EP2483475A1 - A security feature for inclusion in a security paper - Google Patents

A security feature for inclusion in a security paper

Info

Publication number
EP2483475A1
EP2483475A1 EP10757437A EP10757437A EP2483475A1 EP 2483475 A1 EP2483475 A1 EP 2483475A1 EP 10757437 A EP10757437 A EP 10757437A EP 10757437 A EP10757437 A EP 10757437A EP 2483475 A1 EP2483475 A1 EP 2483475A1
Authority
EP
European Patent Office
Prior art keywords
security
wavelength
region
paper
security feature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10757437A
Other languages
German (de)
French (fr)
Inventor
Gary Donald Spinks
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DW Spinks Embossing Ltd
Original Assignee
DW Spinks Embossing Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GBGB0917166.1A external-priority patent/GB0917166D0/en
Application filed by DW Spinks Embossing Ltd filed Critical DW Spinks Embossing Ltd
Priority to EP10757437A priority Critical patent/EP2483475A1/en
Publication of EP2483475A1 publication Critical patent/EP2483475A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/40Agents facilitating proof of genuineness or preventing fraudulent alteration, e.g. for security paper
    • D21H21/42Ribbons or strips

Definitions

  • the present invention concerns security features for inclusion in security papers. More particularly, the invention concerns a security feature for inclusion in pulp from which a security paper is manufactured.
  • security features included in security papers are holograms, foils, metallic threads, planchettes, watermarks, and microdots.
  • Another example of a security feature that is incorporated into a security paper is a security fibre.
  • Paper is made from paper pulp, which contains cellulose fibres, for example wood, hemp, straw and cotton linters. (note that, whilst those cellulose fibres are used to make paper, they are not themselves made from paper) .
  • a known security technique is to replace, with artificial fibres made from materials such as polyester, nylon and rayon, some of the cellulose fibres used to make a security paper.
  • a relatively small number of the artificial fibres can be included in the paper pulp, along with a majority of cellulose fibres, which results in the security paper that is manufactured from the pulp having the artificial fibres distributed embedded within it and randomly distributed.
  • the artificial fibres can be dyed or coated, resulting in the paper including a random pattern of small coloured regions.
  • the dye can be a dye that is responsive to ultraviolet (UV) light, so that the coloured random pattern is visible only under UV light.
  • Such artificial fibres are generally fibrous in shape (i.e. predominantly one-dimensional, rather than two- dimensional or sheet-like) , like the cellulose fibres they replace.
  • WO2004/025028A1 D W Spinks (Embossing) Ltd
  • security features that are referred to as "fibres” because they substitute for and bond with the cellulose fibres used in the manufacture of security paper, and because, in the manufactured paper, they give a visual impression that suggests that they are similar to such fibres.
  • the paper fibres described in that document are small strips of paper, and are not fibrous in shape.
  • the "fibres" are intended for incorporation into paper products as a form of counterfeit protection.
  • Each fibre has a plurality of coloured regions visible on front and rear sides of said fibre, wherein the colours are visible only under UV light.
  • the regions may be in the form of stripes, or may be arranged in a pseudo-random pattern.
  • the regions may be differently coloured.
  • planchettes and traditional (fibrous) security fibres are distinct kinds of security feature; however, planchettes are similar to the fibres described in WO2004/025028A1 insofar as they are both made of paper and they are both intended for inclusion in paper pulp used for the manufacture of security paper.
  • planchettes are typically relatively large, circular pieces of paper or film which may be coated with dyes or pigments. They have limited usefulness as security devices, as they are difficult to use in paper making: planchettes do not bond well within sheets of paper; consequently, they A pick out' during subsequent printing processes carried out on the paper sheet. Prior-art fibres are typically more than about 20 times smaller than
  • planchettes (a nylon fibre might typically be 18 microns in width and 4 mm long having a surface area of .072 mm 2 , whereas a planchette might be 1.5 mm diameter having a surface area of 1.77 mm 2 ) . Because they are long and thin, security fibres entwine better than planchettes with the fibres in the base material, and hence better into the sheet of paper.
  • planchette that fluoresces in different colours when illuminated with UV light of different colours.
  • the planchette fluoresces in a blue colour; when illuminated with short-wavelength UV, a green fluorescence is excited; however, the blue fluorescence is also excited to some extent by the short-wavelength UV, resulting in the planchette having a greeny-blue colour overall.
  • the colour response of the planchette to UV illumination of different colours is not well
  • GB 2300596 A describes a security feature that
  • the fluorescent components may be in the form of coatings or incorporated in the substrate.
  • the UV light absorber may be in the
  • WO 02/46528 Al describes a security feature that is used with a substrate.
  • the security feature includes a plurality of fluorescent micro-particles that form a background component of the security feature and a plurality of fluorescent discrete particles that form a foreground component of the security feature.
  • the discrete particles are larger in size than the micro-particles and are
  • micro-particles optionally distinguishable from the micro-particles under at least one illumination condition.
  • illumination condition optionally distinguishable from the micro-particles under at least one illumination condition.
  • the security feature is applied as a coating to the substrate, and the security feature further includes a coating binder in which the micro-particles and the discrete particles are contained.
  • the discrete particles are optically distinguishable from the micro-particles under long wavelength ultraviolet light and/or under short
  • the security feature Under no or low magnification conditions the security feature exhibits a generally uniform color to the naked eye, while in one embodiment under higher magnification conditions the discrete particles exhibit a first color while the micro-particles of the background component exhibit a second color, while in another
  • the discrete particles exhibit a first color while the micro-particles of the background component exhibit a lack of color, while in a further embodiment the micro-particles of the background component exhibit a first color while the discrete particles exhibit a lack of color.
  • the present invention seeks to provide an improved security feature for inclusion in a security paper.
  • the present invention provides a security feature having the features set out in claim 1.
  • the present invention provides a security feature having the features set out in claim 1.
  • invention also provides a method of making a security feature, the method having the features set out in claim 14.
  • Preferred (that is, optional) features of the invention are set out in the dependent claims.
  • the present invention provides, according to a first aspect, a security feature for inclusion in a pulp from which a security paper is to be made, wherein the security feature is a sheet divided into a plurality of regions, said regions comprising: a first region that includes a first pigment that fluoresces in response to illumination by UV light of a first, longer, wavelength, and a second, different, region that includes a second, different, pigment that fluoresces in response to illumination by UV light of a second, shorter, wavelength.
  • the regions of the plurality are not co-extensive, nor are they overlapping and wholly contained one within
  • the regions of the plurality may be discrete regions, with no overlap between adjacent regions. At least some of the regions of the plurality may overlap each other.
  • the invention enables printing of detailed images, such as typographic symbols (e.g. text), that fluoresce when illuminated by UV light of the shorter wavelength, on a security feature on which there is also printed ink that fluoresces when illuminated by UV light of the longer wavelength.
  • prior-art security features that fluoresce at both wavelengths suffer from a problem if fine details are attempted at the shorter
  • pigments that respond to the longer wavelength typically also show some fluorescence at the shorter wavelength, which causes details printed using the ink responsive to the shorter wavelength to be
  • UV part of the electromagnetic spectrum can be divided in different ways.
  • References to "long- wavelength UV” or similar phrases as used herein refer to UV light having a wavelength of 300 nm to 400 nm (also called
  • UV near UV
  • mid UV UV light having a wavelength of 200 nm to 300 nm
  • the longer wavelength may be a wavelength in the near UV.
  • the first pigment may have a peak response at or around 365 nm.
  • the shorter wavelength may be a wavelength in the mid UV.
  • the second pigment may have a peak response at or around 245 nm.
  • the maximum width of the sheet may be for example 0.1 mm, 0.2 mm, 0.3 mm. 0.4 mm, or 0.5 mm.
  • the maximum length of the sheet may be for example 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm or 2 mm.
  • the sheet may be a sheet of paper.
  • the paper may have a basis weight of between 10 gsm and 75 gsm.
  • the paper has a basis weight of between 10 gsm and 35 gsm; according to American Paper Weights and Measures, tissue paper has a basis weight of between 10 gsm and 35 gsm, and thus the sheet may be a sheet of tissue paper.
  • the paper has a wet tensile strength of at least 1 N/15mm, more preferably at least 3 N/15mm. It may be that the paper has a wet tensile strength of less than 15 N/15mm, preferably less than 7 N/15mm.
  • the wet tensile strength may be the wet tensile strength of the paper itself, or it may be the wet tensile strength of the paper including any print, varnishes, or other material which increases the wet tensile strength relative to that of the paper itself.
  • the paper may have a dry tensile strength of about 5 daN/30mm.
  • the paper may have an opacity of up to 90% or more, or alternatively may be transparent.
  • the paper may include a varnish .
  • the fluorescence of the first pigment may be in the visible region of the electromagnetic spectrum.
  • the fluorescence of the second pigment may be in the visible region of the electromagnetic spectrum.
  • the fluorescence of the first region and the fluorescence of the second region may be in different colours (i.e. at different wavelengths) .
  • the plurality of regions may include one or more further regions.
  • One or more of said further regions may be visible under illumination by visible light.
  • One or more of said further regions may fluoresce in response to
  • One or more of said further regions may fluoresce in response to illumination by UV light of the first wavelength.
  • One or more of said further regions may fluoresce in response to illumination by UV light of the second wavelength.
  • One or more of said further regions may fluoresce in response to illumination by UV light of a third wavelength, different from the first and second wavelengths.
  • One or more of said further regions may fluoresce in the same colour as the first region.
  • One or more of said further regions may fluoresce in the same colour as the second region.
  • One or more of said further regions may fluoresce in a colour that is different from the colour or colours in which the first and second regions fluoresce.
  • the first region may comprise a plurality of stripes that fluoresce in at least two (preferably two or three) colours when illuminated by the first wavelength.
  • the stripes may be arranged in a repeating pattern.
  • the first pigment may be present in substantially all of the first region.
  • the first pigment may present in less than all of the first region; for example, there may be one or more sub-regions of the pigment within the first region; the one or more sub-regions may for example form images or text within the first region.
  • the images or text which may be formed within the first region or are within the second region may be microprinting; for example individual characters of text may in their largest dimension be smaller than 1 mm, smaller than 500 microns, smaller than 200 microns, smaller than 100 microns or even smaller than 50 microns.
  • the second region may form a margin on the sheet.
  • the second region may be adjacent to the first region.
  • the second region may substantially surround the first region.
  • the second region may be at the ends of the sheet.
  • the second region may be at the edge of the sheet.
  • the first and/or second pigment may be visible from both sides of the sheet. Alternatively, it may be that the first and/or second pigment is visible from only one side of the sheet.
  • the pigments may be contained in inks present on a first face of the sheet. It may be that at least one of the inks present on the first side of the sheet does not bleed through to the opposite side of the sheet, but it may nevertheless be that the ink is visible from the opposite side of the sheet. It may be that at least one of the inks present on the first face of the sheet does bleed through to the opposite side of the sheet. It may be that at least one f the inks is present on both sides of the sheet, either as a result of bleed through or because it has been applied by printing on both sides.
  • the present invention provides, according to a second aspect, a security paper including a security feature according to the first aspect of the invention.
  • the present invention provides, according to a third aspect, a method of making a security feature for inclusion in a pulp from which a security paper is to be made, the method comprising
  • UV light of a second, shorter, wavelength.
  • the first and/or second pigment may be applied for example by printing (which may be impact or non-impact printing), coating or dyeing.
  • the first and/or second pigment may be applied using print transfer techniques ( i . e . plates or cylinders that transfer the image) .
  • the first and/or second pigment may be applied without using print transfer techniques, for example by slot coating or selective dyeing (i.e. using photoresist chemicals) .
  • print transfer techniques for example by slot coating or selective dyeing (i.e. using photoresist chemicals) .
  • non-impact printing include ink-jet printing, laser printing, and thermal printing.
  • the present invention provides, according to a fourth aspect, a method of making a security paper according to the second aspect of the invention, comprising forming a pulp, including in the pulp a plurality of security features according to the first aspect of the invention, and forming the security paper from the pulp.
  • Another aspect of the invention provides: a security feature for inclusion in a pulp from which a security paper, in which the security feature will be embedded, is to be made, wherein the security feature is a sheet, which is divided into a plurality of regions, and which includes a first pigment, in a region of the
  • the fluorescent pigments may fluoresce under illumination by light of a region of the spectrum other than the ultra-violet region.
  • the first and/or second pigment may fluoresce (that is, emit visible light), in response to illumination by infra-red (IR) light, for example light in the near- infrared (light having a wavelength of 750 nm to 1.4 microns) .
  • IR infra-red
  • Fluorescence under illumination by light in the infrared may be a result of the anti-Stokes effect.
  • the first pigment emits visible light in response to illumination by UV light
  • the second pigment emits visible light in response to illumination by IR light.
  • the UV response of the first pigment provides a first,
  • the IR response of the second pigment provides a second, forensic, test.
  • Figure 1 is a schematic view of an example security device according to a first embodiment of the invention, illuminated by (a) visible light, (b) long-wavelength UV light, and (c) short-wavelength UV light;
  • Figure 2 is a schematic view of an example security paper according to a first embodiment of the invention, illuminated by (a) visible light; and (b) long-wavelength UV light;
  • FIG. 3 is a flowchart showing steps in the
  • Figure 4 is a flowchart showing steps in the manufacture of the example security paper of Fig. 2;
  • Figure 5 is a schematic view of an example security device according to a second embodiment of the invention, illuminated by (a) long-wavelength UV light, and (b) short- wavelength UV light;
  • Figure 6 is a schematic view of an example security device according to a third embodiment of the invention, illuminated by (a) long-wavelength UV light, and (b) short- wavelength UV light; and
  • Figure 7 is a schematic view of an example security device according to a fourth embodiment of the invention, illuminated by (a) visible light, (b) long-wavelength UV light, and (c) short-wavelength UV light.
  • Fig. 1 shows an example of a security device according to an example embodiment of the invention, in the form of a security fibre.
  • the fibre is a small strip of paper 10, in this example 0.2 mm x 1 mm.
  • the fibre 10 includes pigments that are visible only when illuminated with UV light.
  • Fig. 1(a) when the fibre 10 is viewed under visible light (Fig. 1(a)), it appears white.
  • Fig. 1(b) When the fibre 10 is viewed under long-wavelength UV light (Fig. 1(b)), a series of regions 20 appear along the fibre 10, except for at its ends, which remain white regions, forming margins 30.
  • the regions 20 in this example are printed with fluorescent pigments, such that the regions 20 form a series of coloured bands under long-wavelength UV illumination. In this example, the bands form a periodic sequence, [White] -Red- Green-Blue-Red-Green-Blue- [White ] .
  • pigments in margins 30 fluoresce, forming, in this example, text 40 (visible with the aid of a magnifying glass or microscope) .
  • the pigments that fluoresce under long-wavelength UV light typically have a broad response to illumination by UV, so that they will fluoresce weakly even under short-wavelength UV.
  • the fibres 10 are incorporated into the paper pulp used to manufacture a security paper, in this example a banknote 50 (Fig. 2). Under visible light (Fig. 2(a)), the fibres 10 are unremarkable, blending in with other, cellulose, fibres that make up the paper of the banknote 10. However, under long-wavelength UV light, the fibres 10 fluoresce, forming a random pattern of multicolour markings in the banknote 50, indicated schematically by the dotted pattern in Fig. 2(b) . Under short-UV light, the text 40 becomes visible, under magnification (not shown in Fig. 2) . Thus a long-wavelength UV light is used for first-level check of the validity of the security paper, e.g. in a shop, or by a bank teller, and a short-wavelength UV light is used as a further, forensic, occasional, check, and as evidence that the fibres 10 supplied to the manufacturer of the security paper are themselves genuine.
  • a long-wavelength UV light is used for first-level
  • Fibres 10 are in this example manufactured by the process shown in Fig. 3. Paper is drawn from a roll in a paper store 60 and passed to a printing machine 70.
  • Printing machine 70 includes ink reservoirs 80 (a) to (d) , which contain three inks containing pigment fluorescent in different colours when illuminated with long UV wavelengths and one ink containing pigment fluorescent when illuminated with short wavelength UV wavelengths.
  • the printing machine prints regions 20 and text 40 onto fibre 10, to form
  • the printed paper passes to cutting machine 90, where it is cut into fibres 10.
  • the cut fibres 10 are deposited into a bin 100 for transport to a paper mill.
  • Security fibres 10, produced by the method of Fig. 3, are drawn from store 110 and mixed with water and conventional cellulose fibres (from a second store 120) to form a pulp 130.
  • a paper making machine 140 manufactures paper from pulp 130 using conventional methods.
  • further processing of the paper takes place, including printing of standard images and the like.
  • the manufactured and printed paper is then cut (step 160) to form the paper product 170, in this case, banknotes .
  • fibre 510 is similar to fibre 10 of Fig. 1. It is blank under visible light. Again it has a plurality of bands 520 that fluoresce at different colours when illuminated with long-wavelength UV light (Fig. 5(a)) . In this example, however, white regions extend around the whole of the fibre 510, completely surrounding and enclosing the bands 520, and thereby forming a circumferential margin 530. Text 540, visible only when illuminated with short-wavelength UV light (Fig. 5(b)), is printed around the whole extent of margin 530.
  • the fibre 610 has a first region that covers the whole face of the fibre, except for an elliptical central region 640, which forms a second region.
  • the first region is printed with an ink containing a pigment responsive to long-wavelength UV illumination
  • the second region is printed with an ink containing a pigment responsive to short-wavelength UV illumination.
  • the fibre appears blank under visible light, shows a white ellipse surrounded by a fluorescent region (in this example a red region) under long-wavelength UV (Fig. 6(a)), and shows a fluorescent ellipse (in this example a blue region) surrounded by a weakly fluorescent red region under short-wavelength UV (Fig. 6(b)) .
  • a fibre 710 again has bands 720 that fluoresce (in this example yellow and blue) when illuminated with long-wavelength UV light.
  • bands 720 that fluoresce in this example yellow and blue
  • every third band 725 is printed with visible ink
  • Margin 730 extends around the bands 720, 725. In margin 730 there are printed, in ink that fluoresces under short-wavelength UV illumination, a series of typographic characters 740, in this example a repeating sequence triangle-square-circle. Thus, under visible light (Fig. 7(a)), only red bands 725 are visible. Under long- wavelength UV (Fig. 7(b)), bands 720 are visible, and under short-wavelength UV (Fig. 7(c)), typographic characters 740 are visible.

Abstract

A security feature, for inclusion in a pulp from which a security paper (50) is to be made, is a sheet (10). The security feature includes a first pigment that fluoresces in response to illumination by UV light of a first, longer, wavelength, and a second, different, pigment that fluoresces in response to illumination by UV light of a second, shorter, wavelength. The sheet (10) is divided into a plurality of regions (20. The first pigment is in a first region, and the second pigment is in a second, different, region.

Description

A security feature for inclusion in a security paper
Background of the Invention The present invention concerns security features for inclusion in security papers. More particularly, the invention concerns a security feature for inclusion in pulp from which a security paper is manufactured.
Counterfeiters are becoming increasingly sophisticated in their efforts to reproduce security documents.
Reprographic equipment available to counterfeiters becomes more effective with each passing year, and counterfeiters show considerable ingenuity when simulating security features that have been included in genuine security documents. Consequently, there is a continuing demand for innovative security features that can be produced at relatively low cost, but which, when included in a security document, produce an effect that cannot be reproduced using technologies available to counterfeiters, or likely to be available to them in the near future. Examples of security documents include banknotes, passports, driving licences, bank cards, and certificates of various kinds. Examples of security features included in such documents include chips containing biometric or other data, printed features, such as patterns of lines that create interference patterns when copied, and various features incorporated into the security paper from which the security document is made. Examples of security features included in security papers are holograms, foils, metallic threads, planchettes, watermarks, and microdots. Another example of a security feature that is incorporated into a security paper is a security fibre. Paper is made from paper pulp, which contains cellulose fibres, for example wood, hemp, straw and cotton linters. (note that, whilst those cellulose fibres are used to make paper, they are not themselves made from paper) . A known security technique is to replace, with artificial fibres made from materials such as polyester, nylon and rayon, some of the cellulose fibres used to make a security paper. A relatively small number of the artificial fibres can be included in the paper pulp, along with a majority of cellulose fibres, which results in the security paper that is manufactured from the pulp having the artificial fibres distributed embedded within it and randomly distributed. The artificial fibres can be dyed or coated, resulting in the paper including a random pattern of small coloured regions. The dye can be a dye that is responsive to ultraviolet (UV) light, so that the coloured random pattern is visible only under UV light.
Such artificial fibres are generally fibrous in shape (i.e. predominantly one-dimensional, rather than two- dimensional or sheet-like) , like the cellulose fibres they replace. WO2004/025028A1 (D W Spinks (Embossing) Ltd) describes security features that are referred to as "fibres" because they substitute for and bond with the cellulose fibres used in the manufacture of security paper, and because, in the manufactured paper, they give a visual impression that suggests that they are similar to such fibres. In fact, however, the paper fibres described in that document are small strips of paper, and are not fibrous in shape. The "fibres" are intended for incorporation into paper products as a form of counterfeit protection. Each fibre has a plurality of coloured regions visible on front and rear sides of said fibre, wherein the colours are visible only under UV light. The regions may be in the form of stripes, or may be arranged in a pseudo-random pattern. The regions may be differently coloured.
As mentioned above, another security feature that can be included in security paper is a planchette. Planchettes and traditional (fibrous) security fibres are distinct kinds of security feature; however, planchettes are similar to the fibres described in WO2004/025028A1 insofar as they are both made of paper and they are both intended for inclusion in paper pulp used for the manufacture of security paper.
However, unlike fibres, planchettes are typically relatively large, circular pieces of paper or film which may be coated with dyes or pigments. They have limited usefulness as security devices, as they are difficult to use in paper making: planchettes do not bond well within sheets of paper; consequently, they Apick out' during subsequent printing processes carried out on the paper sheet. Prior-art fibres are typically more than about 20 times smaller than
planchettes (a nylon fibre might typically be 18 microns in width and 4 mm long having a surface area of .072 mm2, whereas a planchette might be 1.5 mm diameter having a surface area of 1.77 mm2) . Because they are long and thin, security fibres entwine better than planchettes with the fibres in the base material, and hence better into the sheet of paper.
The applicant has manufactured and sold a planchette that fluoresces in different colours when illuminated with UV light of different colours. When illuminated with long- wavelength UV light, the planchette fluoresces in a blue colour; when illuminated with short-wavelength UV, a green fluorescence is excited; however, the blue fluorescence is also excited to some extent by the short-wavelength UV, resulting in the planchette having a greeny-blue colour overall. Thus, the colour response of the planchette to UV illumination of different colours is not well
differentiated.
It is also known to print text onto banknotes and other security papers in inks containing fluorescent pigments, the pigments being selected so that the ink fluoresces in a first colour under long-wavelength UV illumination, and in a second colour under short-wavelength UV illumination.
GB 2300596 A describes a security feature that
comprises a transparent or translucent substrate and two fluorescent components which fluoresce UV light at different visible colours and a UV light absorber. The fluorescent components may be in the form of coatings or incorporated in the substrate. The UV light absorber may be in the
substrate or as a layer.
WO 02/46528 Al describes a security feature that is used with a substrate. The security feature includes a plurality of fluorescent micro-particles that form a background component of the security feature and a plurality of fluorescent discrete particles that form a foreground component of the security feature. The discrete particles are larger in size than the micro-particles and are
optionally distinguishable from the micro-particles under at least one illumination condition. In the preferred
embodiment the security feature is applied as a coating to the substrate, and the security feature further includes a coating binder in which the micro-particles and the discrete particles are contained. The discrete particles are optically distinguishable from the micro-particles under long wavelength ultraviolet light and/or under short
wavelength ultraviolet light. Under no or low magnification conditions the security feature exhibits a generally uniform color to the naked eye, while in one embodiment under higher magnification conditions the discrete particles exhibit a first color while the micro-particles of the background component exhibit a second color, while in another
embodiment the discrete particles exhibit a first color while the micro-particles of the background component exhibit a lack of color, while in a further embodiment the micro-particles of the background component exhibit a first color while the discrete particles exhibit a lack of color.
The present invention seeks to provide an improved security feature for inclusion in a security paper.
Summary of the Invention
The present invention provides a security feature having the features set out in claim 1. The present
invention also provides a method of making a security feature, the method having the features set out in claim 14. Preferred (that is, optional) features of the invention are set out in the dependent claims.
The present invention provides, according to a first aspect, a security feature for inclusion in a pulp from which a security paper is to be made, wherein the security feature is a sheet divided into a plurality of regions, said regions comprising: a first region that includes a first pigment that fluoresces in response to illumination by UV light of a first, longer, wavelength, and a second, different, region that includes a second, different, pigment that fluoresces in response to illumination by UV light of a second, shorter, wavelength.
The regions of the plurality are not co-extensive, nor are they overlapping and wholly contained one within
another. The regions of the plurality may be discrete regions, with no overlap between adjacent regions. At least some of the regions of the plurality may overlap each other. Advantageously, the invention enables printing of detailed images, such as typographic symbols (e.g. text), that fluoresce when illuminated by UV light of the shorter wavelength, on a security feature on which there is also printed ink that fluoresces when illuminated by UV light of the longer wavelength. In contrast, prior-art security features that fluoresce at both wavelengths suffer from a problem if fine details are attempted at the shorter
wavelength: as discussed above, pigments that respond to the longer wavelength typically also show some fluorescence at the shorter wavelength, which causes details printed using the ink responsive to the shorter wavelength to be
indistinct. By printing the pigments responsive to the different wavelengths in different regions (for example, by providing the second pigment in a region of the fibre that does not contain the first pigment) , fine details can be printed the clarity of which is not compromised by the residual fluorescence of the other regions.
The ultraviolet part of the electromagnetic spectrum can be divided in different ways. References to "long- wavelength UV" or similar phrases as used herein refer to UV light having a wavelength of 300 nm to 400 nm (also called
"near UV") , and references to short-wavelength UV or similar phrases as used herein refer to UV light having a wavelength of 200 nm to 300 nm (also called "mid UV") .
The longer wavelength may be a wavelength in the near UV. The first pigment may have a peak response at or around 365 nm. The shorter wavelength may be a wavelength in the mid UV. The second pigment may have a peak response at or around 245 nm.
The maximum width of the sheet may be for example 0.1 mm, 0.2 mm, 0.3 mm. 0.4 mm, or 0.5 mm. The maximum length of the sheet may be for example 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm or 2 mm.
The sheet may be a sheet of paper. The paper may have a basis weight of between 10 gsm and 75 gsm. Preferably, the paper has a basis weight of between 10 gsm and 35 gsm; according to American Paper Weights and Measures, tissue paper has a basis weight of between 10 gsm and 35 gsm, and thus the sheet may be a sheet of tissue paper. It may be that the paper has a wet tensile strength of at least 1 N/15mm, more preferably at least 3 N/15mm. It may be that the paper has a wet tensile strength of less than 15 N/15mm, preferably less than 7 N/15mm. (The wet tensile strength may be the wet tensile strength of the paper itself, or it may be the wet tensile strength of the paper including any print, varnishes, or other material which increases the wet tensile strength relative to that of the paper itself.) The paper may have a dry tensile strength of about 5 daN/30mm. The paper may have an opacity of up to 90% or more, or alternatively may be transparent. The paper may include a varnish .
The fluorescence of the first pigment may be in the visible region of the electromagnetic spectrum. The fluorescence of the second pigment may be in the visible region of the electromagnetic spectrum. The fluorescence of the first region and the fluorescence of the second region may be in different colours (i.e. at different wavelengths) .
The plurality of regions may include one or more further regions. One or more of said further regions may be visible under illumination by visible light. One or more of said further regions may fluoresce in response to
illumination by UV light of the first wavelength. One or more of said further regions may fluoresce in response to illumination by UV light of the second wavelength. One or more of said further regions may fluoresce in response to illumination by UV light of a third wavelength, different from the first and second wavelengths. One or more of said further regions may fluoresce in the same colour as the first region. One or more of said further regions may fluoresce in the same colour as the second region. One or more of said further regions may fluoresce in a colour that is different from the colour or colours in which the first and second regions fluoresce.
The first region may comprise a plurality of stripes that fluoresce in at least two (preferably two or three) colours when illuminated by the first wavelength. The stripes may be arranged in a repeating pattern.
The first pigment may be present in substantially all of the first region. Alternatively, the first pigment may present in less than all of the first region; for example, there may be one or more sub-regions of the pigment within the first region; the one or more sub-regions may for example form images or text within the first region. The images or text which may be formed within the first region or are within the second region may be microprinting; for example individual characters of text may in their largest dimension be smaller than 1 mm, smaller than 500 microns, smaller than 200 microns, smaller than 100 microns or even smaller than 50 microns.
The second region may form a margin on the sheet. The second region may be adjacent to the first region. The second region may substantially surround the first region. The second region may be at the ends of the sheet. The second region may be at the edge of the sheet.
The first and/or second pigment may be visible from both sides of the sheet. Alternatively, it may be that the first and/or second pigment is visible from only one side of the sheet. The pigments may be contained in inks present on a first face of the sheet. It may be that at least one of the inks present on the first side of the sheet does not bleed through to the opposite side of the sheet, but it may nevertheless be that the ink is visible from the opposite side of the sheet. It may be that at least one of the inks present on the first face of the sheet does bleed through to the opposite side of the sheet. It may be that at least one f the inks is present on both sides of the sheet, either as a result of bleed through or because it has been applied by printing on both sides.
It may be that the inks are present on one side of the fibre in one sequence of colours and on the other side of fibre in the same sequence of fibres. It may be that the inks are present on one side of the fibre in a first sequence of colours and on the other side of the fibre in a second, different sequence. The present invention provides, according to a second aspect, a security paper including a security feature according to the first aspect of the invention.
The present invention provides, according to a third aspect, a method of making a security feature for inclusion in a pulp from which a security paper is to be made, the method comprising
providing a sheet;
applying to a first region of the sheet a first pigment that fluoresces in response to illumination by UV light of a first, longer, wavelength; and
applying to a second, different, region a second, different, pigment that fluoresces in response to
illumination by UV light of a second, shorter, wavelength.
The first and/or second pigment may be applied for example by printing (which may be impact or non-impact printing), coating or dyeing. The first and/or second pigment may be applied using print transfer techniques ( i . e . plates or cylinders that transfer the image) .
Alternatively, the first and/or second pigment may be applied without using print transfer techniques, for example by slot coating or selective dyeing (i.e. using photoresist chemicals) . Examples of non-impact printing include ink-jet printing, laser printing, and thermal printing.
The present invention provides, according to a fourth aspect, a method of making a security paper according to the second aspect of the invention, comprising forming a pulp, including in the pulp a plurality of security features according to the first aspect of the invention, and forming the security paper from the pulp.
Another aspect of the invention provides: a security feature for inclusion in a pulp from which a security paper, in which the security feature will be embedded, is to be made, wherein the security feature is a sheet, which is divided into a plurality of regions, and which includes a first pigment, in a region of the
plurality, which fluoresces in response to illumination by light of a first wavelength, and a second, different, pigment that fluoresces in response to illumination by light of a second wavelength, characterised in that the second pigment is in one or more sub-regions of a second,
different, region of the plurality, wherein said sub-regions form images or text within the second region.
In this aspect, at least one of the fluorescent pigments may fluoresce under illumination by light of a region of the spectrum other than the ultra-violet region. For example, the first and/or second pigment may fluoresce (that is, emit visible light), in response to illumination by infra-red (IR) light, for example light in the near- infrared (light having a wavelength of 750 nm to 1.4 microns) . Fluorescence under illumination by light in the infrared may be a result of the anti-Stokes effect. In an important example embodiment, the first pigment emits visible light in response to illumination by UV light, and the second pigment emits visible light in response to illumination by IR light. In this example embodiment, the UV response of the first pigment provides a first,
preliminary, test for the authenticity of the security feature, whereas the IR response of the second pigment provides a second, forensic, test. By providing the second pigment in a region separate from the region containing the first pigment, the images or text formed by the second pigment are clearer than would otherwise be the case.
It will of course be appreciated that features
described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa. Similarly, features of the invention discussed with regard to the aspects of the invention in which the pigments fluoresce under UV light may be incorporated into embodiments of the invention in which at least one of the pigments may
fluoresce under illumination by light of a region of the spectrum other than the UV region.
Description of the Drawings
Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:
Figure 1 is a schematic view of an example security device according to a first embodiment of the invention, illuminated by (a) visible light, (b) long-wavelength UV light, and (c) short-wavelength UV light;
Figure 2 is a schematic view of an example security paper according to a first embodiment of the invention, illuminated by (a) visible light; and (b) long-wavelength UV light;
Figure 3 is a flowchart showing steps in the
manufacture of the example security device of Fig. 1; Figure 4 is a flowchart showing steps in the manufacture of the example security paper of Fig. 2;
Figure 5 is a schematic view of an example security device according to a second embodiment of the invention, illuminated by (a) long-wavelength UV light, and (b) short- wavelength UV light;
Figure 6 is a schematic view of an example security device according to a third embodiment of the invention, illuminated by (a) long-wavelength UV light, and (b) short- wavelength UV light; and
Figure 7 is a schematic view of an example security device according to a fourth embodiment of the invention, illuminated by (a) visible light, (b) long-wavelength UV light, and (c) short-wavelength UV light.
Detailed Description
Fig. 1 shows an example of a security device according to an example embodiment of the invention, in the form of a security fibre. The fibre is a small strip of paper 10, in this example 0.2 mm x 1 mm. The fibre 10 includes pigments that are visible only when illuminated with UV light.
Consequently, when the fibre 10 is viewed under visible light (Fig. 1(a)), it appears white. When the fibre 10 is viewed under long-wavelength UV light (Fig. 1(b)), a series of regions 20 appear along the fibre 10, except for at its ends, which remain white regions, forming margins 30. The regions 20 in this example are printed with fluorescent pigments, such that the regions 20 form a series of coloured bands under long-wavelength UV illumination. In this example, the bands form a periodic sequence, [White] -Red- Green-Blue-Red-Green-Blue- [White ] . When the fibre 10 is viewed under short-wavelength UV illumination (Fig. 1(c)), pigments in margins 30 fluoresce, forming, in this example, text 40 (visible with the aid of a magnifying glass or microscope) .
It has been found that the pigments that fluoresce under long-wavelength UV light typically have a broad response to illumination by UV, so that they will fluoresce weakly even under short-wavelength UV. By providing the pigments that fluoresce at short wavelengths in a region of the fibre that does not contain the pigments that fluoresce under long-wavelength UV, it becomes possible to provide fine details on the fibre 10, in this example text 40, which would not be clearly visible if printed onto regions also including the pigments responsive to long-wavelength UV (due to such pigments also fluorescing weakly under short- wavelength UV) .
The fibres 10 are incorporated into the paper pulp used to manufacture a security paper, in this example a banknote 50 (Fig. 2). Under visible light (Fig. 2(a)), the fibres 10 are unremarkable, blending in with other, cellulose, fibres that make up the paper of the banknote 10. However, under long-wavelength UV light, the fibres 10 fluoresce, forming a random pattern of multicolour markings in the banknote 50, indicated schematically by the dotted pattern in Fig. 2(b) . Under short-UV light, the text 40 becomes visible, under magnification (not shown in Fig. 2) . Thus a long-wavelength UV light is used for first-level check of the validity of the security paper, e.g. in a shop, or by a bank teller, and a short-wavelength UV light is used as a further, forensic, occasional, check, and as evidence that the fibres 10 supplied to the manufacturer of the security paper are themselves genuine.
Fibres 10 are in this example manufactured by the process shown in Fig. 3. Paper is drawn from a roll in a paper store 60 and passed to a printing machine 70.
Printing machine 70 includes ink reservoirs 80 (a) to (d) , which contain three inks containing pigment fluorescent in different colours when illuminated with long UV wavelengths and one ink containing pigment fluorescent when illuminated with short wavelength UV wavelengths. The printing machine prints regions 20 and text 40 onto fibre 10, to form
multiple copies across fibre 10 of the pattern shown in Fig. 1. The printed paper passes to cutting machine 90, where it is cut into fibres 10. The cut fibres 10 are deposited into a bin 100 for transport to a paper mill.
At the paper mill, the banknote of Fig. 2 is
manufactured by the method shown in Fig 4. Security fibres 10, produced by the method of Fig. 3, are drawn from store 110 and mixed with water and conventional cellulose fibres (from a second store 120) to form a pulp 130. A paper making machine 140 manufactures paper from pulp 130 using conventional methods. At step 150, further processing of the paper takes place, including printing of standard images and the like. The manufactured and printed paper is then cut (step 160) to form the paper product 170, in this case, banknotes .
In an alternative example embodiment (Fig. 5) of a security device according to the invention, fibre 510 is similar to fibre 10 of Fig. 1. It is blank under visible light. Again it has a plurality of bands 520 that fluoresce at different colours when illuminated with long-wavelength UV light (Fig. 5(a)) . In this example, however, white regions extend around the whole of the fibre 510, completely surrounding and enclosing the bands 520, and thereby forming a circumferential margin 530. Text 540, visible only when illuminated with short-wavelength UV light (Fig. 5(b)), is printed around the whole extent of margin 530.
In another alternative example embodiment (Fig. 6) of a security device according to the invention. The fibre 610 has a first region that covers the whole face of the fibre, except for an elliptical central region 640, which forms a second region. The first region is printed with an ink containing a pigment responsive to long-wavelength UV illumination, and the second region is printed with an ink containing a pigment responsive to short-wavelength UV illumination. Thus, the fibre appears blank under visible light, shows a white ellipse surrounded by a fluorescent region (in this example a red region) under long-wavelength UV (Fig. 6(a)), and shows a fluorescent ellipse (in this example a blue region) surrounded by a weakly fluorescent red region under short-wavelength UV (Fig. 6(b)) .
In another alternative example embodiment (Fig. 7) of a security device according to the invention, a fibre 710 again has bands 720 that fluoresce (in this example yellow and blue) when illuminated with long-wavelength UV light. However, every third band 725 is printed with visible ink
(in this case red ink) . Margin 730 extends around the bands 720, 725. In margin 730 there are printed, in ink that fluoresces under short-wavelength UV illumination, a series of typographic characters 740, in this example a repeating sequence triangle-square-circle. Thus, under visible light (Fig. 7(a)), only red bands 725 are visible. Under long- wavelength UV (Fig. 7(b)), bands 720 are visible, and under short-wavelength UV (Fig. 7(c)), typographic characters 740 are visible.
All of the above example describe security features in the form of fibres. However, the invention may also be applied to other security features suitable for inclusion in a pulp from which a security paper is to be made, for example planchettes.
Where in the foregoing description, integers or elements are mentioned which have known, obvious or
foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other
embodiments .

Claims

Claims
1. A security feature for inclusion in a pulp from which a security paper, in which the security feature will be embedded, is to be made, wherein the security feature is a sheet, which is divided into a plurality of regions, and which includes a first pigment, in a region of the
plurality, which fluoresces in response to illumination by UV light of a first, longer, wavelength, and a second, different, pigment that fluoresces in response to
illumination by UV light of a second, shorter, wavelength, characterised in that the second pigment is in one or more sub-regions of a second, different, region of the plurality, wherein said sub-regions form images or text within the second region.
2. A security feature as claimed in claim 1, in which the longer wavelength is a wavelength in the near UV.
3. A security feature as claimed in claim 1 or claim 2 in which the shorter wavelength is a wavelength in the mid UV.
4. A security feature as claimed in any preceding claim, in which the regions of the plurality are discrete regions, with no overlap between adjacent regions.
5. A security feature as claimed in any of claims 1 to 4, in which the sheet is a sheet of paper.
6. A security feature as claimed in claim 5, in which the sheet is a sheet of tissue paper.
7. A security feature as claimed in any preceding claim, in which the plurality of regions include one or more further regions .
8. A security feature as claimed in claim 7, in which one or more of said further regions is visible under
illumination by visible light.
9. A security feature as claimed in any preceding claim, in which the first region comprises a plurality of stripes that fluoresce in at least two (preferably two or three) colours when illuminated by the first wavelength.
10. A security feature as claimed in any preceding claim, in which the first pigment is present in substantially all of the first region, such that no areas of the first region contain no first pigment.
11. A security feature as claimed in any of claims 1 to 9, in which the first pigment is present in less than all of the first region, such that an area of the first region contains no first pigment.
12. A security feature as claimed in any preceding claim, in which the second region forms a margin on the sheet.
13. A security paper including a security feature according to any preceding claim.
14. A method of making a security feature for inclusion in a pulp from which a security paper is to be made, the method compris ing
providing a sheet;
applying to a first region of the sheet a first pigment that fluoresces in response to illumination by UV light of a first, longer, wavelength; and
applying to one or more sub-regions of a second, different, region a second, different, pigment that
fluoresces in response to illumination by UV light of a second, shorter, wavelength.
15. A method of making a security paper according to claim 14, the method comprising forming a pulp, including in the pulp a plurality of security features according to any of claims 1 to 13, and forming the security paper from the pulp.
EP10757437A 2009-09-30 2010-09-28 A security feature for inclusion in a security paper Withdrawn EP2483475A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP10757437A EP2483475A1 (en) 2009-09-30 2010-09-28 A security feature for inclusion in a security paper

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GBGB0917166.1A GB0917166D0 (en) 2009-09-30 2009-09-30 A security feature for inclusion in a security paper
EP10154172 2010-02-19
EP10757437A EP2483475A1 (en) 2009-09-30 2010-09-28 A security feature for inclusion in a security paper
PCT/EP2010/064386 WO2011039199A1 (en) 2009-09-30 2010-09-28 A security feature for inclusion in a security paper

Publications (1)

Publication Number Publication Date
EP2483475A1 true EP2483475A1 (en) 2012-08-08

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Publication number Priority date Publication date Assignee Title
WO2012153116A1 (en) * 2011-05-06 2012-11-15 D W Spinks (Embossing) Limited Improved security device
GB2562262B (en) * 2017-05-10 2019-12-11 De La Rue Int Ltd Security devices and methods for their manufacture
EP3684974A4 (en) 2017-09-22 2021-05-05 Council of Scientific and Industrial Research Shaped objects for use in security applications

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Publication number Priority date Publication date Assignee Title
DE3779918D1 (en) * 1987-08-19 1992-07-23 Gao Ges Automation Org SECURITY PAPER.
GB8724570D0 (en) * 1987-10-20 1987-11-25 De La Rue Thomas & Co Ltd Fluorescent compounds
GB2300596B (en) 1995-05-10 1998-11-04 Portals Ltd Composite material having fluorescent features
US20020066543A1 (en) 2000-12-05 2002-06-06 Spectra Systems Corporation Fluorescent micro-particles embedded in a pigmented fluorescent coating for optical document security
GB2392868B (en) 2002-09-16 2006-02-01 D W Spinks Rainbow fibres
US7192471B2 (en) * 2004-09-24 2007-03-20 Honeywell International Inc. Aryl-ureido benzoxazinone compounds

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