JP5407722B2 - Cleaning device and image forming apparatus - Google Patents

Description

  The present invention relates to a cleaning device for cleaning an intermediate transfer member provided in an ink jet type image forming apparatus for forming an image by applying a recording liquid such as ink to an intermediate transfer member with a head, and to such an image forming apparatus having the same.

  2. Description of the Related Art Conventionally, image forming apparatuses such as ink jet printers that include a head that ejects a recording liquid such as ink from a plurality of nozzles and perform ink jet recording are known (for example, see [Patent Document 1] to [Patent Document 29]). .

  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 10]). 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 11]). 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 12]). 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 the colorant of the ink is applied to a recording material (for example, [Patent Document 13] To [Patent Document 15]). 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 16] and [Patent Document 17]). 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 18]). 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. Methods have been proposed (see, for example, [Patent Document 19] and [Patent Document 20]). 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 21]). 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 22]).
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 23] to [Patent Document 25]). 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 23]). It has also been proposed that scratch resistance can be imparted in the same manner by imparting a water-soluble resin to the image before transfer (see, for example, [Patent Document 24]). 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 25]).
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 26]).

  As described above, various countermeasures for the problems such as bleeding and beading that are peculiar to the intermediate transfer type inkjet image forming apparatus have been proposed.

  On the other hand, an intermediate transfer type image forming apparatus requires an initialization process for removing stains such as ink remaining after transfer, processing liquid and reaction liquid. 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, cleaning means such as a blade (for example, [Patent Literature 16], [Patent Literature 18], [Patent Literature 20] to [Patent Literature 22], [Patent Literature 24] to [Patent Literature 29]) The method of scraping from the surface of the intermediate transfer member is generally used.

  For example, as such a cleaning unit, a configuration in which a cleaning medium having higher wettability than the intermediate transfer body is brought into contact with the intermediate transfer body to transfer and remove the transfer residue such as ink to the cleaning medium (for example, [See Patent Document 27] and [Patent Document 28]). However, if this configuration is simply employed, there is a problem that a part of the removed ink remains attached to the cleaning medium, and the cleaning performance is deteriorated and the reverse transfer to the surface of the intermediate transfer member occurs. For this reason, it is necessary to further remove ink stains adhering to the cleaning medium.

That is, in order to maintain the performance of the cleaning member that removes the ink after transfer from the intermediate transfer member, the cleaning member is further cleaned (for example, [Patent Document 20], [Patent Document 24], [Patent Document]). 27] to [Patent Document 29]).
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 / non-image area A cleaning method provided with a cleaning liquid supply control means for controlling is proposed (see, for example, [Patent Document 29]). However, if the cleaning liquid supply means is an injection method in which the cleaning liquid is sprayed and the liquid amount is controlled in the image area / non-image area, the apparatus becomes large and a certain amount of cleaning liquid is required. There are problems such as.

  However, in the configuration proposed heretofore for further cleaning of the cleaning member, the performance of cleaning the cleaning member may be insufficient, and a proposal of a new technique that can clean the cleaning member satisfactorily has been awaited. It was where it was.

  The present invention is provided in an ink jet type image forming apparatus for forming an image by applying a recording liquid such as ink to an intermediate transfer member by a head, and a cleaning member for cleaning the intermediate transfer member and the cleaning member by a new method. It is an object of the present invention to provide a cleaning device provided with a cleaning means for performing good cleaning, and such an image forming apparatus having the same.

To achieve the above object, a first aspect of the present invention, a cleaning member for cleaning the recording liquid on contact with the intermediate transfer member to an intermediate transfer body which is imparted recording liquid by the head, least the the recording liquid in contact with the cleaning member is cleaned from the said intermediate transfer member by a cleaning member, a cleaning electrode for cleaned by electrolysis, between the cleaning electrode and the intermediate transfer member, wherein The cleaning apparatus includes a voltage applying unit that applies a voltage for electrolyzing the recording liquid conducted to the intermediate transfer member and the cleaning electrode .

  According to a second aspect of the present invention, in the cleaning device according to the first aspect, the cleaning device further includes an electrode cleaning means for cleaning the cleaning electrode.

  According to a third aspect of the present invention, in the cleaning device according to the second aspect, the electrode cleaning means includes an electrode cleaning member that is in contact with the cleaning electrode, and a component that is removed from the cleaning electrode by the electrode cleaning member. And a recovery unit for recovery.

The invention of claim 4, wherein, in the cleaning device according to any one of claims 1 to 3, the cleaning liquid for cleaning the recording liquid reacting with the recording liquid and the cleaning electrode and the intermediate transfer body It has a cleaning liquid supply means which supplies it so that it may touch.

According to a fifth aspect of the invention, the cleaning device according to claim 4, and forming a liquid reservoir by the cleaning liquid and the cleaning electrode and the cleaning member by said intermediate transfer member.

  According to a sixth aspect of the present invention, in the cleaning device according to the fifth aspect, the cleaning liquid supply means is detected by a liquid amount detecting means for detecting the amount of the cleaning liquid in the liquid reservoir, and the liquid amount detecting means. And a liquid amount control means for supplying the cleaning liquid to the liquid reservoir based on the amount and controlling the same amount.

  A seventh aspect of the present invention is the cleaning apparatus according to the sixth aspect, wherein the electrode cleaning member cleans the cleaning liquid adhering to the cleaning electrode, and The collection unit collects the cleaning liquid removed from the cleaning electrode by the electrode cleaning member, and the cleaning liquid supply unit supplies the cleaning liquid collected by the collection unit to the liquid amount control unit. It has a recycling means.

  According to an eighth aspect of the present invention, in the cleaning device according to any one of the first to seventh aspects, the cleaning electrode is integral with the cleaning member.

  According to a ninth aspect of the present invention, in the cleaning device according to any one of the first to seventh aspects, the cleaning electrode is separate from the cleaning member.

  According to a tenth aspect of the present invention, in the cleaning device according to the ninth aspect, the cleaning electrode is a roller.

  An eleventh aspect of the present invention is an image forming apparatus having the cleaning device according to any one of the first to tenth aspects.

The present invention is cleaned and the cleaning member for cleaning the recording liquid on contact with the intermediate transfer member to an intermediate transfer body which is imparted recording liquid by the head, from least the cleaning member by the intermediate transfer member The recording liquid in contact with the cleaning member is electrically connected to the intermediate transfer body and the cleaning electrode between the cleaning electrode for cleaning by electrolysis and the intermediate transfer body and the cleaning electrode. And a voltage applying means for applying a voltage for electrolyzing the recording liquid, the recording liquid attached to the cleaning member can be cleaned by electrolysis, and the intermediate transfer member is cleaned by the cleaning member. The intermediate transfer member over time. Improved performance to keep Kiyoshi state, it is possible to provide a cleaning apparatus that can contribute over time to do that good image formation.

  If an electrode cleaning means for cleaning the cleaning electrode is provided, it becomes possible to clean the recording liquid attached to the cleaning member over time by electrolysis by cleaning the cleaning electrode. It is possible to clean the intermediate transfer member with the member well over time, improving the ability to keep the intermediate transfer member clean over time, contributing to good image formation over time. The resulting cleaning device can be provided.

  If the electrode cleaning means has an electrode cleaning member that is in contact with the cleaning electrode and a recovery unit that recovers the component removed from the cleaning electrode by the electrode cleaning member, the electrode cleaning member performs cleaning with the electrode cleaning member. By cleaning the electrode for cleaning and collecting the components removed by the cleaning in the recovery section, it becomes possible to clean the recording liquid adhering to the cleaning member over time by electrolysis, and the intermediate transfer member can be cleaned by the cleaning member. It is possible to provide a cleaning device that can perform well over time, improve the performance of keeping the intermediate transfer member clean over time, and contribute to performing good image formation over time. it can.

If it has a cleaning liquid supply means for supplying to contact the cleaning fluid for cleaning the recording liquid reacting with the recording liquid to said intermediate transfer member and the cleaning electrode, the recording liquid adhering to the cleaning member Can be cleaned by electrolysis, and the recording liquid can also be cleaned with a cleaning liquid, so that the intermediate transfer member can be cleaned better. It is possible to provide a cleaning device that improves the performance of maintaining a clean state and can contribute to good image formation over time.

If to form a liquid pool by the cleaning liquid and the cleaning electrode and the cleaning member by said intermediate transfer body, it becomes possible to clean by electrolysis recording liquid adhering to the cleaning member, the liquid The recording liquid can be constantly cleaned by the cleaning liquid in the pool, and the intermediate transfer member can be cleaned more satisfactorily. The performance of keeping the intermediate transfer member clean over time is improved and good. It is possible to provide a cleaning device that can contribute to performing accurate image formation over time.

  The cleaning liquid supply means supplies a liquid amount detection means for detecting the amount of the cleaning liquid in the liquid reservoir, and supplies the cleaning liquid to the liquid reservoir based on the amount detected by the liquid amount detection means. And a liquid amount control means for controlling the amount of liquid, the recording liquid adhering to the cleaning member can be cleaned by electrolysis, and the recording liquid can be removed by the cleaning liquid maintained at an appropriate amount in the liquid reservoir. It is possible to clean well at all times, the intermediate transfer member can be cleaned better, the performance of keeping the intermediate transfer member clean over time is improved, and good image formation over time It is possible to provide a cleaning device that can contribute to the above.

  The electrode cleaning member cleans the cleaning liquid adhering to the cleaning electrode, and the recovery unit recovers the cleaning liquid removed from the cleaning electrode by the electrode cleaning member, and the cleaning liquid supply means Is provided with a recycling means for supplying the cleaning liquid recovered in the recovery part to the liquid amount control means, and it becomes possible to clean the recording liquid attached to the cleaning member by electrolysis, It is possible to always clean the recording liquid with the cleaning liquid kept at an appropriate amount of the liquid pool while reducing the running cost by recycling the cleaning liquid, and it is possible to perform the cleaning of the intermediate transfer member better. Yes, intermediate transfer body over time Improved performance to keep clean state, it is possible to provide a cleaning apparatus that can contribute over time to do that good image formation.

  If the cleaning electrode is integrated with the cleaning member, the recording liquid adhering to the cleaning member can be cleaned by electrolysis using the cleaning electrode integrated with the cleaning member. With this configuration, the intermediate transfer member can be satisfactorily cleaned by the cleaning member, and the performance of keeping the intermediate transfer member clean with time is improved, and good image formation is performed with time. A cleaning device that can contribute can be provided.

  If the cleaning electrode is separate from the cleaning member, the recording liquid adhering to the cleaning member can be cleaned by electrolysis using a cleaning electrode separate from the cleaning member. The degree of freedom of installation of the electrodes is relatively high, and the intermediate transfer member can be satisfactorily cleaned by the cleaning member, and the performance of maintaining the intermediate transfer member in a clean state with time is improved and a good image is obtained. A cleaning device that can contribute to the formation over time can be provided.

  If the cleaning electrode is a roller, the recording liquid adhering to the cleaning member can be cleaned by electrolysis using a cleaning electrode separate from the cleaning member. The degree of freedom is relatively high, and it is relatively easy to increase the surface area of the cleaning electrode that can contribute to electrolysis, and the cleaning of the intermediate transfer member with the cleaning member can be performed well over time. Therefore, the performance of maintaining the intermediate transfer member in a clean state with time can be improved, and a cleaning device that can contribute to good image formation with time can be provided.

  Since the present invention is in an image forming apparatus having such a cleaning device, the recording liquid adhering to the cleaning member can be cleaned by electrolysis, and the intermediate transfer member can be satisfactorily cleaned by the cleaning member. In addition, the performance of maintaining the intermediate transfer member in a clean state with time can be improved, and an image forming apparatus capable of performing good image formation with time can be provided.

1 is a schematic front view of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic diagram illustrating a state in which a recording liquid is applied from a head to an intermediate transfer member in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic front view illustrating a configuration example of a cleaning device provided in the image forming apparatus illustrated in FIG. 1. FIG. 6 is a schematic front view illustrating another configuration example of the cleaning device provided in the image forming apparatus illustrated in FIG. 1. FIG. 10 is a schematic front view showing still another configuration example of the cleaning device provided in the image forming apparatus shown in FIG. 1. FIG. 10 is a schematic front view showing still another configuration example of the cleaning device provided in the image forming apparatus shown in FIG. 1. FIG. 2 is a conceptual diagram illustrating a state in which colorants in recording liquid discharged from a head in the image forming apparatus illustrated in FIG. 1 are aggregated via protons. FIG. 2 is a conceptual diagram illustrating a state of a liquid column by a recording liquid formed between a cathode and an anode in the image forming apparatus illustrated in FIG. 1.

  FIG. 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 perform full-color image formation. The image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside.

  The image forming apparatus 100 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, cardboard, cardboard, and envelopes. It is. The image forming apparatus 100 is a 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 can form an image as an image corresponding to each color separated into yellow, magenta, cyan, and black, and can serve as a recording liquid ejector that ejects a recording liquid as ink of that color. The recording heads 61Y, 61M, 61C, and 61BK are the ink heads.

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

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

  The intermediate transfer body 37 is rotated in the A1 direction and is recorded in yellow, magenta, cyan, and black from the heads 61Y, 61M, 61C, and 61BK in an area facing the heads 61Y, 61M, 61C, and 61BK. The liquids are ejected and applied in such a manner that they are sequentially superimposed, and an image that is a primary image is formed on the primary image forming surface that is the surface thereof. 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.

  As illustrated in FIG. 1, the image forming apparatus 100 includes ink discharge devices 60Y, 60M, 60C, and 60BK that include heads 61Y, 61M, 61C, and 61BK, respectively, and an intermediate transfer member 37 in the A1 direction. The transfer unit 10 as a sheet transfer unit that transfers the transfer sheet S in accordance with the rotation of the transfer sheet S, and a transfer unit 10 that can stack a large number of transfer sheets S and transfers only the uppermost transfer sheet S among the stacked transfer sheets S. A paper feed unit 20 that feeds the paper toward the printer, and a paper discharge tray 25 on which a large number of image-formed transfer papers S that have been transported by the transport unit 10 can be stacked.

  The image forming apparatus 100 is also disposed above the intermediate transfer body 37 so as to face the intermediate transfer body 37, and from the intermediate transfer body 37 after the recording liquid is transferred to the transfer paper S, onto the intermediate transfer body 37. That is, a cleaning device 40 as a cleaning unit for removing and cleaning the recording liquid remaining on the primary image forming surface, and a head support that integrally supports the heads 61Y, 61M, 61C, and 61BK. As a carriage 62.

  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. In such a state 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 them is temporarily bridged, an electrode oxidation reaction or the inside of the recording liquid in the liquid column state is performed. An energization unit 33 that energizes including a current component resulting from the electrode reduction reaction, and a control unit (not shown) as a control unit including a CPU, a memory, and the like that control the overall operation of the image forming apparatus 100 are included.

  3 to 6 show various configuration examples of the cleaning device 40. FIG. In each of these drawings, the surface of the intermediate transfer member 37 is drawn so as to have a flat surface. However, in actuality, the surface of the intermediate transfer member 37 has an arc shape as shown in FIG. 1 or FIG. ing.

  As shown in these drawings, the cleaning device 40 has, as a basic configuration, at least an insulating cleaning member for contacting the intermediate transfer member 37 and cleaning the recording liquid on the intermediate transfer member 37. A voltage is applied between the cleaning blade 41 and the intermediate transfer member 37, and at least a cleaning electrode 42 for cleaning the recording liquid cleaned from the intermediate transfer member 37 by the cleaning blade 41 by electrolysis, and an intermediate A power supply as a voltage applying means connected to the transfer body 37 and the cleaning electrode 42 and applying a voltage for electrolyzing at least the recording liquid cleaned from the intermediate transfer body 37 by the cleaning blade 41 between them. 43. The cleaning device 40 shown in FIG. 3 employs such a basic configuration.

  The cleaning blade 41 has a function of scraping the recording liquid on the surface of the intermediate transfer body 37, specifically, the recording liquid remaining after the transfer, by contacting a part, that is, the tip of the cleaning blade 41 with the intermediate transfer body 37. It only needs to be insulating and wear resistant. As a material that satisfies this requirement, for example, silicone rubber, nitrile rubber, urethane rubber, fluororubber, and elastomer coated with fluorine are preferable. The thickness of the cleaning blade 41 is preferably about 1 to 5 mm. This is because if the thickness of the cleaning blade 41 is 1 mm or less, the intermediate transfer member 37 and the cleaning electrode 42 may unexpectedly come into contact with each other, causing a short circuit. In addition, when the thickness of the cleaning blade 41 is 5 mm or more, the gap distance between the intermediate transfer member 37 and the cleaning electrode 42 is long, so that it is difficult to obtain effective cleaning properties. The contact angle of the cleaning blade 41 with respect to the intermediate transfer member 37 is 45 degrees.

  The cleaning electrode 42 only needs to have good conductivity, but when the recording liquid is anionic, the electrode tends to corrode because it is provided as an anode. Therefore, it is preferable to use a metal having high corrosion resistance or a carbon plate such as glassy carbon. Further, as will be described later, the intermediate transfer member 37 may be formed of the same conductive rubber.

  When the cleaning electrode 42 is formed in a blade shape and used as a member integrated with the cleaning blade 41 as in the configuration example shown in FIGS. 3 to 5, the cleaning electrode 42 and the cleaning blade 41 are made of different materials, and these Can be used together. However, the cleaning electrode 42 and the cleaning blade 41 may be integrally formed by using the same material and changing the physical property value depending on the location. For example, the surface of the silicone rubber is insulated without carbon black, but the back surface contains a lot of carbon black and has conductivity. Moreover, the rubber material which changed content of carbon black continuously from the surface to the back surface may be sufficient.

As in the configuration example shown in FIG. 6, when the cleaning electrode 42 is a roller, the same function as that when the cleaning electrode 42 is blade-shaped is necessary. However, since high positional accuracy is required for the gap with respect to the intermediate transfer member 37, it is preferable to form the cleaning electrode 42 with a metal roller instead of an elastic conductive roller.
The remaining points of the cleaning device 40 will be described later.

  In addition to the intermediate transfer member 37, the transport unit 10 is disposed so as to face the intermediate transfer member 37, is driven to rotate by the intermediate transfer member 37, and the transfer sheet S passes through the transfer unit 31 between the conveyance unit 10. A transfer roller 38 that is a pressure roller serving as a transfer unit that is a transfer recording unit that transfers and records a primary image of the recording liquid carried on the intermediate transfer member 37 onto the transfer paper S, and a paper feed unit 20. The transfer sheet S fed from the guide unit 31 is guided to the transfer unit 31, and the guide plate 39 that guides the transfer sheet S that has passed through the transfer unit 31 to the sheet discharge table 25 and the intermediate transfer member 37 are driven to rotate in the A1 direction. And a motor as driving means (not shown). 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.

  As shown in FIG. 2, the intermediate transfer member 37 includes a support 37a made of aluminum and a surface layer 37b made of conductive silicone rubber formed on the support 37a. The material of the support body 37a is not limited to aluminum, but must be highly conductive and have mechanical strength, and is formed of a metal or an alloy. The surface layer 37b is not limited to the conductive silicone rubber, but may be formed of a smooth elastic material having high conductivity and water repellency. The conductivity of the surface layer 37b is a function necessary for causing electrolysis of water by applying a voltage between the intermediate transfer member 37 and the cleaning electrode. The water repellency of the surface layer 37b is an index of ease of transfer when the recording liquid is transferred from the surface layer of the intermediate transfer body 37 to the transfer paper S. The higher the water repellency, the better the transfer rate. Easy to clean. The elasticity of the surface layer 37b is a function required at the time of transfer. When the surface layer 37b is deformed along the fibers of the transfer paper S, the contact area is improved and a high transfer rate is achieved. In order to transfer at a low pressure, a material that is somewhat soft must be selected as the material of the surface layer 37b.

  Examples of the material satisfying these functions of the surface layer 37b include rubber materials such as fluorosilicone rubber, phenylsilicone rubber, fluorine rubber, chloroprene rubber, nitrile rubber, nitrile butadiene rubber, isoprene rubber, carbon black, carbon nanotube, gold And conductive rubber mixed with metal fine particles such as silver. In order to increase the conductivity, it is conceivable to increase the number of conductive fine particles. However, if the density of the conductive fine particles on the surface is high, it causes a decrease in water repellency. It is sufficient that the conductivity is in the film thickness direction of the support 37a and the surface layer 37b, and the anisotropic conductivity may be insulative in the surface direction. The size of the conductive fine particles needs to be sufficiently smaller than the dots of about 20 to 50 μm constituting the image, and there is no problem if it is 0.1 μm or less. Further, the surface layer 37b may be impregnated with silicon oil in order to increase water repellency, and may have either a single layer structure or a multilayer structure.

The bulk physical properties and surface physical properties of the surface layer 37b are preferably as follows. The volume resistivity is 10 ⁴ Ω · cm or less, preferably 10 ² Ω · cm or less. The water repellency has a receding contact angle of water of 60 ° or more, preferably 80 ° or more, and the hardness is 60 or less, preferably 40 or less in JIS-A. The thickness of the surface layer is preferably about 0.1 to 1 mm, and preferably 0.2 to 0.6 mm.

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

  The ink discharge devices 60Y, 60M, 60C, and 60BK have substantially the same configuration with respect to the other points although the colors of the recording liquid to be used are different. Each of the ink ejection devices 60Y, 60M, 60C, and 60BK has a plurality of heads 61Y, 61M, 61C, and 61BK arranged in parallel in the main scanning direction, and the ink ejection devices 60Y, 60M, 60C, and 60BK, and the image forming apparatus 100 are full. It is a 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. Specifically, when the recording liquid discharge by the heads 61Y, 61M, 61C, 61BK is stopped on condition that the ink amount detection sensor detects that the recording liquid amount in the distributor tank is insufficient. It is driven until shortage is no longer detected, and the recording liquid in the ink cartridges 81Y, 81M, 81C, 81BK is supplied to the distributor tank. In this respect, the control unit functions as an ink supply control unit that is a recording liquid supply control unit. The control unit is configured to control the driving of the image forming apparatus 100 even when not specifically described.

  The recording liquid contains at least a colorant corresponding to yellow, magenta, cyan, and black and a solvent for this colorant. The solvent contains water from the viewpoint of safety and from the viewpoint of conductivity for causing electrolysis to be described later, and the recording liquid is a water-soluble recording liquid that is a water-soluble ink. As the colorant, an anionic colorant and / or an anionic resin having an ionic property that is anionic in a solvent is used.

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

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

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

  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 that the clogging characteristic can be secured.

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

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

  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 the electrolysis of water, and hence the cleaning action described later by the cleaning device 40 can be obtained satisfactorily. Such pigments are excellent in storage stability and clogging resistance of the recording liquid.

The recording liquid preferably 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. Can be mentioned.

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

Anionic surfactants are also preferably used as pigment dispersants.
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 and used using an activator.

  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 of the recording liquid and the jetting characteristics of the printer are stable, and high image quality can be obtained. However, it is possible to disperse to such a fine particle size by dispersion operation or classification. The operation becomes complicated and it is difficult to produce the recording liquid economically.

Another preferred example of the colorant used in the recording liquid is a recording liquid using 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, anionic coloring can be achieved by forming the part that hits the fine particle shell with a hydrophilic resin such as polyacrylic acid or polymethacrylic acid, or suspending it with an ionic surfactant such as a reactive surfactant. A recording liquid is obtained in which fine particles are suspended in a liquid medium mainly composed of water.

  Even when using a recording liquid using a colored emulsion, an emulsion emulsified with the anionic surfactant described above and polymerized, or an emulsion whose outer shell is formed of a hydrophilic resin such as polyacrylic acid or polymethacrylic acid is used. This is particularly preferable in that the reactivity with hydrogen ions is high and the cleaning action described below by the cleaning device 40 can be obtained very well. Further, these colored resin fine particles are effective in 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 the hydrophilic polymer compound to the recording liquid, the thickening action and the aggregating action of the recording liquid are strengthened by reaction with hydrogen ions, and the cleaning action described later by the cleaning device 40 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. , 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 for the recording liquid, it is highly reactive with hydrogen ions to use a carboxylic acid as an anion group, and the cleaning action described later by the cleaning device 40 is large. Particularly preferred. Further, like the above-described anionic polymer and resin emulsion, it is effective to improve the transfer rate from the intermediate transfer body 37 to the transfer paper S in the transfer process.

  The recording liquid uses water as a main liquid medium, but the above-mentioned water-soluble organic solvent is used in order to make the recording liquid have desired physical properties or to prevent clogging of a nozzle 61c described later due to drying of the recording liquid. It is preferable.

  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 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, Examples include alkali metal carbonates such as sodium carbonate and potassium carbonate, amines such as diethanolamine and triethanolamine, boric acid, hydrochloric acid, nitric acid, sulfuric acid and acetic acid.

  In addition, you may use additives, such as a pH buffer, a viscosity modifier, antiseptic | preservative, antioxidant, and a rust inhibitor, as needed.

  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, and preferably 500 to 800 mS / m.

  As shown in FIG. 2, each of the heads 61Y, 61M, 61C, 61BK has a conductive orifice 61a, which is a conductive member, and an insulating orifice 61b, which is an insulating member, on the recording liquid discharge side facing downward in the drawing. And a minute nozzle 61c in which holes formed in the conductive orifice 61a and the insulating orifice 61b communicate with each other. Although not shown, each head 61Y, 61M, 61C, 61BK is an actuator driven on the basis of an image signal for ejecting the recording liquid from the nozzle 61c to be ejected and landed on the transfer paper S. Although there is a piezo-type movable actuator that discharges the recording liquid from the nozzle 61c by applying pressure to the recording liquid in the liquid chamber by displacement of the piezo element, the actuator may be another type of movable actuator. In addition, each of the heads 61Y, 61M, 61C, 61BK may use a heating film boiling method such as a thermal method in which the recording liquid is discharged from the nozzle 61c by applying pressure to the recording liquid in the liquid chamber with bubbles generated by heating the heater. good. A number of nozzles 61c are provided in each of the heads 61Y, 61M, 61C, 61BK, but only one of them is shown in the figure.

  The conductive orifice 61a forms the surface of the heads 61Y, 61M, 61C, 61BK on the recording liquid discharge side. Since the conductive orifice 61a is provided as a cathode as will be described later, the conductive orifice 61a does not have to be made of a material resistant to metal elution, and may be made of a highly conductive material such as metal or carbon.

  The insulating orifice 61b is provided so as to be interposed between the recording liquid accommodated in the heads 61Y, 61M, 61C and 61BK and the conductive orifice 61a. The material of the insulating orifice 61b is not particularly limited as long as it has insulating properties.

  In this embodiment, the conductive orifice 61a and the insulating orifice 61b are joined to each other. However, these are not necessarily joined, and other portions are provided between the insulating orifice 61b and the recording liquid. These layers may be interposed.

  As shown in FIG. 2, the energizing means 33 is realized as a part of the function of the power source 33a, an electric circuit (not shown) in which the power source 33a is connected to the support 37a and the conductive orifice 61a, and a control unit. Voltage application control means for controlling the application timing and application time of the voltage. The power source 33a has an anode connected to the support 37a and a cathode connected to the conductive orifice 61a by an electric circuit. Therefore, the energizing unit 33 includes the support 37a and the intermediate transfer body 37 as an anode, and the conductive orifice 61a as a cathode. As will be described later, the energizing unit 33 functions as a voltage applying unit for applying a voltage for electrolyzing the recording liquid between the support 37a and the heads 61Y, 61M, 61C, 61BK.

  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 energization unit 33 is driven by the control unit as the voltage application control unit, and a voltage is applied between the support 37a and the conductive orifice 61a from the power source 33a.
In this state, the recording liquid is applied onto the intermediate transfer member 37 from each of the heads 61Y, 61M, 61C, 61BK. At this time, first, as shown in FIG. 2A, the recording liquid forming the meniscus in the nozzle 61b is transferred from the heads 61Y, 61M, 61C, and 61BK to the intermediate transfer as shown in FIG. A liquid column bridge made of a recording liquid is temporarily formed between the nozzle 61c and the intermediate transfer body 37, and then, as shown in FIG. When the bridge of the liquid column is divided, it is carried on the intermediate transfer member 37, and an image of the recording liquid is formed on the intermediate transfer member 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 conductive orifice 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. Is 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 +), and 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 61c 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. On the other hand, the capacity of the electric double layer E _C, since sufficiently larger than the capacitance of the electric double layer E _A, the surface of the cathode C, water is unlikely to reduction. This is because the area of the conductive orifice 61a which is the cathode C is sufficiently larger than the area of the intermediate transfer member 37 as the anode A. The degree of pigment aggregation can be controlled by the amount of protons generated, that is, the time for forming the bridge of the liquid column, the voltage applied by the energizing means 33, and the like. Further, when water is oxidized and protons are generated, oxygen is also generated. However, since it is considered to be dissolved in water in addition to a small amount, it does not inhibit image formation.

  The time from the formation of the bridge B of the liquid column to the separation is usually several microseconds to several tens of microseconds, and the conductivity of the recording liquid is usually several tens mS / m to several 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 onto the transfer paper S in this way, the recording liquid, and a mixture of aggregating components formed by the reaction of the recording liquid is transferred onto 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.

  Although the above-mentioned mixture hardly remains on the intermediate transfer body 37 that has passed through the transfer section 31 due to the transfer in the transfer section 31, the intermediate transfer body 37 is subjected to cleaning of the mixture by the cleaning device 40 as described below. Thus, the offset of the mixture is further prevented or suppressed to a high degree, and even when image formation is repeatedly performed, background stain due to the offset is prevented or suppressed, and image deterioration and deterioration of the intermediate transfer member 37 are suppressed or prevented. It is possible to perform good image formation over time.

  The cleaning device 40 shown in FIG. 1 employs any of the configurations shown in FIGS. 3 to 6. First, cleaning of the intermediate transfer member 37 performed by the cleaning device 40 having the configuration shown in FIG. 3 will be described. .

  The cleaning blade 41 is in contact with the surface of the intermediate transfer body 37 at a position downstream of the transfer unit 31 in the A1 direction and upstream of the recording liquid application position by the heads 61Y, 61M, 61C, 61BK. The recording liquid or the recording liquid remaining on the surface of the intermediate transfer body 37 that cannot be transferred onto the recording paper S and the mixture containing the above-mentioned aggregating components are scraped together with the cleaning electrode 42 integrated with the cleaning blade 41 to obtain the recording liquid or the mixture. Form lumps.

  The power source 43 uses the intermediate transfer member 37 as a cathode, that is, a cathode, and the cleaning electrode 42 serves as an anode, that is, an anode. Cause decomposition. This electrolysis occurs similarly to the reaction formulas (1) and (2) already shown.

  By this electrolysis, a reaction similar to the reaction described above that occurs in the state where the bridge of the liquid injection composed of the recording liquid shown in FIG.

  That is, in the vicinity of the intermediate transfer body 37 in contact with the recording liquid or the like, that is, at the interface between the intermediate transfer body 37 and the stain due to the recording liquid or the like, the pH increases due to the generation of hydrogen and hydroxyl ions, and the recording liquid or the like Dissolution and dispersion of the pigment in it takes place. This is because the recording liquid is an anionic ink in which the dispersibility of the pigment is increased by negatively charged electrostatic repulsion, and therefore the dispersion / solubility of the pigment tends to increase as the pH increases.

  On the other hand, in the vicinity of the cleaning electrode 42, that is, at the interface between the cleaning electrode 42 and the stain due to the recording liquid, the pH is lowered due to the generation of oxygen and hydrogen ions, and becomes acidic due to aggregation of the coloring material in the lump of the recording liquid and cleaning. Immobilization to the electrode 42 pole surface occurs.

  If this reaction is sufficiently fast, the colorant in the mass of the recording liquid or the like does not pass between the cleaning blade 41 and the intermediate transfer body 37, but is transferred to the cleaning electrode 42 side. It is possible to more effectively remove the dirt on the intermediate transfer body 37 due to the recording liquid or the like, and further the dirt on the cleaning blade 41 due to the recording liquid or the like, than pressing against the intermediate transfer body 37 and scraping. In terms of removing dirt from the cleaning blade 41, the cleaning electrode 42 and the power source 43 function as cleaning member purification means.

  The cleaning operation of the intermediate transfer member by the cleaning device 40 and the cleaning operation of the cleaning blade 41 by the cleaning member purification means differ depending on the feed speed of the intermediate transfer member 37 and the voltage applied to the power source 43 and depend on the amount of current and the amount of charge. Is. In addition, since the recording liquid contains a surfactant and tends to maintain bubbles of hydrogen gas or oxygen gas generated by an electrochemical reaction, the bubbles can easily remove stains from the recording liquid or the like. .

The cleaning device 40 shown in FIG. 4 has an electrode cleaning means 44 for cleaning the cleaning electrode 42 in addition to the configuration shown in FIG.
The electrode cleaning means 44 includes a cleaning roller 45 as an electrode cleaning member in contact with the cleaning electrode 42, and a transfer unit that recovers components such as recording liquid removed from the cleaning electrode 42 by the cleaning roller 45. The remaining collection tank 46 and a drive source (not shown) that rotationally drives the cleaning roller 45 are provided.

  The cleaning roller 45 is rotated by a driving source to rotate in a direction to scrub the cleaning electrode 42 and slides with respect to the cleaning electrode 42, and aggregating components of the recording liquid adhering to the cleaning electrode 42 are removed. The recording liquid contained therein is removed, and the removed components are moved to the transfer residue collection tank 46 side so as to get over the cleaning electrode 42 and collected in the transfer residue collection tank 46.

  Therefore, the cleaning roller 45 is suitable for exerting such an action when the surface has irregularities, a gear shape, or a saw shape. Further, the cleaning roller 45 may be a cylinder having a perfect cross section or an elliptic cylinder. In the case of an ellipse, the area in contact with the cleaning electrode 42 is widened, and effective cleaning and transfer residue can be achieved. Ink stains can be moved smoothly. Further, the transfer residual collection tank 46 is provided with a water-absorbing material (not shown) at the bottom, and by absorbing excess moisture with this material, an increase in humidity in the cleaning device 40 and further in the image forming apparatus 100 is suppressed. ing.

  In the cleaning device 40 having such a configuration, the following operation and operation are performed in addition to the operation and operation of the cleaning device 40 shown in FIG. That is, in the cleaning device 40 shown in FIG. 3, if the cleaning electrode 42 is covered with an aggregating component such as a pigment of the recording liquid, the cleaning effect is reduced, and therefore the surface of the cleaning electrode 42 may need to be refreshed. On the other hand, in the cleaning device 40 shown in FIG. 4, the cleaning roller 45 removes the agglomerated components on the surface of the cleaning electrode 42 and the removed agglomerated components are transferred to the transfer residual collection tank 46. Therefore, the performance of the cleaning electrode 42 is maintained, and the intermediate transfer member 37 and the cleaning blade 41 are cleaned well over time. This refreshing operation of the cleaning roller 45 may be performed constantly or periodically as long as the electrochemical cleaning function of the cleaning electrode 42 is not impaired.

  In addition to the structure shown in FIG. 4, the cleaning device 40 shown in FIG. 5 includes at least the intermediate transfer member 37, the cleaning electrode 42, and in this embodiment, the cleaning blade 41, the recording liquid attached to the cleaning roller 45, and the like. A cleaning liquid for reacting with the above components to clean the recording liquid or the like so as to come into contact with at least the intermediate transfer member 37, the cleaning electrode 42, and in this embodiment, the cleaning blade 41 and the cleaning roller 45. Supply means 50 is provided.

  The cleaning liquid supply means 50 includes a housing 48 of the cleaning device 40, a cleaning liquid tank 51 as a cleaning liquid container, and a cleaning liquid in the cleaning liquid tank 51, an intermediate transfer body 37, a cleaning electrode 42, and a cleaning blade. 41, a liquid feeding means 52 for pumping out of the cleaning liquid tank 51 so as to be in contact with the cleaning roller 45, and at least the intermediate transfer body 37, the cleaning electrode 42, the cleaning blade 41, and further cleaning liquid in this embodiment. Liquid amount detecting means 53 for detecting the amount of cleaning liquid in the liquid reservoir formed by contacting the roller 45 is provided.

  The liquid feeding means 52 extends from the cleaning liquid tank 51 toward the liquid reservoir and forms a cleaning liquid flow path, and pressure-feeds the cleaning liquid in the cleaning liquid tank 51 toward the liquid reservoir through the pipe 54. And a pump 55.

  The liquid amount detection means 53 includes an upper water level measurement sensor 56 and a lower water level measurement sensor 57 arranged in parallel in the vertical direction in order to detect the water level of the cleaning liquid in the liquid reservoir. Each of the upper water level measurement sensor 56 and the lower water level measurement sensor 57 optically detects the water level of the cleaning liquid in the liquid reservoir, and is not in contact with the cleaning liquid. When the water level of the cleaning liquid in the liquid reservoir is between the upper water level measurement sensor 56 and the lower water level measurement sensor 57, the amount of the cleaning liquid in the liquid reservoir does not leak out of the cleaning device 40, and the recording liquid or the like is cleaned. This is a suitable amount with no excess or deficiency. When the lower level sensor 57 detects the cleaning liquid level, the pump 55 is activated to start supplying the cleaning liquid to the liquid reservoir. When the upper level sensor 56 detects the cleaning liquid level, the pump 55 stops. Then, the supply of the cleaning liquid to the liquid reservoir is stopped.

  Accordingly, the liquid feeding means 52 functions as a liquid amount control means for supplying the cleaning liquid to the liquid reservoir based on the amount of the cleaning liquid in the liquid reservoir detected by the liquid amount detecting means 53 and controlling the amount to an appropriate amount. . The liquid amount detection means 53 may detect whether or not the amount of the cleaning liquid in the liquid reservoir is an appropriate amount by a sensor that detects whether or not the liquid liquid is in contact with the cleaning liquid.

  The cleaning liquid is a medium for an electrochemical reaction between the intermediate transfer member 37 and the cleaning electrode 42. Although the base is water, the higher the ionic conductivity of the cleaning liquid, the faster the electrolysis rate of water, so that an effective cleaning effect is exhibited in a short time. Supporting electrolytes that increase ionic conductivity include inorganic alkali metal salts such as sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium nitrate, and potassium nitrate; organic systems such as sodium acetate, potassium acetate, sodium citrate, and potassium citrate Examples thereof include organic ammonium salts such as alkali metal salts, tetramethylammonium chloride, and tetramethylammonium nitrate.

  The higher the concentration of the supporting electrolyte is, the higher the conductivity is. However, when the concentration is too high, so-called salting out occurs in which the colorant in the recording liquid reacts and aggregates. When aggregates are formed in the cleaning liquid, the functions of the cleaning electrode 42 and the cleaning roller 45 are deteriorated, so that the concentration of the supporting electrolyte is set so that salting-out does not occur. In addition, divalent or higher polyvalent metal salts and strongly acidic electrolytes such as hydrochloric acid and sulfuric acid have a high agglomeration effect of the pigment in the cleaning liquid, so that the supporting electrolyte is a monovalent metal salt and a neutral electrolyte. It is preferable.

  The cleaning liquid preferably contains a nonvolatile water-soluble organic solvent to prevent drying. Since the pump 55 is used to supply the cleaning liquid, a low viscosity is desirable. Although the cleaning liquid may contain a surfactant, since the casing 48 is not completely sealed, a certain amount of surface tension is necessary so that the cleaning liquid does not leak during the cleaning operation.

  In the cleaning device 40 having such a configuration, the following operations and operations are performed in addition to the operations and operations of the cleaning device 40 shown in FIG. That is, in the liquid pool, when the colorant of the recording liquid and the aggregation component of the recording liquid come into contact with the cleaning liquid, it reacts with the cleaning liquid and tries to spread throughout the cleaning liquid by decomposition and diffusion. Since the pH is low, aggregation occurs, and in particular, the colorant of the recording liquid is precipitated and fixed on the surface of the cleaning electrode 42. As described above, in the liquid pool, the cleaning liquid reacts with the colorant of the recording liquid and the aggregation component of the recording liquid to exhibit a decomposition function, so that the liquid pool functions as a cleaning region.

  The cleaning roller 45 removes the cleaning liquid adhering to the cleaning electrode 42 together with the recording liquid adhering to the cleaning electrode 42 and the aggregating component, and cleans the transfer residual collection tank 46 by the cleaning roller 45. The cleaning liquid, the recording liquid, the agglomerated components, etc. removed from the electrode for cleaning are collected. Therefore, the cleaning liquid in the liquid pool is transferred to the transfer residual collection tank 46 together with the aggregating component by the rotation of the cleaning roller 45, but is kept fresh and appropriate by the liquid feeding means 52 and the liquid amount detecting means 53. . Accordingly, the cleaning electrode 42, the cleaning roller 45, the intermediate transfer member 37, and the cleaning blade 41 are cleaned well over time. In this way, the cleaning liquid supply unit 50 also functions as an intermediate transfer member cleaning unit, a cleaning member purification unit, and an electrode cleaning unit.

  The cleaning device 40 shown in FIG. 6 is different from the configuration in which the cleaning electrode 42 is integrated with the cleaning blade 41 shown in FIGS. 3 to 5, and the cleaning electrode 42 is separate from the cleaning blade 41, In addition, the cleaning electrode 42 has a drive source (not shown) that rotates the counter electrode counterclockwise in FIG. 6.

Although most of the cleaning electrode 42 is immersed in the cleaning liquid in the liquid reservoir, a part of the upper part of the cleaning electrode 42 appears on the liquid surface of the cleaning liquid and is exposed.
The narrower the gap between the cleaning electrode 42 and the intermediate transfer body 37, the greater the electrochemical cleaning action. However, if the gap is reduced, the cleaning electrode 42 and the intermediate transfer member 37 may come into contact with each other and short-circuit. Therefore, such a gap is set to about 0.5 to 2 mm.

  Further, the cleaning device 40 shown in FIG. 6 is different from the configuration shown in FIG. 5 in which the electrode cleaning unit 44 includes a cleaning roller 45 as an electrode cleaning member in contact with the cleaning electrode 42. 44 includes a cleaning blade 49 as an electrode cleaning member in contact with the cleaning electrode 42. The tip of the cleaning blade 49 is in contact with the portion of the cleaning electrode 42 that appears on the surface of the cleaning liquid.

  Further, in the cleaning device 40 shown in FIG. 6, in addition to the configuration shown in FIG. 5, the cleaning liquid supply means 50 returns the cleaning liquid collected in the transfer residual collection tank 46 to the cleaning liquid tank 51 and returns the amount of liquid. Recycling means 58 for supplying liquid feeding means 52 functioning as control means is provided.

  The recycle means 58 cleans the cleaning liquid in the transfer residual collection tank 46 through the pipe 59 and the pipe 59 extending from the transfer residual recovery tank 46 toward the cleaning liquid tank 51 to form a circulation cleaning liquid flow path. And a pump 55 that pumps the liquid toward the liquid tank 51. The pump 55 is the same as the pump 55 of the liquid feeding means 52, but may be provided separately from the pump 55 of the liquid feeding means 52.

The operation and action of the cleaning device 40 having such a configuration will be described as follows with respect to matters different from the operation and action of the cleaning device 40 shown in FIG. As the cleaning electrode 42 rotates, the cleaning blade 49 is in sliding contact with the portion of the cleaning electrode 42 that appears on the liquid surface of the cleaning liquid, and adheres to the cleaning electrode 42. The agglomerated components are removed and cleaned. The cleaning liquid or the like cleaned from the cleaning electrode 42 moves over the cleaning blade 49 as the cleaning electrode 42 rotates and is transferred to the transfer residual collection tank 46 and collected. Of the cleaning liquid collected in the transfer residue collection tank 46, the aggregation component of the recording liquid is sufficiently agglomerated, and solid-liquid separation occurs after a while. The recycle means 58 drives the pump 55 and returns it to the cleaning liquid tank 51 through the pipe 59 so that the supernatant liquid generated in the transfer residue collection tank 46 by the solid-liquid separation can be used again as the cleaning liquid.
As shown in FIG. 6, even when the cleaning electrode 42 is separated from the cleaning blade 41, the cleaning electrode 42 is not a roller, as shown in FIGS. It may be a plate shape.

〔Example〕
In the following experiment in consideration of the above conditions, the cleaning performance of the cleaning device 40 having each configuration shown in FIGS. 3 to 6 was confirmed.
The experimental conditions are as follows.

<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.

<Yellow recording liquid>
-Sulfonic acid group-bonded yellow pigment dispersion (CAB-O-JET-270Y, solid content 10% by mass, manufactured by Cabot Specialty Chemicals Inc.): 40.0% by mass
・ Triethylene glycol: 15.0 mass%
・ Glycerin: 25.0% by mass
Propylene glycol monobutyl ether: 6.0% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.

<Magenta recording liquid>
-Sulfonic acid group-bonded magenta pigment dispersion (CAB-O-JET-260M, solid content 10% by mass, manufactured by Cabot Specialty Chemicals, Inc.): 40.0% by mass
・ Diethylene glycol: 20.0% by mass
Propylene glycol monobutyl ether: 3.0% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.

<Cyan recording liquid>
-Sulfonic acid group-bonded cyan pigment dispersion (CAB-O-JET-250C, solid content 10% by mass, manufactured by Cabot Specialty Chemicals Inc.): 40.0% by mass
・ Ethylene glycol: 4.0% by mass
Triethylene glycol: 14.0% by mass
Propylene glycol monobutyl ether: 6.0% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.

<Image forming conditions>
The above recording liquids were filled in the heads 61Y, 61M, 61C, 61BK (GX-5000 manufactured by Ricoh) shown in FIG.
The intermediate transfer member 37 is an aluminum base tube with a support 37a having a diameter of 60 mm and a length of 250 mm, and a conductive silicone rubber layer having a volume resistivity of 500 Ω · cm as a surface layer 37b on the outer periphery of the support 37a is 0.2 mm. And is driven to rotate at 200 mm / s.
The distance between the heads 61Y, 61M, 61C, 61BK and the intermediate transfer member 37 may be arbitrary, but is 1 mm.
The transfer roller 38 is pressed against the intermediate transfer body 37 with a load of 20 kgf / cm ² .
The dots formed on the intermediate transfer body 37 by the recording liquid pass through a plain paper (type 6200) as the transfer paper S between the intermediate transfer body 37 and the transfer roller 38, so that the surface of the transfer paper S is transferred. Transcript.

The transfer residual recording liquid remaining on the intermediate transfer member 37 after the transfer is collected by the cleaning device 40 shown in FIGS. 3 to 6, and the surface of the intermediate transfer member 37 is cleaned and initialized.
The results of this cleaning were evaluated for the following Examples 1 to 4 corresponding to the cleaning device 40 shown in FIGS.

Example 1
In Example 1, a cleaning device corresponding to the cleaning device 40 shown in FIG. 3 is used. A glassy carbon plate having a thickness of 2 mm was used as the cleaning electrode 42, and a fluororubber having a thickness of 1 mm molded on the glassy carbon plate was used as the cleaning blade 41. During the rotation of the intermediate transfer member 37, a voltage of 50 V is applied between the glassy carbon plate and the intermediate transfer member support 37a. From the heads 61Y, 61M, 61C, 61BK, the recording liquid is continuously discharged so that the average area of the four colors and the image area ratio of the plain paper as the transfer paper S is 5%. The recording liquid on the intermediate transfer member 37 is transferred onto the plain paper by continuously passing the paper. After printing up to a total of 1000 sheets for every 100 sheets, the recording liquid remaining after transfer of the intermediate transfer body 37, aggregating components, and the like were peeled off with a printer and copied onto paper to measure the image density.

  As a comparative example, even when no voltage was applied between the glassy carbon plate serving as the cleaning electrode 42 and the support 37a of the intermediate transfer member 37, cleaning was performed under the same conditions and the image density was measured.

  Compared with the comparative example, in Example 1, such a decrease in image density was observed, and there was clearly an electrochemical cleaning effect. However, as the number of prints increased, the image density gradually increased and the cleaning function was lowered. After passing 1,000 sheets, the pigment of the recording liquid remaining after transfer was considerably adhered to the surface of the glassy carbon plate.

Example 2
In Example 2, a cleaning device corresponding to the cleaning device 40 shown in FIG. 4 is used. As the cleaning roller 45, an elliptical Teflon (registered trademark) having a major axis of 20 mm and a minor axis of 10 mm was used, and the surface thereof was finely uneven by blasting. The Teflon (registered trademark) roller is in contact with the glassy carbon plate which is the cleaning electrode 42, and the pressure of the Teflon (registered trademark) roller against the glassy carbon plate is always constant at the rotating shaft of the Teflon (registered trademark) roller. As described above, it is pressed by a spring and displaced according to the force applied to the surface of the Teflon (registered trademark) roller. By rotating the elliptical Teflon (registered trademark) roller, the glassy carbon surface area that can come into contact with the roller is cleaned, and the dirt due to the transfer residual recording liquid is flowed to the transfer residual recovery tank 46. The other points are the same as in the first embodiment.

  The cleaning effect of Example 2 was evaluated by the same evaluation method as in Example 1. Compared with Example 1, the decrease in the cleaning effect accompanying the increase in the number of printed sheets was suppressed. It is considered that the adhesion of the residual pigment on the glassy carbon plate surface is almost the same depending on the number of prints, and the electrochemical cleaning effect is maintained.

Example 3
In Example 3, a cleaning device corresponding to the cleaning device 40 shown in FIG. 5 is used. The pump 55 is a diaphragm pump. The following cleaning liquid was used.
<Cleaning liquid>
・ Ethylene glycol: 15.0 mass%
・ Glycerin: 15.0% by mass
-Potassium chloride: 1.0% by mass
Distilled water: remaining amount The physical properties of the cleaning liquid were a viscosity of 6.0 mPas, a conductivity of 1.4 S / m, and a surface tension of 65 mN / m. The rest is the same as that of the second embodiment except that the cleaning liquid supply means 50 having the configuration shown in FIG. 5 is provided.

  The cleaning effect of Example 3 was evaluated by the same evaluation method as in Example 1 and Example 2. Compared with Example 2, the image density on the surface of the intermediate transfer member 37 was greatly reduced, and the electrochemical cleaning effect was greater when the cleaning liquid was used.

Example 4
In Example 4, a cleaning device corresponding to the cleaning device 40 shown in FIG. 6 is used. The cleaning electrode 42 is formed by forming a conductive Teflon (registered trademark) layer having a thickness of 0.2 mm on a stainless steel round bar having a diameter of 15 mm and having carbon black dispersed on the outer periphery. The cleaning blade 49 was made of fluororubber having a shape with a sharp contact portion. The rest is the same as that of the third embodiment except that the cleaning liquid supply means 50 having the configuration shown in FIG. 6 is provided.

  The cleaning effect of Example 4 was evaluated by the same evaluation method as in Example 1, Example 2, and Example 3. Compared with Example 3, the same cleaning effect was obtained. In addition, the cleaning was stable, and the cleaning effect was hardly reduced by the number of printed sheets.

  From the above evaluation, the cleaning system 40 according to the present invention using electrolysis is used in the cleaning device 40 having the configuration shown in FIG. 3 corresponding to the first embodiment and the cleaning device 40 having the configuration shown in FIG. It was found that the effect of can be obtained. However, the cleaning device 40 having the configuration shown in FIG. 4 corresponding to the second embodiment is more effective than the cleaning device 40 having the configuration shown in FIG. 3 corresponding to the first embodiment, and is a diagram corresponding to the second embodiment. The cleaning device 40 having the configuration shown in FIG. 5 corresponding to the third embodiment and the cleaning device 40 having the configuration shown in FIG. 6 corresponding to the fourth embodiment are more effective than the cleaning device 40 having the configuration shown in FIG. Was found to be obtained.

  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 intermediate transfer member may be an endless belt instead of a roller.
The image forming apparatus to which the present invention is applied is not limited to the above-mentioned type of image forming apparatus, but other types of image forming apparatuses, that is, a copying machine, a single facsimile, or a complex machine thereof, or a monochrome machine related thereto. In addition, an image forming apparatus used for forming an electric circuit or an image forming apparatus used for forming a predetermined image in the biotechnology field may be used.

  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.

37 Intermediate transfer member 41 Cleaning member 42 Cleaning electrode 44 Electrode cleaning means 45, 49 Electrode cleaning member 46 Recovery unit 50 Cleaning liquid supply means 52 Liquid amount control means 53 Liquid amount detection means 58 Recycling means 61Y, 61M, 61C, 61BK Head 100 Image forming apparatus

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 JP-A-8-142500 JP-A-10-250216 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 7-164624 A Japanese Patent No. 3114783 JP 2009-149019 A

Claims (11)

A cleaning member for cleaning the recording liquid on contact with the intermediate transfer member is applied to the recording liquid said intermediate transfer member by the head,
The recording liquid in contact with the cleaning member is cleaned from the said intermediate transfer member by least said cleaning member, a cleaning electrode for cleaned by electrolysis,
A cleaning apparatus comprising: a voltage applying unit configured to apply a voltage for electrolyzing the recording liquid that is conducted to the intermediate transfer member and the cleaning electrode between the intermediate transfer member and the cleaning electrode . The cleaning device according to claim 1.
A cleaning apparatus comprising an electrode cleaning means for cleaning the cleaning electrode. The cleaning device according to claim 2, wherein
The electrode cleaning means includes an electrode cleaning member that is in contact with the cleaning electrode, and a recovery unit that recovers a component removed from the cleaning electrode by the electrode cleaning member. The cleaning device according to any one of claims 1 to 3,
A cleaning apparatus comprising: a cleaning liquid supply unit that supplies a cleaning liquid that reacts with a recording liquid and cleans the recording liquid in contact with the cleaning electrode and the intermediate transfer member. The cleaning device according to claim 4.
Cleaning device, and forming a liquid reservoir by the cleaning liquid and the cleaning electrode and the cleaning member by said intermediate transfer member. The cleaning device according to claim 5, wherein
The cleaning liquid supply means supplies a liquid amount detection means for detecting the amount of the cleaning liquid in the liquid reservoir, and supplies the cleaning liquid to the liquid reservoir based on the amount detected by the liquid amount detection means. A cleaning device comprising a liquid amount control means for controlling the amount. The cleaning device according to claim 6, wherein the cleaning device is dependent on claim 3.
The electrode cleaning member cleans the cleaning liquid attached to the cleaning electrode, and the recovery unit recovers the cleaning liquid removed from the cleaning electrode by the electrode cleaning member,
The cleaning apparatus, wherein the cleaning liquid supply means includes a recycle means for supplying the cleaning liquid collected by the collection unit to the liquid amount control means. The cleaning device according to any one of claims 1 to 7,
The cleaning device, wherein the cleaning electrode is integral with the cleaning member. The cleaning device according to any one of claims 1 to 7,
The cleaning device, wherein the cleaning electrode is separate from the cleaning member. The cleaning device according to claim 9, wherein
The cleaning device, wherein the cleaning electrode is a roller.   An image forming apparatus comprising the cleaning device according to claim 1.

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