JPH09123502A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the density irregularity and tailing by mounting a thermal storage member made of thin plate glass covered with a thermal resistor on a board made of at least one type of aluminum, copper, iron and their alloys, thereby making is possible to preferably cool the member and board in a short time. SOLUTION: The board 1 of the thermal head is formed of at least one type of aluminum, copper, iron and their alloys, and a thermal storage member 2 made of thin plate glass having a heating resistor 3 is mounted thereon by solder. The board 1 is formed, for example, an Al-Mg-Si alloy in a thickness of 5mm. Since the board 1 has high heat radiation properties, even if a high speed printing is conducted by increasing the power applied to the heating resistor 4 to set the temperature of the resistor 4 to a specified temperature necessary for printing, it can be preferably cooled in a short time after the printing is finished. The thin plate glass is formed, for example, for borosilicate glass having a thermal conductivity of 0.9kW and a softening point.

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 as a printer mechanism such as a word processor and a facsimile.

[0002]

2. Description of the Related Art Conventionally, a thermal head incorporated as a printer mechanism such as a word processor has a heat storage layer 12 made of a low heat conductive material such as glass deposited on the upper surface of a substrate 11 as shown in FIG. A heating resistor 13 and a pair of electrodes 14 are sequentially formed on the heat storage layer 12,
It has a deposited structure, and applies a predetermined electric power between the pair of electrodes 14 based on a print signal from the outside to selectively heat the heating resistor 13 by Joule heat.
The generated heat is conducted to the thermosensitive recording medium to form a predetermined printed image on the thermosensitive recording medium, thereby functioning as a thermal head.

The substrate 11 supports the heat storage layer 12 on the upper surface of which the heating resistors 13 and the like are adhered, and
It is for absorbing a part of heat of the heat storage layer 12 to maintain the temperature state of the heat storage layer 12 in a good condition, and is usually formed of a ceramic material such as alumina ceramics.

The heat storage layer 12 is for accumulating the heat generated by the heat generating resistor 13 to bring the temperature of the heat generating resistor 13 to a predetermined temperature required for printing in a short time, and is excellent in heat resistance. It is formed of a low thermal conductivity material such as glass having a high softening point of 700 ° C. or higher.

However, in this conventional thermal head, since the thermal conductivity of the alumina ceramics forming the substrate 11 is relatively small at 25.1 W / m · k,
When high-speed printing is performed by increasing the electric power applied to the heating resistor 13 in order to bring the temperature of the heating resistor 13 to the predetermined temperature required for printing in a short time, the temperature of the heat storage layer 12 can be quickly cooled. However, when printing the next line, the printing density becomes extremely high and uneven density is formed, or even when not printing, unnecessary printing is formed. Had.

Therefore, in order to solve the above-mentioned drawbacks, it is possible to improve the heat dissipation of the substrate 11 by forming the substrate with a material having good thermal conductivity (aluminum thermal conductivity: 20 to 24 W / m · k) such as aluminum. Is being considered.

However, the substrate 11 of the thermal head
In the case where the heat-generating layer 12 is formed of aluminum, the melting temperature of aluminum forming the substrate 11 is relatively low at 660 ° C. Therefore, when the heat storage layer 12 is formed on the substrate 11 by the well-known thick film method, the high softening point glass Is baked on the substrate 11 made of aluminum, the substrate 11 is softened and deformed before the glass is melted.

For this reason, when the substrate 11 of the thermal head is made of aluminum or the like, it is necessary to form the heat storage layer 12 with low softening point glass (softening temperature: 400 to 500 ° C.).

However, when the heat storage layer 12 is formed of a glass having a low softening point, the heat generation temperature (250 to 300 ° C.) of the heat generation resistor 13 is relatively close to the softening temperature of the heat storage layer 12, and therefore the heat generation resistor 13 is formed. When the Joule heat is repeatedly generated, the heat storage layer 12 is gradually deformed by the heat of the heat generating resistor 13 and a crack is generated in the heat generating resistor 13 applied thereon.

[0010]

The present invention has been devised in view of the above-mentioned drawbacks, and a heating resistor is deposited on a substrate made of at least one of aluminum, copper, iron and alloys thereof. Directly attach the thin glass heat storage member
It is characterized in that it is attached via solder.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of a thermal head of the present invention, in which 1 is a substrate, 2 is a heat storage member, 3 is solder, 4 is a heating resistor, and 5 is a pair of electrodes.

The substrate 1 is made of at least one of aluminum, copper, iron and alloys thereof, and a heat accumulating member 2 made of thin glass having a heating resistor 3 is directly soldered on the substrate 1. It is attached through.

The substrate 1 supports the heat storage member 2 on its upper surface and absorbs a part of heat in the heat storage member 2 described later to cool the heat storage member 2 in a short time. , Al-Mg-Si alloy with a thickness of 5 mm.

The substrate 1 made of this Al--Mg--Si alloy or the like has an extremely large thermal conductivity of 200 W / m.k,
Since the heat generating resistor 4 has a high heat dissipation property, the temperature of the heat generating resistor 4 is set to a predetermined temperature required for printing in a short time, so
Even when high-speed printing is performed by applying a large amount of electric power to the heat storage member 2, after the printing is completed, the heat storage member 2 and the substrate 1 can be cooled well in a short time, and good printing without uneven density or tailing can be achieved. It becomes possible to form an image.

When the substrate 1 is made of an Al--Mg--Si alloy, it is manufactured by adopting a conventionally known metal working method.

Further, the heat storage member 2 supported on the upper surface of the substrate 1 is for accumulating heat generated by the heat generating resistor 4 and setting the temperature of the heat generating resistor 4 to a predetermined temperature necessary for printing in a short time. As such a heat storage member 2, for example, a thin glass plate having a thickness of about 30 μm is used.

The thin glass used as the heat storage member 2 has, for example, a thermal conductivity of 0.9 W / m · k and a softening point of 70.
It is formed of low-alkali glass at 0 to 800 ° C., more specifically, borosilicate glass, and is manufactured by forming a glass material into a plate shape and then polishing the surface.

As described above, by forming the heat storage member 2 by using the thin plate glass made of the high softening point glass having the softening point of 700 to 800 ° C., the heating resistor 4 is repeatedly heated at a temperature of 250 to 300 ° C. by Joule heat generation. Even if it is done, the heat storage member 2 is not deformed and cracks are not formed in the heat generating resistor 4, and the life of the heat generating resistor 4 is lengthened to allow the thermal head to function well for a long period of time.

A plurality of heat generating resistors 4 and a pair of electrodes 5 are sequentially deposited on the upper surface of the heat storage member 2.

The heating resistor 4 is made of, for example, tantalum nitride or the like, and has a predetermined electric resistivity, so that when an electric power is applied from an external power source through the pair of electrodes 5. Joule heat is generated, and the temperature required to form a printed image on a thermosensitive recording medium is, for example, 200 ° C
It exotherms to a temperature of 350 ° C.

The pair of electrodes 5 deposited on the heating resistor 4 is made of a metal material such as aluminum.
The pair of electrodes 5 have a function of applying a predetermined electric power required for causing Joule heat generation to the heating resistor 4.

The plurality of heat generating resistors 4 and the pair of electrodes 5 have a predetermined pattern on the upper surface of the heat storage member 2 attached on the substrate 1 by adopting the conventionally known sputtering method and photolithography technique. , A predetermined thickness (the heating resistor 4 has a thickness of 0.01 to 0.5 μm, the pair of electrodes 5 has a thickness of 0.
It is formed with a thickness of 5 to 2.0 μm.

Between the substrate 1 and the heat storage member 2,
A solder 3 for bonding the both is interposed.

As the solder 3, a Pb-Sn type solder is used, and more specifically, Cerasolzer # 297 (trade name) manufactured by Asahi Glass Co., Ltd. is preferably used.

This Cerasolzer # 297 comprises glass forming the heat storage member 2 and aluminum, copper forming the substrate 1.
It can firmly bond iron or these alloys by chemical bonding, and its melting temperature is set to 297 ° C.

Therefore, the temperature required for melting the solder 3 is about 300 ° C., which is sufficiently lower than the melting temperature of the aluminum alloy (melting temperature: 660 ° C.), so that the heat storage member 2 is placed on the upper surface of the substrate 1. The substrate 1 is not melted by heat when applied.

The thermal conductivity of this solder 3 is about 35 W / m.
k and the high softening point glass that forms the heat storage member 2, the heat conduction from the heat storage member 2 to the substrate 1 is not hindered by the solder 3, and good high-speed printing is possible. it can.

Further, the melting temperature of the solder 3 is 297 ° C., which is set higher than the heat (about 40 ° C.) applied near the interface between the heat storage member 2 and the substrate 1 when driving the thermal head. Therefore, even when the heating resistor 4 is repeatedly heated, there is no fear that the solder 3 is heated and melted, and the heat storage member 2 can always be firmly attached to the upper surface of the substrate 1. .

In order to bond the heat storage member 2 onto the substrate 1, first, a predetermined solder paste is applied on the upper surface of the substrate 1 in an amount of 10 to 50 μm.
Print coating to a thickness of m, and then heat storage member 2 on top of it.
And then reflow at a temperature of 300 ° C for 5 minutes.

At this time, if the surface of the substrate 1 to which the heat storage member 2 is solder-bonded is oxidized by alumite treatment or the like, the solder 3 is well chemically bonded to oxygen on the substrate surface, and the substrate 1 and the heat storage are The member 2 can be joined more firmly. Therefore, it is preferable to oxidize the surface of the substrate 1 to which the heat storage member 2 is soldered.

Thus, the thermal head described above applies a predetermined electric power between the pair of electrodes 5 based on a print signal from the outside to selectively cause the heating resistor 4 to generate Joule heat and to generate the generated heat. It conducts to the thermal recording medium, and functions as a thermal head by forming a predetermined print image on the thermal recording medium.

The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the scope of the present invention. For example, in the thermal head of FIG. In order to improve wear resistance and corrosion resistance, the heating resistor 4 and the like may be covered with a protective film made of silicon nitride or the like.

[0034]

According to the thermal head of the present invention, even when high-speed printing is performed, the heat storage member and the substrate are satisfactorily cooled in a short time to form a good printed image without density unevenness or tailing. In addition, the life of the heating resistor can be extended and the thermal head can function well for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a thermal head of the present invention.

FIG. 2 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 1 ... Substrate 2 ... Heat storage member 3 ... Solder 4 ... Heating resistor

Claims (1)

[Claims] 1. A thin glass heat storage member for attaching a heating resistor is directly attached to a substrate made of at least one of aluminum, copper, iron, and alloys thereof by soldering. A thermal head that is characterized by