JP5499782B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In Patent Document 1, as a method for eliminating the charge of an image carrier of an image forming apparatus without installing a dedicated neutralization apparatus, a photoconductor including an organic carrier generating substance and an organic carrier transporting substance on a conductive support is disclosed. It is proposed that the linear velocity of rotation of the photosensitive member is 250 mm / sec or more, and the surface of the photosensitive member is exposed at a position separated by 0.2 seconds or more before charging to perform static elimination.

JP-A-8-6450

  In the present invention, when switching from image formation to non-image formation, the transfer voltage applied during the previous image formation is not continuously applied to the transfer member for at least the first period, and is applied during the previous image formation. An image forming apparatus in which potential unevenness on the surface of an image carrier is suppressed as compared with a case where the developed voltage is changed stepwise toward 0 V during the first period and is not applied to the developing member. For the purpose.

  The invention according to claim 1 is an image holding member, a charging member for charging the image holding member, and a first application device that applies a charging voltage to the charging member so that the charging member has a predetermined charging potential. A latent image forming apparatus that forms an electrostatic latent image on the image carrier charged by the charging member; a developing member that develops the electrostatic latent image formed on the image carrier with toner; A second applying device that applies a developing voltage to the developing member so that the developing member has a predetermined developing potential; and a toner image formed on the image holding member by the developing member is transferred to the transfer target. And a transfer member that neutralizes the image carrier, a third application device that applies a transfer voltage to the transfer member so that the transfer member has a predetermined transfer potential, and switching from image formation to non-image formation. Sometimes applied during previous image formation Even if the transfer voltage is not applied, it is continuously applied to the transfer member for the first period, and the development voltage applied at the time of the previous image formation is changed stepwise toward 0 V during the first period. A control device for controlling the first application device, the second application device, and the third application device so as to apply to the developing member and release the application of the charging voltage to the charging member; An image forming apparatus.

According to a second aspect of the invention, the image carrier has a charge generation layer and a charge transport layer in this order on a support, and the charge transport layer comprises a binder resin and the following general formula (1). The image forming apparatus according to claim 1, comprising a charge transporting material having a structure represented.

In General Formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 or more carbon atoms. It represents an alkoxy group having 20 or less, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure. n and m each independently represents 0 or 1.

The invention according to claim 3 is the image forming apparatus according to claim 2, wherein the binder resin includes a structural unit represented by the following general formula (2).

In General Formula (2), R ⁷ and R ⁸ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl having 6 to 12 carbon atoms. E and f each independently represents an integer of 0 or more and 4 or less.

According to a fourth aspect of the present invention, the binder resin includes a copolymer of a structural unit represented by the general formula (2) and a structural unit represented by the following general formula (3). 3. The image forming apparatus according to 3.

In general formula (3), R ⁹ and R ¹⁰ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl having 6 to 12 carbon atoms. And g and h each independently represent an integer of 0 or more and 4 or less. X is —CR ¹¹ R ¹² — (wherein R ¹¹ and R ¹² are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms) Or a 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, —O—, —S—, —SO—, or -SO ₂ - represents a.

According to a fifth aspect of the present invention, when the control device switches from image formation to non-image formation, the control device steps the charging voltage applied at the time of the previous image formation toward 0 V for each rotation of the image carrier. 5. Any one of claims 1 to 4, wherein the first application device is controlled so as to be applied to the charging member with a change in the electric power, thereby controlling the application of the charging voltage to the charging member. The image forming apparatus according to claim 1.

According to a sixth aspect of the present invention, the charging member is disposed in contact with the surface of the image carrier, and the first application device applies a DC voltage to the charging member as the charging voltage. 5. The image forming apparatus according to claim 4.

  According to the first aspect of the present invention, when switching from image formation to non-image formation, the transfer voltage applied during the immediately preceding image formation is not continuously applied to the transfer member for at least the first period, and immediately before In comparison with the case where the developing voltage applied during the image formation is changed stepwise toward 0 V during the first period and is not applied to the developing member, potential unevenness on the surface of the image carrier is suppressed. There is an effect.

  According to the second aspect of the invention, the charge-carrying of the image carrier is effectively performed as compared with the case where the charge-transporting layer does not include the charge-transporting material having the structure represented by the general formula (1). , Has the effect.

  According to the invention of claim 3, there is an effect that neutralization of the image carrier is effectively performed as compared with the case where the binder resin does not include the structural unit represented by the general formula (2). .

  According to the invention of claim 4, the binder resin does not contain a copolymer of the structural unit represented by the general formula (2) and the structural unit represented by the general formula (3). Compared to the case, there is an effect that neutralization of the image carrier is more effectively performed.

  According to the fifth aspect of the present invention, when switching from image formation to non-image formation, the withstand voltage applied at the time of the previous image formation is changed stepwise toward 0 V for each rotation of the image carrier. As compared with the case where no voltage is applied to the charging member, there is an effect that the potential unevenness on the surface of the image carrier is further suppressed.

  According to the invention of claim 6, the charging member is arranged in contact with the surface of the image carrier, and even when the charging voltage is a direct current voltage, the potential unevenness on the surface of the image carrier is suppressed. Play.

1 is a schematic diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic diagram which shows an example of a structure of an image holding body. It is a diagram showing an example of changes in transfer voltage, development voltage, and charging voltage during non-image formation in a conventional image forming apparatus. FIG. 6 is a diagram illustrating an example of changes in transfer voltage, development voltage, and charging voltage during non-image formation in the image forming apparatus according to the present exemplary embodiment. FIG. 6 is a diagram illustrating an example of changes in transfer voltage, development voltage, and charging voltage during non-image formation in the image forming apparatus according to the present exemplary embodiment. 4 is a flowchart illustrating processing performed by the control device of the image forming apparatus according to the present embodiment.

Hereinafter, an embodiment of the image forming apparatus of the present embodiment will be described in detail with reference to the drawings.
As shown in FIG. 1, an image carrier 12 is provided in the image forming apparatus 10 according to the present exemplary embodiment. The image carrier 12 has a cylindrical shape, and is rotationally driven (in the direction of arrow A in FIG. 1) by a motor (not shown).

  As shown in FIG. 2, the image carrier 12 includes a support 60, an undercoat layer 62 formed on the support 60, and a photosensitive layer 63 formed on the undercoat layer 62. It is configured. The photosensitive layer 63 may have a two-layer structure including a charge generation layer 65 and a charge transport layer 66. The photosensitive layer 63 may have a configuration in which a protective layer 64 is provided on the outermost surface. The detailed configuration of the image carrier 12 will be described later.

  Around the image carrier 12, a charging device 15, a latent image forming device 16, a developing device 18, a transfer device 31, and a cleaning device 22 are sequentially arranged along the rotation direction of the image carrier 12.

  The charging device 15 charges the surface of the image carrier 12. The charging device 15 is provided in contact or non-contact with the surface of the image carrier 12, and includes a charging member 14 that charges the surface of the image carrier 12, and a power supply 28 that applies a charging voltage to the charging member 14. Yes. The power source 28 is electrically connected to the charging member 14.

  The power source 28 is electrically connected to a control unit 36 provided in the image forming apparatus 10, and applies a charging voltage to the charging member 14 under the control of the control unit 36. The charging member 14 to which the charging voltage is applied from the charging member 14 charges the image carrier 12 to a charging potential corresponding to the applied charging voltage. Therefore, the image holding body 12 is charged to a different charging potential by adjusting the charging voltage applied from the power source 28.

  The latent image forming device 16 irradiates the surface of the image carrier 12 charged by the charging member 14 with the light L modulated based on the image information of the image to be formed, and the image on the image carrier 12. An electrostatic latent image corresponding to the information image is formed.

  A known developer containing toner is stored in the developing device 18. The toner is stored in a charged state in the developing device 18. Examples of the toner contained in the developer include a toner having a volume average particle diameter of 3 μm or more and 9 μm or less obtained by a polymerization method.

  The developing device 18 includes a developing member 18A that develops the electrostatic latent image formed on the image carrier 12 with toner contained in the developer, and a power source 32. A power source 32 is electrically connected to the developing member 18A. The power source 32 is also electrically connected to a control unit 36 provided in the image forming apparatus 10, and a development voltage is applied from the power source 32 to the developing member 18 </ b> A under the control of the control unit 36. The developing member 18A to which the developing voltage is applied is charged to a developing potential corresponding to the developing voltage.

  The developing member 18A charged to the developing potential holds the developer stored in the developing device 18 on the surface, and supplies the toner contained in the developer from the developing device 18 to the surface of the image carrier 12. . The toner supplied onto the image carrier 12 adheres to the electrostatic latent image on the image carrier 12 by electrostatic force. Specifically, the toner contained in the developer is determined by the potential difference in the area where the image carrier 12 and the developing member 18A face each other, that is, the potential difference between the surface potential of the image carrier 12 and the developing potential of the developing member 18A in the area. Is supplied to the area where the electrostatic latent image is formed on the image carrier 12, and the carrier is contained in the developer, the carrier returns to the developing device 18 while being held by the developing member 18A. As a result, the electrostatic latent image on the image carrier 12 is developed by the toner supplied from the developing member 18 </ b> A, and a toner image corresponding to the electrostatic latent image is formed on the image carrier 12.

  A transfer device 31 is provided around the image carrier 12 and downstream of the position where the developing member 18 </ b> A is disposed in the rotation direction of the image carrier 12. The transfer device 31 includes a transfer member 20 and a power supply 30. The transfer member 20 has a cylindrical shape, and is conveyed with the recording medium 30 </ b> A interposed between the transfer member 20 and the image carrier 12. A power supply 30 that applies a transfer voltage to the transfer member 20 is electrically connected to the transfer member 20. The power supply 30 is also electrically connected to the control unit 36.

  When a transfer voltage having a polarity opposite to that of the toner constituting the toner image formed on the image carrier 12 is applied from the power supply 30 to the transfer member 20, a region where the image carrier 12 and the transfer member 20 face each other (see FIG. 1 (see the transfer region 32A), an electric field having an electric field strength is formed to move each toner constituting the toner image on the image carrier 12 from the image carrier 12 to the transfer member 20 side by electrostatic force.

  The recording medium 30A is stored in a storage unit (not shown), and is transported (in the direction of arrow B in FIG. 1) along the transport path 34 by a plurality of transport members (not shown) from the storage unit. 12 reaches a transfer region 32 </ b> A which is a region where the transfer member 20 faces the transfer member 20. The toner constituting the toner image on the image carrier 12 is transferred to the recording medium 30A reaching the transfer area 32A by an electric field formed in the area when a transfer voltage is applied to the transfer member 20. The That is, the toner image is transferred onto the recording medium 30A by the movement of the toner from the surface of the image carrier 12 to the recording medium 30A.

  Further, the transfer member 20 is applied with a transfer voltage having a polarity opposite to that of the toner constituting the toner image as described above, so that the surface of the image carrier 12 is neutralized and a neutralization potential (for example, 0 V) is obtained. Is done.

A fixing device 26 is provided on the conveyance path 34 of the recording medium 30A downstream of the transfer area 32A in the conveyance direction. The fixing device 26 fixes the toner image transferred onto the recording medium 30A to the recording medium 30A by heat or heat and pressure.
The recording medium 30 </ b> A to which the toner image is transferred by being conveyed along the conveyance path 34 and passing through the area (transfer area 32 </ b> A) where the image carrier 12 and the transfer member 20 face each other is further transferred by a conveyance member (not shown). The fixing device 26 is reached along the conveyance path 34, and the toner image on the recording medium 30A is fixed. The recording medium 30A on which the image is formed by fixing the toner image is discharged to the outside of the image forming apparatus 10 by a plurality of conveyance members (not shown).

  A cleaning device 22 is disposed downstream of the transfer region 32A in the rotation direction of the image carrier 12 in the rotation direction of the image carrier 12 (in the direction of arrow A in FIG. 1).

  The cleaning device 22 removes deposits such as residual toner and paper dust on the image carrier 12. Examples of the cleaning device 22 include a configuration having a plate-like member that comes into contact with the image carrier 12 at a linear pressure of 10 g / cm to 150 g / cm.

  The image carrier 12 that has transferred the toner image to the recording medium 30 </ b> A and has been set to the charge removal potential is again charged to the charge potential by the charging device 15 after the adhering matter is removed by the cleaning device 22.

  As described above, in the image forming apparatus 10, an image is formed on the recording medium 30A.

  The image forming apparatus 10 of the present embodiment corresponds to the image forming apparatus of the present invention, the charging member 14 corresponds to the charging member in the image forming apparatus of the present invention, and the power source 28 forms the image forming apparatus of the present invention. The latent image forming device 16 corresponds to the first applying device in the apparatus, the latent image forming device in the image forming apparatus of the present invention, and the developing member 18A corresponds to the developing member in the image forming apparatus of the present invention. . Further, the power source 32 for applying a developing voltage to the developing member 18A of the present embodiment corresponds to the second applying device of the image forming apparatus of the present invention. The transfer member 20 corresponds to the transfer member of the image forming apparatus of the present invention, and the power source 30 corresponds to the third application device of the image forming apparatus of the present invention. The control unit 36 corresponds to a control device of the image forming apparatus of the present invention.

  Here, in the image forming apparatus 10, when an image is formed on the recording medium 30A, as described above, the image carrier 12 is charged by the charging member 14 by rotation (in the direction of arrow A in FIG. 1). Charging to a potential, exposure by the latent image forming device 16 (formation of an electrostatic latent image), development of the electrostatic latent image by toner, transfer of the toner image by the transfer member 20, and charge removal are performed, and an image is recorded on the recording medium 30A. Is formed.

  Specifically, the control unit 36 of the image forming apparatus 10 according to the present embodiment controls the power supply 28 of the charging device 15 so as to charge the image carrier 12 to a predetermined charging potential VH1 during image formation, thereby developing the developing member. The power source 32 is controlled so that the potential difference between the charging potential 18A and the charging potential VH1 is equal to or greater than the minimum potential difference P at which the toner on the developing member 18A side moves to the image holding member 12 side. Further, the control unit 36 forms an electric field in which the toner held on the image carrier 12 moves to the recording medium 30A side in a region (transfer region 32A) where the image carrier 12 and the transfer member 20 face each other. The transfer voltage applied from the power supply 30 to the transfer member 20 is controlled so that the transfer member 20 has a transfer potential that eliminates the surface of the image carrier 12 by the electric field. As a result, the image carrier 12 is charged to the charging potential VH1 by the charging member 14, an electrostatic latent image is formed by the latent image forming device 16, and the electrostatic latent image is formed by the toner held on the developing member 18A. The toner image is developed and transferred to the recording medium 30 </ b> A, and the image carrier 12 is neutralized by the transfer member 20.

  As described above, in the image forming apparatus 10 of the present embodiment, the surface of the image carrier 12 is neutralized at the time of image formation by the transfer member 20 that transfers the toner image to the recording medium 30A. It is set as the structure which is not equipped with the exclusive static elimination apparatus which neutralizes the surface of this.

  At the time of image formation, the image carrier 12 is neutralized by the transfer member 20, and therefore, it is ideal that the surface of the image carrier 12 after being neutralized by the transfer member 20 has no potential unevenness. It is. However, due to variations in the resistance value of the transfer member 20 and the like, the charge removal of the image carrier 12 by the transfer member 20 becomes non-uniform, and potential unevenness on the surface of the image carrier 12 may not be suppressed. The fluctuation of the resistance value of the transfer member 20 was particularly likely to occur due to environmental changes such as temperature and humidity.

  Further, in the conventional image forming apparatus 10, when non-image formation is not performed on the recording medium 30 </ b> A, the charging voltage applied to the charging member 14 as shown in the diagrams 51 </ b> A, 51 </ b> B, and 51 </ b> C in FIG. 3. Application, development voltage application to the developing member 18A, and transfer voltage application to the transfer member 20 are canceled (all at 0 V during non-image formation). Even when image formation is resumed after switching to, potential unevenness of the image carrier 12 at the time of previous image formation may remain.

Note that the time when switching from image formation to non-image formation is a period of non-image formation that has continued since the time of switching from the end of image formation to non-image formation, and no image formation is performed on the recording medium 30A. Is shown. At this “when switching from image formation to non-image formation”, the latent image forming device 16 does not irradiate light based on the image information, and no image is formed on the recording medium 30A. Specifically, when switching from image formation to non-image formation, this corresponds to the period from the end of the previous image formation period (image formation) to the start of the next image formation period (image formation). To do. For example, “when switching from image formation to non-image formation” is based on a different print job after the image formation for forming the image on the recording medium 30A is completed based on the print job input to the control unit 36. This corresponds to a period until image formation for forming an image on the recording medium 30A is started.
In the following description, “when switching from image formation to non-image formation” is simplified and referred to as “non-image formation”.

  In the image forming apparatus 10 of the present embodiment, at the time of non-image formation, the control unit 36 continues the transfer voltage of the polarity and voltage value applied at the time of the previous image formation for at least the first period. The power source 30 is controlled so as to be applied to the developing member 18A, and the developing voltage of the polarity and voltage value applied at the time of the previous image formation is changed stepwise toward 0V for each rotation of the image carrier 12 to develop the developing member 18A. The power source 32 is controlled so as to be applied to the charging member 14, and the power source 28 is controlled so as to cancel the application of the charging voltage to the charging member 14.

  By the above control of the control unit 36 at the time of non-image formation, as shown in a diagram 50A of FIG. 4, the non-image formation 42 is applied from the power source 30 to the transfer member 20 at the time of the previous image formation 40. The transfer voltage having the voltage value and the polarity that have been applied is continuously applied for the first period 44 from the time of image formation 40. Note that the first period 44 is a period that is within the period of the non-image formation 42 and is continuous with the immediately preceding image formation 40, and at least the time required for one rotation of the image carrier 12, or the image retention. Any multiple of the time required for one rotation of the body 12 may be used. The first period 44 may be the same as the non-image forming period 42 or may be shorter than the non-image forming period 42.

When the first period 44 is shorter than the non-image forming time period 42, the polarity and voltage applied at the previous image forming time 40 as shown in the diagram 50A of FIG. After the power supply 30 is controlled so that the value transfer voltage is continuously applied to the transfer member 20 in the first period 44, the application of the transfer voltage may be canceled (0 V).
If the first period 44 is the same period as the non-image forming period 42, the transfer voltage of the polarity and voltage value applied from the power source 30 to the transfer member 20 at the previous image forming period 40 is used. However, it is continuously applied during the non-image forming period 42.

  Further, during the non-image formation 42, the voltage value applied to the developing member 18A from the power source 32 to the developing member 18A by the control of the control unit 36 as shown in the diagram 50B of FIG. In addition, the power source 32 is controlled so as to apply the developing voltage having a polarity to the developing member 18A in a stepwise manner toward 0 V every rotation of the image holding body 12.

  In FIG. 4, a period 46 indicates the time required for one rotation of the image carrier 12. For this reason, in the example shown in FIG. 4, at the time of non-image formation 42, the development voltage is 0 V for each rotation of the image carrier 12 from the voltage value of the development voltage applied at the previous image formation 40. Gradually changes by 48, and finally becomes 0V.

  During this non-image formation, the change amount 48 of the development voltage when changing toward 0 V for each rotation of the image carrier 12 is a region where the development potential of the development member 18A and the development member 18A of the image carrier 12 face each other. The difference in potential from the surface potential of the toner is the toner held on the developing member 18A (toner when the developer is a one-component developer, toner and carrier when the developer is a two-component developer). What is necessary is just to determine according to the surface potential in the area | region facing the developing member 18A of the image holding body 12 at the time of non-image formation so that it may become less than the minimum electric potential difference P required in order to transfer to the image holding body 12 side.

  During this non-image formation, the difference in potential between the developing potential of the developing member 18A and the surface potential in the region of the image holding member 12 facing the developing member 18A is determined by the fact that the toner held on the developing member 18A is on the image holding member 12 side. The toner (or toner and carrier) from the developing member 18A to the image carrier 12 side during non-image formation is adjusted by adjusting the change amount 48 of the development voltage so as to be less than the minimum potential difference P required for shifting to ) Is suppressed.

  In the example shown in FIG. 4, during non-image formation, the development voltage changes stepwise toward 0 V for each rotation of the image carrier 12, and the development voltage is changed when the image carrier 12 rotates twice. Although the case where the voltage is set to 0 V is shown, the development voltage at the time of non-image formation is changed in a stepwise manner toward 0 V while the development voltage change amount 48 at the time of non-image formation maintains the above relationship. It is not limited to two rotations because it is good.

  In the example shown in FIG. 4, the case where the development voltage is finally set to 0 V during non-image formation is shown to coincide with the time when the transfer voltage is set to 0 V. As described above, the change amount 48 of the development voltage at the time of non-image formation may be changed stepwise toward 0V while maintaining the above relationship. When the development voltage is set to 0V, the transfer voltage is 0V. It may or may not coincide with the time when it is assumed.

  The minimum potential difference P is, for example, the surface potential of the image carrier 12 and the surface potential of the developing member 18A necessary for moving to the image carrier 12 side in the image forming apparatus 10 including the image carrier 12. The minimum value of the potential difference (minimum potential difference P) may be obtained in advance and stored in a storage unit (not shown) of the control unit 36. At the time of non-image formation 42, the control unit 36 supplies power so as to gradually decrease the development voltage toward 0 V for each rotation of the image carrier 12 by a change amount 48 less than the minimum potential difference P. 28 may be controlled.

As for the change amount 48 of the development voltage, for example, the minimum potential difference P is obtained in advance in the image forming apparatus 10. In the image forming apparatus 10, the charging voltage and the transfer voltage change during non-image formation as shown in a diagram 50A and a diagram 50C shown in FIG. 4 or a diagram 50A and a diagram 50D shown in FIG. 5 described later. Then, during the non-image formation, it is measured in advance what value the surface potential of the region facing the developing member 18A out of the entire region of the image carrier 12 shows, Thus, the amount of change 48 that satisfies the above relationship may be determined in advance.
Further, a device for measuring the surface potential of the surface of the image carrier 12 facing the developing member 18A is separately provided, and the device is electrically connected to the control unit 36 and input from the device. Depending on the signal indicating the surface potential of the image carrier 12, a change amount 48 that satisfies the above relationship may be dynamically calculated and used. The apparatus for measuring the surface potential is not particularly limited, and examples thereof include a surface potential meter Trek 334 (manufactured by Trek).

  3 and 4 and FIG. 5 described later are described assuming that the toner has a negative polarity in the image forming apparatus 10 of the present embodiment.

  Further, at the time of non-image formation 42, the application of the charging voltage from the power supply 28 to the charging member 14 is canceled (0 V) as shown by a line 50C in FIG.

  Therefore, in the image forming apparatus 10, during the non-image formation 42, the application of the charging voltage is canceled and the charging to the charging potential of the image holding body 12 is not performed, and the electrostatic latent image is formed by the latent image forming apparatus 16. No formation is performed (the exposure potential is not set), and the development potential of the developing member 18A is stepwise for each rotation of the image holding body 12 toward 0 V while the potential difference from the image holding body 12 is maintained below the minimum potential difference P. In addition, the transfer member 20 maintains the transfer potential at the time 40 immediately before the image formation 40 in the first period 44.

  For this reason, at the time of non-image formation, the transfer voltage applied at the previous image formation is not continuously applied to the transfer member 20 for at least the first period, and the development voltage applied at the previous image formation is used as the image. Compared to the case where the holding member 12 is changed stepwise toward 0 V for each rotation and is not applied to the developing member 18A, the transfer member 20 has a potential unevenness suppressed by the developing member 18A during non-image formation. As a result, the surface of the image carrier 12 is further neutralized, and the potential unevenness of the surface of the image carrier 12 is considered to be suppressed.

  In the example shown in FIG. 4, as shown in a diagram 50 </ b> C, in the non-image formation 42, the application of the charging voltage is canceled (set to 0 V) over the entire period of the non-image formation 42. As described above, with respect to the charging voltage as well as the developing voltage, the charging voltage of the polarity and the voltage value applied to the charging member 14 at the time of the previous image formation changes toward 0 V for each rotation of the image holding body 12. Thus, it is desirable to finally cancel the application of the charging voltage from the viewpoint of further suppressing potential unevenness of the image carrier 12.

  In this case, specifically, at the time of non-image formation 42, the control unit 36 controls the power supply 28 to the charging member 14 as shown in the diagram 50D of FIG. The power supply 28 is controlled so that the voltage value and the polarity charging voltage applied to 40 are applied to the charging member 14 in a stepwise manner toward 0 V for each rotation of the image carrier 12.

  In FIG. 5, a period 46 indicates the time required for one rotation of the image carrier 12. For this reason, in the example shown in FIG. 5, at the time of non-image formation 42, the charging voltage is 0 V for each rotation of the image carrier 12 from the voltage value of the charging voltage applied at the previous image formation 40. Gradually changes by 49, and finally becomes 0V.

  During this non-image formation, the amount 49 of change in the charging voltage when changing to 0 V for each rotation of the image carrier 12 is the charging member 14 with respect to the surface potential in the region facing the charging member 14 of the image carrier 12. As long as the value of the charging potential is within the range of 1 to 1.9 times, it is sufficient. That is, at the time of non-image formation, the charging potential of the charging member 14 at the time of non-image formation is the same as the surface potential in the region facing the charging member 14 of the image carrier 12 or 1.9 times or less of the surface potential. It is desirable to adjust the charging voltage applied to the charging member 14 and the amount of change 49 so as to be higher than the absolute value of the surface potential.

  The amount of change 49 may be determined according to the surface potential in the region facing the charging member 14 of the image carrier 12 during non-image formation 42.

  In the example shown in FIG. 5, during non-image formation, the charging voltage changes stepwise toward 0 V for each rotation of the image carrier 12, and the charging voltage is changed when the image carrier 12 rotates twice. Although the case where the application of the charging voltage is canceled due to 0 V is shown, the charging voltage at the time of non-image formation is directed toward 0 V while the change amount 49 of the charging voltage at the time of non-image formation maintains the above relationship. Therefore, the rotation is not limited to two rotations.

  In the example shown in FIG. 5, a case where the timing when the charging voltage is finally set to 0V coincides with the timing when the transfer voltage and the development voltage are set to 0V during non-image formation will be described. As described above, the charging voltage may be changed stepwise toward 0V while maintaining the above-mentioned relationship, and the timing when the charging voltage is set to 0V coincides. However, it does not have to coincide with the timing when the transfer voltage and the development voltage are set to 0V.

The charging voltage change amount 49 is, for example, when the image forming apparatus 10 changes the transfer voltage and the development voltage during non-image formation as shown in the diagrams 50A and 50B shown in FIG. In the non-image formation, the value of the surface potential of the region facing the charging member 14 in the entire region of the image carrier 12 is measured in advance, and the above relationship is determined according to the measurement result. A change amount 49 that satisfies the above may be determined in advance.
Further, a device for measuring the surface potential of the surface of the image carrier 12 facing the charging member 14 is separately provided, and the device is electrically connected to the control unit 36 and input from the device. Depending on the signal indicating the surface potential of the image carrier 12, a change amount 49 that satisfies the above relationship may be dynamically calculated and used.

  Next, a processing routine performed by the control unit 36 of the image forming apparatus 10 of the present embodiment will be described.

  As shown in FIG. 6, when a power switch (not shown) in the image forming apparatus 10 is operated to supply power to each part of the image forming apparatus 10, the control unit 36 executes the processing routine shown in FIG. 6. The program for reading is read and the processing routine is executed.

  In step 100, it is determined whether or not a signal indicating an image formation instruction has been input. If the determination is negative, this routine is terminated. If the determination is positive, the routine proceeds to step 102. The determination as to whether or not a signal indicating an image formation instruction has been input may be performed, for example, by determining that a signal indicating an image formation instruction has been input by operating an operation panel (not shown). Alternatively, it may be performed by determining that a print job is input from the outside via an input / output device (not shown). Note that the operation panel and the input / output device may be electrically connected to the control unit 36.

  In step 102, an image forming process is executed. The image forming process is a process performed during the image formation described above. By executing the processing of step 102, an image is formed on the recording medium 30A.

  In the next step 104, it is determined whether or not a signal indicating the end of image formation has been input. If the signal is negative, the process returns to step 102. The determination in step 104 may be performed by, for example, determining that an operation panel (not shown) is operated and a signal indicating the end of image formation is input, or printing that performs image formation processing in step 102 described above. The determination may be made by determining that all the printing processes for the image to be printed included in the job have been completed.

  In step 106, after executing the non-image forming process, this routine is finished. The non-image forming process is a process performed during the non-image forming described above (see FIGS. 4 and 5). By executing the processing of step 106, potential unevenness on the surface of the image carrier 12 is suppressed during non-image formation.

  As described above, in the image forming apparatus 10 according to the present embodiment, the unevenness of the potential on the surface of the image carrier 12 is suppressed by executing the above processing during non-image formation.

  A known material may be used as the constituent material of the image carrier 12, and examples of constituent materials of the support 60, the photosensitive layer 63, and the protective layer 64 include a substrate described in Japanese Patent Application No. 2007-333308, and an undercoat. Examples of the material used for the layer, the photosensitive layer, and the protective layer include a charge transporting layer 66 that constitutes the photosensitive layer 63. It is desirable that the structure includes a functional material.

Since the charge transport layer 66 includes a binder resin and a charge transport material having a structure represented by the following general formula (1), the charge mobility of the charge transport layer 66 is increased. This is considered to be larger than when no material is used, and the potential unevenness on the surface of the image carrier 12 after being neutralized by the transfer member 20 is further suppressed.
In addition, the charge transport layer 66 is configured to include a binder resin and a charge transport material having a structure represented by the following general formula (1), so that a developing voltage can be applied during non-image formation 42. The number of rotations of the image carrier 12 up to 0V (see FIGS. 4 and 5) and the number of rotations of the image carrier 12 up to 0V during non-image formation (see FIG. 5) can be suppressed. It is considered that neutralization is effectively performed with a small number of rotations of the image carrier 12 and potential unevenness is suppressed.

In General Formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 or more carbon atoms. It represents an alkoxy group having 20 or less, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure. n and m each independently represents 0 or 1.

  It should be noted that other charge transport materials other than the charge transport material represented by the general formula (1) may be used as long as the function is not impaired. Other charge transport materials include, for example, oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline and other pyrazoline derivatives, triphenylamine, tri (p-methylphenyl) aminyl-4-amine Aromatic tertiary amino compounds such as dibenzylaniline, aromatic tertiary diamino compounds such as N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine, 3- (4′- 1,2,4-triazine derivatives such as dimethylaminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2,4-triazine, 4-diethy Hydrazone derivatives such as aminobenzaldehyde-1,1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran, p Α-stilbene derivatives such as-(2,2-diphenylvinyl) -N, N-diphenylaniline, enamine derivatives, butadiene compounds, carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole and derivatives thereof Pore transport materials, quinone compounds such as chloranil and broanthraquinone, tetraanoquinodimethane compounds, fluorenone compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, Xanthone compounds, thiophene And an electron transporting material such as a polymer, and a polymer having a group composed of the above-described compound in the main chain or side chain. These charge transport materials may be used alone or in combination of two or more. In addition, the ratio (mass ratio) of the content of the charge transport material and the binder resin in the charge transport layer 66 is 10: 1 or more and 1: 5 or less.

  Examples of the binder resin contained in the charge transport layer 66 include acrylic resins, polyester resins such as polyarylate, polycarbonate resins, polystyrene, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, and polyvinyl acetal resins such as polyvinyl butyral. Insulating resins such as polyketone resins, polyvinyl ketone resins, polystyrene resins, polysulfones, polyacrylamides, polyamides, and chlorinated rubbers, and organic photoconductive polymers such as polyvinyl carbazole, polyvinyl anthracene, and polyvinyl pyrene.

  Among these, it is desirable that the binder resin includes a structural unit represented by the following general formula (2) from the viewpoint of further suppressing the charge removal unevenness of the image carrier 12.

In General Formula (2), R ⁷ and R ⁸ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl having 6 to 12 carbon atoms. E and f each independently represents an integer of 0 or more and 4 or less.

As described above, since the binder resin of the charge transport layer 66 includes the structural unit represented by the general formula (2), the charge mobility of the charge transport layer 66 uses the material. It is considered that the mobility is further increased as compared with the case where the mobility is not present, and fluctuations in the mobility due to the environment are also suppressed.
For this reason, it is considered that the charge removal by the transfer member 20 is performed efficiently.
Further, since the binder resin of the charge transport layer 66 includes the structural unit represented by the general formula (2), image retention until the developing voltage is set to 0 V in the non-image formation 42 is performed. The number of rotations of the body 12 (see FIGS. 4 and 5) and the number of rotations of the image carrier 12 (see FIG. 5) until the charging voltage is set to 0 V during non-image formation are further suppressed. It is considered that static elimination is effectively performed with a small number of revolutions.

  Furthermore, from the viewpoint of further suppressing uneven discharge of the image carrier 12 and further efficient charge removal, the binder resin contained in the charge transport layer 66 is a structural unit represented by the general formula (2). And a copolymer of the structural unit represented by the following general formula (3).

In general formula (3), R ⁹ and R ¹⁰ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl having 6 to 12 carbon atoms. And g and h each independently represent an integer of 0 or more and 4 or less. X is —CR ¹¹ R ¹² — (wherein R ¹¹ and R ¹² are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms) Or a 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, —O—, —S—, —SO—, or -SO ₂ - represents a.

  Copolymer ratio of the copolymer of the structural unit represented by the above general formula (2) and the structural unit represented by the above general formula (3) (corresponding to the m: n ratio in the following specific examples) For example, m: n = 95: 5 or more and 5:95 or less, 50:50 or more and 5:95 or less, or 30:70 or more and 10:90 or less.

  Specific examples of the copolymer of the structural unit represented by the general formula (2) and the structural unit represented by the general formula (3) include the following structural formula (A1) to structural formula: Although (A3) is mentioned, it is not limited to these.

  The structural unit represented by the general formula (2), the structural unit represented by the general formula (2), and the structural unit represented by the general formula (3) are within a range not impairing the function. A binder resin other than the binder resin containing a copolymer may be used. Examples of the other binder resin include polycarbonate resin such as bisphenol A type or bisphenol Z type, acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile-styrene copolymer. Resin, acrylonitrile-butadiene copolymer resin, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride resin, Insulating resins such as silicone resin, phenol-formaldehyde resin, polyacrylamide resin, polyamide resin, chlorinated rubber, and polyvinylcarbazole, polyvinylanthracene, polyvinyl chloride Organic photoconductive polymers such as Rupiren like. These binder resins may be used alone or in combination of two or more.

  The charge transport layer 66 may be formed using a coating liquid in which the above constituent materials are added to a solvent.

  In the image forming apparatus 10 of the present embodiment described above, the charging member 14 may be provided in contact with the surface of the image carrier 12 or may be provided in a non-contact manner. The charging voltage applied to the charging member 14 from the power supply 28 may be a superimposed voltage obtained by superimposing an AC voltage on a DC voltage, or may be a DC voltage. Here, when the charging member 14 is provided in contact with the surface of the image holding body 12 and a DC voltage is used as the charging voltage, generally, the potential unevenness of the image holding body 12 is considered to increase. According to the image forming apparatus 10 of the present embodiment, the charging member 14 is provided in contact with the surface of the image carrier 12, and the image carrier is used even when a DC voltage is used as the charging voltage. It is considered that potential unevenness on the surface of 12 is effectively suppressed.

  Hereinafter, the image forming apparatus of the present embodiment will be specifically described with reference to examples, but the present invention is not limited to these examples. Further, unless otherwise specified, “part” represents “part by mass” and “%” represents “mass%”.

<Preparation of image carrier A to image carrier C>
-Production of image carrier A-
100 parts by mass of zinc oxide (average particle size: 70 nm, manufactured by Teica, specific surface area value: 15 m ² / g) is stirred and mixed with 500 parts by mass of methanol, and KBM603 (manufactured by Shin-Etsu Chemical Co., Ltd.) is used as a silane coupling agent. 25 parts by mass was added and stirred for 2 hours. Thereafter, methanol was distilled off under reduced pressure, and baking was performed at 120 ° C. for 3 hours to obtain silane coupling agent surface-treated zinc oxide fine particles.

  60 parts by mass of the zinc oxide fine particles subjected to the surface treatment, 0.6 parts by mass of alizarin, 13.5 parts by mass of blocked isocyanate (Sumidule 3173, manufactured by Sumitomo Bayern Urethane Co., Ltd.) as a curing agent, and butyral resin (BM -1, manufactured by Sekisui Chemical Co., Ltd.) 15 parts by mass of 38 parts by mass of a solution obtained by dissolving 85 parts by mass of methyl ethyl ketone and 25 parts by mass of methyl ethyl ketone, and 4 hours in a sand mill using glass beads having a diameter of 1 mm. Dispersion was performed to obtain a dispersion. To the obtained dispersion, 0.005 parts by mass of dioctyltin dilaurate and 4.0 parts by mass of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicone) are added as a catalyst, and a coating liquid for forming an undercoat layer is added. Obtained. This coating solution was applied on an aluminum substrate having a diameter of 30 mm by a dip coating method, followed by drying and curing at 180 ° C. for 40 minutes to obtain an undercoat layer having a thickness of 25 μm.

  Next, as a charge generation material, it has strong diffraction peaks at Bragg angles (2θ ± 0.2 °) with respect to CuKα characteristic X-rays of at least 7.4 °, 16.6 °, 25.5 ° and 28.3 °. Using a glass bead having a diameter of 1 mm, a mixture of 15 parts by mass of chlorogallium phthalocyanine crystal, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Union Carbide) and 300 parts by mass of n-butyl alcohol was used. Then, it was dispersed in a sand mill for 4 hours to obtain a coating solution for forming a charge generation layer. This coating solution was dip-coated on the undercoat layer and dried to obtain a charge generation layer having a thickness of 0.2 μm.

  Next, 8 parts by mass of tetrafluoroethylene resin particles (average particle size: 0.2 μm) and 0.01 parts by mass of a fluorinated alkyl group-containing methacrylic copolymer (weight average molecular weight 30000), 4 parts by mass of tetrahydrofuran, toluene The mixture was kept at a liquid temperature of 20 ° C. together with 1 part by mass and stirred for 48 hours to obtain a tetrafluoroethylene resin particle suspension A.

Next, as a charge transport material, the following structural formula (1) (in the general formula (1), n = 1, m = 1, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are all H Compound), 4 parts by mass of tris [4- (4,4-diphenyl-1,3-butadienyl) phenyl] amine, and 6 parts of bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40000) as a binder resin Parts, 2,6-di-t-butyl-4-methylphenol 0.1 parts by mass as an antioxidant, 24 parts by mass of tetrahydrofuran and 11 parts by mass of toluene are mixed and dissolved, and mixed solution B is obtained. Obtained.

After the A liquid was added to the B liquid and stirred and mixed, the pressure was increased to 500 kgf / cm ² using a high-pressure homogenizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.) equipped with a through-type chamber having a fine flow path. 5 ppm of fluorine-modified silicone oil (trade name: FL-100 manufactured by Shin-Etsu Silicone Co., Ltd.) was added to the solution obtained by repeating the dispersion treatment six times, and the mixture was sufficiently stirred to obtain a coating solution for forming a charge transport layer. This coating solution was applied onto the charge generation layer and dried at 135 ° C. for 25 minutes to form a charge transport layer having a thickness of 20 μm, thereby obtaining the intended electrophotographic photosensitive member. The electrophotographic photoreceptor thus obtained was designated as an image carrier A.

-Production of image carrier B-
Instead of the bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40000) used as the binder resin for the charge transport layer in the image carrier A, the structural formula (A3) shows the following structural formula (A3). An image carrier B was produced under the same conditions and production method as those of the image carrier A, except that 6 parts by mass of a polycarbonate copolymer having an m of 0.25 and n of 0.75 was used.

-Production of image carrier C-
In the image carrier A, instead of the compound having the structure of the structural formula (1) in the general formula (1) used as the charge transport material in the charge transport layer, N, N′-bis (3-methylphenyl) ) The same conditions and the same as image carrier A except that 2 parts by mass of -N, N'-diphenylbenzidine and 2 parts by mass of N, N'-bis (3,4-dimethylphenyl) biphenyl-4-amine were used. Image carrier C was produced using the production method.

(Example 1 to Example 8, Comparative Example 1 to Comparative Example 2)
The control routine for controlling the charging voltage applied to the charging member 14, the developing voltage applied to the developing member 18A, and the transfer voltage applied to the transfer member 20 in the DocuCentre 505a as the image forming apparatus is executed. The device was modified to run a program to do this.
The type of image carrier, the type of charging voltage applied to the charging member 14 during image formation and non-image formation, the type of image carrier to be mounted, the transfer voltage during image formation, the development voltage during image formation, The following evaluation tests were conducted with combinations of the charging voltage at the time of image formation, the transfer voltage at the time of non-image formation, the development voltage, the voltage value of the charging voltage, and the timing of voltage application as shown in Table 1.

  In Table 1 above, the sequence A is the voltage application method at the time of non-image formation as shown in FIG. 5, and more specifically, when the test environment is a high temperature and high humidity (28 ° C., 85 RH%) environment. The transfer voltage, development voltage, change amount of the development voltage, charge voltage, change amount of the charge voltage are the values shown in Table 2, and the test voltage is the low voltage and low humidity (10 ° C, 15RH%) environment. In this example, the voltage, the change amount of the development voltage, the charging voltage, and the change amount of the charging voltage are set to the values shown in Table 2.

  Further, in Table 1 above, the sequence B is the voltage application method at the time of non-image formation as shown in FIG. 4. Specifically, the test environment is a high temperature and high humidity (28 ° C., 85 RH%) environment. The transfer voltage, development voltage, change amount of the development voltage, charge voltage, change amount of the charge voltage are the values shown in Table 2, and the charge voltage when the test environment is a low temperature and low humidity (10 ° C., 15 RH%) environment. The development voltage, the change amount of the development voltage, the charging voltage, and the change amount of the charging voltage are shown in Table 2.

  In Table 1 above, the sequence C is the voltage application method at the time of non-image formation as shown in FIG. 3, and more specifically, when the test environment is a high temperature and high humidity (28 ° C., 85 RH%) environment. The transfer voltage, charging voltage, and development voltage are the values shown in Table 2, and the transfer voltage when the test environment is a low temperature and low humidity (10 ° C., 15 RH%) environment is shown in Table 2.

  In Table 1 above, the sequence D is a voltage application method during non-image formation, in which only the transfer voltage in the method shown in FIG. 3 is used as the transfer voltage shown in the diagram 50A of FIG. When the test environment is a high temperature and high humidity (28 ° C, 85RH%) environment, the transfer voltage, charging voltage, and development voltage are the values shown in Table 2, and the test environment is a low temperature and low humidity (10 ° C, 15RH%) environment. In this case, the transfer voltage, charging voltage, and development voltage are shown in Table 2.

  For example, in Table 2, in sequence A, the voltage application method at the time of non-image formation is the method shown in FIG. 5, and when evaluation is performed in a high-temperature and high-humidity environment, transfer of 1020 V is performed at the time of non-image formation. The voltage is continuously applied for 6 rotations of the image carrier 12 to 0 V, and the development voltage of −400 V is changed by 120 V toward 0 V for each rotation of the image carrier 12 to obtain a charging voltage of −825 V. Is changed by 100 V toward 0 V for each rotation of the image carrier 12.

  The following evaluation was performed on Examples 1 to 8 and Comparative Examples 1 to 2 which were combinations shown in Table 1 above.

(Evaluation)
-Potential unevenness on the surface of the image carrier immediately after non-image formation-
For each of the modified machines of Examples 1 to 8 and Comparative Examples 1 to 2, an image density of 30 is used as an image forming process during image formation in a high temperature and high humidity environment and a low temperature and low humidity environment. % A4 halftone images were output in succession, and then non-image forming processing during non-image formation was performed under the conditions of the examples and comparative examples shown in Tables 1 and 2. Then, the surface potential of the image holding member immediately after the non-image forming process is measured by using a surface potentiometer Trek 334 (manufactured by Trek Co.) for every 10 mm in the axial direction for every circumference (every 10 mm). It was obtained by measuring the difference ΔV between the maximum value and the minimum value. The measurement results are shown in Table 3.

―Number of static elimination cycles―
For each of the modified machines of Examples 1 to 8 and Comparative Examples 1 to 2, an image density of 30 is used as an image forming process during image formation in a high temperature and high humidity environment and a low temperature and low humidity environment. % A4 halftone images were output in succession, and then non-image forming processing during non-image formation was performed under the conditions of the examples and comparative examples shown in Tables 1 and 2. Then, during this non-image formation, the developing voltage is changed stepwise toward 0V, and the surface potential of the image carrier is counted from the state where all of the developing voltage, the transfer voltage, and the charging voltage are 0V. Measure the number of rotations of the image carrier required until the change amount is 5% or less compared to the previous rotation, and subtract 1 from the measurement result (the number of rotations until immediately before). It was measured as the “number of static elimination cycles” that was the number of rotations required for static elimination. The measurement results are shown in Table 3.

-Density unevenness ΔE during image formation after non-image formation-
For each of the modified machines of Examples 1 to 8 and Comparative Examples 1 to 2, an image density of 30 is used as an image forming process during image formation in a high temperature and high humidity environment and a low temperature and low humidity environment. % A4 halftone images were output in succession, and then non-image forming processing during non-image formation was performed under the conditions of the examples and comparative examples shown in Tables 1 and 2. Then, as an image forming process continuously after the non-image forming process, three A4 halftone images with an image density of 30% are output in succession, and the color difference ΔE of the image printed on the third sheet is determined as a spectral densitometer. Using X-rite 938 (manufactured by X-rite), 19 points were measured at intervals of 5 mm in the circumferential direction for every 10 mm in the axial direction of the image carrier, and the difference between the maximum value and the minimum value was obtained as a color difference ΔE. . The measurement results are shown in Table 3.

-Image flow during image formation after non-image formation-
For each of the modified machines of Examples 1 to 8 and Comparative Examples 1 to 2, an image density of 5 was used as an image forming process at the time of image formation in each of a high temperature and high humidity environment and a low temperature and low humidity environment. % Character images were output continuously on A4 paper, and then non-image forming processing was performed during non-image formation under the conditions of the examples and comparative examples shown in Tables 1 and 2. The above operation was repeated 2000 times, a total of 10,000 sheets were output, and the apparatus was left for 8 hours.
Then, after leaving for 8 hours, one halftone image with an image density of 20% was again output on A4 paper, and the image quality was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.

Evaluation criteria G1: Image flow has not occurred G2: Image flow has occurred in 3 or less locations G3: Image flow has occurred in more than 3 locations

−Abrasion amount−
The amount of wear was determined by incorporating an example and a comparative example into a modified DocuCentre 505a, and a random image density of 5% in a high temperature and high humidity environment of 28 ° C. and 85 RH% and in a low temperature and low humidity environment of 10 ° C. and 15 RH% Using a simple character chart, five images were output continuously, and then non-image processing during non-image formation was performed under the conditions of the examples and comparative examples shown in Tables 1 and 2. The above operation was repeated 16000 times, and after a total of 80000 A4 continuous prints, the film thickness of the photoconductor was evaluated by measuring with an eddy current film thickness measuring device (manufactured by Fisher Instruments). The evaluation results are shown in Table 3.

  As shown in Table 3 above, in the example, the potential unevenness on the surface of the image carrier after non-image formation was suppressed in both the high temperature and high humidity environment and the low temperature and low humidity environment as compared with the comparative example. Further, in the example, the number of static elimination cycles was small in both the high temperature and high humidity environment and the low temperature and low humidity environment, and favorable results were obtained in all of density unevenness, image flow, and wear amount.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus, 12 Image holding body, 14 Charging member, 16 Latent image forming apparatus, 18A Developing member, 20 Transfer member, 28 Power supply, 30 Power supply, 32 Power supply, 36 Control apparatus

Claims (6)

An image carrier,
A charging member for charging the image carrier;
A first application device that applies a charging voltage to the charging member such that the charging member has a predetermined charging potential;
A latent image forming apparatus that forms an electrostatic latent image on the image carrier charged by the charging member;
A developing member for developing the electrostatic latent image formed on the image carrier with toner;
A second application device for applying a developing voltage to the developing member such that the developing member has a predetermined developing potential;
A transfer member for transferring a toner image formed on the image carrier by the developing member to a transfer target member and discharging the image carrier;
A third application device for applying a transfer voltage to the transfer member so that the transfer member has a predetermined transfer potential;
When switching from image formation to non-image formation, the transfer voltage applied during the previous image formation is continuously applied to the transfer member for at least the first period, and the development voltage applied during the previous image formation is applied. In the first period, the first application device, the second application device, and the second application device are applied to the developing member while being changed stepwise toward 0V and the charging voltage is not applied to the charging member. And a control device for controlling the third application device;
An image forming apparatus. The image carrier has a charge generation layer and a charge transport layer in this order on a support,
The image forming apparatus according to claim 1, wherein the charge transport layer includes a binder resin and a charge transport material having a structure represented by the following general formula (1).


(In General Formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 carbon atom. It represents an alkoxy group having 20 or less or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure. m represents 0 or 1 each independently.) The image forming apparatus according to claim 2, wherein the binder resin includes a structural unit represented by the following general formula (2).

(In the general formula (2), R ⁷ and R ⁸ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a group having 6 to 12 carbon atoms. An aryl group, and e and f each independently represent an integer of 0 or more and 4 or less.) The image forming apparatus according to claim 3, wherein the binder resin includes a copolymer of a structural unit represented by the general formula (2) and a structural unit represented by the following general formula (3).


(In General Formula (3), R ⁹ and R ¹⁰ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a carbon group having 6 to 12 carbon atoms. Each is an aryl group, and g and h each independently represent an integer of 0 or more and 4 or less, X is —CR ¹¹ R ¹² — (wherein R ¹¹ and R ¹² are each independently a hydrogen atom, trifluoromethyl; A group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms), a 1,1-cycloalkylene group having 5 to 11 carbon atoms, and 2 to 10 carbon atoms. The following α, ω-alkylene group, —O—, —S—, —SO—, or —SO ₂ — is represented.)   The control device changes the charging voltage applied at the time of the previous image formation stepwise toward 0V during the first period and applies the charging voltage to the charging member during non-image formation. 5. The image forming apparatus according to claim 1, wherein the application device is controlled so as to cancel the application of the charging voltage to the charging member. The charging member is disposed in contact with the surface of the image carrier,
The image forming apparatus according to claim 1, wherein the first application device applies a DC voltage to the charging member as the charging voltage.