SELF ADHESIVE LABELS

Abstract: A self adhesive label (2) has a layer (4) of polymeric material such as polypropylene or polyethylene, the first layer (4) being printed on one face (12) and having an adhesive material (6) on its other face. The upper surface (12) of the layer (4) is printed using u.v. activated inks. A transparent second layer (14) of polymeric material such as polypropylene or polyethylene is laminated to the upper surface (12) of the first layer (4) by means of an adhesive agent (16), which is preferably an u.v. activated adhesive agent. The label (2) may include a removable backing sheet (8) which is removably adhered to the adhesive material (6) on the other face of the first layer (4). A silicon release layer (10) may be located between the backing sheet (8) and the adhesive material (6) on said other face of the first layer (4).

Description: SELF ADHESIVE LABELS This invention relates to self adhesive labels More particularly, the invention relates to self adhesive labels made from polymeric sheet material. The general object of the invention is to provide a self adhesive label which is relatively thin but which has sufficient strength to enable it to be readily dispensed by automatic label dispensers. The label of the invention can be supplied in rolls or in sheets. The label is inexpensive in relation to other plastic labels, and has a superior print surface. It is another object of the invention to provide a polymeric label which can be re-cycled with a plastic bottle or container to which it is applied. It has been suggested " that environmental regulations will call for mandatory recycling of some plastic containers which will make the use of paper labels practically difficult because they would need to be removed before the container is recycled. If the label is of the same material as the container there is no difficulty in recycling. If it is of a different polymeric material, the relatively small volume of the label compared to that of the container still enables recycling. It is a further object to provide a self adhesive label which is resistant to moisture, oils and scuffing and has an attractive appearance. Pearlized polypropylene labels have been printed by various self adhesive label printers with little or no success. The invention adds a laminate to the face stock which overcomes all the disadvantages of the face stock, making it a commercial alternative to paper and a cost advantage to known plastic labels. More particularly the present invention provides a self adhesive label comprising a first layer of polymeric material, said first layer being printed on one face and having adhesive material on its other face, the first layer having a thickness in the range from 15 to 80 microns, and a second layer of polymeric material laminated to said one face of the first layer, said second layer being transparent and having a thickness in the range from 20 to 50 microns. Preferably, the polymeric material of the first and second layers comprises polypropylene or polyethylene. Preferably, the label includes a removable backing sheet which is removably adhered to the adhesive matarial on said one face of the first layer, the first layer and backing sheet comprising a standard self adhesive construction. Preferably also, a silicon release layer is located between the backing sheet and the adhesive material on said one face of the first layer. The silicon release layer is preferably applied to one face of the backing sheet. It is preferred that the first layer of polymeric material is 25 to 30 microns thick. Where the self adhesive labels are supplied in roll form, it is customary to remove the extraneous portions of the first and second layers between adjacent labels so that the back sheet forms the continuous web of the roll. When the labels are formed into a roll, the gaps between adjacent labels can cause embossing marks on adjacent or opposite labels. The greater the combined thickness of the first and second layers, the greater is the likelihood that embossing will occur. The effect is also more apparent with irregular shaped and circular labels. It follows that in order to reduce this effect, it is preferable to use the thinnest commercially available materials, subject to those materials having sufficient strength. It is also preferred that the rolls be wound loose on cores of at least 75m.n diameter. Preferably further, the second layer of polymeric material is 35 microns thick. Preferably further, the second layer is laminated to the first layer by means of an adhesive or bonding agent, preferably a u.v. activated adhesive agent. Surprisingly it has been found that the most effective adhesive agent is a vinyl primer which is normally used to treat vinyl sheet material in order that it may be successfully printed. These materials are not normally used with polypropylene or polyethylene sheets. The vinyl primer may comprise a urethane acrylate resin system comprising acrylate resins diluted in diacrylate and triacrylate monomers. The primer preferably includes photo-initiaters and photo-activators such as benzophenone, benzoin ethers, amino-benzophenones, and tertiary amines. The primer is preferably composed of solids and does not contain solvents cr volatiles. It has also been found that the bonding agent may comprise a polyester acrylate resin system which has similar photo-initiaters and photo-activators and again doer not include solvents or volatiles. The adhesive or bondirg agent is preferably applied in a thin layer to the second layer of polymeric material. The thickness of the adhesive or bonding agent is comparable to the thickness of the ink which is used for the printing on the first layer of polymeric material. Normally analine inks, which are solvent based, are used when printing en polypropylene sheet material. Surprisingly, it has been found that it is possible to use u.v. activated inks of the type which are normally used on paper for printing on the first layer of polymeric material. The inks preferably include activaters to give better keying and faster curing. One suitable ink is "Flash Dry U.V. Ink" made by Toyo. The printing can be carried out on a more or less conventional label printing machine which has some modifications made to it including u.v. driers and a corona discharge unit for treating the first layer prior to printing. The invention will now be further described with reference to the accompanying drawings in which: Figure 1 is a fragmentary view showing the construction of the adhesive label of the invention; Figure 2 is a schematic view showing part of the eguipment used in forming the labels of the invention; and Figure 3 is a schematic view showing part of a modified arrangement. Figure 1 illustrates a self adhesive label 2 constructed in accordance with the invention. The thicknesses of the various layers are not to scale. It comprises a face stock layer 4 which is preferably made of transparent or pearlized polypropylene (biaxially oriented or cast) . Pearlized polypropylene is a micro-voided cavertated structure with a pearlized appearance. White pigment such as titanium oxide can be added to make the pearlized layer white. Alternatively an outer layer of white polypropylene can be formed on the pearlized structure. A further alternative for the material of layer 4 is a transparent film polypropylene which has been metallized on the side which is not printed on. The first layer 4 is in the range from 25 to 80 microns thick. The preferred thickness however is 25 microns. The layer 4 has an adhesive layer 6 bonded to its underside. A peel-off backing layer 8 with a silicon release layer 10 is adhered to the layer 6 in the usual way. It will be appreciated that the layers 4, 6, 8 and 10 form a standard self adhesive construction. The upper surface 12 of the layer 4 is printed using u.v. inks as described. The printing may be carried out on a KOPACK rotary letter press machine to which has been added a corona treating unit for treating the upper surface 12 of the layer 4 prior to being printed by the printing heads of the machine. The corona unit may comprise a GX-20 SHERMAN machine operating at a setting of 38 to 40 dyne and a nominal output power of 2kw. This is suitable for operating at a running speed of 50 to 60 metres per minute. The corona treatment of the surface 12 enables much better keying of the ink to the surface. A u.v. drier is added to the KOPACK printer in order to substantially dry the ink on the surface 12 as it leaves the printing head. The composite layer is then completed by laminating a top layer 14 of transparent polypropylene thereto. The top layer 14 is laminated to the layer 4 by means of an adhesive or bonding agent 16. The adhesive preferably comprises a thin layer of u.v. activated adhesive. As mentioned previously, the adhesive preferably comprises a vinyl primer or polyester acrylate resin system containing photo-initiaters and photo-activators. The underside surface 18 of the layer 14 preferably has been treated by a corona discharge so as to improve adhesion of the agent 16 thereto. Where the layer 14 comprises polypropylene or polyethylene, it is often supplied by manufacturers in rolls which have been corona treated so it is unnecessary to treat the material again prior to lamination. The top layer 14 is preferably in the range 20 to 50 microns. The preferred thickness however is 40 microns. After the layers 4 and 14 have been laminated together, they will normally remain in this condition. The transparent layer 14 adds strength to the label and protects the printing on the top surface 12 of the layer 4 . Thus the label of the invention is guite rigid and scuff resistant compared to known 60 micron pearlized labels without laminate. It is possible to use polymers and copolymers other than polypropylene. For instance one or other of the layers 4 or 14 may comprise polyethylene, the stock layer 4 being transparent or opague and the top layer 14 being transparent. Where one or both of these layers is polyethylene, the thicknesses and treatments of the two layers are the same as described above. Figure 2 diagramatically shows a simple arrangement for laminating the labels of the invention. In this arrangement, the self adhesive feed stock 20 is applied to an impression drum 22. The self adhesive feed stock comprises the first layer 4, backing layer 8 with the adhesive 6 and self-release layer 10. The outer surface 12 of the layer 4 has been printed and u.v. dried as described above. The arrangement includes a supply roll 24 of the second layer 14. The layer 14 passes about a forming roller 26 which in turn cooperates with an adhesive printing roller 28. The drum 22 and roller 26 are both driven such that their surface speeds are the same. The adhesive printing roller 28 applies a thin layer or film of adhesive 16 to the second layer 14. Once the adhesive has been applied, the two layers are pressed together between the forming roller 26 and the drum 22 so as to permanently laminate the layers together. The two layers then pass to a u.v. drier (not shown) which dries the adhesive and bonds or adheres the two layers together. The laminated labels can be then wound into a roll in readiness for use. Figure 3 illustrates an alternative arrangement for laminating the labels of the invention. The printed self adhesive feed stock 20 is fed between an upper pair of rollers 30 and 32 which are both driven in unison by gears (not shown). The roller 32 applies the layer or film of adhesive 16 to the printed outer surface 12 of the layer 4. The feed stock then passes between a lower pair of rollers 34 and 36 and the second layer 14 is pressed into firm engagement with the layer of adhesive. The roller 34 is driven in synchronism with the rollers 30, 32. The roller 36 is friction driven by virtue of its contact with the layer 14. The two layers then pass to a υ.v. drier (not shown) for curing of the adhesive layer 16. Many modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims: CLAIMS 1. A self adhesive label (2) comprising a first layer (14) of polymeric material, said first layer being printed on one face (12) and having adhesive material on its other face, the first layer having a thickness in the range from 25 to 80 microns, and a second layer (14) of polymeric material laminated to said one face of the first layer, said second layer being transparent and having a thickness in the range from 15 to 50 microns. 2. A label as claimed in claim 1 wherein the polymeric material of the first and second layer comprises polypropylene or polyethylene. 3. A label as claimed in claim 1 or 2 wherein said one face is printed using u.v. ink. 4. A label as claimed in claim 1, 2 or 3 wherein said one face (12) is corona treated prior to printing. 5. A label as claimed in any one of claims 1 to 4 wherein the first and second layers (4,14) are laminated by means of an adhesive or bonding agent (16). 6. A label as claimed in claim 5 wherein the second layer (14) is corona treated prior to lamination to the first layer (4) . 7. A label as claimed in claim 5 or 6 wherein the adhesive or bonding agent comprises acrylate resin. 8. A label as claimed in any preceding claim wherein the first layer comprises pearlized polypropylene. 9. A method of making a self adhesive label (2) comprising the steps of: printing on one face (12) of a first layer (4) of polymeric material, there being adhesive material on the other face of the first layer, and laminating a second layer (14) of polymeric material to said one face (12) of the first layer, the second layer being transparent. 10. A method as claimed in claim 9 wherein the first layer has a thickness in the range 25 to 80 microns and the second layer has a thickness in the range 20 to 50 microns. 11. A method as claimed in claim 9 or 10 wherein said one face (12) is corona treated prior to printing thereon. 12. A method as claimed in claim 11 wherein the corona treatment is in the range 38 to 40 dyne. 13. A method as claimed in any one of claims 9 to 12 wherein the printing is carried out using u.v. ink and including the step of u.v. drying the ink prior to laminating the second layer. 14. A method as claimed in any one of claims 9 to 13 including the step of applying a layer or film (16) of adhesive or bonding agent to the second layer (14) in order to laminate the first and second layers. 15. A method as claimed ir. claim 14 wherein the adhesive or bonding agent is u.v. sensitive and the method includes the step of passing the two layers (4,14) with the adhesive or bonding agent therebetween to a u.v. drier. 16. A method as claimed in claim 14 or 15 wherein the adhesive or bonding agent comprises acrylate resin. 17. A method as claimed in claim 16 wherein the acrylate resin includes diacrylate and triacrylate monomers and photo-initiaters and photo-activators. 18. A method as claimed ir. claim 14 or 15 wherein the adhesive or bonding agent comprises a urethane acrylate resin.

Inventors: WRIGHT ALASTAIR GERRANS, WRIGHT, ALASTAIR, GERRANS
Applicants: LABELS ULRICH PTY LTD
Application year: 1989
Main classification: G09F3
IPC codes: G09F3