JP2007114384A - Developing system for liquid development and developing method for liquid development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing system for liquid development that can improve cleaning performance on a developing roller. <P>SOLUTION: The system is characterized in that the bias applied on a bias application roller 22Y that controls the solid content concentration distribution in a liquid developer on a developing roller 20Y is turned off at a position between consecutive paper sheets. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a development system for liquid development and a development method for liquid development that develop a latent image formed on an image carrier with a developer.

Conventionally, a developer container containing a liquid developer in which charged toner particles composed of at least a colorant and a resin are dispersed in an electrically insulating liquid, and the liquid developer from the developer container is removed from the surface of the developing roller. A supply roller that uniformly adheres to the surface of the developing roller, and an electric field application roller that forms a liquid toner layer in which charged toner particles are aggregated by applying an electric field to the liquid developer attached to the surface of the developing roller. There is something.
JP-A-9-185265

  However, in the above conventional technique, when the non-image area (white image) increases on the print screen, the electric field that presses the solid content against the developing roller side is repeated twice in the non-image area, which makes it difficult to clean the developing roller. . In particular, cleaning becomes very difficult at the margins at the leading and trailing edges of the image.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and provide a developing system for liquid development and a developing method for liquid development that improve the cleaning performance of the developing roller.

    The present invention solves the above-described problem, and has a developing roller for carrying a developer and a developer supply roller for supplying the developer to the developing roller, and a latent image formed on the image carrier is obtained. In the developing system for developing liquid using the developing roller, the bias applying roller for adjusting the solid content concentration distribution in the liquid developer on the developing roller and the applying bias of the bias applying roller at the position between the sheets are turned off. And a control means.

  A developing system for liquid development that has a developing roller that carries a developer and a developer supply roller that supplies the developer to the developing roller, and develops the latent image formed on the image carrier by the developing roller. And a bias application roller for adjusting the solid content concentration distribution in the liquid developer on the developing roller, and after the printing operation is completed, the bias of the bias application roller is turned off, and then the developing roller is rotated one or more times. And control means for controlling as described above.

  Furthermore, the method of the present invention is characterized in that the application bias of the bias application roller is turned off at the inter-sheet position.

  Further, at the end of the printing operation, after the application bias of the bias application roller is turned off, the developing roller is rotated one or more times.

  According to the present invention, since the solid content is not pressed twice from the image carrier and the electric field application roller to the developing roller at the position between the paper, the cleaning property and developing property of the developing roller can be improved. The life of the roller blade is extended. In addition, after the printing operation is completed, the surface of the developing roller is not allowed to be left for a long time in a state where the solid content is high, and the developer solid content is not filmed on the developing roller. The lifespan of is extended.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing main components constituting the image forming apparatus according to the embodiment of the present invention. Development units 30Y, 30M, 30C, and 30K are arranged at the lower part of the image forming apparatus, and the intermediate transfer member 40 and the secondary transfer unit 60 Arranged at the top of the image forming apparatus.

  The image forming unit includes image carriers 10Y, 10M, 10C, and 10K, charging rollers 11Y, 11M, 11C, and 11K, and exposure units 12Y, 12M, 12C, and 12K (not shown). The exposure units 12Y, 12M, 12C, and 12K have an optical system such as a semiconductor laser, a polygon mirror, and an F-θ lens. The image bearing members 10Y, 10M, 10C, and 10K are provided by charging rollers 11Y, 11M, 11C, and 11K. Are uniformly charged and irradiated with a modulated laser beam based on the input image signal by the exposure units 12Y, 12M, 12C, and 12K, and charged image carriers 10Y, 10M, 10C, and 10K. An electrostatic latent image is formed thereon.

  The developing units 30Y, 30M, 30C, and 30K generally include liquid developers of respective colors including the developing rollers 20Y, 20M, 20C, and 20K, yellow (Y), magenta (M), cyan (C), and black (K). Developer containers (reservoirs) 31Y, 31M, 31C, 31K to be stored, and developer supply rollers for supplying liquid developers of these colors from the developer containers 31Y, 31M, 31C, 31K to the developing rollers 20Y, 20M, 20C, 20K 32Y, 32M, 32C, 32K and the like, and the electrostatic latent images formed on the image carriers 10Y, 10M, 10C, and 10K are developed with liquid developers of respective colors.

  The intermediate transfer member 40 is an endless belt, and is stretched between the driving roller 41 and the tension roller 42, and is contacted with the image carriers 10Y, 10M, 10C, and 10K by the primary transfer portions 50Y, 50M, 50C, and 50K. It is rotationally driven by the driving roller 41 while in contact. The primary transfer portions 50Y, 50M, 50C, and 50K are arranged such that the image carriers 10Y, 10M, 10C, and 10K and the primary transfer rollers 51Y, 51M, 51C, and 51K are opposed to each other with the intermediate transfer member 40 interposed therebetween, and the image carrier 10Y. 10M, 10C, and 10K are used as transfer positions, and the developed toner images of the respective colors on the image carriers 10Y, 10M, 10C, and 10K are sequentially transferred onto the intermediate transfer body 40 and transferred. A toner image is formed.

  In the secondary transfer unit 60, a secondary transfer roller 61 is disposed opposite to the belt drive roller 41 with the intermediate transfer member 40 interposed therebetween, and a cleaning device including a secondary transfer roller cleaning blade 62 and a developer recovery unit 63 is disposed. The Then, at the transfer position where the secondary transfer roller 61 is disposed, a single color toner image or a full color toner image formed on the intermediate transfer body 40 is conveyed on the sheet material conveyance path L such as paper, film, cloth, etc. Transfer to a recording medium as a transfer material.

  Further, a fixing unit (not shown) is disposed in front of the path sheet material conveyance path L, and a single color toner image or a full color toner image transferred onto a recording medium such as paper is fused to the recording medium such as paper. And fix.

  Further, on the side of the tension roller 42 that stretches the secondary transfer unit 60 together with the belt driving roller 41, an intermediate transfer member cleaning blade 46 and a developer recovery unit 47 are brought into contact with the intermediate transfer member 40 along the outer periphery thereof. A cleaning device is arranged.

  Next, the image forming unit and the developing unit will be described. FIG. 2 is a cross-sectional view showing main components of the image forming unit and the developing unit. 3 is a diagram for explaining compaction by the compaction roller 22Y, FIG. 4 is a diagram for explaining development by the developing roller 20Y, FIG. 5 is a diagram for explaining the squeeze action by the image carrier squeeze roller 13Y, and FIG. 6 is an intermediate transfer member squeeze. It is a figure explaining the squeeze effect | action by the apparatus 52Y. Since the configurations of the image forming unit and the developing unit for each color are the same, the following description will be made based on the yellow (Y) image forming unit and the developing unit.

  The image forming unit includes a cleaning device including a latent image eraser 16Y, an image carrier cleaning blade 17Y, and a developer recovery unit 18Y along the rotation direction of the outer periphery of the image carrier 10Y, a charging roller 11Y, an exposure unit 12Y, and a development unit. A cleaning device including a developing roller 20Y of 30Y, an image carrier squeeze roller 13Y, an image carrier squeeze roller cleaning blade 14Y, and a developer recovery unit 15Y, which are associated with the development roller 20Y, is provided. In the developing unit 30Y, a cleaning blade 21Y, a developer supply roller 32Y using an anilox roller, and a compaction roller 22Y are disposed on the outer periphery of the developing roller 20Y. A liquid developer and a stirring roller are disposed in the liquid developer container 31Y. 34Y and developer supply roller 32Y are accommodated. A primary transfer roller 51Y of the primary transfer portion is disposed along the intermediate transfer body 40 at a position facing the image carrier 10Y, and an intermediate transfer body squeeze roller 53Y, a backup roller 54Y, and an intermediate transfer are disposed downstream in the moving direction. An intermediate transfer body squeeze device 52Y comprising a body squeeze roller cleaning blade 55Y and a developer recovery unit 56Y is disposed.

  The image carrier 10Y is a photosensitive drum made of a cylindrical member having a width wider than about 320 mm of the developing roller 20Y and a photosensitive layer formed on the outer peripheral surface. For example, the image carrier 10Y rotates in a clockwise direction as shown in FIG. To do. The photosensitive layer of the image carrier 10Y is composed of an organic image carrier or an amorphous silicon image carrier. The charging roller 11Y is disposed upstream of the nip portion between the image carrier 10Y and the developing roller 20Y in the rotation direction of the image carrier 10Y, and a bias having the same polarity as the toner charging polarity is applied from a power supply device (not shown) to The carrier 10Y is charged. The exposure unit 12Y irradiates laser light onto the image carrier 10Y charged by the charging roller 11Y on the downstream side in the rotation direction of the image carrier 10Y with respect to the charging roller 11Y, thereby forming a latent image on the image carrier 10Y. To do.

  The developing unit 30Y includes a developer container 31Y for storing a liquid developer in which toner is dispersed in a carrier at a weight ratio of approximately 20 to 25%, a developing roller 20Y for carrying the liquid developer, and stirring the liquid developer. Thus, the developer supplying roller 32Y, the regulating blade 33Y, the stirring roller 34Y, and the compacting roller 22Y for bringing the liquid developer carried on the developing roller 20Y into a compacted state are maintained in a uniform dispersed state and supplied to the developing roller 20Y. And a developing roller cleaning blade 21Y for cleaning the developing roller 20Y.

  The liquid developer accommodated in the developer container 31Y is a low concentration (about 1 to 2 wt%) and low viscosity with Isopar (trademark: exon) as a carrier, which is generally used, and is volatile at room temperature. It is not a volatile liquid developer having a property, but a non-volatile liquid developer having a high concentration and a high viscosity and having a non-volatile property at room temperature. That is, in the liquid developer in the present invention, a solid having an average particle diameter of 1 μm in which a colorant such as a pigment is dispersed in a thermoplastic resin is introduced into a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil. It is a liquid developer having a high viscosity (about 30 to 10000 mPa · s) which is added together with a dispersant and has a toner solid content concentration of about 20 to 25%.

  The developer supply roller 32Y is a cylindrical member having a diameter of about 20 mm. For example, as shown in FIG. 2, the developer supply roller 32Y rotates in a clockwise direction so that the developer can be carried on the surface finely and uniformly. An anilox roller having an uneven surface formed by a spiral groove. The groove dimensions are such that the groove pitch is about 130 μm and the groove depth is about 30 μm. The developer supply roller 32Y supplies the liquid developer from the developer container 31Y to the developing roller 20Y. The stirring roller 34Y and the developer supply roller 32Y may be in sliding contact with each other, but may be arranged in a distant relationship.

  The regulating blade 33Y is an elastic blade having a surface covered with an elastic body, and is composed of a rubber portion made of urethane rubber or the like that comes into contact with the surface of the developer supply roller 32Y, and a metal plate or the like that supports the rubber portion. Composed. Then, the film thickness and amount of the liquid developer carried and conveyed by the developer supply roller 32Y composed of an anilox roller are regulated and adjusted, and the amount of liquid developer supplied to the developing roller 20Y is adjusted. Note that the rotation direction of the developer supply roller 32Y may be the opposite direction instead of the arrow direction shown in FIG. 2, and the regulating blade 33Y at that time requires an arrangement corresponding to the rotation direction.

  The developing roller 20Y is a cylindrical member having an outer diameter of about 24 mm and a width of about 320 mm, and rotates counterclockwise around the rotation axis as shown in FIG. The developing roller 20Y is provided with an elastic layer made of polyurethane rubber, silicon rubber, NBR or the like on the outer periphery of an inner core made of metal such as iron. In the present embodiment, a urethane rubber roller having a thickness of about 4 mm and a hardness of JIS-A 30 ° is coated with a urethane resin having a thickness of about 100 μm. The developing roller cleaning blade 21Y is made of rubber or the like that comes into contact with the surface of the developing roller 20Y. The developing roller 20Y is arranged downstream of the developing nip portion where the developing roller 20Y comes into contact with the image carrier 10Y in the rotation direction of the developing roller 20Y. The liquid developer remaining on the developing roller 20Y is scraped off and removed.

  The compaction roller 22Y is a cylindrical member having an outer diameter of about 20 mm, and is in the form of an elastic roller configured by covering the elastic body 22-1 in the same manner as the developing roller 20Y as shown in FIG. The surface layer is provided with a conductive resin layer or rubber layer. In the present embodiment, a urethane rubber roller having a thickness of about 4 mm and a hardness of JIS-A 30 ° is coated with a urethane resin having a thickness of about 100 μm. Further, as shown in FIG. 2, it rotates in the clockwise direction opposite to the developing roller 20Y. The compaction roller 22Y has means for increasing the charging bias on the surface of the developing roller 20Y, and the developer conveyed by the developing roller 20Y slides into contact with the compaction roller 22Y to form a nip as shown in FIGS. An electric field is applied from the compaction roller 13Y side toward the developing roller 20Y at the compaction site. The electric field applying means for compaction may be corona discharge from a corona discharger instead of the roller shown in FIG.

  With this compaction roller 22Y, as shown in FIG. 3, the toner T uniformly dispersed in the carrier C is moved to the developing roller 20Y side to be aggregated to form a so-called compaction state T ′. A small amount of toner T ″ that has not been compacted is carried, rotated in the direction of the arrow in the figure, scraped off by the compaction roller cleaning blade 23Y, joined with the developer in the reservoir 31Y, and reused. The developer D carried and compacted by the roller 20Y is converted into a latent image on the image carrier 10Y by applying a desired electric field at the developing nip where the developing roller 20Y contacts the image carrier 10Y as shown in FIG. The remaining developer D is developed by the developing roller cleaning blade 21Y. Is reused merged with the developer in the removed developer container 31Y by scraping Te. The carrier and the toner to these joins are not mixed color state.

  The image carrier squeeze device is disposed downstream of the nip portion with the developing roller 20Y so as to face the image carrier 10Y, and collects excess developer of the toner image developed on the image carrier 10Y. As shown in FIGS. 2 and 5, an image carrier squeeze roller 13Y composed of an elastic roller member that covers an elastic member 13-1 on its surface and rotates in sliding contact with the image carrier 10Y, and the image carrier squeeze roller 13Y. A cleaning blade 14Y that presses and slides on the surface to clean the surface. As shown in FIG. 5, excess carrier C and originally unnecessary fog toner T ″ are recovered from the developer D developed on the image carrier 10Y. The function of increasing the toner particle ratio in the visible image is that the recovery ability of the surplus carrier C is the rotational direction of the image carrier squeeze roller 13Y and the peripheral speed of the surface of the image carrier 10Y. The image pickup body squeeze roller 13Y can be set to a desired recovery capability by the difference in the relative circumferential speed of the surface of the image carrier squeeze roller 13Y. When the image carrier 10Y is rotated in the counter direction, the recovery capability is increased. Even if the speed difference is set to be large, the recovery capability is enhanced and this synergistic effect is also possible.The squeeze roller of this embodiment is a urethane rubber roller having an outer diameter of about 14 mm, a wall thickness of about 2 mm, and a hardness of JIS-A 30 °. In addition, a PFA tubing having a thickness of about 20 μm and a roller having a resistance value of about Log 4Ω as an actual resistance value are used.

  In this embodiment, as an example, as shown in FIG. 5, the image carrier squeeze roller 13Y is rotated with the image carrier 10Y at substantially the same peripheral speed, and the weight ratio from the developer D developed on the image carrier 10Y is increased. The excess carrier C of about 5 to 10% is collected to reduce both rotational driving loads and suppress the disturbance effect on the visible toner image of the image carrier 10Y. Excess carrier C and unnecessary fog toner T ″ collected by the image carrier squeeze roller 13Y are collected and pooled from the image carrier squeeze roller 13Y to the developer collecting unit 15Y by the action of the cleaning blade 14Y. Since the collected excess carrier C and fog toner T ″ are collected from the dedicated isolated image carrier 10Y, no color mixing phenomenon occurs at all locations.

  In the primary transfer unit 50Y, the developer image developed on the image carrier 10Y is transferred to the intermediate transfer member 40 by the primary transfer roller 51Y. Here, the image carrier 10Y and the intermediate transfer member 40 are configured to move at a constant speed, reducing the driving load of rotation and movement, and suppressing the disturbance effect on the visible toner image of the image carrier 10Y. Yes. The primary transfer portion 50Y for the first color does not cause a color mixing phenomenon since it is the first primary transfer, but since the second and subsequent colors transfer different toner images onto the already transferred primary toner image portions and superimpose colors, the intermediate transfer body 40 is used. Due to the so-called reverse transfer phenomenon in which the toner moves from the image carrier 10 (M, C, K) to the image carrier 10 (M, C, K), the reverse transfer toner and the untransferred toner are mixed and are carried on the image carrier 10 (M, C, K) together with the surplus carrier. Moved from the image carrier by the action of the cleaning blade 17 (M, C, K) and pooled.

  The intermediate transfer member squeeze device 52Y is disposed on the downstream side of the primary transfer unit 50Y, and removes excess carrier liquid from the intermediate transfer member 40 to increase the toner particle ratio in the visible image. In the stage where the carrier amount of the developer (toner dispersed in the carrier) transferred to the intermediate transfer body 40 by the transfer unit 50Y is secondarily transferred to the above-described final-stage sheet material and proceeds to the fixing process (not shown), In order to exhibit a preferable secondary transfer function and fixing function, excess carrier is further removed from the intermediate transfer body 40 when the approximate toner weight ratio of the desired dispersion state of the liquid developer does not reach about 40% to 60%. It is provided as a means. Similar to the image carrier squeeze device 52, the intermediate transfer member squeeze device 52Y has an intermediate transfer member squeeze roller 53Y composed of an elastic roller member that covers the surface with an elastic member and rotates in sliding contact with the image carrier 40, and the image carrier 40. 6 includes a backup roller 54Y disposed opposite to the intermediate transfer member squeeze roller 53Y, a cleaning blade 55Y that presses and slides against the intermediate transfer member squeeze roller 53Y to clean the surface, and a developer recovery unit 56Y, as shown in FIG. As described above, it has a function of recovering excess carrier C and originally unnecessary fog toner T ″ from the developer D primarily transferred to the intermediate transfer body 40. The developer recovery section 56Y is provided with magenta magenta disposed downstream thereof. Also serves as a recovery mechanism for the carrier liquid recovered by the image carrier squeeze roller cleaning blade 14M. There.

  The surplus carrier collecting ability can be set to a desired collecting ability by the relative circumferential speed difference of the surface of the intermediate transfer member squeeze roller 53Y with respect to the rotation direction of the intermediate transfer member squeeze roller 53Y and the moving speed of the intermediate transfer member 40. When the intermediate transfer member 40 is rotated in the counter direction, the recovery capability is increased, and even when the peripheral speed difference is set to be large, the recovery capability is increased, and this synergistic action is also possible. In this embodiment, as an example, the intermediate transfer member squeeze roller 53Y rotates with the intermediate transfer member 40 at substantially the same peripheral speed, and a weight ratio of about 5 to 10% from the developer primarily transferred to the intermediate transfer member 40 is obtained. The excess carrier and fog toner are collected to reduce both rotational driving loads and to suppress the disturbance effect on the toner image of the intermediate transfer member 40.

  The first color intermediate squeeze squeeze part is the first intermediate squeeze squeeze, so no color mixing phenomenon occurs. However, after the second color, a different toner image is transferred to the already transferred primary toner image part and overlaid. Therefore, when the toner is transferred from the intermediate transfer body 40 to the intermediate transfer body squeeze roller 53Y, the toner is mixed in color and carried and moved by the intermediate transfer body squeeze roller 53Y together with the surplus carrier. Collected from 53Y and pooled. Further, when the squeeze ability by the image carrier 40 at the primary transfer portion upstream of the intermediate transfer member squeeze process and the squeeze ability of the image carrier squeeze roller 53Y are performed with sufficient ability, not all primary transfer processes are necessarily performed. There is no need to provide an intermediate transfer member squeeze device on the downstream side.

  Next, the operation of the image forming apparatus of the present invention will be described. Subsequently, the image forming unit and the developing unit will be described by taking the yellow image forming unit and the developing unit 30Y among the four image forming units and the developing unit as an example.

  In the developer container 31Y, the toner particles in the liquid developer have a positive charge. The liquid developer is stirred by the stirring roller 34Y, and the developer supply roller 32Y rotates, whereby the developer container 31Y. Pumped from. In the liquid development image forming apparatus using the developer in which the toner is dispersed in the carrier of the present embodiment, a developer in which the toner is dispersed in an amount of 20 to 25% in the carrier in an amount of 75 to 80% is used. In the stage of image formation through various process steps, secondary transfer to the final stage sheet material, and proceeding to the fixing step (not shown), the liquid developer is used in order to exhibit a preferable secondary transfer function and fixing function. Is preferably in a dispersed state of about 40% to 60% in terms of toner weight ratio. The developer initially stored in the developer container 31Y is in a state of being dispersed in the carrier at a toner weight ratio of about 20 to 25%. However, in the case of development with a high image duty in the development on the image carrier 10Y. Has a large consumption ratio for the toner, and conversely, in the case of development with a low image duty, the consumption ratio for the toner decreases. That is, the toner weight ratio of the developer stored in the developer container 31Y changes with development on the image carrier 10Y, and this change is constantly monitored to obtain an approximate toner weight ratio of 20 to 25%. It is necessary to maintain and control the system so as to be dispersed to a certain extent.

  Therefore, in this embodiment, a transmission type photo sensor for detecting the dispersion weight ratio of the toner (not shown), torque detecting means for detecting the stirring torque for stirring the developer, and the developer liquid level in the developer container 31Y are detected. A detecting means S such as a reflective photosensor is provided in the developer container 31Y, and when the toner dispersion weight ratio decreases for a predetermined developer amount, the toner is dispersed at a high density of about 35 to 55%. A predetermined amount of developer is replenished from the developer cartridge, and when the toner dispersion weight ratio increases, a predetermined amount of carrier is replenished from the carrier cartridge to control the toner to a toner weight ratio of about 20 to 25%. The developer container 31Y is stirred to make it uniformly dispersed.

  The regulating blade 33Y is in contact with the surface of the developer supply roller 32Y and scrapes off other excess liquid developer while leaving the liquid developer in the uneven grooves of the anilox pattern formed on the surface of the developer supply roller 32Y. Thus, the amount of liquid developer supplied to the developing roller 20Y is regulated. By such regulation, the film thickness of the liquid developer applied to the developing roller 20Y is quantified so as to be about 6 μm. The liquid developer scraped off by the regulating blade 33Y falls back to the developer container 31Y due to gravity, and the liquid developer that has not been scraped off by the regulating blade 33Y forms an uneven groove on the surface of the developer supply roller 32Y. It is accommodated inside and is applied to the surface of the developing roller 20Y by being pressed against the developing roller 20Y.

  The developing roller 20Y coated with the liquid developer by the developer supply roller 32Y usually rotates at a speed of about 210 mm / s, and contacts the compaction roller 22Y downstream of the nip portion with the developer supply roller 32Y. A bias of about +400 V is applied to the developing roller 20Y, and a bias having a polarity higher than that of the developing roller 20Y and having the same polarity as the toner charging polarity is applied to the compaction roller 22Y. For example, a bias of about +600 V + 800 V is applied to the compaction roller 22Y. Therefore, the toner particles in the liquid developer on the developing roller 20Y move toward the developing roller 20Y when passing through the nip with the compaction roller 22Y as shown in FIG. As a result, the toner particles are gently coupled to form a film, and when developing with the image carrier 10Y, the toner particles move from the developing roller 20Y to the image carrier 10Y quickly, and the image density is improved. To do.

  The image carrier 10Y is made of amorphous silicon and normally rotates at a speed of about 210 mm / s. After the surface is charged to about +650 V by the charging roller 11Y upstream of the nip portion with the developing roller 20Y, the exposure unit 12Y As a result, a latent image is formed so that the potential of the image portion becomes + 25V. In the developing nip portion formed between the developing roller 20Y and the image carrier 10Y, a bias + 400V applied to the developing roller 20Y and a latent image (image portion + 25V, non-image portion + 650V) applied to the image carrier 10Y. According to the formed electric field, as shown in FIG. 4, the toner particles T are selectively moved to the image portion on the image carrier 10Y, whereby a toner image is formed on the image carrier 10Y. Further, since the carrier liquid C is not affected by the electric field, as shown in FIG. 4, it is separated at the exit of the developing nip between the developing roller 20Y and the image carrier 10Y, and both the developing roller 20Y and the image carrier 10Y are separated. Adhere to. The image carrier 10Y that has passed through the development nip passes through the image carrier squeeze roller 13Y, and the excess carrier liquid C is removed as shown in FIG. 5 to increase the toner particle ratio in the visible image. The

  Next, the image carrier 10Y passes through the nip portion with the intermediate transfer member 40 in the primary transfer portion 50Y, and primary transfer of the visible toner image to the intermediate transfer member 40 is performed. The primary transfer roller 51Y is applied with about −200 V having the opposite polarity to the charging characteristics of the toner particles, so that the toner is primarily transferred from the image carrier 10Y to the intermediate transfer member 40, and the carrier liquid is transferred to the image carrier 10Y. Only remains. On the downstream side in the rotation direction of the image carrier 10Y from the primary transfer unit 50Y, the electrostatic latent image is erased by the latent image eraser 16Y composed of a lamp or the like after the primary transfer on the image carrier 10Y. The remaining carrier liquid is scraped off by the image carrier cleaning blade 17Y and recovered by the developer recovery unit 18Y.

  The toner image primarily transferred onto the intermediate transfer member 40 by the primary transfer unit 50Y passes through the intermediate transfer member squeeze device 52Y in order to scrape excess carriers on the intermediate transfer member 40. + 400V is applied to the intermediate transfer member squeeze roller 53Y of the intermediate transfer member squeeze device 52Y, and + 250V is applied to the intermediate transfer member squeeze backup roller 54Y, and an electric field is generated to press the toner particles against the intermediate transfer member 40 side. Yes. Therefore, toner particles are not collected on the intermediate transfer member squeeze roller 53Y as shown in FIG. 6, and only the carrier liquid that is not affected by the electric field is transferred between the intermediate transfer member 40 and the intermediate transfer member squeeze roller 53Y. Collected by crying.

  The toner image on the intermediate transfer member 40 then proceeds to the secondary transfer unit 60 and enters the nip portion between the intermediate transfer member 40 and the secondary transfer roller 61. The nip width at this time is set to 3 mm. In the secondary transfer unit 60, −1200 V is applied to the secondary transfer roller 61 and +200 V is applied to the belt driving roller 41, whereby the toner image on the intermediate transfer member 40 is a recording medium such as paper. Is transferred to.

  After passing through the secondary transfer unit 60, the intermediate transfer member 40 advances to the winding portion of the tension roller 42, the intermediate transfer member 40 is cleaned by the intermediate transfer member cleaning blade 46, and again the primary transfer portion 50Y. Head to.

  Next, the squeeze function of the secondary transfer roller 61 will be described. The sheet material is supplied in accordance with the timing at which the toner image overlaid on the intermediate transfer body 40 reaches the secondary transfer portion, and the toner image is secondarily transferred to the sheet material to proceed to a fixing step (not shown). When the final image formation on the sheet material is completed, but a sheet material supply trouble such as a jam occurs, the toner image is transferred in contact with the secondary transfer roller 61 without the sheet material interposed therebetween. Causes backside contamination. The secondary transfer roller 61 of this embodiment has a plurality of image carriers as means for improving the secondary transfer characteristics following the non-smooth sheet material surface, even if the surface is a non-smooth sheet material due to fibers or the like. The toner image formed in FIG. 10 is subjected to primary transfer in sequence, carried in an overlapping manner, and elastically coated with an elastic body on the surface for the same purpose as that of the elastic belt employed in the intermediate transfer body 40 that is collectively transferred to a sheet material. It is composed of rollers. The secondary transfer roller cleaning blade 62 is provided as means for removing the developer (toner dispersed in the carrier) transferred to the secondary transfer roller 61, collects the developer from the secondary transfer roller 61, and is pooled. . Note that the pooled developer is in a mixed color state and may contain foreign matters such as paper dust.

  Next, the cleaning device for the intermediate transfer member 40 will be described. When a sheet material supply trouble such as a jam occurs, not all the toner images are transferred to the secondary transfer roller 61 and collected, and a part remains on the intermediate transfer body 40. Further, even in a normal secondary transfer process, the toner image on the intermediate transfer member 40 is not 100% secondary transferred and transferred to the sheet material, and a secondary transfer residue of several percent occurs. The two types of unnecessary toner images are collected and pooled by an intermediate transfer member cleaning blade 46 and a developer recovery unit 47 arranged so as to contact the intermediate transfer member 40 for the next image formation.

  Next, control of the compaction roller 22Y and the developing roller 20Y by control means (not shown) such as a PC and a printer control unit of the liquid developing development system will be described with reference to FIGS. FIG. 7 is a sequence diagram between the sheets of the compaction roller 22Y and the developing roller 20Y. First, in the normal printing state, the bias of the compaction roller 22Y and the bias of the developing roller 20Y are both turned on. Next, the bias of the compaction roller 22Y is turned OFF. The timing of the compaction roller 22Y is when the starting point between the sheets on the image carrier 10Y comes to the development position (center of the nip portion between the image carrier 10Y and the development roller 20Y), and compaction. This is the timing when the center of the nip portion with the compaction roller 22Y on the developing roller 20Y at the time when the bias of the roller 22Y is turned off is at the development position at the same time. Next, the bias of the compaction roller 22Y is turned ON, and the timing of the compaction roller 22Y is determined when the end point between the sheets on the image carrier 10Y comes to the development position (center of the nip portion between the image carrier 10Y and the development roller 20Y). This is the timing when the center of the nip portion with the compaction roller 22Y on the developing roller 20Y at the time when the bias of the roller 22Y is turned ON is at the same time. While the bias of the compaction roller 22Y is OFF, the developer supplied from the developer supply roller 34Y to the development roller 20Y moves to the compaction roller 22Y and is collected by the compaction roller cleaning blade 23Y.

  By controlling in this way, the image bearing member 10Y and the electric field applying roller 22Y are not subjected to two solid pressings from the developing roller 20Y at the position between the sheets, so that the cleaning property and developing property of the developing roller 20Y are improved. The life of the developing roller 20Y and the developing roller cleaning blade 21Y is extended.

  FIG. 8 is an end sequence diagram of the compaction roller 22Y and the developing roller 20Y. First, in the normal printing state, both the compaction roller 22Y and the developing roller 20Y rotate with a bias ON. Next, the bias of the compaction roller 22Y is turned OFF. The timing is when the end point of the image area on the image carrier 10Y comes to the development position (center of the nip between the image carrier 10Y and the development roller 20Y), and compaction. This is the timing when the center of the nip portion with the compaction roller 22Y on the developing roller 20Y at the time when the bias of the roller 22Y is turned off is at the development position at the same time. Of course, the end point of the image area on the image carrier 10Y may be after the development position (center of the nip portion between the image carrier 10Y and the developing roller 20Y), but simultaneous is most effective. After turning off the bias of the compaction roller 22Y, the developing roller 20Y is rotated by one or more revolutions, and then the bias of the developing roller 20Y is turned off. The developer supplied from the developer supply roller 34Y to the developing roller 20Y moves to the compaction roller 22Y and is collected by the compaction roller cleaning blade 23Y after the compaction roller 22Y is turned off and then the developing roller 20Y is turned off. The The developer on the developing roller 20Y is removed by both bias cleaning by the developing roller cleaning blade 21Y and the compaction roller 22Y. Thereafter, the compaction roller and the developing roller are stopped simultaneously.

  By controlling at the end of the printing operation in this way, after the printing operation is finished, the surface of the developing roller is not left for a long time in a high solid content concentration, and the developer solid content is filmed on the developing roller 20Y. Therefore, the life of the developing roller 20Y and the developing roller cleaning blade 21Y is extended.

  In this embodiment, the compaction roller 22Y, the image carrier squeeze roller 13Y, and the intermediate transfer member squeeze roller 53Y are all used as the squeeze member. However, for example, when only the compaction roller 22Y is applied as shown in FIG. When applying the compaction roller 22Y and the image carrier squeeze roller 13Y as shown in FIG. 11, when applying the compaction roller 22Y and the intermediate transfer member squeeze roller 53Y as shown in FIG. Also good.

The figure which showed the main components which comprise the image forming apparatus which concerns on embodiment of this invention Sectional view showing main components of image forming unit and developing unit The figure explaining the compaction by the compaction roller 22Y The figure explaining the development by the developing roller 20Y The figure explaining the squeeze effect | action by the image carrier squeeze roller 13Y The figure explaining the squeeze effect | action by the intermediate transfer body squeeze apparatus 52Y Sequence diagram between the compaction roller 22Y and the developing roller 20Y End sequence diagram of the compaction roller 22Y and the developing roller 20Y The figure which shows the case where only the compaction roller 22Y is applied as a squeeze roller member. The figure which shows the case where the compaction roller 22Y and the image carrier squeeze roller 13Y are applied as a squeeze roller member. The figure which shows the case where the compaction roller 22Y and the intermediate transfer body squeeze roller 53Y are applied as squeeze roller members

Explanation of symbols

10Y, 10M, 10C, 10K ... image carrier, 11Y, 11M, 11C, 11K ... charging roller, 12Y, 12M, 12C, 12K ... exposure unit, 13Y ... image carrier squeeze roller, 14Y: Image carrier squeeze roller cleaning blade, 15Y: Developer recovery unit, 16Y: Latent image eraser, 17Y: Image carrier cleaning blade, 18Y ... Developer recovery unit, 20Y, 20M, 20C, 20K ... developing roller, 21Y ... developing roller cleaning blade, 22Y ... compaction roller (bias application roller), 23Y ... compaction roller cleaning blade, 30Y, 30M, 30C, 30K ...・ Developing unit, 31Y, 31M, 31C, 31K ... developer container, 32Y 32M, 32C, 32K ... developer supply roller, 33Y ... regulating blade, 21Y, 34Y ... stirring roller, 40 ... intermediate transfer member, 41, 42 ... belt drive roller, 46 ... Intermediate transfer member cleaning blade, 47... Developer collecting unit, 50Y, 50M, 50C, 50K ... primary transfer unit, 51Y, 51M, 51C, 51K ... primary transfer backup roller, 52Y, 52M, 52C , 52K, intermediate transfer member squeeze unit, 53Y, intermediate transfer member squeeze roller, 54Y, intermediate transfer member squeeze backup roller, 55Y, intermediate transfer member squeeze roller cleaning blade, 56Y, developer. Collection unit, 60 ... secondary transfer unit, 61 ... secondary transfer roller, 62 ... secondary transfer roller clear Training blade, 63 ... developer collecting section

Claims (4)

In a developing system for liquid development, which includes a developing roller that carries a developer and a developer supply roller that supplies the developer to the developing roller, and develops the latent image formed on the image carrier with the developing roller. A liquid developing device comprising: a bias applying roller that adjusts a solid content concentration distribution in the liquid developer on the developing roller; and a control unit that controls to turn off the applying bias of the bias applying roller at a position between sheets. Development system. In a developing system for liquid development, which includes a developing roller that carries a developer and a developer supply roller that supplies the developer to the developing roller, and develops the latent image formed on the image carrier with the developing roller. A bias application roller that adjusts the solid content concentration distribution in the liquid developer on the developing roller, and at the end of the printing operation, after the application bias of the bias application roller is turned off, the developing roller is rotated one or more times. And a control unit for controlling the liquid development system. A developing method for liquid development, wherein an application bias of a bias application roller is turned off at a position between sheets. A developing method for liquid development, wherein at the end of printing operation, after the application bias of the bias application roller is turned off, the development roller is rotated one or more times.

Images