JP2003127450A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable thermal head which can maintain an electric resistance value of heating resistors or the like to be nearly constant for a long term. SOLUTION: In the thermal head, a plurality of heating resistors 3 comprising a CrSiO based resistance material are applied on an upper face of a base plate 1 and moreover, the heating resistors 3 are coated with a protecting layer 5. The protecting layer 5 is formed by sequentially laminating a first layer 6 comprised of an inorganic material containing an oxide and/or a nitride of Si, a second layer 7 comprised of a sintered body of perhydropolysilazane and a third layer 8 comprised of an inorganic material containing a nitride and/or a carbide of Si.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head widely used as a recording device such as a facsimile and 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 abrasion resistance such as silicon nitride 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 ), which is largely different from the linear expansion coefficient (3 × 10 ⁻⁶ ° C. ⁻¹ ) of the protective layer 15 made of silicon nitride or the like, and When the temperature of the entire thermal head rises due to the heat generated by the heat-generating resistor 13 or the like because of poor compatibility with the sealing material, a large thermal stress generated between the protective layer 15 and the sealing material causes the sealing material. May be peeled off from the protective layer 15, which may also open the film defect of the protective layer 15.

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 heating resistors made of CrSiO-based resistance material are attached to the upper surface of a base plate and the heating resistors are covered with a protective layer. In the thermal head, the protective layer includes a first layer made of an inorganic material containing Si oxide and / or a nitride, a second layer made of a sintered body of perhydropolysilazane, a Si nitride and And / or a third layer made of an inorganic material containing carbide is sequentially laminated.

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 CrSiO-based resistance material forming the heating resistor is C.
r _x SiO _y (0.7 ≦ x ≦ 5.1, 1.8 ≦ y ≦ 2.
4) and the content ratio of Si contained in each of the heating resistor and the protective layer is 10 at% to 44 at%.
It is characterized by being set to.

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. Since the third layer made of silicon nitride, silicon carbide, etc. is provided as the uppermost layer and wear of the entire protective layer is effectively suppressed, 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.

According to the thermal head of the present invention, the composition ratio of the CrSiO-based resistance material forming the heating resistor is Cr _x SiO _y (0.7≤x≤5.1, 1.8≤y≤2.
4) and by setting the content ratio of Si contained in each layer of the heating resistor and the protective layer to 10 at% to 44 at%, the heating resistor-the protective layer and the interlayers of the protective layer are set. With good familiarity with, since it is possible to adjust the linear expansion coefficient of the heating resistor and each layer of the protective layer to a relatively close value, even if the temperature of the thermal head rises due to heat generated by the heating resistor during printing, It is possible to effectively prevent generation of a large thermal stress between each of 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 CrSi.
Depending on the O-based resistance material, for example, 0.01 μm to 0.2 μm
When the power supply is supplied through the electrodes 4 and the like, Joule heat is generated to reach a predetermined temperature necessary for printing.

CrS forming such a heating resistor 3
As the io-based resistance material, the composition ratio is Cr _x SiO 2.
Those represented by _y (0.7 ≦ x ≦ 5.1, 1.8 ≦ y ≦ 2.4) are preferably used, and the content ratio of Si contained in the heating resistor 3 is 10 atoms. % To 44 atomic%.

A CrSiO-based resistance material having such a composition ratio can easily adjust the amount of heat generation per unit time to a size suitable for printing, and has excellent pulse resistance, so that high-speed recording is possible. Heating resistor 3 suitable for industrial label printing and bar code printing where operation is required
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 conventionally known thin film method, specifically, the above-described CrSiO-based resistance material and a metal material such as aluminum are sequentially deposited on the entire upper surface of the base plate 1 by a conventionally known sputtering method or the like, which is conventionally well known. It is formed by adopting photolithography and etching techniques and processing into 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 ratio of Si contained in each of these layers is set to 10 atom% to 44 atom% similarly to the heating resistor 3 described above.

Here, S contained in each layer of the protective layer 5
The content rate of i is set to 10 atom% to 44 atom% which is the same as that of the heat generating resistor 3 between the heat generating resistor 3 and the protective layer 5, and
This is because the layers of the protective layer 5 are made to have a good familiarity with each other and the linear expansion coefficients of these layers 3, 6, 7, and 8 are set to relatively close values. Even if the temperature of the thermal head rises due to the heat generated or the like, it is possible to effectively prevent a large thermal stress from being generated between the respective layers and firmly adhere the respective layers of the protective layer 5 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 an oxide of Si (silicon oxide) and / or a nitride (silicon nitride) to have a thickness of, for example, 0.1 μm to 2.0 μm. It

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 is formed by a conventionally known thin film method, specifically, a sputtering method, a CVD method, or the like, and is made of silicon oxide, silicon nitride, or a mixed material thereof (Si-O-N). ) Is deposited to a predetermined thickness, and many fine film defects such as pinholes are formed in the first layer 6 thus obtained.

The second layer 7 provided as an intermediate layer of the protective layer 5 is formed of an inorganic material such as silicon oxide, silicon nitride or Si--O--N to a thickness of 0.03 μm to 0.15 μm. It is formed by a sintered body obtained by sintering the perhydropolysilazane shown in.

[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, if the heat treatment of perhydropolysilazane is carried out in a nitrogen atmosphere, the ceramic sintered body containing silicon nitride as a main component is produced, and if it is carried out in a high humidity atmosphere (humidity of 50% or more), silicon oxide is mainly contained. A ceramic sintered body as a component will be 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 Si nitride and / or carbide to a thickness of 2.0 μm to 5.0 μm.

The third layer 8 has a Vickers hardness Hv of 1
Since it is made of a hard material of 500 to 4000 and has excellent abrasion resistance, it is possible to suppress the abrasion amount due to the sliding contact of the recording medium during printing, and the second layer 7 is exposed early by repeating the printing operation. Can be effectively prevented. 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, silicon carbide, silicon nitride, or a mixed material of these (Si-C-N)
The third layer 8 is formed by using a well-known thin film method, specifically, a sputtering method, a CVD method, or the like, and depositing it to a predetermined thickness on the upper surface of the second layer 7.

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.

According to the thermal head of the present invention, the composition ratio of the CrSiO-based resistance material forming the heating resistor is Cr _x SiO _y (0.7≤x≤5.1, 1.8≤y≤2.
4) and by setting the content ratio of Si contained in each layer of the heating resistor and the protective layer to 10 at% to 44 at%, the heating resistor-the protective layer and the interlayers of the protective layer are set. With good familiarity with, since it is possible to adjust the linear expansion coefficient of the heating resistor and each layer of the protective layer to a relatively close value, even if the temperature of the thermal head rises due to heat generated by the heating resistor during printing, It is possible to effectively prevent generation of a large thermal stress between each of 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 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 thermal head comprising a plurality of heating resistors made of a CrSiO-based resistance material deposited on the upper surface of a base plate, and the heating resistors being covered with a protective layer, wherein the protective layer comprises: A first layer made of an inorganic material containing Si oxide and / or nitride, a second layer made of a sintered body of perhydropolysilazane, and a third layer made of an inorganic material containing Si nitride and / or carbide. A thermal head, which is formed by sequentially laminating layers. 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. A CrSiO-based resistor forming the heating resistor.
The composition ratio of the anti-material is Cr _xSiO_y(0.7 ≦ x ≦ 5.
1, 1.8 ≦ y ≦ 2.4), and the heating resistor
And the content rate of Si contained in each layer of the protective layer is 1
It is characterized in that it is set to 0 atom% to 44 atom%.
The thermal head according to claim 1 or 2. 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.