Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DESCRIPTION
The invention relates to a pad printing device for the transfer of clea-
rly defined quantities of printing medium per surface unit, as well
as the use thereof.
Pad printing processes have been known since 1968 and are also suitablefor printing uneven surfaces to which adapt the flexible printing medium-
transferring pad. A pad printer is e.g. described in DE-OS 19 39 437.
The pictorial element to be printed is etched in sunk manner in a block,
i.e. the printing form. The printing medium is transferred into said
block following a doctor blade process which doses the printing medium
received in the block, the pad completely absorbs the printing medium
left behind in the block and transfers it to the object to be printed.
A survey of the uses and characteristics of the pad printing process
appears in the brochure of Tampoprint GmbH, Daimlerstrasse 27/1, Korntal-
Munchingen, to which reference should be made to avoid unnecessary
repetition.
Due to their limited space requirements, pad printers are very advan-
tageous, because they can be integrated without difficulty in production
lines and can also be encapsulated, which is helpful when processing
highly active or toxic printing media, such as medicaments, etching
inks, polymerization initiators, etc., for the protection of operating
personnel and for reducing the evaporation rate of volatile substances.
Hitherto no attempt has been made to use pad printers for the delivery
of precisely controlled printing medium quantities. It has surprisingly
been found that the known pad printing process permits an accurate dosing
of weights per unit area of up to 26 g/m2 in a printing process with
a variance of + 2% and below.
As described in the parallel German application filed by the Applicant
on the same application date and entitled "Process for the production
of an ~r~n~qtration and/or dosage form for medicament active substances
~'
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by means of a printing process", even highly sensitive ~ c~ nts or
control membranes for active substance deliveries can be applied with
a constant weight per unit area to corresponding substrates.
The use of the hitherto known means, namelg variation of the pad material
(more printing medium is transferred in the case of softer pads) and
the viscosity of the printing medium could only lead to the delivery
of a slightly increased, but still constant quantity of printlng medium
to a substrate. However, this quantity was not sufficient for coating
with higher weights per unit area, such as over 100 g/m , so that despite
excellent characteristics, the pad printing process was unsuitable for
uses such as the production of thicker layers of materials in a predeter-
mined pattern and there has also been no interest up to now in applying
coatings by using this process. Instead complicated and costly screen-
process printing or complicated multistage application processes were
used.
The problem of the present invention is to so develop the known device
that it is also possible to transfer to a substrate larger printing
medium quantities than is possible with conventional pads.
According to the invention this problem is solved by a device of the
aforementioned type in that at least the print contact surface of the
overall surface of the pad is increased, whilst essentially retaining
the same outer shape and shape volume.
The surface enlargement can e.g. comprise screening, roughening, grooving
or burling the pad surface and by working a finished pad body, or by
producing the enlarged pad surface during moulding of the pad body in
a suitable mould. Compared with conventional pads with a smooth surface,
the novel pad is suitable for transferring more than three times the
hitherto transferable printing medium quantity.
As a result of the inventive development of the known pad printer, it
is possible for the first time to use these r~ch~nes or this process
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in completely new fields and in advantageous manner for producing coat-
ings. It is therefore e.g. usable in the production of signboards witll
a thicker paint application, integrated circuits, in which photolacquers
or conductor materials can be printed, as well as for the planned appli-
cation of polymerization initlators to prepolymers, for applying etching
liquids for producing etching patterns, for transferring porcelain paints,
for producing pharmaceutical administration and/or dosage forms, such
as tablets, as well as dermally applicable systems, which also includes
those systems supplying substances through mucous membranes, i.e. rectal
and vaginal ~ nl~tration forms. A particularly preferred use is in
the production of plaster-like, transdermal therapeutic systems.
The invention makes it possible to unexpectedly increase the printing
medium quantity delivered in a printing process and still obtain a con-
stant dosing within narrow limits.
The inventive device makes it possible for the first time to produce
in a desired form active substance-containing printing media and small
active substance doses without any loss of the active substance, such
as has been hitherto possible in the surface coating processes, e.g.
for transdermal therapeutic systems, whereby expensive active substance
is saved and it is possible to obviate the problem of active substance
waste Pli n~tion.
It is now possible in a single production stage through tlle use of suit-
able blocks to apply simultaneously and in spatially clearly separated
manner several printing media, such as e.g. several dyes, dyes and adhe-
sive, adhesive and an aseptic or active substance-containing product
in the case of plasters or therapeutic systems and consequently to save
one production stage. The block and also the pad can be thermally cont-
rolled, in the case of having to process temperature-sensitive materials,
or materials only processable in the heated state, such as certain adhe-
sives. It is possible in the same way to cool the same and the complete
device, if temperature-sensitive materials are to be worked or processed.
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Through the choice of a suitable pad material it is possible to take
account of the different requirements, so that all rubber-elastic mater-
ials known to the Expert are suitable, such as natural and synthetic
rubber and in particular silicone rubber, which can be selected in accor-
dance with the required properties, such as workability, solvent resis-
tance, thermal stability or adequate elasticity at low temperatures.
The pad shape can be chosen in accordance with the substrate to be proc-
essed. Thus, it is possible to use any conventional shape, such as
frustum-shaped, as well as flat or oval pads with an enlarged printing
surface.
By means of the inventive device, it is possible in one printing process
to transfer a weight per unit area of approximately 200 g/m2 of printing
medium and more. A further improvement to the transfer quantity can
be achieved by process improvements known to the Expert, such as the
use of softer pads, other printing media, etc.
Further features and advantages of the invention can be gathered from
the following description relative to the drawings, wherein show:
Fig. 1 a pad printer on applying a printing medium coating to a
substrate.
Fig. 2 the pad printer according to fig. 1 on taking up new
printing medium from the block.
Fig. 3 an inventive pad with an enlarged surface area.
Fig. 4 a further inventive pad with an enlarged surface area.
Fig. 5 a cross-section through a transdermal, plaster-like, thera-
peutic system produced by the inventive device.
Fig. 6 a plan view of a further active substance coating produced
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wlth the inventive pad printer and having two different active
substances.
ig. 7 a further preferred administration form, namely a dragee prod-
uced with the inventive device.
Fig. 1 shows the application of a printing medium coating with an inven-
tively constructed pad 20 to a flat substrate 22. An elastic, oval
silicone rubber pad 20 with a printing medium coating on the enlarged
surface area 23 taken in the preceding working stage of the device from
the cavity of a block 24 shaped in accordance Witll the desired pattern
for the application of the printing medium (cf. fig. 2), which was prin-
ted on the flat substrate 22, on which it leaves a uniform printing
medium coating thickness following the removal of pad 20. It is possible
in the same way to print uneven substrates, e.g. circular substrates
or corrugated substrate surfaces, such as utensil shapes, etc.
Fig. 3 shows a preferred development of an inventive oval pad 20, on
whose upper area 23 used for printing medium transfer are formed groove-
like depressions as a surface enlargement and as a result of which it
is possible to absorb and transfer larger printing medium quantities.
The absorbed printing medium quantity in the present process is deter-
mined by the etching depth and shape of the pad 24 from which the prin-
ting medium is completely removed, after previously being placed in
a uniform coating thickness on the block by means of a doctor blade
process and in this form is removed and transferred.
Fig. 4 shows another preferred development of the pad 20, which in thiscase is essentially roller-like. On the transfer or application surface
of the pad are formed cups for enlarging the surface and which also
serve to receive increased printing medium quantities.
Flg. 5 shows an active substance-containing plaster which can be produced
by means of the device according to the invention. This can e.g. be
produced by the uniform pressing of a ring-like, active substance-
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impermeable acrylate contact adhesive coating 16 to a cover film 15,which in this case is siliconized paper removed prior to the use of
the plaster, as well as a circular control coating 18, which controls
through constant thickness and its physicochemical characteristics the
substance passage and prlnting on by means of an inventive pad printer
an active substance-containing reservoir coating 14 and subsequent lamin-
ation with an impermeable backing, in this case an aluminium-polyester
~ n~te 10. Both the control coating 18, whose characteristics are
only ensured in the case of high thickness constancy, and the active
substance coating 14, whose active substance content is also only ensur-
able in the case of high thickness and sur~ace constancy of the applied
coating in a form suitable for pharmaceutical uses, can be applied by
means of the inventive device.
Fig. 6 shows a plaster as in fig. 5 prior to the application of the
backing 10, this plaster having two active substances 14 and 14'. This
embodiment can also be produced with a single active substance appli-
cation stage using the inventive pad printer, it once again being poss-
ible to see the active substance-impermeable contact adhesive ring 16.
Fig. 7 shows another pharmacological administration form which can be
produced with the inventive device, namely a sugar-coated dragee 30
with a two-coat core 34,36, which can be produced by printing the coating
36 on a circular substrate 34, without any wastage of the substrate
material 34, or the print coating 36.
Further developments, combinations and uses oE the inventive device
are readily apparent to the Expert and fall within the protective scope
of the present claims.
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List of Reference Numerals
Backing
14 Active substance coating
Cover film
16 Adhesive coating
18 Control coating
Pad
22 Substrate
23 Enlarged surface
24 Block
Tablet
32 Sugar covering
34 Active substance coating
36 Carrier coating
