thermal printer

Abstract

To properly transport thermal paper.SOLUTION: A thermal printer 1 comprises: a thermal head 20 which has a heater element 22, and performs printing to a printed part of thermal paper S; a platen roller 30 which holds the thermal paper S between itself and the thermal head 20, for transporting the thermal paper S; and a control part 54 for controlling operations of the platen roller 30 and the thermal head 20. The control part 54 preheats the thermal head 20 by supplying a first energization amount as an energization pulse to the heater element 22, then transports the thermal paper S in one direction in the transport path, in first transport, then performs return transport so as to transport the thermal paper S to a reverse direction of the one direction so as to return the printed part of the thermal paper S to a printing position, then supplies a second energization amount which is a greater energization pulse greater than the first energization amount to the heater element 22, for mainly heating the heater element 22 for performing printing on the thermal paper S.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal printer and a printing method. [Background technology]

[0002] Thermal printers are used to print on thermal paper. Thermal printers have a thermal head that prints on the thermal paper by generating heat from a heating element, and a platen roller that transports the thermal paper and holds it between the thermal head and the thermal head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-151010 Summary of the Invention [Problem to be solved by the invention]

[0004] In the thermal printer, the thermal paper remains sandwiched between the thermal head and the platen roller even after printing is completed. Therefore, if the thermal paper is left after the previous printing, it may stick to the thermal head, preventing it from being transported properly the next time it is printed.

[0005] The present invention has been made in consideration of these points, and has as its object to properly transport thermal paper. [Means for solving the problem]

[0006] In a first aspect of the present invention, there is provided a thermal printer comprising: a thermal head having heating elements that generate heat when energized and that print on a printable portion located at a printing position on thermal paper; a platen roller that sandwiches the thermal paper between itself and the thermal head and transports the thermal paper; and a control unit that controls the operation of the platen roller and the thermal head, wherein the control unit controls the following: supplying a first current amount as an energization pulse to the heating elements to preheat the thermal head; performing a first transport to transport the thermal paper, which is sandwiched between the platen roller and the thermal head and has the printable portion located at the printing position, in one direction on a transport path; performing a return transport to transport the thermal paper in the opposite direction to the one direction so as to return the printable portion of the thermal paper to the printing position; and supplying a second current amount as an energization pulse greater than the first current amount to the heating elements to perform main heating of the thermal head and cause printing to be performed on the thermal paper.

[0007] Furthermore, the control unit may, in the first transport, rotate the platen roller in the forward direction while preheating the thermal head, to transport the thermal paper downstream in the transport direction so that the printable portion is located downstream of the printing position in the transport direction, and, in the return transport, rotate the platen roller in the reverse direction to perform a second transport in which the thermal paper is transported upstream in the transport direction so that the printable portion is located upstream of the printing position in the transport direction, and then rotate the platen roller in the forward direction to perform a third transport in which the thermal paper is transported downstream in the transport direction so that the printable portion returns to the printing position.

[0008] In addition, the control unit may, during the first transport, reverse the rotation of the platen roller while preheating the thermal head, thereby transporting the thermal paper upstream in the transport direction so that the printed portion is located upstream of the printing position in the transport direction, and during the return transport, rotate the platen roller forward, thereby transporting the thermal paper downstream in the transport direction so that the printed portion returns to the printing position.

[0009] The device may further include a motor that transmits power to the platen roller via a gear, and the control unit may transport the thermal paper in the second transport by a second transport amount that is greater than the first transport amount of the thermal paper in the first transport, plus a transport amount equivalent to backlash in the meshing of the gears caused by reverse rotation of the motor.

[0010] In addition, the control unit may transport the thermal paper by an amount equal to a third transport amount obtained by subtracting the first transport amount from the second transport amount, plus a transport amount equivalent to backlash in the gear meshing caused by reverse rotation of the motor, during the third transport.

[0011] The control unit may also be configured to start the first transport when a predetermined time has elapsed since starting preheating of the heating element, and to continue the preheating at least until the first transport is completed.

[0012] In addition, the thermal head may print by causing the colorant in the thermal paper to color using the heated heating elements, and the control unit may preheat the thermal head by supplying the first amount of current to the heating elements, which does not cause the colorant to color.

[0013] The control unit may supply the energizing pulse having a predetermined pulse width to the heating element at each pulse interval, and the pulse width may be smaller than the pulse interval.

[0014] In a second aspect of the present invention, there is provided a printing method for printing on a printable portion of thermal paper sandwiched between a thermal head and a platen roller, the printing method comprising the steps of: supplying a first current amount as a current pulse to a heating element of the thermal head to preheat the thermal head; performing a first transport step of transporting the thermal paper sandwiched between the platen roller and the thermal head, with the printable portion located at the printing position, in one direction on a transport path while preheating the thermal head; performing a return transport step of transporting the thermal paper in the opposite direction to the one direction so as to return the printable portion of the thermal paper to the printing position; and supplying a second current amount as a current pulse greater than the first current amount to the heating element to perform main heating of the thermal head and cause printing to be performed on the thermal paper. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an effect that the thermal paper can be transported appropriately. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of a thermal printer 1 according to an embodiment. [Figure 2] 2 is a schematic diagram for explaining the relationship between the thermal head 20, the platen roller 30, and the thermal paper S. FIG. [Figure 3] 5A and 5B are schematic diagrams for explaining the energized state of the heating element 22 and the rotating state of the platen roller 30 during the preliminary treatment. [Figure 4] 10 is a schematic diagram for explaining the supply of an energizing pulse P to a heating element 22. FIG. [Figure 5] 10 is a schematic diagram for explaining the conveyance state of the thermal paper S during the preliminary treatment. FIG. [Figure 6] 5A and 5B are schematic diagrams for explaining the energized state of the heating element 22 and the rotating state of the platen roller 30 during the preliminary treatment. [Figure 7] 10 is a schematic diagram for explaining the conveyance state of the thermal paper S during the preliminary treatment. FIG. [Figure 8] 10 is a flowchart for explaining a first operation example when the thermal printer 1 starts printing. [Figure 9] 10 is a flowchart illustrating a second example of operation of the thermal printer 1 at the start of printing. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Thermal printer configuration> The configuration of a thermal printer according to one embodiment will be described with reference to FIGS.

[0018] Fig. 1 is a schematic diagram illustrating an example of the configuration of a thermal printer 1 according to one embodiment. Fig. 2 is a schematic diagram illustrating the relationship between a thermal head 20, a platen roller 30, and thermal paper S.

[0019] The thermal printer 1 is a printing device that prints on thermal paper S. A color former that changes color when heated is applied to the surface of the thermal paper S, and the thermal printer 1 prints on the thermal paper S by causing the color former to change color when heated. As shown in FIGS. 1 and 2, the thermal printer 1 has a transport unit 10, a thermal head 20, a platen roller 30, and a control device 50.

[0020] The transport unit 10 transports the thermal paper S. The transport unit 10 has a transport path 12 (Fig. 2) along which the thermal paper S is transported, and a motor 14 (Fig. 1) that drives rollers and the like that transport the thermal paper S. The transport path 12 has a guide member 12a that guides the transport of the thermal paper S. The motor 14 transmits power to the platen roller 30 via a gear. The thermal paper S here is roll paper. The thermal paper S is also thick paper, and for example, the thickness of the thermal paper S is 180 μm or more.

[0021] The thermal head 20 is a device that prints on thermal paper S. As shown in FIG. 2, the thermal head 20 has multiple heating elements 22 that generate heat when energized. The current is supplied in pulses. For example, the pulse width is 150 to 250 μm. The multiple heating elements 22 are, for example, heating resistors, and are arranged at predetermined intervals on a flat substrate. Specifically, the heating elements 22 are arranged at predetermined intervals in a direction perpendicular to the transport direction of the thermal paper S (in other words, in the axial direction of the platen roller 30).

[0022] The thermal head 20 is in contact with the surface of the thermal paper S (the surface coated with the color former). The thermal head 20 performs printing by causing the color former of the thermal paper S to develop color using the heated heating elements 22. The thermal head 20 selectively heats the heating elements 22 from among the multiple heating elements 22 arranged in a row, thereby printing at the desired position on the thermal paper S.

[0023] The platen roller 30 is a platen provided at a position facing the thermal head 20 on the transport path. As shown in Fig. 2, the platen roller 30 holds the thermal paper S between itself and the thermal head 20 with a predetermined pressure. Therefore, the thermal head 20 prints on the thermal paper S held between itself and the platen roller 30.

[0024] The platen roller 30 also functions as a transport roller that transports the thermal paper S. That is, the platen roller 30 feeds the thermal paper S by rotating. Here, the platen roller 30 is driven by a motor 14 (e.g., a stepping motor) shown in FIG. 1 via a predetermined gear ratio. The platen roller 30 transports the printed thermal paper S downstream in the transport direction by rotating forward in the C1 direction shown in FIG. 2. The platen roller 30 can also transport the thermal paper S upstream in the transport direction by rotating backward in the C2 direction shown in FIG. 2.

[0025] Although not shown, a cutting unit that cuts the thermal paper S is provided downstream of the thermal head 20 in the conveying path 12. The cutting unit has, for example, a fixed blade and a movable blade, and cuts the thermal paper S by moving the movable blade back and forth relative to the fixed blade, for example, in a direction perpendicular to the thermal paper S.

[0026] The control device 50 controls the operation of the thermal printer 1 that prints on the thermal paper S. As shown in FIG.

[0027] The storage unit 52 includes, for example, a read-only memory (ROM) and a random access memory (RAM). The storage unit 52 stores programs to be executed by the control unit 54 and various control data. For example, the storage unit 52 stores the time elapsed since the previous printing. The elapsed time is measured, for example, by a timer or the like.

[0028] The control unit 54 is, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 54 controls the operation of the platen roller 30 and the thermal head 20 via the motor 14. For example, the control unit 54 performs a transport process that controls the transport distance or transport time of the thermal paper S by the platen roller 30, and a heating process that supplies power, energization pulses, etc. to the heating elements 22 of the thermal head 20, thereby printing on the thermal paper S.

[0029] In the thermal printer 1, even after printing by the thermal head 20 is completed, the thermal paper S remains sandwiched between the thermal head 20 and the platen roller 30. For this reason, if the thermal paper S is left after the previous printing, the thermal paper S (specifically, the surface of the thermal paper S on which the color former is applied) may stick to (or be stuck to) the thermal head 20, which may prevent the platen roller 30 from properly transporting the thermal paper S during the next printing. For example, if the thermal printer 1 is placed in a high-temperature, high-humidity environment and left for a long period of time after printing, the thermal paper S is likely to stick to the thermal head 20. Also, if the thermal paper S is thick paper, the end of the thermal head 20 is likely to be pressed into the thermal paper S and stick to it if left for a long period of time after printing.

[0030] To solve the above problem, the control unit 54 of this embodiment performs a preliminary process, which will be described in detail later, before starting printing on the thermal paper S. The process involves energizing the heating elements 22 to preheat the thermal head 20, transporting the printable portion of the thermal paper S in one direction along the transport path by a predetermined distance, and then returning the printable portion of the thermal paper S to its original printing position. This allows the thermal paper S that has stuck to the thermal head 20 to be separated from the thermal head 20 before starting printing on the thermal paper S, allowing the thermal paper S to be transported smoothly thereafter. The preliminary process will be described in detail below with reference to FIGS. 3 to 5.

[0031] Fig. 3 is a schematic diagram illustrating the energized state of the heating elements 22 and the rotation state of the platen roller 30 during preparatory processing. Fig. 4 is a schematic diagram illustrating the supply of energizing pulses P to the heating elements 22. Fig. 5 is a schematic diagram illustrating the transport state of the thermal paper S during preparatory processing.

[0032] As a preliminary process, the control unit 54 first supplies a first amount of current to the heating elements 22 to begin preheating the thermal head 20. Here, the platen roller 30 is stopped, and the thermal paper S is not being conveyed. The control unit 54 supplies the heating elements 22 with a first amount of current that does not cause the color former to develop color, thereby preheating the thermal head 20. Specifically, the control unit 54 applies current to the heating elements 22 between times t1 and t4 shown in FIG. 3 to preheat the thermal head 20. By preheating the thermal head 20, the color former in the area where the thermal head 20 and the thermal paper S are attached melts. Note that the first amount of current is such that the color former does not develop color, so the thermal paper S does not develop color (print) due to the preheating.

[0033] The control unit 54 supplies a predetermined energization pulse to the heating elements 22 to preheat the thermal head 20. For example, the control unit 54 supplies an energization pulse P having a predetermined pulse width shown in FIG. 4 to the heating elements 22 at each pulse interval. Here, the pulse width (width L1 shown in FIG. 4) is smaller than the pulse interval (interval L2 shown in FIG. 4). That is, the energization pulses P are supplied with a large interval in between. For example, the pulse width L1 is equivalent to 34 μs, preferably 20 to 50 μs. The pulse interval L2 is equivalent to 6000 μs, preferably 1000 to 10000 μs. Furthermore, the control unit 54 supplies the energization pulse P approximately 69 times during preheating, preferably 50 to 150 times. This reduces the amount of current flow during preheating, thereby preventing the color former of the thermal paper S from developing color during preheating and allowing the thermal paper S to be peeled off from the thermal head 20.

[0034] During preheating, the control unit 54 preferably supplies energizing pulses to all of the heating elements 22 of the thermal head 20 .

[0035] The control unit 54 rotates the platen roller 30 to separate the thermal paper S from the thermal head 20, and transports the thermal paper S. That is, the control unit 54 performs a first transport, transporting the thermal paper S sandwiched between the platen roller 30 and the thermal head 20 in one direction along the transport path 12, while preheating the thermal head 20. Preheating the thermal head 20 melts the color former at the portion where the thermal head 20 and the thermal paper S are attached, so that the thermal paper S that was attached to the thermal head 20 is separated from the thermal head 20 by the first transport. It is preferable to transport the thermal paper S while preheating the thermal head 20 during the first transport. After being separated from the thermal head 20, the thermal paper S is transported a predetermined distance.

[0036] The control unit 54 starts the first transport when a predetermined time has elapsed since the start of preheating of the thermal head 20. For example, as shown in Figure 3, the control unit 54 starts preheating at time t1. When preheating continues and a predetermined time has elapsed from time t1 to time t2, the control unit 54 performs the first transport by rotating the platen roller 30 forward and moving it from the print start position, as shown in Figure 3. The period from time t2 to t4 is set to a time during which the color former of the thermal paper S is expected to be melted by preheating.

[0037] The control unit 54 continues preheating at least until the first transport of the thermal paper S is completed. Here, as shown in FIG. 3, the control unit 54 continues preheating of the thermal head 20 until time t4, a predetermined time after time t3, when the first transport of the thermal paper S is completed. However, this is not limited to the above, and the control unit 54 may end preheating when the first transport is completed. Because preheating continues until the first transport is completed, the thermal paper S is likely to be separated from the thermal head 20 when the first transport is completed.

[0038] The control unit 54 can set a predetermined time from the start of preheating of the thermal head 20 to the start of the first transport. Here, as shown in Fig. 3, the control unit 54 may set the predetermined time from the start of preheating of the thermal head 20 to the start of the first transport (the time between times t1 and t2) to be shorter than the time for performing the first transport (the time between times t2 and t3). This allows the heating elements 22 to be preheated in a short time, preventing the preparatory processing time from becoming too long.

[0039] The control unit 54 may also adjust the timing at which the first conveyance is started after preheating, depending on the length of time that has elapsed since the previous printing. Here, the control unit 54 adjusts the timing at which the first conveyance is started depending on the length of time that has elapsed since the previous printing. For example, the control unit 54 lengthens the preheating time before the start of the first conveyance the longer the time that has elapsed since the previous printing. The longer the time that has elapsed since the previous printing, the greater the likelihood that the thermal paper S will stick to the thermal head 20. Therefore, by lengthening the preheating time before the start of the first conveyance the longer the time that has elapsed since the previous printing, the melting of the color former is further promoted, and the thermal paper S that has stuck to the thermal head 20 can be easily separated.

[0040] The control unit 54 sets the rotation speed of the platen roller 30 during the first transport to be slower than the rotation speed of the platen roller 30 during transport of the printed thermal paper S. This allows the thermal paper S to be transported slowly during the first transport, making it easier to smoothly separate the thermal paper S from the thermal head 20.

[0041] (First Example) Next, a first embodiment of a series of operations for preheat control will be described. 5(a), the control unit 54 preheats the thermal head 20 while the platen roller 30 is stopped. The preheating time is, for example, 100 ms, and preferably 50 to 150 ms. Here, the printing portion S1 of the thermal paper S is located at the printing position.

[0042] As the first conveyance, the control unit 54 conveys the thermal paper S downstream in the conveyance direction on the conveyance path 12, as shown in FIG. 5(b). For example, the control unit 54 rotates the platen roller 30 forward in direction C1 to convey the printable portion S1 of the thermal paper S downstream in the conveyance direction from the printing position. The thermal paper S that has been adhering to the thermal head 20 is separated from the thermal head 20 by the first conveyance. The first conveyance distance L1 of the first conveyance that separates the thermal paper S from the thermal head 20 is, for example, 3 mm, and preferably about 1 to 10 mm.

[0043] The surface of the platen roller 30 is formed with unevenness, and when the platen roller 30 rotates forward, contact friction occurs between the unevenness on the surface of the platen roller 30 and the thermal paper S. In order for the platen roller 30 to properly perform its function of transporting the printed thermal paper S downstream in the transport direction, the contact friction that occurs when transporting the thermal paper S downstream in the transport direction is large. Therefore, when the thermal paper S is transported downstream in the transport direction as the first transport, the large contact friction makes it easier to separate the thermal paper S from the thermal head 20 more smoothly.

[0044] After the first transport, as shown in FIG. 5(c), the control unit 54 performs a second transport of the thermal paper S in the opposite direction so that the printing portion S1 of the thermal paper S is positioned upstream of the printing position in the transport direction. Here, as shown in FIG. 3, at time t5, a predetermined time after time t4 when preheating ends (the platen roller 30 is stopped between t4 and t5), the control unit 54 rotates the platen roller 30 in the opposite direction C2 to perform the second transport of the thermal paper S. The second transport amount L2 of the thermal paper S during the second transport is greater than the first transport amount L1 during the first transport. The second transport amount L2 is, for example, 7 mm, and preferably 2 to 11 mm.

[0045] When the motor 14 is rotated in the reverse direction during the second conveyance from the first conveyance, the control unit 54 conveys the thermal paper S by the second conveyance distance L2 plus a conveyance distance La corresponding to backlash in gear meshing caused by the reverse rotation of the motor 14. The conveyance distance La is added to adjust for gear backlash (gap or play) that occurs when the motor 14 is rotated in the reverse direction. The conveyance distance La is, for example, 0.25 mm, and preferably 0.08 to 0.42 mm. As a result, the printing portion S1 of the thermal paper S separated from the thermal head 20 is positioned upstream in the conveyance direction from the printing position before the start of the pre-processing.

[0046] Furthermore, the control unit 54 rotates the platen roller 30 in the opposite direction to that during the first transport to perform the second transport of the thermal paper S, but the rotational speed of the platen roller 30 during the second transport may be the same as the rotational speed of the platen roller 30 during the first transport, but is not limited to this, and the rotational speed of the platen roller 30 during the second transport may be faster than the rotational speed of the platen roller 30 during the first transport.

[0047] After the second transport, the control unit 54 transports the thermal paper S downstream in the transport direction so that the printable portion S1 of the thermal paper S returns to the printing position, as shown in FIG. 5(d). That is, the control unit 54 rotates the platen roller 30 forward in direction C1 to perform a third transport, transporting the thermal paper S downstream in the transport direction. This allows the printable portion S1 of the thermal paper S to return to the printing position. The third transport amount L3 of the thermal paper S during the third transport is the amount obtained by subtracting the first transport amount from the second transport amount, and is greater than the first transport amount L1 in this case. For example, the third transport amount L2 is 4 mm.

[0048] When moving from the second conveyance to the third conveyance, the motor 14 rotates in the reverse direction. During the third conveyance, the control unit 54 conveys the thermal paper S by the third conveyance distance L3 plus a conveyance distance Lb corresponding to backlash in gear meshing caused by the reverse rotation of the motor 14. The conveyance distance Lb is added to adjust for gear backlash (gap or play) that occurs when the motor 14 rotates in the reverse direction. The conveyance distance Lb is, for example, 0.17 mm, and preferably 0.08 mm to 0.42 mm. In the first embodiment, the second and third transfers correspond to return transfers after the first transfer.

[0049] When the third conveyance (in other words, the preliminary process) is completed, the control unit 54 performs printing on the thermal paper S. The control unit 54 supplies a second current amount, which is greater than the first current amount, to the heating elements 22 to cause the thermal head 20 to perform main heating, and causes printing to be performed on the thermal paper S that has been conveyed thirdly. In other words, by causing the thermal head 20 to perform main heating, the control unit 54 causes the color former of the thermal paper S to develop color, and the thermal paper S is printed.

[0050] The control unit 54 supplies different energization pulses to the heating elements 22 when the thermal head 20 is subjected to main heating than when the thermal head 20 is subjected to preheating. For example, the control unit 54 increases the amount of energization during main heating by shortening the pulse interval of the energization pulses during main heating compared to the pulse interval of the energization pulses during preheating. The control unit 54 may also increase the pulse width of the energization pulses during main heating to increase the amount of energization during main heating. It is also preferable to optimally set the interval and pulse width of the energization pulses. For example, the amount of energization is adjusted by changing the pulse width. The pulse width is 150 to 250 μs.

[0051] (Second Example) Next, a second embodiment of a series of operations for preheat control will be described. Fig. 6 is a schematic diagram illustrating the energized state of the heating elements 22 and the rotating state of the platen roller 30 during preparatory processing. Fig. 7 is a schematic diagram illustrating the transport state of the thermal paper S during preparatory processing. Figs. 6 and 7 correspond to Figs. 3 and 5 described above.

[0052] The control unit 54 starts preheating the thermal head 20 at time t1 in FIG. 6 while the platen roller 30 is stopped, and continues preheating until time t4 (FIG. 7(a)). The preheating time is, for example, 100 ms, and preferably 50 to 150 ms. Here, the printing portion S1 of the thermal paper S is located at the printing position.

[0053] Next, the control unit 54 rotates the platen roller 30 in the reverse direction C2 between times t2 and t3 while continuing the preheating, thereby performing a first transport of the printing portion S1 of the thermal paper S upstream in the transport direction (FIG. 7(b)). The thermal paper S that had been adhering to the thermal head 20 is separated from the thermal head 20 by the first transport. The first transport distance L4 of the first transport is, for example, 4 mm, and preferably about 2 to 11 mm.

[0054] Before the first transport, the thermal paper S is transported downstream in the transport direction, so the motor 14 rotates in reverse during the first transport. During the first transport, the control unit 54 transports the thermal paper S by the first transport distance L4 plus a transport distance Lc corresponding to backlash in gear meshing caused by the reverse rotation of the motor 14. The transport distance Lc is added to adjust for gear backlash (gap or play) that occurs when the motor 14 is rotated in reverse. The transport distance Lc is, for example, 0.25 mm, and preferably 0.08 to 0.42 mm.

[0055] Between times t5 and t6, the control unit 54 rotates the platen roller 30 in the forward direction, and performs a return transport downstream in the transport direction so as to return the printable portion S1 of the thermal paper S to the printing position (FIG. 7(c)). The return transport distance L5 of the return transport is the same as the first transport distance. The return transport distance L5 is, for example, 4 mm, and preferably about 2 to 11 mm.

[0056] When the motor 14 is returned from the first conveyance direction to the reverse conveyance direction, the motor 14 rotates in the reverse direction. During the reverse conveyance, the control unit 54 conveys the thermal paper S by the reverse conveyance distance L5 plus a conveyance distance Ld corresponding to backlash in the gear meshing caused by the reverse rotation of the motor 14. The conveyance distance Ld is added in order to adjust for gear backlash (gap or play) that occurs when the motor 14 is rotated in the reverse direction. The conveyance distance Ld is, for example, 0.25 mm, and preferably 0.08 to 0.42 mm. In the second embodiment as well, the thermal paper S that has stuck to the thermal head 20 can be separated before printing on the thermal paper S begins.

[0057] Furthermore, in the above description, the control unit 54 performs preparatory processing before starting printing on the thermal paper S, but the execution of preparatory processing may also be controlled depending on the time elapsed since the previous printing. For example, if the time elapsed since the previous printing exceeds a predetermined time, the control unit 54 performs preparatory processing (i.e., first and second conveyances while preheating the heating elements 22), and then causes printing to be performed on the thermal paper S. On the other hand, if the time elapsed since the previous printing does not exceed the predetermined time, the control unit 54 causes printing to be performed on the thermal paper S without performing preparatory processing. If the elapsed time does not exceed the predetermined time, it is assumed that the thermal paper S is not attached to the thermal head 20, and therefore the processing time can be shortened by not performing preparatory processing.

[0058] <Operation flow when printing starts> This section describes an example of the operation of the thermal printer 1 when it starts printing. In the following, it is assumed that the thermal printer 1 has been left unused for a long time since the previous printing was completed, and the thermal paper S sandwiched between the thermal head 20 and the platen roller 30 is stuck to the thermal head 20.

[0059] (Example of first operation flow) Fig. 8 is a flowchart for explaining the first operation flow at the start of printing by the thermal printer 1. The flowchart in Fig. 8 starts when the control unit 54 receives a command to print on the thermal paper S (step S102). For example, the control unit 54 receives a command to start printing from a terminal or the like connected to the thermal printer 1.

[0060] Next, the control unit 54 energizes the heating elements 22 to start preheating of the thermal head 20 (step S104). That is, the control unit 54 starts preheating by supplying a predetermined current pulse to the heating elements 22 so that the color former of the thermal paper S does not develop color. By preheating the heating elements 22, the color former of the thermal paper S melts.

[0061] Next, while preheating the thermal head 20, the control unit 54 rotates the motor 14 in the forward direction to cause the platen roller 30 to transport the thermal paper S sandwiched between the thermal head 20 and the platen roller 30 downstream in the transport direction (step S106). That is, the platen roller 30 transports the thermal paper S, whose color former has been melted by preheating, downstream in the transport direction while separating it from the thermal head 20. As a result, the portion of the thermal paper S that was adhering to the thermal head 20 is separated from the thermal head 20.

[0062] Next, the control unit 54 rotates the motor 14 in the reverse direction, causing the platen roller 30 to perform a second transport of the thermal paper S upstream in the transport direction (step S108). That is, the platen roller 30 transports the thermal paper S upstream in the transport direction for the second time so that the printable portion S1 of the thermal paper S is located upstream of the printing position in the transport direction. During the second transport, the control unit 54 transports the thermal paper S by an amount that is the second transport amount L2 plus the transport amount La. By adding the transport amount La, it is possible to adjust for misalignment of the printing position caused by backlash when the motor 14 rotates in the reverse direction.

[0063] Next, the control unit 54 rotates the motor 14 forward to cause the platen roller 30 to transport the thermal paper S a third time downstream in the transport direction so that the printable portion S1 of the thermal paper S returns to the print position (step S110). During the third transport, the control unit 54 transports the thermal paper S by an amount that is the third transport amount L3 plus a transport amount Lb. By adding the transport amount Lb, it is possible to adjust for misalignment of the print position caused by backlash when the motor 14 rotates in the reverse direction. As a result, the printable portion S1 can be returned to the print position with high precision.

[0064] Next, the control unit 54 performs main heating of the thermal head 20 (step S112). That is, the control unit 54 supplies a second current amount, which is greater than the first current amount during preheating, to the heating elements 22 to main heat the thermal head 20. The heat from the main heated thermal head 20 enables the color former of the thermal paper S to develop color.

[0065] Next, the control unit 54 performs printing on the thermal paper S (step S114). That is, the control unit 54 performs main heating of the thermal head 20 while intermittently transporting the thermal paper S, thereby printing at a desired position on the thermal paper S. Because the thermal paper S that was stuck to the thermal head 20 is separated from the thermal head 20 before printing, the thermal paper S can be appropriately intermittently transported when printing, and as a result, printing is performed without deviation from the desired position.

[0066] (Second operation flow example) 9 is a flowchart illustrating a second operation flow at the start of printing by the thermal printer 1. In the second operation example, the first and second transport directions of the thermal paper S are different from those in the first operation example, but other points are the same. The flowchart in FIG. 9 also starts when the control unit 54 receives a command to print on the thermal paper S (step S102).

[0067] Next, the control unit 54 energizes the heating elements 22 to start preheating the thermal head 20 (step S104). Then, while preheating the thermal head 20, the control unit 54 rotates the motor 14 in the reverse direction to cause the platen roller 30 to perform a first transport of the thermal paper S sandwiched between the thermal head 20 and the platen roller 30 upstream in the transport direction (step S156). That is, the platen roller 30 transports the thermal paper S, whose printable portion S1 has been melted by preheating, upstream in the transport direction from the thermal head 20 while separating the printable portion S1 from the thermal head 20. This separates the portion of the thermal paper S that was adhering to the thermal head 20 from the thermal head 20. During the first transport, the control unit 54 transports the thermal paper S by an amount equal to the sum of the first transport distance L4 and the transport distance Lc. Adding the transport distance Lc adjusts for misalignment of the print position due to backlash during the reverse rotation of the motor 14.

[0068] Next, the control unit 54 rotates the motor 14 forward to return the printable portion S1 of the thermal paper S to the print position, causing the platen roller 30 to transport the thermal paper S back downstream in the transport direction (step S158). During the return transport, the control unit 54 transports the thermal paper S by an amount equal to the return transport amount L5 plus the transport amount Ld. By adding the transport amount Ld, it is possible to adjust for misalignment of the print position caused by backlash when the motor 14 rotates in the reverse direction. As a result, the printable portion S1 can be returned to the print position with high precision.

[0069] Next, the control unit 54 controls the heating elements 22 to perform main heating (step S112) and performs printing on the thermal paper S (step S114). That is, the control unit 54 performs main heating with the heating elements while intermittently transporting the thermal paper S, thereby printing at a desired position on the thermal paper S.

[0070] It is desirable that the above-described first and second operation flows be executed every time printing is performed on the thermal paper S.

[0071] <Effects of this embodiment> As a preliminary process, the thermal printer 1 of the above-described embodiment supplies a first current amount as a current pulse to the heating elements 22 to preheat the thermal head 20, performs a first transport in which the print-receiving portion of the thermal paper S is transported in one direction on the transport path 12 while preheating, and performs a second transport in which the thermal paper S is transported in the opposite direction to return the print-receiving portion of the thermal paper S to the printing position. Once the preliminary process is complete, the thermal printer 1 supplies a second current amount as a current pulse that is greater than the first current amount to the heating elements 22 to perform main heating of the thermal head 20 and print on the thermal paper S. As a result, by performing the first transport together with the above-described preheating before printing starts, the thermal paper S that has been stuck to the thermal head 20 can be separated from the thermal head 20. As a result, the thermal paper S can be transported appropriately when printing, thereby suppressing misalignment of the printing position.

[0072] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0073] 1. Thermal printer 12 Conveyor path 14 Motor 20 Thermal head 22 Heating element 30 Platen roller 54 Control Unit S thermal paper S1 Printed area

Claims

1. a thermal head having a heating element that generates heat when energized and that prints on a print target portion located at a printing position on the thermal paper; a platen roller that sandwiches the thermal paper between itself and the thermal head and transports the thermal paper; a control unit that controls the operation of the platen roller and the thermal head, The control unit supplying a first current amount as a current pulse to the heating element to preheat the thermal head; a first conveyance in which the thermal paper, which is sandwiched between the platen roller and the thermal head and has the printable portion positioned at the printing position, is conveyed in one direction along a conveyance path; a return conveyance in which the thermal paper is conveyed in a direction opposite to the one direction so as to return the printable portion of the thermal paper to the print position; a second current amount, which is a current pulse greater than the first current amount, is supplied to the heating elements to perform main heating of the thermal head, thereby controlling the thermal head to perform printing on the thermal paper; The control unit In the first conveyance, the platen roller is rotated forward while the thermal head is preheated, and the thermal paper is conveyed downstream in the conveyance direction so that the printable portion is located downstream of the printing position in the conveyance direction; In the return transport, the platen roller is rotated in a reverse direction to transport the thermal paper upstream in the transport direction so that the printable portion is located upstream of the printing position in the transport direction (second transport), and then the platen roller is rotated in a forward direction to transport the thermal paper downstream in the transport direction so that the printable portion returns to the printing position (third transport). Thermal printer.

2. a thermal head having a heating element that generates heat when energized and that prints on a print target portion located at a printing position on the thermal paper; a platen roller that sandwiches the thermal paper between itself and the thermal head and transports the thermal paper; a control unit that controls the operation of the platen roller and the thermal head, The control unit supplying a first current amount as a current pulse to the heating element to preheat the thermal head; a first conveyance in which the thermal paper, which is sandwiched between the platen roller and the thermal head and has the printable portion positioned at the printing position, is conveyed in one direction along a conveyance path; a return conveyance in which the thermal paper is conveyed in a direction opposite to the one direction so as to return the printable portion of the thermal paper to the print position; a second current amount, which is a current pulse greater than the first current amount, is supplied to the heating elements to perform main heating of the thermal head, thereby controlling the thermal head to perform printing on the thermal paper; The control unit In the first conveyance, the platen roller is rotated in a reverse direction while the thermal head is preheated, and the thermal paper is conveyed upstream in the conveyance direction so that the printable portion is located upstream of the printing position in the conveyance direction. In the return transport, the platen roller is rotated forward to transport the thermal paper downstream in the transport direction so that the printable portion returns to the printing position. Thermal printer.

3. a motor that transmits power to the platen roller via a gear; the control unit, in the second transport, transports the thermal paper by a second transport amount that is greater than the first transport amount of the thermal paper in the first transport, plus a transport amount corresponding to backlash in meshing of the gears caused by reverse rotation of the motor.

2. The thermal printer according to claim 1.

4. the control unit, in the third transport, transports the thermal paper by a third transport amount obtained by subtracting the first transport amount from the second transport amount, and adding a transport amount corresponding to a backlash in meshing of the gears caused by reverse rotation of the motor.

4. The thermal printer according to claim 3.

5. a thermal head having a heating element that generates heat when energized and that prints on a print target portion located at a printing position on the thermal paper; a platen roller that sandwiches the thermal paper between itself and the thermal head and transports the thermal paper; a control unit that controls the operation of the platen roller and the thermal head, The control unit supplying a first current amount as a current pulse to the heating element to preheat the thermal head; a first conveyance in which the thermal paper, which is sandwiched between the platen roller and the thermal head and has the printable portion positioned at the printing position, is conveyed in one direction along a conveyance path; a return conveyance in which the thermal paper is conveyed in a direction opposite to the one direction so as to return the printable portion of the thermal paper to the print position; a second current amount, which is a current pulse greater than the first current amount, is supplied to the heating elements to perform main heating of the thermal head, thereby controlling the thermal head to perform printing on the thermal paper; The control unit When a predetermined time has elapsed since the start of preheating of the heating element, the first conveyance is started; The preheating is continued at least until the first conveyance is completed. Thermal printer.

6. the thermal head performs printing by causing a color former in the thermal paper to develop color with the heat generated by the heating elements; the control unit supplies the first amount of current to the heating elements at which the color former does not develop a color, thereby preheating the thermal head.

6. The thermal printer according to claim 1.

7. the control unit supplies the energizing pulse having a predetermined pulse width to the heating element at each pulse interval; The pulse width is smaller than the pulse interval.

7. The thermal printer according to claim 1.

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