JPH08183197A - Manufacture of thermal head - Google Patents

Abstract

PURPOSE: To make an outline of a heat generating part clear when a heat generating resistor is formed by the thick film technique so as to improve print images by supplying pulse current in between individual electrodes and lowering a resistance value of the heat generating resistor at this part so as to form a separate heat generating part individually. CONSTITUTION: A resistance value of a heat generating resistor 6 is adjusted by the pulse trimming method. In this step, the resistance value of the heat generating resistor 6 is constant in its longitudinal direction, so that a part of the electric current flowing in between electrodes leaks in the longitudinal direction of the heat generating resistor 6, a heat generating part in the heat generating resistor 6 becomes unclear and consuming power increases. Accordingly, by applying a pulse current having a pulse width of 1μsec or below in between an exposure part 4a of a common electrode pullout part 4 and an individual electrode 5, the resistance value of the heat generating resistor 6 in between a tip 4b of an opposed common electrode pullout part 4 and a tip 5b of the individual electrode 5 is partially lowered, in which a heat generating part 6' is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thermal head used in a thermal recording apparatus such as a thermal recording type facsimile or a thermal printer, and more particularly to a belt-shaped heat generating resistor formed by a thick film technique. The present invention relates to a method of manufacturing a thermal head having a body.

[0002]

2. Description of the Related Art Thermal heads are widely used as a printing and recording apparatus because they have the advantages of low noise during printing and easy handling because they do not require a developing / fixing process. . The thermal head has a plurality of individual electrodes, a common electrode, and a heating resistor, and supplies electric power between the selected individual electrode and the common electrode to cause the heating resistor in that portion to generate heat, thereby performing thermal recording ( (Printing).

As a method for forming a heating resistor of a thermal head, a method using a thick film technique such as screen printing and a method using a thin film technique such as sputtering are known. In this case, it has an advantage that the manufacturing equipment is inexpensive and the productivity is high as compared with the thin film technology. As a thermal head in which the heating resistor is formed by the thick film technology, the heating resistor is formed in a band shape by screen printing or drawing nozzles or a lift-off method, and the heating resistor is formed by a fine processing technique such as a lift-off method. There are those individually formed. The heating resistor formed in the band shape has an advantage that the yield is higher than that of the individually formed heating resistors.

An example of a thermal head having a strip-shaped heating resistor will be described with reference to FIGS. The thermal head has a glaze heat storage layer 51 formed on the surface of a ceramic insulating substrate 50. On the surface of the heat storage layer 51, a strip-shaped common electrode main body 52 extending along the main scanning direction (X direction) and a common electrode protruding from the main body 52 in a comb shape in the sub scanning direction (Y direction). A common electrode including a lead portion 53 and a plurality of individual electrodes 54 arranged between the common electrode lead portions 53 and arranged in a zigzag pattern with respect to the lead portion 53 are formed. It has a structure. The common electrode lead-out portion 53 and each individual electrode 54 are connected to each other by a strip-shaped heat generating resistor 55 extending on the surface of the heat storage layer 51 along the main scanning direction (X direction). Common electrode body 52,
The surfaces of the lead-out portion 53, the individual electrode 54, and the heating resistor 55 are covered with a wear resistant layer 56 (FIG. 6) made of glaze, and the heating resistor 55 of the wear resistant layer 56 is covered. A portion constitutes a printing unit 57 which transfers heat by contacting a thermal recording paper or an ink donor film. The print portion 57 is formed so as to project from the surface of the other portion of the abrasion resistant layer 56. The thermal head with the above configuration is
As shown in FIG. 6, print recording is performed by pressing the printing unit 57 against the thermal recording paper 61 (or the image receiving paper arranged via the ink donor film) conveyed along the surface of the platen roller 60. Be done.

By the way, when it is attempted to realize a print dot density of 12 dots / mm or more with the thermal head having the above-mentioned structure, the width of one dot becomes 84 μm (1 mm / 12) or less. In the case of adopting the alternate lead type electrode arrangement as described above, as shown in FIG. 5, when the width W1 between both electrodes which is the printed portion and the width W2 between the adjacent electrodes are formed to be the same as above, The width (electrode space) W2 that satisfies the condition is only 21 μm or less. As described above, when the electrode space is 20 μm or less, defects such as a short circuit and a disconnection between adjacent electrodes are likely to occur, which causes a problem that the yield of products is reduced.

In order to solve such a problem, the end portions of the common electrode lead-out portion and the end portions of the individual electrodes are arranged so as to face each other, and a strip-shaped heat is generated so that both electrodes are connected between the facing electrodes. It is conceivable to form a resistor, but in this case, the current flowing between the electrodes leaks in the longitudinal direction of the strip-shaped heating resistor, and the contour of the heating part becomes unclear, so a practical print dot cannot be obtained. There was a drawback.

Therefore, as a countermeasure against this, at the manufacturing stage of the thermal head, a pulse current is supplied between both electrodes (common electrode and individual electrode) of the heating resistor so that the resistance of the heating resistor sandwiched between the two electrodes is increased. It has been proposed to partially reduce the value to form individually separated heat generating portions (see Japanese Patent Laid-Open No. 3-169649). This utilizes the property that the resistance value of the heating resistor is reduced according to the electric field strength by applying an electric field of a predetermined strength between both electrodes.

[0008]

However, when a pulse current is supplied between the common electrode extraction portion and the individual electrodes,
Since the pulse current leaks from the common electrode lead-out side toward the adjacent common electrode lead-out part, not only between both electrodes of the heating resistor whose resistance value is to be partially lowered, but also in the peripheral heating resistor. Since the resistance value is reduced, the effect that the contour of the heat generating portion becomes clear cannot be sufficiently exerted.

The present invention has been made in view of the above circumstances, and in a thermal head having a strip-shaped heating resistor, when the heating resistor is formed by the thick film technique, the contour of the heating portion is clarified and printed. It is an object of the present invention to provide a method of manufacturing a thermal head that can improve image quality.

[0010]

To achieve the above object, the method of the present invention is characterized by including the following steps in a method of manufacturing a thermal head. In the individual electrode forming step, a first individual electrode row composed of a plurality of individual electrodes separated from each other and a second individual electrode row arranged so as to face the individual electrode row are formed. As the resistor formation process,
A strip-shaped heating resistor is formed to connect between the individual electrodes of the first and second individual electrode rows. In the heating portion forming step, a pulse current is supplied between the individual electrodes to reduce the resistance value of the heating resistor in this portion to form the individually heating portions. In the common electrode forming step, one of the individual electrode rows is commonly connected to each other to form a common electrode.

[0011]

According to the present invention, when the pulse current is supplied to the heating resistor, the electrodes serving as the common electrode are not connected to each other. Only a current flows, and it is possible to reduce only the resistance value of this portion.

[0012]

EXAMPLE A method of manufacturing a thermal head according to an example of the present invention will be described with reference to FIGS. 1, 2 and 3. First, the heat storage layer 2 is formed on the surface of the insulating substrate 1 made of alumina.
To form. Next, after an electrode layer made of gold or the like is formed on the surface of the heat storage layer 2, patterning is performed by photolithography etching to form a strip-shaped common electrode body portion 3, a plurality of common electrode lead portions 4, and each end of the lead portion 4. An individual electrode 5 arranged so as to face the portion (FIGS. 1A and 3).
(A)). In this case, the print density is 12 dots / mm with the width of one print dot being 84 μm. For this,
The distance between the tip 4a of the common electrode lead-out portion 4 and the tip 5a of the individual electrode 5 is 40 μm. The common electrode lead-out portion 4a is finally connected to the common electrode main body portion 3 to form a common electrode, as described later.

Next, a resistor forming paste containing ruthenium oxide is formed in the main scanning direction with a width of 60 to 80 μm so as to connect the tip 4b of the common electrode lead-out portion 4 and the tip 5b of the individual electrode 5. The heating resistor 6 is formed in a band shape and fired to form the heating resistor 6 (FIG. 1B). In order to form the resistor forming paste in a strip shape having a width of 60 to 80 μm, a so-called thick film lift-off method, a thick film lift-off method of a thick film paste,
It is performed by using a direct drawing method using a nozzle of a thick film paste. Further, the width of the heating resistor 6 is 60 to 80 μm
Has a positioning error of 10 in the sub-scanning direction Y due to the thick film lift-off method or the direct drawing method using a thick film paste nozzle.
Since it is expected to be in the order of μm, it is determined with a slight safety factor.

Next, the surfaces of the common electrode body portion 3, the common electrode lead-out portion 4, the individual electrodes 5 and the heating resistor 6 formed on the surface of the heat storage layer 2 are partially covered by the lead-out portion side of the common electrode body portion 3. And a part of the common electrode lead-out portion 4 is exposed (exposed portion 3a
And an exposed portion 4a) is covered with a wear resistant layer 7 made of glaze (FIGS. 1C and 2B). Further, depending on the use of the thermal head, a surface smoothing layer made of glaze may be formed near the surface of the heating resistor 6 or the like.

Then, the resistance value of the heating resistor 6 is adjusted by the pulse trimming method. That is, at this stage, since the resistance value of the heating resistor 6 is constant in the longitudinal direction,
The current flowing between the electrodes partially leaks in the longitudinal direction of the heating resistor 6, making the heating portion of the heating resistor 6 unclear and increasing power consumption. Therefore, by applying a pulse current having a pulse width of 1 μsec or less between the exposed portion 4 a of the common electrode lead-out portion 4 and the individual electrode 5, the tip portion 4 b of the common electrode lead-out portion 4 and the individual electrode 5 which are opposed to each other are applied. The resistance value of the heating resistor 6 between the tip portions 5b is partially reduced, and a heating portion 6'is formed in this portion (FIG. 2 (a)).
In the present embodiment, unlike the manufacturing method described in the conventional example, since the common electrode lead-out portions 4 that will eventually become the common electrodes are not connected to each other at this stage, a pulse current in the direction of the adjacent common electrode lead-out portion is obtained. Since there is no leakage and the partial reduction of the resistance value occurs only between the electrodes to which the pulse is applied, the contour of the heating portion 6'can be clearly defined.

The rate of decrease in the resistance value of the heating resistor 6 varies depending on the material of the heating resistor 6, the firing temperature or the material of the abrasion resistant layer 7, the firing temperature, etc., but it also changes depending on the applied voltage and the pulse width. To do. Under the conditions of this embodiment, for example, 5
When a voltage of 00V is applied for 1 μsec, about 50%, 1000
Applying a voltage of V for 0.1 μsec, about 65%, 2000
When a V voltage of 0.01 μsec was applied, the rate of decrease was about 75%. Therefore, if the above voltage and pulse width are appropriately selected and the pulse is applied between the exposed portion 4a of the common electrode lead-out portion 4 and the individual electrode 5, the heating resistor 6 at that portion is applied.
It is possible to lower the resistance value of 40% or more as compared with other portions, and it is possible to simultaneously form a large number of heat generating portions 6 ′ on the heat generating resistor 6 at predetermined intervals.

Thereafter, the exposed portion 4a of the common electrode lead-out portion 4 is formed.
The exposed portion 3a of the common electrode body 3 is connected by the connecting portion 8 made of silver epoxy to complete the common electrode (see FIG. 2).
(B) and FIG.3 (c)). Further, the connection portion 8 made of silver epoxy is covered with an epoxy resin layer 9 to protect it (FIGS. 2 (c) and 3 (d)).

As shown in FIG. 4, the thermal head manufactured by the above-mentioned manufacturing method is arranged on the supporting plate 10 with an adhesive, and the IC connection is formed at the end of each individual electrode 5 of the thermal head. The terminal 5a is connected to a drive IC 12 mounted on a drive substrate 11 arranged on the support plate 10 via a bonding wire 13. Further, an external connection wiring 14 as a signal input terminal is formed on the drive substrate 11, and the external connection wiring 14 and the drive IC 12 are connected via a bonding wire 15. Further, the driving IC 12 and the bonding wires 13 and 15 are covered with a protective resin 16, and further,
The protective resin 16 is protected by a metal or resin cover 17. Heater resistor 6 of thermal head
A platen roller 21 that conveys the recording paper 20 is arranged on the upper side, and the recording paper 20 is brought into close contact with the thermal head side by being pressed by the platen roller 21.

Next, the operation of the thermal head having the above construction will be described. When a current is selectively supplied to a predetermined individual electrode 5 via the driving IC 12 in accordance with an image signal, it is formed between the tip portion 5b of the individual electrode 5 and the tip portion 4b of the common electrode lead-out portion 4. The heat generating portion 6'heats. At this time, the current flowing between the tip portion 5b of the individual electrode 5 and the tip portion 4b of the common electrode lead-out portion 4 has a large resistance value portion between the adjacent heating portion 6'of the heating resistor 6. Therefore, the heat is hardly leaked to the adjacent heat generating portions 6 ', and the regions of the heat generating portions 6'independently generate heat. Therefore,
When the printing portion 7a of the abrasion resistant layer 7 covering the heating resistor 6 is pressed against the recording paper 20 (heat-sensitive recording paper or ink donor film) on the surface of the platen roller 21, the printing portion 7a of the heat-sensitive recording paper or transfer image receiving paper is obtained. A print dot having a clear contour is formed in a portion that comes into contact with.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various small designs can be made without departing from the present invention described in the claims. It is possible to make changes. For example, 16dot / m
It is easy to make the density higher than m, and the distance between the tip portion 5b of the individual electrode 5 and the tip portion 4b of the common electrode lead-out portion 4 is further reduced, so-called sub-scanning division type thermal head for area gradation. Can be manufactured. Further, it is possible to manufacture a so-called heat concentration type thermal head by further reducing the width of both electrodes. As a result, a thermal head having a special configuration such as a sub-scanning split type thermal head or a heat concentration type thermal head used in a color printer can be manufactured by a thick film technique, and the cost of the product can be reduced. be able to. Further, although the counter electrode type thermal head has been described in the above embodiment, the present invention can also be applied to an alternating lead type thermal head.

[0021]

According to the present invention, a pulse current is supplied between the common electrode lead-out portion and the individual electrodes in a state where the common electrode lead-out portion is not connected to the strip-shaped common electrode body portion, and the common electrode lead-out portion is provided. And a step of electrically connecting the common electrode lead-out portion and the common electrode main body portion after partially reducing the resistance value of the heating resistor sandwiched between the individual electrodes to form the individually separated heat generating portion. As a result, it is possible to form the individually-generated heat generating portions on the heat generating resistor. Therefore, when the strip-shaped heat generating resistor is used, it is possible to surely form the heat generating portions that are individually separated, and it is possible to improve the print image quality by clarifying the contour of the heat generating portion.

[Brief description of drawings]

1A to 1C are plan explanatory views showing a part of a manufacturing process of a thermal head according to an embodiment of the present invention.

2A to 2C are plan explanatory views showing a part of the manufacturing process of the thermal head according to the embodiment of the present invention.

3A to 3D are cross-sectional explanatory views showing a manufacturing process of a thermal head according to an embodiment of the present invention.

FIG. 4 is a structural explanatory view of a print recording apparatus using a thermal head according to an embodiment.

FIG. 5 is a plan view of a thermal head having an alternating lead type electrode arrangement.

FIG. 6 is a structural explanatory view of a print recording apparatus using a thermal head.

[Explanation of symbols]

1 ... Insulating substrate, 2 ... Heat storage layer, 3 ... Common electrode main body,
4 ... Common electrode lead-out part, 5 ... Individual electrode, 6 ... Heating resistor, 6 '... Heating part, 7 ... Wear resistant layer, 8 ... Connection part, 9 ... Epoxy resin layer, 10 ... Support plate, 11 ...
Drive board

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B41J 3/20 114 C (72) Inventor Sagawa Shimizu 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Within

Claims (1)

[Claims] 1. A first comprising a plurality of individual electrodes separated from each other
Individual electrode row and an individual electrode forming step of forming a second individual electrode row arranged to face the individual electrode row, and a strip-shaped heat generation for connecting between the individual electrodes of the first and second individual electrode rows A resistor forming step of forming a resistor, and a heating portion forming step of supplying a pulse current between the individual electrodes to reduce the resistance value of the heating resistor in this portion to form individually separated heating portions, A step of forming a common electrode by commonly connecting one of the individual electrode rows to each other to form a common electrode.