Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/03—Chemical or electrical pretreatment
  • B41N3/038—Treatment with a chromium compound, a silicon compound, a phophorus compound or a compound of a metal of group IVB; Hydrophilic coatings obtained by hydrolysis of organometallic compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/136—Coating process making radiation sensitive element

Definitions

• This invention relates to coated paper base planographic printing plates and to methods of producing such plates.
• Planographic printing is printing from plane surfaces, that is level surfaces without either raised or intaglio areas. Such printing depends upon the immiscibility of grease and water, or more specifically, of greasy lithographic printing-ink and aqueous lithographic solutions.
• aqueous wetout liquid such as a solution of glycerine slightly acidified with phosphoric acid, acid phosphates or similar substances.
• the aqueous wet-out liquid Wets all portions of the plate surface not al ready covered by the water-repellent imaging material, but does not, of course, wet the waterrepellent image.
• aqueous lithographic solution when dry the plate shall readily accept a water-repellent image which must adhere tenaciously thereto and shall neither be pulled away by printing-ink nor be washed away by aqueous lithographic solutions. Another requisite is that all unimaged areas of the plate shall be readily wetted by aqueous lithographic solution and shall hold a film thereof on the surface of said unimaged areas and shall not permit the aqueous film to be displaced therefrom by printing ink.
• the original material used for lithographic plates was a slab of limestone, but grained metal plates have been the commonly used material.
• coated paper planographic printing plates have come into extensive use, especially for small size plates in comparatively short runs as on oflice offset duplicators. It is with coated paper planographic printing plates that the present invention is concerned.
• such a coated paper planographic printing plate may be said to comprise a paper base, which preferably but not necessarily possesses wet-strength properties, the paper base bearing on at least one surface a layer of coating comprising a waterinsoluble hydrophilic film-forming adhesive material such as casein, carboxymethyl-cellulose, or polyvinyl alcohol, said hydrophilic film-forming material containing dispersed therein some finely divided mineral filler or pigment material such as clay, blanc fixe or titanium dioxide.
• a waterinsoluble hydrophilic film-forming adhesive material such as casein, carboxymethyl-cellulose, or polyvinyl alcohol
• said hydrophilic film-forming material containing dispersed therein some finely divided mineral filler or pigment material such as clay, blanc fixe or titanium dioxide.
• soluble salts of metals having a valence greater than 2 i. e., salts of multivalent metals such as trivalent and tetravalent metals.
• Metals having a valence greater than 2 are designated as multivalent metals (see hackhs Chemical Dictionary published by Blakiston in 1929).
• Many soluble salts of multivalent metals do exert a transient beneficial effect when incorporated in the surface of a coated paper planographic printing plate.
• the beneficial effects of such salts normally last only from a few hours or days to a very few weeks, and thereafter the good effects cease and deleterious effects set in.
• the so-treated surface begins to develop a tendency to repel or shed water.
• the unimaged surface is no longer sufiiciently wetted by aqueous lithographic solution and in consequence it picks up ink over the whole area and becomes useless as a printing plate.
• coated paper treated with such soluble salts of multivalent metals become water-repellent.
• the originally soluble salt is, in part at least, converted, perhaps by hydrolysis to a Water-insoluble and water-repellent compound or form.
• zirconium acetate is used to Water-proof textiles it has been stated that the Water-repellent effect results from hydrolytic formation of water-insoluble basic zirconyl acetate.
• coated paper treated with such multivalent metal salts gradually, and in a comparatively short time, does develop water-repellent qualities which make it imsuitable for use as a planographic printing plate.
• a paper base preferably one having Wet-strength or water-proof qualities, is provided with a coating comprising finely divided mineral filler or pigment and adhesive matter having hydrophilic properties.
• the coating so formed has interstices orpores in its surface, which interstices are filled at least partially with a water-soluble salt of a multivalent metal and an organic acid, e. g., formic acid or acetic acid, in association with a substantial quantity of an alkali metal or ammonium salt of an organic acid, e. g., formic acid or acetic acid which is capable of forming a water-soluble salt with the particular multivalent metal present in the multivalent metal salt used.
• an organic acid e. g., formic acid or acetic acid
• the action of the organic salt of the alkali metal or ammonium is not fully understood but the effect of its presence is to prevent or very greatly retard the development of the water-repellent or water-shedding effects which otherwise would result from the multivalent metal salt present.
• the alkali metal or ammonium salt may be applied simultaneously with the multivalent metal salt or the two salts may be applied in separate steps. For example, a solution containing both the multivalent metal salt and the alkali metal salt may be applied to the coated paper or a solution of either salt may be applied and dried followed by application of a solution of the other.
• the alkali metal or ammonium salt may, if desired, be included in the pigment-adhesive coating composition at the time of its application, while the multivalent metal salt may be applied subsequently as an aqueous wash.
• the aqueous adhesive-pigment coating composition is one which is not coagulated by the multivalent metal salt
• the said multivalent metal salt may be included in the coating composition together With the alkali metal or ammonium salt or the latter may be applied subsequently.
• the insoluble or slightly soluble multivalent metal compound so formed acts to plug the said pores and interstices and to a considerable extent prevents or decreases further penetration of the surface by lithographic solutions. Consequently, when lithographic fountain-solution is applied to the planographic printing plate having such a plugged surface, the solution remains substantially entirely upon the coated surface of the plate where it is effective in accomplishing its mtended purpose of preventing contact between the said surface and the printing-ink on the inkingrollers of the lithographic printing press upon which the plate may be used.
• the multivalent metal salt to accomplish the desired results it must exist in the pores in soluble condition up to the time the plate is prepared for use on the printing press. That means that the salt must be used in quantity in excess of the amount which will be consumed by possible reaction with the adhesive or other components of the coating with which it is used and that it must not be transformed by hydrolysis into an insoluble compound of the metal.
• the treatments of the present invention may be applied to any of the types of coated papers which are suitable for treatment by bivalent metal salt solutions according to the aforementioned Patent No. 2,534,650.
• the treatment is particularly eflicacious in preparation of coated paper planographic printing plates for printing comparatively long runs of upwards of ten thousand copies to as much as thirty thousand copies.
• the following Example 1 is an embodiment of the invention suitable for printing such long runs.
• a wet-strength paper web of approximately 95 pounds weight, based on a ream of 500 sheets cut to a size of 25 x 38 inches, may be prepared from a paper-making furnish containing beaten fibers from deciduous trees and from coniferous trees .in approximately equal quantities, rosin-size, melamine-formaldehyde resin, and alum.
• the fiber from deciduous trees may be replaced in whole or in part by fiber from coniferous trees, and clay or other suitable filler, although not particularly desirable, may be included in the furnish.
• the formed web is then preferably but not necessarily surface-sized with an aqueous solution of ammoniacal casein made slightly acidic with formaldehyde. Between one and two pounds (dry weight) of the casein size, per ream, should be taken up. The web may then be dried and machine-calendered.
• a paper base sheet web prepared in the manner set forth in the foregoing Step 1 may be coated on one side, which will be the reverse or non-printing side of the finished paper plate, with about pounds, dry weight, per ream of a composition containing 100 parts of clay, 18 parts of casein, and 1% parts of dimethylol urea, and the sheet is again dried.
• the function of this coat is merely to promote flatness of the finished product by counteracting the tendency to curl caused by subsequent application of coating to the other, or printing side, of the sheet.
• Step 3.--To the previously uncoated side of the paper web may be applied about 10 pounds dry weight, per ream, of a barrier coat deposited from an aqueous composition containing dry weights according to the following Formula 1.
• Formula 1 Parts by weight Pigment (finely divided clay) i 50 Copolymer of 60 styrene-40 butadiene (in primary emulsion) 60 Polystyrene, high molecular weight (in primary emulsion) 40 The coating is then well dried.
• the term primary emulsion as used in preceding Formula 1 is used to designate an aqueous emulsion in which the polymeric substance therein has been polymerized in situ.
• the purpose of the barrier coat of Formula 1 is to prevent saturation of the paper fibers by fountain-solution during long runs; any barrier coat may be used which will accomplish this purpose and which is suiliciently non-tacky so that the coated paper may be rolled up Without sticking together and which is satisfactorily wettable by the aqueous coating composition of hydrophilic material to be subsequently applied thereto.
• film-formers which have been found useful for barrier coats include urea-formaldehyde resin, butadiene-acrylonitrile copolymer, polymerized methyl acrylate, plasticized polyvinyl chloride, plasticized polye '6 vinyl butyral, and the like.
• the inclusion of mineral filler or pigment in the barrier coat is optional; the filler acts to decrease tackiness and also probably serves as an anchor for the coating subsequently applied thereto.
• Step 4.-A coated paper web as prepared in the manner set forth in the foregoing Step 3 may be coated on top of the barrier coat of Step 3, with from 8 to 14 pounds, with an optimum of 12 pounds per ream, dry weight, of a mixture having the composition set forth in the following Formula 2 so as to provide a pigmented hydrophilic coating containing interstices which provide capillary spaces or pores:
• Pigment finely divided clay
• Hydrophilic adhesive casein in water solution of ammonia
• Dimethylol urea to insolubilize the casein
• the paper base sheet or web bearing the pigmented hydrophilic adhesive coat of the fore: going Formula 2 thereon may then be suitably dried as, for example, at a temperature of from F. to F. for a period of from 10 to 20 minutes, and calendered, although calendering is not essential.
• Step 5 The thus coated and calendered paper base sheet may then be washed, on the side having the pigmented hydrophilic adhesive coat of Step 4, with an aqueous solution containing an acetate or formate of a multivalent metal and a stabilizer comprising an alkali metal or ammonium formate or acetate similar to that of the following formula:
• Step 6.-'I'he dried coated and treated sheet may then be rubbed against rotating brushes. While not essential to or indispensable in the practice of the present invention, this operation of rubbing or brushing the face of the printing surface of the new paper base planographic printing plates increases the image-reproducing life of the plates and improves the quality of the images reproduced from the treated plates. Moreover, this operation of rubbing or brushing the face of the plate tends to remove any excess of the multivalent metal salt, or of the alkali metal or ammonium salt, which may crystallize on the surface of the plate.
• butanol employed in Formula 3 of Step 5 preceding while not essential in the practice of the invention, facilitates and promotes penetration of the water-soluble salt solution into the capillary spaces formed by the pores or interstices among the finely divided mineral particles in the coating.
• equivalent volatile water-miscible solvents including methanol, ethanol, propanol and thelike maybe used.
• the formaldehyde included in Formula '3 of Step-' preceding isnot essential in practice of the-invention, and is used to hasten theattainment of water-insolubility of the casein in the pigmented hydrophilic coating which otherwise might take somewhat longer to develop.
• Theclay-casein ratio in the clay-casein hydrophilic coating of foregoing Formula 2 may be varied widely from about 12 to '75 parts of casein per 100 parts of clay, and the weight of the clay-casein coating may be varied from 6 to 30 pounds per ream of paper.
• hydrophilic adhesive coatings which may be employed include those containing the following hydrophilic adhesive base-materials: glue, gelatine, soy bean protein, zein, insolubilized starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, gum arabicor any other equivalent hydrophilic adhesive base material which may be pigmented and rendered waterinsoluble while still remaining hydrophilic.
• the clay or pigment component of the pigmented hydrophilic adhesive or claycasein referred to in foregoing Formula 1 may be replaced in whole or in part by-other suitable finely divided mineral pigments including barium sulfate, calcined clay, talc, titanium dioxide and other equivalent finely divided mineral pigments.
• these multivalent metal salts may be used in solutions ranging from about 4 percent concentration to about percent concentration or to the limit of the solubility range in cases where it is lower than about 25 percent.
• the acetate or formate of ammonium or of any alkali metal there may be used in aqueous solution the acetate or formate of ammonium or of any alkali metal.
• Useful concentrations of such ammonium or alkali metal salts range from about 1 percent to a: concentration equal to the concentration of the multivalent metal salt present.
• the following table shows various examples of combinations of multivalent metal salt and ammonium or alkali metal. salt which have satisfactorily replaced the 15 percent of zirconium acetate and 5 percent of sodium acetate in Formula 3 of Step 5.
• the amount of salt solution applied is preferably maintained within a range of from one-half gallon to five gallons per ream.
• the optimum quantity in any particular case will naturally depend in part upon the specific salts used as well as upon the degree of absorbency of the coated surface to which the solution is applied; In most cases, use of from one to two gallons per ream produces very satisfactory results.
• EXAMPLE 2 A medium run plate capable of printing up to 1000 copies was made by following the, procedure of Example 1 with the following exceptions:
• Step 1 awet-strength paper web of approximately 75, pounds weight per ream was used instead of the heavier base used for the long run plate, and the barrier coat of Step 3 was entirely omitted.
• EXAMPLE 3 A short-run plate capable of printing up to 300 copies was made in a manner similar to that of Example 2, except that a 60 pound paper base was used, and the wet strength treatment of Step 1 was entirely omitted.
• the coated paper base planographic printing plate of the invention may have the printing image affixed thereto, by any direct process, such as by a printing press or typewriter, bygreasy pencil or crayon, by-a pen using oily writing fluid such as is commonly used in the so-called ball-point pens, or the like.
• the plate may be photo-sensitized by application thereto of bichromated albumin or similar sensitizer, and a photo-image may be afiixed thereon, by exposure of the sensitized surface to actinic radiation through a negative or other mask having both transparent and opaque areas.
• Such photo-sensitization of the plate is described in the following Example 4.
• EXAMPLE 4 A coated paper planographic printing plate identical with one made accordin to Example 1, preceding, was sponged over with the composition of the following Formula 4.
• Formula 4 Parts by volume Albumin in aqueous solution of 8 Baum 30 Ammonium bichromate in 20% aqueous solution Water 100
• the sheet so sensitized was dried in the absence of light and was then exposed through a halftone negative to radiation from a carbon-arc for about 3 minutes.
• the exposed surface then was swabbed with a sponge, wet with Water, followed by an application of a commercial lithographic wet-out solution; then the plate was used on a rotary offset duplicator to produce several hundred satisfactory copies.
• the invention provides new and improved coated paper base planographic printing plates having the advantages and desirable characteristics mentioned, and others which are inherent in coated paper base planographic printing plates prepared in accordance with the invention.
• the invention provides new and improved compositions and processes for preparing the new coated paper base planographic printing plates.
• a planographic printing plate comprising a paper base having thereon a planographic printing surface layer, said layer comprising insoluble hydrophilic adhesive material and finely divided inert mineral pigment and having therein capillary interstices and pores containing the evaporation residue of an aqueous solution containing a water-soluble multivalent metal salt of an acid of the group consisting of formic acid and acetic acid in quantity in substantial excess of that required for reaction with other ingredients of said layer and the evaporation residue of an aqueous solution containing a water-soluble uniunivalent salt of the group consisting of the alkali metal and ammonium salts of the acids of the group consisting of formic acid and acetic acid in quantity amounting to at least one-fifth of the weight of the multivalent metal salt.
• Process for the production of a planographic printing plate which comprises coating a paper base sheet with an aqueous coating composition comprising hydrophilic adhesive material and a finely divided mineral pigment resulting, when dried, in a surface having therein capillary interstices and pores, and incorporating into said surface the evaporation residue of an aqueous solution containing a water-soluble multivalent metal salt of an acid of the group consistin of formic acid and acetic acid in quantity in substantial excess of that required for reaction with the coating and the evaporation residue of an aqueous solution of a uni-univalent salt of the group consisting of the alkali metal and ammonium salts of an acid of the group consisting of formic acid and acetic acid in quantity amounting to at least onefifth of the weight of the multivalent metal salt.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
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Citations (8)

• 0
  • BE BE503804D patent/BE503804A/xx unknown
  • NL NL76463D patent/NL76463C/xx active
• 1950
  • 1950-07-19 US US174795A patent/US2635537A/en not_active Expired - Lifetime
• 1951
  • 1951-05-04 GB GB10499/51A patent/GB692387A/en not_active Expired
  • 1951-06-05 FR FR1041845D patent/FR1041845A/fr not_active Expired
  • 1951-07-06 DE DEW6193A patent/DE908377C/de not_active Expired

Patent Citations (8)

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