JPH04201357A - Thick film type thermal head and its manufacture - Google Patents

Abstract

PURPOSE:To improve the continuity of printing dots by a method wherein a smoothing layer is provided on the top of a wear-resistant layer, and the printing surface is pressed by a flat and continuous surface. CONSTITUTION:On the top of a wear-resistant layer 5, a smoothing layer 6 is continuously provided, groove-shaped recessed parts 7 are filled, and the top surface forms a continuous flat surface in a range which includes a plurality of heating resistor couples 4. When voltage is selectively applied from an individual electrode, a resistor 4 is heated, and printing is performed on a printing surface which is pressed by the upper surface of the layer 6, and since the layer 6 has a flat upper surface, heat is conducted to the whole surface of the pressing surface, and the continuity of printing dots in the major scanning direction becomes better. For the manufacture of the layer 6, a photosensitive resist 8 is formed on the layer 5, and openings 9 are provided by performing exposure and development. In the openings 9, a paste of lead glass is filled and dried. After drying, wrapping is performed, and after calcining the resist 8 by burn off, it is polished, and the upper surface is finished into a flat surface with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is widely used in thermal color recording devices or thermal transfer recording devices. In particular, the present invention relates to a thick film thermal head that has good continuity of printed dots and excellent energy efficiency in printing, and a method for manufacturing the same.

(Prior Art) As a thick film type thermal head used in a recording section of a thermosensitive color recording device, a thermal transfer recording device, etc., for example, the one shown in FIG. 3 is conventionally known.

FIG. 3 is a schematic diagram showing the structure of a conventional thick-film thermal head, in which (a) is a plan view, (b), and (c) are lines C-C shown in (a). , is a sectional view taken along line DD.

A common electrode 12 and individual electrodes 13 are formed on an insulating substrate 11, and a parallel projecting portion of the common electrode 12 and a plurality of individual electrodes 13 arranged in parallel in the main scanning direction face each other in the sub-scanning direction. These tips are connected by heating resistors 14 that are independent of each other and arranged in parallel in the main scanning direction. This heating resistor 14 is covered with a glass wear-resistant layer 15 formed by screen printing and firing.

In such a thermal head, when a voltage is selectively applied from the plurality of individual electrodes 13, the heating resistor 14 generates heat and prints.

At this time, in the thick-film type thermal head, the heating resistor 14 has a large thickness, and the heating resistor portion has a convex shape, and only the upper surface of this convex portion is pressed against the printing surface. For this reason, it has the advantage that the pressing force is large (and the energy efficiency in printing is improved).

(Problem to be Solved by the Invention) However, the heating resistor 14 formed by printing and firing a paste of heating resistor material has a diameter of about 5 μm to 30 μm.
It has a thickness of about .mu.m, and even after the wear-resistant layer 15 is applied, it still has groove-like recesses 17 between the independent heating resistors 14. For this reason, the upper surface of the wear-resistant layer 15 in contact with the printing surface is not continuous in the main scanning direction, and heat conduction is interrupted, resulting in poor connection of printed dots in the main scanning direction. This becomes noticeable in the case of so-called solid black printing, in which the entire surface is printed in black, and there is a problem that the image quality deteriorates.

It is also possible to cover the heating resistor portion with a thick wear-resistant layer and fill in the groove-like recesses between the independent heat-generating resistors, but when such a wear-resistant layer is applied, the contact area between the heat generating resistor and the printed surface is reduced. It is not possible to take advantage of the advantages of the thick-film thermal head, which is large and has a large pressing force.

In addition, when a wear-resistant layer is screen printed on a heating resistor formed by printing and firing, printing unevenness occurs.
The wear-resistant layer thickness undulates at intervals of about 2 mm to 4 mm. Such unevenness in the thickness of the abrasion-resistant layer causes a difference in the pressing force against the recording paper, causing unevenness in print density and deteriorating image quality.

The present invention has been made in view of the above-mentioned problems, and it improves the continuity of printed dots (and makes the pressing force on the recording paper even, resulting in heavy and double-sided printing), as well as improving the energy efficiency of printing. An object of the present invention is to provide a good thick film type thermal head and a method for manufacturing the same.

(Means for Solving the Problems) In order to achieve the above object, the present invention has a common electrode and a plurality of individual electrodes facing each other in the sub-scanning direction on an insulating substrate, each of which is formed by an independent heating resistor. The connected thick-film thermal head includes a wear-resistant layer that covers the heat-generating resistor, and multiple heat-generating resistors laminated on top of the wear-resistant layer and arranged in the main scanning direction. It shall have a smoothing layer that continuously covers the area and has a flat upper surface.

The method for manufacturing the thick-film thermal head described above includes forming a common electrode and individual electrodes on an insulating substrate, forming a heating resistor to connect these, and printing and baking a wear-resistant layer covering the heating resistor. A resist is formed by forming a resist that includes multiple heating resistors arranged in parallel in the main scanning direction and has an opening that is approximately the same or slightly larger than the resist, and then prints a paste of the material that forms the smoothing layer. The method for manufacturing a thick-film thermal head includes the steps of embedding in the opening of the resist, firing the smoothing layer, and burning off the resist.

(Function) In the thick film type thermal head according to claim 1, a smoothing layer is further provided on the wear-resistant layer covering the heating resistor, and this smoothing layer is a layer on which the wear-resistant layer is applied. Afterwards, the groove-like recesses formed between the heating resistors are filled, and the area including the plurality of heating resistors is extended to have a flat upper surface.
The printed surface is pressed by a continuous surface of a plurality of dots, and heat can be conducted to the entire surface of the pressed surface.

This improves the connection of printed dots in the main scanning direction and improves the image quality when solid black is printed.

Furthermore, since the top surface of the smoothing layer is finished flat, it is pressed against the printing surface with uniform pressure, and high image quality can be obtained without causing a difference in density in the printing.

Furthermore, since the smoothing layer is provided in an area that is approximately the same or slightly wider than the plurality of heating resistors, this area has a convex shape, and the upper surface of the convex portion is the same as that of the heating resistors. Although it is slightly wider than the area, only this part is pressed against the printing surface, so the pressing force is high and energy efficiency is good.

The method for manufacturing a thick-film thermal head according to claim 2 includes forming electrodes and a heating resistor, applying a wear-resistant layer, and then using a resist and baking the opening to form a smoothing layer. A smoothing layer is formed by embedding the paste.
Since openings can be precisely created in the resist,
A smoothing layer can be formed at a precise location. Alternatively, paste may be embedded in the openings of the resist, and after drying and before baking, excess paste may be removed so that the smoothing layer has an even thickness, and the upper surface may be lapped. ′
Therefore, the smoothing layer fills in the groove-like protrusions that occur between the heating resistors, and it also eliminates the uneven thickness of the wear-resistant layer caused by screen printing, making it possible to finish the top surface into a highly accurate flat surface. becomes.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view and a cross-sectional view showing a thick film thermal head which is an embodiment of the present invention, (a) is a plan view, (b)
) The figure (a) is a cross-sectional view taken along the line A-A shown in the figure, and the figure (C) is a cross-sectional view taken along the line B-B shown in the figure (a).

This thick film type thermal head uses a glazed alumina substrate.
A common electrode 2 and individual electrodes 3 made of a thin film of Au are formed thereon. The common electrode 2 has a plurality of overhanging parts 2b extending from the wiring part 2a in the sub-scanning direction, and the individual electrodes 3 are arranged to face these in the sub-scanning direction.

Independent heat generating resistors 4 are deposited on the opposing portions of the protruding portion 2b of the common electrode 2 and the individual electrodes 3, and are connected to each other by these.

A plurality of heating resistors 4 arranged in parallel in the main scanning direction are covered with a wear-resistant layer 5 made of glass. This wear-resistant layer 5 is usually thin (about 3 μm to 8 μm), whereas the heating resistor 4 has a thickness of about 5 μm to 30 μm.
When the film is deposited to cover the heating resistor 4, the upper surface of the heating resistor portion becomes convex, and groove-like recesses 7 are formed between adjacent heating resistors.

On the top of the wear-resistant layer 5, a smoothing layer 6 is continuously provided in an area that is approximately the same as or slightly larger than the area including the plurality of heating resistors, and this smoothing layer 6 has the above-mentioned groove shape. The concave portion 7 is filled in, and the unevenness on the upper surface of the wear-resistant layer is eliminated, so that the upper surface forms a continuous flat surface in the range including the plurality of heating resistors 4.

The material of this smoothing layer 6 is preferably glass formed by low-temperature firing, and for example, lead glass containing about 70% to 80% PB can be used. In addition, not only the above-mentioned materials, but any material that can fill the groove-like recesses 7 between adjacent heating resistors and finish the upper surface smoothly can be used as the material for the smoothing layer, and is durable. The same glass as that used for the wear layer 5 may be used.

In the thick-film thermal head as described above, when a voltage is selectively applied from the individual electrodes 3, the heating resistor 4 to which the voltage is applied generates heat, and the printing surface pressed by the upper surface of the smoothing layer 6 prints. It is done. At this time, since the smoothing layer 6 has a flat upper surface that is continuous in the range that includes the plurality of heating resistors 4, the printing surface is pressed with a continuous surface for the plurality of dots, and the entire surface of the pressing surface is pressed. Heat can be conducted, and the connection between printed dots in the main scanning direction is improved.

Also, since the top surface of the smoothing layer 6 is finished flat,
The printing surface is pressed with even pressure, resulting in high image quality with no difference in density between printed dots.

Furthermore, since only the upper surface of the smoothing layer 6 is pressed against the printing surface, the pressing force is high and energy efficiency is good.

If the smoothing layer 6 is made of a soft and easily abrasive material such as lead glass, the upper surface of the smoothing layer may repeatedly come into contact with the printed surface and wear out if used continuously.

However, under the smoothing layer 6 there is a wear-resistant layer 5 made of a material that does not wear easily.
Even if a part of the heating resistor 4 is exposed, the groove-shaped recess 7 between the heating resistors 4
The smoothing layer 6 remains buried in the recessed portion of the wear-resistant layer 5 on the upper surface, and the upper surface in the area including the plurality of heat generating resistors 4 is maintained in a continuous plane.

Next, a method for manufacturing the above-mentioned thick film type thermal head will be explained.

FIG. 2 is an explanatory diagram showing an embodiment of the method for manufacturing a thick film type thermal head according to claim 2.

First, as shown in FIGS. 2(a) and 2(b), an Au film is deposited on a glazed alumina substrate 1, which is an insulating substrate, and a common electrode 2 and individual electrodes 3 are formed by photolithography. A plurality of heating resistors 4 which are independent of each other in the main scanning direction are formed in the portion where the overhanging portion of the common electrode 2 and the individual electrodes 3 face each other, and a wear-resistant layer 5 covering them is formed by screen printing.

Next, as shown in FIGS. 2(c) and 2(d), a photosensitive resist 8 having a thickness of about 10 μm to 30 μm is formed on the wear-resistant layer 5 using a spin cord or the like, and is exposed and developed. As a result, an accurate opening 9 is provided in an area that includes a plurality of heat generating resistors arranged in parallel in the main scanning direction and is approximately the same or slightly wider than the heat generating resistors.

A lead glass paste is filled into the opening 9 by screen printing and dried. After drying, remove the deposited film on the resist and wrap it with a wrapping sheet so that the upper surface of the part embedded in the opening forms the same plane as the upper surface of the resist (Figure 2, (e) and (f)). .

Thereafter, this is baked and the resist 8 is burnt off to form a smoothing layer 6 as shown in FIGS. 2(g) and 2(h). After firing, the upper surface of the smoothing layer 6 is further polished with a lapping sheet to finish the upper surface into a highly accurate planar shape.

In the above manufacturing method, to form the smoothing layer 6 on the wear-resistant layer 5, a photosensitive resist 8 is used to form openings 9 by exposure and development, and a lead glass paste is applied to the openings 9. The smoothing layer 6 is formed to have an arbitrary thickness within a range of about 30 μm or less, and the smoothing layer 6 is formed accurately in a limited area. In addition, the top surface can be flattened by embedding lead glass paste and lapping after drying, eliminating uneven layer thickness of the wear-resistant layer 5 formed by screen printing and baking, and making the top surface highly accurate. It can be finished flat.

Furthermore, by using lead glass as the material for the smoothing layer 6, it can be fired at a lower temperature than the glass used for the wear-resistant layer 5, and the wear-resistant layer is not melted during firing. The chemical layer 6 can be formed.

Furthermore, lead glass is softer than the glass used for the wear-resistant layer 5 even after firing, and can be polished with a lapping sheet to improve the smoothness of the top surface.

(Effects of the Invention) As explained above, according to the thick-film thermal helad of the present invention, since the smoothing layer has a continuous flat top surface within the range including the plurality of heating resistors, The connection of printed dots in the main scanning direction is improved. Furthermore, since the top surface is finished flat, there is no uneven density of printed dots.

Furthermore, since the smoothing layer includes the heating resistor and is provided only in an area that is approximately the same or slightly wider than the heating resistor, the pressing force against the printing surface is increased and energy efficiency is improved.

Therefore, a thick film thermal head with high image quality and good energy efficiency can be obtained.

Furthermore, according to the method for manufacturing a thick-film thermal head according to claim 2, the smoothing layer is formed by embedding and baking a paste in the openings of the resist. The smoothing layer can be formed accurately in the defined area, and a flat upper surface can be easily formed without uneven thickness.

[Brief explanation of the drawing]

FIG. 1 is a schematic structural diagram showing a thick film type thermal head which is an embodiment of the invention as set forth in claim 1, and FIG. 2 is a schematic structural diagram showing an embodiment of the invention as set forth in claim 2. An explanatory diagram showing a method of manufacturing a certain thick film type thermal head. FIG. 3 is a schematic structural diagram showing a conventional thick film type thermal head. ■...Insulating substrate 2...Common electrode 3...Individual electrode 4...Heating resistor 5...Wear-resistant layer 6...Smoothing layer 8... Resist figure 1

Claims (2)

[Claims] (1) A plurality of heating resistors in which a common electrode and a plurality of individual electrodes face each other in the sub-scanning direction on an insulating substrate, and the common electrode and the plurality of individual electrodes are arranged independently in parallel in the main-scanning direction. In a thick-film thermal head connected by A thick film type thermal head characterized by having a covering and a smoothing layer with a flat upper surface. (2) A common electrode and individual electrodes are formed on an insulating substrate, a heating resistor is formed to connect these, a wear-resistant layer covering the heating resistor is formed by printing and baking, and main scanning is performed. A resist is formed that includes a plurality of heating resistors arranged in parallel in the direction, and has an opening that is approximately the same or slightly larger than the resist, and a paste of a material that forms a smoothing layer is embedded in the opening of the resist by printing. A method for manufacturing a thick-film thermal head, comprising the steps of firing a smoothing layer and burning off a resist.