JP5621376B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

Japanese Patent Application Laid-Open No. 2004-228561 proposes that in an image forming apparatus including a contact charging type charging device, a charging voltage having a polarity opposite to a charging voltage applied during an image forming period is formed before image formation.
Further, in Patent Document 2, in an image forming apparatus including a contact charging type charging device, a charging voltage having an absolute value smaller than a charging voltage applied during the image forming period is applied during a non-image forming period. Has been proposed.

JP-A-8-6358 JP 2006-162802 A

  In the present invention, during the non-image forming period, the transfer voltage having the first voltage value is applied continuously during at least one rotation of the image carrier from the non-image forming period to the image forming period. The generation of a line image different from the image to be formed is suppressed compared to the case where the transfer voltage having the second voltage value is not applied continuously during the image forming period after the image forming period. An object is to provide an image forming apparatus.

According to a first aspect of the present invention, there is provided a rotating image carrier, a charging member disposed in contact with the surface of the image carrier, and charging the surface of the image carrier by applying a DC voltage ; A latent image forming device that forms an electrostatic latent image on the surface of the image carrier charged by a charging member; a developing device that develops the electrostatic latent image formed on the surface of the image carrier with toner; The toner image formed on the surface of the image holding member by the developing device is transferred to the transfer target member, and the transfer member for discharging the image holding member, and the transfer potential of the transfer member is the surface of the image holding member. A voltage applying device that applies a transfer voltage to the transfer member so that the transfer potential has a polarity opposite to that of the toner of the toner image formed on the toner image, and from the non-image formation period to the image formation period during the non-image formation period. At least until switching And period continues the image carrier is rotated 1, applying the transfer voltage of the first voltage value other than and 0V to the toner of the toner image formed on the surface of the image carrier in the reverse polarity, non An image forming unit including: a control unit that controls the voltage applying device so as to apply the transfer voltage having the second voltage value continuously from the switching time in an image forming period continuous after the image forming period. Device.

The invention according to claim 2, before Symbol image holding member comprises a support, a charge generation layer, and a charge transport layer containing a charge-transporting material having a structure represented by the following general formula (1) in this order And an area on the surface of the image carrier that is upstream of the image carrier in the rotational direction from the region charged by the charging member, and a region where the toner image is transferred to the transfer medium by the transfer member. The absolute value Vin of the surface potential of the region downstream in the rotation direction of the image carrier and the downstream of the image carrier in the rotation direction of the image carrier from the region charged by the charging member on the surface of the image carrier. The absolute value Vh of the surface potential of the region upstream of the rotation direction of the image carrier from the region where the electrostatic latent image is formed by the latent image forming device, and the charge transport layer and the charge transport layer of the image carrier Total thickness of layers provided on the surface side And ([mu] m), the relationship of the image formation period, an image forming apparatus according to claim 1 satisfying 7T + 50 ≦ Vh-Vin.

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 an 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 charge transport layer includes a binder resin containing 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.

In the invention according to claim 4, the binder resin contains a copolymer having a structural unit represented by the general formula (2) and a structural unit represented by the following general formula (3). An image forming apparatus according to claim 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 the first aspect of the present invention, during the non-image forming period, the first voltage value is continuously transferred for at least one rotation of the image carrier until the switching from the non-image forming period to the image forming period. Compared to the case where a voltage is applied and the transfer voltage of the second voltage value is not applied continuously in the image forming period subsequent to the non-image forming period, the line image is different from the image to be formed. An image forming apparatus in which the occurrence of the above is suppressed is provided.

  According to the second aspect of the present invention, the charging member is a charging member that is disposed in contact with the surface of the image carrier and charges the surface of the image carrier by applying a DC voltage. However, compared with the case where the charge transporting material in the present invention is not used and the relationship of the formula (7T + 50 ≦ Vh−Vin) in the present invention is not satisfied, generation of a line image different from the image to be formed is suppressed. An image forming apparatus is provided.

  According to the third aspect of the present invention, there is provided an image forming apparatus in which the generation of a line image different from the image to be formed is suppressed as compared with the case where the binder resin in the present invention is not included.

  According to the invention of claim 4, the generation of a line image different from the image to be formed is suppressed as compared with the case where the binder resin contained in the charge transport layer does not contain the copolymer in the present invention. An image forming apparatus is provided.

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. FIG. 10 is a diagram illustrating an example of changes in a transfer voltage, a development voltage, and a charging voltage during a non-image forming period and an image forming period continuous with the non-image forming period in a conventional image forming apparatus. FIG. 6 is a diagram illustrating an example of changes in a transfer voltage, a development voltage, and a charging voltage during a non-image forming period and an image forming period continuous with the non-image forming period in 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 has a two-layer structure of a charge generation layer 65 and a charge transport layer 66.
In the present embodiment, the case where the photosensitive layer 63 of the image carrier 12 has a two-layer structure of the charge generation layer 65 and the charge transport layer 66 will be described. Alternatively, a configuration in which another layer such as a protective layer (not shown) is provided on the charge transport layer 66 (outside the charge transport layer 66) may be used.
The constituent material of the image carrier 12 may be a known material. Examples of constituent materials of the support 60, the photosensitive layer 63, and the protective layer (not shown) are described in Japanese Patent Application No. 2007-333308. Examples include materials used for the substrate, the undercoat layer, the photosensitive layer, and the protective layer.

  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 member 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 includes a charging member 14 and a power source 28. In the present embodiment, the charging member 14 has a cylindrical shape, and is arranged in contact with the surface of the image carrier 12 so as to rotate as the image carrier 12 rotates. The power source 28 is a power source 28 that applies a charging voltage to the charging member 14, and is electrically connected to the charging member 14.
Note that 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 from the power supply 28 to the charging member 14 may be a superimposed voltage obtained by superimposing an AC voltage on a DC voltage, or may be a DC voltage.

  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 an image of information (image to be formed) 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. By fixing the toner image, the recording medium 30A on which the image to be formed is formed is discharged to the outside of the image forming apparatus 10 by a plurality of conveyance members (not shown).

  A cleaning member 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 member 22 removes deposits such as residual toner and paper dust on the image carrier 12. Examples of the cleaning member 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 member 22.

  As described above, in the image forming apparatus 10, an image to be formed 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 latent image forming apparatus 16 is the present invention. The developing device 18 corresponds to the developing device in 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 voltage applying 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 of the present embodiment, during the image forming period in which an image is formed on the recording medium 30A, as described above, the image carrier 12 rotates (in the direction of arrow A in FIG. 1). Thus, charging to the charging potential by the charging member 14, exposure by the latent image forming device 16 (formation of an electrostatic latent image), development of the electrostatic latent image with toner, and transfer and neutralization of the toner image by the transfer member 20 are performed. Thus, an image is formed on the recording medium 30A.

  Specifically, the control unit 36 of the image forming apparatus 10 of the present embodiment charges the image carrier 12 to a predetermined charging potential VH1 (other than 0 V) during the image forming period in which an image is formed on the recording medium 30A. The power supply 28 of the charging device 15 is controlled so that the developing member 18A has a developing potential Vdev1 at which the potential difference from the charging potential VH1 is equal to or larger than the minimum potential difference P at which the toner on the developing member 18A side moves to the image carrier 12 side. The power supply 32 is controlled so as to be charged. 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 voltage value of the transfer voltage applied from the power source 30 to the transfer member 20 is set so that the transfer member 20 has a transfer potential Rp2 (Rp2 ≠ 0) such that the surface of the image carrier 12 is neutralized by the electric field. Control. 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.

  The voltage value of the transfer voltage applied from the power supply 30 to the transfer member 20 during this image formation period will be referred to as a second voltage value. The second voltage value is a value other than 0V. The transfer voltage is a voltage having a polarity opposite to that of the toner constituting the toner image formed on the image carrier 12. For this reason, the transfer voltage of the second voltage value is a voltage applied to the transfer member 20 during the image formation period, and has a polarity opposite to that of the toner, and the surface of the transfer member 20 has the transfer potential Rp2. It is the voltage of the voltage value which becomes.

  As described above, in the image forming apparatus 10 of the present embodiment, the surface of the image carrier 12 is neutralized during the image formation period 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.

  Here, in the conventional image forming apparatus 10, during the non-image forming period in which no image is formed on the recording medium 30A, as shown in the diagrams 51A, 51B, and 51C in FIG. The application of the charging voltage, the development voltage to the developing member 18A, and the transfer voltage to the transfer member 20 are canceled (all non-image forming periods are set to 0 V). Even when image formation is resumed after switching to non-image formation, potential unevenness of the image carrier 12 may remain in the previous image formation period. In some cases, line images other than the image to be formed are formed on the recording medium 30A due to the potential unevenness.

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

  Note that the non-image forming period indicates a period during which no image is formed on the recording medium 30A. During this “non-image forming period”, light irradiation based on image information by the latent image forming device 16 is not performed, and no image is formed on the recording medium 30A. Specifically, the non-image formation period corresponds to a period from the end of the previous image formation (image formation period) to the start of the next image formation (image formation period). Specifically, the “image forming period” indicates a period during which an image forming process for forming an image on the recording medium 30A based on a print job input to the control unit 36 in the image forming apparatus 10 is performed. The “formation period” indicates a period during which the image forming process is not performed in the image forming apparatus 10.

  In the image forming apparatus 10 according to the present embodiment, during the non-image forming period, the first voltage value continues for at least a period in which the image carrier 12 rotates once until the switching from the non-image forming period to the image forming period. The transfer voltage is applied to the transfer member 20, and the transfer voltage having the second voltage value is continuously applied to the transfer member 20 in the image forming period that continues after the non-image forming period. The control unit 36 controls the power supply 28.

  The transfer voltage of the first voltage value is a voltage that is continuously applied during the non-image forming period until switching from the non-image forming period to the image forming period, and is a value other than 0V. Further, as described above, the transfer voltage is a voltage having a polarity opposite to that of the toner constituting the toner image formed on the image carrier 12. For this reason, the transfer voltage of the first voltage value is a voltage applied to the transfer member 20 during the non-image forming period, and is a voltage having a polarity opposite to that of the toner and a voltage value other than 0V.

By the above control of the control unit 36 in the non-image forming period, as shown in a diagram 50A of FIG. 4, in the non-image forming period 42, the image is formed from the power source 30 to the transfer member 20 and from the non-image forming period 42. The transfer voltage of the first voltage value (see voltage value a in FIG. 4) is continuously applied for at least the period 44 in which the image carrier 12 makes one rotation until the switching P to the period 40. The period 44 during which the first voltage value (see voltage value a in FIG. 4) is applied in the non-image forming period 42 may be at least longer than the period during which the image carrier 12 rotates once. It may be a period in which the body 12 rotates two or more times. That is, the period 44 during which the first voltage value (see voltage value a in FIG. 4) is applied in the non-image forming period 42 is a period in which the image carrier 12 rotates N times (N is an integer of 1 or more). If it is.
The N value of the N rotation may be an integer of 1 or more, but is preferably 1 or more and 5 or less for the purpose of improving print productivity or extending the life by suppressing the number of wear cycles. Is more desirable.

  In the image forming period 40 that continues after the non-image forming period 42, the transfer voltage of the second voltage value (see voltage value b in FIG. To the transfer member 20.

  For this reason, when switching from the non-image forming period 42 to the image forming period 40, the transfer voltage of the first voltage value is continuously applied to the transfer member 20 for a period during which the image carrier 12 rotates at least once. The transfer voltage having the second voltage value is applied continuously to the transfer voltage having the first voltage value. Note that “continuously” means that the transfer voltage is never released (set to 0 V) when the transfer voltage is switched from the non-image forming period 42 to the image forming period 40, and is applied to the transfer member 20. It shows that it is continuously applied.

  Note that the value of the first voltage value (see voltage value a in FIG. 4), which is the voltage value of the transfer voltage applied during the non-image forming period 42, only needs to satisfy the above characteristics and is transferred during the image forming period. The voltage value may be the same as the second voltage value (see voltage value b in FIG. 4) that is the transfer voltage applied to the member 20, or may be a different voltage value. In the image forming apparatus 10, when a voltage is applied from the transfer member 20 to the image carrier 12 side in order to measure the resistance value (transfer resistance value) of the image carrier 12 during the non-image formation period 42. May use the same voltage value (absolute value) as the voltage used for the measurement of the resistance value as the first voltage value. Further, the resistance value of the image carrier 12 may be measured based on the measurement result of the current that flows when the transfer voltage having the first voltage value is applied. Thus, by making the first voltage value the same value as the voltage value used for measuring the resistance value of the image carrier 12, the mechanical and electrical configuration of the image forming apparatus 10 is significantly changed. Without application, application of the transfer voltage shown in FIG. 4 is executed.

During the non-image forming period 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 diagram 50C in FIG. Further, during the non-image forming period 42, the application of the developing voltage from the power source 32 to the developing member 18A is canceled (0 V) as shown in the diagram 50B of FIG.
Then, during the image forming period 40, the control unit 36 controls the charging voltage from the power source 28 to the charging member 14 and the developing voltage from the power source 32 to the developing member 18A as shown in a diagram 50C of FIG. Is applied.

As described above, in the image forming apparatus 10 of the present embodiment, in the non-image forming period 42, the application of the charging voltage is canceled and the charging of the image carrier 12 to the charging potential is not performed, so that the latent image is formed. The electrostatic latent image is not formed by the apparatus 16 (the exposure potential is not set), and the developing voltage of the developing member 18A is not applied, but during the non-image forming period 42, the image from the non-image forming period 42 is displayed. The transfer voltage of the first voltage value is continuously applied for a period of at least one rotation of the image carrier 12 until switching P to the formation period 40. For this reason, the transfer voltage of the first voltage value is continuously applied for a period of at least one rotation of the image carrier 12 from the non-image forming period 42 to the image forming period 40 during the non-image forming period 42. As compared with the case where the image forming period 40 is not performed, the surface of the image carrier 12 is neutralized by the transfer member 20 before the switching P of the image forming period 40. Then, in a state in which static elimination has been performed by the transfer member 20 in the non-image forming period 42, the transfer voltage of the second voltage is continuously applied in the image forming period 40 following the non-image forming period 42 from the time of the switching. The charge is applied to the transfer member 20, and the charge removal by the transfer member 20 is continued.
For this reason, even when image formation is resumed after switching from image formation to non-image formation in the image forming apparatus 10, residual potential unevenness of the image carrier 12 during the previous image formation period is suppressed, and this potential is reduced. It is considered that the formation of line images other than the image to be formed due to unevenness is suppressed.

  That is, in the image forming apparatus 10 of the present embodiment, it is considered that the generation of line images other than the image to be formed is suppressed by executing the adjustment of the transfer voltage in the non-image forming period 42 described above.

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. explained. Further, the charging voltage applied from the power source 28 to the charging member 14 may be a superimposed voltage obtained by superimposing an AC voltage on a DC voltage, or may be a DC voltage.
However, when the charging member 14 is provided in contact with the surface of the image carrier 12 and a DC voltage is used as the charging voltage, a line image other than the image to be formed due to potential unevenness on the image carrier 12 is obtained. In addition to the adjustment of the transfer voltage in the non-image forming period 42 in the image forming apparatus 10, at least the charge generation layer 65 and the charge transport are provided on the support 60 from the viewpoint of further suppressing the formation of the image. The layer 66 is configured to include the layer 66 in this order, and the charge transporting layer 66 includes a binder resin and a charge transporting material having a structure represented by the following general formula (1). Is desirable.

  Since the charge transport layer 66 includes a charge transport material having a structure represented by the following general formula (1), the charge mobility of the charge transport layer 66 does not use the material. It is considered that the unevenness of the potential of the surface of the image carrier 12 after being neutralized by the transfer member 20 (hereinafter sometimes referred to as unevenness of neutralization) is further 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 suppressed.
For this reason, it is thought that the static elimination effect by the transfer member 20 further improves.

  Furthermore, from the viewpoint of further suppressing unevenness in static elimination of the image carrier 12, the binder resin contained in the charge transport layer 66 includes a structural unit represented by the above general formula (2) and the following general formula (3). It is desirable to include a copolymer having a structural unit represented by:

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.

  Copolymerization ratio of a copolymer having 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) ) Includes, for example, m: n = 95: 5 to 5:95, 50:50 to 5:95, and 30:70 to 10:90.

  Specific examples of the copolymer having 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 structure: A formula (A3) is mentioned, but it is not limited to these.

  In addition, 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) within a range that does not impair the function. A binder resin other than the binder resin containing the 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.

  Here, the charging member 14 is disposed in contact with the surface of the image carrier 12 (so-called contact charging method), and the image carrier 12 is charged by applying a DC charging voltage from the power supply 28. In addition to the adjustment of the transfer voltage in the non-image forming period 42, the charge transport layer 66 includes at least a charge transport material having a structure represented by the general formula (1), and an image. When the relationship between the absolute value Vh of the surface potential of the holder 12, the absolute value Vin of the surface potential of the image holder 12, and the thickness T (μm) in the image formation period is at least the following first condition: It is desirable that the relationship satisfy the formula (A) 7T + 50 ≦ Vh−Vin.

  The “absolute value Vin of the surface potential of the image carrier 12” is the value after the toner image on the image carrier 12 is transferred to the recording medium 30A by the transfer member 20 and before being charged by the charging member 14. The absolute value of the surface potential of the image carrier 12 is shown. That is, the absolute value Vin of the surface potential is an image on the surface of the image carrier 12 upstream of the region charged by the charging member 14 in the rotation direction of the image carrier 12 and from the region transferred by the transfer member 20. The absolute value of the surface potential of the region downstream of the holder 12 in the rotation direction is shown. More specifically, the absolute value Vin of the surface potential is cleaned by the cleaning member 22 on the surface of the image carrier 12 upstream of the region charged by the charging member 14 in the rotation direction of the image carrier 12. The absolute value of the surface potential of the area downstream of the image holding body 12 in the rotation direction of the image holding area 12 is shown.

  Further, the “absolute value Vh of the surface potential of the image carrier 12” means that the image carrier 12 is charged by the charging member 14 and before the electrostatic latent image is formed by the latent image forming device 16. The absolute value of the surface potential is shown. That is, the absolute value Vh of the surface potential is the electrostatic latent image formed by the latent image forming device 16 on the surface of the image carrier 12 on the downstream side in the rotation direction of the image carrier 12 from the region charged by the charging member 14. The absolute value of the surface potential of the region upstream of the image carrier 12 in the rotation direction from the region where the image is formed is shown.

  In the above formula (A), the absolute value Vin of the surface potential and the absolute value Vh of the surface potential are different from one end side in the width direction (rotation axis direction) of the image carrier 12 in each of the above regions. The absolute value of the average value obtained by measuring the surface potential is shown for one round in the circumferential direction of the image carrier 12 every 10 mm toward the end side. For the measurement of the surface potential in each measurement region, a surface potential probe (for example, Trek 334, manufactured by Trek) was used to provide a surface potential probe in the measurement target region (1 mm away from the surface of the image carrier 12). Position) Obtained by reading the measurement result of measuring the surface potential.

  The thickness T (μm) is the thickness of the charge transport layer 66 in the image carrier 12 and a layer (for example, a protective layer not shown) provided on the surface side of the charge transport layer 66. The average value of the total thickness is shown. This thickness measurement is performed by observing a cross-sectional view of the image carrier 12 and for every 10 mm in the circumferential direction of the image carrier 12 from one end side in the width direction of the image carrier 12 toward the other end side. It is obtained by calculating the average value of the measured measurement results.

  The first condition indicates a condition when the above formula (A) is satisfied. Specifically, the charge transport layer 66 has a charge represented by the above general formula (1). The content of the transportable material is 8% by mass or more and 50% by mass or less, exhibits excellent charge transporting ability, has a small amount of defect sites that prevent uniform charging, and maintains a good image over a long period of time. This indicates that the content is in a range that does not cause a decrease in mechanical strength of the surface layer, which is indispensable for the surface layer.

  In order to adjust the relationship of the above formula (A) to be satisfied under the first condition, the first voltage value of the transfer voltage applied to the transfer member 20 in the non-image forming period 42 is set. The value may be adjusted according to the configuration of the image carrier 12 and the target charging potential.

  Here, in the image carrier 12, as the total thickness T (μm) of the thickness of the charge transport layer 66 and the layer provided on the surface side of the charge transport layer 66 is larger, the defect that hinders uniform charging. Since the amount of site generation increases, it is considered that line images other than the image to be formed are likely to occur.

  Further, when the charging member 14 is disposed in contact with the surface of the image carrier 12 (so-called contact charging method) and a DC charging voltage is applied from the power source 28, the image carrier 12 is charged. As a result, the charging potential of the charging member 14 may become non-uniform. As a result, the surface potential of the area of the image holding member 12 charged by the charging member 14 becomes uneven in the direction of the rotation axis of the image holding member 12. Is considered to occur. The potential unevenness of the surface potential of the image carrier 12 is particularly likely to occur due to environmental changes such as temperature and humidity, and line images other than the image to be formed are recorded on the recording medium due to the potential unevenness. It is thought that it is formed on 30A.

  In particular, during the non-image forming period in which no image is formed on the recording medium 30A as in the conventional image forming apparatus, as shown in the diagram 51A, the diagram 51B, and the diagram 51C in FIG. When the application of the charging voltage is canceled, the application of the developing voltage to the developing member 18A is canceled, and the application of the transfer voltage to the transfer member 20 is canceled (all non-image forming periods are set to 0 V), In the image forming period 40 immediately after switching from the forming period 42 to the image forming period 40, the surface potential of the image carrier 12 is disturbed by the charging member 14, the potential unevenness of the image carrier 12 increases, and the object to be formed It is considered that the generation of line images other than the above image becomes remarkable.

  Therefore, when the charging member 14 is disposed in contact with the surface of the image carrier 12 and the image carrier 12 is charged by applying a DC charging voltage from the power supply 28, the surface of the image carrier 12 is used. When the relationship between the absolute value Vh of the potential, the absolute value Vin of the surface potential of the image carrier 12 and the thickness T (μm) is at least the first condition, the formula (A) 7T + 50 ≦ Vh−Vin If the relationship satisfies the above, generation of line images other than the image to be formed is further 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%”.
In the following examples, aspects other than the contact charging method and the charging voltage being direct current correspond to reference examples.

<Preparation of image carrier A1 to image carrier D>
-Production of image carrier A1-
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 4 parts by weight of tris [4- (4,4-diphenyl-1,3-butadienyl) phenyl] amine, a compound having a bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40000) 6 parts by mass, 0.1 part by mass of 2,6-di-t-butyl-4-methylphenol as an antioxidant are mixed, 24 parts by mass of tetrahydrofuran and 11 parts by mass of toluene are mixed and dissolved, and mixed solution B was 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 C was applied on the charge generation layer so as to have a thickness of 28 μm, and dried at 135 ° C. for 25 minutes to form a charge transport layer having a thickness of 28 μm. Thus, an intended electrophotographic photosensitive member was obtained. . The electrophotographic photoreceptor thus obtained was designated as an image carrier A1. The thickness was measured using the method described above. The same shall apply hereinafter.

-Production of image carrier A2-
In the production of the image carrier A1, the same conditions as those for the image carrier A1 except that the charge transport layer having a thickness of 12 μm was formed by coating the coating solution C so that the coating liquid C had a thickness of 12 μm. And image carrier A2 was produced by the manufacturing method.

-Production of image carrier A3-
In the production of the image carrier A1, the same conditions as in the image carrier A1 except that the charge transport layer having a thickness of 40 μm was formed by coating the coating solution C so that the coating amount was 40 μm. And image carrier A3 was produced by the manufacturing method.

-Production of image carrier A4-
Tris [4- (4,4-diphenyl-1,3-butadienyl) phenyl] amine, which is a compound having the structural formula (1), which is a charge transporting substance, used in the production of the image carrier A1 The image carrier A4 was produced under the same conditions and production method as the image carrier A1 except that 1.5 parts by mass was used.

-Production of image carrier B1-
In the image carrier A1, instead of the bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40000) used as the binder resin for the charge transport layer, it is represented by the following structural formula (A3), and in the structural formula (A3) An image carrier B1 was produced under the same conditions and production method as the image carrier A1, 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 B2-
In the production of the image carrier B1, the same conditions as the image carrier B1 except that the charge transport layer having a thickness of 12 μm was formed by coating the coating solution C so that the coating liquid C had a thickness of 12 μm. Then, an image carrier B2 was produced by the production method.

-Production of image carrier B3-
In the production of the image carrier B1, the same conditions as those for the image carrier B1 except that a charge transport layer having a thickness of 40 μm was formed by coating the coating solution C so that the coating liquid C had a thickness of 40 μm. Then, an image carrier B3 was produced by the production method.

-Production of image carrier C1-
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 in the image carrier A1, N, N′-bis (3-methylphenyl) ) The same conditions and the same as the image carrier A1 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 C1 was produced using the production method.

-Production of image carrier C2-
In the production of the image carrier C1, the same conditions as those for the image carrier C1 except that the charge transport layer having a thickness of 12 μm was formed by coating the coating solution C so that the coating liquid C had a thickness of 12 μm. And the image carrier C2 was produced by the production method.

-Production of image carrier C3-
In the production of the image carrier C1, the same conditions as the image carrier C1 except that a charge transport layer having a thickness of 40 μm was formed by coating the coating solution C so that the coating liquid C had a thickness of 40 μm. And the image carrier C3 was produced by the production method.

-Production of image carrier D-
Next, 6 parts of a compound represented by the following formula (A4), 15 parts of isopropyl alcohol, 9 parts of tetrahydrofuran, and 0.1 part of distilled water are formed on the charge transport layer formed in the same manner as the image carrier A1. Nine parts were mixed, 0.5 part of ion exchange resin (Amberlyst 15E) was added thereto, and the mixture was stirred at room temperature for hydrolysis for 2 hours. Furthermore, 0.5 parts of butyral resin, 4 parts of resol type phenolic resin (PL-2818, manufactured by Gunei Chemical Co., Ltd.) and 0.2 part of dimethylpolysiloxane were added to form a protective layer-forming coating solution for charge transport. It is coated on the layer by a ring-type dip coating method, air-dried at room temperature for 30 minutes, and then heated and cured at 155 ° C. for 35 minutes to form a protective layer having a thickness of about 7 μm. Produced.

(Examples 1 to 16, Comparative Examples 1 to 4)
In the control apparatus for controlling the charging voltage applied to the charging member 14 in the DocuCenter 505a, the developing voltage applied to the developing member 18A, and the transferring voltage applied to the transfer member 20 as an image forming apparatus, a voltage application sequence shown in FIG. The device was modified to run a program to run.
The type of the image carrier to be mounted, the voltage value of the transfer voltage applied to the transfer member in the non-image forming period and the image forming period (first voltage value and second voltage value), and the first in the non-image forming period. The transfer voltage application time (for the image carrier N rotation), the charging voltage in the non-image forming period and the image forming period, the type of charging voltage, the developing voltage in the non-image forming period and the image forming period, etc. The apparatus was improved so that the combination shown in 1 was obtained, and the following evaluation test was performed.

  In Table 1, the absolute value Vin of the surface potential is, as described above, on the upstream side in the rotation direction of the image carrier 12 from the region charged by the charging member 14 on the surface of the image carrier 12 and the transfer. The absolute value of the average value of the surface potential of the area downstream of the image transfer body 12 in the rotation direction from the area transferred by the member 20 is shown. In the present example and the comparative example, as the measurement target area of the absolute value Vin of the surface potential, an area charged by the charging member on the surface of the image holding body mounted on the image forming apparatus DocuCenter 505a, and a cleaning member An intermediate region between the region where the deposit on the image carrier is removed by the (cleaning member) is set as a measurement target region of the absolute value Vin of the surface potential. For the measurement target region of the absolute value Vin of the surface potential, a surface potential probe is provided every 10 mm from one end side to the other end side in the width direction (rotation axis direction) of the image holding body (the image holding body The absolute value of the average value of the measurement results of the surface potential measured by a surface potentiometer (Trek, Trek 334) for one circumference in the circumferential direction of the image holding member Used as the absolute value Vin.

  In Table 1, the absolute value Vh of the surface potential is, as described above, on the downstream side in the rotation direction of the image carrier 12 from the region charged by the charging member 14 on the surface of the image carrier 12 and the latent potential Vh. The absolute value of the average value of the surface potential in the region upstream of the rotation direction of the image carrier 12 from the region where the electrostatic latent image is formed by the image forming device 16 is shown. In the present example and the comparative example, as the measurement target area of the absolute value Vh of the surface potential, an area charged by the charging member on the surface of the image holding body mounted on the image forming apparatus DocuCenter 505a, and a latent image An intermediate area between the area where the electrostatic latent image is formed by the forming apparatus (exposure apparatus) was set as the measurement target area of the absolute value Vh of the surface potential. For the measurement target area of the absolute value Vh of the surface potential, a surface potential probe is provided every 10 mm from one end side to the other end side in the width direction (rotation axis direction) of the image holding body (the image holding body The absolute value of the average value of the measurement results of the surface potential measured by a surface potentiometer (Trek, Trek 334) for one circumference in the circumferential direction of the image holding member Used as absolute value Vh.

  In the measurement of the absolute value Vh of the surface potential and the absolute value Vin of the surface potential, the “one circumferential direction of the image carrier” is switched from the non-image forming period to the image forming period (FIG. 4). The first rotation of the image carrier immediately after the switching (refer to P at the time of switching) (the first rotation after the transition to the image forming period) is shown.

  In Table 1 above, Sequence A to Sequence D are the voltage application method during the non-image forming period as shown in FIG. 4. Specifically, the test environment is a high temperature and high humidity (28 ° C., 85 RH%) environment. The voltage value of the charging voltage, the voltage value of the developing voltage, the voltage value of the transfer voltage (first voltage value), and the continuous voltage application time of the transfer voltage of the first voltage value are the values shown in Table 2. Shows the case.

  Further, in Table 1, the sequence F is a voltage application method during a non-image forming period in which the duration of applying the transfer voltage of the first voltage value is less than the time for which the image carrier 12 rotates once. Specifically, when the test environment is a high temperature and high humidity (28 ° C., 85 RH%) environment, the voltage value of the charging voltage, the voltage value of the developing voltage, the voltage value of the transfer voltage (first voltage value), the first The case where the continuous voltage application time of the transfer voltage of the voltage value is the value shown in Table 2 is shown.

  In Table 1, the sequence F indicates a case where all of the transfer voltage, the charging voltage, and the development voltage are 0V (released) in the non-image forming period (see Table 2).

  The following evaluation was performed on Examples 1 to 16 and Comparative Examples 1 to 5 which were combinations shown in Table 1 above.

(Evaluation)
-Line images other than the image to be formed-
For each of the modified machines of Examples 1 to 16 and Comparative Examples 1 to 5, the image density is 30% as an image forming process in the image forming period in a high temperature and high humidity environment (28 ° C., 85 RH%). After continuously outputting 10,000 A4 halftone images to an A4 recording medium, non-image forming processing was performed in the non-image forming period under the conditions of the examples and comparative examples shown in Tables 1 and 2. Then, after this non-image forming period, an image forming process (image forming period) was performed under the same conditions as the image forming period immediately before the non-image forming period.
In the halftone image to be formed on the recording medium of the first sheet output in this image forming period (the image formed immediately after switching from the non-image forming period to the image forming period is converted to the first sheet) The presence or absence of a line image was evaluated by counting the number of line images that were not present. The evaluation criteria were as follows. The evaluation results are shown in Table 3.

Evaluation criteria G1: No line image is generated G2: One or more line images are generated and less than five G3: Five or more line images are generated and less than ten G4: Ten or more line images are generated

  As shown in Table 3 above, in the example, generation of line images other than the image to be formed was suppressed during the image formation period as compared with the comparative example.

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 (4)

A rotating image carrier;
A charging member disposed in contact with the surface of the image carrier and charging the surface of the image carrier by applying a DC voltage ;
A latent image forming apparatus that forms an electrostatic latent image on the surface of the image carrier charged by the charging member;
A developing device for developing the electrostatic latent image formed on the surface of the image carrier with toner;
A transfer member for transferring a toner image formed on the surface of the image carrier by the developing device to a transfer target member and discharging the image carrier;
A voltage applying device that applies a transfer voltage to the transfer member so that the transfer potential of the transfer member is a transfer potential having a polarity opposite to that of the toner of the toner image formed on the surface of the image carrier;
During the non-image forming period, the toner of the toner image formed on the surface of the image holding member is continuously used for at least one rotation of the image holding member until the switching from the non-image forming period to the image forming period. Applies the transfer voltage having a first voltage value other than 0 V having a reverse polarity, and the transfer voltage having the second voltage value continuously from the time of the switching in the image forming period subsequent to the non-image forming period. Control means for controlling the voltage application device to apply
An image forming apparatus. Before Symbol image holding member comprises a support, a charge generation layer, and a charge transport layer containing a charge-transporting material having a structure represented by the following general formula (1) in this order,
On the surface of the image carrier, on the upstream side of the rotation direction of the image carrier from the region charged by the charging member, and from the region where the toner image is transferred to the transfer member by the transfer member. The absolute value Vin of the surface potential of the region downstream in the rotation direction of the body and the formation of the latent image on the surface of the image carrier on the downstream side in the rotation direction of the image carrier from the region charged by the charging member The absolute value Vh of the surface potential of the region upstream of the image carrier in the rotation direction from the region where the electrostatic latent image is formed by the apparatus, and the surface side of the charge transport layer and the charge transport layer of the image carrier The image forming apparatus according to claim 1, wherein a relationship between the total thickness T (μm) of the provided layers and an image forming period satisfies 7T + 50 ≦ Vh−Vin.

(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 an aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure, where n and m are independent of each other. Represents 0 or 1. The image forming apparatus according to claim 2, wherein the charge transport layer includes a binder resin containing 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 formation according to claim 3, wherein the binder resin contains a copolymer having a structural unit represented by the general formula (2) and a structural unit represented by the following general formula (3). apparatus.

(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.)