Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-12-03
2001-02-27
Yockey, David F. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S045000
Reexamination Certificate
active
06193352
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to ink jet printing and, more particularly, to a method for cleaning ink jet nozzle plates in ink jet print heads by maintaining the anti-wetting character thereof.
BACKGROUND OF THE INVENTION
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
A continuing problem with ink jet printers is the accumulation of ink on ink jet nozzle plates, particularly around the orifice from which ink drops are ejected. The result of ink drops accumulating around the orifice is that it becomes wettable causing ink drops to be misdirected, degrading the quality of the printed image.
To limit or prevent the spreading of ink from the orifice to the nozzle plate, it is common practice to coat the ink jet nozzle plate with an anti-wetting layer. Examples of anti-wetting layers are coatings of hydrophobic polymer materials such as Teflon® and polyimide-siloxane, or a monomolecular layer of a material that chemically binds to the nozzle plate, e.g., alkyl thiols, alkyl trichlorosilanes and partially fluorinated alkyl silanes.
Ink jet nozzle plates are also contaminated by ink drops that land on the nozzle plate. These “satellite” ink drops are created as a by-product of the drop separation process of the primary ink drop that is used to print. Another source of contaminating ink are tiny ink drops that are created when the primary ink drop impacts recording material. Ink drops accumulating on the nozzle plate can also potentially attract contaminants such as paper fibers which cause the nozzles to become blocked. Partially or completely blocked nozzles can lead to missing or misdirected drops on the print media, either of which degrades the quality of the print.
In order to solve this problem, the nozzle plates are periodically wiped clean. Several wiping methods are known including wet wiping techniques utilizing inks as a cleaning solvent. While inks and ink solvents used to dilute inks may be used as a cleaning liquid, they are not optimized for this purpose. Inks may contain additives such as, for example, ethylene glycol, diethylene glycol, and diethylene glycol monobutyl ether which may be environmentally undesirable when released during cleaning in unventilated areas such as a home or an office.
Further, inks often contain various materials which may leave an undesirable residue on the ink jet print head nozzle plate. Thus while wiping removes ink drops from the nozzle plate, the hydrophobic anti-wetting coating on the nozzle plate may be severely contaminated and compromised by ink residue. The ink-fouled coating is therefore unable to prevent the spreading of ink from orifices.
It has also been discovered that hydrophobic coatings on an ink jet print head nozzle plate are susceptible to fouling by certain ink jet inks, such as those containing copper phthalocyanine dyes. The fouling of the nozzle plate by the ink can lead to excessive spreading by ink on to the nozzle plate during normal use, further aggravating drop placement problems. Another disadvantage in using inks as a cleaning solution is that they are expensive.
There remains a need for a simple, economical ink jet nozzle plate cleaning solution that will help maintain the anti-wetting character of ink jet nozzle plates so that an ink jet print head will consistently deliver accurate and reproducible drops of ink to a receiver resulting in photographic quality images.
DESCRIPTION OF RELATED ART
U.S. Pat. Nos. 5,495,272 and 5,589,865 relate to a cleaning solution for an ink jet print head which may include a surfactant. However, there is a problem in that not all surfactants are as effective in cleaning as one would like.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a method for cleaning an ink jet print head nozzle plate comprising applying to said nozzle plate a cleaning solution comprising an aqueous solution of a metal salt of a taurine surfactant.
A taurine surfactant has a hydrophobic moiety and a polar taurine moiety and may be represented by the following formula:
wherein
R represents a substituted or unsubstituted alkyl or arylalkyl group having from about 6 to about 22 carbon atoms or a fluoroalkyl or arylfluoroalkyl group having from about 4 to about 14 carbon atoms, such as hexyl, dodecyl, myristyl, lauryl, oleoyl, dodecylbenzene, fluorobutyl, fluorohexyl, phenylperfluorohexyl, partially fluorinated alkyl groups, etc.;
R
1
and R
2
each independently represents a substituted or unsubstituted alkyl or fluoroalkyl group having from about 1 to about 6 carbon atoms, such as methyl, ethyl, propyl, fluoromethyl, fluoroethyl, partially fluorinated alkyl groups, etc; and
M
+
represents either a metal ion such as sodium, potassium, magnesium, etc.; or an ammonium ion.
The cleaning liquid used in this invention is inexpensive, odor-free and non-toxic. This cleaning solution is effective in restoring the anti-wetting property of coatings on an ink jet printhead after the surface of the print head has been fouled by ink.
In a preferred embodiment of the invention, R is myristyl, lauryl or oleoyl. In another preferred embodiment, R
1
is methyl and R
2
is ethyl. In yet another preferred embodiment, M
+
represents sodium.
Examples of surfactants useful in the invention include the following:
Surfactant
1
: oleoyl methyl taurate, sodium salt (NaOMT);
Surfactant
2
: lauryl methyl taurate, sodium salt (NaLMT); or
Surfactant
3
: myristyl methyl taurate, sodium salt (NaMMT).
Ink jet inks used in ink jet recording elements which the cleaning solution of the present invention will clean are well-known in the art. The ink compositions used in ink jet printing typically are liquid compositions comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives, and the like. The solvent or carrier liquid can be solely water or can be water mixed with other water-miscible solvents such as polyhydric alcohols. Inks in which organic materials such as polyhydric alcohols are the predominant carrier or solvent liquid may also be used. Particularly useful are mixed solvents of water and polyhydric alcohols. The dyes used in such compositions are typically water-soluble direct or acid type dyes. Such liquid compositions have been described extensively in the prior art including, for example, U.S. Pat. Nos. 4,381,946; 4,239,543 and 4,781,758, the disclosures of which are hereby incorporated by reference.
Ink jet nozzle plates which the cleaning solution of the present invention will clean are well known in the art. They are disclosed, for example, in U.S. Pat. Nos. 5,574,485; 5,250,962; 5,117,244; and 5,304,814, the disclosures of which are hereby incorporated by reference.
The following examples are provided to illustrate the invention.
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patent: 5143758 (1992-09-01), Devine
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patent: 5589865 (1996-12-01), Beeson
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Hamilton-Winbush Vincent E.
Penner Thomas L.
Sharma Ravi
Brooke Michael S
Cole Harold E.
Eastman Kodak Company
Yockey David F.
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