WO2005030487A1

WO2005030487A1 - Exchangeable offset printing cylinder sleeve, use of and assembly comprising an offset printing cylinder sleeve of this type

Info

Publication number: WO2005030487A1
Application number: PCT/NL2004/000695
Authority: WO
Inventors: Gerrit Wolters; Adelbert Lucas Schoonman
Original assignee: Drent Holding B.V.
Priority date: 2003-10-02
Filing date: 2004-10-04
Publication date: 2005-04-07
Also published as: NL1024430C2

Abstract

An exchangeable offset printing cylinder sleeve according to the invention comprises a sleeve-shaped core layer and a sleeve-shaped printing layer. At least part of the outer surface of the sleeve-shaped printing layer is defined as a printing surface which is suitable for carrying a removable image. The sleeve-shaped printing layer is a continous sleeve at the location of the printing surface. In this context, continuous sleeve means that the printing layer is physically uninterrupted and that the properties of the printing layer which make it suitable for carrying an image layer do not vary significantly. The exchangeable offset printing cylinder sleeve is thus suitable for carrying a continuous printing image. The sleeve-shaped core layer comprises a plastic.

Description

Short title: Exchangeable offset printing cylinder sleeve, use of and assembly comprising an offset printing cylinder sleeve of this type.

The invention relates to an exchangeable offset printing cylinder sleeve according to the preamble of claim 1. An offset printing cylinder sleeve of this type is known in practice. Offset printing cylinder sleeves of this type are used in offset printing machines which are suitable for exchangeable printing sleeves. By changing the printing cylinder sleeves, an offset printing machine can be provided with a new printing image which is to be printed. Using printing cylinder sleeves of different thicknesses offers the user the possibility of using different pattern repeat lengths in one and the same offset printing machine. EP-Al-0875395, in column 7, line 39 et seq., discloses a printing cylinder sleeve which can comprise two layers. A printing layer made from ceramic can be fitted on a hollow metal base. Fig. 3 of this document shows a sleeve 60, which is made entirely of ceramic material. The thickness of the sleeve may vary between 1 and 10 cm. A drawback of the sleeve from EP-Al-0875395 is that it is made entirely from ceramic material or from ceramic material and metal. Especially with relatively thick sleeves, this results in heavy sleeves which. are difficult to handle when they have to be replaced in a printing machine. The object of the present invention is to provide an exchangeable offset printing cylinder sleeve, in which these drawbacks are at least partially overcome, or to provide a usable alternative. In particular, it is an object of the invention to provide an exchangeable offset printing cylinder sleeve which, at the same thickness, is lighter than the printing cylinder sleeve from EP-Al-0875395. According to the invention, this object is achieved by an offset printing cylinder sleeve according to claim 1. An exchangeable offset printing cylinder sleeve according to the invention comprises a sleeve-shaped core layer and a sleeve-shaped printing layer. At least part of the outer surface of the sleeve-shaped printing layer is defined as a printing surface which is suitable for carrying a removable image. The sleeve-shaped printing layer is a continuous sleeve at the location of the printing surface. In this context, continuous sleeve means that the printing layer is physically uninterrupted and that the properties of the printing layer which make it suitable for carrying an image layer do not vary significantly. The exchangeable offset printing cylinder sleeve is thus suitable for carrying a continuous printing image. The sleeve- shaped core layer is substantially made from a plastic. Due to the use of plastic, a weight reduction is achieved. In particular, a sleeve-shaped bonding layer is provided between the sleeve-shaped core layer and the sleeve-shaped printing layer. This bonding layer facilitates the application of the sleeve-shaped printing layer to the sleeve-shaped core layer. More particularly, the sleeve-shaped bonding layer comprises a metal, in particular zinc. In particular, the sleeve-shaped bonding layer is substantially made from metal, or a metal alloy, in particular zinc. Various metals, inter alia zinc, can be applied to the sleeve-shaped core layer made from plastic at a relatively low temperature in fluid form, so that it is possible to employ plastics which cannot withstand the temperatures that can occur when the printing layer is applied as a continuous sleeve. In one embodiment, the sleeve-shaped core layer comprises a foamed plastic, in particular polyurethane . In particular, the sleeve-shaped core layer is substantially made from a foamed plastic, in particular polyurethane. A foam of this kind makes it possible to produce sleeves having different thicknesses without the weight increasing much. In one embodiment, the printing surface is suitable for carrying a removable image layer. A removable image layer of this kind is generally very thin, so that it can still be considered offset printing. A removable image layer of this kind, together with a the printing surface, forms a printing image by forming areas which retain ink and areas which retain water or repel ink in some other way. In particular, the printing surface is provided with an adhesion layer. An adhesion layer of this kind improves the suitability of the printing surface for carrying a removable image layer . More particularly, the adhesion layer comprises organic molecules, having a first end which can adhere to the printing surface and a second end which can adhere to the removable printing layer. Organic molecules of this type offer good adhesion and can be applied very thinly. A method for producing an exchangeable offset printing cylinder sleeve, according to the invention, comprises supplying printing layer material in fluid form, for example in gaseous, vapour, liquid or dissolved form or in suspension. The printing layer material is also applied on the sleeve-shaped core layer in this fluid form. The step of supplying the material in fluid form can take place prior to or at the same time as the application step. The advantage of "this method is that it produces a sleeve- shaped printing layer, which extends in a continuous manner, i.e. seamlessly and with substantially homogeneous properties, around the sleeve-shaped core layer. This means that a printing image can be applied around the entire printing surface of the offset printing cylinder sleeve, as a result of which it is possible to print continuously. At the same time, no vibrations are produced, as would have been the case with the the prior art sleeve when the seam rolls along another cylinder, a cylinder with a sleeve or an ink application roll. In addition, the method makes it possible to control the amount of printing layer material, resulting in a thinner or thicker printing layer. Expediently, the printing layer material is vaporized before it is supplied and applied. In particular, the vaporization is effected by supplying thermal energy. For example, a pulverulent printing layer material may be introduced into a gas flame. It is also possible to apply a high electric voltage to two wires comprising the printing layer material and subsequently to place the two wires a small distance apart, producing a short-circuit between them. The electric sparkover results in printing layer material in vapour form. Other vaporization techniques , such as the use of a vacuum oven, are likewise possible. An advantage of applying the printing layer material in vapour form is that the layer thickness can be accurately controlled and that a very even layer is obtained. In a variant, the step of applying the printing layer comprises spraying the printing layer material onto the core layer. The advantage of this is that the printing layer material can be applied to the sleeve-shaped core layer in a directed fashion. In a particular form, the method according to the invention also comprises cooling the sleeve-shaped core layer during the application of the printing layer. This offers the advantage that the temperature of the fluid printing layer material can be relatively high during the application, without the temperature of the core layer material increasing to such a degree that it is damaged. In particular, the sleeve-shaped core layer can be cooled by means of a coolant gas. In order to prevent excessive heating up of the sleeve- shaped core layer, the latter may be partially shielded, in such a manner that the sleeve-shaped core layer is only exposed locally and for a short time to the temperature associated with the application of printing layer material in fluid form. In a variant, the method comprises a process step of grinding the printing layer, following the step of applying the printing layer. Grinding the printing layer has the effect that it acquires an exact, presettable and constant outer diameter. It is also possible to impart a specific desired roughness to the outer surface of the printing layer during the grinding operation. This roughness may be important with a view to both the adhesion of water to the surface during a wet offset printing process and the adhesion of a removable polymer intended for carrying an image. In a particular form, the method comprises a step of after- treating the printing layer, following the step of applying the printing layer and the optional grinding. An after-treatment of this kind may comprise polishing, brushing, blasting, chemically treating, electrochemically treating, such as electroplating, or applying laser light to the outer surface of the applied printing layer material. This after-treatment can impart desired lithographic properties to the surface or can improve these properties. In addition, it may improve the roughness for adhesion of the removable polymer. In a variant, the method comprises a step of applying a bonding layer to the sleeve-shaped core layer, prior to the step of applying the printing layer. The advantage of this step is that a material which bonds well to the core layer and also offers a good bonding base for the application of the printing layer can be chosen as the bonding layer material. In addition, it is possible to choose, for a bonding layer of this kind, a material, such as zinc, which may be applied to the core layer at a lower temperature than is required for applying the printing layer material. The bonding layer subsequently acts as an insulating and heat-dissipating layer during the application of the printing layer material. The invention further relates to the use of an exchangeable offset printing cylinder sleeve according to claim 10. An image layer is applied to the printing layer of an offset printing cylinder sleeve according to the invention. Such an image layer may comprise a polymer, for example, which is applied to the printing layer in an aqueous solution. After drying, the image layer is exposed by means of laser light. The polymer in the lasered areas cures and subsequently the non-cured polymer can be washed off the printing layer with the aid of water. Finally, the invention relates to an assembly of an exchangeable offset printing cylinder sleeve and an offset printing machine, according to claim 11. A.n embodiment of the invention will be explained in more detail with reference to the accompanying schematic drawing, in whic : Fig. 1 shows a longitudinal view of an exchangeable offset printing cylinder sleeve according to a preferred embodiment of the invention; Fig. 2 shows a cross section on line II-II of Fig. 1; Fig. 3 shows a perspective view of a printing cylinder support unit, fitted with an offset printing cylinder sleeve according to the invention. In Figs 1-3, the offset printing cylinder sleeve according to the invention is denoted overall by the reference numeral 1. The offset printing cylinder sleeve 1 is provided with a printing surface 2 which is suitable for carrying a removable image layer. The offset printing cylinder sleeve 1 is provided with a cylindrical recess 3 which is intended to be fitted over a mandrel of an offset printing machine (see the description below with reference to Fig. 3) . The offset printing cylinder sleeve 1 comprises a sleeve-shaped core layer 4, substantially made from a foamed plastic, in the illustrated example made from polyurethane foam (PU foam) . This material has the advantage that it is lightweight and can be used in various thicknesses, for example from 15 to 100 mm, so that different offset printing cylinder sleeves with the same inner diameter but different outer diameters and thus pattern repeat lengths can be used. The sleeve-shaped core layer 4 may have been obtained by spraying a foamed plastic in liquid form around and onto a cylindrical mould. After curing, a dimensionally stable sleeve is produced which is ground down to form a sleeve of a predetermined diameter. Such a method of manufacturing a sleeve-shaped core layer is simpler and more economical than that of the metal sleeves known from the prior art. A bonding layer 5, made from zinc, is provided concentrically around the sleeve-shaped core layer 4. A hydrophilic continuous printing layer 6 made from an aluminium alloy is provided, likewise concentrically with respect to the sleeve-shaped core layer 4, on the bonding layer 5. The printing layer 6 is seamless and is produced by applying the aluminium alloy in fluid form. The printing layer 6 is not laminated around the core layer in the form of a fixed layer and therefore does not have a seam. An adhesion layer 7 is applied to the printing layer 6. The adhesion layer 7 comprises organic molecules having, at a first end, a group which bonds well with the substrate, in this case aluminium, and, at the other end, a group which can bond with, for example, a polymer. Such an adhesion layer may be provided on the printing surface very thinly, for example in a thickness of one molecule. Products of this type are also known as self- assembled monolayers . The user applies an image layer in the form of a removable polymer 8 having ink-bearing and water-repelling properties to the adhesion layer 7, or directly to the printing layer 6. A polymer of this type is described in more detail in EP-A- 0802457. The polymer is exposed by the user, for example by means of a laser. As a result, the polymer melts locally and bonds together and to the printing surface 2. The non-exposed portion of the polymer may be removed, for example by washing, so that the exposed portion forms a printing image. Since the polymer forms a very thin layer, in the order of magnitude of 0.003 mm, the printing surface 2 can serve as a printing surface for offset printing. The printing surface 2 of the printing layer 6 is anodized. As a result, the printing layer preferably has substantially cylindrically shaped pores providing good adhesion of the image layer and good water-carrying properties. At the same time, anodized aluminium does not conduct heat well, as a result of which the heat generated locally by laser light does not radiate too quickly. Fig. 3 shows a printing cylinder support unit 9, which, when in operation, in turn forms part of an offset printing machine, having, inter alia, ink application means and substrate feed-through means (not shown) . The illustrated printing cylinder support unit may be incorporated in the offset printing machine so as to be exchangeable, in which case it is also referred to as a printing module, or may form a permanent part thereof. The offset printing cylinder sleeve 1 can be easily exchanged for another printing cylinder sleeve with the same or a different outer diameter. The printing cylinder sleeve 1 is pushed over a mandrel 10 and attached to it by means of clamping means (not shown) . The mandrel 10 is rotatably fixed between rotary arms 11, the rearmost of which is not clearly visible in the figure. The rotary arms 11 are rotatably attached to the frame 12. These rotary arms 11 make it possible to adjust the distance of the mandrel 10 relative to the rubber blanket cylinder 13, depending on the outer diameter of the sleeve 1 employed. By uncoupling the frontmost rotary arm 11 from the mandrel 10 and swinging it away, the printing cylinder sleeve 1 can be slid off the mandrel 1, making it possible to apply and remove the image layer outside the printing machine. This offers the advantage that the printing machine is ready for another print run quickly, that only one installation is required for applying and removing image layers for several printing cylinders and that any chemicals which might be used in the removal of the image layer do not end up in the offset printing machine. Many variants are possible in addition to the illustrated embodiment. A reversible polymer, for example, can be applied to the printing layer as printing layer. A polymer of this kind is affected by, for example, the application of laser light, as a result of which areas are created which attract ink or attract water and repel ink, respectively. It is also possible to apply an exchangeable printing image directly to the printing layer itself, as described in EP-Al-0875395. Other metals and metal alloys as well as ceramic materials are also suitable as hydrophobic alternatives to an aluminium alloy. A metal, metal alloy or ceramic material can also be supplied and applied in fluid form as a metal salt, in which case the metal, metal alloy or the ceramic material is deposited on the sleeve-shaped core layer, for example by a chemical process or by electrolysis. It is also possible to use silanes as adhesion layer, such as a trialkoxysilane compound with an additional functional group. Silanes adhere well to ceramic surfaces, as a result of which this adhesion layer is very suitable for a printing layer made from ceramic material. After hydrolysis of the alkoxy groups, the silane adheres to the printing layer, while the functional group reacts with the removable image layer. The printing layer may also be provided with an adhesion layer by phosphating, chromating or passivating. If desired, the printing layer may be designed to be very thin, having a thickness of less than one tenth of a millimetre, in particular a few hundredths of millimetres. By applying a thin printing layer to a thermally insulating core layer, the heat required for the adhesion of the image layer is retained sufficiently long. It is possible to use alternative materials for the bonding layer as well, such as metals and metal alloys having a lower melting point than the melting point of the printing layer, for example a metal alloy based on nickel. The sleeve-shaped core layer may also comprise a number of sublayers, for example sublayers of mutually different density and compressibility, and may be produced in a variety of ways. A sublayer of the sleeve-shaped core layer may comprise a fibre- reinforced polymer, such as epoxy or polyester. Examples of suitable fibres which may qualify include glass fibres and carbon fibres. The sleeve-shaped core layer does not have to be the innermost layer of the offset printing cylinder sleeve. An additional layer may be provided on the radially inner side of the offset printing cylinder sleeve, which layer may facilitate the installation on and removal from the mandrel. This additional layer may be one of the abovedescribed sublayers of the core layer, but may also be a separate layer, made from a material which is different from that of the core layer. The invention thus provides an exchangeable offset printing cylinder sleeve having a plastic core layer and suitable for use in an offset printing machine for exchangeable printing sleeves. Such an offset printing cylinder sleeve is lightweight and can be exchanged quickly. Due to the continuous printing layer, the sleeve does not cause vibrations and the offset printing cylinder sleeve can be provided with a continuous printing image. The printing image is applied by means of an exchangeable image layer, as a result of which the offset printing cylinder sleeve can be re-used. In this case, it is possible to clean the sleeve outside the offset printing machine, provide it with a new image layer and apply a printing image in the image layer. Depending on the choice of specific printing layer material, it is possible to employ different kinds of image layer materials for both wet and dry offset printing. The offset printing cylinder sleeve according to the invention can be produced inexpensively, without the end user still having to carry out accurate bending on the printing plates.

Claims

1. Exchangeable offset printing cylinder sleeve, comprising a sleeve-shaped core layer and a sleeve-shaped printing layer, in which at least part of the outer surface of the sleeve-shaped printing layer is defined as a printing surface which is suitable for carrying a removable image, and the sleeve-shaped printing layer is a continuous sleeve at the location of the printing surface, characterized in that the sleeve-shaped core layer is substantially made from plastic.

2. Exchangeable offset printing cylinder sleeve according to claim 1, in which a sleeve-shaped bonding layer extends between the sleeve-shaped core layer and the sleeve-shaped printing layer.

3. Exchangeable offset printing cylinder sleeve according to claim 2, in which the sleeve-shaped bonding layer comprises a metal.

4. Exchangeable offset printing cylinder sleeve according to claim 3, in which the sleeve-shaped bonding layer comprises zinc.

5. Exchangeable offset printing cylinder sleeve according to one of claims 1-4, in which the sleeve-shaped core layer comprises a foamed plastic.

6. Exchangeable offset printing cylinder sleeve according to claim 5, in which the foamed plastic comprises polyurethane.

7. Exchangeable offset printing cylinder sleeve according to one of claims 1-6, in which the printing surface is suitable for carrying a removable image layer.

8. Exchangeable offset printing cylinder sleeve according to claim 7, in which the printing surface is provided with an adhesion layer.

9. Exchangeable offset printing cylinder sleeve according to claim 8, in which the adhesion layer comprises organic molecules, having a first end which can adhere to the printing surface and a second end which can adhere to the removable printing layer.

10. Use of an exchangeable offset printing cylinder sleeve according to one of claims 1-9, for applying a removable image layer to the printing layer.

11. Assembly of an exchangeable offset printing cylinder sleeve according to one of claims 1-9, and an offset printing cylinder support unit.