JPH068057B2 - Method of manufacturing thermal head - Google Patents

Description

The present invention relates to a method for manufacturing a thermal head for uniformizing the resistance value of a heating resistor.

[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, there is a trimming process utilizing the phenomenon that the resistance value decreases when a relatively high voltage pulse is individually applied to each heating resistor after forming the heating resistors. .

In this way, the conventional thermal head manufacturing method is to apply a voltage pulse repeatedly to the heating resistor while temporarily 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 heating resistor changes on a curve with a constant rate of change when the applied voltage pulse is increased irrespective of its initial value.

This rate of change 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 applied voltage change steps α and β are constants determined by the thermal head structure, dot density, and the like.

FIG. 2 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 that has largely varied is the target value R _0.
It is homogenized within a narrow range slightly lower. 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, for example, 25 V. 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. 3 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. 3 shows the same data as in FIG. 2 and the vertical axis of FIG. 2 is 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. 3, 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 the resistance drop curve should be used for trimming when using the resistance drop curve to reach the initial resistance of the dot heating resistor. Therefore, a method of making the resistance value uniform by determining the voltage pulse to be applied and the voltage value and reducing the resistance value of the heating resistor to a target value by applying the voltage pulse once has been conceived.

That is, FIG. 4 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. 5 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 FIG. 4, initial setting is performed in step ST1, and then step ST2.
The resistance change of the sample is measured at. 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. The data is sent to the calculation unit 7, and the CPU 9 of the control calculation unit 7 stores it 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. Here, this voltage pulse is, for example, a pulse train in which 15 pulses having a width of 2 μsec and a period of 50 μsec are continuous. Next, the switch 4 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, these 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 = (R−R ₀ ) / R ₀ at each applied voltage by the voltage pulse from the resistance change stored in the memory 10, and calculates it as the above (1). Substitute in an expression. Thus, for each sample, α,
An equation with β and V ₀ as unknowns is created and solved.
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 and β and the boundary voltage value V ₀ are substituted into the equation (1) to calculate the relationship between the resistance change rate ΔR and the applied voltage V. The resistance drop curve A shown in FIG. 6 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, the applied voltage Vn is calculated by substituting the resistance change rate ΔRn into the relational expression in which α, β and V ₀ are substituted. The obtained applied voltage Vn is sent from the control calculation unit 7 to the pulse generator 5. Step S
When the switch 4 is switched at T6, a voltage pulse having a voltage of Vn is sent from the pulse generator 5 and applied to the dot heating resistor for trimming. As a result, the resistance value of the heating resistor falls below 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, when a voltage pulse is applied to an arbitrary heating resistor, the voltage is applied to the adjacent heating resistors 13 by discharging as shown in FIG. And the resistance value drops. Therefore, when the heating resistor 13 affected by the discharge is to be trimmed, the measured initial resistance value is a value that has already dropped slightly, and there is a problem in that an accurate voltage to be applied cannot be calculated. .

The present invention has been made to solve the above problems, and an object thereof is to obtain a method for manufacturing a thermal head capable of calculating an accurate voltage to be applied to all heating resistors. To do. .

[Means for solving problems]

In the method for manufacturing a thermal head according to the present invention, a voltage pulse having different voltage values of a heating resistor is sequentially applied from a low voltage one to decrease its resistance value, and a resistance value decreasing curve showing a relationship between an applied voltage and a resistance change. And the voltage value of the voltage pulse applied to each of the heating resistors is calculated using this resistance drop curve based on the initial resistance value of the heating resistor, and the calculated voltage value is the heating resistance. It is a method to apply uniform resistance to the body by lowering its resistance value.Measure the initial resistance value of all the above heating resistors before trimming and store them in the memory, and then heat each dot during trimming. While selecting the resistor, read the initial resistance value of the selected heating resistor, and use the resistance drop curve to lower the initial resistance value of the heating resistor to the target value. It is a method of calculating the voltage value of the voltage pulse to be applied to.

[Work]

The method of manufacturing the thermal head according to the present invention approximates the resistance drop curve by measuring the sample head of the thermal head, measures the initial resistance values of all the heating resistors in advance during trimming, stores them in the memory, and then generates the heat. A resistor is selected, the initial resistance value of the heating resistor is read out, and the voltage value of the voltage pulse applied to the heating resistor is calculated from the resistance change rate using the expression representing the resistance drop curve.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, ST11 is a step for storing the initial resistance value, ST11
Reference numeral 12 is a step for reading the initial resistance value following the step ST11, ST13 is a step for calculating an applied voltage following the step ST12, and ST14 is a step ST13.
Step ST15 is a step of applying a voltage pulse, ST15 is a step of measuring a resistance value following the step ST14, ST16 is a step of comparing the target value following the step ST15, S
T17 is a printer output information calculation step following step ST16, and ST18 is a trimming all dot end detection step following step ST17.
The process returns from the branch of step ST18 to step ST12. The processing proceeds from the branch of step ST16 to step ST19, and this step ST19
Returns to the processing of step ST14.

Therefore, the apparatus for carrying out the method for manufacturing the thermal head of the present invention uses the apparatus shown in FIG.

Next, the operation will be described. First, in step ST11, initial resistance values of all heating resistors before voltage pulse application by trimming are measured and stored. That is, the switch 4 is switched and connected to the ohmmeter 6 to measure the initial resistance value, and the measured value is sent to the control calculation unit 7 and the CPU 9 of the control calculation unit 7 is measured.
Stores this in the memory 10. Next, step ST12
At the terminal of each heating resistor of the thermal head 1, the probe of the flowbing device 2 is pressed to select the heating resistor by the relay network 3 (64 in this embodiment), and the selected heating resistor is selected. The initial resistance value of is read from the memory 10. Next, in step ST13, the voltage value of the voltage pulse applied to the selected heating resistor is calculated using the equation (1) representing the resistance drop curve. That is, the CPU 9 of the control arithmetic unit 7 calculates the resistance change rate ΔR (R−R ₀ ) / R ₀ in the applied voltage by the voltage pulse from the resistance change between the initial resistance value stored in the memory 10 and the target resistance value.
Then, this is substituted into the equation (1) to calculate the applied voltage.
The obtained applied voltage is sent from the control calculation unit 7 to the pulse generator 5. Then, when the switch 4 is switched in step ST14, a voltage pulse is sent from the pulse generator 5 and applied to the dot heating resistor which is being trimmed.

Next, in step ST16, it is determined whether or not the resistance value of the heating resistor is close to the target value. If the resistance value is extremely close to the target value, the process proceeds to step ST17, and the target value is still open. If there is, proceed to step ST19. Then, in step ST19, a voltage pulse having the same voltage as the voltage pulse applied to the selected heating resistor or a voltage stepped up from the voltage value of the applied voltage pulse by one step is applied again.

After that, the processes after step ST12 are repeated until the trimming of all the dots at step ST18 is completed.

In the above embodiment, a predetermined number of pulse trains are used for the voltage pulse, but a single pulse may be used, and the same effect as that of the above embodiment can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the initial resistance values of all the heating resistors are measured in advance before trimming and stored in the memory,
Next, at the time of trimming, the heating resistor of each dot is selected, and the initial resistance value of the selected heating resistor is read out.
The voltage pulse applied to the heating resistor from the resistance change rate when the initial resistance value of the heating resistor is lowered to the target value by using the resistance drop curve that approximates the relationship between the applied voltage and the resistance change. Since the voltage value of is calculated, the initial resistance value of the heating resistor is measured even if the resistance value of the adjacent heating resistor is reduced by the voltage pulse applied to the heating resistor of the dot during the previous trimming. Therefore, the effect that an accurate voltage to be applied to all the heating resistors can be calculated can be obtained.

[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 a decrease in the resistance value of a heating resistor, and FIG. 3 is an example of a resistance drop curve. The diagram shown in FIG. 4, FIG. 4 is a flow chart showing a conventional method for manufacturing a thermal head, FIG. 5 is a block diagram showing an example of an apparatus for carrying out the method, and FIG. 6 is an example of its resistance drop curve. The diagram shown in FIGS. 7A and 7B is a conceptual diagram showing a state in which a voltage pulse is applied to an arbitrary heating resistor. Reference numeral 1 is a thermal head, 10 is a memory, and the same reference numerals in the drawings denote the same or corresponding portions.

 ─────────────────────────────────────────────────── ─── 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 sample dot selected from a plurality of dot heating resistors is sequentially applied with voltage pulses having different voltage values from a low voltage one, and the relationship between the applied voltage and the resistance value change is expressed as a resistance value drop curve. Approximately, using this resistance drop curve, the voltage value of the voltage pulse applied to each heating resistor of each dot was calculated based on the initial resistance value of each heating resistor of each dot during trimming. In the method of manufacturing the thermal head in which the voltage value is applied to the heating resistors of the dots for performing the above trimming to lower the resistance values to make them uniform, the initial resistance values of the heating resistors of all the dots are trimmed before trimming. Measure and store in memory in advance, then select the heating resistor of each dot during trimming and read the initial resistance value of the heating resistor of the selected dot from the memory. Then, using the resistance drop curve, calculate the voltage value of the voltage pulse to be applied to the heating resistor of the dot from the rate of change in resistance that has lowered the initial resistance value of the heating resistor of the dot to the daily standard value. A method of manufacturing a thermal head, which is characterized in that