DE701827C - Process for producing amalgam printing plates in which the printing, non-amalgamated parts are lower than the non-printing parts - Google Patents

Description

Process for the production of amalgam printing plates, i.e. the printing, non-amalgamated parts are deeper than the non-printing parts The invention relates to amalgam printing plates and the methods of making the same Plates.

The well-known amalgam printing is a planographic printing process. The non-printing ones Parts of the usual amalgam plates consist of or are covered with a layer Amalgam; the amalgam has a repellent effect on the printing ink.

The invention achieves the production of an amalgam printing form for deep Flat printing. Deep flat printing has the advantage over conventional flat printing, that the small pits which together form the picture contain more color can accommodate as small non-repellent parts of a flat plate can. The walls or edges of the recessed parts also prevent lateral splashing or leakage of the ink at the moment the printing takes place so that getting sharp marks is always assured. There is also a deep one The printed image is always less subject to wear than a flat or high lying one Image.

In the case of amalgam printing, whereby printed with relatively little color these benefits will be even more noticeable. Especially when printing Paper with a more or less raw surface shows the beneficial effect the use of deep amalgam printing forms. When using the usual amalgam printing forms you have to be quite a bit more often apply high compressive stress to also print on the deep-set parts of the paper, and it needs to be hard on the plate absorbent papers have a lot of ink added to them, which creates the risk of that the parts that do not have to print fill up too. For deep amalgam printing forms on the other hand, you can add so much color without the risk of running out of color, that even the deep-lying parts of the paper without using too high a compressive stress fully colored. The difficulty of using too high a Compressive stress when printing raw papers does not occur in offset printing, because it removes the color from the plate and also transfers it to the paper takes place with rubber.

For the production of such deep amalgam printing forms you proceed as follows, for example: plan can z. B. assume a photographic one Positive, which is copied onto a light-sensitive layer in a known manner, which is attached to a polished printing plate, the surface of which is made of an amalgamable Made of metal. A negative image is created on the sensitive layer.

Instead of a so-called copy, a lithographic transfer can also be used using an existing picture or using a protective etching base Add engraving, etc. by hand, as is customary in lithography for plates which are used in the production of plates for the printing machine as an original have to serve. The parts of the panels not covered by the image represent the non-printing part thereof. From the in the manner described above with the The formed plate is then made into the deep amalgam mold. In Figures 1 to 5 of the drawing are the various stages of their manufacture specified according to the invention.

The plate provided with the image is z. B. with the help of an etchant or etched with the help of an electric current until the printed image is deeper than the repellent part of the plate. The plate is then transformed into a galvanic cathode Nickel or chrome bath set so that1) the deep parts with a thin layer of nickel be provided. Thereupon the protective layer created by copying or is applied by transfer printing, removed so that the amalgamable at these points Surface becomes free again; this is then amalgamated. With those in that way The printing forms produced can be used in the letterpress press as well as in the offset machine to be printed; in the latter alone when the dampening system is switched off.

It has already been proposed to correct tonal values on amalgam printing forms to undertake, with the printing areas of the form more or less in places are deepened and thereby of the deep amalgam printing forms according to the invention differ significantly.

According to that older method, the picture is made on one with a nickel layer provided plate made of amalgamable metal applied and the nickel layer on the part not covered by the picture is etched away down to the amalgamable plate. The raised, Color-repellent parts built up by alternating treatment with aqueous mercury salt solutions and solutions of other amalgam forming metals. Unlike the printing forms of the invention So here the non-printing parts consist of thick amalgam layers.

It is inevitable that while the amalgam is being built, the latter expands not only in height but also in width, so that the printing Parts get smaller because the non-printing parts formed by the amalgam grow. Such a process is not intended for deep amalgam printing forms to produce, but is intended to change the tonal values of images on already produced ones Amalgam flat pressure forms are used.

According to the invention, after using a positive with the correct tonal value the image has been applied to a plate, a treatment of the plate has been carried out, to allow the printing parts to be lowered to a certain extent without adding amalgam cause. A treatment that would cause the image to lighten, would be disadvantageous.

Furthermore, it is possible according to the invention to produce the To use grid positive plates, which are known to be very easy to correct permit. After applying the image with the help of a corrected, i.e. correct tonal value The depressions are made in the plate in a grid positive manner without becoming attached changes the tonal values of the image even the slightest. The depth is there not dependent on the correction that was necessary on the plate; but is the same everywhere and designed as it is for an impeccable print is most beneficial.

When printing with recessed amalgam printing forms, it is important that the paint repellent parts are very hard and that she one Contain sufficient mercury to repel the paint. The usual amalgams usually do not have the required hardness or property or do not meet the requirement to repel the color sufficiently.

According to the invention, an alloy is now produced with the you can form a very hard amalgam and also keep the mercury longer and holds better than the amalgams commonly used up to now.

As is known, amalgam is very soft compared to the material of the Dzuckylatten. The alloy that forms the amalgam is the softer the higher the mercury content. But the mercury is precisely the component - which causes the paint to repel. The lower the mercury content of the amalgam in the plate, the less perfect the plate will print. It has now been found that by using an alloy of amalgamable and non-amalgamable metals, e.g. B. an alloy of 70 to 80 parts of copper, i 5 to 2 g parts of silver and 5 to i 5 parts of nickel, much better results can be achieved than with a homogeneous amalgam made exclusively with amalgamable metals. This is probably due to the fact that the soft amalgamated metal crystals are united in the mass, finitely hard, non-amalgamated crystals which prevent the movement of the amalgam and control the expulsion of the mercury.

In the way described above it is now possible in a very simple way Way to make a hard amalgam that meets all requirements. For achieving The desired result is the addition of non-amalgamable metal to the amalgamable Metal essential. The above-mentioned silver-containing composition is only named for example. A brass alloy with a pretty good iron content can also be used very well. Can be used for printing with achromatic colors you can also get by with cheaper alloys; for printing with bright colors is to use an alloy with a fairly high silver content, for example the above composition, to be recommended. The ratio of the amalgamable to the non-amalgamable metal can be chosen in such a way that so much non-amalgamable Metal is used that the alloy is still just amalgamated.

Claims (2)

PATENT CLAIM: i. Process for the production of amalgam printing forms, in which the printing, non-amalgamated parts are lower than the non-printing parts Parts, characterized in that on the amalgamable surface a polished Printing plate the image is applied by copying or transfer printing, the exposed areas the plate deeply etched and the walls and bottoms of these wells with a thin chromium or nickel layer are electrolytically coated. 2. Pressure plate for carrying out the method according to claim i, characterized in that the amalgamable surface made of an alloy of 40 to 80 parts copper, 15 to 25 parts silver and 5 to 15 parts nickel.