JP2001063123A - Trimming method for thermal head and thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat each heater at a uniform temperature by regulating the heating characteristics such that the heating temperature of each heater falls within a specified temperature range upon application of a specified voltage thereto at the time of trimming a thermal head comprising a plurality of heaters and electrodes arranged on an insulating substrate. SOLUTION: At the time of trimming the heaters 2 of a thermal head 1, a heater 2 to be trimmed is selected at first and applied with 1000 voltage pulses having energy E. Power of 0.12 W is then conducted through an electrode 3 connected with the heater 2 and heating temperature is measured at the midsection thereof. Subsequently, a decision is made whether the peak heating temperature is higher than a specified level and energy of the voltage pulse is increased by ΔE if the answer is NO, otherwise trimming of the heater 2 is ended and trimming of next heater 2 is started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head trimming method and a thermal head, and more particularly to a method for adjusting characteristics of a heating element provided on an insulating substrate of a thermal head.

[0002]

2. Description of the Related Art Conventionally, as a thermal head used for thermal printing in a printing output device or for thermal plate making in a plate making apparatus, a thick film type thermal head formed by a thick film printing method and a CVD (Chemical Vapor D) are used.
2. Description of the Related Art Thin film thermal heads formed by a film forming technique such as deposition and sputtering are known.

In a plate making apparatus, a thin film type thermal head which can be easily miniaturized as shown in FIG. 4 is often used. Heating elements 2 are arranged in a row in the thermal head 1 for heat-sensitive perforation, and each heating element 2 is electrically connected to an electrode 3. Each electrode 3 is connected to a driving circuit 5 including a latch and shift register 4 as shown in FIG.

When performing stencil making of a stencil sheet, the heating circuit 2 is selectively energized through the electrodes 3 by the drive circuit 5 while keeping the thermal head 1 in close contact with the stencil sheet. Heat is generated to thermally perforate a desired position of the stencil sheet.

FIG. 6 shows a heating temperature profile when 0.12 W of electric power is supplied to the selected heating element 2.
The exothermic temperature reaches 270 ° C. at the exothermic peak 400 μs after the start of energization, and thereafter decreases.

In the film forming process of the heating element 2, since the volume or resistance value of each heating element varies, even if the same amount of power is applied, the heating temperature at the heating peak is shown in FIG. As described above, a variation of about 270 ± 30 ° C. occurs, and there is a possibility that the perforation accuracy may be reduced.

For this reason, conventionally, when energy such as a voltage pulse is applied to a heating element, the resistance of the heating element changes according to the applied energy.
Is formed, the resistance value of each heating element 2 of the thermal head 1 is adjusted by applying a voltage pulse to make the resistance value of the heating element 2 uniform, thereby reducing the variation in the heating temperature. The head is being trimmed.

In the above-mentioned trimming, first, a thermal head in which the resistance values of all the heating elements 2 are slightly higher than the target resistance value R of the trimming is formed. And make it uniform. The details of the trimming method will be described below with reference to the flowchart shown in FIG.

In step 201, a heating element to be trimmed is selected first, and in step 202, an initial energy E'0 is set as the energy E 'of the voltage pulse applied to the heating element.

FIG. 9 shows an example of a result of a step stress test in which a resistance value after energy application is measured while gradually increasing the energy applied to the heating element.
The initial energy E'0 and the target resistance value R at the time of performing the trimming are set from a step stress test performed in advance.

In step 203, a voltage pulse having energy E ', 1000 pulses, is applied to the heating element.
In step 204, the resistance value of the heating element is measured using a resistance value measuring device. In step 205, it is determined whether or not the resistance value is equal to or less than a resistance value R which is a target resistance value for trimming. If it is less than R, the process proceeds to step 207. If the resistance value is larger than the resistance value R, the process proceeds to step 206, where the energy E ′ of the voltage pulse is increased by ΔE ′, and then returns to step 203 to apply the voltage pulse again.

In step 207, it is determined whether or not all the heating elements have been trimmed. If the trimming has been completed, the trimming operation is terminated. If not finished, proceed to step 208, select the next heating element,
Returning to step 202, the next heating element is trimmed.

Therefore, even if there is a variation in the initial resistance values of the heating elements, the resistance values of the individual heating elements can be trimmed substantially the same by the above-described trimming operation.

[0014]

In recent years, the density of a plate-making apparatus using a heat-sensitive stencil has been reduced, and in order to improve plate-making accuracy, it has been required to further uniform the heat-generating temperature of a heating element.

However, in the above-mentioned conventional trimming method,
Trimming is performed on the premise that the heating temperature is the same if the resistance value of the heating element is the same. However, the heating temperature of the heating element is not strictly determined only by the resistance value, but is determined by the resistance. Since it is determined by the heat generation characteristics including the value and the heat capacity, there is a problem that even if the trimming for equalizing the resistance value is performed, the heat generation temperature of the heat generator remains uneven due to the influence of other heat generation characteristics such as the heat capacity.

The present invention has been made in view of the above points, and precisely adjusts the heat generation characteristics of a heat generating element provided on an insulating substrate of a thermal head, and controls the heat generating element so as to generate heat at a uniform heat generating temperature. An object of the present invention is to provide a method of trimming a thermal head and a thermal head in which a heating element generates heat at a uniform temperature.

[0017]

According to the present invention, there is provided a trimming method for a thermal head, comprising a plurality of heating elements provided on an insulating substrate and electrodes for applying a voltage to the heating elements. In addition, a heat generation temperature when a predetermined voltage is applied to each heating element is detected, and heat generation characteristics are adjusted such that the heat generation temperature is within a predetermined range.

The adjustment of the heating characteristics can be performed by applying trimming energy to each heating element.

The energy may be applied by applying a voltage pulse or by irradiating a laser beam.

Further, the thermal head according to the present invention comprises:
A thermal head provided with a plurality of heating elements on an insulating substrate and provided with electrodes for applying a voltage to the heating elements, wherein a heating temperature when a predetermined voltage is applied to each heating element is within ± 5 ° C. The heating characteristics of each heating element are adjusted so as to make a difference,
The resistance value of each heating element has a variation of 5% or more.

The adjustment of the heat generation characteristics can be performed by ion doping or partial peeling of the heat generation member in addition to applying trimming energy to the heat generation member.

[0022]

According to the trimming method of the present invention, when performing trimming for adjusting the heat generation characteristics of the heating element provided on the insulating substrate of the thermal head, the temperature of the heat generated when a predetermined voltage is applied to the heating element is detected. The heating characteristics of the heating element are adjusted so that the heating temperature falls within a predetermined temperature range. For this reason, the heating characteristics of the heating element can be precisely adjusted, and the heating temperature can be made uniform.

As a method of adjusting the heat generation characteristics, the trimming can be performed easily and in a short time by applying the energy for trimming to each heating element.

Further, if a voltage pulse is used as the applied energy for trimming, it is not necessary to provide a complicated trimming device, and trimming can be performed at low cost.

Further, when irradiating a laser beam for trimming, it is possible to irradiate a part of the surface of the heating element with the laser beam, so that the heating characteristics can be more precisely adjusted.

In the thermal head trimmed by the method of the present invention, even if the resistance value has a variation of 5% or more, the heat generation temperature when a predetermined voltage is applied is within ± 5 ° C. Since the heat generation characteristics are adjusted so that the heat generation temperature is constant, the heat generation temperature is constant, and the quality when performing thermal plate making or thermal printing can be improved.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a flowchart showing a thermal head trimming method according to one embodiment.

When energy such as a voltage pulse is applied to the heating element of the thermal head, the heating property including the resistance value of the heating element changes according to the applied energy, and the heating property of the heating element is trimmed. Perform

FIG. 2 shows that after applying a voltage pulse to the heating element,
It is an example showing a result of a step stress test in which an exothermic temperature when a predetermined voltage was applied for a predetermined time through an electrode was measured using an infrared microscope type radiation thermometer. The energy E of the voltage pulse is gradually increased for each step.

From the above test results, it can be seen that the heating temperature of the heating element when energized changes as the energy E increases due to the voltage pulse. Energy Ea at which the exothermic temperature starts to rise as energy E increases
Therefore, the range of the energy Eb at which the highest exothermic temperature is obtained is the energy range that can be used for trimming the heating element. If the energy is equal to or higher than the energy Eb, the heating element may be damaged. Therefore, in order to ensure the reliability of the trimming, trimming is performed in the above energy range.

First, in the thermal head 1 having the same configuration as that of the conventional example shown in FIG. 4, when a predetermined voltage is applied from the electrode 3, the heating temperatures of all the heating elements 2 are set to be lower than the target heating temperatures when trimming is performed. The heating element 2 having a slightly lower temperature is formed.

In the present embodiment, a configuration is adopted in which the same heating power as that used in actual use is applied to measure the heating temperature, and the target heating temperature of the heating element during trimming is actually set at the time of plate making. 295 ° C close to 300 ° C used
Set.

The thermal head 1 has a plate making density of 400
B4 size stencil paper can be made at dpi.
One having 096 heating elements formed in a line was used. Before performing trimming, the thermal head 1
When a power of 0.12 W was supplied to each of the heating elements 2 and the heat generation temperature at the time of the heat generation peak was measured, the heat generation temperature varied within a range of 270 ± 30 ° C. as shown in FIG.

Hereinafter, a method of trimming the heating element 2 of the thermal head 1 will be described with reference to a flowchart shown in FIG.

In step 101, the heating element 2 to be trimmed is selected first, and in step 102, the initial value of the energy E of the voltage pulse applied to the heating element 2 is set. Based on the results of the step stress test shown in FIG.
Is smaller than the energy corresponding to
It is set as the initial applied energy. Note that the relationship between the energy E and the heating temperature varies depending on the heating element, and therefore, it is necessary to perform trimming for each heating element.

In step 103, a voltage pulse having energy E, 1000 pulses, is applied to the heating element. In step 104, via an electrode connected to the heating element,
A power of 0.12 W is supplied, and the heat generation temperature of the central portion of the heat generator is measured using an infrared microscope-type radiation thermometer.

In step 105, it is determined whether or not the heat generation temperature at the time of the heat generation peak when the heating element is energized is 295 ° C. or more. If the temperature is lower than 295 ° C., the process proceeds to step 106. If the heat generation temperature is 295 ° C. or higher, the process proceeds to step 107 because the trimming of the selected heat generator has been completed.

In step 106, the energy E of the voltage pulse is increased by ΔE, and the process returns to step 103 to apply the voltage pulse again.

Δ which is an increase in the energy of the voltage pulse
E is set based on the result of the step stress test shown in FIG. 2, similarly to the initial applied energy E0. From the test results, when the applied energy was increased by ΔE in the applied energy range used for trimming,
The increment by which the heating temperature of the heating element slightly changes is set as ΔE. If the value of ΔE is reduced, the variation in the heating temperature after trimming can be reduced, but the time required for trimming increases, so that ΔE is appropriately set according to the desired heating temperature range.

In step 107, it is determined whether or not all the heating elements have been trimmed. If not completed, the process proceeds to step 108 to select the next heating element, and returns to step 102 to start trimming the next heating element. If it has been completed, the trimming operation is completed.

By the above operation, the heating characteristics of the 4096 heating elements are sequentially trimmed.

When the heating temperature of the heating element after the trimming was measured, as shown in FIG.
The exothermic temperature, which had been varied over a wide range of 0 ± 30 ° C., was adjusted to within 300 ± 5 ° C. after trimming. When the resistance value of each heating element after the adjustment was measured, a variation of 5% or more was recognized.

Therefore, when performing the trimming for adjusting the heat generation characteristics of the heat generating element 2 of the thermal head 1, the heat generating temperature when a predetermined voltage is applied to the heat generating element is detected so that the heat generating temperature falls within a predetermined temperature range. By precisely adjusting the heat generation characteristics of the heat generating element, it is possible to make the heat generating temperature of the heat generating element uniform even if there is a large variation in the resistance value.

Further, since a voltage pulse is used as the applied energy for trimming, there is no need to provide a complicated trimming device, and the trimming can be performed easily at a low cost and in a short time.

Further, since the heat generation characteristic is adjusted so that the heat generation temperature of the heat generating element 2 of the thermal head 1 is within ± 5 ° C., the quality in performing thermal plate making or thermal printing can be improved. Can be.

The method of applying the energy for trimming is not limited to the application of the voltage pulse.
Irradiation with laser light or the like can also be used. Laser light is
Because it is possible to irradiate only a part of the surface of the heating element,
The heat generation characteristics can be adjusted more precisely.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an operation flow of a trimming method according to an embodiment;

FIG. 2 is a graph showing the results of a step stress test.

FIG. 3 is a graph showing a heating temperature of each heating element.

FIG. 4 is a configuration diagram of a thermal head.

FIG. 5 is a circuit diagram of a driving circuit of the heating element.

FIG. 6 is a graph showing a heating temperature profile of a heating element.

FIG. 7 is a graph showing a heating temperature profile of a heating element.

FIG. 8 is a flowchart for explaining the operation flow of a trimming method in a conventional example.

FIG. 9 is a graph showing a result of a step stress test in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal head 2 Heating element 3 Electrode 4 Latch and shift register 5 Drive circuit

Claims (5)

[Claims] 1. A method for trimming a thermal head, comprising: a plurality of heating elements provided on an insulating substrate; and electrodes for applying a voltage to the heating elements, wherein a heating temperature when a predetermined voltage is applied to each heating element is determined. A method for trimming a thermal head, comprising: detecting and adjusting a heat generation characteristic so that the heat generation temperature is within a predetermined range. 2. The thermal head trimming method according to claim 1, wherein the adjustment of the heat generation characteristics is performed by applying trimming energy to each of the heat generating elements. 3. The thermal head trimming method according to claim 2, wherein the application of the energy is an application of a voltage pulse. 4. The method for trimming a thermal head according to claim 2, wherein the application of the energy is irradiation of a laser beam. 5. A thermal head having a plurality of heating elements and an electrode for applying a voltage to the heating elements on an insulating substrate, wherein a heating temperature when a predetermined voltage is applied to each heating element is ± 5.
A thermal head, wherein the heating characteristics of each heating element are adjusted so that the temperature difference is within 5 ° C., and the resistance value of each heating element has a variation of 5% or more.