JP2015114594A - Wet image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet image formation device which enables further improvement in image quality.SOLUTION: A wet image formation device 100 includes developer 12 which contains toner particles 12t and carrier liquid 12w, an image carrier 1 which carries and transports a latent image corresponding to image signal information, a developer carrier 9 which carries and transports the developer 12 on a surface thereof for developing the latent image on the image carrier 1 by using the developer 12, a destaticizing member 19 for destaticizing remaining developer 12 that remains on the developer carrier 9 after developing, a cleaning member 18 for removing the remaining developer 12 after destaticizing from the developer carrier 9, and control means which changes an output of the destaticizing member 19 according to the image signal information.

Description

  The present invention relates to a printer, a copying machine, a facsimile machine, and other electrophotographic image forming apparatuses, and more particularly, to a wet image forming apparatus that employs wet development as a developing system.

  Conventionally, various wet image forming apparatuses using wet electrophotography capable of outputting a high-quality image using toner having a smaller diameter than dry electrophotography have been proposed. Japanese Unexamined Patent Application Publication No. 2012-128094 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2010-44189 (Patent Document 2) disclose such wet image forming apparatuses using wet electrophotography.

JP 2012-128094 A JP 2010-044189 A

In recent years, further improvement in image quality has been demanded in wet image forming apparatuses.
The present invention has been made in view of the above problems, and an object thereof is to provide a wet image forming apparatus capable of further improving image quality.

  The wet developing apparatus of the present invention includes a developer containing toner particles and a carrier liquid, an image carrier for carrying and conveying a latent image according to image signal information, and carrying and carrying the developer on the surface thereof. A developer carrying member that develops a latent image on the carrying member with the developer, a charge removing member for removing the remaining developer remaining on the developer carrying member after development, and the remaining developer after removing the charge A cleaning member for removing the toner from the developer carrier, and a control means for changing the output of the charge removal member in accordance with the image signal information.

  In another embodiment, the control means corresponds to a non-image portion that is a region where the amount of the toner particles in the remaining developer within the unit area of the developer carrier calculated from the image signal information is large. The output of the charge eliminating member is changed according to the ratio between the area and the image area corresponding area where the amount of the toner particles in the residual developer is small.

  In another embodiment, the control means changes the output of the static elimination member according to a printing area ratio within a unit area calculated from the image signal.

  In another embodiment, the control means corresponds to a non-image portion that is a region where the amount of the toner particles in the remaining developer within the unit area of the developer carrier calculated from the image signal information is large. In the area and the image area corresponding area where the amount of the toner particles in the residual developer is small, the non-image area corresponding area is more than the amount of charge applied to the image area corresponding area by the charge eliminating member. The output of the static eliminating member is changed so that the amount of charge applied increases.

  According to the present invention, it is possible to provide a wet image forming apparatus capable of further improving image quality.

1 is a schematic diagram illustrating a configuration of a wet image forming apparatus according to Embodiment 1. FIG. 1 is an enlarged view of a wet developing apparatus according to Embodiment 1. FIG. FIG. 6 is a schematic diagram illustrating a state of a developing portion (nip portion) between an image carrier and a developer carrier during development. FIG. 4 is a schematic diagram illustrating a state of a developing portion (nip portion) immediately after an image carrier and a developer carrier are separated. FIG. 6 is a schematic diagram illustrating a case where charges are uniformly applied to a remaining developer having a non-uniform charge amount. It is a schematic diagram which shows the case where the area | region with an appropriate charge amount and the area | region which is not appropriate exist after static elimination. FIG. 6 is a schematic diagram illustrating a state of a developing unit immediately after an image carrier and a developer carrier are separated in a dot pattern. It is a schematic diagram showing a case where the charge is changed and applied to the remaining developer whose charge amount is not uniform. It is a schematic diagram which shows the case where a charge amount becomes an appropriate area | region after static elimination. FIG. 3 is a functional block diagram for controlling a current flowing into a developer carrier in the first embodiment. 6 is a diagram illustrating a control flow of output adjustment of a static elimination member in Embodiment 1. FIG. FIG. 10 is a schematic diagram showing a state of residual developer in an image portion corresponding region and a non-image portion corresponding region of a developer carrier in the second embodiment. FIG. 10 is a diagram showing a control flow of output adjustment of a static elimination member in Embodiment 2. It is a schematic diagram which shows the modification of the wet image forming apparatus in each embodiment. It is a figure which shows the printing pattern employ | adopted in the Example and the comparative example. It is a figure which shows the evaluation result in an Example and a comparative example. FIG. 6 is a schematic diagram illustrating toner accumulation.

  A wet image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In each embodiment described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

  In recent years, in a developing section in wet electrophotography, a part of the developer collected by the cleaning blade is deposited near the upstream of the blade contact section in the cleaning section of the developing roller (developer carrier), and the developer is discharged. There is a problem that will be difficult (hereinafter referred to as “toner accumulation”).

  As shown in FIG. 17, the layer of the developer 12 that enters the developer cleaning member 18 is unevenly distributed in a layer state on the surface of the developer carrier 9, and the toner particles 12t are formed by the charge of the toner particles 12t. The developer carrier 9 is electrostatically restrained. Therefore, when the developer 12 is cleaned by the developer cleaning member 18, the toner particles 12 t are collected near the edge 18 e of the developer cleaning member 18. The developer 12 in which the toner particles 12t are collected has a very high concentration of the toner particles 12t (because the concentration is high), and thus the viscosity of the developer 12 becomes high.

  On the other hand, the developer 12 that has passed through other than the vicinity of the edge 18e of the developing cleaning member 18 has a low viscosity because the carrier liquid 12w is increased. Since the developer 12 flows over the high-viscosity developer 12 and is quickly discharged (arrow Y in the figure), as a result, the concentration of the toner particles 12t is near the edge 18e of the developing cleaning member 18. The very high developer 12 accumulates without moving. This is the “toner accumulation” phenomenon.

  When toner accumulation occurs, many of the toner particles 12t conveyed by the developer carrier 9 accumulate on the edge 18e of the developing cleaning member 18. From the viewpoint of cost, the developer 12 collected by the development cleaning member 18 is preferably returned to the developer tank (not shown) and used repeatedly for development.

  However, when toner accumulation occurs, it becomes difficult to convey the developer 12 for reuse, and the developer 12 that is discarded during maintenance increases. Furthermore, if the accumulated toner particles 12t are excessively accumulated, it causes deterioration in image quality such as deterioration of maintainability and image noise.

  In the toner accumulation, when the developer 12 after development is neutralized by the neutralizing member and the electrostatic binding force between the developer carrier 9 and the toner particles 12t is weakened, a certain improvement can be obtained. Decreasing the electrostatic binding force means canceling the charge applied during charging.

  Here, if the output of the static elimination member is too weak, electrostatic restraint force at the time of charging remains, causing toner accumulation. Furthermore, if the output of the charge removal member is excessive, the electrostatic binding force due to charge removal (the opposite polarity to the charge applied at the time of charging) increases, which causes a deterioration in toner accumulation. Therefore, there is an appropriate value for the output of the charge removal member, and therefore it is necessary to appropriately control the output based on the toner particle amount and the charge amount.

  However, the amount of toner particles and the amount of charge of toner particles contained in the undeveloped developer after development vary depending on the location depending on the development pattern. In general, a DC corotron charger is often used as the charge eliminating member. However, the DC corotron charger is constant even if the amount of toner particles contained in the development residual developer and the charge amount of the toner particles change. This amount of charge is imparted to the undeveloped developer (toner layer), so that a place deviating from the appropriate charge removal amount is created depending on the place.

  As a result, excessive neutralization and insufficient neutralization partially occur, and the electrostatic restraint force cannot be weakened. As a result, toner accumulation may not be able to be resolved in long-term driving.

  The wet image forming apparatus in each embodiment described below has been made in view of the above-described problems, and can eliminate toner accumulation by performing charge removal of a development residual developer according to an image pattern. A wet image forming apparatus is provided, thereby enabling further improvement in image quality.

[Embodiment 1]
(Example of configuration and operation of wet image forming apparatus 100)
With reference to FIG. 1, the configuration of wet image forming apparatus 100 in the present embodiment will be described. The image forming unit includes an image carrier 1 using a photosensitive drum, a charging device 2, an exposure device 3, a wet developing device 4, an intermediate transfer member 5, a secondary transfer member 6, an image carrier cleaning device 7, and an intermediate A transfer body cleaning device 8 is provided.

  The image carrier 1 has a cylindrical shape with a photoreceptor layer (not shown) formed on the surface thereof, and is driven to rotate in the direction of arrow A in the figure. On the outer periphery of the image carrier 1, a charging device 2, an exposure device 3, a wet developing device 4, an intermediate transfer member 5, an image carrier cleaning device 7, and an eraser lamp 10 are arranged in the rotation direction of the image carrier 1 ( They are sequentially arranged along the direction of arrow A in the figure.

  The charging device 2 charges the surface of the image carrier 1 to a predetermined potential. The exposure device 3 irradiates the surface of the image carrier 1 with light and lowers the charge level in the irradiated area to form an electrostatic latent image. The wet developing device 4 develops the latent image formed on the image carrier 1. That is, the developer 12 is transported to the development area of the image carrier 1. Developer 12 includes toner particles 12t and carrier liquid 12w. The toner particles 12 t contained in the developer 12 are supplied to the electrostatic latent image on the surface of the image carrier 1 to form a toner image on the image carrier 1.

(Development process)
In the developing process using the wet image forming apparatus 100, a developing bias voltage is applied to the developer carrier 9 of the wet developing apparatus 4 from a power source (not shown). In accordance with the electric field generated in balance with the potential of the latent image on the image carrier 1, the toner particles 12 t in the developer 12 are electrostatically attracted to the latent image portion of the image carrier 1, and the latent image on the image carrier 1 is Is developed.

  In the wet image forming apparatus 100, the intermediate transfer unit includes an intermediate transfer member 5, a secondary transfer member 6, and an intermediate transfer member cleaning device 8. The intermediate transfer member 5 is disposed so as to face the image carrier 1 and rotates in the direction of arrow B in the drawing while being in contact with the image carrier 1. The primary transfer of the toner image from the image carrier 1 to the intermediate transfer member 5 is performed at the nip portion between the intermediate transfer member 5 and the image carrier 1.

  In the primary transfer process, a transfer bias voltage is applied to the intermediate transfer member 5 from a power source (not shown). As a result, an electric field is formed between the intermediate transfer member 5 and the image carrier 1 at the primary transfer position, and the toner image on the image carrier 1 is electrostatically attracted to the intermediate transfer member 5, thereby Is transcribed.

  When the toner image is transferred to the intermediate transfer member 5, the image carrier cleaning device 7 removes the remaining developer on the image carrier 1, and the next image formation is performed. An eraser lamp 10 is installed between the image carrier cleaning device 7 and the charging device 2 as necessary.

  The intermediate transfer member 5 and the secondary transfer member 6 are disposed so as to face each other with a recording medium 11 serving as a recording material interposed therebetween, and rotate in contact with each other via the recording medium 11. Secondary transfer of the toner image from the intermediate transfer member 5 to the recording medium 11 is performed at the nip portion between the intermediate transfer member 5 and the secondary transfer member 6. The recording medium 11 is conveyed to the secondary transfer position in the direction of arrow C in the drawing in accordance with the secondary transfer timing.

  In the secondary transfer process, a transfer bias voltage is applied to the secondary transfer member 6 from a power source (not shown). Thus, an electric field is formed between the intermediate transfer member 5 and the secondary transfer member 6, and the intermediate transfer member 5 is transferred onto the recording medium 11 that has passed between the intermediate transfer member 5 and the secondary transfer member 6. The toner image is electrostatically attracted and transferred onto the recording medium 11.

  When the toner image is transferred onto the recording medium 11, the intermediate transfer member cleaning device 8 removes the remaining developer on the intermediate transfer member 5, and the next primary transfer is performed. Thereafter, the recording medium 11 is conveyed to a fixing device (not shown), and the toner on the recording medium 11 is heated and melted to fix the toner image on the recording paper.

  Although FIG. 1 shows a monochromatic wet image forming apparatus having one set of the image carrier 1 and the wet developing device 4, four sets of the wet developing device 4 and the image carrier 1 are prepared, and cyan (Cyan: A color image forming apparatus configured to form images of each color of light blue), magenta (magenta), yellow (yellow), and black (black) and superimpose them on the intermediate transfer member 5. Application of this embodiment is possible.

  Alternatively, four sets of wet developing device 4, image carrier 1, and intermediate transfer member 5 are prepared, and cyan (Cyan: light blue), magenta (Magenta: magenta), yellow (Yellow: yellow), black (black), respectively. The present embodiment can also be applied to a color image forming apparatus configured to form an image of each color and superimpose on the recording medium 11.

  The present embodiment can also be applied to a direct transfer method in which the intermediate transfer member 5 is omitted and the image bearing member 1 is directly transferred to the recording medium 11. In addition, each process technology of electrophotography conventionally used can be combined with an arbitrary configuration according to the purpose of the wet image forming apparatus.

(Configuration of developer 12)
The developer 12 used in this embodiment will be described. The developer 12 is a liquid developer, in which colored toner particles 12t are dispersed in a carrier liquid 12w that is a solvent. An insulating solvent is used as the carrier liquid 12w. The volume average particle diameter of the toner particles 12t is suitably in the range of 0.1 μm or more and 5 μm or less.

  When the average particle diameter of the toner particles 12t is less than 0.1 μm, the developability is greatly deteriorated. On the other hand, when the average particle diameter of the toner particles 12t exceeds 5 μm, the quality of the image including the dot image and the solid image (entire print image) is remarkably deteriorated. The range of 1 μm or more and 2 μm or less is desirable. When the particle size is 1 μm or less, the cleaning property is inferior, and when the particle size is 2 μm or more, the uniformity of the solid portion is deteriorated.

  The ratio of the toner particles 12t to the developer 12 is suitably about 10% by mass to 50% by mass. When the amount is less than 10% by mass, the toner particles 12t are liable to settle, and there is a problem in stability over time during long-term storage. Furthermore, in order to obtain a required image density, it is necessary to supply a large amount of developer 12, the carrier liquid 12w adhering to the recording medium increases, and it is necessary to dry at the time of fixing, and steam is generated, resulting in an environmental problem. Problems arise. If it exceeds 50% by mass, the viscosity of the developer 12 becomes too high, making it difficult to manufacture and handle.

(Details of development process)
Next, the development process will be described in detail with reference to FIG. FIG. 2 is an enlarged view of the wet developing apparatus 4. Developer 12 is stored in developer tank 13. A part of the pumping member 14 is immersed in the developer 12 and rotates in the direction of arrow D in the drawing. The developer 12 is pumped up by the rotation, and is adjusted to a constant film thickness by a regulating blade 15 provided in contact with the pumping member 14.

  After the developer 12 is adjusted to a constant film thickness, the scooping member 14 contacts the supply member 16 and delivers the developer 12 to the supply member 16. The supply member 16 rotates in the E direction in the drawing, which is opposite to the rotation direction of the developer carrier 9, and transports the developer 12 delivered in that direction. The developer 12 is then transferred onto the developer carrier 9 at the facing portion between the supply member 16 and the developer carrier 9.

  The pumping member 14 can be a rubber roller made of urethane or NBR, or an anilox roller having a concave portion on the surface. As the supply member 16, a rubber roller made of urethane or NBR can be used. The pumping member 14 may also serve as the supply member 16 without providing the supply member 16. In the wet developing apparatus 4 shown in the present embodiment, the relative rotational direction relationship between the rollers may be different.

  The developer 12 on the developer carrier 9 is charged with toner particles 12t in the developer 12 by a toner charging device 17 such as a DC corotron charger. A high voltage power source (not shown) is connected to the toner charging device 17, and the amount of charge applied to the toner particles can be changed by changing the output of the toner charging device 17. Specifically, the amount of charge applied to the toner particles is changed by the applied voltage or current. In FIG. 2, the toner charging device 17 illustrates a DC corotron charger, but the toner charging device 17 may select a scorotron charger, a discharge roller, or the like in addition to the DC corotron charger.

  The developer 12 charged with the toner particles 12t moves to a developing nip which is a facing portion between the image carrier 1 and the developer carrier 9. Therefore, the toner thin layer formed on the developer carrier 9 abuts on the image carrier 1 and develops the electrostatic latent image on the image carrier 1.

  In developing, a developing bias voltage is applied to the developer carrier 9 from a power source (not shown), and the toner particles 12t in the developer 12 are changed according to the electric field generated in balance with the potential of the latent image on the image carrier 1. The latent image on the image carrier 1 is electrostatically attracted to the latent image portion, and the latent image on the image carrier 1 is developed.

  The residual developer 12 not used for development and remaining on the developer carrying member 9 is mainly discharged from the developer carrying member 9 by the developing cleaning member 18 after the charge of the toner particles 12 t is mainly removed by the charge removing member 19. Removed. A high-voltage power supply (not shown) is connected to the charge removal member 19 so that the output can be controlled. By changing the output of the charge removal member 19, the amount of charge applied to the toner particles can be changed. Specifically, the amount of charge applied to the toner particles is changed by the applied voltage or current. Details up to the cleaning of the toner particles 12t (developer 12) will be described later.

(Regarding the cleaning mechanism of the toner particles 12t and the control method thereof)
A method for cleaning the toner particles 12t (developer 12) of the present embodiment will be described. In the following description, a case where a DC corotron charger is used as the charge eliminating member 19 will be described as an example.

  The behavior of the toner particles 12t in the development area will be described with reference to FIGS. FIG. 3 is a schematic view showing a state of the developing portion (nip portion) between the image carrier 1 and the developer carrier 9 during development, and FIG. 4 is a diagram in which the image carrier 1 and the developer carrier 9 are separated. FIG. 5 is a schematic diagram showing the state of the developing unit immediately after, FIG. 5 is a schematic diagram showing a case where a charge is uniformly applied to the remaining developer having a non-uniform charge amount, and FIG. FIG. 7 is a schematic diagram showing a state of the developing unit immediately after the image carrier 1 and the developer carrier 9 are separated in the case of a dot pattern. FIG. 8 is a schematic diagram showing a case where the charge is changed and applied to the remaining developer whose charge amount is not uniform, and FIG. 9 is a schematic diagram showing a case where the charge amount becomes an appropriate region after static elimination. FIG.

  In FIG. 3, a latent image having the same polarity as the toner particles 12t is formed on the surface of the image carrier 1, and the potential of the image portion is low and the potential of the non-image portion is high. A potential between an image portion potential and a non-image portion potential is applied to the developer carrier 9. In the developing area, due to the potential difference, the toner particles 12t in the image area move to the surface side of the image carrier 1, and the toner particles 12t in the non-image area move to the surface side of the developer carrier 9.

  FIG. 4 is a diagram schematically showing a state immediately after passing through the developing unit. Most of the toner particles 12t are charged in the normal charging direction (here, positive charge) of the toner particles 12t here. The charged toner particles 12t are in a state of being attracted to the developer carrier 9 by the image force due to the electric charge. Further, the developing unit is further pressed against the developer carrier 9 side by a bias.

  Since the toner particles 12t on the developer carrier 9 are developed in the latent image area (image part) on the image carrier 1 in the developing unit, the toner particles in the remaining developer 12 on the developer carrier 9 are developed. The amount of 12t is reduced. Here, an area on the developer carrier 9 corresponding to the latent image area (image part) on the image carrier 1 is referred to as an “image part corresponding area D1”. Therefore, the amount of toner particles 12t in the remaining developer 12 in the image portion corresponding area D1 is reduced.

  On the other hand, in the area (non-image portion) where there is no latent image on the image carrier 1, since the toner particles 12t on the developer carrier 9 are not developed, the toner particles in the remaining developer on the developer carrier 9 are not developed. The amount of 12t increases. Here, a region on the developer carrier 9 corresponding to a region (non-image portion) where there is no latent image on the image carrier 1 is referred to as a “non-image portion corresponding region D2”. Therefore, the amount of the toner particles 12t in the remaining developer 12 in the non-image area corresponding area D2 is larger than that in the image area corresponding area D1.

  Thus, the amount of the toner particles 12t in the remaining developer 12 on the developer carrier 9 varies according to the image pattern (image signal information). As a result, the charge attenuation of the toner particles 12t in the remaining developer 12 on the developer carrier 9 is not uniform, and the amount of charge varies depending on the image pattern (not uniform).

  FIG. 5 illustrates a case where charges are uniformly applied to the remaining developer 12 having a non-uniform charge amount by using the charge removal member 19. As shown in FIG. 6, if the charge is uniformly applied, depending on the location, for example, the image portion corresponding region D1 may deviate from the appropriate charge removal amount (the charge amount becomes excessive).

  The electric field history to which the developer 12 is exposed in the developing unit is uniform because the electric potential is flat at the center of the latent image on the image carrier 1 while the electric potential is inclined at the end of the latent image. is not. This phenomenon becomes significant when fine lines and / or dots are developed.

  For example, as shown in FIG. 7, when the image pattern (image signal information) of the latent image on the image carrier 1 is a dot pattern, the toner particles 12 t in the remaining developer 12 on the developer carrier 9 are charged. Is not a binary value, and is an intermediate value between a region having a latent image and a region having no latent image. Therefore, the appropriate value of the charge application amount is also an intermediate value between the two.

  The state of the toner particle amount of these undeveloped developer varies depending on the development output conditions. Specifically, in order to avoid gradation control or other problems, the toner particles 12t are developed on the entire surface of the latent image region (image portion) on the image carrier 1 when the charge amount in the developing portion is increased. Even in the case of (solid black), a certain proportion of residual toner particles may be generated in the image portion corresponding region D1 on the developer carrier 9. Furthermore, the amount of residual toner particles in the dot portion can also vary due to tone control.

  As described above, the appropriate charge application amount by the charge removal member 19 varies depending on the image pattern (image signal information) and the development output condition. Therefore, even if the charge is uniformly applied, a region deviating from the appropriate charge removal amount is created depending on the location. (See FIG. 6).

  In order to deal with such a problem, in the present embodiment, the output of the charge removal member is controlled by an image pattern (image signal information). Specifically, the CPU reads the image information input by the user from the host computer, calculates the optimum discharge member output per unit area, and sequentially optimizes each area in the sheet passing direction by the discharge member output control means. Control is performed so that an appropriate output is applied to the charge removal member.

  For example, when a DC corotron charger is used, the amount of charge applied to the toner particles 12t can be controlled by controlling the current flowing into the developer carrier 9. .

  For example, as shown in FIG. 8, the amount of charge applied to the image portion corresponding region D1, which is a region where the amount of toner particles 12t in the residual developer on the developer carrier 9 is small, and the developer carrier 9 The amount of charge applied to the non-image area corresponding region D2, which is a region where the amount of toner particles 12t in the remaining developer is large, is made different.

  Specifically, the non-image area corresponding region D2 having a large amount of toner particles 12t is increased in the amount of charge applied, and the image area corresponding region D1 having a small amount of toner particles 12t is decreased in the amount of charge applied. Apply a static neutralization output. As a result, as shown in FIG. 9, it is possible to perform appropriate static elimination on the toner particles 12t in any region.

  With reference to FIG. 10, the control will be described with reference to a functional block diagram. A CPU (Central Processing Unit) that reads an image pattern in each region in the sheet passing direction from an image signal input to the host computer 22, calculates an optimum output of the charge removal member 19, and converts it into a control signal for controlling the charge removal member 19. ) 21 is installed.

  The CPU 21 has a function of calculating an optimum charge removal output per unit area and an operation control function of various members of the developing unit. Signals are sent from the CPU 21 to the control means for controlling the outputs of the image forming transport system driver (supply member driver 23, developer carrier driver 24), high-voltage power source 32 for static elimination member, and high-voltage power source 33 for charging member. It is done.

  Here, the timing at which the signal is sent is synchronized with the time when the residual developer corresponding to the image pattern has come to the discharge area of the charge removal member 19. Then, the output of the charge removal member 19 is adjusted to the charge removal output corresponding to the pattern of the remaining developer by the control means.

  This output adjustment is sequentially performed for each unit length until image output is completed. Although the output adjustment of the charge removal member 19 is specifically performed, when a DC corotron charger is used, the amount of charge applied to the toner particles 12t is controlled by controlling the current flowing into the developer carrier 9. be able to.

  Here, the output adjustment of the static elimination member 19 will be described in detail. Here, the developer 12 is developed on the entire surface of the latent image region (image portion) on the image carrier 1 (black solid color) by the characteristics of the toner particles 12t, the output setting of the developing unit, or the gradation setting. Development) Consider a state in which toner particles 12t hardly remain in the image portion corresponding region D1 on the developer carrier 9.

  Since almost no toner particles 12t remain in the image portion corresponding region D1 on the developer carrying member 9, here, in accordance with the area ratio of the halftone, the optimum static elimination output in the entire halftone and the non-image portion What is necessary is just to adjust with the optimal static elimination output in the area | region corresponding to the corresponding | compatible area | region D2. Specifically, the toner output is proportionally controlled according to the area ratio between the image area corresponding area D1 (halftone area) and the non-image area corresponding area D2 (white solid) in the unit area. On the other hand, it is possible to control the optimum static elimination output.

  In FIG. 11, the control flow of the output adjustment of the static elimination member 19 is shown. In step 21, the CPU 21 reads an image signal. In step 22, the CPU calculates a ratio of the non-image part corresponding region D <b> 2 (white solid) / image part corresponding region D <b> 1 (halftone region: dot) per unit area based on the read image signal.

  In step 23, the CPU determines the output of the static eliminating member 19 based on the calculated ratio of the non-image part corresponding area D <b> 2 (white solid) / image part corresponding area D <b> 1 (halftone area: dot). In step 24, output by the static eliminating member 19 is started, and in step 25, it is determined whether or not the unit area has been passed. If not, the process returns to step 24. If it has passed, it is determined in step 26 whether or not the image formation has been completed. If the image formation has not ended, the process returns to step 22. If the image formation has been completed, the output adjustment control of the static elimination member 19 is terminated.

  The unit area in the output adjustment of the static elimination member 19 is preferably defined by the discharge region of the static elimination member 19. This is because, if the output is changed at an interval shorter than the discharge area, there may be a place where the output is deviated from the proper charge removal output. When a DC corotron charger is used as in the present embodiment, it is desirable that it be defined by the width of the charger. Specifically, the interval for controlling the charge removal member 19 is preferably equal to or greater than the charge discharge width of the charge removal member 19.

[Embodiment 2]
In the present embodiment, the image forming process and the wet image forming apparatus used are the same as those in the first embodiment. In the present embodiment, the image portion corresponding region D1 (region corresponding to the black solid region) of the developer carrier 9 is also shown in FIG. 12, depending on the toner particle characteristics, the developing unit output setting, and the gradation setting. Thus, a case where a certain amount of toner particles remains is considered. FIG. 12 is a schematic diagram illustrating the state of residual developer in the image portion corresponding region and the non-image portion corresponding region of the developer carrier in the second embodiment.

  The process until the CPU reads the image signal is the same as that in the first embodiment. Here, the output adjustment of the charge eliminating member 19 is performed. In this case, it is also necessary to consider the ratio in the unit area of the image portion corresponding region D1 of the developer carrier 9. In the present embodiment, the optimum charge removal output of the non-image area corresponding region D2 is maximized and the optimum charge removal output of the image area corresponding region D1 is minimized by the print area ratio per unit area, and is inversely proportional to the print area ratio. To control.

  In FIG. 13, the control flow of the output adjustment of the static elimination member 19 in this Embodiment is shown. The outline of the flow is the same as that of the first embodiment, but the method for calculating the static elimination output per unit area is different. In step 31, the CPU 21 reads an image signal. In step 32, the CPU calculates a printing area ratio per unit area based on the read image signal.

  In step 33, the CPU determines the output of the charge removal member 19 based on the calculated ratio of the print area ratio. In step 34, output by the static eliminating member 19 is started, and in step 35, it is determined whether or not the unit area has been passed. If not, the process returns to step 34. If it has passed, it is determined in step 36 whether or not image formation has been completed. If the image formation has not ended, the process returns to step 32. If the image formation has been completed, the output adjustment control of the static elimination member 19 is terminated.

  The unit area in the output adjustment of the charge removal member 19 is preferably defined by the discharge region of the charge removal member 19 as in the first embodiment. This is because, if the output is changed at an interval shorter than the discharge area, there may be a place where the output is deviated from the proper charge removal output. When a DC corotron charger is used as in the present embodiment, it is desirable that it be defined by the width of the charger. Specifically, the interval for controlling the charge removal member 19 is preferably equal to or greater than the charge discharge width of the charge removal member 19.

  In each of the above embodiments, the case where a DC corotron charger is used as the static eliminating member 19 has been described. However, the configuration of the static eliminating member 19 is not limited to the DC corotron charger. For example, an AC corotron charger or a scorotron charger may be used. In either form, an effect on toner accumulation can be obtained by performing control according to the image signal as described above.

  Furthermore, a mechanism such as an ion flow head that can selectively charge each region within the charger width may be used. When such a mechanism is used, it is possible to finely adjust the charge application amount in accordance with the image signal in the axial direction (direction orthogonal to the paper feeding direction).

  As shown in FIG. 14, as a means for assisting in suppressing toner accumulation, a toner dispersion member 20 is installed before the developer cleaning member 18 cleans the developer carrier 9, and the toner particles 12 t in the remaining developer 12 are removed. Good dispersion. The dispersion state of the toner particles 12t after passing through the toner dispersion member 20 becomes better as the charge removal amount at the subsequent charge removal by the charge removal member 19 becomes appropriate. Therefore, the occurrence of toner accumulation can be more effectively prevented by combining appropriate neutralization for each location according to the image pattern shown above and the toner dispersion member 20 in combination.

  As an embodiment of the dispersing member, a method in which a roller to which an AC bias is applied is brought into contact with the developer carrier 9 after static elimination is conceivable. By forming an AC electric field by the bias, the positively charged toner particles and the negatively charged toner particles remaining in the remaining developer 12 (toner layer) are developed in the nip between the developer carrier 9 and the toner dispersion member 20. It separates from the carrier 9 and is moved and dispersed in alternate directions.

  As another form of the toner dispersion member, a method is conceivable in which a vibration member that can impart ultrasonic vibration to the toner particles is provided facing the developer carrier 9 after the charge removal. The ultrasonic vibration member abuts against the developer carrier 9 through the residual developer 12 (toner layer), and the vibrator vibrates during image formation, and the residual developer 12 (toner layer) after charge removal is caused by its action. Floats from the developer carrying member 9 and is dispersed by being disturbed.

  Further, as another form of the toner dispersing member, for example, a method of providing a brush roller that directly contacts the remaining developer 12 (toner layer) and gives a disturbing action is conceivable. The brush comes into contact with the toner particles, and the residual developer 12 (toner layer) after charge removal is lifted from the developer carrier 9 by the mechanical action, and is dispersed by being disturbed.

(Example)
Hereinafter, in order to confirm the effect of the wet image forming apparatus in the present embodiment, an experiment was performed under the conditions of Examples and Comparative Examples described later. As an experimental procedure, an image pattern (to be described later) is transferred to a photosensitive drum (image carrier 1) using a wet image forming apparatus (experimental device) to which a mechanism and a control to be described later are based on the wet developing apparatus shown in FIG. ) Formed on top.

  FIG. 15 shows a print pattern on the recording medium 11. This print pattern includes a black solid print (entire black print) area B1, a dot area H1 (H11: 20%, H12: 30%, H13: 40%) in which a dot area ratio of 20% to 40% is arranged in parallel, white A solid printing (whole surface non-printing) area W1 and a dot area H2 (H21: 60%, H22: 70%, H123: 80%) in which dot area ratios of 60% to 80% are arranged in parallel are each set every 5 cm. Those arranged in order were used.

  As the current amount of the toner charging device 17, 0.32 mA / m and 0.5 mA / m were used. In the wet developing apparatus, continuous printing for 1 hour was performed, and the toner accumulation state on the developing cleaning member 18 was visually evaluated. As evaluation scales, A (no toner accumulation), F (a level where toner accumulation is unacceptable), and FF (toner accumulation was severe), and A or higher were accepted. The evaluation results are shown in FIG.

(Comparative Example 1)
In Comparative Example 1, as the wet developing device 4 used in the wet image forming apparatus, a device in which the neutralizing member 19 was not installed was used. The evaluation result was FF (toner accumulation was terrible) and it failed.

  In Comparative Example 1, toner deposition occurred and grew very rapidly. This is considered to be because the toner particles are strongly restrained by the developer carrier 9 when entering the developing cleaning member 18 because the neutralizing member 19 is not provided.

(Comparative Example 2)
In Comparative Example 2, a static eliminating member 19 was used as the wet developing device 4 used in the wet image forming apparatus, and a non-contact DC corotron charger was installed as the static eliminating member 19 on the developer carrier 9. With respect to the amount of charge removal current, the surface potential after charge removal of the remaining developer in the area (non-image area corresponding area D2) of the developer carrier 9 corresponding to the white solid print (whole area no print) area W1 becomes zero. Current amount (when the current amount of the toner charging device 17 is 0.32 mA / m, the current amount of the charge removing member 19 is 0.3 mA / m, and when the current amount of the toner charging device 17 is 0.5 mA / m, The current amount of the static elimination member 19 was set to 0.45 mA / m). The evaluation result was F (a level at which toner deposition is not acceptable), which was unacceptable.

  In Comparative Example 2, the growth rate of toner deposition was slower than that of Comparative Example 1, but an unacceptable level of toner deposition occurred. This is considered to be due to the fact that neutralization according to the image pattern (image signal information) has not been performed.

(Example 1)
In Example 1, a non-contact DC corotron charger was installed as the charge eliminating member 19 on the developer carrier 9. The current amount of the toner charging device 17 was set to 0.32 mA / m. The maximum amount of current to the charge removal member 19 is the amount of residual developer (toner particles) in the region (non-image portion corresponding region D2) of the developer carrier 9 corresponding to the white solid printing (whole surface non-printing) region W1. The amount of current (0.3 mA / m) at which the surface potential after static elimination was zero was set. Further, the minimum value is set to a half current amount (0.15 mA / m) of the white solid area W1 in consideration of the dot portion development residual toner.

  The static elimination output was controlled according to the flow shown in the first embodiment (FIG. 11). Further, in the region corresponding to the black solid printing (entire black printing) region B1, a setting was made so as to apply the minimum value (0.15 mA / m) of the current amount. At this time, when the amount of current in the dot region H1 portion was measured, it was 0.255 mA / m, and in the dot region H2 portion, it was 0.195 mA / m.

  In Example 1, the evaluation result was A (no toner accumulation), which was a pass. A significant improvement effect was obtained with respect to Comparative Examples 1 and 2 above. That is, toner accumulation did not occur even after driving for 1 hour, and it was at a level that would not cause any problem in repeated use. This is considered to be due to the fact that neutralization according to the image pattern (image signal information) has been performed.

(Example 2)
In Example 2, a non-contact DC corotron charger was installed as the charge eliminating member 19 on the developer carrier 9. The maximum amount of current to the charge removal member 19 is the amount of residual developer (toner particles) in the region (non-image portion corresponding region D2) of the developer carrier 9 corresponding to the white solid printing (whole surface non-printing) region W1. The amount of current (0.45 mA / m) at which the surface potential after static elimination becomes zero was set. Further, the minimum value was set to an amount of current (0.1 mA / m) at which the surface potential of the remaining developer (toner particles) in the black solid printing (entire black printing) region B1 after the charge removal becomes zero.

  The output of the static elimination member 19 was performed according to the control flow shown in FIG. 13 of the second embodiment. At this time, when the amount of current in the dot region H1 portion was measured, it was 0.345 mA / m, and in the dot region H2 portion was 0.205 mA / m.

  Also in Example 2, as in Example 2, the evaluation result was A (no toner accumulation), which was a pass. A significant improvement effect was obtained with respect to Comparative Examples 1 and 2 above. That is, toner accumulation did not occur even after driving for 1 hour, and it was at a level that would not cause any problem in repeated use. This is considered to be due to the fact that neutralization according to the image pattern (image signal information) has been performed.

  In this way, by using the wet image forming apparatus according to the present embodiment and controlling the output of the charge removal member 19 in accordance with the image signal information, the developer carrier 9 can be cleaned with good residual developer. I was able to.

  As a result, according to the wet image forming apparatus in the present embodiment, the occurrence of toner accumulation that occurs when cleaning the remaining developer from the developer carrying member is suppressed, the generation of useless developer is suppressed, and maintenance performance is reduced. As a result, it is possible to provide a wet image forming apparatus that can achieve improvement and suppression of occurrence of image noise and, as a result, further improve image quality.

  As described above, in the wet image forming apparatus according to the present embodiment, the output of the charge removal member 19 is changed according to the image signal information. As a result, even if the developer before neutralization on the developer carrier 9 has a variation in toner particle amount and charge amount for each position depending on the image pattern, an appropriate charge removal amount is given over the entire surface, and the developer carrying It is possible to stably remove the electrostatic binding force of the toner particles from the body 9.

  As a result, toner accumulation can be suppressed, and as a result, generation of useless developer can be suppressed, maintenance performance can be improved, and generation of image noise can be suppressed. As a result, it is possible to provide a wet image forming apparatus that can further improve the image quality.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Charging device 3 Exposure device 4 Wet developing device 5 Intermediate transfer body 6 Secondary transfer member 7 Image carrier cleaning device 8 Intermediate transfer body cleaning device 9 Development Agent carrier, 10 eraser lamp, 11 recording medium, 12 developer, 12t toner particles, 12w carrier liquid, 13 developer tank, 14 pumping member, 15 regulating blade, 16 supply member, 17 toner charging device, 18 developer cleaning member , 19 Static elimination member, 20 Toner dispersion member, 100 Wet image forming apparatus.

Claims (4)

A developer containing toner particles and a carrier liquid;
An image carrier that carries and conveys a latent image according to image signal information;
A developer carrying member that carries and conveys the developer on its surface and develops the latent image on the image carrier with the developer;
A static elimination member for neutralizing residual developer remaining on the developer carrier after development;
A cleaning member for removing the residual developer after static elimination from the developer carrier;
Control means for changing the output of the static elimination member according to the image signal information;
A wet image forming apparatus.   The control means includes a non-image area corresponding area which is an area where the amount of the toner particles in the residual developer within a unit area of the developer carrier calculated from the image signal information is large, and the residual development. The wet image forming apparatus according to claim 1, wherein the output of the charge removal member is changed in accordance with a ratio with an image portion corresponding region that is a region where the amount of the toner particles in the agent is small.   2. The wet image forming apparatus according to claim 1, wherein the control unit changes the output of the charge removal member according to a printing area ratio within a unit area calculated from the image signal.   The control means includes a non-image area corresponding area which is an area where the amount of the toner particles in the residual developer within a unit area of the developer carrier calculated from the image signal information is large, and the residual development. In the image area corresponding area, which is an area where the amount of the toner particles in the agent is small, the amount of charge applied to the non-image area corresponding area is larger than the amount of charge applied to the image area corresponding area by the charge eliminating member. The wet image forming apparatus according to any one of claims 1 to 3, wherein the output of the charge removal member is changed so as to be.

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