JP2014172289A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and an image forming method capable of preventing beading or bleeding when forming an image by discharging a recording liquid such as an ink from a head to allow an intermediate transfer body to carry the recording liquid to electrolyze the recording liquid.SOLUTION: An image forming apparatus 100 includes: heads 61Y, 61M, 61C and 61BK each having a nozzle for discharging a conductive recording liquid containing water; an intermediate transfer body 37 to which the conductive recording liquid discharged by the heads 61Y, 61M, 61C and 61BK is applied, and having at least one part of the surface being conductive; voltage applying means 33 for applying a voltage to between the intermediate transfer body 37 and the heads 61Y, 61M, 61C and 61BK in order to flow a current to the conductive recording liquid while the conductive recording liquid discharged from the heads 61Y, 61M, 61C and 61BK bridges between the heads 61Y, 61M, 61C and 61BK and the intermediate transfer body 37; and cooling means 70 for cooling the intermediate transfer body 37.

Description

  The present invention relates to an inkjet image forming apparatus and an image forming method that employ an intermediate transfer method in which a recording liquid such as ink is ejected from a head and carried on an intermediate transfer member to form an image.

  2. Description of the Related Art Conventionally, ink jet type image forming apparatuses that perform image formation by ejecting a recording liquid such as ink from a head are known (see, for example, [Patent Document 1] to [Patent Document 15]). Inkjet image forming apparatuses eject droplets of recording liquid from a plurality of micro nozzles according to image information using a movable actuator method typified by a piezo method and a heated film boiling method typified by a thermal method. It is attached to a recording medium such as paper. Such an inkjet image forming apparatus is expanding its application range to printers, facsimiles, copiers, and the like because of the simplicity of the apparatus configuration compared to the electrophotographic system. It is also expected to develop into new fields such as electrical circuit formation and biotechnology applications.

Among such image forming apparatuses of the ink jet system, an intermediate transfer system having an intermediate transfer member that carries a recording liquid discharged from a head, that is, an intermediate transfer body, in other words, a transfer type image forming apparatus is known (for example, [See Patent Document 1] to [Patent Document 15]).
In this intermediate transfer type image forming apparatus, since the recording medium such as paper does not normally pass through the position facing the head, the following advantages are generally obtained.

That is, when the recording medium touches the head, it is possible to prevent the nozzles and the like from being damaged and paper dust, dust and the like adhering to the recording medium from being attached to the nozzles and the like. Therefore, it is possible to obtain an advantage that image quality and reliability are prevented from being deteriorated due to disturbance of the flying direction of the liquid droplets ejected from the nozzle or obstruction of the nozzle.
As described above, the intermediate transfer type image forming apparatus is characterized in that it is difficult to cause inkjet clogging due to unintended contact between recording paper or paper dust and the recording head, and high reliability is obtained.

  Technology that uses reaction liquids, processing liquids, powders, etc., which are different from recording liquids, as materials that can prevent beading and bleeding on the intermediate transfer bodies in image forming apparatuses that use intermediate transfer bodies Is known (for example, see [Patent Document 1] to [Patent Document 5]). However, these techniques have a problem that there are many consumables and the apparatus becomes complicated.

  As a technique that can avoid this problem, a bridge of a liquid column of conductive recording liquid is temporarily formed between the nozzle and the intermediate transfer member so that water contained in the bridge of the liquid column is electrolyzed. Techniques for applying a potential have been proposed (see, for example, [Patent Document 6] and [Patent Document 7]). This technology changes the pH of the recording liquid by electrolysis, thereby thickening the recording liquid droplets on the intermediate transfer member, thereby suppressing beading and bleeding and forming a good image with reduced bleeding. It is possible to perform.

In an image forming apparatus provided with an intermediate transfer member, for example, the following techniques for cooling the intermediate transfer member are known.
A technique for cooling the intermediate transfer member in order to lower the temperature of the liquid receptive particles applied to the intermediate transfer member (see, for example, [Patent Document 4] and [Patent Document 5])
A technique for cooling the heated intermediate transfer member to return it to the original state (for example, see [Patent Document 8] to [Patent Document 10])
A technique for cooling the intermediate transfer member in order to cool the heated and melted ink (see, for example, [Patent Document 11] and [Patent Document 12])

By the way, with respect to the above-described technique for changing the pH of the recording liquid by electrolysis, the following has been found by the inventors' diligent research.
When the viscosity increase rate of the recording liquid accompanying a change in pH of the recording liquid is slow, beading or bleeding can occur.
Even when the printing speed is high, adjacent intervals are formed before the recording liquid droplet ejection interval is short and the droplets have sufficiently high viscosity, and beading and bleeding are likely to occur.
Therefore, it has been found that it is necessary to develop a technique for further suppressing beading and bleeding in such a technique.

  The present invention provides an image forming apparatus and an image forming method for preventing beading and bleeding when an image is formed by ejecting a recording liquid such as ink from a head and supporting it on an intermediate transfer member for electrolysis. The purpose is to do.

  In order to achieve the above object, the present invention provides a head having a nozzle for discharging a conductive recording liquid containing water, and at least a part of the surface to which the conductive recording liquid discharged by the head is applied. The intermediate transfer body and the conductive recording liquid discharged from the head in order to flow a current through the conductive recording liquid in a state where the head and the intermediate transfer body are bridged. And an image forming apparatus having a voltage applying means for applying a voltage between the head and the head, and a cooling means for cooling the intermediate transfer member.

  The present invention includes a head provided with a nozzle for discharging a conductive recording liquid containing water, an intermediate transfer body having at least a part of the surface to which the conductive recording liquid discharged by the head is applied, and The conductive recording liquid ejected from the head bridges between the head and the intermediate transfer body, and in order to pass a current through the conductive recording liquid in this state, the intermediate transfer body and the head Since the image forming apparatus has a voltage applying means for applying a voltage and a cooling means for cooling the intermediate transfer body, the recording liquid is thickened by cooling the recording liquid by the intermediate transfer body cooled by the cooling means. Thus, it is possible to provide an image forming apparatus capable of taking measures against beading and bleeding, obtaining a high-quality image, and improving reliability.

1 is a schematic front view of an embodiment of an image forming apparatus to which the present invention is applied. FIG. 2 is a conceptual diagram illustrating a state in which a recording liquid is applied from a head to an intermediate transfer member in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic plan view illustrating the arrangement of nozzles in a head provided in the image forming apparatus shown in FIG. 1. FIG. 2 is a conceptual diagram illustrating a state in which colorants in 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 illustrating a state of a liquid column by a recording liquid formed between a cathode and an anode in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic diagram illustrating a configuration example of a cooling unit and a heating unit provided in or capable of being provided in the image forming apparatus illustrated in FIG. 1. It is the graph which showed notionally the thickening by electrolysis of recording liquid, and the thickening by a temperature fall. FIG. 6 is a schematic diagram illustrating that a transfer medium is curled by a recording liquid. FIG. 6 is a schematic diagram showing that a transfer target curls due to evaporation of moisture. It is a schematic front view of a part of a modification of the image forming apparatus to which the present invention is applied. It is a schematic front view of a part of another modification of the image forming apparatus to which the present invention is applied. FIG. 10 is a schematic front view of a part of another modification of the image forming apparatus to which the present invention is applied. FIG. 10 is a schematic front view of a part of still another modification of the image forming apparatus to which the present invention is applied.

  FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is an ink jet recording apparatus that is a printer as an ink jet 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 forms an image on a recording medium that is a sheet-like recording medium such as plain paper generally used for copying, OHP sheets, thick paper such as cards and postcards, and envelopes. Can be performed. The image forming apparatus 100 is a single-sided image forming apparatus that can form an image on one side of a transfer sheet S that is a recording medium as a recording medium that is a recording medium, but can form an image on both sides of the transfer sheet S. A double-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. The heads 61Y, 61M, 61C, and 61BK function as an inkjet head that is a recording head as a recording liquid discharger that discharges the recording liquid.

  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 as an intermediate transfer member disposed at a substantially central portion of the main body 99 of the image forming apparatus 100. Has been. 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, which is an intermediate transfer roller, 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. As a result, 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 member 37 by the heads 61Y, 61M, 61C, and 61BK so that the image areas of the respective colors of yellow, magenta, cyan, and black are overlapped at the same position on the intermediate transfer member 37. Therefore, the discharge of the recording liquid to the intermediate transfer body 37 by the heads 61Y, 61M, 61C, 61BK is performed at a shifted timing from the upstream side in the A1 direction 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 that is a transport device 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 removes residual ink, which is a 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, and cleans it. The cleaning means 34 is a residual ink removing mechanism as the cleaning means.

The image forming apparatus 100 also includes a carriage 50 as a head support that integrally supports the heads 61Y, 61M, 61C, and 61BK.
The image forming apparatus 100 also includes an energizing unit 33 as a voltage applying unit for applying a voltage to the recording liquid ejected from the heads 61Y, 61M, 61C, 61BK.
The image forming apparatus 100 also includes a cooling unit 70 as a cooling unit for cooling the intermediate transfer body 37 and a heating unit 90 as a heating unit for heating a transfer roller 38 described later.
The image forming apparatus 100 also includes a control unit 40 serving as a control unit including a CPU, a memory, and the like that control the overall operation of the image forming apparatus 100, a display device that displays various states of the image forming apparatus 100, and the like. And an operation panel (not shown).

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 includes a motor 32 as an intermediate transfer body drive mechanism that is an intermediate transfer body rotation drive motor as a drive unit that rotationally drives the intermediate transfer body 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 means 64 is disposed at a position facing the intermediate transfer body 37, functions as a transfer roller 38 driven to rotate by the intermediate transfer body 37, the transfer roller 38 in pressure contact with the intermediate transfer body 37, and the transfer roller 38 as a pressure roller And a spring (not shown) as a pressurizing means.

The transfer roller 38 has a support 38a made of aluminum which is a conductive substrate, and a surface layer 38b formed on the support 38a.
The support 38a needs to have high mechanical conductivity and high thermal conductivity so that it can be quickly heated when heated by the heating unit 90 as described later. Therefore, the support 38a is not limited to aluminum, and may be formed of a metal such as an aluminum alloy, copper, stainless steel, or an alloy.
The surface layer 38b is formed of an elastic body or a rigid body. When the surface layer 38b is formed of an elastic body, rubber may be selected as the elastic body. The rubber is not particularly limited, and examples thereof include silicone rubber, urethane rubber, fluorine rubber, and nitrile butadiene rubber. Further, when the surface layer 38b is formed of a rigid body, a metal may be selected as the rigid body. Although it does not specifically limit as a metal, Aluminum, an aluminum alloy, copper, stainless steel, etc. are mentioned. Note that the surface layer 38 b may be omitted and only the support 38 a may be used as the transfer roller 38.

  The transfer unit 64 pressurizes and conveys the transfer sheet S between the intermediate transfer member 37 and the transfer roller 38. During this pressure conveyance, the transfer roller 38 passes the transfer sheet S between the intermediate transfer body 37 and transfers the recording liquid applied on the intermediate transfer body 37 onto the transfer sheet S as a transfer target. It functions as a transfer body as a transfer member.

As shown in FIG. 2, the intermediate transfer member 37 has an aluminum support 37a as a conductive substrate and a surface layer 37b as a conductive rubber layer formed on the support 37a.
The material of the support 37a is not limited to aluminum, and has good conductivity and mechanical strength, and has high thermal conductivity so that it can be quickly cooled when cooled by the cooling unit 70 as described later. There is a need. Therefore, the support 37a is not limited to aluminum, and may be formed of a metal such as an aluminum alloy, copper, stainless steel, or an alloy.
The surface layer 37b is formed of a smooth elastic material having high conductivity and water repellency.

  The water repellency of the surface layer 37b is an index of the ease of transfer when the recording liquid is transferred from the surface layer 37b to the transfer paper S. The higher the water repellency, the better the transfer rate, and the cleaning with a blade described later. It becomes easy to do.

Further, the elasticity of the surface layer 37b is a function necessary for transfer, and when the surface layer 37b is deformed along the fibers of the transfer paper S, the contact area is improved and a high transfer rate is obtained. To transfer at a low pressure, it is necessary to select a material that is somewhat soft.
Examples of the material satisfying these functions of water repellency and elasticity include rubber materials such as fluorosilicone rubber, phenylsilicone rubber, fluorine rubber, chloroprene rubber, nitrile rubber, nitrile butadiene rubber, and isoprene rubber. The surface layer 37b may be impregnated with silicon oil to increase water repellency. The surface layer 37b may have either a single layer structure or a multilayer structure.

  The surface layer 37b contains carbon black as a conductive agent so as to impart conductivity to the intermediate transfer member 37 so that the electrolysis of the recording liquid described later is performed, and is a conductive layer having conductivity. The conductive agent may be conductive fillers, carbon nanotubes, metal fine particles such as gold and silver, and the like.

  In order to increase the electrical conductivity of the surface layer 37b, it is conceivable to increase the conductive fine particles. However, if the density of the conductive fine particles on the surface is high, it causes a decrease in water repellency. The conductivity is only required to be provided in the film thickness direction of the support 37a and the surface layer 37b, and may be anisotropic conductivity in the surface direction. The size of the conductive fine particles needs to be sufficiently smaller than the dots of about 20 to 50 μm constituting the image, and is preferably 0.1 μm or less.

Regarding the bulk property and surface property of the surface layer 37b related to transfer property and conductivity, the following are preferable. That is, the volume resistivity of the conductive rubber is 10 ⁴ Ω · cm or less, preferably 10 ² Ω · cm or less. The water repellency has a receding contact angle of water of 60 ° or more, preferably 80 ° or more, and the hardness is 60 or less, preferably 40 or less in JIS-A. Further, the thickness of the surface layer 37b is preferably about 0.1 to 1 mm, and preferably 0.2 to 0.6 mm.

  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, increasing the number of conductive fine particles improves the conductivity, but a trade-off relationship that lowers the releasability, so adjustment is necessary as appropriate.

As will be described later, in order to form a desired potential difference in the liquid column by the recording liquid in which the heads 61Y, 61M, 61C, 61BK and the intermediate transfer body 37 are temporarily bridged, the volume resistivity of the conductive rubber is 10 It is preferably less than ³ Ω · cm. Further, 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 the volume of the recording liquid. Desirably less than the resistivity.

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

  The motor 32 can change the driving speed, that is, the rotational speed of the intermediate transfer member 37. The rotation speed of the intermediate transfer member 37 by the motor 32 is controlled and set by the control unit 40. In this regard, the motor 32 that is an intermediate transfer body drive mechanism functions as a drive control mechanism, and the control unit 40 functions as a drive speed control means that is an intermediate transfer body drive speed control mechanism.

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 or the like as a driving means (not shown) that drives the paper feeding roller 22 to rotate and feed the transfer paper S so as to match the discharge timing of the recording liquid in the heads 61Y, 61M, 61C, 61BK. Have.

The cleaning unit 34 scrapes off the recording liquid that has not been transferred to the transfer paper S from the recording liquid constituting the image formed on the intermediate transfer body 37 from the surface of the intermediate transfer body 37 as residual ink that is residual liquid. And a blade (not shown) which is a cleaning blade.
The cleaning means 34 also has a roller (not shown) that is a cleaning roller as the cleaning member.
The cleaning means 34 also has a waste liquid bottle (not shown) which is a waste liquid tank for collecting foreign substances such as recording liquid and dust scraped off from the surface of the intermediate transfer member 37 by a blade or a roller.

  The blade is in contact with the intermediate transfer member 37 in a so-called counter contact manner. The blade is a rubber blade formed of rubber as an elastic body. The material of the blade may be an elastic material such as silicone rubber, nitrile rubber, urethane rubber, fluorine rubber, EPDM, or elastomer, or a metal such as stainless steel or aluminum, or a non-ferrous material.

  In general, when the state of the tip of the blade is switched from the dry state to the moisturizing state, defective removal of the residual ink occurs, and the blade tends to pass through the tip where the residual ink is applied. Therefore, in the image forming apparatus 100, the control is performed to discharge the recording liquid and retain the tip of the blade before the start of image formation to stabilize the cleaning performance.

The carriage 50 can be 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 they are deteriorated, and for easy maintenance. It has become. The carriage 50 is integral with the heads 61Y, 61M, 61C, 61BK and is detachable from the main body 99.
Each of the heads 61Y, 61M, 61C, 61BK can be independently attached to and detached from the main body 99 so that it can be replaced with a new one when deterioration or the like occurs and for easy maintenance. ing.
As a result, replacement work and maintenance work are facilitated.

  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. The ink ejection devices 60Y, 60M, 60C, 60BK and the image forming apparatus 100 are a head-fixed full line type.

The ink ejection devices 60Y, 60M, 60C, and 60BK are ink cartridges 81Y, 81M, and 81C that are recording liquid cartridges as main tanks that store the recording liquids of the corresponding colors supplied to the plurality of heads 61Y, 61M, 61C, and 61BK. , 81BK.
The ink discharge devices 60Y, 60M, 60C, 60BK also have pumps 82Y, 82M, 82C, which feed recording liquids stored in the ink cartridges 81Y, 81M, 81C, 81BK to the heads 61Y, 61M, 61C, 61BK. Has 82BK.
The ink ejection devices 60Y, 60M, 60C, and 60BK are not shown, which are flow paths for transporting the recording liquid stored in the ink cartridges 81Y, 81M, 81C, and 81BK to the heads 61Y, 61M, 61C, and 61BK. Has a pipe.

The ink cartridges 81Y, 81M, 81C, 81BK function as a recording liquid supply unit that supplies the recording liquid to the heads 61Y, 61M, 61C, 61BK.
The ink cartridges 81Y, 81M, 81C, 81BK are replaced with new ones when the internal recording liquid is consumed and the remaining amount is low or no longer used, and in order to facilitate maintenance. 99 is removable.
The ink cartridges 81Y, 81M, 81C, and 81BK are bag-like ink packs formed of a relatively soft plastic material so that they can be deflated as the internal recording liquid is consumed. However, the ink cartridges 81Y, 81M, 81C, and 81BK may be formed of a plastic material having high comparative compatibility.

The recording liquid contains at least the following components.
-Colorant that is a colorant corresponding to yellow, magenta, cyan, black-Solvent of this colorant-ABA type amphiphilic polymer composed of hydrophobic A segment and hydrophilic B segment-This ABA type amphiphilic property Anionic surfactant that dissolves or disperses polymer in solvent

  The solvent is an aqueous solvent containing water from the viewpoint of safety and the conductivity from which electrolysis described later is caused, and the recording liquid is an aqueous ink composition. As the colorant, an anionic colorant and / or anionic resin which is dissolved or dispersed in a solvent and has an ionic property in the solvent is anionic.

  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 cross-linking by hydrophobic association in an aqueous solvent, the hydrophilic B block needs to have a sufficiently long chain length, that is, a larger chain length than the hydrophobic A block. As such a thing, the thing more than 100mers, such as an ethylene oxide polymer containing a linear polyethylene oxide, and a propylene oxide polymer, is mentioned. 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 the hydrophobic association between the hydrophobic A segments, which will be described later, easily occurs, 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.

  An anionic surfactant that dissolves or disperses an ABA type amphiphilic polymer in an aqueous solvent desirably has a buffering action when dissolved in an aqueous solvent. This is because by using an anionic surfactant having a relatively low ionization degree, it is possible to thicken an aqueous solvent containing an ABA type amphiphilic polymer by introducing a small amount of protons. In other words, in order to efficiently hydrophobically associate the ABA type amphiphilic polymer adsorbed by the anionic surfactant with a small amount of proton consumed by the electrolyte component and the coloring material component in the aqueous solvent among the input protons. It is possible to increase the amount of protons consumed in the reactor. As for an anionic surfactant, it is more desirable that a hydrophilic group is hydrophobized by receiving a proton and the function as a surfactant is lost. Here, the buffering action means that the pH value of the aqueous solvent is kept almost constant even when a small amount of acid or base is mixed. As such an anionic surfactant, a carboxylic acid type surfactant is more desirable. More specifically, as the carboxylic acid type surfactant, aliphatic carboxylate, polyoxyethylene alkyl ether carboxylate, N -It is preferable that any one or more of acyl sarcosinate, N-acyl glutamate, alpha sulfo fatty acid ester salt, or multi-chain polyhydrophilic type carboxylate is included. As such, sodium caproate, potassium caproate, triethanolamine caproate, sodium caprylate, potassium caprylate, triethanolamine caprylate, sodium caprate, potassium caprate, triethanolamine caprate, lauric acid Sodium, potassium laurate, triethanolamine laurate, sodium myristate, potassium myristate, triethanolamine myristate, sodium palmitate, potassium palmitate, triethanolamine palmitate, sodium stearate, potassium stearate, stearic acid Triethanolamine, polyoxyethylene lauryl ether sodium acetate, polyoxyethylene lauryl ether potassium acetate, polyoxy Tylene lauryl ether acetate triethanolamine, polyoxyethylene tridecyl ether sodium acetate, polyoxyethylene tridecyl ether potassium acetate, polyoxyethylene tridecyl ether acetate triethanolamine, lauroyl sarcosine sodium, lauroyl sarcosine potassium, lauroyl sarcosine triethanolamine , Myristoyl sarcosine sodium, myristoyl sarcosine potassium, myristoyl sarcosine triethanolamine, stearoyl sarcosine sodium, stearoyl sarcosine potassium, stearoyl sarcosine triethanolamine, coconut oil fatty acid sarcosine sodium, coconut oil fatty acid sarcosine potassium, coconut oil fatty acid sarcosine triethanolamine, lauroyl Methyla Sodium nin, Lauroylmethylalanine potassium, Lauroylmethylalanine triethanolamine, Myristoylmethylalanine sodium, Myristoylmethylalanine potassium, Myristoylmethylalanine triethanolamine, Palm oil fatty acid sodium methylalanine, Palm oil fatty acid methylalanine potassium, Palm oil fatty acid methyl Alanine Triethanolamine, Sodium Lauroyl Glutamate, Potassium Lauroyl Glutamate, Triethanolamine Lauroyl Glutamate, Sodium Myristoyl Glutamate, Potassium Myristoyl Glutamate, Triethanolamine Myristoyl Glutamate, Sodium Stearoyl Glutamate, Potassium Stearoyl Glutamate, Triaroyl Glutamate Trie Tanolamine, coconut oil fatty acid acyl glutamate sodium, coconut oil fatty acid acyl glutamate potassium, coconut oil fatty acid acyl glutamate triethanolamine, 2-sulfotetradecanoic acid-1-methyl ester sodium salt, 2-sulfotetradecanoic acid-1-methyl ester potassium Salt, 2-sulfohexadecanoic acid-1-methyl ester sodium salt, 2-sulfohexadecanoic acid-1-methyl ester potassium salt, alkenyl succinate dipotassium, alkenyl succinate disodium, dilauroyl glutamate lysine sodium, dilauroyl glutamate lysine potassium Etc.

  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. The pKa of the anionic surfactant is preferably about 7 to 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 an anionic 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 the 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 1 S / m, preferably 0.02 to 0.2 S / m. m.

Specific examples of the anionic dye that is a colorant component, that is, an anionic colorant contained in the recording liquid include, for example, dyes classified into acid dyes, direct dyes, and food dyes in the color index.
More specifically, as acid dyes and food dyes, C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142 C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254, 289 C.I. I. Acid Blue 9, 29, 45, 92, 249 C.I. I. Acid Black 1, 2, 7, 24, 26, 94 C.I. I. Food Yellow 3, 4 C.I. I. Food Red 7, 9, 14 C.I. I. Food black 1, 2 etc.

  As a direct dye, C.I. I. Direct Yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144 C.I. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227 C.I. I. Direct Orange 26, 29, 62, 102 C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202 C.I. I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171 and the like.

  As reactive dyes, C.I. I. Reactive. Black 3, 4, 7, 11, 12, 17, C.I. I. Reactive. Yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67, C.I. I. Reactive. Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97, C.I. I. Reactive. Blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95, etc. When recording with the method according to this embodiment, high solubility, good color tone It is preferably used because of its good water resistance.

Examples of the colorant component used in the recording liquid, that is, the pigment that is a colorant include inorganic pigments and organic pigments.
Examples of inorganic pigments include white pigments such as titanium oxide, zinc oxide, and barium sulfate, and black pigments such as iron oxide.
Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelates, acidic dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like.

Further, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used.
More specifically, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 81, 83 (Disazo Yellow HR) ), 95, 97, 98, 100, 101, 104, 408, 109, 110, 117, 120, 138, 153, C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48: 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63 : 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (Quinacridone magenta), 123 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, C I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63, C.I. I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like.

  When using a recording liquid containing a pigment as a colorant component, for example, carbon black having a carboxyl group introduced by an oxidation reaction, a radical generated from a diazonium salt containing a carboxyl group or a sulfonic acid group, and carbon black, phthalocyanine, Self-dispersing pigments made by reacting pigments such as quinacridone, self-dispersing pigments made by reacting radical initiators containing carboxyl groups and sulfonic acid groups with pigments such as carbon black, phthalocyanine, quinacridone, and pigment functionality A self-dispersing pigment obtained by reacting a group and an anhydride of carboxylic acid is preferably used.

  When a recording liquid in which a pigment is dispersed is used, the particle diameter of the pigment is not particularly limited, but it is preferable to use a pigment ink having a particle diameter of 20 to 150 nm in terms of the maximum frequency in terms of the maximum number. When the particle diameter exceeds 150 nm, not only the dispersion stability of the pigment as the recording liquid is deteriorated but also the discharge stability of the recording liquid is deteriorated, and the image quality such as the image density is lowered, which is not preferable. In addition, when the particle size is less than 20 nm, the storage stability of the recording liquid and the jetting characteristics in the printer are stable, and high image quality can be obtained. This is because the classification operation becomes complicated and it is difficult to produce the recording liquid economically.

The recording liquid preferably contains an anionic polymer type such as a polymer dispersant or a low molecular type dispersant such as a surfactant as a dispersant for dispersing the pigment.
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, which will be described later, and are aggregated, they are preferable in terms of aggregation than the self-dispersed 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 step described later.

  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.

Another example of the colorant component used in the recording liquid is a recording liquid that uses a colored emulsion composed of colored resin fine particles.
The colored resin fine particles are those obtained by coloring styrene-acrylic resin, polyester resin, polyurethane resin or the like with an oily dye, a disperse dye or a pigment. For example, anionic coloring can be achieved by forming the part that hits the fine particle shell with a hydrophilic resin such as polyacrylic acid or polymethacrylic acid, or suspending it with an ionic surfactant such as a reactive surfactant. A recording liquid is obtained in which fine particles are suspended in a liquid medium mainly composed of water.

By adding a hydrophilic polymer compound to the recording liquid, it is possible to enhance the thickening action and aggregation action of the recording liquid by reaction with hydrogen ions.
The hydrophilic polymer compounds that can be added to the recording liquid include, in the natural system, plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, alginates, carrageenan , Seaweed polymers such as agar, animal polymers such as gelatin, casein, albumin and collagen, microbial polymers such as xanthene gum and dextran, shellac, etc., semi-synthetic systems such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropyl Fibrin-based polymers such as cellulose and ruboxymethylcellulose, starch-based polymers such as sodium starch glycolate and sodium starch phosphate, sodium alginate, propylene glycol alginate Seaweed polymers such as tellurium, pure synthetic systems such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl methyl ether and other vinyl polymers, non-crosslinked polyacrylamide, polyacrylic acid and alkali metal salts thereof, water-soluble styrene-acrylic resin, etc. Acrylic resin, water-soluble styrene-maleic acid resin, water-soluble vinyl naphthalene-acrylic resin, water-soluble vinyl naphthalene-maleic acid resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalene sulfonic acid formalin condensate, etc. It is done.

A resin emulsion or latex that does not contain a colorant may be added to the recording liquid. Depending on the type of the resin emulsion, the resin emulsion forms a film on the surface of the transfer paper S, and there is an advantage of improving the light resistance, water resistance, and abrasion resistance of the transfer paper S when an image is formed. Examples of the resin component in the suspension phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, and styrene resins. The particle diameter of these resin components is not particularly limited as long as an emulsion is formed, but is preferably about 150 nm or less, more preferably about 5 to 100 nm. Examples of commercially available resin emulsions include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.). Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), SAE-1014 (styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (acrylic resin emulsion, Seiden) Chemical Co., Ltd.).
In the recording liquid, the resin emulsion is preferably added so that the resin component is 0.1 to 40% by weight of the recording liquid, and more preferably in the range of 1 to 10% by weight.

  The above-described polymer type pigment dispersant, colored emulsion, water-soluble polymer compound, and the like are combined with the ABA type amphiphilic polymer, and the transfer rate from the intermediate transfer body 37 to the transfer paper S in the transfer step described later. It is effective to improve.

  The recording liquid uses water as the main liquid medium. In order to make the recording liquid have the desired physical properties or to prevent clogging of the nozzle 61b described later due to the drying of the recording liquid, the water-soluble organic solvent described below is moisturized. It is preferable to use it as an agent component.

  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 And sulfur-containing compounds such as thiodiethanol, propylene carbonate, ethylene carbonate, and γ-butyrolactone.

  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%.

  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.

As the acidic pH adjuster, boric acid, carbonic acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid, ammonium chloride and the like can be used. Examples of alkaline pH adjusters include hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, lithium carbonate, carbonic acid It is possible to use alkali metal carbonates such as sodium and potassium carbonate, and amines such as diethanolamine and triethanolamine.
In addition, you may use additives, such as a pH buffer, a viscosity modifier, antiseptic | preservative, antioxidant, and a rust inhibitor, as needed.

As shown in FIG. 2, each head 61Y, 61M, 61C, 61BK has a nozzle plate 61a as a nozzle plate which is a conductive nozzle member disposed on the recording liquid discharge side facing downward in the figure. ing.
Each head 61Y, 61M, 61C, 61BK also has a nozzle 61b formed on the nozzle plate 61a, through which the recording liquid passes and discharges the recording liquid as droplets.
Each of the heads 61Y, 61M, 61C, 61BK is also an ink chamber that is a liquid chamber that is supplied with recording liquid from the ink cartridges 81Y, 81M, 81C, 81BK by the pumps 82Y, 82M, 82C, 82BK and is filled with the recording liquid and held. 61c.
Each of the heads 61Y, 61M, 61C, 61BK also has an ink discharge means (not shown) that discharges the recording liquid in the ink chamber 61c from the nozzle 61b.
The nozzle plate 61a, the nozzle 61b, the ink chamber 61c, and the ink discharge means are provided as a set, and each head 61Y, 61M, 61C, 61BK is provided in large numbers, but only one of them is shown in FIG. Is illustrated.

  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 61a includes a surface on the ink chamber 61c side as an interface forming portion that forms an interface with the recording liquid in the ink chamber 61c, and functions as a cathode as will be described later.

  The entire nozzle plate 61a may be conductive, or may be a member in which only the surface on the ink chamber 61c side is subjected to conductive treatment, or an intermediate member between the conductive member disposed on the ink chamber 61c side. You may comprise by the insulating member arrange | positioned by the transfer body 37 side.

  Since the conductive portion of the nozzle plate 61a is provided as a cathode as will be described later, it does not need to be made of a material resistant to metal elution, and has a high conductivity such as SUS alloy, metal such as nickel, and carbon. What is necessary is just to be comprised with material.

The nozzle plate 61a is set so that the gap with the intermediate transfer member 37 is 50 to 200 μm during image formation. 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, there is no particular problem even if the gap is less than 50 μm as long as the gap can be maintained.
The nozzle plate 61a is a nozzle portion provided with a nozzle 61b, and in particular, a nozzle surface 61d that is a surface facing the intermediate transfer member 37 is a nozzle portion.

  The ink discharge means has a piezoelectric element as an actuator as a pressure application means for applying a pressure for discharging the recording liquid from each nozzle 61 b to be discharged and landed on the intermediate transfer body 37. Specifically, the ink discharge means discharges the recording liquid from the nozzle 61b according to the voltage pulse applied to the piezoelectric element under the control of the control unit 40. In this respect, the control unit 40 functions as an ink ejection control unit as a drive circuit that drives the piezoelectric element.

The control unit 40 functioning as an ink ejection control unit inputs a voltage pulse for driving the piezoelectric element to each of the piezoelectric elements with a predetermined signal waveform. The control unit 40 functioning as an ink ejection control unit drives each piezoelectric element in time series so that an arbitrary pattern, that is, an image is formed by the recording liquid ejected from each nozzle 61b. In this regard, the control unit 40 functions as an image control device.
The pressure in the ink chamber 61c is maintained at a negative pressure except when the recording liquid is discharged and discharged from the nozzle 61b.

  The actuator of the ink discharge means may be a movable actuator of another type that is a shape deformation element type, such as a piezo type. Such an actuator may be one that discharges the recording liquid from the nozzle 61b by boiling the recording liquid by a heating means that employs a heating method such as a thermal method, or discharges the recording liquid by electrostatic attraction by a voltage applying means. It may be what you do. As described above, such an actuator that discharges the recording liquid by any method can be adopted.

As described above, the image forming apparatus 100 is a head-fixed full line type. FIG. 3 illustrates the configuration of the heads 61Y, 61M, 61C, and 61BK.
In the heads 61Y, 61M, 61C, 61BK shown in FIG. 6A, the nozzle plate 61a has a large number of nozzles 61b in a line so as to form a nozzle row along the main scanning direction corresponding to the horizontal direction in the figure. . Further, the heads 61Y, 61M, 61C, 61BK shown in FIG. 5A have a large number of nozzles arranged in a line along a direction corresponding to the sub-scanning direction, that is, the vertical direction of the figure perpendicular to the main scanning direction. Two rows are provided. As a result, the heads 61Y, 61M, 61C, 61BK shown in FIG. 5A are full-line inkjet heads. The main scanning direction corresponds to a direction perpendicular to the paper surface in FIG.
Heads 61Y, 61M, 61C, 61BK shown in FIG. 6B are nozzle plates 61a having a number of nozzles 61b in the same manner as shown in FIG. A plurality of nozzle plates 61a smaller than the illustrated nozzle plate 61a are further arranged in a grid. As a result, the heads 61Y, 61M, 61C, 61BK shown in FIG. 5B are full-line ink jet heads.

  As described above, in both FIGS. 6A and 6B, the heads 61Y, 61M, 61C, and 61BK are line-type heads that are provided with the nozzle 61b in a two-dimensional shape. However, the heads 61Y, 61M, 61C, 61BK may be a one-dimensional line type head having a plurality of nozzles 61b in the main scanning direction.

  Since the heads 61Y, 61M, 61C, and 61BK are full-line type line heads having nozzle rows corresponding to the width of the image forming area as described above, it is possible to increase the speed of image formation in the image forming apparatus 100. The heads 61Y, 61M, 61C, and 61BK are not fixed types as in this embodiment, in other words, are not driven in the main scanning direction, and are shuttles that perform image formation by reciprocating with respect to the image forming area width. A configuration corresponding to the method may be used. In this case, the heads 61Y, 61M, 61C, 61BK have a small head configuration.

  The energization means 33 applies a voltage so that a potential difference is formed between the intermediate transfer member 37 and the heads 61Y, 61M, 61C, 61BK. This voltage application is performed at least at the following timing. That is, as shown in FIG. 2B, at least the liquid column of the recording liquid immediately after being ejected from the heads 61Y, 61M, 61C, 61BK is between the heads 61Y, 61M, 61C, 61BK and the intermediate transfer member 37. Is performed at the timing of temporarily bridging. By applying this voltage, the energizing means 33 energizes the recording liquid in the liquid column state containing a current component resulting from the electrode oxidation reaction or electrode reduction reaction, and is included in the recording liquid in the state as described later. Promotes agglomeration of existing colorants.

  The energizing means 33 is realized as a part of the function of the power source 33a, a not-shown electric circuit in which the power source 33a is connected to the support 37a and the nozzle plate 61a, and a part of the function of the control unit 40. Voltage application control means for controlling time. The controller 40 as voltage application control means also functions as voltage changing means for changing the voltage of the power supply 33a.

  The power source 33a has an anode connected to the support 37a and a cathode connected to the nozzle plate 61a by an electric circuit. Therefore, the energizing unit 33 includes the intermediate transfer member 37 as an anode and the nozzle plate 61a as a cathode.

In the image forming apparatus 100 having such a configuration, the intermediate transfer body 37 starts to rotate in the A1 direction while facing the heads 61Y, 61M, 61C, 61BK in response to the input of a predetermined signal indicating the start of image formation. . With the intermediate transfer member 37 rotating in the A1 direction while facing the heads 61Y, 61M, 61C, and 61BK, the recording liquids of yellow, magenta, cyan, and black are transferred from the heads 61Y, 61M, 61C, and 61BK. Discharged.
The recording liquid of each color from each head 61Y, 61M, 61C, 61BK is discharged from the upstream side in the A1 direction so that the image area of each color of yellow, magenta, cyan, and black overlaps the same position of the intermediate transfer body 37. This is performed in such a manner that the images are sequentially overlapped at different timings. As a result, an image is temporarily carried on the intermediate transfer member 37.
Thus, the intermediate transfer member 37 functions as an image carrier that carries an image formed by the recording liquid ejected from the nozzle 61b.

When the recording liquids of the respective colors are ejected from the heads 61Y, 61M, 61C, 61BK, the energizing unit 33 is driven by the control unit 40 as the voltage application control unit, and the support 37a, the nozzle plate 61a, and the like are supplied from the power source 33a. A voltage is applied between the two.
In this state, the recording liquid is applied onto the intermediate transfer member 37 from each of the heads 61Y, 61M, 61C, 61BK. At this time, first, as shown in FIG. 2A, the recording liquid forming the meniscus in the nozzle 61b is transferred from the heads 61Y, 61M, 61C, and 61BK to the intermediate transfer as shown in FIG. Move toward the body 37. As a result, a bridge of a liquid column made of a recording liquid is temporarily formed between the nozzle 61 b 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)

According to the reaction formula (1), hydroxide ions are generated on the side of the nozzle surface 61d functioning as the cathode, and as a result, alkalinity is exhibited. Since the colorant of the recording liquid is an anionic pigment, it exhibits high dispersibility under such alkaline conditions, and the recording medium attached to the nozzle surface 61d is easily dissolved.
Further, according to the reaction formula (2), water contained in the bridge of the liquid column of the recording liquid is oxidized on the surface of the intermediate transfer member 37 functioning as the anode, and protons (H +) that are hydrogen ions are generated. Shows acidity.

  Therefore, as shown in FIG. 4, the pigment P dispersed by the anionic dispersant D aggregates via protons. That is, since the colorant of the recording liquid is an anionic pigment, the positive charge of hydrogen ions and the negative charge of the anionic pigment cancel each other, and electrostatic repulsion is reduced, causing phenomena such as aggregation, thickening, and solidification. This phenomenon occurs in the vicinity of the intermediate transfer member 37 that is the counter electrode, particularly on the surface of the intermediate transfer member 37 that is the electrode interface.

  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 voltage pulse applied to the piezoelectric element.

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 the pigment dispersed by the anionic dispersant is aggregated.
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 energization means 33 includes the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK, specifically for electrolyzing the water contained in the recording liquid forming the bridge B of the liquid column. Specifically, it is configured to apply a voltage between the nozzle plate 61a. The energizing means 33 functions as a potential applying means in that a potential capable of performing such electrolysis is applied.

  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.

  The state in which the bridge B of the liquid column is formed can be observed with a high-speed camera. From this observation, the timing at which the recording liquid is ejected from the nozzle 61b after the voltage pulse is input to the piezoelectric element of the ink ejecting means by the control unit 40 functioning as the ink ejection controlling means is in units of μsec for each nozzle 61b. It is possible to measure. Further, the timing from when the recording liquid is discharged to the time when the bridge B is formed with the intermediate transfer member 37 and the duration of the bridge can be measured for each nozzle 61b in units of μsec.

  In addition to the reaction formulas (1) and (2), an oxidation-reduction reaction of the electrode itself occurs simultaneously. The reaction that occurs depends on the electrode material, the electrode potential, and the pH of the recording liquid, but can be easily inferred by referring to a potential-pH state diagram (Pourbaix Diagram).

  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. As a result, 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 rotates, and an image is formed on the surface of the transfer sheet S. The transfer paper S on which an image has been formed by this transfer process is guided to the paper discharge tray 25 and stacked on the paper discharge tray 25.

  When the image is transferred to the transfer paper S in this way, the recording liquid containing the aggregation component is transferred to the transfer paper S. Therefore, even when the transfer paper S is plain paper by forming an image with the colorant aggregated by the above-described aggregation action, high image quality can be achieved at high speed while suppressing feathering, beading, and bleeding. Image formation with high 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, since the aggregating action reduces the absorbability of the recording liquid onto the transfer paper S, such a set-off is prevented or suppressed, which 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 can be suppressed or prevented. 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. Even if image formation is repeatedly performed by this cleaning operation, that is, cleaning operation, background stain due to offset is prevented or suppressed, image deterioration and deterioration of the intermediate transfer body 37 are suppressed or prevented, and good image formation over time Can be done.

As described above, by performing image formation using pH change due to electrolysis of the recording liquid, feathering, beading, and bleeding are suppressed, and favorable image formation can be performed.
However, if the recording liquid viscosity increase rate accompanying the pH change of the recording liquid is slow or the printing speed is high and the interval between the recording liquid droplet ejections is short, the adjacent dots may not be It has been found that beading and bleeding can occur when s.
Therefore, in the image forming apparatus 100, the cooling unit 70 further suppresses beading and bleeding.

Hereinafter, the cooling unit 70 will be described. The heating unit 90 will also be described.
As shown in FIG. 6, the cooling unit 70 and the heating unit 90 can be configured as shown in FIGS. In this embodiment, the configuration shown in FIG. 5A is adopted as the configuration of the cooling unit 70 and the heating unit 90.

  As shown in FIG. 6A, the cooling unit 70 is a cooling unit 71 that forms a circulation path for circulating the refrigerant between the intermediate transfer body 37 and the compressor 71, and a compressor 71 as a compression unit that compresses the refrigerant. It has the pipe | tube 72 and the cooling control means implement | achieved as one function of the control part 40. FIG. The compressor 71 is a rotary compressor from the viewpoint that it is small and light and it is easy to configure the cooling unit 70, but any other compressor may be used. The cooling unit 70 cools the entire intermediate transfer member 37 by circulating and supplying the coolant to the support member 37 a of the intermediate transfer member 37 through the cooling pipe 72. In order to cool the support body 37a, the thermal energy of the support body 37a may be transmitted to the cooling pipe 72. Therefore, in this embodiment, the cooling pipe 72 is configured to pass the refrigerant through the support 37a. However, the cooling pipe 72 may be in contact with the support body 37a. The refrigerant heated by receiving heat from the support 37a returns to the compressor 71 through the cooling pipe 72 and is compressed again.

  The heating unit 90 is realized as a function of the control unit 40 and the heat release pipe 91 as a compression heat release pipe that forms a heat conduction unit that guides heat generated when the refrigerant is compressed in the compressor 71 to the transfer roller 38. Heating control means. Since the compressor 71 is also configured to heat the transfer roller 38, the heating unit 90 includes the compressor 71 in addition to the heat release pipe 91. The heating unit 90 supplies the heat of the compressor 71 to the support 38a of the transfer roller 38 through the heat release pipe 91, thereby heating the entire transfer roller 38 and raising the temperature. In order to heat the support body 38a, the thermal energy of the heat release pipe 91 may be transmitted to the support body 38a. Therefore, in this embodiment, the heat release pipe 91 is connected to the support 38a.

  The driving of the compressor 71 is controlled by the control unit 40 functioning as a cooling control unit and a heating control unit as needed to cool the intermediate transfer member 37 and as necessary to heat the transfer roller 38. The compressor 71 functions as a cooling source to form a part of the cooling unit 70 and functions as a heating source to form a part of the heating unit 90, and waste heat is used for heating. Energy saving can be realized.

The configuration of the cooling unit 70 and the heating unit 90 shown in FIG.
As shown in FIG. 5B, the cooling unit 70 includes a support 37a formed of Peltier effect elements, a power source 73 as a drive unit for driving the Peltier effect elements, and a power source 73 and a support that is a Peltier effect element. And a circuit 74 electrically connected to the body 37a. The cooling unit 70 is also realized as a function of the control unit 40, and includes a cooling control unit that drives the power source 73 to control driving of the Peltier effect element constituting the support 37a. The support 37 a that is a Peltier effect element functions as a first Peltier effect element that is a cooling source for cooling the intermediate transfer body 37. The power source 73 functions as a first control unit that controls a decrease in the temperature of the support 37a that functions as the first Peltier effect element by being controlled by the control unit 40 that functions as a cooling control unit.

  The heating unit 90 is a circuit in which a support 38a formed by a Peltier effect element, a power source 73 as a drive unit that drives the Peltier effect element, and a power source 73 and a support 38a that is a Peltier effect element are electrically connected. 92. The heating unit 90 is also realized as a function of the control unit 40, and includes a heating control unit that drives the power source 73 to control the driving of the Peltier effect element constituting the support 38a. The support 38 a that is a Peltier effect element functions as a second Peltier effect element that is a heating source for heating the transfer roller 38. The power source 73 functions as a second control unit that controls a decrease in temperature of the support 38a that functions as a second Peltier effect element by being controlled by the control unit 40 that functions as a heating control unit.

  Each of the Peltier effect element constituting the support 37a and the Peltier effect element constituting the support 38a has the following configuration. That is, these Peltier effect elements have a configuration in which a P-type semiconductor and an N-type semiconductor are brought into contact with each other, and use a Peltier effect that generates or absorbs heat at a contact portion by flowing current through the circuit 74 and the circuit 92. Element. The Peltier effect element that constitutes the support 37a and the Peltier effect element that constitutes the support 38a are not limited to these types. For example, a Peltier effect element that causes a similar phenomenon by replacing a P-type semiconductor with a metal conductor. There may be. The Peltier effect element constituting the support 37a and the Peltier effect element constituting the support 38a may be different types of Peltier effect elements. The Peltier effect element that cools the intermediate transfer body 37 and the Peltier effect element that heats the transfer roller 38 may be embedded in or supported by the support body 37a and the support body 38a instead of the support body 37a and the support body 38a itself. It may be in contact with the body 37a and the support 38a.

  Since the power source 73 is used in common for the cooling unit 70 and the heating unit 90, the power source 73 is driven by the control unit 40 to cool the support 37a and simultaneously heat the support 38a. Therefore, the control unit 40 functions as a heating control unit simultaneously with the cooling control unit. Therefore, simplification of control can be realized with downsizing of the apparatus. However, the first control unit and the second control unit may be separate. In this case, the control unit 40 exhibits the function as the cooling control unit and the function as the heating control unit at different timings. Yes. The cooling control unit and the heating control unit may be configured separately.

  The cooling units 70 and the heating units 90 shown in FIGS. 1A and 1B may be provided in the image forming apparatus 100 at the same time. Further, the cooling unit 70 shown in FIG. 6A and the heating unit 90 shown in FIG. 5B may be used in combination, or the heating unit 90 shown in FIG. You may use combining the cooling part 70 shown by the same figure (b).

The functions relating to image formation of the cooling unit 70 and the heating unit 90 described above will be described.
First, in order to explain the function of the cooling unit 70 relating to image formation, the relationship between the temperature and viscosity of the recording liquid will be described.
FIG. 7 shows an outline of such a relationship before energization, that is, before thickening by electrolysis, and after energization, that is, after thickening by electrolysis. It is assumed that the temperature of the recording liquid does not increase due to energization.
As shown in the figure, the viscosity of the recording liquid is increased by energization. As described above, this increase in viscosity reaches, for example, 1000 times or more.
On the other hand, as is generally known that the solution viscosity increases as the temperature decreases, also in the example shown in the figure, the viscosity of the recording liquid increases as the temperature decreases. The viscosity of the solution is generally increased by 50% by being reduced by about 15 ° C.

Since the general use environment temperature of the image equipment is 20 to 30 ° C., when this is applied to the image forming apparatus 100, the temperature of the recording liquid is about 15 when the temperature of the intermediate transfer body 37 is lowered to 10 ° C. Accordingly, the viscosity of the recording liquid is expected to increase by 50%. The cooling rate of a 10 pL volume droplet is influenced by the composition, but is a rate at which heat transfer is completed in approximately 100 to 500 μsec or less.
The thickening speed of the recording liquid accompanying the decrease in pH is affected by the composition, but is a speed at which thickening is completed in about several milliseconds to several hundred milliseconds or less.

  Based on the above, reference is made to FIG. If the recording liquid at temperature T1 is ejected and landed on the intermediate transfer body 37 and simply electrolyzed to increase the viscosity, the viscosity is increased only by the formation of a polymer network. It takes about several hundreds of milliseconds. The thickening path at this time is a thickening path indicated by a black arrow in FIG. 7, and the viscosity of the recording liquid increases from V1 to V2. As this thickening takes time of several milliseconds to several hundred milliseconds, beading and bleeding can occur as described above.

However, if the intermediate transfer body 37 is cooled, when the recording liquid at the temperature T1 is discharged and landed on the intermediate transfer body 37, the viscosity of the recording liquid is, for example, a thickening path by a white arrow and a halftone dot. It varies depending on the thickening path by the hanging arrow.
That is, first, the temperature of the recording liquid landed on the intermediate transfer member 37 is decreased from T1 to T2, for example, as indicated by a white arrow in a short time of 100 to 500 μsec, so that the viscosity is changed from V1 to V3. To rise.
Thereafter, the viscosity increases from V3 to V4 as indicated by the shaded arrows in a time of about several milliseconds to several hundred milliseconds.
The increase in viscosity from V1 to V3 is smaller than the increase in viscosity from V1 to V2, but the increase in viscosity from V1 to V3 is completed in a very short time. Compared to the case, beading and bleeding are less likely to occur.

  Accordingly, if the recording liquid is discharged in a state where the intermediate transfer body 37 is cooled by the cooling unit 70 and landed on the intermediate transfer body 37 to be electrolyzed and thickened, and image formation is performed, the thickening due to the cooling of the recording liquid is increased. It will assist the thickening of the electrolysis. As a result, measures for beading and bleeding are advanced. Therefore, image formation for obtaining a high-quality image is performed by increasing the quality of printing or the like.

  In the image forming apparatus 100, when the intermediate transfer body 37 is cooled, the time until the liquid columnar recording liquid is cooled from the intermediate transfer body 37 side to the cooling of the nozzle 61b is about 100 μsec. there were. Although the temperature rise of the recording liquid due to energization occurs slightly, the temperature rise is instantly eliminated by such cooling. However, considering the thickening due to the temperature drop, the smaller the temperature rise of the recording liquid due to energization, the better. It is adjusted to be limited.

Next, the curling of the transfer sheet S by the recording liquid will be described in order to explain the function related to image formation of the heating unit 90.
As shown in FIG. 8A, when the recording liquid permeates into the upper surface side of the transfer paper S as shown by the shade, the force that the upper surface side of the transfer paper S tends to expand as shown by the arrow. Act. When only this force is applied, the transfer paper S is curled so that the upper surface side of the transfer paper S is convex as shown in FIG.

  On the other hand, as shown in FIG. 9A, it is assumed that the upper surface side of the transfer paper S is brought into contact with the low temperature body and cooled, and the lower surface side is brought into contact with the high temperature body and heated. In FIGS. 3A to 3D, circles indicate moisture. In the state shown in FIG. 6A, the moisture content of the transfer paper S is uniform from the upper surface side to the lower surface side. However, when subjected to such cooling and heating, as shown in FIG. The moisture on the lower surface side that is heated in the transfer paper S moves to the low temperature body side, that is, the upper surface side. As a result, the moisture content of the transfer sheet S is increased on the upper surface side. As shown in FIG. 5C, when the moisture in the transfer paper S evaporates, the amount of evaporation increases as the water content increases. Therefore, the amount of evaporation in this state is the upper surface side of the transfer paper S. More. Since the transfer paper S shrinks as the amount of evaporation increases, the transfer paper S curls so that the upper surface side is concave as shown in FIG.

  Here, when the low-temperature body is the intermediate transfer body 37 and the high-temperature body is the transfer roller 38, the recording liquid is transferred onto the upper surface of the transfer paper S, and the direction shown in FIG. The direction shown in FIG. 9 in which the transfer sheet S tends to curl due to the evaporation of moisture is reversed. The force for curling the transfer paper S in the opposite directions is that when the transfer roller 38 heated by the heating unit 90 has the lower surface side of the transfer paper S, that is, the side to which the recording liquid is applied, as the surface. It is obtained by heating the back side.

  Therefore, the heating of the transfer roller 38 by the heating unit 90 suppresses or prevents curling of the transfer paper S after passing through the transfer unit 31. In this regard, the heating unit 90 functions as a first curl suppression unit as a curl suppression unit. As apparent from the description of FIG. 9, the cooling unit 70 moves moisture of the transfer sheet S toward the intermediate transfer body 37, thereby contributing to suppressing curling of the transfer sheet S. The cooling unit 70 also functions as second curl suppression means as curl suppression means.

  In the above, the case where the intermediate transfer member and the transfer member are both roller-shaped has been described. However, as shown in FIGS. 10 to 13, either the intermediate transfer member or the transfer member or both of them are endless. It may be in the form of a belt.

The form in which at least one of the intermediate transfer member and the transfer member shown in FIGS. 10 to 13 is an endless belt will be mainly described with respect to portions different from the above-described form shown in FIG.
10 to 13 includes the cooling unit 70 and the heating unit 90 having the configuration illustrated in FIG. 6A, the cooling unit 70 and the heating unit used in each of the configuration examples. 90 may employ the various configurations already described.

  The configuration example shown in FIG. 10 has an endless belt-shaped transfer belt 38 as a transfer member. Accordingly, the heating unit 90 includes a platen member 93 as a heating member that contacts the inner surface of the transfer belt 38 at a position facing the intermediate transfer body 37 so as to form the transfer unit 31. The platen member 93 is heated by the heat release tube 91 to heat the transfer belt 38 that passes through the transfer unit 31. In the case where a Peltier effect element is used for the heating unit 90, for example, the platen member 93 may be a Peltier effect element.

  In the configuration example shown in FIG. 11, the intermediate transfer member has an endless belt-like conductive intermediate transfer member 37. Accordingly, the cooling unit 70 includes a roller 75 as a cooling member around which the intermediate transfer body 37 is wound at a position facing the heads 61Y, 61M, 61C, 61BK. The roller 75 is made of a metal, alloy, or the like having high conductivity and heat conductivity. The roller 75 is cooled by the refrigerant passing through the cooling pipe 72 and passes the transfer unit 31 in a state where the transfer belt 38 is cooled. The energizing unit 33 applies a voltage to the roller 75 so that a potential difference is formed between the intermediate transfer member 37 and the heads 61Y, 61M, 61C, 61BK. In the case where a Peltier effect element is used for the cooling unit 70, for example, the roller 75 may be a Peltier effect element. The intermediate transfer member 37 can take various configurations such as a configuration in which a conductive rubber layer is formed on a metal endless belt such as nickel or stainless steel.

  The configuration example shown in FIG. 12 is a combination of the configuration example shown in FIG. 10 and the configuration example shown in FIG. That is, the configuration example shown in FIG. 12 has an endless belt-like conductive intermediate transfer member 37 as an intermediate transfer member, and an endless belt-like transfer belt 38 as a transfer member. Accordingly, the cooling unit 70 includes a roller 75 as a cooling member around which the intermediate transfer body 37 is wound at a position facing the heads 61Y, 61M, 61C, 61BK. In addition, the heating unit 90 includes a platen member 93 as a heating member that is in contact with the inner surface of the transfer belt 38 at a position facing the intermediate transfer member 37 so as to form the transfer unit 31. For the roller 75, the matters described in the configuration example shown in FIG. 11 are used, and for the platen member 93, the items described in the configuration example shown in FIG.

  The configuration example shown in FIG. 13 has an endless belt-like conductive intermediate transfer member 37 as an intermediate transfer member. Accordingly, the cooling unit 70 has a platen member 76 as a cooling member that contacts the inner surface of the intermediate transfer body 37 at a position facing the heads 61Y, 61M, 61C, 61BK. The platen member 76 is formed of a metal, an alloy, or the like having high conductivity and heat conductivity. The platen member 76 is cooled by the refrigerant passing through the cooling pipe 72, and passes through the transfer unit 31 with the transfer belt 38 being cooled. The energizing unit 33 applies a voltage to the platen member 76 so that a potential difference is formed between the intermediate transfer member 37 and the heads 61Y, 61M, 61C, 61BK. In addition, when using a Peltier effect element for the cooling unit 70, for example, the platen member 76 may be a Peltier effect element. The configuration using the intermediate transfer member 37 and the platen member 76 may be applied to the above-described configuration examples.

In this configuration example, the intermediate transfer body 37 is formed in a belt shape so that the heads 61Y, 61M, 61C, and 61BK are arranged in parallel, and the degree of freedom in arrangement of the heads 61Y, 61M, 61C, and 61 is increased. Gaining benefits. Another advantage of the intermediate transfer body 37 having a belt shape is that it is possible to increase the transfer nip width.
However, if the intermediate transfer member 37 is in the form of a drum, it is not easy to process the belt-like intermediate transfer member 37 into a shape having no end portions, and flapping may occur during driving, and a plurality of winding rollers are required. There is an advantage that there is no such situation. Accordingly, whether the intermediate transfer member 37 is in the form of a drum or a belt is appropriately selected by comparing and examining various matters.

Using the image forming apparatus considering the above conditions, how the image formation is performed by the following experiment,
(1) Beading (2) Bleeding (3) Each item of curl of transfer paper after image formation was examined.
Examples 1 and 2 and a comparative example were used for comparison of these items.

<Image forming conditions>
The image forming apparatus used in the experiment is an image forming apparatus obtained by remodeling an ink jet printer GX-5000 (manufactured by Ricoh) having the same configuration as that of the image forming apparatus 100.
The recording liquid is a cyan or yellow recording liquid whose composition and weight ratio are adjusted as described below.
The recording liquids of the respective colors were filled in the heads equivalent to the heads 61C and 61Y, and were discharged so that the liquid amount on the intermediate transfer member 37 was 400 mg / A4, thereby forming a green full-color image.
The gap between the head 61C, the head 61Y and the intermediate transfer member 37 was 100 μm.
A voltage of 100 V was applied between the head 61C and the intermediate transfer member 37, and between the head 61Y and the intermediate transfer member 37.
The environmental temperature was 25 ° C.
The above items were evaluated when the printing speed was 50 mm / sec and 300 mm / sec in each of the examples and comparative examples.

The recording liquid is as follows.
<Cyan recording liquid>
-Sulfonic acid group-bonded cyan pigment dispersion (CAB-O-JET-250C, solid content 10% by mass, manufactured by Cabot): 40.0% by mass
・ Ethylene glycol: 4.0% by mass
Triethylene glycol: 14.0% by mass
Propylene glycol monobutyl ether: 0.9% by mass
・ Hydrophobically modified polyether urethane: 0.575% by mass
・ Potassium myristate: 0.38% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount <yellow recording liquid>
-Sulfonic acid group-bonded yellow pigment dispersion (CAB-O-JET-270Y, solid content 10% by mass, manufactured by Cabot): 40.0% by mass
・ Triethylene glycol: 15.0 mass%
・ Glycerin: 25.0% by mass
Propylene glycol monobutyl ether: 0.9% by mass
Hydrophobic modified polyether urethane (corresponding to ABA type amphiphilic polymer: manufactured by ADEKA): 0.575% by mass
-Potassium myristate (corresponding to an anionic surfactant): 0.38% by mass
・ Sodium dehydroacetate: 0.1% by mass
・ Distilled water: remaining amount

[Example 1]
Using the cooling unit and heating unit similar to the cooling unit 70 and heating unit 90 shown in FIG. 6A, the compressor is adjusted so that the surface temperature of the intermediate transfer member becomes 15 ° C., and the discharge at this time The transfer roller was heated with heat.
[Example 2]
Using the cooling unit and the heating unit similar to the cooling unit 70 and the heating unit 90 shown in FIG. 6A, the surface temperature of the intermediate transfer member and the transfer roller is 15 ° C. and 30 ° C. Adjusted the control.

[Comparative example]
The same conditions as in Example 1 were used except that the surface temperature of the intermediate transfer member and the transfer roller was determined by the environmental temperature using an image forming apparatus having a configuration excluding the cooling unit and heating unit from the configuration of Example 1. .

<Criteria>
The criteria for the above items (1) to (3) are as follows.
That is, “good” was evaluated as “good”, “bad” was evaluated as “poor”, and an intermediate between them was evaluated as “△”.

<Evaluation results>
The evaluation results for Examples 1 and 2 and Comparative Example are summarized as shown in Table 1 below.

  From the table, any of the above items (1) to (3) may be used according to the image forming method according to the present invention, in which the intermediate transfer member is cooled and the transfer member is heated to form an image. It was confirmed that the result was obtained. In the comparative example, bleeding deteriorated when the printing speed was high. This indicates that the thickening of the recording liquid cannot catch up when the printing speed is increased only by electrolysis of the recording liquid.

  Here, the control unit 40 includes, in the memory, the heads 61Y, 61M, 61C, 61BK provided with the nozzles 61b for discharging the conductive recording liquid containing water, and the conductivity discharged by the heads 61Y, 61M, 61C, 61BK. An intermediate transfer body 37 to which recording liquid is applied and at least a part of the surface is conductive, and the conductive recording liquid discharged from the heads 61Y, 61M, 61C, and 61BK are transferred to the heads 61Y, 61M, 61C, and 61BK. Energization, which is a voltage application means for applying a voltage between the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK in order to pass a current through the conductive recording liquid in this state with the body 37 being bridged. Using the means 33 and the cooling unit 70 which is a cooling means for cooling the intermediate transfer member 37, the medium is discharged from the heads 61Y, 61M, 61C and 61BK. It was granted to Utsushitai 37 conductive recording fluid, and stores the image forming program for executing an image forming method for thickened by cooling by the intermediate transfer member 37 which is cooled by the cooling unit 70.

  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 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.
Further, the transfer medium is not limited to a recording medium such as a sheet as long as the conductive recording liquid is transferred from the intermediate transfer body. For example, an image carrier such as an intermediate transfer body used when double transfer is performed. It may be.

  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 another type of image forming apparatus. That is, the image forming apparatus to which the present invention is applied may be a shuttle type with respect to the head. The image forming apparatus to which the present invention is applied may be a copier, a single facsimile, or a complex machine such as these, or a complex machine such as a monochrome machine related thereto. In addition, the image forming apparatus to which the present invention is applied may be an image forming apparatus used for forming an electric circuit or an image forming apparatus used for forming a predetermined image in the biotechnology field.

The pigment in the conductive recording liquid may be dispersed by a cationic dispersant, and may aggregate through hydroxide ions generated on the surface of the intermediate transfer member functioning as a cathode.
The number of heads is increased or decreased according to the application of the image forming apparatus, and may be plural or one.

  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 unit 37 Intermediate transfer member 37a First Peltier effect element 38 Transfer member 38a Second Peltier effect element 61Y, 61M, 61C, 61BK Head 70 Cooling unit 71 Compression unit 72 Circulation path 73 First control unit, First Control unit 2 90 Heating means 91 Heat conduction unit 100 Image forming apparatus S Transfer object

JP 2008-62397 A Japanese Patent No. 4908117 Japanese Patent Laid-Open No. 11-188858 JP 2009-184153 A JP 2008-168508 A JP 2010-188665 A JP 2011-189706 A JP 2012-168508 A JP 2012-91342 A JP 2012-91337 A JP 2000-141621 A JP 2000-141710 A Japanese Patent Laid-Open No. 8-04137 International Publication WO94 / 01283 Japanese Patent No. 3177985

Claims (7)

A head having a nozzle for discharging a conductive recording liquid containing water;
The conductive recording liquid discharged by the head is applied, and at least a part of the surface is a conductive intermediate transfer member,
The conductive recording liquid ejected from the head bridges between the head and the intermediate transfer body, and in order to pass a current through the conductive recording liquid in this state, the intermediate transfer body and the head Voltage applying means for applying a voltage;
An image forming apparatus having cooling means for cooling the intermediate transfer member; The image forming apparatus according to claim 1.
The image forming apparatus, wherein the cooling unit includes a compression unit that compresses a refrigerant, and a circulation path that circulates the refrigerant between the intermediate transfer member and the compression unit. The image forming apparatus according to claim 1 or 2,
The image forming apparatus, wherein the cooling unit includes a first Peltier effect element for cooling the intermediate transfer member, and a first control unit for controlling the first Peltier effect element. The image forming apparatus according to any one of claims 1 to 3,
A transfer member disposed at a position facing the intermediate transfer member, and transferring the conductive recording liquid applied on the intermediate transfer member to the transfer member by passing the transfer member between the intermediate transfer member and the intermediate transfer member; ,
An image forming apparatus having a heating means for heating the transfer member. The image forming apparatus according to claim 4, wherein the image forming apparatus is dependent on claim 2.
The image forming apparatus according to claim 1, wherein the heating unit includes a heat conduction unit that guides heat generated when the refrigerant is compressed in the compression unit to the transfer member. The image forming apparatus according to claim 4 or 5, wherein:
The image forming apparatus, wherein the heating unit includes a second Peltier effect element for heating the transfer member, and a second control unit for controlling the second Peltier effect element. A head having a nozzle for discharging a conductive recording liquid containing water;
The conductive recording liquid discharged by the head is applied, and at least a part of the surface is a conductive intermediate transfer member,
The conductive recording liquid ejected from the head bridges between the head and the intermediate transfer body, and in order to pass a current through the conductive recording liquid in this state, the intermediate transfer body and the head Voltage applying means for applying a voltage;
Using a cooling means for cooling the intermediate transfer member,
An image forming method in which the conductive recording liquid discharged from the head and applied to the intermediate transfer member is thickened by being cooled by the intermediate transfer member cooled by the cooling unit.

Images