JP3325787B2 - Thermal head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal head used in a thermal printer and a method of manufacturing the same.
In particular, the present invention relates to a thermal head and a method of manufacturing the same, which are capable of improving printing thermal efficiency, printing quality, and high-speed printing.

[0002]

2. Description of the Related Art A conventional thermal head structure and a method of manufacturing the same generally include a plurality of heating resistors arranged linearly at an end on an alumina substrate, and a current is selectively supplied to each heating resistor. Thus, heat is generated, and dot recording is performed using thermal recording paper or a thermal transfer ribbon.

FIG. 6 is a sectional view of a main part showing a structure of a conventional thermal head. A convex transparent heat insulating layer made of a glass partial glaze layer is provided at an end of a substrate 1 made of ceramic such as alumina. 2 is formed to a thickness of about 30 μm, and T
The heating resistors 3 made of a-SiO2 or the like are stacked by sputtering or the like, and the pattern of the heating resistors 3 is arranged by photolithography so that a plurality of the heating resistors 3 are linearly arranged according to the number of dots.
Is formed.

In order to supply power energy to the heating resistor 3, electrodes 4 made of Al, Cu, Au or the like are laminated by sputtering or the like and formed in a desired pattern by photolithography. I have. Common electrode 4a of the electrode 4
Is formed on one side of the heating resistor 3 sandwiched between the end of the substrate 1 and the heating portion 3a of the heating resistor 3, and the individual electrode 4b of the electrode 4 and the external Connection terminal portions (not shown) are formed at the same time.

A mask (not shown) is provided on the external connection terminal.
In order to prevent the heating resistor 3 and the electrode 4 from being oxidized and worn, a colored protective layer 5 made of SiC, sialon, or the like is laminated by sputtering or the like, and the mask of the terminal portion is peeled off. After a solder-easy metal is plated on the external connection terminals, the substrate 1 is diced to produce a chip-shaped thermal head. like this,
In the conventional thermal head, each heat generating resistor 3 generates Joule heat and heats a thermal paper or a thermal transfer ink ribbon (not shown) which is in close contact with the surface of the protective layer 5 to thereby reduce the thermal paper. Coloring or ink transfer to recording paper is performed, and characters and images are printed.

[0006]

However, since the heat insulating layer 2 of the conventional thermal head is formed of transparent glass, it absorbs and reflects the conduction heat and radiant heat generated by the heating resistor 3. And the thermal resistance is relatively small. As a result, the temperature rise of each heat generating portion 3a (heat generating dot) when power is turned on is relatively small, and the energy applied to each heat generating dot is increased in order to obtain a desired print density. Was low.

Further, an increase in the applied energy increases the amount of ineffective heat, so that the thermal storage of the thermal head becomes large, and there is a problem that the high-speed printability is reduced. In particular, in recent years, high printing quality and high speed printing of thermal printers have been remarkably progressing.
There has been a demand for a printing device having a large number of heating elements of 160 dots at dots / inch (64 μm intervals) and capable of printing at a high speed of 100 characters / second. However, heat control is performed using a heat history correction LSI. However, the crushing of printing and the unevenness of density cannot be eliminated, and the heat insulating performance and the heat radiation performance of the protective layer 2 have reached their limits.

On the other hand, since the protective layer 5 has conventionally been formed by sputtering a ceramic material of SiC or Sialon in an atmosphere of only Ar gas, the protective layer 5 becomes a film deficient in light elements such as oxygen and nitrogen. It was used in a state in which the transparency was lowered. For this reason, the heating resistor 3
In order to absorb and reflect conduction heat and radiant heat due to heat generated by
The thermal resistance becomes relatively large. As a result, the protective layer 5
The heat is accumulated inside the so-called "heat storage", so that the temperature drop at the time of energization OFF of each heating dot becomes small and the thermal responsiveness decreases, so that when printing, the dot area becomes too large, There is a problem that "print collapse" occurs and the print quality is reduced.

[0009]

In order to solve the above-mentioned problems, a thermal head according to the present invention comprises a heat insulating layer laminated on an upper surface of a substrate, and a heating resistor and an electrode laminated on the upper surface of the heat insulating layer. In a thermal head having an upper surface covered with a protective layer, the heat insulating layer is made of a conductive black ceramic film, and the protective layer is made of an insulating transparent ceramic film.

In the method of manufacturing a thermal head according to the present invention, a heat insulating layer is laminated on an upper surface of a substrate, a heating resistor and an electrode are laminated on the upper surface of the heat insulating layer, and the upper surface is covered with a protective layer. Forming a thermal insulation layer comprising a conductive black ceramic film by oxygen-deficient reactive sputter deposition of silicon and a transition metal; and forming the protective layer comprising an insulating transparent ceramic film by vapor deposition. Forming a layer.

Further, the manufacturing method of the present invention is characterized in that the protective layer made of an insulating transparent ceramic film is formed by reactive sputter deposition of a ceramic material with oxygen or nitrogen.

As described above, according to the present invention, the heat insulating layer is formed of a conductive black ceramic film, and the protective layer is formed of an insulating transparent ceramic film. A heating resistor is provided between the heat insulating layer and the protective film. By being formed, radiant heat radiated from the heating resistor toward the substrate is reflected by the released metal in the heat insulating layer, and contributes to a rise in the temperature of the heating resistor. Applied energy
Can be reduced.

Further, the radiant heat radiated from the heating resistor toward the printing medium (such as a thermal transfer ink ribbon) passes through the sufficiently transparent protective layer and is directly applied to the printing medium in close contact with the surface of the protective layer. Reach and convert to heat. For this reason, since the radiant heat energy generated by the heating resistor can be used effectively, the applied energy for obtaining a desired print density can be reduced, and the print heat efficiency can be improved.
Further, by improving the thermal efficiency of the printing, it is possible to reduce the heat capacity of the thermal insulating layer by forming the thickness of the thermal insulating layer to be thin, thereby improving heat radiation during printing and suitable for high-speed printing with excellent thermal responsiveness. Thermal head can be provided.

Further, since the protective film is a transparent insulating ceramic film, the heat storage due to the conduction heat of Joule heat generated from the heat generating resistor and the absorption and reflection of the radiant heat are generated by the conventional colored protection layer. It is much smaller than. Therefore, the heat storage inside the protective layer is reduced, which further contributes to the improvement of the thermal responsiveness, and the collapse of the print is reduced and the print quality can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the structure of a thermal head and a method of manufacturing the same according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part showing the structure of a thermal head according to the present invention. In the figure, a convex portion is formed on a part of the surface of a substrate 11 made of silicon, and silicon and a transition metal (particularly, Ta, W, Cr, Ti, Zr,
A heat insulating layer 12 made of a conductive black ceramic film formed into a columnar crystal by oxygen-deficient reactive sputtering vapor deposition of a high melting point metal group such as Mo and Hf) is formed to a thickness of about 20 μm. The heat insulating layer 12 is formed by sputtering the reactive sputter deposition by adjusting the flow rate of the oxygen gas so as to deplete the oxygen to form a conductive black containing a large amount of unreacted free metal. A black ceramic film is easily formed.

A heating resistor 14 made of Ta-SiO2 or the like is formed on the heat insulating layer 12 via an insulating layer 13 formed by sputtering silicon oxide, alumina or the like in the same manner as in the conventional example. Aluminum, copper,
An electrode 15 made of gold or the like is laminated and formed, and the common electrode 1 is sandwiched between the heat generating portions (heat generating dots) 14 a of the heat generating resistor 14.
5a and individual electrodes 15b are formed.

Finally, the heating resistor 14 and the electrode 1
A protective layer 16 for protecting the layer 5 from oxidation and abrasion is laminated with a thickness of about 5 μm by reactive sputter deposition of oxygen or nitrogen of sialon to complete the thermal head of the present invention. As an atmosphere for the reactive sputter deposition, an oxygen flow rate or a nitrogen flow rate is O2 or N2 gas /
(Ar + O2 or N2 gas) = approximately 5%, and the protective film 16 is an insulating and sufficiently transparent ceramic film.

A comparison of the thermal response characteristics between the thermal head of the present invention thus formed and the conventional thermal head will be described with reference to FIGS. FIG. 2 is a graph showing the temperature change of the heat generating portion 3a or 14a when one pulse of current is applied to the heat generating resistor 3 or 14 of the thermal head. It is an example. Conventionally, as shown in the thermal response graph of FIG.
What was 00 ° C. is 480 ° C. in the case of the present invention, and the thermal efficiency is improved by about 16%.

FIG. 3 similarly shows the temperature change when a continuous pulse current is applied to the heating resistor 3 or 14, wherein graph a is the present invention and graph b is the conventional example. As can be seen from the figure, in the case of a continuous pulse, the thermal head of the present invention is particularly excellent in the thermal response of the temperature drop when the power is turned off.

FIGS. 4 and 5 show a thermal head.
FIG. 4 is an enlarged view of a character “column” actually printed on a print medium.
FIG. 5 shows a thermal head of the present invention, and FIG. 5 shows a conventional thermal head. From these figures, it can be seen that the thermal response of the conventional thermal head is poor, and "print crushing" occurs in a part of characters.
However, in the case of the thermal head of the present invention, high quality printing is obtained.

This is because in the thermal head of the present invention, by applying a voltage to the heating resistor 14,
The heating dots 14a generate Joule heat, and radiant heat is radiated in all directions together with conduction heat. The generated conduction heat is efficiently absorbed and stored in the black heat insulating layer 12 containing a large amount of liberated metal, the heat flow in the direction of the substrate 11 is restricted, the heat resistance becomes large, and the heat generating dots 14a are kept warm. on the other hand,
This is because the heat storage due to the absorption of the conductive heat inside the transparent protective layer 16 is small, and the conductive heat contributing to the heating of the printing medium adhered to the surface increases.

On the other hand, with respect to the radiant heat radiated from the heating resistor, the radiant heat toward
When incident on 2, due to the liberated metal in the heat insulation layer,
The heat is reflected toward the heating resistor 14 to keep the heat of the heating dot 14a. On the other hand, the radiant heat toward the print medium is transmitted because the protective layer 15 is transparent, and is efficiently transmitted to the print medium.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made as necessary. For example, the protective layer 16, in addition to the sialon, oxidized aluminum that can be insulating transparent ceramic layer, a nitride <br/> aluminum, silicon oxide, silicon nitride, tantalum oxide, zirconium oxide, chromium oxide, titanium oxide, nitride A ceramic material such as boron or carbon nitride, or a mixture thereof is suitable, and may be a single layer or a multilayer.
In addition, as a method of manufacturing each layer, a thin film manufacturing method such as CVD or ion plating may be used instead of sputtering.

[0024]

As described above, according to the thermal head of the present invention, since the heat insulating layer formed under the heating resistor is made of the conductive black ceramic film, the thermal dot is generated on the heating dot of the heating resistor. Since the released metal is blackened with respect to the conduction heat of Joule heat, the heat absorption becomes large because of the liberated metal, and the liberated metal increases the reflection power with respect to radiant heat. In addition, the protective layer formed on the top of the heating resistor is made of an insulating transparent ceramic film and is sufficiently transparent to the conduction heat generated in the heating dots, so that it has a small absorption power and reflects radiation heat. Is almost gone. As a result, the thermal head of the present invention has the effect of significantly improving its printing thermal efficiency, printing quality, and high-speed printing performance.

In the method of manufacturing a thermal head according to the present invention, the conductive black ceramic film as the heat insulating layer is formed by oxygen-deficient reactive sputter deposition of silicon and a transition metal. With the above control, a desired conductive black ceramic film can be easily formed. Further, since the insulating transparent ceramic film as the protective layer of the present invention is formed by reactive sputter deposition of oxygen or nitrogen of a ceramic material, a desired film can be easily formed by controlling the flow rate of oxygen gas or nitrogen gas. Can be formed.

[0026]

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a structure of a thermal head according to the present invention.

FIG. 2 is a graph comparing thermal response characteristics of a thermal head of the present invention and a conventional thermal head with respect to one pulse current.

FIG. 3 is a graph comparing thermal response characteristics of a thermal head according to the present invention and a conventional thermal head with respect to a continuous pulse current.

FIG. 4 is an enlarged view of a character “column” printed by the thermal head of the present invention.

FIG. 5 is an enlarged view of a character “column” printed by a conventional thermal head.

FIG. 6 is a sectional view of a main part showing a structure of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Substrate 2, 12 Heat insulation layer 3, 14 Heating resistor 3a, 14a Heating part 4, 15 Electrode 5, 16 Protective layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/335

Claims (2)

(57) [Claims] 1. A forming a heat insulating layer on the upper surface of the substrate, and stacking the heating resistor and the electrode on the upper surface of the heat insulating layer, in the thermal head formed by covering with a protective layer to the upper surface, the heat insulating layer is free Conductive black ceramic film containing a metal , wherein the protective layer is a reactant of oxygen or nitrogen of the ceramic material.
A thermal head comprising an insulative transparent ceramic film formed by live sputter deposition . 2. A method for manufacturing a thermal head, comprising: laminating a heat insulating layer on an upper surface of a substrate, laminating a heating resistor and an electrode on the upper surface of the heat insulating layer, and then covering the upper surface with a protective layer. a step of forming the heat insulating layer made of a conductive black ceramic film containing free metal by oxygen deprivation reactive sputter deposition of transition metal, ceramic
Forming the heat insulating layer made of an insulating transparent ceramic film by reactive sputter deposition of oxygen or nitrogen of a thermal material.