JPH05138906A - Thermal head and its manufacture - Google Patents

Abstract

PURPOSE:To form an image of high grade by using a metal base and projecting a section in which a heating element is disposed. CONSTITUTION:A belt-shaped protrusion 4 extending in the direction vertical to the paper face is formed on the surface of a metal base 2, and a heating element 8a is disposed and formed on the protrusion 4 through a heat insulated layer 6. The protrusion 4 of the metal base 2 is formed by extrusion process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in printers, facsimiles and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art A general type of thermal head is
This is a so-called flat type thermal head in which a heating element is formed on the main surface of a heating substrate. The plane type thermal head can be easily manufactured as a thin film type thermal head or a thick film type thermal head. However, if you try to print on a recording medium such as a plastic card or cardboard with a flat type thermal head, the plastic card cannot be bent greatly, so hit the protective cover provided on the same main plane as the heating element and print. There is a problem that it is difficult.

As a thermal head which is convenient for printing on a recording medium such as a plastic card which is difficult to bend, what is called an end surface type thermal head having a heating element formed on the end surface has been developed (Actual Development 59-59342).
Japanese Patent Laid-Open No. 60-19557, etc.).
However, in the end surface type thermal head, the end surface on which the heating element is formed is orthogonal to the main surface on which the electrodes are formed. Therefore, the process of forming a patterned heating element on the end face and connecting it to the electrode on the main surface is difficult and expensive even if manufactured.

Since it is difficult to form a heating element or the like patterned on the end face by a thin film process or a thick film process, the substrate is obliquely cut from the main surface to the end face, and the heating element or Attempts have also been made to use a thermal head called an inclined surface type that forms a part of the electrodes.
Still another attempt has been proposed in which a heating element array is formed on a curved surface. As an example of using such a curved surface, it has been reported that a glass coating layer is formed on a metal substrate having a curved surface, and a heating element and an electrode are formed thereon (see Japanese Patent Laid-Open No. 3-47977). ..

On the other hand, in order to use the G4 standard in a facsimile or a high speed printer, a thermal method is used in which a ceramic substrate covered with a glassy glaze layer is replaced with an insulating plate made of ceramic or a substrate obtained by applying polyimide on a metal plate. A head has been proposed (Japanese Patent Laid-Open No. 52-100245).
JP, JP-A-59-142167, JP-A-60
-167574). A thermal head using a substrate having a polyimide layer as a heat insulating layer is said to be suitable for high speed printing and low energy printing. As a thermal head for the purpose of obtaining a high-quality image, a partial glaze head in which a glassy glaze layer is partially formed in a belt shape on the substrate surface is used. In this case, the glaze layer is partially formed in a band shape only on the portion where the heating element is formed on the substrate, and the glaze layer is not formed on the other substrate surface.

[0006]

In the partial glaze head, when the substrate is an insulating material such as alumina ceramics, even if the electrode is arranged in the portion of the substrate where the glaze layer does not exist, the substrate and the electrode are not electrically connected. However, when a metal plate is used as the substrate, the electrodes cannot be arranged in the part without the glaze layer in the partial glaze layer. It is an object of the present invention to provide a thermal head that can obtain a high-quality image by using a metal substrate as a substrate and arranging a portion where heat generating elements are arranged to be higher than other portions of the substrate. It is what

[0007]

According to the present invention, in order to make a portion where heat generating elements are arranged more raised than other portions of the substrate, a strip-shaped protrusion is provided on the surface of the metal substrate, or the metal substrate is bent to be convex. A means such as using a striped portion or providing a band-shaped ridge on the heat insulating layer is used. The substrate in the present invention has a heat insulating layer formed on the surface of a metal substrate. As the heat insulating layer, a heat resistant resin or a thermosetting resin is used.
Extrusion or pressing is used to form strip-shaped protrusions or convex portions on the surface of the metal substrate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment. On the surface of the metal substrate 2, a strip-shaped ridge 4 extending in the direction perpendicular to the paper surface is formed. A heat insulating layer 6 is formed on the surface of the substrate 2 on which the ridge 4 is formed.
Are formed on the heat insulation layer 6, and the resistor 8 and the electrode 10 are formed on the heat insulation layer 6.
Are formed by a thin film process. The resistor 8 and the electrode 10 are patterned and include a selection electrode 12 for individually selecting a heating element and a common electrode 10 commonly connected to the heating element. The resistor 6a exposed between the electrodes 10 and 12 serves as a heating element. The protective film 14 covers the heating element and the electrodes 10 and 12 except for the bonding pad portion.

An example of the material of the embodiment shown in FIG. 1 will be described. As the metal substrate 2, a stainless plate or an aluminum alloy plate can be used. The heat insulation layer 6 is a polyimide layer,
It is a heat resistant resin layer such as a polyamide layer or a polyimide polyamide layer, or a thermosetting resin such as a silicone resin or an epoxy resin. As an example, a polyimide layer is used, and the thickness of the polyimide layer 6 after curing is about 15 μm. A Ta-based resistor such as TaSiO ₂ or TaN is used as the material of the resistor 8, and Al or Au—N is used as the electrodes 10 and 12.
iCr (NiCr is the lower layer) is used, and a silicon nitride film is used as the protective film 14. However, these materials are not limited to the examples, and materials generally used as the material of the thermal head may be used. In order to increase the adhesion strength between the heat insulation layer 6 and the resistor 8, SiO is formed on the heat insulation layer 6.
₂ or Ta ₂ O ₅ etc. hard dielectric thin film
It may be formed to a thickness of 3000Å. In the embodiment of FIG. 1, the strip-shaped ridge 4 is formed on the surface of the metal substrate 2. However, in order to perform such processing on the surface of the metal substrate 2, the ridge 4 is formed on the surface of the metal substrate 2 by extrusion, for example. 4 can be formed.

FIG. 2 shows a second embodiment. In the embodiment of FIG. 2, the substrate 22 is pressed so that a strip-shaped ridge 24 extending in the direction perpendicular to the paper surface of the drawing is formed on the surface of the metal substrate 22. On the surface of the substrate 22, the heating elements 8a are arranged on the ridges 24 along the ridges 24 with the heat insulating layer 6 interposed therebetween.
Alternatively, the common electrode 10 and the selection electrode 1 connected to the heating element 8a
The structure of the thermal head including 2 is the same as that of the embodiment of FIG. The embodiment of FIG. 2 is characterized in that press working is used to provide the ridge 24 on the metal substrate 22.

FIG. 3 shows a third embodiment. Metal substrate 3
2 is bent by press working, and in the example of the figure, a ridge line 34 extending in the direction perpendicular to the paper surface is formed. As in the embodiment of FIG. 1, the heat insulating layer 6 is formed on the surface of the substrate having the ridge 34, and the heating elements 8a are formed on the ridge 34 along the ridge 34 and are connected to the heating element 8a. The common electrode 10 and the selection electrode 12 are also formed, and the protective film 14 is also formed. The embodiment of FIG. 3 is characterized in that the substrate 32 is bent.

FIG. 4 shows a fourth embodiment. In FIG. 4, the metal substrate 42 is a flat plate substrate having a flat surface. In the example of the figure, a strip-shaped ridge 48 extending in the direction perpendicular to the paper surface is formed in the heat retaining layer 46 so as to have a ridge in the portion where the heating element is formed. As in the embodiment of FIG. 1, the resistor 8 is formed on the heat retaining layer 46 including the ridge 48, the electrodes 10 and 12 are formed, and the portion exposed from the electrodes 10 and 12 is the heating element 8a.
The same applies to any of the examples. The protective film 14 is similarly formed. In the embodiment of FIG. 4, for example, a polyimide layer is formed as the heat retaining layer 46 by coating using a roll coater, and then the protrusion 48 can be formed by polishing.

In the embodiment shown in FIGS. 1 to 3, the protrusions 4, 24 and 34 are formed on the metal substrate by extrusion or pressing, and then the heat insulating layer is coated on the surface of the metal substrate. For coating, for example, a resin liquid is applied using a roll coater and baked. After that, a resistor film and an electrode film are laminated and formed by sputtering or vacuum deposition, and patterning is performed by photolithography and etching to form the resistor 8 and the electrode 1.
0 and 12 are formed to obtain the heating element 8a. Then, a protective film 14 is deposited and patterned so as to expose the bonding pads. In the embodiment of FIG. 4, the flat metal substrate 4 is used.
After the heat insulating layer 46 is coated on the surface 2, the heat insulating layer 46 is polished so that the protrusions 48 are left in the portions where the heating elements are arranged. After that, a resistor film and an electrode film are laminated and formed by sputtering or a vacuum deposition method, patterned by photolithography and etching, and then a protective film 14 is deposited and patterned. Although the embodiment shows a thin film thermal head, the present invention can also be applied to a thick film thermal head formed by thick film printing.

[0014]

According to the present invention, since the portion where the heating element is formed is raised more than the other portion of the substrate, the contact with the recording medium is improved and the printing quality is improved. Printing can be performed even on a hard recording medium. Moreover, unlike the conventional partial glaze head, since the heat insulating layer of the insulator is formed on the entire surface of the substrate, the metal substrate can be used as the substrate, and the cost is reduced. Since the metal substrate is used in the present invention, the protrusion can be easily formed by extrusion or pressing in order to raise the portion where the heating elements are arranged.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment.

FIG. 2 is a sectional view showing a second embodiment.

FIG. 3 is a sectional view showing a third embodiment.

FIG. 4 is a sectional view showing a fourth embodiment.

[Explanation of symbols]

 2,22,32,42 Metal substrate 4,24 Substrate ridge 6,46 Insulating layer polyimide layer 8 Resistor 10,12 Electrode 8a Heating element 14 Protective film 34 Bent metal substrate ridge line 48 Raising due to heat insulating layer

Claims (7)

[Claims] 1. A strip-shaped ridge is provided on the surface of a metal substrate,
A heat insulating layer is formed on the surface of the metal substrate, a heating element is arranged on the ridge along the ridge, and a metal wiring connected to the heating element is arranged on the heat insulating layer. And a thermal head in which at least the heating element is covered with a protective film. 2. A metal substrate is bent, a heat insulating layer is formed on a convex surface of the metal substrate, and a ridge line is formed on the ridge line formed by bending the substrate on the heat insulating layer. A thermal head in which heat generating elements are arranged along with each other, metal wiring connected to the heat generating element is arranged on the heat retaining layer, and at least the heat generating element is covered with a protective film. 3. A heat insulating layer is formed on a flat metal substrate surface, and a strip-shaped ridge is provided on the heat insulating layer, and a heating element is arranged on the ridge of the heat insulating layer along the ridge.
A thermal head in which metal wiring connected to the heating element is arranged on the heat retaining layer, and at least the heating element is covered with a protective film. 4. The thermal head according to claim 1, 2 or 3, wherein the heat insulation layer is a heat resistant resin or a thermosetting resin. 5. A strip-shaped ridge is provided on the surface of a metal substrate by extrusion, a heat retaining layer is formed on the surface of the metal substrate, and heating elements are arranged on the ridge along the ridge. A method of manufacturing a thermal head, comprising forming a metal wire connected to the heating element on the heat insulation layer and covering at least the heating element with a protective film. 6. A band-shaped ridge is provided on the surface of a metal substrate by press working, a heat retaining layer is formed on the surface of the metal substrate, and heating elements are arranged on the ridge along the ridge. A method of manufacturing a thermal head, comprising forming a metal wire connected to the heating element on the heat insulation layer and covering at least the heating element with a protective film. 7. A metal substrate is bent by press working,
A heat insulating layer is formed on the convex surface of the metal substrate, and a heating element is formed along the ridge line on the ridge line formed by bending the substrate on the heat insulating layer, and A method of manufacturing a thermal head, characterized in that metal wiring connected to the heating element is formed on the heat retaining layer, and at least the heating element is covered with a protective film.