JPH0556441U - Thermal head - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide a thermal head which can be downsized and whose reliability can be remarkably improved. [Structure] A heat storage layer 23 such as glass is provided on the insulating substrate 22.
A common electrode 25 and an individual electrode 26 are formed, and a laminated film 34 formed by laminating an adhesive layer 31, an insulating layer 32, and a conductor layer 33 is attached on the heat dissipation plate 30, and an insulating substrate is formed thereon. 22 is fixed. A conductive adhesive 36 is applied onto the protruding portion 35 of the laminated film 34 on the heat dissipation plate 30, both are fixed, and the conductor layer 33 and the common electrode 25 are electrically connected.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a thermal head.

[0002]

[Prior Art]

FIG. 4 is a sectional view of a typical thermal head 1. In the thermal head 1, a thick film common electrode 8 formed by printing a heat storage layer 3 made of glass or the like and a silver paste or the like on an electrically insulating substrate 2 made of ceramic or the like has a film thickness t1 (for example, 15 μm). Is formed by. A resistor layer 4 made of tantalum nitride Ta ₂ N or the like is formed on the heat storage layer 3 over almost the entire surface of the insulating substrate 2 by a thin film technique such as sputtering or lithographic method. Aluminum or the like is patterned on the resistor layer 4 by the thin film technique to form the common electrode 5 and the plurality of individual electrodes 6. The portion of the resistor layer 4 sandwiched between the common electrode 5 and the individual electrode 6 is configured as a plurality of heating resistors 7 linearly connected in the left-right direction in FIG. A wear resistant layer 9 is formed from silicon nitride SiN or the like by a thin film technique such as sputtering, covering the common electrode 5 and the vicinity of the individual electrode 6.

The thick film common electrode 8 is provided in order to prevent power consumption of the driving power supplied to each heating resistor 7 based on the wiring resistance of the common electrode 5. However, in such a thermal head 1, it is necessary to form the thick film common electrode 8 between the heat storage layer 3 and the insulating substrate 2, and the heating resistor 7 is placed close to the end side of the insulating substrate 3. However, there is a problem that there is a limit to miniaturization of the thermal head 1.

Another conventional technique for solving such a problem is disclosed in Japanese Patent Laid-Open No. 1-299060. This technique is shown in the cross-sectional view of FIG. In this conventional thermal head 1a, a thick conductive layer 10 is formed by printing a silver paste on the insulating substrate 2 as an example. After that, the heat storage layer 3 is formed, and the exposed portion of the conductive layer 10 and the common electrode 5 are brought into contact with each other at the end of the insulating substrate 2 to prevent the conductive layer 10 from consuming power in the common electrode 5 as described above. It is used as an auxiliary electrode. As a result, the heat-generating resistor 7 can be brought as close as possible to the end portion of the insulating substrate 2, and the thermal head 1a can be miniaturized.

[0005]

[Problems to be solved by the device]

 In manufacturing the thermal head 1a of the conventional example, since the heat storage layer 3 made of glass is fired and formed on the thick-film conductive layer 10 as described above, the firing process becomes complicated, and at the time of printing operation. Since the mechanical strength of the conductive layer 10 below the heat storage layer 3 pressed by the platen roller or the like is insufficient, the heat storage layer 3 has a problem of cracking which is a minute crack.

An object of the present invention is to solve the above technical problems, to provide a thermal head which can be downsized and whose reliability can be remarkably improved.

[0007]

[Means for solving the problem]

 The present invention provides a heat storage layer, a plurality of heating elements arranged in a line, a common electrode commonly connected to one side of each heating element, and the other of the heating elements on one main surface of an insulating substrate. In a thermal head including a plurality of individual electrodes individually connected to each side and a drive circuit element for selectively switching the plurality of individual electrodes, the insulating substrate has a conductive layer formed on the other main surface side. The thermal head is characterized in that the conductive layer and the common electrode are electrically connected.

[0008]

[Action]

 According to the invention, a heat storage layer on an insulating substrate, a common electrode commonly connected to one side of a heat generation element line formed by arranging a plurality of heat generation elements on the heat storage layer, and the other of the heat generation element lines. A plurality of individual electrodes respectively connected to the side are formed, and a drive circuit element connected to selectively switch the plurality of individual electrodes is arranged. At this time, the common electrode is formed in such a range as to cover the heat storage layer, and a conductive layer is provided below the insulating substrate to electrically connect the conductive layer and the common electrode. As a result, the heat storage layer can be formed at the edge of the substrate without lowering the mechanical strength.

[0009]

【Example】

FIG. 1 is a sectional view of a thermal head 21 according to an embodiment of the present invention, and FIG. 2 is a plan view of the thermal head 21. The thermal head 21 includes an insulating substrate 22 formed of a ceramic such as aluminum oxide Al ₂ O _3, and a heat storage layer 23 such as glass is formed on the insulating substrate 22. A Ta ₂ N film or the like is formed thereon by a thin film technique such as sputtering vapor deposition to a film thickness of several hundred Å to form a resistor layer 24. Further, a metal conductor layer such as aluminum formed by sputtering or vapor deposition is patterned on the insulating substrate 22 along the outer periphery thereof as shown in FIG. 2 to form a common electrode 25. The common electrode 25 is formed in such a width that the end portion of the insulating substrate 22 on the end portion side covers the heat storage layer 23 on the end portion side of the insulating substrate 22. Further, a plurality of strip-shaped individual electrodes 26 are formed, and the heating resistor array 28 including a plurality of heating resistors 27 as heating elements is obtained. A wear resistant layer 29 is formed by a thin film technique such as sputtering to cover the common electrode 25 and the vicinity of the individual electrode 26.

On the other hand, the insulating substrate 22 is fixed on the heat dissipation plate 30 made of aluminum. On the heat dissipation plate 30, an adhesive layer 31 made of acrylic resin as an example, an insulating layer 32 made of polyimide resin as an example, and a length over substantially the entire length of the insulating substrate 22 in the longitudinal direction (the direction perpendicular to the plane of FIG. 1). Then, a laminated film 34 formed by laminating a conductor layer 33 made of copper Cu, aluminum Al or the like is adhered, and the insulating substrate 22 is fixed thereon. The heat dissipation plate 30 and the laminated film 34 are formed so as to project further outward than the end portion of the insulating substrate 22 on the heating resistor 27 side. After fixing the insulating substrate 22 on the laminated film 34 attached to the heat dissipation plate 30, a conductive adhesive having a specific resistance of 5 μΩ · cm is formed on the protruding portion 35 of the laminated film 34, for example, solder. 36 is applied to at least an area that covers the exposed portion of the common electrode 25, and both are fixed, and at the same time, the common electrode 25 and the conductor layer 33 are electrically connected via the conductive adhesive 36.

In the thermal head 21 having such a structure, the conductor layer 33 of the laminated film 34 serves as an auxiliary electrode of the common electrode 25, and the driving power to each heating resistor 27 is formed by a thin film technique. It prevents the situation where the power consumption of the electrode 25 becomes large. As a result, density unevenness during the printing operation of the thermal head 21 is prevented, and the printing quality is significantly improved. Further, since the laminated film 34 is located under the insulating substrate 22, it is possible to prevent the mechanical strength of the thermal head 21 from being insufficient due to the laminated film 34, and prevent the abrasion resistant layer 29 from being cracked during the printing operation. Therefore, the reliability of the thermal head 21 can be improved. Further, since the laminated film 34 is arranged in the thickness direction of the thermal head 21 with respect to the insulating substrate 22, the miniaturization of the thermal head 21 in the main scanning direction can be remarkably promoted.

FIG. 3 is a sectional view of a thermal head 21a according to another embodiment of the present invention. The feature of this embodiment is that, with respect to the insulating substrate 22 and the common electrode 25 having the shapes shown in FIG. 1, the end of the heat dissipation plate 30 on the end side of the insulating substrate 22 is, for example, the inner side of the insulating substrate 22. That is, a concave portion 37 having a concave shape is formed in the concave portion 37, and a conductive adhesive 38 made of the same material as the conductive adhesive 36 is formed and fixed in the concave portion 37.

In such a thermal head 21a, the conductive adhesive 38 and the heat dissipation plate 30 have the same functions as the conductor layer 33 and the conductive adhesive 36 of the laminated film 34 in the embodiment of FIG. It serves as an auxiliary electrode of the common electrode 25. As a result, also in the present embodiment, it is possible to achieve the same effects as those of the above-described embodiments.

[0014]

[Effect of the device]

 As described above, according to the present invention, the heat storage layer on the insulating substrate, the common electrode commonly connected to one side of the heat generation element line formed by arranging the plurality of heat generation elements on the heat storage layer, and the heat generation described above. A plurality of individual electrodes connected to the other side of the element line are formed, and a drive circuit element connected to selectively switch the plurality of individual electrodes is arranged. At this time, the common electrode is formed in such a range as to cover the heat storage layer, and a conductive layer is provided below the insulating substrate to electrically connect the conductive layer and the common electrode.

As a result, the size of the thermal head can be reduced, and the reliability can be significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermal head 21 according to an embodiment of the present invention.

FIG. 2 is a plan view of a thermal head 21.

FIG. 3 is a sectional view of a thermal head 21a according to another embodiment of the present invention.

FIG. 4 is a sectional view of a thermal head 1 of a first conventional example.

FIG. 5 is a cross-sectional view of a second conventional thermal head 1a.

[Explanation of symbols]

 21,21a Thermal Head 22 Insulating Substrate 25 Common Electrode 30 Radiating Plate 31 Adhesive Layer 32 Insulating Layer 33 Conductive Layer 34 Laminated Film 36, 38 Conductive Adhesive

Claims (1)

[Scope of utility model registration request] 1. A heat storage layer, a plurality of heating elements arranged in a line, a common electrode commonly connected to one side of each heating element, and a heating element of each heating element on one main surface of an insulating substrate. A thermal head comprising a plurality of individual electrodes individually connected to the other side and a drive circuit element for selectively switching the plurality of individual electrodes, wherein the insulating substrate has a conductive layer formed on the other main surface side. And the conductive layer and the common electrode are electrically connected to each other.