JPH04110165A - Thermal head and manufacture thereof - Google Patents

Abstract

PURPOSE:To transmit heat from a heating element to a recording medium efficiently, lower a power demand, and eliminate the reduction of a printing dot size by a method wherein a band-form metallic layer is provided between a first insulating protective layer and a second insulating protective layer, which form a two-layer structure, so as to correspondingly extend above the arrangement of heating elements. CONSTITUTION:A plurality of heating elements 4 arranged separately from each other and electrodes 5a, 5b supplying an electric current to these heating elements are formed on an insulating substrate 3. A first insulating protective layer 6a is formed so as to cover the heating elements 4 and the electrodes 5a, 5b. A paste of a metal organic material is applied so as to cover the first insulating protective layer 6a. The paste is calcined to form a metal film layer. The metal film layer is patterned by a photolithography method to form a band-form metallic layer 7 corresponding to the arrangement of the heating elements 4. A second insulating protective layer is formed so as to cover the band-form metallic layer 7 and the first insulating protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head in a thermal recording device used as a print output means of various information processing devices such as facsimiles and printers, and a method for manufacturing the same.

[Prior Art] This type of thermal head includes a plurality of heating elements arranged on an insulating substrate, electrodes for supplying current to these heating elements, and selectively causing the heating elements to generate heat through the electrodes. In this way, characters or figures are recorded directly on thermal recording paper or on a recording medium such as plain paper via an ink donor sheet.

FIG. 7 is a partially cutaway plan view illustrating an example of the structure of a conventional thermal head, and FIG. 8 is a sectional view taken along the line AA in FIG. 7. In FIG. 7, X indicates the main scanning direction when this thermal head is installed in a thermal transfer recording device, and Y indicates the sub-scanning direction.

7 and 8, l is a ceramic substrate, 2 is a thin glass layer, 3 is an insulating substrate consisting of the ceramic substrate 1 and the thin glass layer 2, 4 is a heating resistor (hereinafter simply referred to as a heating element), 5a 5b is a common electrode, 5b is an individual electrode, and 6 is an insulating protective layer made of an insulator.

The heating element 4 is placed on the thin glass layer 2 constituting the insulating substrate 3.
They are formed separately to constitute a plurality of individual heat generating parts, and the direction in which they are arranged is the main scanning direction X.

A common electrode 5 covering the glass thin layer 2 and connected to one end of the heating element 4 in the Y direction in common to the plurality of heating elements.
a is formed.

Similarly, each heating element 4 is provided at the other end of the heating element 4 in the Y direction.
Individual electrodes 5b are formed which are connected to each of the electrodes separately.

The exposed portion 4a of the heating element 4 sandwiched between the common electrode 5a and the individual electrodes 5b mainly forms a heating section.

An insulating protective layer 5 made of an insulating material such as glass or ceramics is formed to cover the common electrode 5a, the individual electrodes 5b, and the exposed portion 4a of the heating element 4.

This insulating protective layer 6 has the function of preventing oxidation of the exposed portion 4a, reducing wear on the thermal head due to the recording medium that comes into contact with the thermal head, and improves surface smoothness.

During actual recording, a recording medium such as heat-sensitive recording paper or plain paper with an ink donor film is pressed onto this insulating protective layer 6, and characters or figures (hereinafter referred to as characters and the recording is referred to as printing) are printed. A current is applied to individual electrodes selected according to the data, and each selected heating element is used as a recording unit (hereinafter referred to as a dot).

The heating element 4 generates heat when the current is applied, and this heat reaches the recording medium through the insulating protective layer 6, which is the recording medium.
Printing is performed by coloring with a coloring material on thermosensitive recording paper or by melting and transferring ink from an ink donor film.

By the way, as described above, the insulating protective layer 6, which is a surface material that contacts the recording medium and transmits heat from the heating element 4 to the recording medium, is made of silicon dioxide (SiO□) or tantalum pentoxide (Taz O5). ) and other insulators mainly made of glass-based materials are used.

Glass-based materials are mainly used as this insulator, but insulators, including this glass-based material, that serve as the protective layer of the thermal head have low thermal conductivity to begin with, and also have poor contact with the recording medium. In order to protect the thermal head from wear caused by the thermal head, it is necessary to form a layer with a certain thickness, so a distance at least equal to the thickness of the protective layer is formed between the heating element 4 and the recording medium.

Therefore, the area of heat distribution on the recording medium is smaller than the size (area) of the heating element 4.

As a result, the gaps between the dots become large, resulting in printing results that are poorly connected.

That is, in general, the heat distribution of a heating element is maximum at the center of the heating element and gradually decreases from the center to the periphery, so as the distance from the heating element increases, The effective amount of heat achieved (the heat required to develop the coloring material in thermal recording paper, the heat required to melt the ink in those using an ink donor film)
becomes less.

In order to solve this problem, as disclosed in Japanese Patent Publication No. 54-24300, for heating elements that are formed separately from each other, a protective layer covering the heating elements is provided to accommodate each heating element. Some have a thin metal layer for each heating element.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, in order to increase the size of the printed dots, it is necessary to increase the current flowing through the heating element, which causes thermal deterioration of the heating element and also reduces the performance of the recording device. There is a problem that power consumption increases.

Furthermore, in the thermal head disclosed in the above publication, the metal thin layer formed above the heating element relays the heat from the heating element to the recording medium, making it possible to obtain the desired crossroad dot size without particularly increasing the current. can.

However, since the recording medium is in direct contact with the thin metal layer, even if the thin metal layer is formed using a metal material with good wear resistance, the thin layer itself is not formed by vapor deposition or plating. Because of this, it is easily subject to wear and damage, which shortens the life of the thermal head.

It is an object of the present invention to solve the problems of the prior art described above, to efficiently transmit heat from a heating element to a recording medium, to achieve low power consumption, to eliminate reduction in print dot size, and to create a thermal head with a long life. The object of the present invention is to provide a manufacturing method thereof.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides an insulating substrate (3)
A thermal head comprising a plurality of heating elements (4) arranged separately from each other on top of the thermal head, and an insulating protective film laminated to cover these heating elements (4), wherein the insulating protective film is laminated. The first insulating protective layer (6a
) and a second insulating protective layer (6b), the first insulating protective layer (6a) and the second insulating protective layer (6b) constituting the two-layer structure. It is characterized in that a band-shaped metal layer (7) is provided in between, extending above the heating elements in accordance with the arrangement of the heating elements.

The metal layer (7) is gold, silver, platinum, or nickel.

It is preferable to use a metal with high thermal conductivity such as molybdenum or tungsten, or an alloy of at least two of these metals.

In order to manufacture this thermal head, a plurality of heating elements (
4) and electrodes (5a,
5b) and forming a first insulating protective layer (6a, 5b) covering the heating element (4) and the electrodes (5a, 5b).
), forming a metal coating layer by coating the first insulating protective layer (6a) with a metal-organic paste and firing it; and photo-coating the metal coating layer. a step of forming a band-shaped metal layer (7) according to the arrangement of the heating elements (4) by patterning using a lithography technique; and a step of forming a second insulation protection layer by covering the band-shaped metal layer and the first insulation protection layer. The method is characterized by employing a step of forming a layer.

[Function] By interposing the highly thermally conductive metal layer (7) between the heating element (4) and the recording medium, the heat generated from the heating element (4) is transferred to the metal layer (7). and is transmitted toward the recording medium through the first insulating protective layer (6a) and the second insulating protective layer (6b).

By forming the metal layer (7) into a continuous strip in the direction in which the heating elements (4) are arranged, continuity can be obtained in the heat distribution between the heating elements (4) which are individually formed in correspondence with dots. Heating element (4
) The connection of printed dots in the arrangement direction becomes better.

The distribution of heat reaching the recording medium is approximately determined by the area of the metal layer.

Therefore, the size of the strip-shaped metal layer (7) in the direction perpendicular to the arrangement direction of the heating elements (4) is selected depending on the desired dot size.

Furthermore, by increasing this size, which is equal to the size in the same direction of the heating element (4), it is possible to avoid a decrease in the dot size due to the heat distribution of the heating element (4).

Further, by adopting a method of forming the metal layer by thermal decomposition of a metal organic substance, the bonding characteristics with the insulating protective layer are improved, and manufacturing equipment can be simplified.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partially cutaway top view illustrating the structure of a first embodiment of a thermal head according to the present invention, and FIG.
-A sectional view.

1 and 2, 1 is a ceramic substrate, 2 is a thin glass layer, 3 is an insulating substrate consisting of the ceramic substrate 1 and the thin glass layer 2, 4 is a heating resistor (hereinafter simply referred to as a heating element), 5a is a common electrode, 5b is an individual electrode, 6a is a first insulating protective layer, 6b is a second insulating protective layer, and 7 is a metal layer.

Moreover, the mutual structure of each part is the same as that described in FIGS. 7 and 8 above, except for the first insulating protective layer 6a, the second insulating protective layer 6b, and the metal layer 70, so a description thereof will be omitted.

The insulating substrate 3 has a thickness of 50 to 60 μm on the ceramic substrate 1.
A thin glass layer 2 having a certain thickness is formed.

On the thin glass layer 2 of this insulating substrate 3, individual heating elements 4 are provided corresponding to the printed dots.

The heating element 4 has a common electrode 5a for supplying heating current.
and individual electrodes 5b are provided.

The common electrode 5a is commonly connected to a plurality of individual heat generating elements 4 in the X direction (main scanning direction in the recording apparatus), which is the direction in which the heat generating elements 4 are arranged.

On the other hand, the individual electrodes 5b are provided independently on each heating element 4.

A first insulating protective layer 6a is provided to cover the heating element 4, the common electrode 5a, and the individual electrodes 5b.

A strip-shaped metal layer 7 is provided on the first insulating protective layer 6a, located above the heating element 4, and extending in the X direction.

A second insulating protective layer 6b having a thickness of 3 to 5 μm is deposited to cover the band-shaped metal layer 7 and the first insulating protective layer 6a.

In the embodiment shown in FIGS. 1 and 2, the metal layer 7 is
The width W1 is narrower than the width of the heating element 4 (although it is formed), the width W1 is selected depending on the size of the dots to be printed.

For example, as described above, the thickness of the first insulating protective layer 6a is 1 to 2 μm, and the thickness of the second insulating protective layer 6b is 3 to 5 μm.
When the density is 8 dots per 1 mm, Wl is preferably about 150 μm.

FIG. 3 is a schematic diagram illustrating the heat distribution of the thermal head of the first embodiment, in which 8 is the recording medium, 9a is the heat distribution curve of this embodiment, and 9b is the heat distribution curve of the prior art shown for comparison. In the distribution curve, 9c is an arrow indicating heat transfer, and the same symbols as in FIG. 2 correspond to the same parts.

In the figure, the second insulating protective layer 6b of the thermal head is in contact with the recording medium 8, and in a pressed state, current is applied from the individual electrodes 5b to the common electrode 5a.

This energization heats the heating element 4 connected between the individual electrode 5b and the common electrode 5a.

If there is no metal layer 7, the heat generated from the heating element 4 has a distribution as shown in the curve i9b shown in the figure.

Therefore, the recording dots on the recording medium 8 end up being much smaller than the size of the heating element 4.

On the other hand, when the metal layer 7 is present, the heat from the heating element 4 is transferred to the arrow 9c.
As shown in Figure 9a, the heat transfers to the metal layer 7 with good thermal conductivity and heats this metal layer 7, resulting in a heat distribution as shown in Figure 9a using the heated metal layer 7 as a heat source.

As a result, the size of the dots recorded on the recording medium 8 becomes the size of the metal layer 7.

FIG. 4 is a sectional view corresponding to the section AA in FIG. 1, explaining the structure of a second embodiment of the thermal head according to the present invention.

In the figure, the width W2 of the band-shaped metal layer 7 is made larger than the size of the heating element 4 in the same direction.

FIG. 5 is a schematic diagram illustrating the heat distribution of the thermal head of the second embodiment, and the same reference numerals as in FIG. 3 correspond to the same parts.

In the same figure, the heat generated from the heating element 4 has the same distribution as in the case of FIG. 3 above when the metal layer 7 is not present.
Because of the presence of the metal layer 7, as shown by the arrow 9c, the metal layer 7 moves to the metal layer 7 with good thermal conductivity, and this metal layer 7 is heated. The heat distribution becomes like that shown in the image.

Since the size of the metal layer 7 is larger than the size of the heating element 4,
The size of the recording dots on the recording medium 8 is large.

For high-density recording, the size of the heating elements 4 is reduced, but there is a limit to reducing the spacing between the heating elements, but as can be seen from the embodiments described above, According to the present invention, regardless of the size of the heating element 4, the size of the recording dot can be controlled by the size of the metal layer 7, and even when the heating element size is reduced for high-density recording, the size of the heating element can be controlled. A connection of recording dots in the arrangement direction (X direction) can be obtained, and clear recording can be obtained.

Next, a method for manufacturing the above-described thermal head will be described.

FIG. 6 is a schematic process diagram illustrating an example of a method for manufacturing a thermal head according to the present invention, and relates to a method for manufacturing the thermal head of the embodiment shown in FIG. 1.

Note that this figure schematically illustrates the layering process.

In the same figure, 50 to 60
An insulating substrate 3 provided with a glass layer 2 having a thickness of about μm
Prepare. ... (a) On this insulating substrate 3,
For example, a mixed metal organic solution 4a of Ir/Si/Bi is applied, dried and baked, and then a photoresist is applied, dried, exposed with a mask, and developed, and then a mixed aqueous solution of hydronic acid/nitric acid is applied. A photo-etching process is performed using as an etchant to form the heating element 4 separately.

... (b) After coating the gold metal organic paste on the glass layer 2 on which the heating element 4 has been separately formed, drying and firing, in the same manner as above,
A photoresist is applied, dried, exposed to light using a mask, developed, and then photoetched using an iodine/potassium iodide mixture as an etchant to form the common electrode 5.
a and the individual electrodes 5b are formed. (C) Next, glass paste is applied to the upper surfaces of the heating element 4, the common electrode 5a, and the individual electrodes 5b, dried, and fired to a thickness of approximately 1.
A first insulating protective layer 6a having a thickness of 2 μm is formed.・・・・・・
(d) On the first insulating protective layer 6a, a metal organic paste used to form the common electrode 5a and the individual electrodes 5b is applied, dried, and fired to form a metal film layer 7a. ...
(e) A photoresist is applied to this metal film layer 7a, dried, exposed to light using a mask, developed, and then photoetched using an iodine/potassium iodide mixture as an etchant to form a gold metal layer 7. form. At this time, the metal layer 7 is formed in the form of a single strap extending above the heat generating elements in the direction in which the heat generating elements 4 are arranged. (f) The width of this metal layer is determined according to the size of the dots to be printed, and is controlled by the size of the photomask pattern during mask exposure.

For example, as described above, at a printing density of 8 dots/mm, the width is approximately 150 μm.

Finally, a glass paste is applied to cover the upper surface of the metal layer 7, dried and fired to form a second insulating protective layer 6b having a thickness of about 3 to 5 μm. ...(g) The metal for forming the metal layer 7 in the present invention is:
In addition to the gold used in the examples, one or two or more alloys of silver, platinum-nickel, molybdenum, etc. can be used.

The above metals exhibit thermal conductivity nearly 200 times that of glass-based materials.

Note that the material is not limited to metal as long as it has high thermal conductivity, is chemically and physically compatible with the glass-based insulating protective layer, and is stable.

〔Effect of the invention〕

As explained above, according to the present invention, the size of the printed dot can be set by the size of the metal layer, regardless of the size of the heating element.

For example, when reducing the size of the heating element for high-density printing such as 16 dots l-/mm, the spacing between the heating elements is limited by manufacturing, and as a result, the width of the heating element becomes narrower, making it difficult to print. The connection between the dots becomes poor.

However, according to the present invention, the size of the heat source when viewed from the recording medium can be increased by the metal layer that is continuous in the arrangement direction above the heating element, so that the connection between the dots is improved and the printing quality can be improved. .

Furthermore, since the recording medium is heated through the metal layer, it is possible to reduce the occurrence of localized high-temperature parts (heat spots) of the heating element, which also has the effect of lengthening the life of the thermal head.

Furthermore, with the configuration of the present invention, it is possible to achieve high-efficiency printing with low power consumption, which makes it possible to obtain large-sized donts with the same applied power as in the past.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway top view illustrating the structure of a first embodiment of a thermal head according to the present invention, and FIG.
3 is a schematic diagram illustrating the heat distribution of the thermal head according to the first embodiment, and FIG. 4 is a schematic diagram illustrating the structure of the thermal head according to the second embodiment of the present invention. A sectional view corresponding to the A-A cross section, FIG. 5 is a schematic diagram illustrating the heat distribution of the thermal head of the second embodiment, and FIG. 6 is a schematic process diagram illustrating an example of the method for manufacturing the thermal head according to the present invention. 7 is a partially cutaway plan view illustrating an example of the structure of a conventional thermal head, and FIG. 8 is a sectional view taken along the line AA in FIG. 1. 1...Ceramink substrate, 2...Glass thin layer, 3
...Insulating substrate, 4...Heating resistor, 5a...
・Common electrode, 5b...Individual electrode, 6a...1st
Insulating protective layer, 6b...Second insulating protective layer, 7...
...Metal layer. Applicant Fuji Xerox Co., Ltd. Agent Yoji Onodera (2 others) Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Figure 1 Figure 8 1 La N.゛・１、＼7）、＼＼＼＼＼＼＼＼＼＼＼＼＼ November 30, 1990

Claims (1)

[Claims] 1. A thermal head comprising a plurality of heating elements arranged separately from each other on an insulating substrate, and an insulating protective film laminated to cover these heating elements, wherein the insulating protective film has a two-layer structure composed of a first insulating protective layer and a second insulating protective layer laminated, and the first insulating protective layer and the second insulating protective layer constituting the two-layer structure A thermal head characterized in that a band-shaped metal layer is provided between the heating elements and extending above the heating elements in accordance with the arrangement of the heating elements. 2. Forming, on an insulating substrate, a plurality of heating elements arranged separately from each other and electrodes for supplying current to these heating elements; a step of forming a protective layer; a step of forming a metal film layer by applying a metal-organic paste to cover the first insulating protective layer (6a) and firing it; forming a band-shaped metal layer according to the arrangement of the heating elements by patterning using a photolithography technique; and forming a second metal layer covering the band-shaped metal layer and the first insulating protective layer.
A method for manufacturing a thermal head, comprising: forming an insulating protective layer;