JPS6013567A - Thermal head - Google Patents

Abstract

PURPOSE:To attain to prolong the life of a thermal head, by laminating a chemical resistant protective film to the anti-wear protective film formed to aluminum oxide. CONSTITUTION:A heat generating resistor layer 3 and a first and a second conductors 4, 5 are covered with an anti-wear protective film 9 formed of aluminum oxide and this film 9 is further coated with a chemical resistant film 51 comprising metal oxide or metal nitride such as Ta2O5, SiO2 or Si3N4. By this constitution, the elongation of the life of a thermal head is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal head, and more particularly to a wear-resistant protective film deposited on a heating resistor and an electrical conductor thereof.

[Technical background of the invention and its problems]

As is generally known, a thermal head, which is formed by forming a film of multiple heat generating resistors and their wiring on an insulating substrate, converts an input electrical signal into a thermal signal, and a thermal head that is in contact with the heat generating dots. to develop color. As a result, an image is formed on the thermal paper based on electrical signals. The heat generating portion of such a thermal head, which is made up of a heat generating resistor, is constructed as shown in FIG. 1, which is a cross-sectional view in the wiring direction.

In FIG. 1, a heating resistor layer (3) is formed on an etching-resistant base film (hereinafter referred to as base film) (2) formed on an insulating substrate (1) made of a glazed alumina substrate. A first electrical conductor (4) having a thickness of about 1000X is formed by exposing a part of this heating resistor layer (3) and depositing an active metal such as chromium or titanium. At this time, the exposed portion of the heating resistor layer (3) becomes a heating section (6). This first electric conductor (4) and the heat generating part (6
) A second electrical conductor (5) made of, for example, gold is formed on the first electrical conductor (4) except for a portion (8) of several hundred microns to approximately one degree from the boundary (7) with the first electrical conductor (4). has been done. Further, a wear-resistant protective film (9) is applied to cover the first electric conductor, the second electric body, and the heat generating portion (6).

Generally, the material for the wear-resistant protective film (9) is BF21.
.

Ta205 + S + Cr and 813 N4 are used.

BT'Si was produced by CVD method (C11<em>C11e Vapo
The film is formed by raised deposition. However, in the CVD method, a high-quality film cannot be deposited unless the substrate temperature is raised when depositing a film on the substrate.For this reason, when the substrate temperature is raised, the other heating resistor layer (3), the first electrical conductor layer ( 4) and the second electrical conductor (5), there is a risk that the performance will be reduced due to heat diffusion. Also, Ta205, SIC
, 5i3N, are formed into films by high frequency sputtering. However, methods using high frequency sputtering have a general problem of slow film formation rate and extremely low productivity.

For example, when forming a Ta, O film, 24
A high frequency sputtering device that can mount 20 substrates of size 0mtn
To form the B film, a planetary rotation method is used. Then, this high-frequency sputtering equipment itself becomes quite large and the distance between the target and the substrate becomes large, so even when using a high-frequency magnetron sputtering equipment, the maximum thickness of the Ta2O film is 100×/mi.
It can only be n. Therefore, the thickness of the wear-resistant protective film (9) is generally required to be 3 μm or more, so Ta, 05
The film formation time requires 5 hours or more, resulting in very low productivity.

Next, with reference to FIG. 2, the relationship between the applied power and the change in resistance value will be explained when a Stemp stress test is performed on a thermal head whose wear-resistant protective film is made of Ta20L. The vertical axis represents the rate of change in the resistance value R of the heating resistor, and the horizontal axis represents the rate of change applied to the heating resistor per dot. The characteristic curve (L]) is for Ta 20 with a film thickness of 28 μm.
The characteristics of the wear-resistant protective film of S film are shown, and the characteristic curve (12
The film thickness is 1500× S; 28 μmn Ta on the 02 film.
Characteristic curve showing the characteristics of the wear-resistant protective film laminated with 205 film (131 is StO with a film thickness of 0.5 μm, 3 μm thick on the film)
Q) It shows the characteristics of a wear-resistant protective film laminated with Ta20B film.

The characteristic curve (1) shows that when the applied power increases with only the Ta2O film, the rate of change in the resistance value of the heating resistor starts to increase halfway through. This is because the heating resistor was oxidized since the Ta 10 B film did not have the property of blocking oxygen. Therefore, with only the Ta205 film, the heating resistor is oxidized and it is difficult to apply high power to the heating resistor.

In addition, as is clear from the characteristic curve ((η) and the characteristic curve side, the 810□ film is interposed between the Ta1O1 film and the heating resistor, and as the number of 810. films is gradually increased, the oxidation prevention of the heating resistor In practical use, 8i0.' with a film thickness of 2 μm improves the im capacity and makes it possible to apply high power.
It is preferable to form a Ta205 film with a thickness of 3 μm on top.

8i0. It is unavoidable that the film forming time will be longer due to the fact that the film is formed with a thickness of 2 μm.
The film formation time with the μm Ta205 film is more than 10 hours, which is a major reason for the low productivity of the substrate.

In addition, the Ta206 film has the advantage that it does not crack due to high-speed thermal cycles, but the wear rate of the Ta2O film is 0.
．． Even if the film thickness is as large as 0.05 μm to 0.1 μm/km and the film thickness is 3 μm, if a 30 km to 60 km thermal head runs on the thermal paper, the heating resistor will be exposed.
There is a problem that oxidation of the heating resistor occurs. This is usually 10
This is a fatal drawback for thermal heads that are required to travel from 0 km to 200 km.

Furthermore, the wear-resistant protective film made of 8iC, St, and N has a remarkable tendency to crack due to high-speed thermal cycling. For this reason, in a thermal head with a crack, oxygen enters through the crack and oxidizes the heating resistor.
There is a problem that the thermal head cannot record.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a thermal head with a long life.

[Summary of the invention]

In order to achieve the above object, the wear-resistant protective film of the present invention is made of an aluminum oxide film, so that the wear-resistant protective film can have both anti-oxidation function and wear resistance.

[Embodiments of the invention]

Embodiments of the thermal head of the present invention will be described below with reference to FIG. Note that the same reference numerals are used for parts equivalent to those in FIG.

In Fig. 3, T
A heating resistor layer (3) made of a-8!02 or the like is formed. A first electrical conductor (4) made of chromium or the like is formed by exposing a portion of this heating resistor layer (3).

At this time, the exposed portion of the heating resistor layer (3) is replaced by the heating section (
6). This N & 1 electric conductor (4) and the heating part (
6) at the boundary with the force (from several hundred microns to approximately 1 mrn
A second electrical conductor (5) made of aluminum or the like is formed on the first electrical conductor (4) except for the second electrical conductor (8). Further, the film thickness is approximately 1 mm so as to cover the first electric conductor (4), the second electric conductor (5), and the heat generating part (6).
Aluminum oxide (hereinafter referred to as kl, 0
, a wear-resistant protective coating (9) is applied.

Next, with reference to FIG. 4, the oxidation prevention function of Al, O, and films will be explained.

FIG. 4 shows the results of a step stress test of a thermal head using an Al2O film with a thickness of 0.5 μm as a wear-resistant protective film. Furthermore, the positive direction of the vertical axis indicates the coloring density of the thermal paper, the negative direction of the vertical axis indicates the rate of change △几/R of the resistance value R of the heating resistor, and the horizontal axis indicates the change in the heating resistor per dot. Indicates the applied power of Characteristic curve t3
1) shows the color density depending on the power applied to the heating resistor per one dot of a thermal head using a 0.5 μm thick hll@O@ film as an abrasion-resistant protective film. Then, when the applied power is about 0.9 W/Do or more, the increased color density shows a constant value.

Characteristic curve (η is 1 (・: γ The resistance value of the heating resistor depending on the power applied to the heating resistor per dot of the thermal head with a 0.5 μm thick A08 film as a wear-resistant protective film) R and /R are shown for the rate of change.In other words, as is clear from the characteristic curve, as the applied power increases, the rate of change of the resistance value of the heating resistor of the Al2O5 film also changes in the same way (two changes. With an Al thickness of 0.5 μm and a wear-resistant protective film of 0.0 μm, it is possible to obtain extremely stable coloring density without being placed on the heating resistor at an applied power of 1.7 W/Do or less.

First, with reference to Table 1, the wear resistance rate of a thermal head using a wear-resistant protective film made of 1 tOs will be explained. The film thickness of the Al2O film was 3 μm, and the applied power was 0.9 to V/I)ot under the same recording conditions as the conventional technology.
The thermal paper was run for 35 I (m) and recorded.

(Batch 4f, white) As is clear from Table 1, the wear rate of the Al2O3 film is 0.014 μrn/km, and the wear rate of the Ta205 film is 0.05 μm11 to 01 μrm/km. I'm 11. Therefore, the A, 7, 03 films are hard and have excellent wear resistance.

Next, the crack resistance of the wear-resistant protective film will be explained with reference to FIG. At this time, the property of resisting cracks caused by high-speed thermal stress is defined as crack resistance. In FIG. 5, the gentler the slope of the straight line, the better the crack resistance. Comparing J, O, with other materials, BP8i*'l°a, 0°≧k120. ) S
iC) Si and then N4, and it is clear that Alto 3 is also superior. That is, Al, 0. The abrasion-resistant protective film made of this material has excellent crack resistance and can sufficiently withstand high-speed thermal stress.

However, although the Al2O film is excellent as a wear-resistant film for a thermal head, it is inferior in chemical resistance. That is, since Al2O is attacked by anodic acid, hydrofluoric acid, sodium hydroxide, etc., restrictions are placed on the manufacturing process of the thermal head. In particular, when the electrical conductor material of the thermal head is aluminum, the etching solution for aluminum is based on positive acid, which may present a fatal drawback.

Another embodiment of the thermal head that avoids this drawback is shown in the sixth example.
This will be explained with reference to the figures.

The thermal head shown in FIG. 6 has a wear-resistant protective film (51) made of Ta2O+3 or the like with a film thickness of 1 μm formed on the wear-resistant protective film (9) of the thermal head shown in FIG. There is. This chemical-resistant protective film (51) is chemically stable and has excellent resistance to chemicals ('-,).

In particular, the chemical-resistant protective film made of Ta and O is chemically stable and has excellent resistance to chemicals such as anodic acid, hydrofluoric acid, and sodium hydroxide. That is, this hl, o,
When a Ta10B film with a film thickness of approximately 1 μm or less is formed on the film, in the subsequent thermal head manufacturing process, even if anodic acid-based chemicals are used as an etching solution, Kl, O,
The film is not damaged, and electrical conductors made of aluminum, for example, can be formed without any problem, and a high-quality thermal head can be completed.

Next, the effects of the chemical-resistant protective film will be described with reference to FIGS. 7(a) and 7(b).

In the enlarged view of the thermal head at the center of the heat generating part shown in FIG. Thermal heat rad, which has only an abrasion-resistant protective film consisting of
After being crushed for a minute, the heating resistor (61) and the electrical conductor (6
2) Direction (66
) with a hitsuki line (63) added.

Then, A2,0. The membrane (62) has crumbled to pieces, and the underlying thin film is adversely affected. Note that (65) is after AI, 0 and the film (62) have collapsed.

In the enlarged view of the thermal head at the center of the heat generating part shown in FIG.
The heating resistor (71) was eroded for 10 minutes by a thermal head of anodic acid using the mno Ta20B film as a chemical-resistant protective film.
A wire (74) is inserted onto the electric conductor (72) using a diamond needle in the direction (73) with a load of 5 g. @7 As is clear from Figure (b), the abrasion-resistant protective film made of u and Og remains intact, and the functions of the AI, o, and film are fully exerted when the thermal head is used thereafter. Ta.

Therefore, on the wear-resistant protective film made of Al, 03 film, T a! In the thermal head shown in FIG. 6 provided with a chemical-resistant protective film made of Os or the like, the AI and 03 films are not corroded by chemicals, so there are no restrictions on the manufacturing process. In addition, by using this chemical-resistant protective film made of Ta2O, etc., when the main component of the electrical conductor is aluminum, it protects the electrical conductor from chemical corrosion, so there is no need to use noble metals for the electrical conductor as in the past. This has the effect of reducing the unit cost of the thermal head.

Note that when using the thermal head shown in Figure 6, the Ta20B film is thin and will wear out in a relatively short period of time;
Since the Al, O, and films under the Ta205 film function as wear-resistant films and anti-oxidation films, the thermal head shown in FIG. 6 has a longer lifespan than conventional thermal heads.

Next, an embodiment of the method for manufacturing a thermal head of the present invention will be briefly described.

In Fig. 3, an etching-resistant base film (2) is formed on a glaze layer (2) on a substrate with good thermal conductivity and flatness and strong mechanical strength, such as an alumina substrate (1).
A Ta1O1 film is then deposited, for example, by electron beam evaporation. A heat generating resistor layer (3) made of fly-8i02 or the like is deposited on the surface of this etching-resistant base film (2) by sputtering. Next, for example, chromium and aluminum are laminated and deposited to a thickness of 2000× and 2 to 3 ttm, respectively, by vacuum evaporation or sputtering. Next, a second plate made of aluminum is formed using a method such as PEP.
electrical conductor (5), a first electrical conductor (4) made of chromium
), and the heat generating resistor layer (3) are etched into stripes according to an electrical conductor pattern.

Next, by a method such as PBP, the aluminum is removed at a certain distance from the part that will become the heat generating part (6) and its boundary to expose the chromium. Next, the heat generating part (6) is removed by the chromium PEP@ method to expose the heat generating part (6). removing the resist, a first electrical conductor (4);
A wear-resistant protective film (9) is formed by depositing an AI, 08 film with a film thickness of approximately 1 μm to approximately 5 μm by electron beam evaporation so as to cover the second electrical conductor (5) and the heat generating portion (6). do. In this way, a thermal head having the shape shown in FIG. 3 is completed.

Furthermore, by forming a chemical-resistant protective film (51) such as a Ta205 film having a film thickness of approximately 1 μm or less on the wear-resistant protective film (9), a thermal head having the shape shown in FIG. 6 is completed.

Note that the chemical-resistant protective film (51) only needs to be present during the manufacturing process of the thermal head, so the film thickness is approximately 1 μm.
If J2 is below, it is sufficient in view of the film formation time.

A7,0 of the present invention. When the film is formed by electron beam evaporation, the film formation rate is substantially an order of magnitude higher than that of conventional sputtering, which improves productivity. It has the effect of improving sex. Additionally, if electron beam evaporation is used, a chemical-resistant protective film (
51) can also be deposited with good productivity in the same way as kl, O, and films. In addition, although the thermal head manufacturing method of the present invention has been described as a method of forming by electron beam evaporation method,
Needless to say, the same effect can be obtained by the ion blating method.

〔Effect of the invention〕

As detailed above, according to the thermal head of the present invention,
Since the abrasion-resistant protective film made of AA203 has both an anti-oxidation function and an abrasion-resistant function, extremely stable printing operation can be performed.

[Brief explanation of drawings]

Figure 1 is a sectional view of the main parts of a conventional thermal head;
The figure is a characteristic diagram showing the results of a step stress test using the thermal head shown in Figure 1, Figure 3 is a cross-sectional view of essential parts showing an embodiment of the thermal head of the present invention, and Figure 4 is Figure 3. Figure 5 is an explanatory diagram illustrating the crank resistance of the wear-resistant protective film of the thermal head shown in Figure 3, Figure 6 is a characteristic diagram showing the results of a step stress test using the thermal head shown in Figure 3. FIGS. 7(a) and 7(b), which are sectional views of main parts showing other embodiments of the thermal head of the present invention, are explanatory diagrams illustrating the effect of the chemical-resistant protective film. (1)...Alumina substrate, (3), (61), (7
1)...heating resistor layer (4)...first electric conductor,
(5)...Second electrical conductor (9)...1IiFl abrasive protective film, (51)...Chemical resistant protective film type J″l
! Person Patent Attorney Noriyuki Chika (one idiot) Figure 5 Figure θ Figure 7 (1st:, N procedural amendment (voluntary) 115 7. Alumnus Commissioner of the Patent Office Mr. 2, Famous appearance of the invention, Relationship with Teamal Head 3 and the amended case Applicant (307) Tokyo Shibaura Electric Co., Ltd. 4, Agent 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Higashi 100 (1) Scope of claims in the specification Column 6, Contents of amendment (1) The scope of claims column of the specification is amended as shown in the attached sheet. (2) The detailed description of the invention in the specification is amended as follows in 4I!lt. (1) On page 16 of the specification, lines 5 and 6, the phrase "Not. [Effects of the invention]" is replaced with "Not." Further, the wear-resistant protective film (51) is a Ta, O. film. However, films made of metal oxides or sulfides may also be used.For example, when using a Sio film, there are restrictions on the chemicals it can withstand, and it is attacked by diluted acids and diluted nitric acids. It is not appropriate to use chemicals. However, since the film is resistant to acids, it is possible to use aluminum as the material for the electrical conductor. Teha A
i! 's abrasion-resistant protective film (9) is applied, and the third
It is exactly the same until you complete the Cheemal Helad in the shape shown in the figure. On this wear-resistant protective film (9), the film thickness is substantially 1.
A chemical-resistant protective film (9) is formed by adhering a film of sin of less than μm. Examples of metal nitrides are Si and N. etc. Alternatively, organic coatings, such as organic films, can be used as chemically resistant overcoats. In this manufacturing method, an organic material dissolved in a solvent is applied to a thermal head and cured to form an organic film. As this organic film, for example, photoresist (both positive and negative are effective), polyimide, epoxy, Teflon, silicone resin, etc. can be used. In this case as well, if it can withstand the chemical process, its role as a chemical-resistant protective film is completed, and the AJI03 film fulfills its function as an abrasion-resistant protective film during recording. [Effects of the invention]”. Claims (1) An insulating substrate, a heating resistor selectively disposed on a selected surface of the insulating substrate, an electrical conductor connected to the heating resistor, and the heating resistor. and a thermal head comprising an abrasion-resistant protective film deposited to cover part or all of the electrical conductor, wherein the abrasion-resistant protective film is made of an aluminum oxide film. head. (2) The thermal head according to claim 1, wherein a chemical-resistant protective film is laminated and adhered on the aluminum oxide film. (3) The thermal head according to claim 1, wherein the aluminum oxide film is formed by an electron beam evaporation method or an ion blating method. (4) The chemical-resistant protective film is Tame, , 8i0
2. Si/J. The thermal head according to claim 2, characterized in that: (6) The thermal head according to any one of claims 1 to 5, wherein the main material of the electric conductor is aluminum. Procedural amendment (voluntary) 8/92/1932 Commissioner of the Japan Patent Office 2 Name of the invention Thermal head 3 Relationship to the case of the person making the amendment Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. 4 Agent 〒 100 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Column 6 of the detailed explanation of the invention in the specification, Contents of the amendment The column of the detailed explanation of the invention in the specification is amended as follows. (1) Specification, page 15, line 10, 1...Thermal head is completed. "...Thermal head is completed. At this time,
After the wear-resistant protective film (9) made of Ad, OB film is deposited by electron beam evaporation or ion blating, the chemical-resistant protective film (51) is also deposited by electron beam evaporation, ion blating, or Alternatively, it can be formed by a sputtering method or the like. ” he corrected. that's all

Claims (5)

[Claims] (1) An insulating substrate, a heating resistor selectively disposed on a selected surface of the insulating substrate, an electrical conductor connected to the heating resistor, and a portion of the heating resistor and the electrical conductor. 1. A thermal head comprising an abrasion-resistant protective film deposited to cover part or all of the thermal head, wherein the abrasion-resistant protective film is made of an aluminum oxide film. (2) Claim 1, characterized in that a chemical-resistant protective film is laminated and adhered on the aluminum oxide film.
Thermal head described in section. (3) The thermal head according to claim 1, wherein the aluminum oxide film is formed by an electron beam evaporation method or an ion blating method. (4) The thermal head according to claim 2, wherein the chemical-resistant protective film is a Ta10B film. (5) The thermal head according to any one of claims 1 to 4, wherein the main material of the electric conductor is aluminum.