JP2888584B2 - Sputter target Wear-resistant coating and thermal head using it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a sputter target suitable for forming a protective film used for a thermal head, a contact sensor, and the like, and an abrasion resistance formed using the same. The present invention relates to a thermal head using the abrasion-resistant coating as a protective film.

(Prior Art) A thermal head has been frequently used in various recording apparatuses such as a facsimile and a printer for a word processor, taking advantage of low noise, low maintenance and low running cost. On the other hand, various electronic devices are required to be reduced in size, price, and power consumption, and a small, inexpensive, and highly efficient thermal head is also desired.

As a thermal head that satisfies such demands, a thermal head using a resin having excellent heat resistance such as a polyimide resin and having a low thermal diffusivity as a heat insulating layer has attracted attention.

The above-described thermal head using a heat-resistant resin as the heat insulating layer has, for example, the following structure.

That is, in the thermal head, a heat insulating layer made of a polyimide resin or the like is provided on a metal substrate, a heating resistor layer, a conductive layer serving as an individual electrode and a common electrode are sequentially formed on the heat insulating layer, and the outermost surface is made of Si. -O-N, Si ₃ N ₄ , SiC, etc. are covered with a protective film.

As the protective film, an antioxidant film and a wear-resistant film may be provided as separate layers, or an adhesive layer may be provided as necessary. In addition, we protect thermal insulation layer from ashing processing
In order to facilitate the control of the resistance value when forming the resistance layer and to further improve the wire bonding property, an underlayer made of SiO ₂ , SiN, SiC or the like is provided between the heat insulation layer and the heating resistor layer.

It has been confirmed that such a thermal head can sufficiently withstand the operation of the thermal head in terms of heat resistance and adhesion. However, as a result of a running test in which this thermal bed was incorporated in a device such as a facsimile machine, an abnormal change in resistance value during running was observed, and many phenomena affecting printing were observed.

As a result of examining the singular point showing such an abnormal change in resistance in detail, foreign matter such as dust caught between the thermal head and the thermal paper causes cracks in the protective film of the thermal head. It has been found that a singular point occurs when the crack reaches the heating resistor. In addition, when a conventional alumina substrate having a glaze glass layer is used as a high-resistance substrate, or when a metal substrate having a glass layer is used as a high-resistance substrate, such a phenomenon occurs even in a thermal head having the same other configuration. The present inventors have found that the phenomenon is unique when a resin is used as the heat insulating layer.

In these, when a glass layer is used as a heat insulating layer, the glass layer has a high hardness, and since only the same deformation as the protective film occurs, local deformation of the protective film is prevented. Resins have high elasticity and deformability is significantly greater than that of the protective film, so if a localized concentrated load is applied to the protective film, the thermal insulation layer made of resin will be greatly deformed, but the protective film can follow this deformation. It is considered that the protective film was broken.

For this reason, various protective film materials have been studied, but Ta ₂ O ₅ and SiO ₂ have poor hardness, and Si ₃ N ₄ , Si ₃
The inventors of the present invention have found that C, Al ₂ O _{3, and the} like have poor toughness and are liable to crack, so that they cannot withstand practical use.

On the other hand, as a protective film material capable of preventing the occurrence of general cracks, a high-hardness, high-toughness Si-Al-O-N described in JP-A-60-4077 and JP-A-62-2968 are disclosed. Attention has been paid to sialon films mainly composed of sialon.

However, the above-mentioned sialon film has a problem that when sputtered in an Ar atmosphere, the sputter rate is low, and in this atmosphere, Al is easily precipitated as a metal component, and the insulating property is reduced.

The problem of the precipitation of Al can be improved by adding about 5% to 10% of O ₂ or N ₂ to Ar, but the sputter rate is further reduced, which causes a cost increase.

(Problems to be Solved by the Invention) As described above, in the thermal head, by using a resin having a low thermal diffusivity such as a polyimide resin as the heat insulating layer, the thermal head is excellent in thermal efficiency, can be bent, and can be easily reduced in size. Despite the advantages, the resin layer is soft, and when a local stress is applied to the protective film due to entrapment of dust, there is a large difference in the amount of deformation between the resin layer and the protective film. When this reaches the heating resistor, there occurs a problem that a resistance value abnormality is caused and printing performance is deteriorated.

Such a problem occurs not only in the thermal head but also in a solid-state device such as a complete contact sensor.

The present invention has been made to address such a conventional problem, and has no cracks even when a local stress is applied, and can form a highly reliable protective film. A stable sputter target that hardly changes the composition of the target and the characteristics of the sputtered film when used for a long time, a wear-resistant coating formed using the same,
It is another object of the present invention to provide a thermal head having excellent printing performance stability.

[Structure of the Invention] (Means for Solving the Problems) That is, the first sputter target in the present invention is at least one selected from titanium oxide, zirconium oxide, and hafnium oxide (except when zirconium oxide alone is used). ) Containing 1 mol% to 40 mol%, and the balance substantially consisting of silicon nitride, wherein the second sputter target is at least 1 mol% selected from titanium oxide, zirconium oxide and hafnium oxide. 40 mol% and at least one selected from yttrium oxide and aluminum oxide (however,
(Excluding the use of zirconium oxide alone in the case of yttrium oxide alone) of 0.05 mol% to 10 mol%, with the balance being substantially composed of silicon oxide.

Further, the wear-resistant coating of the present invention is a wear-resistant coating made of a sputtered film formed by using the above-mentioned sputter target, wherein at least a part of the structure is in an amorphous state.

Further, the thermal head of the present invention comprises a supporting base having a heat-resistant resin layer, a heating resistor layer disposed on the heat-resistant resin layer, and a power supply provided on the heating resistor layer to supply power to the external heating resistor. In a thermal head having an electrode conductor layer for use and a protective film for protecting the heating resistor and the electrode conductor layer, the protective film is formed of the above-described wear-resistant coating.

The oxides of the Group IVa metals of Ti, Zr and Hf contained in the first silicon nitride-based sputter target increase the toughness of the obtained sputtered film and increase the composition stability of the target itself, thereby increasing the sputtering stability. It is intended to improve the rate and prevent a decrease in the sputter rate due to the type of sputter gas, and its content is in the range of 1 mol% to 40 mol% as the total amount of the oxide of the Group IVa metal.

When the content of the oxide of these IVa group metals is less than 1 mol%, the strength of the obtained sputtered film is not sufficient.
If the amount exceeds mol%, the group IVa metal is likely to be precipitated as a metal component, which may cause a decrease in the insulating property of the sputtered film. A more preferred content is in the range of 5 mol% to 20 mol%.

The above oxides of the Group IVa metal can be used alone or as a mixture of two or more, but in the present invention, zirconium oxide alone is excluded.

In addition, yttrium oxide and aluminum oxide contained in the second silicon nitride-based sputter target can further enhance the above-mentioned effects and facilitate the production of the target itself, in combination with the above-described oxide of a Group IVa metal. The content is 0.05 mol% as a total amount of yttrium oxide and aluminum oxide.
1010 mol%.

Further, the content of the oxide of the Group IVa metal in the second sputter target is in the range of 1 mol% to 40 mol% similarly to the first sputter target, and the contents of yttrium oxide and aluminum oxide are as follows: The content is determined in consideration of the content of the oxide of the Group IVa metal, and the more preferred content is in the range of 0.3 mol% to 1 mol%.

The reasons for limiting the contents of yttrium oxide and aluminum oxide are as follows.

That is, if their content is less than 0.05 mol%, the effect of improving the strength of the obtained sputtered film is not sufficient.
If it exceeds 10 mol%, Y or Al tends to precipitate as a metal component, which may cause a decrease in the insulating property of the sputtered film.

The above effects can be obtained by containing at least one of the above yttrium oxide and aluminum oxide, but it is more preferable to contain both. In the present invention, the use of zirconium oxide alone in the case of yttrium oxide alone is excluded.

Specific compositions of the sputter target of the present invention include, for example, the compositions shown in Table 1.

The sputter target of the present invention is produced by a sintering method such as a normal pressure sintering method, an atmospheric pressure sintering method, a hot press method, and a HIP method, similarly to a normal ceramic sintered body.

The sputter target of the present invention obtained by such a sintering method preferably has a sintering density in the range of 60% to 95% of the theoretical density. This is because the sputtering rate can be improved by making the sintering density relatively small. Also, if the sintering density is less than 60% of the theoretical density, the brazing material used for joining with the backing plate easily penetrates into the sintered body and the workability decreases,
On the other hand, if it exceeds 95%, the sputtering rate is reduced, and thermal stress cracking due to the difference in thermal expansion with the backing plate is likely to occur.

Further, the wear-resistant coating of the present invention is formed of a sputtered film formed by using the above-described sputter target of the present invention, and at least a part of its structure is formed of amorphous.

Such an amorphous sputtered film exhibits excellent toughness and high hardness, and thus is suitable as a wear-resistant coating.

The composition of the wear-resistant coating of the present invention is the same as that of the above-mentioned target, but does not always match because the composition ratio varies depending on sputtering conditions and the like.

The abrasion-resistant coating is formed by performing sputtering under ordinary sputtering conditions using the sputter target of the present invention. As the sputtering gas, an inert gas is used. In order to prevent the group IVa metal, Y and Al from being precipitated as a metal component, an argon gas containing about 5% to 10% of oxygen or nitrogen is used. Is preferred.

The abrasion-resistant coating has high hardness, excellent film breaking strength and the like, and is excellent in adhesion to a substrate to be adhered, and thus is suitable as a protective film for a thermal head, a contact type sensor and the like.

The thermal head of the present invention uses the above-described wear-resistant coating of the present invention as a protective film of the thermal head using a resin layer made of a polyimide resin or the like as a heat insulating layer. The abrasion resistant film also functions as an antioxidant film for the heating resistor layer and the electrode conductor layer.

(Operation) The sputter target of the present invention contains silicon nitride as a main component, an oxide of a Group IVa metal, yttrium oxide, aluminum oxide, and the like. Here, when sputtering is performed using a sputter target having such a composition, while maintaining the high hardness of the sputtered film containing silicon nitride as a main component, a Group IVa metal as a metal component, Y, Al And the like are appropriately dispersed in the sputtered film, so that the toughness of the sputtered film is significantly improved, excellent wear resistance is provided, and the occurrence of cracks and the like is prevented. Further, the sputter target of the present invention has a high sputter rate, and even if a gas obtained by adding O ₂ or N ₂ to Ar gas as a sputter gas is used, there is almost no decrease in the sputter rate. Is obtained.

In addition, the sputtered film formed using the above-mentioned sputter target is in an amorphous state and increases the toughness.
A high quality abrasion resistant coating is obtained. Furthermore, by using this abrasion-resistant coating as a protective film for a thermal head having a resin heat-insulating layer, cracks in the protective film caused by the deformability of the resin layer are prevented, so that it can be used stably for a long time. Thus, a thermal head that can be used is obtained.

(Example) Hereinafter, an example of the present invention will be described.

Example 1 A TiO ₂ powder having an average particle size of 0.03 μm was added so that 5 mol% of TiO ₂ was contained in a Si ₃ N ₄ powder having an average particle size of 0.5 μm, and mixed and dispersed in ethanol by a ball mill for 12 hours. And dried to produce a raw material powder.

Next, the raw material powder was subjected to hot press sintering in an N ₂ atmosphere at 1775 ° C. × 2 hours, and then subjected to diamond grinding to obtain a sputter target having a diameter of 203 mm and a thickness of 8 mm.

Using the sputter target thus obtained, a protective film for a thermal head was formed.

FIG. 1 is a view showing the configuration of a thermal head used in this embodiment, and is manufactured by, for example, the following method.

First, a metal substrate 1 made of, for example, an Fe alloy containing about 18% by weight of Cr and having a thickness of about 0.5 mm is leveled, cut into predetermined dimensions, deburred, and degreased and washed in an organic solvent.
The substrate is immersed in dilute sulfuric acid maintained at 50 ° C. to 70 ° C. to remove an oxide layer formed on the surface and perform an activation process for microscopically roughening the surface.

Next, the polyamic acid is adjusted to a predetermined viscosity using a solvent such as N-methyl-2-pyrrolidone, applied to the metal substrate 1 to a predetermined film thickness, and heated at 50 ° C. for 1 hour using a firing furnace. 30 minutes at 80 ° C., then 30 minutes at 120 ° C., 1 hour at 250 ° C.
A heat treatment is performed at 450 ° C. for 1 hour to remove the solvent component and to advance a dehydration cyclization reaction to form a film, thereby forming a heat insulating layer 2 made of a polyimide resin which is a heat-resistant resin.

Next, SiH ₄ gas, N ₂ gas and Si
The underlayer 3 composed of the SiN layer 31 and the SiC layer 32 is continuously formed by plasma CVD using a H ₄ gas and a CH ₄ gas at a substrate temperature of 150 ° C. to 300 ° C.

Next, a heat-generating resistor layer 4 made of Ta-SiO ₂ and an electrode conductor layer made of Al are formed, and are patterned by wet etching or dry etching so that an opening to be a heat-generating portion 5 is provided. And the common electrode 7 is formed.

Thereafter, the protective film 8 is formed by sputtering so that the heat generating portion 5 is covered at least. The thickness of the protective film 8 is generally 1 μm to 7 μm, preferably 2 μm to 4 μm.

Then, in forming the protective film 8, using the sputtering target of this embodiment, sputtering is performed by high frequency magnetron sputtering under an output condition of 2 kW in an Ar gas containing 5% of O ₂ to form the protective film 8. A thermal head of this example was obtained.

Using the thermal head thus obtained, the following characteristic evaluation was performed.

The hardness was measured using an ultra-small Knoop hardness tester for thin films.

The film breaking strength was measured using a scratch tester having a sensor for detecting AE (acoustic emission) generated at the time of film breaking.

Also, the sputter rate when forming the protective film was measured. Table 2 shows the results.

Examples 2 to 20 Sputter targets having the compositions shown in Table 2 were produced under the same conditions as in Example 1, and the protective film 8 was formed in the same manner as in Example 1 using each of these sputter targets.
Was formed to obtain respective thermal heads. The starting material of the sputter target was ZrO ₂ having an average particle size of 0.03 μm.
Powder, HfO ₂ powder with average particle size 0.03 μm, average particle size 1.0 μm
Of Y ₂ O ₃ powder, Al ₂ O ₃ powder having an average particle size of 0.1μm were used, respectively.

The characteristics of these thermal heads were evaluated in the same manner as in Example 1. Table 2 also shows the results.

Comparative Example 1~4 Si ₃ N ₄ (Comparative Example 1), SiON (Comparative Example _{2), 1SiO 2 / Ta 2} O 5
(Comparative Example 3), Sputter targets made of Si ₃ N ₄ -10 wt% Al ₂ O ₃ (Comparative Example 4) were produced, and a thermal head having a protective film formed by using these targets was compared with that of Example 1. It was manufactured under the same conditions, and its characteristics were measured under the same conditions as in Example 1.

The results are shown in Table 2 together with the results of the examples.

As is clear from the above results, the protective film formed using the sputter target of the present invention was excellent in strength, and was able to prevent the occurrence of cracks even when a resin was used as the heat retaining layer.

Furthermore, the sputter target of the present invention has a high sputter rate, and the cost in the protective film forming step can be reduced.

Further, even after long-time film formation, there was no change in the composition of the target and the characteristics of the sputtered film.

Although the thermal head has been described in this embodiment, the sputter target of the present invention is not limited to the above-described thermal head, but may be a protective film for a thermal head using an Al ₂ O ₃ substrate or a protective film for a magneto-optical disk. It is also effective when forming.

[Effects of the Invention] As described above, according to the present invention, a sputtered film having high hardness and high toughness can be obtained, and thereby a highly reliable wear-resistant film can be provided. Further, a thermal head using this wear-resistant coating as a protective film can suppress cracks and the like of the protective film, and thus can exhibit stable and excellent printing performance.

Further, the sputter target of the present invention is excellent in composition stability and the like, and thus is excellent in sputter rate, whereby cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a view showing a thermal head using a wear-resistant coating of the present invention as a protective film. 1 ... metal substrate, 2 ... heat insulating layer, 3 ... underlayer, 4 ...
Heating resistor, 5 ... Heating section, 6 ... Individual electrode, 7 ... Common electrode, 8 ... Protective film.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-189253 (JP, A) JP-A-59-148002 (JP, A) Jpn. Field (Int.Cl. ⁶ , DB name) B41J 2/335 C23C 14/34

Claims (4)

(57) [Claims] (1) containing at least one kind selected from titanium oxide, zirconium oxide and hafnium oxide (excluding the case of zirconium oxide alone) in an amount of 1 mol% to 40 mol%, and the balance substantially consisting of silicon nitride; A sputter target characterized by the following. 2. At least one selected from titanium oxide, zirconium oxide and hafnium oxide in an amount of 1 mol% to 40 mol.
% And at least one selected from yttrium oxide and aluminum oxide (excluding the use of zirconium oxide alone when yttrium oxide is used alone) 0.05 mol
% To 10 mol%, with the balance substantially consisting of silicon nitride. 3. A wear-resistant coating comprising a sputtered film formed by using the sputter target according to claim 1 or 2, wherein at least a part of its structure is in an amorphous state. Coating. 4. A support base having a heat-resistant resin layer, a heating resistor layer disposed on the heat-resistant resin layer, and an electrode conductor provided on the heating resistor layer for supplying power to the heating resistor. A thermal head having a layer and a protective film for protecting the heating resistor and the electrode conductor layer, wherein the protective film is constituted by the wear-resistant coating according to claim 3.