JPH06417B2 - Thermal head resistance adjustment device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resistance adjusting device for a thermal head that equalizes the resistances of heating resistors.

[Conventional technology]

As is well known, a thick film type thermal head is formed by printing a paste-like resistance material in a predetermined pattern by a screen printing method or the like and then firing it to form a heating resistor. Therefore, the thick-film type thermal head can be manufactured at a low cost by a relatively short manufacturing process, but has a drawback that the resistance value of the heating resistor varies greatly. Since the variation in the resistance value of the heating resistor directly affects the quality of printing and the like, it is an extremely important factor to make the resistance value of the heating resistor uniform in the production of the thick film type thermal head. . To make the resistance values of the heating resistors uniform, a trimming process using the phenomenon that when the heating resistors are formed and a relatively high voltage pulse is individually applied to each heating resistor, the resistance value decreases is used. is there.

In this way, the conventional thermal head manufacturing method involves repeatedly applying a voltage pulse to the heating resistor while gradually increasing the voltage value to set the resistance value of the heating resistor to a certain target value. It was found that the resistance value of the resistor changes on a curve with a constant rate of change as the applied voltage pulse is gradually increased, regardless of its initial value.

This rate of change is Can be approximately represented by. In the equation (1), V is the applied voltage, R is the resistance value of the heating resistor, R ₀ is the initial resistance value of the heating resistor, V ₀ is the boundary value of the applied voltage at which the resistance value starts to change, and ΔV Is the change step of applied voltage, α, β
Is a constant determined by the thermal head structure, dot density, and the like.

FIG. 3 is a diagram showing a decrease in the resistance value of the heating resistor when a voltage pulse is applied to the heating resistor by such a method. Before trimming, R ₁ , R ₂ , R ₃ Due to the trimming process, the resistance value, which was greatly varied, is the target value R.
It is homogenized within a narrow range slightly below ₀ . In the figure, V _s is the initial value of the voltage pulse, and since the boundary voltage at which the resistance value of the heating resistor starts to decrease due to the application of the voltage pulse is usually around 25 V, it is set to 25 V, for example. Further, ΔV is an increment of the voltage value of the voltage pulse, and is set to, for example, 2.5 V so that the resistance value of the heating resistor does not decrease too much, and the resistance value is gradually decreased.

FIG. 4 is a diagram in which the horizontal axis represents the applied voltage value by the voltage pulse and the vertical axis represents the resistance change rate of the heating resistor by the voltage pulse application. FIG. 4 shows the same data as in FIG. 3 with the vertical axis of FIG. 3 represented by the resistance change rate. Even if the initial resistance values of the individual heating resistors vary, the change rate curve is As shown by the broken line in FIG. 4, a diagram showing a decrease in the resistance value of the heating resistor that follows a substantially constant curve Y regardless of the initial resistance value can be drawn.

In such a thermal head manufacturing method, in order to trim a one-dot heating resistor, it is necessary to apply a voltage pulse 20 to 30 times and to measure the resistance value, so that the resistance value of the heating resistor can be made uniform. Will take a great deal of time.

Therefore, recently, the resistance drop curve is approximated by measuring the sample dot in the thermal head, and this trimming curve is used during trimming to determine the initial resistance value of the heating resistor of the dot and the resistance value to be reached. Therefore, a method of making the resistance value uniform by determining the voltage value of the voltage pulse to be applied and reducing the resistance value of the heating resistance value to the target value by applying the voltage pulse once has been conceived.

That is, FIG. 5 is a flow chart showing a conventional method for manufacturing a thermal head. In the figure, ST1 is an initial setting step, ST2 is a step for measuring a resistance change of a sample following the step ST1, ST3 is a step for approximating a resistance value drop curve following the step ST2, and ST.
4 is a resistance value measuring step following the step ST3,
ST5 is a step for determining an applied voltage following step ST4, ST6 is a step for applying a voltage pulse following step ST5, and ST7 is a step for detecting the end of all trimming dots following step ST6. Returns to step ST4.

FIG. 6 is a block diagram showing an example of an apparatus for carrying out this thermal head manufacturing method. In the figure, 1 is a thermal head on which trimming processing is performed, and 2 is a terminal of each heating resistor of this thermal head 1. A probing device 3 for pressing the probe is connected to the probing device 2 to select the heating resistor. A relay network 4 is connected to the relay network 3 to switch between application of a voltage pulse and measurement of a resistance value. A switch 5 is a pulse generator connected to one side of the switch 4 to send out a voltage pulse of a designated voltage value, 6 is a resistance meter connected to the other side of the switch 4, 7 is an input / output unit 8, and a central processing unit. A control arithmetic unit 12 for controlling the above-mentioned devices and performing necessary arithmetic processing, including a unit (hereinafter referred to as CPU) 9, a memory 10, a keyboard 11 and the like. A printer connected to the control calculation unit 7.

Next, the operation will be described. First, in step ST1, initial setting is performed, and then in step ST2, resistance change measurement of the sample is performed. That is, the relay network 3 is controlled to select the dot heating resistor designated as a sample of the thermal head 1, and the switch 4 is switched to switch the resistance meter 6
And the resistance value is measured, and the measured value is controlled by the calculation unit 7
Then, the CPU 9 of the control calculation unit 7 stores it in the memory 10. Next, the switch 4 is switched to switch the pulse generator 5
A voltage pulse with a more predetermined voltage value is applied to the heating resistor. Here, this voltage pulse is a pulse train in which, for example, 15 pulses having a width of 2 μsec and a period of 50 μsec are continuous. Next, the switch is switched again to connect the heating resistor to which the voltage pulse is applied to the resistance meter 6 to measure the resistance value and send it to the control calculation unit 7. The CPU 9 of the control calculation unit 7 stores it in the memory 10 together with the voltage value of the applied voltage pulse. Hereinafter, similarly, the processes are repeated while appropriately increasing the voltage value of the voltage pulse. This process is repeated at least three times, switching relay network 3 and executing for some samples.

Next, in step ST3, the resistance drop curve is approximated based on the measured resistance change. That is, the CPU 9 of the control calculation unit 7 obtains the resistance change rate ΔR = (RR ₀ ) / R ₀ at each applied voltage by the voltage pulse from the resistance change stored in the memory 10, and this is expressed by the above formula (1). substitute. As a result, α, β, V _{0 for} each sample
Create an equation with unknown and solve it. If there are four or more equations for three unknowns, they are statistically processed to obtain a solution. The obtained solution is further statistically processed between each sample, and the obtained constants α, β,
The boundary voltage value V ₀ is substituted into the equation (1), and the resistance value drop curve A of FIG. 2 showing the relationship between the resistance change rate ΔR and the applied voltage V is approximated.

This completes the preparatory stage and starts the trimming process from step ST4. First, in step ST4, a dot to be trimmed by the relay network 3 is selected, and this is connected to the ohmmeter 6 by the switch 4, and the resistance value is measured. Next, in step ST5, the resistance change rate ΔRn for lowering the resistance value obtained by the CPU 9 to the target value is calculated, and further, the applied voltage Vn of the voltage pulse is determined using the resistance value decrease curve A described above. To do. That is,
In the relational expression in which the above α, β, and V ₀ are substituted, the resistance change rate ΔR
The applied voltage Vn is calculated by substituting n. The obtained applied voltage Vn is sent from the control calculation unit 7 to the pulse generator 5.
When the switch 4 is switched at step ST6, a voltage pulse having a voltage Vn is sent from the pulse generator 5 and applied to the dot heating resistor pair for trimming.
As a result, the resistance value of the heating resistor falls near the target value. Thereafter, steps ST4 and subsequent steps are repeated until step ST7 detects the end of trimming of all dots.

[Problems to be solved by the invention]

Since the conventional thermal head manufacturing method is configured as described above, the resistance value actually generated when the voltage calculated using the resistance value drop curve A shown in FIG. 2 is applied to the heating resistor. As is clear from the mark ◯ indicating the rate of change, the distribution is centered on the resistance drop curve A. Further, the resistance value decrease curve A becomes steeper as the applied voltage value becomes higher. Therefore, the deviation of the absolute value of the resistance value change rate from the resistance value drop curve A also becomes large, so that the resistance value of the heating resistor can be accurately set in the vicinity of the target resistance value only by applying one voltage pulse. It was difficult to reach the target, and the resistance value dropped excessively.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a resistance adjusting device for a thermal head, which can make the resistance values of the heating resistors uniform in a short time and with high accuracy. To aim.

[Means for solving problems]

A resistance adjusting device for a thermal head according to the present invention applies a voltage pulse having different voltage values to a heating resistor selected as a sample sequentially from a low voltage one to decrease its resistance value, thereby applying voltage and resistance change. Is corrected to a steep curve and the corrected resistance drop curve is used to calculate the resistance change rate for lowering the initial resistance of each heating resistor to the target value. The voltage value of the voltage pulse applied to each of the heating resistors is determined, and the determined voltage value is applied to each of the heating resistors to lower the resistance value and make it uniform.

[Work]

The resistance adjusting device of the thermal head in this invention is
The voltage applied from the resistance value of the heating resistor at that dot measured by approximating the resistance drop curve by measuring the sample dot in the thermal head and using the curve that sharply corrects this resistance drop curve during trimming The voltage value of the pulse is determined so that the resistance value of the heating resistor approaches a range in which it does not drop below the target value with one application of the voltage pulse.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, ST11 is an initial setting step, ST12 is a step for measuring a resistance change of the sample following the step ST11, ST13 is a step for approximating a resistance drop curve following the step ST12, and ST14 is the step S.
Step of resistance drop curve correction following T13, ST15
Is a resistance measurement step following step ST14,
ST16 is a step for determining an applied voltage following step ST15, ST17 is a step for applying a voltage pulse following step ST16, and ST18 is a step ST1.
7 is a step of comparing the target value, ST19 is a step of measuring the resistance value following the step ST18, ST20 is a step of determining the applied voltage following the step ST19, and S
T21 is a step of applying a voltage pulse following step ST20, ST22 is a step of detecting the end of all the trimming dots following step ST21, and the processing is returned from step ST22 to step ST15. The process proceeds from the branch of step ST18 to step ST22.

The steps following step ST18 to step ST
21 becomes unnecessary. "Is the step of resistance value measurement ST
It may be 15. In this case, steps ST19 and S
T20 and ST21 are unnecessary, and step ST18
According to the judgment, the resistance value is narrowed down until it reaches the target value. However, the number of loops must be limited in advance so that the branch from NO to ST15 following ST18 is not formed as an infinite loop.

Therefore, the device for implementing the resistance adjusting device of the thermal head of the present invention uses the device shown in FIG.

Next, the operation will be described. FIG. 2 is a diagram showing an example of the resistance drop curve, in which the solid line A is the resistance drop curve, the horizontal axis shows the voltage value applied by the voltage pulse, and the vertical axis shows the voltage pulse applied. The resistance change rate of the heating resistor is calibrated.

In this embodiment, first, the initial setting is performed in step ST11, and then the resistance change measurement of the sample is performed in step ST12. That is, the relay network 3 is controlled to select the dot heating resistor specified as the sample of the thermal head 1, the switch 4 is switched and the resistance value is measured by connecting to the resistance meter 6, and the measured value is controlled. Send to the calculation unit 7,
The CPU 9 of the control calculation unit 7 stores this in the memory 10. Next, the switch 4 is switched to apply a voltage pulse of a predetermined voltage value from the pulse generator 5 to the heating resistor.
Next, the switch 4 is switched again and the heating resistor to which this voltage pulse is applied is connected to the resistance meter 6 to measure the resistance value and sent to the control calculation unit 7. The CPU 9 of the control calculation unit 7 stores it in the memory 10 together with the voltage value of the applied voltage pulse.

Hereinafter, similarly, these processes are repeated while appropriately increasing the voltage value of the voltage pulse. This process is at least 3
It is executed repeatedly, and the relay network 3 is switched to be executed for some samples. Next, step ST13
In the above, from the resistance change stored in the memory 10,
The resistance change rate ΔR at each applied voltage due to the voltage pulse is obtained by the CPU 9, and this is substituted into the above equation (1).
Accordingly, an equation having α, β, and V ₀ as unknowns is created for each sample and solved. The obtained solution is further statistically processed between the respective samples, and the obtained constants α and β and the boundary voltage value V ₀ are substituted into the equation (1) to approximate the resistance drop curve A. Next, by correcting the numerical values of α and β calculated in step ST14, for example, α ′ = α × 1.1, a corrected resistance drop curve A ′ is obtained.

This completes the preparatory stage and the trimming process starts from step ST15. First, in step ST15,
A dot to be trimmed is selected by the relay network 3 and is connected to the resistance meter 6 by the switch 4 to measure its resistance value. Next, in step ST16, the resistance change rate ΔRn for lowering the resistance value obtained by the CPU 9 to the target value is calculated, and the applied voltage Vn of the voltage pulse is further calculated using the above-mentioned resistance value decrease curve A ′. decide. When the switch 4 is switched in step ST17, a voltage pulse having a voltage Vn is sent from the pulse generator 5 and applied to the heating resistor. Now, for example, the answer is that the applied voltage to the heating resistor that requires a change in resistance change rate of -30% is 106V. However, when this voltage is applied, the amount of change in the resistance value of the heating resistor is actually changed. The average value of is 22%. The difference of 8% is a margin for the variation when the pulse is applied for the first time. That is, by performing this correction, it is possible to prevent the generation of a heating resistor whose resistance value is excessively decreased from the target value by the first pulse application. And step ST
At 18, it is judged whether or not the resistance value of the heating resistor is close to the target value. If the resistance value is extremely close, the process proceeds to step ST22, and if there is still a difference from the target value, step ST19. Proceed to. Then, in step 19, the resistance value of the heating resistor is measured again by the same means as described above, and the applied voltage for lowering the resistance value obtained in step ST20 to the target value is determined. Next, in step ST21, a voltage pulse is sent from the pulse generator 5 to apply a voltage to the heating resistor. If the applied voltage in this case has the same value as the voltage of the first time, the resistance value of the heating resistor can be slightly decreased. In this way, the resistance value of the heating resistor can be brought close to the target value with high accuracy. Below, step ST
The processes after step ST15 are repeated until 22 detects the end of trimming of all dots.

In the above-described embodiment, the voltage pulse is applied at least three times to one sample to approximate the resistance drop curve, but the boundary value V _{0 of the} applied voltage at which the resistance value starts to change. It is also possible to approximate the resistance value drop curve by applying the voltage pulse twice if 25 V is fixedly applied.

Further, in the above-mentioned embodiment, a pulse train in which a predetermined number of continuous pulse trains are used is used.

〔The invention's effect〕

As described above, according to the present invention, a plurality of samples are selected from among the heating resistors, voltage pulses having different voltage values are sequentially applied to the sample from the lower one, and the resistance drop showing the relationship between each applied voltage and the resistance change. A curve is obtained, and the resistance drop curve is corrected so that the resistance value of the heating resistor does not drop below a target value by the application of one voltage pulse, and the voltage value of the voltage pulse applied to the heating resistor is Since the resistance value of the heating resistor is determined based on the initial resistance value of the heating resistor, the resistance value of the heating resistor does not drop excessively and is uniform in a short time. There is an effect that can be converted.

[Brief description of drawings]

FIG. 1 is a flow chart showing a method of manufacturing a thermal head according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a resistance drop curve thereof, and FIG. 3 is a graph showing a decrease in resistance value of a heating resistor. FIG. 4 is a diagram showing another example of the resistance drop curve, FIG. 5 is a flow chart showing an example of a conventional method for manufacturing a thermal head, and FIG. 6 is an apparatus for carrying it out. It is a block diagram showing an example. 1 is a thermal head, A and A'are resistance drop curves.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Ozaki 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Sanryo Electric Co., Ltd. Communication Machinery Works (72) Inventor Yahei Takase 8-chome, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. 1-1 Sanryo Electric Co., Ltd. Communication Equipment Factory (56) Reference JP-A-61-131404 (JP, A)

Claims (1)

[Claims] 1. A resistance adjusting device for a thermal head, wherein a voltage pulse is applied to each heating resistor of a thermal head to lower and equalize the resistance value thereof, and a probing connected to each heating resistor. And a switch circuit connected to the probing device for selecting the heating resistor and switching between application of a voltage pulse to the heating resistor by a pulse generator and resistance measurement of the heating resistor by an ohmmeter. , A plurality of samples are selected from the heating resistors, voltage pulses having different voltage values are sequentially applied to the sample from the lowest value, and a resistance drop curve showing the relationship between each applied voltage and resistance change is obtained and the resistance drop curve is obtained. The voltage applied to the heating resistor is corrected so that the resistance value of the heating resistor does not drop below a target value with a single voltage pulse application. The voltage value of the pulse, the resistance value adjusting device of a thermal head is characterized in that a control arithmetic unit which determines using the corrected resistance drop curve based on the initial resistance value of the heating resistor.