JPH01128848A - End face thermal head - Google Patents

Abstract

PURPOSE:To make it possible to manufacture a highly-dense thermal head with good yield, by bonding in a manner that a heat generating means of one substrate and a heat generating means of another substrate are alternately spaced at equal distances. CONSTITUTION:A pair of substrates 6a and 6b each having wear resisting and heat resisting properties are provided at one end surfaces 7a and 7b thereof with heat generating means 8a and 8b which are connected to electrodes 9a and 9b, respectively. Moreover, the substrates 6a and 6b have ICs 10a and 10b mounted thereon for driving a circuit. The electrodes 9a and 9b are connected to each other. The heat generating means 8a and 8b formed in U shape have one ends connected to common electrodes 10a, 10b, and the other ends connected to the ICs 10a, 10b, respectively. The heat generating means 8a, 8b are thus connected to the respective discrete electrodes. The heat generating means 8a, 8b are all spaced at equal distances, and so arranged that the heat generating means of on substrate is positioned in the middle of the adjacent heat generating means of the other substrate. The end surfaces 7a an 7b at the side where the heat generating means of the bonded substrate 6a, 6b are formed are chamfered so that is becomes convenient for a heat sensitive paper or an ink ribbon to slide there.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a thermal head used in a printer such as a video printer or a handy printer or a facsimile machine, and in particular, printing is performed by sliding a recording medium along the edge of a substrate. This invention relates to an end face type thermal head.

The thermal head of the present invention is not limited to a heat-sensitive type thermal head, but can also be used as a transfer type thermal head using a color ribbon or a wax ribbon, or a gradation type thermal head using a colored dot type.

(Conventional technology) FIG. 8 shows the main parts of a conventional end face type thermal head.

1 is a substrate that also functions as a heat sink.

For example, alumina ceramics are used. A glass glaze 2 is formed as a heat insulating layer on the end face of the substrate 1, and a heating resistor 3 is formed on the glass glaze 2. 4,
Reference numeral 5 denotes an electrode for supplying electricity to the heating resistor 3. Although a protective film is provided on the heating resistor 3, illustration thereof is omitted.

The advantages of the end-face type thermal head are as follows.

(1) Good contact with the recording medium, and peripheral input devices become simple.

(2) Since the heating resistor has a convex shape, it is easy to apply pressure uniformly to a recording medium such as an ink ribbon, and image quality is improved particularly in applications such as transfer type image printers.

(3) It has a structure that allows printing even on flat recording media.

(4) It is easy to use a multi-thermal head for color printing.

(5) The outer shape of the substrate does not depend on the diameter of the platen.

However, on the other hand, since the heating resistor 3 is formed on the end surface of the substrate 1, there are the following drawbacks.

(1) Since the end face of the substrate is used, only two rows of heating resistors 3 can be patterned on one substrate. Therefore, multi-sided printing is impossible, and mass productivity is low.

(2) It is necessary to perform a glass glaze treatment on the end face of the substrate, which is not only technically difficult but also increases cost.

(3) The pattern of the heating resistor 3 and the electrodes 4 and 5 must be formed three-dimensionally from the end surface to the flat surface.

Such a process has technical difficulties in resist coating, photomasks for exposure, exposure, etc., and requires a large number of man-hours.

(Purpose) The present invention is a thermal head that can manufacture a thermal head that functions as an edge-type thermal head by taking advantage of the manufacturing process of conventional flat-type thermal heads, and that can achieve high printing density. The purpose is to provide the following.

(Structure) The edge-type thermal head of the present invention includes: - two substrates in which heating elements are arranged along one end of the main surface, and a gap between adjacent heating elements in which one heating element is provided; 1. The heating element forming surfaces are placed opposite each other, the one end is aligned, and the heating elements of one substrate and the heating element of the other substrate are bonded so that they are arranged alternately and at equal intervals, and the heating elements of the one end are aligned. Printing is performed by sliding the recording medium on the end surface.

Examples will be specifically described below.

Fig. 1 is a perspective view showing one embodiment, Fig. 2 is a plan view showing the heating element forming surfaces of both substrates when the same embodiment is separated from the adhesive surface, and Fig. 3 is a partial perspective view showing the heating element forming surfaces. , FIG. 4 is a plan view of one of the substrates showing the arrangement of the heating elements.

A pair of substrates 13a and 6b having wear resistance and heat resistance are bonded and integrated, with their heating element forming surfaces facing each other, and with one end of the side on which the heating element is formed aligned with each other. Alumina ceramics, hard glass, or the like can be used for the substrates 6a and 6b.

Each substrate 6a, 6b has one end surface 7 as shown in FIG.
heating elements +3a along a, 7b, respectively;

8b is formed. Each heating element 8a, 8b has an electrode 9
a, 9b are connected, and driver circuit ICs 10a, 10b are mounted on the substrates 6a, 6b, and ICl0a
, 10b and the electrodes 9a and 9b are wire bonded,
They are connected by face-down bump bonding or TAB method. As the heating elements 8a and 8b,
Ta-5ion, TaN, NiC:r, etc. can be used, and as the electrodes 8a and 8b, A(1, Au
, NiCr-Au, etc. can be used.

As shown in FIG. 3, the heating elements 8a and 8b are arranged along one end surface 7a and 7b of each of the substrates 6a and 6b, and are formed in a U-shape with an opening in the opposite direction to the end surface 7a+7b. One end thereof is connected to the common electrodes 10a, 10b, and the other end is connected to an individual electrode having a terminal connected to the driving IC 10a, 10b. heating element 8
a and 8b are both arranged at equal intervals, but when both substrates 6a and 6b are bonded with their heating element forming surfaces facing each other as shown by the arrow 11 in FIG. The positions of the heating elements are shifted so that they are located exactly in the middle of adjacent heating elements. In addition.

Although not shown in the figure, 1 heating element 8a, 6b and electrode 9a
, 9b, 10a, and lob are made of polyimide or sinus, for example, except for the terminals that connect with ICs 12a and 12b.
An insulator is formed by :: etc.

Returning to FIG. 2, when the substrates 6a and 6b are bonded together, the ICs 10a and 10b are mounted at different positions so that they do not overlap each other, and the other IC 10a
, 10b are provided with holes 12a, 12b in the substrates 6a, 6b for accommodating protrusions formed by ICs.

Each of the substrates 6a and 6b is provided with a protrusion, and the protrusion is provided with terminals 13a and 13'b. The terminals 13a, 13b are connected to the ICl0a, lob, and the heating elements 8a, 8b through wiring and wire bonding, etc. When the two boards 6a, 6b are superimposed, the terminal 13a becomes the terminal 13a.
, 13b are arranged so that the positions of the protrusions are shifted. For example, an inorganic adhesive or an organic adhesive may be used to bond the two substrates 6a and 6b which have been subjected to a normal resin sealing process to the ICs 10a and 10b. However, the ICs 10a and 10b Since there are restrictions on the heat treatment temperature after mounting, it is preferable to use a silicone-based, phenol-based, or epoxy-based adhesive that can be processed at a relatively low temperature.

Returning to FIG. 1, the bonded open substrates 6a, 6
The end faces 7a and 7b on the side where the heating element b is formed are chamfered so that it is convenient for the thermal paper or the ink ribbon to slide on them.

Reference numeral 14 denotes a flexible printed wiring board to be connected to the outside, and conductor wiring is formed on one surface of the flexible printed wiring board. Flexible printed wiring board 14 is connected to terminals 13a and 13b.

Although not shown, the open substrate 6a of FIG.

It is preferable to provide a heat sink on the outside of 6b so as to sandwich it from both sides. This heat sink preferably serves as a cover for the thermal head.

For example, if the density of the heating elements on each of the substrates 6a and 6b is 8 dots/mm, a thermal head of 16 dots/mm can be obtained in this embodiment.

Next, a method of manufacturing this embodiment will be explained.

The heating element 8a, 8b and electrodes 9a, 9b
1. Form an insulating film on predetermined portions of the heating elements 8a, 8b and electrodes 9a, 9b. 6. Next, apply I to each substrate 6a, 6b.
Implement CI 0atlOb. The mounting method may be wire bonding or any other method.

The ICs 10a and 10b are sealed with a resin and the open substrates 6a and 6b are bonded together with an adhesive so that the mutual relationship between the zero-order heating elements 8a and 8b is as shown in FIG. After that, one board 6a.

The end surfaces 7a and 7b of 6b are chamfered, and the flexible printed circuit board 14 is connected to the terminal 13a.

Connect to 13b. For connecting the flexible printed circuit board 14 and the terminals 13a, 13b, normal means such as thermocompression bonding, soldering, pressure welding, etc. can be used.

When the substrates 6a, 6b are transparent like high-quality glass, it is easy to arrange the heating elements 8a, 8b as shown in FIG. 4, but when the substrates are opaque like ceramics,
One end surface 15a of each substrate 6a, 6b in the heating element arrangement direction
, 15b are used as reference surfaces to position the heating elements 8a, 8b, and the reference surfaces 15a, 15b are pressed against a surface plate while being bonded.

In the above embodiment, the holes 12a are provided in the substrates 6a and 6b.

12b, but instead of holes, recesses may be provided by counterbore processing.

The present invention also includes: It can also be applied to semiconductor type thermal heads. In the semiconductor type thermal head, the drive circuit is formed integrally with the heating element, and no protrusions appear on the opposing surface of the substrate, so there is no need to provide holes or recesses.

Although the embodiment is an example of a thin film thermal head, the present invention can also be applied to a thick film thermal head. RuO can be used as the heating element of the thick film thermal head.

Other shapes of the heating element are shown in FIGS. 5 to 7.

In FIG. 5, reference numeral 20 denotes a resistance value determination unit which is connected to the electrode 9 of the heating element and determines the resistance value.

The resistance value determination section 20 is formed at a position recessed inward from the end surface 7 of the substrate 6, and a heat conduction path 21 is provided between the resistance value determination section 20 and the end surface 7. The heat conduction path 21 and the resistance value determining section 20 are formed of the same heat generating layer. It is desirable that the material of the heating elements 20 and 21 has high thermal conductivity.

Since the end surface 7 of the substrate 6 is a sliding surface on which the recording medium slides, the number of heat conduction paths 21 decreases as the substrate 6 wears. Further, since the end face of the heat conduction path 21 is exposed, it is oxidized and deteriorates. However, since it is the resistance value determination unit 20 that determines the resistance value of the heating element, the heat conduction path 21 may wear out.

The length is set to several μm to several hundred μm so that even if it is oxidized and deteriorated, it does not affect the resistance value and print characteristics. Generally, the thermal head is driven with a constant voltage, so the resistance value of the resistance value determining section 20 does not change, so that the recording density does not change. In addition, the heat conduction path 2
If 1 is too long, thermal efficiency will deteriorate and print quality will be affected, such as bleeding, so it is preferable to set it to several μm to several hundred μm as described above.

In FIG. 6, the resistance value determining section is formed into a ring shape 20a, and in FIG. 7, it is formed into a rectangular shape 20b.

The heating elements shown in FIGS. 5 to 7 can be applied to the embodiment shown in FIG. 1. However, the spacing between the heating elements is wider than that in Figure 1. Such heating elements also. It can be applied not only to thin film type thermal heads but also to thick film type or semiconductor type thermal heads.

In the heating elements shown in FIGS. 5 to 7, even if the sliding surface is mechanically scratched, the resistance value is hardly affected.

Even if the resistance value determining section is trimmed or otherwise corrected, there is little effect on printing quality.

(Effects) In the present invention, - a heating element is arranged along one end of the main surface;
In addition, two substrates having a gap in which one heating element is provided between adjacent heating elements are arranged so that the heating element forming surfaces thereof face each other, and the one ends thereof are aligned, so that the heating element of one substrate and the heating element of the other substrate are aligned. Glue the bodies so that they are arranged alternately and at equal intervals,
Since printing is performed by the recording medium sliding on the end face of the one end, manufacturing a thermal head with N dots/mm requires only forming a rough pattern of N/2 dots, resulting in lower yields. improves.

After the driving IC is mounted, only good substrates are bonded to each other, so the rate of good products is improved and a thermal head can be manufactured at low cost.

A high-density thermal head, which has been difficult to manufacture in the past, can be manufactured without deteriorating pattern yield or assembly yield.

In a thermal head equipped with a driving IC, the bonding pitch between the driving IC and the electrode can be made twice as large as the density of the heating element, so a high-density thermal head can be easily manufactured. For example, wire bonding has a pitch of 100 μm, and TAB has a pitch of 60 μm.
Since the mass production limit is around the pitch, the limit for conventional thermal heads is 10 to 16 dots/mm.
According to the present invention, 20 to 32 dots/mm can be achieved.

In the end face type thermal head of the present invention, it is not necessary to form a wear-resistant film in the film forming process.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment, Fig. 2 is a plan view showing the substrate separated from the adhesive surface in the same embodiment, Fig. 3 is a partial perspective view showing the heating element forming surface, and Fig. 4 is a heating element forming surface. 5 to 7 are plan views showing other heating elements, and FIG. 8 is a sectional view showing a conventional end-face type thermal head. 6a, 6b...Substrate, 7a, 7b...End face, 8a, 8b...Heating element. 9a, 9b... Electrodes.

Claims (1)

[Claims] A heating element is arranged along one end of one main surface, and two substrates each having a gap between adjacent heating elements in which one heating element is provided are placed with the heating element forming surfaces facing each other, and the one ends are aligned. Then, the heating element on one board and the heating element on the other board alternate,
and an end-face type thermal head which is adhesively arranged at equal intervals and in which printing is performed by sliding a recording medium on the end face of the one end.