JPH03176163A - Thermal head drive method and thermal head drive circuit - Google Patents

Abstract

PURPOSE:To eliminate the blur and bleeding of a printed result thermally affected by adjacent heating resistors and to obtain a sharp printing by a method wherein different STR signals are respectively inputted to adjacent output control circuits, and the STR signals prevent the simultaneous enable state of adjacent output drivers. CONSTITUTION:STR signals 9-1 and 9-2 are alternately inputted to an output control circuit 3. When the output of a latch circuit 2 is low and either the STR signals 9-1 or 9-2 is low, an output driver 4 is turned ON to pass an electric current to a heating resistor 5, and printing is conducted. On the other hand, when the output of the latch circuit 2 is high or the STR signal is high, the output driver 4 is not turned ON and, thus, an electric current does not pass to the heating resistor 5, and printing is not conducted. Therefore, by a method wherein different STR signals are respectively inputted to the adjacent output control circuits 3 and these two or more STR signals prevent the simultaneous enable state of the adjacent output drivers, printing can be made without passing an electric current to the adjacent heating resistors at the same time. In this manner, the heating temperature and cooling temperature of the heating resistors can be uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a thermal head in a thermal head printing device and a driving circuit.

[Prior Art] In a thermal head drive circuit in a conventional thermal head printer, a shift register l shown in FIG.
and the latch circuit 2, the latch circuit output data, and the external output driver control signal 9 (hereinafter referred to as the STR signal. In the embodiment of the present invention, 9-1, 9-2 are used, but in the past, only one signal was used). The S
There is only one TR signal and the same S
When the TR signal was input, adjacent output drivers were turned on at the same time, causing current to flow through the heating resistor and printing.

[Problem to be Solved by the Invention 1] For this reason, in the past, the heating resistor used for printing with a thermal head was used to turn on adjacent bits at the same time, as shown in Figure 2(a).
As a result, the temperature of the head changes due to the thermal influence of adjacent bits, causing print deterioration such as blurring or blurring. Furthermore, in order to improve the printing quality, the method of waiting for the temperature of the heating resistor to decrease before printing is performed, which has the problem of slow printing speed.

The present invention is intended to solve these problems, and its purpose is to provide a thermal head printer with good print quality and high print speed.

[Means for Solving the Problems 1] The thermal head driving method of the present invention includes a shift register that converts serial data into parallel data, a latch circuit that latches output data of the shift register, and a link between the output data of the latch circuit and external data. In a multi-output thermal head drive circuit comprising an output control circuit that calculates an output driver control signal, and an output driver that operates based on the output of the output control circuit, the multi-output thermal head drive circuit has two or more of the STR signals, and has two or more of the STR signals, Input each different STR signal,
The invention is characterized in that two or more of the STR signals do not enable adjacent output drivers at the same time.

[Operation] Since the present invention has the above configuration, the same S
Since no TR signal is input and two or more STR signals prevent adjacent bits from generating heat at the same time, good printing quality and high printing speed can be obtained.

[Embodiment] FIG. 1 shows an embodiment of the present invention, and is a circuit block diagram for realizing a method of driving a thermal head. This will be explained below based on FIG.

1 is a shift register that controls the output driver 4 (sequentially captures and transfers the input data signal 7 in synchronization with the clock signal 6. 2 is a latch circuit that controls the output driver 4 and transfers it sequentially in synchronization with the clock signal 6. 3 is an output control circuit that connects the latch circuit output and STR signal 9.
-1. Turns on output driver 4 in combination with 9-2/
Turn off.

Here, in the output control circuit 3, the STR signal 9-1 is input into the odd numbered signal from the beginning, and the STR signal 9-2 is inputted into the even numbered signal. That is, the STR signals 9-1 and 9-2 are alternately input to the output control circuit 3. When the output of the latch circuit 2 is low and the STR signal 9-1 or 9-2 is low, the output driver 4 is turned on and current flows through the heating resistor 5 to print, but the latch circuit outputs When the signal is high ``°H'' or the STR signal is high ``H'', the output driver 4 is not turned on, so no current flows through the heating resistor 5 and no printing is performed.

The relationship between the latch circuit output, STR signal, and printing is shown in the table below.

Table 9: Output of latch circuit 2 and STR signal 9-1.9
Printing is controlled in combination with -2. Therefore, STR
By inputting the signals 9-1 and 9-2 without matching the low timing as shown in FIG.
Even if all the outputs of are low, when the STR signal 9-1 is low, the signal 9-2 is high, so the odd numbered output driver 4 from the beginning turns on and prints, but the even numbered one does not turn on, so it prints. It will not be done.

From the above, it has a plurality of 5TR ("), and inputs different STR signals to adjacent output control circuits 3, and
If the TR signals are not enabled at the same time, printing can be performed without flowing current to adjacent heating resistors at the same time. This makes it possible to equalize the heat generation temperature and cooling time of one heating resistor.

Further, the driving method of the present invention uses a conventional driver and arranges the drivers on both sides of the heating resistor, connects the driver outputs to the heating resistor alternately, and alternately activates the output of the driver on one side (111). It can be achieved by this.

[Effect of the Invention J] The present invention has a plurality of STR signals, and inputs the different STR signals to adjacent output control circuits.
By not enabling adjacent output drivers at the same time, the signals do not enable adjacent bits at the same time, as shown in Figure 2 (b). This prevents printing from blurring or blurring due to the thermal influence of adjacent heating resistors. clear print. This means that when performing gradation printing, it is possible to distinguish between many gradations. Figure 2(a)
As shown in Figure 2, in the conventional driving method, the temperature becomes high in spots depending on the printed content, so the cooling time to bring it to the off temperature is longer than the average head cooling time. Due to the configuration of the driver circuit, the cooling time cannot be varied depending on the print content, so it is necessary to set the cooling time for each print as a standard.The present invention eliminates the spot-like high-temperature areas that existed in the past, so the longest cooling time is shortened. can do.

As a result, the printing time of the printer can be reduced by 1i (10% to several 100%) compared to the conventional method.

As described above, the present invention enables high-speed, high-quality printing without using complicated thermal control in the driving method of a thermal head printer.

[Brief explanation of drawings]

FIG. 1 is a thermal head drive circuit diagram according to the present invention. FIG. 2(a) is a diagram showing an example of conventional heat generation temperature distribution. FIG. 2(b) is a diagram showing an example of heat generation temperature distribution according to the present invention. FIG. 3 is a timing diagram showing the operation of the drive circuit shown in FIG. 1. 1 ・ ・ 2 ・ ・ 3 ・ ・ 4 ・ ・ 5 ・ 6 ・ ・ 7 ・ ・ 8 ・ ・ -1 -2 ・Shift register・Latch circuit・Output control circuit・Output driver・Heating resistor・Clock signal input data signal・Latch signal ・External output driver control signal ・External output driver control signal or higher

Claims (2)

[Claims] (1) A method for driving a thermal head in a thermal head printing device that performs printing using a heat generating resistor array, characterized in that adjacent bits of the heat generating resistor array are not made to generate heat at the same time. (2) A shift register that converts serial data into parallel data, a latch circuit that latches the output data of the shift register, an output control circuit that calculates the latch circuit output data and an external output driver control signal, and the output control A multi-output thermal head drive circuit comprising an output driver operated by the output of a circuit, which has a plurality of output driver control signals, inputs each different output driver control signal into the adjacent output control circuits, and outputs a plurality of the output driver control signals. A thermal head drive circuit characterized in that a control signal does not enable adjacent output drivers at the same time.