JPH04103365A - Thermal head driving method - Google Patents

Abstract

PURPOSE:To obtain a desired printing density immediately by applying subpulse signals for a certain quantity that printing will not be done to heat generating resistors for making collective printing undone among a plurality of heat generating resistors. CONSTITUTION:When a non-print signal is transferred to a history controlling table ROM, a control circuit C selects a subpulse signal SP3. Among the maximum heat generating times in 1 line, 2 subpulse signals SP3 are applied at an optional time to a heat generating resistor for making printing undone. On the other hand, a heat generating resistor for making printing done applies a main pulse signal MP and subpulse signals SP1, SP2, SP3. Accordingly, when a method to apply the subpulse signal SP3 to the heat generating resistor for making printing undone is combined with a distributed printing, a difference in temperature of a thermal head between the heat generating resistor which has made printing done and the heat generating resistor which has made printing undone becomes smaller. As a result, a print data signal is applied to the heat generating resistor which has made printing undone so far, so that a desired printing density can be obtained immediately when a printing is to be done.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for driving a thermal head of a thermal transfer recording device capable of binary recording or gradation recording.

(b) Conventional technology When printing using a thermal transfer recording device capable of binary recording or gradation recording, a recording paper and an ink sheet are superimposed and inserted between the pressure contact between the platen and the thermal head. Imprinting is performed by applying a pulse signal of a predetermined length corresponding to a desired printing density to a plurality of heating resistors arranged in parallel on the thermal head.

Here, the pulse signal length is approximately proportional to the printing density and is predetermined as a density table for each temperature of the thermal head. The temperature of this thermal head is detected by a temperature sensor such as a thermistor provided at the center of the thermal head. Then, by setting the density table according to this detected temperature and using this density table, it is possible to always perform printing with a predetermined density.

The pulse signal length t applied during printing is determined according to the desired density value from the density table described above, and the third
As shown in the figure, printing is performed on the n-th line by concentrating the heat generation time t + (t t < t o) in the first time period out of the heat generation time t0 of one line. Thereafter, the same applies to the printing of the (n+1)th line.

On the other hand, for example, 30% of the heating resistors on the left side (hereinafter referred to as heating resistor A) are set to a state in which they do not generate heat, and the remaining 70% heating resistor on the right side (hereinafter referred to as heating resistor B) is set to a state in which no heat is generated. ) is heated to perform printing, and then the above state is reversed and printing is performed.

In this case, the temperature of the thermal head immediately after reversal is lower on the left side and higher on the right side. However, since only one temperature sensor is usually provided at the center of the thermal head, the temperature sensor detects the temperature T of the center of the thermal head, that is, the temperature of the thermal head caused by the heat generated by the heating resistor B. Detects temperature.

Therefore, when printing is performed by the heating resistor A immediately after the reversal, the pulse signal length to be applied to the heating resistor A is determined from the density table based on the detected temperature T. Immediately after the reversal, the printing density by the heating resistor A becomes thinner.

The reason for this is that among the plurality of heat generating resistors, heat generating resistor A that does not generate heat and heat generating resistor B that generates heat exist in groups, and if printing is continued in this state, the entire thermal head will This results in large variations in temperature.

As a method to prevent this phenomenon, as disclosed in Chapter 5 of Dye Sublimation Thermal Transfer Recording Technology, Trikebbs (1988), the temperature on the thermal head is detected.
Feedback is sent to a high-precision control circuit using a timer to adjust the signal pulse length applied to the heating resistor.
Alternatively, the power supply voltage may be adjusted.

However, even such a method cannot adequately cope with the problem.

(c) Problems to be Solved by the Invention The present invention was made in view of the above-mentioned problem, and the heating resistor A, which was not printed, and the heating resistor B, which was printed, exist in a group. However, after continuous printing is performed in this state, when this state is reversed and printing is attempted, the heating resistor A, which has not been used for printing until now, is forced to reach the desired density. The purpose is to immediately obtain a desired printing density by applying a corresponding pulse signal.

(D) Means for Solving the Problems The present invention provides a method for inserting a recording medium and an ink sheet in a superimposed manner between a platen and a thermal head having a plurality of heating resistors disposed opposite to the platen. The method for driving a thermal head that prints ink on the ink sheet onto a recording medium is characterized in that a pulse signal that does not perform any printing is applied to the heating resistor that does not perform any printing. .

(E) Effect A sub-pulse signal is applied to the heating resistors that are not collectively printed among the plurality of heating resistors, so as not to be printed.

(f) Example An example of the present invention is shown in FIGS. 1 and 2 (a) and (b).
Shown below.

In FIG. 1, the microprocessor MPU applies printing data for each line of four consecutive lines to arbitrary data buffers DB1 to DB4. These data buffers DB1 to DB4 transfer the print data one line at a time to the respective input buffers LBI to LB4.

These input buffers LBI to LB4 transfer printing data in units of bytes of one line of printing data to the line switch LI via data latches DRI to DR4. This line switch Ll is connected to data latches DR1 to DR.
It has a function of rearranging the printing data of four consecutive lines in the printing data in the printing order and transferring the data to the latch shift register SR.

After being sorted by the line switch Ll, the data transferred to the latch shift register SR is written to the history control table ROM. This history control table ROM stores the printing data for each dot using four signals, namely, a main pulse signal MP, a sub-pulse signal SPI,
It is converted into a sub-pulse signal SP2 or a sub-pulse signal SP3, and these signals are applied to a pulse selection circuit PK.

The signals applied to the pulse selection circuit PK are appropriately combined by the pulse selection signal PS applied from the control circuit C, and this combined signal is applied to the thermal head S)l.

On the other hand, the control circuit C sends and receives control signals and the like to and from the microprocessor MPU and data buffers DB1 to DB4, and also receives a count clock signal CC1 and a clear signal C8.
is applied to the address counter AC. This address counter AC has four input buffers LBI~
Specify the address where the print data is temporarily held for LB4.

The control circuit C also sends control signals such as a chip select signal TS and a write signal WS to manual buffers LBI to LB, respectively.
4, the latch pulse signal RPI is connected to the data latch DRI~
DR4 and line selection signal LN to line switch Ll.
, the latch pulse signal RP2 is transferred to the latch shift register S.
Apply to R.

Furthermore, the control circuit C applies a pulse selection signal PS to the pulse selection circuit PK, and also applies a reading tarlock signal YC and a heat generation control signal HC to the thermal head 5t-1.

Next, the operation of the above configuration will be explained.

The control circuit C applies a clear signal C8 to the address counter AC in order to erase the contents of the address counter AC before writing printing data for each of four consecutive lines, and then applies a clear signal C8 to the address counter AC. Based on this, the address to write data is specified to input buffers LBI to LB4 via address bus AB.

Then, the control circuit C applies a signal to the microprocessor MPU to write printing data into the data buffers DBI to DB4.

In accordance with the signal, the microprocessor MPtJ writes four consecutive lines of print data one line at a time into the respective data buffers DBI to DB4.

When the control circuit C detects the end of this writing, in order to write the printing data in the data buffers DBI to DB4 to the manual buffers LBI to LB4 line by line, the control circuit C sends the printing data to the input buffers LBI to LB4 into which the printing data is written. , write signal WS, and chip select signal TS are applied. Then, each 1 in the data buffers DB1 to DBJ
Line printing data is transferred to input buffers 7LB1 to LB4, respectively.

Among the four consecutive lines of printing data transferred to the input buffers LBI to LB4, one byte of printing data is applied to the count clock signal C from the control circuit C.
C, the data is read out sequentially according to the address specified by the address counter AC.

The read printing data is sent to data latches DRI to D which are connected to the respective input buffers LBI to LB4.
It is transferred to the line switch Ll via R4. By this line switching operation of the line switching device Ll, the four consecutive lines of print data in the data latches DRI to DR4 are rearranged so as to be continuous, and after being transferred to the latch shift register SR, history control is performed. Table ROM for
will be forwarded to.

This history control table ROM converts the data into a main pulse signal MP, sub-pulse signal SPI, sub-pulse signal SP2, or sub-pulse signal SP3 as information for each dot, and sends the pulse selection circuit P for each signal.
Sequentially transfer to K.

Here, among the four signals transferred to the pulse selection circuit PK, the control circuit C selects the main pulse signal MP alone, or the main pulse signal MP and the sub-pulse signal SP1. A pulse selection signal PS for determining whether to print SF3 and SF3 in combination is sent to a pulse selection circuit P.
Apply to K.

At this time, when a signal indicating that printing is not to be performed is transferred to the history control table ROM, the control circuit C sends a pulse selection signal PS that selects the sub-pulse signal SP3 among the four signals to the pulse selection circuit PK. It is now possible to apply.

The printing data signal transferred to the pulse selection circuit PK is read out by a read signal YC applied from the control circuit C to the thermal head SH, and transferred to the thermal head SH.

The printing data signal transferred to the heating resistor of the thermal head SH generates heat according to the ON/OFF signal of the heating control signal HC applied from the control circuit C, thereby forming a desired dot diameter on the recording paper. .

The print data from the fifth line onwards are sequentially written into the data buffer that held the print data for the first line of the first four lines. Therefore, four consecutive lines of printing data are always written in the data buffers DBI to DB4 even while printing is being performed.

The above has explained the flow of the first byte of the four consecutive lines of print data, but the data from the second byte onward is
When the transfer to H is completed, the flow as shown above is repeated.

By repeating printing for each line in this manner, printing for one screen is completed.

As described above, when the signal indicating that printing is not to be performed is transferred to the history control table ROM, the control circuit C selects the sub-pulse signal SP3 as described above, and
As shown in Figure (a), two sub-pulse signals SP3 are applied to the heating resistor which is not to be printed at any time during the maximum heating time t0 of one line.

However, the two sub-pulse signals SP3 have a pulse length that is not printed on the recording paper. Further, the length of the sub-pulse signal SP3 may be set at any time and any number as long as it is a pulse length that is not printed.

By the driving method according to the present invention, without changing the conventional configuration, the heating resistor portions that were subjected to printing collectively and continuously, and the heating resistor portions that were not subjected to printing, can be collectively and continuously removed. The temperature difference between the thermal heads becomes smaller. As a result, even if the heating resistor that was not used for printing is made to print, the desired printing density can be obtained immediately.

On the other hand, as shown in FIG. 2(b), the heating resistor for printing is supplied with a main pulse signal MP and a sub-pulse signal SP1.
．． Apply SF3, SF3. As shown in the figure, these four signals have different pulse lengths, and the main pulse signal MP and sub-pulse signals SPI, SF3, SF3 have different pulse lengths.
3 is transferred to the pulse selection circuit T'K as a printing data signal for each line. At this time, the above-mentioned respective signals are distributed within the heating time t0 of one line, and printing is performed.

Therefore, if this distributed printing is combined with the method of applying the sub-pulse signal SP3 to the heating resistor that does not perform printing, it is possible to eliminate the part of the heating resistor that was being printed and the part that was not being printed. The temperature difference between the thermal head and the heating resistor portion is further reduced.

By adopting the above method of driving the thermal head, the temperature difference of the thermal head between the heating resistor part that was printing and the heating resistor part that was not printing is reduced. As a result, when a printing data signal is applied to a heating resistor that has not been used for printing up to now and printing is to be performed, the desired printing density can be immediately obtained.

In this embodiment, the length of each pulse is set as shown in FIG. 2(b), but the length is not limited to this.

(G) Effects of the Invention According to the present invention, heat can be stored in the heating resistor portion where printing was performed and the heating resistor portion where printing was not performed, without changing the configuration of the conventional control circuit. The temperature difference in the thermal head due to this decreases, and as a result, when printing is attempted by applying a printing data signal to the heating resistor that was not printing, the desired printing density can be obtained immediately. It becomes like this.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a control circuit used in the thermal head driving method of the present invention, and Fig. 2 (a) and (b) show pulses of the main pulse signal and sub-pulse signal of the present invention. FIG. 3 is a pulse waveform diagram showing the pulse length of a conventional pulse signal. MPU...Microprocessor, DB1~DB4...
・Data buffer, LBI to LB4 ・Power buffer, C. Control circuit, R latch shift register, Ll... line switch, KI ・thermal head, K pulse selection circuit.

Claims (2)

[Claims] (1) A recording medium and an ink sheet are superimposed and inserted between a platen and a thermal head having a plurality of heating resistors disposed opposite to the platen, and the ink on the ink sheet is applied onto the recording medium. A method for driving a thermal head that performs printing, characterized in that a pulse signal that does not perform any printing is applied to the heating resistor that does not perform any printing. (2) The method for driving a thermal head according to item 1, characterized in that pulse signals divided into a plurality of parts are distributed and applied within the heating time of one line to the heating resistor to perform printing.