JPH0115385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for thermal printing by bringing thermal paper into contact with a printing head in which a large number of heating resistive elements are linearly arranged on a ceramic substrate, and selectively generating heat in the heating resistive elements. The present invention relates to a thermal head used in a thermal printing device.

This will be explained in detail below.

Figure 1 is a perspective view showing the configuration of the thermal head;
FIG. 2 is a plan view of FIG. 1. In FIGS. 1 and 2, 1 is a ceramic substrate, and 2 heating elements are disposed on it. 3 is a matrix wiring board, and conductors 4 are formed on the surface of a resin material. Reference numeral 5 denotes a thyristor array having lead wire portions 6 and 7 at both ends, and the terminals of the lead wires 6 and 7 are formed on the lead portion 2-1 of the heating element 2 disposed on the ceramic substrate 1 and on the matrix substrate 3. It is welded to the conductor 4. 8 is a mounting plate made of iron material and has a ceramic substrate 1
and the matrix wiring board 3 are adhesively held. 9
10 is the adhesive that fixes the ceramic substrate 1 to the mounting plate 8, and 10 is the adhesive that fixes the matrix wiring board 3 to the mounting plate 8.
This is the adhesive that fixes it to.

Conventionally, the adhesives 9 and 10 in this thermal head have been adhesives having rubber elasticity after curing (hereinafter referred to as rubber adhesives).

The reason for this is that when a thermal head is used for continuous printing, the temperature rises by approximately 30°C due to the heat generated by the heating element, and when the operating temperature range is 5°C to 40°C, the maximum temperature is approximately 65°C.
This results in a temperature difference of Therefore, for example, if an adhesive that hardens after curing is used as the adhesive, a bimetallic effect will occur between the ceramic substrate 1 and the mounting plate 8, which have different coefficients of thermal expansion. FIG. 3 is an explanatory view showing the warping of the thermal head in the longitudinal direction, and shows a state in which the adhesive is cured at a high temperature and then returned to room temperature. In the figure, 1 indicates the ceramic substrate, 8 indicates the mounting plate, and δ indicates the amount of warpage at room temperature. As a result, when the thermal head is operated, the warp δ of the thermal head changes (warps) due to the bimetal effect in the temperature range, and the heating element 2 disposed on the ceramic substrate 1 and the The contact with the paper became poor, and uneven printing density occurred in the longitudinal direction of the thermal head. As a countermeasure to this problem, by using a rubber thread adhesive, the bimetallic effect is absorbed by the rubber of the adhesive layer, and the amount of warpage δ can be practically ignored, resulting in a good I was getting good printing results.

However, absorbing the bimetallic effect with the adhesive layer as in the past means that the ceramic substrate 1 and the matrix substrate 3 will be affected by the arrows shown in FIG. As shown in Figures 11 and 12, thermal expansion and contraction occur on the mounting plate 8 based on their respective coefficients of thermal expansion.
Here, a ceramic substrate 1, a mounting plate 8 made of iron material
When the coefficients of thermal expansion of matrix wiring board 3 made of ceramic substrate 1 and resin material are α ₁ , α ₂ and α ₃ , there is a relationship of α ₁ < α ₂ < α ₃ . The relative positional deviation has a magnitude based on the difference between α ₁ and α ₃ .

Therefore, the lead wires 6 and 7 of the thyristor array 5 shown in FIG. 3 are repeatedly bent due to the relative positional deviation between the ceramic substrate 1 and the matrix wiring board 3 based on the difference between α ₁ and α ₃ , resulting in fatigue fracture. Something happened.

The purpose of the present invention is to solve this problem by reducing the amount of relative positional deviation between the ceramic substrate 1 and the matrix wiring board 3 on the mounting plate 8, thereby preventing fatigue breakage of the lead wires 6 and 7 of the thyristor array. This will be explained in detail below.

The structure of the first embodiment is the same as that of the thermal head shown in FIG. 1, so the explanation will be based on this. In FIG. 1, in the present invention, the adhesive 9 of the ceramic substrate 1 is a rubber adhesive that has rubber elasticity after curing, and the adhesive 10 of the matrix wiring board 3 made of a resin material is an adhesive that hardens after curing. . The rubber adhesive 9 and the adhesive 10 that hardens after curing are used to connect the ceramic substrate 1 and the matrix wiring substrate 3.
has a structure in which it is adhesively held on a mounting plate 8 made of iron.

With such a structure, each thermal expansion and contraction when the above-mentioned temperature difference or temperature change occurs is as follows.
Since the ceramic substrate 1 is bonded to the mounting plate 8 with a rubber adhesive 9, it is almost independent of the mounting plate 8, but the matrix wiring board 3 is bonded to the mounting plate 8 with a hardening adhesive 10. Since it is fixed, it is affected by the expansion and contraction of the mounting plate 8 and becomes almost the same as the mounting plate 8. Therefore, the amount of relative positional deviation between the ceramic substrate 1 and the matrix wiring board 3 is based on the difference between the thermal expansion coefficients α ₁ and α ₂ . In other words, the displacement stroke of the lead wires 6 and 7 of the thyristor array 5 can be made shorter than in the conventional case.
At this time, a bimetal effect occurs between the matrix wiring board 3 and the mounting plate 8, but since the matrix wiring board 3 is made of resin, it has little effect on warping of the thermal head compared to the effect of a ceramic board. Can be ignored.

As explained above, in the first embodiment, the magnitude of the relative positional deviation due to thermal expansion and contraction between the ceramic substrate ₁ and the matrix substrate ₃ is in the relationship α ₁ < α ₂ < α ₃ ; α ₁
Since it is based on the difference _between

Although iron is used as the mounting plate 8 in the first embodiment, if a material with a coefficient of thermal expansion close to that of ceramic material, such as an iron-nickel-cobalt alloy, is used, the ceramic substrate 1 and the matrix wiring board can be bonded together. 3 can be almost eliminated, and the effects of the present invention can be further improved.

As described above, according to the thermal head of the present invention, the relative positional deviation between the ceramic substrate and the matrix wiring board can be made based on the difference in coefficient of thermal expansion between the ceramic substrate and the mounting plate. In addition, it is possible to obtain good printing results without uneven printing density.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the configuration of the thermal head;
FIG. 2 is a plan view of FIG. 1, and FIG. 3 is an explanatory diagram showing warping of the thermal head. 1... Ceramic substrate, 2... Heating element, 3...
Matrix wiring board, 4... Conductor, 5... Thyristor array, 6, 7... Lead wire, 8... Mounting plate, 9, 10... Adhesive.

Claims (1)

[Claims] 1. A ceramic substrate having a large number of heat generating resistive elements arranged in a straight line and having a small coefficient of thermal expansion, and a wiring having a lead wire for electrically connecting the heat generating resistive elements and having a large coefficient of thermal expansion. In a thermal head in which a substrate is bonded to a mounting plate having a medium coefficient of thermal expansion, the ceramic substrate is bonded to the mounting plate with an adhesive having rubber elasticity after curing, and the wiring is bonded with an adhesive that hardens after curing. A thermal head characterized in that the substrate is bonded to the mounting plate.