Self-adhesive stamps

Details Self-adhesive stamps Self-adhesive stamps

1996-09-27

1999-05-11

Green, Brian K.

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

40638, 40630, 156267, 156277, 156291, 283 71, G09F3/04

Patent

active

059024399

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to self-adhesive stamps which may be used for a variety of purposes, such as fiscal stamps, redemption stamps, savings stamps, gift stamps etc. In particular, it relates to self-adhesive postage stamps.
Conventional postage stamps are provided with a backing layer of water-soluble adhesive that must be moistened prior to affixing the postage stamps to an envelope or mail piece. In recent years, a demand has developed for self-adhesive postage stamps provided with a coating of pressure-sensitive adhesive that does not need to be moistened prior to use. Such self-adhesive stamps are merely peeled off a releasable backing sheet and then pressed onto an envelope or mail piece. The layer of pressure-sensitive adhesive forms a bond between the stamp and the mail piece substrate. In this way, the mess and unreliability of the moistening step necessary with conventional postage stamps is avoided.
Existing self-adhesive postage stamps are manufactured from self-adhesive label stock or purpose-prepared self-adhesive stock. The self-adhesive stock consists of a sheet of coated paper bonded to a peelable backing sheet by a layer of pressure-sensitive adhesive. The backing sheet can be peeled off (or the stamp can be peeled from a backing board) to expose the pressure-sensitive adhesive, which has been applied as an all-over coating. The pressure-sensitive adhesive is normally an aqueous based polymer adhesive. The self-adhesive postage stamps are manufactured from the said adhesive stock by, first, printing a plurality of postage stamp designs on the prepared stock, followed by die cutting the coated paper (but not normally the backing sheet) along the edges of the postage stamp designs, so that individual postage stamps can be peeled off the backing. Self-adhesive postage stamps made in this way are currently available in several countries, including France, Australia and the U.S.A..
Self-adhesive stamps comprising a layer of stamp paper and a layer of pressure-sensitive adhesive mounted on a backing sheet are described in GB-A-1414777, GB-A-2048817 and DE-A-4215834.
The self-adhesive postage stamps made as described above suffer from numerous drawbacks. First, the coated paper used for making label stock is not normally ideally suitable for high quality postage stamps. When printing on paper which is part of a self-adhesive sandwich it is seldom possible to obtain the best print quality. The coating on the paper may or may not contain the luminescent compounds conventionally included on postage stamp papers for recognition by automatic sorting machines. Still more importantly, the cancellation marks applied to the stamps by the Post Office can sometimes be wiped off the coated papers used for making the self-adhesive stock.
A second drawback of the above method is the impracticality of making traditional perforation holes with the adhesive and release backing in situ. The problem is that the pieces of adhesive-coated paper punched out by a conventional perforating die tend to stick together in unmanageable clumps that obstruct the perforating machinery. This means that the self-adhesive stamps obtained by the above process do not currently have perforated edges. That is to say, they do not have edges with the characteristic profile produced by tearing or die cutting along a line of perforations (such as a line of circular holes approximately 0.75-1.2 mm in diameter spaced 0.2-0.8 mm apart, measured between edges of adjacent holes). The absence of perforated edges makes forgery of the stamps easier, and results in reduced customer acceptance. This drawback has been addressed by die cutting around the stamps using a die cutting tool having a zig-zag or wave-shaped blade so as to simulate the appearance of perforated edges. However, the stamps produced in this way are always readily distinguishable from stamps having true perforated edges when examined by experienced persons.
A third drawback of self-adhesive stamps produced according to the existing art is leakage of adhesive through the

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