JPH08290599A - Thermal print head and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a long-life thermal head wherein an increase in the resistance of a heating resistor is small and stable. CONSTITUTION: A substrate 1, a backing layer 3 which is made of an oxide ceramic located on the substrate 1, multiple heating resistors 4 placed on the backing layer 3, electrodes 5, 6 connected with the heating resistors 4, and a protective layer 7 covering at least the heating section of the heating resistors 4 are provided, and the composition ratio of non-oxide components and oxygen of the oxide ceramic forming the backing layer 3 represents an oxygen deficient state against the stoichiometry of 100% in the oxidation rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-definition type thermal head having a high energy density applied to a heating resistor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Thermal heads have the advantages of low noise, easy maintenance, and low running costs. For this reason, fax machines, word processor printers, etc.
It is used in various recording devices. Also, 400dp
High-definition type thermal heads exceeding i (dots per inch) are also used for stencil printing. By the way, in such a high-definition type thermal head, in order to improve the resolution, it is required to miniaturize the shape of the heating resistor and increase the input energy density.

When the heating resistor is miniaturized and the input energy density increases, the peak heating temperature of the heating resistor rises. This promotes diffusion of impurities from the underlying glaze layer in contact with the resistance film. As a result, the resistance value of the heating resistor may increase during operation, and may exceed the specified resistance value, making it unusable for use.

In order to eliminate such a problem, for example,
Between the glaze layer and the resistance film, SiNxOy (0.2 <
There is a method of suppressing the diffusion of impurities from the glaze layer to the resistance film by providing a layer of x <1.1, 0.2 <y <1.8) (for example, refer to JP-A-61-297159). There is also a method of using ceramics of oxides and nitrides for the underlayer of the thermal head.

[0005]

The conventional thermal head described above is, for example, in terms of the underlayer, from the viewpoints of suppressing the diffusion of impurities from the glaze layer to the resistance film and ensuring the adhesion between the layers. Has been formed.

However, the inventors of the present invention prototyped devices using various materials for the underlayer and the resistance film, and confirmed the characteristics thereof, and found that the underlayer and the protective layer were as follows. There was a problem.

1) When the base layer and the protective layer are oxides: When the applied power density is large, the resistance value of the heating resistor is likely to increase with the lapse of operating time. For this reason, the resistance value deviates from the standard, and a predetermined density cannot be obtained during printing.

2) When the underlying layer or the protective layer is a nitride or a nitride oxide When the underlying layer or the protective layer is formed by a thin film forming method such as a sputtering method, the nitride or the nitride oxide is unbonded as compared with the oxide. Film defects such as hands are likely to occur, and the film stress increases. For this reason, process defects are likely to occur due to peeling at the film interface or deformation of the substrate due to film stress. Further, when forming a target, a nitride or a nitride oxide is inferior in sinterability to an oxide, and its composition is difficult to control.

The above description is for the base film located below the heating resistor. However, the same problem occurs with the protective film located above the heating resistor.

An object of the present invention is to solve the above-mentioned drawbacks, and an object thereof is to provide a thermal head having a small increase in the resistance value of the heating resistor, a stable and long life, and a method for manufacturing the same.

[0011]

According to the present invention, a substrate, a base layer made of oxide ceramics, which is located on the substrate, a plurality of heating resistors located on the base layer, and a connection to the heating resistor. In the thermal head including an electrode for protecting the heat generating resistor and a protective layer formed so as to cover at least the heat generating portion of the heat generating resistor, the oxide ceramics forming the underlayer has a composition ratio of an oxidizable component and oxygen. , Oxidation rate 10
It is characterized by being in an oxygen deficient state for 0% stoichiometry.

The substrate, a plurality of heat generating resistors located on the substrate, electrodes connected to the heat generating resistors, and a protective layer formed so as to cover at least the heat generating portion of the heat generating resistors. In the thermal head described above, the oxide ceramic forming the protective layer is characterized in that the composition ratio of the component to be oxidized and oxygen is in an oxygen-deficient state with respect to stoichiometry with an oxidation rate of 100%.

The oxide ceramics constituting the underlayer or the protective layer are characterized by being composed of Si and O and having an atomic concentration ratio of O to Si of 1.8 or less.

In the method of manufacturing a thermal head, a base layer, a heating resistor, an electrode connected to the heating resistor, and a protective layer covering at least the heating portion of the heating resistor are sequentially formed on the substrate. The oxide ceramics forming at least one of the ground layer and the protective layer is formed by a sputtering method using a target containing an oxygen-deficient oxide.

[0015]

The present invention has solved the problem of increased resistance when an oxide is used for the underlayer and the protective layer. That is,
It is thought that the main cause of the increase in the resistance value during the operation of the thermal head is the solid phase diffusion of the constituent elements of the underlayer-resistive film layer, the resistive film layer-the protective layer, or the reaction after the diffusion, Then, a simple modeling was performed to analyze these phenomena. For example, various inorganic oxide films were used as bases, and various resistance films were formed thereon to form a structure. Then, these structures were subjected to heat treatment, and changes in sheet resistance and composition of the resistance film were confirmed. In this case, the forced heating condition was 800 ° C., and heating in vacuum for 30 minutes was used.

According to the results, when the composition ratio of the positive element of the oxide used in the underlayer and oxygen is stoichiometric or close to this, the oxygen-deficient state after heat treatment is more It was found that the increase in the sheet resistance value of the resistance film was small.

In particular, when the oxygen content of the oxide forming the underlayer is substantially equal to or less than the oxygen content of the resistance film, the sheet resistance value of the resistance film does not increase after the heat treatment. I could hardly see it.

Here, FIG. 2 shows an experimental result of a structure in which a cermet resistance film containing Si, O and Ta as a main component is formed on an underlayer containing Si and O as a main component. Figure 2
The horizontal axis represents the O / Si composition ratio of the underlayer, that is, the atomic concentration ratio, and the vertical axis represents the change rate of the sheet resistance value of the resistor layer before and after heating. In this case, the oxygen content of the underlayer was determined by the relative sensitivity method by analyzing each film by X-ray photoelectron spectroscopy (hereinafter referred to as XPS). Furthermore, the composition change in the resistance film before and after the heat treatment was also analyzed by XPS. According to the results, the greater the degree of increase in sheet resistance after heat treatment, the greater the oxygen content in the resistance film, and the relative content of oxidizable components such as Si and Ta (Nb). Was falling to.

The above-mentioned heat treatment test involves the diffusion of constituent elements between the underlayer and the resistance film when the thermal head operates, or between the resistance film and the protective layer having the opposite layer structure, and the reaction after the diffusion. It is considered that the experiment was simplified and evaluated. These experimental results suggest that it is necessary to limit the oxygen concentration in the underlayer and the protective layer in order to suppress the increase in the resistance value during the operation of the thermal head.

By the way, the sputtering method and plasma C
In the case of forming a thin film of an inorganic oxide by the VD method, the composition ratio of the metal element and oxygen has heretofore been set to stoichiometry or close thereto in terms of the stability of the material composition. However, according to the experimental results, it can be said that the oxygen-deficient state is rather desirable when the underlayer and the protective layer of the thermal head are formed.

Therefore, according to the present invention, when the underlayer or the protective layer is formed, an oxide target in an oxygen-deficient state is used instead of an ordinary oxide target close to an oxygen saturated state by stoichiometry. . If sputtering is performed with an inert gas such as Ar that is generally used, a film having a composition that almost reflects the target composition is obtained. Therefore, when forming an oxygen-deficient film, it is considered necessary to use an oxygen-deficient oxide for the target itself, and the present invention uses an oxygen-deficient oxide target.

In forming an Amorphous thin film by sputtering or the like, from the viewpoint of binding energy,
It is expected that oxygen will preferentially proceed from the site where the bond with the oxidizable component is stable. Therefore, it is considered that when the oxygen content approaches stoichiometry, the bond-unstable oxygen content rapidly increases. Conversely speaking, even if the oxygen deficiency from stoichiometry is in a small range,
It is considered that the bond-unstable oxygen amount sharply decreases, and the effects of the underlayer and protective layer according to the present invention are exhibited.

[0023]

Embodiments of the present invention will be described with reference to FIG. 1 is a substrate made of Al ₂ O ₃ , on the substrate 1,
A glass glaze layer ₂ containing SiO ₂ as a main component and having a thickness of 60 μm is formed. The substrate 1 is not limited to Al ₂ O ₃ , but various metals and nonmetals are used. The glass glaze layer can also be selected from those containing various additive materials.

Next, an underlayer 3 containing Si and O as main components was formed on the heat-resistant resin substrate having the above structure by a sputtering method under a plurality of conditions shown in Table 1.

In this case, the targets are Si and SiO ₂
The powder was mixed at a molar ratio of 1: 1, hardened by hot pressing, and then sintered in a non-oxidizing atmosphere.

Table 1: Sputtering conditions Target input power density: 4.3 W / cm ² Sputtering gas and flow rate: Ar ... 24 sccm O ₂ ... (a) 0.0 sccm (b) 1.2 sccm (c) 2.4 sccm (d ) 3.6 sccm (e) 4.8 sccm (f) 6.0 sccm Sputtering pressure: 3.0 × 10 ⁻¹ Pa Substrate heating temperature: 220 ° C. O ₂ flow rate when forming the underlayer is from (a) to (). The film composition was analyzed by XPS (ESCA) relative sensitivity method with 6 levels of f). The value of the film composition is 1 from the surface of the underlayer.
The depth profile up to 200 nm is taken in steps of 0 nm, and the respective compositions are averaged. The results are shown in Table 2.

Table 2: Film composition of base layer Condition O ₂ flow rate Si ₂ O C O / Si ratio (a) 0.0 sccm 55 44 1 0.8 (b) 1.2 sccm 50 49 1 0.98 (c) 2 .4 sccm 45 54 1 1.2 (d) 3.6 sccm 40 59 1 1.48 (e) 4.8 sccm 35 64 1 1.83 (f) 6.0 sccm 33 66 1 2.0 On this underlayer 3. In addition, the Nb—SiO ₂ -based heating resistor 4, and the individual electrode 5 and the common electrode 6 made of Al.
Was formed. A mixed acid of phosphoric acid, acetic acid and nitric acid was used for etching the Al electrode layer. In addition, Nb-S
The CDE method was used for etching the iO ₂ resistance film. In this example, CF ₄ and O ₂ were used as introduction gases, and the ratio thereof was 7: 3. The materials for the heating resistor and the electrodes are not limited to these. Further, various process techniques are used for the film forming method and the patterning method.

Next, most of the individual electrodes 5 and the common electrode 6,
Then, a SiON protective film 7 having a film thickness of 3 μm was formed by a sputtering method so as to cover the heating resistor.
In this case, the protective film 7 is formed so as to cover at least the heat generating portion of the heat generating resistor located between the individual electrode 5 and the common electrode 6.

Regarding the prototype constructed by the above method,
After passing through the mounting process, it was subjected to a power resistance performance test. The results are shown in Table 3 below. Table 3: Evaluation results Conditions (a) (b) (c) (d) (e) (f) Power resistance ○○○ □□ △ × ○ is good, and in the following order is □, △, ×.

The above description is based on the case where Si--O based oxide ceramics is used for the underlayer and when the oxygen concentration of Si--O is in an oxygen deficient state as compared with stoichiometric SiO _2. The result is excellent power. It should be noted that the same tendency is obtained when Si—O oxide ceramics is used for the protective layer.

As the inorganic ceramic material, Al-
Similar results are obtained when other oxides such as O-based, Al-Si-O-based, and Zr-O-based are used.

[0032]

According to the present invention, it is possible to realize a thermal head with improved power resistance.

[Brief description of drawings]

FIG. 1 is a schematic structural view showing an embodiment of the present invention, in which a part is shown in an exploded view.

FIG. 2 is a diagram illustrating characteristics of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Glass glaze layer 3 ... Underlayer 4 ... Heating resistor 5 ... Individual electrode 6 ... Common electrode 7 ... Protective film

Claims (4)

[Claims] 1. A substrate, an underlayer made of oxide ceramics, which is located on the substrate, a plurality of heating resistors located on the underlayer, electrodes connected to the heating resistors, and the heating resistor. A thermal head having a protective layer formed so as to cover at least the heat-generating portion of the oxide ceramics constituting the underlayer, the stoichiometric composition in which the composition ratio of the oxidizable component and oxygen is 100%. A thermal head that is in a state of oxygen deficiency with respect to measurement. 2. A substrate, a plurality of heat generating resistors located on the substrate, electrodes connected to the heat generating resistors, and a protective layer formed so as to cover at least a heat generating portion of the heat generating resistors. In the thermal head described above, the oxide ceramic forming the protective layer is characterized in that the composition ratio of the component to be oxidized and oxygen is in an oxygen-deficient state with respect to stoichiometry with an oxidation rate of 100%. head. 3. The oxide ceramics constituting the underlayer or the protective layer is composed of Si and O, and O with respect to Si.
3. The thermal head according to claim 1 or 2, wherein the atomic concentration ratio is 1.8 or less. , 4. A method of manufacturing a thermal head, wherein a base layer, a heating resistor, an electrode connected to the heating resistor, and a protective layer covering at least a heating portion of the heating resistor are sequentially formed on a substrate. A method of manufacturing a thermal head, characterized in that the oxide ceramic forming at least one of the formation layer and the protective layer is formed by a sputtering method using a target containing an oxygen-deficient oxide.