CA1166070A - Method for preparing dry lithographic plates - Google Patents
Method for preparing dry lithographic platesInfo
- Publication number
- CA1166070A CA1166070A CA000953939A CA953939A CA1166070A CA 1166070 A CA1166070 A CA 1166070A CA 000953939 A CA000953939 A CA 000953939A CA 953939 A CA953939 A CA 953939A CA 1166070 A CA1166070 A CA 1166070A
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- Canada
- Prior art keywords
- silicone rubber
- layer
- plate
- ink
- image
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
- B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
- B41C2210/16—Waterless working, i.e. ink repelling exposed (imaged) or non-exposed (non-imaged) areas, not requiring fountain solution or water, e.g. dry lithography or driography
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- Printing Plates And Materials Therefor (AREA)
Abstract
METHOD FOR PREPARING DRY LITHOGRAPHIC PLATES
Abstract of the Disclosure There is provided a dry planographic printing plate that can be employed for lithography and which requires no water fountain. The plate includes a base layer and at least two additional layers both overlying the base layer and dis-posed in superimposed relationship to each other. One of the additional layers is of silicone rubber material, while another of the layers is capable of being removed in selected areas so as to define the boundaries of an image to be printed from the plate. The silicone rubber material is adapted in the absence of dampening to provide an ink repellent back-ground for the image.
Abstract of the Disclosure There is provided a dry planographic printing plate that can be employed for lithography and which requires no water fountain. The plate includes a base layer and at least two additional layers both overlying the base layer and dis-posed in superimposed relationship to each other. One of the additional layers is of silicone rubber material, while another of the layers is capable of being removed in selected areas so as to define the boundaries of an image to be printed from the plate. The silicone rubber material is adapted in the absence of dampening to provide an ink repellent back-ground for the image.
Description
o This invention relates generally to printing and more particularly it pertains to a method for preparing dry lithograph plates.
Offset printing has traditionally been performed with greasy ink and water repellent. The developed out image on the lithograph plate consisted of bare metallic background and pigmented printing positions.
In the printing press the plate was exposed to both a water fountain and ink fountain with the desired effect that wet metallic background repelled the ink while the pigmented area attracted it~
This practice is satisfactory as long as a careful balance of ink and water is maintained, and further that no interruptions are incurred where the plate may dry and become oxidized.
An object of an aspect of this invention is to provide a lit~ograph plate which when exposed and developed presents an ink repellant image background in the dry state.
An object of an aspect of this invention is to provide new materials and methods for lithography which require no water fountain.
An obejct of an aspect of the invention is to proviee a photo-lithographic plate which prints a sharper impression for a greater number of copies and will resist the corrosive affects of the atmosphere both in the press and in storage.
Various aspects of the invention are as followso ~ O
A dry planographic printing plate comprising a base layer, and at least two additional layers disposed in superimposed relation to each other and both overlying said base layer, one of said additional layers being a layer of silicone rubber material and another of said additional layers being capable of being removed in selected areas so as to define the boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to pr~vide an ink repellent background for said image.
A dry planographic printing plate comprising a base layer and at least two additional layers disposed in superimposed relatlon to each other and both overlying said base layer, one o said additional layers being a layer of silicone rubber material, and another of said additional layers being light sensitive and capable of being removed in selected areas so as to define the boundaries of an image to be pxinted from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background for said image.
: 20 A dry planographic printing plate comprising a base layer, a layer of silicone rubber material overlying said base layer, and a continuous chemically etchable metallic layer mounted on the outside surface of.the silicone rubber layer and capable of ~ being etched away in selected areas so as to define the - 25 boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background fox said image.
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7(3 A dry planographic master to be sensitized, imaged and developed in accordance with known methods wherein said master is comprised of a flexible substrate capable of being rolled and mounted on an offset lithographic press, a layer of 5 silicone rubber bonded ~o at least one surface of the flexible substrate and a chemically etchable metallic foil mounted on the expos.ed surface of the silicone rubber layer in the area to be imaged.
An imaged dry p~anographic printing plate, which accepts 10 ink in the image area and prints therefrom, and repels ink in - the non-image area, comprising a base layer, an ink-receptive image area, and a silicone rubber materi~al overlying said base layer and providing the ink repellent non-image area.
A process for printing planographically in the absence of dampening with an imaged dry planographic printing plate which accepts ink in the image area and prints therefrom and which repels ink in the non-image area, which process comprises rolling the surface of the imaged dry planographic prinking plate with ink in the absence of dampening, whereby the ink is contacted with the image and the non-image areas of the plate, the ink being repelled in the non-image area by a silicone rubber material and the ink being accepted in the image area, and thereafter transferring ink accepted in the image area to an ink-receptive surface.
Other objects and attendant advantages of this invention will become more readily apparent and understood from the following detailed specification and single sheet of accompanying drawings in which:
-lb-Figs, 1, 2, 3, and 4 are much enlarg~d Cros~-sections of a novel photo-lithograph plate in the respective or~er of preparation for a representative plate according to this inven-tion;
Fig. 5 schematically depicts the burn or formation of the image on a-photo-lithograph plate such as that of Fiy. A;
Figs. 6 and 7 are much enlarged cross sections of exposed plates depicting the subsequent steps of development and etching respectively; and Fig, 8 is a somewhat schematic depiction of the printing press arrangement using the-plates of this invention.
Referring now to the details of the invention there is first provided a lithograph plate base indicated by reference numeral 10. This base 10 may be of any material such as metal, plastic, or paper which is capable of being rolled and mounted on a standard offset lithograph press.
The base 10 is then given a coat 12 of offset ink repellent material such as silicone rubber solution on one face as shown in Fig. 2. The preferred method of coating is to first clean or etGh the base and then roll or squeegee thereon a solution hereafter called Formula X, comprising any of the above in paste form dissolved in two parts by weight of ~ola-tile solvent film cleaner. The former rubher constituent is made by the Dow Corning Corp.
and also by the General Electric Company. The solvent is manufactured by the P, & J0 Corporation. The solvent is P & J Cleaner and its chemical name trichloroethane, A thin to~ping web 14 which may be of metal is applied on the still tacky surface of the silicone rubber coat 12 and rolled flat so as to adhere well and be perfectly smooth as shown in Fig, 3.
~2-After allowing this assembl~ to dry, it is given a coating 16 of the usual photo sensitizing ammonium dichromate solution as shown in Fig. 4 to resuli in a sensitive photo~
lithograph plate 18.
The plate 18 is mounted in contact with a photo-transparency T and exposed to strong light from an arc lamp L
as shown in Fig. 5. This causes the coating 16 to harden in the exposed areas. When rub-developed with the usual developing solutions as shown in Fig. 6, the soft background of coating 16 washes away down to the topping web l4 while the image areas remain.
An etch of acid or solvent suited for material of the web 14 is then performed removing the web 14 at the exposed background areas only as shown in Fig. 7. This exposes the silicone rubber coat 12 as a bac~ground image and this portion even when dry is repellent to offset ink unlike bare metal, while the remaining raised print areas are receptive thereto.
~ or this reason the thus prepared exposed, and developed lithogxaph plate 20 may be installed as shown in Fig.
8 on an offset pre~s P and used without a water fountain.
The unique nature of the coat 12 in repellin~ ink, - water, and the like can be utilized in various other offset, gravure and letter press plates other than the above described laminated dry surface plate. Typical procedures (not illustrated~
will now be discussed.
For preparation o~ positive lithograph or offset plates, a presensitized plate is rolled or squeegeed with ihe Formula X to deposit an overall coat of silicone rubber. After a half hour drying period, it is exposed to a light image in the _3_ 7~
usual manner for about 1 and 1/2 minutes and developed out with a zylene, ethylene glycol and P. & J. ~ilm cleaner solution made up in the respective proportions o~ l/Z r 1/8 and 1/2 ~z.
The plate is ~hen flooded with light in the presence of heat for 3 minutes. The plate is then ready for the press or it may first be etched, copperized or filled with a filler as desired.
For preparation of negative lithograph or offset plates, a presensitized plate is e~posed, lacquered, washed and dried in the normal ~anner but not gummed up.
~ ext the plate is recoated with sensitizing material and Formula X is applied and allowed to dry a half houx for the silicone rubber to form a coat overall. The plate is then fl~oded with light for 3 minutes in the presence of heat.
Finally the plate is developed out using the zyleneJ
ethylene glycol ~nd P. & J~ film ~leaner solution as I~lentioned above.
Okviously, many other modifications and variations of the present invention are possible in light of the above teachings~
It is~ therefore, to ba understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically describedO
-SUPPLEMEN~ARY DISCLOSURE
This supplementary disclosure is directed to supplementary features of the planographic plate, the method of producing th~
same and the planographic printing method employing the same which is disclosed in the principal disclosure.
Various aspects of the invention set out in this Supple-mentary Disclosure are as follows:
A planographic plate comprising, on a flexible substrate, a continuous silicone rubber containing layer, and overlying 0 said silicone rubber containing layer a layer of a photo-responsive diazo compound which, upon exposure to light, is oleophilic and ink receptive when dry.
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A proces~ of dry planographic ~rinting which comprises providing a flexible planographic plate comprised of a flexible 15 substrate and a silicone rubber containing layer having a surface energy which is so low that the silicone rubber surface will not remove conventional lithographic printing ink from an inking roller passed thereover, subjecting said plate to an imaging treatment whereby at selected areas thereof an ink 20 receptive image is formed, attaching the imaged plate to the plate cylinder of a printing press, and without wetting the unimaged areas of the plate, repeatedly (1) rolling the surface of the imaged plate with an ink roller to ink the imaged areas and (2) printing from the ink image on to a receiving surface.
The process of producing a dry planographic plate which comprises coating at least on~ surface of a flexible substrate having sufficient strength to withstand the stresses normally produced by the lithographic process with a silicone rubber containing material which upon curing gives a surface having low enough surface energy that the silicone rubber containing material will not remove conventional lithographic ink from rotating inking rollers, and thereafter curing said silicone rubber containing material.
~; -5-The new planographlc plate of this supplementar~
disclosure comprises a sheet of flexible substrate sufficient-ly strong to withstand the stresses normally employed in a lithographic printing process~ said substrate having coated on at least one surface thereof a layer of silicone rubber having a surface energy low enough that the silicone rubber will not remove conventional lithographic printing ink from an inking roller of a printing press.
The term silicone rubber as employed in the present specification and claims represents a diorganopolysiloxane composition which upon curing to a solid elastic state provides a surface having a surface energy low enough that it will not remove conventional lithographic printing lnk from an inking roller. Representative silicone rubbers to be employed in the present invention result from the curing of a diorganopolysiloxane selected drom the yroup consist-ing of:
(a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal reactive end-blocking groups and a metal salt of carboxylic acid; and (c) linear -~luid diorganopolysiloxanes having terminal silicon-bonded hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate or methyl hydrogen polysiloxanes.
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~6~07~) 1 The term diorganopolysiloxane as employed herein represent~
disubsti~uted polysiloxanes wherein the substituents are mono-valent aliphatic or cyanoalkyl groups having rom l to 4 carbon atoms, inclusive. Representative aliphatic and cyanoalkyl groups include methyll ethyl, propyl, butyl, vinyl, allyl, beta-cyanoethyl, beta-cyanopropyl and halo alkyl groups such as 3,3,3-trifluoro-propyl and chloromethyl. Representative organic carboxylic acida include tin naphthenate, tin octoate, lead octoate, tin oleate, iron stearate, tin butyrate, dibutyl tin dilaura~e, dibutyl tin diacetate, zinc naphthenate, lead 2-ethylhexoate and the like with the tin and zinc salts generally being preferred. The term reactive end groups as employed in the present invention designates acetoxy, hydroxy and oxime groups.
The diorganopolysiloxane compositions employed to pro-duce the solid but elastic sillcone rubber films of the present invention are conveniently applied to at least one surface of the flexible substrate in the form of an aqueous emulsion or acqueous or solvent dispersion. The diorganopolysilox~ne compositions are applied to the substrate by means o a blade coater, Mayer bar~
reverse roll coater, knife or by other commonly employed coating techniques. The surface to be coated should be clean and preferably dry when the diorganopolysiloxane composition is applied. The silicone rubber film can be of any desired thickness as long as the film is coherent, continuous and securely bonded ~o the substrate. It has been found convenient to apply the diorgano-polysiloxane composition in an amount sufficien~ to provide a coating of silicone rubber having a thickness of from 0.02 to 0.2 mils. Films thicker than 0.2 mils can be employed; however, they are generally not deemed to be necessary.
Following the application of the diorganopolysiloxane 1 composition to the surface of ~he subs~rate, the diorganopoly-siloxane composition must be allowed to cure to produce the solid but elastic silicone rubber. Most of the diorganopolysiloxane compositions of the present invention cure at room temperature.
The curing generally takes place within minutes to 24 hours.
However~ the curing time will vary according to thickness of the film, humidity and temperature. While most of the diorganopoly-siloxanes cure at room temperatures and, therefore, do not require additional heating, the coated plate can be keated to decrease the cure time if desired. When employing a diorganopolysiloxane composition comprising a fluid diorganopolysiloxane having terminal silicone bonded hydroxy groups, a metal salt of a carboxylic acid and a methylhydrogen polysiloxane, heat curing is recommended, temperatures of from 90 to 500~F are operable and temperatures between 90- and 160~F are preferred. Curing is obtained by hea~ing the fil~ to be cured for a period of from about 10 seconds to about 3 minutes or more. The cured solid but elastic silicone rub-- ber films of the present invention have a free surface energy (Ts) of 25 or less ergs/cm. . The use of silicone rubbers havi~g a - ~ 20 surface energy above about ~ ergs/cm.2 resul~s in background areas which remove ink from a rotating ink roller and thereby cause back-ground inking and toning.
The flexible substrate employed in the present invention should be sufficiently flexible that it can be mounted on a lltho-graphic press and strong enough that it can withstand the s~resses normally produced by the lithographic process. Representative substrates include coated papers, metals or plastics such as poly-(ethylene-glycol terephthalate). While aluminum appears to be the preferred metal aubstrate on the basis of cost, handling properties, and the like, sheets of lithographic zinc, foils of copper, steel - 7 ~
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1 and copper surfaces all can be employed as the flexible subs~rate in the present invention.
, Any grade of paper can be employed as the substrate in the present invention provided that it has the s~rength to with-stand the stresses normally employed in the lithographic process.
Such papers are well known in the art and generally range from 70 to 250 pounds per ream. The diorganopolysiloxane compositions employed to produce the solid but elas~ic silicone rubber coating can be applied directly to the surface of the paper. However, such 10 application often requires the use of relatively large amount of diorganopolysiloxane compositions and the use of such large amounts is generally not economically desirable. Therefore, in a convenient pro~edure~ the surface of the paper plate is precoated prior to the application of the diorganopolysiloxane composition.
The precoat serves to "hold out" the aqueous emulsion or organic solvent carrier employed in the application of the diorganopoly-siloxane compositipn. Coatings which provide the deqired carrier "hold out" and are useful in the present invention include poly-vinyl alcohol, casein, starch9 carboxylated starch, hydroxy-20 ethylated starch, alpha protein, styrene butadiene based coatings, acrylic copolymer coatings, vinyl acetates, fluorocarbons and the like. Such coatings may contain fillers, pigments, antlfoam agents, spreading agents and other additives commonly employed in ` ~ paper coating compositions. A coated paper substrate designed to give 15,000 or more copies is easily provided by a paper base made from moderately beaten che~mical wood pulp fibers and weighing from 80-90 pounds per ream of 500 sheets (25 x 38 inches in size).
A specific example of a suitable paper is one weighing 87 pounds per ream made from a furnish containing beaten wood pulp fibers of 30 coniferousand deciduous trees, a small portion of clay filler~
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1 rosin size and alum. The paper is then coated on one or both sides with about 10 pounds per ream dry weight o clay and casein in a 5:1 ratio. '~he sheet is then dried and calendered.
Figures 9, 10, 11, 12, 13aand 13b are enlarged cross-sections of plates having an ink repellent silicone rubber back-ground.
The new planographic plate of the supplementary disclosure as depicted by Figure 9 is comprised of a flexible substrate 1-05 having at least one surface thereof continuously coated with a fil~
106 of solid but elastic ink-repellent silicone rubber. Following the curing of the diorganopolysiloxane to obtain the solid but elastic silicone rubber layer, the plate is ready to be imaged. A
short run imaged plate is produced by passing the plate through a xerographic electrophotographic copier. In this process, a powder image previously electrostatically formed on a selenium-plated drum is transferred by contact to the plate. The plate and image are then heated to~cause the powder particles to fuse to each other and to the surface of the plate. The i~aged plate produced in this manner is mounted on a printing press, inked and used to produce clean copies having no ink in the background areas. This method of imaging the plate is useful for producing copies of line copy and the like.
A pre-sensitized plate as illustrated by Figure lO is prepared by applying to the cured solid but elastic surface of the silicone rubber film 106 one of the water soluble photo-responsive diazo compounds employed in conventional diazo-sensitized litho-graphic plates. The dried powdered photo-responsive diazo compound is rubbed over and onto the surface of the silicone rubber to pro-duce a photo-responsive diazo layer 113 which adheres to the surface of the silicone rubber. The excess diazo not adhering to the _ 9 _ ,~
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1 surface is removed by light brushing~ air knife or the like. The sensitized plate thus prepared is exposed through a negative transparency 114 to radiation having a wave length of the proper magnitude to initiate the photo-response of the diazo layer.
Cenerally, actinic radiation will be suffi~ient to initlate ~he photo-responsive reaction. However, radiation having a wave length outside of the range of actinic radiation may be employed when necessary. During the radiation procedure, those areas of the plate exposed to radiation become insoluble and oleophilic forming an image area 115 which adheres to the silicone rubber layer 116.
Following the radizton or exposure procedure, the surface of the plate is washed with water to remove the unexposed water soluble diazo compound leaving bared surfacesll6 of ink repelling silicone rubber as the background. The washed plate is then dried and mounted on a printing press. The rota~ing ink roIlers of the press are applied to the sur~ace of the plate inking the oleophilic image areas but leaving the unimaged silicone rubber background areas clear.
In another embodiment of the present invention as illustrated by Figure 11, the ink repellent silicone rubber i8 applied to the surface of a conventional pre-sensitized litho-- graphic plate to provide in the non-imaged areas a silicone rubber surface which will not remove ink from ink rollers and, therefore, does not require wétting with a fountain solution. This embodiment results in the formation of a long run pre-sensitized plate that can be imaged by exposure through a posi~ive transparency and can be made as follows. A flexible substrate such as an aluminum-base diazo-sensitized plate as disclosed in the Case and Jewett U.S.
Patent No. 2,714,066 or a pàper-base sensi~ized plate as disclosed in the Brinnick et al UJS. Patent No~ 2,778,735 is prepared.
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t The diazo sensi~ized pla~e comprised o~ a subs~ra~e 120 and a diazo coating 121 is then coated with a layer 122 of silicone rubber as hereln defined. The silicone rubber i8 applied by conventional coating methods, and if desired, can be further squeegeedor wiped down with a soft cloth to leave a film which after hardening may be as thin as 0.05 mils or even 0.02 mils.
A thicker film, for example from 0.05 to 0.2 mils, can be left if desired. A very thin film may harden sufficiently in about half an hour, especially if the atmosphere is rather humid. But ordinarily, especially for thicker films, it is preferred to let the film age for about 24 hours before developing an i~age formed thereo~. A latent image itself can be for~ed in the film any time after the film has become reasonably firm by exposure of the plate through a positive transparency 123. This exposure insolub_ ilizes the underlying diazo compound in the exposed areas 124, that is the background or non-image area, but leaves the diazo compound unchanged and still soluble in the image area 126.
The latent image so formed can then be developed at once, or if desired the development can be postponed for 24 hours or longerO
Development is readily accomplished merely by swabb~ing the surface with a cotton pad wet with water containing a small amount of a wetting agen~ such as sodium lauryl sulfonate~ alkyl phenyl ethers, polyethylene glycol, trimethyl nonyl ether of prupylene alkylene glycol ethers and the like. The swabbing does not affect the background area 124 where the exposed diazo compound apparently acts to bond the sil$cone rubber to the underlying base; but in the imaged areas 126 the silicone rubber and the- underlying still soluble diazo compound are removed by the swabbing, laying bare the surface of the original substrate. In those cases where the si-licone rubber layer is unusually thick or has been aged for a D
6V7(~
t considerable period, the swabbing liquid may be a m~x~ure o~ equal parts of trichlo~oethane (sold a~ P & J cleaner) and xylene and about 1/4 part of ethylene glycol. The bared surface of the substrate in the image area 126 accepts ink from the rotating anking rollers and prints it either directly upon paper or upon an offset blanket which will transfer the print to paper. Normally the substrate image, when dry, will accept either oil-base ink or aqueous-base ink, depending upon which is applied first. In most cases~ the layer of silicone rubber will be ~in enough that the recesses left by its removal in the image area are so shallow that the plate can be considered to be a planographic plate. Of course, thicker layers of silicone rubber can be used, `~ and in such cases the image areas 126 may be too deep to be inked by the usual inking roller. Deep image recesses may be filled with ink-receptive matter to make the image flush with the plate surface. For use when printing with greasy lithographic ink is contemplated the recess filler used should be oleophilic, e.g., a viscous polyvinyl acetate emulsion, asphaltum, lacquers or the like. When use of aqueous ink is contemplated, the recess filler should be hydrophilic, for example, a mixture of zinc-carboxymethylcellulose and clay, or the li~e.
In a still further embodiment of the present inven ion, - - as illustrated by Figure 12, a long las~ing plate tha~ can be . given a laten~ image by exposure through a negative transparency is made as follows. A flexible metal substrate 130 such as aluminum or zinc is coated with from 1 to 50 grams per square meter of diorganopolysiloxane composition to form silicone layer 131. Immediately after applying the diorganopolysiloxane layer 131 and while the layer is still tacky, a sheet of soft chemically ; etchable me~allic foil 133 ls pressed into intima~e contact with ~. , ` ,' .
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1 the liquid layer. Representative chemically ethable metallic foils include ~inc, copper and alu~lnum. The sandwich so formed is allowed to age for from 12 to 96 hours to permit the silicone rubber to cure or become solid, and to form an adhesive bond with the metallic foil 133. Thereafter, the exposed surface of the foil 133 is cleaned by brief immersion in a standard etching solution, washed and dried. Next the clean and dry surface is given a photopolymerizable photo-resist layer 134 and exposed through a negative transparency 136. The exposure hardens and insolubilizPs the photopolymerizable material in the exposed areas 138 to form a latent image. Thereafter, the surface s swabbed with a photo-resist developer which removes all the unexposed photopolyermizabl material in area 140 and leaves the underlying foil 133 bare, but does not remove the photopolymerized layer in the image area 138.
Then the surface is again immersed in the same etching solution in which the foil 133 had previously been cleaned and allowed to remain there until all of the foil 133, except that covered by the photopolymer image, has been disso~ved down to the underlying silicone rubber background 131. The plate is then thoroughly washed and dried. This plate, after the background had been etched away, has an image area of metal, still covered by ~he photopolymer resist, raised slightly above the silicone background, and so is not, strictly speaking, a planographic plate. However, the plate can be used in the same way, and on the same printing press, as the other plates having si~icone rubber background areas as described above. In such use the rotating inking rollers and offset blanket will come in contact with the sillcone rubber background. The sillcDne rubber background remalns free of ink as in the previously discussed cases and doesnot print on the offset blanket or paper.
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7 [) ~ nother embodimen-t o~ the present invention as illustrated by Figures 13, 14 is prepared as follows- a silicated aluminum plate 50 is sensitized with a conventional diazo compou~d, exposed and developed by swabbi~g with an aqueous emulsion of lacquer which removes unreacted diazo and leaves a layer of lacquer 51 on the exposed image area 52. ~fter washing, the entire surface of the plate is again swabbed with aqueous solution of a photo-responsive diazo compound such as the formaldehyde condensate of a paradiazo-diphenyl amine salt or the like to form the layer 53. The plate is then allowed to dry, and thereafter coated with a layer of sili-cone rubber 54. The silicone layer is cured and the en-tire plate exposed to radiation of sufficient wave length to initiate the photo-responsive reaction o~ the diazo compound. By this -treatment the diazo compound is insolubilized and its adherence to the silicone rubber layer is improved, and likewise the silicone rubber layer itself is further cured. ~ext, the plate is swabbed vigorously with a mixture of e~ual parts of l,l,l-trichloroethane and xylene and 1/4 part of ethylene glycol which penetra~es through the silicone layer 54 and loosens the lacquer layer 51 covering the image area 52. The lacquer and overlying silicone rubber come away from the image leaving the imaged area 52 slightly recessed. The plate thus prepared can be used in this condition or the recessed areas can be filled with oleophilic material such as viscous polyvinyl acetate emulsion. In the la-tter case the resulting plate has a level surface, with imaged areas of oleophilic polyvinyl acetate and ink-repellent background areas of a silicone rubber.
By way of amplifying the description of Figures 13 and 14, the silicated aluminum plate 50 is sensitized, exposed and ~ - 1~
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developed. During development of this plate by use o~ the aqueou~
-- lacquer emulsion, the unexposed and soluble diazo in the non-image areas is removed leaving the insoluble exposad diazo image layer 5~ coated with the layer of lacquer 51. The exposed and developed plate comprised of the substrate 50, the insoluble diazo image 52 and the lacquer layer 51 is then coated with an aqueous solution of photosensitive diazo material to produce the anchoring diazo layer 53. The plate is then allowed to dry and a layer of silicone rubber 54 is applied over the unexposed anchoring diazo layer 53. After the silicone layer is allowed to cure the entire plate depicted by Figure 13 is exposed to actinic radiation which insolubilizes the entire anchoring diazo layer 53.
The exposed plate is then swabbed with a mixture of trichloroethane, xylene and ethylene glycol. This mixture penetrates the silicone layer 54 and the anchoring diazo layer 53 and dissolves the lacquer layer 51 causing the lacquer and anchoring diazo and silicone layers immediately above the image to come free leaving ; a plate shown in Figure 14 consisting of a substrate 50, an insoluble diazo image area 52 and e~posed anchor diazo layer 55 covered by the silicone rubber layer 54. The relative thic~nesses of the various layers are not accurately depicted by the drawings.
The second exposure of the entire plate causes the anchor diazo layer to become insolubilized and to bond the silicone to the non-image areas of the plate. The lacquer layer prevents the anchoring diazo layer from bonding securely to the diazo image area and -thereby allows the silicone and anchoring diazo layer to be removed by the trichloroethane containing mixture.
Other plates can be made by coating a metal or paper plate with layer of silicone rubber, curing the silicone rubber at room temperature for several hours, and then using an engraver's 14a -1 tool to cut a pattern ~hrough the silicone to the un(lerl~ln~ ~ase, The pattern is then ink-receptive, but the silicone layer is not.
Tl1is plate thus prepared can then be employed on a press or the pattern can be ~illed with an oleophilic substance before the plate is so employed.
EXAMPLE l A paper plate is prepared from paper stock which is - composed of about equal amounts of long fibers and short fibers and contains from ~ to 8 percent mineral filler. The paper stock is ` 10 sized with rosin and alum and weighs-about 52 pounds per ream ~500 sheets - 25" x.38"). One side of the paper is base-coated with lO pounds per ream dry weight of a coating comprised of clay (lOO parts), casein (20 parts) and dimethylol urea (2 par~s) and is then dried and calendered. The paper plate is then revers-roll coated with 2 pounds dry weight per ream of a xylene disper-sion of a diorganopolysiloxane composition comprised of a dimethylpolysiloxane, methylhydrogensiloxane and ~inc octoate, and the resulting layer of diorganopolysilo~ane is dried and cured for 40 seconds at 500F. The silicone rubber coated plate is then fed through a Xerox~ 91~ copy machine, (an ofice si~e seleniu~
drum copies). As a result of this procedure, a powder image previously elec~rostatically formed on a selenium-plated drum i8 transferred to the plate. ~l'hiE~ image is then heated to cause powder particles to fuse to each other and to the surface of the plate, The plate thus prepared is then mounted on a rotary offset duplicator (Addressograph-Multigraph Corporation, Multilith*
No. 1250, an office size offset duplicating machine,) from which the molleton rollers (water fountain rollers3 have been removed.
The plate is merely clamped to the plate cylinder and while dry is inked with regular lithographic ink (Addressograph-Multigraph ink No. Ml* 3~, a linseed oil based medium tack test ink) by the inking roller and the ima~e is printed on the off~let blanket ~rom which it was transferred to a paper sheet. Fifty copies having ~r~ -15 -~ *Indicates a Trade Mark 1 clean un-inked background areas are produced from this plate.
A paper substrate as prepared in ~xample 1 is air ~ni~e coated with 3 pounds per ream dry welght of a diorganopolysiloxane composition composed of dimethylpolysiloxane ha~ing silicon-bonded hydroxy groups, methylhydrogen polysiloxanes and dibutyl tin laurate, The diorganopolysiloxane composition is dispersed in toluene ln an amount sufficient to provide a dispersion having about 10 percent by weight of solids. The coating layer is cured at 300~F for about 5 minutes. This plate is then sensitized by rubbing the silicone rub-ber surface with a cotton pledget filled with powdered double chloride of zinc and the para-formaldehyde condensate of diazotized para-aminodiphenyl amine. Excess diazo powder is then carefully wiped off. The sensitized plate thus prepared is then exposed through a negative transparency to a 35 amp. double carbon arc at a distance of 36 inches for one minutes. The partially exposed plate is then washed or developed with water to remove the diazo compound from the unexposed areas. The plate thus prepared was completely dried and clamped to the plate cylinder of a rotary offRet dupli-cator as described in Example 1 and the plate inked and employed toproduce over 50 copies. The copies thus produced were clean with no toning or inking in the bac~ground areas.
E~AMPLE 3 An aluminum based diazo sensi~itzed plate is prepared by coating an aluminum plate with an aqueous solution of sodium sili-cate and thereafter coating the silicated surface with an aqueous 1 percent solution of the double salt of ~inc and condensa~e of para-formaldehyde and para-dia~o-diphenyl amine as described in United States Patent No. 2,714,066. After the diazo coating has dried, a layer of the diorganopolysiloxane composition is applied by Mayer bar coater. The diorganopolysiloxane composition com~ises dimethyl-v 1 polysiloxane gums, silane oxime and titanium dioxide. '~'he ~rface bearing the dior~anopolysiloxane coating i~ wiped down ~/ith ~ 80ft cloth to leave a film which has a thickness o 0.05 mils after curing for about 12 hours at room temperature. The plate thus prepared is exposed through a positive transparency for 60 seconds - to a 35 ampere double arc at~a distance of 36 inches. Following the exposure, the surface of the exposed plate is swabbed with a water solution containing a small amount of ~astman Kodak's FOTOFLO*,~
a wetting agent, currently used in the lithographic trade of unknoT~n ~0 compositions. This water removes the silicone layer and soluble diazo compound rom the unimaged areas, laying bare the surface of the original substrate in these areas. Thereafter, the plate is dried~ mounted on a rotary press as described in Example 1, inked and employed to produce lOOO clean copies.
A S mil sheet of aluminum foil having a surface roughened by sand blasting is coated with a 0.2 mil layer of a diorganopoly-siloxane comprised of hydroxyl end-blocked dimethylpolysiloxane and vinyltriacetoxy silane, said composition on curing forming an acetoxy end-blocked vinyl substituted dimethylpolysiloxane silicone rubber~ Immediately thereafter while the diorganopolysiloxane layer is still llquid, a 3 mil sheet of soft copper foil is pressed i~to intimate contact with the aforesaid layer. The sandwich so formed is allowed to age for 72 hours. Following the aging period, the exposed surface of the copper is cleaned by immersing for two minutes in a standard etching solution consistlng of the following:
lOO milliliters of calcium chloride solution of 40-41 F Baume, 380 grams of ~inc chloride, 285 milliliters of ferric chloride solution of 50-41 F Baume, and ~Indicates a Trade Mark 1 14 milliliters o~ 38 percent hydrochloric acid.
Following the etching procedure; the copper surface is immediately washed and dried, The dry copper surface is then given a photo-resist layer of a photopolymerizable material containing a poly-vinyl cinnamate polymers. The photo-resist layer is dried and the surface exposed through a negative transparency to the light from a 35 ampere double arc at a distance of 36 inches for three minutes. Following the exposure period, the surface of the pla~e is swabbed with developer which removes all of the unexposed 1p photopolymerizable material and leaves the underlying copper bare but does not remove the photopolymerized layer in the image area.
The surface of the plate is then immersed in the same etching solution in which the copper was previously cleaned and allowed to remain there until all the copper except that covered by the photopolymer image has been dissolved. The plate is then washed and driedO The plate thus prepared is then mounted on a rotary press as described in Example 1, coated with ink and used to print 10,000 copies.
A sand blasted aluminum plate is treated with sodium silicate, washed and dried, and thereafter sensitized by swabbing with an aqueous 2 percent solution of a zinc salt of the con-densate of para-formaldehyde and para-diazodiphenyl amineO
-~ ~ Following the coating procedure the plate is dried and the dried plate ~exposed through a negative transparency for 60 seconds to a 35 ampere double arc at a distance o 36 inches. The image so formed is developed by swabbing the surface of the pla~e with `~ an emulsified colored nitrocellulose lacquer in an aqueous solution- of gum arabic. This procedure removes the diazo compound from the unexposed or background area but does not remove the exposed .
- 18~--13 ' ' ' ~6~
l image. In addition, the emulsion breaks su~icientl~J ~o permit - the lacquer to adhere to and coat the surface of the image. ~he plate is then uashed with water to remove all traces of the gum arabic from the surface of the plate without removing the lacquer from the image area. ~ollowing the removal of the gum arabic, the pla~e is again swabbed all over with an aqueous solu~ion of theformaldehyde condensate of a para-diazodiphenyl amine salt and then allowed to dry. The dried plate is ~hen roller coated wi~h a diorganopolysiloxane composition comprises of an acetoxy end-blocked dimethylpolysiloxane and dibutyl tin diacetate in an amount sufficient ot provide about 35 grams per square meter of the diorganopolysiloxane composition. This layer is allowed to aircure for 30 minutes and then it is exposed over its entire surface to radiation from a 35 ampere double arc lamp at a distance of 24 inches for 3 minutes. By this treatment the diazo compound is insolubilized and its adherence to the silicone layer improved, and likewise the silicone layer itself is further cured~ Next, the plate is rubbed with a mixture` of equal parts of 1,1,1-trichloroethane and xylene and 1/4 part of ethylene glycolO Thia liquid penetrates through the silicone layer and loos~ens the lacquer layer covering the image and the rubbing removes the loosened silicone rubber leaving the image area slightly recessed.
Thé depressions thus formed are filled with polyvinyl acetate emulsion and allowed to dry. The resulting plate has a level surface, with image areas of oleophilic polyvinyl acetate and ink repellent background areas of silicone rubberO The plate thus prepared is mounted on a lithographic press as described in Example l and used to print 1500 copies.
The various diorganopolysiloxane compositions employed in the present invention are known in ~ha art and are prepared in D
.
f~
1 accordance with known methods. Represèn~a~ive acetoxy end-blocked diorganopolysiloxanes to be employed in the present inventlon, such as the dimethylpolysiloxanes, vinyl substitu~ed dimethyl-polysiloxanes, alkyl substituted dimethylpolysiloxanes, cyanoalkyl Subs~ituted dimethlypolysiloxanes and 3,3,3-trifluoropropyl and other haloalkyl substituted dimethylpolysiloxanes, are prepared in accordance with methods known to the skilled in the art as illustrated by ~he teachings of United States Patent Nos.
3,035,016 and 3,077,465. Representative diorganopolysiloxane compositions comprised of dimethylpolysiloxanes having terminal silicon-bonded hydroxy groups, methyl hydrogen polysiloxane and dibutyl tin 'dilaurate or dibutyl tin diacetate are also well known in the art and are produced in accordance with known methods. A
representative method of production is taught in United States Patent No. 2,985,545. Similarly, the diorganopolysiloxane com-positions comprised of diorganopolysiloxanes having terminal sllicon-bonded hydroxy groups, an alkyl silicate and a metallic salt of an organic carboxylic acid are known in the art and are produced by known methods such as the procedures taught by United States Patent No. 2,843,555.
The photo-responsive diazo compounds to be employed in the present invention are well known in the art. Representative diazo compounds are described in United States Patent Nos.
Offset printing has traditionally been performed with greasy ink and water repellent. The developed out image on the lithograph plate consisted of bare metallic background and pigmented printing positions.
In the printing press the plate was exposed to both a water fountain and ink fountain with the desired effect that wet metallic background repelled the ink while the pigmented area attracted it~
This practice is satisfactory as long as a careful balance of ink and water is maintained, and further that no interruptions are incurred where the plate may dry and become oxidized.
An object of an aspect of this invention is to provide a lit~ograph plate which when exposed and developed presents an ink repellant image background in the dry state.
An object of an aspect of this invention is to provide new materials and methods for lithography which require no water fountain.
An obejct of an aspect of the invention is to proviee a photo-lithographic plate which prints a sharper impression for a greater number of copies and will resist the corrosive affects of the atmosphere both in the press and in storage.
Various aspects of the invention are as followso ~ O
A dry planographic printing plate comprising a base layer, and at least two additional layers disposed in superimposed relation to each other and both overlying said base layer, one of said additional layers being a layer of silicone rubber material and another of said additional layers being capable of being removed in selected areas so as to define the boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to pr~vide an ink repellent background for said image.
A dry planographic printing plate comprising a base layer and at least two additional layers disposed in superimposed relatlon to each other and both overlying said base layer, one o said additional layers being a layer of silicone rubber material, and another of said additional layers being light sensitive and capable of being removed in selected areas so as to define the boundaries of an image to be pxinted from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background for said image.
: 20 A dry planographic printing plate comprising a base layer, a layer of silicone rubber material overlying said base layer, and a continuous chemically etchable metallic layer mounted on the outside surface of.the silicone rubber layer and capable of ~ being etched away in selected areas so as to define the - 25 boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background fox said image.
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7(3 A dry planographic master to be sensitized, imaged and developed in accordance with known methods wherein said master is comprised of a flexible substrate capable of being rolled and mounted on an offset lithographic press, a layer of 5 silicone rubber bonded ~o at least one surface of the flexible substrate and a chemically etchable metallic foil mounted on the expos.ed surface of the silicone rubber layer in the area to be imaged.
An imaged dry p~anographic printing plate, which accepts 10 ink in the image area and prints therefrom, and repels ink in - the non-image area, comprising a base layer, an ink-receptive image area, and a silicone rubber materi~al overlying said base layer and providing the ink repellent non-image area.
A process for printing planographically in the absence of dampening with an imaged dry planographic printing plate which accepts ink in the image area and prints therefrom and which repels ink in the non-image area, which process comprises rolling the surface of the imaged dry planographic prinking plate with ink in the absence of dampening, whereby the ink is contacted with the image and the non-image areas of the plate, the ink being repelled in the non-image area by a silicone rubber material and the ink being accepted in the image area, and thereafter transferring ink accepted in the image area to an ink-receptive surface.
Other objects and attendant advantages of this invention will become more readily apparent and understood from the following detailed specification and single sheet of accompanying drawings in which:
-lb-Figs, 1, 2, 3, and 4 are much enlarg~d Cros~-sections of a novel photo-lithograph plate in the respective or~er of preparation for a representative plate according to this inven-tion;
Fig. 5 schematically depicts the burn or formation of the image on a-photo-lithograph plate such as that of Fiy. A;
Figs. 6 and 7 are much enlarged cross sections of exposed plates depicting the subsequent steps of development and etching respectively; and Fig, 8 is a somewhat schematic depiction of the printing press arrangement using the-plates of this invention.
Referring now to the details of the invention there is first provided a lithograph plate base indicated by reference numeral 10. This base 10 may be of any material such as metal, plastic, or paper which is capable of being rolled and mounted on a standard offset lithograph press.
The base 10 is then given a coat 12 of offset ink repellent material such as silicone rubber solution on one face as shown in Fig. 2. The preferred method of coating is to first clean or etGh the base and then roll or squeegee thereon a solution hereafter called Formula X, comprising any of the above in paste form dissolved in two parts by weight of ~ola-tile solvent film cleaner. The former rubher constituent is made by the Dow Corning Corp.
and also by the General Electric Company. The solvent is manufactured by the P, & J0 Corporation. The solvent is P & J Cleaner and its chemical name trichloroethane, A thin to~ping web 14 which may be of metal is applied on the still tacky surface of the silicone rubber coat 12 and rolled flat so as to adhere well and be perfectly smooth as shown in Fig, 3.
~2-After allowing this assembl~ to dry, it is given a coating 16 of the usual photo sensitizing ammonium dichromate solution as shown in Fig. 4 to resuli in a sensitive photo~
lithograph plate 18.
The plate 18 is mounted in contact with a photo-transparency T and exposed to strong light from an arc lamp L
as shown in Fig. 5. This causes the coating 16 to harden in the exposed areas. When rub-developed with the usual developing solutions as shown in Fig. 6, the soft background of coating 16 washes away down to the topping web l4 while the image areas remain.
An etch of acid or solvent suited for material of the web 14 is then performed removing the web 14 at the exposed background areas only as shown in Fig. 7. This exposes the silicone rubber coat 12 as a bac~ground image and this portion even when dry is repellent to offset ink unlike bare metal, while the remaining raised print areas are receptive thereto.
~ or this reason the thus prepared exposed, and developed lithogxaph plate 20 may be installed as shown in Fig.
8 on an offset pre~s P and used without a water fountain.
The unique nature of the coat 12 in repellin~ ink, - water, and the like can be utilized in various other offset, gravure and letter press plates other than the above described laminated dry surface plate. Typical procedures (not illustrated~
will now be discussed.
For preparation o~ positive lithograph or offset plates, a presensitized plate is rolled or squeegeed with ihe Formula X to deposit an overall coat of silicone rubber. After a half hour drying period, it is exposed to a light image in the _3_ 7~
usual manner for about 1 and 1/2 minutes and developed out with a zylene, ethylene glycol and P. & J. ~ilm cleaner solution made up in the respective proportions o~ l/Z r 1/8 and 1/2 ~z.
The plate is ~hen flooded with light in the presence of heat for 3 minutes. The plate is then ready for the press or it may first be etched, copperized or filled with a filler as desired.
For preparation of negative lithograph or offset plates, a presensitized plate is e~posed, lacquered, washed and dried in the normal ~anner but not gummed up.
~ ext the plate is recoated with sensitizing material and Formula X is applied and allowed to dry a half houx for the silicone rubber to form a coat overall. The plate is then fl~oded with light for 3 minutes in the presence of heat.
Finally the plate is developed out using the zyleneJ
ethylene glycol ~nd P. & J~ film ~leaner solution as I~lentioned above.
Okviously, many other modifications and variations of the present invention are possible in light of the above teachings~
It is~ therefore, to ba understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically describedO
-SUPPLEMEN~ARY DISCLOSURE
This supplementary disclosure is directed to supplementary features of the planographic plate, the method of producing th~
same and the planographic printing method employing the same which is disclosed in the principal disclosure.
Various aspects of the invention set out in this Supple-mentary Disclosure are as follows:
A planographic plate comprising, on a flexible substrate, a continuous silicone rubber containing layer, and overlying 0 said silicone rubber containing layer a layer of a photo-responsive diazo compound which, upon exposure to light, is oleophilic and ink receptive when dry.
~ .
A proces~ of dry planographic ~rinting which comprises providing a flexible planographic plate comprised of a flexible 15 substrate and a silicone rubber containing layer having a surface energy which is so low that the silicone rubber surface will not remove conventional lithographic printing ink from an inking roller passed thereover, subjecting said plate to an imaging treatment whereby at selected areas thereof an ink 20 receptive image is formed, attaching the imaged plate to the plate cylinder of a printing press, and without wetting the unimaged areas of the plate, repeatedly (1) rolling the surface of the imaged plate with an ink roller to ink the imaged areas and (2) printing from the ink image on to a receiving surface.
The process of producing a dry planographic plate which comprises coating at least on~ surface of a flexible substrate having sufficient strength to withstand the stresses normally produced by the lithographic process with a silicone rubber containing material which upon curing gives a surface having low enough surface energy that the silicone rubber containing material will not remove conventional lithographic ink from rotating inking rollers, and thereafter curing said silicone rubber containing material.
~; -5-The new planographlc plate of this supplementar~
disclosure comprises a sheet of flexible substrate sufficient-ly strong to withstand the stresses normally employed in a lithographic printing process~ said substrate having coated on at least one surface thereof a layer of silicone rubber having a surface energy low enough that the silicone rubber will not remove conventional lithographic printing ink from an inking roller of a printing press.
The term silicone rubber as employed in the present specification and claims represents a diorganopolysiloxane composition which upon curing to a solid elastic state provides a surface having a surface energy low enough that it will not remove conventional lithographic printing lnk from an inking roller. Representative silicone rubbers to be employed in the present invention result from the curing of a diorganopolysiloxane selected drom the yroup consist-ing of:
(a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal reactive end-blocking groups and a metal salt of carboxylic acid; and (c) linear -~luid diorganopolysiloxanes having terminal silicon-bonded hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate or methyl hydrogen polysiloxanes.
-5a-.
, ~
~6~07~) 1 The term diorganopolysiloxane as employed herein represent~
disubsti~uted polysiloxanes wherein the substituents are mono-valent aliphatic or cyanoalkyl groups having rom l to 4 carbon atoms, inclusive. Representative aliphatic and cyanoalkyl groups include methyll ethyl, propyl, butyl, vinyl, allyl, beta-cyanoethyl, beta-cyanopropyl and halo alkyl groups such as 3,3,3-trifluoro-propyl and chloromethyl. Representative organic carboxylic acida include tin naphthenate, tin octoate, lead octoate, tin oleate, iron stearate, tin butyrate, dibutyl tin dilaura~e, dibutyl tin diacetate, zinc naphthenate, lead 2-ethylhexoate and the like with the tin and zinc salts generally being preferred. The term reactive end groups as employed in the present invention designates acetoxy, hydroxy and oxime groups.
The diorganopolysiloxane compositions employed to pro-duce the solid but elastic sillcone rubber films of the present invention are conveniently applied to at least one surface of the flexible substrate in the form of an aqueous emulsion or acqueous or solvent dispersion. The diorganopolysilox~ne compositions are applied to the substrate by means o a blade coater, Mayer bar~
reverse roll coater, knife or by other commonly employed coating techniques. The surface to be coated should be clean and preferably dry when the diorganopolysiloxane composition is applied. The silicone rubber film can be of any desired thickness as long as the film is coherent, continuous and securely bonded ~o the substrate. It has been found convenient to apply the diorgano-polysiloxane composition in an amount sufficien~ to provide a coating of silicone rubber having a thickness of from 0.02 to 0.2 mils. Films thicker than 0.2 mils can be employed; however, they are generally not deemed to be necessary.
Following the application of the diorganopolysiloxane 1 composition to the surface of ~he subs~rate, the diorganopoly-siloxane composition must be allowed to cure to produce the solid but elastic silicone rubber. Most of the diorganopolysiloxane compositions of the present invention cure at room temperature.
The curing generally takes place within minutes to 24 hours.
However~ the curing time will vary according to thickness of the film, humidity and temperature. While most of the diorganopoly-siloxanes cure at room temperatures and, therefore, do not require additional heating, the coated plate can be keated to decrease the cure time if desired. When employing a diorganopolysiloxane composition comprising a fluid diorganopolysiloxane having terminal silicone bonded hydroxy groups, a metal salt of a carboxylic acid and a methylhydrogen polysiloxane, heat curing is recommended, temperatures of from 90 to 500~F are operable and temperatures between 90- and 160~F are preferred. Curing is obtained by hea~ing the fil~ to be cured for a period of from about 10 seconds to about 3 minutes or more. The cured solid but elastic silicone rub-- ber films of the present invention have a free surface energy (Ts) of 25 or less ergs/cm. . The use of silicone rubbers havi~g a - ~ 20 surface energy above about ~ ergs/cm.2 resul~s in background areas which remove ink from a rotating ink roller and thereby cause back-ground inking and toning.
The flexible substrate employed in the present invention should be sufficiently flexible that it can be mounted on a lltho-graphic press and strong enough that it can withstand the s~resses normally produced by the lithographic process. Representative substrates include coated papers, metals or plastics such as poly-(ethylene-glycol terephthalate). While aluminum appears to be the preferred metal aubstrate on the basis of cost, handling properties, and the like, sheets of lithographic zinc, foils of copper, steel - 7 ~
` ~L6~7V
1 and copper surfaces all can be employed as the flexible subs~rate in the present invention.
, Any grade of paper can be employed as the substrate in the present invention provided that it has the s~rength to with-stand the stresses normally employed in the lithographic process.
Such papers are well known in the art and generally range from 70 to 250 pounds per ream. The diorganopolysiloxane compositions employed to produce the solid but elas~ic silicone rubber coating can be applied directly to the surface of the paper. However, such 10 application often requires the use of relatively large amount of diorganopolysiloxane compositions and the use of such large amounts is generally not economically desirable. Therefore, in a convenient pro~edure~ the surface of the paper plate is precoated prior to the application of the diorganopolysiloxane composition.
The precoat serves to "hold out" the aqueous emulsion or organic solvent carrier employed in the application of the diorganopoly-siloxane compositipn. Coatings which provide the deqired carrier "hold out" and are useful in the present invention include poly-vinyl alcohol, casein, starch9 carboxylated starch, hydroxy-20 ethylated starch, alpha protein, styrene butadiene based coatings, acrylic copolymer coatings, vinyl acetates, fluorocarbons and the like. Such coatings may contain fillers, pigments, antlfoam agents, spreading agents and other additives commonly employed in ` ~ paper coating compositions. A coated paper substrate designed to give 15,000 or more copies is easily provided by a paper base made from moderately beaten che~mical wood pulp fibers and weighing from 80-90 pounds per ream of 500 sheets (25 x 38 inches in size).
A specific example of a suitable paper is one weighing 87 pounds per ream made from a furnish containing beaten wood pulp fibers of 30 coniferousand deciduous trees, a small portion of clay filler~
3D ~
6~7~
1 rosin size and alum. The paper is then coated on one or both sides with about 10 pounds per ream dry weight o clay and casein in a 5:1 ratio. '~he sheet is then dried and calendered.
Figures 9, 10, 11, 12, 13aand 13b are enlarged cross-sections of plates having an ink repellent silicone rubber back-ground.
The new planographic plate of the supplementary disclosure as depicted by Figure 9 is comprised of a flexible substrate 1-05 having at least one surface thereof continuously coated with a fil~
106 of solid but elastic ink-repellent silicone rubber. Following the curing of the diorganopolysiloxane to obtain the solid but elastic silicone rubber layer, the plate is ready to be imaged. A
short run imaged plate is produced by passing the plate through a xerographic electrophotographic copier. In this process, a powder image previously electrostatically formed on a selenium-plated drum is transferred by contact to the plate. The plate and image are then heated to~cause the powder particles to fuse to each other and to the surface of the plate. The i~aged plate produced in this manner is mounted on a printing press, inked and used to produce clean copies having no ink in the background areas. This method of imaging the plate is useful for producing copies of line copy and the like.
A pre-sensitized plate as illustrated by Figure lO is prepared by applying to the cured solid but elastic surface of the silicone rubber film 106 one of the water soluble photo-responsive diazo compounds employed in conventional diazo-sensitized litho-graphic plates. The dried powdered photo-responsive diazo compound is rubbed over and onto the surface of the silicone rubber to pro-duce a photo-responsive diazo layer 113 which adheres to the surface of the silicone rubber. The excess diazo not adhering to the _ 9 _ ,~
6~iQ~
1 surface is removed by light brushing~ air knife or the like. The sensitized plate thus prepared is exposed through a negative transparency 114 to radiation having a wave length of the proper magnitude to initiate the photo-response of the diazo layer.
Cenerally, actinic radiation will be suffi~ient to initlate ~he photo-responsive reaction. However, radiation having a wave length outside of the range of actinic radiation may be employed when necessary. During the radiation procedure, those areas of the plate exposed to radiation become insoluble and oleophilic forming an image area 115 which adheres to the silicone rubber layer 116.
Following the radizton or exposure procedure, the surface of the plate is washed with water to remove the unexposed water soluble diazo compound leaving bared surfacesll6 of ink repelling silicone rubber as the background. The washed plate is then dried and mounted on a printing press. The rota~ing ink roIlers of the press are applied to the sur~ace of the plate inking the oleophilic image areas but leaving the unimaged silicone rubber background areas clear.
In another embodiment of the present invention as illustrated by Figure 11, the ink repellent silicone rubber i8 applied to the surface of a conventional pre-sensitized litho-- graphic plate to provide in the non-imaged areas a silicone rubber surface which will not remove ink from ink rollers and, therefore, does not require wétting with a fountain solution. This embodiment results in the formation of a long run pre-sensitized plate that can be imaged by exposure through a posi~ive transparency and can be made as follows. A flexible substrate such as an aluminum-base diazo-sensitized plate as disclosed in the Case and Jewett U.S.
Patent No. 2,714,066 or a pàper-base sensi~ized plate as disclosed in the Brinnick et al UJS. Patent No~ 2,778,735 is prepared.
6~f~J
t The diazo sensi~ized pla~e comprised o~ a subs~ra~e 120 and a diazo coating 121 is then coated with a layer 122 of silicone rubber as hereln defined. The silicone rubber i8 applied by conventional coating methods, and if desired, can be further squeegeedor wiped down with a soft cloth to leave a film which after hardening may be as thin as 0.05 mils or even 0.02 mils.
A thicker film, for example from 0.05 to 0.2 mils, can be left if desired. A very thin film may harden sufficiently in about half an hour, especially if the atmosphere is rather humid. But ordinarily, especially for thicker films, it is preferred to let the film age for about 24 hours before developing an i~age formed thereo~. A latent image itself can be for~ed in the film any time after the film has become reasonably firm by exposure of the plate through a positive transparency 123. This exposure insolub_ ilizes the underlying diazo compound in the exposed areas 124, that is the background or non-image area, but leaves the diazo compound unchanged and still soluble in the image area 126.
The latent image so formed can then be developed at once, or if desired the development can be postponed for 24 hours or longerO
Development is readily accomplished merely by swabb~ing the surface with a cotton pad wet with water containing a small amount of a wetting agen~ such as sodium lauryl sulfonate~ alkyl phenyl ethers, polyethylene glycol, trimethyl nonyl ether of prupylene alkylene glycol ethers and the like. The swabbing does not affect the background area 124 where the exposed diazo compound apparently acts to bond the sil$cone rubber to the underlying base; but in the imaged areas 126 the silicone rubber and the- underlying still soluble diazo compound are removed by the swabbing, laying bare the surface of the original substrate. In those cases where the si-licone rubber layer is unusually thick or has been aged for a D
6V7(~
t considerable period, the swabbing liquid may be a m~x~ure o~ equal parts of trichlo~oethane (sold a~ P & J cleaner) and xylene and about 1/4 part of ethylene glycol. The bared surface of the substrate in the image area 126 accepts ink from the rotating anking rollers and prints it either directly upon paper or upon an offset blanket which will transfer the print to paper. Normally the substrate image, when dry, will accept either oil-base ink or aqueous-base ink, depending upon which is applied first. In most cases~ the layer of silicone rubber will be ~in enough that the recesses left by its removal in the image area are so shallow that the plate can be considered to be a planographic plate. Of course, thicker layers of silicone rubber can be used, `~ and in such cases the image areas 126 may be too deep to be inked by the usual inking roller. Deep image recesses may be filled with ink-receptive matter to make the image flush with the plate surface. For use when printing with greasy lithographic ink is contemplated the recess filler used should be oleophilic, e.g., a viscous polyvinyl acetate emulsion, asphaltum, lacquers or the like. When use of aqueous ink is contemplated, the recess filler should be hydrophilic, for example, a mixture of zinc-carboxymethylcellulose and clay, or the li~e.
In a still further embodiment of the present inven ion, - - as illustrated by Figure 12, a long las~ing plate tha~ can be . given a laten~ image by exposure through a negative transparency is made as follows. A flexible metal substrate 130 such as aluminum or zinc is coated with from 1 to 50 grams per square meter of diorganopolysiloxane composition to form silicone layer 131. Immediately after applying the diorganopolysiloxane layer 131 and while the layer is still tacky, a sheet of soft chemically ; etchable me~allic foil 133 ls pressed into intima~e contact with ~. , ` ,' .
~L6~V
1 the liquid layer. Representative chemically ethable metallic foils include ~inc, copper and alu~lnum. The sandwich so formed is allowed to age for from 12 to 96 hours to permit the silicone rubber to cure or become solid, and to form an adhesive bond with the metallic foil 133. Thereafter, the exposed surface of the foil 133 is cleaned by brief immersion in a standard etching solution, washed and dried. Next the clean and dry surface is given a photopolymerizable photo-resist layer 134 and exposed through a negative transparency 136. The exposure hardens and insolubilizPs the photopolymerizable material in the exposed areas 138 to form a latent image. Thereafter, the surface s swabbed with a photo-resist developer which removes all the unexposed photopolyermizabl material in area 140 and leaves the underlying foil 133 bare, but does not remove the photopolymerized layer in the image area 138.
Then the surface is again immersed in the same etching solution in which the foil 133 had previously been cleaned and allowed to remain there until all of the foil 133, except that covered by the photopolymer image, has been disso~ved down to the underlying silicone rubber background 131. The plate is then thoroughly washed and dried. This plate, after the background had been etched away, has an image area of metal, still covered by ~he photopolymer resist, raised slightly above the silicone background, and so is not, strictly speaking, a planographic plate. However, the plate can be used in the same way, and on the same printing press, as the other plates having si~icone rubber background areas as described above. In such use the rotating inking rollers and offset blanket will come in contact with the sillcone rubber background. The sillcDne rubber background remalns free of ink as in the previously discussed cases and doesnot print on the offset blanket or paper.
D
7 [) ~ nother embodimen-t o~ the present invention as illustrated by Figures 13, 14 is prepared as follows- a silicated aluminum plate 50 is sensitized with a conventional diazo compou~d, exposed and developed by swabbi~g with an aqueous emulsion of lacquer which removes unreacted diazo and leaves a layer of lacquer 51 on the exposed image area 52. ~fter washing, the entire surface of the plate is again swabbed with aqueous solution of a photo-responsive diazo compound such as the formaldehyde condensate of a paradiazo-diphenyl amine salt or the like to form the layer 53. The plate is then allowed to dry, and thereafter coated with a layer of sili-cone rubber 54. The silicone layer is cured and the en-tire plate exposed to radiation of sufficient wave length to initiate the photo-responsive reaction o~ the diazo compound. By this -treatment the diazo compound is insolubilized and its adherence to the silicone rubber layer is improved, and likewise the silicone rubber layer itself is further cured. ~ext, the plate is swabbed vigorously with a mixture of e~ual parts of l,l,l-trichloroethane and xylene and 1/4 part of ethylene glycol which penetra~es through the silicone layer 54 and loosens the lacquer layer 51 covering the image area 52. The lacquer and overlying silicone rubber come away from the image leaving the imaged area 52 slightly recessed. The plate thus prepared can be used in this condition or the recessed areas can be filled with oleophilic material such as viscous polyvinyl acetate emulsion. In the la-tter case the resulting plate has a level surface, with imaged areas of oleophilic polyvinyl acetate and ink-repellent background areas of a silicone rubber.
By way of amplifying the description of Figures 13 and 14, the silicated aluminum plate 50 is sensitized, exposed and ~ - 1~
6'6'~
developed. During development of this plate by use o~ the aqueou~
-- lacquer emulsion, the unexposed and soluble diazo in the non-image areas is removed leaving the insoluble exposad diazo image layer 5~ coated with the layer of lacquer 51. The exposed and developed plate comprised of the substrate 50, the insoluble diazo image 52 and the lacquer layer 51 is then coated with an aqueous solution of photosensitive diazo material to produce the anchoring diazo layer 53. The plate is then allowed to dry and a layer of silicone rubber 54 is applied over the unexposed anchoring diazo layer 53. After the silicone layer is allowed to cure the entire plate depicted by Figure 13 is exposed to actinic radiation which insolubilizes the entire anchoring diazo layer 53.
The exposed plate is then swabbed with a mixture of trichloroethane, xylene and ethylene glycol. This mixture penetrates the silicone layer 54 and the anchoring diazo layer 53 and dissolves the lacquer layer 51 causing the lacquer and anchoring diazo and silicone layers immediately above the image to come free leaving ; a plate shown in Figure 14 consisting of a substrate 50, an insoluble diazo image area 52 and e~posed anchor diazo layer 55 covered by the silicone rubber layer 54. The relative thic~nesses of the various layers are not accurately depicted by the drawings.
The second exposure of the entire plate causes the anchor diazo layer to become insolubilized and to bond the silicone to the non-image areas of the plate. The lacquer layer prevents the anchoring diazo layer from bonding securely to the diazo image area and -thereby allows the silicone and anchoring diazo layer to be removed by the trichloroethane containing mixture.
Other plates can be made by coating a metal or paper plate with layer of silicone rubber, curing the silicone rubber at room temperature for several hours, and then using an engraver's 14a -1 tool to cut a pattern ~hrough the silicone to the un(lerl~ln~ ~ase, The pattern is then ink-receptive, but the silicone layer is not.
Tl1is plate thus prepared can then be employed on a press or the pattern can be ~illed with an oleophilic substance before the plate is so employed.
EXAMPLE l A paper plate is prepared from paper stock which is - composed of about equal amounts of long fibers and short fibers and contains from ~ to 8 percent mineral filler. The paper stock is ` 10 sized with rosin and alum and weighs-about 52 pounds per ream ~500 sheets - 25" x.38"). One side of the paper is base-coated with lO pounds per ream dry weight of a coating comprised of clay (lOO parts), casein (20 parts) and dimethylol urea (2 par~s) and is then dried and calendered. The paper plate is then revers-roll coated with 2 pounds dry weight per ream of a xylene disper-sion of a diorganopolysiloxane composition comprised of a dimethylpolysiloxane, methylhydrogensiloxane and ~inc octoate, and the resulting layer of diorganopolysilo~ane is dried and cured for 40 seconds at 500F. The silicone rubber coated plate is then fed through a Xerox~ 91~ copy machine, (an ofice si~e seleniu~
drum copies). As a result of this procedure, a powder image previously elec~rostatically formed on a selenium-plated drum i8 transferred to the plate. ~l'hiE~ image is then heated to cause powder particles to fuse to each other and to the surface of the plate, The plate thus prepared is then mounted on a rotary offset duplicator (Addressograph-Multigraph Corporation, Multilith*
No. 1250, an office size offset duplicating machine,) from which the molleton rollers (water fountain rollers3 have been removed.
The plate is merely clamped to the plate cylinder and while dry is inked with regular lithographic ink (Addressograph-Multigraph ink No. Ml* 3~, a linseed oil based medium tack test ink) by the inking roller and the ima~e is printed on the off~let blanket ~rom which it was transferred to a paper sheet. Fifty copies having ~r~ -15 -~ *Indicates a Trade Mark 1 clean un-inked background areas are produced from this plate.
A paper substrate as prepared in ~xample 1 is air ~ni~e coated with 3 pounds per ream dry welght of a diorganopolysiloxane composition composed of dimethylpolysiloxane ha~ing silicon-bonded hydroxy groups, methylhydrogen polysiloxanes and dibutyl tin laurate, The diorganopolysiloxane composition is dispersed in toluene ln an amount sufficient to provide a dispersion having about 10 percent by weight of solids. The coating layer is cured at 300~F for about 5 minutes. This plate is then sensitized by rubbing the silicone rub-ber surface with a cotton pledget filled with powdered double chloride of zinc and the para-formaldehyde condensate of diazotized para-aminodiphenyl amine. Excess diazo powder is then carefully wiped off. The sensitized plate thus prepared is then exposed through a negative transparency to a 35 amp. double carbon arc at a distance of 36 inches for one minutes. The partially exposed plate is then washed or developed with water to remove the diazo compound from the unexposed areas. The plate thus prepared was completely dried and clamped to the plate cylinder of a rotary offRet dupli-cator as described in Example 1 and the plate inked and employed toproduce over 50 copies. The copies thus produced were clean with no toning or inking in the bac~ground areas.
E~AMPLE 3 An aluminum based diazo sensi~itzed plate is prepared by coating an aluminum plate with an aqueous solution of sodium sili-cate and thereafter coating the silicated surface with an aqueous 1 percent solution of the double salt of ~inc and condensa~e of para-formaldehyde and para-dia~o-diphenyl amine as described in United States Patent No. 2,714,066. After the diazo coating has dried, a layer of the diorganopolysiloxane composition is applied by Mayer bar coater. The diorganopolysiloxane composition com~ises dimethyl-v 1 polysiloxane gums, silane oxime and titanium dioxide. '~'he ~rface bearing the dior~anopolysiloxane coating i~ wiped down ~/ith ~ 80ft cloth to leave a film which has a thickness o 0.05 mils after curing for about 12 hours at room temperature. The plate thus prepared is exposed through a positive transparency for 60 seconds - to a 35 ampere double arc at~a distance of 36 inches. Following the exposure, the surface of the exposed plate is swabbed with a water solution containing a small amount of ~astman Kodak's FOTOFLO*,~
a wetting agent, currently used in the lithographic trade of unknoT~n ~0 compositions. This water removes the silicone layer and soluble diazo compound rom the unimaged areas, laying bare the surface of the original substrate in these areas. Thereafter, the plate is dried~ mounted on a rotary press as described in Example 1, inked and employed to produce lOOO clean copies.
A S mil sheet of aluminum foil having a surface roughened by sand blasting is coated with a 0.2 mil layer of a diorganopoly-siloxane comprised of hydroxyl end-blocked dimethylpolysiloxane and vinyltriacetoxy silane, said composition on curing forming an acetoxy end-blocked vinyl substituted dimethylpolysiloxane silicone rubber~ Immediately thereafter while the diorganopolysiloxane layer is still llquid, a 3 mil sheet of soft copper foil is pressed i~to intimate contact with the aforesaid layer. The sandwich so formed is allowed to age for 72 hours. Following the aging period, the exposed surface of the copper is cleaned by immersing for two minutes in a standard etching solution consistlng of the following:
lOO milliliters of calcium chloride solution of 40-41 F Baume, 380 grams of ~inc chloride, 285 milliliters of ferric chloride solution of 50-41 F Baume, and ~Indicates a Trade Mark 1 14 milliliters o~ 38 percent hydrochloric acid.
Following the etching procedure; the copper surface is immediately washed and dried, The dry copper surface is then given a photo-resist layer of a photopolymerizable material containing a poly-vinyl cinnamate polymers. The photo-resist layer is dried and the surface exposed through a negative transparency to the light from a 35 ampere double arc at a distance of 36 inches for three minutes. Following the exposure period, the surface of the pla~e is swabbed with developer which removes all of the unexposed 1p photopolymerizable material and leaves the underlying copper bare but does not remove the photopolymerized layer in the image area.
The surface of the plate is then immersed in the same etching solution in which the copper was previously cleaned and allowed to remain there until all the copper except that covered by the photopolymer image has been dissolved. The plate is then washed and driedO The plate thus prepared is then mounted on a rotary press as described in Example 1, coated with ink and used to print 10,000 copies.
A sand blasted aluminum plate is treated with sodium silicate, washed and dried, and thereafter sensitized by swabbing with an aqueous 2 percent solution of a zinc salt of the con-densate of para-formaldehyde and para-diazodiphenyl amineO
-~ ~ Following the coating procedure the plate is dried and the dried plate ~exposed through a negative transparency for 60 seconds to a 35 ampere double arc at a distance o 36 inches. The image so formed is developed by swabbing the surface of the pla~e with `~ an emulsified colored nitrocellulose lacquer in an aqueous solution- of gum arabic. This procedure removes the diazo compound from the unexposed or background area but does not remove the exposed .
- 18~--13 ' ' ' ~6~
l image. In addition, the emulsion breaks su~icientl~J ~o permit - the lacquer to adhere to and coat the surface of the image. ~he plate is then uashed with water to remove all traces of the gum arabic from the surface of the plate without removing the lacquer from the image area. ~ollowing the removal of the gum arabic, the pla~e is again swabbed all over with an aqueous solu~ion of theformaldehyde condensate of a para-diazodiphenyl amine salt and then allowed to dry. The dried plate is ~hen roller coated wi~h a diorganopolysiloxane composition comprises of an acetoxy end-blocked dimethylpolysiloxane and dibutyl tin diacetate in an amount sufficient ot provide about 35 grams per square meter of the diorganopolysiloxane composition. This layer is allowed to aircure for 30 minutes and then it is exposed over its entire surface to radiation from a 35 ampere double arc lamp at a distance of 24 inches for 3 minutes. By this treatment the diazo compound is insolubilized and its adherence to the silicone layer improved, and likewise the silicone layer itself is further cured~ Next, the plate is rubbed with a mixture` of equal parts of 1,1,1-trichloroethane and xylene and 1/4 part of ethylene glycolO Thia liquid penetrates through the silicone layer and loos~ens the lacquer layer covering the image and the rubbing removes the loosened silicone rubber leaving the image area slightly recessed.
Thé depressions thus formed are filled with polyvinyl acetate emulsion and allowed to dry. The resulting plate has a level surface, with image areas of oleophilic polyvinyl acetate and ink repellent background areas of silicone rubberO The plate thus prepared is mounted on a lithographic press as described in Example l and used to print 1500 copies.
The various diorganopolysiloxane compositions employed in the present invention are known in ~ha art and are prepared in D
.
f~
1 accordance with known methods. Represèn~a~ive acetoxy end-blocked diorganopolysiloxanes to be employed in the present inventlon, such as the dimethylpolysiloxanes, vinyl substitu~ed dimethyl-polysiloxanes, alkyl substituted dimethylpolysiloxanes, cyanoalkyl Subs~ituted dimethlypolysiloxanes and 3,3,3-trifluoropropyl and other haloalkyl substituted dimethylpolysiloxanes, are prepared in accordance with methods known to the skilled in the art as illustrated by ~he teachings of United States Patent Nos.
3,035,016 and 3,077,465. Representative diorganopolysiloxane compositions comprised of dimethylpolysiloxanes having terminal silicon-bonded hydroxy groups, methyl hydrogen polysiloxane and dibutyl tin 'dilaurate or dibutyl tin diacetate are also well known in the art and are produced in accordance with known methods. A
representative method of production is taught in United States Patent No. 2,985,545. Similarly, the diorganopolysiloxane com-positions comprised of diorganopolysiloxanes having terminal sllicon-bonded hydroxy groups, an alkyl silicate and a metallic salt of an organic carboxylic acid are known in the art and are produced by known methods such as the procedures taught by United States Patent No. 2,843,555.
The photo-responsive diazo compounds to be employed in the present invention are well known in the art. Representative diazo compounds are described in United States Patent Nos.
2,714,066 and 2,778,735, and include 4-(N-benzyl-N-ethyl)-amino-aniline, 4-(N-2,6-dichloro-benzyl)-amino-aniline, 4-(N-cyciohexyl~-amino-aniline, 4-amino-2,5,4'-tribromo diphenylamine, 4-amino-2', 4',6'-trichloro-diphenylamine, 4-amino-2-[N-~2 9 5-diethoxy-phenyl)-sulfamido]-diphenylamine, 4-amino-3,6-dimethoxy-diphenylamine-2'-carboxylic acid, l-amin~-2,5-di-n-propoxy-4'-me~hyl-diphenylsulfide, N-(2,6-dichlorobenzyl)-3-amino-carbazol, 4-N-2,3,4,6-tetrachloro-benzyl)-amino-aniline, 4-(N-2,6-dichloro-benzyl-N-ethyl)-amino-2,5-- 20 ~
~ , ' ` , 1 diethoxy-anilin~ and 4-amino-2,5,4'-triethoxy-diphenylether and their aldehyde condensates and the sulfonates of both.
The term conventional lithographic ink as employed in the present invention refers to the inks commonly employed by tpose skilled in the art and may be generally de~ined as being hlghly pigmented varnishes of hèa~bodied linseèd oil or ~he equivalen~ and giving inkometer values from about 12-20 when measured at 90F and 40b r.p.m. Thie inkometer values are standard test values and the test is fully set for~h in United States Patent No. 2,101,322.
~ ..
~ , ' ` , 1 diethoxy-anilin~ and 4-amino-2,5,4'-triethoxy-diphenylether and their aldehyde condensates and the sulfonates of both.
The term conventional lithographic ink as employed in the present invention refers to the inks commonly employed by tpose skilled in the art and may be generally de~ined as being hlghly pigmented varnishes of hèa~bodied linseèd oil or ~he equivalen~ and giving inkometer values from about 12-20 when measured at 90F and 40b r.p.m. Thie inkometer values are standard test values and the test is fully set for~h in United States Patent No. 2,101,322.
~ ..
Claims (26)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A dry planographic printing plate comprising a base layer, and at least two additional layers disposed in superimposed relation to each other and both overlying said base layer, one of said additional layers being a layer of silicone rubber material and another of said additional layers being capable of being removed in selected areas so as to define the boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background for said image.
2. The printing plate of claim 1 wherein said second layer overlies said layer of silicone rubber material.
3. The printing plate of claim 1 wherein said second layer is between said layer of silicone rubber material and said base layer.
4. A dry planographic printing plate comprising a base layer and at least two additional layers disposed in superimposed relation to each other and both overlying said base layer, one of said additional layers being a layer of silicone rubber material, and another of said additional layers being light sensitive and capable of being removed in selected areas so as to define the boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background for said image.
5. The printing plate of claim 4 wherein said light sensitive layer overlies said layer of silicone rubber material.
6. The printing plate of claim 4 wherein said light sensitive layer is between said layer of silicone rubber material and said base layer.
7. A dry planographic printing plate comprising a base layer, a layer of silicone rubber material overlying said base layer, and a continuous chemically etchable metallic layer mounted on the outside surface of the silicone rubber layer and capable of being etched away in selected areas so as to define the boundaries of an image to be printed from said plate, said silicone rubber material being adapted in the absence of dampening to provide an ink repellent background for said image.
8. A dry planographic master to be sensitized, imaged and developed in accordance with known methods wherein said master is comprised of a flexible substrate capable of being rolled and mounted on an offset lithographic press, a layer of silicone rubber bonded to at least one surface of the flexible substrate and a chemically etchable metallic foil mounted on the exposed surface of the silicone rubber layer in the area to be imaged.
9. The printing plate of claim 7 further comprising a layer of photo-sensitive material overlying said metallic layer.
10. The printing plate of claim 7 or claim 9 wherein said metallic layer is adhered to said outside surface of said silicone rubber layer.
11. The dry planographic master of claim 8 further comprising a layer of photo-sensitive material overlying said metallic foil.
12. The dry planographic master of claim 8 or claim 11 wherein said metallic foil is adhered to said outside surface of said silicone rubber layer.
13. An imaged dry planographic printing plate, which accepts ink in the image area and prints therefrom, and repels ink in the non-image area, comprising a base layer, an ink receptive image area, and a silicone rubber material overlying said base layer and providing the ink repellent non-image area.
14. The printing plate according to claim 13 wherein said layer is formed of metal.
15. A process for printing planographically in the absence of dampening with an imaged dry planographic printing plate which accepts ink in the image area and prints therefrom and which repels ink in the non-image area, which process comprises rolling the surface of the imaged dry planographic printing plate with ink in the absence of dampening, whereby the ink is contacted with the image and the non-image areas of the plate, the ink being repelled in the non-image area by a silicone rubber material and the ink being accepted in the image area, and thereafter transferring ink accepted in the image area to an ink-receptive surface.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE:
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE:
16. The printing plate of claim 1 wherein the silicone rubber results from the curing of a diorganopolysiloxane selected from the group consisting of: (a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups; (b) linear diorganopolysiloxanes having terminal reactive end blocking groups and a metal salt of a carboxylic acid; and (c) linear fluid diorganopolysiloxanes having terminal silicon-bonded hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate and methyl hydrogen polysiloxanes.
17. A planographic plate comprising, on a flexible substrate, a continuous silicone rubber containing layer, and overlying said silicone rubber containing layer a layer of a photo-responsive diazo compound which, upon exposure to light, is oleophilic and ink receptive when dry.
18. The planographic plate of claim 17 wherein said silicone rubber containing layer consists of silicone rubber.
19. The planographic plate of claim 17 or claim 18 wherein the photo-responsive diazo compound is a salt of the para-formaldehyde condensate of diazotized para-aminodiphenyl amine.
20. A process of dry planographic printing which comprises providing a flexible planographic plate comprised of a flexible substrate and a silicone rubber containing layer having a surface energy which is so low that the silicone rubber surface will not remove conventional lithographic printing ink from an inking roller passed thereover, subjecting said plate to an imaging treatment whereby at selected areas thereof an ink receptive image is formed, attaching the imaged plate to the plate cylinder of a printing press, and without wetting the unimaged areas of the plate, repeatedly (1) rolling the surface of the imaged plate with an ink roller to ink the imaged areas and (2) printing from the ink image on to a receiving surface.
21. The process of claim 20 wherein said silicone rubber containing layer consists of silicone rubber.
22. The process of claim 20 or claim 21 wherein the silicone rubber containing layer results from the curing of a diorganopolysiloxane composition selected from the group consisting of:
(a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal reactive end blocking groups and a metal salt of a carboxylic acid; and (c) linear fluid diorganopolysiloxanes having terminal silicon-bonded-hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate and methyl hydrogen polysiloxanes.
(a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal reactive end blocking groups and a metal salt of a carboxylic acid; and (c) linear fluid diorganopolysiloxanes having terminal silicon-bonded-hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate and methyl hydrogen polysiloxanes.
23. The process of-claim 20 or claim 21 wherein the ink receptive image is formed by the action between a light responsive diazo compound and the silicone rubber containing layer.
24. The process of producing a dry planographic plate which comprises coating at least one surface of a flexible substrate having sufficient strength to withstand the stresses normally produced by the lithographic process with a silicone rubber containing material which upon curing gives a surface having low enough surface energy that the silicone rubber containing material will not remove conventional lithographic ink from rotating inking rollers, and thereafter curing said silicone rubber containing material.
25. The process of claim 24 wherein said silicone rubber containing material consists of silicone rubber.
26. The process of claim 24 or claim 25 wherein the flexible substrate is coated with a diorganopolysiloxane composition selected from the group consisting of:
(a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal reactive end blocking groups and a metal salt of a carboxylic acid; and (c) linear fluid diorganopolysiloxanes having terminal silicon-bonded hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate and methyl hydrogen polysiloxanes.
(a) linear diorganopolysiloxanes having terminal silicon-bonded acyloxy groups;
(b) linear diorganopolysiloxanes having terminal reactive end blocking groups and a metal salt of a carboxylic acid; and (c) linear fluid diorganopolysiloxanes having terminal silicon-bonded hydroxy groups, a metal salt of an organic carboxylic acid and a member of the group consisting of an alkyl silicate and methyl hydrogen polysiloxanes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000953939A CA1166070A (en) | 1966-03-05 | 1966-03-05 | Method for preparing dry lithographic plates |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000953939A CA1166070A (en) | 1966-03-05 | 1966-03-05 | Method for preparing dry lithographic plates |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1166070A true CA1166070A (en) | 1984-04-24 |
Family
ID=4142468
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000953939A Expired CA1166070A (en) | 1966-03-05 | 1966-03-05 | Method for preparing dry lithographic plates |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1166070A (en) |
-
1966
- 1966-03-05 CA CA000953939A patent/CA1166070A/en not_active Expired
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