JP2011168389A - Inkjet recorder and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an image of a high image quality and a high grade, without image unevenness such as fixing unevenness and gloss unevenness, without causing wrinkles and a curl. <P>SOLUTION: This inkjet recorder is provided with a liquid discharge head for discharging aqueous ultraviolet-curing ink to a recording surface of a recording medium, a restricting drying unit having a suction restricting cylinder for restricting and carrying the recording medium of forming the image by sticking the aqueous ultraviolet-curing ink by attracting the reverse surface side of the recording surface to an outer peripheral surface via a suction hole formed on the outer peripheral surface and a hot air dryer oppositely arranged to the outer peripheral surface of the suction restricting cylinder, a delivery carrier for holding the leading edge of the recording medium on the downstream side of the restricting drying unit and curving and carrying the reverse surface side of the recording surface in a projecting shape, and a fixing unit having an ultraviolet ray irradiator for irradiating an ultraviolet ray to the image formed on the recording surface of the recording medium on the downstream side of the delivery carrier. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method, and more particularly, to a recording medium conveyed through a large number of drums, printing is performed with aqueous ultraviolet curable ink from an ink jet head, and the recording medium after printing is used. The present invention relates to an ink jet recording apparatus and an ink jet recording method for drying and fixing.

  Conventionally, in an inkjet recording method using water-based ultraviolet curable ink, ink moisture soaks into a recording medium such as paper, and the recording medium absorbs the ink moisture, whereby the recording medium expands and deforms, and wrinkles called cockle are generated, Even after drying, wrinkles and curls remain, causing deterioration in image quality.

  In addition, if moisture is present in the ink during ultraviolet irradiation, there is a problem that ink curing does not proceed efficiently and high-speed fixing cannot be realized.

  On the other hand, for example, water-based UV curable ink is not used, but in order to suppress wrinkles and curling, a sheet of printing paper is provided on the outer peripheral surface of a cylindrical printing paper suction roller. A hot air drying area and cooling for sucking through the plurality of air intake holes, rotating in close contact with the surface of the cylindrical printing paper suction roller, and drying the printing paper at a suitable location on the outer periphery of the printing paper suction roller There is known a drying apparatus in which a drying area is provided and printing paper is dried through these drying areas (for example, see Patent Document 1).

  Also, for example, in order to dry the ink on the sheet conveyed by the sheet conveying member in a short time, the ink is sprayed from the plurality of nozzles of the inkjet head onto the printing surface of the sheet, and then separated from the sheet conveying member. Inkjet recording apparatus in which printed sheet is adsorbed to the outer peripheral surface of the rotator so that the printing surface faces outward, and the ink on the sheet is dried by a heating element arranged to face the outer peripheral surface of the rotator Is known (see, for example, Patent Document 2).

  In addition, for example, in order to improve the drying efficiency by stably transporting the sheet, and to dry uniformly and enable high-quality printing, a gas heated in advance to promote the drying of the back surface of the sheet is used. A double-sided sheet having a first intermediate cylinder provided with a gas blowing means that blows out toward the head and a drying device having an irradiation lamp that dries the sheet around the second intermediate cylinder having a gas suction means for adsorbing and holding the sheet A printing machine is known (see, for example, Patent Document 3).

  For example, in an image forming method using water-based ultraviolet curable ink, in order to realize high-speed fixing on a recording medium, hot air is blown on the image by means of hot air blowing to the image to evaporate water and volatile components. After that, an image is cured and fixed by irradiating the ultraviolet ray with the maximum intensity by an ultraviolet ray irradiating means (see, for example, Patent Document 4).

JP 2002-144528 A JP 2008-179012 A JP 2005-22398 A JP 2007-245653 A

  However, in an ink jet recording apparatus using water-based ultraviolet curable ink, after the recording medium is dried while being restrained by suction with a drum, fixing is performed by ultraviolet irradiation in a state where the recording medium is sucked and restrained on the same drum. As a result, there is a problem in that a convex curl is formed on the recording surface side of the recording medium in a drum shape.

  In addition, the suction hole of the drum that sucks and restrains the recording medium causes the portion of the recording medium to be slightly dented and fixed in a depressed state, thereby causing uneven fixing or uneven gloss due to uneven fixing or drying. There was also a problem.

  The present invention has been made in view of such circumstances, and is an ink jet recording apparatus capable of forming high-quality and high-quality images without occurrence of wrinkles and curls, and without image unevenness such as fixing unevenness and gloss unevenness. And an inkjet recording method.

  In order to achieve the above object, according to the first aspect of the present invention, an image is formed by adhering a liquid discharge head for discharging aqueous ultraviolet curable ink to a recording surface of a recording medium, and the aqueous ultraviolet curable ink. A suction restraining cylinder for transporting the recording medium by sucking and restraining the back surface side of the recording surface to the outer peripheral surface through a suction hole formed on the outer peripheral surface, and facing the outer peripheral surface of the suction restricting cylinder. A constraining drying unit having hot air drying means disposed on the downstream side of the constrained drying unit, and a transfer unit that holds the leading end of the recording medium on the downstream side of the constraining drying unit and curves the back side of the recording surface into a convex shape And a fixing unit having ultraviolet irradiation means for irradiating ultraviolet rays onto the image formed on the recording surface of the recording medium on the downstream side of the transfer conveying means. .

  As a result, the recording medium on which the image is formed is sufficiently hot-air dried in the constrained drying unit before fixing, so that the occurrence of cockle is suppressed, and after that, the recording medium is bent and conveyed in the direction opposite to the curling direction during drying. In addition, there is no wrinkle or curling, and high-quality and high-quality image formation without image unevenness such as fixing unevenness and gloss unevenness becomes possible.

  According to a second aspect of the present invention, there is provided a smoothing unit that smoothes the recording medium on the downstream side of the transfer conveying unit and on the upstream side of the ultraviolet irradiation unit.

  As a result, since the image is fixed after the wrinkles and curls are suppressed by the smoothing means, high-quality and high-quality images can be formed without wrinkles and curls and without image unevenness such as uneven fixing and gloss.

  According to a third aspect of the present invention, the fixing unit includes a fixing cylinder that winds and conveys the recording medium around an outer peripheral surface, and the ultraviolet irradiation unit that is disposed to face the outer peripheral surface. The smoothing means is a pressing roller that presses the recording medium against the fixing cylinder.

  As described above, even if the recording medium is pressed by the pressing roller, it is after drying, so that it can come into contact with the image surface, and the recording medium can be smoothed with a simple configuration called a roller.

  According to a fourth aspect of the present invention, there is provided the ink jet recording apparatus according to any one of the first to third aspects, further comprising suction assisting means for assisting the suction of the recording medium to the suction restraining cylinder. It is characterized by.

  Further, according to a fifth aspect of the present invention, the adsorption assisting means is a blowing means disposed on the upstream side of the hot air drying means so as to face the suction restraining cylinder, and toward the recording medium rear end side. It is characterized by blowing air at an angle.

  As described above, by providing the suction assisting means, it is possible to suppress the occurrence of suction flaws even when the thickness or size of the recording medium cannot be dealt with only by the suction of the suction restraining cylinder.

  According to a sixth aspect of the present invention, the transfer / conveying means includes a drying means for drying the recording surface side of the recording medium.

  Further, according to a seventh aspect of the present invention, the drying unit of the transfer conveying unit is a unit for drying by blowing hot air on the recording surface side of the recording medium.

  Thus, by providing a drying means in the transfer conveying means, it becomes possible to make the drying unevenness due to the suction holes or the like in the constraining drying cylinder of the constraining drying unit uniform.

  Further, according to an eighth aspect of the present invention, the transfer / conveying means includes a guide member with a rib for conveying the recording medium by curving the back side of the recording surface into a convex shape.

  As a result, the transfer conveying means can reliably convey the recording medium such that the back side of the recording surface has a convex shape.

According to a ninth aspect of the present invention, the constrained drying unit includes a baffle plate for directing the hot air blown from the hot air drying means toward the outer peripheral surface of the suction constraining cylinder.

  As a result, it is possible to improve the thermal efficiency and exhaust performance of the constrained drying unit.

  Similarly, in order to achieve the object, an invention according to claim 10 includes an ink discharge step of discharging aqueous ultraviolet curable ink onto a recording surface of a recording medium, and an image in which the aqueous ultraviolet curable ink is attached to the recording surface. The recording medium on which the recording medium is formed is heated on the recording surface of the recording medium while the rear surface side of the recording surface is attracted to and restrained by the outer peripheral surface through a suction hole formed on the outer peripheral surface of the drum. A constrained drying process for applying and drying, a transfer conveying process for holding the tip of the recording medium dried in the constrained drying process, and curving the back side of the recording surface into a convex shape, and the transfer conveying process And a fixing step of fixing the image formed on the recording surface of the recording medium conveyed through the step by irradiating with ultraviolet rays.

  As a result, the recording medium on which the image is formed is sufficiently hot-air dried in the constrained drying process before fixing, so that the occurrence of cockle is suppressed, and after that, it is conveyed while being bent in the direction opposite to the curling direction at the time of drying. In addition, there is no wrinkle or curling, and high-quality and high-quality image formation without image unevenness such as fixing unevenness and gloss unevenness becomes possible.

  Further, the present invention is characterized in that it has a smoothing step of smoothing the recording medium before fixing the recording medium dried in the constrained drying step in the fixing step.

  As described above, since smoothing is performed before fixing, the recording medium can be wrinkled.

  As described above, according to the present invention, the recording medium on which an image is formed is sufficiently hot-air dried in the constrained drying unit before fixing, so that the occurrence of cockle is suppressed, and the reverse of the curling direction after drying. Since it is bent and transported in the direction, there is no wrinkle or curling, and high-quality and high-quality image formation without image unevenness such as unevenness of fixing and unevenness of gloss becomes possible.

1 is a schematic configuration diagram illustrating an embodiment of an inkjet recording apparatus according to the present invention. It is a principal part block diagram which shows the system configuration | structure of the inkjet recording device of this embodiment. It is a block diagram which shows the principal part of the inkjet recording device of this embodiment. It is a block diagram which expands and shows the part in which the hot air drying means of the drying drum was installed.

  Hereinafter, an ink jet recording apparatus and an ink jet recording method according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an ink jet recording apparatus according to the present invention.

  In the inkjet recording apparatus 100, water-based ultraviolet curable inks of a plurality of colors are applied from the inkjet heads 172M, 172K, 172C, and 172Y to the recording surface of the recording medium 124 held by the impression cylinder (drawing drum 170) of the drawing unit 116. It is an impression cylinder direct drawing type ink jet recording apparatus that forms a desired color image by dropping, and a treatment liquid (including an aggregating agent for aggregating components in the ink composition) on the recording medium 124 before ink ejection. And an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method for forming an image on a recording medium 124 by reacting a treatment liquid and an ink liquid is applied.

  That is, as shown in FIG. 1, the inkjet recording apparatus 100 mainly includes a paper feeding unit 112, a treatment liquid application unit 114, a drawing unit 116, a drying unit 118, a fixing unit 120, and a paper discharge unit 122. ing.

  The paper feeding unit 112 is a mechanism that supplies the recording medium 124 to the processing liquid application unit 114, and the recording medium 124 that is a sheet is stacked on the paper feeding unit 112. The paper feed unit 112 is provided with a paper feed tray 150, and the recording medium 124 is fed from the paper feed tray 150 to the processing liquid application unit 114 one by one. In order to prevent the recording medium 124 from being lifted, the paper feed tray 150 may be provided with a suction hole on the outer surface, and a suction unit that performs suction from the suction hole may be connected.

  In the inkjet recording apparatus 100 of the present embodiment, a plurality of types of recording media 124 having different paper types and sizes (paper sizes) can be used as the recording medium 124. A mode is also possible in which a plurality of paper trays (not shown) are provided in the paper feed unit 112 to distinguish and collect various recording media and the paper to be fed to the paper feed tray 150 is automatically switched from among the plurality of paper trays. In addition, a mode is also possible in which the operator selects or replaces the paper tray as necessary. In this example, a sheet (cut paper) is used as the recording medium 124, but a configuration in which continuous paper (roll paper) is cut to a required size and fed is also possible.

  The processing liquid application unit 114 is a mechanism that applies the processing liquid to the recording surface of the recording medium 124. The treatment liquid includes an aggregating agent that agglomerates the components in the ink composition applied by the drawing unit 116, and causes an aggregation reaction with the ink when the treatment liquid comes into contact with the ink. Separation is promoted, and it is possible to form a high-quality image without causing blurring after ink landing, landing interference (unification), or color mixing. In addition, as a process liquid, it can also comprise using another component other than a coagulant | flocculant as needed. 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 with high speed recording (for example, reproducibility of fine lines and fine portions).

  As shown in FIG. 1, the treatment liquid application unit 114 includes a paper feed drum 152, a treatment liquid drum 154, and a treatment liquid application device 156. The treatment liquid drum 154 is a drum that holds and rotates the recording medium 124. The processing liquid drum 154 includes a claw-shaped holding means (gripper) 155 on the outer peripheral surface thereof, and the recording medium 124 is sandwiched between the claw of the holding means 155 and the peripheral surface of the processing liquid drum 154. The tip can be held. The treatment liquid drum 154 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 124 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A processing liquid coating device 156 is provided outside the processing liquid drum 154 so as to face the peripheral surface thereof. In the recording medium 124, the processing liquid is applied to the recording surface by the processing liquid application device 156.

  The recording medium 124 to which the processing liquid is applied by the processing liquid applying unit 114 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 116 via the intermediate transfer unit 126 (first transfer cylinder transfer unit).

  The drawing unit 116 includes a drawing drum 170 and inkjet heads 172M, 172K, 172C, and 172Y. Although not shown in FIG. 1, a sheet suppression roller for removing the wrinkles of the recording medium 124 is disposed on the front side of the ink jet heads 172M, 172K, 172C, and 172Y with respect to the drawing drum 170. Also good.

  Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) 171 on its outer peripheral surface, and holds and fixes the leading end of the recording medium. The drawing drum 170 has a plurality of suction holes on the outer peripheral surface, and the recording medium 124 is attracted to the outer peripheral surface of the drawing drum 170 by negative pressure. As a result, contact with the head due to paper floating is avoided, and paper jam is prevented. In addition, image unevenness due to fluctuations in the clearance with the head is prevented.

  The recording medium 124 thus fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and water-based ultraviolet curable ink is ejected from the inkjet heads 172M, 172K, 172C, 172Y onto this recording surface. Is done.

  The inkjet heads 172M, 172K, 172C, and 172Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 124. 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 172M, 172K, 172C, 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 124 (the rotation direction of the drawing drum 170).

  The droplets of the corresponding color ink are ejected from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held in close contact with the drawing drum 170, whereby the processing liquid application unit 114 The ink comes into contact with the treatment liquid previously applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. As a result, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  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 ink are used as necessary. Color ink may be added. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The drawing unit 116 configured as described above can perform drawing on the recording medium 124 in a single pass. Thereby, high-speed recording and high-speed output are possible, and productivity can be improved.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128 (second transfer cylinder conveyance unit).

  The drying unit 118 is a mechanism that dries moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum 176 and a solvent drying device 178 as shown in FIG.

  Similar to the processing liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) 177 on the outer peripheral surface thereof, holds the tip of the recording medium 124 by the holding unit 177, and sucks holes on the outer peripheral surface of the drum. The recording medium 124 can be adsorbed to the drying drum 176 by a negative pressure. Further, an air blowing means 180 (adsorption assisting means) and a solvent drying device 178 are provided so as to face the outer peripheral surface of the drying drum 176.

  The blowing unit 180 is for assisting the adsorption of the recording medium 124 to the drying drum 176, and blows air obliquely toward the end of the recording medium 124 in the width direction, and the front end thereof is held by the holding unit 177. Is ensured to be sucked from the front end side toward the rear end side without generating wrinkles.

  The solvent drying device 178 is arranged at a position facing the outer peripheral surface of the drying drum 176, and includes hot air drying means 182 in which a plurality of combinations of IR heaters and fans are arranged. Various drying conditions can be realized by appropriately adjusting the temperature and air volume of the hot air blown from each hot air jet nozzle of the hot air drying means 182 toward the recording medium 124. The recording medium 124 is transported while being attracted and restrained to the outer peripheral surface of the drying drum 176 so that the recording surface faces outward, and the recording surface is dried by the IR heater and the hot air jet nozzle.

  Further, the drying drum 176 has suction holes on the outer peripheral surface thereof, and has suction means for performing suction from the suction holes. As a result, the recording medium 124 can be held in close contact with the peripheral surface of the drying drum 176. Further, by performing negative pressure suction, the recording medium 124 can be restrained by the drying drum 176, so that the recording medium 124 can be prevented from being clogged.

  The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate conveyance unit 130 (third transfer cylinder conveyance unit).

  The fixing unit 120 includes a fixing drum 184, a pressure roller 188 (smoothing unit), and an ultraviolet light source 190 (ultraviolet irradiation unit). Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) 185 on the outer peripheral surface, and the leading end of the recording medium 124 can be held by the holding unit 185.

  With the rotation of the fixing drum 184, the recording medium 124 is conveyed with the recording surface facing outward. The recording surface is smoothed by the pressing roller 188, and then irradiated with ultraviolet rays from the ultraviolet light source 190. Curing / fixing is performed.

  The pressure roller 188 smoothes the recording medium 124 by pressurizing the recording medium 124 dried with ink.

  The ultraviolet light source 190 irradiates the image formed with the aqueous ultraviolet curable ink discharged on the recording medium 124 with ultraviolet rays to fix the ink.

  An in-line sensor that inspects an image formed on the recording medium 124 may be provided so as to face the outer peripheral surface of the fixing drum 184. The in-line sensor 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 124. For example, a CCD line sensor can be preferably used.

  Subsequent to the fixing unit 120, a paper discharge unit 122 is provided. A paper discharge unit 192 is installed in the paper discharge unit 122. A transfer drum 194 and a transport chain 196 are provided between the fixing drum 184 and the paper discharge unit 192 of the fixing unit 120. The conveyance chain 196 is wound around the tension roller 198. The recording medium 124 that has passed through the fixing drum 184 is sent to the transport chain 196 via the transfer drum 194 and is transferred from the transport chain 196 to the paper discharge unit 192.

  Although not shown in FIG. 1, the ink jet recording apparatus 100 of the present example has an ink storage / loading unit that supplies ink to each of the ink jet heads 172M, 172K, 172C, and 172Y, and a treatment liquid application, in addition to the above configuration. A head maintenance unit for supplying a processing liquid to the unit 114 and cleaning the ink jet heads 172M, 172K, 172C, 172Y (wiping, purging, nozzle suction, etc. of the nozzle surface) A position detection sensor for detecting the position of the recording medium 124, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

  FIG. 2 is a principal block diagram showing the system configuration of the inkjet recording apparatus 100.

  The inkjet recording apparatus 100 includes a communication interface 80, a system controller (system controller) 82, an image memory 84, a motor driver 86, a heater driver 88, a print controller 90, a maintenance controller 92, a head driver 94, and the like.

  The communication interface 80 is an interface unit that receives image data sent from the host computer 96. As the communication interface 80, 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 for speeding up communication may be mounted. The image data sent from the host computer 96 is taken into the ink jet recording apparatus 100 via the communication interface 80 and temporarily stored in the image memory 84.

  The image memory 84 is a storage unit that temporarily stores an image input via the communication interface 80, and data is read and written through the system control unit 82. The image memory 84 is not limited to a memory composed of semiconductor elements, and a magnetic medium such as a hard disk may be used.

  The system control unit 82 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. To do. That is, the system control unit 82 controls the communication interface 80, the image memory 84, the motor driver 86, the heater driver 88, and the like, and generates control signals for controlling the heater 99 and the host computer 96.

  The image memory 84 stores programs executed by the CPU of the system control unit 82 and various data necessary for control. Note that the image memory 84 may be a non-rewritable storage means or a rewritable storage means such as an EEPROM. The image memory 84 may be used as a temporary storage area for image data, and may be used as a program development area and a calculation work area for the CPU.

  The system control unit 82 is connected to an EEPROM 85 that stores various control programs and an image processing unit 87 that performs various image processes on image data. In response to a command from the system control unit 82, a control program is read from the EEPROM 85 and executed. Note that the EEPROM 85 may also be used as a storage unit for operating parameters and the like.

  The motor driver 86 is a driver that drives the motor 98 in accordance with an instruction from the system control unit 82. In FIG. 2, the motor (actuator) disposed in each part of the inkjet recording apparatus 100 is represented by reference numeral 98. For example, the motor 98 shown in FIG. 2 includes motors that drive the intermediate transport units 126, 128, and 130, the paper feed drum 152, the processing liquid drum 154, the drawing drum 170, the drying drum 176, and the fixing drum 184 shown in FIG. included.

  The heater driver 88 is a driver that drives the heater 99 in accordance with an instruction from the system control unit 82. In FIG. 2, a plurality of heaters provided in the ink jet recording apparatus 100 are represented by reference numeral 99. For example, the heater 99 shown in FIG. 2 includes the heater of the treatment liquid application unit 114 and the IR heater of the drying unit 118 shown in FIG.

  In addition, a maintenance control unit 92 is connected to the system control unit 82. The maintenance control unit 92 controls a maintenance drive unit 93 that drives a maintenance unit (not shown) including a cap and a cleaning blade in accordance with an instruction from the system control unit 82.

  The print control unit 90 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 84 under the control of the system control unit 82. The controller is a controller that controls the treatment liquid application driver 95 to apply the treatment liquid from the treatment liquid application device 156 to the recording medium 124 and supplies the generated print data (dot data) to the head driver 94. . Necessary signal processing is performed in the print controller 90, and the ejection droplet amount (droplet ejection amount) and ejection timing of the inkjet heads 172M, 172K, 172C, 172Y are controlled via the head driver 94 based on the image data. Is done. Thereby, a desired dot size and dot arrangement are realized.

  Further, a UV irradiation means driver 97 for controlling the ultraviolet light source 190 is connected to the system control unit 82.

  FIG. 3 is an enlarged view of the treatment liquid application unit 114, the drawing unit 116, the drying unit 118, and the fixing unit 120, which are main parts of the inkjet recording apparatus 100 of the present embodiment, and the inkjet recording apparatus according to the present invention is described in more detail. explain.

  As shown in FIG. 3, the processing liquid drum 154, the intermediate transport unit 126 (first transfer drum transport unit), the drawing drum 170, the intermediate transport unit 128 (second transfer drum transport unit), the drying drum 176, and the intermediate transport unit 130. (Third transfer cylinder transporting means) and fixing drum 184 are arranged side by side, and the recording medium 124 is transported by each drum, and while being transported, processing liquid application, drawing, drying, and fixing (curing) are sequentially performed. It has come to be.

  Each intermediate conveyance section (the first transfer drum transfer means 126, the second transfer drum transfer means 128, and the third transfer drum transfer means 130) includes guide members 127, 129, and 131 with ribs, respectively, and sandwiches the rotation shaft. A holding claw (not shown) at the tip of the arm extending in the direction facing 180 degrees grips the tip of the recording medium 124 and rotates around the rotation axis, and the rear end of the recording medium 124 is free. The recording medium 124 is conveyed along the guide members (127, 129, 131) so that the back side of the recording surface is convex.

  The intermediate transport units 126, 128, and 130 may be configured to use a chain gripper to grip the recording medium 124 and transport it with the back side convex.

  The ink jet recording apparatus 100 according to the present embodiment records an image on a recording surface of a recording medium 124. The recording medium 124 is not particularly limited, but is a so-called high-quality paper used for general offset printing. Ordinary printing paper mainly composed of cellulose, such as coated paper or art paper, 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, the inkjet recording apparatus 100 of the present embodiment can perform high-quality image recording excellent in color density and hue by suppressing color material movement.

  Of the recording media, so-called coated paper used for general offset printing is preferred. 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 is liable to cause quality problems such as glossiness and scratch resistance of the image in normal aqueous inkjet image formation. However, in the inkjet recording apparatus 100 of the present embodiment, gloss unevenness is suppressed and glossiness is reduced. An image having good abrasion resistance 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.

  As described above, the processing liquid application unit 114 applies the processing liquid to the recording surface of the recording medium 124.

  The film thickness of the processing liquid applied to the recording surface by the processing liquid coating apparatus 156 is sufficiently smaller than the droplet diameter of the ink ejected from the inkjet heads 172M, 172K, 172C, 172Y of the drawing unit 116. Is desirable. For example, when the ink droplet ejection amount is 2 pl (picoliter), the average diameter of the droplets 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 124. 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.

Although not shown in the figure, the processing liquid coating device 156 is mainly composed of a processing liquid container, a metering roller, and a coating roller. A processing liquid is stored in the processing liquid container, and a part of the measuring roller is immersed in the processing liquid. As the metering roller, a metal roller and an anilox roller in which a large number of cells are regularly formed with a certain number of lines on a roller peripheral surface having a ceramic coating on the surface of the metal roller are preferably used. As the material of the metal roller, iron, SUS, or the like is used. When iron is used as the material, the surface may be plated with chromium or the like in order to improve surface hydrophilicity, wear resistance, and rust resistance. As the cell structure of the anilox roller, for example, those having 150 to 400 lines, a cell depth of 20 to 75 μm, and a cell capacity of 30 cm ³ / m ^{2 to} 60 cm ³ / m ² can be suitably used. . The diameter of the measuring roller is, for example, 20 mm or more and 100 mm or less.

  The metering roller is rotatably supported and connected to a motor (not shown), and is driven to rotate at a constant speed. Therefore, the processing liquid in the processing liquid container can be attached to the surface of the measuring roller, and this processing liquid can be transferred to the surface of the coating roller. The rotation direction of the metering roller may be the same as that of the application roller, and the peripheral speed of the outer periphery of the roller may be the same as that of the application roller, or a speed difference may be provided. When providing a speed difference, the peripheral speed of the metering roller is preferably 80% or more and 140% or less with respect to the peripheral speed of the application roller. By adjusting the peripheral speed between the application roller and the metering roller, the transfer rate from the metering roller to the application roller can be adjusted, and the coating film thickness on the recording medium 124 can be adjusted.

  A metering doctor blade is provided on the surface of the metering roller so as to come into contact therewith. The doctor blade is arranged on the upstream side in the rotation direction of the measuring roller with respect to the contact position between the measuring roller and the applying roller, and can measure the application liquid by scraping off the application liquid on the surface of the measuring roller. Thereby, the coating liquid measured by the doctor blade can be supplied to the coating roller.

  As the coating roller, a rubber roller having a rubber layer such as EPDM or silicon on the surface is preferably used. The application roller is rotatably supported and connected to a motor (not shown) and is driven to rotate at a constant speed. The rotation direction of the application roller is the same as that of the processing liquid drum 154, and the peripheral speed of the roller outer periphery is also rotated at the same speed as that of the processing liquid drum 154. As a result, the processing liquid transferred from the metering roller to the application roller is applied to the recording medium 124 held on the processing liquid drum 154.

  As described above, since the processing liquid coating apparatus 156 applies the processing liquid with the roller, the processing liquid can be uniformly applied to the recording medium 124 with a small coating amount. Further, the processing liquid coating apparatus 156 contacts and separates the rollers of the processing liquid coating unit for each recording medium so as not to contaminate the processing liquid coating conveyance cylinder (processing liquid drum 154). It is preferable. The treatment liquid drum 154 conveys the recording medium 124 with a holding claw that holds the tip of the recording medium 124. As a result, the recording medium 124 can be conveyed at high speed, and the occurrence of paper conveyance jams can be reduced.

Note that the processing liquid applied to the recording medium 124 may be dried by providing an IR heater and a hot air jet nozzle on the outer periphery of the processing liquid drum 154 so as to face the peripheral surface. When an IR heater or a warm air ejection nozzle is provided, the IR heater is controlled to a high temperature (for example, 180 ° C.), and the warm air ejection nozzle generates a high temperature (for example, 70 ° C.) of warm air at a constant air volume (for example, 9 m). ³ / min) and sprayed toward the recording medium 124. By the heating by the IR heater and the hot air jet nozzle, moisture in the solvent of the processing liquid is evaporated, and a thin film layer of the processing liquid is formed on the recording surface of the recording medium 124. By thinning the treatment liquid in this way, the dots of ink that are ejected by the drawing unit 116 come into contact with the recording surface of the recording medium 124 to obtain the required dot diameter, and the thinned treatment liquid component Reacts with the colorant to cause aggregation of the color material, and an effect of fixing to the recording surface of the recording medium 124 is easily obtained. The processing liquid drum 154 may be controlled to a predetermined temperature (for example, 50 ° C.).

  Further, the treatment liquid contains an aggregating agent that aggregates the components in the ink composition applied by the drawing unit 116.

  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 embodiment, from the viewpoint of the cohesiveness of the ink composition, a compound that can change the pH of the ink composition is preferable, and a compound that can lower the pH of the ink composition is more preferable. Preferred examples of the compound capable of lowering the pH of the ink composition include highly water-soluble acidic substances (phosphoric acid, oxalic acid, malonic acid, citric acid, derivatives of these compounds, and salts thereof).

  As described above, as the flocculant, an acidic substance having high water solubility is preferable, and an organic acid is preferable and an organic acid having a valence of 2 or more is more preferable from the viewpoint of improving the aggregation property and fixing the entire ink. Furthermore, an acidic substance having a valence of 2 to 3 is particularly preferable. As the divalent or higher organic acid, an organic acid having a first pKa of 3.5 or less is preferable, and an organic acid of 3.0 or less is more preferable. Specifically, phosphoric acid, oxalic acid, malonic acid, Preferred examples include citric acid.

  In the flocculant, the acidic substance may be used alone or in combination of two or more. Thereby, cohesion can be improved and the whole ink can be fixed. 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. is there. Further, it is preferable that the pH (25 ° C.) of the ink composition is 8.0 or more and the pH (25 ° C.) of the treatment liquid is in the range of 0.5 to 4. As a result, it is possible to increase the image density, resolution, and speed of inkjet recording.

  Further, the processing liquid can contain other additives. These additives include anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, antiseptics, anti-fungal agents, pH adjusters, surface tension adjusters, antifoaming agents, Well-known additives, such as a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, and a chelating agent, are mentioned.

  As described above, in this embodiment, the configuration in which the application method using the roller is applied is exemplified, but the application of the treatment liquid is not limited to the application method, and is performed by applying a known method such as an inkjet method or an immersion method. be able to. The coating method can be performed by a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, or the like.

  The treatment liquid application step may be provided either before or after the ink application step using the ink composition. In the present embodiment, an aspect in which the ink application process is provided after the treatment liquid is applied in the treatment liquid application process is preferable. Specifically, before applying the ink composition, a treatment liquid for aggregating the pigment and / or self-dispersing polymer particles in the ink composition is applied on the recording medium 124 in advance. A mode in which an image is formed by applying an ink composition so as to come into contact with the treatment liquid applied on the medium 124 is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

The amount of the treatment liquid applied is not particularly limited as long as the ink composition can be aggregated. However, the amount of the aggregation agent applied is preferably an amount that makes the amount of the aggregation agent 0.1 g / m ² or more. Especially, the quantity from which the provision amount of a flocculant will be 0.2-0.7 g / m < ² > is preferable. When the applied amount of the flocculant is 0.1 g / m ² or more, good high-speed flocculence can be maintained according to various usage forms of the ink composition. Further, it is preferable that the amount of the flocculant applied is 0.7 g / m ² or less because the surface properties of the applied recording medium are not adversely affected (such as a change in gloss).

  The processing liquid application unit 114 records the processing liquid while measuring the processing liquid by the processing liquid coating device 156 while holding and transporting the leading end portion of the recording medium 124 by the holding means 155 provided on the outer peripheral surface of the processing liquid drum 154. A treatment liquid is applied to the medium 124.

  The recording medium 124 to which the processing liquid is applied by the processing liquid application unit 114 is conveyed to the next drawing unit 116 by the intermediate conveyance unit (first transfer cylinder conveyance means) 126. The recording medium 124 is held such that its leading end is held by a holding claw (not shown) of the first transfer drum conveying means 126, and is conveyed so that the recording surface faces inward and the back surface is convex along the guide member 127. Is done.

  Further, the first transfer drum transport means 126 has hot air drying means (not shown) inside (near the rotation axis), and blows hot air on the recording surface (front surface) side of the recording medium 124 facing inward during transport. The treatment liquid applied to the surface is dried. Thereby, when ink is ejected onto the recording medium 124 in the drawing unit 116, movement of the landing ink on the recording medium 124 at the time of ink adhesion is prevented.

  The drawing drum 170 of the drawing unit 116 holds the leading end portion of the recording medium 124 conveyed by the first transfer drum conveying unit 126 by the holding unit 171 provided on the outer peripheral surface of the drawing drum 170 and the outer periphery of the drawing drum 170. The recording medium 124 is sucked and fixed to the outer peripheral surface of the drawing drum 170 by a suction hole provided on the surface and conveyed. Then, water-based ultraviolet curable ink is applied from the inkjet heads 172M, 172K, 172C, and 172Y toward the surface (recording surface) of the recording medium 124 fixed to the outer peripheral surface of the drawing drum 170, to which the processing liquid is applied. Dropped.

  Here, the ink (aqueous ultraviolet curable ink) used in the present invention will be described.

  The aqueous ultraviolet curable ink includes a pigment, polymer particles, and a water-soluble polymerizable compound that is polymerized by active energy rays. Thereby, it can be hardened by irradiating with ultraviolet rays, and has excellent abrasion resistance and high film strength.

  The ink composition in the present invention contains a pigment, and can be constituted using a dispersant, a surfactant, and other components as necessary. The ink composition 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. The pigment is preferably a water-dispersible pigment in which at least a part of its surface is coated with a polymer dispersant.

  The ink composition of the present invention can contain at least one dispersant. The dispersant for the pigment 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, particularly preferably. 10,000 to 40,000.

  The acid value of the polymer dispersant is preferably 100 KOHmg / g or less from the viewpoint of good aggregation when the treatment liquid comes into contact. Furthermore, the acid value is more preferably 25 to 100 KOH mg / g, further preferably 25 to 80 KOH mg / g, and particularly preferably 30 to 65 KOH mg / g. 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, and the polymer dispersant has a carboxyl group and an acid value of 25 to 80 KOHmg / g. More preferably.

  In the present embodiment, from the viewpoint of light resistance and quality of the image, it is preferable to include a pigment and a dispersant, more preferably to include an organic pigment and a polymer dispersant, and further to include an organic pigment and a carboxyl group. It is particularly preferred to contain a polymer dispersant. 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 diameter is 200 nm or less, the color reproducibility is good, and the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 100 nm or less, 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 increasing the viscosity of the ink by aggregation and dispersion instability when contacted with a treatment liquid described later or a dried region thereof. It is possible to further improve the fixing property of an object to a recording medium and the scratch resistance of an image.

  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 aggregating the ink to increase the viscosity of 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 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 further preferably 30 to 50 KOH mg / g. 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 3,000 to 200,000, more preferably 5,000 to 150,000 in terms of weight average molecular weight, and 10,000 to 10,000. More preferably, it is 100,000. By setting the weight average molecular weight to 3,000 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). As conditions, the sample concentration was 0.35 / min. The flow rate is 0.35 ml / min. The sample injection volume is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, calibration curves are manufactured by Tosoh Corporation, “Standard sample TSK standard, polysrene”, “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”. , “A-2500”, “A-1000”, “n-propylbenzene”.

  The average particle size 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 / 0.0 from the viewpoint of image scratch resistance. 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.

  As the polymerizable compound, a nonionic or cationic polymerizable compound is preferable in that the reaction between the flocculant, the pigment, and the polymer particles is not hindered. 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, 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 the reaction between the flocculant, the pigment, and the polymer particles is not hindered, 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.

  At least one of the ink composition and the treatment liquid further includes an initiator that initiates polymerization of the polymerizable compound by active energy rays.

(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 the treatment liquid. 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 more, 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.

  The penetration accelerator 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. Among these, 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.

  Returning to FIG. 3 again, the drawing unit 116 ejects droplets of the corresponding color ink from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held in close contact with the drawing drum 170. 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 114, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. As a result, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  The amount of ink droplets ejected from each of the inkjet heads 172M, 172K, 172C, and 172Y is preferably 1 to 10 pl (picoliter) and more preferably 1.5 to 6 pl from the viewpoint of obtaining a high-definition image. preferable. In addition, from the viewpoint of improving the unevenness of the image and the connection between the continuous gradations, it is also effective to discharge different droplet amounts in combination, and the present invention is suitably applied even in such a case.

  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 ink are used as necessary. Color ink may be added. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The drawing unit 116 configured as described above can perform drawing on the recording medium 124 in a single pass.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit (second transfer cylinder conveyance unit) 128. The second transfer drum transport unit 128 holds the leading end of the recording medium 124 received from the drawing drum 170 by a holding claw (not shown), the recording surface of the recording medium 124 faces inward, and the back side is a guide member. 129 is conveyed so as to have a convex shape.

  The second transfer drum transport means 128 has a hot air drying means (drying means) (not shown) inside, and blows hot air on the recording surface side of the recording medium 124 facing the inside during the conveyance to the surface. The ejected ink is dried. As a result, since ink can be dried immediately after ink ejection, it becomes easy to reduce the clogging of the recording medium 124 due to ink permeation, and the occurrence of suction flaws at the time of suction restraint in the drying drum 176 in the drying unit 118 is suppressed. It becomes easy to do.

  The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action. As shown in FIG. 3, the IR heater is disposed at a position facing the drying drum 176 and the outer peripheral surface of the drying drum 176. It is composed of hot air drying means 182 in which a plurality of combinations of fans and the like are arranged. Further, a blowing unit 180 (adsorption assisting unit) is provided on the upstream side (in the rotation direction of the drying drum 176) of the plurality of hot air drying units 182 so as to face the outer periphery of the drying drum 176.

  Similar to the processing liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) 177 on the outer peripheral surface thereof, and the holding unit 177 can hold the leading end of the recording medium 124. Further, the drying drum 176 has a plurality of suction holes on the outer peripheral surface thereof, and the recording medium 124 is attracted to the outer peripheral surface of the drying drum 176 by negative pressure and restrained so as to be in close contact with the recording medium. The recording medium 124 is dried by applying hot air from the hot air jet nozzle of the hot air drying means 182 to the recording medium 124 constrained by the drying drum 176 in this way.

  This prevents the occurrence of cockle. Further, by causing the recording medium 124 to be in close contact with the outer peripheral surface of the drying drum 176, it is possible to prevent the occurrence of jam and paper burning due to the recording medium 124 coming into contact with the hot air drying means 182.

The hot air ejection nozzle of the hot air drying means 182 is configured to blow hot air controlled at a predetermined temperature (for example, 50 ° C. to 70 ° C.) toward the recording medium 124 at a constant air volume (12 m ³ / min). Each IR heater is controlled to a predetermined temperature (for example, 180 ° C.). By these hot air jet nozzles and IR heaters, moisture contained in the recording surface of the recording medium 124 held on the drying drum 176 is evaporated, and drying processing is performed. At that time, since the drying drum 176 of the drying unit 118 is structurally separated from the drawing drum 170 of the drawing unit 116, in the inkjet heads 172M, 172K, 172C, 172Y, the head meniscus portion is dried by thermal drying. Ink ejection failure can be reduced. Further, there is a degree of freedom in setting the temperature of the drying unit 118, and an optimal drying temperature can be set.

  In addition, it is preferable to discharge | evaporate the evaporated water | moisture content outside with the air by the discharge means which abbreviate | omitted illustration. Further, the collected air may be cooled by a cooler (radiator) or the like and collected as a liquid.

  Further, it is preferable that the outer peripheral surface of the drying drum 176 is controlled to a predetermined temperature. Drying is accelerated by heating from the back surface of the recording medium 124, and image destruction during fixing can be prevented. The range of the surface temperature of the drying drum 176 is preferably 50 ° C. or higher, more preferably 60 ° C. or higher. 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 176 (preventing burns due to high temperature).

  The drying drum 176 is preferably heated to a predetermined temperature before the recording medium 124 is conveyed. By drying the drying drum 176, drying can be promoted, so that image destruction can be prevented and cuckling can be prevented. The heating temperature is preferably in the same temperature range as the surface temperature of the drying drum 176.

  Heating is preferably performed at a predetermined temperature in the sucked state in order to prevent a temperature drop when sucked. In addition, when heating is performed without suction, it is preferable to perform heating so that the temperature is higher than a predetermined temperature in consideration of a decrease in temperature at the time of suction. In addition, the recording medium 124 is held so that the recording surface faces outward (that is, in a state where the recording surface of the recording medium 124 is curved so as to be a convex side), and is dried while being rotated and conveyed. The occurrence of wrinkles and floats 124 can be prevented, and uneven drying due to these can be reliably prevented.

  The air blowing means 180 (adsorption assisting means) provided on the upstream side of the hot air drying means 182 is for assisting the adsorption of the recording medium 124 to the drying drum 176. The blowing unit 180 blows in an oblique direction toward the rear end side of the recording medium 124 so as to be applied obliquely toward the end portion side in the width direction of the recording medium 124, and further controls to increase the wind force at the rear end. . As a result, the sheet is prevented from floating at the rear end of the recording medium 124, and the recording medium 124 is picked up by suction to enable uniform drying and uniform suction. In this way, by using the suction assisting means that is not in contact with the recording medium 124 as the air blowing means 180, when the suction assist is performed using the contact means, the ink that has not yet dried on the recording medium 124 is contacted with the contact means. It is possible to prevent image defects from being transferred to the image.

  The suction force of the drying drum 176 can be expressed by (opening area) × (pressure per unit area). The suction force can be increased by increasing the area occupied by the suction holes in the recording medium suction holding region, that is, the aperture ratio.

  In addition, the opening ratio of the suction holes provided on the outer peripheral surface of the drying drum 176 is preferably 1% or more and 75% or less with respect to the contact area between the outer peripheral surface of the drying drum 176 and the recording medium 124. This is because if the aperture ratio is less than 1%, the expansion deformation of the recording medium 124 due to water absorption after recording cannot be sufficiently suppressed, and the drying drum 176 itself is also warmed. Drying is also promoted by contact, but if the aperture ratio exceeds 75%, the contact area between the back surface of the recording medium 124 and the outer peripheral surface of the drying drum 176 decreases, so that the recording medium 124 is held by suction. However, sufficient drying performance cannot be obtained, and the cockle is also deteriorated.

  Therefore, by setting the opening ratio of the suction holes on the outer peripheral surface of the drying drum 176 to 1% or more and 75% or less, it is possible to prevent the suppression of cockle and improve the drying performance.

  The aperture ratio is set by the diameter of the suction holes, the hole pitch, the shape and arrangement of the holes. The hole diameter is preferably designed to be not less than 0.4 mm and not more than 1.5 mm so as not to cause a dent mark (suction mark) of the recording medium 124 due to negative pressure suction. The hole pitch is preferably from 0.1 mm to 5 mm in order to prevent thermal deformation of the outer peripheral surface of the drying drum 176 and to ensure rigidity. This is because if the distance between the holes is too far away, the effect of suppressing the deformation of the recording medium is insufficient and the generation of wrinkles cannot be suppressed so much. Further, the shape of the suction hole is preferably a shape with rounded corners because stress is concentrated at the corners if there are corners (acute angles).

  In the rotary conveyance body, the deformation amount of the recording medium 124 due to the adsorption pressure is larger in the axial direction than in the circumferential direction. Therefore, the suction hole is formed in 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 124 are made uniform. You can also.

  Further, it is held on the outer peripheral surface of the drying drum 176 so that the recording surface of the recording medium 124 faces outward (that is, in a state where the recording surface of the recording medium 124 is curved so as to be convex), and is rotated and conveyed. While drying, it is possible to prevent the recording medium 124 from wrinkling and floating, and to reliably prevent drying unevenness due to these.

  Further, as shown in an enlarged view of the portion of the drying drum 176 where the hot air drying means 182 is installed, a rectifying plate 181 may be provided so that the hot air can be reused.

  As shown in FIG. 4, the current plate 181 is formed so as to cover the hot air drying means 182 on the upper side and so that the hot air blown out from the hot air drying means 182 is directed again toward the drying drum 176.

  At this time, a guide plate 183 is further provided on the downstream side of each hot air drying means 182 in the rotational direction of the drying drum 176, and the hot air blown out from each hot air drying means 182 once hits the surface of the drying drum 176 is indicated by an arrow in the figure. It is preferable to flow again to the drying drum 176 side.

  By providing the current plate 181 in this way, it is possible to improve the thermal efficiency and improve the exhaust performance.

  The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate transfer unit (third transfer cylinder transfer unit) 130.

  The recording medium 124 has its front end held by a holding claw (not shown) of the third transfer cylinder transfer unit 130 (transfer transfer unit), the recording surface faces inward, and the rear end side is in a free state. The side is conveyed along the guide member 131 so as to have a convex shape.

  That is, the third transfer drum transport unit 130 (passing transport unit) does not adsorb and restrain the recording medium 124, so that the drying unit 118 is sucked and restrained by the drying drum 176 and dried. The restraint of the recording medium 124 is once released, and the recording medium 124 is bent and corrected in the reverse direction, thereby flattening the recording medium 124 and preventing curling.

  Further, the third transfer drum transport means 130 has a hot air drying means (drying means) (not shown) inside, and blows hot air on the recording surface side of the recording medium 124 facing the inner side during transport to the surface. The ejected ink is dried. As a result, the drying unevenness caused by the suction holes of the drying drum 176 in the drying unit 118 can be made uniform.

  The hot air drying means provided inside the third transfer drum transport means 130 may be blown air, and the temperature thereof is lower than that of the hot air drying means 182 of the drying unit 118 to reduce power consumption.

  When the fixing drum 184 receives the recording medium 124 from the third transfer drum conveying unit 130, the fixing drum 184 holds the leading end portion of the recording medium 124 by the holding unit 185 provided on the outer peripheral surface of the fixing drum 184, thereby holding the recording medium 124 on the outer peripheral surface. Wrap around and transport. The fixing drum 184 does not have a suction hole that sucks the recording medium 124.

  The recording medium 124 wound around the outer peripheral surface of the fixing drum 184 and conveyed is pressed by a pressing roller (smoothing means) 188 disposed facing the fixing drum 184 and pressed against the fixing drum 184 to curl. Is corrected and wrinkles are removed.

  The pressing roller 188 is disposed so as to be in pressure contact with the fixing drum 184 and constitutes a nip roller with the fixing drum 184. As a result, the recording medium 124 is sandwiched between the pressing roller 188 and the fixing drum 184 and nipped at a predetermined nip pressure (for example, 0.15 MPa), and smoothing processing is performed.

  Further, the pressing roller 188 may be a heating roller. For example, the pressing roller 188 may be configured as a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and may be controlled at a predetermined temperature (for example, 60 to 80 ° C.). By heating and pressing the recording medium 124 with the pressing roller 188 configured as this heating roller, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex contained in the ink is applied, and the latex particles are melted. The unevenness of the image surface of the recording medium 124 is leveled, and glossiness is obtained.

  Next, the recording medium 124 is cured and fixed by being irradiated with ultraviolet rays from an ultraviolet light source 190 disposed opposite to the fixing drum 184. Here, a plurality of ultraviolet light sources 190 may be provided as shown in FIG. Accordingly, by reducing the irradiation intensity of each ultraviolet light source 190, it becomes possible to increase the curing conditions with the irradiation time, and it is possible to reduce the cost and reduce the heat generation amount of the ultraviolet light source 190.

  The ultraviolet light source 190 is not particularly limited, and for example, a metal halide lamp, a high-pressure mercury lamp, a black light, a cold cathode tube, a UV-LED, or the like is preferably 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.

  Note that the surface temperature of the fixing drum 184 may be set to 50 ° C. or more, for example, and the recording medium 124 held on the outer peripheral surface of the fixing drum 184 may be heated from the back surface. Thereby, drying of the recording medium 124 is promoted, image destruction at the time of fixing can be prevented, and image intensity can be increased by an effect of increasing the image temperature.

  As described above, in the present embodiment, the recording medium 124 on which the image has been drawn is sucked and held by the drying drum 176, dried with hot air while being transported, and then the third transfer cylinder transport unit 130. In this case, the restriction by suction of the recording medium 124 is once released, and the recording medium 124 is curved and conveyed so that the back side of the recording surface of the recording medium 124 has a convex shape contrary to the drying drum 176, Since the fixing unit 120 is smoothed by the pressure roller 188 and then fixed by ultraviolet curing, generation of cockle can be suppressed, and there are no wrinkles or curls, and there is no image unevenness such as uneven fixing or gloss, high image quality and high A quality image can be formed.

  As described above, the ink jet recording apparatus and the ink jet recording method of the present invention have been described in detail. However, the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.

  DESCRIPTION OF SYMBOLS 100 ... Inkjet recording device, 112 ... Paper feed part, 114 ... Processing liquid provision part, 116 ... Drawing part, 118 ... Drying part, 120 ... Fixing part, 124 ... Recording medium, 126 ... Intermediate conveyance part (1st transfer cylinder conveyance) Means), 128... Intermediate conveyance section (second transfer cylinder conveyance means), 130... Intermediate conveyance section (third transfer cylinder conveyance means), 154... Processing liquid drum, 156. DESCRIPTION OF SYMBOLS ... Drying drum, 178 ... Solvent drying apparatus, 180 ... Air blowing means, 182 ... Hot air drying means, 184 ... Fixing drum, 190 ... Ultraviolet light source, 192 ... Paper discharge unit

Claims (11)

A liquid discharge head for discharging aqueous ultraviolet curable ink onto the recording surface of the recording medium;
Suction for transporting the recording medium on which the aqueous ultraviolet curable ink is adhered and the image is formed by adsorbing and restraining the back surface side of the recording surface to the outer peripheral surface through a suction hole formed on the outer peripheral surface. A constraining drying unit having a constraining cylinder and hot air drying means disposed to face the outer peripheral surface of the suction constraining cylinder;
A transfer conveying means for holding the front end of the recording medium on the downstream side of the constraining drying unit and curving the back surface side of the recording surface into a convex shape;
A fixing unit having ultraviolet irradiation means for irradiating ultraviolet rays to an image formed on the recording surface of the recording medium on the downstream side of the transfer conveying means;
An ink jet recording apparatus comprising:   2. The ink jet recording apparatus according to claim 1, further comprising a smoothing unit that smoothes the recording medium on the downstream side of the transfer conveying unit and on the upstream side of the ultraviolet irradiation unit. The fixing unit includes a fixing cylinder that wraps and conveys the recording medium around an outer peripheral surface, and the ultraviolet irradiation unit that is disposed to face the outer peripheral surface.
The inkjet recording apparatus according to claim 2, wherein the smoothing unit is a pressing roller that presses the recording medium against the fixing cylinder.   4. The ink jet recording apparatus according to claim 1, further comprising suction assisting means for assisting suction of the recording medium to the suction restraining cylinder.   The suction assisting means is a blowing means disposed on the upstream side of the hot air drying means so as to face the suction restraining cylinder, and blows obliquely toward the rear end side of the recording medium. Item 5. The ink jet recording apparatus according to Item 4.   The inkjet recording apparatus according to claim 1, wherein the transfer conveying unit includes a drying unit that dries the recording surface side of the recording medium.   The ink jet recording apparatus according to claim 6, wherein the drying unit of the transfer conveyance unit is a unit that blows hot air on a recording surface side of the recording medium to dry the recording medium.   The said delivery conveyance means was equipped with the guide member with a rib for curving the back surface side of the said recording surface to convex shape, The guide member with a rib in any one of Claims 1-7 characterized by the above-mentioned. Inkjet recording device.   The inkjet according to any one of claims 1 to 8, wherein the constraining drying unit includes a rectifying plate for directing hot air blown from the hot air drying means toward an outer peripheral surface of the suction constraining cylinder. Recording device. An ink discharge step of discharging aqueous ultraviolet curable ink onto the recording surface of the recording medium;
The recording medium on which the aqueous ultraviolet curable ink is adhered and the image is formed is transported by adsorbing and restraining the back surface side of the recording surface to the outer peripheral surface via a suction hole formed on the outer peripheral surface of the drum. However, a constrained drying step of drying by applying hot air to the recording surface of the recording medium;
A transfer conveying step of holding the leading end of the recording medium dried in the constrained drying step and curving the back side of the recording surface into a convex shape;
A fixing step of fixing the image formed on the recording surface of the recording medium conveyed through the transfer conveying step by irradiating with ultraviolet rays;
An ink jet recording method comprising:   The inkjet recording method according to claim 10, further comprising a smoothing step of smoothing the recording medium before the recording medium dried in the constrained drying step is fixed in the fixing step.

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