US3070008A - Oxide image printing plate - Google Patents

Description

Dec. 25, 1962 w. c. 'HUEBNER OXIDE IMAGE PRINTING PLATE Filed Feb. 2, 1959 INVENTOR ATTORNEY ilnited States 3,7,3 Patented Dec. 25, i952 ice 3,ii7tl,0tl8 @XTDE IMAGE PRENTHNG PLATE William C. l-lluebner, we Mamaronech Ave, Mamaroneclr, N .Y. Fiied Feb. 2, 1959, Ser. No. 790,586 2 Claims. (Cl. Till-449.2)

This invention relates to improvements in printing elements or press plates of the general type disclosed in my Patent No. 2,042,003 of May 26, 1936 .and to a method of rnalcing the same.

The life or durability of printing elements or press plates depends upon the nature of both the ink-retaining and ink-repellent surfaces, so that they are capable of resisting deterioration or Wearing down during the printing operation. When either of these surfaces becomes Worn down to a material extent, the printed matter is no longer .clear, and if further printed matter is required similar to that which has been produced by the plate in question, then a new plate must be made.

It is consequently an object of this invention to provide a printing element having ink-retaining and inkrepellent surfaces which are capable of long use in a printing apparatus.

Another object of this invention is to provide a printing plate in which the image portion of the plate is oxidized by a series of steps and by use of materials which result in a printing plate capable of use on any type of printing press including offset, letter press or gravure, and which is more durable than similar plates heretofore produced and from which consequently longer editions can be printed.

A further object is to provide a printing plate with an improved ink-repellent surface.

In printing plates of this type, the surfaces of the plate which repel the ink are generally made ink-repellent by various well-known plate etch desentizers, and during printing, by water to which fountain etches are added. The water thus treated is applied to a dampener roller by dipping and rolling over the entire plate area while the press is running.

It is consequently necessary in order to produce high grade printing that the ink-repellent surfaces have an ample supply of Water and fountain-etch solution to prevent the ink rollers from depositing ink on the nonprinting areas.

The nature of Water fountain solutions heretofore used by the water rollers during printing tend to emulsify the ink. Thus water-logged ink loses its brilliancy. The resulting inferior printing also produces a constantly alternating battle for the operator to attain a uniformly printed edition since too much Water produces a grey impression, and too little Water enables the ink to take hold on the non-printing areas.

It is consequently another object of this invention to provide a printing plate with an ink-repellent coating which has a high capacity of retaining an ink-repellent compound of metallic salts in solution and applied to the non-printing areas by humid air.

A further object of this invention is to provide a light sensitive coating for printing plates that is conductive of electric current to accelerate the movement of ink from the image area to the surface of a sheet of paper similarly treated electrically.

@ther objects will be set forth in the following description and claims.

In the accompanying drawings:

FTGS. 14 are diagrammatic sectional views of portions of a printing pl-ate illustrating successive steps in the process of preparing the plate. The thickness of the plate and the various films thereon are greatly exaggerated in order to illustrate my invention more clearly.

In carrying out my invention, the printing surface may be formed of a metal sheet or plate it which may be of steel, zinc, aluminum, copper or other metals and alloys. This plate is first thoroughly cleaned, for example, by means of a cleaning solution containing caustic potash and Water in the proportion of approximately 30 grams of caustic potash and 900 grams of water. The plate is then flushed clean with Water and a neutralizer solution is applied which contains a suitable acid. This solution may, for example, comprise approximately 30 grams of concentrated nitric acid and 909 grams of water. This .solution is flowed over the plate to neutralize any caustic cleaning solution remaining on the plate.

An ink-repellent and hygroscopic base film. ll is then applied to the cleaned surface of the metal plate. This base may, for example, be made up of the following ingredients:

(a) 11 grams of gum ar-abic powder; 109 grams of Water.

(b) 30 grams of potassium dichrornate; 300 grams of water.

(c) 10 grams of phosphoric acid-%; 60 grams of water.

(d) 10 grams lithium bromide syrup or 6 grams of lithium bromide crystals in 240 grams of water.

The steps in mixing the above are as follows:

Pour parts of b into 150 parts of u, add 30 parts of c and then add 20 parts of d.

The plate is then given a coating of the above solution, dried, and exposed to actinic light to light-harden the entire surface of the plate.

This composition has the properties of being hygroscopic and also of bonding itself securely to the metal plate and to any film or coating which may be superposed on it. Any other coating having similar properties may be applied to the metal plate.

The foregoing may be substituted for short editions as follows: The base coating may be directly exposed to a positive image in close contact and, with suit-able light-hardening action, it can be developed with Water and alcohol or the developing procedure herein after described, to clear the metal based image and to better receive the oxide-forming procedure hereinafter described.

A sensitizer gum solution is then applied to the surface of the ink-repellent base film, and this solution may be of any Well known type such as heretofore employed in connection with lithography. For example, the following ingredients may be employed in this solution.

(a) 40 grams gum arabic powder; grams of Water.

(b) 50 grams of ammonium dichromate; 160 grams of Water.

(c) Ammonia concentrate.

These parts are mixed as follows: 21 parts of b with 64 parts of a.

The ammonia is used only to lighten the color of the sensitizer solution to permit a normal exposure, but it is generally advisable to avoid using the ammonia concentrate if possible.

The next step in the process of making this printing plate is to apply a sensitized gelatin solution 12 which may, for example, consist of 900 grams of water and 50 grams of gelatin powder. The gelatin is soaked in cold water for A2 an hour and then heated to degrees While agitating, and then six grams of potassium dichromate are added to this solution. This potassium dichromate gelatin solution is mixed with 85 parts of the sensitizer gum solution comprising the parts a and b as above stated and c if necessary. This gelatin solution Will be sensitized for producing the photo image on a a the light hardened base coating or film on the metal base plate.

The plate with the base film applied thereto is flushed with water long enough to remove any soluble salts that may remain in this coating, whereupon the sensitized gum and gelatin solution is applied to cover the plate. When this coating has been dried, the plate may be put in a printing frame and exposed in contact with a positive image in close and uniform contact for the necessary exposure time.

The next step after exposure consists of supplying a developer solution to the plate. The developer solution may be made in any usual or suitable manner, for example, by adding 360 grams of calcium chloride to 900 grams of water after which 60 grams of lactic acid and grams of concentrated hydrochloric acid are added. The lactic acid is preferably 85% U.S.i This developer solution or any other suitable developer solution is poured over the exposed plate after it has been removed from the printing frame and placed on a horizontal table. This developer solution is rubbed over the upper surface of the plate with a rubber or felt pad for the necessary time to develop parts of the light sensitive coating that have been protected by the positive image. When the development has been carried on to the proper point Where the image can be seen, the plate is subjected to a remover for the developer which may, for example, comprise anhydrous denatured alcohol. This alcohol is poured over the plate and removes the developer solution. The plate should then be cleaned with a rubber squeegee until almost dry, and will then appear as illustrated in PEG. 1.

Thet next step comprises the removal of the first mentioned light-hardened base coating from the image areas, thus forming spaces or depressions M in the coating through which the metal plate is exposed, as shown in FIG. 2, and this may be accomplished by first using a pro-oxide compound or cleaner. A pro-oxide metal cleaner for the image areas consists of a perchlorate of iron solution at approximately 40 Baum, to which has been added citric or nitric acid in proportions of approximately grams of acid to 400 grams of iron solution.

An alternate step is to use a pre-oxide wash consisting of a mixture of the developer solution and perchlorate of iron, in proportions as needed up to one-half of each compound. This solution is poured over the plate and wiped with a carpet pad over the work area and is then flushed with the same alcohol above referred to. When the alcohol has been removed with a rubber squeegee and fanned dry, the following solutions are poured on the plate: First a solution of 258 grams of water with grams of potassium chromatc is poured over the entire plate to cover the work areas and is removed by a squeegee, but not dried, and immediately after an oxidizer solution is flowed over the plate. This solution may consist of 100 grams of water and 10 grams of concentrated nitric acid and is removed from the plate by draining, and the plate is then dried slowly, for example, by slow rotation in a whirler, or by any other means. The combination of these two solutions produces an oxide surface 15, FIG. 3 on those areas of the metal plate which are exposed by the depressions 14 which are to be made ink-receptive. Oleic acid on a carpet pad may be rubbed downwardly over the oxide work areas.

An oxide binder 16 is then applied to the plate which for example, may be made of 100* grams of red lead oxide powder and 28 grams of a linseed oil varnish of the type commonly used in connection with lithographic work. These two are mixed thoroughly with a mortar and pestle and are ground together and put into a container, after which this mixture is rubbed over the work areas of the plate which have been oxidized. This combination of the oxide binder with the oxidized metal of the base plate produces a foundation for the rubdown ink binder which may be made as follows: 48 grams of black etching ink are put in a container with a Preparation known as 0429, which is a hydrocarbon solution having a boiling range from 475 to 498 degrees F. This rubdown binder 17 is applied with a separate pad over the oxide binder in the image areas. The entire plate is now treated with the following ink-repeller rubdown solution, which may, for example, be made as follows:

350 grams of water are thoroughly mixed with 5 grams of a water soluble resin in the form of a carboxy vinyl polymer of extremely high molecular weight, such as commercially designated by the term carbopol 932. Then 10 grams of lithium bromide powder and 17 grams of glycerine U.S.P. are added. This solution is then neutralized by the addition of 18 grams of a caustic soda or other alkali metal solution of 10% strength. This mixture is put into a suitable glass or plastic jar and is applied with a carpet pad and rubbed manually over the entire plate. The plate is then ready for the press, FIG. 4.

After the plate has been secured in the press it may be used to print a number of copies, for example, about 50 copies, because of the moisture contained in the base coating, and the non printing surfaces of the plate to which moisture is supplied by the base coating. However, it is better to supply moisture to these ink-repelling areas before the supply of moisture in the hygroscopic portions of the coatings is lost, and this is preferably done by passing humidified air into contact with the surface of the plate. This may be done in any suitable manner, but preferably by means of any suitable humidifying apparatus. Preferably this air is humidified with a solution which may consist of grams of the above mentioned solution of water, lithium bromide, glycerine, caustic soda and carbopol, mixed with 603 grams of water. This solution is put into a container of the air humidifying apparatus and is reduced into a fog or mist which humidifies the air which is blown upon the entire surface of the printing plate. This humid air fog supplies enough of the wet ink repelling salts to the coating of ink-repelling areas to attain superior brilliancy and hold a uniform quality for the entire edition, eliminating entirely the con tact of water roller fountain and etching solutions.

To obtain this result the plate coating, which is inkrepellent, has two functions:

(1) To repel the ink from the non-printing areas. (2) To stop emulsification action of the ink.

Since there is no surplus of water compound etch on the plate during printing, the repellent coating, supplied with this humid air, retains the needed repellent action during long-run editions.

The various chemicals hereinstated have been mentioned, merely as illustrative of what may be used for the various purposes, but it is not intended to limit this invention to any of the chemicals specified except as specified in the claims, since obviously other ingredients may be substituted for those herein specified.

The new printing plate has two newly formed areas on the surface of the printing plate. One of these areas is the ink-receptive image area which is produced by a series of novel steps including an oxide bond with the metal plate which is superior in its holding power to any bond heretofore employed, and makes deeper oxide surfaces because of penetration by the materials mentioned into the metal so as to form a firm bond with the materials contacting these oxidized surfaces. The non-printing or ink-repellent areas are made up of a compound contain ing hygroscopic metal salts, such for example as lithium salts which have the characteristic of very effectively repelling greasy ink. These two areas of the printing plate cooperate with each other to form a very durable surface which makes it possible to use the printing plate with much longer editions than has heretofore been possible. So long as the ink-repellent areas are kept moist with the air moist with the ink-repellent ingredient, the printing may continue for long periods of time.

It will be understood that various changes in the details, materials and arrangements of parts Which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A printing plate having a metal base, a base coating of a hygroscopic material applied to said base, inkrepellent non-image areas on said base coating which are also hygroscopic and which repel ink when supplied with moisture obtained from humidified air, and which receive moisture from and transmit moisture to said base coating, said plate also having ink-retaining image-forming areas bonded to said metal base, said base coating being rendered hydroscopic by lithium bromide.

2. A printing plate having a metal base, a base coating of a hygroscopic material applied to said base, ink-repellent non-image areas on said base coating which are also hygroscopic and which repel ink when supplied with moisture obtained from humid air, and which receive moisture from and transmit moisture to said base coating, said plate also having ink-retaining image-forming areas bonded to said metal base, said base coating comprising gum arabic, potassium dichromate, phosphoric acid and lithium bromide.

References Cited in the file of this patent UNITED STATES PATENTS 391,065 Osborne Oct. 16, 1888 428,472 Dubois May 20, 1890 1,574,378 Dobinson Feb. 23, 1926 1,759,956 Reed et a1. May 27, 1939 1,789,138 Glaser Jan. 13, 1931 1,895,125 Darham Jan. 24, 1933 1,977,646 Rowell Oct. 23, 1934 1,992,966 Rowell Mar. 5, 1935 2,042,003 Huebner May 26, 1936 2,063,672 Goddard Dec. 8, 1936 2,178,583 Grembecki Nov. 7, 1939 FOREIGN PATENTS 6,626 Great Britain 1898 626,844 Great Britain July 22, 1949

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