Multi-Axis Polarizer Film For Anti-Counterfeit Applications And Method Of Making The Same
A polarizer film is formed to include sets of polarized lines (sets of parallel lines) oriented at several directions across the surface of the film. The lines may be created using a printing process that transfers grooves from a printing plate to the film (e.g., an embossing process). A rotogravure printing process (or other suitable process) is then used to apply a liquid polarizing dye material to the printed film. The dye molecules align along all of the various grooves embossed in the film, forming a multi-axis polarizer film. The film may be used to form separate multi-axis polarizer labels (useful in anti-counterfeiting applications), and a process of easily removing the individual labels from the original film is described.
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The present invention relates to polarizer films used, for example, in the formation of anti-counterfeit labeling and, more particularly, to a multi-axis polarizer film that exhibits a random quality that defeats attempts to copy the label.
BACKGROUND OF THE INVENTIONInvisible indicia printed with an optically active material on a substrate can be used as a covert security feature on products and product packaging. The product is then authenticated by revealing the invisible indicia with the use of an appropriate source of polarized light or a polarized filter.
To select a suitable anti-counterfeit technology, it needs to be not only easy to be recognized but also difficult to be copied, so that the selected anti-counterfeit technology can truly provide the desired protection. One such technology utilizes a polarizer film (linear or circular) to create indicia that is only revealed when viewed with polarized light (and thus otherwise “invisible” to the naked eye).
In the field of linear polarizers, some improvements in anti-counterfeiting have been associated with the use multiple layers of polarizing film, each oriented at a different polarization, such that a given “stack” of multiple films will exhibit a more complicated polarization pattern. However, the cost and complexity of such a multilayer process is considered to be a disincentive to widespread use.
SUMMARY OF THE INVENTIONThe needs remaining in the art are addressed by the present invention, which relates to polarizer films and, more particularly, to a multi-axis polarizer film created using a printing process of multiple sets of axes at different spatial locations on a single layer of film.
Instead of “stretching” a film to create polarization axes as in the prior art, a printing plate (patterned to include several sets of grooves at various orientations; a “multi-axis” pattern) is used to transfer the multi-axis groove pattern to a plastic film. The patterns take the form of shallow grooves embossed in the film. The grooved film is then saturated with an appropriate polarizing liquid dye material (e.g., iodine or any other suitable dichroic liquid dye). The dye molecules align with the multi-axis grooves in the film, and thus create a polarizer with a multi-axis pattern, defined only by the printed groove pattern. This is in contrast to prior art arrangements where the polarizer film was limited to a two-axis form defined by the stretch direction of the film itself.
In addition to the creation of a multi-axis polarization film, the present invention provides an improved manufacturing process that allows for the transfer of labels formed from this polarizer film to end-use products.
Other and further aspects and embodiments of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.
Referring now to the drawings, where like numerals represent like parts in several views:
Most film-based polarized sheets are made by a stretching process that applies a tension to the film so as to create an “absorbing axis” that runs parallel to the stretch direction, with the “transmitting axis” thus running perpendicular to the stretch direction.
Instead of using a stretching process, a multi-axis polarizer film is formed in accordance with the present invention by using a printing process to create a plurality of sets of “grooves” at various, different locations across the surface of the film. As described in detail below, a printing plate may be used in one process of introducing the sets of grooves to a standard film, where the printing plate is formed to include a number of grooves (in the form of sets of parallel grooves in different spatial locations organized in any desired pattern, including a random pattern). The printing plate then transfers the grooves to a plastic film (such as PVA, or cellulose triacetate (CTA), or any other plastic film material used for this purpose) in a simple printing (embossing) process. A rotogravure printing process (or other suitable process) is then used to apply a liquid polarizing dye material (e.g., iodine or other suitable dichroic liquid dye) to the printed film. The dye molecules will thus align along the various grooves formed in the film, forming a multi-axis polarizer film in accordance with the present invention, where the specific “groove pattern” in the film defines the orientations of the multi-axis polarizer. Indeed, a significant aspect of the present invention is that a specific, unique set of grooves may be associated with a particular product, vendor, or the like, providing yet another level of source authenticity.
Lastly, a polarizing liquid dye material 30 is applied to the embossed film, as shown in
Once the multi-axis polarizer is created on a film, an adhesive is applied to the film and then the film is cut into the individual elements. A coating of clear or reflective material may be applied to the multi-axis polarizer film prior to applying the adhesive. Typically, laser or die cutting is used to define the outline of the individual elements. A protective layer of masking material is preferably used to protect the “raw” surface of the polarizer film during the cutting procedure. The masking layer may be applied to only one side of the polarizer film, or both sides of the film. The masking layer is typically thin, and needs to be easily “peelable” once the individual devices have been formed. Depending on the size of the individual devices, it may be difficult (or tedious) to peel away the small size, thin masking material.
Another aspect of the present invention relates to a simplified process for later separating out individual elements (e.g., labels used for products as an anti-counterfeiting device) from a polarizer film.
In accordance with the present invention, instead of attempting to remove layer 40 from the individual devices 100-i, a covering layer 50 is disposed over and attached to protective masking layer 40 subsequent to the laser cutting step. This is shown in
Once it is desired to place individual devices 100-i on end-use products or labeling, the user peels off one or both of layers 50 (as the case may be), which takes protecting covering layer(s) 40 along during the removal process, as shown in
Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the spirit and scope of the invention. Indeed, it should be understood that this invention is not limited to the illustrative embodiments set forth herein and is instead contemplated as being limited only by the scope of the claims appended hereto.
Claims
1. A method of making a multi-axis polarizer film comprising the steps of:
- a) providing a sheet of plastic film;
- b) embossing the sheet of plastic film with a plurality of sets of grooves, each set comprising several parallel grooves of a given length and each set disposed at a different location across a surface of the sheet of plastic film and oriented at a different direction with respect to a longitudinal axis of the sheet of plastic film;
- c) applying a polarizing liquid dye to the embossed sheet of plastic film, wherein molecules of the polarizing liquid dye align with the plurality of sets of grooves and form multiple axes of polarization within the embossed sheet of plastic film.
2. The method as defined in claim 1 wherein the sheet of plastic film provided in step a) is a sheet of polyvinyl-alcohol (PVA) film.
3. The method as defined in claim 1 wherein the sheet of plastic film provided in step a) is a sheet of cellulose triacetate (CTA) film.
4. The method as defined in claim 1 wherein in performing step c), the polarization liquid dye comprises iodine.
5. The method as defined in claim 1, wherein in performing step b), the embossing comprises
- 1) providing a printing plate;
- 2) creating the plurality of sets of grooves as a pattern on a surface of the printing plate;
- 3) pressing the printing plate into a section of the sheet of plastic film to imprint the plurality of sets of grooves into a surface of the section of the sheet of plastic film.
6. The method as defined in claim 5 wherein steps b1) through b3) are repeated as subsequent sections of the sheet of plastic film are positioned adjacent to the printing plate.
7. The method as defined in claim 5 wherein in performing step b2), an aluminum material is used as the printing plate.
8. The method as defined in claim 5 wherein in performing step b2), a photolithographic etching process is used to create the plurality of sets of parallel grooves across the surface of the printing plate.
9. A method of making anti-counterfeit polarized labels, the method comprising the steps of:
- a) providing a sheet of polarizer film formed to include an anti-counterfeit polarization pattern;
- b) applying a masking layer over an exposed major surface of the polarizer film;
- c) cutting through a portion of the thickness of the structure of step b) at predetermined locations defined as boundaries for individual label elements, retaining a web frame portion of the masking layer;
- d) applying a covering layer over the cut surface of the masking layer so as to adhere to each cut portion of the masking layer; and
- e) pulling the covering layer away from the major surface of the sheet of polarizer film, wherein the act of pulling the covering layer also removes the underlying, adhered cut portions of the masking layer.
10. The method as defined in claim 9 wherein steps b) through d) are repeated on a remaining, opposing major surface of the polarizer film, with step e) used to pull the covering layer away from both major surfaces of the polarizer film.
11. The method as defined in claim 9, wherein step a) is further defined as providing a multi-axis polarizer film, and includes the individual steps of:
- a1) providing a sheet of plastic film;
- a2) embossing the sheet of plastic film with a plurality of sets of grooves, each set comprising several parallel grooves of a given length and each set disposed at a different location along the sheet of plastic film and oriented at a different direction with respect to a longitudinal axis of the sheet of plastic film; and
- a3) applying a polarizing liquid dye to the embossed sheet of plastic film, wherein molecules of the polarizing liquid dye align with the plurality of sets of grooves and form multiple axes of polarization within the embossed sheet of plastic film to create a multi-axis polarizer film.
12. A multi-axis polarizer film comprising
- a sheet of plastic material including a plurality of sets of embossed grooves formed at different spatial locations across a major surface of the sheet of plastic material, each set of grooves including several parallel grooves of a given length and each set oriented at a different direction with respect to a longitudinal axis of the sheet of plastic film; and
- a polarizing dye, with molecules of the polarizing dye disposed within and aligned along the plurality of sets of grooves, forming multiple axes of polarization within the embossed sheet of plastic film to form the multi-axis polarizer film.
13. The multi-axis polarizer film as defined in claim 12 wherein the sheet of plastic material comprises a sheet of polyvinyl-alcohol (PVA) film.
14. The multi-axis polarizer film as defined in claim 12 wherein the sheet of plastic material comprises a sheet of cellulose triacetate (CTA) film.
15. The multi-axis polarizer film as defined in claim 12 wherein the polarizing dye comprises iodine.
Type: Application
Filed: Oct 3, 2019
Publication Date: Apr 8, 2021
Applicant: American Polarizers, Inc. (Reading, PA)
Inventor: Nicholas K. Bentley (Fleetwood, PA)
Application Number: 16/591,680