printer

Abstract

The printer prevents uneven coloring from occurring in prints, or prevents any uneven coloring that does occur from being noticeable. [Solution] The printer 100 includes a print unit 10 having a thermal head 12 and an ink ribbon 13, a standby unit 20 provided on the upstream side in the transport direction, a supply unit 50 provided on the downstream side in the transport direction, a transport unit 30 that transports paper 200 between the supply unit 50 and the standby unit 20, and a control unit 40 that controls the transport unit 30 and the print unit 10 based on image information S input corresponding to the image P to be printed on the paper 200. When the control unit 40 transports the paper 200 to the standby unit 20, if the image information S satisfies certain conditions, it switches to a second operation in which the used area of ​​the ink ribbon 13 is placed in front of the thermal head 12, and if the certain conditions are not met, it switches to a first operation in which the unused area of ​​the ink ribbon 13 is placed.

Description

Technical Field

[0001] The present invention relates to a printer.

Background Art

[0002] There is known a printer that performs printing with sublimation dyes by thermally diffusing and transferring the sublimation dyes applied to an ink ribbon onto paper (image receiving paper) (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The printer of Patent Document 1 performs printing on a sheet of paper cut to a predetermined length. However, prior to actually performing the printing, the paper (sheet of paper) is conveyed to a standby section upstream of the printing section, and in the process of this conveyance, the leading end of the sheet of paper (paper) on the standby section side is detected.

[0005] Then, the printer reverses the feeding direction of the conveying means and prints on the paper at the printing section while passing the paper from the standby section through the printing section. The timing via the printing at the printing section is set based on the detection of the leading end of the paper on the standby section side.

[0006] The printer completes the head start of the ink ribbon prior to conveying the paper to the standby section. That is, the printer arranges the unused area of the ink ribbon used for printing on the paper in the printing section before the paper is sent to the standby section.

[0007] Here, as the paper is transported along the curved transport path from the printing unit to the standby unit, a portion of the paper that curves and protrudes towards the ink ribbon may rub against a specific part of the unused area of ​​the ink ribbon as it is transported.

[0008] In certain parts of the ink ribbon that have rubbed against the paper, the sensitivity of the ink ribbon (the characteristic of the sublimation dye's color intensity in response to applied heat) may change due to the effects of additives on the paper's surface. Therefore, even in unused areas of the ink ribbon, if printing is performed using an ink ribbon whose sensitivity has changed in only certain parts, color unevenness will occur in the printed image, with differences in color intensity between the specific areas and other areas.

[0009] This invention has been made in view of the above circumstances, and aims to provide a printer that can prevent color unevenness from occurring in prints, or prevent color unevenness from being noticeable if it does occur. [Means for solving the problem]

[0010] The present invention relates to a printer comprising: a print unit having a thermal head and an ink ribbon; a standby unit provided upstream of the print unit in the transport direction; a supply unit provided downstream of the print unit in the transport direction; a transport unit that transports paper between the supply unit and the standby unit; and a control unit that controls the transport unit and the print unit based on image information input corresponding to an image to be printed on the paper, wherein the control unit switches to a second operation in which, when the image information satisfies certain conditions, it places the used area of ​​the ink ribbon in front of the thermal head when transporting the paper from the supply unit to the standby unit; and when the image information does not satisfy certain conditions, it switches to a first operation in which it places the unused area of ​​the ink ribbon in front of the thermal head when transporting the paper from the supply unit to the standby unit. [Effects of the Invention]

[0011] The printer according to the present invention can prevent color unevenness from occurring in prints, or prevent any color unevenness that does occur from being noticeable. [Brief explanation of the drawing]

[0012] [Figure 1A] This is a schematic diagram illustrating the operation of a dye-sublimation thermal printer, showing the paper being placed in the paper feed unit and the thermal head and ink ribbon in their retracted positions. [Figure 1B] This is a schematic diagram illustrating the operation of a dye-sublimation thermal printer, showing the state where ribbon feeding is complete and paper feeding is continuing. [Figure 1C] This is a schematic diagram illustrating the operation of a dye-sublimation thermal printer, showing the state after the paper has been fed to the front. [Figure 1D] This is a schematic diagram illustrating the operation of a dye-sublimation thermal printer, showing the thermal head and ink ribbon positioned at the print location. [Figure 1E] This is a schematic diagram illustrating the operation of a dye-sublimation thermal printer, showing the state where printed paper is placed in the paper feed unit. [Figure 2] This diagram shows the arrangement of sublimation dyes in a ribbon. [Figure 3] This is a magnified view of the contact area between the ribbon and the paper in Figure 1B. [Figure 4] This is an example of an image printed on paper, showing the upper body of a person wearing a white dress shirt. [Figure 5A] This is a schematic diagram illustrating the operation in which, prior to the ribbon's lead-out in the first operation, the ribbon is rewound onto the feed roller, and the used portion of the ribbon is positioned in front of the thermal head. [Figure 5B] This is a schematic diagram illustrating the operation in which, prior to the ribbon's initial feed in the first operation, the ribbon is rewound onto the feed roller to position the used portion of the ribbon in front of the thermal head, and it shows the state in which the paper is being continuously fed out. [Figure 6A]A flowchart showing the process flow of the control unit for determining whether the content of the image information meets specific conditions for switching between the first operation and the second operation before printing the yellow image. [Figure 6B] A flowchart showing the process flow of the control unit for determining whether the content of the image information meets specific conditions for switching between the first operation and the second operation before printing the magenta image. [Figure 6C] A flowchart showing the process flow of the control unit for determining whether the content of the image information meets specific conditions for switching between the first operation and the second operation before printing the cyan image. [Figure 7] A schematic diagram showing the state where the paper is not completely conveyed to the standby unit but stopped at a position L4 in front when the paper is fed.

Embodiments for Carrying Out the Invention

[0013] Embodiments of the printer according to the present invention will be described below with reference to the drawings.

[0014] <Configuration> FIGS. 1A, 1B, 1C, 1D, and 1E are schematic diagrams for explaining the operation of the sublimation thermal printer 100 (hereinafter referred to as the printer 100). FIG. 1A shows a state where the paper 200 is placed in the supply unit 50 and the thermal head 12 and the ink ribbon 13 are placed in the retracted position. FIG. 1B shows a state where the head feeding of the ribbon 16 is completed and the head feeding of the paper 200 is continuing. FIG. 1C shows a state where the head feeding of the paper 200 is completed. FIG. 1D shows a state where the thermal head 12 and the ink ribbon 13 are placed in the printing position. FIG. 1E shows a state where the printed paper 200 is placed in the supply unit 50 (the rear end 201 of the paper 200 is not disengaged from the thermal head 12).

[0015] FIG. 2 is a diagram showing the arrangement of the sublimation dye on the ribbon 16, and FIG. 3 is an enlarged view of the contact portion where the unused area of the ribbon 16 and the paper 200 contact in FIG. 1B.

[0016] Printer 100 is one embodiment of the printer according to the present invention. Printer 100 prints an image P corresponding to input CMY image information S onto a sheet of paper 200 that has been pre-cut to a predetermined length. Paper 200 is a receptive paper having a receptive layer that develops color by receiving sublimation dye that has been thermally diffused and transferred from the ribbon 16. As shown in Figure 1A, the printer 100 includes at least a print unit 10, a standby unit 20, a supply unit 50, a transport unit 30, a paper sensor 60, a ribbon sensor 70, and a control unit 40.

[0017] The supply unit 50 is the area that supplies paper 200 to the standby unit 20, and is also the area from which the printed paper 200 is sent out after passing through the print unit 10 from the standby unit 20. The supply unit 50 is located downstream of the print unit 10 in the forward transport direction (the transport direction of the paper 200 when the print unit 10 prints on the paper 200).

[0018] The standby section 20 is an area where the paper 200 temporarily waits before being sent to the print section 10. The standby section 20 is located upstream of the print section 10 in the forward transport direction.

[0019] Under the control of the control unit 40, the printer 100 places the paper 200 in the supply unit 50 and positions the print unit 10 in the retracted position, as shown in Figure 1A. Then, as shown in Figure 1B, the printer 100 drives the transport means 32. Driven by the transport means 32, the printer 100 sends the paper 200 along the transport path 31 to the standby unit 20, as shown in Figure 1C. With the paper 200 in the standby unit 20, the printer 100 moves the print unit 10 to the print position.

[0020] After the print unit 10 is positioned at the print location, the printer 100 drives the transport means 32 to pull the paper 200 back to the supply unit 50 along the transport path 31, as shown in Figure 1D, and prints on the paper 200 using the print unit 10 based on the input image information S.

[0021] Since the printer 100 in this embodiment is a color printer, it sequentially prints yellow on the paper 200 based on the yellow (Y) image signal Sy, magenta on the magenta (M) image signal Sm, and cyan on the cyan (C) image signal Sc, respectively. Furthermore, to protect the printed surface, it prints an overcoat (OC) after the cyan print. Therefore, the printer 100 moves the paper 200 back and forth between the supply unit 50 and the standby unit 20 from the state shown in Figure 1A to the state shown in Figure 1E, and repeats the operation of printing on the paper 200 four times during this back and forth movement.

[0022] (Transportation section) The transport unit 30 includes a transport path 31 and a transport means 32. The transport means 32 is provided on the transport path 31. The transport path 31 is provided between the supply unit 50 and the standby unit 20. As shown in Figure 1A, the transport path 31 is formed with a cross-sectional shape that is curved in an arc shape, for example. Specifically, the transport path 31 is formed with a cross-sectional shape that is convex to the side of the print unit 10, which will be described later, where the thermal head 12 and ink ribbon 13 are provided. Note that the transport path 31 may be formed with a straight cross-sectional shape instead of a curved shape.

[0023] The conveying means 32 includes a drive roller 33 and a driven roller 34. The drive roller 33 and the driven roller 34 are positioned opposite each other across the conveying path 31. The drive roller 33 and the driven roller 34 grip the paper 200, which is placed along the conveying path 31, in the thickness direction. As the drive roller 33 rotates, the paper 200 is conveyed along the conveying path 31. The driven roller 34 rotates due to friction with the moving paper 200. The drive roller 33 can be switched between forward rotation, reverse rotation, and stopping by the control unit 40.

[0024] In this specification, forward rotation of the drive roller 33 is in the direction of transporting the paper 200 from the standby unit 20 to the supply unit 50, and reverse rotation of the drive roller 33 is in the direction of transporting the paper 200 from the supply unit 50 to the standby unit 20.

[0025] In the printer 100, the driven roller 34 is provided on the side of the transport path 31 with a convex cross-sectional shape, and the drive roller 33 is provided on the side of the transport path 31 with a concave cross-sectional shape (the side opposite to the side with a convex cross-sectional shape). Alternatively, the printer 100 may have the drive roller 33 provided on the side of the transport path 31 with a convex cross-sectional shape, and the driven roller 34 provided on the side of the transport path 31 with a concave cross-sectional shape.

[0026] (Printing Department) The printing unit 10 is located on the transport path 31. The printing unit 10 includes a platen roller 11, a thermal head 12, and an ink ribbon 13. The platen roller 11 is located on one side of the transport path 31, that is, on the side with a concave cross-sectional shape. The thermal head 12 and ink ribbon 13 are located on the other side of the transport path 31, that is, on the side with a convex cross-sectional shape. The platen roller 11, the thermal head 12, and the ink ribbon 13 are positioned opposite each other.

[0027] The ink ribbon 13 comprises a feed roller 14, a take-up roller 15, and a ribbon 16. The ribbon 16 is formed by coating a long base film with sublimation dyes of the three primary colors, yellow (Y), magenta (M), and cyan (C), as shown in Figure 2, and also by coating it with a transparent overcoat material (OC). One end of the ribbon 16 in the longitudinal direction is fixed to the feed roller 14, and the other end in the longitudinal direction is fixed to the take-up roller 15. Almost all of the unused portion of the ribbon 16 is wound onto the feed roller 14, and the portion used for printing is wound onto the take-up roller 15.

[0028] The ribbon 16 is divided in the longitudinal direction into four regions, starting from the side closest to the winding roller 15: a Y region 16y coated with yellow sublimation dye, an M region 16m coated with magenta sublimation dye, a C region 16c coated with cyan sublimation dye, and an OC region 16o coated with an overcoat material. The ribbon 16 is formed by repeating the Y region 16y, M region 16m, C region 16c, and OC region 16o in the longitudinal direction.

[0029] Region Y 16y and region M 16m are in contact at boundary 17ym, region M 16m and region C 16c are in contact at boundary 17mc, region C 16c and region OC 16o are in contact at boundary 17co, and region OC 16o and region Y 16y are in contact at boundary 17oy.

[0030] The ribbon 16 has a portion stretched across the front of the thermal head 12 between the portion wound on the feed roller 14 and the portion wound on the take-up roller 15. The portion of the ribbon 16 stretched across the front of the thermal head 12 has the base film surface facing the front of the thermal head 12. Therefore, the ribbon 16 is positioned so that the surface coated with sublimation dye faces the platen roller 11.

[0031] The ribbon 16 is unwound from the feed roller 14 and wound onto the feed roller 15 when the winding roller 15 is driven in the forward direction by the control unit 40. At this time, in order to apply tension to the ribbon 16 so that the portion of the ribbon 16 stretched across the front of the thermal head 12 does not become loose, a torque is applied to the feed roller 14 that rotates it in the reverse direction.

[0032] Furthermore, under the control of the control unit 40, the feed roller 14 and the take-up roller 15 are driven in the reverse direction to rewind the used ribbon 16 onto the feed roller 14. As the feed roller 14 rewinds the ribbon 16 and the take-up roller 15 unwinds the used ribbon 16, the used ribbon 16 moves towards the feed roller 14.

[0033] Furthermore, as mentioned above, a torque is applied to the feed roller 14 that rotates it in the reverse direction. Therefore, to prevent excessive tension from being applied to the portion of the ribbon 16 that is stretched across the front of the thermal head 12, a torque limiter is provided on the feed roller 14.

[0034] Except when printing on paper 200 (see Figure 1D), the thermal head 12 and ink ribbon 13 are positioned in a retracted position away from the transport path 31, as shown in Figures 1A, 1B, and 1C, under the control of the control unit 40. When printing on paper 200, the thermal head 12 and ink ribbon 13 are positioned in a print position closer to the platen roller 11, as shown in Figure 1D, under the control of the control unit 40. In the print position, the thermal head 12 and ink ribbon 13 sandwich the paper 200, which is being transported along the transport path 31, between themselves and the platen roller 11.

[0035] Furthermore, when the printer 100 prints on the paper 200, the control unit 40 controls the transport means 32 to transport the paper 200 in the forward direction, while the thermal head 12 generates heat according to the input signal value, causing the sublimation dye of the ribbon 16 to be thermally diffused and transferred to the receiving layer of the paper 200 in contact with the ribbon 16, thereby printing an image corresponding to the signal value on the paper 200.

[0036] (Control Unit) When the printer 100 receives image information S corresponding to the image P to be printed on the paper 200, the control unit 40 controls the operation of the transport means 32 and the print unit 10 based on the content of the input image information S, and prints the image P represented by the image information S onto the paper 200.

[0037] The control unit 40 switches the paper transport operation by the transport means 32 and the ribbon feeding operation of the print unit 10 between a first operation (normal operation) and a second operation (color unevenness reduction operation) according to the input image information S.

[0038] [First action] The first operation is the normal transport operation of the paper 200 by the transport means 32 and the normal feeding operation of the ribbon 16 by the print unit 10. Specifically, the control unit 40 performs the first operation shown in (1) to (5) below when the content of the input image information S does not satisfy the specific conditions described later.

[0039] (1) With the paper 200 placed in the supply unit 50, the control unit 40 places the thermal head 12 and ink ribbon 13 in the retracted position (see Figure 1A). Note that when the previous print operation is completed, the state shown in Figure 1A is not required to repeat the operation in (1), and in that case, the operation in (1) may be omitted.

[0040] (2) The control unit 40 rotates the winding roller 15 in the forward direction so that the unused Y region 16y of the ribbon 16 is positioned in front of the thermal head 12. When the ribbon sensor 70 detects the boundary 17oy (see Figure 2) between the unused Y region 16y and the used OC region 16o that precedes the unused Y region 16y, the control unit 40 stops the rotation of the winding roller 15 and rotates the unwinding roller 14 and the winding roller 15 in the reverse direction to rewind the ribbon 16 by a predetermined length, and then stops (see Figure 1B).

[0041] The reason the printer 100 rewinds the ribbon 16 by a predetermined length is that the ribbon sensor 70 is located downstream of the front of the thermal head 12 in the transport direction during printing. However, when the ribbon sensor 70 detects the boundary 17oy, the end region of the unused Y region 16y in the transport direction (the end region of the Y region 16y close to the boundary 17oy) has already passed the front of the thermal head 12. If printing proceeds as is, this portion will not be used for printing and will be wasted.

[0042] Therefore, the control unit 40 rewinds the unused end region of the Y region 16y in the transport direction to the front of the thermal head 12, allowing the printer 100 to effectively utilize the unused end region of the Y region 16y in the transport direction for printing. However, if it is acceptable for the unused end region of the Y region 16y in the transport direction to remain unused and go to waste, the control unit 40 may be controlled not to perform the operation of rewinding the ribbon 16 by a predetermined length.

[0043] In this way, the state in which the unused Y region 16y of the ribbon 16 is positioned in front of the thermal head 12 and stopped is the state in which the Y region 16y of the ribbon 16 for printing has been fully extended, that is, the state in which the Y region 16y of the ribbon 16 is positioned at a predetermined location when printing is to start. The predetermined length to unwind the ribbon 16 can be detected by the control unit 40 by detecting the amount of rotation of the winding roller 15 using an encoder or the like provided on the winding roller 15.

[0044] (3) The control unit 40 controls the printer 100 to start the paper 200 leading operation in parallel with the ribbon 16 leading operation described in (2). Specifically, as shown in Figure 1A, the control unit 40 rotates the drive roller 33 in the reverse direction to transport the paper 200 from the supply unit 50 along the transport path 31 toward the standby unit 20 (see Figure 1B). The control unit 40 stops the rotation of the drive roller 33 after the paper sensor 60 detects the leading edge (the leading edge closer to the standby unit 20) 201 of the paper 200 in the transport direction and transports it for a certain length further (see Figure 1C). This certain length is stored in the control unit 40 beforehand. Since the drive roller 33 is driven by a stepping motor, the control unit 40 can control the transport of the certain length by controlling the rotation of the stepping motor. The state in which the transport of the certain length is completed is the state in which the paper 200 leading for printing is completed, that is, the state in which the paper 200 is positioned in the predetermined position when printing is started.

[0045] Furthermore, when the printer 100 has finished printing the previous time (see Figure 1A), the boundary between the used area of ​​the ribbon 16 used in the previous print and the unused area of ​​the ribbon 16 to be used for the next print is advanced to a position close to the ribbon sensor 70. Therefore, the length of the ribbon 16 used to advance the ribbon 16 in the transport direction (e.g., 2 cm) as shown in (2) is very short compared to the length of the paper 200 used to transport the paper 200 from the supply unit 50 to the standby unit 20 as shown in (3) (e.g., 30 cm). Consequently, when the ribbon 16 advancement operation (operation (2)) is completed (see Figure 1B), the paper 200 advancement operation (operation (3)) is still ongoing, and only after that does the paper advancement operation end (see Figure 1C).

[0046] (4) After the ribbon 16 and the paper 200 are brought forward, the control unit 40 positions the thermal head 12 and the ink ribbon 13 at the print position (a position where the paper 200 and the ink ribbon 13 are sandwiched between the platen roller 11 and the thermal head 12) (see Figure 1D).

[0047] (5) The control unit 40 rotates the drive roller 33 in the forward direction to transport the paper 200 from the standby unit 20 along the transport path 31 toward the supply unit 50, and also drives the take-up roller 15 in the forward direction by torque control so that the ribbon 16 is subjected to appropriate tension. In parallel with the transport of the paper 200 and the feeding of the ribbon 16, the control unit 40 controls the thermal head 12 to generate heat corresponding to the image signal Sy corresponding to the yellow color in the input image information S (see Figure 1D). After the paper 200 has been transported to the position corresponding to the image information S, the control unit 40 stops the rotation of the drive roller 33 and the take-up roller 15, and moves the thermal head 12 and ink ribbon 13 to the retracted position (see Figure 1E).

[0048] In the first operation, in which the printer 100 does not control the rewinding of the ribbon 16, after printing the first, second, and third colors and the overcoat on the paper 200, the printer 100 stops transporting the paper 200 when the paper 200 is not completely removed from the front of the thermal head (the rear end 201 of the paper 200 remains in a part of the front of the thermal head). On the other hand, in the second operation, described later, in which the printer 100 rewinds the ribbon 16, the printer 100 performs the ribbon rewinding operation before printing, so when the print before that print is completed, the printer stops transporting the paper 200 when the rear end 201 of the paper 200 has completely passed the front of the thermal head 12.

[0049] Through the operations (1) to (5) described above, the printer 100 prints a yellow image Py on the paper 200, corresponding to the image signal Sy that corresponds to the yellow color in the input image information S.

[0050] Next, the control unit 40 repeats operations (2) to (5) to superimpose a magenta image Pm corresponding to the image signal Sm corresponding to the magenta color development onto the same paper 200, then repeats operations (2) to (5) to superimpose a cyan image Pc corresponding to the image signal Sc corresponding to the cyan color development onto the same paper 200, and then repeats operations (2) to (5) to superimpose an overcoat Po corresponding to the image signal So corresponding to the overcoat onto the same paper 200, and then finishes printing.

[0051] Furthermore, when repeating operations (2) to (5) on the paper 200 after printing the yellow image Py, as operation (2), the control unit 40 rotates the take-up roller 15 in the forward direction so that the unused M region 16m of the ribbon 16 is positioned in front of the thermal head 12. When the ribbon sensor 70 detects the boundary 17ym between the unused M region 16m and the preceding used Y region 16y, it rewinds the ribbon 16 by a predetermined length and then stops the rotation of the take-up roller 15, completing the position where the M region 16m of the ribbon 16 is exposed.

[0052] Furthermore, as part of operation (5), in parallel with the transport of the paper 200 and the feeding of the ribbon 16, the control unit 40 controls the thermal head 12 to generate heat corresponding to the image signal Sm that corresponds to the magenta color development among the input image information S, thereby superimposing the magenta image Pm onto the yellow image Py of the paper 200.

[0053] Similarly, when repeating operations (2) to (5) on a sheet of paper 200 that has been printed with a magenta image Pm superimposed on a yellow image Py, operation (2) is performed by the control unit 40, which rotates the take-up roller 15 in the forward direction so that the unused C region 16c of the ribbon 16 is positioned in front of the thermal head 12. When the ribbon sensor 70 detects the boundary 17mc between the unused C region 16c and the preceding used M region 16m, it rewinds the ribbon 16 by a predetermined length and then stops the rotation of the take-up roller 15, completing the position where the beginning of the C region 16c of the ribbon 16 is exposed.

[0054] Furthermore, as part of operation (5), in parallel with the transport of the paper 200 and the feeding of the ribbon 16, the control unit 40 controls the thermal head 12 to generate heat corresponding to the image signal Sc that corresponds to the development of cyan color in the input image information S, thereby superimposing the cyan image Pc onto the yellow image Py and magenta image Pm of the paper 200.

[0055] Similarly, when repeating operations (2) to (5) on a sheet of paper 200 after printing a cyan image Pc superimposed on a yellow image Py and a magenta image Pm, as operation (2), the control unit 40 rotates the take-up roller 15 in the forward direction so that the unused OC region 16o of the ribbon 16 is positioned in front of the thermal head 12. When the ribbon sensor 70 detects the boundary 17co between the unused OC region 16o and the preceding used C region 16c, the control unit 40 rewinds the ribbon 16 by a predetermined length and then stops the rotation of the take-up roller 15, completing the positioning of the OC region 16o of the ribbon 16.

[0056] Furthermore, as part of operation (5), in parallel with the transport of the paper 200 and the feeding of the ribbon 16, the control unit 40 controls the thermal head 12 to generate heat corresponding to the input overcoat, thereby superimposing the overcoat onto the yellow image Py, the magenta image Pm, and the cyan image Pc on the paper 200.

[0057] [Second action] Next, the second operation performed by the control unit 40 will be described. The second operation is a control operation performed in place of the first operation described above when the content of the CMY image information S input to the printer 100 satisfies specific conditions. The specific conditions for the content of the image information S under which the control unit 40 performs the second operation will be described later. When the content of the image information S satisfies specific conditions, if the printer 100 prints the image P on the paper 200 in the first operation, noticeable color unevenness may occur in a specific area of ​​the image P. Therefore, when the content of the input image information S satisfies specific conditions, the printer 100 switches the control of the control unit 40 to the second operation, which is different from the first operation, in order to avoid the occurrence of noticeable color unevenness.

[0058] The mechanism by which this print color unevenness occurs will be explained below. Figure 4 shows an example of image P printed on paper 200, which is an image of the upper body of a person wearing a white dress shirt.

[0059] In the first operation described above, the printer 100 completes the ribbon 16 leading operation before the paper 200 leading operation (see Figure 1B). Therefore, while the paper 200 is leading, as shown in Figures 1B and 3, the ribbon 16, which has completed leading, stops with an unused area facing the paper 200. In this state, the paper 200, which is sent to the standby unit 20 along the curved transport path 31, comes into contact with a specific position 16A in the unused area of ​​the ribbon 16 facing it. The paper 200 then continues to slide along that specific position 16A in the unused area of ​​the ribbon 16 until the paper 200 leading operation (operation (3)) is completed.

[0060] The sublimation dye at a specific position 16A of the ribbon 16 is affected by additives that bleed out onto the surface of the paper 200 due to sliding with the paper 200. This changes the characteristics (sensitivity) of the color intensity to heat, causing it to develop color differently from the sublimation dye in other parts of the ribbon 16. When printing (operation (5)) is performed using the ribbon 16 with the changed sensitivity at the specific position 16A, the image P printed on the paper 200 will exhibit color unevenness, as shown in Figure 4. This uneven coloring occurs in a specific part of the printed paper 200 in the transport direction corresponding to the specific position 16A of the ribbon 16 (the part at a distance L1 from the leading edge 202 in the transport direction of the paper 200 during the printing operation), resulting in a different density of color development compared to other parts of the paper 200 in the transport direction.

[0061] The changes in sensitivity of the sublimation dyes described above occur in each color region of the ribbon 16 (Y region 16y, M region 16m, C region 16c). Furthermore, this color unevenness is noticeable to human vision in light gray and yellow, light tonal ranges (ranges with small signal values ​​for image information S), and conversely, it is hardly noticeable in dark, dense tonal ranges (ranges with large signal values ​​for image information S).

[0062] Therefore, the printer 100's control unit 40 determines, based on the input image information S, whether the image signals Sy, Sm, and Sc of each color corresponding to a specific position 16A on the ribbon 16 are within a specific grayscale range. If it determines that the image signals Sy, Sm, and Sc of each color corresponding to a specific position 16A are within a specific grayscale range, then a specific condition is met, and the control unit 40 performs control to switch from the first operation to the second operation.

[0063] Figures 5A and 5B are schematic diagrams illustrating the operation in which, prior to the leading edge of the ribbon 16 in (2) of the first operation, the ribbon 16 is rewound onto the feed roller 14, thereby positioning the used portion of the ribbon 16 in front of the thermal head 12.

[0064] Specifically, the second operation involves the control unit 40, before the ribbon 16 is extended in the first operation, starting the operation (2') to rewind the ribbon 16 onto the feed roller 14, as shown in Figure 5A, to position the used portion of the ribbon 16 in front of the thermal head 12. Once the used portion of the ribbon 16 is positioned in front of the thermal head 12, the control unit 40 stops rewinding the ribbon 16 (see Figure 5B).

[0065] Ideally, the paper 200 should be transported in the same direction as the ribbon 16 (towards the standby unit 20) in synchronization with the rewinding of the ribbon 16. By transporting the paper 200 in synchronization with the rewinding of the ribbon 16, the ribbon 16 can be rewound stably without being affected by static electricity or frictional loads between the ribbon 16 and the paper 200. The control unit 40 continues to transport the paper 200 to complete the leading-out of the paper 200, and then controls the leading-out of the ribbon 16.

[0066] As a result, when the paper 200 being transported to the standby unit 20 passes in front of the thermal head 12, the used area of ​​the ribbon 16 is positioned in front of the thermal head 12. Therefore, the printer 100 can prevent the transported paper 200 from coming into contact with the unused area of ​​the ribbon 16, and prevent the sensitivity of the unused area of ​​the ribbon 16 from changing.

[0067] Then, after the ribbon 16 and the paper 200 have been led out, the control unit 40 controls the system to (4) position the thermal head 12 and ink ribbon 13 at the print position and to perform the print operation (5).

[0068] In this way, the printer 100 can prevent the sensitivity of the sublimation dye at a specific position 16A in the unused area of ​​the ribbon 16 from changing by controlling the process to avoid the paper 200 sliding into the unused area of ​​the ribbon 16 when the paper 200 is first fed out. As a result, the printer 100 can prevent the occurrence of color unevenness that is noticeable to the human eye in the image P printed on the paper 200.

[0069] [Specific conditions regarding the content of image information S] The following describes in detail the specific conditions regarding the content of the image information S under which the control unit 40 performs the second operation.

[0070] Image information S is composed of, for example, 2448 pixels in the horizontal direction (main scanning direction x; corresponding to the width direction W in Figure 4) and 3036 lines in the vertical direction (sub-scanning direction y; corresponding to the length direction L in Figure 4). Therefore, the image signal Sy corresponding to the yellow image Py is composed of the signal value Sy(x,y) of each pixel with a total of 2448 × 3036 pixels, the image signal Sm corresponding to the magenta image Pm is composed of the signal value Sm(x,y) of each pixel with a total of 2448 × 3036 pixels, and the image signal Sc corresponding to the cyan image Pc is composed of the signal value Sc(x,y) of each pixel with a total of 2448 × 3036 pixels.

[0071] First, as shown in Figure 3, the specific position 16A that the paper 200 contacts on the ribbon 16, which has been fully deployed in the printing unit 10, differs depending on the number of layers already printed in the printing unit 10. Specifically, when paper 200 that has not been printed at all (number of printed layers is 0) is sent to the standby unit 20, that is, when the unused Y region 16y of the ribbon 16 is positioned in front of the thermal head 12, the inventors have confirmed that the specific position 16A is the portion of the ribbon 16 corresponding to the position (y=250) of the L1=250 line in the transport direction (sub-scanning direction y by the thermal head 12) of the yellow image Py in the Y region 16y.

[0072] In contrast, when a sheet of paper 200 with only the yellow image Py printed on it (1 printed layer) is sent to the standby unit 20, that is, when the unused M region 16m of the ribbon 16 is positioned in front of the thermal head 12, the inventors have confirmed that the portion of the ribbon 16 in the M region 16m corresponding to the position (y=300) of the L1=300 line in the transport direction (sub-scanning direction y by the thermal head 12) of the magenta image Pm is a specific position 16A.

[0073] Furthermore, the inventors have confirmed that when a sheet of paper 200 with a yellow image Py and a magenta image Pm printed on it (2 printed layers) is sent to the standby unit 20, that is, when the unused C region 16c of the ribbon 16 is positioned in front of the thermal head 12, the portion of the ribbon 16 in the C region 16c corresponding to the position (y=300) of the L1=300 line in the transport direction (sub-scanning direction y by the thermal head 12) of the cyan image Pc is a specific position 16A.

[0074] It is presumed that the reason why a specific position 16A on the ribbon 16 changes depending on the number of printed layers is because the position where the paper 200 makes strong contact with the unused area of ​​the ribbon 16 changes depending on the number of printed layers, but this has not been clearly explained.

[0075] Furthermore, the inventors have confirmed that when the signal values ​​(yellow image signals Sy) for 40% or more of the total number of pixels on the L1=250 line of the yellow image Py in the image information S input to the printer 100 are between 15 and 55 (in the case of 8-bit signal values ​​(0 to 255)), color unevenness due to fluctuations in the intensity of yellow color becomes noticeable on the L1=250 line of the yellow image Py.

[0076] Furthermore, if the signal values ​​(magenta image signal Sm) of 40% or more of the total number of pixels on the L1=300 line of the magenta image Pm in the image information S input to the printer 100 are between 15 and 55 (in the case of 8-bit signal values ​​(0 to 255)), then color unevenness due to fluctuations in the intensity of magenta color development will be noticeable on the L1=300 line of the magenta image Pm. Confirmed by the inventors of this invention.

[0077] Furthermore, the inventors have confirmed that when the signal values ​​(cyan image signals Sc) of 40% or more of the total number of pixels on the L1=300 line of the cyan image Pc in the image information S input to the printer 100 are between 15 and 55 (in the case of 8-bit signal values ​​(0 to 255)), color unevenness due to fluctuations in the intensity of cyan color development becomes noticeable on the L1=300 line of the cyan image Pc.

[0078] Based on the inventor's analysis described above, the printer 100 controls the transport operation of the transport means 32 and the feeding operation of the ink ribbon 13 before printing each color, by switching between the first operation and the second operation in response to specific conditions defined in (A), (B), or (C) below, and then printing each color.

[0079] Figure 6A is a flowchart showing the process flow for determining whether the content of image information S meets a specific condition when the control unit 40 prints a yellow image Py and switches between the first and second operations. Figure 6B is a flowchart showing the process flow for determining whether the content of image information S meets a specific condition when the control unit 40 prints a magenta image Pm and switches between the first and second operations. Figure 6C is a flowchart showing the process flow for determining whether the content of image information S meets a specific condition when the control unit 40 prints a cyan image Pc and switches between the first and second operations.

[0080] (A) The control unit 40 determines whether a specific condition is met for color unevenness to occur on the L1=250 line in image P (an image in which the yellow image Py, the magenta image Pm, and the cyan image Pc are superimposed) based on the change in sensitivity of the Y region 16y in the ribbon 16, and controls the operation before printing the yellow image Py to switch between the first operation and the second operation.

[0081] Specifically, as shown in Figure 6A, the control unit 40 first sets the initial values ​​to x=1 and the number of pixels that satisfy the condition Ny=0 among the 250 lines of the yellow image signal Sy (S11). Next, the control unit 40 determines whether the signal value Sy(x,250) of each pixel (x,250) on the 250 line (y=250) in the sub-scanning direction y of the yellow image Py satisfies the condition of being 15 or more and 55 or less (S12), whether the signal value Sm(x,250) of each pixel (x,250) on the 250 line (y=250) in the sub-scanning direction of the magenta image Pm satisfies the condition of being 15 or more and 55 or less (S13), and whether the signal value Sc(x,250) of each pixel (x,250) on the 250 line (y=250) in the sub-scanning direction y of the cyan image Pc satisfies the condition of being 15 or more and 55 or less (S14).

[0082] Then, if all of the conditions in S12 to S14 are met (if all of S12 to S14 are YES), the control unit 40 increments the number of pixels that meet the conditions Ny by 1 (S15). If even one of S12 to S14 is not met (if even one of S12 to S14 is NO), the control unit 40 does not increment the number of pixels that meet the conditions Ny, but instead sequentially replaces the pixels in the main scanning direction x with the adjacent pixels (S16), and repeats the same process (S12 to S16) until the last pixel in the main scanning direction (x=2448) (S17).

[0083] The control unit 40 determines whether the number of pixels Ny that satisfy the condition among all pixels (2448 pixels) on the 250 lines in the sub-scanning direction y (main scanning direction x) is 40% or more (980 or more) (S18). If it determines that it is 40% or more (YES in S18), the control unit 40 switches the operation before printing the yellow image Py to the second operation (S19). If it determines that the number of pixels is less than 40% (less than 980) (NO in S18), the control unit 40 switches the operation before printing the yellow image Py to the first operation (S20).

[0084] (B) The control unit 40 determines whether a specific condition is met for color unevenness to occur on the L1=300 line in image P (an image in which the yellow image Py, the magenta image Pm, and the cyan image Pc are superimposed) based on the change in sensitivity of the M region 16m in the ribbon 16, and controls the operation before printing the magenta image Pm to switch between the first operation and the second operation.

[0085] Specifically, as shown in Figure 6B, the control unit 40 first sets the initial values ​​to x=1 and the number of pixels that satisfy the condition among the 300 lines of the magenta image signal Sm, Nm=0 (S21). Next, the control unit 40 determines whether the signal value Sm(x,300) of each pixel (x,300) on the 300 lines (y=300) in the sub-scanning direction y of the magenta image Pm is 15 or more and 55 or less (S22), and whether the signal value Sc(x,300) of each pixel (x,300) on the 300 lines (y=300) in the sub-scanning direction of the cyan image Pc is 64 or less (S23).

[0086] Then, if all of the conditions in S22 and S23 are met (if all of S22 and S23 are YES), the control unit 40 increments the number of pixels Nm that satisfy the conditions by 1 (S24). If even one of S22 or S23 is not met (if even one of S22 or S23 is NO), the control unit 40 does not increment the number of pixels Nm that satisfy the conditions, but instead sequentially replaces the pixels in the main scanning direction x with the adjacent pixels (S25), and repeats the same process (S22 to S25) until the last pixel in the main scanning direction (x=2448) (S26).

[0087] The control unit 40 determines whether the number of pixels Nm that satisfy the condition among all pixels (2448 pixels) on the 300 lines in the sub-scanning direction y (main scanning direction x) is 40% or more (980 or more) (S27). If it determines that it is 40% or more (YES in S27), the control unit 40 switches the pre-print operation of the magenta image Pm to the second operation (S28). If it determines that the number of pixels is less than 40% (less than 980) (NO in S27), the control unit 40 switches the pre-print operation of the magenta image Pm to the first operation (S29).

[0088] (C) The control unit 40 determines whether a specific condition is met for color unevenness to occur on the L1=300 line in image P (an image in which the yellow image Py, the magenta image Pm, and the cyan image Pc are superimposed) based on the change in sensitivity of the C region 16c in the ribbon 16, and controls the operation before printing the cyan image Pc to switch between the first operation and the second operation.

[0089] Specifically, as shown in Figure 6C, the control unit 40 first sets the initial values ​​as x=1 and the number of pixels that satisfy the condition among the pixels on the 300 line of the cyan image signal Sc, Nc=0 (S31). Next, the control unit 40 determines whether the signal value Sm(x,300) of each pixel (x,300) on the 300 line (y=300) in the sub-scanning direction y of the magenta image Pm is 127 or less (S32), and whether the signal value Sc(x,300) of each pixel (x,300) on the 300 line (y=300) in the sub-scanning direction of the cyan image Pc is 15 or more and 55 or less (S33).

[0090] Then, if all of the conditions in S32 and S33 are met (if all of S32 and S33 are YES), the control unit 40 increments the number of pixels Nc that satisfy the conditions by 1 (S34). If even one of S32 or S33 is not met (if even one of S32 or S33 is NO), the control unit 40 does not increment the number of pixels Nc that satisfy the conditions, but instead sequentially replaces the pixels in the main scanning direction x with the adjacent pixels (S35), and repeats the same process (S32 to S35) until the last pixel in the main scanning direction (x=2448) (S36).

[0091] The control unit 40 determines whether the number of pixels Nc that satisfy the condition among all pixels (2448 pixels) on the 300 lines in the sub-scanning direction y (main scanning direction x) is 40% or more (980 or more) (S37). If it determines that it is 40% or more (YES in S37), the control unit 40 switches the pre-print operation of the cyan image Pc to the second operation (S38). If it determines that the number of pixels is less than 40% (less than 980) (NO in S37), the control unit 40 switches the pre-print operation of the cyan image Pc to the first operation (S39).

[0092] Furthermore, as the rewinding operation of the ribbon 16 in operation (2') of the second operation, the control unit 40 preferably sets the length to which the ribbon 16 is rewound to a dimension that exceeds the length L1 in the transport direction (sub-scanning direction y) in the image P.

[0093] As described above, in this embodiment, the printer 100 can prevent color unevenness from occurring in the image P printed on the paper 200 by the control unit 40 switching the paper transport operation by the transport means 32 and the ribbon feeding operation of the print unit 10 to a second operation (color unevenness reduction operation) according to the content of the input image information S.

[0094] On the other hand, in the printer 100 of this embodiment, even if color unevenness occurs, if it occurs only in less than 40% of the total number of pixels in the main scanning direction x, as described above, the color unevenness is not noticeable to the human eye, and therefore there is little need to perform the second operation to reduce color unevenness. Therefore, in the printer 100 of this embodiment, even if color unevenness occurs, if it is not noticeable to the human eye, the first operation can be performed without performing the second operation, thereby reducing the time required before printing compared to the second operation.

[0095] In this embodiment, the printer 100's control unit 40 indicates that the number of pixels Ny, Nm, Nc satisfying the conditions is 40% or more of the total number of pixels in the main scanning direction x, as specified in (A), (B), or (C). However, instead of 40%, the number of pixels Ny, Nm, Nc satisfying the conditions may be 35% or more of the total number of pixels in the main scanning direction x, or 30% or more of the total number of pixels in the main scanning direction x. The specific value of this % representing the ratio to the total number of pixels will change depending on the characteristics of the media used (ribbon 16 and paper 200), so it is desirable to adjust it according to the media used.

[0096] [Control to prevent or suppress the effects of static electricity] In this embodiment, the printer 100 performs ribbon leading in step (2) of the first operation. More specifically, this leading operation is performed by the control unit 40 rotating the take-up roller 15 in the forward direction so that the unused Y region 16y of the ribbon 16 is positioned in front of the thermal head 12. When the ribbon sensor 70 detects the boundary 17oy (see Figure 2) between the unused Y region 16y and the used OC region 16o that precedes the unused Y region 16y, the control unit 40 stops the rotation of the take-up roller 15 (see Figure 1B) and rotates the feed roller 14 and the take-up roller 15 by a certain amount in the reverse direction.

[0097] The reason for rotating the feed roller 14 and the take-up roller 15 in the reverse direction by a certain amount is, as mentioned above, to rewind the leading edge of the unused Y region 16y to the front of the thermal head 12, thereby making effective use of the Y region 16y. The printer 100, through the above control by the control unit 40, also makes effective use of the other unused M region 16m, C region 16c, and OC region 16o, similar to the Y region 16y.

[0098] When the ribbon sensor 70 detects the boundary 17oy between the Y region 16y and the OC region 16o, the control unit 40 calculates the amount of rewind needed to bring the Y region 16y to the front of the thermal head 12 by rewinding the leading edge of the Y region 16y to the front of the thermal head 12, and also calculates the amount of feed needed to position (bring to the front) the leading edge of the subsequent M region 16m to the front of the thermal head 12.

[0099] Then, during the period when yellow printing is being performed using the Y region, the control unit 40, based on the calculated feed amount, moves the thermal head 12 and ink ribbon 13 to a retracted position away from the platen roller 11 after the yellow printing is finished, so that the leading edge of the M region for magenta printing is positioned in front of the thermal head 12 from the position where the boundary 17oy between the Y region 16y and the OC region 16o passes in front of the ribbon sensor 70 again and the ribbon sensor 70 detects the boundary 17oy, and then feeds the ribbon 16 in the forward direction, thereby completing the leading edge of the M region 16m and eliminating the need to rewind the ribbon 16.

[0100] Furthermore, the lengths of the Y region 16y, the M region 16m, the C region 16c, and the OC region 16o are known, the length from the position where the ribbon sensor 70 detects the boundary 17oy to the front of the thermal head 12 is also known, and the feed amount of the ribbon 16 corresponding to the counter value of the rotation amount of the winding roller 15 (such as the count value of an encoder provided coaxially with the winding roller 15) is also known. Since these lengths and feed amounts are stored in the control unit 40 beforehand, the control unit 40 can calculate the position of the tip of the M region 16m from the position where the ribbon sensor 70 detects the boundary 17oy between the Y region 16y and the OC region 16o based on this stored data. The calculation of the tip of the C region 16c and the tip of the OC region 16o, which will be described below, is done in the same way.

[0101] Similarly to this control, during the period when magenta printing is in progress, when the ribbon sensor 70 detects the boundary 17ym between the M region 16m and the Y region 16y, the control unit 40 also calculates the feed amount to position the leading edge of the subsequent C region 16c in front of the thermal head 12. Based on the calculated feed amount to position the leading edge of the C region for cyan printing in front of the thermal head 12 from the position where the boundary 17ym is detected by the ribbon sensor 70, after the magenta printing is completed, the thermal head 12 and ink ribbon 13 are moved to a retracted position away from the platen roller 11, and the ribbon 16 is fed in the forward direction, thereby completing the leading edge of the C region 16c and eliminating the need to rewind the ribbon 16.

[0102] Similarly to this control, during the period when cyan printing is in progress, when the ribbon sensor 70 detects the boundary 17mc between the C region 16c and the M region 16m, the control unit 40 also calculates the feed amount to position the leading edge of the subsequent OC region 16o in front of the thermal head 12. Based on the calculated feed amount to position the leading edge of the OC region 16o for overcoat printing in front of the thermal head 12 from the position where the boundary 17mc was detected by the ribbon sensor 70, after the cyan printing is completed, the thermal head 12 and ink ribbon 13 are moved to a retracted position away from the platen roller 11, and the ribbon 16 is fed in the forward direction, thereby completing the leading edge of the OC region 16o and eliminating the need to rewind the ribbon 16.

[0103] Incidentally, while this is not a problem in the rewinding operation of the ribbon 16 for leading out the Y region 16y in the first operation described above, static electricity generated between the ribbon 16 and the paper 200 can be a problem in the rewinding operation of the ribbon 16 for leading out the Y region 16y in the second operation.

[0104] In other words, in the second operation, with the paper 200 placed in the standby unit 20, the used OC area 16o is positioned in front of the thermal head. From this state, in order to bring out the Y area 16y of the ribbon 16, the control unit 40 rotates the take-up roller 15 in the forward direction so that the ribbon 16 is fed in the forward direction, and after the ribbon sensor 70 detects the boundary 17oy, the control unit 40 rotates the feed roller 14 and the take-up roller 15 in the reverse direction to rewind the ribbon 16 by a certain amount to bring out the Y area 16y.

[0105] However, in the second operation, when the ribbon 16 is being fed in the forward direction, it is fed in close proximity to the paper 200 located in the standby unit 20, so static electricity is generated between the paper 200 and the ribbon 16, and an electric charge accumulates on the ribbon 16. Therefore, when the ribbon sensor 70 detects the boundary 17oy and the control unit 40 rotates the feed roller 14 and the take-up roller 15 in the reverse direction to rewind the ribbon 16, the ribbon 16 may be attracted to the paper 200 or the like due to the accumulated electric charge.

[0106] As mentioned above, the feed roller 14 has a torque limiter, so when the ribbon 16 is attracted to the surrounding rollers, the feed roller 14 may spin freely due to the torque limiter's effect, preventing it from rewinding the ribbon 16. On the other hand, when the ribbon 16 is rewound, the take-up roller 15 also rotates in the reverse direction, so the used ribbon 16 that was wound on the take-up roller 15 is unwound. As a result, the ribbon 16 becomes irregularly loose between the feed roller 14 and the take-up roller 15, making it impossible to bring out the end of the ribbon 16.

[0107] Figure 7 is a schematic diagram showing a state in which, when the paper 200 is being led out, the paper 200 is not fully transported to the standby unit 20, but is stopped by a length L4 before it.

[0108] In this embodiment, the printer 100, during the second operation in which the lead-out operation of the paper 200 is performed in parallel with the rewinding of the ribbon 16, controls the drive roller 33 so that the paper 200 is not transported completely to the predetermined position of the standby unit 20, but is stopped by a length L4 before the predetermined position, as shown in Figure 7.

[0109] The printer 100 stops the paper 200 in front of a predetermined position in the standby unit 20 and then brings out the Y region 16y of the ribbon 16. When the feed roller 14 and take-up roller 15 are rotated in the reverse direction to rewind the ribbon 16, the control unit 40 feeds the ribbon 16 in the reverse direction and simultaneously transports the paper 200 to the predetermined position in the standby unit 20.

[0110] Due to the effect of static electricity between the ribbon 16 and the paper 200, the ribbon 16 is attracted to the paper 200 as it is being transported in the reverse direction. This makes it easier for the ribbon 16 to move in the reverse direction as well, allowing it to be wound onto the feed roller 14 and enabling the ribbon 16 to be properly brought out.

[0111] In this way, the printer 100 of this embodiment can eliminate or reduce the effects of static electricity generated on the ribbon 16 by performing the second operation, stopping the paper 200 from being completely transported to the standby unit 20 even when static electricity is generated on the ribbon 16, and simultaneously sending the paper 200 to the standby unit 20 when the ribbon 16 is rewound. [Explanation of Symbols]

[0112] 10 Printing Department 12 Thermal Heads 13 Ink Ribbon 20 Waiting section 30 Conveying section 40 Control Unit 50 Supply section 100 Dye-sublimation thermal printers (printers) 200 sheets

Claims

1. A printing unit having a thermal head and an ink ribbon, A waiting section is provided on the upstream side in the transport direction relative to the printing section, A supply unit provided downstream of the printing unit in the transport direction, A transport unit that transports paper between the supply unit and the standby unit, The system includes a control unit that controls the transport unit and the printing unit based on image information input corresponding to the image to be printed on the aforementioned paper, A printer wherein the control unit switches to a second operation when the image information satisfies certain conditions, in which it places the used area of ​​the ink ribbon in front of the thermal head when transporting the paper from the supply unit to the standby unit, and switches to a first operation when the image information does not satisfy certain conditions, in which it places the unused area of ​​the ink ribbon in front of the thermal head when transporting the paper from the supply unit to the standby unit.

2. The printer according to claim 1, wherein the control unit, when transporting the paper from the supply unit to the standby unit, determines that the specific condition is met and switches to the second operation when the image information on the line corresponding to a specific position where the paper contacts the ink ribbon positioned in front of the thermal head is a signal value corresponding to a specific bright color.

3. The printer according to claim 2, wherein the control unit switches to the second operation when the image information of 40% or more of the total number of pixels on the line is a signal value corresponding to a specific bright color, thus satisfying the specific condition.

4. The printer according to any one of claims 1 to 3, wherein the control unit, in the second operation, stops the paper before a predetermined position in the standby unit when transporting the paper from the supply unit to the standby unit, and after stopping the paper, transports the paper to the predetermined position in the standby unit when rewinding the used area of ​​the ink ribbon, which is positioned in front of the thermal head, back into the unused area of ​​the ink ribbon.

Images