JPH0635185B2 - Thermal print head - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal print head.

(Prior Art) In a thermal print head, a glaze layer is provided on the surface of a ceramic substrate, and a large number of heat-generating parts consisting of resistors are installed along the straight line on the surface of the glaze layer, and one of the heat-generating parts An individual lead at the end and a common lead common to these at the other end are
It is already well known.

FIG. 3 is a cross-sectional view of a conventional head of this type, in which 1 is a substrate made of ceramics, 2 is a glaze layer provided on the surface of the head, and a large number of heat generating portions 3 are formed in layers on the surface, And it is installed along a straight line. Actually, the resistance film 3A is uniformly formed on the surface, and a part of the resistance film 3A is used as the heat generating portion 3. Reference numeral 4 is an individual lead provided at one end of each heat generating portion 3, 5 is a common lead commonly provided at the other end, and 6 is a protective layer.

The common lead 5 is connected to one terminal of a power source for heat generation, and the individual lead 4 is selectively connected to the other terminal of the power source so that each heat generating section is selectively heated. Make the required prints.

By the way, the row of the heat generating portions 3 is connected to one edge 1A of the substrate 1.
(Refer to FIG. 2; the same applies to the following). In that case, the row of the heat generating portions 3 is made parallel to the above-mentioned one edge 1A of the substrate 1 and the common lead 5 is provided. It is pulled out to the edge 1A side, and this is further heated
Is extended to one or both ends of the row, and is extended from here to the other edge side of the substrate in the same manner as the individual lead 4.

By the way, according to such a configuration, the common lead 5 is routed toward the end of the row along the direction parallel to the row of the heat generating portions 3, so that it is formed longer by the length of the routing. . Therefore, due to the resistance of the common lead 5, the resistance of the common lead 5 becomes larger as it goes from the end of the row toward the center of the row.

Due to the action of this resistance component, the voltage drop along the column direction of the heat generating portion 3 becomes large, and the heat generating portion 3 on the center side of the heat generating portion 3 has a larger heat generation amount than the heat generating portion 3 on the end side of the row. Get smaller. Therefore, when actually printed, the density on the center side becomes lighter than that on the end side, and uneven density occurs.

In order to improve this, the common lead portion 5A along the row of the heat generating portions 3 may be manufactured so that the resistance thereof is as small as possible. Therefore, in the related art, there is a conventional one in which the common lead portion 5A is formed in two layers so as to be thickened. However, it is extremely troublesome to apply the film twice to form the common lead portion 5A. Not preferred.

(Problems to be Solved by the Invention) An object of the present invention is to reduce the resistance of a common lead routed along a row of heat generating portions to the end of the row with a simple configuration.

(Means for Solving the Problems) According to the present invention, a glaze layer is provided on the surface of a substrate, a heating portion is provided on the surface of the craze layer, and an individual lead is provided at one end of each heating portion and the other is provided at the other end. In a thermal print head in which a common lead is provided in common to the ends of the heat generating portion and the common lead is laid out toward the end side of the row along the row direction of the heat generating portion, the common lead is provided on the surface of the substrate. It is characterized in that it is provided so as to be parallel to the glaze layer and to straddle the surface of a separate glaze layer provided separately from the craze layer.

(Operation) In the conventional configuration, most of the common leads are formed on the surface of the ceramic substrate, but in the present invention, most of the common leads are formed on the surface of the newly formed glaze layer. did. Generally, the surface of ceramic has fine irregularities, and numerous small holes are present. Therefore, when a film-like layer, for example, a layer for leads, is formed on the surface, the film thickness becomes nonuniform, so that the resistance value becomes relatively large.

However, the surface of the glaze layer is smoother than that of ceramic, so that the thickness of the film formed on the surface is uniform. Therefore, the resistance value is smaller than that of the film formed on the surface of the ceramic, even if the film is made of the same material. For example, although it depends on the ceramic used, the type of glaze, and the printing condition of the film, it has been confirmed that the resistance value of the glaze layer surface is about 20% smaller than that of the ceramic surface. ing.

When the common lead is formed on the surface of the newly formed glaze layer in this manner, the resistance value becomes lower than that when the common lead is provided on the surface of the ceramic as in the past, and therefore, the common lead along the row of the heating portions is provided. The resistance value of is almost constant. As a result, the amount of voltage drop along the row of the heat generating portions becomes small, so that the heat generation amount of each heat generating portion becomes substantially uniform, and unevenness in color density can be avoided.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 and 2.
In addition, the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. According to the invention, a separate glaze layer 7 is provided on the surface of the substrate 1 in parallel with the glaze layer 2 between the glaze layer 2 and the edge 1A of the substrate 1 as the glaze layer 2. If this is provided together with the glaze layer 2, no special process need be added.

The common lead 5 extends over the surface of the glaze layer 7.
To provide. Reference numeral 5A indicates a common lead portion parallel to the row of the heat generating portions 3. Actually, the resistance film 3 for forming the heat generating portion 3
Since A is formed from the surface of the glaze layer 2 to the side of the edge 1A, the common lead 5 is provided so as to overlap the surface of this resistance film.

The common lead 5 extends from the end portion of the row of the heat generating portions 3 along the side edge 1B of the substrate 1 and further toward the other end edge of the substrate 1 similarly to the individual lead 4. This structure is not particularly different from the conventional one.

With this structure, most of the common lead portions 5A parallel to the rows of the heat generating portions 3 are on the surface of the glaze layer 7, so that the resistance value along the row direction is provided on the surface of the ceramic substrate as in the conventional case. Smaller than the ones. Therefore, the voltage drop of the common lead along the column direction becomes small, so that it is possible to sufficiently avoid the unevenness of the coloring density of each heating portion 3.

In this configuration, the glaze layer 7 needs to be provided separately from the glaze layer 2. If both glaze layers 2 and 7 are provided continuously to each other, the glaze layer 7 directly acts as a heat storage layer for the heat from the heat generating portion 3, and as a result, heat is excessively stored and uneven printing or tailing occurs. It may be a cause.

However, if the two glaze layers 2 and 7 are separated, the heating portion 3
A part of the heat generated from the heat is diffused to the substrate 1 side through the common lead, whereby excessive heat storage by the glaze layer 7 is prevented, and the occurrence of print unevenness can be avoided.

(Effect of the Invention) As described in detail above, according to the present invention, the resistance value of the common lead portion along the row direction is smaller than that of the conventional one even when the heat generating section of the common lead is provided in parallel with the row. As a result, the voltage drop is reduced at this portion, so that it is possible to sufficiently avoid uneven coloring due to the heat generating portion along the column direction.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view showing a conventional example. 1 ... Substrate, 2 ... Glaze layer, 3 ... Heating part, 4 ...
Individual lead, 5 …… common lead, 5A …… common lead part, 7 …… glaze layer,

Claims (1)

[Claims] 1. A ceramic substrate is provided with a glaze layer on the surface thereof, a heating portion is provided on the surface of the glaze layer, and an individual lead is provided at one end of each heating portion and a common end is provided at the other end. In the thermal print head in which a common lead is provided along the column direction of the heat generating portion to the end side of the column, the common lead is parallel to the glaze layer on the surface of the substrate. And a thermal print head provided so as to straddle the surface of a separate glaze layer provided separately from the glaze layer.