Improvements in the Preparation and Production of Plates for Printing Purposes.
Year: 1895

page_text: Date of Application, 8th Oct., 1895
Complete Specification Left, 7th July, 1896-Accepted, 15th Aug., 1896
PROVISIONAL SPECIFICATION.
Improvements in the Preparation and Production of Plates for
Printing Purposes.
I, OTTO CARL STRECKER of Maiuz in the Empire of Germany, Doctor of
Philosophy do hereby declare the nature of this invention to be as follows:-
This invention has for its object to provide plates for printing purposes which
will give improved results in printing: the said plates consisting of aluminium
alone or of aluminium coated with a layer of zinc, or other suitable metal, or alloy,
and having the surface corresponding to the design (that is the surface by which
the printing is to be effected) elevated, or raised, above the other portions. The
metallic surface is treated with a solution of salts preferably the chlorine
compounds of the heavy metals which are electrically opposite to the metal of the
surface being treated, or a mixture of such salts and a suitable acid, such as
sulphuric acid for instance may be used. Where a surface of zinc, or other metal,
or alloy, is applied to the aluminium nitric acid or other acid may be employed
which will etch away the zinc or other metal, or alloy, forming the coating without
acting on the aluminium beneath. The design or drawing to be printed is trans-
ferred or otherwise applied to the surface of the plate, in an ink, or matter which
will protect the metal surface beneath the ink or matter, from the action of the
acid or salt, or both, employed as aforesaid. When a coating of zinc or other
metal, or alloy, is used upon the aluminium the action of the acid or salt, or both,
should be continued until the whole of the metallic coating at the unprotected
portions is etched away. In certain cases a suitable etching solution consists of
one part of crystallized cupric-chloride in five parts of water, but nitric acid is
suitable where zinc is to be etched away from the aluminium plate, the acid being
of variable strength in accordance with the particular work. After the etching is
performed the impurities and precipitated metal are removed which may be done
by nitric acid, first, if necessary reinforcing the design upon the plate. The plate
then has a white, or silvery appearance and the parts corresponding to the design
are above the other parts. The plate is then dried and polished which may be
done by means of a hard brush and talc, and the plate is then treated as described
in the Specification of Letters Patent No. 16312 of 1892 and thus rendered fit for
printing purposes by employing phosphoric acids, such as ortho-meta or pyro-
hypophosphoric acid, phosphorous acid, hypophosphorous acid, phosphoric-tunstic
and phosphoric-molybdic acids, hydro-fluoric or silico or boro-fluoric acids, or acids
derived from the oxygen compounds of sulphur except sulphuric acid.
Dated this 8th day of October 1895
JOHNSONS & WILLCOX,
47 Lincoln's Inu Fields, London, W.C., Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in the Preparation and Production of Plates for
Printing Purposes.
I, OTTO CARL STRECKER of Mainz in the Empire of Germany, Doctor of
Philosophy, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:-
This invention has for its object to provide plates for printing purposes which
will give improved results in printing especially in the case when printing after the
manner of lithographic printing and if the paper or material to be printel on his a
rough and hard surface. The said plates consist of aluminium alone or of
aluminium coated with a layer of zinc or other suitable metal or alloy and having
the surface corresponding to the design (that is the surface by which the printing
is to be effected) elevated or raised above the other portions.
The aluminium surface is treated with a solution of salts, preferably suitable
chlorine compounds of the heavy metals which are electrically opposite to the
metal of the surface being treated, or a mixture of such salts and a suitable acid,
such as sulphuric acid, for instance may be used. Where a surface of zinc, or other
metal, or alloy, is applied to the aluminium, nitric acid or other acid may be
employed, which will etcb away the zinc or other metal or alloy, forming the
coating, without acting on the aluminium beneath. The design or drawing to be
printed is transferred or otherwise applied to the surface of the plate in an ink or
matter which will protect the metal surface beneath the ink or matter from the
action of the acid or salt or both, employed as aforesaid.
When a coating of zinc or other metal or alloy is used upon the aluminium the
action of the acid or salt or both should be continued until the whole of the metallic
coating at the unprotected portions is etched away, the protected parts, corre-
sponding to the design being left standing, raised, or elevated.
As an example for treating plates of aluminium alone, a suitable etching
solution consists of one part of crystallized cupric chloride in say five to six parts
of water, but I do not limit myself to the exact proportions stated. Instead of the
water a suitable acid such as sulphuric acid or a mixture of water and a suitable
acid may be used. If a layer of zinc or other metal or alloy covers the surface of
an aluminium plate, suitable acids to be employed are those which etch away the
unprotected portion of the layer, but do not act at all or only very slightly on the
aluminium beneath, such, for example, is nitric acid, the acid being of variable
strength in accordance with the particular work to be done.
The etching solution is put on the plate and equally dispersed, for instance by
means of a broad brush. The decomposition of the unprotected portions of the
metal surface, with a strong precipitate of copper at once begins to take place with
a great development of heat. When the action of the etching solution on the
plate ceases which is the case after a few seconds, the precipitated copper is washed
off by water. The application of the etching solution and the washing off of the
precipitated copper is continued until the unprotected portions of the plate are
etched sufficiently deep and the design or parts corresponding to the drawing stands
or stand sufficiently elevated or raised. After the etching is performed any
impurities and precipitated metal, which present a blackish red appearance and
which may have been left on in spite of the water washing, are removed. This
may be done by nitric acid, of variable strength first if necessary reinforcing the
design upon the plate. The plate is then dried and brushed which may be done by
means of a hard brush and tale and the plate is then treated for printing purposes
after the manner of lithographic printing as described in the Specification of
Letters Patent No. 16312 of 1892 by employing phosphoric acids such 24 ortho-,

page_text: meta-, or pyrophosphoric-acid, hypo phosphoric acid P₂OH (Roscoe Schorlemmer),
phosphorous acid, hypo-phosphorous acid, phosphoric-tungstic and phosphoric
molybdic acids, hydrofluoric or silico- or boro-fluoric acids or acids derived from
the oxygen compounds of sulphur except sulphuric acid.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what 1
claim is :-
1. The preparation of aluminium plates for printing purposes consisting in
treating the plates with a solution of salts, preferably the chlorine compoun:ls of
the heavy metals which are electrically opposite to the metal of the surface under
treatment or with a mixture of such salts and a suitable acid and subsequently
cleaning the plate and removing impurities and precipitated copper substantially
in the manner and for the purposes hereinbefore described.
2. The preparation for printing purposes of aluminium plates coated with a
layer of zinc or other suitable metal or alloy, by etching away by means of a
suitable acid the layer of zinc or other suitable metal or alloy on the unprotected
portions of the plate down to the aluminium surface, so that the protected
portions corresponding to the design or drawing stand raised substantially as
hereinbefore described.
3. Treating the plates claimed in the preceding claims after the manner described
in the Specification of Letters Patent No. 16312 of 1892 for rendering them fit for
lithographic printing substantially as hereinbefore described.
Dated this 7th day of Jul 1906
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.