JPS6292414A - Manufacture of thick film thermal head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a thick film type thermal head, and particularly to a thick film type thermal head that has small variations in resistance value of each heating resistor and is stable over a long period of time. A method for providing a thermal head.

[Prior art and its problems]

In recent years, there has been an increasing demand for higher image quality in heat-sensitive recording heads (thermal heads) used in recording units of printers, facsimile machines, etc. Stabilization of resistance values has become a serious problem.

In particular, thick-film thermal heads, in which peripheral circuits including a resistor layer are formed by baking a pattern created by screen-printing a thick-film paste, are easy to manufacture and low-cost. Due to its high mechanical strength, it has become the mainstream of thermal heads, but on the other hand, compared to thin-film types, pattern accuracy is poor, resistance values are more likely to vary, and resistance values deteriorate early. The problem was that it was easy. Incidentally, this thick film type thermal head is generally manufactured according to a flowchart as shown in FIG.

That is, first, an insulating substrate such as a glazed ceramic substrate is used as a starting material (F1), and a conductor is printed using a screen printing method, followed by firing (F2), and then the conductor is patterned using a photolithographic etching method to form an electrode. (F3).

Thereafter, a resistor layer pattern for configuring the heating resistor element is formed by screen printing and baking (F
4).

Finally, the wear-resistant layer is printed and fired to complete F5).

The resistance value of each heating resistor element of the thermal head after completion is
It is determined by the sheet resistance value of the resistor paste used, the pattern dimensions of the resistor pattern, and the firing temperature.

However, there are many variable factors such as differences in the composition of the resistance paste due to loft variations or viscosity changes, printing conditions such as the screen tension of the screen used or degree of wear of the squeegee, and firing conditions such as the reproducibility of the firing profile. It has been considered extremely difficult to align the resistance values of the heating resistive elements with an accuracy of within ±10%.

For this reason, a method has been proposed in which resistance correction (trimming) is performed by removing a portion of the resistor pattern using a rotary file, sandblasting, laser, etc. in order to equalize the resistance value of each heating resistor element. Although a combined automatic trimming device has been developed, it is difficult to make fine adjustments and requires the preparation of a special device.

In addition, the thick-film thermal head formed in this manner selectively applies electric pulses of a constant magnitude and power value to a heating resistor element made of a thick-film resistor according to image information.
It is used to generate heat to a desired temperature. This thick film resistor generally has a property that its resistance value changes depending on the applied power. Therefore, the resistance value changes during use, and the amount of heat generated changes, causing problems such as changes in print density. For this reason, in the past, it was possible to use only a relatively small amount of power so that the change in resistance value was small, and when used with a large amount of power, there was a drawback that the change in resistance value was large and the lifespan was extremely short.

Furthermore, when driving with a constant voltage, the voltage is fixed to match the initial resistance value, so as power continues to be applied, the resistance value decreases. For this reason, the actual applied power increases, accelerating the change in resistance value, and in some cases even leading to destruction.

Therefore, it is necessary to dissipate the accumulated heat by applying an electrical load for a long time or by forming a heat conduction path (Japanese Patent Application Laid-open Nos. 57-72875 and 57-72876).
Attempts have been made to reduce the initial change in each thick film resistor.

However, in a method of applying electrical load over a long period of time, for example, when applied to a thick film thermal head of 8 lines/m+, the applied power W/dot (pulse width/m5ec, duty 10%) is shown in Figure 5. As shown in the resistance change rate, it is difficult to obtain a stable image because the initial change cannot be made sufficiently small.

On the other hand, although the method of forming a heat conduction path can reduce the initial change, it is difficult to manufacture and is not practical.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a thick-film thermal head that can maintain stable printing characteristics over a long period of time with small variations in each heating resistor element.

(Means for Solving the Problems) Therefore, in the method for manufacturing a thick film thermal head of the present invention, after forming a thick film resistor by printing and baking, a high voltage pulse of a desired magnitude is applied to each thick film. After adjusting (trimming) the resistance value by applying the voltage to the resistor, an electrical load is applied for a short time.

[For production]

That is, in the method of the present invention, first, after forming the heating resistor of each heating resistor element, the resistance value is measured, and a high voltage pulse of a desired magnitude is applied to each heating resistor according to each measured value. Adjust the resistance value and make it uniform. Thereafter, by applying an electrical load for a short period of time, an initial change in resistance value is further caused to stabilize the resistance value.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

1, 2(a) and 2(b) are a flowchart showing the manufacturing process of an 8-dot/dark thick-film thermal head according to an embodiment of the present invention, and a cross-sectional view of the same thick-film thermal head. . (Figure 2(b) is A-A in Figure 2(a)
sectional view).

This thick film type thermal head has lead electrodes (A > Am, 8 m + 1°, 8 m + 2.A
m+3. Am+4. (Ao) and a linear thick-film resistor R mainly composed of ruthenium oxide disposed on the upper layer.A current is supplied to each lead electrode according to image information, and the thickness A predetermined element region of the film resistor R is selectively heated.

Next, a method for manufacturing this thick film type thermal head will be explained.

First, prepare the glass substrate 1 (N1), and on this surface,
Full thickness 1 by screen printing and baking (900℃)
After forming IIW (N2>, lead electrode A1...80 is patterned by photolithography. (N3) After this, screen printing and baking (870 ℃) to form a linear thick film resistor R. (N4) Next, measure the resistance value of each element region of the thick film resistor of this thick film thermal head. (N5) This measured value In order to equalize the resistance value in each element region to a predetermined value according to the voltage, a voltage value is calculated for each element region, and a high voltage pulse of each size is applied.(N6) The pulse width was set to be 10TrLSeC or less, and the voltage was set to be in the range of 1 to 200V.

Subsequently, power of 1.0 to 1.2 W is applied on duty for 10 seconds. (N7) When a step stress test was performed on the thick-film thermal head thus formed by applying an electric pulse with a pulse width of 1TrLSeC and a duty of 10%, as shown in Figure 3, an undervoltage was detected. Shoot amount is -2
, 0% or less, and the resistance change rate becomes +10% when the power is 1.5 W or more, and both the initial change and the strength are at a level that can be used for practical purposes.

In this way, this thick-film thermal head maintains an extremely stable resistance value even during long printing operations, making it highly reliable.

In the examples, a full-thick film was used for the lead electrode, and a material containing ruthenium oxide as the main component was used as the resistor layer, but the invention is not necessarily limited to these, and other thick films may be used. Needless to say, it is also effective when using other materials.

The method of the present invention can also be applied to the case where a protective layer such as a wear-resistant layer is formed on the upper layer of a thick film resistor, and in this case, trimming and stabilization by applying power are performed after all layers are formed. Alternatively, it may be performed prior to forming the protective layer.

In addition, good results were obtained when the electric pulses applied for trimming were high voltage pulses with a size of 50 to 200 square meters.

In addition, the electrical load applied after that is 10-odd V to 20 V.
Good results were obtained in this case.

[Effects] As explained above, according to the present invention, a thick film circle head can be manufactured which is formed from a large number of lead electrodes and a thick film resistor, and which constitutes a plurality of heat generating resistor element regions. After forming the heat generating resistor element area by printing and baking, the thick film resistor pattern of each element area is
The resistance value is adjusted by applying an electric pulse of the desired size to each element, and then an electrical load is applied for a short time to stabilize the resistance value, so the resistance value of each element area is uniform. It is possible to form a thick-film thermal head that is stable over a long period of time, has a long life, and is highly reliable.

[Brief explanation of drawings]

FIG. 1 and FIGS. 2(a) and 2(b) are a flowchart showing the manufacturing process of a thick-film thermal head according to an embodiment of the present invention, a partial schematic diagram of a same-thickness WA thermal head, and a third The figure shows the step stress test results of the thick film thermal head, Figure 4 is a flowchart showing the manufacturing process of the conventional thick film thermal head, and Figure 5 shows the results of the thick film thermal head. It is a figure showing a step stress test result. <A), -Am, Am+1. Am+2°8m+3.
Am+4. (A)...Lead electrode, R...Thick film resistor. Figure 5 = 671

Claims (4)

[Claims] (1) In a method for manufacturing a thick film thermal head in which a large number of heat generating resistive elements made of thick film resistors are arranged on an insulating substrate, a thick film resistor that constitutes a large number of heat generating resistive elements by printing and firing is used. a trimming step of applying desired electric pulses to the heat generating resistor of each heat generating resistor element in order to adjust the resistance value of each heat generating resistor element to be constant; A method for manufacturing a thick-film thermal head, including a stabilization step of stabilizing a resistance value by applying an electrical load to a heating resistor for a short time. (2) The method for manufacturing a thick-film thermal head according to claim (1), wherein the heating resistor has ruthenium oxide as a main component. (3) The method for manufacturing a thick film thermal head according to claim (1), wherein the electric pulse is a high voltage short pulse having a magnitude of 50 to 200V. (4) The method for manufacturing a thick-film thermal head according to claim (1), wherein the electrical load is about 10-odd volts to about 20 volts.