US1640961A - Superdurable photo plates for ink printing - Google Patents

Description

Io Drawing.

Patented Aug. 30, 1927.

UNITED STATES ALBERT :r. rmcxnnx, or NEW YonxQN. x.

SUIEEBDUBABLE PHOTO PLATES FOR INK PBINTmG.

This invention relates to the art of producing photo-plates of the type employedin thejofi'set process of ink-printing. The object of the invention is primarily to increase the life of such a plate from a capability of printing only a few thousand co ies up to several tens of thousand copies. n fact, I have increased the life of such a plate to such an extent that a quarter of a million copies have been reproduced from it without the plate becoming defective.

In general, it is an object of my invention to improve both a photo-plate of the type employed for offset printing and to cheapen and improve the process by which such plates are fabricated.

In the preferred practice of my invention,

' I started with a sheet of sheet metal, such 'of the plate in dry weather with any suitable water solution of egg albumen and a light sensitive salt of a character capable of hardening the albumen upon exposure to light. I prefer to employ thefollowing ingredients by weight in the formation of this solution: 3 ozs. of ammonium dichromate; 3 ozs. dry egg albumen; .and 32 ozs. of water. I

= This solution must be used fresh, that is,-

before any decomposition of the egg albumen has taken place, and is suitable for use in dry weather.

For damp weather, toeach 10 ozs. of the above solution, I prefer to add from one half to one ounce of grain alcohol. The alcohol renders this solution suitable for use in damp weather and insures an adherent tough albuminous film on the plate.

Fifth, I dry the "film coated plate in a whirler which throws off all'excess solution and by maintaining a dry atmosphere over.

the plate dries the surface into a substantially dry film-coated surface.

S'xth, he film coated surface of the plate is' exposed to an image carrying beam or Application filed December 10, 1926. Serial no. 154,039.

flood of light as by causing li ht to shine through an ordinary photo rap ic negative of the desired image in light and shade. This step in my process is similar to the printing of any sensitized surface through a negative. I prefer, however, to employ a large metal plate many times larger than the images to be made upon its surface and to repeat them by uniformly timed exposures first on one spot and then on another spot, until the surface of the metal plate is covered with the desired number of light impressions. The exposure of each light impression should take from about one and a half to two minutes each. Speaking generally, this exposure should be of the normal and proper amount to give the desired clarity of image. It is not at' this step that durability is imparted to the film in accordance with my invention.

Seventh, I rub over the film coated surface after it has beenexposed to the image producing light with an oily developing blacking ink, preferably of the type known in the trade as Directof although any inky substance comprising crayon black mixed with castor oil and a little turpentine is suitable. The adherence or embedding of this black ink upon the surface of the film varies according to the variation in the lightformed images upon the albuminous film. But this does not appear to the sense of sight, until after the next step.

Eighth, after drying the ink surface I submerge it in water and while carefully keeping the entire surface of the plate under watergently rub the inked albuminous surace preferably with a soft sponge of cotton dberlg The images then appear in light and Ninth, I take the plate out of the water and dry it.

Tenth, I expose thev entire film-coated surface of the plate upon which the images appear in varying degrees of the black ink as nearly as possible to surface normal rays from a powerful actinic'light for from five to ten minutes. I have successfully used carbon are light, two arcs about six inches apart in the flaring hood with the .arc separated something like four or five feet from the center of a single plate, approximatelly about 3 by 4 feet in surface dimensions. t is to beunderstood that this expeosure to the intense actinic light is not to limited to are light, as an; suitable source of actinic light is contemplated, such as sun-light. It should also be understood that this exposure to light at this stage of my process is of extreme importance. I found further that without light treatment at this time. the durability of the finished photo plate is less than ten percent of what it is when so treated. It is probable that by this procedure 'I-eff'ect the light hardening of the entire film of albuminous matter without changing any of the detail already produced on the film. In other words, I imprison all the refinements of the photographic art practiced under favorable conditions by employing a separate uniform exposure to lightto accomplish the hardening after I have first used only the most favorable amount of ex posure to produce the image.

Eleventh, I coat the entire surface of the plate with a thin water solution of gum arabic and dry the surface.

Twelfth, the gum arabic coated surface of the plate is rubbed off with crayon black and washed off with water clean and then is dried.

Thirteenth, I dust off the surface of the plate with a black powder, preferably asphaltum powder.

Fourteenth, the functioning surface of the plate is edged. In accordance with my process, the edging may be accomplished in any of the usual Ways, for example,

with an ammonia edge, or with a. chromic acid edge.

Fifteenth, after edging the surface of the plate is washed off clean with distilled water.

Sixteenth, the entire'surface is rubbed off with a thin solution of gum arabic and dried.

Seventeenth, the surface of the late is carefully washed over with turpentine and subjected to light abrasion as with a cotton fiber sponge. This turpentine washing removes all visible black.

Eighteenth, the surface'of the plate is then rubbed over with liquid asphaltum which adheres to the film foundation in image producing proportions. The asphaltum does not adhere to the surface, except where and in the amount required to produce the dark parts of the desired image. The applied liquid asphaltum is allowed to dry and it is this asphaltum surface which constitutes the ink printed surface of the finished photo plate; and as I have previously set forth by this process produce a photo plate capable of reproducing in an offset printing machine a quarter of a million impressions, whereas heretofore I have found that photo-plates would reproduce only at best a few-thousand impressions.

In its broader aspects, my process is equally applicable to the production of albuminous printing films upon stone lates, which should be treated in substantial y the same way as described above in connection with the grained surface in'a sheet metal plate. The type of stones to which I am re- I 1. A photoplate of the type employed in Y offset printing comprising a surface-grained flexible sheet-metal plate; an image imparting printing film of light-hardened albuminous matter which is over-exposed but with highlights, whereby the finished plate is of markedly increased durability for the production of offset impressions.

2. A photoplate of the type employed in offset printing comprising a plate; an image imparting printing film of light hardened albuminous matter which is over-exposed but with highlights, whereby the finished plate is of markedly increased durability for the production of offset impressions.

3. A form of plate of the type employed in offset printing comprising means providing a grained surface; an image imparting printing film of over-exposed lighthardened albuminous matter with its printing surface corresponding as to its image qualities with that of a -film normally exposed to image strained light but of increased durability in the reproduction of offset impressions.

4. The process of forming photo-plates of the type employed in offset printing comprising coating the grain surface of a sheet metal plate with a water solution of albumen and a light sensitive salt of the type capable of hardening albumen on exposure to light; exposing the said coated surface to image strained light; spreading an ink mixture of pulvurent black substance and oil over said surface; subjecting said inked surface to the solvent action of water and gentle abrasion; then exposing said entire surface for some five to ten minutes to the direct action of strong actinic light; and subsequently edging and finishing said plate in accordance with any usual procedure here allowable whereby because of the said exposure of the: incomplete printing surface to strong act-inic light between the time it' is edged and the time it is exposed to image strained light,

a toughening of the image carrying film is effected.

5. The toughening of offset printable films on photo-plates comprising exposing a light sensitive albuminous film to i the desired image in light and shade; coating the said film with an oily black ink; subjecting said film to the solvent action of Water and gentle surface rubbing to bring out said image into visibility from said ink; then exposing said entire surface to intense actinic light for a considerable period of time, such as ing a light printed image on a light sensi- 10 tive albuminous film with a black oily ink and then subjecting said film to relatively long exposure to strong actinic light shining directly upon said ink developed image.

In witness whereof, I have signed my 15 name to this specification, this 4th day of September, 1926.

. ALBERT J. PINCKNEY.