JPS61293868A - Thermal printing head - Google Patents

Abstract

PURPOSE:To improve printing quality, by flattening the area where a protective film which covers a heat generating resistor and an electric wiring conductor covers the heat generating resistor and the electric wiring conductor. CONSTITUTION:After an electrode wiring layer 4 and a heat generating resistor layer 3 are patterned, an oxidation inhibitor layer 61 is applied to the above to form a coating. The formation of the coating film over the heat generating resistor element 5 is performed in such a way as to form a concave at the heat generating resistor element 5 at the portion of th electrode wiring layer 4. Subsequently to the above, a resistor pattern is provided only at a region (l) of the heat generating resistor element, and exclusively rest of the regions are selectively removed by etching to make the region to be of the same thickness as of the film of the heat generating resistor element portion (until becoming flat). Then, an abrasion resistant layer 62 is applied for coating. Therefore, a platen roller is evenly pressure-bonded onto the protective film 6, and at the same time, a recording paper 8 also uniformly sticks onto the heat generating resistor element. In other words, the protective film surface is flattened, resulting in reduction in local accumulation of paper dusts and the quality of picture elements is remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the structure of a thermal printing head, and particularly to the structure of a heating resistor protective film.

[Background of the invention]

The structure of a thermal print head in the prior art, particularly the structure of a heating resistor element portion, is generally as shown in FIG. This thermal printing head is an example of a thin film method in which thin films are sequentially formed by a vacuum film forming method (for example, vapor deposition, sputtering method, etc.) and produced by a photolithography process. Generally, a high-resistance base material 1 (such as an alumina substrate) with a glaze glass layer 2 is used as the substrate, and a heating resistor layer 3 and an electrode wiring layer 4 are sequentially formed thereon, and then a photoresist layer is formed. It is patterned into a desired shape by formation and etching. Thereafter, a protective film 6 is formed to cover the heating resistor element portion 5 (indicated by t in the figure). The protective film 6 is generally coated with an oxidation prevention layer 61 and a platen roller 7 over the heat generating resistor element 5 in order to ensure the resistance value of the heat generating resistor element 5 over time.
A wear-resistant layer 62 is laminated to protect against abrasion of the recording paper 8 which is pressed into contact with the recording paper 8 and slides. The head is usually
A pulsed voltage is applied between both electrodes to apply heat from the heating resistor element 5, which repeatedly generates heat instantaneously, to the recording paper 8 for recording.

When recording with a head having the above structure, the protective film 6
The state of close contact with the recording paper 8 sliding on the recording paper 8 is insufficient because the heat-generating resistor element portion 5 has a concave shape, and the heat dissipation to the electrode wiring 4 is also insufficient, as shown in Fig. 4 (α) and (A). ),
As shown in (C), the area of the soaking part (indicated by t1 in the figure) becomes smaller than the length of the heating resistor element (t), and the size of one pixel also becomes smaller than the resistor element length t. . At the same time, colored and fused paper waste accumulates at the corners of the concave grooves, causing a deterioration in print quality. As these improvement measures,
In ``Unexamined Japanese Patent Publication No. 53-57045'', a wear layer is provided on top of the wear-resistant layer 62 due to the concave shape, and the shape of the platen roller is transferred to the wear layer over time to improve adhesion and paper waste accumulation. Although the effect of reducing this is obtained, the effect is small. Moreover, in "Unexamined Japanese Patent Publication No. 55-128477", the protective film 6
After forming the anti-oxidation layer 61 constituting the heat-generating resistor element 5, the film thickness is selectively reduced by etching only the area excluding the top of the heating resistor element 5 to form a convex shape, and the wear-resistant layer 62 is laminated thereon by a conventional method to form the convex shape. A protective film 6 was formed. In this method, since the concave corners are removed from the concave structure, the adhesion of the recording paper 8 is improved, and the effect is greater than that of the previous method. Figure 4Cb)
As shown in , Cc), the contact area of the heat soaking section apparently expands, and as a result, the size of one pixel (indicated by 4 in the figure) also increases. However, paper waste accumulates on the step portion at the end of recording when the recording paper 8 travels, resulting in deterioration of printing quality over time. In addition, pressure tends to concentrate on the stepped portion pressed by the platen roller 7, which impairs the reliability of the retainer #ff146.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal print head that eliminates the drawbacks of the prior art described above and improves print quality.

[Summary of the invention]

Based on the above-mentioned object, the present invention solves the problem of the prior art in which the heating resistor element of the thermal printing head has a concave groove structure, which is disadvantageous in that it causes a deterioration in printing quality, by changing it to a flattened structure. Furthermore, it has been improved so that recording efficiency can also be improved.

[Embodiments of the invention]

Specific embodiments of the present invention will be described below with reference to FIGS. 1 and 2. Figure 1 shows the cross-sectional structure of the heating resistor element of the present invention, and the film structure is basically the conventional technology. 41 is the same. Electrode wiring layer 42 heating resistor.

After patterning N3 into a desired shape by photoprocessing, an anti-oxidation layer 61 constituting the protective film 6 was formed by high-frequency sputtering. The film thickness formed at this time is the film thickness on the heating resistor element 5, and the electrode wiring layer 4 has a third film thickness.
As in the conventional method shown in the figure, the heating resistor element 5 is formed into a concave shape. After this, the area of the heating resistor element (t in the figure)
A resist pattern was provided only for the resist pattern (indicated by ), and only the other regions were selectively etched away until the film thickness was equal to that of the heating resistor element (flat state). In the embodiment, silicon oxide (5i0
2), and the etching solution at this time was buffer H.
This is liquid F. Note that the film thickness of the 8102 layer on the heating resistor element is approximately 3 μm. Thereafter, tantalum pentoxide (Ta205) was formed as a wear-resistant layer 62 by high frequency sputtering to a thickness of 3 μm to form a protective film 6 with a thickness of 6 μm.

In the case of this flattening protective film, as shown in the figure, the platen roller is evenly pressed onto the protective film 6, and at the same time, the recording paper 8 is also brought into uniform contact with the heating resistor element, and its area is smaller than that of the conventional technology.
JP-A No. 55-128477).

Therefore, although the influence of heat dissipation to the electrode portion remains, it is expected that the printing area of one pixel will be larger than in the case of the method shown in FIG. 4(C) (indicated by 4 in the figure).

FIG. 2 shows a comparison between the thermal printing head described above and the head structure of the prior art when printing and recording was performed using the thermal printing head.

Prints were recorded in all black, and the reflection density was compared. The comparison density at this time is the average density D-1,0 value (arbitrary). The shape of the heating resistor element of the head is resistance length: 250 μm.
1 width: 90 μm, the resistor formation density is 8 element parts wm, and the recording density in the recording paper running direction is Z7 pixels/.

The pulse voltage applied between the electrodes had a period of 10 m5° and a pulse width of 1 town. From the results of the characteristic diagram, it can be seen that in the conventional head with the structure shown in Figure 3, the power required to obtain the density -to value is 0.
．． 55 W/dot (curve 11 in the figure), whereas in the conventional head shown in FIG. 5, the power was reduced by about 10% to 0.49 w/dot (in the middle W2). Furthermore, in the head of this example, the power is reduced by about 5%, and the power is reduced by about 0.47 vrldot (13 songs 11 in the figure).
[). From this result, a certain print density (for example, D=
The power required to obtain the tO value is the lowest in this embodiment, which has the largest pixel area, and this has a significant effect on the resistance value stability of the continuously operated thermal print head. In addition, because the protective film surface is flatter compared to the conventional head (Japanese Patent Application Laid-open No. 55-128477), the accumulation of colored and melted paper waste in localized areas is reduced. The interference with printing has also been reduced, and the quality of pixels has been significantly improved.

〔Effect of the invention〕

As described above, the thermal printing head having the structure according to the present invention has improved recording efficiency due to lower power consumption as head performance;
The quality of pixels can be improved, and the pulse resistance life (resistance value stability) of the head can be improved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional structural diagram of a head according to an embodiment of the present invention, Fig. 2 is a characteristic comparison diagram showing printing characteristics of the head, Fig. 3 is a cross-sectional structural diagram of a conventional thermal printing head, and Fig. 4 (α). is a plan view of the heating resistor element section, <b) is a schematic diagram showing the temperature distribution in the element region, (C) is a schematic diagram showing the size of the pixel,
The figure is a cross-sectional structural view of the head in ``Japanese Patent Application Laid-Open No. 55-128477''. 1: Alumina substrate, 2: Glaze glass layer, 3: Heat generating resistor layer, 4: Polar wiring layer, 7: Platen roller, 8: Recording paper. 2nd shot + 1) 77c @ Katana (w/ctot) No. jIj! ll

Claims (1)

[Claims] 1. A thermal printing head comprising a heating resistor on a high-resistance base material, an electrical wiring conductor for supplying power to the heating resistor, and a protective film formed to cover the heating resistor and the electrical wiring conductor. A thermal printing head characterized in that the film is flattened in a region covering a heating resistor and an electrical wiring conductor.