Printer, Printing Control Method, Program

Abstract

To efficiently apply thermal energy to a heating element of a thermal head.SOLUTION: A printer for performing printing on a printing medium having a thermosensitive color developing layer includes: a thermal head having a plurality of heating elements arrayed in a line; and a control part for controlling thermal energy for the plurality of heating elements according to presence / absence of application of an energization pulse for a plurality of prescribed periods in a printing cycle of one line on the basis of image data. The plurality of periods in the printing cycle are set in order from the longest period to the shortest period.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a printer, a printing control method, and a program.

Background Art

[0002] Generally, a thermal head generates heat by independently passing a predetermined current through a plurality of heating elements arranged in a line, and prints information by forming a dot pattern on a printing medium having a heat-sensitive coloring layer. At this time, the presence or absence of color development of the dot corresponding to the heating element is controlled by the time during which current is passed through the heating element (that is, the energization pulse width). In addition, since the thermal head has a heat storage characteristic that heat accumulates in the heating element when energization continues in the same heating element, thermal history control is known in which the energization pulse width is adjusted according to the history of energization of the heating element to make the thermal energy applied to the heating element constant (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] By the way, Patent Document 1 describes controlling the ON time of the heating element corresponding to the pixel of the print data of the current line according to the thermal history pattern, but does not consider efficiently applying thermal energy to the heating element. For example, after determining the ON time of the heating element, there is no description of how to set (arrange) the ON time during the printing cycle of one line.

[0005] Therefore, an object of the present invention is to efficiently apply thermal energy to the heating element of the thermal head.

Means for Solving the Problems

[0006] One aspect of the present invention is a printer that prints on a printing medium having a heat-sensitive coloring layer, a thermal head having a plurality of heating elements arranged in a line, a control unit that controls the thermal energy applied to the plurality of heating elements by the presence or absence of an energization pulse for a plurality of preset periods in one line printing cycle based on image data, and includes in the printing cycle, the plurality of periods are set in the order from the longest period to the shortest period and the ratio of the lengths of the plurality of periods is 8:4:2:1 is a printer.

Effects of the Invention

[0007] According to one aspect of the present invention, thermal energy can be efficiently applied to the heating elements of the thermal head.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0009] FIG. 1 illustrates a printer 1 according to an embodiment. The printer 1 is a thermal printer that prints on a label having a heat-sensitive color-developing layer on one side. As shown in FIG. 1, the printer 1 includes a roll paper storage chamber 9, a platen roller 10, a thermal head 15, a printer cover 25, a coil spring 29, and the like. The roll paper R can be loaded into the roll paper storage chamber 9 by opening and closing the printer cover 25. The roll paper R is formed by winding a strip-shaped continuous paper P in a roll shape. Although not shown, in one embodiment, the continuous paper P has, for example, a strip-shaped base paper and a plurality of labels temporarily attached at predetermined intervals on the base paper. The label attachment surface of the base paper is coated with a release agent such as silicone so that the labels can be easily peeled off. In another embodiment, the continuous paper P may be a label without a base paper.

[0010] As shown in FIG. 1, in the printer 1, the platen roller 10 is supported in a state where it can rotate in both forward and reverse directions. The platen roller 10 is a conveying means for conveying the continuous paper P drawn from the roll paper R, and is formed in a state of extending along the width direction of the continuous paper P. A gear (not shown) is provided at one end of the platen shaft of the platen roller 10, and this gear is mechanically connected to a stepping motor (not shown) for driving the roller. The platen roller 10 rotates in response to the rotation of the stepping motor that operates based on a signal transmitted from a circuit board (not shown).

[0011] The thermal head 15 is a printing means for printing information such as characters, symbols, graphics, or codes on a label on the continuous paper P. The thermal head 15 includes a plurality of heating elements (heating resistors) arranged along the width direction of the continuous paper P, and performs printing by selectively energizing the plurality of heating elements based on a signal transmitted from a circuit board. The thermal head 15 is arranged to face the platen roller 10 when the printer cover 25 is in the closed state, and sandwiches the continuous paper P together with the platen roller 10. The coil spring 29 is a biasing means for biasing the thermal head 15 toward the platen roller 10, and generates an appropriate nip pressure for printing between the thermal head 15 and the platen roller 10. In the following description, the direction orthogonal to the conveyance direction of the continuous paper P (that is, the direction in which the heating elements are arranged) is referred to as the "main scanning direction", and the same direction as the conveyance direction of the continuous paper P is referred to as the "sub-scanning direction". The thermal head 15 will be described in more detail later.

[0012] Next, with reference to FIG. 2, the internal configuration of the printer 1 will be described. FIG. 2 is a block diagram showing the internal configuration of the printer 1. As shown in FIG. 2, the printer 1 includes, for example, a control unit 11, a storage 12, a drive circuit 13, a motor 14 mechanically connected to the platen roller 10, a thermal head 15, and a communication interface (I / F) 16.

[0013] The control unit 11 includes a controller and a memory, and controls the operation of the printer 1. The processor reads and executes the firmware stored in the ROM when the printer 1 is started up. The controller includes a CPU (Central Processing Unit) as will be described later, and controls the thermal head 15 to print predetermined information on the label by executing the firmware. Storage 12 is a storage device such as an SSD (Solid State Drive). Storage 12 stores, for example, a printing file acquired from a host computer via a communication interface 16. Storage 12 may store information on a printing format when printing information on each label.

[0014] Drive circuit 13 is a circuit that drives a motor 14 that controls the rotation of a platen roller 10 in response to a conveyance request from control unit 11. Motor 14 is, for example, a stepping motor. The conveyance request includes, for example, information on a conveyance direction (forward or reverse direction) and a conveyance amount (e.g., number of steps).

[0015] Control unit 11 executes a printing process by controlling to selectively pass current through each of a plurality of heating elements included in thermal head 15 based on image data to be printed. The image data is data obtained by rendering a printing file into bitmap data. The heating elements of thermal head 15 heated by the current are continuously conveyed by platen roller 10 Paper P When pressed against the upper label, the heat-sensitive coloring layer of the label against which the heating element is pressed develops color, thereby printing information on the label.

[0016] Communication interface 16 includes a communication circuit for communicating with an external device such as a host computer.

[0017] Next, with reference to FIGS. 3 and 4, the printing operation of printer 1 will be described. FIG. 3 is a functional block diagram focusing on the control unit and the thermal head in printer 1 according to an embodiment. FIG. 4 is a schematic circuit diagram of thermal head 15 according to an embodiment.

[0018] As shown in FIG. 3, control unit 11 includes a CPU 111, a head controller 112, and a memory 113 (an example of a storage unit), and is configured such that each unit can communicate via a bus 114. The CPU 111 controls the entire printing operation in the control unit 11. The head controller 112 supplies various signals for printing to the thermal head 15 under the control of the CPU 111. The signals supplied to the thermal head 15 by the head controller 112 include a clock pulse CLK, a latch pulse LATCH, a data signal DATA, and a strobe signal STB.

[0019] The memory 113 is, for example, a RAM (Random Access Memory), and has a FIFO (First In First Out)-configured image buffer, a line buffer, and a thermal history data table.

[0020] The CPU 111 performs thermal history control to execute printing. Thermal history control is control that adjusts the energization pulse width (that is, the width of the strobe signal STB; hereinafter, appropriately referred to as the "strobe application period") based on data of past energization to the heating element and / or data scheduled to be energized to the heating element, and makes the thermal energy to the heating element constant. To perform thermal history control, the CPU 111 generates data (hereinafter referred to as "thermal history reflected data") obtained by changing the original image data based on the printing data of the dot of interest and the printing data of the dots around the dot in the original image data to be printed. The thermal history reflected data is stored in the image buffer. In the following description, "image data" means the original image data before being changed to the thermal history reflected data.

[0021] In thermal history control, a plurality of data signals and a plurality of strobe signals corresponding to each data signal are generated during one printing cycle (i.e., the printing cycle of one line). In the example described later, four data signals and strobe signals are generated during one printing cycle. In this case, for example, if M heating elements are arranged in a line in the thermal head 15 and the data of one line of image data (line data) is M bits, the data of one line of thermal history reflection data (line data) will be data of M×4 bits.

[0022] The line data of the image data includes printing data (an example of information on whether to print) indicating whether to print for each dot. The printing data is either "print" or "non-print". On the other hand, the data for each dot of the line data of the thermal history reflection data corresponding to one line of image data corresponds to a plurality of data signals and is data indicating either "energized" or "non-energized".

[0023] The line data of the thermal history reflection data is sequentially stored in the line buffer. As described above, the thermal history data table is referred to when generating the thermal history reflection data. Details of the thermal history data table will be described later.

[0024] The head controller 112 generates the data signal DATA based on the line data sequentially transferred from the line buffer and generates the strobe signal STB at a predetermined timing. The transfer of the line data from the line buffer to the head controller 112 is performed, for example, by DMA (Direct Memory Access).

[0025] The thermal head 15 includes a drive circuit 2 and a heating element group 3. The heating element group 3 is composed of a plurality of heating elements (heating resistors) arranged on a line. The drive circuit 2 selectively passes current through each heating element of the heating element group 3 to generate heat based on various signals supplied from the head controller 112. Details of the drive circuit 2 and the heating element group 3 will be described later.

[0026] As shown in FIG. 4, the drive circuit 2 of one embodiment includes at least a shift register (S / R) 21 for temporarily storing data signals DATA for one line, a latch circuit (L) 22, a gate circuit group 23, and a transistor group 24. The heating element group 3 includes heating elements (heating resistors) 31_1 to 31_M.

[0027] The drive circuit 2 operates based on the data signal DATA, the clock pulse CLK, the latch pulse LATCH, and the strobe signal STB. These data and signals are input or transferred from the head controller 112. The transfer of the data signal DATA for one line may be divided and transferred using a plurality of line buffers in order to shorten the transfer time. In that case, a divided part of the data signal DATA for one line is stored in each line buffer, and serial transfer is performed from each line buffer.

[0028] In the drive circuit 2 of FIG. 4, the strobe signal STB is positive logic (current flows through the heating element and generates heat when at a high level). In another embodiment, the strobe signal STB may be negative logic (current flows through the heating element and generates heat when at a low level).

[0029] The shift register 21 receives and holds the data signal DATA for one line in synchronization with the clock pulse CLK. The data signal DATA (an example of an energization pulse) is composed of a bit string where the "energized" state is at a high level and the "non-energized" state is at a low level. The latch circuit 22 is connected in parallel to the shift register 21 and transfers and holds the bit string on the shift register 21 simultaneously and in parallel. The transfer timing of data from the shift register 21 to the latch circuit 22 is controlled by the latch pulse LATCH.

[0030] The gate circuit group 23 includes gate circuits (AND circuits) 23_1, 23_2, …, 23_M corresponding to the first to Mth dots on one line respectively. A strobe signal STB is supplied to one input terminal of each gate circuit, and the other input terminal of each gate circuit is connected to the output of the latch circuit 22. Each gate circuit of the gate circuit group 23 outputs the logical product of the corresponding data signal DATA and the strobe signal STB. The transistor group 24 includes MOS transistors 24_1 to 24_M. Each MOS transistor turns on / off according to the output of the corresponding gate circuit.

[0031] While the strobe signal STB is at a high level, the logical level of the output terminal of each gate circuit of the gate circuit group 23 coincides with the output level of the latch circuit 22. For example, when the output level of the latch circuit 22 is a high level indicating "energized", the output of the corresponding gate circuit becomes high level, so the corresponding MOS transistor turns on and current flows through the heating element 31. Conversely, when the output level of the latch circuit 22 is a low level indicating "non-energized", the output of the corresponding gate circuit becomes low level, so the corresponding MOS transistor turns off and no current flows through the heating element 31.

[0032] When the strobe signal STB is of negative logic, it may be configured as follows. That is, in FIG. 4, each gate circuit of the gate circuit group 23 is a NAND circuit, and the inverted signal of the strobe signal STB is input to the NAND circuit. Thereby, when the strobe signal STB is at a low level, the NAND circuit outputs the inverted signal of the output of the latch circuit 22. The corresponding MOS transistor is configured to turn on and current flows through the heating element when the output of the NAND circuit is at a low level.

[0033] When thermal history control is not performed, one data signal DATA is sent to the drive circuit 2 of the thermal head 15 once during the printing period for one line of line data. On the other hand, when thermal history control is performed, a plurality of data signals DATA (for example, data signals DATA_1 to DATA_4 described later) are sent to the drive circuit 2 of the thermal head 15 during a plurality of periods within the printing period for one line of line data.

[0034] In the thermal history control according to one embodiment, the head controller 112 supplies four data signals DATA_1 to DATA_4 to the drive circuit 2 at a predetermined timing synchronized with the clock pulse CLK during the printing period. When one line of image data is M bits, the corresponding line data of the thermal history reflection data is M×4-bit data. Each M-bit of this M×4-bit data is supplied to the drive circuit 2 as data signals DATA_1 to DATA_4 in four portions.

[0035] The head controller 112 supplies a latch pulse LATCH and strobe signals STB_1 to STB_4 to the drive circuit 2 of the thermal head 15 at a predetermined timing synchronized with the clock pulse CLK. The relationship between the transfer timing of the data signal and the application timing of the strobe signal in one printing period when thermal history control is performed will be described later.

[0036] Next, the thermal history data table will be described in more detail. The thermal history data table shows the relationship between the applied data of the dot to be processed (hereinafter referred to as "target dot") in the line to be printed (hereinafter referred to as "target line") in the image data, and the printed data of the dots corresponding to the target dot in the lines before and after the target line (that is, past printed data, future printed data), and the strobe level for the target dot during the printing period.

[0037] Here, the strobing level indicates the level (high level or low level) of each data signal in a plurality of strobing application periods for the heating element corresponding to the dot of interest. The level of the data signal indicates the presence or absence of the application of an energization pulse in each strobing application period. The strobing level indicates the length of the time during which current substantially flows through the heating element in the printing cycle. The higher the strobing level, the longer the current flows through the heating element during printing period and thus a large amount of thermal energy is applied to the heating element.

[0038] The CPU 111 refers to the thermal history data table and determines the level of each data signal (high level indicating "energization" or low level indicating "non-energization") in a plurality of strobing application periods for each dot of the line of interest. Thereby, considering the printing data of the current dot of interest and the printing data before and after it, the thermal energy applied to the heating element corresponding to the current dot of interest is appropriately controlled.

[0039] In the thermal history data table of another embodiment, it further includes the relationship between the printing data of each dot adjacent to the dot of interest and the strobing level for the dot of interest during the printing cycle. By referring to the printing data of the dots adjacent to the dot of interest on the left and right, since the thermal energy received by the heating element corresponding to the dot of interest from the adjacent heating elements is also considered, the thermal energy applied to the heating element corresponding to the current dot of interest is more appropriately controlled.

[0040] In the following description, the past printing data of the dot of interest means the dot before the dot of interest in the sub-scanning direction data and is appropriately referred to as "past data". The future printing data of the dot of interest means the dot after the dot of interest in the sub-scanning direction data and is appropriately referred to as "future data".

[0041] Fig. 5 shows the relationship between the strob level (STB level) and the timing at which current substantially flows through the heating element during each period when the strob signals STB_1 to STB_4 are applied in the thermal history control according to one embodiment. In the case of a positive logic thermal head, the fact that current substantially flows through the heating element means that the corresponding data signals DATA_1 to DATA_4 are at a high level. That is, the data signals DATA_1 to DATA_4 are associated with the strob level. For example, the data signals DATA_1 to DATA_4 corresponding to the dot of interest are 4-bit data corresponding to the strob level. For example, the data signals DATA_1 to DATA_4 are "0000" when the strob level is "0", "0110" when the strob level is "6", and "1111" when the strob level is "15".

[0042] In one embodiment, when the strob level is 4 or more, heat energy for discoloring the heat-sensitive coloring layer of the label is given to the heating element, and when the strob level is less than 4, heat energy for discoloring the heat-sensitive coloring layer of the label is not given to the heating element, but a preheating effect on the heating element is exerted.

[0043] In one embodiment, as shown in Fig. 5, the four strob signals STB_1 to STB_4 corresponding to the four data signals in the printing cycle are set in the order from the longest period to the shortest period. That is, if the lengths of the four strob signals STB_1 to STB_4 are L1 to L4 respectively, L1 > L2 > L3 > L4 is satisfied. The advantages of setting in this way will be described later.

[0044] Preferably, the ratio of the lengths of the four strobe signals STB_1 to STB_4 is 8:4:2:1. By setting the ratio of the lengths in this way, the number of combinations of the time for applying thermal energy to the heating element during one printing cycle (that is, the energization time for the heating element; referred to as the "strobe length") can be increased as much as possible, and precise setting of the applied energy becomes possible. The ratio of the lengths of the four strobe signals STB_1 to STB_4 is not limited to 8:4:2:1, but by making each length different, 16 (= 2 4 ) different strobe length patterns can be set.

[0045] An exemplary thermal history data table is shown in FIG. 6. In FIG. 6, the target dots mean each dot of the line data of the target line in the image data (referred to as "target line data") when generating the thermal history reflection data. The thermal history data table in FIG. 6 shows the strobe level set for the current target dot according to the combination of the printing data (●: "printed", 〇: "not printed") of the current target dot, the past data one before the target dot, the past data two before the target dot, the future data one after the target dot, and the future data two after the target dot.

[0046] In FIG. 6, the front and rear dot pattern 101 shows 32 (= 2 5 ) different combination patterns of the printing data corresponding to the past data one before the current target dot (indicated by "-1"), the past data two before (indicated by "-2"), the future data one after (indicated by "+1"), and the future data two after (indicated by "+2").

[0047] In one embodiment, when generating the thermal history reflection data, the left and right dots adjacent to the current target dot are also considered. In FIG. 6, the adjacent dot pattern 102 shows 4 (= 2 2 ) different combination patterns of the printing data of the left and right dots adjacent to the current target dot. In FIG. 6, the strob level data 103 indicates the strob level (a value of any of 0 to 15) for each of 32×4 combinations based on the front and rear dot patterns 101 and the adjacent dot pattern 102 with respect to the current dot of interest.

[0048] FIG. 7 shows, for 32 combinations out of the 32×4 combinations shown in FIG. 6 where the printing data of the left and right dots adjacent to the current dot of interest are both "printed" (●), the timing when current flows through the heating element substantially during the period when each strob signal is applied. The relationship between the strob level corresponding to each pattern specified by the strob level data 103 and the timing when current flows through the heating element substantially is the same as that shown in FIG. 5.

[0049] The CPU 111 determines the strob level from the strob level data 103 with reference to the heat history data table illustrated in FIG. 6 for each dot of interest in the line data of interest. The CPU 111 generates heat history reflection data by assigning 4-bit data corresponding to the strob level to each dot of interest. The head controller 112 assigns the data of the 1st bit to the 4th bit to the data signals DATA_1 to DATA_4, respectively, for each dot of interest in the line data of the heat history reflection data.

[0050] Next, with reference to FIGS. 8 and 9, the transfer timing of the data signal and the application timing of the strob signal when performing heat history control for printing will be described. FIG. 8 is a timing chart showing the transfer timing of the data signal and the application timing of the strob signal in the printing cycle SLT in the printer 1 of one embodiment. FIG. 9 is a timing chart showing the transfer timing of the data signal and the application timing of the strob signal in the printing cycle SLT in a comparative example. In FIGS. 8 and 9, a standby time WT is set between consecutive strob application periods.

[0051] In addition, in each of the timing charts of FIGS. 8 and 9, "without correction" shows the timing chart when printing is performed at the standard printing density. In each of the timing charts of FIGS. 8 and 9, "correction (-)" and "correction (+)" respectively show the timing charts with timing correction when printing is performed at a printing density lower than the standard and at a printing density higher than the standard. In the timing correction according to the printing density, the length of each strobe signal after correction is determined by multiplying the length of each strobe signal at the standard printing density by a predetermined proportional constant (a positive value less than 1 in the case of "correction (-)", and a value greater than 1 in the case of "correction (+)") according to the printing density set in the printer 1. In each of the timing charts of FIGS. 8 and 9, the last strobe applied timing correction is performed so that the period falls within the cycle SLT.

[0052] As shown in FIG. 8, in one embodiment, the four strobe signals STB_1 to STB_4 corresponding to the four data signals DATA_1 to DATA_4 are set in the order from the longest period to the shortest period. On the other hand, in the comparative example shown in FIG. 9, the three strobe signals STB_1 to STB_3 corresponding to the three data signals DATA_1 to DATA_3 are set in the order from the shortest period to the longest period. As shown in FIG. 8, by setting the plurality of strobe signals within the printing cycle SLT in the order from the longest period to the shortest period, the following advantageous effects can be obtained with respect to the comparative example shown in FIG. 9.

[0053] (i) For example, in FIG. 8, the long-term strobe signals STB_1 and / or STB_2 are set for printing purposes, and the short-term strobe signals of the strobe signals STB_3 and / or STB_4 are set for preheating purposes. By arranging the strobe signal set for this preheating purpose near the end of the printing cycle SLT, the time until the strobe signal for printing in the next printing cycle SLT is shortened, and the preheating efficiency can be increased. If the period between the strobe signal set for preheating purposes and the strobe signal for printing in the next printing cycle SLT is long, the heating element preheated during that period will cool down, and the effect of preheating cannot be fully exerted. On the other hand, in FIG. 8, since the period between the strobe signal set for preheating purposes and the strobe signal for printing in the next printing cycle SLT is relatively short, it is possible to prevent the heating element preheated during that period from cooling down, and the effect of preheating can be exerted. That is, the preheating efficiency can be increased.

[0054] (ii) By arranging them in order from the long-term strobe signal within the printing cycle SLT, the waiting time WT is shortened and the data transfer efficiency becomes good. Referring to FIG. 9, since the length of the first strobe signal STB_1 in the printing cycle SLT is shorter than the data transfer time of the data signal DATA_2, a relatively long waiting time WT for waiting for the data transfer time of the data signal DATA_2 occurs to make the next strobe signal STB_2 high level. Similarly, since the length of the strobe signal STB_2 is shorter than the data transfer time of the data signal DATA_3, a relatively long waiting time WT for waiting for the data transfer time of the data signal DATA_3 occurs to make the next strobe signal STB_3 high level. In the comparative example of FIG. 9, the case where the data signal is transferred three times is shown, but when the data signal is transferred four times as in FIG. 8, even more waiting time WT occurs. On the other hand, as shown in FIG. 8, if arranged in order from a long strobe signal within the printing cycle SLT, it becomes possible to intensively arrange a plurality of strobe application periods, and the waiting time WT can be shortened. In other words, the time from the start time of the first strobe application period to the end time of the last strobe application period in a plurality of strobe application periods can be shortened, and thereby the ratio of this time to the printing cycle SLT can be reduced. Further, from another perspective, the ratio of the time occupied by the strobe application period in the time from the start time of the first strobe application period to the end time of the last strobe application period in a plurality of strobe application periods can be increased.

[0055] (iii) By arranging in order from a long strobe signal within the printing cycle SLT, the waiting time WT is shortened and the thermal energy control becomes stable. During the waiting time WT, the heating element is cooled, but when the waiting time WT is long, it is difficult to predict how much the heating element is cooled. Therefore, there are cases where the expected effect for the preheating strobe signal cannot be obtained. Also, in the timing chart of FIG. 8, the change in the waiting time WT with respect to density correction is relatively small, whereas in the timing chart of FIG. 9, the change in the waiting time WT with respect to density correction is relatively large. This is because in the timing chart of FIG. 9, the lengths of the strobe signals STB_1 and STB_2 arranged first in the printing cycle SLT are shorter than the data transfer time of the data signal. That is, as shown in FIG. 9, when arranged in order from short strobe signals within the printing cycle SLT, there is a problem that the variation in the waiting time WT becomes large and the thermal energy control for the heating element becomes unstable. Conversely, as shown in FIG. 8, by arranging in order from a long strobe signal within the printing cycle SLT, there are advantages that the preheating effect becomes easy to predict and the thermal energy control for the heating element becomes stable.

[0056] The printing control method according to an embodiment is executed in the control unit 11 and includes the following steps (a) and (b). Step (a): sequentially transmitting line data of the image data. Step (b): The printing data of the target dot in the printing line and the target line of A step of determining whether or not to apply a DATA signal (energizing pulse) during each of a plurality of strobe application periods to each dot on the line of interest based on print data of dots corresponding to the dot of interest on the previous and next lines. Here, in step (b), the multiple strobe application periods are set in the order of longest to shortest in the printing cycle.

[0057] The program according to the embodiment is a program for causing a computer to execute the above-mentioned print control method. For example, the CPU 111 included in the control unit 11 of the printer 1 executes the program, printing A control method is implemented. In one embodiment, the program may be recorded on a non-transitory computer-readable recording medium.

[0058] Although the printer, print control method, and program of the present invention have been described in detail above, the scope of the present invention is not limited to the above-mentioned embodiments. Furthermore, the above-mentioned embodiments can be improved or modified in various ways without departing from the spirit of the present invention. In the above embodiment, an example in which the strobe application period is set four times during the printing cycle has been described, but this is not limited thereto, and the number of times may be five or more. By increasing the number of strobe application periods, more strobe levels can be set, enabling more precise control. [Explanation of symbols]

[0059] 1. Printer 9. Containment room 10...Platen roller 11...Control section 111...CPU 112…Head controller 113…Memory 114…Bus 12… Storage 13… Drive circuit 14… Motor 15… Thermal head 2… Drive circuit 2 21… Shift register 22… Latch circuit 23… Gate circuit group 23_1~23_M… AND circuit 24… Transistor group 24_1~24_M… MOS transistor 3… Heating element group 31_1~31_M… Heating element 16… Communication interface 20… Issue port 25… Printer cover 29… Coil spring 101… Front and back dot pattern 102… Adjacent dot pattern 103… Strobe level data P… Continuous paper DATA_1~DATA_4… Data signal STB_1~STB_4… Strobe signal L1~L4… Pulse width R… Roll paper WT… Standby time

Claims

1. A printer that performs printing on a printing medium having a heat-sensitive color-developing layer, comprising a thermal head having a plurality of heating elements arranged in a line, and a control unit that controls the thermal energy applied to the plurality of heating elements by the presence or absence of energization pulses for a plurality of preset periods within one line printing cycle based on image data. The printer is provided with: in the printing cycle, the plurality of periods are set in the order from the longest period to the shortest period, and the ratio of the lengths of the plurality of periods is 8:4:2:

1. Printer.

2. The lengths of the plurality of periods are different from each other. The printer according to Claim 1.

3. The length of the shortest period among the plurality of periods is such that the printing medium does not develop color when an energization pulse is applied to the period. The printer according to Claim 1 or 2.

4. The length of the shortest period among the plurality of periods is shorter than the transfer time of the image data for one line. The printer according to any one of Claims 1 to 3.

5. When the control unit adjusts the printing density, within one line printing cycle, the length of each of the plurality of periods is set to a value obtained by multiplying the corresponding length when the printing density is not adjusted by the same proportionality constant. The printer according to any one of Claims 1 to 4.

6. A storage unit that stores pulse application information in which information on the presence or absence of printing of a target dot in a printing target line, information on the presence or absence of printing of dots corresponding to the target dot in the lines before and after the printing target line, and the presence or absence of application of energization pulses for each of the plurality of periods to the heating element corresponding to the target dot are associated with each other. The control unit determines the presence or absence of application of energization pulses for each of the plurality of periods for each dot in the printing target line by referring to the pulse application information. The printer according to any one of Claims 1 to 5.

7. In the pulse application information, further, information on the presence or absence of printing of each dot adjacent to the target dot and the presence or absence of application of energization pulses for each of the plurality of periods to the heating element corresponding to the target dot are associated with each other. The printer according to Claim 6.

8. A printing control method for a printer that performs printing by a thermal head having a plurality of heating elements arranged in a line on a printing medium having a heat-sensitive color-developing layer. A plurality of periods are set in advance in one-line printing cycle, The printing control method is, sequentially transferring data for each line of image data; based on information on whether or not a dot of interest in a printing target line is printed, and information on whether or not dots corresponding to the dot of interest in lines before and after the printing target line are printed, determining whether to apply an energization pulse for each of the plurality of periods to each dot of the printing target line; including in the printing cycle, the plurality of periods are set in order from a long period to a short period, the ratio of the lengths of the plurality of periods is 8:4:2:1, Printing control method.

9. A program for causing a computer to execute a predetermined method for printing with a thermal head having a plurality of heating elements arranged in a line on a printing medium having a heat-sensitive coloring layer, a plurality of periods are set in advance in one-line printing cycle, the method includes sequentially transferring data for each line of image data; based on information on whether or not a dot of interest in a printing target line is printed, and information on whether or not dots corresponding to the dot of interest in lines before and after the printing target line are printed, determining whether to apply an energization pulse for each of the plurality of periods to each dot of the printing target line; including in the printing cycle, the plurality of periods are set in order from a long period to a short period, the ratio of the lengths of the plurality of periods is 8:4:2:1, Program.

Images