JP2000098694A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of dealing with the stop of a device caused by jamming, executing development and cleaning at the same time without causing color mixture in toner, and obtaining a satisfactory image free from color mixture without requiring a special cleaning member. SOLUTION: In the developing units of image forming parts PM, PC, PY and PK along a carrying belt 13, the magenta, cyan and yellow developing units 10M, 10C and 10Y use non-magnetic toner, and the black developing unit 4 uses magnetic toner. All of them allow a development cleaning operation. When image formation is interrupted due to a jam and the device is resumed after the removal of the jam, only the photoreceptor drum 1K of the black image forming park PK is allowed to contact the carrying belt 13, and the non- magnetic toner stuck to the carrying belt 13 from the photoreceptor drums 1M-1Y of the other image forming parts is stuck to the photoreceptor drum 1K and recovered by the black developing unit 4.

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 using an electrophotographic method used for, for example, a printer, a copying machine, a facsimile, and the like. The present invention relates to a possible image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in a full-color image forming apparatus, four electrophotographic photosensitive members are arranged in a straight line along a belt-shaped transfer member, that is, a transfer belt, and cyan, magenta, yellow, and black are arranged on the photosensitive members. A so-called tandem method in which a toner image is formed, a transfer material is linearly and continuously conveyed to each photoconductor by a transfer belt, and a toner image is superimposed and transferred onto a transfer material between straight passes to obtain a full-color image, A full-color image is obtained by wrapping a transfer material around the surface of a drum-shaped transfer member facing the photoreceptor, that is, a transfer drum by a mechanical force such as an electrostatic force or a flap, and performing a development-transfer process four times. The development-transfer process for each color is performed on the surface of the intermediate transfer drum of the intermediate transfer member facing the one photosensitive member by the transfer drum system.
A so-called intermediate transfer body transfer method, in which a full-color image is formed on an intermediate transfer body, and then a full-color image is formed by collectively transferring four colors to a transfer material, is generally used. . A transfer belt or an intermediate transfer belt may be used as the transfer member or the intermediate transfer member.

First, a tandem type image forming apparatus will be described with reference to FIG.

[0004] This image forming apparatus has a first,
Second, third, and fourth image forming units PM, PC, PY, and PK
The paper supply unit 107 is provided on the right side, and the fixing unit 113 is provided on the left side. The paper feeding unit 107 described above
An endless transfer material transporting means for transporting the transfer material, that is, a transport belt (transfer belt) 109 is installed under the path from the printer to the fixing device 113 by being stretched around the drive roller 111 and the driven roller 112. I have.

[0005] The transport belt 109 is
The transfer material P, which is rotationally driven in the direction of arrow a by the rotation of arrow 1 in the direction of arrow b, is transported through the paper supply unit 107, and is transported sequentially to the image forming units PM, PC, PY, and PK.

The image forming units PM to PK have substantially the same configuration. Image forming units PM, PC, PY and PK
Denotes drum-shaped electrophotographic photosensitive members each serving as an image carrier, that is, photosensitive drums 101M, 101C, and 101Y.
And a primary charger 102 that uniformly charges the photosensitive drum in the rotation direction around the photosensitive drum in order.
M, 102C, 102Y and 102K, image exposure apparatuses 103M, 103C for forming an electrostatic latent image on a photosensitive drum,
103Y and 103K, developing units 104M, 104C, 104Y and 10 for developing an electrostatic latent image on the photosensitive drum
4K, transfer chargers 105M and 105 each composed of a corona charger for transferring a toner image obtained by development to a transfer material.
C, 105Y and 105K, and drum cleaning members 106M, 106C, 106Y and 106K for removing transfer residual toner remaining on the photosensitive drum are provided.

The developing device 104M contains magenta toner, the developing device 104C contains cyan toner, the developing device 104Y contains yellow toner, and the developing device 104K contains black toner. Image exposure apparatus 103M, 1
03C, 103Y and 103K are LEDs in this example.
It is composed of an LED array in which light emitting elements are arranged in the generatrix direction of the photosensitive drum. Image exposure apparatuses 103M, 103
C, 103Y and 103K denote digital pixels corresponding to image signals of respective colors converted into digital signals by reading and converting into a large number of pixels by an image sensor such as a color CCD, or image signals transmitted from an external computer. In response to the input of the signal, between the primary charger 102M and the developing unit 104M, between 102C and 104C, 102
Y and 104Y, and between 102K and 104K, the photosensitive drums 101M, 101C and 101Y, respectively.
And 101K are exposed to form an electrostatic latent image of a corresponding color.

A pixel signal corresponding to a magenta component image of a color image is supplied to the image exposure device 103M.
A pixel signal corresponding to a cyan component image is input to C, a pixel signal corresponding to a yellow component image is input to the image exposure device 103Y, and a pixel signal corresponding to a black component image is input to the image exposure device 103K. You.

In the above-described image forming apparatus, a conveyor belt 109 is fed from a paper cassette (not shown) via a paper feeding unit 107.
The transfer material P fed above is electrostatically attracted by an attraction charger (not shown), and is transported in the same direction as the transport belt 109 moves in the direction of arrow a. In response to the transfer of the transfer material P, the magenta toner image is formed on the photosensitive drum 101M of the first image forming unit PM, and the photosensitive drum 10M of the second image forming unit PC is changed.
1C, the yellow toner image on the photosensitive drum 101Y of the third image forming portion PY, and the fourth image forming portion P
A black toner image is formed on the K photosensitive drum 101K through the steps of primary charging, image exposure and development, respectively.

In general, the developing method is such that a non-magnetic toner is coated on a developing sleeve with a blade or the like, or a magnetic toner is coated on the developing sleeve by a magnetic force and is conveyed to a photosensitive drum. On the other hand, a one-component non-contact development method for providing development in a non-contact state, a one-component contact development method for providing development with the coated toner in contact with the photosensitive drum,
A two-component contact developing method in which a two-component developer in which a toner and a magnetic carrier are mixed is coated on a developing sleeve by magnetic force and transported to a photosensitive drum, and the coated developer is developed in contact with the photosensitive drum; And a two-component non-contact developing method in which the coated developer is subjected to development in a non-contact state with respect to the photosensitive drum.

In recent years, a developing device using a one-component contact developing method using a non-magnetic toner, that is, a non-magnetic one-component contact developing device has been widely used in an image forming apparatus for the purpose of simplifying the structure of the apparatus and reducing the cost. It is getting.

FIG. 12 shows the developing units 104M to 104K.
FIG. 1 is a schematic view showing a conventional non-magnetic one-component contact developing device used as a device. The developing device 104 contains a non-magnetic toner T as a one-component developer. The developing device 104 is in contact with the photosensitive drum 101 and rotates in the direction of arrow Y. The developing device 104 is in contact with the developing roller 114 and rotates in the direction of arrow Z. Developing blade 1 of developer controlling means
16 and a developer stirring member 117 and the like.

At the time of development, the stirring member 117 rotates to stir the contained non-magnetic toner T and to supply the toner.
15 and the supply roller 115 rotating in the direction of the arrow Y
Is a developing roller 1 that rotates the toner T in the arrow Z direction.
The toner is supplied to the developing roller 114 by rubbing with the developer 14 and is carried on the developing roller 114. The toner T carried on the developing roller 114 reaches the developing blade 116 as the developing roller 4 rotates, and the developing blade 116
Regulates the toner T to give a desired amount of charge and form a predetermined toner thin layer.

The regulated toner T is supplied to the developing roller 114.
, The photosensitive drum 101 and the developing roller 114
Is transported to the developing unit in contact with the electrostatic latent image formed on the surface of the photosensitive drum 101 by a DC developing bias applied to the developing roller 114 from a power supply (not shown). Develop.

The toner remaining on the surface of the developing roller 114 without contributing to the development is returned into the developing device 104 with the rotation of the developing roller 114, and is separated from the developing roller 114 by a rubbing portion with the supply roller 115. Collected. The collected toner is stirred and mixed with the remaining toner T by the stirring member 117.

As described above, in the contact developing device in which the photosensitive drum 101 and the developing roller 114 come into contact with each other to perform development, the photosensitive drum 101 is made rigid, and the developing roller 114 used for this is an elastic roller. Is preferred.
As the elastic body, a solid rubber single layer or a solid rubber layer coated with a resin in consideration of the charging property to the toner is used.

The image forming operation of the image forming apparatus will be described.
01M to 101K start rotating in the direction of the arrow, and during the rotation process, the surfaces of the photosensitive drums 101M to 101K are uniformly charged by the primary chargers 102M to 102K, and then the photosensitive drums 101M to 103K are exposed by the image exposure devices 103M to 103K.
An electrostatic latent image is formed on the 1K surface. Then, the latent images are developed by the developing devices 104M to 104K, and are visualized as magenta, cyan, yellow, and black toner images, respectively.

The photosensitive drums 101M, 101C, 1
The toner images formed on 01Y and 101K are transferred to the transfer chargers 105M, 105C, and 1K while the transfer material P conveyed by the conveyance belt 109 sequentially passes below the photosensitive drums 101M, 101C, 101Y, and 101K.
The composite color image is formed by superimposing and transferring the toner images of four colors on the transfer material P in order by 05Y and 105K.

Transfer material P on which four color toner images have been transferred
After passing through the fourth image forming unit PK, the charge is removed by a charge removing charger (not shown) to which an AC voltage is applied, and is separated from the transport belt 109. The transfer material separated from the transport belt 109 is discharged from the transfer material discharge port after the four color toner images are fixed by the fixing device 113.

On the other hand, the photosensitive drum 10 after the transfer of the toner image
The transfer residual toner remaining on the surfaces of 1M, 101C, 101Y, and 101K is transferred to the drum cleaning member 106.
The toner is cleaned and removed by M, 106C, 106Y, and 106K, and stored in a waste toner box provided side by side. In this example, the drum cleaning members 106M to 106M
6K employs a method in which an elastic blade is brought into contact with a photosensitive drum to scrape off toner. Dirt such as toner on the transport belt 109 is cleaned by contacting the belt cleaning member 110.

The image forming apparatus of the intermediate transfer type will be described with reference to FIG.

In FIG. 13, reference numeral 101 denotes a rotating drum type electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum. The photosensitive drum 101 is clockwise indicated by an arrow in response to an external print signal or the like. At the peripheral speed (process speed). The photosensitive drum 101 is uniformly charged to a predetermined polarity and potential by a primary charger (corona charger) 102 during the rotation process.
(Such as a color separation / imaging exposure optical system for color original images, a scanning exposure system using a laser scanner that outputs a laser beam modulated according to a time-series electric digital pixel signal of image information, etc.) Then, an electrostatic latent image corresponding to the first color component image (for example, a magenta component image) of the target color image is formed.

Next, the electrostatic latent image is transferred to the photosensitive drum 101.
Reaches the magenta developing device 104M of the first developing device with the rotation of the first developing device, and is developed by the first color magenta toner, and is visualized as a magenta toner image. At this time, the operations of the second to fourth cyan developing devices 104C, the yellow developing device 104Y, and the black developing device 104K are stopped, and do not act on the photosensitive drum 101.
01 does not affect the magenta toner image.

The above-mentioned first to fourth developing units 104M to 104M
K is mounted on the rotary developing unit 141 at intervals in the circumferential direction, and is installed so as to be able to freely contact and separate from the photosensitive drum 101. The developing devices 104M to 104K move in the direction of the arrow to be sequentially conveyed to a position facing the photosensitive drum 101, where they come into contact with the photosensitive drum 101 and are used for development.

Reference numeral 118 denotes an intermediate transfer drum, which is in contact with the photosensitive drum 101 and is driven to rotate at the same peripheral speed in the counterclockwise direction indicated by the arrow. The intermediate transfer drum 118 includes a pipe-shaped cored bar and an elastic layer formed on the outer peripheral surface thereof.

The first color magenta toner image formed on the photosensitive drum 101 is formed by the primary transfer bias applied to the intermediate transfer drum 118 while passing through the nip between the photosensitive drum 101 and the intermediate transfer drum 118. The transferred electric field causes the image to be transferred onto the outer peripheral surface of the intermediate transfer drum 118 (primary transfer, intermediate transfer).

After the transfer of the magenta toner image, the surface of the photosensitive drum 101 is cleaned by a drum cleaning member 106, and is used for the next image formation.

Thereafter, similarly, the second color cyan toner image, the third color yellow toner image, and the fourth color black toner image are sequentially superimposed and transferred onto the intermediate transfer drum 118, and are synthesized corresponding to the target color image. A color toner image is formed.

The four color toner images superimposed and transferred on the intermediate transfer drum 118 are transferred to the transfer material P fed to the intermediate transfer drum 118. The transfer material P is supplied to the sheet cassette 121.
From the intermediate transfer drum 11 at a predetermined timing.
8 and at the same time, the transfer roller 120 to which the secondary transfer bias is applied abuts on the intermediate transfer drum 118 with the transfer material P interposed therebetween.
The upper four toner images are collectively transferred to the transfer material P (secondary transfer).

The transfer roller 120 is provided on the intermediate transfer drum 11
8 and is installed on the lower surface of the intermediate transfer drum 118 so as to be freely contacted and separated. The transfer roller 120 and the cleaning member 119 for the intermediate transfer drum can be separated from the intermediate transfer drum 118 during the transfer of the first to fourth color toner images from the photosensitive drum 101 to the intermediate transfer drum 118.

Transfer material P to which four color toner images have been transferred
Is introduced into the fixing device 113 and the toner image is heated and fixed. After the transfer of the toner image to the transfer material P, the intermediate transfer drum 118 is cleaned of the transfer residual toner on the surface thereof by contact of the cleaning member 119, and is ready for the next image formation.

The developing units 104M to 104K are the same as those of the non-magnetic one-component contact developing unit in the tandem type image forming apparatus, and therefore, the description is omitted.

In order to save energy and reduce running costs in recent years, the cleaning is not provided in the one-component contact developing device, and the developing is performed by the developing roller in contact with the photosensitive drum. Attention has been focused on a so-called simultaneous development cleaning method for cleaning and collecting the transfer residual toner remaining in the toner.

FIG. 14 shows a conventional image forming apparatus adopting a simultaneous cleaning system using a non-magnetic one-component contact developing device.

As shown in FIG. 14, in the image forming apparatus, a primary charger 102, an image exposing device 103, a developing device 104, and a transfer charger 105 are arranged around a photosensitive drum 101 rotating in the direction of an arrow. Has become. The developing device 104
It has basically the same configuration as the developing device of FIG. FIG.
4, the same reference numerals as those shown in FIG. 12 indicate the same members.

The photosensitive drum 10 is developed by the developing device 104.
1 is transferred onto the transfer material P by the transfer roller 105, and the transferred toner image is fixed by the fixing device 113.

The transfer residual toner remaining on the photosensitive drum 101 passes through the primary charging device 102 and the developing roller 11
The contact point with No. 4 is reached. At this time, a DC developing bias is applied to the developing roller 114, and the transfer residual toner is collected by the developing roller 114 and used for development together with another toner T at the next image formation.

Referring to FIG. 15, the principle of simultaneous development and cleaning will be described. In FIG.
1 indicates a transfer residual toner remaining on the developing roller 1, and T indicates new toner before development carried on the developing roller 114. Both the transfer residual toner T ′ and the new toner T are negatively charged (−).

The transfer residual toner T 'on the photosensitive drum 1 is
After being charged to the negative polarity by the primary charger 102, the charge reaches the contact portion between the photosensitive drum 101 and the developing roller 114, is rubbed by the contact portion, and is further negatively charged. The electrostatic latent image on the photosensitive drum 101, that is, the exposed portion potential (image portion potential) is about -100 V due to exposure. At this time, the transfer residual toner T ′ is directly transferred to the photosensitive drum 101.
The toner T on the developing roller 114 remains on the photosensitive drum 101 due to a potential difference between a developing bias, for example, −460 V and an exposed portion potential −100 V on the photosensitive drum 101.
The electrostatic latent image on the photosensitive drum 101 is developed by transferring to the upper exposure portion.

At the same time, the negatively charged transfer residual toner T 'in the non-exposed portion (non-image portion) is developed with the non-exposed portion potential (non-image portion potential, ie, primary charging potential) on the photosensitive drum 101, for example, -700V. The toner is transferred onto the developing roller 114 by a potential difference from the bias of -460 V, that is, is cleaned and collected by the developing device 104. At this time, the black toner T on the developing roller 114 is
4 remains on.

Thus, at the time of development by the developing device 104,
The transfer residual toner on the photosensitive drum 101 is cleaned and collected in the developing device 104.

[0042]

In order to reduce the size and cost of a color image forming apparatus, FIG.
1, the drum cleaning members 106M to 106K and the belt cleaning member 11
0, the drum cleaning member 106 and the intermediate transfer body cleaning member 119 are removed by the intermediate transfer drum type apparatus shown in FIG. 13, and a simultaneous development and cleaning method as shown in FIG. 14 is employed instead. if you did this,
If image formation is interrupted during image formation due to some cause, for example, a jam (paper jam), the following problems occur.

In the tandem type image forming apparatus, when a jam occurs during the image formation and the image formation is interrupted, the transfer material P is not on the conveyor belt 109.
The toner images of each color on 1M to 101K are
9 is transferred. When the transport belt 109 is rotated in this state in order to return the image forming apparatus after the jam processing, for example, the magenta toner image on the transport belt 109 is removed from the subsequent photosensitive drums 101C, 101Y, 101Y,
01K, the drum cleaning member 106C, 1
06Y and 106K, the developing device 104
C, 104Y, and 104K, and these cyan, yellow, and black toners are mixed.

The color mixture of the toner of the subsequent developing device is cyan,
The same occurs with a yellow toner image. As a result, the color of the color image obtained at the time of the next image formation changes due to the color mixture of the toner.

Even in the image forming apparatus of the intermediate transfer drum type,
If a jam occurs during image formation, toner images of each color exist on the intermediate transfer drum 118 in a mixed color state. The toner image on the intermediate transfer drum 118 is
If the photosensitive drum 101 is formed of negatively charged toner, a high voltage of negative polarity is applied to the intermediate transfer drum 118 with the photosensitive drum 101 as a ground potential. It is possible to transfer However, in this toner image, each color is in a mixed state, and it is difficult to return each color to the developing units 104M to 104K of each color.

A problem arises even in a transfer drum type apparatus. That is, if a jam occurs immediately after the development has changed from the developing device of the previous color to the developing device of the next color, the toner image of the previous color exists near the transfer portion on the photosensitive drum,
Immediately after the developing device of the next color, there is a toner image of the next color, and a two-color toner image is present on the photosensitive drum although it is not in a mixed state. Although the two-color toner images are not mixed, the jamming timing varies, and it is practically difficult to collect the toner images in the respective developing devices by adjusting the leading end position of the toner image for each color.

As described above, in the full-color image forming apparatus using the one-component developing device, even if an attempt is made to apply the simultaneous development cleaning method, after the apparatus is stopped due to a jam or the like, the cleaning is performed by mixing the toners of the respective colors. There were difficulties that I could not do.

Therefore, an object of the present invention is to cope with a stoppage of the apparatus due to a jam or the like, and to carry out simultaneous development and cleaning without causing toner color mixing. It is an object of the present invention to provide an image forming apparatus which can obtain a good color image without any problem, and can be reduced in size and cost.

[0049]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention develops and visualizes an electrophotographic photosensitive member, primary charging means for charging the electrophotographic photosensitive member, and an electrostatic latent image formed by image exposure of the charged electrophotographic photosensitive member. And a plurality of developing devices containing one-component developers of different colors.The visualized images of the respective colors are superimposed and transferred onto a transfer material or an intermediate transfer body. The image forming apparatus, wherein the carrier is brought into contact with the electrophotographic photosensitive member, and the developer remaining on the electrophotographic photosensitive member is collected on the developer carrier by a potential difference from the developer carrier. One of the developing devices is a magnetic one-component developer using a magnetic one-component developer as a developer, and the other developing device is a non-magnetic one-component developer using a non-magnetic one-component developer. An image forming apparatus characterized in that:

According to the present invention, when the image forming apparatus is stopped in the middle of image formation and then returned, the developer carrying member of the magnetic one-component developing device is brought into contact with the image carrying member, and A voltage is applied to the carrier to urge the developer on the electrophotographic photoreceptor toward the developer carrier, and the developer adhering to the electrophotographic photoconductor charged together with the electrophotographic photoconductor by the primary charger is removed. And collected on a developer carrier.

Further, a plurality of the electrophotographic photosensitive members are provided, and the plurality of developing devices are arranged one by one on the electrophotographic photosensitive member, and a visible image formed on each electrophotographic photosensitive member is The image forming apparatus is superimposed and transferred onto the transfer material conveyed by the transfer material conveying member in contact therewith, and when returning after the image forming apparatus is stopped, leaving only the electrophotographic photosensitive member in which the magnetic one-component developing device is disposed. The contact with the transfer material conveying member is released, and the developer attached to the transfer material conveying member is transferred from the electrophotographic photosensitive member on which the non-magnetic one-component developing device is disposed to the electronic device on which the magnetic one-component developing device is disposed. It is adhered to a photographic photoreceptor and collected by the magnetic one-component developing device. The developer adhered to the transfer material conveying member can be applied to the electrophotographic photosensitive member on which the magnetic one-component developing device is disposed by applying a bias having a polarity opposite to that of the transfer to the transfer material conveying member. .

Further, one electrophotographic photosensitive member is installed, and the plurality of developing devices are installed so as to be able to contact and separate from the electrophotographic photosensitive member, and the visible image formed on the electrophotographic photosensitive member is transferred to the intermediate transfer member. Superimposed transfer, upon return after stopping the image forming apparatus, the developer carrying member of the magnetic one-component developing unit was brought into contact with the electrophotographic photosensitive member, and adhered to the electrophotographic photosensitive member from the intermediate transfer member. The developer is collected in the magnetic one-component developing device. The developer adhering to the intermediate transfer member can be applied to the electrophotographic photoreceptor by applying a bias having a polarity opposite to that of the transfer to the intermediate transfer member.

Further, the magnetic one-component developing device may include an elastic regulating member in contact with the developer carrier as a regulating member for regulating the magnetic one-component developer carried on the developer carrier. The magnetic one-component developing device can include a developer peeling member that is in contact with the developer carrier. At the time of collecting the developer, a peeling bias in a direction of urging the developer adhered on the developer carrier toward the developer peeling member can be applied to the developer peeling member.

According to the present invention, the developer comprises a non-magnetic toner containing at least a binder resin, a colorant and a wax, and the toner particles are in a state where the wax is not compatible with the binder resin. In a substantially spherical and / or spindle-shaped island form. Spherical coefficient S of the developer
F-1 is 100 to 160, and SF-2 is 100 to 140. More preferably, the spherical coefficient SF-1 of the developer
Is 100 to 140, and SF-2 is 100 to 120.
The ratio SF-2 of the spherical coefficient SF-2 and SF-1 of the developer
/ SF-1 is 1.0 or less. The melting point of the wax is 40 to 130 ° C. An external additive is added to the developer, and the coverage of the external additive on the developer surface is 5 to 99%.

[0055]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic view showing an embodiment of the image forming apparatus of the present invention.

The image forming apparatus of this embodiment is a tandem type full-color image forming apparatus. The overall configuration and image forming operation of the image forming apparatus will be described.

This image forming apparatus has a first
Second, third, and fourth image forming units PM, PC, PY, and PK
The paper supply unit 11 is provided on the right side, and the fixing unit 1 is provided on the left side.
2 are provided respectively. An endless transfer material transporting means for transporting the transfer material, that is, a transport belt (transfer belt) 13 is attached to a driving roller 14 and a driven roller 15 below the path from the paper feeding unit 11 to the fixing device 12. It is installed on a bridge.

The transport belt 13 is driven to rotate in the direction of arrow a by the rotation of the drive roller 14 in the direction of arrow b, carries the transfer material P fed through the sheet feeding unit 11, and forms the image forming units PM and PC. , PY and PK.

First, second, third, and fourth image forming units P
M, PC, PY, and PK are magenta, cyan,
In the yellow and black image forming units, the first to third image forming units PM to PY have substantially the same configuration, and only the fourth image forming unit PK is magnetically applied to the black developing device (black developing device) 4. The difference is that a magnetic one-component contact developing method using toner is employed. First, second, third image forming units PM, PC, P
The Y color developing devices, that is, the magenta developing device 10M, the cyan developing device 10C, and the yellow developing device 10Y employ a non-magnetic one-component contact developing method using a non-magnetic toner. The developing device 10M contains a magenta non-magnetic toner, the developing device 104C contains a cyan non-magnetic toner, the developing device 10Y contains a yellow non-magnetic toner, and the developing device 4 contains a black (black) magnetic toner. Is housed.

Image forming units PM, PC, PY and PK
Has a drum-shaped electrophotographic photosensitive member, which is an image carrier, that is, a photosensitive drum 1M, 1C, 1Y, and 1K, and a primary charge that uniformly charges the photosensitive drum in the rotation direction around each photosensitive drum. Chargers 2M, 2C, 2Y and 2K, image exposure device 3 for forming an electrostatic latent image on a photosensitive drum
M, 3C, 3Y and 3K, color developing devices 10M, 10C and 10Y and a black developing device 4 for developing an electrostatic latent image on a photosensitive drum, and a corona charger for transferring a toner image obtained by development to a transfer material A transfer charger 9M comprising
9C, 9Y and 9K are provided. Primary charger 2
As the transfer chargers M to 2K and the transfer chargers 9M to 9K, not only corona chargers but also roller chargers made of conductive rollers, blade chargers made of conductive flat plates, and the like can be used.

Image exposure devices 3M, 3C, 3Y and 3K
In the present example, the light emitting device comprises an LED array in which LED light emitting elements are arranged in the generatrix direction of the photosensitive drum. The image exposure devices 3M, 3C, 3Y, and 3K are decomposed into a large number of pixels by an image sensor such as a color CCD, read, and converted into digital signals, image signals of each color, or transmitted from an external computer. In response to the input of the digital pixel signal for the image signal, the photosensitive drum is connected between the primary charger 2M and the developing unit 10M, between 2C and 10C, between 2Y and 10Y, and between 2K and 4 respectively. 1
The surfaces of M, 1C, 1Y and 1K are exposed to form electrostatic latent images of corresponding colors.

A pixel signal corresponding to a magenta component image of a color image is supplied to the image exposure device 3M, and a pixel signal is supplied to the image exposure device 3C.
A pixel signal corresponding to a cyan component image is input to the image exposure device 3Y, and a pixel signal corresponding to a black component image is input to the image exposure device 3K.

In the above-described image forming apparatus, the transfer material P fed onto the transport belt 13 from the paper feed cassette (not shown) via the paper feed unit 11 is electrostatically attracted by a suction charger (not shown), Are conveyed in the same direction as they move in the direction of arrow a. In response to the transfer of the transfer material P,
A magenta toner image is formed on the photosensitive drum 1M of the first image forming unit PM, a cyan toner image is formed on the photosensitive drum 1C of the second image forming unit PC, a yellow toner image is formed on the photosensitive drum 1Y of the third image forming unit PY. Photosensitive drum 1K of image forming unit PK
A black toner image is formed through the steps of primary charging, image exposure and development, respectively.

The developing device will be described. First, magenta, cyan, and yellow color developing units 10M, 10C,
Y will be described. FIG. 2 is a schematic diagram showing a non-magnetic one-component contact developing device used as the developing devices 10M to 10Y. The developing device 10 contains a non-magnetic toner T as a one-component developer. The developing device 10 is in contact with the photosensitive drum 1 and rotates in a direction indicated by an arrow Y. The developing device 10 comes in contact with the developing roller 17 and rotates in a direction indicated by an arrow Z. And a developer stirring member 20 and the like.

At the time of development, the stirring member 20 rotates to stir the stored non-magnetic toner T,
Supply roller 18 rotating in the direction of arrow Y supplies the toner T to the developing roller 17 by rubbing against the developing roller 17 rotating in the direction of arrow Z.
Carry on top. The toner T carried on the developing roller 17 causes the developing blade 1 to rotate as the developing roller 17 rotates.
At 9, the developing blade 19 regulates the toner T, imparts a desired amount of charge, and forms a predetermined toner thin layer.

As the developing roller 17 rotates, the regulated toner T is conveyed to the developing section where the photosensitive drum 1 and the developing roller 17 are in contact, and in the developing section, the DC voltage applied to the developing roller 17 from the developing bias power supply 21 is applied. The developing bias adheres to the electrostatic latent image formed on the surface of the photosensitive drum 1 to develop the latent image.

The toner remaining on the surface of the developing roller 17 without contributing to the development is returned into the developing device 10 with the rotation of the developing roller 17, and is separated from the developing roller 17 by a rubbing portion with the supply roller 18. Collected. The collected toner is stirred and mixed with the remaining toner T by the stirring member 20.

As described above, in the contact developing device in which the photosensitive drum 1 comes in contact with the developing roller 17 to perform development, the photosensitive drum 1 is made rigid and the developing roller 17 used for this is a roller having an elastic body. Is preferred. As the elastic body, a solid rubber single layer or a solid rubber layer coated with a resin in consideration of the charging property to the toner is used.

The toner image formed on the photosensitive drum 1 is transferred onto a transfer material P conveyed by the conveying belt 13 in FIG. 1, and the untransferred toner remaining on the photosensitive drum 1 without being transferred is As the photosensitive drum 1 rotates, the photosensitive drum 1 passes through the primary charger 2 and, in the same manner as the conventional simultaneous cleaning of the development described with reference to FIGS. The photosensitive drum 1 is cleaned and removed by the roller 17 and
Collected inside.

In the present invention, the reversal development is performed by using a negatively charged toner as the non-magnetic toner T, and even if the transfer residual toner contains a toner charged to both polarities, the primary charger 2 is used. Since it is charged again to the negative polarity, it can be collected by the developing roller 17.

The black developing device 4 will be described. As shown in FIG. 3, the black developing device 4 contains a magnetic toner t as a one-component developer. The developing device 4 includes a developing roller 5 that rotates in the direction of arrow Y in contact with the photosensitive drum 1, a magnet roller 6 fixedly and non-rotatably disposed coaxially within the developing roller 5, and a developer disposed adjacent to the developing roller 5. It comprises a developing blade 8 as a regulating means, a developer stirring member 7, and the like.

At the time of development, the stirring member 7 rotates, stirs the contained magnetic toner t and conveys it to the developing roller 5, and the magnetic roller 6 in the developing roller 5 draws up the toner t by the pole S2. The surface of the roller 5 is adsorbed. The magnetic toner t carried in this way reaches the developing blade 8 with the rotation of the developing roller 5 in the direction of the arrow Y, and the toner t is generated by the magnetic binding force between the developing blade 8 and the regulating pole N1 of the magnet roller 6. Is regulated to form a predetermined thin toner layer.

The regulated toner t is conveyed to the developing unit where the photosensitive drum 1 and the developing roller 5 are in contact with each other as the developing roller 5 rotates while being held at the magnetic pole S1 of the magnet roller 6, and the developing bias is applied to the developing unit. Due to the DC developing bias applied to the developing roller 5 from the power supply 16, the toner adheres to the electrostatic latent image formed on the surface of the photosensitive drum 1,
Develop the latent image.

The toner remaining on the surface of the developing roller 5 without contributing to the development is returned into the developing device 4 with the rotation of the developing roller 5, and the blow-out preventing pole N
2 and between the prevention pole N2 and the pumping pole S2, the magnetic binding force weakens and the toner t in the developing device 4
Of the developing roller 5 by the stirring of
Collected inside. The collected toner is stirred and mixed with the magnetic toner t contained in the developing device 4 by the stirring member 5.

The black toner image formed on the photosensitive drum 1 is transferred onto the transfer material P conveyed by the conveyer belt 13 in FIG. 1, and the untransferred magnetic toner remaining on the photosensitive drum 1 without being transferred. Passes through the primary charger 2 with the rotation of the photosensitive drum 1, and when the next black toner image is developed by the developing device 4 in the same manner as the color developing device 10, It is cleaned and collected.

The image forming operation of the image forming apparatus will be described.
M-1K starts to rotate in the direction of the arrow, and during the rotation process, the surfaces of the photosensitive drums 1M-1K are uniformly charged by the primary chargers 2M-2K, and then the photosensitive drums 1M-1K are charged by the image exposure devices 3M-3K. An electrostatic latent image is formed on the surface. Then, the latent images are developed by the color developing units 10M, 10C, 10Y and the black developing unit 4, and are respectively magenta, cyan, and cyan.
It is visualized as yellow and black toner images.

The toner images formed on the photosensitive drums 1M, 1C, 1Y, and 1K are transferred while the transfer material P transported by the transport belt 13 sequentially passes under the photosensitive drums 1M, 1C, 1Y, and 1K. , A transfer charger 9M,
By 9C, 9Y, and 9K, the composite color image is formed by superimposing and transferring the toner images of four colors on the transfer material P in order.

At this time, the transfer residual toner remaining on each of the photosensitive drums 1M, 1C, 1Y and 1K is transferred to the developing units 10M, 10C, 10Y and 4K as described above.
As a result, cleaning and collection are performed during the next development. In this way, even in a full-color image forming apparatus, simultaneous cleaning with development can be achieved, and the amount of consumed toner can be reduced by the collected toner.

Transfer material P on which four color toner images have been transferred
After passing through the fourth image forming section PK, the charge is removed by a charge removing charger (not shown) to which an AC voltage is applied, and is separated from the transport belt 13. The transfer material separated from the transport belt 13 is discharged from the transfer material discharge port after the four color toner images are fixed by the fixing device 12.

Next, each member of the developing device will be described.

The developing roller 5 of the black developing device 4 was formed to have an outer diameter of 20 mm by providing an elastic layer of about 1.5 mm on a thin hollow metal cylinder having a thickness of about 1 mm and an outer diameter of 17 μm. . Silicone rubber was used for the elastic layer. Examples of the rubber used for the elastic layer include, in addition to silicone rubber, general rubbers such as nitrile rubber (NBR rubber), butyl rubber, natural rubber, acrylic rubber, hydrin rubber, and urethane rubber. Usually, the hardness is reduced by increasing the oil impregnation amount of these rubber materials.

When the developing roller 5 has a single rubber layer,
When a negatively chargeable toner is used, urethane rubber, silicone rubber, NBR rubber, or the like can be suitably used from the viewpoint of charge imparting property to the toner. When a positively chargeable toner is used, fluorine rubber or the like can be preferably used.

A coating layer can be provided on the surface of the elastic layer in consideration of the chargeability of the toner. The coating layer may be made of polyamide resin, urethane resin, silicone resin, or the like.
An acrylic resin, a fluororesin, or a resin obtained by mixing these resins can be suitably used.

The developing rollers 17 of the color developing units 10M to 10Y
Was formed to have an outer diameter of 20 mm by providing an elastic layer having a thickness of about 4 mm on a solid metal cylinder having an outer diameter of 12 μm. A coat layer can also be provided on the surface of the elastic layer. As the material of the elastic layer and the coat layer, the same material as that of the developing roller 5 described above is used.

The rubber hardness of the developing rollers 5 and 17 was measured by using an Asker C rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). Rubber hardness is Asker C
The hardness is preferably 55 degrees or less. If the rubber hardness exceeds 55 degrees, the contact pressure at the contact portion between the developing roller and the photosensitive drum 1 must be increased, which undesirably causes deterioration of the toner.

Although the surface roughness of the developing rollers 5 and 17 depends on the particle size of the toner to be used, the ten-point average roughness Rz specified in JIS B0601 is preferably 3 to 15 μm. For measurement of the ten-point average roughness Rz, a surface roughness tester SE-30H manufactured by Kosaka Laboratory was used.

When the surface roughness of the developing roller is less than Rz = 3 μm, a sufficient toner conveying force cannot be obtained and the density becomes insufficient. When the surface roughness exceeds 15 μm, sufficient charge cannot be applied to the transfer residual toner. In other words, the transfer residual toner cannot be sufficiently collected, or the toner adheres to the non-image portion, so-called "fogging" occurs. When a toner having an average volume particle diameter of 6 μm is used, preferably, the surface roughness of the developing roller can be set to Rz = 5 to 12 μm. When the particle size of the toner is smaller, it is preferable to make Rz slightly smaller.

The coefficient of kinetic friction in the surface layers of the developing rollers 5 and 7 is preferably 0.01 to 0.8, and more preferably 0.01 to 0.4. Since the transfer residual toner charged to the opposite polarity must be changed to the normal charge polarity, the frictional charging ability to the toner is too low with a developing roller having a dynamic friction coefficient of less than 0.01, and a negative charge is applied to the toner. It will be difficult to do. Conversely, if the kinetic friction coefficient is 0.8 or more, toner scatters around the image area during development,
It is not preferable because so-called “development scattering” increases.

In the present invention, the dynamic friction coefficient of the developing roller is
It was measured by the following method. As shown in FIG. 4, a stainless steel plate L having a thickness of 0.03 mm and a weight W2 is wrapped around the developing roller 5 (developing roller 17), and one end thereof is connected horizontally to the digital force gauge G, and the other end is connected to the other end. The thin plate L is attached to the surface of the developing roller 5 so that the weight Q of the weight W1 is attached and the thin plate L is pulled in the vertical direction, and the angle θ in the drawing becomes 45 degrees. When the value indicated by the digital force gauge G is stabilized (the gauge G is adjusted so that the reading becomes zero when no load is applied when the stainless steel sheet L is not connected), the developing roller 5 is rotated in the direction of arrow R in the figure. The sliding force between the developing roller 5 and the stainless steel sheet L at this time is measured by a gauge G. The measured value analog output from the gauge G is sampled at a frequency of 10 Hz by a recorder (not shown), and the sampled data is used to calculate a kinetic friction coefficient μ by the following equation (1) using a computer PC. 5 was calculated by averaging the calculated values for one rotation.

Μ = 1 / θ × ln (F / W) (1) where F: measured value of digital force gauge W: total weight of W1 and W2

The reason why the coefficient of kinetic friction of the surfaces of the developing rollers 5 and 17 was measured for the stainless steel sheet L as described above is that the photosensitive drum 1 is also formed on a metal substrate such as aluminum and has a thickness of about 10 μm. This is because it is closer to the current situation to compare the dynamic friction coefficients of the surfaces of the developing rollers 5 and 17 with those of a stainless steel plate, and it is judged that the coefficient of dynamic friction is more appropriate.

The contact pressure of the developing rollers 5 and 17 against the photosensitive drum 1 is preferably a linear pressure of 10 to 50 g / cm. To measure the linear pressure, a developing blade 19 shown below was used.
The measurement method similar to the linear pressure measurement in was used. When the linear pressure of the developing roller is less than 10 g / cm, the contact state with the photosensitive drum 1 becomes unstable, and when the linear pressure exceeds 150 g / cm, the external additive mixed with the toner may cause the surface of the toner due to pressure or the like. , The toner is deteriorated, and the chargeability of the toner by the developing blade 9 is reduced.

The developing blade 19 of the color developing unit 10 (10M to 10Y) is formed by bending a stainless steel plate having a thickness of about 0.1 mm in a direction opposite to the developing roller 17 at a position of about 2 mm from the tip. Thus, the bent portion comes into contact with the developing roller 17 in a state where the bent portion bites into the developing roller 17. The contact pressure of the developing blade 19 is preferably about 15 to 35 g / cm in linear pressure. If the linear pressure of the developing blade 19 is less than 15 g / cm, the toner cannot be appropriately charged, resulting in fog and deterioration of image quality. When the linear pressure exceeds 35 g / cm, the external additive mixed with the toner is easily peeled off from the toner surface due to pressure or the like, and the toner is deteriorated.
9 reduces the chargeability of the toner.

A method for measuring the linear pressure of the developing blade 19 is as follows: a drawn plate is 100 mm long × 15 mm wide × 3 mm thick.
A stainless steel thin plate of 0 μm is used
A stainless steel sheet having a size of 30 mm × width 30 mm × thickness 30 μm is prepared by folding it at a half position in the longitudinal direction, a drawing plate is inserted between the folded sandwich plates, and the sandwich plate is developed with the developing roller 17 and the developing blade 19. Insert between In this state, a load meter such as a spring meter is attached to the pull-out plate, the pull-out plate is pulled out at a constant speed by the load meter, and the value (g) of the load meter at that time is read. The length of the drawing plate is 1.5c
By dividing by m, the linear pressure of the developing blade 19 on the developing roller 17 is obtained in units of g / cm.

The developing blade 8 of the black developing device 4 includes
An iron thin plate having a thickness of 1 mm of the magnetic member was used. Developing roller 5
The gap between the blade and the developing blade 8 was about 100 μm.

The magnet roller 6 in the developing roller 5 has an outer diameter of 14 mm and has four magnetic poles N1, S1, N2 and S2. The strength of the magnetic force is N1: 80 mT, S1:
60 mT, N2: 75 mT, and S2: 95 mT.

In the present invention, the non-magnetic toner for one-component development is obtained by observing the tomographic surface of the toner particles using a transmission electron microscope (TEM) in a state where the wax component is not compatible with the binder resin. Preferably, they are dispersed in the form of islands in a spherical and / or spindle shape. By dispersing the wax component as described above and encapsulating in the toner,
Since deterioration of the toner, contamination of the image forming apparatus, and the like can be prevented, good chargeability is maintained, and a toner image excellent in dot reproduction can be formed for a long period of time. In addition, since the wax component acts efficiently at the time of heating, the low-temperature fixability and the offset resistance can be satisfied.

A specific method for observing the tomographic plane of the toner particles is to obtain an effect obtained by sufficiently dispersing the toner particles in an epoxy resin curable at room temperature and then curing the same in an atmosphere at a temperature of 40 ° C. for 2 days. The product is stained using ruthenium tetroxide and, if necessary, osmium tetroxide, and then a flaky sample is cut out using a microtome with diamond teeth, and the tomographic morphology of the toner particles is observed with a TEM. .

In observing the tomographic morphology, a ruthenium tetroxide dyeing method was used to give a contrast between the materials by utilizing a slight difference in crystallinity between the wax component used and the resin constituting the outer shell. Preferably, it is used. FIG. 5 schematically shows two typical tomographic forms of toner particles observed in this manner. In the toner particles used in this example, it was observed that the wax component was encapsulated by the outer shell resin.

The wax component was measured at a temperature of 40 to 130 ° C. when the temperature was raised in a DSC curve measured by a differential scanning calorimeter.
Those having the maximum endothermic peak in the region are used. By having the maximum endothermic peak in the above-mentioned temperature range, it greatly contributes to low-temperature fixing, and also effectively develops releasability. When the maximum endothermic peak is less than 40 ° C., the self-cohesive force of the wax component becomes weak, and as a result, the hot offset resistance deteriorates and the gloss becomes too high. On the other hand, when the maximum endothermic peak exceeds 130 ° C., the fixing temperature becomes high, and it becomes difficult to appropriately smooth the surface of the fixed image. Not preferred from the point.

Further, when a toner is directly obtained by a polymerization method in which granulation and polymerization are performed in an aqueous medium, if the maximum endothermic peak temperature is high, problems such as precipitation of a wax component mainly during granulation occur. Absent.

The measurement of the maximum endothermic peak temperature of the wax component is performed according to ASTm D3418-8. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of the calorific value uses the heat of fusion of indium. An aluminum pan (dish) was used as a measurement sample, an empty pan was set as a control, the temperature was raised and lowered once, a pre-history was obtained, and the measurement was performed at a rate of 10 ° C./min. .

As the above wax component, paraffin wax, polyolefin wax, Fischer-Tropsch wax, amide wax, higher fatty acid, ester wax, derivatives thereof, and graft / block compounds thereof can be used.

In the present invention, the toner preferably has a shape factor SF-1 value of 100 to 160 and a shape factor SF-2 value of 100 to 140, more preferably a value measured by an image analyzer. Shape factor SF-1 is 100
To 140 and SF-2 are 100 to 120. By setting the value of SF-2 / SF-1 to 1.0 or less while satisfying the above conditions, not only the various characteristics of the toner but also the matching with the image analysis device become extremely good.

In the present invention, the shape factors SF-1, SF
"-2" means that FE-SEM (S-800) manufactured by Hitachi, Ltd. was used, and 100 toner particle images magnified 500 times were randomly sampled, and the image information was obtained from an image manufactured by Nicole via an interface. Analysis equipment (Lusex
It was introduced in 3), analyzed, and defined as a value calculated from the following equation.

SF-1 = ｛(MXLNG) ² / ARE
A｝ × (π / 4) × (100) SF-2 = {(PERI) ² / AREA} × (1/4
π) × (100) where AREA: projected area of toner, MXLNG: absolute maximum length, PERI: circumference

The shape factor SF-1 of the toner indicates the degree of roundness of the toner particles. As the SF-1 increases, the shape gradually changes from spherical to irregular. SF-2 indicates the degree of unevenness of the toner particles. As SF-2 increases, the unevenness of the toner surface becomes remarkable.

When SF-1 exceeds 160, the transfer efficiency is lowered and the amount of untransferred toner is increased, so that the fusion of the toner to the photosensitive drum 1 or the like is likely to occur.

To increase the transfer efficiency of the toner image, the shape factor SF-2 is 100 to 140, and SF-2 / S
The value of F-1 is preferably 1.0 or less. SF-2 / S
When F-1 exceeds 1.0, the surface of the toner particles is not smooth, the toner particles have many irregularities, and the transfer efficiency from the photosensitive drum to the transfer material (paper or the like) tends to decrease. is there.

When the transfer efficiency is reduced, it becomes difficult to uniformly charge the surface of the photosensitive drum with the primary charger (when a large amount of toner remains, the surface below the photosensitive drum is hardly charged). In order to stabilize, it is preferable to have as high a transfer efficiency as possible.

In the present invention, the particle diameter of the toner is preferably 10 μm or less in terms of weight average particle diameter in order to solidly develop minute latent image dots for the purpose of improving image quality. It is preferably 4 to 8 μm, and the coefficient of variation (A) in the number distribution is preferably 35% or less.

In the case of toner particles having a weight average particle diameter of less than 4 μm, a large amount of toner remains on the photosensitive drum or the intermediate transfer member due to a decrease in transfer efficiency, and further, causes non-uniform unevenness of an image due to fogging or poor transfer. Which is not preferable for use in the present invention. The toner has a weight average particle size of 10
If it exceeds μm, fusion of the toner to members such as the surface of the photosensitive drum and the intermediate transfer member tends to occur. When the coefficient of variation in the number distribution of toner particles exceeds 35%, the tendency is further enhanced.

The particle size distribution of the toner can be measured by various methods. In the present invention, the measurement was performed using a Coulter counter.

For example, a call counter TA-II type (manufactured by Coulter) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number distribution and a volume distribution, and a personal computer were connected. As the electrolytic solution, a 1% NaCl aqueous solution was prepared using primary grade sodium chloride. As a commercially available 1% NaCl aqueous solution, for example, ISOTON II (manufactured by Coulter Scientific Japan) can be used.

To 100 to 150 ml of the above-mentioned electrolytic solution, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 2 to 20 mg of the toner of the measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and is subjected to a dispersion treatment of, for example, 100 μm by the above-mentioned Coulter Counter TA-II.
Using an aperture of μm, 2 to 40
The particle size distribution of the μm toner particles is measured, and then the value of the particle size distribution according to the present invention is determined.

Coefficient of variation A in number distribution of toner particles
Is a coefficient of variation A = (S / D1) × 100, where S is a standard deviation value in the number distribution of toner particles, and D1: a number average particle diameter of toner particles (μm).

The surface of the toner particles is coated with an external additive,
It is preferable to use the toner so that a desired amount of charge is easily imparted to the toner. The coverage of the toner particles with the external additive is preferably 5 to 99%, more preferably 10 to 9%.
9%.

In order to determine the coverage of the external additive on the surface of the toner particles, 100 toner particle images were randomly sampled using FE-SEM (S-800) manufactured by Hitachi, Ltd.
The image information is introduced into an image analysis device (Lusex3) manufactured by Nicole via an interface. The obtained image information is binarized because the brightness of the toner particle surface portion and that of the external additive portion are different, and is binarized and the area SG of the external additive portion and the area of the toner particle portion (including the area of the external additive portion). It is obtained by dividing into ST, and is calculated from the formula of external additive coverage (%) = (SG / ST) × 100.

[0120] From the viewpoint of durability when added to the toner, the external additive is 1/1/1 of the weight average particle diameter of the toner particles.
The particle size is preferably 0 or less. In the present invention, the particle diameter of the external additive means an average particle diameter thereof obtained by observing the surface of the toner particles with an electron microscope.

Examples of the external additive include metal oxides (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide,
Tin oxide, zinc oxide, etc., nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal salt (calcium sulfate, barium sulfate, calcium carbonate, etc.), aliphatic metal salt (zinc stearate, calcium stearate, etc.) , Carbon black, silica and the like are used.

These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, per 100 parts by weight of the toner particles. These external additives
They may be used alone or in combination. Those subjected to a hydrophobizing treatment are more preferable.

When the amount of the external additive is less than 0.01 parts by weight, the fluidity of the toner is deteriorated, the efficiency of transfer and development is reduced, and the density unevenness of the image and the area around the image area are reduced. Toner scattering occurs. On the other hand, when the amount of the external additive is 10
When the amount exceeds the weight part, an excessive amount of the external additive adheres to the photosensitive drum and the developing roller, thereby deteriorating the chargeability to the toner and disturbing the image.

In the present invention, the magnetic toner for one-component development has a spherical shape as follows. As a method for producing a spherical toner, a resin, a release agent composed of a low softening point substance, a colorant, a charge control agent, and the like, after uniformly dispersed using a pressure kneader, an extruder, or a media disperser, The target is impinged mechanically or under a jet stream to pulverize to a desired particle size, and then subjected to a plastic sphering treatment. Further, through the classification process, sharpen the particle size distribution,
Obtain toner.

Examples of an apparatus for performing the plastic sphering treatment include a "hybridization system" manufactured by Nara Machinery Co., Ltd. and a "Turbomill" manufactured by Turbo Kogyo.
For example, a hybridization system has a rotating plate on which a blade is mounted, and by rotating the rotating plate at a high speed, the toner in the circulating airflow strikes the blade rotating at a high speed. At the time of the collision, the convex portion on the toner surface undergoes plastic deformation due to impact energy and is smoothened, and the toner as a whole undergoes a spherical shape change.

As a result, the toner shape factor SF-
1. A magnetic toner satisfying SF-2 can be manufactured, and high transfer efficiency can be achieved for the magnetic toner.

A major feature of the present invention is that simultaneous development and cleaning can be performed even when image formation is interrupted due to some cause during image formation, for example, occurrence of a jam. This will be described with reference to FIG. FIG. 6 shows a sequence in a recovery from a jam occurrence.

First, normal image formation is performed (step S1). During image formation, conveyance of the transfer material P is observed by a jam detection sensor (not shown) (S2, S
3) If no jam occurs, the process returns from step S3 to step S2. As the jam detection sensor, a known sensor such as a lever system or an optical detection system can be used.

When the jam is detected, the user is notified of the jam and the transfer material P being transported is removed (S4). After the user removes the transfer material P, the process enters a return mode.

In the return mode, first, the drive roller 14
Moves in the direction of arrow C, and moves downward on the upstream side of the conveyor belt 13 (S5). Accordingly, the photosensitive drums 1M, 1C, and 1Y of the magenta, cyan, and yellow colored image forming units PM, PC, and PY are separated from the contact state with the transport belt 13 and the photosensitive drums of the black image forming unit PK are exposed. The drum 1K stays in contact with the conveyor belt 13.

Steps S6 to S10 are for the black image forming unit PK, and steps S11 to S14 are for the color image forming units PM, PC and PY.

First, in step S6, the power of the transfer charger 9K of the black image forming portion PK is turned on. The bias applied to the transfer charger 9K has the opposite polarity to the bias applied during normal image formation. That is, a negative bias is applied when the negatively charged toner is used. Thus, the non-magnetic toner T and the magnetic toner t on the transport belt 13 are urged from the transport belt 13 in the direction of the photosensitive drum 1K, and are transferred to the photosensitive drum 1K. Since the transport belt 13 and the photosensitive drum 1K rotate, the toner on the transport belt 13 transfers to the photosensitive drum 1K one after another (S7).

Next, the primary charger 2K is turned on (S
8) The developing bias power supply 16 to the developing roller 5 is turned on (S9). The non-magnetic toner T and the magnetic toner t transferred to the photosensitive drum 1K in step S7 are charged to a negative polarity by being charged by the primary charger 2K, and are contacted with the developing roller 5 by the developing bias applied to the developing roller 5. At the contact portion with the drum 1K, the toner is transferred to and collected on the developing roller 5 carrying new magnetic toner. There is no problem if the developing bias applied at this time is a voltage that urges the non-magnetic toner T and the magnetic toner t transferred to the photosensitive drum 1K in step S7 to the developing roller side.

The above-described steps S6 to S9 are executed almost simultaneously without a time interval. Note that there is no problem if the steps S6 to S9 are performed simultaneously.
After the steps S6 to S9 have been executed for a predetermined time, in step S10, an instruction to end the collection of the non-magnetic toner and the magnetic toner is issued.

The non-magnetic toner and the magnetic toner collected by the developing roller 5 are, as described above,
When it reaches between the blow-out prevention pole N2 of the magnet roller 6 and the pumping pole S2, the magnetic binding force weakens,
The stirring of the magnetic toner t in the developing device 4 causes the magnetic toner t to be peeled off from the developing roller 5 and collected in the developing device 4. The collected toner is stirred and mixed with the remaining toner t by the stirring member 7.

Of the collected toner, the magnetic toner is again restrained by the pumping pole S2 and is carried by the developing roller 5, and is used for developing a black toner image.

Since the collected non-magnetic toner has the same charge polarity as the magnetic toner, a repulsive force is generated and it is easy to be separated, and since it is non-magnetic, a magnetic binding force does not work. And is not basically carried on the developing roller 5. However, since the toner particles are mixed in the magnetic toner, the toner particles may be carried on the developing roller 5 by a small amount of adhesion between the powder particles. However, the presence of a small amount of color toner in the black toner does not cause a problem because it does not change the color tone of the image.

As described above, in the present embodiment, the black developing device 4 also functions as a developing device and as a cleaning member for color toner.

Next, toner collection in the colored image forming units PM to PY in steps S11 to S14 will be described. First, in step S11, the photosensitive drums 1M, 1C, 1
Y starts to rotate. Since the transport belt 13 has already been separated in step S5, there is no toner transfer from the transport belt 13 to the photosensitive drums 1M, 1C, and 1Y. Next, the primary chargers 2M, 2C, and 2Y are turned on (S12), and the developing device 1
0M, 10C, 10Y developing rollers 17M, 17C, 1
The developing bias power supply 21 to 7Y is turned on (S1
3).

When the photosensitive drum 1 is stopped during the image formation,
The magenta non-magnetic toner remaining in M is charged by the primary charger 2M and charged to a negative polarity, and the developing bias applied to the developing roller 17M causes the developing roller 1 to be charged.
At the contact portion between the photosensitive drum 7M and the photosensitive drum 1M, the toner is transferred onto the developing roller 17M carrying new non-magnetic toner, and collected by the magenta developing device 10M. Similarly, the cyan non-magnetic toner remaining on the photosensitive drum 1C is
At 0C, the yellow non-magnetic toner remaining on the photosensitive drum 1Y is collected by the yellow developing unit 10Y.

The steps S11 to S13 are executed almost simultaneously without a time interval. There is no problem if the steps S11 to S13 are executed simultaneously. After the steps S11 to S13 have been executed for a predetermined period of time, an instruction to end the collection of the non-magnetic toner is given in step S14.

When the toner collecting process in all the image forming units PM to PK is completed in steps S10 and S14, it is detected in step S15, and the transport belt 13 is moved upward in the direction opposite to the arrow C to return to the original position. The image forming apparatus returns to the state at the time of image formation (S16), and notifies that the image forming apparatus has returned and the next image formation is possible (S17).

In this embodiment, the transfer material is transported by the transport belt 13 and the image forming units (PM, PC, PY, P
K), the toner image was directly transferred onto the transfer material.
An intermediate transfer member (intermediate transfer drum) is used in place of the conveyor belt, images of four colors are formed on the intermediate transfer member, and the images are collectively transferred onto a transfer material by a separately provided known transfer unit. The same is true for

In this embodiment, 2,000 color images are formed by the image forming apparatus shown in FIG. 1, and the image forming apparatus is intentionally stopped during the formation of one image for every 500 sheets. The operation of the compliant return process was performed.
The image immediately after the return of the image forming apparatus was sampled, and the change in the color tone due to the color mixture of the toner was visually observed, but no change in the color tone was observed.

As described above, in this embodiment, the non-magnetic toner is used for the magenta, cyan, and yellow color developing devices, while the magnetic toner is used for the black developing device.
This black developing device was used as a developing device for recovering toner when a jam occurred. If magenta, cyan, and yellow non-magnetic color toners are collected by a black developing device, even if color toners are mixed into black magnetic toners,
Since the color toner is not carried by the magnet roller on the developing roller of the black developing device, the development of the black toner image is not affected. As a result, simultaneous development and cleaning can be performed without causing toner color mixing, and a good full-color image free from density unevenness and color mixing can be obtained without requiring a special cleaning member. Can be reduced in size and cost.

Embodiment 2 FIG. 7 is a schematic structural view showing another embodiment of the image forming apparatus of the present invention. This embodiment shows a case where the present invention is applied to an intermediate transfer drum type full-color image forming apparatus.

The overall configuration of the image forming apparatus of this embodiment and the image forming operation will be described.

The photosensitive drum 1 is driven to rotate at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow in response to a print signal or the like from the outside. During rotation, the photosensitive drum 1 has a predetermined polarity by a primary charger (corona charger) 2.
Image exposure device 3 (a color separation / imaging exposure optical system for a color original image, a laser scanner for outputting a laser beam modulated corresponding to a time-series electric digital pixel signal of image information) 1) of a target color image by receiving image exposure by a scanning exposure system or the like.
An electrostatic latent image corresponding to a color component image (for example, a magenta component image) of the color is formed.

Next, the electrostatic latent image reaches the magenta developing device 10M of the first developing device as the photosensitive drum 1 rotates, and is developed by the first color magenta toner.
Visualized as a magenta toner image. At this time, the second to fourth cyan developing units 10C and the yellow developing unit 10C
The operation of the Y and black developing units 22 is stopped, does not act on the photosensitive drum 1, and does not affect the magenta toner image on the photosensitive drum 1.

The first to fourth developing units 10M to 10Y and 22 are mounted on the rotary developing unit 31 at intervals in the circumferential direction, and are installed so as to be able to freely contact and separate from the photosensitive drum 1. The developing devices 10M to 10Y and 22 move in the direction of the arrow to be sequentially conveyed to a position facing the photosensitive drum 1, where they come into contact with the photosensitive drum 1 and are used for development. Since the developing units 10M to 10Y are the same as in the first embodiment, the description is omitted.

Reference numeral 24 denotes an intermediate transfer drum which is in contact with the photosensitive drum 1 and is driven to rotate at the same peripheral speed in the counterclockwise direction indicated by the arrow. The intermediate transfer drum 24 includes a pipe-shaped metal core and an elastic layer formed on an outer peripheral surface thereof.

The magenta toner image of the first color formed on the photosensitive drum 1 includes the photosensitive drum 1 and the intermediate transfer drum 2
In the process of passing through the nip portion with No. 4, the image is transferred to the outer peripheral surface of the intermediate transfer drum 24 by the electric field formed by the primary transfer bias applied to the intermediate transfer drum 24 by the primary transfer bias power supply 29 (primary transfer, Intermediate transfer).

After the transfer of the first magenta toner image onto the intermediate transfer drum 24, the surface of the photosensitive drum 1 is finished.
As in the first embodiment, the magenta toner remaining after transfer is collected by the magenta developing device 10M by receiving the charge of the primary charger 2.

After the development of the magenta toner image is completed, the magenta developing device 10M is used only for the time corresponding to one rotation of the photosensitive drum 1 in order to collect the transfer residual toner corresponding to the rear end portion of the image. May be brought into contact with the photosensitive drum 1.

Similarly, the cyan toner image of the second color, the yellow toner image of the third color, and the black toner image of the fourth color are successively superimposed and transferred onto the intermediate transfer drum 24 in the same manner, and are synthesized corresponding to the target color image. A color toner image is formed. Similarly, in each of the developing devices 10C to 10K,
Each transfer residual toner is collected from the photosensitive drum 1.

The 4 superimposedly transferred on the intermediate transfer drum 24
The color toner image is transferred to the transfer material P fed to the intermediate transfer drum 24. The transfer material P is fed from the paper feed cassette 25 and supplied to the intermediate transfer drum 24 at a predetermined timing. At the same time, the transfer roller 26 to which the secondary transfer bias is applied sandwiches the transfer material P between the intermediate transfer drum 24. , The four color toner images on the intermediate transfer drum 24 are collectively transferred to the transfer material P (secondary transfer).

The transfer roller 26 is mounted on the lower surface of the intermediate transfer drum 24 so as to freely contact and separate from the intermediate transfer drum 24. The transfer roller 26 can be separated from the intermediate transfer drum 24 during the transfer of the first to fourth color toner images from the photosensitive drum 1 to the intermediate transfer drum 24.

Transfer material P to which four color toner images have been transferred
Is introduced into the fixing device 12, and the toner image is heated and fixed.

Next, regarding the black developing device 22, FIG.
This will be described below. This embodiment is different from the black developing unit 4 shown in FIG. 3 in that a contact-type developing blade 27 having elasticity is used as a toner regulating member of the black developing unit 22. Other configurations of the black developing device 22 are basically the same as those of the black developing device 4 of FIG. 3, and the same reference numerals in FIG. 8 as those in FIG. 3 denote the same members.

The contact type developing blade 27 has a thickness of about 0.1 mm.
Urethane rubber piece 2 on the tip of 1mm stainless steel plate
7a, and has rubber elasticity. The developing blade 27 is not limited to this, and may be a developing blade having a bent end portion of a stainless steel plate, like the developing blade 19 used in the color developing device 10 shown in FIG. It is also possible to make contact with spring elasticity. Further, since an elastic layer is provided on the surface of the developing roller 5, it is possible to directly contact a metal material as a developing blade.

In this embodiment, since the toner regulating member is the developing blade 27 which comes into contact with the developing roller 5, the toner carried on the developing roller 5 can be regulated by a mechanical force. Even if the non-magnetic toner mixed with the magnetic toner is slightly carried on the developing roller 5, the passage of the non-magnetic toner through the restricting portion is prevented as shown in FIG.
Thus, the black toner image can be more effectively prevented than the developing blade 8 having the above magnetic property, and the development of a black toner image with further improved prevention of color mixture of the color toner can be performed.

Next, when any trouble occurs during image formation,
For example, a description will be given of a process performed when image formation is interrupted due to a jam.

The steps from the start of image formation to the occurrence of a jam are the same as those in the first embodiment, and a description thereof will be omitted. When the jam is detected, the user is notified of the jam, the transfer material P being transported is removed, and then the recovery mode is entered.

First, the rotary developing unit 31 shown in FIG. 7 is rotated to bring the black developing device 22 into contact with the photosensitive drum 1. When the transfer roller 26 is in contact with the intermediate transfer drum 24, the transfer roller 26 is
Separated from 4.

Next, at the same time as the rotation of the developing roller 5, the photosensitive drum 1, and the intermediate transfer drum 24 of the black developing device 22 is started, the transfer reverse bias power source 30, the primary charger 2, and the developing bias power source 28 are turned on. The transfer reverse bias power supply 30 applies a bias having a polarity reverse to that of the transfer bias to the intermediate transfer drum 24. When a negatively charged toner is used, a negative bias is applied to the non-magnetic toner on the intermediate transfer drum 24 and The magnetic toner is urged from the intermediate transfer drum 24 toward the photosensitive drum 1 and transferred to the photosensitive drum 1 side.

The toner transferred to the photosensitive drum 1 is collected in the black developing unit 22 as in the first embodiment. Similarly, when the collected non-magnetic toner and magnetic toner pass through the blowout prevention pole N2 of the magnet roller 6 in the developing roller 5 and reach the pumping pole S2, the magnetic binding force is weakened. As the magnetic toner t in the developing device 22 is agitated, the magnetic toner t is peeled off from the developing roller 5 and accommodated in the developing device 22 to be mixed with the magnetic toner t.

The magnetic toner thus recovered is
It is again carried on the developing roller 5 by the pumping pole S2 of the magnet roller 6, and is used for developing a black toner image.

The collected non-magnetic toner is not restrained by the pumping pole S2 because the magnetic restraining force does not work, and is basically not carried by the developing roller 5, but is in a state of being mixed in the magnetic toner. In this embodiment, even if the magnetic toner is slightly carried on the developing roller 5 in a mixed state, the developing blade 27 that is in contact with the developing roller 5 may be used.
Is installed, it is possible to restrict the non-magnetic toner from passing through the restricting portion by restricting with a mechanical force. Therefore,
It is possible to develop a black toner image in which color mixture of color toners is further reduced, and as a result, it is possible to obtain a better full-color image without a change in color tone.

The post-jam restoration step is to clean and collect the remaining transfer residual toner remaining on the intermediate transfer drum 24 after the transfer of the four color toner images on the intermediate transfer drum 24 to the transfer material P is completed. The intermediate transfer drum 24 can be cleaned without requiring any special intermediate transfer member cleaning means.

In this embodiment, 2,000 color images are formed by the image forming apparatus shown in FIG. 7, and one image is formed for every 500 sheets. The operation of was performed. The image immediately after the return of the image forming apparatus was sampled, and the change in the color tone due to the color mixture of the toner was visually observed, but no change in the color tone was observed. In addition, the image was appropriately sampled during the image formation, but similarly, no change in the color tone of the image was observed.

As described above, in this embodiment, when a black toner is used for a magenta, cyan, and yellow color developing device using a non-magnetic toner, the black developing device uses a magnetic toner. Since a contact-type developing blade was used as a toner regulating member of the black developing device at that time,
By regulating the non-magnetic toner on the developing roller collected by the black developing device by the toner regulating unit, the prevention of color mixing of the non-magnetic toner with the magnetic toner can be further improved.
Therefore, it is possible to carry out simultaneous development and cleaning without causing color mixing of toner, to obtain a good full-color image free from density unevenness and color mixing without requiring a special cleaning member, and to reduce the size of the image forming apparatus. And cost reduction became possible.

Embodiment 3 Still another embodiment of the present invention will be described with reference to FIG. FIG.
7, the same members as those in FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted.

The present embodiment is characterized in that the non-magnetic toner collected on the developing roller 5 of the black developing device 33 is peeled off by a peeling member, thereby further preventing color mixing.

Hereinafter, the schematic configuration and operation of the image forming apparatus of this embodiment will be described.

The photosensitive drum 1 is rotationally driven at a predetermined peripheral speed in the clockwise direction indicated by an arrow in response to a print signal or the like from the outside. In the rotation process, a primary charger (corona charger) 2 has a predetermined polarity. The image is uniformly charged to a potential and then subjected to image exposure by the image exposure device 3, whereby an electrostatic latent image corresponding to the first color component image (for example, a magenta component image) of the target color image is formed.

In this embodiment, the magenta developing device 10M, the cyan developing device 10C and the yellow developing device 10Y of the first to third developing devices are installed in the rotary developing unit 32, and the black developing device 33 of the fourth developing device is It was set up separately and separately. Magenta, cyan, yellow color developing units 10M-1
0Y is moved toward and away from the photosensitive drum 1 by the rotation of the rotary developing unit 32, and the black developing device 33 is moved toward and away from the photosensitive drum 1 by the movement of the contact / separation member 34 at the rear thereof.

The electrostatic latent image formed on the photosensitive drum 1 is
As the photosensitive drum 1 rotates, the photosensitive drum 1 reaches the magenta developing device 10M of the first developing device, and is developed with the first color magenta toner by the developing bias applied from the developing bias power supply 28, and is visualized as a magenta toner image. At this time, the second and third cyan developing devices 10C, the yellow developing device 10Y, and the black developing device 22 are in the separated state and stopped operating, and do not act on the photosensitive drum 1; Does not affect magenta toner images. Since the developing units 10M to 10Y are the same as in the first embodiment, the description is omitted.

The intermediate transfer drum 24 comes into contact with the photosensitive drum 1 and is driven to rotate at the same peripheral speed in the counterclockwise direction indicated by the arrow. The magenta toner image of the first color formed on the photosensitive drum 1 includes a photosensitive drum 1 and an intermediate transfer drum 2.
In the process of passing through the nip portion with No. 4, the toner image is transferred onto the outer peripheral surface of the intermediate transfer drum 24 by the electric field formed by the primary transfer bias applied to the intermediate transfer drum 24 by the primary transfer bias power supply 29.

After the transfer of the first color magenta toner image onto the intermediate transfer drum 24, the surface of the photosensitive drum 1
As in the first embodiment, the magenta toner remaining after transfer is collected by the magenta developing device 10M by receiving the charge of the primary charger 2.

After the development of the magenta toner image is completed,
In order to collect the transfer residual toner corresponding to the rear end portion of the image, only the time corresponding to one rotation of the photosensitive drum 1 is required.
The magenta developing device 10M may be brought into contact with the photosensitive drum 1.

Thereafter, similarly, the second color cyan toner image, the third color yellow toner image, and the fourth color black toner image are sequentially superimposed and transferred onto the intermediate transfer drum 24, and are synthesized corresponding to the target color image. A color toner image is formed. Similarly, in each of the developing devices 10C to 10K,
Each transfer residual toner is collected from the photosensitive drum 1.

The 4 superimposedly transferred on the intermediate transfer drum 24
The color toner image is transferred to the transfer material P fed to the intermediate transfer drum 24, and then fixed to the transfer material P by the fixing device 12. The steps of the transfer and fixing are the same as those described above, and the description is omitted.

The black developing device 33 will be described with reference to FIG. In the present embodiment, the black developing device 33 includes a peeling roller 35 made of foamed rubber that is in contact with the developing roller 5 as a toner peeling member, and a peeling bias power source 36 that urges the negatively charged toner from the developing roller 5 toward the peeling roller 35. And Although the peeling roller 35 is used as the toner peeling member, the present invention is not limited to this. For example, a brush-like member,
A plate-shaped scraper or the like can also be used.

Now, as in the past, the black developing device 3
3, the developing roller 5 is cleaned.
The non-magnetic toner and the magnetic toner are collected and once carried thereon, but the toner is moved in the direction of the peeling roller 35 by the electric field formed by the peeling bias applied to the peeling roller 35 from the peeling bias power supply 36. Be energized. However, since the magnetic toner adheres to the developing roller 5 by the magnetic force, it is not separated, and only the non-magnetic toner is separated and collected by the stripping roller 35. Therefore, only the black toner can be carried on the developing roller 5 without causing color mixture of the color toners, and can be used for developing the black toner image.

To develop with the black developing device 33,
The developing roller 5 is brought into contact with the photosensitive drum 1 by the pressing of the developing device 33 by the separating member 34, the developing roller 5 is rotated to carry the magnetic toner t, and is regulated by the developing blade 27. Is brought to the developing section in contact with. Then, the magnetic toner adheres to the latent image on the photosensitive drum 1 and is developed by an electric field generated by a DC voltage applied from the developing bias power supply 37 to the developing roller 5.

Next, a description will be given of a process in the case where the image formation is interrupted due to a trouble such as the occurrence of a jam during the image formation.

The steps from the start of image formation to the occurrence of a jam are the same as those in the first embodiment, and a description thereof will be omitted. When the jam is detected, the user is notified of the jam, the transfer material P being transported is removed, and then the recovery mode is entered.

First, the black developing device 33 is brought into contact with the photosensitive drum 1 by the contact / separation member 34 shown in FIG. When the transfer roller 26 is in contact with the intermediate transfer drum 24, the transfer roller 26 is separated from the intermediate transfer drum 24.

Next, at the same time as the rotation of the developing roller 5, the photosensitive drum 1 and the intermediate transfer drum 24 of the black developing device 33 is started, the transfer reverse bias power source 30, the primary charger 2 and the developing bias power source 37 are turned on. The non-magnetic toner and the magnetic toner on the intermediate transfer drum 24 are urged from the intermediate transfer drum 24 toward the photosensitive drum 1 by the electric field generated by the transfer reverse bias power supply 30, and are transferred to the photosensitive drum 1 side. .

The toner transferred to the photosensitive drum 1 is collected in the black developing device 33 as in the first embodiment. When the collected non-magnetic toner and magnetic toner pass through the blowing prevention pole N2 of the magnet roller 6 in the developing roller 5 and reach the contact portion between the developing roller 5 and the peeling roller 35, the non-magnetic toner and the magnetic toner It is mechanically peeled off by rubbing. In this case, a voltage for urging the toner toward the peeling roller 35 may be applied to the peeling roller 35. The non-magnetic toner and the magnetic toner peeled off by the peeling roller 35 are conveyed in the direction of the stirring member 7 by the rotation of the peeling roller 35, and the magnetic toner t stored in the developing device 33 near the stirring member 37. Mixes with.

Only the recovered magnetic toner is carried again on the developing roller 5 by the pumping pole S2 of the magnet roller 6 together with the original magnetic toner t, and is used for developing a black toner image.

As a result, by developing only the magnetic toner, it is possible to develop a black toner image in which color mixture of color toners is further prevented, and it is possible to obtain a good full-color image with further less change in color tone.

As described in the second embodiment, also in this embodiment, after the above-described restoration process after the jam, the transfer of the four color toner images on the intermediate transfer drum 24 to the transfer material P is completed. It can be used for cleaning and collecting the transfer residual toner on the transfer drum 24, and the intermediate transfer drum 24 can be cleaned without a special intermediate transfer body cleaning means.

In this embodiment, 2,000 color images are formed by the image forming apparatus shown in FIG. 9, and the image forming apparatus is deliberately stopped during the formation of one image for every 500 sheets. The operation of was performed. The image immediately after the return of the image forming apparatus was sampled, and the change in the color tone due to the color mixture of the toner was visually observed, but no change in the color tone was observed. In addition, the image was appropriately sampled during the image formation, but similarly, no change in the color tone of the image was observed.

As described above, in the present embodiment, when a black toner is used for a magenta, cyan, and yellow color developing device using a non-magnetic toner, the black developing device uses a magnetic toner. In this case, the toner peeling member was installed on the developing roller of the black developing device. At this time, the non-magnetic toner collected by the black developing device was removed from the developing roller, and the toner was removed to the magnetic toner. This can further prevent the non-magnetic toner from mixing colors. Therefore, it is possible to carry out simultaneous development and cleaning without causing color mixing of toner, to obtain a good full-color image free from density unevenness and color mixing without requiring a special cleaning member, and to reduce the size of the image forming apparatus. And cost reduction became possible.

[0196]

As described above, according to the present invention,
Non-magnetic toner is used for the magenta, cyan, and yellow color developing devices, and magnetic toner is used for the black developing device. This black developing device is used as a developing device for collecting toner when the apparatus is stopped due to a jam or the like. did. If magenta, cyan, and yellow non-magnetic color toners are collected by the black developing device, the color toner is carried on the developing roller of the black developing device by the magnet roller even if the color toner is mixed with the black magnetic toner. Since it does not affect the development of the black toner image. As a result, cleaning can be performed simultaneously with development without causing color mixing of toner, and a good full-color image free of color mixing can be obtained without requiring a special cleaning member, and the image forming apparatus can be downsized. It has become possible to reduce costs.

When a contact-type developing blade is used as a toner regulating member of the black developing device, and the non-magnetic toner on the developing roller collected by the black developing device exerts a regulating force at the toner regulating portion, Alternatively, when a peeling member is provided to peel off the collected non-magnetic toner from the developing roller, the prevention of color mixing of the non-magnetic toner with the magnetic toner can be further improved, and uneven density and color mixing can be prevented. And a more favorable full-color image without defects can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view illustrating a non-magnetic one-component developing device of a color developing device installed in the image forming apparatus of FIG.

FIG. 3 is a cross-sectional view illustrating a magnetic one-component developing device of a black developing device installed in the image forming apparatus of FIG. 1;

FIG. 4 is an explanatory diagram showing a method of measuring a dynamic friction coefficient of a developing roller of a developing device.

FIG. 5 is a schematic diagram showing typical examples of a tomographic form of a toner used in the present invention.

FIG. 6 is a flowchart illustrating a toner collecting process in the image forming apparatus of FIG. 1;

FIG. 7 is a schematic configuration diagram showing another embodiment of the image forming apparatus of the present invention.

8 is a sectional view showing a black developing device installed in the image forming apparatus of FIG.

FIG. 9 is a schematic configuration diagram showing still another embodiment of the image forming apparatus of the present invention.

10 is a cross-sectional view illustrating a black developing device installed in the image forming apparatus of FIG.

FIG. 11 is a schematic view showing a conventional image forming apparatus.

FIG. 12 is a sectional view showing a non-magnetic one-component developing device installed in the image forming apparatus of FIG. 11;

FIG. 13 is a schematic view showing a conventional image forming apparatus of an intermediate transfer drum type.

FIG. 14 is a schematic view showing a conventional image forming apparatus using a simultaneous cleaning with development method.

FIG. 15 is a potential diagram illustrating a cleaning operation of transfer residual toner at the time of development by a developing device of the image forming apparatus of FIG. 14;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 primary charger 3 image exposure device 4, 22, 33 black developing device 5, 17 developing roller 6 magnet roller 8 developing blade 10 color developing device 13 transport belt 16 developing bias power supply 24 intermediate transfer drum 27 contact type developing blade 35 Toner stripping member T Non-magnetic toner t Magnetic toner

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) G03G 15/09 101 G03G 15/08 507L F-term (Reference) 2H005 AA06 AA08 AA15 AA21 AB10 CA14 CB07 EA03 FA06 FA07 2H030 AA04 AD01 AD02 AD03 BB23 BB24 BB33 BB34 BB42 BB44 2H031 AD01 AE01 BA02 BA03 CA02 2H073 AA03 AA07 BA02 BA09 BA21 BA43 CA02 CA22 2H077 AD06 AD35 BA10 DA24 DB08 DB14 EA13 EA14 EA15 EA24 GA01 GA13

Claims (15)

[Claims] 1. An electrophotographic photoreceptor, primary charging means for charging the electrophotographic photoreceptor, and a color developing device for developing and visualizing an electrostatic latent image formed by image exposure of the charged electrophotographic photoreceptor. And a plurality of developing devices each containing a different one-component developer.The visible images of the respective colors are superimposed and transferred onto a transfer material or an intermediate transfer member. In an image forming apparatus which is in contact with an electrophotographic photosensitive member and recovers a transfer residual developer on the electrophotographic photosensitive member to a developer carrier by a potential difference from the developer carrier, the image forming apparatus includes: Is a magnetic one-component developer using a magnetic one-component developer as a developer, and the other developer is a non-magnetic one-component developer using a non-magnetic one-component developer. An image forming apparatus comprising: 2. When the image forming apparatus is stopped in the middle of image formation and then returns, the developer carrier of the magnetic one-component developing device is brought into contact with an electrophotographic photosensitive member and the developer carrier is brought into contact with the developer carrier. A voltage for urging the developer on the electrophotographic photoreceptor toward the developer carrier is applied, and the developer adhering to the electrophotographic photoreceptor charged together with the electrophotographic photoreceptor by the primary charger is removed from the developer. The image forming apparatus according to claim 1, wherein the image is collected on a carrier. 3. A plurality of the electrophotographic photosensitive members are provided,
The plurality of developing devices are arranged one by one on the electrophotographic photosensitive member, and a visible image formed on each electrophotographic photosensitive member is superimposed on a transfer material conveyed by a transfer material conveying member in contact with the electrophotographic photosensitive member. When the image forming apparatus is transferred and returned after stopping, the contact with the transfer material conveying member is released while leaving only the electrophotographic photosensitive member on which the magnetic one-component developing device is disposed, and the non-magnetic The developer adhered to the transfer material conveying member from the electrophotographic photosensitive member provided with the one-component developing device is attached to the electrophotographic photosensitive member provided with the magnetic one-component developing device, and collected by the magnetic one-component developing device. The image forming apparatus according to claim 2. 4. The developer attached to the transfer material transport member is applied to the transfer material transport member with a bias having a polarity opposite to that of the transfer, and is applied to the electrophotographic photosensitive member in which the magnetic one-component developing device is disposed. 4. The image forming apparatus according to claim 3, wherein said image forming apparatus is attached. 5. The electrophotographic photosensitive member is provided with one electrophotographic photosensitive member, and the plurality of developing devices are installed so as to be able to contact and separate from the electrophotographic photosensitive member, and a visible image formed on the electrophotographic photosensitive member is transferred to an intermediate transfer member. Superimposed transfer, upon return after stopping the image forming apparatus, the developer carrying member of the magnetic one-component developing unit was brought into contact with the electrophotographic photosensitive member, and adhered to the electrophotographic photosensitive member from the intermediate transfer member. The image forming apparatus according to claim 2, wherein the developer is collected in the magnetic one-component developer. 6. The image forming apparatus according to claim 5, wherein the developer attached to the intermediate transfer member is applied to the electrophotographic photosensitive member by applying a bias having a polarity opposite to that of the transfer to the intermediate transfer member. 7. The magnetic one-component developing device according to claim 1, further comprising an elastic regulating member abutting on the developer carrier as a regulating member for regulating the magnetic one-component developer carried on the developer carrier. 7. The image forming apparatus according to any one of items 6. 8. The image forming apparatus according to claim 1, wherein said magnetic one-component developing device has a developer peeling member abutting on a developer carrier. 9. A removing bias is applied to the developer peeling member in a direction for urging the developer adhered on the developer carrier toward the developer peeling member when the developer is collected. The image forming apparatus according to any one of the above items. 10. The developer comprises at least a binder resin,
10. A toner comprising a non-magnetic toner containing a coloring agent and a wax, wherein the wax is contained in the toner particles in a substantially spherical and / or spindle-shaped island shape without being compatible with the binder resin. The image forming apparatus according to any one of the above items. 11. The spherical coefficient SF-1 of the developer is 10
0-160, SF-2 is 100-140.
11. The image forming apparatus according to any one of items 10 to 10. 12. The spherical coefficient SF-1 of the developer is 10
0 to 140, 1 to 11 in which SF-2 is 100 to 120
The image forming apparatus according to any one of the above items. 13. The spherical coefficient SF-2 and SF of the developer.
13. The image forming apparatus according to claim 11, wherein a ratio SF-2 / SF-1 of -1 is 1.0 or less. 14. The wax has a melting point of 40 to 130 ° C.
The image forming apparatus according to claim 9, wherein: 15. The image forming apparatus according to claim 1, wherein an external additive is added to the developer, and the coverage of the external additive on the developer surface is 5 to 99%. apparatus.