Patent Publication Number: US-11046096-B2

Title: Adjustment sheet and method for adjusting landing position of droplet

Description:
The present application is based on, and claims priority from JP Application Serial Number 2018-160035, filed Aug. 29, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an adjustment sheet used in a recording device such as an ink-jet type printer, and a method for adjusting a landing position of a liquid droplet on a medium in the recording device using the same adjustment sheet. 
     2. Related Art 
     JP-A-2013-31969 describes one example of an image forming device that records a test chart on a sheet transported by a transport belt and reads the test chart recorded on the sheet by an optical sensor. In this image forming device, correction processing of correcting a discharge timing of an ink droplet by a recording head is performed based on the result of reading the test chart by the optical sensor. 
     In recording devices, recording processing is performed on various types of media. The medium to be recorded includes media in which wrinkling and cockling are more likely to be generated when ink adheres, and media in which wrinkling and cockling are less likely to be generated even when ink adheres. 
     For example, when a test chart is recorded on a medium in which wrinkling and cockling are less likely to be generated and the correction processing as described above is performed, wrinkling and cockling are hardly generated in the medium even when ink adheres to the medium for recording the test chart. In this way, highly accurate correction can be performed by the correction processing. 
     On the other hand, when a test chart is recorded on a medium where wrinkling and cockling are more likely to be generated and the correction processing as described above is performed, wrinkling and cockling may be generated in the medium when ink adheres to the medium for recording the test chart. When wrinkling or cockling are generated in the medium, the lines constituting the test chart may be distorted. Even in a case where such distorted lines are read by the optical sensor and the correction processing is performed, it is difficult to say that the correction accuracy of such correction processing is high. 
     In other words, correction accuracy of the correction processing may vary depending on the type of medium on which a test chart is recorded for performing the correction processing. 
     SUMMARY 
     An adjustment sheet that solves the above-described problem is an adjustment sheet used in a recording device. The recording device includes a transport unit configured to transport a medium in a transport direction, a discharge unit configured to discharge a liquid droplet on a recording surface of the medium transported by the transport unit, and a detection unit configured to detect an image formed on the recording surface of the medium transported by the transport unit. The adjustment sheet is configured to be transported, when the adjustment sheet is set on the recording surface of the medium, together with the medium in the transport direction by the transport unit. The adjustment sheet includes a first surface configured to contact the recording surface, and a second surface that is a surface located on a side opposite to the first surface and that includes an adjustment region being a region configured to be formed with an adjustment pattern detectable by the detection unit. A prescribed pattern has been formed in a region different from the adjustment region on the second surface. 
     Further, an adjusting method of a landing position of a liquid droplet includes: providing a recording device comprising a transport unit configured to transport a medium, a discharge unit configured to discharge a liquid droplet on the medium transported by the transport unit while the discharge unit moves in scanning directions intersecting a transport direction of the medium in the transport unit, and a detection unit configured to detect an image formed on the recording surface of the medium while the detection unit moves in the scanning directions; setting the adjustment sheet described above on the medium; forming, after the first step, the adjustment pattern including a forward direction pattern formed by discharging, on the adjustment region of the adjustment sheet transported together with the medium in the transport direction by the transport unit, a liquid droplet from the discharge unit while the discharge unit moves in a forward direction of the scanning directions, and a return direction pattern formed by discharging, on the adjustment region of the adjustment sheet, a liquid droplet from the discharge unit while the discharge unit moves in a return direction of the scanning directions; reading, after forming the adjustment pattern, the adjustment pattern by the detection unit; and calculating, after reading the adjustment pattern, a correction value for an adjustment of a discharge timing of a liquid droplet from the discharge unit based on the forward direction pattern and the return direction pattern. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram schematically illustrating a recording device in which an adjustment sheet according to an exemplary embodiment is used. 
         FIG. 2  is a diagram schematically illustrating the recording device in which an adjustment sheet according to an exemplary embodiment is used. 
         FIG. 3  is a plan view of an adjustment sheet. 
         FIG. 4  is a cross-sectional view taken along a line  4 - 4  in  FIG. 3 . 
         FIG. 5  is an action diagram illustrating a situation where an adjustment pattern is recorded in an adjustment region of the adjustment sheet set on a medium. 
         FIG. 6  is an enlarged view of a part of a first prescribed pattern of the adjustment sheet. 
         FIG. 7  is a flowchart for describing an adjustment method in the exemplary embodiment. 
         FIG. 8  is an action diagram illustrating a situation where the medium is slanted. 
         FIG. 9  is an action diagram illustrating a situation where an adjustment pattern for checking a degree of variation in the amount of transport of the medium transported by a transport unit is recorded on the adjustment sheet in a modified example. 
         FIG. 10  is an action diagram illustrating a situation where an adjustment pattern for checking a degree of variation in the amount of transport of the medium transported by the transport unit is recorded on the adjustment sheet in a modified example. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     One exemplary embodiment of an adjustment sheet and a method for adjusting a landing position of a liquid droplet will be described below according to  FIGS. 1 to 8 . 
     A recording device  10  in which an adjustment sheet  50  in the exemplary embodiment is used is illustrated in  FIGS. 1 and 2 . The recording device  10  includes a transport unit  11  that transports a medium  100  to be recorded in a predetermined transport direction X, and a recording unit  20  that forms an image on the medium  100  transported by the transport unit  11 . The recording device  10  further includes a support table  15  that supports a portion of the medium  100  where recording is performed by the recording unit  20 . 
     The transport unit  11  can transport various types of the media  100  having different thicknesses and sizes. The transport unit  11  includes a first transport roller pair  12  disposed upstream of the support table  15  in the transport direction X, and a second transport roller pair  13  disposed downstream of the support table  15  in the transport direction X. The first transfer roller pair  12  includes a first driving roller  121  to which power is transmitted from a power source, such as a motor, and a first driven roller  122  that sandwiches the medium  100  with the first driving roller  121 . The second transfer roller pair  13  includes a second driving roller  131  to which power is transmitted from a power source, such as a motor, and a second driven roller  132  that sandwiches the medium  100  with the second driving roller  131 . 
     The recording unit  20  includes a guide member  21  extending in a direction intersecting the transport direction X among directions along a recording surface  101  of the medium  100  transported by the transport unit  11 , and a carriage  22  supported by the guide member  21 . The carriage  22  is supported by the guide member  21  in a state where the carriage  22  is movable in the extending direction of the guide member  21 . Further, a driving force of a carriage motor  23  is transmitted to the carriage  22 . Then, the carriage  22  moves in the extending direction of the guide member  21  by driving of the carriage motor  23 . 
     Note that a direction in which the carriage  22  moves is referred to as a scanning direction Y. The scanning direction Y intersects the transport direction X among directions along the recording surface  101  of the medium  100  transported by the transport unit  11 . Further, one direction in the scanning direction Y may be referred to as a “forward direction Y 1 ”, and the other direction in the scanning direction Y may be referred to as a “return direction Y 2 ”. In other words, the return direction Y 2  is a direction opposite to the forward direction Y 1 . 
     A recording head  24  and an optical sensor  25  are provided on the carriage  22 . The recording head  24  discharges an ink droplet, which is one example of a liquid droplet, onto the recording surface  101  of the medium  100  supported by the support table  15 . In other words, the recording head  24  functions as one example of a “discharge unit”. Although not illustrated, the recording head  24  includes a plurality of nozzles that discharge ink droplets. More specifically, a nozzle row configured by aligning a plurality of nozzles in the transport direction X is formed in the recording head  24 . 
     The optical sensor  25  outputs light toward the recording surface  101  of the medium  100  supported by the support table  15 , and also receives reflected light from the recording surface  101 . The amount of reception of reflected light by the optical sensor  25  varies depending on a density of ink that adheres to a portion of the recording surface  101  where the output light is incident. In this way, the optical sensor  25  can detect an image formed on the recording surface  101 . Then, the optical sensor  25  outputs a signal according to the amount of reception of reflected light, that is, a signal according to a density of an image on the recording surface  101  to a control device  30 , which is one example of a control unit. In other words, the optical sensor  25  functions as one example of a “detection unit”. Then, the optical sensor  25  moves together with the carriage  22  in the scanning direction Y intersecting the transport direction X. 
     Further, a linear encoder  26  is provided on the recording unit  20 . A detection signal of the linear encoder  26  is input to the control device  30 . The control device  30  can detect a movement speed of the carriage  22  in the extending direction of the guide member  21 , that is, in the scanning direction Y, based on the detection signal. The control device  30  can also determine whether the carriage  22  is moving in the forward direction Y 1  or the carriage  22  is moving in the return direction Y 2 , based on the detection signal. 
     The control device  30  includes a CPU  31 , a memory  32 , and an ASIC  33 . The ASIC  33  is an abbreviation for an “Application Specific IC”. The memory  32  stores a program executed by the CPU  31 , various maps, a computation result by the CPU  31 , detection values by various sensors, and the like. Then, the control device  30  records an image on the recording surface  101  of the medium  100  by controlling the transport unit  11  and the recording unit  20 . 
     As illustrated in  FIGS. 1 and 2 , the transport unit  11  can transport the adjustment sheet  50  set on the recording surface  101  of the medium  100  together with the medium  100  in the transport direction X. The adjustment sheet  50  is used for adjusting a landing position of a liquid droplet, adjusting the amount of transport and a transport speed of the medium  100  transported by the transport unit  11 , and the like. 
     As illustrated in  FIGS. 3 and 4 , the adjustment sheet  50  includes a body sheet  51  and an adhesive layer  52 . The body sheet  51  is formed of a material in which wrinkling and cockling are less likely to be generated even when ink adheres. For example, a sheet having an ink receptive layer such as a photographic sheet can be adopted as the body sheet  51 . 
     The adhesive layer  52  is provided on one surface of both surfaces of the body sheet  51 . By pressing the adhesive layer  52  against the medium  100 , the adjustment sheet  50  can be attached to the medium  100 . 
     In the exemplary embodiment, an outermost surface of the adhesive layer  52  functions as a “first surface  501 ” that contacts the recording surface  101  of the medium  100  as illustrated in  FIGS. 1 and 2 . Further, a surface of both surfaces of the body sheet  51  on which the adhesive layer  52  is not provided functions as a “second surface  502 ” as illustrated in  FIGS. 1 and 2 . Therefore, it can be said that the adhesive layer  52  is provided on a surface of the body sheet  51  opposite to the second surface  502 . 
     As indicated by a chain double-dashed line in  FIG. 3 , an adjustment region  60  is prepared on the second surface  502  of the adjustment sheet  50 , and is a region where an adjustment pattern is formed when a landing position of a liquid droplet is adjusted and a transport speed of the medium  100  transported by the transport unit  11  is adjusted. The adjustment pattern is a pattern formed by landing an ink droplet from the recording head  24  onto the adjustment sheet  50 , and is detectable by the optical sensor  25 . 
     Note that  FIG. 5  illustrates one example of a case where an adjustment pattern PT for adjusting a landing position of a liquid droplet is formed in the adjustment region  60 . The adjustment pattern PT includes a forward direction pattern PT 1  and a return direction pattern PT 2 . The forward direction pattern PT 1  is a pattern formed by discharging an ink droplet from the recording head  24  while moving the carriage  22  and the recording head  24  in the forward direction Y 1 . The return direction pattern PT 2  is a pattern formed by discharging an ink droplet from the recording head  24  while moving the carriage  22  and the recording head  24  in the return direction Y 2 . 
     Further, as illustrated in  FIG. 3 , a prescribed pattern  61  has been formed in a region different from the adjustment region  60  on the second surface  502 . In the exemplary embodiment, as the prescribed pattern  61 , a first prescribed pattern  611  and a second prescribed pattern  612  disposed in a position different from that of the first prescribed pattern  611  have been formed on the second surface  502 . 
     A direction in which the first prescribed pattern  611  and the second prescribed pattern  612  are aligned among directions along the second surface  502  is referred to as a first direction C 1 , and a direction orthogonal to the first direction C 1  is referred to as a second direction C 2 . In this case, the adjustment region  60  is disposed between the first prescribed pattern  611  and the second prescribed pattern  612  in the first direction C 1 . In other words, it can be said that the second prescribed pattern  612  is provided in a position different from that of the first prescribed pattern  611  in the first direction C 1 . 
     The first prescribed pattern  611  and the second prescribed pattern  612  each extend in a direction intersecting the first direction C 1  among directions along the second surface  502 . Specifically, the first prescribed pattern  611  also extends in a direction intersecting the second direction C 2 , and the second prescribed pattern  612  also extends in a direction intersecting the second direction C 2 . Then, a gap between the first prescribed pattern  611  and the second prescribed pattern  612  in the first direction C 1  gradually increases from one end toward the other end in the second direction C 2 . 
     Further, one end in the second direction C 2  of the first prescribed pattern  611  is referred to as a first side one end  611   a , and the other end in the second direction C 2  of the first prescribed pattern  611  is referred to as a first side other end  611   b . One end in the second direction C 2  of the second prescribed pattern  612  is referred to as a second side one end  612   a , and the other end in the second direction C 2  of the second prescribed pattern  612  is referred to as a second side other end  612   b . In this case, the first side one end  611   a  is disposed in the same position as that of the second side one end  612   a  in the second direction C 2 . Further, the first side other end  611   b  is disposed in the same position as that of the second side other end  612   b  in the second direction C 2 . In other words, in the exemplary embodiment, the first prescribed pattern  611  overlaps the second prescribed pattern  612  in the first direction C 1 . 
     As illustrated in  FIG. 6 , the first prescribed pattern  611  is a collection of a plurality of marks  65 . The marks  65  adjacent to each other are separated at regular intervals. The mark  65  is configured such that a first portion  651  and a second portion  652  having a density lower than that of the first portion  651  are adjacent to each other in the first direction C 1 . In the example illustrated in  FIG. 6 , the mark  65  includes the first portion  651  being a rectangular annular frame, and the second portion  652  inside the first portion  651 . In other words, the first prescribed pattern  611  is configured such that the first portions  651  and the second portions  652  are aligned alternately in the first direction C 1 . 
     Note that the second prescribed pattern  612  is also a collection of the plurality of marks  65 . In other words, the second prescribed pattern  612  is configured such that the first portions  651  and the second portions  652  are alternately aligned in the first direction C 1 . Note that the configuration of the second prescribed pattern  612  is the same as that of the first prescribed pattern  611 , and thus a specific description thereof is omitted. 
     Next, an adjustment method according to the exemplary embodiment will be described with reference to  FIG. 7 . 
     As illustrated in  FIG. 7 , in first step S 11 , a setting step of setting the adjustment sheet  50  on the recording surface  101  of the medium  100  is performed. In the setting step, the adjustment sheet  50  is attached to the recording surface  101  of the medium  100  on the upstream of the first transport roller pair  12  in the transport direction X. In the exemplary embodiment, step S 11  corresponds to a “first step”. 
     When the adjustment sheet  50  is set on the medium  100 , the adjustment sheet  50  may be set on the medium  100  such that the first direction C 1  of the adjustment sheet  50  matches the scanning direction Y of the carriage  22 . Note that the adjustment sheet  50  may be set on the medium  100  in a state with the first direction C 1  slightly offset with the scanning direction Y. 
     When the adjustment sheet  50  is set on medium  100 , the processing proceeds to next step S 12 . In step S 12 , a transporting step is performed. In the transporting step, by driving the transport unit  11  by the control device  30 , the medium  100  to which the adjustment sheet  50  is attached is transported in the transport direction X. In other words, the adjustment sheet  50  is transported together with the medium  100  in the transport direction X. Then, when the control device  30  confirms that a portion of the medium  100  where the adjustment sheet  50  is attached is supported by the support table  15 , the transporting step is terminated. 
     Then, in next step S 13 , a position checking step is performed. In the position checking step, a position of the adjustment region  60  on the adjustment sheet  50  is checked. Specifically, in the position checking step, the first prescribed pattern  611  and the second prescribed pattern  612  that have been formed on the adjustment sheet  50  are detected by the optical sensor  25  provided on the carriage  22  while moving the carriage  22  in the scanning direction Y. Then, the control device  30  recognizes a position of the first prescribed pattern  611  and a position of the second prescribed pattern  612 , based on a detection result of the optical sensor  25 . By recognizing a position of the first prescribed pattern  611  and a position of the second prescribed pattern  612  in this way, the control device  30  can check a position of the adjustment region  60 , that is, a position where the adjustment pattern PT is to be formed. Then, when the position of the adjustment region  60  is checked by the control device  30 , the position checking step is terminated. 
     Next, in step S 14 , a patterning step is performed. In the patterning step, the adjustment pattern PT is formed in the adjustment region  60  of the adjustment sheet  50  by driving the recording unit  20  and the transport unit  11 . Specifically, by discharging an ink droplet from the recording head  24  while moving the carriage  22  in the forward direction Y 1  by the control device  30 , the forward direction pattern PT 1  of the adjustment pattern PT is formed in the adjustment region  60 . When the formation of the forward direction pattern PT 1  is completed, the return direction pattern PT 2  of the adjustment pattern PT is formed in the adjustment region  60  by discharging an ink droplet from the recording head  24  while moving the carriage  22  in the return direction Y 2  by the control device  30 . When the formation of the return direction pattern PT 2  is completed, it can be determined that the formation of the adjustment pattern PT in the adjustment region  60  is completed, and thus the patterning step is terminated. In the exemplary embodiment, step S 14  corresponds to a “second step”. 
     Then, in a next step S 15 , a reading step is performed. In the reading step, by moving the carriage  22  in the scanning direction Y by the control device  30 , the optical sensor  25  reads the forward direction pattern PT 1  and the return direction pattern PT 2  formed in the adjustment region  60 . In the exemplary embodiment, step S 15  corresponds to a “third step” of reading the adjustment pattern PT after the second step. Then, when reading of the forward direction pattern PT 1  and the return direction pattern PT 2  is completed, the reading step is terminated. 
     Next, in step S 16 , a correction value calculating step is performed. In the correction value calculating step, a correction value for an adjustment of a discharge timing of an ink droplet of the recording head  24  during recording is derived based on the information read in the reading step. In the exemplary embodiment, step S 16  corresponds to a “fourth step”. 
     The amount of deviation between a landing position on the adjustment sheet  50  when the recording head  24  discharges an ink droplet while moving in the forward direction Y 1  and a landing position on the adjustment sheet  50  when the recording head  24  discharges an ink droplet while moving in the return direction Y 2  also varies depending on a gap between the recording head  24  and the second surface  502  of the adjustment sheet  50 . In other words, in the exemplary embodiment, the adjustment pattern PT is formed on the adjustment sheet  50  attached to the medium  100 , and the correction value is derived by using the adjustment pattern PT formed on the adjustment sheet  50 . 
     Here, in the exemplary embodiment, the correction value is derived while taking into account a thickness of the adjustment sheet  50 . In other words, an offset value Q of a thickness of the adjustment sheet  50  is calculated by using the following relational expression (Equation 1). Note that, in the relational expression (Equation 1), “Vcr” is a movement speed of the carriage  22  and the recording head  24 , “Vd” is a speed of an ink droplet, and “D” is a thickness of the adjustment sheet  50 . Information about the adjustment sheet  50  is stored in advance in the memory  32  of the control device  30 . In other words, the thickness D of the adjustment sheet  50  is stored in the memory  32 . 
     
       
         
           
             
               
                 
                   
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     When the derivation of the correction value is completed, the correction value calculating step is terminated. Then, the adjustment method in the exemplary embodiment illustrated in  FIG. 7  is terminated. 
     Note that, in the correction value calculating step, in addition to the correction value based on the thickness D of the adjustment sheet  50 , a correction value taking into account an influence of air resistance may be calculated, and an offset value based on each of these correction values may be stored in the memory  32 . A distance between a nozzle surface of the recording head  24  in which each of the nozzles is opened and the recording surface of the medium to be recorded is shortened when the adjustment sheet  50  is attached to the medium  100 , and the distance increases when the adjustment sheet  50  is removed from the medium  100 . An influence of air resistance on an ink droplet increases as the above-described distance increases. In other words, a greater range of an ink droplet is more likely to cause a greater landing deviation of the ink droplet onto the adjustment sheet  50  and the medium  100  due to the air resistance. 
     Therefore, the adjustment pattern PT formed on the adjustment sheet  50  attached to the medium  100  may differ from an adjustment pattern formed directly on the medium  100  due to a difference in degree of an influence of the air resistance on the ink droplet. In this case, a distance between the nozzle surface and the second surface  502  is calculated by subtracting the thickness D of the adjustment sheet  50  from a distance between the recording surface  101  and the nozzle surface. Further, a relationship between the distance between the nozzle surface and the second surface  502  and the landing deviation of the ink droplet due to the air resistance is evaluated in advance based on the movement speed Vcr of the carriage  22  and the recording head  24  and the speed Vd of the ink droplet. The relationship between the distance between the nozzle surface and the second surface  502  and the landing deviation of the ink droplet due to the air resistance can be derived in advance by a simulation, experiments, or the like. When a plurality of types of adjustment sheets  50  are present, each of the adjustment sheets  50  is evaluated. Then, a relationship between the thickness D of the evaluated adjustment sheet  50  and the influence of the air resistance is stored in the memory  32 , the relationship between the thickness D of the adjustment sheet  50  and the influence of the air resistance is read as reference data according to a type of the adjustment sheet  50  to be used, and a correction value is calculated based on the reference data. 
     Next, the action and the effects of the exemplary embodiment will be described. 
     (1) By setting the adjustment sheet  50  on the medium  100  such that the first surface  501  contacts the recording surface  101  of the medium  100 , the recording device  10  can transport the adjustment sheet  50  together with the medium  100  in the transport direction X. As a result, the second surface  502  of the adjustment sheet  50  can face the recording head  24 . In this way, the prescribed pattern  61  that has been formed on the second surface  502  can be detected by the optical sensor  25  of the recording device  10 . In other words, whether or not setting of the adjustment sheet  50  on the medium  100  is forgotten can be determined by the control device  30  of the recording device  10  depending on whether or not the prescribed pattern  61  has been detected by the optical sensor  25 . 
     Then, in a state where the adjustment sheet  50  is set on the medium  100 , the adjustment pattern PT can be formed in the adjustment region  60  of the adjustment sheet  50  by discharging an ink droplet from the recording head  24 . Then, the adjustment pattern PT formed in the adjustment region  60  is read by the recording device  10  side, and thus the recording device  10  can be caused to perform correction using this adjustment pattern PT. 
     Here, when the adjustment pattern PT is recorded on the adjustment sheet  50 , an ink droplet discharged from the recording head  24  lands on the adjustment sheet  50 . Then, by landing the ink droplet onto the adjustment sheet  50 , wrinkling and cockling may also be generated in the adjustment sheet  50 . 
     It is assumed that the adjustment pattern PT is formed on the medium  100 . In this case, in a case where the medium  100  is prone to wrinkling and cockling due to the adhesion of the ink, wrinkling and cockling may be generated in the medium  100  by recording the adjustment pattern PT on the medium  100 . Specifically, even in a case where wrinkling and cockling are not generated in the medium  100  immediately after the ink adheres to the medium  100 , wrinkles and cockling may be generated over time in the medium  100 . Then, when wrinkling and cockling are generated in the medium  100  at a timing at which the adjustment pattern PT is read by the optical sensor  25 , lines constituting the adjustment pattern PT are distorted on the recording surface  101 , and accuracy of detecting the adjustment pattern PT by the optical sensor  25  may decrease. When the accuracy of detecting the adjustment pattern PT is low, correction accuracy may decrease. 
     Note that, depending on a type of ink and the medium  100 , wrinkling and cockling generated in the medium  100  may be reduced when the ink is dried. In this case, a reading operation of the optical sensor  25  may be made to wait until the ink dries, but the time for drying the ink depends on the type of ink and the medium  100 . For example, a longer time required for drying the ink also increases a waiting time, which reduces throughput. 
     In this regard, in the exemplary embodiment, for correction, the adjustment pattern PT is recorded on the adjustment sheet  50  instead of the medium  100 . In this case, a generation aspect of wrinkling and cockling due to the adhesion of the ink to the adjustment sheet  50  is determined by characteristics of the adjustment sheet  50 . In this way, variations in the generation aspect of wrinkling and cockling in a sheet used for correction are suppressed. Therefore, variations in correction accuracy due to a type of the sheet on which the adjustment pattern PT is formed can be suppressed. Further, since there is no need to wait until wrinkling and cockling generated in the medium  100  is reduced, a decrease in throughput can be suppressed. 
     (2) It is also conceivable that the prescribed pattern is a single thick line. In this case, it is difficult to distinguish the prescribed pattern from a line that had been formed on the second surface  502  of the adjustment sheet  50  apart from the prescribed pattern. In this regard, in the exemplary embodiment, the prescribed pattern  61  including the first portion  651  and the second portion  652  having different densities from each other has been formed on the second surface  502 . Therefore, by using the optical sensor  25  of the recording device  10 , even when a line has been formed on the second surface  502  in addition to the prescribed pattern  61 , the line different from the prescribed pattern  61  is easily distinguished from the prescribed pattern  61 . 
     (3) The prescribed pattern  61  extends in the direction intersecting the first direction C 1  among directions along the second surface  502 . It is assumed that the adjustment sheet  50  is set on the medium  100  such that the scanning direction Y of the optical sensor  25  substantially matches the first direction C 1 , and in this state, the adjustment sheet  50  is transported together with the medium  100  in the transport direction X. In the exemplary embodiment, when the adjustment sheet  50  is transported together with the medium  100  in the transport direction X, a direction in which the prescribed pattern  61  extends includes a component of the transport direction X. In this way, the prescribed pattern  61  can be continuously read by the optical sensor  25  even while the medium  100  is transported in the transport direction X. Therefore, an occurrence of a detection error such that the prescribed pattern  61  cannot be read by the optical sensor  25  can be suppressed in comparison to a case where the prescribed pattern  61  is interrupted partway. Note that, in this case, an interval between the first portion  651  and the second portion  652  being aligned in a direction intersecting the first direction C 1  may be less than or equal to a detection resolution of the optical sensor  25 . In this way, when the optical sensor  25  detects the prescribed pattern  61 , the recording device  10  can recognize that the first portion  651  and the second portion  652  are continuous, and thus an effect of suppressing the occurrence of the detection error described above can be increased. 
     (4) Even when the adjustment sheet  50  is set on the medium  100  such that the scanning direction Y substantially matches the first direction C 1 , the medium  100  may be slanted during transport as illustrated in  FIG. 8 . In this regard, in the exemplary embodiment, the first prescribed pattern  611  and the second prescribed pattern  612  have been formed as the prescribed pattern  61  on the second surface  502  of the adjustment sheet  50 . Then, the first side one end  611   a  is disposed in the same position as that of the second side one end  612   a  in the second direction C 2 . Further, the first side other end  611   b  is disposed in the same position as that of the second side other end  612   b  in the second direction C 2 . For example, when the medium  100  is slanted, one pattern of the first prescribed pattern  611  and the second prescribed pattern  612  can be read by the optical sensor  25  that moves in the scanning direction Y, but the other pattern may not be able to be read. In the example illustrated in  FIG. 8 , in a region surrounded by broken lines, the first prescribed pattern  611  can be read by the optical sensor  25  while the second prescribed pattern  612  cannot be read by the optical sensor  25 . In such a case, whether or not the medium  100  is slanted can be determined through reading of the prescribed pattern  61  by the optical sensor  25 . 
     Note that, in the exemplary embodiment, in the first direction C 1 , the first prescribed pattern  611  is located farther toward one side than the adjustment region  60 , and the second prescribed pattern  612  is located farther toward the other side than the adjustment region  60 . In other words, the first prescribed pattern  611  is disposed away from the second prescribed pattern  612  in the adjustment sheet  50 . For example, when the first prescribed pattern  611  is located closer to the second prescribed pattern as in a case where both of the first prescribed pattern  611  and the second prescribed pattern  612  are located farther toward one side in the first direction C 1  than the adjustment region  60 , the first side one end  611   a  is located closer to the second side one end  612   a . In this case, the first side one end  611   a  and the second side one end  612   a  may both enter a detection range of the optical sensor  25 . As a result, even though the medium  100  is slanted, both of the first side one end  611   a  and the second side one end  612   a  are detected by the optical sensor  25 , and it may not be possible to detect that the medium  100  is slanted. 
     In contrast, in the exemplary embodiment, in the first direction C 1 , the first prescribed pattern  611  is located farther toward one side than the adjustment region  60 , and the second prescribed pattern  612  is located farther toward the other side than the adjustment region  60 . In other words, the first side one end  611   a  is located away from the second side one end  612   a  by a range of the adjustment region  60  in the first direction C 1 . In this way, when the adjustment sheet  50  is attached to the medium  100 , the first side one end  611   a  is offset with respect to the second side one end  612   a  in the transport direction X, and the second side one end  612   a  falls outside the detection range of the optical sensor  25  when the optical sensor  25  detects the first side one end  611   a  and then reaches near the second side one end  612   a . In other words, by adopting the configuration of the exemplary embodiment, when the medium  100  is slanted, a state where one of the first prescribed pattern  611  and the second prescribed pattern  612  is read and the other of the first prescribed pattern  611  and the second prescribed pattern  612  is not read is more likely to be achieved. Therefore, accuracy of determining whether or not the medium  100  on which the adjustment sheet  50  is set is slanted can be increased as described above. 
     (5) In the exemplary embodiment, a distance between the first prescribed pattern  611  and the second prescribed pattern  612  in the first direction C 1  varies in the second direction C 2 . In this way, a gap between the first prescribed pattern  611  and the second prescribed pattern  612  detected by the recording device  10  gradually changes as the adjustment sheet  50  is transported together with the medium  100 . Thus, by monitoring the above-described gap changing in such a manner, the amount of transport and a transport speed of the medium  100  and the adjustment sheet  50  transported by the transport unit  11  can be estimated. For example, by recognizing a current amount of transport of the medium  100  is being transported, a discharge timing of an ink droplet can be optimized according to the amount of transport, and the adjustment pattern PT can be formed according to the amount of transport. Therefore, a correspondence between the amount of transport and the adjustment pattern PT can be produced with higher accuracy. 
     (6) On the second surface  502  of the adjustment sheet  50 , the adjustment region  60  is provided between the first prescribed pattern  611  and the second prescribed pattern  612  in the first direction C 1 . In this way, the recording device  10  side recognizes a position of the first prescribed pattern  611  and a position of the second prescribed pattern  612  in the first direction C 1 , and thus the recording device  10  side can recognize a position of the adjustment region  60  in the first direction C 1 . As a result, formation of the adjustment pattern PT in a position different from that of the adjustment region  60  can be suppressed. 
     (7) The adjustment pattern PT including the forward direction pattern PT 1  and the return direction pattern PT 2  is formed in the adjustment region  60  of the adjustment sheet  50  set on the medium  100 . In this way, a correction value for an adjustment of a discharge timing of an ink droplet of the recording head  24  can be derived based on the forward direction pattern PT 1  and the return direction pattern PT 2 . Then, the discharge timing of the ink droplet by the recording head  24  is controlled by using the derived correction value, and thus a quality of an image formed on the medium  100  can be increased. 
     (8) Note that the correction value is derived while taking into account the thickness D of the adjustment sheet  50 . Then, the discharge timing of the ink droplet by the recording head  24  is controlled by using the correction value with consideration given to the thickness D of the adjustment sheet  50 , and thus the quality of an image that will be formed on the medium  100  can be increased. 
     The exemplary embodiment described above may be modified as follows. The exemplary embodiment described above and the modified examples below may be implemented in combination within a range in which a technical contradiction does not arise.
         In a case where the adjustment sheet  50  can be transported together with the medium  100  by setting the adjustment sheet  50  on the medium  100 , an adhesive layer may not be provided on the adjustment sheet  50 . For example, the adjustment sheet  50  may be attached to the medium  100  by static electricity, or the adjustment sheet  50  may be set on the medium  100  by using a permanent magnet or an electromagnet. In particular, when a permanent magnet and an electromagnet are used, the adjustment sheet  50  may be configured to contain a magnetic metal such as iron, cobalt, and the like.   In a case where the adjustment region  60  is provided on the second surface  502  of the adjustment sheet  50 , the adjustment region  60  may be provided at a location other than a location between the first prescribed pattern  611  and the second prescribed pattern.   In a case where a gap between the first prescribed pattern  611  and the second prescribed pattern  612  changes from one end toward the other end in the second direction C 2 , the extending direction of any one pattern of the first prescribed pattern  611  and the second prescribed pattern  612  may be the second direction C 2 .   The first prescribed pattern  611  and the second prescribed pattern  612  might have been formed such that a gap between the first prescribed pattern  611  and the second prescribed pattern  612  gradually narrows from one end to an intermediate point in the second direction C 2 , and the gap between the first prescribed pattern  611  and the second prescribed pattern  612  increases from the intermediate point toward the other end.   Both of the first prescribed pattern  611  and the second prescribed pattern  612  may extend in the second direction C 2 .   In a case where at least a part of the first prescribed pattern  611  overlaps the second prescribed pattern  612  in the first direction C 1 , the first side one end  611   a  of the first prescribed pattern  611  may not be located in the same position as that of the second side one end  612   a  of the second prescribed pattern  612  in the second direction C 2 .   In a case where at least a part of the first prescribed pattern  611  overlaps the second prescribed pattern  612  in the first direction C 1 , the first side other end  611   b  of the first prescribed pattern  611  may not be located in the same position as that of the second side other end  612   b  of the second prescribed pattern  612  in the second direction C 2 .   In the exemplary embodiment described above, the design of the first prescribed pattern  611  is the same as the design of the second prescribed pattern  612 . However, the design of the first prescribed pattern  611  may be different from the design of the second prescribed pattern  612 .   The first prescribed pattern  611  may not be a pattern as illustrated in  FIG. 6  as long as the first portion  651  having a high density and the second portion  652  having a density lower than that of the first portion  651  are adjacent to each other in the first direction C 1 . For example, the first prescribed pattern  611  may have a shape in which a plurality of lines extending in one direction are aligned in the first direction C 1  with an interval between the lines.   The second prescribed pattern  612  may not be a pattern as illustrated in  FIG. 6  as long as the first portion  651  having a high density and the second portion  652  having a density lower than that of the first portion  651  are adjacent to each other in the first direction C 1 . For example, the second prescribed pattern  612  may have a shape in which a plurality of lines extending in one direction are aligned in the first direction C 1  with an interval between the lines.   The first prescribed pattern  611  may be a single thick line.   The second prescribed pattern  612  may be a single thick line.       

     A prescribed pattern that has been formed on the adjustment sheet  50  may be only one of the first prescribed pattern  611  and the second prescribed pattern  612 .
         The prescribed pattern may not be a pattern extending in an arbitrary direction as long as the pattern can be detected by the optical sensor  25 . For example, the prescribed pattern may be constituted by a single mark such as a circle or a square.       

     The adjustment sheet  50  may be used during another adjustment other than an adjustment of a landing position. Examples of another adjustment may include an adjustment of the amount of transport of the medium  100  transported by the transport unit  11 . In one transport processing, the amount of transport is controlled based on the amount of rotation of a rotating roller during transport of the medium  100 . In other words, in a case where the center of rotation of the roller is eccentric, the amount of transport varies even with a constant amount of rotation of the roller. Thus, the adjustment pattern formed in the adjustment region  60  may be a pattern for checking a degree of variation in the amount of transport of the medium  100  transported by the transport unit  11 . 
       FIGS. 9 and 10  illustrate one example of a method for forming an adjustment pattern for checking a degree of variation in the amount of transport of the medium  100  transported by the transport unit  11 . First, as illustrated in  FIG. 9 , an adjustment pattern PT 1 A extending in the scanning direction Y is recorded in the adjustment region  60 . Then, the roller is rotated by a predetermined amount to perform transport by a predetermined transport amount ΔX in the transport direction X. When the transport of the medium  100  is stopped, as illustrated in  FIG. 10 , a new adjustment pattern PT 1 B is recorded in the adjustment region  60  by using the nozzles downstream of the nozzles that record the adjustment pattern PT 1 A in the transport direction X. The nozzles that record the adjustment pattern PT 1 B are shifted downstream by a distance corresponding to the predetermined transport amount ΔX from the nozzles that record the adjustment pattern PT 1 A. At this time, when the roller is not eccentric and an actual amount of transport of the medium  100  is equal to the predetermined amount, the adjustment pattern PT 1 B is recorded such that the adjustment pattern PT 1 B overlaps the adjustment pattern PT 1 A. 
     In  FIG. 10 , the adjustment pattern PT 1 A deviates from the adjustment pattern PT 1 B in the transport direction X. The amount of transport can be corrected based on this amount of deviation. 
     Note that such an adjustment of the amount of transport of the medium  100  transported by the transport unit  11  can also be performed by the recording device  10  of a type that does not move the recording head  24  in the scanning direction Y. Therefore, the recording device in which the adjustment sheet  50  is used may be a recording device other than the serial scan type illustrated in  FIGS. 1 and 2 .
         The recording device may be a fluid jet device that sprays and discharges liquids other than ink and performs recording. Examples of other liquids include liquids in which particles of a functional material are dispersed or mixed in a liquid, and a fluid like a gel.       

     Hereinafter, a technical idea derived from the exemplary embodiment and the modification examples described above and the effects thereof are described. 
     An adjustment sheet is an adjustment sheet used in a recording device. The recording device includes a transport unit configured to transport a medium in a transport direction, a discharge unit configured to discharge a liquid droplet on a recording surface of the medium transported by the transport unit, and a detection unit configured to detect an image formed on the recording surface of the medium transported by the transport unit. The adjustment sheet is configured to be transported, when the adjustment sheet is set on the recording surface of the medium, together with the medium in the transport direction by the transport unit. The adjustment sheet includes a first surface configured to contact the recording surface, and a second surface being a surface located opposite to the first surface and including an adjustment region being a region configured to be formed with an adjustment pattern detectable by the detection unit. A prescribed pattern has been formed in a region different from the adjustment region on the second surface. 
     According to the above-described configuration, by setting the adjustment sheet on the medium such that the first surface contacts the recording surface of the medium, the recording device can transport the adjustment sheet together with the medium in the transport direction. As a result, the second surface of the adjustment sheet can face the discharge unit of the recording device. In this way, the prescribed pattern that has been formed on the second surface can be detected by the detection unit of the recording device. In other words, whether or not setting of the adjustment sheet on the medium is forgotten may be determined by the recording device side depending on whether or not the prescribed pattern has been detected by the detection unit. 
     Then, in a state where the adjustment sheet is set on the medium, the adjustment pattern can be formed in the adjustment region of the adjustment sheet by discharging a liquid droplet from the discharge unit. Then, the adjustment pattern formed in the adjustment region is read by the recording device side, and thus the recording device can perform correction using this adjustment pattern. 
     Here, in order to record the adjustment pattern on the adjustment sheet, a liquid droplet discharged from the discharge unit lands on the adjustment sheet. Then, by landing the liquid droplet onto the adjustment sheet, wrinkling and cockling may also be generated in the adjustment sheet. 
     For correction, it is assumed that the adjustment pattern is formed on the adjustment sheet described above instead of the medium. In this case, variations in the generation aspect of wrinkling and cockling in a sheet used for correction are suppressed. As a result, variations in correction accuracy due to a type of the sheet on which the adjustment pattern is formed can be suppressed. 
     The recording device includes the detection unit configured to move in scanning directions intersecting the transport direction among directions along the recording surface of the medium transported by the transport unit, and the detection unit is configured to output a signal according to a density of the image on the recording surface. In this case, the prescribed pattern might have been formed such that a first portion and a second portion are aligned adjacent to each other. Here, the second portion has a density lower than that of the first portion. 
     It is also conceivable that the prescribed pattern is a single thick line. In this case, it is difficult to distinguish the prescribed pattern from a line formed on the second surface of the adjustment sheet apart from the prescribed pattern. In this regard, in the above-described configuration, the prescribed pattern including the first portion and the second portion having different densities from each other is formed on the second surface. Therefore, by using the detection unit of the recording device, even when a line is formed on the second surface in addition to the prescribed pattern, this line is easily distinguished from the prescribed pattern. 
     In the above-described adjustment sheet, the prescribed pattern may be configured to include the first portion and the second portion being aligned in a first direction among directions along the second surface, and the prescribed pattern may extend in a direction different from the first direction among directions along the second surface. 
     It is assumed that the adjustment sheet is set on the medium such that the scanning direction of the detection unit substantially matches the first direction, and in this state, the adjustment sheet is transported together with the medium in the transport direction. According to the above-described configuration, when the adjustment sheet is transported together with the medium in the transport direction, a direction in which the prescribed pattern extends includes a component of the transport direction. In this way, even in a case where the medium is transported in the transport direction, the prescribed pattern can be continuously read by the detection unit. Therefore, an occurrence of a detection error such that the prescribed pattern cannot be read by the detection unit can be suppressed in comparison to a case where the prescribed pattern is interrupted partway. Note that, in this case, an interval between the first portion and the second portion being aligned in a direction different from the first direction may be less than or equal to a detection resolution of the detection unit. In this way, when the detection unit detects the prescribed pattern, the recording device can recognize that the first portion and the second portion are continuous, and thus an effect of suppressing the occurrence of the detection error described above can be increased. 
     In the above-described adjustment sheet, as the prescribed pattern, a first prescribed pattern and a second prescribed pattern might have been formed on the second surface, the second prescribed pattern has been formed at a position different from that of the first prescribed pattern in the first direction and, when a second direction is defined as a direction orthogonal to the first direction among directions along the second surface, in the second direction, one end of both ends of the first prescribed pattern might have been disposed at the same position as one end of both ends of the second prescribed pattern, and in the second direction, the other end e of both ends of the first prescribed pattern might have been disposed in the same position as a position of the other end of both ends of the second prescribed pattern. 
     Even when the adjustment sheet is set on the medium such that the scanning direction of the detection unit substantially matches the first direction, the medium may be slanted during transport. With the adjustment sheet having the above-described configuration being set on the medium, when the medium is slanted, one pattern of the first prescribed pattern and the second prescribed pattern can be read by the detection unit that moves in the scanning direction, but the other pattern may not be able to be read. In such a case, whether or not the medium is slanted can be determined by reading the prescribed pattern by the detection unit. 
     In the above-described adjustment sheet, as the prescribed pattern, a first prescribed pattern and a second prescribed pattern might have been formed on the second surface, the second prescribed pattern have been formed at a position different from a position of the first prescribed pattern in the first direction, the first prescribed pattern and the second prescribed pattern might have been each disposed such that at least a part of the first prescribed pattern overlaps with at least a part of the second prescribed pattern in the first direction, and, when a second direction is defined as a direction orthogonal to the first direction among directions along the second surface, the first prescribed pattern and the second prescribed pattern might have been each formed such that a distance between the first prescribed pattern and the second prescribed pattern in the first direction, varies in the second direction. 
     In the recording device, a gap between the first prescribed pattern and the second prescribed pattern can be detected by reading the first prescribed pattern and the second prescribed pattern by the detection unit while the adjustment sheet is transported together with the medium. 
     In the above-described configuration, the prescribed pattern is formed to have a distance between the first prescribed pattern and the second prescribed pattern in the first direction to vary in the second direction. For this reason, a gap between the first prescribed pattern and the second prescribed pattern detected by the recording device gradually changes as the adjustment sheet is transported together with the medium. Thus, by monitoring the above-described gap changing in such a manner, a transport speed of the medium and the adjustment sheet by the recording device can be estimated. 
     In the above-described adjustment sheet, the adjustment region might have been disposed between the first prescribed pattern and the second prescribed pattern in the first direction. 
     According to the above-described configuration, when the adjustment pattern is recorded on the adjustment sheet, it is easy to determine which position on the second surface of the adjustment sheet a liquid droplet should land. 
     In the above-described adjustment sheet, as the prescribed pattern, a first prescribed pattern and a second prescribed pattern might have been formed on the second surface, the second prescribed pattern have been formed at a position different from a position of the first prescribed pattern, the adjustment region might have been disposed between the first prescribed pattern and the second prescribed pattern, and, when a first direction is defined as a direction in which the first prescribed pattern, the adjustment region, and the second prescribed pattern are aligned, among directions along the second surface, the first prescribed pattern and the second prescribed pattern may each extend in a direction different from the first direction among directions along the second surface. 
     According to the above-described configuration, when the adjustment pattern is recorded on the adjustment sheet, it is easy to determine which position on the second surface of the adjustment sheet a liquid droplet should land. 
     It is assumed that the adjustment sheet is set on the medium such that the scanning direction of the detection unit substantially matches the first direction, and in this state, the adjustment sheet is transported together with the medium in the transport direction. According to the above-described configuration, when the adjustment sheet is transported together with the medium in the transport direction, a direction in which the first prescribed pattern extends and a direction in which the second prescribed pattern extends each include a component of the transport direction. Thus, the detection unit can be prevented from forgetting to read the first prescribed pattern and the second prescribed pattern formed on the adjustment sheet transported in the transport direction together with the medium. 
     The above-described adjustment sheet further includes a body sheet including the second surface, and an adhesive layer provided on a surface of the body sheet opposite to the second surface. the first surface is an outermost surface of the adhesive layer. 
     According to the above-described configuration, the adjustment sheet can be attached to the medium by adhesion of the adhesive layer. 
     An adjusting method of a landing position of a liquid droplet includes: providing a recording device comprising a transport unit configured to transport a medium, a discharge unit configured to discharge a liquid droplet on the medium transported by the transport unit while the discharge unit moves in scanning directions intersecting a transport direction of the medium in the transport unit, and a detection unit configured to detect an image formed on the recording surface of the medium while the detection unit moves in the scanning directions; setting the adjustment sheet described above on the medium; forming, after setting the adjustment sheet, the adjustment pattern including a forward direction pattern formed by discharging, on the adjustment region of the adjustment sheet transported together with the medium in the transport direction by the transport unit, a liquid droplet from the discharge unit while the discharge unit moves in a forward direction of the scanning directions, and a return direction pattern formed by discharging, on the adjustment region of the adjustment sheet, a liquid droplet from the discharge unit while the discharge unit moves in a return direction of the scanning directions; reading, after forming the adjustment pattern, the adjustment pattern by the detection unit; and calculating, after reading the adjustment pattern, a correction value for an adjustment of a discharge timing of a liquid droplet from the discharge unit based on the forward direction pattern and the return direction pattern. 
     According to the above-described configuration, the adjustment pattern including the forward direction pattern and the return direction pattern is formed in the adjustment region of the adjustment sheet set on the medium. Then, a correction value for an adjustment of a discharge timing of the discharge unit can be derived based on the amount of deviation between the forward direction pattern and the return direction pattern. Then, the discharge timing of the liquid droplet by the discharge unit is controlled by using the derived correction value, and thus the quality of an image formed on the medium can be increased. 
     In the adjusting method of a landing position of a liquid droplet, may comprise: adjusting, while calculating the correction value, a discharge timing of a liquid droplet from the discharge unit based on the forward direction pattern, the return direction pattern, and a thickness of the adjustment sheet. 
     According to the above-described configuration, the discharge timing of the liquid droplet from the discharge unit and the discharge timing of the liquid droplet during movement of the discharge unit in the return direction can be adjusted with consideration given to a thickness of the adjustment sheet.