[0001] The present invention relates to a laser marking process for use on thin flexible
plastic films of the type commonly used for the packaging of various types of foodstuffs,
and especially to such a process using an ink which contains or is associated with
a laser sensitive material.
[0002] Many types of foodstuffs, for example snacks, confectionery, dry and frozen food,
etc., are packaged in wrappings composed of thin flexible films of plastic materials.
Although most of the printing on such wrappers can be done well in advance of use
of the packaging, some, such as "use by" or "best before" dates, of necessity, must
be printed soon after or soon before the foodstuff is packaged. There are, of course,
many printing methods known, but none is completely satisfactory for this purpose.
Desirably, the printing should be of the same quality as that of the rest of the printing
on the wrapper. It should also be economical and be capable of being printed at the
site where the food is packaged, as well as at the site where the rest of the wrapper
is printed. Moreover, because the date will change every day, and it may also be necessary
to accommodate other changes, for example to deal with products of varying shelf lives,
it should be easy to change the content of what is printed, preferably via software
in a computer-controlled printing operation. Where the contents of the packaging are
fragile, if the printing has to be done afterpackaging, it is also essential that
the printing should not involve any impact or any other form of applied pressure.
Finally, and of great importance, the printing should be indelible under normal conditions
of use. Most printing methods currently used for the application of such markings
as "use by" or "best before" dates fail to achieve several of these desiderata. Similar
requirements also apply to bar codes, which often have to be printed as a separate
exercise from the main printing of the packaging.
[0003] We have now discovered that a laser marking technique can achieve all of these desired
aims most effectively.
[0004] Laser marking of plastics materials is now well known [see, for example, "
Laser Marking" by Paul D. Hartung, Chapter 17 of "Plastics Finishing and Decoration"
edited by Donatas Satas, published by Van Nostrand Reinhold Co., New York, 1986]. It is a valuable method of marking which has found many applications. Its advantages
include: the laser does not directly contact the item to be marked, and so there is
no mechanical wear, neither is there any impact on the contents of the packaging;
it allows extremely small characters or symbols to be drawn; accurately and legibly,
markings can be made at extremely high speeds; lasers are extremely reliable and require
minimal maintenance, and other moving parts on the marking system are limited.
[0005] In the past, most proposals for the use of laser marking have involved using the
laser to remove material thermally or carbonise the polymer from a solid object composed
of a resin, polymer or other laser sensitive material and so form a mark or impression
on the object. Examples of such processes are described in
US patents No. 5,928,780;
5,977,514; and
6,214,917, and in manufacturers' literature such as that issued by Merck KgaA ("Iriodin®LS
for the laser marking of plastics", June 1997). Such processes have the disadvantage
that the plastic materials chosen for this use have to be restricted to those susceptible
to thermal removal in this way. This can restrict the choice of materials and so may
not be useable for some purposes. Moreover, this technique may result in localised
thinning and weakening of the plastic substrate, which would be undesirable or unacceptable
in wrappers for foodstuffs and many other materials.
[0006] Another laser marking technique comprises using a laser to remove thermally a covering
layer, thereby exposing a lower layer of a different colour from that of the covering
layer, so providing visible markings. An example of such a process, for the marking
of optical fibres or electric cables, is described in
US Patent No. 5,111,523.
[0007] A further laser marking method employs the heat generated by laser radiation striking
a substrate to cause a change in the colour of a thermosensitive material, as described,
for example, in
US Patent No. 5,608, 429.
[0008] There has also been a proposal for using the ability of a laser to change the colour
of an ink containing a non-black inorganic lead compound to black, thereby forming
a black mark on an object such as a printed circuit board, as described in
US Patent No. 5,035,983. However, the use of a lead compound in these inks would not be acceptable for food
use, as is envisaged by the present invention.
[0009] Another type of laser marking process uses thin aluminium layers which are deposited
by vacuum evaporation. Because these absorb in the range of the Nd:YAG-radiation,
such aluminium layers can be removed by laser radiation. This can be used to remove
coloured ink layers, printed on the aluminium layer or to make contrast forming layers
visible, as describe in
US Patent No. 6,066,437. For this kind of laser marking, aluminium-coated films are necessary, which are
expensive and the deposition of the aluminium requires specialised equipment, which
means that it often cannot be done or cannot be done economically at the site where
the packages are printed.
[0010] It is also known to mark paper and cardboard by using the heat generated by a laser
for the selective thermal removal of some of the ink applied to the surface thereof.
[0011] Laser ablative imaging methods are also known in which a donor sheet containing a
material which absorbs at the wavelength of the laser and a dye (rather than the pigment
necessary in the present invention) is irradiated with a laser. The absorbing material
converts the laser energy to heat, which is transferred to the immediately proximate
dye. The dye vaporises and is transferred to the receptor, which is the material to
be printed. Methods ofthis type are disclosed in
GB 2083726.
[0012] In European Patent application No.
0 756 942A1 (and corresponding
US Patent No. 5,633,118) laser ablative imaging methods are disclosed in which layers including water-soluble
infra-red (IR) absorbing dyes are ablated in selected areas to expose an underlying
hydrophilic dye receiving layer; this underlying layer is then treated with aqueous
ink to provide a colour contrast with unexposed areas. These methods are suitable
for the production of optical masks, monochrome transparencies, and the like.
[0013] Other disclosures relating to the use of IR absorbing dyes in laser ablative imaging
include
US Patent No. 5,330,876, which discloses a dye layer comprising an image dye and an IR absorbing dye dispersed
in a high molecular weight binder, and
US Patent No. 5,576,268, which discloses a similar dye ablative recording element in which the support is
a microvoided composites film.
[0014] However, none of these prior proposals has addressed the question of applying a marking
by means of a laser to a thin flexible film of a plastic material, such as is commonly
used for the wrapping of foodstuffs.
[0015] The present invention consists in processes for marking a flexible plastic film useful
for packaging according to the appended claims.
[0016] The expression "in association with" is here defined to mean that the ink and the
laser sensitive material are in sufficiently close physical proximity that the heat
induced in the laser sensitive material by the laser radiation is sufficient to cause
the thermal removal of the ink. The laser sensitive material and the ink may be applied
in separate layers or together in one composition.
[0017] If desired, other layers, such as inks, non-pigmented coatings or varnishes, similar
to the above-mentioned layers, or of other materials, as described in more detail
below, may be applied to the coated substrate obtained as described above, either
before or after exposure to the laser radiation.
[0018] The layer of ink or layers of ink and laser sensitive material referred to above
may cover the entire surface of the substrate, if desired. However, it is a benefit
of the present invention that they need not do so. Thus, the layers may, if desired,
cover only that portion or those portions of the substrate on which markings are subsequently
to be printed, and they may be applied by conventional printing processes with considerable
accuracy. For example, if the markings to be printed are "use by" or "best before"
information, a single patch of the coating layers may be applied to the substrate
in the position where this information is to be inserted. Alternatively, the invention
is equally applicable to the printing of statutory information, which may vary from
country to country and/or which may need to be in different languages for different
countries. In this case, several patches of ink/varnish and laser sensitive material
may need to be applied. Similarly, bar codes can be marked on areas that have been
selectively coated with laser sensitive material.
[0019] When the laser sensitive material is exposed to the laser radiation, it absorbs the
energy of the radiation, becomes hot and generally removes the layer containing it
and any other layers above it by thermal action. It therefore follows that the ink
or non-pigmented coating should burn, degrade, evaporate or otherwise be thermally
removable at a temperature to which the laser heats the laser sensitive material.
The majority of inks and coatings currently available will do so, and so the selection
of an appropriate ink or coating is not a difficult task.
[0020] Several laser systems are commercially available, including excimer, Nd:YAG, frequency
doubled Nd:YAG, frequency tripled Nd:YAG, helium, neon and CO
2 systems. In practice, the most readily available systems, and those preferred for
use in the present invention, are the CO
2 and Nd:YAG [neodymium (dopant): yttrium, aluminium, garnet] laser systems. The construction
and use of such laser systems is well known.
[0021] In general terms, the laser sensitive material is a material which can convert the
energy of the laser radiation to thermal energy. The nature of the laser sensitive
material used in the present invention will depend on the laser system chosen, as
is well known in the field of laser marking. For example, if the laser is of the CO
2 type, which operates at a wavelength of 10600 nm, the laser sensitive material is
preferably: mica or metal oxide-coated mica particles, such as those sold by Merck
KgaA, Darmstadt, Germany under the trade names Iriodin LS 800, Iriodin LS 805, Iriodin
LS 810, Iriodin LS 830, Iriodin LS 835 or Iriodin LS 850, or those sold by EMI (BMI
Industries, Inc. Hawthorne, New York, USA) under the trade names Laser Flair LS 800,
Laser Flair LS 805, Laser Flair LS 810, Laser Flair LS 830, Laser Flair LS 835 or
Laser Flair LS 850; aluminium powders, such as that sold by Silberline (Silberline
Ltd., Leven, Scotland) under the trade names Silvet LR10, Silvet LR20, Silvet LR30,
Silvet ET917, or Silvet ET1630, that sold by Eckart (Eckart GmbH & Co. KG, Fürth,
Germany) under the trade name Ultrastar GX 2550, that sold by Wolstenholme (Wolstenhohne
International Ltd., Darwen, Blackburn, England) under the trade name Metasheen 1015
or that sold by Eckart under the trade name Rotosafe 751 or Rotosafe 700; carbon black,
such as that sold by Degussa (Degussa AG, Frankfurt, Germany) under the trade name
Printex XE2, Printex 3 or Printex L or that sold by Avecia (Avecia, Manchester, England)
under the trade name Pro-Jet 900 NP Bx2005; kaolin and other silicates; titanium dioxide;
and calcium carbonate.
[0022] On the other hand, if the laser is of the Nd:YAG type, which operates at a wavelength
of 1064 nm, the laser sensitive material is preferably: mica or metal oxide-coated
mica particles, such as Iriodin LS 820, Iriodin LS 825, Iriodin LS 830, Iriodin LS
835 or Iriodin LS 850 (all ex Merck), or Laser Flair LS 820, Laser Flair LS 825, Laser
Flair LS 830, Laser Flair LS 835 or Laser Flair LS 850 (all ex EMI); aluminium powders,
such as Silvet LR10, Silvet LR20, Silvet LR30, Silvet ET917, or Silvet ET1630 (all
ex Silberline), Ultrastar GX 2550 (ex Eckart), Metasheen 1015 (ex Wolstenholme) or
Rotosafe 751 or Rotosafe 700 (both ex Eckart); carbon black, such as Printex XE2,
Printex 3 or Printex L (all ex Degussa) or Pro-Jet 900 NP Bx2005 (ex Avecia); titanium
dioxide; and calcium carbonate.
[0023] It is also possible to use a combination of laser sensitive materials such that any
one of several laser types would be effective in marking according to the process
of the present invention.
[0024] Other laser systems may be able to use some of the above laser sensitive materials
or may use others. However, these materials are well known to those skilled in the
art
[0025] There is no particular restriction on the nature of the ink used in the present invention,
and any ink known for use in the printing of flexible plastic films may be used, subject
only to the restriction, as explained above, that it should be capable of being removed
by the heat generated in the laser sensitive material by the laser radiation. Preferred
examples of such inks include those comprising: nitrocellulose (NC) based inks, polyvinyl
butyrate (PVB) based inks, polyurethane (PUR) based inks, cellulose acetate propionate
(CAP) based inks, polyvinyl chloride (PVC) based inks, polyamide (PA) based inks,
water based inks.
[0027] The laser sensitive material may also be applied as part of an essentially transparent
pigment-free coating. The formulation of these coatings is essentially similar to
that of the inks, but with the coloured pigment absent.
[0028] Whether the laser sensitive material is incorporated into an ink or into a non-pigmented
coating, it is preferably present in an amount from 1 to 40%, more preferably from
5 to 20%, and most preferably from 10 to 15% by weight of the whole composition.
[0030] There is no particular restriction on the nature of the plastic film used as the
substrate in the process of the present invention, and any plastic materials commonly
used in the industry, especially for food wrapping, may be used. Examples of such
materials include synthetic and semi synthetic organic polymers, such as cellulose
acetate, cellulose acetate butyrate (CAB), cellophane, polyvinyl chloride (PVC), polyvinyl
fluoride, polyvinylidene chloride (PVDC), polyethylene, polypropylene (PP), polyamides,
polyesters, polyphenylene oxide, polyethylene terephthalate (PET), polybutylene terephthalate
(PET), polymethyl methacrylate, poly(methyl pentene (TPX), polyvinyl acetal, polystyrene,
acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), polycarbonate,
polystyrene, polyether sulphone, polyether ketones, polyimides, and copolymers and/or
mixtures thereof. If desired, films made from any of these polymers may be coated
with coating materials well known in the art, and/or may be laminated to a film or
films made of the same or different polymers. Further examples of such plastic materials
may be found in standard reference texts, such as "
Plastic Films", 3rd Edition, by J. H. Briston, published by Longman Group in 1989.
[0031] If desired, the substrate may be coated with a colouring layer impervious to the
laser radiation, so as to provide a layer of a contrasting colour to that of the ink
subsequently applied. When the ink is removed by thermal action in accordance with
the process of the invention, the lower, laser-impervious, layer will be seen as a
contrasting colour and will form the printed markings generated by the laser. Alternatively,
the coating layer of ink which is selectively removed may be coloured, so that, when
it is removed, the native colour of the substrate is seen as a contrast
[0032] Once the ink has been applied to the substrate comprising the flexible plastic film,
it is cured or dried to form a coherent layer on the substrate. If desired, one or
more further films of plastic material may be laminated to the coated substrate. This
may be any of the polymers listed above, but should be transparent to the radiation
of the laser employed. If another film is laminated on top of the ink, and the ink
emits gases or otherwise undergoes an increase in volume on being heated by the heat
resulting from absorption of the laser energy by the laser sensitive material, the
portion of the laminated film above the markings will be raised, thus giving an embossed
effect which otherwise would be difficult to achieve and which can be very desirable.
[0033] The present invention can thus provide thin flexible plastic films which may be coated
in many ways. Examples of these include:
- 1. The film may be coated with a single layer of an ink containing the laser sensitive
material;
- 2. The film may be coated with a layer of laser sensitive material, which, in turn,
is coated with a layer of ink;
- 3. The film may be coated with a layer of ink, which, in turn, is coated with a single
layer of an ink containing the laser sensitive material;
- 4. The film may be coated with a layer of ink, which, in turn, is coated with a layer
of laser sensitive material, that being coated with a layer of ink.
[0034] In general terms, we prefer that either the laser sensitive material is mixed with
the ink or that the ink and the laser sensitive material are in separate, but associated,
layers, the layer of ink to be removed by the process of the present invention being
on the side of the layer of laser sensitive material remote from the substrate.
[0035] Any of the above may be coated with further layers of material, for example, varnish,
provided that any such further layers are transparent or essentially transparent,
to the laser radiation. Moreover, if desired, the film may be coated with one or more
other layers of materials, such as inks, varnishes and the like, prior to being coated
with the first layer in accordance with the present invention.
[0036] In the embodiment of the present invention where a laser sensitive material is or
is associated with a material which evolves gas when heated, it may be the laser sensitive
material which evolves gas. Alternatively, the laser sensitive material may be associated
with, e.g. mixed with, another material which evolves gas. The material is then coated
with a gas impermeable layer, which can be any such known material. As a result, when
exposed to laser radiation, the exposed portions emit a gas. However, this is trapped
by the coating layer, and, as a result, forms minute bubbles under the coating layer.
These can be perceived both by the eye and by touch and give a desirable embossed
appearance, suitable for Braille or Moon script.
[0037] The present invention is further illustrated by the following non-limiting Examples.
Example 1
[0038] A laser sensitive solvent based coating was printed on transparent oriented polypropylene
(OPP) film, and then overprinted with a nitrocellulose based cyan ink. The formulation
of the laser sensitive coating was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
11 |
Ethyl acetate |
22 |
Ethanol |
32 |
Methoxypropanol, Dowanol PM ex Dow |
15 |
Plasticiser Plastifiant 1026 ex SNPE |
10 |
Iriodin LS 825 ex Merck |
10 |
Total |
100 |
The cyan ink was Europa cyan ex Sun Chemical. After exposure to a Nd:YAG laser, marks
were visible as a result of removal of the cyan ink from the regions exposed to the
laser beam.
Example 2
[0039] A laser sensitive solvent based coating was printed on transparent OPP film, and
then overprinted with a nitrocellulose based cyan ink. The formulation of the laser
sensitive coating was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
11 |
Ethyl acetate |
22 |
Ethanol |
32 |
Methoxypropanol, Dowanol PM ex Dow |
15 |
Plasticiser Plastifiant 1026 ex SNPE |
10 |
Iriodin LS 800 ex Merck |
10 |
Total |
100 |
The cyan ink was Europa cyan ex Sun Chemical. After exposure to a CO
2 laser, marks were visible as a result of removal of the cyan ink from the regions
exposed to the laser beam.
Example 3
[0040] A laser sensitive solvent based coating was printed on transparent OPP film, and
then overprinted with a nitrocellulose based cyan ink. The formulation of the laser
sensitive coating was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
36.5 |
Ethanol |
36.5 |
Urethane, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter Lutonal M40 ex BASF |
1.0 |
Kaolin |
10.0 |
Total |
100.0 |
The cyan ink was Europa cyan ex Sun Chemical. After exposure to a CO
2 laser, marks were visible as a result of removal of the cyan ink from the regions
exposed to the laser beam.
Example 4
[0041] A laser sensitive solvent based coating was printed on transparent OPP film, and
then overprinted with a nitrocellulose based cyan ink. The formulation of the laser
sensitive coating was (parts by weight):
Polyvinyl butyral, Pioloform BN18 ex Wacker |
15 |
Ethanol |
75 |
Iriodin LS 825 ex Merck |
10 |
Total |
100 |
The cyan ink was Europa cyan ex Sun Chemical. After exposure to a Nd:YAG laser, marks
were visible as a result of removal of the cyan ink from the regions exposed to the
laser beam.
Example 5
[0042] A laser sensitive water based coating was printed on transparent OPP film, and then
overprinted with a nitrocellulose based cyan ink. The formulation of the laser sensitive
coating was (parts by weight):
Acrylic Solution Joncryl 678 ex Johnson |
59.0 |
Acrylic Emulsion Joncryl 80 ex Johnson |
22.5 |
Water |
5.0 |
Defoamer TPE714 ex Henkel |
0.5 |
Levelling agent Surfynol SE-F ex Air Products |
3.0 |
Iriodin LS 825 ex Merck |
10.0 |
Total |
100.0 |
The cyan ink was Europa cyan ex Sun Chemical. After exposure to a Nd:YAG laser, marks
were visible as a result of removal of the cyan ink from the regions exposed to the
laser beam.
Example 6
[0043] A laser sensitive solvent based coating was printed on transparent OPP film, and
then overprinted with a nitrocellulose based yellow ink. The formulation of the laser
sensitive coating was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
11 |
Ethyl acetate |
17 |
Ethanol |
27 |
Methoxypropanol, Dowanol PM ex Dow |
15 |
Plasticiser Plastifiant 1026 ex SNPE |
10 |
Iriodin LS 800 ex Merck |
10 |
Iriodin LS 825 ex Merck |
10 |
Total |
100 |
The cyan ink was Europa yellow ex Sun Chemical. After exposure to a Nd:YAG or CO
2 laser, marks were visible as a result of removal of the cyan ink from the regions
exposed to the laser beam.
Example 7
[0044] A nitrocellulose based white ink was printed on transparent polyethylene terephthalate
(PET), and was overprinted with a solvent based laser sensitive magenta ink. The formulation
of the laser sensitive magenta ink was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
18.5 |
Ethanol |
18.5 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin,. Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Magenta pigment, Symular Brilliant 363SD ex DIC |
18.0 |
Iriodin LS 825 ex Merck |
15.0 |
Total |
100.0 |
The white ink was Europa white ex Sun Chemical. After exposure to a Nd:YAG laser,
marks were visible as a result of removal of the magenta ink from the regions exposed
to the laser beam, while the white ink film had not been removed by the laser.
Example 8
[0045] A cellulose acetate propionate based orange ink was printed on transparent polypropylene
(PP), and then overprinted with a solvent based laser sensitive coating, which, in
turn, was overprinted with cellulose acetate propionate based green ink. The formulation
of the laser sensitive coating was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
11 |
Ethyl acetate |
22 |
Ethanol |
32 |
Methoxypropanol, Dowanol PM ex Dow |
15 |
Plasticiser Plastifiant 1026 ex SNPE |
10 |
Iriodin LS 825 |
10 |
Total |
100 |
The orange ink was Europa orange ex Sun Chemical. The green ink was Europa green ex
Sun Chemical. After exposure to a Nd:YAG laser, marks were visible since the orange
ink was not removed by the laser and gave contrast to the green ink which had been
removed.
Example 9
[0046] A polyvinyl butyral based laser sensitive coating was printed on PET and overprinted
with a polyvinyl butyral based red ink. This film was laminated with a two-pack adhesive
onto polyethylene (PE). The formulation of the laser sensitive coating was (parts
by weight):
Polyvinyl butyral Pioloform BN18 ex Wacker |
15 |
Ethanol |
75 |
Iriodin LS825 |
10 |
Total |
100 |
The red ink was Optiprint red ex Sun Chemical. The adhesive was Mor-Free 402A/Mor-Free
C79 ex Rohm &Haas. After exposure to a Nd:YAG laser, marks were visible as a result
of removal (or change in colour) of the red ink from the regions exposed to the laser
beam.
Example 10
[0047] A nitrocellulose based white ink printed on PET was overprinted with a nitrocellulose
based laser sensitive coating and a polyvinyl butyral based yellow ink. This film
was laminated with a two-pack solvent free adhesive onto PP. The formulation of the
laser sensitive coating was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
36.5 |
Ethanol |
36.5 |
Urethane, Surkopak SE-F ex SNPE |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Iriodin LS 825 |
10.0 |
Total |
100.0 |
The white ink was Europa white ex Sun Chemical. The yellow ink was Optiprint yellow
ex Sun Chemical. The solvent based adhesive was Herberts EPS71-72 / KS65 ex Herberts.
After exposure to a Nd:YAG laser, marks were visible as a result of removal of the
yellow ink from the regions exposed to the laser beam.
Example 11
[0048] A nitrocellulose based laser sensitive green was printed on polyamide (PA). The formulation
of the laser sensitive green ink was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
18.5 |
Ethanol |
18.5 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Green pigment, Sunfast green 264-5504 ex Sun Chemical |
18.0 |
Iriodin LS 825 ex Merck |
15.0 |
Total |
100.0 |
After exposure to a Nd:YAG laser, marks were visible as a result of removal of the
green ink from the regions exposed to the laser beam.
Example 12
[0049] A nitrocellulose based laser sensitive blue ink was printed on PA. The formulation
of the laser sensitive blue ink was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
18.5 |
Ethanol |
18.5 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Blue pigment, Fastogen Blue 5412 SD ex DIC PBI 15:4 |
18.0 |
Iriodin LS 800 ex Merck |
15.0 |
Total |
100.0 |
After exposure to a CO
2 laser, marks were visible as a result of removal of the blue ink from the regions
exposed to the laser beam.
Example 13
[0050] A polyvinyl butyral based laser sensitive blue ink was printed on PA. The formulation
of the laser sensitive blue ink was (parts by weight):
Polyvinyl butyral, Pioloform BN18 ex Wacker |
10.0 |
Adhesion promoter, Lutonal M40 ex BASF |
5.0 |
Ethanol |
52.0 |
Blue pigment, Heliogen blue 7086 ex BASF, Pub115:3 |
18.0 |
Iriodin LS 800 ex Merck |
15.0 |
Total |
100.0 |
After exposure to a CO
2 laser, marks were visible as a result of removal of the blue ink from the regions
exposed to the laser beam.
Example 14
[0051] A water based laser sensitive blue ink was printed on PA. The formulation of the
laser sensitive blue ink was (parts by weight):
Acrylic Emulsion, Joncryl 80 ex Johnson |
50.0 |
Water |
14.5 |
Defoamer TPE714 ex Henkel |
0.5 |
Levelling agent, Surfynol SE-F ex Air Products |
3.0 |
Pigment, Meghafast Blue BD909 ex Meghmani, PB115:3 |
17.0 |
Iriodin LS 825 ex Merck |
15.0 |
Total |
100.0 |
After exposure to a Nd:YAG laser, marks were visible as a result of removal of the
blue ink from the regions exposed to the laser beam.
Example 15
[0052] A nitrocellulose based laser sensitive yellow ink was printed on PA. The formulation
of the laser sensitive yellow ink was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
16.0 |
Ethanol |
16.0 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Yellow pigment Permanent yellow P-GRL06 ex Clariant |
18.0 |
Iriodin LS 825 ex Merck |
10.0 |
Iriodin LS 800 ex Merck |
10.0 |
Total |
100.0 |
After exposure to a Nd:YAG or CO
2 laser, marks were visible as a result of removal of the blue ink from the regions
exposed to the laser beam.
Example 16
[0053] A laser sensitive nitrocellulose based orange ink was printed on PET. The film was
laminated with a two-pack adhesive onto PE. The formulation of the laser sensitive
orange ink was (parts by weight):
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
18.5 |
Ethanol |
18.5 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Orange pigment, Diacetanil orange 3426C ex Cappelle |
18.0 |
Iriodin LS 825 ex Merck |
15.0 |
Total |
100.0 |
The adhesive was Mor-Free 402A/Mor-Free C79 ex Rohm &Haas. After exposure to a Nd:YAG
laser, marks were visible as a result of removal of the orange ink from the regions
exposed to the laser beam.
Example 17
[0054] A polyvinyl butyral based white ink was printed on PE, and was overprinted with laser
sensitive polyvinyl butyral based violet ink. This film was laminated with water based
adhesive on PP. The formulation of the laser sensitive violet ink was )parts by weight):
Polyvinyl butyral, Pioloform BN18 ex Wacker |
10 |
Adhesion promoter, Lutonal M40 ex BASF |
5 |
Ethanol |
53 |
Blue pigment, Heliogen blue BD909 ex BASF |
17 |
Iriodin LS 825 |
15 |
Total |
100 |
The white ink was Europa white ex Sun Chemical. The water based adhesive was Aqua-LAM
300A/Aquabond 444C ex Rohm & Haas. After exposure to a Nd:YAG laser, marks were visible
as a result of removal of the violet ink from the regions exposed to the laser beam.
Example 18
[0055] A laser sensitive water based coating was printed on a transparent OPP film, and
was then overprinted with a water based, irreversible, thermochromic ink. The formulation
of the laser sensitive coating was:
Acrylic Solution, Joncryl 678 ex Johnson |
59.0 |
Acrylic Emulsion, Joncryl 80 ex Johnson |
22.5 |
Water |
5.0 |
Defoamer TPE714 ex Henkel |
0.5 |
Levelling agent, Surfynol SE-F ex Air Products |
3.0 |
Iriodin LS 825 ex Merck |
10.0 |
Total |
100.0 |
The thermochromic ink was a water based flexo ink ex Sun Chemical with irreversible
colour change at 90 °C from colourless to dark grey. After exposure to a NdYAG laser,
marks were visible as a result of irreversible colour change of the thermochromic
ink, due to energy absorption in the laser sensitive coating and temperature increase
to more than 90 °C. The laser power has to be in a range such that there is enough
energy to reach the recommended temperature for the colour change but not to remove
the ink layer.
Example 19
[0056] A laser sensitive solvent based coating was printed on shrinkable PET film, and was
then overprinted with a nitrocellulose based white ink. The film was shrunk on a glass
bottle where the printed side has contact with the bottle. The formulation of the
laser sensitive coating was:
Polyvinylbutyral, Pioloform BN18 ex Wacker |
15 |
Ethanol |
75 |
Iriodin LS 825 ex Merck |
10 |
Total |
100 |
The white ink was Europa white ex Sun Chemical. After exposure to a NdYAG laser, dark
marks were visible as a result of removal of the white ink from the regions of the
film exposed to the laser beam. The ink was transferred to the surface of the bottle,
so a copy of the marks was visible after removal of the film. This can be used as
a security characteristic.
Example 20
[0057] A nitrocellulose based laser sensitive blue ink was printed on shrinkable PET. The
film was shrunk on a PET bottle where the printed side was in contact with the bottle.
The formulation of the laser sensitive blue ink was:
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
18.5 |
Ethanol |
18.5 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Blue pigment, Fastogen Blue 5412 SD ex DIC PBI 15:4 |
18.0 |
Iriodin LS 800 ex Merck |
15.0 |
Total |
100.0 |
After exposure to a CO
2 laser, marks were visible as a result of removal of the blue ink from the regions
exposed to the laser beam. The ink was transferred to the surface of the bottle, so
a copy of the marks was visible after removal of the film. This can be used as a security
characteristic.
Example 21
[0058] A laser sensitive solvent based coating was printed on transparent OPP film, and
was then overprinted with a nitrocellulose based cyan ink. The same coating layers
were applied to paper. The printed film over-wrapped the printed paper. The formulation
of the laser sensitive coating was:
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
11 |
Ethyl acetate |
22 |
Ethanol |
32 |
Plasticiser, Plastifiant 1026 ex SNPE |
10 |
Methoxypropanol, Dowanol PM ex Dow |
15 |
Iriodin LS 825 ex Merck |
10 |
Total |
100 |
The cyan ink was Europa cyan ex Sun Chemical. The laser exposure was partly on film
and partly on paper. After exposure to a NdYAG laser, marks were visible as a result
of removal of the cyan ink from the regions of the film and the paper exposed to the
laser beam. This can be used as a security characteristic.
Example 22
[0059] A nitrocellulose based yellow ink was printed on polyvinyl acetal film as micro text.
It was then overprinted with a solvent based laser sensitive blue ink. The formulation
of the laser sensitive blue ink was:
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
10.0 |
Ethyl acetate |
18.5 |
Ethanol |
18.5 |
Methoxypropanol, Dowanol PM ex Dow |
10.0 |
Urethane resin, Surkopak 5244 ex Tennants Inks |
6.0 |
Adhesion promoter, Lutonal M40 ex BASF |
1.0 |
Plasticiser, Dioctyl phthalate ex BASF |
3.0 |
Blue pigment, Fastogen Blue 5412 SD ex DIC Pub115:4 |
18.0 |
Iriodin LS 800 ex Merck |
15.0 |
Total |
100.0 |
The yellow ink was Europa yellow ex Sun Chemical. After exposure to a CO
2 laser, marks were visible as a result of removal of the blue ink from the regions
exposed to the laser beam. Inside the marks, formed by the removal of the blue ink,
the yellow micro text underneath was visible. This can be used as a security characteristic.
Example 23
[0060] A nitrocellulose based yellow ink was printed on transparent OPP film as micro text
It was then overprinted with a laser sensitive solvent based coating which was overprinted
with a nitrocellulose based cyan ink. The formulation of the laser sensitive coating
was:
Nitrocellulose, Nitro CA4 A15 ex Bergerac |
11 |
Ethyl acetate |
22 |
Ethanol |
32 |
Plasticiser, Plastifiant 1026 ex SNPE |
10 |
Methoxypropanol, Dowanol PM ex Dow |
15 |
Iriodin LS 825 ex Merck |
10 |
Total |
100 |
The yellow ink was Europa yellow ex Sun Chemical, the cyan ink was Europa cyan ex
Sun Chemical. After exposure to a CO
2 laser, marks were visible as a result of removal of the blue ink from the regions
exposed to the laser beam. In the marks, formed by the removal of the blue ink, the
yellow micro text underneath was visible. This can be used as a security characteristic.
Example 24
[0061] A polyvinyl butyral based laser sensitive coating was printed on PE. This film was
laminated onto PET using a 2-compound adhesive. The formulation of the laser sensitive
coating was:
Polyvinylbutyral, Pioloform BN18 ex Wacker |
15 |
Ethanol |
75 |
Iriodin LS825 |
10 |
Total |
100.0 |
After exposure to a NdYAG laser, marks were visible and tangible as a result of bubbles,
formed in between the two plastic films, caused by the thermal destruction of the
laser sensitive coating. The intensity of bubble formation can be influenced by the
laser power. These marks can also be fdt by blind people. They can, therefore, be
used as Braille or Moon script.
1. Verfahren zum Beschriften eines flexiblen, zum Verpacken verwendbaren Kunststofffilms
unter Verwendung eines Lasers, wobei das Verfahren die Schritte umfasst: Aufbringen
auf eine Oberfläche eines Substrats, welches den flexiblen Kunststofffilm umfasst,
in einer oder mehreren Schichten einer Tinte in Verbindung mit einem laserempfindlichen
Material; Trocknen der Tinte; Aussetzen von Teilen der Tinte einer Laserstrahlung
bei einer Wellenlänge, gegenüber welcher das laserempfindliche Material empfindlich
ist, so dass Laserstrahlung, die vom laserempfindlichen Material absorbiert wird,
die Tinte erwärmt und thermisch entfernt oder einen Farbwechsel der Tinte bewirkt,
um so zu bewirken, dass Beschriftungen an den ausgesetzten Teilen erscheinen.
2. Verfahren gemäß Anspruch 1, wobei das laserempfindliche Material auf das Substrat
aufgebracht wird und dann eine Schicht der Tinte über dem laserempfindlichen Material
aufgebracht wird.
3. Verfahren gemäß Anspruch 1, wobei die Tinte das laserempfindliche Material enthält.
4. Verfahren gemäß einem der Ansprüche 1 bis 3, wobei Erwärmen die Tinte entfernt.
5. Verfahren zum Beschriften eines flexiblen, zum Verpacken verwendbaren Kunststofffilms
unter Verwendung eines Lasers, wobei das Verfahren die Schritte umfasst: Aufbringen
eines laserempfindlichen Materials, welches ein Material ist oder mit einem Material
verbunden ist, das beim Erwärmen Gas erzeugt, auf eine Oberfläche eines den flexiblen
Kunststofffilm umfassenden Substrats; Beschichten des laserempfindlichen Materials
mit einer gasundurchlässigen Schicht; Aussetzen von Teilen des laserempfindlichen
Materials einer Laserstrahlung bei einer Wellenlänge, gegenüber der das laserempfindliche
Material empfindlich ist, so dass durch das laserempfindliche Material absorbierte
Laserstrahlung dieses erwärmt und die Erzeugung von Gas verursacht, welches durch
die Beschichtung eingeschlossen wird und als Folge davon winzige Blasen unter der
Beschichtung bildet, um dadurch erhöhte Beschriftungen zu bilden, welche auf den ausgesetzten Teilen erscheinen.
6. Verfahren gemäß einem der Ansprüche 1 bis 5, wobei der Laser ein CO2-Laser ist.
7. Verfahren gemäß Anspruch 6, wobei das laserempfindliche Material Glimmer, Metalloxid-beschichtete
Glimmerteilchen, Aluminiumpulver, Ruß, Kaolin oder ein anderes Silikat, Titandioxid
oder Calciumcarbonat ist.
8. Verfahren gemäß einem der Ansprüche 1 bis 5, wobei der Laser ein Nd:YAG Laser ist.
9. Verfahren gemäß Anspruch 8, wobei das laserempfindliche Material Glimmer, Metalloxid-beschichtete
Glimmerteilchen, Aluminiumpulver, Ruß, Titandioxid oder Calciumcarbonat ist.