Abstract

Optically variable devices made from optical-interference coatings create chromatic color mirrors that have minimal polarization differences with increasing incidence angle. These metal–dielectric–metal designs produce narrowband, high reflectance in the visible wavelength region. Broader-band reflectance regions, similar to those created by multilayer dielectric stacks, can be replicated on a high-reflecting metal base such as aluminum, maintaining the same nonpolarizing effects of the narrowband designs. These designs are intended for reflective systems used for display where reduced angle sensitivity is paramount. However, these designs can also be adapted for large angular-dependent color shift, such as in effect pigments. Design examples and layer material suggestions are given depending on the application requirements.

© 2014 Optical Society of America

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References

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2011 (1)

1996 (1)

1995 (1)

1990 (1)

R. W. Phillips, “Optically variable films, pigments, and inks,” Proc. SPIE 1323, 98–109 (1990).

1972 (1)

1970 (1)

1950 (1)

1947 (1)

Apfel, J. H.

Baloukas, B.

B. Baloukas, “Thin film-based optically variable security devices: from passive to active,” Ph.D. thesis (École Polytechnique de Montréal, 2012).

Baumeister, P.

P. Baumeister, Optical Coating Technology (SPIE, 2004).

Bleikolm, A. F.

Coombs, P.

P. Coombs and R. Phillips, “Optically variable interference device with peak suppression,” patent EP0,472,371 B1 (21October1998).

P. Coombs and R. Phillips, “Transparent optically variable device,” U.S. patent5,278,590 (11January1994).

Costich, V. R.

Dennison, D. M.

Dobrowolski, J. A.

Hadley, L. N.

Kemp, R. A.

Kruschwitz, J.

J. Kruschwitz, “Designing nonpolarized high reflecting coatings within immersed high-index media,” in Optical Interference Coatings (Optical Society of America, 2001), paper TuB3.

Li, L.

Lin, F.

Ma, P.

Macleod, H. A.

H. A. Macleod, Thin-Film Optical Filters, 4th ed., Series in Optics and Optoelectronics (CRC Press/Taylor & Francis, 2010).

Nofi, M.

R. W. Phillips, M. Nofi, and R. Slusser, “Color effects from thin film designs,” in 8th International Conference on Vacuum Web Coating, Las Vegas, Nevada, 1994, pp. 270–284.

Phillips, R.

P. Coombs and R. Phillips, “Optically variable interference device with peak suppression,” patent EP0,472,371 B1 (21October1998).

P. Coombs and R. Phillips, “Transparent optically variable device,” U.S. patent5,278,590 (11January1994).

Phillips, R. W.

R. W. Phillips and A. F. Bleikolm, “Optical coatings for document security,” Appl. Opt. 35, 5529–5534 (1996).
[CrossRef]

R. W. Phillips, “Optically variable films, pigments, and inks,” Proc. SPIE 1323, 98–109 (1990).

R. W. Phillips, M. Nofi, and R. Slusser, “Color effects from thin film designs,” in 8th International Conference on Vacuum Web Coating, Las Vegas, Nevada, 1994, pp. 270–284.

Scott, G. D.

Sennett, R. S.

Slusser, R.

R. W. Phillips, M. Nofi, and R. Slusser, “Color effects from thin film designs,” in 8th International Conference on Vacuum Web Coating, Las Vegas, Nevada, 1994, pp. 270–284.

Appl. Opt. (5)

J. Opt. Soc. Am. (2)

Proc. SPIE (1)

R. W. Phillips, “Optically variable films, pigments, and inks,” Proc. SPIE 1323, 98–109 (1990).

Other (8)

R. W. Phillips, M. Nofi, and R. Slusser, “Color effects from thin film designs,” in 8th International Conference on Vacuum Web Coating, Las Vegas, Nevada, 1994, pp. 270–284.

P. Coombs and R. Phillips, “Optically variable interference device with peak suppression,” patent EP0,472,371 B1 (21October1998).

B. Baloukas, “Thin film-based optically variable security devices: from passive to active,” Ph.D. thesis (École Polytechnique de Montréal, 2012).

P. Baumeister, Optical Coating Technology (SPIE, 2004).

P. Coombs and R. Phillips, “Transparent optically variable device,” U.S. patent5,278,590 (11January1994).

“OptiLayer Thin Film Software. Ver. 9.96,” http://www.optilayer.com (2014).

H. A. Macleod, Thin-Film Optical Filters, 4th ed., Series in Optics and Optoelectronics (CRC Press/Taylor & Francis, 2010).

J. Kruschwitz, “Designing nonpolarized high reflecting coatings within immersed high-index media,” in Optical Interference Coatings (Optical Society of America, 2001), paper TuB3.

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Figures (8)

Fig. 1.
Fig. 1.

Design layout of metal layers (M1, M2, M3) and dielectric layers.

Fig. 2.
Fig. 2.

Black layers represent metal layers, and gray layers represent dielectric layers. (a) A standing wave in the electric field between the metal layers indicates wavelengths that will experience low absorption. (b) Wavelengths without a standing wave between the metal layers can undergo significant absorption [4].

Fig. 3.
Fig. 3.

Ratio of Rp to Rs versus angle of incidence for absorbing and nonabsorbing materials. Index of refraction of material (λ=550nm) is indicated in legend.

Fig. 4.
Fig. 4.

Circle diagrams for (a) Al (nAl=0.912i6.55), (b) Ni (nNi=1.75i3.19), (c) TiO2 (nT=2.3), and (d)  Al2O3 (nA=1.65). Indices used for λ=550nm. When the base layer is highly reflecting, the metal layers can work to maintain both the high reflectance for some wavelengths (outside perimeter of circle) and low reflectance (near the origin, plus sign) for others. Dielectric layers alone cannot steer the reflectance to the center of the diagram over broad wavelength regions [12].

Fig. 5.
Fig. 5.

Reflectance of the blue, red, and green mirrors at 20° incidence angles for s and p polarizations. Designs are listed in Table 1.

Fig. 6.
Fig. 6.

Electric-field standing wave between nickel layers for a high-reflectance wavelength (450 nm) and the absence of a standing wave for a low-reflectance wavelength (650 nm).

Fig. 7.
Fig. 7.

Circle diagrams represent a 16-layer design on aluminum using TiO2 (nT=2.3) and Al2O3 (nA=1.65) for dielectric materials and nickel (nN=1.75i3.19) for the metal layers (λ=550nm). (a) The circle at 450 nm where there is high reflectance. (b) The circle at 650 nm where there is low reflectance. The star represents the starting position, and the black dot represents the ending position in the circle diagrams. Thick dashed and solid lines represent the nickel layers in the design.

Fig. 8.
Fig. 8.

Color shift of three red mirrors using different dielectric-refractive-index pairs in a MD design. The shifts are measured at the 50% reflectance point for reflectance of average polarization from 20° to 45° incidence, where one set of data has the design immersed in air and the other immersed in a medium with index of 1.41 (propylene glycol n-propyl ether).

Tables (1)

Tables Icon

Table 1. Sixteen-Layer Blue Mirror, 19-Layer Red Mirror, and 22-Layer Green Mirror on Aluminum (nS=0.912i6.55) from Fig. 5, Where nT=2.3, nY=1.8, nA=1.65, and nN=1.75i3.19 (λ=550nm)a

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

ρ=r1+r2eiϕ1+r1r2eiϕ,
[BC]=[cosϕ(iη)sinϕ(iη)sinϕcosϕ][1ns]where,ϒ=CB
ρ=1ϒ1+ϒ.

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