Thermal printer, power-on method, and storage medium

Abstract

The present application relates to a thermal printer, an energization method, and a storage medium, the thermal printer having a plurality of heat generating elements arranged in a prescribed direction, being capable of printing a dot corresponding to each heat generating element in a plurality of gray scales by controlling an energization time or an energization number of times of each heat generating element, the thermal printer having a control mechanism, the control mechanism executing a heat adjustment process, in the heat adjustment process, in a case where there is a heat generating element to which a minimum gray scale value is assigned in a previous print field, for a heat generating element to which a maximum gray scale value is assigned in a current print field, performing energization for a prescribed time in the current print field as a history energization, on the other hand, in a case where there is no heat generating element to which a minimum gray scale value is assigned in the previous print field, omitting the history energization in the current print field, the control mechanism executing the heat adjustment process for each group on the basis of dividing the plurality of heat generating elements into a plurality of groups.

Description

TECHNICAL FIELD

[0001] The present application relates to a thermal printer, a power supply method, and a storage medium. BACKGROUND

[0002] In the past, a thermal printer having a heating element that prints a character by outputting a dot of the character is known. For example, in Japanese Patent Application Laid-Open No. 8-156307, a thermal printer is disclosed in which the number of power supply pulses is selected according to the immediately preceding power supply history at the time of outputting each dot, for the purpose of achieving uniformization of the print character density. SUMMARY

[0003] PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] However, in the technology disclosed in the above-described Patent Document 1, since the power supply history of each dot is observed separately, there is a problem that the amount of heat storage differs depending on the power supply history of the surrounding dots, and the print character density varies. In particular, in the case of performing gradation printing, since the variation in the print character density causes a gradation deviation, it has an influence on the gradation expression.

[0005] The present application has been achieved in view of such a problem, and aims to prevent a gradation deviation due to a difference in the amount of heat storage that occurs in accordance with a difference in the density of dots composed of high gradation values.

[0006] MEANS FOR SOLVING THE PROBLEMS

[0007] In order to solve the above-described problems, one mode of the thermal printer of the present application is a thermal printer characterized by having a plurality of heating elements arranged in a prescribed direction, and being capable of printing dots corresponding to the heating elements in a plurality of gradations by controlling the power supply time or the number of power supply for each of the heating elements, the thermal printer being provided with a control mechanism that performs a heat adjustment process in which, in the case of a heating element to which the smallest gradation value was assigned in the previous print field, power supply for a prescribed time in the present print field is performed as a history power supply, and, on the other hand, in the case of a heating element to which the smallest gradation value was assigned in the previous print field, the history power supply in the present print field is omitted, the control mechanism performing the heat adjustment process for each of a plurality of groups into which the plurality of heating elements are divided.

[0008] EFFECTS OF THE INVENTION

[0009] According to the present application, it is possible to prevent a gradation deviation due to a difference in the amount of heat storage that occurs in accordance with a difference in the density of dots composed of high gradation values. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a plan view schematically showing the external configuration of the thermal printer of the embodiment.

[0011] Figure 2 is a plan view showing the state after the cover of the thermal printer shown in Figure 1 is opened.

[0012] Figure 3 is a block diagram showing the control configuration of the thermal printer of the embodiment.

[0013] Figure 4 is a view showing the print surface of the tape member.

[0014] Figure 5 is a view showing the printed image and the energization waveform corresponding to each gray value.

[0015] Figure 6 is a graph showing the relationship between the energization time (heating temperature) and the gray value (print density).

[0016] Figure 7 is a flowchart showing the control sequence of the history data generation processing.

[0017] Figure 8 is a table showing each dot and the gray value of the dot after scanning a certain line (the previous line and the current line) as the target in the history data generation processing.

[0018] Figure 9 is a view showing an example of the generation method of the history data. DETAILED DESCRIPTION

[0019] Hereinafter, the embodiment of the present application will be described based on the drawings.

[0020] Figure 1 is a plan view schematically showing the external configuration of the thermal printer in the embodiment. Figure 2 is a plan view showing the state after the cover of the thermal printer shown in Figure 1 is opened. Further, Figure 3 is a block diagram showing the configuration of the function of the thermal printer.

[0021] The thermal printer 1 of the embodiment is a label printer that prints an image of a character, a mark, a figure, a table, or the like on a tape member 5 as a long strip-shaped printed medium, and produces a label. The thermal printer 1 has a function of performing printing of a plurality of gray values of print density in black and white by white (no printing on a white (background, for example, white) base) and black (black base). Further, the thermal printer 1 has a function of cutting the printed tape member 5, and the like.

[0022] In addition, the following explanation will use a label printer that uses thermal paper as an example, but there are no particular limitations on the printing method. For example, it can also be a thermal transfer method using ink ribbon.

[0023] like Figure 1 as well as Figure 2 As shown, the thermal printer 1 has a device housing 2 with a box housing 21 inside.

[0024] The box housing 21 houses the tape box 51. The tape box 51 houses the tape component 5 and the ink tape (not shown).

[0025] A cover 3 is provided at the location where it covers the box receiving section 21, which is part of the device housing 2. The cover 3 is released by pressing button 3a, which releases a locking mechanism (not shown). Figure 2 It opens by rotating upwards as shown. With the cover 3 open, the user can load and unload the cartridge 51.

[0026] In this embodiment, notches, recesses, or other irregularities (not shown) are provided at the corners and other locations of the tape cassette 51, depending on the type of tape component 5 housed, such as tape width. Inside the cassette housing 21, a tape type detection unit (not shown) is provided at a position corresponding to the corners and other locations of the tape cassette 51 to detect whether the tape cassette 5 has irregularities or unevenness. By obtaining the detection information obtained using the tape type detection unit, the control unit 10 can determine the type of tape component 5 housed in the tape cassette 51, such as tape width, and whether the tape cassette 51 is provided inside the cassette housing 21.

[0027] In addition, a printing mechanism is provided in the box housing 21 for printing on the strip component 5, which is a strip-shaped printing medium.

[0028] In this embodiment, the printing mechanism includes a thermal printhead 7 equipped with multiple heating elements 71 (see reference). Figure 2 (etc.). The thermal printhead 7 (heating element 71) is driven by the printhead drive circuit 17 (see reference). Figure 3 The controlled actions are carried out to print according to the printing data and historical data (described later).

[0029] With the tape cassette 51 housed in the cassette housing 21, the thermal printhead 7 has a line along the width direction of the tape component 5 (see reference). Figure 4 Multiple heating elements 71 arranged in a row.

[0030] In addition, a thermistor 72 is embedded in the thermal printhead 7 (see reference). Figure 3 Thermistor 72 measures the temperature of the thermal printhead 7 (heating element 71) and outputs the result to the control unit 10.

[0031] Furthermore, a pressure roller 8 is provided at a position opposite to the thermal printhead 7, which is located between the belt component 5 and the thermal printhead 7, as a pressure roller along the length direction (see reference). Figure 4 The conveying direction () Figure 1 , Figure 2 The conveying mechanism (in the direction of the arrow) transports the belt component 5, which is the printing medium, along the direction of the arrow.

[0032] like Figure 2 As shown, the pressure roller 8 and the thermal printhead 7 are positioned opposite each other at the portion where the heating element 71 is located. When the belt component 5 passes between the pressure roller 8 and the thermal printhead 7, the pressure roller 8 presses the belt component 5 against the side of the thermal printhead 7 (heating element 71). This is how printing is performed.

[0033] The pressure roller 8 is conveyed by a conveying motor 80 (see below). Figure 3 The conveying mechanism rotates and appropriately conveys the belt component 5 along the conveying direction (the length direction of the belt component 5). In this embodiment, the pressure roller 8, which is the conveying mechanism, is configured to perform forward conveying, which conveys the belt component 5 in the positive direction (from the upstream side of the conveying direction to the downstream side, the positive direction) from the thermal print head 7, which is the printing mechanism, toward the discharge port 22 that discharges the belt component 5 out of the device.

[0034] Furthermore, the cartridge housing 21 is provided with: a core engagement shaft and a take-up shaft (neither shown in the figure), the core engagement shaft engages the core of the tape component 5 inside the tape cartridge 51 which is wound into a roller shape; the take-up shaft (takes up the printed ink tape. The take-up shaft is rotated by a drive motor (not shown) to properly wind up the ink tape.

[0035] On the side of the device housing 2 (in this embodiment, Figure 1 As shown, a discharge port 22 is formed on the right side (corresponding to the box receiving section 21), serving as a discharge section for discharging the label cut off from the tape component 5 after printing. The tape component 5 (label) printed in the thermal printer 1 is discharged out of the device through the discharge port 22.

[0036] Inside the device housing 2, a full cutting mechanism 9a and a half cutting mechanism 9b are provided between the thermal print head 7, which serves as the printing mechanism, and the outlet 22, to serve as the cutting mechanism for the tape component 5.

[0037] Both the full-cutting mechanism 9a and the half-cutting mechanism 9b are arranged throughout the width direction of the tape component 5, and are cutting mechanisms that cut the tape component 5, which is the printing medium, along the width direction of the medium. In this embodiment, as... Figure 2 As shown, a full-cutting mechanism 9a is arranged downstream of the thermal printhead 7, which serves as the printing mechanism, in the transport direction, and a half-cutting mechanism 9b is arranged downstream of the full-cutting mechanism 9a in the transport direction.

[0038] Although the illustration is omitted, the tape component 5, which serves as the printing medium in this embodiment, includes: a substrate having an adhesive layer (not shown); and a release layer (release paper) provided to cover the adhesive layer, which is peeled off from the substrate when the label is used (when it is pasted).

[0039] The full-cutting mechanism 9a has a cutting blade that cuts the substrate of the tape component 5, which is the printing medium, together with the release layer along the width direction, and performs a so-called full-cutting action that cuts the tape component 5 entirely along the thickness direction. The full-cutting mechanism 9a is driven by a full-cutting mechanism motor 90a (see reference). Figure 3 The cutting action is performed using the power of the engine.

[0040] The semi-cutting mechanism 9b has a cutting blade that cuts only the substrate in the strip member 5 along the width direction, performing a so-called semi-cutting action that cuts a portion of the strip member 5 in the thickness direction. The semi-cutting mechanism 9b is driven by a semi-cutting mechanism motor 90b (see reference). Figure 3 The cutting action is performed using the power of the engine.

[0041] Furthermore, in order to visually confirm whether the tape cassette 51 is contained in the thermal printer 1 even when the cover 3 is closed, a window 31 is formed in the cover 3. In addition, a display unit 4 is provided in the cover 3.

[0042] The display unit 4 may be composed of, for example, a liquid crystal display (LCD), an organic light-emitting display, or other flat panel displays.

[0043] In this embodiment, the display unit 4 may also display various settings input by the user, strings printed on the tape component 5, and appearance designs, so that the user can confirm them.

[0044] Alternatively, a touch panel for various inputs can be integrally formed on the surface of the display unit 4. In this case, the touch panel also functions as the input unit 6.

[0045] In addition, an input section 6 is provided on the device housing 2.

[0046] The input section 6 includes various keys such as character input keys, cross keys, change keys, and confirmation keys.

[0047] Furthermore, as described above, when a touch panel is integrally provided on the surface of the display unit 4, the touch panel functions as an input unit 6, and the user can perform various input / setting operations by touching the touch panel.

[0048] As described above, the thermal printer 1, in addition to having a display unit 4, an input unit 6, a thermal printhead 7 (heating element 71), a thermistor 72, a pressure roller 8, a full-cutting mechanism 9a, and a half-cutting mechanism 9b, also includes... Figure 3 As shown, it also includes a control unit 10, a storage unit 11, a power supply circuit 12, a display unit drive circuit 14, a printhead drive circuit 17, a conveyor motor drive circuit 18, and a cutter motor drive circuit 19.

[0049] The control unit 10 is, for example, a control mechanism that includes a processor such as a CPU (Central Processing Unit).

[0050] In addition, the storage unit 11 includes ROM (Read Only Memory) and RAM (Random Access Memory), which are not shown, as well as FLASH (Trademarked) memory, which functions as a non-volatile semiconductor memory that functions as ROM and RAM.

[0051] The control unit 10 and the storage unit 11 constitute a computer. The control unit 10 expands and executes various programs stored in ROM and the like in the working area of ​​RAM, thereby uniformly controlling the operation of each part of the thermal printer 1.

[0052] Specifically, through the cooperation of the control unit 10 and the program (such as a printing processing application), the thermal printer 1 realizes various functions for printing.

[0053] In addition, the functions of the control unit 10 can be implemented by executing programs (software) on the control unit 10, or by using dedicated components (hardware).

[0054] The storage unit 11 (e.g., a FLASH memory serving as the storage unit 11) stores the program for printing the tape component 5 (the program's source code, etc.), various data required to execute the program (e.g., character data composed of various fonts (Kanji, Katakana, Hiragana, letters, etc.), data such as symbols and graphics, spacing between graphics / characters, white space of a specified width, and other data required for printing operations). Furthermore, if user-generated data is available, user-generated data can also be stored in the storage unit 11.

[0055] The power supply circuit 12 is a power supply unit that generates an output voltage from the voltage from the power source and supplies power to various parts of the thermal printer 1.

[0056] Alternatively, the power source can be an internal battery or an external power source connected via cables.

[0057] The display unit drive circuit 14 is a controller that controls the operation of the display unit 4. Based on the control of the control unit 10, it controls the driver of the display unit 4 to perform display based on display data.

[0058] That is, the display unit driving circuit 14 receives display data output from the control unit 10, and displays various display screens on the display unit 4 based on the display data.

[0059] The printhead drive circuit 17 is a printhead drive unit that drives the thermal printhead 7 (heating element 71) based on control signals, printing data and historical data (described later) supplied from the control unit 10.

[0060] If a user provides printing instructions, the data specifying characters, symbols, graphics, etc., selected or entered by the user from the input unit 6 for label production is sent to the printhead drive circuit 17 via the control unit 10 as printing data. Based on this printing data, the printhead drive circuit 17 prints the label according to each line (see reference). Figure 4 The printhead drive circuit 17 controls the energization or de-energization of the voltage for multiple heating elements 71. Furthermore, the printhead drive circuit 17 generates data based on historical data generated later (see reference). Figure 7 The historical data generated is arranged according to each row (refer to...). Figure 4 It controls whether the voltage of multiple heating elements 71 is energized (historically energized) or de-energized.

[0061] Then, the printhead drive circuit 17 selectively directs current to the heating element 71 based on printing data and historical data, thereby heating the heating element 71 and heating the ink ribbon. Thus, the thermal printhead 7 transfers ink from the end of the ribbon component 5 through thermal transfer. Figure 4 The right end of the belt component 5 shown is printed row by row along the length direction.

[0062] In the thermal printer 1 of this embodiment, 8-grayscale black and white printing (monochrome printing) with grayscale values ​​ranging from 0 to 7 is performed. During 8-grayscale black and white printing, power-on control is performed as follows: Specifically, a predetermined pulse is input to the heating element 71 of the thermal printhead 7 via the printhead drive circuit 17, and power is applied (main power-on) corresponding to the number of input pulses (pulse count). Furthermore, each point (refer to...) Figure 4 The grayscale value corresponds to the number of input pulses. Furthermore, the more pulses input to a heating element 71, the longer the energizing time to that heating element 71.

[0063] Figure 5 It is a diagram that represents the printed image and the electrical waveform corresponding to each grayscale value.

[0064] like Figure 5As shown, in the printing of a dot D, when the grayscale value is 0, no pulse is input to the heating element 71, the number of times the heating element 71 is energized (energizing time) is also 0, and the printing density of the printed matter is the lowest value (white). When the grayscale value of dot D is 1, a pulse is input to the heating element 71, and the heating element 71 is energized for an energizing time corresponding to the input pulse, and the printing density of the printed matter becomes denser (black) than when the grayscale value is 0. Similarly, if the grayscale value of dot D is gradually increased, the energizing time corresponding to the number of pulses input to the heating element 71 (energizing times) also becomes longer, and the printing density of the printed matter becomes even denser (black). Moreover, when the grayscale value of dot D is 7, seven pulses are input to the heating element 71, and the heating element 71 is energized for an energizing time corresponding to the input seven pulses, and the printing density of the printed matter becomes the densest (black). In this embodiment, one dot (one dot D) is printed corresponding to one heating element 71 in the thermal print head 7. Furthermore, in this embodiment, the energizing (main energizing) of the heating element 71 corresponding to each grayscale value from 1 to 7 is performed within a predetermined main energizing period allocated for this main energizing within a pre-determined printing character cycle (3.12 ms). Furthermore, in this embodiment, as... Figure 6 The graph showing the relationship between energizing time (heating temperature) and grayscale value (print density) (thermal transfer characteristics) indicates that the energizing time corresponding to the first input pulse (for setting the grayscale value to 0-1) and the energizing time corresponding to the seventh input pulse (for setting the grayscale value to 6-7) are set to be longer than the energizing time corresponding to the second to sixth input pulses. This is to reliably perform color development with a grayscale value of 1 and a grayscale value of 7.

[0065] Furthermore, in the printing of a point D, with a grayscale value of 7, such as Figure 5 As shown, there are printing processes that do not perform historical power-on and printing processes that perform historical power-on. Historical power-on is a period of time that occurs before the power-on (main power-on) performed according to the input of the aforementioned pulse. Furthermore, for historical power-on, it is based on the historical data generation process described later (see [reference]). Figure 7 The historical data generated is used as the basis for historical power-on, with points where the historical data is set to be active being used, while points where the historical data is set to be inactive are not used for historical power-on. In this embodiment, historical power-on is performed within the historical power-on period allocated to it within a predetermined printing character cycle (3.12ms). Alternatively, historical power-on can be performed within the printing character cycle (3.12ms), for example, it can be performed after the main power-on, i.e., the historical power-on period is set after the main power-on period.

[0066] return Figure 3The block diagram illustrates that the conveyor motor drive circuit 18 drives the conveyor motor 80, causing the pressure roller 8 to rotate.

[0067] The conveying motor 80 is, for example, a stepper motor, which is driven according to each step number corresponding to the pulse signal input by the conveying motor drive circuit 18, enabling accurate conveying. As described above, the pressure roller 8 of this embodiment can rotate in the forward direction (positive direction) of the conveying direction, and the conveying motor drive circuit 18 inputs a signal to the appropriate conveying motor 80 to make the pressure roller 8 rotate in the forward direction.

[0068] During the printing process, the conveyor motor drive circuit 18 controls the drive of the conveyor motor 80 in a manner that synchronizes the rotation of the pressure roller 8 (i.e., the conveying action of the belt component 5) with the travel speed of the printing using the thermal print head 7.

[0069] In addition, during the printing process, a drive motor (not shown) that rotates the take-up shaft that takes up the ink tape also operates synchronously with the rotation of the pressure roller 8, so that the timing of the conveying of the tape component 5, the printing using the thermal print head 7, and the take-up of the printed ink tape are matched with high precision.

[0070] The cutter motor drive circuit 19 controls the operation of the full-cutting mechanism drive motor 90a, which actuates the full-cutting mechanism 9a, and the half-cutting mechanism drive motor 90b, which actuates the half-cutting mechanism 9b. Thus, full or partial cutting of the component 5 is performed at the appropriate position.

[0071] Next, refer to Figure 7 to 9 The operation of the thermal printer 1 in this embodiment will be explained. Figure 7 This is a flowchart showing the control sequence of historical data generation processes performed during grayscale printing.

[0072] Figure 8 It is a table representing the points and grayscale values ​​of a row (the previous row and the current row) after scanning it as an object in the historical data generation process. Figure 9 This is a diagram illustrating an example of how historical data is generated.

[0073] like Figure 7 As shown, when the historical data generation process begins, firstly, the control unit 10 of the thermal printer 1 scans the printing data of the row (previous row) that is the target row for historical data generation (current row) from the printing data of the grayscale printing process, sequentially from one end of the row in 4-dot units (step S1). Specifically, as... Figure 4As shown, the four points belonging to each historical reference group G1 to G6 are scanned in the order of historical reference groups G1, G2, G3, G4, G5, and G6. Here, if the row that is the object of historical data generation (this row) is the first row of printed data (the initial row), there is no previous row. Therefore, in this case, it is treated as the previous row where there are points with a gray value of 0 (the minimum gray value) side by side.

[0074] Next, the control unit 10 determines whether there are any points with a grayscale value of 0 (minimum grayscale value) in the area scanned in step S1 (historical reference group; 4 points) (step S2). Here, as described above, if the row (current row) that is the object of generating historical data is the first row of printed data, step S2 will be handled as if there are points with a grayscale value of 0 in the scanned area.

[0075] In step S2, if it is determined that there are points with a grayscale value of 0 in the area scanned in step S1 (step S2; Yes), the control unit 10 sets the historical data of points with a grayscale value of 7 (maximum grayscale value) in the current row area corresponding to the scanned area to be enabled only (step S3). That is, in step S3, for points with a grayscale value (grayscale value of 0 to 6) smaller than the grayscale value of 7 (maximum grayscale value) in the current row area corresponding to the scanned area, the historical data is set to be disabled.

[0076] For example, such as Figure 8 as well as Figure 9 As shown, in the scanned first area (printing field) R1 (historical reference group G1), point D4 among points D1 to D4 is determined to have a grayscale value of 0 (white), indicating insufficient heat storage in the first area R1. Therefore, in the area corresponding to the first area R1 (historical reference group G1), only two points D13 and D14 with a grayscale value of 7 (maximum grayscale value) in the current row have their historical data set to be enabled. Thus, printing with a grayscale value of 7 (referring to historical power supply) is performed in points D13 and D14 where the historical data in the current row is set to be enabled. Figure 5In other words, if a heating element 71 with a grayscale value of 0 (minimum grayscale value) was previously assigned to the first area (printing field) R1, under the control of the control unit 10, a heat adjustment process of energizing for a predetermined time is performed on the heating element 71 that corresponds to the current first area (printing field) R1 and has a grayscale value of 7 (maximum grayscale value) in the current first area (printing field) R1, as a historical power-on process.

[0077] Furthermore, in step S2, if it is determined that there are no points with a gray value of 0 in the area scanned in step S1 (step S2; no), the control unit 10 sets the historical data of the area of ​​the current row corresponding to the scanned area to be turned off (step S4).

[0078] For example, such as Figure 8 as well as Figure 9 As shown, if it is determined that there are no points with a grayscale value of 0 (white) in points D5 to D8 of the scanned second area (printed field) R2 (historical reference group G2), meaning that the heat storage capacity of the second area R2 is sufficient, the historical data of the area corresponding to the current row of the second area R2 (historical reference group G2) is set to be closed. That is, if no heating element 71 with a grayscale value of 0 (minimum grayscale value) was assigned in the previous second area (printed field) R2, the heat adjustment process corresponding to the historical power-on established in the current second area (printed field) R2 is executed under the control of the control unit 10. In other words, if a heating element 71 with a grayscale value of 7 (maximum grayscale value) is assigned in the current second area (printed field) R2, the heat adjustment process corresponding to the historical power-on established in the current second area (printed field) R2 is executed under the control of the control unit 10.

[0079] Next, the control unit 10 determines whether the scan of a row that took the previous row as the object has ended (step S5).

[0080] In step S5, if it is determined that the scan of one row that was previously the target row has not been completed (step S5; no), the control unit 10 updates the area (4 points) that was the target row for scanning (step S6). For example, the area that was previously the target row for scanning belonged to the historical reference group G1 (reference).Figure 4 In the case of a region that is being scanned, the region to be scanned will be updated to the historical reference group G2 (reference). Figure 4 The control unit 10 then returns the processing to step S1 and repeats the processing thereafter.

[0081] Furthermore, in step S5, if it is determined that the scan of a row that was the target of the previous row has ended (step S5, yes), the control unit 10 updates the previous row that was the target of the scan to the next row (step S7).

[0082] Next, the control unit 10 determines whether the updated previous row is the final row of the printed data (step S8).

[0083] In step S8, if it is determined that the updated previous line is not the final line of the printed data (step S8; no), the control unit 10 returns the processing to step S1 and repeats the processing thereafter.

[0084] Furthermore, in step S8, if it is determined that the last row of the updated previous line of printed data is the last row (step S8, yes), the control unit 10 ends the historical data generation process.

[0085] As described above, when a heating element 71 with a gray value of 0 (minimum gray value) was assigned in the previous printing field, the control unit 10 of the thermal printer 1 applies power to the heating element 71 with a gray value of 7 (maximum gray value) that corresponds to the current printing field for a predetermined time as historical power-on. On the other hand, when a heating element 71 with a gray value of 0 (minimum gray value) was not assigned in the previous printing field, the heating adjustment process that omits the historical power-on corresponding to the current printing field is performed.

[0086] Therefore, according to the thermal printer 1, if there are points with a gray value of 0 in the previous printing field, it is determined that the heat storage of the heating element 71 corresponding to that printing field is low, and the heating element 71 with a gray value of 7 assigned to the current printing field is historically powered on. On the other hand, if there are no points with a gray value of 0 in the previous printing field, it is determined that the heat storage of the heating element 71 corresponding to that printing field is high, and the historical power-on corresponding to the current printing field is omitted. Thus, gray deviation can be prevented due to the difference in heat storage caused by the different density of points with high gray values.

[0087] Furthermore, the control unit 10 performs the above-mentioned heat adjustment process according to each of the historical reference groups (4 points) G1 to G6, based on dividing the multiple heating elements 71 into multiple historical reference groups G1 to G6.

[0088] Therefore, by judging the density of high grayscale points according to multiple historical reference groups G1 to G6 based on the thermal printer 1, this judgment can be made accurately. As a result, the above-mentioned heat adjustment process can be performed more appropriately according to each of the multiple historical reference groups G1 to G6, thus further preventing grayscale deviations caused by differences in heat storage due to differences in the density of high grayscale points.

[0089] The present invention has been specifically described above based on the embodiments, but the present invention is not limited to the above embodiments and can be modified within the scope without departing from its spirit.

[0090] For example, in the above implementation, in the historical data generation process (refer to...) Figure 7 In step S1, the printing data of the previous line was scanned in units of 4 dots. However, it is also possible to scan in units of 5 dots or more, or in units of 2 dots or 3 dots. That is, the historical reference group can be set as a group of 5 dots or more, or as a group of 2 dots or 3 dots.

[0091] Furthermore, in the above embodiment, a thermal printer 1 that performs black and white printing with a minimum gray value of 0 and a maximum gray value of 7 with 8 gray levels was described as an example. However, the gray level of printing is not limited to 8 gray levels. For example, it can also be a thermal printer that performs black and white printing with 16 gray levels (minimum gray value of 0 and maximum gray value of 15) or 256 gray levels (minimum gray value of 0 and maximum gray value of 255).

[0092] Furthermore, in the above embodiments, in the historical data generation process (refer to...) Figure 7 In step S2, it is determined whether there are points with a grayscale value of 0 (minimum grayscale value) in the scanned area (4 points). However, it is also possible to determine whether there are points with a grayscale value of 1 or less in the scanned area (4 points). Then, in step S2, if it is determined that there are points with a grayscale value of 1 or less in the scanned area (step S2; yes), in step S3, for example, historical data of points with a grayscale value of 6 (second grayscale value) and a grayscale value of 7 (grayscale value greater than the second grayscale value) in the current row area corresponding to the scanned area can be set to be enabled, and historical data of points with a grayscale value of 0 to 5 (grayscale value less than the second grayscale value) can be set to be disabled. On the other hand, in step S2, if it is determined that there are no points with a grayscale value of 1 or less in the scanned area (step S2; yes), in step S4, historical data of the current row area corresponding to the scanned area can also be set to be disabled.

[0093] Furthermore, in the above embodiments, an example of using a storage unit 11 (e.g., a FLASH memory) as the medium that a computer can read as the program of the present invention is disclosed, but it is not limited to this example. Other media that a computer can read can be a portable recording medium such as a CD-ROM. Furthermore, a carrier wave (transmission wave) can also be used as the medium for providing data of the program of the present invention via a communication line.

[0094] The embodiments of the present invention have been described, but the scope of the present invention is not limited to the above-described embodiments, but also includes the scope of the invention as set forth in the claims and its equivalents.

Claims

1. A thermal printer, characterized in that, The thermal printer has multiple heating elements arranged in a predetermined direction. By controlling the energizing time or number of energizing cycles for each heating element, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The thermal printer has a control mechanism that performs heat adjustment. In the heat treatment, In the case of a heating element that was assigned the minimum grayscale value in the previous printing field, for the heating element that was assigned the maximum grayscale value in the current printing field, energizing it for a specified period of time in the current printing field is recorded as historical energizing. On the other hand, if there is no heating element assigned the minimum grayscale value in the previous printing field, the historical power-on in the current printing field is omitted. The control mechanism divides the multiple heating elements into multiple groups and performs the heat adjustment process according to each group.

2. The thermal printer according to claim 1, characterized in that, In the heat adjustment process, for heating elements in the current printing field that are assigned a gray value smaller than the maximum gray value, the historical power-on information in the current printing field is omitted.

3. A thermal printer, characterized in that, The thermal printer has multiple heating elements arranged in a predetermined direction. By controlling the energizing time or number of energizing cycles for each heating element, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The thermal printer has a control mechanism that performs heat adjustment. In the heat treatment, In the case of heating elements that were assigned a gray value lower than the first gray value in the previous printing field, for heating elements that are assigned a gray value greater than the first gray value or higher in the current printing field, energizing them for a predetermined time in the current printing field is recorded as historical energizing. On the other hand, if no heating element with a grayscale value below the first grayscale value was assigned in the previous printing field, the historical power-on in the current printing field is omitted. The control mechanism divides the multiple heating elements into multiple groups and performs the heat adjustment process according to each group.

4. The thermal printer according to claim 3, characterized in that, In the heat adjustment process, for heating elements in the current printing field that are assigned a gray value smaller than the second gray value, the historical power-on information in the current printing field is omitted.

5. A thermal printer, characterized in that, The thermal printer has multiple heating elements arranged in a predetermined direction. By controlling the energizing time or number of energizing cycles for each heating element, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The thermal printer has a control mechanism that performs heat adjustment. In the heat treatment, In the case where there is a heating element assigned the largest grayscale value in the current printing field and a heating element assigned the smallest grayscale value in the previous printing field, the heating element assigned the largest grayscale value in the current printing field is energized for a specified period of time in the current printing field as a historical energization. On the other hand, if there is no heating element assigned the maximum grayscale value in the current printing field, the historical power-on in the current printing field is omitted. The control mechanism divides the multiple heating elements into multiple groups and performs the heat adjustment process according to each group.

6. A method for energizing, characterized in that, The power-on method is performed by a thermal printer, which has multiple heating elements arranged in a predetermined direction. By controlling the power-on time or number of times each heating element is powered on, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The energizing method includes heat adjustment treatment. In the heat treatment, In the case of a heating element that was assigned the minimum grayscale value in the previous printing field, for the heating element that was assigned the maximum grayscale value in the current printing field, energizing it for a specified period of time in the current printing field is recorded as historical energizing. On the other hand, if there is no heating element assigned the minimum grayscale value in the previous printing field, the historical power-on in the current printing field is omitted. Based on dividing the plurality of heating elements into multiple groups, the heat adjustment process is performed according to each group.

7. A method for energizing, characterized in that, The power-on method is performed by a thermal printer, which has multiple heating elements arranged in a predetermined direction. By controlling the power-on time or number of times each heating element is powered on, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The energizing method includes heat adjustment treatment. In the heat treatment, In the case of heating elements that were assigned a gray value lower than the first gray value in the previous printing field, for heating elements that are assigned a gray value greater than the first gray value or higher in the current printing field, energizing them for a predetermined time in the current printing field is recorded as historical energizing. On the other hand, if no heating element with a grayscale value below the first grayscale value was assigned in the previous printing field, the historical power-on in the current printing field is omitted. Based on dividing the plurality of heating elements into multiple groups, the heat adjustment process is performed according to each group.

8. A method for energizing, characterized in that, The power-on method is performed by a thermal printer, which has multiple heating elements arranged in a predetermined direction. By controlling the power-on time or number of times each heating element is powered on, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The energizing method includes heat adjustment treatment. In the heat treatment, In the case where there is a heating element assigned the largest grayscale value in the current printing field and a heating element assigned the smallest grayscale value in the previous printing field, the heating element assigned the largest grayscale value in the current printing field is energized for a specified period of time in the current printing field as a historical energization. On the other hand, if there is no heating element assigned the maximum grayscale value in the current printing field, the historical power-on in the current printing field is omitted. Based on dividing the plurality of heating elements into multiple groups, the heat adjustment process is performed according to each group.

9. A storage medium storing a program readable by a computer that contains a thermal printer, characterized in that, The thermal printer has multiple heating elements arranged in a predetermined direction. By controlling the energizing time or number of energizing cycles for each heating element, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The program causes the computer to perform a heat adjustment process. In the heat treatment, In the case of a heating element that was assigned the minimum grayscale value in the previous printing field, for the heating element that was assigned the maximum grayscale value in the current printing field, energizing it for a specified period of time in the current printing field is recorded as historical energizing. On the other hand, if there is no heating element assigned the minimum grayscale value in the previous printing field, the historical power-on in the current printing field is omitted. Based on dividing the plurality of heating elements into multiple groups, the heat adjustment process is performed according to each group.

10. A storage medium storing a program readable by a computer that contains a thermal printer, characterized in that, The thermal printer has multiple heating elements arranged in a predetermined direction. By controlling the energizing time or number of energizing cycles for each heating element, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The program causes the computer to perform a heat adjustment process. In the heat treatment, In the case of heating elements that were assigned a gray value lower than the first gray value in the previous printing field, for heating elements that are assigned a gray value greater than the first gray value or higher in the current printing field, energizing them for a predetermined time in the current printing field is recorded as historical energizing. On the other hand, if no heating element with a grayscale value below the first grayscale value was assigned in the previous printing field, the historical power-on in the current printing field is omitted. Based on dividing the plurality of heating elements into multiple groups, the heat adjustment process is performed according to each group.

11. A storage medium storing a program readable by a computer that contains a thermal printer, characterized in that, The thermal printer has multiple heating elements arranged in a predetermined direction. By controlling the energizing time or number of energizing cycles for each heating element, it is possible to print dots corresponding to each heating element in multiple grayscale levels. The program causes the computer to perform a heat adjustment process. In the heat treatment, In the case where there is a heating element assigned the largest grayscale value in the current printing field and a heating element assigned the smallest grayscale value in the previous printing field, the heating element assigned the largest grayscale value in the current printing field is energized for a specified period of time in the current printing field as a historical energization. On the other hand, if there is no heating element assigned the maximum grayscale value in the current printing field, the historical power-on in the current printing field is omitted. Based on dividing the plurality of heating elements into multiple groups, the heat adjustment process is performed according to each group.

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