JP2582293B2 - Developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly, to a developing device using a one-component developer applied to an image forming apparatus such as an electrophotographic copying machine, an electrostatic recording machine, and a magnetic recording machine. .

2. Description of the Related Art Conventionally, there is a jumping development method as a development method using a one-component developer. In this jumping development method, a developer (hereinafter, also referred to as toner) is applied with a predetermined thickness on the surface of a developer supporting means to form a uniform thin coat layer, and the coat layer is transported to a developing position. Then, the developer is caused to face the electrostatic latent image carrying surface of the latent image supporting means at a required interval, and the developer is caused to fly from the developer supporting means to the electrostatic latent image carrying surface by the electrostatic attraction for developing. (See, for example, Japanese Patent Publication No. 41-9475 and U.S. Pat. No. 2,833,400).

In this method, not only the developer is not attracted to the non-image portion of the electrostatic latent image carrying surface having no latent image potential, but also the developer is carried on the surface of the developer supporting means as in the conventional contact developing method. Since the developer does not come into contact with the electrostatic latent image carrying surface, good development can be realized without any fogging on non-image areas. Further, since no carrier particles are used, good effects such as no change in the mixing ratio of the developer and no deterioration of the carrier particles can be obtained.

In addition, the present applicant has disclosed in Japanese Patent Application Nos. 52-109240 (first developing method) and Japanese Patent Application No. 53-92108 (second developing method) different developing methods from the above-mentioned developing methods. A completely new development method as described above was proposed earlier.

In the first developing method described above, a one-component magnetic developer, a developer supporting means (non-magnetic), and a magnetic field generating means are arranged in this order, and the magnetic force of the magnetic field generating means causes a magnetic force on the surface of the developer holding means. A thin coat layer of a uniform developer is formed, and the coat layer is opposed to the latent image supporting means at a small interval so as not to contact the electrostatic latent image holding surface. Then, the portion of the developer coat layer facing the image portion is extended by electrostatic attraction of the electrostatic latent image carrying surface of the latent image supporting means, and the latent image is developed on the carrying surface. Also in the case of this developing method, the non-image portion of the electrostatic latent image bearing surface is not in contact with the coat layer of the developer in the developer supporting means, so that a developed image having no fog at the time of development can be obtained.

In the second developing method, when performing the first developing method, a low-frequency AC bias voltage is applied as a developing bias voltage to the developer supporting means, and further, the electrostatic force of the latent image supporting means is increased. The distance between the latent image carrying surface and the surface of the developer supporting means opposed thereto is changed with time. In such a developing method, in the early stage of development, the developer reaches the non-image area of the electrostatic latent image carrying surface, and the halftone portion is developed. Is returned to the original developer support means side, and as a result, only the image portion is reached. Thereby, the reproducibility of the halftone portion is improved as compared with the jumping development method. In addition, fog-free development can be realized.

As described above, using a one-component developer, the developer is moved from the developer supporting means to the non-contact latent image supporting means by electrostatic attraction, and the method of developing is performed.
It is extremely excellent in the life of the developer.

Problems to be Solved by the Invention However, even in the developing method as described above, in practical use, there is a case where a difference occurs in image density due to a difference in image history. It has been proposed to use a scraper blade by a mechanical means in contact with the developing sleeve as a method of removing the residual toner on the developing sleeve (hereinafter also referred to as a developing sleeve) and always supplying fresh toner.

Further, in order to eliminate a difference in image history, a method of disturbing residual toner on the developing sleeve by providing a magnetic particle group constrained by magnetic force means included in the developing sleeve on the toner container side on the developing sleeve, Alternatively, a method has been proposed in which fresh toner is forcibly supplied onto the developing sleeve in which the image history remains, and a toner supply roller is rotated in contact with the developing sleeve in order to disturb the remaining toner on the developing sleeve, or It has been implemented.

In addition, the present applicant has proposed a method of disposing an electric field generating means on the toner container side of the developing sleeve, removing the remaining toner on the developing sleeve in a non-contact and electrostatic manner, and eliminating the image history difference. .

However, in the method of using the scraper blade by the mechanical means of the above-described conventional example, the surface of the developing sleeve and the scraper abutting portion are worn and damaged in order to strongly rub the developing sleeve with the scraper blade. As a result of locally applying a strong tribo to a scrape-defective toner, a defect such as a black stripe or a white stripe may occur on an image.

Further, in the method using the above-mentioned disturbing means, there is a problem that the disturbing force is not sufficient, the image history on the developing sleeve cannot be completely erased, and the image density becomes uneven.

Further, according to the above-described method using the electric field generating means, the present invention is applied to an image forming apparatus such as an electrophotographic copying machine, an electrostatic recording machine, and a magnetic recording machine. This is an effective and effective method.However, when low-resistance foreign matter, paper dust, etc. are mixed in the toner, or when the toner is operated in a high humidity or in a dew condensation state, the electric field generating means grounded and the developing There is a problem that the sleeve is electrically short-circuited, the developing bias voltage for developing the electrostatic latent image applied to the developing sleeve drops, and normal image formation is not performed.

It has been found that this problem can be solved by coating the conductive member for forming the developer peeling electric field of the electric field generating means with a dielectric. However, it has been found that when the surface of the dielectric coating layer is charged by friction, a new problem occurs in that the peeling effect is reduced due to electrostatic attraction of the developer and a canceling action of the peeling electric field.

Here, the above-described image history will be described below. The “image history” as used herein means an image on the electrostatic latent image carrying surface of the latent image support means, a process of forming a non-image,
This affects the image density because there is a problem with the toner coating layer on the developing sleeve.
To be more specific about this point, the toner in the developing sleeve is attracted to the electrostatic latent image carrying surface by an electrostatic attraction in order to develop the image portion of the electrostatic latent image carrying surface at the developing position. It is removed or only a small amount remains.

On the other hand, in the non-image portion, all or most of the toner on the developing sleeve remains on the developing sleeve even at the developing position. As a result, new toner is supplied to the surface of the developing sleeve that has received the image history at the time of the next toner supply, but the previous toner remains on the surface of the developing sleeve that has received the non-image history. When the next toner is supplied, no new toner is supplied. If such a non-image history is repeatedly received at the same location, the amount of toner tribo-coating at that portion on the surface of the developing sleeve changes, and further, the toner may be deteriorated, and the surface of the developing sleeve may be contaminated. .

As a result, the difference between the history of the image and the non-image causes a difference in the state of the toner on the surface of the developing sleeve, resulting in a difference in the developing ability and the quality of the final image. Especially,
This development becomes remarkable when a large number of originals having a black band image or white band image in the vertical direction are copied.

Therefore, a difference in image density occurs due to a difference in image history,
In particular, density unevenness tends to occur in the above-described halftone portion, and in extreme cases, thickening or thinning of characters may occur.

Of course, the difference between images (especially a halftone image) due to the difference between the history of the image and the non-image is not uniform due to various conditions. For example, if the supply of new toner to the image sleeve after the image history is insufficient, if there is an electrostatic latent image corresponding to the location again in the next stage, the image density to be developed decreases. Further, when the coating amount after the non-image history becomes small, if there is an electrostatic latent image corresponding to the location in the next stage, the image density to be developed is reduced.

As described above, the difference in the developability due to the difference in the image history is caused by peeling off all the residual toner on the surface of the developing sleeve after passing the developing position, constantly supplying new toner to the entire surface, and uniforming the predetermined thickness. As a result of earnest experimental studies by the present inventors, it has been found that such a thin coat layer can be eliminated by forming the thin coat layer.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is that residual developer attracted from the surface of the developer supporting means by the action of the electric field generating means is deposited on the surface of the electric field generating means. A developer removing means for removing the developer held in the electric field generating means to prevent the occurrence of the electric field, repeatedly stabilizing the effect of stripping the developer by the electric field generating means, good regardless of the difference in image history An object of the present invention is to provide a developing device capable of obtaining a natural image.

Means for Solving the Problems The above object is achieved by a developing device according to the present invention. That is, in summary, the present invention provides a developer supporting means for carrying a developer on a surface and transporting the developer to a developing position, a regulating member for regulating a thickness of a developer layer on the developer supporting means, and a developer supporting means. Peeling means for peeling the developer from the developer supporting means downstream of the developing position in the moving direction of the means and upstream of the regulating position by the regulating member, and the peeling means is provided between the developing means and the developer supporting means. In a developing device having a conductive member for forming a developer peeling electric field and a dielectric layer covering the conductive member, a ground or static elimination voltage for contacting the dielectric layer and peeling the developer on the dielectric layer is reduced. A developing device comprising a conductive scraped member applied.

As described above, according to the present invention, the conductive scraping member as the developer peeling unit is brought into contact with the surface of the electric field generating unit coated with the dielectric layer, and the conductive blade is connected to the ground or the voltage applying unit. By connecting, it is possible to remove or charge the dielectric layer in which the charge is stored, and it is possible to repeatedly stabilize the effect of peeling off the developer by the electric field generating means, which is good regardless of the difference in image history. It is possible to obtain a perfect image.

That is, in the developing device of the present invention, the developer on the developer supporting means is peeled off, the state of the residual developer on the developer supporting means having received the history of the image / non-image is made uniform, and then the developing apparatus is newly developed. By supplying the agent, the difference in the image histories is eliminated, and a good image is obtained.

Here, according to the present invention, by providing an electric field generating means covered with a dielectric layer while keeping a gap with the developer supporting means as a developer stripping means on the developer supporting means, the developer supporting means Further, the developer on the developer supporting means can be effectively peeled off without damaging the developer peeling means.

Further, when the electric field generating means is moved in the counter direction with respect to the developer supporting means, the developer may be clogged or spilled.In the developing device of the present invention, the moving direction of the electric field generating means is Since it is moved in the same direction as the support means, that is, in the forward direction, it is possible to prevent the developer from being clogged and the developer from spilling. Further, by providing a conductive scraping member as a developer peeling means for peeling and removing the developer held by the electric field generating means covered with the dielectric layer, the developer on the developer supporting means is made of a dielectric material. With the electric field generating means covered with the layer, the film can be peeled off uniformly and stably and effectively. If the developer peeling means is not provided, the electric field generating means rubs the developer supporting means while holding a large amount of developer, so that the developer on the developer supporting means can be sufficiently peeled off. It becomes impossible and unevenness tends to occur. This developer peeling means does not need to completely peel off the developer held by the electric field generating means.For example, the developer removing means is provided with a gap with the electric field generating means, that is, in a non-contact state, By regulating the layer thickness of the developer on the electric field generating means, it is possible to effectively peel off the developer on the developer supporting means even if the electric field generating means holds some developer. In addition, the mechanical precision of the developer removing means is not strictly required.
Furthermore, even if the developer removing means and the electric field generating means are damaged by long-term use, the developer on the developer supporting means can be sufficiently peeled off by the electric field generating means.

At this time, when the developing sleeve includes a magnetic field generating means, the electric field generating means is preferably a non-magnetic metal electrode cylinder or a round bar, and a known organic or inorganic material is used as the covering dielectric. Although it can be used, the volume impedance of the latent image support to be developed is preferably equal to or less than that in order to effectively peel off the developer on the developer supporting means. On the other hand, in the case of more than that, the gap between the developer peeling contrast potential acting between the developing sleeve and the electric field generating means is equal to that of the developing contrast potential acting between the latent image support and the developing sleeve. This is because in the case of (1), the size becomes small, and the image history on the developing sleeve cannot be sufficiently erased.

In the case of a developing method in which the developer supporting means rotates,
The peripheral speed ratio between the electric field generating unit and the developer supporting unit has an appropriate range. As the peripheral speed ratio, the moving speed of the electric field generating unit can be set to 20 to 100% of the moving speed of the developer supporting unit. More preferably, it is more preferably set to 30 to 100%. However, the present invention is not limited to the above numerical values, but when the peripheral speed ratio is small, that is, when the relative speed of the electric field generating means is low, the image history eliminating effect is reduced,
If the peripheral speed ratio is large, that is, if the relative speed of the electric field generating means is high, the torque increases, and image unevenness is likely to occur. Here, the electric field generating means called peripheral speed ratio of the developer support means, when the Vse moving speed V _E of the electric field generating means, the moving speed of the developer support means That is.

Here, when the peripheral speed ratio is 100%, the gear configuration can be simplified and the cost can be reduced.

The field at the closest position between the developer supporting member with such a latent image supporting means of the photosensitive drum with respect to the electric field strength E ₁ at the closest position between the developer supporting means and field generating means (developing position) when the intensity E ₂ is E ₁ ≧ E ₂ is the residual developer on the surface of the developer support means has received the non-image history, dividing the surface of the developer support means for development at the developing position by the image history Since the peeling can be performed at a portion more than the cut portion, the history of the image / non-image is sufficiently eliminated.

Embodiment Hereinafter, the present invention will be described based on an embodiment with reference to an attached screen.

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention, in which a drum type photosensitive drum 6 is used as a latent image supporting means.
This is applied to a reversal developing copier that uses.
Although not shown in the drawing, around the photosensitive drum 6 rotatably supported in the illustrated arrow direction, a charging mechanism, an image exposure mechanism, and
A developing mechanism, a transfer mechanism, a cleaning mechanism, a charge eliminating mechanism, and the like are provided.

In order to develop the latent image on the photosensitive drum 6, the developing mechanism is disposed at a position facing the photosensitive drum 6, and the developing mechanism serves as a developer supply unit containing the developer 2. Between the hopper 1 and the opening of the hopper 1 and the peripheral surface of the photosensitive drum 6.
Predetermined distance g ₂ magnets roller 4 which is disposed so as not to rotate to the non-magnetic developing sleeve 3 and the developing sleeve 3 as a developer support means opposing each other via, attached to the hopper 1, the developing predetermined between the regulating blade 5, and the developing sleeve 3 on the surface as a developer layer thickness regulating member for regulating the developer on the surface of the sleeve 3 in the thickness of the required coating layer (set to a predetermined distance g ₁₎ electrode roller 7 are respectively arranged as electric field generating means which is rotatably supported in the arrow direction at a distance g ₃ in the hopper 1. The electrode roller 7 is, for example, a metal cylinder or column made of non-magnetic SUS (stainless steel) or the like as a conductive member, and the surface thereof prevents a short circuit (leak) with the developing sleeve 3. For this reason, the electrode roller 7 is grounded while being covered with a dielectric layer 11.

In this embodiment, the magnet roller 4 as the magnetic field generating means in the developing sleeve 3 is
The magnetic poles N ₁ , S ₁ , N ₂ , and S ₂ are arranged in this order in the longitudinal direction of the circumferential surface of the magnet roller 4 as shown in FIG. Are formed in parallel.

The position at which the electrode roller 7 is rotatably supported in the hopper 1 is determined with respect to the developer conveyance direction.
Position for developing the latent image on the photoreceptor drum 6, i.e., the position of the photosensitive drum 6 facing the developing sleeve 3 facing position (set at intervals g ₂₎ subsequent in and the regulating blade 5 than Is also set in the previous stage.

The moving direction (rotation direction) of the electrode roller 7 is as follows.
At the position facing the developing sleeve 3, it is set in the direction of conveyance of the developer 2 by the developing sleeve 3 (indicated by an arrow a) and in the forward direction (indicated by an arrow b).

Further, with respect to the electrode roller 7, a conductive scraping member, that is, a conductive scraper blade as a developer removing means attached to the hopper 1 with its blade edge abutting in the forward direction with respect to the moving direction of the electrode roller 7, 8 are provided. The scraper blade 8 is made of a flexible member such as a phosphor bronze metal sheet, and is grounded. At this time, it is needless to say that the scraper blade 8 can be arranged in contact with the moving direction of the electrode roller 7 in the opposite direction.

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

Here, in the case of the developing method in which the developing sleeve as the developer supporting means rotates, there is an appropriate range in the peripheral speed ratio between the electrode roller as the electric field generating means and the developing sleeve. Is preferably set to 20 to 100% of the moving speed of the developing sleeve, and more preferably to 30 to 100%. In addition,
The peripheral speed ratio between the electric field generating means and the developer supporting means is defined assuming that the moving speed of the electric field generating means is V _E and the moving speed of the developer supporting means is Vse. That is.

In such a configuration, when the developing sleeve 3 receives a driving force from a driving source (not shown) and rotates in the direction of arrow a, the developer 2 in the hopper 1 is supported by a supporting force such as a magnetic force or an electrostatic force. It is constrained on the surface of the developing sleeve 3 and is transported together with the developing sleeve 3 in the rotation direction.
The regulating blade 5 is adapted to move the developing sleeve 3
The upper developer 2 is magnetically cut or regulated so as to have a required thickness of the coating layer. As a result, the developer on the surface of the developing sleeve 3 has a uniform layer thickness t (t = g ₁ ). Becomes
When this developer comes to the developing position by the rotation of the developing sleeve 3, the latent image pattern (image) on the photosensitive drum 6
Corresponding to electrostatically interval g ₂ jumping or extended exercise spread to the surface of the photosensitive drum 6 is subjected to development to.

In this case, in the above embodiment, because the reversal development, as shown in FIG. 2, the non-image portion of the non-exposed latent image on the surface of the photosensitive drum 6, a dark potential V _D, exposure The image portion thus set has the bright potential _VL . Then, DC component Vbias of the developing bias of the developer supporting means intermediate the dark potential V _D and the bright potential V _L. Since the inversion phenomenon polar ,, developer used as the latent image with the same polarity, in the non-image developed image portion are repelled by the potential (V _D -Vbias), but development is not performed, the image portion By the potential ( _VL- Vbias), the developer flies or elongates from the surface of the developing sleeve 3 to the photosensitive drum 6, and development is performed on the photosensitive drum 6. Here, the contrast potential V ₁ in the image _{portion, V 1 = | Vbias-V} L | a is, the contrast potential V ₂ in the non-image _{portion, V 2 = | V D -Vbias} | a.

In this way, the history of the image / non-image is left on the surface of the developing sleeve 3 after passing through the developing position. That is, when the image history is received, the development is performed, and the developer is completely or almost completely removed from the corresponding portion of the developing sleeve 3. When the non-image history is received, the development is not performed. 3, the developer remaining on the surface of the developing sleeve 3 is electrostatically peeled off or almost completely removed by the electrode roller 7 serving as an electric field generating means. The amounts of the remaining developer on the surfaces of the developing sleeves 3 are almost the same.

After that, the developer 2 is both newly supplied from the inside of the hopper 1 onto the developing sleeve 3 in the same manner, and the thickness of the developer layer is regulated by the regulating blade 5 in the same manner, and the developer is used again for development. .

Therefore, the image is provided for development in a state where the history of the image / non-image is eliminated.

On the other hand, the developer transferred to the surface of the electrode roller 7 as the electric field generating means is turned by an arrow b by the rotation of the electric field generating means.
, And is separated and removed by a scraper blade 8 as a developer removing means and returned to the hopper 1.
Then, the electrode roller 7, which has been peeled and removed and holds the developer in a small amount, again effectively removes and removes the developer on the developing sleeve 3 by the electric field on the opposite surface of the developing sleeve 3.

In this case, the electric field E ₁ at the closest position between the electrode roller 7 as an electric field generating means and the developing sleeve 3 as a developer supporting means (indicated by spacing g ₃₎ is a developer supporting means and the latent image supporting means Electric field at the nearest point (indicated by the spacing g ₂ )
It is preferable that the E ₂ or more. Here, the "electric field E _1"
The DC component of the developing bias applied to the developer supporting means is defined as Vbias, and the DC component of the bias applied to the electric field generating means is defined as Vbias.
When the component is Vbias _2, it means (Vbias−Vbias ₂ ) / g ₃ .

In this embodiment, since the electric field generating means is grounded, Vbias ₂ = 0 and E ₁ = Vbias / g ₃ . The “electric field E ₂ ” is (Vbias−Vimage) / g ₂ when the latent image potential in the image portion of the photosensitive drum is Vimage. In this case, since Vimage = _VL , E ₂ = ( Vbias−V _L )
/ A g _3.

The potential Vbia between the developer supporting means and the electric field generating means
s is a potential Vbias−V _L between the latent image supporting means and the developer supporting means.
Therefore, for example, the gap g ₃ between the developer supporting means and the electric field generating means is set to be larger than
Equivalent to the latent image support means a gap g ₂ between the developer supporting means in the same, and further the volume impedance of the latent image carrier volume impedance of the dielectric layer covering the electric field generating means,
Or if it has been below the electric field E ₁ becomes reliably greater than the electric field E _2, in the electric field generating means to the developer in the developer supporting means on the surface which receives the non-image history, image developing unit Since it can be peeled off at the same time or more than when developed with the history, the developer image and
The non-image history can be completely eliminated.

That is, even if the developer remains on the surface of the developer supporting means (the surface of the developing sleeve 3), most or all of the developer on the developer supporting means is removed by the electric field generating means, so that the image is removed. The history of the non-image is eliminated, and then the developer 2 is newly placed on the developing sleeve 3 from the hopper 1.
Is magnetically and electrostatically constrained, is supplied to both the previous image portion and the non-image portion in the same manner, and as described above, the developer layer thickness is regulated by the regulating blade 5 in the same manner.
Thus, new developer is supplied onto the developing sleeve 3. In the case of performing reversal development as in the above embodiment, the electric field generating means can be grounded, and voltage applying means to the electric field generating means becomes unnecessary.
Safety can be improved and costs can be reduced.

Further, by forming the electric field E ₁ to the electric field E ₂ or more, strip the developer in the developer support means has received the non-image history by electric field generating means, the above is developed with a developing unit by image history Therefore, the history of images and non-images can be eliminated even if any developer is used. That is, any developer can be used without being limited by the type of the developer.

 Next, the superiority of the present invention will be experimentally disclosed.

In the above embodiment, the outer diameter of the electrode roller 7 is 8 m.
An aluminum sol made by hydrolyzing aluminum alcoholate is applied to a round bar (non-magnetic material) of SUS304
A dielectric layer 11 coated with a 3 μm-thick alumina film (Al ₂ O ₃ ) produced by heating and drying at about 500 ° C. was used. The photosensitive drum 6 as a latent image support means is a 20 μm-thick laminated function-separable organic layer mainly composed of polycarbonate as a photosensitive layer as an electrostatic latent image carrier on an aluminum drum having an outer diameter of 60 mm. A developing sleeve 3 as a developer carrying member, which is coated with a photoconductor layer, is a non-magnetic aluminum cylinder having an outer diameter of 20 mm and including a fixed magnet roller therein. Was used.

Then, the dark potential V _D of the electrostatic latent image on the photosensitive drum 6 -70
0 V, the light potential _VL is -130 V, a rectangular wave alternating electric field (frequency 1800 Hz, amplitude 1600 V) is applied as a developing bias to the developing sleeve 3 as the developer supporting means, and a DC bias of -480 V is superimposed and applied thereto. doing. Further, 240 .mu.m apart g ₁ between the developing sleeve 3 and the regulating blade 5, the distance g ₂ between the developing sleeve 3 and the photosensitive drum 6 300 microns
m, the distance g ₃ between the developing sleeve 3 and the electrode roller 7 is 30
0 μm to 800 μm. Further, the peripheral speeds of the photosensitive drum 6 and the developing sleeve 3 are each set to 200 mm / sec, and the peripheral speed ratio of the electrode roller 7 to the developing sleeve 3 is set to 20 mm / sec.
Considered in the range of ~ 150%.

Furthermore, a bright potential band latent image (image history portion on the developing sleeve) and a dark potential band latent image (non-image history portion on the developing sleeve) are formed in the circumferential direction of the photosensitive drum 6, and after 30 copies, the character An image and a halftone image were formed, and it was examined whether or not a difference would occur in the image due to a history difference between the image and the non-image portion.

Under these conditions, various experiments were conducted using the developing device of the above-described embodiment. The distance g ₃ between the developing sleeve 3 and the electrode roller 7 was set to 300 μm,
When the peripheral speed ratio between the image and the rotating sleeve 3 was set to 20%, although there was a slight difference in image density in the halftone image, it was at an acceptable level, and there was almost no difference in the character image.

At a peripheral speed ratio of 30% or more, there was no difference in the halftone image, or even a slight difference was not noticeable, and the image was good.

However, when the peripheral speed ratio was set to 150% or more, although there was an effect of eliminating the difference between the history of the image and the non-image, after the durability test of several thousand sheets was performed, image unevenness occurred. Therefore, when the peripheral speed ratio is set to 150% or more, it is necessary to reduce the torque applied to the electrode roller 7 and increase the outer diameter of the electrode roller 7 to prevent image unevenness.

Then, under the conditions of 60% circumferential speed ratio, the distance g ₃ 300μm~800
μm, and image formation was performed in the same manner as described above, using several types of one-component magnetic toner. The spacing g ₃ = 400 μm to 500 μm
In the range of m, good results with no difference in image history could be obtained regardless of the type of toner, but the interval g ₃ = 500 μm to 8 μm.
In the range of 00 μm, an image history difference may occur depending on the type of toner.

That is, the maximum electric field E ₁ is the maximum electric field of the interval g ₁ interval g ₃
When E ₂ greater than, no good image of image history difference regardless of the type of toner was obtained.

Further, a similar study was actually performed using toner in a developing device on which image formation was repeatedly performed on about 10,000 sheets.
Therefore, this toner contains paper dust, talc, fiber waste,
A foreign material having a hygroscopic or low resistance such as abrasion metal powder is mixed. As a result of performing development using such a toner, the distance between the developing sleeve 3 and the electrode roller 7 was determined.
Also the g ₃ through the above foreign substance, an alternating electric field and superimposed DC bias as a developing bias without being short-circuited to ground via the electrode roller 7, the image on did not occur image loss due to the developing bias shorting. Further, when the same examination was performed under high temperature and high humidity (32 ° C., 85% RH), good images were repeatedly obtained without any problem similarly to the above.

Comparative Example 1 On the other hand, in Comparative Example 1 showing the prior art, a non-magnetic SUS (stainless steel) round bar not covered with a dielectric layer was used as the electrode roller 7 of the developing device shown in FIG. Otherwise, the same configuration as in the above embodiment of the present invention was used, and as a result of examining image formation, when toner containing moisture-absorptive and low-resistance foreign matters was used, the interval g ₃ When the foreign matter passes through the developing roller, the developing bias is short-circuited to the ground via the electrode roller 7, and the image may be missing on the image due to the short-circuiting of the developing bias. Further, when the same examination was performed under a high temperature and a high humidity (32 ° C., 85% RH), the frequency of image omission due to the development bias short circuit increased as described above. This phenomenon, was a frequent interval g ₃ about the clamping physician.

Comparative Example 2 Further, in Comparative Example 2 showing the prior art, a 1.5 mm thick urethane rubber blade which is a non-conductive material was used as the scraper blade 8 of the developing device shown in FIG. As a result of examining the image formation under the same conditions as in the above embodiment, there was no problem at the initial stage of the image formation under each condition, but when the image formation was repeatedly performed, the residual image on the developing sleeve 3 by the electrode roller 7 was obtained. Unevenness occurs in the toner stripping effect, the image history erasing effect gradually decreases,
It fell below the allowable range.

This is because charge is accumulated in the dielectric layer 11 on the rotating electrode roller 7 due to friction with toner or urethane rubber blade due to repetition of image formation, but the scraper blade is non-conductive. It is considered that this occurred because the charge could not be removed sufficiently.

Next, another embodiment of the developing device of the present invention will be described with reference to FIG.

The same parts and portions as those of the above-described embodiment shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 3 is a schematic sectional view of a second embodiment in which the developing device of the present invention is applied to a copying machine which uses a drum type photoreceptor and performs reversal development. Although not shown in FIG. 3, a charging mechanism, an image exposure mechanism, a transfer mechanism, a cleaning mechanism, a static elimination mechanism, and the like, which are well-known electrophotographic processes, are arranged around the photosensitive drum 6.

This embodiment is different from the above-described embodiment in that the developing device shown in FIG.
Is not included, that the toner 2 used is a one-component non-magnetic toner, and that the toner layer thickness regulating means is a regulating blade 5 ′ made of a non-magnetic metal thin plate in contact with the developing sleeve 3. is there. Other configurations are almost the same as those in FIG. 1 showing one embodiment of the developing device of the present invention described above.

In this embodiment, as the electrode roller 7, a dielectric layer whose surface is coated with a 10 μm-thick polycarbonate resin is used.
A round rod of SUS304 (stainless steel) having an outer diameter of 8 mm and having a diameter of 11 was used.

Also in this embodiment, the photosensitive drum 6 serving as a latent image support means is formed by stacking a 20 μm thick polycarbonate-based film as a photosensitive layer serving as an electrostatic latent image carrier on an aluminum drum having an outer diameter of 60 mm. A non-magnetic aluminum cylinder having an outer diameter of 20 mm was used as the developing sleeve 3 as a developer carrier using a function-coated organic photoconductor layer.

Then, the dark potential V _D of the electrostatic latent image on the photosensitive drum 6 -70
0 V, the light potential _VL is -130 V, and a rectangular wave alternating electric field (frequency 2000 Hz, amplitude 2000 V) is applied as a developing bias to the developing sleeve 3 as the developer supporting means, and a DC bias -480 V is superimposed and applied thereto. doing. Further, the distance g ₂ between the developing sleeve 3 and the photosensitive drum 6 300 [mu] m, the distance g ₃ between the developing sleeve 3 and the electrode roller 7 and 300 [mu] m, further, the photosensitive drum 6 and the developing sleeve 3 The peripheral speed was set to 200 mm / sec, and the peripheral speed ratio of the electrode roller 7 to the developing sleeve 3 was examined at 60%. as a result,
Almost the same results as in the above example were obtained.

Next, the thickness of the coated polycarbonate film of the electrode roller 7 was changed to 15 μm, 20 μm, 25 μm, 30 μm, and 50 μm, and the same examination was performed. As a result, the effect of removing the residual toner on the developing sleeve 3 was reduced to 25 μm. Although a satisfactory result was obtained, as the film thickness was further increased, the effect of removing the residual toner was reduced, the effect of erasing the image history was reduced, and a difference in image density was caused.

This is because the volume impedance of the film increases as the film thickness increases.
It is considered that this is due to a phenomenon that the peeling effect is lower than the developing efficiency with respect to the photosensitive drum 6 due to the partial pressure drop of the developing bias electric field applied during the period.

Therefore, by setting the volume impedance of the coating dielectric layer of the electrode roller 7 at least equal to or less than the volume impedance of the photosensitive layer of the photosensitive drum,
Particularly in the interval g ₂ ≧ g _3, at least the image portion latent image potential Vimage = V _L min only can maintain the stripping development contrast to the electrode roller 7 increases, can be erased image history.

Next, another embodiment of the developing device of the present invention will be described with reference to FIG.

The same parts and portions as those of the above-described embodiment shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 4 is a schematic sectional view of still another embodiment of the developing device of the present invention.

This embodiment is different from the above-described embodiment in that a voltage applying means 10 is connected to a conductive scraper blade 8 in contact with an electrode roller 7 covered with a dielectric layer 11 in the developing device shown in FIG. The configuration is the same as that of FIG. 1 showing the embodiment of the developing device of the present invention described above, except that the static elimination voltage is applied.

In this embodiment, the voltage application means 10 has an alternating electric field at a frequency of 50 Hz to 2000 Hz,
A power supply having an amplitude of 100 V to 500 V was used. As the alternating electric field, a single power source may be used, or the developing bias applied to the developing sleeve 3 may be cut down by applying a DC component through a capacitor and an impedance element, and then applied in a step-down manner. Under the conditions described above, the same image formation as in the above-described embodiment was examined. As a result, the effect of removing electricity from the electrode roller 7 with respect to the covering dielectric 11 was effectively obtained, and the effect of deleting the image history was large.

In particular, even if the contact of the conductive scraper blade 8 with the electrode roller 7 was uneven or the scraper was slightly defective, the static eliminating effect was reliably obtained.

Here, if the scraper blade is conductive and is not connected to the voltage applying means, or is not grounded as in the above-described embodiment, the electric charge accumulated in the coated dielectric is discharged. Not only is it impossible, but also the charge accumulation is promoted by rubbing, and the effect of peeling off the residual toner from the developing sleeve is reduced, which is not preferable.

In the above-described embodiment, as the developer removing means for peeling and removing the transferred developer from the electric field generating means,
There are mechanical means, electrical means, magnetic means, etc., but in terms of simple configuration and low cost, and mechanical means for removing electricity from the surface of the dielectric layer covered by the electric field generating means. It is preferable to use the conductive scraper blade 8. In the above embodiment, the case where the conductive scraper blade 8 is brought into contact with the electric field generating means such as the electrode roller 7 in the forward direction has been described. You may make contact.

Although the cylindrical electric roller has been described as an example of the electric field generating means, a belt-shaped electric roller may be used.

The regulating member (blade 5) for regulating the thickness of the developer coating layer on the surface of the developer supporting means is exemplified by a regulating blade formed by magnetic cutting and a metal sheet contact blade. A rubber blade may be used. Further, in the above embodiment, since the developer on the surface of the developer supporting means is always removed by the electric field generating means,
Since the tribo of the developer in the developing region tends to be low, the elastic blade controls the layer thickness of the constrained developer on the surface of the developer supporting means, and the tribo is given to the developer. Good. In this case, when a polymer elastic body reacted with a charge controlling agent such as nigrosine or chromium / monoazo complex is used as the material of the elastic blade, it is possible to increase the tribo-imparting ability.

In the above embodiment, the case where the magnet roller is fixed and the developing sleeve rotates is described.However, the present invention is applied to the case where the magnet roller rotates and the developing sleeve is fixed, or the magnet roller and the developing sleeve rotate together. It can also be applied to cases where

Further, in the above-described embodiment, the cylindrical sleeve is exemplified as the developer supporting means. However, the developer may be configured in a form of developer conveyance using an endless belt, or a structure of an elastic roller may be used. Good.

Further, in the above-described embodiment, the developing bias is applied to the developer supporting means in a manner that a direct current is superimposed on the alternating electric field. However, only the direct current electric field can be used as the developing bias. Also, an example has been described in which the developer on the developer supporting means is in non-contact with the latent image supporting means, and development is performed by electrostatically jumping or extending the developing means. The present invention is also applicable to a case where the image is developed by sliding on the latent image supporting means. Further, the electric field generating means does not have to completely remove the developer held therein, and it is sufficient that the electric field generating means has an ability to electrostatically remove the residual developer from the developer supporting means. Therefore, the developer removing means such as the scraper blade 8 can be installed with a wide allowable range. In addition, even if the electric field generating means and the developer removing means are scratched in a long-term use, the ability to peel and remove the residual developer from the developer supporting means is not affected. Not bring.

Effects of the Invention As described above, according to the developing device of the present invention, the developer supporting means for carrying the developer on the surface and transporting the developer to the developing position, and the thickness of the developer layer on the developer supporting means And a peeling means for peeling the developer from the developer support means at a position downstream of the developing position in the moving direction of the developer support means and at a position upstream of the position regulated by the control member. The means includes a conductive member that forms a developer peeling electric field between the conductive member and the developer supporting means, and a dielectric layer that covers the conductive member. And a conductive scraping member to which a grounding or static elimination voltage is applied for peeling off the developer, so that the developer on the surface of the dielectric layer of the electric field generating means is peeled off and the dielectric layer on which electric charges are accumulated To remove or charge It is possible to repeatedly stabilize the effect of peeling off the development by the electric field generating means, and to obtain a good image regardless of the difference in the image histories.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of a main part of an embodiment of a developing device according to the present invention. FIG. 2 is a diagram for explaining a latent image potential when reversal development is performed using the developing device shown in FIG. FIG. 3 is a schematic side sectional view of a main part of another embodiment of the developing device according to the present invention. FIG. 4 is a schematic side sectional view of a main part of still another embodiment of the developing device according to the present invention. 1: Hopper 2: Developer 3: Developing sleeve 5: Regulator blade 7: Electric field generating means 8: Conductive scraper blade 11: Dielectric layer

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Claims (1)

(57) [Claims] A developer supporting means for carrying a developer on a surface thereof and transporting the developer to a developing position; a regulating member for regulating a thickness of a developer layer on the developer supporting means; and a moving direction of the developer supporting means. Peeling means for peeling the developer from the developer supporting means at a position downstream of the developing position and at a position upstream of the regulating position by the regulating member. In a developing device having a conductive member that forms an electric field and a dielectric layer that covers the conductive member, a ground or static elimination voltage is applied to contact the dielectric layer and peel off the developer on the dielectric layer. A developing device comprising a conductive scraping member.