EP0342982A2

EP0342982A2 - Printed self-adhesive tape

Info

Publication number: EP0342982A2
Application number: EP89305051A
Authority: EP
Inventors: Stephen Allen Wilson
Original assignee: DRG UK Ltd
Current assignee: DRG UK Ltd
Priority date: 1988-05-18
Filing date: 1989-05-18
Publication date: 1989-11-23
Also published as: GB8811731D0; EP0342982A3

Abstract

Self adhesive tapes and labels especially suitable for security purposes comprise by way of example a conventional release layer 1 whereby the tape may be rolled into or unrolled from a spiral form, an ink layer 2 visible under ultraviolet light, applied as an expanse of ink, a pattern or one or more alphanumeric characters or other markings; a support substrate 3 typically consisting of UPVC, a conventional primer layer 4, and a conventional pressure-sensitive adhesive layer 5. As an alternative the ink which is visible under ultraviolet light can be printed upon the under surface of the substrate provided that this is transparent. Such tapes or labels can be used for packaging or labelling as a security feature which is visible under ultraviolet light but not otherwise visible.

Description

THIS INVENTION relates to self-adhesive tapes and labels and more especially to printed tapes and labels.
It is known to provide rolls of tape, or sequences of labels separated for example by perforations, with one face self-adhesive by virtue of a pressure-sensitive adhesive and with the other face exhibiting printed matter. Usually the outer surface is printed; less usually, printing is effected on the inner surface of the transparent outer face. Moreover, an outermost release layer can be provided to facilitate unrolling the tape from a roll.
Security printing of tapes, for example of a visible intricate pattern peculiar to one organisation, is also known. This gives a visible sign of origin upon packaging made up using such tape.
The present invention sets out to provide printed tape of a higher degree of security against theft or counterfeit contents provided in a package or the like.
In one aspect the invention consists in a length of polymer or cellulosic thin flexible substrate coated on one face with a pressure-sensitive adhesive and exhibiting an indicium of an ink which has an altered visibility, or a sole visibility, under applied light of non-visible wavelength.
The length of substrate can be a roll or a strip or a label or sequence of labels. Usually the present invention is concerned with polymeric substrates.
Preferably the ink is such that it changes appearance under ultraviolet light, most preferably the ink is such that it is invisible except under ultraviolet light, although the invention extends to materials in which such u.v.-sensitive ink is mixed with an ink normally visible i.e. under light within the normal spectrum. The indicium is normally upon the top surface, that is to say the surface most remote from the pressure-sensitive adhesive. However, if a transparent polymeric tape is used printing could be affected beneath the polymeric layer, upon its undersurface.
In a preferred embodiment the substrate is UPVC polymer, and the ink is soluble in methylethylketone to facilitate printing on such a polymer, being preferably invisible (or if visible, only as matt ghosting) except under applied ultraviolet light.
In another aspect the invention consists in a method of manufacture of the above material in which the ink having altered or sole visibility under the applied light is printed upon the substrate before, during the course of , or subsequent to other printing visible under the normal light spectrum.
In a further embodiment the invention consists in a method of security marking of article such as a package, in which a material as described above, especially a tape or a label, is applied to the package as a fastening or decorative feature carrying a security indicium of altered visibility or of sole visibility under the applied light of non-visible wave-length.
The invention will be further described with reference to the accompanying drawings in which:-

Figure 1 is a diagrammatic section through one embodiment of pressure-sensitive adhesive tape,and
Figure 2 is a section through a second embodiment of a pressure-sensitive adhesive tape.

In Figure 1 the composite consists of five layers.
The uppermost layer 1 is optional but usual, and consists of a conventional release material whereby the tape may be rolled into or unrolled from a spiral, as well known in the art. The layer 2 is an ink soluble in methylethyl ketone and visible under ultraviolet light, applied as an expanse of ink or as one or more alphanumeric characters or a dot or other mark. Layer 3 is the basic support substrate of tape and consists in this embodiment of a UPVC layer, typically 35 microns in thickness, which can be transparent or coloured. Layer 4 is a layer of primer, suitable to cause layer 5 which is a conventional pressure-sensitive adhesive either clear or coloured, to adhere to the UPVC. Some such adhesives can be used without such a primer layer 4.
Figure 2 shows a modified embodiment. Layer 6 is thesrelease layer, which as before is optional but usual. Layer 7 is a layer of the UPVC polymer, which in this embodiment must be clear and transparent. Layer 8 is the ultraviolet sensitive ink, as described above, but printed upon the underface of the polymer.
Layer 9 is again a layer of primer, which is usual although not essential. If used it should be chosen to be compatible with the ultraviolet sensitive ink.Layer 10 is the conventional adhesive as before.
It will be apparent to the man skilled in the art that a conventional type of tape and conventional pressure-sensitive adhesives can be used. For example, the tape substrate can be of from 20 to 60 microns in thickness, more preferably 30 to 40 microns. Any width of tape can be used. UPVC is a valuable substrate, since it provides ready printing with methylethyl ketone, but polypropylene or polyester substrates may also be used with a suitable solvent (such as for example n-propyl alcohol) for the UV-sensitive ink. The tape can of course be used in any conventional thickness. The adhesives used are conventionally natural or synthetic rubbers tackified with resin and are well known per se.
The printing proceses s used to produce tapes of the nature described in relation to Figures 1 and 2 are typically flexographic, that is to say, printing processes using flexible rubber or polymer printing plates or cylinders. Gravure processes using metal cylinders may also be possible for long runs of such printing.
Th indicia applied by the printing processes can be for example an expanse of ink, a specific pattern, one or more dots, specific words or letters, numbers, number sequences, a logo indicating origin in commerce, or a background print for printing of a normally visible nature. Typically, the printing in UV sensitive ink is in some way incorporated into a conventional visible print design.
Printing with the UV-sensitive ink can be carried out during the same pass through the machine as normal printing. Typically, normal printing is carried out through a sequence of different printing stations, which (for example) print various colours. The UV-sensitive ink could supplement or replace such a printing station.
It is within the scope of the invention to add the UV sensitive ink, or the like, to an existing visible coloured ink. Care should be taken that the chemicals in the ink, or the visibility characteristics, do not nullify any visibility-change effect which takes place under applied light.
The use of ultraviolet light to cause the ink to have an increased visility, or sole visibility, is most preferably such that a longwave ultraviolet light is used, rather than shortwave. It is however within the confines of the invention to print upon the tape more than one security feature which show up at different wavelengths of applied light. Typically, the applied light can be a handheld or stationary ultraviolet lamp or other such light source. It is moreover within the scope of the invention to utilise an ink which, under applied light, gives an alteration of visibility itself not detectable by the naked eye, but detectable by a suitable sensor. In such a case, security-printed tape would be even more secure, since no ready determination could be made as to its labelling without prior knowledge of the system used.
The use of UPVC as a substrate makes it valuable to use an ink which is sensitive to ultraviolet light and also soluble in methylethyl ketone. For example, the ink available from Coates Limited under the reference AN 69292 gives a strong yellowish green fluorescence under ultraviolet light and is valuable in the practice of this invention. However, the man in the art will appreciate that any ink fluorescing under,or otherwise sensitive to ultraviolet light and soluble without detrimental change in methylethyl ketone can be used for such security printing on UPVC.
It is possible to apply the method of the invention upon polypropylene or polyester tape. In such an instance, the ink as well as being sensitive to ultraviolet radiation should also be soluble in an alcohol such as propyl alcohol, to facilitate printing.
It will be apparent therefore that the invention provides a material which may be used for packaging, strapping, or labelling of packages or articles thereby to give a concealed but readily ascertainable mark of the origin, whereby theft or counterfeiting of the packaged article in question is more readily detectable and eventually deterred. The use of pressure-sensitive tapes as packaging is or course widespread, and if any such tape might contain security marking invisible to the naked eye (and possibly even invisible to a particular applied light utilised by determined counterfeiters or thieves) there will be a reluctance to handle such goods.
The invention can also be used in more specialised circumstances to provide non-visible dating or sequencing of labels or packages.

Claims

1. A length of thin flexible polymeric or cellulosic substrate coated on one face with a pressure-sensitive adhesive and exhibiting an indicium of an ink which has an altered visibility, or a sole visibility, under applied light of non-visible wavelength.

2. A length of coated substrate as claimed in Claim 1 in the form of a roll of tape.

3. A length of coated substrate as claimed in Claim 1 in the form of a roll of labels separated by perforations.

4. A length of coated substrate as claimed in any of Claims 1 to 3, in which the substrate is from 20 to 60 microns in thickness.

5. A length of coated substrate as claimed in any one preceding claim in which the ink consists of, or comprises as the component of a mixture, material which is invisible except under ultraviolet light.

6. A length of coated substrate as claimed in Claim 5 in which the substrate material is UPVC (unplasticised polyvinyl chloride) and the ink is soluble in methylethylketone.

7. A length of coated substrate as claimed in Claim 6 in which the ink is AN 69292.

8. A length of coated substrate as claimed in any one of Claims 1 to 5 in which the substrate material is polypropylene or polyester and the ink is soluble in n-propyl alcohol.

9. A length of coated substrate as claimed in any one preceding claim in which the ink is printed on that face of the substrate further from the adhesive layer.

10. A length of coated substrate as claimed in any one of Claims 1 to 8 in which the ink is printed on that surface of the substrate closer to the adhesive layer.

11. A method of manufacture of a length of coated substrate as claimed in Claim 1 in which the ink is printed upon the substrate before, during the course of, or subsequent to other printing visible under the normal light spectrum.

12. A method as claimed in Claim 11 in which the ink is printed upon the substrate in a supplemental or replacement printing station within a sequence of different printing stations.

13. A method as claimed in Claims 11 or 12 using flexographic printing procedures.

14. A method of security marking of articles such as packages in which a coated substrate as claimed in any one of claims 1 to 10 in the form of a tape or label is applied to the article as a fastening, identifying or decorative feature.