JP2013103475A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet type image forming apparatus that can satisfactorily clean an intermediate transfer body with time even in a liquid column energization system.SOLUTION: A cleaning means 34 includes a cleaning member 53 moved to a B1 direction opposite from a direction A1 which is a movement direction of the intermediate transfer body 37 in an abutting position with the intermediate transfer body 37 and wiping the intermediate transfer body 37, a conductive abutting member 56 abutting against a rear side of the cleaning member 53 and making the cleaning member 53 abut against the intermediate transfer body 37, and a second voltage applying means 59 for applying a voltage of reverse polarity to the polarity applied to the intermediate transfer body 37 by a voltage applying means 33 performing voltage application to electrolyze the conductive recording liquid between heads 61Y, 61M, 61C and 61BK and the intermediate transfer body 37 to the intermediate transfer body 37 and applying a voltage between the abutting member 56 and the intermediate transfer body 37 to electrolyze the conductive recording liquid positioned between the cleaning member 53 and the intermediate transfer body 37.

Description

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

  Conventionally, image forming apparatuses that perform image formation by various methods are known (for example, see [Patent Document 1] to [Patent Document 35]). Among them, a recording liquid such as ink is ejected from a plurality of nozzles. 2. Description of the Related Art An image forming apparatus such as an ink jet printer that includes a head for performing ink jet recording is known (see, for example, [Patent Document 1] to [Patent Document 34]).

  Ink jet recording ejects ink from a fine nozzle of several tens of μm, and therefore, a dye having high solubility has been used as a colorant for the ink because of problems such as ink clogging. Dye inks have excellent color developability, and can obtain image quality comparable to silver salt photographs in photographic prints, but on the other hand, they have inferior image storage stability such as water resistance, light resistance and gas resistance. Yes. In order to compensate for this problem, the use of pigments as an ink colorant has been promoted, and it is now installed in printers in the personal market and office market, from industrial large format printers.

  When printing a color image on plain paper, in order to suppress bleeding (bleeding) at the color boundary of the two-color overlapped portion, etc., by adding a surfactant or the like to the ink, the permeability of the ink to the paper is increased. (For example, see [Patent Document 1] for adding a surfactant or the like to the ink). Bleeding at the color boundary can be reduced by increasing the penetrability of the ink into the paper, but on the other hand, it penetrates along the cellulose fibers that form the plain paper, so it blurs around the printed area of characters and fine lines (feathering) Is likely to occur.

  In order to achieve both prevention of bleeding and feathering, measures such as using ink with low penetrability only for black character printing have been made, but in that case, black ink is poorly dry and high-speed printing is difficult. The problem remains.

  In view of this, there has been proposed a recording material for exclusive use with an ink jet in which a material for fixing a colorant in ink (water-soluble polymer, white pigment, etc.) is applied in advance (for example, [Patent Document 2] to [Patent Document 2] Reference 5]). By using special paper suitable for these ink jet recordings, the image quality is remarkably improved. However, dedicated paper has a problem in terms of cost, and in particular for business use, printing on plain paper with high image quality is required.

  In order to cope with general recording materials such as plain paper, a polymer solution such as carboxymethylcellulose, polyvinyl alcohol, and polyvinyl acetate is sprayed onto the recording material in advance, and then ink is ejected to the part where the polymer solution adheres. Ink jet recording methods have been proposed (see, for example, [Patent Document 6]). However, feathering was not suppressed with these polymer solutions, and water resistance was not improved.

  An apparatus for forming an image using an ink jet recording head, comprising: means for applying water-absorbing resin particles that absorb ink to a recording material; and water-absorbing resin particles applied to the recording material with ink. An image forming apparatus having means for discharging and means for fixing the water-absorbing resin particles to a recording material has been proposed (for example, see [Patent Document 7]). However, the water-absorbing resin particles are easy to absorb moisture, and are liable to be agglomerated due to moisture absorption in the apparatus or during storage, so that it is difficult to uniformly apply the water-absorbing resin powder to the recording material.

  In addition, after a recording material pretreatment liquid containing a compound that insolubilizes the colorant in the ink is deposited on the recording material by an ink jet method, the ink is ejected to a portion of the recording material to which the pretreatment liquid has adhered. Ink jet recording methods for forming images have been proposed (see, for example, [Patent Document 8] to [Patent Document 11]). These methods improve both bleeding and feathering to some degree. However, in these methods, in order to discharge the pretreatment liquid stably, it is necessary to lower the viscosity of the pretreatment liquid, and thus it is necessary to reduce the concentration of the compound that insolubilizes the colorant. In order to obtain a sufficient image quality improvement effect with such a pretreatment liquid, it is necessary to apply a relatively large amount of the pretreatment liquid, and to apply a large amount of liquid containing moisture to the recording material. The material curled and cockled easily.

  In addition, an image in which an ink containing an anionic component is attached to a recording material by an inkjet recording method after a colorless liquid composition containing at least a silicone compound such as silicone oil and a cationic compound is applied to the recording material. A forming method has been proposed (see, for example, [Patent Document 12]). However, the portion of the recording material to which the silicone compound is adhered has a problem that the drying of the image portion is slow because the ink permeability is extremely low.

  Further, in order to improve the penetrability and wettability of the ink, after applying an image recording acceleration liquid containing a compound that insolubilizes the colorant and a predetermined surfactant to the recording material, the ink is applied by an ink jet recording method. A method of forming an image by adhering to a recording material has been proposed (see, for example, [Patent Document 13] and [Patent Document 14]). According to this method, the surfactant in the image recording promoting liquid improves the penetrability and wettability of the ink with respect to the recording material, so that the drying property of the image is improved and high-speed recording is possible. Since the amount of the component that insolubilizes the material is small, the effect of preventing bleeding and feathering is insufficient, and further improvement has been demanded.

  In addition, a technique has been proposed in which a reaction liquid containing a polyvalent metal salt that insolubilizes an ink colorant is applied to a recording material (for example, Patent Document 15 discloses that a reaction liquid contains a polyvalent metal salt. To [Patent Document 17]). This technology has greatly improved image quality.

  On the other hand, a method called an intermediate transfer method is proposed in which an ink image is formed on an ink impermeable intermediate transfer member by an ink jet recording method, and then the ink image is transferred from the intermediate transfer member to a recording material (for example, [See Patent Document 18] and [Patent Document 19]). In the intermediate transfer method, the recording head can be arranged away from the recording paper, and clogging of the nozzles of the recording head due to adhesion of paper dust can be suppressed. In addition, it is generally difficult to keep the gap between the recording head and the recording paper constant, but the gap between the recording head and the intermediate transfer member can be kept constant, and the paper type compatibility is good. Therefore, the method using the intermediate transfer member is highly reliable. However, if the intermediate transfer member is made of a material having good releasability in order to obtain a high transfer rate, bleeding and beading of adjacent droplets called beading are likely to occur violently and the image quality is likely to deteriorate. There was a problem.

  In order to improve such an intermediate transfer method, after ink is ejected onto an intermediate transfer member to form an ink image, most of the water in the ink is evaporated on the intermediate transfer member, and the concentrated ink is applied to a sheet such as paper. A method of transferring to a recording material has been proposed (see, for example, [Patent Document 20]). In this method, once a good image is formed on the intermediate transfer member, good image quality can be obtained even on commonly used so-called plain paper. However, since it takes time to concentrate the ink at room temperature, it is necessary to heat the intermediate transfer member to promote the evaporation of the solvent in the ink, and there is a problem of requiring large energy.

  In addition, a layer of water-absorbing resin particles such as polyacrylic acid is provided on the surface of the intermediate transfer member to absorb moisture in the ink applied to the intermediate transfer member, and then the entire water-absorbing resin particles are transferred to the recording material. A method has been proposed (see, for example, [Patent Document 21] and [Patent Document 22]). Although this method can obtain good image quality even on plain paper, it absorbs water due to moisture absorption during storage, similar to the above-described technique using means for applying water-absorbing resin particles that absorb ink to a recording material. There is a problem that the conductive resin particles are agglomerated and it is difficult to uniformly coat the intermediate transfer member.

  In addition, before or after forming an image by ejecting ink onto a recording material, a reaction liquid containing a polyvalent metal salt or polyallylamine that reacts with components in the ink is adhered onto the intermediate transfer member to form the recording material. A method of giving has been proposed (see, for example, [Patent Document 23]). This method can reduce the amount of reaction liquid adhering to the recording material as compared with the conventional method, and can reduce curling and cockling generated on the recording material.

  Further, a treatment liquid containing a cationic polymer compound and a surfactant and / or a wetting accelerator is applied onto the intermediate transfer member, and the treatment liquid and ink ejected by an ink jet method are contacted and mixed, An image forming method for transferring to a recording material has been proposed (see, for example, [Patent Document 24]).

  Similarly, a treatment liquid containing a polyvalent metal salt that reacts with an anionic ink colorant to cause an aggregating action is applied on the intermediate transfer member, and the treatment liquid and the ink ejected by the ink jet method are contacted and mixed. Then, an image forming method for transferring to a recording material has been proposed (see, for example, [Patent Document 25] to [Patent Document 27]). More specifically, it has been proposed that the image can be further provided with scratch resistance by further containing a water-soluble resin having a minimum film-forming temperature (MFT) of 30 ° C. or less in the ink or the processing liquid. (For example, see [Patent Document 25]). It has also been proposed that scratch resistance can be imparted in the same manner by imparting a water-soluble resin to an image before transfer (see, for example, [Patent Document 26]). As another reaction component different from the colorant that reacts with the treatment liquid, a resin emulsion having an ionic group on the surface of the resin particles is further included in the ink, and the cohesive force of the colorant is increased by the additional effect of the coagulation action. Has been proposed (see, for example, [Patent Document 27]).

In addition, it has been proposed to apply a treatment liquid that greatly changes the pH of the mixed liquid to the intermediate transfer member when contacting and mixing with ink (see, for example, [Patent Document 28]).
Further, in a state where the conductive ink discharged from the head forms a liquid column that bridges the head and the intermediate transfer member, a voltage is applied to the ink in this state to aggregate the pigment in the ink on the intermediate transfer member. Thus, a so-called liquid column energization method has been proposed that takes measures against bleeding and beading (see, for example, [Patent Document 29] and [Patent Document 33]).
As described above, various solutions for problems such as bleeding and beading that are peculiar to the intermediate transfer type inkjet image forming apparatus have been presented.

  On the other hand, an intermediate transfer type image forming apparatus requires an initialization process for removing stains such as ink remaining after transfer and treatment liquid and reaction liquid from the intermediate transfer body. If the stain removal is incomplete, the stain will be transferred to the recording material at the next transfer, causing the image to be disturbed. As a method for removing dirt, a method of scraping from the surface of the intermediate transfer member with a cleaning means such as a blade is generally used. In addition, various methods have been proposed as described below.

  A method has been proposed in which a transfer medium such as ink is transferred to a roller-shaped cleaning medium and removed by bringing a cleaning medium having higher wettability than the intermediate transfer body into contact with the intermediate transfer body (for example, [Patent Documents] 30] and [Patent Document 31]). However, in this method, although the cleaning medium is cleaned, the cleaning medium is rotated and repeatedly used. Therefore, a part of the removed ink remains attached to the cleaning medium, and the cleaning performance is deteriorated or the surface of the intermediate transfer member is removed. There is a problem such as reverse transition of. For this reason, it is necessary to further remove ink stains adhering to the cleaning medium.

  In addition, the cleaning liquid supply means for supplying the cleaning liquid to the area to be cleaned of the intermediate transfer body, the wiping means for wiping the intermediate transfer body supplied with the cleaning liquid, and the supply amount of the cleaning liquid by the image portion / non-image portion A cleaning method provided with a cleaning liquid supply control means for controlling is proposed (see, for example, [Patent Document 32]). However, in this method, the cleaning liquid supply means sprays the liquid in a spray form, and the liquid volume is controlled in the image area and non-image area, so the apparatus becomes large and a certain amount of cleaning liquid is required. There are problems such as becoming.

  In addition, in the liquid column energization method, a predetermined voltage is applied between the insulating cleaning blade in contact with the surface of the intermediate transfer member, the cleaning electrode integrated with the cleaning blade, and the intermediate transfer member and the cleaning electrode. A cleaning method (see, for example, [Patent Document 33]) including means for performing the above-mentioned is proposed. By applying a predetermined voltage to the waste ink collected on the cleaning blade, the dispersion and solubility of the pigment increases at the interface between the intermediate transfer body and the ink, while the aggregation of the pigment occurs at the interface between the cleaning electrode and the ink. The cleaning effect of the intermediate transfer member is improved. However, when a long time elapses after cleaning, it is conceivable that water in the ink deposited on the blade surface and the interface between the blade and the intermediate transfer member evaporates and a solid content is deposited. If cleaning is performed in this state, the precipitated solid content may enter the contact portion between the blade and the intermediate transfer member, which may damage and damage the blade and the intermediate transfer member. Due to this damage, cleaning failure occurs, so it is considered that the long-term reliability of the cleaning performance may be lacking.

  In addition, in an intermediate transfer type image forming apparatus that uses toner instead of the ink jet system, it can be wound or endlessly moved so that the surface moves in the direction opposite to the surface movement direction of the surface of the object to be cleaned. A cleaning method is provided that includes a belt-shaped film member that is stretched over and a cleaning blade that abuts the surface of the object to be cleaned with the film member sandwiched between the film member and the surface of the object to be cleaned (for example, [ Patent Document 35]). By adopting this cleaning method, it is possible to prevent the solidified deposits from staying at the contact portion between the cleaning blade and the object to be cleaned and thereby damaging the surfaces of the cleaning blade and the object to be cleaned. And long-term reliability of the cleaning performance can be obtained. However, in the liquid column energization method, since the pigment aggregates and adheres at the interface between the intermediate transfer member and the ink image, if this cleaning method is used as it is in the liquid column energization method, the ink image is completely removed from the intermediate transfer member. It has been found by the inventor's earnest examination that this is difficult.

  In view of the above circumstances, there has been an awaited proposal of an image forming apparatus capable of cleaning the intermediate transfer member well over time without using a cleaning liquid even in the liquid column energization method.

  The present invention provides an ink jet image forming apparatus using an intermediate transfer body, which can satisfactorily clean the intermediate transfer body over time without using a cleaning liquid even in a liquid column energization system. For the purpose.

  In order to achieve the above object, the invention described in claim 1 is provided with a head having a nozzle for discharging a conductive recording liquid, and a conductive recording liquid that moves in a predetermined direction and is discharged by the head. An intermediate transfer member having at least a conductive surface, and the intermediate transfer member for electrolyzing the conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer member; A first voltage applying means for applying a voltage to the head; a transfer means for transferring an image carried on the intermediate transfer member to the recording material by a conductive recording liquid; and the predetermined direction. The first cleaning of the intermediate transfer body upstream of the position where the conductive recording liquid is applied by the head and downstream of the position where the image is transferred to the recording material by the transfer means. And a first cleaning means for cleaning the intermediate transfer body, wherein the first cleaning means contacts the intermediate transfer body at a first cleaning position and is in a direction opposite to the predetermined direction. The first cleaning member that wipes the intermediate transfer member by moving, and the first cleaning member are fed out toward the first cleaning position and wound up after passing through the first cleaning position. A first moving member that moves the one cleaning member in the reverse direction; and a first cleaning member that is in contact with the first cleaning member from the opposite side of the intermediate transfer member; A conductive first contact member that contacts the transfer body and a voltage having a polarity opposite to the polarity applied to the intermediate transfer body by the first voltage applying means A voltage applied to the copy body to electrolyze the conductive recording liquid positioned between the first cleaning member and the intermediate transfer body between the first contact member and the intermediate transfer body The image forming apparatus includes a second voltage applying unit for applying the voltage.

  The present invention relates to a head having a nozzle for discharging a conductive recording liquid, an intermediate transfer body having at least a surface that is provided with the conductive recording liquid that is moved in a predetermined direction and is discharged by the head. In order to apply a voltage between the intermediate transfer member and the head for electrolyzing the conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer member. A first voltage applying means, a transfer means for transferring an image carried on the intermediate transfer body by a conductive recording liquid to a recording material, and the head of the intermediate transfer body in the predetermined direction by the head. The intermediate transfer member is cleaned at a first cleaning position upstream of the position where the conductive recording liquid is applied and downstream of the position where the image is transferred to the recording material by the transfer means. A first cleaning unit that contacts the intermediate transfer member at the first cleaning position and moves in a direction opposite to the predetermined direction to wipe the intermediate transfer member. The first cleaning member and the first cleaning member are fed out toward the first cleaning position and moved in the opposite direction so as to be wound up after passing through the first cleaning position. A first moving means to be brought into contact with the first cleaning member from the opposite side of the intermediate transfer member, and the first cleaning member is brought into contact with the intermediate transfer member at the first cleaning position. A voltage having a polarity opposite to the polarity applied to the intermediate transfer member by the first voltage applying means is applied to the intermediate transfer member. An image having a second voltage applying means for applying a voltage for electrolyzing the conductive recording liquid positioned between the first cleaning member and the intermediate transfer member, between the intermediate transfer member and the intermediate transfer member. Since the first cleaning member and the second voltage applying unit are used in the liquid column energization method, the conductive recording liquid remaining on the intermediate transfer member is removed by the first cleaning member. It is possible to provide an ink jet image forming apparatus that can efficiently wipe and clean the intermediate transfer member with time without using a cleaning liquid.

1 is a schematic front view of an example 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 schematic front view illustrating an example of a cleaning unit provided in the image forming apparatus illustrated in FIG. 1. 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. 5 is a schematic front view illustrating another configuration example of a cleaning unit provided in the image forming apparatus illustrated in FIG. 1. FIG. 6 is a schematic front view showing still another configuration example of the cleaning unit provided in the image forming apparatus shown in FIG. 1.

  FIG. 1 shows an outline 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 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 recording heads 61 </ b> Y, 61 </ b> M, 61 </ b> C, and 61 </ b> BK are recording heads that are ink heads as recording liquid discharge bodies.

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

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

  The intermediate transfer body 37 is rotated in the A1 direction and is recorded in yellow, magenta, cyan, and black from the heads 61Y, 61M, 61C, and 61BK in an area facing the heads 61Y, 61M, 61C, and 61BK. The liquids are ejected and applied in such a manner that they are sequentially superimposed, and an image is formed on the surface. 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 ejected or applied to the intermediate transfer member 37 by the heads 61Y, 61M, 61C, 61BK upstream of the A1 direction so that the image areas of yellow, magenta, cyan, and black are overlapped at the same position on the intermediate transfer member 37. The timing is shifted from the side toward the downstream side.

  The image forming apparatus 100 includes ink discharge devices 60Y, 60M, 60C, and 60BK that are provided with heads 61Y, 61M, 61C, and 61BK, and an intermediate transfer member 37 that is transferred as the intermediate transfer member 37 rotates in the A1 direction. A transport unit 10 serving as a paper transport unit for transporting the paper S, and a feeding unit that can load a large number of transfer sheets S and feeds only the top transfer sheet S among the stacked transfer sheets S toward the transport unit 10. It has a paper unit 20 and a paper discharge tray 25 on which a large number of printed transfer papers S that have been transported by the transport unit 10 can be stacked.

  In the image forming apparatus 100, as shown in FIG. 2B, the liquid column of the recording liquid immediately after being ejected from the heads 61Y, 61M, 61C, 61BK is changed to the heads 61Y, 61M, 61C, 61BK, the intermediate transfer body 37, and the like. The electrode oxidation reaction is performed 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 in a state where the space between the intermediate transfer body 37 and the head 61Y is changed. Alternatively, it has energization means 33 as a first voltage application means for energizing the recording liquid in a state in which energization including a current component resulting from the electrode reduction reaction is promoted as described later. 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 device 34 as a cleaning means for cleaning, 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 40 as control means.

  In addition to the intermediate transfer member 37, the transport unit 10 is disposed so as to face the intermediate transfer member 37, and when the transfer sheet S passes through the transfer unit 31 that is an area between the transfer unit S and the intermediate transfer member 37. The transfer means 64 for transferring the image of the recording liquid carried thereon onto the transfer paper S and the transfer paper S fed from the paper supply unit 20 are guided to the transfer unit 31 and passed through the transfer unit 31. A guide plate 39 that guides the transfer sheet S to the paper discharge table 25, and a motor or the like as a driving unit (not shown) 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 unit 64 includes a transfer roller 38 as a pressure roller that is driven to rotate by the intermediate transfer member 37. The transfer roller 38 may include a heater for fixing the image transferred onto the transfer paper S to the transfer paper S. Further, the transport unit 10 may include a fixing roller as a fixing unit for fixing the image transferred from the intermediate transfer body 37 to the transfer sheet S by the transfer roller 38 on the transfer sheet S.

  As shown in FIG. 2, the intermediate transfer member 37 includes a support 37a made of aluminum, which is a conductive substrate, and a surface layer 37b made of silicone rubber formed on the support 37a. The material of the support 37a is not limited to aluminum, and may be formed of a metal or an alloy such as an aluminum alloy, copper, or stainless steel as long as it has good electrical conductivity and mechanical strength.

  The material of the surface layer 37b may be a smooth elastic material having high conductivity and water repellency. The conductivity is necessary for causing electrolysis described later of the recording liquid. The water repellency is an index of the ease of transfer when the recording liquid is transferred from the intermediate transfer body 37 to the transfer sheet S. The higher the water repellency, the better the transfer rate and the easier the cleaning. Elasticity is necessary when the recording liquid is transferred from the intermediate transfer body 37 to the transfer paper S, and the surface layer 37b and the transfer paper S are deformed along the fibers of the paper of the transfer paper S due to elasticity. The contact area is improved and a high transfer rate is obtained. In order to transfer at a low pressure, it is necessary to select a material that is somewhat soft for the surface layer 37b.

  Therefore, the material of the surface layer 37b is not limited to silicone rubber, and may be an elastic material having low surface energy and high followability to the transfer paper S for the advantage of high releasability of the recording liquid. For example, it may be formed of fluorosilicone rubber, phenyl silicone rubber, fluorine rubber, chloroprene rubber, nitrile rubber, nitrile butadiene rubber, isoprene rubber or the like.

  The surface layer 37b is a conductive material obtained by dispersing and mixing metal fine particles such as carbon black, carbon nanotube and the like carbon, gold and silver as a conductive agent in the rubber material in order to impart conductivity to the intermediate transfer body 37. It is made of conductive rubber and is a conductive layer. However, increasing the number of conductive fine particles improves the conductivity, but if the density of the conductive fine particles on the surface is high, the water repellency is reduced and there is a trade-off relationship in which the releasability is lowered. is necessary.

  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 may be 0.1 μm or less. Further, it may be impregnated with silicone oil to increase water repellency. The surface layer 37b may have either a single layer structure or a multilayer structure.

As will be described later, in order to form a desired potential difference in the liquid column of 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 ^4. It is preferable that it is Ω · cm or less, and it is desirable that it be smaller than the volume resistivity of the recording liquid. Thus, with respect to the bulk properties and surface properties of the surface layer 37b, the volume resistivity is 10 ⁴ Ω · cm or less, preferably 10 ² Ω · cm or less, and the water repellency has a receding contact angle of water of 60 °. As mentioned above, it is preferably 80 ° or more, and the hardness is 60 or less, preferably 40 or less in JIS-A.

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

  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. The sheet feeding roller 22 fed toward the unit 10, the casing 23 supporting the sheet feeding tray 21 and the sheet feeding roller 22, and the sheet feeding roller 22 are ejected from the recording liquid in the heads 61Y, 61M, 61C, 61BK. It has a motor or the like as a driving means (not shown) that rotates and feeds the transfer paper S so as to match the timing.

  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 includes a plurality of heads 61Y, 61M, 61C, and 61BK that are arranged in the main scanning direction. The ink ejection devices 60Y, 60M, 60C, and 60BK, and the image forming apparatus 100 are heads. It is a 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, a pump (not shown) as a supply pump for pumping and feeding the recording liquid stored in the ink cartridges 81Y, 81M, 81C, 81BK toward the heads 61Y, 61M, 61C, 61BK, and a pump Is a distributor as an ink supply unit that is a recording liquid supply unit that distributes and supplies the recording liquid supplied from the ink cartridges 81Y, 81M, 81C, and 81BK to the heads 61Y, 61M, 61C, and 61BK. With distributor tank

  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. An amount detection sensor, a pipe (not shown) that forms a feeding path for the recording liquid between the ink cartridges 81Y, 81M, 81C, 81BK and the distributor tank together with a pump; a distributor tank and each head 61Y, 61M, 61C; And a pipe (not shown) that forms a recording liquid feeding path between the unit 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 40. Specifically, on the condition that the ink amount detection sensor detects the shortage of the recording liquid amount in the distributor tank, it is driven until this shortage is not detected, and the recording in the ink cartridges 81Y, 81M, 81C, 81BK is performed. Supply liquid to distributor tank. In this respect, the control unit 40 functions as an ink supply control unit that is a recording liquid supply control unit. The control unit 40 controls the driving of the image forming apparatus 100 even when not specifically described.

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

Specific examples of the anionic dye that is a colorant to be 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 are available.
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.
These are preferably used because of their high solubility, good color tone, and good water resistance when recorded by a liquid column energization method.
As dyes, especially those containing 3 or more carboxyl groups and sulfonic acid groups in the molecule are highly reactive with hydrogen ions generated by electrolysis of water, and have a storage stability and resistance to recording. This is preferable in terms of securing clogging characteristics.

Examples of the pigment that can be used as a colorant to be contained in the recording liquid include inorganic pigments and organic pigments.
As the inorganic pigment, white pigments such as titanium oxide, zinc oxide, and barium sulfate, and black pigments such as iron oxide can be used.
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.

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.

In the case of using a recording liquid containing a pigment as a colorant, 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, quinacridone Self-dispersing pigments made by reacting pigments such as, self-dispersing pigments made by reacting carbon black, phthalocyanine, quinacridone and other radical initiators containing carboxyl groups and sulfonic acid groups, and functional groups of pigments A pigment in which an ionic group, particularly a carboxyl group is bonded by a covalent bond, such as a self-dispersing pigment obtained by reacting a carboxylic acid anhydride with a carboxylic acid, is preferably used.
These pigments have high reactivity with hydrogen ions generated by electrolysis of water, and therefore, the intermediate transfer member 37, which is performed by applying a voltage by the cleaning device 34, is well cleaned as will be described later. Further, it is preferable in terms of ensuring storage stability and anti-clogging properties of the recording liquid.

The recording liquid preferably used in the image forming apparatus 100 contains a pigment dispersed with an anionic polymer dispersant.
Examples of the polymer dispersant having an anionic group include polyacrylic acid and its salt, polymethacrylic acid and its salt, acrylic acid-acrylonitrile copolymer and its salt, acrylic acid-alkyl acrylate copolymer and its Salt, styrene-acrylic acid copolymer and salt thereof, styrene-methacrylic acid copolymer and salt thereof, styrene-acrylic acid-alkyl acrylate copolymer and salt thereof, styrene-methacrylic acid-alkyl acrylate copolymer Polymer 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 copolymer Copolymer and its salt, vinylnaphthalene-maleic acid copolymer Polymer 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. is there.
These anionic polymers are preferable to the self-dispersion pigment alone because they react with hydrogen ions generated by electrolysis of water and aggregate. Further, since these anionic polymers have a colorant adhesion function, there is an advantage of improving the transfer rate from the intermediate transfer body 37 to the transfer paper S in the transfer process.

An anionic surfactant is also preferably used as the pigment dispersant.
Specifically, oleic acid and its salt, lauric acid and its salt, behenic acid and its salt, stearic acid and its salt, such fatty acid and its salt, dodecylsulfonic acid and its salt, decylsulfonic acid and its Salts, and also such alkyl sulfonic acids and salts thereof, alkyl sulfate ertels such as lauryl sulfate and oleyl sulfate, dodecylbenzene sulfonic acid and salts thereof, lauryl benzene sulfonic acid and salts thereof, and such alkyl benzene sulfonic acids And salts thereof, dioctylsulfosuccinic acid and salts thereof, dihexylsulfosuccinic acid and salts thereof, and dialkylsulfosuccinic acid and salts thereof, naphthylsulfonic acid and salts thereof, naphthylcarboxylic acid and salts thereof, and the like Aromatic anionic surfactant Fluorine anionic interfaces such as polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl ether sulfonates, fluorinated alkyl carboxylic acids and their salts, fluorinated alkyl sulfonic acids and their salts A pigment is dispersed using an activator or the like.
When these surfactants are used as pigment dispersants, it is possible to use surfactants containing carboxyl groups such as alkyl carboxylates, alkylbenzene carboxylates, polyoxyethylene alkyl ether acetates, etc. High reactivity with generated hydrogen ions is preferable.

  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. If the particle size is less than 20 nm, the storage stability and jetting characteristics of the recording liquid are stable and high image quality can be obtained. Dispersion to such a fine particle size complicates the dispersion operation and classification operation. It becomes difficult to produce ink economically.

Another example of a preferable colorant used in the recording liquid of the image forming apparatus 100 is a so-called colored emulsion in which colored resin fine particles are suspended.
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, an anionic property can be obtained by forming a portion corresponding to 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 in which the colored fine particles are suspended in a liquid medium mainly composed of water is obtained.
As for the recording liquid using a colored emulsion, it is preferable to use an emulsion obtained by emulsifying and polymerizing with the above-mentioned anionic surfactant, or an emulsion having an outer shell formed of a hydrophilic resin such as polyacrylic acid or polymethacrylic acid. This is particularly preferable in that the reactivity with ions is high and the cleaning of the intermediate transfer member 37 performed by applying a voltage with the cleaning device 34 is performed satisfactorily. Further, these colored resin fine particles have the advantage of improving the transfer rate from the intermediate transfer body 37 to the transfer paper S in the transfer process, although it depends on the minimum film forming temperature. If the film is heated to a temperature equal to or higher than the minimum film-forming temperature in the transfer step, a printed matter having a high transfer rate and good gloss, light resistance, water resistance, and abrasion resistance can be obtained.

By adding a hydrophilic polymer compound to the recording liquid, the thickening and aggregating actions of the recording liquid are strengthened by reaction with hydrogen ions, and the intermediate transfer member 37 that is implemented by applying voltage by the cleaning device 34 is used. There is an advantage that the cleaning property is improved.
Examples of hydrophilic polymer compounds that can be added to the recording liquid include natural gums such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, alginic acid, 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, hydroxypropylcellulose , Fiber polymers such as ruboxymethylcellulose, starch polymers such as sodium starch glycolate and sodium starch phosphate, sodium alginate, propylene glycol alginate Seaweed polymers such as water, vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl methyl ether, 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.
Even when a water-soluble polymer compound is used in the recording liquid, it is highly reactive with hydrogen ions to use a carboxylic acid as an anion group, and an intermediate transfer is performed by applying a voltage with the cleaning device 34. This is particularly preferable because the cleaning property of the body 37 is improved. Further, similarly to the above-described anionic polymer dispersant and resin emulsion, there is an advantage that the transfer rate from the intermediate transfer body 37 to the transfer paper S in the transfer process is improved.

The recording liquid uses water as a main liquid medium. However, in order to make the recording liquid have desired physical properties or by drying the recording liquid, clogging of nozzles 61b described later provided in the heads 61Y, 61M, 61C, 61BK is blocked. In order to prevent this, it is preferable to use a non-volatile water-soluble organic solvent.
Specific examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4 -Butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, 1,2,4-butanetriol Polyhydric alcohols such as 1,2,3-butanetriol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono Polyhydric alcohol alkyl ethers such as chill ether, triethylene 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- Nitrogen-containing heterocyclic compounds such as methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, formamide, N-methylformamide, N, N- Amides such as dimethylformamide, amines such as monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, dimethyl Examples thereof include sulfur-containing compounds such as sulfoxide, sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate, and γ-butyrolactone.
These solvents are used alone or in combination with water. The content of these water-soluble organic solvents is not particularly limited, but is preferably 1 to 60% by weight, more preferably 5 to 30% by weight based on the entire recording liquid.

Examples of the pH adjuster include hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, lithium carbonate, Alkali metal carbonates such as sodium carbonate and potassium carbonate, amines such as diethanolamine and triethanolamine, boric acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid and the like can be used.
In addition, additives such as a pH buffer, a viscosity modifier, an antiseptic, an antioxidant, and a rust inhibitor can be used as necessary.

  The preferred range of physical properties of the recording liquid is a pH of 6 to 12, preferably 8 to 10, a surface tension of 10 to 60 mN / m, preferably 20 to 50 mN / m, and a viscosity of 1 to 20 mPa · s at around 25 ° C. Preferably, the conductivity is 10 to 1000 mS / m, preferably 500 to 800 mS / m.

  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 an ink chamber 61c supplied with the recording liquid from the 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. 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. The nozzle plate 61a is provided in each of the heads 61Y, 61M, 61C, 61BK, and is common to all the nozzles 61b in each of the heads 61Y, 61M, 61C, 61BK.

  Although detailed illustration is omitted, the nozzle plate 61 a includes a conductive substrate and a water repellent film formed on the surface of the substrate facing the intermediate transfer body 37. The water-repellent film may be formed by applying a fluorine-based water repellent or a silicon-based water repellent, or may be formed by plating a fluorine-based polymer or a fluorine-metal compound eutectoid, Any film having water repellency is not particularly limited. The nozzle plate 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 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. However, if the gap can be maintained, there is no particular problem even if it is less than 50 μm, and even if it is 200 μm or more, there is no problem if a stable liquid column bridge is formed.

  The ink ejecting means has a piezoelectric element as an actuator for ejecting the recording liquid from each nozzle 61b to be ejected and landed on the transfer paper S, and responds to a voltage pulse applied to the piezoelectric element under the control of the control unit 40. Thus, the recording liquid is discharged from the nozzle 61b. In this regard, the control unit 40 functions as an ink ejection control unit. 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 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 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. Therefore, the energizing unit 33 includes the intermediate transfer member 37 as an anode and the nozzle plate 61a as a cathode. The power source 33a is provided in each of the heads 61Y, 61M, 61C, 61BK.

  As shown in FIG. 3, the cleaning device 34 is upstream of the position where the recording liquid is applied by the heads 61Y, 61M, 61C, and 61BK of the intermediate transfer body 37 in the A1 direction. In addition, the first cleaning position P1 on the downstream side has a cleaning device 52 as a first cleaning device as a first cleaning means for cleaning the intermediate transfer body 37.

  The cleaning device 52 includes a web 53 as a first cleaning member in contact with the circumferential surface of the intermediate transfer member 37 at the first cleaning position P1, in other words, a shaft 54 to which one end of the web 53 is fixed, and the web 53. And a shaft 55 to which the other end is fixed.

  The cleaning device 52 also serves as a conductive first abutting member that abuts against the web 53 from the opposite side of the intermediate transfer body 37 and causes the web 53 to abut against the intermediate transfer body 37 at the first cleaning position P1. The cleaning blade 56, the shaft 57 around which the web 53 is wound between one end of the web 53 and the first cleaning position P1, and the web 53 between the other end of the web 53 and the first cleaning position P1. And a wound shaft 58.

  The cleaning device 52 also includes a voltage applying means 59 as a second voltage applying means for applying a voltage between the cleaning blade 56 and the intermediate transfer body 37, specifically, the support 37a, and the web 53 with a first cleaning. It has a motor 70 as a driving means as a first moving means for moving in the direction B1 which is the direction opposite to the direction A1 at the position P1.

  The cleaning device 52 is also realized as a function of the ink receiver 51 as a first recording liquid receiver for receiving the recording liquid that is removed from the intermediate transfer member 37 by the web 53 and drops, and a voltage applying unit. 59, a cleaning control means for controlling the driving of the motor 70, and a housing (not shown) that rotatably supports the shaft 54, the shaft 55, the shaft 57, and the shaft 58 and accommodates the web 53, the cleaning blade 56, and the ink receiver 51 inside. Have a body.

  The web 53 is stretched by the shaft 54, the shaft 55, the shaft 57, the shaft 58, and the cleaning blade 56 so that the surface thereof is in contact with the surface of the intermediate transfer body 37. The web 53 is wound on a shaft 55 to form a web roll 53a. At the start of use of the web 53, almost all of the web 53 is wound around the shaft 55 to form the web roll 53a as shown in FIG. When all the web rolls 53a are unwound, the web 53 is replaced by mounting a new web roll 53a.

  The web 53 is formed of a material that is hard to fray, does not cut even when stretched with a certain strong tension, and is thin and has a relatively small winding diameter even if it is long. Specifically, the web 53 is preferably made of an aramid or pet ultrafine fiber material that absorbs and adsorbs components generated by the aggregation of the recording liquid and the recording liquid described later.

  The web 53 abuts on the intermediate transfer body 37 that moves in the A1 direction at the first cleaning position P1 and moves in the B1 direction, thereby wiping the intermediate transfer body 37 and after passing through the transfer unit 31, the intermediate transfer body 37. The recording liquid remaining on the surface is removed from the intermediate transfer member 37.

  The cleaning blade 56 is in contact with the back surface of the web 53 so as to face the counter direction with respect to the peripheral surface of the intermediate transfer body 37 at the first cleaning position P1. Thereby, the recording liquid or the like remaining on the surface of the intermediate transfer body 37 is difficult to pass through the first cleaning position P1 and is efficiently removed by the web 53. The material of the cleaning blade 56 is preferably a conductive rubber like the surface layer 37b. The thickness of the cleaning blade 56 is preferably about 1 to 10 mm.

  The cleaning blade 56 may be formed by bonding a conductive member to a conductive rubber in order to increase its strength. As the conductive member, it is desirable to use a metal having high corrosion resistance, an alloy thereof, or a carbon plate such as glassy carbon.

  The voltage applying means 59 is realized as a function of the power source 59a, an electric circuit (not shown) in which the power source 59a is connected to the support 37a and the cleaning blade 56, and the control unit 40 functioning as a cleaning control means. Voltage application control means for controlling the application timing and application time.

  The power source 59 a has a cathode connected to the support 37 a and an anode connected to the cleaning blade 56. Therefore, the voltage applying unit 59 applies a polarity opposite to the polarity applied to the intermediate transfer member 37 by the energizing unit 33 to the intermediate transfer member 37, and is opposite to the energizing unit 33 with respect to the intermediate transfer member 37. It functions as a potential applying means for applying the potential of.

  The motor 70 rotates the shaft 54 so that the web 53 moves in the B1 direction and winds up the web 53. Thereby, the web 53 before use forming the web roll 53a is fed out toward the first cleaning position P1, and the web 53 after passing through the first cleaning position P1, that is, the intermediate transfer member 37 is cleaned. The used web 53 is wound around the shaft 54.

  The driving of the motor 70 is controlled by a moving speed setting unit realized as a function of the control unit 40 that functions as a cleaning control unit. The control unit 40 that functions as a moving speed setting unit is configured to control the web by the motor 70 according to the amount of the recording liquid discharged from the heads 61Y, 61M, 61C, and 61BK and / or the moving speed of the intermediate transfer member 37 in the A1 direction. The amount of movement of 53 in the B1 direction and / or the movement speed in the B1 direction is set. For example, if the amount of recording liquid ejected from the heads 61Y, 61M, 61C, and 61BK is large, the motor 70 is driven so that the moving amount of the web 53 in the B1 direction and / or the moving speed in the B1 direction is increased. If the moving speed of the intermediate transfer member 37 in the A1 direction is high, the motor 70 is driven so that the moving amount of the web 53 in the B1 direction and / or the moving speed in the B1 direction increases.

  The ink receiver 51 has a function of preventing the recording liquid that has been removed from the intermediate transfer body 37 by the web 53 and dropped from adhering to other members and causing contamination. The ink receiver 51 may be configured by a part of the housing.

  In the image forming apparatus 100 having such a configuration, the intermediate transfer body 37 rotates 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. In the process, the yellow, magenta, cyan, and black recording liquids are transferred from the heads 61Y, 61M, 61C, and 61BK so that the image areas of the respective colors of yellow, magenta, cyan, and black overlap with the same position on the intermediate transfer body 37. The images are ejected in such a manner that they are sequentially overlapped from the upstream side toward the downstream side in the A1 direction, and an image is temporarily carried on the intermediate transfer member 37.

At this time, the energizing unit 33 is driven by the control unit 40 as the voltage application control unit, and a voltage is applied between the support 37a and the nozzle plate 61a from the power source 33a.
In this state, the recording liquid is applied from the heads 61Y, 61M, 61C, 61BK onto the intermediate transfer body 37. At that time, first, the heads 61Y, 61M, 61C, 61BK are used as shown in FIG. As shown in FIG. 2B, the recording liquid forming a meniscus in the nozzle 61b moves toward the intermediate transfer body 37 as shown in FIG. 2B, and the recording liquid is recorded between the nozzle 61b and the intermediate transfer body 37. A bridge of a liquid column made of liquid is temporarily formed, and then, as shown in FIG. 2C, the bridge of the liquid column made of recording liquid is divided so as to be carried on the intermediate transfer body 37, and the intermediate transfer. An image of the recording liquid is formed on the body 37.

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

  As a result, the 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 to generate protons (H +). Therefore, as shown in FIG. The pigment P dispersed by D aggregates via protons. Thereby, the occurrence of bleeding between adjacent dots is suppressed, and a high-definition image is formed. In addition, there is an advantage that clogging of the nozzle 61b is prevented by such voltage application. The time for forming such a bridge can be controlled by the peak voltage and pulse width of the electromagnetic pulse applied to the piezoelectric element.

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. This is because the anionic recording liquid has increased dispersibility of the pigment due to negatively charged electrostatic repulsion, so that the dispersion and solubility of the pigment increase with an increase in pH. Is due to the loss of electrostatic repulsion and aggregation.

  Therefore, 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 aggregation of the pigment is performed simultaneously with the landing of the recording liquid onto the intermediate transfer body 37. As a result, pigment bleeding does not occur between adjacent recording liquid dots, and a very high-definition solute image is formed.

  As described above, the energizing means 33 includes the intermediate transfer body 37 and the heads 61Y, 61M, 61C, 61BK, specifically the nozzle plate 61a for electrolyzing the recording liquid forming the bridge B of the liquid column. It is the structure for performing the voltage application between.

  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.

  In synchronization with the timing at which the leading edge of the image carried on the intermediate transfer body 37 reaches the transfer unit 31, a single sheet of transfer paper S fed from the paper supply unit 20 is supplied to the transfer unit 31, and the transfer roller 38. , The image carried on the intermediate transfer body 37 is transferred to the transfer sheet S passing through the transfer unit 31, and an image is formed on the surface of the transfer sheet S. The transfer sheet S on which the image is formed is guided to the paper discharge tray 25 and stacked on the paper discharge tray 25.

  When the image is transferred to the transfer paper S in this way, the recording liquid containing the aggregation component is transferred to the transfer paper S. Therefore, by forming an image with the colorant aggregated by the above-described aggregation action, even when the transfer paper S is plain paper, high image density can be achieved at high speed while preventing or suppressing feathering and bleeding. High-quality image formation 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 is suppressed or prevented, and thereby the transfer paper S carrying an image is conveyed. The handling of the transfer sheet S is facilitated, for example, the property is improved and jamming is prevented or suppressed.

  Almost no components due to the recording liquid remain on the intermediate transfer body 37 that has passed through the transfer section 31 due to the transfer in the transfer section 31, but the intermediate transfer body 37 is obtained by the cleaning device 34 as described below. By receiving the cleaning, the offset of the recording liquid is highly prevented or suppressed, and even if image formation is repeatedly performed, background contamination due to the offset is prevented or suppressed, and image deterioration and deterioration of the intermediate transfer member 37 are suppressed or prevented. Thus, it is possible to perform good image formation over time.

The cleaning operation of the intermediate transfer member 37 by the cleaning device 34 will be described.
The components due to the recording liquid remaining on the intermediate transfer body 37 that has passed through the transfer section 31 are scraped off by the web 53 when they reach the first cleaning position P1. At this time, the voltage application unit 59 applies a voltage opposite to the polarity applied to the intermediate transfer member 37 by the energization unit 33 to the intermediate transfer member 37 so that the voltage between the intermediate transfer member 37 and the cleaning blade 56 is increased. Applying.

  Therefore, the voltage application unit 59 causes the intermediate transfer body 37 to function as a cathode, and more precisely causes the web 53 at the first cleaning position P1 in contact with the cleaning blade 56, more precisely, the cleaning blade 56 to function as an anode.

  The voltage of the power source 59a causes an electrochemical reaction according to the reaction formula (1) on the surface of the intermediate transfer member 37, and also causes an electrochemical reaction according to the reaction formula (2) on the surface of the cleaning blade 56, more precisely, the web 53. The recording liquid between the cleaning blade 56 and the intermediate transfer member 37 is set to be electrolyzed.

  Therefore, the voltage applying unit 59 applies a voltage for electrolyzing the recording liquid positioned between the cleaning blade 56, more precisely, the web 53 and the intermediate transfer member 37, and components resulting therefrom. ing. By applying this voltage, components such as solids aggregated on the surface of the intermediate transfer member 37 are dispersed and dissolved in the liquid component, aggregated on the surface of the web 53, fixed, and adsorbed. The liquid component 53 also wipes and absorbs the liquid component from the intermediate transfer member 37 by the movement in the B1 direction.

  By moving the web 53 in the B1 direction, components caused by the recording liquid and other foreign matters such as paper dust and dust attached to the intermediate transfer member 37 are attached to the web 53 and conveyed. While moving away from the cleaning position P1, a new portion of the web 53 comes into contact with the intermediate transfer member 37 at the first cleaning position P1, so that such a cleaning operation is always performed satisfactorily. In this way, the surface of the intermediate transfer member 37 is kept in a highly clean state.

  Therefore, the cleaning device 34 removes the contamination due to the components caused by the recording liquid of the intermediate transfer member 37 by utilizing the electrolysis action, and performs the cleaning efficiently and maintains this cleaning performance for a long period of time. It has become.

  The control unit 40 functioning as the moving speed setting means is the amount of the recording liquid ejected from the heads 61Y, 61M, 61C, 61BK so that the web 53 can sufficiently perform the above-described adsorption and absorption and obtain such cleaning performance. And / or the amount of movement of the web 53 in the B1 direction and / or the movement speed in the B1 direction by the motor 70 is set according to the moving speed of the intermediate transfer member 37 in the A1 direction. Since the web 53 is an end member, in order to use the web 53 for as long as possible without consuming the web 53 more than necessary, the amount of movement is possible within the range in which such cleaning performance can be obtained. Suppressed as long as possible.

A modification of the cleaning device 34 will be described with reference to FIGS. 6 and 7.
In these modified examples, the cleaning device 34 is upstream of the position where the recording liquid is applied by the heads 61Y, 61M, 61C, and 61BK of the intermediate transfer member 37 in the A1 direction in addition to the cleaning device 52. The second cleaning position P2 downstream of the first cleaning position P1 has a cleaning device 82 as a second cleaning device as a second cleaning means for cleaning the intermediate transfer body 37. . Since the configuration, operation, and the like of the cleaning device 52 are the same as those already described, description thereof is omitted here.

  In the modification shown in FIG. 6, the cleaning device 82 includes a film member 83 as a second cleaning member that is in contact with the circumferential surface of the intermediate transfer body 37 at the second cleaning position P2, in other words, the surface of the film member 83. It has a shaft 84 with one end fixed and a shaft 85 with the other end fixed to the film member 83.

  The cleaning device 82 is also in contact with the film member 83 from the opposite side of the intermediate transfer body 37, and serves as a second contact member in which the film member 83 is in contact with the intermediate transfer body 37 at the second cleaning position P2. A cleaning blade 86, a shaft 87 around which the film member 83 is wound between one end of the film member 83 and the second cleaning position P2, and a film between the other end of the film member 83 and the second cleaning position P2. And a shaft 88 around which the member 83 is wound.

  The cleaning device 82 also has a motor 90 as a second moving means for moving the film member 83 in the C1 direction opposite to the A1 direction at the second cleaning position P2 and an intermediate position between the film member 83 and the motor 90. An ink receiver 91 as a second recording liquid receiver for receiving the recording liquid removed from the transfer body 37 and dripping, a cleaning control means for controlling the driving of the motor 90, which is realized as a function of the control unit 40, and a shaft 84, a shaft 85, a shaft 87, and a shaft 88 are rotatably supported, and a film member 83, a cleaning blade 86, and a casing (not shown) in which an ink receiver 91 is accommodated.

  The film member 83 is stretched by a shaft 84, a shaft 85, a shaft 87, a shaft 88, and a cleaning blade 86 so that the surface thereof is in contact with the surface of the intermediate transfer body 37. The film member 83 is wound around the shaft 85 to form a film roll 83a. As shown in FIG. 6, when the film member 83 starts to be used, almost all of the film member 83 is wound around the shaft 85 to form a film roll 83a. When all the film rolls 83a are unwound, the film member 83 is replaced by mounting a new film roll 83a.

  The film member 83 is formed of a material that does not cut even when stretched with a certain amount of strong tension, and is thin and has a relatively small winding diameter even if it is long. Specifically, the material of the film member 83 is not particularly limited, and examples thereof include a PE film, a PVC film, a PET film, a PVA film, a PP film, and a PC film.

  The film member 83 abuts on the intermediate transfer body 37 moving in the A1 direction at the second cleaning position P2 and moves in the C1 direction to wipe the intermediate transfer body 37 and pass the first cleaning position P1. The recording liquid remaining on the surface of the intermediate transfer member 37 is removed from the intermediate transfer member 37.

  The cleaning blade 86 is in contact with the back surface of the film member 83 so as to face the counter direction with respect to the peripheral surface of the intermediate transfer body 37 at the second cleaning position P2. Thereby, the recording liquid or the like remaining on the surface of the intermediate transfer member 37 is difficult to pass through the second cleaning position P2, and is efficiently removed by the film member 83. The material of the cleaning blade 86 is preferably a material resistant to abrasion with the film member 83, and silicone rubber, nitrile rubber, urethane rubber, fluorine rubber, EPDM, and the like are suitable. The thickness of the cleaning blade 86 is preferably about 1 to 10 mm.

  The motor 90 rotates the shaft 84 so that the film member 83 moves in the C1 direction and winds up the film member 83. Thereby, the web 83 before use forming the film roll 83a is fed toward the second cleaning position P2, and the film member 83, that is, the intermediate transfer body 37 after passing through the second cleaning position P2, is cleaned. The used film member 83 is wound around the shaft 84.

  The driving of the motor 90 is controlled by a moving speed setting unit realized as a function of the control unit 40 that functions as a cleaning control unit. The control unit 40 that functions as a moving speed setting unit drives the motor 90 at a constant speed, and sets the moving amount of the film member 83 in the C1 direction and / or the moving speed in the C1 direction, similarly to the motor 70. You may do it.

  The ink receiver 91 has a function of preventing the recording liquid that has been removed from the intermediate transfer body 37 by the film member 83 and dropped from adhering to other members and causing contamination. The ink receiver 91 may be configured by a part of the housing.

  With the above-described configuration, the cleaning device 82 is configured to transfer components due to the recording liquid that the cleaning device 52 has not completely removed from the intermediate transfer body 37 at the first cleaning position P1 to the intermediate transfer at the second cleaning position P2. Wipe off body 37 and remove. In this way, the cleaning device 82 cleans the components caused by the recording liquid on the intermediate transfer member 37 that could not be scraped off by the web 53 with the film member 83, so that the intermediate transfer member 37 is further removed. Highly clean.

Regarding the modification shown in FIG. 7, differences from the modification shown in FIG. 6 will be mainly described.
In the modification shown in FIG. 6, the film member 83 has an end shape. However, in the modification shown in FIG. 7, the film member 83 has an endless shape. That is, the film member 83 provided in the modification shown in FIG. 7 is an endless belt-like film member.

  As the film member 83 is endless, the motor 90 drives the shaft 84 to move the film member 83 endlessly in the C1 direction, and unwinds the film member 83. FIG. The film roll 83a and the shaft 85 provided in the illustrated modification are omitted.

  Further, since the film member 83 is endlessly moved along with the endless shape of the film member 83 and is repeatedly used for cleaning the intermediate transfer body 37, the cleaning device 82 cleans the film member 83. Cleaning means 92 is provided. In addition, the cleaning means 92 may be provided in the modification shown in FIG.

  Since the film member 83 is repeatedly used for cleaning the intermediate transfer member 37, the modification shown in FIG. 7 reduces the cost required for the film member 83 itself and its replacement work, compared to the modification shown in FIG. Has been. However, in the modification shown in FIG. 6, since a new part of the film member 83 contacts the intermediate transfer body 37, there is an advantage that the cleaning is always performed well.

  In the modification shown in FIG. 7A, the cleaning unit 92 includes a blade-shaped cleaning member 93 as a film member cleaning blade that is in contact with the film member 83 to clean the film member 83, and a cleaning member 93. It has a housing 94 that houses a cleaning member 93 that is a deposit receiving member as a collecting member for collecting a substance such as a recording liquid removed from the film member 83.

  The cleaning member 92 is in contact with the surface of the film member 83 rotating in the C1 direction so as to face the counter direction. Thereby, the recording liquid or the like remaining on the surface of the film member 83 is difficult to pass through the contact position with the cleaning member 93 and is efficiently removed by the cleaning member 93.

  In the modification shown in FIG. 7B, the cleaning unit 92 includes a brush-like cleaning member 95 as a film member cleaning brush that is in contact with the film member 83 to clean the film member 83, and a cleaning member 95. The housing 96 containing the cleaning member 95, which is a deposit receiving member as a recovery member for recovering the substance such as the recording liquid removed from the film member 83, and the cleaning member 95 at the contact position with the film member 83 are C1. A motor (not shown) that rotates in the direction opposite to the direction and a cleaning control unit that is realized as one function of the control unit 40 that functions as a cleaning control unit and controls the driving of the motor.

  Since the cleaning member 95 rotates in the counter direction with respect to the surface of the film member 83 rotating in the C1 direction, the recording liquid remaining on the surface of the film member 83 is unlikely to pass through the contact position with the cleaning member 95. And is efficiently removed by the cleaning member 95.

  The casing 94 and the casing 96 have a function of preventing the recording liquid removed from the intermediate transfer body 37 by the film member 83 from being attached to other members and causing contamination. The casing 94 and the casing 96 may be members common to the ink receiver 91. If the casing 94, the casing 96, and the ink receiver 91 are a common member, advantages such as reduction in the number of parts of the cleaning unit 92, the cleaning device 82, and the cleaning device 34, size reduction, and cost reduction can be obtained.

Whether the cleaning of the intermediate transfer member 37 and the image formation were performed satisfactorily was confirmed by the following experiment using the cleaning device 34 of each configuration example described above as an example.
The experimental conditions are as follows. Note that the configuration of the image forming apparatus 100 is not limited to the following conditions.

  The image forming apparatus used in the experiment is an image forming apparatus obtained by remodeling an ink jet printer GX5000 (manufactured by Ricoh) having the same configuration as that of the image forming apparatus 100 that satisfies the following conditions.

  The intermediate transfer member 37 uses an aluminum base tube, which is a base material having a length of 250 mm and a diameter of 60 mm, as the support member 37a, and a volume resistivity of 500 Ω · cm and a thickness of 0. It has a 2 mm conductive silicone rubber layer. The intermediate transfer member 37 is rotationally driven in the A1 direction at a linear velocity of the outer periphery of 200 mm / second.

The gap between each of the heads 61Y, 61M, 61C, 61BK and the intermediate transfer member 37 was 100 μm, and a voltage of 100 V was applied between them. The polarity of the applied voltage is as described above. The heads 61Y, 61M, 61C, 61BK are provided with a piezo element as an actuator for ejecting the recording liquid from each nozzle 61b to be ejected and landed on the transfer paper S. By driving the piezo element, the intermediate transfer body 37 is driven. An arbitrary pattern of ink dots can be formed on the surface. However, in this experiment, the recording liquid was discharged only from the head 61BK.
The pattern used in the experiment is adjusted so that the image area ratio is 5%, and the head 61BK continuously discharges the recording liquid so as to achieve this image area ratio.

The transfer roller 38 is pressed against the intermediate transfer member 37 with a load of 20 kgf / cm ² , and rotates with the intermediate transfer member 37.

  As the transfer paper S, plain paper (my paper) was used. The transfer sheet S is continuously passed through the transfer unit 31 so that an image having an image area ratio of 5% is continuously transferred.

As for the cleaning device 34, a blade made of fluoro rubber having a thickness of 6 mm mixed with CNT (carbon nanotubes) is used as the cleaning blade 56, and a cloth having a thickness of 50 μm made of ultrafine fibers made of a pet-based material is used as the web 53. Was used.
A voltage of 50 V was applied between the cleaning blade 56 and the intermediate transfer member 37. The polarity of the applied voltage is as described above.
The moving speed of the web 53 is automatically set based on the discharge amount of the recording liquid from the heads 61Y, 61M, 61C, 61BK and the rotational speed of the intermediate transfer body 37. It was 1 mm / s.

In the cleaning device 34 shown in FIGS. 6 and 7, a PET film having a thickness of 100 μm was used as the film member 83, and a blade made of EPDM having a thickness of 6 mm was used as the cleaning blade 86.
In the cleaning device 34 shown in FIG. 7A, a blade made of EPDM having a thickness of 6 mm was used as the cleaning member 93.

The following recording liquid was used as the recording liquid discharged from the head 61BK.
<Black recording liquid>
-Sulfonic acid group-bonded carbon black pigment dispersion (CAB-O-JET-200, solid content 20% by mass, manufactured by Cabot Specialty Chemicals Inc.): 35.0% by mass
2-pyrrolidone: 10.0% by mass
・ Glycerin: 14.0% by mass
Propylene glycol monobutyl ether: 0.9% by mass
・ Sodium dehydroacetate: 0.1% by mass
・ Distilled water: remaining amount
Thereafter, the pH was adjusted to 9.1 with a 5% by mass aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore size of 0.8 μm.

The first embodiment is an image forming apparatus using the cleaning device 34 having the configuration shown in FIGS. 1 and 3 that satisfies the above conditions. In each of the second, third, and fourth embodiments, the above conditions are satisfied. FIG. 6 shows an image forming apparatus using the cleaning device 34 configured as shown in FIGS. 6, 7 (a), and 7 (b).
Further, as a comparative example, an image forming apparatus provided with the cleaning device 34 having a configuration in which the web 53 is excluded and the cleaning blade 56 and the intermediate transfer member 37 are not energized from the configuration of the first embodiment is used.

The evaluation procedure for each example and comparative example is as follows.
As described above, the transfer sheet S is continuously passed through and a total of 1000 sheets are passed. During that time, the recording liquid on the intermediate transfer member 37 cleaned by the cleaning device 34 is printed every 100 sheets. And image density was measured by copying on paper. The image density in this case is called the image density before being left.
After passing 1,000 sheets, the image density was measured in the same manner again after being left for one week. The image density in this case is called the image density after being left.

The evaluation results are as follows.
As a result of comparing Example 1 and the comparative example, as for the image density before being left, the image density of Example 1 was lower than the image density of the comparative example. As for the image density after being left, the image density in Example 1 was almost the same as the image density before being left, but the image density in the comparative example was higher than the image density before being left. When the cleaning device 34 of the comparative example after being left is checked, the first cleaning position P <b> 1 where the solid content deposited by evaporation of the moisture in the recording liquid is the contact portion between the cleaning blade 56 and the intermediate transfer member 37. It was confirmed that the cleaning blade 56 was partially damaged.
Based on these results, the cleaning performance of the intermediate transfer body 37 is improved by using the web 53 and energizing the cleaning blade 56 and the intermediate transfer body 37 with the polarity described above. It was confirmed that the cleaning performance was maintained for a long time.

It was confirmed that Example 2, Example 3, and Example 4 were almost the same as Example 1 or slightly lower in image density than Example 1.
Accordingly, it was confirmed that the cleaning performance of the intermediate transfer member 37 is improved by using the cleaning device 82.

  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 pigment in the conductive recording liquid may be dispersed by a cationic dispersant and aggregated via hydroxide ions generated on the surface of the intermediate transfer member functioning as a cathode.
The intermediate transfer member does not need to be conductive as a whole, and at least the surface may be conductive.

  The image forming apparatus to which the present invention is applied is not limited to the above-described type of image forming apparatus, but may be other types of image forming apparatuses, that is, a shuttle type with respect to the head, or a copying machine or a facsimile alone. Alternatively, these multifunction peripherals, multifunction peripherals such as monochrome machines related thereto, other image forming apparatuses used for forming electric circuits, and image forming apparatuses used for forming predetermined images in the biotechnology field 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 First voltage application unit 37 Intermediate transfer member 40 Movement speed setting unit 51 First recording liquid receiver 52 First cleaning unit 53 First cleaning member 56 First contact member 59 Second voltage application unit 61b Nozzles 61Y, 61M, 61C, 61BK Head 64 Transfer means 70 First moving means 82 Second cleaning means 83 Second cleaning member 86 Second contact member 91 Second recording liquid receiver 92 Cleaning means 93 Blade shape Cleaning member 94 Recovery member 95 Brush-like cleaning member 96 Recovery member 100 Image forming apparatus A1 Predetermined direction B1 Reversed direction to predetermined direction C1 Reversed direction to predetermined direction P1 First cleaning position P2 First cleaning position S Recording material

JP 55-65269 A JP-A-56-86789 JP-A-55-144172 JP 52-53012 A JP-A-56-89594 JP-A-56-89595 Japanese Patent Laid-Open No. 5-96720 JP-A-64-63185 JP-A-8-20159 Japanese Patent Laid-Open No. 8-20161 Japanese Patent No. 3461202 JP-A-8-142500 JP-A-10-250216 Japanese Patent No. 3583257 Japanese Patent Laid-Open No. 11-10856 JP 2000-44855 A JP 2000-63719 A US Pat. No. 4,538,156 US Pat. No. 5,099,256 Japanese Patent Application Laid-Open No. Sho 62-92849 Japanese Patent Laid-Open No. 11-188858 JP 2000-343808 A Japanese Patent No. 3658765 JP 2003-246135 A JP 2002-370441 A JP 2005-170036 A JP 2003-82265 A JP 2008-019286 A JP 2010-188665 A JP 7-164624 A Japanese Patent No. 3114783 JP 2009-149019 A JP 2011-079196 A1 Japanese Patent No. 2676699 JP 2011-034048 A

Claims (10)

A head having a nozzle for discharging a conductive recording liquid;
An intermediate transfer body that moves in a predetermined direction and is provided with the conductive recording liquid discharged by the head, and at least the surface of which is conductive;
For applying a voltage between the intermediate transfer member and the head for electrolyzing a conductive recording liquid discharged from the head and temporarily bridging between the head and the intermediate transfer member. First voltage applying means;
Transfer means for transferring an image carried on the intermediate transfer member by a conductive recording liquid to a recording material;
In the predetermined direction, the intermediate transfer member is upstream of the position where the conductive recording liquid is applied by the head and downstream of the position where the image is transferred to the recording material by the transfer unit. First cleaning means for cleaning the intermediate transfer member at a first cleaning position;
The first cleaning means
A first cleaning member that contacts the intermediate transfer member at a first cleaning position and wipes the intermediate transfer member by moving in a direction opposite to the predetermined direction;
First moving means for moving the first cleaning member in the reverse direction so that the first cleaning member is drawn out toward the first cleaning position and wound up after passing through the first cleaning position; ,
A conductive first contact member that contacts the first cleaning member from the opposite side of the intermediate transfer member and contacts the first cleaning member to the intermediate transfer member at a first cleaning position;
A voltage having a polarity opposite to the polarity applied to the intermediate transfer member is applied to the intermediate transfer member by a first voltage applying means, and a first voltage is applied between the first contact member and the intermediate transfer member. And a second voltage applying means for applying a voltage for electrolyzing the conductive recording liquid positioned between the cleaning member and the intermediate transfer member. The image forming apparatus according to claim 1.
Depending on the amount of the conductive recording liquid discharged from the head and / or the moving speed of the intermediate transfer member in the predetermined direction, the amount of movement of the cleaning member in the reverse direction by the moving means and / or An image forming apparatus comprising a moving speed setting means for setting a moving speed in the opposite direction. The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein the first cleaning means includes a first recording liquid receiver for receiving the conductive recording liquid which is removed from the intermediate transfer member by the first cleaning member and drops. The image forming apparatus according to any one of claims 1 to 3,
In the predetermined direction, the intermediate transfer member at the second cleaning position upstream of the position where the conductive recording liquid is applied by the head and downstream of the first cleaning position. A second cleaning means for cleaning the body,
The second cleaning means is
A second cleaning member that contacts the intermediate transfer member at a second cleaning position and wipes the intermediate transfer member by moving in a direction opposite to the predetermined direction;
Second moving means for moving the second cleaning member in the reverse direction;
An image forming apparatus comprising: a second abutting member that abuts against the second cleaning member from the opposite side of the intermediate transfer member, and abuts the second cleaning member against the intermediate transfer member at a second cleaning position. . The image forming apparatus according to claim 4.
The second cleaning member is a member that is fed out toward the second cleaning position by being moved in the reverse direction by the second moving means and wound up after passing through the second cleaning position. An image forming apparatus. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the second cleaning member is an endless member that is moved in the reverse direction by a second moving unit. The image forming apparatus according to any one of claims 4 to 6,
The image forming apparatus, wherein the second cleaning unit has a second recording liquid receiver for receiving the conductive recording liquid that is removed from the intermediate transfer member by the second cleaning member. The image forming apparatus according to any one of claims 4 to 7,
The image forming apparatus, wherein the second cleaning unit includes a cleaning unit that cleans the second cleaning member. The image forming apparatus according to claim 8.
The cleaning means collects a blade-like or brush-like cleaning member that is in contact with the second cleaning member to clean the second cleaning member, and a material removed from the second cleaning member by the cleaning member. An image forming apparatus comprising: a collecting member. The image forming apparatus according to claim 9, wherein the image forming apparatus is subordinate to the image forming apparatus according to claim 7.
The image forming apparatus, wherein the recovery member and the second recording liquid receiver are a common member.

Images