JP3237198B2 - Thin film thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film thermal head used for printing on a thermal transfer printer or a facsimile.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view showing an example of the configuration of a conventional thin film thermal head. In this figure, a glaze glass layer 2 is formed on one side of an insulating alumina substrate 1 by firing. A resistor film 3 and an electrode film 4 are sequentially formed on the glaze glass layer 2 by a sputtering process or a vapor deposition process, and are patterned by an etching process. The electrode film 4 is composed of the electrodes 4a and 4b, and a portion of the resistor film 3 sandwiched between the electrodes 4a and 4b is a heating portion 3a. In addition, Ta ₂ N, TaSiO _2, or the like is adopted as a material of the resistor film 3. A protective film 5 is laminated on the upper part of the electrode film 4 by a sputtering process. The protective film 5 prevents oxidation and abrasion of the surface.

[0003]

Incidentally, in the above-mentioned conventional thermal head, since the film thickness distribution of the resistor film 3 is uniform and the sheet resistance value is not deviated, each portion of the heat generating portion 3a is uniform. Fever. Further, the heat is more easily released in the peripheral portion of the heat generating portion 3a. As a result, the temperature of the central portion of the heat generating portion 3a becomes higher than that of the peripheral portion. FIG. 10 shows the result of calculating the temperature distribution of the wax ink within one dot by the finite element method on the assumption that the heating section 3a is heated to heat the wax ink in the configuration shown in FIG. FIG. 10 shows that the ink temperature is high at the center and low at the periphery. Further, as a result of actually performing transfer using the thermal head shown in FIG. 9 and verifying the density within one dot,
In the sublimation printing method, the periphery was thinner than the center. In addition, in the melting thermal transfer printing method, if the heat generation of the resistor film 3 is uniform, the ink temperature becomes uneven and there is an unmelted portion, and an untransferred portion that should not originally occur in the print dot is formed. There was a problem that occurred.

[0004] The present invention has been made under such a background, and an object of the present invention is to provide a thermal head which can make the density distribution within one dot into a desired state.

[0005]

According to the present invention, there is provided a heat insulating layer laminated on a substrate surface, a resistor film laminated on the heat insulating layer, and a resistive film arranged on the resistive film so as to face each other. First and second electrodes, wherein the heat insulating layer protrudes to a position in a region sandwiched between the first and second electrodes.
Has a detecting portion, the resistance value of <br/> Ru said resistive thin film put on the side surface portion of the step of the protrusion, prior to upper surface portion of the step
The resistance value is larger than the resistance value of the resistor thin film .

[0006]

According to the above structure, the amount of heat generated on the side wall of the step of the heat insulating layer is increased, and the first and second layers on the resistor film are formed.
Temperature difference between the central part and the peripheral part in the region sandwiched by the electrodes can be eliminated.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. Parts corresponding to the respective parts in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a sectional view showing the structure of a thin-film thermal head according to a first embodiment of the present invention. On the alumina substrate 1, a glaze glass layer 2, a resistor film 3, an electrode film 4, and a protective film 5 are sequentially laminated. Here, the electrode film 4 is composed of the electrodes 4a, 4b separated by a predetermined distance We.
Consists of Further, a part of the glaze glass layer 2 forms a protruding portion 2a below the heat generating portion 3a of the resistor film 3, as shown in FIG. Length Wh of this protrusion 2a
Is smaller than the distance We between the electrodes 4a and 4b. The projection 2a of the glaze glass layer 2 is formed, for example, by the following method.

First, as shown in FIG. 8A, a glaze glass layer 2 having a thickness of 50 μm is formed on the entire surface of an alumina substrate 1 having a thickness of 0.635 mm by a known means. Then, as shown in FIG. 8B, a Ti-W layer 7 having a thickness of 0.05 μm is formed on the substrate, and an Au layer 8 having a thickness of 1.0 μm is subsequently formed by electron beam evaporation. I do. Then, heat treatment is performed at 400 ° C. for 10 minutes. Next, as shown in FIG. 8 (c), a photoresist 9 is applied and the projection 2a is formed by a well-known lithography (lithographic printing) technique.
Is formed to cover a region corresponding to.
Then, using the aqua regia and hydrogen peroxide solution, the Au layer 8 and subsequently the portion of the Ti—W layer 7 that are not covered with the photoresist 9 are etched as shown in FIG. 8D. After that, the resist is stripped. Next, the glaze glass layer 2 is etched as shown in FIG. Here, the treatment liquid used for the etching treatment is an aqueous solution of hydrogen fluoride (volume ratio,
(HF: H2O = 1: 60) is used. The etching rate is about 1 μm / min at a liquid temperature of 22 ° C. Then, by arbitrarily selecting the etching time, the protrusion 2a having an arbitrary height d can be obtained. Finally, the Au layer 8 and T
The iW layer 7 is removed to obtain the protrusion 2a as shown in FIG.

As described above, after the glaze glass layer 2 having the protrusion 2a is formed by the etching process, the resistor film 3 is formed on the glaze glass layer 2 by the sputtering process. Here, since the projection 2a is formed as described above, a step is generated in the glaze glass 2;
As shown in (1), the film thickness of the side walls 6a and 6b of the protruding portion 2a is reduced, and the resistance value of this portion is increased. When the resistor film 3 generates heat, the same current flows between the electrodes 4a and 4b. Therefore, the heat value is particularly large on the side walls 6a and 6b having a high resistance value. The resistance values of the side walls 6a and 6b can be set to appropriate values by changing the height d of the protruding portion of the glaze glass layer 2. FIG. 2 shows the protrusion 2a
The results are obtained by preparing a plurality of substrates having different heights d, forming a resistor film 3 and an electrode film 4 on each of them, and measuring the resistance value between each of the electrodes 4a and 4b. Here, the X-axis indicates the height d of the protruding portion, and the Y-axis indicates the rate of increase in resistance shown below. Resistance value increase rate (%) = [{(measured resistance value) − (measured resistance value of d = 0)} / (d = 0 measured resistance value)] × 10
0 (%) However, the resistance value of d = 0 is 1500Ω.

As described above, in the resistor film 3 shown in FIG. 1, since the resistance value around the heat generating portion 3a can be increased, the amount of heat generated within one dot is not uniform, and the heat generated in the peripheral portion is not uniform. The amount can be increased. Therefore, by changing the length Wh of the protruding portion 2a and the dimension of the height d of the protruding portion 2a, it is possible to eliminate the bias in the temperature distribution of the ink layer. FIG. 3 shows an example. As shown in FIG. 3, the temperature distribution of the ink layer in one dot can be made more uniform than in FIG.

FIG. 4 is a plan view and a sectional view showing the structure of a thin film thermal head according to a second embodiment of the present invention.
In the thin-film thermal head of this example, as shown in FIG. 4A, a stepped portion 2b obliquely crossing the heat generating portion 3a is formed in the glaze glass layer 2. In the thin-film thermal head of this example, the resistance value on the side wall 6 of the step portion 2b shown in FIG.
It becomes particularly large at.

FIG. 5 is a plan view and a sectional view showing the structure of a thin film thermal head according to a third embodiment of the present invention.
In the thin film thermal head of this example, as shown in FIG. 5A, a stepped portion 2b is formed in the glaze glass layer 2 so as to cross the heat generating portion 3a in a V-shape. In the thin-film thermal head of this example, the side walls 6a, 6a shown in FIG.
6b, the heat generation becomes particularly large.

FIG. 6 is a plan view and a sectional view showing the structure of a thin film thermal head according to a fourth embodiment of the present invention.
In the thin-film thermal head of this example, as shown in FIG. 6B, the projection 2a of the glaze glass layer 2 has a two-stage structure. In the thin-film thermal head of this example, heat generation is particularly large on the side walls 6a to 6d shown in FIG.

FIG. 7 is a plan view and a sectional view showing the structure of a thin-film thermal head according to a fifth embodiment of the present invention.
In the thin-film thermal head of this example, as shown in FIG. 7B, the glaze glass layer 2 is formed with a plurality of protrusions 2a. In the thin-film thermal head of this example, heat generation is particularly large on the side walls 6a to 6f shown in FIG.

As described above, by changing the position and number of steps formed on the surface of the glaze glass layer 2 and the height d of the protrusion 2a, it is possible to arbitrarily control the temperature distribution in the heating portion 3a. It becomes possible.

[0017]

As described above, according to the present invention, by arbitrarily adjusting the temperature distribution in the heating element,
There is an effect that the density distribution within one dot at the time of transfer can be set to a desired state.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a thin-film thermal head according to a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the height of the protrusion and the rate of increase in the resistance value in the example.

FIG. 3 is a graph showing a temperature distribution of wax ink in one dot in the embodiment.

FIG. 4 is a plan view and a cross-sectional view showing a configuration of a thin-film thermal head according to a second embodiment of the present invention.

FIGS. 5A and 5B are a plan view and a cross-sectional view showing a configuration of a thin-film thermal head according to a second embodiment of the present invention.

FIG. 6 is a plan view and a cross-sectional view showing a configuration of a thin-film thermal head according to a third embodiment of the present invention.

FIGS. 7A and 7B are a plan view and a sectional view showing a configuration of a thin-film thermal head according to a third embodiment of the present invention.

FIG. 8 is a sectional view showing the method of manufacturing the thin-film thermal head according to the first embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a configuration example of a conventional thermal head.

FIG. 10 is a graph showing the temperature distribution of wax ink in one dot in a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina substrate 2 Glaze glass layer 3 Resistor film 3a Heating part 4 Electrode film 5 Protective film

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/335

Claims (1)

(57) [Claims] 1. A thermal insulation layer laminated on a surface of a substrate, a resistor film laminated on the thermal insulation layer, and first and second layers disposed on the resistor film so as to face each other. comprising an electrode has a protrusion at the position of the thermal insulating layer is the first and a region sandwiched between the second electrode, the resistor film in the side surface portion content of the step of the protruding portion of resistance, a thin film thermal head is characterized in that is larger than the resistance value of the upper surface portion amount the resistor film of the step.