Printing device, printing control method, and program

Abstract

To provide a printing device equipped with a thermal head, which can efficiently suppress sticking from occurring.SOLUTION: A control device (40) of a printing device (10) sets a dot group set to be subjected to sticking-measures including a second dot group, when satisfying a condition that a ratio of printing regions with first densities or more is above a first threshold in a first dot group and a result of comparison of the printing regions with the first densities or more in the first dot group with printing regions whose densities are over second densities lower than the first densities of the second dot group following the first dot group is above a second threshold; sets a second power distribution control period of time (TB) for adjusting temperature variation of a thermal head (30) without performing printing on a medium to be printed (20), in addition to a first power distribution period of time (TA) for performing printing on the medium to be printed; and generates data on measures for distributing power to at least some of a plurality of heating elements (30a) in the second power distribution period of time in each dot group of the dot group set to be subjected to sticking-measures.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a printing apparatus, a print control method, and a program related to the processing thereof. [Background technology]

[0002] In printing devices (thermal printers) that print on print media by applying heat from a thermal head to a thermal color former or ink ribbon, the thermal head may stick during printing. For example, in a thermal printer that uses heat to develop the color former contained in the print media, the thermal head may stick to the print media, causing sticking. In a thermal transfer printer that transfers ink applied to an ink ribbon to the print media by heating, the thermal head may stick to the ink ribbon, causing sticking. Sticking can cause a decrease in print quality.

[0003] When printing with a thermal printer, the temperature of the thermal head changes depending on the print pattern, and sticking is likely to occur when the temperature of the thermal head changes suddenly from high to low.

[0004] Patent Document 1 describes a thermal printer that prevents sticking by using chopper control. Chopper control is a technique that frequently switches between energizing and deenergizing the thermal head, and chopper control has the effect of preventing sudden temperature changes in the thermal head. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-52539 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 1, the existing anti-sticking measures are based on suppressing temperature changes (particularly temperature drops) of the thermal head by not reducing the frequency of current application to the thermal head. However, the measures described in Patent Document 1 may not be adequate for some print expressions. For example, even when the risk of sticking is low, current may be applied to prevent sticking. Applying current to the thermal head to prevent sticking when the risk of sticking is low wastes energy. In addition, it is required that printing quality is not affected even if current is applied to the thermal head to prevent sticking. In other words, there is a problem of identifying situations where the risk of sticking is high and implementing just the right amount of anti-sticking measures.

[0007] An object of the present invention is to provide a printing apparatus, a print control method, and a program that can efficiently suppress the occurrence of sticking in a thermal head. [Means for solving the problem]

[0008] A printing device according to one aspect of the present invention has a plurality of heating elements, and a dot group consisting of a plurality of dots corresponding to the plurality of heating elements. A group of dots printed based on set print data a thermal head that prints on a print medium for each dot group; and a control device, the control device being configured to: Prescribed The ratio of a printing area having a first density or more is equal to or greater than a first threshold value, and the first dot group In The first concentration or more Printed at print density A printing area and the first dot group As a chronology Subsequent indicates the dots printed on Second dot group In lower than the first concentration A given value indicating the print density When the result of the comparison with the print area exceeding the second density is equal to or greater than the second threshold value, the second dot group is determined to include at least the second dot group. The dot group set is likely to cause sticking, a phenomenon in which the thermal head sticks to the print medium. Anti-sticking dot group set As and setting the first power supply control period for printing on the print medium, separately from the first power supply control period for printing on the print medium, without printing on the print medium. Prevents sticking and countermeasure data for energizing at least a part of the plurality of heating elements during the second energization control period for each dot group of the sticking countermeasure target dot group set. The power supply to the thermal head is controlled based on the , characterized in that

[0009] A print control method according to one aspect of the present invention includes: death A dot group consisting of a plurality of dots corresponding to the plurality of heating elements A group of dots printed based on set print data Printing is performed on the print medium every A printing control method for controlling a thermal head, comprising: In the first group of dots, Prescribed The ratio of a printing area having a first density or more is equal to or greater than a first threshold value, and the first dot group In The first concentration or more Printed at print density A printing area and the first dot group As a chronology Subsequent indicates the dots printed on Second dot group In lower than the first concentration A given value indicating the print density When the result of the comparison with the print area exceeding the second density is equal to or greater than the second threshold value, the second dot group is determined to include at least the second dot group. The dot group set is likely to cause sticking, a phenomenon in which the thermal head sticks to the print medium. Anti-sticking dot group set As and setting the first power supply control period for printing on the print medium, separately from the first power supply control period for printing on the print medium, without printing on the print medium. Prevents sticking and countermeasure data for energizing at least a part of the plurality of heating elements during the second energization control period for each dot group of the sticking countermeasure target dot group set. The power supply to the thermal head is controlled based on the , characterized in that

[0010] A program according to one aspect of the present invention includes: The thermal head has a plurality of heating elements, and is configured to print on a print medium for each dot group that is made up of a plurality of dots corresponding to the plurality of heating elements and is printed based on set print data. printing device Installed in To your computer On the other hand , in the first dot group, Prescribed The ratio of a printing area having a first density or more is equal to or greater than a first threshold value, and the first dot group In The first concentration or more Printed at print density A printing area and the first dot group As a chronology Subsequent indicates the dots printed onSecond dot group In lower than the first concentration A given value indicating the print density When the result of the comparison with the print area exceeding the second density is equal to or greater than the second threshold value, the second dot group is determined to include at least the second dot group. The dot group set is likely to cause sticking, a phenomenon in which the thermal head sticks to the print medium. Anti-sticking dot group set As and setting the first power supply control period for printing on the print medium, separately from the first power supply control period for printing on the print medium, without printing on the print medium. Prevents sticking and setting a second current control period for energizing at least a part of the plurality of heating elements during the second current control period for each dot group of the sticking countermeasure target dot group set. and controlling power supply to the thermal head based on the above. , characterized in that Effect of the Invention

[0011] According to the above aspect, the implementation of anti-sticking measures can be minimized to the extent necessary, thereby efficiently suppressing the occurrence of sticking. [Brief description of the drawings]

[0012] [Figure 1] FIG. [Diagram 2] 11 is a front view of the cassette storage section with the tape cassette stored therein; FIG. [Diagram 3] FIG. 2 is a block diagram showing a hardware configuration of the printing device. [Figure 4] 11A and 11B are diagrams illustrating an example of energization control of a thermal head in one dot period. [Diagram 5] FIG. 2 is a block diagram showing the functional structure of a printing device. [Figure 6] 11A and 11B are diagrams for explaining a method of determining a sticking occurrence estimated dot group and a method of setting a pattern of countermeasure data. [Figure 7] 13 is a flowchart of a sticking countermeasure process. [Figure 8] 13 is a flowchart of a process for determining a sticking occurrence estimated dot group. [Figure 9]13A and 13B are diagrams for explaining a method of determining a sticking occurrence estimated dot group and a method of setting a pattern of countermeasure data in a printing device of another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a front view of a printing device 10 according to this embodiment. The printing device 10 is a thermal printer equipped with a thermal head 30 (see Fig. 2) as a printing unit, and performs printing on, for example, a tape 20, which is a long, band-shaped printing medium, by a single pass method.

[0014] The tape 20 is a heat-sensitive tape that changes color when heated. For example, the tape 20 is configured by laminating a base material having an adhesive layer, a color-developing layer containing a color former, a peelable release paper attached to the adhesive layer of the base material, and the like.

[0015] The printing device 10 has a device housing 11, an input unit 12 on the top front side of the device housing 11, and a display device 13 and an opening / closing cover 14 on the top rear side of the device housing 11.

[0016] The input unit 12 is equipped with a plurality of input keys, and operations on the input unit 12 are used to input print contents such as characters and figures to be printed, input related to various operations including execution of printing, and selection of other functions and settings. Note that input of print contents to the printing device 10 may be performed using a storage medium such as a memory card, or communication with an external device.

[0017] The display device 13 is equipped with a display means such as a liquid crystal display panel, and displays characters and figures corresponding to input to the input unit 12, displays a selection menu for various settings, displays messages related to various processes, displays the progress of the printing process, etc. The display device 13 may be of a type capable of receiving input (such as a touch panel input type) and may have the function of the input unit 12.

[0018] The opening / closing lid 14 is attached to the device housing 11 so as to be openable and closable. A cassette storage section 15 (see FIG. 2) that is covered by the opening / closing lid 14 in the closed state is provided inside the device housing 11. The internal structure of the cassette storage section 15 will be described later. The opening / closing lid 14 can be locked in the closed state, and by pressing a release button 16, the lock is released and the opening / closing lid 14 is opened.

[0019] An outlet 17 (see FIG. 2) that leads to the cassette storage section 15 is formed on the side of the device housing 11. The tape 20 that has been printed inside the printer 10 is discharged to the outside of the printer 10 through the outlet 17.

[0020] 2 shows the tape cassette 21 stored in the cassette storage unit 15 of the printing device 10. The tape cassette 21 includes a tape core 23 inside a box-shaped cassette case 22, and a roll-shaped tape 20 is supported by the tape core 23.

[0021] A thermal head 30 is provided inside the cassette storage section 15. The thermal head 30 has a plurality of heating elements 30a (see FIG. 3) whose heat generation is controlled when printing on the tape 20. A thermistor 31 (see FIG. 3) is embedded in the thermal head 30 as a head temperature measurement section that measures temperature. In addition, a platen roller 32 and a tape core engagement shaft 33 are provided inside the cassette storage section 15.

[0022] Further provided inside the cassette storage section 15 are a plurality of cassette receiving sections 34 for supporting the tape cassette 21 in a predetermined position, and a tape width detection switch 35 (see FIG. 3) for detecting the width of the tape 20 contained in the tape cassette 21. The tape width detection switch 35 is a detection section that detects the width of the tape 20 based on the shape of the tape cassette 21.

[0023] A full cutter 36 and a half cutter 37 for cutting the tape 20 widthwise are provided near the discharge port 17 of the device housing 11. The full cutter 36 cuts the entire thickness of the tape 20, including the release paper. The half cutter 37 cuts the tape 20 while leaving the release paper.

[0024] When the tape cassette 21 is stored in the cassette storage section 15, the tape core 23 of the tape cassette 21 engages with the tape core engagement shaft 33, and the tape 20 pulled out from the tape core 23 passes between the thermal head 30 and the platen roller 32. When the opening / closing lid 14 is closed, the thermal head 30 approaches the platen roller 32, and the tape 20 is sandwiched between the thermal head 30 and the platen roller 32.

[0025] When a command to execute printing is input to the printer 10, the platen roller 32 is rotated and the tape 20 is unwound and conveyed from the tape core 23. Then, when the tape 20 passes between the thermal head 30 and the platen roller 32, the color-developing layer of the tape 20 develops color in the portion heated by the thermal head 30 and is printed.

[0026] The printed tape 20 that has passed between the thermal head 30 and the platen roller 32 is cut (full cut or half cut) by the full cutter 36 or half cutter 37 and is discharged from the discharge port 17 to the outside of the cassette storage section 15.

[0027] 3 is a block diagram showing the hardware structure of the printing device 10. This block diagram includes the above-mentioned input unit 12, display device 13, thermal head 30, thermistor 31, platen roller 32, tape width detection switch 35, full cutter 36, and half cutter 37. The printing device 10 further includes a control device 40, a ROM (Read Only Memory) 41, a RAM (Random Access Memory) 42, a display device drive circuit 43, a head drive circuit 44, a conveyance motor drive circuit 45, a stepping motor 46, a cutter motor drive circuit 47, a cutter motor 48, and a temperature sensor 49.

[0028] The control device 40 includes a processor 40a such as a CPU (Central Processing Unit). The control device 40 reads out a program stored in a ROM 41, expands it in a RAM 42, and executes it to control the operation of each part of the printing device 10. A series of controls and processes related to anti-sticking measures, which will be described later, are also performed based on the program stored in the ROM 41. At least the control device 40, the ROM 41, and the RAM 42 constitute the computer of the printing device 10.

[0029] The ROM 41 stores a print program for printing on the tape 20 and various data (e.g., fonts, energization tables, etc.) required to execute the print program. The RAM 42 includes a print data storage unit 42a (see FIG. 5) that stores print data indicating a pattern (image) of the print content.

[0030] The display device drive circuit 43 includes a display driver that drives the display device 13. The print contents based on the print data stored in the RAM 42, the progress of the print process, and the like are displayed on the display device 13 under the control of the display device drive circuit 43.

[0031] The head drive circuit 44 is a head drive unit that drives the thermal head 30 based on a strobe signal, which is a control signal, print data, and countermeasure data supplied from the control device 40. The head drive circuit 44 applies or removes electricity to the multiple heating elements 30a.

[0032] The thermal head 30 is a print head having a plurality of heating elements 30a arranged in a main scanning direction (see FIG. 6), which is also the width direction of the tape 20. The head drive circuit 44 selectively applies voltage to the plurality of heating elements 30a of the thermal head 30 in accordance with the print data or countermeasure data during a period of energization control of a strobe signal supplied from the control device 40, causing the heating elements 30a at locations specified by the print data or countermeasure data to generate heat.

[0033] The tape 20 is transported to the position of the thermal head 30 by moving in the sub-scanning direction, with its length oriented in a sub-scanning direction (see FIG. 6) perpendicular to the main scanning direction. Then, by controlling the heat generation of each heating element 30a of the thermal head 30 while transporting the tape 20 in the sub-scanning direction, the thermal head 30 prints on the tape 20 dot groups each consisting of a plurality of dots corresponding to the plurality of heating elements 30a. In other words, a plurality of dot groups are printed sequentially on the tape 20 by changing the relative positions of the thermal head 30 and the tape 20 in the sub-scanning direction and controlling the heat generation of each heating element 30a of the thermal head 30.

[0034] The transport motor drive circuit 45 drives the stepping motor 46, which rotates the platen roller 32. The platen roller 32 rotates by the power of the stepping motor 46, transporting the tape 20 in the longitudinal direction (sub-scanning direction). By counting the number of pulses input to the stepping motor 46, information regarding the transport amount of the tape 20 can be obtained.

[0035] The cutter motor drive circuit 47 drives the cutter motor 48. The full cutter 36 and the half cutter 37 are operated by the power of the cutter motor 48 to fully cut or half cut the tape 20.

[0036] The temperature sensor 49 is an environmental temperature measuring unit that measures the temperature around the printing device 10 as the environmental temperature.

[0037] When printing is performed with the printer 10, if a sudden temperature change (temperature drop) occurs in the thermal head 30 from a high temperature state to a low temperature state, sticking, a phenomenon in which the thermal head 30 sticks to the tape 20, may occur. Such a sudden drop in temperature in the thermal head 30 is likely to occur when the print content suddenly switches from a dot group with a high print rate (a large number of heat generating elements 30a) to a dot group with a low print rate (a small number of heat generating elements 30a). In other words, sticking is likely to occur when printing a boundary part where the print rate suddenly decreases between dot groups adjacent or close to each other in the sub-scanning direction.

[0038] The printer 10 also supports multi-tone printing, which prints at three or more different densities for each printing area (dot) corresponding to each heating element 30a of the thermal head 30. The higher the printing density in each printing area, the more electricity is supplied to the heating elements 30a, and the higher the temperature of the thermal head 30 tends to be. Therefore, in addition to the printing rate in the dot group, the printing density of each dot also relates to the occurrence of sticking. Specifically, sticking is likely to occur when the printing content suddenly switches from a dot group with a high printing density to a dot group with a low printing density.

[0039] In the printing device 10, the occurrence of sticking is suppressed by controlling the energization of the heating elements 30a of the thermal head 30. Specifically, within one dot period corresponding to each dot group, a first energization control period for printing on the tape 20 and a second energization control period for adjusting the temperature change of the thermal head 30 without printing on the tape 20 are set, and energization and de-energization of the heating elements 30a during the first energization control period and the second energization control period are controlled.

[0040] FIG. 4 is a diagram showing an example of energization control of one dot period T of each heating element 30a of the thermal head 30 corresponding to multi-tone printing. The first energization control period TA includes a plurality of energization times P1-P7. In each energization time P1-P7, ON means energization, and OFF means non-energization. The number of energizations corresponds to the gradation of the print, and the maximum gradation density is obtained when energization is performed for all energization times P1-P7. As the number of energizations decreases, the print density becomes lighter (the gradation becomes lower), and when energization is performed only for the minimum number of energizations, printing is performed at the lightest density. Also, when no current is applied for all energization times P1-P7, a non-printing area (white dots) where no printing is performed is obtained. In other words, the energization control in FIG. 4 illustrates a case where printing is performed at the maximum gradation (highest density) in the thermal head 30 capable of eight gradation expressions from non-printing to the maximum gradation.

[0041] The second energization control period TB is a period for adjusting the temperature change of the thermal head 30 without printing on the tape 20, and is set as a period spaced later than the first energization control period TA. When no current is applied during the first energization control period TA or when the current application time is short (the number of times current is applied is small), the heating element 30a is energized (ON) during the current application time P8 during the second energization control period TB, thereby suppressing the temperature drop of the heating element 30a. In this way, the printing device 10 suppresses the occurrence of sticking by utilizing the application of a voltage to the thermal head 30 during the second energization control period TB, and the details thereof will be described below.

[0042] Fig. 5 is a block diagram showing the functional structure of the printing device 10 with respect to suppressing the occurrence of sticking. Fig. 5 mainly shows the functional structure of the control device 40 included in the printing device 10. The control device 40 includes a determination unit 50, a data generation unit 60, and a head control unit 70. Note that the control device 40 does not necessarily include individual electronic components and circuits corresponding to each functional block shown in Fig. 5, and there are cases where a specific electronic component or circuit has the role of multiple functional blocks, or where multiple electronic components and circuits work together to form one functional block.

[0043] The determination unit 50 determines whether or not a second dot group subsequent to a first dot group (a dot period a predetermined number of times after the first dot group) is a dot group likely to cause sticking (hereinafter, referred to as a sticking occurrence estimated dot group) based on print data including a plurality of dot group data corresponding to each of a plurality of dot groups printed by the thermal head 30. A dot group likely to cause sticking is a dot group that may cause a sudden drop in temperature of the thermal head 30. The print data used by the determination unit 50 is read from the print data storage unit 42a of the RAM 42. In this embodiment, a case where the first dot group and the second dot group are two consecutive dot groups will be described as an example, and the first dot group will be represented as the (n-1)th dot group, and the second dot group will be represented as the nth dot group (n is an integer of 2 or more).

[0044] The determination unit 50 includes a preceding dot group determination unit 51 and a comparison unit 52. The preceding dot group determination unit 51 determines whether the dot group data of the (n-1)th dot group immediately preceding the nth dot group meets a predetermined condition. The comparison unit 52 compares the dot group data of the (n-1)th dot group with the dot group data of the nth dot group to determine whether the relationship between these two dot groups meets a predetermined condition. Then, when both the preceding dot group determination unit 51 and the comparison unit 52 determine that the predetermined condition is met, the determination unit 50 determines that the nth dot group is an estimated dot group where sticking occurs.

[0045] More specifically, the preceding dot group determination unit 51 determines whether the ratio of the printed area of ​​the first density or more in the (n-1)th dot group is equal to or more than the first threshold value. For example, it is desirable to set the highest density maximum gradation among the multiple gradations of printing (for example, 8 gradations realized by the power supply control in FIG. 4) as the first density. It is also desirable to set two-thirds of the entire printed area in the width direction (main scanning direction) of the tape 20 as the first threshold value. In other words, when the printed area of ​​the maximum gradation (the number of dots printed at the maximum gradation) is two-thirds or more of the printed area in the width direction of the tape 20 (the total number of dots constituting one dot group), the preceding dot group determination unit 51 determines that the dot group data of the (n-1)th dot group meets the first condition for the occurrence of sticking. For the printed area in the width direction of the tape 20, in addition to the dot group data, information on the tape width detected by the tape width detection switch 35 may be referenced.

[0046] The first condition determined by the preceding dot group determination unit 51 is related to how high the temperature of the thermal head 30 becomes when printing the (n-1)th dot group. If the first condition is met, it is estimated that the temperature of the thermal head 30 will become high because the printing rate at high gradations is high in the (n-1)th dot group.

[0047] The comparison unit 52 determines whether the ratio between the printing area of ​​the (n-1)th dot group having a first density or more and the printing area of ​​the nth dot group having a second density or more lower than the first density is equal to or more than a second threshold value. For example, it is preferable to set the printing area of ​​the second density to a non-printing area (white dots). It is also preferable to set the second threshold value to 1.5 times. In other words, when the printing area of ​​the maximum gradation of the (n-1)th dot group (the number of dots printed at the maximum gradation) is 1.5 times or more compared to the printing area of ​​the nth dot group other than the non-printing area (the number of dots printed at any density from the minimum gradation to the maximum gradation), the comparison unit 52 determines that the relationship between the dot group data of the (n-1)th dot group and the dot group data of the nth dot group meets the second condition for the occurrence of sticking.

[0048] The second condition determined by the comparison unit 52 relates to the degree to which the temperature of the thermal head 30 drops when switching from printing the (n-1)th dot group to printing the nth dot group. If the second condition is met, the printing level obtained by multiplying the printing rate and gradation in the (n-1)th dot group is significantly higher than the printing level obtained by multiplying the printing rate and gradation in the nth dot group, and it is estimated that the temperature drop of the thermal head 30 will be significant.

[0049] If both the first and second conditions are met, it is estimated that when printing shifts from the (n-1)th dot group to the nth dot group, the temperature of the thermal head 30 drops rapidly from a high state, making it easy for sticking to occur. Therefore, when the preceding dot group determination unit 51 and the comparison unit 52 determine that the first and second conditions are met, the determination unit 50 determines that the nth dot group is a dot group estimated to cause sticking.

[0050] In this way, by making a judgment based on two dot group data corresponding to two dot groups printed adjacent to each other, it is possible to predict the sudden temperature change that occurs between two dot groups printed adjacent to each other and determine the dot group where sticking is likely to occur. In particular, by making a judgment based not only on the printing rate of each dot group but also on the gradation information of the printing area, it is possible to estimate the temperature change of the thermal head 30 with high accuracy, and it is possible to obtain the effect of minimizing the implementation of sticking countermeasures.

[0051] In this embodiment, the first density print area is the maximum gradation print area, the second density print area is the non-print area, and the difference in gradation at which the most rapid temperature drop is likely to occur between the (n-1)th dot group and the nth dot group is used as the criterion for judgment, but it is also possible to set the first density and the second density as densities of intermediate gradations among multiple gradations. In other words, it is sufficient to satisfy the relationship that the second density is at least a lower print density (gradation) than the first density.

[0052] Furthermore, in the comparison between the (n-1)th dot group and the nth dot group by the comparison unit 52, the comparison judgment may be made based on the gradation difference rather than the absolute value of the gradation (specified print density). That is, the second condition for the occurrence of sticking may be set based on the number of dots with a gradation difference of a predetermined level or more between the (n-1)th dot group and the nth dot group. As an example, in printing with eight gradations from 0 (non-printed) to 7 (maximum gradation), when the number of dots in the nth dot group that is m gradations or more (m is an integer of 7 or less) lower than the (n-1)th dot group is p (p is any integer) or more, the comparison unit 52 judges that the second condition for the occurrence of sticking is met.

[0053] Furthermore, the first threshold value (two-thirds in this embodiment) and the second threshold value (1.5 times in this embodiment) in the above judgment by the judgment unit 50 are merely examples and may be different values. For example, these values ​​may be changed based on the environmental temperature measured by the temperature sensor 49. In general, the lower the environmental temperature, the greater the temperature difference between when the heating element is generating heat and when it is not generating heat, and sticking is more likely to occur. Therefore, when changing the settings based on the environmental temperature, it is desirable to lower the first threshold value and the second threshold value as the environmental temperature decreases.

[0054] The determination unit 50 outputs data for identifying the sticking occurrence estimated dot group (hereinafter, referred to as sticking occurrence estimated dot group data) to the data generation unit 60.

[0055] The data generation unit 60 generates countermeasure data that specifies whether or not current is applied to the multiple heating elements 30a during the second current control period TB based on the printing data read out from the printing data memory unit 42a of the RAM 42 and the sticking occurrence estimated dot group data generated by the judgment unit 50.

[0056] In the printing device 10, during a period in which a temperature drop that is likely to cause sticking is expected, the heating elements 30a are heated based on countermeasure data, which is data separate from the print data, to suppress a sudden drop in temperature of the thermal head 30 and suppress the occurrence of sticking. The data generating unit 60 generates countermeasure data based on the print data so that a voltage is applied to at least some of the heating elements 30a during the second current control period TB in the sticking countermeasure target dot group set that includes the sticking occurrence estimated dot group (nth dot group).

[0057] The data generating unit 60 includes a dot group number setting unit 61. The dot group number setting unit 61 sets the number of dot groups included in the countermeasure target dot group set to which a voltage is applied to the heating element 30a during the second energization control period TB according to the countermeasure data. More specifically, the dot group number setting unit 61 sets at least the sticking occurrence estimated dot group (nth dot group) to the sticking countermeasure target dot group set based on the print data. More preferably, the dot group number setting unit 61 sets the sticking occurrence estimated dot group (nth dot group) and a predetermined number (at least one) of subsequent dot groups printed consecutively from the sticking occurrence estimated dot group to the countermeasure target dot group set based on the print data.

[0058] The dot group number setting unit 61 may set the number of dot groups included in the sticking prevention target dot group set based on the environmental temperature detected by the temperature sensor 49. In general, the lower the environmental temperature, the more likely sticking occurs. Therefore, when setting based on the environmental temperature, it is desirable to increase the number of dot groups included in the sticking prevention target dot group set as the environmental temperature decreases, thereby suppressing a sudden drop in temperature caused by a drop in the environmental temperature. This makes it possible to suppress the occurrence of sticking regardless of the environment in which the printing device 10 is placed. On the other hand, sticking is less likely to occur in an environment where the environmental temperature is relatively high. Therefore, when the environmental temperature is higher than a preset threshold value (for example, 40°C), only the sticking occurrence estimated dot group (n-th dot group) may be set as the sticking prevention target dot group set.

[0059] The dot group number setting unit 61 may also set the number of dot groups included in the sticking countermeasure target dot group set based on the print data. For example, in the dot group following the sticking occurrence estimated dot group (nth dot group), if a voltage is applied to a sufficient number of heating elements 30a during the first energization control period TA, it can be determined that the temperature does not decrease in the dot group following the sticking occurrence estimated dot group (nth dot group), and energization control during the second energization control period TB can be omitted. Therefore, the dot group number setting unit 61 may calculate how many low print rate dot groups with low print rates are consecutively lined up after the sticking occurrence estimated dot group (nth dot group) based on the print data, and set the number of dot groups to be included in the sticking countermeasure target dot group set based on the calculated number of consecutive low print rate dot groups.

[0060] The data generating section 60 further includes a pattern setting section 62. The pattern setting section 62 sets the pattern of each of the countermeasure data for each dot group included in the sticking countermeasure target dot group set.

[0061] FIG. 6 is a diagram for explaining a method for determining a dot group where sticking is estimated to occur and a method for setting a pattern of countermeasure data. FIG. 6 shows an example in which each dot Q1-Q8, which is a printing area corresponding to each heating element 30a of the thermal head 30, can be printed in three gradations: maximum gradation (dark), intermediate gradation (light), and non-printing (white). The main energization data is a part of the print data, and is print data indicating a print pattern to be formed in the dot group where printing is performed during the first energization control period TA. In FIG. 6, in the main energization data, a black circle indicates a case where the heating element 30a is heated corresponding to the density of the maximum gradation, a gray circle indicates a case where the heating element 30a is heated corresponding to the density of the intermediate gradation, and a white circle indicates a case where the heating element 30a is not heated and non-printing is performed. In addition, in the countermeasure data regarding energization during the second energization control period TB, the cases where energization is performed on the heating element 30a are indicated by hatched circles, and the cases where energization is not performed on the heating element 30a are indicated by dashed white circles.

[0062] The determination unit 50 determines whether the n-th dot group, which is the second dot group, corresponds to a dot group estimated to cause sticking. For example, the first condition for sticking occurrence in the preceding dot group determination unit 51 is set to "the number of dots with the maximum gradation in the (n-1)-th dot group is more than two-thirds of the total number of dots in the width direction of the tape 20". In addition, the second condition for sticking occurrence in the comparison unit 52 is set to "the number of dots with the maximum gradation in the (n-1)-th dot group is more than 1.5 times the number of dots other than non-printed dots in the n-th dot group".

[0063] In the example of FIG. 6, in the main energization data for the (n-1)th dot group, which is the first dot group, the number of dots with the maximum gradation is 6, and the total number of dots in the width direction of the tape 20 is 8, so the first condition is met. Also, in the main energization data for the (n-1)th dot group, the number of dots with the maximum gradation is 6, and in the main energization data for the nth dot group, the number of dots other than non-printed dots is 2, so the second condition is met. Therefore, the determination unit 50 determines that the nth dot group is a sticking occurrence estimated dot group. Then, sticking occurrence estimated dot group data for the nth dot group is sent from the determination unit 50 to the data generation unit 60.

[0064] Fig. 6 shows that the positions of the (n-1)th dot group, the nth dot group, the (n+1)th dot group, and the (n+2)th dot group are different in the sub-scanning direction. The main energization data and countermeasure data for each dot group are data for the same printing area in the sub-scanning direction, and for convenience, the main energization data and countermeasure data for each dot group are shown separately in Fig. 6.

[0065] The dot group number setting unit 61 of the data generation unit 60 sets the nth dot group determined to be a dot group estimated to cause sticking, and the (n+1)th dot group and the (n+2)th dot group, which are the two subsequent dot groups following the nth dot group, as a dot group set subject to sticking countermeasures.

[0066] The pattern setting unit 62 generates countermeasure data for the print area (heating element 30a) of interest such that when the main energization data in the (n-1)th dot group corresponds to the maximum gradation and the main energization data in each dot group (n, n+1, n+2) of the sticking countermeasure target dot group set is non-printing (non-energization), energize the heat element 30a in the second energization control period TB. That is, the countermeasure data is generated so that, among the multiple heat elements 30a, the heat element 30a corresponding to the print area having a first density or more in the (n-1)th dot group and a second density or less in each dot group of the sticking countermeasure target dot group set is energized in the second energization control period TB.

[0067] For example, for dot Q1, the current energization data corresponds to the maximum gradation for both the (n-1)th dot group and each of the dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set. Therefore, since a sudden drop in temperature of the heating element 30a does not occur in the sticking countermeasure target dot group set (n, n+1, n+2), the pattern setting unit 62 does not include dot Q1 in the targets of energization during the second energization control period TB for all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set.

[0068] For dot Q2, the main energization data corresponds to the maximum gradation in the (n-1)th dot group and the (n+1)th dot group, and corresponds to an intermediate gradation in the nth dot group and the (n+2)th dot group. In other words, since it is estimated that the dot group next to dot Q2 printed at the maximum gradation will not be unprinted and a sudden drop in temperature will not occur in the heating element 30a, the pattern setting unit 62 does not include dot Q2 in the targets of energization during the second energization control period TB in all dot groups (n, n+1, n+2) of the sticking countermeasure target dot group set.

[0069] For dots Q3 and Q4, the main energization data corresponds to the maximum gradation in the (n-1)th dot group, and the main energization data corresponds to non-printing (non-energization) in the nth dot group and the (n+1)th dot group. Since it is estimated that the gradation difference between the (n-1)th dot group and the nth dot group is large and a sudden temperature drop is likely to occur in the heating element 30a, the pattern setting unit 62 includes dots Q3 and Q4 as targets for energization during the second energization control period TB for the nth dot group and the (n+1)th dot group.

[0070] In the (n+2)th dot group, the main energization data for dots Q3 and Q4 corresponds to a halftone. Since the possibility of sticking is reduced by generating heat from the heating element 30a for printing halftones, the pattern setting unit 62 does not include dots Q3 and Q4 in the energization targets for the second energization control period TB for the (n+2)th dot group.

[0071] For dots Q5 and Q6, the main energization data in the (n-1)th dot group corresponds to the maximum gradation, and the main energization data in all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set is non-printing (non-energized). Therefore, this is a condition in which a sudden drop in temperature of the heating element 30a is likely to occur, and the pattern setting unit 62 includes dots Q5 and Q6 in all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set as targets for energization during the second energization control period TB.

[0072] For dot Q7, the main energization data in the (n-1)th dot group corresponds to a halftone, and the main energization data in the first energization control period TA in all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set is non-printed (non-energized). For dot Q7, the (n-1)th dot group immediately preceding the non-printed nth dot group is printed in a halftone, and it is estimated that the heating element 30a does not become very hot when printing the (n-1)th dot group, and there is no sudden drop in temperature thereafter. Therefore, the pattern setting unit 62 does not include dot Q7 in the targets of energization in the second energization control period TB in all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set.

[0073] For dot Q8, the main energization data is non-printing (non-energized) in the (n-1)th dot group and all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set. Therefore, no sudden temperature drop occurs in the heating element 30a, and the pattern setting unit 62 does not include dot Q8 in the energization target for the second energization control period TB in all dot groups (n, n+1, n+2) in the sticking countermeasure target dot group set.

[0074] In this manner, countermeasure data for each dot group is generated by the pattern setting unit 62. To summarize the pattern setting of countermeasure data by the pattern setting unit 62, for each dot group (n, n+1, n+2) in the sticking countermeasure target dot group set, countermeasure data is generated so that current is applied to the heating element 30a during the second current application control period TB for a print area that is printed at maximum gradation in the previous dot group and is non-printed in the line.

[0075] To summarize the pattern setting of the countermeasure data by the pattern setting unit 62 in another aspect, in the nth dot group, the heating element 30a is energized in the second energization control period TB, and in the subsequent dot group, for the printing area where the density is less than the second density, the heating element 30a is energized in the second energization control period TB. Specifically, this applies to the dots Q3 to Q6 in the (n+1)th dot group and the dots Q5 and Q6 in the (n+2)th dot group. Also, in the nth dot group, the heating element 30a is energized in the second energization control period TB, and in the subsequent dot group, for the printing area where the density exceeds the second density, the heating element 30a is not energized in the subsequent dot group. Specifically, this applies to the dots Q3 and Q4 in the (n+2)th dot group.

[0076] For dots whose main energization data is the maximum gradation, energizing the heating element 30a based on the countermeasure data after printing at the maximum gradation during one dot period does not noticeably change the print expression of the dot that has already been printed at the maximum gradation, and does not substantially affect the print quality. On the other hand, for dots whose main energization data is an intermediate gradation, energizing the heating element 30a based on the countermeasure data during one dot period may affect the print quality by making the dot darker than the original print gradation due to heating by the heating element 30a.

[0077] In generating countermeasure data in the pattern setting unit 62 of this embodiment, for dots for which the main energization data in the first energization control period TA corresponds to a middle gradation, the heating elements 30a are de-energized in the second energization control period TB. As a result, energization of the heating elements 30a for the anti-sticking measure in the second energization control period TB is prevented from affecting print quality, and it is possible to achieve both anti-sticking measures and high print quality in multi-tone printing.

[0078] In the example of Figure 6, no current is applied to the (n-1)th dot group during the second current control period TB, but the dot group number setting unit 61 may include the (n-1)th dot group in the dot group set subject to sticking countermeasures, and the pattern setting unit 62 may generate countermeasures data for the (n-1)th dot group.

[0079] For example, for dots Q3, Q4, Q5, and Q6 in Fig. 6, after energizing the heating elements 30a in the first energization control period TA by the main energization data in the (n-1)th dot group, a period of one dot period or more is required before energizing the heating elements 30a in the second energization control period TB by the countermeasure data in the nth dot group. Therefore, by energizing the heating elements 30a in the second energization control period TB by the countermeasure data in the (n-1)th dot group, it becomes easier to suppress a sudden temperature drop of the heating elements 30a between the (n-1)th dot group and the nth dot group.

[0080] The data generating unit 60 outputs the countermeasure data generated as described above to the head control unit 70.

[0081] The head control unit 70 generates a strobe signal, which is a control signal that specifies energization and non-energization during the first energization control period TA and the second energization control period TB, and outputs it to the head drive circuit 44. More specifically, the head control unit 70 calculates the energization time during the first energization control period TA (e.g., each of energization times P1-P7 in FIG. 4) and the energization time during the second energization control period TB (e.g., energization time P8 in FIG. 4) based on the energization time data read from the energization table stored in the ROM 41 and the head temperature measured by the thermistor 31. Then, the head control unit 70 outputs a strobe signal (control signal) according to the energization time, the print data, and the countermeasure data generated by the data generation unit 60 to the head drive circuit 44.

[0082] According to the printing device 10 configured and controlled as described above, by controlling the power supply to the heating elements 30a during the second power supply control period TB based on the countermeasure data, it is possible to suppress a sudden drop in temperature of the thermal head 30. Therefore, the occurrence of sticking can be suppressed with simple control, and a decrease in print quality due to sticking can be avoided.

[0083] In particular, the determination unit 50 determines the sticking occurrence estimated dot group based on the above first and second conditions, so that it is possible to isolate the situation where sticking occurs with high accuracy. As a result, it is possible to minimize the implementation of sticking occurrence countermeasures (energization of the heating element 30a in the second current control period TB). By minimizing the implementation of sticking occurrence countermeasures, it is possible to obtain the effect of suppressing power consumption.

[0084] In addition, in the conventional control method, even in a situation where no sticking prevention measures are required, there are cases where the heating elements are energized during the second energization control period TB. The energization of the heating elements during the second energization control period TB is intended to adjust the temperature of the thermal head without printing, but since heating the heating elements may affect the print quality, it is desirable to avoid unnecessary sticking prevention measures as much as possible. In particular, in a printing device capable of printing in multiple gradations of three or more, if energization for sticking prevention measures is performed following printing in intermediate gradations, the print density may become higher than the original print data.

[0085] In the printing device 10 of this embodiment, the implementation of countermeasures against sticking is minimized based on the judgment of the judgment unit 50, and the data generation unit 60 (pattern setting unit 62) generates countermeasure data with settings that do not affect gradation expression (when the main current application data prints in intermediate gradations, no current is applied for anti-sticking measures). This prevents the countermeasures against sticking from affecting gradation expression, achieving excellent print quality.

[0086] Fig. 7 is a flowchart of the sticking countermeasure processing in the printing device 10. Fig. 8 is a flowchart of the process of determining a sticking occurrence estimated dot group, which is included in the sticking countermeasure processing. The flow of the sticking countermeasure performed by the printing device 10 will be described with reference to Figs. 7 and 8.

[0087] When print data is input, the control device 40 of the printing device 10 starts the sticking countermeasure process shown in Fig. 7. First, a process of determining a sticking occurrence estimated dot group (step S100) is executed.

[0088] The process of determining the sticking occurrence estimated dot group is executed by the subroutine shown in Fig. 8. The determination unit 50 counts the data "0xff" indicating eight consecutive print dots included in the dot group data of each dot group of the print data, and obtains the number of dots in one dot group (the number of 0xff) (step S200).

[0089] Next, the preceding dot group determination unit 51 of the determination unit 50 determines whether the ratio of the number of dots with a first density or more in the (n-1)th dot group immediately preceding the nth dot group is equal to or greater than a first threshold value (step S201). For example, the number of dots with the maximum gradation in the (n-1)th dot group is compared with the total number of dots in the (n-1)th dot group to determine whether the number of dots in the former is equal to or greater than two-thirds of the number of dots in the latter (first threshold value).

[0090] If the result of the determination in step S201 is YES (first threshold or more), the comparison unit 52 of the determination unit 50 determines whether the ratio of the printed area of ​​the (n-1)th dot group having a first density or more to the printed area of ​​the nth dot group having a second density or more lower than the first density is a second threshold or more (step S202). For example, the number of dots of the maximum gradation in the (n-1)th dot group is compared with the number of dots other than non-printed dots in the nth dot group to determine whether the number of dots of the former is 1.5 times the number of dots of the latter (second threshold) or more.

[0091] If the result of the determination in step S202 is YES (greater than or equal to the second threshold), the determining unit 50 sets a flag indicating that the n-th dot group is a dot group in which sticking is likely to occur (step S203).

[0092] Next, the control device 40 determines whether the n-th dot group is the final dot group of the print data (step S204).

[0093] If the determination results in steps S202 and S203 are NO, the process skips the flag setting in step S203 and proceeds directly to step S204. In other words, in these cases, the n-th dot group is determined to not be a sticking occurrence estimated dot group.

[0094] If the determination result in step S204 is NO (not the final dot group), the control device 40 performs a dot group update process to increase the number n by 1 (step S205), and returns to step S200.

[0095] If the result of the determination in step S204 is YES (it is the final dot group), the control device 40 exits from the subroutine in Fig. 8 and completes step S100 in Fig. 7. At the completion stage of step S100, each dot group other than the first dot group of the print data has been determined to be a dot group estimated to cause sticking.

[0096] Next, the control device 40 develops the main energization data of the nth dot group (step S101), and determines whether or not a flag is set for the sticking occurrence estimated dot group in the nth dot group into which the main energization data is developed (step S102).

[0097] If the judgment result in step S102 is YES (the nth dot group is a dot group estimated to cause sticking), the data generation unit 60 generates countermeasure data for the dot group set that is the target of sticking countermeasures and includes the nth dot group based on the main current data expanded in step S101 (step S103).

[0098] In step S103, the dot group number setting unit 61 sets the number of dot groups included in the sticking countermeasure target dot group set. In addition, the pattern setting unit 62 creates countermeasure data for each dot group in the sticking countermeasure target dot group set. Specifically, the pattern setting unit 62 generates countermeasure data so that for dots that are printed at the maximum gradation in the previous dot group and are not printed in the current dot group, current is applied to the heating element 30a during the second current application control period TB.

[0099] If the result of the determination in step S102 is NO (the nth dot group is not a dot group estimated to have sticking), no new countermeasure data is created for the nth dot group, and existing countermeasure data is applied (step S104). In other words, if the nth dot group is included in the dot group set that is the target of sticking countermeasures for the dot group prior to that, the countermeasure data for the nth line that has already been created is applied as is, and combined with the main energization data, it is determined as the final dot group data for the nth dot group. Also, if the nth dot group is not included in the dot group set that is the target of sticking countermeasures for the dot group prior to that, there is no countermeasure data for the nth dot group (in other words, the countermeasure data is that no current is applied to any of the heating elements 30a during the second energization control period TB), so the main energization data is determined as the final dot group data for the nth dot group.

[0100] Following step S103 or step S104, the control device 40 determines whether or not the n-th dot group is the final dot group of the print data (step S105).

[0101] If the result of the determination in step S105 is NO (not the final dot group), a dot group update process is performed to increase the number n by 1 (step S106), and the process returns to step S101.

[0102] If the determination result in step S105 is YES (this is the final dot group), the process of Fig. 7 is completed. At the stage when the process of Fig. 7 is completed, the dot group data including the countermeasure data has been finalized for each dot group of the print data.

[0103] By performing the process according to the above flowchart, it is possible to minimize the implementation of measures to prevent sticking, thereby suppressing the impact of the measures on print quality and reducing the power consumption required for the measures to prevent sticking.

[0104] Although the printing device 10 of the above embodiment is capable of printing in three or more tones, the present invention is also applicable to printing devices that print in two tones.

[0105] A method for determining a sticking occurrence estimated dot group and a method for setting a pattern of countermeasure data in a different printing device that prints in two gradations will be described with reference to Fig. 9. This different printing device has a similar configuration to the printing device 10 of the above embodiment, and detailed descriptions of the configuration of each part are omitted and the same reference numerals as the configuration of the printing device 10 are used.

[0106] 9, in the power supply data, the cases where the heating element 30a is heated to print are indicated by black circles, and the cases where the heating element 30a is not heated to print are indicated by white circles. In the countermeasures data, the cases where the heating element 30a is energized are indicated by diagonally shaded circles, and the cases where the heating element 30a is not energized are indicated by dashed white circles.

[0107] In the case of printing in two gradations, the determination unit 50 treats the printed areas in the main energization data as a first density print area, and the non-printed areas as a second density print area. Therefore, the determination unit 50 sets the first condition for the occurrence of sticking in the preceding dot group determination unit 51 to "the number of printed dots in the (n-1)th dot group is at least two-thirds of the total number of dots in the width direction of the tape 20". In addition, the determination unit 50 sets the second condition for the occurrence of sticking in the comparison unit 52 to "the number of printed dots in the (n-1)th dot group is at least 1.5 times the number of dots other than the non-printed dots in the nth dot group".

[0108] 9, the number of dots to be printed in the main energization data for the (n-1)th dot group is 6, and the total number of dots in the width direction of the tape 20 is 8, so the first condition is met. Also, the number of dots to be printed in the main energization data for the (n-1)th dot group is 6, and the number of dots other than non-printed dots in the main energization data for the nth dot group is 2, so the second condition is met. Therefore, the determination unit 50 determines that the nth dot group is a dot group estimated to be subject to sticking.

[0109] By performing the above-described determination of the sticking occurrence estimated dot group by the determination unit 50, it is possible to obtain the effect of minimizing the implementation of measures against sticking occurrence.

[0110] The dot group number setting unit 61 of the data generation unit 60 sets the nth dot group determined to be a dot group estimated to cause sticking, and the (n+1)th dot group and the (n+2)th dot group, which are the two dot groups subsequent to the nth dot group, as a dot group set subject to sticking countermeasures.

[0111] The pattern setting unit 62 generates countermeasure data for the nth dot group for the printing area (heating element 30a) of interest so that when the main current flow data for the (n-1)th dot group is printing and the main current flow data for the nth dot group is non-printing (non-current flow), current is flowed during the second current flow control period TB.

[0112] Furthermore, the pattern setting unit 62 applies the same countermeasure data as the countermeasure data for the nth dot group to the (n+1)th dot group and the (n+2)th dot group, which are dot groups subsequent to the nth dot group.

[0113] The main energization data for the (n+2)th dot group is different from the main energization data for the nth dot group and the (n+1)th dot group, and is for printing dots Q3 and Q4 in addition to dots Q1 and Q2. Therefore, in the (n+2)th dot group, after main energization in the first energization control period TA, countermeasure energization in the second energization control period TB is performed for dots Q3 and Q4. In the case of two-tone printing, for dots for which the main energization data is printed, even if the heating element 30a is energized based on countermeasure data during the same one dot period, the print expression of the dots that have already been printed does not change noticeably. Therefore, even if the countermeasure data for the (n+2)th dot group is the same as the countermeasure data for the nth dot group and the (n+1)th dot group, it does not substantially affect the print quality. Furthermore, by sharing the countermeasure data for each dot group of the sticking countermeasure target dot group set, the processing load for generating countermeasure data can be reduced.

[0114] The above-described embodiment is a specific example shown to facilitate understanding of the invention, and the present invention is not limited to this embodiment. Various modifications and changes are possible without departing from the gist of the invention.

[0115] For example, in the above embodiment, the present invention is applied to a thermal printer 10 in which the tape 20 containing a color-developing layer is used as a printing medium, but the present invention can also be applied to a thermal transfer printer in which an ink ribbon conveyed over the tape is heated to cause the ink of the ink ribbon to adhere to the tape. Thermal transfer printers are often used in the two-tone type printers described with reference to FIG. 9.

[0116] The printing device 10 of the above embodiment can print on the tape 20 of a plurality of different tape widths, but the present invention can also be applied to a printing device that prints only on a tape of one fixed tape width. In this case, the number of heating elements of the thermal head is uniquely determined according to the tape width. Therefore, for the second condition for the determination of the sticking occurrence estimated dot group performed by the determination unit, it is also possible to determine the second threshold value not by the ratio between the printing area of ​​the (n-1)th dot group having a first density or more and the printing area of ​​the nth dot group having a second density or more, but by the difference in the number of heating elements corresponding to each of these printing areas. Therefore, in the present invention, the comparison result regarding the second threshold value may be obtained as the ratio of the printing areas of the two dot groups, or may be obtained as the difference in the number of heating elements corresponding to the printing areas of the two dot groups.

[0117] In the above embodiment, the sticking countermeasure control is described based on the case where the preceding first dot group and the following second dot group are consecutive, but the present invention can also be applied when the first dot group and the second dot group are not consecutive, that is, when the second dot group is two or more dot periods after the first dot group. For example, when the second dot group is set in the dot period two dot periods after the first dot group, the (n-1)th dot group in the above embodiment can be read as the (n-2)th dot group to be applicable.

[0118] Furthermore, the printing device and printing method to which the present invention is applied are not limited to the above-described embodiment and modified examples, and may be any device in which sticking may occur. [Explanation of symbols]

[0119] 10:Printing device 15: Cassette storage section 20: Tape (printing medium) 21: Tape cassette 30: Thermal head 30a: Heating element 31: Thermistor 32: Platen roller 40: Control device 40a: Processor 41: ROM 42: RAM 44: Head drive circuit 49: Temperature sensor 50: Judgment section 51: Leading dot group determination unit 52: Comparison section 60: Data generation section 61: Dot group number setting section 62: Pattern setting section 70: Head control section T: 1 dot period TA: First power supply control period TB: Second power supply control period

Claims

1. a thermal head having a plurality of heating elements, the thermal head printing on a print medium for each dot group that is made up of a plurality of dots corresponding to the plurality of heating elements and that is printed based on set print data; A control device; Equipped with The control device includes: In the first dot group, the ratio of the printing area having a predetermined first density or higher is equal to or higher than a first threshold value; and a comparison result between a print area in the first dot group that is printed at a print density equal to or higher than the first density and a print area exceeding a predetermined second density that indicates a print density lower than the first density in a second dot group that indicates a dot group that is printed chronologically subsequent to the first dot group is equal to or higher than a second threshold value; If the above condition is satisfied, a dot group set including at least the second dot group is set as a dot group set to be subjected to sticking countermeasures in which sticking, which is a phenomenon in which the thermal head sticks to the print medium, is likely to occur; a second current control period for preventing the sticking without printing on the print medium, which is set separately from a first current control period for printing on the print medium, and current control of the thermal head is performed based on countermeasure data for currenting at least a part of the plurality of heating elements during the second current control period for each dot group of the sticking countermeasure target dot group set; A printing device comprising:

2. The thermal head is capable of printing in three or more gradations, the first density printing area is a maximum gradation printing area, and the second density printing area is a non-printing area, The control device includes: generating the countermeasure data so as to energize the heating elements during the second energization control period for a print area in which the previous dot group is printed at the maximum gradation and the current is not printed in the current dot group in each dot group of the sticking countermeasure target dot group set; 2. The printing device according to claim 1.

3. 3. The printing apparatus according to claim 1, wherein the first threshold value is two-thirds of the entire printing area of ​​the first dot group.

4. 3. The printing apparatus according to claim 1, wherein the second threshold value is 1.5 times.

5. The control device includes: generating the countermeasure data so as to energize the heating elements among the plurality of heating elements, which correspond to a print area in which the density in the first dot group is equal to or higher than the first density and the density in each dot group in the sticking countermeasure target dot group set is equal to or lower than the second density, during the second energization control period; 3. The printing apparatus according to claim 1, wherein the first and second printing units are arranged in a first direction.

6. The control device includes: The second dot group and a predetermined number of subsequent dot groups printed consecutively from the second dot group are set as the sticking countermeasure target dot group set; In the second dot group, the heating elements are energized during the second energization control period, and in the subsequent dot group, for a printing area having a density equal to or lower than the second density, the heating elements are energized during the second energization control period; generating the countermeasure data so as to energize the heating elements in the second dot group during the second energization control period, and not energize the heating elements in the subsequent dot group during the second energization control period for a printing area in the subsequent dot group that exceeds the second density; 3. The printing apparatus according to claim 1, wherein the first and second printing units are arranged in a first direction.

7. A print control method for controlling a thermal head that has a plurality of heat elements, each of which is a dot group consisting of a plurality of dots corresponding to the plurality of heat elements, and that performs printing on a print medium for each dot group printed based on set print data, comprising: In the first dot group, the ratio of the printing area having a predetermined first density or higher is equal to or higher than a first threshold value; and a comparison result between a print area in the first dot group that is printed at a print density equal to or higher than the first density and a print area exceeding a predetermined second density that indicates a print density lower than the first density in a second dot group that indicates a dot group that is printed chronologically subsequent to the first dot group is equal to or higher than a second threshold value; If the above condition is satisfied, a dot group set including at least the second dot group is set as a dot group set to be subjected to sticking countermeasures in which sticking, which is a phenomenon in which the thermal head sticks to the print medium, is likely to occur; a second current control period for preventing the sticking without printing on the print medium is set separately from a first current control period for printing on the print medium; performing a current control for the thermal head based on countermeasure data for currenting at least a part of the plurality of heating elements in the second current control period for each dot group of the sticking countermeasure target dot group set; A printing control method comprising:

8. A computer mounted on a printing device having a thermal head that has a plurality of heating elements, each of which is a dot group consisting of a plurality of dots corresponding to the plurality of heating elements, and which prints on a printing medium each of the dot groups printed based on set print data, In the first dot group, the ratio of the printing area having a predetermined first density or higher is equal to or higher than a first threshold value; and a comparison result between a print area in the first dot group that is printed at a print density equal to or higher than the first density and a print area exceeding a predetermined second density that indicates a print density lower than the first density in a second dot group that indicates a dot group that is printed chronologically subsequent to the first dot group is equal to or higher than a second threshold value; if the above condition is satisfied, a dot group set including at least the second dot group is set as a dot group set subject to sticking countermeasures in which sticking, which is a phenomenon in which the thermal head sticks to the print medium, is likely to occur; a second current control period for preventing the sticking without printing on the print medium is set separately from a first current control period for printing on the print medium; performing a current control for the thermal head based on countermeasure data for currenting at least a part of the plurality of heating elements in each dot group of the sticking countermeasure target dot group set during the second current control period; A program characterized by:

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