GB2131767A - Marking packaging - Google Patents

Abstract

A method of marking packaging with information specific to the material to be packed therein which includes providing a specific area of the packaging with a chemical component or components which can subsequently be reacted by external means to generate a required image. The components may be reacted by the application of pressure and/or heat, ultra-violet light or laser energy. The image may be formed on the packaging material itself e.g. a sheet of plastics or paper, or on an adhesive label.

Description

SPECIFICATION Method of marking packaging and packaging marked by such a method This invention relates to a method of marking packaging and packaging marked by such a method, and in particular to packaging to which data specific to the material being packed has to be applied at the time of packing.

Packages for certain materials, especially perishable foodstuffs and drugs, are required to carry "sell-by" or "use by" dates. These and other materials may also need to carry information such as manufacturing dates, batch numbers, article numbers or inspection codes. It is not possible to apply such data during the manufacture of the packaging or the printing on it of more general information since the data is not normally available at those stages.

It is necessary therefore to apply data of this kind at the time when the material is packed. This is currently effected by the technique of hot foil stamping in which a ribbon of a thin polyester film coated with a pigmented holt melt coating is driven into contact with the packaging by a heated die acting through the reverse of the film. A part of the holt melt coating is thereby transferred to the packing to produce an image conforming to that of the die.

The foil ribbon is however an expensive material and the cost of use is aggravated by the fact that the residue of the hot melt coating remaining on the foil is wasted. There is also a further disadvantage in that the packager is under a constant obligation to ensure that the image is transferring satisfactorily to the package. The present invention seeks to alleviate some of the difficulties which arise from the use of hot foil stamping techniques in the application of such data to packaging.

According to the present invention a method of marking packaging with information specific to the material to be packed therein includes providing a specific area of the packaging with a chemical component or components which can subsequently be reacted by external means to generate a required image.

The chemical component or components can be provided as a coating, and in one convenient method the coating can be applied to a separate element which is secured to the packaging, for example, as a label.

Preferably such an element is permanently secured in position.

The packaging could be in the form of a plastics film to which the label can be permanently heat sealed.

The method may include the use of a chemical component which is adapted to be reacted by the application of pressure and/or heat, or by ultraviolet light or lazer energy.

In general, where the packaging consists of sheet material such as paper or film, it will be convenient to use a reactable ink formulation whereas labels may be more advantageously used for other forms of packaging such as cartons, bottles or cans. Where labels are used, they are preferably of such a nature or incorporate adhesives for example hot melt adhesives which render them impossible to remove from the packaging after application, so as to prevent alteration of the data.

The coating can include microcapsules which generate a colour when pressure is applied thereto and the image is created by application of a pressure die.

Alternatively the coating can include chromogenic material and coreactants which are brought into chemical association by the application of heat.

If desired the label may carry the coating on the front and a hot melt adhesive on the reverse, the label being secured in position by the application of a heated die which simultaneously generates a coloured image in the coating.

The invention also includes packaging marked by the method set forth above.

The invention will now be further described by way of example by reference to the following drawings and examples. In the drawings: Figure 1 shows a portion of a reel of packaging material intended for use in packaging a perishable food product.

Figure 2 is an elevation on the line Il-Il of Figure 1, Figure 3 is an elevation of an alternative configuration on the line Ill-Ill of Figure 1.

Figure 4 is an underplan view of a die for pressure forming an image on the material according to the invention, Figure 5 is an elevation showing the die of Figure 4 in use in forming a pressure image, Figure 6 is an underplan view of a die for forming a heat generated image on material according to the invention and (optionally) simultaneously bonding a heat sealable label to a substrate, Figure 7 shows the die of Figure 6 in use, and Figure 8 shows a drug packaging container carrying a label, according to the invention.

Referring first to Figure 1, a strip 1 of sheet material is shown which may be, for example, of paper or plastics foil. In use, the sheet 1 will be cut into segments 2 along the lines 3, each segment having been preprinted with information 4 identifying the product. Each segment 2 also carried one or more areas 5 having applied thereto a coating of a chemical formulation which can be reacted by externally applied means to form an image. Referring to Figures 2 and 3, the coating 6 may be applied directly to the segment 2 as an ink as shown in Figure 2. Alternatively, and as shown in Figure 3, it may be applied as a coating 7 on a label 8 which is in turn adhered to the segment 2 by an adhesive 9.

When a label is used as described with reference to Figure 3, it is preferred that the adhesive used is such as to provide a sufficiently high tack to prevent removal from the segment 2 after application. Where the sheet material 1 is of paper, a high tack latex adhesive may be appropriate. Alternatively, a hot melt adhesive could be used. Where the sheet 1 is of plastics film, the label 8 may also be made of such film and heat sealed directly to the film 1 without the use of an adhesive.

Referring now to Figure 4, a die 10 is shown the underside 11 of which carries raised lettering 12. As shown in Figure 5, the die 10 can be used to pressure form an image on a coating 6 or label 7/8 provided on a segment 2. Typically, the coating 6 or 7 will comprise a mixture of microcapsules containing a solution of chromogenic materials and coreactants which generate colour when brought into chemical association with such materials. The action of the die 10 ruptures the capsules and causes an image to be formed in conformity with the lettering on the die.

Figure 6 shows a die 13 having an underside 14 on which raised lettering 1 5 is provided in a similar manner to the die 10. The die 13 incorporates heating means (not shown) which may typically comprise electrical heating coils. The die 13 may also optionally carry a peripheral raised rib 1 6 for a purpose to be described below with reference to Figure 7.

Turning now to Figure 7, this shows the die 13 in use for forming a heat generated image on a coating 6 or label 7/8 provided on a segment 2.

The coatings 6 or 7 in this case will consist of a mixture of chromogenic materials, coreactants therefor and binders, the formulation being such that the chromogenic materials and coreactants are only brought into chemical association when raised to a predetermined temperature.

The die 13 may optionally be used not only to form an image on the coatings 6/7, but also to adhere a label which is heat sealable or carries a hot melt adhesive to the segment 2. In this case, the peripheral rib 1 6 will ensure that the edges of the label are sufficiently heated to achieve such adhesion.

Figure 8 shows a drug container in the form of a bottle 1 7 of plastics material. The contents are identified on a conventional label 1 8 and a separate coating or label 19 of the kind described above with reference to Figures 2 and 3 carries a discard date which can be applied by pressure or heat at the time when the bottle contents are introduced. Data on the label 1 9 may be applied as described above with reference to Figures 5 and 7.

Although the use of pressure and heat has been described specifically above, it will be appreciated that the ink/coating formulations may be such as to permit the use of other forms of external energy to generate the necessary image. For example formulations responsive to ultraviolet light or laser energy may be used.

The following examples will further illustrate the invention.

EXAMPLE 1 40 grams of 25% (by weight) aqueous dispersion of capsules containing a solution of colour formers (prepared according to British Patent No. 1 507739) were mixed with 20 grams of dry, powdered phenolic resin, Bisphenol A (2,2 bis(4'-hydroxyphenyl)propane). 6 grams of kaolin were then added to the mixture, followed by 4 grams of a latex binder (Vinacryl 7191 supplied by Vinyl Products Limited). The mixture was stirred to give a uniform dispersion and was then applied by bar coating to a packaging paper (39 grams per square metre 'M' paper supplied by Schoeller and Hoesch) to give a coatweight of 2 grams per square metre when hot air dried.

The resulting coating was white in appearance and readily formed a coloured image when stamped with an engraved character.

EXAMPLE 2 The method described in Example 1 was repeated, except that the coating was applied to a packaging film (Propafilm M.G., co-extruded polypropylene, supplied by ICI).

The resulting dry film showed good adhesion and gave a coloured image when stamped with an engraved marker.

EXAMPLE 3 The method of Example 2 was repeated and the film then cut into label sized elements which could be applied by heat sealing to packaging film of the same material. The use of such film labels has the advantage that the data can be applied to the labels separately from the packaging line and the labels then applied to the packaging film during the packaging process.

EXAMPLE 4 The method described in Example 1 was repeated, except that the coating was applied to a self adhesive label paper. The treated label could then be removed from its release paper and attached to any packaging material or article for subsequent use as a pressure sensitive coding indicator. The adhesive preferably has a high "tack" so that once applied to the packaging material it cannot be removed without damage.

EXAMPLE 5 20 grams of the capsule dispersion used in Example 1 were mixed with 10 grams of an acidic clay. 2 grams of Vinacryl 71 91 latex binder were then added and the mixture was stirred to give a uniform dispersion. The pH of the dispersion was adjusted to 10.5 using 25% sodium hydroxide solution. The mixture was bar coated onto a wrapping paper to give a coatweight of about 3 grams per square metre when dry. The resulting coating was white in appearance and gave a coloured image when stamped with an engraved marker.

EXAMPLE 6 7 grams of an aqueous capsule dispersion (64.5% by weight) were added to 2 grams Vinacryl 71 91 latex binder and stirred to give a uniform mixture. 3 grams of acid treated clay were then dispersed in the mixture together with 1 gram of a 10% solution of polyvinyl alcohol (MOWIOL 4-88 supplied by Hoechst A.G.). The pH of the mixture was adjusted to 10.5 using a 25% solution of sodium hydroxide.

The resulting coating gave good adhesion when bar coated on polypropylene film and produced a coloured image when stamped.

EXAMPLE 7 The method described in Example 6 was repeated except the coating was applied to a medium grammage well beaten supercalendered glassine food wrapping paper supplied by Wiggins Teape (UK) PLC. The resulting area of coating was pressure sensitive and could be used to record information by the application of pressure.

EXAMPLE 8 7. Grams of the capsule dispersion used in Example 6 were added to 2 grams Vinacryl 7191 latex and the mixture was stirred to give a uniform dispersion, then bar coated to give an area of coating on polypropylene film. The coating was then hot air dried. A second coating mix, comprising 2 grams of a para-alkyl phenol formaldehyde resin of low molecular weight dissolved in 20 grams toluene was prepared. A thin film of the resin solution was applied to the previously coated capsule coating. After drying, the resulting double layered coating produced an image when impacted.

EXAMPLE 9 The following Example illustrates the preparation of a dispersion of the coating components in an aqueous/methanol medium of a type which is similar to some flexographic printing inks.

6 grams of the capsule dispersion used in Example 6 were dispersed in 3 grams of a mixture of methanol and water (containing 75% methanol, by weight). 2 grams of a 10% aqueous solution of polyvinyl alcohol and 3 grams powdered Bisphenol A were then added and the mixture stirred to give a uniform dispersion.

The coating mix showed good adhesion and imaging properties when applied to a range of substrates including glassine paper, packaging paper and plastics film.

EXAMPLE 10 5 grams of Vinacryl 7191,7.5 grams Bisphenol A, 1.5 grams of the colour former Crystal Violet Lactone and 7.5 grams water were mixed together then bar coated onto a sheet of glassine wrapping paper to provide a coated label. The coating was found to give a blue image, when marked with a heated metal stamp.

EXAMPLE 11 A mix of the kind used in Example 10 was coated onto labels cut from polypropylene sheet of the kind referred to in Example 2. These labels were then adhered to a similar polypropylene packaging sheet by a heated die carrying a sell-by date and a peripheral rib which imaged and heat sealed the label to the sheet in the areas of contact.

EXAMPLE 12 A mix of the kind used in Example 10 was coated onto labels cut from paper having a hot melt adhesive coating on the reverse side. These labels were then applied to a sheet of packaging paper by a heated die as described in Example 11.

It will be appreciated that the invention may be put into effect in alternative ways. Thus, for example, the method of Example 1 may be carried out with the capsules containing a solution of the powdered phenolic resin Bisphenol A and the colour formers being added to the capsule dispersion. It is merely necessary to ensure that the colour former and resin are separated until used.

If desired, the carbonless coatings of the present invention may be overlaid and sealed with a flexible transparent coating, paper or film through which pressure or heat can be applied to form an image. This both protects the coating prior to use and prevents removal or tampering after use. The overlay may be locally applied to the coating or may be formed by a complete secondary transparent wrapping, for example a shrink wrap for a primary package carrying a carbonless coating or label.

Claims (17)

1. A method of marking packaging with information specific to the material to be packed therein which includes providing a specific area of the packaging with a chemical component or components which can subsequently be reacted by external means to generate a required image.

2. A method as claimed in claim 1 which includes providing a chemical component or components as a coating.

3. A method as claimed in claim 2 in which the coating is applied to a separate element which is secured to the packaging.

4. A method as claimed in claim 3 in which the separate element is in the form of a label.

5. A method as claimed in claim 3 or claim 4 in which said separate element is permanently secured in position on application.

6. A method as claimed in claim 5 in which the packaging is a plastics film to which the label can be permanently heat sealed.

7. A method as claimed in claims 1 to 6 which includes using a chemical component which is adapted to be reacted by the application of pressure and/or heat, or by ultraviolet light, or laser energy.

8. A method as claimed in claims 1 to 7 which includes using a chemical component in the form of a reactable ink formulation.

9. A method as claimed in claims 1 to 8 in which the coating includes microcapsules which generate a colour when pressure is applied thereto and the image is created by application of a pressure die.

10. A method as claimed in claims 1 to 8 in which the coating includes chromogenic material and coreactants which are brought into chemical association by the application of heat.

11. A method as claimed in claim 10 in which the label carries the coating on the front and a hot melt adhesive on the reverse, the label being secured in position by the application of a heated die which simultaneously generates a coloured image in the coating.

12. A method as claimed in claims 1 to 11 which includes applying an overlay over the marking.

1 3. A method as claimed in claim 12 which includes applying the overlay as a secondary transparent wrapping.

14. A method as claimed in claim 13 in which the secondary transparent wrapping is in the form of a shrink wrap.

1 5. A method of marking packaging substantially as set forth in any one of Examples 1 to 12.

1 6. A method of marking packaging substantially as described herein with reference to and as shown in the accompanying drawings.

17. Packaging marked by the method set forth in any one of the preceding claims.