Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-06-03
2003-04-29
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06554400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nozzle plate for use in an ink jet type print head and a manufacturing process of the nozzle plate, and more particularly to a nozzle plate provided with nozzle orifices through which ink is to be ejected, the orifices being formed by an excimer laser using a working lens having the numerical aperture set in a range of 0.1 to 0.35, and a manufacturing process of the nozzle plate.
2. Description of Related Art
A nozzle plate used in an ink jet type print head is conventionally provided with minute nozzle orifices through which ink droplets can be ejected, the nozzle orifices being formed by a perforating operation with an excimer laser (for instance, ArF=198 nm, KrF=248 nm, XeKr=308 nm) which emits ultraviolet light. For a working lens used in the perforating operation, the working lens having a numerical aperture (NA) being usually about 0.05 has been used.
This numerical aperture (NA) represents an amount of the performance in connection with brightness and resolving power and the like of an optical system. In engineering instruments, if assuming the angle formed by a radius of an entrance pupil with respect to a point-shaped object (object point) on an optical axis as &agr; and the refractive index of a medium in which the object point exists as “n”, the numerical aperture (NA) is represented by n sin &agr;.
Here,
FIGS. 7 through 9
show the shapes of nozzle orifices formed in the conventional nozzle plate, which are formed by a working lens having NA=0.5. FIG.
7
(
a
) is a front view of the conventional nozzle plate and FIG.
7
(
b
) is a sectional view of the same. FIG.
8
and
FIG. 9
are microphotographs of the nozzle orifices in the conventional nozzle plate.
The conventional nozzle plate
31
is formed of a material having the solution resistance with respect to a solvent included in the constituent of ink to be used, and is provided with many nozzle orifices
32
through which the ink can be ejected as shown in FIG.
7
(
a
). FIG.
7
(
b
) is a sectional view of the conventional plate
31
in the case where the perforating operation is performed on the nozzle plate
31
by irradiating it with a laser beam from above in the figure. As shown in the figure, the sag (round portion) is produced around the nozzle orifice
32
in the nozzle plate
31
by the perforating operation.
Next, the relation between the size of the sag and the numerical aperture (NA) of the working lens as shown in FIGS.
5
(
a
) and
5
(
b
), in which the length L of the sag is defined as an amount of sag L (&mgr;m). It is found, as shown in FIG.
5
(
a
), that as the sag amount is smaller, the processing precision is higher. As the conventional nozzle plate is subjected to a perforating operation usually using the working lens the numerical aperture (NA) of which is 0.05, the sag amount becomes about 5 &mgr;m as shown in FIG.
5
(
b
). The actual shape of the nozzle orifice formed in the conventional nozzle plate in the above manner is shown in
FIGS. 8 and 9
which are microphotographs.
For a nozzle plate, it is generally required to reduce the amount of sag to be produced around the ink ejection orifice into 2 &mgr;m or less, which is because a large amount of sag tends to cause the reduction of the speed of ink droplets when ejected and the deflection of ink upon ink ejection, thus resulting in a deterioration in print quality.
Accordingly, in the conventional nozzle plate, a plane thereof on which the laser is incident is adhered to an actuator after the perforating operation. Specifically, the laser incident plane on which sag is produced is adhered to the actuator with an adhesive agent to form a print head in order to raise a processing precision of the nozzle orifice at a side from which ink is to be ejected and thereby to form a stable meniscus of ink. This is because, if the form of the meniscus of ink is unstable, a direction of ink ejecting from the nozzle orifice may become unstable due to a curvature of ink droplet, and variations in the timing of ink ejection may occur, thereby resulting in a deterioration in print quality.
However, there are the following disadvantages in the conventional nozzle plate and the manufacturing process thereof.
The conventional nozzle plate is manufactured such that nozzle orifices are first formed in the nozzle plate by a laser processing operation and, after that, the processed nozzle plate is adhered to an actuator with an adhesive agent. Upon the adhering operation, it is likely that excess adhesive agent flows into the inside of the nozzle orifices. This may cause the nozzle orifices to become unstable in shape and also the meniscus of ink to be unstable. In addition, the nozzle plate is adhered to the actuator after the nozzle orifices are formed, so that it needs to accurately make positioning between the nozzle orifices and the actuator to prevent a positional deflection therebetween. This is because such the positional deflection causes ink ejection in an unstable direction and variations in the timing of ink ejecting. Due to the above disadvantages, an adhering operation requires an extremely high-level and difficult technique.
To the contrary, to prevent the above disadvantages upon the adhering operation, conceivable is a process in which the nozzle plate is first adhered to the actuator and then is subjected to a perforating operation using an excimer laser. In such the case where the perforating operation is performed on the nozzle plate by using an excimer laser after the adhering operation, it is preferable to execute the perforating operation by making a laser beam be incident on a plane of the nozzle plate from which ink is to be ejected. This is because, if the nozzle plate is processed from the side of the plane adhered to the actuator, the energy of the excimer laser incident onto the nozzle plate may weaken the adhesive strength between the nozzle plate and the actuator and deflect the mating position of the nozzle plate and the actuator and, in the worst case, may take the nozzle plate off the actuator.
Accordingly, after the adhering operation, the perforating operation on a nozzle plate is conducted by making the excimer laser be incident onto the plane of the nozzle plate from which ink is to be ejected. In this case, sag is produced on the nozzle orifices at the ink ejecting side, i.e., the surface irradiated by the excimer laser upon the perforating operation. When the perforating operation is performed with the working lens having NA=0.05 as above, the sag amount becomes about 5 &mgr;m as shown in FIG.
5
(
b
), which is so large to make a meniscus of ink unstable.
As a result, there are such disadvantages that the ejecting direction of ink ejected from the nozzle orifice becomes unstable due to the curvature of ink droplet, and variations in the timing of ink ejection is produced, resulting in a deterioration in print quality.
As mentioned above, the adhering operation requires a difficult technique when the perforating operation using an excimer laser is performed on the nozzle plate before the nozzle plate is adhered to the actuator, to the contrary, the shapes of the nozzle orifices become unstable when the perforating operation is performed after the adhering operation. Consequently, both ways can not produce a satisfactory processed nozzle plate.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a nozzle plate for an ink jet head provided with nozzle orifices and a manufacturing process of the nozzle plate, capable of reducing sag which will be produced in processing the nozzle plate by an excimer laser device to form the nozzle orifices through which ink can be ejected, of easily adhering the nozzle plate to an actuator and the like, and of forming the nozzle orifices in desired shapes thereby to increase the print quality.
Additional objects and advantages of the invention will be set
Barlow John
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
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