JP2009143163A - Thermal printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply optimal pre-heating corresponding to the temperature of a thermal head even if high speed printing is performed, and to enable the printing of a high grade in a thermal printer. <P>SOLUTION: This thermal printer is equipped with an accumulating means which accumulates printing data, a pre-heating control means which determines a pre-heating pulse based on the printing data accumulated in the accumulating means, and a thermal head which performs a printing output by applying the pre-heating pulse. In the thermal printer, the determination of the pre-heating pulse by the pre-heating control means is performed depending on a printing speed which is acquired from a control command included in the printing data, and the temperature of the thermal head. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to preheating control of a thermal head capable of realizing high-quality printing in a thermal printer.

  In a printer having a thermal head, in both the thermal method and the thermal transfer method, if the temperature of the thermal head is low, the dots become smaller or thinner, and the print quality deteriorates. In order to prevent this deterioration, Patent Document 1 discloses a technique for preheating the thermal head before printing is started.

  However, in Patent Document 1, since the thermal head is preheated during the preparation time before the start of printing, the print quality can be prevented from deteriorating, but the ratio of the heating elements in the continuous printing (printing rate) changes suddenly. Can not respond.

  An abrupt change in the ratio of the heat generating elements means, for example, a transition from a low density line area with many white pixels (pixels not recording dots) to a high density line area with many high density pixels, or conversely This is a phenomenon that occurs when shifting from a high density line area to a low density line area (see FIG. 5). At this time, in the former case, there was a problem that a line having a low density (hereinafter abbreviated as white stripes) and a line having a high density (hereinafter abbreviated as black stripes) were entered in the latter case.

  On the other hand, Patent Document 2 discloses the following solution. In the low density line area in front of the high density line area, the preheating time given to the white pixels is gradually increased so as not to print. Occurrence is prevented. Also, in the low density line next to the area of the high density line, the preheating given to the white pixels is gradually reduced to the extent that printing is not performed, thereby eliminating the rapid temperature fluctuation of the thermal head. Prevents black streaks.

JP-A-9-254426 Japanese Patent Laid-Open No. 11-123840

  However, in Patent Document 2, pre-heating is performed so as to eliminate the rapid temperature fluctuation of the thermal head by checking the print density level from the continuously printed drawing data. Correspondingly, it does not give an appropriate preheating. In particular, when the printing speed is high, the interval for hitting one line is shortened, so that the time for applying the application pulse for printing is limited (see FIG. 6). Therefore, when the printing speed is high, it is difficult to give appropriate preheating only with the drawing data to be printed, which may cause deterioration of the print quality.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide high-quality printing by providing optimum preheating corresponding to the temperature of the thermal head even when performing high-speed printing.

  The thermal printer of the present invention includes an accumulating unit that accumulates print data, a preheating control unit that determines a preheating pulse based on the print data accumulated in the accumulating unit, and a thermal head that performs printing output by applying the preheating pulse. The preheating pulse is determined by the preheating control means based on the printing speed acquired from the control command included in the print data and the temperature of the thermal head. To do.

According to the present invention, since preheating control is possible following the change in printing speed and the temperature of the thermal head, there is an effect that high-quality printing can be realized.
Further, according to the present invention, since preheating considering the printing speed and the temperature of the thermal head is given to the heating element without drawing data, the effect of extending the life of the heating element and realizing high-quality printing can be achieved. Play.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a configuration for explaining preheating control of a thermal printer according to an embodiment of the present invention. In FIG. 1, a thermal printer 10 includes a drawing data memory unit 1, a preheating control unit 2, an energization time calculation processing unit 3, a thermal head driver 4, and a thermal head 5.

  Next, the printing operation of the thermal printer 10 will be described.

  The thermal printer 10 receives print data from the host system 6, analyzes the data by an analysis / development / drawing unit (not shown), and develops the drawing data to be used for printing by the thermal printer 10. The image data is stored in the drawing data memory unit 1 as print image data. By repeating these processes, data for one page is accumulated in the drawing data memory unit 1. Then, the drawing data of the oldest line stored in the drawing data memory unit 1 is sent to the energization time calculation processing unit 3.

  The preheating control unit 2 includes a thermal head rank resistance (average resistance value) reading unit 21, a printing speed information acquisition unit 22, a thermal head temperature acquisition unit 23, and a heat history table 24, as shown in FIG. The preheating pulse determination flow is processed. In the preheating control unit 2, the rank resistance reading unit 21 of the thermal head reads the rank resistance of the thermal head (S201). Next, the print speed information acquisition unit 22 analyzes the control command included in the print data transmitted from the host system 6 and acquires the print speed (S202). Next, the thermal head temperature acquisition unit 23 acquires the temperature of the thermal head using a thermistor (not shown) attached to the thermal head (S203). Here, the preheating control unit 2 determines a preheating pulse from the heat history table storage unit 24 based on the printing speed acquired by the printing speed information acquisition unit 22 and the temperature of the thermal head acquired by the thermal head temperature acquisition unit 23. (S204).

The determination of the preheating pulse from the heat history table storage unit 24 will be described in detail. In the thermal history table storage unit 24, a thermal history table is prepared for each printing speed, and the thermal history table shown in FIG. 3 has a printing speed of 6 inches / second. In the thermal history table, the optimum preheating pulse to be given is expressed by the pulse width for each thermistor temperature. The relationship between the thermistor temperature and the preheating pulse is represented by a downward-sloping curve, but the curve differs depending on the density of the printed pixels. In FIG. 3, three patterns of different density curves are shown as representative examples, but actually, density information of 20 patterns or more is expressed.
The process in which the preheating control unit 2 determines the preheating pulse from the printing speed acquired by the printing speed information acquisition unit 22 and the temperature of the thermal head acquired by the thermal head temperature acquisition unit 23 is as follows. First, based on the printing speed acquired by the printing speed information acquisition unit 22, a thermal history table corresponding to the printing speed is extracted from the thermal history table storage unit 24. Next, in the extracted thermal history table, the thermal head is extracted. The pulse width corresponding to the temperature of the thermal head acquired by the temperature acquisition unit 23 is determined. Note that the preheating control unit 2 analyzes and selects a control command included in the print data transmitted from the host system 6 for the pixel density level generated by the preheating pulse.
Here, the preheating pulse will be described in detail. FIG. 4 is an exploded view of the applied pulse. The normal applied pulse is output in four divisions, such as Fire1, Fire2, Fire3, and Fire4, at the time of output. The preheating pulse is performed using Fire3 of a heating element to which no applied pulse is assigned. The pulse width of the thermal history table in FIG. 3 corresponds to the pulse width of Fire3. Here, when the printing speed is increased, as shown in FIG. 6, the applied pulse width is limited, so the applied pulse width of Fire3 is also limited. Therefore, there may be a case where a sufficient preheating effect cannot be obtained with the preheating pulse of only Fire3. In such a case, in addition to Fire 3 used for the preheating pulse, Fire 4 may also be used to ensure a desired preheating effect with the total pulse width. In that case, in addition to the Fire3 heat history table, a Fire4 heat history table is also prepared in the heat history table storage unit 24, and the preheating control unit 2 determines a preheating pulse from the Fire3 and Fire4 heat history tables. It will be.
The preheating control unit 2 transmits the determined preheating pulse to the energization time calculation unit 3. In the energization time calculation unit 3, the transmitted preheating pulse is assigned to the corresponding heating element. The heating element to which the preheating pulse is given is a heating element when there is no current drawing data and there is drawing data in the future. The absence of drawing data means that the drawing data is zero, so that the pixel is a white background, and only the residual heat pulse is applied to the heating element that records this white background. On the other hand, for each heating element in which drawing data currently exists, a necessary applied pulse is calculated by the energization time calculation unit 3 based on the drawing data in the drawing data memory unit 1 and assigned to the corresponding heating element.

  The thermal head driver 4 drives each heating element 5a of the thermal head 5 to generate heat in accordance with the preheating pulse and application pulse calculated by the energization time calculation unit 3. The heat-sensitive recording paper and the like are heated by these heating elements 5a, and printing for one line is performed. Here, the preheating of FIG. 2 is also completed (S205).

  When the printing for one line is completed, the next one line is printed. Immediately before this, in order to acquire the printing speed and the temperature of the thermal head, the preheating control unit 2 provides information on the printing speed. Returning to the acquisition step (S202 in FIG. 2), the preheating pulse determination flow (FIG. 2) is executed, and new preheating is performed. When the printing speed is unchanged, the process returns to the thermal head temperature acquisition step (S203 in FIG. 2), and the preheating pulse determination flow (FIG. 2) is executed to newly perform preheating. As described above, since the optimum preheating can be given to the thermal head on the basis of the change in the printing speed and the change in the temperature of the thermal head every time one line is printed, high-quality printing can be realized.

1 is an overall configuration diagram of the present invention. Preheating pulse determination flow. Thermal history table. The exploded view of an applied pulse. An example of printing when a sudden change in the ratio of heating elements occurs. The figure which shows the relationship between a printing speed and an applied pulse.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drawing data memory part 2 Preheating control part 3 Energizing time calculation process part 4 Thermal head driver 5 Thermal head 6 Host system 10 Thermal printer 21 Thermal head rank resistance reading part 22 Printing speed information acquisition part 23 Thermal head temperature acquisition part 24 Thermal history Table storage

Claims (3)

Storage means for storing print data;
In a thermal printer comprising preheating control means for determining a preheating pulse based on the print data accumulated in the accumulating means, and a thermal head for applying the preheating pulse and performing print output,
The thermal printer according to claim 1, wherein the preheating pulse is determined by the preheating control means based on a printing speed acquired from a control command included in the print data and a temperature of the thermal head. The thermal printer according to claim 1,
The thermal printer according to claim 1, wherein the preheating pulse is determined by the preheating control means in accordance with a change in printing speed acquired from the print data and a change in temperature of the thermal head. The thermal printer according to claim 1,
The heating element to which the preheating pulse is assigned is provided in the thermal head, and the preheating pulse is given to the heating element when there is no printing data in the current printing and there is printing data in the future printing. A thermal printer.

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