JP2606881Y2 - Thermal head - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermal head incorporated in a printer mechanism such as a word processor or a facsimile.

[0002]

2. Description of the Related Art Conventionally, a thermal head incorporated in a printer mechanism such as a word processor is, as shown in FIG.
On the upper surface of the electrically insulating substrate 11, a heat storage layer 12 made of a heat-resistant resin such as a polyimide resin is applied in a band shape, and a plurality of heating resistors 13 made of tantalum nitride or the like are formed on the band-shaped heat storage layer 12 and It has a structure in which a pair of conductive layers 14 and 14 made of aluminum or the like, which are connected to both ends of the heat generating resistor 13, are applied, and a predetermined power is applied between the pair of conductive layers 14 and 14 to generate heat. A recording medium, such as thermal paper, to which the resistor 13 is selectively heated by Joule heat and the heated heat is slid.
The recording medium 15 forms a predetermined print on the recording medium 15 and functions as a thermal head.

The heat storage layer 12 accumulates heat generated by the heat generating resistor 13 so as to have an appropriate temperature, and functions to keep the thermal response characteristics of the thermal head good.

When the heat storage layer 12 is made of, for example, a polyimide resin, the electrically insulating substrate 11 is first arranged below a dispenser to which a varnish to be a polyimide resin is supplied, and then a predetermined amount of varnish is dropped from the dispenser. At the same time, the varnish is applied in a strip shape on the electrically insulating substrate 11 by moving the electrically insulating substrate 11 by a predetermined distance at a predetermined speed, and then heat is applied to the varnish to condense and polymerize the varnish to obtain a polyimide. By being made of resin, it was attached to the upper surface of the electrically insulating substrate 11 in a band shape with a thickness of, for example, 40 μm.

[0005]

However, in this conventional thermal head, when the heat storage layer 12 is applied to the electrically insulating substrate 11, a varnish is formed on the electrically insulating substrate 11 using a dispenser or the like. When applied to
The dispenser is normally controlled to start dripping varnish at the same time as the electric insulating substrate 11 starts moving from the stopped state, and to stop dripping of the varnish at the same time as the movement of the electric insulating substrate 11 stops. Since a constant amount of varnish is constantly dropped, the varnish slightly covers the electrically insulating substrate 11 when the movement of the electrically insulating substrate 11 stops, that is, when the varnish starts and stops. As a result, the band varnish is thicker at both ends than in other regions of the varnish. When heat is applied to such a band-shaped varnish to form the heat storage layer 12, since the heat storage layer 12 is formed by condensation polymerization of the varnish, both ends of the heat storage layer 12 are similar to the above-described band-shaped varnish. As a result, the heat storage layer 12 is formed thicker than the other areas of the heat storage layer 12, and as a result, the heat storage layer 12 varies in the amount of heat storage during printing, and the recording medium 15 is slid in contact with the heat storage layer 12 with uniform strength. Recording medium 15
Had the disadvantage that uneven print density was formed.

In order to solve the above-mentioned drawback, the amount of varnish dropped from the dispenser is adjusted by changing the amount of varnish dropped from the electrically insulating substrate 11.
It is conceivable to make an appropriate adjustment according to the movement of the varnish, and to control the band-shaped varnish applied on the electrically insulating substrate 11 to have a uniform thickness.

However, in order to make the thickness of the varnish applied on the electrically insulating substrate 11 uniform by such control, it is necessary to adjust the amount of the varnish dripped with extremely high precision. In addition, it is necessary to use a coating device such as a dispenser. It has become complicated,
A drawback that makes a thermal head as a product expensive is induced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a small-sized thermal head capable of forming a good print without uneven density on a recording medium.

[0009]

According to the thermal head of the present invention, a heat storage layer made of a heat-resistant resin is applied in a band shape on the upper surface of an electrically insulating substrate, and a plurality of heating resistors are provided on the band-shaped heat storage layer. A thermal head for forming a print by causing the heating resistor to generate Joule heat and slidingly contacting a recording medium, wherein both ends of the band-shaped heat storage layer are in sliding contact with each other. A metal common electrode extending to the outside of the recording medium and commonly connected to one of the conductive layers is provided between the extending portion and the electrically insulating substrate. Things.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1A to 1C are partial views showing an embodiment of a thermal head according to the present invention. FIG.
(B) is a cross-sectional view taken along the line XX of (a), and (c) is a Y view of (a).
FIG. 4 is a sectional view taken along line -Y. In the figure, reference numeral 1 denotes an electrically insulating substrate, 2 denotes a heat storage layer, 3 denotes a heating resistor, 4 and 4 denote a pair of conductive layers, and 5 denotes a recording medium such as thermal paper.

The electrically insulating substrate 1 is made of an electrically insulating material such as alumina ceramics, and is made of alumina, silica,
A ceramic green sheet is formed by adding and mixing an appropriate organic solvent and a solvent to a ceramic raw material powder such as magnesia to form a slurry by adopting a conventionally known doctor blade method, a calendar roll method, and the like. Thereafter, the ceramic green sheet is manufactured by stamping into a predetermined shape and firing at a high temperature.

On the upper surface of the electrically insulating substrate 1, a heat storage layer 2 is attached in a strip shape, and a plurality of heating resistors 3 and a pair of conductive layers 4, 4 are provided on the heat storage layer 2. Attachment
Are arranged.

The belt-shaped heat storage layer 2 is made of a heat-resistant resin such as a polyimide resin and accumulates heat generated by the heat generating resistor 3 at an appropriate temperature, and has a function of maintaining good thermal response characteristics of the thermal head. .

When the heat storage layer 2 is made of, for example, a polyimide resin, as shown in FIG. 2, an electric insulating substrate 1 is first arranged below a dispenser 6 for supplying a varnish 2a to be a polyimide resin. Varnish from dispenser 6
2a is dropped by a predetermined amount, and the insulating substrate 1 is moved at a predetermined speed and a predetermined distance to apply the varnish 2a on the insulating substrate 1 in a strip shape. The varnish 2a is formed by applying heat to the varnish 2a to cause condensation polymerization of the varnish 2a.

Both ends of the band-shaped heat storage layer 2 extend to the outside of the recording medium 5 in sliding contact.

Since the band-shaped heat storage layer 2 has both ends located outside the recording medium 5 in sliding contact,
Even if the thickness of both ends of the band-shaped heat storage layer 2 becomes thicker than the thickness of the other areas of the heat storage layer 2, the recording medium 5 does not slide on the both ends of the thick heat storage layer 2 at all during printing. On the other hand, the recording medium 5 comes into sliding contact only with the heat storage layer 2 having a substantially uniform thickness. As a result, the recording medium 5 is brought into sliding contact with the heat storage layer 2 with almost uniform strength, and the heat storage layer 2 is effectively prevented from having a variation in the amount of heat storage, and
It is possible to form a good print without shading.

If the both ends of the heat storage layer 2 are located at least 5 mm outside the recording medium 5 to be slid in contact with, the thickness of the heat storage layer 2 in slidable contact with the recording medium 5 becomes more uniform. As a result, it is possible to eliminate any variation in the amount of heat stored in the heat storage layer 2, and as a result, even when performing gradation printing or high-speed printing, it is possible to form a clear print without uneven density on the recording medium 5. Becomes possible. Therefore, the heat storage layer
2 has both ends 5 mm wider than the recording medium 5 to be slid.
It is preferable to be located outside the above.

The varnish 2a is polycondensed to form a heat storage layer 2.
Is formed at a temperature of 80 ° C. for 30 minutes, at a temperature of 140 ° C. for 30 minutes, at a temperature of 240 ° C. for 30 minutes, 300 ° C.
If heat is applied to the varnish 2a in four steps at a temperature of 350 ° C. for 60 minutes, the varnish 2a undergoes condensation polymerization after the organic solvent evaporates.
The upper surface of the heat storage layer 2 is effectively prevented from being depressed by its own weight, whereby the upper surface of the heat storage layer 2 is made flat and the recording medium 5 is stored in the heat storage layer.
2 can be adhered well. Therefore,
When the heat storage layer 2 is formed by condensation polymerization of the varnish 2a,
Temperature for 30 minutes, 140 ° C. for 30 minutes, 240
It is preferable to apply heat to the varnish 2a in four steps of 30 ° C. for 30 minutes and 300 to 350 ° C. for 60 minutes.

Further, between both ends of the strip-shaped heat storage layer 2 extending to the outside of the recording medium 5 to be slid and the electrically insulating substrate 1, a common connection is made to one of the conductive layers 4 described later. The common electrode 4a made of metal is interposed.

For this reason, even if a large amount of heat is to be stored at both ends of the thick band-shaped heat storage layer 2, a part of the heat is well absorbed by the metal common electrode 4a and the heat is transferred to the electrically insulating substrate 1. As a result, a large amount of heat is accumulated at both ends of the thick band-shaped heat storage layer 2 and the temperature becomes high, so that an unnecessary print is formed on the recording medium 5 or a print formed on the recording medium 5 is formed. The generation of uneven shading is effectively prevented, whereby the occurrence of uneven shading can be more reliably prevented.

Further, in this case, since the common electrode 4a can be disposed close to the recording medium 5 to be slid, the overall structure of the thermal head can be reduced in size.

The heating resistor 3 attached to the heat storage layer 2 is made of, for example, tantalum nitride and has a predetermined electric resistivity.
When electric power is applied through the medium, Joule heat is generated, and the temperature required to form a print on the recording medium 5, for example, 25
Heat is generated to a temperature of 0 ° C to 350 ° C.

A pair of conductive layers 4 and 4 attached on the heating resistor 3 are made of a metal such as aluminum, and the conductive layers 4 and 4 are necessary for causing the heating resistor 3 to generate Joule heat. The operation of applying a predetermined electric power is performed. Here, one of the pair of conductive layers 4, 4 is led out to the above-mentioned common electrode 4a and is commonly connected to the common electrode 4a.

The heat generating resistor 3 and the pair of conductive layers 4, 4 attached on the heat accumulating layer 2 are attached on the heat accumulating layer 2 with a predetermined thickness by employing conventionally known sputtering or the like. Then, it is processed into a predetermined pattern by employing photolithography technology.

On the heating resistor 3 and the pair of conductive layers 4 and 4, a protective layer (not shown) is further adhered. Medium 5
The heating resistor 3 and the pair of conductive layers 4 and 4
Acts to protect

The protective layer is made of, for example, silicon nitride, sialon, or the like, and is applied with a thickness of about 4 μm to the upper surface of the heating resistor 3 or the like by employing a conventionally known sputtering or the like.

Thus, in the above-described thermal head, a predetermined power is applied between the pair of conductive layers 4 and 4 to cause the heating resistor 3 to selectively generate Joule heat and to conduct the generated heat to the recording medium 5. The recording head 5 functions as a thermal head by forming a predetermined print on the recording medium 5.

It should be noted that the present invention is not limited to the above embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.

[0030]

According to the thermal head of the present invention, since both ends of the band-shaped heat storage layer extend to the outside of the recording medium in sliding contact, the thickness of both ends of the band-shaped heat storage layer is different from that of the heat storage layer. Even when the recording medium becomes thicker than the thickness of the area, the recording medium does not slide on both ends of the thick heat storage layer during printing, and the recording medium slides only on the heat storage layer having a uniform thickness. become. As a result, the recording medium is brought into sliding contact with the heat storage layer with uniform strength, and it is possible to effectively prevent the heat storage layer from having a variation in the amount of heat storage, and to form a good print without uneven density on the recording medium. It becomes possible.

Further, according to the thermal head of the present invention, a metal common electrode commonly connected to one of the conductive layers is provided between both ends (extending portions) of the band-shaped heat storage layer and the electrically insulating substrate. Because of the interposition, even if a large amount of heat is accumulated at both ends of the thick band-shaped heat storage layer, part of the heat is well absorbed by the metal common electrode and quickly transmitted to the electrically insulating substrate. As a result, a large amount of heat is accumulated at both ends of the thick band-shaped heat storage layer and the temperature becomes high, and unnecessary prints are formed on the recording medium, or density unevenness occurs in the print formed on the recording medium. Is effectively prevented, whereby the occurrence of shading can be more reliably prevented.

Further, according to the thermal head of the present invention, since the common electrode can be disposed close to the recording medium to be slid, the overall structure of the thermal head can be reduced in size.

[Brief description of the drawings]

1A is a perspective view showing an embodiment of a thermal head according to the present invention, FIG. 1B is a cross-sectional view taken along line XX of FIG. 1A, and FIG.
FIG. 3 is a sectional view taken along line YY in FIG.

FIG. 2 is a diagram for explaining a method of applying a varnish 2a by a dispenser 6.

FIG. 3 is a perspective view of a conventional thermal head.

[Explanation of symbols]

1 ・ ・ ・ Electrically insulating substrate, 2 ・ ・ ・ Band-shaped heat storage layer, 2a
・ Varnish, 3 ... heating resistor, 4, 4 ... a pair of conductive layers, 4a ... common electrode, 5 ... recording medium, 6 ... dispenser

Claims (1)

(57) [Scope of request for utility model registration] 1. A heat storage layer made of a heat-resistant resin is applied in a band shape on an upper surface of an electrically insulating substrate, and a plurality of heating resistors and a pair of conductive layers are applied on the band-shaped heat storage layer. A thermal head that forms a print by causing the heating resistor to generate Joule heat and slidingly contact a recording medium, wherein both end portions of the band-shaped heat storage layer extend to the outside of the recording medium in sliding contact, A thermal head, wherein a metal common electrode commonly connected to one of the conductive layers is disposed between the extending portion and the electrically insulating substrate.