CA1100371A - Driographic master - Google Patents

Abstract

ABSTRACT
A driographic plate capable of being direct imaged by pen, pencil, typewriter, toner powder, etc.
comprising a substrate having a coating thereon, the coating comprising a continuous medium having a solid fluorinated compound containing at least one fluorinated aliphatic radical uniformly dispersed therethrough in a manner such that the coating surface is ink repellent when dry. On direct imaging, the imaged areas will readily accept ink and prints can be made therefrom without necessity of a press dampening system.

Description

ilO03'71 DRIOGRAPHI~ MASTER
This ln~ention relates to waterless planographic printing. More particularly, it relates to novel sheet constructions which are capable of being direct imaged and are suitable for use ir. planographic printing wherein conventional fountain solutlons are not necessary.
Conventional lithographic plates generally require a dempening thereof with an aqueous fountain solution to effectively wet the background plate area, after which ink is rolled over the plate~ The oily ink selectively wets the oleophilic image areas but is repelled from the dempened background areas.
Recently, planographic printing plates not requiring dampening have been developed. These plates require only an inking system to be operative and inher-ently con~ain ink repellent non-imaged or background areas. This relatively new concept has come to be known by the term driography, and plates useful thereln have been termed driographic plates. Such a printing plate is disclosed in U~S. Patent No. 3,511,178.
Such plates generally operate on the principle that the background surface areas inherently having sufficienkly low adhesion to driographic printing inks that ink applied to the plate by an inking roller will not split away or transfer from the roller to the plate A surface exhibiting such characteristics has come to be termed "abhesive".
Present techniques for imaging such driographic printing plates, i~eO pro~iding ink-recepti~e image areas 1~0037~

thereon, generally involve selectlve removal of the abhesive coating, removal of a light-sensitive layer after imagewise exposure thereof to actinic radiatlon, etc. To my knowledge, there is not commercially available a direct image driographic plate, lOe. one that can be imaged by conventional marking techniques, such as pen, pencil or office duplicating machines. In U.S.
patent No. 3,859,090 there is disclosed a driographic printing plate asserted to be directly imageable by toner powder in an electrographic imaging process. However, the abhesive composition therein requires utilization of a fluorinated or polysiloxane oil, i.e. a liquid, to obtain adequate ink repellency in the background or non-image areas of the plate. Such olls wiil typically cause blinding of the plate, i.e. the image areas will also tend to repel ink during continued press operation by wetting of the total plate surface by the olls due to their lnherent mobility; furthermore, the plate therein is not taught to be imageable by marking techniques such as pen, pencil or typewriter.
The only plates presently commerclally avallable for such imaging techniques are conventional llthographic plates, which agaln require the complex ink-water balance ~n the printing operation. Besides the complexity in printlng operatlon using conventional lithographic plates, such plates are costly to produce because they of necessity must require wet strength for durability on the pressO
It has now been discovered that certain compo-sitions hereinafter defined, which contain fluorinated ll003n aliphatic radicals, are capable of providing the requisite abhesiveness todriographic inks when functioning on a printing press, can be directly imaged by conventional direct-image techniques, yet will not blind during press operation.
In accordance with the invention there is provided an article capable of providing a driographic printing plate which can be direct imaged, comprising a substrate having a coating on at least one surface thereof, said coating comprising a fused particulate binder compound characterized by high surface energy and easy wettability when exposed to printing ink having a solid, at less than 100F, heat-sofenable fluorinated compound uniformly dispersed therethrough in a manner such that the surface of said coating is oleo ink repellent when dry; said fluorinated compound containing at least one fluorinated aliphatic radical therein having at least one terminal perfluoromethyl group, said coating containing no material serving to flow at ordinary image-marking temperatures to heal image-marked areas therein.
The coating can be direct imaged, i.e. with a pen, typewriter, toner powder, etc. whereupon it will accept ink in the imaged areas.
The coating can also be coated over light-sensitive systems, e.g.
diazos, for conventional imaging and development or over a photoconductive surface for electrophotographic imaging.
The ink repellent or adhesive component of the invention herein must be a solid below about 100F and contain at least one fluorinated aliphatic radical. The radical can be described as a fluorinated, saturated, monovalent, non-aromatic, aliphatic radical of at least three carbon atoms in chain length. The chain may be straight, branched or, if sufficiently large, cyclic, and may be interrupted by divalent oxygen atoms or trivalent nitrogen atoms bonded only to carbon atoms. Preferably, the chain of the fluorinated aliphatic ~lOQ3ql radical does not contain more than one hetero atom, i.e.
nitrogen or oxygen, for every two carbon atoms in the chain. A fully fluorinated group is preferred, but hydrogen or chlorine atoms may be present as sub-stituents in the fluorinated aliphatic radical provided that not more than one atom of either is present in the radical for every two carbon atoms, and that the radical must contain at least a terminal perfluoromethyl group.
"Terminal" in this connection refers to the position in the chain of the radical which is furthest removed from the backbone chain of a polymer segment or in case of a non-polymeric material, at one end thereof. Preferably, the fluorinated aliphatic radical does not contain more than twenty carbon atoms because such a large radical results in inefficient use of the fluorine content.
When the radical is included in a polymer chain, it must, by definition, be pendant, i.e. a side chain or end group. For this reason, fluorinated polymers such as DuPont Viton A ~tradename for a copolymer of vinylidene fluoride and perfluoropropene) and polytetrafluoroethylene do not have utility in the invention herein.
Methods for the preparation of polymers con-taining appropriate pendent fluorinated aliphatic radicals is thoroughly discussed in United States Patent No. 3,574,7gl.
Non-polymeric fluorinated aliphatic radical-containing compounds useful herein are low molecular weight compounds which are solids at room temperature and having a polar group at the end opposite the fluorinated radical, e.g. C8F17S3K, and C8F17C02NH4.

~003!71 Other examples of nonpolymerlc materials include the following:
1. CF3(cF2)7so2N(cH3)cH2cH2oH

2. CF3(CF2)3SO2N(CH3)CH(CH3)CH2OH

3(CF2)3SO2N(CH2CH3)CH2CH2OH

4. CF3(CF2)3SO2N(CH3)CH2CH(CH3)OH

5. CF3(CF2)7sO2N(cH3)(cH2)5

6. CF3(cF2)7so2N(c2H5)cH2co

7. CF3(CF2)7sO2N(c4Hg)(cH2)4

8. CF3(cF2)7so2N(cH2cH3)cH2cH2NH2

9. [cF3(cF2)7so2N(cH2cH3)cH2cH2]2NH

10. CF3(CF2)7sO2N(cH2cH3)cH2cH2N( 3)

11. CF3(CF2)7sO2N(cH3)cH2cH2sH

12. C2F5O(c2F4O)3cF2coNHc2H4oH
3(CF2)7SO2N(C3H7)CH2OCH2CH2CH2OH
14. CF3CF(CF2Cl)(CF2CF2)6CF2CQN(CH3)CH2CH2OH
15. CF3(CF2)SO2CH2CH2OH
16. CF3(CF2)7sO2N(cH3)cH2cH2sH
17- C7F15CON(C2H5)C2H4OH
18. CF3(cF2)7cH2cH2cH2oH

It is of course known that such fluoroaliphatic radlcal-contalnlng materlals are increaslngly more oil repellent as the weight percent~ge of the fluorinated aliphatic radical in them is increasedO Therefore, the aliphatic radical-containing segment of compos~tions used herein should contain at least about 10 percent by weight of fluorine which is derived from fluoroaliphatic radicals. It is preferred that such materials contain at least absut 30 percent by weight of fluorine derived llU0371 from fluoroallphatic radicals so as to optimlze the abhesive tendencies of the compound.
The ability of the above-described perfluoro-aliphatic radical-containing materials to be imaged by conventional marking techniques is hypothesized to be due to their "orientation" properties combined with their thermosensitive nature. When coated on a sub-strate, the fluorinated aliphatic radical portions thereof tend to extend or orient themselves toward the air interface, thereby presenting the abhesive char-acteristics at the coated surface/air interface. When the surface is damaged by a marking instrument, eOg., a pen, pencil, etc., there is no highly mobil abhesive material to "heal" the damage. In the aforementioned U.S. Patent No. 3,859,090, containing a liquid fluoro-carbon or silicone oil, this oil would "heal", at least partially, this damaged area. Similarly, silicone elastomers typically contain highly mobil silicone polymer chains and also some amount of uncrosslinked material within the elastomer network, which would "heal"
any damaged area and thus not provide the differential inking capabilities in marked areas.
The surprising capability of the fluorinated ma~erials to bond to fused toner powder from a conven-tlonal office copier is believed to be due to the thermo-sensltive nature of the compounds, l.e. the ability thereof to heat soften During the fusing operation, the fluorinated materials can partially surround the toner particles, and yet upon cooling, the fluorinated material will typically regain its more rigid stateO It 110C)371 is also suspected that when conventlonal toner powder ls being fused by heat and the fluorlnated material ad-~acent to the toner powder is in a heat softened state, there ls less tendency to present the low surface energy abhesive perfluoroaliphatic radicals to the toner melt than to the air interface. This tends to increase the ability of the toner melt to bond to the fluorinated material.
The fluoroaliphatic radical-contalning com-pounds having utility hereln tend to be waxy or brittle, and thus do not have optimum physical properties necessary to form a durable film on a substrate.
Furthermore, compounds containing high percentages of fluorinated aliphatic radicals tend to be poorly soluble in most common solvents, and in order to obtain adequate solubility, the molecular weight of the compounds must be kept low. This feature contributes to poor film strength and also results in very low solution viscos-ities thereby making it impossible to obtain good holdout on paper or other porous substrates. Durabillty is of course necessary in a printing operation due to the tack of the ink, abrasion of the inking rollers, offset blanket, paper, etc.
Therefore, it is obvious that a binder compound is desirable to optimize the film strength. Convent1onal binders in coating solutions are typically solution polymers. Examples of such materials are acrylics, epoxies, etc. In order to provide an abhesive surface, it is necessary that the fluorinated material come to the surface to form the thermodynamically lowest energy 11003~

interrace wlth air, i.e. there must be some layering or stratiflcation of the coating as it dries. When this occurs, the coating surface exhibits the aforementioned difficultles of the fluorinated material itself with the exception that inclusion of the binder may provide better holdout on porous substrates.
A novel and surprising solution to this problem is to employ a medium which is substantially insoluble in the coating application solvent, i.e. the medium is a discrete phase in the coating mixtureO Upon application to a substrate and solvent evaporation, the particles of the medium must have sufficient capabilities of fusing to form a continuous durable film. In this instance, the fluoroaliphatic radical-containing compound is apparently trapped in the voids between interlocking particles and is thus uniformly dispersed therein. The coating exhibits the necessary abhesive properties while the binder contributes to the coating durability and imageability. In other words, upon marking the film, the abhesive fluorlnated material is disrupted, thereby exposing the high surface energy binder particles which are easily wettable by the printing ln~.
The binder medium when in particulate form must contain particles of small size, generally less than 50 microns being sufficient. Furthermore, the particles may swell in, but must not be soluble in, the coating application solvent and the particles must be sufficiently fusible, either upon drylng of the coating or by subsequent treatment such as heating, to provide 110~)3~7i a continuous film.
Examples of particulate reslns lnclude poly-vinylchloride resins such as B.F. Goodrich Geon 128, which fuses upon drying of the coating and polyethylene-vinyl acetate copolymers such as USI Chemical Company's Microthene FE532 which is capable of fusing upon application of heat thereto subsequent to drying of the coating.
Substrates for the plates of the invention typically include porous materials, e.g. paper, films, e.gO polyester and metallic foils.
Solvents utilized to prepare solutions of the fluoroaliphatic radical-containing compound typically include oxygenated solvents, such as alcohols, ketones or esters, although solvent selection generally depends on the polymer structure. For example, water soluble polymers can be prepared in which case water can be a suitable solvent.
Concentration of total solids in the coatlng solution can typically range up to 50 percent by weight for ease of coating and control Or dry coating welghts.
Coating weights of up to about 1.0 gram per square foot are satisfactoryO Lower coating weights are acceptable providing a uniform film can be obtained, and coating weights greater than about 1.0 gram per s~uare foot, while not detrimental, tend to be wasteful.
The driographic plates of this invention may be imaged by conventional marking techniques presently utilized for direct lmage lithographic plates~ The fluorinated composition can also be o~ercoated over a 110~)371 light-sensitive system, e.g. diazo, for con~entlonal exposure and aqueous development. Furthermore, the fluorinated composition may be coated over a photo-conductive receiver, e.g. a zinc oxide coated substrate, for electrophotographic imaging.
Another technique found useful for imaging the plate involves the elastomeric transfer prlnciple enunciated in U.S. patent No. 3,554,836. Utllizing the toner powder transfer techniques disclosed therein, one embodiment of my inventlon may be utilized as both the ultimate printing plate and the photoconductive received for the toner powder during imaging~ This can be under-taken by utilizing a substrate, e.g. paper, polyester film, metal, etc. having a coating on one surface thereof which provides the abhesive properties necessary herein, and having on the opposite surface of the substrate a coating of a photoconductor which is an electrophoto-graphic material such as zinc oxide, titanium dioxide or selinium conventionally applied thereto. In this instance, the photoconductor surface of the substrate is imaged and developed with copier toner powder in conventional fashion. A sllicone elastomer surface is then contacted with the toner powder image-bearing photo-conductor surface, in accordance with the teachings of aforementioned U.S. Patent No 3,554,8360 The toner powder is transferred to and retained by the silicone surface. The toner-bearing silicone surface is then contacted to the reverse of fluoroaliphatic ~oated s~de of the driographic plate surface. Heat is applied at 3~ the area of contact to attain the fusing temperature Qo3n required for the tonlng powder whereupon the sllicone elastomer surface and the driographic plate surface are separated. The toner powder is transferred to the fluorinated plate surface, and has been substantially released completely by the silicone elastomer surface.
The invention will now be further illllstrated by the use of the following specific non-limiting examples, wherein all parts are by weight unless other-wise specified.

Example 1 A fluoroaliphatic radical-containing polymer was prepared by charging to a reaction vessel 70 parts of C8F17SO2N(C2H5)C2H4O2CCH-CH2 and 30 parts of HOC2H4O2 CCH=CH2, and tetrahydrofuran solvent was added to attain a 50 percent solids solution. The vessel was evacuated and purged with nitrogen for two hours. The ves el was then heated to 50C in the nitrogen atmosphere for twenty-four hours. A solution polymer of the above components was obtainedO
To 15 parts of the solution polymer were added 70 parts of methyl ethyl ketone.
A binder slurry was prepared by high shear mlxing 30 parts of Geon 128 (trademark for a polyvinyl chloride dispersion resin available from the ~.F. GoGdrich Co.) in 70 parts of toluene which effectively wet the par-ticles tc form a slurry.
A coating application solution was prepared by stirring the polymer solution with the slurry for three hours during which the pclyvinyl chloride particles B

- `` f ~10~37~

swelled in the presence of the polymer solution solvents but were substantially undissolved by same.
The coating solution was knife coated onto paper and corona primed 3 mil polyester film and dried to provide a coating weight of 1.0 gram per squ~re foot.
The coatings were easily imaged by pencil, ball-polnt, pen, typewriter, IBM Copier II (trademark for a toner powder imaging copier machine commercially avail-able from the IBM Corp.) and a Xerox 3100 (trademark for a toner powder imaging copier machine commercially available from the Xerox Corp.).
After imaging, the plates were mounted on a conventional offset printing press with the dampening system removed and ink was supplied to the ink train.
More than 700 quality copies were produced on the press.
To illustrate the effectiveness of the dispersion resin binder in the coating, a coating solution was pre-pared as above but excluding the polyvinyl chloride resin therefrom and coated on 3 mil corona primed polyesterO
After imaging with toner powder, the plate was placed on one side of the plate cylinder of the offset press, and a similar plate prepared as above with the polyvinyl chloride resin was placed on the other side of the plate cylinder.
Although both plates produced prints, the loss of fused copier toner into the printing ink was evident on the binderless plate at from 10 to 100 copies, while the plate containing the binder evidenced no toner "picklng" by the printing ink over a 700 copy press runO

B

At about 150 copies, the binderless plate coating was visibly abraded, and printing ink was depositing on the exposed polyester film. No abrasion loss was exhibited on the plate containing the binder.
Most surprisingly, the toning, i.e. the casual deposition of ink in the non-image or background areas of the plate, was equal for the two plates at the beginning of the run, yet the toning at the end of the run was greater in the binderless plate.

Example 2 A water-soluble fluorinated polymer was pre-pared by free-radical polymerization in butyl cello-solve as per the conditions of Example 1, the polymer containing 50 percent by weight of C8F17S02N(C2H5)02CC
(CH3)=CH2 and 50 percent by weight of Carbowax 400/
diacrylate. Carbowax 400 is a polyethylene glycol available from the Union Carbide Co., and the diacrylate was prepared by well known esterification techniques utilizing acrylic acid. The butyl cellosolve was stripped ~rom the polymer and the polymer was mixed wlth water to obtain a 10 percent by weight solids solution thereof.
By conventional emulsion polymerization techniques, a terpolymer aqueous emulsion was prepared consisting of 35 percent by weight isooctylacrylate, 50 percent by weight acrylonitrile, and 15 percent by weight of acrylic ac~d. The emulsion was dlluted to 10 percent solids in water.

` 1100371 Equal parts of the solution and emulslon were mixed and knife coated onto a corona primed polyester sheet and dried to provide a dry coating weight of 1.0 gram per square foot.
A durable direct imageable film was obtained which after imaging functioned similar to Example 1 on the printing press.

Sixty-five grams of a powdered polyethylene-vinyl acetate copolymer commercially available from the USI Chemicals Co. as Microthene FE532*, was added to 32.5 grams of the fluorinated polymer of Example 1, 32.5 grams of tetrahydrofuran, and 32.5 grams of methyl ethyl ketone.
The requlring slurry was thoroughly mixed for two hours, knife coated onto 3 mil corona primed polyester film, and dried to provide a coating weight of about 1.0 gram per square foot. The coated sheet was heated by passing it through a 325F nip roll at 5 inches per second. The heating caused the dispersion copolymer to fuse producing a durable film.
Upon direct imaging and placing on a press as per Example 1, press copies were produced.

*Trade l~lark ~B

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An article capable of providing a driographic printing plate which can be direct imaged, comprising a substrate having a coating on at least one surface thereof, said coating comprising a fused particulate binder compound characterized by high surface energy and easy wettability when exposed to printing ink having a solid, at less than 100°F, heat-softenable fluorinated compound uniformly dispersed therethrough in a manner such that the surface of said coating is oleo ink repellent when dry; said fluorinated compound containing at least one fluorinated aliphatic radical therein having at least one terminal perfluoromethyl group, said coating containing no material serving to flow at ordinary image-marking temperatures to heal image-marked areas therein.

2. The article of claim 1 wherein said binder compound comprises polyvinyl chloride resin.

3. The article of claim 1 wherein said radical is monovalent saturated, and contains at least three carbon atoms.

4. The article of claim 1 wherein said fluorinated compound is a polymer and said radical is a pendant group within said polymer.

5. The article of claim 1 wherein said substrate is paper.

6. The article of claim 1 wherein said substrate is polyester.