JP3176097B2 - Manufacturing method of thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermal head incorporated as a printer mechanism for a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a thermal head conventionally incorporated as a printer mechanism for a word processor, a facsimile or the like has a heat storage layer 12 made of glass or the like on a substrate 11 made of an electrically insulating material such as alumina.
And a heating resistor layer 13 made of tantalum nitride or the like and a pair of conductive layers 14a and 14b made of aluminum or the like, and the heating resistor layer 13 and the pair of conductive layers 1
4a and 14b are covered with a protective layer 15 made of silicon nitride or the like. A predetermined power is applied between the pair of conductive layers 14a and 14b, and the heating resistor layer 13 is printed. Joule heat is generated to a temperature required for forming the thermal paper, and the generated heat is conducted to the thermal paper 17 or the like, thereby forming a printed image on the thermal paper 17 or the like, thereby functioning as a thermal head.

The heat-generating resistor layer 13 and the pair of conductive layers 14a and 14b are prevented from being worn by sliding of thermal paper or the like, and are not limited to moisture in the atmosphere, chlorine ions and sodium contained in the thermal paper and the like. This is to prevent ions and the like from coming into contact with the heating resistor layer 13 and the like, thereby causing corrosion of the heating resistor layer 13 and the like.

However, in this conventional thermal head, the protective layer 15 is usually formed by a thin film forming technique such as a sputtering method. At this time, the protective layer 15 is provided with a pinhole 15a or the like. A large number of film-forming defects cannot be formed to completely cover the surfaces of the heating resistor layer 13 and the pair of conductive layers 14a and 14b.
Therefore, chlorine ions, sodium ions, and the like contained in the moisture in the air, the thermal paper, and the like are removed from the pinhole 15 of the protective layer 15.
a through the heating resistor layer 13 and the pair of conductive layers 14a, 1a.
4b, the heating resistor layer 13 and the like are corroded to cause a break in the heating resistor layer 13 and the pair of conductive layers 14a and 14b, or to cause variations in the conductive resistance. Therefore, the function as a thermal head is lost.

In order to solve the above-mentioned drawbacks, as shown in FIG. 2, an overcoat layer 16 made of resin, glass, or the like is applied to the upper surface of the protective layer 15 to form a pinhole 15a formed in the protective layer 15. Overcoat layer 16 on top
It is possible to close with.

However, since the thermal head merely covers the upper portion of the pinhole 15a formed in the protective layer 15 with the overcoat layer 16, the thermal head is initially contained in moisture in the atmosphere, thermal paper, or the like. Chlorine ions, sodium ions, etc. do not come into contact with the heating resistor layer 13 and the pair of conductive layers 14a, 14b. Although the thermal head can be operated normally, the thermal head is operated repeatedly to print on thermal paper. When an image is formed, the overcoat layer 16 is worn by sliding of the thermal paper 17 or the like, and as a result, the pinhole 15a formed in the protective layer 15 is opened in a short period of time, and the above-mentioned defect recurs. Had a problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a method of manufacturing a thermal head according to the present invention comprises forming a heating resistor layer and a pair of conductive layers on an upper surface of an electrically insulating substrate. A thermal head comprising a heat-resistant resistor layer and a pair of conductive layers coated with a protective layer made of silicon nitride, wherein the surface of the protective layer has a viscosity of 3 cps or less and a surface tension of 25 dyn · s / cm ² or less. An alkoxide glass solution containing a silicon compound is applied and a part of the alkoxide glass solution is allowed to penetrate into pinholes formed in the protective layer. Characterized in that a layer is applied.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of a thermal head according to the present invention, wherein 1 is a substrate, 2 is a heat storage layer, 3 is a heating resistor layer, 4a and 4b are a pair of conductive layers, and 5 is a protection layer. Layer, 6
Is a glass layer.

The substrate 1 is made of an electrically insulating material having excellent heat resistance, such as alumina ceramics, and a heat storage layer 2 is adhered on the upper surface thereof.

The heat storage layer 2 is made of glass, polyimide resin or the like, and functions to maintain and satisfactorily maintain the thermal response characteristics of the thermal head by accumulating and dissipating the heat generated by the heating resistor layer 3.

A heating resistor layer 3 is attached on the upper surface of the heat storage layer 2, and a pair of conductive layers 4a and 4b are attached on the upper surface of the heating resistor layer 3 at a constant interval. Have been.

The heating resistor layer 3 is made of, for example, tantalum nitride and has a predetermined electric resistance. Therefore, when a predetermined power is applied through a pair of conductive layers 4a and 4b, the heating resistor layer 3 is made of joule. It generates heat and generates heat at a temperature required for forming a printed image, for example, 300 to 450 ° C.

The pair of conductive layers 4a and 4b provided on the heating resistor layer 3 are made of a metal such as aluminum, and supply electric power necessary for causing the heating resistor layer 3 to generate Joule heat. It acts to apply.

The heating resistor layer 3 and a pair of conductive layers 4
A protective layer 5 made of silicon nitride is also formed on the upper surfaces of the a and 4b so that the heating resistor layer 3 and the pair of conductive layers 4a and 4b may be worn by sliding with a heat-sensitive paper or the like or may be exposed to air. It protects against corrosion by contaminants such as moisture in the inside, chlorine ions and sodium ions contained in the thermal paper.

The protective layer 5 is formed of a heating resistor layer 3 and a pair of conductive layers 4 by a well-known sputtering method or the like.
a and 4b, and a large number of pinholes 5a are formed in the protective layer 5 at this time.

On the upper surface of the protective layer 5 in which the pinhole 5a is formed, a glass layer 6 partially covers the pinhole 5a.
a.

The glass layer 6 functions to prevent corrosion of the heating resistor layer 3 and the like due to contaminants by closing a pinhole 5a formed in the protective layer 5, and a part of the glass layer 6 is formed. Since the glass layer 6 is affixed to the upper surface of the protective layer 5 while being filled in the pinhole 5a, the glass layer 6 is filled in the pinhole 5a even when the glass layer 6 is worn due to sliding of thermal paper or the like during printing. The glass layer 6 does not wear,
The pinhole 5a can always be closed, so that contaminants can be generated through the pinhole 5a.
Or the pair of conductive layers 4a and 4b contact with each other, causing almost no corrosion.

Thus, in the above-described thermal head, electric power is applied between the pair of conductive layers 4a and 4b in response to an external electric signal to cause the heating resistor layer 3 to have a Joule heating resistor layer at a predetermined temperature, and to apply the power to the Joule heating resistor layer. The generated heat is conducted to the thermal paper or the like to form a printed image on the thermal paper or the like, thereby functioning as a thermal head.

Next, a method of manufacturing the above-described thermal head will be described.

(1) First, a substrate 1 made of an electrically insulating material such as alumina ceramics is prepared.

The substrate is formed into a slurry by adding a suitable organic solvent and a solvent to a ceramic material powder such as alumina, silica, magnesia or the like to form a slurry, and the ceramic green sheet is formed by employing a conventionally known doctor blade method. Then, the ceramic green sheet is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.).

(2) Next, a heat storage layer 2 made of glass or the like is deposited on the substrate 1.

The heat storage layer 2 is formed by applying a glass paste obtained by adding and mixing a suitable organic solvent and a solvent to glass powder, for example, on the substrate 1 by employing a conventionally known screen printing method or the like. Thereafter, it is deposited on the substrate 1 by baking it at a high temperature.

(3) Next, a heating resistor layer 3 made of tantalum nitride or the like and a pair of conductive layers 4a and 4b made of aluminum or the like are sequentially deposited on the heat storage layer 2.

The heating resistor layer 3 and the pair of conductive layers 4
a and 4b are sequentially deposited on the heat storage layer 2 by employing a conventionally known sputtering method or the like.

(4) Next, a protective layer 5 made of silicon nitride is applied to the upper surfaces of the heating resistor layer 3 and the pair of conductive layers 4a and 4b.

The protective layer 5 is formed on the heating resistor layer 3 and the pair of conductive layers 4a and 4b by using silicon nitride by a conventional sputtering method or the like.

(5) Finally, a glass layer 6 is applied on the upper surface of the protective layer 5, whereby a thermal head is completed.

The glass layer 6 is made of a silicon compound (RnSi).
(OH) 4-n: R represents an organic functional group, and n represents a positive number.
An alkoxide glass solution having a viscosity of 3 cps or less and a surface tension of 25 dyn · s / cm ² or less is prepared by adding and mixing an appropriate organic solvent and a solvent (eg, methanol) to the alkoxide glass solution. By adopting a conventionally known dip method or the like, the protective layer 5
And leave it on for about 2 minutes.
The applied alkoxide glass solution is heated at a high temperature of, for example, 500 ° C. for about 1 hour using an oven or the like, and the alkoxide glass is heat-condensed and polymerized. , Solvent and the like are evaporated to form a glass layer 6 and a protective layer 5
On the upper surface.

In this case, the alkoxide glass solution applied on the protective layer 5 has a viscosity of 3 cps or less and a surface tension of 2 cps.
The alkoxide glass solution is adjusted to 5 dyn · s / cm ² or less, and since the alkoxide glass solution containing a silicon compound wets very well with the silicon nitride forming the protective layer 5, the alkoxide glass solution is applied to the upper surface of the protective layer 5. In this case, a part of the alkoxide glass solution was
a, the glass layer 6 obtained by heating the alkoxide glass solution at a high temperature partially covers the pinhole 5a within the pinhole 5a. 5 is applied.

The alkoxide glass solution has a viscosity exceeding 3 cps and a surface tension of 25 dyn · s /.
If it exceeds cm ² , when the alkoxide glass solution is applied to the surface of the protective layer 5, the alkoxide glass solution will not sufficiently penetrate into the pinholes 5 a formed in the protective layer 5. Therefore, in order to apply the glass layer 6 on the surface of the protective layer 5 in a state where a part of the glass layer 6 is filled in the pinhole 5 a formed in the protective layer 5, the viscosity of the alkoxide glass solution is 3 cps or less, the surface tension is Is 25 dyn · s /
It must be specified below cm ² .

In this case, a part of the glass layer 6 is
0.5 μm from the upper surface of the protective layer in the pinhole 5a of the protective layer
By filling up to a depth region of m or more, it is possible to effectively prevent contaminants from penetrating the glass layer 6 and corroding the heating resistor layer 3 and the pair of conductive layers 4a and 4b. Therefore, the heating resistor layer 3 and the pair of conductive layers 4
In order to prevent corrosion of the thermal head more effectively and to make the thermal head function stably and satisfactorily for a long period of time, the glass layer 6 is used.
Is preferably filled in the pinhole 5a formed in the protective layer 5 to a depth of 0.5 μm or more from the upper surface.

Next, the operation and effect of the present invention will be described based on the following two experimental examples.

(Experimental Example 1) As an experimental sample, as shown in FIG. 1, a plurality of heating resistor layers and a pair of conductive layers are applied on the upper surface of a substrate, and the heating resistor layers are covered with a protective layer. In the thermal head, an alkoxide glass solution having a viscosity of 1 cps and a surface tension of 22 dyn · s / cm ² is applied to the surface of the protective layer. The pinhole (diameter:
(0.1 μm, depth: 3 μm) Prepare the product of the present invention in which the glass layer is applied and filled to a depth of 40% from the upper surface within the upper surface, and the conventional product in which no glass layer is applied on the surface of the protective layer. I do.

Next, for each of the samples, a temperature of 35
In a predetermined printing standby state (a state in which a thermal paper is brought into contact with a protective layer of a thermal head and a voltage of 24 V is applied between a pair of conductive layers to generate heat in a heating resistor layer) in an environment of 85 ° C. and humidity of 85%. Then, the time until the number of corroded heating resistor layers reaches 0.1% of the entire heating resistor layer (this is defined as the initial destruction time) was examined.

According to such an experiment, the initial breakdown time of the conventional product was about 20 hours, while that of the present invention was about 100 hours, which is five times longer than that of the conventional product. It can be seen that was improved.

(Experimental Example 2) As an experimental sample, as shown in FIG. 1, a plurality of heating resistor layers and a pair of conductive layers were applied on the upper surface of a substrate, and the heating resistor layers were covered with a protective layer. In the thermal head, an alkoxide glass solution having a viscosity of 1 cps and a surface tension of 22 dyn · s / cm ² is applied to the surface of the protective layer. Pinholes formed in the protective layer (diameter: 0.1
μm, depth: 3 μm), the product of the present invention in which the glass layer is applied and filled to a depth of 40% from the upper surface, and the protective layer surface has a viscosity of 10 cps and a surface tension of 30 dyn · s / cm ^2. The alkoxide glass solution thus prepared is applied, and then heated at a high temperature to prepare a conventional product in which a glass layer is applied only to the surface of the protective layer.

Next, for each of the samples, a predetermined power (power:
0.2 W / dot, application cycle: 10.0 msec, application time: 2.0 msec) and a high ion content (sodium ion: 2) in the protective layer of the thermal head.
(000 ppm or more) was slid, and the sliding distance of the heat-sensitive paper when corrosion first occurred in the heating resistor layer was examined.

According to the experimental results, the conventional product caused the first corrosion when the thermal paper was slid about 10 km, whereas the product of the present invention was about 30 km, which is about three times longer than that of the conventional product. It can be seen that the reliability of the thermal head was improved.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention.

[0042]

According to the thermal head manufacturing method of the present invention, the viscosity is 3 cps or less, and the surface tension is 25 dyn · s / c.
An alkoxide glass solution containing a silicon compound adjusted to m ² or less is applied on a protective layer made of silicon nitride, and a part of the alkoxide glass solution is penetrated into pinholes formed in the protective layer. Since the glass layer is formed by heat polycondensation, the glass layer is adhered on the protective layer in which the pinhole is formed so as to close the pinhole while partially filling the pinhole. You. Therefore, when the thermal head is used, the pinhole formed in the protective layer is not opened in a short period of time due to sliding of the thermal paper or the like, and the pinhole can be always closed with the glass layer. Corrosion caused by contact of the contaminant with the heating resistor layer and the pair of conductive layers is minimized, and the thermal head can function well for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a thermal head manufactured by a manufacturing method of the present invention.

FIG. 2 is a sectional view of a conventional thermal head.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric insulating substrate, 3 ... Heating resistor layer, 4
a, 4b ... a pair of conductive layers, 5 ... protective layer, 5a
..Pinhole, 6 ... Glass layer

Claims (1)

(57) [Claims] 1. A thermal head comprising: a heating resistor layer and a pair of conductive layers formed on an upper surface of an electrically insulating substrate; and the heating resistor layer and the pair of conductive layers covered with a protective layer made of silicon nitride. And a viscosity of 3 cps on the surface of the protective layer.
Hereinafter, silicon compounds having a surface tension of 25 dyn · s / cm ² or less
The addition to applying the alkoxide glass solution containing things
Part of the alkoxide glass solution is formed on the protective layer.
Penetrate the inside of the pinhole.
A method for manufacturing a thermal head, comprising applying a glass layer by subjecting an oxide glass solution to heat condensation polymerization.