JPH0848050A - Thermal printing head - Google Patents

Abstract

PURPOSE:To reduce the power required in the printing of a thermal printing head by constituting the substrate of the thermal printing head of a flat surface and internal hollow regions extending to the vicinity thereof in a longitudinal direction and forming the substrate from a uniform material and providing heating regions along the hollow regions. CONSTITUTION:A rectangular parallelepiped second green sheet 4 having slits 4a made therein is superposed on a first green sheet 3 having almost the same dimensions as those of the sheet 4 and the whole is held under pressure and heating to form an almost rectangular parallelepiped upper molded object 6 having a plurality of recessed parts 5 provided in the surface thereof by the slits 4a. A plurality of the first green sheets 3 are stacked to be held under pressure and heating to form a lower molded object 7. The surface having the recessed parts 5 made therein of the upper molded object 6 is superposed on the lower molded object 7 and the whole is held under pressure and heating to be integrated and baked to obtain a baked substrate 8. Subsequently, common and individual electrodes are patternwise formed on the surface of the baked substrate 8 to provide heating resistors along hollow regions 2.

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. The conventional thermal print head will be described by taking a thick film type as an example. As shown in FIG. 4, 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 are used. The formed glass glaze layer 22 as a heat storage body, and the common electrode 23 formed in a comb shape on the glaze layer 22 from one surface of the insulating substrate 21.
Individual electrodes 24 extending from the other side of the insulating substrate 21 toward the glaze layer 22 between the tips of the common electrodes 23, and heat generated so as to cross over the tips of the common electrodes 23 and the individual electrodes 24. And a resistor 25. Each individual electrode 24 is connected to a driving IC 26 mounted correspondingly on the insulating substrate 21 by a conductive wire 27 such as gold. A heat dissipation plate 28 made of a metal having a good heat conductivity such as aluminum is mounted on the back surface side of the insulating substrate 21.

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

[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 printer which can be easily carried around is also increasing, and the demand for energy saving as well as the miniaturization of the thermal print head is gradually increasing. ing. 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, the polyimide resin has elasticity by its nature, and its mechanical strength is insufficient, and the temperature is about 500.degree.
There is a problem in reliability such as deterioration at the temperature 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 to achieve the above object, an electrically insulating substrate, common and individual electrodes formed on the substrate, and common and individual electrodes adjacent to each other are provided. And a heating resistor provided so that a heating area is formed between the two, and the substrate has a substantially flat surface and its vicinity along the longitudinal direction. There is provided a thermal print head comprising a hollow region formed inside so as to extend and is made of a uniform material, 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 and a lower wall located below the hollow region of the substrate, and a side wall located between them. The walls can each be constructed by forming them parallel to the surface. The above-mentioned thermal print head can be made of a substance whose substrate is formed by firing a material containing alumina, a glass material, and a resin material as main components.

[0009]

[Operation and effect] The substrate of the thermal print head is composed of a substantially flat surface and a hollow region formed in the vicinity thereof in the vicinity thereof so as to extend in the longitudinal direction, and is formed of a uniform material. Since the heat generating area is provided along the hollow area, the hollow area formed by the hollow space prevents the heat generated from the heat generating resistor from being dissipated to the outside through the area near the heat generating resistor of the substrate. It acts so as to hinder the image formation, and makes it possible to form an image on the thermal paper with much smaller electric power than the conventional head.

Therefore, in particular, when the present invention is applied to a portable type battery-driven thermal print head which needs to be driven under a limited power source, a desired image can be formed with lower power. Further, the thermal print head of the present invention enables a larger dot size to be enlarged 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, a substrate 1 for a thermal print head according to an embodiment of the present invention includes a substantially flat surface and a hollow region formed in the vicinity thereof so as to extend in the longitudinal direction. Consisting of a substance of uniform material, namely glass-ceramic or crystallized glass,
It is formed by. The hollow region is composed of a space defined by an upper wall located above, a lower wall located below and a side wall located therebetween, and the upper wall and the lower wall are formed parallel to the substrate surface. There is. The substrate having such a structure can be formed by laminating and firing a plurality of green sheets as described in detail below.

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. is applicable.

In manufacturing the substrate, first, the composition is as described above, for example, the vertical and horizontal dimensions are about 130 mm and about 320 mm, and the thickness is about 0.
A 2 mm first green sheet 3 and a second green sheet 4 as shown in FIG. 2 in which a plurality of slits 4a having substantially the same dimensions as the slits 4a are formed by punching by a press or the like are prepared.

After the first and second green sheets 3 and 4 are prepared in this way, as shown in FIG. 3 (a), the second green sheet 4 is superposed on the first green sheet 3, and about 200 kg / cm. ^The slit 4a is formed on the surface by keeping it heated to about 90 ° C under the pressure of ² for about 30 minutes.
To form a generally rectangular parallelepiped upper molded body 6 in which a plurality of concave portions 5 are defined, and as shown in FIG.
A rectangular parallelepiped lower molded body 7 is also formed by holding the material heated to a temperature of about 90 ° C. under a pressure of kg / cm ² for about 30 minutes.

As described above, since the resin components contained in the green sheets 3 and 4 are softened when they are heated to impart adhesiveness to the green sheets themselves, they are bonded to each other by heating them under a constant pressure. It will be possible. As shown in FIG. 3 (c), the upper compact 6 thus formed is placed under a pressure of about 200 kg / cm ² with the surface having the recess 5 formed on the lower compact 7. After being kept at a temperature of 90 ° C for about 30 minutes to be integrated, the temperature is gradually raised from room temperature in a firing furnace, and the temperature is gradually raised to about 900 ° C for about 2 hours. By lowering the temperature, the baked substrate 8 as shown in FIG. 3 (d) is obtained.

The green sheets 3 and 4 shrink about 30% in the pressing direction and about 13% in the direction perpendicular to the length ratio in the process of firing or the like, so that such shrinkage should be taken into consideration. Then, the size of the green sheet, the number of stacked layers, etc. may be determined in advance according to the size of the completed substrate. Further, in the above, the case where the sheets of the same size are used as the first and second green sheets 3 and 4 is shown.
The present invention is not limited to this, and for example, the first and second green sheets having different thicknesses are used, or the thickness of the first green sheet is partially changed to form the upper and lower molded bodies. It goes without saying that it is also possible to do.

In the first and second green sheets or molded bodies as described above, the resin components contained by heating contribute to mutual bonding, and after the upper and lower molded bodies are integrated with each other. By firing at a temperature higher than the heating temperature, the resin component is thermally decomposed and vaporized, and the alumina and glass components are partially crystallized, so that a physically or chemically stable fired substrate 8 is obtained. .

Next, common and individual electrodes (not shown) are patterned on the surface of the fired substrate 8 as in the conventional method.
And the hollow region 2 in response to electrical signals through these electrodes
A heat generating resistor 9 is provided as a heat generating region along which the heat generating resistor 9 is formed, and a protective film for covering and protecting these electrodes, heat generating resistors and the like is formed, and then divided along the dividing line and necessary outer shape cutting is performed. As a result, an individual substrate 1 made of a substance having a uniform material and having a hollow region 2 formed therein is obtained.

In the present embodiment, the electrodes and the heating resistors are directly formed on the substrate, but it goes without saying that they may be provided on the surface of the glaze layer formed wholly or partially on the substrate surface. . In addition, the substrate of this embodiment is formed so that both ends of the hollow region are closed, but by providing slits continuously in the longitudinal direction of the second green sheet, one end or both ends are opened to the outside. It is also possible to form a hollow region in the.

When an individual substrate having a hollow region formed therein is obtained in this manner, a driving IC is mounted on the substrate by a method similar to the conventional one, and necessary processing such as wire bonding is performed to perform thermal printing. A head can be formed. Incidentally, in the above-mentioned embodiment, the upper molded body 6
An example in which the lower green body 7 and the lower molded body 7 are once formed, and these are superposed and fired to obtain the fired substrate 8 is shown. Instead of this, the first green sheet 3 and the second green sheet 4 are once provided. It is also possible to form the fired substrate 8 by heating and integrating them in a state of being superposed on each other and then firing. For such integration by heating, the pressure and heating temperature according to the formation of the molded bodies 6 and 7 in the above-mentioned embodiment can be applied, and the pressure and the firing temperature at the time of firing can be the same as those at the time of firing. It is possible to apply conditions according to the conditions.

As described above in detail, the thermal print head of the present invention has a substrate having a substantially flat surface and a hollow formed therein so as to extend in the longitudinal direction at and near the surface. The heat generating area is formed along with the hollow area because it is made of a uniform material, and the heat generated by the heat generating resistor is close to the heat generating resistor of the substrate. It acts so as to prevent radiation to the outside through the area (1), and makes it possible to form an image on the thermal paper with much smaller electric power than the conventional head.

Therefore, particularly when the present invention is applied to a portable type battery-operated thermal print head which requires driving under a limited power source, desired image formation can be performed with lower power. Further, the thermal print head of the present invention enables a larger dot size to be enlarged with a smaller power increase.

The processing conditions and the like shown in the above-mentioned examples are appropriately changed according to the composition of the green sheet, and
Needless to say, the size of the green sheet, the shape of the hollow region, and the like are not limited to those in the above-described embodiments, and can be appropriately changed according to the type of the thermal print head, the size of the substrate, and the like.

[Brief description of drawings]

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

FIG. 2 is a plan view of a second green sheet used for manufacturing the substrate of FIG.

FIG. 3 is an explanatory diagram showing a manufacturing process of the substrate of FIG.

FIG. 4 is a schematic side view of a conventional thermal print head.

[Explanation of symbols]

 1 Substrate 2 Hollow Area 3 First Green Sheet 4 Second Green Sheet 4a Slit 5 Recess 6 Upper Molded Body 7 Lower Molded Body 8 Firing Base

Claims (3)

[Claims] 1. An electrically insulating substrate, a common electrode and an individual electrode formed on the substrate, and a heating region provided between the common and individual electrodes adjacent to each other. A heat-generating resistor, wherein the substrate comprises a substantially flat surface and a hollow region formed in the interior thereof so as to extend in the longitudinal direction in the vicinity of the surface. The thermal print head is formed of a uniform material and is provided along the hollow region. 2. The 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 therebetween, and the upper wall and the lower wall are respectively The surface is formed parallel to the surface.
The thermal print head described in. 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.