Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
  • G08B13/2408—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using ferromagnetic tags
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2428—Tag details
  • G08B13/2437—Tag layered structure, processes for making layered tags
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2428—Tag details
  • G08B13/2437—Tag layered structure, processes for making layered tags
  • G08B13/2442—Tag materials and material properties thereof, e.g. magnetic material details
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F10/00—Thin magnetic films, e.g. of one-domain structure
  • H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
  • H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
  • H01F10/12—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys
  • H01F10/13—Amorphous metallic alloys, e.g. glassy metals
  • H01F10/132—Amorphous metallic alloys, e.g. glassy metals containing cobalt
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F10/00—Thin magnetic films, e.g. of one-domain structure
  • H01F10/26—Thin magnetic films, e.g. of one-domain structure characterised by the substrate or intermediate layers
  • H01F10/265—Magnetic multilayers non exchange-coupled

Definitions

• the present invention relates to a security device comprising as security feature a (first) soft-magnetic thin film with a thickness ranging from 100 nm (nanometer) to 2000 nm.
• security device are herein defined as comprising anti- pilferage labels, authentication labels and data carrying labels.
• soft-magnetic generally refers to material having a rather low coercive force H c ranging from 3 A/m (0.037 Oersted) to 500 A/m (6.28 Oersted).
• hard or semi-hard magnetic material has a much higher coercive force H c , for example the coercive force H c of semi-hard magnetic material ranges from 2000 A/m (about 25 Oe) to 8000 A/m (about 100 Oe), and the coercive force H c of hard magnetic material is higher than 25000 A/m (about 312 Oe).
• the magnetization of a soft-magnetic material is easily affected by a small external magnetic field, whereas for a hard- magnetic material a strong external magnetic field is necessary to change its magnetization.
• US-A-4,960,651 discloses an anti-pilferage label comprising a soft- magnetic thin film with a preferable composition along following lines : Co a Fe Ni c Mo d Si e B f , where a to f are atomic percentages and a ranges between 35 % and 70 %, b between 0 % and 8 %, c between 0 % and 40 %, d between 0 % and 4 %, e between 0 % and 30 %, f between 0 % and 30 %, with at least one element of each of the groups (b, c, d) and (e, f) being non zero.
• Such a Co a Fe Ni c Mo d Si e B f composition is hereinafter referred to as a CoFeNiMoSiB composition.
• the soft-magnetic thin film must have a thickness greater than 500 nm. Below 500 nm, surface pinning effects become dominant and the signal obtained from the security device in an interrogating gate is rather poor.
• Another drawback is that the soft-magnetic thin film has its easy axis in a direction perpendicular to the direction of winding the magnetic thin film. This makes it difficult to make and/or use labels with a high aspect ratio, e.g. with dimensions 40 mm x 1 mm, where the long axis is in the roll- direction. For example, use of such labels at high speed in source- tagging or using application guns is causing more failures and production stand stills.
• a security device which comprises as security feature a soft-magnetic thin film having a thickness ranging from 100 nm to 2000 nm.
• the thin film is composed of an amorphous Co x Zr y Nb z alloy, where x, y and z are atomic percentages and fulfil following conditions :
• Co x Zr y Nb z alloys are referred to as CZN compositions. Following CZN compositions are given as examples : Co 87 Zr s Nb 8
• CZN compositions are known as such for use in magnetic recording applications (e.g. as materials used in recording heads) and for use in antennas.
• the effective relative permeabilities ⁇ e reported in these applications are significantly lower in magnitude than those found in the present invention.
• Thin films made of CZN compositions have an effective relative magnetic permeability ⁇ e ranging between 20000 and 200000, of course very dependent on sample dimensions.
• the effective relative magnetic permeability ⁇ e is determined as the slope of a hysteresis curve as measured by means of a magneto meter at the coercive point, i.e. the point where the magnetic induction flux B is zero.
• ⁇ e are higher than the effective relative magnetic permeability ⁇ e of comparable CoFeNiMoSiB thin films, i.e. with an equal thickness.
• the CoFeNiMoSiB thin films have an effective relative magnetic permeability ⁇ e ranging between 20000 and 60000.
• the effective relative permeability ⁇ e of a magnetic security tag i.e. the magnetic permeability as seen from outside the tag, may be derived approximately from the formula :
• ⁇ r is the intrinsic relative magnetic permeability and where N is the demagnetisation factor.
• the demagnetisation factor N or its inverse, 1 / N, the shape factor, can be calculated as function of the geometrical shape of the security tag.
• the demagnetisation factor N and the shape factor 1 / N change as follows with decreasing thickness T of the security tag :
• the increased shape factor also results in an improved non-linear behaviour of the hysteresis curve to small interrogating magnetic fields so that the security device is not only better detected in security detecting devices, but this is also the case in anti-pilferage systems based on harmonics as in "Barkhausen" anti-pilferage systems (as commercialized by Sensormatic and Certus).
• the fact that with CZN thin films one is able to reduce the thin film thickness to below 500 nm also means that there will be - in comparison with CoFeNiMoSiB thin films a reduced amount of eddy-currents and a reduced hysteresis loss with high frequencies.
• Still another advantage of the thin CZN thin films is that they also allow to reduce the thickness of the substrate, due to lower heat-load of the deposition process on the substrate. This results in the advantage of lower cost, possibility of longer production runs and a more environment- friendly process.
• the CZN thin films further have following magnetic properties : a coercive field H c ranging between 5 A/m and 80 A/m ; an anisotropy field H k ranging between 500 A m and 5000 A/m.
• CZN thin films have proved to give an easy axis in the direction of the winding of the thin film during manufacturing by means of a webcoater.
• CZN thin film suitable for elongated labels with e.g. a length to width ratio being higher than 2, for example ranging from 10 to
• FIGURE 1 schematically illustrates how a CZN soft-magnetic thin film is applied to a substrate ;
• FIGURE 2A, FIGURE 2B, FIGURE 2C, FIGURE 2D, FIGURE 2E and FIGURE 2F illustrate various embodiments of a 360° label by combining a CZN thin film with a CoFeNiMoSiB thin film.
• reference number 10 represents a cross-section of a high vacuum chamber, i.e. a chamber at 10 '1 to 10 "5 Pa.
• Vacuum pumps (not shown) are connected to chamber 10 by means of conduit pipes 11.
• a flexible substrate 12 such as a polymer film is unwound from a storage drum 14 and guided to a coating or cooling drum 16.
• magnetrons 18, 20, 22 and 24 When passing along magnetrons 18, 20, 22 and 24, ultra-thin layers of the CZN target material are sputtered onto the surface of the substrate 12.
• the coated substrate 26 is then rewound on the other side of the coating drum 16 on another storage drum 28.
• the sputtering starts when a negative voltage is applied to the CZN target material and when an inert gas flow is introduced into the vacuum chamber 10 up to a total pressure of between 8.10 "4 mbar and 5.10 "2 mbar.
• Positive argon ions which originate due to the electric and magnetic fields, are accelerated towards the negatively biased target, impinge on it with high energy and release atoms from the target. These atoms have enough energy to travel to the substrate where they are stopped and bonded, forming a high precision coating.
• the CZN soft-magnetic coating according to the invention can be made by means of a single, double or multiple pass vacuum magnetron- sputtering operation.
• the anisotropic behaviour of the magnetic properties can be tailored by proper arrangement of magnetic flux lines.
• the deposition power, cooling of drum and type of substrate are important factors that influence the anisotropic behaviour and magnetic properties in general. This anisotropic behaviour makes the soft-magnetic coating according to the invention different from soft-magnetic coatings of similar CZN composition, as used in magnetic recording heads.
• the deposition process according to the invention results in softer magnetic properties in the direction of the easy axis, than soft-magnetic coatings of similar composition, as used in magnetic recording heads. This is achieved by the nature of the webcoating process.
• a 360° label can be obtained by combinations of CZN thin films with easy axis in the direction of winding and CoFeNiMoSiB thin films with easy axis perpendicular to the direction of winding. These combinations can be obtained by lamination or in-situ deposition of the two different materials. For example the following combinations can be deposited in-situ, in the vacuum-coating chamber as given in FIGURE 1.
• FIGURE 2A A double layer comprising a CZN layer 30 and a CoFeNiMoSiB layer 32 can be obtained with CZN targets on magnetron positions 18 and 20, and CoFeNiMoSiB targets on magnetron positions 22 and 24.
• FIGURE 2B A multi-layer comprising alternating CZN layers 30 and
• CoFeNiMoSiB layers 32 can be obtained with CZN targets on magnetron positions 18 and 22, and CoFeNiMoSiB targets on magnetron positions 20 and 24.
• FIGURE 2C A double layer comprising a CZN layer 30 and a CoFeNiMoSiB layer 32 can be obtained with a CZN target on magnetron position 18, and CoFeNiMoSiB targets on magnetron positions 20, 22 and 24.
• FIGURE 2D A double layer comprising a CZN layer 30 and a
• CoFeNiMoSiB layer 32 can be obtained with CZN targets on magnetron positions 18, 20 and 22 and a CoFeNiMoSiB target on magnetron position 24.
• FIGURE 2E A double layer comprising a CZN layer 30 and a
• CoFeNiMoSiB layer 32 can be obtained with a CoFeNiMoSiB target on magnetron position 18, and CZN targets on magnetron positions 20, 22 and 24.
• FIGURE 2F A double layer comprising a CZN layer 30 and a
• CoFeNiMoSiB layer 32 can be obtained with CoFeNiMoSiB targets on magnetron positions 18, 20 and 22, and a CZN target on magnetron position 24.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Automation & Control Theory (AREA)
• Computer Security & Cryptography (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Power Engineering (AREA)
• Thin Magnetic Films (AREA)
• Magnetic Heads (AREA)
• Soft Magnetic Materials (AREA)
• Burglar Alarm Systems (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

Country Status (5)

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• 1999
  • 1999-07-12 DE DE69903352T patent/DE69903352T2/de not_active Expired - Lifetime
  • 1999-07-12 EP EP99936527A patent/EP1145204B1/de not_active Expired - Lifetime
  • 1999-07-12 AT AT99936527T patent/ATE225549T1/de not_active IP Right Cessation
  • 1999-07-12 WO PCT/EP1999/004942 patent/WO2000005693A2/en active IP Right Grant
  • 1999-07-12 AU AU51593/99A patent/AU5159399A/en not_active Abandoned

Non-Patent Citations (1)

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