JPS63197665A - Thermal head and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a projected type thermal head having favorable thermal transfer efficiency, excellent environmental resistance, excellent abrasion resistance and a long useful life, by providing a dot part protective layer comprising a product obtained by a chemical vapor deposition method, on the heat generating parts of a resistance heat generating element layer. CONSTITUTION:A dot part protective layer 10 is provided on heat generating parts 4a of a resistance heat generating element layer 4, with a protective layer 6 therebetween. The protective film 10 is provided in a thickness of 2 mum, and heat generating dot parts A are projected above the surrounding part due to the presence of the layer 10. The protective layer 10 is formed of diamond. The dot part protective layer 10 is provided in the state of filling each recess 9 provided in the surface of the protective layer 8 at the part between a discrete electrode 5a and a common electrode 5b, which constitute a current- supplying conductor layer 5, namely, at the heat generating part 4a of the resistance heat generating element layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a thermal head used in a thermal printer, a thermal transfer printer, etc., and a method for manufacturing the same.

"Conventional technology" FIG. 10 shows a conventional thermal head.

In this thermal head, an approximately hemispherical glass glaze layer 2 is partially formed on the surface of an insulating substrate 1 made of alumina or the like, and an undercoat layer (not shown) made of tantalum oxide or the like is formed on top of the glass glaze layer 2. The resistive heating element layer 4 is made of a two-component material of tantalum/nitrogen or a ternary material of tantalum/tungsten/nitrogen, and the protective layer 6 is made of an oxide material such as silicon dioxide. It is formed by a prevention layer 7 and a wear-resistant layer 8 made of tantalum oxide or the like. In addition, the power feeding conductor layer 5 is
It is formed from an individual electrode 5a and a common electrode 5b, and the portion of the resistance heating element layer 4 sandwiched between the individual electrode 5a and the common electrode 5b serves as a heat generating portion 4a. The position where this heat generating portion 4a exists is a heat generating dot portion A of this thermal head.

In this thermal head, when electricity is applied to the power supply conductor layer 5, the heat generating portion 4a between the individual electrodes 5a and the common electrode 5b generates heat, and this heat is transferred from the heat generating dot portion A to the thermal paper etc. as thermal energy for coloring. Supplied as.

"Problems to be Solved by the Invention" However, such conventional thermal heads have the following problems.

(I) Since the power supply conductor layer 5 is disconnected from the individual electrodes 5a and the common electrode 5b above the heat generating portion 4a of the resistance heating element layer 4, there is a concave portion approximately corresponding to the thickness of the power supply conductor layer 5. 9 is formed in the heating dot part A, and as a result,
A gap is created between the heating dot portion A and the thermal paper, etc., and the efficiency of heat transfer to the thermal paper, etc. is reduced.

(II) In addition, in the conventional thermal head described above, the protective layer 6 is formed by coating tantalum oxide or silicon dioxide by sputtering, so pinholes are prevented from forming in the protective layer 6. Since oxidation of the resistive heating element layer 4 easily progresses through these pinholes, there is a problem in that the environmental resistance of the thermal head cannot be sufficiently improved.

(I[r) Furthermore, in the conventional thermal head described above, the protective layer 6 is formed by a sputtering method 1, and the protective layer 6 is formed at a temperature lower than the temperature of the heating dot part A when the thermal head is used. As a result, heat resistance was insufficient, and changes occurred in the protective layer 6 over time as the thermal head was used, making it impossible to extend the life of the thermal head sufficiently.

In addition to the above-mentioned thermal head, a wear-resistant layer is formed only on the heat-generating dot part A to make the heat-generating dot part protrude, and the above (1) is applied.
A thermal head has been proposed that addresses this problem. However, since such a thermal head uses a photoresist or uses a foot-off method to partially form a wear-resistant layer, it requires a complicated manufacturing process and has the problem of rising manufacturing costs. Furthermore, as a result of using a photoresist, the film formation temperature is limited, and as a result, the strength of the wear-resistant layer cannot be sufficiently increased. Furthermore, according to the lift-off method, the thickness of the wear-resistant layer formed on the heat-generating dots A is limited to a maximum of about 1μ, which is insufficient to compensate for the depth of the recesses 9 of the heat-generating dots A. Ta.

On the other hand, a thermal head in which a protective layer 6 made of diamond is formed on the entire surface has been proposed in order to improve wear resistance, but conventionally, in order to manufacture such a thermal head, the entire surface must be heated to about 800°C or higher. Since it was necessary to heat the head to a high temperature of there were.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal head, particularly a protruding type thermal head, which has good heat transfer efficiency, excellent environmental resistance and wear resistance, long life, and low manufacturing cost. purpose.

"Means for Solving the Problems" The thermal head of the first invention solves the above problems by providing a dot protection layer formed of a product by chemical vapor deposition on the heat generating portion of the resistance heating element layer. This is an attempt to resolve the issue.

The dot protection layer may be provided in contact with the resistance heating layer, but may also be provided via another layer.

In addition, the chemical vapor deposition method here refers to a method of exciting a reactive gas and utilizing the resulting chemical reactions to obtain various films.The excitation source for the reactive gas is heat, electron beam, high-frequency plasma, micro Wave plasma, ultraviolet light, etc. can be used.

In such a thermal head, the recesses of the heat generating dots are filled with the dot protection layer formed on the heat generating parts, so that the heat generating dots of the thermal head can be brought closer to the thermal paper, etc. This makes it possible to improve the heat transfer efficiency from the thermal head to the thermal paper or the like.

When the heat-generating dots are made to protrude beyond the surrounding area by the dot-protecting layer, the heat-generating dots of the thermal head can be brought into close contact with thermal paper, etc., thereby further improving the heat transfer efficiency of the thermal head.

There are many types of substances produced by chemical vapor deposition, such as silicon dioxide, silicon nitride, aluminum oxide, titanium carbide, silicon carbide, and boron nitride. Among these materials, diamond or diamond-like carbon is suitable.

Since diamond or diamond-like carbon is hard and has good thermal conductivity, the dot protective layer formed of these is hard and can effectively guide the heat generated from the resistance heating layer. As a result, the heat-generating dot portion has excellent wear resistance and quick heat-generating response.

The dot protection layer of this thermal head may be formed of a single layer, but it can also be formed of a plurality of layers. In this case, it is desirable that the outermost layer be formed of diamond or diamond-like carbon.

A method for manufacturing a thermal head according to a second aspect of the present invention is a method for manufacturing a thermal head according to the first aspect of the present invention, wherein the heating portion is heated by chemical vapor deposition while passing a current through the resistance heating layer to generate heat. This is a method in which a dot protection layer is formed on top.

When current is applied, only a predetermined portion of the resistance heating element M94 generates heat. When the chemical vapor deposition method is performed in this state, the raw material gas decomposes and reacts in the heat generating portion, and a dot portion protective layer is formed in the heat generating portion.

Although current may be passed continuously through the resistive heating element layer, the dot portion protective layer can also be formed by passing current intermittently to cause the resistive heating element layer to generate heat intermittently.

This dot protective layer is preferably formed of diamond or diamond-like carbon, and the dot protective layer made of such diamond or diamond-like carbon is formed by using a mixed gas of hydrogen and a hydrocarbon such as methane as the raw material gas. It can be formed by using etc.

"Embodiments" Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Components that are the same as those of the conventional thermal head shown in FIG. 1O are given the same reference numerals to simplify the explanation.

(Embodiment 1) FIG. 1 shows a first embodiment of the thermal head of the first invention, and the reference numeral IO in the figure indicates a dot portion protective layer.

This dot portion protective layer 10 covers the heating portion 4 of the resistance heating element layer 4.
a with a protective layer 6 in between.

This dot part protective layer 10 is formed with a thickness of 2 μm, and the heat generating dot part A is formed by this dot part protective layer 10.
It is made to protrude more than the surrounding parts. This dot protection layer 10 is made of diamond.

Since the insulating substrate or wear-resistant layer 8 is constructed in the same manner as the conventional thermal head shown in FIG. 10, the materials forming them and their thicknesses are shown and explained in Table 1. Simplify.

Note that the wear-resistant layer 8 of the protective layer 6 is provided as necessary, and may not be provided if unnecessary.

The dot portion protective layer 10 has concavities formed on the surface of the protective layer 8 in a portion between the individual electrodes 5a and the common electrode 5b forming the power supply conductor layer 5 (i.e., the heat generating portion 4a of the resistance heating layer 4). It is formed so as to be filled in the space 9.

Next, a method of manufacturing this thermal head will be explained.

First, a glass glaze layer 2, a resistance heating element layer 4, and a power supply conductor layer 5 were sequentially formed on an insulating substrate l by a well-known means.

Next, this material is placed in a chemical vapor deposition device (P-CVD device) equipped with a high-frequency plasma generator to form a pinhole-free oxidation prevention layer 7 and a wear-resistant layer 8.
The condition was as shown in the figure.

Next, electricity was applied to the power feeding conductor layer 5 of this product to cause the heat generating portion 4a of the resistance heating element layer 4 to generate heat. 2. per dot. When OW power was supplied, the surface of the protective layer 6 on the heat generating portion 4a was heated to about 700 to 850°C.

In this state, a mixed gas of methane and hydrogen (methane concentration 0.5 to 2
%) was supplied at a pressure of 40T Orr% flow of 15-50 SCCM. Then, an electron beam with a density of 15fflA/cra'' was injected from an electron beam generator into the chemical vapor deposition apparatus to excite the raw material gas and cause it to react on the substrate 1.As a result, 2 to 5 people/ A diamond film was deposited at a rate of seconds to form a dot protection layer IO, and the thermal head shown in FIG. 1 was obtained.

(Embodiment 2) FIG. 3 shows a second embodiment of the thermal head of the first invention.

In the thermal head of this example, the dot portion protective layer I
O is composed of a first dot protection layer 11 and a second dot protection layer 12. First, the first dot protection layer 11 is formed between the individual electrodes 5a of the power supply conductor layer 50 and the common electrode 5b. This first dot portion protective layer 11 is formed on the resistance heating element layer 4. [
Hall! The individual electrode 5a and the common electrode 5 are formed by the growth layer 11.
The recess formed between b is filled. The first dot protection layer 11 is made of silicon oxide, silicon nitride, aluminum oxide, or the like, which is a product of chemical vapor deposition.

The power supply conductor layer 5 and the first dot protection layer 11 are covered with an oxidation prevention layer 7 made of silicon nitride, and the second dot protection layer 12 is covered with the first dot protection layer 7 on the surface of the oxidation prevention layer 7.
The dot protection layer ll is located on the dot protection layer ll. This second dot protection layer L2 is made of diamond.

Next, a method of manufacturing this thermal head will be explained.

First, a glass glaze layer 2 is applied to an insulating substrate 1 using well-known means.
, a resistive heating element layer 4 and a power supply conductor layer 5 are formed, and a fourth
The condition was as shown in the figure. Next, this product is placed in a chemical vapor deposition apparatus, and the first dot protection layer 11 is formed while the power supply conductor layer 5 is energized to generate heat in the heat generating portion 4a of the resistance heating layer 4. The state was as shown in Figure 5. When the first dot protection layer 11 is formed of silicon dioxide,
A mixed gas of silicon hydride and oxygen or a mixed gas of silicon chloride and oxygen is used as the raw material gas. When the first dot protection layer 11 is formed of silicon nitride, a mixed gas of silicon hydride and ammonia or a mixed gas of silicon chloride and ammonia is used as the reactive gas.

In addition, when forming with aluminum oxide, aluminum chloride, oxygen, etc. are used.

Thereafter, the power supply to the power supply conductor layer 5 is interrupted, and a mixed gas of silicon hydride and ammonia is supplied as a raw material gas into the chemical vapor deposition apparatus to coat the entire surface of the oxidation prevention layer 7 made of silicon nitride. It was formed into the state shown in FIG. Activation energy was supplied to the raw material gas using high frequency plasma.

After that, electricity is supplied to the power supply conductor layer 5 again to make the resistance heating element layer 4
A mixed gas of methane and hydrogen was supplied into the chemical vapor deposition device while generating heat in the heat generating portion 4a of the device, and an electron beam was injected from the electron beam generator to excite the mixed gas and cause it to react on the substrate 1. A second dot protection layer 12 made of diamond was formed, and the thermal head shown in FIG. 3 was obtained.

(Embodiment 3) FIG. 7 shows a third embodiment of the thermal head of the first invention.

In the thermal head of this example, the power feeding conductor layer 5 is formed of two layers, a lower layer 51 and an upper layer 52.

The lower layer 51 is made of a conductive material such as molybdenum, chromium, tantalum, tungsten, etc., from which a product (for example, diamond-like carbon) can easily be deposited by chemical vapor deposition. Further, the upper layer 52 is made of aluminum or the like having good conductivity. The lower layer 51 of the power feeding conductor layer 5 is provided from near the center of the protrusion formed by the glass glaze layer 2, and the upper layer 52 is provided from near the end of the protrusion. In this thermal head, when electricity is applied to the power supply conductor layer 5, electricity is mainly conducted through the upper layer 52, which has good conductivity.
Heat is generated from the discontinued portion of the upper layer 52 through the lower layer 51 to the heat generating portion 4a of the resistance heating element M4.

The dot protection layer 10 of this thermal head is provided in a recess 14 (see FIG. 8) formed by the lower layer 51 of the power supply conductor layer 5, and is made of diamond or diamond-like carbon.

Further, the entire surface of this thermal head is covered with an anti-oxidation layer 7 made of silicon nitride.

Next, a method of manufacturing this thermal head will be explained.

A glass glaze layer 2, a resistance heating element layer 4, and a power supply conductor layer 5 were provided on an insulating substrate l made of aluminum oxide by well-known means, and the state shown in FIG. 8 was obtained.

Next, this is housed in a chemical vapor deposition apparatus, and electricity is applied to the power supply conductor layer 5 to cause the heat generating portion 4a of the resistance heating element layer 4 to generate heat. When a mixed gas of methane and hydrogen is supplied to the chemical vapor deposition apparatus in this state, a dot protection layer 10 made of diamond or diamond-like carbon is formed in the recess 14.
is formed. In this thermal head, the lower layer 51 of the power supply conductor layer 5 is formed of a material from which products produced by chemical vapor deposition are easily deposited. It quickly precipitates into the state shown in FIG. 9.

After that, when the raw material gas for forming the antioxidant layer 7 was introduced into the chemical vapor deposition apparatus while the power supply to the power supply conductor layer was stopped, the antioxidant layer 7 was formed, as shown in FIG. A thermal head was manufactured.

"Effects of the Invention" As explained above, the thermal head of the present invention is provided with a dot protection layer made of a product obtained by chemical vapor deposition on the heat-generating portion of the resistance heating layer. It is possible to form a heating dot portion that can be more closely approached.

Therefore, the thermal head of the present invention has excellent heat transfer efficiency to thermal paper and the like.

In addition, in the thermal head of the present invention, the dot protective layer is formed of a material produced by chemical vapor deposition, which can form a dense film with high hardness and excellent corrosion resistance. The film is excellent in wear resistance and corrosion resistance, has no pinholes, and has excellent heat resistance, and can reliably protect the heat generating portion of the resistance heating element layer.

Therefore, the thermal head of the present invention has excellent environmental resistance and wear resistance, and has a long life and high reliability with little deterioration over time.

Further, the method for manufacturing a thermal head according to the second invention is a suitable method for manufacturing the thermal head according to the first invention.

According to this manufacturing method, the dot protective layer can be formed only on the heat generating part of the resistance heating element, and the dot protective layer is formed by heating only the heat generating part, so the thermal head as a whole can be can be maintained at a low temperature, preventing troubles such as deformation of the glass glaze layer, and forming a dot protection layer made of diamond or the like on a predetermined portion. Therefore, according to this manufacturing method, it is possible to manufacture a protruding type thermal head in which the dot portion is protected by a dot portion protective layer made of diamond or the like.

Furthermore, according to the manufacturing method of the present invention, the dot protective layer can be formed on a predetermined portion, that is, the heat generating portion, without using a mask, so the dot protective layer can be provided in a simple process. It is possible to reduce the manufacturing cost of the thermal head.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of a first embodiment of the thermal head of the first invention, FIG. 2 is a cross-sectional view for explaining the manufacturing method of the thermal head of the first embodiment, and FIG. 1 is a cross-sectional view showing the main part of the second embodiment of the thermal head of the invention;
6 to 6 are cross-sectional views for explaining the manufacturing method of the thermal head of the second embodiment, FIG. 7 is a cross-sectional view showing the main parts of the third embodiment of the thermal head of the first invention, and FIG. 9 is a cross-sectional view for explaining a method of manufacturing a thermal head according to the third embodiment, and FIG. 10 is a cross-sectional view showing essential parts of a conventional thermal head. 4... Resistance heating element layer, 4a... Heat generating portion, 10...
- Dot part protective layer, 11... first dot part protective layer,
12...Second dot part protective layer, A...Heating dot part.

Claims (10)

[Claims] (1) A thermal head that generates heat by passing an electric current through a resistive heating element layer, characterized in that a dot protection layer made of a product obtained by chemical vapor deposition is provided on the heating portion of the resistive heating element layer. thermal head. (2) The thermal head according to claim 1, wherein the portion where the dot portion protective layer is provided is made to protrude more than the surrounding portion. (3) The thermal head according to claim 1, wherein the dot portion protective layer is made of diamond or diamond-like carbon. (4) The thermal head according to claim 1, wherein the dot portion protective layer is formed of a plurality of layers. (5) The thermal head according to claim 4, wherein the dot portion protective layer is formed of a plurality of layers, the outermost layer of which is formed of diamond or diamond-like carbon. (6) When manufacturing a thermal head that generates heat by passing an electric current through the resistance heating element layer, a dot protection layer is formed on the heat generating part by chemical vapor deposition while passing an electric current through the resistance heating element layer to generate heat. A method for manufacturing a thermal head characterized by: (7) The thermal device according to claim 6, characterized in that the dot protection layer is formed on the heat generating portion by chemical vapor deposition while a current is intermittently passed through the resistance heating layer to generate heat. Head manufacturing method. (8) The method for manufacturing a thermal head according to claim 6, wherein the dot portion protective layer formed is made of diamond or diamond-like carbon. (9) A method for manufacturing a thermal head according to claim 8, characterized in that a mixed gas of hydrocarbon and hydrogen is used as the raw material gas. (10) The method for manufacturing a thermal head according to claim 9, wherein the hydrocarbon is methane.