, when pressure is applied to the toner, the wax component may exude and adhere to the developing sleeve, or when the external additive or fine powder toner is rubbed against the developing sleeve while being held by the magnetic brush. Further, it has been found that these components gradually and thermally and electrostatically adhere to the concave portions of the developing sleeve, thereby contaminating the developing sleeve. When such contamination progresses, the surface roughness of the developing sleeve becomes substantially small, and the conveying force is reduced.
A phenomenon occurs in which the M / S amount gradually decreases. Further, it was also found that when a magnetic carrier having a large amount of magnetization was used, the above phenomenon became more remarkable. In other words, in such an embodiment, the magnetic adhesion between the developing sleeve and the magnetic carrier is increased, so that the toner adhering to the carrier is pressed against the developing sleeve with a stronger force. It is considered that such a phenomenon is more likely to adhere to the developing sleeve, thereby increasing the contamination of the developing sleeve.

Accordingly, an object of the present invention is to provide a conventional two-component magnetic brush developing method using a polymerized toner having a small particle diameter containing a wax component, an external additive, etc. It effectively prevents the adhesion of components and external additives, suppresses the occurrence of contamination of the developing sleeve, prevents the M / S amount on the developing sleeve from decreasing, and stably and uniformly deposits the developer on the developing sleeve. An object of the present invention is to provide an image forming method capable of forming a high-quality image by coating, and an image forming apparatus to which the method is applied.

[0009]

The above object is achieved by the present invention described below. That is, the present invention forms an electrostatic latent image on an initially charged latent image forming medium by erasing a charge corresponding to an image signal by an image exposure unit, and then forming the electrostatic latent image on the latent image forming medium. A non-magnetic toner having a plurality of fixed magnetic field generating means provided inside the latent image forming medium and containing a lubricant component (wax or the like) produced by a polymerization method; Image forming method comprising a step of developing by a developing device having a developer carrier rotatably configured to carry and convey a two-component developer having the following formula to a developing area: a weight average particle diameter of 4 to 9 μm Having a shape factor SF-1 of 100 to
When a non-magnetic toner having 140 and SF-2 in the range of 100 to 120 is used and the surface roughness is Rz, blasting is performed so as to satisfy the condition of 2.0 μm <Rz <4.5 μm. An image forming method comprising using a developer carrier having a processed surface shape, and, on a latent image forming medium that has been subjected to initial charging, a charge of a portion corresponding to an image signal is transferred by an image exposure unit. In an image forming apparatus having a developing unit for erasing and forming an electrostatic latent image and developing the electrostatic latent image into a visible image in a developing area, the developing unit faces the latent image forming medium. A two-component developer having a plurality of fixed magnetic field generating means therein, a non-magnetic toner containing a lubricant component (eg, wax) produced by a polymerization method, and a magnetic carrier. Carry and transport to the development area A non-magnetic toner having a weight average particle diameter of 4 to 9 μm, and a shape factor S of the non-magnetic toner.
F-1 is a non-magnetic toner in the range of 100 to 140 and SF-2 is in the range of 100 to 120. Further, the surface of the developer carrying member is blasted, and the surface shape has a surface roughness of Rz. 2.0 μm <Rz <4.5 μ
m is an image forming apparatus configured to satisfy the condition of m.

In a preferred embodiment of the present invention, the developer carrying member has relatively smooth concave and convex portions on the surface, and
When the average interval between the peaks of the concave portion and the convex portion is represented by Sm, the configuration is such that the condition of 20 μm <Sm <80 μm is satisfied. In a preferred embodiment of the present invention, the magnetic carrier used as described above has a magnetization in a magnetic field of 1 kOe within a range of ³⁰ to 200 emu / cm ³ and a number average particle size of 10 to 60 μm. It is within the range. Further, in a preferred embodiment of the present invention, in the developing area where the latent image forming medium and the developer carrier are opposed to each other, the two carriers are configured to move in opposite directions to each other.

[0011]

Next, the present invention will be described in detail with reference to preferred embodiments. FIG. 1 is a schematic configuration diagram of an electrophotographic full-color image forming apparatus having the configuration of the present invention. This image forming apparatus includes a photosensitive drum 3 rotating in the direction of an arrow, and a rotary developing device 1 including a charger 4, four developing units 1M, 1C, 1Y, and 1BK, a transfer charger around the photosensitive drum 3. 10, an image forming means including a static elimination charger 13, a separation charger 14, a cleaning means 12, and a laser beam scanner LS disposed above the photosensitive drum 3. Each of the developing units is for supplying a two-component developer of each color containing toner particles and carrier particles onto the photosensitive drum. Magenta toner is used for the developer in the developing device 1M, cyan toner is used for the developer in the developing device 1C, yellow toner is used for the developer in the developing device 1Y, and black toner is used for the developer in the developing device 1BK. , Respectively, thereby making it possible to form a toner image of each color. CCD
In a document reading device having a photoelectric conversion element such as a magenta image information, a cyan image information, a yellow image information, and an image signal corresponding to black and white image information of the document,
A semiconductor laser incorporated in the laser beam scanner LS is controlled in accordance with these image signals, and emits a laser beam L. In the same manner, printing can be performed in accordance with the output signal of each color image from the electronic computer.

The overall sequence of the full-color image forming apparatus configured as described above will be described. First, the photosensitive drum 3 is uniformly charged by the charger 4. Next, scanning exposure is performed by the laser beam L modulated by the magenta image signal, an electrostatic latent image is formed on the photosensitive drum 3, and the electrostatic latent image is formed by the magenta developing device 1M fixed at the developing position. Is reverse developed. on the other hand,
The transfer material such as paper taken out of the paper feed cassette C and advanced through the paper feed guide 5 a, the paper feed roller 6, and the paper feed guide 5 b is held by the gripper 7 of the transfer drum 9, The transfer drum 9 is electrostatically wound around the transfer drum 9 by the counter electrode 8 and its opposite pole. The transfer drum 9 rotates in the direction indicated by the arrow in synchronization with the photosensitive drum 3, and the magenta image developed by the magenta developing device 1M is transferred to a transfer material by a transfer charger 10 in a transfer section. The transfer drum 9 continues to rotate as it is, and prepares for transfer of an image of the next color (cyan in FIG. 1).

On the other hand, the photosensitive drum 3 is neutralized by the charger 11 and cleaned by the cleaning means 12, charged again by the charger 4, and exposed by the laser beam L modulated by the next cyan image signal. As a result, an electrostatic latent image is formed based on the cyan image signal. During this time, the developing device 1 rotates, the cyan developing device 1C is fixed at a predetermined developing position, and the reversal development of the electrostatic latent image corresponding to cyan is performed to form a cyan image. Subsequently, the above steps are also performed on the yellow image signal and the black and white image signal, respectively. When the transfer of the image (toner image) for four colors is completed, the transfer material is discharged by the chargers 13 and 14. The gripper 7 is released, and is separated from the transfer drum 9 by the separation claw 15.
Sent to The fixing unit 17 fixes four color images formed on the transfer material so as to overlap each other. Thus, a series of full-color image forming sequences is completed, and a desired full-color image is formed.

Next, the developing device will be described with reference to FIG. Since each developing device has the same configuration, only the developing device 1M will be described. The developing device 1M includes a developing container 18, the inside of which is partitioned into a developing chamber R1 and a stirring chamber R2 by a partition wall 19, a toner storage chamber R3 is provided above the stirring chamber R2, and a replenishing toner 20 is contained therein. Have been. From the supply port 21 at the bottom of the toner storage chamber R3,
An amount of toner corresponding to the toner consumed in the development is dropped and supplied into the stirring chamber R2. On the other hand, the developer 22 in which the toner particles and the magnetic carrier are mixed is accommodated in the developing chamber R1 and the stirring chamber R2. Details of the toner particles and the magnetic carrier used in the present invention will be described later. A developer conveying screw 23 is housed in the developing chamber R1, and the developer 22 is rotated to drive the developer 22 into the developing sleeve 25.
Is transported along the longitudinal direction. The direction in which the developer is conveyed by the screw 24 is the opposite direction to that by the screw 23. The partition wall 19 is provided with openings on the near side and the back side, and the developer conveyed by the screw 23 is delivered to the screw 24 from one of the openings, and the developer conveyed by the screw 24 It is delivered to the screw 23 from the other one of the openings.

An opening is provided in a portion of the developer container 18 close to the photosensitive drum 3, and the opening is made of a material such as aluminum or non-magnetic stainless steel, and has a surface having moderate irregularities on the surface. A blasted non-magnetic developing sleeve 25 is provided. The developing sleeve 25
Is rotated at a peripheral speed Vb in the direction of arrow b (in the developing area 26, in the direction opposite to the rotation direction of the photosensitive drum 3), and is controlled by a layer thickness regulating blade 28 at the lower end of the opening of the developing container.
After a developer layer having an appropriate thickness is formed on the surface thereof, the developer is carried and transported to a developing area 26 facing the photosensitive drum 3. Note that the rotation direction of the developing sleeve 25 is not limited to the above-described direction, and may rotate in the same direction as the photoconductor rotation direction.

Then, the magnetic brush formed by the developer carried on the developing sleeve 25 comes into contact with the photoreceptor 3 rotating at the peripheral speed Va in the direction of arrow a in the developing area 26, and as a result, the magnetic brush is formed on the photosensitive drum 3. The developed electrostatic latent image is developed in the developing area 26. At this time, the developing sleeve 2
The peripheral speed Vb of No. 5 is a photosensitive drum peripheral speed ratio of 130 to 200%.
Is desirable, and more preferably 150% to 180%. In other words, below the above range, it is difficult to obtain a sufficient image density, and above this range, the developer tends to be scattered.

As shown in FIG. 2, a roller-shaped magnet 29 is fixedly arranged in the developing sleeve 25. As for the configuration of the magnet 29, first, a development magnetic pole S1 is arranged so as to face the development region 26. This developing magnetic pole S1 is
By the developing magnetic field formed in the developing region 26, the magnetic brush of the developer is formed on the developing sleeve 25, and this magnetic brush comes into contact with the photosensitive drum 3, and the electrostatic latent image formed on the photosensitive drum 3 is formed. Develop. At this time, not only the toner adhering to the magnetic brush but also the toner adhering to the surface of the developing sleeve 25 is transferred to the image area of the electrostatic latent image, and the electrostatic latent image is developed. In the example shown in FIG. 2, the magnet 29 includes N1 and N1 in addition to the developing magnetic pole S1.
2, N3 and S2 poles. With this configuration, as in the related art, while the developing sleeve 25 moves on the surface of the magnet 29 having the above configuration due to its rotation, the developer applied by the N3 pole passes through the layer thickness regulating blade 28. The developing magnetic pole S in a state where the layer thickness is regulated.
1 and rises in the magnetic field, where the developer develops the electrostatic latent image on the image carrier 3 as described above. Thereafter, the developer on the developing sleeve 25 is changed to N2 pole and N3.
It falls into the stirring chamber R1 due to the repulsive magnetic field between the poles. Furthermore,
The developer that has fallen into the stirring chamber R1 is stirred and transported by the screws 23 and 24, and the above process is repeated.

Next, the developing sleeve used in the present invention will be described in detail. As described in the conventional example, the present inventors believe that the phenomenon of M / S amount reduction on the developing sleeve is caused by contamination of the developing sleeve surface by a wax component or the like of the toner. That is, according to the study of the present inventors, as the use of a small particle size toner is required with the recent improvement in image quality, when the weight average particle size of the toner is small, specifically, about 4 to 9 μm In the case of the toner having a small particle diameter, it was found that the smaller the roughness Rz of the surface of the developing sleeve was, the more effective it was to suppress the occurrence of contamination of the developing sleeve. As a result of further study, the surface roughness R of the developing sleeve
It has been found that z is optimally set to about 1/2 of the particle diameter of the toner used. That is, when the surface roughness Rz of the developing sleeve is larger, the transportability can be improved, but on the other hand, the rubbing force applied to the developer becomes too strong, so that the deterioration of the developer at the time of durability is reduced. It is not preferable because it becomes large. Further, when Rz increases, minute toner components and impurities smaller than the average particle diameter of the toner used for image formation enter into the concave portions on the sleeve surface and accumulate, so that Rz on the sleeve surface fluctuates, and This also leads to a decrease in the M / S amount. Therefore, in the present invention, when the surface roughness of the developing sleeve is Rz, the surface shape of the developing sleeve is 2.0 μm <Rz <
The one that satisfies the value of 4.5 μm is used. More preferably, a developing sleeve having a surface shape satisfying a value of 2.0 μm <Rz <3.0 μm is used.

Further, as a result of further studies by the present inventors, a developing sleeve used for image formation using a non-magnetic toner having a small average particle diameter of about 4 to 9 μm has been developed. One having relatively smooth concave and convex portions and satisfying the condition of 20 μm <Sm <80 μm when the average interval between the peaks of the concave portions and convex portions is represented by Sm. Use has been found to be more preferable. It was also found that the developing sleeve having such a configuration can be produced by performing a surface treatment of the developing sleeve by blasting with glass beads instead of the conventional sandblasting.
That is, according to the blasting process using glass beads, FIG.
As shown in the above, the peak-to-peak interval (Sm) of the irregularities can be increased without changing the value of Rz, which greatly affects the conveying force, as compared with the conventional sandblasting process. Can be smoothed. By using a developing sleeve having such smooth irregularities, the force of pressing the toner against the irregularities on the surface of the developing sleeve can be reduced, so that the wax and external additives are effectively prevented from adhering to the developing sleeve. You.

Further, in the present invention, as a developer,
A two-component developer having a nonmagnetic toner containing a lubricant component (eg, wax) produced by a polymerization method and a magnetic carrier is used. In this case, the toner has a small weight average particle size of about 4 to 9 μm. It is preferable to use a magnetic carrier having a number average particle diameter in the range of 10 to 60 μm together with the non-magnetic toner having the particle diameter. In this case, particularly, as a surface shape, 20 μm <Sm <80
It is preferable to use a developing sleeve configured to satisfy the condition of μm.

That is, when the average interval Sm between the peaks of the concave and convex portions on the surface of the developing sleeve is narrowed to 20 μm or less, the developing sleeve is contaminated by wax and external additives contained in the toner. And Sm is 80
If the width is as large as μm or more, the transportability is reduced due to a decrease in the number of irregularities, and the developer on the developing sleeve is not coated in a stable state. In addition, the surface treatment method for obtaining the developing sleeve having the above-mentioned surface shape used in the present invention is not limited to the above-described blasting method using glass beads. Any method may be used as long as the unevenness to be formed can be made smooth, such as by blasting using a method.

The method for measuring the surface shape of the developing sleeve used in the present invention will be described below. In the present invention, Rz and Sm of the developing sleeve are JIS-B06.
Using the measured values used to define the ten-point average roughness and the average interval between the irregularities described in ISO 01 and ISO468, it was determined by the following equation. Each measurement was performed using a contact type surface roughness measuring instrument SE-3300 (manufactured by Kosaka Laboratories).

[0023]

(Equation 1)

Next, the carrier used in the present invention will be described. As described above, in the present invention, a two-component developer having a spherical non-magnetic toner containing a lubricant component (eg, wax) produced by a polymerization method and a magnetic carrier is used as the developer. In this case, the amount of magnetization in a magnetic field of 1 kOe is in the range of ³⁰ to 200 emu / cm ³ as a magnetic carrier, and
It is preferable to use a low-magnetization carrier having a number-average particle diameter in the range of 10 to 60 μm. In a two-component developing method using such a carrier in combination with the spherical polymerized toner, further improvement in image quality can be achieved. Aim.

According to the study of the present inventors, the gap between SD and D is 300 to 1000 μm, and the M / S amount is 20 to 50 m.
In the case of using a two-component developer having a T / D ratio (weight ratio of toner in the developer) of 5 to 12% under the condition of g / cm ^2, the amount of magnetization is 200 emu as a carrier.
/ Cm ³ or less, preferably 140 emu / cm ³ or less, the force for magnetically attracting the developer to the developing sleeve is Cu-Zn ferrite (about 280 emu / cm ³ ) which is widely used. Is much smaller than in the case of. As a result, the magnetic adhesion between the developing sleeve and the carrier is reduced, so that the force with which the toner sandwiched between the developing sleeve and the carrier is pressed against the developing sleeve is reduced. It is possible to more effectively prevent the contamination of the sleeve due to the attachment of wax, external additives, and the like. Furthermore, high releasability of polymerized toner containing wax,
In consideration of the suppression of carrier adhesion, it is appropriate to use a carrier having a magnetic property in a magnetic field of 1 kOe in a range of ^{30 to} 200 emu / cm ³ , preferably 80 to 140 emu / cm ³ . In other words, when a magnetic carrier having a magnetic property whose value is smaller than ³⁰ emu / cm ³ is used, not only the carrier adhesion increases, but also the developer is stably magnetically placed on the developing sleeve. It becomes difficult to apply and transport. In this case, when the polymerized spherical toner is used as in the present invention, the transportability is particularly deteriorated due to the shape factor.
On the other hand, the magnetization amount in a magnetic field of 1 kOe is 200 emu
If it exceeds / cm ³ , in a system using a polymer toner containing a wax, development sleeve contamination becomes severe.

At the same time as optimizing the amount of magnetization of the carrier,
By optimizing the average particle size range of the carrier and further the range of the specific resistance, it is possible to further suppress the carrier adhesion and prevent the developing sleeve from being contaminated while reliably preventing the image deterioration. Is solved. That is,
By controlling the number average particle size of the carrier to be used within the range of 10 to 60 μm, it is possible to effectively prevent the fine particle carrier from adhering to the photoreceptor, and the large particle size carrier from easily observing the burrs. Becomes Further, by setting the specific resistance of the carrier within the range of 10 ¹⁰ to 10 ¹⁴ Ω · cm or more, even if a carrier having a low magnetization amount as described above is used, carrier adhesion due to charge injection can be prevented. It is possible to effectively prevent image deterioration due to charge-up of the carrier.

Further, by using the above-mentioned carrier having a low magnetization amount, it is possible to achieve high image quality for the following reasons, in addition to the suppression of unevenness which may occur in a formed solid image or the like. That is, when a carrier having a low magnetization amount is used, when a magnetic brush is formed on the developing sleeve, the magnetic interaction between adjacent magnetic brushes can be reduced, so that the formed magnetic brush ears are densely formed. In addition, it becomes shorter, and as a result, it is possible to provide a high-resolution image. The low magnetization amount carrier that can be suitably used in the present invention is obtained, for example, by producing a resin magnetic carrier comprising a binder resin and a magnetic metal oxide and a nonmagnetic metal oxide by a polymerization method,
Not only this manufacturing method but also a method in which the amount of magnetization of a ferrite carrier or the like is appropriately controlled may be used.

Next, methods for measuring the amount of magnetization, particle diameter and specific resistance of the magnetic carrier will be described. The amount of magnetization of the carrier is measured by using an oscillating magnetic field type automatic magnetic recording device manufactured by Riken Denshi Co., Ltd. and placing the carrier packed in a cylindrical shape in an external magnetic field of 1 kOe (kOe). , And then multiplied by the true specific gravity of the carrier to calculate the amount of magnetization (emu / cm ³ ).

Regarding the particle size of the carrier, 300 randomly extracted carrier particles were photographed by a scanning electron microscope, and the photographed particles were analyzed by an image processing analyzer Luzex3 manufactured by Nireco Co., Ltd. The diameter was taken as the carrier particle diameter, and the number average particle diameter of the carrier was calculated.

Further, the specific resistance of the carrier was measured by the following method. Using the measuring device shown in FIG.
Then, electrodes 30 and 31 were arranged so as to be in contact with the carrier 33, a voltage 32 was applied between the electrodes, and a current flowing at that time was measured to obtain a specific resistance. The specific resistance measurement conditions used at this time were as follows: the contact area S between the filled carrier and the electrode was about 2.3 cm ² , the thickness d was about 2 mm, and the upper electrode 3
The load of 1 was 180 g, and the measured electric field strength was 5 × 10 ⁴ V / m.

Next, the toner used together with the above-described magnetic carrier constituting the two-component developer used in the present invention will be described. In the present invention, a non-magnetic toner containing a lubricant component produced by a polymerization method, having a weight average particle diameter of 4 to 9 μm and a shape factor SF-1 of 100 to 100 μm.
Non-magnetic toners having 140 and SF-2 in the range of 100 to 120 are used. As described in the conventional example, the toner used in the present invention can realize high transfer efficiency, and in order to achieve oil-less fixing, a polymerized toner containing a wax component as an active agent component is used. It is preferred to use. Polymerized toner, for example, using a suspension polymerization method, to prepare a monomer composition in which a colorant and a charge control agent are added to the monomer component of the binder resin, and suspend and polymerize the monomer composition in an aqueous medium. Thus, the toner particles can be easily obtained as spherical toner particles. The method for producing the polymerized toner is not limited to the above-described method, and may be produced by an emulsion polymerization method or the like, or may include other additives in the monomer composition.

The spherical toner particles obtained as described above particularly have a shape factor SF-1 of 100.
To 140 and SF-2 of 100 to 120 are used. This is because high transfer efficiency can be maintained when used for image formation. Here, the shape factors SF-1 and SF-2 are FE-SEM of Hitachi, Ltd.
Using (S-800), 100 toners were randomly sampled, and the image information was introduced into an image analyzer (Lusex3) manufactured by Nicole via an interface, analyzed, and calculated by the following equation. Defined as a value. That is, SF-1 indicates a degree of sphere, and a value of 100 indicates that the toner particle is a true sphere. When the value of SF-1 increases, the toner particle gradually changes from a sphere to an irregular shape. SF-2 indicates the degree of unevenness on the particle surface. The larger the value, the more the surface shape of the toner particles is not smooth and the more unevenness is significant.

[0033]

(Equation 2)

Next, the counter developing method used in the image forming apparatus according to a preferred embodiment of the present invention will be described. That is, in the present invention, in the developing area where the latent image forming medium and the developer carrier are opposed to each other, when a counter development system is used in which both carriers are configured to move in opposite directions to each other, Excellent effects can be obtained. As mentioned above, 4
When a non-magnetic toner containing a lubricant component (eg, wax) produced by a polymerization method having a weight average particle size of about 9 μm is used, blasting is performed using particles having few projections such as glass beads. By using a developing sleeve having a smaller surface roughness than the obtained conventional one and further using a carrier having a low magnetization amount, the developing sleeve contamination which has conventionally occurred can be effectively reduced. Can be prevented. However, according to the study of the present inventors, the problem of developing sleeve contamination is that the moving directions of the developing sleeve and the photosensitive drum are opposite to each other in a developing area where the developing sleeve and the photosensitive drum are opposed to each other. It has been found that the so-called counter development system can be further improved.

That is, in the case of the conventionally used forward developing method in which the moving direction of the developing sleeve and the photosensitive drum is the same at the opposed portion of the developing sleeve and the photosensitive drum, the developer on the developing sleeve is Coating amount (M / S amount)
Of the developer necessary for the stability of the developer, but the developer in the reservoir is pressed against the developing sleeve by a magnetic restraining force. Therefore, it is considered that the force of pressing the developer against the developing sleeve is smaller in the counter developing method without the accumulation portion than in the forward developing method. Further, in the case of the forward developing method, the developer regulated in the developer regulating section is:
While it is compressed by its own weight and the developer conveyed later and pressed against the developing sleeve, in the counter developing method, the regulated developer naturally circulates to the lower part. It is believed that as a result, the force with which the developer is pressed against the developing sleeve is reduced, and the contamination of the developing sleeve is improved.

[0036]

Next, the present invention will be described in more detail with reference to examples and comparative examples of the present invention. Using the image forming apparatus having the configuration shown in FIGS. 1 and 2 and applying the two-component developer and the developing sleeve under the following conditions, the image forming apparatuses of Examples 1 to 4 and Comparative Example 1 were manufactured. Obtained. (Example 1) In the image forming apparatus of Example 1, a two-component developer composed of a magnetic carrier and a polymerized toner having the following configuration and a developing sleeve having the following configuration were used. First, as a two-component developer, a polymer toner having the following characteristics and a resin magnetic carrier were used, and the toner was contained so that the weight ratio of the toner in the developer was 8% by weight. As the carrier, a resin magnetic carrier produced by a polymerization method was used. The carrier had a magnetization of 280 emu / cm ³ in a 1 kOe magnetic field, a number average particle size of 40 μm, and a specific resistance of 10 ¹³ Ω · cm. Was used. As the toner, a polymerized toner produced by a suspension polymerization method was used. The toner has a shape factor SF-1 of 115 and SF-2 of 110, and has a substantially spherical smooth surface shape. Had. Further, the toner has a weight average particle diameter of 6 μm and a specific gravity of 1.05 g / c.
m ³ , and the average charge per unit mass is 25 μC /
g.

As the developing sleeve, the surface thereof is A # 4
What had been sandblasted with 00 abrasive grains was used. The surface roughness Rz of the developing sleeve was 2.4 μm, and the value of the average distance Sm between the peaks of the concave and convex portions formed on the surface of the developing sleeve was 19 μm.
Further, the weight per unit area of the developer carried on the developing sleeve was measured and found to be 25 mg / cm ² . The rotation direction of the developing sleeve used in the present embodiment is a forward developing method in which the developing sleeve moves in the same direction as the photosensitive drum at a portion facing the developing sleeve and the photosensitive drum.

Comparative Example 1 An image forming apparatus of Comparative Example 1 was constructed in the same manner as in Example 1, except that the surface of the developing sleeve was sandblasted with A # 180 abrasive grains. . The surface state of the developing sleeve used in this comparative example is such that the surface roughness Rz is 5.3 μm, and the value of the average distance Sm between the peaks of the concave and convex portions formed on the surface of the developing sleeve is 21 μm. there were.

(Example 2) An image forming apparatus of this example was constructed in the same manner as in Example 1 except that a developing sleeve whose surface was blasted with glass beads of FGB # 300 was used. . The surface state of the developing sleeve used in this embodiment is such that its surface roughness Rz is 2.6 μm.
m, and the value of the average distance Sm between the peaks of the concave and convex portions formed on the surface of the developing sleeve was 45 μm.

Example 3 The same as Example 1 except that a ferrite carrier having a magnetization of 135 emu / cm ³ in a 1 kOe magnetic field having a different magnetization from that used in Example 1 was used as the magnetic carrier. Thus, the image forming apparatus of the present embodiment was configured.

(Embodiment 4) The rotation direction of the developing sleeve is
An image forming apparatus according to the present exemplary embodiment was configured in the same manner as in the first exemplary embodiment, except that a reverse developing method in which the developing sleeve was moved in a direction opposite to the photosensitive drum was used at a facing portion between the developing sleeve and the photosensitive drum.

<Evaluation> Using the image forming apparatuses of Examples 1 to 4 and Comparative Example 1 obtained as described above, the degree of contamination of the developing sleeve generated during image formation was evaluated by the following method. That is, a two-component developer composed of a non-magnetic toner and a magnetic carrier produced by the polymerization method having the structure shown in Example 1,
A plurality of magnetic field generators fixedly provided inside each having the configuration shown in FIG. 2 are supported on a rotatable developing sleeve in which a plurality of magnetic field generating devices are arranged, and the developing sleeve is continuously rotated for 5 hours. Examined. First, the M / S amount on the developing sleeve in the initial stage before rotation was measured, and after the rotation was completed for 5 hours, the operation was stopped, and the M / S amount on the developing sleeve when the developing sleeve was removed was measured. The amount of the M / S carried on the developing sleeve was calculated from the initial value and calculated, and evaluated based on the following criteria. The results are shown in Table 1. M on early developer sleeve
Compared with the value of the / S amount, when the reduction rate of the value of the M / S amount after the completion of the rotation for 5 hours is less than 10%, ◎, the reduction rate is 1
When 0% or more and less than 20%, it was evaluated as ○, and when the reduction rate was 20% or more, it was evaluated as ×.

As is clear from Table 1, when Example 1 and Comparative Example 1 are compared, the decrease in the M / S amount due to the development sleeve contamination is the same as in Example 1 where Rz on the surface of the development sleeve is small. And the effect of sandblasting with smaller abrasive grains was observed. Furthermore, comparing Example 1 and Example 2, it was found that the M / S
The decrease in the amount was suppressed in Example 2 where Sm was large, and the effect of the surface treatment of the developing sleeve with spherical particles such as glass beads was recognized. Further, in the third embodiment using a carrier having a lower magnetization than that used in the first embodiment, a decrease in the M / S amount due to contamination of the developing sleeve is suppressed as compared with the case of the first embodiment. The effect of using was recognized. Furthermore, compared to the case of using the forward developing method of Example 1, in Example 4 using the counter developing method, the decrease in the M / S amount due to contamination of the developing sleeve was suppressed, and the counter developing method was adopted. Effect was observed.

[0044]

[Table 1] Table 1: Evaluation results

[0045]

As described above, according to the present invention,
Effectively prevents the wax component and external additives from adhering to the surface of the developing sleeve, which occurs in the conventional two-component magnetic brush developing method using a polymer toner having a small particle diameter containing a wax component and an external additive. The occurrence of contamination of the developing sleeve is suppressed, and the M / S amount on the developing sleeve is prevented from lowering.
An image forming method capable of forming a high-quality image as a result of stable and uniform coating of a developer on a developing sleeve, and an image forming apparatus to which the method is applied are provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a developing device of an electrophotographic color image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a developing device portion of the image forming apparatus of the present invention.

FIG. 3 is a schematic diagram for explaining a surface shape of a developer carrying member used in the present invention.

FIG. 4 is a schematic view of an apparatus for measuring the specific resistance of a carrier used in the present invention.

[Explanation of Symbols] 3: Photosensitive drum 6: Paper feed roller 7: Gripper 8: Contact roller 9: Transfer drum 10: Transfer charger 12: Cleaning means 15: Separating claw 17: Fixing device 18: Developing container 19: Partition wall 23: Agent transport screw 25: Development sleeve 26: Development area 28: Layer thickness regulating blade 29: Magnet 30, 31: Electrode 32: Voltage 33: Carrier

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G03G 15/09 G03G 15/08 507L F-term (Reference) 2H005 AA06 AA15 AB06 BA02 CA14 EA02 EA05 FA01 2H031 AC10 AC14 BA08 BA09 2H077 AB02 AC02 AD02 AD06 EA03 FA03 FA19 GA03 GA13

Claims (5)

[Claims] 1. An electrostatic latent image is formed on an initially charged latent image forming medium by erasing charge of a portion corresponding to an image signal by an image exposing means. A two-component system having a plurality of fixed magnetic field generating means provided inside the image forming medium, a nonmagnetic toner containing a lubricant component produced by a polymerization method, and a magnetic carrier; An image forming method comprising a step of developing by a developing device having a developer carrier rotatably configured to carry and transport the developer to a developing area,
Having a weight average particle size of 9 μm and a shape factor SF
-1 is in the range of 100 to 140, SF-2 is in the range of 100 to 120, and the surface roughness is R.
An image forming method comprising: using a developer carrier having a surface shape blasted so as to satisfy a condition of 2.0 μm <Rz <4.5 μm, where z. 2. An electrostatic latent image is formed on an initially charged latent image forming medium by erasing a charge corresponding to an image signal by an image exposure means, and the electrostatic latent image is formed in a developing area. In an image forming apparatus having a developing unit for developing a visible image, the developing unit is provided to face the latent image forming medium, and has a plurality of fixed magnetic field generating units therein, and A developing device having a rotatable developer carrier for carrying and transporting a two-component developer having a non-magnetic toner containing a lubricant component produced by a polymerization method and a magnetic carrier to a development area, In addition, the non-magnetic toner has a weight average particle diameter of 4 to 9 μm, and its shape factor SF-1 is 100 to 140, and SF-2 is 100 to 120.
And 2.0 μm <Rz <4.5 when the surface of the developer carrier is blasted and the surface shape is Rz.
An image forming apparatus configured to satisfy a condition of μm. 3. The developer carrier has relatively smooth concave and convex portions on its surface, and the average distance between the peaks of the concave and convex portions is represented by Sm, where 20 μm <Sm <80.
The image forming apparatus according to claim 2, wherein the image forming apparatus is configured to satisfy a condition of μm. 4. The magnetic carrier according to claim 2, wherein the amount of magnetization in the magnetic field of 1 kOe is in the range of ³⁰ to 200 emu / cm ³ , and the number average particle size is in the range of 10 to 60 μm. Item 4. The image forming apparatus according to Item 3. 5. The developing device according to claim 2, wherein the two carriers are moved in directions opposite to each other in a development area where the latent image forming medium and the developer carrier are opposed to each other. 1
Item 10. The image forming apparatus according to item 1.