A printing forme of this type is known in the art as a nickel stencil for rotary screen printing, which is provided with a barcode which unambiguously defines the stencil. The barcode can be detected with the aid of a suitable barcode reader. A stencil of this type comprises a thin-walled hollow cylinder as the support, in which there is a regular pattern of openings which are delimited by the walls of the dykes. A metal printing screen, for example made from nickel, can be produced, for example, by electroforming. The printer usually provides the printing screen with a layer of photoresist or resin, which is then exposed and developed using light in accordance with a design which is to be printed, and the exposed or unexposed parts of the layer of photoresist or resin are removed, depending on whether a positive or negative photoresist is used. After stoving (hardening) of the remaining layer of photoresist, a stencil is thus obtained, i. e. a printing screen provided with a design which is defined by the exposed (printing) openings. A stencil of this type is ready for use for screen-printing. The support may be of cylindrical shape for rotary screen printing or may be flat for flat-bed screen printing.

During the production of another known printing forme, there is no photosensitive photoresist used as a coating layer on a printing screen, but rather the design is made in a suitable layer of resin or plastic by means of engraving (down to the printing screen).

This engraving can be carried out with the aid of a laser, such as a CO2 laser. The structure of a stencil produced in this way is similar to the stencil in which the photoresist technique is used.

Yet another known printing forme for screen-printing is produced by the electrodeposition (electroforming) of metals on a mould which bears a pattern of printing openings to be formed which determine the design to be printed. After sufficient metal has grown on, the printing forme obtained in this way is removed from the mould. In this way, a printing forme with printing openings which therefore does not include a coating layer which covers the printing openings is formed in one step. A printing forme produced in such a way is referred to in the trade as an"galvano".

Furthermore, a plastic printing forme which comprises a cylindrical or plate-like support in which the design to be printed, i. e. the printing openings, are made directly by means of perforation is also known in the art. Like the electroformed printing forme, this printing forme is known as a"galvano", even though there is actually no electrodeposition of metals. The perforations may be made, for example, using a laser, as described, for example, in NL-A-8802144.

The above-described examples of printing formes may have variable dimensions, such as length, width, diameter, open surface area, material thickness, fineness, pattern of the screen openings, etc. In addition, in finished stencils and galvanos, the designs will vary.

In the current state of the art, to provide recognition an identification is usually arranged by hand on stencils, in the form of an inscription, for example on the end ring of cylindrical stencils. However, identification of this nature is laborious, often unclear and is generally not user-friendly. Moreover, the information contained in the inscription concerning the printing forme in question is limited.

In the abovementioned nickel stencils, the possibilities of identification are improved compared to the codes applied by hand through the application of a barcode. However, a drawback of the use of barcodes in printing formes of this type is that during printing the barcode is soiled by printing ink and the like, and a barcode which has been covered with printing ink in this way is no longer machine-readable.

Broadly, the object of the invention is to improve the

identification of printing formes, both printing screens and finished stencils and galvanos, in particular the identification of printing formes which have been or are being used.

According to the invention, to this end the machine- readable identification means comprises an integrated circuit or a magnetizable material in which the code which is unique to the printing forme is present. The printing forme according to the invention comprises an identification means which is not an optically readable barcode, but rather can be detected and read inductively or capacitively with the aid of a suitable detection/reader device, such as sensors and the like. With reading of this type, it is not necessary for the identification means to be visible. On the one hand, this allows simple identification even of printing formes which have been used (and are therefore coated with printing ink and the like). On the other hand, this allows the identification means to be embedded in the material of the printing forme, so that the possibilities of fraud using the identification means are limited.

The identification means contains at least one unique code, for example a combination of numerals and/or letters and/or other symbols, which unambiguously identifies the corresponding printing forme. This unique code may include information about the properties of the printing forme and/or about the production process/manufacturer and/or the design (image). This information may, for example, be stored in a database, for example in a memory of a computer to which the detection device is connected. However, information of this type is preferably completely or partially incorporated in the code of the identification means itself. If information about the manufacturer is permanently stored in the identification means, it is possible at all times to establish the origin of the printing forme.

In this context, it is expressly pointed out that in the present application, both in the description and the associated claims, the term"printing forme"is understood as meaning all the printing screens mentioned above, including stencils and galvanos, both for rotary screen printing and for flat-bed screen printing. In addition to the conventional use of the printing forme according to

the invention for rotary screen printing, in which case a printing ink or printing paste is applied through the continuous openings to a substrate which is to be printed, the printing forme is also suitable for applying other coating materials to a substrate. One example of a coating material of this type is a hot-melt adhesive.

A preferred embodiment of an identification means according to the invention is a chip (a complex of electronic circuits on a carrier). A chip of this type can, for example, be read inductively, as is customary for protecting access to buildings. In addition to a read-only memory (ROM), the chip can also contain a writable and erasable memory (RAM), in which the user himself can record data about the printing process used, the design, and the like. A chip of this type may advantageously comprise organic semiconductive polymers on a nonconductive organic polymer substrate. The shape of a chip produced from these materials can easily be adapted to the surface structure of the support of the printing forme, on account of its flexibility.

One example of an identification means made from a magnetizable material is a magnetic strip.

The identification system can be used not only to identify stencils but also for authorization purposes in the printing device itself. That is to say, the printing device will only be enabled for printing when it has been verified, with the aid of the identification means, that a preset printing screen has been installed at the correct printing position (printing station) in the device. For authorization of this nature, each printing station has to be provided with a detection system for reading the identification means.

The identification means may, in addition to a memory in which non-erasable information about the printing forme and the production process is stored, also have a writable part in which customer-specific information can be recorded, such as the design, last date of use, etc.

The identification means will be provided in or on the printing forme at a location which is such that the printing process is not interfered with, for example those sections where printing

openings can never be formed or be present irrespective of the design.

Preferably, the support of the printing forme according to the invention is made from plastics material (reinforced with (oriented) fibres), such as epoxy which is reinforced with unidirectional carbon fibres, or a laminate, so that it is impossible for the induction signal from the identification means to be shielded, as may be the case with metal, for example nickel stencils.

One embodiment of the printing forme according to the invention is a galvano, in which the continuous openings are printing openings which define the image which is to be printed. The information about an image, either on a galvano or on a stencil, is preferably also stored in the identification means.

The invention also relates to a sleeve, in particular a preform for a printing forme as described above, comprising a thin- walled hollow cylinder, provided with a machine-readable identification means, comprising a code which is unique to the sleeve, wherein the machine-readable identification means comprises an integrated circuit or a magnetizable material in which the code which is unique to the sleeve is present. However, a sleeve of this type can also be used for numerous other purposes apart from screen- printing, for example for relief printing and intaglio printing, in which case a relief which includes recesses is written into the outer surface, for example with the aid of a laser, or for use as a thin metal support for printing plates for flexographic printing which can be mounted on and removed from an air roll. Other applications of thin-walled hollow cylinders of this type include, inter alia, the use as a transfer medium for transferring coatings and inks, an electroforming mould, as a coating material for example as a surface with specific frictional/sliding properties on an optionally driven roll. For all these applications, it is advantageous to be able to identify the sleeve, as discussed above with regard to a screen- printing forme. Important information about the sleeve include, for example, the length, internal diameter or external diameter, layer compositions, fibre directions, etc. The sleeve according to the invention is also advantageously produced from plastics material, as has already been discussed above with regard to the printing forme according to the invention.