JPS6211659A - Edge type thermal head - Google Patents

Abstract

PURPOSE:To suppress the voltage drop of a common electrode and to make it possible to arrange a heat generator to the end part of a substrate, by wiring the common electrode or indivisual electrode arranged in an end part side to an opposite side. CONSTITUTION:Lead parts 2a constituting an indivisual electrodes 2 are parallelly provided on the surface of a substrate 4 at a predetermined intervals so as to cross the direction along which a substrate end part 4a extends and a partial glaze layer 5 as a heat accumulating layer is laminated onto the lead parts 2a along the substrate end part 4a so as to laterally cross said lead parts 2a. Rectangular heat generators 1 provided to the upper surface of the partial glaze layer 5 an indivisual part 2b is connected not only to one end part of each heat generator 1 in the side of the substrate end part 4a but also to each lead part 2a. The indivisual electrode 2 is constituted of the indivisual part 2b and the lead part 2a. Each of said lead parts 2a passes under the partial glaze layer 5 to be drawn around to the side opposite to the substrate end part 4a and wired up to a drive circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a thermal head, particularly an edge type thermal head.

(Background of the Invention) There are so-called line type thermal heads in which dot-shaped heating elements are arranged in a straight line. There is also a center type in which a heating element is placed in the center of the board and drive circuits are placed on both sides of the heating element.

As a recent trend, the edge type is becoming mainstream.

The reasons for this are that, although there are disadvantages to the higher packaging density of ICs (integrated circuits), (1) the overall width of the board is narrower, allowing the printer to be made more compact; and (2) the heating element is located at the edge. , the printer can be configured to make it easier for the operator to check the print results immediately after printing.
This will reduce the waste of feeding the recording paper.1
etc. can be mentioned.

To explain with reference to FIGS. 5 and 6, a thermal head generally consists of a dot-shaped heating element L and a pair of electrodes for energizing it. , 3 are required, and in a line type thermal head, one of the pair of electrodes 2.3 is called an individual electrode for selectively energizing, and the other electrode 3 is called a common electrode. Then, an individual electrode 2 is placed on the side of the group of heating elements arranged in a straight line.
A common electrode 3 is placed on the other side. This common electrode 3 consists of an individual part 3a connected to each heating element dot and a common part 3b for making all the heating elements common.

Further, since the substrate 4 on which the group of heating elements is formed, for example an alumina substrate, has too good thermal conductivity and reduces heat generation efficiency, a heat storage layer 5, for example a glass glaze layer, is provided on the substrate 4. In this case, there are two types of heat storage layer 5: a partial type where the heat storage layer 5 is provided only under and near the heating element, and a whole type where the heat storage layer 5 is provided on the entire substrate.

5 and 6 show an example of a conventional etching type thermal head, in which a common portion 3b of a common electrode 3 is disposed along the periphery of a substrate 4. In FIG. A partial glaze layer 5 as a heat storage layer 5 is provided inside the substrate 4 from the common portion 3b, and a plurality of dot-shaped heating elements l are arranged in a straight line in the longitudinal direction of the glaze layer 5 near the top of the partial glaze layer 5. There is. One end of each heating element l is connected to the individual portion 3a of the common electrode 3, the other end is connected to the individual electrode 2, and the individual electrode 2 is connected to a plurality of drive circuits 6.

The common part 3b is made of gold or aluminum, which has a sufficiently low resistivity compared to the heating element l, but since the total length of the common part 3b is long (for example, in the case of an A4 size head, the longitudinal direction of the substrate 4 (length of approximately 210 mm) shows a non-negligible resistance value for the central heating element. Therefore, an undesired voltage drop occurs, and even if each heating element is driven under a constant voltage, the amount of heat generated by the side heating element and the central heating element is different, causing recording unevenness.

Therefore, in this type of conventional edge type thermal head, the width W (see Fig. 5) of the common part 3b is set wide, and the thickness T (see Fig. 6) of the common part 3b is increased to reduce the voltage drop. is suppressed. Therefore, the heating element 1
The group is separated inward from the end portion 4a of the substrate 4, and the advantages unique to the edge-type thermal head described above are lost.

On the other hand, FIG. 7 shows the positional relationship between the platen 7 and the thermal head 8. The heating element l and the protective cover 9 should be spaced sufficiently apart so that the protective cover 9 of the drive circuit 6 does not interfere with the platen 7. ing.

Therefore, in this kind of conventional edge-type thermal head, an undesired space is required between the heating element 1 and the substrate end 4a and between the heating element 1 and the protective cover 9, which reduces the size of the edge-type thermal head. It was hindering the development of

(Objective of the Invention) The object of the present invention is to eliminate such conventional problems, suppress undesirable voltage drop at the common portion of the common electrode, and further dispose the heating element on the substrate compared to the conventional method. An object of the present invention is to provide an etch-type thermal head that can be placed at an end.

(Summary of the Invention) The present invention is characterized in that the common electrode or the individual electrode arranged on the end side is passed under the heat storage layer and wired to the opposite side.

(Embodiment) Fig. 1 and Fig. 2 show an embodiment of the etched thermal head of the present invention, Fig. 1 is a plan view thereof, and Fig. 2 is its A.
-A sectional view.

Referring to FIGS. 1 and 2, reference numeral 4 denotes an alumina substrate, and on the surface of the substrate 4, individual electrodes 2 are formed at predetermined intervals perpendicular to the direction in which the end portion 4a of the substrate extends. Lead portions 2a are arranged in parallel. A partial glaze layer 5 serving as a heat storage layer is laminated on top of the lead portion 2a and extending across the lead portion 2a along the substrate edge portion 4a. A rectangular heating element l is arranged on the upper surface of the partial glaze layer 5. The heating elements 1 are arranged in parallel along the longitudinal direction of the partial glaze layer 5 at predetermined intervals. The spacing is determined so as to obtain a desired recording resolution, and the dots are arranged at a density of, for example, 8 dots/mm.

An individual portion 2b is connected to one end of the heating element 1, in other words, an end on the substrate end 4a side, and the individual portion 2b is connected to the lead portion 2a. Here, the individual part 2b and the lead part 2a
The individual electrode 2 is constituted by the above.

The other end of the heating element l is connected to the individual portion 3a of the common electrode 3. The individual portions 3a protrude from the common portion 3b extending parallel to the partial glaze layer 5 at predetermined intervals in a comb-like shape, and the common electrode 3 is constituted by the individual portions 3a and the common portion 3b. .

As can be seen from FIG. 2, an insulating layer 10 is laminated on the lead portion 2a constituting the individual electrode 2 in a manner that crosses the lead portion 2a, and a common electrode 3 is laminated on the insulating layer 10. The common portions 3b are stacked, and the individual electrodes 2 and the common electrodes 3 are electrically insulated from each other. Further, a protective film it (not shown) is applied to the heating element 1 to prevent oxidation of the heating element 1 and to improve wear resistance. The common electrode 3 is connected to a power source (not shown), and the individual electrode 2
can be grounded via a drive circuit (not shown). Then, the switching elements of the drive circuit are turned on and off by a control signal from a control circuit (not shown), and a desired heating element is energized to generate heat.

Note that the protective film 11 is omitted in FIGS. 1 and 2.

That is, as can be seen from FIGS. 1 and 2, the individual portion 2b connected to the substrate end side of the heating element 1 is connected to the lead portion 2a forming the remaining portion of the individual electrode 2 and the substrate end portion 4a side. The lead portion 2a is routed under the partial glaze layer 5 to the side opposite to the substrate end 4a, and is wired to a drive circuit (not shown). The upper surface of the lead portion 2a routed to the opposite side of the substrate end is covered with an insulating layer 10, and the common electrode 3 is disposed on the upper surface of the insulating layer 10.

According to the edge type thermal head having such a configuration, even if the width of the common portion 3b of the common electrode 3 is increased in order to suppress the voltage drop at the common electrode 3, the distance between the substrate end portion 4a and the heating element l remains constant. has no effect on

The manufacturing process of the edge type thermal head of this embodiment configured in this way is shown in FIGS. 3(a-1) to (d-
This will be explained below with reference to 3). In addition, the following items (a
) to (d) correspond to symbols (a-1) to (d-3) in FIG.

(a) A thick film gold paste was screen printed on the alumina substrate 4, and then baked to form a thick gold film with a thickness of 5 layers. Then, by photolithography and etching, a width of 105
The lead portions 2a of the individual electrodes 2 were formed at intervals of 20 gm.

(b) Thick film glass paste was formed into the shape of the partial glaze layer 5 by screen printing along the substrate edge 4a and across the lead portion 2a, and then fired. The thickness of the partial glaze layer 5 was set to 60 cm, and the lead portion 2a on the end side of the substrate was exposed for a length of about 200 p-m. At the same time, a glaze insulating layer 10 having a thickness of 20 gyr was formed by screen printing on the lead portion 2a on the side opposite to the substrate end 4a, and then baked.

(C) A thin film of tantalum nitride Ta2N having a thickness of 700^ is formed on the top of the partial glaze layer 5 by sputtering,
By photolithography and etching, a rectangular heating element l with a line width of 1105p as shown in FIG.
It was formed by patterning in the gaps.

(d) Nichrome alloy with thickness 1000λ and thickness IpL+a
By vacuum evaporating two layers of gold and then photolithographically etching the edges 4 of the substrate, as shown in FIG. 3(d-1),
On the a side, an individual part 2b connecting the heating element l and the lead part 2a is formed, and on the opposite side, an insulating layer lO is formed.
A common electrode 3 is formed thereon. The common electrode 3 is integrally composed of a common part 3b and an individual part 3a protruding from the common part 3b, and also includes a lead part 2a and an individual part 2, which are separate parts.
b constitute the individual electrode 2. In this example, the distance between the common electrode 3 and the individual portions 2b, in other words, the exposed length of the heating element 1 is 160 l.

Finally, as a protective film 11, centering on one group of heating elements,
A two-layer structure of silicon oxide with a thickness of 2 gm and tantalum pentoxide with a thickness of 5 gm was formed by sputtering using a vapor deposition mask. Here, silicon oxide is used for oxidation prevention, and tantalum pentoxide is used for wear resistance.

Note that in FIG. 3, the proportional relationships for the purpose of making it easier to understand each component of the thermal head are not correct; for example, the width of the partial glaze layer 5 is 2 mm, and the width of the common electrode 3 is 5 mm.

As described above, in this embodiment, the individual electrode 2 disposed between the substrate end 4a and the heating element l is routed under the heating element l to the side opposite to the substrate end 4a. I wired it, so
Even if the width of the common portion 3b of the common electrode 3 is increased in order to suppress the voltage drop, there is no need to arrange the heating element 1 inside the substrate 4, and the heating element 1 can be placed at the end portion 4a of the substrate. As a result, as shown in FIG. 4, the alumina substrate 4 can be made smaller in size compared to the conventional example shown in FIG. 7, and the advantages of the etch-type thermal head can thereby be made even more effective.

Note that the common electrode 3 may be formed on the upper surface of the substrate 4, and the individual electrodes 2 may be formed thereon with an insulating layer interposed therebetween. In that case, the individual portions 3a of the common electrode 3 may be extended to the substrate end 4a. A lead portion is required to connect the individual portion 3a and the heating element 1 on the end portion 4a side. Furthermore, since one individual electrode 2 is arranged on the right side of the glaze layer 5, the lead portion 2a is not required.

(Effects of the Invention) According to the present invention, the common electrode or individual electrode placed on the edge side of the substrate is wired to the opposite side by passing under the heat storage layer, so that voltage drop at the common electrode can be suppressed. Even if the width of the common electrode is widened, the position of the heating element does not have to be moved away from the edge of the substrate, which makes it possible to make the edge-type thermal head more compact, which eliminates the inherent advantages of the etch-type thermal head. There is no.

Furthermore, the common portions 3b (see 5th UA), which were routed at both ends of the conventional partial glaze layer 5 in the longitudinal direction, are no longer necessary, and not only the width of the substrate 4 but also the length in the longitudinal direction can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A, and FIGS.
3 (a-2) to (d-3) are respective cross-sectional views, and FIG. 4 is an edge-type thermal head according to this embodiment. FIG. 5 is a conceptual perspective view of a conventional edge-type thermal head. FIG. 6 is a longitudinal sectional view thereof, and FIG. 7 is a conceptual diagram showing the relationship between a conventional edge type thermal head and a platen. ■= Heating element 3: Common electrode (3a: Individual part 3b: Common part 4: Substrate 5: Heat storage layer 1O: Insulating layer 11: Protective film Applicant Nippon Kogaku Kogyo Co., Ltd. Representative Patent Attorney Kiyoshi Fuyu Nagai 6 Figure 7

Claims (1)

[Claims] An edge type consisting of a substrate having a heat storage layer on its surface, a group of dot-shaped heating elements arranged in a straight line on the surface of the heat storage layer near the end of the substrate, and individual electrodes and a common electrode for supplying electricity to each heating element. 1. An edge-type thermal head characterized in that a common electrode or individual electrodes arranged on an end side of a substrate are wired to the opposite side by passing under the heat storage layer.