JPS5872477A - Heat-sensitive recording head - Google Patents

Abstract

PURPOSE:To obtain a heat-sensitive recording head having a long life and capable of giving excellent-quality printing by providing a substantially non- steped flat protective layer over a resistor layer and a conductor layer provided on the surface of a substrate. CONSTITUTION:On an alumina substrate 1 with a graze layer 2, an undercoat layer 3 and a resistor layer 4 are formed, a wiring conductor layer 6 (Al film of a thickness of about 1mu) is formed through an adhesive layer 5 (Cr film of a thickness of about 1,000Angstrom ) on the layers 3 and 4, and then a resistor protective layer consisting of an oxidation-resistant protective layer 7 (SiO2 film of a thickness of about 3mu) and a wear-resistant protective layer (Ta2O5 film of a thickness of about 4mu) is formed over these layers to manufacture a heat- sensitive recording head. In this case, a step difference between the protective layer part located on the conductor layer 6 and the protective layer part located on the resistor layer 4 is regulated to 5,000Angstrom or less. To implement this, the protective layers are formed by a bias sputtering method in which a bias boltage of 200-1,000V is applied to the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film type thermal recording head.
Furthermore, the present invention relates to a heating resistor having a structure in which the protective layer 1 of the heating resistor is formed flat.

A resistor of a thin film type thermal recording head usually has a cross-sectional structure as shown in FIG. In the 1g1 diagram, 1 is a substrate made of alumina or the like, 2 is a heat storage glaze glass layer, 3 is an anti-antibody undercoat layer, 4Fi heating resistor layer, 5 is an adhesive layer between the heating resistor and the wiring conductor layer, 6 is a wiring conductor layer; 7.
8 is a resistor protective layer, 7 is usually an oxidation-resistant layer of the resistor, and 8 is a wear-resistant layer of the resistor.

In the structure shown in FIG. 1, the heating resistor section 10 is lower than the wiring section 11 by the total thickness of the wiring conductor and the adhesive layer, and has a concave shape.

When the heat-generating resistor generates heat during printing, molten components of the printing paper are collected in this recess, which is cooled during non-printing and adheres to the recess. The adhered paper residue will not be melted by the next heat generation, and the thickness of the adhered paper will gradually increase. As the amount of paper residue increases, the contact between the heating resistor and the photographic paper deteriorates, and the transmission of heat to the photographic paper also deteriorates, resulting in variations in the print density of pixels.

This leads to a decrease in print density.

In order to deal with these problems, it is currently necessary to set a large amount of power input to the heat generating resistor, which in turn shortens the life of the heat generating resistor.

In addition, in FIG. 1, since the resistor protection layer is formed on a substrate with unevenness, portion 9 has a large film strain.

As a result, micro-cracks occur in the 99th part of the body that undergoes the heat generation and cooling cycle, and components of the photographic paper that were melted during printing seeped into the cracked part and corroded the wiring conductor.
This reduces the lifespan of the heating resistor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure of a heating resistor that eliminates the drawbacks of the above-mentioned prior art and improves printing quality and extends its life.

The present invention is the same as the conventional method up to the photo-etching process of the heat-generating antibody, and - By simply selecting the conditions for forming the resistor protective layer, the concave part of the heat-generating resistor part is eliminated and the heat-generating resistor and the wiring part are flattened. A thermal recording head is made.

In other words, when considering the formation method of the resistor protective layer as a method for preventing recesses in the heat-generating resistor part, forming the resistor protective layer by bias sputtering is not recommended. A heat generating resistor having the structure shown in FIG. 2 with a body protection layer formed thereon was formed.

In other words, the bias sputtering method is a method in which a bias voltage is applied to the substrate in addition to applying power to the target electrode, and a target material is sputter-formed while performing sputter etching on convex portions on the substrate. be. In this case, the ratio of the target power to the bias voltage applied to the substrate is changed, the deposition rate, and the flatness after deposition are different.

In Figure 2, silicon oxide (S102) was formed to a thickness of 3 μm by bias sputtering as the oxidation-resistant layer of the resistor, and tantalum 95 oxide (Ta205) was formed to a thickness of 4 μm by high-frequency sputtering as the wear-resistant layer. The structure was shown.

The bias sputtering conditions at this time were that the power applied to the target was 4.0 KW, the power applied to the substrate was 400 V, the sputtering gas was argon, and the pressure was 5 m Torr.

The heat generating resistor formed by heating in this manner has an amount of paper residue attached to the resistor that is 1. compared to that of a conventional structure. As below, the life of the heating resistor is the heating energization pulse width α9m5
It had a lifespan of more than 100 million pulses under the conditions of iec, pulse period of 1 omsec, and power applied to the heating resistor α70W.

In addition, the print density averaged 1.30 under the above conditions, but even after 100 million pulses were applied, the density change was as small as about 4 cm, and no change from the initial state was observed in the print density variation between each pixel.

Here, the bias sputtering conditions for forming the concave portion of the resistor portion, the film formation rate, and the degree of planarization after film formation will be explained. In the above case, ``increasing the bias power increases the planarization degree, but the sputter etch rate increases.As a result, the film formation rate decreases and the production efficiency decreases.However, there is no risk of causing sputter damage to the underlying substrate side. If the bias power is small, the sputter etch rate becomes small and the desired degree of planarization decreases.

According to the inventor's experimental study on 8102, the total thickness of the adhesive layer and wiring conductor layer in FIG. 2 is 1.1 μm,
When the power applied to the target is 4.0 KN, if the bias voltage applied to the substrate is 400 V or more, the
2 is flat with unevenness of less than 500X, bias voltage 20
Under the 0V condition, the unevenness was 5oaoX.

From the above results, the appropriate bias voltage to the substrate is 200 to 1 onov in conventional high frequency sputtering.

The present invention will be explained below using examples.

Example 1 On an alumina substrate provided with a glaze layer, a Ta205 film with a thickness of about 125 OA was used as an undercoat layer, a CrSi alloy thin film with a thickness of 1200 Å was used as a heating resistor layer, a Cr film was used as an adhesive layer between the resistor and the wiring layer, and wiring After forming a 1 .mu.m thick A1 film as a conductive layer, a heating resistor having a width of 90 .mu.m and a length of 250 .mu.m was formed by photoetching.

A 3 μm thick 5i02 film was formed as an oxidation-resistant layer on this upper layer. This 5in2 is the distance dOm between the board and the 8102 target.
, IA5MHz high frequency power 4.0 KW Bias voltage to the substrate side 400V, Argosi pressure during sputtering S,
Ql! It was formed by sputtering for 9 hours under I'jO1''r conditions.

A 4 μm Ta205 film is added as a wear-resistant layer on top of this layer.
m was formed. This 'ra2o5 was formed by sputtering for 12 hours using the same electrical manufacturing equipment as the 5102 forming apparatus, using a high frequency power of 4.0 KW and no bias voltage applied to the substrate side.The shape of the resistor part formed in this way was As shown in FIG.
The film thickness was 4 μm, which corresponded to dimensions 12 and 13 in FIG. 2, respectively, and no step difference between the heating resistor portion and the wiring portion could be detected on the wear-resistant layer.

In a thin film thermosensitive recording head having such a structure, the current pulse width α9m81i10. Pulse interval 10ff18eQ
The life test was conducted under the condition that the power applied to the heating resistor was 170 W. At this time, the average initial concentration was 1.28. The concentration variation in 1728 heating elements is ±[L06, the average concentration is 1.24 even after applying 100 million pulses.
, concentration variation ± CL (38, resistance value change rate average 4,
8% maximum 45%, minimum &7%-t'foot, practical 1
Confirmed lifespan of over 100 million pulses.

Example 2 On an alumina substrate with a glaze, 7a2Q was used as an undercoat layer, the film was about 1250^1, Cr-8i alloy thin film was used as a heating resistance layer, Cl-100OA was used as an adhesive layer between the resistor and the wiring layer, and the wiring conductor was used. Al as a layer
A heating resistor having a width of 90 μm and a length of 250 μm was formed (by photoetching after forming a resistor of 1 μm). On this upper layer, a 3 μm thick 5102 film was formed as an oxidation-resistant layer.

In this 5102, the distance between the board and the target is 60cm, and the power input to the target is 4.0KW.

Bias voltage to substrate 200V, argon pressure during sputtering! It was formed by sputtering under L OmTorr conditions for 7 hours.

Furthermore, on this upper layer, a 4μ film of 'ra2o' is applied as an abrasion resistant layer.
m was formed. This Ta2O was formed by sputtering for 12 hours using the same apparatus as the 5102 forming apparatus at a high frequency power of 4.0 KW and no bias voltage applied to the substrate side.

The shape of the resistor thus formed is a cylinder as shown in FIG. a2
0. The film thickness was 4 μm using methods 12 and 13 in FIG.

The difference in height between the heating resistor part and the wiring part in the upper layer of FIG.

In addition, in terms of step and clearance properties, the concave portion near the contact between the resistor and the wiring portion was significantly improved compared to the shape 14 in FIG. 3 and the shape 9 in FIG. 1 of the conventional method.

A life test was conducted on the thin film thermosensitive recording head formed by this method under the conditions of a current pulse width of n9 maeo, a pulse period of 1 omega, and a power applied to the heating resistor of α6OW. At this time, the average initial concentration was 1.08, and the number of heating elements was 172.
The density variation in the 8 lines was α08, and even after applying 100 million pulses, the average density was [1,05, and the density variation was ±109. Average rate of change in resistance value is 2.1%.

(maximum &59g, minimum 1.7% To#), and even after applying 100 million pulses, no slight rack was generated in the part 15 in Fig. 3.

As explained above, on the upper surface of the resistor film-holding layer, the height difference between the heating resistor portion and the wiring conductor portion was set to be 5000 A or less.

According to the method of the present invention, the life of the heating resistor is 100 million pulses or more, which is compared to 50 million pulses of the conventional method.
The lifespan is more than 5 times longer. Also, the applied concentration variation is 1
After applying 100,000,000 pulses, it was significantly improved to within ±7.

In addition, in the present invention, 5102° Ta2 is used as the resistor protective layer.
Although we have explained about ES K, the same effect can be obtained with other materials such as silicon nitride and silicon carbide, as long as the height difference between the heating resistor part and the wiring part is within 5000A on the top surface of the resistor protective film layer. This is to be expected.

[Brief explanation of drawings]

FIG. 1 is a plan view of a heat generating resistor section according to a conventional method, and FIGS. 2 and 3 are plan views of a heat generating resistor section according to the present invention when a resistor protective layer is formed by bias sputtering. 1... Alumina substrate 2... Glaze layer 3... Undercoat layer, 4... Resistor layer 5... Adhesive layer. 6... Wiring conductor layer 7... Oxidation-resistant protective film layer 8... Wear-resistant protective layer 9... Step coverage portion 10... Heat generating resistor section 11...Wiring section 12...Oxidation-resistant layer thickness measurement position 13...
・・Position for measuring the thickness of the wear-resistant layer

Claims (1)

[Claims] a substrate, a resistor layer formed on the substrate, a conductor layer, a protective layer formed to cover the resistor layer and the conductor layer), and protection located on the resistor layer; A thermal recording head characterized in that the step difference between the layer and the protective layer located on the conductor layer is 5000'A or less.