JPS5949983A - Thermal printing head - Google Patents

Abstract

PURPOSE:To provide a thermal printing head such that no discontinuous part is generated in a protective layer even when misregistration of a pattern is generated in the second photo-etching, by a method wherein a common lead in a specified form is provided at a position spaced from the tip of small width grooves separating heating elements from each other. CONSTITUTION:In a thermal head wherein the heating elements 3 and conductor wires are provided on the surface of a glaze layer 2 provided on an insulating substrate 1 consisting of a ceramic or the like and the protective layer 8 for contriving to enhance abrasion resistance and preventing the heating elements 3 from being oxidized is provided on the surface thereof, the common lead 5 is provided at a position spaced from the tip of the small width grooves 4 separating the heating elements 3 from each other, and an end edth of the lead 5 is provided in a rectilinear form. Accordingly, in the range of ordinary misregistration of a pattern, the tip part of the grooves 4 is prevented from intruding into the common lead 5, and generation of a discontinuous part in the protective layer 8 is prevented.

Description

[Detailed description of the invention] The present invention relates to thermal printheads.

In general, a thermal print head has a heating element and conductor wiring formed on the surface of a glaze layer provided on an insulating substrate such as a ceramic. A protective layer is provided to prevent this.

FIG. 1 is a perspective view showing the peripheral part of the heating element of a conventional thermal print head, in which 1 is an insulating substrate such as ceramic with a glaze layer 2 formed on its surface, and 3 is a substrate separated by a narrow groove 4. A common lead 5 is connected to one end of the heating element 3, and an individual lead 6 is connected to the other end. However, in FIG. 1, the protective layer is omitted. To briefly explain the manufacturing method of such a thermal print head with reference to FIG. 2, the hatched portion shown in the figure of the double layer 7 of the resistor layer and conductor layer formed on the glaze layer is removed by etching (first photo). etching) to provide the thin grooves 4 described above. Then, by further removing the conductor layer edges within the chain lines shown in the figure (second photo-etching), the heating element and each lead having the pattern shown in FIG. 1 are formed.

Since such partial removal of the conductive layer and the like is performed by a so-called photo engraving method, some pattern deviation is inevitable.

FIG. 3 is a perspective view showing an example of pattern deviation in the second photoetching. From the same figure, it is clear that,
If pattern displacement occurs in the direction of the individual leads 6, the edges of the common leads 5 will have a very intricate shape. As a result, when forming the protective layer, the protective layer tends to become discontinuous at the edge portions.

FIG. 4 shows a discontinuous state of the protective layer, and this figure is, for example, a sectional view taken along the line AA' shown in FIG. 3. That is, the discontinuous portion of the protection R8 occurs at the stepped portion of the protective layer 8, particularly from the upper edge 3 of the common lead 5 to the lower portion of the stepped portion of the protective layer 8, as shown by the broken line.

Therefore, in conventional thermal print heads, air (oxygen) enters from the discontinuities created in the protective layer due to the pattern shift in the second photoetching as described above and oxidizes the heating element. The disadvantage is that it significantly shortens the lifespan of the

The present invention was made in order to eliminate the above-mentioned drawbacks, and even if pattern deviation occurs in the second photo etching,
It is an object of the present invention to provide a thermal print head in which no discontinuity occurs in the protective layer.

To this end, the thermal print head according to the present invention is characterized in that a common lead is provided at a distance from the tip of the thin groove that separates the heat generating elements, so that the edge of the common lead is straight. .

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

FIG. 5 is a perspective view showing the periphery of a heating element in a thermal print head according to an embodiment of the present invention.

In FIG. 5, the same parts as in FIG. Since the pattern is formed by etching, the edges of the common leads 5 are straight.

In the case of this embodiment, the separation dimension is, for example, 10 to 15I.
It is set to 1m. As a result, although the end portion of the heating element 3 on the common lead side is not completely separated, the dimensions of that portion are small as described above, so that the printing quality is not adversely affected. In addition, the separation dimension is 5~
30 μm is preferred. In other words, it is manufacturing Ueda 41 to reduce the pattern deviation to 5 μm or less, and the separation dimension is 30 μm.
If this is exceeded, smearing may occur in the print.

As is clear from the description of the embodiments above, the thermal print head according to the present invention has a common lead spaced apart from the tip of the thin groove separating the heating elements, and the edge of the common lead is straight. This prevents the tips of the 6Q narrow grooves from digging into the common lead within the range of normal pattern deviations, thereby preventing the formation of discontinuous portions in the protective layer.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the peripheral part of the heating element of a conventional thermal print head, Fig. 2 is an explanatory diagram of the manufacturing method of the conventional thermal print head, and Fig. 3 shows an example of pattern deviation in the second photo etching. FIG. 4 is a perspective view showing a discontinuous state of the protective layer, and FIG. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Glaze layer, 3... Heating element,
4... Thin groove, 5... Common lead, 6... Individual lead, 8... Protective layer. Patent Applicant: Koji Onishi, Patent Attorney, ROHM Co., Ltd. Figure 1 2 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A thermal print head characterized in that a common lead is provided at a distance from the tip of a thin groove that separates a heating element, and the edge of the common lead is formed in a straight line.