JPH02275977A - developing device - Google Patents

Abstract

PURPOSE:To perfectly remove developer remaining on the surface of a developer supporting means by providing an electric field generation means between the repulsive magnetic poles of a magnetic field generation means in the developer on an upstream side from a regulating member and peeling and removing the developer held in the electric field generation means. CONSTITUTION:The electric field generation means 7 is provided between the repulsive magnetic poles S2 and S3 of the magnetic field generation means 4 in the developer on the upstream side from the regulating member 5 and a developer peeling means 8 for peeling and removing the developer 2 held in the means 7 is disposed. Since all the developer 2 remaining on the surface of the developer supporting means 6 after passing a developing position is peeled off and new developer 2 is always supplied to all the surface to form a thin coating layer having uniform specified thickness, the difference of development caused by the difference of image history is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a development device using a one-component developer applied to a developing device, particularly an image forming device such as an electrophotographic copying machine, an electrostatic recording machine, or a magnetic recording machine. It relates to a developing device.

[Kutateogi] Conventionally, there is a jumping development method as a development method using a -component developer. In this jumping development method, a developer (hereinafter also referred to as toner) is applied to the surface of a developer support means at a predetermined thickness to form a uniform thin coat layer, and the coat layer is transported to a development position. The electrostatic latent image bearing surface of the latent image supporting means is opposed to the electrostatic latent image bearing surface of the latent image supporting means with a required distance maintained, and the developer is caused to fly from the developer supporting means to the electrostatic latent image bearing surface by the electrostatic attraction. Yes (for example, Special Publication No. 41947
5, US Pat. No. 2,833,400).

In this method, not only is the developer not attracted to the non-image area of the electrostatic latent image bearing surface where there is no latent image potential, but the developer is not carried on the surface of the developer support means as in the conventional contact development method. Since the developer does not come into contact with the electrostatic latent image bearing surface, good development can be achieved with no fogging in non-image areas.

Furthermore, since no carrier particles are used, good effects such as no fluctuation in the developer mixing ratio and no deterioration of the carrier particles can be obtained.

In addition, the present applicant has proposed Japanese Patent Application No. 52-109240 (first development method) and Japanese Patent Application No. 53-92108 (second development method) as a development method different from the development method described above. ) has previously proposed a completely new development lJ: as described in .

In the first developing method described in 1, a -component magnetic developer, a developer supporting means (non-magnetic), and a magnetic field generating means are arranged in this order, and the surface of the developer holding means is heated by the magnetic force of the magnetic field generating means. A thin uniform coating layer of a developer is formed thereon, and the coating layer is opposed to the latent image supporting means with a small distance therebetween so as not to contact the electrostatic latent image bearing surface. Then, by the electrostatic attraction of the electrostatic latent image bearing surface of the latent image supporting means, the portion of the developer coating layer facing the image area is stretched, and the image is developed on the supporting surface. In this developing method as well, the developer coating layer of the developer supporting means does not come into contact with the non-image area of the electrostatic latent image bearing surface, and a developed image with no fog can be obtained during development.

In addition, in the second developing method described in "-", when carrying out the first developing method, a low frequency AC bias voltage is applied to the developer supporting means as a developing bias voltage, and furthermore, a low frequency AC bias voltage is applied to the developer supporting means as a developing bias voltage. The distance between the electrostatic latent image bearing surface and the opposing surface of the developer supporting means is changed over time. In this type of development method, the developer reaches the non-image area of the electrostatic latent image bearing surface at the beginning of development to develop the halftone area, and over time, the developer that has reached the non-image area is removed. The developer is returned to the original developer supporting means side, and as a result, it reaches only the image area. As a result, compared to the jumping development method described above, the 14 developability of the halftone portion becomes better. Moreover, it is possible to realize fog-free development.

In this way, in the method of developing by using a -component developer and moving the developer from the developer support means to the non-contact latent image support means by electrostatic attraction, the development performance, image reproducibility, Extremely superior in terms of agent life, etc.

However, even in the above-mentioned developing method, there are problems as described below when putting it into practical use.

That is, differences in image history cause differences in image density. Particularly, density unevenness tends to occur in halftone areas, and in extreme cases, characters become thick or thin.

"Image history" as used herein means the progress of image and non-image formation on the electrostatic latent image bearing surface of the latent image supporting means, and the image density is affected by the developer in the developer supporting means. This is because there is a problem with the coating layer.

To explain this point in detail, the developer in the developer support means is placed in the electrostatic latent image 1[!] at the development position. In order to develop the image area on the striking surface, the developer is drawn to the electrostatic latent image bearing surface by electrostatic attraction, and is removed from the surface of the developer supporting means, or only a small amount remains.

On the other hand, in the non-image area, all or most of the developer in the developer support means remains in the developer support means even at the development position. As a result, new developer is supplied to the surface portion of the developer support means that has received an image history at the next developer supply, but to the surface portion of the developer support means that has received a non-image history, new developer is supplied. , the previous developer remains and no new developer is supplied at the next developer supply. If such a non-image history is repeatedly experienced at the same location, the amount of developer tripo-coating at that location on the surface of the developer support means changes, and furthermore, developer deterioration and surface contamination of the developer support means occur. etc. may occur.

As a result, the difference in history between images and non-images causes a difference in the state of the developer on the surface of the developer supporting means, resulting in a difference in developing ability and quality of the final image. In particular, this phenomenon occurs when a large number of originals with black or white band images in the vertical direction are copied.

Of course, differences in images (particularly halftone images) due to differences in history between images and non-images vary depending on various conditions. For example, if the supply of new developer to the developer support means is insufficient after the image history, if there is an electrostatic latent image corresponding to that location again in the next stage, the density of the developed image will decrease. do. Furthermore, when the amount of coating after the non-image history is reduced, if an electrostatic latent image is present at that location in the next stage, the density of the developed image will decrease.

In this way, the difference in developability due to the difference in image history can be solved by stripping off all the remaining developer on the surface of the developer supporting means after passing the development position, and constantly supplying new developer to the entire surface. This problem can be solved by forming a thin coating layer with a uniform thickness.

For this reason, as shown in FIG. 5, conventionally, residual developer is scraped off from the surface of the developing sleeve 3 as the developer supporting means at a location past the development position using a mechanical means such as a scraper 11. has already been done. However, in such a mechanical method, the scraper 11 must be brought into strong sliding contact with the surface of the developer supporting means, which causes scratches on the surface, wear and tear on the scraper, and causes the scraper to become loose. I had something to do.

As a result, black lines, white lines, etc. may appear on the image.

For this purpose, as shown in FIG. 6, a gap g3 between the developing sleeve 3 and a gap
A method has also been proposed in which the toner is removed from the developing sleeve L without damaging the developing sleeve 3 and the electrode roller 7 by providing an electric field generating means such as the electrode roller 7. However, even with these methods,
Because one-component magnetic toner is used as a developer,
Some of the toner remained on the surface of the developing sleeve 3 due to the magnetic force of the magnet roller 4 inside the developing sleeve 3, and could not be stripped off.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and its first object is to remove residual developer after development on the surface of the developer support means, and to remove the remaining developer from the surface of the developer support means in the next stage of development. An object of the present invention is to provide a developing device that achieves the supply of new developer to all of the surfaces and eliminates the difference in history between images and non-images.

Further, a second object of the present invention is to provide a developer removing means for removing residual developer from the surface of the developer supporting means, and having a predetermined distance from the developer supporting means;
Damage to the surface and the electric field generating means is avoided by providing an electric field generating means at a predetermined position and removing the residual developer using the magnetic force within the developer supporting means and the electrostatic attraction of the electric field generating means. The object of the present invention is to provide a durable developing device.

A third object of the present invention is to set the moving direction of the electric field generating means in the forward direction of the developer transport direction on the surface of the developer supporting means, thereby preventing developer clogging.
To provide a developing device which avoids spillage and the like.

Furthermore, a fourth object of the present invention is to retain the residual developer in the electric field generating means in order to prevent the residual developer attracted to the electric field generating means from being deposited on the surface of the electric field generating means. It is an object of the present invention to provide a developing device equipped with a developer removing means for removing the developer.

The above object is achieved by the developing device according to the present invention. That is, in summary, the present invention provides a developer supporting means that carries a developer on its surface and transports it to a developing position by the magnetic force of a magnetic field generating means fixedly arranged in an internal space, and a developer supporting means that supports the developer on the surface thereof and transports the developer to a developing position. a developer supply means for supplying the developer;
In a developing device having a regulating member for regulating the thickness of the developer coat layer on the developer supporting means, a repulsive magnetic pole is disposed in the magnetic field generating means in the developer on a second flow side from the regulating member. An electric field generating means that moves while maintaining a gap with the developer supporting means is disposed in between, and a developer stripping means is disposed for peeling and removing the developer held by the electric field generating means. This is a developing device.

That is, in the developing device of the present invention, the developer on the developer support means 2 is stripped off, the state of the remaining developer on the developer support means that has received an image/non-image history is made uniform, and then a new developer is removed. By supplying developer, differences in image history are eliminated and good images are obtained.

Here, by providing an electric field generating means as the developer stripping means on the developer supporting means while maintaining a gap with the developer supporting means, the developer can be removed without damaging the developer supporting means and the developer stripping means. The developer from the support means can be peeled off.

Furthermore, by providing this developer stripping location between the repelling magnetic poles of the magnet roller 4 as shown in FIG. 1, it is possible to strip the developer from the developer supporting means more effectively. Become.

Furthermore, if the electric field generating means is moved in one direction relative to the developer supporting means and the counter, developer clogging, spillage, etc. will occur, but in the developing device δ of the present invention, the moving direction of the electric field generating means is Since it is moved in the same direction as the means, that is, in the forward direction, clogging of the developer, spillage of the developer, etc. can be prevented.

Furthermore, by providing a developer peeling means for peeling off and removing the developer held by the electric field generating means, the developer supporting means is provided.
The developer can be removed uniformly and stably by the electric field generating means. If this developer stripping means is not provided, the electric field generating means will rub the developer support means while holding a large amount of developer, and the developer on the developer support means will not be sufficiently stripped off. It may become impossible to do so or cause unevenness. It is not necessary for this developer removing means to completely strip off the developer held by the electric field generating means. By regulating the layer thickness of the developer on the electric field generating means, the electric field generating means
Even if a certain amount of developer is retained, it is possible to effectively strip off the developer from the developer support means, and the mechanical precision of the developer stripping means is not strictly required. Further, even if the developer removing means and the electric field generating means are damaged due to long-term use, the developer on the developer supporting means can be sufficiently stripped off by the electric field generating means.

In addition, in the case of a developing method in which the developer supporting means rotates, there is an appropriate range for the circumferential speed ratio of the electric field generating means and the developer supporting means, and the moving speed of the electric field generating means is defined as the circumferential speed ratio. 10 to 1 of the moving speed of the agent supporting means. It is preferable to set it to 0%, and more preferably to set it to 20 to 100%. However, although the present invention is not limited to the above numerical values, when the circumferential speed ratio is small, that is, when the relative speed of the electric field generating means is slow, the image history elimination effect is reduced, and when the circumferential speed ratio is large, the image history cancellation effect is reduced. That is, when the relative speed of the electric field generating means is high, the torque becomes large and image unevenness is likely to occur. Note that the circumferential speed ratio of the electric field generating means and the developer supporting means herein means that the moving speed of the electric field generating means is VC1.
(%) of developer support means.

Here, when the circumferential speed ratio is 100%, the gear structure can be made simple and the cost is low.

Furthermore, the electric field strength at the closest position (development position) between the developer supporting means and the latent image supporting means such as a photoreceptor drum is compared to the electric field strength E1 at the closest position between the developer supporting means and the electric field generating means. When Ez is E)≧EZ, the residual developer on the surface of the developer support means that has undergone non-image history is removed from the surface of the developer support means for development at the development position according to the image history. Since it can be peeled off immediately, the history of images and non-images can be sufficiently eliminated.

1. Hereinafter, the present invention will be explained based on one embodiment thereof with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention, which is applied to a reversal developing copying machine using a drum-shaped photosensitive drum 6 as a latent image supporting means. Although not shown in the figure, the photosensitive drum 6, which is rotatably supported in the direction of the arrow shown in the figure, is surrounded by a charging mechanism, an image exposure mechanism, a developing mechanism, and a transfer mechanism used in the electrophotographic process, as is well known. A mechanism, a cleaning mechanism, a static elimination mechanism, etc. are provided.

In order to develop the latent image on the photoreceptor drum 6, the developing mechanism is disposed at a position facing the photoreceptor drum 6, and this developing mechanism includes a developer supply means containing the developer 2. A non-magnetic developer supporting means is located at the opening 11 of the hopper 1 and faces the circumferential surface of the photosensitive drum 6 with a predetermined distance GL therebetween. A rotary sleeve 3, a magnet roller 4 disposed so as not to rotate within the rotary sleeve 3, and an L hopper 1 are used to transfer the developer on the surface of the rotary sleeve 3 to a required coating layer. Thickness (set at predetermined interval g1)
A regulating blade 5 as a developer layer thickness regulating member regulating the thickness of the developer layer.
, and the surface of the rotating sleeve 3 at a predetermined distance g.
Electrode rollers 7 are respectively disposed as electric field generating means, which are supported rotatably in the direction of the arrow in the hopper 1 while maintaining the same angle as the electrode rollers 7. This electrode roller 7 is, for example, a non-magnetic metal cylinder or cylinder, and is grounded.

In this embodiment, the magnetic roller 4 as a magnetic field generating means within the rotating sleeve 3 is provided concentrically and fixed within the rotating sleeve 3, and as shown in FIG. Magnetic poles N, SNz, Sz, and s3 are formed in this order parallel to the longitudinal direction of the circumferential surface of the magnetic roller 4.

The position at which the electrode roller 7 is rotatably supported in the hopper 1 is the position at which the latent image on the photoreceptor drum 6 is developed with respect to the developer transport direction, that is, the position at which the latent image on the photoreceptor drum 6 is developed. The magnetic poles Sz and S of the magnet roller 4 are located after the facing position of the opposing rotating sleeves 3 (set by the interval gz) and before the position of the regulating blade 5.
It is set between 3 poles. That is, the electrode roller 7 is set between the magnetic poles Sz and S3, which are the same repelling magnetic poles. At this time, if the electrode roller 7 is magnetic, the electrode roller 7 will be attracted by the magnetic force of the magnet roller 4 and will bend, making it impossible to keep the predetermined distance g3 constant and making it impossible to peel it off. It is important to avoid magnetism, as this may cause unevenness.

Further, the moving direction (rotation direction) of the electrode roller 7 is a direction in which the developer 2 is conveyed by the rotating sleeve 3 at a position facing the rotating sleeve 3 (indicated by the arrow a) and a forward direction (indicated by the arrow 2). is set to .

Here, in the case of a developing method in which the developer supporting means rotates,
There is an appropriate range for the circumferential speed ratio of the electric field generating means and the developer supporting means, and the moving speed of the electric field generating means can be set to 10 to 100% of the moving speed of the developer supporting means. Preferably, it is more preferably set to 20 to 100%. The circumferential speed ratio of the electric field generating means and the developer supporting means herein is defined as the moving speed of the electric field generating means being vE and the moving speed of the developing agent supporting means being Vs.
A scraper blade 8 serving as a developer removing means is disposed on the electrode roller 7 and is attached to the hopper 1 with its cutting edge in contact with the electrode roller 7 in the forward direction relative to the moving direction of the electrode roller 7 . The scraper blade 8 may be made of a flexible member such as a resilient member such as urethane rubber, silicone rubber, or styrene-butadiene rubber, a sheet of polyethylene terephthalate or polyethylene, or a thin metal plate. At this time, of course, the scraper blade 8 can also be disposed in contact with the electrode roller 7 in a direction opposite to the moving direction thereof.

Further, a bias power source 9 for applying a developing bias to the rotating sleeve 3 is connected to the rotating sleeve 3.

In such a configuration, the rotating sleeve 3 is a driving source (
When the developer 2 in the hopper 1 is rotated in the direction of the arrow a by receiving a driving force from the rotating sleeve 3 (not shown), the developer 2 in the hopper 1 is restrained on the surface of the rotary sleeve 3 by supporting forces such as magnetic force and electrostatic force. 3 and is conveyed in the direction of rotation. The regulation blade 5 magnetically cuts or regulates the developer 2 on the rotating sleeve 3 being conveyed so that it has a required coating layer thickness, and as a result, the developer 2 on the rotating sleeve 3 is
The developer on the surface has a uniform layer thickness t (t=g). When this developer reaches the developing position by the rotation of the rotating sleeve 3, a latent image pattern (image) is formed on the photoreceptor drum 6''.
In response to this, the toner electrostatically jumps or stretches the distance gz and is transferred to the surface of the photoreceptor drum 6, where it is subjected to development.

In this case, since reversal development is performed in the above embodiment, as shown in FIG. The bright potential of the image area becomes bright potential vL. The DC component Vbias of the developing bias of the developer supporting means is between the dark potential Vo and the bright potential VL. In reversal development,
Since the polarity of the developer used is the same as that of the latent image, in the non-image area it is repelled by the potential (Vo - V b i a S) and no development is done, but in the image area the potential (VL - Vb i as), rotating sleeve 3
The developer is ejected or elongated from the surface to the photoreceptor drum 6, and development is performed on the photoreceptor drum 6. Here, the contrast potential ■1 in the image area is
V, = l Vb i as - V 1, and the contrast potential Vz in the non-image area is z = l
VDVbiasl.

In this way, a history of images and non-images remains on the surface of the rotating sleeve 3 after passing through the development position. That is, when an image history is received, development is performed and the developer is completely or almost completely removed from the corresponding location on the rotating sleeve 3, and when a non-image history is received, no development is performed and the developer is removed from the corresponding location on the rotating sleeve 3. The developer will remain in the location corresponding to 3.

The developer remaining on the surface of the rotating sleeve 3 is collected into the hopper 1 by rotation of the rotating sleeve 3 in the direction of arrow a while being held by the magnetic force of the magnet roller 4.
Furthermore, this developer is applied to the magnetic poles SZ and S3 shown in FIG.
is conveyed between the magnetic poles of the magnetic field, and is electrostatically peeled off or removed completely or almost completely by the electrode roller 7, which is an electric field generating means.
The amounts of developer remaining on the surfaces of both rotating sleeves 3 are substantially the same. In this case, the closest position (
The electric field E1 at the closest position between the developer support means and the latent image support means (represented by the distance gz)
It is preferable to set the electric field to be equal to or higher than the electric field EZ at . Note that the "electric field E" here is defined as: (
Vbias-Vbiasz)7g3.

In this embodiment, since the electric field generating means is grounded, V b i a S Z = 0, and EV
b i as / g 3. Also, “Electric field EZJ
Vim is the latent image potential in the image area of the photoreceptor drum.
When set to age, (Vbi as-Vimage)/
g z, and in this case, V i m a g
e = ■, so EZ - (Vbias - VL) / g
It becomes 3.

Here, the potential Vbi between the developer supporting means and the electric field generating means
as is the potential Vbi between the latent image supporting means and the developer supporting means.
Since it is set larger than as-VL, therefore, for example, the gap g between the developer support means and the electric field generation means
3, when the gap gz between the latent image support means and the developer support means is made the same, the electric field E1 will definitely be larger than the electric field Ez, and the electric field generation means will cause the developer support means to receive a non-image history. Since the image history can be removed from the developer on the two surfaces by applying electrostatic attraction to it after it has been developed, it is possible to more efficiently separate the image and non-image on the developer. This will allow you to completely clear your history.

That is, even if the developer remains on the surface of the developer support means (the surface of the rotating sleeve 3), most or all of the developer on the developer support means is removed by the electric field generation means. After the image/non-image history is cleared, a new developer 2 is added to the rotating sleeve 3 from the hopper 1.
is magnetically and electrostatically restrained and supplied to both the previous image area and non-image area in the same way, and as described above, the developer layer thickness is similarly regulated in both areas by the regulating pred 5, and thus the rotation New developer is supplied to sleeve 3]-. In addition, when performing reversal development as in the above embodiment, the electric field generating means can be grounded, and a means for applying voltage to the electric field generating means is not required.
Safety is also improved and costs can be reduced.

On the other hand, the developer transferred to the surface of the electrode roller 7 as an electric field generating means is conveyed in the direction indicated by the arrow by the rotation of the electric field generating means, and is peeled off and removed by a scraper blade 8 as a developer removing means. brought back inside. Then, the electrode roller 7 holding the peeled and removed developer in a small amount peels off and removes the developer on the rotary sleeve 3 again by an electric field on the opposing surface of the rotary sleeve 3.

Next, the superiority of the present invention will be disclosed experimentally with reference to Table 1. To explain each experimental example, the dark potential Vo was -700V, the light potential (L) was -1130V, and an alternating electric field (frequency 1800V) was applied to the rotating sleeve 3 as a developer supporting means.
Hz, amplitude 1,600 cm), and a DC bias of -480 V is superimposed on this. The photoreceptor drum 6 as a latent image supporting means is an OPC drum with a diameter of 60 mm, and the rotating sleeve 3 is an Ann cylinder with an outer diameter of 20 mm. The electrode roller 7 is a cylindrical body made of non-magnetic SUS material, and its outer diameter is 6 mm. The distance gz between drum 6 is 300 gm,
The distance g3 between the rotating sleeve 3 and the electrode roller 7 is 30
It is set to 0gm. Further, the circumferential speed of the photosensitive drum 6 is 211 mm/sec, the circumferential speed of the rotating sleeve 3 is 211 mm/sec, and the magnetic roller 4 is
Magnetic rollers having magnetic poles S2 and S3 of 600 Gauss each are used, and the peripheral speed ratio of the electrode roller 7 and the rotating sleeve 3 is set to 5 to 150% (see Experimental Examples 1 to 5 described below). Then, a black belt image (image history part) and a white belt image (non-image history part) extending in the traveling direction are formed on the photoreceptor drum 6, and after 30 copies of these are made, character images and halftone images are transferred to the photoreceptor drum 6. We are currently investigating whether or not there will be a difference in the image due to the difference in history between images and non-images. In order to show the superiority of the present invention in comparison with the conventional method, data in that case are also listed in Table 1. Furthermore, the degree of effect due to differences in the aspects of the constituent elements of the present invention is also described to make it clear.

In this example, as a developer, 60 parts of magnetic particles were contained in 100 parts of binder resin, and the average particle size was 1.
A one-component magnetic toner of 2JLm is used.

That is, Experimental Examples 1 to 5 are the results when the peripheral speed ratio of the electrode roller 7 and the rotating sleeve 3 is selected in the above-mentioned example, and in Experimental Example 2 where the peripheral speed ratio is 10%, a halftone image is obtained. Although there was a slight difference in image density, it was at a sufficiently acceptable level, and there was no difference at all in character images. In addition, in experimental examples 3 to 10 where the circumferential speed ratio is 20% or more, /
＼-A good image with no difference at all was obtained in the futon image. However, Experimental Examples 5 and 9 where the circumferential speed ratio is 150%
Although this method was effective in eliminating the history difference between images and non-images, image unevenness occurred when durability tests were subsequently performed on several thousand sheets. Therefore, when the circumferential speed ratio is 150% or more, it is necessary to take measures to reduce the torque applied to the electrode roller 7 and to increase the outer diameter of the electrode roller 7 to prevent image unevenness.

On the other hand, in Comparative Example 1 showing the conventional technology, Experimental Example 1
In comparison, the developing device shown in FIG. 4 was used instead of the developing device shown in FIG. In Comparative Example 1, when images were formed under the same conditions as in Experimental Example 1, as shown in Table 1, the difference in density between images and non-images caused a difference in image density. The difference between the text images was also noticeable, and the images were difficult to see. In particular, the image density of the image history portion is higher than that of the non-image history portion, and the characters are thicker.

In Comparative Example 2, unlike Experimental Example 1, the developing device shown in FIG. 5 was used instead of the developing device shown in FIG. 1. In Comparative Example 2, when images were formed under the same conditions as in Experimental Example 1, as shown in Table 1, the difference in image history was almost eliminated; however, due to long-term use, As the rotating sleeve wears and the surface shape of the rotating sleeve changes, the image quality changes and
%) may cause uneven images, and
There were cases where the scraper 11 was worn out, causing a scrape spring failure and causing black and white streaks on the image. In addition,
The developer on the rotating sleeve 3- is peeled off with the scraper 11,
In order to allow the peeled developer to escape from the scraper during removal, an escape window has been added to the scraper 11, but there is a slight density difference in the halftone image depending on whether there is an escape window or not. It was confirmed.

In Comparative Example 3, unlike Experimental Example 1, the developing device shown in FIG. 6 was used instead of the developing device shown in FIG. 1. In Comparative Example 3, images were formed under the same conditions as in Experimental Example 1, and as shown in Table 1, the difference in image history was significant and the images were difficult to see. At this time, the electrode roller 7 continued to hold a large amount of developer. This is considered to be because the electrode roller 7 continues to hold a large amount of developer, making it impossible for the electrode roller 7 to sufficiently remove the residual developer that has received the image history on the rotating sleeve 3. This indicates that the developer must be thoroughly removed from the surface of the electrode roller 7.

In Comparative Example 4, unlike Experimental Example 1, the developing device shown in FIG. 7 was used instead of the developing device shown in FIG. 1. In Comparative Example 4, when image formation was performed under the same conditions as in Experimental Example 1, as shown in Table 1, developer accumulated under the electrode roller 7 and agglomerated. , an uneven image (white streak image) was generated, and the developer sometimes spilled from the hopper 1.

In Comparative Example 5, as shown in FIG. 9, the developing device used was the same as in Experimental Example 1, except for the scraper blade. In Comparative Example 5, image formation was performed under the same conditions as in Experimental Example 1, and as shown in Table 1, even with the repulsion pole, there was a significant difference in image history. The image was difficult to see. At this time,
The electrode roller 7 continued to hold a large amount of developer.

This is because, as in Comparative Example 3, the electrode roller 7 still holds a large amount of developer, so the electrode roller 7 sufficiently removes the remaining developer that has received the image history of the rotating sleeve 37. This is probably because it is no longer possible. This indicates that the developer must be thoroughly removed from the surface of the electrode roller 7.

Next, Experimental Examples 6 to 10 will be explained. In this experimental example, in Experimental Example 1 according to the present invention, the developer stripping section for stripping the developer from the top of the rotating sleeve 3 was replaced with the location between the repelling poles of the magnetic roller 4 having the same polarity. Instead, as shown in FIG. 8, the developing device is different in that it is provided between the different poles of the magnetic pole N1 near the magnetic pole 32 and the magnetic pole Sz (that is, the electrode roller as the electric field generating means is
Unlike the case where the developing device is located between repulsive poles between the same poles according to the experimental examples of the present invention, in these experimental examples, the developing device is installed between different poles). Table 1 shows the results of image formation under similar conditions.

In an experimental example with a circumferential speed ratio of 20%, although there was a slight difference in image density in halftone images, it was at an acceptable level, and there was almost no difference in character images. Further, in Experimental Examples 6 to 8 where the circumferential speed ratio was 30% or more, there was no difference at all in halftone images, or even if there was a slight difference, it was not noticeable, and the images were good. However, in Experimental Example 9 where the circumferential speed ratio was 150%, although it was effective in eliminating the difference in history between images and non-images, image unevenness occurred when several thousand sheets were subsequently subjected to a durability test. Therefore, when setting the circumferential speed ratio to 150% or more, efforts are made to reduce the torque applied to the electrode roller 7, and by increasing the outer diameter of the electrode roller 7,
It is necessary to prevent image unevenness.

Next, Experimental Examples 11 to 13 will be explained. In this experimental example, the same developing device as in experimental example 6 above is used, but
The gap g3 between the rotating sleeve 3 and the electrode roller 7 is set to 400~
As can be easily understood from Table 1 showing the results of image formation under the same conditions as Experimental Example 6 with a selection between 800 pL and 800 pL, in Experimental Example 11 where the gap g3 was 400 pL,
A good image with no difference in image history was obtained, but in Experimental Examples 12 and 13 in which the gap g3 was 600 g and 800 g, there was a difference in image history, but it was at an acceptable level. That is, it will be understood that when the electric field in the gap g3 is larger than the electric field in the gap g1, a good image with no difference in image history can be obtained.Next, Experimental Example 14 will be explained. In this experimental example, regular development was performed using the developing device shown in FIG.
The difference is that a DC bias of -300V was superimposed on the amplitude 1600V (7) alternating electric field, and that a DC bias of -800V was applied to the electrode roller 7.

As can be easily understood from Table 1, which shows the results of image formation under the same conditions as Experimental Example 6, good images with no difference in image history were obtained.

In the above embodiment, the scraper blade 8, which is a mechanical means with a simple structure and low cost, is used as a developer removing means for peeling off and removing the transferred developer from the electric field generating means.
The case has been described in which the scraper blade 8 is brought into contact with the electric field generating means such as the electrode roller 7 in the forward direction, but the scraper blade may be brought into contact with the electric field generating means such as the electrode roller 7 in the counter direction.
It is preferable to contact the electrode roller 7 in the counter direction because the developer can be efficiently stripped off from the electrode roller 7 when there is no fear of developer clogging. Further, although a magnetic cut regulating blade is shown as an example of the regulating member (blade 5) that regulates the thickness of the developer coating layer on the surface of the developer supporting means, a blade made of an elastic member may also be used. . In addition, in the above embodiment, since the developer on the surface of the developer supporting means is always removed by the electric field generating means, the tripod of the developer in the developing area tends to be low. It is preferable to control the layer thickness of the restrained developer on the surface of the developer supporting means and to apply tripo to the developer. In this case, if an elastic polymer reacted with a charge control agent such as nigrosine or a chromium monoazo complex is used as the material for the elastic flade, it is possible to
It becomes possible to increase one's ability to give.

Further, in the above embodiment, a cylindrical sleeve is used as the developer supporting means, but the developer may be conveyed using an endless belt, or an elastic roller structure may be used. good.

Further, in the above embodiment, a developing bias was applied to the developer supporting means by superimposing a direct current on an alternating electric field.
It is also possible to use only a direct current electric field as the heirence. Furthermore, an example has been shown in which the developer on the developer support means is not in contact with the latent image support means, and development is performed by electrostatic jumping or elongation movement. The present invention is also applicable to the case where the latent image is developed by slidingly contacting the latent image supporting means. Further, the electric field generating means does not have to completely remove the developer held therein, but only needs to have the ability to electrostatically remove the remaining developer from the developer supporting means. Therefore, the developer removing means such as the scraper blade 8 can be installed with a wide tolerance. In addition, even if the electric field generation means and developer removal means become scratched due to long-term use, this will not affect the ability to peel and remove residual developer from the developer support means, thereby preventing deterioration of image quality over time. It doesn't bring.

As described above, according to the developing device of the present invention, there is provided a developer supporting means for supporting a monocomponent developer on its surface and transporting it to a developing position, and In a developing device having a developer supplying means for supplying a one-component developer to the means, and a regulating member regulating the thickness of the developer coat layer on the developer supporting means, in the developer upstream of the regulating member. and an electric field generating means that moves in the forward direction of the developer supporting means while maintaining a gap with the developer supporting means between the generating magnetic poles of the magnetic field generating means, the developed image being held by the electric field generating means. By providing a developer stripping means for stripping and removing the developer, it is possible to obtain a good image regardless of the difference in image history.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view of essential parts of an embodiment of a developing device according to the present invention. FIG. 2 is a diagram for explaining the latent image potential when reversal development is performed using the developing device shown in FIG. 1. FIG. 3 is a schematic side sectional view of a developing device having a configuration corresponding to Experimental Example 14. FIG. 4 is a schematic side sectional view of a developing device having a configuration corresponding to Comparative Example 1 as a prior art. FIG. 5 is a schematic side sectional view of a developing device having a configuration corresponding to Comparative Example 2 as a conventional technique. FIG. 6 is a schematic side sectional view of a developing device having a configuration corresponding to Comparative Example 3, which lacks one of the requirements of the present invention. FIG. 7 is a schematic side sectional view of a developing device having a configuration corresponding to Comparative Example 4 in which one requirement of the present invention is changed. FIG. 8 is a schematic side sectional view of a developing device having a configuration in which one requirement of the present invention is changed. FIG. 9 is a schematic side sectional view of a developing device having a configuration in which one requirement of the present invention is changed. 5: Regulation blade 7: Magnet roller 8 Varnish scraper blade S,, S3: Repulsion magnetic pole 1: Hopper 3: Rotating sleeve 4: Magnet roller

Claims (1)

[Claims] 1) A developer support means that carries a developer on its surface and transports it to a development position by the magnetic force of a magnetic field generation means fixedly arranged in an internal space, and a developer supply that supplies the developer to the developer support means. and a regulating member for regulating the thickness of the developer coat layer on the developer supporting means, the magnetic field generating means being disposed in the developer upstream of the regulating member. An electric field generating means that moves while maintaining a gap from the developer supporting means is disposed between the repulsive magnetic poles, and a developer stripping means is disposed for peeling off and removing the developer held by the electric field generating means. A developing device.