U.S. patent application number 09/328860 was filed with the patent office on 2001-07-19 for high resolution pigment ink for impulse ink jet printing.
Invention is credited to SALISBURY, BRIAN, SARADA, THYAGARAJA, SARMA, DEVERAKONDA S..
Application Number | 20010008909 09/328860 |
Document ID | / |
Family ID | 26795807 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008909 |
Kind Code |
A1 |
SARMA, DEVERAKONDA S. ; et
al. |
July 19, 2001 |
HIGH RESOLUTION PIGMENT INK FOR IMPULSE INK JET PRINTING
Abstract
Impulse ink jet compositions are provided which are suitable for
printing clear, well-defined alphanumeric text or low spread,
narrow bar width bar codes on porous substrates such as Kraft paper
or corrugated cardboard. In one embodiment, the ink compositions
preferably comprise from about 20 to 50 percent by weight of a
carbon black dispersion, from about 10 to 20 percent by weight of a
dispersion medium, from about 40 to 60 percent by weight of a
plasticizer and optionally an antioxidant additive. The antioxidant
additive lowers the dissolved oxygen level in the ink, thereby
enhancing the jetting performance of the printhead.
Inventors: |
SARMA, DEVERAKONDA S.;
(DANBURY, CT) ; SALISBURY, BRIAN; (MIDDLEBURY,
CT) ; SARADA, THYAGARAJA; (HORSHAM, PA) |
Correspondence
Address: |
DAVID R BAILEY
WOODCOCK WASHBURN KURTZ
MACKIEWICZ & NORRIS
ONE LIBERTY PLACE 46TH FLOOR
PHILADELPHIA
PA
19103
|
Family ID: |
26795807 |
Appl. No.: |
09/328860 |
Filed: |
June 9, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60099230 |
Sep 4, 1998 |
|
|
|
Current U.S.
Class: |
523/160 ;
524/590 |
Current CPC
Class: |
C09D 11/36 20130101;
C09D 11/324 20130101 |
Class at
Publication: |
523/160 ;
524/590 |
International
Class: |
C03C 017/00; C08K
003/00 |
Claims
What is claimed is:
1. A dispersion ink composition for use in impulse ink jet
printers, comprising: (a) from about 20 to about 50 percent by
weight of a pigment dispersion, wherein said pigment dispersion
comprises from about 25 to about 45 percent by weight of a pigment;
from about 15 to about 45 percent by weight of a polymeric
dispersant; and from about 25 to about 45 percent by weight of a
dispersion medium, wherein the ratio of pigment to polymeric
dispersant is from about 1:1 to about 1:0.68; (b) from about 10 to
about 20 percent by weight of a glycol ether; and (c) from about 40
to about 60 percent by weight of a plasticizer.
2. The dispersion ink composition of claim 1 wherein the pigment
comprises carbon black.
3. The dispersion ink composition of claim 1 wherein the polymeric
dispersant comprises polyurethanes, polyacrylates, polymeric/fatty
acid condensation polymers, and mixtures thereof.
4. The dispersion ink composition of claim 1 wherein the dispersion
medium comprises an ester.
5. The dispersion ink composition of claim 1 wherein the dispersion
medium comprises diethyl oxalate, dibutyl oxalate, dimethyl
malonate, diethyl malonate, di-tert-butyl malonate, dimethyl
succinate, diethyl succinate, diethyl adipate, dimethyl sebacate,
dibutyl sebacate, diethyl azelate, methylene diacetate, ethylene
glycol diacetate, 2,2,4-trimethyl-1,3-penta- nediol diisobutyrate,
triacetin, or mixtures thereof.
6. The dispersion ink composition of claim 1 wherein the pigment
dispersion comprises from about 30 to about 40 percent by weight of
the pigment; from about 20 to about 40 percent by weight of the
polymeric dispersant; and from about 30 to about 40 percent by
weight of the ester.
7. The ink composition of claim 1 wherein the glycol ether
comprises propylene glycol methyl ether, dipropylene glycol phenyl
ether, propylene glycol phenyl ether, tripropylene glycol phenyl
ether, ethylene glycol phenyl ether, diethylene glycol methyl
ether, triethylene glycol butyl ether, propylene glycol n-propyl
ether, dipropylene glycol n-propyl ether, dipropylene glycol
n-propyl ether, or mixtures thereof.
8. The ink composition of claim 1 wherein the plasticiser comprises
alkyl benzyl phthalates, dioctyl phthalate, butyl benzyl phthalate,
dioctyl phthalate, diethyl phthalate, dimethyl phthalate,
di-(2-ethylhexy)-adipat- e, diisobutyl phthalate, diisobutyl
adipate, dicyclohexyl phthalate, glycerol tribenzoate, sucrose
benzoate, polypropylene glycol dibenzoate, neopentyl glycol
dibenzoate, dimethyl isophthalate, or mixtures thereof.
9. The ink composition of claim 1 wherein the average particle size
of the pigment is less than about 1.0 microns.
10. The ink composition of claim 1 wherein the average particle
size of the carbon black is less than about 0.6 microns.
11. A process of recording information on a substrate with an
impulse-type ink jet printer comprising: providing an ink
composition comprising: from about 20 to about 50 percent by weight
of a pigment dispersion, wherein said pigment dispersion comprises
from about 25 to about 45 percent by weight of a pigment; from
about 15 to about 45 percent by weight of a polymeric dispersant;
and from about 25 to about 45 percent by weight of a dispersion
medium, wherein the ration of pigment to polymeric dispersant is
from about 1:1 to about 1:0.68; from about 10 to about 20 percent
by weight of a glycol ether; and from about 40 to about 60 percent
by weight of a plasticizer; ejecting one or more droplets of the
ink composition from an orifice; and contacting the droplets with a
receiving surface on the substrate.
12. The process of claim 11 wherein the pigment is carbon
black.
13. The process of claim 11 wherein the average particle size of
the pigment is less than about 1.0 microns.
14. The process of claim 11 wherein the average particle size of
the pigment is less than about 0.6 microns.
15. The process of claim 11 wherein the pigment dispersion
comprises from about 30 to about 40 percent by weight of the
pigment; from about 20 to about 40 percent by weight of the
polymeric dispersant; and from about 30 to about 40 percent by
weight of an ester.
16. The process of claim 11 wherein the glycol ether comprises
propylene glycol methyl ether, dipropylene glycol phenyl ether,
propylene glycol phenyl ether, tripropylene glycol phenyl ether,
ethylene glycol phenyl ether, diethylene glycol methyl ether,
triethylene glycol butyl ether, propylene glycol n-propyl ether,
dipropylene glycol n-propyl ether, dipropylene glycol n-propyl
ether, or mixtures thereof.
17. The process of claim 11 wherein the plasticiser comprises alkyl
benzyl phthalates, dioctyl phthalate, butyl benzyl phthalate,
dioctyl phthalate, diethyl phthalate, dimethyl phthalate,
di-(2-ethylhexy)-adipate, diisobutyl phthalate, diisobutyl adipate,
dicyclohexyl phthalate, glycerol tribenzoate, sucrose benzoate,
polypropylene glycol dibenzoate, neopentyl glycol dibenzoate,
dimethyl isophthalate, or mixtures thereof.
18. The process of claim 11 wherein the polymeric dispersant
comprises polyurethanes, polyacrylates, polymeric/fatty acid
condensation polymers, or mixtures thereof.
19. The process of claim 11 wherein the polymeric dispersant
comprises a polymeric/fatty acid condensation polymer.
20. The process of claim 11 wherein the polymeric dispersant
comprises a polyamine/fatty acid condensation polymer.
21. The process of claim 11 wherein the dispersion medium is an
ester.
22. The process of claim 21 wherein the ester is selected from the
group consisting of diethyl oxalate, dibutyl oxalate, dimethyl
malonate, diethyl malonate, di-tert-butyl malonate, dimethyl
succinate, diethyl succinate, diethyl adipate, dimethyl sebacate,
dibutyl sebacate, diethyl azelate, methylene diacetate, ethylene
glycol diacetate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate,
and triacetin.
23. The process of claim 21 wherein the ester comprises dibutyl
sebacate.
Description
[0001] This application claims benefit of U.S. Provisional
Application Ser. No. 60/099,238, filed Sep. 4, 1998, the disclosure
of which is hereby incorporated by reference in its entirety.
RELATED APPLICATIONS
[0002] The present invention is related by subject matter to the
inventions disclosed in commonly assigned application Ser. No.
______, filed on Jun. 9, 1999, entitled "Method for Reducing
Cavitation in Impulse Ink Jet Printing Devices," Attorney Docket
No. TRID-0156.
FIELD OF THE INVENTION
[0003] This invention is directed to ink compositions for use in
impulse or drop on demand (DOD) ink jet printers, and more
specifically, to solvent-based, pigment and dye inks formulated for
high resolution and low spread bar code and graphics printing
applications on porous substrates such as Kraft paper or corrugated
cardboard and other porous materials like web off-set paper. The
inks of this invention are also for printing on non-porous
substrates.
BACKGROUND OF THE INVENTION
[0004] Ink jet printing is performed by discharging ink droplets
from a print head to a substrate. The droplets are ejected through
orifices or nozzles in the print head and are directed to the
substrate to form an image thereon. In contrast to many other types
of printing, there is no contact between the printer and the
substrate in ink jet techniques.
[0005] Most of the ink jet printers known in the art may be
characterized as either continuous, thermal, or impulse devices,
depending upon the mechanism by which the ink droplets are directed
to the substrate. In continuous ink jet systems, an essentially
uninterrupted stream of ink is ejected from a nozzle and breaks up
into droplets. The droplets bear an electric charge so that they
can be deflected by an applied electric field which is modulated
according to the particular image to be recorded. The electric
field directs the droplets toward either the substrate or an ink
re-circulating reservoir. The inks employed in conjunction with
continuous ink jet systems typically comprise a colorant such as a
dye or pigment, an electrolyte to facilitate droplet deflection,
and a liquid vehicle to dissolve or disperse the colorant and the
electrolyte. While the vehicle in many continuous-type inks
comprises water, U.S. Pat. No. 4,142,905, in the name of Cooke,
disclosed a water-free ink composition consisting essentially of a
low molecular weight glycol, an inorganic salt electrolyte, and a
dye which is soluble in the glycol.
[0006] With so-called "impulse" or "drop-on-demand" ink jet
printers, image formation is controlled by changing the rate of
energization of a piezoelectric transducer rather than by
modulating in applied electric field. Ink is stored in the print
head or nozzle until it is necessary to form an image on the
substrate on demand. The printer is then activated to apply
pressure to the ink and discharge a selected number of discrete ink
droplets toward the substrate. These ink droplets need not bear an
electric charge. Accordingly, impulse ink compositions can be free
of corrosive substances such as water and electrolytes which
continuous ink jet inks often comprise.
[0007] However, impulse ink jet printers present a number of
problems which are not encountered in continuous ink jet systems.
For example, unlike continuous ink jet printers, impulse printers
typically are maintained in a stand-by or temporarily inoperative
mode between printing cycles. Thus, the ink is allowed to stand and
possibly solidify in the discharge orifices of the print head.
Impulse printers normally begin a printing cycle with such material
in place. Many of the start-up problems encountered with impulse
printers are attributable to ink which has been allowed to stand in
the discharge orifices during stand-by periods. Such material is
less of a concern in continuous systems because there typically are
fewer interruptions in the flow of ink. Even where ink is allowed
to stand and solidify, it is more easily purged due to the
considerably higher pressures at which continuous ink jet printers
operate. Accordingly, impulse-type inks must be specially
formulated to minimize start-up problems.
[0008] Numerous ink compositions for impulse ink jet printers are
known in the art. However, many of these inks are not suitable for
bar code printing applications on porous, non-porous, or fibrous
substrates. As will be appreciated by those of skill in the art, an
ink applied to a substrate such as paper will tend to migrate or
wick along the fibers of the paper until the wicking forces are
countered by the ink viscosity. The extent to which the ink wicks
will be dependent upon both its viscosity and the porosity of the
substrate. Where highly porous substrates such as Kraft paper or
corrugated cardboard are employed, many inks tend to wick
excessively, leading to blurry, ill-defined printed images. One
approach to clearer, more well-defined print images has involved
the employment of a rapidly evaporating ink composition. However,
rapid evaporation of the impulse-type ink often leads to clogging
of discharge orifices during stand-by periods. Moreover, such rapid
evaporation compositions are less desired because they commonly
contain volatile organic components (VOCs) that can be harmful to
the environment and human health. Another approach to clearer, more
well-defined print images has involved the use of a pigment as a
colorant instead of a dye. Where pigments are used as the colorant,
the particle size employed must be small enough to achieve reliable
performance in the printhead. Water-based pigment dispersions are
known in the art that satisfy the printhead performance
requirement, however, the reliability of these dispersions in the
present application are unknown. In addition, for water-based
pigment dispersions, the current state of the art limits the
driving frequency of the of the printhead to between 3 and 8 kHz,
resulting in a slower printing operation and through-put. Moreover,
water-based pigmented ink systems have two major drawbacks. First,
they are unreliable as they tend to settle during storage and in
ink reservoirs. Second, water-based pigmented ink systems
especially when the particle size of the pigment gets smaller--tend
to entrap more air which results in inconsistent jetting of ink
drops.
[0009] In certain applications, it is necessary that the image
created by an ink jet printer possess a relatively intense
threshold color. For example, many optical character reading
devices cannot read images unless they possess a minimum color
intensity. Those skilled in the art will recognize that bar code
images typically must possess a good print contrast signal (PCS)
(preferably greater than about 90 percent) to be machine readable.
However, many of the known techniques for increasing the color
intensity of an ink--such as increasing the concentration of the
colorant--often adversely affect important ink properties such as
viscosity, surface tension, and stability.
[0010] Therefore, there exists a need for a solvent-based
impulse-type ink jet ink composition capable of producing clear,
well-defined, color-intense images on even porous and non-porous
substrates.
SUMMARY OF THE INVENTION
[0011] The present invention provides a non-aqueous-based
dispersion ink composition for use in impulse ink jet printers.
Preferably, the ink compositions comprise from about 20 to about 50
percent by weight of a pigment dispersion. The pigment dispersion
comprises from about 25 to about 45 percent by weight of a pigment,
such as carbon black, from about 15 to about 45 percent by weight
of a polymeric dispersant, and from about 25 to about 45 percent by
weight of a dispersion medium. Preferably, the ink compositions
further comprise from about 15 to about 40 percent by weight of a
diol ether and from about 20 to about 60 percent by weight of a
plasticizer.
[0012] The present invention also provides a method for preventing
the formation of gas bubbles inside of a print head of an inkjet
ink printer. The method is practiced by adding an antioxidant in
the ink jet ink compositions. The antioxidant is used in an amount
of up to about 2 weight percent of the ink jet ink composition.
[0013] The ink jet ink composition of the present invention
improves the ability to store and use a pigment dispersion that is
suspended uniformly without entraining a detrimental amount of air,
particularly wherein the average particle size of the pigment is
less than 1.0 micron.
DETAILED DESCRIPTION OF THE DRAWINGS
[0014] The foregoing summary, as well as the following detailed
description of the preferred embodiments, are better understood
when they are read in conjunction with the appended drawings. The
drawings illustrate preferred embodiments of the invention to
illustrate aspects of the invention. However, the invention should
not be considered to be limited to the specific embodiments that
are illustrated and disclosed. In the drawings:
[0015] FIGS. 1A-E are diagrams of a device according to the present
invention showing a firing signal applied to a piezoelectric print
head chamber and the movement of ink within the chamber in response
to the signal;
[0016] FIG. 2 illustrates the effect of an antioxidant on the ink
compositions according to the present invention; and
[0017] FIG. 3 depicts an impulse ink jet printing apparatus
operated by a method in accordance with the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0018] The present invention provides improved dispersion ink
compositions for use with drop-on-demand or impulse ink jet
systems. The invention further provides ink jet ink compositions
capable of printing clear, well-defined alphanumeric text and
narrow bar width bar codes on porous and non-porous substrates.
Throughout the description, the invention is described in
connection with a solvent based pigment dispersion wherein the
dispersed pigment is carbon black. However, the particular pigment,
and its associated color described herein, only illustrate the
present invention and are not intended to be limitations. The
invention is equally applicable to other pigments as long as the
performance characteristics as herein described are not adversely
affected. Accordingly, the invention should not be limited to the
particular pigment described as the invention contemplates the
application of other pigments.
[0019] As used herein, numerical ranges preceded by the term
"about" should not be considered to be limited to the recited
range. Rather, numerical ranges preceded by the term "about" should
be understood to include a range accepted by those skilled in the
art for any given element in impulse ink jet ink formulations
according to the present invention.
[0020] The dispersion ink compositions of the present invention
contain a pigment dispersion. The pigment dispersion contains at
least a pigment, a polymeric dispersant, and a dispersion medium.
Preferably, the dispersion medium is an ester, however other
dispersion mediums recognized by those skilled in the art, such as,
for example, a glycol alkyl ether, a diol, or a diol ether are also
suitable.
[0021] The pigment dispersion is present in the dispersion ink
compositions according to the present invention in an amount from
about 20 to about 50, preferably about 30 to about 40, more
preferably about 40 percent by weight.
[0022] According to the present invention, the pigment is present
in the pigment dispersion from about 25 to about 45, preferably
about 30 to about 40, more preferably about 35 to about 40, most
preferably about 40 percent by weight. The preferred pigment is
carbon black. It is further preferred that the pigment be processed
such that it has an average particle size of about 0.01 to about 5,
preferably less than 1, most preferably about 0.6 or less microns
in the final ink composition. Preferably, this is accomplished by
filtering the final ink jet ink composition through filter such as,
for example, a POLYFLOW.RTM. 0.6 micron filter (commercially
available from Arbor Tech, Ann Arbor, Mich.).
[0023] The selection of the pigment and its concentration is based
primarily on its dispersability in the ink composition and the
intensity of its color in light of the particular application. The
pigment is selected to render the ink composition visible to the
human eye or a mechanical data collection device such as a bar code
scanner or other type of optical character readers as specified in
the American National Standard Institute's Bar Code Print Quality
Guideline (ANS X3.182-1990). Such optical reading devices generally
operate in the wavelength range of from about 400 to about 980
nanometers. Preferably, images produced by the ink composition have
a print contrast signal greater than about 90 percent. It will be
recognized that print contrast signal is determined by subtracting
the reflectance of the print from the reflectance of the paper and
dividing the result by the reflectance of the paper. A preferred
pigment is REGAL 660 carbon black (commercially available from
Cabot Corporation, Billerica, Mass.).
[0024] The dispersant medium provides a substantially non-aqueous
environment in which to disperse the pigment. The dispersion medium
is present in the pigment dispersion in an amount of from about 25
to about 45, preferably about 30 to about 40, more preferably about
30 to about 35 percent by weight. Suitable dispersion mediums
include glycol alkyl ethers, diols, diol ethers, and esters.
Preferably, the dispersion medium is an ester. Preferred esters are
one or more of the many chemically distinct, low molecular weight
esters or diesters, such as, for example, diethyl oxalate, dibutyl
oxalate, dimethyl malonate, diethyl malonate, di-tert-butyl
malonate, dimethyl succinate, diethyl succinate, diethyl adipate,
dimethyl sebacate, diethyl azelate, methylene diacetate, ethylene
glycol diacetate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate,
and triacetin. The preferred ester is dibutyl sebacate (n-decanoic
acid di-n-butyl ester), such as, for example, UNIFLEX DBS
(commercially available from Union Camp Corporation, Jacksonville,
Fla.).
[0025] The polymeric dispersant is present in the pigment
dispersion in an amount of from about 15 to about 45, preferably
from about 20 to about 40 percent by weight. Preferred polymeric
dispersants are polyurethanes, polyacrylates, and polymeric/fatty
acid condensation polymers. More preferably, the polymeric
dispersant is a polymer/fatty acid condensation polymer. Most
preferably, the polymeric dispersant is a polyamine/fatty acid
condensation polymer. The preferred polymer/fatty acid condensation
polymer is SOLSPERSE 13940 (commercially available from Zeneca,
Inc., Wilmington, Del.).
[0026] The polymeric dispersant is selected to effectively disperse
the pigment. Preferably, the polymeric dispersant operates to
disperse the pigment by adsorption onto the surface of the pigment
and providing enough steric hindrance to keep the pigment
dispersed. Preferably, the polymeric dispersant is also miscible
with the dispersion medium. In this connection, the ratio of
pigment to polymeric dispersant is critical to the storage
stability and printhead performance of the ink compositions.
Preferably, the pigment dispersion is prepared wherein the ratio of
pigment to polymeric dispersant is from about 1:1 to about 1:0.68,
more preferably, from about 1:0.8 to about 1:0.7, most preferably,
about 1:0.75, based on neat dispersant that is 40% active.
[0027] The dispersion ink compositions according to the present
invention further comprise from about 15 to about 40, more
preferably about 15 to about 25, percent by weight of a diol ether
having a molecular weight less than about 400. More preferably, the
diol ether constitutes about 19.8 percent by weight of the ink
composition. The diol ether should have a liquid phase between
about 20 and about 70.degree. C., as this is the temperature range
within which impulse-type ink jet printers are most commonly
operated. The diol ether can comprise one or more of the many
chemically distinct, low molecular weight diol ethers known in the
art, such as, for example, ethylene-glycol monomethyl ether,
ethylene-glycol monoethyl ether, diethylene-glycol monomethyl
ether, diethylene-glycol monobutyl ether,
1-butoxyethoxy-2-propanol, diethylene-glycol monethyl ether,
ethylene-glycol monobutyl ether, ethylene-glycol monohexyl ether,
phenyl glycol ethers, butoxytriglycol, methoxytriglycol, and
ethoxytriglycol. Polyoxyethylene glycols such as ethoxytriglycol
and methoxytriglycol are preferred. Propylene glycol phenyl ether
(DOWANOL PPh, W.H. Dow Center, Midland, Mich.) is particularly
preferred.
[0028] The dispersion ink compositions according to the present
invention further comprise from about 20 to about 60, preferably
about 25 to 35, more preferably about 30 percent by weight of a
plasticizer. The plasticizer can comprise one or more of the many
chemically distinct plasticizers known in the art, for example,
butyl benzyl phthalate, dioctyl phthalate, diethyl phthalate,
dimethyl phthalate, di-(2-ethylhexy)-adipate, diisobutyl phthalate,
diisobutyl adipate, dicyclohexyl phthalate, glycerol tribenzoate,
sucrose benzoate, polypropylene glycol dibenzoate, neopentyl glycol
dibenzoate, and dimethyl isophthalate. Dibutyl phthalate is
preferred.
[0029] The dispersion ink compositions as described above are
substantially free of water. As used herein, the term
"substantially free of water" refers to a concentration of water of
from about 0 to about 5.0 percent by weight.
[0030] It is desirable that the ink compositions of the present
invention further comprise from about 0.01 to about 5.0, preferably
between about 0.01 and about 2.0, more preferably less than 1.0
percent by weight of an antioxidant. Preferably, the antioxidant
constitutes about 0.2 percent by weight of the dispersion ink
composition. The antioxidant is selected for its ability to improve
the dynamic throughput performance in the printhead. Cavitation is
the formation of gas bubbles in a liquid and is caused by the
presence of dissolved gasses in the liquid. Typically, the effects
of cavitation are often compounded when the particular jetting
fluid, as described by the present invention, includes particles
(i.e., the pigment). Typically, the particles create more
nucleation sites for bubble growth.
[0031] Inside of an impulse-type printhead device, there is a piezo
attached to a wall of a liquid chamber that expands and contracts
causing an oscillating pressure field within the chamber. Referring
now to FIGS. 1A-1E, one or more ink droplets 14c can be ejected
from the nozzles 12 toward a substrate by selectively energizing
and de-energizing piezoelectric transducers 13. In preferred
embodiments, each transducer 13 is attached to a membrane, sealant,
or some other flexible member 15a in physical contact with a volume
of ink 14a contained within chamber 15. It is possible, however,
that the transducer can be the chamber wall. The transducers are
energized and de-energized through application of control signals.
Although the control signal waveform could be selected from many
known ink droplet firing signals, for brevity and simplicity of
understanding, the firing control signal is shown in FIG. 1A in the
form of a square wave.
[0032] Formation of bubbles and the likelihood of their initial
growth and subsequent shrinkage in the oscillating pressure field
significantly reduce the printhead jetting performance. FIG. 2
illustrates the effect of the antioxidant in the dispersion ink.
The antioxidant present in the ink composition lowers the dissolved
oxygen in the ink, thereby significantly improving its
performance.
[0033] Preferably, the antioxidant can comprise one or more of the
many chemically distinct, known antioxidants such as naphthols,
substituted phenols, oximes, and aromatic amines. Suitable
antioxidants include, for example, eugenol, hydroquinone,
pyrocatechol, guaiacol (methyl catechol), butylated hydroxytoluene,
butylated hydroxyanisole, methyl ethyl ketoxime, butylaldoxime, and
cyclohexanone oxime. Cyclohexanone oxime is particularly
preferred.
[0034] It will be appreciated that an antioxidant, as disclosed
above, can be added to other fluids that can be used and jetted in
a piezo-type impulse ink jet apparatus to effectively reduce
cavitation in the print head and improve the printhead jetting
performance. Exemplary fluids include polymer solutions (both
aqueous and non-aqueous), adhesives, and any kind of coating.
[0035] Suitable fast-drying ink jet ink formulations and apparatus
are disclosed in U.S. patent application Ser. No. ______, filed on
Jun. 9, 1999, Attorney Docket No. TRID-0155, which is incorporated
herein by reference.
[0036] Preferred fast-drying ink compositions comprise a solvent or
a combination of solvents at from about 20 to about 95% by weight,
a polymeric resin system at from about 1 to about 20% by weight,
and a colorant at from about 1 to about 20% by weight.
[0037] The preferred fast-drying ink compositions comprise
low-boiling solvents. Generally, the solvents selected have a
boiling point below 150.degree. C. Preferred low-boiling solvents
include glycol alkyl ethers having about 3 to 20 carbon atoms, more
preferably about 3-7 carbon atoms, and most preferably 4 carbon
atoms, a ketone alcohol, such as, for example, diacetone alcohol,
1,4-butanediol, denatured ethanol, benzyl alcohol, and alkyl
lactates. Glycol alkyl ethers are particularly preferred. The
preferred glycol alkyl ether is propylene glycol methyl ether. The
ink compositions according to this invention can comprise any one
of the above solvents or mixtures thereof. Preferably, such solvent
or combination of solvents will be present in the ink jet ink
composition at from about 20 to about 95% by weigh, more preferably
at from about 50 to 90% by weight, and most preferably at from
about 70 to about 88% by weight.
[0038] The preferred fast-drying ink compositions further comprise
from about 1 to about 20% of a polymeric resin. Preferred polymeric
resins include polyester resins, polyamides, polyvinylbuterol
resins, such as for example, MOWIFOL B3020H (commercially available
from Hoechst, United Kingdom), phenolic resins, such as, for
example, ALNOVOL PN 320 (commercially available from Hoechst,
United Kingdom), and acrylic resins, such as styrene acrylic resin.
The polymeric resin system of the ink compositions according to
this invention can comprise any one of the above polymeric resins
or mixtures thereof and preferably contain only those stated resins
as the polymeric resin compound. Preferably, the ink composition
comprises about 1 to about 20% by weight of an alcohol-soluble
polyester-based resin and about 1 to about 10% by weight of a
styrene acrylic polymer resin. More preferably, about 5 to 15% of
the alcohol-soluble polyester-based resin and about 3 to about 6%
by weight of the styrene acrylic polymer resin, and most preferably
about 9% by weight of the alcohol-soluble polyester-based resin and
about 4.5% by weigh of the styrene acrylic polymer resin. One
preferred alcohol soluble polyester is Prince 5180, manufactured by
Lawter International, Northbrook, Ill. One preferred styrene
acrylic polymer is Joncryl 678, available from S.C. Johnson &
Son, Inc.
[0039] Preferred fast-drying ink compositions also comprise a
colorant. The choice of colorant and its concentration principally
depend on the solubility of the colorant and the intensity of its
color for a particular application. Preferably, the colorant is
selected to render the ink composition visible to the human eye or
some mechanical data collection device, such as a bar code scanner
or other type of optical character reader. A preferred colorant
comprises a dye such as Orasol Black RLI, which is available from
Ciba-Geigy Co. of Ardsley, N.Y. Preferably, the colorant comprises
from about 1 to about 20% by weight of the ink composition.
[0040] The fast drying impulse ink jet ink compositions for use in
the present invention have been formulated to typically dry in from
about 3 to about 35 seconds when used to print 150 dots per inch
(DPI) text, and from about 5 to about 100 seconds for 150 DPI block
characters. All print tests were performed with a Microcoder 32/16
printhead (commercially available from Trident International, Inc.,
Brookfield Conn.). As a baseline, the dry times were measured on a
glass substrate at ambient temperature with no extraneous heating
device applied. Measure dry times is typically an imprecise art. As
referred to hereinafter, the dry times were obtained by measuring
the time required to observe no visible smearing of the printed
characters or blocks when rubbed with a substrate such as, for
example, paper or a cotton swab. Those skilled in the art will
recognize that the drying times of the fast-drying impulse ink jet
ink compositions of the present invention will vary based upon the
composition of the solvent or solvents selected and the particular
amounts of each solvent.
[0041] For example, one preferred fast-drying ink jet ink
composition that demonstrates the desired fast-drying properties
has been prepared as follows:
1 Propylene Glycol Methyl Ether (solvent) about 44.0% Diacetone
Alcohol (solvent) about 40.6% Prince 5180 (resin) about 6.3%
Joncryl 678 (resin) about 1.7% Orasol Black RLI (dye) about
7.4%
[0042] This formulation typically exhibits a dry time on a glass
substrate of about 50 seconds for 150 DPI bock characters and about
19 seconds for 150 DPI text at ambient temperature. This ink jet
ink formulation, when printing 150 DPI text on a high density
polyethylene substrate, will dry in about 7 to 9 seconds at ambient
temperature. On matte-coated, non-glossy stock paper, ink jet ink
formulation will dry in about 3 to 4 seconds at ambient temperature
when printing 150 DPI text.
[0043] In comparison, a more preferred fast-drying ink jet ink
composition that demonstrates the desired fast-drying properties
has been prepared as follows:
2 Propylene Glycol Methyl Ether (solvent) about 22.5% Denatured
Ethanol (solvent) about 55.0% Benzyl Alcohol (solvent) about 5.0%
Prince 5180 (resin) about 9.0% Joncryl 678 (resin) about 4.5%
Orasol Black RLI (dye) about 5.0%
[0044] This formulation typically exhibits a dry time on a glass
substrate of about 6 seconds for 150 DPI bock characters and about
3 seconds for 150 DPI text at ambient temperature. This ink jet ink
formulation, when printing 150 DPI text on a high density
polyethylene substrate, will dry in about 4 seconds at ambient
temperature. On matte-coated, non-glossy stock paper, ink jet ink
formulation will dry in about 2 seconds at ambient temperature when
printing 150 DPI text.
[0045] Still, a most preferred fast-drying ink jet ink composition
that demonstrates the desired fast-drying properties has been
prepared as follows:
3 Propylene Glycol Methyl Ether (solvent) about 80.0% Diacetone
Alcohol (solvent) about 5.0% Prince 5180 (resin) about 6.3% Joncryl
678 (resin) about 1.7% Orasol Black RLI (dye) about 7.4%
[0046] This formulation typically exhibits a dry time on a glass
substrate of about 20 seconds for 150 DPI bock characters and about
8.0 seconds for 150 DPI text at ambient temperature.
[0047] In one embodiment, water can be added to the fast-drying ink
jet ink compositions as an additive to control an ink formulation's
drying time, i.e., decrease the rate of drying, where especially
fast-drying solvents are used, such as, for example, denatured
ethanol. The water can be present at from about 1 to about 40% by
weight. The particular amount of water used will depend on the
volatility of the solvents used. The following fast-drying ink jet
ink formulation illustrates another preferred fast-drying ink
composition wherein water was added to control a dry time that was
otherwise too fast to allow for control of the print quality:
4 Denatured Ethanol (solvent) about 67.0% Distilled Water
(additive) about 10.0% 1,4-butanediol (solvent) about 3.0% Mowifol
B3020H (resin) about 1.0% Alnovol PN 320 (resin) about 14.0%
Valifast 3806 (dye) about 5.0%
[0048] This formulation typically exhibits a dry time on a glass
substrate of about 6.0 seconds for 150 DPI bock characters and
about 3.0 seconds for 150 DPI text at ambient temperature. In
comparison, this formulation, without the water added, would dry
almost instantly and the print quality was difficult to
maintain.
[0049] One skilled in the art will recognize that the fast-drying
impulse ink jet ink formulations not only readily form a viscosity
barrier at the orifice of the nozzle, but also eliminate the need
for extraneous heating devices such as, for example, microwave
heaters, forced hot air heaters, convection heaters, and the like,
that are typically employed to increase the rate at which the ink
dries on a substrate.
[0050] A preferred process according to the present invention is
depicted in FIG. 3, wherein one or more droplets (12) of the ink
composition are ejected from orifices (14) by selectively
energizing and de-energizing piezoelectric transducers (not shown)
in a print head (10). The operation of the transducers and, hence,
the ejection of the droplet is controlled by a processing means
(16) such as a computer. Such a process and system are disclosed in
U.S. Pat. No. 4,646,106, which is incorporated herein by
reference.
[0051] After ejection from the print head (10), the droplet (12) is
directed to a receiving surface (21) on the substrate (20) to form
a printed image. The printed image should be clear and
well-defined, even on porous substrates such as kraft paper and
corrugated cardboard. It will be recognized that the edge
definition of a printed letter or character produced by an ink jet
printer can be related to the capacity of the printer to form
circular dots of perfect or near perfect circularity. It is
preferred that the print images recorded in accordance with the
present invention have circularity greater than about 0.7 and that
said circularity be determined as set forth in U.S. Pat. No.
4,361,843 in the names of Cooke, et al., which is incorporated
herein by reference.
[0052] Numerous printing substrates such as papers, glasses,
metals, and plastics are known in the art to comprise receiving
surfaces with which ink droplets can be contacted. It will be
recognized that substrates can vary greatly in terms of
physicochemical properties such as smoothness, porosity and surface
treatment, and that such physicochemical properties will greatly
influence the printing process and the choice of an ink
composition. The ink compositions of the present invention form
clear, well-defined bar code images on kraft paper, corrugated
cardboard, and other relatively porous substrates having a
smoothness of about 300 to about 450 Sheffield units, preferably
between about 345 and about 400 Sheffield units. In comparison,
various of the prior art dye-based ink compositions form
ill-defined bar code images on the same porous substrate.
[0053] It is preferred that the processes of the present invention
be performed at temperatures between about 20 and about 70.degree.
C., more preferably between about 30 and about 60.degree. C. At
these temperatures, suitable application viscosities of the ink
compositions can be obtained. It is preferred that the ink have a
viscosity between about 10 and about 15 cps at 60.degree. C.
[0054] It is also preferred that the ink composition has a surface
tension of from about 32 to about 38 dynes/cm at 25.degree. C.
[0055] As shown in FIG. 2, the substrate (20) preferably has a
component of movement transverse to the path of the droplet (12).
Such relative movement can be produced by moving the substrate (20)
past a stationary print head (10), as shown in FIG. 2, or by moving
the print head past a stationary substrate. The accuracy and/or
clarity of the recorded information optionally can be determined by
reading the information with a mechanical data collection device
(30) positioned upstream from the print head (10).
[0056] Additional objects, advantages, and novel features of this
invention will become apparent to those skilled in the art upon
examination of the following examples thereof, which are not
intended to be limiting, wherein parts and percents are by weight
unless otherwise indicated.
EXAMPLE 1
[0057] A pigment dispersion ink was made by mixing the 400 grams of
REGAL 660 carbon black pigment (Cabot Corporation, Billerica,
Mass.) together with about 300 grams of UNIFLEX DBS dibutyl
sebacate (Union Camp Corporation, Jacksonville, Fla.) and about 300
grams of 40-45 percent active SOLSPERSE 13940 polymeric dispersant
(Zenica Colors, Inc., Wilmington Del.). The pigment to polymeric
dispersant ratio was 1:0.75. The mixture was pre-mixed for about 2
hours in order to ensure proper wetting of the pigment. Next, the
dispersion was charged into a media mill consisting of about 0.8 to
about 1.0 millimeter zirconium-silicon dioxide beads. The
dispersion was then mixed at high speeds in the media mill for
about 5 hours to achieve grinding of the carbon black pigment. The
dispersion was then filtered through a coarse filter to remove the
media for additional use. The pigment dispersion of this example
was very stable, exhibiting no gellation or separation of solids,
indefinitely.
[0058] Next, about 400 grams of the above dispersion was diluted
under agitation with about 198 grams of propylene glycol phenyl
ether (DOWANOL PPh, W.H. Dow Center, Midland, Mich.) and about 400
grams of dibutyl phthalate. About 20 grams of 10 the antioxidant,
hydroquinone, was added next and the resultant ink composition was
mixed for about 2 hours at room temperature. The ink composition
was then filtered first through a 1.0 micron Glass-tech II filter
followed by filtration through a 0.6 micron PolyFlow filter. The
ink jet ink composition of this example exhibited excellent dynamic
performance; excellent print qualities; a desirable viscosity of
about 35 cps at about 25.degree. C.; a desirable viscosity of about
12 cps at about 60.degree. C.; and a surface tension of about 36
dynes/cm at 25.degree. C.
[0059] Dynamic performance was measured by continuously printing
bar codes for one hour using an Ultrajet II 352/32 impulse ink jet
printhead (Trident International, Brookfield, Conn.). This impulse
ink jet printhead has 11 orifices per channel. After one hour has
passed, the print quality of the bar codes is evaluated. A clogged
or air-entrained orifice will manifest as a visible defect in the
printed bar code.
EXAMPLE 2
[0060] A pigment dispersion ink was made by mixing 400 grams of
REGAL 660 carbon black pigment (Cabot Corporation, Billerica,
Mass.) together with about 350 grams of UNIFLEX DBS dibutyl
sebacate (Union Camp Corporation, Jacksonville, Fla.) and about 250
grams of 40-45 percent active SOLSPERSE 13940 polymeric dispersant
(Zenica Colors, Inc., Wilmington Del.). The pigment to polymeric
dispersant ratio was 1:0.62. The mixture was pre-mixed for about 2
hours in order to ensure proper wetting of the pigment. Next, the
dispersion was charged into a media mill consisting of about 0.8 to
about 1.0 millimeter zirconium-silicon dioxide beads. The
dispersion was then mixed at high speeds in the media mill for
about 5 hours to achieve grinding of the carbon black pigment. The
dispersion was then filtered through a coarse filter to remove the
media for additional use. The pigment dispersion of this example
was unstable as solid pigment separated after about an hour.
EXAMPLE 3
[0061] A pigment dispersion ink was made by mixing 400 grams of
REGAL 660 carbon black pigment (Cabot Corporation, Billerica,
Mass.) together with about 300 grams of UNIFLEX DBS dibutyl
sebacate (Union Camp Corporation, Jacksonville, Fla.) and about 300
grams of 40-45 percent active SOLSPERSE 13940 polymeric dispersant
(Zenica Colors, Inc., Wilmington Del.). The pigment to polymeric
dispersant ratio was 1:0.75. The mixture was pre-mixed for about 2
hours in order to ensure proper wetting of the pigment. Next, the
dispersion was charged into a media mill consisting of about 0.8 to
about 1.0 millimeter zirconium-silicon dioxide beads. The
dispersion was then mixed at high speeds in the media mill for
about 5 hours to achieve grinding of the carbon black pigment. The
dispersion was then filtered through a coarse filter to remove the
media for additional use. The pigment dispersion of this example
was very stable, exhibiting no gellation or separation of solids,
indefinitely.
[0062] Next, about 400 grams of the above dispersion was diluted
under agitation with about 600 grams of UNIFLEX DBS dibutyl
sebacate (Union Camp Corporation, Jacksonville, Fla.). The
resultant ink composition was mixed for about 2 hours at room
temperature. The ink composition was then filtered first through a
1.0 micron Glass-tech II filter followed by filtration through a
0.6 micron PolyFlow filter. The ink jet ink composition of this
example exhibited good print qualities, however, compatibility
problems were experienced with components of the printhead. The
resulting viscosities were about 30 cps at about 25.degree. C. and
about 8.5 cps at about 60.degree. C. The surface tension was about
30 dynes/cm at 25.degree. C.
EXAMPLE 4
[0063] The pigment dispersion ink was made by mixing 400 grams of
REGAL 660 carbon black pigment (Cabot Corporation, Billerica,
Mass.) together with about 300 grams of UNIFLEX DBS dibutyl
sebacate (Union Camp Corporation, Jacksonville, Fla.) and about 300
grams of 40-45 percent active SOLSPERSE 13940 polymeric dispersant
(Zenica Colors, Inc., Wilmington Del.). The pigment to polymeric
dispersant ratio was 1:0.75. The mixture was pre-mixed for about 2
hours in order to ensure proper wetting of the pigment. Next, the
dispersion was charged into a media mill consisting of about 0.8 to
about 1.0 millimeter zirconium-silicon dioxide beads. The
dispersion was then mixed at high speeds in the media mill for
about 5 hours to achieve grinding of the carbon black pigment. The
dispersion was then filtered through a coarse filter to remove the
media for additional use. The pigment dispersion of this example
was very stable, exhibiting no gellation or separation of solids,
indefinitely.
[0064] Next, about 400 grams of the above dispersion was diluted
under agitation with about 198 grams of propylene glycol phenyl
ether (DOWANOL PPh, W.H. Dow Center, Midland, Mich.) and about 400
grams of dibutyl phthalate. The resultant ink composition was mixed
for about 2 hours at room temperature. The ink composition was then
filtered first through a 1.0 micron Glass-tech II filter followed
by filtration through a 0.6 micron PolyFlow filter. The ink jet ink
composition of this example exhibited poor dynamic performance
without the antioxidant. The print quality was satisfactory; the
viscosity was about 44 cps at about 25.degree. C.; the viscosity
was about 13.5 cps at about 60.degree. C.; and the surface tension
was about 36 dynes/cm at 25.degree. C.
[0065] Those skilled in the art will appreciate that numerous
changes and modifications can be made to the preferred embodiments
of the invention and that such changes and modifications can be
made without departing from the spirit of the invention. It is
therefore intended that the appended claims cover all such
equivalent variations as fall within the true spirit and scope of
the invention.
* * * * *