JP2017054094A - Image forming method and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method for suppressing optical fatigue of a surface of a photoreceptor with electricity eliminating light as weak as possible even when the thickness and surface potential of the photoreceptor are changed over time and due to environment, enabling sufficient elimination of electricity on the surface of the photoreceptor, and achieving stable image quality without afterimage.SOLUTION: Since the charging potential Vd of a photoreceptor and the thickness of the photoreceptor vary over time and due to environment, light for eliminating electricity on the photoreceptor is controlled with arbitrary values as thresholds for the charging potential and thickness. Since afterimage is not likely to occur when the charging potential of the photoreceptor is high, the electricity eliminating light is controlled to be turned off; since afterimage is likely to occur when the charging potential of the photoreceptor is low, the electricity eliminating light is controlled to be turned on. Thus, electricity can be eliminated to such a level that afterimage does not occur with the minimum required light intensity without irradiating the photoreceptor with excessive electricity eliminating light, and thereby suppressing optical fatigue of the photoreceptor.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an image forming method that involves photo-staticizing a photoreceptor, and an image forming apparatus that forms an image using this method.

  An image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system uses an electrostatic latent image formed on an image carrier such as a photoconductor as a toner image by a developing device. Thereafter, a primary transfer voltage is applied to the primary transfer means to temporarily transfer the toner image from the image carrier to an intermediate transfer member such as an intermediate transfer belt. Further, after that, a secondary transfer voltage is applied to a secondary transfer portion composed of an intermediate transfer body, a secondary transfer roller and an opposing roller facing each other with the toner image on the intermediate transfer body sandwiched therebetween, Secondary transfer to a recording medium such as transfer paper. As described above, a configuration is known in which fixing is performed on a recording medium by applying pressure and heating with a fixing device.

  In this type of electrophotographic image forming apparatus, a user's demand in recent market trends is that good toner image transfer is possible while maintaining stable image quality under any conditions. It has become. For this reason, a stable image is provided by detecting the environment over time, controlling the charging potential of the photoconductor accordingly, and controlling the toner adhesion amount on the photoconductor. However, when the charging potential Vd of the photosensitive member is low, there is a problem that an afterimage is generated due to the influence of the transfer bias. As a countermeasure, it is already known that after the primary transfer, a photostatic device is installed and the photoconductor is photostatically reset to reset the surface potential and then recharged. In the present specification, the afterimage is due to the effect of the transfer bias, and the surface potential on the photosensitive member of the exposure pattern on the first round of the photosensitive member remains even at the time of recharging after the second round of the photosensitive member. An abnormal image in which an eye exposure pattern history appears as an image.

  Patent Document 1 discloses that the amount of charge removed on the photoreceptor is changed according to the magnitude of the transfer bias in order to suppress the promotion of light fatigue on the photoreceptor surface due to the light removal. Although the present invention certainly changes the amount of charge removed on the photoconductor, the surface of the photoconductor is sufficiently neutralized even when the photoconductor film thickness and photoconductor surface potential change depending on the environment over time. I try to irradiate strong static elimination light as much as possible. Therefore, the problem that light fatigue on the surface of the photoreceptor is promoted cannot be solved.

  That is, in the conventional image forming method, in order to ensure a stable image with no afterimage generation, for example, even when the photosensitive member film thickness and the photosensitive member surface potential change depending on the environment over time. In order to sufficiently remove the surface of the photosensitive member, a sufficient amount of strong neutralizing light is constantly emitted. However, since the surface of the photoconductor deteriorates as it receives light, there is a problem in that light fatigue on the surface of the photoconductor is promoted when such strong neutralizing light is irradiated.

  Therefore, the present invention can suppress photofatigue on the surface of the photoconductor with the weakest neutralizing light even when the photoconductor film thickness and surface potential change depending on the environment over time, and can sufficiently eliminate the photoconductor surface, thereby eliminating afterimages. An object of the present invention is to provide an image forming method that realizes stable image quality.

  The image forming method according to the present invention includes a photoconductor that carries a toner image, a charging device that charges the photoconductor, a writing device that forms an electrostatic latent image on the photoconductor, and a static on the photoconductor. An image forming apparatus comprising: a developing device that visualizes an electrostatic latent image with toner; a transfer device that primarily transfers the visualized toner image; and a static elimination device that is provided separately from the writing device and that neutralizes the photoconductor The image forming method according to claim 1, further comprising: a current detection unit configured to detect a charging current, wherein the charging device is a charging roller that contacts the photoconductor and applies the voltage to charge the photoconductor; The film thickness X of the charge transport layer of the photoconductor is estimated from the relationship between the voltage and the current value of the charging current detected by the current detection means, and according to the estimated value of the film thickness X, the photostatic device Varying the static elimination light intensity control method In the image forming method, when the film thickness X is not less than an arbitrary value α and a predetermined charging potential Vd1 of the photoconductor is detected, a first light quantity variable control is executed, and the film thickness X is less than α. In addition, when it is detected that the absolute value of the charging potential of the photoconductor is a charging potential Vd2 lower than the predetermined charging potential Vd1, a second light amount variable control content different from the first light amount variable control. Control is executed.

  According to the present invention, it is possible to provide an image forming method that prevents deterioration of a photoreceptor due to light fatigue and realizes stable image quality over a long period of time.

1 is a diagram illustrating a schematic configuration of an example of a printer serving as an image forming apparatus, which is an implementation target of the present invention. FIG. FIG. 2 is a diagram illustrating a schematic configuration of an image forming unit included in the image forming apparatus. It is a figure which shows the layer structure of a photoreceptor. FIG. 5 is a diagram illustrating a positional relationship between a gradation pattern of each color and an optical sensor of each color on an intermediate transfer belt. FIG. 6 is a diagram illustrating a developing potential at a low / high charging potential of a photoreceptor. FIG. 6 is a diagram illustrating a configuration around a photoconductor and a time-series change in the surface potential of the photoconductor. It is a figure which shows the relationship graph of a photoreceptor film thickness and a voltage-current, and is a figure which shows the relationship between the alternating voltage Vpp when an electric current is 0.8 mA in detail, and the film thickness of a charge transport layer. It is a figure which shows the relationship (photoconductor film thickness 37 micrometers) of light quantity and (DELTA) Vd. It is a figure which shows the relationship (photoconductor film thickness 27 micrometers) of light quantity and (DELTA) Vd. It is a figure which shows the control flowchart 1. FIG. It is a figure which shows the light quantity and photoconductor surface potential (target electric potential = -440V) of an optical static elimination apparatus. FIG. 3 is a diagram showing a control flowchart 2. FIG. 5 is a diagram showing a control flowchart 3.

An embodiment of the present invention will be described. The present invention has the following characteristics when performing photostatic charge on a photoreceptor.
In short, the charging potential Vd of the photoconductor and the film thickness of the photoconductor vary depending on the time and environment, but the photoconductor discharge light is controlled using an arbitrary value as a threshold value in each case. Since the afterimage is unlikely to occur when the photosensitive member is at a high charge potential, the charge removal light is turned off, and when the photoreceptor is at a low charge potential, an afterimage is likely to be generated, so that the charge removal light is turned on. As a result, it is possible to eliminate the charge with a minimum amount of light without irradiating the photosensitive member with excessive charge removal light, and to suppress photoconductor light fatigue. In addition, the photosensitive member film thickness is estimated, and the Vd threshold value for controlling the photosensitive member charge removal light is changed in accordance with the value (the film thickness is large and an afterimage is likely to occur). By doing so, the photosensitive member can be discharged with a minimum amount of light with higher accuracy, and the photoconductor light fatigue can be more effectively suppressed.

  Further, since the bias applied to the charging roller is different from the photoreceptor surface potential, the bias applied to the charging roller is applied with a correction amount so that the target photoreceptor surface potential is obtained. However, when this is done, when the photosensitive member neutralizing light is turned on, the photosensitive member charging potential becomes smaller than the target value due to leakage light. In order to prevent this, when the photosensitive member charge-off light is turned on, the correction amount of the charge application bias is made larger than when the light is turned off.

The features of the present invention will be described below with reference to the drawings. First, an example of a printer as an image forming apparatus that is an object of the present invention will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer 100 that is an image forming apparatus. The printer 100 forms a full-color image, and mainly includes an image forming unit 120, an intermediate transfer device, and a paper feeding unit 130. In the following description, the subscripts Y, C, M, and K indicate members for yellow, cyan, magenta, and black, respectively.

  The image forming unit 120 is provided with a yellow toner process cartridge 121Y, a cyan toner process cartridge 121C, a magenta toner process cartridge 121M, and a black toner process cartridge 121K in order from the left side in the drawing. These process cartridges 121 (Y, C, M, K) are arranged in a substantially horizontal direction.

  The intermediate transfer device 160 includes a primary transfer roller 161 (Y, C, M, K), an endless intermediate transfer belt 162 that is an intermediate transfer member stretched around a plurality of support rollers, a secondary transfer roller 165, Consists mainly of. The intermediate transfer belt 162 is a drum-shaped photoconductor 10 as a latent image carrier that is an image carrier that moves on the surface of each process cartridge 121 (Y, C, M, K). It is arranged along the surface movement direction of (Y, C, M, K). The intermediate transfer belt 162 moves on the surface in synchronism with the surface movement of the photoreceptor 10 (Y, C, M, K). Each primary transfer roller 161 (Y, C, M, K) is disposed on the inner peripheral surface side so as to come into contact with the photoreceptor via the intermediate transfer belt 162. The outer peripheral surface (surface) positioned below the intermediate transfer belt 162 by the primary transfer roller 161 (Y, C, M, K) is the outer peripheral surface (surface) of each photoconductor 10 (Y, C, M, K). ).

  The configuration and operation of forming a toner image on each photoconductor 10 (Y, C, M, K) and transferring the toner image to the intermediate transfer belt 162 is the same as each process cartridge 121 (Y, C, M, K). Is substantially the same. However, the primary transfer roller 161 (Y, C, M) corresponding to the three color process cartridges 121 (Y, C, M) is provided with a swinging mechanism (not shown) that swings them up and down. . The swing mechanism operates so that the intermediate transfer belt 162 does not contact the photoconductor 10 (Y, C, M) when a color image is not formed.

  An intermediate transfer device that is an intermediate transfer unit is configured to be detachable from the main body of the printer 100. Specifically, the front cover (not shown) on the front side of the sheet in FIG. 1 covering the image forming unit 120 of the printer 100 is opened, and the intermediate transfer device 160 is slid from the rear side to the front side in FIG. By doing so, the intermediate transfer device 160 can be removed from the main body of the printer 100. When the intermediate transfer device 160 is attached to the main body of the printer 100, an operation opposite to the removal operation may be performed. In addition, an intermediate transfer belt cleaning device 167 is provided for removing deposits adhered to the intermediate transfer belt 162 such as residual toner after the secondary transfer. The first arrangement is downstream of the secondary transfer roller 165 in the intermediate transfer belt 162 in the surface movement direction and upstream of the process cartridge 121Y. The intermediate transfer belt cleaning device 167 is configured to be detachable from the main body of the printer 100 as an intermediate transfer device while being supported integrally with the intermediate transfer belt 162.

  Above the intermediate transfer device, toner cartridges 159 (Y, C, M, K) corresponding to the process cartridges 121 (Y, C, M, K) are arranged in a substantially horizontal direction. Further, below the process cartridge 121 (Y, C, M, K), the surface of the charged photoreceptor 10 (Y, C, M, K) is irradiated with laser light to form an electrostatic latent image. An exposure device 140 is arranged. A paper feeding unit 130 is disposed below the exposure device 140. The paper feed unit 130 is provided with a paper feed cassette 131 and a paper feed roller 132 for storing transfer paper as a recording material. These feed the transfer paper at a predetermined timing toward the secondary transfer nip portion between the intermediate transfer belt 162 and the secondary transfer roller 165 via the registration roller pair 133. A fixing device 90 is disposed downstream of the secondary transfer nip portion in the transfer paper conveyance direction, and a discharge roller and a discharged transfer paper are placed downstream of the fixing device 90 in the transfer paper conveyance direction. A paper discharge storage unit is provided for storage.

FIG. 2 is a schematic configuration diagram illustrating a process cartridge 121 provided in the printer 100.
Here, since the configuration of each process cartridge 121 is almost the same, in the following description, the subscripts Y, C, M, and K for color coding are omitted, and the configuration and operation of the process cartridge 121 will be described. The process cartridge 121 includes a photoconductor 10, a cleaning device 30 disposed around the photoconductor 10, a charging device 40, a developing device 50, and a photostatic device 60.

  The charging device 40 is mainly composed of at least one charging roller 41 facing the photoconductor 10 and at least one charging roller cleaner 42 rotating in contact with the charging roller 41. The developing unit (developing device) 50 supplies toner to the surface of the photoreceptor 10 to make the electrostatic latent image visible, and a developer carrying member that carries the developer (carrier, toner) on the surface. The developing roller 51 is provided. The developing device 50 includes the developing roller 51, an agitation screw 52 that conveys the developer accommodated in the developer accommodating portion while agitating, and a supply screw 53 that conveys the agitated developer while supplying the developer to the developing roller 51. And is mainly composed of.

  The four process cartridges 121 having the above-described configuration can be detached and replaced independently by a service person or a user. Further, with respect to the process cartridge 121 removed from the printer 100, the photoconductor 10, the charging device 40, the developing device 50, and the cleaning device 1 can be replaced with new devices. The process cartridge 121 may include a waste toner tank that collects the transfer residual toner collected by the cleaning device 1. In this case, if the configuration is such that the waste toner tank can be detached and replaced independently in the process cartridge 121, the convenience is improved.

Next, the operation of the printer 100 will be described with reference to FIGS.
The printer 100 receives a print command from an external device such as an operation panel (not shown) or a personal computer. First, the photoconductor 10 is rotated in the moving direction (rotation direction) indicated by the arrow A in FIG. 2, and the surface of the photoconductor 10 is uniformly charged to a predetermined polarity by the charging roller 41 of the charging device 40. The exposure device 140 irradiates, for example, laser beam light, which is light-modulated in accordance with the input color image data, on the surface of each photoconductor 10 with respect to the surface of each photoconductor 10. The electrostatic latent image is formed. Each electrostatic latent image is supplied with a developer of each color from the developing roller 51 of the developing device 50 of each color, and the electrostatic latent image of each color is developed with the developer of each color to form a toner image corresponding to each color. To visualize it.

  Next, a primary transfer electric field is formed between the photoconductor 10 and the primary transfer roller 161 with the intermediate transfer belt 162 interposed therebetween by applying a transfer voltage having a polarity opposite to that of the toner to the primary transfer roller 161. At the same time, a primary transfer nip is formed by weakly pressing the intermediate transfer belt 162 with the primary transfer roller 161. By these actions, the toner image on each photoconductor 10 is efficiently primary-transferred onto the intermediate transfer belt 162. On the intermediate transfer belt 162, the toner images of the respective colors formed on the respective photoconductors 10 are transferred so as to overlap each other, thereby forming a laminated toner image.

  For the laminated toner image primarily transferred onto the intermediate transfer belt 162, the transfer paper stored in the paper feed cassette 131 is fed at a predetermined timing via the paper feed roller 132, the resist roller pair 133, and the like. Is done. A secondary transfer electric field is formed between the intermediate transfer belt 162 and the secondary transfer roller 165 across the transfer paper by applying a transfer voltage having a polarity opposite to that of the toner to the secondary transfer roller 165. The laminated toner image is transferred to the surface. The transfer paper onto which the laminated toner image has been transferred is sent to the fixing device 90 and fixed by heat and pressure. The transfer paper on which the toner image is fixed is discharged and placed in the paper discharge storage unit 135 by the paper discharge roller. On the other hand, the transfer residual toner remaining on each photoconductor 10 after the primary transfer is scraped off and removed by the cleaning blade 5 of each cleaning device 1.

<Embodiment 1>
Next, the layer structure of the photoreceptor 10 applicable to the embodiment of the present invention will be described in detail.
FIG. 3 is an explanatory diagram of the layer structure of the photoreceptor 10 provided in the printer 100. FIG. 3A is a diagram in which a photosensitive layer 92 in which a charge generation layer 92a and a charge transport layer 92b are stacked on a conductive support 91 is provided. It is an example. FIG. 3B shows an example in which an undercoat layer 94 is provided on a conductive support 91, and a photosensitive layer 92 in which a charge generation layer 92a and a charge transport layer 92b are stacked is provided.

  The photoreceptor 10 is configured to have a photosensitive layer 92 in which at least a charge generation layer 92a and a charge transport layer 92b are laminated on a conductive support 91, and the outermost layer may be the charge transport layer 92b. May be combined arbitrarily.

  As the conductive support 91, a conductive support having a volume resistance of 10 10 Ω · cm or less can be used. For example, a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, or platinum, or a metal oxide such as tin oxide or indium oxide is coated on a film or cylindrical plastic or paper by vapor deposition or sputtering. Things can be used. Alternatively, a plate made of aluminum, aluminum alloy, nickel, stainless steel, or the like, and a tube subjected to surface treatment such as cutting, superfinishing, polishing, or the like after forming the raw tube by a method such as extrusion or drawing can be used. The sign “^” shown above indicates a power (or a power), and the number immediately after that is an exponent. The same applies hereinafter.

  The charge generation layer 92a shown in FIG. 3 is a layer mainly composed of a charge generation material. A known charge generation material can be used for the charge generation layer 92a, and representative examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycycles. Examples thereof include compounds and squaric acid dyes. Other phthalocyanine pigments, naphthalocyanine pigments, azulenium salt dyes, and the like are also used. These charge generation materials may be used alone or in combination of two or more.

  In addition, the charge generation layer 92a is prepared by dispersing the charge generation material as described above together with a binder resin, if necessary, in a predetermined solvent using a ball mill, attritor, sand mill, ultrasonic wave, or the like. Then, it can be formed by applying it on the conductive support 91 and drying it.

  Examples of the binder resin used for the charge generation layer 92a as needed include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, and polyvinyl ketone. Further, polystyrene, polysulfone, poly-N-vinylcarbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, and polyamide are also included. Moreover, polyvinyl pyridine, a cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, etc. are also mentioned. The amount of the binder resin is 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generation material.

  Here, examples of the predetermined solvent used when forming the charge generation layer 92a include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, and methyl acetate. Further, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like can be mentioned, and ketone solvents, ester solvents, and ether solvents can be particularly preferably used. Moreover, as a coating method of a coating liquid, methods such as dip coating, spray coating, beat coating, nozzle coating, spinner coating, and ring coating can be used. The film thickness of the charge generation layer 92a is preferably about 0.01 to 5 μm, more preferably 0.1 to 2 μm.

  The charge transport layer 92b can be formed by dissolving or dispersing a charge transport material and a binder resin in a predetermined solvent, and applying and drying the solution on the charge generation layer 92a. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.

  Here, the charge transport material includes a hole transport material and an electron transport material. Examples of the charge transport material include electron acceptors such as chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone and 2,4,5,7-tetranitro-9-fluorenone. Substances. In addition, electrons such as 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one Examples include receptive substances. Moreover, electron-accepting substances such as 1,3,7-trinitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives are also included.

  Examples of the hole transporting material include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, and polyvinylphenanthrene. . Moreover, materials, such as polysilane, an oxazole derivative, an oxadiazole derivative, an imidazole derivative, a monoarylamine derivative, a diarylamine derivative, a triarylamine derivative, a stilbene derivative, an α-phenylstilbene derivative, are also included. In addition, materials such as a benzidine derivative, a diarylmethane derivative, a triarylmethane derivative, a 9-styrylanthracene derivative, a pyrazoline derivative, a divinylbenzene derivative, a hydrazone derivative, an indene derivative, a butadiene derivative, and a pyrene derivative are also included. Moreover, other well-known materials, such as a bis stilbene derivative and an enamine derivative, are mentioned. These charge transport materials may be used alone or in combination of two or more.

  As the binder resin, thermoplasticity such as polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, etc. A thermosetting resin is mentioned. Moreover, thermoplastic or thermosetting resins such as polyvinyl acetate, polyvinylidene chloride, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, and polyvinyl toluene are also included. In addition, thermoplastic or thermosetting resins such as poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine fat, urethane resin, phenol resin, alkyd resin, and the like are also included. The amount of the charge transport material is 20 to 300 parts by weight, preferably 40 to 150 parts by weight with respect to 100 parts by weight of the binder resin.

  Here, examples of the predetermined solvent used when forming the charge transport layer 92b include tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, and acetone. In the case of the photoreceptor 10 of this embodiment, a plasticizer or a leveling agent may be added to the charge transport layer 92b.

  As the plasticizer used for forming the charge transport layer 92b, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is 0 with respect to the binder resin. About 30% by weight is preferable. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers having a perfluoroalkyl group in the side chain, or oligomers can be used, and the amount used is 0 with respect to the binder resin. ˜1% by weight is preferred.

  In the photoreceptor 10 of this embodiment, a configuration in which an undercoat layer 94 is provided between the conductive support 91 and the photosensitive layer 92 (charge generation layer 92a) as shown in FIG. 3B will be described. The undercoat layer 94 generally contains a resin as a main component. However, considering that the photosensitive layer 92 is applied on the resin with a solvent, the resin has a solvent resistance against a general organic solvent. It is desirable for the resin to be high. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, and alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon. Moreover, the curable resin etc. which form three-dimensional network structures, such as a polyurethane, a melamine resin, a phenol resin, an alkyd-melamine resin, and an epoxy resin, are also mentioned.

  In addition, a metal oxide fine powder pigment exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like is added to the undercoat layer 94 in order to prevent moire and reduce residual potential. Also good. The undercoat layer 94 can be formed using a predetermined solvent and coating method like the photosensitive layer 92 described above.

  Furthermore, in this embodiment, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer 94. In addition, the undercoat layer 94 is made by vacuuming Al2O3 provided by anodic oxidation, organic matter such as polyparasilylene (parylene), or inorganic matter such as SiO2, SnO2, TiO2, In2O3 / SnO2 (ITO), CeO2. Those provided by the thin film preparation method can also be used favorably. In addition, known ones can also be used. The thickness of the undercoat layer 94 is preferably 0 to 5 μm.

  Here, the photoreceptor 10 is used repeatedly over a long period of time, and is used while the charge transport layer 92b on the outermost layer is worn over time. When charging the surface of the photosensitive member with the charging member of the charging device 40, ozone and NOX gas may be generated and adhere to the surface of the photosensitive member 10, and if these deposits are present, image flow may occur. This image flow can be prevented by wearing the lens.

  If the charge transport layer is thin, the margin for carrier adhesion decreases, so it is desirable to use the charge transport layer at 20 μm or more. Since the charge transport layer is used while being worn, the wear life of the photosensitive member can be increased as the initial film thickness is thicker. However, if it is thicker, γ linearity and afterimage may be deteriorated. In this embodiment, a three-layer photoconductor is taken as an example, but the present invention is not limited to this, and the same can be said for a four-layer photoconductor.

Hereinafter, the photoconductor light neutralization control, which is a feature of the present invention, will be described.
First, the toner density control and an abnormal image generation mechanism called an afterimage will be described.
In this image forming apparatus, image density control for optimizing the image density of each color is executed when the power is turned on or every time a predetermined number of prints are performed.

  In the image density control, first, as shown in FIG. 4, gradation patterns Sk, Sm, Sc, Sy of each color are automatically formed at positions facing the optical sensors 151Y, C, M, K on the intermediate transfer belt. . The gradation pattern of each color is composed of 10 toner patches having an area of 2 [cm] × 2 [cm] having different image densities. The charging potentials of the photoconductors Y, M, C, and K when the gradation patterns Sk, Sm, Sc, and Sy of each color are created are different from the uniform drum charging potential in the printing process, and the values are gradually increased. To do. Then, while forming a plurality of patch electrostatic latent images for forming a gradation pattern image on the photoconductors Y, M, C, and K by scanning with laser light, they are used for Y, M, C, and K, respectively. Develop with a developing device. During this development, the value of the developing bias applied to the Y, M, C, and K developing rollers is gradually increased. By such development, gradation pattern images of Y, M, C, and K are formed on the photoreceptors Y, M, C, and K. These are primarily transferred so as to be arranged at a predetermined interval in the main scanning direction of the intermediate transfer belt. At this time, the toner adhesion amount of the toner patch in the gradation pattern of each color is 0.1 [mg / cm ^ 2] at the minimum and 0.55 [mg / cm ^ 2] at the maximum, and the toner Q / When the d distribution is measured, it is almost aligned with the normal charging polarity.

  Each toner pattern (Sk, Sm, Sc, Sy) formed on the intermediate transfer belt passes through a position facing the optical sensor 151 as the intermediate transfer belt moves endlessly. At this time, the optical sensor 151 receives an amount of light corresponding to the toner adhesion amount per unit area with respect to the toner patch of each gradation pattern.

  Next, the adhesion amount of each color toner pattern in each toner patch is calculated from the output voltage of the optical sensor 151 when each color toner patch is detected and the adhesion amount conversion algorithm, and the image forming condition is based on the calculated adhesion amount. Adjust. Specifically, a linear graph is shown based on the result of detecting the toner adhesion amount on the toner patch and the development potential (difference between the development bias Vb and the photoreceptor exposure potential VL) when each toner patch is imaged. The function (y = ax + b) is calculated by regression analysis. Then, an appropriate development bias value is calculated by substituting the target value of the image density into this function, and the development bias values for Y, M, C, and K are specified.

  In the memory, an image forming condition data table in which several tens of development bias values and appropriate charging potentials of the corresponding photosensitive members are associated in advance is stored. For each of the process units Y, M, C, and K, a developing bias value closest to the specified developing bias value is selected from the image forming condition table, and the charging potential of the photoconductor associated therewith is specified. Generally, when the toner is in the initial state or the environment is low temperature and low humidity, the charge amount of the toner is high, and in order to develop an arbitrary amount of toner on the photoreceptor, it is necessary to increase the development potential. There is. Since the difference between the developing bias Vb and the charging potential Vd of the photosensitive member is a constant value, the charging potential Vd of the photosensitive member increases as a result. On the other hand, the toner charge amount tends to be low over time, and the toner charge amount is low when the environment is high temperature and high humidity. Therefore, when developing an arbitrary amount of toner on the photoreceptor, the development potential is small, that is, The charging potential Vd of the photosensitive member becomes small (see FIG. 5).

  In addition, the bias applied to the charging roller and the photoreceptor surface potential Vd do not always match, and the difference differs depending on the system. Therefore, in order to obtain the target photoreceptor surface potential, a bias obtained by adding a correction amount P to the charging application bias is applied to the charging roller.

FIG. 6 shows changes in the photoreceptor surface potential in time series.
In step 1, the photosensitive member is charged by the charging unit, and the surface potential becomes Vd.
In step 2, the exposure unit exposes the photosensitive member by the exposure device, and the surface potential becomes VL.
In step 3, a transfer bias is applied at the transfer portion, and the surface potential further shifts in the + potential direction.
In step 4, the photosensitive member is recharged by the charging unit.
In step 4, recharging is performed. However, if the photosensitive member surface potential is positively charged in step 3 due to the influence of the transfer bias, at the time of recharging, charging tends to be lower than the target surface potential Vd. Then, in the second round of the photoconductor, the surface potential of the photoconductor is different between the exposed portion and the non-exposed portion in the first round of the photoconductor, so that an image density difference occurs and appears as an afterimage. In particular, when the surface potential is low Vd, the after-transfer photoreceptor surface potential easily shifts to +, and thus an afterimage is likely to occur. The low Vd is when the toner is low charged, and the toner is easy to develop on the photoreceptor. As a result, even with a slight potential difference in the photoreceptor surface potential, the difference in the amount of toner adhesion becomes large, and the difference in image density tends to appear, so that the afterimage becomes noticeable.

Further, the thickness of the charge transport layer of the photoreceptor also affects the afterimage. If the film thickness is large,
Q = CV, C = Sε / d
(Q: electric charge, C: electrostatic capacity, V: potential, S: area, ε: dielectric constant, d: thickness)
According to the relational expression, since the thickness d is large, the electrostatic capacity is small, the charge amount is small even at the same potential, and the influence of the transfer is large, so that the afterimage is deteriorated. On the other hand, if the film thickness is small, the capacitance increases, and the amount of charge increases, making it difficult to be affected by the transfer.

  Until now, between step 3 and step 4, the photoconductor was irradiated with light by a photostatic device, and the photoconductor surface potential shifted to + after transfer was reset to prevent afterimage generation. However, photoirradiation on the surface of the photoconductor is promoted if a constant amount of neutralizing light with a large amount of light is applied so that the surface of the photoconductor can be sufficiently discharged.

Therefore, the light amount control by the photostatic device is performed according to the value of the charging potential Vd of the photoconductor and the film thickness X of the charge transport layer of the photoconductor.
The film thickness X of the charge transport layer of the photoreceptor is estimated, and 30 μm is set as a threshold value. If the thickness is 30 μm or more, the first light quantity variable control is executed, and if it is less than 30 μm, the second light quantity variable control is executed. In this embodiment, an image forming apparatus having a linear speed of 146 mm / sec is taken as an example. However, the same effect can be obtained at different linear speeds. Since the relationship between charging AC voltage and current depends on the thickness of the charge transport layer of the photoreceptor, the film thickness over time of the photoreceptor should be estimated from the relationship between the current and voltage detected when a voltage is applied to the charging roller. Can do. FIG. 7 is a graph showing the relationship between the photoreceptor film thickness and voltage-current, and shows the relationship between the AC voltage Vpp and the charge transport layer thickness when the current is 0.8 mA.

First, the first light quantity variable control will be described.
When the value is 30 μm or more by the charge transport layer thickness X estimation means described above, the first light quantity variable control is performed. As shown in Table 1 below, when the surface potential Vd1 is 600 V or more, the photostatic device is turned off. Further, when the surface potential Vd1 is 500 V or more and less than 600 V, the photostatic device is turned on, and at that time, the photostatic device application bias (hereinafter referred to as QL bias) is 13 V (light amount: small). When Vd1 is less than 500V, the light neutralizing device is turned on, and the QL bias at that time is 24V (light quantity: large).
FIG. 8 shows the relationship between the charging potential difference ΔVd1 between the first and second photoconductors and the QL bias (bias: large = light quantity: large) when the film thickness X is 37 μm.

  When the potential difference ΔVd1 at which no afterimage is generated is set to 10 V or less, if the surface potential Vd1 is 600 V or more, no afterimage is generated even if the light static eliminator is turned off. However, when the surface potential Vd1 is less than 600 V, it is necessary to turn on the photostatic device and discharge the photosensitive member in order not to generate an afterimage. In addition, when the surface potential Vd1 is 500V or higher, the QL bias that does not generate afterimages is sufficient to be 13V. However, when the surface potential Vd1 is less than 500V, the QL bias needs to be further increased. ΔVd1 can be set. When the thickness of the photoconductor is large, the region of the surface potential Vd1 where an afterimage is generated is wide. Therefore, it is effective to prevent light fatigue of the photoconductor by controlling the light amount in multiple stages. By performing such first light quantity variable control, it is possible to eliminate the charge of the photoreceptor with the minimum necessary light quantity without irradiating excessive light in order to prevent an afterimage, and to reduce the light fatigue of the photoreceptor. It can be suppressed as much as possible. However, the film thickness threshold value of the charge transport layer of the photosensitive member and the threshold value of the surface potential Vd1 for controlling the amount of charge removal are not limited to this because they can be optimized by the system.

Next, the second light quantity variable control will be described.
When the value is less than 30 μm by the means for estimating the charge transport layer thickness X of the photoreceptor, the second variable light quantity control is performed. As shown in Table 2 below, when the surface potential Vd2 is 500 V or more, the photostatic device is turned off. When the surface potential Vd2 is less than 500V, the photostatic device is turned on, and at that time, the QL bias is set to 13V (light quantity: small).
FIG. 9 shows the relationship between the charging potential difference ΔVd2 between the first and second photoreceptors and the QL bias when the film thickness X is 27 μm.

  When the potential difference ΔVd2 at which no afterimage is generated is 10 V or less, if the charge potential Vd2 is 500 V or more, no afterimage will be generated even if the light neutralizing device is turned off. However, when the charging potential Vd2 is less than 500 V, it is necessary to turn on the photostatic device and discharge the photosensitive member in order not to generate an afterimage. However, even when the charging potential Vd2 = 400V (the Vd lower limit value by the process control), the QL bias of 13V can sufficiently satisfy the condition that no afterimage is generated. By carrying out such second light quantity variable control, it is possible to eliminate the charge of the photoreceptor with the minimum necessary light quantity without irradiating excessive light in order to prevent an afterimage, and to reduce the light fatigue of the photoreceptor. It can be suppressed as much as possible. However, the film thickness threshold value of the charge transport layer of the photosensitive member and the Vd2 threshold value of the charge removal light amount control can be optimized by the system, and are not limited thereto.

FIG. 10 shows a control flowchart of the first light amount variable control and the second light amount variable control described above.
First, the film thickness of the charge transport layer of the photoreceptor is estimated (step S1). If the estimated film thickness is 30 μm or more (step S2), the photosensitive member charging potential Vd1 is detected (step S3). If the film thickness is not 30 μm or more (step S2), the photosensitive member charging potential Vd2 is detected. (Step S4). If the absolute value of the charging potential Vd1 of the photoconductor is 600 V or more (step S5), the photostatic device is turned off (step S6). Otherwise, it is determined whether or not the absolute value of the charging potential Vd1 of the photosensitive member is 500 V or more (step S7). If the absolute value of the charging potential Vd1 of the photosensitive member is 500 V or more, the light neutralizing device is turned on by reducing the amount of light (step S8). Otherwise, the light neutralizing device is turned on with a large amount of light (step S9).

  On the other hand, if the absolute value of the charging potential Vd2 of the photosensitive member is 500 V or more (step S10), the light static eliminator is turned off (step S11). Otherwise, the light static eliminator is turned on with a small amount of light (step S11). .

  That is, in the first variable light quantity control, when the absolute value of the charging potential Vd1 of the photoconductor is less than an arbitrary value A, the photostatic device is turned on, and when the absolute value of the charging potential Vd1 is A or more, the photostatic device. Turn off the light. At low Vd, where afterimages are likely to occur, the photo neutralization device is turned on to reduce the residual potential of the photoconductor, eliminating static to the level where no afterimage occurs, and at high Vd, afterimages are unlikely to occur. The static eliminator can be turned off and light fatigue of the photoreceptor can be suppressed.

  In the first variable light amount control, when the absolute value of the charging potential Vd1 is less than an arbitrary value B that is lower than an arbitrary value A, the light amount of the photostatic device is controlled. By controlling the light quantity of the photostatic device in accordance with the value of the charging potential Vd, light fatigue of the photoreceptor due to excessive light quantity is suppressed. In the first variable light amount control, when the value of the charging potential Vd1 is less than the arbitrary value B lower than the arbitrary value A, the light amount of the photostatic device is increased. That is, by controlling the light amount to be increased only at the low charging potential Vd, light fatigue of the photoreceptor due to excessive light amount is suppressed.

  In the second variable light quantity control, the light static eliminator is turned on when the absolute value of the charging potential Vd2 is lower than an arbitrary value C lower than the arbitrary value A, and the light is emitted when the absolute value of the charging potential Vd2 is C or higher. Turn off the static eliminator. Since the residual potential of the photosensitive member is reduced by turning on the light neutralizing device, it is possible to neutralize to a level at which no afterimage occurs even at a low charged potential Vd where an afterimage is likely to occur. If the film thickness is small, afterimages are unlikely to occur, and the threshold value of the charging potential Vd for turning on the light neutralizing device may be low.

<Embodiment 2>
As described above, the bias applied to the charging roller and the photoreceptor surface potential Vd do not always match, and the difference differs depending on the system. Therefore, in order to obtain the target photoreceptor surface potential, a bias having a value obtained by adding the correction amount P to the charging application voltage is applied to the charging roller. However, there is a problem that the leakage light of the static elimination light is slightly irradiated to the surface of the photosensitive member after charging, and the photosensitive member surface potential is made smaller than the target value. This is because if the amount of charge removal light is large, the amount of leakage light also increases, so that the surface potential of the photoconductor becomes even smaller than the target value.

  FIG. 11 shows a graph of the light quantity of the photostatic device and the photosensitive member surface potential when the target photosensitive member surface potential is −440V. It can be seen that the greater the amount of charge removal light, the greater the amount of leakage light, so that the photoreceptor surface potential is smaller than the target value. Therefore, when the light static eliminator is turned on, the correction amount of the bias applied to the charging roller is controlled.

In the first variable light quantity control, when Vd1 is 600 V or more, the light neutralizing device is turned off, so no leakage light is generated, so there is no need to change the correction amount of the bias applied to the charging roller (the correction amount is P And). On the other hand, when Vd1 is 500V or more and less than 600V, the QL bias is 13V and the photostatic discharge device is turned on. Therefore, the correction amount of the charging roller application bias is P + 11V, which is larger than when the light is turned off. When Vd1 is less than 500V, the QL bias is 24V and the light static eliminator is turned on. Therefore, the correction amount of the charging roller application bias is P + 27V.
In the second light quantity variable control, when Vd2 is 500 V or more, the light neutralizing device is turned off, and no leakage light is generated. Therefore, the correction amount of the charging roller application bias may remain P. On the other hand, when Vd2 is less than 500V, the QL bias is 13V and the light static eliminator is turned on. Therefore, the correction amount of the charging roller application bias is P + 11V, which is larger than when the light is extinguished.
As a result, even if leakage light of the static elimination light generated by the optical static elimination device occurs, the photosensitive member can be charged to the target charging potential Vd, and stable image quality can be provided. However, the correction amount can be optimized by the system, and is not limited to this.

FIG. 12 is a control flowchart of the first light quantity variable control and the second light quantity variable control described above.
Shown in
First, the film thickness of the charge transport layer of the photoreceptor is estimated (step S1). If the estimated film thickness is 30 μm or more (step S2), the photosensitive member charging potential Vd1 is detected (step S3). If the film thickness is not 30 μm or more (step S2), the photosensitive member charging potential Vd2 is detected. (Step S4). If the absolute value of the charging potential Vd1 of the photosensitive member is 600 V or more (step S5), the photostatic device is turned off and the charging roller application bias correction amount is not changed (step S6). Otherwise, it is determined whether or not the absolute value of the charging potential Vd1 of the photosensitive member is 500 V or more (step S7). If the absolute value of the charging potential Vd1 of the photosensitive member is 500 V or more, the light neutralizing device is turned on by decreasing the light amount, and the charging roller application bias correction amount is increased (step S8). Otherwise, the light neutralizing device is turned on with a large amount of light, and the charging roller application bias correction amount is further increased (step S9).

  On the other hand, if the absolute value of the charging potential Vd2 of the photosensitive member is 500 V or more (step S10), the photostatic device is turned off and the charging roller application bias correction amount is not changed (step S11). Otherwise, the light neutralizing device is turned on with a small amount of light, and the charging roller application bias correction amount is increased (step S11).

That is, in the first variable light quantity control, when the absolute value of the charging potential Vd1 of the photoconductor is less than an arbitrary value A, the photostatic device is turned on, and when the absolute value of the charging potential Vd1 is A or more, the photostatic device. Turn off the light. At low Vd, where afterimages are likely to occur, the photo neutralization device is turned on to reduce the residual potential of the photoconductor, eliminating static to the level where no afterimage occurs, and at high Vd, afterimages are unlikely to occur. The static eliminator can be turned off and light fatigue of the photoreceptor can be suppressed.
Further, when the light static eliminator is turned off, the correction amount of the bias applied to the charging roller is P, and when it is turned on, the correction amount is larger than P (P + P ′). By doing so, it is possible to prevent the photosensitive member surface potential from becoming smaller than the target value due to leakage light caused by lighting of the light neutralizing device.

In the first variable light amount control, when the absolute value of the charging potential Vd1 is less than an arbitrary value B that is lower than an arbitrary value A, the light amount of the photostatic device is controlled. By controlling the light quantity of the photostatic device in accordance with the value of the charging potential Vd, light fatigue of the photoreceptor due to excessive light quantity is suppressed. In the first light quantity variable control, when the value of the charging potential Vd1 is less than the arbitrary value B lower than the arbitrary value A, the light quantity of the photostatic device is increased. That is, by controlling the light amount to be increased only at the low charging potential Vd, light fatigue of the photoreceptor due to excessive light amount is suppressed.
Further, at this time, the bias correction amount applied to the charging roller is further increased (P + P ″ (P ′ <P ″)), so that the surface potential of the photosensitive member can be increased even if the intensity of leakage light from the light neutralizer increases. Can be charged to a target value.

In the second variable light quantity control, the light static eliminator is turned on when the absolute value of the charging potential Vd2 is lower than an arbitrary value C lower than the arbitrary value A, and the light is emitted when the absolute value of the charging potential Vd2 is C or higher. Turn off the static eliminator. Since the residual potential of the photosensitive member is reduced by turning on the light neutralizing device, it is possible to neutralize to a level at which no afterimage occurs even at a low charged potential Vd where an afterimage is likely to occur. If the film thickness is small, afterimages are unlikely to occur, and the threshold value of the charging potential Vd for turning on the light neutralizing device may be low.
Similarly to the first light quantity variable control, the correction amount of the charging roller application bias is set to P when the light neutralizing device is turned off, and the correction amount is set to be larger than P when the light is turned on (P + P ′). By doing so, it is possible to prevent the photosensitive member surface potential from becoming smaller than the target value due to leakage light caused by lighting of the light neutralizing device.

<Embodiment 3>
As described above, the bias applied to the charging roller and the photoreceptor surface potential Vd do not always match, and the difference differs depending on the system. Therefore, in order to obtain the target photoreceptor surface potential, a bias having a value obtained by adding the correction amount P to the charging application voltage is applied to the charging roller. Further, as described in the first embodiment, the residual potential of the photosensitive member is reduced by using the charge eliminating light so that an afterimage is hardly generated.

  However, as shown in FIGS. 9 and 10, even if static elimination light is used, ΔVd of about 5 to 10 V is generated except when the photosensitive film is thin and at high Vd. For example, in a system in which the diameter of the photoconductor is small and there are many areas around the photoconductor in a sheet of paper, ΔVd of about 5 to 10 V is accumulated every photoconductor and becomes visible as an afterimage or the leading edge of the paper This causes a problem that the potential difference between the high end and the high end increases, resulting in a density difference. In order to achieve higher image quality, it is necessary to further reduce ΔVd. Therefore, in order to make ΔVd smaller, control is performed to vary the correction amount of the bias applied to the charging roller between the first and second rounds of the photoreceptor.

  In the first light quantity variable control, the value of ΔVd1 is 5V or more and 10V or less regardless of the value of Vd1. Control is performed to vary the correction amount of the charging roller applied bias between the first and second rounds of the photoreceptor. For example, to make ΔVd1 5V or less, regardless of the value of Vd1, when the correction amount of the charging roller applied bias for the first round of the photoconductor is P, the correction amount for the second and subsequent rounds of the photoconductor is P + 5V And As a result, ΔVd1 is 5 V or less for any Vd1, and a high-quality image without an abnormal image can be obtained.

  In the second variable light quantity control, when Vd2 is 600V or higher, ΔVd2 is 5V or lower, so there is no need to change the correction amount of the charging roller application bias between the first and second rounds of the photoconductor. The amount can be constant P. On the other hand, when Vd2 is less than 600V, the value of ΔVd2 is 5V or more and 10V or less. Set the correction amount to P + 5V. As a result, ΔVd2 is 5 V or less regardless of Vd2, and a high-quality image without an abnormal image can be obtained. However, the correction amount can be optimized by the system, and is not limited to this.

FIG. 13 shows a control flowchart of the first light quantity variable control and the second light quantity variable control described above.
First, the film thickness of the charge transport layer of the photoreceptor is estimated (step S1). If the estimated film thickness is 30 μm or more (step S2), the photosensitive member charging potential Vd1 is detected (step S3). If the film thickness is not 30 μm or more (step S2), the photosensitive member charging potential Vd2 is detected. (Step S4). If the absolute value of the charging potential Vd1 of the photosensitive member is 600 V or more (step S5), the light neutralizing device is turned off, and the charging roller applied bias correction amount is made different between the first and second rotations of the photosensitive member (step S6). ). Otherwise, it is determined whether or not the absolute value of the charging potential Vd1 of the photosensitive member is 500 V or more (step S7). If the absolute value of the charging potential Vd1 of the photosensitive member is 500 V or more, the light neutralizing device is turned on by reducing the light amount, and the charging roller applied bias correction amount is made different between the first and second rotations of the photosensitive member (step S8). ). Otherwise, the light neutralizing device is turned on with a large amount of light, and the charging roller applied bias correction amount is made different between the first and second rotations of the photoreceptor (step S9).

  On the other hand, if the absolute value of the charging potential Vd2 of the photosensitive member is 600 or more (step S10), the light neutralizing device is turned off, and the bias correction amount applied to the charging roller is not different between the first and second rotations of the photosensitive member. (Step S11). If the absolute value is not 600 or more, it is determined whether or not the absolute value of the charging potential Vd2 of the photosensitive member is 500 V or more (step S12). If it is 500 V or more (step S13), the photostatic device is turned off, and the charging roller applied bias correction amount is made different between the first and second rotations of the photoreceptor (step S14). If it is not 500 V or more, the light neutralizing device is turned on with a small amount of light, and the charging roller applied bias correction amount is made different between the first and second rotations of the photoreceptor (step S15).

That is, in the first variable light quantity control, when the absolute value of the charging potential Vd1 of the photoconductor is less than an arbitrary value A, the photostatic device is turned on, and when the absolute value of the charging potential Vd1 is A or more, the photostatic device. Turn off the light. At low Vd, where afterimages are likely to occur, the photo neutralization device is turned on to reduce the residual potential of the photoconductor, so that the afterimage can be eliminated to a level where it is difficult for afterimages to occur, and afterimages are unlikely to occur at high Vd. Therefore, the light neutralizing device can be turned off, and light fatigue of the photoreceptor can be suppressed.
In addition, depending on the system, even if the afterimage cannot be made completely non-occurrence level, regardless of the value of Vd1, the correction amount of the charging roller applied bias is different from P for the first round of the photoreceptor and P for the second and subsequent rounds. (P + Qa (a = 1,2,3)). Thus, ΔVd1 can be further reduced, and a high-quality image with no afterimage can be obtained.

In the second variable light quantity control, the light static eliminator is turned on when the absolute value of the charging potential Vd2 is lower than an arbitrary value C lower than the arbitrary value A, and the light is emitted when the absolute value of the charging potential Vd2 is C or higher. Turn off the static eliminator. By turning on the light neutralizing device, the residual potential of the photoconductor is reduced, so that the residual image can be neutralized to a level at which the residual image is not easily revealed even at the low charged potential Vd where the afterimage is likely to occur. If the film thickness is small, afterimages are unlikely to occur, and the threshold value of the charging potential Vd for turning on the photostatic device may be low.
Also, depending on the system, when the absolute value of Vd2 is less than A, the correction amount of the charging roller applied bias is P for the first round of the photoconductor, even if the afterimage cannot be made completely ungenerated. After the first, make it different from P (P + Qa (a = 4,5)). Thus, ΔVd2 can be further reduced, and a high-quality image without an afterimage can be obtained.

In an image forming apparatus using the image forming method described above, stable image quality can be provided. Further, in an image forming apparatus having a process cartridge including a photosensitive member and at least one of a charging device and a developing device as an image forming unit, the image forming means is integrated to improve setability and maintainability. . Further, the positional accuracy with respect to the photosensitive member such as the developing member and the charging member is improved. In the above-described embodiment, an example in which a multifunction machine such as a copying machine, a printer, or a facsimile is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited to this, and the present invention can also be applied to other image forming apparatuses such as a copying apparatus, a printer, a facsimile, and a plotter.
The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

1: Cleaning device 5: Cleaning blade 10: Photoconductor 30: Cleaning device 40: Charging device 41: Charging roller 42: Charging roller cleaner 50: Developing device 51: Developing roller 52: Stirring screw 53: Supply screw 60: Photostatic device 90: fixing device 91: conductive support 92: photosensitive layer 92a: charge generation layer 92b: charge transport layer 94: undercoat layer 100: printer 120: image forming unit 121: process cartridge 130: paper supply unit 131: paper supply Cassette 132: Paper feed roller 133: Registration roller pair 135: Paper discharge storage unit 140: Exposure device 151: Optical sensor 151Y: Optical sensor 159: Toner cartridge 160: Intermediate transfer device 161: Primary transfer roller 162: Intermediate transfer belt 165: Secondary transfer roller 167: Intermediate Copy belt cleaning device

JP 2009-008906 A

Claims (18)

A photoreceptor carrying a toner image;
A charging device for charging the photoreceptor;
A writing device for forming an electrostatic latent image on the photoreceptor;
A developing device for visualizing the electrostatic latent image on the photoreceptor with toner;
A transfer device for primary transfer of the visualized toner image;
An optical charge eliminating device that is provided separately from the writing device, and that performs photostatic charge on the photosensitive member;
An image forming method in an image forming apparatus comprising:
Having a current detection means for detecting the charging current;
The charging device is a charging roller that contacts the photoconductor and charges the photoconductor by applying a voltage;
Estimating the film thickness X of the charge transport layer of the photoreceptor from the relationship between the charging voltage and the current value of the charging current detected by the current detection means,
In the image forming method of varying the charge removal amount control method by the light charge removal device according to the estimated value of the film thickness X,
When the film thickness X is not less than an arbitrary value α and a predetermined charging potential Vd1 of the photoconductor is detected, a first light quantity variable control is executed,
When it is detected that the film thickness X is less than α and the absolute value of the charging potential of the photosensitive member is a charging potential Vd2 lower than the predetermined charging potential Vd1, the first light quantity variable control is Execute second variable light quantity control with different control contents,
An image forming method. The image forming method according to claim 1,
The first light quantity variable control is:
When the absolute value of the charging potential Vd1 is less than the arbitrary value A, the photostatic device is turned on.When the absolute value of the charging potential Vd1 is the arbitrary value A or more, the photostatic device is turned off.
An image forming method. The image forming method according to claim 2.
The first light variable control controls the light amount of the light neutralizing device when the absolute value of the charging potential Vd1 is less than an arbitrary value B lower than the arbitrary value A.
An image forming method. The image forming method according to claim 2 or 3,
In the first variable light amount control, when the value of the charging potential Vd1 is less than an arbitrary value B lower than the arbitrary value A, the light amount of the photostatic device is increased.
An image forming method. The image forming method according to claim 2.
In the first light quantity variable control, when the charging potential Vd1 is an arbitrary value A or more, the correction amount applied to the charging application voltage applied to the charging roller is not changed.
An image forming method. The image forming method according to claim 3 or 4,
In the first light quantity variable control, when the charging potential Vd1 is less than an arbitrary value A, a correction amount applied to the charging roller is made larger than when the charging potential Vd1 is a value A or more.
An image forming method. The image forming method according to claim 3 or 4,
In the first light quantity variable control, when the charging potential Vd1 is less than an arbitrary value B lower than an arbitrary value A, the charging roller is applied to the charging roller more than when the charging potential Vd1 is greater than or equal to a value B and less than a value A. Increase the amount of correction to be applied to the applied charging voltage.
An image forming method. The image forming apparatus according to claim 2.
In the first light quantity variable control, the correction amount applied to the charging application voltage applied to the charging roller is different between the first and second rotations of rotation of the photoconductor,
An image forming method. The image forming method according to claim 1,
In the second light quantity variable control, when the absolute value of the charging potential Vd2 is less than an arbitrary value C lower than the arbitrary value A, the light static eliminator is turned on,
When the absolute value of the charging potential Vd2 is equal to or greater than the arbitrary value C, the light static eliminator is turned off.
An image forming method. The image forming method according to claim 9.
In the second light quantity variable control, when the charging potential Vd2 is equal to or higher than an arbitrary value C lower than the arbitrary value A, the correction amount applied to the charging application voltage applied to the charging roller is not changed.
An image forming method. The image forming method according to claim 9.
In the second light quantity variable control, when the charging potential Vd2 is less than an arbitrary value C lower than the arbitrary value A, the charging applied to the charging roller is more than when the charging potential Vd2 is greater than or equal to the value C. Increase the amount of correction applied to the applied voltage,
An image forming method. The image forming apparatus according to claim 9.
In the second variable light quantity control, when the charging potential Vd2 is equal to or greater than the arbitrary value A, the correction amount applied to the charging application voltage applied to the charging roller is the first and second rounds of the photoreceptor. And the same
When the charging potential Vd2 is less than the arbitrary value A, the correction amount applied to the charging application voltage applied to the charging roller is different between the first and second rounds of the photoreceptor.
An image forming method. In the image forming method according to any one of claims 1 to 12,
Arbitrary value α of the film thickness X of the charge transport layer of the photoreceptor is 30 μm,
An image forming method. In the image forming method according to any one of claims 2 to 8,
The arbitrary value A is 600V,
An image forming method. In the image forming method according to any one of claims 3 to 8,
The arbitrary value B is 500V,
An image forming method. The image forming method according to any one of claims 9 to 11,
The arbitrary value C is 500V,
An image forming method.   An image forming apparatus using the image forming method according to claim 1. 18. The image forming apparatus according to claim 17, further comprising a process cartridge including a photoconductor as an image forming unit and further including at least one of a charging device and a developing device.