JPH0159115B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head, and more particularly, first and second partial glaze layers are formed on both ends of a thermal head substrate, and a layer between the first and second partial glaze layers is formed. The present invention relates to a thermal head in which a third partial glaze layer is further formed, and a heat generating portion is formed on the third partial glaze layer.

In the thermal printing method, a pulsed current is passed through a heat-generating resistor, and the generated heat is transferred to thermal recording paper to create color recording, or ink from a thermal ribbon is transferred to plain paper using heat to perform recording. .

The thermal printing method has many advantages such as a simple mechanism, high reliability, low cost, and low noise, so it has been applied to a wide range of fields from large line printers to ultra-compact and lightweight printers. It is becoming indispensable in the information processing field, including facsimile machines and personal computer peripherals.

Various types of thermal recording paper have been devised, including multicolor recording,
It is also regarded as a promising image recording method such as simultaneous copy recording and gradation recording. In particular, the thermal transfer method solves the problem of storage stability, which was a problem with conventional thermal printing methods, and the printing quality is clear, so it is expected to be developed in the future.

The heating resistor, which is the lifeblood of the thermal printing method, i.e., the thermal head, can be a thin film method, a thick film method, or
Although there are semiconductor methods, the superiority of thin film methods has been proven in many respects, including resolution, printing speed, long-term reliability, and cost. In order to explain a thin film thermal head, an outline of an example thereof is shown in FIG.

FIG. 1 is a cross-sectional view of a thin film thermal head. A glass glaze layer 2 forming a smooth surface is coated on an insulating substrate 1 made of alumina or the like to a thickness of 40 to 60 μm, and a heating resistor film 3 made of Ta ₂ N or the like is formed thereon. Furthermore, an electrode 5 made of Au or the like is patterned on top of the electrode 5 for supplying power to the heat generating part 4. On top of that, an oxidation-resistant protective layer 6 is provided.
The wear-resistant layer 7 is further formed to have a thickness of about 10 μm. Usually, the oxidation-resistant protective layer 6 is SiO ₂ and the wear-resistant layer 7 is
Ta ₂ O ₂ is formed using a sputtering method.

FIG. 1 shows an example of a thin film thermal head, in which various improvements have been made to the structure, shape, material, etc. in order to achieve even higher performance.

FIG. 2 shows an example of a structure for improving printing quality. A glaze layer 9 is formed on an insulating substrate 7 made of alumina or the like only in a portion corresponding to the lower part of the heat generating part 8 to improve contact with the thermal paper, efficiently transmit heat to the thermal paper, and improve print quality. It is improving. The structure of the upper part of the partial glaze layer 9 is the same as the example shown in FIG.
A wear-resistant layer 13 is formed and patterned.

These thermal printers have different arrangements and patterns of heating elements depending on their use.

Facsimile machines, line printers, etc. use dot-shaped heads in a horizontal row. This is an arrangement of dots perpendicular to the paper feed direction. alphanumeric characters,
Serial printers that print kanji, katakana, etc. use a dot-shaped head with dots lined up in a vertical line in the same direction as the paper feed direction. Other types of heads used for serial printers include dot matrix type heads and segment type heads.

FIG. 3 shows an example of a horizontal single-row dot type head. A large number of heat generating parts 15 are formed on the insulating substrate 14 in a direction perpendicular to the paper feeding direction indicated by the arrow. Heat generating part 15
An electrode 16 is formed for supplying current to the insulating substrate 14, and a connection terminal 17 for connecting to an external circuit is formed at the end of the insulating substrate 14. In some cases, attempts may be made to improve printing quality by forming a partial glaze layer 18 as shown by the dotted line.

FIG. 4 shows an example of a vertical dot type head. A large number of heat generating parts 20 are formed on an insulating substrate 19 in parallel to the paper feeding direction indicated by the arrow. It seems that the number of dots is usually 7 dots. An electrode 21 for supplying current to the heat generating part 20 is formed, and a connection terminal 22 for connecting to an external circuit is formed at the end of the insulating substrate 19. In some cases, attempts have been made to improve printing quality by forming a partial glaze layer 23 as shown by the dotted line.

As mentioned earlier, the partial glaze layer improves adhesion to the thermal paper, improves print quality, and reduces energy consumption, but the height of the glaze layer is usually on the order of several tens of microns. be. Therefore, even a partial glaze layer which is highly effective as described above may not be effective at all depending on how it is used. In particular, printers have recently become capable of printing on large areas and with high resolution. Therefore, there is an inevitable tendency for thermal heads to become larger. For example, in line printers such as facsimile machines, the area and width of the thermal head itself is large, and it needs to be the same width as thermal paper or thermal ribbon. Especially when the width in the direction of relative movement with the thermal paper or thermal ribbon becomes large, the height of the partial glaze layer on the thermal head must be very high to prevent damage from the undulations of the thermal paper and have little effect. I can't accomplish it. However, there is a limit to how thick the partial glaze layer can be made, and problems arise when making the partial glaze layer thick. Attempts have been made to resolve these inconsistencies by providing a plurality of partial glaze layers, and to bring out the original effects of the partial glaze layers.

However, in a thermal head in which partial glaze layers are formed near both ends of the thermal head substrate and a heat generating portion is formed only on one partial glaze layer, the following two problems occur. First of all, the partial glaze layer forming the heat generating part on the thermal head comes into surface contact with the recording paper, reducing the adhesion between the heat generating part and the recording paper, resulting in variations in print density. Second
In order to prevent this variation, it is necessary to either increase the printing voltage supplied to the heat generating section or to set a large pressure force between the thermal head and the recording paper, which increases the printing energy and increases the frictional force applied to the thermal head. becomes large and wear resistance decreases.

The present invention eliminates the above-mentioned drawbacks, and forms first, second, and third partial glaze layers on a thermal head substrate, and when the third partial glaze layer forming the heat generating part comes into pressure contact with the recording paper, The first and second partial glaze layers bias the recording paper toward the platen from both ends of the third partial glaze layer, thereby making the recording paper almost parallel to the platen. The purpose is to bring the recording paper into a line contact state and to improve the adhesion between the thermal head and the recording paper.

That is, the present invention provides a thermal head substrate;
The first thermal head substrate is formed on both ends of the thermal head substrate.
a second partial glaze layer, a third partial glaze layer formed between the first and second partial glaze layers, and a resistance layer formed on the third partial glaze layer; electrodes formed on the resistance layer to sandwich the heat generation part and face each other in order to energize the resistance layer on the third partial glaze layer and cause the heat generation part of the resistance layer to generate heat; and the heat generation part. and a protective layer formed on the heat generating part and the electrode to protect the electrode, and a platen that presses the recording paper against the thermal head substrate, and the third partial glaze layer is The first and second partial glaze layers are formed higher than the first and second partial glaze layers, and when the thermal head substrate and the platen are pressed together, the first and second partial glaze layers contact the third partial glaze layer. The present invention is characterized in that the portion of the recording paper is biased toward the platen from both ends. With the structure of the present invention, even if the thermal head becomes larger, the original effect of the partial glaze layer, which is the adhesion to the thermal paper, is not impaired, and the printing performance is good, and printing power is low and high-speed printing is possible.

FIGS. 5a and 5b show an embodiment in which the present invention is applied to a dot type head in a single vertical row. FIG. 5a is a front view of the thermal head, and FIG. 5b is a sectional view. A partial glaze A25, a partial glaze B26, and a partial glaze C27 are formed on the alumina substrate 24, and a heat generating portion 28 is formed near the top of the partial glaze C27 near the center.
is formed. The partial glaze C27 where the heat generating part 28 is formed is the other partial glaze A25,
It is configured higher than the partial glaze B26.
For example, partial glaze A25, partial glaze B26
is 30 microns, and partial glaze C27 is 60 microns. With this configuration, even when the width of the thermal head substrate 24 was 2 cm or more, the original effect of the partial glaze layer was exhibited, the printing quality was good, the thermal response was good, and defects such as trailing did not occur. Although FIG. 5 shows an example in which the present invention is applied to a vertical single-row dot type, it goes without saying that the present invention can be similarly applied to a horizontal single-row dot type.

As described above, the present invention includes a thermal head substrate,
first and second partial glaze layers formed on both ends of the thermal head substrate; a third partial glaze layer formed between the first and second partial glaze layers; and a third partial glaze layer. electrodes formed on the resistive layer to face each other with the heat generating part sandwiched therebetween in order to energize the resistive layer formed on the resistive layer and the resistive layer on the third partial glaze layer to generate heat in the heat generating part of the resistive layer; a protective layer formed on the heat generating part and the electrodes to protect the heat generating part and the electrodes; and a platen that presses the recording paper against the thermal head substrate; The recording paper is formed higher than the first and second partial glaze layers, and the portion of the recording paper where the first and second partial glaze layers contact the third partial glaze layer when the thermal head substrate and platen are pressed together is Since the third partial glaze layer in which the heat generating portion is formed is kept almost parallel to the platen without causing the recording paper to undulate by the first and second partial glaze layers. This allows for line contact between the recording paper and the thermal head, and there is little sliding friction between the recording paper and the thermal head, and the heat generation efficiency between the heat generating part and the recording paper is improved, resulting in good printing quality. Furthermore, when the thermal head moves for printing, the first and second partial glaze layers prevent the edges at both ends of the thermal head substrate from digging into the recording paper.
Paper waste does not adhere to the glaze layer and affect print quality.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a thin film thermal head. FIG. 2 shows a cross section of a thin film thermal head with a partial glaze layer. FIG. 3 is a diagram showing an example of a horizontal single row dot type head. FIG. 4 is a diagram showing an example of a dot type head with a single vertical row. FIGS. 5a and 5b are diagrams illustrating an embodiment of the present invention. 1: Insulating substrate, 2: Glass glaze layer, 3: Heat generating resistor film, 4: Heat generating part, 5: Electrode, 6: Oxidation resistant protective layer, 7: Wear resistant layer, 8: Heat generating part, 9: Glaze layer, 10: Heat generating resistor film, 11: Electrode, 12:
oxidation-resistant protective layer, 13: wear-resistant layer, 14: insulating substrate, 15: heat generating part, 16: electrode, 17: connecting terminal, 18: partial glaze layer, 19: insulating substrate,
20: Heat generating part, 21: Electrode, 22: Connection terminal, 2
3: partial glaze layer, 24: alumina substrate, 2
5: Partial glaze A, 26: Partial glaze B, 2
7: Partial glaze C, 28: Heat generating part.

Claims (1)

[Scope of Claims] 1. A thermal head substrate, first and second partial glaze layers formed on both ends of the thermal head substrate, and a thermal head substrate formed between the first and second partial glaze layers. a third partial glaze layer formed on the third partial glaze layer; a resistive layer formed on the third partial glaze layer; and a current is applied to the resistive layer on the third partial glaze layer to cause a heat generating portion of the resistive layer to generate heat. electrodes formed on the resistance layer to face each other with the heat generating part in between; a protective layer formed on the heat generating part and the electrodes to protect the heat generating part and the electrode; a platen that presses paper against the thermal head substrate, the third partial glaze layer is formed higher than the first and second partial glaze layers, and the thermal head substrate and the platen are connected to each other. When pressed together, the first and second partial glaze layers contact the third partial glaze layer.
1. A thermal head characterized in that a portion of the recording paper in contact with a partial glaze layer is urged toward the platen from both ends.