JP4703951B2 - Developing apparatus and electrophotographic apparatus - Google Patents

Description

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

  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 that uses a non-magnetic toner and does not use a carrier. Conventionally, developing devices corresponding to this non-magnetic one-component developing method have been proposed (for example, see Patent Documents 1 to 6).

Japanese Patent Laid-Open No. 7-44007 (5th page, FIG. 1) JP 7-64394 A (page 3, FIG. 3) Japanese Patent Laid-Open No. 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) Japanese Patent Laid-Open No. 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 disposed opposite to the photosensitive drum 110 and a supply roller 101 that supplies 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 oppositely. A blade 103 that scrapes off the toner adhering to the outer peripheral surface is in contact with the outer peripheral surface of the toner regulating roller 102. 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 adhering to the outer peripheral surface of the developing roller 100, the toner that is not transferred to the photosensitive drum 110 (denoted by reference symbol A) is the collection roller 104 provided below the developing roller 100 or the above-described supply roller. 101. The basic configuration of the developing apparatus described in the 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. Therefore, 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. For this reason, in the conventional developing device, the coefficient of friction of the outer peripheral surface of the developing roller 100 is relatively large, and therefore the releasability with respect to the toner is low. May not be removed. If such 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 the thickness thereof increases locally. When the developing roller 100 rotates once, the photosensitive drum A so-called afterimage is formed by adhering to a portion other than the electrostatic latent image 110. As a result, the recording paper (printing medium) is smudged in portions other than the image that should be originally formed, and the image quality is degraded.

  Further, since the blade 103 is pressed against the toner regulation roller 102 with a relatively strong force, a so-called filming phenomenon occurs in which the toner melts due to frictional heat and adheres to the outer peripheral surface of the toner regulation roller 102 or the like. It may occur. When such a filming phenomenon occurs, the thickness of the toner layer formed on the outer peripheral surface of the developing roller 100 becomes non-uniform, so that a part of the image to be originally formed is missing on the recording paper, or The portion other than the image that should be originally formed is soiled and the image quality is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device and an electrophotographic apparatus that can prevent deterioration in image quality.

In order to solve the above problems, a developing device according to the present invention includes a developing member that develops the electrostatic latent image by attaching nonmagnetic toner to the electrostatic latent image formed on the electrostatic latent image carrier. , provided in contact with said developing member, and the toner supply member for supplying the nonmagnetic toner to the developing member, have a peripheral surface in contact with said developing member, a toner layer forming member having elasticity, the toner layer A toner layer regulating member that regulates the thickness of the toner layer attached to the outer peripheral surface of the forming member, and the releasability of the outer peripheral surface of the developing member is that of the outer peripheral surface of the toner layer forming member. The developing layer that passes through the contact portion between the toner layer forming member and the developing member through a toner layer that is higher than the toner layer and adheres to the outer peripheral surface of the toner layer forming member and whose thickness is regulated by the toner layer regulating member. by transferring the toner layer on the member It is characterized in.

  The electrophotographic apparatus according to the present invention prints the above-described developing device, the electrostatic latent image carrier developed by the developing device, and the 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 this 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 toner layer can be formed on the outer peripheral surface of the developing member by transfer. Since the releasability with respect to the toner is improved by reducing the friction coefficient of the outer peripheral surface of the developing member, unnecessary toner remaining on the outer peripheral surface of the developing member can be surely removed. Therefore, it is possible to prevent the occurrence of an afterimage due to unnecessary toner remaining on the outer peripheral surface of the developing member, and to prevent the image quality from deteriorating. Further, 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 weak force, whereby the toner is melted by frictional heat. Thus, the filming phenomenon that occurs can be prevented, and deterioration of image quality can be prevented. In addition, the thickness of the toner layer formed on the outer peripheral surface of the developing member can be freely changed by changing the friction coefficient of the developing member and the toner layer forming member, the applied voltage, etc. Can be adjusted.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
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 photosensitive drum 1 has an insulating property when not exposed, and has a conductivity when exposed to release charged charges. The photosensitive drum 1 rotates in one direction (clockwise in the figure). Around the photosensitive drum 1, a charging roller 2, an LED head 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are sequentially arranged 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 the uniformly charged photosensitive layer of the photosensitive drum 1 according to image information by LEDs (light emitting diodes) arranged in an array. Of the photosensitive layer of the photosensitive drum 1, the charged portion is removed from the exposed portion, but the charged portion remains in the unexposed portion to form an electrostatic latent image. As will be described later, the developing device 4 attaches toner to the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 1 and performs so-called toner development. The transfer roller 5 sandwiches a recording paper (print medium) (not shown) between the photosensitive drum 1 and transfers a toner image formed on the outer peripheral surface of the photosensitive drum 1 to the recording paper. The cleaning device 6 includes a cleaning blade 60 and removes 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 disposed opposite to the photosensitive drum 1 and a toner storage chamber 15 that stores 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 in the toner storage chamber 15, and the left portion in the drawing protrudes out of 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 the direction opposite to the rotation direction of the photosensitive drum 1 and adheres toner on the outer peripheral surface thereof to the photosensitive drum 1.

  This developing roller 10 has a coating layer 10a made of a resin (for example, polyimide resin, urethane resin, or fluorine resin) formed on the outer peripheral surface of a roller 10b made of a semiconductive elastic body (specifically, rubber). It is. The reason why the coating layer 10a is provided is to reduce the coefficient of friction of the outer peripheral surface of the developing roller 10 and to improve the releasability with respect to the toner (that is, the ease of separation of the toner). The rubber hardness of the roller 10b is 30 to 60 degrees as JIS C hardness. The developing roller 10 may have a configuration in which a tube made of polyimide resin or the like is covered around a roller made of resin (sponge) having open cells.

  FIG. 3 is a diagram illustrating a method for measuring the friction coefficient (here, the static friction coefficient) of the outer peripheral surface of the developing roller 10. In this measurement method, an inclined plate 31 having an average surface roughness (Rz) of about 2 μm formed of an acrylic resin is used. The developing roller 10 is placed on the inclined plate 31 so that the axial direction coincides with 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 the sliding angle θ (θ> 0 degrees), there is a relationship μ = tan θ between the sliding angle θ and the static friction coefficient μ. The coefficient of static friction μ with respect to the surface of the inclined plate 31 on the outer peripheral surface of the developing roller 10 is preferably 0.58 or less (that is, the sliding angle θ is 30 degrees or less), more preferably 0.36 or less (that is, slipping). 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 developing roller 10 is provided in the toner storage chamber 15 adjacent to the developing roller 10. . The supply roller 11 is formed of a semiconductive resin having open cells, and the outer peripheral surface thereof 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 respectively applied between the developing roller 10 and the supply roller 11 by power sources (potential applying means) 40 and 41. Between these potentials VD and VS, toner is supplied to the developing roller 10 side. The potential difference to be attracted is set. Specifically, when the toner is negatively charged by frictional charging (described later), the potentials VD and VS are both negative potentials. When the toner is positively charged, the potentials VD and VS are both positive potentials. To do. The potentials VD and VS satisfy the relationship | VD | ≦ | VS |. Here, it is assumed that the toner is negatively charged. For example, the potential VD is set to −300V and VS is set to −450V. When the toner is positively charged, for example, the potential VD is set to + 300V and VS is set to + 450V.

  An inclined plate 15 a that is inclined toward the supply roller 11 is formed in the lower portion of the toner storage chamber 15. This is for the purpose of collecting toner 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 (that is, the upper side of the developing roller 10 in FIG. 2), a toner layer having a rotation axis parallel to the rotation axis of the developing roller 10 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. Of the outer peripheral surface of the toner layer forming roller 12, the right portion in the drawing is located in the toner storage chamber 15, and the left portion in the drawing protrudes 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. The rotational peripheral speed of the toner layer forming roller 12 is set to be slower than or the same as that of 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 diagram schematically illustrating a toner conveyance state 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. The outer peripheral surface of the toner layer forming roller 12 preferably has a larger coefficient of friction than the outer peripheral surface of the developing roller 10 (that is, the releasability with respect to the toner is low). This is because the toner layer adhering to the outer peripheral surface of the toner layer forming roller 12 can be thickened. The toner layer forming roller 12 is given a potential VL by a power source 42. Between the above-described potential VD of the developing roller 10 and the potential VL of the toner layer forming roller 12, a potential for attracting toner to the developing roller 10 side is provided. Specifically, the 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 −300V and the potential VL is set to −450V.

  A blade (toner layer regulating member) 13 is provided on the toner layer forming roller 12 on the side substantially opposite to the developing roller 10 (upper side in the drawing). The 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-like member made of phosphor bronze, for example, 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 showing 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 the vicinity of the outer peripheral surface of the toner layer forming roller 12 and is bent in a direction away from the outer peripheral surface. The contact surface 14 on the toner layer forming roller 12 side of the bent portion of the blade 13 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 can be elastically deformed in a direction away from the outer peripheral surface of the toner layer forming roller 12, and 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. 4. The thickness of the toner is configured to pass through. As a result, a toner layer having a certain 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 toner storage chamber 15 is filled with at least toner that can be filled with the supply roller 11 (only a part of the toner is shown in FIG. 4). The supply roller 11 rotates while adhering the toner in the toner storage chamber 15 to the outer peripheral surface thereof. The toner adhering to the outer peripheral surface of the supply roller 11 is conveyed to the vicinity of the 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 the potential difference between the supply roller 11 and the developing roller 10 and adheres to the outer peripheral surface thereof. As a result, 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 the 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 between the developing roller 10 and the toner layer forming roller 12 by the rotation of the developing roller 10. It passes through and 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. A toner layer having a uniform thickness is formed on the outer peripheral surface of the layer forming roller 12.

  Note that the ratio of the toner adhering to the developing roller 10 and the toner adhering to the toner layer forming roller 12 at the contact portion between the developing roller 10 and the toner layer forming roller 12 is the ratio between the developing roller 10 and the toner layer forming roller 12. It depends on the friction coefficient, the rotational peripheral speed, the potential difference between the two, and the like. Here, the rotational 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. Is within 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 the rotation of the toner layer forming roller 12, and outside the contact portion between the toner layer forming roller 12 and the developing roller 10. It is transported to the vicinity. 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 that has passed between the toner layer forming roller 12 and the developing roller 10 are added together. A thick toner layer is formed. Thus, the thickness of the toner layer formed on the outer peripheral surface of the developing roller 10 on the photosensitive drum 1 side is the friction coefficient, rotational peripheral speed or applied voltage of the developing roller 10 and the toner layer forming roller 12, or the blade 13. The pressure can be freely changed by adjusting the pressure applied to the toner layer roller 12.

  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 the contact portion between the supply roller 11 and the developing roller 10 as the developing roller 10 rotates, and is supplied by the supply roller 11. To be recovered. Since the coating layer 10a having a small friction coefficient is provided on the outer peripheral surface of the developing roller 10, the releasability of the outer peripheral surface of the developing roller 10 with respect to 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 sheet (not shown) between the photosensitive drum 1 and the transfer roller 5 and fixed on the recording sheet 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.

  Using the electrophotographic apparatus described above, a printing test of 20,000 sheets was continuously performed using toner having an average particle diameter of 7 μm manufactured by suspension polymerization. As a result, no afterimage was observed in the obtained printed matter. Further, there was no filming phenomenon in which the toner melted and fixed to the toner layer forming roller 12 or the like.

  Next, the effect of preventing afterimage generation in the first embodiment will be described. In order to prevent the afterimage from occurring, it is necessary to reduce the friction coefficient of the outer peripheral surface of the developing roller 10 and to increase the releasability of the outer peripheral surface with respect to the toner. However, if the coefficient of friction on the outer peripheral surface of the developing roller 100 is reduced in the conventional developing device shown in FIG. 16, the toner conveyed to the photosensitive drum 110 side by the developing roller 100 becomes insufficient, resulting in a transfer failure. It will be. In contrast, 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 transfer failure. can do. Thereby, the releasability with respect to the toner on the outer peripheral surface of the developing roller 10 can be improved, and the remaining toner can be reliably collected.

  Here, the relationship between the friction coefficient of the developing roller 10 and the afterimage generation will be described. FIG. 6 is a graph showing the results of examining the state of occurrence of afterimages by changing the static friction coefficient μ of the developing roller 10. In FIG. 6, the horizontal axis represents the sliding angle θ and the static friction coefficient μ of the developing roller 10 measured using the inclined plate 31 illustrated in FIG. 3. The vertical axis indicates the afterimage evaluation level that evaluates the presence or absence and density of afterimages observed in the printed matter printed using the developing roller 10 having different static friction coefficients μ. The afterimage evaluation level is assumed to be a level at which no afterimage is observed with the naked eye, and is expressed by a smaller numerical value as the afterimage is observed. A level at which an afterimage is slightly observed but does not cause a problem as a normal printed matter is set to 9.

  From FIG. 6, level 9 or higher which 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) It can be seen that the static friction coefficient μ is 0.58 or less (slip angle θ is 30 degrees or less). If 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 unnecessary toner remaining on the outer peripheral surface of the developing roller 10 is reliably removed by the supply roller 11. Because. Further, a 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). Therefore, the static friction coefficient μ with respect to a plane having an average surface roughness Rz made of acrylic resin of the outer peripheral surface of the developing roller 10 of about 2 μm is preferably 0.58 or less, and is 0.36 or less. It turns out that it is more preferable. The static friction coefficient μ of the outer peripheral surface of the toner layer forming roller 12 used for the measurement of FIG. 6 with respect to the surface of the inclined plate 31 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 the 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 is melted by frictional heat. Therefore, there is a possibility that 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 to the toner layer with a relatively weak force that allows a certain thickness of toner to pass 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 a filming phenomenon can be prevented more reliably.

  As described above, according to the first embodiment, a toner layer with a regulated thickness is formed on the outer peripheral surface of the toner layer forming roller 12, and this 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. Thereby, the releasability of the outer peripheral surface of the developing roller 10 with respect to the toner can be improved. Therefore, 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 a residual image can be prevented and deterioration of image quality can be prevented.

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

  Further, 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 melted by the frictional heat and fixed to the toner layer forming roller 12 or the like. It is possible to prevent the occurrence of a ming phenomenon and to prevent a decrease in image quality.

  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 transferred to the developing roller 10 outside the toner layer. It is possible to prevent other toner from adhering to the toner layer whose thickness is regulated by the blade 13 and to keep the thickness of the toner layer uniform.

  Further, by making the releasability of the outer peripheral surface of the developing roller 10 with respect to the toner higher than the releasability of the toner layer forming roller 12 with respect to the toner, the toner transport capability of the toner layer forming roller 12 is increased. On the other hand, it is possible to easily remove the toner from the developing roller 10 and to prevent the afterimage from occurring more reliably.

  Further, a resin coating layer 10a is provided on the outer peripheral surface of the developing roller 10, and a static friction coefficient μ with respect to a plane having an average surface roughness Rz made of acrylic resin of about 2 μm 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, the radius of curvature of the contact surface 14 of the blade 13 is set to 0.3 to 0.5 mm, and pressed against the toner layer forming roller 12 with a force of 10 to 50 g / cm ² , so that the outer peripheral surface of the toner layer forming roller 12 is applied. 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 set to the friction of the outer peripheral surface of the developing roller 10. Even when the coefficient is larger than the coefficient, the toner layer formed on the toner layer forming roller 12 can be reliably transferred to the developing roller 10.

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

Embodiment 2. FIG.
FIG. 7 is a diagram showing 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 disposed 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 equipped with. The developing device 4A is configured in the same manner as the developing device 4 according to the first embodiment except that the 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 on the right side of the toner layer forming roller 12 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 an open cell (so-called silicon sponge) and is semiconductive. The auxiliary supply roller 16 is given a potential VH by a power source 43. A potential difference that attracts toner to the toner layer forming roller 12 side 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, the 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 to be the same as the charging of the toner.

  The auxiliary supply roller 16 rotates while adhering the toner in the toner storage chamber 15 to the outer peripheral surface and in contact with the toner layer forming roller 12. The toner adhering to the outer peripheral surface of the auxiliary supply roller 16 is conveyed to the vicinity of the contact portion between the auxiliary supply roller 16 and the toner layer forming roller 12, and is negatively charged by friction between the toners. The charged toner is attracted to the toner layer forming roller 12 due to the potential difference between the auxiliary supply roller 16 and the toner layer forming roller 12, and adheres to the outer peripheral surface thereof. As a result, 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 adhering 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 storage chamber 15 as in the first embodiment. Transition 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 4A according to the second embodiment, the toner conveyed from the auxiliary supply roller 16 in addition to the toner conveyed from the developing roller 10 adheres to the outer peripheral surface of the toner layer forming roller 12. Even when the amount of toner supplied from the supply roller 11 to the developing roller 10 decreases for some reason (for example, uneven distribution of toner in the toner storage chamber 15), a sufficient amount of toner is present on the outer peripheral surface of the developing roller 10. Is supplied. Therefore, transfer failure due to toner shortage can be prevented.

  In particular, when 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 thinly printed, so-called reverse afterimage may occur. In the second embodiment, the developing roller 10 Since the toner is sufficiently supplied to the outer peripheral surface of the toner, the occurrence of a reversal afterimage can be minimized.

  Further, as in 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 the occurrence of afterimages is prevented. be able to. Further, since the force that presses 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, it is possible to prevent the image quality from being deteriorated.

Embodiment 3 FIG.
FIG. 8 shows 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 developing device 4 (FIG. 2) according to the first embodiment. It is a thing. The developing device 4B is configured in the same manner as the developing device 4 according to Embodiment 1 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.

  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. Similar to the supply roller 11, the additional supply roller 17 is made of urethane resin having a continuous cell (so-called urethane sponge) and has semiconductivity. The additional supply roller 17 is given a potential VT by a power supply 44. A potential difference that attracts toner to the supply roller 11 side is set between the potential VT of the additional supply roller 17 and the potential VS of the supply roller 11 described above. Specifically, the 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 to be the same as the charging of the toner.

  The additional supply roller 17 rotates while adhering the toner in the toner storage chamber 15 to the outer peripheral surface and in contact with the supply roller 11. The toner adhering to the outer peripheral surface of the additional supply roller 17 is conveyed to the vicinity of the 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 due to 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 4B 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, and therefore the toner around the supply roller 11 is caused by some reason (for example, the toner storage chamber). When the toner is reduced due to the uneven distribution of toner in the toner 15, it is possible to prevent the toner supply capability of the supply roller 11 from being lowered. Accordingly, transfer failure due to toner shortage can be prevented, and occurrence of reversal afterimages due to toner shortage can also be suppressed.

  Further, as in the first and second embodiments, the friction coefficient of the outer peripheral surface of the developing roller 10 can be reduced, so that unnecessary toner remaining on the outer peripheral surface of the developing roller 10 can be reliably removed, and an afterimage is generated. Can be prevented. Further, since the force that presses 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, it is possible to prevent the image quality from being deteriorated.

Embodiment 4 FIG.
In the fourth embodiment, the optimum range of the pressing force for pressing 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 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 the axial direction of the developing roller 10 is increased. Long groove-like recesses 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, 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 non-uniform, and as a result, the horizontal stripe (developing roller 10 in the image) Long unevenness in the axial direction) may occur. Further, when the outer diameter of the toner layer forming roller 12 changes due to wear with continuous printing, there is a possibility that the thickness of the toner layer on the developing roller 10 may change over time. In the fourth embodiment, the above pressing force is determined so as to prevent the occurrence of horizontal stripes and to suppress the change with time of the thickness of the toner layer.

  FIG. 9 shows the experimental results for the generation of the transverse muscle. The pressing 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 with respect to the developing roller 10. As schematically shown in FIG. 10, this “push amount” is an amount (reference numeral 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 pushing amount is changed by adjusting the position of the support member. Here, the pushing amount is changed in the range of 0 to 0.5 mm.

  In FIG. 9, a recess is formed in advance in the developing roller 10, and the depth of the recess is changed in the range of 0 to 10 μm. The concave portion 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. Further, the depth of the concave portion is changed by adjusting the time for stopping the developing roller 10 in a state where the developing roller 10 is in contact with the toner layer forming roller 12. The presence or absence of transverse stripes in the printed material is observed with the naked eye.

  As shown in FIG. 9, when the pushing amount is 0.1 mm, no horizontal streak is observed unless a recess is formed in advance in the developing roller 10, but a recess having a depth of 3 to 10 μm is formed in the developing roller 10 in advance. If you do, you can see the horizontal stripes.

  When the pushing amount is 0.2 mm, no horizontal stripe 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, but this horizontal streak is at a level causing no practical problem.

  When the pushing amount is 0.3 mm and 0.4 mm, no horizontal stripe is observed in any case where the depth of the concave portion of the developing roller 10 is 0 to 10 μm.

  When the push-in amount is 0.5 mm, the torque necessary for rotating the toner layer forming roller 12 becomes large, and the toner layer forming roller 12 becomes non-rotatable.

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

  FIG. 11 shows the experimental results of 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 thickness of the toner layer on the developing roller 10 is measured after printing 0, 5000 pages, 10000 pages, 15000 pages, and 20000 pages. The thickness of the toner layer is represented by the amount (weight) of 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 pressing amount is 0.1 mm, the thickness of the toner layer on the developing roller 10 increases as the number of printed sheets increases. From this result, it can be seen that the change with time 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, the amount of pushing of the toner layer forming roller 12 into the developing roller 10 is 0.2 mm or more, thereby suppressing the occurrence of horizontal stripes and improving the image quality. In addition, it is possible to suppress a change with time in the thickness of the toner layer on the developing roller 10 when continuous printing is performed.

Embodiment 5 FIG.
FIG. 12 is a view showing 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 and urged 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 a single unit. The frame 21 is movable in a direction approaching and separating from the outer peripheral surface of the developing roller 10, and is biased in a direction approaching the developing roller 10 by a spring 20.

  In the fifth embodiment, since the toner layer forming roller 12 can move in the direction approaching and separating from the developing roller 10 and is biased toward the developing roller 10 by the spring 20, the outer periphery of the developing roller 10 is 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 stripes in the image can be prevented. That is, the 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 made constant, and the image quality is improved. Can do.

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

  FIG. 15 shows the experimental results regarding the change with time of 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 thickness of the toner layer on the developing roller 10 is measured after printing 0, 5000 pages, 10000 pages, 15000 pages, and 20000 pages. The toner layer forming roller 12 is urged against the developing roller 10 by a spring 20 with a pressing urging force such that the pressing amount is within a range of 0.1 to 0.4 mm. For comparison, FIG. 14 also shows the experimental results when the pushing amount is 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 urged against the developing roller 10 by the spring 20 with a pressing urging force such that the pushing amount is within a range of 0.1 to 0.4 mm, the toner layer forming roller 12 is moved. The torque required for rotation is 3.5 kgf. On the other hand, when the pushing amount is 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 stripes and improve the image quality. . It is also possible to rotate the toner layer forming roller 12 with a relatively small torque.

  Note that 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 have to rotate as a whole. It may be a cylindrical sleeve or an endless belt that rotates only the surface.

1 is a diagram showing an electrophotographic apparatus including a developing device according to Embodiment 1 of the present invention. It is a figure which shows the developing device which concerns on Embodiment 1 of this invention. It is a figure which shows the measuring method of the friction coefficient of a developing roller. FIG. 6 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 braid | blade. It is a figure which shows the relationship between the friction coefficient of a developing roller, and afterimage generation. It is a figure which shows the developing device which concerns on Embodiment 2 of this invention. It is a figure which shows the developing device which concerns on Embodiment 3 of this invention. It is a table | surface which shows the experimental result about the generation | occurrence | production state of a horizontal muscle in Embodiment 4 of this invention. FIG. 4 is a schematic diagram for explaining a concept of a pressing amount of a toner layer forming roller. 10 is a table showing experimental results on changes in the thickness of a toner layer on a developing roller in Embodiment 4 of the present invention. It is a figure which shows the electrophotographic apparatus containing the developing device which concerns on Embodiment 5 of this invention. It is a front view which shows the principal part of the developing device which concerns on Embodiment 5 of this invention. It is a table | surface which shows the experimental result about generation | occurrence | production of a horizontal stripe in Embodiment 5 of this invention. 10 is a table showing experimental results on changes in the thickness of a toner layer on a developing roller in Embodiment 5 of the present invention. It is a figure which shows an example of the conventional developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 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 (25)

A developing member for developing the electrostatic latent image by attaching a non-magnetic toner to the electrostatic latent image formed on the electrostatic latent image carrier;
A toner supply member that is provided in contact with the developing member and supplies non-magnetic toner to the developing member;
Have a peripheral surface in contact with said developing member, a toner layer forming member having elasticity,
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,
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 toner on the developing member that has passed through the contact portion between the toner layer forming member and the developing member passes through the toner layer that adheres to the outer peripheral surface of the toner layer forming member and whose thickness is regulated by the toner layer regulating member. A developing device for transferring to a layer . A toner storage chamber for storing toner;
Inside the toner storage chamber, the toner supply member supplies toner to the developing member, the toner layer forming member causes a toner layer to adhere to the outer peripheral surface, and the toner layer regulating member forms the toner layer. Configured to regulate the thickness of the toner layer attached to the member,
The toner layer that adheres to the toner layer forming member and whose thickness is regulated by the toner layer regulating member is transported to the outside of the toner storage chamber by the rotation of the toner layer forming member, and outside the toner containing chamber, The developing device according to claim 1, wherein 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 from the toner supply member to the developing member is passed between the developing member and the toner layer forming member in the rotating direction of the developing member by rotating the developing member, and the toner The developing device according to claim 1, wherein the developing device adds the toner layer transferred from the 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, respectively. The developing device according to any one of the above.   5. The developing device according to claim 1, wherein each of the developing member, the toner layer forming member, and the toner supplying member is configured by a roller.   6. The developing device according to claim 1, wherein a surface roughness of the 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.   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 pressed into the developing member, and the pressing amount is 0.2 mm or more.   The developing device according to claim 1, further comprising an elastic pressing unit that elastically presses and urges the toner layer forming member against the developing member.   The static friction coefficient with respect to a plane having an average surface roughness made of acrylic resin of an outer peripheral surface of the developing member of about 2 μm is greater than 0 and 0.58 or less. The developing device described.   12. The developing device according to claim 11, wherein a static friction coefficient of an outer peripheral surface of the developing member with respect to a plane having an average surface roughness made of acrylic resin of about 2 [mu] m is greater than 0 and equal to or less than 0.36.   The developing device according to claim 1, wherein a rotational peripheral speed of the outer peripheral surface of the toner layer forming member is slower 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 a center 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 the longitudinal direction of the blade. Development device. The developing device according to claim 14, 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. The 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 expressions (1) and (2). The developing device according to any one of claims 1 to 16,
| VD | ≦ | VS | (1)
| VD | ≦ | VL | (2)   The developing device according to claim 1, further comprising an auxiliary supply member that supplies toner to the toner layer forming member.   The developing device according to claim 18, 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. The developing device according to claim 18 or 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)   21. The developing device according to claim 1, further comprising an additional supply member that supplies toner to the toner supply member.   The developing device according to claim 21, 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. 23. The developing device according to claim 21, wherein potentials VT and VS are applied to the additional supply member and the toner supply member, respectively, and the potentials VT and VS satisfy the following expression (4).
| VT | ≧ | VS | (4) The developing member rotates in a certain direction,
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 24;
An electrostatic latent image carrier to be developed by the developing device;
A transfer device for transferring a toner image on the electrostatic latent image carrier developed by the developing device to a print medium;
An electrophotographic apparatus comprising:

Images