JPH04232071A - Thermal head - Google Patents

Abstract

PURPOSE:To improve the surface smoothness of a protecting layer which comes in contact with a recording sheet without deterioration of hardness in a thick film thermal head used on a thermal printer. CONSTITUTION:A glazed layer 2 is formed on an insulator substrate 1 and a conductor for a common electrode 3 and a conductor for an individual electrode 4 are formed on the glazed layer 2. In addition, a thermal resistor layer 5 and a protecting layer 6 consisting of glass to which a filler is added, are formed. If the filler is added, the heat resistance and hardness of the glass are improved. Further, the smoothness of the surface is improved by setting the average granular diameter of the filler to 1 to 2mum max.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head, and particularly to a thick-film thermal head for a thermal printer having a protective layer with excellent surface smoothness and hardness.

0002

2. Description of the Related Art A thermal head installed in a thermal printer has, for example, a plurality of heat generating resistor elements arranged on the same substrate, and the heat generating resistor elements are heated with electricity according to the information to be printed, and printed via an ink ribbon. It is used for transferring and recording onto recording paper.

FIG. 6 shows a cross-sectional view of this thermal head. A glaze layer 2 made of glass is formed on an insulating substrate 1, and a common electrode conductor 3 and individual conductors are formed on this glaze layer 2. The electrode conductor 4 is made of Au or the like. Further, a heating resistor layer 5 made of RuO2 or the like is formed in the gap between the electrode conductors, and a protective layer 6 made of glass or the like is formed.

[0004] When a voltage is selectively applied to the individual electrode conductor 4 according to the information, the heat generating resistor layer 5 generates heat, and this heat is transmitted to generate heat in the heat generating portion on the surface of the protective layer 6. As a result, coloring energy is applied to an ink ribbon or the like.

[0005] Here, the protective layer 6 is usually made of SiO2.
Glass such as -PbO-B2 O is used, and α-Al2 O3 is usually used to improve the heat resistance and hardness of this glass.
Fillers such as

[0006]

[Problems to be Solved by the Invention] As described above, filler-added glass is used in the conventional protective layer.
The average particle size of fillers is usually 0.7 to 0.8 μm and 20 to 20 μm.
30wt% is added, and the surface roughness Ra of the glass is 0.
．． It is about 1 to 0.20 μm.

However, the surface roughness Ra is 0.1 μm.
If this is the case, the recording paper moving in contact with the protective layer 6 will be scratched and the print quality will worsen.
It has been proposed to increase the amount of PbO in order to lower the softening point of the PbO system. However, although this method does reduce the surface roughness, there is a problem in that the abrasion resistance, that is, the hardness, which is an important factor for a protective layer of a thermal head, conversely decreases.

FIG. 7 shows the relationship between glass softening point and hardness. It can be seen that as the glass softening point decreases, the hardness (indicated by Knoop hardness in FIG. 8) decreases significantly.

[0009] Therefore, without changing the glass system of the protective layer,
It is possible to reduce the surface roughness by reducing the amount of filler added, but fillers were originally introduced to increase hardness, so if the amount of filler is reduced, the desired hardness cannot be obtained. There was a problem.

FIG. 8 shows the relationship between the amount of filler added to glass and hardness. It can be seen that when the amount of filler is reduced, the surface roughness decreases, but on the contrary, the hardness deteriorates.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide a thermal head having a protective layer having excellent hardness and surface smoothness.

0012

[Means for Solving the Problems] In order to achieve the above object, the thermal head according to the present invention has an average particle diameter of 1 μm to 2 μm of the filler added to the glass forming the protective layer.
It is characterized in that it is set within the range of m.

[0013]

[Operation] As described above, the present invention does not change the proportion of glass or the amount of filler, but changes the shape of the filler, that is, the average particle size of the filler.

[0014] The applicant of the present application focused on the average particle size of the filler, which had not been paid attention to in the past, and found that this filler particle size has a large effect on the surface roughness of the glass. It has been discovered that by setting the thickness within the range of 2 μm, the surface roughness can be reduced without deteriorating the hardness.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the thermal head according to the present invention will be described below with reference to the drawings.

The structure of the thermal head of this embodiment is almost the same as that of the conventional one, in which a glaze layer 2 is formed on an insulating substrate 1 such as alumina ceramic, and a common electrode conductor 3 and individual conductors are formed on this glaze layer 2. The electrode conductor 4 is made of Au or the like. Furthermore, Ru is added to the gap between the electrode conductors.
A heating resistor layer 5 made of O2 or the like is formed, and a protective layer 6 made of glass or the like is formed by firing.

The characteristic feature of this embodiment is that in the thermal head having such a configuration, the particle size of the amount of filler added to the glass forming the protective layer 6 is controlled to improve the surface smoothness of the protective layer 6. The point is that the hardness has been improved without decreasing it.

FIG. 1 shows glass-based materials used for the protective layer 6;
The results of measuring the surface roughness Ra and Knoop hardness of the protective layer 6 by changing the type of filler added to this glass system, the amount of filler added, and the average particle size of the filler are shown. Here, the surface roughness Ra is obtained by scanning the surface of the formed protective layer 6 with a roughness meter and measuring the amount of deviation thereof.

First, in Example 1, SiO2-PbO-B2O3 was used as the glass system, α-Al2O3 was used as the filler, and the amount of filler added was 25%.
The average particle size of the filler was 0.7 μm. At this time, the surface roughness Ra was 0.08 μm, which was good, but the Knoop hardness was low, 540, and the wear resistance was not sufficient.

Therefore, in Example 2, the glass system was
Changed to iO2 -PbO-Al2 O3 -CdO,
The type of filler, the amount added, and the average particle size were the same as in Example 1, and the surface roughness Ra and Knoop hardness were measured. As a result, the Knoop hardness improved to 600, but the surface roughness increased to 0.1.
The thickness was 3 μm, which was worse, and many paper scratches occurred on the recording paper after printing. The glass-based SiO2 had a high Knoop hardness of 600.
This is thought to be due to the use of -PbO-Al2O3-CdO, while the poor surface roughness of 0.13 μm is believed to be due to the following reasons.

That is, as shown in FIG. 4, when the filler particle size is 0.8 μm, a large number of fillers enter the glass network consisting of Pb0 and SiO2, and the melting point of the filler is higher than that of glass. It is thought that the softening point increases. It is thought that this increase in the softening point impairs the flow of the glass during firing, which is why the surface roughness deteriorated in this way.

Therefore, in Example 3, the glass system, type of filler, and amount added were the same as in Example 2, the average particle size of the filler was increased to 1.3 μm, and the surface roughness and Knoop hardness were measured. As a result, the surface roughness was improved to 0.06 μm, and the Knoop hardness was also good at 598. Furthermore, in Example 4, the filler average particle diameter was further increased by 1.
As a result of measuring the surface roughness and Knoop hardness with the surface roughness increased to 8 μm, good results were obtained with a surface roughness of 0.06 μm and a Knoop hardness of 578.

Furthermore, in Example 5, a protective layer was formed in which the average particle size of the filler was increased to 2.5 μm, and the surface roughness and Knoop hardness were measured.

However, in the case of Example 5, the surface roughness exceeded the level that could be detected by a surface roughness meter, and it was impossible to quantify it, and the recording paper also had many large holes. It was happening. The reason why the surface roughness deteriorates when the average particle size of the filler becomes as large as 2.5 μm is considered to be due to the following reasons.

That is, as shown in FIG. 5, when the average particle size of the filler is increased to 2.5 μm, the number of filler particles decreases because the amount of filler added is the same, and the amount of filler that enters the glass network also decreases. It becomes less. As a result, the flow of the glass during firing improved, but since the average particle size of the filler was large, the flow of the glass deteriorated only where the filler was present, and it is thought that this caused protrusions to easily occur and the surface roughness to deteriorate.

For comparison, the amount of filler added was 12
The surface roughness and Knoop hardness were also measured at % and 0% (Example 6 and Example 7), but the Knoop hardness was low at 480 and 246, respectively, so it could not be used for thermal heads in terms of wear resistance. could not. This is, of course, because the amount of filler added was small, and the heat resistance improving function and hardness improving function of the filler could not be obtained.

[0027] As described above, the amount of filler added is 25 wt%, which is the same as before, and the average particle size of the filler is 1 μm to 2 μm.
By setting the surface roughness to μm, it was possible to achieve a surface roughness Ra≦0.1 μm without reducing Knoop hardness.

FIG. 2 shows the relationship between filler particle size and surface roughness, and FIG. 3 shows the relationship between filler particle size and Knoop hardness. By setting the particle size of the filler to 1 to 2 μm, the surface roughness is reduced, that is, the surface is smoothed,
Moreover, it can be seen that the Knoop hardness hardly changes.

[0029]

As explained above, according to the thermal head according to the present invention, a thermal head having a protective layer with excellent surface smoothness and hardness can be obtained, and high quality printing with less paper damage can be achieved. There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between surface roughness and Knoop hardness in each example of a thermal head according to the present invention.

FIG. 2 is a graph diagram showing the relationship between filler particle size and surface roughness in Examples.

FIG. 3 is a graph showing the relationship between filler particle size and Knoop hardness in Examples.

FIG. 4 is an explanatory diagram showing the state of filler mixture in the glass network.

FIG. 5 is an explanatory diagram showing the state of filler mixture in the glass network.

FIG. 6 is a sectional view of the thermal head.

FIG. 7 is a graph showing the relationship between glass softening point and Knoop hardness.

FIG. 8 is a graph showing the relationship between filler amount, Knoop hardness, and surface roughness.

[Explanation of symbols]

1 Insulating substrate 2 Glaze layer 3 Conductor for common electrode 4 Conductor for individual electrodes 5 Heat generating resistor layer 6 Protective layer

Claims (1)

[Claims] 1. A glaze layer formed on a substrate, a heat generating resistor layer formed on the glaze layer, a power supply layer for supplying power to the heat generating resistor layer, the power supply layer and the heat generating resistor layer. a protective layer formed on a heating resistor layer, the protective layer is made of glass to which a filler is added, and the filler has an average particle size of 1 μm.
A thermal head characterized in that the thermal head is within a range of 2 μm to 2 μm.