Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1330177
t
PRINTING INR SYSTEM ~OR THE PRODUCTION OF RUB-OFP
pRINTINGS
Thi~ invention belongs to the ~ield of the docu~ent
println0 art and i~ related more specifically to an
off6et or typographic printing ink system for the
production o opaque printing~ which can be removed by
5 rubbing.
It ls well known to produce prin~ed products having
mec~anically removable regions or area~ where under-
lying, generally pxinted indi~ia are covered by an
opague layer which can be removed by rubbing under
di~lntegration of the covering layer. Application
example~ thereof are lottery ticke~s where th~ customer
may find out, immed~ately after the p~rchase of tho
ticket, whether it has won or not when he rubs off the
indicated areas to loo~ what i~ printed benea~h.
A6 a general rule, damage free removable cove~ing
layers on secu~lty documcnts serve to temporarily hiding
of alphanumeric indicia or information such as numbers,
name~, other group~ of ~etters as well as combinations
of numbers and names, but al~o of image in~ormation
including colour~. ~he covoring layer must be perfcctly
opaque when seen ln incident or traversing light.
; Untll now, the covering~ of the l~dicated kind
are produced by offset p~inting of a printing carrier on
` the whole surface, including the region~ to be cover~d
~termed as "cover area~"), and then printing by ~he
method of scre~n printing a transparent release layer
which may be coloured at will, onto the cover areas. In
a fur~her ~creen printing step, the pigment containing
. cov~rlng layer forming a d~troyable film, thus the true
rub-o~f layor, is appliod. ~he plgment~ are preferably
metal particles, espocially o~ aluminum, which could
also bo coloured by anodising, in ordor to o~tain a
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perf-ct opaclt~.
Screen printing ink~ ~re solvent containing ~y8tem8
which must be applied in very thick layers. Scroen
printing i~ a time con¢uming coating pro~ess, and after
5ink application, the solvent must be evaporated in the
~o called heat tunnel and tho ink ~ust be dried. ~he
solvent which ha~ been evaporated con~titute~ a ~trin-
gent problem for mo6t owners of su¢h pr~ntlng plants due
to the eevere cloan alr legi~lation in most countries.
10The appllcation of ~uch high layer thicknes~es has
of course a great lnfluenco on the costs of the flnal
produ~ts.
Screen printing lnstallations do not exlst in mogt
offset printing shops so that ~he products having beon
printed by off~et or typography must generally be
shipped to another printing plant in order to apply the
~`; rub-off coatlngs. Th~refore, there is already a long
lasting no~d for a possibility to apply al80 the rub-off
layer by typography or offset.
~ 20The reali6atlon of this demand ha~ been hindered by
`-~ the technical prejudlce that offset te~hniques would not
be capabl~ to proauce cov~ring layers. This opinion i~
b~sed on all exper$ence~ maae until now~ it i~ an
accepted ~act that of~set can only produce layer thick-
nes~c~ of about 2 - 3 ~m per pr~nting pa~sagc wherea~ by
~creen printing, layers of 20 ~um and more can be ob-
~ained.
It h~s now been found th~t ~his prejudice is based
on known off~et in~s and their developments and impro~o~
mentR which are ~lthin the knowledge of the m~n ~killed
in eh- art.
;The fir~t and main ob~ect of this invention i~ to
dov~l~p o~et or typcg~phic ink- which will p~oduce
prlnting layer~ bein~ perfectly opaquc when seen ln
inciaen~ and trav-r-inq light.
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133~ 77
Another object of the invention is to provide such
offset or typographlc inks which for~ a ~ystem capable
of producln~ opa~ue printed layers, whlch can be removed
by rubbing, on flexible ~ubstrates.
5Still another object o~ the invention is to p~ovide
such printlng lnks which can be printed on flexible
substrates already printed with indicla or other infor-
mation, and which will well adbere even on the already
pr~nted area~ the man ~killed in the art knows th~t ~t
0 i8 generally di~ficult to overprint such areais where the
adherence of the overprinting is normally low, often
unsufficient.
And a further ob~ect oP the invention i8 to provide
curable o~fset or typographic ink systems givinq opaque
covering layer~ wieh a minlmum of printing passage~ and
at low cost.
Theso ob~ects and still other6 are met by the
printing ink ~ystem of the invention which will be
defined and described below in more detail.
The rub-off prlnt~ng ink ~ystem of the invention now
elim~n~tes the drawba~ks of the screen printing pro~
~esses and t~e ~creen printing inks. The printing ink of
the inventlon which is applied by the techniques of
typography or offset and which gives printing layers
capable of being removed by rubbin0 i8 composed of two
partial systems whicb will bo described below in detail.
The system comprises a release ink for the production of
a relea8e printing, and a covering ink for the production
of an opaque, rubbing-off printing on said release
pr~nting, wherein ~he release ink and the covering ink
are chemical ~urab;le lnks printable by typographic oe
o~fset proce~ses. The releaee ink contains at lea~t one
unsaturated, polymer~able compound as a binder and an
oleophobic polymer or wax as a release agent. ~he
covering ink, th~ second part of the ~ys~em, contains at
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1330177
lea~t one unsaturated, polymerizable compound as a
b1nd~tr 1~l~ A It~ C~ YIU~IIL a4 all up~:lfl~r-
Prlntlng can be accompli~hRd by typography, dry
off~et or wet offset~ All ~lexible substrate~ which can
5 be prlnted by the~e processes can be ~sed a~ printing
support~. Tbe ink distinguishes by a perfectly approp-
riate printing behaviour on all known offs~t printlng
machines. The results which are obtain~d can be compared
with the 6creen printing quality r~garding opaeity and
rubbing~of properties. The mechanical re~i~t~nce~ of
the covering metal pigmented printings are better than
tho~e of the gcreen prlnting ink~. Furthermore, the
printing 6peed i8 substantlally high~r than screen
~rinting ~p~d
lS Accoraing to thl6 lnvention, the release lnk is a
highly reactive system with chemical drying. Chemical
dryl~g ~ ln contra4t to phy~ical d~ylng only compri~i
evaporating a volatile solvent, i9 kno~n to be a poly~
merization and/or a curing reactlon tran~Sormin~ liquid
component~ lnto soiid one~ (~ee Klages, Lehrbuch der
-~ organischen Chemle, ~erl~n 1967, Vol. III, p. 394).
~ow~ver, t~i~ doeJ not necessarily mean that a chemi-
cally drying printin0 ink i~ totally free from ~physi-
cally drylng) ~olatile ~olvents.
Surprislngly, it ha~ been ound that already very
thin rele~se layer~ will be sufficient for the aimed
purpo~e, namely the degree of re~ection of the covering
layer. Witbout willing to ~e bound by an explanation
which co~ld bc l~mit t~e inventlon, there ~e indica~
~n 1 i ~n~ th~t ~h~ o ~gor~o ln ~ho rclo~e~c p~ln~lng
ink will mlqrate during the poly~erization of the
binde~ ~oward~ ~he surPac-s or will be displaced thereto
~ c~ Lh~y ~L~ IIU lu~ cumpatlb~e wl~n tne po~ymerlzea
blnder. ~n ~ny ca~e, the release effect is enhanced
after polymerlzation.
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As a polymerizable system, modified un~atur~ted
vegetable oil~ and fat~ can be used in the relea~e ink
a~ well a~ in the covering ink~ Modifylng component~ are
I for example colophonium and rosin optionally partially
e~terified, aromat$c acids or allphatic alcohol~. In
this case, the knOwn metalic cataly~ts, specially
; ~obalt or manganese nophthenate or octoate, can be used.
These ink~ may contain small a~ounts of hlgh boiling
solvent~, about up to 10 ~, a~ a vi~cosity controlling
¦ 10 agent.
~he lnvention fur~her comprisee release and covering
I ink~ whose dryl~g is initiated by radiation, namely
I whose binder~ polymeriz~ or reticulate under the ln-
¦ fluence of ultraviolet light (UV light) and which will
1~ 15 be used in ~uch cases where the already existing offset
- printing machine is equipped wlth an ultraviolet dryer.
The~e in~ sy~eems of the lnventlon will be used on
sheet and rotary printlng machines. An important advan-
tage of the printing ~ystems of the invention is the
immediate drying of all come~nents ~nd tbus the possi-
bility of immediate further proce~sing.
` ~ As a general ~ule, the covering prlntlng ink is a
two component ~ys~em. One component contains ~he poly-
merizable binder together with the accelerator and any
othor additive6, and the other component is a metal
'~ pigment paste. Both component~ ar~ normally mixed
together lmmediately before printing accordin,g to a
' predete`rminated mlxing ratio.
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A~ a pigment, very finely devided metals normally
u~ed in p~inting in~ will the employed. Such metal~ are
aluminum whlch ~ay b- coloured by anodisation, bras~
but even copper, sll~er and gold for very high quality
I purpo~es.
The compon~nt~ to bo used in ~he peinting inks are
3S gen-rally known per se. Pre~erably, the rele~ae ink
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cont~ini as a release agent, a polysiillcon compound
together with a mi~rocrystallin~ wax, but these two
substance~ can al50 be used separately. Particularly
prefered are polysiloxane acrylates a~ release agents in
S the relea~e ink.
The following examples are given only for illustra-
tion purpo~es. They w~ll no~ llml~ the invention whose
s~ope i8 defined by the claims. All amo~nts given in the
examples are by weight and refer to the weiqht of the
finiished ~nk lf not otherwise indicated.
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ExamPle 1
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Air-drying infrared active printing ink ~ -
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A. Relea~e ink
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The following components are mixed together:
- vegetable oil haviny an eleastearinic :~
acid content of about 75 ~ by weight and
modified with rosln (Oil CP):25 to 35
- llnseed oil refined and modified with
acid, alcohol and ro6in tOil CL~: 30 to 36
- polysillcono and microcrystalline wax: 25 to 35
25 - cobalt naphthenate, mangane~e
; naph~henate 0,10 to 0,20
- aromate free mineral oil, b.p. 240
to 310 Cs 5 to 10~ - -
30 ~ Coverinq lnk -~
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- Ol~ CP: S to 15
- Oil C~s 40 to 50
- ~luminum paisite, calculated as Al 35 to 4S~
- cobalt naphthenAte, manganese
n~phthenate 0,1 to 0,2
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- aromate free mineral oil, b.p. 240 -
to 310 Cs 5 to 10~
For printing, fir~t the releasing ink i~ printed by
wet offset or preferably by typography and ary off~et
until a glossy printing is produced after drying. In
most cases, t~o pas~age~ are sufficient. ~he printing ls
then stored for about 48 hour~ in order to complete
curing by oxidation.
~hereafter, the covering ink is printed in the same
manner where only one passa~e is generally ~ufflcient.
After the chemical drying o~ the covering layer, the
rub-off printin~ i6 ready for use.
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W drying println~ ink
A ~elease ink
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- - prepolymer ba~ed on epoxy-, urethane~
polye~ter- or styrene-butadiene-acrylate,
alone o~ in combination tPrepolyme~20 to 50
- - multifunct~onal acrylat~ monomers:20 to 40%
- poly8110xane ~crylate: 10 to 30%
- benzoph~none 4 to 6
` - amine based co-lnltiators 6 to 15S
- acetophenone deri~ative~ or benzil ketals: 4 to 6S
- 1uorinated organic ~alts: 1 to 3
- paraf~ine and teflon waxe~ 5 to 10
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- prepolymer I~ 80 to 90~ `
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~ multifunc~lonal acrylate monomers:o to 10
- acetophenone deriv~tives or benzll ketals: 4 to 64
ne ba~ed co-lnltlatori~ 4 to 6%
:
5component 2:metal paste
~ aluminum bron~e (gold or silver bronze) 2 60 to 70%
- solvent and wetting agent: 40 to 30
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The drying of thiiEi ~ystem requires UV drying in~
8tallations which are g~nerally used presently in the
field of o~fset and typographic printing. The drying ~8
effected by intermediate and/or final drying and is
accompli~ihed ~a~iter than the heat induced chemical
drying.
In general, both inks of the system may be applied
in dry offset processes and by typography, thicker ~-
coverlng layer6 ~elng obtained in typography by means of
nyloprint clichQs.
First, the release ink i8 printecl. According to the
proper~les of the support, one or two applications may
be nece~sary for complete covering. The application can
be made ln two printing units by wet-in-wet or wet-on-
dry, an intermediate drying being effected by UV. A ~ -
su~iciently thick release layer is visible by gloss and
the illing degreo o the printing and is a ne~esa~ry
condition for the good rubbing effe~t of ~he me~al
pigmented covering layer printed afterwards. ~ ;~
When the release printing paiss~8 the UV dryer,
spontaneou3 drying, i.e. polymerizatlon~ of the layer i8
obtained. This lay~r will then be oveS~prlnted by the
covering printinq ink.
~n order to obtain the covering ink ready for use,
~he Yarni~h (component 1) is thoroughly mixed with the -
metal pa~te (component 2) in a weight ratio eomprii3ed
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1330177
between about 5:5 and abou~ B22, preferably about 6:4 to
about 7:3, according to the desired covering degree. In
order to perfeetly coverin~ the undergroUnd colour which
i8 already covered by the teansparent release prlnting
and which should correspond, as far as pos~ible, to the
tone of the metal ink, the appllcation of the covering
ink ~hould be made in two prlnting units by wet-in-wet
or wet-on-dry with an intermediate drying by UV.
The intermediate drying prod~ce~ a thicker co~ering
layer and a ~ub~tantially better overall dryin~ of the
printing~
The printing inks of the ~nvention can be modlfled
in the scope of the cla~m6 and its aqulvalents. For
example, pigments or other dyestuffs can be incorporated
in All inks. The nature and the amount of the components
can be chan~ed and adapted to speclal uses. It is only
important that the inks must be capable o~ chemlcally
drying~ The 6ubstrate to be printed may be a paper or
any other substrate, for example plastic sheets.
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