JPH028773Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a thermal print head.

As is well known, a thermal print head includes a pair of conductive layers sandwiching a heat generating resistor, and a voltage is applied between both conductive layers to cause the resistor to generate heat. Actually, there is not one resistive portion that generates heat, but multiple resistive portions that are lined up in a straight line. One conductive layer for each heat generating part is a common conductive layer, that is, the common conductive layer is commonly used for each heat generating part, and the individual conductive layers opposite to this are installed in each heat generating part. .

By the way, in some types of thermal print heads, there are cases where it is required that the heat generating portion be installed on the edge side of the substrate. However, as the heat generating portion is brought closer to the edge of the substrate in this manner, the area where the common conductive layer is installed between the heat generating portion and the edge of the substrate becomes narrower. Since the common conductive layer is arranged in a straight line in which the heat generating parts are lined up, the narrower the installation area, the narrower the width of the common conductive layer must be.As a result, the resistance value of the common conductive layer will inevitably decrease. It gets expensive. Needless to say, this increase in resistance value leads to wasteful power consumption.

The purpose of this invention is to enable the installation of the resistor at the edge of the substrate without increasing the resistance of the common conductive layer.

An embodiment of this invention will be described with reference to the drawings. 1 is a substrate made of ceramic such as alumina, 2 is a protruding glaze provided as close as possible to the edge 1A of the substrate 1, and 3 is a common conductive layer. It is formed to cover the entire surface. The common conductive layer 3 is formed, for example, by vapor deposition or sputtering of aluminum. FIG. 2 shows the pattern of the common conductive layer 3. The shaded portion in the figure is the common conductive layer. As will be understood, at least a portion of the common conductive layer 3 is formed extending to the surface of the substrate 1. The end of this extension 3A is used as a terminal electrode for connection to an external circuit (for example, a power source).

Reference numeral 4 denotes an insulating layer (eg, SiO ₂ film), which is formed so as to substantially overlap the surface of the common conductive layer 3 . In this case, the end portion 3B of the common conductive layer 3 on the edge 1A side is exposed. An insulating layer 4 covers a region defined by a chain line P in FIG. 5 is a resistive layer (for example
A Ta ₂ N film) is formed on the surface of the insulating layer 4. Resistive layer 5 and common conductive layer 3 are insulated from each other by insulating layer 4 . The insulating layer 4 and the resistive layer 5 are formed by sputtering or vapor deposition.

Reference numerals 6 and 7 designate a pair of conductive layers, which are formed so as to be located on both sides of the resistor section 5A, which serves as a heat generating section. The illustrated example is formed on the surface of the resistance layer 5. To explain this in more detail, the conductive layer 6 is formed closer to the edge 1A than the heat generating portion 5A, and is overlapped with the common conductive layer 3 at its end 3B. The conductive layer 6 is therefore electrically connected to the common conductive layer 3. Further, a plurality of conductive layers 7 are arranged in parallel at appropriate intervals. Then, it extends from the surface of the resistance layer 5 to the surface of the insulating layer 4. Alternatively, it may be extended to the surface of the substrate 1 where the extension portion 3A is not present. FIG. 1 shows this state. The conductive layer 7 consists of a plurality of layers parallel to each other, and the edge 1A
The opposite end is provided for individual connection to an external circuit. A plurality of heat generating portions 5A interposed between each conductive layer 7 and conductive layer 6 are arranged in a straight line substantially on the top surface of the glaze 2. Each heat generating part 5A is 1
It fulfills its role as a dot. Each of the conductive layers 6 and 7, like the common conductive layer 3, is formed, for example, by vapor deposition or sputtering of aluminum.

8 is an oxidation-resistant film made of SiO ₂ or the like, and 9 is a wear-resistant film made of Ta ₂ O ₅ or the like, both of which serve as protective films.

As understood from the above configuration, the heat generating portion 5
To supply current to A, it is sufficient to apply a voltage between the common conductive layer 3 and the selected individual conductive layer 7, so that the current is supplied from the common conductive layer 3 to the conductive layer 6 via the end portion 3B. Become. Therefore, glaze 2 and edge 1A
Even if the area between the conductive layer 6 and the conductive layer 6 is narrow, the common conductive layer 3 can be formed sufficiently wide. This can be reliably prevented.

Note that as a means to achieve the purpose of forming the common conductive layer 3 widely, it is conceivable to form the conductive layer 6 by extending it to between the lower surface of the glaze 2 and the surface of the substrate 1. Then, the extended conductive layer is interposed between the glaze 2 and the substrate 1. This is not preferable because the thermal conductivity between the glaze 2 and the substrate 1 is impaired.

However, if the conductive layer 6 is extended to the surface of the glaze 2 and the extended conductive layer is used as a common conductive layer, the thermal conductivity as described above will not be impaired. Therefore, it is most preferable to form the common conductive layer 3 on the surface of the glaze 2.

As detailed above, according to this invention, even if the heat-generating portion is provided sufficiently close to the edge of the substrate, the formation area of the common conductive layer can be sufficiently wide, and therefore the formation of the common conductive layer can be made sufficiently large. The effect is that no increase in resistance value due to narrowing of the area occurs.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an embodiment of this invention, Figure 2 is a sectional view showing an embodiment of this invention.
The figure is a partial plan view. 1...Substrate, 1A...Edge, 2...Glaze,
3... Common conductive layer, 3B... End, 4... Insulating layer, 5... Resistance value, 5A... Heat generating portion, 6, 7...
...conductive layer.

Claims (1)

[Scope of utility model registration request] a glaze provided protrudingly close to one edge of the substrate; a common conductive layer provided on the surface of the glaze; an insulating layer provided on the surface of the common conductive layer; An end portion of the conductive layer provided on the edge side of the pair of conductive layers, consisting of a heat generating portion provided on the surface and a conductive layer provided in a pair with the heat generating portion sandwiched therebetween. of,
A thermal print head formed by overlapping the edge portion of the common conductive layer and connecting them to each other.