Multilayer polymeric reflective bodies for decorative and security applications

A multilayered reflective polymeric body of alternating layers of polymers wherein at least a portion of the layers are in a folded-over relationship is provided along with a coextrusion apparatus and method of preparing the multilayer polymeric body. The reflective polymeric body includes at least first and second diverse polymeric materials having a sufficient number of alternating layers of the first and second polymeric materials such that a portion of the light incident on the body is reflected. The first and second polymeric materials differ from each other in refractive index by at least about 0.03. The reflective body is thermoformable and may be fabricated into wall panels, dishware, decorative trims, and the like, and may also find use in security applications such as credit cards, credit card emblems, or on currency.

BACKGROUND OF THE INVENTION 
The present invention relates to a multilayered polymeric body comprising 
multiple optical thickness layer types, at least a portion of which are in 
a folded relationship, which body reflects light and which can be 
fabricated to have an iridescent or silvery appearance; to decorative 
articles produced therefrom which may find use as wall panels, dishware, 
and decorative trims; and to security articles produced therefrom which 
may find use in anticounterfeiting applications. 
Highly reflective articles (i.e., articles having a reflectance of 70-85% 
or greater) are generally sought by industry for a number of uses. 
Conventional methods for fabricating reflective surfaces include forming 
such surfaces of highly polished metals. However, because of the high 
costs and fabricating problems involved in using metals, more recently 
fabricators have used plastic surfaces which contain thin coatings of 
metal thereon. Thus, metal coated plastic articles are now commonly found 
as both decorative and functional items in a number of industries. Such 
articles are used as bright work for consumer appliances such as 
refrigerators, dishwashers, washers, dryers, radios, and the like. These 
types of articles are also used by the automotive industry as head lamp 
reflectors, bezels, radio knobs, automotive trim, and the like. 
Typically, such metal coated plastic articles are formed by electroplating 
or by the vacuum, vapor, or chemical deposition of a thin metal layer on 
the surface of the article. However, such coatings are subject to the 
chipping and flaking of the metal coatings as well as corrosion of the 
metal over time. If additional protective layers must be applied over the 
metal coating to protect it, additional labor and materials costs are 
involved. Further, there may be environmental disposal problems with some 
metal deposition processes. 
Multilayer articles of polymers are known, as are methods and apparatuses 
for making such articles. For example, such multilayered articles may be 
prepared utilizing multilayer coextrusion devices as described in 
commonly-assigned U.S. Pat. Nos. 3,773,882 and 3,884,606 to Schrenk. Such 
devices are capable of simultaneously extruding diverse thermoplastic 
polymeric materials in substantially uniform or varying layer thicknesses. 
The number of layers may be multiplied by the use of a device as described 
in commonly-assigned U.S. Pat. No. 3,759,647 to Schrenk et al. 
Im et al, U.S. Pat. No. 4,540,623, teach a multilayer laminated article 
which includes a polycarbonate as one of the alternating layers. The 
articles of Im et al, however, are intended to be transparent rather than 
reflective and to exhibit optical properties comparable to a pure 
polycarbonate polymer. 
Alfrey, Jr. et al, U.S. Pat. No. 3,711,176, teach a multilayered highly 
reflective thermoplastic body fabricated using thin film techniques. That 
is, the reflective optically thin film layers of Alfrey, Jr. et al rely on 
the constructive interference of light to produce reflected visible, 
ultraviolet, or infrared portions of the electromagnetic spectrum. Such 
reflective optically thin films have found use in decorative items because 
of the iridescent reflective qualities of the film. 
However, because the film relies solely on the optically thin layers, such 
films are limited to uses requiring iridescent reflective properties and 
are not practical for uses which require a silvery or colorless 
reflectivity. 
In the security field, artisans have used optically variable reflective 
devices on credit cards and currency in attempts to foil counterfeiters 
These reflective devices include metal and prismatic foils, embossed 
foils, and holographic foils which can be incorporated onto or into credit 
cards and the like. Baird et al, U.S. Pat. No. 3,858,977, teach the use of 
optically thin iridescent films as an anticounterfeiting device. However, 
the costs of fabrication of these devices make them expensive to use. 
Further, many of these devices require the use of metal to obtain their 
reflective properties. 
Accordingly, there remains a need in the art for a highly reflective 
polymeric sheet or body which can be post formed into a variety of 
decorative and useful reflective items. Further, there is a need for 
iridescent, silvery or metallic appearing articles which do not use metal. 
SUMMARY OF THE INVENTION 
The present invention meets those needs by providing a multilayered 
polymeric reflective body which can be iridescent or silvery in 
appearance, highly reflective, post formable, and capable of being 
fabricated into a variety of decorative and/or security articles. The 
introduction of folded-over layers into the otherwise substantially planar 
layer structure of the body produces unique optical effects. The terms 
"reflective", "reflectivity", "reflection", and "reflectance" as used 
herein refer to total reflectance (i.e., ratio of reflected wave energy to 
incident wave energy). For bodies which are silvery in appearance, the 
reflectance is sufficiently specular in nature such that the polymeric 
body has a metallic appearance. The use of these terms is intended to 
encompass semi-specular or diffuse reflection such as that of brushed 
metal, pewter, and the like. 
A specific intensity of reflectance, when used herein, is the intensity of 
reflection which occurs at a wavelength where negligible absorption 
occurs. For example, a silver appearing article reflects substantially all 
visible wavelengths (white light), whereas the introduction of a dye to 
achieve other metallic hues will necessarily lower reflectivity of the 
body at the absorbing wavelengths. Wavelengths unaffected by the dye will 
be reflected at essentially the same intensity as a non-dyed sample, and 
it is at these unaffected wavelengths to which the intensity of 
reflectance is referring. Likewise, where an article exhibits iridescent 
color, the intensity of reflection is measured at a wavelength 
corresponding to the color exhibited. 
According to one aspect of the present invention, a multilayer reflective 
polymeric body of at least first and second diverse polymeric materials is 
provided in which the first and second polymeric materials differ from 
each other in refractive index by at least about 0.03. The body should 
comprise a sufficient number of alternating layers of the first and second 
polymeric materials such that at least a portion of the light incident on 
the body is reflected. As used herein, the term "light" is meant to 
encompass not only visible light but also electromagnetic radiation in 
both the infrared and ultraviolet regions of the spectrum. The term "a 
portion of the light incident on the body is reflected" refers, as 
discussed above, to reflected light at wavelengths where negligible 
absorption occurs. 
At least a portion of the reflective polymeric body includes the 
alternating layers in a folded-over relationship which produces striations 
on portions on the body and results in a number of optically unique, 
advantageous properties. The folded-over layers are formed while the body 
is in a freshly extruded condition. Excess material from several surface 
layers is caused to build up and then double over on itself causing a 
layer multiplication for that part of the body and producing the unique 
optical effects. Alternatively, the entire body may be caused to be folded 
upon itself. This folding can increase the number of layers in the body to 
double or greater than the original number. 
The portion of the body containing the folded-over layers has a greater 
reflectivity than the remaining portions of the body because of the 
presence of additional layers. Further, in one embodiment of the 
invention, addition of a coloring agent to one of the layers in the 
polymeric body imparts a three-dimensional appearance to the surface of 
the body where the folded-over layers are located. The body is also 
versatile in its construction in that it may be constructed so as to 
appear silvery and/or iridescent in color, depending on the arrangement 
and optical thicknesses of the layers. 
The optical thicknesses of the alternating layers may vary. In one 
embodiment of the invention, a substantial majority of the alternating 
layers have optical thicknesses of at least about 0.45 .mu.m or less than 
about 0.09 .mu.m (optically thick or optically very thin layers, 
respectively). In an alternative embodiment, a portion of the alternating 
layers have optical thicknesses between 0.09 and 0.45 .mu.m (optically 
thin), and the remaining layers have optical thicknesses of not greater 
than 0.09 .mu.m or not less than 0.45 .mu.m (optically thick/very thin 
layers). In other embodiments of the invention, the alternating layers may 
all have optical thicknesses in the range of from 0.09 .mu.m to 0.45 
.mu.m. Thus, the polymeric body may comprise alternating optically thick 
layers, combinations of optically thick/very thin layers, combinations of 
optically thin and optically thick/very thin layers, or alternating 
optically thin layers. 
Optically very thin layers (i.e., less than about 0.09 .mu.m optical 
thickness) as well as optically thick layers (i.e., greater than about 
0.45 .mu.m) reflect substantially white light over a wide spectrum of 
visible wavelengths. Multilayer bodies of alternating polymer layers which 
are optically thick or a combination of optically thick and optically very 
thin possess a silvery, metallic appearance, while multilayer bodies 
comprising alternating polymer layers which are optically thin have an 
iridescent appearance with intense varying colors. The appearance of the 
body may be controlled by the positioning and percentage of optically thin 
layers in the body. Further, in the practice of the present invention, the 
presence of folded-over layers adds a unique optical appearance to the 
surface of the body. The folded-over layers may comprise any of the three 
layer types described above. 
The reflective body of the present invention may be made up of two or more 
generally transparent polymer resins. Preferred are thermoplastic resins 
which are capable of being post formed into a variety of shapes. In a 
preferred embodiment of the invention, the first polymeric material 
comprises polycarbonate and the second polymeric material comprises 
polymethyl methacrylate. In other embodiments of the invention, elastomers 
may be used to provide a body which can be stretched and relaxed. 
More than two different polymers may be present in the multilayer body. For 
example, the optically thin layers may comprise a pair of first and second 
polymers and the optically thick/very thin layers may comprise a pair of 
different first and second polymers Folded-over layers may be introduced 
into either or both of the layer stacks. The layer types may then be 
laminated together as desired to form the reflective body. 
The reflective polymeric body is preferably in the form of a sheet having 
two major exterior surfaces An outer layer may be included as a surface or 
skin layer on both major exterior surfaces of the reflective body. The 
skin layer may be sacrificial, or may be permanent and serve as a scratch 
resistant and weatherable protective layer. The skin layer is preferably 
applied to the body during or after extrusion of the multilayer 
construction. For example, a skin layer may be applied as a sprayed on 
coating which acts to level the surface of the body to improve optical 
properties and impart scratch resistance, chemical resistance and/or 
weatherability. The skin layer may also be laminated to the multilayered 
body. 
In certain embodiments of the invention, to obtain high reflectivity it is 
desirable to form the reflective polymeric body to comprise at least 500 
or more layers. Increasing the total number of layers in the polymeric 
body has been found to increase its reflectivity (i.e., the percentage of 
incident light reflected from the body). Thus, by controlling the number 
of layers, the degree of reflectivity of the article may be controlled. 
Areas of the body having folded-over layers will exhibit greater 
reflectivity because of the presence of additional layers in that portion 
of the body. 
In some embodiments of the invention, it may be desirable to incorporate 
coloring agents such as dyes or pigments into one or more of the 
individual layers of the polymeric body. We have found that the use of 
pigmented coloring agents in the interior layers causes light either to be 
absorbed or to reflect off the surface of the body so as to impart a 
three-dimensional appearance, especially in those areas of the body where 
folded-over layers are present. The coloring agent is preferably 
incorporated into at least one interior layer in the body. Alternatively, 
the coloring agent may be incorporated into an outer (i.e., exterior) 
layer. The coloring agents may be selected to give the polymeric body a 
metallic appearance other than a silvery or iridescent appearance such as 
bronze, copper, or gold, for example. 
Different colors such as black, blue, red, yellow, white, and the like may 
also be used. Coloring agents may also be used in combination to provide 
desirable coloring and optical properties. 
The multilayer reflective polymeric bodies of the present invention may be 
post formed into a number of decorative or useful items. Such post forming 
operations may include thermoforming, vacuum forming, or pressure forming. 
Further, through the use of forming dies, the multilayer reflective body 
may be initially formed into a variety of useful shapes including profiles 
such as bodies having angled portions, flanges, T-shapes, and the like. 
The multilayer reflective polymeric bodies of the present invention may 
also find uses in security applications such as on currency or as credit 
card emblems as indicia of authenticity or as devices which cannot be 
readily reproduced or copied by counterfeiters. The multilayer reflective 
bodies may also be formed into the credit card substrate itself. 
The present invention also provides an extrusion apparatus for preparation 
of the multilayer reflective body of the present invention comprising at 
least first and second sources of heat plastified thermoplastic material, 
and combining means for receiving the heat plastified material from the 
first and second sources and arranging the first and second sources of 
heat plastified materials in a layered relationship to form a composite 
stream. A shaping die in communication with the combining means is also 
provided which is arranged so as to permit substantially streamlined flow 
of the composite stream through the die to form the multilayer body. 
Means are also included adjacent the shaping die for modifying at least the 
surface of at least a portion of the multilayer body to fold over at least 
some of the layers onto themselves. Such means includes at least two 
cooling rolls positioned on opposing sides of the multilayer body exiting 
the die. A means for driving the cooling rolls is also provided wherein 
the cooling rolls are operated at a slower linear speed than the speed of 
the multilayer body exiting the die (or material from the die is supplied 
at a faster rate than the speed of operation of the rolls), causing an 
excess of layered material on the intake side of the rolls to be built up 
and folded over as the multilayer body passes between the rolls. The speed 
of the rolls may be cyclically varied to create and maintain the folding 
of the layers on a substantially continuous basis. Alternatively, the 
apparatus may be controlled to cause the entire body to fold over upon 
itself. Lateral fold over in the machine direction may also be promoted by 
extruding a sheet having a non-uniform surface using a die having serrated 
or saw-tooth shaped die lips. 
The present invention also provides a method for preparing a multilayer 
reflective polymeric body comprising the steps of providing at least first 
and second streams of heat plastified thermoplastic materials, receiving 
and combining the first and second streams of materials in a layered 
relationship to form a composite stream, directing the composite stream to 
flow through a shaping die to form a multilayer body, and modifying at 
least the surface of at least a portion of the multilayer body by folding 
over a portion of the layers onto themselves. Alternatively, the entire 
body may be caused to fold over upon itself. 
A preferred method of modifying at least the surface of the multilayer body 
includes the step of passing the multilayer body through at least two 
cooling rolls positioned on opposing sides of the body. The cooling rolls 
are operated so that an excess of layered material on the intake side of 
the rolls is built up and then flattened onto the surface of the sheet as 
the sheet passes between the rolls to form folded-over layers on the 
multilayer body. Preferably, the cooling rolls are operated at a slower 
linear speed than the speed of the multilayer body exiting the die. 
Alternatively, the amount of multilayer material exiting the die may be 
increased. In addition, the speed of the cooling rolls is preferably 
cyclically varied so as to create and maintain the folding of the layers 
on a substantially continuous basis. 
Accordingly, it is an object of the present invention to provide a 
multilayer reflective polymeric body having unique optical properties 
comprising multiple optical thickness layer types which have folded-over 
layers on at least a portion of the surface of the body and which can be 
fabricated into a variety of decorative and security articles, is post 
formable, and which may have an iridescent or colorless appearance. This, 
and other objects and advantages of the invention will become apparent 
from the following detailed description, the accompanying drawings, and 
the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention provides a highly reflective multilayer polymeric 
body made up of from a hundred to several thousand layers of the same or 
different types of optical layers. The alternating layers of polymeric 
materials may have an optical thickness of at least 0.45 .mu.m (optically 
thick), or may have a combination of optically thick layers with layers 
having an optical thickness of not greater than 0.09 .mu.m (optically very 
thin), or may have optical thicknesses between 0.09 and 0.45 .mu.m 
(optically thin), where the optical thickness is defined as the product of 
the individual layer thickness times the refractive index of the polymeric 
material which makes up that layer. Different combinations of layer types 
will produce a reflective body having different appearances. Likewise, the 
optical thicknesses of the folded-over or striated layers will affect the 
appearance of the body giving the surface of the body a three-dimensional 
appearance. The thicknesses of the individual layers may be controlled to 
some extent by the layer forming and manipulation steps explained in 
greater detail below. Generally, as the layers are folded over, a thinning 
of individual layer thicknesses occurs. 
Thus, in one form of the invention, the polymeric reflective body comprises 
either optically thick layers of at least 0.45 .mu.m, or combinations of 
optically thin layers and optically thick and/or very thin layers having 
optical thicknesses of not greater than 0.09 .mu.m or not less than 0.45 
.mu.m, respectively, to produce a silvery reflective appearance. The use 
of a substantial number of optically thin layers in the body produces 
vivid, iridescent reflected colors. 
For purposes of optical properties, i.e., reflectance and transmittance, an 
optically thin layer can be described as a layer having an optical 
thickness in the range of from .lambda./4 to 5 .lambda./4, where .lambda. 
represents the visible wavelength range. Thus, for layers to be used in 
the visible wavelength band, an optically thin layer has been described in 
the literature as one whose thickness, D, is less than about 0.5 .mu.m or 
whose optical thickness, ND (where N is the refractive index of the 
material) is less than about 0.7 .mu.m. Vasicek, Optics of Thin Films 
(1960) at pages 100 and 139. 
Optically thin film layers rely on the constructive optical interference of 
light to produce intense reflected light in the visible, ultraviolet, or 
infrared portions of the electromagnetic spectrum according to the 
equation (for a two component system): 
EQU .lambda..sub.m =(2/m) (N.sub.1 D.sub.1 +N.sub.2 D.sub.2), 
where .lambda..sub.m is the reflected wavelength in nanometers, N.sub.1 and 
N.sub.2 are the refractive indices of the alternating polymers, D.sub.1 
and D.sub.2 are the thickness of the respective layers of polymers in 
nanometers, and m is the order of reflection (m=1, 2, 3, 4, 5). Each 
solution of the equation determines a wavelength at which an intense 
reflection, relative to surrounding regions, is expected. The intensity of 
the reflection is a function of the "f-ratio" where, 
EQU f=N.sub.1 D.sub.1 /(N.sub.1 D.sub.1 +N.sub.2 D.sub.2) 
By proper selection of the f-ratio, one can exercise some degree of control 
over the intensity of reflection of the various higher order reflections. 
For example, first order visible reflections of violet (0.38 .mu.m 
wavelength) to red (0.68 .mu.m wavelength) can be obtained with layer 
optical thicknesses between about 0.075-0.25 .mu.m. Iridescent films may 
also be designed to reflect visible light at higher order reflectances, 
although at lower intensities. 
For certain embodiments of the invention, it is desirable to use optically 
thin layers in combination with optically thick layers or combinations of 
optically thick/very thin layers so that the reflective body will exhibit 
a colored or silvery iridescence. The optically thin layers may be in the 
folded-over layers or may be in the remainder of the body. 
In other embodiments of the invention, the multilayer bodies are designed 
so that they do not display vivid iridescence. By combining layers which 
are too thick or too thin to cause iridescence, a reflection which is 
essentially silver and non-iridescent results. This silvery appearance is 
due to higher order reflections from the optically thick and/or very thin 
layers being so closely spaced that the human eye perceives the reflection 
to be essentially non-iridescent. 
For a two component system of alternating layers of polymers having optical 
thicknesses in the thick or very thin range, the reflective 
characteristics of articles are governed by the following equation: 
EQU R=(kr)/(1+(k-1)r).times.100, 
where R is the amount of reflected light (%), k is the sum of optically 
thick and optically thick/very thin layer interfaces, and r=[(N.sub.1 
-N.sub.2)/(N.sub.1 +N.sub.2)].sup.2, where N.sub.1 and N.sub.2 are the 
refractive indices of the polymers. See Vasicek, Optics of Thin Films 
(1960) at pages 69-70. 
This equation indicates that the intensity of the reflected light is a 
function only of r and k, where r and k are defined as above. As a close 
approximation, R is a function only of the refractive index mismatch of 
the two polymer components and the number of layer interfaces. 
The present invention judiciously combines layers having differing optical 
thicknesses to obtain a multilayer reflective polymeric body which 
exhibits a unique iridescent or colorless reflectance, depending upon the 
desired combination of layers. By positioning the folded-over layers at 
different portions of the surface of the body, additional unique optical 
effects are provided. 
The reflective polymeric bodies of the present invention become more highly 
reflective of incident light (i.e., transmit less light) as the number of 
layers is increased. Preferably, the number of layers is sufficient to 
produce an article which will reflect at least 30% of the incident light 
for those wavelengths for which there is negligible absorption. 
Reflectances below about 30% are not sufficient to be readily observed 
except for iridescence. 
The reflectivity of the body is affected by the difference in refractive 
index between the various polymers making up the reflective body. That is, 
the greater the difference in refractive index at each layer interface, 
the greater the reflectivity of the body. Accordingly, it can be seen that 
the reflective nature of the polymeric bodies may be controlled by the 
selection of polymers. 
The reflective multilayered polymeric bodies of the present invention may 
comprise alternating layers of a wide variety of generally transparent 
thermoplastic materials. Suitable thermoplastic resins, along with 
representative refractive indices, which may be used in the practice of 
the present invention include, but are not limited to: copolycarbonates of 
bisphenol and thiodiphenol (refractive index=1.59 to 1.64), blends of 
polymethyl methacrylate and polyvinylidene fluoride (1.38 to 1.49), 
bisphenol A polycarbonate (1.59), copolymers of methyl methacrylate and 
vinylidene fluoride (1.42 to 1.38), polymethyl acrylate (1.48), polymethyl 
methacrylate (1.49), blends and copolymers of polymethyl methacrylate and 
polyvinylidene fluoride; copolymers of vinylidene fluoride and other 
halogenated monomers such as chlorofluoroethylene, chlorodifluoroethylene, 
chlorotrifluoroethylene, hexafluoroacetone, hexafluoropropylene, 
hexafluoropropene, pentafluoropropylene, trifluoroethylene, 
tetrafluoroethylene, and vinyl fluoride blended with polymethyl 
methacrylate; blends of polyvinylidene fluoride and poly(vinyl acetate); 
copolymers of methyl methacrylate, vinylidene fluoride, and a monomer 
selected from the group consisting of chlorofluoroethylene, 
chlorodifluoroethylene, chlorotrifluoroethylene, hexafluoroacetone, 
hexafluoropropylene, hexafluoropropene, pentafluoropropylene, 
trifluoroethylene, tetrafluoroethylene, and vinyl fluoride blended with 
polymethyl methacrylate; blends of polyvinylidene fluoride and poly(vinyl 
acetate); perfluoroalkoxy resins (1.35); polytetrafluoroethylene (1.35); 
fluorinated ethylenepropylene copolymers (1.34); silicone resins (1.41); 
polyvinylidene fluoride (1.42); polychlorotrifluoroethylene (1.42); epoxy 
resins (1.45); poly(butyl acrylate) (1.46); poly(4-methylpentene-1) 
(1.46), poly(vinyl acetate) (1.47), ethyl cellulose (1.47), 
polyformaldehyde (1.48), polyisobutyl methacrylate (1.48), polymethyl 
acrylate (1.48), polypropyl methacrylate (1.48), polyethyl methacrylate 
(1.48), polyether block amide (1.49); cellulose acetate (1.49); cellulose 
propionate (1.49); cellulose acetate butyrate (1.49), cellulose nitrate 
(1.49), polyvinyl butyral (1.49), propylene (1.49); polybutylene (1.50); 
ionomeric resins such as Surlyn (trademark) (1.51), low density 
polyethylene (1.51), polyacrylonitrile (1.51), polyisobutylene (1.51), 
thermoplastic polyesters such as Ecdel (trademark) (1.52); natural rubber 
(1.52); perbunan (1.52); polybutadiene (1.52); nylon (1.53); polyacrylic 
imides (1.53); poly(vinyl chloro acetate) (1.54); polyvinyl chloride 
(1.54); high density polyethylene (1.54); copolymers of methyl 
methacrylate and styrene such as Zerlon (trademark) (1.54); transparent 
acrylonitrile-butadiene-styrene terpolymer (1.54); allyl diglycol resin 
(1.55), blends of polyvinylidene chloride and polyvinyl chloride such as 
Saran resins (trademark) (1.55); polyalpha-methyl styrene (1.56); 
styrene-butadiene latexes such as Dow 512-K (trademark) (1.56), 
polyurethane (1.56); neoprene (1.56); copolymers of styrene and 
acrylonitrile such as Tyril resin (trademark) (1.57); copolymers of 
styrene and butadiene (1.57); polycarbonate (1.59); other thermoplastic 
polyesters such as polyethylene terephthalate and polyethylene 
terephthalate glycol (1.60); polystyrene (1.60); polyamide (1.61); 
polyvinylidene chloride (1.61); polydichlorostyrene (1.62); polysulfone 
(1.63); polyethylene naphthalate (1.64); polyether sulfone (1.65); and 
polyetherimide (1.66). 
A condition for the selection of the polymers to make up the layers of the 
body is that the polymers selected have refractive indices which differ 
from each other by at least about 0.03. Further, the polymers should 
preferably be compatible in processing temperatures so that they may be 
readily coextruded. 
Multilayer bodies in accordance with the present invention are most 
advantageously prepared by employing a multilayered coextrusion device as 
described in U.S. Pat. Nos. 3,773,882 and 3,884,606, the disclosures of 
which are incorporated herein by reference. Such a device provides a 
method for preparing multilayered, simultaneously extruded thermoplastic 
materials. Preferably, a series of layer multiplying means are employed as 
described in U.S. Pat. No. 3,759,647, the disclosure of which is 
incorporated herein by reference. Such devices are capable of providing 
substantially continuous multilayered, simultaneously extruded 
thermoplastic materials. An extrusion device such as that disclosed in 
Alfrey, Jr. et al, U.S. Pat. No. 4,094,947 may also be used to produce 
multilayered articles in which the layer thicknesses of the inner layers 
can be varied. 
A typical extrusion apparatus for the preparation of the multilayer 
reflective body of the present invention is illustrated schematically in 
FIG. 1. There, extrusion apparatus 10 includes, in cooperative 
combination, first, second, and optional third sources of heat plastified 
polymeric resins for extruders 11, 12, and 13, respectively. An optional 
third source of polymer resin may used when it is desired to produce a 
body having different layer repeating unit patterns such as ABCABC or 
ABCBABCB or when it is desired to provide protective boundary layers with 
the body. The third polymer may differ in refractive index from the first 
and second polymers. In one embodiment, the third polymer may comprise a 
copolymer of the first and second components. 
Extruders 11, 12, and (optionally) 13 discharge the heat plastified 
polymeric resins into conduits 14, 15, and 16, respectively. A coextrusion 
feedblock die 17 is in operative combination with conduits 14, 15, and 16 
and receives first, second, and optional third heat plastified streams 
therefrom. A heat plastified polymer stream may also be fed into the 
upstream end of feedblock die 17 to form protective boundary layers as the 
polymers are coextruded. Die 17 combines and arranges the heat plastified 
polymers into layered relationships as taught in the aforementioned U.S. 
Pat. Nos. 3,773,882 and 3,884,606. Die 17 further defines an extrusion 
orifice 18 from which issues a composite stream of polymeric material 
having alternating substantially planar layers of first and second (and 
optionally third) polymeric materials. 
From orifice 18, the composite stream passes optionally through a 
mechanical manipulating section 20 which serves to rearrange the 
alternating layers into a stream having more than the original number of 
layers as taught in the aforementioned U.S. Pat. Nos. 3,565,985 and 
3,759,647. Additional manipulating sections may be arranged in series to 
further multiply the number of layers in the stream. The number of 
additional layers created using the manipulation devices of the 
aforementioned patents is determined by the number of layers divided by 
the layer-dividing vane in those devices. 
The multilayered stream is then passed into a shaping die 22 which is so 
constructed and arranged that streamlined flow is maintained therein. Such 
an extrusion die is described in U.S. Pat. No. 3,557,265, the disclosure 
of which is incorporated by reference herein. While a sheet or film 
forming die 22 is illustrated, it will be appreciated by those skilled in 
the art that a forming die of any desired configuration may be use to 
extrude not only films and sheets, but also other profiles and shapes. 
Further, the lips of the die may be serrated, saw-toothed, or wavy in 
configuration to provide non-uniformities 42 in the surface of the 
extruded body 44 as illustrated in FIGS. 4A (sinusoidal waves) and 4B (saw 
tooth ridges). These surface non-uniformities promote the folding over of 
the layers in the machine direction of travel of the body as described in 
greater detail below. 
The configuration of the shaping die can vary and can be such as to reduce 
the thickness of each of the layers. The precise degree of reduction in 
thickness of the layers delivered from the mechanical orienting section, 
the configuration of the die, and the amount of mechanical working of the 
body after extrusion are all factors which affect the thickness of the 
individual layers in the final body. 
Means are also included adjacent the shaping die for modifying at least the 
surface of at least a portion of the multilayer body to fold over at least 
some of the layers onto themselves. As illustrated in FIG. 2, such means 
comprise two cooling rolls 30, 31 positioned on opposing sides of the 
multilayer body 32 exiting the die. A means for driving the cooling rolls 
is also provided in which at least one of the cooling rolls is operated at 
a slower speed than the speed of the multilayer body exiting the die, 
causing an excess of layered material 34 on the intake side of the rolls 
to be built up and folded over as the multilayer body passes between the 
rolls. Depending on the relative speeds of rolls 30, 31 and the 
orientation of the body, excess material may be built up on one or both 
surfaces of the body. FIG. 3 illustrates the alternating layers 36 as they 
appear in the final sheet of the polymeric reflective body. As is shown, 
layers 40 are in a folded-over relationship which increase the total 
numbers of layers in that portion of the body. 
It must be remembered that the multilayer bodies of the present invention 
may comprise up to several hundred or a thousand or more layers having 
thicknesses of only a fraction of a micrometer. Thus, illustration of the 
layers in the drawings, both as to number and thickness, is greatly 
simplified and exaggerated for ease of understanding. 
Thus, in the embodiment illustrated in FIG. 2, the excess material is built 
up and flattened on the surface of the sheet to form folded-over layers on 
the final multilayer body. This produces layer fold over in a direction 
generally normal to the direction of travel of the sheet (machine 
direction). In order to maintain the proper layer multiplication on a 
continuous basis, the speed of the cooling rolls is preferably cyclically 
varied. As an example, the speed of the cooling rolls may be cyclically 
varied between about 1 ft/min and 5 ft/min. Where the layered body is 
extruded downwardly in a vertical direction between cooling rolls 30, 31, 
a bank of excess material may be caused to build up on both surfaces of 
the body. 
In another embodiment of the invention, one or both of the die lips on 
forming die 22 may have a serrated, saw-toothed, or wavy configuration to 
produce non-uniformities 42 in one or both surfaces of the extruded 
bodies. These non-uniformities promote lateral fold over of the layers as 
shown in FIGS. 5A and 5B. As the sheet or body passes between cooling 
rolls 30, 31, the layered polymeric material in areas 46 (best seen in 
FIGS. 5A and 5B) flows and folds into the areas of non-uniformity. 
Reflective polymeric bodies produced by the practice of the present 
invention have a wide variety of useful applications. In some embodiments 
of the invention it may be desirable to incorporate coloring agents such 
as dyes or pigments into one or more of the individual layers of the 
polymeric body. It is desirable to use pigmented coloring agents in the 
interior layers to impart a three-dimensional appearance to the surface of 
the body. This can be done to one of the outer or skin layers of the body, 
or alternatively, the coloring agent may be incorporated into one or more 
interior layers in the body. The coloring agents may be selected to give 
the polymeric body a metallic appearance other than its normal silvery 
appearance such as bronze, copper, or gold, for example. 
Different colors such as black, blue, red, yellow, white, and the like may 
also be used. Coloring agents may be used in combination to provide 
desirable coloring and optical properties. 
Additionally, the highly reflective polymeric bodies may be fabricated as 
non-corroding metallic appearing articles for indoor or outdoor exposure. 
For example, the polymeric bodies may be fabricated into signs, or bright 
work for appliances. The bodies may be post formed into highly reflective 
decorative items such as wall panels, dishware, decorative trims, or the 
like, by processes such as thermoforming, vacuum forming, shaping, 
rolling, or pressure forming. 
The bodies may also be used for security applications such as credit card 
emblems or on currency. For example, the body may be embedded into or 
secured onto the surface of a credit card similar to the manner in which 
holographic or prismatic foils are currently used. Alternatively, the body 
may be formed into the credit card itself. The body may also be secured to 
a portion of a document, such as a document indicating title. The body may 
also be used on paper currency, or be formed into plastic currency. 
In order that the invention may be more readily understood, reference is 
made to the following example, which is intended to be illustrative of the 
invention, but is not intended to be limiting in scope. 
EXAMPLE 1 
A 2,625 layer melt stream of Calibre 303-22 (trademark) polycarbonate 
(refractive index 1.59) and Acrylite H15-003 (trademark) polymethyl 
methacrylate (refractive index 1.49) was produced using a 165 layer 
feedblock and four layer multipliers as taught in U.S. Pat. Nos. 3,773,882 
and 3,759,647. In addition, skin layers were extruded onto both exterior 
surfaces of the melt stream which comprised 75% by weight Calibre 303-22 
(trademark) polycarbonate and 25% by weight polycarbonate dye concentrate. 
Roll speed was cycled manually between 1 ft/min and 5 ft/min in order to 
continually produce folded-over layers in the body like those illustrated 
in FIGS. 2 and 3. The multilayer sheet which was produced had an overall 
silvery reflective appearance with areas of varying intense iridescent 
color indicating the presence of both optically thick and/or optically 
very thin layers as well as optically thin layers. The folded-over layers 
exhibited a three-dimensional stepped visual effect of overlapping stacked 
layers similar to a deck of cards where the cards are offset from adjacent 
cards in the deck. 
While certain representative embodiments and details have been shown for 
purposes of illustrating the invention, it will be apparent to those 
skilled in the art that various changes in the methods and apparatus 
disclosed herein may be made without departing from the scope of the 
invention, which is defined in the appended claims.