JP5503331B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming apparatus and an image forming method capable of stably transporting a recording medium without affecting an image formed by curved surface transport.

  In a system in which a recording medium is conveyed by a carrier having a curvature such as an impression cylinder, when an image is formed by ink jet, the recording medium does not float or wrinkle so that the recording medium does not contact the ink jet head. It is necessary to carry it in close contact with it.

  For example, in Patent Document 1 described below, in order to securely hold the ink on the recording medium after printing, drying is performed while adsorbing and conveying the recording medium to the rotating drum in order to dry the ink on the recording medium after printing in a short time. An apparatus with means for performing has been proposed. However, when suction conveyance is carried out by a conveyance body having a curvature such as a rotating drum, this results from uneven density due to ink liquid collecting in the suction holes in thin paper, and high rigidity of the paper itself in thick paper. There is a problem that the recording medium is not adsorbed on the surface of the carrier due to floating at the rear end.

  Japanese Patent Application Laid-Open No. H10-228667 describes a roller holding means as an auxiliary means for the suction means. However, in order to suppress the recording medium by contacting with the roller, the image cannot be applied to the recording medium on which an undried image is formed immediately after recording because the image is transferred to the roller.

  Patent Document 3 discloses the contents of changing the suction air volume depending on the type (rigidity, thickness) of the recording medium. Patent Documents 4 and 5 disclose non-contact paper suppression means for pressing the recording medium against the medium surface. A printing apparatus and a printing method are provided.

JP 2008-179012 A JP 2004-90490 A JP 2004-338175 A JP 2003-211652 A Japanese Patent Laid-Open No. 10-193772

  However, it is difficult to transport the cardboard while keeping the entire cardboard in close contact with the curved carrier surface simply by controlling the suction air volume and providing the air blowing means. In addition, the necessary suction pressure can be applied to the recording medium and sucked and transported in a state in which the wind pressure to be blown is increased and the cardboard is forcibly adhered to the impression cylinder, but the air pressure such as compressed air is applied to the image immediately after recording. When high air is applied, a liquid image flows on the recording medium, and there is a problem that the image quality is impaired.

  The present invention has been made in view of such circumstances, and provides an image forming apparatus and an image forming method capable of stably transporting a recording medium without damaging a formed image. With the goal.

According to a first aspect of the present invention, in order to achieve the above object, a treatment liquid application means for applying a treatment liquid containing a flocculant having a function of increasing the viscosity of the ink onto the recording medium, and the ink on the recording medium. Ink ejection means for ejecting ink, a transport body provided with a curvature for carrying and transporting the recording medium, a holding means for holding the leading end of the recording medium in the transport direction, and a plurality of means for sucking the recording medium under negative pressure A suction means, a suction means for sucking from the suction hole, a heating means for heating the transport body and the recording medium from the opposite side of the transport body of the recording medium, Non-contact type recording medium holding means provided on the upstream side in the recording medium conveyance direction and pressing the rear end of the recording medium from the opposite side of the conveyance body in a non-contact manner , and depending on the type of the recording medium , the non-contact type recording medium Pressing force by the medium restraining means And a control means for controlling the said control means, when the conveying direction trailing end passage of the recording medium only, to provide an image forming apparatus, characterized by pressing in the non-contact type recording medium suppressed unit.

According to the first aspect, first, by applying a treatment liquid containing a flocculant onto the recording medium, it is possible to increase the viscosity of the ink and improve the durability of the image. In addition, since the non-contact type recording medium restraining means that presses the rear end of the recording medium is provided, the rear end of the recording medium having high rigidity can be pressed on the conveyance body to which the curvature is given, so that it does not float. It can be adhered. Therefore, in a recording medium with high rigidity, by thickening the ink with an aggregating agent, image damage caused by the non-contact type recording medium suppressing means is reduced, and the trailing edge is suppressed, thereby bringing the recording medium into close contact with the carrier. Can do. Further, since the viscosity of the ink can be increased by the aggregating agent, it is possible to suppress the occurrence of unevenness in the image density at the suction hole.
Further, since the pressing force of the non-contact type recording medium suppressing means is adjusted depending on the type of the recording medium, unnecessary pressing can be suppressed in the recording medium with low rigidity, and deterioration of the image can be suppressed. .
Further, since only the rear end in the conveyance direction of the recording medium is pressed by the non-contact type recording medium, only the rear end can be suppressed without damaging the image, and the conveyance can be performed stably.

Claim 2 in claim 1, and providing a region not ejected the ink in the conveying direction trailing end portion of the recording medium.

According to the second aspect of the present invention , the area where ink is not ejected is provided at the rear end in the conveyance direction of the recording medium. By pressing this area, the recording medium is brought into close contact with the conveyance body without damaging the image. Can be made.

A third aspect of the present invention is characterized in that, in the first or second aspect , the non-contact type recording medium suppressing means is a blowing means.

According to the third aspect , since the non-contact type recording medium suppressing means is the air blowing means, the recording medium can be easily suppressed.

A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the flocculant is an organic acid.

According to the fourth aspect , since the thickening action at the time of aggregation can be enhanced by using an organic acid as the coagulant, the fixing force of the ink to the recording medium can be increased. Accordingly, it is possible to suppress image damage due to pressing and density unevenness due to suction holes.

According to a fifth aspect of the present invention, in order to achieve the above object, a treatment liquid application step for applying a treatment liquid containing a flocculant having a function of increasing the viscosity of the ink onto the recording medium, and the ink on the recording medium. The recording medium is placed on a conveyance body to which ink is ejected and a curvature is given, and the recording medium is sucked through the suction hole while holding the front end of the recording medium in the conveyance direction, and the recording medium is conveyed. A conveying step, a non-contact type recording medium restraining step of pressing the recording medium from the opposite side of the conveying member in a non-contact manner, and heating the conveying member and the recording medium from the opposite side of the conveying member of the recording medium. A heating step, and a control step for controlling the pressing force of the non-contact type recording medium restraining step depending on the type of the recording medium, and the control step is performed only when the recording medium passes in the conveyance direction rear end, Non-contact recording medium It is controlled so as to press in example step to provide an image forming method comprising.

A sixth aspect of the present invention according to the fifth aspect is characterized in that the non-contact type recording medium restraining step is a blowing step of blowing air to the recording medium.

Claims 5 and 6 are obtained by developing the above-described image forming apparatus as an image forming method. According to Claims 5 and 6 , the same effect as described above can be obtained.

  According to the image forming apparatus and the image forming method of the present invention, by increasing the viscosity of the ink with a flocculant, it is possible to improve the resistance against pressing of the image from the printing surface side, and to suppress the trailing edge of the recording medium. Can do. Therefore, for a recording medium with high rigidity, it is possible to achieve both suppression of the trailing edge of the recording medium and avoidance of image damage. For recording media with low rigidity, ink thickening due to agglomeration can prevent liquid ink from flowing into the dent generated in the suction hole, thereby suppressing density unevenness. it can.

It is a schematic block diagram of an inkjet recording device provided with the recording-medium conveying apparatus of this invention. It is an enlarged view of the recording medium conveyance apparatus (drying part) concerning 1st Embodiment. It is the schematic of a ventilation nozzle. It is a top view which shows direction and arrangement | sequence of a ventilation nozzle. It is an enlarged view of a recording medium conveyance layer concerning a 2nd embodiment. FIG. 6 is an enlarged view of a recording medium transport layer according to a third embodiment. It is a principal block diagram showing the system configuration of the ink jet recording apparatus. It is a figure explaining the wind speed setting in the test example 3. FIG.

  Preferred embodiments of an image forming apparatus and an image forming method according to the present invention will be described below with reference to the accompanying drawings. In the following embodiments, an inkjet recording apparatus will be described as an example of an image forming apparatus. However, the present invention is not limited to this, and any apparatus that conveys a recording medium after image formation on a curved surface may be used. it can. Further, curved surface conveyance is not limited to drum conveyance, and can also be used for belt conveyance.

[Overall configuration of inkjet recording apparatus]
First, the overall configuration of an ink jet recording apparatus to which the present invention is applied will be described.

  FIG. 1 is a configuration diagram schematically showing an inkjet recording apparatus 1 according to the present embodiment. An inkjet recording apparatus 1 shown in FIG. 1 is an apparatus that forms an image on a recording surface of a recording medium 22, and mainly includes a paper feeding unit 10, a treatment liquid application unit 12, a drawing unit 14, a drying unit 16, an exposure curing unit 18, and a discharge. The unit 20 is configured. A recording medium 22 (sheets) is stacked on the paper supply unit 10, and the recording medium 22 is sent from the paper supply unit 10 to the treatment liquid application unit 12, and the treatment liquid application unit 12 processes the treatment liquid on the recording surface. Is applied to the recording surface by the drawing unit 14. The recording medium 22 to which ink has been applied is dried by the drying unit 16, dried by the exposure curing unit 18, and then transported by the discharge unit 20.

  Intermediate conveyance units (transfer cylinders) 24, 26, and 28 are provided between the respective units, and the recording medium 22 is transferred by the intermediate conveyance units 24, 26, and 28. That is, a first intermediate transport unit 24 is provided between the processing liquid application unit 12 and the drawing unit 14, and the recording medium from the processing liquid application unit 12 to the drawing unit 14 by the first intermediate transport unit 24. 22 delivery is performed. Similarly, a second intermediate transport unit 26 is provided between the drawing unit 14 and the drying unit 16. The recording medium 22 is transferred from the drawing unit 14 to the drying unit 16 by the second intermediate transport unit 26. Is done. Further, a third intermediate transport unit 28 is provided between the drying unit 16 and the exposure curing unit 18, and the recording medium 22 from the drying unit 16 to the exposure curing unit 18 is provided by the third intermediate transport unit 28. Delivery takes place.

  Hereinafter, each part of the inkjet recording apparatus 1 (the paper feeding unit 10, the treatment liquid application unit 12, the drawing unit 14, the drying unit 16, the exposure curing unit 18, the discharge unit 20, the first to third intermediate conveyance units 24 and 26, 28) will be described.

(Paper Feeder)
The paper feed unit 10 is a mechanism that supplies the recording medium 22 to the drawing unit 14. The paper feed unit 10 is provided with a paper feed tray 50, and the recording medium 22 is fed from the paper feed tray 50 to the processing liquid application unit 12 one by one.

(Processing liquid application part)
The processing liquid application unit 12 is a mechanism that applies the processing liquid to the recording surface of the recording medium 22. The treatment liquid includes a color material aggregating agent that agglomerates or deposits the color material (pigment) in the ink applied by the drawing unit 14, and the ink comes into contact with the color material when the treatment liquid comes into contact with the ink. Separation from the solvent is facilitated. A more detailed description of the treatment liquid will be described later.

  As shown in FIG. 1, the treatment liquid application unit 12 includes a transfer drum 52, a treatment liquid drum 54, a treatment liquid application device 56, an IR heater 58, and a hot air blowing nozzle 60. The transfer drum 52 is disposed between the paper feed tray 50 of the paper feed unit 10 and the processing liquid drum 54 and includes a claw-shaped holding means (such as a gripper) on the outer peripheral surface thereof. Is driven to rotate. The recording medium 22 fed from the paper feed unit 10 is received by the transfer drum 52 and transferred to the processing liquid drum 54.

  The treatment liquid drum 54 is a drum that holds and rotates the recording medium 22 and is driven to rotate. Further, the processing liquid drum 54 includes a claw-shaped holding means 55 on the outer peripheral surface thereof, and the holding means 55 can hold the tip of the recording medium 22. The recording medium 22 is rotated and conveyed by rotating the processing liquid drum 54 with the tip held by the holding means 55. A processing liquid coating device (corresponding to a coating device) 56, an IR heater 58, and a hot air blowing nozzle 60 are provided outside the processing liquid drum 54 so as to face the peripheral surface thereof. The treatment liquid coating device 56, the IR heater 58, and the hot air blowing nozzle 60 are sequentially arranged from the upstream side in the rotation direction of the treatment liquid drum 54 (counterclockwise direction in FIG. 1). The processing liquid is applied to the recording surface by the processing liquid application device 56. The film thickness of the treatment liquid is desirably sufficiently smaller than the droplet diameter of ink ejected from the inkjet heads 72M, 72K, 72C, 72Y of the drawing unit 14. For example, when the ink droplet ejection amount is 2 pl, the average droplet diameter is 15.6 μm. At this time, when the film thickness of the processing liquid is large, the ink dots float in the processing liquid without contacting the surface of the recording medium 22. Therefore, in order to obtain a landing dot diameter of 30 μm or more when the ink droplet ejection amount is 2 pl, it is desirable that the film thickness of the treatment liquid is 3 μm or less.

The recording medium 22 coated with the treatment liquid by the treatment liquid application device 56 is conveyed to the positions of the IR heater 58 and the hot air blowing nozzle 60. The IR heater 58 is controlled to a high temperature (for example, 180 ° C.), and the hot air blowing nozzle 60 blows the high temperature (for example, 70 ° C.) warm air toward the recording medium 22 at a constant air volume (for example, 9 m ³ / min). Composed. By the heating by the IR heater 58 and the hot air blowing nozzle 60, water in the solvent of the processing liquid is evaporated, and a thin film layer of the processing liquid is formed on the recording surface. By thinning the treatment liquid in this way, the dots of ink that are ejected by the drawing unit 14 come into contact with the recording surface of the recording medium 22 to obtain the required dot diameter, and the thinned treatment liquid component Reacts with the colorant to cause aggregation of the coloring material, and an effect of fixing to the recording surface of the recording medium 22 is easily obtained. The processing liquid drum 54 may be controlled to a predetermined temperature (for example, 50 ° C.).

(Drawing part)
As shown in FIG. 1, the drawing unit 14 includes a drawing drum 70 and ink jet heads 72M, 72K, 72C, and 72Y that are disposed in proximity to a position facing the outer peripheral surface of the drawing drum 70. The inkjet heads 72M, 72K, 72C, and 72Y correspond to inks of four colors, magenta (M), black (K), cyan (C), and yellow (Y), and are upstream in the rotation direction of the drawing drum 70. Arranged in order from the side.

  The drawing drum 70 is a drum that holds the recording medium 22 on its outer peripheral surface and rotates and conveys the recording medium 22 and is driven to rotate. Further, the drawing drum 70 includes a claw-shaped holding unit 71 on the outer peripheral surface thereof, and the holding unit 71 can hold the leading end of the recording medium 22. The recording medium 22 is rotated and conveyed by rotating the drawing drum 70 with the leading end held by the holding means 71. At this time, the recording medium 22 is transported so that the recording surface faces outward, and ink is applied to the recording surface from the inkjet heads 72M, 72K, 72C, 72Y.

  The inkjet heads 72M, 72K, 72C, and 72Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area in the recording medium 22, and the ink ejection surfaces thereof are arranged on the ink ejection surface. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each inkjet head 72M, 72K, 72C, 72Y is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 22 (the rotation direction of the drawing drum 70).

  Corresponding color ink cassettes are attached to each of the inkjet heads 72M, 72K, 72C, 72Y. The ink droplets are ejected from the inkjet heads 72M, 72K, 72C, 72Y toward the recording surface of the recording medium 22 held on the outer peripheral surface of the drawing drum 70. As a result, the ink comes into contact with the treatment liquid applied to the recording surface in advance by the treatment liquid application unit 12, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. Thereby, the color material flow on the recording medium 22 is prevented, and an image is formed on the recording surface of the recording medium 22. At that time, since the drawing drum 70 of the drawing unit 14 is structurally separated from the processing liquid drum 54 of the processing liquid applying unit 12, the processing liquid may adhere to the ink jet heads 72M, 72K, 72C, 72Y. In addition, the cause of ink ejection failure can be reduced.

  In addition, as an example of the reaction between the ink and the treatment liquid, using a mechanism in which an acid is contained in the treatment liquid and the pigment dispersion is destroyed and aggregated by lowering the pH, the color material bleeds, the color mixture between the inks of each color, and the liquid upon landing of the ink droplet It is conceivable to avoid droplet ejection interference due to coalescence.

  In addition, the droplet ejection timing of each of the inkjet heads 72M, 72K, 72C, 72Y is synchronized with an encoder that detects the rotational speed disposed on the drawing drum 70. Thereby, the landing position can be determined with high accuracy. Further, the fluctuation of the speed due to the fluctuation of the drawing drum 70 or the like is learned in advance, and the droplet ejection timing obtained by the encoder 91 is corrected to obtain the fluctuation of the drawing drum 70, the accuracy of the rotation axis, and the speed of the outer peripheral surface of the drawing drum 70. Irregular droplet ejection can be reduced without depending on it.

  Furthermore, maintenance operations such as cleaning the nozzle surfaces of each of the inkjet heads 72M, 72K, 72C, and 72Y and discharging the thickened ink may be performed by retracting the head unit from the drawing drum 70.

  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 special colors are used as necessary. Ink 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.

  In the present invention, it is preferable to provide a region where no image is formed at the rear end of the recording medium 22 in the conveyance direction. By providing an area where no image is formed, the recording medium can be brought into close contact with the drying drum 76 by pressing the area with the non-contact type recording medium suppressing means in the drying unit 16, and the image Does no damage.

(Drying part)
The drying unit 16 is a step of drying moisture contained in the solvent separated by the color material aggregating action. The drying drum 76 and a first IR heater disposed at a position facing the outer peripheral surface of the drying drum 76. 78, a hot air jet nozzle 80, a second IR heater 82, and a blower nozzle 83 as non-contact type recording medium restraining means for bringing the recording medium 22 into close contact with the drying drum 76. The first IR heater 78 is provided upstream of the hot air jet nozzle 80 in the rotation direction of the drying drum 76 (counterclockwise direction in FIG. 1), and the second IR heater 82 is jetted of hot air. Provided downstream of the nozzle 80. The blower nozzle 83 is provided on the most upstream side of the drying unit 16 and on the upstream side of the first IR heater 78 in order to bring the recording medium 22 and the drying drum 76 into close contact with each other.

  The drying drum 76 is a drum that holds and rotates the recording medium 22 on its outer peripheral surface, and the rotation of the drying drum 76 is controlled by a motor driver (not shown). The recording medium 22 is rotated and conveyed by rotating the drying drum 76 with the tip held by the holding unit 77. At that time, the recording surface of the recording medium 22 is conveyed so as to face outward, and the recording surface is dried by the IR heater 78 and the hot air jet nozzle 80.

The hot air jet nozzle 80 is configured to blow hot air controlled at a predetermined temperature (for example, 50 ° C. to 70 ° C.) toward the recording medium 22 with a constant air volume (12 m ³ / min), and an IR heater. Each of 78 is controlled to a predetermined temperature (for example, 180 ° C.). The hot air jet nozzle 80 and the IR heater 78 evaporate moisture contained in the printing surface of the recording medium 22 held on the drying drum 76, and a drying process is performed. At that time, since the drying drum 76 of the drying unit 16 is structurally separated from the drawing drum 70 of the drawing unit 14, in the inkjet heads 72 </ b> M, 72 </ b> K, 72 </ b> C, 72 </ b> Y, the head meniscus portion is dried by thermal drying. Ink ejection failure can be reduced. Moreover, there is a degree of freedom in setting the temperature of the drying unit 16, and an optimal drying temperature can be set.

  The evaporated water may be discharged out of the apparatus together with air by a discharge means (not shown). Further, the recovered air may be cooled by a cooler (radiator) or the like and recovered as a liquid.

  The drying drum 76 has suction holes provided on the outer peripheral surface thereof, and has suction means for performing suction from the suction holes. As a result, the recording medium 22 can be held in close contact with the peripheral surface of the drying drum 76. Further, by performing negative pressure suction, the recording medium can be constrained to the conveyance body, so that the recording medium can be prevented from being clogged.

  Moreover, it is preferable that the outer periphery of the drying drum 76 is controlled to a predetermined temperature. Drying is promoted by heating from the back surface of the recording medium 22, and image destruction at the time of fixing can be prevented. The range of the surface temperature of the drying drum 76 is preferably 50 ° C. or higher, more preferably 60 ° C. or higher. Further, the upper limit is not particularly limited, but is preferably 75 ° C. or lower from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 76 (preventing burns due to high temperature).

  The adsorption force of the carrier can be expressed by (opening area) × (pressure per unit area). The suction force can be further increased by increasing the area occupied by the suction holes in the recording medium suction holding region, that is, the aperture ratio.

  The opening ratio of the suction holes is preferably 1% or more and 75% or less, more preferably 10% or more and 50% or less, with respect to the contact area between the conveyance body and the recording medium. By setting the aperture ratio within the above range, it is possible to prevent the suppression of cockle and improve the drying performance. If the aperture ratio is less than 1%, expansion deformation of the recording medium due to water absorption after recording cannot be sufficiently suppressed. On the other hand, if it exceeds 75%, the contact area between the back surface of the recording medium and the surface of the conveying member is reduced, so that sufficient drying performance cannot be obtained even in the adsorption holding state. Further, since drying is not promoted, cockle tends to deteriorate.

  The aperture ratio can be controlled by the diameter of the suction holes, the hole pitch, and the shape and arrangement of the holes. The hole diameter is preferably 0.4 mm or more in order to secure the aperture ratio and increase the suction force, and is designed to be 1.5 mm or less so that the recording medium does not have a dent mark (suction mark) due to negative pressure suction. It is preferable to do. In addition, the hole pitch is preferably 0.1 mm or more in order to prevent thermal deformation and rigidity of the surface of the carrier, and if the gap between the holes is too far away, the effect of inhibiting deformation of the recording medium is insufficient. Since wrinkles occur, it is preferable to design to 10 mm or less in order to prevent such wrinkles.

  If the shape of the suction hole is a corner (acute angle), stress concentrates on the corner, so that the corner is preferably rounded. Further, in the rotary conveyance body, the deformation amount of the recording medium due to the adsorption pressure is larger in the axial direction than in the circumferential direction. Therefore, the suction hole may have an elliptical shape or a long hole shape in which the circumferential direction is the major axis direction and the axial direction is the minor axis direction, so that the circumferential deformation and the axial deformation of the recording medium can be made uniform. it can.

  In the present invention, in order to stably hold the recording medium 22 in contact with the drying drum 76 having a curvature, a blowing nozzle 83 is provided as a non-contact type recording medium restraining means. As the non-contact type recording medium holding means, a blowing means such as the blowing nozzle 83 shown in FIG. 1 can be used. As the air blowing means, conventionally known air blowing means such as a blower and a fan can be used. By suppressing the rear end of the recording medium by the non-contact type recording medium suppressing means, the recording medium can be pressed and brought into close contact with the carrier having the curvature. The formed image can be thickened by applying a treatment liquid containing a flocculant by the treatment liquid application unit 12. Accordingly, when the rigidity of the recording medium is high, even if the pressing force by the non-contact type recording medium suppressing means is increased, the recording medium can be conveyed without damaging the image. In addition, when the recording medium has low rigidity, when the suction is performed from the recording medium conveyance body side, the suction of the suction hole portion may cause the recording medium to be dented, the ink may flow, and uneven density of the image may occur. However, since the viscosity can be increased by aggregating the ink, the density unevenness of the image can be suppressed.

  In FIG. 2, the enlarged view of the drying part 16 is shown. As described above, the drying unit 16 has suction holes provided on the outer peripheral surface of the drying drum 76, and can control the suction start position of the recording medium 22 through the suction holes. The suction start position is preferably set so that the range indicated by the arrow on the outer periphery of the drying drum 76 in FIG. 2 is the suction start position. The positional relationship between the pressing position and the suction start position is preferably controlled by the diameter of the drum, the size of the recording medium, and the rigidity. The suction start position is preferably downstream in the transport direction with respect to the air blowing position as the recording medium has lower rigidity. The recording medium with low rigidity can be sucked after sufficiently suppressing wrinkles by setting the suction to the downstream in the transport direction. If the recording medium has a high rigidity, the suction can be stably performed on the recording medium having a high rigidity by starting the suction before pressing by the non-contact type recording medium restraining means.

  The control of the suction start position with respect to the pressing position can control the timing of starting the suction by the suction means of the drying drum 76 when the position of the non-contact type recording medium holding means is fixed. Further, when the suction timing is fixed, it can be controlled by installing the blower nozzle 83 so as to be movable in the transport direction.

  The pressing force (wind force) of the non-contact type recording medium holding means is preferably controlled by the rigidity of the recording medium. By controlling the pressing force, image damage due to strong wind can be avoided. Further, the pressing force (wind force) of the non-contact type recording medium holding means can be adjusted according to the position of the recording medium. For example, the area where the pressing force (wind force) is increased as it goes to the rear end of the recording medium in the conveying direction, or the pressing (air blowing) is performed only when the recording medium passes through the rear end, and the air blowing is not performed otherwise. Intermittent ventilation can also be performed. By controlling the pressing force, it is possible to reduce the time during which the image is pressed by the non-contact type recording medium suppressing means and to avoid unnecessary pressing, so that damage to the image can be reduced.

  It is preferable that the wind speed by a ventilation means is the range of 5-200 [m / s]. If the wind speed is less than 5 [m / s], the effect of suppressing wrinkles is insufficient, and if it is greater than 200 [m / s], the amount of ink applied to the image portion is large and the image is not dried. There is a concern of being damaged by air blow. With respect to an image in a dry state, the air can be blown without any particular limitation. The measurement of the wind speed is performed by measuring the wind speed V [m / s] at a distance from the wind outlet (such as an air nozzle jet outlet) of the blowing means by a distance from the recording medium surface. As an anemometer, for example, Anemo Master 6004 manufactured by Kanomax Co., Ltd. can be used.

The air volume (air flow rate) required for the blowing means varies depending on the width and thickness of the recording medium, but for example, in the range of 0.1 to 2 [m ³ / min] for a chrysanthemum half-size recording medium. Preferably there is. The air volume is calculated from the measured wind speed using the following formula. The wind speed (air volume) can be adjusted with a regulator if it is compressed air, or can be adjusted by controlling the blower input power source if it is a blower.

Q = V × A × 60 [m ³ / min]
Q: Air volume [m ³ / min], V: Wind speed [m / s], A: Air blowing area [m ² ]
For example, the non-contact type suppression means can perform blowing by connecting the blowing nozzles 83 (nozzle width: 50 mm) shown in FIG. 3 in the recording medium width direction, but the desired wind speed (air volume). Can be used without particular limitation on the shape and material of the member. However, regarding the material, when the non-contact type recording medium suppressing means is provided near the drying means, or as described below, it is preferably a heat resistant material.

  FIG. 3B is a diagram showing the shape of the nozzle opening 83a. FIG. 3B is a diagram in which a plurality of fine round holes (nozzle diameter: 1.2 mm) are arranged in the opening 83a, but the shape and size are not particularly limited, and in order to spray a wider area, The nozzle diameter of the opening 83a can be increased, and the shape is not limited to a round shape, but may be a rectangle.

  The wind speed (air volume) distribution can also be changed by individual nozzles. For example, the image portion can increase the wind speed and suppress floating, and the non-image portion can decrease the wind speed. Further, when the size of the recording medium is different, air can be blown only at a portion corresponding to the length in the width direction of the recording medium. By supplying the wind to the area where the recording medium on the side surface of the transport body does not pass, it is possible to prevent the wind from flowing around the back surface of the recording medium and causing the recording medium to float or flutter.

  FIG. 4 is a plan view showing the orientation and arrangement of the individual nozzles 83. The wind is ejected toward the recording medium 22. FIG. 4A shows an arrangement of normal nozzles that are not rotated. Each nozzle 83 can be rotated. For example, as shown in FIG. 4B, both ends from the center of the recording medium or one end as shown in FIG. 4C. And can be rotated to tilt to the other end. With the arrangement shown in FIGS. 4B and 4C, the wrinkles can be scattered at the width direction end portion of the recording medium, or can be released to the width direction end portion.

  Further, the individual nozzles do not have to be arranged in the same row with respect to the width direction of the recording medium. FIG. 4D shows the direction from the center of the recording medium to both ends, or FIG. As shown, the wind can be arranged in order from one end to the other end. With such an arrangement, it is possible to improve the effect of further wrinkling the wrinkles at the end portions in the width direction of the recording medium or letting them escape to the end portions in the width direction.

  4A to 4E have been described in the form of a plurality of nozzles 83, but as shown in FIG. 4F, the length of the opening is the same as the width direction of the recording medium 22. Alternatively, the nozzle 83 can be used. By using one nozzle, the wind speed (air volume) can be made uniform, and for example, wrinkles can be prevented from being concentrated locally.

  As shown in FIG. 2, it is preferable that the wind direction of the air blown by the blower nozzle 83 is arranged so as to blow in an oblique direction from the front end side to the rear end side in the conveyance direction of the recording medium 22. Thereby, the recording medium 22 can be made to follow the drying drum 76 and the pressing effect by wind can be improved. The blowing direction is preferably such that the angle θ formed by the blowing direction of the wind and the normal of the point where the wind contacts the recording medium 22 (drying drum 76) is 0 ° or more and 75 ° or less. An inclination exceeding the above range is not preferable because the suppressing effect is insufficient.

  Further, the blow nozzle 83 can be configured to be able to adjust the angle θ. For example, when the rigidity of the recording medium is low, the emphasis is on keeping the paper along the surface of the conveyance body, and the angle θ is increased, and when the rigidity is high, it is important to attach the recording medium to the surface of the conveyance body. Thus, the angle θ can be reduced. As shown in FIG. 4, when the non-contact type recording medium restraining means includes a plurality of blower nozzles 83 and the like, the angle θ can be controlled by each blower nozzle 83.

  Further, the non-contact type recording medium suppressing means may also serve as the drying means. Drying can be performed by using a drying fan that incorporates a heater and blows hot air from an air nozzle toward the recording medium as a non-contact type recording medium suppressing means. The drying condition is a drying unit in which drying fans are arranged in a plurality of rows in the carrying direction. The air flow of the drying fan in the first row is increased, the air speed is increased by narrowing the opening of the air nozzle, or the spray angle is set in the carrying direction. This can be done by tilting upstream.

  The adsorption is preferably carried out stepwise from the downstream side in the transport direction (the recording medium leading end side). By performing adsorption in stages, it becomes possible to absorb the area immediately after correction of wrinkles and floats through the non-contact type recording medium suppression means without taking time, so it is more reliable and uniform. Can be adsorbed. If adsorption of the entire adsorption area of the adsorption surface can only be performed at once, if the size of the recording medium is large, it will take time after correction by the non-contact type recording medium suppressing means at the leading end of the recording medium, and again In some cases, wrinkles or floats occur, or at the rear end of the recording medium, the wrinkles or floats are not corrected and are attracted to the transport body. Therefore, by performing the adsorption stepwise, the conveyance body can be adsorbed in a more preferable state, and the conveyance can be performed stably.

  The air blown from the blowing means is preferably heated. By blowing the heated air, the drying of the recording medium 22 can be accelerated. Therefore, when the rigidity of the recording medium is low, the image is destroyed by suppressing the cuckling generated in the recording medium 22 and the drying. This can be prevented.

  The blowing means is preferably divided into a plurality of areas in the width direction of the recording medium 22, and the pressing force (wind force) in each area is preferably controllable according to the image data. Similarly, the suction means is preferably divided into a plurality of areas in the width direction of the recording medium 22. By controlling the pressing force by the blowing means and the suction force by the suction means according to the image data, it is possible to improve the effect of suppressing wrinkles at locations where the droplet ejection amount is large. Further, it is preferable that each of the blowing unit and the suction unit increase the pressing force and the suction force in the area of the central portion in the width direction of the recording medium 22. Since wrinkles are likely to occur at the central portion of the recording medium 22, wrinkles at the central portion can be suppressed by increasing the pressing force and suction force at the central portion in the width direction of the recording medium 22. Wrinkling of the entire medium can be prevented.

<< Second Embodiment >>
FIG. 5 is a schematic diagram of a recording medium transport apparatus according to the second embodiment. In the recording medium conveying apparatus according to the second embodiment, a blowing nozzle (non-contact type recording medium suppressing means) 283 is provided inside an intermediate conveying body (transfer cylinder) 30 connected in front of the drying drum 76. This is different from the first embodiment.

  By providing the blower nozzle 283 in the intermediate conveyance body 30, the entire inkjet recording apparatus 1 can be saved. Further, by providing the non-contact type recording medium holding means inside the intermediate conveyance body 30, in the case of thin paper, it is possible to press the upstream side before being delivered to the drying drum 76, so that the upstream side of the drying drum 76. Adsorption can be started on the side. Therefore, in the drying drum 76, the heating efficiency from the back surface can be improved. Further, when the drawing drum 70 is used, it is possible to reduce the influence of the flutter at the rear end of the recording medium.

  In addition, about the pressing force (wind force) of a wind by a ventilation means, and a ventilation direction, it can carry out by the method similar to 1st Embodiment.

«Third embodiment»
FIG. 6 is a schematic diagram of a recording medium transport apparatus according to the third embodiment. In the recording medium conveyance device according to the third embodiment, the non-contact type recording medium holding unit is arranged on the outer peripheral surface of the first non-contact type recording medium holding unit 283 provided in the intermediate conveyance body 30 and the drying drum 76. The second embodiment is different from the first embodiment and the second embodiment in that the second non-contact type recording medium restraining means 83 is provided.

  As shown in the third embodiment, there are two blowing nozzles (first non-contact type recording medium holding means) 283, two blowing nozzles (second non-contact type recording medium holding means) 83 and non-contact type recording medium holding means. By providing at the location, the recording medium 22 can be more reliably brought into close contact with the drying drum 76 and can be stably conveyed.

  The recording medium conveying apparatus according to the third embodiment can be performed in the same manner as in the first embodiment and the second embodiment with respect to the pressure (wind force) of the wind by the blow nozzle and the blow direction.

  In the third embodiment, the upstream side of the air blowing position at the suction start position is the upstream side of the first non-contact type recording medium restraining means 283, and the second non-contact with the downstream side of the air blowing position. This is on the downstream side of the type recording medium holding means 83. The same position as the air blowing means means the same position as the position where the air is blown by the first air blowing means or the second air blowing means.

  The example of the recording medium transport apparatus has been described by taking the drying unit of the ink jet recording apparatus as an example, but the present invention is not limited to this, and the recording medium needs to be adsorbed to the curved surface transport body without wrinkling or floating. In some cases, the present invention can be applied. For example, the present invention is applied to other configurations of an ink jet recording apparatus, to improve paper passing by preventing wrinkles and floating of the recording medium on the drawing drum, and to suppress wrinkles at the heat roller fixing nip by preventing the recording medium from floating on the fixing drum. be able to. In particular, in the drying section, an image is formed on the recording medium by the drawing section 14, and the pressing means by the roller cannot be used. Therefore, the pressing by the non-contact type recording medium suppressing means of the present invention is particularly effective. .

(Exposure cured part)
The exposure curing unit 18 includes a UV lamp 88 and an inline sensor 90. The UV lamp 88 and the in-line sensor 90 are disposed at a position facing the peripheral surface of the exposure / curing drum 84, and are sequentially disposed from the upstream side in the rotation direction of the exposure / curing drum 84.

  The exposure curing drum 84 is a drum that holds the recording medium 22 on its outer peripheral surface and rotates and conveys the recording medium 22, and is driven to rotate. Further, the exposure curing drum 84 is provided with a claw-shaped holding means 85 on its outer peripheral surface, and the holding means 85 can hold the leading end of the recording medium 22. The recording medium 22 is rotated and conveyed by rotating the exposure curing drum 84 in a state where the leading end is held by the holding unit 85. At that time, the recording surface of the recording medium 22 is conveyed so that it faces outward, and the recording surface is exposed and cured by the UV lamp 88 and inspected by the in-line sensor 90.

  The UV lamp 88 irradiates the dried ink with UV light, whereby the actinic ray curable resin contained in the ink is cured and the ink is formed into a film. As the UV lamp 88, various ultraviolet light sources such as a metal halide lamp, a high-pressure mercury lamp, a black light, a cold cathode lamp, and a UV-LED can be used.

  The peak wavelength of ultraviolet rays irradiated by the ultraviolet light source 190 is preferably 200 to 600 nm, more preferably 300 to 450 nm, and still more preferably 350 to 450 nm, although it depends on the absorption characteristics of the ink composition.

The irradiation energy of the ultraviolet light source 190, preferably 2000 mJ / cm ² or less, more preferably from 10 to 2000 mJ / cm ^2, more preferably from 20~1000mJ / cm ^2, particularly preferably 50 to 800 mJ / Cm ² .

  In the ink jet recording apparatus of the present invention, it is appropriate to irradiate the recording surface of the recording medium with ultraviolet rays for 0.01 to 10 seconds, more preferably for 0.1 to 2 seconds.

  Further, the exposure curing drum 84 may be controlled to a predetermined temperature. Thereby, the curing sensitivity of the ink can be improved, and the ink can be suitably cured and formed into a film with a low irradiation intensity.

  On the other hand, the in-line sensor 90 is a measuring unit for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 22, and a CCD line sensor or the like is applied.

(Discharge part)
As shown in FIG. 1, a discharge unit 20 is provided following the exposure curing unit 18. The discharge unit 20 includes a discharge tray 92. Between the discharge tray 92 and the exposure curing drum 84 of the exposure curing unit 18, a transfer drum 94, a conveyance belt 96, and a stretching roller 98 are in contact with each other. Is provided. The recording medium 22 is sent to the transport belt 96 by the transfer drum 94 and discharged to the discharge tray 92.

(Intermediate transport section)
Next, the structure of the first intermediate transport unit 24 will be described. Note that the second intermediate conveyance unit 26 and the third intermediate conveyance unit 28 have the same configuration as the first intermediate conveyance unit 24, and a description thereof will be omitted.

  The first intermediate transport unit 24 includes an intermediate transport body 30. The intermediate conveyance body 30 is a drum for receiving the recording medium 22 from the preceding drum, rotating and conveying it to the subsequent drum, and is rotatably attached. Further, the intermediate transport body 30 is rotated by a motor (not shown).

  Claw-shaped holding means are provided at 90 ° intervals on the outer peripheral surface of the intermediate conveyance body 30. The holding unit rotates while drawing a circular locus, and the tip of the recording medium 22 is held by the operation of the holding unit. Accordingly, the recording medium 22 can be rotated and conveyed by rotating the intermediate conveyance body 30 with the holding means holding the tip of the recording medium 22. The recording surface of the recording medium may be conveyed in a non-contact manner by providing a plurality of air outlets on the surface of the intermediate carrier 30 and blowing out air from the air outlets.

  The recording medium 22 transported by the first intermediate transport unit 24 is transferred to the subsequent drum (that is, the drawing drum 70). At this time, the recording medium 22 is delivered by synchronizing the holding means of the intermediate transport unit 24 and the holding means of the drawing unit 14. The transferred recording medium 22 is held and drawn by the drawing drum 70.

  Further, the first intermediate transport unit 24 has a hot air drying means (drying means) (not shown) inside, and hot air is blown to the recording surface side of the recording medium facing inside during the transport to the surface. The applied treatment liquid may be dried.

  Similarly, the second and third intermediate transport units 26 and 28 have hot air drying means (drying means) (not shown) inside, and hot air is applied to the recording surface side of the recording medium facing inside during transport. May be sprayed to dry the ink deposited on the surface.

(Description of control system)
FIG. 7 is a principal block diagram showing the system configuration of the inkjet recording apparatus 1. The ink jet recording apparatus 1 includes a communication interface 120, a system controller 122, a print controller 124, a treatment liquid application controller 126, a first intermediate transport controller 128, a head driver 130, a second intermediate transport controller 132, and a drying controller 134. , A third intermediate conveyance control unit 136, a fixing control unit 138, an inline sensor 90, an encoder 91, a motor driver 142, a memory 144, a heater driver 146, an image buffer memory 148, a suction control unit 149, a blower control unit 162, and the like. Yes.

  The communication interface 120 is an interface unit that receives image data sent from the host computer 150. 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 150 is taken into the inkjet recording apparatus 1 via the communication interface 120 and temporarily stored in the memory 144.

  The system controller 122 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 1 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 122 includes the communication interface 120, the treatment liquid application controller 126, the first intermediate transport controller 128, the head driver 130, the second intermediate transport controller 132, the drying controller 134, and the third intermediate transport controller 136. , Fixing control unit 138, memory 144, motor driver 142, heater driver 146, suction control unit 149, blower control unit 162, etc., and control of communication with host computer 150, read / write control of memory 144, etc. At the same time, a control signal for controlling the motor 152 and the heater 154 of the transport system is generated.

  The memory 144 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 122. The memory 144 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The ROM 145 stores programs executed by the CPU of the system controller 122 and various data necessary for control. The ROM 145 may be a non-rewritable storage unit, or may be a rewritable storage unit such as an EEPROM. The memory 144 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 142 is a driver that drives the motor 152 in accordance with an instruction from the system controller 122. In FIG. 7, the motors arranged in the respective units in the apparatus are represented by reference numeral 152 as a representative. For example, the motor 152 shown in FIG. 7 includes a transfer drum 52, a treatment liquid drum 54, a drawing drum 70, a drying drum 76, an exposure / curing drum 84, a transfer drum 94, and the like. A pump 75 drive motor for sucking negative pressure from the suction holes, a motor for a retraction mechanism of the head units of the ink jet heads 72C, 72M, 72Y, 72K, and the like are included.

  The heater driver 146 is a driver that drives the heater 154 in accordance with an instruction from the system controller 122. In FIG. 7, a plurality of heaters provided in the inkjet recording apparatus 1 are represented by reference numeral 154 as a representative. For example, the heater 154 shown in FIG. 7 includes a preheater (not shown) for heating the recording medium 22 to an appropriate temperature in the paper feeding unit 10 in advance.

  The print control unit 124 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 144 under the control of the system controller 122, and the generated print. It is a control unit that supplies data (dot data) to the head driver 130. Necessary signal processing is performed in the print control unit 124, and the ejection amount and ejection timing of the ink droplets of the inkjet head 100 are controlled via the head driver 130 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 124 includes an image buffer memory 148, and image data, parameters, and other data are temporarily stored in the image buffer memory 148 when image data is processed in the print control unit 124. In FIG. 7, the image buffer memory 148 is shown in a mode associated with the print control unit 124, but it can also be used as the memory 144. Also possible is an aspect in which the print control unit 124 and the system controller 122 are integrated to form a single processor.

  An outline of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 120 and stored in the memory 144. At this stage, for example, RGB image data is stored in the memory 144.

  In the inkjet recording apparatus 1, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the memory 144 is sent to the print control unit 124 via the system controller 122, and the print control unit 124 performs halftoning processing using a threshold matrix, an error diffusion method, or the like. Is converted into dot data for each ink color.

  That is, the print control unit 124 performs a process of converting the input RGB image data into dot data of four colors K, C, M, and Y. Thus, the dot data generated by the print control unit 124 is stored in the image buffer memory 148.

  The head driver 130 is a drive signal for driving the actuator 116 corresponding to each nozzle 102 of the inkjet head 100 based on print data (that is, dot data stored in the image buffer memory 148) given from the print control unit 124. Is output. The head driver 130 may include a feedback control system for keeping the head driving condition constant.

  When the drive signal output from the head driver 130 is applied to the inkjet head 100, ink is ejected from the corresponding nozzle 102. An image is formed on the recording medium 22 by controlling the ink ejection from the inkjet head 100 while conveying the recording medium 22 at a predetermined speed.

  Further, the system controller 122 includes a processing liquid application control unit 126, a first intermediate conveyance control unit 128, a second intermediate conveyance control unit 132, a drying control unit 134, a third intermediate conveyance control unit 136, a fixing control unit 138, and suction control. The unit 149 and the air blow control unit 162 are controlled.

  The treatment liquid application control unit 126 controls the operation of the treatment liquid application device 56 of the treatment liquid application unit 12 in accordance with an instruction from the system controller 122.

  The first intermediate conveyance control unit 128 controls the operation of the intermediate conveyance body 30 of the first intermediate conveyance unit 24 in accordance with an instruction from the system controller 122. Specifically, in the intermediate transport body 30, the rotational drive of the intermediate transport body 30 itself, the rotation of the holding means provided in the intermediate transport body 30, and the like are controlled. The second intermediate transfer control unit 132 and the third intermediate transfer control unit 136 also perform the same control as the first intermediate transfer control unit 128.

  The suction control unit 149 and the air blowing control unit 162 are a suction unit and an air blowing unit provided in the drying drum 76 for conveying the image-formed recording medium 22 in close contact with the drying drum 76 according to the control of the system controller 122. Control 83 is performed. In the suction unit and the air blowing unit 83, the suction start position by the suction unit and the air blowing position by the air blowing unit 83 are controlled by the rigidity of the recording medium 22. Control of the suction start position by the suction control unit 149 can be performed by operating the pump 75 when the recording medium passes through the suction start position. The suction force by the suction unit and the pressing force (wind force) by the blowing unit are controlled according to the type of the recording medium 22. Control can also be performed by recording the suction force and pressing force corresponding to the rigidity of the recording medium in the ROM 145 and directly inputting the type of the recording medium 22 to be used by a personal computer (not shown).

  Further, based on the image data in the memory 144 or the print data (dot data) generated by the print control unit 124, the suction force by the suction unit and the pressing force (wind force) by the blower unit are controlled. Further, the suction force and the pressing force (wind force) in the width direction of the recording medium are controlled.

[Ink composition]
The ink composition in the present invention contains a pigment, and can be constituted by using a dispersant, a surfactant, and other components as necessary. In the present invention, in order to improve the durability of an image, it is possible to make the ink difficult to spread on the recording medium by increasing the viscosity or surface tension of the ink liquid. For example, among the following components, increasing dispersed particle components such as pigments and resin particles is preferable because it not only increases the viscosity of the ink liquid, but also accelerates aggregation and can be expected to improve the strength of the aggregate itself. .

(Pigment)
The ink composition in the invention contains at least one pigment as a color material component. There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient. The pigment is preferably a pigment that is almost insoluble or hardly soluble in water from the viewpoint of ink colorability.

(Dispersant)
The ink composition of the present invention can contain at least one dispersant. The pigment dispersant may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, and particularly preferably 10,000. 000 to 40,000.

  The acid value of the polymer dispersant is preferably 100 or less mgKOH / g or less from the viewpoint of good aggregation when the treatment liquid comes into contact. Furthermore, the acid value is more preferably from 25 to 100 mgKOH / g, further preferably from 25 to 80, and particularly preferably from 30 to 65. When the acid value of the polymer dispersant is 25 or more, the stability of self-dispersibility is improved.

  The polymer dispersant preferably contains a polymer having a carboxyl group from the viewpoint of self-dispersibility and aggregation rate when the treatment liquid comes into contact. The polymer dispersant has a carboxyl group and an acid value of 25 to 80 mgKOH / g. More preferably.

  In the present invention, from the viewpoint of image light resistance and quality, it is preferable to contain a pigment and a dispersant, more preferably an organic pigment and a polymer dispersant, and a polymer dispersant containing an organic pigment and a carboxyl group. It is particularly preferred that Moreover, it is preferable that a pigment is coat | covered with the polymer dispersing agent which has a carboxyl group from a cohesive viewpoint, and is water-insoluble. Furthermore, from the viewpoint of cohesiveness, it is preferable that the acid value of the self-dispersing polymer particles described below is smaller than the acid value of the polymer dispersant.

  The average particle size of the pigment is preferably 10 to 200 nm, more preferably 10 to 150 nm, and even more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 10 nm or more, the light resistance is good. Further, the particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.

  The average particle size and particle size distribution of the pigment particles are determined by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is what

  You may use a pigment individually by 1 type or in combination of 2 or more types.

  The content of the pigment in the ink composition is preferably 1 to 25% by mass, more preferably 2 to 20% by mass, and more preferably 5 to 20% by mass with respect to the ink composition from the viewpoint of image density. Is more preferable, and 5 to 15% by mass is particularly preferable.

(Polymer particles)
The ink composition in the invention can contain at least one kind of polymer particles. The polymer particles have a function of fixing the ink composition by destabilizing and agglomerating and aggregating the ink to increase the viscosity of the ink when the polymer particles come into contact with a treatment liquid described later or a dried region thereof. The fixing property to the recording medium and the scratch resistance of the image can be further improved.

  In order to react with the aggregating agent, polymer particles having an anionic surface charge are used, and generally known latex is used as long as sufficient reactivity and ejection stability are obtained. It is preferable to use polymer particles.

<Self-dispersing polymer particles>
The ink composition in the invention preferably contains at least one kind of self-dispersing polymer particles as polymer particles. This self-dispersing polymer has a function of fixing the ink composition by destabilizing and agglomerating and thickening the ink when it comes into contact with a treatment liquid described later or a dried region thereof. Fixability of the composition to a recording medium and image scratch resistance can be further improved. Self-dispersing polymers are also preferred resin particles from the viewpoints of ejection stability and liquid stability (particularly dispersion stability) of the system containing the pigment.

  Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (especially acidic groups or salts thereof) of the polymer itself in the absence of other surfactants. Means water-insoluble polymer particles which do not contain free emulsifiers.

  The acid value of the self-dispersing polymer in the present invention is preferably 50 or less KOHmg / g or less from the viewpoint of good cohesiveness when the treatment liquid comes into contact. Furthermore, the acid value is more preferably 25 to 50 KOH mg / g, and still more preferably 30 to 50. When the acid value of the self-dispersing polymer is 25 or more, the stability of the self-dispersing property is improved.

  The self-dispersing polymer particles in the present invention preferably contain a polymer having a carboxyl group from the viewpoint of self-dispersibility and agglomeration speed when the treatment liquid comes into contact, and have a carboxyl group and an acid value of 25 to 25. More preferably, it contains a polymer of 50 KOH mg / g, more preferably a polymer having a carboxyl group and an acid value of 30 to 50 KOH mg / g.

  The molecular weight of the water-insoluble polymer constituting the self-dispersing polymer particles is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. Further preferred. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). For GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and as columns, TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as eluents. Use THF (tetrahydrofuran). The conditions are as follows: the sample concentration is 0.35 / min, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

  The average particle diameter of the self-dispersing polymer particles is preferably in the range of 10 nm to 400 nm, more preferably in the range of 10 to 200 nm, and still more preferably in the range of 10 to 100 nm. When the volume average particle size is 10 nm or more, the production suitability is improved, and when it is 1 μm or less, the storage stability is improved.

  The average particle size and particle size distribution of the self-dispersing polymer particles are measured by the dynamic light scattering method using Nanotrac particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Is required.

  The self-dispersing polymer particles can be used singly or in combination of two or more. The content of the self-dispersing polymer particles in the ink composition is preferably 1 to 30% by mass with respect to the ink composition from the viewpoint of aggregation rate and image glossiness, and 5 to 15 More preferably, it is mass%.

  In addition, the content ratio of the pigment and the self-dispersing polymer particles in the ink composition (for example, water-insoluble pigment particles / self-dispersing polymer particles) is 1/0 from the viewpoint of image scratch resistance and the like. 5 to 1/10 is preferable, and 1/1 to 1/4 is more preferable.

(Polymerizable compound)
The ink composition in the present invention can contain at least one water-soluble polymerizable compound that is polymerized by active energy rays.

The term “water-soluble” means that it can be dissolved in water at a certain concentration or higher, and it can be dissolved in water-based ink (preferably uniformly). Further, the solubility may be increased by adding a water-soluble organic solvent to be described later, and it may be dissolved (desirably uniformly) in the ink. Specifically, the solubility in water is preferably 10% by mass or more, and more preferably 15 % by mass or more.

  As the polymerizable compound, a nonionic or cationic polymerizable compound is preferable in that it does not interfere with the reaction between the flocculant, the pigment, and the polymer particles, and the solubility in water is 10% by mass or more (more preferably 15% by mass or more). The polymerizable compound is preferable.

  As the polymerizable compound in the present invention, a polyfunctional monomer is preferable from the viewpoint of enhancing scratch resistance, and a bifunctional to hexafunctional monomer is preferable, and from the viewpoint of compatibility between solubility and scratch resistance, bifunctional to tetrafunctional. Are preferred.

  A polymeric compound can be contained individually by 1 type or in combination of 2 or more types.

  The content of the polymerizable compound in the ink composition is preferably 30 to 300% by mass, more preferably 50 to 200% by mass, based on the total solid content of the pigment and the self-dispersing polymer particles. When the content of the polymerizable compound is 30% by mass or more, the image strength is further improved and the image has excellent scratch resistance, and when it is 300% by mass or less, it is advantageous in terms of pile height.

(Initiator)
The ink composition in the present invention may contain at least one initiator that initiates polymerization of the polymerizable compound by active energy rays with or without being contained in a treatment liquid described later. A photoinitiator can be used individually by 1 type or in mixture of 2 or more types or using together with a sensitizer.

  The initiator can contain a compound capable of initiating a polymerization reaction by active energy rays as appropriate. For example, the initiator starts generation of active species (radicals, acids, bases, etc.) by radiation or light, or electron beams. An agent (for example, a photopolymerization initiator) can be used.

  When the initiator is contained, the content of the initiator in the ink composition is preferably 1 to 40% by mass and more preferably 5 to 30% by mass with respect to the polymerizable compound. When the content of the initiator is 1% by mass or more, the scratch resistance of the image is further improved, which is advantageous for high-speed recording, and when it is 40% by mass or less, it is advantageous in terms of ejection stability.

(Water-soluble organic solvent)
The ink composition in the invention can contain at least one water-soluble organic solvent. The water-soluble organic solvent can obtain the effect of preventing drying, wetting or promoting penetration. In order to prevent drying, the ink adheres to and drys at the ink discharge port of the ejection nozzle and is used as an anti-drying agent to prevent clogging. For drying prevention and wetting, the vapor pressure is lower than that of water. A water-soluble organic solvent is preferred. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water.

  Anti-drying agents may be used alone or in combination of two or more. The content of the drying inhibitor is preferably in the range of 10 to 50% by mass in the ink composition.

  As a penetration accelerator, it is suitable for the purpose of allowing the ink composition to penetrate better into the recording medium (printing paper or the like). A penetration enhancer may be used individually by 1 type, or may be used together 2 or more types. The content of the penetration enhancer is preferably in the range of 5 to 30% by mass in the ink composition. Moreover, it is preferable to use the penetration enhancer within a range that does not cause image bleeding and paper loss (print-through).

(water)
The ink composition contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

(Other additives)
The ink composition in the present invention can be constituted using other additives in addition to the above components. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

[Treatment solution]
The treatment liquid contains at least an aggregating agent for aggregating the components in the ink composition described above, and can be configured using other components as necessary. By using the treatment liquid together with the ink composition, it is possible to increase the speed of ink jet recording, and an image with excellent density and resolution can be obtained even when recording at high speed (for example, reproducibility of fine lines and fine portions). Further, by improving the prescription of the treatment liquid and the ink composition, the strength of the formed image itself can be increased, and the durability of the image by high-pressure air blowing can be reinforced.

  The aggregating agent may be a compound capable of changing the pH of the ink composition, a polyvalent metal salt, or polyallylamines. In the present invention, from the viewpoint of cohesiveness of the ink composition, a compound capable of changing the pH of the ink composition is preferable, and a compound capable of lowering the pH of the ink composition is more preferable.

  In the present invention, it is preferable to select a flocculant that can quickly separate the solid component and the sediment component (liquid component) after aggregation, or can make the aggregate itself rigid. Such a flocculant is preferably an organic acid, more preferably a divalent or higher valent organic acid, and particularly preferably a divalent or higher valent acid substance. The divalent or higher organic acid is preferably an organic acid having a first pKa of 3.5 or less, more preferably an organic acid of 3.0 or less. Specific examples include phosphoric acid, oxalic acid, malonic acid, citric acid and the like.

  A flocculant can be used individually by 1 type or in mixture of 2 or more types.

  The content of the flocculant for aggregating the ink composition in the treatment liquid is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and still more preferably 5 to 40% by mass.

  The treatment liquid can further contain other additives as other components within a range not impairing the effects of the present invention. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, anti-foaming agents. Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

<Recording medium>
The inkjet recording method of the present invention records an image on a recording medium.

  The recording medium is not particularly limited, and general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing and the like can be used. General printing paper mainly composed of cellulose is relatively slow in ink absorption and drying in image recording by a general ink jet method using water-based ink, and color material movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. However, according to the ink jet recording method of the present invention, it is possible to record a high-quality image excellent in color density and hue by suppressing the movement of the color material.

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper tends to cause quality problems such as image gloss and scratch resistance in image formation by ordinary aqueous inkjet, but in the inkjet recording method of the present invention, gloss unevenness is suppressed and gloss and resistance are reduced. An image having good rubbing properties can be obtained. In particular, a coated paper having a base paper and a coat layer containing an inorganic pigment is preferably used, and a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate is more preferably used. Specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

  In the present invention, it is preferable to control the pressing force of the non-contact type recording medium restraining means based on the rigidity of the recording medium. The rigidity of the recording medium can be determined by, for example, the basis weight. A recording medium having a basis weight of 127.9 gsm or less has a lower pressing by the non-contact type recording medium pressing means, and the basis weight is higher than 230 gsm. Can raise the trailing edge of the recording medium by increasing the pressure. Depending on the basis weight, the pressing may be controlled stepwise.

  EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

[Test Example 1] Control of trailing edge of cardboard and image damage Chrysanthemum half-size (636 ×) obtained by applying a treatment liquid (containing malonic acid) to a recording medium and drawing a solid image by ink jetting (average ink ejection amount 5 pl) After drying a paper of 469 mm and eye vest W basis weight: 310 gsm (manufactured by Nippon Paper Industries) with an adsorption drying cylinder, the trailing edge of the recording medium was floated and image damage was evaluated according to the following criteria.

(1) Rear end floating: Degree of inhibition of rear end floating by non-contact type recording medium restraining means <Evaluation> Visual evaluation of the contact state of the rear end of the recording medium on the suction cylinder.
○: Adsorbed normally up to the rear end.
(Triangle | delta): Although the rear end has floated slightly, it is within tolerance.
X: The rear end is completely floated and cannot be adsorbed.

(2) Image damage: Degree of blown image damage by the non-contact type recording medium restraining means <Evaluation> Visual evaluation of density unevenness and paper background occurrence due to ink flow in the entire solid image portion of the sample.
A: No damage to the image.
○: There is a portion where the density unevenness is slightly seen in the image, but it is within the allowable range.
Δ: Density unevenness occurs in the image.
X: An image flows and a part of the paper surface is exposed.
XX: The image has flowed as a whole and does not form an image.

[Test Example 2] Density unevenness in the adsorption area of thin paper An image is obtained in the same manner as in Test Example 1 except that the recording medium is OK top, the basis weight is 73.3 gsm (manufactured by Oji Paper), and the wind speed is 10 [m / s]. Formation and drying were performed. Thereafter, density unevenness was evaluated according to the following criteria.

<Evaluation> The density difference between the suction hole part and the non-suction hole part of the solid image part of the sample was observed with an optical microscope.
○: Concentration difference is not confirmed.
X: A density difference is confirmed.

[Test Example 3] Control of wind speed (air volume) Except that the average ink droplet ejection volume was 7.5 pl and the wind speed from the blowing nozzle was the wind speed shown in Tables 3 and 4, the same method as in Test Example 1 was used. Image formation and drying were performed. Thereafter, evaluation was performed according to the same criteria as in Test Example 1.

  The wind speed setting shown in Table 4 was performed while changing the wind speed from the front end to the rear end of the recording medium as shown in FIG.

[Test Example 4] Influence of flocculant Using the flocculants shown in Table 5 as the types of flocculants contained in the treatment liquid, image formation and drying were performed in the same manner as in Test Example 1 for evaluation. . The treatment liquid was prepared by adding the same mass of each flocculant.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus, 10 ... Paper feed part, 12 ... Processing liquid provision part, 14 ... Drawing part, 16 ... Drying part, 18 ... Exposure hardening part, 20 ... Discharge part, 22 ... Recording medium, 24 ... 1st Intermediate transport section, 26 ... second intermediate transport section, 28 ... third intermediate transport section, 30 ... intermediate transport body, 55, 71, 77, 85 ... holding means, 70 ... drawing drum, 72M, 72C, 72Y, 72K ... inkjet head, 76 ... drying drum, 78 ... first IR heater, 80 ... warm air ejection nozzle, 82 ... second IR heater, 81 ... auxiliary suction means, 83 ... blower nozzle (non-contact type recording medium) 84 ... exposure curing drum, 88 ... UV lamp

Claims (6)

A treatment liquid applying means for applying a treatment liquid containing a flocculant having a function of thickening the ink on the recording medium;
Ink ejection means for ejecting the ink onto the recording medium;
A transport body provided with a curvature for carrying and transporting the recording medium, holding means for holding the leading end of the recording medium in the transport direction, a plurality of suction holes for sucking the recording medium under negative pressure, and the suction holes A conveying means having suction means for sucking;
Heating means for heating the transport body and the recording medium from the opposite side of the transport body of the recording medium;
A non-contact type recording medium restraining means which is provided upstream of the heating means in the recording medium conveyance direction and presses the rear end of the recording medium from the opposite side of the conveyance body in a non-contact manner;
Control means for controlling the pressing force by the non-contact type recording medium holding means according to the type of the recording medium ,
The image forming apparatus according to claim 1 , wherein the control unit presses the non-contact type recording medium suppressing unit only when passing through the rear end in the conveyance direction of the recording medium . The image forming apparatus according to claim 1, characterized by providing a region not ejected the ink in the conveying direction trailing end portion of the recording medium. The non-contact type recording medium suppressed means, an image forming apparatus according to claim 1 or 2, characterized in that the blowing means. The image forming apparatus according to claim 1, 3 any one, wherein the coagulant is an organic acid. A treatment liquid application step of applying a treatment liquid containing a flocculant having a function of thickening the ink onto the recording medium;
An ink ejection step of ejecting the ink onto the recording medium;
A conveying step of placing the recording medium on a conveying body provided with a curvature, sucking through the suction hole from the conveying body while holding the leading end of the recording medium in the conveying direction, and conveying the recording medium;
A non-contact type recording medium pressing step for pressing in a non-contact manner from the opposite side of the conveyance body of the recording medium;
A heating step of heating the transport body and the recording medium from the opposite side of the transport body of the recording medium;
A control step of controlling the pressing force of the non-contact type recording medium holding step according to the type of the recording medium ,
The image forming method according to claim 1, wherein the control step is controlled so as to press the non-contact type recording medium suppressing step only when the recording medium passes in the rear end in the conveyance direction . The image forming method according to claim 5 , wherein the non-contact type recording medium suppressing step is a blowing step of blowing air to the recording medium.

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