JPH0867023A - Thermal print head - Google Patents

Abstract

PURPOSE: To reduce the consumption of power required for printing by preventing generated heat from being diffused outside through the inside of a substrate by forming a heat generating domain along a hollow space. CONSTITUTION: The substrate 1 of a thermal print head comprises a surface having an upward projected wall surface 3a which is formed in the longitudinal direction and a hollow space 2 which is formed by a recessed wall surface on the lower surface side of the projected wall surface and is made of a uniform material. The hollow space 2 is formed by a space with a cross section of a trapezoidal shape which is formed by an upper wall, a lower wall, and side wall, and in which the upper wall and the lower wall are formed in parallel with the substrate surfaces other than the projected wall surface. Electrode wiring is made on the projected wall surface 3a of the substrate 1, and a heat generating resistance is placed between them. In this way, since a heat generating domain in which heat is generated by an electric signal given to the resistance through the electrode wiring is formed on the projected wall surface, or above the hollow space 2, the heat generated can be prevented from being diffused outside through the inside of the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head, and more particularly to a thermal head having improved required power characteristics.

[0002]

2. Description of the Related Art Conventionally, printers for office automation equipment such as facsimiles, printers for ticket vending machines, label printers, etc.
A thermal print head that forms necessary image information by selectively applying heat to a thermal paper is widely used. A conventional thermal print head will be described by taking a thick film type as an example. As shown in FIG. 6, a solid insulating substrate 21 made of ceramic or the like and a partial or entire surface on the surface of the insulating substrate 21. The formed glass glaze layer 22 as a heat storage body, and the common electrode wiring 23 formed in a comb shape on the glaze layer 22 from one surface of the insulating substrate 21.
And the individual electrode wiring 2 extending from the other side of the insulating substrate 21 toward the glaze layer 22 between the tip portions of the common electrode wiring 23.
4 and a heating resistor 25 formed so as to cross over the respective tip portions of the common electrode wiring 23 and the individual electrode wiring 24. Each individual electrode wiring 24 is an insulating substrate 21.
The driving IC 26 mounted corresponding to the above is connected via a conductive wire 27 such as gold. Insulating substrate 21
A heat radiating plate 28 made of a metal having good heat conductivity such as aluminum is mounted on the back surface side of the.

In use of the thermal print head thus constructed, the common electrode wiring 23 and the common electrode wiring 23 are applied by applying a required voltage to the driving IC 26 while keeping the common electrode wiring 23 at a constant potential. A heating resistor (so-called heating dot) between the individual electrode wiring 24 and the individual electrode wiring 24 is selectively energized to form an image by heating on the thermal paper.

[0004]

However, in the conventional thermal print head, as described above, the heating resistor 25 is provided on the solid insulating substrate 21 via the glaze layer 22 or directly. Therefore, a part of the heat generated from the heating resistor 25 directly acts on the heating of the thermal paper or the like as the print medium, while the other part contributes to the heat storage of the glass glaze layer 22 as the heat storage body, It is dissipated into the atmosphere through the heat radiating plate 28 provided on the back surface side of the insulating substrate 21. As described above, since a part of the heat generated from the heating resistor 25 is inevitably used for heat dissipation, it is difficult to reduce the supplied power more than a certain amount, or to achieve sufficient energy saving. Could not be achieved.

In particular, in recent years, with the development of various OA equipment, the demand for a portable thermal print head that can be easily carried around has been increasing,
With the miniaturization of thermal print heads, the demand for energy saving is gradually increasing. Under such a situation, instead of using the glass glaze layer as described above, a heating resistor or the like is provided on the layer formed of a polyimide resin having a lower thermal conductivity to prevent the heat generated through the insulating substrate. Some attempts have been made to reduce power consumption by reducing the emission.

However, since the polyimide resin has elasticity due to its nature, its mechanical strength is insufficient and about 50%.
There is a problem in reliability such as deterioration in heat at about 0 ° C. and poor heat resistance, and it has not yet been put to practical use. Therefore, it is an object of the present invention to provide a thermal print head that reduces the power required for printing.

[0007]

According to the present invention, an electrically insulating substrate, common and individual electrodes formed on the substrate, and the common and individual electrodes adjacent to each other generate heat. A heating resistor provided so that a region is formed,
A thermal printhead having a uniform surface made of a substrate having a convex wall surface projecting upward and a hollow region formed below the convex wall surface so as to extend along the longitudinal direction. And a heat generating region is provided along the hollow region.

The thermal print head comprises a space defined by an upper wall located above the hollow region of the substrate, a lower wall located below and a side wall located between them, and the upper wall and the lower wall. Can be formed so as to be parallel to the surface other than the convex wall surface. The thermal print head may be made of a substance formed by firing a substrate containing alumina, a glass material, and a resin material as main components.

[0009]

The substrate has a surface formed with a convex wall surface protruding upward and a hollow region formed below the convex wall surface so as to extend along the longitudinal direction, and is made of a uniform material. Since the heat generating area is provided along the hollow area, the hollow area acts to prevent the heat generated from the heat generating area from being dissipated to the outside through the inside of the substrate. Then, it becomes possible to form an image on the thermal paper with a significantly small electric power.

Therefore, it is possible to form a desired image with lower power, especially for a portable battery-powered thermal print head which needs to be driven under a limited power source. Further, a larger dot size can be achieved with a smaller power increase.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a thermal print head according to the present invention will be described in detail according to embodiments with reference to FIGS. As shown in FIG. 1, the substrate 1 of the thermal print head according to the present invention is defined by a surface formed with a convex wall surface 3 formed in the longitudinal direction and protruding upward and a concave wall surface on the lower surface side of the convex wall surface. The hollow region 2 and the uniform material are formed of glass ceramic or crystallized glass. The hollow region 2 is composed of a trapezoidal space in transverse cross section defined by an upper wall located above, a lower wall located below and a side wall located between them, and the upper wall and the lower wall are other than convex wall surfaces. Is formed parallel to the substrate surface. The substrate having such a structure can be formed by stacking and firing using a plurality of green sheets as described in detail below.

Common and individual electrode wirings are formed on the convex wall surface 3a of the substrate 2, and a heating resistor made of an electrically resistive material is provided between these electrode wirings. The heat generation region where heat is generated by an electric signal applied to the heat generation resistor via the electrode wiring is on the convex wall surface, that is, above the hollow region 2,
The thermal print head of the present invention is constituted by the above.

In the embodiment of FIG. 1, the hollow region 2 is formed so as to be closed by the side walls 1a at both ends, but it may be formed so as to be open to the outside at both ends. . The composition of the green sheet as the substrate material is about 35% by weight of powdered alumina and about 3% by weight.
It consists of 5% borosilicate glass as a glass material and about 30% thermoplastic polyvinyl butyral resin as a resin material. The thermoplastic resin used for the green sheet is not limited to the above-mentioned polyvinyl butyral resin, and for example, a polyacrylic resin or the like may be used.
When heated to a temperature of 00 ° C, it softens and obtains adhesiveness,
Any material having a property of being thermally decomposed and vaporized into a gas when heated to a temperature higher than this, for example, about 500 ° C. can be used.

The thermal print head of the present invention can be formed relatively easily as described below. That is, first, a flat first green sheet 4 having a composition as described above and having a thickness of about 0.05 mm and a second green sheet 5 having substantially the same size but slightly smaller in size in one direction than this. To prepare. As will be described later, the first green sheet 4 has a convex wall surface and a concave wall surface respectively provided on the upper and lower surfaces thereof, and thus is formed to have a slightly larger size than the other second green sheet 5. These first and second green sheets 4 and 5 are prepared in a large size in advance so that they can be divided into a plurality of individual substrates in a dividing step after forming the base body.

As shown in FIG. 2A, such first and second green sheets 4 and 5 are used for forming the first green sheet 4 having a trapezoidal concave surface in a sectional view. It is inserted between the upper die 7a and the lower die 7b which is also a trapezoidal convex surface corresponding to the concave surface, and the upper die 6 is lowered to deform the green sheet 4 to form the convex wall portion 3. In addition, by heating and holding at a temperature of about 90 ° C. for about 5 minutes under a pressure of about 200 kg / cm ² ,
As shown in (b), the upper molded body 8 having the convex wall surface 3a on the upper surface and the concave wall surface 3b on the lower surface is formed. The upper molded body thus formed has an upper mold 7a as shown in FIG. 2C by using a knockout pin or the like (not shown) for the mold.
When it is raised, it is raised in close contact with its surface.

On the other hand, in parallel with or before or after the formation of the upper molded body 8, a plurality of, for example, five, the above-mentioned second green sheets 5 are laminated on the lower mold 9 having a flat surface to be flat. About 200 kg / cm ² using the upper mold with a smooth surface
The lower molded body 6 having a substantially rectangular parallelepiped shape is formed by heating and maintaining the temperature at about 90 ° C. for about 30 minutes under application of the pressure. The resin components contained in the second green sheet 5 are softened by this heating, and at the same time, their surfaces are provided with an adhesive property so that they can be joined to each other.

Next, as shown in FIGS. 2 (d) and 2 (e), the upper molded body 8 closely attached to the above-mentioned upper mold 7a is positioned on the lower molded body 6 placed on the lower mold 9. 2 (f) by lowering in a combined state, superposing the upper compact 8 on the lower compact 6 and heating and holding at a temperature of about 90 ° C. for about 30 minutes under the application of a pressure of about 200 kg / cm ² . ), An integrally molded body 10 in which both molded bodies 6 and 8 are closely adhered to each other is formed, and the temperature is gradually raised from room temperature in a firing furnace to about 8
A calcined substrate can be obtained by calcining at a temperature of 70 ° C. for about 2 hours and then gradually lowering the temperature.

The green sheets 4 and 5 having the above composition have a length ratio of about 13% in the non-pressurizing direction in the process of heating and firing.
Since the shrinkage is about 30% in the pressing direction, it is advisable to determine the size of the green sheets, the number of sheets to be used, and the like in advance according to the dimensions of the completed substrate in consideration of such shrinkage. In this way, the green sheet or the molded body contributes to the mutual bonding of the resin components contained in the green sheet or the molded body, and further, by firing at a firing temperature higher than the heating temperature after integration of the molded body. With pyrolysis and vaporization, the alumina and glass components are partially crystallized,
A physically or chemically stable calcined substrate is obtained.

After the fired substrate is obtained, although not shown here, common and individual electrode wirings are formed in a desired pattern on the surface as in the conventional method, and a heating resistor is provided above each hollow region. After the formation, the thermal printhead substrate 1 having the hollow region 2 defined by the concave wall surface 3b therein is obtained by dividing it individually with a dicer or the like and cutting the outer shape. In this case, it goes without saying that the electrode wiring and the heating resistor may be formed directly on the individual substrate obtained by dividing the firing substrate.

The fired substrate may also be formed using an additional green sheet 11 of the same size as the second green sheet 5, in addition to the first and second green sheets 4, 5. As shown in FIG. 3, the additional green sheet 11 is provided with a plurality of longitudinally extending slits 12 in the upper molded body 8.
It is formed so as to correspond to the concave wall surface 3b formed in. These slits 12 are formed in a penetrating shape by, for example, pressing.

The additional green sheet 11 is
As shown in the partial cross section of FIG. 4, the slit 12 is sandwiched between the upper molded body 8 and the lower molded body 6 in a state where the slit 12 is aligned with the concave wall surface 3b of the upper molded body 8. , 8 are superposed on each other, and the upper green body 8 and the lower green body 6 are pressed in the close contact direction via the additional green sheet 11 to bring them into close contact with each other. The pressing for the close contact is performed, for example, so that a large pressure is applied to the area 11a between the slits shown by hatching in FIG. 3 as compared with other areas. Upper molded body 8
By applying such a pressing force to the lower molded body 6 and the lower molded body 6, the green sheet 11 is partially raised in the space defined by the concave wall surface 3b corresponding to the region 11a of the upper molded body 8 and this is the same. In order to fill the space, the finished substrate 1 is formed such that the hollow regions 2 are closed at both side surfaces 1a, 1a thereof as shown in FIG.

In a state where the upper molded body 8 and the lower molded body 6 are in close contact with each other through the additional green sheet 11, they are integrated by heating under the same temperature conditions as in the first embodiment, and at a temperature of about 870 ° C. in a firing furnace. When a calcined substrate is obtained by calcining at a temperature for about 2 hours, the substrate having a uniform composition having the hollow region 2 inside is obtained by dividing the calcined substrate. The convex wall surface 3
The portion a may be formed such that the thickness B of the upper end wall thereof is thinner than the thickness A of the portion joined to the lower molded body 8 as shown in FIG. As shown in FIG. 3B, the cross-sectional view may be formed in an arc shape.

As described in detail above, the thermal print head according to the manufacturing method of the present invention prevents the hollow area formed on the substrate from dissipating the heat generated from the heating resistor to the outside. Therefore, it is possible to form an image on the thermal paper with much smaller electric power than the conventional head. Therefore, it is possible to form a desired image with lower power, particularly for a portable battery-driven thermal print head or the like that needs to be driven under a limited power source.

Further, in the thermal print head of the present invention, a larger dot size can be enlarged with a smaller power increase.

[Brief description of drawings]

FIG. 1 is a perspective view of a substrate according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a substrate according to a first embodiment of the present invention.

FIG. 3 is a plan view of an additional green sheet used in the second embodiment.

FIG. 4 is a partial cross-sectional view showing a state in which a molded body is brought into close contact with an additional green sheet.

FIG. 5 is a partial cross-sectional view showing a modified example of the present invention.

FIG. 6 is a sectional view of a conventional thermal print head.

[Explanation of symbols]

 1 Substrate 2 Hollow Area 3a Convex Wall Surface 3b Concave Wall Surface 4 First Green Sheet 5 Second Green Sheet 6 Lower Molded Body 8 Upper Molded Body 11 Additional Green Sheet 12 Slit

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[Procedure amendment]

[Submission date] June 12, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Conventionally, printers for office automation equipment such as facsimiles, printers for ticket vending machines, label printers, etc.
A thermal print head that forms necessary image information by selectively applying heat to a thermal paper is widely used. A conventional thermal print head will be described by taking a thick film type as an example. A solid insulating substrate made of ceramic or the like and a glass glaze as a heat storage member partially or wholly formed on the surface of the insulating substrate. Layer, the common electrode wiring formed on the glaze layer in a comb shape from the surface on one side of the insulating substrate, and extends between the tip of the common electrode wiring from the other side of the insulating substrate toward the glaze layer Individual electrode wiring,
The heating resistor is formed so as to cross over the respective tip portions of the common electrode wiring and the individual electrode wiring. Each individual electrode wiring is connected to a driving IC mounted correspondingly on the insulating substrate via a conductive wire such as gold. A heat dissipation plate made of a metal having a good heat conductivity such as aluminum is mounted on the back surface side of the insulating substrate.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

In use of the thermal print head thus constructed, the common electrode wiring and the individual electrodes are applied by applying a required voltage to the driving IC while keeping the common electrode wiring at a constant potential. A heating resistor (so-called heating dot) between the wiring is selectively energized,
An image is formed on the thermal paper by heating.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

However, in the conventional thermal print head, as described above, the heat generating resistor is provided on the solid insulating substrate via the glaze layer or directly, so that the heat generation is prevented. A part of the heat generated from the resistor directly acts on the heating of thermal paper as a print medium, while the other part contributes to the heat storage of the glass glaze layer as a heat storage body while passing through the insulating substrate. The heat is dissipated into the atmosphere through a heat radiating plate provided on the back side thereof. In this way, a part of the heat generated from the heating resistor is inevitably consumed for heat dissipation, so it is difficult to reduce the supplied power above a certain level, or achieve sufficient energy saving. I couldn't.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a perspective view of a substrate according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a substrate of the present invention.

FIG. 3 is a plan view of an additional green sheet.

FIG. 4 is a partial cross-sectional view showing a state in which a molded body is brought into close contact with an additional green sheet.

FIG. 5 is a partial cross-sectional view showing a modified example of the present invention.

[Explanation of reference numerals] 1 substrate 2 hollow region 3a convex wall surface 3b concave wall surface 4 first green sheet 5 second green sheet 6 lower molded body 8 upper molded body 11 additional green sheet 12 slit

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Delete

Claims (3)

[Claims] 1. An electrically insulating substrate, a common electrode and an individual electrode formed on the substrate, and a heating region formed between adjacent ones of the common electrode and the individual electrode. A heat generating resistor, wherein the substrate is a hollow formed inside so that the substrate has a surface formed with a convex wall surface protruding upward and a longitudinal direction below the convex wall surface. And a heat generating region provided along the hollow region. 2. A hollow region of the substrate comprises a space defined by an upper wall located above, a lower wall located below and a side wall located between them, and the upper wall and the lower wall are respectively formed. The thermal print head according to claim 1, wherein the thermal print head is formed parallel to the surface other than the convex wall surface. 3. The thermal printhead according to claim 1, wherein the substrate is made of a material formed by firing a material containing alumina, a glass material, and a resin material as main components.