JP3167198B2 - Thermal print head and method of forming conductive pattern thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head used as a printing portion of a facsimile or the like, and a method for forming a conductive pattern for supplying power to each heating dot portion in the thermal print head.

[0002]

2. Description of the Related Art Generally, there are two types of thermal print heads of this type: a thick-film type and a thin-film type. The former thick-film type has a top surface of a head substrate 1a as shown in FIG. Then, a heat-resistant insulating layer 2a such as glass is partially formed,
On the upper surface of the insulating layer 2a, a thick-film heating resistor 3a is provided.
The heating resistor 3a is formed so as to extend in a line shape (however, the heating resistor 3a is formed after the formation of the conductor patterns 4a and 5a described later is completed), while the heating resistor 3a is formed on the upper surfaces of the head substrate 1a and the insulating layer 2a. , The heating resistor 3a
A plurality of power supply conductor patterns 4a, 5a extending outward from both left and right sides of the heating resistor 3a are formed, and the heating dot portion 3 between the two conductor patterns 4a, 5a of the heating resistor 3a is formed.
a 'is configured to generate heat.

In the latter thin film type, as shown in FIG. 6, a heat resistant insulating layer 2b of glass or the like is partially formed on the upper surface of a head substrate 1b, and a thin film is formed on the entire upper surface. A heating resistor layer 3b is formed, and a plurality of power supply conductor patterns 4b, 5b extending from the left and right outer sides toward the insulating layer 2a are formed on the upper surface of the heating resistor layer 3b.
Are formed so as to face each other, and heat is generated in the heat generating dot portion 3b 'between the conductor patterns 4b and 5b in the heat generating resistor layer 3b.

However, as described above, the head substrates 1a, 1
b, the insulating layers 2a and 2b are partially formed on the upper surface of the head substrate 1 while the conductive patterns 4a, 5a, 4b and 5b for supplying power to the heating dot portions 3a 'and 3b' are
In a thermal print head of a type formed so as to extend over both the upper surfaces of the insulating layers 2a and 2b and the upper surfaces of the insulating layers 2a and 2b, the heating dots are formed due to the presence of the partial insulating layers 2a and 2b. Since the portions 3a 'and 3b' can make good contact with the paper to be printed, there is an advantage that the printing quality can be improved, but the conductor patterns 4a, 5a, 4b and 5 have the advantage.
When forming b, the following problems occur frequently.

[0005]

By the way, each of the above 4
The methods for forming a, 5a, 4b, and 5b include a method in which they are formed by a photolithographic method and a method in which they are formed by a screen printing method. That is, the former method of forming by the photolithography method, the upper surface of the head substrate 1a,
The insulating layer 2a is partially formed, and on the entire upper surface thereof,
As shown in FIG. 7, after the conductor thin film 6 for the conductor patterns 4a and 5a is formed, a photoresist film 7 is formed on the upper surface of the conductor thin film 6 so as to cover the entire conductor thin film 6. On the photoresist film 7, a photomask plate 8 having a slit-shaped cutout window 8a having the same shape as the conductor patterns 4a, 5a is placed, exposed, and developed, as shown in FIG. By removing the remaining portions of the photoresist film 7 except for the portions corresponding to the conductor patterns 4a and 5a, the portions corresponding to the conductor patterns 4a and 5a have the same shape as the photoresist. A film 7 'is formed, and then the whole is removed by dissolving a portion of the conductive thin film 6 other than the partial photoresist film 7' with an etchant. After performing management, by removing the portion photoresist film 7 ', as shown in FIG. 5, in which the conductor patterns 4a, the 5a formed.

On the other hand, in the formation method by the screen printing method, an insulating layer 2a is partially formed on the upper surface of the head substrate 1a, and the conductor patterns 4a, 5a are formed on the entire upper surface thereof.
After stacking a screen plate having a slit-shaped cutout window having the same shape as a, a conductive paste is applied by filling a conductive paste into each of the cutout windows in the screen plate, and then, After removing the screen plate, the conductive paste is dried to form the conductor patterns 4a and 5a as shown in FIG.

However, when the conductive thin film 6 is formed by the photolithography method, the thickness of the conductive thin film 6 is increased at a step portion from the upper surface of the head substrate 1a to the upper surface of the insulating layer 2a. Therefore, in the etching process using the etching solution, insufficient etching occurs in the portion where the film thickness is large, so that the insufficient etching occurs on both left and right sides of each of the conductor patterns 4a and 5a as shown in FIG. The formation of the bumps 4a 'is formed by the above, and the occurrence of defective products is such that the bumps 4a' are connected to each other, that is, the conductor patterns 4a and 5a are short-circuited to each other. Is high.

In the above-mentioned screen printing method, the conductive paste applied by filling the slit-shaped opening in the screen plate is applied from the upper surface of the head substrate 1a to the upper surface of the insulating layer 2a. The thickness of the stepped portion becomes thicker, spreads in the horizontal direction, and the adjacent portions are frequently connected at the same time, so that the occurrence rate of defective products is also high.

Further, the problem of high occurrence rate of defective products occurs even when the conductor patterns 4b and 5b in the thin film type thermal print head shown in FIG. 6 are formed by the photolithography method or the screen printing method. It occurred similarly. The present invention provides a thermal print head capable of reliably reducing the occurrence rate of defective products, and also provides a method of forming a conductor pattern capable of reliably reducing the occurrence rate of defective products. It is an issue.

[0010]

In order to achieve the above technical object, the present invention employs the following technical means. That is, the thermal print head described in claim 1 is
`` An insulating layer is partially formed on the upper surface of the head substrate, and a large number of power supply conductor patterns for each heating dot portion on the upper surface of the insulating layer are extended from the upper surface of the insulating layer to the upper surface of the head substrate. In the formed thermal print head, the width dimension of each of the conductor patterns is partially narrowed at a step portion extending from the upper surface of the head substrate to the upper surface of the insulating layer. "

Further, <br/> method of forming a conductive pattern according to claim 2, the upper surface of the "head substrate and on the upper surface of the partially-formed insulating layer to the upper surface, extend over both of the large number of feeding conductor pattern extending I, in the method for forming a conductor pattern formed by photolithography, of a slit die-cut windows in the photomask plate to be used in the <br/> photolithography, an upper surface of the head substrate In a portion corresponding to a stepped portion extending from the upper surface of the insulating layer, a projection projecting inward from both left and right inner side surfaces of the slit-type cutout window is provided, and using the photomask plate, the conductive pattern is formed. Exposure to the photoresist film covering the conductive thin film
After the development, an etching process is performed. Is the thing.

Furthermore, the method for forming a conductor pattern according to a third aspect of the present invention is a method of forming a conductive pattern, comprising: "extending over both of the upper surface of the head substrate and the upper surface of the insulating layer formed partially on the upper surface. the large number of feeding conductor pattern forming method odor of the conductor pattern formed by a screen printing method <br/> Te, of the slit type vent windows in the screen plate for use in the screen printing method, from the upper surface of the head substrate In a portion corresponding to a stepped portion over the upper surface of the insulating layer, a projection is provided inwardly protruding from both left and right inner surfaces of the slit-shaped cutout window, using this screen plate,
The conductive paste for the conductive pattern is screen-printed on the upper surfaces of the head substrate and the insulating layer, and then dried. Is the thing.

[0013]

According to the present invention, the width of each conductor pattern is partially narrowed at a step portion extending from the upper surface of the head substrate to the upper surface of the insulating layer.
The occurrence of a short circuit in adjacent conductor patterns at a stepped portion from the upper surface of the head substrate to the upper surface of the insulating layer in each conductor pattern can be greatly reduced as compared with the conventional case.

According to a second aspect of the present invention,
By exposing and developing the photoresist film using a photomask plate, the upper and lower conductive films are formed in the same shape as the conductor pattern. In a portion corresponding to a stepped portion on the upper surface of the insulating layer, a concave portion can be formed for a projection provided on the left and right inner side surfaces of the slit-type cutout window in the photomask plate, in other words, each portion Since the interval between the photoresist films can be partially widened at the recess at the step, the gap between the conductor patterns at the step at the time of etching the conductive thin film is reduced. The occurrence of connection due to insufficient etching can be greatly reduced as compared with the conventional case.

According to a third aspect of the present invention, when the conductive paste is screen-printed on the upper surface of the head substrate and the insulating layer using a screen plate, the width of the conductive paste is reduced. In a portion corresponding to a stepped portion extending from the upper surface of the head substrate to the upper surface of the insulating layer, the projections provided on the left and right inner surfaces of the slit-type cutout window in the screen plate can be partially narrowed. In addition, it is possible to greatly reduce the possibility that the conductive paste is connected to each other at the stepped portion as compared with the conventional case.

[0016]

As described above, according to the present invention, when manufacturing a thermal print head, there is an effect that the occurrence rate of defective products, that is, the connection of the conductor patterns to each other can be reliably reduced.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing an embodiment of the present invention applied to forming a large number of conductor patterns by photolithography in the above-mentioned thick film type thermal print head. Will be described. FIGS. 1 to 3
Reference numeral 11 denotes a head substrate made of a heat-resistant insulator such as ceramic, and reference numeral 12 denotes a heat-resistant insulating layer 12 made of glass or the like partially formed on the upper surface of the head substrate 11.

A conductive thin film 16 for a conductive pattern is formed on the upper surface of the head substrate and the upper surface of the insulating layer 12, and a photoresist film is formed on the upper surface of the conductive thin film 16 so as to cover the entire conductive thin film 16. 17 is formed. Then, a slit-shaped opening window 18a having the same shape as the conductor patterns 14 and 15 is formed on the photoresist film 17.
A photomask plate 18 having a photomask plate 18 is exposed and developed, and as shown in FIG. 2, other portions of the photoresist film 17 except for portions corresponding to the conductor patterns 14 and 15 are left. Is removed, a partial photoresist film 17 'having the same shape as that of the conductor patterns 14 and 15 is formed in portions corresponding to the conductor patterns 14 and 15.

Next, the whole of the conductor thin film 16 is subjected to an etching process of dissolving and removing portions other than the partial photoresist film 17 'with an etchant, and then the partial photoresist film 17' is removed. By removing, as shown in FIG.
Is formed, and a thick-film heating resistor 13 is formed on the upper surface of the insulating layer 12 so as to extend linearly.

In this case, according to the present invention, of the left and right inner side surfaces of the slit-type cutout window 18a of the photomask plate 18, the insulating layer 1 is formed from the upper surface of the head substrate 11.
An inwardly protruding projection 18a 'is integrally provided at a portion corresponding to a stepped portion extending over the upper surface of 2. Then, each partial photoresist film 1 formed by exposing and developing the photoresist film 17 is formed.
A recess 17 a ′ can be formed by the projection 18 a ′ in a portion corresponding to a step between the upper surface of the head substrate 11 and the upper surface of the insulating layer 12 on both right and left sides of 7 ′. As a result, the interval between the respective partial photoresist films 17 'is set at the stepped portion by the recess 1
Since the conductor patterns 14 and 15 formed by the subsequent etching process can be partially expanded as shown in FIG. It becomes a form like
When the conductive thin film 16 is etched, it is possible to reliably reduce the occurrence of connection between the conductive patterns 14 and 15 due to insufficient etching at the step.

FIG. 4 shows an embodiment in which the conductor patterns 14 and 15 in the thick film type thermal print head are formed by a screen printing method. A screen plate 19 having a slit-shaped cutout window 19a having the same shape as the conductor patterns 14 and 15 is overlaid on the upper surface of the head substrate 11 on which the insulating layer 12 is partially formed in advance. Each open window 1 in 19
By filling conductive paste into 9a,
The conductive paste is applied.

In this case, in the present invention, the insulating layer 1 from the upper surface of the head substrate 11 on the left and right inner side surfaces of each slit-type cutout window 19a of the screen plate 19 is formed.
An inwardly protruding projection 19a 'is integrally provided at a portion corresponding to a stepped portion extending over the upper surface of 2. Then, the conductive paste is applied to the head substrate 11 and the insulating layer 1.
When screen printing is performed on the upper surface of the conductive paste 2 using the screen plate 19, the width dimension of the conductive paste is set at a portion corresponding to a step between the upper surface of the head substrate 11 and the upper surface of the insulating layer 12. Since the projections 19a 'provided on the left and right inner surfaces of the slit-shaped cutout window 19a in the screen plate 19 can be partially narrowed, it is ensured that this conductive paste is connected to each other at the step portion. It can be reduced to

The above embodiment has been described with reference to a case where the present invention is applied to a thick-film type thermal print head.
However, it is needless to say that the present invention can be similarly applied to the thin film type thermal print head shown in FIG.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a state after exposing and developing a photoresist film in the first embodiment.

FIG. 3 is a perspective view showing a state in which a large number of conductor patterns are formed according to the first embodiment.

FIG. 4 is a perspective view showing a second embodiment of the present invention.

FIG. 5 is a perspective view of a thick film type thermal print head.

FIG. 6 is a perspective view of a thin-film thermal print head.

FIG. 7 is a perspective view showing a conventional method.

FIG. 8 is a perspective view showing a state after exposing and developing a photoresist film in a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Head board 12 Insulating layer 13 Heating resistor 14, 15 Conductor pattern 16 Conductor thin film 17 Photoresist film 17 'Partial photoresist film 18 Photomask plate 18a Open window 18a' Projection 19 Screen plate 19a Open window 19a 'Projection

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinya Yukawa 21 Ryozo-cho, Niinin, Ukyo-ku, Kyoto Inside Rohm Co., Ltd. (56) References Jikai Sho 63-184735 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B41J 2/345 B41J 2/335 H01L 23/00

Claims (3)

(57) [Claims] An insulating layer is partially formed on an upper surface of a head substrate, and a large number of power supply conductor patterns for each heat generating dot portion on the upper surface of the insulating layer are transferred from the upper surface of the insulating layer to the upper surface of the head substrate. A thermal print head formed so as to extend in a width direction, wherein a width dimension of each of the conductor patterns is partially reduced at a step portion extending from an upper surface of the head substrate to an upper surface of an insulating layer. Print head. And the upper surface of 2. A head substrate and on the upper surface of the partially-formed insulating layer to the upper surface, a large number of feeding conductor pattern extending straddling both these conductors formed by photolithography in the method for forming a pattern, said one of the slit-type vent windows in the photomask plate to be used for photolithography, the portion corresponding from the upper surface of the head substrate in the step portion of the over the top surface of the insulating layer, the slit type vent windows The present invention is characterized in that a protruding portion protruding inward from both left and right inner side surfaces is provided, and a photoresist covering the conductive thin film for the conductive pattern is exposed and developed using this photomask plate and then etched. A method for forming a conductor pattern in a thermal print head. 3. A plurality of power supply conductor patterns extending over both of the upper surface of the head substrate and the upper surface of the insulating layer partially formed on the upper surface by a screen printing method. In the method of forming a conductor pattern, the slit die-cutting window in the screen plate used for the screen printing method may be provided with a slit die-cut in a portion corresponding to a step from the upper surface of the head substrate to the upper surface of the insulating layer. Providing projections projecting inward from both left and right inner surfaces of the window, using this screen plate, screen-printing the conductive paste for the conductive pattern on the upper surfaces of the head substrate and the insulating layer, and then drying. A method for forming a conductor pattern in a thermal print head, comprising: