US1557354A - Process for producing photomechanical printing plates - Google Patents

Description

No Drawing.

Patented Oct. 13, 1925.

UNITED STATES PATENT OFFICE.

AMBROS GALETZKA, OF DRESDEN, GERMANY, .ASSIGNOR OF ONE-HALF TO SKCHSISCHES SERUMWERK AKTIENGESELLSCHAFT, OF DRESDEN, GERMANY.

PROCESS FOR PRODUCING PHOTOMECHANICAL PRINTING PLATES.

T0 at whom/it may concern:

Be it known that I, AMBRos GALETZKA, a citizen of Saxonia, Germany, residing at Dresden, Germany, have invented certain new and useful Improvements in Processes for Producing Photomechanical Printing Plates, of which the following is a specification. l

This invention relates to processes for producing photomechanical printing plates particularly plates for flat printingand letter press printing. An object of the invention is to produce printing plates which may be used for practically all printing processes, such as book, lithographic, photolithographic and offset printing and for all kinds of printing machines including special machines. A further object of the invention is to produce printing plates which, in distinction from such plates produced by other processes that require the use of particular kinds of paper (lithography: chalk paper, illustration printing with autotypes: enamelled paper, offset printing: well sized paper), enables all kinds of paper and cardboard and also fabrics, metal sheet, wood, celluloid etc. to be directly printed upon.

The novel process enables types and pictures to be combined on one and the same printing plate. The new process enables printing blocks for screen pictures to be produced without necessitating the selection of a particular width of screen on account of the roughness of the paper to be printed p v -,A'fter these printing blocks havebeen produced, they may be used directly in any kind of machine without any preparatory operations and give pictures which, as regards high lights and deep shades and the softness of half tones are equal to copper deep-printing.

The cost of producing the printing plates and the time required for their production is very small in comparison with other processes.

The novel printing plates can also be used for rotation printing and .enable the productionof sterotypes to be dispensed with.

The weight of the new printing plates is small so that the cost of the material 'of which they are made is correspondingly low. It therefore pays to keep them for impressions that might be subsequently required.

Application filed June 26, 1925. Serial No. 39,813.

The novel printingplates enable extreme 1y large editions to be produced with uniform high class impressions. I

In the process which constitutes the present invention the base plate may consist of a plate of practically any kind of material, such as zinc, aluminum, glass, cellon, stone or the like on which if necessary a thin coating' may be spread in a known manner to ensure the adhesion of the next layer. This thin coating may consist for example of a mixture of gelatme water-glass and chromealum. I

A non-sensitive layer of elastic material is now placed on the thin'coating, this material being preferably such as will absorb moisture and then swell up, and which in a moist state is elastic and repels printing ink. For example a layer of pure gelatine may be employed. The thickness of this layer may vary between wide limits. Thus, its thickness in a dry state may be 0.3 mms. and in a moist state 0.5 mms. A sensitive layer which may consist of chromate gelatine or albumin is spread on the elastic layer and the thickness of the sensitive layer may also vary. Its thickness may be 0.2 mms.

for example.

The different layers adhere firmly to each other, both when the gelatine layer'is dry and when it is moistened, as when the upper layer is developed after a photograph has been taken on it or during printing. In order to make the gelatine layer, when dry. incapable of absorbing moisture and traces therewith of sensitive substances, such as bichromate, from the sensitive layer spread or poured upon it, the gelatine layer maybe hardened on its surface a slight degree before the sensitive layer is placed upon it. This may be accomplished by a solution of alum. This hardening must only be suffi- "cient to prevent the absorption of moisture during the short drying period of the sensitive layer. The hardening must not, however, be such as to prevent the absorption of moisturewhen the gelatine' layer is subjected for a long time to the action of water, as for example during the development of the plate.

Thepicturethat is to be printed is now photographed on the plate prepared as described above. This may be done by exposing the plate beneath a negative, whereupon the finest pores so that they can easily be washed out. 'After the water has been active for a considerable time it commences penetrating from the sides into the gelatine surfaces located beneath the exposed surface elements so that finally the entire surface of the gelatine layer is completely moistened and caused to swell up uniformly in its entirety. Theexposed parts of the surface of the upper layer are also lifted when the gelatine layer swells and remain in a common plane. The printing plate is now ready and after printing ink being rolled onto it it may be used for printing. printing plate can be regarded ,as a letter press printing form because the printing surfaces project a distance equal to the thickness of the uppermost layer. The sensitive layer can, however, be made so thin that the printing plate can be regarded as a flat printing form. In both cases the printing ink is repelled by the moist gelatine at the white surfaces 10- cated between the printing surfaces. The negative may be the photogram of a line drawing or a type printing sheet. It may. however, also be a screen negative.

Print and illustrations or pictures may be copied'on the same printing plate, so that a mixed printing plate can be immediately produced. As it is only necessary to pro duce one photogram before printing, the type employed is immediately available for at er purposes. This has the advantage that the printer only requires a small quantity of type and this small quantity even is not subjected to wear. A further advantage is that, since it is possible to reduce and enlarge the objects of photographic means, the printer is not limited to a certain size oftype and can carry on his work with onlyfafew sizes of types. Furthermore he caniobt am any desired size of printed sheet by photographic reduction and enlargement.

All of the impression producing surface elements, even the smallest screen spots have an elastic support. Consequently even a screen picture produced with a very narrowmeshed screen can be printed on rough paper. But as the thickness of the elastic intermediate layer is considerably smaller than the thickness of the rubber plates in oflset printing, the danger in the latter process that the various impression producing surface elements will be squashed flat during printing so as to give false toning, is

avoided.

As the surface elements WhlCll are not to lent impressions, pictures with rich contrasts produce an impression repel the printing ink by their moist gelatine, it is not neces sary to deepen these parts as in the case of a Iine-electro or to allow the small screen spots to remain even at the lightest parts as in the caseof an autotype block. In the novel process, irrespective of the size of the surfaces, the lightest parts need not have any screen spots and require no deepening.

. In order to use the new printing plates for rotation printing it is only necessary to bend them in the form of a cylinder and to fix them on the cylinder of the machine.

The rapid and cheap production of the printing plates, the avoidance of all etching and engraving, the absence of any transf'erring operation, the avoidance of all operations preparatory to printing the possibility of employing the novel printing plates in any kind of printing machine, the fact 35 that special kinds of printing paper are not 3 necessary, the avoidance of a large quan-- tity of type and of a large number of different sizes of types, the obtaining of exceland soft middle tones by extremely simple means, and the possibility of printing large editions ensure an extensive use of the novel process in the most various branches of printing.

I claim 2-- 1. Process for producing printing plates consisting in placing an elastic, nonsensitive layer on a base, placing a sensitive layer on the non-sensitive layer, and transferring the object to be printed onto the sensitive layer by photographic means. 7

2. Process for producing printing plates consisting in placing an elastic, non-sensitive, ink-repelling layer on a base, placing a sensitive layer on the non-sensitive layer, and transferring the object to be printed onto the sensitive layer by photographic means.

3. Process for producing printing plates consisting in placing an elastic, non-sensitive, inlcrepelling, moisture absorbing layer on a base, placing a sensitive layer on the non-sensitive layer, and transfering the object to be rinted onto the sensitive layer by photograp ic means.

4'." Process for producing printing plates consisting in placing on a base an elastic, non-sensitive layer of material that swells when -moistened, placing a sensitive layer on the non-sensitive layer, and transferring the object to be printed onto the sensitive layer by photographic means. q

5. Process for producing printing plates consisting in placing on a base an elastic non-sensitive layer of gelatine, placinga sensitive layer on the non-sensitlve layer, and transferring the object to beprinted onto the sensitive layer b photographic means.

6. Process for pro ucing printing plates consisting in placing on a base an elastic non-sensitive layer of gelatine, hardening the surface of the gelatine layer, placing a sensitive layeron the non-sensitive layer,

and transferring the Object to be printed 5 onto the sensitive layer by photographic means.

7 Printing plate consisting of a base, an

elastic non-sensitive layer on the base, and a sensitive layer v0n the non-sensitive layer onto Whiclrthe object to be printed has 10 been transferred by photographic means. In testimony whereofI alfix my signature.

AMBROS GALETZKA.