Thermal printer, energization method, and program

Abstract

To prevent gradation deviation from occurring due to a difference in stored heat amount caused by a difference in sparseness of dots including a high gradation value.SOLUTION: A control unit 10 of a thermal printer 1 performs a heat adjustment process for energizing, as history energization for a prescribed time, a heater element 71 assigned a gradation value 7 (largest gradation value) in a current printing field in association with the current printing field when there is a heater element 71 assigned a gradation value 0 (smallest gradation value) in the last printing field, and omitting the history energization associated with the current printing field when there is no heater element 71 assigned a gradation value 0 (smallest gradation value) in the last printing field. The control unit 10 divides a plurality of heater elements 71 into a plurality of groups (4 dots) G1-G6 for history reference, and performs the heat adjustment process for each of the groups G1-G6 for history reference.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a thermal printer, an energization method, and a program.

Background Art

[0002] Conventionally, a thermal printer having a heating element that prints characters and the like by dot output is known. Regarding this thermal printer, in order to make the printing density uniform, it is disclosed that the number of energization pulses is selected according to the previous energization history state when each dot is output (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique disclosed in Patent Document 1 above, since the energization history of each dot is viewed individually, there is a problem that the heat storage amount varies depending on the energization history of surrounding dots and the printing density changes. In particular, when halftone printing is performed, halftone deviation occurs due to the change in printing density, which affects the halftone expression.

[0005] The present invention has been made in view of such problems, and an object thereof is to prevent halftone deviation from occurring due to differences in heat storage amounts that occur due to differences in the density of dots composed of high halftone values.

Means for Solving the Problems

[0006] To solve the above problems, the thermal printer according to the present invention A thermal printer having a plurality of heating elements arranged in a predetermined direction, and capable of printing dots corresponding to the heating elements in multi-level by controlling the energization time or the number of energizations to each heating element, Control means for dividing the plurality of heating elements into a plurality of groups and performing heat conditioning treatment for each group is provided. The control means, as the heat conditioning treatment, For the groups included in The previous printing Among The heating element to which the minimum gradation value is assigned is For the groups included 、 For the heating elements included in the group that are for this printing For the heating element to which the maximum gradation value is assigned, energization is performed for a predetermined time as history energization Processing and 、 Among the plurality of groups, the The previous printing Among The heating element to which the minimum gradation value is assigned is For the groups not included in The current printing Among The history energization is omitted Processing and Execute Characterized by this.

Effect of the Invention

[0007] According to the present invention, it is possible to prevent gradation deviation from occurring due to differences in the amount of heat storage generated due to differences in the density of dots composed of high gradation values.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] FIG. 1 is a plan view schematically showing the external configuration of the thermal printer in the present embodiment. FIG. 2 is a plan view showing a state in which the lid of the thermal printer shown in FIG. 1 is opened. Further, FIG. 3 is a block diagram showing the functional configuration of the thermal printer.

[0011] The thermal printer 1 of the present embodiment is a label printer that heats a tape member 5, which is a long printing medium, to print images such as characters, marks, figures, and tables to create labels. The thermal printer 1 has a function of performing printing with a plurality of gradations of black and white printing densities in white (no printing on the base (background, for example, white)) and black (black on the base). Further, the thermal printer 1 has a function of cutting the printed tape member 5. In the following, a thermal label printer using thermal paper will be described as an example, but the printing method is not particularly limited, and for example, a thermal transfer method using an ink ribbon may be used.

[0012] As shown in FIGS. 1 and 2, the thermal printer 1 includes a device housing 2 having a cassette housing portion 21 inside. A tape cassette 51 is housed in the cassette housing portion 21. The tape cassette 51 houses the tape member 5 and an ink ribbon (not shown). A lid 3 is provided at a part on the device housing 2 that covers the cassette storage section 21. By pressing a button 3a, a lock mechanism (not shown) is released, and the lid 3 pivots upward and opens as shown in Fig. 2. When the lid 3 is open, the user can attach and detach the tape cassette 51.

[0013] At the corners and other parts of the tape cassette 51 in this embodiment, unevenness such as notches and recesses (not shown) are provided at different positions according to the type of the tape member 5 to be accommodated, such as the tape width. Inside the cassette storage section 21, at positions corresponding to the corners and other parts of the tape cassette 51, a tape type detection section (not shown) for detecting the presence or absence of unevenness of the tape cassette 5 is provided. By acquiring the detection information from the tape type detection section, the control unit 10 can grasp the type of the tape width and other characteristics of the tape member 5 accommodated in the tape cassette 51 and whether the tape cassette 51 is set in the cassette storage section 21.

[0014] Also, inside the cassette storage section 21, printing means for printing on the tape member 5, which is a long printing medium, is provided. In this embodiment, the printing means includes a thermal head 7 (see Fig. 2 etc.) having a plurality of heating elements 71. The thermal head 7 (heating elements 71) is operationally controlled by a head drive circuit 17 (see Fig. 3) and performs printing according to print data and history data (described later). The thermal head 7 has a row of a plurality of heating elements 71 arranged in a line in the width direction of the tape member 5 (see Fig. 4) when the tape cassette 51 is accommodated in the cassette storage section 21. Also, a thermistor 72 (see Fig. 3) is embedded in the thermal head 7. The thermistor 72 measures the temperature of the thermal head 7 (heating elements 71) and outputs it to the control unit 10.

[0015] Also, at a position facing the thermal head 7 with the tape member 5 interposed therebetween, a platen roller 8 is provided as conveyance means for conveying the tape member 5, which is the medium to be printed, in the conveyance direction (the direction of the arrows in FIGS. 1 and 2) along the long direction (see FIG. 4). As shown in FIG. 2, the platen roller 8 faces the thermal head 7 at the portion where the heating element 71 is disposed. When the tape member 5 passes between the platen roller 8 and the thermal head 7, the platen roller 8 presses the tape member 5 against the thermal head 7 (heating element 71) side. Thereby, printing is performed.

[0016] The platen roller 8 is rotated by a conveyance motor 80 (see FIG. 3) described later and is a conveyance mechanism for appropriately conveying the tape member 5 along the conveyance direction (the long direction of the tape member 5). In the present embodiment, the platen roller 8, which is the conveyance mechanism, is configured to perform forward conveyance for conveying the tape member 5 in the forward direction (the direction from the upstream side to the downstream side in the conveyance direction, the positive direction) toward the discharge port 22 for discharging the tape member 5 out of the apparatus from the thermal head 7, which is the printing means. Furthermore, in the cassette housing portion 21, a tape core engagement shaft with which a tape core around which the tape member 5 in the tape cassette 51 is wound in a roll shape is engaged, and a take-up shaft (both not shown) for taking up the printed ink ribbon are provided. The take-up shaft is rotated by a drive motor (not shown) and is configured to appropriately take up the ink ribbon.

[0017] At a side portion of the apparatus housing 2 (in the present embodiment, the right side portion as shown in FIG. 1) corresponding to the cassette housing portion 21, a discharge port 22 is formed as a discharge portion through which a label separated from the tape member 5 after printing is discharged. The tape member 5 (label) printed in the thermal printer 1 is discharged out of the apparatus from the discharge port 22.

[0018] Inside the apparatus housing 2, between the thermal head 7, which is the printing means, and the discharge port 22, a full cut mechanism 9a and a half cut mechanism 9b are provided as a cut mechanism for cutting the tape member 5. Both the full cut mechanism 9a and the half cut mechanism 9b are provided across the width direction of the tape member 5, and are cutting means for cutting the tape member 5, which is the medium to be printed, along the width direction of the medium. In the present embodiment, as shown in FIG. 2 and the like, the full cut mechanism 9a is disposed on the downstream side in the conveyance direction of the thermal head 7, which is the printing means, and the half cut mechanism 9b is disposed on the further downstream side in the conveyance direction than the full cut mechanism 9a.

[0019] Although not shown, the tape member 5, which is the medium to be printed in the present embodiment, includes a base material having an adhesive layer (not shown) and a release layer (release paper) provided so as to cover the adhesive layer and peeled from the base material when using the label (when sticking). The full cut mechanism 9a has a cutting blade for cutting the base material of the tape member 5, which is the medium to be printed, along the width direction together with the release layer, and performs a so-called full cut operation for cutting the entire thickness direction of the tape member 5. The full cut mechanism 9a performs the cutting operation by the power of the full cut mechanism drive motor 90a (see FIG. 3).

[0020] The half cut mechanism 9b has a cutting blade for cutting only the base material of the tape member 5 along the width direction, and performs a so-called half cut operation for cutting a part of the thickness direction of the tape member 5. The half cut mechanism 9b performs the cutting operation by the power of the half cut mechanism drive motor 90b (see FIG. 3).

[0021] In addition, a window portion 31 is formed in the lid 3 so that it is possible to visually confirm whether the tape cassette 51 is accommodated in the thermal printer 1 even when the lid 3 is closed. Further, a display unit 4 is provided on the lid 3. The display unit 4 is composed of, for example, a liquid crystal display (LCD: Liquid Crystal Display), an organic electroluminescence display, or other flat displays. In the present embodiment, various setting values input by the user, character strings and designs printed on the tape member 5 may be displayed on the display unit 4 so that the user can confirm them.

[0022] Note that a touch panel for performing various inputs may be integrally configured on the surface of the display unit 4. In this case, the touch panel also functions as the input unit 6.

[0023] Also, an input unit 6 is provided on the apparatus housing 2. The input unit 6 includes various keys such as, for example, a character input key, a cross key, a conversion key, and a determination key. Note that as described above, when a touch panel is integrally provided on the surface of the display unit 4, the touch panel functions as the input unit 6, and the user can perform operations such as various inputs and settings by touching the touch panel.

[0024] In addition to the display unit 4, the input unit 6, the thermal head 7 (heating element 71), the thermistor 72, the platen roller 8, the full cut mechanism 9a, and the half cut mechanism 9b as described above, the thermal printer 1 includes, as shown in FIG. 3, a control unit 10, a storage unit 11, a power supply circuit 12, a display unit drive circuit 14, a head drive circuit 17, a conveyance motor drive circuit 18, a cutter motor drive circuit 19, and the like.

[0025] The control unit 10 is a control means including a processor such as a CPU (Central Processing Unit), for example. The storage unit 11 includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory) not shown, and a FLASH (registered trademark) memory (Flash memory), which is a non-volatile semiconductor memory functioning as a ROM and a RAM. The control unit 10 and the storage unit 11 constitute a computer, and the control unit 10 expands and executes various programs stored in the ROM and the like in the working area of the RAM, thereby integrally controlling the operations of each part of the thermal printer 1.

[0026] Specifically, the control unit 10 realizes various functions for the thermal printer 1 to perform printing in cooperation with a program (for example, a print processing application program or the like). Note that each function of the control unit 10 may be realized by the control unit 10 executing a program (software), or may be realized by a dedicated module (hardware).

[0027] In the storage unit 11 (for example, a FLASH memory or the like as the storage unit 11), a program (source code of the program, etc.) for printing on the tape member 5, various data necessary for executing the program (for example, character data (Chinese characters, katakana, hiragana, alphabet, etc.) composed of several types of fonts, data of symbols, figures, etc., intervals between figures and characters, margins of a predetermined width, etc., various data necessary for the printing operation) are stored. Also, when there is data created by the user, the user-created data is also stored in the storage unit 11.

[0028] The power supply circuit 12 is a power supply unit that generates an output voltage from the voltage from the power supply and supplies power to each part of the thermal printer 1. Note that the power supply may be an internal battery or the like, or an external power supply connected via a cable or the like.

[0029] The display unit driving circuit 14 is a controller that controls the operation of the display unit 4. Under the control of the control unit 10, it controls the driver of the display unit 4 to perform a display based on the display data. That is, the display unit driving circuit 14 receives the display data output from the control unit 10, and based on this display data, causes various display screens to be displayed on the display unit 4.

[0030] The head driving circuit 17 is a head driving unit that drives the thermal head 7 (heating element 71) based on the control signal, print data, and history data (described later) supplied from the control unit 10. Data specifying characters, symbols, figures, etc. selected or input by the user from the input unit 6 or the like for label creation is sent as print data to the head drive circuit 17 through the control unit 10 when there is a print instruction from the user. The head drive circuit 17 controls the energization or non-energization of voltages for a plurality of heating elements 71 for each line (see FIG. 4) based on the print data. Further, the head drive circuit 17 controls the energization (history energization) or non-energization of voltages for a plurality of heating elements 71 for each line (see FIG. 4) based on history data generated by a history data generation process (see FIG. 7) described later. Then, by selectively flowing current to the heating element 71 by the head drive circuit 17 according to the print data and the history data, the heating element 71 generates heat and heats the ink ribbon. As a result, the thermal head 7 performs printing one line at a time along the longitudinal direction from the end of the tape member 5 (the rightmost line of the tape member 5 shown in FIG. 4) on the tape member 5 by thermal transfer.

[0031] In the thermal printer 1 of the present embodiment, 8-level black-and-white printing (monochrome printing) in which the gradation value takes values from 0 to 7 is performed. When 8-level black-and-white printing is performed, the following energization control is performed. Specifically, a predetermined pulse is input to the heating element 71 of the thermal head 7 by the head drive circuit 17, and energization (main energization) corresponding to the number of input pulses (pulse number) is performed. Further, the gradation value of each dot (see FIG. 4) corresponds to the number of input pulses. Also, the longer the number of pulses input to one heating element 71, the longer the energization time to the heating element 71.

[0032] FIG. 5 is a diagram showing a print image and an energization waveform corresponding to each gradation value. As shown in FIG. 5, in the printing of one dot D, when the gradation value is 0, no pulse is input to the heating element 71 at all, the number of energizations (energization time) of the heating element 71 is also 0, and the printing density of the printed matter becomes the lowest value (white). When the gradation value of the dot D is 1, one pulse is input to the heating element 71, and the heating element 71 is energized for the energization time corresponding to the one input pulse, and the printing density of the printed matter becomes darker (blacker) than the printing density when the gradation value is 0. Similarly, when the gradation value of the dot D is increased, the energization time corresponding to the number of pulses (number of energizations) input to the heating element 71 also becomes longer, and the printing density of the printed matter also becomes darker (blacker). When the gradation value of the dot D is 7, seven pulses are input to the heating element 71, and the heating element 71 is energized for the energization time corresponding to the seven input pulses, and the printing density of the printed matter becomes the darkest (blackest). In the present embodiment, one dot (one dot D) is printed corresponding to one heating element 71 among the thermal heads 7. Further, in the present embodiment, the energization (main energization) of the heating element 71 corresponding to each of the gradation values 1 to 7 is performed within the main energization period assigned for the main energization within a predetermined printing cycle (3.12 ms). Further, in the present embodiment, as shown in the graph showing the relationship (thermal transfer characteristics) between the energization time (heating temperature) and the gradation value (printing density) in FIG. 6, the energization corresponding to the first input pulse (energization for changing the gradation value from 0 to 1) and the energization corresponding to the seventh input pulse (energization for changing the gradation value from 6 to 7) are set to be longer than the energizations corresponding to the pulses input in the second to sixth. This is to ensure that the color development with a gradation value of 1 and the color development with a gradation value of 7 are surely performed.

[0033] Also, in the printing of one dot D, when the gradation value is 7, as shown in FIG. 5, there are printing without history energization and printing with history energization. The history energization is to be performed for a predetermined time before the energization (main energization) performed in response to the input of the above-described pulse. Further, the history energization is performed based on the history data generated by a history data generation process (see FIG. 7) described later, targeting the dots for which the history data is set to ON, and is not performed for the dots for which the history data is set to OFF. In the present embodiment, the history energization is to be performed within the history energization period allocated for the history energization within a predetermined printing cycle (3.12 ms). Note that the history energization may be performed within the printing cycle (3.12 ms), for example, it may be performed after the main energization, that is, the history energization period may be provided after the main energization period.

[0034] Returning to the description of the block diagram of FIG. 3, the conveyance motor drive circuit 18 drives the conveyance motor 80 to rotate the platen roller 8. The conveyance motor 80 is, for example, a stepping motor, and is driven by the number of steps corresponding to the pulse signal input from the conveyance motor drive circuit 18, enabling accurate conveyance. As described above, the platen roller 8 of the present embodiment can rotate in the forward direction (positive direction) in the conveyance direction, and the conveyance motor drive circuit 18 appropriately inputs a signal to the conveyance motor 80 to rotate the platen roller 8 in the forward direction.

[0035] During the printing operation, the conveyance motor drive circuit 18 controls the drive of the conveyance motor 80 so that the rotation operation of the platen roller 8 (that is, the conveyance operation of the tape member 5) synchronizes with the progress speed of printing by the thermal head 7. Note that during the printing operation, a drive motor (not shown) that rotates the take-up shaft for taking up the ink ribbon also operates in synchronization with the rotation operation of the platen roller 8, and the conveyance of the tape member 5, printing by the thermal head 7, and take-up of the printed ink ribbon are performed with high precision in synchronization.

[0036] The cutter motor drive circuit 19 controls the operations of the full cut mechanism drive motor 90a that operates the full cut mechanism 9a and the half cut mechanism drive motor 90b that operates the half cut mechanism 9b. Thereby, a full cut or a half cut of the tape member 5 is performed at an appropriate position.

[0037] Next, with reference to FIGS. 7 to 9, the operation of the thermal printer 1 of the present embodiment will be described. FIG. 7 is a flowchart showing the control procedure of the history data generation process performed during halftone printing. FIG. 8 is a table showing each dot scanned for a certain line (previous line and current line) and the tone value of each dot in the history data generation process. FIG. 9 is a diagram showing an example of a method for generating history data.

[0038] As shown in FIG. 7, when the history data generation process is started, first, the control unit 10 of the thermal printer 1 scans the print data of the line (previous line) immediately before the line (current line) that is the generation target of the history data from among the print data for performing halftone printing, in units of 4 dots in order from the end of the line (step S1). Specifically, as shown in FIG. 4, 4 dots belonging to each of the history reference groups G1 to G6 are scanned in the order of the history reference groups G1, G2, G3, G4, G5, and G6. Here, when the line (current line) that is the generation target of the history data is the first line (the first line) of the print data, there is no previous line. For this reason, in such a case, it is assumed that there is a previous line in which dots with a tone value of 0 (the minimum tone value) are arranged in a row and corresponding processing is performed.

[0039] Next, the control unit 10 determines whether there is a dot with a tone value of 0 (the minimum tone value) in the area (history reference group; 4 dots) scanned in step S1 (step S2). Here, as described above, when the line (current line) that is the generation target of the history data is the first line of the print data, in step S2, it is assumed that there is a dot with a tone value of 0 in the scanned area.

[0040] In step S2, when it is determined that there are dots with a tone value of 0 in the area scanned in step S1 (step S2; YES), the control unit 10 sets the history data of only the dots with a tone value of 7 (maximum tone value) in the area of the current line corresponding to the scanned area to ON (step S3). That is, in step S3, for dots with a tone value smaller than 7 (maximum tone value) (tone values 0 to 6) in the area of the current line corresponding to the scanned area, the history data is set to OFF.

[0041] For example, as shown in FIGS. 8 and 9, when it is determined that dot D4 among dots D1 to D4 in the scanned first area (printing field) R1 (history reference group G1) has a tone value of 0 (white), that is, when it is determined that the heat storage amount in the first area R1 is not sufficient, only the two dots D13 and D14 with a tone value of 7 (maximum tone value) among dots D11 to D14 in the area of the current line corresponding to the first area R1 (history reference group G1) have their history data set to ON. As a result, for dots D13 and D14 in the area of the current line where the history data is set to ON, printing with a tone value of 7 with history energization (see FIG. 5) will be performed. That is, when there is a heating element 71 to which a tone value of 0 (minimum tone value) was assigned in the previous first area (printing field) R1, under the control of the control unit 10, in association with the current first area (printing field) R1, a heat adjustment process in which energization is performed for a predetermined time as history energization is executed on the heating element 71 to which a tone value of 7 (maximum tone value) is assigned in the current first area (printing field) R1. In other words, when there is a heating element 71 to which a tone value of 7 (maximum tone value) is assigned in the current first area (printing field) R1 and there was a heating element 71 to which a tone value of 0 (minimum tone value) was assigned in the previous first area (printing field) R1, under the control of the control unit 10, in association with the current first area (printing field) R1, a heat adjustment process in which energization is performed for a predetermined time as history energization is executed on the heating element 71 to which a tone value of 7 (maximum tone value) is assigned in the current first area (printing field) R1.

[0042] Also, in step S2, when it is determined that there are no dots with a gradation value of 0 in the area scanned in step S1 (step S2; NO), the control unit 10 sets the history data of the area of the current line corresponding to the scanned area to OFF (step S4).

[0043] For example, as shown in FIGS. 8 and 9, when it is determined that there are no dots with a gradation value of 0 (white) among the dots D5 to D8 in the scanned second area (printing field) R2 (history reference group G2), that is, when it is determined that the heat storage amount of the second area R2 is sufficient, the history data of the area of the current line corresponding to the second area R2 (history reference group G2) is set to OFF. That is, when there is no heat generating element 71 to which a gradation value of 0 (minimum gradation value) was assigned in the previous second area (printing field) R2, under the control of the control unit 10, a heat adjustment process in which the history energization associated with the current second area (printing field) R2 is omitted is executed. In other words, when there is no heat generating element 71 to which a gradation value of 7 (maximum gradation value) is assigned in the current second area (printing field) R2, under the control of the control unit 10, a heat adjustment process in which the history energization associated with the current second area (printing field) R2 is omitted is executed.

[0044] Next, the control unit 10 determines whether or not the scanning for one line targeting the previous line has been completed (step S5).

[0045] In step S5, when it is determined that the scanning for one line targeting the previous line has not been completed (step S5; NO), the control unit 10 updates the area to be scanned (4 dots) (step S6). For example, if the area to be scanned has been an area belonging to the history reference group G1 (see FIG. 4) until then, the area to be scanned is updated to an area belonging to the history reference group G2 (see FIG. 4). Then, the control unit 10 returns the process to step S1 and repeats the subsequent processes.

[0046] Also, in step S5, when it is determined that the scan for one line of the previous line has been completed (step S5; YES), the control unit 10 updates the previous line to be scanned to the next line (step S7).

[0047] Next, the control unit 10 determines whether the updated previous line is the last line of the print data (step S8).

[0048] In step S8, when it is determined that the updated previous line is not the last line of the print data (step S8; NO), the control unit 10 returns the process to step S1 and repeats the subsequent processes.

[0049] Also, in step S8, when it is determined that the updated previous line is the last line of the print data (step S8; YES), the control unit 10 ends the history data generation process.

[0050] As described above, when there is a heating element 71 to which the gradation value 0 (minimum gradation value) was assigned in the previous print field, the control unit 10 of the thermal printer 1 performs energization for a predetermined time as history energization on the heating element 71 to which the gradation value 7 (maximum gradation value) is assigned in the current print field, in association with the current print field. On the other hand, when there is no heating element 71 to which the gradation value 0 (minimum gradation value) was assigned in the previous print field, the control unit 10 executes a heat adjustment process in which the history energization associated with the current print field is omitted. Therefore, according to the thermal printer 1, when there is a dot with a tone value of 0 in the previous print field, it is determined that the heat storage amount of the heating element 71 corresponding to the print field is low. While associating with the current print field, history energization is performed on the heating element 71 to which a tone value of 7 is assigned in the current print field. On the other hand, when there is no dot with a tone value of 0 in the previous print field, it is determined that the heat storage amount of the heating element 71 corresponding to the print field is high, and the history energization associated with the current print field is omitted. Thus, it is possible to prevent gradation deviation from occurring due to the difference in heat storage amount generated by the difference in the density of dots with high tone values.

[0051] Further, the control unit 10 divides the plurality of heating elements 71 into a plurality of history reference groups (4 dots) G1 to G6, and then executes the above heat adjustment process for each of the history reference groups G1 to G6. Therefore, according to the thermal printer 1, since the density of dots with high tone values is determined for each of the plurality of history reference groups G1 to G6, the determination can be made accurately. As a result, the above heat adjustment process can be performed more appropriately for each of the plurality of history reference groups G1 to G6, so that it is possible to further prevent gradation deviation from occurring due to the difference in heat storage amount generated by the difference in the density of dots with high tone values.

[0052] As described above, the present invention has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments and can be modified without departing from the gist thereof. For example, in the above embodiment, in step S1 of the history data generation process (see FIG. 7), the print data of the previous line is scanned in units of 4 dots. However, it may be scanned in units of 5 dots or more, or may be scanned in units of 2 dots or 3 dots. That is, the history reference group may be a group with 5 dots or more as one unit, or may be a group with 2 dots or 3 dots as one unit.

[0053] In addition, in the above-described embodiment, the thermal printer 1 that performs 8-bit grayscale printing with a minimum gradation value of 0 and a maximum gradation value of 7 has been described as an example. However, the gradation of printing is not limited to 8 bits. For example, it may be a thermal printer that performs black-and-white printing with 16 bits (minimum gradation value 0, maximum gradation value 15) or 256 bits (minimum gradation value 0, maximum gradation value 255).

[0054] In addition, in the above-described embodiment, in step S2 of the history data generation process (see FIG. 7), it is determined whether there is a dot with a gradation value of 0 (minimum gradation value) in the scanned area (4 dots). However, for example, it may be determined whether there is a dot with a gradation value of 1 (first gradation value) or less in the scanned area (4 dots). Then, in this step S2, if it is determined that there is a dot with a gradation value of 1 (first gradation value) or less in the scanned area (step S2; YES), in step 3, for example, only the dots with gradation values of 6 (second gradation value) and 7 (gradation value equal to or greater than the second gradation value) in the area of the current line corresponding to the scanned area are set to ON for the history data, and the history data is set to OFF for the dots with gradation values of 0 to 5 (gradation values smaller than the second gradation value). On the other hand, in the above step S2, if it is determined that there is no dot with a gradation value of 1 (first gradation value) or less in the scanned area (step S2; YES), in step 4, the history data of the area of the current line corresponding to the scanned area may be set to OFF.

[0055] In addition, in the above-described embodiment, an example in which the storage unit 11 (for example, a FLASH memory or the like) is used as a computer-readable medium for the program according to the present invention has been disclosed. However, the present invention is not limited to this example. As other computer-readable media, portable recording media such as CD-ROMs can be applied. In addition, a carrier wave is also applied to the present invention as a medium for providing the data of the program according to the present invention via a communication line.

[0056] Although embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0057] 1 Thermal printer 2 Device housing 3 Lid 4 Display unit 5 Tape member 6 Input unit 7 Thermal head 8 Platen roller 9a Full cut mechanism 9b Half cut mechanism 10 Control unit 11 Storage unit 12 Power supply circuit 14 Display unit drive circuit 17 Head drive circuit 18 Conveyor motor drive circuit 19 Cutter motor drive circuit 21 Cassette storage unit 22 Discharge port 31 Window portion 51 Tape cassette 71 Heating element 72 Thermistor 80 Conveyor motor 90a Full cut mechanism drive motor 90b Half cut mechanism drive motor

Claims

1. A thermal printer having a plurality of heating elements arranged in a predetermined direction, capable of printing dots corresponding to the heating elements in multi-levels by controlling the energization time or the number of energization times to each heating element, comprising control means for dividing the plurality of heating elements into a plurality of groups and performing preheating treatment for each group, wherein the control means, as the preheating treatment, for a group including a heating element to which the minimum gradation value was assigned in the previous printing among the plurality of groups, for a heating element included in the group and to which the maximum gradation value is assigned in the current printing, performs a process of energizing for a predetermined time as history energization, and for a group not including a heating element to which the minimum gradation value was assigned in the previous printing among the plurality of groups, performs a process of omitting the history energization in the current printing, and executes, a thermal printer characterized by the above.

2. In the preheating treatment, for a heating element to which a gradation value smaller than the maximum gradation value in the current printing is assigned, the history energization is omitted in the current printing, a thermal printer according to Claim 1, characterized by the above.

3. A thermal printer having a plurality of heating elements arranged in a predetermined direction, capable of printing dots corresponding to the heating elements in multi-levels by controlling the energization time or the number of energization times to each heating element, comprising control means for dividing the plurality of heating elements into a plurality of groups and performing preheating treatment for each group, wherein the control means, as the preheating treatment, for a group including a heating element to which a gradation value equal to or lower than a first gradation value was assigned in the previous printing among the plurality of groups, for a heating element included in the group and to which a gradation value equal to or higher than a second gradation value greater than the first gradation value is assigned in the current printing, performs a process of energizing for a predetermined time as history energization, and for a group not including a heating element to which a gradation value equal to or lower than the first gradation value was assigned in the previous printing among the plurality of groups, performs a process of omitting the history energization in the current printing, a thermal printer characterized by the above.

4. In the preheating treatment, for a heating element to which a gradation value smaller than the second gradation value in the current printing is assigned, the history energization is omitted in the current printing, The thermal printer according to claim 3, characterized in that...

5. A method of energization executed by a thermal printer having a plurality of heating elements arranged in a predetermined direction and capable of printing dots corresponding to the heating elements in multi - tones by controlling the energization time or the number of energizations to each heating element, wherein the plurality of heating elements are divided into a plurality of groups and heat - conditioning processing is executed for each group, the heat - conditioning processing includes, for the group including the heating element to which the minimum gradation value was assigned in the previous printing among the plurality of groups, a process in which energization is performed for a predetermined time as history energization on the heating element included in the group and to which the maximum gradation value is assigned in the current printing, and for the group not including the heating element to which the minimum gradation value was assigned in the previous printing among the plurality of groups, a process in which the history energization is omitted in the current printing, including A method of energization, characterized in that...

6. A computer of a thermal printer having a plurality of heating elements arranged in a predetermined direction and capable of printing dots corresponding to the heating elements in multi - tones by controlling the energization time or the number of energizations to each heating element, functions as a control means for dividing the plurality of heating elements into a plurality of groups and executing heat - conditioning processing for each group, the control means, as the heat - conditioning processing, for the group including the heating element to which the minimum gradation value was assigned in the previous printing among the plurality of groups, a process in which energization is performed for a predetermined time as history energization on the heating element included in the group and to which the maximum gradation value is assigned in the current printing, and for the group not including the heating element to which the minimum gradation value was assigned in the previous printing field among the plurality of groups, a process in which the history energization is omitted in the current printing, executes A program, characterized in that...

Images