JPS6183052A - Preparation of thermal head - Google Patents

Abstract

PURPOSE:To reduce the irregularity in the resistance value of the heat generating resistor of a thick film type thermal head, by reducing the resistance value by applying a voltage pulse to the heat generating resistor. CONSTITUTION:The initial setting of a pulse condition such as the peak value Vs of apply voltage or the number (n) of pulses is performed by a calculation part 12. Next, the above mentioned set pulse is applied to a thermal head 7, of which the resistance value is equal to or more than a predetermined value R0, from a pulse generation circuit 10 and, thereafter, the resistance value of the thermal head 7 is measured by a resistance meter 11. Then, it is confirmed whether this measured value enters a definite range (e.g., 0.9-1.0 times) as compared with the preceding one and said lately measured value is compared with R0. When the above mentioned measuring range is larger than R0, the peak value Vs of an apply voltage pulse is increased by DELTAV to apply voltage. By this method, the peak value of apply voltage is increased to set the measur ing range of the resistance value of a heat generating element to the above mentioned range so as to set the same to R0 or less to complete adjustment. As a result the irregularity in the resistance value is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a thermal head mainly used in facsimiles and printers.

[Conventional technology]

Thermal heads, which do not require development or fixing, are noiseless, have a high speed/tenure, and are highly reliable, are becoming more popular as thermal recording paper improves. In thermal recording, a recording current is applied to a resistor provided on a substrate, and the Joule heat generated by the current flowing through the resistor is used to color the thermal paper that is heated on the resistor.

This is a technology that melts the ink layer of thermal transfer paper and prints and records recording signal information on the transfer paper.

A general structural diagram of the thermal head is shown in FIG.

The thermal head is mounted on an insulating substrate (A4 Au, C
The lead part (2) is made of a good electrically conductive material such as U by film-forming technology, and the film-like element resistor (3) with both ends connected to the lead part (2) constitutes a heating element as a whole.
As the material for 11, an alumina ceramic substrate or an alumina ceramic substrate with a glaze layer is often used. In the case of a thin film type, Ta is used as the material for the element resistor (3).
gN, Ta-8ins, Ta-8i, Ni-0u
, Ti2oa, etc. may be used. In addition, in the case of a thick film method, oxides of noble metals such as Ru2O and PtO are mixed with a glass material and sintered by coating. Although not shown, the element resistor +31'f! : After forming, a glass pattern is fired to protect the dough. When a constant voltage is applied to both ends of the lead portion of this thermal head for a certain period of time, heat is generated in the resistor portion due to Joule heat. This @ke 10th
The color is transmitted to the thermal paper (5) at part A of the two-ring device configured as shown in the figure, and the thermal paper +51 develops color and is printed on its surface. In addition, along FIG. 10, the same reference numerals as in FIG. 9 indicate corresponding parts. The direction in which the push roll (4) is pressed is shown. For example, in a facsimile thermal head, about 2000 resistors are independently arranged in parallel as heating resistors per head.

These heating resistors are heated to a surface temperature of about 250:C to 600℃ by Joule heat, and the applied energy equivalent to reaching this temperature is about 0.2 mJ, although it varies depending on the resolution of each thermal head. (Joule)~2 mJ is required.

Conventionally, this thermal head has been available in thick film type, thin film type F, and semiconductor type depending on the manufacturing process of the resistor and the difference in its material. A desired pattern is formed in advance on a screen or photoresist film using thick film forming or paste-like resistance material, and then the resistance material is printed using screen printing technology, embedded in a layer, and fired as a post-process. A heating resistor is formed. In the thin film type, a tantalum-based material is vapor-deposited or sputtered to form a basic pattern that can be used as a resistor in advance, and then,
By photo-etching, a desired pattern of independent resistors is completed. Semiconductor shaping, for example, by performing resistance diffusion on a part of a silicon base material to form a resistor and utilizing the heat generated at the P-N junction surface, uses all the same means as the semiconductor manufacturing process.

Of the three manufacturing methods mentioned above, the only ones that have been put into practical use are the thick film type and the thin film type. By the way, although the thin film type requires a large manufacturing process, it has the great advantage that there is little variation in the resistance value of the heating resistor and a fine pattern can be formed. On the other hand, the thick film type can be manufactured at low cost through a relatively short manufacturing process, but it also has the serious drawback of large variations in the resistance value of each heating resistor.

Heat-sensitive recording is determined by the resistance value of a resistor and utilizes the generated Joule heat, so variations in resistance value naturally cause density unevenness in the image quality printed thereon.

Figure 11 shows an example of the resistance values R1, R2, . While the uniformity is within ±15%, the thick film type is uniform within ±15%.
Although it is inferior to the thin film type with a variation of 30%, it has been making a living for a lifetime, but it has the advantages of high reliability such as overload power and wear resistance, and low cost. This is because .

Even with a thick film type, it is now possible to form fine patterns just as thin as with a thin film type. For example, in forming a conductor pattern, a printed film thickness of 3 μm or more was conventionally required, but a conductor film thickness of 300 OA or less can be used. This advantage is due to the fact that the etching factor during photoetching is comparable to that of the thin film type, ie, zero, compared to the conventional etching factor of 20tm. On the other hand, regarding improvement of the variation in resistance value of thick film type,
In addition to improvements in conventional screen printing techniques such as improvements to mesh screens and metal mask screens, photo-etching of thick film resistors as described in Japanese Patent Publication No. 59-226 'i'5, -18506
There are a method of embedding a thick film resistor in a photoresist pattern as described in JP-A-54-99443, and a method of polishing the surface of a thick-film resistor as described in JP-A-54-99443. Furthermore, there is a thin film conductor printed with a thick film resistor, as disclosed in Japanese Patent Application Laid-open No. 55-4'759'i'. In this way, the shape of the heating resistor is made uniform, and the resulting effect is an attempt to completely reduce the variation in resistance value.

We have also made progress in improving thick film resistor materials.

As a thick film resistor material, for example, Japanese Patent Application Laid-Open No. 53-954.4
Ruthenium oxide, high melting point frit glass, zirconium oxide, etc., as described in No. 1999 and JP-A-53-9543 are suitable. However, is the reliability of kneading, mainly as a thick-film type head? This has been improved to maintain the heat resistance, and the variation in the heating resistance value has not been significantly improved. By the way, if the shape of the thick film resistor is geometrically arranged to be the same as that of the thin film resistor, there is a question as to whether the variation in resistance value is really the same as that of the thin film resistor. Theoretically, the resistance value of a resistor can be expressed by the following equation.

Here, ρ: Specific resistance of the resistor (Ω-am) t: Length of the resistor (cm) W: Width of the resistor (cm) t: Thickness of the resistor (am) Screen-printed heating resistor Normally, there are slight variations in the length of the resistor5), the width of the resistor (W), and the thickness of the resistor (1), but ultimately the problem is basically whether the resistor is made of thick film or not. This is the variation in the specific resistance of the resistor itself caused by the difference in the degree of bonding that occurs during firing of ruthenium oxide, glass frit, zirconium oxide, etc. that maintain the same particle size, and the resulting variation in resistance value.

This problem cannot be solved even by strict screen printing and firing conditions in the thick film production process, and even by improving the front and back processes of the entire production of heat generating resistors such as lanterns. The particle size of ruthenium oxide, etc. is 5 fim, which cannot be ignored, as described in JP-A No. 53-9544; - Also, in determining the resistance value of a thick film resistor, Mainly ruthenium oxide, M at the contact interface with glass frit
This is because the cause is ultimately due to the heterogeneous bonding state of e-engineered s-Me (metal-insulator metal).

Basically, although the resistance value of thick film resistive materials changes significantly regardless of the firing temperature, atmosphere, and firing speed even if the materials are the same, the bonding state of M e - I B - M e changes. As a result of this assumption, thick-film resistive materials made of ruthenium oxide, glass frit, etc. with even finer grain sizes have recently become commercially available. However, the desired effect was not achieved.

From the above, it can be seen that the unevenness of thick film resistance due to the non-uniformity of the contact interface @
It can be seen that if the entire resistance is not improved, there is no improvement at all due to variations in resistance values. By the way, in order to improve the dispersion of resistors, adjustment of resistance values, etc., has been conventionally carried out mainly on thick film circuit boards, thin film circuit boards, etc. using a laser trimming method or the like. Also, JP-A-58-'
In the liquid jet recording head described in I'360 or JP-A-58-7350, a thin IN resistance element? Laser trimming is performed and the resistance value is adjusted to match the electrical-heat exchange characteristics.

[Problem that the invention seeks to solve]

All conventional methods for improving the variation in resistance values of thick film resistors have been insufficient. Since there is a mechanical tracing motion caused by the movement of a rotating roller located above the heating resistor and pressing against the thermal paper, chemical trimming methods that are susceptible to impact cannot be used.

In addition, since a uniform temperature distribution is required, the shape of the heating resistor is also an important factor.

Mechanical trimming methods such as diamond cutting and sandblasting could not be used because the changes in shape would deteriorate the overall performance of the thermal head.

What is the shape of the heating resistor of this invented thick film thermal head? The purpose is to provide a manufacturing method that changes the resistance value without changing the resistance value.

[Means for resolving sentry points]

The present invention reduces the resistance by applying a paper pressure pulse to the heating resistor of the thermal head, thereby reducing the total variation in resistance.

[Function] According to the present invention, it is possible to significantly reduce the variation in resistance value by making full use of the fact that the resistance value of the heating resistor decreases by applying a pressure pulse. By kneading, it is possible to significantly reduce manufacturing unevenness in the print quality of the thermal head.

[Actual gun array of invention]

I! of the thermal head according to this invention! ! ! ! The force building method is based on the process of reducing the resistance value of a heating resistor after the main production process. That is, a heating resistor is placed on the board,
After forming the lead wire and the protective glass film, the process of reducing the resistance value according to the present invention is implemented.

FIG. 1 σ is a diagram showing the principle of productivity E of the thermal head according to the present invention.

This generation (7) utilizes the phenomenon that when a voltage is applied to a thick film resistor, the resistance value decreases. This effect i M engineering S (Metal -In5ulator -Sem1
Thick film resistor insulator (conductor) structure
We do not think that this is because the voltage (In5ulator) causes a breakthrough due to voltage. Anyway, the resistor lol
J Rationality Characteristics that change to voltage application tiI
M is real.

FIG. 1 shows a case where the resistance Wi of the heating resistor whose initial resistance values are R1, R2, F, and a is adjusted to RO.

First, the resistance value of each heating resistor is measured and compared with the target resistance value RO. F, like R4.

No voltage pulses are applied to heating resistors with lower resistance values. Resistance value Hz larger than Ro, R2゜R3
A voltage pulse is applied to a heating resistor with a

First, a voltage pulse whose peak value is initially set to Vo is applied 111 to reduce the resistance value. Resistance value after reduction k Q
li, and if the value is on Ro J2L, then vO+ΔV
A voltage pulse with a wave height of 11 is applied. After that, measure the resistance value, and if the value is above RaJ2, Vo+2ΔV
A rolling pulse with a wave height value of is applied. In this way, the resistance value is gradually decreased while gradually increasing the peak value of the applied voltage pulse until the % resistance value falls below ROa. If the resistance value falls below Roa, the adjustment ends there. In this way, the resistance area of the heating element is set within a certain range below Roa. Variation in resistance value? Since the purpose of this invention is to reduce the resistance value, it is not necessary that the resistance value be kept below rho, but it is necessary that it be within a certain range below ROa.

Therefore, gradually decrease the resistance (II 5ra),
It is stopped at a certain point when Ro becomes lower.

FIGS. 2 and 3 are diagrams showing the distribution of resistance values of the heating resistor when the manufacturing method f of the present invention is not implemented and when it is implemented. Several heating resistor tl groups are shown, and the maximum value among them is shown by a white circle, the average value is all black, and the i and small values are shown by an X.

If you do not actually do it, the variation in resistance value may be very large.
When implemented, it can be seen that there is almost no variation in the values.

FIG. 4 is a configuration diagram showing an example of an apparatus used in the production method of the present invention.

FIG. 5 is a waveform diagram of the main signals in FIG. 4.

(6) C: A groping device that presses a probe against the thermal head (7) to be adjusted; (8) is a relay network that guides the applied voltage pulse to the desired heating resistor; (91 is the voltage application and resistance Switch to switch between measurements (101
teeth! J1 Pulse generation circuit that generates regulated paper pressure, 11
1 is the resistance meter, α2+ is the calculation unit, (13 is the input/output unit, 0 is the central processing unit (hereinafter referred to as CPU),
(151 is memory, u61i keyboard, t17H1m
It's a printer.

The procedure for reducing the resistance value according to the present invention will be explained.

Calculation unit (from 121 to setting of the peak value v8 of the applied voltage,
The setting of the number of pulses n included in one voltage application is given as follows. The voltage application from the calculation unit 121 starts at No. +9TA.
When receiving RT, the pulse generator circuit ENABIJ sends the signal back to the calculation section. Also, the switch (9) is switched to the pulse generation circuit (10) side. During the period when the ENAB LE signal is being output, changes in the peak value v8 and generation of the 5TART signal are prohibited. This is because the peak value Ve should not be changed while the voltage pulse is being applied, and the start signal 5TART for applying the σ-th voltage pulse should not be issued until the application of the current voltage pulse is finished. .

5TAI'jT When a certain period of time T1 has elapsed after the application of r1, the pulse generating circuit t101 sends n pulses with a peak value of ve to the heating resistor of the thermal head (7) through the switch (91, relay network (8)). After the application of the pulse voltage is finished and T2 hours have passed, the switch (9) is switched to the H side of the resistance meter.Then, after VcTs hours, NABIJ No. 1 is released and the next It becomes possible to apply a voltage.The resistance value is measured during time T3, and the measurement result is sent to calculation section 0?.Total lL section f1
2' cptr H compares the measured value with the previous measured value.

If the measured value is not within a certain range based on the previous measurement value, it is determined that there is a misbehavior. There are various ways to set a certain range, but the simplest method is to compare the value to see if it is significantly better than the previous measured value.

The case of this method will be described below as an example. If a value higher than the previous measurement value is obtained, CPU(l(1
) adopts this measurement value, and then releases the contact of the probe to the thermal head (71) to be measured to the probing device +G+, and sends out all the re-globe signals in order to make contact again.Then, the resistance value is re-measured. As can be understood from Figure 1, there is no possibility that the resistance value will increase due to the application of a voltage pulse, but if it does, the resistance value will increase due to the suction of the probe. This is because it is thought to be due to poor contact.

In this case, when re-contacting the probe, Ft is placed at the same location as before.
) Because of this, there is a possibility of poor contact again. Therefore, we will do it at the spot before the redistricting, and then do it at a spot 7'C a little further away. The probe contacts the tip of the lead wire at a place called a pad where the IC is thrown, or makes contact again at a position t''17'c a little apart within the same pad.

If the resistance measurement value is lower than the previous measurement value, cpU (14
The measured value of one digit is adopted and compared with the adjustment target value Ro.

If it does not reach Rn or less, C! PU (+41, E
After NABLE ta is released, the set value 7 of the peak value of the voltage pulse to be applied is increased by ΔV and applied to the pulse generation circuit (101). occurs.

In this way, the resistance value of the heating resistor is completely decreased while gradually increasing the peak value of the applied voltage pulse. If the resistance value is below the adjustment target value ROa, the resistance value of the heating resistor is adjusted! End of the process.

The switch (9) has a time limit TI IT21TI.

This is to avoid the influence of chattering in the relay network (8). Even if the pulse generating circuit (lO) generates all the voltage pulses before the switch (9) and relay network (8) are completely switched, the pulses will not reach the thermal head (7).
No voltage is applied. In addition, a switch (6), a relay network (
8) Even if you measure the resistance value before switching completely, you will not be able to get an accurate measurement.

Can the voltage pulse be applied as a single pulse?
Rather, it is easier to control by applying a pulse group consisting of several pulses. It is defined by the energy peak value of the voltage pulse and the pulse width Δt, but if this becomes too large, the heating resistor will be destroyed. Therefore, when the voltage pulse has a certain amount of energy and there is a risk of damaging the heat generating resistor rod, the pulse width must be adjusted to decrease according to the peak value of the voltage pulse. Rather than adjusting the pulse width of a single pulse, the width Δti of each pulse in a pulse group consisting of a plurality of pulses is kept constant,
It is easier to adjust the ratio Δt/Ir between the pulse period and the pulse width Δt to a value below which does not destroy the heating resistor in response to changes in the peak value. Alternatively, Δt/T may be kept constant and the number of pulses ni constituting the pulse group may be varied according to changes in the peak value. If the energy of the voltage pulse is sufficiently small, it may be applied as a single pulse or a Kehals group.

When the peak value of the applied voltage pulse is low, the phenomenon that the resistance value decreases is no longer observed. Therefore, the application of the voltage pulse σ of the first LgI is started from the peak value at which a decrease in the resistance value is expected. vO in FIG. 1 shows the peak value of the first applied voltage pulse.

The adjustment target resistance value Ro and the number of pulses n are performed using the keyboard (161).The resistance value after adjustment and CP
The calculation result of U (+41 is printed out as pre/ri[171.

6 is a flowchart of a method for adjusting the resistance value of a heating resistor using the apparatus of FIG. 4; FIG.

In step 4, pulse conditions such as the peak value VS and the number of pulses n are initialized. Next, in step, blowing to the thermal head (7+) by the blow big device r1t+61 and switching of the relay network (8) are performed.After that, in step 4, w, n pulse trains having the set peak value are applied. Then, the resistance value is measured.The current measurement value is compared with the previous measurement value 91 in step (c), and if it is larger than the previous measurement value, blobbing is performed again in step (4).

Mae I! l! l is smaller than the measured value and h is the adjusted target resistance value R,
Comparison is done in steps (to). If the measured value is less than or equal to RO, the adjustment for that heating resistor is completed.

If it is not below Ro 32, increase the peak value of the applied voltage nozzle by ΔV and apply a pulse (step @).

In this way, as a general rule, the measured value should be adjusted to be below Ro X2. However, no matter how much pressure is applied to the middle pulse 1, the resistance value decreases.
There are also six children. Further, there is a limit to the peak value of the pulse voltage generated by the pulse generating circuit (lO). Therefore, even if the resistance value does not fall below Ro 5d, when the number of pulse voltage applications reaches a certain number, the adjustment is ended there. Step @Geson is set up for that purpose.

・Resistance value III of several @thermal resistors as one group
I have already mentioned in Figures 2 and 3 that this is a sure thing.

When the adjustment for one group is completed, the CPU (141 is the average value,
Calculation for calculating standard@deviation '5J? , , XR'' and the maximum value and average value of the printer a7rxx group.

The minimum value is printed as shown in FIG. After adjusting all the heating resistances of the thermal head, the CPU α1 calculates the standard deviation σ. The result is printed on the printer α71.

FIG. 7 is a detailed explanatory diagram of the pulse generating circuit (10) shown in FIG. On the right side of the figure, (7), (2), ■ flip-flop circuit, (III, (G), @2 are timer circuits, (to) Geno(russe generator), (7) is monostable multi circuit. , (to) digit transistor, @ digit voltage power supply, C1 digit counter, and ① digit comparator.

When the starting j word 5TART from the calculation unit α21 receives '5j, the flip-flop circuit is turned off and the value is set.

Flip-flop + Oj path (1) ETh to Karaage calculation section
NABLE signal is sent. Changes in the intermittent wave high value signal Vs that KNABLFi shield number continues and 5TART @
The occurrence of issues is prohibited. Due to the output of the flip-flop circuit, the coil (91) of the switch (9) is energized, and the contacts (92) and (93) are switched to the opposite side j. After setting the flip-flop circuit (2), the timer circuit (311 outputs) after T1 hours. When the Shiffrin differential circuit (to) is set, the gate (2) is opened, and the pulse generator is turned on. The generated pulse is given to the monostable multicircuit (7).The monostable multicircuit (7) shapes the pulse width of the pulse generator (to) into a pulse with the desired pulse width Δt. It is determined by the resistor capacitor in the circuit (7).Figure 8 shows the output pulse waveform of the pulse generator (to) and the output waveform of the monostable multi-circuit 4.

Due to the pulse of the monostable multi-circuit (to), the gate drive current of the transistor is not supplied, and the transistor is in the ON state during the period when the transistor close pulse exists. While the transistor (to) is in the ON state, the output voltage of the voltage power source is applied to the contacts (92) and (93) of the switch (9).

It is applied to the sample via a relay network (8). The peak value of the voltage power supply (1) is not determined by the peak value official code V day sent to the calculation unit (121).

It is counted by the pulse count (7) passing through the gate diagram. The count value of the counter (2) is compared with the number n given from the calculation section α21 by the comparator -.

When the count value reaches n, the flip-flop circuit %g2'r is reset by the output of the comparator. This allows gate 1
'(4Bd closes, completing one pulse voltage application to the sample.

The output of comparator Q is also not given to the timer circuit (g).

Timer time Fj1 after time limit T2! (4f) is output, the flip-flop (43) is set by kneading, and when the switch is turned, the contacts (92) and (93) are switched to the positions shown in the figure, and the resistance meter (11) measures the heat generated by the sample. The resistance value of the resistor is measured.

When 13 hours have elapsed since the output of the timer circuit (6), the timer circuit (6) outputs an output, which resets the flip-flop circuit and sets the mutual terminal output level 11 to HI+ level, causing the ENABLE signal to disappear. fq, V
It is possible to apply a voltage pulse of ζyos&Kf! Ru.

An example of the result of the change in resistance value according to the present invention is as follows:
If the present invention is not implemented, the absolute value of the deviation is 20 h and the standard deviation σ is 5.6%, whereas the present invention f! : When using a real planer, the variation in resistance value will be significantly improved, with an absolute value of ±3 inches and a color deviation of 0.4. Therefore,
7L of thermal head printing! The degree of unevenness is almost a loaf〈
It was winter with something to do.

The inventors determined the initial setting value (vO in Figure 1) of the peak value of the voltage pulse applied to adjust the resistance value. Several tens of V, the increase in lI%fij of the applied pulse voltage ΔV'i IV, II! The number n included in the voltage port of J1 is 10~
20, one pulse width Δt −1r−1)t to 07
Adjustment of the resistance value of the heating element as seconds, pulse interval total μ seconds? I did it.

Time limit Tl, Tl ke lom seconds around lko, time limit Tzifim
The inventors adjusted the resistance value by setting the resistance value to seconds.

The specific numerical values of the parameters used to adjust the resistance value are not limited to the example described above, and various numerical values may be used within the range that produces the effects of the present invention. In step 24 of the figure, the previous resistance measurement 11
α is compared in size, but instead of Kneading VC, it is within a certain range, for example 0.9 to 1
．． It is also possible to check whether it is within the range of 0 times or not, and if it is not within this range, the resistance value may be re-measured.

An example of the thermal head manufacturing apparatus according to this invention (7) is shown in Figure 44 and Lua diagram, but this invention is limited to these.
7r.

Although the peak value V of the pulse voltage and the pulse number nk calculation unit 121 are automatically given to the pulse generation circuit (lO), it is also possible to set it by a complete hand stamp operation. This can be easily achieved by setting the peak value V and the number of pulses ni in the pulse generation circuit and using all the switches for the reverse purpose. Also, both the self-help setting and manual operation may be used together for a total of $121 (121 swords).

The switch (9) is a relay that energizes the σ coil (gl) in the row shown in Figure 7 and connects the suction points (92) and (93) k HA 4, but it can also be used with a thyristor inch instead of a kneader. It is possible.

rEffects of the Invention] According to the method for manufacturing a thermal head according to the present invention, a voltage pulse is applied to the heating resistor to reduce the resistance a, so that the resistance value of the heating resistor of the thermal head is less likely to be distorted. 9 (This is achieved by significantly reducing the unevenness of the applied a change of the thermal head.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the principle of the method for manufacturing a thermal head according to the present invention, and Figures 2 and 3 are diagrams showing the principle of the method for manufacturing a thermal head according to the present invention. Figure 4 is a diagram showing the distribution of resistance values; Figure 4 is a block diagram showing an embodiment of a device for manufacturing a thermal head according to the present invention; Figure 5 is a waveform diagram of the main parts of Figure 4; Figure 6 is a cross-section diagram showing the procedure for producing a thermal head according to the present invention, Figure 1 is a diagram explaining the state of use of the thermal head in a thermosensitive recording device d, and Figure 11 is a diagram of a general thermal head. FIG. 3 is a diagram showing an example of the distribution of resistance values in two heads. In the figure, (11) board, (2) lead wire, (
3) Heating resistance element, (61 heating device, ('
h l”f-thermal head, (8) relay network, (9
1 switch, (lO) pulse generation circuit, 111) is a resistance meter, 02' is a calculation unit, α-equipped CPU-311, chrysanthemum, '(6) is a timer circuit, 2) pulse generator, □□ □
Put I tool stable multi tc + J path, (9) to voltage type α, ■
q is a comparator. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (4)

[Claims] (1) A method for manufacturing a thermal head, which comprises applying a voltage pulse to a heating resistor of the thermal head to reduce the resistance value of the heating resistor to a predetermined range. (2) The method for manufacturing a thermal head according to claim 1, wherein the predetermined range is less than or equal to a predetermined value. (3) The method for manufacturing a thermal head according to claim 1 or 2, wherein the voltage pulse is a single pulse. (4) The method for manufacturing a thermal head according to claim 1 or 2, wherein the voltage pulse consists of a plurality of pulses.