US3276361A - Deletion fluid - Google Patents

Description

United States Patent 3,276,361 DELETION FLUID Thomas I. Abbott and Donaid A. Smith, both of Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jerse No Drawing. Filed Aug. 17, 1965, Ser. No. 480,510 29 Claims. (Cl. Mil-149.2)

This invention concerns a deletion fluid and a process of using the deletion fluid to delete printing areas from a lithographic plate comprising an oleophilic oxidized image area in hardened colloid.

In one method of preparing lithographic printing plates photographically, as described in Yackel and Abbott, US. Patent 3,146,104, issued August 25, 1964, a developable silver halide image is formed by means of exposure to a line or half-tone subject in a hardened hydrophilic organic colloid-silver halide emulsion such as a gelatino-silver halide emulsion.

Development is carried out using polyhydroxybenzene silver halide developer, which is either present in the emulsion or a layer effectively adjacent thereto. When the developer is oxidized in the development reaction in the presence of the hydrophilic organic colloid vehicle present in the silver halide emulsion layer, an oleophilic image is formed. Upon inking the moistened plate with a greasy ink and printing in a lithographic printing press the desired lithographic reproduction, which is negative to the original subject is obtained.

If, however, a positive working plate is desired, the photographic element described above may contain, in addition, a fogged silver halide emulsion as the uppermost layer. When this photographic element is exposed to a subject, and its contiguous silver halide developing agent activated, the developing agent reacts with the sensitive lower silver halide emulsion layer to form the negative image, and the unused silver halide developing agent present in the unexposed areas of the sensitive lower silver halide emulsion layer then migrates upward to the fogged silver halide emulsion layer, and when oxidized in the presence of a hydrophilic organic colloid present in this layer, forms an oleophilic image in the surface which is positive in respect to the original subject.

Occasionally it is desirable to delete part of the image on the lithographic plate prepared as above without affecting the remaining areas. Moreover, it has been desirable to delete areas from a plate which has completed a partial run so that the plate with the modified image can then be used to make additional copies with the undeleted areas unaffected.

Many agents have been applied to lithographic plates prepared as above in an attempt to delete the image. Among these have been metal salts, gums, latexes, gelatin, dichromate bleaches, and silica. None of these treatments permanently remove the image without producing other effects such as press contamination, etc. Mechanical means, such as rubbing the undesired image area with fine steel wool, have also been unsatisfactory.

One of the temporary deletion systems operates by the precipitation of a hydrophilic pigment in the area to be deleted so that the hydrophobic character of the image is overcome. Such precipitates being loosely bound in the gelatin structure are soon extracted and the hydrophobic image prevails. If a replenishment is carried out through the fountain solution so that new precipitate is continually being formed then permanent deletion can be accomplished. Such systems require special fountain solution preparations which often are not compatible with other lithographic plates.

We have found that an aqueous solution containing a hardenable polymer can be used to delete the image on 3,276,351 Patented Oct. 4, 1966 a processed photographic lithographic plate by crosslinking of the polymer with the oleophilic image.

One object of this invention is to provide a deletion solution for use in deleting the image from a photographic lithographic plate comprising a tanned image area in hardened colloid. An additional object is to provide a process for deleting the image from a photographic lithographic plate comprising a tanned image area in hardened colloid. An additional object is to provide a method of deleting an image from a hardened gelatin colloid layer containing therein oleophilic areas by means of a hardenable polymer which is crosslinked on the areas to be deleted. A further object is to provide a deletion method which can be used with conventional fountain solutions and which results in permanent deletion by forming a hydrophilic polymer on the areas to be deleted.

The above objects are attained by treating the surface of the plate with a solution of at least 2 percent watersoluble polymer, for example, water-soluble copolymer of acrylamide and N-methacryloyl-N-cyano-acetyl hydrazine. The useful range is from 2 to 8 percent. Much larger concentrations may be used if desired with good deletion. The area to be deleted is then coated with .a solution of cross-linking agent, such as, for example, a 10 percent aqueous formaldehyde solution. Sufficient cross-linking agent must be used, but the particular amount may be varied depending upon the polymer used, the cross-linking agent, etc. The water-soluble polymer which may be used in carrying out the invention is a matter of choice, provided that it results in covering the area to be treated with a hydrophilic polymer which is firmly bound to the lithographic surface in the area from which the hydrophobic printing area is to be omitted. The hydrophilic polymer covers the formerly oleophilic area so that printing no longer takes place in all of those areas wherein the polymer is firmly bound to the gelatin.

A large number of water-soluble polymers which are capable of being cross-linked or hardened may be used including, for example, polyvinyl alcohol, copolymers of acrylamide and N-cyanoacetyl-N'-methacryloyl hydrazine with 5090 mole percent acrylamide, copolymers of N- glycyl-N'-methacryloyl hydrazine hydrochloride with sodium-3-acryloyloxypropane-lssulfonate (-95 mole percent) or with acrylamide (70 97.5 mole percent), etc.

In a particularly useful embodiment of the invention, the cross-linkable polymer and the cross-linking agent are mixed together before applying to the lithographic plate.

It will also be appreciated that the deletion fluid may contain other components such as thickener, and the like, provided these components do not react adversely with the polymer or its cross-linking reaction. Suitable thickneners include hydrophilic organic colloids such as, for example, gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, starch, guar gum, etc.

The deletion fluid may be applied by a swab, brush, quill, sponge, or by other means which will delineate the area to be deleted. If prepared in a viscous form, it may be squeezed from a compressible tube. Although it is preferable that the deletion fluid may be applied to the moist plate, it can be applied to a plate which is in a dried-down condition. However, the ink should be removed from any area to be treated sufficiently to insure adhesion to the gelatin surface.

The following examples are intended to illustrate the practice of our invention but not to limit it in any way.

Example 1 A lithographic plate was prepared as follows according to Yackel et al. US. Patent 3,146,104.

"a o A photographic emulsion was prepared by combining the following ingredients:

Fine grain silver chloride emulsion containing 1 mole of Ag per 4350 cc. g 43.5

Parafiin dispersion prepared as follows: 80 g. molten parafiin dispersed in 400 cc. photographic The emulsion was coated at 6.5 grams per sq. foot on a film base and dried.

The film was exposed to a line negative, then activated for seconds in a 4 percent solution of sodium carbonate monohydrate. The development was stopped in an acidic stop bath by a 20-second immersion. After drying, a portion of the image area was treated in the following way to render it non-printing. A solution of a 90:10 weight percent copolymer of acrylamide and N cyanoacetyl N methacryloyl hydrazine in distilled water, made up to 12 percent by weight of the polymer, was brushed onto the plate with a small brush. The polymer was prepared as in Example 12 of U.S. Patent 2,940,956. The area to which the polymer had been applied was then brushed with a 10 percent aqueous formaldehyde solution and permitted to dry. When the plate was run on a standard lithographic press using conventional inks and acid fountain solution, all printing areas reproduced well and the area treated as above showed no printing or scumming. Thirteen hundred copies were made. Other copolymers of the class described in U.S. Patent 2,940,956 were tested in a similar manner using formaldehyde as the hardening agent with similar results.

Example 2 As a matter of convenience in the application of the polymer solution to the lithographic printing plate, pigment may be added. Barium sulfate was used as a suitable pigment. Similarly, a dye may also be used for purposes of identifying the extent of coverage during the application step as illustrated below.

T o 15 grams of the polymer used in Example 1, 10 percent aqueous solution was added ml. of distilled water and 10 grams of a 30 percent BaSO aqueous slurry. This was ball milled for 1 /2 hours.

The above polymer-B2180 slurry was brushed over a dried processed plate as described in Example 1. Immediately afterward, a 10 percent aqueous solution of formaldehyde, which contained 1 drop of 54 percent acid magenta dye (Color Index 692) aqueous solution per 10 ml. was brushed over the polymer, BaSO slurry. The combination was again dried and press run as in Example 1. Good deletion resulted.

Example 3 A printing plate prepared by the transfer process described in Example 7 of U.S. Patent 3,146,104 was run in the customary manner to produce good copies.

After normal printing, the excess ink was removed from the plate surface by raising the ink rollers and letting the ink on the printing area run out on paper 4i stock. An area containing a column of printing characteristics was deleted from further printing in the following way.

A solution containing 2 ml. of a 9 percent solution of a poly(vinyl acetal) of 2,4 disulfobenzaldehyde at pH 0.7 plus 2 drops of a wetting agent was rubbed into an inking area with a cotton swab. Over this and while still wet, a solution of 5 percent glutaraldehyde in distilled water was also rubbed in with a cotton swab. After waiting 30 seconds, a continuation of the press run showed no printing where the reactants had been applied while normal printing occurred elsewhere.

The reverse order of application was done. The wetting agent solution was added to the glutaraldehyde solution and this was applied to the plate with the ink removed. Then the polymer solution was added over the glutaraldehyde. This was dried for 15 seconds in warm air from a gun type hair dryer. Excellent deletion was observed.

Example 4 The process of our invention is applicable to all those polymer-hardener combinations which provide crosslinking of a hydrophilic polymer to the gelatin of the processed plate of the type described in U.S. Patent 3,146,104. Any polymer-copolymer combination which contains suflicient sites which may be crosslinked to the gelatin plate surface to provide a hydrophilic surface may be used. Such hydrophilic polymers may be selected from those which contain active hydrogen atoms, e.g., active methylene, hydroxyl, amino, amido and carboxyl groups. Suitable hardening agents, such as dialdehydes, dihydric alcohols, diamines, bis-epoxides, bis-aziridines, dicarboxylic esters, diisocyanates including the bisulfite derivatives thereof, etc., may be used in place of formaldehyde.

Example 5 In some instances it is advantageous to apply a mixture of the hardener and the polymer at the same time. The following example illustrates such an embodiment.

Fifty-eight grams of a 10 percent aqueous solution of a poly(vinyl acetal) of 2,4-disulfobenzaldehyde at pH 1.8 was combined with 5.8 grams of titanium oxide and ball milled for 20 hours.

Five ml. of a 30 percent aqueous glyoxal solution was added to 50 grams of the above slurry.

A printing plate prepared as in Example 4 of U.S. Patent 3,146,104 was run on a Multilith press with normal treatment to produce good copies.

After normal printing, the excess ink was removed from the plate surface by raising the ink rollers and letting the ink on the printing area run out on paper stock. The last traces of ink were removed in the general area to be deleted by rubbing with a cotton swab containing 0.6 ml. of a surfactant per ml. of distilled water.

Without drying, the solution of polymer and hardener above was brushed carefully over the particular area to be deleted. This area was dried for about 15 seconds in warm air from a gun type hair dryer. The plate was then rewetted overall with fountain solution and normal printing was resumed but with complete deletion of the desired area.

Example 6 Fifty-eight grams of a 10% aqueous solution of poly(vinyl alcohol), 100% hydrolyzed, was combined with 5.8 grams of titanium oxide and ball milled for 20 hours. A second dispersion was made in a similar manner except that 88% hydrolyzed poly(vinyl alcohol) was utilized therein.

Five ml. of a 30 percent aqueous glyoxalsolution Was added to 50 grams of each of the above slurries.

Printing plates prepared as in Example 4 of US. Patent 3,146,104 was run on a Multilith press with normal treatment to produce good copies.

After normal printing, the excess ink was removed from the plate surface by raising the ink rollers and letting the ink on the printing area run out on paper stock. The last traces of ink were removed in the general area to be deleted by rubbing with a cotton swab containing 0.6 ml. of a surfactant per 100 ml. of distilled water.

Without drying, the solution of polymer and hardener above was brushed carefully over the particular area to be deleted. This area was dried for about seconds in warm air from a gun type hair dryer. The plate was then rewetted overall with fountain solution and normal printing was resumed but with complete deletion in the desired area.

Example 7 Other embodiments employing a hardened colloid layer containing an oleophilic tanned image are also treated with the deletion fluid with satisfactory results. These include those of the positive-positive process, wherein the developer is in a layer under the silver halide emulsion and wherein a fogged silver halide emulsion is coated over the positive-negative element, as well as those wherein the image is obtained by the diffusion transfer process, by the colloid transfer process, etc. In each instance, the lithographic plate carries a gelatin layer which contains oxidation agents which render the gelatin oleophilic in the image area and the gelatin has a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin, i.e., it should have a melting point in water greater than 150 F. and preferably greater than 200 F.

Example 8 Lithographic plates prepared as in Example 1 were taken olf the lithographic press after having made 40 good copies and subjected to treatment as in Example 1. Commercial bleach comprising a bic-hromate-sulfuric acid combination gave bad toning. Colloidal silica in an aqueous suspension resulted in deleting the image temporarily but it returned after several prints. Excess silica builds up in the fountain, causing an obliteration of the complete image on the plate and contaminating the press.

Commercially available sodium hypochlorite not only did not remove the image area treated but rendered this area ink receptive. Sodium hydroxide resulted in complete obliteration of the plate surface. Metal salts, gelatin and tannic acid were also unsuccessful.

It will be appreciated that the support on which the lithographic plate is coated may be any of the customary supports used for lithographic plates. Moreover, the components of the sensitive elements of the lithographic plate can be varied appreciably in the known photographic silver halide emulsions such as silver chloride, silver bromide, silver iodide, silver bromochloride, silver bromoiodide, and silver bromochloroiodide emulsions. Direct positive emulsions may be used such as those described in Leermaker U.S. Patent 2,184,013; Kendall and Hill U.S. 2,541,472; Fallesen U.S. 2,497,875, etc.

A variety of hydrophilic organic colloid vehicles can be used for the silver halide emulsions for making the plate. Proteins such as gelatin, soy bean protein, casein, as well as synthetic organic colloids which are hydrophilic, such as polyvinyl alcohol, hydrolyzed cellulose esters, etc., may be used to the extent that they form the desired oleophilic image with the oxidized developing agent in the development reaction.

It will be appreciated, of course, that our method of deletion may also be used on lithographic plates prepared by other methods than those described above. For example, lithographic plates made by using light-sensitive polymers, for example, diazo sensitized, electrostatically formed plates, mechanically prepared plates, etc. may be used providing adhesion is obtained between the hydrophilic polymer and the areas to be deleted.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the inven tion as described hereinabove and as defined in the appended claims.

We claim:

1. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a crosslinkable hydrophilic organic polymer and a crosslinking agent.

2. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top hydrophilic colloid layer containing an oleophilic image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a crosslinkable hydrophilic organic polymer and a crosslinking agent.

3. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a crosslinkable hydrophilic organic polymer and a crosslinking agent.

4. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a crosslinkable hydrophilic organic polymer and then coating the image area with a crosslinking agent.

5. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a'support having thereon a top hydrophilic colloid layer containing an oleophilic image area, comprising coating the image area to 'be rendered hydrophilic with an aqueous solution of a crosslinkable hydrophilic organic polymer and then coating the image area with a crosslinking agent.

6. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a crosslinkable hydrophilic organic polymer and then coating the image area with a crosslinking agent.

7. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a copolymer of acrylamide and N-cyanoacetyl-N-methacryloyl hydrazine and then coating the image area with a crosslinking agent.

8. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top hydrophilic colloid layer containing an oleophilic image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a copolymer of acrylamide and N-cyanoacetyl-N- methacryloyl hydrazine and then coating the image area with a crosslinking agent.

9. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area comprising coating the image area to be rendered hydrophilic with an aqueous solution of a copolymer of acrylamide and N- cyanoacetyl-N'-methacryloyl hydrazine and then coating the image area with a crosslinking agent.

It). A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of poly(vinyl acetal) of 2,4-disulfo-benzaldehyde and then coating with a crosslinking agent.

11. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of poly(vinyl alcohol) and then coating with a crosslinking agent.

12. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of poly(vinyl acetal) of 2,4-disulfo- 'benzaldehyde and then coating with a crosslinking agent.

13. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of poly(vinyl acetal) of 2,4-disulfobenzaldehyde and a crosslinking agent.

14. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top hydrophilic colloid layer containing an oleophilic image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of poly(vinyl alcohol) and a crosslinking agent.

15. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of poly(vinyl acetal) of 2,4-disulfobenzaldehyde and a crosslinking agent.

16. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer capable of adherence to a crosslinkable hydrophilic organic polymer by means of a crosslinking agent, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a hydrophilic polymer containing at least one active hydrogen atom which can be crosslinked to the top layer to provide a hydrophilic surface and then coating with a crosslinking agent.

17. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top hydrophilic colloid layer containing an oleophilic image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a hydrophilic polymer containing at least one active hydrogen atom which can be crosslinked to the top layer to provide a hydrophilic surface and then coating with a crosslinking agent.

18. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area comprising coating the image area to be rendered hydrophilic with an aqueous solution of a hydrophilic polymer containing at least one active hydrogen atom which can be crosslinked to the top layer to provide a hydrophilic surface and then coating with a crosslinking agent.

19. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top hydrophilic colloid layer containing an oleophilic image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a hydrophilic polymer containing at least one active hydrogen atom which can be crosslinked to the top layer and a crosslinking agent.

20. A process for rendering hydrophilic an image area on a lithographic printing plate comprising a support having thereon a top layer comprising gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area, comprising coating the image area to be rendered hydrophilic with an aqueous solution of a hydrophilic polymer containing at least one active hydrogen atom which can be crosslinked to the top layer and a crosslinking agent.

References Cited by the Examiner UNITED STATES PATENTS 7/1959 Miller. 3/1966 Nadeau 10l149.2

Claims (1)

1. A PROCESS FOR RENDERNG HYDROPHILIC AN IMAGE AREA ON A LITHOGRAPHIC PRINTING PLATE COMPRISING A SUPPORT HAVING THEREON A TOP LAYER CAPABLE OF ADHERENCE TO A CROSSLINKING HYDROPHILIC ORGANIC POLYMER BY MEANS OF A CROSSLINKING AGENT, COMPRISING COATING THE IMAGE AREA TO BE RENDERED HYDROPHILIC WITH AN AQUEOUS SOLUTION OF A CROSSLINKABLE HYDROPHILIC ORGANIC POLYMER AND A CROSSLINKING AGENT.