JP2012224019A - Head and image forming apparatus - Google Patents

Abstract

A head for ejecting a liquid such as ink used in an image forming apparatus such as an ink jet printer and such an image forming apparatus provided with the head, in particular, cleaning of the head is performed by mechanically operating a blade with respect to the head. Provided is a head and an image forming apparatus which can be carried out without any contact.
A nozzle member 61a having a nozzle 61b for discharging a liquid in a liquid chamber is provided, and the nozzle member 61a is disposed inside the insulating film 61a2 and a liquid-repellent insulating film 61a2 on which the surface is formed. And a plurality of electrodes 63 arranged in a predetermined direction B along the surface, and the liquid in contact with the surface is applied by periodically applying a voltage along the direction B to the plurality of electrodes 63. Heads 61Y, 61M, 61C, 61BK which are moved along the direction B and whose surfaces are cleaned, and an image forming apparatus having the heads.
[Selection] Figure 6

Description

  The present invention is a head for ejecting a liquid such as ink used in an image forming apparatus such as an ink jet printer and the like, and such an image forming apparatus provided with the head, and particularly capable of cleaning such a head. The present invention relates to a head and an image forming apparatus.

  Conventionally, inkjet recording is performed by using a movable actuator system typified by a piezo system, a heating film boiling system typified by a thermal system, and the like, which has a head that ejects a recording liquid such as ink from a minute nozzle. 2. Description of the Related Art Inkjet image forming apparatuses such as inkjet printers are known (for example, see [Patent Document 1] to [Patent Document 5]). Such an image forming apparatus uses an image forming technique for forming an image by attaching the recording liquid to a recording medium such as paper according to image information.

  Inkjet image forming apparatuses are being applied to printers, facsimiles, copiers, and the like because of the simplicity of the apparatus configuration compared to electrophotographic image forming apparatuses using a photoreceptor or the like. Inkjet image forming apparatuses are expected to develop into new fields such as electric circuit formation and biotechnology.

  In an inkjet image forming apparatus, the ink droplet flying direction due to adhesion of foreign matter or paper dust due to ejection failure due to thickening or drying of ink near the nozzle portion provided in the head, mist generated during image formation Deterioration of image quality due to disturbance of the image is a problem.

  In order to solve this problem, a blade made of a flexible material such as rubber, in other words, wipes the surface of the nozzle with a wiper, wiping the ink around the nozzle to remove deposits such as ink pool, ink mist, dust, and paper dust. A head cleaning method for removal has been widely known (see, for example, [Patent Document 1]).

  In general, when a conductive droplet is placed on the surface of the hydrophobic insulating film, and a voltage is applied via the insulating film between the flat plate electrode disposed on the inner surface of the insulating film and the droplet, It is known that the surface energy corresponding to electrostatic energy due to the capacitance formed by the droplet and the flat plate electrode is reduced, and the contact angle of the droplet is lowered. This phenomenon is called electrowetting. be called. As an application of the electrowetting phenomenon to an ink jet image forming apparatus, a technique for spreading the liquid on the surface of the plate on which the nozzle is formed by the electrowetting phenomenon and moistening the liquid to reduce drying of the nozzle portion (for example, [ [Patent Document 2]), a technique for controlling bubble adsorption and purging to the filter unit by applying electrowetting phenomenon to the filter unit in the head and controlling the wettability of the filter unit (for example, [Patent Document 3] ]) Is known. Furthermore, it is known that by applying the electrowetting phenomenon, a liquid droplet sandwiched between an insulating film and a counter electrode on a plurality of electrodes can be conveyed in one direction by voltage control of the plurality of electrodes ( For example, see [Non-Patent Document 1] and [Non-Patent Document 2]). In addition, in an ink jet image forming apparatus, a technique using an intermediate transfer member to suppress bleeding of ink applied to a recording medium is known (for example, [Patent Document 4] and [Patent Document 5]. 〕reference)

  However, mechanical contact of the blade with the nozzle surface leads to deterioration of the nozzle surface and blade over the long term. In particular, in an inkjet head, the surface of the nozzle surface is often treated with a water-repellent film in order to increase the ink ejection performance and meniscus retention, and such mechanical contact damages the water-repellent film. . Damage to the water-repellent film causes flying bends, mist generation, and dispersion of the ejected droplets, which significantly deteriorates the image quality. Further, when the blade is deteriorated, the wiping performance is deteriorated, so that mist, foreign matter and the like adhering to the nozzle surface cannot be removed well, and the image quality is also deteriorated. Such a problem due to mechanical contact generally occurs in a head that ejects liquid.

  Therefore, a technique for cleaning the nozzle surface without damaging the water-repellent film on the nozzle surface is desired in order to stably operate an inkjet image forming apparatus and the like for a long period of time.

  The present invention relates to a head for ejecting a liquid such as ink used in an image forming apparatus such as an ink jet printer, and such an image forming apparatus provided with the head. It is an object of the present invention to provide a head and an image forming apparatus that can be performed without involving any specific contact.

  In order to achieve the above object, the present invention has a nozzle member having a nozzle for discharging a liquid in a liquid chamber, and the nozzle member has a liquid-repellent insulating film having a surface formed thereon, and the insulating film. A plurality of electrodes disposed inside and arranged in a predetermined direction along the surface, and a voltage is periodically applied to the plurality of electrodes along the direction to contact the surface. The liquid is moved along the direction and the surface is in the head to be cleaned.

  The present invention also resides in an image forming apparatus having such a head and a head cleaning unit including a first voltage applying unit that periodically applies a voltage to the plurality of electrodes along the direction.

  The present invention includes a nozzle member having a nozzle for discharging a liquid in a liquid chamber, and the nozzle member is disposed on the inner surface of the liquid-repellent insulating film that forms the surface of the nozzle member. A plurality of electrodes arranged in a predetermined direction along the direction, and a voltage is periodically applied to the plurality of electrodes along the direction, so that the liquid in contact with the surface is along the direction Since the head is moved and the surface is cleaned, the nozzle member is cleaned by moving the liquid using electrowetting, so that the life of the nozzle member can be extended, and the life can be extended. A head that can contribute to good image formation over a long period of time can be provided.

  Further, the present invention is an image forming apparatus having such a head and a head cleaning unit including a first voltage applying unit that applies a voltage to the plurality of electrodes periodically along the direction. As the nozzle member is cleaned by moving the liquid using the ting, it is possible to extend the life of the head by extending the life of the nozzle member, and image formation that enables good image formation over a long period of time. An apparatus can be provided.

1 is a schematic front view according to an embodiment of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic perspective view of a head provided in the image forming apparatus shown in FIG. 1 and its periphery. FIG. 2 is a schematic diagram illustrating a state in which liquid is ejected from a head provided in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic plan view illustrating an arrangement mode of nozzle rows provided in a head provided in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a schematic bottom view of a configuration of a head provided in the image forming apparatus shown in FIG. 1 and its periphery. FIG. 2 is a schematic diagram illustrating a configuration mode of a plurality of electrodes provided in a head provided in the image forming apparatus illustrated in FIG. 1 and a mode of arrangement of nozzles. FIG. 2 is a schematic bottom view showing a configuration aspect of a plurality of electrodes around a nozzle provided in a head provided in the image forming apparatus shown in FIG. 1. It is a conceptual diagram for demonstrating the application aspect of the voltage with respect to the several electrode shown in FIG. FIG. 2 is a conceptual diagram for explaining the principle of liquid conveyance by an electrowetting phenomenon applied to the image forming apparatus shown in FIG. 1. FIG. 2 is a schematic sectional side view showing a configuration for eliminating ink accumulation around nozzles provided in a head provided in the image forming apparatus shown in FIG. 1. FIG. 5 is a schematic front sectional view showing another configuration example of a cleaning unit provided in the image forming apparatus shown in FIG. 1. FIG. 5 is a schematic front sectional view showing a configuration example of a liquid supply unit and a liquid recovery unit provided in another embodiment of the image forming apparatus to which the present invention is applied. It is a schematic front view concerning another embodiment of the image forming apparatus to which this invention is applied. FIG. 15 is a schematic front view illustrating an operation of a part of the image forming apparatus illustrated in FIG. 14. It is the schematic plan view which showed another structure aspect of the some electrode provided in the head with which the image forming apparatus to which this invention was applied was provided. It is the schematic plan view which showed another structure aspect of the some electrode provided in the head with which the image forming apparatus to which this invention was applied was provided.

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

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

  The image forming apparatus 100 is an ink head that can form an image as an image corresponding to each color separated into yellow, magenta, cyan, and black, and that is an ink ejector that ejects ink of the color. It has heads 61Y, 61M, 61C, 61BK as recording heads. The image forming apparatus 100 has a tandem structure in which heads 61Y, 61M, 61C, and 61BK are arranged in parallel in the horizontal direction.

  The heads 61Y, 61M, 61C, 61BK are disposed at a substantially central portion of the main body 99 of the image forming apparatus 100, and above the guide plate 11 as a flat guide member that guides the transfer paper S on the upper surface thereof. The plate 11 is disposed at a position facing the upper surface of the plate 11. The heads 61Y, 61M, 61C and 61BK are arranged in this order from the upstream side in the A1 direction along the left direction in FIG. 1, which is the moving direction of the transfer paper S on the upper surface of the guide plate 11. In the drawing, Y, M, C, and BK added after the numerals of the reference numerals indicate members for yellow, magenta, cyan, and black.

  The heads 61Y, 61M, 61C, and 61BK are respectively provided in the ink ejection devices 60Y, 60M, 60C, and 60BK for forming yellow (Y), magenta (M), cyan (C), and black (BK) images. ing. Each head 61Y, 61M, 61C, 61BK is a shuttle type, and is provided in the ink ejection devices 60Y, 60M, 60C, 60BK so as to move in a direction perpendicular to the paper surface of FIG. Yes.

  The guide plate 11 guides the transfer sheet S conveyed in the A1 direction on the upper surface of the guide plate 11 while facing the heads 61Y, 61M, 61C, 61BK. In this process, the guide plates 11 from the heads 61Y, 61M, 61C, 61BK Yellow, magenta, cyan, and black inks are ejected in such a manner that they are sequentially superimposed on the transfer paper S, and an image is formed on the transfer paper S.

  The ejection of ink onto the transfer paper S by the heads 61Y, 61M, 61C, 61BK is directed from the upstream side in the A1 direction to the downstream side so that the image areas of each color of yellow, magenta, cyan, and black overlap the same position on the transfer paper S. This is done at different timings.

  As shown in FIG. 1, the image forming apparatus 100 includes ink ejection devices 60Y, 60M, 60C, and 60BK that include heads 61Y, 61M, 61C, and 61BK, a belt 11, and a transfer sheet S that is an upper surface of a guide plate 11, respectively. A transport unit 10 as a paper transport unit that is a paper transport system that transports the paper in a guided state, and a transfer unit 10 that can stack a large number of transfer sheets S and only transfer 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 also includes a carriage 50 as a head support that integrally supports the heads 61Y, 61M, 61C, and 61BK, and a control unit that includes a CPU (not shown), a memory, and the like that control the overall operation of the image forming apparatus 100. Control unit 70.

  The image forming apparatus 100 also moves the carriage 50 back and forth in the B direction which is the main scanning direction corresponding to the direction perpendicular to the paper surface of FIG. , 61BK reciprocally move in the B direction, and a head cleaning device 30 as a head cleaning mechanism as a liquid removing means for cleaning the heads 61Y, 61M, 61C, 61BK. In FIG. 2, the guide plate 11 is not shown.

  The image forming apparatus 100 also includes a voltage applying unit 33 that applies a voltage to each of the heads 61Y, 61M, 61C, and 61BK, as will be described later, for cleaning the heads 61Y, 61M, 61C, and 61BK. Yes.

  In addition to the guide plate 11, the transport unit 10 is disposed on the upstream side and the downstream side of the guide plate 11 in the A1 direction, and is a roller for transporting the transfer paper S transported from the paper supply unit 20 in the A1 direction. The pair 12 and 13 and the roller pair 12 and 13 have a motor or the like as driving means (not shown) that rotationally drives the pair of rollers 12 and 13 so that the transfer paper S is conveyed in the A1 direction.

  As shown in FIG. 1, the paper feeding unit 20 transports only the uppermost transfer paper S among the paper feed tray 21 on which a large number of transfer papers S can be stacked and the transfer paper S stacked on the paper feed tray 21. Ink discharge timing at the heads 61Y, 61M, 61C, and 61BK with the paper feed roller 22 that feeds the unit 10, the housing 23 that supports the paper feed tray 21 and the paper feed roller 22, and the paper feed roller 22 And a motor or the like as a driving means (not shown) that rotates and feeds the transfer sheet S so as to match the above.

  The carriage 50 includes a main body portion 50a that houses the heads 61Y, 61M, 61C, and 61BK, and a convex portion 50b that protrudes on the right side of the main body portion 50a in FIG. The main body portion 50a is arranged so that the heads 61Y, 61M, 61C, 61BK can be replaced with new ones when the heads 61Y, 61M, 61C, 61BK are deteriorated, and in order to facilitate maintenance, the heads 61Y, 61M, 61C, It can be attached to and detached from the main body 99 integrally with 61BK. Each of the heads 61Y, 61M, 61C, 61BK can be independently attached to and detached from the main body 50a so that the heads 61Y, 61M, 61C, and 61BK can be replaced with new ones when deterioration or the like occurs. It has become. This facilitates replacement work and maintenance work. The convex portion 50b is integrated with the head driving mechanism 80 shown in FIG. In FIG. 2, the projection 50b is not shown.

  The ink discharge devices 60Y, 60M, 60C, and 60BK have substantially the same configuration with respect to the other points although the colors of the recording liquid to be used are different.

  The ink ejection devices 60Y, 60M, 60C, and 60BK are ink cartridges 81Y, 81M, 81C, and 81BK, which are recording liquid cartridges as main tanks that store the recording liquids of the colors supplied to the heads 61Y, 61M, 61C, and 61BK. And ink cartridges 81Y, 81M, 81C, 81BK are connected to the heads 61Y, 61M, 61C, 61BK, respectively, and the recording liquid contained in the ink cartridges 81Y, 81M, 81C, 81BK is connected to the heads 61Y, 61M, 61C, It has flexible tubes 82Y, 82M, 82C and 82BK which are supply paths for supplying to 61BK.

  The ink ejection devices 60Y, 60M, 60C, and 60BK include the ink tank 81 that accommodates the ink cartridges 81Y, 81M, 81C, and 81BK, and the flexible that is illustrated in FIG. 2 that accommodates the tubes 82Y, 82M, 82C, and 82BK. The recording liquid stored in the ink cartridges 81Y, 81M, 81C, 81BK is pressure-fed toward the heads 61Y, 61M, 61C, 61BK via the tube storage section 82 and the tubes 82Y, 82M, 82C, 82BK. And a pump (not shown) as a supply pump for feeding. The operation of this pump is controlled by the control unit 70. In this respect, the control unit 70 functions as a recording liquid supply control unit.

  The ink cartridges 81Y, 81M, 81C, 81BK are replaced with new ones when the internal recording liquid is consumed and the remaining amount is low or no longer used, and in order to facilitate maintenance. 99 is removable.

  The ink cartridge 81 can be easily replaced with a new ink cartridge 81Y, 81M, 81C, 81BK when the recording liquid in the ink cartridges 81Y, 81M, 81C, 81BK is consumed or is low In order to make it possible and to facilitate maintenance, it is detachable from the main body 99.

  As shown in FIG. 3, each of the heads 61Y, 61M, 61C, 61BK has a nozzle plate 61a, which is a nozzle plate as a nozzle member disposed on the recording liquid discharge side facing downward in the figure, and a nozzle plate 61a. The formed nozzle 61b and an ink chamber 61c that is a liquid chamber having an insulating inner wall filled with the recording liquid supplied from the ink cartridges 81Y, 81M, 81C, and 81BK and having an insulating inner wall. is doing.

  Each head 61Y, 61M, 61C, 61BK is also provided with a liquid chamber electrode 61d that is an electrode that is disposed on the inner wall of the ink chamber 61c and is electrically connected to the recording liquid in the ink chamber 61c, and a recording liquid that is a liquid in the ink chamber 61c. And an ink discharge means (not shown) as a pressurizing mechanism for pressurizing and ejecting the ink from the nozzle 61b. The liquid chamber electrode 61d may be disposed so as to be electrically connected to the recording liquid in the ink cartridges 81Y, 81M, 81C, 81BK or in the tubes 82Y, 82M, 82C, 82BK.

  The nozzle plate 61a, the nozzle 61b, the ink chamber 61c, and the ink discharge means are provided as a set, and each head 61Y, 61M, 61C, 61BK is provided in large numbers, but only one of them is shown in FIG. Is illustrated. The pressure of the recording liquid in the ink chamber 61c is maintained at a predetermined pressure by which a meniscus is stably formed in the nozzle 61b as shown in FIGS. 3 (a), 3 (c), and 6 (b). Has been. In this respect, the pump functions as a pressure adjustment mechanism.

  The ink ejecting means has a piezoelectric element as an actuator for ejecting the recording liquid from each nozzle 61b to be ejected and landed on the transfer paper S. In accordance with the applied voltage pulse, the recording liquid forming a meniscus in the nozzle 61b as shown in FIG. 2A is ejected from the nozzle 61b as shown in FIG. 2B. Yes. In this respect, the control unit 70 functions as an ink ejection control unit.

  The control unit 70 functioning as an ink ejection control unit inputs a voltage pulse for driving the piezoelectric element to each of the piezoelectric elements with a predetermined signal waveform. This signal waveform is generated by an image control device realized as one function of the control unit 70 in accordance with an image to be formed, and is input to the control unit 70 functioning as an ink ejection control unit. Thereby, each head 61Y, 61M, 61C, 61BK discharges an arbitrary pattern in time series, and the image forming apparatus 100 can form an arbitrary image.

  As shown in FIG. 2B, the recording liquid ejected from the nozzle 61b moves toward the transfer paper S, and a bridge of a liquid column made of the recording liquid is temporarily formed between the nozzle 61b and the transfer paper S. Next, as shown in FIG. 2C, the bridge of the liquid column made of the recording liquid is divided to be carried on the transfer paper S, and an image of the recording liquid is formed on the transfer paper S. The

  The actuator of the ink discharge means may be a movable actuator of another method that is a shape deformation element method such as a piezo method, or the recording liquid is discharged from the nozzle 61b by a heater method such as a thermal method. Also good. The ink discharge means can individually control the discharge timing of the recording liquid from each nozzle 61b.

  In the recording liquid used in the image forming apparatus 100, the black ink is a water-based ink having the following composition. Other color inks are formed by changing the solid pigment. Note that the recording liquid needs to be a conductive ink when it is moved using the electrowetting phenomenon as described later.

  35.0% by mass of sulfonic acid group-bonded carbon black pigment dispersion CAB-O-JET-200 (Cabot Specialty Chemicals Inc.) having a solid content of 20% by mass, 10.0% by mass of 2-pyrrolidone, 14.0% by mass of glycerin, 0.9% by mass of propylene glycol monobutyl ether, 0.1% by mass of sodium dehydroacetate and distilled water (residue)

  As shown in FIG. 4, a plurality of nozzles 61b are provided along the B direction in each of the heads 61Y, 61M, 61C, and 61BK, forming nozzle rows 61bY, 61bM, 61bC, and 61bBK. Therefore, the B direction coincides with the arrangement direction of the nozzle rows 61bY, 61bM, 61bC, and 61bBK. The nozzle rows 61bY, 61bM, 61bC, 61bBK are arranged in this order along the A1 direction.

  The nozzle plate 61a is common to all the nozzles 61b in each of the heads 61Y, 61M, 61C, 61BK. Therefore, the nozzle rows 61bY, 61bM, 61bC, and 61bBK are provided on the same nozzle plate 61a in each of the heads 61Y, 61M, 61C, and 61BK. Each nozzle plate 61a includes nozzles 61b that discharge recording liquids of the same quality, that is, the same composition and the same color, as nozzle rows 61bY, 61bM, 61bC, and 61bBK arranged in parallel along the B direction.

  In this embodiment, the nozzle rows 61bY, 61bM, 61bC, and 61bBK are arranged in a manner in which a plurality of nozzle rows 61BY, 61bM, 61bC, and 61bBK are arranged in parallel in the A1 direction that intersects the B direction in a manner orthogonal to the B direction. The nozzle rows 61bY, 61bM, 61bC, and 61bBK are arranged one by one in the A1 direction, but the nozzle rows 61bY, 61bM, 61bC, and 61bBK are each arranged in a direction that intersects the B direction, for example, in the A1 direction. A plurality of them may be arranged side by side. When a plurality of nozzle arrays 61bY, 61bM, 61bC, and 61bBK are arranged side by side in the direction intersecting with the B direction, high-speed image formation is possible. Further, the nozzle plate 61a may have a configuration common to the heads 61Y, 61M, 61C, and 61BK, and may include all of the nozzle rows 61bY, 61bM, 61bC, and 61bBK.

  As shown in FIG. 5 or 6A, the nozzle rows 61bY, 61bM, 61bC, 61bBK are not provided over the entire width of the heads 61Y, 61M, 61C, 61BK in the B direction. 5 and 6A show the heads 61Y, 61M, 61C, and 61BK as viewed from the recording liquid ejection side.

  Specifically, the nozzle rows 61bY, 61bM, 61bC, and 61bBK are not formed in the area on the front side in FIG. 1 where the head cleaning device 30 is provided in the B direction. In other words, the heads 61Y, 61M, 61C, 61BK have non-formation regions 61aY, 61aM, 61aC, 61aBK of the nozzle rows 61bY, 61bM, 61bC, 61bBK in the B direction. Therefore, in the non-formation regions 61aY, 61aM, 61aC, and 61aBK, the nozzle plate 61a does not form the nozzle 61b.

  As shown in FIG. 1 or FIG. 2, the head driving mechanism 80 is a driving member for fixing the convex portion 50b and reciprocating the carriage 50 in the B direction to reciprocate the heads 61Y, 61M, 61C, 61BK in the B direction. 80a, and the driving member 80a has a motor 80b as a driving source for driving the driving member 80a so as to reciprocate the carriage 50 in the B direction and reciprocate the heads 61Y, 61M, 61C, 61BK in the B direction. Yes.

  The head driving mechanism 80 reciprocates the carriage 50 in the B direction to eject the recording liquid from the heads 61Y, 61M, 61C, and 61BK toward the transfer paper S, thereby moving the heads 61Y, 61M, 61C, and 61BK to B. Reciprocate in the direction.

  When the head cleaning device 30 cleans the heads 61Y, 61M, 61C, and 61BK, the head driving mechanism 80 positions the carriage 50 at the frontmost position in FIG. 1 within the movable range of the carriage 50 in the B direction. To do.

  The positions of the carriage 50 and the heads 61Y, 61M, 61C, 61BK occupied at this time are referred to as a head cleaning position that is a home position of the carriage 50, the heads 61Y, 61M, 61C, 61BK. In the state where the heads 61Y, 61M, 61C, 61BK occupy the head cleaning position, the non-formation regions 61aY, 61aM, 61aC, 61aBK of the nozzle plate 61a Located on the outside.

  As shown in FIG. 5, the head cleaning device 30 includes the non-formation regions 61aY, 61aM, 61aC, and 61aBK of the nozzle plate 61a in a state where the carriage 50 and the heads 61Y, 61M, 61C, and 61BK occupy the head cleaning position. It is arrange | positioned so that the position which opposes may be included.

  The head cleaning device 30 corresponds to the non-formation regions 61aY, 61aM, 61aC, 61aBK of the nozzle plate 61a in the B direction with the carriage 50 and the heads 61Y, 61M, 61C, 61BK occupying the head cleaning position. The wiper 30a as a wiping member that is disposed in contact with the nozzle plate 61a and the wiper 30a is driven in a direction opposite to the A1 direction and the A1 direction to wipe the non-formation regions 61aY, 61aM, 61aC, 61aBK by the wiper 30a. A wiping drive means (not shown) for scraping off and removing the recording liquid adhering to the non-formation regions 61aY, 61aM, 61aC, 61aBK and foreign matters such as paper dust, dust and other solid matter adsorbed thereto. A wiping mechanism 30b having To have.

  The head cleaning device 30 also includes a waste liquid recovery mechanism (not shown) that collects the foreign matter scraped and removed from the nozzle plate 61a by the wiping mechanism 30b, and a head cleaning control that is realized as one function of the control unit 70 and controls the driving of the wiping mechanism 30b. Means.

  The head cleaning device 30 scrapes and removes the recording liquid or the like that has moved to the non-formation regions 61aY, 61aM, 61aC, 61aBK as a foreign matter by the wiping mechanism 30b as described later, and the heads 61Y, 61M, 61C, 61BK. Is kept in a clean state.

  As shown in FIG. 3 or FIG. 6B, the nozzle plate 61a is formed on the recording liquid discharge side surface of the substrate portion 61a1 in contact with the recording liquid in the ink chamber 61c and the substrate portion 61a1. And a water-repellent film 61a2 which is a liquid-repellent insulating film on which the surface is formed. 6B is a cross-sectional view taken along the line AA ′ of FIG. 6A, that is, the nozzle plate including the B direction at the position having the nozzle rows 61bY, 61bM, 61bC, 61bBK in the A1 direction of the nozzle plate 61a. It is sectional drawing by the plane perpendicular | vertical to 61a.

The nozzle plate 61a and the base material 61a1 are provided with the surface on the ink chamber 61c side as an interface forming portion that forms an interface with the recording liquid in the ink chamber 61c.
Since the water repellent film 61a2 is preferably formed of a fluorine-based resin, polytetrafluoroethylene (PTFE) is used as a material, and the film thickness is 20 nm.

  As shown in FIG. 6B or 6A, the substrate portion 61a1 includes an insulating substrate 62 in contact with the recording liquid in the ink chamber 61c, and a surface of the substrate 62 opposite to the ink chamber 61c. The ink chamber 61c of the substrate 62 is formed so as to cover the plurality of electrodes 63 and the terminal portions 65 made of a metal thin film pattern arranged on the upper surface and the exposed portions of the plurality of electrodes 63 and terminal portions 65 and the substrate 62. And an insulating film 64 having a film thickness t formed on the opposite surface.

  The insulating film 64 is made of silicon oxide as a material and has a thickness t of 1000 nm. Other insulating film materials for forming the insulating film 64 include inorganic materials such as aluminum oxide, titanium oxide, tantalum pentoxide, barium titanate, and silicon nitride, and various organic materials such as epoxy resin, melamine resin, alkyd resin, and polyimide. It is possible to use materials. As the insulating film material for forming the insulating film 64, a polymer material including inorganic fine particles, an organic-inorganic hybrid material, or the like may be used. As the material of the insulating film 64, a material having a high dielectric breakdown voltage is preferable even if the film thickness is thin.

  As shown in FIG. 6, the plurality of electrodes 63 extend along the B direction, which is the direction along the surface of the nozzle plate 61a formed by the water repellent film 61a2, in other words, the extension of the nozzle rows 61bY, 61bM, 61bC, 61bBK. Arranged parallel to the installation direction. The plurality of electrodes 63 include first electrodes 63a and second electrodes 63b which are alternately arranged at a pitch p / 2 along the B direction and extend in the A1 direction and are parallel to each other.

  The terminal portion 65 has a terminal portion 65a for the first electrode 63a located on the downstream side in the A1 direction, and a terminal portion 65b for the second electrode 63b located on the upstream side in the A1 direction. The first terminal portion 65a and the second terminal portion 65b extend in the B direction and are arranged in parallel to each other.

  The first electrode 63a and the second electrode 63b are arranged in parallel in the B direction at equal intervals of the pitch p. In this way, the first electrode 63a and the second electrode 63b are formed in a comb shape on the first terminal portion 65a and the second terminal portion 65b, respectively.

  However, as shown in FIG. 7, the first electrode 63a and the second electrode 63b are alternately arranged around the nozzle 61b so as to bypass and surround the nozzle 61b, and cross the nozzle 61b. It has become impossible.

  That is, a portion where the first electrode 63a and the second electrode 63b are not formed is provided around the nozzle 61b. More specifically, neither the first electrode 63a nor the second electrode 63b is provided in the portion in contact with the nozzle 61b.

  The shape of the first electrode 63a and the second electrode 63b in the portion that bypasses the nozzle 61b is a circular or elliptical arc shape in which the curvature gradually decreases as the distance from the nozzle 61b increases in the example shown in FIG. However, as long as the first electrodes 63a and the second electrodes 63b are alternately arranged, the shapes thereof may be rectangular or rectangular.

  As a material of the electrode 63 and the terminal portion 39, a material generally used as an electrode material such as aluminum, copper, gold, or chromium can be used. In this embodiment, aluminum is used and the film thickness is increased. 100 nm.

  As shown in FIG. 6A, the first electrode 63a and the second electrode 63b are respectively connected to the first terminal portion 65a by the power source 33a as the first voltage applying means provided in the voltage applying means 33. A voltage is applied by applying a voltage to the second terminal portion 65b. As shown in FIGS. 2 and 10, the power source 33a is configured to apply a voltage between the liquid chamber electrode 61d and the first electrode 63a.

  The drive control of the power source 33a is performed by the control unit 70. Specifically, as shown in FIG. 8 (a) or FIG. 8 (b), the first electrode 63a and the second electrode 63b are indicated by the solid line and the broken line in FIG. In an embodiment, an alternating voltage is applied so that the phase is reversed.

  In this way, a voltage is periodically applied to the plurality of electrodes 63 along the B direction by the power source 33a, and as shown in FIG. A mist-like, droplet-like (hereinafter referred to as “droplet”) recording liquid, which is a charged liquid on the surface of the plate 61a, moves along the B direction to clean the nozzle plate 61a.

Based on [Non-Patent Document 1] and [Non-Patent Document 2], the principle that the charged liquid such as the recording liquid moves by the electrowetting phenomenon will be described with reference to FIG.
Generally, when a charged droplet exists on the surface of a hydrophobic insulating film formed on an electrode, a capacitance is formed between the electrode and the droplet through the insulating film, and the surface energy corresponding to the electrostatic energy is reduced. However, it is known that the contact angle of the droplets is reduced. This phenomenon is called electrowetting.

  By applying this electrowetting phenomenon, it is known that a droplet on an insulating film formed on a comb electrode can be conveyed in one direction by voltage control of the electrode. This is described in [Non-Patent Document 1] and [Non-Patent Document 2].

  More specifically, it is as follows. As shown in FIG. 9, it is assumed that charged droplets formed by water-based ink mist are arranged on a hydrophobic insulating film. A first electrode E1 and a second electrode E2 are disposed below the insulating film, a voltage of 0 volts is applied to the first electrode E1, and a voltage of V volts is applied to the second electrode E2. Is applied. When no voltage is applied to the first electrode E1 and the second electrode E2, the droplet contacts the insulating film at a contact angle θ (0) and forms a dotted line in the figure. When the voltage V is applied to the electrode E2, the droplet has a solid line shape, and the contact angle at the interface between the droplet and the insulating film on the second electrode E2 changes to θ (V). As described above, when the voltage V is applied to the second electrode E2, a difference in contact angle between the liquid and the insulating film occurs on the right and left of the liquid, and a force is generated in the liquid in the direction of the arrow in the drawing. Move.

It is known that the change amount of θ (V) with respect to θ (0) is approximately expressed by the following equation (1). In this equation, γ _LG is the gas-liquid interface energy, ε _r is the dielectric constant of the insulating film, ε ₀ is the vacuum dielectric constant, and t is the thickness of the insulating film. The second item of the equation corresponds to the electrostatic energy stored between the droplet and the second electrode E2.

  In the heads 61Y, 61M, 61C, and 61BK, the voltages applied to the first electrode 63a and the second electrode 63b by the power source 33a are AC voltages having different phases as shown in FIG. Thus, the voltage is periodically applied to the plurality of electrodes 63 along the B direction by being controlled in such a manner that they are continuously switched. The controller 70 also functions as head cleaning control means in this respect.

  As a result, it is possible to continuously cause the droplet transport operation similar to that shown in FIG. 9, and the droplet of the recording liquid adhering to the nozzle plate 61a is transported in the B direction. Accordingly, the recording liquid adhering to the nozzle plate 61a is quickly transported to the non-formation areas 61aY, 61aM, 61aC, 61aBK, and is removed from the nozzle plate 61a by the head cleaning device 30 in the non-formation areas 61aY, 61aM, 61aC, 61aBK. Thus, the recording liquid itself is removed from the nozzle plate 61a and cleaning is performed. Therefore, even when used for a long time, the recording liquid is prevented from being deposited in the non-formation regions 61aY, 61aM, 61aC, 61aBK.

  In addition, foreign matters such as paper dust, dust, and other solid substances attached to the nozzle plate 61a are also taken into the recording liquid in the process in which the recording liquid is conveyed to the non-formation areas 61aY, 61aM, 61aC, and 61aBK. 61aY, 61aM, 61aC, and 61aBK are quickly transported and removed from the nozzle plate 61a together with the recording liquid by the head cleaning device 30 in the non-formation regions 61aY, 61aM, 61aC, and 61aBK, thereby being removed from the nozzle plate 61a and cleaned. Is done. Therefore, even when used for a long time, the accumulation of foreign matters in the non-formation regions 61aY, 61aM, 61aC, 61aBK is prevented or suppressed.

  As already described, the nozzles 61b provided in each of the heads 61Y, 61M, 61C, 61BK are juxtaposed along the B direction in each of the heads 61Y, 61M, 61C, 61BK, and the nozzle rows 61bY, 61bM, 61bC, and 61bBK are formed. The first electrodes 63a and the second electrodes 63b are also alternately arranged along the B direction, and the recording liquid droplets discharged from the nozzles 61b and attached to the nozzle plate 61a are conveyed in the B direction. .

  Therefore, when the recording liquid droplets of each color discharged from the nozzles 61b forming the nozzle rows 61bY, 61bM, 61bC, and 61bBK and attached to the nozzle plate 61a are transported in the B direction, the nozzle rows 61bY, Mixing between 61bM, 61bC, and 61bBK is prevented. Therefore, the recording liquid conveyed by applying the electrowetting phenomenon is prevented from causing color mixing. Therefore, the color of the recording liquid ejected from each nozzle 61b is always stable, and good image formation is performed.

  The ink mist, that is, the mist of the recording liquid is generally charged, and the recording liquid droplets adhering to the nozzle plate 61a are also often charged. Are transported in this way. When such conveyance is performed, the heads 61Y, 61M, 61C, 61BK are positioned at the head cleaning position.

  FIG. 8 shows an example in which the phase of the voltage applied by the power source 33a is completely reversed between the first electrode 63a and the second electrode 63b. However, if the recording liquid is transported, it is not always necessary. There is no need for such an antiphase, and it is sufficient if there is a phase shift. As for the magnitude of the voltage, the minimum value is not limited to 0 as shown in FIG. 5A, and may have a predetermined value different from 0.

  Since the first electrode 63a and the second electrode 63b are arranged as shown in FIG. 7 around the nozzle 61b, the recording liquid moves away from the nozzle 61b as shown by the broken arrow in the figure. However, as it moves away from the nozzle 61b, the conveyance in the B direction becomes dominant, and generally, the conveyance is performed in the B direction, and color mixing is avoided, and the non-formation regions 61aY, 61aM, 61aC are avoided. 61aBK.

  Further, since the recording liquid is transported in the direction away from the nozzle 61b as shown by the broken arrow in the figure, the liquid droplets around the nozzle 61b are easily removed, and the nozzle 61b is down, that is, clogged by the recording liquid or foreign matter. Is prevented. Accordingly, the heads 61Y, 61M, 61C, 61BK and the image forming apparatus 100 are robust and highly durable.

  As shown in FIG. 10A, the recording liquid inside and outside the nozzle 61b is united, and an ink pool that deteriorates the meniscus shape is generated from the inside of the nozzle 61b to a position near the nozzle 61b on the surface of the nozzle plate 61a. There are things to do. Such ink reservoirs cause mists and satellites to adhere to the vicinity of the nozzle 61b during the recording liquid ejection operation from the heads 61Y, 61M, 61C, and 61BK, or ejection failure from the heads 61Y, 61M, 61C, and 61BK. For example, the recording liquid adheres to the vicinity of the nozzle 61b, and the recording liquid adhering to the vicinity of the nozzle 61b thus merges with the recording liquid in the nozzle 61b. When such an ink pool occurs, it may cause ejection failure including bending of the recording liquid ejected from the nozzle 61b where the ink pool has occurred. Therefore, it is preferable to quickly eliminate this ink pool.

  Therefore, as already described with reference to FIG. 10, the power source 33a is configured to apply a voltage between the liquid chamber electrode 61d and the first electrode 63a. The power source 33a is controlled between the liquid chamber electrode 61d and the first electrode 63a between the ink reservoir near the nozzle 61b and the first electrode 63a under the control of the control unit 70 functioning as a head cleaning control unit. A predetermined voltage having a magnitude that allows a capacitance to be formed is applied. When this capacitance is formed, a force that moves toward the first electrode 63a acts on the recording liquid forming the ink reservoir.

  Therefore, if a sufficient potential difference is formed between the liquid chamber electrode 61d and the first electrode 63a by the power source 33a, as shown in FIG. 10B, the recording liquid forming the ink pool is formed. Are separated to form independent recording liquid droplets, and a normal meniscus is formed in the nozzle 61b. When a normal meniscus is formed, ejection failure caused by ink accumulation is prevented. Further, as described above, the independent recording liquid droplets quickly reach the non-formation regions 61aY, 61aM, 61aC, 61aBK and are cleaned. In this respect, the power source 33a functions as a meniscus recovery voltage application unit, and the control unit 70 that functions as a head cleaning control unit functions as a meniscus recovery voltage application control unit.

  For example, as shown in FIG. 8B, the voltage applied to the liquid chamber electrode 61d is preferably lower than the minimum value of the voltage applied to the first electrode 63a and the second electrode 63b. . This is because a strong force acts on the recording liquid in the vicinity of the nozzle 61b.

  In order to obtain such an action, the power supply 33a functioning as a meniscus recovery voltage applying means applies a voltage between the second electrode 63b and the liquid chamber electrode 61d instead of the first electrode 63a. There may be. Further, as described above, the power source 33a as the first voltage applying unit that periodically applies a voltage to the plurality of electrodes 63 and the power source 33a functioning as the meniscus recovery voltage applying unit may have different configurations. good.

  As shown in FIG. 6 (a), the head cleaning device 30, the power source 33a, and the control unit 70 functioning as a head cleaning control means for controlling them clean the nozzle plate 61a and set the heads 61Y, 61M, 61C, 61BK. A cleaning device 90 is configured as a cleaning means for cleaning. It may be understood that the cleaning device 90 includes the first electrode 63a, the second electrode 63b, and the water repellent film 61a2 provided in the heads 61Y, 61M, 61C, and 61BK to be cleaned.

  In addition to functioning as a head cleaning control unit, the control unit 70 constitutes a control system for the image forming apparatus 100 such as functioning as an ink ejection control unit as described above.

  The control unit 70 constituting the control system applies a voltage between the liquid chamber electrode 61d and the first electrode 63a by the timing at which the voltage is periodically applied to the plurality of electrodes 63 by the power source 33a and the power source 33a. The timing and timing of operating the wiping mechanism 30b in the head cleaning device 30 and cleaning the surface of the nozzle plate 61a by the wiper 30a are also controlled.

  In order to suppress power consumption, the control unit 70 constituting the control system is configured to periodically apply a voltage to the plurality of electrodes 63 by the power source 33a and between the liquid chamber electrode 61d and the first electrode 63a. The time for applying the voltage is shortened.

  Specifically, the timing at which the voltage is applied to the power source 33a is when a predetermined time has elapsed or after a predetermined number of recording liquids have been discharged. In addition, in order to control such timing, a detection unit that detects recording liquid ejection bends and non-ejections is installed, and based on the output signal of the detection unit, there are more than a predetermined number of ink ejection bends and non-ejections In addition, a voltage may be applied to the power source 33a.

  The frequency of wiping by the wiping mechanism 30b may be even lower. Specifically, the control unit 70 constituting the control system performs a wiping operation when a predetermined number of prints, in other words, image formation is completed, when the image forming apparatus is started, and when the image forming apparatus is stopped. I have control.

  Thereby, for example, when the voltage is constantly applied to the plurality of electrodes 63 by the power source 33a, when the voltage is always applied between the liquid chamber electrode 61d and the first electrode 63a, the wiping is always performed. The power consumption is reduced as compared with the case where the operation is performed.

  In the cleaning method using the cleaning device 90, in the region where the nozzle 61b is formed in the nozzle plate 61a, the nozzle plate 61a is not contacted with a member such as a wiper as conventionally used. Therefore, the cleaning operation prevents or suppresses the deterioration of the area of the nozzle plate 61a or the wiper with time, and maintains a good state for a long time. In such a region, damage to the water repellent film 61a2 is prevented or suppressed, so that ejection droplets, that is, occurrence of flying mist, mist generation, and dispersion due to damage to the water repellent film 61a2 are prevented or suppressed. The image forming operation by the forming apparatus 100 is stably performed over a long period of time, and the image quality is kept good.

  The above description is based on the premise that the droplet of the recording liquid is charged, and the embodiment of the cleaning device 90 in which the droplet is transported using the electrowetting phenomenon has been described. If not, it is not easy to transport the droplets by such a form. For this reason, it is preferable that the cleaning device 90 has a configuration in which electric charges are applied to the droplets of the recording liquid adhering to the nozzle plate 61a.

  Therefore, the cleaning device 90 shown in FIG. 11 includes a guide plate 11 and a drive unit 91 including a motor (not shown) that moves the guide plate 11 close to and away from the nozzle plate 61a. If the droplet is transported using the electrowetting phenomenon, the “proximity” here includes contact. The same applies to each example described later.

  The guide plate 11 is made of aluminum and has conductivity. The drive unit 91 positions the guide plate 11 at the home position shown in FIG. 1 when image formation is performed. When performing the cleaning operation of the nozzle plate 61a, the drive unit 91 moves the guide plate 11 further from the home position. It is positioned at a cleaning position that is close to 61a and contacts the recording liquid droplets adhering to the nozzle plate 61a. The operation of the drive unit 91 is controlled by a control unit 70 that functions as a head cleaning control unit. Other configurations and operations are the same as described above.

  In such a configuration, when the guide plate 11 occupies the cleaning position, the recording liquid droplets adhering to the nozzle plate 61 a can exchange charges with the guide plate 11. Accordingly, when charges are periodically applied to the plurality of electrodes 63 as described above, the recording liquid droplets adhering to the nozzle plate 61 a are the closest ones of the plurality of electrodes 63. The charge is opposite to that of the first electrode 63a or the second electrode 63b. Therefore, a capacitance is formed between the droplet and the first electrode 63a or the second electrode 63b that is closest to the droplet among the plurality of electrodes 63. At this time, a voltage, specifically, an alternating voltage is applied between the guide plate 11 and the first electrode 63a or the second electrode 63b. In this respect, the power source 33a functions as a second voltage applying unit that applies such a voltage. The second voltage application means may be provided separately.

  When charges are periodically applied to the plurality of electrodes 63 as described above, such droplets are conveyed as described above. In this respect, the guide plate 11 functions as a cleaning member. The guide plate 11 that functions as a cleaning member is not made of aluminum as long as it is conductive, and may be made of a metal material such as copper, gold, or chromium, carbon, or a conductive polymer, or a glass substrate. A thin film made of metal or carbon may be formed thereon.

  When the recording liquid droplets are transported in this way, the positions occupied by the heads 61Y, 61M, 61C, 61BK are on the head cleaning device 30 side in the B direction as shown in FIG. The end portion is a position facing the end portion of the guide plate 11 on the head cleaning device 30 side. This position is called a droplet movement position.

  When the droplets are transported to the non-formation regions 61aY, 61aM, 61aC, and 61aBK, the heads 61Y, 61M, 61C, and 61BK move to the head cleaning position and are cleaned by the head cleaning device 30. The cleaning member is not limited to the guide plate 11 and may be any member that is positioned close to the nozzle plate 61a as described above when cleaning the nozzle plate 61a. Further, the heads 61Y, 61M, 61C, 61BK may be driven so as to be close to the cleaning member.

  As already described, the droplets conveyed using the electrowetting phenomenon have a function of taking in and cleaning the foreign matter adhering to the nozzle plate 61a. This effect is enhanced when the droplets are positively attached to the nozzle plate 61a rather than using only the recording liquid attached to the nozzle plate 61a as such droplets.

  Therefore, in the cleaning device 90 having the configuration shown in FIG. 11, when the nozzle plate 61a is cleaned by droplets transported utilizing the electrowetting phenomenon, the head 61Y is controlled by the control unit 70 that functions as an ink discharge control means. , 61M, 61C, 61BK may be ejected from the recording liquid. In this case, the control unit 70 that functions as an ink discharge control unit also functions as a head cleaning control unit.

  Further, instead of this idle ejection or together with this idle ejection, the recording liquid in the ink chamber 61c is pressurized by driving the pump by the control unit 70 as the recording liquid supply control means, and the heads 61Y, 61M, 61C, 61BK. The recording liquid may be oozed out from. In this case, the control unit 70 that functions as recording liquid supply control also functions as a head cleaning control unit.

  As described above, when the recording liquid is ejected or exuded so as to positively attach the droplets to the nozzle plate 61a for cleaning, the recording liquid needs to have conductivity. Since the recording liquid has a conductive composition as described above, it is suitable for such cleaning.

  In order to perform cleaning by actively attaching droplets to the nozzle plate 61a, the conductive liquid dedicated for cleaning is used in place of or in addition to the recording liquid supplied from the inside of the heads 61Y, 61M, 61C, 61BK as droplets. The cleaning liquid may be used.

  In addition to the cleaning device 90 shown in FIG. 11, the cleaning device 90 shown in FIG. 12 has a surface of the nozzle plate 61a in the heads 61Y, 61M, 61C, 61BK occupying the droplet movement positions, specifically, a water repellent film 61a2. The cleaning liquid supply means 34 is a cleaning liquid supply mechanism serving as a liquid supply means for supplying a cleaning liquid droplet L which is a conductive liquid between the surface of the guide plate 11 and the guide plate 11, and is supplied by the cleaning liquid supply means 34. The surface of the nozzle plate 61a, specifically, the surface of the water repellent film 61a2, has a cleaning liquid recovery means 35 that is a cleaning liquid recovery mechanism as a liquid recovery means for recovering the droplets L.

  The cleaning liquid recovery means 35 is provided as the above-described waste liquid recovery mechanism in the head cleaning device 30. In the head cleaning device 30 provided with the cleaning liquid recovery means 35, the above-described wiping mechanism 30b is omitted. However, the waste liquid recovery mechanism may be as described above as long as the droplet L, which has been cleaned by the above-described wiping mechanism 30b, can be scraped off and removed from the nozzle 61a.

  In addition, in the form shown in FIG. 12, the heads 61Y, 61M, 61C, 61BK are full line types. Accordingly, the non-formation regions 61aY, 61aM, 61aC, and 61aBK are omitted, but may not be omitted. Further, in the image forming apparatus 100, the head driving mechanism 80 is omitted, and operations related thereto are also changed.

  Note that the form shown in FIG. 1 and the like can also be a full-line type. In this case, the non-formation regions 61aY, 61aM, 61aC, and 61aBK are removed from the guide plate 11 in the B direction in order to scrape and remove the droplets L that have been cleaned by the wiping mechanism 30b from the nozzle 61a. The heads 61Y, 61M, 61C, 61BK may be extended so as to be positioned in front of the paper surface, and the non-formation regions 61aY, 61aM, 61aC, 61aBK may be disposed so as to face the head cleaning device 30.

  In the form shown in FIG. 12, a shuttle type can be adopted. The configuration and operation of the cleaning device 90 are appropriately changed depending on whether the image forming apparatus 100 is a shuttle type or a full line type.

  In the configuration shown in FIG. 12A, the cleaning liquid supply means 34 includes a supply port 34a that is a discharge port that discharges the cleaning liquid in a manner that exudes the cleaning liquid, a cleaning liquid tank 34b that contains the cleaning liquid, and a cleaning liquid In order to discharge the cleaning liquid in the tank 34b as droplets L from the supply port 34a, a pressurizing unit (not shown) that pressurizes the cleaning liquid in the cleaning liquid tank 34 is provided. The cleaning liquid supply means 34 has a supply port 34 a in the guide plate 11. That is, the supply port 34a is configured by a hole formed in the end portion of the guide plate 11 that faces the end portion of the nozzle plate 61a opposite to the cleaning liquid collecting means 35 in the B direction.

  The cleaning liquid that oozes out from the supply port 34a contacts the end of the nozzle plate 61a and enters between the nozzle plate 61a and the guide plate 11 by capillary force. The cleaning liquid that has entered between the nozzle plate 61a and the guide plate 11 is separated by the electrowetting effect and is transported toward the cleaning liquid recovery means 35 in the B direction as droplets L, while cleaning the nozzle plate 61a. .

  The cleaning liquid recovery means 35 includes a recovery port 35a for recovering the droplet L, and has a waste liquid tank 35b for storing the droplet L recovered at the recovery port 35a. The cleaning liquid recovery means 35 has a recovery port 35 a in the guide plate 11. That is, the recovery port 35a is configured by a hole formed in the end portion of the guide plate 11 facing the end portion of the nozzle plate 61a opposite to the cleaning liquid supply means 34 in the B direction. The inner surface of the recovery port 35a has a lower surface tension than the surface of the guide plate 11, and the droplet L conveyed to the entrance of the recovery port 35a by the electrowetting effect is drawn into the recovery port 35a. When the droplets L drawn into the collection port 35a accumulate to some extent, they drop by gravity and are stored in the waste liquid tank 35b.

  In the cleaning liquid supply means 34 and the cleaning liquid recovery means 35 configured as described above, since the supply port 34a and the recovery port 35a are provided in the guide plate 11, the number of parts can be suppressed and the cost can be reduced. Further, since the droplet L is directly supplied and recovered from the guide plate 11, the droplet L is supplied and recovered from the guide plate 11 with high positional accuracy, and the structure is relatively simple.

  In the configuration shown in FIG. 12B, the cleaning liquid supply unit 34 and the cleaning liquid collection unit 35 are separate from the guide plate 11.

  The cleaning liquid supply means 34 includes a cleaning liquid tank 34b that contains the cleaning liquid, and a dispenser 34c that supplies the cleaning liquid in the cleaning liquid tank 34b onto the guide plate 11 in a dropping manner. The dispenser 34c drops the droplet L at a position on the guide plate 11 that faces the end of the nozzle plate 61a. The droplet L dropped on the guide plate 11 contacts the end of the nozzle plate 61a and enters between the nozzle plate 61a and the guide plate 11 by capillary force. The droplets L that have entered between the nozzle plate 61a and the guide plate 11 are separated as droplets by the electrowetting effect, and are transported toward the cleaning liquid recovery means 35 in the B direction, thereby cleaning the nozzle plate 61a. .

  The cleaning liquid recovery means 35 abuts and presses the sponge roller 35c that absorbs the droplet L that has been transported by the electrowetting effect in the space between the nozzle plate 61a and the guide plate 11 and the sponge roller 35c. A pressure roller 35d for squeezing the droplet L, a waste liquid tank 35b for collecting the droplet L of the droplet L squeezed from the pressure roller 35d, and a sponge roller 35c and a pressure roller 35d are driven to rotate. A rotation drive mechanism.

  In the configuration shown in FIG. 12A, a plurality of, that is, four, supply ports 34a are provided corresponding to the arrangement positions of the nozzle rows 61bY, 61bM, 61bC, 61bBK in the A1 direction. In the configuration shown in FIG. 12B, the dispenser 34c supplies the droplets L corresponding to the arrangement positions of the nozzle rows 61bY, 61bM, 61bC, 61bBK in the A1 direction, similarly to the supply port 34a. It is supposed to be.

  Therefore, in both the configuration shown in FIG. 12A and the configuration shown in FIG. 12B, the droplets L supplied from the cleaning liquid supply means 34 are supplied to the nozzle rows 61bY, 61bM, 61bC, 61bBK. In this case, cleaning is performed while preventing or suppressing the mixing of the colorants contained in the inks ejected from the nozzle rows 61bY, 61bM, 61bC, and 61bBK. .

  As described above, according to the cleaning device 90 shown in FIG. 12, so-called color mixing, in which different color inks are mixed when the nozzle plate 61a is cleaned, is prevented or suppressed. Since mixed colors cause image quality degradation, a general multicolor inkjet image forming apparatus performs an empty discharge, that is, an operation of discharging droplets without using them for printing immediately after cleaning with a wiper that easily causes mixed colors. The color mixing is eliminated by discarding the mixed color ink. However, in the cleaning device 90, as described above, the supply position of the droplet L is set to a position that occupies the same position as each of the nozzle rows 61bY, 61bM, 61bC, and 61bBK in the A1 direction, and the droplet L that is supplied at this position. In the A1 direction, cleaning is performed while transporting in the B direction only at the positions where the nozzle rows 61bY, 61bM, 61bC, and 61bBK are disposed, so that good cleaning can be achieved while avoiding ink loss due to color mixing and empty ejection. To be done.

  In the configuration shown in FIG. 12A, unlike the supply port 34a, the recovery port 35a is formed wider than the entire width of the nozzle rows 61bY, 61bM, 61bC, 61bBK in the A1 direction, and the droplets after cleaning L is collected efficiently.

  In the configuration shown in FIG. 12B, the sponge roller 35c and the pressure roller 35d are formed wider than the entire width of the nozzle rows 61bY, 61bM, 61bC, 61bBK in the A1 direction, like the above-described recovery port 35a. Thus, the droplet L after cleaning is efficiently collected.

  The cleaning liquid constituting the droplet L is obtained by adding an electrolyte to distilled water. Examples of the electrolyte include various salts such as sodium chloride, potassium chloride, sodium nitrate, and potassium nitrate. The composition of the cleaning liquid is not limited to this as long as the electrowetting effect can be obtained, and a wetting agent and a pH adjuster are added for the purpose of improving the cleaning property regarding the components of the recording liquid as being close to the ink composition. May be.

  In the configuration shown in FIG. 12A and the configuration shown in FIG. 12B, the former configuration can be a simpler configuration. This is because, for example, the supply port 34 a and the recovery port 35 a can be disposed in the guide plate 11. On the other hand, the latter configuration has an advantage that the cleaning liquid supply means 34 may have the supply port 34a in the nozzle plate 61a. That is, there is an advantage that the recording liquid held by the heads 61Y, 61M, 61C, 61BK or the ink cartridges 81Y, 81M, 81C, 81BK can be partially branched and supplied from the supply port 34a.

  In the cleaning device 90 shown in FIG. 12, while the droplet L is being conveyed by the electrowetting effect, the internal pressure of the ink chamber 61c is lowered to retract the meniscus position to the back of the nozzle 61b, and the droplet L is discharged. You may make it reduce contacting and mixing with the recording liquid in the nozzle 61b. Conversely, by bringing the meniscus position closer to the surface of the nozzle plate 61a, the droplet L is positively brought into contact with the recording liquid in the nozzle 61b, thereby diluting the thickened recording liquid in the nozzle 61b. Also good.

  According to the cleaning device 90 shown in FIG. 12, the recording liquid discharged from the nozzle 61a is not changed into the droplet L, but the recording liquid is discharged as the droplet L from the nozzle 61a by having the cleaning liquid supply means 34. Such control becomes unnecessary.

  When cleaning is performed only with the recording liquid supplied from the nozzle 61a, the position of the nozzle 61a that discharges the recording liquid is restricted in order to clean the nozzle plate 61b in the entire B direction. According to the cleaning device 90 shown in FIG. 4, the supply of the droplet L by the cleaning liquid supply means 34 eliminates the need for control such as discharging the recording liquid as the droplet L from the nozzle 61a as described above. , It becomes easy to efficiently transport the droplets of the droplets L over the entire width of the nozzle plate 61a in the B direction.

  In addition, since the cleaning liquid supply means 34 is provided, a cleaning liquid that is different from the recording liquid and has a physical property suitable for cleaning, and particularly a liquid having a large surface tension that can be easily transported due to the electrowetting effect. This enables the cleaning droplets to be transported even at a lower applied voltage, reducing the energy consumption for cleaning, and efficiently performing the cleaning function by transporting the droplets for cleaning. It has become.

  On the other hand, in the configuration in which the cleaning is performed using the cleaning liquid and the configuration in which the cleaning is performed by using the recording liquid supplied from the nozzles 61b of the heads 61Y, 61M, 61C, and 61BK, the latter is supplied with the cleaning liquid. There is an advantage that the means 34 becomes unnecessary and the control of an appropriate amount of the liquid droplet L can be controlled with high accuracy.

  In the image forming apparatus 100 configured as described above, a sheet of transfer paper S is supplied from the paper supply unit 20 to the transport unit 10 in response to the input of a predetermined signal to start image formation. The transfer sheet S supplied to the transport unit 10 is transported and moved in the A1 direction on the upper surface of the guide plate 11 by the rotation of the roller pairs 12 and 13. In this process, ink is ejected from the heads 61Y, 61M, 61C, 61BK according to the image to be formed, and an image is formed on the surface of the transfer paper S. The transfer sheet S on which the image is formed passes over the upper surface of the guide plate 11, is guided to the paper discharge tray 25, and is stacked on the paper discharge tray 25.

When such an image is repeated, the heads 61Y, 61M, 61C, 61BK are in a state to be cleaned.
Specifically, the recording liquid ejected from the nozzle 61c and landed on the transfer paper S rebounds on the transfer paper S, and the nozzle 61c and its foreign substances together with foreign matters such as paper dust, dust, and other solid matter adhering to the transfer paper S. The nozzle plate 61a is contaminated by adhering to the peripheral portion. The recording liquid in which such a stain has occurred increases in viscosity due to drying, that is, evaporation of the solvent or the inclusion of such foreign matter, and can adhere to the nozzle plate 671a together with the foreign matter and cause the nozzle 61c to be clogged.

  When clogging occurs, the ink is no longer ejected from the nozzle 61c, is difficult to eject, or the flying direction of the ink ejected from the nozzle 61c and the ink speed are disturbed, resulting in a reduction in image quality. Further, when the ink attached to the peripheral portion of the nozzle 61c adheres to the transfer paper S, the image quality is degraded. In order to prevent or suppress such a decrease in image quality, the nozzle plate 61a is cleaned by the movement of the droplets described above. This cleaning is preferably performed before the nozzle 61c is clogged.

  Whether or not the nozzle plate 61a is in a state to be cleaned is determined by the control unit 70 depending on whether or not the timing already described is reached. Such timing is set with the aim before the nozzle 61c is clogged. However, the nozzle 61c may be clogged at such timing.

  When it is determined that such a state has been reached, the nozzle plate 71a is cleaned by moving the recording liquid or cleaning liquid droplets using the electrowetting effect as described above. When this cleaning is performed using a recording liquid, this cleaning can also be performed during image formation. When this cleaning is performed using a cleaning liquid, this cleaning is performed while the image forming operation is stopped. . Thereafter, when the wiping mechanism 30b is provided, cleaning by the wiping mechanism 30b is performed as necessary. By performing such cleaning, the heads 61Y, 61M, 61C, 61BK, specifically, the nozzle plate 61a are kept clean, and image formation is performed satisfactorily.

  The image forming apparatus 100 is not a type that directly forms an image on the transfer paper S as described above, but instead forms an image by an indirect method having an intermediate transfer body 73 as shown in FIG. The type to perform may be sufficient. Hereinafter, the image forming apparatus 100 shown in FIG. 13 will be described mainly regarding the differences from the image forming apparatus 100 shown in FIG.

  In the drawing, reference numeral 83 denotes a transfer roller as a transfer means that is a pressure roller that is provided in the transport unit 10 and is disposed to face the intermediate transfer body 73 and is driven to rotate by the intermediate transfer body 73. Reference numeral 93 guides the transfer sheet S fed from the paper supply unit 20 to a transfer section between the intermediate transfer body 73 and the transfer roller 83, and discharges the transfer sheet S that has passed through the transfer section. A guide plate for guiding to 25 is shown. Reference numeral 34 denotes a cleaning means 34 as an intermediate transfer body cleaning means for cleaning the intermediate transfer body 37.

  In addition, the image forming apparatus 100 shown in the figure includes an intermediate transfer member driving unit (not shown) that rotationally drives the intermediate transfer member 73 in the C1 direction.

The intermediate transfer member 37 has a drum shape.
Although not shown, the intermediate transfer member 73 has a support made of aluminum which is a conductive substrate and a surface layer made of silicone rubber formed on the support. The material of the support is not limited to aluminum, and may be formed of a metal such as an aluminum alloy, copper, or stainless steel as long as it has mechanical strength. The material of the surface layer is not limited to silicone rubber. For the advantage of high releasability of the recording liquid, any elastic material having low surface energy and high followability to the transfer paper S may be used. For example, fluorosilicone Rubber, phenyl silicone rubber, fluorine rubber, chloroprene rubber, nitrile rubber, nitrile butadiene rubber, isoprene rubber or the like may be used.

The surface layer is a conductive rubber obtained by dispersing and mixing fine metal particles such as carbon black, carbon nanotube, gold, and silver as a conductive agent in such a rubber material in order to impart conductivity to the intermediate transfer member 73. It is a conductive layer. However, when the number of conductive fine particles is increased, the conductivity is improved, but since there is a trade-off relationship in which the releasability is lowered, adjustment is necessary as appropriate. As will be described later, since a current flows between the nozzle plate 61a of the heads 61Y, 61M, 61C, and 61BK and the intermediate transfer body 73, the volume resistivity of the conductive rubber is 10 ⁶ Ω · cm or less, and further 10 ^4. It is desirable that it is less than Ω · cm. In this embodiment, the surface layer is a carbon-dispersed silicone rubber layer having a volume resistivity of about 5 Ω · cm and a thickness of 0.2 mm.

  It is necessary to include at least a colorant corresponding to yellow, magenta, cyan, and black, an anionic dispersant that is a dispersant for the colorant, and a solvent. Due to the colorant and the dispersant, the ink component of the recording liquid has an anionic group. The solvent needs to contain water, that is, an aqueous system from the viewpoint of safety and from the viewpoint of conductivity for causing electrolysis, which will be described later, and from the viewpoint of moving the recording liquid using the electrowetting phenomenon. The recording liquid is a water-soluble recording liquid that is a conductive ink and a water-soluble ink. The recording liquid is desirably alkaline from the viewpoint of storage stability.

  The voltage application means 33 has a power supply 33b as a third voltage application means connected between the support constituting the intermediate transfer body 37 and the liquid chamber electrode 61d. The power source 33b functions as a voltage applying unit that causes the intermediate transfer body 73 to function as an anode and the liquid chamber electrode 61d to function as a cathode, so that the colorant of the recording liquid on the intermediate transfer body 73 side will be described later. It is provided to produce a cohesive action of the components. The voltage application means 33 has the power source 33a described above, although not shown in the figure. The electrode functioning as the anode is not limited to the liquid chamber electrode 61d, and may be any electrode that conducts with the recording liquid in the ink chamber 61c.

  The transfer roller 83 is formed by pressing the transfer sheet S passing through the transfer portion against the intermediate transfer body 37 to which the recording liquid discharged from each of the heads 61Y, 61M, 61C, 61BK is applied. The image is transferred to the transfer paper S. The transfer roller 83 constitutes a transfer mechanism that performs transfer in this way.

  The cleaning unit 34 is provided to remove the recording liquid remaining on the intermediate transfer body 37 from the intermediate transfer body 37 after the image of the recording liquid is transferred to the transfer paper S and perform cleaning. Yes. For this reason, the cleaning unit 34 is omitted from the surface of the intermediate transfer member 37, although the illustration is omitted, the recording liquid that has not been transferred to the transfer paper S among the recording liquids constituting the image formed on the intermediate transfer member 37 is used as the residual ink. A cleaning blade which is a rubber blade as a cleaning member formed of rubber as an elastic body, which is scraped off and brought into contact with the intermediate transfer body 37 in a so-called counter contact manner, and the cleaning blade is used as the intermediate transfer body 37. And a waste liquid bottle for collecting foreign matter such as recording liquid, paper dust, dust, and other solid substances scraped off from the surface of the intermediate transfer member 37 by the cleaning blade.

  In the image forming apparatus 100 having such a configuration, the intermediate transfer member 73 rotates in the A1 direction while facing the heads 61Y, 61M, 61C, and 61BK in response to the input of a predetermined signal to start image formation. In the process, recording liquids of yellow, magenta, cyan, and black are transferred from the heads 61Y, 61M, 61C, and 61BK so that the image areas of yellow, magenta, cyan, and black are overlapped with the same position of the intermediate transfer member 73. 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 73.

At this time, the power supply 33b is driven by the control unit 40 serving as a voltage application control unit to apply a voltage to the support, and a potential difference is formed between the support and the nozzle plate 61a.
In this state, the recording liquid is applied from the heads 61Y, 61M, 61C, 61BK onto the intermediate transfer body 73. At that time, first, the heads 61Y, 61M, 61C, 61BK are used as shown in FIG. As shown, the recording liquid forming a meniscus in the nozzle 61b moves toward the intermediate transfer member 73 in the same manner as shown in FIG. 2B, and the nozzle 61b and the intermediate transfer member are moved. 73 is temporarily formed with a liquid column bridge made of the recording liquid, and then the liquid column bridge made of the recording liquid is divided in the same manner as shown in FIG. As a result, an image is formed on the intermediate transfer body 73 by the recording liquid.

Then, in the state in which 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 power source 33b. Specifically, by applying voltage to the intermediate transfer body 73 from the power source 33b, the following electrode reaction occurs between the liquid chamber electrode 61d functioning as the cathode and the intermediate transfer body 73 functioning as the anode, respectively. Water contained in the bridge of the recording liquid column 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, water contained in the bridge of the liquid column of the recording liquid is oxidized on the surface of the intermediate transfer member 73 functioning as the anode to generate protons (H +), so that the pigment dispersed by the anionic dispersant is removed. Aggregates via protons. Thereby, the occurrence of bleeding between adjacent dots is suppressed, and a high-definition image is formed. In addition, there is an advantage that clogging of the nozzle 61b is prevented by such voltage application. The time for forming such a bridge can be controlled by the peak voltage and pulse width of the electromagnetic pulse applied to the piezoelectric element.

  In this image forming apparatus 100, each of the heads 61Y, 61M, 61C, 61BK can eject an arbitrary pattern in time series as in the above-described image forming apparatus 100, but each head 61Y, 61M, 61C, The recording liquid of each color ejected from 61BK is once carried on the intermediate transfer body 37 rotating in the C1 direction. Thereby, an arbitrary full-color image can be formed on the intermediate transfer member 37.

  The image carried on the intermediate transfer member 37 is pressed against the intermediate transfer member 37 by the transfer roller 83 when the transfer sheet S fed from the paper supply unit 20 passes through the transfer unit. As a result, the image is transferred onto the transfer paper S. As a result, an image is formed on the transfer paper S. The transfer sheet S on which the image carried on the intermediate transfer member 37 is transferred and the image is formed is guided by the guide plate 93 and guided to the sheet discharge tray 25, and the sheet discharge tray as the image-formed transfer sheet S. 25 is loaded.

  Thus, in the intermediate transfer type image forming apparatus 100, since the heads 61Y, 61M, 61C, 61BK do not directly face the transfer paper S, foreign matters such as paper dust, dust, and other solid matter adhere to the nozzle plate 61a. There is an advantage that it is difficult to do.

Further, according to the image forming apparatus 100, since image formation is performed using electrolysis of the recording liquid, there is an advantage that bleeding of an image, which is a problem of the ink jet method, is prevented or suppressed.
On the other hand, as a measure against such bleeding, as is well known, an image forming apparatus including a coating device that applies a water-absorbing polymer to an intermediate transfer member has been proposed. This coating device functions as a pre-processing mechanism for suppressing the phenomenon that the recording liquid discharged to the intermediate transfer body bleeds by applying the water-absorbing polymer to the intermediate transfer body before the recording liquid is applied. To do.
The image forming apparatus 100 may employ such a pre-processing mechanism instead of the above-described configuration in which image formation is performed using electrolysis of a recording liquid. However, the countermeasure against bleeding by the image forming apparatus 100 shown in FIG. 13 has advantages that it is simple and has a lower running cost, and that bleeding is prevented or suppressed satisfactorily.

  For cleaning the heads 61Y, 61M, 61C, 61BK, the image forming apparatus 100 shown in FIG. 13 employs the cleaning device 90 of the type shown in FIG. 11, so that the intermediate transfer body 37 functions as a cleaning member. It has become. Therefore, it is not necessary to provide another member that functions as a cleaning member, and the number of parts is suppressed.

  In the image forming apparatus 100, as shown in FIG. 14, the drive unit 91 moves the intermediate transfer member 37 functioning as a cleaning member close to and away from the nozzle plates 61a of the heads 61Y, 61M, 61C, and 61BK. Specifically, the drive unit 91 positions the intermediate transfer member 37 at the home position shown in FIGS. 13A and 13 when image formation is performed, and performs the cleaning operation of the nozzle plate 61a. The guide plate 11 is positioned from the home position to the cleaning position shown in FIG. 14B, which is closer to the nozzle plate 61a and contacts the recording liquid droplets attached to the nozzle plate 61a. In the cleaning position, the intermediate transfer member 37 is separated from the transfer roller 83.

In the image forming apparatus 100 shown in FIG. 13, the cleaning device 90 is different from that shown in FIG. 11 in that the intermediate transfer body 37 is provided as a cleaning member.
Other configurations and operations are the same as described above.

  For example, when cleaning the nozzle plate 61a of each head 61Y, 61M, 61C, 61BK, the cleaning device 90 shifts from the state shown in FIG. 14A to the state shown in FIG. The recording liquid is discharged from the nozzles 61b of 61Y, 61M, 61C, and 61BK, and is brought into contact with the intermediate transfer member 37 that functions as a cleaning member. Thereafter, using the electrowetting phenomenon in the same manner as described above, the recording liquid is moved to the front side of the paper surface in the main scanning direction corresponding to the direction B described above and perpendicular to the paper surface in FIG. Then, the nozzle plate 61a is cleaned.

The recording liquid collected on the front side of the paper surface is removed from the nozzle plate 61a by the head cleaning device 30 (not shown in FIG. 13).
Note that the cleaning device 90 in the image forming apparatus 100 illustrated in FIG. 13 may omit the head cleaning device 30 and include an intermediate transfer member 37 and a cleaning unit 34 instead of the head cleaning device 30.

When the intermediate transfer member 37 and the cleaning unit 34 are used instead of the head cleaning device 30, the recording liquid conveyed to the front side of the sheet of the drawing using the electrowetting phenomenon is rotated in the C1 direction of the intermediate transfer member 37. Thus, the sheet is transported in a state of being carried on the intermediate transfer member 37 and is separated from the nozzle plate 61a. As a result, the recording liquid is removed from the nozzle plate 61a and cleaning is performed. The recording liquid that is separated from the nozzle plate 61 a and carried on the intermediate transfer member 37 is removed from the intermediate transfer member 37 by the cleaning unit 34, and the intermediate transfer member 37 is cleaned. Since the intermediate transfer member 37 is separated from the transfer roller 83 at the cleaning position, the recording liquid carried on the intermediate transfer member 37 does not adhere to the transfer roller 83 and the transfer roller 83 is not soiled.
The head cleaning device 30, the intermediate transfer member 37 and the cleaning means 34 may be used in combination to remove the recording liquid from the nozzle plate 61a and clean the nozzle plate 61a.

The intermediate transfer type image forming apparatus 100 shown in FIG. 13 may employ the cleaning device 90 of the type shown in FIG. 6 or the cleaning device 90 of the type shown in FIG.
Further, the intermediate transfer member may not be a drum like the intermediate transfer member 37 but may be an endless belt, or a sheet if possible.

Hereinafter, various modifications applicable to the above-described embodiments will be described.
FIG. 15A shows another configuration example of the plurality of electrodes 63. In the example shown in FIG. 5A, the plurality of electrodes 63 include not only the first electrode 63a and the second electrode 63b but also the third electrode 63c. The first electrode 63a, the second electrode 63b, and the third electrode 63c are arranged along the B direction periodically in this order, in other words, in a repeated pattern.

  The first electrode 63a, the second electrode 63b, and the third electrode 63c are applied with sinusoidal voltages that are periodically out of phase in this order, as shown in FIG. Is done. Specifically, voltages are applied to the first electrode 63a, the second electrode 63b, and the third electrode 63c in such a manner that the phases are shifted from each other in the form indicated by the solid line, the broken line, and the alternate long and short dash line in FIG. Thus, as described above, the droplets of the cleaning liquid are conveyed using electrowetting. In this configuration example, by using three kinds of electrodes including the first electrode 63a, the second electrode 63b, and the third electrode 63c, the first electrode 63a and the second electrode 63b are formed as described above. Compared to when two types of electrodes are used, there is an advantage that the droplets are reliably conveyed with high accuracy in the B direction.

  As described above, the plurality of electrodes 63 are arranged along the B direction by combining a plurality of electrodes to which a voltage is applied at the same time, as long as a voltage is periodically applied along the B direction. From the viewpoint of obtaining the above-mentioned advantages, it is desirable that the number is large. The plurality of electrodes disposed along the B direction may be independent electrodes and may be applied with a voltage periodically along the B direction. Also in this case, it is better that the number of electrodes is larger from the viewpoint of obtaining the above-mentioned advantages.

  As shown in FIG. 16, the first electrode 63a and the second electrode 63b are not in a form in which the first terminal portion 65a and the second terminal portion 65b are comb-like, that is, the edges are orthogonal to the B direction. A saw blade shape, that is, an end edge may be provided so as to intersect obliquely with respect to the B direction. In the configuration shown in the figure, the droplets occupying positions on the edges of the first electrode 63a and the second electrode 63b are more conveyed because the contact angle continuously changes on the edges. It becomes easy to be carried out, and it is efficiently transported even at a low applied voltage to perform a cleaning function. Therefore, the plurality of electrodes 63 having the configuration shown in the figure can reduce energy consumption for cleaning compared to the plurality of electrodes 63 having the configuration already described.

  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, in the form shown in FIG. 13, the ionicity of the ink colorant used in the solvent is anionic, but the ionicity may be cationic. In this case, the positive and negative of the power source are reversed from those described above so that the intermediate transfer member side is the cathode and the electrode that is in fluid communication with the liquid in the liquid chamber is the anode. Is replaced with the above-mentioned form.

  The present invention does not exclude performing cleaning by bringing a wiper, a blade, or the like into contact with the nozzle member, but using a combination of liquid movement by electrowetting and contact with the wiper, blade, etc. May be cleaned. When such a combination is used, it is possible to weaken the pressure of the contact or the like as compared with the case where cleaning is performed only by the contact or the like.

  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, a complex machine of these, a monochrome machine related thereto, and the like. The image forming apparatus may be a multifunction peripheral, an image forming apparatus used for forming an electric circuit, or an image forming apparatus used for forming a predetermined image in the biotechnology field.

  The 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.

DESCRIPTION OF SYMBOLS 11 Cleaning member 30 Liquid removal means 34 Liquid supply means 37 Cleaning member, intermediate transfer body 33a 1st voltage application means, 2nd voltage application means 33b 3rd voltage application means 61Y, 61M, 61C, 61BK Head 61a Nozzle member 61a2 Insulating film 61bY, 61bM, 61bC, 61bBK Nozzle array 61b Nozzle 61c Liquid chamber 61d Liquid chamber electrode 63 Multiple electrodes 90 Head cleaning means 100 Image forming apparatus A1 Crossing direction B Predetermined direction C1 Predetermined direction

Japanese Patent No. 3247545 JP 2006-82459 A JP 2007-38658 A JP 2010-188665 A Japanese Patent Laid-Open No. 11-188858

J. et al. H. Song R. Evans Y. -Y. Lin B. -N. Hsu · R. B. Fair, “A scaling model for electrifying-on-dielectric microfluidic actors”, Microfluidics and Nanofluidics, 2009, vol. 7, pp. 75-89 Hyejin Moon and Sung Kwon Cho, Robin L. Garrell Chang-Jin “CJ” Kim, “Low voltage electrifying-on-dielectric”, Journal of Applied Physics, 2002, vol. 92 (7), pp. 4080-4087

Claims (11)

A nozzle member having a nozzle for discharging the liquid in the liquid chamber;
This nozzle member has a liquid-repellent insulating film that forms the surface thereof, and a plurality of electrodes that are arranged inside the insulating film and arranged in a predetermined direction along the surface,
A head in which a voltage is periodically applied to the plurality of electrodes along the direction so that the liquid in contact with the surface is moved along the direction and the surface is cleaned. The head according to claim 1, wherein
A head comprising a liquid chamber electrode which is electrically connected to a liquid in a liquid chamber and to which a voltage is applied between at least one of the plurality of electrodes. The head according to claim 1 or 2,
The head is characterized in that the plurality of electrodes are arranged around the nozzle so as to bypass the nozzle. The head according to any one of claims 1 to 3,
The head, wherein the nozzle member includes a nozzle row including a plurality of nozzles that discharge liquid of the same quality along the direction. A head according to any one of claims 1 to 4;
An image forming apparatus comprising: a head cleaning unit including a first voltage applying unit configured to periodically apply a voltage to the plurality of electrodes along the direction. The image forming apparatus according to claim 5.
The head cleaning unit is a liquid that removes, from the nozzle member, the liquid that has moved along the direction when a voltage is periodically applied to the plurality of electrodes along the direction by the first voltage applying unit. An image forming apparatus comprising a removing unit. The image forming apparatus according to claim 5 or 6,
The head cleaning unit cleans the surface by moving the conductive cleaning member in contact with the liquid between the nozzle member and the liquid in contact with the cleaning member and the surface along the direction. Therefore, when a voltage is periodically applied to the plurality of electrodes along the direction by the first voltage application unit, a voltage is applied between the cleaning member and at least one of the plurality of electrodes. An image forming apparatus comprising: a second voltage applying unit. The image forming apparatus according to claim 7.
An intermediate transfer member to which the liquid discharged from the head is applied and the applied liquid is transferred to form an image;
The image forming apparatus, wherein the cleaning member is the intermediate transfer member. The image forming apparatus according to claim 8.
The liquid in the liquid chamber is conductive,
A third voltage for applying a voltage between the intermediate transfer member and the head for electrolyzing the liquid discharged from the nozzle and temporarily bridging between the head and the intermediate transfer member. An image forming apparatus comprising a voltage applying unit. The image forming apparatus according to any one of claims 7 to 9,
The image forming apparatus, wherein the head cleaning unit includes a liquid supply unit configured to supply the liquid between the cleaning member and the surface. The image forming apparatus according to any one of claims 5 to 9,
The image forming apparatus, wherein the liquid is a liquid discharged from the head.

Images