JP7023777B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus that forms an image using a liquid developer.

Conventionally, there is an image forming apparatus that forms an image by using a liquid developer containing a particulate toner and a liquid carrier (hereinafter referred to as a carrier liquid). In the image forming apparatus, the surface of the rotating photosensitive drum is uniformly charged by the charging device, and then the surface of the photosensitive drum is exposed by the exposure apparatus to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image formed on the photosensitive drum is developed into a toner image by a developing device. The development of the toner image is realized by moving the toner from the developing roller to the photosensitive drum via the liquid developer carried on the rotating developing roller by electrophoresis. After that, the toner image of the photosensitive drum is transferred to a recording material, an intermediate transfer belt, or the like. The toner remaining on the photosensitive drum after transfer is removed by a cleaning blade that rubs the photosensitive drum. However, the carrier liquid (more specifically, the liquid developer having a lower toner concentration than the liquid developer before development carried on the developing roller) remains attached to the photosensitive drum after cleaning, and the state thereof. The following electrostatic latent image was formed on the photosensitive drum.

Generally, the carrier liquid is a liquid having a high resistance close to insulation and a small refractive index. Therefore, if the carrier liquid remains attached to the photosensitive drum, the exposed portion exposed by the exposure device cannot be exposed to the target potential when the next electrostatic latent image is formed, or the exposed portion has potential unevenness. Is likely to occur and image defects are likely to occur. However, the carrier liquid cannot be completely removed by the cleaning blade alone. Therefore, in order to prevent the carrier liquid from remaining on the photosensitive drum before charging as much as possible, a device that removes the excess carrier liquid by a squeeze device before transfer and further dries it by using a drying device to remove the residue. Has been proposed (Patent Document 1). Alternatively, a device has been proposed in which a liquid application roller and a cleaning roller are provided in addition to the cleaning blade so as to reduce the amount of the carrier liquid passing through and to make the liquid thickness of the carrier liquid uniform (Patent Document). 2).

Japanese Unexamined Patent Publication No. 2006-201320 Japanese Unexamined Patent Publication No. 2006-285237

Like the devices described in Patent Document 1 and Patent Document 2 described above, conventionally, various devices for preventing the carrier liquid from remaining on the photosensitive drum before charging are provided, so that the image forming device is increased in size. This is unfavorable, contrary to the recent demand for miniaturization. Therefore, an image forming device capable of reducing the influence on the image caused by the carrier liquid adhering to the photosensitive drum before charging has been conventionally provided without specially providing a device for leaving no carrier liquid on the photosensitive drum. It was hoped for, but no such thing has yet been proposed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of reducing the influence on an image caused by the carrier liquid adhering to the photosensitive drum before charging.

The image forming apparatus of the present invention exposes a rotating image carrier, a charging means for charging the image carrier, and the charged image carrier to form an electrostatic latent image on the image carrier. The image carrier is rotated by carrying a liquid developer containing a toner and a carrier liquid, an exposure means capable of adjusting the amount of light, a potential detection means for detecting the exposure portion potential of the exposed portion exposed by the exposure means, and the image carrier. A developer carrier that develops an electrostatic latent image formed in the image into a toner image via a carrier liquid that fills the space between the image carrier and the image carrier, and a toner image of the image carrier are different images. A transfer means for transferring to the image carrier, a cleaning means for contacting the image carrier and removing toner remaining on the image carrier after transfer, and an adjusting means for adjusting the amount of light of the exposure means at the time of image formation are provided. In the initial stage or at the time of non-image formation, the adjusting means performs exposure with a plurality of different light amounts by the exposure means in a state where the carrier liquid does not adhere to the image carrier, and responds to the plurality of light amounts. In the first mode in which the potential of the exposed portion is detected by the potential detecting means, and in a state where the carrier liquid is attached to the image carrier, exposure is performed with a plurality of different light amounts by the exposure means to obtain the plurality of light amounts. It is characterized in that it is possible to execute a second mode in which the corresponding exposure unit potential is detected by the potential detecting means.

The image forming apparatus of the present invention exposes a rotating image carrier, a charging means for charging the image carrier, and the charged image carrier to form an electrostatic latent image on the image carrier. An exposure means capable of adjusting the amount of light, a potential detection means for detecting the exposure portion potential of the exposed portion exposed by the exposure means, a separation position separated from the image carrier, and a proximity position close to the image carrier. A liquid developer containing a toner and a carrier liquid is carried and rotated so as to be movable between the two, and when the liquid developer is in the close position, an electrostatic latent image formed on the image carrier is applied with a voltage. A developer carrier that develops into a toner image, a transfer means that transfers the toner image of the image carrier to another image carrier, and toner that comes into contact with the image carrier and remains on the image carrier after transfer. The cleaning means for removing and the adjusting means for adjusting the amount of light of the exposure means at the time of image formation are provided, and the adjusting means initially has the developer carrier located at the separated position. A first mode in which exposure is performed with a plurality of different light amounts by the exposure means and the exposure unit potential corresponding to the plurality of light amounts is detected by the potential detection means, and after the first mode, the developer carrier is separated from the developing body. It is possible to execute a second mode in which the photographic processing means is used to detect the exposure portion potential corresponding to the plurality of light amounts by moving the photographic processing unit from the position to the proximity position and performing exposure with a plurality of different light amounts by the photographic processing means. , Characterized by that.

The image forming apparatus of the present invention exposes a rotating image carrier, a charging means for charging the image carrier, and the charged image carrier to form an electrostatic latent image on the image carrier. An exposure means capable of adjusting the amount of light, a potential detection means for detecting the exposure portion potential of the exposed portion exposed by the exposure means, a separation position separated from the image carrier, and a proximity position close to the image carrier. A liquid developer containing a toner and a carrier liquid is carried and rotated so as to be movable between them, and when the liquid developer is located at the close position, the electrostatic latent image formed on the image carrier is subjected to voltage. A developer carrier that develops into a toner image by application, a transfer means that transfers the toner image of the image carrier to another image carrier, and toner that abuts on the image carrier and remains on the image carrier after transfer. A cleaning means for removing As it is, a first detection mode in which exposure is performed with a plurality of different light amounts by the exposure means and the exposure unit potential corresponding to the plurality of light amounts is detected by the potential detection means, and after the first detection mode, the developer. The carrier was moved from the close position to the remote position, the image carrier was rotated over a predetermined time, and then exposed by the exposure means with a plurality of different light amounts to respond to the plurality of light amounts. It is characterized in that it is possible to execute a second detection mode in which the exposure unit potential is detected by the potential detecting means.

According to the present invention, with respect to an image forming apparatus that forms an image using a liquid developer containing toner and a carrier liquid, the influence on the image due to the carrier liquid adhering to the image carrier before charging. Will be able to be made smaller.

The schematic diagram which shows the structure of the image forming apparatus of this embodiment. The schematic diagram which shows the structure of the image forming part. Sectional drawing which shows the surface layer of a photosensitive drum. A control block diagram illustrating a control unit. It is a figure explaining the reflection of a laser beam irradiated by an exposure apparatus, (a) is a liquid-free state, (b) is a liquid-containing time. The figure which showed the refractive index of a photosensitive drum surface layer and a carrier liquid, and the reflectance of each layer. The flowchart which shows the correction data generation processing of 1st Embodiment. The flowchart which shows the liquid application process. The graph which shows the relationship between the grid voltage of the upstream charge and the charge potential of a photosensitive drum. The graph which shows the relationship between the grid voltage of the downstream charge and the charge potential of a photosensitive drum. The graph which shows the relationship between the laser light amount of an exposure apparatus and the exposure part potential of a photosensitive drum in the time with liquid and the time without liquid. The graph which shows the relationship between the laser light amount of an exposure apparatus, and the potential difference between the exposure part potential with liquid and the exposure part potential with liquid. The graph which shows the correction data of the laser light amount of the exposure apparatus in the time with liquid with respect to the time without liquid. The flowchart which shows the correction data generation processing of 2nd Embodiment.

<First Embodiment>
[Image forming device]
The schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus 100 of the present embodiment is an apparatus adopting an electrophotographic method, and in the present embodiment, a tandem type intermediate transfer type full-color printer in which a plurality of image forming units PY, PM, PC, and PBk are arranged is shown as an example. rice field. Four image forming portions PY to PBk are arranged in series in the moving direction of the intermediate transfer belt 91 at equal intervals in the order of yellow, magenta, cyan, and black from the upstream side in the moving direction.

The image forming apparatus 100 can output a color image formed according to image information from an external device (not shown) such as a personal computer or an image reading device capable of communicating with the apparatus main body to the recording material S. Examples of the recording material S include cut paper, OHT (OverHead Transparency) sheet, and cloth. When outputting a color image, the image forming apparatus 100 generates a color-separated image signal according to a print signal sent from an external device, and each image forming unit PY to PBk forms a toner image of each color according to the image signal. .. Then, the image forming apparatus 100 primary transfers the toner images of each color formed by the image forming portions PY to PBk to the intermediate transfer belt 91. The image forming portions PY to PBk will be described later (see FIG. 2).

The intermediate transfer belt 91 as another image carrier is stretched over the tension roller 94, the drive roller 95, and the secondary transfer inner roller 96, and is driven by the drive roller 95 in the direction of arrow G2 in the figure. Moving. The toner image primaryly transferred onto the intermediate transfer belt 91 is collectively secondary transferred onto the recording material S conveyed to the secondary transfer unit T2. The secondary transfer unit T2 is a toner image transfer nip unit formed by abutting the secondary transfer outer roller 10 on the intermediate transfer belt 91 stretched on the secondary transfer inner roller 96 to the recording material S. In the secondary transfer unit T2, the toner image is secondarily transferred from the intermediate transfer belt 91 to the recording material S by applying a secondary transfer voltage to the secondary transfer outer roller 10 by a power source (not shown).

The recording material S to which the toner image is transferred is conveyed to the fixing device 13. The recording material S is conveyed to the fixing device 13 and heated and pressurized or irradiated with ultraviolet rays to fix the toner image on the recording material S. The recording material S on which the toner image is fixed by the fixing device 13 is discharged to the outside of the machine body.

[Image forming part]
Next, the image forming portions PY to PBk that form the images of each color of yellow (Y), magenta (M), cyan (C), and black (Bk) will be described with reference to FIG. However, since the image forming units PY to PBk are configured to be the same except that the colors of the toners used in the developing devices 4Y to 4Bk are different, each image forming unit PY to PBk is distinguished if no particular distinction is required. The reference numerals Y, M, C, and Bk at the end will be omitted.

As shown in FIG. 2, in the image forming unit P, a corona charging device 2, an exposure device 3, a surface potential sensor 9, a developing device 4, a drum cleaning device 7, and a static elimination device 73 are arranged so as to surround the photosensitive drum 1. ing. In the image forming unit P, the photosensitive drum 1 sandwiches the intermediate transfer belt 91 in the primary transfer roller 92 so that the primary transfer nip portion T1 is formed between the photosensitive drum 1 and the intermediate transfer belt 91 by the primary transfer roller 92. It is located at the opposite position. The photosensitive drum 1 is rotated by a motor at a predetermined process speed (for example, a peripheral speed of 700 mm / s) in the direction of arrow G1 in the figure.

[Sensitive drum]
Here, the configuration of the photosensitive drum 1 will be described with reference to FIG. In the present embodiment, the photosensitive drum 1 as an image carrier is interchangeably provided on the main body of the apparatus. Further, in the present embodiment, a photosensitive drum 1 having a diameter of 84 mm was used. The photosensitive drum 1 is a drum in which an amorphous silicon photosensitive layer is formed on an outer peripheral surface of a cylindrically formed conductive aluminum cylinder (conductive substrate 1a). As shown in FIG. 3, the amorphous silicon photosensitive layer is formed by a blocking layer 1b, a photosensitive layer 1c, a blocking layer 1d, and a protective layer 1e. The photosensitive layer 1c is sandwiched between the blocking layer 1b and the blocking layer 1d. As an example, the thickness of the photosensitive layer 1c is 40 μm, and its relative permittivity is “10”. The thickness of the protective layer 1e is 0.6 μm, and its refractive index is about “2.1”. The volume resistivity of the protective layer 1e is 1.0 × 10 ¹⁰ to 1.0 × 10 ¹⁵ Ω · cm.

[Charging device]
Returning to FIG. 2, the corona charger 2 as a charging means charges the photosensitive drum 1 to a uniform negative electrode potential by corona discharge. The corona charger 2 applies a voltage having the same polarity as the toner from the charging power supply V1 (see FIG. 4 described later) to make the surface of the photosensitive drum 1 a desired charging potential (also referred to as a dark part potential, for example, −500V). To be charged. In the case of the present embodiment, the corona charger 2 is composed of two scorotron chargers, an upstream charger 21 arranged on the upstream side in the rotation direction of the photosensitive drum 1 and a downstream charger 22 arranged on the downstream side in the rotation direction. It is configured. For example, the width direction length of the corona charger 2 (rotational length of the photosensitive drum 1) is 44 mm, and the longitudinal length of the discharge region (rotational axis direction length of the photosensitive drum 1) is 340 mm.

The upstream charger 21 and the downstream charger 22 each have discharge wires 21a and 22a, grid electrodes 21b and 22b, and shield electrodes 21c and 22c, respectively. Further, in order to prevent a current from leaking between the upstream charger 21 and the downstream charger 22 when different voltages are applied between the shield electrodes, the length in the width direction is, for example, about 2 mm. The insulating plate 2a is arranged.

The discharge wires 21a and 22a are, for example, oxidized tungsten wires having a wire diameter of φ60 μm. A variable constant current is passed through the discharge wires 21a and 22a in the range of 0 to −2000 μA. The grid electrodes 21b and 22b are plate-shaped members made of stainless steel (SUS) on which a corrosion prevention layer such as nickel plating is formed. A mesh is formed on the grid electrodes 21b and 22b by etching treatment so that the aperture ratios are 90% and 80%, respectively. These grid electrodes 21b and 22b are arranged along the curvature of the photosensitive drum 1 with different inclination angles between the upstream charging device 21 and the downstream charging device 22. Further, the grid electrodes 21b and 22b are arranged so that the closest contact distance with the photosensitive drum 1 is 1.25 ± 0.2 mm. A variable constant voltage is applied to the grid electrodes 21b and 22b within the range of 0 to -1300V. Further, the same voltage as that of the grid electrodes 21b and 22b is applied to the shield electrodes 21c and 22c.

The air supply fan F1 is arranged above the corona charger 2, and the intake fan F2 is arranged downstream of the corona charger 2 in the rotational direction of the photosensitive drum 1. The air supply fan F1 sends air into the corona charger 2, and the intake fan F2 sucks the air sent into the corona charger 2 by the air supply fan F1 and discharges it to the outside of the image forming apparatus.

A static eliminator 73 made of, for example, an LED array is arranged on the upstream side of the photosensitive drum 1 in the rotation direction from the corona charger 2. The static eliminator 73 is provided to uniformly lower the surface potential of the photosensitive drum 1 to a predetermined potential (for example, 0 V) before being charged by the corona charger 2. The wavelength of the light emitted by the static eliminator 73 is, for example, 635 nm, and the exposure amount is variable in the range of 1.0 to 7.0 μJ / cm ² . In the case of this embodiment, the exposure amount is set to 4.0 μJ / cm ² as an initial condition.

The exposure apparatus 3 as an exposure means has a semiconductor laser (not shown), a polygon mirror, an F−θ lens, or the like, and irradiates the charged photosensitive drum 1 with a laser beam L modulated according to an image signal. An electrostatic latent image is formed on the surface of the photosensitive drum 1. As an example, the wavelength of the laser beam L is 685 nm, and the exposure amount is variable in the range of 0.1 to 0.5 μJ / cm ² . In the exposure apparatus 3, the amount of light of the laser beam L irradiated by the exposure power supply V3 (see FIG. 4 described later) is adjusted, and an electrostatic latent image can be formed on the surface of the photosensitive drum 1 at a desired exposure portion potential. That is, the potential of the portion (called the exposed portion) irradiated with the laser beam L on the photosensitive drum 1 decreases, so that an electrostatic latent image corresponding to the image information is formed. The exposed potential (also referred to as the bright potential) of the photosensitive drum 1 is adjusted to, for example, "-100 V".

A surface potential sensor 9 for measuring the surface potential of the photosensitive drum 1 is arranged on the downstream side in the rotation direction of the photosensitive drum 1 from the exposure apparatus 3. In the case of the present embodiment, the surface potential sensor 9 as the potential detecting means at least determines the potential of the exposed portion of the photosensitive drum 1 exposed by the exposure device 3 at the time of executing the “correction data generation process” (see FIG. 7) described later. It is provided so that it can be measured.

The developing device 4 is a device that develops an electrostatic latent image formed on the photosensitive drum 1 into a toner image using a liquid developer. The developing apparatus 4 contains a liquid developer in which a powder toner as a dispersoid is dispersed in a carrier liquid as a dispersion medium. The toner is a resin toner containing a colorant and a binder as main components, to which a charging aid and the like are added. The toner is formed to have an average particle size of, for example, about 0.5 to 3 μm. On the other hand, the carrier liquid is a non-volatile liquid having a high resistivity and a low dielectric constant, for example, having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more, a relative permittivity of 10 or less, and a viscosity adjusted to 0.1 to 100 cP. Is a liquid. As the carrier liquid, a liquid containing an insulating solvent such as silicone oil, mineral oil, and Isopar M (registered trademark, manufactured by Exxon Co., Ltd.) as a main component and, if necessary, a charge control agent or the like can be used. Further, as long as it is within the above-mentioned physical property values, a liquid monomer that is cured by ultraviolet rays can also be used. In the case of the present embodiment, the carrier liquid has transparency and has a refractive index smaller than the refractive index (for example, 2.1) of the photosensitive layer (see FIG. 3) of the photosensitive drum 1 (for example, 1.4). ~ 1.6) is used.

A liquid developer is supplied to the developing device 4 from the mixer 63. The liquid developer supplied from the mixer 63 to the developing device 4 is supported on a developing roller 41 rotating in the developing device 4 and used for development. The liquid developer that has not been subjected to development is returned from the developing apparatus 4 to the mixer 63 and reused. In the present embodiment, the developing roller 41 is provided so as to be movable between a separated position separated from the photosensitive drum 1 and a close position close to the photosensitive drum 1.

The toner image developed on the photosensitive drum 1 by the developing device 4 is applied to the intermediate transfer belt 91 by applying a voltage (for example, + 500V) having a polarity opposite to the charging characteristics of the toner to the primary transfer roller 92 as a transfer means. Primary transcription. A small amount of carrier liquid and a few percent of toner remain on the photosensitive drum 1 after the primary transfer, but the liquid developer containing these is arranged on the downstream side in the rotation direction from the primary transfer nip portion T1. It is collected by the drum cleaning device 7.

The drum cleaning device 7 has a cleaning blade 70 that can come into contact with the photosensitive drum 1. In the cleaning blade 70 as a cleaning means, a metal plate-shaped member such as stainless steel extending in the longitudinal direction of the photosensitive drum 1 is provided with a resin or rubber contact member as a free end on the photosensitive drum 1 side. It is provided in. The cleaning blade 70 removes the toner remaining on the photosensitive drum 1 after the primary transfer by contacting the contact member with the photosensitive drum 1. At this time, a part of the carrier liquid is not removed and remains attached to the photosensitive drum 1. The thickness of the carrier liquid remaining attached to the photosensitive drum 1 after cleaning is, for example, 100 nm or less. This is the liquid thickness that volatilizes from the photosensitive drum 1 in about 30 seconds to 1 minute. However, since the photosensitive drum 1 rotates in, for example, about 370 ms per cycle, the liquid thickness cannot be completely volatilized from the photosensitive drum 1 until the liquid developer is supplied from the developing device 4 to the photosensitive drum 1. In the present embodiment, the cleaning blade 70 is provided so as to be movable between an abutting position that abuts on the photosensitive drum 1 and a non-contact position that does not abut on the photosensitive drum 1.

[Developer]
Next, the details of the above-mentioned developing apparatus 4 will be described. As shown in FIG. 2, the developing apparatus 4 has a developing container 40 forming a casing, a developing roller 41, a film forming roller 42, a film forming electrode 44, a supply tray 45, and a cleaning roller 43. The developing container 40 contains a liquid developer. A part of the developing container 40 facing the photosensitive drum 1 is open, and a developing roller 41 is rotatably provided so that a part is exposed in this opening.

The developing roller 41 as the developer carrier is formed in a cylindrical shape and is rotated in the same direction as the photosensitive drum 1 on the surface facing the photosensitive drum 1. On the opposite side of the surface of the developing roller 41 facing the photosensitive drum 1, the film forming electrode 44 is arranged facing the developing roller 41 with a film forming GAP (gap) at a predetermined interval (for example, 0.1 mm or more). Has been done. A supply tray 45 is arranged below the film forming electrode 44, and the liquid developer is pumped from the supply tray 45 to the film forming GAP by the rotational force of the developing roller 41. The supply tray 45 temporarily stores the liquid developer supplied from the mixer 63 so that the developing roller 41 can pump up the liquid developer by rotation. The mixer 63 as a mixer mixes and disperses the toner and the carrier liquid to generate a liquid developer having an adjusted toner concentration, and supplies the generated liquid developer to the developing device 4.

The film forming electrode 44 forms an electric field with the developing roller 41 by applying a voltage of, for example, "-1100V" by a power source (not shown). According to this electric field, the toner contained in the liquid developer pumped up by the film-forming GAP moves toward the surface side of the developing roller 41. The film forming roller 42 is arranged on the downstream side of the developing roller 41 in the rotational direction with respect to the film forming electrode 44. The film forming roller 42 abuts on the developing roller 41 to form the nip portion N1. Of the liquid developer on the developing roller 41 that has passed through the region facing the film forming electrode 44, the toner and a part of the carrier liquid that have been brought to the surface side of the developing roller 41 use the nip portion N1 of the film forming roller 42. pass. The liquid developer that has not passed through the nip portion N1 of the film forming roller 42 flows along the upper surface of the film forming electrode 44 and falls to the bottom side of the developing container 40. A voltage of, for example, "-350V" is applied to the film forming roller 42 by a power source (not shown).

Then, a developing voltage of, for example, "-300V" is applied to the developing roller 41 in a state of being in contact with the photosensitive drum 1 by, for example, a developing power supply V2 (see FIG. 4 described later) whose voltage is variable in the range of 0 to −1000V. Will be done. In that case, the liquid developer that has passed through the nip portion N1 of the film forming roller 42 is conveyed to the developing nip portion N2 to fill the space between the photosensitive drum 1 and the electrostatic latent portion 1 on the photosensitive drum 1. The image is developed into a toner image (so-called electrophoresis). That is, the toner in the liquid developer conveyed to the developing nip portion N2 is selectively adhered to the electrostatic latent image formed on the photosensitive drum 1 by the electric field due to the developing voltage. In this way, the electrostatic latent image on the photosensitive drum 1 is developed into a toner image.

A cleaning roller 43 is arranged on the downstream side in the rotation direction of the developing roller 41 from the film forming roller 42. The cleaning rollers 43 are arranged to face each other with a predetermined interval (for example, 0.05 mm) from the developing rollers 41, and are arranged in the same direction as the moving direction of the developing rollers 41 on the surface facing the developing rollers 41 by a motor (not shown). Is rotated to. The cleaning roller 43 is made of a metal such as stainless steel. The cleaning roller 43 electrically removes the toner remaining on the developing roller 41 without being subjected to the development of the electrostatic latent image formed on the photosensitive drum 1 by interposing the carrier liquid by the action of the electric field (so-called so-called). Electrophoresis). A voltage having a polarity opposite to that of the toner, for example, "+ 600V" is applied to the cleaning roller 43. Then, the toner remaining on the developing roller 41 is moved from the developing roller 41 to the cleaning roller 43 via the liquid layer of the liquid developer formed between the developing roller 41 and the cleaning roller 43. In this way, the cleaning roller 43 collects the toner remaining on the developing roller 41 after the development of the toner image together with the liquid developer.

[Control unit]
As shown in FIG. 1, the image forming apparatus 100 of the present embodiment includes a control unit 200. The control unit 200 will be described with reference to FIGS. 1 and 2 with reference to FIG. However, although various devices such as a motor and a power source for operating the image forming apparatus 100 are connected to the control unit 200 in addition to those shown in the illustration, the illustration and description thereof will be omitted here because it is not the main purpose of the invention.

The control unit 200 as an adjusting means controls various types of the image forming apparatus 100 such as an image forming operation, and has a CPU (Central Processing Unit) (not shown). A memory 201 such as a ROM or RAM as a storage means or a hard disk device is connected to the control unit 200. Various programs, data, and the like for controlling the image forming apparatus 100 are stored in the memory 201. The control unit 200 may execute the image forming job stored in the memory 201 to operate the image forming apparatus 100 to perform image forming. In the case of the present embodiment, the control unit 200 can execute the "correction data generation process" for calculating the correction data used to correct the amount of laser light emitted by the exposure apparatus 3 at the time of image formation. The correction data generation process will be described later (see FIG. 7). Further, various data such as correction data calculated by the correction data generation process (see FIG. 11) are stored in the memory 201. Further, the memory 201 may temporarily store the calculation processing results and the like accompanying the execution of various programs.

Here, the image forming job is a series of operations from the start of image formation to the completion of the image forming operation based on the print signal for forming an image on the recording material. That is, after starting the preliminary operation (so-called forward rotation) required for performing image formation, the preliminary operation required for completing image formation (so-called backward rotation) is completed through the image forming step. It is a series of operations up to. Specifically, it refers to the period from the front rotation (preparatory operation before image formation) after receiving the print signal (reception of the image formation job) to the rear rotation (operation after image formation), and the image formation period. , Including between papers.

In the present specification, the non-image forming time is, for example, a front rotation time, a back rotation time, a space between papers, and the like. The pre-rotation period is a period from the start of rotation of the photosensitive drum 1 or the like without forming a toner image by receiving a print signal at the start of image formation to the start of exposure to the photosensitive drum 1. The post-rotation time is a period from the end of the final image formation of the image forming job to the stop of the rotation of the photosensitive drum 1 and the like which are continuously rotated without forming the toner image. Further, the space between papers is a period between the image area corresponding to the recording material S and the image area, and when various controls are performed during the space between papers, the period between papers may be extended as appropriate.

In addition to the memory 201, the control unit 200 includes a charging power supply V1, a developing power supply V2, an exposure power supply V3, a surface potential sensor 9, a fan control unit 300, a developing roller attachment / detachment mechanism 301, and a cleaning blade attachment / detachment via an input / output interface. The mechanism 302 is connected. The control unit 200 controls the charging power supply V1 and can charge the photosensitive drum 1 to a desired charging potential (dark area potential) by the corona charging device 2. The control unit 200 can individually control the upstream charger 21 and the downstream charger 22 by the charging power supply V1. Further, the control unit 200 can control the developing power supply V2 and develop the electrostatic latent image on the photosensitive drum 1 into a toner image by the developing roller 41.

Further, the control unit 200 controls the exposure power supply V3, and the light amount can be adjusted in order to expose the photosensitive drum 1 to a desired exposure part potential (bright part potential) with a different light amount depending on the exposure device 3. Although details will be described later, in the case of the present embodiment, the control unit 200 refers to the amount of the laser beam L used at the time of image formation based on the "correction data" (see FIG. 13 described later) stored in the memory 201. Correct and set the amount of light. The reference light amount is the amount of light of the laser beam L to irradiate the photosensitive drum 1 required when the exposed potential is set to the target potential (for example, −100 V) when there is no liquid. The control unit 200 can change the target potential according to image formation conditions such as image density, and can change the reference light amount according to the change of the target potential.

The control unit 200 can detect the surface potential of the photosensitive drum 1 based on the detection result of the surface potential sensor 9. The control unit 200 can control the fan control unit 300 to appropriately operate the air supply fan F1 and the intake fan F2. The control unit 200 can control the developing roller contact / detachment mechanism 301 to move the developing roller 41 to a position close to or separated from the photosensitive drum 1. When the developing roller 41 is located in a close position, the space between the developing roller 41 and the photosensitive drum 1 is filled with the carrier liquid. On the other hand, when the developing roller 41 is located at a separated position, the space between the developing roller 41 and the photosensitive drum 1 is not filled with the carrier liquid. In this case, since the liquid developer (mainly the carrier liquid) is separated from the developing roller 41 and is difficult to move to the photosensitive drum 1, it is difficult for the carrier liquid to adhere to the photosensitive drum 1.

Further, the control unit 200 can control the cleaning blade contact / detachment mechanism 302 to move the cleaning blade 70 to the contact position or the non-contact position. In the present embodiment, when the cleaning blade 70 is in the contact position, the cleaning blade 70 can remove the toner from the photosensitive drum 1. On the other hand, when the cleaning blade 70 is in the non-contact position, the cleaning blade 70 cannot remove the toner from the photosensitive drum 1.

By the way, as already described, conventionally, when the next electrostatic latent image is formed with the carrier liquid adhering to the photosensitive drum 1, the exposure is appropriate due to the carrier liquid adhering to the photosensitive drum 1. Image defects were likely to occur without being performed. This is a state where the carrier liquid does not adhere to the photosensitive drum 1 (referred to as when there is no liquid) and a case where the carrier liquid adheres to the photosensitive drum 1 (referred to as when there is liquid). This is because the reflectance of the irradiated laser beam L is different. When the reflectance of the laser beam L differs between when there is no liquid and when there is liquid, the amount of light of the laser light L that reaches the photosensitive layer 1c (see FIG. 3) of the photosensitive drum 1 changes, and as a result, the amount of light of the laser light L changes between when there is no liquid and when there is liquid. There is a difference in the exposed area potential between the time and the time. In the present specification, the "state in which the carrier liquid does not adhere to the photosensitive drum 1" means that the carrier liquid has adhered to the photosensitive drum 1 in addition to the case where the surface of the photosensitive drum 1 is dry. However, the case where the liquid thickness does not affect the reflectance of the laser beam L is included.

FIG. 5 schematically shows how the laser beam L emitted from the exposure apparatus 3 reaches the photosensitive drum 1. FIG. 5A shows the case without liquid, and FIG. 5B shows the case with liquid. The reference numeral Δd in FIG. 5B represents the thickness of the carrier liquid adhering to the photosensitive drum 1, and the reference numeral ΔS represents the thickness of the protective layer 1e. As can be understood by comparing FIGS. 5 (a) and 5 (b), the reflection mode of the laser beam L on the photosensitive drum 1 is different between the time without liquid and the time with liquid.

FIG. 6 shows the refractive index of air (n0), the refractive index of carrier liquid (n2), the refractive index of the protective layer 1e of the photosensitive drum 1 (n1), and the reflectance of light (R1 to R3). The reflectance of light (R1 to R3) is the reflectance at each position represented by the same reference numerals in FIGS. 5 (a) and 5 (b). That is, the reflectance R1 is the reflectance of the photosensitive drum 1 when there is no liquid, the reflectance R2 is the reflectance of the carrier liquid surface when there is liquid, and the reflectance R3 is the reflectance of the photosensitive drum 1 when there is liquid. These reflectances (R1 to R3) are the reflectances when the photosensitive drum 1 is irradiated with vertical light from the air layer side, and are obtained by the following equations 1 to 3. The difference ΔR in the reflectance of light between the case without liquid and the time with liquid is obtained by the following equation 4.

R1 = (n0-n1) ² / (n0 + n1) ² × 100 (%) ... Equation 1
R2 = (n0-n2) ² / (n0 + n2) ² × 100 (%) ... Equation 2
R3 = (n1-n2) ² / (n1 + n2) ² × 100 (%) ... Equation 3
ΔR = R1- (R2 + R3) ... Equation 4

As shown in FIG. 6, in the case of this embodiment, the reflectance R1 of the photosensitive drum 1 when there is no liquid is 12.6%. On the other hand, the reflectance R2 on the surface of the carrier liquid in the presence of liquid is "5.3%", and the reflectance R3 of the photosensitive drum 1 in the presence of liquid, that is, the reflectance R3 at the interface between the carrier liquid and the protective layer 1e is ". 1.8% ". Therefore, the sum of the reflectances (R2 + R3) with respect to the laser beam L in the presence of the liquid is "7.1%". Then, the difference ΔR of the reflectance between the time without liquid and the time with liquid is “5.5%” according to the above equation 4. This means that the reflectance is lower when there is liquid than when there is no liquid. Therefore, when the laser beam L of the same amount of light as that irradiated without the liquid is irradiated with the liquid, the exposed potential becomes higher than that without the liquid (for example, about 20 V, the exposure per 1% of the reflectance difference (ΔR)). The amount of change in the local potential is about 4V). Therefore, it is preferable to reduce the amount of laser light L when there is liquid as compared with when there is no liquid.

In view of the above points, in order to obtain the same exposure potential (specifically, the target potential) with and without liquid, the laser beam used with liquid (that is, during image formation) with reference to the time without liquid. The amount of light of L may be adjusted. In order to do so, in the present embodiment, correction data for correcting the amount of light of the laser beam L is created and stored in the memory 201 (see FIG. 4). Therefore, the "correction data generation process" for creating the correction data will be described with reference to FIGS. 2 and 4 with reference to FIGS. 7 to 13.

[Correction data generation process]
FIG. 7 shows the correction data generation process of the first embodiment. In the case of the present embodiment, the control unit 200 is the first embodiment when the image forming apparatus 100 equipped with the new photosensitive drum 1 (including after replacement with the new photosensitive drum 1) is started for the first time (initial time). Executes the correction data generation process of. This is because the reflectance of the laser beam L differs depending on the individual difference of the photosensitive drum 1 and the cleaning blade 70. That is, the reflectance of the photosensitive drum 1 may differ depending on the image forming apparatus 100, and the thickness of the carrier liquid after cleaning may not be constant, and the reflectance may also differ depending on the thickness. Therefore, in the present embodiment, the correction data generation process is executed at the initial stage.

As shown in FIG. 7, the control unit 200 starts driving the photosensitive drum 1 (S1). At this time, the static elimination device 73 is also started to operate. Then, the control unit 200 controls the charging power supply V1 to charge the photosensitive drum 1 with the corona charger 2 (S2).

Here, the charge control of the photosensitive drum 1 by the corona charger 2 will be described. Here, the code relating to the charge control by the upstream side charger 21 is represented by “U”, and the code relating to the charge control by the downstream side charger 22 is represented by “L”. Further, with respect to the rotation direction of the photosensitive drum 1, the position (sensor position) of the surface potential sensor 9 is represented by the reference numeral “sens”, and the development position by the developing roller 41 is represented by the reference numeral “dev”.

First, charging control by the upstream charging device 21 will be described with reference to FIG. 9 with reference to FIG. The upstream side charger 21 charges the photosensitive drum 1 by applying a predetermined grid voltage “Vg (U)” to the grid electrode 21b and passing a direct current Ip (U) through the discharge wire 21a. FIG. 9 shows the relationship between the grid voltage “Vg (U)” applied to the grid electrode 21b when the photosensitive drum 1 is rotating at 700 mm / s and the surface potential of the photosensitive drum 1 after charging. When the grid voltage "Vg (U)" is "-700V" and the DC current Ip (U) is "-1600μA", the surface potential is about "-430V" (Vd (U)) at the sensor position as shown in FIG. ) Sensor), it is charged to about "-400V" (Vd (U) dev) at the developing position. That is, the dark attenuation amount of the photosensitive drum 1 in this embodiment is about 30 V at the sensor position and the developed position. In the upstream charger 21, the grid voltage “Vg (U)” is adjusted so that the surface voltage at the sensor position is about “−450 V”.

Next, charging control by the downstream charging device 22 will be described with reference to FIG. 10 with reference to FIG. The charging control by the downstream charging device 22 is performed together with the charging control by the upstream charging device 21. The downstream side charger 22 charges the photosensitive drum 1 by applying a predetermined grid voltage “Vg (L)” to the grid electrode 22b and passing a direct current Ip (L) through the discharge wire 22a. FIG. 10 shows the relationship between the grid voltage “Vg (U)” applied to the grid electrode 22b when the photosensitive drum 1 is rotating at 700 mm / s and the surface potential of the photosensitive drum 1 after charging. When the grid voltage "Vg (L)" is "-600V" and the DC current Ip (L) is "-1600μA", the surface potential is about "-530V" (Vd (U + L) sensors) at the sensor position and at the development position. It is charged to about "-500V" (Vd (U + L) dev). In the downstream side charger 22, the grid voltage "Vg (L)" is adjusted so that the surface potential of the developing position becomes about "-500 V" (synthetic surface potential) in combination with the charge control by the upstream side charger 21. As described above, in the present embodiment, the upstream charging device 21 and the downstream charging device 22 are independently controlled so that the surface potential at the developing position becomes a desired charging potential.

Returning to FIG. 7, the control unit 200 executes the “EV measurement (DRY) process” as the first mode in order to acquire the data when there is no liquid (S3). When the "EV measurement (DRY) process" is executed (in the first mode), the developing roller 41 is located at a separated position. Therefore, by executing the "EV measurement (DRY) process", the carrier liquid does not adhere to the photosensitive drum 1, that is, the light amount of the laser beam L and the light amount of the laser light L with respect to "when there is no liquid" in a state where the surface is dry. Data showing the relationship with the exposed portion potential (data without liquid, see FIG. 11 to be described later) can be obtained. After executing the "EV measurement (DRY) process" (after the first mode), the control unit 200 executes the "EV measurement (WET) process" as the second mode, but before that, "liquid application" is performed. "Processing" is executed (S4). By executing the "liquid coating process", "when there is liquid" in a state where the carrier liquid is attached to the photosensitive drum 1 is created. Then, in the same manner as when there is no liquid, the control unit 200 sets the control unit 200 to obtain data (data when there is liquid, see FIG. 11 to be described later) showing the relationship between the amount of light of the laser beam L and the potential of the exposed part with respect to the time when there is liquid. "EV measurement (WET) processing" is executed (S5). When the "EV measurement (WET) process" is executed (in the second mode), the developing roller 41 is located in a close position.

The above "liquid coating process" (see S4) will be described with reference to FIGS. 2 and 4 with reference to FIG. As shown in FIG. 8, the control unit 200 starts driving the developing device 4 (S11). That is, the developing roller 41, the film forming roller 42, and the cleaning roller 43 rotate. Further, a voltage "0V" is applied to the developing roller 41, the film forming roller 42, the cleaning roller 43, and the film forming electrode 44. Then, the control unit 200 controls the developing roller contact / detachment mechanism 301 to execute a “development roller attachment operation” of moving the developing roller 41 from the separated position to the close position with respect to the photosensitive drum 1 (S12). In the case of the present embodiment, the developing roller 41, the film forming roller 42, and the cleaning roller 41 are cleaned so as not to cause toner consumption due to the detection electrostatic latent image being developed into a toner image by moving the developing roller 41 to a close position. A voltage "0V" is applied to the roller 43 and the film forming electrode 44. After that, after the development roller 41 moves to the close position and at least one rotation of the photosensitive drum 1 elapses, the control unit 200 executes the "cleaning blade attachment operation" (S13). That is, the control unit 200 controls the cleaning blade contact / detachment mechanism 302 to move the cleaning blade 70 from the separated position to the close position with respect to the photosensitive drum 1. By rotating the photosensitive drum 1 one or more turns and then moving the cleaning blade 70 to a close position, the cleaning blade 70 comes into contact with the photosensitive drum 1 with the liquid developer on the surface of the photosensitive drum 1. This makes it possible to prevent the cleaning blade 70 from being worn, chipped, or curled.

The above-mentioned "EV measurement (DRY) processing" (S3) and "EV measurement (WET) processing" (S5) will be described with reference to FIG. The "EV measurement (DRY) process" and the "EV measurement (WET) process" are performed only by the difference between whether the carrier liquid is attached to the surface of the photosensitive drum 1 or not. The procedure is the same.

The control unit 200 controls the amount of laser light of the exposure apparatus 3 to expose the surface of the charged photosensitive drum 1 to form an electrostatic latent image for detection. The detection electrostatic latent image is, for example, an electrostatic latent image capable of forming an output image (solid image) having a printing rate of 100%. As shown in FIG. 11, in the present embodiment, the photosensitive drum 1 is exposed by irradiating the laser beam L with a different laser beam amount (E1 to E4) each time. Then, the control unit 200 acquires the potential of the electrostatic latent image for detection detected by the surface potential sensor 9, that is, the potential of the exposed unit (white circles and black circles in the figure), and the amount of laser light (E1 to E4) irradiated with this. Is stored in the memory 201 in association with. When a photosensitive drum 1 having an amorphous silicon photosensitive layer formed therein is used, an approximate straight line as shown in FIG. 11 is stored. The approximate straight line based on the white circle is "data without liquid" representing the EV (laser light amount-exposure part potential) characteristic in the state where the carrier liquid is not attached to the photosensitive drum 1. On the other hand, the approximate straight line based on the black circle is "data with liquid" representing the EV characteristic in the state where the carrier liquid is attached to the photosensitive drum 1. As shown in FIG. 11, when exposed with the same amount of laser light, the potential of the exposed part is smaller when there is liquid than when there is no liquid (about 20 V). From a different point of view, it can be understood that in order to obtain the same exposure potential (for example, the target potential "-100V"), it is sufficient to expose the photosensitive drum 1 with a smaller amount of laser light in the presence of liquid than in the absence of liquid. ..

Returning to FIG. 7, the control unit 200 obtains “potential difference data” based on the “data without liquid” and the “data with liquid” shown in FIG. 11 (S6). FIG. 12 shows “potential difference data”. As shown in FIG. 12, the "potential difference data" is data showing the relationship between the potential difference (ΔV) from the exposed part potential when the liquid is present and the laser light amount based on the exposed part potential when there is no liquid. It is stored in the memory 201.

Further, the control unit 200 obtains "correction data" for correcting the amount of laser light in the presence of liquid based on the "data without liquid" and "data with liquid" shown in FIG. 11 (S7). , This is stored in the memory 201. After that, the control unit 200 ends the "correction data generation process" and shifts the image forming apparatus 100 to a standby state in which the image forming operation can be started in response to the reception of the image forming job. FIG. 13 shows “correction data”. As shown in FIG. 13, the “correction data” is data showing the relationship between the exposed potential and the correction amount. More specifically, at the developing position, a laser that can have the same exposed part potential as when there is no liquid shown by the dotted line from the reference light amount irradiated to obtain the desired exposed part potential (target potential) when there is no liquid shown by the solid line. It is data representing the correction amount ΔE for obtaining the light amount. In the case of the present embodiment, the control unit 200 can obtain the amount of light of the laser beam L to be applied to the exposure apparatus 3 based on the "correction data" stored in the memory 201 at the time of image formation (when there is liquid).

As described above, in the present embodiment, "data without liquid" and "data with liquid" are obtained by irradiating laser light of different light amounts and actually measuring the potential of the exposed part at the initial stage, and based on these, "data with liquid" is obtained. The "correction data" is obtained and stored in the memory 201. By creating and storing the above-mentioned "correction data", the exposure device 3 emits the amount of light of the laser beam L to be irradiated to the exposure device 3 in order to set the exposure unit potential to the target potential at the time of image formation. It becomes possible to correct and set the light amount (reference light amount) of the laser light L as a reference. The "data without liquid" is data that reflects the reflectance of the laser beam L that may fluctuate mainly due to the photosensitive drum 1, and the "data with liquid" may fluctuate mainly due to the carrier liquid. This is data reflecting the reflectance of the laser beam L. According to this, even if the reflectance of the laser beam L differs depending on the individual difference of the photosensitive drum 1 and the cleaning blade 70, it is possible to obtain an appropriate amount of laser beam capable of exposing the exposed portion potential to the target potential at the time of image formation. Therefore, in the present embodiment, in the image forming apparatus 100 that forms an image using a liquid developer, the carrier liquid is attached to the photosensitive drum 1 before charging even though the carrier liquid is attached. The effect that the influence on the image caused by the above can be reduced can be obtained.

<Second embodiment>
In the first embodiment described above, the correction data generation process may be executed at the first start-up of the image forming apparatus 100 equipped with the new photosensitive drum 1, in addition to the case described as the example. For example, the correction data generation process may be executed at the time of non-image formation, and the above-mentioned "correction data" (see FIG. 13) may be updated. The reason for updating the "correction data" is that the reflectance of the laser beam L irradiated from the exposure apparatus 3 that causes a difference in the exposed portion potential between the case without liquid and the time with liquid deteriorates the photosensitive drum 1 due to long-term use. This is because it changes as the carrier liquid deteriorates. It is necessary to update the "correction data" in order to reflect the change in the reflectance of the laser beam L.

Therefore, the correction data generation process of the second embodiment in which the "correction data" can be updated at the time of backward rotation will be described with reference to FIGS. 2 and 4 with reference to FIG. In the second embodiment shown in FIG. 14, the same reference numerals are given to the same processes as the correction data generation process of the first embodiment shown in FIG. 7, and these processes will be briefly described. Further, here, in order to make the explanation easier to understand, the case of executing the execution at the time of the rear rotation will be described as an example, but the present invention is not limited to this, and the execution may be performed at the time of the front rotation or between papers. Examples of execution between papers include a case where a correction data generation process is executed every time the cumulative number of image-formed recording materials S reaches an integral multiple of a predetermined number (for example, every 3000 sheets).

As shown in FIG. 14, the control unit 200 executes "EV measurement (WET) processing" as the first detection mode while maintaining the developing roller 41 at a close position (S5). However, unlike the first embodiment described above, the "EV measurement (WET) process" is executed without executing the "liquid coating process" (see S4 in FIG. 7). This is because the carrier liquid is attached to the photosensitive drum 1 during the post-rotation (when there is liquid), so that it is not necessary to execute the “liquid coating treatment”. By executing the "EV measurement (WET) process", data with liquid can be obtained (see FIG. 9).

The control unit 200 executes "cleaning blade deoperation" after executing "EV measurement (WET) processing" (after the first detection mode) (S21). That is, the control unit 200 controls the cleaning blade contact / detachment mechanism 302 to move the cleaning blade 70 from the contact position to the non-contact position with respect to the photosensitive drum 1. Further, the control unit 200 executes the "development roller de-operation" (S22). That is, the control unit 200 controls the developing roller contact / detachment mechanism 301 to move the developing roller 41 from the close position to the separated position with respect to the photosensitive drum 1. In this way, when the "EV measurement (DRY) process" (see S3) described later is executed, the cleaning blade 70 and the developing roller 41 are separated from the photosensitive drum 1. The control unit 200 controls the developing power supply V2 to stop the application of the developing voltage applied for image formation (for example, 0V), and also stops the rotation of the developing roller 41 (S23). In order to suppress toner consumption, the control unit 200 controls the developing power supply V2 at the time of "EV measurement (WET) processing" (S5) to apply the developing voltage applied for image formation. You may stop.

The control unit 200 executes "EV measurement (DRY) processing" as a second detection mode in order to obtain data when there is no liquid. However, in that case, it is necessary to remove the carrier liquid from the photosensitive drum 1 to create a state in which the carrier liquid does not adhere to the photosensitive drum 1 (when there is no liquid). Therefore, the control unit 200 controls the fan control unit 300 after executing the "EV measurement (WET) process" (after the first detection mode) to operate the supply air fan F1 and the intake fan F2. (S24). That is, in the present embodiment, the air supply fan F1 and the intake fan F2 are used to forcibly circulate air on the surface of the photosensitive drum 1 to dry the surface of the photosensitive drum 1, thereby causing the carrier liquid from the photosensitive drum 1. Is being removed. In order to dry the surface of the photosensitive drum 1, it is necessary to operate the air supply fan F1 and the intake fan F2 for a predetermined time. Therefore, the control unit 200 activates the timer (S25) and operates the supply air fan F1 and the intake fan F2 until the timer elapses for 1 minute or more (NO in S26). When the timer has elapsed for 1 minute or more (YES in S26), the control unit 200 executes the "EV measurement (DRY) process" (S3) and obtains the data when there is no liquid (see FIG. 9).

In the present embodiment, the time for operating the air supply fan F1 and the intake fan F2 is set to 1 minute or more, but the time is not limited to this, and the volatility of the carrier liquid, the amount of liquid that passes through the cleaning blade 70, and the air supply fan F1 are not limited to this. And may be arbitrarily set based on the air volume of the intake fan F2 and the like. Further, the photosensitive drum 1 may be rotated for a predetermined time to be naturally dried without using the air supply fan F1 and the intake fan F2.

The control unit 200 obtains the "potential difference data" shown in FIG. 12 based on the "data without liquid" and the "data with liquid" shown in FIG. 11 (S6). Further, the control unit 200 has the "correction data" shown in FIG. 13 for correcting the amount of laser light in the presence of liquid based on the "data without liquid" and the "data with liquid" shown in FIG. (S7) and stores this in the memory 201. After that, the control unit 200 controls the charging power supply V1 to stop the application of the charging voltage (S28), and stops the rotation of the photosensitive drum 1 (S29). Then, the control unit 200 ends the "correction data generation process" and shifts the image forming apparatus 100 to a standby state in which the image forming operation can be started in response to the reception of the next image forming job.

As described above, in the present embodiment, "data without liquid" and "data with liquid" are obtained by irradiating laser light of different light amounts and measuring the exposed potential at the time of non-image formation. Based on this, the "correction data" can be updated. As a result, even if the reflectance of the laser beam L changes due to deterioration of the photosensitive drum 1 or carrier liquid due to long-term use, the target is the amount of light of the laser beam L to be irradiated to the exposure apparatus 3 at the time of image formation. It can be set to an appropriate amount of light to obtain the potential. Therefore, also in the second embodiment, although the carrier liquid is attached to the photosensitive drum 1 before charging, the influence on the image due to the carrier liquid being attached can be reduced. The same effect as that of the embodiment can be obtained.

<Other embodiments>
In the second embodiment described above, the "EV measurement (WET) process" is executed in order to obtain the data in the presence of liquid (S5 in FIG. 14), but the process of obtaining the data in the presence of liquid is performed. Not limited to this. For example, the "data without liquid" in FIG. 11 obtained by executing the "EV measurement (DRY) process" (S3 in FIG. 14) without executing the "EV measurement (WET) process", and the figure. Based on the "potential difference data" of 12, the "data with liquid" of FIG. 11 may be obtained. Specifically, in the correction data generation process shown in FIG. 14, "EV measurement (WET) process" (S5) is deleted, and "EV measurement (DRY) process" (S3) is followed by "liquid". A process for obtaining "data with liquid" may be added based on "data without liquid" and "potential difference data".

In order to obtain the "data with liquid", the "potential difference data" shown in FIG. 12 stored in the memory 201 is obtained from the exposed part potentials of the light amounts E1, E2, E3, and E4 of the "data without liquid" shown in FIG. The potential difference ΔV in the light amounts E1, E2, E3, and E4 of the above is subtracted. Then, different exposure potentials in the light amounts E1, E2, E3, and E4 can be obtained (black circles in FIG. 11), but the approximate straight lines thereof represent the EV characteristics in the state where the carrier liquid is attached to the photosensitive drum 1. Data when there is liquid ". In this way, after obtaining the "data without liquid" by actual measurement, the "data with liquid" is obtained by calculation based on the "data without liquid" and the "potential difference data" without actually measuring. You can do it.

By doing so, it is not necessary to execute the "EV measurement (WET) process" (see S5 in FIG. 14) in order to obtain the "data with liquid", so that the "EV measurement (WET) process" is executed. This can suppress an increase in equipment downtime and toner consumption. However, since this method is based on the premise that the "potential difference data" is stored in the memory 201, it cannot be applied when the "potential difference data" is not stored in the memory 201 (at the time of initial startup).

In the first and second embodiments described above, a state in which the carrier liquid is attached to the photosensitive drum 1 and a state in which the carrier liquid is not attached to the photosensitive drum 1 are created by contacting and separating the developing roller 41. The case has been described as an example, but the present invention is not limited to this. For example, a carrier liquid supply device provided so as to be in contact with and detachable from the photosensitive drum 1 may be used to create a state in which the carrier liquid is attached and a state in which the carrier liquid is not attached. As the carrier liquid supply device, for example, a dedicated device for supplying the carrier liquid to the photosensitive drum 1 may be used, or a transfer belt unit including an intermediate transfer belt 91 to which the carrier liquid is supplied by a pre-wet roller may be used. good.

1 (1Y to 1Bk) ... image carrier (photosensitive drum), 1c ... photosensitive layer, 2 (2Y to 2Bk) ... charging means (corona charger), 3 (3Y to 3Bk) ... exposure means (exposure device), 9 ... Potential detecting means (surface potential sensor), 41 ... Developer carrier (development roller), 70 ... Cleaning means (cleaning blade), 91 ... Another image carrier (intermediate transfer belt), 92 ... Transfer means (primary transfer) Roller), 200 ... Adjustment means (control unit), 100 ... Image forming device, F1 ... Air supply fan, F2 ... Intake fan

Claims (11)

With a rotating image carrier,
A charging means for charging the image carrier and
An exposure means capable of adjusting the amount of light, which exposes the charged image carrier to form an electrostatic latent image on the image carrier.
A potential detecting means for detecting the exposed portion potential of the exposed portion exposed by the exposure means, and a potential detecting means.
A liquid developer containing a toner and a carrier liquid is supported and rotated, and an electrostatic latent image formed on the image carrier is filled between the image carrier and the image carrier by applying a voltage. A developer carrier that develops into an image and
A transfer means for transferring the toner image of the image carrier to another image carrier,
A cleaning means that comes into contact with the image carrier and removes toner remaining on the image carrier after transfer.
An adjusting means for adjusting the amount of light of the exposure means at the time of image formation is provided.
The adjusting means performs exposure with a plurality of different light amounts by the exposure means in a state where the carrier liquid does not adhere to the image carrier at the initial stage or at the time of non-image formation, and the exposure corresponding to the plurality of light amounts is performed. In the first mode in which the partial potential is detected by the potential detecting means, and in a state where the carrier liquid is attached to the image carrier, exposure is performed with a plurality of different light amounts by the exposure means, and the exposure is performed according to the plurality of light amounts. It is possible to execute a second mode in which the exposed portion potential is detected by the potential detecting means.
An image forming apparatus characterized in that. The developer carrier is provided so as to be movable between a separated position separated from the image carrier and a close position close to the image carrier.
The developer carrier is located at the separated position in the first mode and at the close position in the second mode.
The image forming apparatus according to claim 1. With a rotating image carrier,
A charging means for charging the image carrier and
An exposure means capable of adjusting the amount of light, which exposes the charged image carrier to form an electrostatic latent image on the image carrier.
A potential detecting means for detecting the exposed portion potential of the exposed portion exposed by the exposure means, and a potential detecting means.
A liquid developer containing toner and a carrier liquid is supported and rotated so as to be movable between a separated position separated from the image carrier and a close position close to the image carrier. In the case of, a developer carrier that develops an electrostatic latent image formed on the image carrier into a toner image by applying a voltage, and a developer carrier.
A transfer means for transferring the toner image of the image carrier to another image carrier,
A cleaning means that abuts on the image carrier and removes toner that remains on the image carrier after transfer.
An adjusting means for adjusting the amount of light of the exposure means at the time of image formation is provided.
At the initial stage, the adjusting means performs exposure with a plurality of different light amounts by the exposure means in a state where the developer carrier is located at the separated position, and obtains an exposure portion potential corresponding to the plurality of light amounts. The first mode detected by the potential detecting means, and after the first mode, the developer carrier is moved from the separated position to the close position, and the exposure means exposes the developer with a plurality of different amounts of light. It is possible to execute a second mode in which the exposure portion potential corresponding to a plurality of light amounts is detected by the potential detecting means.
An image forming apparatus characterized in that. The adjusting means forms an image based on the exposure part potential corresponding to the plurality of light amounts detected by the first mode and the exposure part potential corresponding to the plurality of light amounts detected by the second mode. Occasionally, correction data used for adjusting the amount of light of the exposure means is generated.
The image forming apparatus according to any one of claims 1 to 3. The cleaning means is movably provided between an abutting position that abuts on the image carrier and a non-abutment position that does not abut on the image carrier.
The cleaning means is located at the non-contact position in the first mode.
The image forming apparatus according to any one of claims 1 to 4. With a rotating image carrier,
A charging means for charging the image carrier and
An exposure means capable of adjusting the amount of light, which exposes the charged image carrier to form an electrostatic latent image on the image carrier.
A potential detecting means for detecting the exposed portion potential of the exposed portion exposed by the exposure means, and a potential detecting means.
A liquid developer containing toner and a carrier liquid is supported and rotated so as to be movable between a separated position separated from the image carrier and a close position close to the image carrier. A developer carrier that develops an electrostatic latent image formed on the image carrier into a toner image by applying a voltage when it is located on the image carrier.
A transfer means for transferring the toner image of the image carrier to another image carrier,
A cleaning means that abuts on the image carrier and removes toner that remains on the image carrier after transfer.
An adjusting means for adjusting the amount of light of the exposure means at the time of image formation is provided.
During the post-rotation of the image forming job, the adjusting means exposes the developer carrier with a plurality of different light amounts by the exposure means while maintaining the developer carrier at the close position, and the exposure unit corresponding to the plurality of light amounts. After the first detection mode in which the potential is detected by the potential detecting means and the first detection mode, the developer carrier is moved from the close position to the separated position, and the image carrier is rotated over a predetermined time. Then, it is possible to execute a second detection mode in which exposure is performed with a plurality of different light amounts by the exposure means, and the exposure unit potential corresponding to the plurality of light amounts is detected by the potential detection means.
An image forming apparatus characterized in that. The adjusting means is based on the exposure unit potential corresponding to the plurality of light amounts detected by the first detection mode and the exposure unit potential corresponding to the plurality of light amounts detected by the second detection mode. Generates correction data used to adjust the amount of light of the exposure means at the time of image formation.
The image forming apparatus according to claim 6. The cleaning means is movably provided between an abutting position that abuts on the image carrier and a non-abutment position that does not abut on the image carrier.
The cleaning means is moved from the contact position to the non-contact position after the first detection mode.
The image forming apparatus according to claim 6 or 7. After the first detection mode, the adjusting means moves the developer carrier from the near position to the separated position, and then removes the carrier liquid adhering to the image carrier.
The image forming apparatus according to any one of claims 6 to 8. The charging means is a corona charger that charges the image carrier by electric discharge.
An air supply fan that sends air to the corona charger,
It is equipped with an intake fan that sucks in the air discharged to the outside from the corona charger.
The adjusting means removes the carrier liquid adhering to the image carrier by operating the air supply fan and the intake fan.
The image forming apparatus according to claim 9. The image carrier is a photosensitive drum having a photosensitive layer having a higher refractive index than the carrier liquid.
The image forming apparatus according to any one of claims 1 to 10.

Images