JPH0631968A - Driving method for thermal recording head - Google Patents

Abstract

PURPOSE:To provide a method for driving a thermal recording head capable of recording high grade images without thinness and skip. CONSTITUTION:When recording pulse is to be applied to a heat generating element of a thermal recording head by a present printing data, a reference is made to a printing data of the next line. When the printing data of the next line is non-printing, an application end time of the recording pulse is made earlier than at a time that the printing data of the next line is printing by a time (tn), so that the application time of the recording pulse is shortened. In order to compensate the influence of the shortening of the application time, an additional recording pulse of a time T3 is applied before the application start time of the recording pulse at the time that the printing data for the next line is printing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a thermal recording head for recording a desired image or characters according to an applied electric signal.

[0002]

2. Description of the Related Art In recent years, various proposals have been made regarding a method for driving a thermal recording head in order to improve printing quality during high speed recording. In particular, the history control method of controlling the recording energy at the time of current printing with reference to past print history and future print information has an excellent effect in improving print quality.

An example of a method for driving the above-mentioned conventional thermal recording head will be described below with reference to the drawings.

FIG. 5 is a block diagram showing a drive circuit of the thermal recording head. In FIG. 5, 1 is original print data sent from an external device such as a computer, 2 is a line buffer for storing the original print data 1 for a required number of print lines, and 3 is a line buffer 2. An arithmetic circuit for generating print data 4 for printing the present print line based on the original print data 1 of the past to future print lines, 5 is a thermal head for printing by heat, and 6 is a thermal head 5. Is a power supply control circuit that outputs a power supply control signal 7 for controlling the power supply time. In the drive circuit of the thermal recording head configured as described above, the recording pulse applied to each heating element of the thermal head 5 is determined by the print data 4 and the energization control signal 7, and is as shown in FIG. 6, for example.

FIG. 6 is a diagram showing a recording pulse waveform of a conventional thermal recording head driving method, which is a history control method in which print data up to two lines before and print data of the next line are referred to. The major feature of this method is that when the print data of the next line is non-printed (indicated by a circle), the recording pulse application end time is advanced by tn to increase the cooling time of the heating element more than usual. This is the point that the non-printed dots of the line can be reproduced without being crushed by the trailing.

[0006] A to C are recording pulses applied to the heating elements when printing dots (marked with ⊚) of the current line when print data of the next line is marked (marked with ●). Is the waveform of. First, the waveform A is a case of non-printing dots up to two lines before, and at this time, the longest recording pulse application time (t2 + t1 + t0 + tn) is given. Waveforms B and C have print dots two lines before or one line before, respectively, and the application start time of the recording pulse is delayed by t2 or t2 + t1 depending on the heat storage degree of the heating element, and the application time is shortened accordingly. As a result, the influence of the heat accumulated in the heating element due to the printing of the dots two lines before or one line before is corrected.

D to F are waveforms when the print data of the next line is non-printing. As described above, in order to reproduce the non-printing dots of the next line, the application end time of the recording pulse is advanced by tn. Therefore, the application time is shortened by that amount (JP-A-61-295056).

[0008]

However, in the method of applying the recording pulse as described above, when the non-printed dots have continued in the past and the next line is the non-printed dots as in the case of the waveform D, for example. (Image-wise isolated dots or isolated lines in the main scanning direction) are t2 + t1 + t in the same manner as in the case of the waveform A in order to reproduce the dots of the current line.
Although the recording pulse application time of 0 + tn is required, the energy for forming the dot of the current line is insufficient because the application time is shortened by the time of tn, and there is a problem that the print dot is worn out or cannot be formed at all. is there.

An object of the present invention is to provide a method for driving a thermal recording head, which can obtain a high-quality recorded image without blurring or missing in consideration of the conventional problems as described above.

[0010]

The present invention refers to the next print data when a recording pulse is applied to the heating element of the thermal recording head according to the current print data, and when the next print data is non-printing, A thermal recording head that applies a current recording pulse application end time a first predetermined time earlier than when the next print data is printed, and applies a correction recording pulse a second predetermined time before the current recording pulse application start time. Is a driving method of.

[0011]

According to the present invention, the effect of shortening the application time by advancing the recording pulse application end time when the next print data is non-printing is corrected by the correction recording pulse applied before the application of the recording pulse. This eliminates the shortage of recording energy for printing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a diagram showing recording pulse waveforms in a method of driving a thermal recording head according to the first embodiment of the present invention. That is, A to C are waveforms of recording pulses applied to the heating elements when printing the dots of the current line when the print data of the next line is printing. First, the waveform A is a case of non-printed dots up to two lines before, and the recording pulse application time at this time is t2 + t1 + t0 +
tn. Waveforms B and C have print dots two lines before or one line before, respectively, and the application start time of the recording pulse is delayed by t2 or t2 + t1 depending on the heat storage degree of the heating element, and the application time is shortened accordingly. Therefore, the heat storage of the heating element is suppressed. The waveforms A to C are exactly the same as A to C of FIG. 6 described as the conventional technique.

D to F are waveforms of recording pulses when the print data of the next line is non-printing. At this time, the recording pulse application end time is advanced by tn, and the application time is shortened accordingly. As a result, it is possible to make the energization pause time of the heating element longer than that when the print data of the next line is printed, and it is possible to lower the temperature of the heating element. As a result, the next non-printed dot can be reproduced without the printed dot trailing to the next line. At this time, an additional recording pulse (t3) which is a correction recording pulse is applied before the application of the recording pulse is started. This makes it possible to compensate for the shortage of recording energy caused by shortening the application time of the recording pulse by tn, and thus it is possible to obtain the recording energy required to reproduce the isolated dot. Moreover, since the additional recording pulse is applied before the start of the application of the recording pulse, it does not affect the energization pause time of the heating element for reproducing the non-printed dots of the next line. It is appropriate that the value of t3 is equal to or less than the value of tn.

As described above, according to the present embodiment, when the print data of the next line is non-printing, the application end time of the recording pulse is advanced and the additional recording pulse is applied before the application of the recording pulse is started. By doing so, it is possible to obtain a high-quality recorded image that suppresses blurring and tailing due to heat storage of the head and does not cause blurring or missing on isolated dots or isolated lines.

In the above embodiment, the additional recording pulse in the waveforms E and F of the recording pulse is added separately from the recording pulse before the time t2, but not limited to this, for example,
For waveform E, t1 hours before, or for waveform F, t0
It may be added before the time and applied so as to be continuous with the recording pulse.

Next, a method of driving the thermal recording head of the second embodiment according to the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing the waveform of the recording pulse of the second embodiment. That is, A to C are waveforms of the recording pulse applied to the heating element when printing the dots of the current line in the case where the print data of the next line is printing, which is exactly the same as in the first embodiment. Is.

D to F are waveforms of recording pulses when the next line is not printed. At this time, similarly to the first embodiment, the application end time of the recording pulse is advanced by tn and the application time is shortened by that much, so that the energization pause time of the heating element is longer than usual. The difference from the first embodiment is the way of giving an additional recording pulse (t3) applied before the start of the application of the recording pulse. When there is a print dot two lines before or one line before as in waveforms E and F, the additional recording pulse is not applied, and as in waveform D, the additional recording pulse is applied only when there are no print dots up to two lines before. I decided to do it. This means that if there is a print dot two lines before or one line before, it is possible to form print dots without applying additional recording pulses due to heat storage, and by applying additional recording pulses, the recording energy becomes excessive and blurring occurs. And the like, and the print quality is rather deteriorated.

As described above, according to this embodiment, when the next line is non-printing, the application end time of the recording pulse is shortened and the application of the recording pulse is started by the information of the print dots up to two lines before. By applying the additional recording pulse before, the recording energy due to the additional recording pulse does not become excessive, the blurring and tailing due to the heat accumulation of the head is suppressed and the isolated dot or the isolated line is free from blurring or missing. It is possible to obtain a high quality recorded image.

In this embodiment, the recording pulse is t
The continuous pulses of 3 to t2 to t1 to t0 to tn are applied, but the present invention is not limited to this, and for example, as shown in FIG. 3, separate pulses having respective application times may be applied separately. It doesn't matter.

Next, a method of driving a thermal recording head according to a third embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a diagram showing the waveform of the recording pulse of the third embodiment. That is, this is a method of referring to the print data up to three lines before and the print data of the next line.

A to C are waveforms of recording pulses applied to the heating elements when printing the dots of the current line when the print data of the next line is printing. At this time, the application of the recording pulse is controlled by referring to the print data up to two lines before (the past plural print data or normal reference lines) without referring to the print data before three lines. Therefore, it is exactly the same as in the first embodiment.

D to F are waveforms of recording pulses when the print data of the next line is non-printing. At this time, similarly to the first embodiment, the application end time of the recording pulse is advanced by tn and the application time is shortened by that much, so that the energization pause time of the heating element is longer than usual. The difference from the first embodiment is the way of giving the additional recording pulse (t3) applied before the start of the application of the recording pulse, as in the second embodiment, by additionally referring to the print dots three lines before. It is determined whether or not the additional pulse is applied. Therefore, the waveforms D2, E, F
When there is a print dot up to three lines before, the additional recording pulse is not applied, and only when there is no print dot up to three lines before as shown by the waveform D1, the additional recording pulse is applied. By referring up to three lines before, it is possible to add appropriate recording energy to an isolated dot or an isolated line from a wider range of viewpoints with an additional recording pulse.
This is effective when performing recording at a higher speed than the second embodiment.

As described above, according to the present embodiment, when the print data of the next line is non-printing, the application end time of the recording pulse is shortened and three lines before (normal reference line + 1 line). By applying the additional recording pulse before the start of applying the recording pulse according to the information of the print dot, it is possible to suppress blurring and tailing due to heat accumulation of the head and to cause blurring or missing in the isolated dot or line especially at high speed recording. It is possible to obtain a high quality recorded image.

In the above embodiment, a plurality of print data in the past is up to two lines before, but the present invention is not limited to this and may be three or more lines.

In the third embodiment, printing up to three lines before (normal reference line + 1) is performed to determine whether to apply the additional recording pulse when the print data of the next line is non-printing. I referred to the data, but not limited to this,
For example, print data up to four lines before (normal reference line + 2) or more may be referred to.

[0029]

As is apparent from the above description, according to the present invention, when the next print data is not printed, the next print data is printed in order to correct the influence of the application time of the recording pulse. Before the recording pulse application start time of
Since the correction recording pulse for a predetermined time is applied, there is an advantage that a high-quality recorded image without blurring or missing can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing recording pulse waveforms in a method of driving a thermal recording head according to a first embodiment of the present invention.

FIG. 2 is a diagram showing recording pulse waveforms in a method of driving a thermal recording head according to a second embodiment of the invention.

FIG. 3 is a diagram showing a recording pulse waveform of another pulse application example of the second embodiment.

FIG. 4 is a diagram showing recording pulse waveforms in a method of driving a thermal recording head according to a third embodiment of the invention.

FIG. 5 is a block diagram of a drive circuit of the thermal recording head.

FIG. 6 is a diagram showing recording pulse waveforms in a conventional thermal recording head driving method.

[Explanation of symbols]

 1 original print data 2 line buffer 3 arithmetic circuit 4 print data 5 thermal head 6 energization control circuit 7 energization control signal

Front page continued (72) Inventor Koji Ikeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Nobuyoshi Taguchi, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd

Claims (3)

[Claims] 1. When the recording pulse is applied to the heating element of the thermal recording head according to the current print data, the next print data is referred to, and when the next print data is non-printing, the application of the current record pulse is terminated. The thermal recording is characterized in that the time is advanced by a first predetermined time from the time when the next print data is printed, and a correction recording pulse of a second predetermined time is applied before the application start time of the current recording pulse. How to drive the head. 2. The application start time of the current recording pulse is determined with reference to a plurality of past print data, and the correction recording pulse is applied only when all the past plurality of print data are non-printing. The method for driving a thermal recording head according to claim 1, wherein the thermal recording head is driven. 3. The application start time of the current recording pulse is determined with reference to a plurality of past print data, and the correction recording pulse is at least one previous to the past plurality of print data. 2. The method of driving a thermal recording head according to claim 1, wherein the print data including the print data is applied only when all the print data is not printed.