JPH10305606A - Apparatus and method for heat treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optionally control a heat treatment to an object on the basis of a change amount of a resistance value, by setting a heat treatment condition to the object in accordance with the change amount of the resistance value, and carrying out the heat treatment to the object on the basis of the set heat treatment condition. SOLUTION: A current is fed to each heat-generating resistance body (bit). A current value is input to a CPU 4, so that a resistance value of each bit is calculated. A target resistance value Ra is input to the CPU 4 for each bit. An actually measured resistance value Rn and the target resistance value Ra set in the CPU 4 are compared with each other for each of all bits. Bits satisfying Rn>Ra are selected. An emission time (t) of a laser light calculated from a difference ΔR of the Rn and Ra of the selected bits and position data of the bits are recorded in the CPU 4. After an XY table 1 is positioned on the basis of a pickup signal from a CCD camera 33, the laser light L is oscillated for the emission time (t) calculated from the Rn of the bits required to be adjusted and recorded in the CPU 4. After all bits are subjected to heat treatment by the laser light, the resistance value is measured again for the bite, when the heat treatment is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment apparatus and a heat treatment method for changing the resistance of an object by irradiating the object with a laser beam, and more particularly to trimming the resistance of a heating resistor of a thermal print head. The present invention relates to a heat treatment apparatus and a heat treatment method suitable for the present invention.

[0002]

2. Description of the Related Art Various types of さ れ る A equipment such as stencil printing machines, facsimile machines, video printers, etc.
Due to advantages such as low maintenance cost and low running cost, a thermal recording method using a thermal print head has been frequently used. In general,
The thermal print head has the following configuration. That is, as shown in FIGS. 5A and 5B, the thermal print head 8 has heating resistors 10a to 10e provided on a substrate 9 made of alumina or the like, and an end of the heating resistor 10 Parts are lead wires 11a-1
1j, and the protective film 12 is arranged so as to cover the heating resistors 10a to 10e and the lead wires 11a to 11j. FIG. 5A is a schematic view of the thermal print head from the heating resistor side.
FIG. 5B is a diagram showing a cross section cut along the line AB in FIG.

The heating resistors are made of Ta—SiO ₂ , Nb—S
By sputtering using a target combining a metal such as iO ₂ , Zr-SiO ₂ or Cr-SiO ₂ with SiO ₂ ,
It is formed as a thin film having a thickness of 200 to 5000 angstroms. Normally, when the heating resistor formed as a thin film by sputtering is used as it is, the resistance value decreases due to Joule heat due to energization at the time of driving the thermal print head, and the flowing current increases, and subsequently, the increased current causes By repeating a cycle in which the heating value further increases and the resistance value further decreases, an excessive current flows through the heating resistor.
When an excessive current flows through the heating resistor in this manner, a desired amount of heat cannot be obtained from the heating resistor, so that the image quality of a printed image deteriorates. Further, since an excessive load is applied to the heating resistor, the heating resistor is destroyed and the life of the thermal print head is shortened. It is considered that the phenomenon in which the resistance value of the heating resistor decreases is because the molecular structure of the heating resistor changes due to heat generation. Therefore, when the heating resistor is formed by the above-described method, in order to further stabilize the fine structure of the heating resistor, current aging, annealing in a heating furnace, or irradiation of laser light is performed on the heating resistor. Heat treatment such as laser annealing. In this way, by previously performing the heat treatment on the heating resistor at a temperature higher than the heating temperature used when using the thermal print head, it is possible to prevent a decrease in the resistance value of the heating resistor due to heat generation.

In general, when a heating resistor is provided on a substrate by sputtering, the resistance of the heating resistor differs among the heating resistors. When heat-generating resistors having different resistance values are annealed by a heating furnace, the heat-generating resistors are controlled under substantially the same conditions, although the resistance value of the heat-generating resistors is controlled by the annealing temperature and time. Since the processing is performed at one time, even if the reduction of the resistance value of the heating resistor can be prevented, the fluctuation (variation) of the resistance value between each of the heating resistors is not improved. However, in a thermal print head used in a color printer or the like, since the fluctuation (variation) in the resistance value between each of the heating resistors is directly reflected in the deterioration of the image quality of the image, the resistance value between each of the heating resistors is reduced. Must be eliminated. Therefore,
In order to eliminate the variation (variation) in the resistance value between each of the heating resistors, heat treatment is performed by irradiating the heating resistor with a laser beam to reduce the variation in the resistance value between each of the heating resistors. In other words, the resistance values of the heating resistors are matched.

Here, an annealing process of the heating resistor by laser light irradiation will be described. As shown in FIG. 6, there is a variation (variation) in the resistance value between the heating resistors (bits) before the annealing process is performed. Therefore, the magnitude of the change in the resistance value required in the annealing, that is, the amount of change in the resistance value ΔR (the difference between the resistance value before annealing and the target resistance value Ra) differs between the bits of the heating resistor. The larger the resistance value of the heating resistor before the annealing process is, the larger the required change amount ΔR of the resistance value is.
Also, in annealing by laser light irradiation, FIG.
As shown in (2), when the output of the laser beam is constant, the amount of change ΔR in the resistance of the heating resistor due to the irradiation of the laser beam is a function of the irradiation time t of the laser beam. In order to increase the resistance change amount ΔR, it is necessary to increase the irradiation time t.

[0006]

As described above, since the amount of change ΔR in the resistance value of the heating resistor is a function of the irradiation time t of the laser beam, the annealing by the laser beam in the conventional heat treatment apparatus is not shown in FIG. As shown in FIG. 8, the irradiation of the laser beam and the measurement of the resistance value are repeatedly performed until the resistance value of the heating resistor after the irradiation of the laser beam reaches the target resistance value Ra. I was going. That is, when the first heating resistor is irradiated with a laser for a certain time (Δt: t1 = Δt) through steps 801 to 805, the resistance value is measured, and the actual measured value Rn of the resistor and the target resistance value Ra are calculated. (Step 806). If the measured value Rn of the resistor does not reach the target resistance Ra, the second irradiation of the heating resistor with the laser is performed for a predetermined time (Δt: t2 = 2Δt). Then, the resistance value is measured, and then the measured resistance value Rn of the resistor is changed to the target resistance value R
If the temperature has not reached a, the heating resistor is irradiated with the third laser for a certain period of time (Δt: t3 = 3Δt) to measure the resistance value. On the other hand, when the measured value Rn of the resistor reaches the target resistance value Ra, the number of bits is checked (step 8).
07) If all the bits have not been annealed, the next bit is annealed by laser irradiation (step 808), and if all the bits have been annealed, all the bits are re-executed. Is measured and the annealing is completed (steps 809 and 81).
0).

However, as described above, when annealing is performed by a conventional heat treatment apparatus, the number of times of irradiation of laser light and measurement of the resistance value increases as the heating resistor having a larger variation ΔR in resistance value of the heating resistor increases. Therefore, it sometimes takes about 100 seconds to anneal one of the heating resistors (one bit).

In addition, since the output of the laser beam is constant and the irradiation time of the laser beam is constant, the resistance value of the heating resistor becomes a target while the heating resistor is repeatedly irradiated with the laser beam. There is a problem that the resistance value becomes smaller than the resistance value Ra, and the fluctuation of the resistance value between the bits does not easily decrease.

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional example, and performs an accurate and prompt heat treatment on an object. It is an object of the present invention to provide a heat treatment apparatus which can perform heat treatment accurately and quickly and can impart substantially the same characteristics to each object, and which is excellent in economic efficiency.

Further, the present invention provides an accurate and prompt heat treatment for an object, and an accurate and rapid heat treatment for a group of objects even when a plurality of objects exist. It is an object of the present invention to provide a heat treatment method that gives substantially the same properties to a product and is excellent in economic efficiency.

[0011]

According to the present invention, there is provided a heat treatment apparatus, comprising: means for setting heat treatment conditions for an object in accordance with an amount of change in resistance; and performing heat treatment on the object based on the set heat treatment conditions. And means for applying.

According to the heat treatment apparatus of the present invention, heat treatment conditions for the object are set according to the amount of change in the resistance value, and the object is subjected to heat treatment based on the set heat treatment conditions. The heat treatment of the object can be arbitrarily controlled based on the amount of change in the resistance value. Therefore, the heat treatment can be accurately and quickly performed on the object, and even when there are a plurality of objects, the heat treatment is accurately and quickly performed on the group of objects, and substantially the same It is possible to impart characteristics.

Further, the heat treatment method according to the present invention comprises the steps of: setting a heat treatment condition for the object in accordance with the amount of change in the resistance value; and performing a heat treatment on the object based on the set heat treatment condition. It is characterized by having.

According to the heat treatment method of the present invention, heat treatment conditions for the object are set according to the amount of change in the resistance value,
By subjecting the object to heat treatment based on the set heat treatment conditions, the heat treatment of the object can be arbitrarily controlled based on the amount of change in the resistance value. Therefore, the heat treatment is performed accurately and quickly on the objects, and even when there are a plurality of objects, the heat treatment is performed accurately and quickly on the group of the objects, and each of the objects has substantially the same characteristics. Can be granted.

In the heat treatment apparatus and the heat treatment method according to the present invention, the resistance value is conscious of a value represented by R = V / I when a current I flows with a potential difference V between two terminals of the conductor. In particular, it is not necessary to limit to this value, and for example, a magnetic resistance or the like can be considered. Further, the amount of change in the resistance value may be a value determined in advance or a value that fluctuates as appropriate according to the situation. Further, the difference may be defined as a difference between an actual measured value of the resistance value of the object and a predetermined resistance value.

Examples of the object to be subjected to the heat treatment include a hybrid IC using a thin film resistor obtained by sputtering beta-Ta or NiCr on a ceramic substrate, a thick film resistor obtained by baking silver palladium, and various resistors. Preferably, the above-described heat generating resistor of the thermal print head can be preferably used.

Further, in setting the heat treatment conditions, the heat treatment method, heat treatment time, heat treatment strength, and the like are set as heat treatment conditions. For example, when the method of heat treatment is laser light irradiation, the time for laser light irradiation, the intensity of laser light irradiation, and the like can be dynamically set. Further, the laser light irradiation time may be fixed to change the laser light intensity, or the laser light irradiation time may be changed while the laser light intensity is fixed. That is, the setting of the heat treatment condition is performed by appropriately setting each necessary element according to the amount of change in the resistance value. The heat treatment may be irradiation of the object with the laser light or direct contact with a heat source, which can be appropriately selected depending on the situation. In the case where the heat treatment is performed by irradiating the object with laser light, for example, a YAG laser can be suitably used.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the heat treatment apparatus according to the present invention.

As shown in FIG. 1, the heat treatment apparatus according to this embodiment includes a ΧY table 1, and the XY table 1 is driven by a driver 2 in XY directions orthogonal to each other on a plane. I have. A drive signal to the driver 2 is output from the control unit 3, and the control unit 3
And an expansion board 5 is connected by a signal line 6. The XY table 1 is provided with a vacuum chuck 7, and the thermal print head 8 is held by the vacuum chuck 7. In the thermal print head 8, as shown in FIG. 5, a large number of heating resistors 10a to 10e are formed on an insulating substrate 9 made of alumina or the like at predetermined intervals along the longitudinal direction of the substrate 9. At the same time, lead wires 11a to 11j made of aluminum are connected to both ends in the longitudinal direction of the heating resistors 10a to 10e, respectively, and the heating resistors 10a to 10e are covered with a protective film 12.

The resistance value of each heating resistor of the thermal print head 8 is measured by a measuring unit 14 having a digital multimeter 13.
a to 10e, as shown in FIG. 2, are a pair of constant current wirings 16a and 16b via a shift register # C15 of a device circuit D provided in the thermal print head 8.
Can be connected. That is, of the pair of constant current wires 16a and 16b, the positive side constant current wire 16a is connected to the DC power supply unit 1 provided in the measurement unit 14.
7 is connected. The shift register # C15 is connected to a drive signal line 18 connected to the extension board 5, and a drive signal is applied to the drive signal line 18 from the CPU 4 via the extension board 5. Shift registerΙ
C15 is driven one bit at a time by a drive signal from the CPU 4 and turned on, thereby generating the heating resistors 10a to 10a.
A current is sequentially passed through each of the reference numerals 0e. Heating resistors 10a to 10
The current flowing in each of the e is input to the CPU 4 via the digital multimeter 13 and the extension board 5 through the other constant current wiring 16b, and the CPU 4 calculates the resistance value of each of the heating resistors 10a to 10e from the current value. You. As a result, for a heating resistor (bit) whose resistance value has not reached the target resistance value Ra, as described later, from the value calculated from the difference between the actually measured resistance value Rn and the target resistance value Ra, as described later. The required irradiation time t of the laser beam and bit position data are recognized by the CPU 4.
The digital multimeter 13 and the extension board 5 are G
P- 接 続 B19.

Further, a part of a pipe 21 provided with a solenoid valve 20 in the middle thereof is connected to the vacuum chuck 7.
A vacuum pump 22 is provided at the other end of the pipe 21.
The solenoid valve 20 is controlled to open and close by a drive signal output from the CPU 4 via the extension board 5. Then, as a result of the measurement of the resistance value by the measuring unit 14, the laser light L oscillated and output from the laser oscillator 23 is applied to the bit not reaching the predetermined resistance value, and the bit is subjected to heat treatment (annealing). Be executed. here,
The laser oscillator 23 has a laser beam L having a wavelength transmitted through a protective film covering each heating resistor of the thermal print head 8.
And output, for example, YAG as the medium of the laser.
A YAG laser using a crystal is used.

A control power supply 24 is connected to the laser oscillator 23, and the output is controlled by a drive signal from the CPU 4 via the control power supply 24 expansion board 5. The output is controlled by changing the irradiation time t while keeping the intensity of the laser light L constant. The irradiation time t is determined by the resistance value Rn of the bit actually measured by the measuring unit 14 and the target resistance value Ra. , That is, according to the amount of change in resistance, ΔR. That is, as shown in FIG.
Can be expressed as a function f (t) of the irradiation time t when the intensity of the laser light L is constant.
(t) gives the amount of change Δ in the resistance required for the k-th bit.
The irradiation time t _k of R _k laser beam L required calculated in CPU 4, the laser beam L is irradiated to the k-th bit by the time of the irradiation time t _k.

Further, a cooler 25 for cooling the laser oscillator 23 is provided in the laser oscillator 23, and cooling water for cooling a heat generating portion of the laser oscillator 23 is provided between the laser oscillator 23 and the cooler 25. It is circulating. In the optical path of the laser light L output from the laser oscillator 23, a molding member 27 having a slit 26 is provided.
Is provided, and the molding member 27 is driven by a driver 28. That is, the driving of the forming member 27 according to the size of the bit causes the slit 26
The shape of the beam of the laser light L passing therethrough can be set. Here, the shape of the beam of the laser light L is heat-treated (annealed).
It will be trimmed to match the size of the bit to be made. Thus, the laser light L passing through the slit 26 is
The light is reflected downward by the dichroic mirror 29 arranged at an angle of 45 degrees, is focused by the objective lens 30, and irradiates the bit of the thermal print head 8 on the ΧY table 1. In addition, dichroic mirror 29
A half mirror 31 is arranged above the half mirror 31. Observation light S from an observation light source 32 is incident on the half mirror 31. The observation light S passes through the dichroic mirror 29 and irradiates the thermal print head 8, and the reflected light passes through the dichroic mirror 29 and the half mirror 31, and passes through the eyepiece 34 to the CCD camera 33 of the imaging unit 32. It is imaged. The imaging signal from the CCD camera 33 is input to the television monitor 35 to display an image, and is also input to the CPU 4 via the extension board 5.
Thus, the XY coordinates of each bit of the heating resistor provided in the thermal print head are calculated. Next, the operation of the heat treatment apparatus will be described with reference to FIG.

First, a thermal print head 8 as shown in FIG. 5 provided with each heating resistor (bit) whose resistance value has not been adjusted is placed on the vacuum chuck 7 of the ΔY table 1 and 8, a constant current wiring 16a,
After the connection of the drive signal line 16b and the drive signal line 18, a key (not shown) for measuring the resistance value is operated to instruct the CPU 4 to measure the resistance value (step 401). Here, the measurement of the resistance value of each bit is performed as follows. That is, the control unit 14
A constant current is applied to the constant current wirings 16a and 16b from the DC power supply unit 17 provided at the
5 is driven one bit at a time, and a current is sequentially passed through each bit. The current value flowing through each bit is input to the CPU 4, and the resistance value of each bit is calculated from the current value (step 40).
2). Next, for each bit, the target resistance value Ra
Is input to the CPU 4 (step 403),
The resistance value Rn actually measured for all bits is compared with the target resistance value Ra set in the CPU 4 (step 4).
04 to step 407), a bit whose resistance value needs to be adjusted, that is, a bit whose measured resistance value Rn is higher than the resistance value Ra is selected (step 408). Note that the target resistance value Ra can be input to the CPU 4 in advance, and in this case, step 403 can be omitted.

Next, the irradiation time t of the laser beam calculated from the difference ΔR between the measured resistance value of the selected bit and the target resistance value Ra and the position data (k,
.. N) are recorded in the CPU 4, the thermal print head 8 on the ΧY table 1 is imaged by the image signal from the CCD camera 33, and the selected bit is set to the laser light L based on the image signal. Is driven based on the position data stored in the CPU 4 so as to be located at the irradiation position of. For example, the XY table 1 is positioned by an imaging signal from the CCD camera 33 so that the k-th bit is located at the irradiation position of the laser light L. The bit size is measured by the image pickup signal, and the driver 28 is driven by a drive signal from the CPU 4 according to the measured value, and the molding member 27 is driven in the optical axis direction to move the thermal print head 8. The size of the beam of the laser light L to be irradiated is made to match the size of the bit.と When Y table 1 is positioned,
A control signal is input from the CPU 4 to the control power supply unit 24 of the laser oscillator 23, and the irradiation time t calculated from the resistance value (actually measured value Rn) of the bit requiring adjustment recorded in the CPU 4
During this time, the laser oscillator 23 operates to oscillate and output the laser light L. The laser beam L from the laser oscillator 23 is incident on the dichroic mirror 29 after the beam shape is adjusted by the slit 26 of the molding member 27, and is focused by the objective lens 30 by reflection at the dichroic mirror 29, and k Irradiation is performed on the third heating resistor (bit) (step 409). At this time, the XY table 1 is driven at a predetermined speed in the Y direction so that the laser light L scans along the longitudinal direction of the bit (this direction is defined as the Y direction). Next, for example, the ΧY table 1 is driven and positioned in the X direction so that the (k + 1) th bit is located at the irradiation position of the laser beam, and the resistance value is adjusted similarly to the kth bit (step 409). Step 411). When the heat treatment by the laser beam is performed on all the selected bits, the resistance value is measured again on all the bits of the heating resistor (step 412), and the heat treatment is terminated (step 413). If there is no bit in step 408 where the actually measured resistance value Rn is higher than the resistance value Ra, the resistance values are measured again for all the bits of the heating resistor (step 412), and the process ends. (Step 413).

Next, an attempt was made to adjust the resistance value of the heating resistor of the thermal print head by using the above heat treatment apparatus. The thermal print head has a bit number of 460.
8 and has the same configuration as that shown in FIG. Also,
In adjusting the resistance value of the heating resistor, in order to set a control group, 20 thermal print heads manufactured under the same conditions were prepared, and these were randomly selected to obtain two groups (group A and group A). Group B), and one (Group A) was subjected to the heat treatment by the above-described heat treatment apparatus, and the other (Group B) was subjected to the conventional heat treatment shown in FIG. As a result, the processing time per thermal printhead of the group A thermal printhead is significantly reduced as compared with the group B thermal printhead, and the resistance value variation (variation) between bits is also greatly reduced. We were able to.

Thus, the resistance value of each heating resistor (bit) is measured using the shift register # C15 of the device circuit D of the thermal print head 8, and the measured value R is measured.
The irradiation time t required for the heat treatment is calculated from the difference ΔR between n and the target resistance value Ra, and each heating resistor (bit) is irradiated with the laser beam L only for the calculated irradiation time t to generate the heating resistance. Since the resistance value of the body can be adjusted, it is not necessary to repeat the irradiation of the laser beam L and the measurement of the resistance value of the changed bit until the actual measurement value Rn of the heating resistor reaches the target resistance value Ra. The processing time per bit was about 0.4 seconds at the maximum. Further, since the bit can be irradiated with the laser beam L only during the irradiation time t required for the heat treatment, the resistance value of the bit is prevented from being lower than the target resistance value Ra, and the resistance of the heating resistor is accurately determined. The value could be adjusted.

The present invention is not limited to the above embodiment, but can be modified without departing from the scope of the invention. For example, as described above, the output of the laser beam may be controlled by changing the power applied to the laser oscillator instead of the irradiation time,
R may be calculated, and a laser beam may be applied to each bit as needed from the calculation result.

[0030]

As described in detail above, according to the heat treatment apparatus of the present invention, heat treatment conditions for an object are set in accordance with the amount of change in the resistance value, and the object is set based on the set heat treatment conditions. Since the object is subjected to the heat treatment, the heat treatment for the object can be arbitrarily controlled based on the amount of change in the resistance value. Therefore, the heat treatment can be accurately and quickly performed on the object, and even when there are a plurality of objects, the heat treatment is accurately and quickly performed on the group of objects, and substantially the same It is possible to provide a heat treatment apparatus which can impart characteristics and is excellent in economic efficiency.

According to the heat treatment method of the present invention,
Since the heat treatment conditions for the object are set according to the change amount of the resistance value, and the heat treatment is performed on the object based on the set heat treatment condition, the heat treatment for the object is arbitrarily controlled based on the change amount of the resistance value. it can. Therefore, the heat treatment is performed accurately and quickly on the objects, and even when there are a plurality of objects, the heat treatment is performed accurately and quickly on the group of the objects, and each of the objects has substantially the same characteristics. It is possible to provide a heat treatment method which can be applied and is excellent in economic efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a heat treatment apparatus according to the present invention.

FIG. 2 is a diagram showing a connection between a digital multimeter 13 and each of heating resistors 10a to 10e of a thermal print head 8;

FIG. 3 is a diagram showing a relationship between a change amount ΔR of a resistance value of a heating resistor due to laser light irradiation and a laser light irradiation time t.

FIG. 4 is a flowchart showing an annealing process performed by the heat treatment apparatus shown in FIG. 1;

FIG. 5 is a diagram illustrating a configuration of a thermal print head.

FIG. 6 is a diagram showing a change in resistance value between respective heating resistors (bits) before an annealing process is performed.

FIG. 7 is a diagram showing a relationship between a change amount ΔR of a resistance value of a heating resistor due to laser light irradiation and a laser light irradiation time t.

FIG. 8 is a flowchart showing a process of annealing by laser light in a conventional heat treatment apparatus.

[Explanation of symbols]

1 ... Y table 2 ... Driver 3 ... Control unit 4 ... CPU 5 ... Expansion board 6 ... Signal line
7 Vacuum chuck 8 Thermal print head 9 Substrates 10a to 10e Heating resistors 11a to 11j
Lead wire 12 ... Protective film 13 ... Digital multimeter 14 ... Measurement unit 15 ... Shift register @C 16a, 16b ... Constant current wiring 17 ... DC power supply unit 18 ... Drive signal line 19 ... GP-B 20 ...
… Solenoid valve 21… Piping 22… Vacuum pump 23… Laser oscillator 24… Control power supply unit 25… Cooler 26… Slit 27… Molded member 28… Driver 29… Dichroic mirror 30… Objective lens 31 Half mirror 32
…… Imaging unit 33 …… CCD camera 34 …… Eyepiece 35
…… TV monitor

Claims (8)

[Claims] 1. A heat treatment apparatus for setting heat treatment conditions for an object in accordance with a change amount of a resistance value, and means for performing heat treatment on the object based on the set heat treatment conditions. Heat treatment equipment. 2. The heat treatment apparatus according to claim 1, wherein the amount of change in the resistance value is a difference between an actual measurement value of the resistance value of the object and a predetermined resistance value. 3. The heat treatment apparatus according to claim 1, wherein the object is a heating resistor of a thermal print head. 4. The heat treatment apparatus according to claim 1, wherein the heat treatment is irradiation with a laser beam. 5. The method according to claim 1, further comprising: setting a heat treatment condition for the object in accordance with the amount of change in the resistance value; and performing a heat treatment on the object based on the set heat treatment condition. Heat treatment method. 6. The heat treatment method according to claim 5, wherein the amount of change in the resistance value is a difference between a measured value of the resistance value of the object and a predetermined resistance value. 7. The heat treatment method according to claim 5, wherein the object is a heating resistor of a thermal print head. 8. The heat treatment method according to claim 5, wherein the heat treatment is laser light irradiation.