JPH09314877A - Thermal head and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve the adhesion with an ink ribbon and achieve a high quality printing. SOLUTION: Common electrodes 5 and individual electrodes 6 are formed on a heat retaining layer formed on a substrate 1. A heat resistive member 7 is formed on the upper surface of each electrode. An overcoat layer is formed on the substrate 1, the heat retaining layer 2, the electrodes 5, 6 and the heat resistive member 7. The heat retaining layer and the overcoat layer are made from a heat resistive resin, and the heat resistive member 7 is made from a material prepared by dispersing conductive powders in a heat resistive resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head and a method for manufacturing the thermal head, and more particularly to a thermal head which can remarkably enhance the adhesion to an ink ribbon and enables high quality printing, and the manufacturing thereof. Regarding the method.

[0002]

2. Description of the Related Art Generally, a thermal head mounted on a thermal transfer printer has, for example, a plurality of heating resistors formed linearly on an insulating substrate, and the heating resistors are selectively selected based on print information. By heating by applying electricity, the ink of the ink ribbon is melted and transferred and recorded on a predetermined recording medium.

In a conventional thermal head, for example, a heat insulating layer made of a material having low thermal conductivity such as heat resistant glass is formed on the upper surface of a substrate made of an insulating material such as alumina, and the upper surface of the heat insulating layer is formed. , For example, Al, C
The common electrode and the individual electrode made of a conductive material such as u or Au are formed in a comb-shaped pattern.
Then, on the upper surface of each of these electrodes, a paste of ruthenium oxide fine powder dispersed in a binder glass is applied and fired to form a linear heating resistor across each of the electrodes. A heating portion corresponding to one dot, which is the minimum printing unit, is formed between the electrodes. Further, it may be prepared by forming an overcoat layer on the upper surface of the substrate, the heat insulating layer, each electrode and each heating resistor to cover all parts of each electrode except the terminal part of each electrode, for example. Has been done.

In such a conventional thermal head, while the thermal head is pressed against the platen of the thermal transfer printer through a desired recording medium, the individual electrodes are selectively energized based on predetermined print information. By doing so, the heat generating portion of the corresponding heat generating resistor is caused to generate heat, and the ink of the ink ribbon is melt-transfer recorded on the recording medium to perform desired printing.

[0005]

However, in the above-mentioned conventional thermal head, the heat retaining layer, the heating resistor and the overcoat layer formed on the upper surface of the substrate are each formed of a material such as metal oxide or glass. Therefore, the heat generating portion of the thermal head is formed to have high rigidity, and therefore, when the thermal head is pressed against the platen via the ink ribbon and the recording medium,
Adhesion between the heat-generating part of the thermal head and the ink ribbon becomes insufficient, and when printing is performed in this state, print fading or missing, uneven print density, etc. occur, adversely affecting print quality. Has the problem of giving.

Further, in recent years, there has been a tendency for printing dots formed by a thermal head to become finer, and moreover, multi-gradation printing is required, and the heat generating portion of the thermal head and the ink ribbon are in close contact with each other. The adverse effects of poor sex are becoming more pronounced.

The present invention has been made in view of the above points, and provides a thermal head capable of remarkably enhancing the adhesion to an ink ribbon and capable of high-quality printing, and a method of manufacturing the same. The purpose is.

[0008]

In order to achieve the above object, the thermal head according to the invention of claim 1 forms a heat retaining layer on a substrate, and forms a common electrode and an individual electrode on the heat retaining layer. At the same time, a heat-generating resistor is formed on the upper surface of each of these electrodes, and an overcoat layer is formed on the upper surface of the substrate, the heat retaining layer, each electrode and the heat-generating resistor. In addition to being made of a heat-resistant resin, the heating resistor is made of a material in which a conductive powder is dispersed in a heat-resistant resin.

According to the first aspect of the present invention, the overcoat layer is formed of a heat-resistant resin, and the heating resistor is formed of a material in which conductive powder is dispersed in the heat-resistant resin. Therefore, as compared with the conventional thermal head, the heat generating portion of the thermal head can be formed flexibly, and as a result, when the thermal head is pressed against the platen via the ink ribbon and the recording medium, it is easily deformed. Therefore, it is possible to sufficiently secure the adhesion between the heat generating portion of the thermal head and the ink ribbon.

[0010] The invention described in claim 2 is the same as the claim 1.
In the above, the heat insulating layer is formed of a heat resistant resin.

According to the second aspect of the invention, since the heat retaining layer is formed of the heat resistant resin, the heat generating portion of the thermal head can be formed more flexibly.

Further, the invention described in claim 3 is the first invention.
Alternatively, in claim 2, a polyimide resin is used as the heat resistant resin.

According to the third aspect of the present invention, by using the polyimide resin as the heat resistant resin, the heat retaining layer, the heating resistor and the overcoat layer can be flexibly formed.

Further, the invention according to claim 4 is characterized in that, in any one of claims 1 to 3, carbon black powder is used as the conductive powder.

According to the invention of claim 4, the conductivity of the heating resistor can be secured by the carbon black powder, and the resistance value can be changed by changing the ratio of carbon black to the heat resistant resin. Is something that can be done.

In the method of manufacturing a thermal head according to a fifth aspect of the present invention, a heat insulating layer is formed on a substrate, a common electrode and individual electrodes are formed on the heat insulating layer, and the upper surface of each of these electrodes is formed. A heat-generating resistor is formed by printing a material in which a conductive powder is dispersed in a heat-resistant resin in a predetermined pattern and baking the heat-resistant resin. The heat-resistant layer, each electrode and the top surface of each heat-generating resistor are heat-resistant. An overcoat layer is formed by applying a resin and baking it.

According to the fifth aspect of the present invention, the overcoat layer is formed of a heat resistant resin, and the heating resistor is formed of a material in which conductive powder is dispersed in the heat resistant resin. Therefore, as compared with the conventional thermal head, the heat generating portion of the thermal head can be formed flexibly, and as a result, when the thermal head is pressed against the platen via the ink ribbon and the recording medium, it is easily deformed. Therefore, it is possible to sufficiently secure the adhesion between the heat generating portion of the thermal head and the ink ribbon.

The invention described in claim 6 is the same as the invention in claim 5
In the above, the heat insulating layer is formed of a heat resistant resin.

According to the sixth aspect of the invention, since the heat retaining layer is formed of the heat resistant resin, the heat generating portion of the thermal head can be formed more flexibly.

The invention according to claim 7 is the same as claim 5
Alternatively, in claim 6, a polyimide resin is used as the heat resistant resin.

According to the invention of claim 7, by using the polyimide resin as the heat resistant resin, the heat retaining layer, the heat generating resistor and the overcoat layer can be flexibly formed.

Further, the invention described in claim 8 is characterized in that, in any one of claims 5 to 7, carbon black powder is used as the conductive powder.

According to the invention of claim 8, the conductivity of the heating resistor can be secured by the carbon black powder, and the resistance value can be changed by changing the ratio of carbon black to the heat resistant resin. Is something that can be done.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
This will be described with reference to FIG.

1 and 2 show an embodiment of a thermal head according to the present invention. A substrate 1 made of a heat-resistant metal material such as an alumina sintered body or aluminum.
A heat insulating layer 2 made of a heat resistant resin such as a polyimide resin or a silicon-based polymer resin is formed on the upper surface of the so as to have a thickness of about 20 μm. In addition, this heat insulation layer 2
May be made of a material having low thermal conductivity such as heat resistant glass.

On the upper surface of the heat retaining layer 2, a base line 3 linearly extending along one side edge of the substrate 1 and a direction orthogonal to the base line 3 at predetermined intervals from one side of the base line 3 are provided. Comb-shaped common electrode 5 consisting of a plurality of branch lines 4, 4 ...
Is formed on the upper surface of the heat insulating layer 2 and between each branch line 4 of the common electrode 5, and extends in parallel to the branch line 4 and alternates in the extending direction of the branch line 4 and the base line 3. The individual electrodes 6, 6 ...
Each of the common electrode 5 and the individual electrode 6 is made of a conductive material such as copper, aluminum, or gold, and is formed to have a thickness of about 1 μm.

On the upper surfaces of the common electrode 5 and the individual electrodes 6, for example, a conductive material in which a heat resistant resin such as polyimide resin is used as a binder resin and conductive powder such as carbon black powder is dispersed therein is used. The linear heating resistor 7 extending parallel to the base line 3 of the common electrode 5 is formed to have a thickness of about 5 μm, and the heating resistor 7 includes the common electrode 5 and Between the individual electrodes 6, a heating portion 7a corresponding to one dot, which is the minimum printing unit, is formed. In this case, for example, when the dot density is 100 dpi (dot, par, inch), the spacing between the branch lines 4 of the common electrode 5 is 0.25 m.
m, the distance between the branch line 4 of the common electrode 5 and the individual electrode 6 is 0.
It is arranged so as to be 125 mm.

Further, the heat insulating layer 2, the heating resistor 7 and the electrodes 5, 6 are made of a heat-resistant resin such as a polyimide resin on the upper surface of the heating resistor 7, the electrodes 5, 5.
The overcoat layer 8 for protecting 6 is formed to have a thickness of about 5 μm.
Covers all parts of the electrodes 5 and 6 except the terminal part.

Next, a method of manufacturing the thermal head of the present invention will be described.

First, for example, carbon black as a conductive powder is dispersed in a polyimide resin as a heat resistant resin by a ball mill to prepare a carbon paste as a material for forming the heating resistor 7. In this case, as shown in FIG. 3, the resistance value of the conductive material changes depending on the ratio (% by weight) of carbon black to the polyimide resin. Therefore, the ratio of carbon black is set to have a necessary resistance value. .

Then, for example, a polyimide resin as a heat resistant resin is applied on the upper surface of the substrate 1 made of an alumina sintered body so as to have a thickness of about 20 μm to form the heat insulating layer 2.

Next, a low temperature firing resinate paste or a silver paste is printed on the upper surface of the heat insulating layer 2 by screen printing in a predetermined comb-shaped pattern.
The common electrode 5 and the individual electrode 6 are formed by firing for 5 minutes under the firing temperature of 500 ° C. and the heating rate of 5 ° C./min.

Subsequently, the common electrode 5 and the individual electrode 6
After printing the carbon paste in a predetermined linear pattern on the upper surface of the plate by screen printing, the firing temperature is set to 3
70 ° C., heating rate 3 ° C./min, peak temperature 1
The heating resistor 7 is formed by holding and firing for 0 minutes.

Further, a polyimide resin as a heat resistant resin is applied on the upper surfaces of the heat insulating layer 2, the heating resistor 7 and the electrodes 5 and 6 by dipping and coating, and the firing temperature is 370 ° C.
The overcoat layer 8 is formed by baking under the above conditions.

In the above embodiment, the common electrode 5 and the individual electrode 6 are formed by baking after screen printing. However, the common electrode 5 and the individual electrode 6 are made of, for example, a predetermined material made of an electrically conductive material. It may be formed by plating or may be formed into a predetermined pattern by a photolithography process after sputtering a predetermined material.
And if such a means is used, for example, 300-
It is possible to make the dot density as small as 600 dpi.

In the above-described embodiment, the alumina sintered body is used as the material of the substrate 1. However, for example, by applying a polyimide resin as the heat retaining layer 2 to a metal substrate made of aluminum, the cost can be reduced. Can be formed.

Next, the operation of the present embodiment will be described.

In the present embodiment, while the thermal head is pressed against the platen of the thermal transfer printer via the ink ribbon and the predetermined recording medium, the individual electrodes 6 are selectively energized based on predetermined print information. By doing so, the heat generating portion of the corresponding heat generating resistor 7 is caused to generate heat, and the ink of the ink ribbon is melt-transfer recorded on the recording medium to perform desired printing.

In this case, in this embodiment, the heat insulating layer 2 and the overcoat layer 8 are each formed of a heat resistant resin such as a polyimide resin, and the heating resistor 7 is made of a heat resistant resin such as a polyimide resin and carbon. Since it is made of a material in which conductive powder such as black is dispersed, compared to the conventional thermal head,
It is possible to flexibly form the heat generating portion of the thermal head. For example, in the present invention, the heat insulating layer 2 and the heating resistor 7 are used.
The Young's modulus of the polyimide resin used for forming the overcoat layer 8 is about 300 to 400 Kg / mm ² , whereas the Young's modulus of the metal oxide forming the conventional thermal head is 3 × 10 5. ⁵ ~9 × 10 ⁵ Kg /
a mm ² approximately, lower towards the polyimide resin is Young's modulus, it is extremely flexible as compared to the metal oxide.

As a result, the thermal head of the present invention can be easily deformed when the thermal head is pressed against the platen via the ink ribbon and the recording medium, and the heat generating portion of the thermal head and the ink ribbon are separated. Adhesion can be sufficiently ensured. When the pressure contact of the thermal head is released, the polyimide resin is elastically deformed and returned to its original shape due to the flexibility of the polyimide resin.

FIG. 4 shows the result of measuring the heat generation temperature of the heat generating portion 7a of the heat generating resistor 7 by applying a voltage of 24 V to the thermal head according to the present invention at the pulse intervals shown in FIG. .

According to the measurement results, it can be seen that the thermal head of the present invention can generate heat at a temperature of about 525 ° C. and has sufficient performance as a thermal head.

Therefore, in the present embodiment, the heat retaining layer 2, the heating resistor 7 and the overcoat layer 8 of the thermal head are formed by using a heat resistant resin such as a polyimide resin, respectively. Compared to the above, since the heat generating portion of the thermal head is formed flexibly, when the thermal head is pressed against the platen via the ink ribbon and the recording medium, it is easily deformed and the heat of the thermal head is generated. Adhesion between the portion and the ink ribbon can be sufficiently secured, and it is possible to reliably prevent the occurrence of print faintness or omission, nonuniform print density, and the like, and it is possible to significantly improve print quality. As a result, it becomes possible to appropriately deal with the miniaturization of the printing dots and the multi-gradation of printing.

Further, in this embodiment, the heat insulating layer 2,
Each electrode 5, 6, heating resistor 7 and overcoat layer 8
Since it is formed by coating or baking after printing such as screen printing, it is possible to easily manufacture even a long line thermal head. Since the material is also inexpensive, the material cost can be reduced and the manufacturing cost can be reduced. Moreover, since the firing temperature is 400 ° C. or less, expensive firing equipment capable of firing at high temperature is not required, and the equipment cost can be reduced.

The present invention is not limited to the above embodiments, but can be variously modified as needed.

[0046]

As described above, in the thermal head and the method for manufacturing the same according to the present invention, the heating resistor and the overcoat layer are each formed of a heat resistant resin such as a polyimide resin, or a heat insulating layer is formed. The thermal head is made of heat-resistant resin so that the heat generating part of the thermal head can be formed more flexibly than the conventional thermal head, so the thermal head is pressed against the platen via the ink ribbon and recording medium. In the case of deformation, it can be easily deformed to ensure sufficient adhesion between the heat generating part of the thermal head and the ink ribbon, and it is possible to reliably prevent faint or missing prints and uneven print density. The printing quality can be remarkably improved. As a result, there is an effect that it is possible to appropriately deal with the miniaturization of printing dots and the increase in gradation of printing.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a thermal head of the present invention.

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

FIG. 3 is a diagram showing a relationship between a mixing ratio of carbon black to a polyimide resin according to the present invention and a resistance value.

FIG. 4 is a diagram showing a result of measuring a heat generation temperature of a heat generating portion of a heat generating resistor by the thermal head of the present invention.

5 is an explanatory diagram showing pulse intervals of a voltage applied when measuring a heat generation temperature of the thermal head shown in FIG.

[Explanation of symbols]

 1 substrate 2 heat insulation layer 5 common electrode 6 individual electrode 7 heating resistor 8 overcoat layer

Claims (8)

[Claims] 1. A heat insulating layer is formed on a substrate, a common electrode and an individual electrode are formed on the heat insulating layer, and a heating resistor is formed on the upper surface of each of the electrodes, the substrate, the heat insulating layer, and each electrode. And a thermal head in which an overcoat layer is formed on the upper surface of the heating resistor, wherein the overcoat layer is made of a heat-resistant resin, and the heating resistor has a conductive powder dispersed in the heat-resistant resin. A thermal head characterized by being formed of a material. 2. The thermal head according to claim 1, wherein the heat insulating layer is formed of a heat resistant resin. 3. The thermal head according to claim 1, wherein a polyimide resin is used as the heat resistant resin. 4. The thermal head according to claim 1, wherein carbon black powder is used as the conductive powder. 5. A heat insulating layer is formed on a substrate, a common electrode and an individual electrode are formed on this heat insulating layer, and a material obtained by dispersing a conductive powder in a heat resistant resin is formed on a predetermined surface of each electrode. A heating resistor is formed by printing on a pattern and firing, and an overcoat layer is formed by coating a heat-resistant resin on the upper surface of the heat retaining layer, each electrode and each heating resistor and firing. A method of manufacturing a thermal head, characterized in that 6. The method of manufacturing a thermal head according to claim 5, wherein the heat insulating layer is formed of a heat resistant resin. 7. The method of manufacturing a thermal head according to claim 5, wherein a polyimide resin is used as the heat resistant resin. 8. The method of manufacturing a thermal head according to claim 5, wherein carbon black powder is used as the conductive powder.