US3441486A - Process for producing printing plates - Google Patents

Description

United States Patent 3,441,486 PROCESS FOR PRODUCING PRINTING PLATES William Rupert Deighton, Reigate, Surrey, England, as-

signor, by Inesne assignments, to International Printers Limited, London, England No Drawing. Filed Apr. 27, 1965, Ser. No. 451,352 Claims priority, application Great Britain, June 11, 1964, 24,300/ 64 Int. Cl. C23b 7/08 US. Cl. 204-6 Claims ABSTRACT OF THE DISCLOSURE A mould is produced from an original by spraying a relatively low melting metal or metal alloy on to the original and subsequently stripping the sprayed mould from the original.

This invention relates to the production of printing plate moulds, printing plates and shells produced therefrom.

It is an object of the invention to produce an improved printing plate mould by employing metal spraying techniques.

Another object of the invention is to produce a shell using metal spraying techniques.

A further object of the invention is to produce an improved duplicate plate using metal spraying techniques.

A still further object of the present invention is to provide a shell wherein the backing-up is performed using metal spraying techniques.

Thus, according to one aspect of the present invention there is provided a method of producing a mould from an original characterised in that the original is sprayed with a metal to form a layer thereon which is subsequently stripped from the original.

Preferably, the sprayed metal is a bismuth based alloy, or similar metals or alloys may be used. Initially the original is cleaned and the metal or metal alloy sprayed thereon by any suitable means, such as a low temperature metal spray gun in which the metal or metal alloy to be sprayed, is contained in molten state, within a chamber of the gun, provided with an electric heating element. However, any conventional metal spraying equipment may be used for this purpose. The metal is initially deposited very slowly on the original, but as the thickness of deposited metal increases, the speed of deposition is increased correspondingly.

When a required thickness of sprayed metal alloy has been deposited, the sprayed mould is removed from the original. It will be appreciated that the mould will be brittle when removed and in order to strengthen the mould, reinforcing materials in lamina or powder form may be introduced during the spraying operation. The sprayed metal mould may, if required, be inserted in a plating bath to allow a nickel and/or copper layer to be deposited thereon, following which the back of the deposited metal is sprayed with metal or metal alloy, or a thermosetting polyester or epoxy resin may be applied.

The techniques of the present invention allow moulds to be produced from resilient materials such as rubber, thermoplastic materials, photopolymer plates, gelatine moulds and negative or positive prints and may be used for the reproduction of litho plates.

According to a further feature of the invention there is provided a method of producing duplicate printing plates from a mould characterised in that a least one layer of metal or metal alloy is sprayed on to the mould, to produce the plate and subsequently plated, e.g. by electrodeposition.

In a preferred embodiment of the invention, a thermo- 3,441,486 Patented Apr. 29, 1969 plastic, papier mache (flong), rubber, plastics or other type of mould is used, or the mould may be of the type" described above formed by metal spraying techniques. Tin or other metal or metal alloy is sprayed on to the surface of the mould and a second layer of metal or metal alloy e.g. tin, zinc, is then deposited on the first and the second layer may be of harder metal containing, for example, antimony. The total thickness of the sprayed metal is preferably between .001" and .0025 and while the metal is still attached to the mould, the whole assembly is located within, and held down, by, a vacuum.

A thermosetting plastics material e.g., a polyester or epoxy based resin, may be spread on the back of the sprayed metal while attached to the mould, or after removal thereof from the mould, and the plastics material left to cure for 30 minutes or more.

After curing, the plate is machined and then inserted in a plating bath where a thin deposit of nickel chrome or similar wear resistant metal is grown thereon, to impart wear resistant properties to the plate.

It will be appreciated that the duplicate plates produced in accordance with the invention, may be of fiat or curved form suitable for use with flat bed or rotary printing presses. The advantages of the duplicate plates produced by metal spraying techniques, is that they can be produced far more quickly than conventional electrotype plates and yet have the quality and flexibility necessary for use with modern printing presses. Although the production of plates according to the invention, involves little saving in time, compared with conventional stereos, the quality of the sprayed plates is superior to that of stereos and this is of considerable advantage and importance in connection with colour processing and reproduction.

In a further embodiment of the present invention, shells produced from plastic or other suitable moulds, by electrodeposition techniques, are backed up using metal spraying techniques.

Heretofore, replicas of an original have been produced by forming a mould from a mouldable, impressionable material, e.g., wax or plastics material or other suitable moulding mediums, to which the original is applied to produce a negative image of the original in the mould, the mouldable material being rendered electrically conductive to allow a metal shell to be deposited or grown thereon by any suitable electroplating or electrodeposition process, and the electroplated shell being backed up with a suitable metal or plastics composition.

A copper or nickel shell is grown on the mould by electrodeposition, and heretofore such shells have been backed up by pouring molten metal on the shell or by plating or electrodeposition methods, or by spreading a thermosetting plastics material over the rear surface of the shell.

With such prior known methods, it is necessary to machine the electrotypes formed by electrodeposition methods, and where molten metal is poured on to the shell, workmanship of the highest standard is required to perfect and level the surface of the electrotypes which become deformed by the heat.

In this embodiment of the invention, a metal shell preferably of copper, is plated on the mould which may be of plastics material and before the shell is removed from the mould, the plating is sprayed with Zinc, aluminum, copper, tin or any suitable metal or metal alloy, by any conventional metal spraying equipment. Advantageously, a metal or alloy of relatively low melting point, e.g., cadmium, bismuth, tin or lead based alloys, could be flowed into the depressions in the non-printing side of the shell, in order to minimise the amount of spray metal used.

The use of sprayed metal techniques for backing up the shells has considerable advantages over the prior known methods. The requirement of a high degree of craftmanship to level the surface is eliminated, since with metal spraying, it is possible to maintain the temperature of the sprayed metal below the point where deformation of the electrotype occurs. This can be achieved by blowing cold air on to the surface at the point of impact of the sprayed metal with the surface, or by controlling the distance of the nozzle of the spray gun from the surface.

With the present embodiment, it is possible to backup the shell whilst in position on the mould, and then to remove the finished plate, providing an electrotype in a fraction of the time necessary to produce electrotypes by other methods.

It will be appreciated that the invention is susceptible of considerable modification and is not to be deemed limited to the particular features described by way of example only I claim:-

1. A method of producing a duplicate printing plate from a printing plate mould produced from an original to be duplicated which comprises spraying directly on to the mould at least one layer of non-ferrous meal or nonferrous metal alloy of relatively low melting point in molten state, backing off the plate with a coating of 4 plastics material, and subsequently electroplating the backed off plate.

2. A method according to claim 1, wherein reinforcing materials are introduced during the spraying operation.

3. A method according to claim 2, wherein reinforcing materials in lamina or powder form are introduced.

4. A method according to claim 1, wherein the metal or metal alloy is cadmium, bismuth, tin or a lead based alloy.

5. A method according to claim 1, wherein the metal is bismuth or a bismuth based alloy.

References Cited UNITED STATES PATENTS 1,681,447 8/1928 Torrison 204-6 1,978,791 10/1934 Hale 204 6 2,327,762 8/1943 Bull 204-6 2,400,518 5/1946 Kreber etal 204-6 FOREIGN PATENTS 653,367 5/1951 Great Britain. 864,672 4/1961 Great Britain. 969,090 9/1964 Great Britain.

ROBERT K. MIHALEK, Primary Examiner.

T. TUFARIELLO, Assistant Examiner.