JPH07205462A - Thermal record head - Google Patents

Abstract

PURPOSE:To reduce the leakage of the heat from a heating resistor via an electrode in the printing of an image by a constitution wherein a thickness of each thin film of a common electrode and individual electrodes in an area right beneath or in the vicinity of the heating resistor is smaller than that of the other section. CONSTITUTION:For example, a width of a heating resistor 1 is about 190-240mum and a pitch L of individual electrodes 3 is about 125mum. When printing on a thermal paper using a thermal head, a supply voltage is applied to a common electrode 2 and an individual electrode 3 corresponding to a pixel dot to be colored is grounded. Thereby, an electric current flows into the grounded individual electrode 3 from both of the adjacent common electrodes 2 through the heating resistor 1, then the heating resistor 1 adjacent to the grounded individual electrode 3 is heated so that any point on the paper can be heated. At that time, the heat leaks out via the electrodes 2, 3. In order to prevent the leakage, the electrode is so constituted that the thickness of the film indicated by slanted lines of the electrode is smaller than that of the other section thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a thick film type thermal recording head used in a thermal recording device such as a facsimile and a printer.

[0002]

2. Description of the Related Art In a conventional thick film type thermal recording head, as described in Japanese Patent Laid-Open No. 64-20163, even if there is a difference in film thickness between an individual electrode and a common electrode, a heating resistance is generated at each electrode. The electrode in the part that contacts the body and the electrode in the other parts had the same film thickness.

[0003]

As described above, in the conventional thermal recording head, if the thickness of the electrode is large, heat will escape through the electrode even if the heating resistor is activated by energization. On the contrary, if the thickness of the electrode is reduced, the resistance value of the electrode itself rises, and the electric power that should have been consumed by the heat-generating resistor is converted into heat at the electrode part. Had been an obstacle for.

An object of the present invention is to improve the heat exchange rate of the thermal recording head.

[0005]

In order to achieve the above object, the present invention uses the following means.

(1) In a thick film type thermal recording head comprising a ceramic substrate, a heat insulating layer, an electrode, a heating resistor, and a protective film, which are sequentially laminated, the electrode comprising a common electrode and an individual electrode opposed thereto. The film thicknesses of the common electrode and the individual electrodes immediately below the heating resistor and in the peripheral portion are made thinner than the film thicknesses of the electrodes in other regions.

(2) In the thick film type thermal recording head described in (1), the electrode is composed of electrodes having two kinds of film thickness, and the electrode having the smaller film thickness is provided directly under the heating resistor and in the periphery thereof. And an electrode having a thicker film thickness is formed on other portions.

(3) In the thick film type thermal recording head described in (1), an electrode part having a thin film thickness immediately below the heating resistor and its peripheral portion, and an electrode part having a thick film thickness in other regions. The film thickness of the electrode at the connecting portion is formed in a tapered shape.

[0009]

In the thick-film type thermal head, a power supply voltage, for example, 24 V is applied to the common electrode and any individual electrode is grounded, so that the grounded individual electrode is adjacent to the common electrode and the individual electrode. An electric current flows through the heat generating resistor portion in the above, whereby the heat generating resistor generates heat by Joule heat, whereby the medium such as thermal paper in contact with the protective film can be colored. Gold is usually used for the electrodes of this thick film type thermal head, and the heat outflow through the electrodes cannot be ignored because of its good thermal conductivity. Due to this outflow of heat, the heat to be used for raising the temperature of the heating resistor is propagated to other parts of the thermal head. In order to reduce heat outflow, it is necessary to reduce the cross-sectional area of the electrode, that is, to reduce the film thickness. However, if the film thickness of the entire area of the electrode is made thin, the resistance value of the electrode becomes high as described above. Therefore, in order to avoid this, the electrode film thickness of only the portion in direct contact with the heating resistor should be made thin. Is the most effective. As a result, most of the paths through which the current flows can have a film thickness such that the resistance value can be ignored.
Further, the electrode portion which is in contact with the heating resistor and which has a small film thickness and a small amount of heat outflow has a short length itself, so that the resistance value can be ignored. As a result, the heat outflow through the electrodes is reduced and the increase in the resistance value of the electrodes is suppressed, so the power required to bring the surface of the thermal head to the temperature required for color development of the media is reduced, that is, thermal efficiency. It becomes possible to improve.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the arrangement of electrodes and heating resistors of the thick film type thermal recording head according to the present embodiment as viewed from above. The heating resistor 1 is formed on the common electrode 2 and the individual electrode 3, and 1, 2, 3 are formed on the glaze layer 4 which is a heat insulating layer. A protective film is further formed thereon as the uppermost layer to form a thermal head. This embodiment is a thermal head for printing on a B4 size thermal paper mounted in a G3 standard facsimile machine. The heating resistor 1 has a width W of 190 to 240 μm and a pitch L of the individual electric telescope 3 is 125 μm. The individual electrode 3 is 20
48 elements are arranged. When printing is performed on thermal paper using the head shown in this embodiment, a power supply voltage is applied to the common electrode 2, and the individual electrode 3 in the portion corresponding to the pixel dot to be colored is grounded. As a result, a current flows from the common electrodes 2 adjacent to both sides to the grounded individual electrode 3 through the heating resistor 3, thereby causing the heating resistor 1 near the grounded individual electrode 3 to generate heat. , Any point on the thermal paper can be colored. At that time, heat flows out through the electrodes 2 and 3, and in order to prevent this, the electrode is formed so that the film thickness of the electrode in the shaded portion in FIG. 1 is thinner than that in the other portions. . In this embodiment, the film thickness of the electrode in the shaded area is 0.2 μm.
, And the film thickness of other portions is 0.4 μm. FIG. 2 shows a perspective view of this embodiment so that the sectional structure of the electrode can be seen. As shown in the figure, in the present embodiment, the cross section of the electrode is stepwise in the thin portion and the thick portion. When manufacturing a thermal head having such a cross-sectional structure, as shown in FIG. 3A, first, a gold film 5 as a material of an electrode is formed on the glaze layer 4.
To have a film thickness of 0.2 μm, and a gold film 6 having a thickness of 0.2 μm corresponding to the area excluding the shaded area in FIG. 1 is overlaid, and then the portion other than the portion corresponding to the electrode pattern is formed by photolithography. 3 by removing the gold film of
It becomes possible to easily form electrode films having partially different film thicknesses in the shape as shown in (b). According to this embodiment, it is possible to improve the thermal efficiency of the thick film type thermal recording head, and it is possible to form electrodes having different film thicknesses depending on locations by a simple manufacturing process.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the common electrode 7 and the individual electrode 8
In order to avoid a step-like step at the connecting portion between the thick portion and the thin portion in, the electrodes are formed so that the thickness varies gently from the thick portion to the thin portion. When printing with a thermal head, it is the protective film that is in direct contact with media such as thermal paper, but the unevenness of the shape due to the heating resistor, etc. affects the surface shape of the uppermost protective film, but If there is a step, a complicated unevenness is generated on the surface of the protective film around the heating resistor, which is disadvantageous for the surface shape of the heating portion where a simple convex structure is desirable to secure the pressure on the printing screen. Become. According to the present embodiment, since there is no step in the electrode in the vicinity of the heating resistor, the surface of the protective film does not have unevenness that adversely affects printing.

FIG. 5 shows how the electric power required for printing changes by reducing the electrode film thickness in the vicinity of the heating resistor. As shown in the figure, by making the electrode film thin, it is possible to reduce the power consumption of the head and improve the thermal efficiency. As a result, it is possible to downsize the power source of the thermal recording apparatus equipped with the thermal head according to this embodiment.

[0013]

According to the present invention, it is possible to reduce the outflow of heat from the heating resistor via the electrode when printing with a thick film type thermal recording head. Therefore, for example, when printing on a thermal paper or the like, it is possible to reduce the power required to print at a constant density.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a perspective view of the first embodiment of the present invention.

FIG. 3 is a perspective view showing the construction method of the first embodiment of the present invention.

FIG. 4 is a perspective view of a second embodiment of the present invention.

FIG. 5 is a correlation diagram between the electrode film thickness and the electric power required for thermal recording.

[Explanation of symbols]

1 ... Heating resistor, 2, 7 ... Common electrode, 3 ... Individual electrode, 4
... Glaze layer, 5 ... Gold film first layer, 6 ... Gold film second layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahisa Aoyagi 502 Jinritsucho, Tsuchiura-shi, Ibaraki Machinery Research Laboratories, Hiritsu Manufacturing Co., Ltd. Video Media Business Unit (72) Inventor Akira Shimizu 1410 Inada, Katsuta City, Ibaraki Prefecture Hitachi, Ltd. Information Video Media Business Unit

Claims (3)

[Claims] 1. A thick film type thermal recording head comprising a ceramic substrate, a heat insulating layer, an electrode, a heating resistor, and a protective film, which are sequentially laminated, the electrode comprising a common electrode and an individual electrode opposed thereto. A thermal recording head characterized in that the film thicknesses of the common electrode and the individual electrode immediately below and around the heating resistor are smaller than the film thicknesses of the electrodes in other regions. 2. The electrode according to claim 1, which is composed of electrodes having two types of film thickness, and the electrode having the smaller film thickness is the electrode having the larger film thickness immediately below and around the heating resistor. Is a thick film type thermal recording head formed in a portion other than directly below the heating resistor. 3. The thick film portion of an electrode at a connecting portion between the thin electrode portion and the thick electrode portion immediately below and around the heating resistor according to claim 1. A thick film type thermal recording head that changes gradually from the thin part to the thin part.