JP2958374B2 - Thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head having a heating value self-adjustment function.

[Summary of the Invention]

According to the present invention, at a location thermally separated from the heating resistor of the thermal head, the electrical conductivity is metallic (conductor region, hereinafter referred to as metallic) on a low temperature side and non-conductive on a high temperature side with respect to a specific temperature region. A wiring portion made of a substance causing a change that becomes metallic (semiconductor or non-conductive region, hereinafter referred to as non-metallic) is arranged electrically in series with the heating resistor, and the line resistance of the wiring portion is set to the above-mentioned value. It is smaller than the heating resistor, larger than the line resistance of the power supply line to the heating resistor, and the energization to the heating resistor causes the wiring portion to generate Joule heat. When the wiring section reaches the specific temperature, the metal-non-metal change occurs, and the wiring section self-interrupts the current, so that a heat generation temperature control function that does not raise the temperature to or above the specific temperature range is provided by the thermal head. Prepared for Is shall.

[Conventional technology]

In a conventional thermal head, as a heating resistor, a metal compound resistor such as ruthenium oxide or tantalum nitride, or a cermet resistor in which an insulator such as silicon oxide is dispersed in a high melting point metal such as tantalum has been used. .

When an appropriate voltage is applied to the heating resistor of the above-described conventional thermal head, a current flows through the heating resistor to generate Joule heat, and this state is maintained for a certain period of time to apply heat energy necessary for recording to a thermal paper or the like. . The Joule heat energy generated by the heating resistor is determined by the resistance value of the heating resistor, the voltage to be applied, and the time for applying this voltage. In general thermal recording equipment, the thermal sensitivity characteristics of the thermal paper used Depending on the heat transfer characteristics from the heating resistor to the thermal paper, the background temperature around the heating resistor, the temperature of the recording medium itself, or the like, the applied voltage or the voltage application time is adjusted to optimize the recording quality or the recording quality. It has been practiced to adjust the heat energy generated by the heating resistor to an optimum value so as to obtain a target recording density in tone recording.

[Problems to be solved by the invention]

In the conventional thermal head, the adjustment of the thermal energy related to recording by adjusting the voltage applied to the heating resistor and the pulse width of the voltage applied to the heating resistor is extremely complicated, and the recording device is large and expensive for the following reasons. Was.

As described above, the heat 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 cycle of the pulse, the number of continuous applications, and the like. , The pulse application history of the heating resistor around the heating resistor of interest, that is, the heating history, the temperature of the support substrate of the thermal head, the environmental temperature, and the like.

The thermal energy transmitted to the recording medium depends not on the thermal energy directly generated by the heating resistor but on the surface temperature of the heating resistor. Therefore, if the surface temperature of the heat generating resistor is to be made uniform in order to apply uniform heat energy to the thermal paper or the like, the heat generating resistor at the moment when the heat is to be generated is placed as described above. After collecting or predicting thermal environment information and thermal history information, the applied voltage or the voltage applied pulse width is adjusted and determined so that the surface temperature of the heating resistor rises to a specific temperature. The body must be fevered. The information collecting means, the predicting means, and the recording condition determining means as described above include various temperature sensors for detecting the temperature of the thermal head substrate and the environmental temperature,
The load on the hardware such as a memory for storing past record data for grasping the record history, a simulator such as a thermal equivalent circuit for predicting a thermal state, a CPU for processing, and a gate circuit is extremely large. The software supporting these hardware is also very complicated. In particular, large-sized, high-definition thermal recording equipment having a large number of heat-generating resistors, and equipment performing density gradation recording, the processing information becomes enormous, and it is unavoidable to increase the size and cost of the apparatus and to improve the recording quality. There are also sacrifices. In addition, information collection,
The processing time for the prediction and the determination of the recording conditions is also restricted by the CPU and the like, which is an obstacle to high-speed recording.

Furthermore, the thermal head generally has a glaze layer as a heat insulating layer to increase the thermal efficiency, but since this glaze layer is made by a thick film process, the thickness variation is ± 20 of the average value of the thickness. % Or more, and the thermal insulation effect of this glaze layer varies greatly in individual thermal heads at random. Therefore, as described above, even if information on the thermal environment of the heating resistor is accurately captured and processed, and the recording conditions are determined each time, even if the thermal characteristics of the thermal head vary, a highly accurate heating resistor temperature can be obtained. There is no control. If the heating temperature control is to be performed with higher accuracy, the variation of the thermal characteristics of the thermal head must be included as a control parameter.
A great deal of sacrifice must be made to mass production, such as by adjusting one unit. Also, considering the replacement of the thermal head inside the recording device due to the failure or life of the thermal head, it is practically impossible to adjust the settings of the recording device to the characteristics of the individual thermal head. Have difficulty.

[Means for solving the problem]

The present invention has been made in order to solve the various problems for uniforming the surface temperature of the heating resistor, and has a self-temperature control function for preventing the temperature of the heating resistor from rising above a specific temperature. With this configuration, the complicated temperature control of the heating resistor as in the related art is eliminated.

The present invention provides a wiring portion made of a substance that causes a change in electrical conductivity between a specific temperature region and a metallic material on a low temperature side, and a non-metallic material on a high temperature side, at a location thermally separated from the heating resistor. Electrically arranged in series with the heating resistor, the wire resistance of this wiring portion is smaller than the heating resistor, and larger than the wire resistance of the power supply line to the heating resistor. The wiring section is configured to slightly generate Joule heat.

[Action]

The electric conductivity changes from a specific temperature range to a metallic one at a low temperature and a non-metallic one at a high temperature, for example, a substance that undergoes a phase transition. When a voltage is applied to the resistor to generate Joule heat and the temperature reaches the above-described specific temperature, that is, a phase transition temperature of metal or nonmetal, due to self-heating of the wiring portion, the wiring portion substantially reduces the resistance value. The current is almost cut off if it is made high as an insulator or a semiconductor. Therefore,
The temperature of the heating resistor does not rise at least until the temperature at which the wiring portion exceeds the phase transition temperature, and the peak temperature of the heating resistor can be controlled uniformly.

〔Example〕

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

FIG. 1 is a plan view of a thermal head according to a first embodiment of the present invention. On a substrate 6 made of glazed amylna ceramic or the like, metallic at low temperature side at about 300 ° C,
A thin-film heating resistor 1 made of a material having non-metallic electrical conductivity characteristics at a high temperature side is provided. One end of the heating resistor is connected to the individual electrode 2 and the other end is connected to the first common electrode 3. I do. The individual electrodes are connected to a current switching element 4 such as a transistor. 5 is the switching element 4
And a second common electrode connected to the second common electrode. The switching element 4 and the second common electrode 5 are used as a thermal head.
May be provided separately as a recording device.

A positive potential is applied to the first common electrode and a negative potential is applied to the second common electrode, and a voltage pulse is applied to the heating resistor 1 by opening and closing the switching element 4. When a voltage pulse is applied to the heating resistor 1, as in a conventional thermal head, appropriate power consumption occurs depending on the applied voltage and the resistance value of the heating resistor 1 to generate Joule heat, and the temperature of the heating resistor 1 rises. Starts.

FIG. 2 is a diagram showing a time change of the surface temperature of the heating resistor 1 according to the pulse application. In this figure, T _C denotes the temperature of the metal non-metallic phase transition in the electrical conductivity of the heating resistor, t _on the application start time of the pulse, t _P is the heating resistor surface temperature above phase transition temperature (T _C) to reach the time, t _off represents the application end time of the pulse. from t _P
t the heat generating resistor 1 until _off the low temperature-side metal nonmetallic phase transition from the higher temperature side, repeat from the low temperature side and high temperature side, the surface temperature of the heat generating resistor, most near the phase transition temperature T _C It is in a calm state. The actual heating resistor temperature is sometimes slightly higher than the T _C from thermal inertia due to the heat capacity and thermal resistance of the structural member surrounding the heating resistor itself. t
the rise of the surface temperature of the heating resistor to t _P from _on the area of the heating resistor 1 of the heat generating resistor density equivalent of 8 dots / mm 0.015
mm ^2, 1000 [Omega] around the resistance heat at the cold side of the heat generating resistor, when the applied voltage was set to 20V, if brought into contact with the heat absorber of the heat-sensitive paper or the like to the heating resistor surface from t _on about 0.5 ms It reaches a T _C of about 300 ° C. in less than a time. This time, the glaze thickness of the glazing substrate of the thermal head,
Since the thermal resistance and heat capacity around the heating resistor change depending on the thickness and the like of the protective layer coated on the surface of the heating resistor, they vary depending on the structure of the thermal head.
However, the peak temperature of the heating resistor, to come determined by the phase transition temperature T _C with the material constituting the heating resistor, thermal properties such as the above thermal head, not dependent on the structure of the thermal head .

As described in the problems of the conventional thermal head technology, although variations in the thermal characteristics of the heat dissipation characteristics for the heat generating resistor is dependent, this variation is the variation of the temperature increase gradient of the t _on to t _P to, that is, appear in the variation of the time of t _P. By the way, the coloring mechanism in thermal recording is a chemical reaction due to the heat of a coloring agent in the direct thermal method, and the reaction speed depends on the temperature.In the thermal transfer method, it is a kind of physical phase change such as physical melting or sublimation of ink. The recording is controlled by the temperature of the ink. Therefore, influence on the recording characteristics of the variation in thermal characteristics of the thermal head appearing only in the variation of t _P, compared to a case where fluctuated until the exothermic peak temperature, such as by the prior art, much smaller.

The resistance variation of the heating resistor, the conventional thermal head by resistance film thickness and the like, but can depend both thermal head according to the present invention, this variation also, the present invention time from the t _on to t _P It only appears as variation,
The exothermic peak temperature does not change. Heating gradient due to the resistance value variation of the heating resistor, more strictly small time variation of t _P, if you try to be uniform, in phase of metallic electrical conductivity at a low temperature side of the heat generating resistor Depending on the resistance value of the heating resistor, make it uniform with power.
The applied voltage may be adjusted and set.

As described above, the influence on the recording characteristics due to the thermal characteristic variation and the resistance value variation of the thermal head is extremely small in the case of the present invention, but in particular, the applied pulse width is smaller than the temperature rise time from t _on to t _P. That is, t _{on in} FIG.
The longer the time from to t _off , that is, the change rate and the variation rate of the retention time (t _off -t _P ) of the heat generation peak temperature that most contributes to the recording characteristics are reduced, and the recording quality is further improved.

In the above embodiment, the temperature of the metal-to-metal transition of the heating resistor is set to about 300 ° C., but in the case of a thermal head requiring higher speed recording, a phase transition temperature as high as 400 ° C. or 450 ° C. If the power is increased by lowering (or increasing the applied voltage) the resistance value of the heating resistor, the temperature rises rapidly and at a high peak temperature. enough place, t from the t _{P
Even with an} applied pulse width (t _off -t _on ) with a short _off time, the heat generation peak temperature holding time can be secured, and uniform recording can be performed. Conversely, in a low-speed and low-power-consumption type thermal head, the power consumption value of the heating resistor may be reduced by lowering the applied voltage (or increasing the resistance value of the heating resistor). The transition temperature may be lowered to 250 ° C. or a combination thereof.

FIG. 4 shows a substance which undergoes a metal-non-metal phase transition as used in the above-described first embodiment of the heating resistor so as to come into contact with the heating resistor 7 made of a normal heating resistor material such as tantalum nitride. FIG. 3 is a plan view of a principal part of a thermal head in which a wiring 8 made of is arranged in series with the heating resistor 7 and the individual electrode 2. FIG. 12 is a sectional view of a main part of the thermal head. The wiring 8 is set to have a lower line resistance than the heating resistor 7, and when a voltage is applied between the individual electrode 2 and the common electrode 3, heat that contributes to recording is mainly generated by the heating resistor 7. The wiring 8 generates a small amount of heat compared to the heat generated by the heat generating resistor, but hardly generates heat. If a film having a sheet resistance smaller than the resistance value of the heating resistor 7, for example, a sheet resistance of several tens of milliohms can be formed by the material having a metal-to-metal transition used as the wiring, the individual electrode 2 and the wiring 8 are formed. Without distinction, the individual electrodes can also be made of the above-mentioned metal-to-metal transition material.

When a voltage is applied to the heating resistor 7, the heating resistor and its peripheral portion are heated by Joule heat. The temperature of the wiring 8 rises with the heat generated by the heating resistor 7. For example, if the phase transition temperature of metal and nonmetal is 200 ° C., the temperature of the wiring 8 becomes 200 ° C.
Continue to flow current until When the temperature reaches the above-mentioned phase transition temperature, it becomes nonmetallic electric conductivity, almost interrupts the current, and stops the generation of Joule heat of the heating resistor 7. When the temperature of the wiring 8 falls below 200 ° C., a current flows again, and the heating resistor generates heat. The temperature change of the wiring 8 due to the temperature rise of the heating resistor causes a distribution and a gradient in this wiring, but the above-described current adjusting function is exhibited.
Thus, as in the case of the first embodiment, at least the temperature of the wiring 8 is maintained at 200 ° C. while the voltage application is continued. Maintaining the temperature of the wiring 8 at a certain distance from the heating resistor 7 means that the temperature of the heating resistor 7 is substantially constant at least at a temperature higher than the temperature of the wiring 8. As in the case of the first embodiment, the surface temperature of the heating resistor 7 cannot be higher than a certain temperature, and the temperature is controlled. The accuracy of the temperature control at the heating resistor portion is higher as the wiring 8 is closer to the heating resistor, and the wiring may be provided in a heating area of the heating resistor.

In the above embodiment, the wiring 8 is provided in contact with one side of the heating resistor, but may be provided on both sides as shown in FIG. In the case where the electric conductivity in the non-metallic phase of the substance that undergoes the metal-metal transition used for the wiring 8 does not decrease so much, and the current leaks even on the high temperature side and the temperature of the heating resistor continues to rise, Alternatively, in the case where the wiring 8 generates heat due to the leak current on the high temperature side, the provision of the wiring 8 on both sides of the heating resistor 7 as shown in FIG. This is a better configuration from a control point of view.

Even if a short electrode 22 is interposed between the heating resistor 7 and the wiring 8 as shown in the plan view of FIG. 6 and the sectional view of the main part in FIG. The rise in temperature is unchanged. In particular, when there is a concern that the wiring material that undergoes a metal-to-metal transition with the heating resistor material may change its characteristics due to a chemical reaction or the like at a high temperature, a stable combination with at least the wiring 8 material is obtained. It is effective to use a stable metal such as gold for the electrode 22 and separate it from the heating resistor 7.

As in the above-described embodiment, forming the heating resistor from a generally used resistance material having high heat generation reliability has an advantage that a material that cuts off current at high temperature does not require high heat generation high temperature reliability. There is also.

The thermal head of the embodiment shown in FIG. 1 and FIG.
FIG. 3 shows how the temperature of the heating resistor surface changes when driven by continuous pulses. The heat generation peak temperature is constant from the first pulse to the n-th pulse, and the temperature rise time by the first pulse is longer by the lower the initial background temperature of the heat-generating resistor. Thereafter, the heat generation curves are almost the same. In this way, self-control to a constant heat generation temperature can be performed without performing any drive control. The long heat-up time of the first pulse does not cause any particular problem even in a sublimation type gradation printer, but when strict recording density control is required, the first pulse, that is, the background Only when the temperature is low, the applied pulse width may be extended by the longer heating time to uniformly control the peak temperature holding time.

For recording devices that perform gradation recording, the direct thermal method,
Regardless of the sublimation transfer method, it is common to perform gradation control with the length of the applied pulse width. With a conventional thermal head,
Since the heat generation peak temperature changes with the length of the pulse width, gradation control was difficult due to the change in the heat generation peak temperature. However, in the thermal head of the present invention, since the heat generation temperature is self-controlled to a constant value, With only the time parameter, the gradation control can be performed without concern for the heat generation peak temperature, and more strict gradation can be realized. In the conventional example, the relative density control of about 64 tones may be performed, but the absolute density control is limited to at most 16 tones. However, in the thermal head of the present invention, as apparent from the above description, the absolute density control is easy, and 128 gradations and 256 gradations are possible. FIG. 15 is a diagram showing a temperature waveform of a heating resistor surface temperature with respect to a pulse width applied to the heating resistor when the thermal head of the present invention is applied to gradation control.
The heating resistor temperature waveform (18-1) due to the first gradation pulse (19-1) starts to cool down in the middle of the temperature rising process. If the heat generation peaks due to most of the pulses up to the Nth gradation are in the time region where the temperature is controlled flat, the gradation accuracy will be high.

Incidentally, the substance that undergoes the metal-to-metal transition is a vanadium oxide-based compound. Trace amounts of vanadium oxide
Doping with Cr causes a change in electrical conductivity like a metal non-metal in a region higher than room temperature. It has non-metallic conductivity at higher temperatures and metallic conductivity at lower temperatures.
Both vanadium and vanadium oxide are high melting point materials and can be used as a heating resistor. The heat-generating resistor film can be formed by a thin film process such as sputtering, and can also be manufactured by a thick film process such as powdering and mixing with a binder or the like, or organic metalizing and coating. In any case, the formed vanadium oxide component needs at least a polycrystalline structure. In the case of sputtering, an alloy target of metal vanadium and chromium, or a metal vanadium target in which chromium is embedded is sputtered using argon and oxygen gas, and a target obtained by sintering vanadium oxide powder and chromium oxide powder is treated with argon gas. Alternatively, there is a method in which a small amount of oxygen is mixed with argon gas to perform high-frequency sputtering. In any of the sputterings, it is desirable that the temperature of the deposited portion is several hundred degrees Celsius or more to ensure a more crystalline state.

When an appropriate amount of Cr is doped, the electrical conductivity changes by two to three 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 an electrically conductive paper, the above-mentioned transition temperature can be obtained under a constant voltage applied state. Above and below, the power consumption value changes by two to three digits, and from the viewpoint of thermal recording, a substantial change in heat generation and non-heat generation is involved. The transition temperature can be changed by the ratio of Cr to be doped, and the peak temperature of the heating resistor can be set. In the case of vanadium oxide not doped with Cr, the rate of change in resistance is small,
Although the change is gradual with respect to the temperature, the resistance value increases by one digit from the low temperature side to the high temperature side at about 400 ° C., and can be used for the thermal head of the present invention.

FIG. 16 is a diagram showing a temperature change of the line resistance of the heating resistor having a metal-to-metal transition in the first embodiment. The line resistance itself is a reference value because it changes depending on the film thickness and the line width. However, in the case of vanadium oxide doped with about 0.5% of Cr with respect to vanadium, about three digits at about 150 ° C. as shown in the line resistance characteristic curve 31. There is a change in the resistance value. The temperature range where the resistance value changes depending on the doping amount of Cr changes,
As the Cr doping amount is increased, the temperature range of the change in the resistance value gradually shifts to a lower temperature side. If the doping amount of Cr with respect to vanadium exceeds several percent, the change in the increase in the resistance value from the low-temperature side to the high-temperature side disappears, and the object of the present invention cannot be achieved. As described above, since the doping amount of Cr changes the temperature characteristic of the resistance change, the change in the line resistance due to the microscopic non-uniformity of the doping amount of Cr with respect to vanadium oxide in the sample is, for example, as shown in FIG. It can be gentle with a certain temperature range, like the curve of 32. The object of the present invention can be achieved even with such a gentle change. In addition, for example, when trying to raise the temperature by energizing a heating resistor having a side of 0.1 mm, since the temperature does not uniformly increase in the heating resistor, the above-described heating resistor of the thermal head may be used. When a substance is used, the change in the resistance value of the heating resistor becomes apparently gentle as shown in FIG. 32. As a result, the temperature of the heating resistor as a whole can be increased or decreased without any problem.

Next, another driving method of the thermal head according to the present invention will be described with reference to embodiments.

FIG. 7 is a plan view of a thermal head in which the switching elements in the thermal head of FIG. 1 are formed by thyristors. A turn-on signal is input at an arbitrary timing to a gate 11 of a thyristor 10 connected 1: 1 to each heating element 1 that makes a metal-to-metal transition according to recorded data,
The thyristor 10 is turned on. A positive potential is applied to the first common electrode 3 and a negative potential is applied to the second common electrode 5, and when the thyristor is turned on,
Most of the positive and negative potential differences are applied to the heating resistor 1, and current starts to flow. The heating resistor generates Joule heat by this energization, and starts increasing the temperature. When the temperature of the heating resistor 1 reaches the metal-nonmetal transition temperature of the material constituting the heating resistor, for example, if the heating resistor is a Cr-doped vanadium oxide heating resistor, a current flowing through the heating resistor is used. If the value is reduced by two to three digits and an appropriate element having the turn-off characteristic of the thyristor is selected, the current flowing through the heating resistor is cut off.
The thyristor turns off. Once turned off, the heating resistor 1 cannot be energized again unless a turn-on signal is input to the gate 11, so that the heating resistor 1
The heat generation at stops. That is, the heating resistor 1 is
When the temperature is raised to the phase transition temperature by energization, heat generation is automatically stopped, and cooling standby is performed until the next thyristor turn-on signal is input.

FIG. 8 is a diagram showing a time change of the surface temperature of the heating resistor when the heating resistor 1 of the thermal head of FIG. 7 is continuously driven by the thyristor. 13 is a heating element surface temperature, 14 is a gate input signal of the thyristor, and is a timing signal for starting heating. T _C is the phase transition temperature. As is clear from this figure, no matter what timing the gate input signal is input, the heating resistor surface temperature will
The temperature rise and cooling curves near the heat generation peak temperature, which is the most important temperature region in thermal recording, do not exceed T _C , and are almost the same in any heat generation.

In the above description of the heating and cooling curves, it has been shown that the specific heating resistor is not affected by the heating history of the heating resistor. The heat generation peak waveform described above is not affected by heat generation, the history of past heat generation, or the temperature of the thermal head substrate, and uniform heat generation can always be realized. In addition, variations in applied power due to variations in resistance of the heating resistor, variations in thermal characteristics due to variations in the glaze layer thickness, etc., exist between individual heating resistors or between individual thermal heads, and the phase transition temperature is different. The determined exothermic peak temperature and the exothermic waveform near this peak temperature are uniform.

In the case of a thermal head using a combination of the above-mentioned metal-non-metal transition material and thyristor, since the heat generation peak temperature of the heat generation resistor is always constant, the color development due to the difference in the type of heat-sensitive paper under the same heat generation drive conditions. If there is a difference in sensitivity, a difference occurs in recording density. As shown in FIG. 14, the change in the surface temperature of the heating resistor shows a rise curve (15,16,1) of the surface temperature of the heating resistor depending on the voltage applied to the heating resistor.
7) changes, for example, when using thermal paper of standard sensitivity, the applied voltage is set so as to have a rising curve of the surface temperature of the heating resistor such as 16; in the case of thermal paper of low sensitivity, By lowering the applied voltage, increase the temperature maintenance time near the peak heat generation temperature as shown in 17; conversely, in the case of high-sensitivity thermal paper, increase the applied voltage to instantly increase the peak as shown in 15. If the temperature is set so as to reach the temperature, one thermal head can cope with a difference in recording sensitivity characteristics of thermal paper or the like.

As a means for coping with the difference in sensitivity, preheating just before the heating resistor of the thermal paper or ink sheet is also an effective means. For example, in the case of low-sensitivity thermal paper, setting the preheating temperature to a higher value can cope with the above without particularly changing the voltage applied to the heating resistor.

In the above-described heating driving method using a thyristor,
When a gate signal of about several microseconds is input, the drive control circuit is completely released from the heat generation operation. Accordingly, the buffer circuit of the recording image data can perform the operation of rewriting the recording image data of the next line in parallel with the heating operation of the heating resistor, and the recording can be easily speeded up.

FIG. 9 shows an embodiment of the heat generation drive control circuit, and FIG. 10 shows a drive timing chart of a thermal head using this drive control circuit. In FIG. 9, 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 signal from the heat generation timing signal input terminal 33 as inputs. An AND gate having an output terminal at 34. The output terminal 34 of the AND gate is connected to the gate 11 of the thyristor 10 connected to the heating resistor, so that the thyristor can be selectively turned on. In FIG. 10, 41 is image data for one line of recording, 42 is a shift clock, and when the image data is aligned in the shift register 35, a heat generation timing signal 43 is input with a pulse of several microseconds. The input signal 44 of the gate 11 of the thyristor is changed to the output terminal according to the content of the image data.
It is output with a pulse of several microseconds from 34. When the thyristor gate input signal 44 is output, the drive control circuit 37 in FIG. 9 is released from the heat generation operation and can proceed to the above-described series of preparation operations for the next line.

General drive control circuits for conventional thermal heads include:
The latch circuit enables high-speed processing so that recorded image data can be written in parallel with the heating operation of the heating resistor. High-speed parallel processing can be performed without the need. Therefore, the size of the drive control circuit can be reduced, the price can be reduced, and the size of the thermal head having the drive control circuit can be reduced.

In all of the above-described embodiments, the heat generation peak temperature of the heating resistor does not change even if a recording medium such as a thermal paper as a heat absorbing source is in contact with the heating resistor or not. Therefore, the thermal head according to the present invention does not cause deterioration or destruction of the heat generating resistor due to an abnormal rise in the heat generating peak temperature in the conventional thermal head when the heat generating resistor is not fed. It also demonstrates high reliability against malfunctions and runaway of the drive control circuit and CPU due to noise and the like.

FIG. 11 is a plan view of a main part of a thermal head in which a heat generation simulator 23 made of a material that undergoes a metal-to-metal transition is arranged in series with an individual electrode 2 at a position away from the heat generation resistor 7 as in FIG. It is. The heating simulator 23 has a line resistance smaller than the heating resistor 7 and larger than the individual electrodes 2. When power is supplied to generate heat from the heating resistor 7, the heating simulator 23 also starts gently generating heat. For example, if the temperature of the metal-metal transition of the heat generation simulator is about 120 ° C., the heat generation simulator 2
No. 3 simultaneously raises the temperature of the heating resistor 7 to about 120 ° C. by its own Joule heat, and changes to a non-metallic phase. As a result, individual electrodes connected in series with the heat generation simulator 23
2. The current flowing through the heating resistor 8 is cut off, and the heat generation in the heating resistor 7 can be controlled in the same manner as in the above-described embodiments. The manner of heating and cooling of the heating simulator is substantially similar to the manner of heating and cooling of the heating resistor, and the peak temperature is greatly different. Since the heating simulator is located away from the heating resistor, it is not directly affected by a temperature change due to pulse application of the heating resistor. The heat generation simulator is most affected by the heat storage in the peripheral portion of the heat generation simulator due to its own heat generation, and the background temperature due to the environmental temperature and the slow heat storage of the thermal head substrate caused by the heat generation of the heat generation resistor. Therefore, the heat generated by the heating resistor cannot be completely controlled. However, it is sensitive to a change in apparent color sensitivity due to a change in temperature of the thermal paper itself due to a change in environmental temperature or temperature in a recording apparatus. . Further, since the heat generation simulator does not become very high in temperature and has a small thermal shock, it is advantageous in terms of the heat resistance of a substance which undergoes a metal-to-metal transition. If a protective layer on the heat generating resistor is similarly provided on the heat generating simulator, the reliability of the heat generating simulator is improved with respect to oxidation, thermal deterioration, and shock deterioration due to the crystal structure change accompanying the phase transition.

In all of the above-described embodiments, the characteristics of the heating resistor, the wiring, and the material used for the heating simulator do not necessarily require that the electrical conductivity change discontinuously at a specific temperature, but a specific width. May be a substance that continuously changes temperature in a temperature range having In order to ensure the effect of the present invention, the change in the electrical conductivity is at least one digit or more, preferably two digits or more.

〔The invention's effect〕

As described above, according to the present invention, it is possible to uniformly control the heat generation peak temperature of the heating resistor even in any temperature environment where the heating resistor is placed. Variations in recording characteristics can be suppressed even for variations in thermal characteristics of layers, etc. Variations in recording characteristics can be suppressed even for variations in resistance values of heating resistors. High-precision density gradation control Easy, the heat generation drive control circuit can be completed with a simple configuration.
Thermal head substrate can be miniaturized, recording can be speeded up easily, temperature information collection circuit such as temperature detection in recording equipment and recording density correction circuit are not required, equipment can be provided small and inexpensive, heat generation resistance It is possible to provide an inexpensive thermal head that exhibits excellent effects such as high reliability and anti-runaway of the body.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a thermal head according to the present invention, FIGS. 2 and 3 are diagrams showing heat generation temperature characteristics of the thermal head according to the present invention, FIGS. 4, 5, and 6, respectively. FIG. 7 is a plan view of a main part of a thermal head according to the present invention, FIG. 7 is a plan view showing another embodiment of the thermal head according to the present invention, FIG. 9 is a drive control circuit diagram of the thermal head of the present invention, FIG. 10 is a drive control timing diagram of the present invention, FIG. 11 is a plan view of a main part of the thermal head according to the present invention, FIG. 12 and FIG. FIG. 14 is a diagram showing a heat generation temperature characteristic of the thermal head according to the present invention, FIG. 15 is a diagram showing a gradation heat generation temperature characteristic of the thermal head of the present invention, FIG. Is the wiring member resistance of the thermal head of the present invention. Is a diagram representing the characteristic. 1,7 Heat generating resistor 2,22 Individual electrode 3,5 Common electrode 4 Switching element 8 Wiring 23 Heat generating simulator 10 Thyristor 11 Gate 33 Heat generating timing signal Input terminal 35: Shift register 43: Heating timing signal 14, 44: Thyristor gate input signal 13, 15, 16, 17: Heating resistor surface temperature

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-207270 (JP, A) JP-A-60-244563 (JP, A) JP-A 64-27962 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B41J 2/335

Claims (1)

(57) [Claims] At a location thermally separated from a heating resistor, the electrical conductivity is made of a substance showing a conductor region on a low temperature side and showing a semiconductor or non-conductor region on a high temperature side with respect to a specific temperature region. A wiring portion, electrically arranged in series with the heating resistor,
The wire resistance of the wiring portion is smaller than that of the heating resistor, larger than the wire resistance of a power supply line to the heating resistor, and the energization of the heating resistor causes the wiring portion to generate Joule heat. Thermal head.