JPS60259469A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a very stable thermal head whose resistance value is less changed with time by enabling a low resistance region to be produced by the self-heating of heating elements in the center of dots. CONSTITUTION:A thermal resistance layer 3 of a glass glaze is formed on an insulator base plate 2 of alumina ceramic material, and Ta2N film is formed by sputtering on the layer 3 to make up a heating element 4. A power feeder 5 consisting or Al film and Ni film is formed on the element 4 by vacuum vapor deposition. Photo-etching is then made in the order of the power feeder pattern and the heating element pattern to form the pattern of a thermal head. The resist is removed by plasma etching using O2 gas, the terminal portion is covered with a metal mask, and a wear-resistant layer 7 consisting of Ta2O5 and a heating element protective layer 6 consisting of SiO2 are formed by sputtering. As shown by line-B, annealing is made in such a way as tomake the resistance value of the dot center 4a of the heating element 4 lower than that of the dot peripheral portion 4b.

Description

[Detailed Description of the Invention] "Technical Field" The invention relates to a thermal head used for heat-sensitive recording, and more specifically relates to the structure of a heating element constituting a thermal head. .

"Prior art and its problems" As shown in Fig. 2, this type of thermal head l consists of an insulating substrate 2 made of alumina ceramics or the like, a heat resistance layer 3 made of glass glaze or the like, and a heat generating layer made of Ta2N or the like. It has a structure in which a power supply body 5 consisting of a body 4, ^1, etc., a protective layer 6 of a heat generating element consisting of Sin, etc., and a wear-resistant layer 7 consisting of Ta, (], etc. are laminated. 5
By energizing the heating element 4 through the ink, the heating element 4 generates heat, and printing is performed by, for example, welding ink to the recording paper via an ink ribbon.

By the way, the Ta2N used as the heating element 4 is formed by a known reactive sputtering method, but when looking at the characteristics of the heating element 4 in a step stress test (SST) of a thermal head, as shown in Figure 3. As the load applied to the heating element 4 is increased, there is a clear inflection point in the resistance value, and the resistance value changes greatly in the negative direction, which has a basic characteristic that leads to disconnection and failure. This is because the substrate temperature is generally low in film formation by sputtering, etc., so the degree of stabilization of the TL2N crystal is low (,
This is because the olfactory stress is high, and the temperature at which the heating head is used in practice is higher than the substrate temperature during film formation by Ta2N sputtering, etc., so the crystal becomes more stable and the resistance value increases. It brings about change.

For this reason, in manufacturing the thermal head', the substrate 2 on which the heating element 4 is formed is heated in a diffusion furnace or the like to perform annealing over the entire surface, but there is a problem that the film forming process is divided and production efficiency is reduced. Ta. In addition, the film formation temperature was increased (5
00'C! Although it is possible to obtain an annealing effect by using 8QO'C), it is difficult to obtain a sufficient annealing effect with this method due to limitations such as the heat resistance of the vacuum equipment.As a result, as shown in Figure 4, In addition, the temperature generated during energization is high at the dot center 4a and low at the dot periphery 4b. At the same time, the resistance value changes significantly over time, which is one of the causes of changes in recording quality.

``Object of the invention'', j ``One object of the invention is self-heating of the heating element'' 161
6. Low resistance By creating a pile area in the center of the dot, there is little change in resistance value over time, resulting in extremely stable thermal.
The goal is to provide lido.

The S-type head of the present invention has a heating element, a power supply, a protective layer, and a wear-resistant layer laminated on an insulating substrate, and a low resistance region due to self-heating is formed in the heating element. There is.

The thermal 7 door according to the present invention is structurally the 2nd door.
This is the same as the conventional one shown in A.

In the tfj2 diagram, the resistance value of the heating element 4 after being formed by svar-cutting can be considered to be uniform over the entire dot area. Therefore, at the start of energization, radio waves flow uniformly over the entire area, and heat is generated uniformly. But what about the energizing power and time? As the temperature increases, as shown by the line in FIG.
The resistance value of the dot peripheral portion 4a is lower than that of dot b. In this way, the dot peripheral portion 4a is energized and adjusted for a predetermined amount of time so that the resistance value is appropriately low.

Incidentally, at this time, a screening effect is also obtained, and the reliability of the thermal head is increased.

By configuring the thermal head using the heating element 4 having such a resistance value distribution, the temperature distribution in the dot region is made smaller than that in the dot center portion 4a, as shown by line B in FIG. The temperature around the dot 4b becomes high, and the dot center no longer has a sharp peak temperature, but is flattened. Further, the resistance change is extremely small within the power range actually used, and the heat generation efficiency and coloring efficiency of the thermal paper are good, and the printing quality is stable over a long period of time.

Note that in FIG. 1, line C indicates the coloring temperature.

Furthermore, by performing current annealing as described above, as shown in FIG. 5, for example, the pulse width t m5ec,
Pulse period 5 m5ec, application time 10 minutes, 0.1
Step stress test (SST) under the condition of w/5tep
), it is possible to obtain extremely stable results in which the resistance value does not change and is flat up to the power applied during energization annealing. In addition, in Figure 5, DI! Embodiments of the Invention A thermal head having a layered structure as shown in FIG. 2 was manufactured. That is, a heat resistance layer 3 made of glass glaze is formed on an insulating substrate 2 made of alumina ceramics, and Ta2N is formed on this heat resistance layer 3 by sputtering to a thickness of 0.05 to 0.2 gm to form a heating element. It was set as 4. Next, an A1 film with a thickness of i p, m and about 0.5
A power supply body 5 made of a Ni film having a thickness of about 100 mL was formed by vacuum deposition. Then, photoetching is performed in the order of the power supply pattern and the heating element pattern to form the pattern of the thermal head. After removing the resist by plasma ashing using gas and covering the terminals with a metal mask, a heating element protective layer 8 made of a 5i07 film with a thickness of about 2 cm and an abrasion resistant film made of a Ta205 film with a thickness of about 5 gm are applied. Layer 7 was formed by sputtering.

The thermal head manufactured in this way has a power of 1.5W/DOT.
The heating element 4 is electrically heated for 0.5 hours with an applied power of 0.5 hours, so that the resistance value of the dot center part 4a of the heating element 4 is lower than the resistance value of the peripheral part 4b of the heating element 4, as shown by the line B in FIG. Annealing was performed.

With this thermal printing method, a uniform temperature distribution was obtained over almost the entire area of the dot, and good continuity of the image could be expressed during printing. Also, during use, the heating element 4
In the Ste-Knob Stress Test (SST), it showed extremely excellent collective stability with no change in resistance value up to an applied load of 1.5 W/DOT.

"Effects of the Invention" υAs explained above, according to the present invention, a low resistance region due to self-heating is formed in the heating element, so a substantially uniform heating temperature can be obtained over the entire area of the dot. In addition to good printing, there is little change in the resistance value of the heating element over time during use, and it is excellent *! & stability can be obtained.

[Brief explanation of drawings]

Fig. 1 is a chart showing the temperature distribution of the heat generating part of the thermal head according to the present invention, Fig. 2 is a sectional view showing the general structure of the thermal head, and Fig. 3 is a step stress test of the conventional thermal head. Figure 4 is a diagram showing the temperature distribution of the heat generating part of a conventional thermal head; Figure 5 is a diagram showing the results of a step stress test (SST) of the thermal head according to the present invention. . 1 threshold, [is a thermal head, 2 is an insulated furnace plate, 3 is a thermal resistance layer, 4 is a heating element, 4a is a dot center, 4b is a dot periphery, 5 is a power supply body, 6 is a protective layer, 7 is the wear-resistant layer. J'+11 2nd adventure 1 Figure 3 Figure 4

Claims (1)

[Claims] In a thermal head, a heating element, a power supply, a protective layer and an abrasion resistant layer are laminated on an insulating substrate, and the heating element is energized through the power supply to generate heat to form a desired recorded image on thermal recording paper. Thermal is characterized by a low resistance region formed in the heating element due to self-ignition.