JP3298780B2 - Thermal head and method of manufacturing thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a thermal printer, and more particularly to a thermal head capable of realizing a thermal head and improving print quality in a thermal transfer printer, and a method of manufacturing the thermal head.

[0002]

2. Description of the Related Art A thermal head mounted on a thermal printer has a plurality of heating elements arranged linearly on a substrate, and selectively energizes any one of the heating elements based on desired print information. In the thermal printer, heat-sensitive recording paper is colored by heating the heating element.
In a thermal transfer printer, printing is performed by partially melting the ink of an ink ribbon and transferring it to plain paper.

FIG. 11 shows a conventional general thermal head in which a heat insulating layer 2 made of glass or the like is formed on a heat radiating substrate (hereinafter referred to as a substrate) 1 made of an insulating material such as alumina. The heat insulating layer 2 is formed such that the upper surface thereof has an arc shape. A plurality of heat generating resistors 3 are formed on the top portion 2a of the heat insulating layer 2 so as to be linearly aligned in a direction perpendicular to the plane of the drawing. This heating resistor 3 is
The heating resistor 3 made of Ta-SiO ₂ or the like is formed on the surface of the heat insulating layer 2 by sputtering or the like, and then is etched by a photolithography technique. On one side of the upper surface of these heating resistors 3,
A common electrode 4 a connected to each heating resistor 3 is laminated, and each heating resistor 3 is provided on the other side of each heating resistor 3.
In addition, individual electrodes 4b for independently supplying current are laminated. Common electrode 4a and individual electrode 4b
Is formed of, for example, Al, Cu, or the like, and is formed in a desired shape pattern by etching after being deposited by vapor deposition, sputtering, or the like.

Further, the heating resistor 3 and the common electrode 4
a, individual electrode 4b, exposed substrate 1 and heat insulating layer 2
The surface of the heating resistor 3 and the electrodes 4a, 4b
A protective layer 5 having a thickness of about 5 to 10 μm is formed to protect the electrodes 4a and 4b, and covers all surfaces except the terminal portions of the electrodes 4a and 4b.

In such a conventional thermal head, the resistance of the common electrode 4a must be reduced by forming the width of the common electrode 4a wider. Therefore, as shown in FIG. Reference numeral 3a is provided near the center or the end of the substrate 1 of the thermal head, and the dimension from the heating portion 3a of the heating resistor 3 to the end of the substrate 1 (hereinafter, referred to as edge distance L) is 1 mm or more. Was.

However, in recent years, there has been an increasing demand for a real edge in which the heating resistor 3 of the thermal head is disposed at an end of the substrate 1, and it is necessary to greatly reduce the space on the common electrode 4 a side of the substrate 1. I'm being shy.

The real edge of the thermal head can reduce the loss of the pressure between the head and the platen and improve the printing energy efficiency. In a thermal transfer printer using an ink ribbon, a wax-based It can be used widely from inks to resin-based inks, and has the advantage that the printing quality of rough paper can be significantly improved.

However, for example, when the edge distance is set to 0.
When the real edge of the thermal head is set to 2 mm or less, the space for arranging the common electrode 4a is significantly reduced. Therefore, the width of the common electrode 4a must be extremely small. The electrode 4a is turned into a resistor and its resistance value rises.
, The difference in voltage drop between both ends and the central part becomes large. In addition, a shortage of current capacity of the common electrode 4a occurs, and when current is supplied to each of the heating resistors 3, a problem such as fusing of the common electrode 4a occurs. Therefore, it is difficult to manufacture a highly practical real edge head. It was extremely difficult.

As other electrodes of the thermal head for realizing a real edge, although not shown, for example, a common electrode 4a is used as a folded electrode or a comb-shaped electrode.
b, the common electrode 4a and the individual electrode 4b are derived in the same direction.
In the case of a resolution of 600 dpi, a processing accuracy equivalent to that of a resolution of 600 dpi is required. Similarly, in the case of a resolution of 400 dpi, a processing technique of high definition equivalent to that of a resolution of 800 dpi is required. And so on
In addition to the increase in the number of manufacturing steps, the yield and the reliability are reduced, and the manufacturing cost is increased.

Further, there is a thermal head in which a common electrode 4a is formed from the end face of the substrate 1 to the back side.
Since the electrode formation is performed after dividing and polishing, the number of manufacturing steps is increased, the manufacturing efficiency is reduced, and the reliability of real edge formation within 0.2 mm is extremely low.

Further, the end face head in which the heat insulating layer 2 is formed by polishing the end face of the substrate 1 and the heating resistor 3 is formed on the upper face thereof requires a large number of man-hours in the same manner as described above, and the real edge is reduced. In this case, mass productivity is inferior and cost is high.

[0012] In view of these points, there has conventionally been an attempt to achieve a real edge by forming the common electrode 4a in a multilayer wiring structure in the heat generating portion. In this method, a conductive layer 6 made of a metal is formed on the heat insulating layer 2 and Si is formed thereon.
After laminating an interlayer insulating layer 7 made of O2 or the like by means of sputtering or the like, the interlayer insulating layer 7 is partially removed by a photolithography technique, and the heating resistor 3 is laminated thereon, thereby forming the conductive layer 7. And the heating resistor 3 are electrically connected to each other, and the interlayer insulating layer 7 and the conductive layer 6 are formed in a layer just below the heating resistor 3 that generates heat at a high temperature. .

In the thermal head having such a multilayer wiring structure, the individual electrodes 4 are formed based on a desired print signal.
When the desired heating resistor 3 is energized via the “b”, the common electrode 4 whose width dimension is formed extremely thin by real edge formation
In addition to a, since the voltage is sent to the terminal portion via the conductive layer 6, the resistance value of the common electrode 4a does not increase, and the generation of a partial voltage difference of the heating resistor 3 and the common voltage It is possible to prevent the shortage of the current capacity of the electrode 4a or the like, and to perform high-quality printing.

[0014]

However, in the above-described conventional thermal head, an interlayer insulating layer 7 is formed on the upper surface of the conductive layer 6, and these layers generate heat at a high temperature. 3, the stress between the layers is large, the reliability of the adhesion between the layers against thermal shock is significantly reduced, and the interlayer insulating layer 7 is formed by etching. In addition, a step is formed on the surface of the interlayer insulating layer 7 and the conductive layer 6, and this step may cause a connection failure between the heating resistor 3 and the conductive layer 6. When formed by the vapor deposition method, there is a problem that a pinhole is generated in the interlayer insulating layer 7 due to foreign matter or the like, and insulation failure of the interlayer insulating layer 7 occurs.

If the thickness of the interlayer insulating layer 7 is increased in order to overcome the above-mentioned problems, the stress imbalance between the respective layers is increased, and the connection failure due to an increase in the etching step is caused. However, there is a problem that the reliability is significantly reduced.

A conventional connection type thermal head as shown in FIG.
Has the same layer configuration as a normal thermal head, except that the terminal 9 of the common electrode 4a is provided on only one of the left and right sides. That is, in the conventional connection type thermal head, two thermal head blocks 8 having a symmetrical shape with each other are bonded to the connection substrate 1.

Conventionally, two thermal head blocks are connected because the common electrode 4a shown in FIG.
This is because the terminals 9 and 9 can be formed only on either the right or left side of each thermal head block 8. That is,
This is because, when three or more thermal head blocks 8 are connected, there is no practical way to connect the common electrode 4a of the thermal head block 8 at the center other than the left end and the right end to the terminal 9.

The present invention overcomes the above-mentioned problems in the prior art, and when a multi-layer wiring structure is used, the occurrence of connection failure and insulation failure in each layer can be reliably prevented. In addition, it is possible to provide a thermal head and a method of manufacturing a thermal head that can maintain reliability and that does not hinder the connection of the terminals of the common electrode even when the number of connected thermal head blocks is three or more. Aim.

[0019]

According to a first aspect of the present invention, there is provided a thermal head in which a heat insulating layer, a conductive layer, an interlayer insulating layer, a heating resistor, a common electrode, an individual electrode, and a protective layer are laminated on a heat radiating substrate. Wherein the conductive layer is made of a fusion product of a nitride or an oxide and a metal, and the interlayer insulating layer is formed with at least an oxide film of the conductive layer. Oxide film of the first interlayer insulation
And an insulating cell laminated on the first interlayer insulating layer.
It is a multi-layered interlayer insulating layer with lamic as the second interlayer insulating layer.
Characterized in that the conductive layer is made of a material as described above.
High temperature thermal oxidation treatment
Can have excellent adhesion to the substrate.
In addition, the first interlayer insulating layer is formed by surface oxidation of the conductive layer.
Therefore, the second interlayer insulating layer is a thin insulating layer of 1 μm or less.
As a result, sufficient insulation is obtained, and the surface of the insulating layer and the conductive layer
Height difference from the surface can be reduced
Therefore, the heating resistor and electrode formed on the upper surface
The electrical connection with the layers can be reliably made,
Completely eliminate reliability and yield loss due to linearization
Can be.

[0020]

[0021]

According to a second aspect of the present invention , in the thermal head according to the first aspect , the second interlayer insulating layer is formed of a silicon nitride, a silicon oxide, an aluminum nitride, and an aluminum nitride. It is characterized by being made of at least one of oxides, and can greatly improve the reliability of insulation.

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

According to a third aspect of the present invention, in the method of manufacturing a thermal head, a heat insulating layer is formed at a position corresponding to the heat generating portion on the heat radiating substrate, and a conductive material made of a resistor material is formed on the upper surface of the substrate and the heat insulating layer. Laminating layers, laminating an oxidation-resistant mask layer on the conductive layer, and forming a mask pattern at a position corresponding to a formation position of a common electrode of the mask layer and an external circuit connection portion of the common electrode. Forming,
Forming a first interlayer insulating layer by heat or plasma oxidation in an oxidizing atmosphere on the surface of the conductive layer other than the mask layer forming portion by the mask pattern; and forming an insulating ceramic material on the first interlayer insulating layer. Laminating an insulating layer consisting of, a step of forming a second interlayer insulating layer by exposing the conductive layer by etching the position corresponding to the formation position of the common electrode and the terminal portion of the common electrode by photolithography, Forming a predetermined heating resistor such that both end portions thereof are located above the second interlayer insulating layer and the conductive layer, and forming an end of the upper surface of the heating resistor on the second interlayer insulating layer side. The method is characterized by comprising a step of forming an individual electrode, a step of forming a common electrode at the end on the conductive layer side, and a step of laminating and forming a protective layer on the uppermost surface thereof.

Since the first interlayer insulating layer is formed by oxidizing the surface of the conductive layer, the inside of the pinhole of the conductive layer is also sufficiently oxidized to have insulating properties, and moreover, it is integrated with the conductive layer. Since it can be formed, there is no step and the insulation, adhesion, and heat resistance are extremely high. Further, since the upper surface of the first interlayer insulating layer is further coated with a second interlayer insulating layer having excellent insulation, adhesion and heat resistance, the reliability of the insulation can be improved.

According to a fourth aspect of the present invention, in the method of manufacturing a thermal head according to the third aspect , the oxidation-resistant mask layer is formed of silicon dioxide. The method for manufacturing a thermal head according to claim 5 is the method for manufacturing a thermal head according to claim 3 , wherein the oxidation-resistant mask layer comprises:
It is characterized by being formed of molybdenum silicide.

[0032]

[0033]

[0034]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 10 will be described.

FIG. 1 is a sectional view of a thermal head according to a first embodiment of the present invention, and FIG. 2 is a plan view of the same. FIG. 3 shows a multilayer wiring board in the course of manufacture.

In the thermal head shown in FIG. 1, a heat insulating layer 12 made of glass or the like is formed in an arc shape on an insulating substrate 11 made of ceramic or the like, and the upper surfaces of the substrate 11 and the heat insulating layer 12 are formed. A conductive layer 1 made of a fusion product of a metal nitride and a metal having low thermal conductivity and low thermal expansion.
3 is formed to a thickness of approximately 3 to 10 μm by sputtering or the like. As the fusion body of the metal nitride and the metal, a fusion body of aluminum nitride and tantalum is preferable, but instead of the fusion body of the metal nitride and the metal, a fusion of the metal oxide and the metal is used. It is also possible to use a fusion, in which case a fusion of aluminum oxide and tantalum is preferred.
The target material used when the film formation of the conductive layer 13 is performed by the sputtering method is a sintered body of aluminum nitride and tantalum in the former case, and a sintered body of aluminum oxide and tantalum in the latter case. The composition ratio of tantalum of 50 to 70% is suitable for satisfying the function described below. In the present embodiment, the composition of tantalum is 60% and aluminum nitride is 40%. A sintered target was used. The conductive layer 13
Can be replaced by conductive ceramics such as boride, nitride and silicide of high melting point metal.

As shown in FIG. 3, the conductive layer 13 is covered with an oxidation-resistant mask layer 14 so as to cover the portion where the common electrode 17a of the thermal head is provided and the connection with the external circuit. By oxidizing, the interlayer insulating layer 15 becomes substantially 1
It is formed to a thickness of ２2 μm. At this time, by partially exposing the conductive layer 13 from the interlayer insulating layer 15,
The conductive pads 13a and 13b are formed so as to be exposed. The height difference between the surface of the interlayer insulating layer 15 and the surface of the conductive pad 13a of the conductive layer 13 is within about 1 μm, and the edge is formed in a smooth shape.

The oxidation-resistant mask layer 14 used for forming the interlayer insulating layer 15 is made of insulating silicon dioxide or conductive molybdenum silicide.
The conductive layer 13 is formed to a thickness of about 0.3 μm by sputtering or the like.
When silicon dioxide is used by photolithography after the film is continuously formed, buffered hydrofluoric acid (BH
The common electrode multilayer wiring board is completed by etching and removing in F). On the other hand, when molybdenum silicide is used, dry etching is performed using CF ₄ + O ₂ gas to form a mask pattern, and a thermal oxidation process is performed. In this case, since molybdenum silicide is conductive, removal of the mask layer 14 is optional. For these etchants, materials are selected for the conductive layer 13 and the interlayer insulating layer 15 so that aluminum nitride and alumina serve as etching-resistant materials to perform a protective action.

In this embodiment, the conductive layer 13
The oxidation treatment for forming the heat insulating layer 1 is made of glass or the like.
From the heat resistance limit of 2, for 3-9 hours at a temperature of 700 ° C,
It is formed by heat treatment in an air atmosphere. In addition,
The thermal oxidation treatment of the conductive layer 13 can be replaced with a plasma oxidation treatment.

The conductive pad 13 of the conductive layer 13
a, a material of the heat generating resistor 16, for example, Ta—SiO ₂ or the like is applied by sputtering or the like on the upper surface of the a and the interlayer insulating layer 15;
By etching with ₄ + O ₂ gas, a plurality of heating resistors 16 are formed, and both ends of the heating resistors 16 are linearly arranged such that both ends thereof are located above the conductive pad portion 13a of the conductive layer 13 and the interlayer insulating layer 15, respectively. It is formed in alignment. Further, on the upper surface of the conductive pad portion 13a of the conductive layer 13 of each heating resistor 16, a common electrode 17a connected to each heating resistor 16 is formed to a thickness of about 1 to 2 μm by sputtering of aluminum or copper or the like. It is laminated. This common electrode 1
7a denotes a conductive layer 13 at a position outside the heating resistor 16.
Is connected to On the upper surface of the interlayer insulating layer 15, there are provided individual electrodes 17 for independently supplying current to each heating resistor 16.
b are formed and connected in the same manner as the common electrode 17a. Although the structure of both electrodes 17a and 17b has been described as a single-layer structure of aluminum or copper, a two-layer structure formed of a thin refractory metal molybdenum, tungsten, or the like is more accurate when the heating resistor is formed. 16 can be configured. This will be described later as a second embodiment.

Further, in order to protect the surfaces of the heat generating resistor 16, the upper common electrode 17a, the individual electrode 17b, the exposed interlayer insulating layer 15 and the like from oxidation and friction, approximately 5 to 10 μm of sialon or the like is used. Thick protective layer 1
8 is formed, and the protective layer 18
All surfaces other than the external circuit connection portions 7a and 17b (not shown) are covered.

Next, a method for manufacturing a multilayer wiring board for a thermal head according to the present embodiment will be described with reference to the flowchart shown in FIG.

First, in FIG. 3, a heat insulating layer 12 made of glass or the like having an upper surface formed in an arc shape protrudes from an upper surface of a flat substrate 11 made of ceramic or the like (step ST1).

Then, a conductive layer 13 made of tantalum aluminum nitride cermet is formed on the upper surfaces of the substrate 11 and the heat insulating layer 12 by sputtering or the like so as to have a thickness of about 3 to 10 μm (step ST2).

Next, a mask layer 14 of silicon dioxide or molybdenum silicide having heat resistance and oxidation resistance is formed on the upper surface of the conductive layer 13 by sputtering to a thickness of about 0.3 μm (step ST3). .

By photolithography, etching is performed using buffered hydrofluoric acid in the case of silicon dioxide, or by using CF ₄ + O ₂ gas in the case of molybdenum silicide, so that the wiring portion of the common electrode 17a and the external circuit connection portion are etched. A mask pattern is formed at a corresponding position (step ST4).

The etching agent used for forming the mask is
Since the aluminum nitride and aluminum oxide contained in the conductive layer 13 and the interlayer insulating layer 15 are not etched and have sufficient selectivity, the reliability of the multilayer wiring can be increased.

Then, using a heat treatment furnace in an oxygen atmosphere,
The exposed conductive layer 13 is forcibly oxidized at about 700 ° C. for several hours to form an interlayer insulating layer 15 made of tantalum pentoxide and alumina of about 1 to 2 μm in step ST.
5). Then, by removing the mask layer 14 by etching, the manufacture of the common electrode multilayer wiring board of the present invention is completed (step ST6). At this time, when molybdenum silicide is used as the material of the mask layer 14, the conductivity can be ensured even after thermal oxidation, so that it is not necessary to remove the mask layer 14, thereby reducing the number of steps. it can.

Then, the heating resistor 16, the electrodes 17a, the electrodes 17a,
By stacking and patterning the protective layer 17b and the protective layer 18, a real edge thermal head as shown in FIGS. 1 and 2 is manufactured.

In the thermal head described above, a plurality of thermal heads 12, a conductive layer 13, an interlayer insulating layer 15, a heating resistor 16, a common electrode, and a plurality of thermal heads are provided on a heat radiating substrate 11 having a multiple area of each thermal head. 17a, individual electrode 1
7b, after forming the thermal head unit 20 on which the protective layer 18 is formed, these thermal head units 20 are cut into individual thermal head blocks 21 and 21 for manufacture.

The method of cutting the thermal head unit 20 will be described below with reference to FIGS.

The method of manufacturing a thermal head according to the present embodiment utilizes laser light in a cutting step of a thermal head unit 20 having a plurality of thermal head blocks 21. The laser light is preferably excimer laser light. Was.

The excimer laser is 308 nm in XeCl gas and Kr depending on the type of gas used for the laser oscillation.
The F gas emits ultraviolet light having a wavelength of 248 nm, and the ArF gas emits ultraviolet light having a wavelength of 193 nm. Generally, in laser processing, a CO ₂ laser or a YAG laser is used.
Since the processing is performed by using a high heat spot, there is a problem that the workpiece is left with thermal damage, or a hot-melt scattered substance is attached, and is not suitable for fine processing. On the other hand, an excimer laser is an ultraviolet laser, which instantly decomposes, scatters, and removes a workpiece, and has a feature of a small heat effect and high processing quality.

In the method of manufacturing a thermal head according to the present embodiment, a groove is formed in a cut portion by excimer laser light in the cutting step of the thermal head unit 20 by applying the characteristics of the excimer laser, and then the bottom of the groove is formed. It is cut by dicing.

FIG. 5 shows the thermal head unit 20.
It is explanatory drawing which shows the cutting process of.

That is, after the formation of the protective layer 18 is completed, the substrate 11 of the thermal head immediately before the cutting step is started is removed as shown in FIG.
It is shown in (a). On the other hand, as shown in (b), after appropriately adjusting the dimension a from the end of the common electrode 17a,
The groove 22 is formed by irradiating the KrF excimer laser beam B. At this time, the depth of the groove 22 reaches the substrate 11. The output of the laser was preferably 10 to 50 W.

Next, as shown in (c), the section from the bottom of the groove 22 to the back surface of the substrate 11 is cut from the direction C by dicing.

According to this method, mechanical stress and thermal stress applied to the film laminated portion of the thermal head at the time of cutting can be extremely reduced, so that defects such as chipping and cracks can be eliminated. That is, conventionally, the dimension a from the end to the cut surface of the common electrode 17a was required to be at least 20 μm, but by the method of the present embodiment, it can be reduced to several μm. Further, the time required for forming grooves by laser is one minute to several minutes, and the time can be reduced by 1/5 to 1/10 as compared with the case where the same is performed by polishing, and low cost can be realized.

FIG. 6A is a plan view of a heat generating portion when a thermal head cut by the above-described cutting method is connected in the main scanning direction to form a long thermal head. ) Is a cross-sectional view taken along the line XX ′.

The dot gap G shown in the plan view (a)
Becomes smaller as the heating element density increases, and is about 20 μm at present. Therefore, the connecting portion 23
In this case, the distance between the ends of the heating resistors 16 of both thermal head blocks 21 must be about 20 μm. That is, it is necessary to cut the substrate within 10 μm from the end of the heating resistor 16, and the method according to the present invention is effective in consideration of cost.

In this embodiment, FIG.
As can be seen from the cross-sectional view (b), only the substrate 11 is polished so that the laser cut surface 25 of the laminated film and the end surface 26 of the substrate 11 are substantially the same. In this case, since a single kind of substance called the substrate 11 is polished, processing can be performed with high accuracy in a short time. The connection precision of the connectable thermal head blocks 21 can be increased by lapping the substrate 11 obliquely so that the laser cut surface of the laminated film is most protruded.

As described above, in the present embodiment, when the desired heating resistor 16 is energized via the individual electrode 17b based on the desired print signal, the common electrode 17a Since the conductive layer 13 having the same function is provided, the conductive pad portion 1 as an external circuit connection portion is provided.
From 3b, a uniform voltage can be applied to each heating resistor 16, and print density unevenness can be eliminated.

In a line thermal head in which the aspect ratio of the substrate is significantly increased, when a voltage is applied from both ends of the substrate 11, the distance to the center of the substrate 11 is long. As the value increases, a voltage drop occurs in the substrate 11 and the heating temperature of the heating resistor 16 decreases, causing print density unevenness. In the thermal head of the present embodiment,
Since the conductive layer 13 is laid on the entire surface of the substrate 11, as shown in FIG. 2, the conductive pad portion 13b serving as an external circuit connection portion of the common electrode 17a can be taken out at an arbitrary position on the upper surface of the substrate 11, It is possible to connect three or more thermal heads without considering the connection of the common electrodes 17a. That is, in the line thermal head as described above, a voltage can be applied not only from both ends of the substrate 11 but also from the center of the substrate 11.
Since a uniform voltage is applied to 6, the occurrence of print density unevenness can be eliminated.

In the present embodiment, the conductive layer 13
A fusion film of a metal nitride and a metal used as a material has low thermal conductivity and low thermal expansion, has excellent adhesion to the substrate, can withstand high-temperature annealing, and has a higher thermal conductivity than the metal film. Has the advantage that the thermal characteristics of the thermal head are not reduced.

Further, since the interlayer insulating layer 15 made of tantalum pentoxide and alumina is formed by thermal oxidation of the conductive layer 13 and used, a problem occurs when the interlayer insulating layer is formed by a deposition film or a coating film. A short circuit due to pinholes and dust between the conductive layer 13 and the heating resistor 16 can be eliminated. Further, the interlayer insulating layer 15 formed by such a thermal oxidation treatment has a high hardness, does not easily cause abrasion due to handling, and tantalum pentoxide and alumina have a high insulating reliability. Has a definitive theory. In addition, since the conductive layer 13 and the interlayer insulating layer 15 are formed integrally, it is possible to remarkably enhance the adhesiveness in addition to the insulating property. Furthermore, since the entire substrate 11 is annealed at a high temperature by passing through the thermal oxidation process, the mechanical and thermal reliability of the multilayer wiring substrate can be ensured.

The interlayer insulating layer 15 is formed by thermal oxidation.
Is formed, the conductive connection pad portion 13a of the conductive layer 13 is formed.
And the surface height of the interlayer insulating layer 15 can be made substantially the same, and the electrical connection between the heating resistor 16 formed thereon and the conductive layer 13 can be reliably performed.

Therefore, according to the thermal head of this embodiment, even if the space of the wiring portion of the common electrode 17a is extremely small and is made to be a real edge, the conductive layer 13 having the same function as the common electrode 17a is formed on almost the entire surface of the substrate 11. Is provided, it is possible to evenly apply a voltage to each heating resistor 16, and it is possible to reliably prevent problems such as uneven printing density and insufficient current capacity, and Can be achieved.

As described above, since it is possible to achieve an appropriate real edge, the size of the substrate 11 can be reduced, and the manufacturing cost can be reduced. Further, a resin-based ink ribbon, which cannot be used in the conventional line thermal head, can be used, so that the printing quality of rough paper can be significantly improved. Further, in the thermal head having a real edge, the loss of the pressure contact pressure of the heating resistor 16 with respect to the platen is reduced, and power saving can be achieved.

Further, real edge formation can be realized by a method of cutting a substrate using laser processing.
High quality printing on rough paper and plain paper becomes possible. Further, according to the method for cutting a substrate, precise cutting can be performed without causing chipping or cracking on the cut surface. Since the required time is short, there is an effect that it can be manufactured at low cost.

FIGS. 7 and 8 show the second and third embodiments of the thermal head of the present invention, and FIG. 9 is a flow chart showing a method of manufacturing a multilayer wiring board for the thermal head of the present embodiment.

In the second embodiment shown in FIG. 7, a heat insulating layer 12 made of glass or the like is formed in an arc shape on an insulating substrate 11 made of ceramic or the like.
And a conductive layer 1 made of a resistor material on the heat insulating layer 12.
3 is formed to a thickness of approximately 3 to 10 μm. A first interlayer insulating layer 15a is formed on the upper surface of the conductive layer 13 other than the portion where the common electrode 17a of the thermal head is provided and the portion connected to an external terminal (not shown) by heat or plasma oxidation. It is formed to a thickness of about 1 to 2 μm, and a conductive or insulating mask layer 14 made of molybdenum silicide or silicon dioxide having oxidation resistance is laminated on the conductive layer 13 in other portions.

The first interlayer insulating layer 15 on the conductive layer 13
On the upper surface of a, a second interlayer insulating layer 15b made of silicon or aluminum oxide or nitride is formed to a thickness of about 0.1 to 1.0 μm by sputtering or the like, and then etched by a photolithographic technique. As a result, the conductive mask layer 14 is exposed, and the multi-layered interlayer insulating layers 15a, 1 are exposed.
5b is formed. In this case, when the insulating mask layer 14 is formed, the entire mask layer 14 is removed as in the first embodiment.

On this, a plurality of heating resistors 16 are formed by forming a heating resistor 16 made of Ta-SiO2 or the like by sputtering or the like and then etching the film by photolithography. . Both ends of each heating resistor 10 have the conductive mask layer 1
4 and the second interlayer insulating layer 15b.

Further, a common electrode 17a made of a refractory metal or a silicide thereof, which is connected to each of the heating resistors 16, is laminated on the upper surface of the side of the conductive mask layer 14 of each of the heating resistors 16. The second of the heating resistor 16
On the upper surface of the end portion on the side of the interlayer insulating layer 15b, there are provided an individual electrode 17b made of a refractory metal or a silicide thereof and an individual electrode 17c made of aluminum, copper, gold, or the like for independently supplying current to each heating resistor 16. It is connected.
Here, the common electrode 17a side can be formed as a hard and thin electrode without the need of disposing a soft good conductor material such as the individual electrode 17c by multi-layer wiring. Can be prevented from deteriorating the printing durability life.

Further, the heating resistor 16, the common electrode 17a, and the individual electrodes 17b and 17c are protected by approximately 5-10
A protective layer 18 having a thickness of μm is formed so as to cover all surfaces except for external connection terminals (not shown).

In the third embodiment shown in FIG. 8, the order of formation of the heating resistor 16 and the electrodes 17a and 17b is reversed, and the lower layer of the heating resistor 16 is made of a high melting point metal or a high melting point metal. The common electrode 17a and the individual electrode 17b are formed by laminating silicide to a thickness of approximately 0.1 to 0.5 μm by sputtering or the like and etching by photolithography. The heating resistor material is similarly laminated on the upper surface and etched to form the heating resistor 1.
6 are formed. A conductive material made of aluminum, copper, gold, or the like is laminated on the upper surface by sputtering or the like, and is etched by photolithography to form individual electrodes 17.
Only c was formed. As described above, the common electrode 17a is made of a refractory metal or a silicide thereof and is formed thinly only under the heating resistor 16 without using a soft electrode material, thereby covering the common electrode 17a of the real edge thermal head. The durable life is longer with respect to the printing concentrated load.

Next, a method of manufacturing a real edge thermal head according to the second and third embodiments will be described with reference to a flowchart showing a manufacturing process of a multilayer wiring board shown in FIG.

First, in FIG. 9, a heat insulating layer 12 made of glass or the like having an upper surface formed in an arc shape protrudes from the upper surface of a flat substrate 11 made of alumina or the like (step ST1).

Next, the refractory metals Ta, Cr, Mo, W, Ti, Zr, and N are deposited on the upper surfaces of the substrate 11 and the heat insulating layer 12.
b, Hf, V and insulators SiO ₂ , Si ₃ N ₄ , Al ₂
A conductive layer 13 is formed by sputtering a resistor cermet of O ₃ or AlN or a conductive ceramic of a high melting point metal such as boride, nitride, carbide, or silicide into a thin film having a thickness of approximately 3 to 10 μm. (Step ST2).

Next, a mask layer 14 made of molybdenum silicide or insulating SiO ₂ having heat resistance, oxidation resistance and conductivity is formed on the upper surface of the conductive layer 13 to a thickness of about 0.1 to 0.5 μm by sputtering or the like. A layer is formed to have a film thickness (step ST3).

Next, the common electrode 17 is formed by photolithography.
An oxidation-resistant mask pattern is formed at a position corresponding to the wiring portion a and a connection portion with an external terminal (not shown) (step ST4).

Next, heat treatment in an oxygen atmosphere (about 700 to 8)
2 hours at 00 ° C.) or by plasma oxidation treatment
The surface of the conductive layer 13 is forcibly oxidized to form a first interlayer insulating layer 15a of about 1 to 2 μm (step ST5).

Next, SiO ₂ , Si ₃ N having heat resistance, oxidation resistance and insulating properties are formed on the upper surface of the first interlayer insulating layer 15a.
_4. Any one of Al ₂ O ₃ and AlN is formed in a thickness of about 0.1 to 1.0 μm by sputtering or the like (step ST6).

Next, the common electrode 17 is formed by photolithography.
By removing the insulating film at a position corresponding to the arrangement portion a and the connection portion with the external terminal (not shown) by etching to expose the conductive portion of the mask layer 14, the multilayer wiring board of the present embodiment Is completed (step ST7).

After that, the heating resistor 16 and the electrodes 17a, 17b and 17c are formed on the multilayer wiring board.
By coating the protective layer 18 thereon, a real edge thermal head as shown in FIG. 7 can be manufactured.

Before the heating resistor 16 is formed on the multilayer wiring board, the electrodes 17a and 17b are formed of a refractory metal or a silicide thereof to a thickness of about 0.1 to 0.5 μm. Forming a resistor 16 and an individual electrode 17c;
By coating the protective layer 18 thereon, a real edge thermal head as shown in FIG. 8 can be manufactured.

Next, the operation of the second and third embodiments will be described.

In the present embodiment, when a desired heating resistor 16 is energized through the individual electrodes 17b and 17c based on a desired print signal, a conductive material having the same action as the common electrode 17a is formed on substantially the entire surface of the substrate 11. Since the layer 13 is provided, current flows through the conductive layer 13 in addition to the common electrode 17a, so that a uniform voltage can be applied to each heating resistor 16.

In this case, in this embodiment, the conductive layer 13, the heating resistor 16, and the electrodes 17a, 17b, 1
7c, the first interlayer insulating layer 15a made of an insulating oxide formed by forcibly oxidizing the surface of the conductive layer 13
Is used, the inside of the pinhole of the conductive layer 13 also has an insulating property, and since it can be formed integrally with the conductive layer 13, the reliability of the insulating property and adhesion can be improved. Further, on the upper surface of the first interlayer insulating layer 15a, a second interlayer insulating layer 15b made of an oxide or nitride of silicon or aluminum and having excellent insulation and adhesion is laminated and formed to form a multilayer interlayer insulating layer. Layers 15a, 1
5b, the multilayer wiring board of the present embodiment can have extremely high reliability of insulation and adhesion. In the present embodiment, the first interlayer insulating layer 15a is integrally formed by oxidizing the surface of the conductive layer 13, and when the conductive mask layer 14 is used, this is also applied. Since it can be used without being removed, the height of the surface of the first interlayer insulating layer 15a and the surface of the conductive mask layer 14 which is the exposed portion of the conductive layer 13 can be made substantially the same. The thickness of the interlayer insulating layer 15b is approximately 0.
Since the heating resistor 16 and the common electrode 17a can be formed thereon with a small step in the range of 1 to 1.0 μm, electrical connection can be performed more reliably.

Further, since the conductive layer 13 of the present embodiment uses a resistor material made of a cermet of a high melting point metal and a ceramic, the conductive layer 13 is essentially excellent in heat resistance, heat insulation and adhesion. In particular, even if it is formed on the entire surface of the substrate 11, the thermal efficiency of the heating element does not decrease. Further, since a soft conductive material does not need to be provided on the common electrode 17a side, a thermal head having excellent printing durability life can be obtained even if the real edge is formed near the limit.

Therefore, according to the real edge thermal head of this embodiment, even if the space of the wiring portion of the common electrode 17a is reduced to a real edge, the conductive surface having the same action as the common electrode 17a is formed on substantially the entire surface of the substrate 11. Since the layer 13 is provided and has a plurality of interlayer insulating layers 15a and 15b,
A voltage can be evenly applied to each of the heating resistors 16, and it is possible to reliably prevent problems such as uneven printing density, insufficient current capacity, and inconvenience due to current leakage. Can be manufactured well.

Incidentally, the edge distance of the real edge thermal head of the present embodiment is determined by serially calculating the distance from the center of the heating element disposed at the end of the substrate 11 to the edge of the substrate 11 at which the ink ribbon is peeled off. 100 μm easily in both head and line head
It can be: As a result, an unprecedented new improvement effect has been produced. In this way, it is possible to make a real edge near the time limit,
The size of the substrate 11 can be reduced, and the manufacturing cost can be reduced. In addition, a resin-based ink ribbon, which cannot be used with a conventional line thermal head, can be used, and the printing quality of rough paper can be significantly improved.

Further, in the thermal head having a real edge as close to the limit as possible, the loss of the pressure contact pressure of the heating element with respect to the platen is remarkably reduced, and the effect of crushing the irregularities of the fiber of the paper is increased. While improving significantly,
Transfer efficiency is improved, and power saving can be achieved.

FIG. 10 is a sectional view of a thermal head block 21 showing a fourth embodiment of the thermal head of the present invention.

The thermal head block 21 of the present embodiment
Is that a silicon wafer is used as the heat radiating substrate 11 and the heat generating portion 11a is formed in a convex shape, and the heat insulating layer 12 is formed on the heat generating portion 11a. And the heating resistor 1
6 in that a common electrode side lower electrode layer 24a and an individual electrode side lower electrode layer 24b are formed in a lower layer, and the other configuration is the same as that of the above-described first embodiment.

The silicon wafer constituting the radiating substrate 11 has a thermal conductivity approximately five times as large as that of alumina ceramics frequently used as a material of the radiating substrate 11, so that the silicon wafer has good heat radiation and the thermal response of the thermal head. Performance is improved, and high-speed driving becomes possible.

Further, since the silicon wafer is a single crystal, anisotropic etching can be performed. Therefore, by utilizing this feature, a portion corresponding to the heat generating portion 11a can be formed as a convex portion. Since anisotropic etching is used, the dimensional reproducibility of the convex shape is good.

Next, the heat retaining layer 12 is made of a fusion of silicon oxide and metal oxide, and the metal oxide is preferably tantalum oxide and tungsten oxide. Also, if a sputtering method is used for film formation,
Variation in film thickness can be suppressed to ± 5%.

As described above, the thermal head block 21 according to the present embodiment has high three-dimensional dimensional accuracy,
The thermal characteristics determined by the thickness of the heat insulating layer 12 are also uniform in a large number of blocks, and the thermal head blocks 21 that can be combined at the time of connection can be easily selected, so that the productivity of the connection type thermal head can be improved.

The lower electrode layer 24 is made of a thin film of molybdenum and is formed by dry etching. Therefore, the size of the heating resistor in the sub-scanning direction is uniform, and variation in the resistance value of the heating resistor can be suppressed. When the lower electrode layer 24 is formed as in this embodiment, only the individual electrode 17b is formed as the electrode layer, and the common electrode 17a need not be provided. In other words, as a configuration,
On the common electrode side, only the lower electrode layer 24a is provided, and the conductive layer 1
3 and the heating resistor 16 to form the lower electrode layer 24 on the common electrode side.
a, the individual electrode side is the individual electrode 17a and the lower electrode 2
The heating resistor 16 is sandwiched between the two layers 4b and 4b. This is because the common electrode-side lower electrode layer 24a is electrically connected to the conductive layer 13 so that the common electrode 1
It is not necessary to provide 7a, but rather, by disposing a soft film such as aluminum as an electrode layer on the common electrode side, the mechanical strength of this portion is increased, and the film is peeled against the pressing force applied during printing. This realizes a structure in which no problem occurs.

As described above, according to the thermal head of this embodiment, the print durability of the thermal head can be improved.

Note that the present invention is not limited to the above-described embodiment, and can be changed as needed.

[0103]

As described above, according to the present invention, according to the present invention, a conductive material made of a cermet material of a nitride-metal fusion or oxide-metal fusion, having low thermal conductivity and thermal expansion. Since the layer is a layer, even if a high-temperature thermal oxidation treatment is performed, the layer has excellent adhesion to a substrate.

Further, since a conductive layer having the same function as the common electrode of the thermal head is provided on the entire surface of the substrate, a uniform voltage can be applied to each heating resistor, and the thermal characteristics can be improved. Since defects such as reduction, unevenness of print density, insufficient current capacity, and current leak can be reliably prevented, it is possible to appropriately cope with real edge of the thermal head. Furthermore, if the interlayer insulating layer is formed in a plurality of layers, the reliability of the insulating property is further improved.

In the manufacturing process of the multi-layer substrate, nitride (eg, aluminum nitride) and oxide (eg, aluminum oxide) constituting the conductive layer are converted into an etchant such as buffered hydrofluoric acid or CF ₄ + O ₂ gas. On the other hand, since it is difficult to etch, the thermal oxidation mask and the resistor pattern can be formed with high precision without damaging the conductive layer and the interlayer insulating layer, thereby increasing the production yield.

Further, since an oxidation-resistant mask is formed on the surface of the conductive layer and thermally oxidized, an interlayer insulating layer integrated with the conductive layer is formed, so that a step between the exposed portion of the conductive layer and the interlayer insulating layer is formed. Can be minimized, and insulation, adhesion, and electrical conductivity with the heating resistor can be ensured. Further, the high-temperature annealing in the oxidation step of forming the interlayer insulating layer can increase the mechanical and thermal reliability of the multilayer wiring board.

Further, by using a real edge thermal head using the multilayer wiring board of the present invention, it is possible to form at least three or more external circuit connection portions of the common electrode in the substrate, and to achieve uneven printing density and current capacity. Insufficiency or the like due to shortage can be reliably prevented. Further, the size of the line thermal head substrate can be reduced, and the manufacturing cost can be reduced. Further, even when the real edge is formed near the limit, the common power supply at the edge portion can be formed thinly with a hard material, so that the printing life can be extended with the protection layer. In addition, the real edge makes it possible to use a resin-based ink ribbon, and by optimizing the ink ribbon, the printing quality of rough paper can be significantly improved. Furthermore, the loss of the pressure contact pressure of the heating resistor to the platen can be significantly reduced, and the effect of crushing the irregularities of the paper fibers is significantly increased. Can be achieved.

Also, by realizing the real edge of each thermal head block by the method of cutting the substrate of the thermal head unit using laser processing, high quality printing on rough paper or plain paper is possible. Become. Further, according to the method for cutting a substrate, precise cutting can be performed without causing chipping or cracking on the cut surface. Since the required time is short, there is an effect that it can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal head according to a first embodiment of the present invention.

FIG. 2 is a plan view of the thermal head according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a multi-layer wiring board in the course of manufacture according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a method for manufacturing a multilayer wiring board of the thermal head according to the first embodiment.

5A is a cross-sectional view showing the substrate of the thermal head immediately before the cutting step is started. FIG. 5B is a cross-sectional view showing a state in which a groove is formed by irradiating a laser beam. Sectional view showing the state of cutting up to the dicing method

6A is a plan view of a heat generating portion of the thermal head connected in the main scanning direction. FIG. 6B is a cross-sectional view taken along line XX ′ in FIG.

FIG. 7 is a sectional view of a thermal head according to a second embodiment of the present invention.

FIG. 8 is a sectional view of a thermal head according to a third embodiment of the present invention.

FIG. 9 is a flowchart illustrating a method for manufacturing a multilayer wiring board of a thermal head according to the second and third embodiments.

FIG. 10 is a sectional view of a thermal head showing a fourth embodiment of the present invention.

FIG. 11 is a sectional view showing the configuration of a conventional general thermal head.

FIG. 12 is a plan view showing a configuration of a conventional connection type thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 11a Heating part 12 Heat insulating layer 13 Conductive layer 13a Conductive pad part 14 Mask layer 15 Interlayer insulating layer 15a First interlayer insulating layer 15b Second interlayer insulating layer 16 Heating resistor 17 Electrode 17a Common electrode 17b Individual electrode 18 Protective layer 19a Common electrode external circuit connection portion 19b Individual electrode external circuit connection portion 20 Thermal head unit 21 Thermal head block 22 Groove 23 Connecting portion 24 Lower electrode layer 24a Common electrode side lower electrode layer 24b Individual electrode side lower electrode layer 25 Laser cut surface 26 End face

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-32630 (JP, A) JP-A-5-50628 (JP, A) JP-A-5-104760 (JP, A) 162349 (JP, A) JP-A-5-286995 (JP, A) JP-A-5-261948 (JP, A) JP-A-6-106758 (JP, A) JP-A-57-79641 (JP, A) JP-A-58-131761 (JP, A) JP-A-2-94563 (JP, A) JP-A-5-221000 (JP, A) JP-A-5-330110 (JP, A) JP-A-63-49451 (JP, A) JP-A-5-301364 (JP, A) JP-A-6-115133 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/335

Claims (5)

(57) [Claims] 1. A heat insulating layer, a conductive layer, and an interlayer insulating layer on a heat radiating substrate.
Layer, heating resistor, common electrode, individual electrode and protective layer.
A thermal head comprising:
And a common electrode consisting of a fusion of
Are electrically connected, and the interlayer insulating layer is at least
Is also formed with an oxide film of the conductive layer.
The oxide film of the electric layer is used as a first interlayer insulating layer, and the first interlayer insulating layer
Insulating ceramic laminated on top of the second interlayer insulating layer
Characterized in that it is a multi-layered interlayer insulating layer.
Head. Wherein said second interlayer insulating layer, a nitride of silicon, oxide of silicon, according to claim 1, characterized in that it consists of at least one of a nitride and aluminum oxide in the aluminum Thermal head. 3. A step of projecting a heat insulating layer at a position corresponding to a heat generating portion on a heat radiating substrate, laminating a conductive layer made of a resistor material on the substrate and the upper surface of the heat insulating layer, and forming an acid-resistant layer on the conductive layer. Laminating a maskable layer, a step of forming a mask pattern at a position corresponding to a formation position of a common electrode of the mask layer and an external circuit connecting portion of the common electrode, and a mask layer forming portion by the mask pattern A step of forming a first interlayer insulating layer by heat or plasma oxidation in an oxidizing atmosphere on the surface of the conductive layer other than the above, laminating an insulating layer made of an insulating ceramic material on this first interlayer insulating layer, A step of etching the position corresponding to the formation position of the common electrode and the terminal portion of the common electrode by photolithography to expose the conductive layer to form a second interlayer insulating layer; Forming a predetermined heating resistor so as to be located above the two interlayer insulating layers and the conductive layer; and forming an individual electrode at an end of the upper surface of the heating resistor on the side of the second interlayer insulating layer. Forming a common electrode at an end on the conductive layer side; and laminating and forming a protective layer on the uppermost surface of the common electrode. Wherein said oxidation-resistant mask layer, manufacturing method for a thermal head according to claim 3, characterized in that it is formed of silicon dioxide. Wherein said oxidation-resistant mask layer, manufacturing method for a thermal head according to claim 3, characterized in that it is formed of molybdenum silicide.