JP2003103820A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable thermal head in which the electric resistance of heating resistors can be kept substantially constant over a long term. SOLUTION: In the thermal head where a plurality of heating resistors 3 composed of a TiC-Si-O based resistive material are fixed onto the upper surface of a base plate 1 and covered with a protective layer 5, the protective layer 5 is obtained by forming a first layer 6 of an inorganic material containing SiO and/or SiN, a second layer 7 of sintered perhydropolysilazane, and a third layer 8 of an inorganic material containing SiN and/or SiC sequentially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head incorporated as a recording device such as a facsimile or a video printer.

[0002]

2. Description of the Related Art Conventionally, thermal heads have been widely used as recording devices for facsimiles and the like.

As such a thermal head, for example, as shown in FIG. 3, a plurality of heating resistors 1 are provided on the upper surface of a base plate 11 made of glaze alumina ceramics or the like.
There is known a structure in which 3 and an electrode 14 for energization are adhered in a predetermined pattern, and these are covered with a protective layer 15 made of SiN (silicon nitride) or the like to protect a recording medium such as thermal paper. While slidingly contacting the surface of the layer 15, the heating resistors 13 are selectively and selectively heated by Joules based on image data from the outside, and these heats are conducted to the recording medium through the protective layer 15 to a predetermined level. Print is formed.

The protective layer 15 protects the heating resistor 13 and the electrode 14 from abrasion due to sliding contact with the recording medium, and is well known in the prior art such as sputtering and CVD.
(Chemical Vapor Deposition) method is adopted, and an inorganic material having excellent wear resistance such as SiN is deposited on the upper surface of the heating resistor 13 or the like by about 4 μm to 8 μm.

[0005]

By the way, when the protective layer 15 of the thermal head is formed by the sputtering method or the CVD method, many fine film defects such as pinholes are formed in the protective layer 15.

Therefore, upon printing, water contained in the atmosphere and Na ⁺ , K ⁺ , Cl ⁻ contained in the recording medium.
Through the film defects of the protective layer 15
3 has a drawback that the heating resistor 13 and the like are corroded when they come into contact with the electrode 3 and the electrode 14 and the electric resistance value of the heating resistor 13 and the like fluctuates significantly.

Further, in order to solve the above-mentioned drawbacks, the protective layer 1
It has been proposed that a sealing material made of an epoxy resin, a polyimide resin or the like be applied to the upper surface of 5 to close the film defect of the protective layer 15 with this sealing material.

However, the protective layer 1 of the thermal head
When the above-mentioned encapsulant is applied on the recording medium 5, since the epoxy resin, polyimide resin, etc. forming the encapsulant are relatively soft, the recording medium becomes the encapsulant on the protective layer 15 during printing. When the sliding contact is made, the sealing material is significantly worn and a part of the sealing material disappears from the protective layer 15 in a short time, and the film defect of the protective film 15 described above is opened relatively early. There was an inconvenience to do.

Further, the linear expansion coefficient of epoxy resin, polyimide resin or the like forming the sealing material is relatively large (20 ×
10 ^{−6 to} 90 × 10 ⁻⁶ ° C. ⁻¹ ) and the coefficient of linear expansion (3 × 10 ⁻⁶ ° C. ⁻¹ ) of the protective layer 15 made of SiN or the like, and that the protective layer 15 and the sealing layer 15 are sealed. Since it is not very familiar with the stopper, if the temperature of the entire thermal head rises due to the heat generated by the heat-generating resistor 13 or the like, the sealing material will be damaged due to the large thermal stress generated between the protective layer 15 and the sealing material. The protective layer 15 may be peeled off from the protective layer 15 and the film defect of the protective layer 15 may be opened.

The present invention has been devised in view of the above drawbacks, and an object thereof is to provide a highly reliable thermal head capable of keeping the electric resistance value of a heating resistor or the like substantially constant for a long period of time. is there.

[0011]

In the thermal head of the present invention, a plurality of heat-generating resistors made of TiC-Si-O-based resistance material are deposited on the upper surface of the base plate, and the heat-generating resistors are protected by a protective layer. A thermal head formed by coating, wherein the protective layer is a first layer made of an inorganic material containing SiO and / or SiN, a second layer made of a sintered body of perhydropolysilazane, and SiN and / or SiC. It is characterized in that it is formed by sequentially laminating a third layer made of an inorganic material containing.

In the thermal head of the present invention, the first and third layers of the protective layer are formed by sputtering or CVD.
It is characterized by comprising a thin film formed by the method.

Further, in the thermal head of the present invention, the composition ratio of the TiC-Si-O-based resistance material forming the heating resistor is (TiC) _x SiO _y (3.4≤x≤29.0, 1.8).
≦ y ≦ 2.2), and the content ratio of Si contained in each of the heating resistor and the protective layer is 3 atomic% to 4
It is characterized by being set to 4 atom%.

Further, in the thermal head of the present invention, the inorganic material forming the third layer of the protective layer has a specific resistance of 1 × 1.
It is characterized by being set to 0 ⁷ Ω · cm to 1 × 10 ¹¹ Ω · cm.

According to the thermal head of the present invention, among the three layers constituting the protective layer, the film defect of the first layer which is the lowermost layer is sealed by the second layer which is a sintered body of perhydropolysilazane. Therefore, it is possible to satisfactorily protect the heat generating resistor and the like from corrosion due to contact with water contained in the atmosphere and ions contained in the recording medium, and moreover, the second layer is made of a hard material. A third layer made of SiN, SiC, etc. is provided as the uppermost layer, and wear of the entire protective layer is effectively suppressed. Therefore, a part of the second layer does not disappear at an early stage. By reliably shutting off from the atmosphere by the second layer, it becomes possible to keep the electric resistance value of the heating resistor or the like substantially constant for a long period of time.

Further, according to the thermal head of the present invention, the composition ratio of the TiC-Si-O-based resistance material forming the heating resistor is (TiC) _x SiO _y (3.4≤x≤29.0, 1.
8 ≦ y ≦ 2.2), and the content ratio of Si contained in each layer of the heating resistor and the protective layer is 3 at% to 44 at%.
By setting to, the heating resistor-protective layer, and
It is possible to adjust the linear expansion coefficient of the heating resistor and each layer of the protective layer to a value relatively close to each other by making the familiarity between each layer of the protective layer good. Even if the temperature rises, it is possible to effectively prevent generation of a large thermal stress between these layers, and it becomes possible to firmly adhere each layer of the protective layer to the underlayer. This improves the reliability of the thermal head.

Further, according to the thermal head of the present invention, the resistivity of the third layer, which is the uppermost layer of the protective layer, is 1 × 10 ⁷ Ω.
-If a suitable conductivity is imparted by setting to cm to 1 x 10 ¹¹ Ω-cm, the surface of the recording medium is charged when the recording medium is brought into sliding contact with the surface of the recording medium for printing. Even if part of the static electricity is applied to the thermal head, these charges do not stay in one place on the protective layer and are well diffused throughout the protective layer, so a large local voltage is applied to the protective layer. It is possible to effectively prevent the protective layer from being electrostatically destroyed due to this, and this also makes it possible to improve the reliability of the thermal head.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. 1 is a perspective view of a thermal head according to an embodiment of the present invention, FIG. 2 is a sectional view of the thermal head of FIG. 1, 1 is a base plate, 3 is a heating resistor,
Reference numeral 4 is an electrode, and 5 is a protective layer.

The base plate 1 is made of glazed alumina ceramics which is externally processed to have a rectangular shape, single crystal silicon whose surface is covered with an oxide film, polycrystal silicon, or the like. The body 3, the electrodes 4 for energization, the protective layer 5 and the like are adhered and function as a support base material for supporting them.

When the base plate 1 is made of glazed alumina ceramics, first, a ceramic green sheet is formed by adding and mixing an appropriate organic solvent to ceramic raw material powder such as alumina, silica, magnesia, etc. Form an alumina substrate by punching into a predetermined shape and sintering at high temperature,
It is manufactured by printing and applying a glass paste on the upper surface of the obtained alumina substrate by a conventionally well-known screen printing or the like, and baking this at a high temperature to form a glaze layer.

The glaze layer of the above-mentioned glaze alumina ceramics substrate accumulates a part of heat generated by the heating resistor 3 which will be described later at the time of printing, and the temperature of the heating resistor 3 is set to a predetermined value required for printing in a short time. It functions as a heat storage layer for raising the temperature.

The plurality of heating resistors 3 provided on the upper surface of the base plate 1 are, for example, 600 dpi (do
They are arranged linearly in the main scanning direction (longitudinal direction of the base plate 1) at a density of t per inch.

Each of the heating resistors 3 is made of TiC-.
Depending on the Si—O-based resistance material, for example, 0.01 μm to 0.
It is formed to have a thickness of 2 μm, and when power source power is supplied through the electrodes 4 and the like, Joule heat is generated to reach a predetermined temperature necessary for printing.

TiC forming such a heating resistor 3
-Si-O resistance material has a composition ratio of (TiC) _x
SiO _y (3.4 ≦ x ≦ 29.0, 1.8 ≦ y ≦ 2.
The material represented by 2) is preferably used, and the content ratio of Si contained in the heating resistor 3 is set to 3 atom% to 44 atom%.

TiC-Si-O having such a composition ratio
The system resistance material is easy to adjust the amount of heat generation per unit time to a size suitable for printing, and has excellent pulse resistance, and is especially suitable for applications such as photographic printing where gradation expression is required. The heating resistor 3 is obtained.

A pair of electrodes 4 made of a metal material such as aluminum is connected to both ends of the heating resistor 3.

The pair of electrodes 4 are commonly connected to all the heating resistors 3 on one end side of the heating resistor 3 and individually connected to each heating resistor 3 on the other end side thereof, and are not shown. Power supply power is applied to the heating resistor 3 based on the turning on / off of the driver IC.

The heating resistor 3 and the pair of electrodes 4 are
A well-known thin film method, specifically, the TiC-Si-O-based resistance material described above and a metal material such as aluminum are sequentially deposited on the entire upper surface of the base plate 1 by a sputtering method or the like. The photolithography and etching techniques described above are used to form a predetermined pattern.

A protective layer 5 having a thickness of, for example, 3 μm to 15 μm is deposited on the heating resistor 3 and the pair of electrodes 4 described above. With the protective layer 5, the heating resistor 3 and the electrode 4 are formed.
Are commonly coated.

The protective layer 5 is abraded by the sliding contact of the recording medium, and is in contact with moisture contained in the atmosphere and ions (Na ⁺ , K ⁺ , Cl ^−, etc.) contained in the recording medium. It is for protecting the heating resistor 3 and the electrode 4 from corrosion, and has a three-layer structure in which three layers of the first layer 6, the second layer 7 and the third layer 8 are sequentially laminated from the heating resistor 3 side. The content of Si contained in each of these layers is set to 3 atom% to 44 atom% as in the heating resistor 3 described above.

Here, S contained in each layer of the protective layer 5
The content rate of i is the same as that of the heating resistor 3 3 at% to 44 at%
Is set to be good in conformity between the heating resistor 3 and the protective layer 5 and between the layers of the protective layer 5, and the linear expansion coefficients of these layers 3, 6, 7 and 8 are relatively close to each other. This is for setting the value, and thereby effectively prevents a large thermal stress from being generated between the layers even when the temperature of the thermal head rises due to heat generated by the heating resistor 3 during printing, and the protective layer. Each layer of No. 5 can be firmly adhered to the base.

Each of the first layer 6 to the third layer 8 constituting the protective layer 5 will be individually described below. The first layer 6 provided as the lowermost layer of the protective layer 5 is formed of an inorganic material containing SiO (silicon oxide) and / or SiN (silicon nitride) to have a thickness of, for example, 0.1 μm to 2.0 μm.

When the second layer 7 disposed on the first layer 6 is formed through a heat treatment process, the organic solvent in the perhydropolysilazane solution, which will be described later, is used as the heating resistor 3
This is to effectively prevent the contact with the electrodes 4 and the like to try to oxidize them, so that the variation of the resistance value of the heating resistor 3 in the manufacturing process of the thermal head can be suppressed very effectively.

The first layer 6 employs a conventionally known thin film method, specifically, a sputtering method, a CVD method, or the like, and is made of SiO, SiN, or a mixed material thereof (Si.
ON) is deposited to a predetermined thickness,
Many fine film defects such as pinholes are formed on the first layer 6 thus obtained.

The second layer 7 provided as an intermediate layer of the protective layer 5 is made of an inorganic material such as SiO, SiN or SiON and has a thickness of 0.03 μm to 0.15 μm.
It is formed of a sintered body obtained by sintering the perhydropolysilazane shown in Chemical formula 1.

[0036]

[Chemical 1]

This perhydropolysilazane is, for example, 1
A ceramic precursor polymer that polymerizes at a temperature of 50 ° C to 220 ° C, and is a perhydropolysilazane solution (viscosity: 0.5 cps to 1.0 cps) prepared by dissolving perhydropolysilazane in an organic solvent such as xylene or cyclohexene.
cps) is thinly applied to the upper surface of the first layer 6 by a conventionally known thick film method such as a dipping method, a spin coating method, or a bar coater method, and this is first applied in a temperature range of 150 ° C. to 220 ° C. for about 1 hour, then About 1 to 400 ℃ ~ 500 ℃
The second layer 7 is formed by heat-treating for a time and ceramming the perhydropolysilazane.

At this time, when the heat treatment of the perhydropolysilazane is performed in a nitrogen atmosphere, the ceramic sintered body containing SiN as a main component also has a high humidity atmosphere (humidity of 50% or more).
By doing so, a ceramic sintered body containing SiO as a main component is formed.

Since the second layer 7 formed by the thick film process as described above has almost no film defects such as pinholes, the film defects of the first layer 6 are satisfactorily closed by the second layer 7. be able to. Therefore, the heating resistor 3 and the electrode 4 are favorably sealed by the protective layer 5, and the heating resistor 3 and the electrode 4 are corroded by the contact of moisture contained in the atmosphere or ions contained in the recording medium. It becomes possible to satisfactorily be protected.

The third layer 8 provided as the uppermost layer of the protective layer 5 is formed of a hard inorganic material containing SiN and / or SiC (silicon carbide) to a thickness of 2.0 μm to 5.0 μm.

SiN or SiC forming the third layer 8
Is a hard material having a Vickers hardness Hv of 1500 to 4000 and is excellent in abrasion resistance, so that the abrasion amount due to the sliding contact of the recording medium during printing can be suppressed to be small.
It is possible to effectively prevent the second layer 7 from being exposed early by repeating the printing operation. Therefore, the heating resistor 3 and the electrode 4 can be surely kept shielded from the atmosphere by the second layer 7, and the electric resistance values of the heating resistor 3 and the electrode 4 can be kept substantially constant for a long period of time.

In this case, carbon (C), TiC, HfC, VC or the like is added in a predetermined amount to the inorganic material forming the third layer 8 and the specific resistance thereof is 1 × 10 ⁷ Ω · cm to 1 × 1.
If it is set to 0 ¹¹ Ω · cm, the third layer 8 will be provided with appropriate conductivity, so that when the recording medium is brought into sliding contact with the surface of the protective layer 5 for printing. Even if some of the static electricity charged on the surface of the recording medium is applied to the thermal head, these charges do not remain in one place on the protective layer 5 and are well diffused over the entire protective layer 5,
It is possible to effectively prevent the protective layer 5 from being electrostatically destroyed by applying a large local voltage to the protective layer 5, which also makes it possible to improve the reliability of the thermal head. Therefore, the specific resistance of the third layer 8 is 1 × 10 ⁷ Ω · cm
It is preferably set to 1 × 10 ¹¹ Ω · cm.

The third layer 8 is the first layer 6 described above.
It is formed by the same forming method as. For example, SiC or S
iN or a mixed material (SiCN) thereof is used as a conventionally known thin film method, specifically, a sputtering method or a CVD method.
The third layer 8 is formed by adopting a method or the like and depositing it on the upper surface of the second layer 7 to a predetermined thickness.

Thus, in the above-mentioned thermal head, a recording medium such as thermal paper is provided on the surface of the protective layer 5, specifically, the third layer 8.
While slidingly contacting the surface of the heating resistor, electric power is selectively applied to the plurality of heating resistors 3 based on the image data from the outside, and the heating resistors 3 are individually and selectively heated by Joule heat. Heat is conducted to the recording medium through the protective layer 15 to form a print, thereby functioning as a thermal head.

The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, the electrode 4
However, instead of this, the electrode 4 may be formed of a conductive material containing Si such as Al—Si and Al—Si—Cu. In this case, the electrode 4 is protected. There is an advantage that the adhesion between the layers 5 is also improved.

[0047]

According to the thermal head of the present invention, of the three layers constituting the protective layer, the film defect of the first layer which is the lowermost layer is sealed by the second layer which is a sintered body of perhydropolysilazane. Since it is stopped, the heating resistor can be well protected from corrosion due to contact with moisture contained in the atmosphere and ions contained in the recording medium. A third layer made of hard SiN, SiC, etc. is provided as the uppermost layer, and wear of the entire protective layer is effectively suppressed, so that part of the second layer does not disappear early and the heating resistor It is possible to keep the electric resistance value of the heat generating resistor or the like substantially constant for a long period of time by keeping the second layer reliably blocked from the atmosphere by the second layer.

Further, according to the thermal head of the present invention, the composition ratio of the TiC-Si-O-based resistance material forming the heating resistor is (TiC) _x SiO _y (3.4≤x≤29.0, 1.
8 ≦ y ≦ 2.2), and the content ratio of Si contained in each layer of the heating resistor and the protective layer is 3 at% to 44 at%.
By setting to, the heating resistor-protective layer, and
It is possible to adjust the linear expansion coefficient of the heating resistor and each layer of the protective layer to a value relatively close to each other by making the familiarity between each layer of the protective layer good. Even if the temperature rises, a large thermal stress can be effectively prevented from being generated between these layers, and each layer of the protective layer can be firmly adhered to the underlayer. This improves the reliability of the thermal head.

Further, according to the thermal head of the present invention, the specific resistance of the third layer, which is the uppermost layer of the protective layer, is 1 × 10 ⁷ Ω.
-If a suitable conductivity is imparted by setting to cm to 1 x 10 ¹¹ Ω-cm, the surface of the recording medium is charged when the recording medium is brought into sliding contact with the surface of the recording medium for printing. Even if part of the static electricity is applied to the thermal head, these charges do not stay in one place on the protective layer and are well diffused throughout the protective layer, so a large local voltage is applied to the protective layer. It is possible to effectively prevent the protective layer from being electrostatically destroyed due to this, and this also makes it possible to improve the reliability of the thermal head.

[Brief description of drawings]

FIG. 1 is a perspective view of a thermal head according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the thermal head shown in FIG.

FIG. 3 is a sectional view of a conventional thermal head.

[Explanation of symbols]

1 ... Base plate, 3 ... Heating resistor, 4 ...
・ Electrodes for energization, 5 ... Protective layer, 6 ... First layer, 7
... Second layer, 8 ... Third layer

Claims (4)

[Claims] 1. A TiC-Si-O on the upper surface of a base plate.
A thermal head comprising a plurality of heating resistors made of a system resistance material and a heating layer covering the heating resistors, wherein the protection layer is made of an inorganic material containing SiO and / or SiN. A thermal head comprising a first layer, a second layer made of a sintered body of perhydropolysilazane, and a third layer made of an inorganic material containing SiN and / or SiC, which are sequentially laminated. . 2. The thermal head according to claim 1, wherein the first layer and the third layer of the protective layer are thin films formed by a sputtering method or a CVD method. 3. TiC-Si-O forming the heating resistor.
The composition ratio of the system resistance material is (TiC) _x SiO _y (3.4 ≦
x ≦ 29.0, 1.8 ≦ y ≦ 2.2), and the content ratio of Si contained in each layer of the heating resistor and the protective layer is set to 3 atom% to 44 atom%. The thermal head according to claim 1 or 2, wherein 4. The specific resistance of the inorganic material forming the third layer of the protective layer is set to 1 × 10 ⁷ Ω · cm to 1 × 10 ¹¹ Ω · cm. Claim 3
The thermal head according to any one of 1.