JPS59209892A - Thermal recording head - Google Patents

Abstract

PURPOSE:To obtain a thermal recording head which is high in thermal efficiency and does not lower the quality of recorded images, by a method wherein the thickness of a protective layer covering the outside surfaces of a plurality of minute heating resistors is reduced at parts between the heating resistors. CONSTITUTION:A glass glaze layer 12 constituting a heat-insulating layer is provided on a substrate 11, a plurality of thin film minute heating resistors 13 arranged with spacing therebetween and lead electrodes 16a, 16b led out to both sides of the arranging direction of the heating resistors 13 are provided thereon, and the protective layer 14 is provided thereon in a covering manner. When an electric current is passed to the heating resistors 13 to generate heat, the heat is rapidly conducted to the surface through the protective layer 14 having a high thermal conductivity. Simultaneously, the head tends to diffuse to the surroundings through the protective layer 14, but the diffusion of heat is restricted or interrupted by grooves 15, so that image quality is not lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thermal recording head used in a thermal recording device such as thermal transfer recording or thermal color recording.

[Background of the invention]

A description will be given below by taking thermal transfer recording as an example.

In thermal transfer recording, a transfer film coated with wax containing a pigment on one side of a base sheet is heated from the other side by a thermal recording head to melt the wax containing the pigment and transfer it to recording paper. In the thermal recording head, minute heating resistors are arranged on the contact surface with the transfer film, and each minute heating resistor is energized and controlled according to the image information to be recorded. Such thermal transfer recording has features such as less operating noise than wire dot recording and the ability to use commercially available plain paper as the recording paper. However, conventional thermal recording heads have the disadvantage that thermal efficiency (amount of heat for melting wax/amount of heat generated) is poor, or that improving thermal efficiency results in a decrease in recorded image quality.

Figures 1 and 2 show the main parts of a conventional thermal recording head. Figure 1 is a plan view with the protective layer on the surface partially removed, and Figure 2 is the same as in Figure 1. ■-■ It is a sectional view. A glass glaze layer 2 serving as a heat insulating layer is formed on the substrate 1, and a plurality of thin film micro heating resistors 32 are arranged on the glass glaze layer 2 at intervals and connected to the side in the arrangement direction of the thin film micro heating resistors 3. -n lead electrodes 6a, 6b are provided. The protective layer 4 is made of a material with excellent wear resistance, and is made using a thin film machine/JS
Heat generating resistor 3 and lead electrodes 6a, 6b: AE wear 16 covers the outer surfaces of these to prevent disconnection.

Conventional materials used for the protective layer 4 include tantalum pentoxide, silicon nitride, and silicon dioxide, which are easy to form and have sufficient hardness. However, these materials have a thermal conductivity less than 10 times that of the glass glaze layer 2 as a heat insulating layer, and therefore cannot effectively transfer the heat generated by the thin film micro-heating resistor 3 to the transfer sheet. Power: cannot. Incidentally, the thermal efficiency of such a conventional thermal recording head is about 30 inches. On the other hand, in order to increase thermal efficiency, there have been proposals to use a material with good thermal conductivity as the material for the protective layer 4. Alumina (A1203) has a thermal conductivity 10 to 100 times higher than that of the above materials.
) or silicon carbide (S i C) improves thermal efficiency, but this protective layer 4 has the disadvantage of diffusing heat to the surroundings, expanding the transfer recording area, and lowering the self-recorded image quality 'e(ff).

[Purpose of the invention]

Therefore, an object of the present invention is to provide a thermal recording head that has good thermal efficiency and does not deteriorate the quality of recorded images.

[Summary of the invention]

To achieve this objective, the present invention includes a heat insulating layer formed on a substrate and a heat insulating layer 711 arranged at intervals on the heat insulating layer.
A heat-sensitive recording device comprising a plurality of micro-heating resistors, lead electrodes led out on both sides in the arrangement direction of the micro-heating resistors, and a protective layer covering the outer surface of these resistors. It is characterized in that the protective layer between the resistors is made thinner than other parts, and the thermal resistance of this thin part prevents heat diffusion.

In the present invention, "making the wall thinner" and "thin wall portion" mean, in its extreme state, "elimination of the protective layer" and "portion without the protective layer."

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to embodiments and FIGS. 3 to 7. Figures 3 and 4 show the main parts of the thermal recording head. Figure 3 is a plan view with the protective layer on the surface partially removed, and Figure 4 is the part shown in Figure 3. FIG.

A glass glaze layer 12 serving as a heat insulating layer is formed on the substrate 11, and a plurality of thin film heat generating resistors 13 are arranged at intervals on the glass glaze layer 12, and a plurality of thin film heat generating resistors 13 are led out on both sides in the arrangement direction of the thin film heat generating resistors 13. A protective layer 14 is formed on the lead electrodes 16a and 16b to cover them.

The thickness of the thin film micro-heating resistor 13 is 1000, and the protective layer 1
Reference numeral 4 denotes an alumina layer having a thickness of 6 μm, and grooves 15 are formed between each of the thin-film minute heating resistors 13 by etching.

According to such a thermal recording head, when the thin film minute heating resistor 13 is energized to generate heat, the heat is transmitted through the high thermal conductivity protective layer 14 and quickly reaches the surface 751. At the same time, it tries to diffuse to the surrounding area through this protective layer 14, but this diffusion is suppressed because it is blocked by the groove 15 between the adjacent thin film microheating resistor 13. Therefore, the temperature of the surface of the protective layer 14 on the thin-film minute heating resistor 13 that generates heat can be effectively raised without enlarging the transfer recording area and reducing the overall image quality. It was possible to obtain a thermal efficiency of 38 inches, which is 1.2 times or more the thermal efficiency of the recording head. Therefore, sufficient transfer recording can be performed even if the heat generation amount of one thin film microheating resistor 13 is reduced to about 75% of the conventional one, and the conventional input power is 0.7W. I was able to reduce it to .53W. As a result of this reduction in input power, the power supply device is made smaller, the switching circuit that controls the energization to the thin film minute heat generating resistor 13 is made smaller, and the IFC becomes faster with the same human power. This enables accurate transcription recording. Furthermore, if the amount of heat generated by the thin-film micro-heating resistor 13 is reduced, the temperature rise of the heat-generating resistor itself is also reduced, and thermal stress and high-temperature oxidation reactions accompanying heat generation can be suppressed, so the life of the thin-film micro-heating resistor 13 is extended. . In conventional thermal recording heads, the thin film micro-heating resistor generates heat approximately 50 million times before reaching the end of its life (the resistance value falls outside the range of 90% to 110% of the initial value). 1 in the recording head
It is expected that the lifespan will not be reached even after 100 million heat generation cycles, and that the lifespan will be more than twice as long.

Using a thermosensitive recording head having a structure similar to that of the above embodiment, the heat generation amount was reduced by about 63% and the input power was reduced to 0.44 W. The lifespan is the same as in the previous example.

FIG. 5 is a characteristic diagram of a conventional thermal recording head configured to transfer and record 8 dots per 1 mm and a thermal recording head of the present invention, in which the recording dot width is preferably stable around 125 μm. It's good. The characteristic of the conventional thermal recording head is that the recording dot width also changes as the input power increases, as shown by curve (2), but this is the case with the thermal recording head of the present invention. Curve (2) is the case where alumina is used for the protective layer 14, and curve (2) is the case where silicon carbide is used. This stable region is obtained by forming grooves 15 in the protective layer 14 between the thin film minute heating resistors 13 to completely prevent heat diffusion.

By the way, such grooves 15 are removed by photo-etching after uniformly forming the protective layer 14 (71). to be accomplished. Below, the dimensions of the groove 15, the thickness of the protective layer 14 remaining at the bottom of the groove 15, and their effects will be explained.

FIG. 6 shows the relationship between the groove width l (FIG. 4) and the surface temperature of the protective layer on the adjacent thin film microheating resistor 13 when the protective layer 14 is not left at the bottom of the groove 15. show. Generally, the melting temperature of wax for transfer film is 65°C to 7.
The temperature is 0° C., and this temperature is indicated as the transfer limit temperature TL. When the protective layer 14 is a silicon carbide layer with a thickness of 6 μm, the surface temperature of the protective layer 140 in the adjacent resistor region will not exceed the transfer limit temperature if the groove width l is 1 μm or more. In the case of the protective layer 14 formed of alumina, the thermal conductivity is lower than that of silicon carbide, so that the influence on the adjacent resistor region is much less.

From this, when the groove width is 1 μm, the protective layer 14
Thickness ratio (thickness of protective layer remaining at the bottom of groove 15/groove 1)
FIG. 7 shows the results of an experiment to see how the surface temperature of the protective layer on the adjacent thin-film micro-heating resistor changes by changing the thickness of the protective layer in areas other than the area 5. Curve (2) shows the characteristics when alumina is used for the protective layer 14, and curve (2) shows the characteristics when silicon carbide is used. As is clear from this result, the wall thickness ratio is 0.4 in any case.
If it is below, the surface temperature of the protective layer 14 in the adjacent resistor region will not exceed the transfer limit temperature.

Therefore, the total thickness of the protective layer 14 to be removed by photoetching may vary by 3.15 mm or more;
If the hole is formed with a thickness of 2.4 μm at the bottom of the groove 15.
It is allowed to remain at the wall thickness of .

'-Also, it is better to form this groove 15 so as not to expose the thin film minute heating resistor 14.

Furthermore, the protective layer 14 is not limited to the material used in the above embodiment, and the same force effect can be obtained by using any other material with similar properties, and the minute heating resistor can be made of a thick film. The same thing can be said when it is formed.

〔Effect of the invention〕

As described above, according to the present invention, the protective layer covering the outer surface of a plurality of arranged micro-heating resistors is made thin between the micro-heating resistors, and this thin part suppresses heat diffusion. Therefore, it is possible to obtain a thermal recording head that has good thermal efficiency and does not deteriorate the recorded image quality.

[Brief explanation of the drawing]

Figures 1 and 2 show the main parts of a conventional thermal recording head. Figure 1 is a plan view with the protective layer on the surface partially removed, and Figure 2 is the same as in Figure 1. -■ Cross-sectional view, FIGS. 3 and 4 show the main parts of the thermal recording head according to the present invention, FIG. 3 is a plan view with the protective layer on the surface partially removed, and FIG. The figure is a sectional view taken along the line IV-ff in FIG. 3, and FIGS. 5 to 7 are characteristic diagrams. 11...Substrate, 12...Glass glaze layer, 13...Thin film micro heating resistor, 14...
...Protective layer, 15...Groove, 16a, 16b
...Lead electrode. $ 1 Mouth b No. Z Hard 3 Fig./61゜v 4 Hard 2θθ1 Input power <W) 6th Hard” “L Layer thickness -1 Groove width (h

Claims (1)

[Scope of Claims] 1. A rough heat insulating layer formed on a substrate, a plurality of minute heat generating resistors arranged at intervals on the heat insulating layer, and leads out on both sides in the arrangement direction of the minute heat generating resistors. ．． A thermal recording head that is completely equipped with a hole lead electrode and a protective layer covering the outer surface thereof, wherein the protective layer between each of the minute heating resistors is made thinner than other parts. recording head. 2. The thermal recording head according to claim 1, wherein the thickness of the thin portion of the protective layer is 0.4 or less of the thickness of the other portion. 3. In claim 1 or 2, the thin portion of the protective layer has a thickness of 1.5 mm in the direction in which the micro heating resistors are arranged.
A thermal recording head characterized by having a width of μm or more.