US2962364A - Process and composition for developing images and designs on metal - Google Patents

Description

ZbZ'lUU United States Patent PROCESS AND COMPOSITION FOR DEVELOPING IMAGES AND DESIGNS ON METAL John M. Cornish, Morris Plains, NJ., assignor to Modern Engraving and Machine Company, Hillside, NJ a corporation of New Jersey No Drawing. Filed Aug. 15, 1958, Ser. No. 755,122

Claims. (Cl. 41-43) My invention relates to a process for forming images and designs on metal surfaces.

The etching of metal surfaces is, generally speaking, a well-known technique for forming a design on a metal surface. The method commonly employed is to cover a cleaned metal surface with a material which is impervious, or at least substantially so, to the action of an etching bath, remove portions of the material from those areas of the metal surface which are to form the design, and thereafter to treat the exposed metal surface in an etching bath. The etching bath is commonly composed of an acidic material which has the facility of eating away at least part of a metal surface by chemical action. Acids with this capability can be easily determined by reference to an electromotive series of various metals and tables of acid strengths, the chemical action primarily resulting in oxidation and dissolution of the metal with release hydrogen. Other chemical reactions can also take place and oxidizing acids or other agents effect the process in an additional manner independent of the acid strength.

However, while it is thus known how to etch metal surfaces, it is still impossible to obtain all desired surface treatments or to predict the nature of a surface treatment which will be obtained from a given treatment with etching baths containing different components and with different metals.

The achievement of my invention lies in providing a novel process for etching metal surfaces which will provide a. particular desired surface treatment, namely a frosted background comparable to that formed by final embossing. This surface effect is one that is in great demand and an etching process to form it is highly desirable.

It is, therefore, an object of my invention to provide a process employing particular types of etching materials which will achieve a particular desired surface treatment yielding a frosted background comparable to an embossed background. A further object of my invention is to provide a novel etching composition for use in such process.

The following description will fully describe my invention so that it will be understood by those skilled in the art of etching. The description will relate primarily to the technique of forming the protective coating by a photographic or light sensitive process, but it will be appreciated that this coating may be formed in other conventional ways, although with disadvantages.

The sheet of metal, aluminum, on which the design is to be etched must first be cleaned, and I prefer to do this with Tripoli powder. This cleaning is followed by treating the metal surface with pre-etch solution of hydrochloric acid substantially saturated with salt. A concentration of hydrochloric acid of is best for this stage, but concentrations within the range from 5% to may be used. After this treatment, which may last from V2 to 3 minutes at normal temperatures, the plate is dried and then coated with a suitable light sensitive material. In this process if the temperature is below 65 F., the reaction is too slow to produce the desired matte QFFEPEt- E finish, but if above F., the reaction is too violent to control, is. no resist can be made to hold in the metal. Many of these are known and commercially available and my invention is not limited to any particular such coating. After drying the coating, it becomes light sensitive and subsequent operations must be conducted under nonactinic light.

The sensitized plate is exposed to the desired photo positive, in a vacuum technique, with a suitable light source, such as a double carbon arc lamp of about 35 amperes. The plate is then developed with a developer suitable for the coating employed and dyed to make the image visible. It is now possible to work under normal illumination for the rest of the process.

Flushing with cold water will remove the excess dye and the plate is then dried. Any extraneous areas not to be etched may be staged out at this point by applying a suitable coating material such as asphalt, and the plate is then ready to be etched.

At this point, I employ a particular etching solution in order to obtain the particular effect I desire, namely the desired frosted surface which will match that of final embossing. This solution contains iron perchloride to which has been added a quantity of salt-saturated hydrochloric acid. The best iron perchloride solution will be at a concentration of about 40 Baum and will contain, per gallon, about 12.8 ounces of hydrochloric acid of about 31% concentration (the usual commercial form) saturated with salt. The concentration of the iron perchloric solution may vary from 35 to 46, Baum, preferably 38 to 42, and the hydrochloric acid employed may vary from 5 to 20, preferably 10 to 15, ounces per gallon of the perchloride solution. It is important to use the above-named ingredients for I have tested many other acids and found them to be unsuitable. For instance, various combinations of hydrochloric, hydrofluoric, and nitric acids have been tried; but only the above-described solution will give the effect I desire.

Shortly after the solution is applied, a violent etching reaction will set in and increase as the heat of reaction builds up. It is best to intermittently swab the surface with a suitable material such as cotton during this period until the first sign of a white scale begins to float on the surface. short period in the solution and is then removed and exposed to the air for a brief period, the pressure of oxygen in the air causing the reaction to become very violent. The plate is then immersed in water to stop the etching process. Finally, the plate will be cleaned with paint remover and steel wool to remove the protective coating.

The following example will further illustrate my invention:

Example A sheet of aluminum was cleaned with Tripoli powder and then treated with a pre-etching solution of 10% hydrochloric acid saturated with sodium chloride, and dried. The plate was spray'coated with Kodak Photo Resist and dried under heat under non-actinic light. The coated plate was then placed in a vacuum box and exposed under a photo-positive to a double carbon arc lamp of 35 amueres at a distance of six feet for six minutes.

The plate was developed in a solution of Kodak Photo Resist developer for three minutes and dyed to make the image visible. After flushing with cold water to remove excess dye, the plate was then etched.

The etching bath was prepared by adding 12.802. of concentrated hydrochloric acid saturated with sodium chloride to a gallon of 40 Baum solution of iron perchloride. The plate was immersed in this bath at 70 F. and after about 20 seconds a violent reaction set in. Every 30 seconds the plate was swabbed with cotton until Emirate:

The etching is then allowed to continue for a l after about 120 seconds a white scale appeared on the surface of the bath. The plate was left in the bath for an additional 45 seconds and then exposed to the air for 15 seconds. The reaction was quite violent in this stage. The plate was then immersed in water and the etching stopped.

After cleaning the plate with paint remover, the final effect was found to match the frosted background obtained from a final embossing.

It will be appreciated that the above example is not limitive of the scope of my invention as to the exact conditions employed therein. The time of treatment in the etching bath may be varied from 60 to 240 seconds, preferably 120 to 190 seconds in actual operation and the exposure to air may be from 10 to 25 seconds, preferably from 12 to 20 seconds. It will also be understood that, while I have described the preparation of the etching bath by the convenient method of adding the hydrochloric acid solution to the iron perchloride solution, it is of course the final composition of that solution which is important, and not any manner of addition of the reagents thereof. Thus, iron perchloride solutions prepared by the common technique of adding a small amount of hydrochloric acid to avoid hydrolysis are contemplated and may be used.

The above description makes it clear that my invention has the very great advantage of avoiding the necessity of preparing and using embossing rolls, tools, and dies to obtain an embossed effect. Preparation of embossing rolls, for instance, is an expensive and difficult process and requires a technique such as that described in United States Patent No. 2,662,002. Especially in cases where only a few plates are desired, the cost of making the embossing rolls, etc., can be prohibitive. My invention now enables such plates to be prepared, with the embossed appearance, at a commercially practical cost.

While the invention has been illustrated in the specific examples, it will be appreciated that it is limited only by the spirit and scope of the following claims.

I claim:

1. A process for forming etched designs on aluminum metal surfaces which comprises cleaning said metal surfaces, applying a pre-etch solution of hydrochloric acid saturated with sodium chloride, drying the thus-treated metal surface, depositing an image-forming resist coating on said metal surface, removing said coating from the area to be etched, and treating the thus coated metal surface with an etching solution consisting essentially of iron perchloride containing hydrochloric acid saturated with sodium chloride.

2. A process of etching an image on an aluminum metal surface, pre-treated with a solution of hydrochloric acid substantially saturated with sodium chloride, which comprises, blocking out areas which are not to be etched and treating the remaining etching areas with a solution corresponding to a mixture obtained by adding from to 20 oz. of concentrated hydrochloric acid substantially saturated with sodium chloride to a gallon of a 35 to 46 Baum of iron perchloride.

3. A process of etching an image on an aluminum metal surface, pre-treated with a solution of hydrochloric acid substantially saturated with sodium chloride, which comprises, blocking out areas which are not to be etched and treating the remaining etching areas with a solution corresponding to a mixture obtained by adding from to 15 oz. of concentrated hydrochloric acid substantially saturated with sodium chloride to a gallon of a 38 to 42 Baum of iron perchloride.

4. An etching composition consisting essentially of an aqueous solution corresponding to that obtained by adding from 5 to oz. of concentrated hydrochloric acid saturated with sodium chloride to a gallon of solution of iron perchloride having a concentration from to 46 Baum.

5. An etching composition consisting essentially of an aqueous solution corresponding to that obtained by adding from 10 to 15 oz. of concentrated hydrochloric acid saturated with sodium chloride to a gallon of solution of iron perchloride having a concentration from 38 to 42 Baum.

References Cited in the file of this patent UNITED STATES PATENTS 2,211,400 Wood Aug. 13, 1940 2,270,712 Wood Jan. 20, 1942 2,283,170 Batcheller May 19, 1942 2,336,846 Clark Dec. 14, 1943 2,762,694 Newman Sept. 11, 1956 FOREIGN PATENTS 484,159 Great Britain Apr. 28, 1938

Claims (1)

1. A PROCESS FOR FORMING ETCHED DESIGNS ON ALUMINUM METAL SURFACES WHICH COMPRISES CLEANING SAID METAL SURFACES, APPLYING A PRE-ETCH SOLUTION OF HYDROCHLORIC ACID SATURATED WITH SODIUM CHLORIDE, DRYING THE THUS-TREATED METAL SURFACE, DEPOSITING AN IMAGE-FORMING RESIST COATING ON SAID METAL SURFACE, REMOVING SAID COATING FROM THE AREA TO BE ETCHED, AND TREATING THE THUS COATED METAL SURFACE WITH AN ETCHING SOLUTION CONSISTING ESSENTIALLY OF IRON PERCHLORIDE CONTAINING HYDROCHLORIC ACID SATURATED WITH SODIUM CHLORIDE.