Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
Field Of Tbe Invention
This invention relates to aqueous compositions to be employed as ink in ink jet
printing for the purpose of producing a lithographic master.
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Descri~tion Of The Prior Art
Ink jet printing has been investigated for the purpose of producing a direct
lithographic image for of~set printing. Considering the significant advantage of being able to
write directly onto a printing plate afforded by ink jet technology, this technique appears to be
have been substantially underexploited. Some explanation for this lack of attention is now
considered.
Solvent based ink formulations appear to function well in terms of lithographic
contrast and runlength, especially where the deposit is produced by the polymeriution of
monomers as occurs, for example, in U.S. Patent No. 4,003,312. However, environmental
considerations render this a much less desirable approach than a water based option.
The prindng industry has tight demands in terms of resolution. The least
demanding reqDment perlains to a 40,u dot size for newspaper printing. This has been
difficult to attain due to the combination of ink droplet size produced by the ink jet printer and
the spread of that droplet on impact with the printing plate. The latter point is highlighted when
a water based ink is used in conjunction with a hydrophilic printing plate.
The aqueow bascd inks so farproposed essentially involve ~e deposition of all~ali
Jolubb polymers with subsoquent water resistance being achieved by the vaporization of a
vola~le base as described in U.S. Pat. No. 3,903,034. Such formulations are capable of
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yroducing only relatively short print runlengths. While short runlength work has its place in the
market, it becomes a severe .~estriction when coupled with an inability to produce high image
qua1ity due to poor resolution.
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Summary Of The Invention
It is accordingly an object of the present invention to provide aqueous based ink
jet compositions capable of producing a deposit on a hydrophilic printing plate that are able to
provide a substantial printing runlength.
It is a further aim, that the combination of the ink jet composition and the image
developing process is capable of producing a satisfactory resolution. Specifically, the plate
deposit dot size should not have a diameter larger than 40,u.
Another object is to provide a composition that has good functional performan~
with re&ard to the ink jet printer. Specifically, this requires that the composition provide~ good
drDp ~abiliq and also, does not cause the jet nozzle to become blocked.
The foregoing objects are achieved by the present invention which provides for
an aqueous bascd ink compodtion that conttins polymers which can be cros~linloed such that
a lesultant depo6it is used to produce a cohesive matrLl~ that is resistant to an acidic fountain
.~ solution of an offset printing process.
Prefaably, the cro~linl~ing is taken to complc~ion by a cunng proce~ involving
dt~er tbennal ladiation or thermal t~ansfcr. Morc prcferably, thc curing prooe~ functions at
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a temperature within the range of about 70 to about 180C so that a cure is produced which
gives a matrix that provides a substantial lithographic prindng runlength.
Suitable cross-linking polymers are those that can be formulated into a jet
composition such that their common reaction is readily controllable and in particular, is allowed
to proceed only as required. Preferably these polymers include one or more from a Group A
such as po1ymeric cyclic anhydrides or derivadves thereof and one or more from a Group B that
includes polymers that contain hydroxyl functionality.
The required resolution may be obtained by using a sufficiently small ink jet
printing nozzle, namely 10~ and an appropriate printing master substrate. In addition, and
depending on the nature of the surface of this substrate, the printed drop siæ can be further
controLled by limiting the spread of the composition droplets by pre-heating the substrate prior
to tbe imaging operation. Preferably, such a pre-heating process is provided within the
temperature range of about 60C to about 110C.
The cross-linlcing function may be controlled to tbe degree that the rea~:tion
prooeods only after the substrate has been imaged. This is of importance a~ any premature
Iraction could cause significant jetting instability and in the most severe scenario lead to
bloclcing of the jet nozzle.
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In another embodiment of the invention a water based ink composition is provided
for ink jet printing that is used for the generation of an offset printing master deposit, where the
composition includes a first polymer containing a cyclic anhydride or derivadve thereof and a
second polymer that contains hydroxyl functionality such that the first and second polymers can
be cross-linked.
The various features of novelty which characterize the invention are pointed out
with particularity in the claims annexed to and forming a part of the disclosure. For a better
understanding of the invention, its operating advantages, and specific object attained by its use,
reference should be had to the drawing and descriptive matter in which there are illustrated and
described preferred embodiments of the invention.
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Detailed Description Of The Preferred Embodiments
In a preferred embodiment of the invention the process involves using continuous
jet ink printing and, in particular, the Hertz ink jet technology which speciffcally provides a
nozzle of 10~ in diameter. Droplets are generated onto a hydrophilic master such as a metal
plate or a ceramic substrate. The deposit is fused in terms of temperature and time to affect
cross-linking of the deposit. The imaged master is then used with an offset printing press to
generate a substantial quantity of prints.
The required resolution may be achieved not only by using the 10~ jet nozzle but
also by choosing an appropriate offset master material. A ceramic substrate such as ~0, or
ZrSiO" where the surface is somewhat textured and may also be chaTacterized by a limited
po~osiq, has been found to be most suitable. The strong hydrophilic nature, and the
comparative lacl~ of texture of conventional anodized aluminum printing plates causes the inl~
droplets to spread to a size unsuitable for good resolution.
This spreading howeva, is minimized by pre heating the plate to behveen about
60C aod about 110C just prior to imaging. This additional process step limits spreading by
ncrcasJng the evaporation rate of the volatUe components as wdl as initiating the cro~linldng
funcdon.'
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The resu1ting deposit may be finally cross-linked due to a curing process which
involves the application of heat within a temperature range of about 70C to about 180C.
Suitable thermal processes include incident radiation produced by Infra-red lamps, convection
as occurs within an oven and thermal transfer as is provided by an induction heating process.
The induction technique is preferred since this involves an initial heating of the substrate which
then subsequently heats the deposit. This achieves curing which commences at the interface of
the deposit and substrate and proceeds through the deposit to the surface so that a more complete
matrLx is produced. This method is especially pertinent when the substrate used is a metal plate
and is in contrast to the Infra-red lamp and oven pro esses which can allow a slightly less
efficient curing due to the tendency for curing to be initiated at the deposit surface.
The cross-linking polymers suited to this process may include one or more from
a Group A that comprises those which contain an anhydride group or modified anhydride group
and that are either water soluble or soluble in an aqueous aL~aline vehicle and one or more from
a Group B that comprises polymers that contain a hydroxyl functionality.
Polymer Group A consists of polymers and copolymers cont~ning anhydride
group or modifications thereof and suitable cxamples include styrene maleic anhydride (SMA);
st~mne maldc anhydride disodium and half amide/half ammonium salts; sqrene maldc
anhyd ide where anhydride ha~ been partially esterified with a lower alcohol such as methanol,
~nol, n-propanol, isop opanol, n-butanol; methyl vinyl ether/maleic anhydride; and methyl
vinyl ether/maleic anhydride where the anhydride group has been partially esterified with a
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I~,wer alcohol such as methano1, ethanol, n-propanol, isopropanol, or n-butanol. Styrene maleic
anhydride where the anhydride has been partially esterified with a lower a1cohol as recited
above, e.g. Scripset 550 produced by Monsanto Chemical Co. are particularly preferred.
Preferred ranges of partially esterified SMA polymer of Group A are from about 0.2% to about
0.8% by weight.
In decreasing order of preference, also preferred are SMA, SMA half amide/half
ammonium salt and SMA disodium salt within the range of from about 0.2% to about 0.5% by
weight. The preferred range of methyl vinyl ether/maleic anhydride is from about 0.1% to
about 0.5%.
Polymer Group B comprises polymers or copolymers that contain hydrmyl
fi~nctionality and suitable materials include polymers such as polyethylene glycol, polypropylenc
glycol, hydroxyethylated polyethyleneimine, hydroxypropylated polyethyleneimine, fully and
par~ally hydrolysed polyvinyl alcohol. Suitable copolymers include those containing ylic
monomers where the hydro~cyl bearing monomer may be hydroxyethyl acrylate, hydrw~yethyl
me~ucrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydrw~ybutyl acrylate,
hydto~ybutyl methacrylate, glycetol diacrylate, glycerol dimethacrylate, glycetol methacrylate
acrybte and whcte said monomer is polymetized with at least actylic acid ot methacrylic acid
monomcr.
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Hydroxyl bearing acrylic copolymers, e.g. Acrysol 162 or hydroxyethylated
polyethyleneimine e.g. HEPEI 110 or a mixture of thereof are particularly preferred and utilized
within the prefer ed range of from about 0.5% to about 5% by weight. In decreasing ordet of
preference, hydroxypropylated polyethyleneimine is preferred within the range of from about
0.5% to about 5% by weight; polyethylene and polypropylene glycols are preferred within the
range of about 0.1% to about 3% by weight, while polyvinyl alcohol is preferred within the
range of from about 0.2% to about 0.7% by weight. It is understood that the above-noted
percentage ranges are largely the result of the low viscosity (up to approximately 2 mPa.s)
requitement of the Hertz ink jet printers utilized in the preferred embodiment. Accordingly, it
is also understood that the present invention may also be utilized at different ranges with otber
jet printi~g equipment where the ink viscosity is not so constrained.
Though not essential to the performance of the ink in the ink jet equipment and
therefore the production of the imaged master, it is most desirable for these inks which comprise
a volatile base to also contain a stabilizing agent. Said agent is added to reduce the tendency
of tbe ink to produce a crust at the noz~le tip during a down time. Suitabb materials for tbis
pulpose include triethanolamine, dimethylamino ethanol, methyldietbanol amine and N,N'-
dimetbylkpiperazine witbin the preferred range of from about 0.1% to about 0.7ff by weigbt.
To function in an inlc jet composition, the formulation may contain a conductivity
co~trol agent and a bac~ricide. Suitabb conductivity control agents include NaCI, LiCI,
IINO" NH,CI, te~amethylammonium chloride, and tetraethylammonium chloridc witbin a
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preferred range of from about 0.1% to about 0.8% by weight. Suitable bactericides include Na
Omadine available from Olin Chemicals, Neosept 95 available from Tenneco Chemicals, and
Dowicil 75 available from Dow Chemicals within a preferred range of from about 0.1% to about
0.5% by weight.
While a coloring agent such as a dye can also be included in the formu1atdon, it
is not a necessary constituent since only the cross-linkable polymers are vital for the producdon
of the master. However, suitable dyes include those from the azo group including monoazo,
disazo, triazo, and polyazo; the triarylmethane group and the phthalocyanines. Specifically,
suitable dyes include Direct black 19, Direct black 38, Direct black 168, Acid red 52, Direct
blue 86, Direct blue 199, Acid blue 9, and Acid violet 19. Preferred ranges are from about
0.5% to about 10% by weight.
The invendon is further explained by the following e~ampla but is not limited
by them. All constituent quantities are expressed as a weight percent.
E~b 1:
Sa~sct SS0 0.5%
NHpH ~28%) 0.6%
Dime~ylamino ~anol 0.1%
P~G 200 1.8%
N(CHl),CI 0.4%
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Na Omadine 0.3%
Duasyn Direct Black
HEF-SF VP 332 0.8%
H20 (deionized) 95.5%
Scripset S50 is part esterified SMA produced by Monsanto Chemical Co. Duasyn
Direct Black HEF-SF VP 332 is supplied by Hoechst. PEG200 is a polyethylene glycol supplied
by ICI.
This ink was prepared by initially mixing the water, Scripset 550 and an amount
of ammonium hydroxide sufficient to solubilize the alkali soluble resin and by heating the
resulting mixture to 70C until a solution was affected. The remainder of the constituents were
then added and mixed until all were dissolved. The resultant mixture was then passed through
a Sl- pore size filter and then a 0.451- membrane filter.
The ink was used to generate an image with the 10,u Hertz jet nozzle on an Agfa-
Geva~t CRAA alumina plate that had been oven p~heated to 95C. Subsequently the imagc
was oven fused for 10 minutes at a temperature of 150C.
The image plate was fitted to a MAN Roland Laborman offset pre~ to a~e~ the
print runlen~. The runleng~h was determined by plotdng the change in the ~os of the 30%
and 70X ~creens compared to the 100% screen.
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The printed dot diameter was determined to be 35~ while the runlength was
40,000 copies.
To demonstrate the importance of the cross-linking reaction to achieve a
significant runlength, this comparative example is provided where the co-reactant for the maleic
anhydride half ester has been omitted.
Comparative example:
Scripset 550 0.5%
Dimethylamino ethanol 0.1%
NH,OH (28%) 0.6%
N(CH3),Cl 0.4%
Na Omadine 0.3%
Duasyn Direct Black HEF-SF VP332 0.8%
H2O (deionized) 97.3%
This ink was produced by the method used in example 1 and the master similarly
p~pared using a pre-heated alumina plate that was also oven fused at 150C for 10 minutes.
Again printing was conducted on the l~bor nan press where the run1ength was found ~o be only
4,000 copies.
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Example 2:
An Agfa CRAA alumina plate was mounted on a cylinder and heated to 95C
using an induction heating apparatus. The plate was immediately imaged using the Her~z jet
printer with the ink of Example 1. The image was fused at a 150C, again using the induction
heating technique. The print runlength was determined as before and found to be 45,000 copies
while the dot size was measured at 35,u.
e 3:
An Al203 ceramic drum was imaged at room temperature using the ink from
E~arnple 1. The image was then fused at a temperature of 150C using an infra-red lamp. The
celamic drum was fitted to the Laborman press. The runlength was determined to be 35,000
and the printed dot diameter was 40~.
Example 4:
Gantrez AN 119 0.4%
Scripset 550 0.2%
N}I.OH (28%) 0.6%
Triethanolamine 0.2%
HPPEI 110 2.0%
NaCI 0.2ff
Noosept 9S 0.1%
Spo~ nolet S4B-F 0.5X
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H2O (deionized) 95.8%
Gantrez ANl l9 is a methyl vinyl ether/maleic anhydride copolyma produced by
International Specialty Products.
HPPEI ll0 is a hydroxypropylated polyethyleneimine produced by Morton
Intanational.
Special violet S4B-F is produced by Bayer.
The ink was prepared by initially mixing the water, Scripset 550 and ammonium
hydro~cide and heating to 70C until a so1ution was produced. The Gantrez AN 119 was then
dissolved, followed by the addition of remaining raw materials. After mi~dng for a further hour
the solution was passed through a 5,u pore size filter and then a 0.4S~ membrane filter. The
Hertz inlc jet was used to image an Agfa CRAA plate that had been oven preheated to 8SC.
The image was oven fused at a temperature of 130C for 10 minutes and subsequently asse~sed
as an offset masta on the Idborman press.
The rudeng~ was determined as 65,000 copies and the printed dot diameter was
32~ .
13~le 5:
Scripset SS0 0.5%
-~ NH,OH (2896) 0.S%
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Dimethylamino ethanol 0.5%
Airvol 325 0.5%
N(CH3),C1 0.4%
Na Omadine 0.3%
Duasyn Acid Rhodamine B-SF VP 353 0.3%
H20 (deionized) 97.0%
Airvol 325 is a 98% hydrolysed polyvinylalcohol produced by Air Products and
Chemicals.
Duasyn Acid Rhodamine is supplied by Hoechst.
This ink was prepared by the method used in E.~ample 1. An Agfa CRAA platc
was hcated to 90C with the induction heating equipment and then imaged with thc above inlc.
The induction heating was also used to fusc the image at a temperature of lS0C.
After printing, the runlength produced was 55,000 copies and the printed dot
diameter was 35J .
E~amvb 6:
Scripset SS0 0.S%
Acrysol 162 2.2%
NH,OH (28X) 1.3%
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Dimethylamino ethanol 0.3%
HEPPI 110 0.4%
N(CH3)4CI 0.4%
Na Omadine 0.3%
Specia1 Violet S4BF 0.1%
H2O (deionized) 94.5%
Acrysol 162 is an acrylic copolymer with an acid value of 100 and a hydroxyl
value of 70 that is made by Rohm and Haas. It is supplied as a 50% aqueous emulsion.
This ink was prepared by inibally mixing the water, ammonium hydro~ide and
Acrysol 162 to produce a solution. The Scripset 550 was added and a solution was affected by
heating to 70C. The solution was cooled and the remaining raw materials were dissolved by
mi~ing for a further hour. This solution was passed through a 5,u pore sizo filter and then a
0.6SI membrane filter. An Agfa CRAA plate was heated to 90C with the induction l~ng
equipment and then imaged with the above ink. Induction heating was also used to fuse the
image at a temperature of lS0C.
The runlength was determined to be 6S,000 copies and the printed dot d_
was 3SI .
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The invention is not limi~ed by the embodiments described above which are
presented as examples only but can be modified in various ways within the scope of protection
defined by the appended patent claims.
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