US3300309A

US3300309A - Moisture-resistant planographic plates and methods of producing same

Info

Publication number: US3300309A
Application number: US307025A
Authority: US
Inventors: Simon L Chu
Original assignee: Polychrome Corp
Current assignee: Polychrome Corp
Priority date: 1963-09-06
Filing date: 1963-09-06
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24
Also published as: NL6410224A; GB1055079A; DE1447916A1; DE1447916B2; BE652748A; NL128965C; SE313997B

Description

United States Patent M 3,300,309 MOISTURE-RESISTANT PLANGGRAPHIC PLATES AND METHODS OF PRODUCING SAME Simon L. Chu, New York, N.Y., assignor to Polychrome Corporation, Yonkers, NY.

N0 Drawing. Filed Sept. 6, 1963, Ser. No. 307,025 18 Claims. (Cl. 96-75) This invention relates to a novel planographic plate and in particular to a planographic plate comprising a moisture impermeable and light-harden-able coating.

The art of planographic printing depends upon the immiscibility of grease and water, upon the preferential retention of a greasy image-forming substance by the image areas, and a similar retention of an aqueous dampening fluid by the non-image areas. When a greasy image is imprinted upon a suitable surface and the entire surface is then moistened with an aqueous solution, the image areas will repel the water, and the non-image areas will retain the water. Upon subsequent applications of greasy ink, the image portions retain the ink, whereas the moist,

non-image areas repel it. The image is then transferred to paper or cloth and so on, etc., via an intermediary socalled offset or blanket cylinder, which is necessary to prevent mirror-image printing.

In the case of negative plates, a plate with a light-sensitive coating is exposed to light through a negative transparency, and the image portion of the plate becomes hard and is made insoluble to desensitizing compositions by the action of the light. The unexposed light-sensitive coating is then removed by a desensitizing solution leaving a water-receptive surface as a non-image area.

The ordinary desensitizing solution use-d in the art must completely remove the non-sensitized, i.e. non-light harddened, compound. There-fore, this non-light hardened compound must have considerable solubility in desensitizing solutions. It has been a common problem with planographic plates in the art that non-light hardened diazo compounds sufiiciently soluble to be completely removed by ordinary desensitizers are also s-ufiiciently permeable to moisture to seriously interfere with the performance of planographic plates by allowing moisture to penetrate the diazo layer, interact with interlayers between the lightsensitive diazo layer and the base plate susceptible to moisture deterioration, and even corrode the metal base plate if the particular planographic plate is metal based. For example, in plates where a K ZrF -type int-erlayer, described in US. Patent 2,946,683, lies between a diazo coating and the base, moisture penetrates the diazo coating and reacts with the interlayer in such a way as to cause the bond between the light-hardened material and the remainder of the plate to weaken. This type of action results in walk-off; that is, the disappearance of image area during printing. Furthermore, in other types of planographic plates, moisture permeates the diazo coating. reacts chemically with the interlayer, and causes the formation of unwanted image area on the plate, prematurely terminating the usefulness of the plate.

In general, the useful life of presensitized plates coated with diazo compounds is shortened and the performance of such plates is adversely affected by the above-mention-ed problems caused by the affinity of these diazo com pounds for water. These problems are especially troublesome during periods of high humidity.

It is an object of this invention to provide a moistureresistant planographic plate having a novel light-hardena-ble coating which has relatively low affinity for water and which is an intermediate addition product of a diazo with a coupling agent. Another object of the invention is to provide a moisture-resistant coating that is readily removed by ordinary desensitizers known to the art, for example those containing gum arabic, phosphoric acid,

Patented Jan. 24, 1967 and a wetting agent like sodium lauryl sulfonate which is sold under the trade name Duponol by E. I. du Pont de Nemours & Company. Another object of the invention is to provide a presensitized plate useful in long press runs because of an improved bonding of the new coating to the remainder of the plate and the improved durability of the coating material when light hardened. It is also an object of this invention to provide a light-sensitive coating for planographic plates that has reduced susceptibility to undesirable chemical reactions during dark storage and thus has an increased shelf life. It is a further object of this invention to provide a novel process by which the novel moisture-resistant coating may be applied to planographic plates.

The novel planographic plates of the present invention comprise a coating which is a product of a reaction between a diazo compound and a coupling agent which reacts with the diazo com-pound forming, surprisingly, excellent light-sensitive and moisture-resistant coatings. These coatings consist of an intermediate protective compound formed when a light-sensitive diazo is reacted with a coupling agent under such reaction condition that resinification and the resultant formation of a non-lightsensitive compound are avoided. These intermediate compounds, postulated to be addition compounds of the diazo and coupling agent, are sufiiciently resistant to moisture permeation to eliminate the aforementioned problems of specking, toning, and walk-off in normal, and even severe heat and humidity.

Diazo compounds of the type commonly used in the planographic plate industry are resinified when reacted with a coupling agent in excessively basic medium. Such a reaction is of no value as a. method of forming a protective coating for a planographic plate inasmuch as it destroys the light-sensitive potential of the diazo compound. However, applicant has discovered that coupling agents reacted in relatively acid media form a novel moisture-resistant intermediate azo addition product which also has the light-sensitive character of the original diazo compound.

Applicant has further discovered that such products are resist-ant to dark reactions, i.e. reactions occurring without exposure to light, have increased press life, and generally provide most excellent coatings for planographic printing plates.

The number of coupling agents useful for the purposes of this invention is large. They are best described by a recitation of their main characteristic, i.e. an ability to react with the chosen diazo under reaction conditions that will not cause resinification and result-ant loss of the reaction products light-sensitive characteristics. Those coupling agents reacting with the diazo in an acid medium, i.e. at a pH of about 7.5 or below, are found to be especially advantageous for the practice of the instant invention.

Among the coupling agents that are suitable for use in the reaction of the present invention are hydroxy benzophenones, diphenolic acids such as 4,4-bis(4-hydroxyphenyl)pentanoic acid, resorcinol, diresorcinol, lnaphthol-3-sulfonamide, 2-naphthol-3,6-disulfonic acid disodium salt and N-alkyl-S-sulfonanthranilic acids such as the methyl and ethyl compounds. These materials may have as substituents groups such as aldehyde, carboxyl or sulfonic groups. Group tending to impart watersolubility are favored whereas those tending to impart water-insolubility are less desirable unless their effect is counterbalanced. In fact, very little water solubility, perhaps 0.05 percent, is required of the coupling agent at normal reaction temperatures. Among the hydroxy benzophenones suitable for the present invention are 2,4-dihydroxy-benzophenone, 2-hy-droxy-4-methoxy-benzophenone, 2,2-dihydroxy-4,4'-dimethoxy-benzophenone, 2,2,

4,4-tetrahydroxy-benzophenone, sodium 2,2'-dihydroxy- 4,4-dimethoxysulfobenzophenone, 2-hydroxy-4-rnethoxy-benzophenone-S-sulfonic acid, the trihydrate of the last-named acid, and mixtures of such compounds.

num and copper are among the more suitable metals. Furthermore, plastic and paper base members are also suitable for use in constructing planographic plates of the present invention.

The 2,2-4,4'-tetrahydroxy-benzophenone is preferr d 5 Various metal-protective coatings may be used as interamong these compounds. layers between the light-sensitive coating and metal base The diazo compounds conveniently used as reactants member. Among such interlaye-rs are aluminum oxide with the above-identified coupling agents are of the type (for example, as found in anodized aluminum plates), the useful on planographic printing plates generally and which reaction products of an aqueous solution of soluble silicate are capable of reacting with the coupling agent at a pH with the met-a1 base, and reaction products of aqueous sufficiently low to avoid forming a resinified reaction prodsolutions of zirconium hexahalides, like potassium zircouct with the coupling ag P t Which h nium hexachloride, with the metal base. All of these sufiicient sensitivity to light to remain useful as a planoillustrative interlayers are known to the art. graphic plate coating. Among such compounds are the In order to point out more fully the nature of the prescondensation products of para-diazo-diphenyl-amine and ent invention, the following specific examples are given fomlaldehyde, p the condensation PTOdIIC'E 0f as various embodiments of the present process and prodp'ara-diazo-diphenyl-amine sulfate and formaldehyde zinc ucts produced thereby. chloride, and the diazo compound sold by Fairmont Chemical 00., Inc. under the trade designation Diazo Example 1 Resin No. 4 as well as other diazos which are well known An aluminum offset plate 10 inches by 15 inches and to those skilled in the art. .O05-inch thick was coated consecutively with a K ZrF In one embodiment of the instant invention, the planocoating and a light-sensitive diazo compound according graphic plate, initially having a top coating of the convento U.S. Patent 2,946,683. tional diazo compounds known to the art, is coated with a A water solution was prepared containing 0.1% saposolution of the coupling agent. This solution, in which m a d 0.5% 2,2,4,4'-tetrahydroxy-benzophenone. This the diazo is somewhat soluble, will preferably contain solution was coated over the planographic plate. After a from 0.01 to 0.5% of the coupling agent and, preferably, contact time between solution and plate of one to two secsmall quantities of additives such as a wetting agent or a ends, the excess solution was wiped off from the plate and polyhydroxy acid. This solution is coated on the diazo the plate was dried, leaving the p-latecoated with the relayer and reacts therewith forming the intermediate azo 3 action product of the diazo and 2,2',4,4'-tetrahydroxyaddition compound. Depending on circumstances such benzophenone. as concentration, temperature and the particular solvent The plate prepared at about 2050 C. a indicated employed, the reaction will be very nearly instantaneous above was exposed to a high humidity environment in a or it may take up to several minutes or more. The prodchamber with a number of other pre-sensitized lithouct of the foregoing reaction is the light-hardenable reacgraphic lates having conventional diazo coatings and tion product which is exceedingly well bonded to the plate otherwise characterized as follows: and thus has a longer press life than diazo coated plano- Plat A i a commercially-available plate having a digraphic plates even before storage deterioration. azo coating.

In another embodiment of the present invention, th Plate B is a plate comprising a silicate layer interposed diazo and coupling compounds are reacted in a solvent. 40 between the aluminum base plate and a diazo layer, the The solution containing the light-sensitive intermediate manuafcture of which is described in U.S, Patent 220 product so formed is coated onthe interlayer of the 2,922,715. planog-raphic plates. Upon the evaporation of the sol- Plate C is a plat comprising a K ZrF interlayer bevent, the moisture-resistant diazo polymer coating retween a diazo coating and an aluminum base and differs mains on the plate. from the plate prepared in accordance with this example In this latter embodiment, the reaction normally has a only in the light-sensitive coating used. greater time in which to proceed. Thus the most irn- The plates subjected to the test were exposed .at F. permeable and resistant coatings may be achieved. and 90% relative humidity.

Solvents in which the reaction may be advantageously The results of the test are shown in the following table:

CONDITION OF PLATE Plate of Ex. 1 A B C 3days Satisfactory Satisfactory Satisfactory Unsatisfactory; excussive walk off. 7 days .do Specking, unsatisfac- Speckiug, unsatisfac- 14 days do .2213) sp e c l ing and toning,

unsatisfactory. 28 days "do; Corrosion on plate, Corrosion and toning unsatisfactory. on plate, unsatis factory. 45 days .Jlo

carried out include, for example, water, alcohols such Upon treating Plates A, B and C with 2,2,4,4'-tetraas lower alkyl alcohols, acetates such as ethyl acetate, and hydroxy-benzophenone as described above, they too relower alkyl ketones. The common commercial grades of mained in satisfactory condition for 45 days when subthese solvents are used advantageously and, in deed, water jected to the indicated humidity and heat environment. contained therein is useful in promoting the desired reac- Anodized plates, mechanically grained plates, and even tion. Mixtures of the aforementioned solvents may also paper plates were also improved in moisture resistance be used. When such solvents as acetates and ketones are d ll performance h coated i h th@ i di- USCd, is preferable to include in the SOlVCTlt mixture ate E reaction product of the present invention quantities of water, preferably about 20 to 80% of the solvent. Methanol and water are two preferred solvents Example 2 for use in the present invention.

As is known in the art, various metals may be used An aluminum ofi'set plate 10 inches by 15 inches and for base members for planographic plates. Zinc, alumi- 75 .005-inch thick was coated, consecutively with a K ZrF l coating .and a light-sensitive diazo compound according to U.S. Patent 2,946,683.

A Water solution was prepared containing 0.1% saponin and 0.25 diresorcinol. This solution was coated over the planographic plate. After a contact time between solution and plate of one to two seconds, the excess solution was wiped from the plate and the plate was dried.

An azo addition product resin coated the surface which was light-hardenable and impermeable to rnoisture as indicated by its remaining in satisfactory condition even when subjected to 90% relative humidity and 90 F. for 45 days .and testing as follows:

The plate was removed from the high humidity environment, exposed to light through a negative transparency, desensitized with a conventional desensitizing agent, coated with a protective lacquer, and mounted upon a press. The nin was successful, being discontinued after 8000 prints were run off. The last copies were still excellent, indicating the fine performance of the plate,

. Example 3 An aluminum offset plate inches by inches and .OOS-inch thick was coated, consecutively with a K ZrF coating and a light-sensitive diazo compound according to U.S. Patent 2,946,683.

An isopropanol solution was prepared containing 0.1% saponin and 0.05% sodium 2.2'-dihydroxy-4,4-dimethoxy-5-sul-fobenzophenone. This solution "was coated over the planographic plate. After a contact time between solution and plate of one to two seconds, the excess solution was wiped from the plate and the plate was dried.

An azo addition product coated the surface which was light-harden-able and impermeable to moisture as indicated by its remaining-in satisfactory condition even when subjected to 90% relative humidity and 90 F. for 45 days and its performing well in the test described in Example 2.

Example 4 An aluminum offset plate 10 inches by 15 inches and .005-inch thick was coated, consecutively with a K ZrF coating and :a light-sensitive diazo compound according to U.S. Patent 2,946,683.

A 50% butyl acetate and 50% water solution was prepared containing 0.1% saponin and 0.25% 2,2,4,4-tetrahydroxy-benzophenone. This solution was coated over the planographic plate. After a contact time between solution and plate of one to two seconds, the excess solution was wiped from the plate and the plate was dried.

An azo addition product coated the surface which was light-hardenable and impermeable to moisture as indicated by its remaining in satisfactory condition even when subjected to 90% relative humidity and 90 F. for 45 days and its performing well in the test described in Example 2.

Example 5 An aluminum offset plate 10 inches by 15 inches and .005-inch thick was coated, consecutively with a K ZrF coating and :a light-sensitive diazo compound according to U.S. Patent 2,946,683.

A 50% acetone and 50% water solution was prepared containing 0.1% saponin and 0.40% N-ethyl-S-sulfoanthranilic acid. This solution was coated over the planographic plate. After a contact time between solution and plate of one to two seconds, the excess solution was wiped from the plate and the plate was dried.

An azo addition product coated the surface which was light-hardenable and impermeable to moisture as indicated by its remaining in satisfactory condition even when subjected to 90% relative humidity and 90 F. for 45 days and its performing well in the test described in Example 2. a v 1 1 1 Example 6 An aluminum offset plate 10 inches by 15 inches and .005-inch thick was coated, consecutively with a K ZrF 6 coating and a light-sensitive diazo compound according to U.S. Patent 2,946,683.

A Water and 10% ethanol solution was prepared containing 0.1% saponin and 0.15% 4,4-bis(4-hydroxyphenyl) pentanoic acid. This solution was coated over the planographic plate. After a contact time between solution and plate of one to two seconds, the excess solution was wiped from the plate and the plate was dried.

Example 7 An aluminum offset plate 10 inches by 15 inches and .005-inch thick was coated, consecutively with a K ZrF coating and a light-sensitive diazo compound according to U.S. Patent 2,946,683.

A methanol solution was prepared containing 0.1% saponin and 0.30% 1-naphthol-3-sulfonamide. This solution was coated over the planographic plate. After a contact time between solution and plate of one to two seconds, the excess solution was wiped from the plate and the plate was dried.

Example 8 An aluminum offset plate 10 inches by 15 inches and .005-inch thick was coated with a K ZrF coating according to U.S. Patent 2,946,683.

Five parts by volume water solution containing 2% of the diazo compound were mixed into four parts of isopropyl alcohol containing 5 grams of 2,2,4,4'-tetrahydroxy 'benzophenone. One part water was added to the mix, and the plate was coated therewith.

Upon wiping off the excess solvent and drying the plate, an azo addition compound coated the surface which was light-hardena'ble and impermeable to moisture as indicated by its remaining in satisfactory condition even when subjected to 90% relative humidity and 90 F. for 45 days and its performing well in the test described in Example 2.

It is of course to be understood that the foregoing examples are intended to be illustrative and that various changes can be made in the ingredients, proportions, and conditions set forth therein without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. A moisture-resistant planographic plate which comprises a base member having coated thereon a lightsensitive, moisture-resistant compound that is the reaction product of a light-sensitive diazonium compound and a phenolic hydroxyl-containing aromatic coupling agent formed in a medium having a pH of less than about 7.5 substantially to prevent resinification.

2. A moisture-resistant planographic plate which comprises a base member having coated thereon a lightsensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the reaction of a diazo compound and a reactive carbonyl-containing compound and (b) a phenolic coupling agent formed in a medium having a pH of less than about 7.5 substantially to prevent resinification.

3. A moisture-resistant planographic plate which comprises a base member having coated thereon a light-sensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the reaction of a diazo-diphenylamine and formaldehyde and (b) a phenolic compound, said reaction product being formed at a pH of less than about 7.5 substantially to prevent resinification.

4. A moisture-resistant planographic plate which comprises a base member having coated thereon a light-sensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the reaction of a diazo-diphenylamine and formaldehyde and (b) a phenolic compound selected from the group consisting of hydroxybenzophenones, diphenolic alkanoic acids, dihydroxy-benzenes, tetrahydroxy-biphenyls, naphthol sulf-onamides, naphthol sulfonic acids, naphthol sulfonic acid salts and sulfanthranilic acids, said reaction product being formed at a pH of less than about 7.5 substantially to prevent resinification.

5. A moisture-resistant planographic plate which comprises a base member having coated thereon a lightsensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the condensation of para-diazo-diphenylamine sulfate with formaldehyde zinc chloride and (b) a coupling agent selected from the group consisting of 4,4-bis (4-hydroxyphenyl)-pentanoic acid, resorcinol, diresorcinol, l naphthol-3-sulfon-amide, 2-naphthol-3,6-disulfonic acid disodium salt, N-lower alkyl-S-sulfoanthranilic acid, 2,4-dihydroxy-benzophenone, 2-hydroXy-4-methoxybenzophenone, 2,2 dihydroxy 4,4-dimethoxy-benzophenone, 2,2',4,4'-tetrahydroXy-benzophenone, sodium 2, 2 dihydroxy 4,-4-dimethoxy-5-sulfobenzophenone, 2- hydroxy 4 methoxy-benzophenone-S-sulfonic acid and 2-hydroxy-4-meth-oxy-benzophenone-S-sulfonic acid trihydrate, said reaction product being formed at a pH of less than about 7.5 substantially to prevent resinification.

6. A method for the preparation of a storagestable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive, moisture-resistant compound that is the reaction of a light-sensitive diazonium compound and a phenolic hydroxyl-containing aromatic coupling agent formed in a medium having a pH of less than about 7.5 substantially to prevent resinification.

'7. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the reaction of a diazo compound and a reactive carbonyl-containing compound and (b) a phenolic coupling agent formed in a medium having a pH of less than about 7.5 substantially to prevent resinification.

8. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the reaction of a diazodiphenylamine and formaldehyde and (b) a phenolic compound, said reaction product being formed at a pH of less than about 7.5 substantially to prevent resinification.

5 A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the reaction of a diazO-diphenylamine and formaldehyde and (b) a phenolic compound selected from the group consisting of hydroxy-benzophenones, diphenolic alkanoic acids, dihydroXy-benzenes, tetrahydroxy-biphenyls, naphthol sulfonamides, naphthol sulfonic acids, naphthol sulfonic acid salts and sulfanthranilic acids, said reaction product being formed at a pH of less than about 7.5 substantially to prevent resinification.

10. A method for the preparation of a storage-stable,

light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive moisture-resistant compound that is the reaction product of (a) a light-sensitive diazonium compound obtained by the condensation of paradiazo-diphenylamine sulfate with formaldehyde zinc chloride and (b) a coupling agent selected from the group consisting of 4,4 bis(4 hydroxyphenyl) pentanoic acid, resorcinol, diresorcinol, 1 naphthol 3 sulfon amide, 2- naphthol 3,6 disulfonic acid disodium salt, N lower alkyl 5 sulfoanthranilic acid, 2,4 dihydroxy benzophenone, 2 hydroxy 4 methoxy benzophenone, 2,2 dihydroxy 4,4 dimethoxy benzophenone, 2,2, 4,4- tetrahydroxy benzophenone, sodium 2,2 dihydroxy- 4,4 dimethoxy 5 sulfobenzophenone, 2 hydroxy- 4 methoxy benzophenone 5 sulfonic acid and 2- hydroxy 4 methoxy benzophenone 5 sulfonic acid trihydrates, said reaction product being formed at a pH of less than about 7.5 substantially to prevent resinification.

11. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate, with a light-sensitve diazonium compound, applying a phenolic hydroxyl-oontaining aromatic coupling agent to said diazonium-coated base at a pH of below about 7.5 to form a substantially unresinified light-sensitive moisture-resistant reaction product, and removing unreacted residues from said plate.

12. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive diazonium compound obtained by the reaction of a diazo compound and a reactive carbonyl-containing compound, applying a phenolic coupling agent to said diazonium-coated base at a pH of below about 7.5 to form a substantially unresinified lightsensitive moisture-resistant reaction product, and removing unreacted residues from said plate.

13. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive moisture-resistant compound that is the reaction product of a light-sensitive diazonium compound obtained by the reaction of a diazo-diphenylamine and formaldehyde, applying a phenolic coupling agent to said diazonium-coated base at a pH of below about 7.5 to form a substantially unresinified light-sensitive moisture-resistant reaction product, and removing unreacted residues from said plate.

14. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive diazonium compound obtained by the reaction of diazo-dipheuylamine and formaldehyde, applying a phenolic coupling agent selected from the group consisting of hydroxybenzophenones, diphenolic alkanoic acids, dihydroxy-benzenes, tetrahydroxybiphenyls, naphthol sulfonamides, naphthol sulfonic acids, naphthol sulfonic acid salts and sulfanthranilic acids to said diazonium-coated base at a pH of below about 7.5 to form a substantially unresinified light-sensitive moisture-resistant reaction product, and removing unreacted residues from said plate.

15. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate with a light-sensitive diazonium compound obtained by the condensation of para-diazo-diphenylamine sulfate with formaldehyde zinc chloride, applying a phenolic coupling agent selected from the group consisting of 4,4- bis(4 hydroxyphenyl) pentanoic acid, resorcinol, diresorcinol, 1 naphthol 3 sulfon amide, 2 naphthol- 3,6 disulfonic acid disodium salt, N lower alkyl 5- sulfoanthranilic acid, 2,4 dihydroxy benzophenone, 2-

hydroxy 4 methoxy benzophenone, 2,2 dihydroxy- 4,4 dimethoxy benzophenone, 2,2, 4,4 tetrahydroxybenzophenone, sodium 2,2 dihydroxy 4,4 dimethoxy 5 sulfobenzophenone, 2 hydroxy 4 methoxybenzophenone 5 sulphonic acid and 2 hydroxy 4- methoxy benzophenone 5 sulfonic acid trihydrates to said diazonium-coated base at a pH of below about 7.5 to form a substantial unresinified light-sensitive moisture-resistant reaction product, and removing unreacted residues from said plate.

16. A moisture-resistant planographic plate which comprises a base member having coated thereon a light-sensitive, moisture-resistant compound that is the reaction product of a light-sensitive diphenylamine diazonium compound and a phenolic hydroxyl-containing aromatic coupling agent formed in a medium having a pH of less than about 7.5 substantially to prevent resinification.

17. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating a base for said planographic plate With a light-sensitive, moisture-resistant compound that is the reaction product of a light-sensitive diphenylamine diazonium compound and a phenolic hydroxylcontaining aromatic coupling agent formed in a medium having a pH of less than about 7.5 substantially to prevent resinification.

18. A method for the preparation of a storage-stable, light-sensitive, moisture-resistant planographic plate which comprises coating 21 base for said planographic plate with a light-sensitive diphenylamine diazonium compound, applying a phenolic hydroxyl-containing aromatic coupling agent to said diazonium-coated base at a pH of less than about 7.5 to form a substantially unresinified light-sensitive moisture-resistant reaction product, and removing unreacted residue from said plate.

References Cited by the Examiner UNITED STATES PATENTS 2,702,242 2/1955 Neugebauer et a1. 9633 2,946,683 7/1960 Mellan et a1. 96-33 3,169,864 2/ 1965 Holmen 9675 3,186,845 6/1965 Sus et al. 96--75 3,210,184 10/1965 Uhlig.

J. TRAVIS BROWN, Acting Primary Examiner.

ALEXANDER D. RICCI, Examiner.

Claims

1. A MOISTURE-RESISTANT PLANTOGRAPHIC PLATE WHICH COMPRISES A BASE MEMBER HAVING COATED THEREON A LIGHTSENSITIVE, MOISTURE-RESISTANT COMPOUND THAT IS THE REACTION PRODUCT OF A LIGHT-SENSITIVE DIAZONIUM COMPOUND AND A PHENOLIC HYDROXYL-CONTAINING AROMATIC COUPLING AGENT FORMED IN A MEDIUM HAVING A PH OF LESS THAN ABOUT 7.5 SUBSTANTIALLY TO PREVENT RESINIFICATION.