US2097831A - Surface printing plate, more particularly offset-printing plate and the process for printing therewith - Google Patents

Description

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AND THE P E F'i Ja Nov. 2, 1937. w. A; BOEKELMAN ET AL 5 3 SURFACE PRINTING PLATE, RE PARTICULA OFFSET PRINTING PLATE S FOR PRINTI EWITH v n 3 WJZjgm flnt'lond as Bevin/man .2"! fl/Zertlus [5/275 1 Patented Nov. 2, 1937 UNITED STATES SURFACE PRINTING PLATE, MORE PAR- TICULARLY OFFSET-PRINTING PLATE AND THEREWITH THE PROCESS FOR PRINTING Willem Anthonius lioekelman, Bilthoven, and

Alberthus Elfers, Haarlem, Netherlands Application January 30, 1935, Serial No. 4,191 In the Netherlands February 15, 1934 11 Claims. (Cl. 41-415) The invention relates to a surface printing plate, more particularly an offset printing plate and to a process for printing therewith.-

The object of the invention is to manufacture in a simple manner an offset printing plate suitable for obtaining better prints in editions comprising a large number of copies in which the design elements are etched on the plate to the right tone values.

Up to the present an offset printing plate was generally made as follows:

A zinc or aluminium plate grained and provided with a light-sensitive albumen or gelatine layer is taken as a starting material. After the copy has been formed on the same, the plate is powdered, treated with Strecker salt and then washedwith water.

After this the plate is gummed and dried, washed with turpentine, given a tincture treatment, dried again and finally washed with water.

A fixing dye or permanenting agent is then applied to the plate by means of a roller, the plate is dried once more and dusted with talcum powder, after which the plate is again treated with Strecker salt and-washed with turpentine.

Finally the desired printing ink may be applied to the plate by means of a roller or otherwise and printing'may be started as a controlling means and in order to find out whether the printing 30 elements are good. The said treatments gener ally are repeated.

If an offset plate with different tone values in a given colour is tobe made, grating negatives for the said colour are made of the original, but up to the present a grating negative has never been equal to the original with regard to the right tone values, so that it is necessary to retouch or correct either the negative or the positive or both,

taining the desired result.

The quality of the printing plate depends on the degree of accuracy in retouching; however, it is possible to see whether the retouching has been correctly done only by making the proofs. As

so' that the operator is never entirely sure of obattracting surface consists of an extremely thin or skin-like layer of metal etched through to a water attracting or hydrophile surface. The said skin layer has a thickness of 0.01 millimetre at the utmost and preferably not more than 0.005 millimetre.

According to the invention the ink attracting surface may consist of a metal deposit obtained by electro-plating and etching through onto an un-grained surface.

' 10 According to the invention the water attracting sists in depositing by means of electroplating on a hard carrier of copper or some other material an intermediate layer of lead or a lead alloy or some other material and in depositing by means of electro-plating on the said intermediate layer a skin-thin upper layer of copper or some other metal, which latter layer is etched through by means of an etching agent against which the-v intermediate layer is proof.

The skin-thin metal design elements are more lasting than the elements which have been hitherto used, and may be readily cleaned without detriment by means of a brush.

Up to the present it was necessary to remove the plates from the machine after each period of operation, to entirely clean and gum them, which caused a great loss of time.

When applying the present invention the design elements are no longer attacked by the printing ink, and the ink is readily removed from the smooth metal surface with a little turpentine before the plate is used for the next operation period.

The novel plate has great mechanical resistance, the design is exceptionally sharply defined and it is always possible to carry out retouching even after printing proofs are already made, as well as in any other stage.

The invention moreover offers the possibility of obtaining an offset printing plate which may be etched to the right tone value with all the associated advantages.

It is now possible after having etched through the upper layer of metal down to the intermediate or basic layer, to carry out a continued etching acting on the size (diameter) of the points or other design elements only, since the deposit of lead or some other material obtained by electroplating is proof against the etching agent, so that no deep etching can occur in spite of the toneetching operation. It is therefore possible to carry out any tone etching without any difficulty. If desired, before printing the plate may be treated with turpentine or gasoline and sulphuric acid or phosphoric acid or other means.

With the present invention there is no need of retouching the negative. A point or some other design element may be etched thinner (reduced in diameter or width) according to the right tone value on the printing plate itself. The etch-proof intermediate or basic layer only admits of the etching influencing the size (diameter or width) of a point, whereas its depth is not influenced at all, so that it is possible to obtain "a needle-sharp etching of the grating point or line. As the skin-like upper layer has a thickness of 0.005 millimetre only, the basis of an extremely fine point or of a very thin line always is of much greater dimensions than its height.

Although one might be inclined to think that it would be impossible to complete the etching on so skin-thin a layer of metal, it has been proved in practice that the correct and clean shape of the points may be retained when a light-sensitive copying-layer is not too thickly applied. Also when copying a negative which possesses 'its right tone-value the use of a skin-thin metal layer is absolutely necessary in practice, since if this upper layer is thicker, the period of .time needed for etching through is so much increased and the size of the points so much reduced, that the right tone value is missed. After printing, a grey design without marked contrasts then is obtained and after a longer period of printing the ink will adhere to the sides of the grating points and the prints obtained from the rubber cloth are blurred. The use of a skin-thin layer insures that the printing points or lines have hardly any height, which renders it impossible for the-said points or lines to be pressed into the rubber cloth.

If during fore or provisional printing the etch-proof layer of enamel or some other material should have disappeared, a layer of printing ink or some other etch-proof material may be applied for correction. With a surface printing plate according to the invention any retouching work may be carried out at any time, without the necessity of repeating the treatment from the starting point.

The known running of the copy during printing on account of the design layer being attacked by harmful ingredients of the ink on the slight high relief printing portions will not occur when using the present invention.

When a printing plate manufactured according to the known method is to be prepared for receiving a new design, a great deal of time is lost. However, this loss of time may be considerably reduced when applying the present invention.

It is easy to' copy on the printing plates according to the invention by using cold enamel or albumen, after which, later on, the parts which are already etched to their right tone value may be temporarily covered with a layer of protecting paint and fat chalk. This treatment may be repeated until all the desired tonevalues are present in the different parts. After this the protecting layers may be removed e. g. by means of a brush and turpentine, without danger of damage to the printing surface. a

The printing plate according to the invention will readily take a good amount of ink and will give off the same quickly and readily to the rubber surface, so that the machine may operate at top speed and the production may be increased. With an equal thickness of the layer of ink supplied the printing plate will give off much more ink to the rubber cylinder than was hitherto possible, which results in a very true printed design without the necessity of overloading the plate with ink.

If thelayer of copper or some other material for forming the elements of the design is applied on a thin deposit of lead, a lead alloy or some other suitable material obtained by means of electro-plating, a smooth, water attracting surface is obtained as a basic layer which surface need not be grained, as has hitherto been the case. A copper or iron plate may serve as a carrier for the whole, this plate having the advantage over zinc that it is less liable to stretch.

The term smooth is intended to refer to an ungrained surface.

Although in the present specification mention has been made of a surface printing plate only, it is obvious that the present invention also relates to surface printing forms deviating from the plate shape e. g. to cylinders. It is also evident that it is not necessary for making a new surface printing plate to apply the metal layer or layers by electro-plating, as it is also possible to use e. g. cathode atomization or some spraying method.

With reference to the annexed drawing the invention will be further explained with a single embodiment on a much enlarged scale.

In this drawing l is a carrier made of copper or some other material, on which is deposited a layer 2 of lead, a lead alloy, or some other suitable material having a thickness of approximately 0.03-0.05 mm. On this layer is deposited a copper layer having a thickness of 0.005-0.01 mm. on which an image is formed. This image after being developed, fixed and washed, is used 'for the purpose of etching entirely through the copper onto the layer of lead, e. g. by means of ferric chloride, for the formation of design points 3, 4, 5.

Itis possible according to the invention to etch the points 3 smaller, down to the dimensions of point 4 or 5, without increasing the height of the said points so that only their diameter will then be reduced. Even with the smallest point the supporting surface is many times larger than its height, which only amounts to 0.005-0.01

It is also possible to employ a different metal instead of copper, provided it may likewise be deposited in a skin-thin layer and that it is possible to etch through the same with an etching agent against which the layer 2 is proof.

We claim:

1. A printing plate for offset printing, comprising a metallic layer and metallic ink-receptive design elements carried by said layer, said layer having a naturally water-receptive surface to provide an ink-repelling surface, the said metal of the layer at the same time being proof against an etching agent with which the metal of the design elements can be removed.

2. A printing plate for offset printing, comprising a carrier layer and a deposit of metallic mam ink-receptive design elements on said layer. said layer being of a metal having a naturally waterreceptive surface to provide an ink-repelling surface, the said metal at the same time being proof 5 against an etching agent with which the metal of the design elements can be removed. 3. A printing plate for ofiset printing accor'd ing to claim 1, in which the metal layer providing the water-receptive ink-repelling surface consists of the naturally water-retaining surface of lead.

4. A printing plate for offset printing according to claim 1, in which the metal layer providing the water-receptive ink-repelling surface consists of the naturally water-retaining surface of a lead alloy. l

5. A printing plate for offset printing according to claim 2, in which the metal layer providing the water-receptive ink-repelling surface consists of the naturally water-retaining surface of lead. 6. A printing plate for offset printing according to claim 2, in which the metal layer providing the water-receptive ink-repelling surface consists of the naturally water-retaining surface of a lead alloy. 25 7. A printing plate for oflset printing according to claim 1, in which the water-receptive surface is smooth and unprepared.

8. Method of printing from a printing form for offset printing having a closed surface of lead bearing a metal ink-receptive design, comprising thefstep of applying water directly to the closed surface of lead.

'8.'Method or printing from a printing form for offset printing having a closed surface of a lead alloy bearing a metal ink-receptive design, comprising the step of applying water directly to the closed surface of a lead alloy.

10. Method of printing from a printing form for offset printing having a closed smooth surface of lead bearing a metal ink-receptive design, comprising the step of applying water directly to the closed smooth surface of lead.

11. Method of printing from a printing form for offset printing having a closed smooth surface of a lead alloy bearing a metal ink-receptive design, comprising the step of applying water directly to the closed smooth surface of a lead alloy.

WILLEM ANTHONIUS BOEKELMAN. ALBERTHUS ELFERS.

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