JPH03185476A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the charge-up of an application roller by forming the application roller of an elastic body having a prescribed specific resistance value and providing a bias power source which impresses bias whose polarity is switched between the application roller and a sleeve. CONSTITUTION:The application roller 4 is formed of the elastic body having the specific resistance value 10<7>-10<12>OMEGAcm. The bias power source 7 is provided between the sleeve 3 and the application roller 4 and the bias is impressed so as to obtain a potential difference between them and the polarity of the bias is switched. In the case of the specific resistance value <10<7>OMEGAcm, the resistance of the application roller 4 is so low that the bias passes and leaks from the application roller 4 even though the bias is impressed between the sleeve 3 and the application roller 4 to obtain the potential difference. In the case of the specific resistance value >10<12>OMEGAcm, the resistance of the application roller 4 is so high that charges are accumulated on the application roller 4, which is charged up.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to a developing device used to develop an electrostatic latent image formed on an image bearing member in an image forming apparatus using an electrophotographic method or the like. The present invention relates to a developing device including an IF & minute developer consisting only of toner.

In an image forming apparatus that uses an electrophotographic method, an electrostatic latent image is formed on an image carrier, developed to make it visible as a toner image, and the toner image is transferred onto a transfer material. The image is obtained by transferring.

In the above development, the one-component developing method using an l-component developer consisting only of toner has a simpler structure of the developing device and has better development characteristics than the two-component developing method using a mixture of magnetic particles and toner. It has advantages such as being stable and easy to maintain, and several methods and devices have been devised and put into practical use in recent years.

FIG. 6 shows an example of the developing device.

The developing device is provided close to the photosensitive drum 11 of the image forming apparatus, as shown in FIG. This photosensitive drum 11
A photoconductive layer is provided on a conductive substrate, and an electrostatic latent image is formed on the photosensitive drum 11 by a charging means and an exposure means (not shown), and the electrostatic latent image is developed and visualized by a developing device. Ru.

This developing device has an application roller 4 in a toner container l,
A conductive sleeve 3 like A4 rotating in the direction of arrow A
The applicator roller 4 rotates in the direction of arrow B in the figure so that the application roller 4 has a relative speed with respect to Apply. In order to perform this application well,
The application roller 4 is preferably spongy or knurled.Next, the toner applied onto the sleeve 3 is spread into a predetermined layer by a blade 2 made of an elastic material such as urethane rubber or phosphor bronze. It is heavily regulated.

The sleeve 3 and the photosensitive drum 11 are in contact or non-contact state, and in the case of non-contact state, the distance between them is 50 to 500 μm.
are held with a gap between them. The toner regulated to a predetermined layer thickness by the blade 2 is conveyed to the development position facing the photosensitive drum 11 by the rotation of the sleeve 3, where it adheres to the electrostatic latent image on the photosensitive drum 11 and is developed. Visualizes the electrostatic latent image as a toner image. When developing, sleeve 3
A bias power supply 6 applies a developing bias of DC or a DC 6 and AC.

Note that a sheet 5 is provided to prevent the toner from blowing out from the lower part of the toner container 1 .

The toner image formed on the photosensitive drum 11 as described above is transferred onto a transfer material by a transfer means (not shown),
After that, it is made into a fixed image through a fixing process.

However, the conventional developing device described above has two major problems as described below.

The first problem is that the amount of charge held by the toner on the sleeve 3 increases and the toner is charged up, resulting in a sleeve ghost phenomenon.

For example, as shown in Figure 7(a), an image with vertical lines is first printed, and then a halftone image is printed as shown in Figure 7(b). In this case, vertical lines corresponding to the vertical lines in the first print image appear darker in the halftone print image obtained from the second print, and the quality of the print image is significantly affected. damage.

The causes of this sleeve ghost are as follows.

In the first print, the toner on the sleeve 3 is consumed in the area corresponding to the vertical line, which is one image area, and is not consumed in the area corresponding to the non-image area excluding the vertical line. Therefore, the toner on the sleeve 3 is consumed. New toner is applied to the removed area by the application roller 4, and the layer thickness is regulated to a predetermined thickness by the blade 2 in preparation for the next development.

However, in the part of the sleeve 3 where the toner is not consumed, although some of the toner is stripped off by the applicator roller 4, most of the toner remains on the sleeve 3, and the remaining toner is removed by the applicator roller 4 and the blade 2. As the sleeve 3 is rubbed again, the process of increasing the amount of charge to 0 or more is repeated, and the amount of charge of the toner in the non-consumed portion of the sleeve 3 increases greatly and is charged up. , there is a difference in the amount of toner charge between the non-consumed portion and the consumed portion.

When the amount of electric charge of the toner on the sleeve 3 was measured using a Faraday gauge under the situation where the sleeve ghost occurs as shown in FIGS. 7(a) and (b), the amount of electric charge of the toner was determined by A large difference was observed, with 15 μc/g in the area and 30 μc/g in the non-consumption portion.

On the other hand, the toner adheres to the sleeve 3 due to the reflection force due to its own charge, and the larger the amount of charge, the greater the reflection force and the stronger the toner adhesion onto the sleeve 3. Therefore, when there is a difference in the charge amount of the toner as described above, a difference occurs in the amount of toner transferred from the sleeve 3 onto the photosensitive drum 11. That is, toner with a low charge amount easily transfers to the photosensitive drum 11 and is used for development, whereas toner with a high charge amount remains attached to the sleeve 3 and does not contribute to development, and as a result, is not used for development. There is a difference in the amount of toner used, as shown in Figure 7 (
Sleeve ghosts shown in a) and (b) occur.

The second problem is the charge-up phenomenon, which tends to be particularly strong in low-humidity environments, and when printing is performed continuously, electric charge accumulates on the surface of the application roller 4 that applies toner onto the sleeve 3. occurs and sleeve 3
The problem is that toner cannot be applied satisfactorily on the surface.

Specifically, as the sleeve 3, a cylindrical body made of AI2 with a diameter of 20 mm was used, and as the application roller 4, a stainless steel core metal with a diameter of 6 mm was coated with foamed urethane rubber with a layer thickness of 5 mm. The coating roller 4 was rotated at a circumferential speed of 50 mm/sec, and the coating roller 4 was rotated at a circumferential speed of 60 mm/sec, and used for development in printing an image. A nonmagnetic toner that is negatively charged was used as the toner.

When I performed continuous printing under the above conditions at a temperature of 15°C and a humidity of 10% Rh, good print images were obtained for up to a few dozen sheets, but after that the density gradually decreased and density unevenness occurred. did. When the developing device was removed from the printer in this state and observed, it was found that the toner layer was not uniformly formed on the sleeve 3 and the toner layer was very uneven. When the coating roller 4 was removed from the developing device and the surface potential of the coating roller 4 was measured using a surface electrometer (manufactured by Monroe Co.), 1. +3
There was a high potential of more than kV, which exceeded the measurement range of the surface electrometer. This is considered to be because the application roller 4 is frictionally charged by rubbing against the toner and the sleeve 3, and the generated electric charge is accumulated in the application roller 4.

In order to solve the second problem, a method has been devised in which the coating roller 4 is made of conductive material. This is achieved by making the applicator roller 4 conductive so that electric charges can be transferred to the applicator roller 4.
This is because the charge-up is prevented from accumulating.

However, in this case, since both the sleeve 3 and the applicator roller 4 are conductors, it is not possible to create a potential difference between them.
When applying toner on the sleeve 3, the toner is applied onto the sleeve 3 only by the mechanical sliding force of the application roller 4. Therefore, in order to perform good coating, the coating roller 4 must strongly contact the sleeve 3 and rotate at high speed.As a result, the torque of the sleeve 3 increases, and the coating roller 4 must be rotated at high speed.
This leads to problems such as faster wear of the parts.

Furthermore, when controlling the amount of toner applied on the sleeve 3, it is necessary to change the peripheral speed of the application roller, which poses a major restriction. This method also has the disadvantage that it cannot solve the first problem.

Therefore, an object of the present invention is to be able to apply toner on a sleeve without strongly contacting the application roller on the sleeve or rotating at high speed, and to easily control the amount of toner applied. To provide a developing device capable of eliminating sleeve ghost by preventing charge-up of toner applied on a sleeve, and capable of eliminating image unevenness by preventing charge-up of an application roller. That's true.

The above-mentioned object is achieved by the developing device according to the present invention. In summary, the present invention involves coating and carrying a one-component developer by a developer application member on a developer carrier facing the image carrier in a contact or non-contact state, and applying the developer by the developer carrier. transporting the agent to a developing section facing the image carrier;
In the developing device for developing the electrostatic latent image formed on the image carrier with the developer, the developer applying member is formed of an elastic body having a specific resistance value of 10 7 to 10 12 Ωcm, and the developer applying member The special copying apparatus is characterized in that a bias power source for applying a bias whose polarity is switched is provided between the developer carrier and the developer carrier.

According to a preferred embodiment of the present invention, the polarity of the bias is switched when the electrostatic latent image is not developed, and the elastic body has a resistivity value of 100% by dispersing a double oxide.
7 to 101 Ωcm is obtained.

1L example Examples of the present invention will be described in detail below.

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention.

As shown in FIG. 1, the developing device is provided in close proximity to a photosensitive drum 11 serving as an image bearing member of the image forming apparatus. This photosensitive drum 11 has a photoconductive layer provided on a conductive substrate.1 An electrostatic latent image is formed on the photosensitive drum 11 by a charging means and an exposure means (not shown), and the electrostatic latent image is developed by a developing device. and visualized.

The developing device has an application roller 4 in a toner container 1, and the application roller 4 rotates in the direction of arrow B in the figure so that it has a relative speed with respect to a conductive sleeve 3 such as 84 that rotates in six directions of arrows. The sleeve 3 is rotated to apply the negative polarity non-magnetic one-component toner as a one-component developer stored in the toner container l onto the sleeve 3. In order to perform this coating well, it is preferable that the coating roller 4 is spongy or knurled.1! The spread toner is regulated to a predetermined layer thickness by an elastic blade 2 made of urethane rubber, phosphor bronze, or the like.

The sleeve 3 and the photosensitive drum 11 are in contact or non-contact state, and in the case of non-contact state, the distance between them is 50 to 500 um.
are held with a gap between them. The toner regulated to a predetermined layer thickness by the blade 2 is conveyed to the development position facing the photosensitive drum 11 by the rotation of the sleeve 3, where it adheres to the electrostatic latent image on the photosensitive drum 11 and is developed. Visualizes the electrostatic latent image as a toner image. When developing, sleeve 3
A developing bias is applied by the bias power supply 6 to.

Note that a sheet 5 is provided on the lower side of the sleeve 3 to prevent the toner from blowing out from the lower part of the toner container l.

The first feature of the present invention is that the coating roller 4 has a resistivity of 1
The second feature is that a bias power supply 7 is provided between the sleeve 3 and the coating roller 4, and a bias is applied to create a potential difference between them. The purpose is to switch the polarity.

The lower limit of the specific resistance value of the elastic body constituting the application roller 4 is set to 10
The reason why the specific resistance value is set to be 7Ωcm or more is because if the resistivity value is less than 107Ωcm, the resistance of the application roller 4 is too low, and the sleeve 3
This is because even if an attempt is made to create a potential difference between the application roller 4 and the application roller 4 by applying a bias, the bias will leak through the application roller 4. Also, the upper limit of the specific resistance value was set to 101
The specific resistance value of the elastic body is 1013 to 3Ωam or less.
This is because if it exceeds Ωcm, the resistance of the coating roller 4 will be too high, and electric charges will accumulate on the coating roller 4, causing the coating roller 4 to be charged up.

If the layer thickness of the elastic body constituting the coating roller 4 is too thin than 1 mm, it will not be possible to create a sufficient nip between the sleeve 3 and the coating roller 4, which will lead to leakage if foreign matter gets between them. There is a risk. Conversely, if the layer thickness of the elastic body is 10
If the thickness is too thick, there will be a problem that a large space will be required for the application roller 4. Therefore, the layer thickness of the elastic body is preferably 10 mm, preferably 2 to 6 mm.

In the present invention, natural rubber, EPDM, N
It is also possible to use an elastic material such as BR%CR, silicone rubber, or urethane rubber in which carbon black is added and dispersed. Since the resistance value changes rapidly when carbon black is added, slight differences in the degree of dispersion and scattering of carbon black when carbon black is added will appear in changes in the specific resistance value, making it difficult to stably obtain a medium resistance value in a single elastic body. As a result, the yield of the coating nozzle 4 is poor, mass productivity is lacking, and costs are high, which is undesirable.

Therefore, in the present invention, by adding and dispersing a double oxide in the above-mentioned rubber or resin, the specific resistance value is 107 to 10.
An elastic body of 12 Ωcm is obtained.

In the present invention, a double oxide refers to a compound of two or more types of oxides, and is therefore different from simply adding a metal oxide. An example is a double oxide.

ZnO and Alx Os, Snow and sb20. .

Examples include I n l Os and Snow. The characteristics of these double oxides are that the atomic radii of each metal are close, forming a substitutional solid solution, and that the valence numbers of each metal are different, resulting in electrical conductivity that cannot be obtained with each metal oxide alone. is obtained.

The specific resistance value of these multiple oxides is approximately 107~10''Ω
cm, which is higher than the resistivity of conductive carbon black, reinforcing carbon black, TiOt, ruthenium oxide, etc., which has a resistivity of 10-' to 107Ωcm, and is higher than the resistivity of triiron tetroxide, tin oxide, etc., which has a resistivity of 107Ωcm or more. low.

When a filler with a specific resistance value of less than 107 Ωcm, such as carbon black, is used as a filler to be dispersed in a dispersion medium such as a polymer such as rubber or resin, as mentioned above, a filler with a specific resistance value of 107 to 10 Ωcm is used. Since the resistance region corresponds to a region where the resistance value changes rapidly with respect to the amount of carbon black added, the reproducibility of the medium resistance of the elastic body and the stability of mass production of the coating roller 4 are lacking. If it is higher than 101 Ωcm, a considerably large amount of filler is required to make the elastic body exhibit a medium resistivity of 10 7 to 10 12 Ωcm, making it difficult to add and disperse the filler. Even if uniform dispersion could be achieved, the physical properties of the elastic body would be significantly inferior, and the coating roller 4 would not be able to reach a practical level.The hardness of the elastic body would also increase, making it difficult for the coating roller 4 to have sufficient and stable contact with the sleeve 3, etc. This may cause problems such as not being able to achieve pressure contact.

On the other hand, as in the present invention, the specific resistance value lO-~10sΩ
When using a double oxide of cm as a filler, the specific resistance value of 107 can be achieved in the elastic body at an amount that does not cause any disadvantage to the physical properties.
Among the above-mentioned double oxides, the combination of ZnO and Al2*Os is particularly effective because a medium resistance of ~10"Ωcm can be stably obtained, and the reproducibility of the medium resistance of the elastic body and the stability of mass production of the coating roller 4 are also good. The reason for this is that the double oxide of this combination has a specific resistance value of 1O3 to IO3Ωcm.
The resistance value is the most ideal value for resistance stability in the medium resistance range due to changes in the amount added to the elastic body and the amount added, and it is easy to disperse in polymer dispersion media such as rubber and resin. Al2 < Al2m
For example, the resistance value can be controlled and achieved by adjusting the doping amount of o-).

Next, further explanation will be given with specific examples.

EPDM is used as the elastic material, and Zn0-Al
20. When 100 parts of was added, dispersed, and foamed, an elastic body with a medium resistance of 107 Ωcm was obtained. This elastic body was provided in a layer with a thickness of 5 mm on a core metal with a diameter of 6 mm to obtain a coating roller with a diameter of 16 mm. This sleeve was then assembled into the developing device shown in FIG. 1 and used in an image forming apparatus.

Here, the sleeve 3 and the photosensitive drum 11 were kept in a non-contact state, and the gap therebetween was, for example, 150 μm. A developing bias was applied to the sleeve 3 by a developing bias power source 6 in order to develop the latent image on the photosensitive drum 11. On the photosensitive drum II, the non-image area -700V, the image area -50V
A latent image was formed at a potential of , and a developing bias of -600 V was applied to the sleeve 3 by the developing bias power supply 6 to perform reversal development. At this time, the peripheral speed of the sleeve 3 and photosensitive drum 11 is 50 mm/sec, and the peripheral speed of the application roller 4 is 6
The speed was set to 0 mm/sec.

When continuous printing was performed under the above conditions at a temperature of 15° C. and a humidity of 10% Rh, no charge-up of the application roller 4 was observed.

Next, the circumferential speed of the application roller 4 is reduced to 40 mm/sec, and a bias is applied between the sleeve 3 and the application roller 4 by a bias power supply 7, and the change in the bias and the amount of toner applied on the sleeve 3 are We investigated the relationship between The results are shown in FIG. 2. Here, the bias value is the potential of the sleeve 3 when the application roller 4 side is set as a reference potential, and the amount of toner applied on the sleeve 3 is the unit area of the surface of the sleeve 3. The amount of charge of the toner on the sleeve 3 at this time was constant at approximately -20 μc/g.

As is clear from FIG. 2, the sleeve 3 and the application roller 4
The amount of toner on the sleeve 3 also increases as the bias applied between the two becomes more positive. This is because the toner used has negative polarity, so when the above bias is set to positive, the electric force acting on the toner goes from the application roller 4 to the sleeve 3, so the amount of toner applied onto the sleeve 3 increases, and vice versa. When the bias is made negative, the electric force is directed from the sleeve 3 to the application roller 4, so that the amount of toner applied onto the sleeve 3 is reduced.

Therefore, if a bias of -600 V is applied between the sleeve 3 and the application roller 4, almost all of the toner on the sleeve 3 will be stripped off by the application roller 4. Therefore, as the bias power supply 7, +600V, -6
Using a power supply capable of switching between 00V (732 outputs), printing was performed according to the image forming sequence shown in FIG.

FIG. 3 shows a sequence regarding exposure, developing bias, and bias between the sleeve and the application roller when printing two sheets in succession as one image formation. Note that exposure is performed by turning on a light emitting element such as a laser based on one image information.
0FFL is an operation for forming a latent image on the photosensitive drum 11.

As shown in FIG. 3, a pre-rotation is performed to flatten the surface potential on the photosensitive drum 11 after a print command is issued until exposure is performed (Step 5 in a). At this time, exposure and The developing bias is turned off. The bias between the sleeve 3 and the application roller 4 is turned on at -600V.
state, and no toner is applied onto the sleeve 3.

Next, the pre-rotation is completed and coating is performed (step b).
Since the exposure position and the development position on the photosensitive drum 11 are usually different, the development bias is turned on a little after exposure starts, and a predetermined development bias is set between the sleeve 3 and the photosensitive drum 11'. is applied. Then, the bias between the sleeve 3 and the application roller 4 is switched to +600V, and the toner is applied onto the sleeve 3.

A short while after the exposure of the first sheet is completed, the developing bias is turned off (step C).At this time, the bias between the sleeve 3 and the application roller 4 is switched to -600V, and the toner on the sleeve 3 is turned off. is peeled off by the application roller 4.

Next, the second sheet is exposed (step d), and the bias between the developer bias, sleeve 3, and application roller 4 is also set to 1.
It is controlled in the same way as in the case of the second image.

When the exposure of the second sheet is completed, the process of post-rotation begins (step e), the developing bias is turned off, and the bias between the sleeve 3 and the coating roller 4 is maintained for at least one rotation period of the sleeve 3. The voltage is switched to -600V, the toner on the sleeve 3 is removed, and the voltage is turned off.

The above describes the case where two sheets are printed consecutively, but
If you want to print 3 or more sheets in a row, follow step d in Figure 3.
After that, steps C and d may be repeated for the required number of sheets.

When printing was performed under the above sequence, not only the phenomenon of charge-up of the application roller 4 but also the phenomenon of sleeve ghost due to charge-up of the toner on the sleeve 3 did not occur. This is done by switching and applying a bias between the sleeve 3 and the application roller 4 during non-development.

This is because toner charge-up can be prevented by removing the toner on the sleeve 3 and applying new toner on the sleeve 3 again during development.

Furthermore, as can be seen from FIG. 2, the amount of toner applied onto the sleeve 3 can be freely controlled by changing the bias voltage applied between the sleeve 3 and the application roller 4 during development. This eliminates the need to forcefully press the coating roller 4 onto the sleeve 3 or rotate the coating roller 4 at high speed.

In the above description, a non-magnetic toner is used for development, but it goes without saying that magnetic toner can be used as well, and the sequence of image formation is not limited to that shown in FIG. The key is to use sleeve 3 when not developing.
It goes without saying that a conventional image forming sequence can be applied as long as there is only an operation to switch the bias between the roller 4 and the application roller 4.

FIG. 4 is a schematic diagram showing another embodiment of the developing device of the present invention.

In this embodiment, as shown in FIG. 4, a bias circuit 17 is provided between the sleeve 3 and the coating roller 4 so that the bias applied between them is obtained from the developing bias applied to the sleeve 3. It is characterized by what it did. The developing bias power source 6 is a bias power source capable of outputting a bias obtained by superimposing alternating current on direct current. According to this embodiment, only one of the developing bias power sources 6 is required as a bias power source, which reduces the size and cost of the developing device. It is possible to downsize.

The rest of the structure of this embodiment is basically the same as that of the developing device shown in FIG. 1, and the same reference numerals in FIG. 4 as in FIG. 1 indicate the same members.

The bias circuit 17 connects the coating roller 4 to the sleeve 3.
Diode D is connected in the forward direction toward
A grounded capacitor C is connected to the positive electrode side of the capacitor C, and a switch S is inserted between the coating roller 4 and the capacitor C so as to be able to switch between the capacitor C and the ground. The bias circuit 17 rectifies the developing bias applied to the sleeve 3 by the developing bias power supply 6 during development with a diode D, smoothes it with a capacitor C, and applies the resulting bias to the application roller 4. It is 9.

Specifically, as shown in FIG. 5(a), as the developing bias that the developing bias power supply 6 applies to the sleeve 3, DC voc = -500 V and AC V ac = 1400 Vp-.
When a voltage on which p is superimposed is output, the output voltage is rectified by the diode D of the bias circuit 17 to a voltage V of only the part where V oc + V Ac < O, as shown in FIG. 5(b). . Then that rectified voltage v
l is smoothed by a capacitor C, and the resulting potential shown as Vt''-800V is applied to the coating roller 4. Therefore, the potential of the sleeve 3 seen from the coating roller 4 is (VDe+VAC) -VT = (-500f700
)-(-800)=-400, +1000V, and changes between -400 and +tooov with the cycle of the developing bias vAc.

When an AC bias is applied between the sleeve 3 and the applicator roller 4 in this way, whether the toner is applied onto the sleeve 3 or peeled off from the sleeve 3 depends on the relationship between the sleeve 3 and the applicator roller 4. determined by the average value of the bias between Under the above conditions, the average value of the bias is the potential difference between the developing bias VIIG and the potential of the application roller 4.

-500-(-800)=300V, so the toner receives a force directed toward the sleeve 3 and is applied onto the sleeve 3.

Next, when not developing, switch S is switched to the ground side to ground the application roller 4. Then, the average value of the bias between the sleeve 3 and the application roller 4 is -500-0=-500
V, and the toner is peeled off from the top of the sleeve 3.

When printing was carried out under the above conditions, not only the charge-up phenomenon of the applicator roller 4 but also the sleeve ghost phenomenon due to the charge-up of the toner on the sleeve 3 did not occur as in the previous embodiment.

As explained above, in the developing device of the present invention, the developer applying member for applying the one-component developer to the developer carrier is formed using an elastic body having a resistivity of 107 to 1Q12ΩCm. Therefore, it is possible to prevent the developer applying member from being charged up, and a bias power source can apply a bias between the developer carrying member and the developer applying member to create a potential difference. Therefore, it is possible to properly apply the developer onto the developer carrier with the developer coating member without strongly contacting the developer coating member with the developer carrier or operating the developer coating member at high speed. In addition, the polarity of the bias between the developer carrying member and the developer applying member can be reversed during non-development to remove the developer on the developer carrying member. By doing so, it is possible to prevent charge-up of the developer, and therefore it is possible to eliminate the problem of sleeve ghost development.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention. FIG. 2 is a graph showing the relationship between the bias between the sleeve and the application roller and the amount of toner applied on the sleeve in the developing device shown in FIG. FIG. 3 is an explanatory diagram showing an image forming sequence in an image forming apparatus incorporating the developing device shown in FIG. FIG. 4 is a schematic diagram showing another embodiment of the developing device of the present invention. FIG. 5(a) is a graph showing the developing bias caused by the developing bias power supply provided in the developing device of FIG. FIG. 5(b) is a graph showing the bias between the sleeve and the application roller obtained from the developing bias using the same bias circuit. FIG. 6 is a schematic configuration diagram showing a conventional developing device. FIGS. 7(a) and 7(b) are explanatory diagrams showing sleeve ghosts occurring in printing using the developing device shown in FIG. 6. FIGS. : Toner container blade: Sleeve: Application roller: Developing bias power supply: Bias power supply: Photosensitive drum 17: Bias circuit diagram Figure 2-600-400-20002■400600800 Bias between sleeve and application roller (V) Figure 5 (a) ) (b) Figure 6, 7 (b)

Claims (1)

[Scope of Claims] 1) A one-component developer is coated and carried by a developer application member on a developer carrier facing the image carrier in a contact or non-contact state, and the developer carrier In a developing device that conveys a developer to a development position opposite to the image carrier and develops an electrostatic latent image formed on the image carrier with the developer, the developer applying member has a specific resistance. It is formed of an elastic body having a value of 10^7 to 10^1^2 Ωcm, and between the developer application member and the developer carrier,
A developing device characterized by being provided with a bias power supply that applies a bias whose polarity is switched. 2) The developing device according to claim 1, wherein the polarity of the bias is switched when the electrostatic latent image is not being developed. 3) The elastic body obtains the specific resistance value of 10^7 to 10^1^2 Ωcm by dispersing a double oxide.
Or the developing device according to 2.