JP2019116032A - Ink jet recording device - Google Patents

Abstract

To provide an ink jet recording device capable of heating ink on a recording medium while curbing an increase in a temperature of a recording head.SOLUTION: An ink jet recording device 100 comprises: recording heads 10a to 10d which have ink discharge surfaces 11; thermal heads 20a to 20d which are arranged opposite to the ink discharge surfaces 11 with a recording medium carrying passage 2 placed in between and heat a recording medium 1; and a control section 110. Each of the thermal heads 20a to 20d has a plurality of element arrays L21, arranged in a width direction, respectively provided with a plurality of heat generation elements 21 arranged in a recording medium carrying direction. The control section 110 causes at least a portion of the heat generation elements 21, in the element array L21 corresponding to an ink discharge port 12 which executes discharge of ink, to generate heat.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an inkjet recording apparatus provided with a recording head for ejecting ink onto a recording medium and a thermal head for heating the recording medium.

  As a recording apparatus for printing on recording media such as paper, plastic film, and cloth, an ink jet recording apparatus that discharges ink to form an image is widely used because it can form a high definition image.

  In such an inkjet recording apparatus, the ink ejected onto the recording medium mixes with the ink ejected from the recording head downstream of the recording medium conveyance direction, or the conveyance roller pair disposed downstream of the recording medium conveyance direction It may adhere (move). Such a problem is likely to occur when the ink dries slowly, particularly when using a water-based ink.

  In order to improve the above-mentioned problems, it is conceivable to provide a heating device for heating the ink on the recording medium near the downstream side of the recording head.

  An ink jet recording apparatus using a water-based ink is disclosed, for example, in Patent Document 1.

JP, 2016-155240, A

  However, when the heating device for heating the ink on the recording medium is provided in the vicinity of the downstream side of the recording head, the temperature of the recording head is increased by the heat from the heating device. Therefore, there is a problem that the ink in the ink discharge port of the recording head is dried and solidified, and the ink discharge port is clogged.

  The present invention has been made to solve the above problems, and the object of the present invention is to heat the ink on the recording medium while suppressing the temperature of the recording head from rising. Providing an inkjet recording apparatus.

  In order to achieve the above object, an inkjet recording apparatus according to one aspect of the present invention includes: a recording head having an ink discharge surface having a plurality of ink discharge ports for discharging ink on the recording medium; And a thermal head that heats the recording medium, and a heat generation control unit that controls the thermal head. In the thermal head, a plurality of element arrays each including a plurality of heating elements arranged in the recording medium conveyance direction are provided in the width direction orthogonal to the recording medium conveyance direction so as to correspond to each one or more ink ejection ports. ing. The element array is provided at least on the downstream side in the recording medium conveyance direction with respect to the landing position where the ink discharged from the ink discharge port lands on the recording medium. The heat generation control unit can selectively generate heat from the plurality of heat generating elements, and heats at least a part of the heat generating elements of the element array corresponding to the ink discharge port for executing the ink discharge. In addition, the heat generation control unit changes at least one of the heat generation amount of the heat generation area for generating heat of the heat generation element in the element row and the length of the heat generation area in the recording medium conveyance direction according to the conveyance speed of the recording medium. .

  According to the inkjet recording apparatus of one aspect of the present invention, the recording apparatus includes the thermal head which is disposed to face the ink ejection surface of the recording head with the recording medium conveyance path interposed therebetween, and heats the recording medium. As a result, it is possible to suppress the transfer of excess heat to the recording head as compared to the case where a heating device for heating the recording medium is provided on the recording head side with respect to the recording medium conveyance path, so the temperature of the recording head It is possible to suppress the rise. Therefore, the ink in the ink discharge port of the recording head can be prevented from drying and solidifying, so that clogging of the ink discharge port can be suppressed. Therefore, the ink on the recording medium can be heated while suppressing the temperature of the recording head from rising.

  Further, the heat generation control unit can selectively heat the plurality of heat generating elements, and heats at least a part of the heat generating elements of the element array corresponding to the ink discharge port for executing the ink discharge. Thus, unlike the case where the entire thermal head is heated, only the necessary part (at least a part of the heating elements of the element row corresponding to the ink discharge port for executing the ink discharge) can be heated, so recording The ink on the medium can be efficiently dried with a small amount of heat generation, and the transfer of excess heat to the recording head can be further suppressed.

  In addition, the heat generation control unit changes at least one of the heat generation amount of the heat generation area for generating heat of the heat generation element in the element row and the length of the heat generation area in the recording medium conveyance direction according to the conveyance speed of the recording medium. . As a result, the ink on the recording medium can be efficiently dried in an optimum state, and the transfer of excess heat to the recording head can be further suppressed.

Schematic diagram showing the overall configuration of an ink jet recording apparatus according to an embodiment of the present invention The figure which shows the structure around the recording head of the inkjet recording device of one Embodiment of this invention, and a thermal head. A view of a recording head of an ink jet recording apparatus according to an embodiment of the present invention as viewed from an ink discharge surface side Block diagram for explaining a control path of an ink jet recording apparatus according to an embodiment of the present invention The figure which shows the recording medium with which the reference mark was printed by the inkjet recording device of one Embodiment of this invention. The figure which shows the structure of the thermal head of the inkjet recording device of one Embodiment of this invention It is a figure for demonstrating the setting method of the heat generation area | region of the thermal head of the inkjet recording device of one Embodiment of this invention, and a figure which shows the example which heats only the heating element of an impact position. FIG. 8 is a view for explaining the setting method of the heat generation area of the thermal head of the ink jet recording apparatus according to the embodiment of the present invention, showing an example in which only the heat generating element downstream of the landing position in the recording medium conveyance direction is heated. FIG. 17 is a view for explaining the method of setting the heat generation area of the thermal head of the inkjet recording apparatus according to an embodiment of the present invention, showing an example of generating heat in a predetermined range downstream of the landing position in the recording medium conveyance direction. FIG. 8 is a view for explaining a setting method of a heat generation area of the thermal head of the ink jet recording apparatus according to an embodiment of the present invention, showing an example of moving the heat generation area corresponding to the movement of ink. FIG. 11 is a view for explaining the setting method of the heat generation area of the thermal head of the ink jet recording apparatus according to the embodiment of the present invention, in which the ink and the heat generation area further move downstream in the recording medium conveyance direction from the state of FIG. Figure shown A diagram for explaining an example of the relationship between the element array of the thermal head and the ink discharge port of the ink jet recording apparatus according to an embodiment of the present invention. FIG. 17 is a view showing a structure around a recording head and a thermal head of an ink jet recording apparatus according to a modification of the present invention, showing a structure provided with an auxiliary heating device for heating a recording medium from the upper surface side.

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

  As shown in FIG. 1, an inkjet recording apparatus 100 according to an embodiment of the present invention discharges ink onto a recording medium 1 to form an image, and a plurality of ink jet recording apparatuses 100 (here, four) are provided along the recording medium conveyance path 2. Recording heads 10a, 10b, 10c and 10d.

  The recording medium 1 is wound in a roll shape in the present embodiment. As the recording medium 1, plastic film, paper (plain paper, glossy paper, etc.), cloth and the like can be used.

  The inkjet recording apparatus 100 further includes a feed rotary shaft 3 for feeding the roll-shaped recording medium 1, a take-up rotary shaft 4 for winding the recording medium 1 on which an image is formed into a roll, and the recording medium 1 for the recording head 10a to 10d, a conveyance roller pair 6 that conveys the recording medium 1 on which an image is formed to the take-up rotation shaft 4, and a plurality of (here, four) thermal heads 20a that heat the recording medium 1, 20b, 20c and 20d.

  The recording medium 1 delivered by the feed rotating shaft 3 is image-formed by the recording heads 10a to 10d, dried to some extent while passing through the thermal heads 20a to 20d, and taken up by the take-up rotating shaft 4 . Since the ink on the recording medium 1 is dried (temporarily dried) to some extent by the thermal heads 20a to 20d, the ink adheres to the transport roller pair 6, and the ink adheres to the back surface of the recording medium 1 after being wound up. There is almost no problem, but if necessary, a heating device may be provided on the downstream side of the thermal head 20 d in the recording medium conveyance direction.

  The recording heads 10a to 10d are disposed at a height such that a predetermined distance is formed with respect to the upper surfaces of the thermal heads 20a to 20d, and the width direction perpendicular to the recording medium conveyance direction (perpendicular to the sheet of FIG. Is formed to extend along the direction).

  As shown in FIGS. 2 and 3, a plurality of ink discharge ports 12 are provided on the ink discharge surface 11 of the recording heads 10a to 10d at a predetermined pitch in the width direction (arrow YY 'direction, main scanning direction) There is. The plurality of ink discharge ports 12 may not be arranged linearly in the width direction, and may be arranged in a zigzag or in a row inclined with respect to the width direction.

  The recording heads 10 a to 10 d correspond to, for example, cyan, magenta, yellow, and black, respectively, and eject the water-based ink of each color from the ink ejection port 12. As a result, a color image is formed on the recording medium 1.

  As shown in FIG. 4, the control unit 110 of the inkjet recording apparatus 100 is configured of a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like. Further, the control unit 110 can control the recording heads 10a to 10d, the feed rotary shaft 3, the take-up rotary shaft 4, the conveyance roller pairs 5 and 6, the thermal heads 20a to 20d, etc. It is possible. The control unit 110 can control the support member 31 and the blower 32 described later, and can communicate with the mark detection sensor 33.

  The ROM contains a control program for the inkjet recording apparatus 100, data necessary for control, and other data that can not be changed during use of the inkjet recording apparatus 100. The RAM stores necessary data generated during control of the inkjet recording apparatus 100, data temporarily necessary for controlling the inkjet recording apparatus 100, and the like.

  Further, the control unit 110 is configured to be able to communicate with an operation panel or a personal computer (neither shown) through which information on the type of the recording medium 1 and the like is inputted by the user, and the operation panel or the personal computer Get (receive) information from Further, the control unit 110 determines, for example, the amount of ink ejected from each ink ejection port 12 according to the image data received from the personal computer, or according to the type of the recording medium 1 or the printing speed setting by the user. The transport speed of the recording medium 1 is determined.

  Here, in the present embodiment, as shown in FIG. 2, the thermal heads 20 a to 20 d are disposed so as to face the ink ejection surfaces 11 of the recording heads 10 a to 10 d across the recording medium conveyance path 2. Is heated from the back side (opposite to the recording surface).

  The recording heads 10a to 10d are disposed at predetermined intervals along the recording medium conveyance direction (arrow X direction), and the thermal heads 20a to 20d are also disposed at predetermined intervals along the recording medium conveyance direction. It is arranged. Support members 31 for supporting the recording medium 1 are provided on the upstream side and the downstream side in the recording medium conveyance direction with respect to each of the thermal heads 20a to 20d. That is, at least one (here, two) support members 31 are disposed between the thermal heads 20a to 20d. The uppermost position of the support member 31 is disposed at a height position which is the same as or slightly lower than the upper surfaces of the thermal heads 20a to 20d (the lower surface of the recording medium conveyance path 2, the upper surface of the sliding layer 41 described later in this embodiment). There is.

  Here, the support member 31 is formed by a transport roller which is rotated by a rotational drive force from a drive source (not shown). The support member 31 may be formed by a driven roller, or may be formed by a guide member for guiding the recording medium 1.

  Between the recording heads 10a to 10d, a blower 32 is provided which is a fan for blowing air toward the recording medium 1 from between the recording heads 10a to 10d. Thus, the recording medium 1 is in close contact with the upper surfaces (the lower surface of the recording medium conveyance path 2) of the thermal heads 20a to 20d by the air flow. Although three air blowers 32 are provided one by one between the recording heads 10a to 10d in FIG. 2, the air blower 32 does not have to be disposed between the recording heads 10a to 10d. For example, one duct may be disposed between the recording heads 10a to 10d, and only one blower 32 may be provided to send air to each duct. Also in this case, air can be blown toward the recording medium 1 from between the recording heads 1a to 10d. When the ink jet recording apparatus 100 is large (for example, when the distance between the recording heads 10a to 10d is 50 cm or more), the recording medium 1 is the upper surface of the thermal heads 20a to 20d due to its own weight. It does not have to be provided with the blower 32 because it is in close contact with the lower surface of the

  When the supporting member 31 is provided between the thermal heads 20a to 20d, the recording medium 1 can be prevented from being bent downward between the thermal heads 20a to 20d. However, when the air blower 32 is provided, recording is performed. Depending on the thickness of the medium 1 and the strength of the waist, the recording medium 1 may be bent downward between the thermal heads 20a to 20d. In this case, since the timing at which the recording medium 1 reaches the thermal heads 20b, 20c, and 20d is delayed by the amount of bending, color misregistration occurs.

  Therefore, in the present embodiment, the recording head (uppermost head) 10a disposed at the uppermost stream among the recording heads 10a to 10d prints the reference mark M (see FIG. 5) for timing correction on the recording medium 1 Is configured as. The reference mark M is printed on the outside of the printing area R1 at a size of 2 mm × 2 mm, for example, and at a pitch of several cm. In FIG. 5, the reference mark M and the print area R1 are hatched to facilitate understanding. A reflective or transmissive mark detection sensor (mark detection unit) 33 for detecting the reference mark M is provided for each of the recording heads 10b to 10d other than the recording head 10a. The detection result of the mark detection sensor 33 is transmitted to the control unit 110.

  Then, the control unit (head control unit) 110 corrects the ink discharge timing of the recording heads 10 b to 10 d based on the detection timing at which the mark detection sensor 33 detects the reference mark M. Thus, even when the recording medium 1 is bent downward between the thermal heads 20a to 20d, it is possible to suppress the occurrence of color misregistration.

  A sliding layer 41 with which the recording medium 1 contacts and slides is provided on the top surfaces of the thermal heads 20a to 20d (opposite surfaces facing the recording heads 10a to 10d). As a result, when the recording medium 1 passes through the thermal heads 20a to 20d, the recording medium 1 can be prevented from being scratched.

  The sliding layer 41 is formed of a thin hard glass plate in this embodiment. The sliding layer 41 is formed to a thickness of 100 μm or less, and more preferably to a thickness of 20 μm or less.

  The sliding layer 41 may be made of resin. In this case, the sliding layer 41 is preferably formed of polyimide or polyamideimide from the viewpoint of heat resistance. By using polyimide or polyamideimide, the sliding layer 41 can be easily formed to a thickness of 20 μm or less. Also, in order to further reduce the friction coefficient of the sliding layer 41 with respect to the recording medium 1, PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexa) A fluorine resin such as a fluoropropylene copolymer) may be coated on the surface (upper surface) of the sliding layer 41 in contact with the recording medium 1.

  Further, in the present embodiment, as shown in FIG. 6, a plurality of heating elements 21 are provided in the thermal heads 20a to 20d. The heating elements 21 are arranged in the recording medium conveyance direction (the arrow X direction), whereby an element row L21 extending in the recording medium conveyance direction is configured. A plurality of element rows L21 are provided in the width direction (arrow YY 'direction) so as to correspond to one or more ink ejection openings 12 (see FIG. 3).

  The element row L21 is at least on the downstream side (arrow X direction) of the recording medium conveyance direction with respect to the landing position P1 (a position just below the ink discharge port 12) at which the ink discharged from the ink discharge port 12 lands on the recording medium 1. It is provided. Here, the element row L21 is provided on the downstream side (arrow X direction) in the recording medium conveyance direction from the landing position P1 (or a position slightly upstream of the landing position P1 in the recording medium conveyance direction (arrow X 'direction)). It is done.

  Each of the heating elements 21 includes a heating resistor, a thin film transistor, an individual electrode, a common electrode and the like (all not shown), and the control unit (heating control unit) 110 selectively selects the plurality of heating elements 21. It can generate heat.

  The control unit 110 causes the ink on the recording medium 1 to be heated by causing the heat generating elements 21 of the element row L21 corresponding to the ink discharge port 12 that executes the ink discharge to generate heat. And drying to a certain extent (temporary drying) before reaching conveyance roller pair 6. Here, since the water-based ink is used, the control unit 110 sets the calorific value of the heating element 21 so that the upper surface (the surface on which the ink lands) of the recording medium 1 is approximately 100.degree.

  There are various methods for setting the heat generation area R21 for generating heat in the heat generation element 21.

  For example, as shown in FIG. 7, the control unit 110 may heat only the heating element 21 at the landing position P1. According to this structure, when the ink 50 discharged from the ink discharge port 12 lands on the recording medium 1, the ink 50 on the recording medium 1 is temporarily dried. In order to facilitate understanding, in FIGS. 7 to 11, the heat generation area R21 for heating the heat generating element 21 is hatched and the recording medium 1 is omitted.

  Further, as shown in FIG. 8, the control unit 110 may generate heat only from the heating element 21 downstream in the recording medium conveyance direction (arrow X direction) than the landing position P1. According to this structure, when the ink 50 on the recording medium 1 passes the heat generation region R21, the ink 50 on the recording medium 1 is temporarily dried.

  Further, as shown in FIG. 9, the control unit 110 is located in a predetermined range from the landing position P1 (or a position downstream of the landing position P1 in the recording medium conveyance direction) downstream of the recording medium conveyance direction (right side in FIG. 9). The heat generating element 21 of may be heated. That is, the control unit 110 may form the heat generation region R21 so as to extend in the recording medium conveyance direction. According to this structure, since the ink heating time can be extended, the amount of heat generation of each heating element 21 can be suppressed accordingly. At this time, since the temperature of the upper surface of the recording medium 1 can be lowered to, for example, about 80 ° C. to 85 ° C. to temporarily dry the recording medium 1, the resin such as PP (polypropylene) having relatively low heat resistance can be used as the recording medium 1 Even in the case where the recording medium 1 is used, it is possible to suppress the thermal contraction (thermal deformation) of the recording medium 1.

  In the configurations of FIG. 7, FIG. 8 and FIG. 9, the control unit 110 generates heat in a state where the heat generation region R21 is at rest at a predetermined position.

  Further, as shown in FIGS. 10 and 11, the heat generation region R21 may be moved downstream in the recording medium conveyance direction in accordance with the movement of the ink 50 on the recording medium 1. With this configuration, as in the case of FIG. 9, the ink heating time can be extended, and accordingly, the amount of heat generated by each heating element 21 can be suppressed. In addition, the temperature of the upper surface of the recording medium 1 can be lowered to, for example, about 80 ° C. to 85 ° C. to temporarily dry the recording medium 1. In FIG. 10 and FIG. 11, the movement of the heat generation region R21 is indicated by thick arrows.

  Here, in the present embodiment, the control unit 110 controls the heat generation amount of the heat generation area R21 and the length of the heat generation area R21 in the recording medium conveyance direction according to the dryness of the ink 50 on the recording medium 1. You may change one.

  Specifically, the control unit 110 controls at least one of the heat generation amount of the heat generation area R21 and the length of the heat generation area R21 according to the amount of ink discharged from the ink discharge port 12 (the amount of ink per dot). May be changed. In this case, when the amount of ink discharged from the ink discharge port 12 is large (when the ink 50 does not dry easily), the control unit 110 increases the amount of heat generation of the heat generation region R21 or the length of the heat generation region R21. To lengthen. On the other hand, when the amount of ink discharged from the ink discharge port 12 is small (when the ink 50 is easily dried), the control unit 110 reduces the calorific value of the heat generation area R21 or reduces the length of the heat generation area R21. Or shorten it.

  Further, the control unit 110 may change at least one of the heat generation amount of the heat generation area R21 and the length of the heat generation area R21 according to the type of the recording medium 1. In this case, for example, when the thickness of the recording medium 1 is large (when the ink is difficult to dry), the control unit 110 increases the calorific value of the heat generation area R21 or lengthens the heat generation area R21. . On the other hand, when the thickness of the recording medium 1 is thin (when the ink tends to dry), the control unit 110 reduces the calorific value of the heat generation area R21 or shortens the length of the heat generation area R21. Further, for example, when using the recording medium 1 in which the surface of the label paper, the film, etc. is smooth and the ink 50 hardly penetrates (when the ink does not dry easily), the control unit 110 increases the heat generation amount of the heat generation region R21. Or lengthening the length of the heat generation region R21. On the other hand, when using the recording medium 1 in which the ink 50 such as plain paper easily penetrates (when the ink tends to dry), the control unit 110 reduces the calorific value of the calorific region R21 or lengthens the calorific region R21. Reduce the length of

  The control unit 110 can change the calorific value of the calorific region R21 according to the ease of drying of the ink 50 on the recording medium 1 when using the calorific method shown in FIGS. 7 to 11. In addition, when the heat generation method shown in FIG. 9 is used, the control unit 110 may change the length of the heat generation region R21 in the recording medium conveyance direction according to the dryness of the ink 50 on the recording medium 1. it can.

  Further, in the present embodiment, even if the control unit 110 changes at least one of the calorific value of the heat generation area R21 and the length of the heat generation area R21 in the recording medium conveyance direction according to the conveyance speed of the recording medium 1. Good.

  In this case, when the conveyance speed of the recording medium 1 is high (in the case of high-speed printing), the control unit 110 increases the heat generation amount of the heat generation region R21 or lengthens the heat generation region R21. On the other hand, when the conveyance speed of the recording medium 1 is low (in the case of low speed printing), the control unit 110 reduces the calorific value of the heat generation area R21 or shortens the length of the heat generation area R21.

  Note that the control unit 110 can change the amount of heat generation of the heat generation region R21 according to the transport speed of the recording medium 1 when using the heat generation method illustrated in FIGS. Further, when the heat generation method shown in FIG. 9 is used, the control unit 110 can change the length of the heat generation region R21 in the recording medium conveyance direction according to the conveyance speed of the recording medium 1.

  Further, in the present embodiment, the heat generation region R21 is disposed so as to substantially face the region on the recording medium 1 through which the ink (hereinafter, also referred to as ink dots) 50 passes. In the present specification, "the heat generating area is disposed substantially opposite to the area through which the ink dots pass on the recording medium" means that the heat generating area is disposed so that 50% or more of the ink dot area passes through the heat generating area. It means to be done. Here, the heat generation area R21 is disposed such that 80% or more of the area of the ink dot 50 passes through the heat generation area R21. That is, the element array L21 of the thermal heads 20a to 20d is provided with high accuracy without being displaced in the width direction (arrow YY 'direction) with respect to the ink ejection openings 12 of the recording heads 10a to 10d.

  Further, in the present embodiment, the control unit 110 causes the heat generation region R21 to generate heat in accordance with the timing at which the ink dots 50 on the recording medium 1 pass through the recording medium conveyance path 2. Specifically, the control unit 110 causes the heat generation area R21 to generate heat at a predetermined timing based on the transport speed of the recording medium 1 and the distance from the landing position P1 to the heat generation area R21. The timing at which the heat generation region R21 generates heat is corrected by the control unit 110 based on the timing at which the mark detection sensor 33 detects the reference mark M, as in the above-described ink discharge timing.

  For example, when the control unit 110 uses the heat generation method shown in FIG. 7, when the ink 50 lands on the recording medium 1 (or a little earlier than when the ink 50 lands in consideration of the time required for temperature rise) The heat generation area R21 generates heat, and the heat generation of the heat generation area R21 is stopped immediately after the ink dot 50 passes through the heat generation area R21.

  Further, when the heat generation method shown in FIG. 8 is used, the control unit 110 detects when the ink dot 50 reaches the heat generation area R21 (or the ink dot 50 reaches the heat generation area R21 in consideration of the time required for temperature rise). Heat generation region R21 slightly earlier than when the ink dot 50 passes through the heat generation region R21 and stops the heat generation of the heat generation region R21.

  In addition, when the heat generation method shown in FIG. 9 is used, the control unit 110 causes the ink 50 to land on the recording medium 1 (or slightly earlier than the ink 50 lands in consideration of the time required for the temperature rise). The heat generation area R21 generates heat, and the heat generation of the heat generation area R21 is stopped immediately after the ink dot 50 passes through the heat generation area R21.

  Further, when the heat generation method shown in FIGS. 10 and 11 is used, the control unit 110 sequentially switches on and off the heat generation element 21 so that the ink dots 50 are always positioned on the heat generation region R21, and heats the heat generation region R21. The recording medium 1 is moved downstream in the recording medium conveyance direction at the same speed as the movement speed of the dots 50 (the conveyance speed of the recording medium 1).

  In the case where the heat generation area R21 generates heat in accordance with the timing at which the ink dot 50 passes, the control unit 110 generates heat in the heat generation area R21 at the timing when the ink dot 50 is substantially opposed to the heat generation area R21. Let In the present specification, “the ink dots are disposed substantially in opposition to the heat generation area during heat generation” means that 50% or more of the ink dot area passes through the heat generation area during heat generation (overlap with the heat generation area during heat generation Means to be placed). Here, the control unit 110 causes the heat generation region R21 to generate heat at a timing when 80% or more of the area of the ink dot 50 passes the heat generation region R21.

  In FIGS. 7 to 11, in order to facilitate understanding, a plurality of element rows L 21 are shown in the width direction (arrow YY ′ direction) so as to correspond to each ink ejection port 12, but As indicated by 12, a plurality of element rows L 21 may be provided in the width direction (arrow YY ′ direction) so as to correspond to each of two or more (two in FIG. 12) ink ejection openings 12.

  That is, the element array L21a is provided corresponding to the ink discharge ports 12a and 12b, the element array L21b is provided corresponding to the ink discharge ports 12c and 12d, and the element array L21c is provided corresponding to the ink discharge ports 12e and 12f. It is also good. In this case, for example, when at least one of the ink ejection openings 12a and 12b performs ink ejection, the predetermined area (heat generation area R21) of the element row L21a is heated.

  In the present embodiment, as described above, the thermal heads 20 a to 20 d are disposed to face the ink ejection surfaces 11 of the recording heads 10 a to 10 d with the recording medium transport path 2 interposed therebetween and heat the recording medium 1. Thus, it is possible to suppress the transfer of excess heat to the recording heads 10a to 10d as compared with the case where a heating device for heating the recording medium 1 is provided on the recording heads 10a to 10d side with respect to the recording medium conveyance path 2. Since this can be performed, it is possible to suppress an increase in the temperature of the recording heads 10a to 10d. Thus, the ink 50 in the ink ejection openings 12 of the recording heads 10a to 10d can be prevented from drying and solidifying, and therefore clogging of the ink ejection openings 12 can be suppressed. Therefore, the ink 50 on the recording medium 1 can be heated while suppressing the temperature of the recording heads 10a to 10d from rising.

  Further, the control unit 110 can selectively generate heat from the plurality of heat generating elements 21 and generates heat from at least a part of the heat generating elements 21 of the element row L21 corresponding to the ink discharge port 12 that executes ink discharge. Thus, unlike in the case where the entire thermal heads 20a to 20d are heated, only the necessary part (heat generating elements 21 of at least a part of the element row L21 corresponding to the ink discharge port 12 that performs ink discharge) is heated As a result, the ink 50 on the recording medium 1 can be efficiently dried with a small amount of heat generation, and the transfer of excess heat to the recording heads 10a to 10d can be further suppressed.

  Further, the control unit 110 changes at least one of the calorific value of the heat generation area R21 and the length of the heat generation area R21 in the recording medium conveyance direction according to the conveyance speed of the recording medium 1. As a result, the ink 50 on the recording medium 1 can be efficiently dried in an optimal state, and the transfer of excess heat to the recording heads 10a to 10d can be further suppressed.

  Further, as described above, when the plurality of recording heads 10a to 10d are provided along the recording medium conveyance direction, the ink 50 on the recording medium 1 discharged from the recording heads 10a to 10d is the thermal head 20a to According to 20d, it can be dried to some extent (temporary drying) before reaching the next recording heads 10b to 10d or the conveyance roller pair 6. Therefore, color mixing of the ink 50 and adhesion to the transport roller pair 6 can be suppressed, so that deterioration in image quality can be suppressed.

  Further, as described above, as shown in FIGS. 7 and 8, the control unit 110 generates heat in a state where the heat generation area R21 is kept at a predetermined position, and the heat generation area R21 is generated according to the transport speed of the recording medium 1. You may change the calorific value of.

  Further, as described above, as shown in FIG. 9, the control unit 110 forms the heat generation area R21 so as to extend in the recording medium conveyance direction, and generates heat while the heat generation area R21 is kept at a predetermined position. The length of the heat generation region R21 in the recording medium conveyance direction may be changed according to the conveyance speed of the recording medium 1. According to this structure, since the time for the ink 50 on the recording medium 1 to pass through the heat generation area R21 can be extended, the set temperature of the heat generation area R21 is lowered (the temperature of the upper surface of the recording medium 1 is lowered). )be able to. Therefore, even when the heat resistance of the recording medium 1 is relatively low, the thermal deformation of the recording medium 1 can be suppressed.

  Further, as described above, as shown in FIGS. 10 and 11, the control unit 110 moves the heat generation region R21 to the downstream side in the recording medium conveyance direction in accordance with the movement of the ink 50 on the recording medium 1, and performs recording. The heat generation amount of the heat generation region R21 may be changed according to the transport speed of the medium 1. According to this structure, since the time for the ink 50 on the recording medium 1 to pass through the heat generation area R21 can be extended, the set temperature of the heat generation area R21 is lowered (the temperature of the upper surface of the recording medium 1 is lowered). )be able to. Therefore, even when the heat resistance of the recording medium 1 is relatively low, the thermal deformation of the recording medium 1 can be suppressed.

  Further, the ink 50 on the recording medium 1 can be efficiently dried with a smaller amount of heat generation as compared to the case where the heat generation area R21 is formed to extend in the recording medium conveyance direction (in the case of FIG. 9) It is possible to further suppress the transfer of excess heat to the heads 10a to 10d.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the description of the embodiments described above but by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

  For example, in the above embodiment, the roll-shaped recording medium 1 is used. However, the present invention is not limited to this, and the recording medium 1 cut into a predetermined size (for example, A4 size or the like) may be used.

  Moreover, although the example using a water-based ink was shown in the said embodiment, this invention may use non-water-based inks, such as an organic solvent type ink, not only this.

  Moreover, although the said embodiment showed the example which provides the sliding layer 41 which consists of glass plates, for example on the upper surface of thermal head 20a-20d, this invention is not limited to this. The sliding layer 41 may be provided by coating the upper surfaces of the thermal heads 20 a to 20 d with a fluorine resin or the like.

  Further, in the above embodiment, an example is shown in which the recording medium 1 is heated only from the back side using the thermal heads 20a to 20d, but the present invention is not limited to this. For example, in addition to the thermal heads 20 a to 20 d as in the inkjet recording apparatus 100 according to the modified example of the present invention shown in FIG. 13, an auxiliary heating device 34 may be provided for auxiliary heating the recording medium 1 from the upper surface side. Also in this case, the temperature rise of the recording heads 10a to 10d can be suppressed as compared with the case where the recording medium is heated only from the upper surface side. In addition, as a suitable example using the auxiliary heating device 34, for example, in order to print on the low heat resistant recording medium 1 such as PP, when the thermal heads 20a to 20d can not generate heat sufficiently, the auxiliary The auxiliary use of the heating device 34 at a temperature lower than the thermal heads 20a to 20d may be mentioned.

  In the above embodiment, the recording heads 20a to 20d are provided along the recording medium conveyance direction. However, the present invention is not limited thereto. Only one recording head is provided along the recording medium conveyance direction. May be

  In the above embodiment, when the control unit 110 changes at least one of the heat generation amount of the heat generation area R21 and the length of the heat generation area R21 according to the type of the recording medium 1, the thickness of the recording medium 1 is used. Accordingly, although an example is shown in which at least one of the calorific value of the calorific region R21 and the length of the calorific region R21 is changed, the invention is not limited thereto. The control unit 110 may change at least one of the heat generation amount of the heat generation area R21 and the length of the heat generation area R21 according to the material (thermal conductivity) of the recording medium 1.

  In the above embodiment, the support members 31 are provided on the upstream side and the downstream side in the recording medium conveyance direction with respect to the thermal heads 20a to 20d. However, the present invention is not limited thereto, and the support members 31 are provided. It does not have to be.

  In the above embodiment, the sliding layer 41 is provided on the upper surfaces of the thermal heads 20a to 20d. However, the present invention is not limited thereto, and the sliding layers 41 are not provided on the upper surfaces of the thermal heads 20a to 20d. It may be

Reference Signs List 1 recording medium 2 recording medium conveyance path 10a recording head, most upstream head 10b to 10d recording head 11 ink ejection surface 12, 12a to 12f ink ejection port 20a to 20d thermal head 21 heating element 31 support member 32 air blower 33 mark detection sensor (Mark detection unit)
41 sliding layer 50 ink, ink dot 100 inkjet recording apparatus 110 control unit (head control unit, heat generation control unit)
L21, L21a to L21c Element row M Reference mark P1 Landing position R21 Heat generation area

Claims (4)

A recording head having an ink discharge surface in which a plurality of ink discharge ports for discharging ink onto a recording medium are opened;
A thermal head disposed opposite to the ink ejection surface across the recording medium transport path and heating the recording medium;
A heat generation control unit that controls the thermal head;
Equipped with
The thermal head has a width direction orthogonal to the recording medium conveyance direction such that an element array including a plurality of heating elements arranged in the recording medium conveyance direction corresponds to each of the one or more ink discharge ports. More than one are provided in
The element array is provided at least on the downstream side in the recording medium conveyance direction with respect to an impact position where the ink ejected from the ink ejection port lands on the recording medium.
The heat generation control unit
It is possible to selectively heat the plurality of heating elements,
Generating heat by at least a part of the heating element of the element row corresponding to the ink discharge port for executing the ink discharge;
Changing at least one of the calorific value of the heat generating area which heats the heat generating element of the element row and the length of the heat generating area in the recording medium conveyance direction according to the conveyance speed of the recording medium; An inkjet recording apparatus characterized by the above.   The inkjet recording apparatus according to claim 1, wherein a plurality of each of the recording head and the thermal head are provided along the recording medium conveyance direction. The heat generation control unit
The heat is generated while the heat generation area is kept at a predetermined position,
The ink jet recording apparatus according to claim 1 or 2, wherein the calorific value of the heat generation area is changed according to the conveyance speed of the recording medium. The heat generation control unit
The heat generation area is formed so as to extend in the recording medium conveyance direction, and the heat generation area is allowed to generate heat in a state where the heat generation area is stopped at a predetermined position.
The ink jet recording apparatus according to claim 1 or 2, wherein the length of the heat generation area in the recording medium conveyance direction is changed according to the conveyance speed of the recording medium.

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