EP0976580A1

EP0976580A1 - Pressure sensitive transfer label and method of applying such a label

Info

Publication number: EP0976580A1
Application number: EP98202537A
Authority: EP
Inventors: Thomas Lynn Brandt
Original assignee: Heineken Technical Services BV
Current assignee: Heineken Technical Services BV
Priority date: 1998-07-28
Filing date: 1998-07-28
Publication date: 2000-02-02

Abstract

The invention relates to a transfer label (1) comprising a carrier portion (2) having a substrate (3) which is on each side provided with a release layer (4,5). A transfer portion (6) is printed on the substrate and is provided with a pressure sensitive adhesive (8). The transfer label according to the present invention can be supplied from a roll or stack at high speeds at relatively low temperatures and provides for accurate alignment with relatively simple applicator equipment at room temperatures. The transfer labels can be applied in a permanent or in a removable manner on containers such as crates, glass or plastic bottles, metal beverage cans and the like.

Description

Background of the invention

The invention relates to a transfer label comprising:

a carrier portion having a substrate and a release layer overlying the substrate, and
a transfer portion printed on the release layer, comprising an ink layer and on top of the ink layer an adhesive layer.

The invention also relates to a method of applying such a label to a container, such as plastic crates, glass or plastic bottles, beverage cans and other containers used in the packaging industry. From EP-B-0,441,858 it is known to label containers with "ink-only" transfer labels wherein a removable backing layer is reverse printed with for instance a vinyl or acrylic ink which is then cured and wherein the printed inks overprinted with a heat activated adhesive. The label is applied to the container with its adhesive surface in contact with the container and the backing layer is separated from the label by the application of heat to cause a mechanical release of the ink from the backing layer. The labelled container is subsequently applied with a suitable coating which is then cured.
A method and device for applying removable transfer labels from a backing onto containers such as plastic crates is described in WO 97/35290, WO 97/35291, WO 97/35292 and European patent application number 96200780.3. In these patent applications it is described how a removable transfer label is applied to a pre-heated crate surface by means of a heated pressure roller. For short contact times between the label and the pressure roller, the crates are pre-heated and the pressure roller is heated to high temperatures. The use of high temperatures on the surface of a crate may cause an uneven surface resulting in visual deformations. The high temperatures of the heated pressure roller will reduce its life time when the pressure roller has a silicone rubber outer layer over a steel core, higher temperatures causes detachment of the silicone rubber from the core. Furthermore, heating of the substrate web may cause undesired stretch, which results in an inaccurate alignment of the transfer portions and the containers. Finally, heating the inks to higher temperatures may result in a degrading of ink quality, and loss of brightness of the colours.
It is therefore an object of the present invention to provide a transfer label and method of applying the same, which can be operated at high speeds with a simple applicator device at moderate temperatures, and whereby the above problems are mitigated.

Summary of the invention

Thereto the present invention is characterised in that the adhesive is a pressure sensitive adhesive, the substrate being provided on a second side with a second release layer which is adapted to prevent attachment of the adhesive to the second side of the substrate.
By using a pressure sensitive adhesive, the containers need not be pre-heated to high temperatures for efficient transfer. For pressure sensitive adhesives, the pressure applicator need not be heated, or is only heated to moderate temperatures, e.g. not higher then 50°C. This results in a long lifetime of the applicator and prevents problems of temperature induced deformation of the substrate of the container, and of the inks. The use of low temperatures results in reduced deformations and stress in the carrier material, which can be thinner than for the heat-activated transfer labels such that a cost saving is obtained. Furthermore, a postcuring step (heat treatment) as described in prior art reference EP-B-0.441.858 can be omitted.
The term "pressure sensitive adhesive" as is used herein is intended to mean an adhesive which have a substantially instantoneous adhesion at room temperature upon application of a light pressure.
By providing the second release layer on the substrate, the labels according to the present invention can be placed in a stack wherein the top layer of a lower label, which is comprised of the pressure sensitive adhesive, is contacted by the outer release layer of the adjacent transfer label. In particular, the labels can be supplied from a roll of a continuous web of label material without the pressure sensitive adhesive attaching (blocking) to the substrate, for reel-to-rel transfer to the container with mechanical release of the inks from the carrier portion.
The term "release layer" as is used herein, is intended to mean a layer which is coated on the substrate, or which may comprise a physical or chemical surface treatment of the substrate such as corona treatment, calendering, etc. causing a change in its release properties. It need not be possible in each case to define for the release layer a clear boundary or a dimension of predetermined thickness.
The transfer portions of the transfer labels according to the present invention have no structural integrity when removed from the carrier portion while not being supported by a container surface. The weight of the transfer portion according to the present invention is less than 25 g/m² preferably less than 15 g/m², most preferably about 12 g/m². The weight of the pressure sensitive adhesive is less than 10 g/m², preferably between 1 and 5 g/m², most preferably between 3 and 4 g/m².
Preferably the pressure sensitive adhesive comprises any of the group of acrylic based, urethane based or rubber (natural and synthetic) materials, which may be mixed with lacquer or bonding layer material (specify lacquer and bonding layer material in a chemical way.
The second release layer may comprise a polyethylene, silicone, acrylic, teflon or polyamide material or a combination thereof. A preferred combination of pressure sensitive adhesive and second release layer material is an acrylic based adhesive in combination with a silicon release layer.
Other suitable pressure sensitive adhesive compositions and release materials are described in WO 88/07931 WO 89/00106, which are incorporated herein by reference.
The inks may comprise acrylic, urethane, acrylic/urethane, polyester, vinyl, polyester/vinyl or epoxy ink materials, UV-curable inks or any combination thereof with or without the addition of external crosslinkers. A suitable material for the ink according to the present invention includes a waterborne organic as available from Environmental Inks and Coatings, Morganton, North-Carolina under type number Aqua BW EH-31721, EH-53016, EH-90967. These inks have a high stability even at temperatures over 200°C without discoloration or loss of adhesion, but other inks with lower temperature resistance may also be used, such as PLX8200, PLX8300 and PLX8530.
A boundary layer may be comprised between the ink layer and the first release layer. After transfer of the transfer portion to a container, the boundary layer will form the outermost layer that covers the ink and protects it against the intrusion of moisture, scratching, and other mechanical damage typical of filling line and post handling operations. A suitable boundary layer may be comprised of an acrylic, urethane, an acrylic/urethane, polyester, vinyl, polyester/vinyl, epoxy or lacquer material or any combination thereof. It is however also possible to apply a boundary layer, such as a polyethylene layer or a UV-curable acrylic material layer, after transfer of the transfer portion to the container, such as for instance described in US patent number 5,458,714.
In a further embodiment, a bonding layer is placed between the ink layer and the pressure sensitive adhesive. The bonding layer is compatible with both the ink and the adhesive and prevents interdiffusion of the ink and the adhesive layer. The bonding layer may be comprised of an acrylic, urethane, acrylic/urethane, polyester, vinyl, polyester/vinyl, epoxy, lacquer or a UV-curable material. Preferably the perimeter of the boundary layer overlaying the ink and the perimeter of the bonding layer extend beyond the ink patterns and contact each other to form an envelope around the ink layer. Such envelopes are very favourable in case a removable transfer label is applied such as described in WO 97/35290 and prevent the ink from dissolving in the wash solution during removal of the labels in a washing process.
A suitable peel force for removal of the transfer portion from the first release layer is 30 g/cm or less, preferably between 0.5 and 10 g/cm, more preferably between 0.5 and 1.5 g/cm on the press in a standard tape peel test within 5 hours after printing the labels. The peel force of the boundary layer may be about 60% lower upon ageing of the label after printing. The above peel forces allow a proper mechanical separation upon transfer of the transfer portion to a container. The peel force for removal of the adhesive from the second release layer is lower than the peel force of the transfer portion from the first release layer and is lower than 10 g/cm, such as between 0.2 and 5.0 g/cm, preferably between 0.2 and 1.0 g/cm. This allows for an easy separation of for instance stacked transfer labels or rolled up transfer labels upon supply from a storage cartridge or reel and prevents that, upon removal of a transfer label from the stack or upon unwinding of the storage reel, the transfer portion prematurely becomes detached.
The substrate may be formed from a single web of material which is provided on each side with a release layer, by means of coating, printing or physical treatment such as calendering, corona or plasma treatment. It is however also possible to combine two webs of material each provided on a single side with a specific release layer, in a back-to-back fashion into a laminate substrate material.
A method of applying a transfer portion from a label according to the present invention may be derived from the method as described in any of WO 97/35290, WO 97/35291, WO 97/35292 or European patent application number 96200780.3, wherein instead of a heated pressure applicator and the use of a pre-heating step of the container material, the labels can be transferred at room temperature at relatively low temperatures of the container and the pressure applicator.

Brief description of the drawings

The invention will be described in detail with reference to the accompanying drawings, wherein:
Figure 1 shows a cross-sectional view of a transfer label comprising a boundary layer, an ink layer and a pressure sensitive adhesive layer and a substrate having on each side a release layer,
Figure 2 shows a cross-sectional view of a transfer label wherein a bonding layer is comprised between the ink and the pressure sensitive adhesive,
Figure 3 shows a cross-sectional view of an embodiment of a transfer label without the boundary layer,
Figure 4 shows a schematic view of a supply reel comprising a rolled up web of transfer label material according to the present invention, and
Figure 5 shows a schematic view of a reel-to-reel application process of a transfer label according to the present invention.

Detailed description of the invention.

Figure 1 shows an embodiment of a transfer label 1 comprising a carrier portion 2 comprised of a substrate 3 and first and second release layers 4,5. On the first release layer 4, the transfer portion 6 is located for transfer to a container. The transfer portion 6 comprises an ink layer 7 and a pressure sensitive adhesive layer 8 overlaying the ink layer 7. A boundary layer 9 is comprised between the ink layer 7 and the first release layer 4. After detaching the transfer portion 6 from the carrier portion 2, the boundary layer 9 will form a protective, transparent coating over the ink layer 7 on the container. The adhesive layer 8 provides attachment of the ink to a container surface during storage and use conditions.
Figure 2 shows an embodiment wherein similar materials to those in figure 1 have been given like reference numerals and wherein an additional bonding layer 10 is applied between the ink layer 7 and the pressure sensitive adhesive layer 8. The bonding layer 10 prevents migration of the ink material 7 into the adhesive layer 8, and vice versa, and provides a proper bonding of the ink and the adhesive.
Finally, figure 3 shows an embodiment wherein no boundary layer is applied and the ink layer 7 and the bonding layer 10 are directly contacting the first release layer 4.
Upon stacking several transfer labels 1 according to the present invention, or when a continuous substrate web is used in a rolled up configuration as shown in figure 4, the second release layer 5 will contact the pressure sensitive adhesive layer 8. Hereby attachment of the pressure sensitive adhesive layer 8 to the substrate 3 is prevented.

The carrier portion

The carrier portion 2 may be formed of a substrate 3 comprised of a paper web, a plastic film, or a laminate of paper and plastic. A suitable substrate 3 is formed by example a double siliconized oriented polypropylene (OPP) layer.
The release material 4 of the first release layer may be comprised of a polyethylene, silicone, acrylic, teflon or polyamide release material. The release material 4 may comprise a silica-alumina material such as for instance a Plankton Marine Diatomite as a separating agent containing for instance 89.6 weight % SiO₂, 4.0 weight % A1₂O₃, 1.3 weight % Fe₂O₃ and about 3.3 weight % NA₂O + K₂O. This specific release agent provides for a reliable anti-static release of the transfer portion from the carrier web.
A suitable substrate 3 and release material for first and second release layers 4 and 5 is for instance produced by the Mobil Chemical Company of Pittsford New York, as Mobiliner 2000, which is a silicon coated 2.0 mil biaxially oriented polypropylene film. This substrate has a release force of between 10 and 40 g/in, preferably around 25 g/in, as measured according to reference test procedure REL-401.
The first release layer 4 will provide a mechanical release from the boundary layer 9 or from the ink 7 and the bonding layer 10 after attachment of the adhesive 8 to a container and peeling off the carrier portion 2 from the transfer portion 6. Suitable peel forces at transfer are between 0.5 g/cm and 10 g/cm, preferably between 0.5 and 1.5 g/cm.
The second release layer 5 may be comprised of the same materials as the first release layer 4, but is preferably adapted to provide a release surface for the pressure sensitive adhesive 8. Suitable release materials for the second release layer 5 are silicone based. Another carrier portion 2 is availabe from DCP-LOHJA,Inc. of 770 Griffin Way, Willowbrook, IL 60521-5623 USA under product type nr. 2-2 BOPPLA 8000A and 2-2 BOPPLA 8250.
Suitable methods of manufacturing the carrier portion 2 comprise:

providing a single web 3 and coating both sides with a single release layer material,
providing a single web 3 and treating one or both surfaces with electric charge followed by coating the other side with a release material, and
providing two webs, each on one side provided with a release layer and combining them in a back-to-back manner.

The transfer portion

The boundary layer 9 of the transfer portion 6 may be formed of an acrylic, urethane, acrylic/urethane, polyester, vinyl, polyester/vinyl, epoxy or lacquer material, a UV-curable material or any combination thereof. The ink layer 7 may be formed of acrylic, urethane, polyester, vinyl, polyester/vinyl, or epoxy ink materials or combinations thereof. A suitable pressure sensitive adhesive 8 is formed by an acrylate based material such as available from EIC of nr. 1 Quality products road, Morganton, N.C. 28655 USA under type nr. XP-002117.
An example of a transfer portion 6 comprises a central ink layer 7, a boundary layer 9 made of lacquer and a bonding layer 10 made of lacquer. The uncured lacquer consists of di- and tri-acrylated UV-curable prepolymers and a photo-initiator. After a curing under UV-radiation (degree of curing 95-98%) a highly crosslinked (hydrophobic) polymer network is formed that chemically binds and traps most of the starting components. The inks can be composed of pigments and UV-curable acrylates. The two layers of lacquer are meant to prevent loss of ink components. The adhesive layer may be a UV-curable material or a solvent type adhesive which may comprise a solid contents of about 50% of synthetic rubber and a solvent contents of about 42% solvent naphtha and about 7% methylpentane.
When the transfer portion of the label according to the present invention is to be attached to glass surfaces, it is advantageous to add to Silane to the adhesive composition.
Figure 4 shows a supply reel 14 of a rolled up web of label material 13. The web 13 comprises a substrate 19 having continuous first and second release layers 17,18. Transfer portions 16, 16' are placed at regular intervals on the substrate 19. In the rolled up state, the adhesive of the transfer portions 16,16' will contact the second release layer 18.
Upon unwinding of the substrate 19 from the supply reel 14, the peel force for detaching the adhesive of the transfer portions 16,16' from the second release layer 18 is lower than the peel force required for removal of the transfer portions 16,16' from the first release layer 17, such that the transfer portions remain in the properly aligned position until the moment of transfer to a container.

Application method

Figure 5 shows a schematic overview of the application process of a transfer portion from the transfer label according to the present invention onto a container, such as a returnable plastic crate 20. The crates are supplied in a direction of transport T indicated by the arrows, along an applicator station 21, at a rate of for instance 40 crates per minute. A web of label material 22 is supplied from a supply reel 23 to a pressure applicator head 24. After transfer of the transfer portions to the crates 20, the empty carrier portion of the web 22 is taken up on the take up reel 25. The pressure applicator head 24 comprises two film guides 26,27 and an air cylinder 28 which is movable between an application position, as shown in the dashed and dotted lines, and a retracted position wherein the web 22 runs free from the crates 20.
As the applicator process proceeds at relatively low temperatures, the film stretch of the web material 22 can be limited and the film guides 26,27 may in that case even be omitted. For more flexible substrates however, the use of the film guides 26,27 is preferred.
After label application, the ink of the transfer portion may be protected against scratching by casual handling as well as being provided with increased weatherability when subjected to outdoor storage, by the application of an acrylic based wax and water emulsion at the station 30. This coating is applied by a roll applicator 31 which is supplied from a wet roller with a controlled amount of coating. Control is achieved with a doctor blade. The coating extends well past the edges of the ink pattern and seals the edges from intrusive moisture.
The final processing step may be to coalesce the layers of the coating, label ink and adhesive at the station 32 by means of a flame heater 33 and also to interdiffuse the adhesive layer with the polyethylene substrate formed by the crate 20, although the latter step can, by use of the pressure sensitive adhesive material, be omitted.
Even though the invention has in figure 5 been described with reference to plastic crates, it can also be applied to other containers such as plastic or glass bottles, metal beverage cans and other type of containers that are used in the packaging industry. The present invention can also be used with good effects for instance for high speed bottle labelling at for instance 1000 bottles per minute. The transfer labels according to the present invention can be applied to containers in a permanent manner or can be washable, for instance by means of high pressure liquid jets or by a soaking process such as described in WO 97/35290, WO 97/35291, WO 97/35292 and European patent application nr. 96200780.3.

Claims

Transfer label (1) comprising:

a carrier portion (2) having a substrate (3) and a release layer (4) overlying the substrate, and

a transfer portion (6) printed on the release layer (4), comprising an ink layer (7) and on top of the ink layer an adhesive layer (8),
characterised in that, the adhesive is a pressure sensitive adhesive, the substrate (3) being provided on a second side with a second release layer (5) which is adapted to prevent attachment of the adhesive layer (8) to the second side of the substrate.
Transfer label according to claim 1, characterized in that the weight of the transfer portion (6) is less than 25 g/m², preferably less than 15 g/m², the weight of the adhesive being less than 10 g/m², preferably being between 1 and 5 g/m², most preferably between 3 and 4 g/m².
Transfer label (1) according to claims 1 or 2, wherein the adhesive comprises any of the group of acrylic based, urethane based, synthetic or natural rubber based materials.
Transfer label (1) according to claims 1, 2 or 3, wherein the second release layer (5) comprises a polyethylene, silicone, acrylic, teflon or polyamide material, or any combination thereof.
Transfer label (1) according to any of the previous claims, wherein a boundary layer (9) is comprised between the ink layer (7) and the first release layer (4).
Transfer label (1) according to claim 5, wherein the boundary layer (9) comprises an acrylic, urethane, an acrylic/urethane, polyester, vinyl, polyester/vinyl, epoxy or lacquer material, or any combination thereof.
Transfer label (1) according to any of the previous claims, wherein perimeter of the boundary layer (9) extends beyond the perimeter of the ink layer (7).
Transfer label (1) according to any of the previous claims, wherein a bonding layer (10) is placed between the ink layer (7) and the adhesive layer (8), the bonding layer (10) comprising acrylic, methane, acrylic/methane, polyester, vinyl, polyester/vinyl, epoxy or lacquer material, or any combination thereof.
Transfer label (1) according to claims 7 and 8, wherein the boundary layer (9) and the bonding layer (10) contact each other beyond the perimeter of the ink layer (7) to form an envelope around the ink layer.
Transfer label (1) according to any of the previous claims, wherein the peel force for removal of the transfer portion (6) from the first release layer (4) is larger than the peel force for removal of the adhesive layer (8) from the second release layer (5).
Transfer label (1) according to claim 10, wherein the peel force for removal of the transfer portion (6) from the first release layer (4) is less than 30 g/cm, preferably between 0.5 g/cm and 10 g/cm, more preferably between 0.5 g/cm and 1.5 g/cm, the peel force for removal of the adhesive layer (8) from the second release layer (5) being lower than 10g/cm, preferably between 0.2 g/cm and 5 g/cm, more preferably between 0.2 g/cm and 1.0 g/cm.
Transfer label (1) according to any of the previous claims, wherein the substrate (3) comprises a laminate of a first web carrying the first release layer (4) and a second web carrying the second release layer (5), the first and second webs being combined back to back.
Rolled up web (14) comprising transfer labels according to any of the previous claims, comprising a continuous substrate (19) and transfer portions (16,16') at regularly spaced intervals on the substrate (19).
Rolled up web (14) according to claim 13, characterised in that, the first and second release layers (17,18) are continuous layers.
Stack comprising transfer labels according to any of claims 1 to 12, wherein the second release layer (5) of an upper label contacts the adhesive layer (8) of an adjacent, lower label.
Method of applying a label according to any of claims 1 to 12 claims to a container (20), comprising the steps of:

supplying a label to a transfer station with the adhesive layer (8) facing the container (20),

pressing the label against the container at a temperature between 0°C and 50°C, preferably about room temperature, and

peeling off the substrate (3) from the attached transfer portion (6).