JP2003220720A - Thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal head which can remove well a static electricity of a recording medium surface by a simple structure and can serve for miniaturization of a thermal printer, constitutional simplification and productivity improvement. <P>SOLUTION: In the thermal head, a head board 1 where many heating elements 3 and a circuit pattern 4 are applied, and an external wiring board 7 having a plurality of wiring conductors to be electrically connected to the circuit pattern 4 are set together, and at the same time a head cover 9 formed of a metal having one end extending to the vicinity of the heating elements 3 is disposed above the external wiring board 7. Printing is carried out by selectively letting the heating elements 3 heat while guiding the recording medium onto the heating elements 3 by an outer surface of the head cover 9. At least one of the plurality of wiring conductors is held at an earth potential, and moreover a part of the head cover 9 is butted against the earthed wiring conductor 8a to electrically connect each other. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head incorporated as a recording device such as a facsimile or a video printer.

[0002]

2. Description of the Related Art Conventionally, a thermal head has been used as a recording device such as a facsimile.

As such a conventional thermal head, for example, as shown in FIG. 3, a radiator plate 2 made of aluminum or the like is used.
8, a head substrate 21 on which a large number of heating elements 23 arranged in a straight line and a circuit pattern 24 are attached, and a plurality of wiring conductors 2 electrically connected to the circuit pattern 24.
6 has a structure in which a flexible wiring board 25 having 6 is placed and installed side by side, and a metal head cover 27 having one end extended to the vicinity of the heating element 23 is disposed on the flexible wiring board 25. While sequentially feeding a recording medium such as a thermal paper onto the heating elements 23 of the head substrate 21, a large number of heating elements 23 are individually and selectively heated by Joule based on image data from the outside. A predetermined print is formed by transmitting the heat of the recording medium to the recording medium.

The head cover 27 protects the connecting portion between the head substrate 21 and the flexible wiring board 25 by applying an external force by covering the connecting portion between the head substrate 21 and the flexible wiring board 25, and at the time of printing, recording is performed along the outer surface thereof. It functions as a guide member for guiding the recording medium onto the heating element 23 by conveying the medium, and is attached to the heat dissipation plate 28 by conventionally known screwing or the like.

The flexible wiring board 25 receives image data, print control signals, electric power, etc. from the outside on the head substrate 2.
The first heating element 23, the driver IC, and the like are supplied to the head substrate 21 by soldering, a metal thin wire, or the like.

When printing is performed using the above-mentioned thermal head, a static elimination brush is arranged upstream of the thermal head in the conveying direction of the recording medium, and the static elimination brush is brought into contact with the recording medium before printing. In this way, the static electricity on the surface of the recording medium is removed.

[0007]

However, when the static electricity of the recording medium is removed by the static elimination brush as described above, it is necessary to incorporate the static elimination brush in the housing of the thermal printer, which increases the number of parts of the thermal printer. Therefore, the structure is complicated and the entire structure is enlarged.

The head substrate 2 of the above-mentioned thermal head
Since a platen roller having a diameter of about 8.0 mm to 25.4 mm is usually disposed on the first unit, it is difficult to dispose the charge removal brush sufficiently close to the heat generating element 23, and the recording medium after charge removal is disposed. In many cases, static electricity is charged again. In that case, the static electricity charged in the recording medium due to the sliding contact between the recording medium and the head substrate 21 is applied to the heating element 23 and the protective film 29 provided thereon, thereby causing a defect of electrostatically destroying these films. It

In order to solve the above-mentioned drawbacks, therefore, the head cover 26 that comes into contact with the recording medium is made of metal, and the head cover 27 is held at the ground potential, so that the recording medium has static electricity on the surface of the heating element 23. Immediately before being guided, it is proposed that the heat is released to the ground (GND) through the head cover 26 to prevent electrostatic destruction of the heating element 23 and the protective film 29, and prevent the thermal printer from becoming large and the structure from becoming complicated. ing.

However, in order to maintain the head cover 27 at the ground potential, the head cover 27 or the heat radiating plate 28 electrically connected to the head cover 27 is directly connected to a blanket for mounting the thermal head by using a jumper wire or the like. In that case, the work of incorporating the thermal head into the printer main body becomes complicated, and the connection work such as soldering and screwing is required in connection with the connection of the jumper wire etc., It has a drawback that the productivity of the thermal printer and the workability of the assembling work are significantly reduced.

The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to easily remove static electricity on the surface of a recording medium with a simple structure and to downsize the thermal printer and simplify the configuration. Another object of the present invention is to provide a thermal head capable of improving productivity.

[0012]

A thermal head of the present invention has a head substrate on which a large number of heating elements and circuit patterns are adhered, and a plurality of wiring conductors electrically connected to the circuit patterns. An external wiring board is provided side by side, and a metal head cover whose one end extends to the vicinity of the heating element is disposed on the external wiring board, and the recording medium is placed on the heating element on the outer surface of the head cover. A thermal head for selectively heating a heating element while guiding the heating element to print an image, wherein at least one of the plurality of wiring conductors is held at a ground potential, and the wiring conductor is grounded. It is characterized in that a part of the head cover is brought into contact with each other to electrically connect them.

Further, the thermal head of the present invention is characterized in that the wiring conductor has a convex portion protruding toward the head cover side at an abutting portion of the head cover.

Further, the thermal head of the present invention is characterized in that a thermal recording medium is brought into sliding contact with the outer surface of the head cover during printing.

According to the thermal head of the present invention, a part of the head cover made of metal is a wiring conductor of the external wiring board (hereinafter, abbreviated as a ground conductor) which is held at the ground potential.
Since the head cover is held at the ground potential by contacting the head cover with the ground conductor, the static electricity on the surface of the recording medium is transferred via the ground conductor of the head cover and the external wiring board immediately before the recording medium is conveyed onto the heating element during printing. It can escape to the ground, and it is possible to reliably prevent electrostatic breakdown of the heating element and the protective film provided thereon.

Further, according to the thermal head of the present invention, static electricity can be reliably removed from the recording medium by a simple mechanism in which a part of the head cover for guiding the recording medium is kept in contact with the ground conductor of the external wiring board. Therefore, no complicated work such as connecting the head cover and an external blanket with a jumper wire or the like is required, and the productivity of the thermal printer can be improved, and the configuration of the thermal printer is simplified. Moreover, it is possible to reduce the size of the entire structure.

Further, according to the thermal head of the present invention, if the convex portion protruding toward the head cover is provided on the ground conductor of the external wiring board at the portion where the head cover is in contact, the contact portion of the head cover is grounded. Since it is easy to contact the conductor, the electrical connection between the two can be made more reliably,
It is also possible to improve the reliability of the thermal head.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. 1 is a perspective view of a thermal head according to an embodiment of the present invention, and FIG. 2 is a sectional view of the thermal head of FIG. 1. The thermal head shown in FIG. It is composed of a board (external wiring board) 7, a head cover 9, and a heat dissipation plate 10.

The head substrate 1 has a structure in which a large number of linear heating elements 3, a circuit pattern 4 and a driver IC 5 are arranged on an upper surface of a base plate 2 formed in a rectangular shape. There is.

The base plate 2 is made of a ceramic material such as alumina ceramics, or single crystal silicon whose surface is covered with an oxide film, and has a heating element 3, a circuit pattern 4, a driver IC 5 and the like provided on the upper surface thereof.
It functions as a support base material for supporting these.

When the base plate 2 is made of alumina ceramics, a suitable organic solvent or solvent is added to and mixed with ceramic material powder such as alumina, silica, magnesia, etc. to form a sludge, and this is formed by a conventionally known doctor blade. A ceramic green sheet is formed by adopting the method, and thereafter, the obtained ceramic green sheet is punched into a predetermined rectangular shape and then fired at a high temperature (about 1600 ° C.).

A large number of heating elements 3 provided on the upper surface of the base plate 2 are, for example, 600 dpi (do
They are arranged linearly in the main scanning direction (longitudinal direction of the base plate 2) at a density of t per inch), and the power supply circuit patterns 4 are connected to both ends of each heating element 3.

Each of the heating elements 3 is made of TaSi.
Since it is formed of an electric resistance material such as O and TiSiO, Joule heat is generated when power source power is applied through the circuit pattern 4, the driver IC 5, etc., and the temperature required to form a print on the recording medium, For example, 150 ° C to 2
A temperature of 50 ° C is reached.

The circuit pattern 4 connected to the heating element 3 is formed of a conductive material such as aluminum or copper so as to have a predetermined shape, and a part of the circuit pattern 4 is formed.
Is commonly connected to all the heating elements 3 on one end side of the heating elements 3 and functions as a common electrode, and a part of the circuit pattern 4 is on the other end side of the heating elements 3 and each of the heating elements 3 and the driver I.
It functions as an individual electrode that connects to the output terminal of C5, and the remaining circuit pattern 4 functions as a signal wiring that connects the input terminal of the driver IC 5 and the wiring conductor 8 of the flexible wiring board 7.

Such a heating element 3 and a circuit pattern 4
Has a predetermined thickness on the upper surface of the base plate 2 by employing a well-known thin film forming technique such as a sputtering method, a photolithography technique, and an etching technique.
It is deposited / formed in a predetermined pattern and then covered with a protective film 6 made of an inorganic material having excellent abrasion resistance such as silicon nitride or glass.

The plurality of driver ICs 5 mounted on the base plate 2 are arranged substantially parallel to the above-mentioned arrangement of the heating elements 3 with a predetermined gap therebetween.

Such a driver IC 5 is for individually controlling the power supply to the heating elements 3 based on image data from the outside.
A flip-chip type driver IC is preferably used for this.

For example, a flip chip type driver I
When C5 is used, electronic circuits such as a shift register, a latch, and a switching transistor, and input / output terminals are provided on the lower surface of the C5, and conventionally known face-down bonding, that is, the input / output terminals are formed into the corresponding circuit pattern 4. It is mounted at a predetermined position on the base plate 2 by being electrically connected through a brazing material such as solder.

Then, the upper surface of a part of the head substrate 1 described above,
Specifically, one end of the flexible wiring board 7 having a plurality of wiring conductors 8 is overlapped between the driver IC 5 and the edge of the head substrate 1, and the wiring conductor 8 is overlapped at the overlapping portion.
Is soldered to the circuit pattern 4 on the head substrate 1.

The flexible wiring board 7 is for supplying image data, printing control signals, electric power, etc. from the outside to the heating element 3, driver IC 5 and the like on the head substrate 1, and is made of, for example, polyimide resin. A plurality of wiring conductors 8 made of a metal material such as copper are adhered on the base film made of, and the wiring conductors 8 are partially covered with a cover film made of a polyimide resin or the like. A connector 12 for connecting the thermal head to the electric circuit of the printer body is attached to the other end of the wiring board 7.

Of the wiring conductors 8 described above, the upper surface of the ground conductor 8a held at the ground potential (GND) is partially exposed by peeling off a part of the cover film or the base film, The exposed portion comes into contact with the inner surface of the head cover 9 described later.

Then, such a flexible wiring board 7
Is mounted and installed on the upper surface of the heat dissipation plate 10 made of aluminum or the like together with the head substrate 1 described above via an adhesive such as a double-sided tape.

The heat dissipation plate 10 supports the head substrate 1 and the flexible wiring board 7 on its upper surface, and
Part of the heat of the head substrate 1 is absorbed and dissipated, and the head substrate 1
This is for effectively preventing the temperature of (1) from becoming excessively high, and is manufactured to have a predetermined shape by adopting a conventionally known metal processing method.

On the other hand, above the flexible wiring board 7, a metal head cover 9 having one end extended to the vicinity of the heating element 3 is provided.

The head cover 9 protects the connecting portion between the head substrate 1 and the flexible wiring board 7 from the application of external force, and guides the recording medium onto the heating element 3 while supporting the traveling of the recording medium on its outer surface. It functions as a guide member for aluminum and stainless steel (SU
A plate body made of a metal such as S) is formed into a predetermined shape by conventionally known sheet metal working, and is fixed to a predetermined position on the flexible wiring board 7 by attaching it to the heat dissipation plate 10 by screwing or the like. .

Further, as described above, the head cover 9 has a part of its inner surface abutted against the ground conductor 8a of the flexible wiring board 7, and is electrically connected to the ground conductor 8a at the corresponding contact portion.

In this way, the head cover 9 made of metal
Part of the head cover 9 is brought into contact with the ground conductor 8a of the flexible wiring board 7 held at the ground potential (GND).
Is held at the ground potential (GND),
During printing, the static electricity on the surface of the recording medium can be released to the ground via the head cover 9 and the ground conductor 8a of the flexible wiring board 7 immediately before the recording medium is conveyed onto the heating element 3, and the heating element 3 and its components can be discharged. Protective film 6 provided on top
It is possible to improve the reliability of the thermal head by surely preventing the electrostatic damage of.

The head cover 9 is held at the ground potential (GND) by a simple mechanism in which a part of the head cover 9 is kept in contact with the ground conductor 8a of the flexible wiring board 7. There is no need for complicated work such as connecting an external blanket with jumper wires, etc., and the productivity of the thermal printer can be improved, and the configuration of the thermal printer is simplified and It is also possible to downsize the structure.

Further, if a convex portion 8b protruding toward the head cover 9 is provided on the ground conductor 8a of the flexible wiring board 7 with which the inner surface of the head cover 9 abuts, the inner surface of the head cover 9 is opposed to the ground conductor 8a. Since it is easier to make contact with each other, it is possible to more securely make an electrical connection between the two.
This can also improve the reliability of the thermal head. Therefore, it is preferable to provide the convex portion 8b protruding toward the head cover 9 side on the ground conductor 8a of the flexible wiring board 7 with which the inner surface of the head cover 9 contacts. The convex portion 8b is preferably formed of a conductive material such as nickel or gold that is not easily oxidized. For example, a conventionally known electroless plating method or the like is used, and nickel and gold are placed on the upper surface of the ground conductor 8a. It is formed by depositing it to a thickness of 2 μm to 50 μm.

Furthermore, the head cover 9 is attached to the heat sink 10.
If the screw 11 used for screwing is made of metal such as Zn-plated iron, the heat sink 1
Since 0 is electrically connected to the head cover 9 via the screw 11, the heat dissipation plate 10 is also held at the ground potential (GND) like the head cover 9, and in this case,
It is not necessary to separately ground the heat sink 10 for noise measures or the like. Therefore, it is preferable that the screw 11 used to screw the head cover 9 to the heat sink 10 is formed of metal so that the heat sink 10 is also held at the ground potential (GND).

Thus, the above-described thermal head of the present embodiment guides the recording medium on the heating element 3 of the head substrate 1 on the outer surface of the head cover 9 while selectively selectively generating the heating element 3 as the driver IC 5 is driven. To generate Joule heat and to transfer the generated heat to the recording medium,
It functions as a thermal head by forming a predetermined print on the recording medium.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, it goes without saying that a glaze layer or the like may be interposed between the heating element 3 and the base plate 2 or the driver IC 5 may be covered with a sealing material made of epoxy resin or the like. .

[0044]

According to the thermal head of the present invention, a part of the head cover made of metal is brought into contact with the wiring conductor of the external wiring board (hereinafter abbreviated as ground conductor) held at the ground potential. Since the head cover is kept at the ground potential, the static electricity on the surface of the recording medium must be released to the ground via the ground conductor of the head cover and the external wiring board immediately before the recording medium is conveyed onto the heating element during printing. Therefore, it is possible to reliably prevent electrostatic destruction of the heating element and the protective film provided thereon.

Also, according to the thermal head of the present invention, the recording medium can be surely discharged by a simple mechanism in which a part of the head cover for guiding the recording medium is brought into contact with the ground conductor of the external wiring board. Therefore, no complicated work such as connecting the head cover and an external blanket with a jumper wire or the like is required, and the productivity of the thermal printer can be improved, and the configuration of the thermal printer is simplified. Moreover, it is possible to reduce the size of the entire structure.

Further, according to the thermal head of the present invention, if the convex portion protruding toward the head cover is provided on the ground conductor of the external wiring board at the portion where the head cover is in contact, the contact portion of the head cover is grounded. Since it is easy to contact the conductor, the electrical connection between the two can be made more reliably,
It is also possible to improve the reliability of the thermal head.

[Brief description of drawings]

FIG. 1 is a perspective view of a thermal head according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the thermal head shown in FIG.

FIG. 3 is a sectional view of a conventional thermal head.

[Explanation of symbols]

1 ... Head substrate, 2 ... Base plate, 3 ...
・ Heating element, 4 ... Circuit pattern, 5 ... Driver IC, 6 ... Protective film, 7 ... External wiring board (flexible wiring board), 8 ... Wiring conductor, 8a ... Ground Conductor, 8b ... convex portion, 9 ... head cover, 10 ...
・ Heat sink, 11 ... Screw, 12 ... Connector

Claims (3)

[Claims] 1. A head substrate on which a large number of heating elements and circuit patterns are adhered, and an external wiring board having a plurality of wiring conductors electrically connected to the circuit patterns are provided side by side, and A metal head cover, one end of which extends to the vicinity of the heating element, is arranged on the wiring board, and the heating element is selectively heated while guiding the recording medium onto the heating element on the outer surface of the head cover. In this thermal head, at least one of the plurality of wiring conductors is held at a ground potential, and a part of the head cover is brought into contact with the grounded wiring conductor so as to connect both of them. A thermal head characterized by being electrically connected. 2. The thermal head according to claim 1, wherein the wiring conductor has a convex portion protruding toward the head cover side at a contact portion of the head cover. 3. The thermal head according to claim 1, wherein a recording medium is brought into sliding contact with the outer surface of the head cover during printing.