U.S. patent application number 14/362257 was filed with the patent office on 2014-10-02 for electro-optical security element.
The applicant listed for this patent is Bundesdruckerei GmbH. Invention is credited to Joerg Fischer, Arthur Mathea, Oliver Muth, Manfred Paeschke.
Application Number | 20140291495 14/362257 |
Document ID | / |
Family ID | 47748363 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140291495 |
Kind Code |
A1 |
Fischer; Joerg ; et
al. |
October 2, 2014 |
ELECTRO-OPTICAL SECURITY ELEMENT
Abstract
The invention relates to a security element for a security
and/or valuable document, comprising a matrix based on an organic
polymeric material, at least one electrically conductive pigment
dispersed in the matrix, and at least one organic luminescent
substance dispersed in the matrix, which luminescent substance is
capable, in the presence of the conductive pigment, of non-contact
excitation of light emission, and the particle size of which is
less than 200 nm, wherein the luminescent substance is not
encapsulated, and is directly surrounded by the matrix and is
embedded therein, and to uses of such a security and/or valuable
document and to security and/or valuable documents produced by such
uses.
Inventors: |
Fischer; Joerg; (Berlin,
DE) ; Paeschke; Manfred; (Wandlitz OT Basdorf,
DE) ; Muth; Oliver; (Berlin, DE) ; Mathea;
Arthur; (Berlin, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bundesdruckerei GmbH |
Berlin |
|
DE |
|
|
Family ID: |
47748363 |
Appl. No.: |
14/362257 |
Filed: |
November 30, 2012 |
PCT Filed: |
November 30, 2012 |
PCT NO: |
PCT/DE2012/001196 |
371 Date: |
June 2, 2014 |
Current U.S.
Class: |
250/216 ; 257/40;
438/46 |
Current CPC
Class: |
G06K 19/06046 20130101;
C09K 2211/1011 20130101; B42D 25/29 20141001; C09D 11/52 20130101;
B42D 2035/20 20130101; C09D 11/037 20130101; B42D 2033/32 20130101;
C09K 2211/185 20130101; B42D 2033/30 20130101; B42D 25/36 20141001;
C08G 2261/90 20130101; C09D 11/033 20130101; C09D 169/00 20130101;
C09K 11/02 20130101; C09D 11/10 20130101; H01L 51/007 20130101;
C08G 2261/3142 20130101; B42D 2035/34 20130101; C08L 65/00
20130101; C08L 69/00 20130101; B42D 2033/20 20130101; G07D 7/12
20130101; B42D 25/364 20141001; H01L 51/0085 20130101; H01L 51/52
20130101; H01L 51/56 20130101; B42D 25/373 20141001; C09D 11/50
20130101; B42D 25/378 20141001; C09D 169/00 20130101; G06K 7/14
20130101; C08L 65/00 20130101; C09K 11/06 20130101 |
Class at
Publication: |
250/216 ; 257/40;
438/46 |
International
Class: |
G06K 19/06 20060101
G06K019/06; H01L 51/56 20060101 H01L051/56; G06K 7/14 20060101
G06K007/14; H01L 51/52 20060101 H01L051/52 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2011 |
DE |
10 2011 119 821.4 |
Claims
1. A security element for a security and/or valuable document,
comprising a matrix based on an organic polymeric material, at
least one electrically conductive pigment dispersed in the matrix,
and at least one organic light-emitting semiconductor dispersed in
the matrix, which semiconductor is capable, in the presence of the
conductive pigment, of non-contact excitation of light emission,
and the particle size of which is less than 200 nm, wherein the
organic light-emitting semiconductor is not encapsulated, and is
directly surrounded by the matrix and is embedded therein.
2. The security element according to claim 1, wherein the organic
polymeric material is selected from the group consisting of PC
(polycarbonate, particular bisphenol A polycarbonate), PET
(poly-ethylene glycol terephthalate), PMMA (polymethyl
methacrylate), TPU (thermoplastic polyurethane elastomers), PE
(polyethylene), PP (polypropylene), PI (polyimide or
poly-trans-isoprene), PVC (polyvinyl chloride), polystyrene,
polyacrylates and methacrylates, vinyl acetate, ABS and copolymers
of such polymers, preferably is a polycarbonate derivative, in
particular based on bisphenol A, preferably based on a geminally
disubstituted dihydroxybiphenyl cycloalkane.
3. The security element according to claim 1, wherein the organic
light-emitting semiconductor is an OLED material, wherein the
organic light-emitting semiconductor is preferably non-particulate,
and preferably homogeneously dispersed, in particular dissolved in
the matrix.
4. The security element according to claim 1, wherein the
electrically conductive pigment is platelet-shaped, in particular
with an aspect ratio of at least 2:1, and a mean particle diameter
from 1 to 500 .mu.m, and preferably is transparent, or a nanorod or
a nanotube.
5. The security element according to claim 1, further comprising at
least one charge carrier transport material.
6. The security element according to claim 1, additionally
comprising one or a plurality of substances or materials selected
from the group consisting of color pigments, effect pigments,
optically variable pigments, UV blockers, preservatives, and
stabilizers.
7. The security element according to claim 1 in the embodiment as a
printing layer or film, wherein the security element (if
applicable, after drying) preferably contains: A) 0.1 to 5 wt-%
organic light-emitting semiconductor, B) 60 to 95 wt-% matrix, C) 2
to 15 wt-% electrically conductive pigment, D) 0 to 37.9 wt-%
additives and/or pigments different from C), the relative amounts
of the components A) to D) always totaling 100%.
8. A printable composition, in particular a printing ink, for the
production of a security element according to claim 1, comprising
an organic polymeric material, at least one electrically conductive
pigment, at least one organic light-emitting semiconductor, which
is capable, in the presence of the electrically conductive pigment,
of non-contact excitation of light emission, and at least one
aqueous and/or organic solvent, wherein the organic light-emitting
semiconductor is not encapsulated and has a particle size less than
200 nm.
9. A preparation according to claim 8, further comprising at least
one charge carrier transport material.
10. The preparation according claim 8, additionally comprising one
or a plurality of substances or materials selected from the group
consisting of color pigments, effect pigments, optically variable
pigments, UV blockers, preservatives, rheology-modifying agents,
and stabilizers.
11. A security and/or valuable document, comprising a substrate
layer, optionally one or a plurality of additional layers, and at
least one printing layer or film according to claim 8, wherein the
printing layer or film is applied over the entire surface or over
part of the surface of the substrate layer or an additional
layer.
12. A method for producing a security and/or valuable document
according to claim 11, wherein the substrate layer and/or the
additional layer is formed from a paper material or an organic
polymeric material, wherein on the substrate layer or the
additional layer, a printing layer or film according to claim 7 is
applied, and wherein, if applicable, said substrate layer and
additional layer, optionally with a cover layer, are laminated
together, before or after the application of the printing layer or
film.
13. A method of verification of a security and/or valuable document
according to claim 11, wherein the security and/or valuable
document is exposed to physical conditions, which, in presence of
the electrically conductive particles, stimulate the organic
light-emitting semiconductor to emit light, wherein the light
emission is observed or measured, and wherein the security and/or
valuable document, in accordance with the observation or
measurement, is classified as genuine or forged.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a security element, particularly
for a security and/or valuable document, comprising a matrix based
on an organic polymeric material, at least one electrically
conductive pigment dispersed in the matrix, and at least one
luminescent substance dispersed in the matrix, which luminescent
substance is capable, in the presence of the conductive pigment, of
non-contact excitation of light emission, and a printable
composition for the preparation of such a security element, a
security and/or valuable document having such a security element,
as well as methods for the preparation and verification of such a
security and/or valuable document.
BACKGROUND OF THE INVENTION AND PRIOR ART
[0002] Safety and/or security documents, identity cards, passports,
ID cards, access control cards, visas, control characters, tickets,
driver's licenses, motor vehicle documents, bank notes, checks,
postage stamps, credit cards, any smart cards and adhesive labels
(e.g. for product protection) often comprise at least one substrate
and a partially or completely transparent cover layer. Substrate
and cover layer may in turn consist of a plurality of layers. To
make forgery of such documents more difficult, they are equipped
with security elements. For example, bank notes and postage stamps
may consist of one substrate or substrate layer only, to which
security elements can then be applied, for example in the form of a
printing ink. Some security elements include substances being
luminescent under certain physical conditions, and a verification
can be carried out by visual inspection or automatic detection of
the luminescence under these conditions.
[0003] Security elements of the type mentioned are known in the
art, for example from the documents WO 2005/115766 A1 or WO
2010/006583. Particulate luminescent substances are used, which may
be encapsulated, i.e. have a core/shell structure. These core/shell
structures are embedded in a polymeric matrix. In general, the
substances having the electroluminescent properties are always
present in a particulate form, with particle sizes above 200
nm.
[0004] A disadvantage of the security elements known so far is the
relatively low luminescence obtained under given excitation
conditions and the high cost of production of core/shell
structures.
[0005] From the document EP 0688839 A2, polycarbonates based on a
geminally disubstituted dihydroxydiphenyl cycloalkane are per se
known. In this prior art, such polycarbonates are used as binders
for screen-printing inks. This document also describes methods for
making such polycarbonates.
TECHNICAL OBJECT OF THE INVENTION
[0006] The invention is therefore based on the technical object of
specifying a security element, which can be produced at relatively
low cost and satisfies all requirements in view of the observable
and/or measurable luminescence under excitation conditions and may
also have other advantages, in particular have an increased
diversity in the selection of radiation-emitting substances (UV,
VIS, IR) and/or an increased security against counterfeiting.
BRIEF DESCRIPTION OF THE DRAWING
[0007] FIG. 1 shows an illustrative spectrum arising from one
embodiment of the invention.
PRINCIPLES OF THE INVENTION AND PREFERRED EMBODIMENTS
[0008] To achieve this technical object, the invention teaches a
preferably machine-readable or machine-detectable security element
for a security and/or valuable document comprising a
(non-conductive) matrix based on an organic polymeric material, at
least one electrically conductive pigment dispersed in the matrix,
and at least one luminescent substance dispersed in the matrix,
which luminescent substance is capable, in the presence of the
conductive pigment, of non-contact excitation of light emission,
and wherein the luminescent substance is preferably not
encapsulated and is directly surrounded by the matrix and is
embedded therein.
[0009] The term "in the presence" means that the luminescent
substance can in any case be stimulated for non-contact emission
when the conductive pigment, in addition to the luminescent
substance, is also present in a sufficient quantity in the
matrix.
[0010] In principle, the organic polymeric material may be an
arbitrary polymeric material used in the field of security and/or
valuable documents. Examples are: transparent, opaque, or
non-transparent polymeric materials, such as PC (polycarbonate,
especially bisphenol A polycarbonate), PET (polyethylene glycol
terephthalate), PMMA (polymethyl methacrylate), TPU (thermoplastic
polyurethane elastomers), PE (polyethylene), PP (polypropylene), PI
(polyimide, or poly-trans-isoprene), PVC (polyvinyl chloride),
polystyrene, polyacrylates and methacrylates, vinyl esters, ABS and
copolymers of such polymers. Preferred is a polycarbonate
derivative, in particular based on bisphenol A, preferably based on
a geminally disubstituted dihydroxy diphenyl cycloalkane.
[0011] It is preferred that the polymer, for example the
polycarbonate derivative has an average molecular weight (weight
average) of at least 10,000, preferably 20,000 to 300,000.
[0012] In detail, the polycarbonate derivative may contain
functional carbonate structural units of formula (I),
##STR00001##
[0013] wherein R.sup.1 and R.sup.2 are independently from each
other hydrogen, halogen, preferably chlorine or bromine,
C.sub.1-C.sub.8 alkyl, C.sub.5-C.sub.6 cycloalkyl, C.sub.6-C.sub.10
aryl, preferably phenyl, and C.sub.7-C.sub.12 aralkyl, preferably
phenyl-C.sub.1-C.sub.4 alkyl, in particular benzyl; m is an integer
from 4 to 7, preferably 4 or 5; R.sup.3 and R.sup.4 can be
individually selected for each X, and independently represent
hydrogen or C.sub.1-C.sub.6 alkyl; X is carbon and n an integer
greater than 20, with the proviso that at least at one atom X,
R.sup.3 and R.sup.4 are both alkyl.
[0014] Further, it is preferred that at 1 to 2 atoms X, in
particular at one atom X only, R.sup.3 and R.sup.4 both are alkyl.
R.sup.3 and R.sup.4 may in particular be methyl. The X atoms in the
alpha position to the diphenyl-substituted C atom (C1) cannot be
dialkyl-substituted. The X atoms in the beta position to C1 can be
disubstituted with alkyl. Preferably is m=4 or 5. The polycarbonate
derivative may for instance be formed based on monomers, such as
4,4'-(3,3,5-trimethyl cyclohexane-1,1-diyl)diphenol,
4,4'-(3,3-dimethyl cyclohexane-1,1-diyl)diphenol, or
4,4'-(2,4,4-trimethyl cyclopentane-1,1-diyl)diphenol.
[0015] A polycarbonate derivative according to the invention may
for instance be made from diphenols of formula (Ia) according to
the document DE 38 32 396.6, the scope of disclosure of which with
its complete contents is hereby included in the scope of disclosure
of this description.
[0016] A diphenol of formula (Ia) under formation of
homopolycarbonates as well as several diphenols of formula (Ia)
under formation of copolycarbonates can be used (the meaning of
radicals, groups and parameters same as in formula I).
##STR00002##
[0017] Furthermore, the diphenols of formula (Ia) can also be used
in a mixture with other diphenols, for instance with those of
formula (Ib)
HO--Z--OH (Ib),
for making high-molecular, thermoplastic, aromatic polycarbonate
derivatives.
[0018] Suitable other diphenols of formula (Ib) are those, wherein
Z is an aromatic radical with 6 to 30 C atoms, which may contain
one or several aromatic nuclei, be substituted and contain
aliphatic radicals or other cycloaliphatic radicals than those of
formula (Ia) or heteroatoms as bridge members.
[0019] Examples for the diphenols of formula (Ib) are:
hydroquinone, resorcin, dihydroxydiphenyls,
bi-(hydroxyphenyl)alkanes, bis-(hydroxyphenyl)cycloalkanes,
bis-(hydroxyphenyl) sulfides, bis-(hydroxyphenyl) ethers,
bis-(hydroxyphenyl) ketones, bis-(hydroxyphenyl) sulfones,
bis-(hydroxyphenyl) sulfoxides,
alpha,alpha'-bis-(hydroxyphenyl)diisopropylbenzenes and their
nuclear-alkylated and nuclear-halogenated compounds.
[0020] These and other suitable diphenols are e.g. described in the
documents U.S. Pat. Nos. 3,028,365, 2,999,835, 3,148,172,
3,275,601, 2,991,273, 3,271,367, 3,062,781, 2,970,131, and
2,999,846, in the documents DE-A 1 570 703, 2 063 050, 2 063 052, 2
211 956, the FR-A 1 561 518 and in the monograph "H. Schnell,
Chemistry and Physics of Polycarbonates, Interscience Publishers,
New York 1964", which with its complete contents is hereby included
in the scope of disclosure of the present application.
[0021] Preferred other diphenols are for instance:
4,4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl) propane,
2,4-bis-(4-hydroxyphenyl) 2-methylbutane,
1,1-bis-(4-hydroxyphenyl)cyclohexane,
alpha,alpha-bis-(4-hydroxyphenyl) p-diisopropylbenzene,
2,2-bis-(3-methyl-4-hydroxyphenyl) propane,
2,2-bis-(3-chloro-4-hydroxyphenyl) propane,
bis-(3,5-dimethyl-4-hydroxyphenyl) methane,
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl) propane,
bis-(3,5-dimethyl-4-hydroxyphenyl) sulfone,
2,4-bis-(3,5-dimethyl-4-hydroxyphenyl) 2-methylbutane,
1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)cyclohexane,
alpha,alpha-bis-(3,5-dimethyl-4-hydroxyphenyl)
p-diisopropylbenzene, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)
propane, and 2,2-bis-(3,5-dibromo-4-hydroxyphenyl) propane.
[0022] Particularly preferred diphenols of formula (Ib) are for
instance: 2,2-bis-(4-hydroxyphenyl) propane,
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl) propane,
2,2-bis-(3,5-dichloro-4-hydroxyphenyl) propane,
2,2-bis-(3,5-dibromo-4-hydroxyphenyl) propane, and
1,1-bis-(4-hydroxyphenyl)cyclohexane. In particular,
2,2-bis-(4-hydroxyphenyl) propane is preferred. The other diphenols
may be used individually as well as in a mixture.
[0023] The molar ratio of diphenols of formula (Ia) to, if
applicable, the optionally also used other diphenols of formula
(Ib) should be between 100 mol-% (Ia) to 0 mol-% (Ib) and 2 mol-%
(Ia) to 98 mol-% (Ib), preferably between 100 mol-% (Ia) to 0 mol-%
(Ib) and 10 mol-% (Ia) to 90 mol-% (Ib), and in particular between
100 mol-% (Ia) to 0 mol-% (Ib) and 30 mol-% (Ia) to 70 mol-% (Ib),
especially between 100 mol-% (Ia) to 0 mol-% (Ib) and 50 mol-% (Ia)
to 50 mol-% (Ib).
[0024] The high-molecular polycarbonates from the diphenols of
formula (Ia), if applicable, in combination with other diphenols,
may be made according to the known polycarbonate production
methods. The different diphenols may be linked in a statistical
manner as well as also block-wise.
[0025] The polycarbonate derivatives used according to the
invention may be branched in a per se known manner. If branching is
desired, this can be achieved in a per se known manner by
condensation of small amounts, preferably amounts between 0.05 and
2.0 mol-% (referred to the used diphenols), of three or more than
three-functional compounds, in particular such with three or more
than three phenolic hydroxyl groups. Some branching agents with
three or more than three phenolic hydroxyl groups are:
phloroglucin,
4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene-2,4,6-dimethyl-2,4,6-tri-
-(4-hydroxyphenyl)-heptane, 1,3,5-tri-(4-hydroxyphenyl)-benzene,
1,1,1-tri-(4-hydroxyphenyl)-ethane,
tri-(4-hydroxyphenyl)-phenylmethane,
2,2-bis-[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propane,
2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol,
2,6-is-(2-hydroxy-5-methylbenzyl)-4-methylphenol,
2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane,
hexa-[4-(4-hydroxyphenyl-isopropyl)-phenyl]-orthoterephthalic acid
ester, tetra-(4-hydroxyphenyl)-methane,
tetra-[4-(4-hydroxyphenyl-isopropyl)phenoxy]-methane, and
1,4-bis-[4',4''-dihydroxytriphenyl)-methyl]-benzene. Some of the
other three-functional compounds are 2,4-dihydroxy benzoic acid,
trimesic acid, cyanuric chloride, and
3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindol.
[0026] As chain stoppers for the per se known control of the
molecular weight of the polycarbonate derivatives are used
monofunctional compounds in usual concentrations. Suitable
compounds are e.g. phenol, tert-butylphenols or other
alkyl-substituted phenols. For controlling the molecular weight, in
particular small amounts of phenols of formula (Ic) are
suitable
##STR00003##
[0027] wherein R is a branched C8 and/or C9-alkyl radical.
[0028] Preferably the share of the CH.sub.3 protons in the alkyl
radical R is between 47 and 89% and the share of the CH and
CH.sub.2 protons is between 53 and 11%; also preferably R is in an
o and/or p position to the OH group, and particularly preferably
the upper limit of the ortho share is 20%. The chain stoppers are
used in general in amounts from 0.5 to 10, preferably 1.5 to 8
mol-%, referred to the used diphenols.
[0029] The polycarbonate derivatives may preferably be made
according to the phase boundary method (cf. H. Schnell, "Chemistry
and Physics of Polycarbonates", Polymer Reviews, Vol. IX, page
33ff., Interscience Publ. 1964) in a per se known manner.
[0030] Herein, the diphenols of formula (Ia) are dissolved in an
aqueous alkaline phase. For making copolycarbonates with other
diphenols, mixtures of diphenols of formula (Ia) and the other
diphenols, for instance those of formula (Ib), are used. For
controlling the molecular weight, chain stoppers e.g. of formula
(Ic) may be added. Then a reaction is performed in presence of an
inert, preferably polycarbonate-dissolving, organic phase with
phosgene according to the method of the phase boundary
condensation. The reaction temperature is between 0.degree. C. and
40.degree. C.
[0031] The optionally also used branching agents (preferably 0.05
to 2.0 mol-%) may either be presented with the diphenols in the
aqueous alkaline phase or may be added dissolved in the organic
solvent before the phosgenation. Beside the diphenols of formula
(Ia) and, if applicable, other diphenols (Ib), their mono and/or
bis-chlorocarbonic acid esters can also be used, the latter being
added dissolved in organic solvents. The amount of chain stoppers
and of branching agents then depends on the molar amount of
diphenolate radicals corresponding to formula (Ia) and, if
applicable, formula (Ib); when chlorocarbonic acid esters are also
used, the amount of phosgene can correspondingly be reduced in a
known manner.
[0032] Suitable organic solvents for the chain stoppers and, if
applicable, for the branching agents and the chlorocarbonic acid
esters are for instance methylene chloride, chlorobenzene and in
particular mixtures of methylene chloride and chlorobenzene. If
applicable, the used chain stoppers and branching agents can be
dissolved in the same solvent.
[0033] As an organic phase for the phase boundary polycondensation
serves for instance methylene chloride, chlorobenzene and mixtures
of methylene chloride and chlorobenzene.
[0034] As an aqueous alkaline phase serves for instance a NaOH
solution. Making the polycarbonate derivatives according to the
phase boundary method can by catalyzed in a usual manner by
catalysts such as tertiary amines, in particular tertiary aliphatic
amines such as tributylamine or triethylamine; the catalysts can be
used in amounts from 0.05 to 10 mol-%, referred to the moles of
used diphenols. The catalysts can be added before the phosgenation
or during or also after the phosgenation.
[0035] The polycarbonate derivatives can be made according to the
prior art method in a homogeneous phase, the so-called "pyridine
method" and according to the prior art method for the melt
transesterification by using for instance diphenyl carbonate
instead of phosgene.
[0036] The polycarbonate derivatives may be linear or branched,
they are homopolycarbonates or copolycarbonates based on the
diphenols of formula (Ia).
[0037] By the arbitrary composition with other diphenols, in
particular with those of formula (Ib), the polycarbonate properties
can be varied in a favorable manner. In such copolycarbonates, the
diphenols of formula (Ia) are contained in polycarbonate
derivatives in amounts from 100 mol-% to 2 mol-%, preferably in
amounts from 100 mol-% to 10 mol-% and in particular in amounts
from 100 mol-% to 30 mol-%, especially in amounts from 100 mol-% to
50 mol-% referred to the total amount of 100 mol-% of diphenol
units.
[0038] A particularly advantageous embodiment of the invention is
characterized by that the polycarbonate derivative comprises a
copolymer in particular consisting of monomer units M1 based on
bisphenol A, and monomer units M2 based on the geminally
disubstituted dihydroxydiphenyl cycloalkane, preferably of the
4,4'-(3,3,5-trimethyl cyclohexane-1,1-diyl)diphenol, wherein the
molar ratio M2/M1 is preferably greater than 0.5, in particular
greater than 0.8, for instance greater than 1.0. For such
copolymers it has namely been found that surprisingly the glass
temperature Tg is below 150.degree. C. after a first heating cycle
and may be increased in a second heating cycle, which substantially
improves the stability of the obtained structure.
[0039] Very particularly preferred is a liquid preparation
comprising: A) 1 to 30 wt-% of a polycarbonate derivative used
according to the invention, and B) 70 to 99 wt-% of an organic
solvent or of a mixture of organic solvents.
[0040] The used organic solvents are preferably halogen-free
solvents. These may in particular be aliphatic, cycloaliphatic,
aromatic hydrocarbons, such as mesitylene, 1,2,4-trimethylbenzene,
cumene and solvent naphtha, toluene, xylene; esters, such as
methylacetate, ethylacetate, butylacetate, methoxypropylacetate,
ethyl-3-ethoxypropionate. Preferred are mesitylene,
1,2,4-trimethylbenzene, cumene and solvent naphtha, toluene,
xylene, acetic acid methyl ester, acetic acid ethyl ester,
methoxypropylacetate, ethyl-3-ethoxypropionate. Particularly
preferred are: mesitylene (1,3,5-trimethylbenzene),
1,2,4-trimethylbenzene, cumene (2-phenylpropane), solvent naphtha
and ethyl-3-ethoxypropionate.
[0041] A suitable mixture of solvents comprises for instance, L1) 0
to 10 wt-%, preferably 1 to 5 wt-%, in particular 2 to 3 wt-%
mesitylene, L2) 10 to 50 wt-%, preferably 25 to 50 wt-%, in
particular 30 to 40 wt-% 1-methoxy-2-propanolacetate, L3) 0 to 20
wt-%, preferably 1 to 20 wt-%, in particular 7 to 15 wt-%
1,2,4-trimethylbenzene, L4) 10 to 50 wt-%, preferably 25 to 50
wt-%, in particular 30 to 40 wt-% ethyl-3-ethoxypropionate, L5) 0
to 10 wt-%, preferably 0.01 to 2 wt-%, in particular 0.05 to 0.5
wt-% cumene, and L6) 0 to 80 wt-%, preferably 1 to 40 wt-%, in
particular 15 to 25 wt-% solvent naphtha, the relative amounts of
the components L1) to L6) always totaling 100 wt-%. Instead of L2
and/or L4, or in addition thereto, the solvent mixture may also
contain L7) with 10 to 50 wt-%, preferably 25 to 50 wt-%, in
particular 30 to 60 wt-% butyl glycol acetate, the relative amounts
of the components L1) to L7) always totaling 100 wt-%.
[0042] The term matrix means, for the purpose of the invention,
that the polymeric material forming the matrix forms the main
structural component, in which the other components are embedded
and dispersed, preferably homogeneously dispersed. A homogeneous
distribution is defined by that the amounts of the other
components, be it on a molecular basis or as particles, are equal
in each volume element, at least, referred to volume elements of
the matrix of 1000 .mu.m.sup.3, differ from each other by less than
10%.
[0043] The luminescent substance may preferably be an organic
substance, in particular an organic light-emitting semiconductor,
for example an OLED material. This organic substance is
non-particulate, and preferably is homogeneously dispersed in the
matrix, in particular dissolved. Thereto belong so-called small
molecules (typically <3000 da), including triplet emitters, and
luminescent polymers, for example having a HOMO-LUMO gap in the
range from 1.5 to 3.5 eV.
[0044] Examples of small molecules include N,N-diphenylaniline and
derivatives thereof, 9H-fluorenes and derivatives thereof,
anthracene and derivatives thereof, 4,4'-bis[(9-ethyl-3-carbazoyl)
vinylenyl)]anthracene,
9,10-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl,
4,4'-bis-(diphenylvinylenyl) biphenyl,
1,4-bis(9-ethyl-3-carbazovinylene)-2-methoxy-5-(2-thylhexyloxy)benzene,
4,4'-bis(diphenylvinylenyl) anthracene,
1,4-bis(9-ethyl-3-carbazovinylene)-9,9-dihexyl fluorene,
9,9,9',9',9'',9''-hexakis(hexyl)-2,7',2',7''-trifluorene, analogous
penta- and heptafluorenes,
9,9,9',9',9'',9''-hexakis(octyl)-2,7',2',7''-trifluorene, analogous
penta- and heptafluorenes,
3,7-bis-(9,9-di-n-hexylfluorene-2-yl)-dibenzothiophene-SS-dioxide,
2,7-bis-[(7-(9,9-di-n-hexylfluorene-2-yl)-dibenzothiophene-SS-dioxide-3-y-
l]-9,9-di-n-hexylfluorene, tetra-(2-methyl-8-hydroxyquinolinato)
boronic, tetra-(8-hydroxyquinolinato) boronic,
bis-(8-hydroxyquinolinato) zinc,
bis-(2-methyl-8-hydroxyquinolinato) zinc,
tris-(benzoylacetonato)mono(phenanathroline) europium (III),
tris-(benzoylmethane)mono(phenanathroline) europium (III),
tris-(benzoylmethane)mono(5-aminophenanathroline) europium (III),
tris-(dinaphtoylmethane)mono(phenanathroline) europium (III)
tris-(dibiphenoylmethane)mono(phenanathroline) europium (III),
tris-[di(4-(2-(2-ethoxyethoxy) ethoxy)
benzoylmethane)]mono(phenanathroline) europium (III),
tris-(dibenzoylmethane)mono(4,7-diphenylphenanathroline) europium
(III), bis-(2-methyl-quinolinolato) (phenolato)aluminum (III) (Y.
QIU et al., Jpn. J. Appl. Phys. 39:1151-1153 (2000)),
tris-(8-hydroxyquinolinato)aluminum (III) (J. Kalinowski et al.,
Chemical Physics Letters 380 (5-6): 710-715 (2003)),
tris-(8-hydroxyquinolinato) gallium (III), platinum (III)
[2-(4,6-difluorophenyl) pyridinato-N,C2) (acetyl-acetonate),
iridium (III) bis-(2-(4,6-difluorophenyl) pyridinato-N,C2), iridium
(III) bis-(2-(2'-benzothienyl) pyridinato-NC3') (acetyl-acetonate),
tris-(1-phenylisoquinoline) iridium (III),
bis-(1-phenylisoquinioline) (acteylacetonate (iridium (III),
iridium (III) bis-(dibenzo[f,h]quinoxaline) (acetylacetone),
iridium (III) bis-(2-methyldibenzo[f,h]quinoxaline)
(acetylacetonate), bis-(2-(9,9-dibutylfluorenyl)-1-isoquinoline
(acetylacetonate) iridium (III),
bis-(2-(9,9-dihexylfluorenyl)-1-pyridine (acetylacetonate) iridium
(III), tris-(3-methyl-1-phenyl-4-trimethyl-acetyl-5-pyrazolines)
terbium (III), tetraphenyl porphyrin, tetraphenyl butadiene,
tris-(2-phenylpyridine) iridium (III), derivatives of
tris-(2-phenylpyridine) iridium (III) which are methylated or
halogenated, in particular fluorinated one or two times on the
phenyl ring at an arbitrary position, bis-(2-phenylpyridine)
(iridium-platinum octaethylporphyrin,
europium-(dibenzoylmethanido).sub.3-based molecules
(Eu(DBM).sub.3)X), such as Eu(DBM).sub.3-(dipyrido (3,2a-2',3'-c)
phenazine), Eu(DBM).sub.3-(1,10-phenanthroline),
Eu(DBM).sub.3-(2-(2-pyridyl)benzoxazole),
Eu(DBM).sub.3-(2-(2-pyridyl)benzothiazole),
terbium-(acetylacetone).sub.3-(1,10-phenanthroline), substances
according to the document P. Schrade, Proc. SPIE, Photonic Mater.
And Devices, V 2003, 4991, 45 (the disclosure of which is
incorporated herein to its full extent). Small molecules may also
be derivatized with functional groups, which improve the solubility
in organic solvents, such as toluene, or in the solvents mentioned
in context with the matrix.
[0045] Examples of polymers being capable of luminescing include
poly(p-phenylene vinylene), alkyl-substituted, particularly
dialkyl-, for example dimethyl-, diethyl- or dibutyl-substituted
poly(p-phenylene vinylene) derivatives (substituents in para to
each other), poly[2-methoxy-5-(3,7-di-methyloctyloxy)-p-phenylene
vinylene), poly[2-methoxy-5-(3,7-dimethyloctyloxy)-p-phenylene
vinylene) with POSS (polyoctahedral oligomeric silsesquioxane), DMP
(dimethyl phenyl), N,N-bis-(4-methyl-phenyl)-4-aniline or
2,5-diphenyl-1,2,4-oxadiazole end caps,
poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene),
poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) with POSS
or DMP end caps, poly[2,5-bis-(3,7-dimethyloctyloxy)-1,4-phenylene
vinylene], poly[2,5-bis-(3,7-dimethyloctyloxy)-1,4-phenylene
vinylene], all optionally with POSS, DMP,
N,N-bis-(4-methyl-phenyl)-4-aniline or
2,5-diphenyl-1,2,4-oxadiazole end caps, polyfluorene,
poly(9,9-dialkylfluoreneyl-2,7-diyl), in particular
poly(9,9-dioctylfluoreneyl-2,7-diyl) or
poly[9,9-di(2-ethylhexyl)-fluorene-2,7-diyl] or
poly(9,9-di{2-[2-(2-methoxy-ethoxy)-ethoxy]ethyl}-fluoreneyl-2,7-diyl),
all optionally with POSS, DMP, N,N-bis-(4-methyl-phenyl)-4-aniline
or 2,5-diphenyl-1,2,4-oxadiazole end caps, poly-N-vinylcarbazole,
poly(p-phenylene), alkyl-substituted, in particular 2,5-dialkyl-,
for example dimethyl-, diethyl- or dibutyl-substituted
poly(p-phenylene) derivatives,
poly[2-(6-cyano-6-methyl-heptyloxy)-1,4-phenylene],
poly(2,5-dioctyl-1,4-phenylene), all optionally with POSS, DMP,
N,N-bis-(4-methyl-phenyl)-4-aniline or
2,5-diphenyl-1,2,4-oxadiazole end caps, poly(spirofluorene),
spiro(fluorene-benzofluorene), spirofluorene-based polymers
according to U.S. Pat. No. 7,524,567 B2 or H. Becker et al., Proc.
SPIE 4464:49-58 (2002) (the disclosure of which is hereby
incorporated to its full extent), ladder-poly(p-phenylene) or
ladder-poly(fluorene) according to R. Fiesel et al., Angew. Chem.
108:2233 (1996) (the disclosure of which is hereby incorporated to
its full extent), polythiophenes, polythiophene derivatives, mono-
or di-substituted PFOOPV copolymers according to A. Holmes et al.,
Proc. SPIE 4464:42-48 (2002).
[0046] Suitable copolymers are, for example,
poly[9,9-dioctyl-2,7-divinylene fluoreneylene)-alt-co
(9,10-anthracene)], poly[9,9-dioctyl-2,7-divinylene
fluoreneylene)-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}],
poly[(9,9-dioctylfluoreneyl-2,7-diyl)-co-(1,4-vinylene phenylene)],
poly[(9,9-dioctylfluoreneyl-2,7-diyl)-co-1,4-benzo{2,1'-3}-thiadiazole)],
poly[(9,9-2-dihexylfluoreneyl,7-diyl)-co-(2-methoxy-5-{2-ethylhexyloxy}-1-
,4-phenylene)],
poly[(9,9-dihexylfluoreneyl-2,7-diyl)-co-(2,5-9-xylene)],
poly[(9,9-di(3,3'-N,N'-trimethylammonium)propylfluoreneyl-2,7-diyl)-alt-(-
9,9-dioctylfluoreneyl-2,7-diyl)],
poly[(9,9-dioctylfluoreneyl-2,7-diyl)-co-(N,N'-diphenyl-N,N'-di(p-butyl-o-
xyphenyl)-1,4-diaminobenzene,
poly[(9,9-dioctylfluoreneyl-2,7-diyl)-co-(1,4-benzo{2,1',3}-thiadiazole)]
(9:1), all optionally with POSS, DMP
N,N-bis-(4-methyl-phenyl)-4-aniline or
2,5-diphenyl-1,2,4-oxadiazole end caps.
[0047] Of an independent importance in the context of the invention
is an embodiment wherein the luminescent substance is a particulate
quantum dot material, and wherein the quantum dot material is
preferably homogeneously dispersed in the matrix.
[0048] Quantum dots are small (crystalline) particles the exciton
propagation of which is limited in all three spatial directions to
values in the order of or less than the exciton Bohr radius. This
ultimately leads to a width of the band gap between the valence
band and the conduction band, which is variable depending on the
geometric size of the particle. The smaller the particle, the
greater the band gap, and the correspondingly higher the energy
emitted after excitation, for example color. By reduction, for
example, the color can be shifted from the long-wavelength range to
ranges of shorter wavelengths. The size of the quantum dots is
typically in the range from 1 to 20 nm, in particular 2 to 10 nm,
and then the number of atoms of a particle is between 20 and
500,000, or between 100 and 100,000.
[0049] Quantum dots can uniformly consist of one material, but
core/shell structures may also be formed, wherein core and shell
are made of different materials, typically semiconductor materials
having different band-gap widths, the material having a higher band
gap generally forming the shell.
[0050] In the context of the invention, all materials may be used
for quantum dots that have band gaps or exciton energies in the
range from 1.5 to 3.5 eV for the above-mentioned particle sizes.
Typical materials include CdSe, ZnS, ZnSe, CdZnSe, CdS, InAr, InP,
CdSeS, generally all the semiconductor materials, which are found
in the field of luminescent diodes, particularly group III/V
semiconductors with the group III elements Al, Ga and In, and the
group V elements N, P, As and Sb. From the mentioned elements can
be formed binary, ternary and quaternary (and higher complexity)
compounds in any combination, and the molar ratio of the group III
elements to the group V elements is 1:1. For all mentioned
materials, dopings are possible, if applicable, with atoms, which
belong to none of the mentioned groups of elements. Other materials
include phosphorus nanoparticles, which are doped with a rare earth
element. Various Cd-free quantum dots are for example available
from the company Nanoco Technologies Ltd., Manchester, UK, or from
Aldrich Materials Science.
[0051] For the purpose of the present invention, mixtures of at
least two, but also three, four or more substances being capable of
light emission can be used, especially substances emitting with
different colors, then mixed colors being formed, which makes the
analysis and consequently counterfeiting even more difficult. If,
for example, blue, green, and red luminescent materials are used,
practically every color of the spectrum can be obtained by varying
the proportions of the different substances.
[0052] For the purpose of the invention, a pigment containing an
electrically conductive material or a mixture of such pigments is
provided in the matrix. Electrically conductive pigments comprise
at least one electrically conductive layer or electrically
conductive particles, or consist thereof. It is not necessary,
though preferable, that the pigment is homogeneously dispersed in
the matrix. These pigments may be both so-called leafing pigments
(when curing the matrix, they will be oriented toward the surface)
and non-leafing pigments. In principle, the pigment may be
transparent or non-transparent.
[0053] The addition of electrically conductive pigments is
particularly advantageous when using electroluminophores as a
luminescent substance, as therewith a reliable and non-contact
excitation of the luminescence with electric fields can be secured.
In addition, platelet-shaped conductive pigments act as field
amplifiers due to the sharp edges or points present in this pigment
form.
[0054] The electrically conductive layer and an electrically
conductive particle may, for example, comprise or consist of one or
a plurality of metal oxides made conductive by doping, for example,
tin oxide, zinc oxide, indium oxide, and/or titanium oxide. For
doping, Ga, Al, In, Th, Ge, Sn, P, Ar, Sb, Se, Te, W, and/or F can
be used. Further, materials can be used, which are based on a
carrier layer, for example based on titanium dioxide, synthetic or
natural mica, other phyllosilicates, glass, silicon dioxide, and/or
Al.sub.2O.sub.3, and carry thereon the electrically conductive
layer, preferably are enwrapped by this layer. In addition to the
carrier layer and the electrically conductive layer, other layers
may be present, for example containing metal oxides, metal oxide
hydrates, metal suboxides, metal fluorides, metal nitrides, metal
oxynitrides, or mixtures of such substances. Preferably, the
carrier layer and/or the other layers, if provided, and/or the
electrically conductive layer are optically transparent or
substantially transparent, i.e., they transmit at least 10%,
preferably at least 70% of the incident light. The transparent or
semi-transparent layers may be colorless or colored. The color
properties of the electrically conductive pigments can also be
modified by the additional layers, particularly if they are located
below the conductive layer or between the carrier layer and the
conductive layer. By application of other layers on the
electrically conductive layer, the conductivity of the electrically
conductive layer can be adjusted in accordance with given
specifications.
[0055] The electrically conductive pigment is preferably mica
coated with at least one electrically conductive metal oxide layer,
especially mica coated with antimony-doped tin oxide. In addition,
upon or below the electrically conductive layer, one or a plurality
of metal oxide layers may be provided, such as a titanium oxide
layer.
[0056] The diameter of an electrically conductive pigment is
preferably in the range from 0.1 .mu.m to 500 .mu.m, preferably
from 2 .mu.m to 100 .mu.m, more preferably from 5 .mu.m to 70
.mu.m. A narrow particle size distribution is preferred.
Preferably, platelet-shaped electrically conductive pigments are
used. The aspect ratio (diameter/thickness) for platelet-shaped
conductive pigments is typically at least 2:1, in particular at
least 10:1, better at least 100:1.
[0057] Particularly transparent with high conductivity are
electrically conductive platelet-shaped pigments, the
number-weighted mean grain area F50 (grain area: size of a main
surface) of which is at least 150 .mu.m.sup.2, in particular at
least 200 .mu.m.sup.2. It is advantageous, if the number-weighted
rate of pigments having a particle size preferably less than 80
.mu.m.sup.2 is not more than 33%, in particular less than 25%,
based on the total amount of electrically conductive pigment. Even
better is a rate with a grain area less than 40 .mu.m.sup.2 of not
more than 15%, particularly not more than 10%. This reduction of
fine portions reduces light scattering and thus an opacity of the
marking layer. The average grain area, based on the transparency,
ideally is 1,000 .mu.m.sup.2, and may be up to 4,000 .mu.m.sup.2 or
even more.
[0058] Suitable electrically conductive pigments are commercially
available for example from Germany's leading providers of
specialized pigments.
[0059] Also suitable are metallic effect pigments being established
for the technology of coating agents, for example, Al-based, such
as Al--MgF. Other base metals include copper, bronze, gold, silver,
lead, zinc, and tin. Further can be used platelets of carbon, as
they are available, for example, from pseudo-single crystals of
carbon. For the particle dimensions, the statements made above
apply in an analogous manner.
[0060] Instead of platelet-shaped conductive pigments, so-called
nanorods can also be used. As already discussed above, as
materials, in particular metals (in particular silver-colored),
alloys and semiconductors can be used, but also carbon. The lengths
are typically in the range from 1 to 200 nm, the aspect ratio
(length to diameter) being in the range from 3 to 100, usually from
3 to 20. Likewise, nanotubes can be used, the diameter of which is
typically less than 100 nm, in most cases less than 10 nm. In
particular, nanotubes with a carbon structure are suitable.
However, boron nitride, molybdenum, tungsten, or copper sulfide,
nickel or cadmium chloride, cadmium iodide, or other sulfides or
halides are also suitable. Nanotubes may have one or a plurality of
walls. The ends may be open or closed. The interior may be empty,
but also filled. The latter is recommended for tubular structures,
which themselves are not conductive or semi-conductive. Filling
will then include a conductive species, in particular metal, such
as lead.
[0061] It is further possible to use mixtures of the above
mentioned pigments, which, by the different work functions of the
various pigment types, can result in local diode structures, when
the appropriate HOMO/LUMO levels of the substance or particles
capable of emitting light are achieved.
[0062] The electrically conductive pigments are arranged in the
matrix preferably substantially in parallel to a main surface or a
surface of the (cured) matrix, respectively. As a part of the
security element, the matrix itself is typically formed as a film,
coating agent layer, printing layer, or foil. The layer thickness
is usually in the range from 5 .mu.m to 500 .mu.m, in particular
from 20 .mu.m to 500 .mu.m.
[0063] For improving the electroluminescence, a charge carrier
transport material may also be provided in the matrix. This is
particularly advisable, for example, for triplet emitters, which
will then reduce the required amount of triplet emitter substance
for a given luminescence intensity. That is typically a hole
transport material and an electron transport material. Examples of
hole transport materials include arylamines, isoindoles,
N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)benzidine,
N,N'-bis-(4-methylphenyl)-N,N'-bis-(phenyl)benzidine,
N,N'-bis-(2-naphtalenyl)-N,N'-bis-(phenyl)benzidine,
1,3,5-tris-(3-methyldiphenylamino)benzene,
N,N'-bis-(1-naphtalenyl)-N,N'-bis-(phenyl)benzidine,
N,N'-bis-(2-naphtalenyl)-N,N'-bis-(phenyl)benzidine,
4,4',4''-tris-(N,N-phenyl-3-methylphenylamino)triphenylamines,
4,4', N,N'-diphenylcarbazole,
poly[9,9-dihexylfluorenyl-2,7-diyl)-co-(N,N'-bis-{p-butylphenyl}-1,4-diam-
inophenylene)],
poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-bis-(4-butylphenyl-1,1'-bip-
henylene-4,4-diamine)],
poly(N,N'-bis-(4-butylphenyl)-N,N'-bis-(phenyl)benzidine,
N,N'-bis-(1-naphtalenyl)-N,N'-bis-(phenyl)-9,9-spirobifluorene,
N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-9,9-spirobifluorene,
N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-9,9-dimethylfluorene.
As a hole transport material, in particular,
N,N,N',N'-tetrakis(4-methylphenyl)benzidine is suitable. If triplet
emitters are used, besides electroluminescent materials and hole
transport materials, an additional matrix polymer is preferably
also employed, such as polyvinylcarbazole (PVK) or polystyrene
(PS).
[0064] Examples of electron transporting materials include
oxadiazole, imidazole, 8-hydroxyquinolinolato-lithium,
2-(4-biphenyl)-5-(4-tert.-butylphenyl)-1,3,4-oxadiazole,
4,7-diphenyl-1,10-phenanthroline,
2,2',2''-(1,3,5-benzenetriyl)tris-(1-phenyl-1-H-benzimidazole),
2,9-dimethyl-4,7-di-phenyl-a,10-phenanthroline,
bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminum. An
exemplary combination is tris-(2-(4-tolyl) pyridinato-N,C2) iridium
(III) as an electroluminescent material,
N,N'-bis-(4-methylphenyl)-N,N'-bis-(phenyl)benzidine as a hole
transport material, and
2,2',2''-(1,3,5-benzinetriyl)-tris-(1-phenyl-1-H-benzimidazole) as
an electron transport material.
[0065] The matrix may additionally comprise converting phosphors.
For this purpose, by way of example, reference is made to the
document EP 22299424 with respect to appropriate conversion
phosphors. Conversion phosphors convert at least a portion of the
primary radiation into a secondary radiation having a different
wavelength. Thereby, a displacement of the emission spectrum is
obtained. Thus, at a predetermined emission wavelength of the
primary radiator, conversion phosphors still enable a variation of
the emission wavelength, i.e., a defined predetermined modification
thereof, whereby a greater variability with regard to the
observable color or emission wavelength is achieved.
[0066] Apart from that, the matrix may additionally contain one or
a plurality of substances or materials selected from the group
consisting of color pigments, effect pigments, optically variable
pigments, UV blockers, preservatives, and stabilizers. The pigments
are in particular laser-sensitive pigments, such as, for example,
described in the document WO 2010/006583 A, which also allows a
modulation of the luminescence in the manner described therein.
[0067] With respect to additional pigments (different from the
electrically conductive pigment used), it is possible that the
matrix additionally comprises an organic or inorganic (absorbing)
color pigment and/or effect pigment, or a mixture of such pigments.
These may be, for example, at least one platelet-shaped effect
pigment and/or an organic or inorganic color pigment.
[0068] Platelet-shaped effect pigments are designated
platelet-shaped pearlescent pigments, predominantly transparent or
semi-transparent interference pigments, and metallic effect
pigments. Liquid crystal pigments, so-called LCPs, or structured
polymeric platelets, so-called holographic pigments, are also
included here. These platelet-shaped pigments are composed of one
or a plurality of layers of different materials, if
appropriate.
[0069] Pearlescent pigments consist of transparent platelets of a
high refractive index and show, in a parallel orientation, a
characteristic pearly luster by multiple reflection. Those
pearlescent pigments, which in addition also show interference
colors, are referred to as interference pigments.
[0070] Although, of course, conventional pearlescent pigments such
as TiO.sub.2 platelets, basic lead carbonate, BiOCl pigments or
fish silver pigments, are in principle suitable, preferably
interference pigments or metallic effect pigments are used as
platelet-shaped effect pigments, which have on an inorganic
platelet-shaped carrier at least one coating of a metal, metal
oxide, metal oxide hydrate or mixtures thereof, a mixed metal
oxide, metal suboxide, metal oxynitride, metal fluoride, BiOCl, or
a polymer. The metallic effect pigments preferably comprise at
least one metal layer.
[0071] The inorganic platelet-shaped carrier is preferably made of
natural or synthetic mica, kaolin or other phyllosilicates, of
glass, SiO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3,
polymeric platelets, graphite platelets, or metal platelets, such
as aluminum, titanium, bronze, silver, copper, gold, steel, or
various metal alloys. Carriers made of mica, glass, graphite,
SiO.sub.2, TiO.sub.2, and Al.sub.2O.sub.3, or mixtures thereof are
preferred.
[0072] The size of these carriers is not critical. They generally
have a thickness between 0.01 and 5 .mu.m, in particular between
0.05 and 4.5 .mu.m. The extension in length or width is typically
between 1 and 250 .mu.m, preferably between 2 and 200 .mu.m and in
particular between 2 and 100 .mu.m. They generally have an aspect
ratio (ratio of the average diameter to the average particle
thickness) from 2:1 to 25,000:1, in particular from 3:1 to
2,000:1.
[0073] Preferably, a coating applied to the carrier consists of
metals, metal oxides, mixed metal oxides, metal suboxides, and
metal fluorides, and in particular of a colorless or colored metal
oxide selected from TiO.sub.2, titanium suboxides, titanium
oxynitrides, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, SnO.sub.2,
Sb.sub.2O.sub.3, SiO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2,
B.sub.2O.sub.3, Cr.sub.2O.sub.3, ZnO, CuO, NiO, or mixtures
thereof. Coatings of metals are preferably made of aluminum,
titanium, chromium, nickel, silver, zinc, molybdenum, tantalum,
tungsten, palladium, copper, gold, platinum, or alloys comprising
these. The preferred metal fluoride is MgF.sub.2.
[0074] As platelet-shaped effect pigments are preferably used
multi-layer effect pigments. These have multiple layers on a
platelet-shaped, preferably non-metallic carrier, said layers
preferably consisting of the materials mentioned above and having
different refractive indexes in such a way that there are at least
two layers each having a different refractive index alternately on
the carrier, the refractive indices in the individual layers
differing by at least 0.1 and preferably by at least 0.3. The
layers on the carrier may be nearly transparent and colorless as
well as transparent and colored or semi-transparent.
[0075] Further, the so-called LCPs consisting of crosslinked,
aligned cholesteric liquid crystals, or also structured polymeric
platelets designated holographic pigments may be used as
platelet-shaped effect pigments.
[0076] The platelet-shaped effect pigments used are (same as the
electrically conductive pigments) preferably transparent or
semi-transparent. Semi-transparent pigments transmit at least 10%,
transparent pigments, however, at least 70% of the incident visible
light. Such platelet-shaped effect pigments are preferably used,
since in a security and/or valuable product, their transparency
contributes to a wide variety of possible background or subsurface
colors and at the same time does not affect the intensity of the
light emission generated by electroluminescence.
[0077] In certain embodiments of the present invention, it is
however also possible that a platelet-shaped effect pigment is
used, which has at least one metal layer. Insofar, some pigments,
such as described herein, can form or complement the electrically
conductive pigments.
[0078] A platelet-shaped effect pigment may be used, which creates
a different visually perceivable color and/or brightness impression
under different lighting and/or viewing angles. In the case of
different color impressions, this property is referred to as color
flop. In particular those pigments that have a color flop, create
in the security element or security and/or valuable products made
therewith color and gloss impressions that cannot be copied and
that are well visible to the naked eye without vision aids. Such
pigments are also referred to as optically variable. The optically
variable platelet-shaped effect pigments comprise, for example,
under at least two different lighting or viewing angles, at least
two and not more than four, but preferably, under two different
lighting or viewing angles, two or under three different lighting
or viewing angles, three optically clearly distinguishable discrete
colors. Preferably, there are only the discrete colors, but no
intermediate stages, that is, a clear change from one color to a
different color is detectable when tilting the security element
comprising the optically variable pigments. This property, on the
one hand, helps the viewer to recognize the security element as
such, and at the same time, makes copying of this feature
difficult, since in the commercial color copiers, color flop
effects cannot be copied and reproduced.
[0079] Of course, however, optically variable platelet-shaped
effect pigments can also be used that, when tilting over different
lighting and/or viewing angles, have a color gradient, i.e. many
different shades, such as the typical pearlescent luster. Such
diffuse color changes, too, are readily detectable by the human
eye.
[0080] In order to exert their full optical effect, it is
advantageous if the platelet-shaped effect pigments used according
to the invention are present in the marking layer or the security
and/or valuable product in an oriented form, i.e. they are
approximately parallel to the surfaces of the security product
provided with the security element. Such alignment normally is
obtained by means of the usual methods for applying the security
element, such as for example by conventional printing processes. It
is also preferred, as already mentioned, that the electrically
conductive pigments are aligned in a corresponding manner.
[0081] As platelet-shaped effect pigments, for example, the
commercially available interference pigments can be used, which are
sold, for example, by Mearl under the name Mearlin.RTM., metallic
effect pigments from Eckhard and goniochromatic (optically
variable) effect pigments such as Variochrom.RTM. from BASF,
Chromafflair.RTM. from Flex Products Inc., Helicone.RTM. from
Wacker, or holographic pigments from Spectratec, and other similar
commercially available pigments. This list, however, should only be
regarded as illustrative rather than exhaustive.
[0082] As inorganic color pigments, all common, transparent and
opaque, white, colored and black pigments, such as Prussian blue,
bismuth vanadate, goethite, magnetite, hematite, chromium oxide,
chromium hydroxide, cobalt aluminate, ultramarine, chromium-iron
mixed oxides, spinels such as cobalt blue, cadmium sulfides and
selenides, chromate pigments or carbon black are suitable, whereas
as organic pigments, in particular quinacridones, benzimidazoles,
copper phthalocyanine, azo pigments, perinones, anthanthrones,
other phthalocyanines, anthraquinones, indigo, thioindigo and their
derivatives, or carmine can be used. Generally, all organic or
inorganic color pigments are suitable, in particular those being
conventional in the printing field.
[0083] To shield against ultraviolet radiation, pigments can be
used, which absorb UV light. Examples are titanium dioxide and zinc
oxide.
[0084] In principle, a security element according to the invention
can be prepared in various ways. On the one hand, it is for example
possible to produce a mixture of the polymeric material of the
matrix and the other components described above and to extrude a
film, wherein the extrusion is carried out in a conventional manner
in accordance with the polymeric material used. The film thus
obtained can then optionally be separated into individual film
pieces and laminated or glued into or onto a security and/or
valuable document.
[0085] Alternatively, a printable composition according to the
invention, in particular a printing ink, can be produced. It will
contain the organic polymeric material of the matrix, the at least
one luminescent substance, which is capable of non-contact
excitation of light emission in the presence of the conductive
pigment, the at least one electrically conductive pigment, and
optionally at least one aqueous and/or organic solvent (preferred
are organic solvents), the luminescent substance not being
encapsulated. In addition, the composition may contain at least one
charge carrier transport material, as well as the other components
described above, such as color pigments, effect pigments, optically
variable pigments, UV blockers, preservatives, rheology-modifying
agents, and stabilizers. Suitable organic solvents are the solvents
described above in connection with the polymeric material of the
matrix and its preparation, and all conventional solvents and
solvent mixtures being conventional in the printing technology, in
particular the ink jet printing technology. However, the use of
aqueous dispersions, which contain less than 10 wt-% organic
solvents, is also possible. Then the matrix with its further
components according to the invention consists of dispersed
film-forming particles. The composition may, depending on the
intended application, be a solution, dispersion, emulsion, or
paste.
[0086] As printing techniques, all techniques being conventional in
the field of security and/or valuable documents can be used, such
as screen printing, flexo printing, offset printing, letterpress
printing, gravure printing, intaglio printing, thermosublimation,
or inkjet printing. Alternatively, of course, spreading, use of
squeegees or rollers, stamping, casting, such as film casting,
painting, dipping, rolling or grid application processes, spin
coating, calendering, etc. are also possible. As a substrate for
the application of the security element, all substrates available
in the field of security and/or valuable documents can be used,
such as plastic films based on polymers, as already mentioned above
in connection with the polymeric material of the matrix. However,
substrates made of paper, cardboard, textile materials, etc. are
also possible. Finally, any objects, such as branded products, may
serve as substrates. In the latter case, these items are then
marked by the application of the security element according to the
invention and are thus authenticatable and distinguishable from
counterfeit products.
[0087] A security element according to the invention (if
applicable, after drying) comprises, for example: A) 0.1 to 5 wt-%,
particularly 1 to 5 wt-% luminescent substance, B) 60 to 95 wt-%,
in particular 85 to 95 wt-% matrix, C) 2 to 15 wt-%, particularly 5
to 10 wt-%, electrically conductive pigment, D) 0 to 37.9 wt-%,
particularly 0.1 to 9 wt-% additives, and/or pigments different
from C), the relative amounts of the components A) to D) always
totaling 100%.
[0088] The invention further relates to a security and/or valuable
document, comprising a substrate layer, optionally one or a
plurality of additional layers, as well as at least one printing
layer or film according to the invention, the printing layer or
film being applied over the entire surface or over part of the
surface of the substrate layer or an additional layer. The printing
layer or film may be incorporated in so far in the layer structure
of a security and/or valuable document or be stacked thereon. Such
a document can be produced by that the substrate layer and/or the
additional layer is formed from an organic polymeric material
(e.g., as a film), wherein on the substrate layer or the additional
layer, a printing layer or a film according to the invention is
applied, and wherein, if applicable, the substrate layer and
additional layer, optionally with a cover layer, are laminated
together, before or after the application of the printing layer or
film. Such a security and/or valuable document is verifiable or
authenticatable by exposing the security and/or valuable document
to physical conditions, which stimulate the luminescent substance
to emit light, wherein the light emission is observed or measured,
and wherein the security and/or valuable document, in accordance
with the observation or measurement, is classified as genuine or
forged. Such conditions include, for example, that the document is
introduced in a gap electrode, which is supplied with an
alternating electric field being dimensioned for the excitation of
light emission.
[0089] All above detailed explanations in connection with the
security element can be applied accordingly to the other
above-mentioned aspects of the invention.
[0090] By means of the invention, a number of advantages and
possibilities can be achieved. A machine-readable security element
with the greatest variety of usable electroluminescences,
preferably in the UV, visible light and IR ranges is provided.
Emitter materials having different emission characteristics
(color/wavelengths) at different excitations can be used, for
example in the visible range, UV, or electrical excitation. By
appropriate mixtures of the emitter materials, practically any
emission colors/wavelengths can be obtained. Furthermore, effects
being time-resolved and accordingly detectable and thus evaluable
by measurement are achieved by that different lifetimes of excited
states and the corresponding selection of the emitter materials are
provided. Therefore, different levels of security for a security
element can be obtained, starting with the visible color
information of the emission, up to (forensic) information, such as
the shape of the emission spectrum, decay behavior, and phase
shifts of the emission. By appropriate selection of the emitter
materials, so to speak a fingerprint of the matrix can be provided,
which is characterized by a unique intensity profile of the
emission spectrum. Because of the used (organic) emitter materials,
a chemically qualitative and/or quantitative analysis of the
security element for counterfeiting purposes is made considerably
more difficult. Finally, "starry sky"-like patterns, such as
described in the documents DE 10304805 A1 and WO 2010/006583, i.e.
random patterns, can be generated. The local luminescence then also
depends, for example, on the random lateral distribution of the
electrically conductive particles, which may be statistically
uniform, while in the micro range (5 to 100 times the lateral
dimension of the electrically conductive particles) they may be
laterally dispersed in an uneven manner. These patterns can be also
used to generate random patterns, such as they are necessary for
the generation of cryptographic keys, or can serve as the basis for
material-based PUFs (physical unclonable functions). Furthermore,
these random patterns allow an electro-optical personalization and
machine-detectable information/identification as a "serial number",
such as described in the document WO 2010/006583.
[0091] In the following the invention is explained in more detail
with reference to non-limiting embodiments.
Example 1
Preparation of Usable Polycarbonate Derivatives
Example 1.1
Preparation of a First Polycarbonate Derivative
[0092] 183.3 g (0.80 mol) of bisphenol A (2,2-bis-(4-hydroxyphenyl)
propane, 61.1 g (0.20 mol) of
1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethyl cyclohexane, 336.6 g (6
moles of KOH and 2,700 g of water were dissolved in an inert
atmosphere with stirring). Then a solution of 1.88 g of phenol in
2,500 ml of methylene chloride was added. Into the well-stirred
solution, 198 g (2 mol) phosgene were introduced at pH 13 to 14 and
21 to 25.degree. C. Then 1 ml of ethyl piperidine was added and
stirred for another 45 min. The bisphenolate-free aqueous phase was
separated, and the organic phase was washed, after acidification
with phosphoric acid, with water until neutral and freed from
solvent.
[0093] The polycarbonate derivative exhibited a relative solution
viscosity of 1.255.
Example 1.2
Preparation of a Second Polycarbonate Derivative
[0094] Analogously to Example 1.1, a mixture of 127.1 g (0.56 mol)
of bisphenol A and 137.7 g (0.44 mol) of
1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane was reacted to
polycarbonate.
[0095] The polycarbonate derivative exhibited a relative solution
viscosity of 1.263.
Example 1.3
Preparation of a Third Polycarbonate Derivative
[0096] As in Example 1, a mixture of 149.0 g (0.65 mol) of
bisphenol A and 107.9 g (0.35 mol) of
1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane was reacted to
polycarbonate.
[0097] The polycarbonate derivative exhibited a relative solution
viscosity of 1.263.
Example 2.1
Preparation of a First Liquid Composition Used According to the
Invention
[0098] As a liquid composition to be applied by printing, for
example by screen printing, the following solution was prepared:
17.5 parts by weight of the polycarbonate of Example 1.3, 82.5
parts by weight of the following solvent mixture, consisting
of:
TABLE-US-00001 Mesitylene 2.4 1-methoxy-2-propanolacetate 34.95
1,2,4-trimethylbenzene 10.75 Ethyl-3-ethoxypropionate 33.35 Cumene
0.105 Solvent naphtha 18.45
[0099] There was obtained a colorless, highly viscous solution with
a solution viscosity of 800 m Pas at 20.degree. C.
[0100] To 90 wt-% of this solution, 8 wt-% of a commercially
available solution of a polyfluorene in toluene (1.5 wt-%
polyfluorene in toluene) were added as a component capable of
emitting light. Finally, 2 wt-% of an electrically conductive
pigment, for example of a mica pigment as described in the general
part, were added. The mixture was homogenized and was thus ready to
use.
[0101] Alternatively to the solution of the matrix polymer, a
corresponding amount of the commercially available solution APEC
PUD 6581-9 (Merck) can also be used.
Example 2.2
Preparation of a Second Liquid Composition Used According to the
Invention
[0102] The preparation was made analogous to Example 2.1, except
that instead of the polyfluorene solution, the same amount of the
following solution was used.
[0103] In toluene, a solution of a mixture of 5 wt-% iridium (III)
tris-(2-(4-totyl) pyridinato-N,C2) (electroluminescence material),
10 wt-% N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)benzidine (hole
transporting material, TPD), 25 wt-%
2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,2,4-oxadiazole (electron
transport material, TBPO), and 60 wt-% polystyrene was prepared.
The total amount of said four compounds is 2.5 wt-% finished
solution.
Example 3
Preparation of a Security Element According to the Invention
[0104] A polycarbonate film Makrofol.RTM. 6-2 (thickness approx.
100 .mu.m) was imprinted, for example, with the preparation of
Example 2.1 or 2.2 using digital printing, such as ink printing.
Alternatively, screen printing may be used.
[0105] After drying, the printed film contains 0.5 wt-% luminescent
substance, 90 wt-% organic polymeric material of the matrix, 8 wt-%
conductive pigments.
[0106] The imprinted polycarbonate film thus obtained can be then
laminated with other polycarbonate films, and that directly, i.e.
without the use of interposed adhesive layers. The individual film
layers practically form a continuous piece of polycarbonate, as the
materials laminated together, including the printed structures, are
all based on polycarbonate. The layers can no longer be detached
from one another, thus an extremely high protection against forgery
being achieved, since access to the printed structures is
practically impossible.
Example 4
Different Emission Wavelengths of a Security Element According to
the Invention
[0107] A security and/or valuable document prepared according to
the invention may contain within the printing layer (identical or
different) luminescent substances, which at different excitation
modes emit at different wavelengths or show a center wavelength. In
any case, an emission takes place with non-contact electrical
stimulation.
[0108] In FIG. 1, spectra of an embodiment according to the
invention are shown. The spectrum shown by the solid line is the
light component reflected in the visible range (or not absorbed)
and reproduces the color impression of the security element without
any other excitation. The short-dashed spectrum represents the
emission of the security element for non-contact electrical
excitation. The long-dashed spectrum shows the emission when
excited with UV. As can be seen, a different color, depending on
the type of excitation, is detected by the viewer (or an automatic
test device). Depending on the type of excitation, a shift or
change in the shape of the spectrally dispersed emission takes
place.
* * * * *