Optically variable thin film flake and collection of the same

• US 5,135,812 A
• Filed: 03/27/1991
• Issued: 08/04/1992
• Est. Priority Date: 12/28/1979
• Status: Expired due to Term

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: Flex Products Incorporated (Sicpa Holding SA)
• Inventors: Mayer, Thomas, Phillips, Roger W., Ash, Gary S.
• Primary Examiner(s): CANNON, JAMES
• Application Number:
  US07/675,799
• Time in Patent Office: 496 Days
• Field of Search: 106/403, 106/404, 428/403, 428/404, 428/913, 428/916
• US Class Current: 428/403
• CPC Class Codes: B05D 1/286 using a temporary backing to which the coating has been applied
• CPC Class Codes: B05D 5/06 to obtain multicolour or other optical effects B05D5/02 takes precedence
• CPC Class Codes: B41M 3/00 Printing processes to produce particular kinds of printed work, e.g. patterns printing apparatus or machines of special type or for particular purposes B41F17/00; special designs or pictures per se B44F; manufacturing printed circuits using printing techniques H05K3/12 ; manufacturing organic semiconductor devices using printing techniques H10K71/13
• CPC Class Codes: B41M 3/14 Security printing securities B42D25/29
• CPC Class Codes: C01P 2004/54 Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
• CPC Class Codes: C03C 17/00 Surface treatment of glass, not in the form of fibres or filaments, by coating optical coatings of optical elements G02B1/10
• CPC Class Codes: C09C 1/0015 Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings
• CPC Class Codes: C09C 1/0051 comprising a stack of coating layers with alternating low and high refractive indices, wherein the first coating layer on the core surface has the low refractive index
• CPC Class Codes: C09C 1/0078 Pigments consisting of flaky, non-metallic substrates, characterised by a surface-region containing free metal
• CPC Class Codes: C09C 2200/1054 the core consisting of a metal
• CPC Class Codes: C09C 2200/24 Interference pigments comprising a metallic reflector or absorber layer, which is not adjacent to the core
• CPC Class Codes: C09C 2220/20 PVD, CVD methods or coating in a gas-phase using a fluidized bed
• CPC Class Codes: C09D 11/50 Sympathetic, colour changing or similar inks
• CPC Class Codes: F24S 70/225 for spectrally selective absorption
• CPC Class Codes: Y02E 10/40 Solar thermal energy, e.g. solar towers
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10S 428/916 Fraud or tamper detecting
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide
• CPC Class Codes: Y10T 428/258 Alkali metal or alkaline earth metal or compound thereof
• CPC Class Codes: Y10T 428/259 : Silicic material
• CPC Class Codes: Y10T 428/2991 : Coated
• CPC Class Codes: Y10T 428/2993 : Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
• CPC Class Codes: Y10T 428/31507 : Of polycarbonate
• CPC Class Codes: Y10T 428/31786 : Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 428/31797 : Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31855 : Of addition polymer from unsaturated monomers

Abstract

Articles and methods for forming optically variable thin film flakes and replicated coatings having preselected optical properties. The articles generally comprise a flexible web of material and an optically variable thin film coating formed on one surface of the web. The optically variable coating is separated from the web to form optically variable thin film flakes. The flakes are disposed in ink and paint vehicles to provide optically variable inks, paints and the like.

Claims

1. A collection of optically variable thin film flakes adapted to be added to a liquid medium for producing a predetermined optical response to radiation incident on a surface of a solidified version of said medium, each of said flakes in said collection of flakes comprising a symmetrical optically variable multilayer thin film interference structure having first and second parallel planar surfaces, the collection of flakes being characterized in that they have physical dimensions such that when the flakes are measured parallel to and perpendicular to respectively the planar surfaces an aspect ratio of at least 2 to 1 is provided, the multilayer thin film structure being of symmetrical design and having at least one dielectric layer formed of an inorganic material with an index of refraction of 1.65 or less, at least one thin semi-transparent metal layer and at least one thick substantially opaque metal reflecting layer, the multilayer thin film structure producing a shift in color between the two distinct colors when the angle of incidence of light on the structure is shifted between two angles.

2. A collection as in claim 1 wherein each of said flakes comprises an opaque metallic layer having first and second surfaces, a dielectric layer of low index of refraction on each of said first and second surfaces and a thin metal layer carried by each of said dielectric layers, said multi-layer thin film structure producing a shift in color when the angle of incidence of light on the structure is shifted between two angles.

3. A collection as in claim 2 wherein said opaque metal layer is aluminum, wherein said dielectric of a low index of refraction is magnesium fluoride and wherein said thin metal layer is chromium.

4. A collection as in claim 1 wherein said thick substantially opaque metal layer is aluminum, wherein at least one dielectric layer is magnesium fluoride and wherein said thin semi-transparent layer is chromium.

5. An optically variable flake comprising a multi-layer thin film interference structure having first and second parallel planar surfaces, the flake having physical dimensions such that when the flake is measured in a direction parallel and perpendicular respectively to the planar surfaces an aspect ratio of at least 2:

1 is provided, the multi-layer thin film structure including a metal reflector having first and second surfaces parallel to the first and second parallel planar surfaces, at least one period disposed on one of said first and second surfaces of the metal reflector, each period being comprised of a dielectric layer with an index of refraction of 1.65 or less and a semi-opaque layer.

6. An optical variable flake as in claim 5, wherein the multi-layer thin film structure is of symmetrical design and wherein at least one period is disposed on each of the first and second surfaces of the metal reflector.