JP2009000916A - Inkjet recorder and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely remove a residue on an intermediate transfer body. <P>SOLUTION: The inkjet recorder comprises: an image formation part which forms an image on an intermediate transfer body by performing ink discharge from an inkjet head; an image transfer part which transfers the image formed on the intermediate transfer body to a recording medium; a cleaning part which comprises an endless cleaning belt whose surface is composed of a porous body and removes an after-transfer residue on the intermediate transfer body by bringing the cleaning belt into contact with the surface of the intermediate transfer body; and a conveying control part which performs conveying control of the intermediate transfer body and the cleaning belt in such a manner that a velocity difference arises between the conveying speed of the intermediate transfer body and the cleaning belt. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and a recording method, and more particularly to a transfer type ink jet recording apparatus and a recording method in which an image is once formed on an intermediate transfer member and then transferred to a recording medium.

  An ink jet recording apparatus performs recording by ejecting ink droplets from a large number of nozzles formed on an ink jet head. The noise during recording operation is low, the running cost is low, and various recording media are used. It is widely used because it can record high-quality images.

  Among ink jet recording apparatuses, there is known an apparatus in which an ink is discharged from an ink jet head to an intermediate transfer member to form an image on the intermediate transfer member and then transfer the image to a recording medium. According to such a transfer-type recording apparatus, it is possible to transfer an image onto a recording medium after removing the ink solvent (for example, water) on the intermediate transfer member, and the image can be smeared or exposed through the ink solvent. In addition, a high-quality image can be obtained without causing problems such as deformation of the recording medium (so-called cockling).

  On the other hand, in a transfer type recording apparatus, image transfer from the intermediate transfer member to the recording medium is not completely performed, and residues such as ink may remain on the intermediate transfer member. If the residue on the intermediate transfer member is not sufficiently removed and the subsequent image formation and transfer processes are repeatedly performed, it causes deterioration in image quality. In order to solve such problems, various types of devices including a cleaning unit (cleaning unit) for cleaning the surface of the intermediate transfer member have been proposed (for example, see Patent Documents 1 to 4).

  In the ink jet printer described in Patent Document 1, residual ink is removed by sliding a cleaning member made of a material such as felt on the surface of an intermediate transfer member (endless belt).

  In the ink jet printer described in Patent Document 2, a cleaning member (cleaning roller) having a surface made of a material that easily wets with ink rather than a surface material of an intermediate transfer body (transfer drum) is used.

  In the ink jet recording apparatus described in Patent Document 3, the speed Va when the cleaning member is moved continuously or intermittently is set to be lower than the speed Vb of the intermediate transfer body (transfer drum, transfer belt). The remaining ink is removed. Further, this recording apparatus is provided with a mechanism for decolorizing or cleaning and removing residual ink from a cleaning member from which the residual ink has been wiped out in order to maintain the cleaning capability semipermanently.

In the ink jet printing machine described in Patent Document 4, as in Patent Document 2, a cleaning member (cleaning roller) having a surface made of a material that is more easily wetted with ink than the surface material of the intermediate transfer body (blanket cylinder) is used. ing. The document also discloses an aspect in which the residual ink on the intermediate transfer member (blanket cylinder) is adsorbed to the cleaning member while winding the cleaning member (cleaning belt) made of felt according to the printing amount. Yes.
Japanese Patent Laid-Open No. 5-147207 JP 7-164624 A JP 2000-127356 A JP 2002-166532 A

  However, Patent Documents 1 to 4 described above do not take into consideration that the residue on the intermediate transfer member includes both a liquid component (liquid residue) and a solid component (solid residue). It is difficult to reliably remove the liquid residue and solid residue from the intermediate transfer member.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an ink jet recording apparatus and a recording method capable of reliably removing the residue on the intermediate transfer member.

  In order to achieve the above object, an invention according to claim 1 is directed to an image forming unit that forms an image on an intermediate transfer member by discharging ink from an inkjet head, and an image formed on the intermediate transfer member. An image transfer portion for transferring the image to a recording medium, and an endless cleaning belt whose surface is formed of a porous body, and the transfer on the intermediate transfer body by bringing the cleaning belt into contact with the surface of the intermediate transfer body A cleaning unit that removes post-residues, and a conveyance control unit that controls conveyance of the intermediate transfer member and the cleaning belt such that a speed difference occurs between the conveyance speeds of the intermediate transfer member and the cleaning belt. It is characterized by that.

  According to the present invention, a cleaning belt having a porous surface is used, and the cleaning belt is brought into contact with the surface of the intermediate transfer member while causing a speed difference between the transfer speeds of the intermediate transfer member and the cleaning belt. As a result, the liquid residue on the intermediate transfer member can be sucked and removed by the capillary force of the porous body, and the solid residue can be moved from the intermediate transfer member to the cleaning belt with high efficiency by the shear force generated by the above speed difference. The solid residue can be removed from the intermediate transfer member.

  A second aspect of the present invention is the ink jet recording apparatus according to the first aspect, wherein a treatment liquid containing a component that agglomerates a colorant component contained in the ink ejected from the ink jet head is added to the intermediate liquid. It is characterized in that a treatment liquid application unit provided on the transfer body is provided.

  In a two-liquid reaction type recording apparatus that forms an image by reacting ink and a processing liquid on an intermediate transfer body, the solid residue after the transfer becomes a color material aggregate and needs to have a strong exclusion force. By providing a speed difference between the transfer speed of the intermediate transfer member and the cleaning belt, a larger exclusion force can be obtained compared to the case of the same speed, and solid residue on the intermediate transfer member can be more reliably removed. it can. Therefore, more effective cleaning performance can be realized.

  The invention described in claim 3 is the ink jet recording apparatus according to claim 1 or 2, wherein the hardness of the porous body is 30 to 70 °.

  A fourth aspect of the present invention is the ink jet recording apparatus according to any one of the first to third aspects, wherein the porous body has an average pore diameter of φ10 to 100 μm. .

  A fifth aspect of the present invention is the ink jet recording apparatus according to any one of the first to fourth aspects, further comprising a cleaning tank for cleaning the cleaning belt.

  According to the aspect of claim 5, it becomes possible to maintain a permanent cleaning performance.

  A sixth aspect of the present invention is the ink jet recording apparatus according to the fifth aspect, wherein the cleaning tank is separated into at least two tanks.

  According to the aspect of the sixth aspect, cleaning with at least two kinds of liquids becomes possible. Moreover, it can be separated into a tank for cleaning the cleaning belt and a tank for rinsing the cleaning belt. Moreover, it becomes possible to circulate the liquid of each tank for every tank according to a dirt state, and the cleaning effect of a cleaning belt can be improved.

  A seventh aspect of the present invention is the ink jet recording apparatus according to any one of the first to sixth aspects, wherein the cleaning unit observes the dirt state of the cleaning belt, and the monitoring unit observes the dirt. And a cleaning control unit that switches a cleaning mode of the cleaning belt according to a state of contamination of the cleaning belt.

  According to the aspect of the seventh aspect, when the cleaning belt becomes very dirty, it is possible to enhance the cleaning of the cleaning belt and maintain the cleaning performance by the cleaning belt.

  According to an eighth aspect of the present invention, in the ink jet recording apparatus according to the seventh aspect, when the cleaning control unit determines that the contamination of the cleaning belt exceeds a reference value, the intermediate transfer member The cleaning belt is separated to enhance cleaning of the cleaning belt.

  According to the aspect of the present invention, even when the cleaning belt is very dirty, the cleaning belt can be reliably cleaned without contaminating the intermediate transfer member.

  A ninth aspect of the present invention is the ink jet recording apparatus according to any one of the fifth to eighth aspects, wherein the cleaning belt is disposed upstream of the cleaning tank in the transport direction of the cleaning belt. The liquid suction part which sucks and removes the liquid component inside the porous body which comprises is provided.

  According to the aspect of the ninth aspect, when cleaning the cleaning belt in the cleaning tank, the liquid component (liquid residue) inside the porous body is removed in advance to reduce liquid contamination in the cleaning tank. Thus, the frequency of liquid replacement / liquid circulation in the cleaning tank can be kept low.

  In order to achieve the above object, an invention according to claim 10 includes a step of forming an image on an intermediate transfer member by discharging ink from an inkjet head, and an image formed on the intermediate transfer member. A step of transferring to a recording medium, a step of contacting an endless cleaning belt having a porous surface with the surface of the intermediate transfer member, and removing post-transfer residues on the intermediate transfer member; And a step of controlling the conveyance of the intermediate transfer member and the cleaning belt so that a difference in speed occurs between the conveyance speeds of the intermediate transfer member and the cleaning belt.

  According to the present invention, a cleaning belt having a porous surface is used, and the cleaning belt is brought into contact with the surface of the intermediate transfer member while causing a speed difference between the transfer speeds of the intermediate transfer member and the cleaning belt. As a result, the liquid residue on the intermediate transfer member can be sucked and removed by the capillary force of the porous body, and the solid residue can be moved from the intermediate transfer member to the cleaning belt with high efficiency by the shear force generated by the above speed difference. The solid residue can be removed from the intermediate transfer member.

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

  FIG. 1 is a schematic configuration diagram showing the overall configuration of an inkjet recording apparatus according to an embodiment of the present invention. An ink jet recording apparatus 10 shown in FIG. 1 includes a processing liquid applying unit 14 that applies a processing liquid to an intermediate transfer body 12 and inks of cyan (C), magenta (M), yellow (Y), and black (K). And a printing unit (image forming unit) 18 having a plurality of inkjet heads (hereinafter simply referred to as “heads”) 16 (16C, 16M, 16Y, and 16K) provided corresponding to the Formed on the intermediate transfer body 12, a solvent removal unit 20 that removes the solvent on the intermediate transfer body 12 after the mixed liquid of the ink and the processing liquid is separated into the color material aggregate and the solvent. A transfer unit 24 that transfers an ink image (hereinafter simply referred to as “image”) to the recording medium 22 and a cleaning unit 26 that removes residual ink on the intermediate transfer body 12 are provided.

  Each color ink used in this example is a pigment ink containing a pigment as a coloring material (colorant) or a dye ink containing a dye. The treatment liquid is a liquid containing a component that reacts with the ink to aggregate (undisperse or insolubilize) the coloring material (pigment or dye) contained in the ink. For each color ink and treatment liquid, known ones may be used. For example, the ink is water as a solvent, a coloring material (pigment or dye), a water-soluble organic solvent, a surface tension adjusting agent (surfactant), and others. The processing liquid is configured to contain water as a solvent, a water-soluble organic solvent, a surface tension adjusting agent (surfactant), and a colorant flocculant. Detailed description thereof will be omitted.

  As shown in FIG. 1, an endless belt member is used for the intermediate transfer member 12. The intermediate transfer member 12 made of this intangible belt member is wound around a plurality of rollers 32, and the range of the belt surface facing at least the nozzle surface (ink ejection surface) of each head 16 constituting the printing unit 18 is as follows. The printing unit 18 is configured to form a horizontal plane (flat plane) as an area where an image (ink image) is formed. Further, the entire intermediate transfer body 12 or at least the image forming area on which the ink ejected from the printing unit 18 lands is made of a material that does not allow ink droplets to penetrate (such as resin, metal, rubber). Is done.

  Preferred materials used for the surface of the intermediate transfer body 12 include, for example, a polyimide resin, a silicon resin, a polyurethane resin, a polyester resin, a polystyrene resin, a polyolefin resin, a polybutadiene resin, a polyamide resin, and a polychlorinated resin. Known materials such as vinyl resins, polyethylene resins, and fluorine resins can be used.

  The surface tension of the surface layer of the intermediate transfer body 12 is desirably 10 mN / m or more and 50 mN / m or less. If the surface tension is greater than 50 mN / m, there will be no difference in surface tension with the recording medium 22, and the transferability of the ink image (ink aggregate) will deteriorate. On the other hand, if the surface tension is less than 10 mN / m, considering the wettability of the treatment liquid, the surface tension of the treatment liquid needs to be smaller than the surface tension of the surface layer, and the surface tension of the treatment liquid is 10 mN / m or less. It is difficult to do, and the degree of freedom of design is narrowed.

  Further, it is desirable that the surface layer of the intermediate transfer body 12 has irregularities with a surface roughness (Ra) of about 0.3 μm, which has the effect of suppressing the movement of the color material.

  When the power of the motor is transmitted to at least one of the plurality of rollers 32 on which the intermediate transfer body 12 is stretched, the intermediate transfer body 12 is driven in the counterclockwise direction of FIG. In this example, the roller 32A is a driving roller (main roller) to which the power of the motor is transmitted.

  The treatment liquid application unit 14 for applying the treatment liquid to the intermediate transfer body 12 includes an application roller 34, and the application roller 34 is disposed at a position facing the roller 32B with the intermediate transfer body 12 interposed therebetween. 12 can be rotated by being driven by the motor 12 or can be rotated independently of the intermediate transfer body 12. A processing liquid is supplied to the surface of the application roller 34 by a processing liquid supply means (not shown), and the application roller 34 rotates while contacting the surface (recording surface) of the intermediate transfer body 12, thereby The processing liquid is applied to the intermediate transfer body 12.

  The thickness (application thickness) of the treatment liquid applied to the intermediate transfer body 12 is preferably set in the range of 3 to 10 μm. This is because if the thickness of the treatment liquid applied by the application roller 34 is too thin, uneven coating occurs, while if the thickness is too thick, the burden of removing the solvent increases. In particular, it is desirable that the thickness of the treatment liquid is thicker than the thickness of the ink applied at the downstream printing unit 18. This is because when the treatment liquid is applied so as to be thinner than the thickness of the ink, an interface is formed between the ink droplet surface and the air layer, and droplet coalescence (landing interference) occurs due to surface tension.

  The application roller 34 is preferably a porous material or a material with irregularities on the surface, and for example, a gravure roll can be used.

  In the present embodiment, the application of the treatment liquid is performed using the application roller 34 as the treatment liquid application unit. However, the present invention is not particularly limited, and the treatment liquid is applied using a blade. A method, a method of applying a treatment liquid using a spray or an inkjet head, and the like can be appropriately applied. In particular, when an inkjet head is used, the treatment liquid can be accurately applied in a pattern according to the recorded image.

  The printing unit 18 disposed downstream of the processing liquid application unit 14 includes cyan (C), magenta (M), and yellow (Y) along the belt surface from the upstream side along the conveyance direction of the intermediate transfer body 12. , Heads 16C, 16M, 16Y, and 16K corresponding to the respective color inks are provided in the order of black (K).

  Each head 16 (16C, 16M, 16Y, 16K) has a length corresponding to the maximum width of the image forming area in the intermediate transfer body 12, and a plurality of ink discharge ports (nozzles) are arranged over the entire width of the image forming area. It consists of a full line type head. Each head 16 is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the intermediate transfer body 12. An ink image can be formed on the intermediate transfer body 12 by ejecting the color ink from each of the heads 16C, 16M, 16Y, and 16K while conveying the intermediate transfer body 12.

  As described above, according to the configuration in which the full line head having the nozzle row covering the entire width of the image forming area of the intermediate transfer body 12 is provided for each ink color, the intermediate transfer body 12 is intermediate in the transport direction (sub-scanning direction). An image can be recorded in the image forming area of the intermediate transfer body 12 by performing the operation of relatively moving the transfer body 12 and the printing unit 18 once (that is, by one sub-scan). Accordingly, the head can perform high-speed printing as compared with a serial head in which the head reciprocates in a direction (main scanning direction) orthogonal to the conveyance direction of the intermediate transfer body 12, and print productivity can be improved.

  In the present embodiment, as an example, a mode in which the printing unit 18 is configured by a full line head has been illustrated. However, the present invention is not particularly limited, and the printing unit 18 is configured by a serial head. Of course it is also good.

  In the head 16 used in this example, as an ink ejection method, a piezoelectric method that ejects ink by using displacement of a piezoelectric element, a thermal method that ejects ink by using thermal energy generated by a heating element, and other various methods are appropriately used. Can be adopted.

  In this example, the configuration of CMYK 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, dark ink, and other color inks are used as necessary. May be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  An ink storage / loading unit (not shown) that stores ink to be supplied to each head 16 is provided with an ink tank that stores color ink corresponding to each head 16, and each tank has a required flow path. Is communicated with the head 16 via The ink storage / loading unit 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.

  A solvent removal roller 36 is provided in the solvent removal unit 20 disposed downstream of the printing unit 18. In this example, two solvent removal rollers 36A and 36B are provided at positions facing the rollers 32C and 32D, respectively, with the intermediate transfer body 12 interposed therebetween. The solvent removal roller 36 (36A, 36B) is a roller-shaped member having at least a surface formed of a porous body, and is disposed so as to contact the surface (recording surface) of the intermediate transfer body 12.

  It is desirable that the surface energy of the solvent removal roller 36 is smaller than that of the intermediate transfer body 12 and is 30 mN / m or less. This is because the ink aggregates do not adhere and only the solvent can be removed. As other modes, there are a method of removing excess solvent from the intermediate transfer body 12 with an air knife, a method of evaporating and removing the solvent by heating, and the like. Any solvent removal method may be used, but it is preferable to use a method that does not rely on heat. In the means for heating the surface of the intermediate transfer member 12 or applying heat to the aggregates on the intermediate transfer member 12 to evaporate the solvent, the solvent is excessively removed by overheating the aggregates, and the viscosity of the preferred aggregates at the time of transfer is reduced. The elasticity cannot be maintained, and the transferability may be deteriorated. There is also concern about the influence of the heat of the intermediate transfer body 12 on the ink ejection characteristics of the inkjet head.

  In the solvent removal unit 20, the solvent on the intermediate transfer body 12 is removed by the solvent removal roller 36. For this reason, even when a large amount of processing liquid is applied onto the intermediate transfer body 12, the solvent is removed by the solvent removal unit 20, so that a large amount of solvent (dispersion medium) is added to the recording medium 22 by the downstream transfer unit 24. ) Is not transcribed. Therefore, even when paper is used as the recording medium 22, problems characteristic to aqueous solvents such as curl and cockle do not occur.

  By removing the excess solvent from the ink aggregate by the solvent removing unit 20, the aggregate can be concentrated and the internal aggregating force can be further increased. Further, by concentrating the ink aggregates by removing the solvent, fixability and glossiness can be imparted to the image even after transfer to the recording medium 22.

  Note that it is not always necessary to remove all of the solvent by the solvent removing unit 20. If the ink aggregate is excessively removed by excessive removal, the adhesion force of the ink aggregate to the intermediate transfer body 12 becomes too strong, and an excessive pressure is required for transfer, which is not preferable. Rather, in order to maintain viscoelasticity suitable for transferability, it is desirable to leave a small amount. As an effect obtained by leaving a small amount of the solvent, since the aggregate is hydrophobic and the solvent component that hardly volatilizes (mainly organic solvent such as glycerin) is hydrophilic, the ink aggregate and the residual solvent component are solvent. A thin liquid layer composed of residual solvent components is formed between the ink aggregate and the intermediate transfer body 12 after separation. Accordingly, the adhesive force of the ink aggregate to the intermediate transfer body 12 becomes weak, which is advantageous for improving transferability.

  Further, the solvent removal unit 20 is provided with a suction pump 38 having a suction port 38a opened near the surface of the solvent removal roller 36 for each solvent removal roller 36. The liquid component (solvent) inside the porous body of the removing roller 36 can be removed by suction through the suction port 38a.

  The transfer unit 24 includes a heating and pressing roller 40 with a built-in heater. Specifically, as shown in FIG. 1, two heating and pressing rollers 40A and 40B are arranged at positions facing the rollers 32E and 32F, respectively (between the heating and pressing rollers 40A and 32E, heating The intermediate transfer body 12 and the recording medium 22 are sandwiched between the pressure roller 40B and the roller 32F, and are heated to a predetermined temperature and pressed with a predetermined pressure (nip pressure), whereby an image on the intermediate transfer body 12 is displayed. It is configured to transfer to the recording medium 22.

  The heating temperature is preferably 60 ° C to 170 ° C, and more preferably 100 ° C to 150 ° C from the viewpoint of transferability. When the temperature is 170 ° C. or higher, there is a problem such as deformation of the intermediate transfer body 12, and when the temperature is 60 ° C. or lower, the transferability is deteriorated.

  As a means for adjusting the nip pressure at the time of transfer, for example, a mechanism (not shown) for moving the heating and pressing roller 40 up and down in FIG. 1 is provided.

  The transfer unit 24 of this example further includes small rollers 42A and 42B having the same structure as the heat and pressure rollers 40A and 40B. The small rollers 42A and 42B are provided between the heat and pressure rollers 40A and 40B. A support member 44 is provided at the opposing position. Further stable transfer is possible by heating and pressurizing the intermediate transfer body 12 and the recording medium 22 with the small rollers 42A and 42B as well as the heat and pressure rollers 40A and 40B.

  A fixing unit 46 that fixes the image transferred to the recording medium 22 is provided at the subsequent stage of the transfer unit 24. The fixing unit 46 includes a fixing roller 48 having a built-in heater. The recording medium 22 on which the image is transferred by the transfer unit 24 is peeled off from the intermediate transfer body 12 and then sent between the fixing roller 48 and the backup roller 49, and is heated by the fixing roller 48 while being supported by the backup roller 49. By applying pressure, the image on the recording medium 22 is fixed.

  The ink jet recording apparatus 10 of this example includes a mechanism (reversing mechanism) 50 that reverses the recording surface of the recording medium 22. When single-sided recording is selected by a selection unit (operation unit) (not shown), image transfer is performed on one surface of the recording medium 22 by the transfer unit 24 and image fixing is performed by the fixing unit 46. The recording medium 22 recorded on one side is sent to a paper discharge unit (not shown). On the other hand, when double-sided recording is selected, the transfer unit 24 performs image transfer on one surface of the recording medium 22, the fixing unit 46 performs image fixing, and then the single-sided recording medium 22. Is sent to the reversing mechanism 50. Then, after the recording surface of the recording medium 22 is reversed by the reversing mechanism 50, the recording medium 22 is sent again to the transfer unit 24. Thereafter, image transfer is performed on the other surface of the recording medium 22 by the transfer unit 24, and after image fixing is performed by the fixing unit 46, the recording medium 22 recorded on both sides is sent to the paper discharge unit.

  A cooling unit 52 is disposed on the downstream side of the transfer unit 24 at a position facing the intermediate transfer body 12. The cooling unit 52 includes a heat sink and a cooling fan, and cools the intermediate transfer body 12 by exhausting heat to the intermediate transfer body 12 after the recording medium 22 is peeled off by the heat sink and the cooling fan. It is desirable that the cooling temperature by the cooling fan is adjustable. The cooling unit 52 may use a water cooling method by circulating water. Further, the cooling unit 52 has a configuration in which a conveyance time (cooling time) is secured so as to cool the intermediate transfer body 12 heated by the transfer unit 24 to a desired temperature.

  A cleaning unit (cleaning unit) 26 that cleans the surface of the intermediate transfer body 12 after image transfer is performed by the transfer unit 24 is provided on the downstream side of the cooling unit 52. The cleaning unit 26 includes a cleaning belt 54, and the post-transfer residue on the intermediate transfer body 12 is removed by bringing the cleaning belt 54 into contact with the surface of the intermediate transfer body 12.

  The cleaning belt 54 is an endless belt member having a porous surface and is wound around a plurality of rollers 56. As the cleaning belt 54, a polyimide belt is preferably used as a belt support, and a porous body made of polyurethane or PVA is bonded to the polyimide belt. In this example, a cleaning belt 54 is used in which a ruby cell made of Toyo Polymer is attached to a polyimide belt and the belt surface is a porous body.

  The hardness (hardness) of the porous body constituting the surface of the cleaning belt 54 is preferably in the range of 30 to 70 °. In addition, the hardness of a porous body shall be measured with the Asker C-type hardness meter. This is because, if the hardness of the porous body is softer than 30 °, it is too crushed and the water absorbability is impaired, whereas if it is harder than 70 °, the belt flexibility is impaired.

  The average pore diameter of the porous body is preferably φ100 μm or less. The smaller the average hole diameter, the faster the water supply. However, if the average pore diameter is smaller than φ10 μm, it is difficult to remove the moisture once absorbed, and the load for refreshing is increased. Therefore, the average pore diameter of the porous body is more preferably φ10 μm or more.

  When the power of the motor is transmitted to at least one of the plurality of rollers 56 around which the cleaning belt 54 is stretched, the cleaning belt 54 is driven in the clockwise direction of FIG. In this example, the roller 56A is a driving roller (main roller) to which the power of the motor is transmitted.

  In particular, in the present embodiment, the conveyance speed V1 of the intermediate transfer body 12 and the cleaning belt at a portion (contact portion) where the cleaning belt 54 contacts the intermediate transfer body 12 by a transfer system control unit 108 (see FIG. 2) described later. The conveyance control of the intermediate transfer body 12 and the cleaning belt 54 is performed so that a speed difference occurs in the conveyance speed V2 of the medium 54. The conveyance speed V2 of the cleaning belt 54 may be faster (V1 <V2) or slower (V1> V2) than the conveyance speed V1 of the intermediate transfer body 12.

  When the speed difference between the transport speed V1 of the intermediate transfer body 12 and the transport speed V2 of the cleaning belt 54 is expressed by the following expression {(| V2-V1 | / V1) × 100} [%], the speed difference is A range of 2 to 7% is preferred. If the speed difference is too small (less than 2%), the wiping efficiency of the residue on the surface of the intermediate transfer body 12 is deteriorated. On the other hand, if the speed difference is too large (greater than 7%), the belts rub. This is because the problem of the system load and the durability of the belt is increased. Therefore, it is preferable that the cleaning is performed by bringing the cleaning belt 54 into contact with the surface of the intermediate transfer body 12 in a state where the speed difference in the above range is generated.

  The inkjet recording apparatus 10 of the present embodiment is provided with a mechanism (not shown) that moves a roller 56A disposed opposite to the roller 32A to the left and right in FIG. 1, and cleans the surface of the intermediate transfer body 12. In this case, it is necessary to enhance the cleaning of the cleaning belt 54 as described later while moving the roller 56A toward the roller 32A (leftward in FIG. 1) so that the cleaning belt 54 contacts the intermediate transfer body 12. When it is determined that the cleaning belt 54 is separated from the intermediate transfer body 12, the roller 56A is moved to the opposite side (rightward in FIG. 1) from the roller 32A.

  The pressure between the intermediate transfer body 12 and the cleaning belt 54 is preferably in the range of 0.2 to 1.0 MPa. If the pressure is less than 0.2 MPa, the wiping efficiency of the residue on the surface of the intermediate transfer body 12 is deteriorated. On the other hand, if the speed difference is larger than 1.0 MPa, the problem of system load and belt durability increases. is there.

  Using the cleaning belt 54 having a porous surface, the cleaning belt 54 is brought into contact with the surface of the intermediate transfer body 12 while generating a speed difference between the transfer speeds of the intermediate transfer body 12 and the cleaning belt 54. Thus, the liquid residue on the intermediate transfer body 12 can be removed by suction by the capillary force of the porous body, and the solid residue from the intermediate transfer body 12 to the cleaning belt 54 by the shearing force acting in the shearing direction caused by the speed difference. The grains can be moved with high efficiency, and the solid residue can be removed from the intermediate transfer member 12.

  When it is known that only liquid residue is present on the intermediate transfer body 12 (for example, purging process), the conveyance speeds of the intermediate transfer body 12 and the cleaning belt 54 are made equal. There may be a mode in which the conveyance load of the intermediate transfer body 12 is reduced.

  It is preferable that a cleaning auxiliary agent applying unit 58 for applying a cleaning auxiliary agent to the surface of the intermediate transfer member 12 is provided upstream of the contact portion between the intermediate transfer member 12 and the cleaning belt 54. In this example, the cleaning assistant applying unit 58 supplies the cleaning assistant inside the container 62 to the belt while rotating the endless belt 60 in contact with the surface of the intermediate transfer body 12 according to the conveyance of the intermediate transfer body 12. The cleaning aid is applied to the intermediate transfer body 12 via the belt 60 by being attached to the surface of the belt 60. By applying a cleaning aid to the surface of the intermediate transfer body 12, residues (liquid residue, solid residue) can be easily removed from the surface of the intermediate transfer body 12 by the cleaning belt 54.

  Thus, by removing the residue on the surface of the intermediate transfer body 12 by the cleaning belt 54, a good transfer image can be obtained on the recording medium 22 without deterioration in image quality in the subsequent transfer process.

  By the way, the residue (liquid residue, solid residue) on the intermediate transfer body 12 is transferred to the cleaning belt 54. If the residue continues to be accumulated on the cleaning belt 54, the cleaning performance of the cleaning belt 54 is improved. It is conceivable that the residue on the surface of the intermediate transfer body 12 cannot be sufficiently removed due to the decrease in the thickness of the intermediate transfer body 12, which causes a reduction in the quality of the transferred image. Therefore, in the inkjet recording apparatus 10 of the present embodiment, in order to permanently maintain the cleaning performance of the cleaning belt 54, a liquid suction unit 64 that removes the liquid residue transferred to the cleaning belt 54, and a solid residue A belt cleaning unit 66 is provided for removing the toner.

  The liquid suction part 64 is provided with a suction pump 68 having a suction port 68a that opens near the surface of the cleaning belt 54. By driving the suction pump 68, the liquid inside the porous body of the cleaning belt 54 is provided. The residue can be removed by suction through the suction port 68a. The liquid residue sucked by the suction pump 68 is collected in a waste liquid tank (not shown).

  The belt cleaning section 66 is provided with a cleaning tank 70, and a part of the cleaning belt 54 guided by the plurality of rollers 56 passes through the cleaning tank 70, so that the intermediate transfer body 12 moves to the cleaning belt 54. The transferred solid residue is washed away.

  The cleaning tank 70 is preferably divided into at least two tanks. For example, as in the example shown in FIG. 1, when the cleaning tank 70 is divided into two tanks, the cleaning belt 54 is cleaned in the first tank 72A, and the cleaning belt 54 is cleaned in the second tank 72B. Rinsing can be performed, and the solid residue of the cleaning belt 54 can be efficiently removed. Further, when the cleaning tank 70 is divided into three or more layers, it becomes possible to repeatedly perform cleaning and rinsing in a stepwise manner and further improve the effect of removing the solid residue of the cleaning belt 54. Can be made.

  In the first tank 72A, cleaning liquid is stored, and brush rollers 76A and 76B are provided at positions facing the rollers 56C and 56D, respectively, with the cleaning belt 54 interposed therebetween. The brush rollers 76 </ b> A and 76 </ b> B remove (remove) the solid residue of the cleaning belt 54 by rotating in accordance with the conveyance of the cleaning belt 54 while pressing the surface of the cleaning belt 54. In addition, a pump 74A is connected to the first tank 72A. By driving the pump 74A according to the dirt of the cleaning liquid, the cleaning liquid in the first tank 72A is circulated and appropriately replaced with a new cleaning liquid. .

  Similarly, a rinsing liquid (for example, water) is stored in the second tank 72B, and a pump 74B is connected to replace the rinsing liquid. By driving the pump 74B according to the dirt of the rinsing liquid, the rinsing liquid in the second tank 72B is circulated and appropriately replaced with a new rinsing liquid.

  When the apparatus is stopped, the liquid is drained from each of the tanks 72A and 72B of the cleaning tank 70, and the cleaning belt 54 is stopped so as not to be immersed in the liquid. Thereby, deterioration of the cleaning belt 54 can be prevented.

  By disposing the liquid suction unit 64 upstream of the belt cleaning unit 66 (cleaning tank 70) in the transport direction of the cleaning belt 54, the cleaning belt 54 is cleaned before the cleaning belt 54 is cleaned in the cleaning tank 70. Since the liquid component (liquid residue) in the porous body of 54 is sucked and removed, the liquid contamination of the cleaning tank 70 can be alleviated, and the frequency of liquid replacement / liquid circulation in the cleaning tank 70 can be kept low. It becomes.

  Further, in the inkjet recording apparatus 10 of the present embodiment, a belt drying unit 80 and a monitor unit 82 are sequentially arranged on the downstream side of the belt cleaning unit 66.

  The belt drying unit 80 includes a heater, for example, and dries the cleaning belt 54 cleaned by the cleaning unit 66 from the front side.

  The monitor unit 82 disposed on the downstream side of the belt drying unit 80 includes a CCD, for example, and monitors (observes) the contamination state of the cleaning belt 54 from the surface side. The result observed by the monitor unit 82 is sent to a cleaning control unit 112 (see FIG. 2) described later. When the cleaning control unit 112 determines that the degree of contamination of the cleaning belt 54 exceeds the reference value (threshold value), the roller 56A is opposite to the roller 32A side so that the cleaning belt 54 is separated from the intermediate transfer body 12. The cleaning belt 54 is cleaned by moving the cleaning belt 54 to the side (right direction in FIG. 1), for example, by delaying the conveyance time of the cleaning belt 54, rotating the cleaning belt 54 a plurality of times, or combining them. Strengthen. Note that while the cleaning belt 54 is separated from the intermediate transfer body 12, the residue of the intermediate transfer body 12 cannot be removed. Therefore, the conveyance of the intermediate transfer body 12 and the recording medium 22 is stopped and the intermediate transfer body 12 is stopped. It is preferable not to perform the steps from image formation to the body 12 to image transfer to the recording medium 22.

  FIG. 2 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. As shown in FIG. 2, the inkjet recording apparatus 10 includes a communication interface 120, a system controller 102, an image memory 104, a ROM 106, a transport system control unit 108, a treatment liquid application control unit 109, a solvent removal control unit 110, and a cleaning control unit 112. A print control unit 114, an image buffer memory 116, a head driver 118, and the like.

  The communication interface 120 is an interface unit that receives image data sent from the host computer 100. As the communication interface 120, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a 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 100 is taken into the inkjet recording apparatus 10 via the communication interface 120 and temporarily stored in the image memory 104. The image memory 104 is a storage unit that temporarily stores an image input via the communication interface 120, and data is read and written through the system controller 102. The image memory 104 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 102 is a control unit that controls the communication interface 120, the image memory 104, the transport system control unit 108, the solvent removal control unit 110, the cleaning control unit 112, and the like. The system controller 102 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 100, read / write control of the image memory 104, and the like, and each control unit 108, 110, 112. A control signal for controlling a motor or the like connected to is generated.

  Various programs are stored in the ROM 106, and a control program is read and executed in accordance with a command from the system controller 102. Instead of the ROM 106, a magnetic disk or the like may be used. Also, an external interface may be provided and a memory card or PC card may be used. Of course, you may provide several storage media among these storage media. The ROM 106 may also be used as storage means (not shown) for operating parameters.

  The transport system control unit 108 is a control unit that controls the motor 124 and the heater 126 of the transport system in accordance with instructions from the system controller 102. The motor 124 includes a motor used to transport the intermediate transfer body 12, the recording medium 22, and the cleaning belt 54, a motor for driving a cooling fan provided in the cooling unit 52, and the like. The heater 126 includes a heater used in the transfer unit 24 and the fixing unit 46.

  The processing liquid application control unit 109 is a control unit that controls the motor 127 that transmits power to the application roller 34 provided in the processing liquid application unit 14 in accordance with an instruction from the system controller 102. The treatment liquid application control unit 109 includes a drive circuit that drives the motor 127.

  The solvent removal control unit 110 is a control unit that controls the motor 128 and the pump 130 provided in the solvent removal unit 20 in accordance with instructions from the system controller 102. The motor 128 includes a motor that constitutes a part of the moving mechanism of the solvent removal roller 36. The pump 130 corresponds to a suction pump 38 provided along with the solvent removal roller 36. The solvent removal control unit 110 controls the driving of the motor 128 and appropriately adjusts according to the amount of solvent on the intermediate transfer body 12 so that the separation distance between the solvent removal roller 36 and the intermediate transfer body 12 is optimized. Then, the drive of the pump 130 (suction pump 38) is controlled to remove the solvent absorbed by the solvent removal roller 36 by suction.

  The cleaning control unit 112 is a control unit that controls the motor 132, the heater 134, and the pump 136 provided in the cleaning unit 26 in accordance with instructions from the system controller 102. The motor 132 includes a motor that constitutes a part of the moving mechanism of the roller 56A. The heater 134 includes a heater provided in the drying unit 80. The pump 136 includes a suction pump 68 provided in the liquid suction unit 64, pumps 74A and 74B provided in the belt cleaning unit 66, and the like.

  In addition, the cleaning control unit 112 is notified of the contamination state of the surface of the cleaning belt 54 observed by the monitor unit 82. The cleaning control unit 112 determines whether or not the contamination state of the surface of the cleaning belt 54 exceeds a reference value (threshold value). When the cleaning control unit 112 determines that the cleaning value exceeds the reference value, the cleaning control unit 112 shifts from the normal mode to the cleaning mode. Is controlled so that the cleaning belt 54 is separated from the intermediate transfer member 12 to enhance the cleaning of the cleaning belt 54. Specifically, a method of slowing the conveying speed of the cleaning belt 54, a method of rotating the cleaning belt 54 a plurality of times, a method combining these methods, or the like can be given. Thereafter, when the cleaning control unit 112 determines that the contamination state of the surface of the cleaning belt 54 notified from the monitor unit 82 is less than the reference value, the cleaning control unit 112 shifts from the cleaning mode to the normal mode, and controls the driving of the motor 132 to perform an intermediate operation. The cleaning belt 54 is brought into contact with the transfer body 12.

  The print control unit 114 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 104 according to the control of the system controller 102, and the generated print A control unit that supplies a control signal (dot data) to the head driver 118. The required signal processing is performed in the print control unit 114, and the ejection amount and ejection timing of the ink droplets of the heads 16C, 16M, 16Y, and 16K are controlled via the head driver 118 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 114 includes an image buffer memory 116, and image data, parameters, and other data are temporarily stored in the image buffer memory 42 when image data is processed in the print control unit 114. In FIG. 2, the image buffer memory 116 is shown in a mode accompanying the print control unit 114, but it can also be used as the image memory 104. Also possible is an aspect in which the print controller 116 and the system controller 102 are integrated and configured with one processor.

  The head driver 118 generates drive signals for driving the actuators of the heads 16C, 16M, 16Y, and 16K based on the print data supplied from the print control unit 114, and supplies the generated drive signals to the actuators. The head driver 118 may include a feedback control system for keeping the head driving condition constant.

  According to the ink jet recording apparatus 10 of the present embodiment, the cleaning belt 54 is provided with a speed difference between the transfer speeds of the intermediate transfer body 12 and the cleaning belt 54 using the cleaning belt 54 having a porous surface. By cleaning by contacting (pressing) the surface of the intermediate transfer body 12, the liquid residue on the intermediate transfer body 12 can be sucked and removed by the capillary force of the porous body, and the difference in speed occurs. The solid residue on the intermediate transfer body 12 can be more reliably removed by the shear force.

  Although the ink jet recording apparatus and the recording method of the present invention have been described in detail above, the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the spirit of the present invention. Of course it is good.

Schematic configuration diagram showing the overall configuration of the inkjet recording apparatus Main block diagram showing the system configuration of the inkjet recording apparatus

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Intermediate transfer body, 14 ... Treatment liquid provision part, 16 ... Head, 18 ... Printing part, 20 ... Solvent removal part, 22 ... Recording medium, 24 ... Transfer part, 26 ... Cleaning part, 32 ... Roller, 34 ... Application roller, 36 ... Solvent removal roller, 40 ... Heating and pressing roller, 42 ... Small roller, 46 ... Fixing section, 48 ... Fixing roller, 52 ... Cooling section, 54 ... Cleaning belt, 56 ... Roller, 58 ... Cleaning aid application unit, 64 ... Liquid suction unit, 66 ... Belt cleaning unit, 68 ... Suction pump, 70 ... Cleaning tank, 80 ... Belt drying unit, 82 ... Monitor unit, 102 ... System controller, 108 ... Conveyance system Control unit 109 ... Treatment liquid application control unit 110 ... Solvent removal control unit 112 ... Cleaning control unit 114 ... Print control unit

Claims (10)

An image forming unit that forms an image on the intermediate transfer member by discharging ink from an inkjet head; and
An image transfer unit for transferring an image formed on the intermediate transfer member to a recording medium;
A cleaning unit that includes an endless cleaning belt having a porous surface, and that removes post-transfer residue on the intermediate transfer body by bringing the cleaning belt into contact with the surface of the intermediate transfer body;
A transport control unit that controls transport of the intermediate transfer member and the cleaning belt so that a speed difference occurs between transport speeds of the intermediate transfer member and the cleaning belt;
An ink jet recording apparatus comprising:   The apparatus according to claim 1, further comprising a treatment liquid application unit that applies a treatment liquid containing a component that aggregates a color material component contained in the ink ejected from the ink jet head onto the intermediate transfer member. The ink jet recording apparatus described.   The inkjet recording apparatus according to claim 1 or 2, wherein the hardness of the porous body is 30 to 70 °.   The inkjet recording apparatus according to any one of claims 1 to 3, wherein the porous body has an average pore diameter of 10 to 100 µm.   The inkjet recording apparatus according to claim 1, further comprising a cleaning tank that cleans the cleaning belt.   6. The ink jet recording apparatus according to claim 5, wherein the cleaning tank is separated into at least two tanks. A monitor unit for observing the state of dirt on the cleaning belt;
The cleaning control unit according to any one of claims 1 to 6, further comprising: a cleaning control unit that switches a cleaning mode of the cleaning belt in accordance with a dirt state of the cleaning belt observed by the monitor unit. The inkjet recording apparatus according to Item.   The cleaning control unit strengthens cleaning of the cleaning belt by separating the cleaning belt from the intermediate transfer member when determining that the contamination of the cleaning belt exceeds a reference value. Item 8. The ink jet recording apparatus according to Item 7.   The liquid suction part for sucking and removing the liquid component inside the porous body constituting the cleaning belt is provided upstream of the cleaning tank in the conveying direction of the cleaning belt. The inkjet recording apparatus according to any one of the above. Forming an image on the intermediate transfer member by discharging ink from an inkjet head; and
Transferring the image formed on the intermediate transfer member to a recording medium;
A step of bringing an endless cleaning belt having a porous surface into contact with the surface of the intermediate transfer member to remove post-transfer residues on the intermediate transfer member;
Carrying out conveyance control of the intermediate transfer member and the cleaning belt such that a speed difference occurs between the conveyance speeds of the intermediate transfer member and the cleaning belt;
An ink jet recording method comprising:

Images