Thick-film thermal printhead

Details Thick-film thermal printhead Thick-film thermal printhead

2000-11-06

2002-07-23

Tran, Huan (Department: 2861)

Incremental printing of symbolic information

Thermal marking apparatus or processes

Specific resistance recording element type

C347S202000

Reexamination Certificate

active

06424367

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a thick-film thermal printhead.
BACKGROUND ART
An example of a conventional thick-film thermal printhead is shown in FIG.
5
and FIG.
6
. Each of these conventional thermal printheads (indicated by reference code P) comprises a rectangular head substrate
1
′ and a print substrate
2
′, As shown in
FIG. 5
, the head substrate
1
′ has a first longitudinal edge
1
a
′ and a second longitudinal edge
1
b
′ extending in parallel to each other. Further, the head substrate
1
′ has a first end
1
c
′ and a second end
1
d
′ extending between the first and the second longitudinal edges. Likewise, the print substrate
2
′ has two longitudinal edges and two ends.
The head substrate
1
′ has an upper surface entirely covered by a glaze layer
10
′ (
FIG. 6
) made of amorphous glass. On an upper surface of the glaze layer
10
′, a linear heating resistor
11
′ extending along the first longitudinal edge
1
a
′ is formed. The head substrate
1
′ is further formed with a common electrode
12
′ and a plurality of individual electrodes
13
′. As shown in
FIG. 5
, the common electrode
12
′ extends along the first end
1
c
′, the first edge
1
a
′, and the second end
1
d
′. Further, the common electrode
12
′ has a plurality of comb-like teeth
12
A′ extending in parallel to each other. Each of the comb-like teeth
12
A′ has a tip potion
12
a
′ contacting the heating resistor
11
′.
Each of the individual electrodes
13
′ has a first end portion
13
a
′ and a second end portion
13
b
′ away therefrom. The first end portion
13
a
′ contacts the heating resistor
11
′ and extends between two adjacent comb-like teeth
12
A′ On the other hand, the second end portion
13
b
′ is formed with a bonding pad
13
c
′. The bonding pad
13
c
′ is electrically connected to a drive IC
14
′ via a connecting wire W′.
With the above constitution, the heating resistor
11
′ is divided into a plurality of regions
15
′ by the comb-like teeth
12
A′. (
FIG. 5
shows only one region
15
′.) In each of the regions
15
′, electric current is passed selectively via the drive IC
14
′, to heat the selected region
15
′, making each of the regions
15
′ function as a heating dot.
The prior-art thick-film thermal printhead P as described above has a following disadvantage: Specifically, the thermal printhead P can provide a good printing result if the printing is performed at a speed of about 2 inches per second (2 ips). However, if the printing speed is increased to about 6 ips for example, printed image can be partially blurred, or an unintended whisker-like projection (feathering) can be printed on a printing sheet.
DISCLOSURE OF THE INVENTION
A thick-film thermal printhead provided by a first aspect of the present invention comprises: an oblong rectangular substrate having at least one longitudinal edge; a partial glaze layer provided on the substrate along the longitudinal edge; a linear heating resistor formed on the partial glaze layer; a common electrode formed on the substrate and electrically connected to the heating resistor; and a plurality of individual electrodes formed on the substrate and electrically connected to the heating resistor.
According to a preferred embodiment, the partial glaze layer has an arcuate cross section. Further, the partial glaze layer has a thickness of 10-25 &mgr;m and a width of 400-1000 &mgr;m.
Preferably, the common electrode includes a plurality of comb-like teeth each including a tip portion having a smaller width and a base portion having a larger width.
The tip portion of each comb-like tooth may be entirely formed on the partial glaze layer. In this case, preferably, the base portion of each comb-like tooth is formed only partially on the partial glaze layer.
Preferably, the base portion of each comb-like tooth is spaced from the heating resistor.
Preferably, the base portion of each comb-like tooth extends on both of the partial glaze layer and the substrate.
According to the preferred embodiment, each of the individual electrodes includes a tip portion having a smaller width for contact with the heating resistor, and an intermediate portion having a larger width.
Preferably, the intermediate portion of each individual electrode is spaced from the heating resistor.
Preferably, the intermediate portion of each individual electrode extends on both of the partial glaze layer and the substrate.
Other object, characteristics and advantages of the present invention will become clearer from an embodiment to be described with reference to the attached drawings.


REFERENCES:
patent: 5003324 (1991-03-01), Yoshiike et al.
patent: 5914743 (1999-06-01), Tagashira et al.
patent: 5917531 (1999-06-01), Nagahata et al.
patent: 4-128058 (1992-04-01), None
patent: 05-318793 (1993-12-01), None
patent: 7-304198 (1995-11-01), None
patent: WO97/29915 (1997-08-01), None

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