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Claims  |
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We claim:
1. A security thread for use in security articles, said thread comprising a
substrate bearing indicia, the thread having a thermochromic coating on
one side of the thread, said thermochromic coating comprising a coating
containing a thermochromic material selected from pigments and dyestuffs,
which material is coloured when the temperature of said thermochromic
coating is below an activation temperature and is colourless when the
temperature is at or above said activation temperature, the indicia being
obscured when the material is coloured and visible when the material is
colourless.
2. A security thread as claimed in claim 1 in which the substrate has a
thermochromic coating on both sides of the thread.
3. A security thread as claimed in claim 1 in which said indicia comprise
indicia printed on the substrate beneath the thermochromic coating.
4. A security thread as claimed in claim 1 in which one side of the
substrate has a metallized coating, which is partially demetallised to
form said indicia, and the thermochromic coating is provided on one side
of the thread over the metallised coating such that at a temperature below
the activation temperature when viewed from one side the thread appears as
a continuous coloured line and when viewed from an opposite side appears
as a metallised thread with demetallised coloured indicia and at the
activation temperature or above both sides of the thread are viewed as
metallised thread having colourless demetallised indicia.
5. A security thread as claimed in claim 1 in which one side of the
substrate has a metallised coating, which is partially demetallised to
form said indicia, and the thermochromic coating is provided on the one
side of the thread over the metallised coating and on the other side of
the thread, such that when the thermochromic material is colourless the
demetallised indicia are visible.
6. A security thread as claimed in claim 1 in which the indicia are printed
on the substrate with an ink comprising a thermochromic material.
7. A security thread as claimed in claim 1 in which the thermochromic
coating is composed of a variety of thermochromic compounds which display
differing colours, which compounds are coloured or clear at different
activation temperatures, such that as the thread is warmed or subsequently
cooled it progresses through a pattern of changing colours.
8. A security thread as claimed in claim 1 further including, a fluorescent
dye or material in the substrate.
9. A security thread as claimed in claim 1 further including, on one side
of the thread beneath the thermochromic coating, a UV fluorescent or
luminescent material in the substrate.
10. A security thread as claimed in claim 1 which further includes a
machine readable feature.
11. A security paper comprising opposed surfaces for the provision of
printing to identify a document formed from the paper, and positioned at
least partially between the two surfaces of the paper as a security
feature a security thread claimed in claim 1.
12. Security paper as claimed in claim 11 in which the thread is wholly
embedded between the surfaces of the paper.
13. Security paper as claimed in claim 11 in which the thread is positioned
partially between the surfaces of the paper, portions of the thread being
positioned in windows where there is no or virtually no paper fibres on
the thread.
14. Security paper as claimed in claim 11 in which the thread has indicia
thereon, and the thread is slit to produce registered indicia with respect
to the edge of the thread, or unregistered indicia.
15. Security paper as claimed in claim 11 wherein the paper is made from
fibres selected from synthetic fibres, a mixture of synthetic and natural
fibres, and natural fibres.
16. Security paper as claimed in claim 11 wherein said paper is a laminate
of two sheets with the security thread positioned between the laminated
sheets.
17. A banknote or other security document when produced from the security
paper claimed in claim 11.
18. A security thread for use in security articles, said thread comprising
a substrate bearing indicia, the thread having a thermochromic coating on
one side of the thread, said thermochromic coating comprising a coating
containing a thermochromic material selected from pigments and dyestuffs,
which material is colourless when the temperature of the thermochromic
coating is below an activation temperature and which is coloured when the
temperature of the thermochromic coating is at or above the activation
temperature, the indicia being visible when the material is colourless and
obscured when the material is coloured.
19. A security thread as claimed in claim 18 in which the indicia are
printed on the substrate with an ink comprising a thermochromic material.
20. A security thread as claimed in claim 18 in which the thermochromic is
composed of a variety of thermochromic compounds which display differing
colours, which compounds are activated at different activation
temperatures, such that as the thread is warmed or subsequently cooled it
progresses through a pattern of changing colours.
21. A security thread as claimed in claim 18 further including a
fluorescent dye or material in the substrate.
22. A security thread as claimed in claim 18 further including, on one side
of the thread beneath the thermochromic coating, a UV fluorescent or
luminescent material in the substrate.
23. A security thread as claimed in claim 18 which further includes a
machine readable feature.
24. Security paper comprising opposed surfaces for the provision of
printing to identify a document formed from the paper, and positioned at
least partially between the two surfaces of the paper as a security
feature a security thread claimed in claim 18.
25. Security paper as claimed in claim 24 in which the thread is wholly
embedded between the surfaces of the paper.
26. Security paper as claimed in claim 24 in which the thread is positioned
partially between the surfaces of the paper, portions of the thread being
positioned in windows where there is no or virtually no paper fibres on
the thread.
27. Security paper as claimed in claim 24 in which the thread is slit to
produce registered indicia with respect to the edge of the thread.
28. Security paper as claimed in claim 24 wherein the paper is made from
fibres selected from synthetic fibres, a mixture of synthetic and natural
fibres, and natural fibres.
29. Security paper as claimed in claim 24 wherein said paper is a laminate
of two sheets with the security thread positioned between the laminated
sheets.
30. A banknote or other security document when produced from the security
paper claimed in claim 24.
31. Security paper comprising opposed surfaces for the provision of
printing to identify a document formed from the paper, and positioned at
least partially between the two surfaces of the paper as a security
feature a security thread as claimed in claim 1.
32. A security thread as claimed in claim 1 in which the indicia comprise a
coloured coating on the substrate beneath the thermochromic coating.
33. A security thread as claimed in claim 18 in which the indicia comprise
a coloured coating on the substrate beneath the thermochromic coating.
34. A security thread as claimed in claim 4 in which both sides of the
substrate have a partially demetallised metallised coating.
35. A security thread as claimed in claim 5 in which both sides of the
substrate have a partially demetallised metallised coating.
36. A security thread as claimed in claim 1 further including a fluorescent
dye or material on the surface of the substrate beneath the thermochromic
coating.
37. A security thread as claimed in claim 36 further including in
fluorescent dye or material on both surfaces of the substrate beneath
thermochromic coatings on both sides of the thread.
38. A security thread as claimed in claim 1 further including a fluorescent
dye or material in a coating on the surface of the substrate beneath the
thermochromic coating.
39. A security thread as claimed in claim 38 further including a
fluorescent dye or material in a coating on both surfaces of the substrate
beneath thermochromic coatings on both sides of the thread.
40. A security thread as claimed in claim 1 further including a UV
fluorescent or luminescent material on the surface of the substrate
beneath the thermochromic coating.
41. A security thread as claimed in claim 40 further including a UV
fluorescent or luminescent material on both surfaces of the substrate
beneath the thermochromic coatings on both sides of the thread.
42. A security thread as claimed in claim 1 further including a UV
fluorescent or luminescent material in a coating on the surface of the
substrate beneath the thermochromic coating.
43. A security thread as claimed in claim 42 further including a UV
fluorescent or luminescent material in coatings on both sides of the
substrate beneath thermochromic coatings on both sides of the thread.
44. A security thread as claimed in claim 1 further including a UV
fluorescent or luminescent material above the thermochromic coating.
45. A security thread as claimed in claim 44 further including a UV
fluorescent or luminescent material on both sides of the thread above
thermochromic coatings on both sides of the thread.
46. A security thread as claimed in claim 1 further including a UV
fluorescent or luminescent material in a coating above the thermochromic
coating.
47. A security thread as claimed in claim 44 further including a UV
fluorescent or luminescent material in coatings on both sides of the
thread above thermochromic coatings on both sides of the thread.
48. Security paper as claimed in claim 11 in which the thread is slit to
produce unregistered indicia.
49. A security thread as claimed in claim 18 in which the thread has a
thermochromic coating on both sides thereof.
50. A security thread as claimed in claim 18 further including a
fluorescent dye or material on the surface of the substrate beneath the
thermochromic coating.
51. A security thread as claimed in claim 50 further including a
fluorescent dye or material on both surfaces of the substrate beneath
thermochromic coatings on both sides of the thread.
52. A security thread as claimed in claim 18 further including a
fluorescent dye or material in a coating on the surface of the substrate
beneath the thermochromic coating.
53. A security thread as claimed in claim 52 further including a
fluorescent dye or material in a coating on both surfaces of the substrate
beneath thermochromic coatings on both sides of the thread.
54. A security thread as claimed in claim 18 further including a UV
fluorescent or luminescent material on the surface of the substrate
beneath the thermochromic coating.
55. A security thread as claimed in claim 54 further including a UV
fluorescent or luminescent material on both surfaces of the substrate
beneath thermochromic coatings on both sides of the thread.
56. A security thread as claimed in claim 18 further including a UV
fluorescent or luminescent material in a coating on the surfaces of the
substrate beneath the thermochromic coating.
57. A security thread as claimed in claim 56 further including a UV
fluorescent or luminescent material in coatings on both sides of the
substrate beneath thermochromic coatings on both sides of the thread.
58. A security thread as claimed in claim 18 further including a UV
fluorescent or luminescent material above the thermochromic coating.
59. A security thread as claimed in claim 58 further including a UV
fluorescent or luminescent material on both sides of the thread above
thermochromic coatings on both sides of the thread.
60. A security thread as claimed in claim 24 further including a UV
fluorescent or luminescent material in a coating above the thermochromic
coating.
61. A security thread as claimed in claim 18 in which said indicia comprise
indicia printed on the substrate beneath the thermochromic coating.
62. A security thread for use in security articles, said thread comprising
a substrate bearing indicia, the substrate incorporating a thermochromic
material selected from pigments and dyestuffs, which material is coloured
when the temperature of the substrate is below an activation temperature
and is colourless when the temperature is at or above said activation
temperature, the indicia being obscured when the material is coloured and
visible when the material is colourless.
63. A security thread for use in security articles, said thread comprising
a substrate bearing indicia, the substrate incorporating a thermochromic
material selected from pigments and dyestuffs, which material is
colourless when the temperature of the substrate is below an activation
temperature and is coloured when the temperature is at or above said
activation temperature, the indicia being obscured when the material is
coloured and visible when the material is colourless. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is concerned with security threads for security articles such
as banknotes, cheques and the like.
2. The Prior Art
It is widely to known to use in banknotes security strips or threads which
are made from a transparent film provided with a continuous reflective
metal layer, vacuum deposited aluminium on polyester film being the
commonest example. Banknotes made from such paper have been in general
circulation in many countries for many years. When such security devices
are embedded in a security paper and the paper is subsequently printed to
provide the security document, e.g. a banknote, the thread cannot be
readily discerned in reflected light but is immediately apparent as a dark
image when the document is viewed in transmitted light. Such threads are
extremely effective against counterfeiting by printing or photocopying,
since the optically variable effect which is provided cannot be accurately
simulated, for example by printing a line on the paper.
The composition, size and positioning of security threads currently in use
vary depending on the desired security of the document. Typical security
threads are composed of a polymeric film such as polyester, which may be
metalised or coloured and may include microprinted lettering denoting a
title or message. The lettering can be produced by printing onto the
substrate or by de-metallising a metallic layer on the substrate. One
example of microprinted thread can be found in British patent
specification No. 1095286. The threads can be slit to produce either
registered lettering with respect to the edge of the thread, or
unregistered lettering designed so that the message always appears in
respect of thread slitting.
The widths of threads typically used vary from 0.5 mm to 2 mm and may have
thicknesses typically ranging from 12 microns up to 50 microns.
The positioning of the thread within the document may be strictly
controlled to agreed criteria and may be concurrent with additional
security features, such as watermarks. Security threads may be fully
embedded within security paper in such a way that paper fibres cover both
sides of the thread, making it considerably less visible in reflective
light, but clearly visible in transmitted light.
In recent times, however, in order to enhance security documents against
modern counterfeiting techniques making use of sophisticated colour
separation, printing and colour photocopy technology, it has become common
to use a security thread comprising a thin layer of aluminium on a plastic
support which is exposed on one side of the sheet at intervals along the
length of the thread, the region of exposure being referred to as a
window. British Patent Specification Nos. 1552853 and 1604463 disclose
banknotes containing such windows. Paper for use in producing such
banknotes can be made using the method disclosed in European Patent
Specification No. 0059056. The dimensions of the windows typically used
are from 3 mm to 14 mm lengthways, with bridges ranging from 4 mm to 30 mm
therebetween. Again, the positioning of the windows may be controlled to
allow registration of the window with respect of the document and other
security features such as watermarks.
This latter development has resulted in enhanced security and windowed
paper has been used for banknotes by many countries. A banknote of this
type provides added security against counterfeiters as, when viewed in
transmitted light, the strip is seen as a dark line and when viewed in
reflected light on the appropriate side, the bright shining aluminium
portions which are exposed at the windows are readily visible. However,
there is a need for even greater security by the use of more sophisticated
security devices in order to render the task of a would-be counterfeiter
more difficult as the reflected light appearance of the exposed aluminium
portions of a security device can be simulated to a degree by modern
materials and techniques, for example by the use of hot foil stamping.
Other threads in use can be coated with protective lacquers and these may
contain, for example, fluorescent inks which are only visible on
illumination with ultra violet light of a specific wavelength, e.g. 366
nm.
It is also possible to make threads that are machine readable by
incorporating into or onto the substrate, substances which can be
identified by a detector, such as magnetic material.
Other known threads can be a single layer or multiple layers bonded or
laminated together, and in some instances each layer may be coated with
metal such as aluminium, stainless steel, tin and/or metal oxide such as
tin oxide. The coating may be protected with the lacquer which may also
contain coloured or invisible fluorescent pigment, for example rare earth
chelates, such as europium acetylacetonate and the like.
SUMMARY OF THE INVENTION
The present invention is concerned with providing a security thread of
enhanced security to provide security articles such as banknotes, cheques
and the like which is even more difficult to counterfeit than the present
banknotes containing windowed thread.
The present invention provides a security thread for use in security
articles, the thread comprising a substrate having a coating on one or
both sides of the substrate, the coating containing a thermochromic
material selected from pigments and dyestuffs which material changes from
coloured to colourless when the temperature of the pigment or dyestuff is
changed to an activation temperature.
According to the invention there is provided in a second aspect a security
thread for use in security articles, the thread comprising a substrate
having a coating on one or both sides of the substrate, the coating
containing a thermochromic pigment or dyestuff which is coloured when the
temperature of the coating is below an activation temperature and which
becomes colourless when the coating is warmed to the activation
temperature or above.
Preferably the substrate is printed with indicia beneath the coating, the
colour of the indicia being such that when the thermochromic coating
becomes colourless the indicia are revealed.
In a first preferred embodiment of the invention one or both sides of the
substrate have a metallised coating, which is partially demetallised to
provide the indicia, and the coating containing the thermochromic material
is provided on one side of the substrate such that at a temperature below
the activation temperature the thread when viewed from one side is seen as
a continuous coloured thread and when viewed from an opposite side appears
as a metallised thread with demetallised coloured indicia and at the
activation temperature or above both sides of the thread are seen as
metallised thread having colourless demetallised indicia.
In a second preferred embodiment one or both sides of the substrate have a
metallised coating, which is partially demetallised to produce indicia,
and the coating containing the thermochromic material is provided on both
sides of the metallised coating, such that when the thermochromic material
becomes colourless the demetallised indicia are revealed.
The coating containing the thermochromic material may be applied as printed
indicia to the substrate, such that at the activation temperature or above
the printed indicia disappear.
In a third aspect of the invention a security thread is provided for use in
security articles, the thread comprising a substrate having a coating on
one or both sides of the substrate, the coating containing a thermochromic
pigment or dyestuff which is colourless when the temperature of the
coating is below an activation temperature and which becomes coloured when
the coating is warmed to the activation temperature or above.
Preferably the coating containing the thermochromic material is applied as
printed indicia to the substrate such that at the activation temperature
or above the coating becomes coloured and the indicia becomes visible.
The coating or coatings are preferably composed of a variety of
thermochromic compounds which display differing colours, which compounds
are activated at different activation temperatures, such that as the
thread is warmed or subsequently cooled it progresses through a pattern of
changing colours.
In a preferred embodiment of the invention there is further included on one
or both sides of the thread beneath the coating or coatings containing the
thermochromic material, a dye or fluorescent material either in the
substrate, on the surface of the substrate or in a coating on the surface
of the substrate.
The security thread preferably further includes on one or both sides of the
thread, above or beneath the coating or coatings containing the
thermochromic material, a UV fluorescent or luminescent material either in
the substrate, on the surface of the substrate or in a coating on the
surface of the substrate.
Preferably the security thread further includes a machine readable feature.
The present invention provides in a further aspect a security paper
comprising opposed surfaces for the provision of printing to identify a
document formed from the paper, and positioned between the two surfaces of
the paper as a security feature a security thread as previously described.
The thread may be wholly embedded between the surfaces of the paper;
however, the thread is preferably positioned partially between the
surfaces of the paper, portions of which thread being positioned in
windows where there are no or virtually no paper fibres on the thread.
The thread preferably has indicia thereon, and the thread is slit to
produce registered indicia with respect to the edge of the thread, or
unregistered indicia.
The paper is preferably made from synthetic fibres, or from synthetic and
natural fibres, or from natural fibres.
The security paper is preferably a laminate of least two sheets with the
security thread positioned between the two sheets.
A banknote or other security document may be produced from the security
paper.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, by way of example only, with reference
to the accompanying drawings in which:
FIG. 1 is a plan view of a sheet of security paper containing a security
thread according to the invention viewed in transmitted light at a
temperature below the activation temperature;
FIG. 2 is a plan view of the security paper of FIG. 1 viewed in transmitted
light at a temperature greater than activation temperature;
FIG. 3 is a plan view of the security paper of FIG. 1 viewed in reflected
light at a temperature below the activation temperature; and
FIG. 4 is a plan view of the security paper of FIG. 1 viewed in reflected
light at a temperature greater than the activation temperature.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, there is shown a sheet of security paper 10, which can
be made from synthetic fibres, natural fibres or a combination of
synthetic and natural fibres.
Embedded either fully or at least partially within the paper 10 is a
security thread 11. The substrate of the thread 11 is preferably a
polymeric film such as polyester, e.g. MYLAR (Trade Mark) from DuPont or
MELINEX (Trade Mark) from ICI.
The security thread 11 is coated on one or both sides with a formulation
containing a thermochromic pigment which, in one embodiment of the
invention, is coloured when inactivated, but becomes colourless on warming
to its activation temperature. The activation temperature will depend on
the pigment being used. Many have activation temperatures of 35.degree.
C., but this is not true for all. The coating is applied to a web of the
thread substrate prior to slitting and the thickness of the coating may
vary from one micron to 10 microns, depending on the strength of visible
colour afforded by the pigment.
The coating may be applied, preferably in the form of an ink, by a number
of techniques using, for example, a roll coater or alternatively using a
printing press by flexographic, offset lithographic or gravure techniques.
Two or more different thermochromic coatings may be applied to the
substrate, which have slightly differing activation temperatures and
different inactive colours. When blended together, two or more inks may
produce a coating such that when warmed to one activation temperature, one
ink becomes colourless giving a different base colour; as the temperature
increases, the other ink(s) either change colour or become colourless
until all inks are activated. At this point the thermochromic coating
becomes colourless.
In an alternative embodiment of the invention, a thermochromic coating may
be used which has no colour at ambient temperature, and becomes coloured
at its activation temperature.
After the coating or coatings have been applied to the substrate and have
dried, a further protective lacquer may be applied and also an adhesive to
promote bonding of the thread to paper during manufacture.
The web of coated substrate is slit to the desired width and, if required,
any lettering or design registered with respect to the edge of the slit
thread. The thread is wound onto bobbins containing for example, 6000
meters of thread.
The slit thread may be incorporated into paper by one of a number of known
processes. The thread can be sandwiched between two separate paper layers
which are laminated together to form the security paper. Alternatively,
the thread can be fed into the paper thinstock during paper making and
allowing fibres to form paper on either side of the thread. Alternatively,
a windowed thread technique using a cylinder mould machine as described in
Patent Specification EP 0059056 may be employed producing a defined format
of windows 12 visible on the topside of the sheet 10 separated by embedded
thread bridges 13. The inclusion of windows 12 in the security paper 10
provides enhanced security for the reasons explained below.
FIG. 1 illustrates the appearance of thread 11 when the paper 10 is viewed
in transmitted light at a temperature below the activation temperature of
the thread coating. Here the thread 11 is seen as a solid line as the
thermochromic pigment is inactive and coloured. A message may be printed
on the thread substrate beneath the thermochromic coating. If printed in
an ink which has a similar colour to the inactive colour of the
thermochromic coating, it would be obscured.
When the thermochromic coating of the thread 11 is warmed to its activation
temperature or above, it becomes colourless. A message printed on the
thread substrate beneath the thermochromic coating, which was obscured by
the colour of the inactive pigment, now becomes clearly visible in
transmitted light as can be seen in FIG. 2.
In the sample shown in FIG. 3, the security paper 10 is viewed in reflected
light at a temperature below the activation temperature. Here, the
coloured thread 11 can be seen in the windows 12 in the surface of the
paper 10.
In FIG. 4, the thermochromic coating is warmed to its activation
temperature or above. When viewed in reflected light, the coating has
become colourless, thus revealing the message printed on the substrate of
the thread 11 in the windows at the surface of the paper 10.
Although the invention can be used without windows the addition of windows
in the security paper 10 provides enhanced security as it provides an
additional two variations in the optical viewing characteristics. The
views shown in FIGS. 1 and 2 will be similar, whether or not windows are
included in the paper. The views shown in FIGS. 3 and 4, however, will
only be available for windowed paper. In reflected light, a fully embedded
thread will not be very visible even when the coating is not activated.
The following are different examples of different security papers in
accordance with the invention. It should be noted that the invention is
not restricted to security paper.
EXAMPLE 1
A web of 23 mm Mylar film is coated with a semi-transparent magenta
coloured thermochromic ink (supplied by SICPA UK). The web is slit to
produce 1.2 mm wide thread and wound onto a bobbin. This thread is wholly
embedded between opposing surfaces of a sheet of paper during manufacture
so that it is completely encased by paper fibres. In reflected light the
visibility of the thread is considerably reduced by the overlying paper
fibres. In transmitted light the thread appears as a magenta coloured
line.
On warming to the activation temperature of 35.degree. C., the thread
becomes colourless making it virtually invisible in transmitted light.
EXAMPLE 2
This example utilises a thread made by the procedure described in Example
1, except in that the original Mylar web is coated with a different colour
(for example, semi-transparent yellow lacquer) prior to the coating of the
thermochromic ink. In reflected light the visibility of the thread is
considerably reduced. In transmitted light it appears as a continuous
coloured line a blend of magenta and yellow.
On warming to the activation temperature of 35.degree. C., the colour of
the thread changes to yellow when viewed under transmitted light.
EXAMPLE 3
This Example utilises a thread made by the procedure described in Examples
1 and 2, except in that the thread is embedded between two paper layers at
a nip prior to pressing.
EXAMPLE 4
In this Example the web of Mylar is first printed with a message such as
`VALID` or a name, logo or other indicia in a colour similar to that of
the thermochromic ink. The thermochromic ink is subsequently coated over
the printed film. The printing may be registered or unregistered whereby,
after slitting, the message, name, logo or other indicia appears central
to the thread if registered or is staggered in such a way as to ensure
that the message is readily seen irrespective of slitting position if
unregistered.
When the paper is viewed in reflected light the visibility of the thread is
considerably reduced. In transmitted light it appears as a continuous line
the colour of the thermochromic ink (see FIG. 1).
On warming to 35.degree. C. the thermochromic ink becomes colourless
revealing the message or indicia when viewed in transmitted light (see
FIG. 2).
EXAMPLE 5
In this Example the procedure described in Example 4 is followed except in
that the message is provided by negative indicia prior to coating with the
thermochromic ink.
When the paper is viewed in reflected light, the visibility of the thread
is considerably reduced. In transmitted light it appears as a continuous
line the colour of the thermochromic ink.
On warming to 35.degree. C. the thermochromic ink becomes colourless
revealing the negative microprinted message or indicia when viewed in
transmitted light.
EXAMPLE 6
In this Example, the thread is made by the procedure described in Example
1, except in that the thread is embedded in paper having windows at the
surface of the paper. In reflected light the thread can be seen in the
windows showing the colour of the thermochromic ink with considerable
reduction of visibility in the bridges (see FIG. 3). In transmitted light
the thread appears as a continuous line the colour of the thermochromic
ink.
On warming to 35.degree. C., the thermochromic ink becomes colourless, and
in reflected light the windows become virtually invisible. In transmitted
light the window and embedded portions of thread become virtually
invisible.
EXAMPLE 7
In this Example, the thread is made by the procedure described in Examples
4 and 5 whereby the thread, after slitting, is embedded in paper having
windows at the surface of the paper. In reflected light, the thread can be
seen in the windows showing the colour of the thermochromic ink with
considerably reduced visibility in the bridges. In transmitted light, the
thread appears as a continuous line the colour of the thermochromic ink.
On warming to 35.degree. C., the thermochromic ink becomes colourless
revealing a partial message or indicia in the windows in reflected light
(see FIG. 4) and a continuous message or indicia in transmitted light.
EXAMPLE 8
In this Example, the thread is made according to the procedure described in
Example 4, except in that the base thread is of metallised polyester with
a demetallised image, message, logo or other indicia as described in
Patent Specification EP 0319157. The thread is coated on both sides with
thermochromic ink and embedded into paper. In reflected light the
visibility of the thread is considerably reduced. In transmitted light the
thread appears as a continuous dark line.
On warming to 35.degree. C., the thermochromic ink becomes colourless and
the thread appears in transmitted light as a dark line with light
lettering or indicia.
EXAMPLE 9
In this Example, the thread is made according to the procedure described in
Example 6, except in that the base thread is of metallised polyester with
a de-metallised image, message, logo or other indicia. The thread is
coated on both sides with thermochromic ink prior to slitting and is
embedded in paper having windows. In reflected light, the thread can be
seen in the windows having the colour of the thermochromic ink. In
transmitted light, the embedded portion of the thread appears as a
continuous dark line with negative lettering or indicia the colour of the
thermochromic ink.
On warming to 35.degree. C., the thermochromic ink becomes colourless. In
reflected light the windows appear grey with light lettering or indicia.
In transmitted light they appear as a dark line with clear lettering or
indicia.
EXAMPLE 10
The thread in this Example is made by the procedure described in Example 7,
except in that the demetallised thread is coated on one side only with
thermochromic ink. After embedding in paper, the visibility of the thread
in reflected light is considerably reduced. In transmitted light the
thread appears as a continuous dark line with faint lettering or indicia
the colour of the thermochromic ink.
On warming to 35.degree. C. the thermochromic ink becomes colourless and
the lettering or indicia becomes clear and colourless.
EXAMPLE 11
The thread in this Example is made by the procedure described in Example 9,
except in that the demetallised thread is coated on one side only with
thermochromic ink. In reflected light, if the thread is ink side down,
demetallised stri | | |
