GB2552013A

GB2552013A - Labelstock

Info

Publication number: GB2552013A
Application number: GB1611850.7A
Authority: GB
Inventors: Crouch Tarquin; Lowe Tim
Original assignee: Utroque Ltd
Current assignee: Utroque Ltd
Priority date: 2016-07-07
Filing date: 2016-07-07
Publication date: 2018-01-10
Anticipated expiration: 2036-07-07
Also published as: GB2552013B; GB201611850D0

Abstract

The labelstock comprising a label face material releasably adhesively laminated to each side of a two side siliconised release liner. Each label face material comprises a polymer film substrate, and the outer surfaces of the polymer film substrates when laminated to the release liner have different surface properties. Each polymer film substrate may have a first side and a second side with different surface properties, and both film substrates may be the same, simply with their surfaces reversed relative to the release liner. The first side and the second side are capable of being either printed or adhesive coated. The outer surfaces of the polymer film substrates when laminated to the release liner are preferably printable surfaces, and the printable surfaces may be selected so as to be printable by different printing technologies. The different surface properties of the polymer film substrate employed in the invention may be achieved by selecting from the following: substrate polymer type, surface polymer type, polymer composition, surface chemistry, surface coating, surface cross-linking, surface corona treatment, surface flame treatment, surface plasma treatment. The preferred films contain anti-blacking additives.

Description

(54) Title of the Invention: Labelstock Abstract Title: Two-sided labelstock (57) The labelstock comprising a label face material releasably adhesively laminated to each side of a two side siliconised release liner. Each label face material comprises a polymer film substrate, and the outer surfaces of the polymer film substrates when laminated to the release liner have different surface properties. Each polymer film substrate may have a first side and a second side with different surface properties, and both film substrates may be the same, simply with their surfaces reversed relative to the release liner. The first side and the second side are capable of being either printed or adhesive coated. The outer surfaces of the polymer film substrates when laminated to the release liner are preferably printable surfaces, and the printable surfaces may be selected so as to be printable by different printing technologies. The different surface properties of the polymer film substrate employed in the invention may be achieved by selecting from the following: substrate polymer type, surface polymer type, polymer composition, surface chemistry, surface coating, surface cross-linking, surface corona treatment, surface flame treatment, surface plasma treatment. The preferred films contain anti-blacking additives.

Labelstock

Field of the Invention

This invention relates to labelstock comprising label face material releasably applied to both sides of a two side siliconised release liner.

Background

Often, treated or uncoated polymeric films such as those made from isotactic polypropylene, may not provide adequate adhesion to the full range of inks without a coating or surface treatment. These coatings or treatments make the films much more useful across the targeted range of applications. However when similar treatments or coatings with increased surface energies are brought into contact with each other, they tend to stick together or block. This usually occurs in the roll or when sheeted, in a stack of sheets, when the surfaces are brought into contact. With the application of pressure and/or heat, the likelihood of blocking increases. On these occasions the front side coating comes into contact with the backside coating.

If blocking occurs, when the layers are separated the surface of the coating can be damaged or if very badly blocked, then the layers cannot be separated at all. If blocking is only marginal it can still cause jerking of the substrate which can cause printing presses to lose register and/or create noise as the layers peel apart. Static electricity can also be created by the separation process with implications for safety and damage to sensitive electrical equipment. The static discharge itself can also change the nature of the film's surface, damaging its printability.

In self-adhesive labelling, one surface of the label face material film may be coated or treated for printability and the other is often left untreated. The adhesion of the adhesive to the untreated side is often sufficient without special coatings or treatments. If treatments or coatings are applied to the other side, then they are often completed in-line along with adhesive coating, which means that two surfaces with high energy do not come into contact with each other in the roll. This is because the adhesive coated side is immediately laminated to a one side siliconised release liner which stops it coming into contact with the first side and the second side of the release liner is either a different or low energy surface so blocking is unlikely to occur.

One way to achieve the high clarity and high modulus of a biaxially oriented polypropylene (BOPP) film but the better printability of a polyethylene film is to coextrude a polyethylene surface onto one side of the BOPP film leaving the other side as a standard BOPP film. The coextruded surface may be a homopolymer, copolymer or terpolymer with or without corona, plasma or other surface treatment. The substantially different surfaces do not block and are both printable and adhesive receptive. An example of such a film was LH302, a white label film from Jindal Films.

Films coated on one side for printability and treated on the second side for adhesive adhesion are also known and are described by Musclow et al in U.S. Pat. Nos 5,380,587 and 5,382,473 but are more prone to blocking than untreated films and difficult to produce.

McGee et al describe in U.S. Pat No 6,025,059 a plastic film coated with a top side printable epoxy coating. This is a reaction product of a water-dispersible or water soluble epoxy resin and an acidified aminoethylated vinyl polymer produced by polymerizing acrylate or another monomer with methacrylic or acrylic acid. These are reported not to block to uncoated polyolefin surfaces.

Whilst permanent or repositionable adhesives can be applied to and function perfectly well and achieve a good bond to untreated and uncoated surfaces, removable adhesives do not. This type of adhesive requires the surface to be treated or coated prior to application or there is a danger of adhesive residue remaining on the labelled article when the label is removed. This is particularly prevalent when the conditions are humid and warm.

U.S. Pat. No. 6,844,034 from Tousant describes how an anionic acrylic polymer and epoxy acrylate can be cross-linked to improve label adhesion, degradation resistance to isopropyl alcohol and/or hot water, but the patent does not disclose how to make the material resistant to blocking to the printable surface.

McGee in U.S. Pat. No 6,893,722 discloses a cationically stabilized amino-functional polymer coating for promotion of the adhesion of curable inks but does not describe how to stop blocking to a second treated or coated side. In U.S. Pat. No. 2007248810A the same inventor describes a coating for a two side coated plastic label film in which the film is opaque and the adhesive receiving skin has a matte, open cell structure The mattness is caused by the fact that the surface is rough. Roughness R_a>0.5 microns is known in the art to impart anti-blocking characteristics. Jindal Films produce such a film, Label-Lyte™ 60LH538, but this is a white film and such a matte coating is unsuitable for use on the front printable side of a clear or white film or on the adhesive receiving backside of a clear film.

Two side coated clear films which are resistant to blocking even at elevated temperatures, pressures and humidity are relatively recently available, an example of these is Jindal Films LabelLyte™ 50LL539. A method for making such films is described in U.S. Pat. No. 2007/0248810 Al and attributed to McGee et al and which describes a printable, two-side coated clear polymer film comprising a polymer substrate with a back-side coating consisting of an ionomer and particles of a colloidal mineral and a front side printable coating.

Innovia, another manufacturer of biaxially oriented polypropylene (BOPP) films with coating facilities, has solved the front to backside blocking issue on their clear ACPA and white WPCA products with their XK90 chemistry which uses a UV oligomer in the print surface and an over cross linked, functional aziridine additive on the other side. This mix of heavy cross linking on one side and standard cross linking on the other helps make the film blocking free.

Self-adhesive labels can be printed by a number of technologies and digital printing using the HP system requires an ethylene acrylic acid (EAA) copolymer coating plus corona treatment to be printable by their electro inks. To stop blocking, these films often have an acrylic coating on the second side. Again as the coatings are substantially different in chemistry, they do not block.

In all the above examples, the problems and solutions proposed and executed are based around a single substrate whether it consists of a coated and/or treated single polymer film or coated and/or treated multiple layer film manufactured by coextrusion of a single or multiple polymers and/or copolymers.

The problems faced in laminations however are different. Each individual film prior to lamination must not block to itself when wound in a roll at higher temperatures, pressures and humidities, but when laminated into a complex self-adhesive structure such as converted labelstock, the two faces in contact with each other in the roll must also not block.

For standard self-adhesive laminates which consist of a label face material, adhesive and a one side siliconised release liner this is not a problem, as whilst the energy level of the printable surface of the label face material is high, the energy of the backside of the release liner is low.

The release liner is often made of a different material than the label face material. Similar materials are known to have a greater tendency to block, so this alone means a much lower likelihood for in-roll blocking to occur. The backside of a siliconised release liner is also often slightly contaminated with a small amount of offset silicon which further reduces any tendency to block to the printable face once the laminate has been produced.

If any of the standard films known to the art as discussed above are used for lamination to both sides of a two side siliconised release liner, surfaces of the same chemistry would come into contact and blocking would result.

Summary of the Invention

The invention provides a labelstock comprising a label face material releasably adhesively laminated to each side of a two side siliconised release liner, wherein each label face material comprises a polymer film substrate, and wherein the outer surfaces of the polymer film substrates when laminated to the release liner have different surface properties.

Preferably, each polymer film substrate has a first side and a second side with different surface properties. This provides the advantage that the likelihood of the polymer film substrate blocking in the roll prior to lamination is significantly reduced or eliminated. In a further embodiment, each polymer film substrate preferably has a first side and a second side and each polymer film substrate has the same surface property on the first side and the same surface property on the second side. In a further preferred embodiment, one polymer film substrate has the first side outermost on the laminate and the other polymer film substrate has the second side outermost on the laminate. Effectively, the substrates are the same but are reversed relative to the release liner.

The different surface properties of the polymer film substrate employed in the invention may be achieved by selecting from the following: substrate polymer type, surface polymer type, polymer composition, surface chemistry, surface coating, surface cross-linking, surface corona treatment, surface flame treatment, surface plasma treatment.

In a preferred embodiment, the polymer film substrate is partially or substantially made from any of the following resin families: polyethylene, polypropylene, polyester, polyamide, polyvinylchloride.

The polymer film substrate may have a first surface that is coated, coextruded, corona treated, flame treated or plasma treated or has its surface chemistry altered in any way on one or both sides to provide a substantially different surface property from the surface of the second side of the same film.

In a preferred embodiment, the polymer film substrate is clear, white cavitated, white filled, matte, gloss or metallised.

The polymer film substrate may include a colloidal mineral to improve blocking resistance, comprising at least one of: silica, alumina, titanium dioxide, calcium carbonate, sodium magnesium fluorosilicate, synthetic sodium hectorite, white bentonite, montmorillonite, alkaline polyphosphates, talc, alkaline silicate salts, water glass, surface treated silica, surface treated alumina, surface treated titanium dioxide, surface treated calcium carbonate and surface treated talc in natural or synthetic form, where available.

A majority by weight of the colloidal mineral particles may be characterised by a mean diameter in at least two dimensions of preferably not greater than about 0.075 micron, more preferably not greater than about 0.050 micron, and still more preferably not greater than about 0.025 micron, the measurement being in each of the at least two dimensions, wherein each of the at least two dimensions are substantially perpendicular with respect to each other.

In a further embodiment, a majority by weight of the colloidal mineral particles may be characterised by an overall mean diameter of from about 0.01 micron to not greater than about 0.1 micron.

In a preferred embodiment, the polymer film substrate surface is printed with a radiation curable ink. Additionally or alternatively, the polymer film substrate surface may be printed with an ink selected from the group consisting of one-component inks, two component inks, oxidative curing inks, aqueous-based inks, solvent based inks, electro inks and dispersed inks. The first polymer film substrate outer surface may be printed with a different ink from the second polymer film substrate outer surface.

Preferably, the polymer film substrate inner surface is coated with an adhesive from any of the following families: rubber-resin blends, acrylics or hot melt adhesives. In a preferred embodiment, the first polymer film substrate inner surface is coated with an adhesive from any of the following families: rubber-resin blends, acrylics or hot melt adhesives, and the second polymer film substrate inner surface is coated with a different adhesive from that selected for the first polymer film substrate.

In at least the preferred embodiments, the invention provides a laminate which the likelihood of blocking is significantly reduced or eliminated at all normal ranges of temperature, pressure and humidity. The first side and the second side are capable of being either printed or adhesive coated. The outer surfaces of the polymer film substrates when laminated to the release liner are printable surfaces, and the printable surfaces may be selected so as to be printable by different printing technologies.

Detailed Description of the Invention

Label facestock on both sides of a two side siliconised release liner which is free of blocking at all normal ranges of temperature, pressure and humidity can only be achieved by using printable faces that come from different surface types (different polymers or different coating types) or be the same but having undergone significantly different treatments such as level of cross-linking, corona, flame or plasma treatment.

As it is usual to coat and treat prior to adhesive lamination and if they are to be blocking free in the roll prior to adhesive coating and lamination to the release liner, then the front and backside surfaces on the label facestock must also come from different polymer or coating types or be the same but having undergone significantly different treatments such as level of cross-linking, corona, flame or plasma treatment.

In trying to find a solution to the need for printable and adhesive receptive films that are both free of blocking in the roll prior to lamination and following lamination to both sides of a two side siliconised release liner, it has surprisingly been found that in general, the printability of the backside adhesive receiving side of the films discussed in the Background section are acceptable, meeting the requirements of many applications and being found to be acceptable for ink adhesion, meeting firstly the need for <50% ink removal following three repeated pulls of a testing tape such as Scotch 810 made by 3M, St. Paul Minn, (or equivalent) following ink drying, curing and conditioning. Secondly inking quality as measured by light transmission is also acceptable. The printability of the backside adhesive receiving coating is not disclosed in the any of the patents found.

A further surprise is that adhesive anchorage to the printable surface is also acceptable and found to work even with repositionable (shelf marking) adhesives such as Rohm & Haas, Spring House, Pa. adhesive type Robond PS-9260 or a removable adhesive such as their Robond PS-8120HV, both of which are considered as difficult and are susceptible to having their anchorage weakened by exposure to warm and moist conditions.

This invention therefore offers a solution to manufacturing a blocking resistant, double side labelstock. If one side of the labelstock uses a label face material, as described in the above patent, in the way it was intended and the other side uses the label face material in the reverse manner, with the printable face being used as adhesive receiving surface and the adhesive receiving surface being used as the printable face, then a double side labelstock can be produced which is blocking free in the manner that the original polymeric film was blocking free prior to adhesive lamination.

Further preferred variations on U.S. Pat. No. 2007/0248810 Al and attributed to McGee et al especially para (0046-0063) also offer themselves. The colloidal mineral component described in the original patent is added to the backside, adhesive receiving coating to improve blocking resistance. As this colloidal mineral decreases print definition and increases the haze of the coating, it is preferable for the purpose of this invention when the same film is used on both sides of a two side siliconised release liner, that it is added at half the quantity but to the coatings on both sides of the polymeric film to decrease its impact on haze and to ensure the printability of both coatings is the same. Colloidal minerals as described are well known in the art as ways to decrease blocking and as they work by increasing the separation of the two layers, having them in both layers at half the addition rate will not affect the resistance to blocking characteristics but will make each coating more similar to the other. This is important when labels on both sides of a two side siliconised release liner are either printed using the same technique or with the same image and the requirement is that they should look and or print in the same manner.

However there may be occasions when films of substantially different natures might be required on each side of the labelstock, for instance when the label on one side will be printed by a different technology than the labelstock on the second side. In this case, two different films from the list described in the Background section may be selected to be laminated to different sides of a two side siliconised release liner. As long as they do not block in the roll prior to lamination and as long as the surface chemistry is substantially different they should not block after lamination.

In this way by for example, selecting the EAA coated surface as the printable face on one film and for example the UV oligomer printable coating used on the Innovia film, a labelstock with a face material on one side that can be printed by an HP digital press and on the other by UV flexo technologies can be created. As many presses have a multitude of different printing technologies on the same press this has the benefit of increasing flexibility and capacity utilisation by the use of a turn bar to turn the film over and present the film with the correct printable surface to the print heads.

In all aspects of this invention the films can be clear, white, gloss, matte or metallised and may be manufactured from any polymer family and with any combination of these options on either side of the lamination.

Claims

Claims:

1. A labelstock comprising a label face material releasably adhesively laminated to each side of a two side siliconised release liner, wherein each label face material comprises a polymer film substrate, and wherein the outer surfaces of the polymer film substrates when laminated to the release liner have different surface properties.

2. The labelstock of claim 1, wherein each polymer film substrate has a first side and a second side with different surface properties.

3. The labelstock of claim 2, wherein each polymer film substrate has a first side and a second side and each polymer film substrate has the same surface property on the first side and the same surface property on the second side.

4. The labelstock of claim 3, wherein one polymer film substrate has the first side outermost on the laminate and the other polymer film substrate has the second side outermost on the laminate.

5. The labelstock of any preceding claim, wherein the different surface properties of the polymer film substrate are achieved by selecting from the following: substrate polymer type, surface polymer type, polymer composition, surface chemistry, surface coating, surface crosslinking, surface corona treatment, surface flame treatment, surface plasma treatment.

6. The labelstock of any preceding claim, wherein the polymer film substrate is partially or substantially made from any of the following resin families: polyethylene, polypropylene, polyester, polyamide, polyvinylchloride.

7. The labelstock of any preceding claim, wherein the polymer film substrate has a first surface that is coated, coextruded, corona treated, flame treated or plasma treated or has its surface chemistry altered in any way on one or both sides to provide a substantially different surface property from the surface of the second side of the same film.

8. The labelstock of any preceding claim, wherein the polymer film substrate is clear, white cavitated, white filled, matte, gloss or metallised.

9. The labelstock of any preceding claim, wherein the polymer film substrate includes a colloidal mineral to improve blocking resistance, comprising at least one of: silica, alumina, titanium dioxide, calcium carbonate, sodium magnesium fluorosilicate, synthetic sodium hectorite, white bentonite, montmorillonite, alkaline polyphosphates, talc, alkaline silicate salts, water glass, surface treated silica, surface treated alumina, surface treated titanium dioxide, surface treated calcium carbonate and surface treated talc in natural or synthetic form, where available.

10. The labelstock of claim 9, wherein a majority by weight of the colloidal mineral particles are characterised by a mean diameter in at least two dimensions of not greater than about 0.075 micron in each of the at least two dimensions, wherein each of the at least two dimensions are substantially perpendicular with respect to each other.

11. The labelstock of claim 9, wherein a majority by weight of the colloidal mineral particles are characterised by a mean diameter in at least two dimensions of not greater than about 0.050 micron in each of the at least two dimensions, wherein each of the at least two dimensions are substantially perpendicular with respect to each other.

12. The labelstock of claim 9, wherein a majority by weight of the colloidal mineral particles are characterised by a mean diameter in at least two dimensions of not greater than about 0.025 micron in each of the at least two dimensions, wherein each of the at least two dimensions are substantially perpendicular with respect to each other.

13. The labelstock of claim 9, wherein a majority by weight of the colloidal mineral particles are characterised by an overall mean diameter of from about 0.01 micron to not greater than about 0.1 micron.

14. The labelstock of any preceding claim, wherein the polymer film substrate surface is printed with a radiation curable ink.

15. The labelstock of any preceding claim, wherein the polymer film substrate surface is printed with an ink selected from the group consisting of one-component inks, two component inks, oxidative curing inks, aqueous-based inks, solvent based inks, electro inks and dispersed inks.

16. The labelstock of any preceding claim, wherein the first polymer film substrate outer surface is printed with a different ink from the second polymer film substrate outer surface.

5

17. The labelstock of any preceding claim, wherein the polymer film substrate inner surface is coated with an adhesive from any of the following families: rubber-resin blends, acrylics or hot melt adhesives.

18. The labelstock of any preceding claim, wherein the first polymer film substrate inner

10 surface is coated with an adhesive from any of the following families: rubber-resin blends, acrylics or hot melt adhesives, and wherein the second polymer film substrate inner surface is coated with a different adhesive from that selected for the first polymer film substrate.

Intellectual

Property

Office

Application No: GB 1611850.7 Examiner: Mr Robert Black