JP2006102975A - Discharge device and image recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge device and an image recording device which form a desirable image free of irregularities and mixed colors by preventing impact interference such as unification of liquid droplets and mixture of the different liquid droplets on a discharged medium by using a liquid having an ER effect. <P>SOLUTION: As an ink discharged from a print head 12, an ultraviolet setting ink having an electroviscous effect is used. Ink droplets 16 impacting an intermediate rotary drum 18 increases viscosity by expressing an electroviscous effect due to an electric field generated from an electrode pair 28. As a result, unification of ink droplets can be avoided and the shapes of the ink drops can be retained at impact. After transfer to a recording paper 20 from the intermediate transfer drum 18, fixation is administered by irradiation with UV light from a UV light source 24, blurs and color mixture immediately after transfer can be avoided and a desirable image is recorded on the recording paper 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ejection apparatus and an image recording apparatus, and more particularly to a technique for forming an image or the like in an ejection apparatus using a liquid that exhibits an electrorheological effect.

  In recent years, ink jet recording apparatuses have become widespread as data output apparatuses for images and documents. The ink jet recording apparatus can drive a nozzle provided in a print head according to data, and can form an image (data) on a medium such as recording paper by ink ejected from the nozzle.

  When forming an image at high speed by ejecting ink as recording liquid onto the media, adjacent droplets coalesce and the dot formation position deviates from a predetermined landing position, resulting in unevenness in the image. To do. Further, when forming a color image, inks of respective colors are mixed on the medium, and color mixing occurs.

  In order to suppress such unevenness due to unification of the recording liquids and deterioration of the quality of the printed image due to color mixing that occurs between different color inks, an electrorheological effect (ER effect) that increases the viscosity by applying an electric field is used. There has been proposed a method of forming an image on a medium using the ink that has been held.

  In the recording apparatus described in Patent Document 1, a recording liquid having an ER effect is attached to an intermediate transfer medium on which an electric field is formed by a recording head, and the viscosity of the recording liquid is increased on the intermediate transfer medium to cause excessive dots. Transfer from the intermediate transfer medium to the transfer medium is performed with the recording liquid dried and its viscosity increased, or with the recording liquid's viscosity increased due to the electroviscous effect of the recording liquid. It is configured to be

Further, in the recording apparatus described in Patent Document 2, a recording droplet having an ER effect is attached to a transfer medium to which an electric field is applied by a recording head to increase the viscosity of the recording liquid on the transfer medium. The dot formed by the recording liquid is prevented from whiskering, bleeding, and color mixing, and the electric field is maintained until the recording liquid is dried and penetrated into the transfer medium, and bleeding and color mixing do not occur.
JP-A-5-4342 Japanese Patent Laid-Open No. 5-4343

  However, ink with ER effect has the property that the rate of increase in ink viscosity changes depending on the direction of the applied electric field and the strength of the electric field. When an electric field is applied, the apparent viscosity increases instantaneously and the electric field is cut off. Then, the viscosity has reversibility that returns to the original. Therefore, the generation timing and generation time (period) of the electric field must be controlled in accordance with the ink ejection.

  Since the recording apparatus described in Patent Document 1 does not have a means for fixing and curing the recording liquid after transfer, bleeding and color mixing on the surface layer of the transfer medium cannot be avoided after transfer to the transfer medium. Further, even if an electric field is formed on the recording liquid adhering surface of the intermediate transfer medium, an electric field cannot be effectively applied to the ink, so that an effect of increasing the viscosity of the ink cannot be expected so much.

  Further, the recording apparatus described in Patent Document 2 is configured to form an electric field on the recording liquid adhesion surface of the transfer medium and to form an image using the recording liquid on this surface. The electric field of the transfer medium is not stable depending on the environment such as the water content, and it is difficult to stably develop the ER effect.

  The present invention has been made in view of such circumstances, and prevents landing interference such as coalescence of droplets on a medium to be ejected, mixing of different types of droplets using a liquid having an ER effect, It is an object of the present invention to provide an ejection apparatus and an image recording apparatus that form a preferable image without unevenness or color mixing.

  In order to achieve the above object, the invention according to claim 1 is directed to an ejection head that ejects a recording liquid having an electrorheological effect into droplets, and a recording droplet from the ejection head at a position facing the ejection head. An ejected intermediate transfer medium, an electrode pair comprising a positive electrode and a negative electrode, which is disposed on the intermediate transfer medium and applies an electric field to a recording droplet landed on the intermediate transfer medium, and the electrode pair Voltage supply means for supplying a predetermined voltage, transfer means for transferring the recording droplet landed on the intermediate transfer medium onto the recording medium, and the recording droplet transferred to the recording medium by the transfer means And a main fixing unit for performing a fixing process on the recording medium to the recording droplet transferred onto the recording medium immediately after.

  Recording droplets that have an electrorheological effect ejected from the ejection head are subjected to an electric field generated from an electrode pair on the intermediate transfer medium to develop an electrorheological effect (ER effect), and coalescence and landing interference are suppressed. Is done. Further, since the recording droplets on the intermediate transfer medium are fixed to the recording medium by the main fixing means immediately after being transferred to the recording medium by the transfer means, bleeding, unevenness, color mixing on the recording medium is performed. Image deterioration such as the above can be avoided, and a high-quality preferred image is recorded on the recording medium.

  The recording liquid includes various liquids that can be ejected as droplets from recording elements (ejection holes, nozzles, etc.) of the ejection head, such as ink, resist, chemicals, and processing liquid.

  In the ejection head, a full-line type ejection head in which recording elements are arranged over a length corresponding to substantially the entire width of the intermediate transfer medium, or a recording element is arranged over a length shorter than the length corresponding to the entire width of the intermediate transfer medium. There are serial type ejection heads (shuttle scan type recording heads) that eject droplets onto the intermediate transfer medium while scanning the short head in the width direction of the intermediate transfer medium.

  Also, in the full-line type ejection head, short heads having short recording element arrays that are less than the length corresponding to the full width of the intermediate transfer medium are arranged in a staggered manner and joined together to obtain the full width of the intermediate transfer medium. It may be a corresponding length.

  The intermediate transfer medium is a liquid receiving medium that receives liquid droplets ejected by the ejection head, and has a drum shape, a belt shape, or the like. In addition, it has predetermined lyophilicity and removability of droplets during transfer.

  Recording media include continuous paper, cut paper, sealing paper, resin sheets such as OHP sheets, film, cloth, and other various media and shapes, recording media, recording media, printing media, image formation Including what is called a medium.

  Here, the positive electrode and the negative electrode represent the relative relationship between them, which means that the potential of the positive electrode is relatively larger than the potential of the negative electrode.

  The fixing means includes radiation irradiation means for irradiating recording droplets with radiation (radiation rays) such as UV light, and heating means (drying means) for evaporating (drying) the solvent of the recording droplets by heat or air blowing. Applicable.

  The mode of permanently fixing the droplets on the recording medium includes an aspect in which the solute of the recording droplets is solidified on the surface of the recording medium and an aspect in which the recording droplets penetrate and fix in the recording medium. Whether it is an aspect or not depends on the combination of the type of recording medium and the type of recording liquid.

  According to a second aspect of the present invention, there is provided the discharge device according to the first aspect, wherein the electrode pair is arranged corresponding to a region where a recording liquid droplet discharged from the discharge head of the intermediate transfer medium lands. It is provided.

  Since the electrode pair is disposed corresponding to the area where the recording droplets land, the electroviscous effect can be efficiently expressed with respect to the recording droplets landed on the intermediate transfer medium.

  The electrode pair may have a structure that is disposed on the opposite side of the surface on which the recording droplets of the intermediate transfer medium land, or may have a structure in which another member is disposed between the intermediate transfer medium and the electrode pair.

  According to a third aspect of the present invention, there is provided the discharge apparatus according to the first or second aspect, further comprising voltage control means for variably controlling a voltage supplied from the voltage supply means to the electrode pair.

  The voltage supplied from the voltage supply means and the strength of the electric field generated from the electrode pair are in a proportional relationship, and the electric field strength and the viscosity of the recording liquid are in a proportional relationship. Therefore, when the voltage supplied from the voltage supply means to the electrode pair is varied, the strength of the electric field generated from the electrode pair can be varied, and the viscosity of the recording droplet landed on the intermediate transfer medium can be varied. be able to.

  A fourth aspect of the present invention relates to an aspect of the discharge apparatus according to the first, second, or third aspect, wherein the electrode pair includes a plurality of the positive electrode and the negative electrode, and at least one of the electrode pairs. The portion has a structure in which the positive electrode and the negative electrode are alternately arranged.

  When the positive electrode and the negative electrode are alternately arranged, the electric field applied to the recording droplets can be generated densely.

  The invention according to claim 5 relates to an aspect of the ejection device according to any one of claims 1 to 4, wherein the planar shape of the positive electrode and the negative electrode constituting the electrode pair is: Each has a substantially comb-tooth shape having a plurality of comb-tooth portions, and the electrode pair has a structure in which the comb-tooth portions of the positive electrode and the comb-tooth portions of the negative electrode are alternately arranged. Features.

  By alternately disposing each of the positive and negative electrode comb teeth formed on the comb teeth, a strong electric field can be applied to the recording droplets landed on the intermediate transfer medium. It becomes possible.

  A sixth aspect of the present invention relates to an aspect of the ejection device according to any one of the first to fifth aspects, wherein a distance P between the adjacent positive electrode and the negative electrode is determined from the ejection head. The minimum recording droplet diameter D of the ejected recording droplets on the intermediate medium satisfies the following formula P ≦ D.

  By making the interval P between the positive electrode and the negative electrode smaller than the minimum recording droplet diameter D on the intermediate transfer medium, an electrorheological effect can be developed for each recording droplet.

  The interval between the positive electrode and the negative electrode may be the minimum distance between the electrodes, or may be the pitch between the electrodes.

  A seventh aspect of the invention relates to an aspect of the ejection device according to any one of the third to sixth aspects, further comprising a moving unit that relatively moves the ejection head and the intermediate transfer medium, and the electrode. The pair has a structure in which a plurality of electrode pair blocks each including at least a pair of the positive electrode and the negative electrode are arranged in a relative movement direction of the intermediate transfer medium, and supplies the voltage from the voltage control unit. A switching means for selectively switching the pair block is provided.

  Since a plurality of electrode pair blocks are arranged in the relative movement direction of the intermediate transfer medium and the electrode pair blocks for supplying voltage from the voltage switching means are selectively switched, it is possible to process recording droplets on the intermediate transfer medium. Accordingly, the electrode pair that generates the electric field can be selectively switched. Further, the electric field can be turned off in a region where it is not necessary to generate an electric field, and the electric field does not adversely affect the processing of the recording droplet on the intermediate transfer medium. It also contributes to the realization.

  The invention according to claim 8 relates to an aspect of the discharge apparatus according to claim 7, wherein the voltage control means variably controls the voltage supplied from the voltage supply means of the electrode pair block selected by the switching means. It is characterized by doing.

  Since the voltage supplied for each electrode pair block is made variable, the viscosity of the recording droplet can be finely controlled for each region on the intermediate transfer medium.

  The voltage control means and the switching means described in claim 7 may be shared, and the voltage supplied to each electrode pair may be variably controlled from 0 V to a predetermined voltage.

  A ninth aspect of the invention relates to an aspect of the ejection device according to any one of the third to eighth aspects, wherein the intermediate transfer is performed based on data of a recording liquid ejected onto the intermediate transfer medium. Predicting means for predicting the recording droplet amount on the medium is provided, and the voltage control means varies the voltage supplied from the voltage supply means to the electrode pair according to the recording droplet amount predicted by the predicting means. It is characterized in that control is performed.

  By variably controlling the voltage supplied to the electrode pair in accordance with the amount of recording droplets on the intermediate transfer medium, a minute current flowing in the recording droplets can be recorded regardless of the amount of recording droplets on the intermediate transfer medium. Uniformity can be achieved for each drop.

  The prediction means obtains dot information such as the size and number of dots of each dot from the recording droplet data (dot data), and the recording droplet amount on the intermediate transfer medium is predicted based on this dot information. The recording droplet amount may be the volume of the recording droplet on the intermediate transfer medium, or the number of recording droplets if the recording droplet size on the intermediate transfer medium is substantially uniform.

  A tenth aspect of the present invention relates to an aspect of the ejection device according to any one of the seventh to ninth aspects, wherein the intermediate transfer medium after the image is transferred onto the recording medium by the transfer unit. A cleaning means for removing the remaining recording liquid is provided.

  By removing the recording droplets remaining on the intermediate transfer medium by the cleaning means, the quality of the image formed on the intermediate transfer medium can be maintained.

  For the cleaning means, an aspect in which the recording liquid is absorbed by a liquid absorbing means such as a porous member, an aspect in which a cleaning liquid for dissolving the recording liquid is applied on the intermediate transfer medium, a wiping member (peeling member) such as a blade, etc. There is a mode of using. Moreover, you may combine the aspect mentioned above.

  An eleventh aspect of the invention relates to an aspect of the ejection device according to the tenth aspect, wherein the voltage control unit is configured to remove the recording liquid remaining on the intermediate transfer medium by the cleaning unit. The voltage supply means is controlled so as not to supply a voltage to the electrode pair.

  While the recording liquid remaining on the intermediate transfer medium is being cleaned, the voltage supply means is controlled so as not to generate an electric field, so that the recording droplets remaining on the intermediate transfer medium can be easily removed and cleaned. At this time, the viscosity of the recording liquid is low, and it is possible to avoid damaging the intermediate transfer medium surface and the cleaning means.

  A twelfth aspect of the invention relates to an aspect of the ejection device according to the eleventh aspect of the invention, wherein the switching unit corresponds to a cleaning region in which the cleaning unit removes the recording liquid remaining on the intermediate transfer medium. The electrode pair block that supplies a voltage from the voltage supply means is switched so that a voltage is not supplied from the voltage supply means to the electrode pair block.

  In the cleaning area where the residual recording liquid on the intermediate transfer medium is removed by the cleaning means, control is performed so that no voltage is supplied from the voltage control means to the electrode pair block corresponding to this area, so the cleaning means operates. In particular, a voltage can be supplied to the electrode pair block in a region corresponding to another region, and an electrorheological effect can be exerted on the recording liquid on the intermediate transfer medium.

  A thirteenth aspect of the present invention relates to an aspect of the discharge apparatus according to any one of the first to twelfth aspects, and is provided between the discharge head and the transfer unit, and is disposed on the intermediate transfer medium. Preliminary fixing means for performing preliminary fixing processing on the landed recording droplets is provided.

  Before the transfer from the intermediate transfer medium to the recording medium, a preliminary fixing process such as curing the surface of the recording droplets landed on the intermediate transfer medium is performed, so that the adjacent recording liquid on the recording medium immediately after the transfer Drop coalescence and interference can be avoided.

  The preliminary fixing unit may have the same configuration as the main fixing unit or a different configuration.

  According to a fourteenth aspect of the present invention, there is provided the discharge apparatus according to the thirteenth aspect, wherein the preliminary fixing process performed on the recording droplets on the intermediate transfer medium by the preliminary fixing unit and the voltage control unit performs the preliminary fixing process. The unevenness of the recording droplets on the intermediate transfer medium is controlled using at least one of variable control of the voltage supplied to the electrode pair.

  The electric field strength applied to the recording droplets on the intermediate transfer medium is varied to control the viscosity of the recording droplets, and the recording droplets on the intermediate transfer medium are balanced by balancing the viscosity of the recording droplets and the surface tension. The unevenness of the droplet can be controlled. On the other hand, the unevenness of the recording droplets on the intermediate transfer medium can also be controlled by using the preliminary fixing means described in claim 13. By using at least one of these, it is possible to control the recording medium surface state (glossy, mat, etc.) in which the concavo-convex recording droplets are transferred to the recording medium by the transfer means.

  A fifteenth aspect of the present invention relates to an aspect of the ejection device according to the thirteenth or fourteenth aspect, wherein the preliminary fixing unit is configured to perform the intermediate operation when the recording medium is impermeable to a recording liquid. The surface of the recording droplet on the transfer medium is cured.

  When the recording medium is impermeable to the recording liquid, the recording liquid on the recording medium is transferred immediately after the transfer by curing the surface of the recording droplet on the intermediate transfer medium using a preliminary fixing unit. Drop coalescence and interference can be avoided.

  A sixteenth aspect of the present invention relates to an aspect of the ejection apparatus according to any one of the first to fifteenth aspects, further comprising a conveying unit that conveys the recording medium, and the main fixing unit includes the transfer unit. Provided on the downstream side of the conveying unit in the conveying direction of the conveying unit, in the conveying direction of the conveying unit from the transfer position of the recording medium by the conveying unit to the end position of the fixing process by the fixing unit from the transfer position by the transfer unit. The length s along and the penetration time T of the recording liquid into the recording medium satisfy the following expression s / u <T.

  The recording medium by the fixing unit is determined from the conveyance speed u of the recording medium and the transfer position by the transfer unit so that the time for fixing processing by the fixing unit (fixing processing time) is shorter than the penetration time T of the recording medium. Since the length s of the area up to the position where the fixing process is completed is determined, the main fixing process of the recording droplet is performed earlier than the recording droplet permeates into the recording medium, and bleeding on the recording medium is caused. In addition to avoiding this, recording speed on the recording medium is controlled by controlling the conveyance speed u of the recording medium and the length s of the area from the transfer position by the transfer means to the fixing processing end position on the recording medium by the fixing means. The unevenness of the droplet can be controlled.

  In order to variably control the main fixing process time, the conveyance speed u of the recording medium may be changed, or the length s of the area where the fixing process is performed (main fixing process area) may be changed.

  The permeation time T may be a time (primary permeation time) when recording droplets disappear from the surface of the recording medium.

  According to a seventeenth aspect of the present invention, there is provided the discharge apparatus according to any one of the first to sixteenth aspects, wherein the intermediate transfer medium has a cylindrical drum shape.

  By making the intermediate transfer medium into a drum shape, the configuration of the intermediate transfer medium can be simplified.

  If the electrode pair and the voltage supply means according to claim 1 are built in the drum, the configuration of the apparatus can be further simplified.

  In order to achieve the above object, an invention according to claim 18 is an image recording apparatus for recording an image on a recording medium using a recording liquid, and ejects the recording liquid having an electrorheological effect as droplets. A recording head to be formed, an intermediate transfer medium that forms an image at a position facing the recording head by recording droplets ejected from the recording head, and the intermediate transfer medium disposed on the intermediate transfer medium. An electric field is applied to the recorded droplet, and an electrode pair composed of a positive electrode and a negative electrode, voltage supply means for supplying a predetermined voltage to the electrode pair, and an image formed on the intermediate transfer medium are recorded. Transfer means for transferring onto the medium, and fixing processing on the recording medium to the recording droplets that form the image transferred onto the recording medium after the image is transferred to the recording medium by the transferring means The fixing hands that give Characterized by comprising a and.

  On the intermediate transfer medium, the shape of the recording droplets is maintained by the electrorheological effect, and after the image is transferred from the intermediate transfer medium to the recording medium, the fixing process is performed by the fixing unit. On the medium, it is possible to record a preferable image in which bleeding, unevenness, color mixing, and the like are avoided.

  The recording head may have a plurality of recording heads corresponding to each color.

  According to the present invention, an electrode pair for generating an electric field to be applied to a recording droplet having an electrorheological effect ejected from an ejection head onto an intermediate transfer medium, and landing on the intermediate transfer medium from the intermediate transfer medium to a recording medium. After the recorded droplets are transferred, the fixing means for fixing the recorded droplets to the recording medium is provided, so that the landing interference on the intermediate transfer medium is avoided by the electroviscous effect and the recording medium is blurred. And the like can be avoided by the main fixing process by the main fixing unit.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[Overall Configuration of Inkjet Recording Apparatus According to the Present Invention]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a print unit 12 having print heads 12C, 12M, 12Y, and 12B provided for each ink color (C, M, Y, and B), and each print. The ink storage / loading unit 14 that stores ink to be supplied to the heads 12C, 12M, 12Y, and 12B, and the ink droplets 16 ejected and landed from the print heads 12C, 12M, 12Y, and 12B are held on the surface (printing). The intermediate transfer drum 18 (intermediate transfer medium) on which an image is formed on the heads 12C, 12M, 12Y, and 12B (positions facing the ink discharge surfaces), and the image formed on the intermediate transfer drum 18 on the recording paper 20 ( A transfer roller 22 (transfer means) for transferring to a recording medium), a main fixing unit for performing a main fixing process on the recording paper 20 with ink droplets constituting an image transferred onto the recording paper 20; An ultraviolet light source (UV light source) 24 (main fixing means) that functions as a printer, a discharge unit 26 that discharges printed recording paper 20 (printed matter) on which ink droplets have been fixed, and a discharge unit 26 And a paper discharge tray 27 for storing printed matter. Although not shown in FIG. 1, the paper output unit 26 for the target prints is provided with a sorter for collecting prints according to print orders.

  In addition, the image here has shown the image in the wide meaning containing a character, a symbol, a line (line drawing), etc.

  The ink ejected from the print heads 12 </ b> C, 12 </ b> M, 12 </ b> Y and 12 </ b> B is an ink having an electrorheological effect (ER effect), and the ink droplets 16 that land on the printable area of the intermediate transfer drum 18 are provided on the intermediate transfer drum 18. The ER effect can be obtained by applying an electric field obtained by applying a high voltage of several kilovolts to several tens of kilovolts from a high voltage power source (not shown in FIG. 1, described as reference numeral 94 in FIG. 5) to the plurality of electrode pairs 28 And pseudo-thickening.

  There are a plurality of types of ink having an ER effect (hereinafter referred to as ER ink or simply ink), such as dispersed ink and uniform ink, but the ink jet recording apparatus 10 has any type. ER ink may be used.

  The ink storage / loading unit 14 has a tank that stores ink of a color corresponding to each print head, and each tank communicates with each print head via a conduit (not shown). Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  The intermediate transfer drum 18 is configured to be rotatable by a rotation mechanism (not shown). The intermediate drum rotating mechanism is a stepping motor, servo motor, or other motor capable of position control and speed control (reference numeral 88 in FIG. 5), a belt for transmitting driving force generated from the motor, a pulley gear, etc. It is comprised by the member etc.

  The intermediate transfer drum 18 is provided with printable areas corresponding to the print heads 12C, 12M, 12Y, and 12B. The printable area is configured by a member having a predetermined ink affinity for the ink droplets ejected from the print heads 12C, 12M, 12Y, and 12B, and is preferably used when transferring to the recording paper 20. And releasability.

  On the downstream side of the rotation direction of the intermediate transfer drum 18 of the printing unit 12 (clockwise direction indicated by an arrow line in FIG. 1), ink droplets 16 landed on the intermediate transfer drum 18 are preliminarily placed on the intermediate transfer drum 18. A preliminary fixing unit 30 for fixing is provided, and further, a print detection unit 32 for reading an image (printing result) formed on the intermediate transfer drum 18 is provided on the downstream side thereof.

  The print detection unit 32 includes an image sensor for imaging the droplet ejection result of the print unit 12, and functions as a means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  The print detection unit 32 of this example is composed of a line sensor having a light receiving element array that is wider than at least the ink discharge width of each print head 12C, 12M, 12Y, 12B. The line sensor includes an R sensor row in which photoelectric conversion elements (pixels) provided with red (R) color filters are arranged in a line, a G sensor row provided with green (G) color filters, The color separation line CCD sensor is composed of a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  At the transfer section 34 where the intermediate transfer drum 18 contacts the transfer roller 22 via the recording paper 20, the transfer roller 22 is rotated while the transfer roller 22 is rotated counterclockwise (in the direction indicated by the arrow k in FIG. 1). By pressing the intermediate transfer drum, the image formed on the intermediate transfer drum 18 is transferred to the printing surface of the recording paper 20.

  The recording paper 20 is supplied from the paper supply unit 36 to the transfer unit 34. The paper supply unit 36 includes a mode using a magazine for rolled paper (continuous paper) and a mode using a cassette in which cut sheets are stacked and filled. A plurality of magazines and cassettes having different paper widths and paper qualities may be provided, or a roll paper magazine and a cut paper cassette may be used in combination.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

  In a mode in which a roll paper magazine is used for the paper supply unit, the recording paper 20 delivered from the paper supply unit retains curl due to having been loaded in the magazine. In order to remove the curl, a decurling unit (not shown) is provided, and heat is applied to the recording paper 20 by a heating drum (not shown) in a direction opposite to the curl direction of the magazine. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  In the case of an apparatus configuration using roll paper, a cutter for cutting (not shown) is provided, and the roll paper is cut into a desired size by the cutter. In addition, when using cut paper, this cutter is unnecessary.

  When the recording paper 20 passes through the transfer unit 34, the ink droplets 42 constituting the image transferred onto the recording paper 20 are subjected to a main fixing process to the recording paper 20 by the UV light source 24. In this example, a UV light source is applied to the main fixing process, and UV curable ink is applied to the ink ejected from the print heads 12C, 12M, 12Y, and 12B.

  That is, the ink jet recording apparatus 10 uses UV effect ink having an ER effect in which inorganic fine particles are mixed with UV curable ink.

  In the present embodiment, the UV curable ink is given an ER effect. As a method for producing such an ink, for example, solid fine particles (silica gel) are added to a liquid containing at least a radiation curable monomer and a polymerization initiator. , Starch, dextrin, carbon, gypsum, gelatin, alumina, cellulose, mica, zeolite, kaolinite, etc.), a method of using pigment fine particles themselves as a dispersant for electrorheological effect, and a microcapsule of dye or pigment It can be considered that the surface is insulated and used as a dispersant for the electrorheological effect by insulating the surface, or a homogeneous electrorheological fluid is mixed.

  The light source used in the fixing process is not limited to a UV light source, and a light source (radiation source, radiation source) having another frequency such as an electron beam (EB light) or infrared light may be used.

  Further, instead of the UV light source 24, a heating fan that dries the image surface by heat or air blowing may be used, or a means for promoting the penetration of the ink solvent when the penetrating ink is used may be used. In addition to this, a heater for curing thermosetting ink, a means for solidifying solid ink by cooling, a means for solidifying ink droplets by chemical reaction, and the like can be applied.

  Note that it is not always necessary to completely fix the ink by the main fixing process (the reaction is completed), and the ink droplets are cured to the extent that image deterioration does not occur due to handling in the subsequent process (downstream process). It only has to penetrate.

  The handling here means [1] rubbing between rollers, guides, and the like during conveyance with the image surface, [2] rubbing between prints in the stocker (print stacking unit), and [3] when actually handling the finished print. It means rubbing by various objects.

  On the other hand, ink droplets remaining on the surface having the printable area of the intermediate transfer drum 18 or adhering dust etc. on the downstream side of the transfer unit 34 in the rotation direction (traveling direction) of the intermediate transfer drum (upstream side of the printing unit 12). A cleaning blade 44 for wiping and removing (scraping off) the foreign matter, and a collection tray 46 for collecting the removed ink droplets and foreign matter.

  The cleaning blade 44 is composed of an ink droplet such as rubber and a member having a good foreign matter removal property. Note that, instead of or in combination with the cleaning blade 44, a sponge made of a porous member may be provided so that the remaining ink droplets can be absorbed and removed.

  Here, when ink droplets are removed by the cleaning blade 44, the electric field generated from the electrode pair 28 is turned off, and control is performed so as to lower the viscosity of the ink droplets on the surface of the intermediate transfer drum 18. The performance (removal performance of ink droplets) can be improved, which is preferable.

  That is, a period from when printing is performed by the print heads 12C, 12M, 12Y, and 12B until transfer from the intermediate transfer drum 18 to the recording paper 20 is performed in the transfer unit 34 (indicated by one-dot broken lines A to A in FIG. 1). The area shown in FIG. 1 is a cleaning period in which the electric field generated from the electrode pair 28 is turned on and residual ink droplets and foreign matter are removed by the cleaning blade 44 (area shown by one-dot broken lines B to B in FIG. 1) Electric field on / off control is performed to turn off the electric field generated from the electrode pair 28.

[Print head structure]
Next, the detailed structure of the printing unit 12 will be described with reference to FIGS. Since the structures of the print heads 12C, 12M, 12Y, and 12B provided for each ink color are common, the print head is represented by reference numeral 50 in the following.

  FIG. 2 is a view of the printing unit 12 as viewed from the upper surface side of the printing unit 12, and is a plan view showing a planar structure of the printing unit 12.

  As shown in FIG. 2, the printing unit 12 moves a line-type head having a length corresponding to the maximum paper width and the width of the intermediate transfer drum 18 in the outer peripheral direction of the intermediate transfer drum 18 (advancing direction of printable area, in FIG. 2). This is a so-called full-line type head arranged in the direction orthogonal to the arrow line (in the main scanning direction). Each of the print heads 12 </ b> C, 12 </ b> M, 12 </ b> Y, 12 </ b> B is composed of a line type head in which a plurality of nozzles are arranged over a length exceeding the width of the intermediate transfer drum 18. The width of the intermediate transfer drum 18 has a length that exceeds at least one side of the maximum size recording paper 20 targeted by the inkjet recording apparatus 10.

  Print heads 12C, 12M, 12Y, and 12B corresponding to the respective color inks are arranged in the order of cyan (C), magenta (M), yellow (Y), and black (B) from the upstream side along the outer peripheral direction of the intermediate transfer drum 18. Has been. By discharging the color ink from each of the print heads 12C, 12M, 12Y, and 12B while rotating the intermediate transfer drum 18 so that the printable area on the intermediate transfer drum 18 moves in the outer circumferential direction, the intermediate transfer drum 18 A color image can be formed in the printable area.

  Thus, according to the printing unit 12 in which the full line head that covers the entire area of the paper width is provided for each ink color, the operation of relatively moving the intermediate transfer drum 18 and the printing unit 12 in the sub-scanning direction is performed. Single pass printing that records an image on the entire printable surface of the intermediate transfer drum 18 can be performed only by performing it once (that is, by one sub-scan). Thereby, it is possible to perform high-speed printing as compared with a shuttle type head in which the print head reciprocates in the main scanning direction, and productivity can be improved.

  In this example, the configuration of CMYB standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink and dark ink are added as necessary. May be. For example, it is possible to add a print head that discharges light ink such as light cyan and light magenta.

  FIG. 3 (a) is a plan perspective view showing an example of the structure of the print head 50, and FIG. 3 (b) is an enlarged view of a part thereof. 3C is a perspective plan view showing another example of the structure of the print head 50, and FIG. 4 is a sectional view showing the three-dimensional configuration of the ink chamber unit (4- in FIGS. 3A and 3B). 4 is a cross-sectional view taken along line 4).

  In order to increase the dot pitch printed on the intermediate transfer drum 18 and the recording paper 20, it is necessary to increase the nozzle pitch in the print head 50. As shown in FIGS. 3A to 3C and FIG. 4, the print head 50 of this example includes a plurality of nozzles 51 from which ink droplets are ejected and pressure chambers 52 corresponding to the nozzles 51. It has a structure in which the ink chamber units 53 are arranged in a staggered matrix, thereby achieving a high density of the apparent nozzle pitch.

  That is, as shown in FIGS. 3A and 3B, the print head 50 according to the present embodiment includes a plurality of nozzles 51 for ejecting ink in the direction substantially perpendicular to the outer peripheral direction of the intermediate transfer drum 18. This is a full line head having one or more nozzle rows arranged over a length corresponding to the entire width.

  Further, as shown in FIG. 3 (c), short two-dimensionally arranged print heads 50 'may be arranged in a staggered manner and connected to form a length corresponding to the entire width of the intermediate transfer drum 18.

  As shown in FIG. 4, the pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape, and the nozzle 51 and the supply port 54 are provided at both corners on the diagonal line. ing. Each pressure chamber 52 communicates with a common flow channel 55 through a supply port 54.

  An actuator 58 having an individual electrode 57 is joined to a pressure plate (vibration plate) 56 constituting the top surface of the pressure chamber 52, and the actuator 58 is deformed by applying a drive voltage to the individual electrode 57. Thus, ink is ejected from the nozzle 51. When ink is ejected, new ink is supplied from the common channel 55 to the pressure chamber 52 through the supply port 54.

  As shown in FIG. 3B, the large number of ink chamber units 53 having such a structure are arranged along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. It has a structure that is arranged in a lattice pattern with a fixed arrangement pattern. With a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along a certain angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to be aligned in the main scanning direction is d × cos θ. .

  That is, in the main scanning direction, each nozzle 51 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, a high-density nozzle configuration can be realized.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example. For example, one nozzle row may be arranged in the main scanning direction, or an arrangement having a plurality of nozzles in the sub-scanning direction may be used.

  Further, in this example, the method of giving the ejection force to the ink in the pressure chamber 52 by the deformation of the actuator 58 is shown. However, the heater is provided in the pressure chamber 52 (ink chamber) to heat the ink. A thermal method in which ink is ejected by the pressure of the bubble generated may be used.

[Description of nozzle maintenance]
Next, nozzle maintenance of the inkjet recording apparatus 10 will be described.

  In general, in an ink jet recording apparatus, the frequency of use of a specific nozzle 51 is low during printing or standby, and if the ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. turn into. Further, as a result of the ER effect appearing in the ink in the nozzle 51, the ink viscosity in the nozzle may increase. In such a state, ink cannot be ejected from the nozzle 51 even if the actuator 58 operates.

  Before such a state is reached (within the range of viscosity that can be discharged by the operation of the actuator 58), the actuator 58 is operated, and the deteriorated ink (ink near the nozzle whose viscosity has increased) is not shown. Preliminary ejection (purging, idle ejection, spit ejection, dummy ejection) is performed toward the cap (ink receiver).

  Further, the ejection abnormality of each nozzle is determined based on the detection result of the print detection unit 32 shown in FIGS. 1 to 3, and preliminary ejection is performed on the nozzle determined to be ejection abnormality.

  On the other hand, when air bubbles are mixed into the ink in the print head 50 (in the pressure chamber 52), the ink cannot be ejected from the nozzle 51 even if the actuator 58 operates. In such a case, the cap is applied to the print head 50, the ink in the pressure chamber 52 (ink mixed with bubbles) is removed by suction with a suction pump (not shown), and the suctioned ink is removed from the collection tank (not shown). (Liquid)

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 52, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

[Explanation of control system]
FIG. 5 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet, and wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74.

  The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 72 controls each part such as the communication interface 70, the image memory 74, the motor driver 76, the heater driver 78, etc., performs communication control with the host computer 86, read / write control of the image memory 74, etc. A control signal for controlling the rotation mechanism of the intermediate transfer drum 18 and the motor 88 and heater 89 of the conveyance system of the recording paper 20 is generated.

  Note that the motor driver 76 and the motor 88 shown in FIG. 5 include a plurality of motor drivers and motors. For example, the motor 88 includes a motor that rotates the intermediate transfer drum 18, a motor that is used in the suction belt conveyance unit 36 that conveys the recording paper 20, a motor that rotates the transfer roller 22, and the like.

  The image memory 74 stores programs executed by the CPU of the system controller 72 and various data necessary for control. Note that the image memory 74 may be a non-rewritable storage means, or may be a rewritable storage means such as an EEPROM. The image memory 74 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 76 is a driver that drives the motor 88 in accordance with instructions from the system controller 72. The heater driver 78 is a driver that drives the heater 89 such as the preliminary fixing unit 30 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated dot It is a control unit that applies data to the head driver 84. Necessary signal processing is performed in the print controller 80, and the ejection amount and ejection timing of the ink droplets of the print head 50 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. In FIG. 5, the image buffer memory 82 is shown in a form associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  Image data to be printed is input from the outside via the communication interface 70 and stored in the image memory 74. At this stage, RGB image data is stored in the image memory 74.

  The image data stored in the image memory 74 is sent to the print controller 80 via the system controller 72, and is converted into dot data (image information) for each ink color in the print controller 80. That is, the print control unit 80 performs processing for converting the input RGB image data into dot data of four colors of CMYB. The dot data generated by the print controller 80 is stored in the image buffer memory 82.

  The head driver 84 drives the actuators 58 of the print heads 12 </ b> C, 12 </ b> M, 12 </ b> Y, and 12 </ b> B for each color based on the dot data given from the print controller 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  Various control programs are stored in the program storage unit 90, and the control programs are read and executed in accordance with instructions from the system controller 72. The program storage unit 90 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media.

  The program storage unit 90 may also be used as a recording means (not shown) for operating parameters.

  As described with reference to FIG. 1, the print detection unit 32 is a block including a line sensor, reads an image printed on the recording paper 20, performs predetermined signal processing, and performs a print status (whether ejection is performed, droplet ejection is performed). Variation), and the detection result is provided to the print controller 80.

  The print control unit 80 performs various corrections on the print head 50 based on the read information obtained from the print detection unit 32 as necessary.

  The voltage control unit 92 performs control (on / off control, output voltage variable control, etc.) of the high-voltage power supply 94 that is a supply source of the voltage applied to the electrode pair 28 in response to a command from the system controller 72. When printing is performed on the intermediate transfer drum 18 by the print head 50, a voltage of several kilovolts to several tens of kilovolts is applied from the high-voltage power source 94 to the electrode pair 28, and the electric field generated in the electrode pair 28 is applied to the intermediate transfer drum 18. Acts on the ink droplet landed on (reference numeral 16 in FIG. 1), and the ER effect appears in the ink droplet.

  Further, the system controller 72 controls the preliminary fixing unit 30 that cures or thickens the surface layer of ink droplets (shown by reference numeral 16 in FIG. 1) that has landed on the intermediate transfer drum 18, and records from the intermediate transfer drum 18. On / off control and light amount control of the UV light source 24 for performing the main fixing process on the recording paper 20 with the ink droplet transferred to the paper 20 (illustrated by reference numeral 42 in FIG. 1) are performed. Details of the control of the UV light source 24 and the control of the preliminary fixing unit 30 will be described later.

[Description of electrode pair]
Next, the structure of the electrode pair 28 will be described in detail with reference to FIGS.

  6 is a perspective view showing the intermediate transfer drum 18 provided with the electrode pair 28, and FIG. 7 is an enlarged view of a part of the electrode pair 28 shown in FIG.

  As shown in FIG. 6, the surface side (image forming surface side) of the intermediate transfer drum 18 includes a positive electrode 100 and a negative electrode 102, and as shown in FIG. 7, the positive electrode 100 and the negative electrode Are provided with a plurality of electrode pairs 28 each having a comb-like shape.

  The comb-tooth shape of the positive electrode 100 and the negative electrode 102 shown in this example is a cross shape having comb-tooth portions 100A and 102A in both the upward and downward directions in FIG. It has a structure in which two comb-shaped electrodes are combined.

  Of course, the shape may have the comb-tooth portions 100A and 102A only on either the upper side or the lower side in FIG. 7, but in order to arrange the positive electrode 100 and the negative electrode 102 as densely as possible, FIG. As shown in FIG. 7, the aspect which has the comb-tooth parts 100A and 102A on both the upper side and the lower side is preferable.

  Further, FIG. 7 shows a mode in which the comb-tooth portions 100A of the positive electrodes 100 adjacent to each other in the outer circumferential direction have the same phase in the width direction, but these may be out of phase in the width direction. Similarly, the comb tooth portions 102A of the negative electrodes 102 adjacent in the outer peripheral direction may also be out of phase in the width direction.

  Note that the positive electrode 100 has a relatively high potential with respect to the negative electrode 102, and the potential Vp of the positive electrode 100, the potential Vn of the negative electrode 102, and the potential difference between the positive electrode 100 and the negative electrode 102 ( The relationship with the voltage (V) satisfies the following equation [Equation 1].

[Equation 1]
V = Vp -Vn (V> 0)
For example, when Vn = 0V (GND), Vp may be a predetermined potential at which the ER effect can be exhibited, or the potential difference V becomes a predetermined potential difference at which the ER effect can be manifested with Vn being a negative potential. It is good also as such Vp.

In other words, it is sufficient that the electric potential difference V can generate an electric field that causes the ER effect to be generated on the ink droplet, and the electric potential Vp of the positive electrode 100 and the electric potential Vn of the negative electrode 102 are positive electric potentials, 0 V (GND ) Or a negative potential.

  The electrode pair 28 shown in the present embodiment has a width substantially equal to or larger than the dischargeable width of the print head 50 in the width direction of the intermediate transfer drum 18, and the intermediate transfer drum 18 is arranged over the entire surface in the outer peripheral direction, and this electrode pair arrangement area becomes a printable area.

  In addition, the plurality of positive electrodes 100 provided on the intermediate transfer drum 18 has a structure connected at the ends thereof. Similarly, the plurality of negative electrodes 102 provided on the intermediate transfer drum 18 also have a structure connected at their ends. Thus, when the positive electrode 100 and the negative electrode 102 are configured, It is sufficient to provide at least one power feeding portion for applying a voltage to each of the electrode 100 and the negative electrode 102, and the structure of the power feeding portion can be simplified.

  As shown in FIG. 7, the electrode pair 28 has a structure in which positive electrodes 100 and negative electrodes 102 are alternately arranged in the outer peripheral direction of the intermediate transfer drum 18. In the width direction, there is a structure in which the comb teeth 100A of the positive electrode 100 and the comb teeth 102A of the negative electrode are alternately arranged.

  The electrode pair 28 shown in this example includes an interelectrode distance Pr in the outer peripheral direction of the intermediate transfer drum 18, an interelectrode distance Pw in the width direction of the intermediate transfer drum 18, and a droplet diameter of ink droplets landed on the intermediate transfer drum 18. It has a structure in which the relationship between the (diameter) and the minimum value D satisfies both the following equations [Equation 2] and [Equation 3].

[Equation 2]
Pw ≤ D
[Equation 3]
Pn ≤ D
That is, the distance between the positive electrode 100 and the negative electrode 102 is smaller than the minimum value D of the droplet diameter of the ink droplets that land on the intermediate transfer drum 18 in both the outer circumferential direction and the width direction of the intermediate transfer drum 18. Therefore, a stable electric field can be applied to each ink droplet landed on the intermediate transfer drum 18 (a stable weak current can flow), and the ink droplet can be reliably supplied to each ink droplet. ER effect can be expressed.

  The electric field strength generated between the positive electrode 100 and the negative electrode 102 is inversely proportional to the interelectrode distance Pr in the outer peripheral direction of the intermediate transfer drum 18 and the interelectrode distance Pw in the width direction. That is, when the voltages supplied between the positive electrode 100 and the negative electrode 102 are the same, the electric field strength increases as the distance between the positive electrode 100 and the negative electrode 102 decreases. Therefore, the inter-electrode distance Pr in the outer peripheral direction of the intermediate transfer drum 18 and the inter-electrode distance Pw in the width direction are preferably small, and more preferably about 0.1 to 2 mm.

  Further, when the electrode width W1 of the positive electrode 100 and the electrode width W2 of the negative electrode 102 are narrower, the intensity of the electric field generated between the positive electrode 100 and the negative electrode 102 becomes uniform, so The electroviscous effect on the ink droplets landed on the ink increases, which is preferable.

  When the electrode width W1 of the positive electrode 100 and the electrode width W2 of the negative electrode 102 are wide, the vertical component on the surface of the intermediate transfer drum 18 of the electric field lines generated between the positive electrode 100 and the negative electrode 102 is large. Thus, a sufficient electrorheological effect cannot be obtained for the ink droplets that have landed on the intermediate transfer drum 18.

  Therefore, the electrode width W1 of the positive electrode 100 and the electrode width W2 of the negative electrode 102 are preferably narrow, more preferably about 0.01 mm to 1 mm.

  Although FIG. 7 shows a mode in which the interelectrode distance Pr in the outer peripheral direction of the intermediate transfer drum 18 and the interelectrode distance Pw in the width direction are different distances, these may be the same distance. Further, the electrode width W1 of the positive electrode 100 and the electrode width W2 of the negative electrode 102 may be the same or different.

  FIG. 8 shows an arrangement example of the high-voltage power supply 94 shown in FIG. FIG. 8 shows a mode in which the high-voltage power supply 94 is incorporated in the intermediate transfer drum 18.

  As shown in FIG. 8, the intermediate transfer drum 18 incorporates a high-voltage power supply 94 that applies a voltage to an electrode pair 28 including a positive electrode 100 and a negative electrode 102, and is located outside the intermediate transfer drum 18. There is a mode in which the main power source (+ DC) of the high-voltage power source 94 is supplied from a DC power source (not shown) via the DC coupling 120.

  When configured as shown in FIG. 8, a wiring for transmitting a high voltage of several kiloV to several tens of kiloV can be disposed on the intermediate transfer drum 18 and the length of the wiring is shortened. Safety is improved by preventing danger, and noise resistance is improved by reducing radiation noise radiated from the wiring. Further, in order to improve noise resistance, the wiring is preferably shielded.

  FIG. 9A shows a cross-sectional structure of the intermediate transfer drum 18 shown in FIGS.

  According to FIG. 9 (a), a conductive coating layer (electrode layer) 142 is formed on the insulating material (insulating layer) 140 on the surface side of the intermediate transfer drum 18, and is patterned by etching or the like to form a positive electrode. An electrode pair 28 composed of 100 and the negative electrode 102 is formed.

  In addition, an insulating member 144 is provided in a portion of the electrode layer 142 where the conductive member from which the electrode between the positive electrode 100 and the negative electrode 102 is not formed is provided, and the positive electrode 100 and the negative electrode are provided. The insulation performance between 102 is ensured.

  Further, a microconductive layer 146 that is a thin layer having a minute conductivity is laminated on the electrode layer 142, and a surface 146 A of the microconductive layer 146 opposite to the electrode layer 142 is discharged from the print head 50. It functions as a landing surface on which ink droplets land.

  That is, the surface of the slightly conductive layer 146 opposite to the electrode layer 142 faces the ink ejection surface of the print head 50, and the ink droplet 160 ejected from the print head 50 lands and forms an image formation surface on which an image is formed. Become.

  The surface 146A opposite to the electrode layer 142 of the microconductive layer 146, which is the ink droplet landing surface, preferably has a physical property such that the contact angle with the ink droplet is 45 degrees or more. An ink landing layer including a member having physical properties such that the contact angle with the ink is 45 degrees or more may be laminated on the surface 146A of the microconductive layer 146 opposite to the electrode layer 142 on the microconductive layer 146.

  The electrical resistivity of the microconductive layer 146 in this example is preferably 10 8 to 10 12 Ωcm, and the thickness of the microconductive layer 146 is preferably about 0.01 mm to 1 mm.

[Explanation of ER effect]
In the ink jet recording apparatus 10, an ink in which an inorganic fine particle color material 164 is mixed with a UV curable ink (non-conductive solvent) 162 is used. As shown in FIG. 9A, in a state where no voltage is applied between the positive electrode 100 and the negative electrode 102 (or in a state where a voltage smaller than a predetermined voltage is applied), the intermediate transfer drum 18 is placed on the intermediate transfer drum 18. The inorganic fine particle color material 164 in the landed ink droplet 160 exists in a state dispersed in the non-conductive ink solvent 162.

  Here, as shown in FIG. 9B, when a predetermined voltage is applied between the positive electrode 100 and the negative electrode 102 from the high-voltage power supply 94 shown in FIG. An electric field (electric force lines) 180 indicated by a two-point broken line heading is generated, and the inorganic fine particle color material 164 in the ink solvent 162 is dielectrically polarized, arranged along the electric force lines 180, and slightly in the ink droplet 160. Electric current is generated. FIG. 9B shows a part of electric lines of force indicating an electric field generated between the positive electrode 100 and the negative electrode 102.

  Thus, when the inorganic fine particle color material 164 is arranged along the lines of electric force 180 in the ink solvent 162, the viscosity of the ink droplet 160 increases in a pseudo manner, and the shape of the ink droplet 160 upon landing is maintained. The

  Here, coalescence of ink droplets will be described.

  As shown in FIG. 10A, the ink droplet 202 that has landed on the intermediate transfer drum 18 so as to overlap (at least contact with) the ink droplet 200 that has landed on the intermediate transfer drum 18 first, Ink droplets (dots) that are flattened as shown by the solid line 204 in FIG. 10 (b) are drawn together in the direction of the ink droplet 200 that has landed (the direction of x indicated by the arrow line in FIG. 10). ) Is formed.

  When ink droplets (dots) having such a shape are formed, the ink droplets are easily visually recognized as unevenness and streaks on the image, and the image quality is degraded.

  Accordingly, an electric field is applied to the ink droplet 200 and the ink droplet 202 that have landed on the intermediate transfer drum 18 to develop an ER effect, and the ink droplet 200 and the ink droplet 202 are pseudo-thickened, and the broken line in FIG. By maintaining the shapes of the ink droplet 200 and the ink droplet 202 immediately after landing, the coalescence of ink droplets (landing interference) shown in FIG. 10B can be suppressed, and a preferable image can be obtained.

  In the inkjet recording apparatus 10, control is performed so as to vary the voltage applied to the electrode pair 28 in accordance with the ink droplet amount on the intermediate transfer drum 18 in order to stably develop the ER effect.

  That is, the current A flowing between the electrode pair 28 (between the positive electrode 100 and the negative electrode 102) and the current A / V flowing through the ink droplet per unit volume obtained from the ink volume V on the intermediate transfer drum 18 are constant. Thus, the voltage applied to the electrode pair 28 is varied. The ink volume on the intermediate transfer drum 18 is represented by (ink droplet size) × (number of ink droplets). When the ink droplet size is substantially constant, the number of ink droplets N is used to calculate A / N ( The voltage applied to the electrode pair 28 may be controlled so that the current flowing per ink droplet is constant.

  Note that the ER effect has a property that immediately appears when an electric field is applied and disappears immediately when the electric field is interrupted, and at least substantially simultaneously when ink droplets ejected from the print head 50 land on the intermediate transfer drum 18. It is necessary to generate an electric field from the timing and maintain the electric field until the transfer from the intermediate transfer drum 18 to the recording paper 20 is completed in the transfer unit 34 shown in FIG.

  Accordingly, the electric field application region shown in FIG. 1 (the region indicated by the one-dot broken lines A to A in FIG. 1) is advanced from the upstream side of the intermediate transfer drum in the intermediate transfer drum direction relative to the printing unit 12 to the intermediate transfer drum. Up to the position downstream of the direction. This indicates that the electric field application region is determined to be slightly larger than the region where ink droplets actually exist on the intermediate transfer drum 18.

  In the inkjet recording apparatus 10 configured as described above, ink having an ER effect is ejected from the printing unit 12 (printing head 50) onto the intermediate transfer drum 18, and the ink droplets landed on the intermediate transfer drum 18 are subjected to intermediate transfer. An electric field generated from the electrode pair 28 provided on the drum 18 is applied, and the ink droplets on the intermediate transfer drum 18 are pseudo-thickened.

  While maintaining this state, the transfer unit 34 uses the transfer roller 22 to transfer the image (ink droplets) on the intermediate transfer drum 18 to the recording paper 20 and immediately after the transfer unit 34 downstream of the recording paper 20 in the traveling direction. A UV curing process (main fixing process) is performed on the ink droplets on the recording paper 20 by the UV light source 24 provided on the recording medium 20.

  Therefore, on the intermediate transfer drum 18, the ink droplets are prevented from being coalesced (landing interference) by the ER effect, and the UV curing process is performed immediately after the transfer to the recording paper 20, so that image deterioration such as bleeding and color mixing occurs. Thus, a preferable image is formed on the recording paper 20.

  In the present embodiment, an intermediate transfer medium having a drum shape in which ink droplets are ejected from the print head is shown. However, other than the drum shape, a belt shape or other shapes can be applied.

[Modification]
Next, a modification of the electrode pair 28 disposed on the intermediate transfer drum 18 shown in FIG. 6 will be described.

  The electrode pair 28 shown in FIG. 11 has a structure that is divided in the outer peripheral direction of the intermediate transfer drum 18. In other words, the electrode pair 28 has a plurality of electrode pair blocks 28A, 28B, 28C, 28D,.

  Each electrode pair block is configured to be supplied with a voltage from a common high-voltage power supply 94, and includes a switch unit 210 that switches on and off the voltage supplied from the high-voltage power supply 94 for each electrode block.

  Therefore, it is possible to control on / off of voltage supply to each electrode pair block according to the rotation speed (rotation control) of the intermediate transfer drum 18.

  For example, in a cleaning region including a region where the cleaning blade 44 is in contact with the surface of the intermediate transfer drum 18, the control is performed so that the voltage supply to the corresponding electrode pair block is cut off (the voltage supply is turned off). It is easy to remove residual ink droplets in the region, and the cleaning efficiency by the cleaning blade 44 is expected to be improved. Further, since an ink having a low viscosity can be obtained by not applying an electric field, wear of the electrode pair 28 and the cleaning blade 44 can be suppressed, and durability of the cleaning blade 44 can be improved.

  It is preferable that the length y in the outer peripheral direction of each electrode pair block is smaller than the distance in the direction along the outer peripheral direction of the cleaning region described above.

  FIG. 12 shows a detailed structure of the electrode pair blocks 28A, 28B,. FIG. 12 shows only two electrode pair blocks 28A and 28B among the plurality of electrode pair blocks. Each electrode pair block has the same structure, and here, the electrode pair block 28A is used as a representative of the description of each electrode pair block.

  As shown in FIG. 12, the electrode pair block 28A is composed of a positive electrode 100 and a negative electrode 102, like the electrode pair 28 shown in FIG. 7, and each of the positive electrode 100 and the negative electrode 102 is a comb. It has a comb-like shape having teeth 100A and comb teeth 102A.

  Further, positive electrodes 100 and negative electrodes 102 are alternately arranged in the outer peripheral direction, and comb teeth portions 100A of the positive electrode 100 and comb teeth portions 102A of the negative electrode 102 are alternately arranged in the width direction. Has been. In addition, the distance between each electrode pair block should just be a distance which can hold | maintain predetermined insulation performance, and is about 0.1-2 mm like the distance between the positive electrode 100 and the negative electrode 102. FIG.

  In this example, each electrode pair block has the same shape (size) and the same configuration. However, these blocks may have different shapes or different configurations. Moreover, although the same voltage was supplied to each electrode pair block from a common high-voltage power supply, a different high-voltage power supply may be provided for each electrode-pair block, and the supply voltage can be varied. And may be configured to apply different voltages for each electrode pair block to generate electric fields having different intensities.

[Control of ink droplets]
Next, ink droplet control according to the present embodiment will be described with reference to FIGS. 13 and 14.

  The two ink droplets 300 and ink droplets 302 landed on the intermediate transfer drum 18 shown in FIG. 13A are united (integrated) while maintaining the shape at the time of landing by the action of the ER effect. Ink droplets 304 are formed.

  The surface of the ink droplet 304 formed in this way has an uneven shape. In the ink droplet 304 shown in FIG. 13, the height of the concave portion is h1, and the height of the convex portion is h2.

  On the other hand, the unevenness of the ink droplets can be controlled by varying the electric field strength applied to the ink droplets and controlling the viscosity of the ink droplets so as to balance the surface tension of the ink droplets.

  For example, as shown in FIG. 13B, the unevenness of the ink droplet 304 formed by combining the ink droplet 300 and the ink droplet 302 can be leveled so that the height of the ink droplet is h1 ′. .

  By controlling the uneven shape of the ink droplets on the intermediate transfer drum 18 in this way, it is possible to control the surface state (glossy, matte) of the recording paper 20 after being transferred to the recording paper 20.

  Here, in order to vary the electric field intensity, voltage variable control for varying the voltage supplied to the electrode pair 28 may be applied, or the voltage supplied to the electrode pair 28 in a cycle shorter than the uniting time of the ink droplets. PWM control (duty control) for turning on / off may be used.

  Next, the preliminary fixing process in this example will be described with reference to FIG.

  As shown in FIG. 1, a preliminary fixing unit 30 is provided between the printing unit 12 and the transfer unit 34. As shown in FIG. 14, the ink droplets 400 and ink landed on the intermediate transfer drum 18 are provided. The surface layers 402, 412 of the droplet 410 are cured.

  In this way, by pre-curing the ink droplet 400 and the ink droplet 410 on the intermediate transfer drum 18, immediately after the image formed on the intermediate transfer drum 18 is transferred to the recording paper 20, The coalescence of the ink droplets that occurs can be avoided.

  In the preliminary fixing process (preliminary fixing step), the surface layer of the ink droplets may be cured or thickened to such an extent that the ink droplets do not coalesce on the recording paper 20. The peelability between 410 and the intermediate transfer drum 18 is deteriorated, and the transfer property to the recording paper 20 is also deteriorated.

  The preliminary fixing unit 30 may use a UV light source as in the main fixing process, or may use a heating means such as a heater.

  Next, the main fixing process of the ink jet recording apparatus 10 will be described.

  FIG. 15 is an enlarged view of the periphery of the transfer unit 34 and the UV light source 24 that is the main fixing unit shown in FIG. 1, and shows the relationship between the UV light source 24 and the conveyance control of the recording paper 20.

  As shown in FIG. 15, the conveyance speed u of the recording paper 20, the length s on the recording paper conveyance path from the transfer position of the transfer unit 34 to the UV light source 24 irradiation end position, and the ink droplets on the recording paper 20 The permeation time T is configured to satisfy the following equation [Equation 4].

[Equation 4]
s / u <T
That is, the main fixing processing time T ′ (= s / u) determined from the conveyance speed u of the recording paper 20 and the length s of the UV light irradiation area is shorter than the ink droplet permeation time T of the recording paper 20. In addition, the conveyance speed u of the recording paper 20 is controlled.

  The ink droplet permeation time T here refers to the time until the ink droplet solvent runs out of the recording paper 20 (primary permeation).

  By controlling the main fixing processing time T ′ so as to satisfy the relationship expressed by [Equation 4], bleeding of an image formed on the recording paper 20 can be avoided and ink droplets (dots) on the recording paper 20 can be prevented. Unevenness can be controlled.

  Note that a mode in which the recording paper 20 is irradiated with UV light immediately after the transfer unit 34 is preferable, and the UV light irradiation region is provided on the downstream side in the traveling direction of the recording paper 20 immediately after the transfer unit 34. Immediately after the transfer part 34 here, the transfer part 34 may be included.

  The length s shown in [Equation 4] may be the length of the UV light irradiation region (main fixing processing region) of the UV light source 24.

  Since the permeation time T differs depending on the combination of the type of recording paper 20 (media type) and the type of ink, the permeation time T is obtained in advance for each combination of the type of recording paper 20 and the type of ink, and this is converted into a data table. The penetrating time T may be read from the data table in accordance with the type of recording paper 20 and the type of ink.

  Furthermore, a plurality of data tables may be prepared for each environment (temperature, humidity, etc.), and the data table to be referred to may be changed according to the environment. As the memory for recording the data table, the image memory 74 or the image buffer memory 82 shown in FIG. 5 may be used, or a memory not shown in FIG. 5 may be used.

  In this example, the mode in which the conveyance speed u of the recording paper 20 is controlled to vary the main fixing processing time T ′ is shown. However, instead of or in combination with the control of the conveyance speed u of the recording paper 20, a UV light source is used. The amount of light (intensity of UV light) may be controlled.

  In the present embodiment, an embodiment in which an ink having an ER effect is used and an electric field is applied to the ink droplets on the intermediate transfer drum to control the viscosity of the ink droplets has been described. , And the viscosity (state) of the ink may be controlled by varying the temperature of the ink landing surface of the intermediate transfer drum 18.

  Further, a heater may be provided in place of the electrode pair 28 provided on the intermediate transfer drum 18, and the temperature of the intermediate transfer drum 18 may be controlled so that the ink droplets on the intermediate transfer drum 18 do not coalesce.

  Furthermore, a heater for controlling the temperature of the recording paper 20 is provided, and the temperature of the intermediate transfer drum and the recording paper 20 is controlled at a transfer unit 34 at a temperature with good transfer efficiency that is preferable for transfer from the intermediate transfer drum 18 to the recording paper 20. Also good.

  In the cleaning area, the temperatures of the intermediate transfer drum 18 and the cleaning blade 44 may be controlled so that residual ink and foreign matters on the intermediate transfer drum can be easily removed.

  By using these temperature controls together with the ER effect, it is possible to reliably control the state of the ink droplets on the intermediate transfer drum 18 and the ink droplets on the recording paper 20.

  In the present embodiment, an ink jet recording apparatus that records an image on a recording medium with ink ejected from nozzles provided in the print head is illustrated, but the scope of application of the present invention is not limited to this, and the target medium ( The present invention can also be widely applied to liquid ejection devices (dispensers, etc.) that eject liquids (water, processing liquids, resists, etc.) onto wafers, printed boards, etc.

1 is a basic configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 1 is a plan view of the main part around the printing of the ink jet recording apparatus shown in FIG. Plane perspective view showing structural example of print head Sectional view along section 4-4 in FIG. Main part block diagram which shows the system configuration | structure of the inkjet recording device which concerns on this embodiment. The perspective view which shows the three-dimensional structure of the electrode pair shown in FIG. The top view which shows the planar structure of the electrode pair shown in FIG. The figure which shows the example of arrangement | positioning of the electrode pair and high voltage power supply which are shown in FIG. Conceptual diagram explaining electrorheological effect Conceptual diagram explaining coalescence of ink droplets The perspective view which shows the modification of the electrode pair shown in FIG. The top view which shows the planar structure of the electrode pair block shown in FIG. Illustration explaining leveling on ink droplets The figure explaining the preliminary fixing process by the preliminary fixing part shown in FIG. FIG. 1 is an enlarged view showing details of the main fixing unit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Printing part, 12C, 12M, 12Y, 12B, 50 ... Print head, 18 ... Intermediate transfer drum, 20 ... Recording paper, 22 ... Transfer roller, 24 ... UV light source, 28 ... Electrode pair, DESCRIPTION OF SYMBOLS 30 ... Preliminary fixing part, 44 ... Cleaning blade, 72 ... System controller, 80 ... Print control part, 92 ... Voltage control part, 94 ... High voltage power supply, 210 ... Switch part

Claims (18)

An ejection head for ejecting the recording liquid having an electrorheological effect into droplets;
An intermediate transfer medium on which recording droplets are ejected from the ejection head at a position facing the ejection head;
An electrode pair comprising a positive electrode and a negative electrode, which is disposed on the intermediate transfer medium and applies an electric field to a recording droplet landed on the intermediate transfer medium;
Voltage supply means for supplying a predetermined voltage to the electrode pair;
Transfer means for transferring the recording droplets landed on the intermediate transfer medium onto the recording medium;
A main fixing unit for performing a fixing process on the recording medium on the recording droplet transferred onto the recording medium immediately after the recording droplet is transferred to the recording medium by the transfer unit;
A discharge device comprising:   2. The ejection device according to claim 1, wherein the electrode pair is disposed corresponding to a region where a recording droplet ejected from the ejection head of the intermediate transfer medium lands.   3. The discharge apparatus according to claim 1, further comprising a voltage control unit that variably controls a voltage supplied from the voltage supply unit to the electrode pair.   The electrode pair includes a plurality of the positive electrode and the negative electrode, respectively, and at least a part of the electrode pair has a structure in which the positive electrode and the negative electrode are alternately arranged. The discharge device according to claim 1, 2 or 3. The planar shapes of the positive electrode and the negative electrode that constitute the electrode pair are each substantially comb-shaped with a plurality of comb-tooth portions,
5. The electrode pair according to claim 1, wherein the pair of electrodes has a structure in which comb teeth of the positive electrode and comb teeth of the negative electrode are alternately arranged. 6. Discharge device. An interval P between the adjacent positive electrode and the negative electrode, and a minimum recording droplet diameter D on the intermediate medium of recording droplets ejected from the ejection head are expressed by the following equation: P ≦ D
The discharge device according to any one of claims 1 to 5, wherein: A moving means for relatively moving the ejection head and the intermediate transfer medium;
The electrode pair has a structure in which a plurality of electrode pair blocks each including at least a pair of the positive electrode and the negative electrode are arranged in the relative movement direction of the intermediate transfer medium, and supplies a voltage from the voltage control unit. The discharge device according to claim 3, further comprising a switching unit that selectively switches the electrode pair block.   8. The discharge apparatus according to claim 7, wherein the voltage control unit variably controls the voltage supplied from the voltage supply unit of the electrode pair block selected by the switching unit. A predicting unit that predicts a recording droplet amount on the intermediate transfer medium based on data of a recording liquid discharged on the intermediate transfer medium;
9. The voltage control unit according to claim 3, wherein the voltage control unit performs control to vary a voltage supplied from the voltage supply unit to the electrode pair according to a recording droplet amount predicted by the prediction unit. The discharge apparatus of any one of them.   10. The cleaning device according to claim 7, further comprising: a cleaning unit that removes a recording liquid remaining on the intermediate transfer medium after an image is transferred onto the recording medium by the transfer unit. The discharge device according to 1.   The voltage control unit controls the voltage supply unit so as not to supply a voltage to the electrode pair when the cleaning unit removes the recording liquid remaining on the intermediate transfer medium. The discharge device according to claim 10.   The switching means supplies the voltage so that a voltage is not supplied from the voltage supply means to the electrode pair block corresponding to a cleaning area where the cleaning liquid is removed from the intermediate transfer medium by the cleaning means. 12. The discharge device according to claim 11, wherein the electrode pair block for supplying voltage from the means is switched.   13. A preliminary fixing unit that is provided between the discharge head and the transfer unit and that performs a preliminary fixing process on a recording droplet landed on the intermediate transfer medium. The discharge device according to claim 1.   Using at least one of preliminary fixing processing performed on the recording droplets on the intermediate transfer medium by the preliminary fixing unit and variable control of the voltage supplied to the electrode pair by the voltage control unit, 14. The ejection device according to claim 13, wherein unevenness of recording droplets on the intermediate transfer medium is controlled.   15. The pre-fixing means hardens the surface of the recording droplet on the intermediate transfer medium when the recording medium is impermeable to the recording liquid. Discharge device. A transport means for transporting the recording medium;
The main fixing unit is provided downstream of the transfer unit in the transport direction of the transport unit, and the recording medium transport speed u of the transport unit, from the transfer position by the transfer unit to the fixing process end position by the main fixing unit. The length s along the transport direction of the transport means and the permeation time T of the recording liquid into the recording medium satisfy the following expression s / u <T. The discharge device according to any one of claims.   The discharge device according to any one of claims 1 to 16, wherein the intermediate transfer medium has a cylindrical drum shape. An image recording apparatus for recording an image on a recording medium using a recording liquid,
A recording head for discharging a recording liquid having an electrorheological effect into droplets;
An intermediate transfer medium that forms an image at a position facing the recording head by the recording droplets discharged from the recording head;
An electrode pair that is disposed on the intermediate transfer medium, applies an electric field to the recording droplet landed on the intermediate transfer medium, and includes a positive electrode and a negative electrode;
Voltage supply means for supplying a predetermined voltage to the electrode pair;
Transfer means for transferring an image formed on the intermediate transfer medium onto a recording medium;
A main fixing unit that applies a fixing process to the recording medium to the recording droplets that form the image transferred on the recording medium after the image is transferred to the recording medium by the transfer unit;
An image recording apparatus comprising:

Images