JP4330681B2 - Thermal head and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal head and a manufacturing method thereof, and more particularly to a thermal head including a plurality of antistatic layers and a manufacturing method thereof.
[0002]
[Prior art]
The thermal head occupies an important position as a recording device for various OA devices such as a facsimile, a video printer, and a plate making machine because it has advantages such as low noise, low maintenance cost, and low running cost.
[0003]
The thermal head records on a recording medium such as thermal paper or plate-making film photographic paper by generating heat from a heating resistor disposed on the substrate. In recent years, much attention has been paid particularly to video printer applications.
[0004]
As with conventional thermal heads, thermal heads for video printers are formed by optionally forming a glaze layer as a heat retaining layer on a ceramic substrate such as alumina, and then using a sputtering method to form a heating resistor layer and a conductive layer such as aluminum. Then, a plurality of pairs of heating resistors and individual electrodes are formed on a single line by a photoengraving process, and a protective film is formed only on the heating resistor layer and the necessary portions of the electrodes. It is manufactured by forming by a thin film forming method such as a sputtering method.
[0005]
In particular, when a special film is used as a recording medium in a video printer application, an antistatic layer for the purpose of antistatic is provided after the protective layer is formed. This is to prevent electrostatic charge on the insulating protective film by sliding contact with the special film. If this layer is not covered, the protective film may be electrostatically broken.
[0006]
However, when the antistatic layer is formed, if the protective layer has film defects such as pinholes, the antistatic layer (film) is in contact with the electrode or resistor through the protective film defect, causing an electrical short circuit. There is a danger of end.
[0007]
Therefore, the antistatic layer is formed after taking measures such as selecting a material with few pinholes on the protective film side, removing foreign matter in the film that becomes pinholes, and then forming a protective layer multiple times. is doing.
[0008]
Such a conventional thermal head will be specifically described with reference to FIG.
[0009]
A glaze layer 2 and a heating resistor layer 3 are formed on the support substrate 1. The heating resistor layer 3 is made of TaSiO, NbSiO, or the like, and constitutes a number of resistors arranged in an array. An electrode layer 4 is formed on the heating resistor layer 3. The electrode layer 4 constitutes a common electrode or an individual electrode, and when printing, a predetermined resistor is selected from a large number of resistors composed of the heating resistor layer 23, and current is supplied to the selected resistor. It is configured to supply and generate heat. When a current is supplied from the electrode, the resistor generates heat in the region sandwiched between the electrode layers 4 as a heat generating portion 3a. The protective layers 5 and 5 ′ formed in two layers are formed of an electrically insulating material such as SiON and cover at least the heat generating portion 3 a of the heat generating resistor layer 3.
[0010]
When the thermal head of FIG. 4 is operated, the ink sheet 9 and the image receiving paper 10 each coated with polyethylene terephthalate are wound around the platen roller 11 and pressed against the heat generating portion 3a of the heat generating resistor layer 3 constituting the thermal head. Rotate in the direction of arrow X. At this time, the image is printed on the image receiving paper 10 by the heat of the heat generating portion 3a.
[0011]
Both the ink sheet 9 and the protective layers 5 and 5 ′ are made of an electrically insulating material, and both come into contact with each other and rub against each other. For this reason, static electricity is generated at the contact portion. The generated static electricity charges the protective layers 5, 5 ′, induces charges with different signs in the electrode layer 4 and the heating resistor layer 3, and generates a high electric field inside the protective layers 5, 5 ′. At this time, if the electric field inside the protective layers 5 and 5 ′ increases, the dielectric strength of the protective layers may be exceeded, and dielectric breakdown occurs in the protective layers 5 and 5 ′. As a result, the protective layer loses its function, leading to destruction of the thermal head.
[0012]
When SiON is used for the protective layer, there are many defects such as shorts as shown in FIG. If SiO ₂ is used instead of SiON, the product life is shortened. Further, when the protective layer having a two-layer structure as shown in FIG. 4 is formed of SiON, there is a problem that the number of through defects is reduced but the number of processes is increased as shown in FIG. In addition, the antistatic layer formed on the protective layer is usually made of TaSiO, but this is inferior in adhesion to SiON, so that the antistatic layer may peel off due to sliding contact with the paper to be printed.
[0013]
As described above, the protective film material is currently changed as a countermeasure against pinholes, the lamination process is divided into two times, and through holes are removed, but there is a limit to the spattering method for reducing foreign matter. As a result, there are problems such as an increase in man-hours, an increase in tact time, and an increase in the area occupied by the apparatus.
[0014]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly reliable and high-quality thermal head that can be easily manufactured and a method for manufacturing the thermal head.
[0015]
[Means for Solving the Problems]
The thermal head of the present invention includes a support substrate, a heating resistor formed on the support substrate, an electrode layer connected to the heating resistor, and a protective layer covering at least a heating portion of the heating resistor. And at least two antistatic layers formed on the protective layer, wherein the at least two antistatic layers are an insulating antistatic layer and an uppermost layer formed so as to be in contact with the protective layer. And a conductive antistatic layer formed on the substrate . The at least two antistatic layers are layers composed of a metal element selected from the group 3A to 7A, silicon and oxygen. The metal element is preferably Ta or Nb. The surface resistance of the insulating antistatic layer has a 1 × 10 ⁴ Ω or more, the surface resistance of the conductive antistatic layer is Ru der less than 1 × 10 ⁴ Ω.
[0016]
That is, the thermal head according to the present invention includes a heating resistor disposed on one main surface of a substrate, an electrode disposed on an individual electrode and a common electrode that are to supply current to the heating resistor, and at least resistor exposure. A protective coating layer so as to cover the portion, and a plurality of layers formed thereon for the purpose of antistatic, and the antistatic layer has a conductivity of less than 1 × 10 ⁴ Ω on the outermost layer of the thermal head By forming a layer, charging due to sliding contact with a film or the like is suppressed, and a protective film contact layer is formed so as to have an insulating layer of 1 × 10 ⁴ Ω or more, thereby preventing a short circuit between the conductive layer and the electrode. It is characterized by that.
[0017]
According to the present invention, an electrode, a resistor, and an antistatic material through a protective film through-hole such as a pinhole or a film defect are provided by providing a layer that retains insulation in the protective film contact of a layer intended for antistatic purposes. It becomes possible to suppress an electrical short circuit with the layer.
[0018]
When the protective film penetrates and the contact between the insulating antistatic layer and the heating resistor is assumed, the surface resistance value of the insulating antistatic layer is set to the 10 ³ Ω level, which is the same level as that of the heating resistor. Therefore, it is necessary to ensure the insulation by setting the resistance value of the insulating antistatic layer to 10 times or more the resistance value of the heating resistor. Therefore, the resistance value of the insulating antistatic layer must be 1 × 10 ⁴ Ω or more, preferably 1 × 10 ⁵ Ω or more, more preferably 1 × 10 ⁶ Ω or more.
[0019]
In addition, by forming the conductive antistatic layer, which is the outermost layer of the thermal head, with a resistance value of less than 1 × 10 ⁴ Ω, it is possible to suppress protective film electrostatic breakdown caused by film sliding contact. In this case, as a matter of course, when the surface resistance value is increased, the insulating property is increased and the static electricity due to the film sliding contact tends to be charged. When the conductive antistatic layer as the outermost layer has a resistance value of 1 × 10 ⁴ Ω or more, it becomes impossible to prevent the occurrence of electrostatic breakdown. Therefore, the surface resistance value of the outermost conductive antistatic layer is less than 1 × 10 ⁴ Ω, preferably less than 1 × 10 ³ Ω.
[0020]
In particular, when the uppermost conductive antistatic layer is formed of a material composed of a metal element belonging to Group 3A to 7A, silicon and oxygen, necessary and sufficient conductivity can be obtained, and the film thickness is set to 0.3 to 2. Sufficient wear resistance can be obtained by setting the thickness to 0 μm, and by using a typical cermet made of general Ta or Nb as the metal element, it can be shared with the film formation process of the heating resistor. Can also be planned. The thickness of the conductive antistatic layer is preferably 0.3 to 1.0 μm, more preferably 0.5 to 1.0 μm.
[0021]
Moreover, sufficient abrasion resistance can be obtained by setting the insulating antistatic layer to a thickness of 0.2 μm or more. The thickness of the insulating antistatic layer is preferably 0.2 to 1.0 μm, more preferably 0.5 to 1.0 μm.
[0022]
Usually, the individual resistance value of the thermal head is set to about 8 × 10 ^{2 to} 5 × 10 ³ Ω. When the antistatic layer is formed on such a thermal head, if the resistance value of the antistatic layer is about the same as the individual resistance value, when the electrode part / resistor is contacted via a defect in the protective film, The present invention has been made to cope with the problem that the electric power of the resistor to be heated is not supplied and an electrical short circuit occurs in the antistatic layer.
[0023]
Therefore, in the thermal head of the present invention, an antistatic layer having a surface resistance value that does not short-circuit the power to be supplied with respect to the resistance value of the heating resistor is defined as insulating. Further, the conductive antistatic layer is defined as having a surface resistance value that is approximately equal to or less than the individual resistance value.
[0024]
As the support substrate used in the thermal head of the present invention, a substrate such as alumina ceramic is usually used, but is not particularly limited.
[0025]
In addition, as the heating resistor formed on the support substrate, various highly stable metal materials such as nickel, chromium, tantalum, etc., and various types such as Ta—SiΟ ₂ , Νb-SiO ₂ , Ti—SiO _2, etc. Cermet materials can be used as appropriate.
[0026]
Furthermore, commonly used Al, Al—Si, Al—Si—Cu, or the like is used as an electrode connected to the heating resistor, but is not particularly limited.
[0027]
In addition, when a glaze glass layer mainly intended to improve surface smoothness and heat storage is provided between the alumina substrate and the heating resistor layer, as the glaze glass layer, for example, silicon dioxide or silicon dioxide. A mixture of calcium, barium, aluminum, strontium and the like is used, but is not particularly limited. However, the glass transition point of the glaze glass layer is preferably 670 ° C. or higher in order to prevent an increase in the resistance value of the thermal print head. Moreover, the film thickness of a glaze glass layer is normally formed in about 30-70 micrometers.
[0028]
Further, the protective layer formed so as to cover at least the heat-generating portion of the heat generating resistor is usually a Si—O—N-based protective layer, which is a powder composed of silicon nitride and silicon dioxide, which are normal constituent components. It is formed by sputtering using a sintered body as a target.
[0029]
The method for manufacturing a thermal head according to the present invention includes a step of forming a heating resistor on one main surface of a substrate, a step of forming an electrode layer on the heating resistor, and covering at least a heating portion of the heating resistor. A step of forming a protective layer, and an insulating antistatic layer formed so as to be in contact with the protective layer by changing an oxygen supply amount on the protective layer, and a conductive layer formed on the uppermost layer. to and forming an antistatic layer of at least two layers of the antistatic layer that features a.
[0030]
According to the manufacturing method of the thermal head of the present invention, since the laminated structure of the antistatic layer is formed by switching the reaction gas at the time of film formation, the conventional anti-pinhole countermeasure and the short circuit with the antistatic layer through the pinhole are performed. In order to prevent this, steps such as the formation of a protective film and the removal of foreign matter from the protective film are no longer necessary. Therefore, the process and the tact time can be greatly reduced.
[0031]
Further, when the antistatic layer is molded, a plurality of insulating and / or conductive layers can be easily formed by defining the amount of oxygen introduced in the film forming process.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
An embodiment of the present invention will be described with reference to FIG.
[0033]
Using a glazed alumina substrate having a glazed layer 2 formed as a heat retaining layer at a predetermined location on the alumina substrate 1 as a supporting base, a Ta-SiO film as the heating resistor layer 3 and Al as the electrode layer 4 in order, forming a thin film such as by sputtering. Formed by the method.
[0034]
Further, the substrate was subjected to a photo-engraving process to form a plurality of pairs of resistors and electrodes in the same pattern.
[0035]
Thereafter, a protective layer 5 made of SiON was formed by using a sintered body in which Si ₃ —N ₄ and SiO ₂ were mixed as a film forming source so as to cover at least the exposed portion of the heating resistor. At this time, the protective film 5 was formed as a single layer with a thickness of 5 μm by sputtering.
[0036]
In the case of forming a film with a single layer, foreign matter in the film taken into the film, pinholes caused by the film, and film defects due to the lack of step coverage are likely to occur, and both were confirmed in this substrate.
[0037]
Thereafter, an insulating antistatic layer 6 and a conductive antistatic layer 7 were formed on the protective layer 5. As a material for these antistatic layers, Ta—SiO, which is the same deposition source as that of the heating resistor 3, was used.
[0038]
Using Tokuda Seisakusho CF-16PS, the lower insulating antistatic layer 6 in contact with the protective film 5 was introduced with a film formation atmosphere of 250 sccm of inert gas Ar and 20 sccm of oxygen as a reaction gas, and a thickness of 0.3 μm. Formed. Thereafter, the upper antistatic layer 7 was continuously formed to have a thickness of 0.2 μm in an atmosphere of only Ar and adjusted so as to hit the surface of the thermal head.
[0039]
When the single layer of the antistatic layer 6 was measured with a surface resistance measuring instrument at this time, it showed a sufficient insulating property of 2 × 10 ⁴ Ω.
[0040]
Further, when the upper conductive antistatic layer 7 which is the outermost layer of the thermal head for the purpose of preventing the original antistatic charge was measured with a mega ohm meter, it showed a sufficient conductivity of 5 × 10 ³ to 1 × 10 ⁴ Ω. .
[0041]
In the thermal head manufactured as described above, the conductive antistatic layer 7 can be formed on the outermost surface of the thermal head without providing an electrical short circuit by providing the lower insulating antistatic layer 6. Thus, no electrostatic breakdown of the protective film occurs. In addition, insulating and conductive antistatic layers can be easily formed by switching the reaction gas during film formation.
[0042]
This eliminates the need for foreign matter removal processes, protective film process bifurcation (lamination), and foreign substance-free protective film materials that were previously implemented as countermeasures against pinholes, and can significantly reduce man-hours and tact time. Material costs can be reduced.
[0043]
In addition, the same effect could be obtained when Nb-SiO was used as the deposition source of the antistatic layer.
[0044]
[Example 2]
Next, a modified embodiment of the present invention will be described with reference to FIG.
[0045]
Using a glazed alumina substrate having a glazed layer 2 formed as a heat retaining layer at a predetermined location on the alumina substrate 1 as a supporting base, a heating resistor layer 3 as a Ta-SiO film, and an electrode layer 4 as a thin film by sputtering or the like. Formed by the method.
[0046]
Further, the substrate was subjected to a photo-engraving process to form a plurality of pairs of resistors and electrodes in the same pattern.
[0047]
Thereafter, a protective layer 5 made of SiON was formed using a sintered body in which Si ₃ —N ₄ and SiO ₂ were mixed as a film deposition source so as to cover at least the resistor exposed portion.
[0048]
At this time, the protective film 5 was formed as a protective layer by sputtering so as to have a thickness of 3 μm as a single layer so as to ensure sufficient hardness.
[0049]
Thereafter, an insulating antistatic layer 6, an antistatic intermediate layer 8, and a conductive antistatic layer 7 were formed on the protective layer 5 while changing the reaction gas flow rate. As long as the layer in contact with the protective film 5 is insulative and the uppermost layer is conductive, one or more layers, preferably 2 to 3 layers, may be formed therebetween.
[0050]
For the formation of the antistatic layer, Ta—SiO, which is the same deposition source as that of the heating resistor 3, was used.
[0051]
Here, as shown in FIG. 3, the relationship between the reactive gas flow rate and the film characteristics (surface resistance value) was confirmed.
[0052]
In the apparatus (CFS16PC manufactured by Tokuda) used in this modified embodiment, a surface resistance value of 1 × 10 ₄ Ω or more was shown by introducing 10 sccm or more of reactive gas O ₂ . However, this requires adjustment so that the reaction gas is introduced in such an amount that a desired surface resistance value can be obtained.
[0053]
The lower insulating antistatic layer 6 in contact with the protective film 5 was formed to a thickness of 0.2 μm by introducing 250 sccm of an inert gas Ar and 20 sccm of oxygen as a reactive gas. Thereafter, the layers were stacked in such a manner that the introduction amount of the reaction gas was sequentially suppressed and an inclination was given, and finally the outermost surface layer of the thermal head was formed continuously so as to be 0.2 μm in an atmosphere of only Ar.
[0054]
In the thus-produced thermal head, the same effect as in the previous embodiment could be confirmed.
[0055]
The thermal head manufactured in Examples 1 and 2 of the present invention and the conventional thermal head (FIG. 4) were incorporated into a sublimation thermal transfer video printer having a resolution of 150 dpi, and an actual machine test was conducted. Electrostatic breakdown occurred on the sheet, but no problem occurred when the thermal head of the present invention exceeded 5000 sheets, which is considered to have a practical life.
[0056]
【The invention's effect】
As described above, according to the present invention, since the antistatic layer can be easily formed with a desired insulating layer or conductive layer by switching the reaction gas, when forming the antistatic layer, a pinhole or the like The protective layer double layer, foreign matter removal process, and countermeasures against minute foreign matter scattered from the target, which are essential to prevent electrical short circuit due to contact between the electrode and the antistatic layer through the film defect, are unnecessary, and the yield is high. A long-life thermal head can be obtained.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of a thermal head according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a thermal head according to a modified embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the amount of oxygen introduced and the surface resistance value of the protective film produced in the production of the thermal head of the present invention.
FIG. 4 is an enlarged sectional view of a conventional thermal head.
FIG. 5 is an enlarged sectional view of a conventional thermal head.
FIG. 6 is an enlarged sectional view of a conventional thermal head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Alumina substrate 2 ... Glaze layer 3 ... Heating resistor layer 4 ... Electrode layer 5, 5 '... Protective layer 6 ... Insulating antistatic layer 7 ... Conductive antistatic layer 8 ... Antistatic intermediate layer 9 ... Ink sheet 10 ... image-receiving paper 11 ... platen roller

Claims (4)

A support base, a heating resistor formed on the support base, an electrode layer connected to the heating resistor, a protective layer covering at least a heating portion of the heating resistor, and formed on the protective layer And at least two antistatic layers formed,
The thermal head according to claim 1, wherein the at least two antistatic layers have an insulating antistatic layer formed so as to be in contact with the protective layer and a conductive antistatic layer formed on the uppermost layer.   2. The thermal head according to claim 1, wherein the at least two antistatic layers are layers composed of a metal element selected from the group 3A to 7A, silicon and oxygen.   3. The thermal head according to claim 2, wherein the metal element is Ta or Nb.   Forming a heating resistor on one main surface of the substrate, forming an electrode layer on the heating resistor, and forming a protective layer so as to cover at least a heating portion of the heating resistor; The charge of at least two layers of the insulating antistatic layer formed so as to contact the protective layer and the conductive antistatic layer formed on the uppermost layer by changing the oxygen supply amount on the protective layer And a step of forming a prevention layer.

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