JPH02111561A - Thermal head - Google Patents

Abstract

PURPOSE:To reduce the deviation between a center of curvature and a center of a band-like projection part by a method wherein groove parts are formed at both side riser parts of the band-like projection part on the surface of a substrate, and a glass layer is burnt to coat the substrate. CONSTITUTION:Since groove parts 1b are formed at both side riser parts of a band-like projection part 1a on a surface of a substrate 1, paste, i.e., glass applied thereonto becomes liquid in burning to flow. However, it flows into the both side groove part 1b, and no riser is generated on side face parts of the band-like projection part 1a. Therefore, a radius of curvature of a surface of a glass layer 2 on the band-like projection part 1a is lessened and besides, the deviation between a center of curvature of the glass layer 2 having this radius of curvature and a center of the band-like projection part 1a becomes very small. Therefore, improvement of printing quality of a thermal head can be achieved and besides, improvement of thermal response and thermal efficiency can be achieved. Further, a part between lead electrodes 4, 4 of this band-like projection part 1a is made to be a thermal resistor 6. Furthermore, a protective film 7 is formed over all the upper surfaces thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermal head used in, for example, a thermal printing device, a thermal transfer printing device, or the like.

2. Description of the Related Art As shown in FIG. 3, a conventional thermal head has a substrate 11 made of an insulating material having high thermal conductivity, such as alumina, and a glass layer 12, a resistive film 13,
In addition to forming the lead electrodes 14 and the protective film 15, a band-shaped protrusion 11a is formed on the substrate 11 at a location corresponding to the heating resistor (part of the resistance film 13) 16 formed between the lead electrodes 14 and 14. It was formed. By the way, when manufacturing the above-mentioned thermal head, the band-shaped protrusion 11a is first formed on the surface of the substrate 11 by etching or grinding.Although there is also a method of forming it by press molding at the green sheet stage, generally the dimensions are poor accuracy),
Next, a glass layer 12 is applied to the paste 1 over the entire surface, and then fired to form a glazed alumina substrate. next,
A resistive film 13 and lead electrodes 14 were formed thereon by photoetching, and a protective film 15 was further formed thereon to obtain a thermal head.

Problems to be Solved by the Invention In such a conventional configuration, even if the glass layer 12 is applied with a paste to the same thickness over the entire surface of the substrate 11 having the band-shaped protrusion 11a, it becomes liquid during firing. The glass flows downward and accumulates on the side surface of the band-like protrusion 11a, and the surface of the glass layer 12 below the heating resistor 16 becomes smooth as shown in FIG. 3, which has the disadvantage that it does not have a sharp convex shape. Ta. Furthermore, during the above firing, if the table on which the substrate 11 is placed is tilted or warped, the liquid glass may be biased toward either side of the band-shaped protrusion 11a due to factors such as the surface condition of the substrate 11. Sisters,
The center of the radius of curvature of the surface of the glass layer 12 in the band-shaped protrusion 11a and the center of the band-shaped protrusion 11a are greatly misaligned,
This has disadvantages in that it adversely affects print quality and reduces thermal response and thermal efficiency.

Therefore, an object of the present invention is to provide a thermal head that can solve the above problems.

Means for Solving the Problems In order to solve the above problems, the thermal head of the present invention has a band-like protrusion formed on its surface, and grooves along the band-like protrusion formed on the surface of the rising portions on both sides of the band-like protrusion. a glass layer fired and coated on the substrate;
The heating resistor and its lead electrodes are formed on the upper surface of the glass layer in the band-shaped protrusion, and a protective film is formed on the upper surface of these elements.

Effects According to the above structure, when paste-like glass is applied to the substrate surface and fired, the glass applied on the band-shaped protrusion flows into the grooves on both sides of the band-shaped protrusion, and the glass paste flows into the grooves on both sides of the band-shaped protrusion. Since the glass does not bulge, the radius of curvature of the surface of the glass layer on the upper surface of the band-like protrusion becomes small, and the deviation between the center of curvature of the glass layer having this radius of curvature and the center of the band-like protrusion becomes very small.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is an enlarged sectional view of the main part of the thermal head. 1st
In the figure, reference numeral 1 denotes an alumina substrate on which a band-shaped protrusion 1a is formed and grooves 1b along the band-shaped protrusion 1a are formed on the surface of the rising portions on both sides of the band-shaped protrusion 1a by an etching method or a grinding method. A glass layer 2 is pasted onto the entire upper surface with a uniform thickness, and then fired to form a glazed alumina substrate 3. Then, after the resistive film 4 is formed on this, lead electrodes 5 are formed on both sides of the portion of the resistive film 4 corresponding to the band-shaped protrusion 1a. Note that the portion between the lead electrodes 4, 4 above the band-shaped protrusion 1a is a heat generating resistor 6 which is a heat generating portion. Further, a protective film 7 is applied over the entire upper surface.
is formed.

As described above, since the grooves 1b are formed on both sides of the band-like protrusion 1a on the surface of the substrate 1, the paste applied thereon, that is, the glass, becomes liquid during firing and flows.
It flows into the grooves 1b on both sides.

Since there is no bulge as in the side surface of the conventional band-shaped protrusion 1a, the radius of curvature of the surface of the glass layer 2 on the top surface of the band-shaped protrusion 1a becomes smaller, and the center of curvature of the glass layer 2 having this radius of curvature and the band-shaped protrusion become smaller. The deviation from the center of portion 1a is very small. In Fig. 2, the groove 1
The relationship between the cross-sectional area b and the radius of curvature of the surface of the glass layer 2 on the strip-like protrusion la is shown (provided that the shape of the strip-like protrusion and the paste thickness are constant). As can be seen from FIG. 2, as the cross-sectional area of the groove portion 1b increases, the radius of curvature of the surface of the glass layer 2 becomes significantly smaller.

Therefore, when the deviation between the two becomes smaller, it is possible to improve the printing quality of the thermal head, and also to improve thermal responsiveness and thermal efficiency.

Note that the shape of the groove 1b depends on the paste material,
IMi is appropriately selected depending on conditions such as thickness and firing temperature.

Effects of the Invention As described above, according to the configuration of the present invention, paste-like glass can be applied to the surface of a substrate and fired.

The glass applied on the band-shaped protrusion flows into the grooves on both sides of the band-shaped protrusion, and the glass layer does not bulge out like in the screen part of the conventional band-shaped protrusion, so the radius of curvature of the glass layer surface on the top surface of the band-shaped protrusion is small. At the same time, the deviation between the center of curvature of the glass layer with this radius of curvature and the center of the band-like protrusion becomes very small, which makes it possible to improve the printing quality of the thermal head and also to improve thermal response and thermal efficiency. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of the main part of a thermal head according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the cross-sectional area of the groove and the radius of curvature of the surface of the glass layer on the band-shaped protrusion, and FIG. 1 is an enlarged sectional view of a main part of a conventional thermal head. 1... Alumina substrate, 1a... Band-shaped protrusion, 1b.
...Groove portion, 2...Glass layer, 5...Lead electrode, 6
...heating resistor, 7...protective film. Agent Yoshihiro Morimoto J Sub's #face top (Mm Riichi Figure 3/.

Claims (1)

[Claims] 1. A substrate having a band-shaped protrusion formed on its surface and grooves along the band-shaped protrusion formed on the surface of the rising portions on both sides of the band-shaped protrusion; a glass layer coated by firing on this substrate; A thermal head consisting of a heating resistor and its lead electrodes formed on the upper surface of a glass layer in the protrusion, and a protective film formed on these upper surfaces.