JPH0611547B2 - Thick film thermal recording head - Google Patents

Description

The present invention relates to a thick film type thermal recording head, and more particularly to a thick film type thermal recording head suitable for use in a full color printer adopting a thermal transfer recording system. Is.

[Conventional technology]

There are two types of thermal recording heads, a thick film type and a thin film type, and different materials and processes are used.

Fourthly, the structure of a conventional thick film type heat-sensitive recording head is shown in a fourth schematic sectional view, and a thermal resistance layer 2, an electrode 3, a heating resistor 4, a protective film 7 made of glaze glass on an alumina substrate 1.
It is configured by sequentially laminating. When a voltage is applied to both ends of the electrode 3, the heating resistor 4 generates heat due to the juule heat, and this heat energy causes the protective film 7 to generate heat.
By supplying the medium to a medium such as a thermal paper or a transfer paper through the sheet, color development and ink transfer are performed.

As the material used for the protective film 7 in the thick film type thermal recording head, amorphous glass containing SiO ₂ , PbO or the like as a main component was used. Unlike the thin film type, the protective film 7 is formed by a thick film process such as printing and firing, and the protective film 7 has a single-layer film structure.

The amorphous glass used for the protective film 7 has small surface irregularities and excellent smoothness, so that the coefficient of friction between the head surface and a medium such as thermal paper or transfer paper is small, and thus the thermal paper. The media such as can be transported very smoothly. Further, Japanese Patent Laid-Open No. 55-73575 discloses a thick-film resistance heating element having an extraction electrode provided on a substrate and a thickness including a wear-resistant glass layer consisting of a plurality of glass layers selectively provided to cover the thick-film resistance heating element. A film type thermal head is disclosed.

On the other hand, in the case of a thin film type thermal recording head, S is used as a protective film.
Vapor-deposited films such as iO ₂ , P-SiN, and Ta ₂ O ₅ and sputter films are known. Also as described in JP-A-56-15407, a first layer protective film comprising a protective film from a mixed film or a Ta and SiO ₂ mixed film of Ta ₂ O ₅ and Si, consists of Ta ₂ O ₅ It has also been proposed that the second-layer protective film has a two-layer structure to suppress the occurrence of cracks caused by thermal strain.

[Problems to be solved by the invention]

Amorphous glass used as a protective film for conventional thick film type thermal recording heads has excellent surface smoothness, but on the other hand, since the material is soft, a medium such as thermal paper is on the head surface, that is, on the protective film. When it moves, it easily wears out, cracks occur due to the medium used or thermal strain, and it is easily damaged by foreign matter such as dust that is caught by static electricity when the medium is transported. There are drawbacks.

When the protective film is damaged in this way, the resistance value of the heating resistor changes only in that portion, and the head becomes defective.

For example, according to a test result of observing a deterioration state of a head surface when a thermal paper is run for 500 m, according to a conventional thermal recording head using an amorphous glass single layer protective film,
As shown in FIG. 5, peeling 8 was observed on a part of the head surface, that is, the surface of the protective film 7.

In this manner, when the protective film 7 is peeled off or otherwise damaged, the resistance value of the heating resistor 4 is 5% of the initial value.
The above changes have made it impossible to use for a product such as a thermal recording head for a full-color printer, which requires a high resistance value accuracy.

In order to avoid such drawbacks, a method of using crystallized glass having high abrasion resistance as a material of the protective film can be considered.
However, crystallized glass lacks smoothness due to too large irregularities on the surface, which increases the coefficient of friction between the medium such as thermal paper and the head surface, which causes some problems in transporting the medium.

That is, as shown in FIG. 2, in the case of a single-layer protective film using crystallized glass, the surface roughness is about 1 μm, and when the medium is conveyed in this surface state, for example, thermal transfer recording is performed. The phenomenon of abnormal transportation in which the head surface and the transfer paper stop without slipping on the head surface, and for the same reason, the transfer paper is conveyed while sliding on the head surface little by little, which is called a step slip. In this case, slip marks appear as stripe patterns on the print sample, resulting in a problem that the printing quality is significantly reduced.

Further, in the structure disclosed in JP-A-55-73575,
As a selectively provided glass layer, on the side of the resistance heating element, a glass having good thermal conductivity that does not deteriorate the withstand power inherent to the resistance heating element is arranged so as to separately cover each of the electrodes arranged in parallel. An uneven layer is selectively provided on the heating element and the heat storage glass layer, and glass having good wear resistance is arranged on the uneven layer so that the surface is substantially uniform. Therefore, the thickness of the glass film on the resistance heating element is different from the thickness of the glass layer on the heat storage glass layer between the resistance heating elements, which causes a problem that cracks are likely to occur due to a difference in thermal expansion.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal recording head having excellent head surface smoothness and abrasion resistance and high reliability.

[Means for solving problems]

The above object is to provide a thick film type thermal recording head having a structure in which a thermal resistance layer, an electrode, a heating resistor, and a protective layer composed of a plurality of glass layers are sequentially laminated on an alumina substrate. A plurality of heating resistors are arranged in parallel, and the heating resistors are laminated on the thermal resistance layer and the electrodes in a continuous layered manner so as to cover the plurality of electrodes, and the plurality of glass layers are laminated on the layered heating resistor. As a continuous layer along the upper surface of the resistor, the upper layer is an amorphous glass softer than the lower layer, and the lower layer is a crystallized glass layer that is harder than the upper layer so as to receive wear, cracks, and damages that occur in the upper amorphous glass layer. It is achieved by stacking them.

[Action]

Since the upper film of the protective film formed in two layers on the heat resistance layer and the heating resistor formed in a continuous layer on the electrode is made of soft glass, the surface has excellent smoothness. It is possible to smoothly convey a medium such as transfer paper. In addition, since hard glass with excellent wear resistance is used for the lower layer, abrasion, cracks,
Even if damage occurs, it will be received by the lower hard glass and will not spread downward, and even if the soft glass is slightly worn, the hard lower layer has abrasion resistance, improving durability. To do.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. According to the present invention, a thermal resistance layer 2, an electrode 3, and a heating resistor 4 made of boule glass are sequentially laminated on an alumina substrate 1, and a crystallized glass protective layer containing SiO ₂ , ZnO or the like as a main component is formed thereon. 5 and a protective film having a two-layer structure composed of the amorphous glass protective layer 6 are laminated.

The amorphous glass protective layer 6 has excellent surface smoothness, and the crystallized glass protective layer 5 has much higher hardness than the amorphous glass protective layer 6 and has excellent wear resistance. Both are formed to a thickness of about 10 μm. The roughness of the formed protective film is 0.2 as shown in FIG.
It is less than or equal to μm, and there is no difference in surface roughness as compared with the surface of a normal protective film of amorphous glass alone.

According to this embodiment, since the surface of the protective film is the amorphous glass protective layer 6 having excellent smoothness, the coefficient of friction during the transportation of the medium such as the transfer paper is small, which causes a problem in the transportation of the medium. It is possible to carry the sheet smoothly without causing it.

Further, since the crystallized glass protective layer 5 has excellent wear resistance, even if the upper amorphous glass protective layer 5 is worn or damaged by cracking or peeling, the lower crystallized glass protective layer 5 is prevented. Since it is received at, there will be no damage. Therefore, since the heating resistor 4 is not affected, the resistance value does not change.
Therefore, the reliability of the thermal recording head is significantly improved. Further, the durability was improved about 5 times or more as compared with the case of the conventional one-layer protective film.

〔The invention's effect〕

As described above, according to the present invention, since the surface of the thermal recording head is excellent in smoothness, it is possible to smoothly convey a medium such as thermal paper, and at the same time, it is excellent in abrasion resistance, so that the heating resistor is formed. Therefore, the thermal recording head has a great effect in practical use such as improvement in reliability and extension of life of the thermal recording head.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, FIG. 2 is a view showing the surface roughness of a protective film made of crystallized glass, and FIG.
FIG. 4 is a diagram showing the surface roughness of the protective film according to the present invention, FIG. 4 is a schematic cross-sectional view of a conventional thick film type thermal recording head, and FIG. 5 is an actual running test of the thermal recording head of FIG. The phase diagram of the head surface is shown. 1 ... Alumina substrate, 2 ... Thermal resistance layer, 3 ... Electrode, 4
...... Heating resistor, 5 …… Crystalline glass protective layer, 6 …… Amorphous glass protective layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Ato 1410 Inada, Katsuta City, Ibaraki Prefecture Inside the Tokai Plant, Hitachi, Ltd. (56) Reference JP-A-61-219490 (JP, A)

Claims (1)

[Claims] 1. A thick film type thermal recording head having a structure in which a thermal resistance layer, an electrode, a heating resistor, and a protective layer composed of a plurality of glass layers are sequentially laminated on an alumina substrate, wherein the electrode is the thermal resistance layer. A plurality of glass resistors are arranged in parallel on top of each other, and the heating resistors are laminated in a continuous layer on the thermal resistance layer and on the electrodes so as to cover the plurality of electrodes, and the plurality of glass layers are on the layered heating resistors. As a continuous layer along the upper surface of this layered heating resistor, the upper layer is an amorphous glass layer that is softer than the lower layer, and the lower layer is a layer that is less than the upper layer to the extent that wear, cracks, and damage that occur in the upper amorphous glass layer are received. A thick film type thermal recording head comprising a laminated hard crystallized glass layer.