TECHNICAL FIELD

The present invention generally relates to an optical device that produces flicker-like optical effects, and more particularly relates to an optical device that employs directionally cured image icons.

BACKGROUND

Micro-optic film materials projecting synthetic images generally comprise: an arrangement of micro-sized image icons; an arrangement of focusing elements (e.g., microlenses, microreflectors); and optionally, a light-transmitting polymeric substrate. The image icon and focusing element arrangements are configured such that when the arrangement of image icons is viewed using the arrangement of focusing elements, one or more synthetic images are projected. The projected images may show a number of different optical effects.

These micro-optic film materials may be used as security devices for authentication of banknotes, secure documents and products. For banknotes and secure documents, these materials are typically used in the form of a strip, patch, or thread and can be partially embedded within the banknote or document, or applied to a surface thereof. For passports or other identification (ID) documents, these materials could be used as a full laminate or inlayed in a surface thereof. For product packaging, these materials are typically used in the form of a label, seal, or tape and are applied to a surface thereof.

Examples of micro-optic film materials are described and shown in U.S. Pat. Nos. 7,333,268 and 7,468,842. These references both describe a microstructure approach to forming image icons, in which the image icons are formed from voids in a microstructure or from solid regions, singly or in combination. The voids are optionally filled or coated with a material having a different index of refraction than the surrounding or underlying material, a dyed material, a metal, or a pigmented material. Such an approach has the benefit of almost unlimited spatial resolution.

SUMMARY

An exemplary method of manufacturing these micro-optic film materials is to form the icons as voids in a radiation cured liquid polymer that is cast against a base film, such as 75 gage adhesion-promoted polyethylene terephthalate (PET) film, then to form the lenses from radiation cured polymer on the opposite face of the base film in correct alignment or skew with respect to the icons, then to fill the icon voids with a submicron particle pigmented coloring material by gravure-like doctor blading against the film surface, solidify the fill by suitable means (e.g., solvent removal, radiation curing, or chemical reaction), and finally apply an optional sealing layer that may be either clear, dyed, pigmented, or incorporate covert security materials. Here, the means for solidifying the fill is non-directional and applied directly to the image icon layer and not through the lenses. Synthetic images of such non-directionally cured icons are viewable over a wide range of angles.

The icon voids may include multiple icon fill materials. For example, in col. 49, lines 36-63, of U.S. Pat. No. 7,468,842, icon voids are underfilled with a first icon fill material, and optionally stabilized (e.g., by radiation curing). The icon voids are then optionally filled with a second icon fill material. In this example, the icon fill material is stabilized by non-directional techniques such as non-directional curing that is applied directly to the icon fill material and not through the lenses.

Another example of a micro-optic film material is known from U.S. Pat. No. 7,738,175. This reference discloses a synthetic micro-optic system that produces a flicker-like optical effect. The system produces an in-plane image formed from an array or pattern of image icons and an array of focusing elements. Here, the in-plane image is defined as an image that has some visual boundary, pattern, or structure that visually lies substantially in the plane of the substrate on which or in which the in-plane image is carried. The system also produces at least one out-of-plane synthetic image, the out-of-plane synthetic image(s) operating to modulate or control the extent of the appearance of the in-plane synthetic image. In one embodiment, the out-of-plane synthetic image serves to control the field of view of the in-plane image and, thus, serves to modulate or control the extent of appearance of the in-plane image. Here, the appearance of the in-plane image visually appears and disappears, or turns on and off, depending upon the viewing angle of the system.

By way of the present invention, it has been discovered that directionally curing the image icon layer of these film materials through the lens layer using collimated light greatly increases the range of optical effects demonstrated by these materials.

The present invention therefore provides an optical device that produces flicker-like optical effects, wherein the optical device comprises at least one arrangement of image icons formed from one or more cured pigmented materials, and at least one arrangement of optionally embedded focusing elements positioned to form one or more synthetic images of at least a portion of the arrangement(s) of image icons, wherein some or all of the pigmented material(s) is cured using collimated light directed through the focusing elements at one or more angles relative to a surface of the optical device (hereinafter “the cure angle(s)”) to form directionally cured image icons, wherein the synthetic image(s) of the directionally cured image icons is viewable at the cure angle(s) and therefore visually appears and disappears, or turns on and off, as the viewing angle of the device moves through the cure angle(s).

The term “pigmented material”, as used herein, is intended to mean any material capable of imparting a color to the image icons and to the synthetic image(s) of the inventive device, which is curable by collimated light. In one contemplated embodiment, the pigmented material is a curable pigment dispersion (i.e., pigment particles in a curable medium or carrier).

As will be explained in more detail below, the synthetic image(s) projected by the inventive optical device may demonstrate a number of distinct visual effects when the device is tilted about an axis substantially parallel to the plane of the device. For example, the synthetic image(s) may show orthoparallactic movement (OPM) (i.e., when the device is tilted the images move in a direction of tilt that appears to be perpendicular to the direction anticipated by normal parallax). Unlike the prior art micro-optic system described above that produces a flicker-like optical effect, the image(s) projected by the present invention is not necessarily an image that visually lies substantially in the plane of the device but may also appear to rest on a spatial plane that is visually deeper than the thickness of the device, or may appear to rest on a spatial plane that is a distance above the surface of the device. The image(s) may also appear to oscillate from a position above the device to a position below the device, or the reverse, as the device is rotated through a given angle (e.g., 90 degrees), then returning to its original position as the device is further rotated by the same amount.

The image icons of the inventive device, which are prepared using one or more cured pigmented materials, may be made in the form of posts, or in the form of voids or recesses on or within a surface of the inventive optical device. The posts may be formed from the pigmented material(s), or the areas surrounding the posts or the voids or recesses may be either coated or partially or completely filled with the pigmented material(s). The size, form and shape of the icons are not limited. In fact, embodiments are contemplated in which two or more types of image icons (e.g., micro- and nano-sized image icons) are in register with one another within one arrangement or layer of image icons within the inventive device.

In one exemplary embodiment, each image icon in the arrangement(s) of image icons is formed from one cured pigmented material, the pigmented material being cured using collimated light at a given angle. In this embodiment, the synthetic image(s) is viewable at the cure angle. In other words, the projected synthetic image(s) flickers or turns on and off, as the viewing angle of the device moves through the cure angle.

Image icons formed from two or more pigmented materials may be prepared by curing each material with collimated light, or by curing one material with collimated light and another material with another means for curing (e.g., non-directional radiation curing, chemical reaction). Synthetic images formed from the directionally cured pigmented materials would be viewable at the cure angle(s), while synthetic images formed from the non-directionally cured pigmented materials would be viewable over a wide range of angles. It is noted that the arrangement(s) of image icons used in the practice of the present invention may also include prior art image icons formed in their entirety from non-directionally cured pigmented materials.

In one such exemplary embodiment, each image icon in the arrangement(s) of image icons is formed from two cured pigmented materials, each having a different color. Each pigmented material is cured using collimated light at an angle through the focusing elements that is different from the angle used to cure the other pigmented material. The optical device, in this exemplary embodiment, will project a synthetic image(s) of a first color that is viewable at the first cure angle, and a synthetic image(s) of a second color that is viewable at the second cure angle.

This exemplary embodiment can be produced by curing a colored pigmented material using collimated light from one angle, washing the uncured pigmented material from the device, and then adding a second colored pigmented material and curing it. As will be readily appreciated, a large number of colored pigmented materials could be added this way.

In another such exemplary embodiment, each image icon in the arrangement(s) of image icons is formed from one cured fluorescent pigmented material and from one cured non-fluorescent pigmented material. As will be readily appreciated, a fluorescent feature that is detectable only at a given angle but not at another given angle may serve as an effective machine readable authenticating feature.

In a preferred embodiment, the inventive optical device is used with an ID card having one or more security print features (e.g., text, photo). The security print feature(s) would be visible at select viewing angles while the synthetic image(s) projected by the inventive device would be visible at other select viewing angles. In this way, the synthetic image(s) would not obscure or impair the security print feature(s).

In a further exemplary embodiment, the inventive optical device is a laser marked optical device that basically comprises an optical device as described above (e.g., an optical film material), and optionally one or more layers located above and/or below the optical device, wherein at least one arrangement or layer of the optical device or at least one layer above or below the optical device is a laser markable arrangement or layer, and wherein the laser markable arrangement(s) or layer(s) has one or more laser marked static two dimensional (2D) images thereon.

The present invention further provides sheet materials and base platforms that are made from or employ the inventive optical device, as well as documents made from these materials. The term “documents”, as used herein designates documents of any kind having financial value, such as banknotes or currency, bonds, checks, traveler's checks, lottery tickets, postage stamps, stock certificates, title deeds and the like, or identity documents, such as passports, ID cards, driving licenses and the like, or non-secure documents, such as labels. The inventive optical device is also contemplated for use with consumer goods as well as bags or packaging used with consumer goods.

In one such embodiment, the optical device is in the form of a patch embedded in a polymer ID card.

Other features and advantages of the invention will be apparent to one of ordinary skill from the following detailed description and drawings. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

