WO1999061252A1

WO1999061252A1 - Flexible carrier for a printing plate

Info

Publication number: WO1999061252A1
Application number: PCT/NL1999/000334
Authority: WO
Inventors: Hans Van Der Horst
Original assignee: Av Flexologic B.V.
Priority date: 1998-05-28
Filing date: 1999-05-28
Publication date: 1999-12-02
Also published as: NL1009274C2; AU4292499A

Abstract

The invention relates to a combination of a substantially cylindrical carrier for a flexible printing plate and a flexible printing plate, wherein the carrier is manufactured from material which is flexible in at least tangential direction but which is substantially non-stretch, wherein the flexible printing plate is formed by a seamless layer of photopolymer adhered to the carrier. A seamless combination is thus obtained with which seamless printing can be performed. According to a first embodiment the carrier is provided on its inner surface with a layer of a smooth material. This provides the option of arranging the carrier round a printing or formatting cylinder, since the smooth layer on the inside enables the sleeve to be pushed around the printing or formatting cylinder in axial direction. According to a preferred embodiment the carrier is adapted for use as flexible printing plate on a printing device provided with a printing cylinder and a tension cylinder.

Description

FLEXIBLE CARRIER FOR A PRINTING PLATE

The invention relates to a combination ^εiuέ' a substantially cylindrical carrier for a flexible printing plate and a flexible printing plate, wherein the carrier is manufactured from material which is flexible in at least tangential direction but which is substantially non-stretch.

Such combinations are known in the graphic industry, in particular in flexography, as sleeves on which flexible printing plate are fixed.

In these prior art combinations the flexographic plate is initially exposed and developed and washed. The plate is Subsequently arranged on the carrier or sleeve. It is therefore unavoidable that on the thus manufactured combination a seam is present which is intrusive when continuous printing work is being printed. The object of the invention is to provide such a combination wherein no seam is present so that continuous printing work can be produced without problem. This objective is achieved in that the flexible printing plate is formed by a seamless layer of photopolymer adhered to the carrier.

A seamless combination is thus obtained with which seamless printing can be performed. Such combinations must therefore be supplied as such in virgin form. In this - cylindrical - form they must then be further processed, such as exposed developed and washed. According to a first embodiment the carrier is provided on its inner surface with a layer of a smooth material .

This provides the option of arranging the carrier round a printing or formatting cylinder, since the smooth layer on the inside enables the sleeve to be pushed around the printing or formatting cylinder in axial direction. Use can be made herein of assist means generally known in the graphic industry such as the holes arranged in the printing cylinder to form an air layer. It is pointed out that the smooth layer is also necessary herein because the stretch of the material is extremely minimal due to the typographical requirements .

According to another embodiment the carrier is manufactured from a polyurethane resin. This material is found to have attractive mechanical and chemical properties, since it must be able to withstand the treatments to which the photopolymer layer has to be subjected. It moreover has sufficient tensile strength and is sufficiently flexible.

When the photopolymer layer is placed on the carrier by means of an adhesive it is already possible to obtain a seamless print, be it with some difficulty.

Herein the seam created during attaching can for instance be filled.

It is however much more elegant to mould the photopolymer layer around the carrier and subsequently allow it to cure. A natural adhesion between the carrier and the photopolymer is then obtained.

In order to obtain the flatness of the printing plate which is absolutely essential for printing, it may be necessary to perform a further flattening process. Polishing is an example of such a process.

A further reduction in material is obtained when the carrier consists of a single photopolymer layer.

The functions of flexible printing plate and carrier are hereby combined within the same element, provided materials with the relevant properties are available. It will be apparent that this will result in considerable material saving.

According to the prior art it is necessary that for each wind-off distance a separate carrier or sleeve must be applied in order to adapt the circumference hereof to the desired wind-off distance. It will be apparent that with the great variety of desired printing work, different sleeves will have to be used regularly and this causes great problems in respect of stocking and processing of such sleeves.

By using the flexible sleeve according to the invention it becomes possible during printing to guide the sleeve around two cylinders, i.e. the printing cylinder and a tension cylinder, wherein the distance between the printing cylinder and the tension cylinder can be varied for adapting the wind-off length and of course the size of the sleeve (printing belt) corresponding therewith. This results in great advantages in respect of availability of the sleeves . The adaptation to the wind-off distance now only has to take place, when endless sleeves (printing belts) are used, by constructing the desired length into a cylinder. This results in particularly great advantages in the flexographic industry.

The invention therefore relates to a printing device for intaglio printing of an image arranged in relief on a flexible printing plate, comprising: - a printing cylinder,-

- a counter-pressure cylinder;

- through-feed means for feeding the substrate for printing between the printing cylinder and the counter-pressure cylinder; - inking means for applying ink to the flexible printing plate; and

- a tension cylinder, the axis of which extends parallel to the axis of the printing cylinder and which is adapted to fix a flexible printing plate arranged around the printing cylinder and the tension cylinder. Other attractive embodiments are specified in the remaining sub-claims.

The present invention will be elucidated hereinbelow with reference to the annexed figures, in which: figure 1 shows a schematic perspective view of a carrier for manufacturing a first embodiment of the present invention; figure 2 is a schematic perspective view of the carrier shown in figure 1 on which an endless layer of photopolymer is arranged; figure 3 is a schematic perspective view of the carrier shown in figures 1 and 2 with exposed, developed and washed polymer,- figure 4 is a view corresponding with figure 2 showing the flexibility of the combination; and figure 5 shows a schematic perspective view of a printing device on which is arranged a combination according to the present invention.

Figure 1 shows a cylindrical carrier 1. This carrier 1 is per se known in the field of flexography as a so-called sleeve, on which are mounted photopolymer plates prepared for printing, and the thus resulting combination is placed in a printing press .

Such a carrier can for instance be manufactured from nickel or a plastic such as polyurethane .

According to the present invention a layer of polymer 2 is arranged around cylindrical carrier 1. This arranging can for instance take place with a moulding process. It is important herein that the carrier be placed in the mould and the mould be then filled with polymer in liquid form, whereafter the polymer cures by a curing process . A certain degree of flexibility of the flexographic plate is herein maintained, as is usual in flexography. It is also important herein that the carrier is in its cylindrical form, so as to prevent deformations later during printing. In order to obtain the flatness of the photopolymer layer necessary for printing, this layer can subsequently also be polished.

A thus processed combination is shown in figure 2. The combination must then be subjected to the usual processing of photopolymer flexographic plates, such as exposure, development and washing. All these treatments will herein have to take place with the polymer fixed onto the cylindrical carrier. In order to ensure the accuracy of the printing work it is important that these processes, but particularly the exposure, all take place with the carrier in its cylindrical form. A combination is then obtained as shown in figure 3, which can subsequently be used in the usual manner in a flexographic printing machine. The above described embodiment relates to a cylindrical carrier which has a certain degree of rigidity,- it is also possible however to make use of a slack carrier as shown in figure 4. It is of the greatest importance herein that the treatments of the photopolymer layer take place in the cylindrical form of the carrier.

It is then also possible to arrange carrier 4 having flexible printing plate 5 fixed thereon around a printing cylinder 6 and a tension cylinder 7, as shown in figure 5. Because the distance between the axis of printing cylinder 6 and tension cylinder 7 is adjustable, it is possible to make use of printing belts with a different wind-off length. For performing the actual printing operation a counter-pressure cylinder 8 is arranged, wherein a layer of substrate 9 for printing is fed between flexible printing plate 5 and counter- pressure cylinder 8. It is noted herein that the angle a between the connecting line between the axis of pressure cylinder 6 and the axis of tension cylinder 7 and the connecting line between printing cylinder 6 and counter- pressure cylinder 8 is greater than 90 °, so that the contact surface between the substrate and printing plate 5 always occurs on that part of printing plate 5 which is in contact with printing cylinder 6. Further arranged on the other side is an inking device 10 which is formed by an anilox roller 11, a vibrating roller 12 and an ink tray 13. The angle β is herein also greater than 90° so as to achieve that anilox roller 11 is only in contact with that part of printing plate 5 which is in contact with printing cylinder 6. It will be apparent that the above stated embodiment can be varied in diverse ways without departing from the invention.

Claims

1. Combination of a substantially cylindrical carrier for a flexible printing plate and a flexible printing plate, wherein the carrier is manufactured from material which is flexible in at least tangential direction but which is substantially non-stretch, characterized in that the flexible printing plate is formed by a seamless layer of photopolymer adhered to the carrier.

2. Combination as claimed in claim 1, characterized in that the carrier is provided on its inner surface with a layer of a smooth material .

3. Combination as claimed in claim 1 or 2 , characterized in that the carrier is manufactured at least partially from polyurethane resin.

4. Combination as claimed in any of the claims 1, 2 or 3 , characterized in that the combination comprises a single layer.

5. Combination as claimed in claim 1, 2, 3 or 4, characterized in that the photopolymer layer is adhered to the carrier during the forming of the layer.

6. Combination as claimed in any of the foregoing claims, characterized in that the carrier is adapted for use as flexible printing plate on a printing device provided with a printing cylinder and a tension cylinder.

7. Device for manufacturing combinations as claimed in any of the foregoing claims, characterized by a moulding device for moulding a photopolymer layer around the carrier and subsequently allowing the polymer to cure.

8. Device as claimed in claim 7 , characterized by polishing means for polishing the photopolymer layer to a constant thickness of the photopolymer layer.

9. Device for performing processes on a combination as claimed in any of the claims 1-6, such as exposure of the polymer layer of the combination, washing or drying of the combination, characterized in that the device comprises support means for supporting the flexible carrier.

10. Printing device for printing of an image arranged in relief on a flexible printing plate as claimed in any of the claims 1-6, comprising:

- a printing cylinder,-

- a counter-pressure cylinder,- - through-feed means for feeding the substrate for printing between the printing cylinder and the counter-pressure cylinder,- and

- inking means for applying ink to the flexible printing plate,- characterized by:

- a tension cylinder, the axis of which extends parallel to the axis of the printing cylinder and which is adapted to fix a flexible printing plate arranged around the printing cylinder and the tension cylinder.