Patent Publication Number: US-10328714-B2

Title: Printing apparatus and printing method

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a printing apparatus and a printing method. 
     2. Related Art 
     Various types of printing apparatuses have thus far been utilized, some of which include a heating unit for heating a medium. 
     For example, JP-A-2012-139822 discloses a recording apparatus (printing apparatus) that includes a heater, corresponding to the heating unit. 
     In some of the conventional printing apparatuses that include the heating unit for heating a medium, however, the transport route of the medium includes a heating range where the heat of the heating unit is applied to the medium, and a non-heating range where the heat of the heating unit is not applied to the medium. Besides, in the heating range of some printing apparatuses, the heat amount applied to the medium differs depending on the position of the medium, in other words the heating range includes a region where a relatively larger amount of heat is applied to the medium, and another region where a relatively smaller amount of heat is applied to the medium. In the printing apparatuses configured as above, when the medium is heated while remaining stopped for a certain period of time, the medium may be unevenly heated depending on the positional relationship between the heating range of the heating unit and the medium, and the shape of the heating range, in particular the shape of the support member of the medium. As result, the color of the image printed on the medium may become uneven, owing to the uneven heating. 
     SUMMARY 
     An advantage of some aspects of the invention is provision of a printing apparatus including a heating unit for heating a medium, configured to prevent color unevenness of an image originating from uneven heating of the medium. 
     In an aspect, the invention provides a printing apparatus including a printing unit that performs printing on a medium transported in a transport direction, a heating unit located downstream of the printing unit in the transport direction and configured to heat the medium, and a control unit that executes a printing operation including printing an image on the medium according to a printing instruction inputted. The control unit is configured to, when the printing operation on the medium according to an Nth (N=an integer not smaller than 1) printing instruction is finished, and then a standby operation including waiting for a start of the printing operation on the medium according to an (N+1)th printing instruction is performed, continue to transport the medium during the standby operation. 
     In the printing apparatus configured as above, the medium continues to be transported, during the standby operation including waiting for the start of the printing operation on the medium according to the (N+1)th printing instruction, after the printing operation on the medium according to the printing instruction of the Nth time is finished. Such an arrangement prevents the medium from being unevenly heated because of being stopped in the heating range of the heating unit, during the standby for the start of the printing operation on the medium according to the (N+1)th printing instruction, after the printing operation on the medium according to the Nth printing instruction is finished. Therefore, the color unevenness of the image, originating from uneven heating of the medium, can be prevented. 
     The expression “continue to transport the medium” herein refers to continuing to transport (move) the medium to restrict the medium from staying at the same position longer than a predetermined time, including both continuously transporting the medium and intermittently transporting the medium. Further, continuing to transport the medium in the transport direction (forward transport), continuing to transport the medium in the reverse direction to the transport direction (reverse transport), and repeating the forward transport and the reverse transport, are also included. 
     In the foregoing printing apparatus, the control unit may continue to transport the medium during the standby operation under a same condition as during the printing operation. 
     With the mentioned arrangement, the medium continues to be transported such that the medium is transported during the standby operation in a same manner as during the printing operation. Therefore, in the heating range of the heating unit, the medium can be heated in the same manner as during the printing operation, during the standby operation that follows the printing operation. Consequently, the medium can be prevented from being unevenly heated owing to a change in heating condition between the printing operation and the standby operation, and the color unevenness in the image can be effectively suppressed. 
     The foregoing printing apparatus may further include a support member that supports the medium along a transport route thereof, and the support member may include a bent portion formed in the heating range of the heating unit. 
     In this case, the support member provided along the transport route of the medium includes the bent portion located in the heating range of the heating unit. Bending the support member, in other words forming the bent portion in the support member, prevents an increase in size of the printing apparatus. Further, forming the bent portion in the support member, instead of bending the support member in an arcuate shape, simplifies the formation process of the support member having the bent shape. 
     In the foregoing printing apparatus, the control unit may finish the standby operation in a case where the (N+1)th printing instruction has not been inputted within a predetermined time, and perform a remedial operation including transporting the medium until the image printed on the medium is located in a predetermined remedial position. 
     With the mentioned arrangement, in the case where the (N+1)th printing instruction has not been inputted within the predetermined time, the standby operation is finished and the medium is transported until the image printed on the medium is located in the predetermined remedial position. Accordingly, setting the remedial position in a location where uneven heating is unlikely to take place prevents the medium from being unevenly heated, owing to a prolonged time before the next printing instruction is inputted. 
     Here, the term “remedial position” herein refers to, for example, a position in the heating range of the heating unit where a whole image is heated under the same condition, and a position where the whole image is located outside the heating range of the heating unit. 
     In the foregoing printing apparatus, the control unit may perform a maintenance operation including performing a maintenance work for the printing apparatus, after the remedial operation is finished. 
     In this case, since the maintenance operation is performed after the remedial operation is finished, the medium can be prevented from being unevenly heated because of remaining in the heating range of the heating unit during the maintenance operation. Therefore, the color unevenness in the image, originating from the uneven heating, can be more effectively suppressed. 
     Here, the term “maintenance operation” herein refers to, for example, correcting uneven distribution of grease on a guide shaft, when the printing unit is configured to reciprocate in a scanning direction intersecting the transport direction, more specifically causing the printing unit to reciprocate over the entire stroke range in the scanning direction, detecting skewed transport of the medium, more specifically transporting the medium in the forward and reverse directions thereby detecting whether the ends of the medium in the width direction are within a predetermined range, and flushing, in other words ejecting a liquid from a nozzle for the purpose of discharging residual liquid, when the printing unit is a liquid ejecting unit. 
     In the foregoing printing apparatus, the control unit may transport the medium in the transport direction during the standby operation, finish the standby operation when the (N+1)th printing instruction is inputted within the predetermined time, and start the printing operation on the medium according to the (N+1)th printing instruction, after transporting the medium in a reverse direction to the transport direction. 
     In this case, the medium is transported in the forward direction during the standby operation, and then transported in the reverse direction after the standby operation is finished, before the next printing operation is started. Such an arrangement prevents a portion of the medium transported during the standby operation from being wasted. 
     In the foregoing printing apparatus, the control unit may transport the medium in the transport direction during the standby operation, finish the standby operation when the (N+1)th printing instruction is inputted within the predetermined time, and start the printing operation on the medium according to the (N+1)th printing instruction, without transporting the medium in the reverse direction to the transport direction. 
     In this case, the medium is transported in the forward direction during the standby operation, and the next printing operation is started, without the medium being transported in the reverse direction, after the standby operation is finished. Accordingly, a portion of the medium unintendedly heated by the heating unit during the standby operation, in other words a portion of the medium that may have been unevenly heated, can be prevented from being used for the printing. Therefore, the image can be printed without color unevenness, in the next printing operation. 
     In another aspect, the invention provides a printing method to be performed by a printing apparatus including a printing unit that performs printing on a medium transported in a transport direction, and a heating unit located downstream of the printing unit in the transport direction and configured to heat the medium. The printing method includes, after finishing a printing operation on the medium according to an Nth (N=an integer not smaller than 1) printing instruction, performing a standby operation including waiting for a start of the printing operation on the medium according to an (N+1)th printing instruction, and continuing to transport the medium during the standby operation. 
     By the method arranged as above, the medium continues to be transported, during the standby operation including waiting for the start of the printing operation on the medium according to the (N+1)th printing instruction, after the printing operation on the medium according to the printing instruction of the Nth time is finished. Such an arrangement prevents the medium from being unevenly heated because of being stopped in the heating range of the heating unit, during the standby for the start of the printing operation on the medium according to the (N+1)th printing instruction, after the printing operation on the medium according to the Nth printing instruction is finished. Therefore, the color unevenness of the image, originating from uneven heating of the medium, can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a schematic side view of a printing apparatus according to an embodiment of the invention. 
         FIG. 2  is a block diagram showing a configuration of the printing apparatus according to the embodiment of the invention. 
         FIG. 3  is a schematic perspective view of an essential part of the printing apparatus according to the embodiment of the invention. 
         FIG. 4  is a graphic drawing for explaining the essential part of the printing apparatus according to the embodiment of the invention. 
         FIG. 5  is a flowchart showing a printing process according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereafter, a printing apparatus according to an embodiment of the invention will be described in detail, with reference to the drawings. 
     First, the outline of the printing apparatus according to the embodiment of the invention will be described. 
       FIG. 1  is a schematic side view of the printing apparatus according to the embodiment of the invention. 
     The printing apparatus  1  according to this embodiment includes a support shaft  2  that supports a roll R 1  of a medium M for printing, formed into a roll. In the printing apparatus  1  according to this embodiment, the support shaft  2  rotates in a rotating direction C, when the medium M is transported in a transport direction A. In this embodiment, the medium M is rolled such that the printing surface is oriented outward. However, the medium M rolled such that the printing surface is oriented inward can also be used, in which case the support shaft  2  is rotated in the reverse direction to the rotating direction C, to feed the roll R 1 . 
     Although the printing apparatus  1  according to this embodiment is configured to use the roll-type medium M, different types of the medium may be employed. For example, a cut-sheet medium may be employed. 
     The printing apparatus  1  according to this embodiment also includes a transport roller pair  5  composed of a drive roller  7  and a slave roller  8 , used to transport the medium M in the transport direction A, along a transport route including a support member  3  that supports the medium M. 
     In the printing apparatus  1  according to this embodiment, the drive roller  7  is constituted of a single roller oriented in a scanning direction B intersecting the transport direction A of the medium M, and a plurality of the slave rollers  8  are aligned in the scanning direction B, so as to oppose the drive roller  7 . 
     Further, a heater  12 , exemplifying the heating unit, for heating the medium M supported by the support member  3  is provided under the support member  3 , at a position downstream of the printing unit  4  to be subsequently described, in the transport direction A of the medium M. Although the printing apparatus  1  according to this embodiment thus includes the heater, corresponding to the heating unit, so as to heat the medium M in a heating range S from the side of the support member  3 , the printing apparatus  1  may include, for example, an infrared heater located so as to oppose the support member  3 . 
     The printing apparatus  1  according to this embodiment also includes, inside a casing  11 , the printing unit  4  configured as an ink jet head that ejects an ink from a plurality of nozzles provided on a nozzle mounting surface, and a carriage  6 , having the printing unit  4  mounted thereon and configured to reciprocate in the scanning direction B. 
     In the printing apparatus  1  according to this embodiment, the transport direction A of the medium M at the position on the support member  3  opposing the printing unit  4  (nozzle mounting surface) corresponds to a Y-direction in  FIG. 1 , which is a horizontal direction, the scanning direction B of the printing unit  4  corresponds to an X-direction which is a horizontal direction orthogonal to the Y-direction, and the ejecting direction of the ink corresponds to a Z-direction which is a vertical direction (vertically downward). 
     As described above, the printing unit  4  is configured to eject the ink from the non-illustrated nozzles onto the medium M being transported, so as to print an image, while reciprocating in the scanning direction B intersecting the transport direction A of the medium M. With the printing unit  4  thus configured, the printing apparatus  1  according to this embodiment alternately repeats the action of transporting the medium M by a predetermined length (one path) in the transport direction A, and causing the printing unit  4  to eject the ink while reciprocating in the scanning direction B, with the medium M stopped, to thereby form a desired image on the medium M. 
     Here, the printing apparatus  1  according to this embodiment is what is known as a serial printer that alternately repeats the transporting of the medium M and the scanning of the printing unit  4 , to perform the printing. Instead, the printing apparatus  1  may be what is known as a line printer that employs a line head having nozzles aligned in the width direction of the medium M, to perform the printing while successively transporting the medium M. Further, printing apparatus  1  may be of a different type from the ink jet printer, for example a transfer printer. 
     Further, a take-up shaft  10 , configured to take up the medium M so as to form a roll R 2 , is provided downstream of the printing unit  4  in the transport direction A of the medium M. Since the medium M is taken up such that the printing surface is oriented outward in this embodiment, the take-up shaft  10  rotates in the rotating direction C to take up the medium M. The medium M can also be taken up such that the printing surface is oriented inward, by rotating the take-up shaft  10  in the reverse direction to the rotating direction C. 
     In addition, a tension bar  9 , oriented so as to contact the medium M along the scanning direction B to apply a desired tension to the medium M, is provided at a position between the downstream end portion of the support member  3  in the transport direction A of the medium M and the take-up shaft  10 . 
     Hereunder, an electrical configuration of the printing apparatus  1  according to this embodiment will be described. 
       FIG. 2  is a block diagram showing a configuration of the printing apparatus  1  according to this embodiment. 
     A control unit  25  includes a CPU  26  that performs overall control of the printing apparatus  1 . The CPU  26  is connected, via a system bus  13 , to a ROM  14  containing various control programs to be executed by the CPU  26 , and a RAM  15  for temporarily storing data. 
     The CPU  26  is also connected to a printing unit driver  17  for driving the printing unit  4 , via the system bus  13 . 
     Further, the CPU  26  is connected, via the system bus  13 , to a motor driver  18 , which is connected to a carriage motor  19 , a transport motor  20 , a feed motor  21 , and a take-up motor  22 . 
     The carriage motor  19  serves to move the carriage  6  having the printing unit  4  mounted thereon, in the scanning direction B. The transport motor  20  serves to drive the drive roller  7  constituting the transport roller pair  5 . The feed motor  21  serves as a rotation mechanism of the support shaft  2 , to drive the support shaft  2  so as to feed the medium M toward the transport roller pair  5 . The take-up motor  22  serves to drive the take-up shaft  10  to rotate. 
     The CPU  26  is also connected to a heater driver  28  that drives the heater  12 , via the system bus  13 . 
     In addition, the CPU  26  is connected, via the system bus  13 , to an input/output (I/O) unit  23  connected to a PC  24  that serves for transmission and reception of data, such as print data, and signals. 
     With the mentioned configuration, the control unit  25  according to this embodiment is capable of controlling the printing unit  4 , the drive roller  7  constituting a part of the transport roller pair serving as a transport unit, and the carriage  6 . 
     Thus, through the control on the printing unit  4 , the drive roller  7 , and the carriage  6  executed by the control unit  25 , the transport of the medium M by a predetermined length (intermittent transport) and the ejection of the ink while moving the printing unit  4  in the scanning direction B can be alternately repeated, so as to perform the printing. 
     Hereunder, the support member  3 , constituting an essential part of the printing apparatus  1  according to this embodiment, will be described. 
       FIG. 3  is a schematic perspective view of the support member  3 , an essential part of the printing apparatus  1  according to this embodiment.  FIG. 4  is a graphic drawing for explaining the support member  3 , more specifically a graphic expression of heat distribution in a region S 1  where the bent portion  27  is formed, in a heating range S heated by the heater  12  when the power thereto is turned on (surface temperature of the medium M located in the region S 1 , measured when the transport is stopped for a certain period of time). 
     As shown in  FIG. 3 , the support member  3  according to this embodiment includes the heating range S of the heater  12 , composed of the region S 1  where a plurality of the bent portions  27  are formed so as to bend the support surface for the medium M, and a region S 2  corresponding to a flat region of the support surface for the medium M. With the region S 1  where the support surface for the medium M is bent, the support member  3  according to this embodiment secures a sufficient area of the heating range S, while reducing the length thereof in the Y-direction. In other words, the printing apparatus  1  according to this embodiment improves the performance of an after heater, without incurring an increase in size of the apparatus. 
     In this embodiment, the region S 1  is formed not by bending the support surface for the medium M in an arcuate (curved) shape, but by forming the plurality of bent portions  27 . Forming the region S 1  as above facilitates the formation of the bent shape of the support surface for the medium M, with a minimized manufacturing error. 
     However, forming the region S 1  in the support member  3  as in this embodiment incurs a difference in contact status of the medium M and the support surface, between the bent portion  27  and a flat portion  16  (region between adjacent bent portions  27 ). Referring here to  FIG. 4 , when the transport of the medium M is stopped for a certain period of time, the surface temperature of the medium M supported in the region S 1  becomes different between the portion corresponding to the bent portion  27  and the portion corresponding to the flat portion  16 . More specifically, as shown in  FIG. 4 , the temperature of the portion of the medium M corresponding to bent portion  27  is approximately 50° C., while the temperature of the portion corresponding to the flat portion  16  is approximately 40° C. This is because the medium M is subjected to a greater force exerted from below (force applied to the medium M by the support member  3  because of the medium M being pressed against the support member  3  by the self-weight) at the bent portion  27 , than at the flat portion  16 . For example, in the region S 1  the medium M is supported by the support member  3 , only in contact with the bent portion  27 , and without contacting the flat portion  16 . Therefore, the ink forming the image may dry unevenly when the image formed on the medium M is stopped in the region S 1 , for a certain period of time after the image is formed, and consequently color unevenness may be incurred. 
     When the image is located in the region S 2 , or in a region outside the support member  3  (heating range S), for example a region downstream of the support member  3  in the transport direction A, the ink forming the image dries evenly, and hence the color unevenness is not incurred. However, for example, when the transport of the medium M is stopped for a certain time, with the image located so as to span over the region S 1  and the region S 2 , or located so as to span over the support member  3  and a region outside the support member  3 , the ink forming the image may dry unevenly, thus incurring the color unevenness. 
     In the printing apparatus  1  according to this embodiment, therefore, the control unit  25  restricts the image from being stopped longer than a predetermined time, at a position where the color unevenness is likely to be incurred, to prevent appearance of the color unevenness originating from the uneven drying of the ink. 
     A specific example of the control performed by the control unit  25 , in other words a printing method, will now be described hereunder. 
       FIG. 5  is a flowchart showing an example of the printing method that may be performed by the printing apparatus  1  according to this embodiment. 
     First, when print data is inputted from the PC24 at step S 110 , the printing apparatus  1  according to this embodiment starts printing (forming the image) on the basis of the print data, at step S 120 . 
     Since the printing apparatus  1  according to this embodiment is configured to perform the printing while intermittently transporting the medium M as described above, the transport condition of the medium M during the printing operation is set to the intermittent transport. However, a line printer may be employed, in which case the medium M may be continuously transported. 
     When the printing based on the print data is finished at step S 130 , the control unit  25  decides whether the next print data has been inputted (step S 140 ). In the case where it is decided that the next print data has not been inputted, the control unit  25  starts the standby operation at step S 150 . Here, before the start of step S 150 , the image formed on the medium M is located so as to span over the region S 1  and the region S 2 . 
     The standby operation according to this embodiment includes continuing to transport the medium M, under the same condition as during the printing operation at step S 120  (intermittent transport). The standby operation started at step S 150  is continued until the operation proceeds to step S 170  or step S 200  to be subsequently described. 
     The control unit  25  executes step S 160 , in parallel with the process of step S 150 . Although the flowchart shows step S 150  and step S 160  in series, actually these steps are executed in parallel. At step S 160 , the control unit  25  decides whether a cumulative duration of the standby operation is shorter than a predetermined time, in other words whether the predetermined time has elapsed. In the case where the cumulative duration of the standby operation is shorter than the predetermined time, the operation returns to step S 140 , and the control unit  25  again decides whether the next print data has been inputted. 
     When the next print data is inputted during the standby operation at step S 140 , the operation is shifted to step S 200 . At step S 200 , the standby operation is finished, and the medium M is transported backward, by a length transported during the standby operation. For example, in the case where the standby operation medium M has been transported by a first length in the transport direction A, the medium M is transported in the reverse direction to the transport direction A (reverse transport) by the first length, at step S 200 . The mentioned arrangement prevents expansion of a blank region in the medium M, when the standby operation is followed by the next printing operation. 
     Here, step S 200  may only include finishing the standby operation, without performing the reverse transport of the medium M. In this case, the next printing operation can be promptly started. 
     In contrast, in the case where the next print data has not been inputted during the standby operation at step S 140 , step S 160  is again performed, while the standby operation of step S 150  is continued. Thus, unless the next print data is inputted within the predetermined time, the operations of step S 160  and step S 140  are repeated at predetermined intervals, which are shorter than the predetermined time. 
     When the predetermined time has elapsed without the next print data being inputted, it is decided at step S 160  that the cumulative duration of the standby operation is not shorter than the predetermined time, and the operation proceeds to step S 170 . At step S 170 , the standby operation is finished. In other words, the transport of the medium M, thus far performed during the standby operation, is stopped. 
     When the standby operation is finished at step S 170 , the operation proceeds to step S 180  (remedial operation), where the medium M is transported until the image formed on the medium M is located at a predetermined remedial position. In this embodiment, continuous transport is adopted in the remedial operation, however intermittent transport may also be adopted. The predetermined remedial position is one of a plurality of remedial positions prepared in advance, selected by the user. However, the remedial position may be a predetermined position, instead of one selected by the user. 
     Here, although not included in the flowchart of  FIG. 5 , in the case where the next print data is inputted after the remedial operation, the user may select whether to start the printing operation after returning the medium M to the position where the medium M was before the standby operation and the remedial operation, or to start the printing operation from the position where the medium M was when the standby operation and the remedial operation were finished. However, instead of allowing the user to select, one of the arrangements may be programmed in advance. 
     In the case of starting the printing operation after returning the medium M to the position where the medium M was before the standby operation and the remedial operation, the portion of the medium M to be wasted (blank portion) can be reduced. 
     In contrast, starting the printing operation from the position where the medium M was, when the remedial operation was finished, prevents a portion of the medium M unintendedly heated by the heater  12  during the standby operation, in other words a portion that may have been unevenly heated, from being used for the printing. 
     In this embodiment, a first remedial position P 1 , a second remedial position P 2 , and a third remedial position P 3  are prepared, as the remedial position. 
     In the first remedial position P 1 , the upstream end of the image formed on the medium M in the transport direction A has passed through the region S 1  and is located in the region S 2 . In this case, the entirety of the image is located inside the region S 2 , unless the image is longer than the region S 2  in the transport direction. Since the bent portion  27  is not provided in the region S 2 , the image is heated under the same condition, in the region S 2 . In other words, in the first remedial position P 1 , the entirety of the image in the heating range S of the heater  12  is heated under the same condition, and therefore uneven heating can be prevented. 
     In the second remedial position P 2 , the upstream end of the image formed on the medium M in the transport direction A is located downstream of the support member  3  in the transport direction A. In other words, in the second remedial position P 2  the entirety of the image formed on the medium M is located in a position deviated from the support member  3 . Thus, the entirety of the image can be deviated from the heating range S of the heater  12  in the second remedial position P 2 , and therefore uneven heating can be avoided. The second remedial position P 2  is particularly advantageous when the image is too large to be located inside the region S 2 . 
     In the third remedial position P 3 , the upstream end of the image formed on the medium M in the transport direction A is located upstream of the heating range S in the transport direction A. More specifically, the upstream end of the image formed on the medium M in the transport direction A is located between the heating range S and the transport roller pair  5 . In the third remedial position P 3 , therefore, although the image is brought back reversely to the transport direction A, the image formed on the medium M is kept from being pinched between the transport roller pair  5 . Accordingly, the image can be exempted from collapsing by being pinched between the transport roller pair  5 . When the third remedial position P 3  is utilized, the portion of the medium M to be wasted (blank portion) can be reduced, even when the next print data is inputted after the remedial operation, and the printing operation is to be started from the position where the medium M was when the remedial operation was finished. 
     When the remedial operation of step S 180  is finished, the control unit  25  proceeds to step S 190  to start the maintenance operation. 
     Here, the maintenance operation according to this embodiment refers, on the assumption that the printing unit  4  is configured to reciprocate in the scanning direction B intersecting the transport direction A, to correcting uneven distribution of grease on the guide shaft, more specifically causing the printing unit  4  to reciprocate over the entire stroke range in the scanning direction B. In this case, the printing unit  4  is made to reciprocate over the entire stroke range in the scanning direction B, without ejecting ink from the nozzles of the printing unit  4 . With such an operation, the grease applied to the guide shaft of the printing unit  4  can be distributed all over the guide shaft. However, the type of the maintenance operation is not specifically limited and may also include, for example, detecting skewed transport of the medium M, more specifically transporting the medium M in the forward and reverse directions, thereby detecting whether the ends of the medium M in the width direction are within a predetermined range, and flushing, in other words ejecting the ink from the nozzles for the purpose of discharging residual ink, on the assumption that the printing unit  4  is a liquid ejecting unit. 
     The conventional printing apparatus is configured to perform the process of step S 190  (maintenance operation) with the medium M stopped, without performing the standby operation after step S 140 . Therefore, the medium M may be unevenly heated during the maintenance operation, and hence the image formed on the medium M may suffer color unevenness. By the printing method according to this embodiment, the maintenance operation is performed after the remedial operation, and therefore the color unevenness of the image originating from the uneven heating of the medium M can be suppressed. 
     When step S 190  is finished, a cycle of the printing method according to this embodiment ends. 
     In the case where step S 140  is performed after the printing operation according to a first print data is finished, the standby operation is not executed. 
     Accordingly, in the case where YES is selected at step S 140  under the mentioned condition, step S 200  is skipped, and the operation proceeds to step S 120 . Such a case takes place, for example, when a first printing instruction and a second printing instruction are successively inputted. 
     As described above, the printing method according to this embodiment is applicable to the printing apparatus  1  including the printing unit  4  that performs printing on the medium M transported in the transport direction A, the heater  12  located downstream of the printing unit  4  in the transport direction A and configured to heat the medium M, and the control unit  25  that executes the printing operation including printing an image on the medium M according to the printing instruction inputted. The printing method includes, after finishing the printing operation on the medium M according to the Nth (N=an integer not smaller than 1) printing instruction (step S 120  to step S 130 ), performing the standby operation (step S 150 ) including waiting for a start of the printing operation on the medium M according to the (N+1)th printing instruction (in the case of YES at step S 140 ), and continuing to transport the medium M during the standby operation. 
     By the mentioned printing method, the medium M can be prevented from being unevenly heated because of being stopped in the region S 1  of the heating range S of the heater  12 , during the standby for the start of the printing operation on the medium M according to the (N+1)th printing instruction, after the printing operation on the medium M according to the Nth printing instruction is finished. Therefore, the color unevenness of the image, originating from uneven heating of the medium M, can be prevented. 
     Here, the expression “continue to transport the medium M” refers to continuing to transport (move) the medium M to restrict the medium M from staying at the same position longer than the predetermined time, including both intermittently transporting the medium M as in this embodiment, and continuously transporting the medium M. Further, continuing to transport the medium M in the transport direction A (forward transport), continuing to transport the medium M in the reverse direction to the transport direction A (reverse transport), and repeating the forward transport and the reverse transport, are also included. 
     From another viewpoint, the printing apparatus  1  according to this embodiment includes the printing unit  4  that performs printing on the medium M transported in the transport direction A, the heater  12  located downstream of the printing unit  4  in the transport direction A and configured to heat the medium M, and the control unit  25  that executes the printing operation including printing an image on the medium M according to the printing instruction inputted. The control unit  25  is configured to, when the printing operation on the medium M according to the Nth (N=an integer not smaller than 1) printing instruction is finished, and then the standby operation including waiting for the start of the printing operation on the medium M according to the (N+1)th printing instruction is performed, continue to transport the medium M during the standby operation. 
     With the mentioned configuration, the medium M can be prevented from being unevenly heated because of being stopped in the region S 1  of the heating range S of the heater  12 , during the standby for the start of the printing operation on the medium M according to the (N+1)th printing instruction, after the printing operation on the medium M according to the Nth printing instruction is finished. Therefore, the color unevenness of the image, originating from uneven heating of the medium M, can be prevented. 
     As described above, the control unit  25  according to this embodiment continues to transport the medium M (intermittent transport) during the standby operation under a same condition as during the printing operation (intermittent transport). Therefore, the medium M can be prevented from being unevenly heated owing to a change in heating condition between the printing operation and the standby operation, and the color unevenness in the image can be effectively suppressed. 
     The expression “transport the medium M during the standby operation under the same condition as during the printing operation” herein refers to the case where the transport modes are generally the same, such that simply both are the intermittent transport, or the continuous transport. It is not mandatory that, for example, an interval between feeding actions or a feed stroke per action in the intermittent transport, or transport speed in the continuous transport, is strictly the same. 
     As described above, further, the printing apparatus  1  according to this embodiment also includes the support member  3  that supports the medium M along the transport route thereof, and the support member  3  includes the bent portion  27  formed in the heating range of the heater  12 . Bending the support member  3 , in other words forming the bent portion  27  in the support member  3 , prevents an increase in size of the printing apparatus  1 . Further, forming the bent portion  27  in the support member  3  instead of bending the support member  3  in an arcuate shape, simplifies the formation process of the support member  3  having the bent shape. 
     As described referring to step S 160  to step S 180  in  FIG. 5 , the control unit  25  finishes the standby operation in the case where the (N+1)th printing instruction has not been inputted within the predetermined time, and performs the remedial operation including transporting the medium M until the image printed on the medium M is located in the predetermined remedial position (first remedial position P 1 , second remedial position P 2 , or third remedial position P 3 ). Accordingly, setting the remedial position in a location where uneven heating is unlikely to take place prevents the medium M from being unevenly heated, owing to a prolonged time before the next printing instruction is inputted. 
     Here, “predetermined remedial position” may be any desired position other than the first remedial position P 1 , the second remedial position P 2 , and the third remedial position P 3 . 
     As described above, further, the control unit  25  according to this embodiment performs the maintenance operation (step S 190 ) including performing a maintenance work for the printing apparatus  1 , after the remedial operation (step S 180 ) is finished. Performing thus the maintenance operation after the remedial operation is finished prevents the medium M from being unevenly heated because of remaining in the region S 1  in the heating range S of the heater  12  during the maintenance operation. Therefore, the color unevenness in the image, originating from the uneven heating, can be more effectively suppressed. 
     Still further, the control unit  25  according to this embodiment transports the medium M in the transport direction A during the standby operation, finishes the standby operation when the (N+1)th printing instruction is inputted within the predetermined time, and starts the printing operation on the medium M according to the (N+1)th printing instruction, after transporting the medium M in the reverse direction to the transport direction A. Such an arrangement prevents a portion of the medium M transported during the standby operation from being wasted. 
     However, the control unit  25  according to this embodiment may also transport the medium M in the transport direction A during the standby operation, finish the standby operation when the (N+1)th printing instruction is inputted within the predetermined time, and start the printing operation on the medium M according to the (N+1)th printing instruction, without transporting the medium M in the reverse direction to the transport direction A. In this case, the next printing operation can be promptly started. In addition, a portion of the medium M unintendedly heated by the heater  12  during the standby operation, in other words a portion of the medium M that may have been unevenly heated, can be prevented from being used for the printing. Therefore, the image can be printed without color unevenness, in the next printing operation. 
     The invention is not limited to the foregoing embodiments but may be modified in various manners, within the scope of the invention set forth in the appended claims, and it is a matter of course that such modifications are included in the scope of the invention. 
     This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2017-018681, filed Feb. 3 2017. The entire disclosure of Japanese Patent Application No. 2017-018681 is hereby incorporated herein by reference.