JP3167264B2 - Thermal printhead structure - 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 print head in a facsimile or a printer apparatus, the thermal print head being made of a heat-resistant insulating material such as a ceramic having a heating resistor for printing. The present invention relates to a structure of a thermal print head including a board, a circuit board made of a synthetic resin having a connector for connection to the outside, and a metal radiator plate to which these are attached.

[0002]

2. Description of the Related Art Conventionally, this type of thermal printhead has a heating resistor for printing, a common wiring pattern and an individual wiring pattern formed on a top surface of a metal heat sink, and a plurality of driving circuits. A circuit board comprising a ceramic head substrate on which elements are mounted, and a wiring pattern for connecting various terminal electrodes on the head substrate side and the connection connector provided with a connector for connection to the outside; By disposing one end of the substrate so as to overlap with each terminal electrode on the head substrate side, pressing one end of this circuit board via a rubber cord with a pressing body screwed to the heat sink. While electrically connecting each wiring pattern on the circuit board side to each terminal electrode on the head board side, a portion of the drive circuit element of the head board by the pressing body And it was configured to say covering the circuit board (for example, see Japanese Patent Laid-Open No. 2-286261, etc.).

[0003]

However, in this conventional thermal print head, a driving circuit element portion of the head substrate and the circuit substrate are connected by a pressing body for connecting the circuit substrate to the head substrate. The cover is configured to ensure the pressure resistance of the drive circuit element and the circuit board against static electricity charged on the printing paper or the like at the time of printing, and the holding body also serving as a cover has strength along its longitudinal direction. In addition to the need to increase the height, at multiple points in the longitudinal direction, it is necessary to strongly tighten the set screw with respect to the heat sink. Due to the tightening, not only is the heat sink distorted and deformed along its longitudinal direction, but also the holding body and the heat sink are Since the heat sink is integrally fixed over the heat sink, distortion deformation due to a difference in thermal expansion occurs in the heat radiation plate along the longitudinal direction, and these distortion deformations reach the head substrate attached to the heat radiation plate. There is a problem that printing unevenness occurs in printing by the heating resistor on the substrate, and the printing quality deteriorates.

According to the present invention, it is possible to extremely easily attach a cover for securing the drive circuit element of the head substrate and the circuit substrate withstand voltage against static electricity without causing the above-mentioned problems. It is a technical problem to provide such a structure.

[0005]

SUMMARY OF THE INVENTION In order to achieve this technical object, the present invention provides a head substrate having a heating resistor for printing formed on an upper surface of a metal heat sink and a driving circuit element mounted thereon. In a thermal print head in which a circuit board and a circuit board are mounted side by side, each terminal electrode on the head board and a terminal electrode on the circuit board are electrically connected by a metal terminal lead fixed to a side edge of the head board. On the back of one side edge of the circuit board opposite to the head substrate, a connector for external connection is mounted such that a part of the connector protrudes from the one side edge, On the upper surface side of the circuit board, a cover plate configured to be fastened to the heat sink with screws is used. And a rib for contacting the upper surface of the connector is provided on the lower surface of the cover plate so as to extend along one side edge of the circuit board, and a contact portion for the upper surface of the circuit board is provided. Provided. "

[0006]

The terminal electrodes on the head substrate and the terminal electrodes on the circuit substrate are electrically connected by metal terminal leads fixed to the side edges of the head substrate, so that the upper surface of the circuit substrate is It is not necessary to configure the cover plate disposed on the circuit board so as to strongly press the circuit board against the head substrate as in the related art, and it can be configured to exclusively cover the head substrate and the circuit board. Since it is not necessary to strongly tighten the screws for mounting the cover plate, the heat sink is deformed by the fastening of the cover plate to the heat sink, and heat is dissipated due to a difference in thermal expansion between the cover plate and the heat sink. It is possible to reliably prevent thermal distortion from occurring on the plate, reduce printing unevenness during printing, and improve printing quality.

[0007] Further, a rib for contacting the upper surface of the connector mounted on the circuit board and a contact portion for contacting the upper surface of the circuit board are provided on the lower surface of the cover plate. Since it can be mounted in a floating state with respect to the drive circuit element and the circuit board in the head board,
When the cover plate is attached, the drive circuit element and the circuit board are not damaged.

Further, the rib provided on the lower surface of the cover plate is configured to extend along one side edge of the circuit board, so that the rib is attached to the one side edge of the circuit board when attaching the cover plate. The cover plate is automatically determined by the position of the cover plate, so that the cover plate shifts in the direction of the heating resistor and contacts the printing paper or shifts in the direction away from the heating resistor. It is extremely easy to accurately mount the drive circuit element at a predetermined position without losing protection.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.
Referring to the drawing of FIG. In FIG.
Denotes a thermal print head composed of at least four members: a heat sink 2, a head substrate 3, a circuit board 4, and a cover plate 5. The heat sink 2 is made of a metal such as an aluminum alloy. On the upper surface, a groove 6 is provided so as to extend in the longitudinal direction.

The head substrate 3 is made of a heat-resistant insulator such as a ceramic, and is mounted on one side of the upper surface of the heat radiating plate 2 with the groove 6 interposed therebetween with an adhesive. The heating resistor 7 for printing is formed so as to extend in a line along one longitudinal side edge 3 a of the head substrate 3, and a plurality of drive circuit elements 8 are connected to the heating resistor 7. Are mounted in a line along the other side, and further, at both ends of the other longitudinal side edge 3b of the head substrate 3,
A plurality of terminal leads 10 that are electrically connected to the various terminal electrodes 9 provided in the portion are fixed so as to project substantially perpendicularly from the other long side edge 3b.

The circuit board 4 is made of a synthetic resin such as a glass epoxy resin.
The circuit board 4 is attached to the other side thereof with an adhesive, and the circuit board 4 is provided on the lower surface of the other long side edge 4b of the two long side edges 4a and 4b opposite to the head substrate 3. A connector 11 having a plurality of terminal pins 11b is mounted on a connector body 11a, and each terminal electrode 12 on each of the left and right ends of the upper surface thereof and each of the terminal pins 11b on the connector 11 are electrically connected. A wiring pattern (not shown) for connection is formed.
Each terminal lead 10 projecting from the head substrate 3 is connected to each of the terminal electrodes 12 by soldering.

Further, the cover plate 5 is made of an insulator such as a synthetic resin, and is configured to cover at least the entire circuit board 4 to a portion of the drive circuit element 8 of the head board 3 and a lower surface thereof. In the connector 11, a rib 13 contacting the upper surface of the connector body 11a of the connector 11 is provided so as to extend along the other longitudinal side edge 4b of the circuit board 4, and is in contact with the upper surface of the circuit board 4. A contact portion 14 is provided, and the cover plate 5
It is configured to be mounted by tightening a mounting screw 16 that is inserted downward from the upper surface into a bolt hole 20 formed therein and screwed into the female screw hole 15 in the heat sink 2.

As shown in FIG. 1, the thermal print head 1 having the above-described structure is mounted on a frame member 17 of a facsimile or printer using the thermal print head 1 so that the heat radiating plate 2 comes into close contact therewith. Then, after screwing a plurality of mounting screws 18 inserted from the lower surface of the frame member 17 into the respective female screw holes 19 formed in the heat sink 2, the mounting screws 18 are tightened. It is attached to the frame member 17.

As described above, the terminal electrodes 9 on the head substrate 3 and the terminal electrodes 12 on the circuit board 4 are electrically connected by the metal terminal leads 10 fixed to the longitudinal side edge 3b of the head substrate 3. This eliminates the need for the cover plate 5 disposed on the upper surface side of the circuit board 4 to be configured to strongly press the circuit board 4 against the head substrate 3 as in the related art. The cover plate 5 can be configured to cover the circuit board 4 and the mounting screws 18 of the cover plate 5 do not need to be strongly tightened, so that the cover plate 5 is deformed by the fastening of the cover plate 5 to the heat sink. And the cover plate 5 and the heat sink 2
Therefore, it is possible to reliably prevent the heat radiation plate 2 from being thermally strained due to a difference in thermal expansion between the heat radiation plate 2 and the heat radiation plate 2.

A rib 1 is provided on the lower surface of the cover plate 5 to contact the upper surface of the connector body 11a mounted on the circuit board 4.
3 and the contact portion 14 that contacts the upper surface of the circuit board 4, so that the cover plate 5 is attached to the drive circuit element 8 of the head substrate 3 and the circuit board 4 in a floating state. Can be. Furthermore, the ribs 13 provided on the lower surface of the cover plate 5 are configured to extend along the longitudinal side edges 4b of the circuit board 4, so that the ribs 13 are attached to the circuit board 4 when the cover plate 5 is mounted. Since the position where the cover plate 4 is attached is automatically determined by contact with the longitudinal side edge 4b, it is extremely easy to accurately attach the cover plate 4 to a predetermined position.

The cover plate 5 made of the insulator has 10
By using an insulating material having a volume resistivity of about ⁴ to 10 ¹⁰ (Ω · cm) and imparting good static electricity,
The withstand voltage of the drive circuit element 8 and the circuit board 4 against static electricity can be further improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which a thermal print head according to an embodiment of the present invention is disassembled.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged sectional view taken along line III-III of FIG. 1;

FIG. 4 is a perspective view showing a state in which a heat sink, a head substrate, and a circuit board are disassembled.

FIG. 5 is a perspective view illustrating a thermal print head according to an embodiment of the present invention.

FIG. 6 is an enlarged sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is an enlarged sectional view taken along line VII-VII of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal print head 2 Heat sink 3 Head board 3a, 3b Side edge of head board 4 Circuit board 4a, 4b Side edge of circuit board 5 Cover plate 6 Groove 7 Heating resistor 8 Drive circuit element 9 Terminal electrode 10 Terminal lead 11 Connector 12 Terminal electrode 13 Rib 14 Contact part 15 Mounting screw

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/345

Claims (1)

(57) [Claims] 1. A thermal print head comprising: a head substrate on which a heating resistor for printing is formed on an upper surface and a drive circuit element is mounted on a top surface of a metal heat sink; Each terminal electrode on the head substrate and the terminal electrode on the circuit board are electrically connected to each other by a metal terminal lead fixed to a side edge of the head substrate. On the back surface of one side edge, a connector for connection to the outside is mounted such that a part of the connector protrudes from the one side edge, and on the upper surface side of the circuit board, a screw with respect to the heat sink is mounted. A cover plate configured to be fastened and fastened is disposed so as to cover the upper surface of the circuit board and the portion of the drive circuit element on the head substrate with the cover plate, and the connector is provided on the lower surface of the cover plate. And a rib contacting the upper surface of the circuit board is provided so as to extend along one side edge of the circuit board, and a contact portion for the upper surface of the circuit board is provided.