JP2008170705A - Image forming device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device and method which can maintain the dispersion stability of the developing agent. <P>SOLUTION: The device has a temperature sensor S to monitor the temperature in the process. The distance from the nip of the secondary transfer section 60 to the nip of the fixing unit 70 is made smaller than the smallest transfer component setup in advance, and the temperature of the temperature sensor S is regulated not to rise higher than the dispersant desorption temperature Td. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a liquid developer is supplied to a developer carrier by a developer supply roller, a latent image on the image carrier is developed by the developer carrier, and an image on the image carrier is transferred to an intermediate transfer member. The present invention also relates to a liquid developer that forms an image by secondary transfer of an image on an intermediate transfer member to a transfer material, and an image forming apparatus using the liquid developer.

  Conventionally, as a patent relating to an apparatus for measuring the electrical characteristics of a toner, the measuring means sandwiches a very small amount of toner sample between both electrodes and applies an electric field, whereby the mobility, conductivity, zeta potential of the toner, etc. Some of them were able to quantify their electrical properties. Here, since the above-described conductivity can be said to be the resistance of the toner, in other words, it is known that this conductivity changes as the amount of charged particles in the entire toner increases or decreases (see Patent Document 1). ).

Further, in an apparatus in which an intermediate transfer roller having a heating device inside and a temperature sensor is provided on a photoconductor in contact with the intermediate transfer roller, when the temperature on the photoconductor becomes equal to or higher than the glass transition temperature of toner particles, storage is performed. Some of them cool the toner in the area (see Patent Document 2).
JP 2001-264294 A JP 2005-282081 A

  When the electrical characteristics of the toner are measured using the apparatus described in Patent Document 1, the toner conductivity is generally found to increase as the temperature rises, as will be described in detail later. This is considered to be because the dispersant adhering to the toner solid content is easily detached from the surface of the toner particles due to an increase in thermal kinetic energy accompanying the temperature increase.

  Further, as described in Patent Document 2, it is well known that such a temperature rise becomes conspicuous due to heat transfer during continuous printing. For example, when the distance from the secondary transfer nip portion to the fixing nip portion is shorter than the minimum paper width and continuous printing is performed, heat is transferred from the fixing device to the upstream through the paper medium as shown in FIG. The temperature of the entire device can rise. In this case, if the state of adsorption of the dispersant, which has the most influence on the dispersion stability of the toner, changes to the toner particles and sometimes comes off, the toner loses its original dispersion stability and is recycled. It becomes impossible to use.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming method capable of solving the above-described problems and maintaining the dispersion stability of a developer.

  The present invention is an image forming apparatus that solves the above problems, a developer container for storing a liquid developer comprising a developer solid content containing a pigment component, a dispersant, and a non-volatile liquid carrier, and a liquid A developer carrying member for carrying a developer; a developer supply member for supplying a liquid developer from the developer container to the developer carrying member; and an image carrier for developing a latent image by the developer carrying member. An intermediate transfer member that forms an image by transferring an image on the image carrier, a secondary transfer portion that transfers the image on the intermediate transfer member to a transfer material, and an image transferred by the secondary transfer portion A minimum transfer with a distance from the nip portion of the secondary transfer portion to the nip portion of the fixing portion provided with a fixing portion for fixing the toner to the transfer material and a temperature sensor for monitoring the temperature in the process. Less than the length of the material, the front Since the temperature of the temperature sensor is controlled so as not to be more dispersant desorption temperature, it is possible to maintain the dispersion stability of the developer.

  In addition, when the temperature of the temperature sensor becomes equal to or higher than a predetermined value lower than the dispersant desorption temperature, it is controlled to a temperature rise suppression mode in which the interval between the transfer material and the next transfer material is longer than that during normal printing. Heat can no longer be transmitted through the transfer material, temperature rise can be suppressed, and the dispersion stability of the developer can be maintained.

  Further, since the process is stopped when the temperature of the temperature sensor becomes equal to or higher than the dispersant desorption temperature, the temperature rise can be suppressed and the dispersion stability of the developer can be maintained.

  Further, since the temperature sensor monitors the temperature of the intermediate transfer member, the dispersion stability of the developer on the intermediate transfer member can be maintained.

  In addition, since the temperature sensor monitors the temperature of the image carrier squeeze roller that removes the liquid carrier on the image carrier, the dispersion stability of the developer on the image carrier can be maintained.

  Further, since the temperature sensor monitors the temperature of the developer carrier, the dispersion stability of the developer on the developer carrier can be maintained.

  In addition, since the liquid developer for recycling the liquid developer is provided, it is possible to maintain the dispersion stability of the developer and to recycle the stable developer.

  Further, when the temperature of the temperature sensor reaches a predetermined value lower than the dispersant desorption temperature, the recycling device is stopped, so that a developer with poor dispersion stability is not recycled.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing main components constituting an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing components for each color of the image forming apparatus. In FIG. 1, for each color composed of yellow (Y), magenta (M), cyan (C), and black (K), the same component is given Y, M, C, and K representing each color. The same number is used. Of these, FIG. 2 shows the configuration of yellow (Y). The image forming apparatus will be described below with reference to FIGS.

  The image forming apparatus 1 includes a cleaning device including a cleaning blade 16Y for the image carrier and a developer recovery unit 17Y, a charging roller 11Y, an exposure unit 12Y, and a developer along the rotation direction (movement direction) of the outer periphery of the image carrier 10Y. A cleaning device including a developing roller 20Y, an image carrier squeeze roller 13Y as an example of a developer carrying member of the unit 30Y, and a cleaning blade 14Y and a developer collecting unit 15Y, which are auxiliary components, is disposed. The development unit 30Y includes a cleaning blade 21Y, a developer supply roller 32Y using an anilox roller as an example of a developer supply member, a regulation blade 33Y for regulating the developer supply amount, and a developer on the outer periphery of the development roller 20Y. A developer that stirs the developer in a uniformly dispersed state in a developer container (reservoir) 31Y in which the compression roller 22Y and the developer on the surface of the compression roller 22Y are written and removed, and the liquid developer is accommodated. A stirring roller 34Y is disposed. Further, a primary transfer roller 51Y of the primary transfer unit 50Y is disposed at a position facing the image carrier 10Y with the intermediate transfer member 40 interposed therebetween, and further along the intermediate transfer member 40, the primary transfer unit of each color further downstream in the moving direction. 50Y (M, C, K) is arranged. A secondary transfer unit 60 is disposed downstream of the primary transfer unit 50Y (M, C, K), and an image is transferred to a transfer material. A fixing unit 70 is disposed on the downstream side of the sheet material conveyance path L from the secondary transfer unit 60.

  The liquid developer 1 accommodated in the developer container 31Y is composed of resin fine particles 2 as a developer solid content containing a pigment component, a dispersant 3, and a carrier oil 4 as a non-volatile liquid carrier. A solid particle having an average particle diameter of 1 μm in which a colorant such as a pigment is dispersed in a plastic resin is added to a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil together with the dispersant, and the toner solid content concentration is increased. It is a liquid developer having a high viscosity (about 30 to 10,000 mPa · s) of about 25%. The liquid developer contained in the developer container 31Y is a developer or carrier dispersed in a high concentration of about 35 to 55% by weight of the toner according to the concentration of the developer that changes as the image carrier is developed. The developer container 31Y is replenished and agitated by the liquid developer agitating roller 34Y to obtain a uniformly dispersed state, and 25% of the toner is dispersed in 75% of the carrier in a weight ratio.

  In the image forming unit and developing unit 30Y, the image carrier 10Y is uniformly charged by the charging roller 11Y, and the input image is input by the exposure unit 12Y having an optical system such as a semiconductor laser, a polygon mirror, and an F-θ lens. Based on the signal, a modulated laser beam is irradiated to form an electrostatic latent image on the charged image carrier 10Y. Then, the amount of developer supplied is regulated by the regulating blade 33Y from the developer container 31Y storing the liquid developer of each color (here yellow), and the developer is supplied from the developer supply roller 32Y to the developing roller 20Y to carry the image. The electrostatic latent image formed on the body 10Y is developed.

  The intermediate transfer member 40 is an endless elastic belt member and is wound around and stretched between a driving roller 41 and a tension roller 42. The image transfer members 10Y, 10M, and 50K are primary transfer units 50Y, 50M, 50C, and 50K. It is rotationally driven by the drive roller 41 while abutting 10C and 10K. The primary transfer portions 50Y, 50M, 50C, and 50K are arranged so that the primary transfer rollers 51Y, 51M, 51C, and 51K are opposed to the image carriers 10Y, 10M, 10C, and 10K with the intermediate transfer member 40 interposed therebetween. Using the contact position with 10M, 10C, and 10K as the transfer position, the developed toner images of the respective colors on the image carriers 10Y, 10M, 10C, and 10K are sequentially superimposed and transferred onto the intermediate transfer body 40 to obtain a full-color toner. An image is formed. The toner images formed on the plurality of image carriers (photosensitive members) 10Y, 10M, 10C, and 10K are sequentially transferred onto the intermediate transfer member 40 in such a manner that the toner images are superimposed and supported on the sheet material. Next transfer. Therefore, when transferring the toner image to the sheet material in the secondary transfer process, even if the sheet material surface is not smooth due to the fiber, etc., the secondary transfer characteristics are improved following this non-smooth sheet material surface. An elastic belt member is employed as the means for making it. In the present embodiment, a temperature sensor S for monitoring the temperature on the intermediate transfer member 40 is provided at a portion where the intermediate transfer member 40 is wound around the tension roller 42.

  In the secondary transfer unit 60, a secondary transfer roller 61 is disposed opposite to the belt driving roller 41 with the intermediate transfer body 40 interposed therebetween, and a cleaning device including a cleaning blade 62 of the secondary transfer roller and a developer recovery unit 63 is disposed. Is done. In the secondary transfer unit 60, the sheet material conveyance path L is adjusted in accordance with the timing at which a full-color toner image or a single-color toner image formed by superimposing colors on the intermediate transfer body 40 reaches the transfer position of the secondary transfer unit 60. Then, a sheet material such as paper, film or cloth is conveyed and supplied, and a single color toner image or a full color toner image is secondarily transferred to the sheet material.

  A fixing unit 70 is disposed downstream of the sheet transfer path L of the secondary transfer unit 60. The fixing unit 70 fuses and fixes a single-color toner image or a full-color toner image transferred onto the sheet material to a recording medium (sheet material) such as paper, and ends the final image formation on the sheet material. . Even if the secondary transfer roller 61 is a sheet material whose surface is not smooth due to fibers or the like, as a means for improving the secondary transfer characteristics following the surface of the non-smooth sheet material, the surface is coated with an elastic body. It is composed of rollers. This is an elastic belt employed in the intermediate transfer body 40 that sequentially transfers the toner images formed on the plurality of image carriers 10Y, sequentially superimposes them on the intermediate transfer body 40, and transfers them to the sheet material collectively. The purpose is the same as that of the member.

  On the side of the tension roller 42 that stretches the intermediate transfer member 40 together with the belt driving roller 41, along the outer periphery thereof, a cleaning blade 43 that contacts the intermediate transfer member 40, and development that collects the developer cleaned by the cleaning blade 43 A cleaning device including the agent recovery unit 44 is disposed. The intermediate transfer body 40 after passing through the secondary transfer section 60 is cleaned on the intermediate transfer body 40 by the cleaning blade 43, and again goes to the primary transfer section 50.

  In the developer container 31Y, the toner particles in the liquid developer have a positive charge. The developer is agitated by the agitation roller 34Y to be in a uniformly dispersed state, and the developer supply roller 32Y rotates. The developer is pumped up from the developer container 31Y, the developer amount is regulated by the regulating blade 33Y, and supplied to the developing roller 20Y. Initially, the developer stored in the developer container 31Y is uniformly dispersed in the carrier at approximately a toner weight ratio of about 25%. However, in the development on the image carrier 10Y, the image duty is high. However, in the case of development with a low image duty, the toner consumption ratio decreases. In other words, 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 and dispersed approximately to a toner weight ratio of about 25%. It is necessary to maintain and control the state.

  In order to control the density of the developer in the developer container 31Y, as a means for detecting the density, a transmission type photosensor for detecting the dispersion weight ratio of the toner (not shown) or torque detection for detecting the stirring torque of the developer stirring roller 34Y. Each developing unit 30Y is provided with a reflection type photosensor for detecting the means and the developer liquid level in the developer container 31Y. When the toner dispersion weight ratio decreases at a predetermined developer amount, the developer container 31Y is replenished with a predetermined amount of developer dispersed at a high density of about 35 to 55%. Conversely, when the toner dispersion weight ratio increases, a predetermined amount of carrier is replenished to the developer container 31Y. By these replenishment, the toner weight ratio is controlled to about 25%.

  In order to exhibit a preferable secondary transfer function and fixing function in a stage where an image is formed through various process steps, is secondarily transferred to a final stage sheet material, and proceeds to a fixing step (not shown) using this developer. It is desirable that the liquid developer is in a dispersion state of approximately 40% to 60% in approximate toner weight ratio. For this reason, the image forming apparatus according to the present exemplary embodiment includes a developer collecting unit that removes and collects excess developer and excess carrier at a plurality of positions as appropriate.

  Next, the developer recovery unit will be described. In the image forming apparatus according to the present exemplary embodiment, the developer is scraped off and collected by a cleaning device included in the developer collecting unit. As the developer recovery means, a developing roller cleaning device 21 that cleans the developing roller 20, a developer compression roller cleaning device 23 that cleans the developer compression roller 22, an image carrier squeeze device 13 to 15, and an image carrier cleaning device. Devices 16 and 17, intermediate transfer member cleaning devices 43 to 44, and secondary transfer roller cleaning devices 62 and 63, and the like.

  In the developing unit 30Y, the cleaning blade 23Y and the developing roller 20Y as an example of a developer compressing roller cleaning device that cleans the developer compressing roller 22Y that compresses the liquid developer toner carried on the developing roller 20Y. And a cleaning blade 21Y as an example of a developing roller cleaning device. The cleaning blade 21Y is disposed on the downstream side in the rotation direction of the developing roller 20Y from the developing nip portion where the developing roller 20Y contacts the image carrier 10Y, and scrapes off the developer remaining on the developing roller 20Y. The developer in the developer compression roller 22Y is scraped off and removed by rotating in the direction of the arrow in the figure, and the developer in the reservoir 31Y is joined (joined) to be reused. Note that the merged carrier and toner are not in a mixed color state. Further, the collected developer may be discarded.

  The image carrier squeeze devices 13Y to 15Y are arranged on the downstream side in the rotation direction from the developing roller 20Y so as to face the image carrier 10Y, and are in pressure-sliding contact with the image carrier squeeze roller 13Y. A cleaning blade 14Y for cleaning the surface and a developer collecting unit 15Y, which collects excess carrier and originally unnecessary fog toner from the developer developed on the image carrier 10Y, and increases the toner particle ratio in the visible image. It has a function. In this embodiment, the image carrier squeeze roller 13Y rotates with the image carrier 10Y at substantially the same peripheral speed, and an excess carrier of about 5 to 10% by weight from the developer developed on the image carrier 10Y. Both the rotational driving loads are collected to reduce the disturbance effect on the visible toner image of the image carrier 10Y. Excess carrier and unnecessary fog toner collected by the image carrier squeeze roller 13Y are collected from the image carrier squeeze roller 13Y to the developer collecting unit 15Y by the action of the cleaning blade 14Y. Note that the collected surplus carrier and fog toner are collected from the dedicated isolated image carrier 10Y, so that no color mixing phenomenon occurs in the image forming portions of the respective colors.

  In the primary transfer unit 50Y, the image carrier 10Y and the intermediate transfer member 40 move at the same speed, and the developer image developed on the image carrier 10Y is transferred to the intermediate transfer member 40 by the primary transfer roller 51Y. In addition, the driving load of movement is reduced, and the disturbance effect on the visible toner image of the image carrier 10Y is suppressed. 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. As a result of the so-called reverse transfer development in which the toner moves from the image carrier 10Y (M, C, K) to the image carrier 10Y (M, C, K), the reverse transfer toner and the transfer residual toner are mixed and are carried on the image carrier 10Y (M, C, K) together with the surplus carrier. The developer recovery unit 17Y (M, C, K) is moved from the image carrier 10Y (M, C, K) by the action of a cleaning blade 16Y (M, C, K) as an example of an image carrier cleaning device. To be recovered.

  The sheet material is supplied in accordance with the timing at which the toner image superimposed on the intermediate transfer body 40 reaches the secondary transfer portion, and the toner image is secondarily transferred to the sheet material and proceeds to the fixing process, and the final sheet material When the above image formation is completed, but a sheet material supply trouble such as a jam occurs, not all the toner images are transferred to the secondary transfer roll and collected. In addition, in the normal secondary transfer process, the toner image on the intermediate transfer body 40 is not 100% secondary-transferred and transferred to the sheet material, and a secondary transfer residue of several percent occurs. In particular, when 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, and the back surface of the sheet material is stained. These unnecessary toner images are cleaned on the intermediate transfer body 40 by the cleaning blade 43 of the intermediate transfer body 40 and the secondary transfer roller 61 is cleaned by the cleaning blade 62 of the secondary transfer roller 61. As described above, the cleaning blade 62 of the secondary transfer roller is provided as means for removing the developer (toner dispersed in the carrier) transferred to the secondary transfer roller 61, and the developer is collected from the secondary transfer roller 61. The

  Next, the temperature change of the developer used in the image forming apparatus having such a configuration will be described. First, a method for measuring developer conductivity will be described. The basic configuration of the developer conductivity measuring device is the same as that shown in Patent Document 1, but, as shown in FIG. 3, the measurement unit 100 has a first heating so as to contact the first electrode unit 101. The part 102 is arranged, and the second heating part 104 is arranged so as to contact the second electrode part 103. Then, a developer sample is set between the first electrode portion 101 and the second electrode portion 103. For example, a silicon rubber heater or the like is applied to the first heating unit 102 and the second heating unit 104. A sample of the developer 110 includes a developer solid content 111, a carrier oil 112, and a dispersant 113.

  In the measuring method using the developer conductivity measuring device having such a structure, the first electrode unit 101 and the second electrode unit 103 are heated to the target temperature by the first heating unit 102 and the second heating unit 104 in advance, and then A sample of the developer 110 is set, and the resistance value, that is, the conductivity is measured. Since the sample amount of the developer 110 is very small, the sample itself reaches the target temperature very quickly and can be measured quickly.

  FIG. 4 is an outline of a graph showing the result of measuring the conductivity with respect to the temperature of the developer. As shown in the graph of FIG. 4, the conductivity of the developer increases from a certain temperature. This is considered to be because the dispersant easily separated from the surface of the toner particles due to an increase in thermal kinetic energy accompanying the temperature increase. In such a graph, the point at which the rate of change in conductivity with respect to the temperature of the liquid developer is maximized is denoted by Td. The glass transition temperature of the resin component of the liquid developer is Tg. At this time, in this embodiment, the maximum change rate point Td, which is the desorption temperature of the dispersant of the liquid developer, satisfies the relationship of the glass transition temperature Tg of the resin component of the liquid developer and Tg <Td. Note that the maximum change rate point Td of the liquid developer may be obtained as an intersection of an approximate line in a region having a small inclination and an approximate line in a region having a large inclination.

  Next, control by temperature monitoring of this embodiment will be described. FIG. 5 shows a flowchart of control by temperature monitoring. First, in step 1, the temperature of the intermediate transfer member 40 in the process is monitored by the temperature sensor S (ST1). Next, in step 2, it is determined whether the temperature T of the intermediate transfer body 40 is equal to or higher than the developer conductivity maximum change point Td (ST2). If the temperature T of the intermediate transfer member 40 is lower than the developer conductivity maximum change point Td, in step 3-1, the developer conductivity maximum change point Td-5 ° C where the temperature T of the intermediate transfer member 40 is a predetermined value. Whether it is the above or not is determined (ST3-1). If the temperature T of the intermediate transfer body 40 is equal to or higher than the developer conductivity maximum change point Td, the process of the image forming apparatus is forcibly stopped in step 3-2 (ST3-2).

  Subsequently, in step 3-1, when it is determined that the temperature T of the intermediate transfer body 40 is equal to or higher than the developer conductivity maximum change point Td-5 ° C. as a predetermined value, in step 4-1, in the normal printing mode. The printing is performed in the temperature rise suppression mode in which printing is performed with an interval larger than the interval between the sheet materials (ST4-1). If it is determined in step 3-1 that the temperature T of the intermediate transfer body 40 is less than the developer conductivity maximum change point Td−5 ° C. as a predetermined value, in step 4-2, the default speed is determined by a print ON signal. Normal printing is executed in the normal printing mode for printing in (ST4-2).

  FIG. 6 shows another embodiment, in which the temperature on the image carrier squeeze roller 13Y in the process is monitored by the temperature sensor S. In FIG. In the present embodiment, a temperature sensor S is installed downstream of the contact portion with the cleaning blade 14Y on the image carrier squeeze roller 13Y and upstream of the nip portion with the image carrier 10Y.

  FIG. 7 shows another embodiment, in which the temperature on the developing roller 20Y in the process is monitored by the temperature sensor S. In FIG. In the present embodiment, the temperature sensor S is installed downstream of the contact portion with the cleaning blade 21Y on the developing roller 20Y and upstream of the nip portion with the image carrier 10Y.

  Next, FIG. 8 shows another embodiment to which the liquid developer recycling apparatus 80 is applied. In FIG. 8, only the yellow liquid developer recycling apparatus 80Y is shown, and the liquid developer recycling apparatuses 80M, 80C, and 80K for other colors are omitted.

  In the figure, 80Y is a recycling apparatus, 81Y is a density adjusting unit, 82Y is a stirring roller, 83Y is a high-concentration developer tank, 84Y is a high-concentration developer pump, 85Y is a developer pump, and 86Y is a recycle path. The roller path, 87Y is a carrier oil tank, 88Y is an opening / closing valve, 89Y is an intermediate transfer member path that is a recycling path, 90Y is an image carrier squeeze roller path that is a recycling path, and 91Y is an image carrier path that is a recycling path. .

  In the present embodiment, an intermediate transfer member path that collects the developer that is mostly carrier oil scraped off and collected by the cleaning blade 43 in the developer recovery unit 44 and connects the developer recovery unit 44 to the opening / closing valve 88Y. 89Y is provided. Further, an image carrier squeeze roller path 90Y that collects the developer, which is mostly carrier oil, scraped off by the cleaning blade 14Y in the developer recovery section 15Y and connects the developer recovery section 15Y to the opening / closing valve 88Y. Is provided. Further, an image carrier path 91Y is provided in the developer collecting section 17Y to collect the developer, which is mostly carrier oil scraped and collected by the cleaning blade 16Y, and to connect the developer collecting section 17Y to the opening / closing valve 88Y. The intermediate transfer member path 89Y, the image carrier squeeze roller path 90Y, and the image carrier path 91Y are connected to each other and connected to a connection path from the carrier oil tank 87Y to the opening / closing valve 88Y, thereby opening and closing the opening / closing valve 88Y. Carrier oil can be replenished to the concentration adjusting unit 81Y.

  Further, the developer scraped and collected by the cleaning blade 21Y can be replenished to the density adjusting unit 81Y through the developing roller path 86Y by the developer pump 85Y, and the developer stored in the high density developer tank 83Y can be replenished. The density developer can be replenished to the density adjustment unit 81Y by the high density developer pump 84Y.

  The replenishment of the carrier oil, the developer, or the high-density developer is executed according to the developer concentration in the density adjusting unit 81Y measured by a density sensor (not shown) or the like.

  The developer in the density adjusting unit 81Y is adjusted to a uniform density by the rotation of the stirring roller 82Y, replenished to the developer container 31Y, and reused.

  Note that the control by temperature monitoring shown in FIG. 5 may be applied to the present embodiment to which the liquid developer recycling apparatus 80 is applied. At this time, the temperature sensor S may monitor the intermediate transfer member 40, the image carrier squeeze roller 13, and the developing roller 20 as described above.

  As described above, the image forming apparatus according to the present exemplary embodiment includes a developer container 31 that stores the liquid developer 110 including the solid developer component 111 containing the pigment component, the dispersant 113, and the non-volatile liquid carrier 112. A developer carrying member 20 carrying the liquid developer 110, a developer supplying member 32 for supplying the liquid developer 110 from the developer container 31 to the developer carrying member 20, and the developer carrying member 20 to form a latent image. An image carrier 10 to be developed; an intermediate transfer member 40 that forms an image by transferring an image on the image carrier 10; and a secondary transfer unit 60 that transfers the image on the intermediate transfer member 40 to a transfer material. A fixing unit 70 for fixing an image transferred by the secondary transfer unit 60 to a transfer material, and a temperature sensor S for monitoring a temperature in the process, and a nip part of the fixing unit 70 from a nip part of the secondary transfer unit 60. Distance to Configured to or less than the length of the minimum transfer material set, the temperature of the temperature sensor S is controlled so as not to be a dispersant desorption temperature Td or more, it is possible to maintain the dispersion stability of the developer 110.

  Further, when the temperature of the temperature sensor S reaches a predetermined temperature Td−5 ° C. which is lower than the dispersant desorption temperature Td, temperature rise suppression that increases the interval between the transfer material and the next transfer material than during normal printing. Since the mode is controlled, heat is not transmitted through the transfer material, the temperature rise can be suppressed, and the dispersion stability of the developer 110 can be maintained.

  Further, since the process is stopped when the temperature of the temperature sensor S becomes equal to or higher than the dispersant desorption temperature Td, the temperature rise can be suppressed and the dispersion stability of the developer 110 can be maintained.

  In addition, since the temperature sensor S monitors the temperature of the intermediate transfer member 40, the dispersion stability of the developer 110 on the intermediate transfer member 40 can be maintained.

  Further, since the temperature sensor S monitors the temperature of the image carrier squeeze roller 13 that removes the liquid carrier on the image carrier 10, the dispersion stability of the developer 110 on the image carrier squeeze roller 13 is maintained. Can do.

  Further, since the temperature sensor S monitors the temperature of the developer carrier 20, the dispersion stability of the developer 110 on the developer carrier 20 can be maintained.

  In addition, since the recycling device 80 for recycling the liquid developer 110 is provided, the dispersion stability of the developer 110 can be maintained and the stable developer 110 can be recycled.

  Further, when the temperature of the temperature sensor S reaches a predetermined temperature Td−5 ° C. or lower, which is lower than the dispersant desorption temperature, the recycling apparatus is stopped, so that a developer with poor dispersion stability is not recycled.

1 is a diagram illustrating an image forming apparatus according to an exemplary embodiment. FIG. 2 is a diagram illustrating a periphery of a developing unit of the image forming apparatus according to the present exemplary embodiment. It is a figure which shows the measurement part of a developer conductivity measuring apparatus. It is a figure which shows the electrical conductivity with respect to the temperature of a developing agent. It is a figure which shows the flowchart of this embodiment. It is a figure which shows embodiment which monitors the temperature on an image carrier squeeze roller. It is a figure which shows embodiment which monitors the temperature on a developing roller. It is a figure which shows other embodiment to which the liquid developer recycling apparatus is applied. FIG. 6 is a diagram illustrating a case where a distance from a secondary transfer nip portion to a fixing nip portion is shorter than a minimum paper width.

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 collecting part, 16Y ... image carrier cleaning blade, 17Y ... developer collecting part, 20Y, 20M, 20C, 20K ... developing roller (developer carrier), 21Y ... developing roller cleaning blade, 22Y ... Developer compression roller (developer compression member), 23Y ... developer compression roller cleaning blade, 30Y, 30M, 30C, 30K ... development unit, 31Y ... developer container, 32Y ... developer supply roller (developer supply member), 33Y: restriction blade, 34Y: stirring roller, 40: intermediate transfer member, 41 Belt drive roller, 42 ... belt driven roller, 43 ... intermediate transfer member cleaning blade, 44 ... developer recovery unit, 50Y, 50M, 50C, 50K ... primary transfer unit, 51Y ... primary transfer backup roller, 60 ... secondary transfer unit , 61 ... Secondary transfer roller, 62 ... Secondary transfer roller cleaning blade, 63 ... Developer recovery unit, 70 ... Fixing unit, 71 ... Heating roller, 72 ... Pressure roller, 80Y ... Recycling device, 81Y ... Density adjustment unit , 82Y: Stirring roller, 83Y: High concentration developer tank, 84Y: Pump for high concentration developer, 85Y: Pump for developer, 86Y ... Development roller path (recycling path), 87Y ... Carrier oil tank, 88Y ... Open / close valve 89Y: Intermediate transfer member path (recycling path), 90Y: Image carrier squeeze roller path (recycling path) 91Y: Image carrier path (recycling path), 100: Measuring unit, 101: First electrode unit 102: First heating unit, 103: Second electrode unit, 104: Second heating unit, 110: Liquid developer, 111 ... Developer solid content, 112 ... Carrier oil (liquid carrier), 113 ... Dispersant

Claims (10)

  A developer container for storing a liquid developer comprising a developer solid content containing a pigment component, a dispersant, and a non-volatile liquid carrier, a developer carrier for supporting the liquid developer, and the developer container A developer supply member for supplying a liquid developer to the developer carrier, an image carrier on which a latent image is developed by the developer carrier, and an image on the image carrier by transferring an image on the image carrier. An intermediate transfer member to be formed, a secondary transfer portion for transferring an image on the intermediate transfer member to a transfer material, a fixing portion for fixing the image transferred by the secondary transfer portion to the transfer material, and a temperature in the process. A temperature sensor for monitoring, and the distance from the nip portion of the secondary transfer portion to the nip portion of the fixing portion is equal to or less than a set minimum transfer material length, and the temperature of the temperature sensor Control so as not to exceed the separation temperature Image forming apparatus characterized by.   When the temperature of the temperature sensor becomes equal to or higher than a predetermined value lower than the dispersant desorption temperature, control is made to a temperature rise suppression mode in which the interval between the transfer material and the next transfer material is made longer than during normal printing. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the process is stopped when the temperature of the temperature sensor becomes equal to or higher than a dispersant desorption temperature.   The image forming apparatus according to claim 1, wherein the temperature sensor monitors a temperature of the intermediate transfer member.   4. The image forming apparatus according to claim 1, wherein the temperature sensor monitors a temperature of an image carrier squeeze roller that removes a liquid carrier on the image carrier.   The image forming apparatus according to claim 1, wherein the temperature sensor monitors a temperature of the developer carrying member.   The image forming apparatus according to claim 1, further comprising a recycling device that recycles the liquid developer.   The image forming apparatus according to claim 7, wherein the recycling apparatus is stopped when a temperature of the temperature sensor becomes equal to or higher than a predetermined value lower than a dispersant desorption temperature.   When a liquid developer composed of a developer solid containing a pigment component, a dispersant, and a non-volatile liquid carrier is used, and the temperature in the process is equal to or higher than a predetermined value lower than the dispersant desorption temperature. An image forming method characterized in that the interval between the transfer material and the next transfer material is made longer than that during normal printing.   Using a liquid developer composed of a developer solid containing a pigment component, a dispersant, and a non-volatile liquid carrier, the process is stopped when the temperature in the process exceeds the dispersant desorption temperature. An image forming method.

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