JPS61233562A - Thermal head - Google Patents

Abstract

PURPOSE:To make it possible to detect the destruction of a heat generating resistor and to enhance the reliability of an apparatus requiring the reliability of bar code printing and to detect the replacement period of a thermal head, by mounting a circuit for detecting and comparing the potentials of the connection points of the heat generating resistors and switching elements, and outputting the signal of the compared result. CONSTITUTION:A thermal head is equipped with a circuit for detecting the potentials of the connection points of the heat generating resistors 2 on an insulating substrate 1 and the switching elements formed on the IC chips 5 mounted on the substrate 1 and outputting the signal of the compared result. The thermal head uses that the potentials of the connection points of the heat generating resistors and the switching elements by the voltage applied from a common electrode are different at either one of the ON- or OFF-times of the switching elements when all of the heat generating resistors are normal and at the time of the destruction of the heat generating resistors and compares the potentials to output a signal.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a thermal head for printing barcodes, etc., which is equipped with a circuit that easily detects destruction of a heating resistor, and a method for detecting the same. It is something.

[Conventional technology]

In recent years, thermal recording methods and thermal transfer recording methods have shown remarkable development due to their simplicity, and many ideas have been made for the thermal heads that are their main parts.

FIG. 4 is a plan view and a sectional view showing the structure of the thermal head as a model. In the figure, (1
) is an insulating substrate, (2) t/i isolation C (heating resistor formed on the substrate (1), (3) is the individual heating resistor (
The individual lead (4) is drawn out from one end of 2), and the common electrode (5) drawn out facing the individual lead (3) through the heating resistor (2) is connected to the individual lead (3). , an integrated circuit (hereinafter referred to as F/C chip) including a drive circuit constituted by a switching element that turns on and off in accordance with a recording information signal, and a circuit for supplying a recording information signal.

) (6) is a metal wire that electrically connects the conductor pattern on the insulating substrate (1) and the engineered C chip (5), (7) is the IC
The signal terminal of the chip, (8) is the protective film covering the vicinity of the heating resistor (2) (fo, not shown in the plan view), and (9) is the thermal paper on the heating resistor (2) (not shown in the plan view). ), (lO)
is a transport roller for the thermal paper (9) (not shown in the plan view).

), (11) are resin covering the C chip (5) and gold wire (6) (not shown in the plan view). Figure 5 is a circuit diagram showing a conventional thermal head. (12) to (15) are the signal terminals (7) of the C chip (5), and (12) is the heating resistor (
2) an input terminal to which an open signal S is input for controlling on/off the current flowing through the switch, (13);
) #': Input terminal to which the latch signal for latching the I print data is input, (14) is the heating resistor (2
) is an input terminal to which print data D for driving and printing is input, and (15) is an input terminal to which taro clock C for synchronization with data D is input.

Next, the operation will be explained. One end of each heating resistor (2) is connected to the common electrode (4).
2) When a voltage VH is applied from K common type ff (4), if the dragon end of the heating resistor (2) on the insulating substrate (1) is grounded, then the heating resistor ( In 2), a current flows and generates heat. This current conduction lasts 1242 minutes of printing. This heat is absorbed by the thermal paper (9), and the transport roller (10)
Continuous printing is performed on the thermal paper (9) by conveyance of the thermal paper (9) and heat generated by the heating resistor (2).

In order to selectively drive the N heating resistors (2) based on the grounding and one line of print data, a simple method is to control the transistor serving as the driver using the parallel output of the shift register.

The print data of one line is expressed by two values "l#, IlO#," and the data DI, D2. . . . D(N-1), DN are output from the signal input terminal (7) in synchronization with taro clock C. 1
Enter line shift register.

When the launch signal is applied to the signal input terminal (7), the serial print data L on the latch 5bKril line
l, L2. . . L(N-1), LN are held, and each print data Ll, L2 . . . L(N-1), LN is input to the HAND circuit 5C together with the strobe signal S.

Therefore, the print data L1 to L held in the latch 5b
When N is #1'', the heating resistor (
2), the heating resistor (2) generates heat.

The above timing chart is shown in FIG. Here, FIGS. 6(a) to (e) are clock C, data D, and
The waveforms of the latch L1 strobe signal S and the applied voltage 'VH are shown.

Now, as shown in Fig. 5, the life of the heating resistor (2) of the thermal head is determined by the failure of the applied pulse.
This is determined by the abrasion resistance of the protective film1, and generally the guaranteed value is tens of millions to billions of lost pulses and tens of miles traveled.

However, when printing labels that display the manufacturer, product name, etc. in black and white binary numbers (barcode display), many pulses are applied to a specific heating resistor (2). Thermal paper (9), which serves as a label for barcode display, is used in places with poor environments such as supermarkets and factories, and small particles such as sand are transported with the thermal paper (9) and the protective film (8) is removed. As a result, the heating resistor (2) may be damaged. If a bar code is printed in a state where this particular heating resistor (2) is destroyed, an incorrect bar code will be displayed, and the reliability of the device will be questioned.

[Problems to be Solved by the Invention] Since the conventional thermal head is configured as described above, it is necessary to visually confirm whether or not the correct printing has been performed after printing is completed, and barcode printing is difficult. could not be trusted. In addition, in stations where it is not known when the pulse life point and running distance life point of the heat generating resistor are, it is necessary to replace the thermal head attached to the device at an early stage, which raises the cost of the device.

This invention was made to solve the above-mentioned problems, and it is possible to detect the destruction of heating resistors, improve the reliability of devices that require reliability such as bar code printing, and improve the reliability of thermal heads. The purpose is to detect when it is time to replace it.

[Means for Solving the Problems] The thermal head according to the present invention adjusts the potential at each connection point between the heating resistor on the insulating substrate and the switching element formed on the ICf7 chip mounted on the substrate. It is equipped with a circuit that outputs a signal as a result of detection and comparison.

[Function] The thermal head in #3AK has a voltage applied from the common i4 pole, which changes the potential at the connection point between the heating resistor and the switching element when the switching element is turned on and off when all the heating resistors are normal. The feature is that the connection point potential between the broken heating resistor and the switching element is different from that in either case, and a comparison is made and a signal is output.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (2) is a heating resistor, and (4) is a common 'M[
i, (5) rizc chip, (12) is the heating resistor (2
) is an input terminal to which a strobe signal S for controlling on/off of the current flowing in a switch-like manner is inputted, (13) is an input terminal to which a latch signal for launching print data D is inputted, (14) is an input terminal into which print data D for driving the heating resistor (2) to print is input;
(15) is an input terminal into which taro clock C for synchronization with data D is input, (16) is the heating resistor (2) and I
A resistor (hereinafter referred to as a detection resistor) connected to the connection point of the C chip (5), (17) an OR circuit input from the connection point of the ri heating resistor (2), and the detection resistor (16), respectively. , (18) is an output terminal to which the signal P20 resulting from the logical homology @ (17) is output.

The operation wJ of the heat generating resistor of the thermal head is the same as in the conventional example, and the detection of destruction of the heat generating resistor of the present invention and its signal output operation will be explained.

The potential at the connection point between the heating resistor (2) and the NAND circuit 5C, which is the switching element of the C chip (5), is the resistance value of the heating resistor (2) R1, the resistance value f of the detection resistor (16)
r and the voltage applied from the common electrode (4) is VH. If there is no OR circuit (17) and the strobe signal S is #L, the connection point potential will be vHXR+r. If the value increases, the node potential will be lower than the normal node potential.

If the potential of each connection point is connected to the OR circuit (17) as input, when all the heating resistors (2) are normal, when the strobe signal 8S is #L1, the output signal EO will be output as #H1. and output from the output terminal (18). Conversely, if even one heating resistor is broken and open, when the strobe signal 9S is #I or #, the output signal Do will be #L#.
The signal is then output from the output terminal (18).

Therefore, the device can detect that when the strobe signal S is #L', if the output signal EO is 1H#, it is normal, and if it is 'L', it is the end of the life of the heating resistor. Here, the resistance value of the heating resistor, which is the key point, is determined by whether or not it can interfere with printing, so the connection point potential at that time is determined by the detection resistor (
16), the resistance value in the logic homology FNr (17), etc. are set and determined, and the input determination level of the OR circuit (17) is determined.

In the above embodiment, the detection resistor (16) is connected to the connection point, and the input to the OR circuit (17) is shown as the input from the latch 5b, as shown in FIG.
A Zener diode (20) may be connected to the connection point, and only the connection point potential may be input to the exclusive OR circuit. This timing chart is shown in FIG.

Further, in the embodiment described above, a resistor is used to detect the potential at the connection point, and a logical sum circuit is used. However, a method for detecting the potential of a pond or a circuit for comparison may be used, and the same effect as in the embodiment described above can be obtained.

[Effects of the Invention] As described above, according to the present invention, the circuit is configured to detect the connection point potential between the heating resistor and the switching element and output a signal as a result of the comparison. This has the effect of being able to detect damage to the body, increase the reliability of devices that require reliability such as one-bar code printing, and detect when it is time to replace the thermal head.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of the thermal head of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the thermal head of the present invention, and FIG. 3 is a timing chart diagram of FIG. 2.
@Figure 4 is a model diagram showing the structure of a thermal head, Figure 5 is a circuit diagram of a conventional thermal head, Figure 6 is a timing chart of a conventional thermal head, and Figure 7 is a pulse application of the heating resistor of the thermal head. It is a figure which shows the number and resistance 1 direct change. In the figure, (1) is an insulating substrate, (2) is a heating resistor,
(5) I/iX C chip, (16) is the detection resistor, (
17) is an OR circuit, and (18) is an EO signal output child. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 4

Claims (2)

[Claims] (1) On an insulating substrate, a drive circuit consisting of a plurality of heat-generating resistors, a switching element connected to the heat-generating resistors that turns on and off according to recorded information, and a circuit that supplies a recorded information signal 1. A thermal head comprising: a circuit that detects a potential at a connection point between a heating resistor and a switching element, compares the potentials, and outputs a signal as a result. (2) The thermal head according to claim 1, wherein the means for detecting the potential at the connection point between the heating resistor and the switching element is a Zener diode.