JP2022187168A - Printer, printing method of printer and program - Google Patents

Abstract

To provide a technique that controls to suppress a reduction in printing quality in changing the printing speed of the printer comprising a thermal head from a preset value.SOLUTION: A printer according to an aspect of the present invention performs printing on a printing medium having a thermosensitive color developing layer. The printer comprises: a thermal head having a plurality of heater elements arranged linearly; a pulse setting part that sets a first application period for an energization pulse for applying heat energy to cause the thermosensitive color developing layer to develop colors to the plurality of heater elements in a printing cycle of one line; a first correcting part that corrects a printing speed at the time of performing printing so that the printing speed is reduced from a preset printing speed before performing printing on the printing medium; and a second correcting part that corrects the printing speed corrected by the first correcting part and/or the length of the first application period so that the difference in the ratio of the energization pulse occupied in the printing cycle in the first application before and after the printing speed is corrected by the first correcting part is below a predetermined value.SELECTED DRAWING: Figure 3

Description

The present invention relates to a printer, a printing method for the printer, and a program.

In general, a thermal head prints information by generating heat by applying a predetermined current independently to a plurality of heating elements arranged in a line to form a dot pattern on a print medium having a thermosensitive coloring layer. At this time, the presence or absence of coloring of the dots corresponding to the heating element is controlled by the duration of current flow through the heating element (that is, the energization pulse width).
2. Description of the Related Art When printing on a print medium with a thermal head, a method is known in which the print speed is variably controlled for each line to be printed. For example, Japanese Patent Laid-Open No. 2002-200001 discloses that a detection means for detecting the ratio of the print area for each line in the direction perpendicular to the conveyance of the recording medium from the print data is associated with the print density, the ratio of the print area, and the conveyance speed. A label printer comprising storage means for storing a transport speed table, and transport means for transporting a recording medium by referring to the transport speed table to determine the transport speed from the value of the ratio of the printing area detected by the detection means. is described.

JP 2010-228259 A

If the print speed is one of a plurality of preset speed settings (for example, the speed set in the transport speed table of Japanese Patent Application Laid-Open No. 2002-200010), the following steps are performed in advance so that a predetermined print density can be obtained. The strobe time for applying thermal energy to the heating elements of the thermal head can be optimally set. That is, it is possible to verify in advance that a predetermined print density is obtained for each of the plurality of speed setting values. However, if you try to change to a speed different from the preset multiple speed settings according to the printing environment of the printer or the layout of the image to be printed, the print quality at such a speed has not been verified. Therefore, print quality may deteriorate.
Therefore, it is conceivable to increase the number of preset speed setting values. However, when many speed setting values are set in advance, trial and error is required to determine the strobe time so as to obtain a predetermined print quality for each speed setting value, which entails a great deal of labor in printer development.

Accordingly, the present invention is intended to provide a control method for suppressing deterioration in print quality when changing the print speed from a preset value in a printer equipped with a thermal head. aim.

One aspect of the present invention is a printer that prints on a print medium having a thermosensitive coloring layer.
This printer
a thermal head having a plurality of heating elements arranged in a line;
a pulse setting unit for setting a first application period of an energizing pulse for applying heat energy for coloring the thermosensitive coloring layer to the plurality of heating elements in a one-line printing cycle;
a first correction unit that corrects a printing speed during printing so as to decelerate from a preset printing speed before printing on the printing medium;
The printing speed after correction by the first correction unit so that the difference in the ratio of the first application period of the energizing pulse to the printing cycle before and after the correction of the printing speed by the first correction unit is equal to or less than a predetermined value, and / Or, a second correction unit that corrects the length of the first application period;
Prepare.

According to one aspect of the present invention, it is possible to provide a control method for suppressing deterioration in print quality when changing the print speed from a preset value in a printer equipped with a thermal head.

4A and 4B are schematic cross-sectional views of the printer for explaining a printing operation by the printer of one embodiment; FIG. 1 is a functional block diagram of a printer according to one embodiment; FIG. 2 is a functional block diagram focusing on a control unit and a thermal head in the printer of one embodiment; FIG. 1 is a schematic circuit diagram of a thermal head of one embodiment; FIG. FIG. 7 is a diagram showing the relationship between the strobe level and the timing at which current substantially flows through the heating element during each period in which the strobe signal is applied during the print cycle, in print control according to an embodiment. It is a figure which shows the data structural example of a reference strobe table. 4 is a timing chart showing transfer timings of data signals and application timings of strobe signals in a printing cycle in the printer of one embodiment. FIG. 5 is a diagram illustrating a printing speed control method according to an example and a comparative example; FIG. 11 illustrates a battery voltage correction table and a dot number correction table; It is a figure which illustrates a temperature correction table. FIG. 4 is a diagram illustrating a continuously variable speed method in the printer of one embodiment; 4 is a flow chart of pre-printing processing in the printer of one embodiment. 13 is a flowchart of deceleration correction processing included in the speed correction processing of FIG. 12; 14 is a flowchart of a density correction simulation included in the deceleration correction process of FIG. 13; 13 is a flowchart of density ratio correction processing included in the speed correction processing of FIG. 12; 4 is a flow chart of processing during printing in the printer of one embodiment. FIG. 4 is a diagram illustrating a continuously variable speed method in the printer of one embodiment;

A printer according to an embodiment will be described below. A printer according to one embodiment is a thermal printer that prints on a print medium having a thermosensitive coloring layer. The print medium may contain any material as a base material, and is not limited to paper as the base material. For example, a film can be used as the substrate.
A printer according to one embodiment includes a thermal head having a plurality of heating elements arranged in a line, and a pulse setting section. The pulse setting unit sets an application period (first application period) of an energizing pulse for applying thermal energy for coloring the thermosensitive coloring layer to the plurality of heating elements of the thermal head in one line printing cycle. A strobe signal, which will be described later, is an example of an energizing pulse.

In one embodiment, the printer corrects the length of the first application period set by the pulse setting unit based on the image to be printed, and prints so that the maximum length of the first application period after correction is within the range. Lengthening the cycle determines the printing speed when printing the entire image at a constant speed. As a result, since the printing speed does not change throughout the period during which the image is printed, uneven printing density can be avoided, and the overall printing quality of one page can be improved.

In the printer of one embodiment, before printing on a print medium, the print speed during printing is corrected so as to decelerate from a preset print speed. Furthermore, the printing speed after correction and/or the length of the first application period is adjusted so that the difference in the ratio of the first application period of the energizing pulse to the printing cycle before and after the correction of the printing speed is equal to or less than a predetermined value. is corrected. As will be described later, according to knowledge obtained by the inventor, since the print density is determined according to the ratio of the first application period of the energizing pulse to the print cycle, the difference in the ratio before and after the correction does not change significantly. By doing so, fluctuations in print density can be suppressed.
Hereinafter, printers according to embodiments will be described in more detail with reference to the drawings.

FIG. 1 illustrates a printer 1 according to one embodiment. The printer 1 is a thermal printer that prints on a label having a thermosensitive coloring layer on one side.
As shown in FIG. 1, the printer 1 has a roll paper chamber 9, a platen roller 10, a thermal head 15, a printer cover 25, a coil spring 29, and the like. The roll paper R can be loaded into the roll paper storage chamber 9 by opening and closing the printer cover 25 .
The roll paper R is a belt-shaped continuous paper P wound into a roll. Although not shown, in one embodiment, the continuous paper P has, for example, a band-shaped mount and a plurality of labels temporarily attached to the mount at predetermined intervals. The labeling surface of the mount is coated with a release agent such as silicone so that the label can be easily peeled off.
In another embodiment, the continuous paper P may be a linerless label.

As shown in FIG. 1, the printer 1 supports a platen roller 10 so as to be rotatable in forward and reverse directions. The platen roller 10 is conveying means for conveying the continuous paper P pulled out from the roll paper R, and is formed in a state extending along the width direction of the continuous paper P. As shown in FIG. A gear (not shown) is provided at one end of the platen shaft of the platen roller 10, and this gear is mechanically connected to a stepping motor (not shown) for driving the roller. The platen roller 10 rotates according to the rotation of a stepping motor that operates based on a signal transmitted from a circuit board (not shown).

The thermal head 15 is printing means for printing information such as characters, symbols, graphics, or codes on a label on the continuous paper P, for example. The thermal head 15 includes a plurality of heating elements (heating resistors) arranged along the width direction of the continuous paper P, and selectively energizes the plurality of heating elements based on signals transmitted from the circuit board. to print.
The thermal head 15 is arranged to face the platen roller 10 when the printer cover 25 is closed, and sandwiches the continuous paper P together with the platen roller 10 . The coil spring 29 is an urging means for urging the thermal head 15 toward the platen roller 10 and generates a nip pressure suitable for printing between the thermal head 15 and the platen roller 10 .
In the following description, the direction orthogonal to the conveying direction of the continuous paper P (that is, the direction in which the heating elements are arranged) is called the "main scanning direction," and the same direction as the conveying direction of the continuous paper P is called the "sub-scanning direction." ”.
Thermal head 15 will be described in more detail later.

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

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

The drive circuit 13 is a circuit that drives a motor 14 that controls the rotation of the platen roller 10 in response to a transport request from the controller 11 . Motor 14 is, for example, a stepping motor. The transport request includes, for example, information on the transport direction (forward or reverse direction) and the transport amount (for example, the number of steps).

Based on the image data to be printed, the control unit 11 executes print processing by selectively applying current to each of the plurality of heating elements included in the thermal head 15 . Image data is data obtained by drawing a file for printing into bitmap data. When the heating element of the thermal head 15 heated by the electric current is pressed against the label on the continuous paper P conveyed by the platen roller 10, the heat-sensitive coloring layer of the label pressed by the heating element develops color, and information is printed on the label. is printed.

The communication interface 16 includes communication circuitry for communicating with an external device such as a host computer.

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

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

The memory 113 (an example of a storage unit) is, for example, a RAM (Random Access Memory), and has a first-in-first-out (FIFO) configuration image buffer, line buffer, thermal history data table, and reference strobe table.

In one embodiment, the CPU 111 performs thermal history control to perform printing. Thermal history control adjusts the length of the strobe application period, which is the energization pulse width, based on the data of past energization of the heating element and/or the data of the scheduled energization of the heating element, and the thermal energy to the heating element is controlled. is a constant control.
In order to perform heat history control, the CPU 111 generates data obtained by changing the original image data based on the print data of the dot of interest in the original image data to be printed and the print data of the dots surrounding the target dot (hereinafter referred to as , referred to as “thermal history reflection data”). The thermal history reflection data is stored in the image buffer.
In the following description, "image data" means original image data before being changed into heat history reflection data.

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

The line data of the image data includes print data indicating whether or not each dot is to be printed. The print data is either "print" or "non-print".
On the other hand, the data for each dot of the line data of the thermal history reflection data corresponding to one line data of the image data corresponds to a data signal for a plurality of times, and is data indicating either "energized" or "non-energized". It has become.

The line buffer sequentially stores the line data of the thermal history reflection data.
As described above, the heat history data table is referred to when generating heat history reflection data.
The thermal history data table includes application data of a dot to be processed (hereinafter referred to as a "dot of interest") in a line to be printed (hereinafter referred to as a "line of interest") in image data, and It shows the relationship between the print data of the dot corresponding to the dot of interest (that is, the past print data and the future print data) and the strobe level for the dot of interest during the printing cycle.

Here, the strobe level indicates the level (high level or low level) of each data signal during a plurality of strobe application periods to the heating element corresponding to the dot of interest. The level of the data signal indicates whether or not the energizing pulse is applied during each strobe application period. The strobe level indicates the length of time during which the current is substantially applied to the heating element in the print cycle. The higher the strobe level, the longer the current flows through the heating element during the printing period, so that the heating element receives a large amount of thermal energy.

The CPU 111 refers to the heat history data table, and determines the level of each data signal (high level indicating “energization” or low level indicating “non-energization”) during a plurality of strobe application periods for each dot of the line of interest. level). As a result, the thermal energy applied to the heating element corresponding to the current dot of interest is appropriately controlled in consideration of the print data of the current dot of interest and the print data before and after it.

The thermal history data table of another embodiment further includes the relationship between the print data of each dot adjacent to the dot of interest and the strobe level for the dot of interest during the printing cycle. By referring to the print data of the dots adjacent to the right and left of the dot of interest, the thermal energy received by the heating element corresponding to the dot of interest from the adjacent heating elements is also taken into consideration. The heat energy delivered is better controlled.

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

As shown in FIG. 3, the thermal head 15 includes a drive circuit 2, a heating element group 3, and a thermistor 4 (an example of a temperature detection section).
The heating element group 3 is composed of a plurality of heating elements (heating resistors) arranged in a line.
Based on various signals supplied from the head controller 112 , the drive circuit 2 selectively applies a current to each heating element of the heating element group 3 to generate heat. The thermistor 4 detects the temperature of the thermal head 15 (thermal head temperature).
A detailed configuration example of the drive circuit 2 and the heating element group 3 will be described later.

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

The drive circuit 2 is operated by data signal DATA, clock pulse CLK, latch pulse LATCH, and strobe signal STB, and these data and signals are input or transferred from head controller 112 . The transfer of the data signal DATA for one line may be divided and transferred using a plurality of line buffers in order to shorten the transfer time. In this case, each line buffer stores a divided part of the data signal DATA for one line and serially transfers from each line buffer.

In the driving circuit 2 of FIG. 4, the strobe signal STB is of positive logic (when the signal is at high level, a current flows through the heating element to generate heat). In another embodiment, the strobe signal STB may be of negative logic (when it is at low level, a current flows through the heating element to generate heat).

The data signal DATA for one line is input to the shift register 21 in synchronization with the clock pulse CLK and held. The data signal DATA (an example of an energization pulse) is composed of a bit string that is high level when energized and low level when not energized. The latch circuit 22 is connected in parallel to the shift register 21 and simultaneously transfers and holds the bit strings on the shift register 21 . Data transfer timing from the shift register 21 to the latch circuit 22 is controlled by a latch pulse LATCH.

The gate circuit group 23 includes gate circuits (AND circuits) 23_1, 23_2, . A strobe signal STB is supplied to one input terminal of each gate circuit, and the other input terminal of each gate circuit is connected to the output of the latch circuit 22 .
Each gate circuit of the gate circuit group 23 outputs the AND of the corresponding data signal DATA and strobe signal STB.
The transistor group 24 includes MOS transistors 24_1 to 24_M. Each MOS transistor is turned on/off according to the output of the corresponding gate circuit.

The logic level of the output terminal of each gate circuit in the gate circuit group 23 matches the output level of the latch circuit 22 while the strobe signal STB is at high level. For example, when the output level of the latch circuit 22 is a high level indicating "energization", the output of the corresponding gate circuit becomes a high level, so the corresponding MOS transistor is turned on and current flows through the heating element 31 . Conversely, when the output level of the latch circuit 22 is at a low level indicating "non-conducting", the output of the corresponding gate circuit is at a low level, so the corresponding MOS transistor is turned off and current flows through the heating element 31. No.

When the strobe signal STB is of negative logic, the configuration may be as follows.
That is, in FIG. 4, each gate circuit of the gate circuit group 23 is a NAND circuit, and an inverted signal of the strobe signal STB is input to the NAND circuit. As a result, the NAND circuit outputs an inverted signal of the output of the latch circuit 22 when the strobe signal STB is at low level. The corresponding MOS transistor is configured to be turned on when the output of the NAND circuit is at a low level so that a current flows through the heating element.

When the thermal history control is not performed, the data signal DATA is sent to the drive circuit 2 of the thermal head 15 once during the printing cycle for one line of line data. On the other hand, when thermal history control is performed, the thermal head 15 is driven by the data signal DATA (for example, data signals DATA1 to DATA4 described later) during a plurality of periods within the printing cycle for one line of line data. sent to circuit 2.

In one embodiment, the head controller 112 supplies the data signals DATA1 to DATA4 to the drive circuit 2 four times at predetermined timings synchronized with the clock pulse CLK during the print cycle.
When one line data of the image data is M-bit data, the corresponding line data of the thermal history reflection data is M×4-bit data. Each M bit of the M×4 bit data is divided into four and supplied to the driving circuit 2 as data signals DATA1 to DATA4.

The head controller 112 supplies a latch pulse LATCH and strobe signals STB1 to STB4 to the drive circuit 2 of the thermal head 15 at a predetermined timing synchronized with the clock pulse CLK. The relationship between the data signal transfer timing and the strobe signal application timing in one printing cycle when thermal history control is performed will be described later.

FIG. 5 shows a strobe level (STB level) and each period during which the strobe signals STB1 to STB4 are applied during a printing cycle (hereinafter referred to as a “strobe period” as appropriate) in thermal history control according to an embodiment. It shows the relationship with the timing (strobe pattern) at which the current flows to the heating element.
In the case of a positive logic thermal head, the current substantially flowing through the heating element means that the corresponding data signals DATA1 to DATA4 are at high level. That is, the data signals DATA1 to DATA4 are associated with strobe levels.
For example, the data signals DATA1 to DATA4 corresponding to the dot of interest are 4-bit data corresponding to the strobe level. For example, the data signals DATA1 to DATA4 are "0000" when the strobe level is "0", "0110" when the strobe level is "6", and "1111" when the strobe level is "15". ”.

In one embodiment, when the strobe level is 4 or more, heat energy is applied to the heating element to change the color of the thermosensitive coloring layer of the label. Although it does not apply to the element, it exerts a preheating effect on the heating element.

In one embodiment, as shown in FIG. 5, the four strobe signals STB1 to STB4 corresponding to the four data signals in the print cycle are set in order from long to short. In other words, when the lengths (strobe lengths) of the four strobe signals STB1 to STB4 are L1 to L4, respectively, L1>L2>L3>L4 is satisfied.
Preferably, the length ratio of the four strobe signals STB1-STB4 is 8:4:2:1. By setting the length ratio in this way, it is possible to maximize the number of combinations of time periods (that is, strobe lengths) for applying thermal energy to the heating elements during one printing cycle, thereby enabling fine setting of applied energy. becomes possible. The ratio of the lengths of the ^four strobe signals STB1 to STB4 is not limited to 8:4:2:1. A pattern can be set.

The CPU 111 refers to the heat history data table to determine the strobe level for each target dot of the target line data. The CPU 111 generates heat history reflection data by allocating 4-bit data corresponding to the strobe level to each dot of interest.
The head controller 112 assigns the data of the 1st bit to the 4th bit to the data signals DATA1 to DATA4 for each target dot of the line data of the thermal history reflecting data.

Next, a method for determining a preferable print speed and strobe length will be described.
In one embodiment, the CPU 111 refers to a reference strobe table to determine the strobe lengths L1-L4 of the strobe signals STB1-STB4 according to the print speed and print density.
FIG. 6 shows a configuration example of the reference strobe table.
As illustrated in FIG. 6, the reference strobe table includes strobe lengths L1 to L4 (that is, 50 different strobe pattern) is described. The print speed and print density defined in the reference strobe table are hereinafter referred to as "speed setting value" and "density setting value", respectively.
The reference strobe table serves as a reference for density correction, which will be described later, and is the strobe length when the thermal head temperature is 25° C., the battery voltage is the maximum voltage V _MAX , and the number of simultaneously printed dots is 1. is shown.

In the reference strobe table, the density setting values are darker (that is, the density is higher) in order from 1A to 10A. Although the numbers of speed setting values and density setting values are not limited, in the example shown in FIG. 6, there are 5 steps of speed setting values and 10 steps of density setting values, so 50 patterns of strobe lengths L1 to L4 are set. It is supposed to be The strobe lengths L1-L4 are not limited, but can be in the ratio of 8:4:2:1 as described above. Five speed setting values are an example of a plurality of printing speeds.
Although the reference strobe table shown in FIG. 6 includes the print cycle for reference, it is not essential to include the print cycle in the reference strobe table. Since the length of one line of the label to be printed is known, the print cycle is uniquely determined according to the speed setting value.
As shown in FIG. 6, the faster the speed setting value, the shorter the print cycle. Therefore, each strobe length is shortened in order to fit all the strobe lengths L1 to L4 within the print cycle. In addition, the higher the density setting value, the greater the required heat energy, and therefore the length of each strobe becomes longer.

In the reference strobe table, the density setting value is a relative setting value for density at a predetermined speed setting value. Therefore, when the speed setting value is different, the actually obtained print density (that is, the degree of density when actually printed on the label) differs even if the density setting value is the same. For example, the print density obtained by the density setting value 5A differs between when the speed setting value is 2 IPS and when it is 3 IPS.

FIG. 7 shows transfer timings of the data signals DATA1 to DATA4 and application timings of the strobe signals STB1 to STB4 when printing is performed with thermal history control in one embodiment. FIG. 7 is a timing chart showing the transfer timing of the data signal and the application timing of the strobe signal in the print cycle SLT. As shown in FIG. 7, a waiting time WT is set between consecutive strobe application periods.
In one embodiment, CPU 111 references a reference strobe table to determine the timing illustrated in FIG. 7 prior to printing. Here, the print cycle SLT is determined by the speed setting value. As shown in the reference strobe table of FIG. 6, in the case of "density setting value: 1 A", each strobe of the four strobe signals STB1 to STB4 is larger than in the case of "density setting value: 5 A" (default setting). length becomes shorter. On the other hand, in the case of "density setting value: 10 A", each strobe length of the four strobe signals STB1 to STB4 is longer than in the case of "density setting value: 5 A" (default setting).

Next, a method of determining the printing speed of the printer 1 of one embodiment will be described.
In one embodiment, instead of having the actual print speed be one of multiple speed settings in a reference strobe table, the print speed is varied from the speed settings based on the image being printed and the operating environment (e.g., battery voltage). change (i.e. variable speed).
In one embodiment, the print speed is set to a speed width (second speed width) smaller than a speed width (an example of the first speed width; 1 IPS in the example of FIG. 6) of a plurality of speed setting values defined in the reference strobe table. One example; for example, 1 mm/sec). The image to be printed is printed at a constant speed based on the adjusted print speed. That is, one page including the image to be printed is printed at a constant speed based on the adjusted printing speed.
As a result, since the actual printing speed may differ from the speed setting value, the printing speed becomes a best-effort type printing speed, but there is an advantage that the printing quality of the entire label is improved. Hereinafter, this printing speed determination method will be referred to as a "continuously variable speed method".

In the continuously variable speed method, the printing speed is adjusted before printing starts, and the printing speed does not change during printing.
As will be described later, in one embodiment, density correction is performed so that the print quality does not deteriorate due to the operating environment of the printer 1, the layout of the image to be printed, or the like. In this density correction, the strobe length is corrected for each line according to the operating environment such as battery voltage and thermal head temperature, the number of simultaneously printed dots in one line in the image to be printed, and the like. At this time, the image to be printed is analyzed before printing, and the printing speed is adjusted so that the strobe signal is within the printing cycle of one line even if the strobe length becomes maximum after correction.

Advantages of determining the printing speed by the continuously variable speed method will be described with reference to FIGS. 8A and 8B in comparison with the conventional method of determining the printing speed. FIG. 8A shows a portion of an exemplary image, and FIG. 8B shows changes in print speed over time (that is, the main in the scanning direction).
Here, as the conventional printing speed determination method, the "stepwise constant speed method" and the "stepwise variable speed method" are mentioned. The stepwise constant speed method is the simplest speed determination method, and the print speed is determined according to the speed setting value preset by the user from among multiple speed setting values, or the speed setting value set by default. It is a method to
The stepwise variable speed method is a method in which the print speed is changed line by line to one of a plurality of preset speed setting values according to the strobe length required as a result of density correction. is.
In FIG. 8B, M1 indicates the printing speed for the stepwise constant speed method, M2 indicates the printing speed for the stepwise variable speed method, and M3 indicates the printing speed for the continuously variable speed method.

In FIG. 8A, the image to be printed includes image portions IM1 to IM3 in which the number of simultaneously printed dots in one line is relatively large. For example, image portions IM1 to IM3 include a straight line, which is a typical example of a large number of simultaneously printed dots in the sub-scanning direction.
Referring to FIG. 8B, in the stepped constant speed method (M1), all lines are printed at a predetermined speed setting (4 IPS in FIG. 8B). Therefore, in order to make the print density uniform over the entire image, the user must select the optimum speed setting value in advance according to the operating environment such as the image to be printed and the battery voltage. However, this is not realistic and results in poor print quality. For example, even if it is necessary to lengthen the strobe length in order to secure the required print density by density correction, if the lengthened strobe length does not fall within the print cycle corresponding to the predetermined speed setting value, Since the necessary heat energy cannot be applied to the heating element, the print density is lowered.

In the stepwise variable speed method (M2), a relatively low speed is set for lines with a large number of dots printed simultaneously in one line, such as image portions IM1 to IM3, and other image portions (that is, dots printed in one line simultaneously) are set at a relatively low speed. It is controlled to be relatively fast for image parts consisting of a small number of lines). For example, a line with a relatively small number of simultaneously printed dots is printed at high speed by batch printing, and a line with a relatively large number of simultaneously printed dots is printed at a low speed by divided printing. Divided printing is a method of printing by dividing one line into a plurality of parts. According to a simple calculation, if one line is divided into two, the printing speed is halved. Therefore, in the stepwise variable speed method (M2), the throughput may be greatly reduced (that is, the time required to print the entire image may become longer) depending on the layout of the entire image to be printed.
Further, when there are few blank portions in the main scanning direction, the printing speed cannot be fully returned, and printing may be performed while the speed is changing. During this speed change, the balance between the printing speed and the strobe length is lost (in other words, the balance between the ON (heating) and OFF (cooling) times is lost). Print quality deteriorates.
In summary, the stepwise variable speed method has the problem that the throughput and image quality may be degraded depending on the print layout.

The continuous variable speed method (M3) according to one embodiment is different from the conventional stepwise constant speed method and stepwise variable speed method, and is intended to improve the print quality of the label by uniforming the print density over the entire image. It is a method that makes it possible. The continuously variable speed system will be described in detail below.

First, density correction according to an embodiment will be described with reference to FIGS. 9 and 10. FIG. As described above, in the density correction, the strobe length is corrected for each line according to the operating environment such as the battery voltage and the number of simultaneously printed dots in one line in the image to be printed.

In one embodiment, concentration correction includes battery voltage correction that corrects strobe length based on battery voltage.
Since the electric power applied to the heating element 31 of the thermal head 15 is reduced due to the decrease in battery voltage, the battery voltage is corrected so as to compensate for the decrease in the applied electric power by lengthening the strobe length.
Battery voltage correction is performed, for example, with reference to a battery voltage correction table shown in FIG.

As shown in FIG. 9, in the battery voltage correction table, the battery voltage and the voltage correction ratio are described in association with each other. The voltage correction ratio is a value by which the strobe length described in the reference strobe table is multiplied in the battery voltage correction. The reference battery voltage is the maximum voltage V _MAX , and the voltage correction ratio (“100%”) at this time does not change the strobe length described in the reference strobe table.
The battery voltage correction table is written so that the voltage correction ratio increases as the battery voltage decreases. Therefore, in the battery voltage correction, as the battery voltage becomes lower, the strobe length is corrected to be longer than the value described in the reference strobe table.
In a non-limiting example, the maximum voltage V _MAX is approximately 16 to 17 V, and the minimum voltage V _MIN is approximately 12 to 13 V, set in steps of 0.01 V to 0.05 V, for example.
In the battery voltage correction, it is not always necessary to refer to the battery voltage correction table, and the voltage correction ratio may be calculated using a known function that defines the relationship between the battery voltage correction and the voltage correction ratio. In that case, the function defines the relationship between the battery voltage and the voltage correction ratio so that the amount of heat applied corresponding to the difference between the maximum voltage V _MAX and the current battery voltage is compensated for by extending the strobe time.

In one embodiment, the density correction includes head voltage drop correction and power supply voltage drop correction for correcting the strobe length based on the number of simultaneously printed dots.
In the thermal head 15, as the number of simultaneously printed dots in one line (printing rate in one line) increases, the voltage drop caused by the ON resistance in the circuit (for example, the ON resistance of the MOS transistor in FIG. 4), the conduction resistance, etc. As a result, the power applied to the heating element 31 is reduced. Therefore, head voltage drop correction is performed so as to compensate for the decrease in applied power by lengthening the strobe length.
On the other hand, as the number of simultaneously printed dots increases in one line, the peak current flowing through the thermal head 15 rises, causing a drop in the power supply voltage and the power applied to the heating element 31 to drop. Therefore, power supply voltage drop correction is performed so as to compensate for the decrease in applied power by lengthening the strobe length.

Head voltage drop correction and power supply voltage drop correction are performed, for example, with reference to a dot number correction table shown in FIG. In one embodiment, individual dot number correction tables are prepared for each of head voltage drop correction and power supply voltage drop correction.

As shown in FIG. 9, in the dot number correction table, the number of simultaneously printed dots and the dot number correction ratio are described in association with each other. The dot number correction ratio is a value by which the strobe length described in the reference strobe table is multiplied in head voltage drop correction and power supply voltage drop correction. The reference number of simultaneously printed dots is "1", and the voltage correction ratio ("100%") at this time does not change the strobe length described in the reference strobe table.
The dot number correction table is written so that the dot number correction ratio increases as the number of simultaneously printed dots increases. Therefore, in head voltage drop correction and power supply voltage drop correction, as the number of simultaneously printed dots increases, the strobe length is corrected to be longer than the value described in the reference strobe table.

In one embodiment, density correction includes head temperature correction that corrects strobe length based on thermal head temperature. The thermal head temperature is detected by a thermistor 4 (FIG. 3).
In order to minimize variations in print density due to temperature variations in the thermal head 15, head temperature correction is performed. Head temperature correction is performed, for example, with reference to a temperature correction table shown in FIG.

As shown in FIG. 10, the temperature correction table describes the thermal head temperature and the temperature correction ratio in association with each other. The temperature correction ratio is a value by which the strobe length described in the reference strobe table is multiplied in head temperature correction. The reference thermal head temperature is 25° C., and the temperature correction ratio (“100%”) at this time does not change the strobe length described in the reference strobe table.
The temperature correction table describes such that the temperature correction ratio increases as the thermal head temperature decreases, and decreases as the thermal head temperature increases. Therefore, in head temperature correction, the strobe length may be longer or shorter than the value described in the reference strobe table depending on the thermal head temperature.
Note that in head temperature correction, it is not always necessary to refer to a temperature correction table, and a function may be defined that assumes a linear relationship between the thermal head temperature and the temperature correction ratio. For example, the temperature correction ratio may be defined in advance as a linear function of the difference between the reference value of the thermal head temperature (25° C. in the example of FIG. 10) and the current value (measured value) of the thermal head temperature.

Note that the density correction in one embodiment includes at least one of battery voltage correction, head voltage drop correction, power supply voltage drop correction, and head temperature correction.
When density correction is performed as described above, the strobe length may not fit within the current print cycle by making the strobe length longer than the value described in the reference strobe table. Therefore, in the continuously variable speed method, simulation of density correction is performed before printing, and the printing speed is controlled to be reduced from the speed setting value so as to fall within the printing cycle even in the case of the maximum strobe length due to density correction. . In other words, the print quality does not fluctuate due to the strobe length being out of the print cycle due to the operating environment such as the battery voltage and the layout of the image to be printed.

Furthermore, as a result of earnest research by the inventors of the present application, the following findings (I) and (II) were obtained.
(I) The print density is roughly determined by the ratio of the continuous pulse time within the print cycle (hereinafter referred to as "density ratio").
Here, the "continuous pulse time" is the length of the strobe period for applying heat energy for coloring the thermosensitive coloring layer, and in the example shown in FIG. It is the length of the period (an example of the first application period) until the timing of the falling edge of STB2.

(II) Even if the density ratio is the same, the lower the printing speed, the higher the print density.
For example, in the reference strobe table shown in FIG. 6, even if the density ratio in the case of a density setting value of 5A (standard) does not differ greatly among a plurality of speed setting values, the lower the speed setting value is, the more the actual density ratio becomes. The resulting print density is darker. Therefore, in order to keep the print density unchanged even when the print speed is decelerated from the speed set value, it is necessary to decrease the density ratio along with the deceleration of the print speed.

Based on the knowledge of (I) and (II) above, in the continuously variable speed method, the deceleration correction processing of the print speed is executed according to the execution result of the density correction simulation before printing, and the print speed after the correction is executed. density ratio correction processing. The deceleration correction process and density ratio correction process will be described with reference to FIG. FIG. 11 is a diagram for explaining deceleration correction processing and density ratio correction processing in the continuously variable speed method.

Referring to FIG. 11, state ST1 shows strobe signals STB1 to STB4 at the speed setting value and density setting value set immediately before printing in the reference strobe table. A print cycle SLT1 is determined according to the speed setting value. FIG. 11 shows the continuous pulse time CP including the application periods of the strobe signals STB1 and STB2 in the state ST1.

State ST2 in FIG. 11 is the result of density correction simulation performed on the strobe signals STB1 to STB4 shown in state ST1. to STB4_max. In one embodiment, each strobe length of the strobe signals STB1_max to STB4_max is the maximum of the voltage correction ratio (FIG. 9)×dot number correction ratio (FIG. 9) with respect to each strobe length of the reference strobe signals STB1 to STB4. It is the value when multiplied by the value. This maximum value varies depending on the layout of the image to be printed and the battery voltage at that time.

The purpose of this density correction simulation is to pre-estimate the maximum strobe length due to density correction during printing in order to determine the printing speed before printing.
When density correction is performed during printing, the reference strobe signals STB1 to STB4 and the strobe signal STB1_max for the maximum strobe length are set according to the number of dots simultaneously printed for each line of the image to be printed and the temperature of the thermal head. to STB4_max, the strobe length of the applied strobe signal varies from line to line.

State ST2 in FIG. 11 shows a case where the strobe signals STB1_max to STB4_max when the strobe length is maximized by the density correction do not fall within the printing cycle SLT1 determined by the speed setting value.
Therefore, in the deceleration correction process, the printing speed is corrected so that the strobe signals STB1_max to STB4_max are within the printing cycle. As described above, adjustment is made at a speed width (for example, 1 mm/sec) that is smaller than the speed width (1 IPS in the example of FIG. 6) of a plurality of speed setting values defined in the reference strobe table. Therefore, the strobe signals STB1_max to STB4_max can be accommodated, and the speed reduction can be minimized with respect to the preset speed setting value.

State ST3 in FIG. 11 shows a state in which deceleration correction processing is performed on the strobe signals STB1 to STB4 in state ST1 to extend the print cycle from SLT1 to SLT2. By extending the print cycle in this way, even when printing any line of the image to be printed (that is, even when printing the line with the maximum number of simultaneously printed dots in the image), ), the strobe signal does not fall within the printing cycle due to the density correction.

As described above, the print density is generally determined by the density ratio (above (I)), but when state ST3 is compared with state ST1, by extending the print cycle from SLT1 to SLT2, the reference strobe signal STB1 ∼ The concentration ratio of STB4 changes (decreases). Specifically, the concentration ratio decreases from CP/SLT1 to CP/SLT2 in FIG.
Therefore, the density ratio correction process is executed for the strobe signals STB1 to STB4 in the state ST3 so that the density ratios before and after the deceleration correction process are the same. State ST4 in FIG. 11 shows the strobe signals STB1_c to STB4_c after density ratio correction processing.
Assuming that the continuous pulse time after the density ratio correction process is CP_c, the strobe signals STB1_c to STB4_c are determined so that the following equation (1) holds. As a result, the continuous pulse time increases by Δt as shown in FIG.

CP_c=(SLT2/SLT1)·CP (1)

Although not shown in FIG. 11, in one embodiment, deceleration correction processing may be performed at least once from strobe signals STB1_c to STB4_c in state ST4 of FIG. That is, as described above, even if the density ratio is the same, the lower the printing speed, the higher the print density ((II)). The print density is set to be darker than in the state ST1 due to the reduced speed. Therefore, it is preferable to make the print density closer to the print density obtained by the strobe signal of state ST1 by further executing deceleration correction processing on the strobe signal of state ST4.

In one embodiment, the deceleration correction process and the density ratio correction process may be repeatedly executed a predetermined number of times.
As shown in the state ST4 of FIG. 11, the strobe length of each of the strobe signals STB1_c to STB4_c after the density ratio correction processing is extended with respect to each strobe length of the strobe signals STB1 to STB4 in the original state ST1. . Therefore, a density correction simulation is performed for the strobe signals STB1_c to STB4_c to check whether the strobe signal when each strobe length is maximized by density correction falls within the printing cycle SLT2. If not, the second deceleration is performed. Execute correction processing. As a result of executing this second deceleration correction process, the density ratio fluctuates before and after execution of the second deceleration correction process, so the second density ratio correction process is executed to adjust the density ratio.
As described above, in one embodiment, a desired strobe signal can be determined by repeating the deceleration correction process and the density ratio correction process a predetermined number of times. As will be described later, the number of execution times of each of the deceleration correction process and the density ratio correction process can be appropriately set.

As described above, the strobe pattern determined by the speed setting value and the density setting value in the reference strobe table is subjected to density correction according to the print layout and operating environment in order to ensure the print quality. However, this density correction alone is not sufficient, and it is necessary to consider the printing speed and the density ratio from the knowledge of (I) and (II) above. Therefore, in the continuous variable speed method, when determining the printing speed before printing, the deceleration correction process and the density ratio correction process are executed at least once while adjusting the printing speed so that the density correction functions appropriately. As a result, it is possible to improve the print quality over the entire image to be printed (make the print density uniform over the entire image).

In one embodiment, the control unit 11 of the printer 1 functions as a pulse setting unit, printing period correcting unit, and printing speed determining unit described below. This corresponds to the change from SLT1 to SLT2 of the print cycle in FIG.
(a1) In a one-line printing cycle, a first strobe period (for example, when strobe signals STB1 and/or STB2 become (a2) Pulse setting unit for setting the application period (an example of the first application period) (a2) Based on the image to be printed (for example, based on the number of simultaneously printed dots in one line of the image), set by the pulse setting unit (a3) The printing period is lengthened so that the maximum length of the first strobe period after the correction by the application period correction unit is accommodated. A print speed determination unit that determines the print speed when printing at a constant speed

Since the control unit 11 of the printer 1 functions as the units (a1) to (a3), even if the density correction is performed, the first strobe period does not fall within the print cycle, and the density correction during printing can be performed. Effective.
In addition, by keeping the printing speed constant over the entire image, compared to the conventional stepwise variable speed method, it is possible to suppress the decrease in throughput that accompanies acceleration and deceleration of the printing speed during printing. This has the advantage of avoiding deterioration in print quality that accompanies changes in print speed.
Furthermore, when compared with the conventional stepwise low-speed printing method that prints at a constant speed depending on the speed setting value, the throughput decreases by lengthening the printing cycle (decreasing the printing speed), but a small speed width (for example, 1 mm /sec), the decrease in throughput can be minimized.

In one embodiment, the printer 1 performs thermal history control, in which case the pulse setting section does not cause the plurality of heating elements of the thermal head 15 to color the thermosensitive coloring layer of the label in addition to the first strobe period. A second strobe period (for example, a period during which the strobe signals STB3 and/or STB4 are applied; an example of the second application period) for applying a certain amount of heat energy is set.
The printing period correction unit corrects the lengths of the first strobe period and the second strobe period, and the printing speed determination unit performs printing so that the corrected maximum lengths of the first strobe period and the second strobe period are accommodated. Lengthening the cycle determines the printing speed when printing the entire image at a constant speed.

In one embodiment, the control unit 11 of the printer 1 further adjusts the length of the first strobe period corrected by the application period correction unit so that the difference in the density ratio before and after the printing cycle is lengthened is equal to or less than a predetermined value. It also functions as a second application period corrector for further correction. This corresponds to the density ratio correction process from state ST3 to state ST4 in FIG. By executing the density ratio correction process, the density ratio is maintained within a predetermined range, so that the print density is made uniform and the print quality of the entire image is further improved.
In FIG. 11, the density ratio correction is performed so that the density ratio is the same between the state ST1 and the state ST4 as shown in equation (1), but this is not the only option. The difference in the density ratio before and after the density ratio correction process should be less than or equal to a predetermined value that does not substantially affect the print density.

Next, a series of processes for realizing the continuously variable speed system will be described with reference to FIGS. 12 to 16. FIG.
12 to 15 are flow charts corresponding to pre-printing processing performed before printing. FIG. 16 is a flowchart corresponding to in-printing processing that is performed during printing. The flowcharts in each figure are executed by the control unit 11 (CPU 111 and head controller 112).

The pre-printing process of one embodiment will be described below.
FIG. 12 shows the overall flow of pre-printing processing according to one embodiment. As described above, this overall flow shows the flow when the deceleration correction process and the density ratio correction process are repeated a predetermined number of times.
First, the control unit 11 sets a deceleration correction counter CTR_1 that defines the upper limit number of times the deceleration correction process is performed (step S2), and sets a density ratio correction counter CTR_2 that defines the upper limit number of times the density ratio correction process is performed (step S2). S4).
For example, the value (set value) set to the deceleration correction counter CTR_1 is 2, and the value (set value) set to the density ratio correction counter CTR_2 is 1. The set value of each counter is not limited, but is set so as to satisfy CTR_1>CTR_2.

Steps S6 to S14 in FIG. 12 are configured to execute the deceleration correction process (step S6) and the density ratio correction process (step S12) the number of times set in steps S2 and S4, respectively. The deceleration execution flag is a flag indicating whether or not the printing speed has been decelerated (that is, the printing cycle has been extended) in deceleration correction processing, and is set to "1" when the printing speed has been decelerated.

As will be described later, in the deceleration correction process, when the print speed is decelerated because the strobe signal does not fit within the print cycle, the deceleration execution flag becomes "1" and the deceleration correction counter CTR_1 is decremented by one. In the deceleration correction process, the deceleration execution flag remains "0" when the strobe signal is within the print cycle. Also, each time the density ratio correction process is executed, the density ratio correction counter CTR_2 is decremented by one.
Therefore, in the flow of FIG. 12, when the deceleration execution flag is "0" as a result of executing the deceleration correction process (step S6) (that is, when the strobe signal falls within the printing cycle) (step S8: NO), The control unit 11 terminates the pre-printing process. If the deceleration execution flag is "1" (step S8: YES), whether or not to execute the density ratio correction process (step S12) is determined based on whether the density ratio correction counter CTR_2 is "0" ( step S10).

After executing the density ratio correction process, it is determined whether or not the deceleration correction counter CTR_1 is "0" (step S14). The control unit 11 ends the pre-printing process when the deceleration correction counter CTR_1 is "0", and returns to step S6 to execute the deceleration correction process when the deceleration correction counter CTR_1 is not "0".
As described above, the deceleration correction process and the density ratio correction process are executed the number of times corresponding to the set value of each counter.

Next, details of the deceleration correction process will be described with reference to FIG.
Referring to FIG. 13, in the deceleration correction process, the control unit 11 first initializes the deceleration execution flag to "0" (step S20).
Next, the control unit 11 generates a first post-correction strobe table based on the reference strobe table (step S22). More specifically, the control unit 11 refers to the battery voltage correction table (FIG. 9) to specify the voltage correction ratio corresponding to the current battery voltage, and applies the specified voltage correction ratio to each strobe of the reference strobe table. A strobe table after the first correction is generated by multiplying by the length.
In step S22, instead of generating the first post-correction strobe table corresponding to all the strobe patterns in the reference strobe table, the strobe pattern corresponding to the current speed setting value and density setting value in the reference strobe table is generated. Alternatively, the strobe length after correction may be calculated.

Next, the control section 11 generates a dot number correction table (step S24). In one embodiment, individual dot number correction tables (FIG. 9) are prepared for each of head voltage drop correction and power supply voltage drop correction. In this case, the control unit 11 multiplies the dot number correction ratio corresponding to each battery voltage in the dot number correction table corresponding to the head voltage drop correction and the dot number correction table corresponding to the power supply voltage drop correction. A dot number correction table is generated by combining head voltage drop correction and power supply voltage drop correction.

Next, the controller 11 executes a density correction simulation whose details are shown in FIG. 14 (step S26).
As described above, the purpose of the density correction simulation is to pre-estimate the maximum value of the strobe length due to density correction during printing in order to determine the printing speed before printing. In other words, even if the strobe length (post-correction strobe length) becomes maximum due to density correction during printing, the density correction simulation is performed so that the maximum post-correction strobe length falls within the print cycle. This is processing for estimating the maximum value of the post-correction strobe length before printing.

Referring to FIG. 14, density correction simulation is performed as follows.
First, the control unit 11 refers to the first post-correction strobe table generated in step S22 to specify the strobe length of each strobe signal corresponding to the current speed setting value and density setting value (step S42). Here, the specified strobe length is the strobe length that reflects the battery voltage correction for the corresponding value in the reference strobe table.
Next, the control unit 11 analyzes the image to be printed, identifies the maximum number of dots simultaneously printed for each line in the image (step S44), and corrects the number of dots (step S46). ). That is, the control unit 11 identifies the dot number correction ratio corresponding to the maximum number of simultaneously printed dots identified in step S44 by referring to the dot number correction table generated in step S42.

Next, the controller 11 performs temperature correction (step S48). More specifically, the control unit 11 refers to the temperature correction table (FIG. 10) to identify the temperature correction ratio corresponding to the current thermal head temperature.
Incidentally, referring to the temperature correction table, if the thermal head temperature becomes lower than the current value, the temperature correction ratio increases and the strobe length becomes longer. There is no need to consider it in the density correction simulation. This is because the thermal head temperature during printing tends to be higher than the thermal head temperature during execution of the density correction simulation.

Finally, the control unit 11 determines the maximum value of the post-correction strobe length (step S50). In step S50, the control unit 11 calculates the dot number correction ratio specified in step S46 and the temperature correction ratio specified in step S48 for each strobe length of the strobe signals STB1 to STB4 specified in step S44. By performing multiplication processing, the maximum value of the post-correction strobe length is determined.

Returning to the description of FIG.
After executing the density correction simulation, the control unit 11 determines whether or not the maximum value of the post-correction strobe length is within the print cycle (step S28). If the maximum value of the post-correction strobe length is within the print cycle, the deceleration correction counter CTR_1 is set to 0 (step S30) because there is no need to change the print speed. In this case, since the deceleration execution flag remains "0", the control unit 11 terminates the pre-printing process (step S8 in FIG. 12: NO).

If the maximum value of the post-correction strobe length does not fall within the print cycle (step S28: NO), the control unit 11 extends the print cycle (that is, reduces the printing speed) so that the maximum value of the post-correction strobe length falls within the print cycle. (step S32). At this time, preferably, the speed width (for example, 1 mm/sec) is adjusted to be smaller than the speed width (1 IPS in the example of FIG. 6) of the plurality of speed setting values defined in the reference strobe table.
The control unit 11 sets the deceleration execution flag to "1" according to the deceleration of the printing speed (step S34), and subtracts 1 from the deceleration correction counter CTR_1 (step S36).

Next, details of the density ratio correction process will be described with reference to FIG.
Referring to FIG. 15, in the density ratio correction process, the controller 11 first selects the continuous pulse time CP (state ST1 in FIG. 11) corresponding to the current speed setting value and density setting value from the reference strobe table (for example, FIG. 6). ) is obtained (step S60), and the density ratio is calculated (step S62). The density ratio is a value obtained by dividing the continuous pulse time CP by the print cycle corresponding to the speed setting value.

Next, the control unit 11 calculates the continuous pulse time after the deceleration correction (that is, after step S32 of the deceleration correction process performed immediately before) is calculated (step S64), and generates a new reference strobe table (step S66). ). Here, as shown in the above formula (1), the continuous pulse time is corrected so that the density ratio is the same before and after the deceleration correction, and a new reference strobe table is generated based on the corrected continuous pulse time. . This new reference strobe table becomes a reference for generating the first post-correction strobe table when the deceleration correction process is subsequently executed.
Finally, the control unit 11 subtracts 1 from the density ratio correction counter CTR_2 (step S68).
In step S66, instead of generating a new reference strobe table corresponding to all strobe patterns, a new strobe length corresponding to the current speed setting value and density setting value strobe pattern may be calculated.

The above is the pre-printing process of one embodiment, and by repeating the deceleration correction process and the density ratio correction process a predetermined number of times, the printing speed, the printing cycle, and the first post-correction strobe table used in the during-printing process are: Determined before printing.

Next, the in-printing process will be described with reference to FIG.
Printing is performed at a constant speed over the entire image to be printed according to the printing speed determined in the pre-printing process. In the in-printing process, a series of processes shown in FIG. 16 are performed for each line. In the following description, the line to be printed is referred to as a "line of interest".
Referring to FIG. 16, the control unit 11 first acquires the thermal head temperature from the thermistor 4 (step S70), refers to the temperature correction table (FIG. 10), and determines the temperature correction ratio corresponding to the acquired thermal head temperature. is obtained (specified) (step S72). As described above, the temperature correction ratio may be calculated based on the reference value and current value of the thermal head temperature.

Next, the control unit 11 corrects the first post-correction strobe table generated in the pre-printing deceleration correction process (step S22 in FIG. 13) using the temperature correction ratio acquired in step S72, thereby obtaining a second post-correction strobe table. A table is generated (step S74). Although the strobe table after the first correction reflects the battery voltage correction, the battery voltage during printing is considered to be approximately the same as the battery voltage before printing, so it is also used in the printing process. be. Each strobe length described in the second post-correction strobe table is a value obtained by multiplying the corresponding strobe length in the first post-correction strobe table by the temperature correction ratio.

Next, the control unit 11 obtains the number of simultaneously printed dots of the target line (step S76), and obtains the dot number correction ratio corresponding to the obtained number of simultaneously printed dots by referring to the dot number correction table (FIG. 9). (step S78). Further, in the second post-correction strobe table, the control unit 11 multiplies the strobe length of each strobe signal corresponding to the current speed setting value and density setting value by the dot number correction ratio obtained in step S78. Thus, the strobe length of each strobe signal applied to the line of interest is determined (step S80).
In the deceleration correction process before printing (step S22 in FIG. 13), instead of generating the first post-correction strobe table, post-correction strobe length corresponding to the strobe pattern of the current speed setting value and density setting value is calculated, in step S74, the strobe length is calculated by correcting the corrected strobe length by the temperature correction ratio obtained in step S72. This process is equivalent to step S80.

The above is the in-printing process of one embodiment, and the strobe length of each strobe signal during the printing cycle is determined by performing density correction based on the thermal head temperature and the number of simultaneously printed dots for each line of interest.
In the pre-printing process, the printing speed is adjusted based on the maximum post-correction strobe length due to the density correction. is within the print cycle.

In one embodiment, the example in which the strobe application period is provided four times during the print cycle in the thermal history control has been described, but the number is not limited to this, and may be three times or five times or more. . By increasing the number of strobe application periods, a greater number of strobe levels can be set, enabling more precise control.

As described above, the flowcharts of FIGS. 12 to 16 are executed by the control section 11 (CPU 111 and head controller 112). At this time, in one embodiment, the control unit 11 of the printer 1 functions as the following pulse setting unit, first correction unit, and second correction unit.
(b1) In a one-line printing cycle, a first strobe period (for example, when strobe signals STB1 and/or STB2 are set to Pulse setting section for setting the period to be applied; an example of the first application period) (b2) Before printing on the label, correct the printing speed when printing so that it decelerates from the speed setting value. First correction unit (b3) The printing speed after correction by the first correction unit and/or the first strobe period so that the difference in the density ratio before and after the correction of the printing speed by the first correction unit is equal to or less than a predetermined value. A second correction unit that corrects the length of

Here, the first correction unit corresponds to the first deceleration correction process. The second correction unit corresponds to the density ratio correction process performed after the first deceleration correction process and/or the second and subsequent deceleration correction processes.
The second correction unit may include at least one of the printing speed correction process and the first strobe period length correction process, or both of them. That is, since the density ratio can change depending on the printing speed and/or the first strobe period, the correction of the printing speed and the correction of the length of the first strobe period can be performed separately, or both can be corrected. , the density ratio can be adjusted to a desired range. At this time, the method of adjusting the density ratio to the desired range is not limited to the method based on the pre-printing correction process of FIG.

With the above configuration, when changing the printing speed from the speed setting value before printing on the label, it is possible to suppress the deterioration of the printing quality (that is, suppress the fluctuation of the printing density during printing). becomes possible. In other words, deterioration of print quality can be suppressed when printing is performed at print speeds different from the plurality of speed setting values defined in the reference strobe table. As a result, from the user's point of view, as long as the speed setting and density setting for the printer 1 are the same, the advantage is that the same level of print quality can always be obtained regardless of the operating environment of the printer 1 or the layout of the image to be printed. There is

Also, the strobe length of each strobe pattern described in the reference strobe table is determined in advance by trial and error so as to obtain a predetermined print density (that is, verified). Therefore, when the print speed is changed from the speed set value specified in the reference strobe table, the print quality is not verified. By executing the above-described deceleration correction process and density ratio correction process even under such conditions, it is possible to match the print density to the same degree as the verified level.

In one embodiment, the second corrector includes the following ratio corrector and print speed corrector.
(c1) a ratio correction unit that executes processing (density ratio correction processing) for correcting the length of the first strobe period so that the density ratio is substantially the same before and after the printing speed is corrected by the first correction unit; ) A print speed correction unit that executes processing (deceleration correction processing) for correcting the print speed so that it is further reduced from the print speed corrected by the first correction unit. That is, as shown in FIG. When controlling both, the strobe length can be determined efficiently by continuously performing the density ratio correction process and the deceleration correction process. As described with reference to FIG. 12, the number of times each process is executed can be defined by the set value of the counter corresponding to each process.

In one embodiment, the printer 1 performs thermal history control, in which case the above-described pulse setting section causes the plurality of heating elements of the thermal head 15 to color the thermosensitive coloring layer of the label in addition to the first strobe period. A second strobe period (for example, a period during which the strobe signals STB3 and/or STB4 are applied; an example of the second application period) is set for applying heat energy to a degree that does not cause the heat to be applied.
The first correction section described above corrects the printing speed so that the first strobe period and the second strobe period are within the printing cycle. The second correction unit adjusts the printing speed after correction by the first correction unit and/or the first strobe period and Correct the length of the second strobe period.

In one embodiment, printing is performed without the thermal history control described above. Even in that case, the continuously variable speed system described above can be applied.
FIG. 17 is a diagram corresponding to FIG. 11 and showing a continuously variable speed method when thermal history control is not performed. When thermal history control is not performed, a single strobe signal STB is set during one line printing cycle. In this case, the length of the strobe period for applying heat energy for coloring the thermosensitive coloring layer is equal to the strobe length L of the strobe signal STB.

State ST2 in FIG. 17 is the result of density correction simulation performed on the strobe signal STB shown in state ST1, and shows the strobe signal STB_max when the strobe length L of the strobe signal STB is maximized by the density correction. . In one embodiment, the strobe length of the strobe signal STB_max is a value obtained by multiplying the reference strobe length L by the maximum value of the voltage correction ratio (FIG. 9)×dot number correction ratio (FIG. 9). .

The state ST2 in FIG. 17 shows the case where the strobe signal STB_max when the strobe length is maximized by the density correction does not fall within the print cycle SLT1 determined by the speed setting value.
State ST3 in FIG. 17 shows a state in which deceleration correction processing is performed on the strobe signal STB in state ST1 to extend the print cycle from SLT1 to SLT2. By extending the print cycle in this way, even when printing a line with the maximum number of simultaneously printed dots in an image, the strobe signal does not fall within the print cycle due to density correction.

The strobe signal STB_c in state ST4 is the result of performing density ratio correction processing on the strobe signal STB in state ST3.
Here, assuming that the strobe length L after the density ratio correction process is L_c, the strobe signal STB_c is determined so that the following equation (2) holds. As a result, the continuous pulse time is increased by Δt as shown in FIG.

L_c=(SLT2/SLT1)·L (2)

In one embodiment, a printer printing method is disclosed having the following steps.
(d1) Setting a first strobe period of a strobe signal for applying heat energy for coloring the thermosensitive coloring layer of the label to a plurality of heating elements of the thermal head 15 in the printing cycle of one line. (d2) Printing. A step of correcting the set length of the first strobe period based on the target image. Step to determine the printing speed when printing the whole at a constant speed

In one embodiment, a printer printing method is disclosed having the following steps.
(e1) Step of setting a first strobe period of a strobe signal for applying heat energy for coloring the thermosensitive coloring layer of the label to a plurality of heating elements in a printing cycle of one line (e2) Printing on the label (e3) correcting the printing speed at the time of printing so as to decelerate from the speed setting value before performing (e3) so that the difference in the density ratio before and after the correction of the printing speed is equal to or less than a predetermined value after correction; and/or correcting the length of the first strobe period

A program according to one embodiment is a program that causes a computer to execute the printing method of the printer. For example, when the CPU 111 included in the control unit 11 of the printer 1 executes a program, the printing method of the printer is executed.
In one embodiment, the program may be recorded on a non-transitory computer-readable recording medium.

Although the embodiments of the printer, the printing method of the printer, and the program according to the present invention have been described above in detail, the scope of the present invention is not limited to the above embodiments. Also, the above embodiments can be modified and modified in various ways without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1... Printer 9... Storage chamber 10... Platen roller 11... Control part 111... CPU
DESCRIPTION OF SYMBOLS 112... Head controller 113... Memory 114... Bus 12... Storage 13... Drive circuit 14... Motor 15... Thermal head 2... Drive circuit 21... Shift register 22... Latch circuit 23... Gate circuit group 23_1 to 23_M... AND circuit 24... Transistor Group 24_1 to 24_M MOS transistor 3 Heating element group 31_1 to 31_M Heating element 4 Thermistor 16 Communication interface 20 Issuing port 25 Printer cover 29 Coil spring DATA1 to DATA4 Data signal STB1 to STB4 Strobe signal L1 ~L4...Pulse width WT...Waiting time P...Continuous paper R...Roll paper

Claims (9)

A printer that prints on a print medium having a thermosensitive coloring layer,
a thermal head having a plurality of heating elements arranged in a line;
a pulse setting unit for setting a first application period of an energizing pulse for applying heat energy for coloring the thermosensitive coloring layer to the plurality of heating elements in a one-line printing cycle;
a first correction unit that corrects a printing speed during printing so as to decelerate from a preset printing speed before printing on the printing medium;
The printing speed after correction by the first correction unit so that the difference in the ratio of the first application period of the energizing pulse to the printing cycle before and after the correction of the printing speed by the first correction unit is equal to or less than a predetermined value, and / Or, a second correction unit that corrects the length of the first application period;
printer with The second correction unit is
a ratio correction unit that corrects the length of the first application period so that the ratio is substantially the same before and after the printing speed is corrected by the first correction unit;
a printing speed correction unit that corrects the printing speed so as to further reduce the printing speed after correction by the first correction unit;
A printer as claimed in claim 1. a storage unit for storing data on the length of the first application period of the energizing pulse in one line printing cycle corresponding to each of a plurality of printing speeds set with a predetermined first speed width;
The preset print speed is one of the plurality of print speeds,
The first correction unit corrects the printing speed so that the printing speed is decelerated in a second speed width that is smaller than the first speed width, based on the preset printing speed.
A printer according to claim 1 or 2. an application period correction unit that corrects the length of the first application period set by the pulse setting unit based on the image to be printed;
The first correction unit corrects the printing speed so that the first application period after correction by the application period correction unit is within a printing cycle.
A printer as claimed in any one of claims 1 to 3. comprising a battery that supplies power to the thermal head;
The application period correction unit corrects the length of the first application period based on the voltage of the battery.
5. A printer as claimed in claim 4. A temperature detection unit that detects the temperature of the thermal head,
The application period correction unit corrects the length of the first application period based on the temperature of the thermal head.
A printer according to claim 4 or 5. The pulse setting unit sets a second application period of an energizing pulse for applying heat energy to the plurality of heating elements to such an extent that the thermosensitive coloring layer does not develop color in one line printing cycle,
The first correction unit corrects the printing speed so that the first application period and the second application period are within a printing cycle,
The second correction unit adjusts the printing speed so that a difference in the ratio of the first application period and the second application period of the energizing pulse to the printing cycle before and after the correction of the printing speed by the first correction unit is equal to or less than a predetermined value. correcting the printing speed after correction by the first correction unit and/or the length of the first application period and the second application period;
A printer as claimed in any one of claims 1 to 6. A printing method for a printer having a thermal head having a plurality of heating elements arranged in a line and printing on a printing medium having a thermosensitive coloring layer, comprising:
setting a first application period of an energizing pulse for applying thermal energy for coloring the thermosensitive coloring layer to the plurality of heating elements in a printing cycle of one line;
before printing on the print medium, correcting the printing speed when printing so as to decelerate from a preset printing speed;
The printing speed after the correction and/or the length of the first application period so that the difference in the ratio of the first application period of the energizing pulse to the printing cycle before and after the correction of the printing speed is equal to or less than a predetermined value. to compensate for
How the printer prints. A program for causing a computer to execute a predetermined method in a printer having a thermal head having a plurality of heating elements arranged in a line and printing on a print medium having a thermosensitive coloring layer,
The method includes:
setting a first application period of an energizing pulse for applying thermal energy for coloring the thermosensitive coloring layer to the plurality of heating elements in a printing cycle of one line;
before printing on the print medium, correcting the printing speed when printing so as to decelerate from a preset printing speed;
The printing speed after the correction and/or the length of the first application period so that the difference in the ratio of the first application period of the energizing pulse to the printing cycle before and after the correction of the printing speed is equal to or less than a predetermined value. compensating for the
program.

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