JP6036353B2 - Image forming apparatus and program - Google Patents

Description

  The present invention relates to an image forming apparatus and a program.

  In Patent Document 1, a photosensitive member for forming an electrostatic latent image and the electrostatic latent image on the photosensitive member are developed with a two-component developer by applying a developing bias in which an AC bias is superimposed on a DC bias. A developing device that forms a toner image, a control unit that controls the developing bias, a transfer device that transfers the toner image onto a transfer material, a fixing device that fixes the toner image onto the transfer material, and a surface of the photoreceptor. Forming a forced discharge toner image in a forced discharge image forming area provided in a non-image forming area other than the image forming area on the photoconductor; A toner forced discharge mode for forcibly discharging toner from the developing device, and in the toner forced discharge mode, an AC bias having a frequency lower than that of the image forming area is forcibly discharged. Is applied to use the image forming region of the forcible discharging the latent image to form a forced discharge toner image by developing, the image forming apparatus characterized by recovering the toner is disclosed in the cleaning device. Further, it is disclosed that the forced toner discharge mode is executed when an integrated image rate in forming a predetermined number of images is equal to or less than a predetermined value.

JP 2006-3313307 A

  An object of the present invention is to provide an image forming apparatus and a program capable of maintaining transfer performance and suppressing local deterioration in cleaning performance.

In order to achieve the above object, the invention according to claim 1 is characterized in that a latent image forming means for exposing the surface of a charged image carrier to form an electrostatic latent image, and a volume average particle diameter of 80 nm to 180 nm. A container containing a developer containing toner to which inorganic particles are externally added; and a voltage applying unit for applying a development contrast voltage between the image carrier and the developer contrast voltage applied. A toner image forming unit that develops the electrostatic latent image with the developer in a state to form a toner image on the image carrier, a transfer unit that transfers the toner image to a transfer target, and the image carrier. Cleaning means for cleaning the image carrier after transfer, and a non-image area corresponding to an image forming area whose accumulated image amount obtained based on the image information is less than a threshold value, from a development contrast voltage at the time of image formation 20% to 60% By applying a high development contrast voltage range so as to form a toner image, and a control means for controlling each of said latent image forming means and said toner image forming means is an image forming apparatus having a.

According to a second aspect of the present invention, the control means divides the image forming area on the surface of the image carrier into a plurality of blocks along the rotation axis direction of the image carrier, and calculates an integrated image amount for each of the plurality of blocks. The image forming apparatus according to claim 1 , wherein the image forming apparatus acquires and controls to form a toner image in a non-image area corresponding to a block whose accumulated image amount is less than a threshold value.

The invention according to claim 3, wherein said control means controls so as to form a toner image on the non-image area accumulated image volume is adjacent in the process direction relative to the image forming area of less than the threshold value, according to claim 1, wherein Item 5. The image forming apparatus according to Item 2 .

According to a fourth aspect of the present invention, in the image according to any one of the first to third aspects, the control means performs control so as to increase the development contrast voltage by changing a development bias voltage. Forming device.

According to the fifth aspect of the present invention, a latent image forming unit that forms an electrostatic latent image by exposing the surface of a charged image carrier and inorganic particles having a volume average particle size of 80 nm to 180 nm are externally added. And a voltage application unit that applies a development contrast voltage between the image carrier and the developer with the development contrast voltage applied thereto. A toner image forming unit that develops an electrostatic latent image to form a toner image on the image holding member, a transfer unit that transfers the toner image to a transfer target, and an image after being transferred in contact with the image holding member A non-image corresponding to an image forming region in which an integrated image amount obtained based on image information is less than a threshold, is a program for controlling an image forming apparatus including a cleaning unit that cleans a holding body. When forming an image in the area The latent image forming unit and the toner image forming unit are caused to function as control units so as to form a toner image by applying a development contrast voltage that is higher than the development contrast voltage by 20% to 60%. It is a program.

According to the first and fifth aspects of the present invention, the transfer performance is maintained and the local degradation of the cleaning performance is suppressed.

According to invention of Claim 2 , the fall of the local cleaning performance is suppressed per block.

According to the third aspect of the present invention, a reduction in cleaning performance that occurs locally in an image forming region where the integrated image amount is less than the threshold value is suppressed as intended.

According to the fourth aspect of the present invention, the development contrast voltage is changed by changing the development bias voltage.

1 is a schematic diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of a configuration of a control system of the image forming apparatus illustrated in FIG. 1. FIG. 3 is a block diagram illustrating in more detail a configuration of a control system of the image forming unit illustrated in FIG. 2. It is a schematic diagram for demonstrating the function of a large particle size external additive. It is a flowchart which shows an example of the process sequence of "external additive supply process." (A) And (B) is explanatory drawing for demonstrating the content of the "external additive supply process." It is a schematic diagram which shows an example of the image for evaluation.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
First, the main configuration of the image forming apparatus will be described.
FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment includes, for example, an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) 12 (an example of an image holding member). The photosensitive member 12 has a cylindrical shape, and is connected to a driving unit 27 such as a motor via a driving force propagation member (not shown) such as a gear, and around the rotation axis indicated by a black dot by the driving unit 27. Driven by rotation. In the example shown in FIG. 1, it is rotationally driven in the direction of arrow A.

  Around the photosensitive member 12, for example, a charging device 15, a latent image forming device 16, a developing device 18, a transfer device 31, a cleaning device 22, and a charge eliminating device 24 are sequentially arranged along the rotation direction of the photosensitive member 12. Has been. The image forming apparatus 10 according to the present embodiment is also provided with a fixing device 26. Details of each part of the image forming apparatus 10 will be described below.

(Photoconductor)
The photoreceptor 12 includes, for example, a conductive substrate, an undercoat layer formed on the conductive substrate, and a photosensitive layer formed on the undercoat layer. This photosensitive layer may have a two-layer structure of a charge generation layer and a charge transport layer. Further, the photosensitive layer may have a configuration in which a protective layer is provided on the outermost surface. The undercoat layer includes a binder resin, metal oxide particles, and an electron accepting compound.

(Charging device)
The charging device 15 charges the surface of the photoconductor 12. The charging device 15 is provided, for example, in contact or non-contact with the surface of the photoconductor 12, and a charging member 14 that charges the surface of the photoconductor 12, and a power source 28 (voltage for the charging member) that applies a charging voltage to the charging member 14. An example of an application unit). The power source 28 is electrically connected to the charging member 14.

  Examples of the charging member 14 of the charging device 15 include a contact-type charger using a conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, and the like. Examples of the charging member 14 include a non-contact type roller charger and a known charger such as a scorotron charger using a corona discharge or a corotron charger.

  The charging device 15 (including the power supply 28) is electrically connected to, for example, a control unit 36 provided in the image forming apparatus 10, and is driven and controlled by the control unit 36 to apply a charging voltage to the charging member 14. To do. The charging member 14 to which the charging voltage is applied from the power supply 28 charges the photoconductor 12 to a charging potential corresponding to the applied charging voltage. Therefore, the photosensitive member 12 is charged to a different charging potential by adjusting the charging voltage applied from the power source 28.

(Latent image forming device)
The latent image forming device 16 (an example of a latent image forming unit) forms an electrostatic latent image on the surface of the charged photoreceptor 12. Specifically, for example, the latent image forming device 16 is electrically connected to a control unit 36 provided in the image forming device 10, is driven and controlled by the control unit 36, and is charged by the charging member 14. The surface of the photoconductor 12 is irradiated with light L modulated based on the image information of the image to be formed, and an electrostatic latent image corresponding to the image of the image information is formed on the photoconductor 12.

  Examples of the latent image forming device 16 include optical equipment having a light source that exposes light such as semiconductor laser light, LED light, and liquid crystal shutter light imagewise.

(Developer)
The developing device 18 is provided, for example, on the downstream side in the rotation direction of the photoconductor 12 from the irradiation position of the light L by the latent image forming device 16. In the developing device 18, an accommodating portion for accommodating the developer is provided. In the present embodiment, a developer containing toner to which inorganic particles having a volume average particle size of 80 nm or more and 180 nm or less (hereinafter referred to as “large particle size external additive”) are externally stored is stored in the storage portion. Has been. For example, the toner is stored in a charged state in the developing device 18. The developer containing the large particle size external additive will be described later.

  The developing device 18 includes, for example, a developing member 18A that develops an electrostatic latent image formed on the surface of the photoreceptor 12 with a developer containing toner, and a power source 32 (for developing member) that applies a developing voltage to the developing member 18A. An example of the voltage application unit of The developing member 18A is electrically connected to the power source 32, for example.

  The developing member 18A of the developing device 18 is selected according to the type of developer, and examples thereof include a developing roll having a developing sleeve with a built-in magnet.

  The developing device 18 (including the power source 32) is electrically connected to a control unit 36 provided in the image forming apparatus 10, for example, and is driven and controlled by the control unit 36 to apply a developing voltage to the developing member 18A. To do. The developing member 18A to which the developing voltage is applied is charged to a developing potential corresponding to the developing voltage. Then, the developing member 18A charged to the developing potential holds, for example, the developer accommodated in the developing device 18 on the surface, and the toner contained in the developer is transferred from the developing device 18 to the surface of the photoreceptor 12. Supply.

  For example, the toner supplied onto the photoconductor 12 adheres to the electrostatic latent image on the photoconductor 12 by electrostatic force. Specifically, for example, the toner contained in the developer by the potential difference in the area where the photosensitive member 12 and the developing member 18A face each other, that is, the potential difference between the surface potential of the photosensitive member 12 and the developing potential of the developing member 18A in the region. Is supplied to the area of the photoreceptor 12 where the electrostatic latent image is formed. If the developer contains a carrier, the carrier returns to the developing device 18 while being held by the developing member 18A.

  For example, the electrostatic latent image on the photoconductor 12 is developed with toner supplied from the developing member 18 </ b> A, and a toner image corresponding to the electrostatic latent image is formed on the photoconductor 12.

(Transfer device)
For example, the transfer device 31 is provided on the downstream side in the rotation direction of the photoconductor 12 from the position where the developing member 18A is disposed. The transfer device 31 includes, for example, a transfer member 20 that transfers a toner image formed on the surface of the photoreceptor 12 to a recording medium 30A (an example of a transfer target), and a power supply 30 (transfer) that applies a transfer voltage to the transfer member 20. An example of a voltage application unit for a member). The transfer member 20 has, for example, a cylindrical shape, and conveys the recording medium 30 </ b> A with the photoreceptor 12. The transfer member 20 is electrically connected to, for example, a power supply 30.

  As the transfer member 20 of the transfer member 20, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade or the like, a scorotron transfer charger using a corona discharge, a corotron transfer charger, or the like is known per se. A non-contact type transfer charger is exemplified.

  The transfer device 31 (including the power supply 30) is electrically connected to, for example, a control unit 36 provided in the image forming apparatus 10, and is driven and controlled by the control unit 36 to apply a transfer voltage to the transfer member 20. To do. The transfer member 20 to which the transfer voltage is applied is charged to a transfer potential corresponding to the transfer voltage.

  When a transfer voltage having a polarity opposite to that of the toner constituting the toner image formed on the photoconductor 12 is applied from the power source 30 of the transfer member 20 to the transfer member 20, for example, between the photoconductor 12 and the transfer member 20. In the facing area (see transfer area 32A in FIG. 1), an electric field having an electric field strength for moving each toner constituting the toner image on the photoreceptor 12 from the photoreceptor 12 to the transfer member 20 side by electrostatic force is formed. The

  The recording medium 30 </ b> A (an example of a transfer target) is accommodated in, for example, a storage unit (not illustrated), and is transported along the transport path 34 by a plurality of transport members (not illustrated) 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. In the example shown in FIG. 1, it is conveyed in the direction of arrow B. For example, when a transfer voltage is applied to the transfer member 20, the toner image on the photoconductor 12 is transferred to the recording medium 30 </ b> A that has reached the transfer area 32 </ b> A by the electric field formed in the area. That is, for example, the toner image is transferred onto the recording medium 30A by the movement of the toner from the surface of the photoreceptor 12 to the recording medium 30A.

(Cleaning device)
The cleaning device 22 is provided on the downstream side in the rotation direction of the photoconductor 12 from the transfer region 32A. The cleaning device 22 transfers the toner image to the recording medium 30 </ b> A, and then removes the deposits attached to the photoconductor 12. The cleaning device 22 removes deposits such as residual toner and paper dust on the photoconductor 12. In the present embodiment, the cleaning device 22 has a plate-like member (hereinafter referred to as “cleaning blade”) 22 </ b> A that contacts the photoconductor 12 with a predetermined linear pressure. The cleaning blade 22A is in contact with the photoconductor 12 at a linear pressure of 10 g / cm or more and 150 g / cm or less, for example.

(Staticizer)
The static eliminator 24 (an example of a static eliminator) is provided, for example, downstream of the cleaning device 22 in the rotation direction of the photoconductor 12. After the toner image is transferred, the neutralization device 24 exposes the surface of the photoreceptor 12 to neutralize the charge. Specifically, for example, the static eliminator 24 is electrically connected to a control unit 36 provided in the image forming apparatus 10, and is driven and controlled by the control unit 36 so that the entire surface of the photoconductor 12 (specifically, For example, the entire surface of the image forming area is exposed to remove electricity.

  Examples of the static eliminating device 24 include a device having a light source such as a tungsten lamp that emits white light and a light emitting diode (LED) that emits red light.

(Fixing device)
For example, the fixing device 26 is provided on the downstream side in the transport direction of the transport path 34 of the recording medium 30A from the transfer region 32A. For example, the fixing device 26 fixes the toner image transferred onto the recording medium 30A. Specifically, for example, the fixing device 26 is electrically connected to a control unit 36 provided in the image forming apparatus 10, and is toner that is driven and controlled by the control unit 36 and transferred onto the recording medium 30 </ b> A. The image is fixed on the recording medium 30A by heat or heat and pressure.

  Examples of the fixing device 26 include a known fixing device such as a heat roller fixing device and an oven fixing device.

  Here, the recording medium 30 </ b> A to which the toner image is transferred by being transported along the transport path 34 and passing through the region (transfer region 32 </ b> A) where the photoconductor 12 and the transfer member 20 face each other is omitted, for example. The conveying member further reaches the installation position of the fixing device 26 along the conveying 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). The photosensitive member 12 is charged to the charging potential by the charging device 15 again after the charge removal by the charge removal device 24.

(Image forming operation)
Here, an image forming operation of the image forming apparatus 10 will be described.
First, the surface of the photoreceptor 12 is charged by the charging device 14. The latent image forming device 16 exposes the surface of the charged photoreceptor 12 based on image information. As a result, an electrostatic latent image corresponding to the image information is formed on the photoreceptor 12. In the developing device 18, the electrostatic latent image formed on the surface of the photoreceptor 12 is developed by a developer containing toner. As a result, a toner image is formed on the surface of the photoreceptor 12. In the transfer device 31, the toner image formed on the surface of the photoreceptor 12 is transferred to the recording medium 30A. The toner image transferred to the recording medium 30 </ b> A is fixed by the fixing device 26. On the other hand, the surface of the photoconductor 12 after the toner image is transferred is cleaned by the cleaning device 22 and discharged by the charge removing device 24.

<Control system of image forming apparatus>
Next, a control system of the image forming apparatus will be described.
FIG. 2 is a block diagram showing an example of the configuration of the control system of the image forming apparatus shown in FIG. FIG. 3 is a block diagram showing in more detail the configuration of the control system of the image forming unit shown in FIG. As shown in FIG. 2, in addition to the control unit 36, the image forming apparatus 10 according to the present embodiment includes an operation display unit 40, an image processing unit 42, an image memory 44, an image forming unit 46, a storage unit 48, and A communication unit 50 is provided.

  The control unit 36 is configured as a computer that controls the entire apparatus and performs various calculations. Specifically, the control unit 36 includes a CPU (Central Processing Unit) 36A, a ROM (Read Only Memory) 36B storing various programs, and a RAM (Random Access Memory) used as a work area when executing the programs. 36C, a non-volatile memory 36D for storing various information, and an input / output interface (I / O) 36E. Each of the CPU 36A, ROM 36B, RAM 36C, nonvolatile memory 36D, and I / O 36E is connected via a bus 36F.

  The operation display unit 40, the image processing unit 42, the image memory 44, the image forming unit 46, the storage unit 48, and the communication unit 50 are connected to the I / O 36E of the control unit 36. The control unit 36 exchanges information with each unit of the operation display unit 40, the image processing unit 42, the image memory 44, the image forming unit 46, the storage unit 48, and the communication unit 50, and controls each unit.

  The operation display unit 40 includes various buttons such as a start button and a numeric keypad, and a touch panel for displaying various screens such as a warning screen and a setting screen. With the above configuration, the operation display unit 40 receives operations from the user and displays various information to the user.

  The image processing unit 42 performs predetermined image processing on the image information acquired from the external device 52 via the communication unit 50, and generates image information to be output to the image forming unit 46. For example, PDL data described in a page description language is expanded and converted into raster data (RGB data) that has been expanded into RGB colors, and the RGB data is color-converted and reproduced by the image forming apparatus. Generates YMCK data expressed in color. Furthermore, screen processing, gamma correction processing, or the like may be performed.

  The image memory 44 stores various image information acquired by the image forming apparatus 10 such as image information acquired from the external device 52 and image information generated by the image processing unit 42. In the present embodiment, the image memory 44 stores at least image information after image processing by the image processing unit 42, that is, image information to be output to the image forming unit 46. Hereinafter, in order to simplify the description, image information to be output to the image forming unit 46 will be described as “K color single color” raster data.

  The image forming unit 46 is described as a main configuration of the image forming apparatus 10. As shown in FIG. 3, the control system of the image forming unit 46 includes a driving unit 27 of the photosensitive member 12, a charging device 15 (including a power source 28), a latent image forming device 16, a developing device 18 (including a power source 32), The image forming apparatus includes a transfer device 31 (including a power supply 30), a charge eliminating device 24, and a fixing device 26. Each of the drive unit 27, the charging device 15, the latent image forming device 16, the developing device 18, the transfer device 31, the charge removal device 24, and the fixing device 26 is connected to the control unit 36. The control unit 36 exchanges information with each of these units and controls each unit.

  The storage unit 48 includes a storage device such as a hard disk. The storage unit 48 stores various data such as log data, various programs, and the like. The communication unit 50 is an interface for communicating with the external device 52 via a wired or wireless communication line. For example, the communication unit 50 acquires image formation information together with an image formation instruction and image information of an electronic document from an external device. The image formation information includes parameters representing attributes such as page, number of copies, and color mode.

  In the present embodiment, a case will be described in which a control program for “external additive supply processing” to be described later is stored in advance in the ROM 36B. The control program stored in advance is read out by the CPU 36A and executed using the RAM 36C as a work area. Further, in the present embodiment, a case will be described in which various setting values such as “threshold value of accumulated image amount” to be described later are stored in advance in the nonvolatile memory 36D. The control program and the set value may be stored in another storage device such as the storage unit 48, or may be acquired from the outside via the communication unit 50.

  Various drives may be connected to the control unit 36. Various drives are devices that read data from or write data to computer-readable portable recording media such as flexible disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and USB memories. is there. When various types of drives are provided, a control program may be recorded on a portable recording medium, and this may be read and executed by a corresponding drive.

<Developer with large particle size external additive>
Next, the developer according to the present embodiment will be described.
(Developer)
The developer according to the present embodiment is a developer including a toner to which a large particle size external additive is externally added. As described above, the large particle size external additive is an inorganic particle having a volume average particle size of 80 nm or more and 180 nm or less. By providing an upper limit with a volume average particle size of 180 nm or less, filming on the photoreceptor is reduced. The lower limit of the volume average particle size may be 100 nm from the viewpoint of transfer maintenance. Further, the upper limit value of the volume average particle diameter may be 170 nm from the viewpoint of suppressing filming on the photoreceptor.

  Examples of inorganic particles include silica particles, titanium oxide particles, and alumina particles. In particular, silica particles are preferably used from the viewpoint of chargeability. The “volume average particle diameter” here is a volume average particle diameter (D50v). The volume average particle diameter of the external additive is determined by observing 100 primary particles of inorganic particles after the inorganic particles are dispersed in the toner particles using a scanning electron microscope (SEM) apparatus and analyzing the primary particles for each particle. The long diameter and the shortest diameter are measured, and the equivalent sphere diameter is measured from the intermediate value. The 50% diameter (D50v) in the cumulative frequency of the obtained sphere equivalent diameter is defined as the volume average particle diameter of the external additive.

  The constitution of the developer is the same as that of a known developer containing toner, except that the large particle size external additive is externally added. 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 developer may be a one-component developer that does not include a carrier, or may be a two-component developer that includes a toner and a carrier.

The volume average particle diameter of the toner particles is measured using a Coulter Multisizer II type (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 50 μm. At this time, the measurement is performed after the toner particles are dispersed in an electrolyte aqueous solution (isoton aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more. As a measuring method, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant, and this is added to 100 to 150 ml of the electrolytic solution. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment for 1 minute with an ultrasonic disperser, and the particle size distribution of the particles is measured. The number of particles to be measured is 50,000. For the measured particle size distribution, a cumulative distribution is drawn from the smaller diameter side with respect to the divided particle size range (channel), and the particle size at which 50% is accumulated is defined as the volume average particle size.

(Function of large particle size external additive)
Here, the function of the large particle size external additive will be described.
When the developer is exposed to stress, such as being stirred for a long time in the developing device, there is a problem that the external additive is buried in the toner base particles and transfer performance is lowered. Conventionally, it has been known that the use of an external additive having a large particle size is effective for the problem of transfer performance degradation due to this stress. That is, the large particle size external additive has a function of maintaining the transfer performance.

  The large particle size external additive also exhibits a function of improving cleaning performance. FIG. 4 is a schematic diagram for explaining the reason why the function is exhibited. In the illustrated example, the developer 60 is a two-component developer including a toner 64 to which a large particle size external additive 62 is externally added and a carrier 66. As shown in FIG. 4, during development, the developing member 18 </ b> A supplies the toner 64 contained in the developer 60 from the inside of the developing device 18 to the surface of the photoreceptor 12.

  The large particle size external additive 62 is easily detached from the surface of the toner 64. The large particle size external additive 62 released from the toner 64 adheres to the photoreceptor 12. The large particle size external additive 62 adhering to the photoconductor 12 is supplied to the cleaning device 22 without being transferred. The large particle size external additive 62 supplied to the cleaning device 22 accumulates between the tip of the cleaning blade 22 </ b> A and the photoconductor 12. It is presumed that the posture of the cleaning blade 22A is stabilized and the cleaning performance is improved by collecting the large particle size external additive 62.

  Therefore, in the image forming area of the photoreceptor 12 where the amount of image formed is small, the amount of toner 64 supplied during development is small, and the amount of free large particle size external additive 62 attached is also small. Examples of the region where the amount of image formed is small include an image forming region at the end in the direction (axial direction) along the rotation axis of the photoconductor 12. When the amount of the attached large particle size external additive 62 decreases, the amount of the large particle size external additive 62 that accumulates at the tip of the cleaning blade 22A also decreases, and the cleaning blade 22A is damaged, resulting in local poor cleaning. Is generated.

  In this embodiment, the large particle size external additive 62 is supplied together with the toner 64 to a region where the amount of image formed is small, so that the large particle size external additive 62 is exposed to light at the tip of the cleaning blade 22A. A reduction in local cleaning performance is suppressed by allowing the body 12 to accumulate evenly in the axial direction.

<External additive supply processing>
Next, a procedure of “external additive supply processing” executed in the image forming apparatus 10 will be briefly described.
FIG. 5 is a flowchart showing an example of the processing procedure of the “external additive supply processing”. The control program for “external additive supply processing” is read from the ROM 36B and executed by the CPU 36A. The control program for “external additive supply processing” is started when an image formation instruction or the like related to unit processing is received from an external device via the communication unit 50. Note that information acquired during processing is stored in the RAM 36C, which is a work area, and used as appropriate.

  As shown in FIG. 5, first, in step 100, the image processing unit 42 performs predetermined image processing on the image information related to unit processing, and acquires image information to be output to the image forming unit 46. . The acquired image information is stored in the image memory 44. Next, in step 102, based on the image information after image processing, an integrated image amount is calculated for each block. Here, the “block” is a division unit of the image forming area on the photoconductor. For example, the image forming area is divided into a plurality of areas along the axial direction, such as 10 divisions. An integrated image amount is calculated for each of the divided regions (blocks).

  The integrated image amount is a value obtained by integrating the density value for each pixel of the image represented by the image information for each block. In the case of K single color (monochrome image), the density value for each pixel is represented by binary values of “0 (white)” and “1 (black)”. A pixel “1 (black)” is an ON pixel on which toner is placed. Accordingly, the integrated value of the density values for each pixel of the image represented by the image information is the same as the integrated pixel number of the image represented by the image information (the integrated value of the on pixels on which the toner is placed). In the present embodiment, a case where the accumulated image amount is “the accumulated pixel number” will be described.

  In step 104, a first block is selected from a plurality of blocks. Next, in step 106, it is determined whether the integrated image amount of the selected block is less than a threshold value. Here, the “threshold value for the accumulated image amount” is appropriately set according to the evaluation result of the cleaning performance and the rule of thumb. For example, the value may be 1% or less of the average image density per 1000 sheets. Here, “image density” is the value of the number of ON pixels per unit area.

  When the integrated image amount is less than the threshold value, the process proceeds to step 108, and the selected block is determined as the target block. Next, in step 110, it is determined whether there is a next block. If there is a next block, the process proceeds to step 112, and the next block is selected from the plurality of blocks. Then, returning to step 106, it is determined whether or not the integrated image amount of the selected block is less than a threshold value. On the other hand, if the accumulated image amount is greater than or equal to the threshold value in step 106, it is not a target block, so step 108 is skipped and the process proceeds to step 110.

  If the determination is made for all the blocks and there is no next block, the process proceeds to step 114, and the image information of the toner band corresponding to all the blocks determined as the target block is generated. For example, image information for forming a toner band corresponding to each block is stored in the image memory 44, and the toner band image corresponding to each of the plurality of target blocks is synthesized. Generate image information.

  Next, in step 116, exposure and development conditions are changed by controlling the exposure apparatus and the development apparatus so that the development contrast voltage is higher than the development contrast voltage during image formation. The development contrast voltage during image formation is set to be higher in the range of 20% or more and 60% or less. Here, the “development contrast voltage” is a potential difference between the development bias potential (VB) and the exposed portion potential (VL) from which charges have been removed by exposure. In order to widen the potential difference (VB−VL), the developing bias potential (VB) is changed in the developing device. Further, the exposure part potential (VL) may be changed by increasing the amount of exposure light in the exposure apparatus.

  Next, in step 118, an image of a toner band is formed in the non-image area of the photoconductor with the changed development contrast voltage applied. The liberated large particle size external additive becomes easy to move by increasing the development contrast voltage by 20% or more, and the adhesion amount of the large particle size external additive to the photoreceptor increases. Further, by setting the increase in the development contrast voltage to 60% or less, the large particle size external additive moves without carrier scattering (BCO). The increase in the development contrast voltage when forming the toner band may be 40% or less from the viewpoint of further suppressing BCO. Next, in step 120, the transfer device is driven and controlled so that the toner band is cleaned without being transferred. The toner band is cleaned, and a large particle size external additive is supplied to the tip of the cleaning blade.

  Next, in step 122, the exposure apparatus and the development apparatus are driven and controlled so that the development contrast voltage returns to the development contrast voltage at the time of image formation, the exposure / development conditions are changed, and the routine ends. In the present embodiment, an example in which “external additive supply processing” is executed before executing a normal image forming operation will be described. However, in order to supply a large particle size external additive, a toner band is applied to a non-image area. What is necessary is just to produce, and execution timing is not restricted before execution of a normal image formation operation. The “external additive supply process” may be executed after execution of a normal image forming operation.

  Here, “normal image forming operation” refers to, for example, a process of charging the surface of the photoconductor 12, a process of forming an electrostatic latent image on the surface of the charged photoconductor 12, and a developer containing toner. The step of developing the electrostatic latent image formed on the surface of the photoconductor 12 to form a toner image, the step of transferring the toner image formed on the surface of the photoconductor 12 to the recording medium 30A, and the step of After the transfer, an image forming sequence is performed in which the surface of the electrophotographic photosensitive member is exposed to remove electricity and the toner image transferred to the recording medium 30A is fixed, and an image is printed.

Next, the content of the “external additive supply process” will be specifically described.
FIGS. 6A and 6B are explanatory diagrams for explaining the contents of the “external additive supply process”. As shown in FIG. 6A, the image PG for one page includes an image portion Pg on which toner is placed and a non-image portion Png on which toner is not placed. In this example, the image PG is formed by rotating the photoconductor 12 three times. FIG. 6B is a development view of the surface of the photoreceptor 12 for three rotations. As shown in FIG. 6B, the surface of the photoreceptor 12 has an image forming region Rg where a latent image and a toner image are formed and a non-image forming region Rng where a latent image and a toner image are not formed. .

  The image forming region Rg is divided into a plurality of blocks B along the axial direction. In the illustrated example, the image forming region Rg is divided into eight blocks B1 to B8. The number of divisions is not limited by the illustrated example, and may be in the range of 1 to 20. Further, when it is 5 or more and 10 or less, there is an advantage that the balance between controllability and effect is improved.

  As can be seen from FIG. 6B, when the image PG is formed, the toner image G1 is formed in the first rotation and the toner image G2 is formed in the second rotation in the image forming region Rg of the photoreceptor 12. The toner image G3 is formed at the third rotation. Based on the image information corresponding to the toner images G1, G2, and G3, the image amount (number of on pixels) formed in each of the blocks B1 to B8 is integrated. There are almost no toner images formed in the blocks B1 and B8. The accumulated image amount is greatly reduced in the block B1 and the block B8 as compared to the other blocks.

  As described above, in a region where the amount of image to be formed is small, the large particle size external additive is not supplied to the tip of the cleaning blade, resulting in a local deterioration in cleaning performance. Therefore, the toner band TB1 is formed in the non-image forming region Rng adjacent to the block B1 in the process direction, and the toner band TB2 is formed in the non-image forming region Rng adjacent to the block B8 in the process direction. Toner bands TB1 and TB2 supply a large particle size external additive to the tip of the cleaning blade, thereby suppressing local deterioration in cleaning performance.

  The shape, image density, size, and formation frequency of the toner band may be set according to the required supply amount of the large particle size external additive. For example, a solid image having a width of about 10 mm may be used.

  Note that the configurations of the image forming apparatus and the program described in the above embodiments are merely examples, and it goes without saying that the configurations may be changed without departing from the gist of the present invention. For example, in the illustrated flowchart, some steps may be omitted, and other steps may be added. Moreover, you may replace the order of each step as needed.

  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%”.

[Production of developer]
(Preparation of developer 1)
-Production of toner particles-
-Preparation of polyester resin particle dispersion-
・ Ethylene glycol [Wako Pure Chemical Industries, Ltd.] 37 parts ・ Neopentyl glycol [Wako Pure Chemical Industries, Ltd.] 65 parts ・ 1,9 Nonanediol [Wako Pure Chemical Industries, Ltd.] 32 parts ・96 parts of terephthalic acid [manufactured by Wako Pure Chemical Industries, Ltd.] The above monomer was charged into a flask, and the temperature was raised to 200 ° C. over 1 hour. After confirming that the reaction system was stirred, dibutyltin oxide was added. 1.2 parts were added. Further, while distilling off the generated water, the temperature was increased from the same temperature to 240 ° C. over 6 hours, and the dehydration condensation reaction was continued at 240 ° C. for another 4 hours. The acid value was 9.4 mgKOH / g, and the weight average molecular weight. A polyester resin A having a glass transition temperature of 13,000 and 62 ° C. was obtained.

Subsequently, the polyester resin A was transferred in a molten state to Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) at a rate of 100 parts per minute. A 0.37% diluted aqueous ammonia solution obtained by diluting reagent ammonia water with ion-exchanged water is put into a separately prepared aqueous medium tank, and the polyester is heated at 120 ° C. with a heat exchanger at a rate of 0.1 liter per minute. The resin melt was transferred to the Cavitron along with the resin melt. The Cavitron is operated under the conditions of a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm ² .
A polyester resin particle dispersion was obtained in which resin particles having a volume average particle size of 160 nm, a solid content of 30%, a glass transition temperature of 62 ° C., and a weight average molecular weight Mw of 13,000 are dispersed.

-Preparation of colorant particle dispersion-
・ Cyan pigment [CIPigment Blue 15: 3, manufactured by Daiichi Seika Kogyo Co., Ltd.] 10 parts ・ Anionic surfactant [Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] 2 parts ・ Ion-exchanged water 80 parts The mixture was mixed and dispersed for 1 hour with a high-pressure impact type disperser [HJP30006, manufactured by Sugino Machine Co., Ltd.] to obtain a colorant particle dispersion having a volume average particle size of 180 nm and a solid content of 20%.

-Preparation of release agent particle dispersion-
Carnauba wax (RC-160, melting temperature 84 ° C., manufactured by Toa Kasei Co., Ltd.) 50 parts Anionic surfactant [Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] 2 parts ・ Ion-exchanged water 200 parts After heating to ℃ and mixing and dispersing with IKA's Ultra Turrax T50, dispersion with a pressure discharge type homogenizer gives a release agent particle dispersion with a volume average particle size of 200 nm and a solid content of 20%. It was.

-Production of toner particles-
・ Polyester resin particle dispersion 200 parts ・ Colorant particle dispersion 25 parts ・ Releasing agent particle dispersion: 30 parts ・ Polyaluminum chloride 0.4 part ・ Ion-exchanged water 100 parts The above ingredients are put into a stainless steel flask. After mixing and dispersing using IKA's ultra turrax, the flask was heated to 48 ° C. with stirring in an oil bath for heating. After maintaining at 48 ° C. for 30 minutes, 70 parts of the same polyester resin particle dispersion as above was added thereto.

Then, after adjusting the pH of the system to 8.0 using a 0.5 mol / L sodium hydroxide aqueous solution, the stainless steel flask was sealed, and the stirring shaft seal was magnetically sealed while stirring was continued. Heat to 90 ° C. and hold for 3 hours. After completion of the reaction, the temperature was lowered at a rate of 2 ° C./min, filtered, washed with ion exchange water, and then subjected to solid-liquid separation by Nutsche suction filtration. This was further redispersed with 3 L of ion exchange water at 30 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 6 times, and when the pH of the filtrate became 7.54 and the electric conductivity was 6.5 μS / cm, No. was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner particles.
When the volume average particle diameter D50v of the toner particles 1 is measured with a Coulter counter, it is 5.8 μm, and SF1 is 130.

-Production of Toner 1-
84.5 parts of methanol and 15.5 parts of 10% aqueous ammonia solution were mixed in a 3 L glass reaction vessel (with a diameter of 16 cm in the vessel) equipped with a stirrer, a dropping nozzle and a thermometer. The mixture was adjusted to 25 ° C. The ammonia concentration at this time was 0.74 mol / L. After the pre-mixed liquid reached 25 ° C., tetramethoxysilane (TMOS) was added from two dropping nozzles to the pre-mixed liquid in a total of 1.10 parts / min, and 6.0% ammonia aqueous solution was pre-mixed. The suspension was adjusted to 0.55 part / min with respect to the same time, and dripping was started at the same time, and dripping was continued for 20 minutes to obtain a suspension of silica particles 1. The dropping positions of the two dropping nozzles were separated by a distance of 15 cm. The volume average particle diameter of the silica particles 1 at this time was 130 nm.

  Thereafter, 84.5 parts of the same amount as methanol was distilled off by heating distillation, and then 84.5 parts of deionized water (DIW) was added in the same amount, followed by drying with a freeze dryer to obtain hydrophilic silica particles. 1 was obtained. Further, after adding 50 parts of trimethylsilane to the hydrophilic silica particles 1, the temperature was raised to 150 ° C. with stirring, followed by heating reaction for 2 hours to obtain hydrophobic silica particles 1.

  To 100 parts of the toner particles, 2 parts of hydrophobic silica particles 1 (volume average particle diameter (D50v) 130 nm) as an external additive were added and mixed with a Henschel mixer at 2000 rpm for 3 minutes to obtain toner 1.

-Production of Developer 1-
The obtained toner and carrier were put in a V blender at a ratio of toner: carrier = 5: 95 (mass ratio) and stirred for 20 minutes to obtain each developer.

In addition, the carrier produced as follows was used.
Ferrite particles (volume average particle diameter: 50 μm) 100 parts toluene 14 parts styrene-methyl methacrylate copolymer 2 parts (component ratio: 90/10, Mw = 80000)
Carbon black (R330: manufactured by Cabot Corporation) 0.2 part First, the above components excluding ferrite particles are stirred with a stirrer for 10 minutes to prepare a dispersed coating solution, and then the coating solution and ferrite particles are combined. After putting in a vacuum degassing type kneader and stirring at 60 ° C. for 30 minutes, the carrier was obtained by further depressurizing while heating and degassing and drying.

(Preparation of silica particles 1)
According to Table 1, the dropping time of the tetramethoxysilane and the aqueous ammonia solution with respect to the pre-mixed liquid was adjusted to obtain silica particles having different volume average particle diameters (D50v). The correspondence with the examples and comparative examples (developers) shown in Table 2 is also shown.

(Production of developers 2 to 5)
According to Table 2, Developers 2 to 5 were produced in the same manner as Developer 1 except that the volume average particle diameter of silica particles as an external additive was changed. In Table 2, D50v represents “volume average particle diameter”.

[Examples 1 to 3, Comparative Examples 1 to 5]
“700 Digital Color Press” manufactured by Fuji Xerox Co., Ltd. was used as an image forming apparatus. This image forming apparatus has the same configuration as that of the image forming apparatus shown in FIG. 1, and includes a charging voltage applied to the charging member 14, an exposure light amount by the latent image forming apparatus 16, a bias voltage applied to the developing member 18A, and a transfer member 20. The bias voltage applied to is modified so that it can be varied.

  Using the developer according to Table 2, the image forming apparatus described above output 10,000 evaluation images shown in FIG. 7 on A4 size paper in an ambient environment of 28 ° C. and 85 RH%. In the example illustrated in FIG. 7, the evaluation image is a two-block case image including a block 1 having an image density of 0.5% and a block 2 having an image density of 10%. In the case of this image, local cleaning failure occurs in the area of block 1.

Prior to image formation, an “external additive supply process” for forming a toner band with a development contrast voltage according to Table 2 was executed. Table 2 shows the charging potential (VH), the developing bias potential (VB), the exposure portion potential (VL), the developing contrast voltage (V _cont = VB−VL), and the ratio (V _cont ratio) to the standard developing contrast voltage. . The unit is V (volt). As a reference example, standard potentials (standard development conditions) at the time of image formation are also shown. For example, “V _cont ratio = 1.4” indicates that the development contrast voltage is 40% higher than the standard development contrast voltage at the time of image formation. And the following evaluation was performed.

-Evaluation of cleaning performance-
The cleaning performance was evaluated by visual observation after transferring the remaining toner on the photosensitive member after being cleaned by the cleaning blade to the tape after running 10,000 sheets. The evaluation criteria are as follows. The evaluation results are shown in Table 2 below.
○: Not generated Δ: Minor cleaning failure occurred (remaining toner is slightly observed)
X: Cleaning failure occurred (remaining toner is clearly observed)

-Transfer maintenance-
Evaluation of transfer maintenance was performed by primary transfer efficiency. After the above 10,000 sheets have been run, image formation is performed, the toner on the photoconductor before the primary transfer of the toner image is taken, its mass M1 is measured, and the toner on the photoconductor after the primary transfer is taken separately. The mass M2 was measured, and the primary transfer efficiency was determined from the measured values of both masses according to the following formula. The evaluation results are shown in Table 2 below.
Primary transfer efficiency (%) = {(M1-M2) / M1} × 100

  From the above results, it can be seen that in this embodiment, the transfer performance is maintained and the local degradation of the cleaning performance is suppressed.

  On the other hand, if the volume average particle size of the large particle size external additive is too small, the transfer performance deteriorates (Comparative Example 1). If the volume average particle size of the large particle size external additive is too large, photoconductor filming occurs (Comparative Example 2). Further, when the toner band is formed and the large particle size external additive is not replenished, the cleaning performance is deteriorated (Comparative Example 3). Further, if the development contrast voltage at the time of forming the toner band is too low, the cleaning performance deteriorates (Comparative Example 4). On the other hand, if the development contrast voltage at the time of toner band formation is too high, white spots are generated due to carrier scattering (BCO), and the photoconductor is damaged (Comparative Example 5).

DESCRIPTION OF SYMBOLS 10 Image forming device 12 Photoconductor 14 Charging device 16 Latent image forming device 18 Developing device 20 Transfer member 22 Cleaning device 22A Cleaning blade 24 Neutralizing device 26 Fixing device 27 Drive unit 30A Recording medium 30 Power supply 31 Transfer device 32A Transfer area 32 Power supply 34 Conveyance path 36 Control unit 40 Operation display unit 42 Image processing unit 44 Image memory 46 Image forming unit 48 Storage unit 50 Communication unit 52 External device 60 Developer 62 Large particle size external additive 64 Toner 66 Carriers B1 to B8 Blocks G1 to G3 Toner image PG Page image Pg Image part Png Non-image part Rg Image formation area Rng Non-image formation area TB1, TB2 Toner band

Claims (5)

Latent image forming means for exposing the surface of the charged image carrier to form an electrostatic latent image;
A storage unit that stores a developer containing toner to which inorganic particles having a volume average particle size of 80 nm or more and 180 nm or less are externally added, and a voltage application unit that applies a development contrast voltage between the image carrier, Toner image forming means for developing the electrostatic latent image with the developer in a state where the development contrast voltage is applied and forming a toner image on the image carrier;
Transfer means for transferring the toner image to a transfer object;
Cleaning means for cleaning the image carrier after transfer in contact with the image carrier;
A large development contrast voltage is applied to a non-image area corresponding to an image formation area whose accumulated image amount obtained based on the image information is less than a threshold in a range of 20% to 60% of the development contrast voltage at the time of image formation. Control means for controlling each of the latent image forming means and the toner image forming means so as to form a toner image .
An image forming apparatus. The control means divides the image forming area on the surface of the image carrier into a plurality of blocks along the rotation axis direction of the image carrier, acquires an accumulated image amount for each of the plurality of blocks, and the accumulated image amount is less than a threshold value The image forming apparatus according to claim 1 , wherein control is performed so as to form a toner image in a non-image area corresponding to the block. The image forming apparatus according to claim 1 , wherein the control unit performs control so that a toner image is formed in a non-image area adjacent to the image forming area in which the integrated image amount is less than a threshold in the process direction. 4. The image forming apparatus according to claim 1 , wherein the control unit performs control to change the development bias voltage to increase the development contrast voltage. 5. Latent image forming means for exposing the surface of the charged image carrier to form an electrostatic latent image;
A storage unit that stores a developer containing toner to which inorganic particles having a volume average particle size of 80 nm or more and 180 nm or less are externally added, and a voltage application unit that applies a development contrast voltage between the image carrier, Toner image forming means for developing the electrostatic latent image with the developer in a state where the development contrast voltage is applied and forming a toner image on the image carrier;
Transfer means for transferring the toner image to a transfer object;
Cleaning means for cleaning the image carrier after transfer in contact with the image carrier;
A program for controlling an image forming apparatus comprising:
Computer
A large development contrast voltage is applied to a non-image area corresponding to an image formation area whose accumulated image amount obtained based on the image information is less than a threshold in a range of 20% to 60% of the development contrast voltage at the time of image formation. A program that functions as means for controlling each of the latent image forming means and the toner image forming means so as to form a toner image.

Images