JP2004046215A - Developing device and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device and an electrophotographic device capable of preventing a deterioration in image quality.
A developing device includes a developing roller facing a photosensitive drum, a supply roller for supplying toner to the developing roller, and a toner storage chamber for storing toner. A toner layer forming roller 12 that rotates in the same direction as the developing roller 10 is provided so as to be in contact with the developing roller 10. At least a part of the toner supplied to the outer peripheral surface of the developing roller 10 adheres to the outer peripheral surface of the toner layer forming roller 12 to form a toner layer, and is regulated to a constant thickness by the blade 13. The toner layer formed on the outer peripheral surface of the toner layer forming roller 12 is conveyed to the outside of the toner storage chamber 15 by the rotation of the toner layer forming roller 12, and is transferred to the outer peripheral surface of the developing roller 10 outside the toner layer.
[Selection diagram] Fig. 1

Description

The present invention relates to an electrophotographic apparatus used for a printer, a copying machine, and the like, and a developing apparatus for developing an electrostatic latent image with toner in the electrophotographic apparatus.

電子 In an electrophotographic apparatus used for a printer, a copying machine, or the like, an electrostatic latent image formed on a photosensitive drum (electrostatic latent image carrier) is developed with toner. As one of the developing methods, there is a so-called non-magnetic one-component developing method which uses a non-magnetic toner and does not use a carrier. Conventionally, a developing device corresponding to the non-magnetic one-component developing method has been proposed (for example, see Patent Documents 1 to 6).

JP-A-7-44007 (page 5, FIG. 1) JP-A-7-64394 (page 3, FIG. 3) JP-A-9-80905 (page 5-6, FIG. 1) JP-A-10-153910 (page 6-8, FIG. 3) JP-A-12-98740 (page 3-4, FIG. 1) JP-A-13-56605 (page 3-4, FIG. 1)

FIG. 16 shows a developing device disclosed in Japanese Patent Application Laid-Open No. 7-44007. The developing device includes a developing roller 100 arranged to face the photosensitive drum 110, and a supply roller 101 for supplying toner to the outer peripheral surface of the developing roller 100. On the upper side of the developing roller 100 in the figure, a toner regulating roller 102 for regulating the thickness of the toner adhering to the outer peripheral surface of the developing roller 100 is disposed to face. The outer peripheral surface of the toner regulating roller 102 is in contact with a blade 103 that scrapes off the toner attached to the outer peripheral surface. The toner that adheres to the outer peripheral surface of the developing roller 100 and whose thickness is regulated by the toner regulating roller 102 is attracted to the electrostatic latent image formed on the photosensitive drum 110 and adheres to the electrostatic latent image. Of the toner adhered to the outer peripheral surface of the developing roller 100, the toner that is not transferred to the photosensitive drum 110 (denoted by A) is a collection roller 104 provided below the developing roller 100 or the above-described supply roller. Collected by 101. The basic configuration of the developing device described in the above-mentioned other documents is almost the same.

However, in such a conventional developing device, the toner supplied from the supply roller 101 to the developing roller 100 passes between the developing roller 100 and the toner regulating roller 102 and is conveyed to the photosensitive drum 110 side. In other words, the friction coefficient of the outer peripheral surface of the developing roller 100 must be larger than the friction coefficient of the outer peripheral surface of the toner regulating roller 102. Therefore, in the conventional developing device, since the friction coefficient of the outer peripheral surface of the developing roller 100 is relatively large, and thus the releasability from the toner is low, the toner A remaining on the outer peripheral surface of the developing roller 100 is completely removed by the supply roller 101 and the like. May not be removed. When such a residual toner A is present on the outer peripheral surface of the developing roller 100, the toner further adheres on the residual toner A and locally increases in thickness. A so-called afterimage is formed by attaching to a portion other than the electrostatic latent image 110. As a result, a portion of the recording paper (printing medium) other than the image to be originally formed is stained, and the image quality is degraded.

Further, since the blade 103 is pressed against the toner regulating roller 102 with a relatively strong force, a so-called filming phenomenon in which the toner melts due to frictional heat and adheres to the outer peripheral surface of the toner regulating roller 102 and the like. It can also occur. When such a filming phenomenon occurs, since the thickness of the toner layer formed on the outer peripheral surface of the developing roller 100 becomes uneven, a part of an image to be originally formed is missing on the recording paper, or Smears occur in portions other than the image to be originally formed, and image quality is degraded.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a developing apparatus and an electrophotographic apparatus capable of preventing a deterioration in image quality.

In order to solve the above-described problems, a developing device according to the present invention includes a developing member that develops the electrostatic latent image by attaching toner to the electrostatic latent image formed on the electrostatic latent image carrier, A toner supply member for supplying toner to the developing member, a toner layer forming member having an outer peripheral surface in contact with the developing member, and a toner layer for regulating a thickness of the toner layer attached to the outer peripheral surface of the toner layer forming member A regulating member, wherein the toner layer adhered to the outer peripheral surface of the toner layer forming member and having a thickness regulated by the toner layer regulating member is transferred to the developing member.

An electrophotographic apparatus according to the present invention prints the developing device described above, an electrostatic latent image carrier developed by the developing device, and a toner image on the electrostatic latent image carrier developed by the developing device. And a transfer device for transferring to a medium.

According to the present invention, since the toner layer having a regulated thickness is formed on the outer peripheral surface of the toner layer forming member and the toner layer is transferred to the developing member, the friction coefficient of the outer peripheral surface of the developing member is reduced. However, a uniform and sufficient thickness toner layer can be formed on the outer peripheral surface of the developing member by transfer. By reducing the coefficient of friction of the outer peripheral surface of the developing member, the releasability from the toner is improved, so that unnecessary toner remaining on the outer peripheral surface of the developing member can be reliably removed. Therefore, it is possible to prevent the occurrence of an afterimage caused by unnecessary toner remaining on the outer peripheral surface of the developing member, and to prevent the image quality from deteriorating. Also, since not all of the toner on the outer peripheral surface of the toner layer forming member is scraped off, the toner layer regulating member can be pressed against the toner layer forming member with a relatively small force, whereby the toner melts due to frictional heat. The filming phenomenon that occurs as a result can be prevented, and a decrease in image quality can be prevented. In addition, by changing the friction coefficient, applied voltage, and the like of the developing member and the toner layer forming member, the thickness of the toner layer formed on the outer peripheral surface of the developing member can be freely changed. Can be adjusted.

Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a main part of an electrophotographic apparatus including a developing device 4 according to Embodiment 1 of the present invention. This electrophotographic apparatus is based on a non-magnetic one-component developing system, and includes a photosensitive drum 1 (electrostatic latent image carrier) having a photosensitive layer on an outer peripheral surface. The photosensitive layer of the photoreceptor drum 1 has an insulating property when not exposed, and has a conductive property when exposed to release charged charges. The photoconductor drum 1 rotates in one direction (clockwise in the figure). Around the photoreceptor drum 1, a charging roller 2, an LED head 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are arranged in this order along the rotation direction.

The charging roller 2 is a conductive roller to which a constant potential is applied, and is pressed against the outer peripheral surface of the photosensitive drum 1 to uniformly charge the photosensitive layer on the outer peripheral surface. The LED head 3 selectively exposes a uniformly charged photosensitive layer of the photosensitive drum 1 by LEDs (light emitting diodes) arranged in an array according to image information. The exposed portion of the photosensitive layer of the photosensitive drum 1 has the charged charge removed, but the unexposed portion has the charged charge remaining thereon to form an electrostatic latent image. The developing device 4 performs so-called toner development by attaching toner to an electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 1 as described later. The transfer roller 5 sandwiches a recording paper (print medium) (not shown) between the photoconductor drum 1 and transfers the toner image formed on the outer peripheral surface of the photoconductor drum 1 to the recording paper. The cleaning device 6 includes a cleaning blade 60 for removing unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 1 after transfer.

FIG. 2 is an enlarged view of the developing device 4. The developing device 4 includes a developing roller (developing member) 10 facing the photosensitive drum 1 and a toner storage chamber 15 for storing toner supplied to the developing roller 10. The developing roller 10 is provided at the bottom of the toner storage chamber 15. Of the outer peripheral surface of the developing roller 10, the right portion in the drawing is located inside the toner storage chamber 15, and the left portion in the drawing protrudes outside the toner storage chamber 15 and faces the photosensitive drum 1. The rotation axis of the developing roller 10 is parallel to the rotation axis of the photosensitive drum 1. The developing roller 10 rotates in a direction opposite to the rotation direction of the photosensitive drum 1, and adheres the toner on the outer peripheral surface to the photosensitive drum 1.

The developing roller 10 is formed by forming a coating layer 10a made of a resin (for example, a polyimide resin, a urethane resin, or a fluororesin) on an outer peripheral surface of a roller 10b made of a semiconductive elastic body (specifically, rubber). It is. The reason for providing the coating layer 10a is to reduce the coefficient of friction of the outer peripheral surface of the developing roller 10 and to improve the releasability of the toner (that is, the ease with which the toner separates). The rubber hardness of the roller 10b is 30 to 60 degrees in JIS C hardness. The developing roller 10 may have a configuration in which a tube made of a polyimide resin or the like is placed around a roller made of a resin (sponge) having open cells.

FIG. 3 is a diagram showing a method of measuring a friction coefficient (here, a static friction coefficient) of the outer peripheral surface of the developing roller 10. In this measurement method, an inclined plate 31 formed of an acrylic resin and having an average surface roughness (Rz) of about 2 μm is used. The developing roller 10 is mounted on the inclined plate 31 such that the axial direction matches the inclined direction of the inclined plate 31, and the inclination angle of the inclined plate 31 is gradually increased. Assuming that the inclination angle of the inclined plate 31 when the developing roller 10 starts to slide is a slip angle θ (θ> 0 degrees), there is a relationship of μ = tan θ between the slip angle θ and the static friction coefficient μ. The coefficient of static friction μ of the outer peripheral surface of the developing roller 10 with respect to the surface of the inclined plate 31 is preferably 0.58 or less (that is, the sliding angle θ is 30 degrees or less), and more preferably 0.36 or less (that is, the sliding angle θ). (The angle θ is 20 or less).

As shown in FIG. 2, a supply roller (toner supply member) 11 having a rotation axis parallel to the rotation axis of the development roller 10 is provided adjacent to the development roller 10 in the toner storage chamber 15. . The supply roller 11 is formed of a semiconductive resin having open cells, and its outer peripheral surface is in contact with the outer peripheral surface of the developing roller 10. The rotation direction of the supply roller 11 is the same as the rotation direction of the developing roller 10.

Potentials VD and VS are applied between the developing roller 10 and the supply roller 11 by power sources (potential applying means) 40 and 41, respectively. Between these potentials VD and VS, toner is supplied to the developing roller 10 side. An attractive potential difference is set. Specifically, when the toner is negatively charged by frictional charging (described later), the potentials VD and VS are both set to a negative potential, and when the toner is positively charged, both the potentials VD and VS are set to a positive potential. I do. The potentials VD and VS satisfy the relationship of | VD | ≦ | VS |. Here, it is assumed that the toner is negatively charged. For example, the potential VD is -300 V, and the potential VS is -450 V. When the toner is positively charged, for example, the potential VD is set to +300 V and the potential VS is set to +450 V.

傾斜 A lower part of the toner storage chamber 15 is formed with an inclined plate 15a which is inclined toward the supply roller 11. This is so that the toner collects around the supply roller 11 even when the toner in the toner storage chamber 15 is low.

In a section from the supply roller 11 to the photosensitive drum 1 along the rotation direction of the developing roller 10 (ie, above the developing roller 10 in FIG. 2), a toner layer having a rotation axis parallel to the rotation axis of the developing roller 10 is provided. A forming roller (toner layer forming member) 12 is provided. The toner layer forming roller 12 is a roller made of semiconductive elastic rubber, and its outer peripheral surface is in contact with the outer peripheral surface of the developing roller 10. In the outer peripheral surface of the toner layer forming roller 12, the right side portion in the drawing is located inside the toner storage chamber 15, and the left side portion in the drawing projects outside the toner storage chamber 15. The rotation direction of the toner layer forming roller 12 is the same as the rotation direction of the developing roller 10. Further, the rotational peripheral speed of the toner layer forming roller 12 is set to be lower than or the same as the developing roller 10 (for example, 0.5 to 1.0 times the rotational peripheral speed of the developing roller 10).

FIG. 4 is a view schematically showing the state of toner conveyance in the developing device 4. The toner layer forming roller 12 adheres at least a part of the toner supplied from the supply roller 11 to the developing roller 10 on the outer peripheral surface thereof. It is preferable that the outer peripheral surface of the toner layer forming roller 12 has a larger coefficient of friction than the outer peripheral surface of the developing roller 10 (that is, the releasability from the toner is low). This is because the thickness of the toner layer attached to the outer peripheral surface of the toner layer forming roller 12 can be increased. The potential VL is applied to the toner layer forming roller 12 by the power supply 42. Between the potential VD of the developing roller 10 and the potential VL of the toner layer forming roller 12 described above, a potential for attracting toner toward the developing roller 10 is provided. Specifically, potentials VD and VL are determined so as to satisfy the relationship | VD | ≦ | VL |. When the toner is negatively charged, for example, the potential VD is set to −300 V, and the potential VL is set to −450 V.

(4) A blade (toner layer regulating member) 13 is provided on a side (upper side in the figure) of the toner layer forming roller 12 substantially opposite to the developing roller 10. This blade 13 regulates the thickness of the toner layer formed on the outer peripheral surface of the toner layer forming roller 12. The blade 13 is a plate-shaped member formed of, for example, phosphor bronze, and has a thickness of 0.06 to 0.15 mm. The contact surface 14 of the blade 13 facing the toner layer forming roller 12 extends in parallel with the axial direction of the toner layer forming roller 12.

FIG. 5 is an enlarged view of the tip of the blade 13. The upper end of the blade 13 is fixed inside the side wall of the toner storage chamber 15, and the lower end of the blade 13 reaches near the outer peripheral surface of the toner layer forming roller 12 and bends away from the outer peripheral surface. The contact surface 14 of the bent portion of the blade 13 on the toner layer forming roller 12 side forms an arc having a radius of 0.3 to 0.5 mm in a plane orthogonal to the longitudinal direction of the blade 13. The contact surface 14 of the blade 13 is pressed against the outer peripheral surface of the toner layer forming roller 12 with a force of 10 to 50 g / cm ² . The blade 13 is elastically deformable in a direction away from the outer peripheral surface of the toner layer forming roller 12, and maintains a constant distance between the outer peripheral surface of the toner layer forming roller 12 and the contact surface 14 of the blade 13 as shown in FIG. The thickness of the toner is configured to pass through. As a result, a toner layer having a constant thickness is formed on the outer peripheral surface of the toner layer forming roller 12.

Next, the operation of the developing device 4 configured as described above will be described with reference to FIG. It is assumed that the inside of the toner storage chamber 15 is filled with at least a toner (only a part of the toner is shown in FIG. 4) enough to fill the supply roller 11. The supply roller 11 rotates while adhering the toner in the toner storage chamber 15 to the outer peripheral surface thereof. The toner attached to the outer peripheral surface of the supply roller 11 is conveyed to the vicinity of a contact portion between the supply roller 11 and the developing roller 10 by the rotation of the supply roller 11. Here, the toner is negatively charged by friction between the toners or by friction with the supply roller 11 or the developing roller 10. The charged toner is attracted to the developing roller 10 by a potential difference between the supply roller 11 and the developing roller 10, and adheres to the outer peripheral surface thereof. Thus, the toner is supplied to the outer peripheral surface of the developing roller 10.

The toner supplied to the outer peripheral surface of the developing roller 10 is conveyed to the vicinity of a contact portion between the developing roller 10 and the toner layer forming roller 12 by the rotation of the developing roller 10. Part of the toner adheres to the outer peripheral surface of the developing roller 10 due to a potential difference between the developing roller 10 and the toner layer forming roller 12, and the rotation of the developing roller 10 causes a gap between the developing roller 10 and the toner layer forming roller 12. After passing through, it is conveyed to the photosensitive drum 1 side. On the other hand, another part of the toner adheres to the outer peripheral surface of the toner layer forming roller 12, and passes between the outer peripheral surface of the toner layer forming roller 12 and the blade 13 by the rotation of the toner layer forming roller 12, and the toner A toner layer having a uniform thickness is formed on the outer peripheral surface of the layer forming roller 12.

In the contact portion between the developing roller 10 and the toner layer forming roller 12, the ratio of the toner adhering to the developing roller 10 and the toner adhering to the toner layer forming roller 12 is determined by the ratio between the developing roller 10 and the toner layer forming roller 12. It is determined by the coefficient of friction, the peripheral speed of rotation and the potential difference between the two. Here, the rotation peripheral speed of the toner layer forming roller 12 is set to, for example, 0.5 to 1.0 times that of the developing roller 10, and the thickness and charge amount of the toner layer formed on the outer peripheral surface of the toner layer forming roller 12 are set. In a preferable range.

The toner layer whose thickness is regulated by the blade 13 is conveyed to the outside of the toner storage chamber 15 by rotation of the toner layer forming roller 12, where the contact portion between the toner layer forming roller 12 and the developing roller 10 is formed. It is transported nearby. Here, the toner layer is transferred to the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side due to a potential difference between the toner layer forming roller 12 and the developing roller 10. On the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side, the toner layer transferred from the toner layer forming roller 12 and the toner layer passed between the toner layer forming roller 12 and the developing roller 10 are added to each other. A toner layer having a thickness is formed. The thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side in this manner depends on the friction coefficient, the rotational peripheral speed or the applied voltage of the developing roller 10 and the toner layer forming roller 12, or the blade 13. By adjusting the pressure applied to the toner layer roller 12, the pressure can be freely changed.

The toner layer formed on the outer peripheral surface of the developing roller 10 is attracted to the electrostatic latent image formed on the photosensitive drum 1 and adheres to the electrostatic latent image. That is, toner development is performed. The toner that does not adhere to the photosensitive drum 1 and remains on the outer peripheral surface of the developing roller 10 is conveyed to the vicinity of a contact portion between the supply roller 11 and the development roller 10 with the rotation of the development roller 10, and is supplied by the supply roller 11. Collected. Since the outer peripheral surface of the developing roller 10 has the coating layer 10 a having a small friction coefficient, the releasability of the outer peripheral surface of the developing roller 10 from the toner is improved, and the toner is reliably collected by the supply roller 11.

Next, the operation of the electrophotographic apparatus including the developing device 4 will be briefly described with reference to FIG. The photosensitive drum 1 is uniformly charged by the charging roller 2 and then exposed by the LED head 3 to form an electrostatic latent image. The electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 1 is developed with toner by the developing device 4 as described above, and a toner image is formed on the outer peripheral surface of the photosensitive drum 1. The toner image formed on the outer peripheral surface of the photosensitive drum 1 is transferred to a recording paper (not shown) between the photosensitive drum 1 and the transfer roller 5, and is fixed on the recording paper by a fixing device (not shown). Unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 1 is removed by the cleaning device 6.

印刷 Using the above-described electrophotographic apparatus, a printing test was continuously performed on 20,000 sheets using a toner having an average particle diameter of 7 μm manufactured by a suspension polymerization method. As a result, no afterimage was observed in the obtained printed matter. Further, a filming phenomenon in which the toner was melted and fixed to the toner layer forming roller 12 or the like did not occur.

Next, the effect of preventing the occurrence of an afterimage in the first embodiment will be described. In order to prevent the occurrence of an afterimage, it is necessary to reduce the friction coefficient of the outer peripheral surface of the developing roller 10 and increase the releasability of the outer peripheral surface from the toner. However, if the friction coefficient of the outer peripheral surface of the developing roller 100 is reduced in the conventional developing device shown in FIG. 16, insufficient transfer of toner to the photosensitive drum 110 by the developing roller 100 causes transfer failure. It will be. On the other hand, in the first embodiment, as shown in FIG. 4, a toner layer is formed on the outer peripheral surface of the toner layer forming roller 12, and this toner layer is formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side. Since the transfer is performed, even if the friction coefficient of the outer peripheral surface of the developing roller 10 is small, a sufficient amount of toner can be conveyed to the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side, thereby preventing poor transfer. can do. Thereby, the releasability of the outer peripheral surface of the developing roller 10 from the toner can be improved, and the remaining toner can be reliably collected.

Here, the relationship between the coefficient of friction of the developing roller 10 and the occurrence of an afterimage will be described. FIG. 6 is a graph showing the result of examining the state of occurrence of an afterimage by changing the static friction coefficient μ of the developing roller 10. 6, the horizontal axis represents the slip angle θ and the static friction coefficient μ of the developing roller 10 measured using the inclined plate 31 shown in FIG. The vertical axis indicates the residual image evaluation level for evaluating the presence or absence and the density of the residual image observed in the printed matter printed using the developing roller 10 having the different static friction coefficient μ. The afterimage evaluation level is assumed to be a level at which no afterimage is observed at all with the naked eye, and is expressed by a smaller value as a darker afterimage is observed. The level at which an afterimage is slightly observed but does not cause a problem in a normal printed matter is set to 9.

From FIG. 6, the level 9 or higher that does not cause a problem as a normal printed matter is obtained because the surface of the inclined plate 31 on the outer peripheral surface of the developing roller 10 (that is, a plane having an average surface roughness Rz made of acrylic resin of about 2 μm) ) Is 0.58 or less (slip angle θ is 30 degrees or less). When the static friction coefficient μ is within this range, the releasability of the outer peripheral surface of the developing roller 10 from the toner is sufficiently high, and the unnecessary toner remaining on the outer peripheral surface of the developing roller 10 is reliably removed by the supply roller 11. That's why. Further, an even better level of 9.5 or more is obtained when the static friction coefficient μ is 0.36 or less (slip angle θ is 20 degrees or less). From this, the coefficient of static friction μ of the outer peripheral surface of the developing roller 10 with respect to a plane having an average surface roughness Rz of about 2 μm made of acrylic resin is preferably 0.58 or less, and if 0.36 or less, It turns out that it is more preferable. The coefficient of static friction μ of the outer peripheral surface of the toner layer forming roller 12 with respect to the surface of the inclined plate 31 used when performing the measurement in FIG. 6 was 0.58 (slip angle θ was 30 degrees).

Next, the effect of preventing the filming phenomenon in the first embodiment will be described. In a configuration in which the toner adhering to the toner regulating roller 102 is scraped off by the blade 103 as in the conventional developing device shown in FIG. 16, the blade 103 is strongly pressed against the toner regulating roller 102, so that the toner melts due to frictional heat. As a result, a filming phenomenon that adheres to the toner regulating roller 102 or the like may occur. On the other hand, in the first embodiment, as shown in FIG. 4, the blade 13 is moved by a relatively weak force such that the toner having a certain thickness passes between the blade 13 and the toner layer forming roller 12. Since it suffices to press against the forming roller 12, heat generation due to friction is small, and the occurrence of the filming phenomenon can be prevented. In particular, if the outer peripheral surface of the toner layer forming roller 12 is formed of a rubber material, the occurrence of the filming phenomenon can be more reliably prevented.

As described above, according to the first embodiment, a toner layer having a regulated thickness is formed on the outer peripheral surface of the toner layer forming roller 12, and the toner layer is formed on the photosensitive drum 1 side of the developing roller 10. Since the toner is transferred to the outer peripheral surface, a sufficient amount of toner can be conveyed to the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side even if the friction coefficient of the outer peripheral surface of the developing roller 10 is reduced. As a result, the releasability of the outer peripheral surface of the developing roller 10 from the toner can be improved. Therefore, the unnecessary toner remaining on the outer peripheral surface of the developing roller 10 can be reliably collected by the supply roller 11, and the occurrence of an afterimage can be prevented, and the deterioration of image quality can be prevented.

Further, by changing the coefficient of friction, the rotational peripheral speed or the applied voltage of the developing roller 10 and the toner layer forming roller 12 or the pressing pressure of the blade 13 against the toner layer forming roller 12, the photosensitive drum 1 of the developing roller 10 is changed. The thickness of the toner layer formed on the outer peripheral surface on the side can be freely changed. Therefore, it is possible to adjust the thickness of the toner adhering to the electrostatic latent image on the photosensitive drum 1, thereby adjusting the density of the image transferred to the recording paper.

Furthermore, in the first embodiment, since the blade 13 only needs to be pressed against the toner layer forming roller 12 with a relatively weak force, the toner that melts due to frictional heat and adheres to the toner layer forming roller 12 and the like. It is possible to prevent the occurrence of the zooming phenomenon and to prevent the image quality from deteriorating.

Further, the toner layer formed on the outer peripheral surface of the toner layer forming roller 12 is transported to the outside of the toner storage chamber 15 by the rotation of the toner layer forming roller 12, and is transferred to the developing roller 10 outside the toner layer. Another toner is prevented from adhering to the toner layer whose thickness is regulated by the blade 13, and the thickness of the toner layer can be kept uniform.

Further, by making the releasability of the outer peripheral surface of the developing roller 10 from the toner higher than the releasability of the outer peripheral surface of the toner layer forming roller 12 with respect to the toner, the toner transport ability of the toner layer forming roller 12 is increased. In addition, it is possible to easily remove the toner from the developing roller 10 and to more reliably prevent the occurrence of an afterimage.

Further, a resin coating layer 10a is provided on the outer peripheral surface of the developing roller 10, and the static friction coefficient μ with respect to a plane having an average surface roughness Rz of about 2 μm made of acrylic resin is 0.58 or less (more preferably 0.36 or less). By doing so, it is possible to reliably prevent the occurrence of an afterimage that causes a practical problem.

Further, by providing the blade 13 in contact with the toner layer forming roller 12, the thickness of the toner layer formed on the outer peripheral surface of the toner layer forming roller 12 can be regulated with a simple configuration. In particular, by setting the radius of curvature of the contact surface 14 of the blade 13 to 0.3 to 0.5 mm and pressing the contact surface 14 against the toner layer forming roller 12 with a force of 10 to 50 g / cm ² , A toner layer having a uniform thickness can be formed.

In addition, by applying a potential to transfer the toner to the developing roller 10 to the developing roller 10 and the toner layer forming roller 12, the friction coefficient of the outer peripheral surface of the toner layer forming roller 12 is reduced. Even when the coefficient is larger than the coefficient, the toner layer formed on the toner layer forming roller 12 can be transferred to the developing roller 10 without fail.

Furthermore, the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 is preferably set by making the rotational peripheral speed of the toner layer forming roller 12 slower (for example, 0.5 to 1.0 times) than that of the developing roller 10. Can be in the range.

Embodiment 2 FIG.
FIG. 7 is a diagram illustrating a developing device 4A according to Embodiment 2 of the present invention. The developing device 4A according to the second embodiment includes an auxiliary supply roller (auxiliary supply member) 16 adjacent to the toner layer forming roller 12 in addition to the components of the developing device 4 (FIG. 2) according to the first embodiment. It is provided with. This developing device 4A has the same configuration as the developing device 4 according to the first embodiment except that an auxiliary supply roller 16 is provided. The developing device 4A is incorporated in the electrophotographic apparatus (FIG. 1) described in the first embodiment.

The auxiliary supply roller 16 is disposed in the toner storage chamber 15 and is in contact with the outer peripheral surface of the toner layer forming roller 12 on the right side in the drawing. The auxiliary supply roller 16 has a rotation axis parallel to the rotation axis of the toner layer forming roller 12, and rotates in the same direction as the toner layer forming roller 12. The auxiliary supply roller 16 is made of, for example, a silicon resin having open cells (so-called silicon sponge) and has semiconductivity. The potential VH is applied to the auxiliary supply roller 16 by the power supply 43. A potential difference that attracts toner toward the toner layer forming roller 12 is set between the potential VH of the auxiliary supply roller 16 and the potential VL of the toner layer forming roller 12 described above. Specifically, potentials VH and VL are determined so as to satisfy the relationship | VH | ≧ | VL |. The positive and negative of the potentials VH and VL are determined so as to be the same as the charge of the toner.

The auxiliary supply roller 16 causes the toner in the toner storage chamber 15 to adhere to the outer peripheral surface and rotates while being in contact with the toner layer forming roller 12. The toner attached to the outer peripheral surface of the auxiliary supply roller 16 is conveyed to the vicinity of a contact portion between the auxiliary supply roller 16 and the toner layer forming roller 12, and is negatively charged due to friction between the toners. The charged toner is attracted to the toner layer forming roller 12 by the potential difference between the auxiliary supply roller 16 and the toner layer forming roller 12 and adheres to the outer peripheral surface thereof. Thus, the toner transported by the auxiliary supply roller 16 adheres to the outer peripheral surface of the toner layer forming roller 12 in addition to the toner transported by the developing roller 10. The toner adhered to the outer peripheral surface of the toner layer forming roller 12 is regulated in thickness by the blade 13 to form a toner layer, and is conveyed to the outside of the toner accommodating chamber 15 as in the first embodiment. It is transferred to the outer peripheral surface on the photosensitive drum 1 side. The toner transferred to the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side adheres to the latent image on the photosensitive drum 1.

As described above, in the developing device 4 </ b> A according to the second embodiment, in addition to the toner conveyed from the developing roller 10, the toner conveyed from the auxiliary supply roller 16 adheres to the outer peripheral surface of the toner layer forming roller 12. Even if the amount of toner supplied from the supply roller 11 to the developing roller 10 is reduced for some reason (for example, uneven distribution of toner in the toner storage chamber 15), a sufficient amount of toner is formed on the outer peripheral surface of the developing roller 10. Is supplied. Therefore, transfer failure due to toner shortage can be prevented.

In particular, if the toner on the outer peripheral surface of the developing roller 10 is insufficient, a portion corresponding to the previously printed image pattern may be printed thinly, that is, a so-called reversal afterimage may occur. Since the toner is sufficiently supplied to the outer peripheral surface of the image forming apparatus, the occurrence of reversal afterimages can be minimized.

Further, similarly to the first embodiment, since the friction coefficient of the outer peripheral surface of the developing roller 10 can be reduced, unnecessary toner remaining on the outer peripheral surface of the developing roller 10 can be reliably removed, and occurrence of an afterimage is prevented. be able to. Further, since the force of pressing the blade 13 against the toner layer forming roller 12 can be made relatively weak, it is possible to prevent the occurrence of a filming phenomenon caused by melting of the toner due to frictional heat. That is, a decrease in image quality can be prevented.

Embodiment 3 FIG.
FIG. 8 is a diagram showing a developing device 4B according to Embodiment 3 of the present invention. The developing device 4B according to the third embodiment includes an additional supply roller (additional supply member) 17 disposed adjacent to the supply roller 11 in addition to the components of the development device 4 (FIG. 2) according to the first embodiment. It is a thing. The developing device 4B has the same configuration as the developing device 4 according to the first embodiment except that an additional supply roller 17 is provided. The developing device 4B is incorporated in the electrophotographic apparatus (FIG. 1) described in the first embodiment.

(4) The additional supply roller 17 is disposed in the toner storage chamber 15 and is in contact with the upper outer peripheral surface of the supply roller 11 in the drawing. The additional supply roller 17 has a rotation axis parallel to the rotation axis of the supply roller 11 and rotates in the same direction as the supply roller 11. Like the supply roller 11, the additional supply roller 17 is made of a urethane resin having open cells (a so-called urethane sponge), and has semiconductivity. The potential VT is applied to the additional supply roller 17 by the power supply 44. A potential difference that attracts toner toward the supply roller 11 is set between the potential VT of the additional supply roller 17 and the potential VS of the supply roller 11 described above. Specifically, potentials VT and VS are determined so as to satisfy the relationship | VT | ≧ | VS |. The positive and negative of the potentials VT and VS are determined so as to be the same as the charge of the toner.

This additional supply roller 17 causes the toner in the toner storage chamber 15 to adhere to the outer peripheral surface, and rotates while being in contact with the supply roller 11. The toner attached to the outer peripheral surface of the additional supply roller 17 is conveyed to the vicinity of a contact portion between the additional supply roller 17 and the supply roller 11, and is negatively charged due to friction between the toners. The charged toner is attracted to the supply roller 11 by the potential difference between the additional supply roller 17 and the supply roller 11, and adheres to the outer peripheral surface thereof. As a result, a sufficient amount of toner is supplied to the outer peripheral surface of the supply roller 11.

As described above, in the developing device 4 </ b> B according to the third embodiment, the toner is supplied to the outer peripheral surface of the supply roller 11 by the additional supply roller 17. 15, the toner supply capability of the supply roller 11 can be prevented from lowering. Therefore, transfer failure due to insufficient toner can be prevented, and occurrence of reversal afterimage due to insufficient toner can be suppressed.

Further, similarly to the first and second embodiments, since the friction coefficient of the outer peripheral surface of the developing roller 10 can be reduced, unnecessary toner remaining on the outer peripheral surface of the developing roller 10 can be reliably removed, and the occurrence of an afterimage can be reduced. Can be prevented. Further, since the force of pressing the blade 13 against the toner layer forming roller 12 can be made relatively weak, it is possible to prevent the occurrence of a filming phenomenon caused by melting of the toner due to frictional heat. That is, a decrease in image quality can be prevented.

Embodiment 4 FIG.
In the fourth embodiment, the optimum range of the urging force for urging the toner layer forming roller 12 against the developing roller 10 is determined.

When the developing roller 10 is stopped for a long time in a state of being in contact with the photosensitive drum 1 or the toner layer forming roller 12, the outer peripheral surface of the developing roller 10 is partially deformed by the contact pressure, and A long groove-shaped recess may be formed. Since the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side is affected by the amount of toner passing through the gap between the developing roller 10 and the toner layer forming roller 12, the developing When the concave portion is formed on the outer peripheral surface of the roller 10, the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side becomes uneven, and as a result, horizontal stripes (developing roller 10 (Unevenness in the axial direction). If the outer diameter of the toner layer forming roller 12 changes due to abrasion during continuous printing, the thickness of the toner layer on the developing roller 10 may change over time. In the fourth embodiment, the above-described urging force is determined so as to prevent the occurrence of horizontal streaks and to suppress the temporal change of the thickness of the toner layer.

Fig. 9 shows the results of experiments on the occurrence of horizontal streaks. The urging force of the toner layer forming roller 12 against the developing roller 10 is represented by the “push amount” of the toner layer forming roller 12 against the developing roller 10. As schematically shown in FIG. 10, the “push amount” is an amount (symbol B) of pushing the toner layer forming roller 12 into the developing roller 10 while elastically deforming the developing roller 10. The toner layer forming roller 12 is rotatably supported by a support member (not shown), and the position of the support member is adjusted to change the pushing amount. Here, the pushing amount is changed in a range of 0 to 0.5 mm.

In FIG. 9, a concave portion is formed in the developing roller 10 in advance, and the depth of the concave portion is changed in a range of 0 to 10 μm. The recess is formed by stopping the developing roller 10 for a long time in a state where the developing roller 10 is in contact with the toner layer forming roller 12. In addition, the depth of the concave portion is changed by adjusting the time during which the developing roller 10 is stopped in contact with the toner layer forming roller 12. The presence or absence of horizontal streaks in the printed matter is visually observed.

As shown in FIG. 9, when the depression amount is 0.1 mm, the horizontal streak is not observed when the concave portion is not formed in the developing roller 10 in advance, but the concave portion having a depth of 3 to 10 μm is formed in the developing roller 10 in advance. If so, horizontal streaks are observed.

横 When the indentation amount is 0.2 mm, no horizontal streak is observed when the depth of the concave portion of the developing roller 10 is in the range of 0 to 8 μm. On the other hand, when the depth of the concave portion of the developing roller 10 is 10 μm, a slight horizontal streak is observed.

と き に は When the pushing amount is 0.3 mm or 0.4 mm, no horizontal streak is observed when the depth of the concave portion of the developing roller 10 is 0 to 10 μm.

(4) When the pushing amount is 0.5 mm, the torque required to rotate the toner layer forming roller 12 increases, and the toner layer forming roller 12 cannot rotate.

か ら From the results shown in FIG. 9, it can be seen that by setting the pushing amount to 0.2 mm or more, a good image without horizontal stripes can be obtained. This is because if the pushing amount is within this range, even if a concave portion is formed on the outer peripheral surface of the developing roller 10, the toner layer forming roller 12 sufficiently contacts the outer peripheral surface of the developing roller 10 via the toner layer. Because you can.

FIG. 11 shows the results of an experiment on the change over time in the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side. The measurement of the thickness of the toner layer on the developing roller 10 is performed after printing pages 0, 5000, 10,000, 15,000, and 20,000, respectively. Note that the thickness of the toner layer is represented by the amount (weight) of the toner per unit area on the outer peripheral surface of the developing roller 10.

As shown in FIG. 11, when the pushing amount is 0.2 mm and 0.3 mm, the thickness of the toner layer on the developing roller 10 is constant regardless of the number of printed sheets. On the other hand, when the pushing amount is 0.1 mm, the thickness of the toner layer on the developing roller 10 increases as the number of prints increases. From this result, it is understood that the time-dependent change in the thickness of the toner layer can be suppressed by setting the pushing amount to 0.2 mm or more.

As described above, according to the fourth embodiment, by setting the amount of pushing of the toner layer forming roller 12 into the developing roller 10 at 0.2 mm or more, it is possible to suppress the occurrence of horizontal streaks and improve image quality. In addition, it is possible to suppress a temporal change in the thickness of the toner layer on the developing roller 10 when continuous printing is performed.

Embodiment 5 FIG.
FIG. 12 shows an electrophotographic apparatus including a developing device according to Embodiment 5 of the present invention. In the fifth embodiment, the toner layer forming roller 12 is elastically pressed against the developing roller 10 by a spring (elastic pressing means) 20.

FIG. 13 is a front view of the developing roller 10, the toner layer forming roller 12, and the blade 13 in the electrophotographic apparatus according to the fifth embodiment. Both ends 12 a of the main shaft of the toner layer forming roller 12 are rotatably supported by a pair of movable frames 21. A blade 13 is further attached to the movable frame 21, and the toner layer forming roller 12 and the blade 13 constitute one unit. The frame 21 is movable toward and away from the outer peripheral surface of the developing roller 10, and is urged by a spring 20 in a direction approaching the developing roller 10.

In the fifth embodiment, since the toner layer forming roller 12 is movable toward and away from the developing roller 10 and is urged toward the developing roller 10 by the spring 20, the outer periphery of the developing roller 10 Even if a concave portion is formed on the surface, the toner layer forming roller 12 can follow the outer peripheral surface of the developing roller 10. Therefore, the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 can be made constant, and the occurrence of horizontal streaks in the image can be prevented. That is, image quality can be improved. Further, even when a concave portion due to friction or the like is formed on the surface of the developing roller 10 by continuous printing for a long time, the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 is kept constant to improve image quality. Can be.

FIG. 14 shows the results of experiments on the occurrence of horizontal streaks. As described in the fourth embodiment, the depth of the concave portion on the developing roller 10 is changed in a range of 0 to 10 μm. The toner layer forming roller 12 is urged by the spring 20 against the developing roller 10 with an urging force such that the pushing amount (FIG. 10) is within the range of 0.1 to 0.4 mm. For comparison, FIG. 14 also shows the experimental results when the pushing amount was set to 0.2 mm in the fourth embodiment. As shown in FIG. 14, according to the fifth embodiment, no horizontal streak is observed when the depth of the concave portion of the developing roller 10 is 0 to 10 μm. On the other hand, when the pressing amount is set to 0.2 mm in the fourth embodiment, a slight horizontal streak is observed when the developing roller 10 has a concave portion having a depth of 10 μm. That is, according to the fifth embodiment, the configuration in which the toner layer forming roller 12 is elastically pressed against the developing roller 10 suppresses the generation of the horizontal streaks more effectively.

FIG. 15 shows the results of an experiment on the change over time in the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side. As described in the fourth embodiment, the measurement of the thickness of the toner layer on the developing roller 10 is performed after printing of pages 0, 5000, 10,000, 15,000, and 20,000, respectively. The toner layer forming roller 12 is urged by the spring 20 against the developing roller 10 with an urging force such that the pushing amount is in the range of 0.1 to 0.4 mm. For comparison, FIG. 14 also shows the experimental results when the pushing amount was set to 0.2 mm in the fourth embodiment. As shown in FIG. 15, according to the fifth embodiment, as in the fourth embodiment, the thickness of the toner layer on the developing roller 10 is constant regardless of the number of printed sheets.

Finally, the torque required to rotate the toner layer forming roller 12 in the developing device according to the fifth embodiment will be described. When the toner layer forming roller 12 is pressed against the developing roller 10 by a spring 20 with a pressing force such that the pushing amount is within a range of 0.1 to 0.4 mm, the toner layer forming roller 12 is pressed. The torque required to rotate is 3.5 kgf. On the other hand, when the pushing amount is set to 0.2 mm in the fourth embodiment, the torque required to rotate the toner layer forming roller 12 is 4.7 kgf.

As described above, according to the fifth embodiment, the configuration in which the toner layer forming roller 12 is pressed and urged against the developing roller 10 by the spring 20 can suppress the occurrence of horizontal streaks and improve the image quality. . In addition, the toner layer forming roller 12 can be rotated with a relatively small torque.

The developing roller 10, the supply roller 11, the toner layer forming roller 12, the auxiliary supply roller 16, and the additional supply roller 17 described in each of the above-described embodiments do not necessarily need to be rollers that rotate the entirety. A cylindrical sleeve or an endless belt that rotates only the surface may be used.

FIG. 1 is a diagram illustrating an electrophotographic apparatus including a developing device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a developing device according to the first embodiment of the present invention. FIG. 6 is a diagram illustrating a method of measuring a friction coefficient of a developing roller. FIG. 4 is a diagram schematically illustrating a toner conveyance state in the developing device. It is a figure which expands and shows the shape of a blade. FIG. 4 is a diagram illustrating a relationship between a friction coefficient of a developing roller and occurrence of an afterimage. FIG. 9 is a diagram illustrating a developing device according to a second embodiment of the present invention. FIG. 13 is a diagram illustrating a developing device according to a third embodiment of the present invention. 14 is a table showing experimental results on the state of occurrence of horizontal streaks in Embodiment 4 of the present invention. FIG. 3 is a schematic diagram for explaining a concept of a pushing amount of a toner layer forming roller. 14 is a table showing experimental results on changes in the thickness of the toner layer on the developing roller according to Embodiment 4 of the present invention. FIG. 13 is a diagram illustrating an electrophotographic apparatus including a developing device according to a fifth embodiment of the present invention. FIG. 15 is a front view illustrating a main part of a developing device according to a fifth embodiment of the present invention. 15 is a table showing experimental results on the occurrence of horizontal streaks in Embodiment 5 of the present invention. 15 is a table showing experimental results on changes in the thickness of a toner layer on a developing roller according to Embodiment 5 of the present invention. FIG. 9 is a diagram illustrating an example of a conventional developing device.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 3 LED head 4 developing device 5 transfer roller 6 cleaning device 10 developing roller 11 supply roller 12 toner layer forming roller 13 blade 14 contact surface 15 toner storage chamber 16 auxiliary supply roller 17 additional supply roller 20 spring 21 flame

Claims (26)

A developing member for developing the electrostatic latent image by attaching toner to the electrostatic latent image formed on the electrostatic latent image carrier;
A toner supply member for supplying toner to the developing member,
A toner layer forming member having an outer peripheral surface in contact with the developing member,
A toner layer regulating member that regulates the thickness of the toner layer attached to the outer peripheral surface of the toner layer forming member,
A developing device, wherein a toner layer adhered to the outer peripheral surface of the toner layer forming member and having a thickness regulated by the toner layer regulating member is transferred to the developing member. A toner storage chamber for storing the toner,
Inside the toner storage chamber, the toner supply member supplies toner to the developing member, the toner layer forming member attaches a toner layer to an outer peripheral surface thereof, and the toner layer regulating member forms the toner layer forming member. The thickness of the toner layer attached to the member is configured to be regulated,
The toner layer adhered to the toner layer forming member and the thickness of which is regulated by the toner layer regulating member is conveyed to the outside of the toner accommodating chamber by the rotation of the toner layer forming member. The developing device according to claim 1, wherein the transfer is performed. The developing member rotates in a certain direction, the toner layer forming member rotates in the same direction as the developing member,
A part of the toner supplied to the developing member from the toner supply member is caused to pass between the developing member and the toner layer forming member in the rotation direction of the developing member by rotation of the developing member, and the toner The developing device according to claim 1, wherein the toner is added to a toner layer transferred from a layer forming member to the developing member. 4. The apparatus according to claim 1, further comprising a potential applying unit that applies a potential to transfer the toner layer attached to the toner layer forming member to the developing member to the developing member and the toner layer forming member. 5. The developing device according to any one of the above. The developing device according to claim 1, wherein each of the developing member, the toner layer forming member, and the toner supply member is configured by a roller. The developing device according to claim 1, wherein the releasability of the outer peripheral surface of the developing member is higher than the releasability of the outer peripheral surface of the toner layer forming member. The developing device according to claim 1, wherein a surface roughness of an outer peripheral surface of the developing member is smaller than a surface roughness of the outer peripheral surface of the toner layer forming member. The developing device according to claim 1, wherein an outer peripheral surface of the developing member is made of a resin. 9. The developing device according to claim 1, wherein the outer peripheral surface of the toner layer forming member is made of rubber. The developing device according to claim 1, wherein the toner layer forming member is pushed into the developing member, and the pushing amount is 0.2 mm or more. The developing device according to claim 1, further comprising an elastic pressing unit configured to elastically press and bias the toner layer forming member against the developing member. 12. The method according to claim 1, wherein a static friction coefficient of an outer peripheral surface of the developing member with respect to a plane having an average surface roughness of about 2 μm made of an acrylic resin is greater than 0 and 0.58 or less. The developing device as described in the above. 13. The developing device according to claim 12, wherein a static friction coefficient of an outer peripheral surface of the outer peripheral surface of the developing member with respect to a plane having an average surface roughness of about 2 [mu] m made of an acrylic resin is greater than 0 and 0.36 or less. The developing device according to claim 1, wherein a rotation peripheral speed of the outer peripheral surface of the toner layer forming member is lower than a rotational peripheral speed of the outer peripheral surface of the developing member. The toner layer regulating member is a blade provided so as to be in contact with the outer peripheral surface of the toner layer forming member, and a contact surface of the blade facing the toner layer forming member is aligned with a central axis of the toner layer forming member. The developing device according to claim 1, wherein the developing device extends in parallel. The contact surface of the blade facing the toner layer forming member has a radius of curvature of 0.3 mm or more and 0.5 mm or less in a plane orthogonal to a longitudinal direction of the blade. Developing device. The developing device according to claim 15, wherein the blade is pressed against the toner layer forming member with a force of 10 g / cm ² or more and 50 g / cm ² or less. Potentials VD, VS, and VL are applied to the developing member, the toner supply member, and the toner layer forming member, respectively, and the potentials VD, VS, and VL satisfy the following equations (1) and (2). The developing device according to any one of claims 1 to 17, wherein:
| VD | ≦ | VS | (1)
| VD | ≦ | VL | (2) 19. The developing device according to claim 1, further comprising an auxiliary supply member that supplies toner to the toner layer forming member. 20. The developing device according to claim 19, wherein the auxiliary supply member contacts the outer peripheral surface of the toner layer forming member and rotates in the same direction as the toner layer forming member. 21. The developing device according to claim 19, wherein potentials VH and VL are respectively applied to the auxiliary supply member and the toner layer forming member, and the potentials VH and VL satisfy the following expression (3).
| VH | ≧ | VL | (3) 22. The developing device according to claim 1, further comprising an additional supply member that supplies toner to the toner supply member. 23. The developing device according to claim 22, wherein the additional supply member contacts an outer peripheral surface of the toner supply member and rotates in the same direction as the rotation direction of the toner supply member. 24. The developing device according to claim 22, wherein potentials VT and VS are respectively applied to the additional supply member and the toner supply member, and the potentials VT and VS satisfy the following expression (4).
| VT | ≧ | VS | (4) The developing member rotates in a certain direction,
25. The developing device according to claim 1, wherein the toner layer forming member rotates in the same direction as the developing member. A developing device according to any one of claims 1 to 25,
An electrostatic latent image carrier developed by the developing device;
A transfer device that transfers the toner image on the electrostatic latent image carrier developed by the developing device to a print medium,
An electrophotographic apparatus provided with.

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