JP2014083773A - Elastic member, intermediate transcript and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elastic member having such a uniform conductivity as to allow good electrolysis of a conductive recording liquid, an intermediate transcript having the elastic member on the surface and an ink-jet image formation apparatus having the intermediate transcript.SOLUTION: A conductive elastic member 51 is used on the surface of an intermediate transcript which is to be applied with a voltage for electrolyzing a conductive recording liquid discharged from a head and bridging between the head and the intermediate transcript and includes a front layer 52 impacted with the conductive recording liquid discharged from the head and a lower layer 53 supporting the front layer 52. The front layer 52 has a resistivity of 50 Ωcm or lower, measured at intervals of 2 mm or shorter by using a resistance measuring member 54 whose part to be brought into contact with the front layer 52 has a diameter of 40 μm or smaller, and the lower layer 53 has a resistivity higher than 50 Ωcm and equal to or lower than 1,000 Ωcm.

Description

  The present invention relates to a conductive elastic member used on the surface of an intermediate transfer member to which a conductive recording liquid such as ink is applied from a head, such an intermediate transfer member having the elastic member on the surface, and an ink jet having the intermediate transfer member. The present invention relates to a type image forming apparatus.

  Conventionally, image formation by an inkjet recording method such as an ink jet printer having a head for ejecting a recording liquid such as ink from a nozzle by a movable actuator method represented by a piezo method, a heating film boiling method represented by a thermal method, etc. Devices are known (see, for example, [Patent Document 1] and [Patent Document 2]).

  In such an image forming apparatus, in the configuration in which the recording liquid is directly discharged from the head to the recording material such as recording paper, the head and the recording material are close to each other, so that paper dust and dust adhering to the recording material Etc. are likely to adhere to the nozzle. When paper dust or the like adheres to the nozzle, the flying direction of droplets ejected from the nozzle is disturbed, or the nozzle is blocked, resulting in a reduction in image quality and reliability.

As a measure for avoiding such a problem, it is general to use a recording liquid having a small viscosity and containing a large amount of moisture, giving priority to ejection stability from the nozzles.
However, such a recording liquid has a problem that bleeding tends to occur when the recording liquid lands on a recording material.

  Therefore, as a technology to prevent paper dust, dust, etc. adhering to the recording material from adhering to the nozzle, an intermediate transfer member carrying the recording liquid discharged from the head is provided, and an image is formed on the intermediate transfer member. After that, an image forming apparatus for transferring to a recording material has been proposed (see, for example, [Patent Document 1] and [Patent Document 2]).

  Among these image forming apparatuses, there has been proposed an image forming apparatus in which a conductive recording liquid in which a pigment is dispersed in a solvent containing water is discharged from the head, and the recording liquid discharged from the head is electrolyzed. (For example, see [Patent Document 1]). Such electrolysis is performed by applying a voltage between the head and the intermediate transfer member in a state where the recording liquid discharged from the head bridges between the head and the intermediate transfer member. In such an image forming apparatus, there is an advantage that bleeding of the recording liquid on the recording material is suppressed by electrolysis of the recording liquid.

Note that an image forming apparatus provided with an intermediate transfer member is also known in the field of image forming apparatuses that use toner to form an image (see, for example, [Patent Document 3] and [Patent Document 4]). .
In general, an intermediate transfer member provided in an image forming apparatus is required to have a so-called transfer property that allows a supported image to be transferred onto a recording material, so that the surface of the intermediate transfer member is elastic. It is often formed of a member having it.

  In addition to transferability, the intermediate transfer member provided in the above-described image forming apparatus that performs electrolysis is required to have appropriate conductivity in order to perform electrolysis of the recording liquid satisfactorily. As a technique relating to these transfer properties and conductivity, an intermediate transfer member using a conductive rubber in which a conductive material is mixed into a rubber material is known (for example, see [Patent Document 1]).

  However, since the recording liquid is ejected from the head in the form of droplets and lands on the surface of the intermediate transfer body, the intermediate transfer body provided in the image forming apparatus that performs the above-described electrolysis further has a conductive property on the surface. The uniformity is required in the pixel region.

  The present invention relates to an elastic member having a conductivity that is uniform enough to cause electrolysis of a conductive recording liquid, an intermediate transfer member having the elastic member on the surface, and an inkjet image forming apparatus having the intermediate transfer member. The purpose is to provide.

  In order to achieve the above object, the present invention is used on the surface of an intermediate transfer member to which a voltage for electrolyzing a conductive recording liquid discharged from the head and bridging between the head and the intermediate transfer member is applied. A conductive elastic member having a surface layer on which the conductive recording liquid discharged from the head lands, and a lower layer supporting the surface layer, and the surface layer has a diameter of a portion of 40 μm in contact with the surface layer. The resistivity measured at intervals of 2 mm or less using the following resistance measurement members is 50 Ωcm or less, and the lower layer is in an elastic member having a resistivity of more than 50 Ωcm and 1000 Ωcm or less.

  The present invention is a conductive elastic member used on the surface of an intermediate transfer member to which a voltage for electrolyzing a conductive recording liquid discharged from the head and bridging between the head and the intermediate transfer member is applied. A resistance measuring member having a surface layer on which the conductive recording liquid discharged from the head lands and a lower layer supporting the surface layer, wherein the surface layer has a diameter of a portion of 40 μm or less in contact with the surface layer. The resistivity measured at intervals of 2 mm or less is 50 Ωcm or less, and the lower layer is in an elastic member having a resistivity greater than 50 Ωcm and 1000 Ωcm or less, so that electrolysis of the electroconductive recording liquid is satisfactorily caused. An elastic member that has uniform conductivity and contributes to good image formation in which bleeding of the recording liquid is suppressed can be provided.

1 is a schematic front view according to an embodiment of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic diagram illustrating a state in which conductive recording liquid is applied from a head to an intermediate transfer member in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a conceptual diagram illustrating an example of a configuration of an elastic member forming the intermediate transfer member illustrated in FIG. 1 and an aspect in which the resistivity of the surface layer of the elastic member is measured using a resistance measurement member. FIG. 2 is a conceptual diagram illustrating a state where pigments in a conductive recording liquid discharged from a head in the image forming apparatus illustrated in FIG. 1 are aggregated via protons. FIG. 2 is a conceptual diagram showing a state of a liquid column by a conductive recording liquid formed between a cathode and an anode in the image forming apparatus shown in FIG. FIG. 6 is a schematic perspective view showing an image formed on the surface of an intermediate transfer member in an experiment for confirming the effect of application of the present invention.

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

  The image forming apparatus 100 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, cardboard, cardboard, and envelopes. It is. The image forming apparatus 100 is a 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. It may be an image forming apparatus.

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

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

  The heads 61Y, 61M, 61C, and 61BK are ink ejection devices that are recording liquid ejection devices as ejection devices for forming yellow (Y), magenta (M), cyan (C), and black (BK) images, respectively. 60Y, 60M, 60C, 60BK are provided. 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. Thereby, 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.

  When the recording liquid, which is a conductive recording liquid, is ejected or applied to the intermediate transfer body 37 by the heads 61Y, 61M, 61C, 61BK, the image areas of yellow, magenta, cyan, and black are placed at the same position on the intermediate transfer body 37. It is done to overlap. Therefore, the application of the recording liquid of each color to the intermediate transfer body 37 for forming the image area of each color is performed while shifting the timing from the upstream side toward the downstream side in the A1 direction. Such control is performed by a control unit described later.

As shown in FIG. 1, the image forming apparatus 100 includes ink ejection devices 60Y, 60M, 60C, and 60BK provided with heads 61Y, 61M, 61C, and 61BK, respectively.
The image forming apparatus 100 also includes a transport unit 10 as a paper transport unit that includes the intermediate transfer body 37 and transports the transfer paper S as the intermediate transfer body 37 rotates in the A1 direction.
The image forming apparatus 100 also includes a paper feeding unit 20 that can stack a large number of transfer papers S and feeds only the uppermost transfer paper S among the stacked transfer papers S to the transport unit 10. .
The image forming apparatus 100 also includes a paper discharge tray 25 serving as a paper discharge tray on which a large number of image-formed, in other words, printed transfer paper S conveyed by the conveyance unit 10 can be stacked.

  The image forming apparatus 100 also includes an energizing unit 33 as a voltage applying unit that energizes the liquid column of the recording liquid immediately after being ejected from the heads 61Y, 61M, 61C, and 61BK, as shown in FIG. ing.

As shown in FIG. 1, the image forming apparatus 100 also removes the recording liquid remaining on the intermediate transfer body 37 from the intermediate transfer body 37 after the recording liquid is transferred to the transfer paper S. A cleaning unit 34 is provided as a cleaning unit for cleaning.
The image forming apparatus 100 is also illustrated as a control unit including a carriage 50 as a head support that integrally supports the heads 61Y, 61M, 61C, and 61BK, a CPU that controls the overall operation of the image forming apparatus 100, a memory, and the like. And a control unit that does not.

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 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. A plate 39 is provided.
The transport unit 10 also has a motor or the like as driving means (not shown) that rotationally drives the intermediate transfer member 37 in the A1 direction.
As described above, the image forming apparatus 100 is an indirect image forming apparatus that indirectly forms an image on the transfer sheet S using the intermediate transfer body 37.

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

  As shown in FIG. 2, the intermediate transfer body 37 has an aluminum support 37a that is a conductive substrate, and a surface layer 37b that is a transfer material formed on the support 37a. The surface layer 37 b is an elastic layer that is an elastic material provided on the surface of the intermediate transfer member 37.

  The material of the support 37a is not limited to aluminum, and may be formed of a metal such as an aluminum alloy, copper, or stainless steel as long as it has mechanical strength. The support 37a may be an insulating base. When the support is insulative, a conductive member to which voltage is applied, for example, a conductive roller, is applied to the surface or end surface of the surface layer 37b so that the recording liquid described later is electrolyzed. Make contact.

As shown in FIG. 3, the surface layer 37 b is formed by a conductive elastic member 51.
The elastic member 51 has a surface layer 52 that constitutes the surface of the intermediate transfer member 37 in a state in which the elastic member 51 is attached to the support 37a, and the recording liquid is landed to carry the recording liquid.
The elastic member 51 has a lower layer 53 that comes into contact with the support 37a and supports the surface layer 52 when the elastic member 51 is attached to the support 37a.

  The surface layer 52 gives elasticity to the surface layer 52 itself, the elastic member 51, and the surface layer 37b, and the base layer 52 functions as an elastic layer on the support 37a to ensure transferability. As an example, silicone rubber is used. The base material of the surface layer 52 is not limited to silicone rubber, and may be any elastic material having low surface energy and high followability to the transfer paper S for the advantage of high releasability of the recording liquid. Therefore, as the base material of the surface layer 52, for example, fluoro rubber, acrylic resin, or acrylic rubber may be used.

  The surface layer 52 gives conductivity to the surface layer 52 itself, the elastic member 51, and the surface layer 37b to form a conductive layer, and contains carbon nanotubes as a conductive agent in order to perform electrolysis of the recording liquid described later. . The resistivity of the surface layer 52 is 50 Ωcm or less. The carbon nanotubes are included in the surface layer 52 in a dispersed state. The carbon nanotube may have a single-layer structure or a multilayer structure.

  The surface layer 52 contains, in addition to carbon nanotubes, a material that improves the releasability in order to obtain the advantage that the recording liquid has high peelability. Since carbon nanotubes improve conductivity in a small amount, it is possible to increase the proportion of this material, or in the case where the substrate itself is an effective material for improving the releasability. It has the advantage of being secured. Examples of the material that improves releasability include a filler. From the viewpoint of improving conductivity, a conductive filler is more desirable.

  The hardness of the surface layer 52 is adjusted to 80 ° or less in the JISA standard. By setting it as such comparatively high hardness, it becomes possible to make the surface smooth and to improve transferability. In addition, the surface layer 52 having a relatively high hardness ensures followability to the transfer paper S and improves transferability when the surface layer 37b is formed together with the lower layer 53 having a low hardness as will be described later. It has been confirmed that even when the hardness of only the surface layer 52 is low, the followability to the transfer paper S and the nip time are insufficient.

  The thickness of the surface layer 52 is 100 μm or less, and more preferably 5 μm to 30 μm. Since the thickness of the surface layer 52 is set to such a thickness, the use amount of the relatively expensive carbon nanotube is suppressed, and the costs of the surface layer 52, the elastic member 51, the intermediate transfer body 37, and the image forming apparatus 100 are suppressed. ing. Further, by using such a thin layer, the followability of the transfer sheet S is ensured in a state where it is combined with the lower layer 53 having a lower hardness than the surface layer 52 as described later.

The receding contact angle of water on the surface layer 52 is preferably greater than 60 °, and more preferably greater than 80 °. This is because when the receding contact angle of water on the surface layer 52 is 60 ° or less, transferability may be deteriorated.
The arithmetic average roughness Ra of the surface layer 52 is preferably 1 or less. This is because if the arithmetic average roughness Ra of the surface layer 52 exceeds 1, transferability may be deteriorated.

  The lower layer 53 provides elasticity to the lower layer 53 itself, the elastic member 51, and the surface layer 37b, and the lower layer 53 itself, the elastic member 51, and the surface layer 37b function as an elastic layer on the support 37a to ensure transferability. As an example, silicone rubber is used. The base material of the lower layer 53 is not limited to silicone rubber, and may be any elastic material that is effective for ensuring transferability and has high followability to the transfer paper S. Therefore, as the base material of the lower layer 53, for example, urethane rubber, fluorine rubber, or nitrile butadiene rubber may be used.

  In the present embodiment, the lower layer 53 is formed only by such a base material. However, like the surface layer 52, the lower layer 53 may contain a carbon nanotube or other conductive agent. The resistivity of the lower layer 53 is set to 1000 Ωcm or less for the reason described later in order to give conductivity to the surface layer 37b to form a conductive layer so that the recording liquid described later is electrolyzed. The lower limit of the resistivity of the lower layer 53 is preferably not too low for cost reduction, and is preferably larger than the resistivity of the surface layer 52, that is, larger than 50 Ωcm. This cost reduction will be described in detail later.

The hardness of the lower layer 53 is lower than the hardness of the surface layer 52 and is adjusted to 60 ° or less in the JISA standard. This is because when the surface layer 37b is configured together with the surface layer 52 having the above-described hardness, the followability to the transfer paper S is ensured and transferability is improved.
The lower layer 53 may have a multilayer structure instead of a single layer structure. Even when the lower layer 53 has a multilayer structure, the resistivity as a whole is greater than 50 Ωcm and equal to or less than 1000 Ωcm. Further, even when the lower layer 53 has a multilayer structure, the overall hardness is adjusted to 60 ° or less in the JISA standard in order to improve transferability.

The remainder of the elastic member 51 and the surface layer 37b will be described in detail later.
The intermediate transfer member 37 is not a drum, but an endless belt, or a sheet if possible, provided that the elastic member 51 described above and described later is provided as the surface layer 37b. Also good. The support 37a can be omitted as appropriate. For example, the endless belt-shaped intermediate transfer member can be constituted by only the elastic member 51.

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 rotates the paper feeding roller 22 counterclockwise in the drawing so as to feed the transfer paper S so as to match the recording liquid ejection timing in the heads 61Y, 61M, 61C, 61BK. And a motor as a driving means.

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

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

  The image forming apparatus 100 may be a shuttle type in which the heads 61Y, 61M, 61C, and 61BK move in the main scanning direction, that is, the direction perpendicular to the A1 direction. Further, an intermediate transfer member 37 and a transfer unit 64 may be provided for each of the heads 61Y, 61M, 61C, and 61BK, that is, for each color.

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, and 60BK also supply the recording liquid stored in the ink cartridges 81Y, 81M, 81C, and 81BK to the heads 61Y, 61M, 61C, and 61BK by pressure. It has a pump (not shown) as a pump.
The ink ejection devices 60Y, 60M, 60C, and 60BK also have distributor tanks (not shown) that distribute the recording liquid supplied from the ink cartridges 81Y, 81M, 81C, and 81BK by the pumps to the heads 61Y, 61M, 61C, and 61BK. Have.

The ink ejection devices 60Y, 60M, 60C, and 60BK are also inks (not shown) as ink amount detection means that are recording liquid amount detection means for detecting the recording liquid amount in order to detect a shortage of the recording liquid amount in the distributor tank. It has a quantity detection sensor.
The ink ejection devices 60Y, 60M, 60C, and 60BK also have a pipe (not shown) that forms a recording liquid feeding path between the ink cartridges 81Y, 81M, 81C, and 81BK and the distributor tank together with a pump. .
The ink ejection devices 60Y, 60M, 60C, and 60BK also have pipes (not shown) that form recording liquid feeding paths between the distributor tank and the heads 61Y, 61M, 61C, and 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 operation of the pump is controlled by the control unit. Specifically, the pump is driven until the shortage is no longer detected on condition that the shortage of recording liquid in the distributor tank is detected by the ink amount detection sensor. In this way, the pump supplies the recording liquid in the ink cartridges 81Y, 81M, 81C, and 81BK to a distributor tank that is a distributor that is a supply tank as an ink supply section that is a recording liquid supply section.
In this respect, the control unit functions as an ink supply control unit that is a recording liquid supply control unit.
The control unit is configured to control the driving of the image forming apparatus 100 even when not specifically described.

  The recording liquid contains at least a pigment that is a colorant corresponding to yellow, magenta, cyan, and black, an anionic dispersant that is a dispersant for the pigment, and a solvent that contains water. Due to the pigment and the dispersant, the ink component of the recording liquid has an anionic group. In the recording liquid, the pigment is dispersed in the solvent by an anionic component dispersant.

  The solvent contains water from the viewpoint of safety and the conductivity from the viewpoint of causing electrolysis to be described later, and the recording liquid is a water-soluble recording liquid that is a conductive ink and a water-soluble ink. The recording liquid is desirably alkaline from the viewpoint of storage stability.

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

  Although it does not specifically limit as an anionic dispersing agent, Fatty acid salt, alkyl sulfate ester salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfo succinate, alkyl phosphate ester salt, naphthalene sulfonate formalin (registered trademark) Examples include condensates and polyoxyethylene alkyl sulfates, and two or more of them may be used in combination.

  The recording liquid is an anion obtained by neutralizing a resin having an acidic group such as a carboxyl group, a sulfonic acid group or a phosphonic acid group with a base such as sodium hydroxide or potassium hydroxide from the viewpoint of transferability. It is preferable to further include a resin having a functional group. Although it does not specifically limit as resin which has an acidic group, Polyacrylic acid, polyamide, polyvinyl alcohol, etc. are mentioned, You may use these 2 or more types together. The content of the resin having an anionic group in the recording liquid is usually 0.5 to 10% by mass, and preferably 0.5 to 5% by mass.

  The recording liquid may further contain a solvent soluble in water. Solvents that are soluble in water are not particularly limited, but are polyvalent such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, and glycerin. Alcohols: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, ethylene oxide adduct of diglycerin Polyhydric alcohol derivatives such as pyrrolidone, N-methyl-2-pyrrolidone, Nitrogen-containing solvents such as hexylpyrrolidone and triethanolamine; alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol; sulfur-containing solvents such as thiodiethanol, thiodiglycerol, sulfolane, and dimethyl sulfoxide; propylene carbonate, ethylene carbonate, and the like These may be used in combination of two or more.

As shown in FIG. 2, each of the heads 61Y, 61M, 61C, 61BK includes a conductive nozzle plate 61a disposed on the recording liquid discharge side facing downward in the drawing and a nozzle 61b formed on the nozzle plate 61a. And have.
Each of the heads 61Y, 61M, 61C, 61BK is also provided with an ink chamber 61c supplied with a recording liquid from a distributor tank and filled with the recording liquid, and an ink discharge means (not shown) for discharging the recording liquid in the ink chamber 61c from the nozzle 61b. have.

  The nozzle plate 61a includes a number of nozzles 61b, and each head 61Y, 61M, 61C, 61BK has one nozzle 61b. That is, each nozzle plate 61a is shared by the plurality of heads 61Y, the plurality of heads 61M, the plurality of heads 61C, and the plurality of heads 61BK. The nozzle 61b, the ink chamber 61c, and the ink ejecting means constitute a set of the heads 61Y, 61M, 61C, and 61BK, respectively, but only one of them is shown in the drawing. .

  The entire nozzle plate 61a is conductive. However, the present invention is not limited to this, and the nozzle plate 61a may be an insulating member in which only the surface on the ink chamber 61c side is subjected to conductive treatment, and is disposed on the ink chamber 61c side. You may comprise with an electroconductive member and the insulating member arrange | positioned at the intermediate transfer body 37 side. The nozzle plate 61a is also composed of an insulating member disposed on the ink chamber 61c side and a conductive member disposed on the intermediate transfer member 37 side in order to suppress generation of bubbles during electrolysis, which will be described later. Alternatively, the ink chamber 61c side may be insulated for the same reason. The nozzle plate 61a may also be a laminate of an insulating layer and a conductive layer.

  Since the conductive portion of the nozzle plate 61a is provided as a cathode as will be described later, it does not have to be made of a material having resistance to metal elution, and if it is made of a highly conductive material such as metal or carbon. Good.

  The nozzle plate 61 a is set so that the gap with the intermediate transfer member 37 is 50 to 200 μm. If the gap is less than 50 μm, it may be difficult to maintain the gap between the intermediate transfer member 37, which is a rotating body, and the nozzle plate 61a. If the gap exceeds 200 μm, the liquid injection described later may be performed. This is because it may be difficult to form a bridge.

  The ink ejecting means has a piezoelectric element as an actuator for ejecting the recording liquid from the nozzle 61b as droplets and landing on the transfer paper S, and the recording liquid is ejected from the nozzle 61b in accordance with a voltage pulse applied to the piezoelectric element. It is designed to discharge. The actuator of the ink discharge means may be a movable actuator of another method that is a shape deformation element method such as a piezo method, or the recording liquid is discharged from the nozzle 61b by a heater method such as a thermal method. Also good.

  The energization means 33 is configured to apply a voltage to the recording liquid while the recording liquid discharged from the heads 61Y, 61M, 61C, 61BK temporarily bridges between the heads 61Y, 61M, 61C, 61BK and the intermediate transfer body 37. Apply. As a result, the energization means 33 causes the electrode oxidation reaction or electrode reduction to occur inside the recording liquid in the liquid column state so that a potential difference is formed between the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK. Energization including the current component resulting from the reaction is performed. Therefore, the recording liquid in such a state is promoted to agglomerate the contained colorant as described above.

Therefore, as shown in FIG. 2, the energizing means 33 includes a power source 33a and an electric circuit (not shown) in which the power source 33a is connected between the support 37a and the nozzle plate 61a.
The energization means 33 also includes voltage application control means that is realized as part of the function of the control unit and controls the voltage application timing, application time, and magnitude of the voltage applied by the power source 33a. The control unit as the voltage application control unit also functions as a voltage changing unit that changes the voltage of the power source 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.

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

The material constituting the cleaning blade is not particularly limited, and examples thereof include elastic bodies such as silicone rubber, urethane rubber, fluorine rubber, and nitrile butadiene rubber.
The cleaning unit 34 may include a cleaning roller as a cleaning member instead of or together with the cleaning blade.

  In the image forming apparatus 100 having such a configuration, the intermediate transfer member 37 rotates in the A1 direction while facing the heads 61Y, 61M, 61C, and 61BK in response to the input of a predetermined signal indicating the start of image formation. In this process, yellow, magenta, cyan, and black recording liquids are transferred from the heads 61Y, 61M, 61C, and 61BK so that the image areas of each color of yellow, magenta, cyan, and black overlap with the same position on the intermediate transfer member 37. The discharged image is temporarily supported on the intermediate transfer member 37. This discharge is performed in such a manner that the discharge is sequentially performed while shifting the timing from the upstream side toward the downstream side in the A1 direction.

At the time of this ejection, the energization means 33 is driven by the control unit as the voltage application control means, and a voltage is applied between the support 37a and the nozzle plate 61a from the power source 33a.
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. By this movement, a bridge of a liquid column made of a recording liquid is temporarily formed between the nozzle 61b and the intermediate transfer member 37, more specifically, the surface layer 37b, more specifically, the surface layer 52. 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, by applying voltage from the energizing means 33, the following electrode reaction occurs between the nozzle plate 61a serving as the cathode and the intermediate transfer member 37 serving as the anode, more specifically to the surface layer 37b and more specifically to the surface layer 52. Occurs.

^{_{Cathode: 4H 2 O + 4e - →}} 2H 2 + 4OH - ··· reaction formula (1)
_{^{Anode: 2H 2 O → 4H + +}} O 2 + 4e - ··· reaction formula (2)
Thus, the water contained in the bridge of the liquid column of the recording liquid is electrolyzed.

  As a result, the water contained in the bridge of the liquid column of the recording liquid is oxidized and protonated on the surface of the intermediate transfer member 37 functioning as the anode, more specifically on the surface of the surface layer 37b and more specifically on the surface of the surface layer 52. (H +) is generated. Therefore, as shown in FIG. 4, the pigment P dispersed by the anionic dispersant D aggregates via protons.

  Therefore, the occurrence of blur 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 changing 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, in other words the conductivity of the bridge B of the liquid column The resistance R _B is almost determined by the concentration of ions contained in the recording 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 and the resin having an anionic group are aggregated. That is, at the moment when such a bridge is formed, ions that cause aggregating action of the pigment are efficiently generated in the bridge, so that the pigment is simultaneously applied to the surface layer 52 from the intermediate transfer body 37 of the recording liquid. Aggregation is performed. As a result, pigment bleeding does not occur between adjacent recording liquid dots, and a very high-definition solute image is formed.

On the other hand, the capacitance C _EC of the electric double layer E _C, since sufficiently larger than the capacitance C _EA of the electric double layer E _A, the surface of the cathode C, water is unlikely to reduction. This is because the area of the nozzle plate 61a that contacts the recording liquid as the cathode C is more specifically the surface layer 37b, more specifically the surface layer, than the intermediate transfer member 37 of the portion that contacts the liquid column as the anode A. This is because the area is sufficiently larger than the area of 52.

  The degree of aggregation of the pigment can be controlled by the control unit by the amount of protons generated, that is, the time for forming the bridge of the liquid column, the voltage applied by the energizing means 33, and the like. Further, when water is oxidized and protons are generated, oxygen is also generated. However, since it is considered to be dissolved in water in addition to a small amount, it does not inhibit image formation.

  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 S / m. For example, 3 S / 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.

  From the viscosity of the recording liquid and the amount of electrolyte added to the recording liquid, the electrical conductivity of the recording liquid can be practically up to about 3 S / m as described above. When the conductivity of the recording liquid is 3 S / m, the resistivity of the recording liquid is 33 Ωcm.

  As shown in FIG. 2, the diameter of the recording liquid on the intermediate transfer member 37 is such that the peak voltage and the pulse width of the voltage pulse applied to the ink discharge means when the recording liquid is discharged from the heads 61Y, 61M, 61C, 61BK. Etc. are controlled in the same manner as the bridge formation time. Such control is performed according to the image to be formed, and this diameter is about 20 μm or more when the diameter of the recording liquid droplets ejected from the heads 61Y, 61M, 61C, 61BK is small. When the diameter of the droplet is large, it is about 40 μm or more.

  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 member 37, more specifically on the surface layer 52, is transferred to the transfer sheet S passing through the transfer unit 31 while the transfer roller 38 rotates. An image is formed on the surface. The transfer sheet S on which the image is formed is guided to the paper discharge tray 25 and stacked on the paper discharge tray 25.

  When the image is transferred to the transfer paper S in this way, the aggregation component and a small amount of excess liquid component are transferred to the transfer paper S. The amount of excess liquid component transferred onto the transfer paper S is so small that curling and cockling are prevented or highly suppressed, so that problems such as jamming of the transfer paper S are prevented or suppressed, and the transfer property of the transfer paper S is good. It is.

  Therefore, the transfer paper S is discharged onto the paper discharge tray 25, and the transfer paper S is loaded on the paper discharge tray 25, and the handling of the transfer paper S after image formation is facilitated. This advantage can also be obtained by reducing the absorbability of the excess liquid component to the transfer paper S by the aggregation component generated by the aggregation action.

  In order to perform high-speed image formation, it is necessary to make the recording liquid dry quickly. Therefore, the recording liquid generally has high absorbability to the transfer paper S. In this case, the recording liquid penetrates deep into the transfer paper S. In other words, so-called back-off occurs, which may be unsuitable for double-sided image formation. However, the amount of surplus liquid component is small and the agglomerated component is generated by the aggregating action, so that the amount of absorption and absorbability of the surplus liquid component to the transfer paper S is reduced to the minimum. Therefore, since the aggregation component is prevented or suppressed from reaching deep inside the transfer paper S while ensuring quick drying, such a set-off is prevented or suppressed, which is suitable for double-sided image formation.

  Further, the above-described aggregation action causes the pigment dispersed by the anionic dispersant to aggregate, and an image is formed by the aggregated pigment, so that even when the transfer paper S is plain paper, feathering is performed. And bleeding are prevented or suppressed. As a result, high-speed image formation with high image density and high image quality is possible.

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

  In performing such image formation, the resistivity of the surface layer 37b is set to a size that allows electrolysis of the liquid columnar recording liquid bridging between the nozzle 61b and the surface layer 37b. And is important for agglomerating the pigment.

  From this point of view, the surface layer 37b may have an overall resistivity of 100 Ωcm or less. This is because the resistivity of the surface layer 37b is set according to the conductivity of the recording liquid as follows. That is, when the recording liquid has a conductivity of 3 S / m as described above, for example, the resistivity of the recording liquid is 33 Ωcm. Therefore, if the resistivity of the surface layer 37 b is 33 Ωcm or less, the electrolysis of the recording liquid is performed. The used image forming system is established. However, when the conductivity of the recording liquid is, for example, a general 1 S / m, the resistivity of the recording liquid is 100 Ωcm, so that the resistivity of the surface layer 37b is 100 Ωcm in order to establish the present image forming system. It is necessary to do the following.

  However, when the resistivity of the surface layer 37b as a whole is set to 100 Ωcm or less, it is preferable that the surface layer 37b has a layer structure of the surface layer 52 and the lower layer 53 as in this embodiment. This is because a combination of a thin elastic layer having a low resistivity like the surface layer 52 of this embodiment and an elastic layer having a resistivity higher than the surface layer 52 and thicker than the surface layer 52 like the lower layer 53 of this embodiment is transferable. This is because it is advantageous in terms of cost and also in terms of cost as follows. That is, in order to reduce the resistivity, it is necessary to disperse a conductive agent such as carbon nanotubes. However, conductive agents are relatively expensive, and carbon nanotubes are particularly expensive. Is suppressed.

  Furthermore, when performing image formation using electrolysis of the recording liquid, the resistivity of the surface layer 37b, more specifically, the surface layer 52 is set to the size of the dots of the recording liquid that land on the surface layer 37b. It is important to make the area uniform, in other words, the pixel area. If the resistivity of the surface layer 37b, more specifically the surface layer 52, is uniform in the pixel region, the liquid columnar recording liquid between the nozzle 61b and the surface layer 37b is electrolyzed to aggregate the pigment. This is because the degree of aggregation is uniform and uniform and high-quality image formation is performed.

  Considering the resistivity of the surface layer 52 from this point of view, when carbon nanotubes are used as a conductive agent as in this embodiment, the resistivity when a minimum amount of uniformly dispersed carbon nanotubes is added is 50 Ωcm. Therefore, the surface layer 37b has a layer structure, and the resistivity of the surface layer 52 is 50 Ωcm or less. This image forming system includes uniform and high-quality image formation due to uniform cost, transferability, and resistivity. It is suitable for any establishment.

  Further, the resistivity of the surface layer 52 is desirably 50 Ωcm or less for the following reason. That is, assuming that the resistivity is higher than 50 Ωcm, the surface layer 52 having a thickness of the surface layer 52 is used to reduce the resistivity of the entire surface layer 37b combined with the lower layer 53 to 100 Ωcm or less that enables electrolysis of the recording liquid. It is necessary to increase the proportion of the thickness of 37b. Then, even if the hardness of the lower layer 53 is lowered to ensure transferability, the overall hardness of the surface layer 37b is increased and transferability is lowered, which is not preferable.

  As described above, the resistivity of the lower layer 53 is set to be greater than 50 Ωcm and less than or equal to 1000 Ωcm. Here, it is considered that the uniformity of the resistivity of the lower layer 53 is not necessary in the pixel region. For example, assuming that the resistivity of the surface layer 52 is 50 Ωcm and the resistivity of the lower layer 53 is 200 Ωcm, even if the lower layer 53 has low uniformity of resistivity in the pixel region, it is conductive at the boundary portion between the lower layer 53 and the surface layer 52. If the property is secured, the recording liquid is well aggregated. This is because when a voltage is applied, a path that can be energized is selected at the boundary and energization is performed.

  Further, regarding the resistivity of the lower layer 53, if this resistivity is higher than 1000 Ωcm, the thickness of the lower layer 53 is set so that the transferability is less than 100 Ωcm as the entire surface layer 37b combined with the surface layer 52. It becomes difficult to make it thick enough to be secured. Further, if this resistivity is higher than 1000 Ωcm, the above-mentioned pass is not ensured, and electrolysis of the recording liquid may be uneven. Therefore, the resistivity of the lower layer 53 is 1000 Ωcm or less. As described above, the lower limit of the resistivity of the lower layer 53 is set to a value larger than 50 Ωcm for cost reasons.

  Even if the resistivity of the lower layer 53 is 1000 Ωcm or less, a material having a high resistivity can be selected as the material of the lower layer 53 as long as it is greater than 50 Ωcm. Therefore, it becomes easy to set the hardness of the lower layer 53 low, and this makes it possible to set a wide nip and to improve the transfer rate.

  Regarding the uniformity of the resistivity of the surface layer 52 in the pixel region, it is assumed that such uniformity is ensured when the following criteria are satisfied. That is, as shown in FIG. 3, the resistivity measured at intervals of 2 mm or less using a needle-like electrode 54 as a resistance measuring member as a probe having a diameter of 40 μm or less in contact with the surface layer 52 is 50 Ωcm or less. When a certain condition is satisfied, it is assumed that such uniformity is satisfied.

  Usually, the resistivity of a conductive material such as the surface layer 37b or the surface layer 52 is measured by Loresta, JIS C2123, JIS K6249, or the like. However, even when the value measured in this way is 50 Ωcm or less, such a material is used to form an image by conducting energization and electrolysis in units of pixels as in the image forming apparatus 100. Therefore, the measurement accuracy is insufficient. This is because the diameter of the measurement terminal of Loresta or JIS is 50 to 100 μm, which is larger than the pixel unit, and only a value averaged with the diameter of the measurement terminal is measured.

  Therefore, the electrode 54 as the probe has a tip diameter that is a portion in contact with the surface layer 52, that is, a size in the left-right direction in FIG. This is because if the tip of the electrode 54 is larger than 40 μm, it becomes too large with respect to the pixel, and the missing portions that are not energized may be averaged. The size of the lower limit side of the electrode 54 is 20 μm or more. This is because if the diameter is smaller than 20 μm, the surface layer 52 which is an elastic body may be stabbed and damaged.

  The reason for setting the measurement interval to 2 mm or less is as follows. That is, when the measurement is performed at intervals wider than 2 mm, it is difficult to distinguish between the resistance change due to the dispersion dispersion of the carbon nanotubes and the resistance change due to the thickness accuracy dispersion of the material.

  The measurement interval is more preferably 1 mm or less. This is because it is recognized that the resistivity is uniform by performing measurement more precisely, and the resistivity distribution state by the carbon nanotube becomes clearer.

  The measurement interval is more preferably 0.1 mm or less. This is because it is possible to measure and manage the energization change due to the dispersion variation of the carbon nanotubes and the energization change due to the thickness accuracy variation of the surface layer 52, which is an elastic body, and an elastic material with uniform resistance is selected. It is. Moreover, it is because it becomes possible to select the material without the location where the amount of energization changes greatly by comparing the resistance values at the measurement points at intervals of 0.1 mm. Furthermore, if the thickness of the surface layer 52 varies, the gap between the nozzle 61b and the surface layer 52 changes, and the resistance of the liquid columnar recording liquid changes, which affects the cohesion, but at intervals of 0.1 mm. This is because a material with less variation is selected if measured.

  When measuring at intervals of 2 mm or less using an electrode 54 having a diameter of 40 μm or less in contact with the surface layer 52 in a state where the surface layer 52 and the lower layer 53 are integrated, the measured resistivity is already If it is 100 Ωcm or less for the reason described, it is suitable for uniform image formation.

When it was confirmed whether image formation was performed satisfactorily by the following experiment considering the above conditions, the evaluation results are as shown in Table 1.
The experimental conditions are as follows.

  The image forming apparatus used in the experiment is an image forming apparatus that uses the inkjet printer IPSiO CX5000 (manufactured by Ricoh) and has the same configuration as the image forming apparatus 100 that satisfies the following conditions.

The heads 61Y, 61M, 61C, 61BK used in the experiment are provided with a metal nozzle plate 61a.
The voltage applied by the power source 33a between the nozzle plate 61a and the support 37a was 120V.
The intermediate transfer member was rotationally driven in the A1 direction so that the outer peripheral linear velocity was 100 mm / second.

The gap between each head 61Y, 61M, 61C, 61BK and the intermediate transfer member was 100 μm.
As the cleaning means 34, a blade made of fluororubber was used.
The transfer roller 38 is formed by forming a rubber layer having a thickness of 1 mm on a metal core.

Using the image forming apparatus as described above, as shown in FIG. 6, a 100 mm square yellow halftone dot image PA and a magenta halftone dot image PB made up of isolated dots having a dot diameter of 50 μm are formed on the intermediate transfer member by 35 mm. Formed at intervals. Further, a 100 mm square black solid image consisting of isolated dots having a dot diameter of 50 μm was formed.
As the transfer paper S, high-quality paper TYPE 6200 (manufactured by Ricoh) was used.

  The recording liquid of each color, that is, the conductive ink used was prepared as follows.

[Preparation of conductive ink]
Black conductive ink Ketjen Black EC-600JD (Ketjen Black International Co., Ltd.) 4% by mass, polyoxyethylene alkyl ether sodium sulfonate 2% by mass, urea 15% by mass, glycerin 5% by mass, 2-pyrrolidone 0.5 mass%, 1,2-octanediol 0.5 mass%, tetramethylammonium nitrate 15 mass%, 2-amino-2-ethyl-1,3-propanediol 0.1 mass% and distilled water (residual ), And pressure filtered using a membrane filter having an average pore size of 0.8 μm to obtain a black conductive ink.
Yellow conductive ink Yellow conductive ink was obtained using Pigment Yellow 152 instead of Ketjen Black EC-600JD.
Cyan conductive ink Cyan conductive ink was obtained using Pigment Blue 15 instead of Ketjen Black EC-600JD.
-Magenta conductive ink Magenta conductive ink was obtained using Pigment Red 83 instead of Ketjen Black EC-600JD.

[Example 1]
The surface layer was an acrylic resin to which 1.5% of carbon nanotubes were added, and the lower layer was carbon-containing urethane. The resistivity of the surface layer measured at 0.1 mm intervals with Loresta and a 40 μm diameter electrode was 5 Ωcm. Further, the hardness of the surface layer was 30 ° in the JISA standard. The lower layer had a resistivity of 150 Ωcm and a hardness of 30 ° according to the JISA standard. The resistivity obtained by measuring 100 or more points at 0.1 mm intervals by applying a voltage of 40 V with a 40 μm diameter electrode to the surface layer including the surface layer and the lower layer was 80 Ωm.

[Example 2]
The surface layer was an acrylic resin to which 3.0% of carbon nanotubes were added, and the lower layer was carbon-containing urethane. The resistivity of the surface layer measured at 0.1 mm intervals with a 40 μm diameter electrode was 0.2 Ωcm. Further, the hardness of the surface layer was 60 ° in the JISA standard. The lower layer had a resistivity of 50 Ωcm. The maximum value of resistivity was 2 Ωm when the surface layer including the surface layer and the lower layer was measured at 100 points or more at 0.1 mm intervals by applying a voltage of 40 V with a 40 μm diameter electrode. The hardness of the surface layer was 30 ° according to the JISA standard. In this example, the hardness of the surface layer was high, but the hardness of the lower layer was low, so that the nip was widened and the transfer rate was good.

[Comparative Example 1]
The surface layer was an acrylic resin to which 2.2% of carbon nanotubes were added, and the lower layer was a carbon-containing urethane. The resistivity of the surface layer measured at 0.1 mm intervals with Loresta and a 40 μm diameter electrode was 40 Ωcm. Further, the hardness of the surface layer was 30 ° in the JISA standard. The lower layer had a maximum resistivity of 3000 Ωcm and a hardness of 30 ° according to the JISA standard, measured at 100 points at 2 mm intervals by applying a voltage of 40 V with a 40 μm diameter electrode. In addition, when the amount of energization was measured at intervals of 0.1 mm after forming a liquid column of the recording liquid, there was a 100% change, and a place where no current was supplied was confirmed. In this example, the resistivity of a macro measuring instrument is low, but in a fine region, the resistivity is high, so that bleeding occurs.

[Comparative Example 2]
The surface layer was an acrylic resin to which 2.5% of carbon nanotubes were added, and the lower layer was carbon-containing urethane. The resistivity of the surface layer measured by Loresta was 40 Ωcm. When the surface layer was measured at 0.1 mm intervals with a 40 μm diameter electrode, there was a portion where the resistivity was 200 Ωcm. Further, the hardness of the surface layer was 60 ° in the JISA standard. The lower layer had a resistivity of 50 Ωcm. The maximum value of the resistivity was 140 Ωm when the surface layer including the surface layer and the lower layer was measured at 100 points or more at 0.1 mm intervals by applying a voltage of 40 V with a 40 μm diameter electrode. The hardness of the surface layer was 60 ° according to the JISA standard. This example is a case where the surface layer has a slightly high resistivity and bleeding occurs, the lower layer has a high hardness, does not follow the transfer paper sufficiently, and the transfer rate is poor.

Evaluation item The evaluation item is bleeding of the recording liquid transferred onto the transfer paper S.
The evaluation of bleeding was performed by observing the dot shape of the halftone dot image transferred to the transfer paper S by visual observation using a microscope and evaluating the state of bleeding. The case where the dots were independent was judged as ◯, the case where the dots were slightly blurred, and the case where the dots were blurred as x.

  As can be seen from the above table, in the first and second embodiments, the dots of the halftone dot image are independent. In Example 1, since the resistivity of the surface layer is uniform and low, fluctuations in the energization amount are small, and a system for electrolyzing the recording liquid and aggregating the pigment is established, and bleeding is prevented or suppressed. by. Further, in Example 2, since the resistivity is uniform and sufficiently low in the surface layer and the lower layer, such a system is established, and bleeding is prevented or suppressed by aggregation of the pigment. In Example 1, both the surface layer and the lower layer have a low hardness. In Example 2, the surface layer has a high hardness but the lower layer has a low hardness. Therefore, in both cases, the nip time is secured and the transferability is maintained. Has been. Therefore, in Example 1, the transfer rate was 93% and good, and in Example 2, the transfer rate was 90% and good.

  On the other hand, in Comparative Example 1, it was confirmed that the dots in the halftone dot image were blurred, and in Comparative Example 2, it was confirmed that the dots in the halftone dot image were slightly blurred. That is, in Comparative Example 1 and Comparative Example 2, no energization or insufficient energization confirms that the pigment does not aggregate or is insufficient, and it cannot be said that such a system is established. This is because in Comparative Example 1, the surface layer has a low resistivity, but the resistivity of the lower layer is high and the variation rate of the energization amount is large. In Comparative Example 2, the surface layer that is measured as low resistivity is measured as a low resistivity in the conventional measuring method that is measured with a commercially available measuring device, Loresta, and is measured as high resistivity when measured with a small-diameter electrode. This is due to the occurrence of spots where pigment aggregation is insufficient and bleeding occurs.

  Thus, unlike Comparative Example 1 and Comparative Example 2, both Comparative Example 1 and Comparative Example 2 cannot be said to have uniform resistivity in the pixel region, and the system is established. That is not the case. In Comparative Example 1, since both the surface layer and the lower layer had low hardness, the nip time was secured and the transferability was maintained, and the transfer rate was 93%, which was good, but in Comparative Example 2, the lower layer hardness was And the transfer paper was not sufficiently followed, and the transferability was as low as 83%.

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

For example, the conductive recording liquid may be agglomerated via hydroxide ions generated on the surface of the intermediate transfer member having a cationic group as an ink component and functioning as a cathode. That is, instead of aggregating the pigment dispersed by the anionic dispersant via the proton generated on the surface of the elastic layer functioning as the anode, the pigment dispersed by the cationic dispersant may be aggregated. Good. In this case, the pigment dispersed by the cationic dispersant is aggregated through hydroxide ions generated on the surface of the elastic layer functioning as the cathode.
The intermediate transfer member does not need to be conductive as a whole, and it is sufficient that the elastic layer constituting the surface is at least conductive.

  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. In addition, it is used to form a predetermined image in the field of a copying machine, a facsimile machine alone, or a multifunction machine such as these, a multifunction machine such as a monochrome machine related to these, an image forming apparatus used for forming an electric circuit, or a biotechnology field. An image forming apparatus may be used. The number of heads is increased or decreased according to the application of the image forming apparatus, and may be one or plural.

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

33 Voltage application means 37 Intermediate transfer member 51 Elastic member 52 Surface layer 53 Lower layer 54 Resistance measurement member 61Y, 61M, 61C, 61BK Head 100 Image forming apparatus

JP 2010-247381 A JP 2008-19286 A JP 2011-90315 A Japanese Patent No. 4915538

Claims (5)

A conductive elastic member used on the surface of the intermediate transfer member to which a voltage for electrolyzing the conductive recording liquid discharged from the head and bridging between the head and the intermediate transfer member is applied;
A surface layer on which the conductive recording liquid discharged from the head lands,
It has a lower layer supporting this surface layer,
The surface layer has a resistivity measured at an interval of 2 mm or less using a resistance measuring member having a diameter of 40 μm or less at a portion in contact with the surface layer, and is 50 Ωcm or less,
The lower layer is an elastic member having a resistivity of greater than 50 Ωcm and less than or equal to 1000 Ωcm. The elastic member according to claim 1,
The surface layer includes carbon nanotubes, and is an elastic member. The elastic member according to claim 1 or 2,
The elastic member characterized in that the hardness of the lower layer is lower than the hardness of the surface layer.   An intermediate transfer member having the elastic member according to any one of claims 1 to 3 on a surface thereof. An intermediate transfer member according to claim 4;
A head for discharging a conductive recording liquid and applying it to the surface of the intermediate transfer member;
An image forming apparatus comprising: a voltage applying unit that applies the voltage between the intermediate transfer member and the head.

Images