JP2014159101A - Image formation device and image formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device and an image formation method that temporarily form a liquid column bridge of a conductive recording liquid between heads and an intermediate transfer body to apply voltage and control curl of a recording material to which the recording liquid is transferred from the intermediate transfer body.SOLUTION: Following means are used: voltage application means 33 for performing voltage application to a liquid column for electrifying the liquid column of a recording liquid bridging between heads 61Y, 61M, 61C, and 61BK (hereinafter, referred to as heads 61) and an intermediate transfer body; curl amount prediction means 40f for predicting a curl amount of a recording material to which the recording liquid is transferred from the intermediate transfer body on the basis of at least one of a recording material characteristic 41a, a use environment 42a of an image formation device, a pattern in which the recording liquid adheres to the recording material, and the voltage applied; and Joule heat control means 44 for controlling Joule heat so that a predicted curl amount becomes less than or equal to an allowable curl amount when the curl amount predicted by the curl amount prediction means 40f exceeds the allowable curl amount.

Description

  The present invention relates to an inkjet image forming apparatus that forms an image by applying a recording liquid such as ink to an intermediate transfer member with a head, and an image forming method using the same.

  2. Description of the Related Art Conventionally, an ink jet type image forming apparatus such as an ink jet printer that includes a head (for example, see [Patent Document 1] and [Patent Document 2]) that ejects a recording liquid such as ink and performs ink jet recording is known. (For example, see [Patent Document 3] to [Patent Document 6]). As such a head, there is known a head that ejects recording liquid such as ink from a plurality of minute nozzles by using a movable actuator system represented by a piezo system, a heating film boiling system represented by a thermal system, or the like. Yes.

  In an inkjet image forming apparatus, in a configuration in which a recording liquid is directly discharged from a head to a recording material such as recording paper, the head and the recording material are close to each other, so paper dust and dust adhering to the recording material Etc. are likely to adhere to the nozzle. When paper dust or the like adheres to the nozzle, the flying direction of droplets ejected from the nozzle is disturbed, or the nozzle is blocked, resulting in a reduction in image quality and reliability. In order to avoid such a problem, priority is given to the ejection stability from the nozzles, and it is common to use a recording liquid having a low viscosity. However, a recording liquid having a low viscosity is applied to the recording material. Bleeding is likely to occur when landing.

  In view of this, an image forming apparatus that includes an intermediate transfer member that carries the recording liquid discharged from the head, forms an image on the intermediate transfer member, and then transfers the image to a recording material has been proposed (for example, Patent Document 3). To [Patent Document 6].

  Further, in the image forming apparatus provided with the intermediate transfer member as described above, an image forming device including a processing liquid applying unit that applies a processing liquid for changing the pH of the recording liquid to the intermediate transfer member in order to further reduce bleeding. Has been proposed (see, for example, [Patent Document 3]). In this image forming apparatus, in the recording liquid, at least a pigment and polymer fine particles are dispersed in a medium composed of water and a water-soluble solvent, and the pigment and polymer fine particles are aggregated by changing pH.

  In addition, in an image forming apparatus provided with an intermediate transfer body, an image forming apparatus is proposed in which a powder that absorbs a recording liquid is previously deposited on the intermediate transfer body in order to reduce bleeding (for example, [Patent Documents] 4]).

  Further, in the image forming apparatus provided with the intermediate transfer member, the following image forming apparatus has been proposed as a countermeasure against bleeding. That is, an image forming apparatus that temporarily forms a bridge of a liquid column of conductive recording liquid between a nozzle and an intermediate transfer member and applies a potential so that water contained in the bridge of the liquid column is electrolyzed (For example, see [Patent Document 5] and [Patent Document 6]).

  However, an image forming apparatus (see, for example, [Patent Document 3] and [Patent Document 4]) that applies a processing liquid or powder to the intermediate transfer member has a problem that the printing speed decreases due to the processing liquid or powder being applied There is a problem that the apparatus becomes large. In particular, in the configuration in which the powder is applied, the powder tends to adhere to the nozzle and the discharge performance of the recording liquid from the head is likely to deteriorate. However, the problems of such a decrease in printing speed and an increase in the size of the apparatus are caused by the recording liquid from the head. It is necessary to solve the problem while ensuring the discharge performance.

  On the other hand, an image forming apparatus of a type that performs electrolysis by temporarily forming a bridge of a liquid column of conductive recording liquid between a head and an intermediate transfer member and applying a voltage (for example, [Patent Document 5] ] And [Patent Document 6]), there is an advantage that no processing liquid or powder other than the recording liquid is required.

  The present inventor conducted intensive research on such type of image forming apparatus and found that the following phenomenon occurs when a voltage is applied when a bridge of a liquid column is formed. This is a phenomenon in which the degree of curling of the recording material is reduced when an image is formed with a recording liquid to which such a voltage is applied, compared to when no voltage is applied. The reason why this phenomenon occurs is considered as follows. That is, when such a voltage is applied, an electric current flows through the liquid column, and Joule heat is generated at this time. When Joule heat is generated, the temperature of the recording liquid rises and the evaporation of the recording liquid is promoted. The degree of curling of the recording material on which an image is formed by the liquid is reduced.

  Such knowledge is a new thing that has not been known so far. Based on this new knowledge, that is, the present inventor obtained an inspiration from this new knowledge, and conducted further research, it is possible to positively control curl by applying this knowledge. I found out. Note that less energy is required for curl control.

  The present invention provides a curling of a recording material on which a recording liquid is transferred from an intermediate transfer body by temporarily forming a bridge of a liquid column of conductive recording liquid between a head and the intermediate transfer body and applying a voltage. An object of the present invention is to provide an image forming apparatus and an image forming method for controlling the above.

  In order to achieve the above object, the present invention provides a head having a nozzle for discharging a conductive recording liquid in response to a drive signal, and at least a part of the surface to which the conductive recording liquid discharged by the head is applied. Is a conductive intermediate transfer body, and the intermediate transfer body for energizing a conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer body. Voltage applying means for applying a voltage to the head, transfer means for transferring an image carried on the intermediate transfer member to the recording material by a conductive recording liquid, characteristics of the recording material, and the image forming apparatus The curl for predicting the curl amount of the recording material when the image is transferred by the transfer means, based on the use environment, the pattern in which the conductive recording liquid adheres to the recording material, and the applied voltage Quantity prediction And Joule heat control means for controlling Joule heat generated by the current flowing in the conductive recording liquid in the state by the energization, and the Joule heat control means is predicted by the curl amount prediction means. When the curl amount exceeds the allowable curl amount, the image forming apparatus performs the Joule heat control in a first range in which the curl amount predicted by the curl amount predicting unit is equal to or less than the allowable curl amount. It is in.

  The present invention provides a head having a nozzle that discharges a conductive recording liquid in accordance with a drive signal, and an intermediate transfer member having at least a part of the surface to which the conductive recording liquid discharged by the head is applied. Voltage application between the intermediate transfer member and the head for energizing the conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer member Voltage applying means for performing the transfer, transfer means for transferring the image carried on the intermediate transfer member to the recording material by the conductive recording liquid, characteristics of the recording material, use environment of the image forming apparatus, conductive recording A curl amount prediction means for predicting a curl amount of the recording material when the image is transferred by the transfer means, based on at least one of a pattern in which the liquid adheres to the recording material and the applied voltage; Before Joule heat control means for controlling Joule heat generated by the current flowing in the conductive recording liquid in the state, and the Joule heat control means is allowed to allow the curl amount predicted by the curl amount prediction means. When the curl amount exceeds the curl amount, the curl amount predicted by the curl amount prediction unit is in the image forming apparatus that controls the Joule heat in the first range that is equal to or less than the allowable curl amount. It is possible to provide an image forming apparatus capable of controlling the curling of the recording material while ensuring the discharge performance of the conductive recording liquid.

1 is a schematic front view according to an embodiment of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic diagram illustrating a state in which conductive recording liquid is applied from a head to an intermediate transfer member in the image forming apparatus illustrated in FIG. 1. It is a control block diagram regarding the information input into the control means, the head, the voltage application means, and the control means shown in FIG. FIG. 2 is a conceptual diagram illustrating a state where pigments in a conductive recording liquid discharged from a head in the image forming apparatus illustrated in FIG. 1 are aggregated via protons. FIG. 2 is a conceptual diagram showing a state of a liquid column by a conductive recording liquid formed between a cathode and an anode in the image forming apparatus shown in FIG. FIG. 4 is a conceptual diagram for explaining the position of a meniscus while a state where a recording liquid temporarily bridges between a head and an intermediate transfer member is formed. An example of the correlation between the energization amount, which is an integrated value of the current flowing through the recording liquid in a state where the head and the intermediate transfer member are temporarily bridged, and the viscosity of the recording liquid energized by this energization amount is schematically FIG. The energization amount, which is an integrated value of the current flowing in the recording liquid in a state where the head and the intermediate transfer member are temporarily bridged, and the curl amount of the recording material to which the recording liquid energized by this energization amount adheres. It is the correlation figure which showed roughly the 1st range which should control the amount of electricity applied in order to optimize this curl amount, and the Joule heat which arises by this electricity supply with an example of correlation between. Along with an example of the correlation between the energization amount, which is the integrated value of the current flowing through the recording liquid in a state where the head and the intermediate transfer member are temporarily bridged, and the viscosity of the recording liquid energized by this energization amount, It is the correlation figure which showed roughly the 2nd range which should control the amount of electricity applied in order to optimize this viscosity, and the Joule heat which arises by this electricity supply. In order to make the proper curl amount and viscosity shown in FIGS. 8 and 9 compatible, the energization amount which is an integrated value of the current flowing through the recording liquid in a state where the head and the intermediate transfer member are temporarily bridged, It is the correlation figure which showed roughly the range which should control the Joule heat which arises by electricity supply by the electricity supply amount. It is a conceptual diagram which shows an example of the drive signal of a head. FIG. 3 is a schematic view corresponding to FIG. 2 of another configuration example of the image forming apparatus to which the present invention is applied. FIG. 13 is a control block diagram corresponding to FIG. 3 of the image forming apparatus shown in FIG. 12. FIG. 4 is a conceptual diagram showing that there is a correlation between an interval between a head and an intermediate transfer member and a maximum current value flowing through a conductive recording liquid discharged from the head. FIG. 4 is a conceptual diagram showing that there is a correlation between an interval between a head and an intermediate transfer member and an amount of energized charge flowing in a conductive recording liquid discharged from the head. FIG. 4 is a conceptual diagram showing that there is a correlation between an interval between a head and an intermediate transfer member and an energization start time of a current flowing in a conductive recording liquid discharged from the head. FIG. 4 is a conceptual diagram showing that there is a correlation between an interval between a head and an intermediate transfer member and an energization duration time of a current flowing through a conductive recording liquid discharged from the head. FIG. 4 is a schematic view corresponding to FIG. 2 of another configuration example of an image forming apparatus to which the present invention is applied. FIG. 19 is a control block diagram corresponding to FIG. 3 of the image forming apparatus shown in FIG. 18. FIG. 3 is a conceptual diagram showing a state in which pigments in a conductive recording liquid discharged from a head in an image forming apparatus having a metal intermediate transfer member surface aggregated via protons and metal cations. FIG. 2 is a schematic front view illustrating a configuration example of an image forming apparatus having a transfer image carrier having an elastic surface in an image forming apparatus having a metal intermediate transfer body surface.

  FIG. 1 shows an outline of an example of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a printer as an inkjet printer, and can perform full-color image formation. The image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside.

  The image forming apparatus 100 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, cardboard, cardboard, and envelopes. It is. The image forming apparatus 100 is a double-sided image forming apparatus capable of forming an image on both sides of a transfer sheet S that is a recording medium as a recording medium that is a recording medium, but the image is formed on one side of the transfer sheet S that is a recording member. A formable single-sided image forming apparatus may be used.

  The image forming apparatus 100 ejects a recording liquid, which is a conductive recording liquid as ink of that color, capable of forming an image as an image corresponding to each color separated into yellow, magenta, cyan, and black. The heads 61Y, 61M, 61C, and 61BK are provided. Each of the heads 61Y, 61M, 61C, and 61BK functions as a recording head that is an ink head as a recording liquid discharger.

  The heads 61Y, 61M, 61C, and 61BK are disposed at positions facing the outer peripheral surface of the intermediate transfer body 37 that is an intermediate transfer drum disposed at a substantially central portion of the main body 99 of the image forming apparatus 100. The heads 61Y, 61M, 61C, 61BK are arranged in this order from the upstream side in the A1 direction, which is the moving direction of the intermediate transfer body 37 and is the clockwise direction in FIG. In the drawing, Y, M, C, and BK added after the numerals of the reference numerals indicate members for yellow, magenta, cyan, and black.

  The heads 61Y, 61M, 61C, and 61BK are respectively ink ejection devices 60Y, 60M, which are recording liquid ejection devices for forming yellow (Y), magenta (M), cyan (C), and black (BK) images. It is provided in 60C and 60BK. Each of the heads 61Y, 61M, 61C, and 61BK is provided in the ink ejection devices 60Y, 60M, 60C, and 60BK in such a manner that a plurality of the heads 61Y, 61M, 61C, and 61BK are arranged in parallel in the direction perpendicular to the paper surface of FIG.

  The intermediate transfer body 37 is rotated in the A1 direction and is recorded in yellow, magenta, cyan, and black from the heads 61Y, 61M, 61C, and 61BK in an area facing the heads 61Y, 61M, 61C, and 61BK. The liquid is discharged and applied in a manner in which the liquids are sequentially superimposed. In this way, an image is formed on the surface of the intermediate transfer member 37. As described above, the image forming apparatus 100 has a tandem structure in which the heads 61Y, 61M, 61C, and 61BK are opposed to the intermediate transfer member 37 and are arranged in parallel in the A1 direction.

  The recording liquid is discharged or applied to the intermediate transfer body 37 by the heads 61Y, 61M, 61C, 61BK in the A1 direction so that the image areas of yellow, magenta, cyan, and black are overlapped at the same position on the intermediate transfer body 37. The timing is shifted from the upstream side toward the downstream side.

The image forming apparatus 100 includes ink ejection devices 60Y, 60M, 60C, and 60BK provided with heads 61Y, 61M, 61C, and 61BK, respectively.
The image forming apparatus 100 also includes a transport unit 10 as a paper transport unit that includes the intermediate transfer body 37 and transports the transfer paper S as the intermediate transfer body 37 rotates in the A1 direction.
The image forming apparatus 100 also includes a paper feeding unit 20 that can stack a large number of transfer papers S and feeds only the uppermost transfer paper S among the stacked transfer papers S to the transport unit 10. .
The image forming apparatus 100 also includes a paper discharge tray 25 on which a large number of image-formed, in other words printed, transfer sheets S conveyed by the conveyance unit 10 can be stacked.

  The image forming apparatus 100 also energizes the recording liquid discharged from the heads 61Y, 61M, 61C, 61BK and temporarily bridged between the intermediate transfer member 37 as shown in FIG. The power supply means 33 is provided as voltage application means for applying a voltage for the purpose.

As shown in FIG. 1, the image forming apparatus 100 also removes the recording liquid remaining on the intermediate transfer body 37 from the intermediate transfer body 37 after the recording liquid is transferred to the transfer paper S. A cleaning unit 34 is provided as a cleaning unit for cleaning.
The image forming apparatus 100 is also controlled as a control unit including a carriage 50 as a head support that integrally supports the heads 61Y, 61M, 61C, and 61BK, a CPU that controls the overall operation of the image forming apparatus 100, a memory, and the like. Part 40.
The image forming apparatus 100 is also a liquid crystal panel that functions as an input device as an input unit capable of various inputs to the image forming apparatus 100 and functions as a display device capable of displaying the state of the image forming apparatus 100. A certain operation unit 41 is provided.
The image forming apparatus 100 also includes an environment sensor 42 as an environment detection unit that detects temperature, humidity, and atmospheric pressure as a use environment of the image forming apparatus 100.

  Although not shown, the image forming apparatus 100 detects a phase of the intermediate transfer body 37 with respect to the reference point by detecting a predetermined reference point of the intermediate transfer body 37 in the A1 direction. It has an encoder as phase detection means.

In addition to the intermediate transfer member 37, the transport unit 10 is disposed so as to face the intermediate transfer member 37, and when the transfer sheet S passes through the transfer unit 31 that is an area between the transfer unit S and the intermediate transfer member 37. The image forming apparatus has transfer means 64 for transferring an image of the recording liquid carried thereon onto the transfer paper S.
The transport unit 10 also has a guide plate 39 that guides the transfer paper S fed from the paper supply unit 20 to the transfer unit 31 and guides the transfer paper S that has passed through the transfer unit 31 to the paper discharge table 25. doing.
The transport unit 10 also has a reverse sheet feeding unit (not shown) that supplies the transfer unit 31 again after switching back the transfer sheet S that has passed through the transfer unit 31 in order to enable double-sided image formation. Yes.
The transport unit 10 also has a motor or the like as driving means (not shown) that rotationally drives the intermediate transfer member 37 in the A1 direction.
As described above, the image forming apparatus 100 is an indirect image forming apparatus that indirectly forms an image on the transfer sheet S using the intermediate transfer body 37.

  The transfer unit 64 includes a transfer roller 38 that rotates following the intermediate transfer member 37. The transfer roller 38 may include a heater for fixing the image transferred onto the transfer paper S to the transfer paper S. Further, the transport unit 10 may include a fixing roller as a fixing unit for fixing the image transferred from the intermediate transfer body 37 to the transfer sheet S by the transfer roller 38 on the transfer sheet S.

  As shown in FIG. 2, the intermediate transfer member 37 includes a support 37a made of aluminum, which is a conductive substrate, and a surface layer 37b made of silicone rubber formed on the support 37a. The material of the support 37a is not limited to aluminum, and may be formed of a metal such as an aluminum alloy, copper, or stainless steel as long as it has mechanical strength. The material of the surface layer 37b is not limited to silicone rubber, and may be an elastic material having low surface energy and high followability to the transfer paper S for the advantage of high releasability of the recording liquid. Therefore, the surface layer 37b may be formed of, for example, urethane rubber, fluorine rubber, nitrile butadiene rubber, or the like.

The surface layer 37b is a conductive rubber in which metal fine particles such as carbon, platinum, and gold as a conductive agent are dispersed and mixed in the rubber material in order to impart conductivity to the intermediate transfer member 37. It has become. However, when the number of conductive fine particles is increased, the conductivity is improved, but since there is a trade-off relationship in which the releasability is lowered, adjustment is necessary as appropriate. As will be described later, in order to form a desired potential difference in the liquid column of the recording liquid temporarily bridged by the heads 61Y, 61M, 61C, 61BK and the intermediate transfer body 37, the volume resistivity of the conductive rubber is 10 ^3. It is preferably less than Ω · cm. In order to form such a potential difference, it is desirable that the volume resistivity is smaller than the recording liquid.

  The thickness of the surface layer 37b is preferably about 0.1 to 1 mm, and preferably 0.2 to 0.6 mm. However, the surface layer 37 b is not an essential component, and only the support 37 a may be used as the intermediate transfer member 37. Further, the intermediate transfer body 37 is not in a drum shape, but may be in an endless belt shape or in a sheet shape if possible.

As shown in FIG. 1, the paper feeding unit 20 transports only the uppermost transfer paper S among the paper feed tray 21 on which a large number of transfer papers S can be stacked and the transfer paper S stacked on the paper feed tray 21. And a paper feed roller 22 that feeds the unit 10.
The paper feed unit 20 also has a housing 23 that supports a paper feed tray 21 and a paper feed roller 22.
The paper feeding unit 20 also includes a motor as a driving means (not shown) that rotates the paper feeding roller 22 so as to match the recording liquid ejection timing in the heads 61Y, 61M, 61C, 61BK and feeds the transfer paper S. have.

  The carriage 50 can be replaced with a new one when the heads 61Y, 61M, 61C, 61BK are deteriorated, and in order to facilitate maintenance, the heads 61Y, 61M, 61C, 61BK can be replaced. And can be attached to and detached from the main body 99. Each of the heads 61Y, 61M, 61C, and 61BK can be independently attached to and detached from the main body 99 so that the heads 61Y, 61M, 61C, and 61BK can be replaced with new ones when deterioration or the like occurs. . This facilitates replacement work and maintenance work.

  The ink discharge devices 60Y, 60M, 60C, and 60BK have substantially the same configuration with respect to the other points although the colors of the recording liquid to be used are different. Each of the ink ejection devices 60Y, 60M, 60C, and 60BK is provided with a plurality of heads 61Y, 61M, 61C, and 61BK in parallel in the main scanning direction. The ink ejection devices 60Y, 60M, 60C, 60BK and the image forming apparatus 100 are a head-fixed full line type.

As shown in FIG. 1 or FIG. 2, the ink ejection devices 60Y, 60M, 60C, and 60BK have heads 61Y, 61M, 61C, and 61BK.
The ink ejection devices 60Y, 60M, 60C, and 60BK also have recording liquid supply means 62Y, 62M, 62C, and 62BK that supply the recording liquid of the color to the heads 61Y, 61M, 61C, and 61BK, respectively.
The recording liquid supply means 62Y, 62M, 62C, and 62BK are tanks 81Y, 81M, 81C, and 81BK, which are ink tanks as main tanks that store the recording liquid of the color to be supplied to the heads 61Y, 61M, 61C, and 61BK. have.
The recording liquid supply means 62Y, 62M, 62C, and 62BK are also pumps 82Y that pump and feed the recording liquid stored in the tanks 81Y, 81M, 81C, and 81BK toward the heads 61Y, 61M, 61C, and 61BK. 82M, 82C, 82BK.
The recording liquid supply means 62Y, 62M, 62C, and 62BK are distributor tanks (not shown) that distribute and supply the recording liquid supplied from the tanks 81Y, 81M, 81C, and 81BK to the heads 61Y, 61M, 61C, and 61BK. have.

The recording liquid supply means 62Y, 62M, 62C and 62BK are not shown as ink quantity detection means which are recording liquid quantity detection means for detecting the recording liquid quantity in order to detect the shortage of the recording liquid quantity in the distributor tank. An ink amount detection sensor is provided.
The recording liquid supply means 62Y, 62M, 62C, and 62BK also have pipes 83Y, 83M, 83C, and 83BK that form a recording liquid feed path between the tanks 81Y, 81M, 81C, and 81BK and the distributor tank. doing.

  The tanks 81Y, 81M, 81C, 81BK can be replaced with new ones when the internal recording liquid is consumed and the remaining amount of the recording liquids is low or has disappeared. It becomes removable with respect to. In this respect, the tanks 81Y, 81M, 81C, and 81BK are configured by ink cartridges that are recording liquid cartridges, but are not limited thereto and may be fixed. Electrodes 65Y, 65M, 65C, and 65BK that form a part of the energizing means 33 are provided on portions of the tanks 81Y, 81M, 81C, and 81BK that are in contact with the recording liquid, specifically on the inner wall. Since the electrodes 65Y, 65M, 65C, and 65BK are used as cathodes for water electrolysis as will be described later, the electrodes 65Y, 65M, 65C, and 65BK do not need to be made of a material that is resistant to metal elution, and are made of a highly conductive material such as metal or carbon. What is necessary is just to be comprised.

  The operations of the pumps 82Y, 82M, 82C, and 82BK are controlled by the controller 40. Specifically, the pumps 82Y, 82M, 82C, and 82BK are driven until the shortage is no longer detected on condition that the shortage of the recording liquid in the distributor tank is detected by the ink amount detection sensor. By this driving, the pumps 82Y, 82M, 82C, and 82BK supply the recording liquid in the tanks 81Y, 81M, 81C, and 81BK to the distributor tank. In this regard, the pumps 82Y, 82M, 82C, and 82BK function as supply pumps, and the control unit 40 functions as ink supply control means that is recording liquid supply control means. The control unit 40 controls the driving of the image forming apparatus 100 even when not specifically described.

  The distributor tank distributes and supplies the recording liquid supplied from the tanks 81Y, 81M, 81C, 81BK by the pumps 82Y, 82M, 82C, 82BK to the heads 61Y, 61M, 61C, 61BK. In this respect, the distributor tank functions as a distributor as an ink supply unit which is a recording liquid supply unit.

The pipes 83Y, 83M, 83C, and 83BK also form a recording liquid feed path between the distributor tank and the heads 61Y, 61M, 61C, and 61BK. The pipes 83Y, 83M, 83C, 83BK together with the pumps 82Y, 82M, 82C, 82BK form a recording liquid feed path from the tanks 81Y, 81M, 81C, 81BK to the heads 61Y, 61M, 61C, 61BK. Yes.
The recording liquid supply means 62Y, 62M, 62C, and 62BK may include tanks 81Y, 81M, 81C, and 81BK, respectively, that are integrated with the heads 61Y, 61M, 61C, and 61BK.

  The recording liquid contains at least a colorant corresponding to yellow, magenta, cyan, and black, an anionic dispersant that is a dispersant for the colorant, and a solvent. Due to the colorant and the dispersant, the ink component of the recording liquid has an anionic group. The solvent contains water from the viewpoint of safety and the conductivity from the viewpoint of causing electrolysis to be described later, and the recording liquid is a water-soluble recording liquid that is a conductive ink and a water-soluble ink. The recording liquid is desirably alkaline from the viewpoint of storage stability.

The pigment that is a colorant used in the recording liquid is not particularly limited, but as a pigment for orange or yellow, C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.
Further, as a pigment for red or magenta, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.
Further, as a pigment for green or cyan, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.
Further, as a pigment for black, C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.
The content of the pigment in the recording liquid is usually 0.1 to 40% by mass, preferably 1 to 30% by mass, and more preferably 2 to 20% by mass.

  In order to electrolyze the water in the recording liquid as described later, it is necessary to add an electrolyte component for increasing the ionic conductivity of the recording liquid. As electrolyte components to be added to the recording solution, sodium chloride, potassium chloride, lithium chloride, rubidium chloride, sodium bromide, sodium iodide, sodium sulfate, sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, potassium sulfate, sodium nitrate, sulfite Inorganic alkali metal salts such as sodium nitrate, potassium nitrate, sodium phosphate, sodium carbonate, sodium bicarbonate, sodium acetate, potassium acetate, sodium oxalate, sodium citrate, sodium hydrogen citrate, potassium citrate, potassium hydrogen citrate Organic alkali metal salts such as ammonium chloride, ammonium nitrate, ammonium sulfate, tetramethylammonium chloride, tetramethylammonium nitrate, and organic ammonium salts such as choline chloride .

  Since a polyvalent metal salt having a valence of 2 or more impairs the solubility or dispersibility of a colorant, an ABA type amphiphilic polymer, or the like, a monovalent metal salt is preferable. In particular, it is preferable to add a quaternary ammonium salt as an electrolyte component. This is because the quaternary ammonium ions are dispersed in charge by an alkyl group bonded to the central element, and the interaction with the colorant, the ABA type amphiphilic polymer, etc. is small and stable. In addition, quaternary ammonium ions hardly form a cluster with water and rarely deprive water of hydration necessary for dissolution or dispersion of a colorant, an ABA type amphiphilic polymer, or the like. The electrical conductivity per unit molecular weight (molar ionic conductivity) is high for compounds having a small molecular weight, and among the quaternary ammonium salts, tetramethylammonium salts are particularly preferred. Counter ions include chloride ions, nitrate ions, sulfate ions, etc., but chloride ions may cause an electrode reaction at the anode to generate chlorine. Therefore, inactive nitrate ions and sulfate ions are preferable.

The anionic dispersant preferably includes a polymer type dispersant such as a polymer dispersant or a low molecular type dispersant such as a surfactant.
Examples of polymer type dispersants having an anionic group include polyacrylic acid and salts thereof, polymethacrylic acid and salts thereof, acrylic acid-acrylonitrile copolymers and salts thereof, and acrylic acid-alkyl acrylate copolymers. And its salt, styrene-acrylic acid copolymer and its salt, styrene-methacrylic acid copolymer and its salt, styrene-acrylic acid-alkyl acrylate copolymer and its salt, styrene-methacrylic acid-alkyl acrylate Ester copolymer and salt thereof, styrene-α methylstyrene-acrylic acid copolymer and salt thereof, styrene-α methylstyrene-acrylic acid copolymer-alkyl acrylate copolymer and salt thereof, styrene-maleic acid Copolymers and salts thereof, vinyl naphthalene-male Inacid copolymer and salt thereof, vinyl acetate-ethylene copolymer and salt thereof, vinyl acetate-crotonic acid copolymer and salt thereof, vinyl acetate-acrylic acid copolymer and salt thereof, β naphthalenesulfonic acid formalin condensate , Etc.

  Since these anionic polymers react with hydrogen ions generated by electrolysis of water and aggregate, they are preferable in terms of aggregation than the self-dispersing pigment alone. Further, since these anionic polymers have a colorant adhesion function, there is an advantage of improving the transfer rate from the intermediate transfer body 37 to the transfer paper S in the transfer process.

  Specific examples of the low molecular weight type dispersant having an anionic group include oleic acid and its salt, lauric acid and its salt, behenic acid and its salt, stearic acid and its salt, and such fatty acid and its salt. Salts, dodecylsulfonic acid and salts thereof, decylsulfonic acid and salts thereof, and alkylsulfuric acid and salts thereof, alkyl sulfate ertels such as lauryl sulfate and oleyl sulfate, dodecylbenzenesulfonic acid and salts thereof, lauryl Benzenesulfonic acid and its salts, and such alkylbenzenesulfonic acid and its salts, dioctylsulfosuccinic acid and its salts, dihexylsulfosuccinic acid and its salts, and such dialkylsulfosuccinic acid and its salts, naphthylsulfonic acid and Its salts, naphthylcarboxylic acid and Salts thereof, such aromatic anionic surfactants, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl ether sulfonates, fluorinated alkyl carboxylic acids and salts thereof, Examples thereof include dispersants using fluorine-based anionic surfactants such as fluorinated alkyl sulfonic acids and salts thereof.

  The recording liquid uses water as a main liquid medium. In order to make the recording liquid have desired physical properties or to prevent clogging of the nozzle 61c due to the drying of the recording liquid, a water-soluble organic solvent described below is used as a humectant component. It is preferable to use as.

  Specific examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-butanediol. 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol, 1, Polyhydric alcohols such as 2,3-butanetriol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethyl Polyhydric alcohol alkyl ethers such as ethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, N-methyl-2 -Pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, nitrogen-containing heterocyclic compounds such as ε-caprolactam, formamide, N-methylformamide, N, N-dimethylformamide, etc. Amides, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine and other amines, dimethyl sulfoxide, sulfolane , Sulfur-containing compounds such as thiodiethanol, propylene carbonate, ethylene carbonate, γ-butyrolactone, and the like, and two or more of them may be used in combination.

  In addition, as other moisturizing components, sugar alcohols such as sorbitol, polysaccharides such as hyaluronic acid, polymers such as polyethylene glycol, and natural moisturizing components such as urea, lactic acid, citrate, and amino acids can be used. is there. These solvents are used alone or in combination with water. Although there is no restriction | limiting in particular in content of these water-soluble organic solvents, Preferably it is 1-60 weight% of the whole ink, More preferably, it uses in the range of 10-40 weight%.

  The recording liquid comprises an ABA type amphiphilic polymer composed of a hydrophobic A segment and a hydrophilic B segment, and a carboxylic acid surfactant that dissolves or disperses the ABA type amphiphilic polymer in the aqueous solvent. It is desirable to include.

  Any of the following can be applied as the hydrophobic A segment of the ABA type amphiphilic polymer, that is, the hydrophobic A block. Examples thereof include dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl and the like, which are linear alkyl groups having 12 or more carbon atoms. Examples of the branched alkyl group include 2-decyl dodecyl, 2-dodecyl dodecyl, 2-decyl hexadecyl, and the like. In addition, the aromatic-containing alkyl group includes phenylalkyl, diphenylalkyl, triphenylalkyl, naphthylalkyl, dinaphthylalkyl, trinaphthylalkyl, anthracenylalkyl, and a phenyl group in which the benzene ring is a branched alkyl group. Examples of dialkylphenylalkyl, trialkylphenylalkyl, and cyclic alkyl group-containing compounds include cyclohexylalkyl, dialkylcyclohexylalkyl, trialkylcyclohexylalkyl, cyclopentylalkyl, dialkylcyclopentylalkyl, and trialkylcyclopentylalkyl. As described above, the hydrophobic A block preferably includes at least one of a linear alkyl group, a branched alkyl group, a cyclic alkyl group, and a phenyl group.

  Further, it may be a block polymer made of a hydrophobic monomer. Examples thereof include styrene polymers, alkyl acrylate polymers, alkyl methacrylate polymers, acrylamide alkyl polymers, and methacrylamide alkyl polymers.

  Any hydrophilic B segment of the ABA-type amphiphilic polymer, that is, hydrophilic B block, can be used as long as it has an affinity for an aqueous solvent. In order to increase the viscosity of the ink composition by physical crosslinking by hydrophobic association in an aqueous solvent, the hydrophilic B block needs to have a sufficiently long chain length (larger) than the hydrophobic A block. Examples of such hydrophilic B block include those having 100-mer or more such as ethylene oxide polymer and propylene oxide polymer containing linear polyethylene oxide. The hydrophilic B block may have a 4-Arms structure or a 6-Arms structure containing a multi-branched polyethylene oxide having a branched hydrophilic portion. Arms means hydrophobic A block. Thus, it is desirable that the hydrophilic B block contains at least one of linear polyethylene oxide and multi-branched polyethylene oxide.

As described above, the ABA type amphiphilic polymer is desirably an _An B type amphiphilic polymer having three or more hydrophobic A blocks. This is because hydrophobic association between the hydrophobic A segments is likely to occur, and the viscosity responsiveness to pH change is improved. The “ABA type” in the ABA type amphiphilic polymer means a structure in which a hydrophilic B block and a plurality of hydrophobic A blocks are bonded around a hydrophilic B block.

Other examples of the hydrophilic B block include vinyl alcohol polymers, vinyl ether polymers, vinyl pyrrolidone polymers, acrylamide polymers, methacrylamide polymers, and derivatives thereof. Also, it may be ionic, acrylate polymer, methacrylate polymer, alkyl quaternary ammonium salt polymer, alkyl quaternary ammonium salt polymer, acrylamide alkyl quaternary ammonium salt polymer, Examples thereof include styrene sulfonate polymer. In addition, cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, starch derivatives such as methyl starch, ethyl starch, hydroxyethyl starch, carboxymethyl starch, alginic acid derivatives such as propylene glycol alginate, gelatin, casein, albumin, collagen, etc. And derivatives of plant polymers such as guar gum, locust bean gum, quince seed gum and carrageenan, and derivatives of microbial polymers such as xanthan gum, dextran, hyaluronic acid, pullulan and curdlan.
The chemical bond between the hydrophobic A block and the hydrophilic B block may be any as long as it is stable, and examples thereof include an ether bond, a urethane bond, an amide bond, and an ester bond.

  Any carboxylic acid surfactant that dissolves or disperses the ABA-type amphiphilic polymer in an aqueous solvent may be used as long as it is composed of a hydrophobic alkyl moiety and a carboxylate. As such, sodium caproate, potassium caproate, sodium caprylate, potassium caprylate, sodium caprate, potassium caprate, sodium laurate, potassium laurate, sodium myristate, potassium myristate, sodium palmitate, Fatty acid salts such as potassium palmitate, sodium stearate, potassium stearate and the like can be mentioned. In addition to the monocarboxylic acid as described above, it may be a dicarboxylate or a tricarboxylate.

  As will be described later, the viscosity of the aqueous ink composition constituting the recording liquid changes depending on the pH. However, the change in pH of the recording liquid in this embodiment means that protons are supplied to the ink composition. means. PKa is a measure of the pH at which a carboxylate ion, which is a weak acid salt, is protonated. The pKa of the fatty acid salt is preferably about pKa: 7-9 and higher.

  There is no restriction | limiting in particular as an average weight molecular weight of an ABA type amphiphilic polymer. However, the molecular weight is preferably small in consideration of the ink jet discharge property in a state completely dissolved or dispersed with a carboxylic acid surfactant or the like, and the polymer molecular weight is preferably large in consideration of the strength in the thickened state after landing. Therefore, the thing of the range of 10,000 or more and 100,000 or less is preferable. Moreover, 20,000 or more and 50,000 or less are more preferable. The number of repeats of the polymer portion is preferably from 100 to 1000 mer. The concentration of the polymer in the ink composition is preferably in the range of 0.1% by weight to 10% by weight, and more preferably 0.5% by weight to 5% by weight.

  The viscosity of the recording liquid during ejection is 1 to 20 mPa · s, preferably 2 to 8 mPa · s. The recording liquid has a viscosity increase at least 10 times, preferably 100 times, more preferably 1000 times or more of the time of ejection due to thickening due to pH change after landing, which will be described later, and becomes a gel state. In addition, the preferable range of physical properties of the recording liquid is a surface tension of 10 to 60 mN / m, preferably 20 to 50 mN / m, and an electrical conductivity of 0.01 to 3 S / m, preferably 0.02 to 1 S / m. is there.

As shown in FIG. 2, each of the heads 61Y, 61M, 61C, 61BK has a conductive nozzle plate 61a disposed on the recording liquid discharge side facing downward in the drawing.
Each of the heads 61Y, 61M, 61C, 61BK also has a nozzle 61b formed on the nozzle plate 61a, and an ink chamber 61c as a liquid chamber supplied with the recording liquid from the distributor tank and filled with the recording liquid. .

As shown in FIG. 3, each of the heads 61Y, 61M, 61C, and 61BK also includes a piezoelectric element 61d that is an ink ejection unit serving as a recording liquid ejection unit that ejects the recording liquid in the ink chamber 61c from the nozzle 61b. Yes.
Each head 61Y, 61M, 61C, 61BK also has a head drive circuit 61e as a head drive means for driving the piezoelectric element 61d.

  The nozzle plate 61a, the nozzle 61b, the ink chamber 61c, and the piezoelectric element 61d are one set, and each head 61Y, 61M, 61C, 61BK is provided in large numbers, but only one of them is shown in the figure. It is shown. One head driving circuit 61e is provided for each of the heads 61Y, 61M, 61C, 61BK.

  The nozzle plate 61a is provided in each of the heads 61Y, 61M, 61C, 61BK, and is common to all the nozzles 61b in each of the heads 61Y, 61M, 61C, 61BK.

  Although detailed illustration is omitted, the nozzle plate 61 a includes a conductive substrate and a water repellent film formed on the surface of the substrate facing the intermediate transfer body 37. The water-repellent film may be formed by applying a fluorine-based water repellent or a silicon-based water repellent, or may be formed by plating a fluorine-based polymer or a fluorine-metal compound eutectoid, Any film having water repellency is not particularly limited.

  The nozzle plate 61 a is set so that the gap with the intermediate transfer member 37 is 50 to 200 μm. If the gap is less than 50 μm, it may be difficult to maintain the gap between the intermediate transfer member 37, which is a rotating body, and the nozzle plate 61a. If the gap exceeds 200 μm, the liquid injection described later may be performed. This is because it may be difficult to form a bridge. However, if the gap can be maintained, there is no particular problem even if it is less than 50 μm, and even if it is 200 μm or more, there is no problem if a stable liquid column bridge is formed.

  The piezoelectric element 61d is an actuator for causing the recording liquid to be ejected from each nozzle 61b as droplets and landed on the transfer paper S. The piezoelectric element 61d discharges the recording liquid from the nozzle 61b in accordance with a drive signal that is a voltage pulse applied to the piezoelectric element 61d under the control of the control unit 40.

  The piezoelectric element 61d is provided as a pressure applying unit that discharges the recording liquid by applying pressure to the ink chamber 61c. This pressure applying means may be a movable actuator of another type which is a shape deforming element type, such as a piezo type, instead of the piezoelectric element 61d. The ink discharge means may be a heating means that discharges the recording liquid from the nozzle 61b by a heater method such as a thermal method, and discharges the recording liquid by film boiling due to heating.

  The energization means 33 is in a state where a liquid column of recording liquid immediately after being ejected from the heads 61Y, 61M, 61C, 61BK temporarily bridges between the heads 61Y, 61M, 61C, 61BK and the intermediate transfer body 37. The recording liquid in the liquid column state is energized. Therefore, the energizing unit 33 applies a voltage so that a potential difference is formed between the intermediate transfer member 37 and the heads 61Y, 61M, 61C, 61BK. By applying this voltage, energization including the current component resulting from the electrode oxidation reaction or electrode reduction reaction is performed inside the recording liquid in the liquid column state. Thereby, the aggregation of the pigment contained in the recording liquid in such a state or the thickening of the recording liquid is promoted.

As described above, the energization means 33 includes the electrodes 65Y, 65M, 65C, and 65BK provided in the portions in the tanks 81Y, 81M, 81C, and 81BK that are in contact with the recording liquid.
The energizing means 33 also forms a predetermined voltage difference between the electrodes 65Y, 65M, 65C, 65BK and the intermediate transfer member 37, and serves as a liquid column application power source that can change the positive and negative polarity while the output voltage is variable. A power supply 33a is provided as power supply means.

The energizing means 33 also includes a power switch 33b for turning on / off the power source 33a, and an electric circuit (not shown) in which the power source 33a is connected to the support 37a and the electrodes 65Y, 65M, 65C, 65BK.
The energization means 33 also includes a voltage application control means and a potential application control means which are realized as part of the function of the control unit 40 and control the switching of voltage, potential application timing, application time, and polarity by the power source 33a. . The control unit 40 as voltage application control means and potential application control means also functions as voltage change means and potential change means for changing the voltage and potential of the power source 33a.

  The power source 33a is normally connected to the support 37a by the electric circuit and the control unit 40, and the cathode is connected to the electrodes 65Y, 65M, 65C, and 65BK. Therefore, the energization means 33 normally includes the intermediate transfer member 37 as an anode and the electrodes 65Y, 65M, 65C, and 65BK as a cathode. In this way, the power source 33a can form a potential difference between the heads 61Y, 61M, 61C, 61BK, specifically, the electrodes 65Y, 65M, 65C, 65BK and the intermediate transfer member 37.

  As shown in FIG. 3, the heads 61Y, 61M, 61C, 61BK and the energizing means 33 provided in each of the heads 61Y, 61M, 61C, 61BK constitute recording head devices 35Y, 35M, 35C, 35BK. ing.

  As shown in FIG. 1, the cleaning means 34 is constituted by a cleaning blade as a cleaning member formed of rubber as an elastic body, which is in contact with the intermediate transfer body 37 in a so-called counter contact manner. . The cleaning unit 34 may include a cleaning roller as a cleaning member together with the cleaning blade.

The operation unit 41 is input with information on the type of transfer paper S to which the image carried on the intermediate transfer body 37 is transferred in the transfer unit 31, for example, whether the transfer paper S is plain paper or thick paper. It can function as a recording material type input means. As shown in FIG. 3, the type of the transfer sheet S input by the operation unit 41 functioning as a recording material type input unit is input to the control unit 40 as sheet type data 41a.
The operation unit 41 can function as an allowable curl value input unit for inputting an allowable curl value (described later) of the transfer paper S. As shown in FIG. 3, the value regarding the allowable curl value input by the operation unit 41 functioning as the allowable curl value input unit is input to the control unit 40 as the allowable curl value 41b.

The temperature, humidity, and pressure detected by the environment sensor 42 are input to the control unit 40 as a use environment 42a that is data related to the use environment.
When the encoder detects the reference point of the intermediate transfer member 37, the encoder inputs a signal to that effect to the control unit 40.

As shown in FIG. 3, the control unit 40 functions as a print signal receiving unit that receives an external print signal 43, and also receives a paper type data 41a, a curl allowable value 41b, a use environment 42a, and the like. 40a.
The control unit 40 also has a liquid column application voltage control means 40b as a voltage application control means for controlling the power supply 33a via the power switch 33b in order to control the voltage applied by the energization means 33.
The control unit 40 also includes a recording liquid discharge control unit 40c as an ink discharge control unit that is a discharge control unit that generates a predetermined drive signal for driving the heads 61Y, 61M, 61C, and 61BK and inputs the drive signal to the head drive circuit 61e. doing.

The control unit 40 also generates drive signals to be input to the power switch 33b in the liquid column application voltage control means 40b, and drive control to generate drive signals to be input to the head drive circuit 61e in the recording liquid discharge control means 40c. It has a table 40d.
The control unit 40 also measures the dimension between the nozzle plate 61a and the intermediate transfer body 37, in other words, the dimension measurement value as an interval storage means that stores the dimension measurement value of the intermediate transfer member including the gap between the nozzle 61b and the intermediate transfer body 37. The storage unit 40e is included.
The control unit 40 also occurs on the transfer sheet S when the image of the recording liquid on the intermediate transfer body 37 is transferred by the transfer unit 64 based on the data input from the signal receiving unit 40a and the drive control table 40d. Curling amount prediction means 40f for predicting the amount of curling is provided.

  The signal receiving unit 40 a is realized as a function of the I / O interface of the control unit 40. The liquid column application voltage control means 40b, the recording liquid discharge control means 40c, and the curl amount prediction means 40f are realized as a function of the CPU of the control unit 40. The drive control table 40d and the dimension measurement value storage means 40e are realized as one function of the memory of the control unit 40.

  The signal receiving unit 40 a receives image information to be formed in the image forming apparatus 100 as a print signal 43 from an external apparatus such as a PC externally connected to the image forming apparatus 100. In this regard, the signal receiving unit 40a functions as a print signal receiving unit. The signal receiving unit 40a also functions as a paper type data receiving unit in receiving the paper type data 41a and functions as a curl allowable value data receiving unit in receiving the curl allowable value 41b, and receives the use environment 42a. In this respect, it functions as a usage environment data receiver.

  The liquid column application voltage control means 40b controls the voltage application timing and application time by the power source 33a. The liquid column application voltage control unit 40b also functions as a voltage changing unit that changes the voltage of the power source 33a.

  The recording liquid ejection control means 40c generates a voltage pulse, which is a head driving waveform as a head driving signal for driving the piezoelectric element 61d, with a predetermined signal waveform by the head driving circuit 61e, and drives each piezoelectric element 61d. Input as pulse and apply. For this purpose, the recording liquid ejection control unit 40c generates a predetermined drive signal to be input to the head drive circuit 61e based on an input image or the like constituting the print signal 43 as described later.

  Therefore, each head 61Y, 61M, 61C, 61BK, specifically each nozzle 61b provided in each head 61Y, 61M, 61C, 61BK, records according to the drive signal generated by the recording liquid discharge control means 40b. The liquid is discharged.

  The liquid column application voltage control unit 40b and the recording liquid discharge control unit 40c are not realized as one function of the control unit 40, but may be provided in each of the recording head devices 35Y, 35M, 35C, and 35BK, for example. .

  The intermediate transfer member dimension measurement values stored in the dimension measurement value storage unit 40e are the individual nozzles 61b and the intermediate transfer member 37, which are measured in advance as the characteristic values of the image forming apparatus 100 before shipment of the image forming apparatus 100. And gap accuracy data for this gap.

The drive control table 40d is referred to by the recording liquid discharge control means 40b when generating a drive signal to be input to the power switch 33b in the liquid column application voltage control means 40b in order to set or change the voltage of the power supply 33a. The In this respect, the drive control table 40d functions as a liquid column application voltage control table.
The drive control table 40d also controls the recording liquid discharge control when generating a drive signal to be input to the head drive circuit 61e in the recording liquid discharge control means 40c in order to discharge the recording liquid from the heads 61Y, 61M, 61C, 61BK. Referenced by means 40c. In this respect, the drive control table 40d functions as a head drive voltage control table.
The drive control table 40d receives the print signal 43 received by the signal receiving unit 40a and the intermediate transfer member dimension measurement value stored in the dimension measurement value storage means 40e. The drive control table 40d functioning as the liquid column application voltage control table is referred to by the recording liquid discharge control means 40b for liquid column application voltage data that is data corresponding to the measured value of the intermediate transfer member. The drive control table 40d that functions as a head drive voltage control table records head drive data that is data according to the data relating to the input image constituting the input print signal 43 and the measured value of the intermediate transfer member dimension. Referenced by the liquid discharge control means 40c.

  The curl amount predicting unit 40f acquires the liquid column application voltage data and the head driving data with reference to the drive control table 40d, and receives the paper type data 41a and the use environment 42a from the signal receiving unit 40a. The amount of curl is predicted based on the data. The definition of the curl amount, that is, the curl amount, and the reason why the curl amount is predicted based on these data will be described later.

The head drive data acquired by the curl amount prediction unit 40f with reference to the drive control table 40d substantially includes a pattern in which the recording liquid adheres to the transfer paper S. Therefore, the data acquired by the curl amount prediction unit 40f with reference to the drive control table 40d includes data related to this pattern.
The data used by the curl amount prediction means 40f to predict the curl amount may be at least one of liquid column application voltage data, head drive data, paper type data 41a, and usage environment 42a data. The curl amount predicting unit 40f only needs to be configured to acquire only data used for predicting the curl amount.

  The curl amount prediction means 40f does not receive the paper type data 41a and the usage environment 42a from the signal receiving unit 40a, but uses the paper type data 41a input from the signal receiving unit 40a to the drive control table 40d. The environment 42a may be acquired from the drive control table 40d. Further, the curl amount predicting unit 40f does not acquire the data related to the pattern described above with reference to the drive control table 40d, but receives the print signal 43 from the signal receiving unit 40a, so that the data related to the pattern described above is obtained. You may get

  The control unit 40 generates a paper feed signal as a media transport signal that drives a motor that rotationally drives the paper feed roller 22, and inputs the generated paper feed signal to the motor to drive the motor to rotate.

The control unit 40 generates an intermediate transfer drive signal for driving a motor that rotationally drives the intermediate transfer body 37 and inputs the generated intermediate transfer drive signal to the motor to rotationally drive the motor. Since the control unit 40 receives a signal indicating that the reference point has been detected from the encoder, the control unit 40 manages and grasps the phase of the intermediate transfer body 37, that is, the rotational posture, by associating this signal with the intermediate transfer drive signal. .
The remainder of the control unit 40 will be described later.

  In the image forming apparatus 100 having such a configuration, the intermediate transfer member 37 rotates in the A1 direction while facing the heads 61Y, 61M, 61C, and 61BK in response to the input of a predetermined signal indicating the start of image formation. During this rotation process, yellow, magenta, cyan, and black recording liquids are ejected from the heads 61Y, 61M, 61C, and 61BK in such a manner that the recording liquids are sequentially overlapped from the upstream side toward the downstream side in the A1 direction. Is done. As a result, the image areas of yellow, magenta, cyan, and black are overlapped at the same position on the intermediate transfer body 37, and the image is temporarily carried on the intermediate transfer body 37.

At this time, the energization unit 33 is driven by the control unit 40 as the voltage application control unit, and a voltage is applied between the support 37a and the electrodes 65Y, 65M, 65C, and 65BK from the power source 33a.
In this state, the recording liquid is applied from the heads 61Y, 61M, 61C, 61BK onto the intermediate transfer member 37 as described above. At this time, first, as shown in FIG. 2 (a), the recording liquid forming the meniscus in the nozzle 61b from the heads 61Y, 61M, 61C, 61BK, as shown in FIG. 2 (b). It moves toward the intermediate transfer member 37. By this movement, a bridge of a liquid column made of a recording liquid is temporarily formed between the nozzle 61b and the intermediate transfer member 37. Next, as shown in FIG. 2 (c), the bridge of the liquid column made of the recording liquid is divided to be carried on the intermediate transfer body 37, and an image of the recording liquid is formed on the intermediate transfer body 37.

In the state where the liquid injection bridge made of the recording liquid is formed as shown in FIG. 2B, the colorant component in the recording liquid is subjected to an aggregating action by the energizing means 33. Specifically, the voltage application of the energizing means 33 causes the following electrode reactions to occur in the nozzle plate 61a serving as the cathode and the intermediate transfer member 37 serving as the anode, respectively, and the water contained in the bridge of the liquid column of the recording liquid. Electrolyzed.
^{_{Cathode: 4H 2 O + 4e - →}} 2H 2 + 4OH - ··· reaction formula (1)
_{^{Anode: 2H 2 O → 4H + +}} O 2 + 4e - ··· reaction formula (2)

  As a result, on the surface of the intermediate transfer member 37 functioning as the anode, water contained in the bridge of the liquid column of the recording liquid is oxidized to generate protons (H +). Therefore, as shown in FIG. 4, the pigment P dispersed by the anionic dispersant D aggregates via protons. This aggregation results in a thickening of the recording liquid. When the recording liquid contains an ABA type amphiphilic polymer and a carboxylic acid surfactant, the hydrophobic groups of the ABA type amphiphilic polymer are bonded to each other when the carboxylic acid surfactant is protonated. Then, the viscosity of the recording liquid increases. The thickening of the recording liquid brings about an action of gelling the recording liquid.

  Thereby, the occurrence of bleeding between adjacent dots is suppressed, and a high-definition image is formed. In addition, there is an advantage that clogging of the nozzle 61b is prevented by such voltage application. The time for forming such a bridge can be controlled by the peak voltage and pulse width of the electromagnetic pulse applied to the piezoelectric element 61d.

Here, the bridge of the liquid column formed between the cathode and the anode will be described with reference to FIG. Inside the bridge B of the liquid column, cations and anions move in the vicinity of the cathode C and the anode A, respectively. As a result, the surface of the cathode C and the anode A, the electric double layer E _C and E _A respectively is formed, the charging speed of the electric double layer E _C and E _A is the conductivity of the bridge B of the liquid column, recording It is almost determined by the concentration of ions contained in the liquid. At this time, when the voltage of the electric double layer E _A reaches several V, Faraday current flows water is electrolyzed. As a result, on the surface of the anode A, water is oxidized to generate protons, and aggregation of the pigment dispersed by the anionic dispersant or thickening of the recording liquid occurs. That is, at the moment when such a bridge is formed, ions that cause an aggregation action of the pigment are efficiently generated in the bridge, so that the pigment is aggregated simultaneously with the landing of the recording liquid on the intermediate transfer body 37. As a result, pigment bleeding does not occur between adjacent recording liquid dots, and a very high-definition solute image is formed.

As described above, the energizing means 33 includes the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK for electrolyzing and energizing the recording liquid forming the bridge B of the liquid column, specifically, Voltage application and potential application are performed between the electrodes 65Y, 65M, 65C, and 65BK. Therefore, the energizing means is configured to form a potential difference between the intermediate transfer member 37 and the electrodes 65Y, 65M, 65C, and 65BK.
This voltage application is controlled by the control unit 40 functioning as a voltage application control means and a voltage changing means in order to control the amount of current flowing through the recording liquid by this voltage application.

  The time from the formation of the bridge B of the liquid column to the separation is usually several microseconds to several tens of microseconds, and the conductivity of the recording liquid is usually several tens mS / m to several hundreds mS / second. m. For this reason, in order to form an image of the recording liquid on the intermediate transfer member 37, the voltage applied by the energizing means 33 is 1.23 V, which is the theoretical decomposition voltage of water, or a number that is a general condition for electrolysis of water. V to several tens of volts is insufficient, and it is preferably several tens of volts to several hundreds of volts.

  One transfer sheet S fed from the sheet feeding unit 20 is supplied to the transfer unit 31 in accordance with the timing at which the leading edge of the image carried on the intermediate transfer member 37 reaches the transfer unit 31. The image carried on the intermediate transfer body 37 is transferred to the transfer sheet S passing through the transfer unit 31 while the transfer roller 38 is rotated, and an image is formed on the surface of the transfer sheet S. The transfer sheet S on which the image is formed is guided to the paper discharge tray 25 and stacked on the paper discharge tray 25.

  When the image is transferred onto the transfer paper S in this way, the aggregated and thickened recording liquid is transferred onto the transfer paper S. Accordingly, an image is formed by the recording liquid that has been agglomerated and thickened by the above-described agglomeration and thickening action, thereby preventing or suppressing feathering and bleeding even when the transfer paper S is plain paper. High-speed image formation with high image density and high image quality is possible.

  In order to perform high-speed image formation, since the recording liquid needs to be quick-drying, the recording liquid generally has high absorbability to the transfer paper S. In this case, the recording liquid is deep in the transfer paper S. Penetrating to the surface and causing so-called offset, making it unsuitable for double-sided image formation. However, the aggregating / thickening action reduces the absorbability of the recording liquid onto the transfer paper S, so that the set-off is prevented or suppressed, and is suitable for double-sided image formation. Furthermore, since the absorbability of the recording liquid to the transfer paper S is reduced, deformation of the transfer paper S such as cockling and curling is also suppressed. This also improves the transportability of the transfer paper S carrying an image and facilitates handling of the transfer paper S, such as preventing or suppressing jamming.

  Almost no components due to the recording liquid remain on the intermediate transfer member 37 that has passed through the transfer unit 31 due to the transfer in the transfer unit 31, but the intermediate transfer member 37 is subjected to cleaning by the cleaning unit 34, thereby recording. Liquid offset is highly prevented or suppressed. Therefore, even when image formation is repeatedly performed, background contamination due to offset is prevented or suppressed, and image deterioration and deterioration of the intermediate transfer body 37 are suppressed or prevented, so that good image formation over time can be performed. .

  In the image forming apparatus 100 as described above, in order to perform good image formation in which bleeding is suppressed or prevented by the above-described aggregation / thickening action, the following conditions must be satisfied. That is, it is necessary that the amount of protons per unit volume of the recording liquid generated on the surface of the intermediate transfer member 37 by the reaction formula (2) is sufficiently secured to perform such good image formation. The amount of such protons is increased by promoting the electrolysis represented by the reaction formula (2).

  Here, the amount of protons generated is determined by the integral value of the current I flowing in the recording liquid in a state where the heads 61Y, 61M, 61C, 61BK and the intermediate transfer body 37 are temporarily bridged per unit time. The current I is determined by the following (a) and (b).

(A) In a state in which the recording liquid forms a liquid column that bridges between the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK, specifically, the electrodes 65Y, 65M, 65C, 65BK, the energizing means 33 Where the current I at a certain time is proportional to this voltage.

(B) Electric resistance of recording liquid The current I at a certain time is inversely proportional to the electric resistance of the recording liquid. The value R of the electrical resistance is determined by the electrical conductivity σ of the recording liquid and the shape of the liquid column of the recording liquid, and is represented by the following equation (A). In the formula (A), r (x) represents the radius of the liquid column at the position x when the discharge direction of the recording liquid is taken on the x-axis, as shown in FIG.

When examining the shape of the liquid column of this recording liquid, the recording liquid ejected from the nozzle generally has a thick tip and a cylindrical shape, and gradually becomes thinner from the vicinity of the nozzle as time passes. I am interrupted.
For this reason, when such a voltage is constant, the current flowing through the recording liquid forming the liquid column is greatest at the moment of landing, and decreases as the liquid column becomes narrower as time passes.

  On the other hand, in the above-described process when the recording liquid is ejected from the nozzle 61b, the recording liquid discharged from the nozzle 61b reaches the intermediate transfer body 37 as the gap between the nozzle 61b and the intermediate transfer body 37 becomes narrower. The time until is shortened. For this reason, the energization start time of the current becomes earlier, and the formation time of the bridge of the liquid column made of the recording liquid becomes longer even if the volume of the ejected recording liquid is constant, and the nozzle plate 61a passes through the liquid column. Energizing time of the current flowing between the intermediate transfer member 37 and the intermediate transfer member 37 becomes longer. Further, if the volume of the ejected recording liquid is constant, the electric resistance of the recording liquid decreases because the thickness of the liquid column tends to increase as the gap becomes narrower.

  On the contrary, when the gap is widened, the time until the recording liquid discharged from the nozzle 61 b reaches the intermediate transfer member 37 becomes longer. Therefore, the energization start time of such current is delayed, and if the volume of the recording liquid to be ejected is constant, the time for forming the bridge of the liquid column made of the recording liquid is shortened. The energization time of the current flowing between the intermediate transfer member 37 is shortened. Further, if the volume of the recording liquid to be ejected is constant, the electric resistance of the recording liquid increases because the liquid column tends to become thinner as the gap becomes wider.

Therefore, if the applied voltage and the volume of the recording liquid to be ejected are constant, the current supply mode changes depending on the size of the gap.
Specifically, the energization amount, which is the amount of current per volume of the recording liquid that flows through the recording liquid while the liquid column bridge is formed, increases as the gap decreases and increases as the gap increases. Become smaller. The current amount and the energization amount mean the total value of the current flowing in the recording liquid while the liquid column bridge is formed, in other words, the integrated value which is the integrated amount.

  In addition, as described above, the recording liquid exhibits aggregating action and gelling action due to thickening when a voltage is applied. Since these actions correspond to the energization amounts, if the applied voltage and the volume of the ejected recording liquid are constant, these actions change when the gap size changes.

  That is, assuming that the applied voltage and the volume of the recording liquid to be ejected are constant, the aggregation and gelling action of the recording liquid due to thickening is a range described later with reference to FIG. The gap becomes wider and the smaller the energization amount, the smaller the gap. Therefore, when the applied voltage and the volume of the ejected recording liquid are constant, the image quality is affected by the size of the gap.

  Such a gap varies depending on the accuracy of the intermediate transfer body 37 itself or the parts supporting it. For example, when the intermediate transfer member 37 is eccentric, the gap changes when the intermediate transfer member 37 rotates. Further, there may be a variation in the gap between each nozzle 61b and the intermediate transfer body 37 along the direction perpendicular to the paper surface of FIG.

Here, FIG. 7 shows the relationship between the energization amount and the viscosity of the recording liquid. As can be seen from the figure, in the region where the energization amount is small, the viscosity of the recording liquid increases as the energization amount increases. This corresponds to protonation occurring in the recording liquid. For example, it corresponds to protonation of a carboxyl group of a carboxylic acid surfactant that dissolves or disperses an ABA type amphiphilic polymer in an aqueous solvent or a carboxyl group of a dispersant that disperses a pigment. When the recording liquid gelates or pigments aggregate due to protonation of the carboxyl group, the viscosity of the recording liquid increases. However, when the energization amount reaches X in the figure, the majority of the carboxyl groups become protonated, and in the region where the energization amount is X or more, the viscosity of the recording liquid does not increase any more and remains almost constant. Show. Therefore, in the range where the viscosity of the recording liquid increases with an increase in the energization amount, the change in the energization amount affects the image quality, while in the region where the viscosity of the recording liquid does not increase even if the energization amount increases, the energization amount The change in does not affect the image quality.
Therefore, if the electrolysis represented by the reaction formula (2) is performed so that the energization amount is X or more, the amount of protons sufficient to perform good image formation in which bleeding is suppressed or prevented by aggregation / thickening action. Will be secured.

The energization amount not only affects the image quality, but also affects the curl of the transfer paper S. This is because the Joule heat generated in the liquid column of the recording liquid changes in accordance with the energization amount and the evaporation amount of the water in the recording liquid changes, so that the water in the recording liquid permeates the transfer paper S. This is because the degree of curl generated by the change is caused.
Specifically, as shown in FIG. 8, when the energization amount is large, the Joule heat generated in the liquid column of the recording liquid increases and the amount of evaporation of the water in the recording liquid increases, The degree of curling, that is, the amount of curling generated when moisture penetrates the transfer paper S is reduced. In addition, when the energization amount is small, the Joule heat generated in the liquid column of the recording liquid decreases and the evaporation amount of the water in the recording liquid decreases, so that the water in the recording liquid permeates the transfer paper S. Increases the amount of curling.

The curl amount is the height from the plane up to the most distant portion of the transfer sheet S when the transfer sheet S on which the recording liquid has been transferred by the transfer unit 31 is placed on the plane. Note that the curl amount is not limited to the height as long as the degree of curl is quantitatively grasped.
The allowable curl value 41b input to the signal receiving unit 40a is a curl amount that means the upper limit value of the allowable range of curl. The allowable curl value 41b is arbitrarily set by the user in the operation unit 41 in consideration of a feeling of use such as handling of the transfer sheet S after image formation.
In FIG. 8, the minimum energization amount A indicates a first energization amount that is an energization amount when the curl amount becomes the allowable curl value.

Joule heat generated in the liquid column of the recording liquid is generated at the same time as protons are generated in the anode by energizing the liquid column. Joule heat uses the resistance value R of the length of the portion with the liquid column in the gap direction from the nozzle 61b toward the intermediate transfer body 37, that is, the height direction of the liquid column, and the potential difference V generated at both ends of this portion. V ² / R. Most of the Joule heat is generated in a portion of the liquid column having a high resistance when a current flows between the electrodes 65Y, 65M, 65C, 65BK and the intermediate transfer member 37. Joule heat is also expressed as IR ² by using a current I flowing through the portion. This current I is equal to the current I at a certain time described above.

  The amount of Joule heat generated in the liquid column of the recording liquid in this way corresponds to the amount of heat that raises the temperature of the liquid column by several tens to several hundreds of degrees. Therefore, the boiling or evaporation of water contained in the recording liquid is promoted by the generation of Joule heat, the water amount of the recording liquid carried on the intermediate transfer member 37 is reduced, and the curl amount is reduced due to the reduction of the water amount. Will be. In addition, the amount of deformation such as cockling of the transfer paper S is also reduced. The degree of reduction of the curl amount or the like changes according to the energization amount as described above.

  Therefore, if the energization amount is controlled to control the amount of Joule heat generated, the curl amount is controlled. Since the energization amount is an integrated value of the current I, the energization amount is controlled by controlling at least one of the voltage applied to the liquid column of the recording liquid and the shape of the liquid column of the recording liquid. In this embodiment, both of these are controlled. Therefore, as shown in FIG. 3, the control unit 40 includes Joule heat control means 44 having a liquid column application voltage control means 40b and a recording liquid discharge control means 40c. The Joule heat generated by the current flowing in the liquid column is controlled. The control of the Joule heat is achieved by controlling the current flowing in the liquid column of the recording liquid, the energization amount, and the charge amount.

The Joule heat control means 44 controls the voltage applied to the liquid column of the recording liquid by the liquid column applied voltage control means 40b. The control of the applied voltage is mainly performed to level the fluctuation of the energization amount due to the gap fluctuation caused by the eccentricity of the intermediate transfer member 37.
The Joule heat control means 44 controls the liquid column state by the recording liquid discharge control means 40c for the shape of the liquid column of the recording liquid. Specifically, by controlling the head drive signal, the position of the meniscus while the liquid column state of the recording liquid is formed is controlled as described later.

When the curl amount predicted by the curl amount prediction unit 40f exceeds the allowable curl value, the Joule heat control unit 44 adjusts the Joule heat so that the curl amount predicted by the curl amount prediction unit 40f is equal to or less than the allowable curl value. Take control.
Therefore, the Joule heat control means 44 refers to the curl amount predicted by the curl amount prediction means 40f. When the curl amount predicted by the curl amount prediction unit 40f exceeds the allowable curl value, the liquid column application voltage control unit 40b performs control to change the applied voltage, and the recording liquid discharge control unit 40c changes the liquid column state. Control to change.

The applied voltage is controlled with reference to a drive control table 40d that functions as a liquid column applied voltage control table. The liquid column shape is controlled with reference to a drive control table 40d that functions as a head drive voltage control table. Therefore, the drive control table 40d is also provided in the Joule heat control means 44. In this respect, the drive control table 40d functions as a Joule heat / energization amount control table.
Further, the drive control table 40d includes liquid column application voltage data and recording liquid discharge control means which are referred to by the liquid column application voltage control means 40b in accordance with the intermediate transfer member dimension measurement values input from the dimension measurement value storage means 40e. The head driving data referred to 40c is determined. Therefore, the drive control table 40d is also provided in the Joule heat control means 44.

  In addition, the Joule heat control means 44, in the drive control table 40d, based on the liquid column applied voltage data and the head drive data, the Joule heat generated in the liquid column by energizing the liquid column of the recording liquid and / or The energization amount in the liquid column is calculated. In this respect, the drive control table 40d and the Joule heat control means 44 function as Joule heat / energization amount calculation means. The drive control table 40d as the Joule heat / energization amount calculation means includes a liquid column application voltage data referred to by the recording liquid discharge control means 40b and a head drive voltage control table referred to by the recording liquid discharge control means 40c. Based on this, Joule heat and energization amount are calculated.

Here, the curl amount prediction by the curl amount prediction means 40f will be described.
As described above, the current I flowing through the liquid column of the recording liquid depends on the voltage applied to the liquid column and the liquid column state.

Therefore, the curl amount prediction unit 40f refers to the drive control table 40d that functions as the liquid column application voltage control table, and acquires the liquid column application voltage data. The liquid column applied voltage data is an initial value corresponding to the intermediate transfer member dimension measurement value input from the dimension measurement value storage means 40e.
The curl amount prediction unit 40f also refers to the drive control table 40d that functions as a head drive voltage control table, and acquires head drive data. This head driving data is an initial value corresponding to the intermediate transfer member dimension measurement value input from the dimension measurement value storage means 40e.
As already described, the curl amount predicting unit 40f obtains these data by inputting the paper type data 41a and the use environment 42a from the signal receiving unit 40a.

The curl amount prediction means 40f predicts the curl amount based on the liquid column application voltage data, the head drive data, the paper type data 41a, and the use environment 42a.
The reason why the curl amount is predicted based on the liquid column application voltage data and the head driving data has already been described roughly. For example, the reason is as follows.

That is, in the liquid column applied voltage data, if the voltage applied to the liquid column of the recording liquid is large, the energization amount increases, so the curling amount decreases, and if the voltage applied to the liquid column of the recording liquid is small, the energization amount decreases. As a result, the curl amount increases.
Further, in the head driving data, if the thickness of the liquid column of the recording liquid is increased, the energization amount is increased and the curling amount is reduced. If the thickness of the liquid column of the recording liquid is decreased, the energization amount is decreased. The curl amount increases. The shape and thickness of the liquid column of the recording liquid depend on the position of the meniscus that is controlled as described later.
In the head driving data, for the pattern in which the recording liquid adheres to the transfer paper S, the total amount of the recording liquid constituting this pattern, that is, for example, the larger the image area, the larger the curl amount. The amount becomes smaller. As for the pattern, when the distribution of the recording liquid on the transfer paper S is likely to cause curl or difficult to curl together with the total amount of the recording liquid or instead of the total amount of the recording liquid. May be used.
Further, for the pattern, the total amount is weighted according to each color of yellow, magenta, cyan, and black. This is because in the image forming apparatus 100, the colors of the recording liquid ejected from a plurality of, specifically the four heads 61Y, 61M, 61C, and 61BK are yellow, magenta, cyan, and black, and the compositions are different. This is because the properties relating to the effect on curl are different. Even when the recording liquids of the same color are ejected from a plurality of heads and have different compositions and different properties regarding the effect on curl, such weighting is performed.

The curl amount prediction using the total amount, distribution, and weight of the recording liquid is performed using, for example, the relationship between the total amount and distribution of the recording liquid and the type of the recording liquid and the curl amount, which are measured in advance. The total amount, distribution, and weighting of the recording liquid may be selectively used. For example, the weighting may be omitted when the influence is small.
The curl amount prediction unit 40f may predict the curl amount based on the Joule heat and / or the energization amount calculated by the Joule heat control unit 44.

Regarding the paper type data 41a, the curl amount decreases as the transfer paper S is thick, and the curl amount increases as the transfer paper S is thin. Therefore, in the operation unit 41, it is possible to input such a thickness, specifically, whether the transfer paper S is a thick paper, a plain paper, or a thin paper.
As described above, the paper type data 41a is included in the characteristics of the transfer paper S, which is used as a characteristic that affects curl in this embodiment. If there are other characteristics that affect the curl as the characteristics of the transfer paper S, it may be used together with the paper type data 41a or in place of the paper type data 41a to predict the curl amount.
For example, such other characteristics include the rigidity of the transfer paper S. This is because the curl amount increases when the rigidity of the transfer paper S is large, and the curl amount decreases when the rigidity of the transfer paper S is small. When rigidity is used as a characteristic, the operation unit 41 can perform input related to rigidity.

The curl amount prediction using the paper type data 41a and rigidity is performed using, for example, the relationship between the paper type and rigidity measured in advance and the curl amount. Note that the paper type data 41a and rigidity may be selectively used, and the paper type data 41a may be omitted when the influence on the curl amount is small.
In this embodiment, the paper type data 41a is input by the user through the operation unit 41 functioning as a recording material type input unit, but the type of the transfer paper S onto which the image carried on the intermediate transfer body 37 is transferred. The image forming apparatus 100 may be provided with a recording material type detecting means for detecting. The same applies to the rigidity. A configuration example of the image forming apparatus 100 having the recording material type detection unit will be described later.

Regarding the usage environment 42a, with respect to the temperature, the higher the temperature, the easier the water in the recording liquid evaporates, so the curl amount decreases. The lower the temperature, the less the water in the recording liquid evaporates, and the curl amount increases. Further, regarding the usage environment 42a, with respect to the humidity, the higher the humidity, the more moisture contained in the transfer paper S and the less the recording liquid penetrates into the transfer paper S, so the curl amount becomes smaller. Since the recording liquid is less likely to penetrate the transfer paper S, the curl amount is reduced. As for the use environment 42a, as for the atmospheric pressure, the higher the atmospheric pressure, the harder the water in the recording liquid evaporates, so the curl amount increases. The lower the atmospheric pressure, the easier the water in the recording liquid evaporates, so the curl amount decreases. .
The prediction of the curl amount using temperature, humidity, and atmospheric pressure is performed using, for example, the relationship between the temperature, humidity, atmospheric pressure, and curl amount measured in advance. Note that temperature, humidity, and pressure may be selectively used, and may be omitted as appropriate when the influence on the curl amount is small.

  The curl amount prediction unit 40f inputs the predicted curl amount to the drive control table 40d. If the curl amount predicted by the curl amount prediction unit 40f is less than or equal to the allowable curl value, the drive control table 40d stores the liquid column application voltage data and the initial value of the head drive data in the liquid column application voltage control unit 40b and the recording. The liquid discharge control means 40c is referred to and used. On the other hand, the drive control table 40d operates as follows if the curl amount predicted by the curl amount prediction means 40f exceeds the allowable curl amount. That is, the drive control table 40d includes liquid column application voltage data for which the curl amount predicted by the curl amount prediction unit 40f is less than or equal to the allowable curl amount, and head drive data for the liquid column application voltage control unit 40b. The control means 40c is referred to and used.

Therefore, the drive control table 40d functions as a curl admissibility determination unit that determines whether or not the curl amount predicted by the curl amount prediction unit 40f exceeds the allowable curl value.
The Joule heat control means 44 functions as a curl amount optimizing means for optimizing the curl amount. The curl optimization unit may include a curl amount prediction unit 40f. The curl amount prediction unit 40f may be included in the Joule heat control unit 44.

  Thus, when the curl amount predicted by the curl amount prediction unit 40f exceeds the allowable curl value, the Joule heat control unit 44 makes the curl amount predicted by the curl amount prediction unit 40f equal to or less than the allowable curl value. Control of Joule heat. Therefore, as shown in FIG. 8, when the curl amount predicted by the curl amount prediction unit 40f exceeds the allowable curl value, the Joule heat control unit 44 sets the energization amount and Joule heat to the minimum energization amount A or more. Control in the range of 1. In other words, when the curl amount predicted by the curl amount prediction unit 40f exceeds the allowable curl value, the Joule heat control unit 44 has the first curl amount predicted by the curl amount prediction unit 40f equal to or less than the allowable curl amount. Control Joule heat in the range.

By the way, when controlling the Joule heat, the energization amount and Joule heat are set so as to reduce the water content of the recording liquid on the intermediate transfer body 37 to the extent that the curl amount is less than the allowable curl value. It is desirable to suppress the energy required for such control as much as possible.
In this regard, when the curl amount predicted by the curl amount predicting means 40f is less than the allowable curl value, the initial values of the liquid column application voltage data and the head drive data are used, and the energization amount is below the minimum energization amount A. Therefore, the energization amount and Joule heat are suppressed, and the energy consumption is suppressed.
On the other hand, when the curl amount predicted by the curl amount predicting means 40f exceeds the allowable curl value, the Joule heat is set to a value in a first range in which the energization amount is not less than the minimum energization amount A. Therefore, in this case, in order to suppress the energization amount and the Joule heat and suppress the energy consumption, the energization amount and the Joule heat are controlled to be the minimum within the first range to suppress the Joule heat and the consumption. It is preferable to suppress energy.

On the other hand, as described with reference to FIG. 7, in the relationship between the energization amount and the viscosity of the recording liquid, in the region where the energization amount is X or more in FIG. In this region, the change in the energization amount does not affect the image quality.
Therefore, as shown in FIG. 9, in the relationship with the viscosity of the recording liquid, the energization amount is set to be equal to or greater than the minimum energization amount B, which is the second energization amount corresponding to X in FIG.
And it is preferable to control Joule heat and energy consumption by controlling the energization amount and Joule heat so that the viscosity is minimized within the second range where the viscosity is substantially maximum and constant.

  Then, when the curl amount predicted by the curl amount prediction means 40f exceeds the allowable curl value, in order to keep the curl amount below the allowable curl value and to ensure the viscosity of the recording liquid, It is desirable to control as follows. That is, as shown in FIG. 10, while satisfying that the energization amount and the Joule heat are within the first range, the viscosity of the recording liquid after the energization ends becomes substantially constant and becomes equal to or higher than a predetermined viscosity. It is preferable to control in the range of 2 to suppress Joule heat and energy consumption. Even when this control is performed, in order to suppress Joule heat and to reduce energy consumption, while satisfying that the energization amount and Joule heat are within the first range as follows, To minimize the control. Note that the relationship between the viscosity of the recording liquid and the curl amount is not clear at present.

FIG. 5A shows a case where the minimum energization amount A and the minimum energization amount B match, and the first range and the second range match. Therefore, by making the energization amount coincide with the minimum energization amount A and the minimum energization amount B, the energization amount is minimized, the curl amount is less than the allowable curl value and the viscosity of the recording liquid is secured, while the Joule heat and the energy consumption are reduced. Minimize.
FIG. 5B shows a case where the minimum energization amount A is less than the minimum energization amount B, and the minimum value in the second range exceeds the minimum value in the first range. Therefore, by making the energization amount coincide with the minimum energization amount B, the energization amount is minimized, the curl amount is less than the allowable curl value, and the viscosity of the recording liquid is ensured, while the Joule heat and the energy consumption are minimized. .
FIG. 5C shows a case where the minimum energization amount B is less than the minimum energization amount A, and the minimum value in the first range is greater than the minimum value in the second range. Therefore, by making the energization amount coincide with the minimum energization amount A, the energization amount is minimized, the curl amount is less than the allowable curl value and the viscosity of the recording liquid is secured, and the Joule heat and the consumed energy are minimized. .

  By the way, the image forming apparatus 100 uses a recording liquid having a property of suppressing bleeding by increasing the viscosity when the liquid column of the recording liquid is energized. However, in the image forming apparatus 100, when the energization is performed for the purpose of optimizing the curl amount without aiming to increase the viscosity of the recording liquid, the energization amount and the Joule heat are set within the first range. Control may be performed as follows. That is, when the curl amount predicted by the curl amount predicting means 40f exceeds the curl allowable value, if the energization amount is the minimum energization amount A, the curl amount is optimized and the Joule heat and energy consumption are minimized. To be suppressed.

  In this way, in order to perform control in consideration of not only the curl amount but also the viscosity and bleeding of the recording liquid, the drive control table 40d has an energization amount calculated by the drive control table 40d functioning as an energization amount calculation unit. Based on this, it functions as a viscosity predicting means for predicting the viscosity of the recording liquid. The drive control table 40d functioning as a viscosity predicting means stores energization-viscosity correlation data, which is data relating to the relationship between the energization amount and the viscosity of the recording liquid, measured in advance, and functions as an energization-viscosity correlation table. To do.

  When the curl amount predicted by the curl amount prediction unit 40f is equal to or less than the allowable curl value, the drive control table 40d displays the liquid column application voltage data and the head drive data as follows. Reference 40b is made to the recording liquid discharge control means 40c. That is, in the case of FIGS. 10A and 10C, liquid column application voltage control and liquid column application voltage control satisfying the minimum current supply amount B and in the case of FIG. The means 40b and the recording liquid discharge control means 40c are referred to and used. Thus, when the curl amount predicted by the curl amount prediction unit 40f is equal to or less than the allowable curl value, the drive control table 40d obtains an energization amount that satisfies the larger one of the minimum energization amount A and the minimum energization amount B. As described, the liquid column application voltage data and the head driving data are referred to and used.

  As a result, even when the curl amount predicted by the curl amount predicting means 40f is equal to or less than the allowable curl value, the curl amount is equal to or less than the allowable curl value and the viscosity of the recording liquid and suppression of bleeding are ensured. The amount of electricity, Joule heat, and energy consumption are minimized.

  When the curl amount predicted by the curl amount prediction means 40f is less than or equal to the allowable curl value, the energization amount is determined based on the energization amount obtained from the initial values of the liquid column application voltage data and the head drive data, and the minimum energization amount B. It may be controlled to the larger one. In this case as well, the amount of energization, Joule heat, and energy consumption are minimized as long as the curl amount is less than the allowable curl value and the viscosity and bleeding of the recording liquid are ensured. However, when the curl amount predicted by the curl amount prediction means 40f is less than or equal to the allowable curl value, even if the energization amount, Joule heat, and energy consumption are not the minimum, the curl amount is within the range where these are suppressed. In the case of the following, the following control may be performed. That is, the energization amount may be controlled to be larger of the minimum energization amount A and the minimum energization amount B.

The curl tolerance used for the above control will be described.
As already described, the allowable curl value 41b is arbitrarily set by the user in the operation unit 41 in consideration of the feeling of use, but a predetermined constant value may always be used.

Further, as the curl tolerance, various values may be used for the purpose of preventing a jam or the like depending on the configuration of the image forming apparatus 100 itself or an apparatus associated therewith.
For example, since the image forming apparatus 100 is a double-sided image forming apparatus, an allowable curl value is used depending on whether an image is formed on the first surface of the transfer paper S or an image is formed on the second surface of the transfer paper S. May be. When an image is formed on the first surface of the transfer paper S, it is a surface printing that is fed from the paper supply unit 20 and passes through the transfer unit 31 for the first time, and usually when the recording liquid is transferred for the first time. It is. Further, when the image is formed on the second surface of the transfer sheet S, it is during back side printing that is switched back by the reversing paper feeding means after passing the transfer portion 31 for the first time and then passes the transfer portion 31 for the second time. Usually, this is when the recording liquid is transferred for the second time. Therefore, for example, if the value of the curl tolerance used when forming an image on the first surface is made smaller than the value of the curl tolerance used when forming an image on the second surface, the following advantages can be obtained. In other words, there is an advantage that troubles such as a jam during the transfer of the transfer sheet S when an image is formed on the second surface, such as during the transfer of the transfer sheet S by the reversing paper feeding means, can be prevented or suppressed.

Further, the curl allowable value may be set according to the time required to form one set of images for performing continuous image formation a plurality of times, and the set value may be used in the one set of image formation. One set of image formation in which a plurality of continuous image formations are performed means a case in which image formation is performed on a plurality of transfer sheets S collectively. For example, image formation in which the same image is continuously formed on a plurality of different transfer sheets S, and image formation in which a large number of images are continuously formed on a plurality of different transfer sheets S, and the like. One unit of image formation processed by the finisher when the image forming apparatus 100 includes a finisher or when the finisher is connected is also included in the one set of image formation.
In such a set of image formation, the transfer sheet S on which the image has been formed and loaded on the paper discharge tray 25 is usually the last time the transfer sheet S on which the image has been formed is stacked on the paper discharge tray 25. It remains loaded on the paper discharge tray 25 for a certain period of time. As described above, while the sheet is still stacked on the paper discharge tray 25, the curl amount of the transfer sheet S is reduced due to evaporation of moisture or decurling due to its own weight. Then, as the time required for forming one set of images is longer, the transfer sheet S on which the image is formed first is stacked on the discharge table 25, and then the transfer sheet S on which the image is formed last is placed on the discharge table 25. It takes longer to load. Therefore, the longer the time required to form one set of images, the smaller the curl tolerance value may be used. Normally, as the number of image formations for one set increases, the time required increases. Therefore, a smaller value may be used as the allowable curl value. The smaller the value used as the allowable curl value, the smaller the amount of heat applied to the liquid column of the recording liquid, so that it is not necessary to use extra energy to suppress the curl amount.
If the allowable curl value is used according to the time required for forming one set of images for performing a plurality of consecutive image formations, the process proceeds from the first image formation to the last image formation constituting one set of image formation. Thus, the curl tolerance to be used may be gradually reduced.

  In addition, when the image forming apparatus 100 includes a curl amount standard value such as a finisher, in other words, a curl amount restriction unit with a limit value set, or such a curl amount restriction unit is connected. In such a case, such a limit value may be used. In this case, if various values are used as the allowable curl value as described above, the limit value may be used as the maximum allowable curl value.

The control of the position of the meniscus, and the shape and thickness of the liquid column of the recording liquid depending on the position of the meniscus will be described.
The shape and thickness of the liquid column of the recording liquid is adjusted by positioning the meniscus outside the nozzle 61b while the liquid column state of the recording liquid is formed. In other words, this adjustment is performed individually for each nozzle 61b. The position of the meniscus is located outside the nozzle 61b means that the position of the meniscus is located outside the nozzle plate 61a or the heads 61Y, 61M, 61C, 61BK.

  Here, as shown in FIG. 6, the position of the meniscus is the x of the central portion of the meniscus formed in the nozzle 61b in a hemispherical shape by the recording liquid when considered excluding the liquid column portion of the recording liquid. Refers to the position that will be the tip in the direction. This position is the position of the tip portion in the x direction of the recording liquid that is cylindrical on the downstream side of the meniscus in the x direction. Therefore, the state where the position of the meniscus in the state where the recording liquid is bridged is located outside the nozzle 61b indicates that the recording liquid is protruding from the entire nozzle 61b.

  The position of the meniscus is changed to change the thickness and shape of the entire liquid column of the recording liquid by adding the liquid column portion omitted in the figure to the liquid column of the recording liquid, that is, the recording liquid shown in FIG. As a result, the electrical resistance of the entire liquid column changes. The energization amount and Joule heat change due to the change in electrical resistance, and the viscosity of the recording liquid, the degree of bleeding, and the curl amount change.

  A drive signal for controlling the shape and thickness of the liquid column of the recording liquid by realizing the liquid column shape generated by the recording liquid discharge control means 40b with the position of the meniscus at the time of bridge formation outside the nozzle 61b. As shown in FIG. 11, it is as follows. That is, the drive signal is formed as a first drive signal as a first drive pulse with a first signal waveform and as a second drive pulse with a second signal waveform formed at a predetermined time interval. And a second drive signal.

  In the example shown in FIG. 6A, the first drive signal is generated by the recording liquid ejected from the nozzle 61b, and the heads 61Y, 61M, 61C, 61BK, specifically the nozzle plate 61a and the intermediate transfer member 37. Is generated to form a bridge between the two. The second drive signal is generated in order to additionally discharge the recording liquid from the nozzle 61b in such a state formed by the first drive signal.

  In the example shown in FIG. 6A, the second drive signal supplies the recording liquid to the portion where the liquid column is narrow in the vicinity of the nozzle 61b, to alleviate the decrease in the diameter of the liquid column. And input to the piezoelectric element 61d. That is, the second drive signal relaxes the decrease in the current flowing through the liquid column of the recording liquid by the voltage applied by the energizing means 33, in other words, the electrolysis represented by the reaction formula (2) is maintained. It is generated for the purpose of doing so and input to the piezoelectric element 61d.

  In the example shown in FIG. 2A, the interval between the first drive waveform and the second drive waveform, that is, the time interval from the input of the first drive signal to the input of the second drive signal is It is set so that the electrolysis is efficiently maintained by the additional discharge of the recording liquid. That is, the shape of the liquid column of the recording liquid is set so as to maintain a shape that maintains the efficiency of electrolysis.

  However, if the recording liquid discharged from the nozzle 61b by the second drive signal lands on the intermediate transfer body 37, the volume of the recording liquid carried on the intermediate transfer body 37, that is, the electrolysis, causes aggregation / thickening. This increases the volume of the recording liquid to be acted on. Further, if the recording liquid discharged from the nozzle 61b by the second drive signal lands on the intermediate transfer body 37, the curl amount increases. In this case, eventually, it is necessary to supply as much electric power as the volume of the recording liquid increases, and it becomes difficult to control the energization amount and Joule heat.

  Therefore, the recording liquid discharge control means 40b generates the second drive signal so that the amount of the recording liquid additionally discharged from the nozzle 61b returns to the nozzle 61b in the example shown in FIG. . In other words, the recording liquid discharge control means 40b generates the second drive signal so that the amount of additional recording liquid discharged from the nozzle 61b does not land on the intermediate transfer body 37.

  However, the second drive signal in the example shown in FIG. 5A is required to be generated so that the total amount of the recording liquid additionally discharged from the nozzle 61b returns to the nozzle 61b side strictly. What is necessary is just to be able to control the amount of energization and Joule heat.

  In addition, compared with the case where only the first drive signal is used, when the first drive signal and the second drive signal are used, there is the following tendency. That is, in such a case, as long as the recording liquid additionally discharged by the second drive waveform does not land on the intermediate transfer body 37, the stronger the second drive signal, the more the landed on the intermediate transfer body 37 and the higher the second drive signal. There is a tendency that the amount of the remaining recording liquid slightly decreases. This is considered to be because a part of the recording liquid ejected by the first drive waveform is dragged toward the nozzle 61b when the additionally ejected recording liquid returns to the nozzle 61b.

  The time interval from the input of the first drive signal to the input of the second drive signal is such that the shape of the liquid column of the recording liquid is maintained in a shape that maintains the efficiency of electrolysis. From the viewpoint, it is also set by corresponding to the vibration cycle of the meniscus in the nozzle 61b.

  Explaining this point, the phase of the residual vibration of the meniscus in the recording liquid ejected by the first driving signal and the phase of the second driving signal, that is, the phase of the recording liquid additionally ejected by the second driving signal are described. If they match, it looks like this: That is, the recording liquid is efficiently supplied to the portion near the nozzle 61b where the liquid column is narrowed.

  Accordingly, the recording liquid discharge control means 40b is set so that the interval between the first drive signal and the second drive signal is an integral multiple of the vibration period. And satisfy | filling the conditions regarding this vibration period will satisfy | fill the conditions regarding this viewpoint, ie, the conditions regarding maintenance of a liquid column shape, and thickness.

  As for the conditions related to the vibration cycle, the interval between the first drive signal and the second drive signal is made to coincide with the vibration cycle so as to satisfactorily satisfy the conditions related to the maintenance of the liquid column shape and thickness. It is preferable to set. This is because it is preferable to supply the recording liquid by the second drive signal before the liquid column becomes too thin, in other words, to replenish it in order to maintain the shape and thickness of the liquid column satisfactorily. .

  The condition relating to the vibration cycle does not require that the interval between the first drive signal and the second drive signal is completely coincident with the meniscus vibration cycle itself or an integral multiple thereof, and may be shifted to some extent. . This is because the amount of energization and Joule heat may be sufficiently controlled even when the vibration period itself or an integer multiple thereof deviates by about ± 20%. Therefore, in order to set the interval between the first drive signal and the second drive signal so as to coincide with the vibration period or an integral multiple thereof, a range in which the control of the energization amount and Joule heat is sufficiently ensured. Including deviations in

The drive signal may be generated not only in the manner shown in FIG. 8A but also in the manner shown in FIG. 8B to FIG.
In the example shown in FIGS. 2B and 2C, the second drive signal is generated so as not to reduce the pressure in the nozzle 61b immediately after the first drive signal. Further, in the example shown in FIG. 4D, the function is merely to reduce the pressure in the nozzle 61b immediately after the first drive signal, and recording is performed in a portion where the liquid column is narrowed by utilizing the reaction. The second drive signal is generated so as to supply the liquid.

  Note that in FIGS. 1A to 1D, the intervals between the first drive signal and the second drive signal correspond to each other between the first drive signal and the second drive signal. It is said that the time interval of the location.

  Further, the drive signal that causes the meniscus position at the time of bridge formation to be outside the nozzle 61b is the difference between the first drive signal and the second drive signal shown in FIGS. It is not limited to the combination.

That is, the drive signal may be generated in any waveform as long as the energization amount and Joule heat are controlled by changing the position of the meniscus at the time of bridge formation.
As long as the energization amount and Joule heat are controlled in this way, the drive signal may be generated in any waveform.
Note that the second drive signal may be generated and used in a plurality of times within a range that satisfies the above conditions.

  As described above, if the shape and thickness of the liquid column during bridge formation are controlled by controlling the drive signal, the energization amount and Joule heat are controlled, and the viscosity and curl amount of the recording liquid are controlled appropriately. Thus, a very high-definition image in which bleeding is prevented or suppressed is formed. Such control is also used to equalize the variation in the gap between the nozzles 61b and the intermediate transfer body 37 along the arrangement direction of the nozzles 61b, in other words, leveling the influence on the energization amount and Joule heat due to the fluctuation. .

  As described above, in order to perform high-speed image formation, it is necessary to make the recording liquid dry quickly. Therefore, the recording liquid generally has high absorbability to the transfer paper S. Penetrates deeply into the transfer paper S, causing so-called back-off, making it unsuitable for double-sided image formation. However, since the amount of water contained in the recording liquid carried on the intermediate transfer member 37 is reduced by Joule heat generated by energization of the liquid column of the recording liquid as compared with the case where no energization is performed, such a set-off. Is prevented or suppressed, and is suitable for double-sided image formation. Further, since the moisture content of the recording liquid is reduced, deformation such as cockling and curling of the transfer sheet S is suppressed or prevented, thereby improving the transportability of the transfer sheet S carrying an image, Handling of the transfer paper S is facilitated such that jamming is prevented or suppressed. Since such energization is obtained by controlling the energization amount to be suppressed, these advantages can be obtained while saving energy consumption.

  In order to perform the above-described control, the image forming apparatus 100 uses the dimension measurement value storage unit 40e to measure the intermediate transfer member dimension measurement value as the intermediate transfer member dimension data, which is measured in advance, as a reference determined for the intermediate transfer member 37. The point is stored in association with the phase of the intermediate transfer member 37. The measured value of the intermediate transfer member dimension includes fluctuations in the gaps between the individual nozzles 61 b and the intermediate transfer member 37.

  At the time of image formation, the control unit 40 grasps the phase of the intermediate transfer body 37 based on the input from the encoder, and drives the intermediate transfer member dimension measurement value from the dimension measurement value storage unit 40e in accordance with the phase. Input to the control table 40d.

  The recording liquid discharge control means 40b refers to the portion of the drive control table 40d corresponding to the input intermediate transfer member dimension measurement value and selects the next drive signal. That is, a drive signal that satisfies the conditions described with reference to FIG. 10 is selected from the drive signals constituting the head drive data stored in the head drive voltage control table of the portion. In this way, the recording liquid discharge control means 40b does not depend on the gap between the nozzle 61b and the intermediate transfer body 37, and the drive signal, in particular the second driving, that makes the amount of current flowing in the liquid column and Joule heat appropriate. Determine and generate a signal.

  The recording liquid discharge control means 40b inputs the generated drive signal to the head drive circuit 61e. As a result, the head drive circuit 61e inputs a voltage pulse to the piezoelectric element 61d to drive the heads 61Y, 61M, 61C, 61B, and ejects the recording liquid from the nozzle 61b.

  On the other hand, the liquid column application voltage control means 40c drives the power switch 33b so as to include the timing at which the liquid column of the recording liquid is formed, and a voltage is applied between the nozzle plate 61a and the intermediate transfer member 37 by the power source 33a. Apply. While this voltage application is being performed, a liquid column is formed between the nozzle 61 b and the intermediate transfer member 37.

  The voltage value applied by the power source 33a is controlled by the liquid column application voltage control means 40c, but the voltage value may be constant or may be changed according to the phase of the intermediate transfer member 37. When changing the voltage value of the power supply 33a, the gap fluctuations related to all the nozzles 61b in the same head are separated from those that are not, the former is the control of the power supply 33a, the latter is the control of the voltage of the second drive pulse, etc. It is better to distribute the drive signal control.

  In the above-described embodiment, the magnitude of the second drive signal is controlled according to the known gap between the nozzle 61b and the intermediate transfer member 37 stored in the dimension measurement value storage unit 40e. However, as shown in FIG. 12, the image forming apparatus 100 may include a gap measurement sensor 36 as an interval measurement unit that measures the gap. In this case, as shown in FIG. 13, the drive signal including the second drive signal is controlled according to the gap measurement value 40g, which is the gap measured by the gap measurement sensor 36.

  As shown in FIG. 12, the gap measurement sensor 36 is provided integrally with each of the heads 61Y, 61M, 61C, and 61BK. The gap measurement sensor 36 is an optical sensor that measures the gap by measuring the surface position of the intermediate transfer body 37 with respect to the nozzle 61b. Since the gap measuring sensor 36 is provided integrally with the heads 61Y, 61M, 61C, 61BK, even if the positions of the heads 61Y, 61M, 61C, 61BK change over time or due to vibrations, the gap is accurate. Is measured.

  The gap measurement sensor 36 is located upstream of the position where the nozzle 61b discharges the recording liquid in the rotational direction of the intermediate transfer body 37, which is the relative movement direction of the nozzle 61b and the intermediate transfer body 37, that is, the intermediate transfer body on the left side in FIG. The surface position of 37 is measured. Therefore, the gap measuring sensor 36 is integrally provided in each of the heads 61Y, 61M, 61C, 61BK on the upstream side of the nozzle 61b in the rotational direction.

  This is because a time lag from when the gap measurement sensor 36 measures the gap to determine a drive signal including the second drive signal and to apply a voltage to the piezoelectric element 61d according to the determined drive signal is considered. Is. Therefore, the gap at the position upstream of the recording liquid landing position on the intermediate transfer body 37 in the rotational direction is measured in advance from the recording liquid discharge timing.

  To what extent the gap measurement position is positioned upstream of the liquid deposition position in the rotation direction depends on the time lag, that is, the gap measurement sensor 36, the control unit 40, the recording head devices 35Y, 35M, 35C, 35BK, and the like. Responsiveness, processing speed, etc.

  As shown in FIG. 13, with the provision of the gap measurement sensor 36, the control unit 40 omits the dimension measurement value storage means 40e shown in FIG. 40a is input.

  The signal receiver 40 a receives the gap measurement value 40 g from the gap measurement sensor 36, and this input is performed in association with the phase of the intermediate transfer member 37. Thereafter, the recording liquid discharge control means 40b refers to the driving voltage control table 40d to determine a driving signal including the second driving signal. The operation of applying a voltage to the piezoelectric element 61d in accordance with the determined drive signal and ejecting the recording liquid from the nozzle 61b is the same as that described above.

  As described above, since the gap is measured and controlled in real time, even when the heads 61Y, 61M, 61C, and 61BK change in position over time, the gap is accurately grasped, and the voltage value is determined. Determination and control based on the determination are performed with high accuracy.

  The gap measuring means does not directly detect the gap optically like the gap measuring sensor 36, but substantially measures by measuring the energization state between the nozzle plate 61a and the intermediate transfer body 37. It may be.

  For example, as the gap between the nozzle 61b and the intermediate transfer body 37 becomes narrower, the time until the recording liquid ejected from the nozzle 61b reaches the intermediate transfer body 37 becomes shorter, and the current application start time becomes faster. Is used. Further, as the gap between the nozzle 61b and the intermediate transfer body 37 becomes narrower, the time until the recording liquid discharged from the nozzle 61b reaches the intermediate transfer body 37 is shortened, and a bridge of liquid columns made of the recording liquid is formed. Take advantage of the increased time. Therefore, the gap is substantially measured by measuring the energized state using at least one of these.

  With reference to FIGS. 14 to 17, it will be described that the gap between the nozzle 61 b and the intermediate transfer body 37 is measured by measuring the energization state between the nozzle plate 61 a and the intermediate transfer body 37.

  FIG. 14 shows the relationship between the maximum current value when the recording liquid in a state where the nozzle 61 b and the intermediate transfer body 37 are bridged is energized and the gap distance between the nozzle 61 b and the intermediate transfer body 37. .

  FIG. 15 shows the amount of electric charge that flows between the nozzle 61b and the intermediate transfer body 37 when the recording liquid in a state where the nozzle 61b and the intermediate transfer body 37 are bridged, and the nozzle 61b and the intermediate transfer body 37. The relationship with the gap distance with the body 37 is shown. This energized charge amount is an integrated value of the current amount and is equivalent to the energized amount.

  FIG. 16 shows the relationship between the energization start time and the gap distance. The energization start time here refers to the state in which the recording liquid bridges between the nozzle 61b and the intermediate transfer member 37 from the start of driving of the heads 61Y, 61M, 61C, 61BK, and between the nozzle 61b and the intermediate transfer member 37. It is the time until energization starts. Further, the cap distance here is a distance between the nozzle 61 b and the intermediate transfer member 37.

  FIG. 17 shows the relationship between the energization duration and the gap distance. The energization continuation time here is a state where the nozzle 61b and the intermediate transfer body 37 are bridged and the state where the recording liquid is applied after the energization starts between the nozzle 61b and the intermediate transfer body 37 is canceled. Is the time until is shut off. Further, the gap distance here is a distance between the nozzle 61 b and the intermediate transfer member 37.

  In each of these figures, the points indicated by black circles indicate data obtained as a result of experiments, and straight lines or curves indicate results obtained by fitting such data using polynomials or the like. From these figures, the following is clear. That is, the energization feature amount indicating the energization state between the nozzle plate 61a and the intermediate transfer body 37, that is, the maximum current value in FIG. 14, the energization charge amount in FIG. 15, the energization start time in FIG. 16, and the energization duration time in FIG. And there is a clear correlation between the gap distance.

  That is, the maximum current value, the energized charge amount, and the time change which are energization feature amounts have dependency on the gap distance. For example, as the gap between the nozzle 61b and the intermediate transfer member 37 becomes narrower, the time until the recording liquid ejected from the nozzle 61b reaches the intermediate transfer member 37 becomes shorter, and the current application start time becomes shorter. Along with this, the energization continuation time, which is the formation time of the bridge of the liquid column made of the recording liquid, becomes longer, and the maximum current value of the current flowing between the nozzle plate 61a and the intermediate transfer body 37 via the liquid column, Energized charge amount increases. Therefore, it is possible to calculate the gap distance by measuring and extracting at least one energization feature amount among the maximum current value, energization charge amount, energization start time, and energization duration time.

  For the calculation of the gap distance, it is possible to employ means for calculating the gap distance based on a coefficient fitted with a polynomial or the like from the result of measurement in advance. Further, instead of this means, or together with this means, a means for calculating a gap distance by creating a lookup table from a result obtained by measuring in advance and referring to the table can be adopted.

  Further, as described above, since the ejection state of the recording liquid from the nozzle 61b differs depending on the signal of the head drive circuit 61e, that is, the drive pulse, fitting coefficients and lookup tables are prepared for a plurality of ejection conditions. More preferred. In order to calculate the gap distance more accurately, an average value may be adopted by calculating the gap distance from a plurality of energization feature amounts.

  18 and 19, an ammeter 33c is provided as an interval measuring means for measuring a gap between the nozzle 61b and the intermediate transfer body 37 by measuring a current-carrying state between the nozzle plate 61a and the intermediate transfer body 37. An example configuration is shown.

  As shown in FIG. 18, the ammeter 33c is provided in each of the heads 61Y, 61M, 61C, and 61BK. In order to measure the gap between the nozzle 61b and the intermediate transfer body 37, the ammeter plate 61a and the intermediate transfer The current between the body 37 is measured as the amount of liquid column current.

As shown in FIG. 19, with the provision of the ammeter 33c, the control unit 40 omits the dimension measurement value storage means 40e shown in FIG. 3, and in this configuration example, FIG. The gap measuring sensor 36 shown is omitted. Further, in this configuration example, instead of the gap measurement value 40g shown in FIG. 13 being input to the signal receiving unit 40a, the liquid column energization current amount is obtained from the ammeter 33c, and the information related to the above-described energization feature amount. Is input as an energization feature amount measurement signal including.
In addition, in this configuration example, the paper type detection as a paper type discrimination sensor as a recording material type detection unit that detects the type of the transfer paper S to which the image carried on the intermediate transfer body 37 is transferred in the transfer unit 31. A sensor 45 is provided. Then, the paper type data 41a acquired by the paper type detection sensor 45 is input to the signal receiving unit 40a.

  The signal receiving unit 40 a receives the liquid column energization current amount measured by the ammeter 33 c from the ammeter 33 c, and this input is performed in association with the phase of the intermediate transfer body 37. The above-described fitting coefficient and lookup table are stored in the drive control table 40d that functions as a head drive voltage control table. Determination of the drive signal including the second drive signal by the recording liquid discharge control means 40b using the drive control table 40d is based on such a liquid column energization current amount and a head corresponding to the fitting coefficient and the lookup table. This is performed using the driving data. At this time, the second drive is performed using at least one of the above-described energization feature amounts indicating the energization state between the nozzle plate 61a and the intermediate transfer body 37, which is included in the liquid column energization current amount. A drive signal including the signal is determined.

The operation of applying a voltage to the piezoelectric element 61d in accordance with the determined drive signal and discharging the recording liquid from the nozzle 61b is the same as in the above-described embodiment.
However, the control based on the determined drive signal cannot be performed for the ejection of the recording liquid used to determine the voltage value due to a delay in the control process.

  Therefore, the generation of the drive signal corresponding to the gap substantially measured based on the measured liquid column energization current amount and the control using the generated drive signal are specifically performed when the subsequent image formation is performed. This is performed when an image is formed by discharging the recording liquid after one rotation of the intermediate transfer member 37. That is, a driving signal is generated each time the recording liquid is ejected, and the control using the generated driving signal uses the liquid column energization current amount measured before one rotation of the intermediate transfer body 37.

  For this reason, the voltage value applied by the power source 33a before one rotation of the intermediate transfer body 37 is also used for determining the drive signal including the second drive signal by the head drive voltage control table 40d. Therefore, in the head drive voltage control table 40d, a fitting coefficient and a lookup table are prepared for such voltage values.

  As described above, the current state of the bridge of the liquid column made of the recording liquid between the nozzle plate 61a and the intermediate transfer body 37, which is generated when the recording liquid agglomerates, gelates and Joule heat is generated, is used. Measure this gap. Therefore, even when the heads 61Y, 61M, 61C, 61BK undergo positional fluctuations over time, the gap is accurately measured, and the determination of the voltage value and the control based on the gap are accurately performed at a relatively low cost. Done.

  Note that for the first image formation immediately after receiving the print signal, that is, the first image formation, the gap measurement is performed using the liquid column energization current measured during maintenance such as pre-printing idle discharge. Then, a drive signal is generated based on this gap, and a voltage is applied using the generated drive signal during subsequent image formation.

Here, in the configuration in which the intermediate transfer body 37 is not provided with the surface layer 37b and is composed of the support body 37a, the support body 37a functions as an anode as described above. In this case, it is possible to oxidize the support body 37a which is a metal together with water on the surface of the support body 37a. When the support 37a, which is a metal, is oxidized, a metal cation excellent in aggregating the colorant is generated. Therefore, as shown in FIG. 20, an anionic property is obtained via the proton and the metal cation (M ^{n +} ). The pigment P dispersed by the dispersant D aggregates. Therefore, the cohesion is increased.

  In such a configuration, as shown in FIG. 21, it is desirable that the transfer means 64 has the following configuration. That is, the transfer means 64 is not only the transfer roller 38 but also a transfer image carrier having a rubber layer 63a as an elastic body layer on the surface to which the image formed on the intermediate transfer member 37 is transferred and temporarily supported. It is desirable to include an intermediate transfer drum 63. The intermediate transfer drum 63 is rotated with the intermediate transfer member 37, and the transfer roller 38 is rotated with the intermediate transfer drum 63. Since the surface of the intermediate transfer drum 63 is an elastic body, the transfer of the image from the intermediate transfer body 37 made of metal and having a high surface hardness is performed well, and the transferability is improved.

  The intermediate transfer drum 63 has a rubber layer 63a and a base 63b covered with the rubber layer 63a. Although it does not specifically limit as a material which comprises the base | substrate 63b, Metals, such as aluminum, an aluminum alloy, copper, and stainless steel, are mentioned. Although it does not specifically limit as a material which comprises the rubber layer 63a, Silicone rubber, urethane rubber, fluorine rubber, etc. are mentioned.

  Here, the control unit 40 is ejected to the memory by the heads 61Y, 61M, 61C, 61BK including the nozzles 61b that eject the conductive recording liquid according to the drive signal, and the heads 61Y, 61M, 61C, 61BK. At least a part of the surface to which the conductive recording liquid is applied is discharged from the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK, and between the heads 61Y, 61M, 61C, 61BK and the intermediate transfer body 37. A current-carrying means 33 for applying a voltage between the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK for conducting a current to the conductive recording liquid in a state where the space is temporarily bridged; Transfer means 64 for transferring the image carried on the intermediate transfer member 37 to the transfer paper S by the liquid, characteristics of the transfer paper S, use environment of the image forming apparatus 100, conductivity A curl amount predicting unit 40f for predicting a curl amount of the transfer sheet S when the image is transferred by the transfer unit 64 based on at least one of the pattern in which the liquid adheres to the transfer sheet S and the applied voltage. Joule heat control means 44 for controlling Joule heat generated by the current flowing in the conductive recording liquid in such a state by energization, and the curl amount predicted by the curl amount prediction means 40f is allowed by the Joule heat control means 44. Image forming program for executing an image forming method for controlling Joule heat in a first range in which the curl amount predicted by the curl amount predicting means 40f is less than or equal to the allowable curl amount when the curl amount exceeds the curled amount Is remembered.

  In this regard, the control unit 40 or the memory functions as an image forming program storage unit. Such an image forming program can be stored not only in the memory provided in the control unit 40 but also in, for example, the following storage medium. That is, a storage medium such as a semiconductor medium (for example, ROM, nonvolatile memory, etc.), an optical medium (for example, DVD, MO, MD, CD-R, etc.), a magnetic medium (for example, hard disk, magnetic tape, flexible disk, etc.) It is. When such an image forming program is stored, such a memory, a storage medium, and the like constitute a computer-readable recording medium that stores the image forming program.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

For example, the conductive recording liquid may contain, in addition to water, a substance whose volatilization and evaporation are promoted by Joule heat by energization, and the curl amount is reduced by this promotion. In this case, the curl amount prediction means predicts the curl amount in consideration of this substance, and the Joule heat control means controls the Joule heat in consideration of this substance.
The pigment in the conductive recording liquid may be dispersed by a cationic dispersant and aggregated through hydroxide ions generated on the surface of the intermediate transfer member functioning as a cathode.

The intermediate transfer member does not need to be conductive as a whole, and at least the surface may be conductive.
The entire surface of the intermediate transfer member does not need to be conductive, and at least a part of the surface may be conductive. In other words, it is only necessary that the portion of the surface of the intermediate transfer body where the recording liquid is ejected in order to energize the liquid column of the recording liquid bridging between the head and the intermediate transfer body.

  The image forming apparatus to which the present invention is applied is not limited to the above-described type of image forming apparatus, but may be other types of image forming apparatuses, that is, a shuttle type with respect to the head, or a copying machine or a facsimile alone. Alternatively, it may be an image forming apparatus used for forming an electric circuit, or a multifunction device such as these multifunction devices, a monochrome device related thereto, or the like. The image forming apparatus to which the present invention is applied may be an image forming apparatus used to form a predetermined image in the biotechnology field. The number of heads is increased or decreased according to the application of the image forming apparatus, and may be one or plural.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

33 Voltage application means 37 Intermediate transfer body 40f Curling amount prediction means 41 Recording material type input means 44 Joule heat control means 45 Recording material type detection means 61b Nozzle 61Y, 61M, 61C, 61BK Head 64 Transfer means 100 Image forming apparatus, Double-sided image forming apparatus S Recording material

JP-A-01-130949 Japanese Patent No. 2724141 JP 2008-62397 A Japanese Patent Laid-Open No. 11-188858 JP 2010-188665 A JP 2011-189706 A

Claims (11)

A head including a nozzle for discharging a conductive recording liquid in response to a drive signal;
The conductive recording liquid discharged by the head is applied, and at least a part of the surface is a conductive intermediate transfer member,
A voltage is applied between the intermediate transfer body and the head for energizing the conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer body. Voltage applying means;
Transfer means for transferring an image carried on the intermediate transfer member by a conductive recording liquid to a recording material;
Based on the characteristics of the recording material, the usage environment of the image forming apparatus, the pattern in which the conductive recording liquid adheres to the recording material, and at least one of the applied voltages, the image is transferred by the transfer unit. Curl amount prediction means for predicting the curl amount of the recording material;
Joule heat control means for controlling Joule heat generated by the current flowing in the conductive recording liquid in the state by the energization,
When the curl amount predicted by the curl amount prediction unit exceeds an allowable curl amount, the Joule heat control unit determines that the curl amount predicted by the curl amount prediction unit is equal to or less than the allowable curl amount. An image forming apparatus that controls the Joule heat in a first range. The image forming apparatus according to claim 1.
The Joule heat control means controls the Joule heat so that the integrated amount of the current is minimized within a first range. The image forming apparatus according to claim 1.
Using a conductive recording liquid having a property of increasing viscosity by energization,
The Joule heat control means controls the Joule heat in a second range within the first range where the viscosity of the conductive recording liquid after completion of the energization is equal to or higher than a predetermined viscosity. Image forming apparatus. The image forming apparatus according to claim 3.
The Joule heat control means controls the Joule heat so that the integrated amount of the current is minimized within a second range. The image forming apparatus according to any one of claims 1 to 4,
The characteristic is acquired by a recording material type input unit that inputs a type of the recording material to which the image is transferred or a recording material type detection unit that detects the type of the recording material to which the image is transferred. An image forming apparatus comprising a type of a recording material to which the image is transferred. The image forming apparatus according to any one of claims 1 to 5,
An image forming apparatus, wherein the total amount of conductive recording liquid constituting the pattern is used as the pattern. The image forming apparatus according to any one of claims 1 to 6,
A plurality of the heads;
The image forming apparatus according to claim 1, wherein the pattern is weighted on the basis of a property of the conductive recording liquid constituting the pattern. The image forming apparatus according to any one of claims 1 to 7,
A double-sided image forming apparatus capable of forming images on both sides of a recording material;
An image forming apparatus using the allowable curl amount according to when an image is formed on a first surface of a recording material and when an image is formed on a second surface of a recording material. The image forming apparatus according to any one of claims 1 to 8,
An image forming apparatus characterized in that the allowable curl amount is used in the one set of image formation according to the time required for one set of image formation in which continuous image formation is performed a plurality of times. The image forming apparatus according to any one of claims 1 to 9,
The Joule heat control means controls the Joule heat by controlling at least one of the applied voltage and the drive signal. A head including a nozzle for discharging a conductive recording liquid in response to a drive signal;
The conductive recording liquid discharged by the head is applied, and at least a part of the surface is a conductive intermediate transfer member,
A voltage is applied between the intermediate transfer body and the head for energizing the conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer body. Voltage applying means;
Transfer means for transferring an image carried on the intermediate transfer member by a conductive recording liquid to a recording material;
Based on the characteristics of the recording material, the usage environment of the image forming apparatus, the pattern in which the conductive recording liquid adheres to the recording material, and at least one of the applied voltages, the image is transferred by the transfer unit. Curl amount prediction means for predicting the curl amount of the recording material;
Using Joule heat control means for controlling Joule heat generated by the current flowing in the conductive recording liquid in the state by the energization,
When the curl amount predicted by the curl amount prediction unit exceeds the allowable curl amount by the Joule heat control unit, the curl amount predicted by the curl amount prediction unit is equal to or less than the allowable curl amount. An image forming method for controlling the Joule heat in a first range.

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