WO2010055008A1

WO2010055008A1 - Magnetised coating effect

Info

Publication number: WO2010055008A1
Application number: PCT/EP2009/064822
Authority: WO
Inventors: Crispin Hawes
Original assignee: Crown Packaging Technology Inc
Current assignee: Crown Packaging Technology Inc
Priority date: 2008-11-11
Filing date: 2009-11-09
Publication date: 2010-05-20
Anticipated expiration: 2011-05-11
Also published as: GB0820611D0

Abstract

A method of producing an image 5 in a coating applied to an article, the method including the steps of - applying one or more magnets 2 to a ferrous substrate 1 to form a magnetic image, - removing the one or more magnets 2, - applying a coating containing magnetic particles, which align with the magnetic image to form the image 5, and - curing the coating to fix the image. The method may include a delay or dwell period between the formation of the magnetic image and the application of the coating containing magnetic particles. Despite the delay or dwell period, the substrate retains the magnetic image and the intensity / clarity of the image will be maintained.

Description

MAGNETISED COATING EFFECT Technical Field

[0001] The present invention relates to a method for decorating a ferrous substrate using a coating containing magnetic particles, which may be aligned to form an image on the substrate. A magnetic field is applied to the ferrous substrate to form a "magnetic image" on the substrate. When the coating is subsequently applied, the metallic particles in the coating are aligned to the "magnetic image", which may then be 'fixed' using conventional techniques, such as thermal drying or UV curing (anionic, cationic or a hybrid technology).

Background Art

[0002] Magnetic Ink Character Recognition (MICR) is well known for security marking of notes, cheques, credit cards etc. MICR technology is dependant on the use of specially formulated magnetic inks to print and is designed to allow electronic equipment to quickly read the encoded data. However, such data is invisible to the human eye.

[0003] Using magnetic particles to provide a metallic "flake" effect using iron compounds is also known from the prior art.

[0004] US 3791864 B (MAGNETFABRIK BONN GMBH) 12.02.1974 discusses production of a patterned effect in coatings applied to any surface, by applying a preliminary coating consisting of a liquid carrier into which permanent magnetic particles are suspended. This preliminary coating is hardened and the particles are subjected to a magnetic field in a predetermined pattern. Another coating containing magnetically orientable particles is then applied and these particles become orientated by the magnetic field produced by the particles in the preliminary coating. After hardening the coating displays the desired pattern.

[0005] Whilst this process allows the preliminary coating or primer to be applied to any surface and the process is described as being particularly suitable for objects made of ferro-magnetic material e.g. steel plate, the method described in this patent requires at least 2 coating layers (a special primer + a coating containing magnetically orientable particles). Disclosure of Invention

[0006] However, the inventor/s have found that when using a material capable of being magnetised e.g. tinplate (sheet steel covered with a thin layer of tin) or TFS Tin Free Steel (ECCS), a magnetic field (having the desired pattern or image) may be applied to the material, which retains this magnetic image and may be stored for a period of time prior to application of a coating containing magnetisable particles.

[0007] This "dwell period", is particularly useful when the material is being used on a production line, because stacks of material having a "magnetic memory" of a desired image may be stored prior to coating and drying. The inventor/s have also found that in a stack of material to which a magnetic image has been applied, the formed magnetic image does not transfer to adjacent sheets of material.

Brief Description of Drawings

[0008] The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a simplified, orthographic view of a printing line, in which the present invention is implemented as part of a production line; and Figure 2 is a schematic, orthographic view of an alternative printing method according to the invention, this time implemented off-line.

[0009] The method cording to the invention may be implemented in-line on a production line, as illustrated in Figure 1. In Figure 1 , a magnet 2 having a required image is mounted onto a roller and a sheet of steel 1 is transported past the magnet 2. The steel sheet having a "magnetic memory" 12 (of the required image) is then transported past a printing roller 3, which applies an ink or coating containing magnetically orientabie particles, which align themselves to the "magnetic image" 5 previously applied to the steel sheet 1. The steel sheet 1 is then transported to a drying station 4, where the image 5 is "fixed".

[0010] In an alternative arrangement, an off-line process is used as illustrated in Figure 2, in which a magnet 2 is applied to a steel of steel 1. The sheet or sheets 1 may then be stored for a "dwell period" (indicated by the letter T) of up to several months before being printed. [0011] This off-line process has the advantage that the magnet 2 may be applied to a plurality of sheets 1 , thereby providing sheets with a "magnetic memory" 12 and this process may be carried out completely separately from the printing of the sheets 1 on a production line. Thus the speed of the production process remains unaffected by the time taken to apply the magnet 2 to the sheet or sheets 1. The inventor has found that such sheets with a "magnetic memory" 12 may be stored for up to several months and the "magnetic image" will not be transferred to adjacent sheets in the stack.

[0012] One or more sheets having a "magnetic memory" 12 may then be printed with an ink or coating containing magnetically orientable particles (as previously described) and the image 5 is fixed in a drying station 4. The time that the magnet 2 is placed in contact with the steel sheet does not influence the intensity or clarity of the image 5.

[0013] The magnet 2 may be provided by a permanent magnet such as ferrite neobymium, magnetic matting of all grades or electromagnets. Additionally, the "magnetic image" can be produced successfully regardless of on which side of the steel sheet the magnet is applied i.e. the side that you are printing or on the reverse side, as the final "image" will still be visible.

Claims

1. A method of producing an image in a coating applied to an article, the method including the steps of

- applying one or more magnets to a ferrous substrate to form a magnetic image,

- removing the one or more magnets,

- applying a coating containing magnetically orientable particles, which align with the magnetic image to form the image, and

- curing the coating to fix the image.

2. A method of producing an image in a coating applied to an article according to claim 1 , wherein the ferrous substrate is left for at least 7 days after forming a magnetic image, but prior to applying the coating containing magnetic particles.

3. A method of producing an image in a coating applied to an article according to claim 2, wherein the ferrous substrate is left in proximity to other ferrous substrates but the magnetic image does not transfer to the other ferrous substrates.

4. A method of producing an image in a coating applied to an article according to any of the preceding claims, wherein the coating includes a pigment containing magnetically orientable particles.

5. A method of producing an image in a coating applied to an article according to any of the preceding claims, wherein the film weight for the coating is 18 — 20gsm wet or 6gsm dry.

6. A method of producing an image in a coating applied to an article according to any of the preceding claims, wherein conventional magnetic matting is used to form the magnetic image on the ferrous substrate.

7. A method of producing an image in a coating applied to an article according to any of the preceding claims, wherein the ferrous substrate is tin plate.