JPH06198933A - Thermal head and preparation thereof - Google Patents

Abstract

PURPOSE:To provide a thermal head with high accuracy and high quality of printing, being suitable for high speed printing and with high heat resistance with little influence of heat build-up. CONSTITUTION:On the surface of a single crystal silicon base sheet 11, the second mesa 11b is laminatedly formed on the first mesa 11a and a heat insulating layer consisting of a metal oxide is formed on the first and the second mesas 11a and 11b and a heat generating resistor 13 is laminatedly formed on this heat insulating layer and a common electrode 14 connected with the heat generating resistor 13 is formed over from the sloped part of the second mesa 11b to the sloped part of the first mesa 11a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head mounted on a thermal printer, and more particularly to a real edge type thermal head which uses a single crystal silicon substrate and has good printing performance and is suitable for high speed printing.

[0002]

2. Description of the Related Art A thermal head mounted on a thermal printer, for example, has a plurality of heating resistors linearly arranged on the same substrate and selectively heats the heating resistors in accordance with a desired print signal. The thermal recording paper is used for color recording or for recording on plain paper through an ink ribbon.

FIG. 4 shows a conventional thermal head. On an insulating substrate 1 made of ceramic such as alumina, a glaze layer made of glass or the like which functions as a heat retaining layer has a substantially arcuate cross section. 2 is formed. On the upper surface of the glaze layer 2, a heating resistor 3 made of Ta ₂ N or the like is deposited on the surface of the substrate 1 by vapor deposition, sputtering, or the like and then etched to reduce the number of dots. Accordingly, a plurality of straight electrodes are formed in line, and a common electrode 4 connected to each heating resistor 3 is provided on one side of the heating resistor 3 and each heating resistor 3 is provided on the other side. The individual electrodes 5 that are independently energized are connected to each. The common electrode 4 and the individual electrodes 5 are made of, for example, aluminum, copper, gold, or the like, and are formed into a pattern of a desired shape by etching after being deposited by vapor deposition, sputtering, or the like.

Further, these heating resistor 3 and common electrode 4
Further, on the surface of the individual electrode 5, a protective layer 6 having a film thickness of approximately 5 to 10 μm for protecting the heating resistor 3, the common electrode 4 and the individual electrode 5 is formed. It is formed so as to cover all surfaces of the electrodes 4 and 5 except the terminal portions. The protective layer 6 is formed of SIALON or the like that protects the heating resistors 3 from deterioration due to oxidation and protects the heating resistors 3, the common electrode 4 and the individual electrodes 5 from abrasion due to contact with an ink ribbon or the like. ing. This protective layer 6 is laminated and formed by means such as sputtering.

In a thermal transfer printer using such a thermal head, a heating resistance is generated based on a predetermined print signal in a state where the thermal head is pressed against a predetermined sheet of paper conveyed to a platen portion via an ink ribbon. By selectively energizing and heating the body 3, the ink of the ink ribbon is melted and transferred to a sheet to perform desired printing. Further, desired printing can be performed on the heat-sensitive recording paper in a state where the thermal head is directly in pressure contact with the thermal recording paper without an ink ribbon.

In such a thermal head, the glaze layer 2 has a low thermal conductivity (2 × 10 ^-3 cal / c).
m.sec..degree. C.) and the thermal conductivity of the insulating substrate 1 made of alumina (40.times.10.sup.- ³ cal / cm.sec..degree. C.) in combination with the heat storage effect of the Joule heat generated in the heating resistor 3. It is used to balance power efficiency and printing characteristics. In other words, the heat storage effect of the glaze layer 2 also lengthens the cooling time constant of the heat generating resistor 3 and causes deterioration of print quality such as tailing, bleeding, and smearing of prints at high-speed printing. In consideration of the above, the thickness of the glaze layer 2 is adjusted according to the use conditions, and is usually about 30 to 60 μm.

In recent years, due to the increasing need for high-quality printing and high-speed printing due to high definition, printing resolution 40
A thermal transfer printer with a printing speed of 0 dpi and a printing speed of 100 cps has been put into practical use. In this thermal transfer printer,
The heating resistor 3 is energized and controlled with a very short pulse width of 300 μs or less. And, in the future, there is a trend toward higher definition and higher speed.

In such a high-definition, high-speed printing thermal transfer printer, the thermal quality of the thermal head is so great that the printing quality deteriorates, so that the thickness of the glaze layer 2 is about 30 μm.
The temperature rise of the thermal head due to heat storage is precisely controlled by reducing the thickness to m and further correcting the energization time to the heating resistor 3 by using the thermal history correction LSI.

[0009]

However, in such a thermal head, the expensive thermal history correction LS is used.
Since I has to be used, it has the disadvantage that the device is consequently expensive. For this reason, generally, those without high-level heat control performance are used, and there is a drawback that the temperature rise due to heat storage of the thermal head cannot be sufficiently controlled.

Conventionally, it was considered that the thermal storage of the thermal head was caused only by the glaze layer 2 having a low thermal conductivity, but in the case of high-speed printing in which the energization cycle to the heating resistor 3 is short as described above, the substrate 1 is used. It was found that the main cause was the low thermal conductivity of.

Further, the driving cycle of the heating resistor 3 is 300 μm.
In order to obtain a desired print quality in energization control with a very short pulse width of s or less, it is necessary to increase the peak temperature of the heating resistor 3 of the thermal head to give a predetermined printing energy to the ink ribbon. However, for example, when the environmental temperature at the time of printing is 5 to 35 ° C., it is necessary to maximize the applied energy at a low temperature of 5 ° C. to obtain the required peak temperature of the heating resistor. The peak temperature of the heating resistor 3 is higher than the heat resistant temperature of the glaze layer 2 and the heating resistor 3 of about 700 ° C.
Has a problem that it cannot be used for high-speed printing in a low temperature environment because it is thermally deformed or melted and the resistance value of the heating resistor 13 changes.

Furthermore, since the heating resistor 3 made of a cermet-based material such as Ta-SiO ₂ has a characteristic that its sheet resistance value is substantially halved by the high temperature vacuum annealing treatment, the heating resistor 3 at a temperature higher than the actual operating temperature is used. Although the high temperature vacuum annealing treatment is an essential condition, there is a problem that the high temperature vacuum annealing treatment cannot be performed because the heat resistant temperature of the glaze layer 2 is low as described above.

Furthermore, since the common electrode 4 is formed in a plane, the width dimension of the common electrode 4 becomes too narrow as the edge becomes a real edge, and the voltage drop (common drop) due to the increase in electrode resistance becomes large. However, there is a problem that the print quality is deteriorated due to the variation in the electric power applied to the heating resistor 3.

Furthermore, since the division of the substrate 1 when manufacturing the thermal head is processed by grinding, the edge of the substrate 1 becomes sharp, chipping occurs, and the printing quality deteriorates. , Had the problem.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a thermal head having high definition, high printing quality, and high heat resistance suitable for high speed printing.

[0016]

In order to achieve the above object, the present invention provides a second mesa formed on a first mesa formed on the surface of a single crystal silicon substrate, and a second mesa formed over the first mesa. A heat insulating layer made of a metal oxide formed on the first and second mesas, a heating resistor formed by stacking on the heat insulating layer, and an inclination of the first mesa from an upper portion of the second mesa. A common electrode formed over the portion and connected to the heating resistor.

The height of the first mesa is approximately 30 to 1.
The height of the second mesa is about 5 to 15 μm.

Further, the intersection of the inclined portion of the first mesa and the inclined portion of the second mesa on the end side of the substrate is a ribbon peeling edge portion for peeling the ink ribbon after printing. Is characterized by.

Furthermore, the distance from the approximate center of the heating resistor to the ribbon peeling edge portion is approximately 100 μm.
It is characterized by

Furthermore, the heat insulating layer is made of a material whose main component is an oxide of Ta and Si.

Furthermore, a first anisotropic etching step of forming a first mesa on the surface of the single crystal silicon substrate,
A second anisotropic etching step of forming a second mesa on the first mesa, and a third anisotropic etching step of reducing the inclination angle of the sloped portions of the first mesa and the second mesa. And a step of rounding and etching the corners of the first mesa and the second mesa, and forming a heat insulating layer made of a material containing a metal oxide of Ta and Si as a main component on the etched substrate. A step, a step of performing a first annealing treatment thereafter, a step of forming a heating resistor on the heat retaining layer, a step of performing a second high temperature annealing treatment, and forming an electrode on the heating resistor. And a step of manufacturing a thermal head.

[0022]

The above means operates as follows.

By forming the common electrode connected to the heating resistor from the upper part of the second mesa to the inclined part of the first mesa, the width of the common electrode can be widened, so that the so-called common is formed. The drop can be prevented.

Further, by using single crystal silicon as the substrate, the heat dissipation of the substrate becomes sufficient, and the influence of heat accumulation on the substrate can be reduced even in the case of high-speed printing in which the energization cycle to the heating resistor is short.

Further, since the heat insulating layer is made of a material whose main component is a metal oxide of Ta and Si, its melting point is about 1
Even if the temperature rises to 500 ° C. or higher and the peak temperature of the heating resistor becomes high, sufficient heat resistance can be obtained.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional structural view showing the structure of a thermal head according to the present invention. As shown in the drawing, a first mesa 11a and a second mesa 11b each having a substantially trapezoidal cross section are formed on one end side of the surface of the substrate 11 made of single crystal silicon so as to overlap each other. A heat insulating layer 12 made of an oxide of Ta and Si is formed as a thin film on the surface of the substrate including the second mesa 11b by a reactive sputter deposition method using high frequency plasma.

Then, at the upper surface position of the second mesa 11b, Ta ₂ N is formed as in the conventional thermal head described above.
Alternatively, a heating resistor 13 made of Ta-SiO ₂ or the like is formed, and each heating resistor 1 is provided on one side of the heating resistor 13.
3 is connected to the common electrode 14, and the other side is connected to the individual electrodes 15 for independently energizing the heating resistors 13. The common electrode 14 and the individual electrode 15 are made of, for example, aluminum, copper, gold, or the like, and are deposited in a desired shape by etching after being deposited by vapor deposition, sputtering, or the like.

Further, on the surfaces of the heating resistor 13, the common electrode 14 and the individual electrode 15, a protective layer 16 having a film thickness of 5 to 10 μm for protecting the heating resistor 13 and the electrodes 14 and 15 is formed. It is formed so as to cover all surfaces of the electrodes 14 and 15 except the terminal portions. The protective layer 16 protects each heating resistor 13 from deterioration due to oxidation and also protects each heating resistor 13 from abrasion caused by contact with an ink ribbon or the like.
And SIALON or the like that protects the electrodes 14 and 15.

Next, a method of manufacturing the thermal head of the above-described embodiment will be described with reference to the flowchart of FIG.

First, a SiO ₂ film is formed on the surface of the substrate 11 made of single crystal silicon by thermal oxidation, or T is formed by vapor deposition.
An a ₂ O ₅ or Si ₃ N ₄ film is formed with a thickness of approximately 1 μm to provide a mask layer. A photoresist is applied onto this mask layer by a spinner or the like, and a resist pattern is formed by a photolithography technique. Then, in the case of a SiO ₂ film, etching is performed with buffered hydrofluoric acid to form Ta ₂ O ₅ or Si.
_In the case of a ₃ N ₄ film, dry etching is performed by reactive ion etching to form a first mask pattern.

Next, the substrate 11 is anisotropically etched with an alkaline solution such as a KOH aqueous solution to form the first mesa 11a at a taper angle of about 55 ° with respect to the plane orientation (100) of about 30 to 30 °.
It is formed to a height of 100 μm. Then, a photoresist is applied again on the remaining mask layer of the mask layer used for forming the first mesa 11a, a mask pattern is formed by the photolithography technique, and then anisotropic etching is performed as described above. Second mesa 11 on the first mesa 11a
b is formed to a height of 5 to 15 μm. Then, after removing the mask layer, the substrate 1 is treated with an alkaline solution such as a KOH aqueous solution.
1 is anisotropically etched over the entire surface to form the second mesa 11b with a small inclination angle of about 25 °.

Next, a fluoronitric acid etchant (HF: HN)
Using O ₃ : CH ₃ COOH = 1: 8: 3), the corners of the first mesa 11 a and the second mesa 11 b are rounded and etched in a round shape.

Next, as the heat retaining layer 12 on the substrate 11 formed by stacking the first mesa 11a and the second mesa 11b in this manner, a low thermal conductivity made of an oxide of Si and Ta. A material having a low coefficient of thermal expansion and high heat resistance is laminated and formed in a thickness of about 30 μm by reactive sputter deposition using high frequency plasma. After that, a high temperature annealing process at about 800 to 1000 ° C. is performed using a vacuum or an atmosphere annealing furnace. As a result, the warp of the substrate 11 is eliminated.

Next, the second mesa 11 on the heat retaining layer 12
A heating resistor 13 made of Ta-SiO ₂ or Ta ₂ N is deposited on the upper surface of b by sputtering and formed into a desired pattern by etching, and then a high-temperature heat treatment of about 800 to 1000 ° C. is applied using a vacuum annealing furnace. . As a result, the heating resistor 13 can obtain high-temperature stability of resistance value.

Next, as in the conventional case, electrodes 14 and 15 for giving a signal to the heating resistor 13 are formed into a desired pattern by etching after depositing aluminum, copper, gold or the like by sputtering or the like. The protective layer 16 is laminated on this to complete the thermal head. At this time, by forming the common electrode 14 from above the inclined portion of the second mesa 11b to above the inclined portion of the first mesa 11a, the width thereof is widened.

The intersection of the inclined portion of the first mesa 11a and the inclined portion of the second mesa 11b on the end side of the substrate 11 is a ribbon peeling edge portion for peeling the ink ribbon after printing. 11c is formed.

Next, the operation of this embodiment will be described.

In this embodiment, the common electrode 14 connected to the heating resistor is formed from above the sloped portion of the second mesa 11a to above the sloped portion of the first mesa 11b.
The width of the common electrode 14 can be formed wide, and so-called common drop can be suppressed.

Further, in this embodiment, by using single crystal silicon as the substrate 11 of the thermal head, its thermal conductivity is about 340 × 10 ⁻³ cal / cm · S.
ec · ° C is about 8 times as high as the thermal conductivity (about 40 × 10 ^-3 cal / cm · Sec · ° C) when a conventional alumina substrate is used, and the energization cycle to the heating resistor 13 is Even in the case of short high-speed printing, it is possible to eliminate the effect of heat storage by the substrate.

Further, in a conventional substrate made of a ceramic material such as alumina, since there are many fine irregularities on the substrate surface, it is not possible to cope with the fine patterning of the electrode wiring due to the high definition of the heating resistor in recent years. Although there is a problem, since the single crystal silicon substrate 11 of the present invention has a high plate thickness accuracy and can easily obtain the smoothness of the surface, it can sufficiently correspond to the fine patterning of the electrodes 14 and 15.

Furthermore, in this embodiment, the heat retaining layer 1
2 has a low thermal conductivity of oxide of Ta and Si (about 1
~ 2 × 10 ⁻³ cal / cm · Sec · ° C.) not only provides good heat storage but also has a coefficient of thermal expansion of approximately 1.0 × 10 ⁻⁶ cm / ° C. It is smaller than the coefficient of thermal expansion (2.6 × 10 ⁻⁶ cm / ° C.) of the crystalline silicon substrate 11, and the formed heat retaining layer 12 has good adhesion to the single crystal silicon substrate 11 and has a high temperature annealing treatment. Does not cause peeling or cracks. Therefore, it becomes possible to form the heat retaining layer 12 by vapor deposition to a thickness of about 30 μm. The heat-resistant temperature of the heat retaining layer 12 is about 1500 ° C.
Therefore, the heat resistant temperature of the single crystal silicon substrate 11 is about 1400.
Higher than ℃. Therefore, even if the peak temperature of the heating resistor 13 exceeds approximately 700 ° C., thermal deformation of the heat retaining layer 12 does not occur at all, and high-speed printing at low temperature becomes possible.

Furthermore, since the heat insulating layer 12 has a high heat resistance temperature of about 1500 ° C., it is possible to anneal it at about 800 to 1000 ° C. using a vacuum annealing furnace after forming the heating resistor 13. By this high temperature annealing treatment, the heat history at a temperature higher than the heat generation peak temperature at the time of actual marking is given to the heat generation resistor 13 to change the resistance value of the heat generation resistor 13 due to the heat change at the time of printing. Can be made smaller.

Furthermore, in an embodiment of the present invention,
The first mesa 11a and the second mesa 11 are formed on the surface of the substrate 11.
b is formed in an overlapping manner, the heating resistor 13 is formed on the upper surface thereof, and the distance from the approximate center of the heating resistor 13 to the ink ribbon peeling edge portion is set to about 100 μm. It can be concentrated on the resistor 13, and because the distance from the print part (substantially the center of the heat-generating resistor 13) to the ribbon peeling part is short, resin-based ink can be used, which is also good for so-called rough paper. Can be printed.

Furthermore, the portion of the thermal head which becomes the ink ribbon peeling edge portion can be formed smoothly by etching the single crystal silicon substrate 11 to prevent the trouble of running the ink ribbon, and the variation of the printing quality. Can be reduced.

[0046]

As described above, the thermal head of the present invention has the following remarkable effects.

Since the common electrode connected to the heating resistor is formed from above the sloped portion of the second mesa to above the sloped portion of the first mesa, the width of the common electrode can be increased and so-called common drop occurs. Can be held down.

Further, by using single crystal silicon as the substrate of the thermal head, the heat dissipation of the substrate is sufficiently improved, and the influence of heat accumulation by the substrate is reduced even in high-speed printing in which the energization cycle to the heating resistor is short. Further, since the plate thickness of the substrate is good and the smoothness of the surface can be easily obtained, it is possible to sufficiently deal with the fine patterning of the electrodes.

Further, by using a material having a low thermal conductivity such as an oxide of Ta and Si for the heat retaining layer, not only good heat storage property is obtained, but also the heat resistant temperature of this heat retaining layer becomes about 1500 ° C. The heat generation peak temperature of the resistor can be made high enough to enable high-speed printing at low temperatures.

Furthermore, the first mesa and the second mesa are formed on the surface of the substrate in an overlapping manner, and the heating resistor is formed on the upper surface of the substrate, from the approximate center of the heating resistor to the ink ribbon peeling edge portion. Since the distance is about 100 μm,
The pressure contact force of the thermal head can be obtained by concentrating on the heating resistor, and because the distance from the printing part (generally the center of the heating resistor) to the ribbon peeling part is short, resin-based ink can be used. Also, good printing can be performed.

Furthermore, the edge portion of the thermal head is etched in advance on the single-crystal silicon substrate, so that the edge portion can be formed smoothly, the trouble of the ink ribbon running is prevented, and the variation of the printing quality is reduced. can do.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing a thermal head according to an embodiment of the present invention.

FIG. 2 is a flowchart showing manufacturing steps of the thermal head of the present invention.

FIG. 3 is a structural cross-sectional view showing a conventional thermal head.

[Explanation of symbols]

 11 substrate 12 heat insulating layer 13 heating resistor 14 common electrode 15 individual electrode 16 protective layer

Claims (6)

[Claims] 1. A second mesa formed overlying a first mesa formed on the surface of a single crystal silicon substrate, and a metal oxide formed on these first and second mesas. A heat insulating layer composed of a main component, a heating resistor formed by stacking on the heat insulating layer, and a first to upper portion of the second mesa.
And a common electrode formed over the inclined portion of the mesa and connected to the heating resistor. 2. The height of the first mesa is approximately 30 to 100.
The thermal head according to claim 1, wherein the second mesa has a height of about 5 to 15 μm. 3. A ribbon peeling edge portion for peeling an ink ribbon after printing is provided at an intersection of the inclined portion of the first mesa and the inclined portion of the second mesa on the end side of the substrate. The thermal head according to claim 1, wherein: 4. The thermal head according to claim 3, wherein the distance from the approximate center of the heating resistor to the ribbon peeling edge portion is approximately 100 μm. 5. The thermal head according to claim 1, wherein the heat insulation layer is made of a material whose main component is an oxide of Ta and Si. 6. A first anisotropic etching step of forming a first mesa on the surface of a single crystal silicon substrate, and a second anisotropic etching step of forming a second mesa on the first mesa. A step, a third anisotropic etching step of reducing the inclination angle of the slopes of the first mesa and the second mesa, and a step of rounding and etching the corners of the first mesa and the second mesa. A step of forming a heat retaining layer made of a material containing Ta and Si metal oxides as main components on the etched substrate, a step of performing a first annealing treatment thereafter, and a heat generation on the heat retaining layer. A method of manufacturing a thermal head, comprising: a step of forming a resistor; a step of performing a second high temperature annealing treatment; and a step of forming an electrode on the heating resistor.