Tape for connecting photographic films to be developed and a method for the manufacture thereof The present invention relates to a tape for con- necting photographic films to be developed, which tape comprises water-proof paper bonded with a first side thereof to a first side of a polyester film, the water- proof paper is on a second side provided with heatseal adhesive, and at substantially regular intervals unique identification codes are printed on the tape.

Such a tape is well-known in the art. Photographic films sent to a film processing laboratory come from a large number of people who want to be certain that the film they get back is their own film. To this end the films are provided with a piece of tape carrying a unique identification code. The tape has to meet a multitude of requirements. The most important ones relate to the ten- sile and tear strength, resistance to water and chemicals, temperature resistance and good readability of the code applied which may be, for example, a bar code. With the known tape, the second side of the water-proof paper is printed by means of a laser printer. This tape is provided with a transparent polyester film which improves the strength properties.

The known tape has the disadvantage that the read- ability may leave something to be desired.

The object of the present invention is to provide a tape with improved readability.

To this end the method mentioned in the preamble is characterized in that the polyester film has good light scattering properties, and on its second side the polyester film carries a print of thermotransfer ink.

The use of a printable, strongly light-scattering polyester film instead of a transparent polyester film, has been found to result in improved readability of the code. For the film processing laboratories where daily very large numbers of films are developed, this is very important since any delay is a set-back for the competi-

tive position, and unreadable codes render the return of the film to the customer more difficult.

According to a favourable embodiment, the polyester is strongly light-diffusing due to the presence of pig- ment, which is preferably titanium oxide, in the polyether film.

Thus this is a simple and relatively cheap manner of obtaining a high contrast between printed and unprinted parts on the second side of the polyester film.

Conveniently, the polyester film and the water- proof paper are bonded by means of a pressure sensitive adhesive.

Such a bond is relatively cheap and reliable. Other manners of bonding are also possible, such as using a heatseal adhesive or co-extrusion.

Preferably the polyester film is provided at the second side with an agent to limit tacking to the heatseal adhesive.

This makes it easy to unroll the tape after having been rolled up, and eliminates the danger of the codes that are printed on the polyester film coming off.

The invention also relates to two methods of manu- facturing tape according to the invention for splicing photographic films to be processed, which method comprises bonding a first side of water-proof paper with a first side of a polyester film, applying a heatseal adhesive to a second side of the water-proof paper, and printing with an ink.

According to a first variant the polyester film used is a strongly light-diffusing polyester film and -in a first step, comprised of a first and a sec- ond stage, the first stage involves the application of the heatseal adhesive to the second side of the water-proof paper, and the second stage involves the provision of at least one of i) the first side of the paper provided with heatseal adhesive; and ii) the first side of the strongly light-diffusing polyester film, whose second side may or may not already have been provided with unique identifica-

tion codes of thermotransfer ink, is provided with a pres- sure sensitive adhesive, and -in a second step, the first side of the water- proof paper and the first side of the polyester film are bonded by means of the pressure-sensitive adhesive, after which, if this is not already done, the second side of the polyester film is provided with the unique identi- fication codes of thermotransfer ink.

This method is very convenient if the devices for applying the heatseal adhesive and the pressure-sensitive adhesive are situated on the same location. The first stage may take place before, after or during the second stage.

One embodiment that will be employed most frequent- ly in practice, is characterized in that the identifica- tion codes of thermotransfer ink are applied on the second side of the polyester film, after the polyester film and the water-proof paper are bonded.

This means that differing demands for the tape can be accommodated by having unprinted tape in stock. That is to say that, although the apparatus for printing is not always utilized to the full, the devices for the applica- tion of adhesives can be exploited more fully.

According to a favourable embodiment, the second side of the polyester film is provided with a coating that limits its adherence to the heatseal adhesive.

This makes it easy to unroll the tape after having been rolled up, and eliminates the danger of the codes that are printed on the polyester film coming off. The application of the agent does not hinder subsequent print- ing with thermotransfer ink, because the latter is able to penetrate the coating agent.

According to a second variant of the method, the polyester film used is a strongly light-diffusing poly- ester film and -in a first step, at least one of i) the first side of the water-proof paper; and ii) the first side of the strongly light-diffusing polyester film whose second side may or may not already have been provided with unique

identification codes of thermotransfer ink, is provided with a pressure-sensitive adhesive, and the first side of the water-proof paper and the first side of the polyester film are bonded by means of the pressure-sensitive adhes- ive; and in a second step the second side of the water-proof paper is provided with heatseal adhesive; after which the second side of the polyester film, if this is not already done, is provided with the unique identification codes of thermotransfer ink.

This method makes it possible to maintain a stock of laminate of water-proof paper and polyester, and/or to have it provided with a heatseal adhesive on another loca- tion.

Additional favourable embodiments of this variant and their advantages have already been described above for the first variant.

The invention will now be elucidated by means of an exemplary embodiment.

Printable polyester film (Petwhite crisper, Lintec, Amsterdam, the Netherlands) having a thickness of 50 ym was provided with a pressure-sensitive adhesive (P5, Lintec) at approximately 18 g/m2 and applied to water- proof paper (CP Papers, Alpha, New Jersey, USA) having a thickness of 125 ym. The water-proof paper was then pro- vided with a coating of 25 g/m2 of a black heatseal adhes- ive (paper with adhesive is available as RD547 from PPI, Waterford, Ireland). In the same processing track the polyester film was provided with a release agent on sili- cone basis (PPI).

The resulting tape was cut to widths of 19 and 25 mm.

Despite the presence of the release agent, it was possible to print on the polyester film by means of a thermotransfer printer (Zebraprinter 90 xiII, Willet, Schiedam, the Netherlands) using thermotransfer ink (TK- FB-R-0028375-00-A, T&K Strichcode service GmbH, Bielefeld, Germany). The result was a printed film which, after assessment according to the NEN standard using an appar-

atus generally known in the art, showed an improved read- ability due to the increased contrast between printed and unprinted parts.

It was shown that the tape can be applied without problems at the temperature and pressure commonly used for heatseal adhesive (170°C (which temperature has been selected from a range of 120-200°C)) and pressure (4-7 atm for 1 sec.)).