JP2533087B2 - Thermal head - Google Patents

Description

Description: (a) Field of Industrial Application The present invention relates to improvement of a thermal head, and more specifically, to contact of a thermal head with a recording paper (contact state).
Regarding the improvement of.

(B) Conventional technology In the thermal printing method, the Joule heat generated when an electric current is applied to the resistance film of the heat generating part provided on the thermal head causes dots (small letters forming a font) to be formed on the thermal recording paper that contacts the thermal head. Point) to print and
Alternatively, the ink on the transfer ribbon interposed between the thermal head and the recording paper is melted by the Joule heat to transfer dots on the recording paper to perform printing.

Conventionally, as a thermal head used for thermal printing, for example, one shown in FIG. 4 is known. FIG. 4 is a plan view of the conventional thermal head 11, in which a resistive film 14, ..., 14 of tantalum nitride or the like is formed on the upper end 12a of the insulating substrate 12 to form a heat generating portion 19.
, 15a are formed on the insulating substrate 12 so that their ends 15a, ..., 15a are overlapped with the right ends of the resistance films 14 ,.

On the other hand, the resistive film 14, ...
A common electrode 16 is formed at the left end of 14 so as to be overlapped and conductive.

The resistance film 14, ..., 14, the lead electrode 15, ..., 15
The common electrode 16 is covered and protected by a protective film (not shown) such as silicon dioxide formed on the upper surface of the insulating substrate 12.
In order to improve the contact with the recording paper, a glass glaze layer 13 is formed on the upper surface of the insulating substrate 12, and a resistance film 14 is formed on the glass glaze layer 13.
... 14 is also formed and used as the heat generating portion 19.

(C) Problems to be Solved by the Invention As a printing method, there is a printing method in which the above-mentioned conventional thermal head is brought into contact with the recording paper while being inclined. Therefore, the closer the formation position of the heat generating portion is to the end portion of the insulating substrate, the better the contact of the thermal head with the recording paper, the more easily the transfer ink can be transferred, and clear printing can be performed.

However, when the heat generating portion is brought closer to the end portion of the insulating substrate, the width of the common electrode formed on the upper surface of the end portion becomes smaller. For this reason, the electric resistance of the common electrode increases, and a difference in applied voltage occurs between the resistance films (the lower the resistance film 14 in FIG. 4, the lower the applied voltage), the size of dots, the degree of color development, etc. There is an inconvenience that uneven printing occurs and the print quality is degraded.

Therefore, the width of the common electrode is currently 250 μm to 350 μm.
Although it is set in the range of m, the thermal head is still insufficient in contact with the recording paper at this level, and there is a problem in that the sharpness of the printing is lacking.

Further, in order to reduce the electric resistance of the common electrode, it may be possible to increase the film thickness of the common electrode, but when the film thickness of the common electrode is large, there is a problem that the contact with the recording paper is poor as a result, It has not been a valid solution.

The present invention has been made in view of the above-mentioned inconvenience, and an object thereof is to provide a thermal head capable of improving the contact with a recording paper without degrading the printing quality.

(D) Means for Solving the Problems As a means for solving the above-mentioned inconvenience, the thermal head of the present invention comprises an insulating substrate and a plurality of resistors provided at the upper end of the insulating substrate and contacting the recording paper. A heat generating part including a film, a plurality of electrodes formed on the insulating substrate and individually conducting with the resistance film, a conducting part formed by exposing a part of the resistance film facing an insulating substrate end, and the heat generating part. And a recording layer, and a thin film provided with a conductive layer that is interposed between the sheet and the recording paper and is in electrical contact with the current-carrying portion.

(E) Action In the thermal head of the present invention, the plurality of resistance films of the heat generating portion have the insulating substrate upper surface end side which is opposite to the insulating substrate upper surface end portion through the conducting portion and the thin film conductive layer. The side portions are individually connected to the drive circuit and the like via the electrodes. For this reason, the common electrode formed between the heat generating portion and the end portion of the insulating substrate is not necessary or the width thereof can be reduced, and the heat generating portion can be brought close to the end portion of the insulating substrate.

(F) Embodiment One embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 3 shows a thermal head 1 according to an embodiment of the present invention.
FIG. Reference numeral 2 is a substrate (insulating substrate) made of alumina ceramic. A belt-shaped vitreous glaze layer 3 is printed and baked on the upper end 2b of the substrate 2. The cross-sectional shape of the glaze layer 3 is semicircular as shown in FIG.

Resistance films 4 made of tantalum nitride or the like are formed on the glaze layer 3 to serve as heat generating portions 9 (first portion).
(See Figures and 3). Resistive film 4, ..., right end 4a of 4,
.., 4a extends to the upper surface of the substrate 2 on the right side of the glaze layer 3.

Lead electrodes 5, ..., 5 are further formed on the upper surface of the substrate 2 by vapor deposition or sputtering (see FIG. 3). One end 5a of each lead electrode 5 is the right end of the resistance film 4.
4a and the right half of the resistive film 4 are superposed (see FIG. 1). The other end 5b of each lead electrode 5 reaches the upper edge 2c of the substrate 2. (See Figure 3). This other end 5
Lead wires (not shown) from the drive circuit are connected to b, ..., 5b.

Further, the common electrode 6 is formed on the upper end 2b of the substrate 2 along the end 2a by vapor deposition or sputtering (see FIG. 3). The common electrode 6 is formed by being superposed on the left end portions 4b, ..., 4b of the resistance films 4, ..., 4 (see FIG. 1).

A silicon dioxide film (protective film) 7 is formed on the upper surface of the substrate 2 by vapor deposition or sputtering (see FIGS. 1 and 3). The silicon dioxide film 7 covers the resistance films 4, ..., 4 and the lead electrodes 5 ,.

The silicon dioxide film 7 covers the entire upper surface of the substrate 2 at the time of formation, but the silicon dioxide film 7 in this portion is removed by cutting the end 2a, and the common electrode 6 and the protective film 4 ,. ... 4 left end part (portion facing end part 2a) 4b, ...
…, 4b is exposed. The exposed portion is used as the energizing portion 8. The inclined portion 2d of the upper surface end portion 2b is generated by cutting at this time, and its width is very small. Further, the common electrode 6 has a reduced width due to the formation of the inclined portion 2d, but its final width is set to about 30 μm.

FIG. 2 is a cross-sectional view illustrating a usage state of the thermal head 1 according to this embodiment. The thermal head 1 is supported below the recording paper P in an inclined posture so that the heat generating portion 9 contacts the lower surface of the recording paper P. Between the thermal head 1 and the recording paper P, a transfer ribbon (thin film) 10 is wound and driven in synchronization with the driving speed of the recording paper P (or the thermal head 1).
Is provided. The transfer ribbon 10 is brought into contact with the lower surface of the recording paper P by the heat generating portion 9.

This transfer ribbon 10, as shown in FIG.
It has a three-layer structure of an ink layer 10a, a base layer 10b, and a conductive layer 10c from the upper surface. The ink layer 10a comes into contact with the lower surface of the recording paper P, and the heat transmitted from the heat generating portion 9 melts the ink in that portion and adheres to the temporary surface of the recording paper P to form dots.

The base layer 10b is a flexible synthetic resin film.

The conductive layer 10c contacts the conducting portion 8. Conductive layer 10c
Is made of aluminum deposited on the lower surface of the base layer 10b or a conductive resin coated on the lower surface of the base layer 10b. The base layer 10b itself may be a conductive resin. The conductive layer 10c is connected to a drive circuit or the like by contacting an electrode (not shown) with the conductive layer 10c.

A voltage is individually applied to each of the resistance films 4, ..., 4 by the drive circuit. The current from the drive circuit is guided to the right side portion 4a of the resistance film 4 by the lead electrode 5. The current flowing through the resistance film 4 is guided from the current-carrying portion 8 into the conductive layer 10c on the lower surface of the transfer ribbon 10. The conductive layer 10c plays a role of a conventional common electrode, so to speak. Conductive layer 10c
The current flowing therein is guided to the drive circuit or the like by the electrode (not shown) that is in contact with the conductive layer 10c.

When a current flows through the resistance film 4, Joule heat is generated.
This heat is transmitted to the ink layer 10a, the ink in the portion corresponding to the resistance film 4 is melted, adheres to the recording paper P, and dots are printed.

The recording paper P (or the thermal head 1) is laterally driven and the dots in the next row are printed. At this time, transfer ribbon
10 is driven to wind, and the new surface of the ink layer 10a is printed on the recording paper P.
Touch the bottom surface. Then, again, an electric current is individually applied to the resistance films 4, ..., 4 to mark dots. This operation is repeated and the recording paper P is printed.

Although the common electrode and the glaze layer are provided in the above embodiment, these are not always necessary and the design can be changed appropriately.

Further, the number and arrangement of the resistance films, the pattern shape of the lead electrodes, and the like are not limited to this, and the design can be changed appropriately.

Furthermore, although the above-mentioned embodiment shows the thermal head using the transfer ribbon, the thermal paper is used as the recording paper,
The present invention is also applicable to a thermal head that does not use a transfer ribbon. In this case, as the thin film, a film having only the conductive layer formed on the lower surface may be used.

(G) Effect of the Invention A thermal head of the present invention is formed on an insulating substrate, a heat generating portion including a plurality of resistance films provided at an end portion of the upper surface of the insulating substrate and in contact with recording paper, and formed on the insulating substrate.
A plurality of electrodes that are individually electrically connected to the resistance film, a protective film that covers the heating portion and the electrodes, a current-carrying portion that exposes a portion of the resistance film facing the end of the insulating substrate, the heating portion, and the recording portion. The thin film is provided with a conductive layer that is interposed between the conductive paper and the paper and is in electrical contact with the current-carrying portion. Therefore, the common electrode can be omitted or the width can be made smaller, and the heat generating portion can be brought closer to the end portion of the insulating substrate. Therefore, there is an advantage that the contact of the thermal head with the recording paper is improved and clear printing can be performed.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of an essential part of a thermal head according to an embodiment of the present invention, FIG. 2 is a side view showing the usage state of the thermal head, and FIG. A partially cutaway plan view and FIG. 4 are plan views of a conventional thermal head. 2: Substrate, 2a: Edge, 2b: Top edge, 4: Resistive film, 5: Lead electrode, 7: Silicon dioxide film, 8: Conducting part, 9: Heating part, 10: Transfer ribbon, 10c: Conductive Part, P: Recording paper.

Claims (2)

(57) [Claims] 1. An insulating substrate, a heat generating portion including a plurality of resistive films provided at an end portion of an upper surface of the insulating substrate and contacting a recording sheet, and a heat generating portion formed on the insulating substrate and individually conducted to the resistive film. A plurality of electrodes, a protective film that covers the heat-generating part and the electrodes, a current-carrying part that exposes a portion of the resistance film facing the insulating substrate end, and an intervening part between the heat-generating part and the recording paper, A thermal head comprising a thin film having a conductive layer that is in contact with and conductive with the current-carrying portion. 2. The thermal head according to claim 1, wherein the thin film is a transfer ribbon having an ink layer formed on a surface that comes into contact with a recording paper.