Visually identifiable optical element

Details Visually identifiable optical element Visually identifiable optical element

2001-02-05

2003-09-23

Fridie, Jr., Willmon (Department: 3722)

Printed matter

Having revealable concealed information, fraud preventer or...

Utilizing electromagnetic radiation

C283S092000, C283S072000, C428S913000

Reexamination Certificate

active

06623042

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention concerns a visually identifiable optical element, in particular a security element for value-bearing documents, for example banknotes, credit cards, passes or cheque documents, or other items to be safeguarded, including a carrier having an in particular diffusely reflecting visible surface and a metallisation applied in a region-wise manner to the visible surface of the carrier, with a surface which appears metallically shining at a glancing angle.
In known optical elements the metallisation appears either light or dark, in front of the background for the metallisation, the background being formed by the carrier. Such an optical element is described for example in WO 93/01057.
The use of a carrier with a metallisation as a visually identifiable optical element for security or decorative purposes is based on the physically explainable phenomenon that light which impinges from a given direction onto a smooth metal surface can be perceived by a viewer in the form of reflected light at a given viewing direction. If on the other hand the light is not incident from a single given direction but if the light for example involves diffusely incident daylight or light from a diffuse light source, then, in dependence on the orientation of the metallised region relative to the range of angle of incidence of the light, that gives a viewing angle range, referred to hereinafter as the glancing angle range, from which a viewer perceives the metallisation as being highly shiny and metallically bright, as a large part of the light which meets the metallisation within the range of the angle of incidence is reflected into that glancing angle range. The reflectivity which is dependent on the viewing angle is thus particularly high in that glancing angle range which is determined by the range of the angle of incidence of the light, in other words, a large part of the radiant energy which passes onto the unit of surface area of the metallisation is reflected into that glancing angle range. In contrast, for viewing directions outside the glancing angle range, the metallisation does not appear shiny to a viewer, but it gives a metallically grey and matt colour impression. In dependence on the light reflectivity of the carrier, that matt colour impression appears either light or dark, relative to the background.
The term metallisation is used hereinafter to denote a layer of any structure, which in particular is very thin, having a metallically shiny surface.
When using visually identifiable optical elements or security elements, the endeavour is to provide that items of authenticity information in respect of the safeguarded article are rendered visible, even to the unpractised lay person, and at the same time forgery, for example in the form of duplication, having regard to known forgery procedures, in particular optical duplication procedures, is made impossible or is made at least sufficiently difficult. Optical elements of that kind however are also used for decorative purposes.
SUMMARY OF THE INVENTION
The object of the present invention therefore is to provide an optical element of the kind described in the opening part of this specification, which is easy to produce in an economical fashion and with which an article to be safeguarded can be protected from forgery even more effectively than is possible with known security elements.
In an optical element as described in the opening part of this specification, in accordance with the invention, that object is attained in that the visible surface of the carrier has two carrier regions having different levels of and in particular diffuse reflectivity for light wherein a respective sub-region or a plurality of sub-regions of each of the carrier regions is or are metallised, and that the reflectivity of the metallisation is lower in viewing directions outside a glancing angle range than the reflectivity of the carrier region having the higher level of reflectivity or substantially corresponds to same and is greater than the reflectivity of the carrier region having the lower level of reflectivity or substantially corresponds to same.
By virtue of the fact that the carrier is divided into at least one region of higher light reflectivity and a region of lower light reflectivity and the levels of reflectivity of those carrier regions and the metallisation satisfy the conditions described above, the visually perceptible information which can be imparted to a viewer by means of the optical element is more varied and diverse, in dependence on the viewing angle; thus, in a given viewing angle, outside the glancing angle range, a metallised sub-region appears dark in front of the background which is formed by the carrier region having the higher level of reflectivity, while another metallised sub-region appears light in front of the background which is formed by the carrier region having the lower level of reflectivity, if the reflectivity of the metallisation is lower in the. first case and greater in the second case, than the reflectivity of the respective carrier region being viewed.
If the reflectivity of the metallisation in a viewing direction outside the glancing angle range substantially corresponds to the reflectivity of the dark carrier region, that is to say if it is not possible to detect a difference in the reflection capability with the naked eye, the metallised sub-region of that carrier region is not perceptible or is scarcely perceptible in front of the background, when viewing outside the glancing angle range. If on the other hand the security element is viewed in the glancing angle range of the metallisation, which is determined by the range of the angle of incidence of the light, the metallisation appears metallically shinny bright relative to both carrier regions. A corresponding consideration applies if the reflectivity of the metallisation, when viewed in a viewing direction outside the glancing angle range, substantially corresponds to the diffuse reflectivity of the bright carrier region.
In that respect, production of the optical element according to the invention is made more difficult only in a fashion which is not worthy of mention, in comparison with the production of known elements. Thus for example one half of the carrier can be adapted to appear white, in particular with a visible surface of diffusely reflecting white paper, while the other half of the carrier can be coloured black with a level of reflectivity which accordingly can be disregarded.
The portion of the metallisation which is applied to the black region of the carrier, therefore to the region having the lower level of reflectivity, appears, in front of that dark background, as a matt metallic light-grey colour shade. The portion of the metallisation which is applied to the white carrier region and therefore to the carrier region having the higher level of reflectivity on the other hand appears, in front of that light background, as a matt metallic dark-grey shade and stands out from the light background, by appearing dark. If now the optical element is so oriented, with respect to the direction of the light impinging thereon, that a viewer has the element or the metallised region in front of his eyes in the above-mentioned glancing angle range, the portion of the metallisation which partially covers the white region of the carrier no longer appears dark but appears brilliantly shiny and gleamingly bright. The portion of the metallisation which is applied to the black region of the carrier also appears metallically shinily bright when it is viewed in a viewing direction within the glancing angle range. In this case also the visually perceptible information changes when the orientation of the element or the viewing direction is altered.
Admittedly, by the use of a carrier with a white and a black region, the optical element according to the invention can be produced in a particularly simple and economical fashion, but it can also be found advantageous to better fulfill in particular aesthetic considerations, if the at least t

Affiliated with

Also associated with

Rating

Visually identifiable optical element does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Visually identifiable optical element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Visually identifiable optical element will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3016599