Security articles comprising multi-responsive physical colorants

• US 20030194578A1
• Filed: 12/02/2002
• Published: 10/16/2003
• Est. Priority Date: 12/20/2001
• Status: Abandoned Application

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Wieczoreck, Juergen, Abdalla, Samir Z., Tam, Thomas Y., Lem, Kwok-Wai
• Application Number:
  US10/308,055
• Publication Number:
  US 20030194578A1
• Time in Patent Office: Days
• US Class Current: 428/690
• CPC Class Codes: B42D 25/355 Security threads
• CPC Class Codes: B42D 25/387 absorbing or reflecting ultraviolet light
• CPC Class Codes: D01D 5/24 with a hollow structure; Spinnerette packs therefor D01D5/38 takes precedence; producing tubes of plastic material B29D; addition of agents forming hollow filaments D01F1/08
• CPC Class Codes: D01D 5/253 with a non-circular cross section; Spinnerette packs therefor D01D5/38 takes precedence
• CPC Class Codes: D01F 1/04 Pigments
• CPC Class Codes: D01F 8/04 from synthetic polymers
• CPC Class Codes: D21H 21/48 Elements suited for physical verification, e.g. by irradiation
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles

Abstract

Security articles comprising elements such as filaments, fibers, including hollow fibers, and threads and thin transverse sections and chopped versions thereof, wherein such elements are dispersed within the articles. Particle scattering and luminescent technology is employed based on scattering, electronic, magnetic and/or light properties to provide compound physical coloration responsive to various portions of the electromagnetic spectrum, including ultraviolet, ambient and infrared. The coloration effects can be highly stable or dependent on specific switching effects linked to, e.g., thermal exposure or actinic radiation. The security articles result in advanced levels of security to avoid counterfeiting of objects including banknote and currency paper, stock and bond certificates, identification, credit, debit and ATM cards, drivers'"'"' licenses and bar codes.

Claims

1. A security article comprising a matrix component in which:

(A) at least one particle scattering colorant is dispersed; and

(B) at least one luminescent substance is dispersed;

wherein;

(1) said at least one particle scattering colorant comprises particles selected from the group consisting of a semiconductor, metallic conductor, metal oxide, metal salt or mixture thereof;

(2) said at least one particle scattering colorant has an average cross-sectional size in the smallest dimension of less than about 0.2 micron;

(3) said polymer matrix component is substantially non-absorbing in the visible region of the spectrum;

(4) said particle scattering colorant has a minimum in the transmitted light intensity ratio in the 380 to 750 nanometer range that is shifted at least by 10 nanometers compared with that obtained for the same semiconductor, metallic conductor, metal oxide, metal salt or mixture thereof having an average particle size above about 20 microns; and

(5) said luminescent substance is selected from the group consisting of at least one fluorescent substance, at least one phosphorescent substance, mixtures of at least one fluorescent and at least one phosphorescent substance, wherein said luminescent substance exhibits a luminescent spectral response peak when excited by at least one wavelength selected from the electromagnetic spectral region of from about 200 to about 2,000 nanometers.

3. The article of claim 1 wherein said particle scattering colorant particles comprise a metallic conductor selected from the group consisting of gold, platinum, copper, aluminum, lead, palladium, silver, rhodium, osmium, iridium, and alloys thereof and said particle scattering colorant particles have an average diameter in the smallest dimension of less than about 0.2 microns.

4. The article of claim 3 wherein the particle scattering colorant particles comprise one or more colloidal particles.

5. The article of claim 4 wherein the transmitted light intensity ratio has two minima in the wavelength region of the visible spectra and the particle distribution of the particle scattering colorant approaches a mononodal distribution.

12. The article according to claims 1 or 2 wherein said matrix component is selected from the group consisting of polymers, cellulosic compositions and glasses and wherein said luminescent substance comprises at least one fluorescent substance and at least one phosphorescent substance.

13. The article of claim 12 wherein said phosphorescent substance has afterglow characteristics.

14. The article according to claims 1 or 2 wherein at least one of said first and second matrix components comprises at least one material selected from the group consisting of homopolymers and copolymers of polyamide, polyester, polyolefin, polyvinyl, acrylic, polysulfone, polycarbonate, polyarylate and polystyrene.

17. An article selected from the group consisting of a filament and a fiber and comprising a composition selected from the compositions recited in any of claims 1 and 2.

18. The article of claim 17 wherein said at least one first composition forms a sheath that substantially covers a core of said filament or of said fiber comprising said second matrix component.

19. The article of claim 18 wherein said sheath and said core have differing cross-sectional shapes.

20. The article of claim 19 in which the maximum ratio of orthogonal axial dimensions in cross-section for an outer surface of said sheath is less than about one-half of the corresponding ratio for said core.

21. The article of claim 18 where said sheath and said core both have a maximum ratio of orthogonal axial dimensions in cross-section that exceeds two and the long axis directions in cross-section of said sheath and said core are unaligned.

22. An element comprising a plurality of articles according to claim 18, wherein said element has either spatially dependent coloration for individual articles or coloration for individual articles resulting from variations in the cross-section of said sheath or the cross-section of said core.

25. The article according to claims 1 or 2 wherein said particle scattering colorant comprises a ferroelectric, antiferroelectric, or photoferroelectric material.

26. The article of claim 25 in which said ferroelectric material is a relaxor ferroelectric ceramic.

27. The article of claim 26 wherein said relaxor ferroelectric ceramic has a Curie transition temperature of from about 250°

K. to about 350°

K.

28. The article of claim 26 wherein said relaxor ferroelectric ceramic has the form A(BF_1/2BG_1/2)O₃ where BF and BG represent the atom types on the B sites in a lead titanate type of structure, or is an alloy of one or more compositions of such form with another ceramic composition, and wherein A is Pb and BF_1/2 and BG_1/2 are independently Sc_1/2, Ta_1/2, Fe_1/2, or Nb_1/2.

29. The article of claim 26 wherein said relaxor ferroelectric ceramic has the form A(BF_1/3BG_2/3)O₃, where BF and BG represent the atom types on the B sites in a lead titanate type of structure, or is an alloy of one or more compositions of such form with another ceramic composition, and wherein A is Pb, BF_1/3 is Mg_1/3, Ni_1/3 or Zn_1/3, and BG_2/3 is Nb_2/3.

30. An article of claim 29 wherein said relaxor ferroelectric ceramic comprises Pb(Mg_1/3 Nb_2/3)O₃.

31. The article of claim 30 which includes up to 35 mole percent of alloyed PbTiO₃.

32. The article according to claims 1 or 2 which is in the form of a film or planar structure in which a layer of said at least one first composition is joined to either one side or to both opposite sides of said at least one second composition comprising said film or planar structure.

33. An article selected from the group consisting of a visual display and a switchable image comprising the article of claim 32, wherein said article further comprises a colorant selected from the group consisting of a particle scattering colorant, an electronic transition colorant, and a matrix switchable in either refractive index or absorption coefficient.

34. The article of claim 33 wherein an applied electric field changes a property selected from the group consisting of refractive index and absorption coefficient of said colorant.

35. The article of claim 33 wherein said article comprises a ferroelectric, antiferroelectric, or photoferroelectric composition.

40. The article of claim 17 wherein said fiber is a hollow fiber comprising a cavity central to said fiber and having an average dimension less than the overall average dimension of said fiber, said hollow fiber comprising a particle scattering colorant wherein:

(a) said particle scattering colorant is present within said cavity;

or

(b) said particle scattering colorant is dispersed in a polymer-containing matrix that forms a sheath surrounding said hollow fiber; and

(c) wherein the internal surface of said hollow fiber adjacent said cavity is colored with a material that significantly absorbs light in the visible region of the spectrum.

41. The hollow fiber of claim 40 comprising a plurality of lateral holes extending from said cavity of said fiber to the external surface of said fiber, wherein the average separation of adjacent holes along the length of said fiber is less than about 25.4 cm, and the average hole diameter is capable of imbibing a liquid into said fiber at a pressure of less than 13.8 MPa.

42. The hollow fiber of claim 40 comprising an electronic transition colorant.

43. The hollow fiber of claim 40, wherein the average particle size of said particle scattering colorant is less than about 0.1 microns and said particle scattering colorant, when dispersed in a colorless, isotropic liquid having a substantially different refractive index, is characterized at visible wavelengths as having an effective maximum absorbance that is at least about 2 times the effective minimum absorbance.

44. The hollow fiber of claim 40, wherein said particle scattering colorant is selected from the group consisting of a semiconductor and a metallic conductor;

said polymer matrix component is substantially non-absorbing in the visible region of the spectrum; and

said particle scattering colorant has a minimum in the transmitted light intensity ratio in the 380 to 750 nm range that is shifted at least by 10 nm compared with that obtained for the same semiconductor or metallic conductor having an average particle size above about 20 microns.

45. The article of claim 17 comprising at least one element selected from the group consisting of at least two of said fibers and at least two of said filaments.

46. The article of claim 17 wherein the effective diameter of said filament is in the range of from about 0.01 to 3 mm.

47. The article of claim 46 comprising at least two of said fibers.

48. The article according to claims 1 or 2 wherein at least one luminescent response is produced by a wavelength in the infrared region of the electromagnetic spectrum.

49. The article according to claims 1 or 2 wherein at least one luminescent response is produced by a wavelength in the visible region of the electromagnetic spectrum.

50. The article according to claims 1 or 2 wherein at least one luminescent response is produced by a wavelength in the ultraviolet region of the electromagnetic spectrum.

51. The article according to claims 1 or 2 wherein at least two excitation wavelengths selected from different members of the group consisting of the infrared, visible, and ultraviolet region of the electromagnetic spectrum produce luminescent responses.

54. The article according to claims 1 or 2, wherein said particle scattering colorant has an average particle size of less than 3 microns and comprises a plurality of layers, each of said layers having a different refractive index.

55. The article of claim 54 wherein said refractive index difference is greater than about 5%.

56. The article of claim 54 wherein said refractive index difference is greater than about 10%.

57. The article according to claims 1 or 2 wherein said luminescent substance comprises at least one fluorescent substance and at least one phosphorescent substance having afterglow characteristics, wherein said article is selected from the group consisting of a filament and a fiber.

58. The article of claim 57 adapted for use on or in an object, said article selected from the group consisting of film, slit film, fibers, dots and fibrils.

59. The article of claim 58 wherein said fiber, film or slit film has an average length substantially equal to the length or width dimension of the object in which it is dispersed or on which it is incorporated.

60. The article of claim 58 wherein said fibril or said dot comprises has an average maximum dimension substantially smaller than the length or width dimension of the object in which it is dispersed or on which it is incorporated.

61. The article of claim 60 wherein said fibril or said dot has a thickness substantially smaller than the thickness of the object in which it is dispersed or on which it is incorporated.

62. The article of claim 58 wherein said object comprises at least one structural element selected from the group consisting of film and sheet.

63. The article of claim 62 wherein at least one surface thereof is suitable for incorporation of information in a form selected from the group consisting of at least one image, typeface and a mixture of at least one image and typeface.

64. The article of claim 63 wherein said object is selected from the group consisting of:

currency, banknotes, negotiable instruments, passports, licenses, identification documents, credit cards, debit cards and bar codes.

2. A security article comprising at least one first composition and at least one second composition:

(A) said first composition comprising a solid first matrix component, a particle scattering colorant and at least one luminescent substance dispersed therein;

(B) said at least one second composition comprising a polymer second matrix component, and a colorant selected from the group consisting of an electronic transition colorant, dye and pigment dispersed therein;

(C) said at least one first composition being either;

(1) disposed on and substantially exterior to said second composition on at least one side of the article;

or

(2) said first and second compositions are substantially mutually interpenetrating;

wherein;

(i) there exists at least one incident visible light wavelength and one incident light angle such that said first composition absorbs less than about 90% of the light incident on said article;

(ii) the absorption coefficient of said at least one first composition is less than about 50% of that of said second composition at a wavelength in the visible region of the spectrum;

(iii) the highest absorption peak of said particle scattering colorant does not fall in the visible region of the spectrum;

(iv) said luminescent substance is selected from the group consisting of at least one fluorescent substance, at least one phosphorescent substance, and a mixture of at least one fluorescent and at least one phosphorescent substance, wherein said luminescent substance exhibits a luminescent spectral response peak when excited by one or more wavelength selected from the electromagnetic spectral region of about 200 to about 2,000 nanometers; and

(v) either;

(a) said particle scattering colorant has a refractive index that matches that of said first matrix component at a wavelength in the visible and has an average particle size of less than about 2000 microns;

or

(b) the average refractive index of said particle scattering colorant differs from that of said first matrix component by at least about 5% in the visible wavelength range, the average particle size of said particle scattering colorant in the smallest dimension is less than about 2 microns, and said particle scattering colorant, when dispersed in a colorless, isotropic liquid having a substantially different refractive index, is characterized at visible wavelengths as having an effective maximum absorbance that is at least about 2 times the effective minimum absorbance.

6. The article of claim 2 wherein said at least one first composition either absorbs or scatters more than about 50% of uniform radiation at the ultraviolet wavelength at which said at least one second composition undergoes the maximum rate of color fading.

7. The article of claim 2 wherein said particle scattering colorant is substantially non-absorbing in the visible region.

8. The article of claim 2 wherein the refractive index of said particle scattering colorant is substantially different than that of said first matrix component at all wavelengths in the visible region of the spectrum and wherein at least about 50% of all particles of said particle scattering colorant have a smallest dimension that is less than about 0.25 microns.

9. The article of claim 2, wherein for said particle scattering colorant:

(a) the average particle size is from about 0.001 to about 0.4 microns;

(b) the average ratio of maximum dimension to minimum dimension for individual particles is less than about four; and

(c) the refractive index is substantially different than that of the matrix at all wavelengths in the visible region of the spectrum.

10. The article of claim 2 wherein:

(a) the average particle size for the particle scattering colorant is less than about 1000 microns;

(b) both the first matrix component and the particle scattering colorants are substantially optically isotropic;

(c) there exists a wavelength in the visible region of the spectrum at which the refractive index of said first matrix component substantially equals that of said particle scattering colorant;

(d) the refractive index difference of said first matrix component and said particle scattering colorant is substantially dependent on wavelength in the visible range;

(e) and said first matrix composition is substantially non-absorbing at wavelengths in the visible region of the spectrum.

11. The article of claim 10 wherein the difference in n_F−

n_C for the particle scattering colorant and for the first matrix component is greater in absolute magnitude than 0.001, wherein n_F and n_C are the refractive indices at 486.1 nm and 656.3 nm respectively of the particle scattering colorant and the first matrix component.

15. The article of claim 2 wherein said first matrix component and said second matrix component are substantially mutually interpenetrating and where α

_ev_eV_e for said second composition and α

_sv_sV_s for said first composition differ by less than a factor of ten at a wavelength in the visible region;

wherein α

_e is the absorption coefficient for the electronic transition colorant;

α

_s is the effective absorption coefficient for the particle scattering colorant;

v_s and v_e are, respectively, the volumes of said at least one first and second compositions; and

V_S and V_e are respectively the volume fraction of said at least one first composition that is the particle scattering colorant and the volume fraction of said at least one second composition that is the electronic transition colorant.

16. The article of claim 2 wherein said at least one first composition is disposed on and is substantially exterior to said second matrix composition on at least one side of said article;

said at least one second composition comprises an electronic transition colorant or a pigment;

there exists a wavelength of visible light and a light incidence angle at which from about 10% to about 90% light transmission occurs through said at least one first composition; and

α

_et_eV_e is greater than 0.1 for said at least one second composition;

wherein α

_e is the absorption coefficient at the wavelength in the visible region at which the maximum absorption occurs for said electronic transition colorant or the pigment;

t_e is a maximum thickness of the layer comprising said at least one second composition; and

V_e is the volume fraction of said at least one second composition comprising said electronic transition colorant or pigment.

23. The article of claim 2 in which said particle scattering colorant in said at least one first composition comprises an inorganic composition.

24. The article of claim 23 wherein said inorganic composition comprises at least one material selected from the group consisting of bismuth oxychloride, titanium dioxide, antimony trioxide, barium titanate, solid solutions of BaTiO₃ with SrTiO₃, PbTiO₃, BaSnO₃, CaTiO₃, or BaZrO₃, potassium lithium niobate, aluminum hydroxide, zirconium oxide, colloidal silica, lithium niobate, lithium tantalite, proustite;

zinc oxide, alpha-zinc sulfide, and beta-zinc sulfide.

36. The article of claim 2 wherein the refractive index difference between said first polymer matrix component and either said particle scattering colorant or said electronic transition colorant undergoes substantial change at a wavelength in the visible spectra as a result of one or more of a temperature change, humidity change, an electric field, integrated thermal exposure, or exposure to either light or actinic radiation.

37. The article of claim 36 which undergoes a detectable color change responsive to one or more of chemical agents, pressure, temperature, moisture pickup, temperature limit, or time-temperature exposure.

38. The article of claim 36 wherein said electronic transition colorant comprises a photochromic anil, fulgide, or spiropyran.

39. The article of claim 2 comprising either an electronic transition colorant or a matrix polymer that displays electronic transition coloration, wherein dichroism in the visible range results from either preferential orientation of said electronic transition colorant or said matrix polymer.

52. The article of claim 2 in which the particle-scattering colorant comprises a gas.

53. The article of claim 52 wherein said gas is air.

65. A specific embodiment of the subject invention can be described as follows:

1. A security article comprising a matrix component in which;

(A) at least one particle scattering colorant is dispersed; and

(B) at least one luminescent substance is dispersed;

wherein;

(1) said at least one particle scattering colorant comprises particles selected from the group consisting of a semiconductor, metallic conductor, metal oxide, metal salt or mixture thereof;

(2) said at least one particle scattering colorant has an average cross-sectional size in the smallest dimension of less than about 0.2 micron;

(3) said polymer matrix component is substantially non-absorbing in the visible region of the spectrum;

(4) said particle scattering colorant has a minimum in the transmitted light intensity ratio in the 380 to 750 nanometer range that is shifted at least by 10 nanometers compared with that obtained for the same semiconductor, metallic conductor, metal oxide, metal salt or mixture thereof having an average particle size above about 20 microns; and

(5) said luminescent substance is selected from the group consisting of at least one fluorescent substance, at least one phosphorescent substance, mixtures of at least one fluorescent and at least one phosphorescent substance, wherein said luminescent substance exhibits a luminescent spectral response peak when excited by at least one wavelength selected from the electromagnetic spectral region of from about 200 to about 2,000 nanometers; and

(6) said particle scattering colorant particles comprise a metallic conductor selected from the group consisting of gold, platinum, copper, aluminum, lead, palladium, silver, rhodium, osmium, iridium, and alloys and mixtures thereof;

(7) said matrix component is selected from the group consisting of polymers, cellulosic compositions and glasses;

wherein;

(a) said luminescent substance comprises at least one fluorescent substance and at least one phosphorescent substance having afterglow characteristics;

(b) said at least one fluorescent substance and said at least one phosphorescent substance having afterglow characteristics are present in said matrix at a total concentration of from about 0.5 to about 15 weight percent;

(c) said article is selected from the group consisting of filaments, fibers, film, slit film, dots and fibrils, said article adapted for use in connection with an object;

(d) said object comprising at least one structural element adapted to accept on at least one surface thereof, information in a form selected from the group consisting of at least one image, typeface and a mixture of at least one image and typeface; and

(e) said object is selected from the group consisting of;

currency, banknotes, negotiable instruments, passports, licenses, identification documents, credit cards, debit cards and bar codes.