JP2004114633A - Thermal head and thermal printer employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance thermal head in which a conductive layer can be protected against corrosion effectively over a long term, and to provide a thermal printer employing it. <P>SOLUTION: A large number of heating resistors 3 and a conductive layer 4 principally comprising aluminum are applied to the upper surface of a substrate 1 and coated with a protective layer 5. In such a thermal head, the conductive layer 4 exposed from a defect in the protective layer 5 is coated with an insulating film 6 of aluminum oxide and then the insulating film 6 and the protective layer 5 are coated with a wear resistant layer 7. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermal head used as a printing device such as a facsimile or a video printer, and a thermal printer using the same.
[0002]
[Prior art]
Conventionally, a thermal head has been used as a printing device such as a facsimile or a video printer.
[0003]
As shown in FIG. 4, for example, such a conventional thermal head includes a large number of heating resistors 13 and a pair of conductive layers 14 electrically connected to the heating resistors 13 on an upper surface of a substrate 11 made of alumina ceramics or the like. And a protective layer 15 made of silicon nitride (Si ₃ N ₄ ) or the like is applied, and a recording medium such as a thermal paper or an ink film is heated using an external transport means. While being conveyed on the heating resistor 13, the heating resistors 13 are individually and selectively heated based on the image data, and the recording medium is brought into sliding contact with the surface of the protective layer on the heating resistor 13. Is transferred to the recording medium via the protective layer 15 to form a print (see Patent Document 1).
[0004]
The protective layer 15 is for protecting the heating resistor 13 and the pair of conductive layers 14 from abrasion due to sliding contact of the recording medium, and the protective layer 15 is formed of an inorganic material such as silicon nitride. It is formed by applying a material to a predetermined thickness on the surfaces of the heating resistor 13 and the pair of conductive layers 14 by employing a conventionally known sputtering method.
[0005]
[Patent Document 1]
JP 2000-135803 A
[Problems to be solved by the invention]
However, a large number of film defects called "pinholes" are formed in the protective layer 15 formed by a thin film method such as a sputtering method. When Na ions, K ions, Cl ions, and the like come into contact with the conductive layer 14, the conductive layer 14 is corroded and melted, thereby significantly increasing the wiring resistance of the conductive layer 14, and causing the heating resistor 13 to generate heat at a desired temperature. Had the drawback of being impossible.
[0007]
In order to solve the above-mentioned drawbacks, it has been proposed to cover the entire surface of the protective layer 5 with an overcoat layer made of an acrylic resin, a silicone resin or the like, and to close film defects with the overcoat layer.
[0008]
However, when the overcoat layer is applied to the entire surface of the protective layer 5, the overcoat layer made of resin has a relatively low adhesion strength to the protective layer. The applied large frictional force causes the overcoat layer to be relatively easily peeled off from the underlayer, opening up a film defect, and is not a measure for effectively preventing corrosion of the conductive layer for a long period of time.
[0009]
The present invention has been made in view of the above-mentioned drawbacks, and has as its object to provide a high-performance thermal head and a thermal printer that can effectively prevent corrosion of a conductive layer for a long period of time.
[0010]
[Means for Solving the Problems]
The thermal head of the present invention is directed to a thermal head having a large number of heating resistors and a conductive layer mainly composed of aluminum deposited on an upper surface of a substrate, and a protective layer formed on the heating resistors and the conductive layer. An insulating film made of aluminum oxide is deposited on a conductive layer exposed from a film defect in the protective layer, and the insulating film and the protective layer are covered with a wear-resistant layer. .
[0011]
The thermal head according to the present invention is characterized in that the protective layer and the wear-resistant layer are made of a Si-N-based or Si-ON-based inorganic material.
[0012]
A thermal printer according to the present invention includes the above-described thermal head and a transport unit that transports a recording medium onto the thermal head.
[0013]
According to the present invention, an insulating film made of aluminum oxide is deposited on the conductive layer exposed from film defects in the protective layer, and the insulating film and the protective layer are covered with a wear-resistant layer. The void of the film defect in the protective layer is closed by the insulating film, and the region where the film defect is formed is well covered with the wear-resistant layer, and is included in the moisture in the atmosphere, the thermal paper, and the like. Even if Na ⁺ ions, K ⁺ ions, Cl ⁻ ions, etc. try to enter through the film defects in the protective layer, the entry is favorably prevented by the insulating film or the wear-resistant layer, and moisture and Inconveniences such as corrosion and melting of the conductive layer due to contact with ions are effectively prevented, the wiring resistance of the conductive layer is kept substantially constant, and the heating resistor can be heated at a desired temperature.
[0014]
Moreover, in this case, since the insulating film is formed of aluminum oxide having good adhesion to a Si-N-based or Si-ON-based inorganic material, the insulating film and the protective layer, and the insulating film and the abrasion resistant. The layers will each be firmly adhered. Therefore, even when the recording medium is repeatedly and strongly slid against the wear-resistant layer and a large stress is applied to the wear-resistant layer and the protective layer, the wear-resistant layer may be peeled off from the insulating film as a starting point. Or, a reliable thermal head and thermal printer that can effectively prevent corrosion of the conductive layer for a long time with little insulation film peeling off from film defects in the protective layer are realized. Will be done.
[0015]
Further, according to the present invention, since the surface of the insulating film is covered with the wear-resistant layer, the recording medium does not directly contact the insulating film, so that no excessive stress is applied to the insulating film. The occurrence of cracks and the like in the film can be effectively prevented, which also makes it possible to maintain high reliability of the thermal head and the thermal printer.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a thermal head according to an embodiment of the present invention, wherein 1 is a substrate, 2 is a partial glaze layer, 3 is a heating resistor, 4 is a conductive layer, 5 is a protective layer, 6 is an insulating film, Reference numeral 7 denotes a wear-resistant layer.
[0017]
The substrate 1 is formed in a rectangular shape using an electrically insulating material such as alumina ceramics, and has a partial glaze layer 2, a heating resistor 3, a pair of conductive layers 4, a protective layer 5, The film 6, the wear-resistant layer 7, etc. are attached, and function as a supporting base material for supporting them.
[0018]
When the substrate 1 is made of, for example, alumina ceramics, a ceramic material powder of alumina, silica, magnesia or the like is mixed with an appropriate organic solvent and a solvent to form a slurry, which is formed by a conventionally known doctor blade method or the like. Then, a ceramic green sheet is formed, punched into a predetermined shape, and then fired at a high temperature.
[0019]
On the upper surface of the substrate 1, a partial glaze layer 2 made of glass is attached in a band shape in the longitudinal direction of the substrate 1, and a number of heating resistors 3 are provided near the top thereof.
[0020]
The partial glaze layer 2 is formed to have, for example, an arc-shaped cross section with a radius of curvature of 1 mm to 4 mm, and the thickness of the top is set to 20 μm to 160 μm.
[0021]
Since the partial glaze layer 2 is formed of glass having low thermal conductivity (thermal conductivity: 0.7 W / m · K to 1.0 W / m · K), the heat generated by the heating resistor 3 inside the partial glaze layer 2. Of the thermal head to maintain good thermal response characteristics of the thermal head, specifically, as a heat storage layer for raising the temperature of the heating resistor 3 to a predetermined temperature required for printing in a short time. Make
[0022]
The partial glaze layer 2 is formed by printing and applying a predetermined glass paste obtained by adding and mixing an appropriate organic solvent to glass powder on the upper surface of the substrate 1 by a conventionally known screen printing or the like. It is formed by baking at high temperatures.
[0023]
Further, a large number of heating resistors 3 provided near the top of the partial glaze layer 2 are linearly arranged in the main scanning direction at a density of, for example, 600 dpi (dot per inch). Is formed of an electric resistance material such as TaN, TaSiO, TiSiO, or the like. When power is applied through a pair of conductive layers 4 and the like electrically connected to both ends thereof, Joule heat is generated, and a recording medium is generated. The temperature is required to form an image on the image, for example, 130 ° C. to 350 ° C.
[0024]
The pair of conductive layers 4 connected to the heating resistor 3 function as a power supply wiring for supplying power to the heating resistor 3 and the like, and are made of a metal material containing aluminum as a main component, and a partial glaze layer. After being attached and led out from the upper side to the surface of the substrate 1, the lead-out portion is electrically connected to a corresponding terminal of the driver IC 6.
[0025]
Such a heating resistor 3 and a pair of conductive layers 4 are made of a conventionally well-known thin film forming technique, for example, a substrate on which a partial glaze layer 2 is made of an electric resistance material such as TaN and a metal material mainly containing aluminum. The upper surface of the substrate 1 is formed by sequentially applying a known method such as sputtering, and processing these sputtered films into a predetermined pattern by employing a conventionally known photolithography technique or etching technique.
[0026]
A protective layer 5 is applied to the surfaces of the above-described many heat generating resistors 3 and the pair of conductive layers 4, and the protective layer 5 allows the many heat generating resistors 3 and the many pair of conductive layers 4 to be shared. Is coated.
[0027]
The protective layer 5 is made of a Si—N-based or Si—O—N-based inorganic material such as silicon nitride (Si ₃ N ₄ ) or sialon (Si—Al—O—N). To protect the conductive layer 4 from corrosion due to contact with moisture or the like contained in the atmosphere.
[0028]
The protective layer 5 is formed by applying a known thin film forming technique, for example, sputtering, and applying the above-mentioned inorganic material to the upper surface of the heating resistor 3 or the pair of conductive layers 4 to a thickness of 0.1 μm to 5 μm. In the protective layer 5 thus formed, a film defect called a “pinhole” is formed at a rate of 10 / cm ² to 50 / cm ² .
[0029]
Then, an insulating film 6 is deposited inside the film defects formed in the protective layer 5 and on the conductive layer exposed from inside the film defects, and further on the insulating film 6 and the protective layer 5. Is provided with a wear-resistant layer 7.
[0030]
The insulating layer 6, the conductive layer 4 was oxidized to aluminum oxide which is formed, on the resistivity of ^{1 × 10 14 Ω · cm~1.2 ×} 10 14 Ω · cm, a density _{(d 2} ), The ratio (d ₁ / d ₂ ) of the density (d ₁ ) of the metal material constituting the conductive layer 4 to 1.20 to 1.70, respectively, and the film defects formed in the protective layer 5 To prevent the moisture in the atmosphere and the ions attached to the surface of the recording medium from entering the conductive layer via the film defect.
[0031]
On the other hand, the wear-resistant layer 7 is made of a silicon-nitride (Si ₃ N ₄ ), a mixed material of silicon nitride containing carbon, a Si—N-based material such as sialon (Si—Al—O—N), or the like. Alternatively, they are formed of Si-ON-based inorganic materials (Vickers hardness Hv is 1500 to 4000), and since these inorganic materials are excellent in abrasion resistance, they are formed on the insulating film 6 and the protective layer 5. To prevent the recording medium such as thermal paper from directly slidingly contacting the insulating film 6.
[0032]
Thus, on the conductive layer 4 exposed from the film defect in the protective layer 5, the insulating film 6 made of aluminum oxide formed by oxidizing the conductive layer 4 is formed, and the insulating film 6 and the protective layer are formed. 5 is covered with the wear-resistant layer 7, the gap of the film defect in the protective layer 5 is closed by the insulating film 6, and the region where the film defect is formed is well covered with the wear-resistant layer 7. That is, even if Na ⁺ ions, K ⁺ ions, Cl ⁻ ions, or the like contained in the moisture in the atmosphere, thermal paper, or the like try to penetrate through the film defect in the protective layer 5, the permeation is caused by the insulation. The conductive layer 4 is effectively prevented by the film 6 and the wear-resistant layer 7, and effectively prevents the conductive layer 4 from being corroded and melted by contact with moisture and ions, thereby substantially reducing the wiring resistance of the conductive layer 4. It is possible to keep the heating resistor 3 at a desired temperature while keeping it constant. That.
[0033]
Moreover, in this case, since the insulating film 6 is formed of aluminum oxide having good adhesion to a Si-N-based or Si-ON-based inorganic material, the insulating film 6 and the protective layer 5 and the insulating film 6 are formed. And the wear-resistant layer 7 are firmly bonded. Therefore, even when the recording medium is repeatedly and strongly slid on the abrasion-resistant layer 7 and a large stress is applied to the abrasion-resistant layer 7 and the protective layer 5, the abrasion-resistant layer 7 is used as a starting point. The wear layer 7 is hardly peeled off, or the insulating film 6 is hardly peeled off from the inside of the film defect in the protective layer 5, and the reliability which can effectively prevent the corrosion of the conductive layer 4 for a long period of time. A high thermal head and a thermal printer will be realized.
[0034]
Further, since the surface of the insulating film 6 is covered with the abrasion-resistant layer 7, the recording medium does not directly contact the insulating film 6, so that no excessive stress is applied to the insulating film 6. In addition, it is possible to effectively prevent the occurrence of cracks and the like in the insulating film 6, thereby maintaining high reliability of the thermal head and the thermal printer.
[0035]
Furthermore, since the set ratio of the density of the conductive layer 4 for the density _{(d 2)} of the insulating film 6 _{(d 1)} to _(d 1 / _{d 2)} to 1.20 to 1.70, an insulating film 6 The constituent aluminum oxide is in a very dense state, and the sealing property for film defects can be further improved.
[0036]
Here, the density of the insulating film 6 ratio of the density of the conductive layer 4 for the _{(d 2) (d 1)} (d 1 / d 2) is smaller than 1.20, the insulating film 6 and the relatively coarse layer On the other hand, if the ratio (d ₁ / d ₂ ) is greater than 1.70, the internal stress of the insulating film 6 increases, and the adhesion to the protective layer 5 and the abrasion-resistant layer 7 becomes very low. It tends to be difficult to maintain at a high level. Therefore, it is preferable to set the ratio (d ₁ / d ₂ ) of the density (d ₁ ) of the conductive layer 4 to the density (d ₂ ) of the insulating film 6 to 1.20 to 1.70.
[0037]
The insulating film 6 is formed to a thickness of 0.05 μm to 0.9 μm inside the film defect by, for example, a conventionally known anodic oxidation method or a high-temperature oxidation method. Specifically, when the insulating film 6 is formed by anodic oxidation, for example, the head substrate 1 formed using an anodic oxidizing apparatus as shown in FIG. Is immersed in a processing tank 12 filled with an electrolytic solution containing 5% to 25% by mass, and the electrode plate 8 in the processing tank 12 is connected to a cathode, and the conductive layer 4 of the head substrate 1 is connected to an anode. Then, a positive voltage of 2.5 V to 30 V is applied between the electrode plate 8 and the conductive layer 4 using the external power supply 9 for 0.5 to 30 minutes to conduct the negative ions OH ⁻ in the electrolytic solution. The insulating film 6 is formed by adhering to a predetermined region of the layer 4 and depositing aluminum oxide inside the film defect. Since the insulating film 6 thus formed is formed by anodizing a part of the conductive layer 4 made of aluminum, the opening area of the film defect existing in the protective layer 5 is very small, not more than 1200 μm ^2. Even if it is small, the film defects can be satisfactorily closed by the insulating film 6 and the insulating film 6 can be formed quickly, thereby improving the reliability and productivity of the thermal head and the thermal printer. Becomes possible.
[0038]
The abrasion-resistant layer 7 is formed by depositing the above-mentioned inorganic material on the upper surface of the protective layer 5 or the insulating film 6 to a thickness of 4 μm to 20 μm by using a conventionally known thin film method, specifically, a sputtering method or the like. Formed.
[0039]
As shown in FIG. 3, the thermal printer incorporating the above-described thermal head includes a platen roller 10 and transport rollers 11a and 11b as transport means for transporting the recording medium onto the heating resistor 3 of the thermal head T. , 11c, 11d, etc. are provided.
[0040]
The platen roller 10 is a cylindrical member in which butadiene rubber or the like is wound around a shaft core made of metal such as SUS to a thickness of about 3 mm to 15 mm, and is rotatable on the heating resistor 3 of the thermal head T. The recording medium is conveyed in a direction perpendicular to the arrangement of the heating resistors 3 (the direction of the arrow in the figure) while pressing the recording medium against the surface of the protective layer on the heating resistors 3.
[0041]
The transport rollers 11a, 11b, 11c, and 11d have their outer peripheral portions formed of metal, rubber, or the like, and are disposed separately from the thermal head T on the upstream side and the downstream side in the recording medium transport direction. The transport of the recording medium is supported by the transport rollers 11a, 11b, 11c, 11d and the platen roller 10 described above.
[0042]
At the same time, a large number of heating resistors 3 are selectively caused to generate Joule heat by driving a driver IC (not shown), and the heat is transmitted to the recording medium via the protective layer 5 to form a predetermined print. .
[0043]
Note that the present invention is not limited to the above-described embodiment, and various changes, improvements, and the like can be made without departing from the gist of the present invention.
[0044]
For example, in the above-described embodiment, if the insulating film 6 is formed in the entire region inside the film defect provided in the protective layer 5, the upper surface of the insulating film 6 and the upper surface of the protective layer 5 may be substantially flush with each other. The base of the wear-resistant layer 7 is in a flat state, the adhesion of the wear-resistant layer 7 to the insulating film 6 and the protective layer 5 is further improved, and the wear-resistant layer 7 is more firmly adhered to the base. In addition to this, the wear-resistant layer 7 having good film quality can be formed.
[0045]
Moreover, in this case, since the base of the wear-resistant layer 7 is flat, the surface of the wear-resistant layer 7 becomes smooth accordingly, and it is assumed that the recording medium has strongly contacted the wear-resistant layer 7. However, there is also an advantage that it is possible to effectively prevent the recording medium from being stuck on the surface of the wear-resistant layer 7 and causing sticking, or the surface of the recording medium from being damaged.
[0046]
In the above-described embodiment, if the specific resistance of the wear-resistant layer 7 is set to 1 × 10 ⁷ Ω · cm to 1 × 10 ¹¹ Ω · cm, a suitable conductivity is imparted to the wear-resistant layer. When printing is performed by sliding the recording medium on the surface of the abrasion-resistant layer, even if a portion of the static electricity charged on the surface of the recording medium is applied to the thermal head, these charges are not applied. Is well diffused throughout the wear-resistant layer without remaining on a part of the wear-resistant layer, and even when a local high voltage is applied to the wear-resistant layer, It is possible to effectively prevent the layer from being electrostatically damaged, and this can also improve the reliability of the thermal head and the thermal printer. In order to set the specific resistance of the wear-resistant layer within the above numerical range, the amount of carbon added to the wear-resistant layer may be adjusted.
[0047]
【The invention's effect】
According to the present invention, an insulating film made of aluminum oxide is deposited on the conductive layer exposed from film defects in the protective layer, and the insulating film and the protective layer are covered with a wear-resistant layer. The void of the film defect in the protective layer is closed by the insulating film, and the region where the film defect is formed is well covered with the wear-resistant layer, and is included in the moisture in the atmosphere, the thermal paper, and the like. Even if Na ⁺ ions, K ⁺ ions, Cl ⁻ ions, etc. try to enter through the film defects in the protective layer, the entry is favorably prevented by the insulating film or the wear-resistant layer, and moisture and Inconveniences such as corrosion and melting of the conductive layer due to contact with ions are effectively prevented, the wiring resistance of the conductive layer is kept substantially constant, and the heating resistor can be heated at a desired temperature.
[0048]
In addition, in this case, since the insulating film is formed of aluminum oxide having good adhesion to the Si-N-based or Si-ON-based inorganic material, the recording medium is repeatedly strong against the wear-resistant layer. Even when a large stress is applied to the abrasion-resistant layer and the protective layer due to the sliding contact, the abrasion-resistant layer is peeled off from the insulating film, or the insulating film is removed from inside the film defect in the protective layer. Thus, a highly reliable thermal head and a thermal printer capable of effectively preventing corrosion of the conductive layer for a long period of time without peeling are realized.
[0049]
Further, according to the present invention, since the surface of the insulating film is covered with the wear-resistant layer, the recording medium does not directly contact the insulating film, so that no excessive stress is applied to the insulating film. The occurrence of cracks and the like in the film can be effectively prevented, which also makes it possible to maintain high reliability of the thermal head and the thermal printer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of the thermal head of FIG.
FIG. 2 is a diagram showing a configuration of an anodic oxidation apparatus used when forming an insulating film.
FIG. 3 is a diagram illustrating a configuration of a thermal printer using the thermal head of FIG. 1;
FIG. 4 is a sectional view of a conventional thermal head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Partial glaze layer 3 ... Heating resistor 4 ... Pair of conductive layers 5 ... Protective layer 6 ... Insulating film 7 ... Abrasion resistant layer 8 ... -Electrode plate 9-External power supply 10-Platen rollers 11a, 11b, 11c, 11d-Transport roller 12-Processing tank

Claims (3)

A thermal head in which a large number of heating resistors and a conductive layer containing aluminum as a main component are deposited on the upper surface of a substrate, and a protective layer is formed on these heating resistors and the conductive layer.
A thermal head, wherein an insulating film made of aluminum oxide is applied on a conductive layer exposed from a film defect in the protective layer, and the insulating film and the protective layer are covered with a wear-resistant layer. The thermal head according to claim 1, wherein the protective layer and the wear-resistant layer are made of a Si-N-based or Si-ON-based inorganic material. 3. A thermal printer, comprising: the thermal head according to claim 1; and transport means for transporting a recording medium onto the thermal head.

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