DE509335C - Process for the production of photomechanical printing forms in which the areas of an exposed chromate colloid layer that have been washed out by development print - Google Patents

Description

Process for the production of photomechanical printing forms in which the areas of an exposed chromate colloid layer that have been washed out by development print '' according to the main patent 508 360 , a mixture of alcohol (spirit) with nitric acid is proposed as an etching agent for deepening the printing elements after development. The alcohol hardens the exposed chromium colloid layer by removing water from the layer; the acid, on the other hand, attacks the zinc and deepens the pressure elements.

In the course of this proceeding, it turned out that the withdrawal of Water from the exposed colloid layer is secondary; is primarily against it keeping water away from the start of deep etching.

In the case of the reversal process, it has proven to be advantageous by means of only one Layer proved, (let the chromium colloid schiclite add hygroscopic agents, to avoid tearing the layer. These means have now (read aspiration, the copied plate to supply water from the air, which then when deep-running the Protective layer can be attacked by the crack.

To avoid this, it is expedient to use the alcohol-nitric acid mixture as well a mixture of nitric acid with anhydrous liquids, such as B. gasoline, Petroleum, ether, chloroform and the like. When using gasoline is also still can be worked more economically, since this means is much cheaper than alcohol.

In the production of one- and two-layer offset printing plates, as is well known, after the lowering of the printing elements, the entire printing area is covered with color rubbed in, whereby the exposed areas repel the color and only the unexposed, on. developed and deep-set printing elements take on the color. This process requires a certain amount of time, a special skill and the two-shift process a special heating device.

According to the present method, this coloring is no longer necessary. the deep-etched printing plate is washed out, decoated and with a washout tincture now etched with the well-known zinc etch, whereupon it is gummed, washed out over the gum and is rolled in; then it is machine-ready. It is therefore a cumbersome one and work that requires special practice. Incorrect results, such as those rubbed in deeply etched, but especially with the simple IT reversal process without deep etching occur frequently with this procedure locked out, provided that the development of the exposed. Plate made properly became.

Claims (1)

PATENT CLAIMS: i. Process for the production of photomechanical printing forms, where the areas of an exposed Chromatkolloi.dschicht washed out by development print, according to patent 50836o, characterized in that as etching for lowering the printing elements after developing nitric acid is used by anhydrous Liquids such as gasoline, benzene, petroleum, ether, chloroform and the like are diluted will. a. Method according to Claim i, characterized in that in the case of the reverse method with and without deep etching, rubbing the printing plate with ink after development or deep etching is omitted, and that after the known rubbing with tincture washed out the plate is decoated, etched, rubberized, washed out over rubber and rolled in becomes known as (read when preparing the printing plate for the machine is.