CA2147388A1 - Method for manufacturing superior ink-water balance and alkaline resistant ps plates - Google Patents
Method for manufacturing superior ink-water balance and alkaline resistant ps platesInfo
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- CA2147388A1 CA2147388A1 CA 2147388 CA2147388A CA2147388A1 CA 2147388 A1 CA2147388 A1 CA 2147388A1 CA 2147388 CA2147388 CA 2147388 CA 2147388 A CA2147388 A CA 2147388A CA 2147388 A1 CA2147388 A1 CA 2147388A1
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Abstract
An alkaline-resistant and excellent ink-water balance lithographic printing plate is provided comprising a layer of a photosensitive composition on an aluminum substrate. The photosensitive composition contains (a) a photosensitive diazo resin comprising a condensation product of an aromatic diazonium salt, a co-polymerizable compound free of diazonium groups and an active carbonyl-containing compound and (b) a binder comprising a high molecular weight acrylic. The aluminum substrate is treated for use by graining, etching with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight, and hydrophilizing. In a preferred embodiment the photosensitive composition comprises:
(a) a photosensitive diazo resin comprising a copolymer containing the recurring monomer units having the general formula (I) --
(a) a photosensitive diazo resin comprising a copolymer containing the recurring monomer units having the general formula (I) --
Description
-2~473~8 METHOD FOR MANUFACTURING SUPER}OR INK-WATER
BALANCE AND Ar~r~Ar~TNR-REsIsTANT PS PLATES
Background of the Invention This invention relates to photosensitive printing plates and, more particularly, to processes and composltions for making such plates which are P~pc.ri;-l ly adapted to be resistant to ~lk~lin~ fountain solutions, alkaline-related chemicals and solvent chemicals used in the plate room and press room, and to provide an improved ink-water balance.
A lithographic printing plate is made by mixing a photosensitive material such as a diazo resin with a binder and other ingredients to produce a photosensitive coating which can be applied to an aluminum or other substrate, which has been pretreated to render it highly hydrophilic. Upon imagewise exposure of the printing plate, the areas on the plate exposed to the light are cured and become insoluble in a developer applied to the plate after light exposure. The developer solubili~es, and thereby, removes, the uncured photosensitive material which had been protected from the light by the negative, creating hydrophilic areas where the aluminum substrate has been uncovered and oleophilic areas where the cured photosensitive coating remains. The contrasting oleophilic and hydrophilic surface areas on the developed plate allow for preferential retention of a greasy image-forming substance by an image area, and retention of an aqueous ~ _ in~ solution by a non-image area, providing a means for printlng by use of water and fatty ink.
Comparative Example 4 describes a prior art lithographic prlnting plate particularly suitable for newspaper printing. Such a printing plate provides for qulck and easy development and exceptional print resolution for newspaper printing when used with acid or 35 neutral fountain solutions. However, the above-described ~ ~ 21~388 printing plate exhibits only poor resistance to alkaline fountain solution~ and some plate and press room chemistry and, therefore, does not work well when used with alkaline-based fountain solutions such as Rycoline, 5 Anchor or PSI alkaline fountain solutions, and does not stand up well to alkaline and other plate and press-room chemicals in common use such as certain plate cleaner solutions. Eiurther, while such printing plates are comparable to others on the market in terms of the ink-10 water balance they produce during printing, a significantwaste of paper occurs during "warm starts" (press stoppages and restarts ) as the water and ink used for printing are brought into balance. Additionally, a high water level must be reached before the ink-water balance 15 is realized, thus necessitating the use of greater amounts of ink during printing.
Thus, the discovery of a photosensitive printing plate which has the attributes described above of easy developability and superior print resolution, but 20 which is resistant to alkaline fountain solutions and other press-room chemicals, particularly such a plate which produces an improved ink-water balance is highly desirable. Moreover, the discovery of a photosensitive printing plate exhibiting one or both of these advantages 25 has been the object of considerable interest in the industry .
Summary of the Irvention Among the several objects of the invention, therefore, may be noted the provision of photosensitive 30 printing plates which exhibit improved resistance to alkaline fountain solutions and other alkaline and press-room chemicals, and produce an i 1 uv~d ink-water balance resulting in reduced roll up time, less spoilage of paper, lower requirements for water and ink in the 35 printing of the plates and faster clean up; the provision ~ 2147388 o~ uved photosensltive compositions and substrates for use in producing such plates; and the provision of methods for producing such improved photosensitive printing plates and substrates.
Briefly, therefore, the present invention is directed to a novel photosensitive printing plate. The printing plate comprises a layer of a photosensitive composition containing a photosensitive diazo resin and a binder on an aluminum substrate. The photosensitive composition contains ~a) a photosensitive diazo resin comprising a cnn~pn~tion product of an aromatic diazonium salt, a co-polymerizable compound free of 7nni groups, and an active carbonyl-containing compound and (b) a binder comprising a high molecular weight acrylic co-polymer. The aluminum substrate has been grained, etched by application of a caustic solution containing from about 1.0% to about 4.759c of an alkali metal hydroxide by weight, and hydrophilized.
The present invention is further directed to an alkaline-resistant photosensitive composition. The photosensitive composition comprises:
(a) a photosensitive diazo resin which is a copolymer containing the recurring monomer units having the general formula (I) --N2C ~XC ~\ / \
~ H ~ H
wherein Rl, R2, and R3 each denote separately a llydl uyt:l~
atom, a halogen atom, an alkyl group having from l to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF4, R is a hydrogen atom, 5 an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of R4 and R5 is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, -SO3H or 10 its salt, or -S02H or its salt, R6 is a llydlug~ll atom, an alkyl group having l or Z carbon atoms or a phenyl group, and the ratio of m to n is from about 70:30 to about 85:15, and the dia~o resin has an average molecular weight of from about 2,000 to about 3,000 and ~b) a binder comprising a high molecular weight acrylic co-polymer, wherein the ratio of (a) to (b) by weight is from about 0.033/1 to about 0.17/lØ
In a preferred embodiment of the photosensitive composition of the invention, (b1 is a binder comprising 20 an acrylic copolymer containing the recurring monomer units having the general formula ( II ) --- C H 2 - C - ) j C - C H 2 - C - ~ k - R 9 CN COOP COOH
wherein R7, RB, and R9 are lntl~rc~nrl~ntly a hydrogen atom or an alkyl group having from l to 3 carbon 25 atoms, and R10 is an alkyl group having from l to 3 carbon atoms or a phenyl group,; is a number from 20 to 30, k i8 a number from 50 to 70, and l a numoer from 4 to 14, the binder polymer has an average molecular weight of from about 50,000 to about 150,000, and has an acid 5 number of from 20-lO0.
The invention also includes a method for producing a photosensitive printing plate. The method comprises the steps of graining an aluminum substrate, etching the grained substrate by contacting it with a 10 caustic solution containing from about l . 096 to about 4. 75% of an alkali metal hydroxide by weight, hydrophilizing the aluminum substrate, coating the substrate with a layer of a photosensitive composition containing a photosensitive diazo resin and a binder as 15 described above, and drying the photosensitive printing plate .
In an alternative: -af- L the invention is directed to a method for producing a photosensltive printing plate. The method comprises the steps of 20 graining an aluminum substrate, etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight at a temperature of f rom about 45 C to about 80 C, hydrophilizing the aluminum 25 substrate, coating the substrate with a layer of a 2l47388 photosensitive composition containing a photosensitive diazo resin and a binder~ and drying the photo6ensitive printing plate.
The invention is further directed to a novel treated aluminum substrate for use in a lithographic printing plate. The novel treated aluminum substrate has an optical density reading of at least about 0 . 38 and is prepared by the steps of graining the aluminum substrate, etching the grained substrate by contacting it with a caustic solution containing from about 1. 0% to about 4. 75% of an alkali metal hydroxide by weight, and hydrophilizing the aluminum substrate.
The invention is further directed to methods for the preparation of such treated aluminum ~ubsLLaLes, as described above, adapted for use ln such photosensitive printing plates.
Other ob~ects and features will be in part apparent and in part pointed out hereinafter.
Description of the Preferred Embodiment It has been discovered in accordance with the invention that by combining a particular photosensitive coating containing an increased ratio of diazo resin to binder with a less aggres~31vely etched aluminum substrate, a photosensitive printing plate i8 produced Z5 which exhibit~ greatly ~nhF-nf~e~ resistance to alkaline fountain solutions and other alkaline and press-room ~ 21~7388 rhPm; rAl ,~, thus permitting longer run times and reduced "down" times during which printing presses must be stopped to replace worn out plates. Moreover, the modi f ied substrate contributes to an improved ink-water 5 balance, allowing for faster roll up, less waste of paper during start up, reduced rnn! tion of ink and easier clean up.
The photosensitive printing plate of this invention comprises a photosensitive composition as 10 described below layered or coated onto a grained, etched, and hydrophilized aluminum substrate. The aluminum sheets which may be employed as substrates include those which are made from aluminum alloys such as Aluminum Association alloys 1050, 1100 and 3003. Sheets used for 15 printing plate substrates preferably have a thickness of from 6 to 20 gauge (1 gauge = 0.001 in).
In the practice of the instant invention, the aluminum sheet is prepared for use as a substrate by subjecting it to a series of treatments which includes 20 degreasing, graining, etching and hydrophili~ing its surface, and preferably also includes an anodizing step after etching.
The foregoing ~ minllm plates are pretreated with a degreaser such as sodium silicate, sodium 25 hydroxide or various surfactants in order to remove any oil adhering to the surface of the aluminum sheets.
38$
After degreasing, the aluminum substrate is grained to create a "roughened" surface having pit8 and peaks which provides a better "grip" for the photosensitive coating and also creates places for miniature ink and water reservoirs on the surface of the developed plate. In a preferred embodiment, 8uch surface roughening is produced by mechanically graining the surface, e.g., by brush graining using a pumice slurry as an abrasive, wire brush graining, or ball graining.
However, it may also be produced by chemical or electrolytic graining techniques or by a combination of such methods. Preferably, the aluminum sheets are grained until reaching an optical density of from about 0.20 to 0.30, and most preferably from about 0.23 to 0 . 27 .
According to the invention, the grained aluminum substrate is then etched using a caustic aqueous solution containing, or consisting essentially of, an alkali metal hydroxide, such as potassium hydroxide or, preferably, sodium hydroxide. Prior to the instant ~=
invention it was widely believed that a relatively high concentration of alkali -- e.g., one above 10%, was required to aggressively etch the plate and create a substrate background sufficiently "white" for plates of the type described herein. Surprisingly, however, applicant has discovered that le88 than half the concentration of alkali previously believed to be ~ ~ 2~388 desirable provides for more than adequate shade contrast and unexpectedly contributes to greater alkaline resistance and to an i _ LVV-:d ink-water balance for the photosensitive printing plate. Accordingly, the concentration of the alkali metal hydroxide in the caustic solution of the invention ifi from about 1 to about 4.7596 by weight, preferably 2 to 4.4%, and most preferably 3.9 to 4.1%. For optimum results, the caustic solution is preheated to a t _~ ~-uLe between about 45 C and about 80 C, preferably from about 50 C to about 60 C, and most preferably at about 55' C, prior to the etching treatment. The grained aluminum is immersed in or otherwise contacted with the caustlc solution for a time sufficient to obtain an optical density of at least 0.38, as measured by a densitometer, e.g., as sold by Litho-Tronics, Wheeling, Illinois, using a yellow filter.
Under the conditions described above, contact time is preferably for from about 4 to about 12 seconds, and most preferably from about 6 to about 8 seconds. An alkaline residue and film of smut left on the surface of the aluminum substrate after graining and etching may readily be neutralized and removed, respectively, by application of an acidic solution, such as a 10-1596 nitric acid solution, followed by washing with water.
If desired, the grained and etched aluminum substrate may be anodically oxidized, e.g., in an acidic solution such as one containing sulfuric acid, phosphoric 2~7388 acid, oxalic acid or a mixture of two or more of these or other oxidizing compounds. In a preferred procedure, the substrate i8 passed through an anodizing bath containing, e.g., 10 to 20% sulfuric acid at a temperature of from 5 25D C to 50 C, resulting in the deposition of an nllm oxide film of between about 160 and 240 mg/ft2 on the substrate ' s surface.
While the anodized plate already has been rendered somewhat hydrophilic, it is advantageous to 10 subject its surface to treatment with silicates such as sodium or potassium silicate, to render it even more hydrophilic. In a preferred ~ ~'i l, the sheet is immersed in a 2 to 5i aqueous solution of sodium silicate at a temperature of between about 75 to 90 C, followed 15 by rinsing in a hot water bath (e.g., at 75 C to 98 C).
Substrates 80 treated provide improved ink-water balance, thereby providing for reduced roll up time, less spoilage of paper, lower ink and water requirements and faster clean up. Moreover, they 20 contribute to alkaline resistance when employed in a printing plate subjected to alkaline fountain solutions.
According to the invention, the aluminum substrate having been treated as described above, is then coated with a photosensitive composition. The 25 photosensitive composition of the present invention comprises a diazo resin and a binder mixed together with other ingredients such as a solvent, a dye or pigment, 2~7388 ll and an acld stabilizer. The diazo resin is substantially organic solvent-soluble and water insoluble, and preferably comprises a rnnti~n~tion product of an aromatic ~i~7nn~llm sal~, a co-polymerizable r~ ' free 5 of diazonium groups, and an actlve carbonyl-contalning compound such as formaldehyde or acetaldehyde. In a preferred: -Ai - t of the invention the diazo resin is a copolymer containlng the recurring monomer unlts havlng the general formula ( I ):
N C ~ ) X
R
wherein Rl, R2, and R3 each denote separately a llyd-og~l atom, a halogen atom, an alkyl group having from 1 to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF~, R is a 11YdLUY~1 15 atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of Ri and RS is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, 2I~7388 -S03H or its salt, or -SO2H or its salt, R6 is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, and wherein the ratio of m to n is from about 70:30 to about 85:15, preferably from about 75:25 5 to about 81:19, the polymer having an average molecular weight of from about 2,000 to about 3,000, preferably from about 2,250 to 2,750, and most preferably about 2,500. Preferably, R is a IIYdLO4~ group and at least one of Rg and R5 is carboxyl. Specific examples of 10 combinations which may be used include the hexafluorophosphate or tetrafluoroborate salts of a conflPnRate between one of 4-diazodiphenylamine or 4-diazo-4 ' -methoxydiphenylamine, one of benzaldehyde, acetaldehyde or formaldehyae, and one of a phenol or a 15 benzoic acid. Particularly preferred is the hexafluorophosphate salt of the polymer of 4-diazodiphenylamine with formaldehyde and 4-hydroxy benzoic acid.
Such a diazo resin can be obtained by 20 I-~nA~n~n~ the aromatic diazonium compound and the co-polymerizable compound with at least one active carbonyl compound, or with agents producing such a carbonyl compound, in a strongly acid medium. Particularly useful rnn~ n~tion media are phn6phnric acid and sulfuric acid, 25 which acids are employed in aqueous solutions of at least 4096 by weight, and preferably 70-100~ by weight.
Particular examples of carrying out the above 13 2~47388 cr~n~pn~tion reaction may by found in, e.g., U.S. Patent 3,867,147, incorporated herein by reference, and are well known to those skilled in this art.
The dia~o resin is mixed with an oleophilic 5 polymeric binder of high molecular weight . Specif ic examples of such resins include polymers derived from hydroxy or carbonyl-containing, ethylenically unsaturated monomers such as polyacrylates, polymethacrylates, polyacrylonitriles, polymethacrylonitriles, lO polyacrylamides, polymethacrylamides, polyacrylic acids, and polymethacrylic acids or a mixed polymer containing monomers of two or more of the above resin types, or one or more of such resins and one or more secondary resins, e.g., polyesters or polystyrenes. Preferably, the 15 oleophilic binder of the present invention is a high molecular weight ~at least about 50,000) acrylic co-polymer including, e.g., a co-polymer of acrylonitrile or methacrylonitrile and one or more acrylates, methacrylates or the acids or amides thereof. In a 20 preferred embodiment, such polymers contain the recurring monomer units having the following general formula (II):
C - C H z - C - ~ j ~ - C H 2 - C - ~ k ( - C H 2 - C~
CN COOQ COOH
wherein R7, R8, and R9 are independently a hydrogen atom or an alkyl group having from 1 to 3 carbon 25 atoms and R10 is an alkyl group having from 1 to 3 carbon 21~7388 atoms or a phenyl group, j is a number from 20 to 30, preferably about 24, k is a number from 50 to 70, preferably about 60.5, and l a number from 4 to 14, preferably about 7, the polymer having an average molecular weight of from about 50,000 to about 150,000, preferably from about 55,000 to about 80,000, and most preferably about 62,000, and having an acid number of from 20-100, preferably about 50-80, and most preferably about 60. Preferably R7 and R8 are llydl~g~ atoms, R9 is methyl and RlO is ethyl. In addition to the above described three classes of monomers, the preferred copolymer o:~ the invention may contain additional amounts, not exceeding about 30%, of other kinds of monomers co-polymerizable therewith including unsaturated carboxylic acid amides such as acrylamides or methacrylamides. A particularly preferred oleophilic polymeric binder is a co-polymer of 4-hydroxyphenyl methacrylamide, acrylonitrile, ethylacrylate, and methacrylic acid in the approximate ratio, respectively, of 8.5:24:60.5:7.
The copolymerization of the above described classes of monomers is carried out by a conventional procedure of radical polymerization in which predetermined amounts of the individual, ~. are mixed and dissolved in a suitable organic solvent such as 2-methoxy ethanol or 3-methoxy propanol with admixture of a radical polymerization initiator such a~ an orçlanic ~1~7388 peroxide, e.g., benzoyl peroxide, and then heated with agitation. As i8 known in the art, the proportions and conditions of the polymerization reaction are controlled so that the optimum amount of polymerization occurs to achieve molecules of the desired molecular weight and relative composltion.
The copolymer resin produced by the solution polymerization discussed above i8 purif ied to remove unreacted monomers and other impurities, e.g., by precipitation, and is then ready to be mixed together with the diazo resin and the other components of the photosensitive composition.
In accordance with the invention it has been discovered that by controlling the relative proportion of the diazo resin, particularly one of formula ~I) to the binder, particularly one of formula (II), 80 that the ratio of diazo to binder by weight is from about 0.033/1.0 to about 0.17/1.0, preferably is from about 0.04Z/l.0 to about O.lZ/l.0, and most preferably is from Z0 about .050/1.0 to about 0.08/1.0, a photosensltive plate results which is markedly more resistant to alkaline fountain 601utions and other chemicals than plates previously produced, e.g., the prior art photosensitive composition as described in Comparative Example 4.
Z5 To formulate the photosensitive composition of the present invention 80 that the desired ratio of diazo resin to binder is achieved, the diazo resin is 21 ~ 7388 ~, preferably incorporated into the photosensitive composition at a concentration by weight of from about .796 to about 2.4% of the total composition, preferably from about .85% to about 2.0%, and most preferably from 5 abo7lt 1. 0% to about 1. 4% . The polymeric binder is preferably incorporated at a concentration by weight of from about 14.0% to about 21.0% of the total composltion, preferably from about 16.0% to about 20.0%, and most preferably from about 17 . 5% to about 19 . 0% .
The photosensitlve composition of the invention preferably also inc~7l~7~ one or more dyes or pigments for visualizing images. Examples of such dyes and pigme7 ts include the following commercially available products:
Crystal Violet (CI 42555), Crystal Violet-carbinol base (CI 42555:1), Acilan Brilliant Blue 5B (CI 42740), Victoria Pure Blue BO~ (CI 42595), B0~-20 Blue Dye, Nile Blue BX (CI 51185) and pigments of other shades and colors. These dyes or pigments are generally used in an amount of from about 0.2% to about 1.5% by weight of the 20 photosensitive composition.
An acid such as polyacrylic acid, phosphoric acid, rh~srh~rous acid, tartaric acid, citric acid, malic acid, or a salt thereof may optionally be added as a stabilizer. In a preferred embodiment, a 25% by weight 25 solution of polyacrylic acid 18 in.ol~ol -Led in an amount of from about 2 to 4g6 by weight of the composition.
~i~738:8 In a preferred embodiment, the photosensltive composition of the instant invention consists essentially of the previously mentioned ingredients -- i . e., a diazo resin and binder, dye or pigment and stabilizer, 5 dissolved in a solvent. However, various additional ingredients, including surface active agents, plasticizers, fillers and other ~ ~ nts whose function and particular ingredients are well known in this art, may also be incorporated into the photosensitive 10 composition if desired for a particular application.
The photosensitive composition of this invention as described above is dissolved in an appropriate organic solvent such as 2-methoxy ethanol, 2-methoxyethyl acetate, propropyleneglycol monomethylether, 15 3-methoxy propanol, 3-methu-Lyy~uyyl acetate, cyrl nh~- ~n~nP, ethylene d~chloride, or a mixture thereof .
The solvent is preferably 2-methoxy ethanol. The concentration of the solvent in the prepared photosensitive coating is from about 60% to 90%, 20 preferably from about 70% to about 80%, and most preferably from about 75% to about 80% by weight. The photosensitive composition thus dissolved is then coated onto an aluminum substrate which has been pretreated as previously described. Preferably, the photosensitive 25 composition is coated to a thickness of about 0 . 35 g/ m2 to about 1. 86 g~ m2, preferably about 1. 2 g/ m2 (dry basis ) using one of a number of techniques known in the 21~73~8 art, including, for example, by whirler coating, swabbing or roller application. The coated aluminum substrate is then dried, preferably at an lnitial temperature a~ about 45 C for about 3 minutes, and then dried at 85 C for 5 about 3 additional minutes.
To develop the photosensitive plate thus prepared, the plate is exposed to a light source, e.g., a metal halide, carbon arc or a high-ples~uld mercury vapor lamp, through a negative and then processed with a 10 developer and gummed up for use, e.g., using an aqueous solution of 596 gum arabic. Any developer can be used for removing the non-exposed areas a~ long as it dissolves the non-e~cposed areas of the photosensitive coating, but not the cured exposed areas. In particular, a suitable 15 developer for use in developing a photosensitive coating of the preferred type disclosed herein is a weakly alkaline aqueous solution comprising an organic solvent, an alkali agent, and at least one anionic surface active agent (e.g., an aromatic or aliphatic ~ulphonate) in de-20 ionized water.
The thus prepared photsensitive printing plateis ready for mounting on a printing press and i8 specially adapted for extended use with an alkaline fountain ~3olution such as the Advantage Fountain Solution 25 3001 sold by PresAroom Solution Inc., Fort Worth, Tx.
The following examples illustrate the invention .
EXAMPLES
Example An aluminum plate of 1100 Alloy raw coil having a thickness of 12 gauge ~0.012 in) was degreased and cleaned by dipping in a mixture of 1% Trisodium Phosphate and 296 of Sodium Metha Silicate solution at 70*C for 10 seconds .
The aluminum plate was then surface-roughened by mechanical graining with a 25-30% slurry concentration oi #Z90 abrasive Sllica material to obtain an optical density reading between 0 . 23 to 0 . 27 .
Thereafter the aluminum plate was etched with 496 Sodium lIyaroxide solution at 55C for 7.4 seconds.
After washing with water, the aluminum substrate was neutralized with 12 . 596 of aqueous Nitric Acid solution, washed with water and then anodized in a 16 . 596 Aqueous Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing the aluminum substrate was dipped in 2.5% aqueous sodium silicate solution at 80C
for 12 seconds, washed with water and dried. Substrate 80 made provided excellent ink-water balance on the press.
,, 21~7388 A light-sen8itive solution having the following formulation was applied onto the surface of the substrate. The amount of the light-sensitive coating weighed after drying was 1.12g~m2.
Light-Sensitive Coating Solution r~ , A.rl t Weight ( g ) Methyl Cellosolve 300 gm PF6 salt of a polymer o~
diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 5 gm 4-hydroxyphenyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 75 gm Polyacrylic acid (25% wgt solution) 10 gm Victoria Blue BOH 3 gm The PS plate so prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the following formula and then gummed up to give a lithographic 20 printing plate.
Developer r~ ellt Weight(9~ _ Phenyl Cellosolve 3 . 75%
Di-Ethanolamine 1. 396 25 Sodium Dibutylnapthalene Sulfonate 1. 2596 Deionized water 93 . 7%
21~73~8 The processea plate was mounted on a newspaper printing press and ran with PSI alkaline fountain solution. The plate so made provided excellent ink-water balance and alkaline fountain solution resistance on 5 press. The results are reported below in Table I.
Example 2 An aluminum plate of 1100 Alloy raw coil having a thickness of 0.30 mm was degreased and cleaned by dipping in a mixture of 1% Trisodium Phosphate and 296 of 10 Sodium Metha Silicate solution at 70C for 10 seconds.
The aluminum plate was then surface-roughened by mechanical graining with a 25-30% slurry concentration of #290 abrasive Silica material to obtain an optical density reading between 0.23 to 0.27.
Thereafter the ~luminlln plate was etched with 4% Sodium Hydroxide solution at 55C for 7.4 seconds.
After washing with water, the aluminum substrate was neutralized with 12.5% of aqueous Nitric Acid solution, washed with water and then anodized in a 16 . 5% Aqueous 20 Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing, the aluminum substrate was dipped in a 2.5% aqueous sodium silicate solution at 80C
for 12 seconds, washed with water and dried. The 25 substrate so ma~e provided excellent ink-water balance on the press.
A light-sensitive solution having the following formulation was applied onto the surface of the substrate. The amount of the light-sensitive solution 30 weighed after drying was 1.12 g/m2.
738~
Light-Sensitive Coating Solution C'~ n, ~InPnt ~ Weight(g) Methyl Cellosolve 300 gm PF6 salt o~ a polymer of 5diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 3 . 75 gm 5-1-y~lL~,..yl,henyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 75 gm Polyacrylic acid (259~ wgt solution) 10 gm 10Victoria Blue 13OH 3 gm The PS plate so prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the iollowing 15 formula and then gummed up to give a lithographic printing plate.
Developer -r)n en t Weiqht ( 96 ) Phenyl Cellosolve 3 . 75%
20 Di-Ethanolamine 1. 3%
Sodium Dibutylnapthalene Suli'onate 1. 25%
Deionized water 93 . 70~6 The processed plate was mounted on a newspaper printing preYs and ran with PSI alkaline fountain solution. The plate 80 made provided excellent ink-water balance but only fairly good resistance toward alkaline fountain solution. The results are outlined below in Table I.
Example 3 An aluminum plate of 1100 Alloy raw coil having a thickness of O . 30 mm was degreased and cleaned by dipping in a mixture of 196 Trisodium Phosphate and 2% o~
Sodium Metha Silicate solution at 70C for 10 seconds.
The aluminum plate was then sur~ace-roughened by mechanical graining with a 25-30% slurry concentration of ~290 abrasive Silica material to obtain an optical density reading between 0 . 23 to 0 . 27 .
Thereafter the aluminum plate wa6 etched with 4% Sodium Hydroxide solution at 55 C for 7 . 4 seconds .
After washing with water, the aluminum ~ubs~-~te was neutralized with 12.5~ of aqueous Nitric Acid solution, washed with water and then anodized in a 16 . 5% Aqueous Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing, the aluminum substrate was dipped in 2.596 aqueous sodium silicate solution at 80C
for 12 seconds, washed with water and dried. The substrate so rl~ade provided an excellent ink-water balance on the press.
A light-sensitive solution having the following formulation was applied onto the surface of the substrate. The amount of the light-sensitive solution weighed after drying was 1. I2 g/m2.
` 2~738~
Light-Sensitive Coatin~ Solution Component Weight ( g ) Methyl Cellosolve 300 gm PF6 salt of a polymer of 5 diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 2 . 5 gm 4-~-ydlo~y~henyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 100 gm Polyacrylic acid (2596 wt solution) 10 gm Victoria Blue BOH 3 gm The PS plate so prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the following 15 formula and then gummed up to give a lithographic printing plate.
Developer ~I "~n nt ~ Weight( Phenyl Cellosolve 3 . 75%
20 Di-Ethanolamine 1. 3%
Sodium Dibutylnapthalene Sulfonate 1. 25%
Deionized water 93 . 7%
The processed plate was mounted on a newspaper printing press and ran with PSI alkaline fountain 25 solution. The plate so made provided excellent ink-water balance, but only fair alkaline resistance on press. The results are outlined below in Table I.
~1~738~
COMPARATIVE EXAMPLE
Example 4 An aluminum plate of 1100 Alloy raw coil having a thickness of 0.30 mm was degreased and cleanea by 5 dipping in a mixture of 1% Trisodium Phosphate and 2%
Sodium Netha Silicate solution at 70~C for 10 seconds.
The aluminum plate was then surface-roughened by mechanical graining with a 25-30% slurry concentration of #290 abrasive Silica material to obtain an optical density reading between 0 . 23 to 0 . 27 .
Thereafter the Al ~ plate was etched with 12% Sodium lIydroxide solution at 55C for 7.4 seconds.
After washing with water, the aluminum substrate was neutralized with 12.596 of aqueous Nitric Acid solution, 15 washed with water and then anodized in a 16 . 5% Aqueous Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing the Alllminllm substrate was dipped in 2.5% aqueous sodium silicate solution at 80C
20 for 12 seconds, washed with water and dried. Substrate so made provided only fair ink-water balance on the press .
A light-sensitive solution having the following formulation was applied onto the surface of the 25 substrate. The amount of the light-sensitive solution weighed after drying was 1.12 g/m2.
` 214~388 Light-Sensitive Coating Solution C~ L Weight ( g ) Methyl Cellosolve 300 gm PF6 salt of a polymer of 5diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 2 . 5 gm 4-11ydlu~-y~henyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 100 gm Polyacrylic acid (25% wt solution) 10 gm Victoria Blue BOE 3 gm The PS plate 80 prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the following 15 formula and then gummed up to give a lithographic printing plate.
Developer C~ ^~ t Weight ( % ) Phynyl Cellosolve 3 . 75%
Di-Ethanolamine 1.3%
Sodium Dibutylnapthalene Sulfonate 1. 25%
Deionized water 93 . 7%
The processed plate was mounted on a newspaper printing press and ran with PSI alkaline fountain 25 solution. The plate 80 made provided only fair ink-water balance and poor ~ nP resistance on press. The results are reported below in Table I.
21 ~ 7388 TABLE I
Characteri6tic Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ink-Water Balance 5 5 5 3 Alkaline Resistance 5 3 2 0 Note: Table I uses a 0-5 sliding scale in which 5 =
excellent and O = poor.
In view of the above, it will be seen that the several ob; ects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above methods and compositions without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.
BALANCE AND Ar~r~Ar~TNR-REsIsTANT PS PLATES
Background of the Invention This invention relates to photosensitive printing plates and, more particularly, to processes and composltions for making such plates which are P~pc.ri;-l ly adapted to be resistant to ~lk~lin~ fountain solutions, alkaline-related chemicals and solvent chemicals used in the plate room and press room, and to provide an improved ink-water balance.
A lithographic printing plate is made by mixing a photosensitive material such as a diazo resin with a binder and other ingredients to produce a photosensitive coating which can be applied to an aluminum or other substrate, which has been pretreated to render it highly hydrophilic. Upon imagewise exposure of the printing plate, the areas on the plate exposed to the light are cured and become insoluble in a developer applied to the plate after light exposure. The developer solubili~es, and thereby, removes, the uncured photosensitive material which had been protected from the light by the negative, creating hydrophilic areas where the aluminum substrate has been uncovered and oleophilic areas where the cured photosensitive coating remains. The contrasting oleophilic and hydrophilic surface areas on the developed plate allow for preferential retention of a greasy image-forming substance by an image area, and retention of an aqueous ~ _ in~ solution by a non-image area, providing a means for printlng by use of water and fatty ink.
Comparative Example 4 describes a prior art lithographic prlnting plate particularly suitable for newspaper printing. Such a printing plate provides for qulck and easy development and exceptional print resolution for newspaper printing when used with acid or 35 neutral fountain solutions. However, the above-described ~ ~ 21~388 printing plate exhibits only poor resistance to alkaline fountain solution~ and some plate and press room chemistry and, therefore, does not work well when used with alkaline-based fountain solutions such as Rycoline, 5 Anchor or PSI alkaline fountain solutions, and does not stand up well to alkaline and other plate and press-room chemicals in common use such as certain plate cleaner solutions. Eiurther, while such printing plates are comparable to others on the market in terms of the ink-10 water balance they produce during printing, a significantwaste of paper occurs during "warm starts" (press stoppages and restarts ) as the water and ink used for printing are brought into balance. Additionally, a high water level must be reached before the ink-water balance 15 is realized, thus necessitating the use of greater amounts of ink during printing.
Thus, the discovery of a photosensitive printing plate which has the attributes described above of easy developability and superior print resolution, but 20 which is resistant to alkaline fountain solutions and other press-room chemicals, particularly such a plate which produces an improved ink-water balance is highly desirable. Moreover, the discovery of a photosensitive printing plate exhibiting one or both of these advantages 25 has been the object of considerable interest in the industry .
Summary of the Irvention Among the several objects of the invention, therefore, may be noted the provision of photosensitive 30 printing plates which exhibit improved resistance to alkaline fountain solutions and other alkaline and press-room chemicals, and produce an i 1 uv~d ink-water balance resulting in reduced roll up time, less spoilage of paper, lower requirements for water and ink in the 35 printing of the plates and faster clean up; the provision ~ 2147388 o~ uved photosensltive compositions and substrates for use in producing such plates; and the provision of methods for producing such improved photosensitive printing plates and substrates.
Briefly, therefore, the present invention is directed to a novel photosensitive printing plate. The printing plate comprises a layer of a photosensitive composition containing a photosensitive diazo resin and a binder on an aluminum substrate. The photosensitive composition contains ~a) a photosensitive diazo resin comprising a cnn~pn~tion product of an aromatic diazonium salt, a co-polymerizable compound free of 7nni groups, and an active carbonyl-containing compound and (b) a binder comprising a high molecular weight acrylic co-polymer. The aluminum substrate has been grained, etched by application of a caustic solution containing from about 1.0% to about 4.759c of an alkali metal hydroxide by weight, and hydrophilized.
The present invention is further directed to an alkaline-resistant photosensitive composition. The photosensitive composition comprises:
(a) a photosensitive diazo resin which is a copolymer containing the recurring monomer units having the general formula (I) --N2C ~XC ~\ / \
~ H ~ H
wherein Rl, R2, and R3 each denote separately a llydl uyt:l~
atom, a halogen atom, an alkyl group having from l to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF4, R is a hydrogen atom, 5 an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of R4 and R5 is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, -SO3H or 10 its salt, or -S02H or its salt, R6 is a llydlug~ll atom, an alkyl group having l or Z carbon atoms or a phenyl group, and the ratio of m to n is from about 70:30 to about 85:15, and the dia~o resin has an average molecular weight of from about 2,000 to about 3,000 and ~b) a binder comprising a high molecular weight acrylic co-polymer, wherein the ratio of (a) to (b) by weight is from about 0.033/1 to about 0.17/lØ
In a preferred embodiment of the photosensitive composition of the invention, (b1 is a binder comprising 20 an acrylic copolymer containing the recurring monomer units having the general formula ( II ) --- C H 2 - C - ) j C - C H 2 - C - ~ k - R 9 CN COOP COOH
wherein R7, RB, and R9 are lntl~rc~nrl~ntly a hydrogen atom or an alkyl group having from l to 3 carbon 25 atoms, and R10 is an alkyl group having from l to 3 carbon atoms or a phenyl group,; is a number from 20 to 30, k i8 a number from 50 to 70, and l a numoer from 4 to 14, the binder polymer has an average molecular weight of from about 50,000 to about 150,000, and has an acid 5 number of from 20-lO0.
The invention also includes a method for producing a photosensitive printing plate. The method comprises the steps of graining an aluminum substrate, etching the grained substrate by contacting it with a 10 caustic solution containing from about l . 096 to about 4. 75% of an alkali metal hydroxide by weight, hydrophilizing the aluminum substrate, coating the substrate with a layer of a photosensitive composition containing a photosensitive diazo resin and a binder as 15 described above, and drying the photosensitive printing plate .
In an alternative: -af- L the invention is directed to a method for producing a photosensltive printing plate. The method comprises the steps of 20 graining an aluminum substrate, etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight at a temperature of f rom about 45 C to about 80 C, hydrophilizing the aluminum 25 substrate, coating the substrate with a layer of a 2l47388 photosensitive composition containing a photosensitive diazo resin and a binder~ and drying the photo6ensitive printing plate.
The invention is further directed to a novel treated aluminum substrate for use in a lithographic printing plate. The novel treated aluminum substrate has an optical density reading of at least about 0 . 38 and is prepared by the steps of graining the aluminum substrate, etching the grained substrate by contacting it with a caustic solution containing from about 1. 0% to about 4. 75% of an alkali metal hydroxide by weight, and hydrophilizing the aluminum substrate.
The invention is further directed to methods for the preparation of such treated aluminum ~ubsLLaLes, as described above, adapted for use ln such photosensitive printing plates.
Other ob~ects and features will be in part apparent and in part pointed out hereinafter.
Description of the Preferred Embodiment It has been discovered in accordance with the invention that by combining a particular photosensitive coating containing an increased ratio of diazo resin to binder with a less aggres~31vely etched aluminum substrate, a photosensitive printing plate i8 produced Z5 which exhibit~ greatly ~nhF-nf~e~ resistance to alkaline fountain solutions and other alkaline and press-room ~ 21~7388 rhPm; rAl ,~, thus permitting longer run times and reduced "down" times during which printing presses must be stopped to replace worn out plates. Moreover, the modi f ied substrate contributes to an improved ink-water 5 balance, allowing for faster roll up, less waste of paper during start up, reduced rnn! tion of ink and easier clean up.
The photosensitive printing plate of this invention comprises a photosensitive composition as 10 described below layered or coated onto a grained, etched, and hydrophilized aluminum substrate. The aluminum sheets which may be employed as substrates include those which are made from aluminum alloys such as Aluminum Association alloys 1050, 1100 and 3003. Sheets used for 15 printing plate substrates preferably have a thickness of from 6 to 20 gauge (1 gauge = 0.001 in).
In the practice of the instant invention, the aluminum sheet is prepared for use as a substrate by subjecting it to a series of treatments which includes 20 degreasing, graining, etching and hydrophili~ing its surface, and preferably also includes an anodizing step after etching.
The foregoing ~ minllm plates are pretreated with a degreaser such as sodium silicate, sodium 25 hydroxide or various surfactants in order to remove any oil adhering to the surface of the aluminum sheets.
38$
After degreasing, the aluminum substrate is grained to create a "roughened" surface having pit8 and peaks which provides a better "grip" for the photosensitive coating and also creates places for miniature ink and water reservoirs on the surface of the developed plate. In a preferred embodiment, 8uch surface roughening is produced by mechanically graining the surface, e.g., by brush graining using a pumice slurry as an abrasive, wire brush graining, or ball graining.
However, it may also be produced by chemical or electrolytic graining techniques or by a combination of such methods. Preferably, the aluminum sheets are grained until reaching an optical density of from about 0.20 to 0.30, and most preferably from about 0.23 to 0 . 27 .
According to the invention, the grained aluminum substrate is then etched using a caustic aqueous solution containing, or consisting essentially of, an alkali metal hydroxide, such as potassium hydroxide or, preferably, sodium hydroxide. Prior to the instant ~=
invention it was widely believed that a relatively high concentration of alkali -- e.g., one above 10%, was required to aggressively etch the plate and create a substrate background sufficiently "white" for plates of the type described herein. Surprisingly, however, applicant has discovered that le88 than half the concentration of alkali previously believed to be ~ ~ 2~388 desirable provides for more than adequate shade contrast and unexpectedly contributes to greater alkaline resistance and to an i _ LVV-:d ink-water balance for the photosensitive printing plate. Accordingly, the concentration of the alkali metal hydroxide in the caustic solution of the invention ifi from about 1 to about 4.7596 by weight, preferably 2 to 4.4%, and most preferably 3.9 to 4.1%. For optimum results, the caustic solution is preheated to a t _~ ~-uLe between about 45 C and about 80 C, preferably from about 50 C to about 60 C, and most preferably at about 55' C, prior to the etching treatment. The grained aluminum is immersed in or otherwise contacted with the caustlc solution for a time sufficient to obtain an optical density of at least 0.38, as measured by a densitometer, e.g., as sold by Litho-Tronics, Wheeling, Illinois, using a yellow filter.
Under the conditions described above, contact time is preferably for from about 4 to about 12 seconds, and most preferably from about 6 to about 8 seconds. An alkaline residue and film of smut left on the surface of the aluminum substrate after graining and etching may readily be neutralized and removed, respectively, by application of an acidic solution, such as a 10-1596 nitric acid solution, followed by washing with water.
If desired, the grained and etched aluminum substrate may be anodically oxidized, e.g., in an acidic solution such as one containing sulfuric acid, phosphoric 2~7388 acid, oxalic acid or a mixture of two or more of these or other oxidizing compounds. In a preferred procedure, the substrate i8 passed through an anodizing bath containing, e.g., 10 to 20% sulfuric acid at a temperature of from 5 25D C to 50 C, resulting in the deposition of an nllm oxide film of between about 160 and 240 mg/ft2 on the substrate ' s surface.
While the anodized plate already has been rendered somewhat hydrophilic, it is advantageous to 10 subject its surface to treatment with silicates such as sodium or potassium silicate, to render it even more hydrophilic. In a preferred ~ ~'i l, the sheet is immersed in a 2 to 5i aqueous solution of sodium silicate at a temperature of between about 75 to 90 C, followed 15 by rinsing in a hot water bath (e.g., at 75 C to 98 C).
Substrates 80 treated provide improved ink-water balance, thereby providing for reduced roll up time, less spoilage of paper, lower ink and water requirements and faster clean up. Moreover, they 20 contribute to alkaline resistance when employed in a printing plate subjected to alkaline fountain solutions.
According to the invention, the aluminum substrate having been treated as described above, is then coated with a photosensitive composition. The 25 photosensitive composition of the present invention comprises a diazo resin and a binder mixed together with other ingredients such as a solvent, a dye or pigment, 2~7388 ll and an acld stabilizer. The diazo resin is substantially organic solvent-soluble and water insoluble, and preferably comprises a rnnti~n~tion product of an aromatic ~i~7nn~llm sal~, a co-polymerizable r~ ' free 5 of diazonium groups, and an actlve carbonyl-contalning compound such as formaldehyde or acetaldehyde. In a preferred: -Ai - t of the invention the diazo resin is a copolymer containlng the recurring monomer unlts havlng the general formula ( I ):
N C ~ ) X
R
wherein Rl, R2, and R3 each denote separately a llyd-og~l atom, a halogen atom, an alkyl group having from 1 to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF~, R is a 11YdLUY~1 15 atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of Ri and RS is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, 2I~7388 -S03H or its salt, or -SO2H or its salt, R6 is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, and wherein the ratio of m to n is from about 70:30 to about 85:15, preferably from about 75:25 5 to about 81:19, the polymer having an average molecular weight of from about 2,000 to about 3,000, preferably from about 2,250 to 2,750, and most preferably about 2,500. Preferably, R is a IIYdLO4~ group and at least one of Rg and R5 is carboxyl. Specific examples of 10 combinations which may be used include the hexafluorophosphate or tetrafluoroborate salts of a conflPnRate between one of 4-diazodiphenylamine or 4-diazo-4 ' -methoxydiphenylamine, one of benzaldehyde, acetaldehyde or formaldehyae, and one of a phenol or a 15 benzoic acid. Particularly preferred is the hexafluorophosphate salt of the polymer of 4-diazodiphenylamine with formaldehyde and 4-hydroxy benzoic acid.
Such a diazo resin can be obtained by 20 I-~nA~n~n~ the aromatic diazonium compound and the co-polymerizable compound with at least one active carbonyl compound, or with agents producing such a carbonyl compound, in a strongly acid medium. Particularly useful rnn~ n~tion media are phn6phnric acid and sulfuric acid, 25 which acids are employed in aqueous solutions of at least 4096 by weight, and preferably 70-100~ by weight.
Particular examples of carrying out the above 13 2~47388 cr~n~pn~tion reaction may by found in, e.g., U.S. Patent 3,867,147, incorporated herein by reference, and are well known to those skilled in this art.
The dia~o resin is mixed with an oleophilic 5 polymeric binder of high molecular weight . Specif ic examples of such resins include polymers derived from hydroxy or carbonyl-containing, ethylenically unsaturated monomers such as polyacrylates, polymethacrylates, polyacrylonitriles, polymethacrylonitriles, lO polyacrylamides, polymethacrylamides, polyacrylic acids, and polymethacrylic acids or a mixed polymer containing monomers of two or more of the above resin types, or one or more of such resins and one or more secondary resins, e.g., polyesters or polystyrenes. Preferably, the 15 oleophilic binder of the present invention is a high molecular weight ~at least about 50,000) acrylic co-polymer including, e.g., a co-polymer of acrylonitrile or methacrylonitrile and one or more acrylates, methacrylates or the acids or amides thereof. In a 20 preferred embodiment, such polymers contain the recurring monomer units having the following general formula (II):
C - C H z - C - ~ j ~ - C H 2 - C - ~ k ( - C H 2 - C~
CN COOQ COOH
wherein R7, R8, and R9 are independently a hydrogen atom or an alkyl group having from 1 to 3 carbon 25 atoms and R10 is an alkyl group having from 1 to 3 carbon 21~7388 atoms or a phenyl group, j is a number from 20 to 30, preferably about 24, k is a number from 50 to 70, preferably about 60.5, and l a number from 4 to 14, preferably about 7, the polymer having an average molecular weight of from about 50,000 to about 150,000, preferably from about 55,000 to about 80,000, and most preferably about 62,000, and having an acid number of from 20-100, preferably about 50-80, and most preferably about 60. Preferably R7 and R8 are llydl~g~ atoms, R9 is methyl and RlO is ethyl. In addition to the above described three classes of monomers, the preferred copolymer o:~ the invention may contain additional amounts, not exceeding about 30%, of other kinds of monomers co-polymerizable therewith including unsaturated carboxylic acid amides such as acrylamides or methacrylamides. A particularly preferred oleophilic polymeric binder is a co-polymer of 4-hydroxyphenyl methacrylamide, acrylonitrile, ethylacrylate, and methacrylic acid in the approximate ratio, respectively, of 8.5:24:60.5:7.
The copolymerization of the above described classes of monomers is carried out by a conventional procedure of radical polymerization in which predetermined amounts of the individual, ~. are mixed and dissolved in a suitable organic solvent such as 2-methoxy ethanol or 3-methoxy propanol with admixture of a radical polymerization initiator such a~ an orçlanic ~1~7388 peroxide, e.g., benzoyl peroxide, and then heated with agitation. As i8 known in the art, the proportions and conditions of the polymerization reaction are controlled so that the optimum amount of polymerization occurs to achieve molecules of the desired molecular weight and relative composltion.
The copolymer resin produced by the solution polymerization discussed above i8 purif ied to remove unreacted monomers and other impurities, e.g., by precipitation, and is then ready to be mixed together with the diazo resin and the other components of the photosensitive composition.
In accordance with the invention it has been discovered that by controlling the relative proportion of the diazo resin, particularly one of formula ~I) to the binder, particularly one of formula (II), 80 that the ratio of diazo to binder by weight is from about 0.033/1.0 to about 0.17/1.0, preferably is from about 0.04Z/l.0 to about O.lZ/l.0, and most preferably is from Z0 about .050/1.0 to about 0.08/1.0, a photosensltive plate results which is markedly more resistant to alkaline fountain 601utions and other chemicals than plates previously produced, e.g., the prior art photosensitive composition as described in Comparative Example 4.
Z5 To formulate the photosensitive composition of the present invention 80 that the desired ratio of diazo resin to binder is achieved, the diazo resin is 21 ~ 7388 ~, preferably incorporated into the photosensitive composition at a concentration by weight of from about .796 to about 2.4% of the total composition, preferably from about .85% to about 2.0%, and most preferably from 5 abo7lt 1. 0% to about 1. 4% . The polymeric binder is preferably incorporated at a concentration by weight of from about 14.0% to about 21.0% of the total composltion, preferably from about 16.0% to about 20.0%, and most preferably from about 17 . 5% to about 19 . 0% .
The photosensitlve composition of the invention preferably also inc~7l~7~ one or more dyes or pigments for visualizing images. Examples of such dyes and pigme7 ts include the following commercially available products:
Crystal Violet (CI 42555), Crystal Violet-carbinol base (CI 42555:1), Acilan Brilliant Blue 5B (CI 42740), Victoria Pure Blue BO~ (CI 42595), B0~-20 Blue Dye, Nile Blue BX (CI 51185) and pigments of other shades and colors. These dyes or pigments are generally used in an amount of from about 0.2% to about 1.5% by weight of the 20 photosensitive composition.
An acid such as polyacrylic acid, phosphoric acid, rh~srh~rous acid, tartaric acid, citric acid, malic acid, or a salt thereof may optionally be added as a stabilizer. In a preferred embodiment, a 25% by weight 25 solution of polyacrylic acid 18 in.ol~ol -Led in an amount of from about 2 to 4g6 by weight of the composition.
~i~738:8 In a preferred embodiment, the photosensltive composition of the instant invention consists essentially of the previously mentioned ingredients -- i . e., a diazo resin and binder, dye or pigment and stabilizer, 5 dissolved in a solvent. However, various additional ingredients, including surface active agents, plasticizers, fillers and other ~ ~ nts whose function and particular ingredients are well known in this art, may also be incorporated into the photosensitive 10 composition if desired for a particular application.
The photosensitive composition of this invention as described above is dissolved in an appropriate organic solvent such as 2-methoxy ethanol, 2-methoxyethyl acetate, propropyleneglycol monomethylether, 15 3-methoxy propanol, 3-methu-Lyy~uyyl acetate, cyrl nh~- ~n~nP, ethylene d~chloride, or a mixture thereof .
The solvent is preferably 2-methoxy ethanol. The concentration of the solvent in the prepared photosensitive coating is from about 60% to 90%, 20 preferably from about 70% to about 80%, and most preferably from about 75% to about 80% by weight. The photosensitive composition thus dissolved is then coated onto an aluminum substrate which has been pretreated as previously described. Preferably, the photosensitive 25 composition is coated to a thickness of about 0 . 35 g/ m2 to about 1. 86 g~ m2, preferably about 1. 2 g/ m2 (dry basis ) using one of a number of techniques known in the 21~73~8 art, including, for example, by whirler coating, swabbing or roller application. The coated aluminum substrate is then dried, preferably at an lnitial temperature a~ about 45 C for about 3 minutes, and then dried at 85 C for 5 about 3 additional minutes.
To develop the photosensitive plate thus prepared, the plate is exposed to a light source, e.g., a metal halide, carbon arc or a high-ples~uld mercury vapor lamp, through a negative and then processed with a 10 developer and gummed up for use, e.g., using an aqueous solution of 596 gum arabic. Any developer can be used for removing the non-exposed areas a~ long as it dissolves the non-e~cposed areas of the photosensitive coating, but not the cured exposed areas. In particular, a suitable 15 developer for use in developing a photosensitive coating of the preferred type disclosed herein is a weakly alkaline aqueous solution comprising an organic solvent, an alkali agent, and at least one anionic surface active agent (e.g., an aromatic or aliphatic ~ulphonate) in de-20 ionized water.
The thus prepared photsensitive printing plateis ready for mounting on a printing press and i8 specially adapted for extended use with an alkaline fountain ~3olution such as the Advantage Fountain Solution 25 3001 sold by PresAroom Solution Inc., Fort Worth, Tx.
The following examples illustrate the invention .
EXAMPLES
Example An aluminum plate of 1100 Alloy raw coil having a thickness of 12 gauge ~0.012 in) was degreased and cleaned by dipping in a mixture of 1% Trisodium Phosphate and 296 of Sodium Metha Silicate solution at 70*C for 10 seconds .
The aluminum plate was then surface-roughened by mechanical graining with a 25-30% slurry concentration oi #Z90 abrasive Sllica material to obtain an optical density reading between 0 . 23 to 0 . 27 .
Thereafter the aluminum plate was etched with 496 Sodium lIyaroxide solution at 55C for 7.4 seconds.
After washing with water, the aluminum substrate was neutralized with 12 . 596 of aqueous Nitric Acid solution, washed with water and then anodized in a 16 . 596 Aqueous Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing the aluminum substrate was dipped in 2.5% aqueous sodium silicate solution at 80C
for 12 seconds, washed with water and dried. Substrate 80 made provided excellent ink-water balance on the press.
,, 21~7388 A light-sen8itive solution having the following formulation was applied onto the surface of the substrate. The amount of the light-sensitive coating weighed after drying was 1.12g~m2.
Light-Sensitive Coating Solution r~ , A.rl t Weight ( g ) Methyl Cellosolve 300 gm PF6 salt of a polymer o~
diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 5 gm 4-hydroxyphenyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 75 gm Polyacrylic acid (25% wgt solution) 10 gm Victoria Blue BOH 3 gm The PS plate so prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the following formula and then gummed up to give a lithographic 20 printing plate.
Developer r~ ellt Weight(9~ _ Phenyl Cellosolve 3 . 75%
Di-Ethanolamine 1. 396 25 Sodium Dibutylnapthalene Sulfonate 1. 2596 Deionized water 93 . 7%
21~73~8 The processea plate was mounted on a newspaper printing press and ran with PSI alkaline fountain solution. The plate so made provided excellent ink-water balance and alkaline fountain solution resistance on 5 press. The results are reported below in Table I.
Example 2 An aluminum plate of 1100 Alloy raw coil having a thickness of 0.30 mm was degreased and cleaned by dipping in a mixture of 1% Trisodium Phosphate and 296 of 10 Sodium Metha Silicate solution at 70C for 10 seconds.
The aluminum plate was then surface-roughened by mechanical graining with a 25-30% slurry concentration of #290 abrasive Silica material to obtain an optical density reading between 0.23 to 0.27.
Thereafter the ~luminlln plate was etched with 4% Sodium Hydroxide solution at 55C for 7.4 seconds.
After washing with water, the aluminum substrate was neutralized with 12.5% of aqueous Nitric Acid solution, washed with water and then anodized in a 16 . 5% Aqueous 20 Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing, the aluminum substrate was dipped in a 2.5% aqueous sodium silicate solution at 80C
for 12 seconds, washed with water and dried. The 25 substrate so ma~e provided excellent ink-water balance on the press.
A light-sensitive solution having the following formulation was applied onto the surface of the substrate. The amount of the light-sensitive solution 30 weighed after drying was 1.12 g/m2.
738~
Light-Sensitive Coating Solution C'~ n, ~InPnt ~ Weight(g) Methyl Cellosolve 300 gm PF6 salt o~ a polymer of 5diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 3 . 75 gm 5-1-y~lL~,..yl,henyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 75 gm Polyacrylic acid (259~ wgt solution) 10 gm 10Victoria Blue 13OH 3 gm The PS plate so prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the iollowing 15 formula and then gummed up to give a lithographic printing plate.
Developer -r)n en t Weiqht ( 96 ) Phenyl Cellosolve 3 . 75%
20 Di-Ethanolamine 1. 3%
Sodium Dibutylnapthalene Suli'onate 1. 25%
Deionized water 93 . 70~6 The processed plate was mounted on a newspaper printing preYs and ran with PSI alkaline fountain solution. The plate 80 made provided excellent ink-water balance but only fairly good resistance toward alkaline fountain solution. The results are outlined below in Table I.
Example 3 An aluminum plate of 1100 Alloy raw coil having a thickness of O . 30 mm was degreased and cleaned by dipping in a mixture of 196 Trisodium Phosphate and 2% o~
Sodium Metha Silicate solution at 70C for 10 seconds.
The aluminum plate was then sur~ace-roughened by mechanical graining with a 25-30% slurry concentration of ~290 abrasive Silica material to obtain an optical density reading between 0 . 23 to 0 . 27 .
Thereafter the aluminum plate wa6 etched with 4% Sodium Hydroxide solution at 55 C for 7 . 4 seconds .
After washing with water, the aluminum ~ubs~-~te was neutralized with 12.5~ of aqueous Nitric Acid solution, washed with water and then anodized in a 16 . 5% Aqueous Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing, the aluminum substrate was dipped in 2.596 aqueous sodium silicate solution at 80C
for 12 seconds, washed with water and dried. The substrate so rl~ade provided an excellent ink-water balance on the press.
A light-sensitive solution having the following formulation was applied onto the surface of the substrate. The amount of the light-sensitive solution weighed after drying was 1. I2 g/m2.
` 2~738~
Light-Sensitive Coatin~ Solution Component Weight ( g ) Methyl Cellosolve 300 gm PF6 salt of a polymer of 5 diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 2 . 5 gm 4-~-ydlo~y~henyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 100 gm Polyacrylic acid (2596 wt solution) 10 gm Victoria Blue BOH 3 gm The PS plate so prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the following 15 formula and then gummed up to give a lithographic printing plate.
Developer ~I "~n nt ~ Weight( Phenyl Cellosolve 3 . 75%
20 Di-Ethanolamine 1. 3%
Sodium Dibutylnapthalene Sulfonate 1. 25%
Deionized water 93 . 7%
The processed plate was mounted on a newspaper printing press and ran with PSI alkaline fountain 25 solution. The plate so made provided excellent ink-water balance, but only fair alkaline resistance on press. The results are outlined below in Table I.
~1~738~
COMPARATIVE EXAMPLE
Example 4 An aluminum plate of 1100 Alloy raw coil having a thickness of 0.30 mm was degreased and cleanea by 5 dipping in a mixture of 1% Trisodium Phosphate and 2%
Sodium Netha Silicate solution at 70~C for 10 seconds.
The aluminum plate was then surface-roughened by mechanical graining with a 25-30% slurry concentration of #290 abrasive Silica material to obtain an optical density reading between 0 . 23 to 0 . 27 .
Thereafter the Al ~ plate was etched with 12% Sodium lIydroxide solution at 55C for 7.4 seconds.
After washing with water, the aluminum substrate was neutralized with 12.596 of aqueous Nitric Acid solution, 15 washed with water and then anodized in a 16 . 5% Aqueous Sulfuric Acid solution to yield an anodic coating weight of 200 mg per square foot.
After anodizing the Alllminllm substrate was dipped in 2.5% aqueous sodium silicate solution at 80C
20 for 12 seconds, washed with water and dried. Substrate so made provided only fair ink-water balance on the press .
A light-sensitive solution having the following formulation was applied onto the surface of the 25 substrate. The amount of the light-sensitive solution weighed after drying was 1.12 g/m2.
` 214~388 Light-Sensitive Coating Solution C~ L Weight ( g ) Methyl Cellosolve 300 gm PF6 salt of a polymer of 5diphenylamine-4-diazonium salt with formaldehyde and 4-hydroxy benzoic acid 2 . 5 gm 4-11ydlu~-y~henyl methacrylamide-acrylonitrile-ethylacrylate-methacrylic acid copolymer 100 gm Polyacrylic acid (25% wt solution) 10 gm Victoria Blue BOE 3 gm The PS plate 80 prepared was exposed to light from a 6 KW metal halide lamp at a distance of 71 cm through a negative film for 24 seconds. The plate was then developed with a developer having the following 15 formula and then gummed up to give a lithographic printing plate.
Developer C~ ^~ t Weight ( % ) Phynyl Cellosolve 3 . 75%
Di-Ethanolamine 1.3%
Sodium Dibutylnapthalene Sulfonate 1. 25%
Deionized water 93 . 7%
The processed plate was mounted on a newspaper printing press and ran with PSI alkaline fountain 25 solution. The plate 80 made provided only fair ink-water balance and poor ~ nP resistance on press. The results are reported below in Table I.
21 ~ 7388 TABLE I
Characteri6tic Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ink-Water Balance 5 5 5 3 Alkaline Resistance 5 3 2 0 Note: Table I uses a 0-5 sliding scale in which 5 =
excellent and O = poor.
In view of the above, it will be seen that the several ob; ects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above methods and compositions without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.
Claims (45)
1. A lithographic printing plate comprising a layer of a photosensitive composition containing a diazo resin on an aluminum substrate, the substrate having been grained, etched by application of a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight, and hydrophilized.
2. A lithographic printing plate as set forth in claim 1 wherein the photosensitive composition contains (a) a photosensitive diazo resin comprising a condensation product of an aromatic diazonium salt, a co-polymerizable compound free of diazonium groups and an active carbonyl-containing compound and (b) a binder.
3. A lithographic printing plate as set forth in claim 2 wherein the binder comprises a high molecular weight acrylic co-polymer.
4. A printing plate as set forth in claim 1 wherein the grained, etched and hydrophilized substrate has an optical density of at least 0.38.
5. A printing plate as set forth in claim 1 wherein the substrate has been etched at a temperature of from about 45°C to about 80°C.
6. A printing plate as set forth in claim 3 wherein the ratio of (a) to (b) is from about 0.05/1.0 to about 0.08/1Ø
7. A printing plate as set forth in claim 6 wherein the ratio of (a) to (b) is about 0.06/1Ø
8. A printing plate as set forth in claim 3 wherein (a) is a copolymer containing the recurring monomer units having the general formula (I):
wherein R1, R, and R3 each denote separately a hydrogen atom, a halogen atom, an alkyl group having from 1 to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF4, R is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of R4 and R5 is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, -SO3H or its salt, or -SO2H or its salt, R6 is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, and wherein the ratio of m to n is from about 70:30 to about 85:15, and (a) has an average molecular weight of from about 2,000 to about 3,000.
wherein R1, R, and R3 each denote separately a hydrogen atom, a halogen atom, an alkyl group having from 1 to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF4, R is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of R4 and R5 is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, -SO3H or its salt, or -SO2H or its salt, R6 is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, and wherein the ratio of m to n is from about 70:30 to about 85:15, and (a) has an average molecular weight of from about 2,000 to about 3,000.
9. A printing plate as set forth in claim 8 wherein the ratio of m to n is from about 75:25 to about 81:19.
10. A printing plate as set forth in claim 8 wherein R is a hydrogen atom and at least one of R4 and R5 is carboxyl.
11. A printing plate as set forth in claim 8 wherein R is a hydrogen atom and at least one of R4 and R5 is hydroxyl.
12. A printing plate as set forth in claim 3 wherein (b) is an acrylic copolymer containing the recurring monomer units having the following general formula (II):
wherein R7, R8, and R9 are independently a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms, and R10 is an alkyl group having from 1 to 3 carbon atoms or a phenyl group, j is a number from 20 to 30, k is a number from 50 to 70, and 1 a number from 4 to 14, (b) having an average molecular weight of from about 50,000 to about 150,000, and having an acid number of from 20-100.
wherein R7, R8, and R9 are independently a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms, and R10 is an alkyl group having from 1 to 3 carbon atoms or a phenyl group, j is a number from 20 to 30, k is a number from 50 to 70, and 1 a number from 4 to 14, (b) having an average molecular weight of from about 50,000 to about 150,000, and having an acid number of from 20-100.
13. A lithographic printing plate as set forth in claim 12 wherein the ratio of (a) to (b) by weight is from about 0.042/1.0 to about 0.12/1Ø
14. A lithographic printing plate as set forth in claim 13 wherein the ratio of (a) to (b) by weight is from about 0.050/1.0 to about 0.08/1Ø
15. A lithographic printing plate as set forth in claim 12 wherein the acrylic copolymer further comprises an acrylamide or a methacrylamide recurring monomer unit.
16. A lithographic printing plate as set forth in claim 3 wherein (a) comprises a hexafluorophosphate salt of the polymer of 4-diazodiphenylamine with formaldehyde and 4-hydroxy benzoic acid, (b) comprises a co-polymer of 4-hydroxyphenyl methacrylamide, acrylonitrile, ethylacrylate, and methacrylic acid, and the ratio of (a) to (b) is from about 0.050/1.0 to about 0.08/1Ø
17. A lithographic printing plate as set forth in claim 16 wherein the substrate has been etched at a temperature of from about 50°C to about 60°C by application of a caustic solution containing from about 3.8% to about 4.2% sodium hydroxide by weight, and wherein the grained, etched and hydrophilized substrate has an optical density of at least about 3.8.
18. A photosensitive composition comprising:
(a) a photosensitive diazo resin comprising a copolymer containing the recurring monomer units having the general formula (I):
wherein R1, R, and R3 each denote separately a hydrogen atom, a halogen atom, an alkyl group having from 1 to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF4, R is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of R4 and R5 is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, -SO3H or its salt, or -SO2H or its salt, R6 is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, and wherein the ratio of m to n is from about 70:30 to about 85:15, and (a) has an average molecular weight of from about 2,000 to about 3,000 and (b) a binder comprising a high molecular weight acrylic co-polymer, wherein the ratio of (a) to (b) by weight is from about 0.033/1 to about 0.17/1Ø
(a) a photosensitive diazo resin comprising a copolymer containing the recurring monomer units having the general formula (I):
wherein R1, R, and R3 each denote separately a hydrogen atom, a halogen atom, an alkyl group having from 1 to 3 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms, X denotes PF6 or BF4, R is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, at least one of R4 and R5 is hydroxyl or carboxyl and the other is a hydrogen atom, hydroxyl, carboxyl, an alkyl group having from 1 to 3 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, halogen, -SO3H or its salt, or -SO2H or its salt, R6 is a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or a phenyl group, and wherein the ratio of m to n is from about 70:30 to about 85:15, and (a) has an average molecular weight of from about 2,000 to about 3,000 and (b) a binder comprising a high molecular weight acrylic co-polymer, wherein the ratio of (a) to (b) by weight is from about 0.033/1 to about 0.17/1Ø
19. A photosensitive composition as set forth in claim 18 wherein the ratio of m to n is from about 75:25 to about 81:19.
20. A photosensitive composition as set forth in claim 18 wherein R is a hydrogen atom and at least one of R4 and R5 is carboxyl.
21. A photosensitive composition as set forth in claim 18 wherein R is a hydrogen atom and at least one of R4 and R5 is hydroxyl.
22. A photosensitive composition as set forth in claim 18 wherein the ratio of (a) to (b) by weight is from about 0.042/1.0 to about 0.12/1Ø
23. A photosensitive composition as set forth in claim 22 wherein the ratio of (a) to (b) by weight is from about 0.050/1.0 to about 0.08/1Ø
24. A photosensitive composition as set forth in claim 18 wherein (b) comprises an acrylic copolymer containing the recurring monomer units having the following general formula (II):
wherein R7, R8, and R9 are independently a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms and R10 is an alkyl group having from 1 to 3 carbon atoms or a phenyl group, j is a number from 20 to 30, k is a number from 50 to 70, and l a number from 4 to 14, (b) has an average molecular weight of from about 50,000 to about 150,000, and (b) has an acid number of from 20-100 .
wherein R7, R8, and R9 are independently a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms and R10 is an alkyl group having from 1 to 3 carbon atoms or a phenyl group, j is a number from 20 to 30, k is a number from 50 to 70, and l a number from 4 to 14, (b) has an average molecular weight of from about 50,000 to about 150,000, and (b) has an acid number of from 20-100 .
25. A photosensitive composition as set forth in claim 24 wherein R7 and R8 are hydrogen atoms, R9 is methyl and R10 is ethyl.
26. A photosensitive composition as set forth in claim 24 wherein the acrylic copolymer further comprises an acrylamide or methacrylamide recurring monomer unit.
27. A photosensitive composition as set forth in claim 18 wherein (a) comprises a hexafluorophosphate salt of the polymer of 4-diazodiphenylamine with formaldehyde and 4-hydroxy benzoic acid, (b) comprises a co-polymer of 4-hydroxyphenyl methacrylamide, acrylonitrile, ethylacrylate, and methacrylic acid, and the ratio of (a) to (b) is from about 0.050/1.0 to about 0.08/1Ø
28. A process for producing a photosensitive printing plate comprising:
(a) graining an aluminum substrate, (b) etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4. 75% of an alkali metal hydroxide by weight, (c) hydrophilizing the aluminum substrate, (d) coating the substrate with a layer of the photosensitive composition of claim 18, and (e) drying the photosensitive printing plate thereby produced.
(a) graining an aluminum substrate, (b) etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4. 75% of an alkali metal hydroxide by weight, (c) hydrophilizing the aluminum substrate, (d) coating the substrate with a layer of the photosensitive composition of claim 18, and (e) drying the photosensitive printing plate thereby produced.
29. A process for producing a photosensitive printing plate comprising:
(a) graining an aluminum substrate, (b) etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight at a temperature of from about 45°C to about 80°C, (c) hydrophilizing the aluminum substrate, (c) coating the substrate with a layer of a photosensitive composition containing a photosensitive diazo resin and a binder, and (d) drying the photosensitive printing plate thereby produced.
(a) graining an aluminum substrate, (b) etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight at a temperature of from about 45°C to about 80°C, (c) hydrophilizing the aluminum substrate, (c) coating the substrate with a layer of a photosensitive composition containing a photosensitive diazo resin and a binder, and (d) drying the photosensitive printing plate thereby produced.
30. A process as set forth in claim 29 wherein the contact time of the substrate with the caustic solution is from about 5 seconds to about 10 seconds.
31. A process as set forth in claim 29 wherein the caustic solution contains from 3.8% to 4.2% of an alkali metal hydroxide by weight.
32. A process as set forth in claim 29 wherein the caustic solution contains sodium hydroxide.
33. A process as set forth in claim 29 wherein the aluminum substrate is mechanically grained.
34. A process as set forth in claim 29 further comprising anodizing the substrate after etching the substrate.
35. A process as set forth in claim 29 wherein the photosensitive coating is the composition of claim 24.
36. A process as set forth in claim 29 wherein the photosensitive coating is the composition of claim 27.
37. A process as set forth in claim 29 wherein the aluminum substrate is etched to an optical density of at least about 0.38.
38. A treated aluminum substrate prepared by the steps comprising graining the aluminum substrate, etching the aluminum substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight, and hydrophilizing the aluminum substrate, thus producing the treated aluminum substrate having an optical density of at least about 0.38 .
39. A treated aluminum substrate as set forth in claim 38 wherein the caustic solution is heated to a temperature from about 50°C to about 60°C.
40. A treated aluminum substrate as set forth in claim 38 wherein the aluminum substrate is mechanically grained.
41. A treated aluminum substrate as set forth in claim 40 wherein the caustic solution used to etch the substrate contains from about 3.8% to about 4.2% sodium hydroxide by weight, and has been heated to a temperature of about 55°C.
42. A process for producing a treated aluminum substrate comprising:
(a) graining an aluminum substrate, (b) etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight, and (c) hydrophilizing the aluminum substrate.
(a) graining an aluminum substrate, (b) etching the grained substrate by contacting it with a caustic solution containing from about 1.0% to about 4.75% of an alkali metal hydroxide by weight, and (c) hydrophilizing the aluminum substrate.
43. A process as set forth in claim 42 wherein the aluminum substrate is etched to an optical density reading of at least about 0.38 .
44. A process as set forth in claim 42 wherein the aluminum substrate is etched in a caustic solution heated to a temperature from about 50°C to about 60°C.
45. A process as set forth in claim 42 wherein the caustic solution contains from 3.8% to 4.2% of an alkali metal hydroxide by weight.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40060495A | 1995-03-08 | 1995-03-08 | |
| US08/400,604 | 1995-03-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2147388A1 true CA2147388A1 (en) | 1996-09-09 |
Family
ID=23584276
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2147388 Abandoned CA2147388A1 (en) | 1995-03-08 | 1995-04-18 | Method for manufacturing superior ink-water balance and alkaline resistant ps plates |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2147388A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7682776B2 (en) * | 2005-07-05 | 2010-03-23 | Gary Ganghui Teng | Negative lithographic printing plate having darker aluminum substrate |
-
1995
- 1995-04-18 CA CA 2147388 patent/CA2147388A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7682776B2 (en) * | 2005-07-05 | 2010-03-23 | Gary Ganghui Teng | Negative lithographic printing plate having darker aluminum substrate |
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