Optical effect layer

Patent metadata

Field	Value
Publication number	US-9834028-B2
Application number	US-201314399325-A
Country	US
Kind code	B2
Filing date	Apr 30, 2013
Priority date	May 7, 2012
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

The disclosure relates to the field of graphical elements and is directed to an optical effect layer (OEL), a device and a method for producing same. The disclosure provides an optical effect that is easy to detect as such and exhibits a viewing-angle dependent apparent motion of image features over an extended length if the viewing angle with respect to the OEL changes. An OEL includes a binder material being at least partially transparent and a plurality of particles dispersed within the layer. Each particle has a non-isotropic reflectivity and may be magnetic or magnetizable. The orientation of the particles forms an orientation pattern extending over a length within an extended surface of the OEL, such that the local average of an angle between (i) a straight line along an observed longest dimension within the corresponding cross-section shape, and (ii) said first direction x varies according to a function (θ) of a position (P) along said first direction.

First claim

The invention claimed is:

1. Optical effect layer (OEL) comprising:
a binder material being at least partially transparent to electromagnetic radiation of one or more wavelengths in a range of 200 nm to 2500 nm; and
a plurality of non-spherical particles having a non-isotropic reflectivity dispersed within said binder material and oriented according to a pattern extending over a length along a first direction (x) within an extended surface of the optical effect layer,
wherein in a first cross-section of said optical effect layer substantially perpendicular to said extended surface and along said first direction (x), the local average of an angle between:
(i) a straight line along an observed longest dimension within the corresponding cross-section shape of those non-spherical particles that intersect with said first cross-section; and
(ii) said first direction (x)

varies according to a function (θ) of a position (P) along said first direction (x), wherein the function is the sum of a monotonically increasing or decreasing first function (θ 1 ) of said position (P) and an alternating second function (θ 2 ) of said position (P) such that, if the viewing angle of the optical effect layer changes, a pattern of bright areas and dark areas on the extended surface of the optical effect layer will appear to move along the first direction (x).

2. Optical effect layer according to claim 1 , wherein the range is of the visible spectrum between 400 nm and 700 nm.

3. Optical effect layer according to claim 1 , wherein the optical effect layer (OEL) is disposed on a substrate to form an optical effect coating (OEC) comprising the substrate and the optical effect layer (OEL).

4. Optical effect layer according to claim 1 , wherein said non-spherical particles comprise a magnetic or magnetizable material.

5. Optical effect layer according to claim 1 , wherein said non-spherical particles are selected from the group consisting of platelet-shaped particles, needle-shaped particles, and mixtures thereof.

6. Optical effect layer according to claim 1 , wherein said non-spherical particles are optically variable magnetic particles.

7. Optical effect layer according to claim 6 , wherein said non-spherical optically variable magnetic particles comprise a thin-film Fabry-Perot interference stack.

8. Optical effect layer according to claim 1 , wherein the values of said monotonically increasing or decreasing first function (θ 1 ) span a difference of at least 30 degrees over said length.

9. Optical effect layer according to claim 1 , wherein in a second cross-section of said optical effect layer (OEL) substantially perpendicular to said extended surface and along a second direction (y) within the extended surface, which is different from the first direction (x), the local average angle between:
(i) a straight line along an observed longest dimension within the corresponding cross-section shape of those non-spherical particles that intersect with said second cross-section; and
(ii) said second direction (y)

varies according to a third function (θ 3 ) of a position along said second direction (y), which function (θ 3 ) is an alternating function of said position along said second direction (y).

10. Optical effect layer according to claim 1 , wherein, in a second cross-section of said optical effect layer (OEL) substantially perpendicular to said extended surface and along a second direction (y) within the extended surface, which is different from the first direction (x), the local average angle between:
(i) a straight line along an observed longest dimension within the corresponding cross-section shape of those non-spherical particles that intersect with said second cross-section; and
(ii) said second direction (y)

varies according to a fourth function (θ 4 ) of a position along said second direction (y), which fourth function (θ 4 ) is the sum of a function being equal to said first function (θ 1 ) of said position along said second direction (y) and an alternating fifth function (θ 5 ) of said position along said second direction (y).

11. Optical effect layer according to claim 1 , wherein, the optical effect layer (OEL) comprises, in addition to said plurality of non-spherical particles, at least one of:
non-color-shifting magnetic particles;
colorless magnetic particles;
color-shifting non-magnetic particles;
non-color-shifting non-magnetic particles; and
colorless non-magnetic particles.

12. Device for producing the optical effect layer (OEL) of claim 1 , by orienting magnetic or magnetizable particles dispersed within a binder material, the device comprising:
an arrangement of one or more magnets comprising one or more first magnets and a magnetized magnetic plate configured to produce a combined magnetic field, the combined magnetic field comprising:
a) a first magnetic field component being substantially similar to a magnetic dipole field and having its North-South direction aligned substantially parallel to said magnetized magnetic plate; and
b) a second magnetic field component comprising a superposition of individual local dipole-like magnetic fields and thus corresponds to an alternation of magnetic North and South poles along a first direction substantially parallel to said North-South direction;
wherein the first magnetic field component and the second magnetic field component overlap at least in a region adjacent to an extended surface of said magnetized magnetic plate,
the one or more first magnets being arranged for orienting magnetic or magnetizable particles within the optical effect layer according to a principal component θ 1 of an orientation function θ, the magnetized magnetic plate being arranged for orienting the magnetic or magnetizable particles within the optical effect layer according to an auxiliary component θ 2 of the orientation function θ,
the orientation function θ being a function of a position (P) along a first direction (x), the principal component θ 1 being a monotonically increasing or decreasing first function of position, the auxiliary component θ 2 being an alternating second function of position,
wherein the achieved respective orientation of the particles coincides, at least on average, with the local direction of the magnetic field lines at the positions of the particles, the device being adapted to produce said optical effect layer.

13. Device according to claim 12 , wherein the arrangement of one or more magnets comprises:
one or more magnets configured to produce the first magnetic field component; and
a magnetized magnetic plate configured to produce the second magnetic field component.

14. Device according to claim 13 , wherein said one or more magnets configured to produce the first magnetic field component comprise a dipole magnet having its North-South direction substantially aligned parallel to said magnetized magnetic plate.

15. Device according to claim 13 , wherein at least one of said one or more magnets configured to produce the first magnetic field component is mounted so as to be rotatable in a plane substantially parallel to the plane of said magnetized magnetic plate.

16. Device according to claim 12 , wherein the arrangement of one or more magnets comprises a magnetized magnetic plate containing a plurality of individual magnet elements arranged within the magnetized magnetic plate and along at least one dimension of the magnetized magnetic plate, the dimension being substantially parallel to said first direction, such that along said dimension, the magnet elements:
form a row,
are separated from their respe

Assignees

• Sicpa Holding Sa

Inventors

• Degott Pierre
• Schmid Mathieu
• Despland Claude Alain
• Amerasinghe Cedric

Classifications

• B42D25/30

  Identification or security features, e.g. for preventing forgery · CPC title

• G02F1/0036

  Magneto-optical materials · CPC title

• G02F1/09 Primary

  based on magneto-optical elements, e.g. exhibiting Faraday effect · CPC title

• B05D3/20

  by magnetic fields · CPC title

• B41M3/14

  Security printing {(securities B42D25/29)} · CPC title