JPH07112740B2 - Thermal head - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal head applied to a thermal transfer printer, a sublimation printer or the like.

[Conventional technology]

As is well known, the heat generating portion of the conventional general thin film type thermal head is constructed as shown in FIGS. 7 and 8. In the figure, 1 is a ceramic substrate formed to a thickness of about 600 μm, 2 is a glaze layer applied to the ceramic substrate 1 to a thickness of about 50 μm, and 3 is a glaze layer formed on the glaze layer 2. A heating element 4 having a thickness of about 0.3 μm is formed, and 4 is a common lead electrode having a thickness of about 0.3 μm for commonly connecting one end of the heating element 3.
Reference numeral 5 is a select lead electrode having a thickness of, for example, about 0.3 μm, to which the other end of the heating element 3 is connected, and 6 is an adjacent heating element 3
An isolation layer 7 for insulating and isolating each other is a protective film.

Next, the operation will be described. First, the thermal head is manufactured by forming the glaze layer 2 on the ceramic substrate 1 and forming the heating element 3 on the front surface by the sputtering method. Next, a conductor pattern is formed on the front surface by the same sputtering method, and then the heating element 3 portion, the common lead electrode 4 and the select lead electrode are selectively etched to form a pattern. Then, the protective film 7 is formed by the sputtering method to complete the thermal head. Such a manufacturing method is usually used as standard when stripping a thin film type thermal head. Then, by applying a pulse voltage to the common lead electrode 4, connecting the select lead electrode 5 to, for example, a driver IC, and selectively turning on / off the switch portion of the driver IC, the temperature on the heating element 3 is controlled. A thermal paper (not shown) or the like on the protective film 7 located on the heat generating element 3 is colored, and a character or a pattern is drawn.

In the conventional thermal head configured in this way,
The surface temperature of the heating element 3 has a temperature distribution in which the highest point is generated in the central portion of the heating element 3 and the temperature decreases as it spreads to the periphery. Then there is the ninth
As shown by gradation 1 in the figure, a certain amount of power is increased in order to make the pixels in independent printing normal, and the heating element 3
If it is attempted to generate heat with a predetermined capacity on the entire surface, the pixels in continuous printing will be large and unclear printing will be performed. For this reason, the power is lowered as shown as gradation 2.
If the heating temperature of the heating element 3 is slightly lowered, the pixels become normal in continuous printing, but the pixels become small in independent printing. Further, when the power is further reduced as shown by gradation 3, the amount of heat generation is small, so that the pixels for both continuous printing and independent printing become smaller and thinner. As described above, the thermal head in which the heating element 3 is simply separated by the isolation layer 6 cannot uniformly generate heat on the entire surface of the heating element 3.

Therefore, in order to uniformly generate heat on the entire surface of the heating element 3, various types of thermal heads have been conventionally improved.

FIG. 10 and FIG. 11 are a plan view and a sectional view showing a conventional thermal head disclosed in, for example, Japanese Patent Laid-Open No. 61-89872, in which the same components as those in FIGS. 7 and 8 are shown. Are denoted by the same reference numerals, and duplicate description thereof will be omitted.
In the figure, 8 is a heating element, and 9 is a slit formed in the central portion of the heating element 8.

Next, the operation will be described.

By applying a pulse voltage between the common lead electrode 4 and the select lead electrode 5, Joule heat is generated in the heating element 8 and heat is generated. Then, the surface temperature distribution of the heating element 8 when a pulse voltage is applied between the common lead electrode 4 and the select lead electrode 5 spreads over the entire surface as shown in FIG.

Further, as shown in FIGS. 12 and 13, by forming a hole 11 in the central portion of the heating element 10 and both side portions thereof, a pulse voltage is applied between the common lead electrode 4 and the select lead electrode 5. The surface temperature distribution of the heating element 10 when
As shown in Figure 12, it will be spread over the entire surface.

[Problems to be solved by the invention]

Since the conventional thermal head is constructed as described above, a slit 9 is formed in the central portion of the heating element 8 as shown in FIG. 10 or a hole 11 is formed in the heating element 10 as shown in FIG.
However, there is a problem in that the heating element has an even temperature distribution over its entire surface, but heat is diffused to the adjacent heating element to deteriorate the print image quality.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a thermal head in which heat diffusion is not applied to an adjacent heating element and print quality is prevented from deteriorating.

[Means for solving problems]

The thermal head according to the present invention comprises a glaze layer formed on a ceramic substrate, and a common lead electrode and a select lead electrode for applying a pulse voltage which are alternately arranged in parallel on the glaze layer at a predetermined interval. And in the thermal head having the glaze layer and the heating element formed on the common lead electrode and the select lead electrode, the heating element corresponds to this boundary with the common lead electrode and the select lead electrode as boundaries. The surface of the heating element is formed to be uneven so that the thickness of the heating element at a position is thinner than the thickness of the area of the effective portion necessary for printing of the heating element existing between the boundary portions, and provided on the surface of the heating element. The protective layer has an uneven surface formed along the surface unevenness of the heating element.

[Action]

The thermal head according to the present invention has a common lead electrode and a select lead electrode as a boundary, and the thickness of the heating element at a position corresponding to this boundary is defined as an effective portion necessary for printing the heating element existing between the boundaries. The unevenness of the surface of the heating element is formed so as to be thinner than the thickness of the region, and the protective layer provided on the surface of the heating element is formed to have the unevenness along the surface unevenness of the heating element. Due to the difference in the resistance value between the boundary part and the boundary part due to the thin film thickness, the boundary part has a high resistance value and generates less heat, and whether there is an air layer between the protective film and the thermal paper in contact with it. As a result, the heat conduction to the thermal paper is reduced in the boundary portion, so that the heat separation between the boundary portions becomes good. As a result, high-quality printing can be performed without giving heat diffusion to the adjacent heating elements.

〔Example〕

Hereinafter, an example of the present invention will be described. FIG. 1 is a plan view showing an embodiment of the present invention, and FIG. 2 is an A- line in FIG.
It is an A line sectional view. In FIGS. 1 and 2, the same components as those in FIGS. 7 to 8 are designated by the same reference numerals, and the duplicate description thereof will be omitted. In FIGS. 1 and 2, 15 is a common lead electrode patterned on the glaze layer 2, and 16 is a common lead electrode.
Is a select lead electrode patterned on the glaze layer 2, and the common lead electrode 15 and the select lead electrode are
16 and 16 are alternately arranged in parallel at a predetermined interval. Reference numeral 17 denotes a heating element formed on the glaze layer 2, the common lead electrode 15 and the select lead electrode 16, and the heating element 17 has a boundary corresponding to the common lead electrode 15 and the select lead electrode 16 at a position corresponding to this boundary. The thickness of the boundary portion 17a is formed to be 30% or more thinner than the thickness of the effective portion 17b necessary for printing. Further, the width of the boundary portion 17a is formed wider than the width of the effective portion 17b.

Next, a method of manufacturing the thermal head of this embodiment will be described. Since the glaze layer 2 is provided on the ceramic substrate 1 and the conductor pattern to be the lead electrode is provided, the metal organic paste is printed on the entire surface. As a result, the conductor film thickness is 0.5 μm
It can be formed below, and the film thickness of the boundary portion 17a can be reduced. There are various kinds of metal organic pastes, but as a component, Au and Rh are the main components, but in the case of the present embodiment, Bi,
Use Pb and Si added within 0.1 wt% to 10 wt% of the total paste. And then included in the gold paste
In order to slightly leave the oxides of Bi, Pb, and Si on the glaze layer 2, the combustion treatment is performed at a temperature of about 780 to 820 ° C. After baking, in order to obtain a desired pattern, a photomask is provided, exposure, development and etching are performed. Next, the heating element 17 is formed by printing and firing using a resistance paste. In this case, there is no inconvenience even if the combustion temperature is 820 ° C. or higher. Next, the protective layer 7 is formed on the surface of the heating element with the unevenness on the surface of the heating element using glass paste. Therefore, when the thermal paper is brought into contact with the surface of the protective layer as shown in FIG. 2, air layers 7a and direct contact portions 7b are alternately formed between the protective layer and the thermal paper. The firing process uses a normal thick film manufacturing process. FIGS. 3 and 4 show performance curve diagrams showing the thickness of the printed resistance paste, the width of the resistor, or the performance of the heating element 17 and the deviation of the resistance variation with respect to the firing temperature of the gold pattern. is there. From now on 820
It can be seen that the thickness and width of the heating element 17 in which the common lead electrode 15, the select lead electrode 16 and the glaze layer 2 are located change around the firing temperature of ℃. this is,
It is understood that when the resistance paste is applied to the lead electrode and the glaze layer 2 and dried, the resistance paste changes due to the influence of wettability. This is contained in the gold paste, Bi, P
The effect was due to b and Si, and a significant difference did not appear when only Au and Rh (rhodium) were used.

Then, apply a pulse voltage to the common lead electrode 15,
By connecting, for example, a driver IC to the select lead electrode 16 and selectively turning on / off the switch part of the driver IC, the temperature on the heating element 17 rises, and the heat-sensitive element positioned on the heating element 17 through the protective film 7 A recording medium such as paper, a thermal transfer ribbon, or a sublimation ribbon develops color, and characters or patterns are drawn on the recording paper. In the thermal head having such a structure, stable pixels were obtained in both independent printing and continuous printing by outputting a predetermined power as shown by gradation 4 in FIG.

In the above embodiment, the common lead electrode 4 and the select lead electrode 5 have the same size, but by making the dimension width of the common lead 4 wider than the dimension width of the select lead electrode 5 as shown in FIGS. , The height of the boundary, the first
It can be made even lower than that shown in FIGS.

〔The invention's effect〕

As described above, according to the present invention, since the protective layer provided on the surface of the heating element is formed to have unevenness along the surface unevenness of the heating element, the boundary portion and the boundary portion due to the difference in the layer thickness of the heating element Due to the difference in resistance between the protective layer and the presence or absence of an air layer between the protective layer and the thermal paper in contact with it, the thermal separation between the boundary parts becomes good, and the heat is not diffused to the heating element, resulting in a high temperature. There is an effect that a printer capable of printing image quality can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing a thermal head according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II--II of FIG. 1, and FIG. 3 is a heating element width and a gold pattern firing of the thermal head of the present invention. FIG. 4 is a graph showing the relationship with temperature, FIG. 4 is a graph showing the relationship between the heating element thickness of the thermal head of the present invention and the gold pattern firing temperature, and FIG. 5 is a plan view showing another embodiment of the present invention. 6 is a sectional view taken along line VI-VI in FIG. 5, FIG. 7 is a plan view showing an example of a conventional thermal head, FIG. 8 is a sectional view taken along line VIII-VIII in FIG. 7, and FIG. FIG. 10 is a plan view showing the sharpness and thinness of printing dots in independent printing and continuous printing, FIG. 10 is a plan view showing another example of a conventional thermal head, and FIG. 11 is a sectional view taken along line XI-XI in FIG. , FIG. 12 is a plan view showing still another example of the conventional thermal head, and FIG. 13 is a XI of FIG.
FIG. 11 is a sectional view taken along line II-XIII. 1 is a ceramic substrate, 2 is a glaze layer, 15 is a common lead electrode, 16 is a select lead electrode, 17 is a heating element, and 17a
Is the boundary part, and 17b is the effective part. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A glaze layer formed on a ceramic substrate, and a common lead electrode and a select lead electrode for applying a pulse voltage, which are alternately arranged in parallel on the glaze layer at a predetermined interval. In a thermal head having a glaze layer and a heating element formed on the common lead electrode and the select lead electrode, the heating element uses the common lead electrode and the select lead electrode as a boundary, and the heat generating element at a position corresponding to the boundary. The surface of the heating element is formed to be uneven so that the thickness of the heating element is thinner than the thickness of the area of the effective portion necessary for printing of the heating element existing between the boundaries, and a protective layer provided on the surface of the heating element is formed. A thermal head characterized in that a surface is formed to be uneven along the surface unevenness of the heating element.