JPH0798400B2 - Thermal head - Google Patents

Description

The present invention relates to a thermal head used in a thermal printer,
In particular, it relates to a thick film type thermal head.

[Conventional technology]

Fig. 4 shows the configuration of a printer that uses a thermal head. From an image source such as a video camera or frame memory (camera in Fig. 4), NTSC signals or RGB signals are sent to the halftone control circuit. Transferred. The halftone control circuit generates a digital image signal of a color to be printed from these signals and transfers it to the thermal head 7. Thermal head 7
Then, as shown in FIG. 5, a large number of heating resistor elements R _{1 to} R _N
Are provided in parallel, and the voltage V _H on the high voltage side is normally the common electrode 11,1
The data D are applied to the signal electrodes 21, 22 and the like from the driver 44 including the latch L, and the image is printed by moving the recording paper 9 in synchronization with the movement of the platen drum 8. All of these controls are performed by a controller using, for example, a one-chip microcomputer.

The thermal head 7 can be classified into a thick film head and a thin film head according to its manufacturing method, and the electrode structure and the resistor structure are largely different. The above-mentioned FIG. 5 shows a schematic wiring diagram in the thick film head, where the signal electrodes 21 are the common electrodes 11 and 12, and two heating elements R ₁ and R ₁ for one signal. ₂
Works.

FIG. 6 shows an enlarged part of the resistor 3 in the thick film head, and FIG. 7 shows a cross section of the entire head. The thick film head has a common electrode 1 (one of 11, 12, ... In FIG. 5) and a signal electrode 2
(One of 21, 22, ... In FIG. 5) is alternately arranged, and the resistor 3 (R1, R2, ... In FIG. 5 is configured) so as to cover both electrodes.
Is provided. Usually, the resistor 3 is formed by mixing an oxide of a noble metal such as ruthenium oxide (Ru ₂ O) with a glass material, applying the mixture, and sintering the mixture. A protective layer of glass material is provided thereon. That is, it includes the common electrode 1 and the signal electrode 2, the resistor 3 on the common electrode 1 and the signal electrode 2, the protective layer 43 on the common electrode 1 and the signal electrode 2, and the driver 44 on a part of the head 7. It is provided.

The thick film head having such a structure is characterized in that the manufacturing process is simple and the cost can be reduced, and the conventional example is disclosed in JP-A-57-95.
484, ibid. 56-37179. Operation is simple,
The energy (usually a pulsed current) flowing from the signal electrode 2 flows to the common electrode 1 on both sides, so that heat is generated at the two locations 31 and 32 of the resistor 3, and printing is performed on recording paper or the like.

Next, for the thin film head, see JP-A-61-162369 and JP-A-61-2621.
42, etc., and its typical configuration will be described. FIG. 8 is an enlarged view around the resistor 3, and FIG. 9 is a cross section of the thermal head. The electrical wiring diagram is almost the same as that of the thick film head shown in FIG. 5, except that one resistance element R _{1 to} R _N is provided for each signal electrode 2. As shown in FIG. 9, the constitution is such that the resistor 3 is applied on the partial glaze 42 provided on the substrate 41, and the resistor 3 is subdivided by etching. Electrodes 1 and 2 are applied on it, and etching is performed to divide each element. The protective layer 43 is baked thereon. In the thin film head, one resistance pair 3 is configured for one pair of electrodes, and further, from the manufacturing method, the resistance value of each subdivided resistance pair 3 is uniform,
In particular, many full color image printers that express halftones use thin film heads. If the image quality is still insufficient, a slit may be provided in the resistor 3 as described in JP-A-61-162369 or JP-A-61-262142. The purpose is to disperse the concentration.

As a measure for improving each of the above heads, both of the thick film type and the thin film type, the resistance value of each heating element is made uniform to achieve high image quality (Japanese Patent Laid-Open No. 61-83050). A resistor at a dividing position for processing is processed to prevent white spots at the dividing point (Japanese Patent Laid-Open No. 62-164560), and a resistor pair is divided into a thick film head in the same manner as the thin film type (special feature). KAISHO 62-42875), another electrode is formed on the resistance pair to increase the resistance between adjacent electrodes (JP-A-61-266267).

[Problems to be Solved by the Invention]

The manufacturing of thin film heads often involves repeated vapor deposition and sputtering, and due to the increase in the number of manufacturing processes, the cost is generally higher than that of thick film heads, and the resistance of the thin film head is thin, resulting in a short life.

On the other hand, the thick film head has a small number of manufacturing steps and can be manufactured at low cost, and since the resistor 3 is continuous to all electrodes,
Although it has the advantage that it is suitable for image printing that requires blurred pixels, it has two heating parts 31 and 32 for one signal electrode 2 as shown in FIG. Difference easily occurs. For this reason, it is often used in a printer that prints in binary, such as a facsimile, rather than a halftone image.

Therefore, for the halftone expression, the method of aligning the resistance value at each dot of the above-mentioned JP-A-61-83050, the method of changing the forming method of the resistor and conductor of JP-A-57-95484, and JP-A-56-37179
Although there is a method of changing the timing of the injection energy of the above method, the drawback that two dots are formed for one pixel remains the same, and the above-mentioned known example has not yet eliminated this drawback.

As a method for eliminating the above-mentioned defects, the shape shown in FIG. 10 is considered. The cross section of this head is shown in FIG.
The common electrode 1 is applied on the partial glaze 42 and the signal electrode 2 is applied at a position facing the common electrode 1, and the resistor 3 is fired thereon. Structurally similar to a thin film head,
This has the same problems as shown in the thick film head of FIG. That is, for example, when a signal is applied to the signal electrode 22 to energize, the common electrode 1 is conducting, and therefore the current is
Not only the current 61 from 12 but also the adjacent common electrodes 11 and 13
A current 62 also flows from there, and heat is generated even in the unexpected portion 6.

The above-mentioned Japanese Patent Laid-Open No. 61-266267 eliminates this defect by increasing the resistance between adjacent electrodes, but the following problems occur. One is to form an electrode on the resistor, perform etching after adjusting the resistance value, and fire the protective layer 43.
The resistance value changes due to heating after the resistance value is corrected. Generally, as the temperature rises, the resistance value tends to decrease, so that the resistance value decreases and the correction effect decreases. The other is that the above-mentioned structure of the electrode and the etching process are involved, and the cost becomes high.

The object of the present invention is to provide a continuous, inexpensive, thick film head resistor.
It is to provide a thermal head having a long life and high image quality of a thin film head.

[Means for Solving the Problems]

The above-mentioned object is to provide a comb-teeth-shaped common electrode, a large number of signal electrodes each of which is aligned with an electrode of each comb-teeth portion of the common electrode (hereinafter, referred to as a partial electrode) and face each other one-to-one, A thermal head comprising a strip-shaped thick film resistor made of ruthenium oxide provided between an electrode and the partial electrode, wherein a partial electrode A and a signal electrode facing the partial electrode A are provided for each partial electrode. A high voltage, in which the ruthenium oxide shows a positive characteristic, is applied between the signal electrode b on the right of a and the current path has a high resistance,
Further, it is achieved by applying a high voltage showing the positive characteristic of the ruthenium oxide between the partial electrode B on the right side of the partial electrode A and the signal electrode a to increase the resistance of the current path.

[Work]

The thermal head of the present invention is of a thick film type and has a counter electrode shape. However, since the current due to crosstalk between adjacent electrodes is limited by the high resistance portion provided in the resistor, It is possible to prevent deterioration of image quality due to crosstalk, and moreover, because the resistors are not thermally insulated between adjacent ones, a certain amount of dot spread occurs, and the image quality of a halftone image can be improved. Furthermore, since the formation of the high resistance portion can be performed only by laser processing or voltage application, there is no fear of change in resistance value due to heat treatment.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a first embodiment of the present invention, in which a resistor portion of a thermal head is enlarged. The common electrode 1 and the signal electrode 2 face each other corresponding to each dot, and the thick film resistor 3 is placed between them.

The signal electrode 2 of the thermal head is usually composed of several hundreds to several thousands arranged in parallel, and the distribution of heat generation differs depending on the energy supplied to each electrode 2, and a halftone image is printed. In the present embodiment, the shape of the resistor 3 is left as it is, and the partial resistance value between the adjacent electrodes is increased by applying a voltage.

Generally, in the thick film head resistor 3, ruthenium oxide (Ru
₂ O) is used, and this statistical value has a characteristic as shown in FIG. 3 with respect to the applied voltage V. That is, a certain voltage V ₀
Up to the vicinity, the resistance value change ΔR shows a negative characteristic with the increase of the voltage V, and shows a positive characteristic rapidly from the vicinity of V ₀ . The present invention utilizes this positive characteristic in the region and locally increases the resistance by applying a voltage of V ₀ or more. To this end, the first
When the electrodes 11 and 12 on the common electrode 1 side in the figure are separated and a voltage of V ₀ or more is applied between the common electrode 12 and the signal electrode 21, the current passage 51 has a high resistance. In this way, the current is passed to increase the resistance, and the resistor 3 is not damaged, so that the concentration of temperature on the low antibody 3 can be prevented and the image quality can be improved.

To further enhance the effect, a voltage is applied between the common electrode 11 and the signal electrode 22 to increase the resistance of the current passage 52.

FIG. 2 shows a second embodiment of the present invention. In addition to the configuration of FIG. 1, the slit 5 is provided on the common electrode 1 side and the signal electrode 2 side.
It is provided between the adjacent electrodes on both sides.

In the first and second embodiments, the voltage application for increasing the resistance may be performed by applying the pulsed voltage V at least once, but the desired value can be obtained by performing the measurement multiple times while measuring the resistance value. To be

In each of the above embodiments, the electrode tip has a parallel shape. However, the electrode tip may have a convex shape or a concave shape as long as it has a counter electrode shape.

〔The invention's effect〕

According to the present invention, a thick film head can achieve a heat generation distribution shape of one pixel and one dot, so that there is an effect that high image quality can be achieved at low cost. Further, since the high resistance portion can be formed even after the protective layer is provided on the upper portion of the resistor, there is no need to consider the change in resistance when the protective layer is fired. Since there is no etching, the composition of the resistor can be prevented from being deformed.

[Brief description of drawings]

1 is a block diagram of a thermal head according to a first embodiment of the present invention, FIG. 2 is a block diagram of a thermal head according to a second embodiment of the present invention, and FIG. 3 is a voltage chart of a thick film resistor. FIG. 4 is a schematic diagram showing the structure of a printer, FIG. 4 is a schematic diagram showing the structure of a printer, FIG. 5 is an electrical wiring diagram of a conventional thick film head, and FIGS. 6 and 7 are resistance of a conventional thick film head. 8 and 9 are enlarged views and cross-sectional views of the vicinity of the body, FIGS. 8 and 9 are enlarged views and cross-sectional views of the vicinity of the resistor of the thin film head, and FIGS. 10 and 11 are resistors of the thick film head by the conventional counter electrode method. It is an enlarged view and a sectional view of the neighborhood. 1,11,12 …… Counter electrode, 2,21,22 …… Signal electrode, 3 …… Resistor, 5 …… Slit, 51,52 …… High resistance part.

Front page continuation (72) Inventor Tatsuo Honda 4026 Kujimachi, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Inc. (72) Inventor Saburo Yasukawa 4026 Kujicho, Hitachi City, Ibaraki Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Toru Takei 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Inc. (72) Inventor Kazuya Oishi 4026 Kuji Town, Hitachi City, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory Ltd. (72) Invention Person Yasuro Hori 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory Ltd. (72) Inventor Ren Ito 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Hiritsukoki Co., Ltd. (56) References JP-A-61-265802 (JP, A) JP-A-61-266263 (JP, A) JP-A-56-28874 (JP, A) JP-A-52-82245 (JP, A) JP-A-62-31101 (JP, A)

Claims (1)

[Claims] 1. A comb-teeth-shaped common electrode, a large number of signal electrodes each of which is aligned with an electrode of each comb-teeth portion of the common electrode (hereinafter referred to as a partial electrode) and faces each other in a one-to-one correspondence, and the signal. A thermal head comprising a strip-shaped thick film resistor made of ruthenium oxide provided between an electrode and the partial electrode, wherein a partial electrode A and a signal electrode facing the partial electrode A are provided for each partial electrode. a high voltage, in which the ruthenium oxide exhibits a positive characteristic, is applied between the signal electrode b on the right side of a and the current path has a high resistance, and the partial electrode B on the right side of the partial electrode A and the signal electrode. a
A high voltage having a positive characteristic of the ruthenium oxide is applied between the heat sensitive head and the current path to have a high resistance.