JPH06414B2 - Thermal head resistance adjustment device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resistance adjusting device for a thick film type thermal head, and more particularly to uniforming the resistance of a heating resistor.

[Conventional technology]

The thick film type thermal head forms a heating resistor by printing a paste-like resistance material in a predetermined pattern by a screen printing method or the like and then firing it. 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 heat-producing low antibody becomes large. Since the variation in the resistance value of the heating resistor directly affects the quality of printing or the like, it is an extremely important factor to make the resistance value of the heating resistor uniform in the manufacture of the thick film type thermal head. . In order to make the resistance value of the resistor according to the present invention uniform, there is a trimming process utilizing the phenomenon that the resistance value is lowered when a relatively high voltage pulse is individually applied to each heating resistor after the heating resistors are formed. .

FIG. 5 is a flow chart showing a conventional method of manufacturing a thermal head disclosed in, for example, Japanese Patent Laid-Open No. 61-83053. In the figure, ST1 is an initial setting step,
ST2 is a prober and switching step following step ST1, ST3 is a voltage pulse applying step following step ST2, and ST4 is step ST.
3 is a resistance value measuring step, ST5 is a step of comparing with previous data following step ST4, ST6 is a step of detecting a resistance value decreasing following step ST5,
ST7 is a step of detecting the end of all dots of trimming following step ST6, ST8 is a step of reprobing branched from step ST5, ST9 is a step of voltage adjustment of the voltage pulse branched from step ST6, and step ST7 Step ST from branch
The processing is returned to step 2, from step ST8 to step ST4, and from step ST9 to step ST3.

Next, the operation will be described. First, in step ST1, initial conditions such as an initial value of a voltage pulse applied to a heating resistor to be trimmed and a trimming target value are set. Next, in step ST2, the thermal head is probed, the dot to be trimmed is selected, and the heating resistor is connected to the voltage pulse generating means.
At T3, the voltage pulse having the initial value set in step 1 is applied. Next, in step ST4, the resistance value of the heating resistor is measured, and in step ST5 it is discriminated whether or not the resistance value has decreased. If not, it is considered that the probe has a poor contact, and probing is performed again in step ST8. Returning to step ST4, the resistance value is measured again. If the resistance value has decreased, it is compared with the target value for trimming set in step ST1 in step ST6. If it is not smaller than the target value, the voltage value of the voltage pulse is increased by ΔV in step ST9. Step ST
Returning to step 3, the voltage pulse is reapplied. This process is repeated until the resistance value of the heating resistor becomes smaller than the target value, and when it becomes smaller than the target value, trimming of the heating resistor of the dot is completed and the process proceeds to step ST7. In step ST7, it is identified whether or not trimming of all dots has been completed. If trimming of all dots has not been completed, the process returns to step ST2. Step ST2
Then, a new dot is selected, the heating resistor is connected to the voltage pulse generating means, and the same processing is repeated until the trimming of all dots is completed.

FIG. 6 is a diagram showing a decrease in the resistance value of the heating resistor. The resistance value which was largely varied with R ₁ , R ₂ and ₃ before the trimming is slightly lower than the target value R ₀ and narrow. It is homogenized within the range. In the figure, V _S is the initial value of the voltage pulse, and 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 2
Since it is near 5V, it is set to 25V, for example. Further, ΔV is an increase in the voltage value of the voltage pulse in step ST9, 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.

[Problems to be solved by the invention]

Since the conventional method of manufacturing a thermal head is configured as described above, it is necessary to apply a voltage pulse and measure the resistance value 20 to 30 times for trimming a 1-dot heating resistor. There is a problem that it takes a lot of time to make the resistance value of the heating resistor uniform.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a resistance adjusting device for a thermal head that does not require a great deal of time to make the resistances of the heating resistors uniform. To aim.

[Means for solving problems]

The resistance adjusting device of the thermal head according to the present invention selects some samples from the dots of the thermal head, applies several voltage pulses having different voltage values in order from the lowest one, and generates a heating resistor each time. The trimming constants α and β for approximating the resistance drop curve are obtained by measuring the resistance change of the, and the deviation of the trimming constants α and β from the predetermined relational expression is tested, and the deviation is within the predetermined range. In some cases, the trimming constants α and β are used to approximate the resistance drop curve, and when trimming each dot, first measure the resistance value of the heating resistor, and then calculate the resistance drop from the required resistance value. The voltage value of the voltage pulse to be applied is determined based on the value drop curve.

[Action]

The resistance adjusting device of the thermal head in this invention is
The resistance drop curve is approximated by measuring the sample dots in the thermal head, and the trimming constants α and β are tested for the approximation so that the approximated resistance drop curve deviates significantly from the true curve. The resistance value drop curve is used for trimming, and the voltage value of the voltage pulse to be applied is determined from the measured resistance value of the heating resistor of the dot, and the heating resistance is determined by applying the voltage pulse once. The body resistance should be close to the target value.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, ST11 is an initial setting step, ST12
Is a step of measuring the resistance change of the sample following step ST11, ST13 is a step of calculating trimming constants α and β following step ST12, ST14 is a step of detecting trimming constants α and β following step ST13, and ST15 is a step of detecting trimming constants α and β. Following step ST14 is a step of approximating the resistance drop curve, and ST16 is the step ST
15 is a resistance value measuring step, ST17 is an applied voltage determining step following the step ST16, and ST18
Is a step of applying voltage pulse following step ST17, ST19 is a step of detecting end of all dots of trimming following step ST18, ST20 is a step of selecting another sample branched from step ST14, and branching of step ST19 From step ST
16, from step ST20 to step ST12,
Each process returns.

FIG. 2 is a block diagram showing an example of an apparatus for carrying out the method for manufacturing a thermal head according to the present invention.
Is a thermal head on which a trimming process is performed, 2 is a probing device for pressing a probe against the terminals of each heating resistor of the thermal head 1, and 3 is a probing device 2.
A relay rope connected to the terminal for selecting the heating resistor,
Reference numeral 4 is a switch which is connected to the relay rope 3 and switches between application of a voltage pulse and measurement of a resistance value. Reference numeral 5 is a pulse generator which is connected to one of the switches 4 and sends out a voltage pulse of a designated voltage value. Is an ohmmeter connected to the other side of the switch 4, and 7 is an input / output unit 8, a central processing unit (hereinafter referred to as CPU) 9, a memory 10, a keyboard 11 and the like for controlling the above-mentioned various devices and required. A control arithmetic unit 12 for performing arithmetic processing is a printer connected to the control arithmetic unit 7.

Next, the operation will be described. FIG. 3 is a diagram showing an example of the resistance drop curve. The solid line Y in the figure is the resistance drop curve, and the horizontal axis shows the applied voltage value by the voltage pulse.
The vertical axis shows the resistance change rate of the heating resistor due to the voltage pulse application. As a result of the experiment, when the vertical axis of FIG. 6 is taken as the resistance change rate and the% drop from the initial resistance value is plotted, as shown by the broken line in FIG. 3, it is almost constant regardless of the initial resistance value. It was found that the curve Y can be approximated by the equation (1).

In the formula (1), R ₀ is the initial resistance value of the heating resistor,
V ₀ is a boundary value of the applied voltage at which the resistance value starts to change, ΔV is a change step of the applied voltage, and α and β are trimming constants determined by the structure of the thermal head, the dot density and the like.

Further, as shown in FIG. 4, the relationship between the trimming constants α and β is such that when α is plotted on the horizontal axis and β is plotted on the vertical axis, they are traced on a substantially constant curve Z, and the curve (reference It was found that the trimming curve) Z is a hyperbola that can be approximated by the equation (2).

β = · α− ^m (2) In the formula (2), and m are constants that take a constant value regardless of the dot density.

Further, as a result of another experiment, the resistance decrease rate when the voltage pulse having the predetermined voltage value is applied only once is as shown in FIG. 3 when the voltage pulse is applied many times while the voltage value is temporarily increased. It was also found that it showed a value equivalent to that of the same voltage value.
The present invention is based on the results of these experiments.

In this embodiment, first, initial setting is performed in step 11, and then, in step 12, resistance change measurement of the sample is performed. That is, the relay network 3 is controlled to select the heating resistor of the designated dot as the sample of the thermal head 1, the switch 4 is switched to connect to the resistance meter 6, the resistance value is measured, and the measured value is controlled. It is sent to the arithmetic unit 7, and the CPU 9 of the control operation 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 resistance heating element. Here, this voltage pulse is, for example, one pulse having a width of 2 μsec.
It is a pulse train that is continuous with five 50 μsec cycles. next,
Switch the switch 4 again, connect the heating resistor to which this voltage pulse is applied to the resistance meter 6, and measure the resistance value.
It is 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. Thereafter, similarly, these processes are repeated while appropriately increasing the voltage value of the voltage pulse. This process is repeated at least three times, switching the relay network 3 and executing for some samples.

Next, in step ST13, the trimming constants α and β for approximating the resistance drop curve are calculated based on the resistance change thus measured. 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 due to the voltage pulse from the resistance change stored in the memory 10, and calculates it as the above ( Substitute into the formula 1). As a result, an equation with α, β, and V ₀ as unknowns is created for each sample and solved. Here, when there are four or more equations for three unknowns, these are statistically processed to obtain a solution. The obtained solution is further statistically processed between each sample,
The desired trimming constants α and β are obtained together with the boundary value V ₀ of the applied voltage.

With respect to the trimming constants α and β thus obtained, a deviation from the relationship of the expression (2) is detected in step ST14. That is, as shown by point A in FIG. 4, if the deviation deviates from a certain range, for example, the ± 5% area hatched in FIG.
Repeat the measurement of the resistance change due to T12. In that case,
In step ST20, a dot to which no voltage pulse has been applied before is selected as a new sample. As shown by point B in FIG. 4, when the deviation is within a certain range, the trimming constants α and β are set in step ST.
It is substituted into the equation (1) together with the boundary value V _{0 of the} applied voltage at 15, and the resistance value drop curve 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 ST16. First, in step ST16,
A dot to be trimmed is selected by the relay network 3, and this is connected to the ohmmeter 6 by a switch to measure its resistance value. Next, in step ST17, the CPU 9 calculates the resistance change rate ΔRn for decreasing the obtained resistance value to the target value, and further determines the applied voltage Vn of the voltage pulse by using the resistance value decrease curve Y described above. . The state is shown in FIG. 3. Specifically, the applied voltage Vn is obtained by substituting ΔRn into the relational expression in which α, β, and V ₀ are substituted.
To calculate. The obtained applied voltage Vn is sent from the control calculation unit 7 to the pulse generator 5. When the switch 4 is switched in step ST18, a voltage pulse having a voltage of Vn is sent from the pulse generator 5 and applied to the heating resistors of the dots to be trimmed. As a result, the resistance value of the heating resistor drops to a value close to the target value. Thereafter, the processes from step ST16 are repeated until step ST19 detects the end of trimming of all dots.

In the above-mentioned embodiment, the voltage drop is applied at least three times to one sample to approximate the resistance drop curve. However, the boundary value V of the applied voltage at which the resistance starts to change. _If fixedly applied as 0.25 V, it is possible to approximate the resistance value drop curve by applying the voltage pulse twice.

Further, in the above-mentioned embodiment, the pulse train in which the predetermined number is continuous is used for the voltage pulse, but a single pulse may be used, and the same effect as that in the above-mentioned embodiment is obtained.

〔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. The trimming constant for approximating the curve is obtained, the deviation between this trimming constant and the reference trimming curve expressed by a predetermined relational expression is tested, and if the deviation is within a certain range, it is applied to the heating resistor. Since the voltage value of the voltage pulse is determined based on the initial resistance value of the heating resistor using the resistance drop curve, trimming is completed by applying the voltage pulse once for each dot. Therefore, the time required to equalize the resistance value of the heating resistor can be significantly reduced, and the trimming constants α and β can be detected when the resistance drop curve is approximated. Therefore, the approximated curve does not deviate significantly from the true resistance drop curve,
It is possible to obtain the resistance value adjusting device of the thermal head which does not cause excessive trimming or destruction of the heating resistor and insufficient trimming or untrimming due to an approximation error of the resistance drop curve.

[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 block diagram showing an example of an apparatus for carrying out the method, and FIG. 3 is an example of a resistance drop curve. 4 is a diagram showing the mutual relationship between the trimming constants α and β, FIG. 5 is a flow chart showing a conventional method of manufacturing a thermal head, and FIG. 6 is a diagram showing the resistance value of the heating resistor. It is a diagram showing a decrease. 1 is a thermal head, 2 is a probing device, 3 is a relay network, 4 is a switch, 5 is a pulse generator, 6 is an ohmmeter, and 7 is a control calculation unit.

Front page continuation (72) Inventor Hiroshi Ozaki 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Sanryo Electric Co., Ltd. Communications Machinery Works (72) Inventor Yahei Takase 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. Sanryo Denki Co., Ltd. (56) References 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, and a trimming constant for approximating a resistance drop curve showing a relationship between each applied voltage and resistance change is set. Then, the deviation between this trimming constant and the reference trimming curve expressed by a predetermined relational expression is tested, and the deviation is within a certain range. For example, a thermal calculation device comprising: a control calculation unit that determines the voltage value of the voltage pulse applied to the heat-generating low antibody using the resistance drop curve based on the initial resistance value of the heat-generating low antibody. Head resistance adjustment device.