Incremental printing of symbolic information – Thermal marking apparatus or processes – Specific resistance recording element type
Patent
1996-05-16
1998-04-14
Tran, Huan H.
Incremental printing of symbolic information
Thermal marking apparatus or processes
Specific resistance recording element type
347205, B41J 2335
Patent
active
057398372
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a thermal printhead used for a facsimile machine or the like. The present invention also relates to a clip-type terminal lead and a cover member which are advantageously used for such a thermal printhead.
BACKGROUND ART
Typical thermal printheads are disclosed in Japanese Patent Application Laid-open No. 2-286267 and Japanese Patent Application Laid-open No. 2-292055 for example. The thermal printheads in these documents have a structure wherein a head substrate made of a ceramic and a printed circuit board made of a synthetic resin are juxtaposed in a coplanar manner on a metallic heat sink plate. The head substrate is provided with a heating resistor constituting a line of printing dots, a common electrode, a plurality of individual electrodes and a plurality of drive IC chips. On the other hand, the printed circuit board is formed with a wiring pattern for connecting each of the drive ICs to a connector for external connection.
However, in the thermal printhead having the above structure, since the head substrate and the printed circuit board are juxtaposed in a common plane, the overall widthwise dimension cannot be made smaller than the total of the widthwise dimensions of the head substrate and printed circuit board, so that the size is inevitably made large. Accordingly, the heat sink plate is also made large, resulting in an increase in the total weight.
For solving such a problem, Japanese Patent Application Laid-open No. 3-57656 proposes a thermal printhead wherein a head substrate and a printed circuit board are mounted at different heights on a stepped heat sink plate. More specifically, the heat sink plate has an upper first supporting surface and a lower second supporting surface. The head substrate is attached to the first supporting surface with one longitudinal edge of the substrate projecting, whereas the printed circuit board is attached to the second supporting surface to partially overlap the projecting edge of the head substrate. As a result, the overall widthwise dimension of the thermal printhead can be reduced by the overlapping amount of the head substrate and the printed circuit board.
However, in the thermal printhead having the above-described stepped structure, since the upper surface of the printed circuit board is arranged to come into direct contact with the lower surface of the head substrate, thermal conduction from the head substrate to the heat sink plate is blocked by the printed circuit board disposed therebetween. As a result, the head substrate dissipates less heat to the atmosphere, thereby failing to deal with high-speed printing which generates a large amount of heat.
Further, the direct contact of the head substrate with the printed circuit board allows the thicknesswise thermal expansion in the printed circuit board to directly affect the head substrate, thereby incurring a problem of deteriorating printing quality due to the deformation of the head substrate.
Further, in the thermal printhead having the stepped structure, since electrical connection between the head substrate and the printed circuit board is provided by wire bonding with the use of thin metal wires, it is also a problem that errors frequently occur when performing wire bondings.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a thermal printhead which solves the foregoing problems.
Another object of the present invention is to provide a thermal printhead by which the printing performance is hardly deteriorated by a rise in temperature.
Another object of the present invention is to provide a clip-type terminal lead which can be advantageously used for such a thermal printhead.
Still another object of the present invention is to provide a cover member which can be advantageously used for such a thermal printhead.
According to a first aspect of the present invention, there is provided a thermal printhead comprising: a stepped heat sink plate having an upper first supporting surface and a lower second supporting s
REFERENCES:
patent: 4327365 (1982-04-01), Noda
patent: 4368491 (1983-01-01), Saito
Kishimoto Tokihiko
Minamino Masanori
Nagahata Takaya
Nishi Koji
Bednarek Michael D.
Rohm & Co., Ltd.
Tran Huan H.
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