JPH03293164A - Thermal head - Google Patents

Abstract

PURPOSE:To prevent the crack of an abrasion-resistant film and to enhance reliability by constituting the resin protective layer of a thermal head equipped with a support substrate, a heat-resistant resin layer, the resin protective layer and a heating resistor of a compound containing Si, Zr, N and O or a compound containing Y other than Si, Zr, N and O. CONSTITUTION:A resin protective layer composed of a compound containing at least Si, Zr, N and O or a compound containing Y other than said components is formed by a sputtering method or an ion plating method. This compound is harder than other inorg. insulating matter such as SiO2 or Al2O3 and more excellent in humidity resistance as compared with SiN or Si3N4 and has no possibility damaging a heat-resistant resin layer when an electrode substance and a heating resistor substance are dissolved and removed in a desired circuit pattern and, since the heating resistor can be formed without generating gas, the control of resistance value becomes easy. Further, the crack generated by the local generation of the heat-resistant resin layer can be prevented because of excellent crack resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a thermal head used in a heat-generating recording device such as a facsimile or a printer.

(Prior Art) Recently, heat-resistant insulating substrates in which heat-resistant resins such as polyimide resins are provided as insulating layers or heat storage layers on various substrates have been developed for use in high-resistance substrates for thermal heads, multilayer circuit boards for hybrid ICs, etc. They are increasingly being used as supporting substrates for various electronic devices that require high reliability against such heat.

For example, in thermal heads, instead of the conventional high-resistance substrate made of a ceramic substrate such as alumina with a glazed glass layer formed as a heat insulating layer to control heat dissipation and heat accumulation, a ceramic substrate or a metal substrate is used as the high-resistance substrate. A heat-resistant insulating substrate on which a heat-resistant resin layer such as a polyimide resin layer is formed is used.

As a thermal head provided with this polyimide resin layer as a heat insulating layer, one having the following structure, for example, is known.

That is, a heat-resistant resin layer made of polyimide resin or the like, which serves as a heat storage layer and an insulating layer, is formed on a metal substrate made of an Fe alloy or the like, and a heating resistor made of Ta5i02, Ti-8L02, etc. is formed on this layer by sputtering or the like. Forms a film. Furthermore, individual electrodes and a common electrode made of Aρ, AΩ-3i-Cu, etc. are formed on the heating resistor so as to form an opening that will become the heating part, and silicon oxynitride (silicone oxynitride) is formed so as to cover at least this heating part. Si
-0-N), etc., and has a wear-resistant layer that also serves as a heat-resistant film.

Such a thermal head uses a polyimide resin layer as a heat insulating layer, so that the thermal diffusivity of the polyimide resin is 1/3 to 1/B higher than that of a conventional glazed glass layer.
Because of its low thermal efficiency, it has excellent thermal efficiency. In addition, since it is possible to use a flexible support substrate such as a metal substrate, it is also possible to perform bending processing, so it is attracting attention as a small, inexpensive, and high-performance thermal head. . However, such a thermal head has the following problems in its manufacturing process.

For example, the heat-resistant resin layer is damaged during etching processing performed when forming heating resistors and electrodes, or during ashing of a masking film.

Further, when depositing the heating resistor material in a vacuum, a large amount of gas is released from within the polyimide resin layer, and the influence of this gas causes a problem in that it is difficult to control the resistance value.

Furthermore, when wiring using the wire bonding method,
A problem arises in that bonding is difficult to perform due to the elasticity of the polyimide resin layer.

As a means to solve these problems, the present applicant first developed a resin protection layer made of an inorganic insulating material such as alumina, silicon oxynitride, or sialon between the heat-resistant resin layer and the heat-generating resistor layer. Thermal heads with layers have been proposed (Japanese Patent Application Laid-Open Nos. 189253-1983, 297066-1983, 38465-1999).
Publication No.). By forming a resin protective layer between the heat-resistant resin layer and the heating resistor layer in this way, damage to the polyimide resin layer and gas release from the polyimide resin layer are prevented during the manufacturing process, and the overall rigidity is also improved. Since this increases to a certain extent, effects such as being able to perform the mounting process stably are obtained.

Forming a resin protective layer on a heat-resistant resin layer in this way is an effective means not only as a high-resistance base for thermal heads, but also as an insulating base for other electronic devices, allowing the mounting process to be performed stably. It is.

(Problem to be Solved by the Invention) As described above, a heat-resistant insulating substrate is provided in which a resin protective layer made of an inorganic insulating material such as alumina, silicon oxynitride, or sialon is provided on a heat-resistant resin layer such as polyimide resin. Although various advantages can be obtained by using it as a high-resistance substrate for a thermal head, for example, the inorganic insulating layer described above does not have sufficient film strength, and the following problems occur, for example. ing.

That is, when the present inventors installed the thermal head having the above-mentioned resin protective layer in a printer and actually conducted a printing running test, it showed an abnormal change in resistance value during running, a phenomenon that adversely affected printing. Recognized many times. A detailed investigation into the abnormal resistance change revealed that foreign matter such as dust caught between the thermal head and the thermal paper or between the thermal paper and the roller caused cracks in the wear-resistant layer that forms the surface layer of the thermal head. It has been found that when these cracks reach the heating resistor, they have an adverse effect on printing characteristics.

Such problems cannot be seen in thermal heads that use conventional high-resistance substrates with a glazed glass layer formed on a ceramic substrate or high-resistance substrates with a glass layer formed on a metal substrate, and which otherwise have the same structure. This is a phenomenon that was not possible.

This is because in thermal heads that use a high-resistance substrate that uses a glazed glass layer or a glass layer as a protective layer, the hardness of the entire substrate is large, and this means that even if local pressure is applied to the wear-resistant layer, the Because it only undergoes the same deformation as
It is thought that local deformation is prevented and racks as described above do not occur.

On the other hand, in the case of a high-resistance substrate made of a heat-resistant resin such as polyimide resin, although the rigidity of the substrate is increased to some extent by the resin protective layer as described above, the deformability of the resin is This is because the deformation of the heat-resistant resin layer cannot be prevented by the resin protective layer or the wear-resistant layer when a locally concentrated load is applied to the wear-resistant layer. It is thought that the deformation of the resin protective layer and wear-resistant layer cannot follow the deformation of the heat-resistant resin layer, resulting in cracks.

Such problems are not limited to thermal heads, but also occur in multilayer circuit boards for hybrid ICs as mentioned above, where deformation of the heat-resistant resin layer during the mounting process causes disconnection of the wiring layer provided on top of it, defective bonding, etc. It invites.

The present inventors, as a means to solve the above problem,
Next, we proposed a thermal head with a resin protective layer made of amorphous silicon carbide (Japanese Patent Laid-Open No. 8
3-229809). According to this, damage to the heat-resistant resin layer during the manufacturing process is prevented. Furthermore, the resistance value can be easily controlled, wire bonding in the mounting process can be performed stably, and cracks in the wear-resistant layer, which is the surface layer during actual printing, can be effectively prevented.

Therefore, it becomes possible to perform stable printing, and its reliability is improved. However, it is necessary to improve the adhesion of the film and to be able to process it at a relatively low temperature.

In order to satisfy the conditions that the physical properties of the film can be easily controlled, the method of forming an amorphous silicon carbide film has tended to be limited to the plasma CVD method.

The plasma CVD method generally requires large-scale and expensive equipment, which requires troublesome maintenance, and also has the risk of using gases harmful to the human body, such as SiH4, in the synthesis of amorphous silicon carbide.

The present invention has been made to address the problems of the prior art, and provides a thermal head that prevents cracks in the abrasion resistant film and improves reliability when installed in a printer or the like and runs. The purpose is to

The thermal head of the present invention includes a highly thermally conductive support substrate,
A heat-resistant resin layer formed on this support substrate, a resin protective layer provided on this heat-resistant resin layer, a large number of heating resistors formed on this resin protective layer, and connections to each of these heating resistors. The thermal head is characterized in that the resin protective layer is made of a compound containing at least St, Zr, N, and O, or a compound containing at least Y in this compound.

In addition, additive elements to increase the hardness and toughness of the resin protective layer, or trace components added as sintering aids for the sputtering target during the production of the sputtering target used to obtain the resin protective layer, may be added to the resin protective layer. I don't care if it gets taken inside. The amounts of Y and Zr added are as follows:
0.1-11-1O% as Y2O3, 1.0-40IIlo1% as ZrO2, preferably 0.5-2mo1% as Y2O3, 5.0-5.0% as ZrO2
20IIli1%. Incidentally, when Y and Zr are added simultaneously, it is particularly effective if the ratio of ZrO2 and Y2O3 is within the range used for stabilized zirconia. Y2
O3 and ZrO2 are each 0. Scooping 01% and 1.0m
If o is less than 1%, sufficient hardness and toughness cannot be obtained, and if it exceeds 1゜mo1% and 40mo1%, respectively, Y and Zr will exist in considerable amounts as metal components in the resin protective layer, and the resin will deteriorate. There is a risk that the insulation properties of the protective layer film will be significantly impaired.

At least St, Zr, N, 0 in the present invention
Methods for forming the resin protective layer made of a compound containing Y or a compound containing at least Y in this compound include sputtering method, ion blating method, physical vapor deposition method (PVD method) such as vacuum evaporation method, normal pressure and Examples include low pressure chemical vapor deposition (CVD), and sputtering is particularly preferred. A method for forming a resin protective layer made of a compound containing at least Si, Zr, N, and O, or a compound containing at least Y in this compound using this sputtering method includes, for example, mixing 0 Si3N4 and ZrO2. Target and Si3N4
5i such as a mixed target of ZrO2 and Y2O3
-Zr-0-N is a compound, or S i -Z r -Y
A method of sputtering using a target made of a -0-N compound in an O group gas atmosphere or an O group gas atmosphere containing 02, and a mixed target of 5i02 and ZrO2 or a mixed target of 5i02, ZrO2, and Y2O3. 5i-Zr-0 compounds such as, or 5i
Examples include a method of sputtering using a target made of a Zr-Y-0 compound in an O group gas atmosphere containing N2 gas or an O group gas atmosphere containing a mixture of N2 and O2 gas.

Further, the thickness of the resin protective layer is preferably in the range of 1 to 5 μm, and if the thickness of the base layer is less than 1 μm, sufficient protection of the heat-resistant resin layer and stabilization of the resistance value and bonding properties cannot be obtained. On the other hand, if the thickness exceeds 5 μm, not only no further effect can be obtained, but also the time required for film formation becomes longer.

(Function) In the thermal head of the present invention, at least St and Zr are present between the heat-resistant resin layer and the heating resistor.

A compound containing N, 0 or at least Y in this compound
It forms a resin protective layer consisting of a compound containing
This compound is similar to other 5i02. Ag2O3, T i 02
, T a205 and other inorganic insulators, and SiN, Si3N4. Superior moisture resistance compared to silicon oxynitride (Si-0-N compound), etc.
Furthermore, it does not react with dry etching gas and exhibits sufficient effects even when the film thickness is reduced, making it an extremely effective material as a base film. In addition, the sputtering rate is faster than when forming a sialon film mainly composed of 5i-AfI-0-N, and there is no decrease in the sputtering rate even when 02 or N2 is added, making it excellent in mass productivity. In addition, in terms of crack resistance, it is equivalent to SiC, which is the most excellent of conventional materials, and whereas it is difficult to obtain a high-quality film with SiC without using plasma CVD, this compound can be used with sputtering. As mentioned above, it is advantageous in terms of cost and safety because a high-quality film can be easily obtained by this method.

These eliminate the risk of damaging the heat-resistant resin layer when dissolving and removing the electrode material and heating resistor material into a desired circuit pattern, and the formation of this resin protective layer eliminates the risk of damaging the heating resistor material without generating gas. Therefore, the resistance value can be easily controlled. Furthermore, during wire bonding in the mounting process, the cushioning effect of the heat-resistant resin layer is offset by the hardness of the resin protective layer, making it possible to perform wire bonding stably. Furthermore, since it has excellent crack resistance, it is possible to prevent cracks caused by local formation of a heat-resistant resin layer such as polyimide resin due to the pressure applied to the wear-resistant film that is the surface layer.

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the thermal head of this embodiment is
For example, on a metal substrate 9 made of an Fe alloy containing 16% by weight of Cr and having a thickness of about 0.5W, a heat-resistant resin layer IO made of polyimide resin or a mixture thereof serving as a heat storage layer and an insulating layer is formed with a thickness of about 30 μm. On this heat-resistant resin layer lO, at least St, Zr, N, 0
A resin protective layer 11 is formed of a compound containing Y or a compound containing at least Y in this compound.

Further, on this resin protective layer 11, Ta-8i02, T
A heating resistor 12 made of 1Si02 or Cr-3i02 is formed, and an opening that becomes the heating part 15 is formed on the heating resistor 12.
Individual electrodes 13 and common electrodes 14 consisting of u are formed,
A wear-resistant film 1B, which also serves as an oxidation-preventing film, is formed to cover at least this heat generating portion 15, and is made of a compound containing at least Si, Zr, N, and O, or a compound containing at least Y in this compound.

In this thermal head, by applying a pulse voltage between the individual electrodes 13 and the common electrode 14 at predetermined time intervals, the heating resistor 12 of the heating section 15 generates heat 34 to perform print recording.

This thermal head is manufactured, for example, as follows.

First, a metal substrate 9 made of an Fe-18% by weight Cr alloy is cut into predetermined dimensions, degreased, cleaned, dried, and then heat-treated at 600° C. to 800° C. in a dry hydrogen atmosphere. (Figure 2-a). Next, on this metal substrate 9, for example, polyimide varnish or polyimide varnish is applied using a roller coater or a spin-on coater, and after baking, a coating of 20 to 30%
The heat-resistant resin layer 10 is formed by applying a predetermined amount to a film thickness of μm, drying, and baking (Fig. 2-port).

Thereafter, in order to improve the adhesion between the heat-resistant resin layer 10 and the resin protective layer 11, the surface of the heat-resistant resin layer IO is subjected to, for example, plasma treatment, sputter etching treatment, ozone gas irradiation treatment, ultraviolet irradiation treatment, or a combination thereof. It is preferable to carry out a surface modification treatment consisting of the following, and particularly a sputter etching treatment using Ar gas to which 1 to 5 mo1% of 02 gas is added is effective (FIG. 2-c).

5 Next, on this surface-treated heat-resistant resin layer IO, a sputtering target consisting of, for example, Zr029.7 mo1%, Y203 mo1%, and the remainder substantially Si3N4 is used to sputter in a 5vo1%-Ar gas atmosphere. Sputtering is performed using at least Si, Zr, and Y.

A resin protective layer 11 made of a compound containing N and O is formed (FIG. 2-2).

Next, Ta-SiO2°Cr-8i0 is deposited on this resin protective layer 11 by sputtering or other known methods.
2 or Ti 5i02 or the like is formed into a film (Fig. 2-E), and then the electrode material AΩ or Ai
)-3i-After forming a film of Cu, Au, etc. by a sputtering method (see Fig. 2-), a masking film with a desired circuit pattern in which openings that will become the heat generating part 15 are formed is formed and then dried. Etching is performed to form individual heating resistors 12, individual electrodes 13, and common electrode 14 (second
Figure-g).

Thereafter, a wear-resistant film 16 which also serves as an oxidation-preventing film is formed by sputtering or other known methods (FIG. 26-h) to complete the thermal head.

Next, the thermal head obtained in this way was mounted on a heat dissipation board made of Al using double-sided tape, and a wiring test was performed using ultrasonic wire bonding with the driver IC mounted in the same manner on the driver board. When I went there, I was able to perform stable bonding. In addition, the thermal head obtained in this way was placed in a constant temperature and humidity chamber at 60°C and 190% for 10 days.
When a standing test was conducted for 00 hours, no peeling of the film occurred and no problems occurred.

In addition, as the resin protective layer 11, Z r 029.7mol
% and Y20B 0.3IIIo1% and the remainder is substantially S
Compound film consisting of i3N4, 500 people each, 1 μm
, 2 .mu.m, 3 .mu.m, and 5 .mu.m thick were formed by the above-mentioned procedure, a thermal head was prepared, and a printing running test was actually performed by incorporating the thermal head into a printer.

The test environment was room temperature and humidity. As a result of a 5km running test, the film thickness was 500 people Zr 029.7IIIo1
% and Y2030.3mo1% and the remainder is substantially Si3N4
In a thermal head with a resin protective layer made of a compound film of On the other hand, 'Z' of 1μm, 2μm, 3μm, 5μm
, r Q29.7mo1% and Y2O30,3m01%
Almost no cracks were observed in any of the compound films in which the remainder was substantially composed of Si3N4.

This test result shows that Ca-8i formed by plasma CVD method
Except for using the C film as a resin protective layer, the print running test results were exactly the same as those for a thermal head having the same structure. Furthermore, for comparison, a similar test was conducted using a thermal head with the same structure except that a 1 μm thick SiAlON layer was formed by sputtering as a resin protective layer in the thermal head of the above-mentioned example. Cracks appeared in about 20 places.

It is clear from the test results that the thermal head of this example has excellent crack resistance.

That is, according to this embodiment, a resin protection layer consisting of a compound containing at least Si, Zr, N, 07 8 or a compound corresponding to a compound containing at least Y in this compound is provided between the heat-resistant resin layer and the heating resistor. Since the resin protective layer acts as a protective layer for the heat-resistant resin layer when the electrode material and heat-generating resistor material are dissolved and removed to form a desired circuit pattern, there is a risk of damaging the heat-resistant resin layer. Furthermore, since no gas is generated during the formation of the heating resistor material in vacuum, it also plays the role of stabilizing the resistance value and provides a good thermal head. Furthermore, the hardness of the resin protective layer offsets the cushioning effect of the heat-resistant resin layer during wire bonding in the mounting process, making it possible to perform wire bonding stably. And this at least Si, Zr, N
, O, or a compound containing at least Y in this compound has excellent moisture resistance, so the resulting thermal head also has excellent moisture resistance. In addition to these effects, Zr029.7mol of this example
% and Y2030J[ll01% and the remainder is substantially Si3
The compound film made of N4 has a much higher hardness than the heat-resistant resin layer, so even if local pressure is applied to the wear-resistant layer during actual printing operations, the heat-resistant resin layer does not thicken too much. It is possible to prevent deformation, that is, local deformation is prevented and cracks in the wear-resistant layer are prevented. Therefore, printing can be performed stably for a long period of time, and reliability is greatly improved. In addition, this compound can easily form a resin protective layer exhibiting the above-mentioned effects by sputtering, which uses relatively inexpensive equipment and is highly operationally safe, so it is excellent in economy and safety.

In this embodiment, a case in which a heat-resistant resin layer is formed on a metal substrate has been described, but the effects of the present invention can be similarly expected even if the supporting substrate is not limited to metal but ceramics or glass.

However, when a metal substrate is used as a support substrate, the metal substrate itself can be used as a common electrode and can be bent, which greatly contributes to miniaturization of the thermal head.

[Effects of the Invention] 9 0 As explained above, in the thermal head of the present invention, at least Si,
Since the base layer is formed of a compound containing Z r, 'N, 0 or a compound containing Y in this compound, there is no damage to the heat-resistant resin layer, and the resistance value can be easily controlled. Become. Furthermore, wire bonding during the mounting process can be performed stably, and cracks in the wear-resistant layer, which is the surface layer during actual printing, can be prevented.
It becomes possible to perform stable printing, and its reliability is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a thermal head according to an embodiment of the present invention, and FIG. 2 is a flowchart showing a method for manufacturing a thermal head according to an embodiment of the present invention. 9...Metal substrate lO...Heat-resistant resin layer 11...Resin protective layer 12...Heating resistor 13...Individual electrode 14...Common electrode 15...Heating part I6...Resistance wear film

Claims (1)

[Claims] A support substrate with high thermal conductivity, a heat-resistant resin layer formed on this support substrate, a resin protective layer provided on this heat-resistant resin layer, and a resin protective layer formed on this resin protective layer. In a thermal head comprising a large number of heating resistors and a conductor connected to each of these heating resistors, the resin protective layer contains a compound containing at least Si, Zr, N, and O, or a compound containing at least Si, Zr, N, and O. A thermal head comprising a compound containing Y.