JPH0626919B2 - Method for manufacturing thermal print head - Google Patents

Description

The present invention relates to a method for manufacturing a thermal print head.

(Prior Art) In this type of thermal print head, it is known that if the density of the heating dots is increased, the image quality is improved. Therefore, there is a strong demand for higher density.

FIG. 5 shows an example of a conventional pattern, which is a strip-shaped resistor R.
The common electrode C and the individual electrode S are alternately arranged so as to cross the line. According to this configuration, one heating dot is configured by the two partitioning resistor portions M adjacent to each other of the resistor body partitioned by the adjacent electrodes.

According to this configuration, each heating dot has a half of the partition resistance portion density. Therefore, in order to increase the density of the heating dots, it is necessary to increase the partition resistance portion density. With such a configuration, the dot density is limited to 8 dots per mm.

FIG. 6 shows another conventional example, in which a resistor R formed separately from each other has a common electrode C at one end and an individual electrode S at the other end. Each of them is formed by stacking them. According to this, each heating dot is constituted by the individual resistor R.

However, when each resistor R is formed of a thick film, each resistor R and the individual electrode S are formed so as to overlap each other.
The resistor R may flow from above, and adjacent resistors R may come into contact with each other. Therefore, the adjacent resistors R cannot be sufficiently brought close to each other, and therefore, it is not possible to expect much increase in the density of the heating dots. Specifically, the limit is 6 dots per mm.

(Problems to be Solved by the Invention) An object of the present invention is to make it possible to easily increase the density of heating dots without requiring the pattern to be too fine.

(Means for Solving the Problems) The present invention increases the resistance of a resistor portion between adjacent electrodes of a pair of electrodes, and a resistor portion for a heating dot between the pair of electrodes. By reducing the resistance of
It is characterized in that the resistor portion between the pair of electrodes can be formed with a sufficiently narrow interval so that the heating dots can be formed at a high density.

It is generally known that when a thick film resistor is supplied with overpower in a short time, the resistance value increases. It is considered that this is because the contact portion between the resistive particles forming the resistance paste is overheated by the supplied electric power and melted, and the contact between the particles is broken, so that the resistance value increases.

Specifically, the power supplied for printing is
In the case of 60 W / mm ² , when the electric power of 120 W / mm ² , which is about twice that, for example, 120 mj / mm ² is supplied for 1 ms, the resistance value rapidly increases to about 2 to 3 times. When an extremely large electric power is supplied, the resistor portion between the electrodes is melted and the resistance value becomes extremely large.

It is generally known that when a pulsed high voltage having a sufficiently narrow width is applied to a thick film resistor, the resistor does not generate heat and the resistance value becomes low. This is because when the resistive particles forming the resistance paste are covered with some kind of insulating film such as an oxide film and are in contact with each other through this oxide film, the pulsed high voltage as described above is applied. Then, due to the high voltage, the oxide film causes discharge breakdown and the particles come into direct contact with each other.

Therefore, it is considered that the resistance value decreases. Specifically, for example, when a pulse of 1000 V / 0.1 mm, 3 ns is applied, the resistance value may be reduced to about half.

By doing this, the resistance value between the pair of electrodes,
The difference from the resistance value between the electrodes adjacent to each other becomes relatively large. Therefore, the resistor portion between the pair of electrodes, that is, the heating dot is equivalently opened or isolated equivalently to the resistor portion between the adjacent electrodes.

Therefore, even if the adjacent electrodes are formed with a sufficiently small interval as described above, it is sufficient that the current supplied between the paired electrodes flows toward the adjacent electrodes. It will be blocked. Thus, even if the space between the adjacent electrodes is sufficient, no trouble occurs. As a result, the heating dots can be manufactured with high density.

(Embodiment) An embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 is a substrate made of an insulating material such as ceramics, and 2 is a resistor for heat generation, which is formed by a thick film on the surface of the substrate 1, and is formed in a long strip shape. Reference numeral 3 is a plurality of first electrodes formed on one side edge of the resistor 2 and 4 is a plurality of second electrodes formed on the other side edge. First,
The second electrodes face each other to form a pair, and the resistance pair portion 2A between the two electrodes 3 and 4 is used as a heating dot. The steps up to this point are as shown in FIGS.

In this case, the resistors 2 are formed on the surfaces of the electrodes 3 and 4 so as to extend over the respective electrodes, and the resistors and the like are not individually overlapped as shown in FIG. Alternatively, it may be formed so that the adjacent electrodes 4 are sufficiently close to each other.

Next, according to the present invention, a surface electrode 5 is formed on the surface of the resistor 1 so as to be located between the paired electrodes 3 and 4, as shown in FIGS. 3 and 4.

Then, for printing, a power sufficiently larger than the power supplied between the paired electrodes 3 and 4 is supplied between the adjacent surface electrodes 5. By this power supply, the sheet resistance value of the resistor portion 2A between the front surface electrodes 5 becomes, for example, 2 to 3 times higher than other portions. Then, the surface electrode 5 is removed by selective etching. After this removal, the form is the same as in FIGS. 1 and 2.

In order to facilitate this etching, the electrodes 3 and 4 and the surface electrode 5 may be made of different metals. For example, when the electrodes 3 and 4 are made of gold, the surface electrode 5 may be made of silver.

Next, a high voltage pulse is applied between the paired electrodes 3 and 4 to reduce the resistance value of the resistor portion 2B between the electrodes 3 and 4. Due to this decrease in resistance value, the difference in resistance value between the resistor portion 2B and the resistor portion 2A adjacent thereto becomes equivalently large. As a result, the resistor portion 2B is almost opened or isolated from other portions.

Therefore, at the time of printing, even if electric power is supplied between the electrode 3 and the electrode 4, it is less likely that the current will flow toward the other electrodes 3 and 4 adjacent to the electric power.
Only the resistor portion 2B between them will generate heat. It has been confirmed that the dot density formed by this method can be up to 16 dots per mm.

Although not shown in the figure, it goes without saying that the surfaces of the resistors and electrodes are actually coated with glass or the like. Further, after the treatment as described above, it is preferable that one electrode, for example, the end portion of the electrode 3 is collectively connected and used as a common electrode.

(Effects of the Invention) As described in detail above, according to the present invention, the resistance between the adjacent electrodes of the pair of electrodes is increased, and the resistance between the paired electrodes is increased. By lowering the resistance of the parts, the resistor part between the paired electrodes is equivalently opened or isolated from the other parts, so it is necessary to form the adjacent electrodes sufficiently close to each other. Therefore, there is an effect that it is possible to increase the density of the heating dots.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, FIG. 2 is the same sectional view, FIG. 3 is a plan view showing a manufacturing process, FIG. 4 is the same sectional view, FIG. 5 and FIG. It is a top view of an example. 2 ... Resistor, 2A, 2B ... Resistor part, 3, 4 ...
Electrodes, 5 ... Surface electrodes,

Claims (1)

[Claims] 1. A plurality of electrodes are formed on one side edge and the other side edge of a strip-shaped heat-generating resistor made of a thick film so as to be paired with each other, and are further paired with each other. A surface electrode is formed on the surface of the resistor so as to straddle between the electrodes, and a power larger than the power supplied between the pair of electrodes for printing is first supplied between the adjacent surface electrodes. By increasing the resistance of the resistor portion existing between the adjacent surface electrodes, and then removing the surface electrode, by applying a pulsed high voltage between the pair of electrodes, A method of manufacturing a thermal print head, wherein a resistance portion for a heating dot existing between the paired electrodes is made lower in resistance than a resistance portion between adjacent electrodes.