Electric heating – Metal heating – By arc
Reexamination Certificate
1999-01-19
2003-01-14
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06507001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to anti-wetting ink jet nozzles and a method of precisely forming anti-wetting ink jet nozzles. One method uses laser ablation and another method uses precision injection molding to create a nozzle with a lip that can prevent unwanted deflection of ink droplets. The ink jet nozzles can be made from materials that avoid damage from inks which have been known to cause damage to nozzles made from silicon wafers or semiconductors. Moreover, the invention enables a wider range of inks, e.g., abrasive or aggressive inks in the upper and lower pH ranges, for use with ink jet nozzles.
2. Description of Related Art
FIG. 1A
shows a prior art ink jet printing device
1
having a conventional nozzle structure that includes an annular bore
3
and a front face
4
that is oriented perpendicular to the axis of the bore
3
. Each bore
3
of an ink jetting device
1
is supplied with a supply of ink
2
that is intended to create characters on a recording medium (not shown).
FIG. 1A
shows the progression of ink
2
as it emerges from the bore
3
and eventually onto a recording medium. The formation of a droplet
5
eventually occurs at the mouth of the bore and gradually builds in size until the ink emerges from the bore and prints the desired character on the recording medium. Thermal ink jet devices of this type suffer in print quality when wetting
6
occurs on the front face
4
of the ink jet nozzle. This type of wetting creates imprecise character printing and often times smudging.
In addition, when a portion
7
of the ink
2
surrounding the orifice
3
dries in an asymmetrical manner as shown in
FIG. 1B
, a next forming droplet
8
is cohesively attracted to the side where the wetting is greatest and deflected in that direction as indicated by arrow
9
. Prior art thermal ink jet devices use a hydrophobic front face coating to minimize front face wetting by the ink in an attempt to avoid these directionality problems.
Another solution is to minimize wetting by microfabricating a nozzle structure surrounding the orifice that minimizes front face wetting. Such a solution to the ink wetting problem is shown in prior art
FIG. 2
which shows an ink jet nozzle
10
having a front face
11
perpendicular to a bore
12
forming a passage for ink
13
to be supplied from an unshown source. In addition, the nozzle
10
of
FIG. 2
includes a lip portion
14
that serves to prevent wetting on the front face
11
of the nozzle. While this nozzle structure helps to eliminate wetting, it suffers because it is currently manufactured by expensive chemical or mechanical processes.
FIG. 3
shows a five-step chemical process by which a lip portion of the prior art device of
FIG. 2
is formed. The first step is to provide a brass plate
15
as shown in step (a) and to drill a first cylindrical hole
16
and a second countersunk bore
17
within the brass plate
15
(step (b)). In step (c), a layer of nickel
18
is applied by the “electroless” method to all surfaces of brass plate
15
of step (b) including top face
19
, bottom face
20
, and the surfaces of throughhole
16
and countersunk hole
17
. In step (d), the bottom surface
21
of the nickel layer
18
and some of the brass, where necessary, are removed by grinding. Finally, in step (e), the surface
20
surrounding the nickel surface
18
b
coated onto annular bore
16
is selectively etched to produce a lip portion
14
of the nozzle.
FIGS. 4A and 4B
show an alternative method for mechanically forming a lip portion on an ink jet nozzle. In this process, the object is to punch a hole using punch
22
in a nickel plate
23
, the nickel plate forming the nozzle. A force F drives the punch
22
into the nickel plate
23
. At the end of the process, a part of the nickel plate
23
will penetrate into a plastic strip
24
. Because of the supporting action of steel plate
25
and the fluid behavior of plastic
24
, a hole
26
without burrs and of the desired shape including a lip
27
is produced in the nickel plate
23
.
It is also known to produce nozzle plates using a laser ablation technique, whereby a laser is used to create a bore, e.g., a countersunk bore, through the nozzle plate. However, such nozzles also suffer from the ink wetting problems described above because they do not have a lip portion, as shown in FIG.
2
.
U.S. Pat. No. 4,961,821 to Drake et al. discloses a method for forming throughholes in silicon wafers using an orientation dependent etching technique, and is incorporated herein by reference. As shown in FIGS. 9E and 9F of Drake, however, the ink jet nozzles encounter the same problems as those discussed in reference to
FIGS. 1A and 1B
. Moreover, the orifices of Drake do not provide for a lip portion that prevents wetting around the area surrounding the ink jetting orifice. In addition, the method for manufacturing the orifice includes an anisotropic method of etching that requires surfaces 31 and 32 to be covered with an etch resistant layer 34 in those areas where it is not desired to form a throughhole. Moreover, Drake anisotropically etches (100) crystallographic planes 35 and 36 using an additional etch resistant layer 34 to mask those portions of the wafer 30 not desired to be etched.
U.S. Pat. No. 5,487,483 to Kubby, incorporated herein by reference, discloses an ink jet nozzle and a method for manufacturing the same. A hollow extension lip is provided to prevent unwanted deflection of ink droplets. The nozzle as well as the hollow extension lip are disclosed as being made, for example, using a two step process including physical sputter erosion and chemically etching the nozzle area surrounding the orifice using an anisotropic etching method. However, this process is limited for use with silicon wafers or other semiconductor materials. Also, silicon/semiconductors are limited because acidic or basic inks can cause damage to those materials, and thus the selection of inks for use in ink jet nozzles using such materials is limited.
SUMMARY OF THE INVENTION
It is an aspect of the present invention to provide an anti-wetting ink jet nozzle for a printing device that prevents unwanted deflection of ink droplets by preventing asymmetrical depositing of ink about the regions surrounding the orifice of the ink jet nozzle.
It is another aspect of the present invention to expand the materials available for producing anti-wetting, precision ink jetting nozzles. For example, the manufacturing processing techniques can be used to create nozzles made, for example, of polymers (e.g., polysulphone), plastics, Teflon®, metals and/or oxides, etc.
It is another aspect to form the nozzles of the ink jetting devices in a cost-efficient and time-efficient manner, and which can eliminate the problems associated with ink selection limitations and ink history defects. Thus, more chemically aggressive inks can be used, e.g., inks having a pH of 3 or 9-10.
According to one aspect of the invention, there is provided a method of microfabrication of an ink jet nozzle. The method comprises the steps of providing a nozzle plate having an upper surface and a lower surface; laser ablating the upper surface of the nozzle plate to create a bore which extends from the upper surface of the nozzle plate to the lower surface of the nozzle plate; and laser ablating the lower surface of the nozzle plate to create a lip which extends away from the lower surface of the nozzle plate.
According to another aspect of the present invention, there is provided a method of microfabrication of an ink jet nozzle. The method comprises the steps of providing upper and lower molds forming therebetween a space defining a shape corresponding to an ink jet nozzle having a nozzle plate and a lip formed in one piece with an extending away from the nozzle plate; injecting the space with a molding material; and removing the upper and lower molds to release the thus formed ink jet nozzle. In this method, the molding material may be a polymer, a plastic material, ceramics, or any material that c
Heinrich Samuel M.
Xerox Corporation
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