JP3961038B2 - Thermal head trimming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal head trimming method in which a predetermined voltage pulse is applied to a plurality of resistors constituting a thermal head and the resistance value of each resistor is made uniform.
[0002]
[Prior art]
For example, a thin film thermal head used in an output device of a printer has a plurality of thin film resistors formed on an insulating substrate. A current is passed through the plurality of resistors to generate heat, and thermal printing is performed on the output paper. In the thin film thermal head having such a configuration, if the resistance value of each resistor varies, the heat generation temperature of each resistor is not uniform, which causes uneven density during thermal printing. In order to prevent such density unevenness, a so-called trimming process for equalizing the resistance value of each resistor is performed at the time of manufacture.
[0003]
When the resistance value is made uniform, a constant target resistance value is set for each resistor formed on the insulating substrate. Then, a predetermined voltage pulse is applied to a resistor higher than the set target resistance value to bring the resistance value of each resistor close to the target value.
[0004]
Here, an example of a pattern in which the resistance values of a plurality of resistors formed on the insulating substrate vary and an example of a pattern in which the resistance values are made uniform by trimming will be described with reference to FIG. The horizontal axis in FIG. 10 indicates the bit numbers corresponding to the arrangement order in the arrangement direction of the resistors. The vertical axis represents the resistance value (Ω). Characteristic a is a resistance value before trimming, and characteristic b is a resistance value after trimming. In this case, the voltage pulse width to be applied is 5 ms, and the cooling time of the resistor before measuring the resistance value is 80 ms.
[0005]
Next, a conventional thermal head trimming method will be described with reference to FIG.
[0006]
P1 is a predetermined voltage pulse (pulse width 5 ms), and this voltage pulse P1 is applied to a resistor having a resistance value higher than the target resistance value. By applying the voltage pulse, the resistance value of the resistor becomes small, approaching the target resistance value, and so-called trimming is performed. Thereafter, the resistance value of the resistor to which the pulse P1 is applied is measured. At this time, the resistor to which the pulse P1 is applied generates heat and the temperature rises. Therefore, it cools for a certain period T1 (100 ms), and then the resistance value is measured in a period T2 (5 ms). In the period T3 (1 ms), whether or not the resistance value is within the target resistance value, or the magnitude when the voltage pulse is applied again is calculated. Then, the next voltage pulse P2 is applied to the resistor, and the same processing as described above is performed.
[0007]
Such application of voltage pulses, measurement of resistance values, and the like are sequentially performed on each resistor, and the resistance values are made uniform. In addition, when the cooling time of the resistor after applying the voltage pulse is 80 ms, the cooling time is set to 100 ms in FIG. 11 because the cooling is insufficient and a correct resistance value cannot be measured. In this case, 106 ms is required until the calculation after applying the voltage pulse.
[0008]
[Problems to be solved by the invention]
In a conventional thermal head trimming method, a series of processes such as application of a voltage pulse, cooling of a resistor, measurement of a resistance value, and calculation are sequentially performed on each resistor. At this time, when the resistance value does not fall to the target resistance value, the application of the voltage pulse and the measurement of the resistance value are repeated to enter the target resistance value. The thermal head is usually composed of several hundred to several thousand resistors, although it differs depending on the size and resistor density. In such a case, a long time may be required for cooling the resistor, and the productivity of the trimming process is deteriorated.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described drawbacks and to provide a thermal head trimming method with good productivity.
[0010]
[Means for Solving the Problems]
In the thermal head trimming method of the present invention, a plurality of resistors formed on an insulating substrate are provided between a predetermined first resistor and another resistor between the first resistor. A first step of applying a voltage pulse to the predetermined first resistor from the plurality of resistors, and the first resistor to which the voltage pulse is applied. A second step of measuring the resistance value, and a third step of applying a voltage pulse to a predetermined second resistor among the plurality of resistors between the first step and the second step; The resistance values of the first resistor and the second resistor become target values by the fourth step of measuring the resistance value of the second resistor to which the voltage pulse is applied after the second step. after trimmed to the first trimming the first resistor and the second resistor Resistance of repeating the steps to fourth step said other resistor is sequentially trimmed to the target value.
[0011]
Further, there are a plurality of predetermined first resistors and a plurality of predetermined second resistors.
[0013]
According to the configuration described above, the voltage pulse is applied to the other second resistor using the time during which the first resistor to which the voltage pulse is applied is cooled. Therefore, the time required for trimming can be shortened compared to the conventional method in which voltage pulses are applied, resistor cooling, resistance measurement, and calculation are performed sequentially for each resistor. A good thermal head trimming method can be realized.
[0014]
At this time, if a plurality of first resistors and second resistors to which a voltage pulse is applied are provided, the plurality of resistors can be trimmed in parallel, and the time required for trimming can be further shortened.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIG.
[0017]
Reference numeral 11 denotes a pulse generator. The pulse generator 11 includes eight pulse power supplies 11a to 11h that generate high-voltage voltage pulses used for trimming resistance values, and one resistor that generates a minute voltage used for measuring resistance values. It consists of a power supply 11i for value measurement. The width of the voltage pulse applied to the resistor during trimming is set to 5 ms, and the number of pulses applied per time is set to 1 pulse.
[0018]
The voltage pulse generated by the pulse generator 11 is applied to the thin film thermal head 13 via the switching device 12. The thermal head 13 includes a resistor and an integrated circuit for a driver that controls on / off of a current flowing through the resistor.
One integrated circuit is composed of 64 bits at 5.46 dots / mm, for example. For example, seven integrated circuits having such a structure are used, and the total number of dots of the thin film thermal head is 448. In FIG. 1, only 64-bit resistors 1 to 64 controlled by one integrated circuit are shown. Each integrated circuit is connected to each resistor through a 64-pin probe.
[0019]
The pulse generator 11 and the switching device 12 are controlled by the control device 14, and the switching device 12 is connected between the eight pulse power supplies 11 a to 11 h and the thermal head 13, and between the thermal head 13 and the resistance measuring device 15. The connection is controlled.
[0020]
In the configuration described above, the pulse power supplies 1 1 a to 1 1 h generate voltage pulses for trimming under the control of the control device 14. These eight voltage pulses are applied to the thermal head 13 through the switching device 12.
[0021]
Further, when measuring the resistance value of the resistor to which the voltage pulse is applied, a voltage is applied to the resistor from the resistance value measuring power source 11i. Then, data necessary for measuring the resistance value is sent from the thermal head 13 to the resistance measuring device 15, and the resistance value is measured. At this time, the resistance values of the eight resistors to which the voltage pulses are simultaneously applied are measured, for example, in dot order. In this way, voltage pulses are applied to each resistor and resistance values are measured, and trimming is performed.
[0022]
Note that when a voltage pulse is applied, the temperature of the resistor to which the voltage pulse is applied rises. At this time, the temperature of the adjacent resistor also rises. Therefore, the resistor to which the voltage pulse is applied is, for example, 8 intervals so that the influence of the temperature rise of the resistor to which the voltage pulse is applied is minimized.
[0023]
For example, the first voltage pulse is applied to each resistor of 1, 9, 17, 25, 33, 41, 49, and 57 dots, and the second voltage pulse is 5, 13, 21, 29, 37, 45, It is applied to each resistor of 53 and 61 dots.
[0024]
Next, the timing for trimming will be described with reference to FIG.
[0025]
Pa is a voltage pulse (pulse width 5 ms) applied to the resistor. Eight voltage pulses Pa are generated from the pulse power sources 1 1 a to 1 1 h. Since these voltage pulses are generated simultaneously, they are shown as one in the figure. Therefore, eight pulses Pa are simultaneously applied to eight resistors (for example, 1, 9, 17, 25, 33, 41, 49, 57 dots) having a resistance value higher than the target resistance value. . The resistors of the first group to which the pulse Pa is applied are cooled for a certain period T1a (100 ms), and then the resistance values are sequentially measured in the period T2a (55 ms). And it calculates in period T3 (92 ms).
[0026]
On the other hand, in a period T1a in which the first group of resistors is cooled, a voltage pulse Pb (pulse width 5 ms) is generated, and another second group of eight resistors (for example, 5, 13, 21, 29, 37, 45, 53, 61 dots). The resistors of the second group are cooled for a certain period T1b (100 ms), and then the resistance values are sequentially measured in the period T2b (55 ms). In the period T3 (92 ms), the calculation is performed following the first group of resistors.
[0027]
The above-described processing, that is, processing such as voltage pulse application and resistance value measurement is repeated until the resistance values of the resistors in the first group and the second group reach the target values.
[0028]
When the trimming of the resistors of the first group and the second group is finished, a total of 16 resistors, 8 in total, are selected as the next third and fourth groups, and the resistors for the first and second groups are selected. The same processing is performed. Such processing is repeated in order, and the resistance values of all the resistors are made uniform.
[0029]
In this case, the time required for the 16-bit trimming process is 302 ms, which is about 19 ms per bit, which is shorter than the conventional 106 ms in FIG.
[0030]
Here, the flow of the trimming method of the present invention will be described with reference to FIG. First, the resistance values of all the resistors formed on the insulating substrate are measured (step 31), and a constant target resistance value is set based on the measured resistance values (step 32). Then, the first integrated circuit is selected, and among the 64 resistors controlled by this integrated circuit, eight resistors of the first group, for example, 1, 9, 17, 25, 33, 41, 49 , 57 are selected (step 33). At this time, the resistance value of each selected dot is read from the memory, and the voltage value of the voltage pulse corresponding to each resistance value is set (step 34). Then, eight voltage pulses Pa are applied to each resistor (step 35).
[0031]
Next, the second group of eight resistors in the first integrated circuit, for example, the resistors of each dot of 5, 13, 21, 29, 37, 45, 53, 61 are selected (step 36), and The voltage value of the voltage pulse Pb to be applied to each resistor is set (step 37) and applied (step 38). Also in this case, the resistance value of each selected dot is read from the memory, and a voltage pulse having a value corresponding to each resistance value is set.
[0032]
Thereafter, the resistance value of each resistor in the first group is measured in order (step 39). Subsequently, the resistance value of each resistor in the second group is measured in order (step 40). Then, it is determined whether or not the 16 resistors of the first group and the second group are within the target resistance value (step 41). If it is determined that the target resistance value is entered, the next 16 resistors selected as the third group and the fourth group are changed (step 42). At this time, it is determined whether or not the above-described processing is completed for the 64 resistors controlled by the first integrated circuit (step 43). When it is determined that the process is finished, it is determined whether or not the finished integrated circuit is the final one (step 44). When it is determined that the process is final, the process is ended.
[0033]
If the resistance values of 16 groups of two groups, for example, the first group, the second group, or the third group, the fourth group, etc. are not within the target resistance value in step 41, the process returns to step 33. 33 to 40 are repeated.
[0034]
If the trimming of the 64 resistors controlled by one integrated circuit is not completed in step 43, the process returns to step 33 and steps 33 to 42 are repeated.
[0035]
If it is not determined in step 44 that the integrated circuit is the final integrated circuit, the next integrated circuit is selected (step 45), the process returns to step 33, and steps 33 to 44 are repeated for the next integrated circuit.
[0036]
Here, another embodiment of the present invention will be described with reference to FIG.
[0037]
41 is a pulse generator. The pulse generator 41 includes four pulse power sources 41a to 41d that generate high voltage pulses used for trimming, and one resistance value measurement that generates a minute voltage used to measure resistance values. It consists of a power supply 41e. The width of the voltage pulse applied to the resistor during trimming is set to 5 ms, and the number of pulses applied per time is set to 1 pulse.
The voltage pulse generated by the pulse generator 41 is applied to the thin film thermal head 43 via the switching device 42. The thermal head 43 is composed of resistors 1 to 2560 having 300 dots / inch and 2560 total dots, for example. Note that the pulse generator 41 and the switching device 42 are controlled by the control device 44. For example, the switching device 42 sends the voltage pulse generated by the pulse generator 41 and the output of the resistance measurement power supply 41e to the thermal head 43. Data that is supplied and used to measure the resistance values of the resistors 1 to 2560 is sent from the thermal head 43 to the resistance measuring device 45.
[0038]
Here, the structure of the thin film thermal head will be described with reference to FIG.
[0039]
Reference numeral 51 denotes an insulating substrate. On the insulating substrate 51, a resistor 52, a driver integrated circuit 53, a drive circuit substrate 54, a common electrode substrate 55, and the like are configured. A heat sink 56 is disposed below the insulating substrate 51, the drive circuit substrate 54, and the common electrode substrate 55.
[0040]
The integrated circuit 53 controls on / off of a current flowing through the resistor 52 in accordance with an input of an image signal or a control signal. The drive circuit board 54 supplies various control signals to the integrated circuit 53.
[0041]
As shown in FIG. 5B, the common electrode substrate 55 is electrically divided into four by three slits S1 to S3. The 2560 resistors are divided into four groups, for example, a set of 1 to 640 dots, a set of 641 to 1280 dots, a set of 1281 to 1920 dots, and a set of 1921 to 2560 dots. The four common electrodes are electrically connected by common wire bonding W1. The common wire bonding W1 is protected by a hard end cap 57. The four divided common electrodes are connected to the drive circuit board 54 through the common wire W2, and are connected to the four pulse power supplies 41a to 41d. Note that the four common electrodes are connected to each other by a common wire W3 as shown in FIG. 5C when the trimming process is completed as will be described later.
[0042]
Here, a configuration in which the resistors 1 to 2560 are divided into four groups will be described with reference to FIG. R1 to R2560 are resistors and divided into four sets K1 to K4 of 640 pieces, and each set K1 to K4 is connected to each of four divided common electrodes C1 to C4. The four sets K1 to K4 are connected to four pulse power sources 41a to 41d through terminals T1 to T4. And 64 each of each resistor R1-R2560 is connected to one integrated circuit IC1-IC40.
[0043]
In the above configuration, when the trimming process is performed, the first resistor is selected one by one from each of the sets K1 to K4. At this time, a control signal (DI or STB1 to 4) is applied to the integrated circuit that controls the selected resistor, and voltage pulses are simultaneously applied to the selected 4-dot resistor.
[0044]
Here, the timing of the trimming process will be described with reference to FIG.
[0045]
P is a voltage pulse used for trimming, and the resistor to which the voltage pulse P is applied is cooled for a certain period T1 (100 ms). Thereafter, in the period T2 (20 ms), the resistance value of the 4-dot resistor is measured by the resistance measuring device 45 one by one. Further, calculation is performed in a period T3 (4 ms). In this way, voltage pulses are applied and resistance values are measured.
[0046]
When the trimming of the first selected resistor is completed, the second resistor is selected one by one from each of the sets K1 to K4, and the trimin process is performed in the same procedure. When the trimming of all the resistors is completed in this way, the common electrode substrates that have been divided into four as shown in FIG. 5C are connected by the common wire W3 and are electrically connected. In this method, the time required for the 4-bit trimming process is 124 ms, which is about 31 ms per bit, which is shorter than the conventional 106 ms in FIG.
[0047]
Here, the flow of the trimming method will be described with reference to FIG.
[0048]
First, after mounting an integrated circuit for a driver, the resistance value distribution of each resistor formed on the insulating substrate is measured (step 81), and a constant target resistance value is set based on this (step 82). . Then, the resistors are grouped (step 83). Thereafter, the voltage value of the voltage pulse applied to each of the four dots selected one by one from each set is set (step 84) and applied simultaneously (step 85). For example, 1 set of K1 for the first pulse power supply, 641 dots of 2 sets of K2 for the 2nd pulse power supply, 1281 dots of 3 sets of K3 for the 3rd pulse power supply, 4 sets of K4 for the 4th pulse power supply A pulse is simultaneously applied to 1921 dots.
[0049]
Then, the resistance values of the four resistors to which the pulse is applied are measured (step 86). At this time, the resistance values are measured in the order of 1 dot, 641 dots, 1281 dots, and 1921 dots. Then, it is determined whether or not the resistance values of the four resistors have entered the target resistance value (step 87). If it is within the target resistance value, a second 4-dot resistor is selected from each group, one by one (step 88).
[0050]
Then, it is determined whether or not the above processing has been completed for the 64 resistors of the first integrated circuit (step 89). If it is determined that the integrated circuit is completed, it is determined whether or not the integrated circuit is the final one (step 90). At this time, if it is determined to be the final one, the process ends.
[0051]
In step 87, if the resistance values of the four resistors are not within the target resistance values, the process returns to step 84 and steps 84 to 86 are repeated. If it is determined in step 89 that the 64 resistors have not ended, the process returns to step 84 and steps 84 to 88 are repeated. If it is not determined in step 90 that the integrated circuit is the final integrated circuit, the next integrated circuit is selected (step 91), the process returns to step 84, and steps 84 to 90 are repeated for the next integrated circuit.
[0052]
Here, an example of the result of equalizing the resistance value according to the present invention will be described with reference to FIG.
[0053]
The horizontal axis in FIG. 9 indicates the bit numbers corresponding to the arrangement order in the arrangement direction of the resistors. The vertical axis represents the resistance value (Ω). Characteristic a is a resistance value before trimming, and characteristic b is a resistance value after trimming. From this figure, it can be seen that the resistance values are uniform.
[0054]
【The invention's effect】
According to the present invention, it is possible to realize a thermal head trimming method with high productivity.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.
FIG. 2 is a diagram illustrating an embodiment of the present invention.
FIG. 3 is a flowchart illustrating an embodiment of the present invention.
FIG. 4 is a circuit configuration diagram showing another embodiment of the present invention.
FIG. 5 is a schematic structural diagram illustrating another embodiment of the present invention.
FIG. 6 is a circuit configuration diagram illustrating another embodiment of the present invention.
FIG. 7 is a diagram for explaining another embodiment of the present invention.
FIG. 8 is a flowchart for explaining another embodiment of the present invention.
FIG. 9 is a characteristic diagram illustrating another embodiment of the present invention.
FIG. 10 is a characteristic diagram for explaining a conventional technique.
FIG. 11 is a diagram illustrating a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Pulse generator 12 ... Switching apparatus 13 ... Thermal head 14 ... Control apparatus 15 ... Resistance measuring apparatus

Claims (2)

The plurality of resistors formed on the insulating substrate include a predetermined first resistor and a predetermined second resistor provided between the first resistor and another resistor. A first step of applying a voltage pulse to a predetermined first resistor from among the plurality of resistors, and a second step of measuring a resistance value of the first resistor to which the voltage pulse is applied; A third step of applying a voltage pulse to a predetermined second resistor among the plurality of resistors between the first step and the second step; and the voltage pulse after the second step. And the fourth step of measuring the resistance value of the second resistor to which the first resistor and the second resistor are trimmed so that the resistance values of the first resistor and the second resistor become target values, and then the first resistor said other resistor repeating the first step to fourth step for trimming body and said second resistive element Trimming method of Sa Maruheddo whose resistance sequentially trimmed to the target value.   2. The thermal head trimming method according to claim 1, wherein a plurality of the predetermined first resistors and the predetermined second resistors are plural.

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