JPS60184856A - Thermal head - Google Patents

Abstract

PURPOSE:To achieve a smooth surface and a higher quality of printing by a method wherein a glass paste is applied and dried on a resistor printed on a substrate and smoothed in the surface and subsequently, pressurized, heated and baked to form a specified glass protective layer. CONSTITUTION:A resistor 3 formed on a substrate 1 by a screen printing, smoothed in the surface and then, baked. Then, a glass paste is set to be 3- 10mum thick after the backing and is applied by a screen printing. After dried, the work is pressurized and heated with a hot press 5 through a press plate 6 to be shaped and smoothed so that the roughness of the surface is less than + or -1mum. Thereafter, a glass protective layer 4 is baked.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a thermal head for a thermal printer, which is often used as an output device in various information equipment, measurement equipment, video processing equipment, etc. This invention relates to a membrane type thermal head.

[Background of the invention]

Thick-film thermal heads are easy to form and can be mass-produced.
Because it is inexpensive, it is used in small printers, facsimile output devices, etc. However, thick-film thermal heads are formed by applying resistive paste by screen printing, drying and baking it, and due to the influence of the screen mesh and volumetric shrinkage after printing, the surface of
Unevenness (undulations) of approximately n or more occurs.

Figure 1 shows such a conventional thermal head. The heating resistor 4 is formed by film technology, and is a glass protective layer printed and fired on the resistor 3. As mentioned above, the glass protective layer 4 on the resistor 3, which has unevenness, also has the same degree of unevenness. When a thermal head with relatively large irregularities on the surface is used, the thermal paper (or ink ribbon for thermal transfer) that comes into contact with the glass protective layer 4 and the glass protective layer 4 are However, it is difficult to make contact with the same area and the same pressure in a large number of heat-generating areas, resulting in uneven printing dots and deterioration of printing quality.

In order to solve this problem, as seen in Japanese Patent Application Laid-Open No. 54-99443, a thick film resistor material is printed and dried, then pressurized or mechanically polished, and then fired to improve the surface of the resistor. Attempts have also been made to achieve a surface roughness of 2 μm or less. However, even if only the resistor is smoothed to such an extent as in this prior application, it is inevitable that the glass layer thereon will be uneven, and good printing quality cannot be guaranteed. After all, if the thickness of the glass layer coated on the resistor is 15μIn or more,
When left at room temperature for a predetermined period of time after coating (printing), it can be expected that the surface will become smoother due to the so-called "leveling effect" due to its fluidity, but as the thickness of the glass layer increases, thermal responsiveness (thermal conduction characteristics) will increase. In practical terms, the thickness of the glass layer must be kept at 10 μm or less. If the glass layer is made thin in this way, the above-mentioned "leveling effect" cannot be expected, and there is no possibility of evacuation on the surface due to the influence of the screen mesh, etc. This resulted in difficult unevenness.

[Purpose of the invention]

Therefore, an object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a thick film type thermal head that has an extremely smooth surface and can ensure good printing quality.

[Summary of the invention]

In order to achieve the above object, the thermal head of the present invention has the following features:
A glass paste is applied onto a resistor whose surface has been smoothed and printed on a substrate, and is dried.Then, the glass paste is pressurized and heated, and then fired, so that the surface roughness is 1 μrn or less. It is characterized in that a glass protective layer having a film thickness of 3 to 10 μm is formed.

[Embodiments of the invention]

As a result of various studies, the inventor of the present application has found that the surface of the resistor is extremely smooth by smoothing the surface of the resistor, applying pressure and heating to the glass layer coated (printed) on the resistor, and then firing it. It has been found that a thermal head (with a surface roughness of ±1 μm' or less) can be obtained.

That is, the resistor formed on the substrate by screen printing is set to have a thickness of 15 to 40 μm after firing, and has a thickness of 100 to 40 μm.
After drying at 180°C for several minutes to several tens of minutes, the surface is polished to within ±2 μm, preferably ±1 μIn, by applying pressure with a press, pressure with a roller, pressure/heating with a hot press, or mechanical polishing. It is set as below. In the case of pressurization by a press or roller, the surface roughness of the member that comes into contact with the resistor surface is 1 μm or less (peak-1 o-pe
ak), and in the case of a flat plate for press, its flatness (undulation,
A material with warp, etc.) of 1 to 5 μm is prepared. and,
For example, in the case of a press machine, the suppressing load is 1 to 100 kg.
/cnl for several seconds to several minutes, and the surface is shaped and smoothed to the above precision. In the case of hot press, the surface of the pressing member is mirror-finished to the above-mentioned degree, and metal or glass is selected. In the case of this heat press, the compression load is 1 to 100 kg/crl and the temperature is 120 to 100 kg/crl.
The heat pressing process is carried out at 200°C for several tens of seconds to several minutes, and the surface of the resistor becomes smooth and smooth by removing only a small amount of the solvent during the heat pressing.
It is expected that the effect of volumetric shrinkage due to solvent removal during the subsequent firing process will be reduced.In addition, in the case of mechanical polishing, for example, polishing jig using abrasive paper and thermal Polishing is performed by relative movement (sliding/rotation) with the head. In this case, it is important to remove wear particles after polishing. After smoothing the surface using one of the above methods, The resistor is fired.

The glass protective layer formed on the resistor has a thickness of 3 to 1 after baking.
After coating by screen printing, it is dried for 3 to 15 minutes at 120 to 180°C, and the surface roughness is reduced to ±1 μrn or less by applying heat using a heat press or applying pressure with a pressure roller under heating. It is shaped and smoothed so that it looks like this. Pressure load is 1 to 100 kg/d,
Heating is carried out at a heating temperature of 120 to 200°C for several seconds to several minutes.

Note that the surface of the pressure member that comes into contact with the glass protective layer is the same as in the case of pressurizing the resistor.

After the above-mentioned pressure and heating are completed, the glass protective layer is fired at a peak temperature of 750 to 850°C for 5 to 10 minutes, which combines with the leveling effect during firing to achieve a thermal surface roughness of ±1 μIn or less. A head is formed.

(Specific example) As shown in Fig. 2 and Fig. 4, a ceramic substrate 1
Above, All-based individual lead electrode 2A and common electrode 2
The layers B are formed alternately at equal intervals using a thick film technique or a thin film technique and a photoprocessing process. The electrodes 2A and 2B had a thickness of 3 to 5 μm and a width of 30 to 50 μIn. next,
A resistor 3 was formed by screen printing an Rg02-based resistor paste to a width of 300 to 400 μm across each of the electrodes 2A and 2B. The thickness of this resistor 3 was set to be 15 to 20 μIn after firing. After drying this resistor 3 at 150° C. for 10 minutes, it was heated to 20 kg/kg using a heat press machine 5 as shown in FIG. 3 through a press plate 6.
The surface was smoothed by applying pressure and heating at C/L and a temperature of 150° C. for 130 seconds. After that, it was baked at a peak temperature of 910°C for 6 to 8 minutes. Subsequently, a glass protective layer 4 was coated on the resistor 3 by screen printing using a 5IO2-based glass paste so as to have a thickness of 7 μm after firing, and was dried at 150° C. for 10 minutes.

Then, using the heat press machine 5 shown in FIG. 3, the material was pressed and heated at a pressure of 20 kg/7 at a temperature of 150° C. for 130 seconds via a press plate 6. After that, the glass protective layer 4 is heated to a peak temperature of 8.
The thermal head shown in FIG. 4 was obtained by firing at 00° C. for 8 minutes.

The surface roughness of the glass protective layer thus formed was 5th
As shown in the figure, it shows extremely good smoothness, ±l/
It was confirmed that the printing quality was not only less than II Ill but also less than 1 μrn even in peak-to-peak, and had extremely good printing quality.

For comparison with this specific example, the resistor 3 shown in FIG. This shows the surface condition of a product that was applied and dried under the same conditions as in the example and then fired without heat pressing, and the surface is rough compared to the smoothness of the specific example.

〔Effect of the invention〕

As described above, according to the present invention, a thick film type thermal head with an extremely smooth surface can be provided, and thermal heads with good printing quality can be manufactured in large quantities at low cost, which is of high value.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional thermal head, Figures 2 to 5
The figures relate to a specific example of the present invention; FIG. 2 is a plan view of the main parts of the thermal head before the formation of the glass protective layer, FIG. 3 is an explanatory diagram of the heat pressing process, and FIG. 5 is a graph showing the measurement results of the surface of the thermal head (surface of the glass protective layer) with the configuration shown in FIG. 4, and FIG. FIG. 3 is a graph diagram showing the measurement results of the surface of a thermal head created without a press. 1...Substrate 2...Electrode 2A...Individual lead electrode 2B...Common electrode 3...Resistor 4...Glass Protective layer patent applicant Copal Co., Ltd. Figure 1 Figure 4 Figure 2 Figure 3 Figure 4

Claims (4)

[Claims] (1) Applying a glass paste onto a resistor whose surface has been smoothed and printed on a substrate, drying it, then pressurizing and heating the glass paste, and then firing it;
Its surface roughness is 1μ! The film thickness is 3 to 10 μIll when it is less than n.
A thermal head characterized by forming a glass protective layer. (2) The thermal head according to claim (1), wherein the resistor is pressurized to smooth the surface after printing and drying. (3) The thermal head according to claim (2), wherein the pressure applied to the resistor is a heat press. (4) The thermal head according to claim (1), wherein the surface of the resistor is smoothed by mechanical polishing after printing and drying.