Patent Application
20140191428
The present invention is directed to an embossing shim and a method of producing embossing shims. More particularly, the present invention pertains to an embossing shim and a method of making embossing shims for the production of diffractive surfaces such as holograms or gratings having enhanced color shifting or optically variable backgrounds.
Reflective transparent, semitransparent, and opaque materials containing embossed holographic images are commonly used in security and decorative applications such as passports, credit cards, security passes, licenses, stamps, as well as gift wrap, book illustrations, and the like. Protection is achieved by affixing holographic or optically variable films to the documents. It is very difficult to forge and counterfeit such documents as such holographic or optically variable films are not easily copied using conventional printing techniques.
Holographic films are generally produced by metalizing an embossed pattern of a three dimensional image. Traditional embossing applies pressure to either side of a material to alter the surface, giving the material a three dimensional or raised effect. In other words, traditional embossing transfers the 3D microstructure image to the material. Typical film embossing machines use two cylindrical rollers, an embossing roller and a backing roller, as shown in
The embossed side of the impression may be aluminized or metalized to turn the 3D microstructure into a reflection hologram. Holographic patterns for the embossing shims are typically created by exposing a photosensitive emulsion-covered substrate to two beams from a coherent light source and etching or developing the resulting interference pattern into the photosensitive emulsion or photoresist.
Holographic patterns typically include optical interference patterns such as diffraction gratings. A diffraction grating is an optical interference pattern in which a component with a regular pattern splits (diffracts) light into several beams traveling in different directions. Single axis diffraction gratings, producing large format rainbow reflective foil/film holograms, as shown in
Holographic images generally require direct illumination for the diffraction colors to be visible. Thus, in order to view the diffraction colors, the holographic image must be viewed from the same angle from which the holographic image is illuminated. Thus, rainbow or iridescent colored light reflecting from the hologram is generally visible in only two directions, usually at 0 degrees and 180 degrees. When viewed from other directions or angles, color is not visible and the hologram appears dark or gray/silver. Thus, the field of view is relatively limited.
A cross-grating pattern, as shown in
When viewed from above, the light diffracts symmetrically at 0, 90, 180, and 270 degrees. Diffracted beams also appear symmetrically at the off angles (diagonals) (45, 135, 225, 315) at certain frequencies. Using two expanded beams and double exposing the substrate after rotating, however, creates only symmetrically diffracted beams. If an asymmetrical output is desired, the geometry and/or frequency of the grating are changed between exposures. Thus, unless the frequency and/or grating is changed, or the substrate is double exposed, the intensity or brightness of the light/color is diminished at certain diffracting angles.
In addition, large format rainbow diffraction gratings created by two beams are twice as susceptible to vibration. The two beam technique requires the substrate to be exposed twice to the interference pattern in order to achieve a desired brightness, and therefore, requires handling of the substrate between exposures. The additional handling of the beams and/or the substrate increases the opportunity for error, vibration, image contamination, or uneven cross grating efficiency.
Accordingly, there is a need to control the field of view of an optical interference pattern, such as a diffraction grating hologram, and increases the brightness and intensity of the diffraction grating patterns while minimizing the handling of the substrate.
An enhanced optical interference pattern for an embossing shim, such as an enhanced diffraction grating hologram, is created using three or more beams from a coherent source to produce a diffraction grating hologram which has a more intense or stronger visual effect than previous holograms when exposed to white light. Three or more beams of coherent light from a single source are directed toward a photodefinable surface, such as a photoresist plate or an ablatable substrate. The three beams interfere with one another and produce, on a given substrate, a diffraction grating hologram with an increased field of view than previous methods provided, without having to expose the substrate twice to the beams and without increased handling of the photoresist plate or ablatable substrate.
In an embodiment, an optical interference pattern, such as a diffraction grating pattern, is incorporated into a photodefineable surface, such as a photosensitive emulsion/photoresist covered glass (“photoresist plate”) by exposing the photodefinable surface to three or more beams from a coherent light source. In another embodiment, a photodefinable surface is directly ablated with three or more beams from a coherent light source. The photodefinable surface is electroplated to form a metal master shim. The photodefinable metal master is nickel-plated for use as an embossing shim. Formation of the optical interference pattern is created by interference of three or more light beams, such as laser light, arc light or other monochromatic light sources producing a suitable spectrum of light when illuminated by a point source such as sunlight, incandescent or florescent light.
The resulting diffraction grating pattern is etched, developed or ablated onto the photodefinable surface. The etched/developed photodefinable surface is used to create embossing shims. The embossing shim can then be used to emboss film or paper in mass. The embossed film/paper can be metalized and laminated onto a substrate to create a holographic product that has shifting patterns and rainbow colors at a variety of viewing angles when exposed to white light.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.
The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein:
While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated.
It should be further understood that the title of this section of this specification, namely, “Detailed Description Of The Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein.
An enhanced optical interference pattern, such as a diffraction grating foil/film hologram is created by directing or shining three or more beams of coherent light from a single source onto a photodefinable surface, such as a photoresist plate or an ablatable substrate. The three beams interfere with one another and produce an optical interference pattern on the photodefinable surface that provides more control of the angular playback resulting in a hologram having a wider field of view than previous methods provided, without having to expose the photodefinable surface twice to the beams and without increased handling of the photoresist plate.
Referring now to
An optical interference pattern, such as a diffraction grating, is produced by interference of light beams from a coherent source.
Similarly,
Light beams 34 and 36 also form interference pattern wave 35 to create greater intensity of light when the two beams intersect at C and D. The diffraction grating pattern 30 can have diffraction at a specific angle to the normal at 45 (π/4), 135 (3π/4), 225 (5π/4), and 315 (7π/4) degrees (with respect to wavelength interference), in addition to a different set of diffractive angles with respect to the first set at 0, 90 (π/2), 180 (π′ and 270 (3π/2) degrees. In other words there can be multiple angles of diffraction for a wider viewing zone, or increased field of view, all achieved with one 3 beam exposure.
Embodiments of the present invention are described as examples of the present method and are not intended to limit the present method to the embodiments described. An example of a diffraction grating pattern using an embodiment of the three beam method is shown in
The cross-grating pattern in
The first embodiment shown in
The resulting mapped photoresist plate 438 is then metalized and electroplated to form an embossing shim having a shallow relief diffraction grating pattern. The embossing shim is used with conventional high speed holographic embossing equipment to form the hologram or embossed image onto the film. The embossed film can then be metalized and laminated onto a substrate to create a product that has shifting patterns that reflect at a variety of viewing angles when exposed to white light.
In an alternate embodiment, shown in
The three beams are manipulated and/or configured by optics/beam positioners 552, 554, 556 to focus each of the light beams 532, 534, 536 respectively down to a very small “dot” ranging from 25 microns to 125 microns. The overlapping light beams 532, 534, 536 contain sufficient energy to directly ablate the surface of a plastic film creating a cross-grating 530. An array of small cross-gratings 530 is created to form a larger image. The narrower beams 532, 534, 536 interfere with each other to form diffraction gratings 530 just as in the first embodiment; these, however, are tiny pixels made on the plastic film 538 surface (rather than a photoresist plate). The plastic film 538 can be used itself without further processing as an embossing shim; however, it is desirable to nickel plate the plastic film 538 to form an embossing shim.
The resulting nickel-plated embossing shim has a holographic relief of the diffraction grating pattern. Additional shim copies are grown for use with traditional high speed holographic embossing equipment. The resulting embossing shim contains an optical image with kinetic playback characteristics.
Those skilled in the art can appreciate the advantages of the present method. The present method 3 beam technique eliminates the need to expose the photodefinable surface twice and eliminates all associated handling between exposures. The three beam technique uniquely uses asymmetry in the beam angles to yield special effects. In addition, the three beam technique also allows the ability to create a cross-grating pixel which can be manipulated into custom images that offer significant improvements in field of view.
All patents referred to herein, are incorporated herein by reference, whether or not specifically done so within the text of this disclosure.
In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular.
From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.
This application is a divisional application of U.S. patent application Ser. No. 12/614,053, filed Nov. 6, 2009, which application claims the benefit of and priority to Provisional U.S. Patent Application Ser. No. 61/113,032, filed Nov. 10, 2008, the diclsoures of which are incorporated herein in their entireities.
| Number | Date | Country | |
|---|---|---|---|
| 61113032 | Nov 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12614053 | Nov 2009 | US |
| Child | 14157500 | US |
