U.S. patent application number 10/215779 was filed with the patent office on 2003-02-20 for method for marking items for identification.
Invention is credited to Krutak, James John SR., Nelson, Gregory Wayne.
Application Number | 20030036201 10/215779 |
Document ID | / |
Family ID | 21913391 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030036201 |
Kind Code |
A1 |
Nelson, Gregory Wayne ; et
al. |
February 20, 2003 |
Method for marking items for identification
Abstract
A method for marking or tagging individual microparticles using
a near infrared fluorophore for identification is provided. The
near infrared fluorophore is included with one or more layers
comprising the microparticle. Desirably, the coating layers contain
colorants such as dyes and/or pigments which increases the total
possible combinations that may be used to identify the marked
material. There is further provided a method for marking a material
using these microparticles containing a near infrared
fluorophore.
Inventors: |
Nelson, Gregory Wayne;
(Kingsport, TN) ; Krutak, James John SR.;
(Kingsport, TN) |
Correspondence
Address: |
George R. Schultz, P.C.
Suite 600W
13601 Preston Road
Dallas
TX
75240
US
|
Family ID: |
21913391 |
Appl. No.: |
10/215779 |
Filed: |
August 9, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10215779 |
Aug 9, 2002 |
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09040864 |
Feb 24, 1998 |
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6432715 |
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Current U.S.
Class: |
436/56 ; 436/166;
436/172 |
Current CPC
Class: |
G06K 19/06009 20130101;
G09F 3/00 20130101; G06K 2019/06234 20130101; Y10T 436/13
20150115 |
Class at
Publication: |
436/56 ; 436/166;
436/172 |
International
Class: |
G01N 021/64 |
Claims
We claim:
1. A method for identifying or locating solid particulate materials
comprising incorporating near infrared fluorophores in or on said
materials.
2. A method of tagging individual units of production of a
substance with microparticles, comprising incorporating into said
substance microparticles having a plurality of distinguishable
layers wherein at least one layer includes at least one near
infrared fluorophore.
3. The method of claim 2 where at least one of said distinguishable
layers comprises a near infrared fluorophore and at least one
visual dye or colorant, wherein said near infrared fluorophore is
selected from the classes of phthalocyanines, naphthalocyanines and
squaraines corresponding to Formulae I, II and III herein.
4. The method of claim 2 wherein each of said microparticles is
about 1 to about 1000 microns at its broadest dimension in the
color sequence.
5. The method of claim 3 wherein said near infrared fluorophore is
present in a concentration less than about 1000 ppm.
6. A method according to claim 3 wherein at least one
distinguishable layer is formed from a polymeric material having
suitable dyes and/or near infrared fluorophores admixed
therein.
7. The method according to claim 6 in which the polymer is a
polyester.
8. The method according to claim 6 in which the polymer is a
polyurethane.
9. The method according to claim 6 in which the polymer is a
polyamide.
10. The method according to claim 6 in which the polymer is an
epoxy.
11. The method of claim 3 wherein each microparticle comprises a
solid nucleus concentrically coated with distinguishable layers of
different colors and at least two near infrared fluorophores, and
said layers having a thickness of from about 5 microns to about 15
microns.
12. The method of claim 11 wherein said layers are formed from
pigmented polymeric material.
13. The method of claim 11 wherein said nuclei are essentially
spherical particles between about 1 and about 1000 microns in
diameter.
14. The method of claim 3 wherein each of said microparticles has
two surfaces that are generally flat and parallel to each other
across its broadest dimension and are substantially the same
thickness.
15. The method of claim 14 wherein said distinguishable layers of
said microparticles are formed by a series of substantially uniform
layers having a thickness less than about 100 microns.
16. The method of claim 14 wherein said distinguishable layers of
said microparticles are formed by a series of substantially uniform
layers having a thickness less than about 50 microns.
17. The method of claim 14 wherein said distinguishable layers of
said microparticles are formed by a series of substantially uniform
layers having a thickness of from about 5 microns to about 25
microns.
18. The method of claim 14 wherein said microparticles have a
thickness less than about 500 microns.
19. Method of claim 14 wherein said microparticles are formed from
colored polyethylene films.
20. A uniquely encoded microparticle comprising a plurality of
distinguishable layers wherein said layers are encoded via a
sequence of visually color distinguishable dyed and/or pigmented
layers, wherein at least one layer includes at least one near
infrared fluorophore of claim 3.
21. The microparticles of claim 20 comprising at least three
colored layers and wherein each microparticle is between about 1
and about 1000 microns in its broadest dimension across the color
sequence.
22. The microparticle of claim 20 wherein each of said
microparticles has two surfaces that are generally flat and
parallel to each other across its broadest dimension and are
substantially the same thickness.
23. The microparticle of claim 22 wherein said distinguishable
layers of said microparticles are formed by a series of
substantially uniform layers having a thickness less than about 100
microns.
24. The microparticle of claim 23 wherein said microparticles have
a thickness less than about 500 microns.
25. The microparticles according to claim 20 wherein said
microparticles are essentially spherical.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an improved method for
marking individual microparticles of a substance for the purpose of
subsequent identification. A further aspect of the invention
relates to the microparticles themselves which include therein a
near infrared fluorophore.
[0002] There has long been interest in methods for identifying
various substances by incorporating materials which provide,
possibly in coded form, information about the source, date, and lot
or batch number of the material. Although there are other obvious
applications for such "taggants", the need for identification of
explosives and certain bulk chemicals which can be used to make
explosives has become increasingly urgent with the increase in the
use of explosives in terrorism. It is desirable for the
manufacturer to be able to incorporate small particles
("microtaggants") into an explosive, some of which will survive the
explosion, and which upon recovery from the debris of the explosion
will provide information about the manufacturer, as well as the
date of manufacture and the particular lot of the explosive.
Reference to the manufacturer's records would make it possible to
trace the explosive to the final seller and possibly to the
ultimate purchaser.
[0003] There are many occasions on which it is necessary or
desirable to mark items or materials so that ownership or the
original manufacturer can be established. It is also frequently
desired to include in the identification information such as the
date of manufacture and, in case the items are made in different
batches or lots, the particular lot with which the item is
associated.
[0004] A color code of some sort is, of course, an obvious method
of identification and a system of this sort has been used for many
years for indicating the resistance value of small electrical
resistors and capacitors. For resistors, colored bands
corresponding to the first and the second significant figures of
the resistance value, followed by a third band corresponding to a
decimal multiplier provide a simple code. The color of each band
further provides a multiplier for that band. Additional bands may
be used to indicate the percent tolerance, or accuracy, of the
indicated resistance value, and the percent change in resistance
value per 1000 hours of use.
[0005] U.S. Pat. Nos. 4,053,433 and 4,390,452 (Minnesota Mining
& Manufacturing Co.) contain reviews of a number of methods for
identifying units of production of bulk substances with identifying
microparticles having properties different from the properties of
particles previously determined to be present in the bulk material.
Analytical methods used to identify such particles include
microscopy (for size, shape, color, phosphorescence, or
fluorescence); determination of density, hardness, or trace
ingredients; or spectrometry to measure light absorption;
fluorimetry; or reflectance. More specific examples include tagging
with refractory microparticles containing low levels of elements
such as manganese, cobalt, zinc, etc. The identity and amount of
each of which may be varied to provide an identification code. It
is obvious that these methods are not adaptable to coding for more
than a very small amount of information.
[0006] Isotopes of the various elements may be used in the same
way. However, complicated equipment not readily available to law
enforcement personnel is required for identification.
[0007] U.S. Pat. No. 4,053,433 describes the use of microparticles
which are encoded with an orderly sequence of visually
distinguishable colored segments. Decoding of the microparticles
can be accomplished with the aid of a microscope or other
magnifying device. According to this patent, identification is
provided by incorporating the encoded microparticles into the
substance and subsequently examining the substance for encoded
microparticles. In practice, the microparticles consist of
refractory particles containing bands of various colors, which are
ordered in the polymer to provide a code which may be read under a
microscope. By using this technique, it is possible to provide up
to C*(C-1).sup.n-1 uniquely coded batches, where C is the number of
available colors and n is the number of segments in the color
sequence. According to this formula, if a library of 12 colors is
used in an eight-layered sequence, with no color adjacent to
itself, a total of 233,846,052 codes are possible if the code is
read in one direction. Half that number of codes is possible if the
colors are arranged so that the same code may be read in either
direction. The broadest dimension across the color sequence of the
particles is between 1 and 1000 microns, and preferably between 50
microns to 250 microns.
[0008] Although this method is extremely flexible and provides a
large number of codes, the desired size of the particles requires
that the coding colors be laid down with great accuracy and in
extremely thin layers. Since each layer can contain only one
visible color, the maximum number of layers for a very small
particle is four. Assuming that seven different colors are
available for use, the number of possible codes is 756.
[0009] U.S. Pat. No. 4,390,452 describes an improvement over U.S.
Pat. No. 4,053,433 in which the microparticles contain at least one
flat surface which bears identifying indicia selected from
alphanumerics and symbols which can be visually interpreted under
magnification. According to this patent, this top layer is
photosensitive, so that the identifying indicia may be applied to
the surface by exposing it to an ultraviolet light.
[0010] The prior art cited in U.S. Pat. Nos. 4,053,433 and
4,390,452 is included herein by reference.
[0011] Taggants have been used in Switzerland for the
identification of explosives since about 1980. These include
"microtaggants" such as those described in U.S. Pat. No. 4,053,433
and U.S. Pat. No. 4,390,452; and those available commercially, such
as "HF-6" (Swiss Blasting AG), which has a code consisting of
several layers of color, each of which represents a distinctive
feature of this particular product; and "Explotracer" (Societe
Suisse des Explosifs), which consists of a basic polymer marked
with fluorescent pigments and rare earth elements. The code is
based upon the melting point of the polymer and the identity of the
elements which are included in it.
[0012] It is necessary not only for the taggant particles to be
identifiable, but they must also be isolated for identification.
Especially in the case of an explosion, the very small particles
are widely scattered and must be separated and isolated from a
large amount of extraneous debris. This has been done by
incorporating finely divided iron or other magnetic particles in
the micro taggants, or by incorporating ultraviolet dyes or
pigments which render them visible when illuminated by ultraviolet
light. However, magnetic material is almost universally dispersed
in the environment, and a large amount of extraneous material is
inevitably recovered with the microtaggant.
[0013] The incorporation of ultraviolet fluorescent material as an
aid to locating the microtaggants is also subject to a great deal
of interference. Many materials which are present in the
environment also fluoresce in the UV region so that, again,
isolating the microtaggant from extraneous material is complicated.
UV fluorescence is also easily quenched or masked by other
materials which may be present in the debris from an explosion.
Another disadvantage of using a UV fluorescent compound is that it
must be place on one of the exposed surfaces of the microtaggant
since most pigments and dyes used to make a layered microtaggant
would interfere with the UV fluorescent material by absorbing the
fluorescent light. (The Physics and Chemistry of Color The Fifteen
Causes of Color, Kurt Nassau, pp. 4-19, U.S. (1983)). Finally,
materials which fluoresce in the visible region are difficult or
impossible to detect during examination of debris in daylight or
artificial light.
[0014] Accordingly, there is a need for a microparticle taggant
that can readily be identified and that overcomes the above
described disadvantages.
SUMMARY OF THE INVENTION
[0015] Briefly, the present invention provides for a method for
identifying and/or locating solid particulate materials by
incorporating a marker or taggant into the materials. In accordance
with the invention, the marker or taggant is a near infrared
fluorophore which is readily detected and identified by using an
appropriate detection device known to those skilled in the
invisible marking art.
[0016] It is another aspect of the invention to provide an encoded
microparticle having a near infrared fluorophore incorporated
therein. Desirably the microparticle has a plurality of
distinguishable juxtaposed layers and the near infrared fluorophore
is incorporated into at least one of the layers.
[0017] It is an object of the invention to provide a method for
identifying a material by including a microparticle therein. More
particularly, it is an object of the invention to provide a means
for identifying a material by incorporating a near infrared
fluorophore compound into the microparticle.
[0018] It is another object of the invention to provide a
microparticle which can be used to carry out the method of the
invention.
[0019] Advantageously, the present method and microparticles used
therein can be of any desired shape, including spherical,
cylindrical, polyhedral or any other shape that may facilitate or
assist in the identification of the material incorporating the near
infrared fluorophore.
[0020] Numerous other objects and advantages of the present
invention will become readily apparent from the following detailed
description of the preferred embodiments and the appended
claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The present invention relates to a method for marking items
or materials, particularly those which are intended to be sold or
used in commerce in solid or particulate form, with a large amount
of coded information useful for identification. The present
invention further relates to a microparticle useful in the method
of the invention.
[0022] The microparticle of the invention has incorporated therein
at least one near infrared fluorophore in a sufficient amount to
permit detection of the microparticle. Advantageously, the near
infrared fluorophore permits the microparticle to be readily
detected using means and methods known to those skilled in the art
of detecting fluorescing compounds. With regards to the
microparticles themselves, in one embodiment, the microparticle has
a spherical shape and includes a center portion or nucleus. The
sphere may further include one or more layers of colored or dyed
layers of material concentrically coated to encapsulate the
nucleus. Each layer coated on the nucleus has a thickness of from
about 5 microns to about 25 microns with from about 5 to 15 microns
being preferred. In accordance with the invention, the nucleus
and/or one or more layers of the coating material contains a near
infrared fluorophore.
[0023] The core or nucleus of the microparticle may be any
monofilament having a diameter sufficiently small to meet the
prescribed requirements, desirably from about 25 to about 250
microns and more desirably from about 25 to about 200 microns. It
is possible to build concentric layers up around the monofilament
nucleus so that the microparticle comprises a plurality of layers
encoded by a sequence of visually distinguishable dyed or pigmented
layers, where at least one layer includes a near infrared
fluorophore. In a preferred embodiment, the microparticle has at
least three (3) layers and a diameter of from about 1 micron to
about 1000 microns at its broadest dimension across the color
sequences.
[0024] Choice of materials comprising the core or nucleus of the
microparticle will depend, in part, on the material to be marked or
tagged, their ultimate use, the ability of the microparticle to
survive further processing, and the ability of forming a
sufficiently strong bond with the immediate surrounding layer.
Suitable core materials for most purposes include plastics such as
polyolefins and polyacrylates, polyesters, modified cellulose,
waxes, glass bubbles and biodegradable materials such as albumin,
gum, gelatin, and polyvinylpyrrolidone.
[0025] The colored layers encircling the core may be applied to the
core by conventional methods including fluid or spouting bed, ball
mill, dipping, or pharmaceutical pill coating processes. A
preferred method for applying a layer to a spherical microparticle
is through the use of a Wurster coater as described in U.S. Pat.
No. 3,241,520. The color resin may be dissolved or dispersed in a
fugitive solvent, or if the pigment exists in a liquid system of
low viscosity, or it may be applied without using a solvent.
[0026] Another advantage of the present invention is that the
microparticles are not limited to different geometric configuration
to facilitate their separation or recognition from the bulk
material into which they are incorporated, although such
geometrical configurations are within the scope of the invention.
Accordingly, the microparticle may be any shape including
spherical, cylindrical, polyhedral or any other shape which may
further facilitate or assist in the identification of the material
incorporating the near infrared fluorophore.
[0027] In another embodiment of the invention, the microparticles
consist of a plurality of pieces of colored plastic films fused
together to form a rectangular hexahedron having color segments in
sequence with the layers generally parallel to one face. The
thickness of each film can be from about 12 microns to about 200
microns.
[0028] In another embodiment, the microparticles are a plurality of
layers formed from sheets of a different colored organic
cross-linkable resin which is sufficiently flexible and resilient
to form a wide sheet of good integrity. The near infrared
fluorophore compound is incorporated into at least one of these
layers. After forming a predetermined number of identification
layers, desirably, they are crosslinked to form a brittle state
which is easily comminuted at room temperature into the desired
sizes. Alternatively, the sheet may be chilled until brittle. If
this is impracticable, the sheet can be fibrillated and the
resultant fibers chopped to provide desirably small
microparticles.
[0029] Such layered microparticles can be manufactured by the
process of making an organic sheet of substantially uniform
thickness, desirably having a total thickness not exceeding 500
microns, and preferably less than about 250 microns. The sheet may
be formed on a flexible carrier having a low-adhesion surface but
should have sufficient rigidity and strength so that the carrier
can be cleanly peeled away. In order to build the sheet up to a
uniform thickness, it may be desirable to sequentially apply a
number of layers and desirably each layer is of a visually
distinguishable color. Each layer may have a thickness of less than
about 100 microns, desirably less than about 50 microns and
preferably from about 5 microns to about 25 microns. The sheet is
then comminuted at random to form a batch of microparticles, each
having two flat surfaces, generally parallel to each other. Each
microparticle has substantially the same thickness. The other
surfaces of the microparticle may have irregular shapes.
[0030] The broadest dimension across the color sequence of the
microparticle(s) described herein may be from 1 micron to about
1000 microns, but upper limits of 250-300 microns are preferred in
order to provide large numbers of microparticles per unit weight.
The preferred microparticles for use in the present invention range
from 50 to 1000 microns at the broadest dimension. Advantageously,
the size of the microparticle is not of any significance since such
particles are detected through fluorescence. One skilled in the art
will appreciate that the microparticles of the invention do not
have to be visually observed under magnification for
identification.
[0031] Any material which is capable of surviving explosive
conditions (generally temperatures greater than about 300.degree.
C. for as long as a few seconds) may be used in forming the layers
of the microtaggant particle. Many known thermoset resins and
highly crosslinked resins are suitable. Some thermoplastic resins
may also be suitable. A preferred material is a
melamine/formaldehyde resin. It should also be appreciated that the
composition of various resin layers may vary.
[0032] In a preferred embodiment, the microparticle can include a
plurality of coating layers and at least two near infrared
fluorophores, and more desirably, each fluorophore having a
distinct and identifiable absorbance and fluorescence. The coating
layer may be any material suitable for having dyes and/or a near
infrared fluorophore admixed and/or copolymerized therein or coated
thereon. Non-limiting examples of such materials include resins,
cellulosic derivatives, polyesters, polyurethanes, polyamides and
epoxy.
[0033] Suitable dyes or pigments which impart visual color to the
particle layers are generally known in the art, and include, for
example, inorganic pigments such as sulfates, chromates, sulfides,
oxides, carbonates, and organic stable pigments. Suitable colors
include red, blue, orange, black, violet, brown, yellow,
fluorescent red, white, green, and fluorescent green. Such
colorants are described in U.S. Pat. No. 4,255,273, the disclosure
of which is incorporated herein by reference. Most frequently the
visual dye or pigment is incorporated into the polymer by admixing
the constituents. Generally only one color is incorporated into
each layer to avoid color contamination. The near infrared
fluorophores, which are described fully below, are used with or
without other established marking methods.
[0034] The near infrared fluorophores of the invention possess
excellent thermal stability and little light absorption in the
visible region; that is, they must not impart interfering color to
the particle layer in which they are incorporated. Also, they
should have strong absorption of near infrared light (high molar
extinction coefficients, e.g. >20,000) and have a strong
fluorescence maximum in the near infrared between the wavelengths
of about 670 to about 2500 nm. Suitable stability to sunlight and
fluorescent light and low extractability or sublimation from the
thermoplastic compositions are also preferred. To insure minimal
interference with any visual color which is also added to a
particular layer, the near infrared fluorophores preferably absorb
little if any light having wavelengths in the 400-700 nm range;
however, since the compounds are present in extremely low
concentrations, a small amount of absorption may be tolerated
without imparting significant color.
[0035] A class of preferred near infrared fluorophores useful in
the practice of the invention are selected from the classes of
phthalocyanines, naphthalocyanines and squaraines (derivatives of
squaric acid) and correspond to Formulae I, II and III: 1
[0036] wherein Pc and Nc represent the phthalocyanine and
naphthalocyanine moieties of Formulae Ia and IIa, 2
[0037] respectively, covalently bonded to hydrogen or to various
metals, halometals, organometallic groups, and oxymetals including
AlCl, AlBr, AlF, AlOH, AlOR.sub.5, AlSR.sub.5, Ge, Ge(OR.sub.6),
Ga, InCl, Mg, SiCl.sub.2, SiF.sub.2, SnCl.sub.2,
Sn(OR.sub.6).sub.2, Si(OR.sub.6).sub.2, Sn(SR.sub.6).sub.2,
Si(SR.sub.6).sub.2, or Zn, wherein R.sub.5 and R.sub.6 are selected
from hydrogen, alkyl, aryl, heteroaryl, lower alkanoyl,
trifluoroacetyl, groups of the formulae: 3
[0038] R.sub.7, R.sub.8 and R.sub.9 are independently selected from
alkyl, phenyl or phenyl substituted with lower alkyl, lower alkoxy
or halogen.
[0039] X is selected from oxygen, sulfur, selenium, tellurium or a
group of the formula N(R.sub.10), wherein R.sub.10 is hydrogen,
cycloalkyl, alkyl, acyl, alkylsulfonyl, or aryl or R.sub.10 and R
taken together form an aliphatic or aromatic ring with the nitrogen
atom to which they are attached.
[0040] Y is selected from alkyl, halogen or hydrogen.
[0041] R is selected from unsubstituted or substituted alkyl,
alkenyl, alkynyl, C.sub.3-C.sub.8 cycloalkyl, aryl, heteroaryl,
4
[0042] (X--R) moiety is alkylsulfonylamino, arylsulfonylamino, or a
group selected from the formulae --X(C.sub.2H.sub.4O).sub.zR.sup.1,
5
[0043] wherein R.sup.1 is hydrogen or R as defined above; z is an
integer of from 1-4.
[0044] Further two (X--R) moieties can be taken together to form
divalent substituents of the formula: 6
[0045] wherein each X.sub.1 is independently selected from --O--,
--S--, or --N(R.sub.10) and A is selected from ethylene; propylene;
trimethylene; and such groups substituted with C.sub.1-C.sub.4
alkyl, C.sub.1-C.sub.4 alkoxy, aryl and cycloalkyl; 1,2-phenylene
and 1,2-phenylene containing 1-3 substituents selected from
C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy or halogen.
[0046] R.sub.1 and R.sub.2 are independently selected from
hydrogen, lower alkyl, lower alkoxy, halogen, aryloxy, lower
alkylthio, arylthio, lower alkylsulfonyl; arylsulfonyl; lower
alkylsulfonylamino, arylsulfonylamino, cycloalkylsulfonylamino,
carboxy, unsubstituted and substituted carbamoyl and sulfamoyl,
lower alkoxycarbonyl, hydroxy, lower alkanoyloxy, 7
[0047] R.sub.3 and R.sub.4 are independently selected from
hydrogen, lower alkyl, alkenyl or aryl; n and m can be an integer
from 0-16, and n, and m, can be an integer from 0-24 provided that
the sums of n+m and n.sub.1+m.sub.1 are 16 and 24, respectively. It
is to be understood that when n, m, n.sub.1 and m.sub.1 is 0 the
respective moiety is absent.
[0048] In a preferred embodiment of this aspect of the present
invention m is from 4 to 12; m.sub.1 is from 0-8; provided that in
the definitions of the substituents (Y)n, (Y)n, and (X--R)m, that
these substituents are not present when n, n, and m, are zero,
respectively. Substituents (X--R) and (Y) are present in compounds
Ia on the peripheral carbon atoms, i.e., in positions 1, 2, 3, 4,
8, 9, 10, 11, 15, 16, 17, 18, 22, 23, 24, 25 and substituents
(X--R) and (Y) are present on the peripheral carbon atoms of IIa,
i.e., in positions 1, 2, 3, 4, 5, 9, 10, 11, 12, 13, 14, 18, 19,
20, 21, 22, 23, 27, 28, 29, 30, 31, 32 and 36.
[0049] In the above definitions, the term alkyl is used to
designate a straight or branched chained hydrocarbon radical
containing 1-12 carbons.
[0050] In the terms lower alkyl, lower alkoxy, lower alkylthio,
lower alkoxycarbonyl, lower alkanoyl and lower allanoyloxy the
alkyl portion of the groups contains 1-6 carbons and may contain a
straight or branched chain.
[0051] The term "cycloalkyl" is used to represent a cyclic
aliphatic hydrocarbon radical containing 3-8 carbons, preferably 5
to 7 carbons.
[0052] The alkyl and lower alkyl portions of the previously defined
groups may contain as further substituents one or more groups
selected from hydroxy, halogen, carboxy, cyano,
C.sub.1-C.sub.4-alkoxy, aryl, C.sub.1-C.sub.4-alkylthio, arylthio,
aryloxy, C.sub.1-C.sub.4-alkoxycarbo- nyl or
C.sub.1-C.sub.4-alkanoyloxy.
[0053] The term "aryl" includes carbocyclic aromatic radicals
containing 6-18 carbons, preferably phenyl and naphthyl, and such
radicals substituted with one or more substituents selected from
lower alkyl, lower alkoxy, halogen, lower alkylthio, N(lower
alkyl).sub.2, trifluromethyl, carboxy, lower alkoxycarbonyl,
hydroxy, lower alkanoylamino, lower alkylsulfonylamino,
arylsulfonylamino, cycloalkylsulfonylamino, lower alkanoyloxy,
cyano, phenyl, phenylthio and phenoxy.
[0054] The term "heteroaryl" is used to represent mono or bi-cyclic
hetero aromatic radicals containing at least one "hetero" atom
selected from oxygen, sulfur and nitrogen or a combination of these
atoms. Examples of suitable heteroaryl groups include: thiazolyl,
benzothiazolyl, pyrazolyl, pyrrolyl, thienyl, furyl, thiadiazolyl,
oxadiazolyl, benzoxazolyl, benzimidazolyl, pyridyl, pyrimidinyl and
triazolyl. These heteroaryl radicals may contain the same
substituents listed above as possible substituents for the aryl
radicals. The term triazolyl also includes structure IV and mixed
isomers thereof, 8
[0055] wherein R.sub.11 is hydrogen or selected from lower alkyl
and lower alkyl substituted with one or two groups selected from
hydroxy, halogen, carboxy, lower alkoxy, aryl, cyano, cycloalkyl,
lower alkanoyloxy or lower alkoxycarbonyl.
[0056] The terms "alkenyl and alkynyl" are used to denote aliphatic
hydrocarbon moiety having 3-8 carbons and containing at least one
carbon-carbon double bond and one carbon-carbon triple bond,
respectively.
[0057] The term halogen is used to include bromine, chlorine,
fluorine and iodine.
[0058] The term "substituted alkyl" is used to denote a straight or
branched chain hydrocarbon radical containing 1-12 carbon atoms and
containing as substituents 1 or 2 groups selected from hydroxy,
halogen, carboxy, cyano, C.sub.1-C.sub.4 alkoxy, aryl,
C.sub.1-C.sub.4 alkylthio, arylthio, aryloxy, C.sub.1-C.sub.4
alkoxycarbonyl, or C.sub.1-C.sub.4 alkanoyloxy.
[0059] The term "substituted carbamoyl" is used to denote a radical
having the formula --CONR.sub.12R.sub.13, wherein R.sub.12 and
R.sub.13 are selected from unsubstituted or substituted alkyl,
alkenyl, alkynyl, cycloalkyl, aryl, or heteroaryl.
[0060] The term "substituted sulfamoyl" is used to denote a radical
having the formula --SO.sub.2NR.sub.12R.sub.13, wherein R.sub.12
and R.sub.13 are as defined above.
[0061] The term "alkylene" refers to a divalent C.sub.1-C.sub.12
aliphatic hydrocarbon moiety, either straight or branched-chain,
and either unsubstituted or substituted with one or more groups
selected from lower alkoxy, halogen, aryl, or aryloxy.
[0062] The term "acyl" refers to a group of the formula
R.sup.0C(O)--O--, wherein R.sup.o is preferably a C.sub.1-C.sub.10
alkyl moiety. The term "alkyl sulfonyl" refers to a group of the
formula R.sup.oSO.sub.2--, wherein R.sup.o is as defined for
acyl.
[0063] Greater detail as to these near infrared fluorophore
compounds and methods for making the compounds are further
described in U.S. Pat. Nos. 5,397,819; 5,461,136; 5,525,516; and
5,553,714, the disclosures of which are incorporated herein by
reference.
[0064] As noted above, the near infrared fluorescing compounds
having reactive groups present may be copolymerized to produce
thermoset compositions containing the near infrared fluorophore
covalently bound so that they will not be leachable, sublimable,
extractable, or be exuded from the polymer composition.
[0065] The dyes, pigments and near infrared fluorophores may be
used alone in each layer, in combination with each other in a layer
or in further conjunction with colored bands as described in U.S.
Pat. No. 4,053,433.
[0066] Incorporating one or more near infrared fluorophores, each
of which has a characteristic fluorescence emission, in addition to
the colorant in each colored band greatly increases the number of
possible codes. For example, according to the formula cited above,
if a particle is prepared which contains five bands (n=5), and five
different colors (c=5) can be used in each band with no color
touching the same color on an adjoining band, so arranged that the
code can be read in either direction, ((5)(5-1).sup.4)/2=640
possible codes are possible. If, on the other hand, each colored
layer can contain a near infrared fluorophore, the number of
detectible "colors" is doubled (e.g., red and red+near infrared
fluorophore are two different colors) and the number of possible
codes, readable in either direction, is ((10)(9).sup.4)/2=32,805.
Thus, incorporation of near infrared fluorophores in the colored
layers permits information to be encoded in fewer layers, thus
simplifying the manufacture of the particles as well as making
reading the codes easier.
[0067] Normally, with suitable fluorescence efficiency, the near
infrared fluorophore is added in the amount of from less than about
1000 ppm, desirably from about 0.5 ppm to about 100 ppm, with about
1 ppm to about 10 ppm being preferred.
[0068] The method of the invention is particularly well suited for
tagging bulk materials such as chemicals, explosives and liquid
products such as non-opaque lacquers and resins. Desirably, the
microparticles are homogeneously incorporated into the substrate to
be tagged, preferably in an amount ranging from 0.01 ppm to about
1000 ppm, more preferably from about 0.1 ppm to about 100 ppm and
yet more preferably from about 1 ppm to about 10 ppm. The use of
near infrared fluorophores in colored taggant particles also
provides an improved method of detection and recovery of particles,
particularly after the tagged particles have been dispersed in the
environment, as by explosion. Prior to the present invention, it
had been necessary to retrieve the microtaggants using such methods
as visually identifying the taggant or collecting a particle having
a magnetic additive using a strong magnet. However, the present
invention has an advantage over the prior art teachings by using an
imaging system and a laser selected to deliver light at the
absorbance maximum of the near infrared fluorophore contained in
the taggant, a sweep of an area can be conducted to detect
dispersed particles, without disturbing the explosion scene. A
suitable imaging systems includes, but is not limited to, a video
capture system comprising a video monitor, video storage device and
a CCD camera equipped with appropriate filters to reject the
reflected laser light and accept fluorescence from the near
infrared fluorophore tagged particles. Thus, patterns or trails of
particles can be detected and recorded to provide a map of tagged
particles. In the case of an explosion, those skilled in the art of
investigation of explosive patterns can use this information to
pinpoint the source of the explosion as well as the type of
explosive material used in the explosion.
[0069] In the case of covertly tagged articles, patterns of near
infrared fluorophores printed or otherwise affixed to an articles
can be detected. Because there are few natural interferences to
near-infrared fluorescence, this detection method can be
accomplished in lighting conditions ranging from full sunlight to
darkness. Non-imaging devices such as disclosed in U.S. Pat. Nos.
5,461,136; 5,397,819; and 5,292,855 can also be used to rapidly
locate and map dispersed particles.
[0070] The near infrared fluorophore may be incorporated into or
onto suitable microparticles in a number of ways. For example, the
near infrared fluorophore may be incorporated into a suitable
coating and applied to the surface of the microparticle.
Alternatively at least one near infrared fluorophore may be
copolymerized with one or more of the materials useful in forming a
coating layer.
[0071] The use of near infrared fluorophores as components of coded
identification systems presents a number of advantages. In general,
any of the near infrared fluorophores cited above may be used,
provided only that they do not undergo destructive reactions with
other ingredients or reaction products of the substrate. Near
infrared fluorophores which react with formaldehyde, for example,
should not be used in conjunction with melamine resins, which
release formaldehyde during cure.
[0072] Although the examples have dealt with near infrared
fluorophores which are incorporated into brittle, cross-linked
resins, they may also be copolymerized into water-dispersible
resins which are suitable for coatings (U.S. Pat. Nos. 5,292,855;
5,336,714 and 5,423,432, incorporated herein by reference);
alternatively, certain near infrared fluorophores are available in
oil-soluble form and may be incorporated into the solvent system
used in resin preparation (U.S. Pat. No. 5,525,516) and may be
introduced into coatings, including cross-linkable coatings, in
that way. These coatings may be applied between or on top of other
microtaggant layers (which may or may not include visual colorants)
to provide more variations without significantly increasing the
size of the final taggant particle.
[0073] Suitable resins may be marked with near infrared
fluorophores by any of the conventional methods for adding
additives such as dry blending, solution blending, etc.
Alternatively, certain near infrared fluorophores are available
which contain reactive groups which may be copolymerized into, the
polymer. Near infrared fluorophores may be incorporated into
cellulose acetate by a technique known as "acid pasting". These
polymers may be used per se as marking layers, or they may be
blended with other components of a marking layer.
[0074] Although the discussion herein has been directed primarily
to the use of near infrared fluorophores as components of
microtaggants for use in marking explosives, there are many other
forms in which they may be used. For example, rods of thermoplastic
may be prepared by extruding successive near infrared
fluorophore-marked layers of the same or a different compatible,
polymeric material. These rods may be cut into pellets similar to
the form in which commercial thermoplastics are sold. Blended into
a batch of plastic, they serve for identification in the same way
that microtaggants are used for explosive identification. They
would be easy to locate and identify in a batch of polymer, even
one which contained fluorescent brighteners or ultraviolet
absorbers, by virtue of their unique near infrared
fluorescence.
[0075] It would also be possible to spin layered fibers from them
which would reveal, upon cross sectioning, the manufacturer and the
identity of the fabric from which a fiber was spun. It is common
practice to spin synthetic fibers which have non-circular cross
sections; for example, a common form has the shape of a Y. Each
limb of the Y might be marked with a different near infrared
fluorophore. Many other cross sections are possible; commercial
spinneret designs permit the manufacture of at least eight unique
cross sections for synthetic fibers, each lobe of which might be
marked with a different near infrared fluorophore.
[0076] Coded disks, rods, etc. may be made by laying down
successive layers of near infrared fluorophore-containing
thermoplastic film, heating them under pressure to fuse the mass
together, and cutting the resulting billet into disks, rods, or
other desired shape.
[0077] Beads of polymer which contain successive layers of
different near infrared fluorophores can be made by successively
coating ceramic or, for example, cross-linked polystyrene beads
with either oil soluble or water-dissipatable near infrared
fluorophores. The bead may be cross-sectioned to reveal the code in
the successive layers of tagged polymer.
[0078] It is emphasized that, in every case in which an application
for a near infrared fluorophore has been indicated, it is also
within the scope of the invention to incorporate a visible dye or
pigment along with the near infrared fluorophore to increase the
number of possible codes. Suitable polymeric colorant technology
for coloration of melt processable polymers and aqueous or oil
solvent-based coating compositions are disclosed in U.S. Pat. Nos
4,403,092 and 5,376,650, which are incorporated herein by
reference.
[0079] If desired, ferromagnetic materials such as iron powder may
also be incorporated into the microtaggants to further facilitate
their collection from the environment.
[0080] The following examples are given by way of illustration of
the invention and are not intended to be a limitation thereof.
EXAMPLES 1-10
[0081] This example illustrates the preparation of a coating such
as could be applied to the surface of a microtaggant so that the
particle could be located by exposure to near infrared light. The
near infrared fluorophore can serve alone as a device for
visualizing and locating microtaggant dispersed in the environment,
or for identification of the manufacturer or country of origin,
etc. Since near infrared fluorophores are visible through a clear
coating when they are illuminated by near infrared light of the
appropriate frequency, while they do not fluoresce when exposed to
ultraviolet light, this coating may be applied beneath the
photosensitive coating described in U.S. Pat. No. 4,390,452 to
provide additional information. As further examples will show, a
similar technique may be used to prepare individual layers or a
multi-layer microtaggant particle.
[0082] The marker composition was added to a homogeneous mixture of
2 grams each of an alkylated melamine resin (Cymel.TM. 248-8) and
an alkyd resin (Beckosol.TM. 12-102) and stirred thoroughly to give
a clear solution. Cymec.TM. 4040 catalyst (a solution of
p-toluenesulfonic acid in isopropanol), 0.1-0.4 grams was stirred
into the mixture, which was then coated on thin polyethylene
terephthalate film, or on white copy paper, using a 2 mil coating
bar. The coated samples were heat set on a heated block at
120-140.degree. C. for a few minutes to give clear, non-tacky
films. The coated samples were illuminated by near infrared light
at 780 nm and the fluorescence at 800-830 nm was measured using
detectors described in U.S. Pat. Nos. 5,292,855; 5,336,714;
5,397,819; 5,423,432; 5,461,136; and 5,525,516. The disclosures of
each are incorporated herein by reference.
[0083] The results for a variety of near infrared fluorophores
(NIRFs) at different concentrations are shown in Table I below.
1TABLE I NIRF in Coating Catalyst Detector (weight, (weight,
Response Example NIRF.sup.a mg) mg) Film Paper 1
(C.sub.6H.sub.5).sub.4NcAlCl 1.6.sup.b 0.1 Yes Yes 2
(t-Bu).sub.4NcAlOH 1.6.sup.b 0.1 Yes Yes 3 NcSi[O(PEG)OMe].sub.2
1.6.sup.b 0.1 Yes Yes 4 (2-EthexylNH).sub.4PcH.sub.2 1.6.sup.b 0.1
Yes 5 NcSi(OH).sub.2 210.sup.c 0.11 Yes Yes 6 NcSi(OH).sub.2
210.sup.c,e 0.11 Yes Yes 7 NcSi(OH).sub.2 250.sup.d 0.25 Yes 8
NcSi(OH).sub.2 400.sup.c 0.1 Yes Yes 9 NcSi(OH).sub.2 400.sup.c 0.4
Yes Yes 10 NcSi(OH).sub.2 430.sup.c 0.23 Yes Yes .sup.aNc = the
naphthalocyanine nucleus Pc = the phthalocyanine nucleus PEG =
polyethylene glycol 200 .sup.b0.1 g in tetrahydrofuran .sup.c5000
ppm as copolymer with sebacic acid and PEG .sup.d2000 ppm in
polyurethane .sup.e+0.2 g toluene
EXAMPLES 11-15
[0084] Several kilograms of a base coating resin were prepared by
combining equal parts of an alkylated melamine resin (Cymel.TM.
248-8) and an alkyd resin (Beckosol.TM. 12-102) and shaking
thoroughly to give a clear homogenous solution. Cymec.TM. 4040
catalyst (a solution of p-toluenesulfonic acid in isopropanol), 2.5
to 10% by weight, was stirred into the mixture. The mixture was
divided into portions and colored pigments were added to give red,
green fluorescent, white, and black coating compounds designated R,
F, W, and B respectively. A portion of the red and fluorescent
green coating solutions were separated and near infrared
fluorophores were added in the amounts shown in Table II below.
2TABLE II Layer Concentration Designa- Example Pigment Color NIRF
(ppm) tion 11 Red (t-Bu).sub.4NcAlOH 110 (NR) 12 Fluorescent
(t-Bu).sub.4NcAlOH 75 (NF1) Green 13 Fluorescent (t-Bu).sub.4NcAlOH
38 (NF2) Green 14 Fluorescent NcSi(OH)2.sup.f 150 (NF3) Green 15
Fluorescent NcSi(OH)2.sup.f 75 (NF4) Green .sup.f5000 ppm as
copolymer with sebacic acid and PEG
[0085] Taggant particles were prepared by spreading the coating
resins described above onto a web using coating bars and curing
with heat. Multiple layer taggants were generated by spreading one
color resin over a partially cured layer of another color resin and
building up a desired number of layers. The cured coatings were
removed from the web and passed through a Wiley mill with #16 mesh
to give taggant particles. All of these particles registered a
"Yes" on the detector device described in examples 1-10. Table III
illustrates the multi-layer particle codes using the designations
described above. These particles were also seen by illuminating the
particles with a laser at 700 nm and viewing with a black and white
video camera at the wavelengths of 800-830 nm.
3TABLE III Example Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6
Layer 7 Layer 8 11 B W NR W F Unused Unused Unused 12 B W R W NF1
Unused Unused Unused 13 B W R W NF2 Unused Unused Unused 14 B W R W
R W R NF3 15 B W R R R W R NF4 16 B W R W
[0086] Although the present invention has been described in terms
of the presently preferred embodiment, it is to be understood that
such disclosure is not to be interpreted as limiting to the
invention described herein. No doubt that after reading the
disclosure, various alterations and modifications will become
apparent to those skilled in the art to which the invention
pertains. It is intended that the appended claims be interpreted as
covering all such alterations and modifications as fall within the
spirit and scope of the invention.
* * * * *