IE60688B1 - Pad printing device for the transfer of clearly defined quantities of printing medium per surface unit - Google Patents

Abstract

In the printing pad device described, the surface of the pad (20) is recessed while retaining essentially the same external form and volume. Also described is the use of the pad for at least partially coating a substrate (22) with a predetermined pattern. The substrate (22) is a printed circuit board for manufacturing integrated circuits, a component of a pharmaceutical presentation and/or dosage form, a label with raised characters, a prepolymer or similar.

Description

The invention relates to a tampon-printing device for transferring specific quantities of printing medium per unit area and to the use of this.

Tampon-printing processes have been known since 1968 and are 5 also suitable for the printing of uneven surfaces, with which flexible tampons transferring the printing medium mate. A tampon printer is described by way of example in German Offenlegungsschrift 1,939,437. The picture element to be printed is etched deep in a block, namely the printing forme.

The printing medium is transferred into this block, and after a doctor operation metering the printing medium received in tha block the printing medium remaining in the block is absorbed completely by the tampon and transferred to the article to be printed. A survey of the uses and properties of the tampon-printing process is found in the prospectus of Messrs TAMPOPRINT GmbH, DaimlerstraBe 27/1, KorntalMunchingen, to which reference is made in its entirety in order to avoid repetition.

Because of the small amount of space required by them, tampon printers are highly advantageous, since they can easily be integrated in production lines and can also ba encased, this being beneficial during the processing of highly active or toxic printing media, such as pharmaceuticals, etching inks, polymerisation starters or the like, for the protection of the » attendance personnel, but also for reducing the rate of evaporation of volatile substances.

Attempts have not been made hitherto to employ tampon printers for delivering exactly controlled quantities of printing medium; it has been shown surprisingly that the already known tampon-printing process allows an accurate metering of weights per unit area of up to 26 g/m2 in one printing operation with a variation of ± 2% and below.

Thus, as indicated in DE-A-3,727 , 237 Process for the production of a form of administration and/or dispensing for pharmaceutical active substances by means of a printing process'" bearing the same filing date as the applicant, it is possible to apply even highly sensitive pharmaceuticals or control membranes for active-substance release with a constant weight per unit area onto corresponding substrates.

With the use of the hitherto known means, namely a variation of the tampon material (with softer tampons more printing medium is transferred) and the viscosity of the printing medium, it was possible to apply only a slightly increased, but still always constant quantity of printing medium to a substrate; however, this quantity was not sufficient for a coating with higher weights per unit area, such as above 100g/m2, and therefore, despite outstanding properties, the tampon-printing process was unsuitable for uses, such as the production of thicker layers of materials in a predetermined pattern, and hitherto there has also been no interest at all in applying layers by this process.

Screen-printing processes involving a high outlay or complicated multi-step application processes have been employed.

It became known from CH-A-259,879, for a better distribution of the ink, to equip printing cloths for use in textile printing with a system of small parallel channels in the longitudinal direction and thereby to improve the ink distribution. It is indicated there, at the same time, that the grooves must be so large that they receive the ink effectively and distribute it easily. But the surface enlargement of a printing cloth, proposed there, does not serve for transferring larger quantities of ink, but for f ensuring a uniform distribution of the ink on the printing cloth and a satisfactory printing quality over the entire image.

The object of the invention is, therefore, further to develop the known device to the effect that even larger quantities of printing medium than are possible with conventional tampons are transferred onto a substrate.

The object was achieved, according to the invention, by a device of the relevant generic type, in that at least the pressure-contact face of the total surface of the tampon is enlarged, whilst essentially the same outer form and form volume are preserved.

The surface enlargement can consist, for example, of a trellising, roughening, grooving or knobbing of the tampon surface and can be obtained by working a finished tampon body or by producing the enlarged tampon surface during the shaping of the tampon body in a suitable mould.

In comparison with conventional ones with a smooth surface, tampons of this type are suitable for transferring more than three times the quantity of printing medium which it has hitherto been possible to transfer with the same shape.

The development according to the invention of the known tampon printers makes it possible for the first time to employ these machines and the process advantageously for the production of ' coatings in completely new sectors of use. Thus, it can be adopted, for example, in the production of labels with a thicker ink coating, and integrated circuits where there is also the possibility of printing photosensitive resists or even conductor material, for the controlled application of polymerisation starters to prepolymers, for the coating of etching fluids to make etching patterns, and for the transfer of porcelain inks, the production of pharmaceutical forms of administration and/or dispensing, such as tablets, and currently applicable systems which are also intended to include systems releasing substances through mucous membranes, that is to say rectal and vaginal forms of application.

An especially preferred use is in the production of transdermal therapeutic systems resembling sticking plasters.

By means of the invention, the quantity of printing medium delivered in a printing operation can be increased in an unexpected way and nevertheless a surprising metering constant within narrow limits obtained.

By the device according to the invention, for the first time even printing media containing active substances and small doses of active substance can be produced in a desired form without the loss of active substance, as occurred in the surface-coating processes used hitherto, for example, for transdermal therapeutic systems, with the result that expensive active substance can be saved and the problem of eliminating the waste of active substance avoided.

It is now possible, furthermore, in one production step and by the use of suitable blocks to apply simultaneously and clearly separately from one another in space a plurality of printing media, such as, for example, a plurality of inks, inks and adhesive, adhesive and an aseptic region or a region containing active substance in sticking plasters or therapeutic systems, and thereby save a production step. Both the block and the tampon itself can be temperature-controlled, if temperature-sensitive materials or even those processable only in the heated state, such as specific adhesives, are to be processed. It is possible in the same way to cool these and the entire device if temperature-sensitive materials are being treated or processed.

The choice of a suitable tampon material can take account of 5 the various requirements, and suitable for this are all the elastomeric materials familiar to an average person skilled in the art, such as natural and synthetic rubber, especially silicone rubber, which can be selected according to the necessary properties, such as processability, solvent resistance, thermal resistance or sufficient elasticity at low temperatures.

The tampon shape can be selected according to the substrate to be processed; all conventional shapes and both frustoconical and flat or egg-shaped tampons with an enlarged printing surface can be used.

In one printing operation, the device according to the invention makes it possible to transfer a weight per unit airaa of approximately 200 g per square metre of printing medium and above, and a further improvement in the transfer quantity can be achieved by process improvements familiar to an average person skilled in the art, such as the use of softer tampons, other printing media and the like.

Further features and advantages of the invention are explained below by means of the accompanying drawing. In thiss Figure 1 shows a tampon printer during the application of a layer of printing medium onto a substrate; Figure 2 shows the tampon printer of Figure 1 during the reception of new printing medium from the block; Figure 3 shows a tampon according to the invention with an enlarged surface region; Figure 4 shows a further tampon according to the invention with an enlarged surface; Figure 5 shows a cross-section through a transdermal therapeutic system resembling a sticking plaster, produced by means of the device according to the invention; and Figure 3 shows a top view of a further active-substance layer produced by the tampon-printing device according to tha invention and having two different active substances; and Figure 7 a further preferred form of administration, namely a coated pill produced by the device according to the invention.

Figure 1 shows diagrammatically the application of a layer of printing medium onto a flat substrate 22 by means of a tampon 20 designed according to the invention. For this, an elastic egg-shaped silicone-rubber tampon 20 with a coating of printing medium on the surface region of increased surface 23, which it removed in the preceding work step of the device from the depression of a block 24 shaped according to the desired pattern of application of the printing medium (see Figure 2), is pressed onto the flat substrate 22, on which it leaves behind a uniform printing-medium layer thickness after the tampon 20 has been lifted off. It is possible in the same way to print uneven substrates, for example round substrates or corrugated substrate surfaces, and also utensil shapes, etc.

Figure 3 illustrates a preferred embodiment of an egg-shaped tampon 20 according to the invention, on the upper region 23 of which, serving for transferring the printing medium, are formed groove-like depressions as a surface enlargement, by means of which it is possible to receive and transfer larger quantities of printing medium. In the process, the quantity of printing medium received is determined by the etching depth and etching shape of the block 24, from which the printing medium is removed completely after it has been applied to the block in a uniform layer thickness by means of a doctor operation, and is removed and transferred in this form.

Figure 4 shows a further preferred embodiment of the tampon 20 which is essentially cylindrical here. Formed here on the application or transfer surface of the tampon for surface enlargement are cups which likewise serve for receiving increased quantities of printing medium.

Figure 5 illustrates a sticking plaster which contains active substance and which can be produced .by the device according to the invention. This can be produced, for example, by the uniform printing of an annular acrylic pressure-sensitive adhesive layer 16 impermeable to active substance onto a covering foil 15, here silicone-treated paper, pulled off before the sticking plaster is used, and of a circular control layer 18 which by a constant thickness and its chemical and physical properties controls the passage of the substance, and by the subsequent printing of a reservoir layer 14 containing active substance by a tampon-printing device according to the invention and subsequent lamination with an impermeable backing layer, here of an aluminium polyester laminate 10. Both the control layer 18, the properties of which are guaranteed only at a high thickness constancy, and the activesubstance layer 14, the content of active substance of which can likewise be obtained in a form suitable for pharmaceutical uses only at a high thickness constancy and surface constancy of the applied layer, can be coated on by means of the device according to the invention.

Figure δ shows a sticking plaster like that of Figure 5, before the backing layer 10 is applied, a sticking plaster with two active substances 14 and 14 s being present here. This embodiment too can be produced with the tampon printer according to the invention in a single active-substance application step, and here again the pressure-sensitive adhesive ring 16 impermeable to active substance can be seen.

Figure 7 illustrates a further pharmacological form of administration which can be produced by means of the device according to the invention, namely a sugar-coated pill 30 with a two layer core 34, 36 which can be produced by printing the layer 36 onto a circular base 34, without any waste of base material 34 or of the printed layer 36.

Further embodiments, combinations and uses of the device according to the invention are possible within the knowledge of an average person skilled in the art and come within the scope of protection of the claims.

Claims (7)

1. 1. Tampon-printing device for transferring specific quantities of printing medium per unit area, wherein the surface of the tampon is enlarged, whilst essentially the same outer form and form volume are preserved.

2. Device according to Claim 1, wherein the surface enlargement consists of a trellising, roughening, grooving or knobbing of at least the part of the tampon surface which is used for transferring the printing medium.

3. Device according to Claim 1 or 2 wherein the tampon surface is enlarged by working a finished tampon body.

4. Device according to one of Claims l or 2 wherein the enlarged tampon surface can be produced in a suitable form during the shaping of the tampon body.

5. A device substantially as hereinbefore described with reference to the drawings.

6. use of the device according to one of the preceding claims for the at least partial coating of substrates in a predetermined pattern, the substrate being a circuit board for the production of integrated circuits, a constituent of a pharmaceutical form of administration and/or dispensing, a label with raised lettering, or a prepolymer.

7. „ use according to Claim δ, wherein the pharmaceutical form of administration and/or dispensing is a currently applicable system, such as a transdermal therapeutic system.