GB1594315A

GB1594315A - Method of treating a printing-plate to repel ink

Info

Publication number: GB1594315A
Application number: GB2997/78A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-01-28
Filing date: 1978-01-25
Publication date: 1981-07-30
Also published as: JPS6221628B2; DE2803492A1; IT7819617A0; BR7800514A; ATA61078A; AT368077B; IT1092321B; DE2803492C2; CA1116461A; JPS53102114A; ES466983A1; CH628289A5

Abstract

The non-printing surfaces of the plate (1, 3) fitted with the cuts of the etching (2) are coated with at least one layer (5) which does not adhere to the printing inks, with a view to saving printing ink and associated cleaning products. <IMAGE>

Description

(54) A METHOD OF TREATING A PRINTING-PLATE TO REPEL INK (71) I, DANIEL BEAUNE, a French citizen of La Prunerie, Marsac Sur L'Isle (dordogne), France, do hereby declare the invention, for which I pray that that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method of treating a printing-plate, particularly for use in smooth cut printing, to repel ink from the non-printing parts, and to a treated printed plate, as well as articles printed from the treated plate.

The usual process for smooth cut printing of documents consists in using a thin plate, a shell, a collar or a cylinder, all of which, for convenience, are referred to as "plate" hereinafter, which is preferably made of metal and on to which the pattern to be reproduced through printing is sunk engraved. Some areas of said plate are coated with ink so that the ink penetrates the hollows or cuts of same. The inked surface is wiped in order to leave ink in the hollows or cuts only and the surface thus inked and wiped is applied against an appropriate support, such as a sheet or strip of paper, by means of a pressing cylinder; thus, a part of the ink is transferrred from the hollows or cuts on to the support.

According to some processes, an indirect transfer of the ink contained in the hollows or cuts of the plate is performed by means of a cylinder carrying a flexible coating and positioned between the plate and the support.

In the known processes, the wiping operation causes a great loss of ink. As a matter of fact, the coating of the engraved plate with ink is performed at 100%, and the wiping thereof removes, depending on the chase, about 75% of said ink; this corresponds to the parts of the area which do not carry any cut and do not serve for printing. Said 75% of wiped ink constitutes waste. Where printing with several colours is involved by using the same plate, respective zones of which receive inks of different colours, the problems raised by waste remain the same.

Furthermore, in view of the wiping, the risk is run to give rise to trails of colours into another one and also to mix colours, which spoils the quality of the print.

A process and a machine for smooth cut printing is already known and disclosed in French Patent No. 1,564,653.

Said process consists in coating the plate before inking it, with a colourless liquid, non-miscible with ink, then in applying the ink. Generally, the non-miscible liquid is filtered water.

Such an improvement to standard processed is aimed to minimise the losses of ink and to increase the sharpness of the printed patterns, as well as to remove or simplify the wiping operation.

Unfortunately, the practice has shown that this process, which rests on a physical balance between the water and ink, is suitable only for a given depth of cut and not for all depths of smooth cuts. This greatly limits the scope of the process and practically prevents one from using it.

An object of the present invention is to remedy these drawbacks and to provide a process particularly for smooth cut printing which makes it possible to save a large quantity of printing ink, as well as, for example, accessory cleaning products used for printing, and to alleviate all the wiping operations which not only result in a loss of ink but furthermore give rise to the risk of mixing inks of various colours or to leave trails.

To this end, the present invention provides a method of treating a printing-plate to repel ink from the non-printing parts of an engraved surface of the plate which comprises coating the non-printing parts with one or more layers of ink-repellent material, and wherein the or each layer of ink-repellent material is a fluorocarbonaceous resin or an organo-silicic grease.

Thanks to this process, the engraved plate may be coated only with the quantity of ink required to fill the engravings, without any excess of ink on the non-engraved surfaces, which will thus perform no printing.

Preferably, so as to lay down the inkrepellent material, the cuts of the engraving of the plate are obstructed with a nonelectrically conductive material, the fluoro carbonaceous resin is then laid down through electrolysis and the material obstructing the cuts of the engraving is subsequently dissolved.

So as to obtain an optimum ink output, the fluorocarbonaceous resin can be overlaid with a very thin layer of the organosilicic grease. The organo-silicic grease may also be used alone as ink-repellent.

Saving of ink according to the method of the invention may be considerable and corresponds, depending on the cuts involved to a saving ranging from 300% to 400%. As a matter of fact, while 100% of ink is used according to standard processes, 25% only really serves for printing and 75% constitutes waste; in the method according to the present invention the ink may be fully used. Thus, according to said method, a quarter or a third part of ink is sufficient in relation to the quantity of same required in standard processes.

Furthermore, this method makes it possible to save the cleaning products of the wiper cylinder. Now, as these products, as well as the inks used, are expensive, this can result in a most important saving.

Preferably the plate is subsequently coated with printing ink which is then compacted in the cuts of the engraving. Said compacting may be performed by means of a compacting cylinder the purpose of which is only to remove any slight surplus of ink in the engravings and to push it down to the bottom of said engravings by opposing the surface tension forces so that the meniscus formed by the ink contained in the engravings become slightly concave, which is a compulsory condition for obtaining a sharp engraving.

A machine for carrying out the method of the present invention may comprise a rotary cylinder carrying one or more plates which themselves carry the smooth cut engravings, one or more groups of devices for applying ink, and a printing cylinder providing sheets of paper, and is characterised in that it preferably carries a cylinder for applying a liquid ink-repellent product, said cylinder being positioned upstream of the groups applying ink, and a compactor cylinder positioned downstream of the groups applying ink.

Said machine not only has the advantage of being simpler than the known ones since it has no wiping cylinders or accessory devices, but, also, it makes it possible to work in better conditions of cleanliness and hygiene. As a matter of fact, as practically there is no surplus of ink, the clogging of the machine is reduced to a minimum. The lack of cleaning devices minimises the use of solvents which produce harmful vapours.

Each group of ink appliers may consist of an applier cylinder proper, cut as a function of the areas of the plates to be inked and located tangentially to the rotary cylinder, of an ink feeding cylinder for the ink applier cylinder, located tangentially to said ink applier and rotating in the reverse direction, as well as of cleaning means located tangentially to the ink applier cylinder downstream of the rotary cylinder, and designed to remove from the ink applier cylinder the ink/ink-repellent mixture.

The presence of the cleaning means is indispensable for obtaining good printing: as a matter of fact, a liquid ink-repellent applied by its applier cylinder tends to mix up with the ink; if said mixture is not removed by the cleaning means, it would cover the ink applier cylinder and the mixture would thus spoil the fresh ink which would not completely fill the cuts of the engraving for the following run.

Where monochromatic printing is involved (printing where the ink applier cylinder is not cut) any scraping system can be used for preventing the pollution of the fresh ink. On the contrary, where the machine is designed to produce polychromatic printing and carries several groups of ink appliers, the cleaning means consists of a cleaning cylinder rotating in the same direction as that of the ink applier cylinder which partly wipes it and collects the mixture of ink and ink-repellent to carry the mixture towards a scraping device.

The scraped mixture can be recovered, then crushed and mixed up with fresh ink so as to be used again.

The present invention will be described in more detail by way of example only, with reference to the drawings attached hereto, wherein: FIGURE 1 is a diagrammatical crosssection view, at an enlarged scale, of a plate used for a smooth cut printing, according to the prior art; FIGURE 2 is a cross-section view, at an enlarged scale, of a cut of the engraving obstructed with a varnish that is a nonconductor of electricity; FIGURE 3 is a cross-section view, at an enlarged scale, of a cut of the engraving after the electrolytic depositing of a solid ink-repellent layer and the dissolution of the varnish; FIGURE 4 is a diagrammatical crosssection view of a cut of the engraving, similar to FIGURE 3, after the application of a second, liquid, ink-repellent layer; FIGURE 5 is a diagrammatical crosssection view, at an enlarged scale, of a cut of the engraving after inking of same; FIGURE 6 is a cross-section view, at an enlarged scale, of a cut of the engraving after compacting of the ink, and FIGURE 7 is a diagrammatical view of a smooth cut printing machine.

FIGURE 1 is a cross-section view of a standard printing-plate 1 made of metal whose thickness is referenced a. Said plate may be a thin plate, a shell, a collar or a cylinder. The cross-section view of the plate diagrammatically shows only one cut 2 of the engraving.

All the surface of said plate is generally coated with a layer of pure bright chromium 3 which protects the plate against the corrosion of the ink.

According to the method provided by the invention, a film of organo-silicic inkrepellent material, or a layer of a fluorocarbonaceous resin ink-repellent material with or without the organo-silicic ink-repellent layer is laid down on to the plate.

The following description refers to the case of a plate coated with a fluorocarbonaceous resin layer and with an organosilicic grease layer.

As a matter of fact, as shown in FIGURE 2, after having made a cut 2 in the plate 1, and after having deposited a layer of chromium 3 on to the surface of the plate 1 and inside the cut 2, said cut 2 is obstructed by means of a mass such as a varnish that is a non-conductor of electricity or with any other non-conductor of electricity. It is preferable to use a varnish capable of being easily dissolved in usual solvents such as, for example, methyl-ethylketone or trichlorethylene.

As shown in FIGURE 3, after solidification of the mass 4, the plate 1 is degreased and covered through electrolysis or, generally, by coating it with a thin layer 5 (ranging, for example, from 5 to 20 microns); said layer 5 is a fluorocarbonaceous resin from which printing inks are repelled. Then, the whole is dipped in a bath of solvent so as to dissolve the material 4 obstructing the cut 2. The filling material 4 contained in the cuts 2 of the engraving is dissolved. Thus, the surface of the plate 1 is coated with a layer of an ink-repellent material 5 while the sides and the bottom of the cut 2 carry only the layer of chromium 3 or any other protecting layer.

As shown in FIGURE 4, the surface of the plate 1 is covered, should it be necessary, with the exception of the cut 2, with a second ink-repellent layer 6 comprising a thin layer of a greasy product based on organosilicic by-products so that the parts of the plate 1 which do not perform any printing are perfectly repellent towards inks.

Said layer 6 may be deposited through coating before the plate is inked.

As shown in FIGURE 5, when inking is performed, a certain quantity of ink 7 goes into the cut 2 but not on the repellent layer or layers 5, 6.

In order to ensure good printing, without any overflow, the ink 7 contained in the cut 2 must show a concave meniscue; so as to achieve such a meniscus, the ink 7 is driven into the cut 2 as shown in FIGURE 6. To perform said driving-in, a means of compression is used which urges said ink into the cut 2 by closing any void which could exist between the ink 7 and the walls of said cut 2.

As shown in FIGURE 7, a machine for smooth cut printing consists of a rotating cylinder 8 the surface of which carries at least one thin plate 1 carrying sink engravings 2 outlining the pattern to be reproduced through printing; said plate is coated, according to the invention with the inkrepellent layer 5. Said plate 1 is continuously fed by as many ink applier groups 20a, 20b as there are various coloured inks to be applied. Said ink applier groups 20a, 20b, as well as the manner in which they work, will be described in greater detail hereafter.

Nevertheless, it is to be stressed that the Figure shows two ink applier groups; obviously, said number could differ from two without departing from the scope of the invention.

A printing cylinder 15 designed to apply sheets 17 of paper to be printed against the plate 1 is associated with a means 16 feeding the blank sheets of paper. As soon as they are printed, sheets 171 are moved away by clearing means 18. The feeding means 16 and clearing means 18 for the sheets of paper 17 and 171 are very diagrammatically shown and may correspond to any similar devices currently used.

Furthermore, and as shown in FIGURE 7, the machine carries upstream of the ink applier groups 20 in the rotating direction of the cylinder 8 (arrow A) an applier cylinder 9 for a liquid ink-repellent layer 6. Said applier cylinder 9 is combined with a mechanism for dosing and levelling the liquid 6.

Furthermore, said machine carries downstream of the ink appliers 20 a contacting cylinder 13 which turns in perfect synchronization with the surface of the plate 1 to force the ink into the cuts 2, and which is combined with a system 14 for recovering inke. Means, not shown, make it possible to strongly apply the cylinder 9 which applies the ink-repellent products 6, the ink applier groups 20 and the printing cylinders 15 against the cylinder 8 which supports the plates 1. In addition, said machine carries means not shown for driving the cylinders in rotation.

As shown in FIGURE 7, the ink applier group 20a consists of an applier cylinder 1 la cut as a function of the areas of the plate 1 to be inked, a feeding cylinder 12a located tangentially to the ink applier cylinder 1 la which turns in the opposite direction thereto and is associated with an ink storage tank 21a, as well as a cleaning means designed to remove from the ink applier cylinder 1 la any trace of ink-repellent product.

Said cleaning means consists of a cleaning cylinder 22a rotating in the same direction as the ink applier cylinder 1 la which partly wipes it and recovers the mixture of ink and liquid ink-repellent so as to carry it towards a scraping device 23a which deposits it into a vessel 24a.

Said ink applier group 20a works as follows: -the fresh ink coming from the ink storage tank 21a is deposited in thin thickness on to the feeding cylinder 12a and transmitted to the ink applier cylinder 1 la cut at point I.

The areas in relief of the applier cylinder 1 la thus inked will at point II deposit ink inside the cuts 2 of the engraving carried by the plate 1.

Between the cuts 2 of the plate 1, on the surface of said plate 1, the organo-silicic ink-repellent product 6 applied by the cylinder 9 tends to mix up with the ink. If said mixture were not removed by the cleaning cylinder 22a, it would go up to the point I on the feeding cylinder 12a and would thus spoil the fresh ink. Such spoiled ink would deposit inside the cuts 2 of the engraving during the following run.

The cylinder 22a which rotates in the same direction as the applier cylinder 1 la partly wipes the surface thereof and carries the mixture of ink-repellent product and ink towards the point III where the scraping device 23a recovers it to deposit it into the vessel 24a.

Thus, the ink which has been mixed up with liquid ink-repellent product 6 does not run the risk of mixing with the fresh ink spread over the feeding cylinder 12a and thus of spoiling the printing.

Claims

WHAT I CLAIM IS:

1. A method of treating a printing plate to repel ink from the non-printing parts of an engraved surface of the plate which comprises coating the non-printing parts with one or more layers of ink-repellent material, and wherein the or each layer of ink-repellent material is a fluorocarbonaceous resin or an organo-silicic grease.

2. A method as claimed in claim 1 in which there are two layers of ink-repellent material comprising a solid layer of fluorocarbonaceous resin overlaid with a liquid layer of the organo-silicic grease.

3. A method as claimed in claim 1 or claim 2 in which the fluorocarbonaceous resin is deposited electrolytically on the non-printing parts of the engraved surface.

4. A method as claimed in claim 3 in which prior to electrolytic depositing of the fluorocarbonaceous resin, the printing parts of the engraved surface are obstructed by a material that does not conduct electricity to prevent the fluorocarbonaceous resin being deposited on said printing parts.

5. A method as claimed in any one of the preceding claims in which ink is subsequently applied to the printing parts and is compacted into said printing parts.

6. A method of treating a printing plate as claimed in claim 1 and substantially as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.

7. A printing plate when treated by the method claimed in any one of the preceding claims.

8. An article when printed from a plate as claimed in claim 7.