U.S. patent application number 10/690465 was filed with the patent office on 2005-02-03 for patterned platelets.
Invention is credited to Faris, Sadeg M..
Application Number | 20050024626 10/690465 |
Document ID | / |
Family ID | 29270124 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050024626 |
Kind Code |
A1 |
Faris, Sadeg M. |
February 3, 2005 |
Patterned platelets
Abstract
Patterned platelets are platelets made with specified shapes and
sizes. The various sizes and shapes of the platelets are used to
code articles and substances to which they are applied. The
patterned platelets can be in inks or paints applied to articles.
The platelets can be further coded by markings thereon or by
spectral or polarization codes rather than just the distribution of
sizes and shapes. The patterned platelets can be made from any
materials buy subtractive or additive processes. A patterned
platelet can also be made by an actinic polymer being applied to a
substrate and a mask applied to allow only the desired size and
shape to be exposed to radiation curing the unmasked portion of the
polymer on the substrate. The polymer can be cholesteric liquid
crystals with the properties of reflecting polarized light of
selected wavelengths to code the crystals in addition to the size
and shape codes. The cholesteric liquid crystals may also be doped
with materials which absorb a portion of the wavelengths which
would otherwise be reflected further coding the patterned
platelets. Codes of the patterned platelets can be composed of the
distribution of the platelets alone or in combination with the
position of the platelets on an object. A code with the presence or
absence of a specified patterned platelet in a specified location
could be a binary code. If n different patterned platelets are used
in each of x positions a code with x to the nth power combinations
is possible.
Inventors: |
Faris, Sadeg M.;
(Pleasantville, NY) |
Correspondence
Address: |
REVEO, INC.
3 WESTCHESTER PLAZA
ELMSFORD
NY
10523
US
|
Family ID: |
29270124 |
Appl. No.: |
10/690465 |
Filed: |
October 20, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10690465 |
Oct 20, 2003 |
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09196583 |
Nov 20, 1998 |
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6643001 |
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Current U.S.
Class: |
356/71 |
Current CPC
Class: |
Y10T 428/2982 20150115;
B33Y 80/00 20141201; B42D 2033/20 20130101; Y10T 428/24901
20150115; B42D 25/29 20141001; B42D 2033/26 20130101; B42D 2033/16
20130101; Y10T 428/2991 20150115; Y10T 428/24893 20150115 |
Class at
Publication: |
356/071 |
International
Class: |
G06K 009/74 |
Claims
What is claimed and desired to be secured by Letters Patent of the
United States is:
1. A coded patterned platelet comprising: a platelet having a
specified shape, a specified surface area and one or more specified
identification markings thereon.
2. A coded patterned platelet as in claim 1 wherein: one or more
specified identification markings are selected from the group
consisting of spatial markings, spectral markings, or polarization
markings on the coded patterned platelet.
3. A coded patterned platelet as in claim 2 wherem: one or more
spatial markings are selected from the group consisting of
geometric shapes, numbers, letters, irregular shapes, notches, and
apertures.
4. A coded patterned platelet as in claim 2 wherein: one or more
spectral markings are produced by materials selected from the group
consisting of dyes, pigments, Cholerestic Liquid Crystals, doped
Cholerestic Liquid Crystals materials, holographic materials,
refractive materials, reflective materials, and metallic
materials.
5. A patterned platelet identity code for use with articles or
substances comprising: a plurality of patterned platelets having
any combination of n specified shapes with m specified surface
areas where n and m are any integers with a value 1 or greater.
6. A patterned platelet identity code for use with articles or
substances as in claim 5 wherein: the identity code is further
defined by one or more markers selected from the group consisting
of the percentage distribution of n sizes and m shapes of patterned
platelets, spectral codes, polarization codes, spatial codes
position on the article codes and angle of observation codes.
7. A method of making polymer patterned platelets comprising:
preparing a mixture of polymer material to be actinically cured,
spreading a layer of the of polymer material to be actinically
cured on a sheet of substrate material, applying a mask with
apertures of the shapes and sizes of the desired patterned
platelets to the poloymer material to be actinically cured,
exposing the masked polymer material to be actinically cured to
radiation, thus forming patterned platelets of a specified shape
and size, removing the patterned platelets from the substrate.
8. A method of making polymer patterned platelets as in claim 7
wherein, the polymer is a cholesteric liquid crystal.
9. A method of making. cholesteric liquid crystal patterned
platelets as in claim 8 wherein there is the additional step of:
varying the concentration of chiral dopants for controlling the
pitch of the cholesteric liquid crystal material such that it
reflects a specified portion the spectrum.
10. A method of making cholesteric liquid crystal patterned
platelets as in claim 8 wherein there is the additional step of:
doping the cholesteric liquid crystal material to absorb a
specified portion the spectrum.
11. A method of making cholesteric liquid crystal patterned
platelets as in claim 9 wherein there is the additional step of:
spatially marking the cholesteric liquid crystal material.
12. A method of making cholesteric liquid crystal patterned
platelets as in claim 8 wherein there is the additional step of:
repeating the process steps of spreading a layer of the of
cholesteric liquid crystal material to be actinically cured on a
sheet of substrate material, applying a mask with apertures of the
shapes and sizes of the desired patterned platelets to the
cholesteric liquid crystal material to be actinically cured,
exposing the masked cholesteric liquid crystal material to be
actinically cured to radiation, thus forming patterned platelets of
a specified shape and size, to obtain successive layers of
cholesteric liquid crystal material.
13. A method of making cholesteric liquid crystal patterned
platelets as in claim wherein the masks are changed to add spatial
markings.
14. A method of making cholesteric liquid crystal patterned
platelets as in claim 12 wherein the masks are changed to create
three-dimensional shapes.
15. A method of making patterned platelets comprising: masking an
area of a substrate to obtain a shape and size for the patterned
platelet, depositing a layer of material through the mask, removing
the patterned platelets from the substrate.
16. A method of making patterned platelets as in claim 15 wherein:
the additional steps of masking an area of the material previously
deposited, and depositing a layer of material through the mask to
add to the previously deposited material.
17. A method of making patterned platelets as in claim 15 wherein:
the additional steps of masking an area of the material previously
deposited, and depositing a layer of a different material through
the mask to add to the previously deposited material.
18. A method of making patterned platelets as in claim 15 wherein:
the additional steps of masking a portion of the area of the
material previously deposited, and depositing a layer of material
through the mask to add to the previously deposited material and
define a spatial marking thereon.
19. A method of making patterned platelets as in claim 15 wherein:
the additional steps of masking a portion of the area of the
material previously deposited, and depositing a layer of material
through the mask to add to the previously deposited material and
add material to make a three-dimensional shaped patterned
platelet.
20. A method of making patterned platelets as in claim 15 wherein:
the additional steps of masking a portion of the area of the
material previously deposited, and subtracting a layer of material
from the unmasked portion of the previously deposited material to
define a spatial marking thereon.
21. A method of making patterned platelets comprising: forming a
film of material on a substrate, masking a portion of the film,
removing material from the unmasked portion of the material, to
form patterned platelets, removing the patterned platelets from the
substrate.
22. A method of making patterned platelets as in claim 21 wherein:
the additional steps of masking a portion of the area of the
material, and subtracting a layer of material from the unmasked
portion of the patterned platelet material to define a spatial
marking thereon.
23. A method of detecting patterned platelet codes comprising the
steps of: observing a sample of the coded patterned platelets,
counting the patterned platelets by type used to determine if it
fits the code pattern.
24. A method of detecting patterned platelet codes as in claim 23
wherein, a charge coupled device pixelizes the image of the
patterned platelets observed, the charge coupled device sends the
image of the platelets to a computer programmed with pattern
recognition software to recognize and count the shapes and sizes
and spatial markings of the patterned platelets used and compare it
to the code used.
25. A method of detecting patterned platelet codes as in claim 23
wherein a spectrum analyzer determines the spectral codes uses.
26. A method of detecting patterned platelet codes as in claim 23
wherein a polarization detector detects the polarization codes
used.
27. A code comprising patterned platelets.
28. A code as in claim 27 wherein, the code comprises one or more
features of the patterned platelets chosen from the group
consisting of specified shapes, specified sizes, spatial markings,
percentage distributions of coded patterned platelets, spectral
markings, polarization markings and angle of viewing codes.
29. A code as in claim 27 wherein, the positions of the patterned
platelets relative to each other on an article are part of the
code.
30. A code as in claim 29 wherein, the code comprises one or more
features of the patterned platelets chosen from the group
consisting of blank spaces, specified shapes, specified sizes,
spatial markings, percentage distributions of coded patterned
platelets, spectral markings, polarization markings and angle of
viewing codes.
31. An coded ink comprising: an ink carrier, a code of a plurality
of coded patterned pigments in the ink carrier.
32. A coded paint comprising: a paint carrier, a code of a
plurality of patterned pigments in the paint carrier.
33. A coded paint as in claim 32 wherein the paint is applied to an
article to code the article.
34. A coded ink as in claim 31 wherein the ink is applied to an
article to code the article.
35. A code as in claim 27 wherein: the patterned platelets are
applied to the surface of an article to identify it.
36. A code as in claim 27 wherein: the patterned platelets are
mixed in with the material comprising an article to identify
it.
37. A code as in claim 27 wherein: the patterned platelets are
mixed in with a liquid to identify it.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to patterned platelets. More
particularly the invention relates to platelets having specified
shapes, sizes and optical properties, optionally with markings
thereon, such that the platelets can be applied to objects to tag
and identify the objects with unique codes. The platelets can be
pigments in inks or paints applied to an object. The platelets can
also be mixed in with other materials to tag them such as in
liquids or solids.
[0003] 1. Description of the Related Art
[0004] Counterfeiting of articles and documents has been a problem
in the past. Further, it is also useful in many industries to be
able to trace of the origin of goods and documents. In the past,
many methods have been introduced to tag articles such that they
can be easily and positively identified in the future and to
prevent tampering or counterfeiting activities. Some of these
methods including using flop colors and holograms on platelet
pigments. For example, the recently issued U.S. currency has flop
colors.
[0005] Presently most platelet pigments are made in sheets or films
and then broken into random sized fragments buy various techniques
such as sand grinding, ball milling, two roll milling, pestle and
mortar or freezing and cracking. These fragments are then sieved by
screens or wet sieving or air classification to sort the sizes of
the fragments. However the shapes of the fragments are random and
the size of the fragments has a wide standard deviation. Further,
the various sieving steps add to the cost of processing the
platelets.
[0006] Marking of platelets of even size and shape was not used to
identify those platelets and use the platelets in codes to help
identify articles and substances and deter counterfeiters.
[0007] One recent development was to make controlled shape and size
platelet pigments by molding polymers as shown in patent WO98/12265
however the molding process is difficult to use, wastes a lot of
expensive material and is costly. Another drawback is removing odd
shaped, notched or angled pieces from the mold.
[0008] Patterned platelets, having controlled shapes and sizes,
have not been coded by spatial features, such as raised or lowered
portions of the patterned platelets with identifiable shapes on the
platelets or spectral features, such as color and polarization, to
deter counterfeiters.
[0009] Low cost, easy to make, coded platelets, which can be easily
applied to articles or documents such that they are easily detected
are needed.
[0010] Three dimensional shaped patterned platelets have not been
used in the past. Three-dimensional platelets add more
possibilities for coding with more shapes and the shapes may be
useful for reflecting or refracting light.
[0011] Low cost, easy to make, coded platelets, which can be mixed
into liquids and solids to identify them are needed. The platelets
can be used in inks and paints applied to objects to identify the
objects.
[0012] Most prior art Cholesteric Liquid Crystal (CLC) pigments are
made by actinic methods on sheets of material. The sheets are then
broken up into fragments of random sizes and then sieved to obtain
particles of approximately the same size and to eliminate platelets
which are too small. This process results in a lot of wasted
materials which are costly to make.
[0013] It will be appreciated that prior art platelet pigments
cannot cost effectively produce the ultra-narrow size distribution,
have not taught low cost easy to make the production of platelets
with regular shapes, and they have not taught how pigments can be
endowed with markings or codes using spatial marks, polarization or
spectral marks.
SUMMARY OF THE INVENTION
[0014] This invention relates to producing platelets, which have a
uniform shape and size. Platelets produced with a uniform size do
not have to be sieved, the resulting standard deviation in the size
of the platelets is smaller than the platelets produced with random
sizes and then sieved. When platelets are produced with a small
standard deviation of size, codes comprising mixes of several sizes
of platelets in various percentages can be made for tagging
objects.
[0015] Similarly when distinct shapes of platelets are made, they
can be applied to objects, to tag those objects. For example, a mix
of 50% circles and 50% squares can be one code. The letters B, K, Y
could be another code. A mix of numbers, letters and shapes could
be yet another code. Any combinations unique to a product can then
identify that product when platelets using that code are applied to
or embedded in the product.
[0016] In addition to the size and shape of the platelets,
platelets can also be made with spatial markings, either raised or
lowered portions, on the platelets such as having letters or shapes
etched on the platelets. The platelets can also have apertures in
the platelets or notches on the perimeter of the platelets to
further distinguish them and make them more useful for tagging.
[0017] The platelets can also be made to reflect distinctive
portions of the spectrum of light to further identify the platelets
for tagging purposes. Each platelet can have one or ore sections of
its surface reflect different spectral codes. CLC platelets can be
made to electively reflect wide or narrow bands of light. For
example, platelets can be made to reflect red or green or blue or
white light or even light not in the visible spectrum. A platelet
can have one section reflect green right circularly polarized light
and another section reflect blue left polarized light. The light
reflected can be used to easily identify the platelets used.
Patterns of colors of light reflecting pigments can be used to
further code the platelets. By using dopant materials in the CLC
platelets, spectral band absorbing identifiers can be placed in the
platelets further coding the platelets to be used as tags.
[0018] The sizes, shapes and spatial markings on the platelets can
be made by masking when an actinic process of CLC production is
used.
[0019] Other techniques for producing specified shapes and sizes of
platelets include the use of masking by screen printing, masking by
ink jet printing, gravure printing, chemical etching, ablating, and
laser cutting methods all of which are well know in the art. Any
additive or subtractive methods used for making the patterned
platelets, either alone or in some combination, are within the
scope of the invention. To make three dimensional shaped patterned
platelets stereolithography methods of adding and subtracting
layers of material may be used.
OBJECTS OF THE INVENTION
[0020] It is therefore an object of this invention to provide
platelets having predetermined regular shapes.
[0021] Another object of this invention is to produce platelets
having substantially identical lateral dimensions or areas,
resulting in a very narrow platelet size distribution.
[0022] Another object of this invention is to provide platelets
with substantially identical sizes and shapes in two or three
dimensions.
[0023] Another object of this invention is to reduce the cost of
producing pigments by eliminating milling and sieving steps.
[0024] Another object of this invention is to eliminate production
of platelets outside a desired range, thus reducing waste.
[0025] Another object of the invention is to produce patterned
platelets without using expensive hard to use molds.
[0026] Yet another object of this invention is to provide platelets
of known size and shape in combinations of different sizes and or
shapes to form codes used for tagging objects.
[0027] Yet another object of this invention is to provide platelets
of known size and shape having spatial markings on the platelets
for additional identification codes.
[0028] Yet another object of the present invention is to provide
platelets of known size and shape having identification codes
created by means of polarization or spectral encoding.
[0029] Yet another object of this invention is to provide platelets
for general printing and in particular, security printing wherein
the platelet shape, size spatial, spectral and polarization
encoding identifies the origin of the ink.
[0030] It is a further object of the invention to provide codes
wherein inks or paints with coded platelets are placed in specified
locations on a product thus forming another code.
[0031] It is yet another object of the invention to provide optical
properties in the three dimensional shaped patterned platelets.
[0032] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1A is an illustration of prior art platelets having
random shapes and sizes.
[0034] FIG. 1B shows a size distribution curve representing a large
number of platelets having different shapes and sizes as shown in
FIG. 1A.
[0035] FIG. 2A is an illustration of groups of platelets each
having the same size and the same triangle shape.
[0036] FIG. 2B is an illustration of groups of platelets each
having the same size and the same rectangle shape.
[0037] FIG. 2C is an illustration of groups of platelets each
having the same size and the same circular shape.
[0038] FIG. 2D shows a size distribution curve representing a group
of platelets all having the same shape and size. It can also
represent different shapes but identical mean area A.
[0039] FIG. 2E is an illustration of narrow size distributions of a
mixture of platelets having identical shape but different mean
areas A.sub.1, A.sub.2, and A.sub.3. It can also illustrate a
mixture of different shapes and different mean areas A.sub.1,
A.sub.2, and A.sub.3.
[0040] FIG. 2F is an illustration comparing the standard deviation
of flake sizes made by prior art methods of fracturing and sieving
to the present method of producing platelets of uniform size.
[0041] FIG. 3A is an illustration of a circular platelet having
added spatial markings or codes inside its boundary.
[0042] FIG. 3B is an illustration of a triangular platelet having
added spatial markings or codes inside its boundary.
[0043] FIG. 3C is an illustration of a platelets having added
spatial marking or code inside or on the boundary.
[0044] FIG. 4A shows representative spectral curves showing the
reflectivity of platelets for red, green and blue wavelengths of
the incident electromagnetic radiators.
[0045] FIG. 4B shows a representative spectral curve showing the
reflectivity of platelets for white wavelengths of the incident
electromagnetic radiators.
[0046] FIG. 4C shows representative spectral curves showing the
reflectivity of platelets for invisible wavelengths of the incident
electromagnetic radiators.
[0047] FIG. 4D shows the reflectivity curve of platelets for
different wavelengths on which narrow absorption bands are
superimposed representing a spectral marking or coding.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] The prior art, such as in U.S. Pat. Nos. 5,415,950,
5,500,313 and 5,362,315, teach methods of producing platelet
pigments 10 which have random sizes and random shapes as
illustrated in FIG. 1A. These platelets 10 are made by making color
producing thin films coated on large substrates. These color films
are then removed from their substrates and broken into smaller
fragments. Several milling steps are used to produce yet smaller
fragments, flakes or platelets having thickness ranging from about
1 micron to about 20 micron and lateral dimensions ranging from
about 3 microns to about 1,000 microns. Platelets are defined as
flat structures with lateral dimensions at least a factor 2 larger
than the average thickness, preferably more than 5 times larger
than the average thickness. This ensures that when the platelets
are applied to a substrate they will lay flat. As defined herein,
patterned platelets, as used in this invention, are on the order of
about 1 micron to about 1000 microns laterally.
[0049] In order to sort the platelet sizes and to achieve a desired
size range of size distribution, the prior art, in the patents
listed above, use sieving steps. For example, standard mesh 200 has
76 .mu.m openings. Milling and sieving steps have to be repeated to
achieve the desired size range or distribution. These sieving and
milling steps lead to a mean area or size distribution which is
illustrated by curve 15 in FIG. 1B, which is difficult and costly
to make narrow. The material that is much smaller than the mean
size is discarded because it would lead to degraded color
properties or because its particles have an aspect ratio about or
less than 2 and may not be considered flat platelets. Therefore,
the prior art process achieves either a relatively broad mean area
distribution, which compromises the quality of the pigment, or a
relatively narrower distribution which requires more costly steps,
and the need to discard material outside the desired distribution.
Prior art platelets and methods of producing them suffer from these
limitations.
[0050] Shaped platelets have been made as shown in patent WO
98/12265, which discloses a method of making shaped platelets by
molding. The process is not easy to use, is expensive and does not
show how to add spatial or spectral makings on the platelets.
Further, it is not practical to mold patterned platelets with
notches or other angled shapes because of the difficulty in
removing such platelets from the mold. In addition, the molding
process shown does not disclose the ability to make three
dimensionally shaped patterned platelets. The molding process shown
also wastes a lot of expensive material increasing the cost of the
molded patterned platelets.
[0051] The present invention overcomes these limitations by
producing patterned platelets which, are easy to make, can be make
in three dimensions, and the process of making the patterned
platelets does not waste material. Further, the patterned platelets
of the present invention have spatial makings and/or spectral
markings, in addition to the well-defined shapes and sizes. With
well-defined shapes and sizes of platelets being produced, repeated
milling and sieving steps are eliminated and wasted material is
avoided. This reduces the production cost. The mean area of the
platelets is illustrated by curve 25 in FIG. 2D. FIG. 2F shows a
comparison of curves 15 and 25 illustrating the smaller standard
deviation of mean area using the platelets made to a specified size
and shape as opposed to the milling and sieving process of the
prior art.
[0052] With regular shapes and sizes of platelets, coding by
various combinations of shapes and sizes becomes possible. FIGS.
2A-C show three representative groups of platelets, triangular 20,
rectangular 22, and circular 24 respectfully. It is understood that
other shapes, letters, numbers or other configurations for the
platelets are possible. In each group, as shown in FIGS. 2A-C the
platelets have substantially the same lateral dimensions and the
same area. This leads to a very narrow size distribution as
illustrated in FIG. 2D. This distribution has a mean area,
{overscore (A)} of the platelets with a standard deviation a such
that .sigma./{overscore (A)}<<1. A mixture of platelets can
be produced from different groups of shapes having substantially
the same areas. Thus a code comprising 1/3 triangles, 1/3
rectangles and 1/3 circles all having the same mean area A , can be
produced to tag an object. The percentages of the shapes can be
changed to create another code.
[0053] FIG. 2E illustrates a mixture of platelets having identical
shapes, for illustration lets pick all rectangles, but having a
different narrow size distribution, with mean areas and standard
deviations, {overscore (A)}.sub.1, {overscore (A)}.sub.2, and
{overscore (A)}.sub.3, .sigma..sub.1, .sigma..sub.2, .sigma..sub.3,
respectively. The code for the platelets is now 1/3 rectangles of
mean area {overscore (A )}, {fraction (1/3 )} rectangles of mean
area {overscore (A)}.sub.2, and 1/3 rectangles of mean area
{overscore (A)}.sub.3. The code can easily be changed by changing
the percentages of rectangles found in each mean area grouping such
that 10% is in {overscore (A)}.sub.1, 30% in {overscore (A)}.sub.2,
and 60% in {overscore (A)}.sub.3. Other codes can be made up using
different shapes or combinations of shapes in each mean area
grouping. Thus, hundreds of different combinations of codes are
possible with only three shapes and three sizes with all the
percentages of mixes changing. Obviously more shapes and sizes can
be used in combination for more codes.
[0054] With well-controlled shapes and sizes of platelets, etchings
or apertures in the surface of the platelets can spatially further
distinguish the identity of the patterned platelets making
counterfeiting even more difficult and expanding the number of
codes possible.
[0055] As illustrated in FIG. 3A, circular platelet 24, has a T 31
etched on its surface, it also has two bars 32 under the T and a
circle 33 under the bars. Thus, the circle platelet has a unique
spatial marking or etching on it to further identify it. A new code
with circles having a T, two bars, and a circle etched on it of a
specified size is now possible. The spatial markings could be
apertures in the circle 24 instead of etchings on the surface thus
providing another distinguishing feature for yet another code. The
spatial markings could also be raised areas on the patterned
platlets.
[0056] Similarly FIG. 3B shows triangle 20 with circles 24 etched
on its surface.
[0057] FIG. 3C shows an irregular shape 28 with a V shaped notch 36
in the perimeter, a square notch 37 in the perimeter, and a U
shaped notch 38 in the perimeter. The irregular shape 28 has a
rectangle 35 etched on it to further uniquely identify it and
thwart counterfeiters.
[0058] In addition to the size and shape combinations listed above
the platelets may also have different spectral coding such as
colors. Thus, another code can be red triangles of mean area
{overscore (A)}.sub.1 blue rectangles of area {overscore (A)}.sub.2
and green circles of mean area {overscore (A)}.sub.3. The
combination of colors with sizes and shapes and percentages now
makes many more combinations of codes possible.
[0059] A further distinguishing feature is having more than one
spectral marking on a patterned platelet's surface. Thus for
example in FIG. 3B the triangle 20 could have circles 34 of the
same or different colors or polarizations, which would further code
the platelets. Many other combinations of spatial and spectral
markings are possible on the platelets.
[0060] The colors can be obtained by pigments which absorb colors
or by pigments which reflect colors. FIGS. 4A to 4D show spectrums
from reflective cholesteric liquid crystals CLC which can make up
the platelets. The CLC materials can be made to have sharply
defined reflective spectra as shown in FIG. 4A. The colors are
distinct with no overlapping reflected wavelengths. As shown the
platelets can now be spectrally coded by color with blue, red,
green or any other color in addition to size and shape.
[0061] CLC materials can also reflect white light as shown by the
reflective spectra in FIG. 4B or reflect invisible portions of the
spectrum as shown in FIG. 4C. The spectra can be easily detected
and analyzed to help identify the code used by simply shining a
light on the object having the spectrally coded platelets and
observing the light reflected therefrom. When CLC reflective
materials make up the platelets a dopant can be added to the CLC to
absorb a portion of the light that would ordinarily be reflected.
As shown in FIG. 4D this further spectrally codes the platelets and
prevents counterfeiting.
[0062] Other optical properties such as polarization can be used to
help identify the CLC platelets. CLC platelets circularly polarize
light such that either a right handed or left handed light will be
reflected.
[0063] Other color characteristics such as pearlescence, iridescent
colors, flop colors (colors which change with the viewing angle)
and metallic luster can further optically identify a platelet.
[0064] A code of platelets with a wavelength observable at a
particular viewing angle is another variable which can be added to
the mix of combinations of codes.
[0065] Another code can be to have a row or matrix with a large
number of spaces for inserting numbers, letters, shapes, or coded
patterned platelets with different identifying spatial spectral or
polarization markings in there assigned positions. The code being
the presence or absence of the expected coded patterned platelets
in each position. For example if a line having 64 positions was
used the presence or absence of the various shapes of patterned
platelets in their assigned spaces would simulate a 64 bit line of
computer code. When the position can contain the correct platelet
or no platelet the system is binary. When the system can have lets
one of x different shapes, with different spatial makings or
different spatial markings a code with a number equal to, x to the
64.sub.th power, combinations is possible. The amount of
information carried is such a system is very large. A large number
of lines of such codes not only would secure a document against
counterfeiters but could carry large amounts of information in a
small space.
[0066] As shown above an almost infinite number of combinations of
shapes, sizes, etchings, notches, apertures, colors, and spectra
absorbing dopants can be used in such combination as to uniquely
identify any object by the platelets used thereon or therein.
Colors can be mixed to any desired hue. Colors can be obtained by
additive primaries (red, green, blue) or subtractive primaries
(cyan, magenta, yellow). The colors can be flop colors, pearlescent
colors, or iridescent colors. The colors may be obtained by CLC
materials, or by holographic or interference techniques.
[0067] Other identifying characteristics of the patterned platelets
may be their magnetic or static electricity properties which will
help to magnetically or electrically separate or detect the
patterned pigments. For example a magnetic ink may be made with the
patterned pigments such that a magnetic ink reader can be used as
part of the tag identifying process.
[0068] Patterned platelets can be made by a large variety of
methods and by using a large variety of substances either alone or
in combination. The materials may be in one layer or stacked in
many layers. The patterned pigments may be flat or layered in three
dimensional shapes such as prisms or spheres or cubes. The
patterned platelets may have reflective surfaces as one layer on
one or more surfaces of the patterned platelet. The patterned
platelets may have shapes combined with reflection or refraction
properties used in optics such as parabolic reflectors, prisms,
mirrors, lenses, diffraction gratings, spherical reflectors.
[0069] For example a thin sheet of aluminum can be cut, etched, or
ablated to leave well-defined shapes and sizes of aluminum.
Similarly a substrate can be masked by such techniques as silk
screening, gravure printing or inkjet printing and aluminum
deposited on the substrate to form the shapes and sizes of the
patterned pigments. Layers of other materials, pigments (reflective
or absorptive) may be applied to have multilayered or stacked
platelets. Many techniques are known for depositing or removing
materials in precise fashion. Any of these techniques may be
employed for use with this invention. Stereolithographic techniques
can be used to make three-dimensional patterned platelets with
three dimensional shapes.
[0070] Examples of techniques for depositing material are
electroplating and vapor deposition.
[0071] Examples of techniques for removing materials include
etching, ablating, use of solvents to remove material.
[0072] For additive methods of making patterned platelets a
substrate is prepared, and a thin film of a substance is added by
painting, or depositing the substance through a mask or stencil of
the desired shape. The substance is then fixed, dried cured or
otherwise adhered and the process repeated for other layers of the
same or different substances until all desired layers are added.
The same or different masks may be used for each layer. For three
dimensional shapes different masks can be used for each layer to
form the desired shape. The various layers added may apply spatial
or spectral markings to the platelets. The patterned platelets are
then removed from the substrate and are the correct size and shape
for immediate use without having to use milling or sieving steps to
obtain the correct sizes needed.
[0073] For subtractive methods a thin film of material is deposited
on a substrate and a mask or a defined pattern is applied. The mask
can be applied by a photo resist, photo lithography, ink jet
printing, gravure printing, silk screen printing or other methods.
the unprotected areas of the material are then etched, ablated or
otherwise remove material from the unprotected area. The mask can
then be removed and a different mask applied if further material
form a different area is to be removed. In this manner layers may
be separately removed to form a three dimensional shape or to form
patterned platelets with notches, apertures, or spatial markings on
their surfaces.
[0074] Any combination of additive and subtractive steps may be
used to produce patterned platelets with the desired combinations
of spatial markings and spectral or polarized markings thereon.
[0075] Using well-known techniques layers of materials may be built
up to tailor the patterned pigments to specific uses. Magnetic
materials may be used as a sole material or as a layer to make the
patterned pigments magnetic for magnetic separation or sorting or
for magnetic reading.
[0076] Hydrophobic or hydrophilic layers may be added to attract or
repel water or to have the platelet attracted to or repelled by
water.
[0077] The materials used to make the patterned platelets can be
organic or inorganic, They may be edible inert materials added to
foods or medicines or biodegradable materials so as not to harm the
environment.
[0078] The platelets can be made of high temperature metals so as
to survive heating without losing their shapes and can survive
fires without the codes breaking down. Heat resistant platelets can
be imbedded in a high temperature metal, which in turn is imbedded
in another material to survive fires or other high temperature
environments.
[0079] The platelets can be added to carriers for inks and paints
and then used in standard ink or paint applications to print on
objects or coat objects. The platelets can be made small enough to
be used in ink jet printers, pens or other applicators with small
apertures without clogging the apertures.
[0080] A protective layer may be added to the patterned platelet to
prevent rust or preventing solvents, acids or bases from destroying
the patterned platelets. Various dyes, pigments, holograms,
interference patterns, polarizers and other materials may be added
to the patterned pigment as shown above to code the patterned
pigment for use in tagging object.
[0081] The patterned platelets can be used in inks for printing
documents where security to prevent counterfeiting in important,
such as currency, stock certificates, bonds, checks, notes or other
commercial paper. These coded inks or patterned platelets can be
used on goods such as compact discs, video tapes, software disks,
packaging material, coupons, airline tickets, lottery tickets or
any number of goods.
[0082] A further coding means is to print with inks having coded
platelets wherein different portions of the object being printed
have different coded pigments. For example the top right hand
corner may have circular and square platelets of two sizes each
platelet having one or more spatially or spectrally distinctive
markings on it. The center of the object may have printing with a
different ink having platelets with a different code such as all
pink triangles in 3 sizes. A line on the left side of the object
can have notched circles with three colors on each platelet. Thus,
a combination of the shape and area printed and the code of the
platelets in each area is another code.
[0083] The patterned platelets with colors can be used in inks or
paints. The inks or paints when applied to objects identify the
objects by the codes in the inks or paints and by the position of
those codes on the object.
[0084] Patterned platelets can be encased in plastics, mixed in
papers, or other substances, which are later to be authenticated.
To authenticate the substances samples are taken, the patterned
pigments are separated out or searched for to determine the code
and authenticate or identify the product so coded.
[0085] Patterned platelets can be made from inert materials for
consumption in foods, drugs, or drinks.
[0086] Patterned platelets can be added to substances such as
munitions or other chemicals to identify the maker, batch number or
other data by the patterned pigment code used.
[0087] Patterned platelets can be added to solids or liquids to
identify them and prevent counterfeit goods made with these tagged
materials from being sold.
[0088] Materials or substances can be made entirely of patterned
platelets.
[0089] To identify the article with coded platelets on or in it or
a substance with the coded platelets in it a sample of the
platelets must be examined. A means of looking at the platelets can
be with a visual aid such as a microscope for a human to evaluate
the platelets and determine the code used, or a machine aided
observation and detection method can be used. For example if an ink
containing the coded platelets is printed on the surface of an
object a magnifying device connected to a scanner or charge coupled
device can make bit maps or pixelized pictures of the platelets, a
pattern recognition program in a computer can then detect the sizes
shapes and spatial codes of the patterned platelets. Spectrum
analyzers and polarization detectors can identify the polarizations
and colors of the patterned platelets and determine the count of
each type of platelet to match it to a code. A picture of the bit
map or pixelized picture can be viewed by a human on a screen or by
printing the image. The information can be stored electronically or
on paper.
[0090] If the platelets are encased in a product the platelets
would have to be nondestructively removed from the substance spread
out and then examined as shown above. If for example the platelets
are in a material which can be crushed and broken up, the platelets
can be separated from the material and examined. If the platelets
are in a material which can be dissolved or melted at a temperature
that will not destroy the platelets, the platelets may be separated
by those means. In the case of the platelets being in a substance
which is a liquid the platelets may be centrifuged out or the
liquid evaporated to obtain the platelets for examination. Many
other means of collecting the platelets for examination are
possible.
[0091] As an aid to observing the platelets the platelets may be
coated with florescent materials which will aid in observing the
platelets when the platelets are exposed to ultraviolet light or
some other wavelength. The platelets may alternatively reflect
light at a frequency which is easily detected by a charge coupled
device.
[0092] One class of patterned platelets are those made from
cholesteric liquid crystals (CLC). CLC is used here as an example
and is not meant to limit the substances which patterned platelets
can be make from. CLC has been selected as an example because it is
easy to make patterned platelets of designated shapes, sizes,
colors, polarizations, and having dopants for spectral
identification using CLC materials.
[0093] The properties of cholesteric liquid crystals (CLC) are
described in detail in U.S. Pat. No. 5,364,557, U.S. Pat. No.
5,599,412, U.S. Pat. No. 5,221,982 and U.S. Pat. No.5,691,789,
which are made a part hereof and incorporated herein by reference,
and summarized below:
[0094] 1. CLC films assume a helical configuration with a helical
axis perpendicular to the film surface.
[0095] 2. CLC films reflect selectively a portion of the spectrum 1
0 = n n _
[0096] where .DELTA.n is the birefringence, .lambda..sub.
.lambda.{overscore (n)} P is the center wavelength, {overscore (n)}
is average index of refraction and P is the helical pitch.
[0097] 3. The CLC film is a circular polarizer, reflecting
left-handed light (P.sub.1) if the helix is left-handed, and
reflects right-handed light (P.sub.2) if the helix is
right-handed.
[0098] 4. Different colors are produced by varying the helical
pitch, P, by means of varying the concentration of chiral
dopants.
[0099] 5. The width of the reflected spectral band of the incident
electromagnetic radiation can be varied from about 20 nm to 2000 nm
in the visible or infrared regions of the spectrum, by creating a
pitch that varies across the thickness of the film.
[0100] 6. The CLC color effects are produced by a reflection
mechanism.
[0101] 7. Platelet pigments have been made by fragmenting CLC
films.
[0102] 8. In order to obtain the CLC phase represented by the
helical configuration, alignment means is required which results
from special treatment of the substrate and superstrate (optional)
and by other external means.
[0103] The CLC platelets according to the above references can have
representative spectral characteristics shown in FIGS. 4A-D. In
FIG. 4A, the red, green and blue reflection spectra of 3 platelets
are shown. Depending on the chiral doping and by imparting a
non-linear pitch distribution taught in U.S. Pat. No. 5,691,789, it
is possible to obtain polarizing white pigments as illustrated in
FIG. 4B, reflecting the visible portion of the incident
electromagnetic radiation (from 400 nm to 700 nm). It is also
possible to obtain invisible pigments which reflect incident
electromagnetic radiation having wavelengths longer than 650 nm, as
illustrated in FIG. 4C. Absorptive dopants can be added to the CLC
material, before or after CLC film formation, which results in a
spectral "marking" or "coding" as shown in FIG. 4D. Curve 45 shows
that in addition to the primary spectral characteristics, another
spectral mark 47 representing the absorption of a dopant. Curve 46
shows the two other spectral marks 48 and 49 representing other
absorptive dopants. Many rare earth compounds produce narrow
absorption characteristics when mixed in host materials. Other dyes
or pigments with narrow absorption bands may be used as spectral
markings. A plurality of narrow spectral markings can be
superimposed on the primary spectrum of the platelets can be used
as a novel encoding means of platelets.
[0104] It is well known in the art that CLC films, holographic film
and multi-layer interference films can exhibit polarization
characteristics, namely, they can be made to reflect on
polarization state P.sub.1 and transmit the other polarization
state P.sub.2. Platelets can be made which reflect P.sub.1 and
P.sub.2, or reflect unpolarized light in the case of notch filter
platelet, which is made of a laminate of two identical layers which
reflect P.sub.1 and P.sub.2 identically.
[0105] U.S. Pat. Nos. 5,364,557; 5,599,412; 5,363,315; and
5,242,617; 5,691,789; 5,506,704; 4,637,896; 4,388,453; 5,514,296;
and the applicant's co-pending applications Ser. Nos. 8/787,282;
8/891,877; S/N 08/739,467; 8/898,658; 8/739,467; 8/890,320 teach
about CLC materials and methods of producing CLC platelets. These
patents and patent applications are hereby made a part hereof and
incorporated herein by reference.
[0106] One method producing patterned platelets with CLC materials
uses the following steps:
[0107] 1. Preparing a CLC mixture comprising components chosen
from:
[0108] a) at least one polymerizable CLC monomer; chosen from the
polyester liquid crystal family, specifically acrylate or
methacrylate materials
[0109] b) At least one cross-linkable oligomer chosen from the
polysiloxan family
[0110] c) A cross-linked nematic liquid crystal material with a
[0111] d) Left-handed or right-handed chiral dopant
[0112] e) Non-polymerizable low molecular weight nematic liquid
crystal
[0113] f) A photo initiator
[0114] g) Appropriate solvent to vary the viscosity
[0115] h) Polymerization inhibitor
[0116] i) Absorptive dopants for spectral markings
[0117] 2. Preparation of the surfaces of substrates and optionally
superstrates to give them the ability to align the CLC films so as
to achieve a helical configuration with a helical axis
substantially perpendicular to the CLC film. Substrate materials
can be chosen from polyester, PET, PVA, Teflon.TM., polycarbonate,
and other substrates. The surface treatment could be rubbing the
surface in one direction to orient the liquid crystal or natural
orientation of the substrate surfaces which occur by appropriately
stretching said substrates in one direction. The substrates and
superstrates can also be prepared such that the surfaces facilitate
alignment as well as release of the CLC films. In this case, the
substrates and superstrates can be recycled (reused) after removal
of the CLC films. It is also possible the surfaces can be coated by
a layer of photo-alignable material that preferentially aligns the
molecules in response to a linearly polarized UV radiation.
[0118] 3. Pre-heating the CLC mixture to achieve the LC phase and
an appropriate viscosity.
[0119] 4. Removing air bubbles, especially oxygen, by placing the
mixture in a chamber that enables pumping out (by a vacuum pump)
the residual air.
[0120] 5. Coating the substrate with the CLC mixture to achieve a
uniform thickness ranging from about 1 micron to about 50 microns.
This coating process is accomplished in an atmosphere devoid of
oxygen, which is known to inhibit or slow down polymerization.
Coating is accomplished by well-known knife-coating, reverse roller
coating, die casting, extrusion, and the like. These coaters are
equipped with a heating means which keeps the substrate and mixture
at an appropriate uniform temperature.
[0121] 6. Laminating a superstrate on the coated film is an
optional step.
[0122] 7. A means of providing shearing forces and an annealing
means to ensure that the CLC mixture has nearly perfect alignment
in the CLC phase. In the CLC mixture may have components which
respond to magnetic or electric fields. In this case, auxiliary
magnetic as electric alignment means may be optionally provided. It
may also be possible to impact ultrasonic forces to substrates,
superstrates and CLC layer to provide the alignment forces
necessary to achieve the CLC phase.
[0123] 8. Patterning means to define the shape of the CLC platelets
on the laminate while simultaneously imparting spatial markings on
said platelets. This step is obtained at essentially no additional
cost because it is incorporated in the essential TV curing
(polymerization or cross-linking) step. This curing step involves
irradiating the laminate with an appropriate intensity of UV
radiation for a period ranging from several seconds to tens of
minutes. A mask is used through which the laminate is exposed with
UV radiation for curing purposes. This mask defines the CLC
platelet shapes as well as the spatial markings and codes as
described above. A series of masks may be used to build up a three
dimensional patterned platelet. Masking with additional masks can
add spatial markings by additive or subtractive processes.
[0124] 9. Removing the superstrate, if there is one employed,
exposing the first CLC film.
[0125] 10. Repeating Steps 5-9 using another CLC mixture which
reflects the second polarization state and a another mask to define
the polarization encoding pattern described above.
[0126] 11. Removing the second superstrate if Step 10 was
necessary.
[0127] 12. Removing the patterned and cured CLC film from the
substrate. This is accomplished by means of scraping the film from
the substrate facilitated by cooling to liquid CO.sub.2
temperature. Since only the cured films are rigid on the substrate
they are easily separated from the non cured CLC materials which
can be reused.
[0128] Obviously many modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that, within the scope of the appended
claims, the invention may be practiced otherwise then as
specifically described.
* * * * *