JPH03130171A - Heat adjustment of thermal head - Google Patents

Abstract

PURPOSE:To make it possible to adjust the heating value in recording by increasing and decreasing the voltage applied on a heating element thereby varying temperature rise rate in heating. CONSTITUTION:A heating element 1 consisting of a thin film made of a material with metallic electric conductivity on the low temperature side and non-metallic electric conductivity on the high temperature side is provided on a substrate 6 of glazed alumina ceramic or other appropriate material. Then one end of this heating element 1 is connected to an individual electrode 2 and the other end is connected to the first common electrode 3. The individual electrode 2 is connected to the second common electrode 5 through a thyrister as a switching element. When heating is performed once but more effectively, a low voltage is applied on the heating element 1, and when heating is performed once but less effectively, a high voltage is applied on the heating element 1. Thus it is possible to control the peak heat temperature of the heating element 1 uniformly in any temperature environment under which the thermal resistor 1 is placed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of driving a thermal head having a self-adjusting function of heat generation.

(1 Summary of the Invention) The present invention includes a heating resistor and an electrode connected to the heating resistor, and at least a part of the heating resistor or the electrode is on the low temperature side with a specific temperature range as a boundary. The switching element, which is composed of a substance whose electrical conductivity changes from metallic to non-metallic at high temperatures, and which controls the conduction of electricity to the heating resistor, conducts electrical conductivity at high temperatures of the constituent member which changes from metallic to non-metallic. A method for developing a thermal head that has a function of turning off due to a decrease in conductivity due to a decrease in conductivity, and a JR adjustment method, in which a voltage applied to the heating resistor is applied when generating more heat in one heating action. The voltage applied to the heating resistor is increased to lower the temperature and generate less heat, and when the heating resistor is energized and the wiring reaches the specific temperature, the metal and nonmetal By causing a change in temperature and causing the wiring section to self-interrupt the current, the temperature does not rise above the specific temperature range, and 1.
The thermal head is equipped with a heat generation temperature control function for completing one heat generation operation, and the heat generation amount can be controlled in the thermal head whose heat generation peak temperature is constant.

[Conventional technology]

In conventional thermal heads, as a heating resistor,
Metal compound resistors such as ruthenium oxide and tantalum nitride, and cermet TG antibodies in which an insulator such as silicon oxide is dispersed in a high melting point metal such as tantalum, have been used.

When an appropriate voltage is applied to the heating resistor of the conventional thermal head mentioned above, a current flows through the heating resistor and generates Joule heat, and this state is maintained for a certain period of time to provide thermal energy necessary for recording to thermal paper, etc. .

The Joule thermal energy generated by the heating resistor is determined by the resistance value of the heating resistor, the applied voltage, and the time for which this voltage is applied. Optimal recording quality or gradation can be achieved by adjusting the applied voltage or voltage application time depending on the heat conduction characteristics from the heating resistor to the thermal paper, the background temperature around the heating resistor, the temperature of the recording medium itself, etc. The thermal energy generated by the heating resistor is adjusted to an optimum value so as to achieve the desired recording density during recording.

[Problem to be solved by the invention]

In conventional thermal heads, due to the following reasons,
Adjusting the thermal energy involved in recording by adjusting the voltage applied to the heating resistor and the voltage application pulse width is extremely complicated.
Moreover, the recording equipment was large and expensive.

As mentioned above, the thermal energy generated by applying a voltage pulse to the heating resistor can be determined by the voltage or pulse width of the applied pulse, but the surface temperature of the heating resistor depends on the application period of the pulse, the number of consecutive applications, etc. pulse application history,
It tends to fluctuate depending on the pulse application history, that is, the heat generation history, of the heating resistor around the heating resistor of interest, the temperature of the support substrate of the thermal head, the environmental temperature, etc.

Thermal energy transferred to the recording medium depends not directly on the thermal energy generated by the heating resistor but on the surface temperature of the heating resistor. Therefore, if you want to make the surface temperature of the heating resistor uniform when it generates heat in order to give uniform thermal energy to thermal paper, etc., it is necessary to thermal environment information,
Heat shoes 111! It is necessary to collect or predict flIi and adjust and determine the applied voltage or voltage application pulse width so that the surface temperature of the heating resistor rises to a specific temperature, and then make the heating resistor generate heat.

The information collection means, prediction means, and recording condition determination means described above include various temperature sensors that detect the temperature of the thermal head board and environmental temperature, a memory that stores past recorded data to understand the recording history, and a thermal The load on hardware such as a simulator such as a thermal equivalent circuit that predicts the physical state, and a CPU and gate circuit that performs 6A calculation processing is extremely large. In addition, the software that supports these hardware is extremely complex.A Particularly large, high-definition thermal recording devices with many heat-generating resistors, and devices that record density gradations, the amount of information to be processed is enormous. As a result, the device inevitably becomes larger and more expensive, and recording quality may be sacrificed. Furthermore, the processing time for collecting information, predicting, and determining recording conditions is also limited by the CPU, etc., and this becomes an obstacle to high-speed recording.

Furthermore, thermal heads generally have a glaze layer as a heat insulating layer to increase thermal efficiency, but since this glaze layer is made using a thick film process, the variation in thickness is ±20% of the average thickness. % or more, and the heat retention effect of this glaze layer varies widely randomly among individual thermal heads. Therefore, as mentioned above, how much information about the thermal environment of the heating resistor can be accurately obtained? if rae,
Even if the recording conditions are determined each time, precise heat generation temperature control cannot be achieved due to variations in the thermal characteristics of the thermal head. If we were to control the heat generation temperature with higher precision, it would be necessary to incorporate variations in the thermal characteristics of individual thermal heads as control parameters, which would require adjustment for each recording device one by one, resulting in a great sacrifice in mass productivity. have to pay. Also, when considering the case where the thermal head in a recording device needs to be replaced due to a malfunction or end of life of the thermal head, it is practically impossible to adjust the settings of the recording device to the characteristics of each thermal head. It's extremely difficult.

[Means to solve the problem]

The present invention has been made in order to solve various problems in making the temperature of the heating resistor surface uniform. This eliminates the complexity of controlling the temperature of the heating resistor as in the past.

The present invention comprises a heating resistor and an electrode connected to the heating resistor, and at least a part of the heating resistor or the electrode is metallic on the low temperature side and non-metallic on the high temperature side, with a specific temperature range as the boundary. In a thermal head made of a substance that causes a change in electrical conductivity, the switching element is used as a switching element to control energization to the heat generating resistor, and is used as a switching element to prevent a decrease in electrical conductivity at high temperatures of the component that causes a metal-nonmetal change. It has a function of turning off due to the accompanying decrease in the conducting current, and 1
heat generation adjustment by adjusting the applied voltage, in which the voltage applied to the heating resistor is lowered to generate more heat in the heat generating action, and the voltage applied to the heating resistor is increased to generate less heat. It's a method.

[Effect]

A material that undergoes a phase transition, such as a change in electrical conductivity that becomes metallic at low temperatures and nonmetallic at high temperatures, across a specific temperature range.
By configuring at least a part of a heating resistor or an electrode, the temperature of the phase change material increases to the specific temperature, that is, the metal-nonmetal temperature by applying a voltage to the heating resistor and generating Joule heat. When the phase transition temperature is reached,
The phase change material has a resistance value as high as that of an insulator or a semiconductor, and almost blocks current. Therefore,
The thermal head can be provided with a heating temperature control function that does not raise the temperature of the surface of the heating resistor above the specified temperature range and also allows one heating operation to be self-completed by turning off the switching element. At this time, the heat generation peak temperature of the heat generation resistor is always constant, but by increasing or decreasing the voltage applied to the heat generation resistor, the temperature rise rate during heat generation is changed, and the holding time near the heat generation peak temperature is changed. Therefore, the amount of heat related to recording can be adjusted.

〔Example〕

The details of the present invention will be explained with reference to examples.

FIG. 1 is a plan view showing an embodiment of a thermal head used in the driving method of the present invention. This thermal head consists of a thin-film heating resistor made of a material that has electrical conductivity characteristics that are metallic on the low temperature side and non-metallic on the high temperature side at a temperature of about 300°C, on a substrate 6 such as glazed alumina ceramic. One end of this heating resistor l is connected to an individual electrode 2, the other end is connected to a first common electrode 3, and the individual electrode 2 is connected to a second common electrode 3 via a thyristor 4 as a switching element. It is configured to be connected to a common electrode 5.

FIG. 2 is a diagram showing a temporal change in the surface temperature of a heating resistor exhibiting a metal-nonmetal phase transition upon application of a pulse. Tc represents the temperature of metal-nonmetal phase transition in the electric conductivity of the heating resistor, ton is the time at which the pulse application starts, t
, the heating resistor surface temperature is the phase transition temperature (Te)
The time at which L off is reached represents the time at which the application of the pulse ends. t.

From t Off to t Off, the heating resistor 1 repeats the metal-nonmetal phase transition from a high temperature side to a low temperature side and from a low temperature side to a high temperature side, and the surface temperature of the heating resistor 1 is almost always at the phase transition temperature. A calm state occurs near Tc. The actual temperature of the heating resistor may be slightly higher than the above Tc due to thermal inertia due to the heat capacity and thermal resistance of structural members around the mature resistor itself.

``The surface temperature rise of the heating resistor from ON to 1P is 0.015 mm, which is equivalent to the heating resistor density of 8 dots/w'', and the resistance value on the low temperature side of the heating resistor. When the resistance is about 1000Ω and the applied voltage is 20V, unless a heat absorbing material such as thermal paper is brought into contact with the surface of the heating resistor, t
Tc of about 300° C. is reached in about 0.5 milliseconds or less after turning on. During this time, the thermal characteristics of the thermal resistance and heat capacity around the heating resistor change depending on the thickness of the glaze on the glazing substrate of the thermal head and the thickness of the protective layer coated on the surface of the heating resistor, so the structure of the thermal head It varies from person to person. However, the peak temperature of the heating resistor is determined by the phase transition temperature Tc of the material that makes up the heating resistor. Not dependent.

As explained in the problems of the prior art, thermal heads are dependent on variations in thermal characteristics such as heat dissipation properties for the heating resistor, and these variations are caused by the temperature increase gradient from L, , 11 to t. In other words, 1. It appears only in the variation in the time of the day.

By the way, the color development mechanism in thermal recording is a chemical reaction caused by the heat of the coloring agent in the direct thermal method, and the reaction rate depends on the temperature, and in the thermal transfer method, it is a physical phase change such as physical melting or sublimation of the ink. Yes, recording is controlled by the temperature of the ink. Therefore, the influence of variations in the thermal characteristics of the thermal head, which appear only due to variations in t, on the recording properties is much smaller than in the case of the prior art, where the temperature fluctuates up to the exothermic peak temperature.

Further, although the resistance value variation of the heating resistor may depend on the resistor film thickness, etc., regardless of whether it is a conventional thermal head or a thermal head used in the present invention, this variation also varies from ton to t in the thermal head used in the present invention. This only appears as a variation in the time taken to reach the peak temperature, and the exothermic peak temperature does not change. Temperature increase gradient due to resistance value variation of the heating resistor,
If we want to make the time variation of t more strictly small and uniform, we should make the power uniform according to the magnitude of the resistance value of the heating resistor in the phase of metallic electrical conductivity on the low temperature side of the heating resistor. All you have to do is adjust and set the applied voltage so that

The driving method of the present invention utilizes the property of a material exhibiting a metal-nonmetal phase transition, which exhibits high resistance when the phase transition temperature (Tc) is reached, as shown in FIGS. 1 and 10. I will explain based on this. A thyristor 4 connected by tit to each heat generating resistor l that undergoes metal-nonmetal transition according to recorded data.
A turn-on signal is manually inputted to the gate 11 at an arbitrary timing to turn on the thyristor 4. A positive potential is applied to the first common electrode 3, and a negative potential is applied to the second common electrode 5. When the thyristor 4 is turned on, the difference in the positive and negative potentials is applied to the heating resistor l. When the voltage is almost applied, current begins to flow. The heat generating resistor l generates Joule heat by this energization and starts to rise in temperature.

When the temperature of the heating resistor l reaches the metal-nonmetal transition temperature (Tc) of the material constituting the heating resistor, for example, if the heating resistor is made of vanadium oxide doped with Cr, the heating resistor If the flowing current value is reduced by two to three orders of magnitude and an appropriate element with the turn-off characteristic of the thyristor is selected, the thyristor is turned off by cutting off the current flowing through the heating resistor. When the heat generating resistor 1 is turned off by - degrees, the heat generating resistor 1 cannot be energized again unless a turn on signal is input to the gate II, so the heat generation in the heat generating resistor 1 stops. That is, when the heat generating resistor 1 is heated to the phase transition temperature by being energized, it automatically stops generating heat, and waits for cooling until the next turn-on signal is input from the cyrisk. Here, when the voltage value of the voltage pulse applied to the heating resistor 1 is changed and the voltage value of the voltage pulse is increased, the heating temperature at the pulse 1 shows a steep rise with respect to the application time. ), when the voltage value of the voltage pulse is lowered, the heating temperature of the heating resistor 1 shows a gradual rise with respect to the application time (
Figure 1O, 16.17).

This is because the current value flowing through the heating resistor 1 depends on the voltage of the voltage pulse, and the heating peak temperature does not depend on the voltage value but on the metal-nonmetal phase transition temperature. The higher the voltage value of the applied pulse, the smaller the amount of heat generated by the heating resistor 1 can be obtained. Therefore, according to the driving method of the present invention, in which the applied voltage is lowered to generate more heat in one heat generation action, and the applied voltage is increased to generate less heat, the standard sensitivity thermal sensitivity When using paper, set the applied voltage so that the heating resistor surface temperature rises as shown in 16. If using low-sensitivity thermal paper, lower the applied voltage and generate heat as shown in 17. If you maintain the temperature near the peak temperature for a long time, and conversely, in the case of highly sensitive thermal paper, you can increase the applied voltage and set it so that the peak temperature is instantaneously reached as shown in 15. One thermal head can handle differences in recording sensitivity characteristics of paper, etc.

FIG. 3 is a diagram showing a temporal change in the surface temperature of a continuously driven heating resistor in the thermal head shown in FIG. 1. FIG.

As is clear from this figure, no matter what timing the gate input pulse 14 is input, the heating resistor surface temperature 13 never exceeds Tc, and remains near the heating peak temperature, which is the most important temperature region in thermal recording. The temperature rise and cooling curves are almost the same for both types of heat generation.

In the explanation of the temperature rise and cooling curves above, it was shown that a specific heat generating resistor is not affected by the heat generation history of this heat generating resistor. The heat generation peak waveform described above is not affected by heat generation, past heat generation history, etc., or thermal head substrate temperature, and uniform heat generation can always be achieved.

Furthermore, even if there are variations in applied power due to variations in heating resistor resistance values, variations in thermal characteristics due to variations in glaze layer thickness, etc., between individual heating resistors or between individual thermal heads, the phase transition The exothermic peak temperature determined by the temperature and the exothermic waveform around this peak temperature are uniform.

FIG. 4 is a block diagram showing an embodiment of the heat generation drive control circuit of the drive method of the present invention, and FIG. 5 is a drive timing chart of the thermal head using the drive control circuit shown in FIG. 4. In FIG. 4, 35 is a serial-in-parallel-out shift register having a serial input terminal at 31 and a shift clock terminal at 32, and 36 is a parallel output of the shift register and a heat generation timing signal input terminal 33.
This is an AND gate that receives a signal from the input terminal and has an output terminal at 34. The output terminal 34 of this AND gate is connected to the gate 11 of the thyristor lO connected to the heat generating resistor, and can selectively turn on the thyristor. In FIG. 5, 41 is image data for one line of recording, 42 is a shift clock, and the shift register 3 is
When the above image data are aligned in 5, the heating signal 43 is manually inputted with a pulse of several microseconds, and the input signal 44 of the Gero 1 of Cyrisk is output from the output terminal 34 within several microseconds according to the content of the image data. Output in pulses. When this risk gate manual signal 44 is output, the drive control circuit 37 shown in FIG. 4 is released from the heat generating operation and can move on to the above-described series of preparatory operations for the next line.

The general drive control circuit of conventional thermal heads has a launch circuit that enables high-speed processing so that recorded image data can be written in parallel with the heating operation of the heating resistor. The combination of the heating resistor and the SIRISK enables high-speed parallel processing without the launch circuit. Therefore, it is possible to reduce the size and cost of the drive control circuit, and also to reduce the size of the thermal head having a structure in which the drive control circuit is mounted.

In the above-described embodiment, the heat generation peak temperature of the heat generating resistor does not change even if the heat absorbing source such as a recording medium such as thermal paper is in contact with the heat generating resistor or not. Therefore, the thermal head of the present invention does not suffer from deterioration or destruction of the heat generating resistor due to an abnormal increase in the heat generation peak temperature of the heat generating resistor in its uncontrolled state in the conventional thermal head. Also, the drive control circuit and CP due to noise etc.
It exhibits high reliability even in situations such as U malfunction or runaway.

Here, the driving method of the present invention has been described using a thermal head whose heating resistor is made of a material that undergoes a metal-nonmetal phase transition at a specific temperature as shown in FIG. 1, but the following description also applies to the thermal head. , it goes without saying that there is a similar effect.

FIG. 6 is a plan view of essential parts showing another embodiment of the thermal head used in the driving method of the present invention.

This thermal head consists of a heat generating resistor 7 made of tantalum nitride or the like, a first electrode 3, an individual electrode 2, and a metal or non-metal that is placed between the heat generating resistor 7 and the individual electrode 2 at a specific temperature. The wiring 8 is made of a material that undergoes a phase change. The wiring 8 is set to have a low parallel wire resistance to the heating resistor 7.
The heat that contributes to recording is mainly generated by the heat generating resistor 7, and the wiring 8 generates only a small amount of heat compared to the heat generated by the heat generating resistor, but it is configured so that it hardly generates heat. If it is possible to form a film with a sheet resistance smaller than the resistance value of the heating resistor 7, for example several tens of milliΩ, by using the material that undergoes metal-nonmetal transition used for the wiring, the individual electrodes 2 and the wiring 8 can be formed. It is also possible to configure the individual electrodes with the above metal-nonmetal transition substance without distinction.

When a voltage is applied to the heating resistor 7, the temperature of the heating resistor and the surrounding area rises due to Joule heat. The temperature of the wiring 8 increases as the heating resistor 7 generates heat. For example, if the phase transition temperature of metal and nonmetal is 200°C, the temperature of the wiring 8 increases to 20°C.
The current continues to flow until the temperature reaches 0°C. When the phase transition temperature is reached, the electric conductivity becomes non-metallic and the current decreases, turning off the thyristor 4 and stopping the generation of Joule heat from the heating resistor 7, resulting in stable heat generation with a constant amount of heat. Can record. Further, by changing the voltage value of the applied voltage, it is possible to generate a low amount of heat generation by increasing the applied voltage value and to generate a high amount of heat generation by decreasing the applied voltage value in one heat generation action.

FIG. 7 is a plan view of essential parts showing another embodiment of the thermal head used in the driving method of the present invention.

This thermal head has wiring 8 made of a material that exhibits a metal-nonmetal phase transition at a specific temperature at both ends of a heating resistor 7 made of tantalum nitride or the like, and a first electrode 3. and the individual electrodes 2 are connected to each other.

In this thermal head, when a constant voltage value is applied between the first electrode 3 and the individual electrode 2, heat is generated in the heating resistor 7, and the temperature of the heating resistor 7 and the temperature of the wiring 8 are equal. When the salinity of the wiring 8 reaches the metal-nonmetal phase transition temperature, the current value is lowered and the thyristor 4 is turned off, allowing stable thermal recording with a constant amount of heat, and the voltage If you increase the value, you can record heat with a lower amount of heat, and if you lower the voltage value, you can record heat with a higher amount of heat.

FIG. 8 is a plan view of main parts showing another embodiment of the thermal drive used in the driving method of the present invention.

In this thermal head, a heating resistor 7 made of tantalum nitride or the like connects a wiring 8 made of a material that exhibits a metal-nonmetal phase transition at a specific temperature and an electrode 22 connected to the first electrode 1 and the individual electrodes 2. It is configured to connect via This thermal head is shown in Figure 6.

Similar to the thermal head shown in Fig. 7, when a constant voltage value is applied, the temperature of the distribution valve A8 reaches the metal-nonmetal phase transition temperature, the current value is lowered, the thyristor 4 is turned off, and a constant amount of heat is generated. It is possible to perform thermal recording, and furthermore, by increasing the voltage value, it is possible to perform thermal recording with a low amount of heat, and by decreasing the voltage value, it is possible to perform thermal recording with a high amount of heat.

By the way, examples of the substance that undergoes metal-nonmetal transition include vanadium oxide compounds. Trace amount of C in vanadium oxide
By doping with r, the electrical conductivity changes like a metal or nonmetal in a temperature range higher than room temperature. It has non-metallic electrical conductivity at higher temperatures and metallic electrical conductivity at lower temperatures.

Both vanadium and vanadium oxide have high melting points and can be used as heating resistors. As a heat-generating resistive film, it is possible to form a bottom film using a thin film process such as sputtering.
It is also possible to make it into a powder and mix it with a binder to make it into a paste, or make it into an organic metal and manufacture it by a thick film process such as coating. In either case, the released vanadium oxide component requires at least a polycrystalline structure.

In the case of spackling, a method is used in which metal vanadium and chromium are spun with a gold target, or a metal vanadium cougend embedded with chromium is spun using argon and oxygen gas, and vanadium oxide powder and chromium oxide powder are sintered. There is a method of high-frequency sputtering using argon gas or a mixture of a small amount of oxygen in argon gas and the like. In any spackling, it is desirable that the temperature of the deposited film be several hundred degrees centigrade or higher to ensure a more crystalline state.

When an appropriate amount of Cr is doped, the electrical conductivity changes by 2 to 3 orders of magnitude at the above transition temperature. Therefore, when used as a heating resistor of a thermal head or a heating resistor layer of current-carrying thermal paper, the above transition temperature will change when a constant voltage is applied. The power consumption value changes by 2 to 3 orders of magnitude above and below, and from the viewpoint of heat recording, this is accompanied by a substantial change in the non-generation of heat generation. It is possible to change the transition temperature by changing the proportion of Cr to be doped, and it is possible to set the heating peak temperature of the heating resistor. With vanadium oxide that is not doped with Cr, the rate of change in resistance is small and changes gradually with temperature;
There is a one-digit increase in resistance value from the low temperature side to the high temperature side across the temperature range, which can be used in the thermal head of the present invention.

FIG. 9 is a diagram showing a temperature change in the linear resistance of a material that undergoes a metal-nonmetal phase transition. The line resistance itself changes depending on the film thickness and line width, so it is a reference value, but for vanadium oxide doped with about 0.5% of vanadium with Cr,
As shown in the line resistance characteristic curve 31, the resistance value changes by three orders of magnitude at about 150°C.

The temperature range where the resistance value changes changes depending on the amount of Cr doped, and as the amount of Cr doped increases, the temperature range where the resistance value changes gradually shifts to the lower temperature side m Cr
If the amount of doping with respect to vanadium exceeds several percent, the object of the present invention cannot be achieved because the change in resistance value increase from the low temperature side to the high temperature side disappears. As mentioned above, C
Since the amount of doping of r changes the temperature characteristics of resistance change,
Depending on the microscopic non-uniformity of the doping amount of Cr to vanadium oxide within the sample, the change in the linear resistance may become gentle with a certain temperature range, as shown in the curve in FIG. 9, for example. Even with such a gradual change, the object of the present invention can be achieved. Furthermore, when an attempt is made to raise the temperature by applying current to a heating resistor with a side O of several mm, for example, the temperature does not rise spatially uniformly within the heating resistor. When a substance is used, the change in resistance value as a heating resistor appears to be gradual as shown in Figure 9, Figure 32 above, but even in this case, from a microscopic perspective, it is a state of temperature rise and energization stop. is occurring, and the temperature of the heating resistor as a whole can be raised or not, and there is no problem.

Note that in all of the above-mentioned examples, the characteristics of the materials used for the heating resistor, wiring, and mature oscillator do not necessarily require a discontinuous change in electrical conductivity at a specific temperature; It does not matter if it is a substance whose temperature changes continuously in a temperature range with a width of . In order to reliably exhibit the effects of the present invention, the change in electrical conductivity is at least one order of magnitude or more, preferably two orders of magnitude or more.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to uniformly control the heat generation peak temperature of the heat generating resistor in any temperature environment in which the heat generating resistor is placed; and ■ the thermal head. ■ Variations in recording characteristics can be suppressed even with variations in thermal properties of the glaze layer, etc.; ■ Variations in recording properties can be suppressed even in response to variations in the resistance value of the heating resistor; ■ High precision Easy density gradation control; ■ The heat generation drive control circuit can be configured simply, allowing for miniaturization of the circuit and thermal head board; ■ Easy recording speed; ■ Temperature information such as temperature detection in recording equipment. No acquisition circuit or recording density correction circuit is required, making it possible to provide equipment that is small and inexpensive.■ Providing a thermal head that exhibits excellent effects such as high reliability in terms of resistance to runaway of the heating resistor, etc., at a low price. It is possible.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the thermal conductor used in the driving method of the present invention, and Fig. 2 shows the temporal change in surface temperature due to pulse application of a heating resistor exhibiting a metal-nonmetal phase transition. Figure 3 is a diagram showing the surface temperature and time change of the continuously driven heating resistor in the thermal head shown in Figure 1;
FIG. 4 is a block diagram showing an embodiment of the heat generation control circuit of the driving method of the present invention, FIG. 5 is a drive timing chart of a thermal head using the drive control circuit shown in FIG. 4, and FIG.
7, and 8 are a plan view of the main part showing another embodiment of the thermal head used in the driving method of the present invention, and FIG.
The figure shows the change in salinity of the linear resistance of a material that undergoes a metal-nonmetal phase transition, and FIG. 10 is a diagram showing the relationship between the heat generation temperature and the voltage application time to explain the driving method of the present invention. 1, 7 ・ ・ ・ 2 ・ ・ ・ ・ 3 ・ ・ ・ ・ ・ 4 ・ ・ ・ ・ 5 ・ ・ ・ ・ ・ 8 ・ ・ ・ ・ 11 ・ ・ ・ ・ ・ 33 ・ ・ ・ ・ 35・ ・ ・ 43. .

Claims (1)

[Claims] Comprising a heating resistor and an electrode connected to the heating resistor, at least a part of the heating resistor or electrode becomes metallic on the low temperature side and non-metallic on the high temperature side, with a specific temperature range as the boundary. The switching element, which is made of a substance that causes a change in electrical conductivity and controls the current flow to the heat generating resistor, is turned off due to a decrease in the conducting current due to a decrease in the electrical conductivity of the metal-nonmetal component at high temperatures. 1. A method for adjusting heat generation of a thermal head having a mechanism for
The thermal head is characterized in that when generating more heat in one heat generating action, the voltage applied to the heating resistor is lowered, and when the heating is generated less, the voltage applied to the heating resistor is increased. How to adjust heat generation.