WO2009141662A2

WO2009141662A2 - Security label

Info

Publication number: WO2009141662A2
Application number: PCT/GB2009/050558
Authority: WO
Inventors: Robin Mansel Mitchell; Stephen Nicholas William Cross
Original assignee: Inveresk Plc
Priority date: 2008-05-22
Filing date: 2009-05-22
Publication date: 2009-11-26
Also published as: GB0809312D0; WO2009141662A3

Abstract

A security label comprising a paper substrate, the paper substrate being impregnated with resin, wherein there is at least 5wt%, preferably at least 10% resin in the label. In preferred embodiments the resin is urea formaldehyde and there is a hardwood to softwood ratio of at least 1.5:1. Embodiments of the invention provide small adhesive labels, less than 20cm ², which may be used as security labels, that is, they are difficult to tamper with and remove and so may be used to demonstrate the authenticity of the goods to which they are affixed. Also disclosed is a method of fabricating such a label.

Description

SECURITY LABEL

This invention relates to a tamper resistant or tamper evident security label and more particularly to a tamper resistant security label which is adapted to resist an attempt to remove the label or demonstrate that the label has been tampered with.

Manufacturers of many different types of consumer goods have to address the problem of the goods being tampered with between leaving the manufacturer's premises and the point of sale. This protects both the manufacturer's commercial operation (such as brand protection) and prevents containers from being refilled with counterfeit products, but also protects the end user who can be assured that they are purchasing goods of the intended origin and quality.

The problems are particularly prevalent in relation to high cost goods such as perfumes or scents and alcohol but also in relation to foods, particularly baby foods and medicines and pharmaceuticals where any tampering with the contents or replacement of the intended contents could have serious consequences to the health of the end user.

Another industry which must address the problem of counterfeit goods is the electronics industry where goods are often labelled with proprietor information, barcodes, licence or calibration data or other important information which assures the consumer that the product they have purchased is authentic or suitable for the intended use. Moreover workplaces often need to maintain an inventory of tangible assets for security and/or accounting purposes and so identifying the particular asset, such as a computer or a monitor, is important.

It has become routine to provide labels on such goods which have built in mechanisms for preventing removal or alerting the end user that an attempt to tamper with the label has occurred. These labels are commonly referred to as tamper resistant or tamper evident security labels.

A simple form of tamper-evident security label is known in which a substrate formed of paper with two or more layers with printed material applied to the upper side of the paper. A weak bond is provided within the paper. A strong adhesive is applied to the underside of the paper substrate to retain the paper in position on a product. The bond strength of the adhesive is greater than the bond strength within the paper. If an attempt is made to remove the label from the product, due to the fact that the bond strength within the paper is weaker than the adhesive bond strength between the paper and the product, the paper layers of the substrate will separate such that the printed material on the top layers of the label with be removed but will leave the lower layer of the paper still adhesively attached to the product. The lower layer may exhibit the word "VOID" or the like as evidence of tampering.

However a limitation with this label is that as the top surface of the paper substrate label separates from the bottom layer which is adhered to the product and the top layer carries the printed information on the product, it may be possible that the top layer could be carefully removed from a genuine product and reapplied to a counterfeit product such that the end user or consumer may not realise that the product being purchased or used is not a genuine product.

An example of a tamper resistant security label is known as an ultra destructible (UD) label which can comprises a poly vinyl chloride (PVC) substrate which is adhered to the product by a very strong adhesive. The substrate is very brittle and readily frangible.

Where such a label is used, if an attempt is made to remove the label, the substrate will fracture into many very small pieces. Due to the combination of the strength of the adhesive and the bhttleness of the label itself is reduced to a large number of very small pieces when tampered with and so is very difficult to remove.

The UD PVC labels described above are often used on electronic equipment for example as asset labels as they cannot readily be removed from a genuine product and applied to a counterfeit product without destruction of the label.

Whilst they provide a reliable means of indicating that the label has been tampered with, due to their composition they suffer from several disadvantages over paper substrate labels including that they are relatively expensive to produce and environmentally unfriendly to dispose of. Furthermore the processing requirements for UD PVC labels are more demanding than for paper substrate labels.

It is an object of the present invention to provide a paper substrate tamper resistant and/or tamper evident security label which addresses or mitigates at least one problem associated with known security labels discussed above. According to one aspect of the present invention there is provided a security label comprising a paper substrate, the paper substrate being impregnated with resin wherein there is at least 5wt% resin in the label.

Thus it has been found that the provision of resin within the paper substrate causes the label according to the invention to become brittle and function as a security label especially a tamper resistant security label.

As used herein, "security labels" comprise, preferably consist of, tamper resistant security labels and tamper evident security labels.

Preferably therefore the invention provides a tamper resistant security labels and a tamper evident security label, especially a tamper resistant security label.

Preferably there is at least 7wt%, more preferably at least 10wt% resin. Typically there is less than 35wt%, especially less than 20wt% resin. Preferred embodiments include around 15wt% resin. For example based on a 75g finished paper product there may be 10.8g/m².

Thus whilst it is known to provide, for example 3-4wt% of certain resins to paper in order to improve their strength when wetted, the resins of the present invention function to make the paper brittle and frangible such that it is likely to be evident to a user when tampered with.

Typically the security label especially the tamper resistant security label has adhesive applied to one side thereof. Backing paper may also be provided over the adhesive, such that the label may be applied to an article in use by removing the backing paper and sticking the label onto the article. The labels can be a variety of sizes. Preferred embodiments are normally less than 1000cm², and often less than 650 cm². Some are less than 400 cm² and may also be less than 100 cm². Preferably the labels are less than 20cm², more preferably less than 10cm², and may indeed be less than 5cm².

The resin may be chosen from the list consisting of formaldehydes such as melamine formaldehyde and urea formaldehyde; and cross-linked, water soluble, polycarboxylic acids. Urea formaldehyde is preferred.

Where urea formaldehyde is used, preferably such embodiments do not include fully cross-linked, water soluble, polycarboxylic acids.

Preferably the resins are water soluble, which allows addition at a size press in a paper manufacturing process. Preferably the resins are cross linkable. For example urea formaldehyde cross-links with itself and, it is thought, may also cross link with paper fibres.

Where polycarboxylic acids are used, preferably they are used with an acrylic dispersion.

In preferred embodiments the label has an additive to increase the flexibility thereof, such as a polymer dispersion. Preferably the polymer dispersion has a glass transition temperature (Tg) less than 110 ⁰C, preferably less than 75 ⁰C, especially less than 50 ⁰C. A styrene acrylic dispersion is preferred, one of which is available from BASF, Ludwigshafen, Germany under the brand Acronal™ S305B and another is made by Polymer Latex, Birmingham, United Kingdom under the brand Plextol™ X4340. This provides some water resistance and allows the label to be handled easier such that it is not too brittle to apply to the product at the outset and so that it facilitates easier manufacture of the labels.

Preferably the paper substrate comprises fibres comprising a mixture of hardwood, such as Eucalyptus, and softwood, such as Scandinavian Pine. Hardwood is a relatively short fibre wood and fibre lengths typically range from 10-25 microns thick and typically average around 12 microns thickness and 1.5mm length. Softwood is relatively long fibre wood. Most fibres in softwood are normally 30 to 60 microns thick and 0.5 - 7mm in length. Hardwood is herein defined as wood where more than 55%, preferably more than 80%, of the fibres in the wood are less than 20 microns in thickness. Softwood is herein defined as wood where more than 55%, preferably more than 80%, of the fibres are more than 20 microns in thickness.

The paper may be made from 10 - 45% soft wood, preferably 20 - 35% soft wood, especially 25 - 30% soft wood. The paper may be made from 55 - 100% hard wood, preferably 65 - 80% hard wood, especially 70 - 75% hard wood. These percentages are based on total wood content not including resins or other additives.

Thus preferably the percentage of hard wood is higher than that of soft wood, ie there is more than a 1 :1 ratio of hardwood to soft wood. Preferably there is a ratio of at least 1.5:1 hard wood to soft wood, more preferably at least 2:1 hardwood to softwood.

The preferred rich proportion of hard wood normally facilitates absorption of the resin. Preferably there is 45% - 75wt% of pulp (ie hard wood and soft wood) in the finished paper. This pulp percentage is calculated on the final paper and so typically includes resins, fillers and pigments for example.

Preferably the paper comprises pigments, such as titanium dioxide, barium sulphate or clay.

The paper may comprise a wettability agent, such as a soap.

Where a formaldehyde resin is used, such as urea formaldehyde or melamine formaldehyde, the wettability agent is preferably urea. Urea may also function to scavenge formaldehyde which can stabilise the resin mixture during manufacture. Moreover the inclusion of urea normally increases the brittleness of the paper. However where the resin is polycarboxylic acids, urea is preferably not included.

Preferably the paper includes 1 - 4.5wt% urea, preferably 2 - 3.5wt%, especially 2.3wt% - 2.75wt%.

Other additives may be used to scavenge formaldehyde, such as starches, although urea is preferred.

The paper may further comprise a wet-strength resin.

According to a further aspect of the present invention, there is provided a method of fabricating a security label comprising the step of impregnating a paper substrate with at least 5wt% resin.

Preferably the method of the invention results in a security label in accordance with the first aspect of the invention. Preferably the porosity of the paper before impregnation is in the range of 500 - 800, preferably 550 - 750, more preferably 600 - 700 mls/min (Bendtsen).

Preferably prior to impregnation, the paper substrate is dried to a moisture content of 2.0% or less.

Preferably also the paper substrate is simultaneously heated to a temperature of > 105° C.

Advantageously, following impregnation, the paper substrate is subjected to a further drying operation.

Preferably the impregnation is done in-line on a paper manufacturing process.

Optionally the paper may be calendared following impregnation.

An embodiment of the present invention will now be described.

A tamper resistant security label comprising a paper substrate according to one aspect of the present invention is described below. The composition of each component of the tamper resistant security label is expressed in grammes per square metre.

The substrate comprises:-

(1 ) Hardwood eucalyptus and Softwood Scandinavian pine fibres, at 56wt%, for a 75.0 g/m² paper, 42.0g/m². (2) Pigments comprising a mixture of titanium dioxide, barium sulphate and clay at 18.8%, for a 75.0 g/m² paper, 14.1 g/m².

The titanium dioxide provides opacity in the finished paper substrate whilst the barium sulphate acts as a titanium dioxide extender increasing the opacifying effect and the clay reduces the overall cost and improves the smoothness of the finished substrate.

(3) Wet strength resin retention aid and pH control chemicals to a total of 0.53wt% , for a 75.0 g/m² paper, 0.4 g/m².

(4) Styrene acrylic resin derived from a styrene acrylic dispersion at 5.6wt%, for a 75.0 g/m² paper, 4.2 g/m².

(5) Urea formaldehyde resin at 14.4wt%, for a 75.0 g/m² paper, 10.8 g/m².

(6) Urea at 2.45wt%, for a 75.0 g/m² paper, 1.84 g/m².

(7) Resin additives at 0.16%, for a 75.0 g/m² paper, 0.12 g/m². (such as ammonia or ammonium nitrate salt as resin hardener or an emulsifier such as Emulan-P™ available from BASF, supra.)

(8) Residual moisture at around 2%, for a 75.0 g/m² paper, 1.54 g/m².

The total grammage of the finished paper in this example is 75.0 g/m².

The paper substrate of the label having the components described above has a very strong internal bond and also takes on some of the properties of the resin system used and therefore becomes brittle and behaves in a similar fashion to UD PVC plastics. Thus the paper substrate fractures when tampered with in use. This means that it is very difficult to remove the label from whatever surface it has been applied to (eg. a piece of electrical equipment) and almost impossible to reapply the label to another piece of equipment. Therefore the label provides strong resistance to and evidence of tampering to the consumer.

Other applications include pharmaceutical and food items.

Embodiments of the invention may not be as inherently brittle as UD PVC plastics but is also less costly to produce and more environmentally friendly to dispose of which makes the labels of the present invention very desirable.

The method of manufacturing the tamper resistant security label described above will now be described.

Items (1 ) to (3) above are produced as a base sheet with a grammage of 56.5 g/m². The base sheet is then dried to a moisture content of 2.0% or less and simultaneously heated to a temperature of > 105⁰C to cure the wet strength resin and to generate sufficient strength for it to survive the online resin impregnation process described below. The air porosity of the base sheet is closely controlled so that the resin picked up during the impregnation process is within the specified limits.

The base paper is then impregnated online with the resin using a modified size press and the resin formulation is made up of items (4) to (7) noted above. After impregnation, the paper substrate is then dried down again so that the finished paper contains 1.54 g/m² of moisture. At this point in the manufacturing process, the paper remains very flexible so that it can be calendared on line if required for surface finish in subsequent processing steps and finally the parent reel is slit into the finished reel sizes.

After slitting, the paper is stored to allow the resin within the substrate to cure up sufficiently for around 3 weeks and then converted into labels. To confirm the paper is sufficiently cured the Cobb Test may be performed. The Cobb test comprises adding water onto a 100cm² sheet of the paper and leaving thereon for 60 seconds. Excess water is then poured off the paper and the paper weighed. The paper is normally considered sufficiently cured is the paper absorbed less than 1 Og water m².

Depending on their end use, certain embodiments may be left blank ie nothing printed on them. However many embodiments of the invention will have images or words printed upon them.

A commonly used label printing method for this type of application is thermal transfer whereby an image is transferred onto the paper substrate digitally using a plenum to heat up a coated ribbon such that the coating melts and transfers the print design directly onto the paper. Depending on the end use of the label and the model of printer used, different ribbons are utilised which have coatings which may comprise anything from 100% wax through to 100% resin. Due to the variation in ribbon composition, the surface smoothness of the paper has to be adjusted so that the required transfer of ribbon coating onto the paper is achieved to meet the necessary print quality. The surface smoothness of the paper substrate is controlled by calendaring the paper. The paper may then be die-cut into label-sizes. Alternatively the labels may be printed upon, after cutting.

Embodiments of the tamper resistant security label, such as the example described above, provide a more cost effective and more environmentally friendly alternative to current ultra destructible PVC tamper resistant security labels. As the paper substrate is inherently less brittle than the UD PVC labels, it is easier to process particularly in the lamination of the paper to a backing paper but may also be easier during the printing step and may also be easier during die-cutting when the brittle nature of the UD PVC labels can lead to damage to the label before it is applied to a product.

Modifications and improvements may be made without departing from the scope of the present invention.

Claims

1. A security label comprising a paper substrate, the paper substrate being impregnated with resin, wherein there is at least 5wt% resin in the label.

2. A label as claimed in claim 1 , wherein the paper substrate has at least 7wt% resin.

3. A label as claimed in claim 1 , wherein the paper substrate has at least 10wt% resin.

4. A label as claimed in any preceding claim, wherein the paper substrate has less than 35wt% resin.

5. A label as claimed in any preceding claim, wherein the paper substrate has less than 20wt% resin.

6. A label as claimed in any preceding claim, wherein the resin is chosen from the list consisting of formaldehydes (such as melamine formaldehyde and urea formaldehyde) and cross-linked, water soluble, polycarboxylic acids.

7. A label as claimed in claim 6, wherein the resin is urea formaldehyde.

8. A label as claimed in any preceding claim, wherein the resin is water soluble.

9. A label as claimed in any preceding claim comprising a styrene acrylic dispersion.

10. A label as claimed in any preceding claim, wherein the security label is a tamper resistant security label and has adhesive applied to one side thereof.

11. A label as claimed in any preceding claim having a surface area of less than 1000cm².

12. A label as claimed in any preceding claim having a surface area of less than 400 cm².

13. A label as claimed in claim 12 having a surface area of less than 20cm².

14. A label as claimed in claim 12 having a surface area of less than 5cm².

15. A label as claimed in any preceding claim, having a ratio of hard wood to soft wood of at least 1.5:1.

16. A label as claimed in any preceding claim, having a ratio of hard wood to soft wood of at least 2:1.

17. A label as claimed in any preceding claim, wherein the paper comprises 70 - 75% hard wood and 25 - 30% soft wood based on total wood content not including any resins or any other additives.

18. A label as claimed in any preceding claim, wherein the paper includes 1 - 4.5wt% urea.

19. A label as claimed in any preceding claim, wherein the paper includes 2-3.5wt% urea.

19. A label as claimed in any preceding claim, wherein the paper includes 2.3wt% - 2.75wt% urea.

20. A method of fabricating a security label comprising the step of impregnating a paper substrate with at least 5wt% resin.

21. A method as claimed in claim 20, wherein the porosity of the paper before impregnation is in the range of 500 - 800 mls/min.

22. A method as claimed in claim 20, wherein the porosity of the paper before impregnation is in the range of 550 - 750 mls/min.

23. A method as claimed in claim 20, wherein the porosity of the paper before impregnation is in the range of 600 - 700 mls/min.

24. A method as claimed in any one of claims 20-23, wherein prior to impregnation, the paper substrate is dried until the moisture content of the substrate is a maximum of 2.0%.

25. A method as claimed in any one of claims 20 to 24, wherein the paper substrate is heated to a temperature of above 105⁰C.

26. A method as claimed in any one of claims 20 to 25, wherein the impregnation is done in-line on a paper manufacturing process.