CA2107980A1

CA2107980A1 - Jet ink for offset printing master

Info

Publication number: CA2107980A1
Application number: CA002107980A
Authority: CA
Inventors: Richard J. Treleaven
Original assignee: Individual
Current assignee: Manroland AG
Priority date: 1992-10-07
Filing date: 1993-10-07
Publication date: 1994-04-08
Also published as: EP0591916A2; JPH06279719A; EP0591916A3

Abstract

Abstract Of The Disclosure An aqueous based ink composition that contains polymers which can be cross-linked by the application of heat such that the cross-linked resultant deposit is used to produce a cohesive matrix that is resistant to an acidic fountain solution of an offset printing process.
The cross-linked composition includes a first polymer containing a cyclic anhydride or derivative thereof and a second polymer that contains hydroxyl functionality. The cyclic anhydride may be a styrene maleic anhydride or derivative thereof, or a methyl vinyl ether/maleic anhydride or derivative thereof. The hydroxyl containing second polymer may be a polyethylene or polypropylene glycol, a hydroxyalkylated polyethyleneimine, a polyvinylalcohol or the hydroxyl containing polymer may be an acrylic copolymer that comprises at least a hydroxy substituted acrylate or methacrylate monomer and an acrylic acid or methacrylic acid monomer.

Description

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.

II~T

;~' 21079~0 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 T -2- ~ l7a 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 ~T ~_ .~ .

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.

I~l~T -S- ~ ~

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.' -7- ~ n~

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 ~I~T -8- ~ "4 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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` 2107980 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 ~s -10- ~ ~7.1 ., ~ .

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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~107980 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.

AT _ _ 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

Ih~la~T -14- ",7., 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%

IS-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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21~7980 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 .

AT - 1 7- ~ ~

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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Claims

1. A water based ink composition forming an offset printing master deposit, comprising:
a first polymer containing a cyclic anhydride or derivative thereof cross-linked with a second polymer containing hydroxyl functionality so as to form said offset printing master deposit.

2. The composition of claim 1, wherein the cyclic anhydride is a styrene maleic anhydride.

3. The composition of claim 1, wherein the cyclic anhydride is selected from the group consisting of styrene maleic anhydride wherein the anhydride has been partially esterified with a lower alcohol, styrene maleic anhydride disodium and half amide/half ammonium salt;
methyl vinyl ether/maleic anhydride and methyl vinyl ether/maleic anhydride wherein the anhydride group has been partially esterified with a lower alcohol.

4. The composition of claim 1, wherein the hydroxyl containing second polymer is selected from the group consisting of polyethylene glycol and polypropylene glycol.

5. The composition of claim 1, wherein the hydroxyl containing second polymer is a hydroxyalkylated polyethyleneimine.

6. The composition of claim 1, wherein the hydroxyl containing polymer is a polyvinylalcohol.

7. The composition of claim 1, wherein the hydroxyl containing polymer is an acrylic copolymer comprising one of a hydroxy substituted acrylate monomer and a methacrylate monomer, and one of an acrylic acid monomer and a methacrylic acid monomer.

8. The composition of claim 1, additionally comprising a stabilizing agent.

9. An ink jet imaging process comprising the steps of:
providing a substrate;
imaging the substrate by depositing thereon in the form of droplets an ink composition including a first polymer containing a cyclic anhydride or derivative thereof and a second polymer having hydroxyl functionality;
and crosslinking the ink composition on the substrate to form a printing master.

10. The ink jet imaging process of claim 9, comprising the additional step of preheating the substrate prior to the imaging step to limit a spread of the droplets on the substrate.

11. The ink jet imaging process of claim 10, wherein said preheating step includes preheating the substrate using infra-red lamps or induction heating.

12. The ink jet imaging process of claim 9, wherein said cross-linking step is performed by the application of heat.

13. The ink jet imaging process of claim 12, comprising the application of heat within a range from about 70°C to about 180°C.

14. The ink jet imaging process of claim 12, wherein the cross-linking step is performed by applying a thermal process selected from the group consisting of incident radiation, convection and induction heating.

15. An imaged offset printing master made by providing a substrate; imaging the substrate by depositing thereon in the form of droplets an ink composition including a first polymer containing a cyclic anhydride or derivative thereof and a second polymer having hydroxyl functionality; and crosslinking the ink composition on the substrate to form the printing master.

16. An offset printing master comprising:
a substrate; and deposited thereon a first polymer comprising a cyclic anhydride or derivative thereof and a second polymer comprising hydroxyl functionality, said first and second polymer being cross-linked.

17. water based ink composition for the generation of an offset printing master deposit by ink jet printing, comprising:
a first polymer containing a cyclic anhydride or derivative thereof;
a second polymer containing a plurality of hydroxyl functionalities for cross-linking said first and second polymer; and a stabilizing agent.

18. The ink composition of claim 17, wherein the stabilizing agent is triethanolamine, dimethylamino ethanol, methyldiethanol amine or N,N'-dimethylpiperazine.