JP2000033723A - Production of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of unevenness, e.g. recording streak, in an image by removing splash particles principally comprising the compositional material of an upper layer protective film, i.e., carbon, produced through arc at the time of forming the upper layer protective film of a thermal head by sputtering. SOLUTION: The protective film of a thermal head 10 has three layer structure of a lower layer protective film 20 covering a heating element 16 and an electrode 18, an intermediate protective film 22 and a carbon protective film 24 formed sequentially. A DC power supply is provided with an arc detector and the primary of the DC power supply is interrupted instantaneously upon detecting arc at the time of forming the carbon protective film 24 by sputtering. At the same time, the DC power supply is discharged to the cathode thus removing splash particles principally comprising the compositional material of the upper layer protective film 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to various printers,
It belongs to the technical field of a thermal head for performing thermal recording used as a recording means in a plotter, a facsimile, a recorder, and the like.

[0002]

2. Description of the Related Art Thermal recording using a thermal material formed by forming a thermal recording layer using a film or the like as a support is used for recording an ultrasonic diagnostic image. In addition, thermal recording has advantages such as no need for wet development processing and easy handling, and in recent years, in recent years, not only small-sized image recording such as ultrasonic diagnosis but also CT diagnosis and MRI diagnosis have been performed. For applications requiring large and high-quality images, such as X-ray diagnosis and the like, the use for image recording for medical diagnosis is also being studied.

[0003] As is well known, thermal recording is performed by using a thermal head having glazes in which heating elements are arranged in one direction (main scanning direction), and pressing both glazes against a thermosensitive material. While relatively moving in the sub-scanning direction orthogonal to the main scanning direction, by applying energy to each heating element to generate heat according to the recorded image, the thermosensitive recording layer of the thermosensitive material is heated to record an image. Do.

In the glaze of the thermal head, a protective film is formed on the surface of the glaze to protect the heating elements and the like. The protective film is usually formed of a ceramic such as silicon nitride, but the surface of the protective film is heated during thermal recording and comes into sliding contact with the thermal material. The recording medium is damaged, and eventually, a state in which image recording cannot be performed (head breakage) occurs. In particular, in applications where high-quality and high-quality multi-gradation images are required, such as in the medical applications described above, a high-rigidity support such as a polyester film is used in order to achieve high quality and high image quality. There is a tendency to use a body and set the recording temperature and the pressing force of the thermal head against the heat-sensitive material higher. Therefore, the load on the protective film of the thermal head is large, and wear and corrosion are apt to progress.

As a method for preventing the abrasion of the protective film of such a thermal head and improving the durability, many techniques for improving the performance of the protective film have been studied, and among them, excellent in abrasion resistance and corrosion resistance. As a protective film, a protective film containing carbon as a main component (hereinafter referred to as a carbon protective film) is known. For example, JP-B-61-53955 discloses that a Vickers hardness of 4500 k is used as a protective film for a thermal head.
A thermal head having a carbon protective film of g / mm ² or more is disclosed in Japanese Patent Application Laid-Open No. Hei 7-132628, in which a lower protective film made of a silicon compound and a carbon protective film (diamond-like carbon film) as an upper layer are provided. Thermal heads having a two-layered protective film are disclosed. Such a carbon protective film has characteristics very similar to diamond, has extremely high hardness, and is chemically stable. Therefore, it exhibits extremely excellent wear resistance and corrosion resistance against sliding contact with the heat-sensitive material.

[0006]

One of the problems in thermal recording using a thermal head as described above is that when protrusions or foreign substances are present on the upper protective film,
There is a problem that image unevenness such as a recording streak occurs and image quality deteriorates. According to the study of the present inventors, such projections and foreign substances of the upper protective film are formed by separating (separating) particles from a target material and other materials when sputtering is performed on a substrate holder (and (The material held here) in many cases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. In a method of manufacturing a thermal head, when forming an upper protective film by sputtering, carbon generated on the upper protective film is reduced. It is an object of the present invention to provide a method of manufacturing a thermal head capable of preventing the occurrence of image unevenness such as recording streaks by removing splash particles as a main component.

[0008]

In order to achieve the above object, a method of manufacturing a thermal head according to the present invention comprises forming a lower protective film composed of at least one layer on a heating element and an electrode, and forming the lower protective film on the lower protective film. Forming an intermediate protective film composed of at least one layer on the intermediate protective film, and forming an upper protective film mainly composed of carbon composed of at least one layer on the intermediate protective film, wherein the upper protective film is When the film is formed by sputtering, splash particles mainly composed of carbon, which is a constituent material of the upper protective film, are removed by an arc generated at the time of sputtering. Further, in the method for manufacturing a thermal head according to the present invention, a lower protective film composed of at least one layer is formed on the heating element and the electrode, and the upper protective film mainly composed of carbon composed of at least one layer is formed on the lower protective film. A method of manufacturing a thermal head for forming a film, wherein, when forming the upper protective film by sputtering, by the arc generated at the time of sputtering, the splash particles mainly composed of carbon as a constituent material of the upper protective film. It is characterized by being removed.
Here, in the sputtering, a DC glow discharge using a DC power supply is used, and when an arc is generated, the energy charged in the DC power supply is released as arc energy, and sputtering is restarted. It is.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal head according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a schematic sectional view of a heating element of a thermal head manufactured by a manufacturing method according to an embodiment of the present invention. The thermal head 10 in the illustrated example includes, for example,
Approximately 300 dp, capable of recording images up to B4 size
The heat-generating element for performing heat-sensitive recording on the heat-sensitive material A in one direction (the main scanning direction, a direction perpendicular to the plane of FIG. ) Has a known configuration in which glazes are arranged. The width (main scanning direction), resolution (recording density), recording gradation and the like of the thermal head 10 according to the present embodiment are not particularly limited, but the width is 5 cm to 50 c.
m, resolution is more than 6dot / mm (about 150dpi),
The recording gradation is preferably 256 or more.

The thermal head 10 according to the present embodiment
The heat-sensitive material A for performing heat-sensitive recording using is a normal heat-sensitive material having a support made of a transparent polyethylene terephthalate (PET) film or the like and having a heat-sensitive recording layer formed on one surface thereof. Note that examples of the lubricant contained in the heat-sensitive material A include pigments, metal soaps, waxes, and the like. Specifically, as the pigment, zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, rubble, kaolin, aluminum hydroxide, amorphous silica, styrene resin, formalin condensate, fluoroethylene resin, Urea resins and the like; metal soaps include calcium stearate,
Emulsions of higher fatty acid metal salts such as aluminum stearate and the like; Examples of the wax include stearic acid, paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, silicone, and emulsions thereof. You.

As shown in FIG. 1, a thermal head 1
Reference numeral 0 denotes a glaze layer (heat storage layer) 14 formed on the substrate 12 (in the illustrated example, the thermal head 10 is pressed from above by the heat-sensitive material A, and therefore becomes lower in FIG. 1).
And a heat-generating (resistor) body 16 formed thereon, an electrode 18 formed thereon, and protection for protecting a heat-generating element formed on the heat-generating body 16 and the electrode 18. And a membrane. The protective film of the thermal head 10 in the illustrated example includes a lower protective film 20 formed to cover the heating element 16 and the electrode 18, and an intermediate protective film (hereinafter, referred to as an intermediate film) 22 formed on the lower protective film 20. And a protective film containing carbon as a main component formed on the intermediate film 22, that is, a carbon protective film 24.

The thermal head 10 according to this embodiment has basically the same configuration as a known thermal head except for a protective film. Therefore, there is no particular limitation on the other layer configuration and the material of each layer, and various known materials can be used.
Specifically, as the substrate 12, heat-resistant glass or alumina,
An electrically insulating material such as ceramics such as silica and magnesia is used. The glaze layer 14 is made of a heat-resistant resin such as heat-resistant glass or polyimide resin. The heating element 16 is made of nichrome (Ni-Cr), tantalum, tantalum nitride or the like. Various types of conductive materials such as aluminum and copper can be used for the heating resistor and the electrode 18. In addition, glaze (heating element)
Includes vacuum evaporation, CVD (Chemical Vapor Deposition)
, A thin film type heating element formed by using a so-called thin film forming technique such as sputtering and a photo-etching method, and a thick film type heating element formed by using a so-called thick film forming technique and etching by printing and firing such as screen printing. However, in the thermal head 10 used in the present invention, the glaze may be formed by any method.

As the lower protective film 20 formed on the thermal head 10 of the present invention, various known materials can be used as long as the material has heat resistance, corrosion resistance and abrasion resistance which can serve as a protective film for the thermal head. And preferably
Various ceramic materials are exemplified. Specifically, silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), tantalum oxide (Ta
₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), sialon (SiAlO
N), Lacion (laSiON), silicon oxide (SiO ₂ ), aluminum nitride (AlN), boron nitride (BN), selenium oxide (SeO), titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiC)
N), chromium nitride (CrN), and mixtures thereof. Above all, nitrides and carbides are preferable in terms of easiness of film formation, production cost, wear resistance against mechanical wear and chemical wear, and silicon nitride, silicon carbide, sialon, and the like are suitably used. The lower protective film 20 includes:
For the adjustment of physical properties, a trace amount of an additive such as a metal may be included.

The method of forming the lower protective film 20 is not particularly limited, and may be formed by using the above-described thick film forming technology or thin film forming technology.
It may be formed by a known method of forming a ceramic film (layer), and among them, CVD is particularly preferably used. As is well known, CVD is a technique in which energy such as heat or light is applied to a gaseous raw material introduced into a reaction chamber to induce various chemical reactions to deposit and coat a substance on a substrate to form a film. However, by forming the lower protective film 20 by CVD, it is possible to form the lower protective film 20 which is very dense and has no defects such as cracks, and as a result, has higher durability and higher image quality. A thermal head that is also advantageous in terms of efficiency can be produced.

The thickness of the lower protective film 20 is not particularly limited, but is preferably about 0.2 μm to 50 μm, more preferably about 2 μm to 20 μm. By setting the thickness of the lower protective film 20 within the above range, a favorable result is obtained in that a balance between abrasion resistance and thermal conductivity (that is, recording sensitivity) can be appropriately obtained. Further, the lower protective film 20 may have a multilayer structure. When the lower protective film 20 has a multilayer structure, the lower protective film 20 may have a multilayer structure using different materials, or may have a multilayer structure having different layers of the same material with different densities or both. It may be something.

In a preferred embodiment, the thermal head 10 in the illustrated example has an intermediate film 2 on such a lower protective film 20.
2 and a protective film having a three-layer structure having a carbon protective film 24 thereon. As described above, since the carbon protective film 24 is chemically very stable, the lower protective film 20
Having the carbon protective film 24 in the upper layer effectively prevents chemical corrosion of the lower protective film 20, the heating element 16, the electrode 18, and the like, and extends the life of the thermal head. By providing the protective layer 22, the adhesion between the lower protective film 20 and the carbon protective film 24, the shock absorption, and the like are improved, and a long-life thermal head having more excellent durability and long-term reliability can be realized.

Intermediate film 2 formed on thermal head 10
Examples of 2 include a metal of Group 4A (Group 4 = titanium group), a metal of Group 5A (Group 5 = vanadium group), a metal of Group 6A (Group 6 = Chromium group), Si (silicon), and Ge
The upper layer of the carbon protective film 2 is mainly composed of at least one selected from the group consisting of (germanium).
4 and the lower protective film 20 which is the lower layer, and the durability of the carbon protective film 24 is preferable. Specifically, Si, Ge, Ti (titanium), Ta (tantalum), Mo (molybdenum), a mixture thereof and the like are preferably exemplified. Among them, particularly, Si and Mo are preferable, and most preferably, Si is preferable in terms of bonding with carbon.

The method for forming the intermediate film 22 is not particularly limited, and may be formed by a known film forming method according to the material for forming the intermediate film 22 using the above-described thick film forming technology, thin film forming technology, or the like. However, sputtering is exemplified as a preferable example, and plasma CVD can also be suitably used.
Further, the intermediate film 22 may have a multilayer structure. Intermediate film 22
When a multi-layer structure is used, a multi-layer structure using different materials may be used, or a multi-layer structure having different layers of the same material with different densities may be used, or both may be used. Is also good.

Here, prior to the formation of the intermediate film 22, it is preferable to perform treatment of the lower protective film 2 by ion irradiation, lapping, or the like. Thereby, between the lower protective film 20 and the intermediate film 22 and between the intermediate film 22 and the carbon protective film 2.
4 can be improved, and the durability of the thermal head can be improved. At this time, the surface roughness of the lower protective film 20 is not particularly limited, but the Ra value is 1 nm to 0.2 nm.
1 μm is preferred. The ion irradiation treatment in the present invention preferably includes plasma irradiation, ion implantation, and the like.

In the illustrated thermal head 10, the carbon protective film 24 mainly composed of carbon is
2 is formed. As described above, since the carbon protective film 24 is chemically very stable, it effectively prevents chemical corrosion of the lower protective film 20 and is suitable for improving the durability of the thermal head as described above. Here, prior to the formation of the carbon protective film 24, it is preferable to perform the treatment of the intermediate film 22 by the above-described ion irradiation or lapping. Thereby, the adhesion between the intermediate film 22 and the carbon protective film 24 can be further improved, and the durability of the thermal head can be improved.

In the present invention, the carbon protective film 24 mainly composed of carbon is a carbon film containing more than 50 atomic% (atm%) of carbon, preferably a carbon film composed of carbon and unavoidable impurities. That is. In the thermal head according to the present invention, the carbon protective film 24
As additional components other than carbon forming hydrogen, nitrogen,
Fluorine, Si, Ti and the like are preferably exemplified. When the additional components are hydrogen, nitrogen and fluorine, their contents in the carbon protective film 24 are preferably less than 50 atm%, and when the additional components are Si and Ti, the carbon protective film 24 Content of these in 20
It is preferably at most atm%. The method for forming the carbon protective film 24 is not particularly limited, and any known film forming method according to the composition of the carbon protective film 24 can be used.
Particularly preferred are magnetron sputtering and CVD, particularly plasma CVD.

When the lower protective film 20 and the intermediate film 22 are formed, after forming the lower protective film 20 and the intermediate film 22, an adhesive tape is adhered to the surface thereof, and the surface is peeled off.
Forming the intermediate film 22 and the carbon protective film 24 thereon is also a method that can be suitably used. Here,
It is considered that the meaning of sticking and peeling of the adhesive tape lies in the removal of impurities. Further, when the lower protective film 20 and the intermediate film 22 are formed, after the lower protective film 20 and the intermediate film 22 are formed, the surfaces thereof are heat-treated in a vacuum, and then the upper intermediate film 22 and the carbon Forming the protective film 24 is also a suitably usable method. It is considered that the meaning of this heat treatment lies in the removal of impurities.

The hardness of the carbon protective film 24 as described above is not particularly limited, as long as it has a sufficient hardness as a protective film of the thermal head. For ^{example, 3000kg / mm 2 ~5000kg / mm} 2 is preferably exemplified by Vickers hardness. The hardness is determined by the carbon protective film 24.
In the case where the hardness is changed in the thickness direction of the carbon protective film 24, the change in the hardness may be continuous or stepwise. There may be. In addition, the carbon protective film 24
It may be formed while heating to about 0 ° C. to 400 ° C., in particular, the operating temperature of the thermal head 10. As a result, the adhesion between the carbon protective film 24 and the intermediate film 22 and further to the lower protective film 20 can be further improved, and cracking and peeling due to mechanical shock due to heat shock or foreign matter inclusion during thermal recording, and carbon film due to high power recording More excellent resistance to deterioration and disappearance of the steel. In addition,
The heating may be performed by a method using a heating means such as a heater or a method of energizing the thermal head 10.

In the thermal head 10 having the lower protective film 20, the intermediate film 22, and the carbon protective film 24, the thicknesses of the intermediate film 22 and the carbon protective film 24 are not particularly limited. 22 is 0.05μ
m to 2 μm, more preferably 0.1 μm to 1 μm, and the thickness of the carbon protective film 24 is 0.5 μm to 5 μm, more preferably 1 μm to 3 μm. If the intermediate film 22 is too thick with respect to the carbon protective film 24, the intermediate film 22 may be cracked or peeled off. Conversely, if the intermediate film 22 is too thin, the function as the intermediate film cannot be sufficiently exhibited. Would. On the other hand, the intermediate film 22 and the carbon protective film 2
By setting the thickness of the layer 4 within the above range, functions such as adhesion to the lower layer of the intermediate film 22 and shock absorption and durability of the carbon protective film 24 can be stably and well-balanced.

FIG. 2 shows a conceptual diagram of a film forming apparatus which can be suitably used for performing each process of forming each protective film of the thermal head according to the present invention. The illustrated film forming apparatus 50 basically includes a vacuum chamber 52, a gas introduction unit 54, a first sputtering unit 56, and a second sputtering unit 58.
, A bias power supply 62, and a substrate holder 64. The film forming apparatus 50 has two film forming means by sputtering in a system, that is, in a vacuum chamber 52, and continuously forms a plurality of layers having different compositions without further opening the system. It is possible.

Therefore, by using the film forming apparatus 50, for example, by sputtering using a different target or by sputtering,
2 (or the lower protective film 20) and the carbon protective film 24 can be easily and efficiently formed. The vacuum chamber 52 is preferably formed of a non-magnetic material such as SUS304, and is provided with a vacuum exhaust unit 66 for exhausting the inside (inside of the film forming system) to reduce the pressure. The location in the vacuum chamber 52 where an arc is generated by plasma or an electromagnetic wave for plasma generation may be covered with an insulating member such as MC nylon or Teflon (PTFE).

The gas introduction section 54 includes two gas introduction pipes 54.
a and 54b. As an example, the gas introduction pipe 54
“a” introduces a gas for generating plasma, and gas introduction pipe 54b introduces a reaction gas of plasma CVD.
In addition, as a gas for plasma generation, for example, an inert gas such as helium or neon is used. On the other hand, examples of a reaction gas for forming the carbon protective film 24 include a gas of a hydrocarbon compound such as methane, ethane, propane, ethylene, acetylene, and benzene, and a reaction gas for forming the intermediate film 22. Examples include various gases including a material for forming the intermediate film 22.

In sputtering, a target material to be sputtered is arranged on the cathode, the cathode is set to a negative potential, and plasma is generated on the surface of the target material, so that the target material (its atoms) is flipped out and arranged opposite to each other. A film is formed by being attached to the surface of a substrate and being deposited. The first sputtering unit 56 and the second sputtering unit 58 both form a film on the substrate surface by sputtering, and the first sputtering unit 56 includes a cathode 68 and a target material 7.
0, shutter 72 and radio frequency (RF) power supply 7
The second sputtering means 58 includes a cathode 76, an arrangement portion of the target material 70, a shutter 78, a DC power supply 80, and the like.

As is clear from the above configuration, the first sputtering means 56 and the second sputtering means 58 have basically the same configuration except that the arrangement position and the power supply for sputtering are different. Otherwise, the first sputtering means 56 is used as a representative example. When generating plasma on the surface of the target material 70, the first sputtering means 56 connects the RF power supply 74 to the cathode 68, and the second sputtering means 58 connects the negative side of the DC power supply 80 to the cathode 76. Then, a current for sputtering is applied. There are no particular limitations on the output and performance of the two power supplies, and those having sufficient performance required for the intended film formation may be selected. For example, in the case of an apparatus for forming the above-mentioned intermediate film 22 and carbon protective film 24, the RF power
A power supply having a maximum output of 10 kW at 3.56 MHz may be used, and a DC power supply having a negative potential of a maximum output of 10 kW may be used as the DC power supply 80. Also, at least one of the two power supplies,
Particularly, a modulator is combined with the one for forming the carbon protective film 24, and the modulator performs pulse modulation, for example,
It is preferable to be able to modulate in a pulse form at 2 kHz to 100 kHz.

In the illustrated example, a backing plate 82 (84) made of oxygen-free copper, stainless steel or the like is fixed to the cathode 68, and the target material 70 is fixed thereon by In-based solder or mechanical fixing means. The target material 70 used for forming the intermediate film 22 is preferably exemplified by metals of the 4A group, 5A group, and 6A group of the periodic table, and single crystals of Ge and Si. The target material 70 used for forming the carbon protective film 24 includes:
Preferable examples include a sintered carbon material and a glassy carbon material. The illustrated apparatus performs magnetron sputtering, and a magnet 68 a (76 a) is arranged inside the cathode 68. In the magnetron sputtering, a magnetic field is formed on the surface of the target material 70 to confine plasma and perform sputtering.
This is preferable because the film formation speed is high.

The substrate holder 64 holds the thermal head 10
It fixes a film-forming material (film-forming substrate) such as (its main body). The illustrated film forming apparatus 50 has two film forming means, and the substrate holder 64 is provided with a substrate holder 64 such that the glaze serving as a substrate can face each film forming means, that is, the sputtering means 56 and 58. Is held by a rotating part 98 that swings the light. Further, the distance between the substrate holder 64 and the target material 70 is configured to be adjustable by a known method. Note that the distance between the substrate and the target material 70 may be selected and set so that the film thickness distribution becomes uniform.

Although the thermal head according to the present invention has been described in detail above, the present invention is not limited to the above-described example, and various modifications and changes can be made without departing from the gist of the present invention. Of course it is good. For example, the present invention can be applied to a method of manufacturing a thermal head having a configuration excluding one or both of a lower protective film and an intermediate protective film as a protective film for protecting a heating element. .

[0034]

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. Example 1 A heat storage layer 14 was formed on a substrate 12, a heating element 16 was formed thereon, an electrode 18 was formed thereon, and an electrode 18 was formed thereon in the same manner as in a known thermal head manufacturing method. Then, a silicon nitride film (Si ₃ N ₄ ) having a thickness of 11 μm was formed, and a base thermal head was manufactured. Therefore, in the present embodiment, the silicon nitride film becomes the lower protective film 20, the intermediate film 22 is formed on the lower protective film 20, and the carbon protective film 24 is formed on the intermediate film 22. An intermediate film 22 and a carbon protective film 24 were formed on such a thermal head by using a film forming apparatus 50 shown in FIG. 2 as described below.

A. The vacuum chamber 52 has a pumping speed of 1500 L (a
Torr) / min rotary pump, 12,000 L / min
Mechanical booster pump and 3000L / s
Made of SUS304 with one turbo pump each
0.5m capacity ^ThreeWas used. turbo
Arrange the orifice valve in the suction part of the pump to
Can be adjusted from 10% to 100%.

B. Gas introduction unit 54 Using a mass flow controller having a maximum flow rate of 100 [sccm] to 500 [sccm] and a stainless steel pipe having a diameter of 6 mm, two gas introduction pipes 54a and 54b for a plasma generation gas and a reaction gas are formed. did.

C. First sputtering means 56 and second sputtering means 58 A rectangular cathode 6 having a width of 600 mm and a height of 200 mm, in which Sm-Co magnets are arranged as permanent magnets 68a and 76a.
8 and 76 were used. Oxygen-free copper processed into a rectangular shape was used as the backing plates 82 and 84 for the cathode 6.
Nos. 8 and 76 were attached with In-based solder. By cooling the insides of the cathodes 68 and 76 with water, the magnets 6
8a and 76a, cathodes 68 and 76, and backing plates 82 and 84 were cooled.
As the DC power supply 80, a DC power supply with a negative potential of a maximum output of 10 kW and a modulator are combined to supply 2
A power supply capable of modulating a pulse in the range of kHz to 100 kHz was used.

D. The substrate holder 64 holds the held substrate (that is, the thermal head 10) so as to face the target material 70 disposed in the first sputtering unit 56 and the second sputtering unit 58 by the operation of the rotating unit 98. When the intermediate film 22 and the carbon protective film 24 were formed by sputtering as described below, the distance between the substrate and the target material 70 was 100 mm. Further, the holding portion of the thermal head was set at a floating potential so that a high frequency voltage for etching could be applied. Further, a heater is provided on the surface of the substrate holder 64 so that film formation can be performed while heating.

E. Bias power supply 62 A high frequency power supply was connected to the substrate holder 64 via a matching box. The high frequency power supply has a frequency of 13.56 MH
At z, the maximum power is 3 kW. The high-frequency power supply monitors the self-bias voltage to provide a negative one.
The high-frequency output is adjustable in the range of 00V to 500V. The bias power supply 62 also serves as an etching unit.

F. DC Power Supply 80 As the DC power supply 80, a DC power supply having an arc detector and having a function of instantaneously shutting off the primary side of the DC power supply 80 when an arc is detected is used. Here, the above interruption time is 10
The time is preferably within msec. Further, it is preferable that the charge inside the DC power supply 80 be discharged to the cathode 76 at the time of cutoff.

<Production of Thermal Head> The film forming apparatus 5
0, the thermal head 10 (heating element) on which the above-described lower protective film 20 is formed is placed on the substrate holder 64 such that the thermal head 10 (heating element) faces the holding position of the target material 70 of the first sputtering means 56. Was fixed. The masking was applied to portions of the thermal head 10 other than the portion where the intermediate film 22 was formed. While continuing the evacuation, a mixed gas of argon and nitrogen is introduced by the gas introduction unit 54, and the pressure in the vacuum chamber 52 is increased to 5.0 by the orifice valve installed in the vacuum chamber 52.
It was adjusted to be × 10 ⁻³ Torr. Next, the RF power supply 74 was driven, and a bias voltage of −300 V was applied to the substrate side by the bias power supply 62 to perform etching.

After completion of the ion irradiation, a single crystal of Si is fixed to the backing plate 82 of the first sputtering means 56 as the target material 70 and the sintered graphite material is fixed to the backing plate 84 of the second sputtering means 58 (In-based material). Paste with solder). afterwards,
After evacuation until the pressure in the vacuum chamber 52 becomes 5 × 10 ⁻⁶ Torr, the argon gas flow rate and the orifice valve are adjusted so that the pressure becomes 2.5 × 10 ⁻³ Torr,
With the shutter 72 closed, a high-frequency power of 0.5 kW was applied to the target material 70 for 5 minutes. Next, while maintaining the pressure in the vacuum chamber 52, the shutter 72 is opened with the supplied power as high frequency power of 2 kW, and sputtering is performed until the film thickness becomes 0.2 μm.
The film was formed as an intermediate film 22. The film thickness of the Si film was controlled in advance by calculating the film forming speed in advance and calculating the film forming time to obtain a predetermined film thickness.

Then, while maintaining the pressure in the vacuum chamber 52, the DC power is set to 5 kW, the shutter 78 is opened, and sputtering is performed by DC glow discharge to obtain a thickness of 2 μm.
m of the carbon protective film 24 was formed. The thickness of the carbon protective film 24 is determined in advance by determining the film forming speed.
The film formation time to achieve a predetermined film thickness was calculated and controlled by the film formation time. During the above-mentioned sputtering, the target material 70 (sintered graphite material) of the second sputtering means 58 and other impurities are scattered, and the carbon protective film 2
When this falls above 4, this may trigger a transition from DC glow discharge to arc discharge.

In the conventional DC power supply 80, the primary circuit breaker was turned off in such a case, and the film formation could not be continued. In the DC power supply 80 used in this embodiment, In such a case, as described above, an arc detector is provided, and the primary side of the DC power supply 80 is instantaneously shut off when an arc is detected. The cutoff time is within 10 msec, and the charge inside the DC power supply 80 is discharged to the cathode 76 simultaneously with the cutoff. Thereby, the carbon protective film 2
On the other hand, even if a splash is generated for the above-mentioned reason, the splash is decomposed (vaporized) by discharging the charge inside the DC power supply 80 to the cathode 76.
Being extinguished.

<Evaluation of Performance> The thermal head 10 manufactured as described above was incorporated into a thermal recording apparatus, and was applied to a B4 size thermal material (Fuji Photo Film Co., Ltd., medical dry image recording film CR-DP). A solid image was thermally recorded. As a result, no image unevenness, recording streak, etc. occurred up to 25,000 sheets. This indicates that there is no splash in the upper protective film 24 of the thermal head 10 which causes image unevenness and recording streaks. That is, even if a splash occurs on the upper protective film 24 for the above-described reason, the splash is decomposed (vaporized) by discharging the charge inside the DC power supply 80 to the cathode 76, and disappears. Because you do.

[Comparative Example 1]
Regarding the thermal head 10 (heating element) on which the lower protective film 20 is formed, the intermediate film 22 and the carbon protective film 2 are formed.
4 was formed. The oxygen etching of the carbon protective film 24 was performed in the same manner, and the thermal head 10 was manufactured. However, here, a conventional arc detector is not provided as the DC power supply 80.
The type that drops the breaker on the primary side is used.

<Evaluation of Performance> The thermal head 10 manufactured as described above was incorporated in a thermal recording apparatus, and was applied to a B4 size thermal material (Fuji Photo Film Co., Ltd., medical dry image recording film CR-DP). A solid image was thermally recorded. As a result, image unevenness and recording streaks occurred up to 5000 sheets. This indicates that, as described above, when the splash occurs, it is not decomposed and remains on the carbon protective film 24.

From the above results, the effect of the present invention is clear.

[0049]

As described above in detail, according to the present invention, when the upper protective film is formed by sputtering, the splash particles mainly composed of carbon generated on the upper protective film are removed. Accordingly, it is possible to realize a thermal head capable of preventing occurrence of image unevenness such as a recording streak.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a heating element of a thermal head according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of an example of a film forming apparatus used for manufacturing a thermal head according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal head 12 Substrate 14 Glaze layer 16 Heat generation (resistance) body 18 Electrode 20 Lower protective film 22 Intermediate layer 24 Carbon protective film 50 Film forming device 52 Vacuum chamber 54 Gas introduction part 56 First sputtering means 58 Second sputtering means 62 Bias Power supply 64 Substrate holder 66 Vacuum exhaust means 68, 76 Cathode 70 Target material 74 RF power supply 80 DC power supply A Heat-sensitive material

Claims (3)

[Claims] 1. A lower protective film comprising at least one layer is formed on a heating element and an electrode, an intermediate protective film comprising at least one layer is formed on the lower protective film, and at least one layer is formed on the intermediate protective film. A method for manufacturing a thermal head for forming an upper protective film containing carbon as a main component, comprising:
A method of manufacturing a thermal head, wherein, when forming the upper protective film by sputtering, splash particles mainly composed of carbon as a constituent material of the upper protective film are removed by an arc generated at the time of sputtering. 2. A method for manufacturing a thermal head, comprising: forming a lower protective film composed of at least one layer on a heating element and an electrode; and forming an upper protective film composed mainly of carbon composed of at least one layer on the lower protective film. A method, wherein, when forming the upper protective film by sputtering, an arc generated at the time of sputtering removes splash particles mainly composed of carbon which is a constituent material of the upper protective film. Head manufacturing method. 3. The thermal power supply according to claim 1, wherein a DC glow discharge using a DC power supply is used, and when an arc is generated, energy charged in the DC power supply is released as arc energy to restart sputtering. Head manufacturing method.