Etching a substrate: processes – Forming or treating thermal ink jet article
Reexamination Certificate
2000-01-27
2002-04-09
Alanko, Anita (Department: 1746)
Etching a substrate: processes
Forming or treating thermal ink jet article
C216S033000, C216S067000
Reexamination Certificate
active
06368515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an ink-jet printer head, which has an excellent workability to efficiently and quickly form (bore) good orifices in an orifice plate.
2. Description of the Related Art
Recently, ink-jet printers are widely used. The ink-jet printers include a thermal jet type which ejects ink droplets under the pressure of bubbles that are generated by heating the ink by means of a heat-generating resistor element and a piezoelectric type which ejects ink droplets by pressure that is applied to the ink by the deformation of a piezoelectric resistor element (piezoelectric element).
Because those types of printers do not require a developing step and transfer step and directly eject ink droplets on a recording medium to record information, they are advantageous over an electrophotographic type which uses powder-like toners in easy miniaturization and lower printing energy. The ink-jet printers are therefore popular particularly as personal printers.
The thermal jet type printer heads are classified into two structures depending on the ejection direction of ink droplets: a side-shooter type thermal ink-jet printer head which ejects ink droplets in a direction parallel to the heat generating surface of the heat-generating resistor element and a roof-shooter type or top-shooter type thermal ink-jet printer head which ejects ink droplets in a direction perpendicular to the heat generating surface of the heat-generating resistor element. The roof-shooter type thermal ink-jet printer head, in particular, is known for its very low power consumption.
FIGS. 1A through 1C
exemplarily and schematically illustrate the printing principle of the roof-shooter type thermal ink-jet printer head. As shown in
FIG. 1A
, a heat-generating resistor element
2
is disposed on a silicon substrate
1
, and an orifice plate
3
is adhered to an unillustrated partition and is so arranged as to face the silicon substrate
1
. A plurality of orifices
4
as ink-ejection nozzles are formed in the orifice plate
3
at a location facing the heat-generating resistor element
2
. Unillustrated electrodes are connected to both ends of the heat-generating resistor element
2
, and ink
5
is always supplied to an ink flow path in which the heat-generating resistor element
2
is provided.
To eject ink droplets from the orifices
4
, first, as shown in
FIG. 1B
, (1) energizing according to image information heats the heat-generating resistor element
2
, thereby causing bubble nucleation on the heat-generating resistor element
2
. (2) The generated bubbles are combined to generate a film bubble
6
. (3) The film bubble
6
is adiabatically expanded and grown, pressing the nearby ink. This drives ink
5
′ out of the orifices
4
so that the ink
5
′ becomes an ink droplet
7
as shown in
FIG. 1C
which are ejected toward the surface of an unillustrated sheet of paper. (4) As the heat of the grown film bubble
6
is taken by the nearby ink, the film bubble
6
contracts. (5) The film bubble
6
disappears to be ready for the next heating of the heat-generating resistor element
2
. This sequence of steps (1) to (5) is performed instantaneously.
One way of manufacturing such a thermal ink-jet printer head is to simultaneously form a plurality of heat-generating resistor elements, drivers for those elements and a plurality of orifices in a monolithic form by utilizing silicon LSI technology and thin film technology.
FIG. 2
presents a table illustrating steps of manufacturing such a thermal ink-jet printer head. As shown in
FIG. 2
, an oxide film, a resistor film and an electrode film are formed on a substrate in step (1). In step (2), the pattern of heat generating sections and the pattern of electrodes are respectively formed on the resistor film and the electrode film by photolithography or the like. In step (3), a partition is formed which separates the area on the substrate into a predetermined pattern, defining ink flow passages. In step (4), an ink feed passage and an ink feed hole are formed in the substrate. In step (5), an orifice plate is adhered onto the partition.
In step (6), a metal film is formed on the surface of the orifice plate and the pattern of orifices is formed on that metal film. In step (7), orifices are formed using an ordinary dry etching system, excimer laser or the like. In step (8), individual substrates collectively formed on a wafer are separated into individual units by dicing. In step (9), each single head substrate is bonded to a mount substrate with its leads connected to the associated leads thereof. This completes a practical unit of a thermal ink-jet printer head.
In the fabrication of a roof-shooter type thermal ink-jet printer head, the orifice plate should be adhered in such a way as not to bury the ink groove or ink passage formed by the partition with a height of about 10 &mgr;m. While designing this partition to have a height of over 15 &mgr;m eliminates the need for such a concern, the partition cannot be formed to a height of over 15 &mgr;m by single application of a photosensitive resin which is the material for the partition. Applying the photosensitive resin twice however doubles the time for the step of forming the partition, thus lowering the working efficiency.
In addition, a high partition with a height of over 10 &mgr;m makes it difficult to form fine ink flow passages that are needed for a head having a resolution of 400 dpi or greater. In this respect too, the height of the partition should be set to about 10 &mgr;m at a maximum. Normally, an orifice plate which is prepared by applying an adhesive of an epoxy base or the like to a resin of polyimide or the like is adhered onto the partition by thermocompression bonding. This scheme requires that an adhesive should be applied to the thickness of, for example, 5 &mgr;m or less just before usage and should be adhered to the substrate immediately thereafter. It is difficult to apply the adhesive uniformly and thin. Even if application of the adhesive to the thickness of 5 &mgr;m is possible, the ink groove or ink flow passages after adhesion are narrowed to the height of 5 &mgr;m by the adhesive that has been pressed from above by thermocompression bonding, so that part of the ink groove and ink flow passages may be blocked depending on a variation in the thickness of the adhesive.
The conventional scheme has a difficulty in applying an adhesive uniformly and thin and a technical problem on storage after application of the adhesive. It is therefore necessary to perform a work of adhering the orifice plate immediately after application of the adhesive. Further, because the adhesive is sticky, care should be taken to handle the partition applied with the adhesive at the time of adhering the orifice plate, i.e., the workability is not high. Even if polyimide which has a reliably high heat resistance is used for the partition and orifice plate as mentioned above, if an adhesive with a low heat resistance is used, deterioration of the adhesive during use would reduce the high heat-resistance reliability of the partition and orifice plate.
Recently, therefore, the aforementioned orifice plate
3
is acquired by forming an adhesive layer, which consists of a thermoplastic adhesive material having such a high glass transition point as not to flow at room temperature and excellent heat resistance, on the adhesion surface of a very thin polyimide film of about 30 to 40 &mgr;m thick which is the essential material. This ensures storage of the orifice plate
3
with the adhesive material applied and allows the orifice plate to be easily adhered to the substrate
1
by thermocompression.
It is to be noted however that this thermoplastic adhesive layer should be adhered to both sides of the orifice plate
3
, i.e., not only on the bottom of the orifice plate where the substrate
1
is to be placed but also on the top surface which does not inherently need such adhesion. This is because application of such an adhesive
Arai Kazuyoshi
Kaminishi Katsuzo
Kohno Ichiro
Shiota Junji
Alanko Anita
Casio Computer Co. Ltd.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
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