JP2005308900A - Developing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus which can prolong its life while suppressing dropping of a non-charged toner, low charged toner, oppositely charged toner or deteriorated toner as aggregation of these inferior toners apt to be generated immediately after replenishing toner in a developing apparatus employing a contact developing system using a positive charge nonmagnetic single component toner, even when the developing apparatus judged to be at the end of its life from the viewpoint of image qualities is replenished with a new external toner to be continuously used. <P>SOLUTION: The developing apparatus 100 employing a developing system using a nonmagnetic single component toner 20 is equipped with such a mechanism that controls the voltage (A) applied on a supply roller 3 to be higher by ≥50 V than the voltage (B) applied on a developing roller 4 after the toner is replenished and during the predetermined number of paper sheets are printed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention continues to use a developing device using an electrophotographic non-magnetic one-component positively charged toner, particularly a developing device that has reached the end of its life, used in an electrophotographic apparatus typified by a laser printer or a copying machine. The present invention relates to a developing device having excellent image quality stability even after replenishment of new external toner.

  Among electrophotographic apparatuses such as laser printers and copiers, the non-magnetic one-component positively charged contact developing system has recently become widespread, particularly for small-sized apparatuses. This one-component positively-charged developing system has the advantage that it can not only reduce the size and price of the developing device, but also excel in high-resolution images compared to a developing system that uses a two-component developer. Therefore, it has come to be widely used. Furthermore, when combined with a cleanerless development method, untransferred toner can be collected and reused in the development process, and the effective utilization of the toner is increased.

  On the other hand, a developing device using a non-magnetic one-component toner is inferior in chargeability and transportability of the toner due to the fact that it does not have a carrier for transporting the toner, compared to a developing device using a two-component developer. In particular, the pulverized toner has a problem in that image quality such as a decrease in uniformity of solid black density and an increase in fogging are observed with long-term repeated use. As an invention paying attention to this point, the bias voltage applied to the toner supply roller is variably controlled in accordance with the change in physical properties generated on the surface of the toner supply roller as the number of sheets to be passed increases. There has been known a developing device improved so as to reduce a decrease in uniformity in a black image (Patent Documents 1-0006, paragraph 0010).

  Furthermore, in image formation using a non-magnetic one-component positively charged toner, defects such as fogging and poor solid density uniformity are identified, the specific surface area of the toner particles is specified, and the developing roller is compared with the supply roller. An invention improved by applying a bias potential that is 100 to 400 V higher than the bias potential (absolute value) is also known (Patent Document 2-0004, paragraph 0005).

In addition, an invention is known in which a bias voltage applied to a thin layer member is controlled in accordance with the degree of toner aggregation to obtain a good thin layer formation and a good image formation without being disturbed by the aggregation toner ( Patent Document 3-Problem, Solution).
JP-A-6-194944 JP-A-9-197710 Japanese Patent Application Laid-Open No. 2000-221776

  However, a general problem with a developing device that combines the non-magnetic one-component positively charged toner and the cleaner-less developing method is that the life of the developing unit is still short, but it has not been solved sufficiently. Not. The cause of the short life is that the untransferred toner is collected and reused in the developing unit, and therefore, the deteriorated toner such as the one in which the external additive or charge control agent is peeled off inside the developing device by repeated printing or the crushed toner pieces It is to increase gradually as it accumulates. For this reason, the chargeability and transportability of the toner are deteriorated and the image quality is liable to deteriorate, and it becomes increasingly difficult to maintain a good image as the number of sheets passed increases. Moreover, this is not basically solved by the inventions described in Patent Documents 1, 2, and 3.

  The cleanerless development method includes both a positively charged type and a negatively charged type process. However, the problem that the image quality is likely to deteriorate is a positively charged type process. This tends to be remarkable when using a toner having a copolymer resin as a base resin. The problem with the former positive charging process is that all resin materials used as the base resin constituting the positively charged toner are inherently easily negatively charged. In other words, the positively charged toner forcibly positively charges the base resin material that is easily negatively charged by the charge control agent, so that it is structurally or geometrically damaged by mechanical damage such as contact friction or electrochemical damage. The charge control agent and the external additive are easily negatively charged because they are easily peeled off from the base resin, buried easily, or easily changed chemically. As the negatively charged toner increases, as described above, the chargeability and transportability of the toner gradually deteriorate and the image quality deteriorates. When using the latter toner based on styrene-acrylic copolymer resin as a base resin, it is superior to the toner based on polyester resin in terms of positive charge and can provide high image quality. However, the mechanical strength of the resin itself is low. Therefore, the toner is easily damaged mechanically, and as described above, the toner is easily negatively charged, and the image quality is deteriorated.

  Thus, in the cleanerless type developing device or developing unit using the positively charged non-magnetic one-component pulverized toner, as described above, the developing device is downsized, the price is reduced, the resolution is high, and the toner is effectively used. On the other hand, there are problems in the stability and reliability of image quality obtained after repeated use. In order to avoid this problem, in an actual apparatus, the toner is consumed when about two-thirds of the initial toner amount is consumed before the deteriorated toner ratio becomes high and the deterioration in image quality becomes conspicuous. In many cases, a developing device or a developing unit including the above is regarded as a life and replaced with a new one. This shortens the life of the positively charged non-magnetic one-component cleaner-less developing device or unit and is a disadvantage in terms of running cost. In addition, the developing device or unit to be discarded includes parts that have not reached the end of their life, such as a developing roller and a supply roller, which are relatively expensive.

  As described above, another reason why the developing device or unit that has reached the end of its life is discarded and replaced with a new one is that only the new toner is applied to the developing device or developing unit that contains the toner that has reached the end of its life. When a new image is formed again after replenishment, the toner in the toner container portion contains a lot of deteriorated toner before replenishment for a while immediately after toner replenishment and before the toner is sufficiently stirred. That is, the state that exists particularly near the supply roller and the developing roller is maintained as it is. When the electrophotographic process is operated in such a state, the deteriorated toner is conveyed to the developing roller by the supply roller, and the ratio of reaching the vicinity of the surface of the photosensitive drum is high, and the deteriorated toner is near the surface of the photosensitive drum. The toner becomes an invalid toner having no effective developing function, such as uncharged toner, low-charged toner, and reversely-charged toner, and exists between the developing roller and the photosensitive drum. Such invalid toner adheres to the unexposed area during development of the photosensitive drum and causes fogging. Furthermore, any of the invalid toners has a weak holding force on the surface of the developing roller, and when present as a reversely charged toner, the reversely charged toner easily adsorbs other normal toners and aggregates. The agglomerated toner also has a weak holding force on the developing roller, and easily falls on the recording sheet from between the photosensitive drum and the developing roller together with the uncharged toner and the low-charged toner, and easily contaminates the image. For this reason, it is not considered a practical method to replenish the toner in the non-magnetic single component cleaner-less development method and extend the life of the development device. It was exchanged.

  On the other hand, Patent Document 1 describes a developing device that reduces density reduction even in a solid image by variably controlling the bias voltage applied to the toner supply roller in accordance with the change in physical properties of the toner supply roller itself. . Certainly, this will slightly extend the life of the developing device. However, the toner described here is a toner using a polyester resin as a base resin, and is a negatively charged toner. In addition, a new external toner is supplied to a developing device or a developing unit that has come to be replaced. There is no idea to extend the service life, and there is no suggestion, and further, the phenomenon of physical property change on the surface of the toner supply roller seems to be irrelevant to the presence or absence of toner replenishment. Therefore, Patent Document 1 seems not to be effective.

  Further, Patent Document 2 discloses a defect in which fogging and solid density uniformity are inferior in image formation using a nonmagnetic one-component positively charged toner (a toner having a polyester resin as a base resin). Although the specific surface area of the particles is specified and the supply roller is applied with a bias potential that is 100 to 400 V higher than the bias potential (absolute value) of the developing roller, there is a description of the invention. There is no disclosure regarding making it higher than the roller. In any case, there is no description or suggestion regarding the life extension of the developing device or the developing unit that has come to be replaced.

  Patent Document 3 is an invention relating to control by varying the bias potential to the thinned member, and it seems that the direct relationship with increasing the applied voltage to the supply roller is thin.

  The present invention has been made in view of the above points. The object of the present invention is determined to be a lifetime from the viewpoint of image quality in a contact developing type developing device using a positively charged nonmagnetic one-component toner. Even if new external toner is replenished to the developing device to be used continuously, uncharged toner, low-charged toner, reverse-charged toner, or deteriorated toner aggregated from them, which is likely to be generated immediately after toner replenishment, or fogged images are generated. It is an object of the present invention to provide a developing device that can suppress the life of the developing device.

  According to the first aspect of the present invention, there is provided a developing device using a developing system that uses non-magnetic one-component toner, at least a toner container having a structure capable of replenishing new external toner, a supply roller, A developing roller and a layer thickness regulating member, wherein the supply roller holds the toner in the toner container portion on the surface of the supply roller and carries the toner to the developing roller by rotation of the supply roller, and the developing roller receives from the supply roller The toner is charged by frictional charging between the developing roller and a layer thickness regulating member, held on the surface of the developing roller and thinned, and then conveyed to a contact surface with the surface of the photoreceptor by rotation of the developing roller, In the developing device having a mechanism for visualizing the electrostatic latent image on the surface of the photosensitive member, when the applied voltage to the supply roller is A and the applied voltage to the developing roller is B, the toner By providing a developing device having a mechanism for setting the applied voltage A to the supply roller to be 50 volts or more higher than the applied voltage B to the developing roller while processing a predetermined number of printed sheets after feeding, the object is Achieved.

  According to the second aspect of the present invention, it is preferable that the predetermined number of printed sheets is 10 to 30 sheets of A4 paper.

  According to the present invention as set forth in claim 3, the developing system is a cleanerless developing system in which the untransferred toner is recovered and reused in the developing process. It is more preferable to use the developing device.

  According to the present invention described in claim 4, it is desirable that the developing device according to claim 1, wherein the toner is a styrene-acrylic copolymer resin as a base resin.

  According to the present invention, in a contact developing type developing device using a positively charged non-magnetic one-component toner, a new external toner is replenished to a developing device that is determined to have a lifetime from the viewpoint of image quality and used continuously. In addition, the present invention provides a developing device capable of extending the life by suppressing the occurrence of uncharged toner, low-charged toner, reverse-charged toner, or deteriorated toner in which the toner is aggregated or fogged images that are likely to occur immediately after toner replenishment. be able to.

  Hereinafter, the developing device of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the examples described below as long as the gist thereof is not exceeded. FIG. 1 is a schematic cross-sectional view of an electrophotographic non-magnetic one-component contact developing image forming apparatus including a developing device according to the present invention.

  The positively charged toner can be divided by the method of making fine particles. A resin obtained by pulverizing various thermoplastic resins such as a polyester resin in which a colorant such as a pigment or a dye, a charge control agent or the like is melted, or a styrene-acrylic copolymer. Using powder as a base, pulverized toner to which external additives such as silica, alumina and titanium oxide fine particles have been added, and monomers of polymer compounds such as styrene and acrylic to which colorants and charge control agents are added Using spherical styrene-acrylic copolymer fine particles obtained by copolymerization by a known polymerization method such as suspension polymerization or emulsion polymerization as a base, fine particles such as silica and titanium oxide for further improving fluidity and chargeability There are polymerized toners to which an external additive comprising:

  As the binder resin used in the nonmagnetic one-component pulverized toner 20 according to the present invention, a resin mainly composed of a general thermoplastic resin which is well known and has good fixability, for example, a polyester resin, a polystyrene resin, Examples thereof include a styrene acrylic copolymer resin, an epoxy resin, a vinyl chloride resin, a vinyl acetate resin and the like, and a resin having a main component of a mixture or two or more copolymer resins. In particular, when a styrene-acrylic copolymer resin is used as a binder resin, the charge control agent is excellent in compatibility when a charge control agent based on a similar copolymer resin is used, and prevents the charge control agent from being detached after repeated use of the toner. It is preferable because it is effective. For example, in the case of a styrene acrylic copolymer resin, in order to satisfy both good fixability and offset resistance of the toner, a weight molecular weight distribution in the range of 200 to 9000000 is shown, thousands of low molecular weights and hundreds of thousands of A resin having a peak distribution in both high molecular weights is preferred.

  The pulverized toner based on the styrene-acrylic copolymer resin is superior to the polyester resin-based toner in that it is less expensive and has higher image quality. It is inferior. However, the former toner based on the styrene-acrylic copolymer resin is more effective than the latter toner based on the polyester resin, so that the advantages of the low price and high image quality can be obtained. The benefits are great.

  The image forming apparatus shown in FIG. 1 is a cross-sectional view of a principal part showing a developing device (developing unit) 100 and a drum unit 200 combined so that the developing roller 4 and the photosensitive drum 6 face each other.

  The developing device (developing unit) 100 includes a toner container portion 1, a toner stirring blade 2, a supply roller 3, a developing roller 4, and a layer thickness regulating blade 5 made of a conductive member such as stainless steel. The DC voltages applied to the supply roller 3, the developing roller 4, and the layer thickness regulating blade 5 are shown in FIG. 1 using so-called electric circuit diagram symbols. The same potential is preferably applied to the supply roller 3 and the layer thickness regulating blade 5. A DC voltage is not applied to the toner container portion 1 and the toner stirring blade 2. The toner container portion 1 includes a toner 20 and a toner stirrer 2 therein, and stirs the toner 20 so that the toner 20 does not aggregate. The toner container portion 1 has an opening facing the supply roller 3 and the developing roller 4 side. From the toner 20 to the supply roller 3. The toner agitator 2 is in the toner container 1, and the supply roller 3, the developing roller 4, the layer thickness regulating blade 5, etc. are outside the opening of the toner container 1.

  The drum unit 200 includes a photosensitive drum 6 and a charger 7. Furthermore, an electrophotographic process member such as an exposure device 8 and a transfer device 9 outside the unit is disposed on the outer periphery of the photosensitive drum 6, and an image forming apparatus is configured by including a fixing device 10 and the like. The photosensitive drum 6 is preferably a photosensitive drum on which a single-layer photosensitive layer for positive charging is formed. However, it may not be a single-layer photosensitive layer for positive charging. Examples of the positive charging device 7 include a corotron, a scorotron, a charging roller, and the like. A low-cost and highly reliable scorotron charging device is preferable.

  In FIG. 1, the developing device (developing unit) 100 and the drum unit 200 are separated from each other. However, the developing unit and the drum unit may be substantially integrated as one unit. Although not shown, the toner container 1 in the developing device (developing unit) 100 may be separated and removed as a toner cartridge. The top of the toner container portion 1 according to the present invention has a lid 1a and the entire top of the container portion can be opened, but may be a small window-like opening that can be opened and closed.

  The developing device 100 according to the present invention performs the electrophotographic process function together with the positive charging device 7, the exposure device 8, the transfer device 9, the paper dust removing device 11, and the like disposed on the outer periphery of the photosensitive drum 6. In addition, the image is formed in order and recorded on a sheet via the fixing device 10 and output.

The toner 20 is formed by using base resin fine particles made of styrene-acrylic copolymer resin as a toner base material, and a charge control agent, a colorant, silica and the like are uniformly fixed on the surface of the base material. The toner 20 is conveyed to the supply roller 3 by the agitator 2, conveyed to the contact portion with the developing roller 4 by the rotation of the supply roller 3 in the direction of the arrow (FIG. 1), and sent to the developing roller 4 side. The supply roller 3 holds the toner 20 on a sponge-like uneven surface and conveys the toner 20 by its rotation. Initially, a DC voltage A having the same potential as that of the developing roller 4 is applied to the supply roller 3. The reason is that if the applied voltage value to the supply roller 3 is lower than the applied voltage value B to the developing roller 4, the toner 20 is suppressed from being conveyed from the supplying roller 3 to the developing roller 4, and the necessary amount of toner becomes insufficient and high. This is because the transport amount and the charge amount are increased, but it is also not preferable from the viewpoint of image quality in any case such as causing the generation of deteriorated toner. When the above-described toner 20 is transported little, specifically, the amount of toner 20 necessary for development is insufficient, and solid black image density non-uniformity (solid black gradually fades) appears.
However, if the deteriorated toner gradually increases in the toner in the toner container as it is repeatedly used, the ratio of normal toner decreases. Will appear. In this case, by setting the applied voltage value A to the supply roller 3 to be higher than the applied voltage value B to the developing roller 4, the amount of toner required for development may be increased, although this may cause an increase in deteriorated toner as described above. Therefore, priority is given to ensuring the toner amount, and the toner charge amount and transport amount are increased to ensure a normal toner amount. However, if the applied voltage A is too high, a fogged image due to deteriorated toner such as reversely charged toner or lowly charged toner tends to appear, and must be avoided.

  Next, when the toner 20 reaches the pressing portion between the blade-shaped metal elastic body (layer thickness regulating member) 5 and the developing roller 4 on the developing roller 4, the toner 20 is pressed or pressed against the developing roller 4 and the layer thickness regulating blade. The toner particles 5 are triboelectrically charged and further thinned to about two layers of toner particles, and are then conveyed to the surface of the photosensitive drum 6 along with the rotation in the direction of the arrow in FIG. Visualize. A predetermined positive direct current voltage is applied to the developing roller 4 to transfer the toner 20 appropriately to the printing portion (exposure portion) which is a relatively low potential portion in the electrostatic latent image. Since it has a function (reversal development), the DC voltage value should be constant.

  The supply roller 3 is for A4 paper. The supply roller 3 is formed by forming a sponge or brush roller of conductive foamed silicone resin or the like on a metal shaft having a diameter of 6 mm in a cylindrical or cylindrical shape having a diameter of 14 to 15 mm. While applying the voltage A, the toner 20 is rotated to the direction indicated by the arrow in FIG. The foamed silicone resin may be a foamed urethane resin. When the surface of the supply roller 3 is a foamable resin, it has irregularities peculiar to the sponge-like surface, so that the toner can be easily conveyed in terms of shape, and the elastic force of the sponge is smaller than that of the rubber. It is desirable because the mutual contact friction force at the contact portion can be suppressed to a rotatable size. Since the developing roller 4 rotates in the direction of the arrow (FIG. 1) so as to be in the opposite direction at an appropriate speed difference at the contact portion with the supply roller 3, the toner 20 before development is supplied to the supply roller 3 above both rollers. Then, the developed toner 20 is scraped off by the supply roller 3 when it reaches the lower part of the contact portion with the supply roller 3 as residual toner on the lower surface of the development roller 4. The toner 20 thus scraped off returns to the toner container 1 and is stirred again and reused.

  The idea of providing a difference in the voltage applied to the supply roller and the developing roller is based on the fact that it is preferable not to provide a potential difference between the two rollers when there is no problem in the chargeability and transport amount of the toner necessary for development. . This is because if a potential difference is provided, the frequency of the deteriorated toner is increased due to the potential difference. However, when the number of sheets to be passed increases and the amount of deteriorated toner increases in the toner in the toner container, the frequency of not only the toner conveyed to the developing roller but also the deteriorated toner increases. Even if such deteriorated toner is conveyed, it is difficult to receive proper positive charging due to frictional charging on the surface of the developing roller, and it cannot be an effective developing toner, and adheres to an unexposed portion of the photosensitive drum. And cause fogging. In addition, since the deteriorated toner conveyed near the surface of the photosensitive drum has a weak holding force on the surface of the developing roller, it easily falls onto the lower sheet from between the photosensitive drum and the developing roller. Further, when the reversely charged toner is included in the deteriorated toner as described above, the toner easily attracts and aggregates with other toner, and the aggregated toner also has a weak holding force on the roller surface, and thus falls on the paper. It will be. However, as described above, when the ratio of the deteriorated toner increases, the amount of normal toner necessary for development becomes insufficient and an image defect occurs. Therefore, the application voltage A to the supply roller is applied to the development roller. By increasing the charge amount of the low-charged toner to be higher than the voltage B, the deteriorated toner is reduced. At this time, it is preferable that the supply roller and the conductive layer thickness regulating blade have the same potential, because a potential difference also occurs between the layer thickness regulating blade and the developing roller, and the charge amount to the toner increases. Further, it is more preferable because an effect of preventing toner filming on the conductive layer thickness regulating blade can be obtained.

  The developing roller 4 is for A4 paper, and a desired property is obtained by winding a 6 mm diameter metal shaft with a conductive silicon rubber having a diameter of 20 mm and treating the surface with Teflon (registered trademark) or urethane coating. ing. The diameter can be appropriately selected from 16 mm to 24 mm. A positive DC voltage B having the same potential as that of the supply roller 3 is also applied to the metal shaft of the developing roller 4 as described above.

  A method of increasing the voltage applied to the supply roller with respect to the voltage applied to the developing roller and the relationship with the image quality when toner is supplied will be described.

  A general drawback of the cleanerless development method using a non-magnetic one-component positively charged pulverized toner is that the life of the development unit is short as described above. The cause is that untransferred toner is collected and reused in the developing unit, so that it is easy to accumulate deteriorated toner in the developing unit by repeated printing, and the ratio of deteriorated toner gradually increases, and the chargeability and transportability of the toner are increased. This is because the image quality deteriorates and the image quality is likely to deteriorate. Therefore, when the predetermined number of sheets (printed) (A4) is completed before the image deterioration appears, the top of the toner container is opened and new external toner is supplied. However, it has been found that there is a problem that a deteriorated image is generated for a while after toner replenishment. Therefore, the relationship between the number of sheets passed after toner replenishment and the image quality was examined. As a result, it was found that if the voltage applied to the supply roller is increased for a while immediately after the replenishment of toner, the effect of increasing the charge amount to the toner by the conductive layer thickness regulating blade is also added and the image deterioration is eliminated. The relationship between the increase in applied voltage to the supply roller and the image quality was investigated.

  Development using a non-magnetic one-component positively charged developing type printer based on a commercially available printer and incorporating the developing device of the present invention until the toner consumption is reduced to two-thirds. A new external toner was replenished to the apparatus, and immediately after that, the voltage applied to the supply roller was increased from the developing roller in the range of 0 to 400 volts, and the relationship with the image quality was examined. Results were obtained.

  In order to prevent the deteriorated toner conveyed between the photosensitive drum and the developing roller from falling on the sheet or fogging image as described above, as shown in Table 1, the voltage applied to the supply roller is set to the developing roller. It has been found that it is better to increase the voltage by 50 volts or more. When the voltage was less than 50 volts, the toner was dropped. When the voltage is increased by 50 volts or more, it is considered that the toner drop does not occur because the charge amount to the normal toner increases or the toner transportability increases on the surfaces of the supply roller and the developing roller. However, if the potential difference between the two rollers is too high, for example, if it is greater than 400 volts, toner drop will not occur, but the occurrence of electrically deteriorated toner due to the potential difference will increase, causing fogging images. I also found that I have to avoid it.

  Normally, as described above, when a new developing device is used, the applied voltage to the supply roller may be increased to the predetermined voltage or higher when the number of passed (printed) sheets (A4) is 10000 to 20000. If the image quality cannot be maintained satisfactorily, new toner is supplied to the toner container from the outside. Replenishing the toner container with the new external toner in this way means that the new external toner is placed in the toner container in a state where about one third of the original toner amount remains as the residual toner. It is to replenish. Moreover, since the residual toner has a high ratio of the deteriorated toner, the image quality cannot be kept good as described above. Therefore, it can be said that by replenishing the new toner while leaving the deteriorated toner in the residual toner as it is, the concentration of the deteriorated toner is reduced and the toner can be used again.

  As described above, the image deterioration suppression effect obtained by increasing the applied voltage to the supply roller in the range of 50 volts or more and less than 400 volts is immediately after the new toner is replenished. This is conspicuous until the toner and the residual toner are sufficiently stirred, that is, while a large amount of residual toner still exists on and near the surfaces of the supply roller and the developing roller. After both the toners are sufficiently stirred together, there is almost no necessity. The period required for the two toners to be sufficiently stirred together is about 10 to 30 sheets. Therefore, after this period, the voltage applied to the supply roller is preferably returned to the same potential as the voltage applied to the developing roller from the viewpoint of electrical deterioration of the toner. However, since there is usually an increase in deteriorated toner due to mechanical friction other than electrical deterioration, it is preferable to make the applied voltage A higher than the applied voltage B after toner replenishment.

1 is a schematic cross-sectional view of an electrophotographic non-magnetic one-component image forming apparatus including a developing device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Toner container part 3 Supply roller 4 Developing roller 5 Layer thickness control member (Layer thickness control blade)
6 Photoconductor (Photoconductor drum)
20 toner 100 developing device

Claims (4)

  A developing device using a developing method using non-magnetic one-component toner, comprising at least a toner container having a structure capable of supplying new external toner, a supply roller, a developing roller, and a layer thickness regulating member, wherein the supply roller The toner in the toner container is held on the surface of the supply roller and is carried to the developing roller by rotation of the supply roller. The developing roller receives the toner received from the supply roller between the developing roller and the layer thickness regulating member. A mechanism that is charged by frictional charging and held on the surface of the developing roller and thinned, and then transported to a contact surface with the surface of the photosensitive member by rotation of the developing roller to visualize the electrostatic latent image on the surface of the photosensitive member. In the developing apparatus, when the applied voltage to the supply roller is A and the applied voltage to the development roller is B, the supply roller is processed while a predetermined number of printed sheets are processed after toner replenishment. Than the applied voltage B of the applied voltage A to La to the developer roller, a developing device, characterized in that it comprises a mechanism for setting high 50 volts or more.   2. The developing device according to claim 1, wherein the predetermined number of printed sheets is 10 to 30 sheets of A4 paper.   3. The developing device according to claim 1, wherein the developing system is a cleanerless developing system in which untransferred toner is collected and reused in a developing process.   The developing device according to claim 1, wherein the toner uses a styrene-acrylic copolymer resin as a base resin.

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