WO1999031643A1

WO1999031643A1 - Self-adhesive stamps

Info

Publication number: WO1999031643A1
Application number: PCT/GB1998/003668
Authority: WO
Inventors: John Alec Pike; James Leslie Board
Original assignee: De La Rue International Limited
Priority date: 1997-12-12
Filing date: 1998-12-09
Publication date: 1999-06-24
Also published as: GB9726394D0; AU1495699A

Abstract

A method of manufacturing self-adhesive stamps, the method comprising providing a plurality of stamps in the form of a web (1) or sheet(s); applying a layer of pressure-sensitive adhesive (5) and peelable surfaces of a plurality of backing sheets (14) to a rear surface of the web or sheet(s) whereby each backing sheet underlies a plurality of stamps; and separating the backing sheets from each other.

Description

SELF-ADHESIVE STAMPS

The invention relates to methods of manufacturing self-adhesive stamps. Self-adhesive stamps may be used for a variety of purposes, such as fiscal stamps, redemption stamps, savings stamps, gifts stamps etc. as well as 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 or reel 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 USA. These postage stamps suffer from a number of disadvantages which are explained in more detail in WO 95/27278. In WO 95/27278, a new form of self-adhesive stamp is described, the stamp comprising a layer of stamp paper having perforated edges; a layer of pressure-sensitive adhesive on the back of the stamp paper; and a peelable backing sheet covering the adhesive, wherein the pressure-sensitive adhesive layer is patterned such that there is little or no adhesive adjacent to the perforated edges of the stamp paper. This development provides a much more easily usable self-adhesive stamp. As described in WO 95/27278, the self-adhesive stamps are manufactured by laminating a web or sheets of stamp paper onto a web of backing material. The resultant web is then cut up into individual sheets carrying a plurality of stamps.

It is important to be able to handle the resultant sheets of stamps in a convenient manner and conventionally postage stamps are supplied in paper board booklets, pads of 50 or 100 sheets, concertina fashion and the like. In the case of conventional postage stamps with a water- soluble adhesive, the stamps are in the form of a perforated sheet which is secured at one end into the booklet. The stamps can then be individually removed by tearing along the perforations. An equivalent booklet for self-adhesive stamps could be provided by securing the self-adhesive stamps on their peelable backing sheet into the booklet in a similar way to conventional postage stamps. It would be desirable, however, to reduce to a minimum the number of steps needed to generate such booklets of self-adhesive stamps.

In accordance with one aspect of the present invention, a method of manufacturing self-adhesive stamps comprises providing a plurality of stamps in the form of a web or sheet (s) ; applying a layer of pressure-sensitive adhesive and peelable surfaces of a plurality of backing sheets to a rear surface of the web or sheet (s) whereby each backing sheet underlies a plurality of stamps; and separating the backing sheets from each other.

In this invention, the stamps in the form of a web or sheet (s) are laminated to a plurality of backing sheets in contrast to the prior art where a single web is used. This enables materials suitable for booklets, pads, cards which can be hung on a hook and the like, such as paper board, to be utilised for the backing sheets in contrast to the prior art where much more flexible materials are needed. Furthermore, the use of separate backing sheets enables those sheets to be prepared in a variety of different ways. For example, complex printing processes can be carried out on the backing sheets prior to lamination with the web or sheets of stamps.

In most cases, each stamp is perforated around its periphery. This will typically be carried out prior to the applying step although in some cases it could be carried out after the stamps have been applied to the backing sheets.

The perforations may be circular, polygonal, star shaped or of more complex shapes. However, preferably the perforations are circular. Preferably, the circular perforations have a diameter of 0.75 -1.2mm and are spaced 0.2 -0.8mm apart, measured between edges of adjacent holes. The provision of self-adhesive stamps having genuinely perforated edges is an important feature of the present invention. Such self-adhesive stamps are harder to counterfeit than previous self-adhesive stamps, and are more acceptable to the public. The perforations could be provided in a conventional manner, by die cutting or laser.

Preferably, the front face of the web or sheet (s) is provided with a coating that contains, in addition to other components, luminescent pigments for recognition by automatic facing, cancelling and sorting machines. Preferably, the front surface of the stamps is printed with a stamp design, such as a postage stamp design. Preferably, the front face of the stamp material is coated in such a way that it permanently retains cancellation marks applied to the material by the Post Office or user authority. In fact, the stamp material is preferably similar to, or the same as, the paper conventionally used for the manufacture of postage stamps bearing a water- soluble adhesive coating.

In certain preferred embodiments, the security of the stamp is enhanced by providing shaped perforations, known as perfins, in the central part of the stamp paper remote from the perforated edges.

The pressure-sensitive adhesive may comprise any of the adhesives of this type commonly known in the art . For example, the pressure-sensitive adhesive may be a water- soluble acrylic adhesive. However, preferably, the pressure-sensitive adhesive is a hot-melt adhesive. This is preferable because the hot-melt adhesive can be applied in one step, without any need for subsequent drying of the adhesive thus having minimal impact on the stamp stability. In contrast, conventional acrylic or other polymer pressure-sensitive adhesive is normally applied in aqueous solution and then dried. This involves an additional step of drying, and the water (or other solvents used) can cause wrinkling, distortion or other problems with the stamp paper. The pressure-sensitive adhesive may be applied to the back of the stamp paper or to the backing sheet by any conventional means for applying a patterned layer, such as a nozzle, slot die or roller. Preferably, the pressure- sensitive adhesive is applied to the back of the stamp paper or to the backing sheet by printing, more preferably screen printing. This permits accurate patterning of the layer of pressure-sensitive adhesive. In particular, it allows the pressure-sensitive adhesive to be applied in a pattern such that there is no adhesive adjacent to the perforated edges around each stamp. The adhesive coating itself could be patterned within the stamp e.g. a dot structure, a stripe, mixture of solid and dot etc .

Preferably, the layer of pressure-sensitive adhesive is printed or slot coated on the back of the web or sheet (s) of stamps, or in some cases may be similarly applied to the backing sheet and then laminated to the rear of the stamps. The pressure-sensitive adhesive typically does not cover the whole of the back surface of the web or sheet (s) of stamps, but instead is preferably patterned such that there is little or no adhesive adjacent to the perforated edges of the stamps. Preferably, an adhesive- free margin of 0.1 to 5mm, more preferably 1 to 4mm, is left between the perforated edges of the stamp paper and the edge of the pattern of pressure-sensitive adhesive. This ensures that no adhesive leaks through the perforations to the front face of the stamps. Furthermore, this makes it easier to peel the stamps away from the backing sheet, since the edges of the stamps are not adhered to the backing sheet.

A layer of water-releasable adhesive may be intercalated between the web or sheets of stamps and the layer of pressure-sensitive adhesive. Preferably, the water-releasable adhesive is a moistenable adhesive of the kind conventionally used for postage stamps. The purpose of this intermediate layer of water-releasable adhesive is to make it possible for philatelists to remove the stamp from an envelope by steaming or soaking. This is difficult and not particularly efficient if there is only a layer of pressure-sensitive adhesive between the stamps and the envelope or postal item.

Preferably, the pressure- sensitive adhesive layer is applied to the back of the web or sheet (s) of stamps, and the adhesive coated layer is then laminated to the peelable backing sheets. However, it is also possible to coat the pressure-sensitive adhesive layer onto the backing sheets and then laminate the coated backing sheets onto the web or sheets (s) of stamps.

The method of the present invention offers the advantage that the stamps can be printed using conventional web or sheet printing techniques, such as web gravure printing, on conventional stamp paper that is optimised for such printing and which can also be provided with suitable luminescent coatings for recognition by automatic sorting machines. The printing can be carried out before the perforation step, if any, or it may preferably be carried out following the step of applying the pressure-sensitive adhesive and the backing sheet.

In some cases, the stamps could remain attached to each other on the backing sheets. However, preferably, following the applying step, the method comprises cutting between the stamps to separate them from each other while leaving the backing sheets intact. This aids separation of the stamps. Where perforations are provided around the periphery of each stamp, the cutting process is typically carried out through the perforations. The cut is preferably a straight line running down the middle of the lines of perforations, whereby the stamps are provided with the characteristic perforated edge profile of conventional stamps . After the applying step (and the cutting step if carried out) , the backing sheets may be separated from one another immediately or the backing sheets may first be scored and optionally folded so that the stamps are protected by respective overlapping parts of the folded backing sheets. The separated backing sheets, either before or after folding, can then be cut to produce individual sheetlets of stamps.

Typically, the stamps will not fill completely the web or sheets and so following the cutting step, surplus parts of the sheet (s) or web are removed.

In the case where a web of stamps is provided or sheets of stamps overlap more than one backing sheet, the method may further comprise removing parts of the web or sheet (s) from the backing sheet while leaving other parts in place extending in the feed direction on either side of the stamps and/or extending between successive backing sheets. This enables the surplus material to assist the feeding of the laminated product prior to being finally removed at a finishing stage.

Each backing sheet should have sufficient rigidity to feed through laminating apparatus (which typically includes a nip through which the sheets are pushed) and the necessary properties to protect the stamps. For example, each backing sheet may comprise a paper board having a weight of at least 65gsm, typically no more than 300gsm, preferably 90-200gsm. The lighter weight papers are acceptable where they have been printed or coated with varnishes etc. which increase their rigidity. Other, synthetic materials such as opaque polypropylene Teslin, Tyvec and composite backing materials such as mixed paper polymer laminates could also be used provided they have sufficient weight to provide a good support for the stamps. Typically, each backing sheet carries a release coating of for example silicone or other conventional material .

One of the important advantages of the invention is that it enables the backing sheets to be printed with indicia prior to lamination. To that end, preferably a part of each backing sheet which does not underlie stamps carries no release coating. Indicia can then be provided on the said part of the backing sheet . A further feature is to provide indicia in an area of each backing sheet which underlies the stamps and subsequently provide a release coating over that area. This has the advantage that the indicia will become visible when the stamps are removed. These indicia can be used to provide information, customer assistance, advertisements and the like. Of course, indicia could be provided underneath a release coating and in areas not provided with such a release coating.

In accordance with a second aspect of the present invention, a backing sheet for carrying self-adhesive stamps has a surface at least part of which has a peelable property, the said surface of the backing sheet also carrying indicia.

Typically, the peelable property is provided by a release coating on the substrate, the indicia being provided underneath the release coating.

Some examples of methods of manufacturing self- adhesive stamps and backing sheets according to the invention will now be described with reference to the accompanying drawings, in which: -

Figure 1 is a schematic view of a web carrying sets of self-adhesive stamps;

Figure 2 is an enlarged, schematic cross-section through part of the web shown in Figure 1 prior to laminating to a backing sheet;

Figure 3 illustrates the rear side of a stamp on the web shown in Figure 1 ;

Figure 4 is a plan view of a backing sheet showing the locations of the self-adhesive stamps; Figure 5 illustrates part of a web carrying a pair of backing sheets; and,

Figure 6 is a schematic block diagram of apparatus for producing self-adhesive stamps on backing sheets.

In a first stage of the process, a web of stamp paper 1 is produced (Figure 1) . This is shown in cross-section in Figure 2. The web comprises a layer of stamp paper 2 of the type conventionally used for printing postage stamps according to the existing art and which are provided with a layer of moistenable water-soluble adhesive only. Postage stamp designs are printed on the front surface 3 of the stamp paper (the rear surface being visible in Figure 1) to define sets of stamps 10, each set having six stamps. The outlines of these stamps 10 are shown in dashed lines in Figure 1, the periphery of each stamp being defined by perforated edges 6 (only some of which are shown in detail) . The front of the stamp paper can also be coated with a luminescent organic (or inorganic) pigment for recognition by automatic sorting machines. The rear face of the stamp paper is entirely coated with a layer 4 of moistenable water-releasable adhesive of the kind that is applied to conventional postage stamps. On the layer 4 of moistenable water-releasable adhesive of each stamp 10, there is provided a layer 5 of hot -melt pressure-sensitive adhesive. The layer 5 of pressure-sensitive adhesive does not extend all the way to the edges 6 of the stamp paper. The ho -melt adhesive is a synthetic thermoplastic rubber based adhesive for application at 150 to 170°C and available from The National Starch Chemical Company Limited under catalog reference no. 08g-1540. The weight of the hot-melt adhesive will be in the range 5 to 50gsm, for example 10 to 25 grams per square metre, preferably 15 to 20 grams per square metre, more preferably about 17% grams per square metre.

Referring to Figure 3 , it can be seen that each stamp 10 has perforated edges 6 formed by making a straight cut along the centre of a line of circular perforations. The layer 5 of pressure-sensitive adhesive is screen printed in a rectangular pattern in the centre of the stamp, leaving a margin 8 in the range 0.1 -5mm, for example approximately 3mm, wide free from adhesive around the edges of the stamp. This prevents leakage of the adhesive around the perforated edges of the stamp to the front face of the stamp, and also makes peeling of the stamp from the backing sheet easier.

The apparatus for assembling the stamps 10 into a booklet is illustrated schematically in Figure 6. The web

1 is provided on a roller 11, the web being unwound from the roller 11 and continuously feed into a screen printer 12. The screen printer 12 prints the pattern of hot -melt adhesive 5 on the back face of the stamp paper, in register with the printed stamp designs on the front face. The screen printer 12 is a hot-melt screen printer available from Meltex GmbH of Luneburg, Germany or Nordson Corporation, Norcross, Atlanta, U.S.A. The screen printed web is then supplied to a nip defined between a pair of rollers 13 where it will be laminated to backing sheets 14. A stock of backing sheets 14 is provided in a store 19 and urged upwardly by a pressure plate 20 against a feed roller 17. The backing sheets are made of paper board or the like and have been preprinted on their outer surface with information relating to their content and this will have been varnished in a conventional manner. The upwardly facing, inner surface of each backing sheet 14 has an appearance similar to that shown in Figure 4. Each backing sheet will be used to define multiple books, although for simplicity only two books of stamps 14A, 14B are shown in the drawing, and at this stage has been coated with a silicone release layer in four separate locations 15A-15D corresponding to locations on which self-adhesive stamps will be provided. In addition, conventional gravure printing has been used to print indicia 16 on areas of the inner surface where there is no silicone. Alternative printing techniques include litho, flexo, screen, gravure and variable (personalisation) print processes such as laser and ink jet. Finally, in the areas 15A, 15C, further printing has been provided as shown at 7 beneath the silicone. Thus, these areas will have been printed prior to providing the silicone release layers.

Feed roller 17 is actuated to feed individual backing sheets 14 onto a conveyor belt 21 which conveys the backing sheets to the nip between the rollers 13 so that they are in register with the stamps 10 on the web 1.

As the web 1 passes through the nip defined by the rollers 13, the self-adhesive layer 5 is facing downwardly towards the inner surface, and hence the regions 15A-15D, of the backing sheet 14. Consequently, the web 1 will adhere to the backing sheet 14 with each set of stamps 10 located within a respective region 15A-15D as shown in Figure 5. For ease of understanding, the outlines of the stamps have been shown in Figure 5 although, of course, these would normally be hidden since the backing sheets 14 are opaque .

The double laminate from the nip between the rollers 13 is then fed to a die cut unit 22 which cuts through the web 1 around the edges of the stamps 10 and thereby cuts through the centre of the perforations 6. As a result of this cut, the portion of the web 1 which is not adhered to the backing sheets 14 can be removed as shown at 23 and wound onto a reel 24. In one approach, cuts are made only around the peripheries of the stamps so that the entirety of the remainder of the web 1 can be separated. In the present example, some other parts of the web 1 are cut so that parts of the web will remain in place, adhered to portions of the silicone release coating 15A-15D which extend beyond the peripheries of the stamps 10 so that the web remains intact and can be fed on through the apparatus relatively easily.

The web is then fed on to a punch unit 25 where tabs 26 are formed in each backing sheet 14A, 14B and then on to a scoring unit 26 which scores each backing sheet along a line 27. Finally, the web is fed to a rotary shear cutter 28 which finally cuts out the individual backing sheets 14A, 14B with their adhered stamps, the individual sheets being stored in a stack 29 while the remaining surplus web material is coiled on to a roller 30. These individual sheets can then be adhered to an adhesive binding along one or more edges to form a pad or alternatively can be supplied to a folding machine which folds each sheet along the score line 27 with the stamps 10 between the folds so as to protect them. Once folded, the shorter fold can be slid under the opposite tab 26 to maintain the booklet closed. It will be appreciated that there are many modifications which could be made to this process. For example, in some cases the silicone release layer could be provided over the entire surface of the backing sheets 14A, 14B and this could be achieved using roller coating or the like. Where selected areas 15A-15D are provided then these would be printed using, for example, flexographic printing.

In another modification, each backing sheet could be provided with a window extending through the sheet to enable one or more of the stamps within a folded sheet to be visible.

In the example described, the sheets are folded only after having been cut into individual sheets. In other examples, the backing sheets 14 could be separated and then folded individually following which they are slit into the booklets 14A,14B.

Claims

1. A method of manufacturing self-adhesive stamps, the method comprising providing a plurality of stamps in the form of a web or sheet (s) ; applying a layer of pressure- sensitive adhesive and peelable surfaces of a plurality of backing sheets to a rear surface of the web or sheet (s) whereby each backing sheet underlies a plurality of stamps; and separating the backing sheets from each other.

2. A method according to claim 1, wherein the step of applying comprises the steps of coating the layer of pressure-sensitive adhesive onto the back of the web or sheet of stamps, followed by laminating the backing sheet (s) onto the coated and perforated web or sheet.

3. A method according to claim 1 or claim 2, wherein the pressure-sensitive adhesive is applied in a pattern such that there is little or no adhesive applied to the back of the stamps adjacent to the edges of the stamps.

4. A method according to claim 3, wherein an adhesive- free margin of 0.1-5mm width is left on the back of the stamps adjacent to the edges of the stamps.

5. A method according to any of the preceding claims, wherein each stamp is perforated around its periphery.

6. A method according to claim 5, wherein a plurality of stamp designs is printed on the web or sheet (s) before the lines of perforations are provided.

7. A method according to claim 5, wherein a plurality of stamp designs is printed on the web or sheet (s) after the steps of perforating and applying and in register with the plurality of stamps.

8. A method according to any of the preceding claims, further comprising, following the applying step, cutting between the stamps to separate them from each other while leaving the backing sheets intact.

9. A method according to claim 8, when dependent on any of claims 5 to 7 , wherein the cutting step comprises cutting through the perforations.

10. A method according to any of the preceding claims, wherein the pressure-sensitive adhesive is a hot-melt adhesive.

11. A method according to any of the preceding claims, wherein the layer of pressure- sensitive adhesive is coated on to the back of the web or sheet (s) or onto the backing sheet by screen printing or slot die coating.

12. A method according to any of the preceding claims, further comprising scoring the backing sheets to enable the sheets to be folded.

13. A method according to claim 12, further comprising folding the backing sheets so that the stamps are protected by respective overlapping parts of the folded backing sheets .

14. A method according to any of the preceding claims, further comprising cutting through the backing sheets to produce individual sheetlets of stamps.

15. A method according to claim 14, when dependent on claim 13, wherein the backing sheets are cut after having been folded.

16. A method according to at least claim 8, wherein, following the cutting step, surplus parts of the sheet (s) or web are removed.

17. A method according to claim 16, wherein in the case where a web of stamps is provided or sheets of stamps overlap more than one backing sheet, the method comprises removing parts of the web or sheet (s) from the backing sheet while leaving other parts in place extending in the feed direction on either side of the stamps and/or extending between successive backing sheets.

18. A method according to any of the preceding claims, wherein each backing sheet comprises a paper board.

19. A method according to any of the preceding claims, wherein each backing sheet carries a release coating, for example silicone.

20. A method according to claim 18 or claim 19, wherein a part of each backing sheet which does not underlie stamps carries no release coating.

21. A method according to claim 20, further comprising providing indicia on the said part of the backing sheet.

22. A method according to claim 20 or claim 21, further comprising providing indicia in an area of each backing sheet which underlies the stamps and subsequently providing a release coating over that area.

23. A method according to claim 22, wherein the indicia under the release coating are provided in register with the stamps .

24. A method of manufacturing a backing sheet for use in a method according to any of the preceding claims, the method comprising providing a substrate with a surface part of which provides a peelable property; and providing indicia on the said surface in an area which does not have the peelable property.

25. A method of manufacturing a backing sheet for use in a method according to any of claims 1 to 23, the method comprising providing indicia on the substrate; and providing a release coating such as silicone over the indicia.

26. A backing sheet for carrying self-adhesive stamps, the backing sheet having a surface at least part of which has a peelable property, the said surface of the backing sheet also carrying indicia.

27. A backing sheet according to claim 26, wherein the peelable property is provided by a release coating on the substrate, the indicia being provided underneath the release coating.

28. A backing sheet according to claim 26 or claim 27, wherein indicia are provided on the surface of the substrate in an area not having the peelable property.

29. A backing sheet according to any of claims 26 to 28, wherein the substrate comprises paper board.

30. A backing sheet according to any of claims 26 to 29, the sheet carrying a plurality of self-adhesive stamps on the area of the surface of the substrate defining a peelable property.

31. A backing sheet according to claim 30, when dependent on at least claim 27, wherein the stamps are provided in register with the indicia underlying the release layer.

32. A backing sheet according to claim 30 or claim 31, wherein the substrate is folded so that the stamps are protected and secured between the folds.

33. A stack of backing sheets according to any of claims 26 to 31, each backing sheet of the stack being removably adhered on one or more sides to a binding.