Printable label comprising a clear face layer and a clear adhesive layer

An adhesive label comprises:

FIELD

Some versions relate to a printable label, which comprises a clear face layer and a clear adhesive layer. Some versions relate to a labelstock, which comprises a plurality of labels. Some versions relate to a method for attaching a label to an item. Some versions relate to a labeled item.

BACKGROUND

It is known that a printed paper label may be attached to an item in order to provide printed information about the product. The label may be attached to an item by using a labeling apparatus. The labeling apparatus may be arranged to operate at a high rate. For example, the labeling apparatus may be arranged to attach labels to glass bottles at a rate, which is higher than 750 labels per minute. The labels may be provided e.g. as a wound roll, which may comprise e.g. thousands of labels.

SUMMARY

Some versions may relate to an adhesive label, which comprises semi-crystalline polymeric film. Some versions may relate to a labelstock comprising a plurality of adhesive labels. Some versions may relate to a method for producing a labelstock. Some versions may relate to a method for attaching a label to an item. Some versions may relate to a labeled item.

According to an aspect, there is provided a label, which comprises:a face layer, andan adhesive layer,
wherein the face layer comprises semi-crystalline polymeric film, the adhesive layer consists of one or more adhesive sub-layers, a lowermost adhesive sub-layer of said adhesive sub-layers comprises transparent polymeric adhesive, the thickness of the face layer is in the range of 10 μm to 50 μm, the thickness of the adhesive layer is in the range of 8 μm to 25 μm, the thickness of the adhesive layer is smaller than 95% of the thickness of the face layer, an uppermost sub-layer of said adhesive sub-layers is in contact with the face layer, and the refractive index of the uppermost adhesive sub-layer is in the range of 80% to 98.5% of the refractive index of the semi-crystalline polymeric film.

According to an aspect, there is provided a labeled item comprising a label attached to the surface of the item, said label comprising:a face layer, andan adhesive layer,
wherein the face layer comprises semi-crystalline polymeric film, the adhesive layer consists of one or more adhesive sub-layers, a lowermost adhesive sub-layer of said adhesive sub-layers comprises transparent polymeric adhesive, the thickness of the face layer is in the range of 10 μm to 50 μm, the thickness of the adhesive layer is in the range of 8 μm to 25 μm, the thickness of the adhesive layer is smaller than 95% of thickness of the face layer, an uppermost sub-layer of said adhesive sub-layers is in contact with the face layer, and the refractive index of the uppermost adhesive sub-layer is in the range of 80% to 98.5% of the refractive index of the semi-crystalline polymeric film.

According to an aspect, there is provided a method for labeling items, the method comprising:separating a label from a release liner by using peel plate,moving the surface of an item in a first direction,moving the label in a second direction, andbringing a leading edge of the label into contact with a surface of the item such that the angle between the first direction and the second direction is in the range of 10° to 30°,
wherein the label comprises:a face layer, andan adhesive layer,

wherein the face layer comprises semi-crystalline polymeric film, the adhesive layer consists of one or more adhesive sub-layers, a lowermost adhesive sub-layer of said adhesive sub-layers comprises transparent polymeric adhesive, the thickness of the face layer is in the range of 10 μm to 50 μm, the thickness of the adhesive layer is in the range of 8 μm to 25 μm, and the thickness of the adhesive layer is smaller than 95% of thickness of the face layer.

The life cycle of the above-mentioned label containing the semi-crystalline polymeric film may include e.g. manufacturing, storing, transportation, labeling, and recycling of waste material. By using the label, the total costs associated with the whole life cycle of the label may be reduced. Using the label may provide a cost-efficient way for improving the visual appearance of an item. Using the label may provide a cost-efficient way for altering the visual appearance of an item. Using the label may provide a cost-efficient way for adding a marking to an item. Using the label may provide a cost-efficient alternative for printing directly on the surface on an item. Using the label may allow less frequent change of rolls for a labeling apparatus, as a single roll may comprise an increased number of labels. Using the label may be facilitate transportation of a large amount of labels. Using the label may be facilitate storing a large amount of label. Producing the labelstock may consume materials. When using the label, the amount of raw materials needed for the production may be substantially reduced. Using the label may be environmentally friendly.

High Speed Labeling

Using the label may facilitate high speed labeling, wherein the rate of labeling may be e.g. higher than or equal to 750 labels per minute. For example, a labeling apparatus may be arranged to attach labels to more than 750 glass bottles per minute.

The polymeric face layer of the label may be oriented by uniaxial or biaxial stretching during manufacturing of the polymeric semi-crystalline film. The uniaxially or biaxially oriented face layer may be dimensionally stable. The dimensional stability may facilitate accurate positioning of the labels during high speed labeling.

When using the stretched polymeric material, the relative stiffness of the face layer may also increase with decreasing thickness of the face layer. The stiffness may be proportional to the second moment of area multiplied by the tensile modulus. The relative stiffness of the face layer may be proportional to the stiffness of the face layer divided by the thickness of the face layer. The stiffness of the label may facilitate dispensing. The stiffness of the label may facilitate separation of leading edge of the label from a release layer during the dispensing. The stiffness of the label may facilitate handling of the label when it is separated from the release layer. Thus, the uniaxially or biaxially oriented face layer may facilitate use of the labels for high speed labeling.

Visual Appearance

The label may comprise a transparent portion. For example, more than 20% of the (one-sided) area of the label may be transparent, and the remaining area of the label may comprise one or more printed markings. The original surface of an item may be observed visually through the label, after the label has been attached to said original surface. The original surface may form a visual background for the markings of the label. The original surface may highlight the markings of the label. Using the markings together with the background may improve the visual appearance of the labeled item. The markings may be associated with a trade mark and/or brand. Combining the markings of the label with the original surface of the item may emphasize the visual appearance of the brand. A potential customer may simultaneously see the marking and the texture of the original surface of the item through the clear portion of the label. Combining the marking of the label with the original surface of the item may emphasize the association formed between the marking and the item.

The dimensionally stable face layer may allow precision printing and accurate positioning of the label with respect to the labelled item. The dimensionally stable face layer may allow accurate positioning of the marking with respect to the label. The dimensionally stable face layer may allow accurate positioning of the label with respect to the item. The dimensionally stable face layer may allow accurate positioning of the marking of the label with respect to the item.

The label may comprise two or more layers, wherein each layer may have a different function. Each layer may have its own optical properties. The visual appearance of the label may depend on the optical characteristics of the layers of the label. In particular, the visual detectability of the label may depend on the optical characteristics of the layers of the label.

The optical properties of the label may be tailored by selecting the optical properties of the structural layers of the label. The optical properties of the label may depend on the optical properties of the structural layers in the visible spectrum of light. The visible spectrum may refer to the wavelength range from 380 nm to 760 nm.

The refractive index of the face layer may be increased by using uniaxially or biaxially oriented polymeric semi-crystalline film. Consequently, the upper surface of the face layer may provide more intense optical reflections. In particular, the label may provide a high gloss effect.

The label may provide a “no-label look”, i.e. the label and the background may be combined such that the color and the texture of the background is visible through the transparent portion of the label.

The transparent portion of the label may allow substantial freedom to select the shape and position of the marking with respect to the background. Using the label may provide a cost-effective solution e.g. when compared with a printed marking, which would be directly printed on the surface of the item.

The shape of the perimeter of a printed region of the label may be substantially different from the shape of the perimeter of the label. For example, the label may be substantially rectangular, wherein the printed region may be e.g. circular, oval, triangular, diagonal and/or slanted. For example, the label may be substantially oval or circular, wherein the printed region may be substantially rectangular. The printed region of the label may comprise e.g. a square, circular or irregular graphical pattern surrounded by a clear portion of the label.

The small thickness of the label may improve the transparency of the label. The small thickness may reduce absorption and scattering in the face layer and in the adhesive layer. The small thickness of the label may make the edges of the label less discernible, by reducing scattering of light from the edges when the label has been attached on the surface of the item.

In an embodiment, the total thickness of the label may be so small that the edge of the label is less discernible when viewed by bare eyes. For example, the total thickness of the label may be smaller than 38 μm (1.5 mils), or even smaller than 25 μm (1.0 mils).

The label may merge visually into the background provided by the surface of the item. The properties of the label may be selected such that it may be rather difficult to visually detect the clear portions of the label when the label has been attached on the surface of the item.

Smoothing Effect

The clear portion of the label may have a capability to hide visually detectable irregularities and/or scratches of the surface of the item. Attaching the label to the item may improve the visual appearance of the item. For example, the adhesive layer may fill imperfections of the surface of the item, wherein the high refractive index of the adhesive layer may reduce optical scattering from the irregularities and/or scratches of the surface of the item.

The face layer and the adhesive layer may be easily bent to conform to cylindrically curved surfaces, e.g. to the surface of a typical glass bottle. The label may conform to the principal radius of curvature of the surface of the item. Consequently, the edges of the label may remain substantially unnoticeable. The thin label may cover the surface of the item so that the edges of the label protrude very little from the surface of the item. The low elevation of the edges of the label and the high dimensional stability of the face layer may reduce the risk of damaging the label during handling of a labeled item.

Controlling the Size of Air Bubbles

Using the thin labels in high speed labeling may sometimes cause trapping of air bubbles between the labels and the items. The air bubbles may be caused e.g. by a high-speed release behavior of the adhesive layer, when the adhesive label is separated from the liner during the labelling process. Rapid separation of the adhesive layer from the release layer during high speed labeling may temporarily increase the roughness of the exposed adhesive layer. The time delay between peeling and contact with the item may be so short that air may be carried to the interface by the irregularities of the exposed adhesive layer. When the adhesive layer is peeled away from the release layer at high speed, the exposed surface of the adhesive layer may remain slightly irregular so that the adhesive layer does not have time to smoothen before being attached on the substrate surface. Consequently, one or more air bubbles may be formed due to air trapped between the label and the substrate surface.

The adhesive of the label may cover the surface of the item by wetting. The wetting may ensure that the label is firmly attached to the surface of the item. The wetting may also (slowly) move air beneath the label so that microscopic air bubbles coalesce to form visually detectable larger air bubbles. The wetting may be arranged to eliminate gas bubbles, by causing overpressure and diffusion of the gas away from the bubbles. Temporal behavior of air bubbles may be controlled by selecting the materials and the dimensions of the label. The materials and the dimensions of the label may be selected such that small air bubbles trapped between the label and the item may substantially disappear e.g. within 24 hours.

An air cushion may be formed due to the rapid movement of the label so that air is entrained to the space beneath the label. The labeling speed may be so high that the air does not have time to escape from the gap between the label and the item. The dispensing geometry may be selected to minimize the effect of the air cushion. The dimensional stability of the label may be utilized when reducing the amount of air trapped between the label and an item. The dimensional stability of the label may substantially prevent formation of large air bubbles during the dispensing, when using a suitable dispensing geometry. Formation of air bubbles may be controlled by selecting the dispensing parameters.

All drawings are schematic.

DETAILED DESCRIPTION

Adhesive Label

Referring toFIGS. 1a, 1b, and 1c, the adhesive label100may comprise a face layer10, and an adhesive layer20. The adhesive label100may optionally comprise a printed region30. The printed region30may be located between the face layer10and the adhesive layer20(FIGS. 1aand1b). The face layer10may mechanically protect the printed region30.

The printed region30may be implemented on top of the face layer10(FIG. 1c). The printed region30may comprise a marking MRK1. The marking MRK1may comprise e.g. alphanumerical symbols and/or graphics.

Referring toFIG. 1a, the adhesive layer20may comprise one or more adhesive sub-layers21,22. The adhesive layer20may consist of one or more adhesive sub-layers21,22. The adhesive layer20may adhere to the surface SRF0of an item ITE1(FIG. 2a). The adhesive layer20may form an adhesive bond between the face layer10and the surface SRF0of the item ITE1. The uppermost sub-layer21may be in contact with the face layer10, and the lowermost sub-layer22may be in contact with the item. At least a portion of the uppermost sub-layer21may be in contact with the face layer10. The label100may comprise a printed region30implemented between the face layer10and the adhesive layer20such that at least a portion of the uppermost sub-layer21is in contact with the face layer10. The lowermost sub-layer22may adhere to the surface of an item. The chemical composition of the uppermost sub-layer21may be different from the chemical composition of the lowermost sub-layer22. The composition of the sub-layers21,22may be tailored to optimize the optical and mechanical properties of the label, and/or in order to reduce material costs. For example, the chemical composition of the lowermost sub-layer22may be selected to maximize adhesion. For example, the chemical composition of the uppermost sub-layer21may be selected to minimize optical reflectivity of the interface between the uppermost sub-layer21and the face layer10. For example, the chemical composition of the lowermost sub-layer22may be selected to minimize optical reflectivity the interface between the lowermost sub-layer22and the item.

Referring toFIG. 1b, the adhesive layer20may consist of only one sub-layer, wherein the uppermost sub-layer may also be act as the lowermost sub-layer.

The label100may comprise a substantially clear portion. The clear portion may be called as substantially transparent portion. The face layer10may comprise or consist essentially of suitable clear, semicrystalline polymeric film, in order to provide the clear portion. The face layer10may comprise semi-crystalline polymeric film. The semi-crystalline polymeric film may be e.g. a polyester film. The polyester film may be e.g. polyethylene terephthalate (PET). The polyester film may be e.g. polyethylene naphthalate (PEN).

The adhesive layer20may comprise transparent polymeric adhesive. The adhesive layer20may comprise acrylic polymeric adhesive. The polymeric adhesive may also be e.g. a non-water whitening polymeric adhesive

The thickness d10of the face layer10may be e.g. in the range of 10 μm to 50 μm, and the thickness d20of the adhesive layer20may be e.g. in the range of 8 μm to 25 μm. The thickness d20of the adhesive layer20may be smaller than 95% of the thickness d10of the face layer10.

The thickness of d10of the face layer10may be e.g. substantially equal to 18 μm. The thickness of d10of the face layer10may be e.g. substantially equal to 19 μm. The thickness of d10of the face layer10may be e.g. substantially equal to 23 μm.

The thickness d20of the adhesive layer may be selected according to the thickness of the face layer. The thickness d20of the adhesive layer20may be e.g. in the range of 50% to 95% of the thickness d10of the face layer10.

When the thickness d10of the face layer10is in the range of 12 μm to 25 μm, the thickness d20of the adhesive layer20may be e.g. in the range of 8 μm to 24 μm.

The refractive index n2of the uppermost adhesive sub-layer20may be e.g. in the range of 80% to 98.5% of the refractive index n1of the semi-crystalline polymeric film. The refractive index n2of the uppermost adhesive sub-layer20may be e.g. in the range of 80% to 98.5% of the refractive index n1of the semi-crystalline polymeric film at the wavelength of 550 nm. Consequently, the reflection coefficient R2of the optical interface between the face layer10and the adhesive layer20may be kept below a predetermined value. The refractive index n1and n2may be determined e.g. at the wavelength of 550 nm. The wavelength of 550 nm may be considered to represent green light.

The label100may be provided such that the label100is carried by a release liner90(FIG. 6a). The adhesive layer20may be located between the face layer10and the release liner90. The release liner90may comprise e.g. polyester or paper. The release liner90may comprise a non-blocking surface layer91(FIG. 9b). The surface layer91may comprise e.g. silicone polymer. The label100may be attached to a release liner90comprising a non-blocking surface layer91, such that the adhesive layer20is between the face layer10and the non-blocking surface layer91of the release liner90.

The uppermost layer of the label100may consist of polyester film, or the face layer10of the label100may be optionally coated with a release coating. The release coating may e.g. facilitate keeping the label clean after it has been attached to an item.

The combination of a plurality of labels and the release layer carrying the labels may be called as a labelstock STO1(FIG. 6a). The release layer may support a plurality of labels. The labelstock STO1may comprise a plurality of labels attached to the release layer90.

The total thickness dtotof the label100may be e.g. in the range of 150% to 195% of the thickness d10of the face layer10, when the label100is not attached to the release layer. The total thickness dtotof the label100may mean the thickness from the uppermost surface of the face layer10to the lowermost surface of the lowermost adhesive sub-layer.

The label100may also be provided as a linerless label (FIG. 10a). A plurality of linerless labels may be supplied as a roll (FIG. 10d). When the label is supplied as a linerless label, the uppermost surface of the label100may be coated with a release coating in order to avoid blocking of the roll.

Face Layer

The face layer10of the label100may provide e.g. one or more of the following functions:the face layer10may carry one or more printed regions30,the face layer10may protect the one or more printed regions30,the face layer10may provide transparency,the face layer10may provide a no-label lookthe face layer10may provide a vanishing edge VE1,the face layer10may provide low visual contrast when compared with an exposed (non-labelled) portion of the labeled item,the face layer10may provide a highly reflective upper surface,the face layer10may provide a lower surface, which has a low optical reflectivity,the face layer10may provide sufficient stiffness for high speed dispensing of the label100,the stiff and thin face layer may facilitate controlling the dispensing geometry,the face layer may provide longitudinal tension for controlling dispensing geometry,the face layer may allow diffusion of air away from air bubbles trapped beneath the label,the face layer10may smooth out irregularities of the item by conforming to the curved shape of an item,the face layer10may carry other labels in linerless applications.
Material of the Face Layer

The face layer10may comprise thermoplastic polymer. Preferably, the face layer10is semi-crystalline polymer, such as polyester. Polyesters such as polyethylene terephthalate and polyethylene naphtalate can be in semicrystalline form. The face layer10may be of polyethylene terephthalate or polyethylene naphtalate. Polyethylene terephthalate of the layer10may have an a density in the range of 1.35 to 1.45 g/cm3, preferably close to 1.4 g/cm3. The density may be determined according to ASTM D-1505.

The optical characteristics of the filmic polyester material may depend on the crystallinity of the polymer, on the alignment of the molecular chains, and on the thickness of the filmic polyester material. The crystallinity of the polymer and the alignment of the molecular chains may be controlled by the manufacturing method of the polyester material. Polyesters such as polyethylene terephthalate or polyethylene naphtalate may have a crystal size distribution. Depending on the crystal size distribution, the polymer material may be arranged to appear transparent, opaque or white. The semi-crystalline polymer material may comprise ordered regions where the polymer chains are both aligned and folded. Said ordered regions may be called e.g. as crystallites, crystals or grains. The crystallites may act as scattering centers for light. The characteristic size of the crystallites may be e.g. smaller than 400 nm, in order to provide a substantially transparent material.

Optical Absorption

The face layer10may be relatively thin. The thickness d10of the face layer may be e.g. smaller than or equal to 25 μm, smaller than or equal to 20 μm, or even smaller than or equal to 15 μm. The thickness d10of the face layer may be e.g. in the range of 10 μm to 25 μm. The thin layers10,20may reduce the length of the optical path of light when said light travels through the label100. The short length of the optical path may reduce the attenuation of the light travelling through the label100. Consequently, the label100may appear to be clear even in a situation where the face layer10and/or the adhesive layer20would contain slightly light-absorbing material. The label100may appear to be clear even in a situation where the face layer10and/or the adhesive layer20contain impurities. This may reduce material costs.

Optical Scattering by the Face Layer (Haze Level)

Optical scattering by the face layer10may be determined from a label or a label layer as a haze value e.g. according to standard ASTM D-1003. The face layer10may have a low haze level. The face layer may be filmic polyester having a haze value equal to or less than 6.5%, advantageously equal to or less than 4.0%, and preferably equal to or less than 3.6%. The haze value of the face layer10may be e.g. in the range of 1.0% to 3.6%. The face layer10may also comprise “ultra” clear polyester film, wherein the haze value of the face layer10may be in the range of 0.5% to 1.0%. The face layer10may be filmic polyester having a thickness in the range of 12 μm to 23 μm (0.48 mil to 0.92 mil) wherein the haze value of the face layer10may be in the range of 0.5% to 3.6%.

Stiffness

The stiffness of the label100may be mainly determined by the stiffness of the face layer10. The stiffness of the face layer10may be equal to the second moment of area multiplied by the tensile modulus. The relative stiffness of the face layer10may be equal to the stiffness of the face layer10divided by the thickness d10of the face layer10. The face layer10may be uniaxially or biaxially oriented to provide a sufficient stiffness for the label100such that the label100may be dispensed at high-speed on a moving item ITE1.

The face layer10has a first tensile modulus in the machine direction (MD) and a second tensile modulus (CD) in the cross direction. The face layer may be filmic polyester having a tensile modulus, which is e.g. higher than 2700 MPa. The face layer may be filmic polyester having a tensile modulus, which is higher than 4000 MPa. The face layer may be filmic polyester having a tensile modulus, which is higher than 4150 MPa.

When the polyester film is bi-axially oriented, the tensile modulus of the polyester film may be substantially similar in both machine direction and cross direction. The face layer10may be made of a PET film, wherein the tensile modulus of the PET film may be e.g. than higher than 4000 MPa in the machine direction (MD), and/or the tensile modulus of the PET film may be higher than 4000 MPa in the cross direction (CD). The face layer10may be made of a PET film, wherein the tensile modulus of the PET film may be e.g. than higher than or equal to 4150 MPa in the machine direction (MD), and/or the tensile modulus of the PET film may be higher than or equal to 4150 MPa in the cross direction (CD). The tensile modulus may be determined according to standard ASTM D 882.

The stiffness of the label may be selected to be in a predetermined range so that the thin face layer may still be able to conform to the shape of the item. When attached to the item, the face material may bend and conforms to a principal radius of curvature of the substrate surface.

Hardness of the Face Layer

The hardness of the face layer10may be increased e.g. by uniaxial or biaxial stretching so as to reduce ghosting of the label when the label is supplied as a part of a wound roll. The term “ghosting” may mean a visible deformation made by the edge of a second label on the surface of a first label when the edge of said second label is pressed against the surface of the first label. The hardness of the face layer10may be e.g. higher than 94 in the Rockwell M scale.

Adhesive Layer

The adhesive layer20of the label100may have e.g. one or more of the following functions:the adhesive layer20may adhere to the surface of an item,the adhesive layer20may provide transparency,the adhesive layer20may reduce the reflection coefficient of the interface between the face layer10and the adhesive layer20,the adhesive layer20may fill and hide optical defects of the surface of the item,the adhesive layer20may allow separation of the label from a release liner,the adhesive layer20may at least partly control longitudinal tension of the label during dispensing,the adhesive layer20may reduce the size of gas bubbles by wetting,

The label100comprises an adhesive layer20of polymeric material. The adhesive layer20may be arranged to attach the label on a substrate surface SRF0. Composition of the adhesive layer in this context refers to an adhesive substance, such as a polymeric compound, which has a tendency to adhere to the surface of an item by means of chemical adhesion and/or by means of dispersive adhesion. The adhesive substance of the layer20may adhere to the surface of an item by means of covalent bonds and/or by intermolecular attraction.

The adhesive layer composition may further be arranged to promote the optical characteristics of the label, such as clarity and “no-label look”.

The adhesive layer may be configured to be self-adhesive, such that the label may be attached on the intended substrate surface material by pressing. The adhesive layer may comprise pressure sensitive adhesive (PSA). The adhesive layer may comprise pressure sensitive acrylic polymer adhesive.

The adhesive layer may comprise or consist essentially of polymeric adhesive. The adhesive layer may comprise or consist essentially of a polymeric adhesive suitable for clear label applications.

The polymeric adhesive of the layer20may be substantially transparent so that the adhesive layer of the label may contribute to the “no-label look”. The refractive index of the polymeric adhesive may be selected to reduce reflectivity of the interface between the adhesive layer20and the face layer10. The refractive index of the polymeric adhesive may be selected to reduce reflectivity of the interface between the adhesive layer20and the item ITE1.

Tack Value

The adhesive may be a pressure sensitive adhesive. The adhesive of the layer20may have a sufficient tack value so that the label is not peeled away from a labeled item during normal use of the labeled item. The adhesive of the layer20may have a sufficient tack value so that the label may withstand temperature fluctuations and humidity.

The tack value of the polymeric adhesive may be e.g. higher than or equal to 9N, such that the label may be firmly attached to the surface of the item.

The polymeric adhesive of the label may be arranged to have a release value higher than 15 g, preferably equal to or higher than 19 g, such as in the range of 19 to 23 g, as measured in a TLI release tester according to a modified FINAT test method, wherein a test tape is pulled at an angle of 180 degrees at a velocity of 1200 inches per minute, wherein the width of the test tape is equal to 2 inch, and the adhesive layer of the test tape consists of said polymeric adhesive.

The loop tack value of the polymeric adhesive may be equal to or higher than 0.4 kN/m. The loop tack value may be measured according to the method “LIB” as specified by the TLMI standardizing organization. TLMI means the Tag and Labels Manufacturing Institute, USA.

Wetting

The adhesive layer have an ability of eliminate small irregularities such as scratches from the substrate surface. A well-wetting adhesive may have an ability to spontaneously spread on a surface when the adhesive has been brought into contact with said surface. Wettability may define the capability of the polymeric adhesive to spread on a solid surface upon contact to the surface. The wetting properties of the polymeric adhesive may be selected such that when applied on a substrate surface having surface roughness, the polymeric adhesive may flow to the lower parts or valleys of the substrate surface. The adhesive material of the label may fill the lower parts or valleys of an irregular surface of the item.

The wetting properties of the polymeric adhesive applied on the surface of a material may be described by a contact angle (θc) of the polymeric adhesive. The contact angle (θc) may depend on the composition of the polymeric adhesive and on the composition of the material. When applied on a solid substrate surface, the polymeric adhesive has a tendency to spread until the internal forces of the adhesive, the gravity forces and the surface tension forces are in balance, such that an equilibrium state is reached. The advancing contact angle (θc) for wetting a polyethylene terephthalate surface with the polymeric adhesive may be e.g. lower than 70° when determined at the temperature of 25° C. In case of spontaneous wetting, the advancing contact angle (θc) for wetting a polyethylene terephthalate surface with the polymeric adhesive may be e.g. lower than 70° when determined at the temperature of 25° C. The contact angle may be different when the adhesive layer20is compressed between the face layer10and the surface SRF0of the item ITE1.

The adhesive layer may have a low surface energy level, so as to improve the wettability of the surface SRF0of the item ITE1. The surface tension of the polymeric adhesive may be e.g. lower than or equal to 40 dyn/cm when determined at the temperature of 25° C. The adhesive having a surface tension lower than or equal to 40 dyn/cm may be suitable for forming an adhesive bond with e.g. polyethylene terephthalate, glass, and/or aluminium.

Bleeding

When the labelstock is wound to form a roll, the pressure of the roll may cause the adhesive to bleed at the edges of the label. When dispensing the labels, the bleeding may cause accumulation of adhesive at different parts of the dispensing unit. The accumulation of adhesive may disturb operation of the labeling apparatus.

The low thickness of the adhesive layer20may reduce the risk of bleeding. The adhesive layer20may have a low coat weight. The coat weight of the adhesive may be e.g. in the range of 5 to 15 g/m2.

Release Liner

The adhesive label100may be carried on a release liner90. The release liner90comprising a release layer91may provide a platform for high speed dispensing of the label100. For example, the release layer91may comprise or consists essentially of a silicone polymer. The release layer91may have low friction, low dusting and/or anti-adhesive properties such that the adhesive label100may be detached from the liner90.

The release liner90may comprise e.g. polyester or paper. The release liner90may be made of clear polyester film having properties equal to the face layer described above. Advantageously, the release liner90may comprise or consist essentially of polyester, such as polyethylene terephthalate. The mechanical properties of the release liner90may be substantially similar to the mechanical properties of the face layer.

The coat weight of the release layer91applied on the release layer90may be e.g. equal to or smaller than 0.2 g/m2. The coat weight of the release layer91applied on the release layer90may be e.g. substantially equal to 0.1 g/m2.

Release Properties

A plurality of labels may be carried on a release liner90. A first label100,100amay be separated from the release liner90before the first label100,100ais attached to an item IE1, ITE1a. The adhesive of the layer20and the release liner90may be selected such that the force needed to separate the label from the liner is higher than a threshold limit. The force may be used e.g. to control the longitudinal tension of the label during the dispensing. The force may be used e.g. to control the dispensing geometry. The release value of the label may be e.g. higher than 0.15 N (15 g) in a situation where a sample piece of the label is separated from the release liner90at an angle of 180° at a velocity of 1200 inches per minute at a temperature of 25° C., wherein the width of said sample piece is equal to 2 inches.

The 180° Peel Adhesion value of the polymeric adhesive may be equal to or higher than 3.2 pounds/inch, when measured after a 15 minutes dwell time. Advantageously, the 180° Peel Adhesion value of the polymeric adhesive may be equal to or higher than 4.0 pounds/inch, when measured after a 24 hour dwell time. The 180° Peel Adhesion may be measured by peeling a test tape from AISI 304 stainless steel surface according to the standard PSTC-1 for Peel Adhesion by the Pressure Sensitive Tape Council. The test tape may comprise a dry film of adhesive cast directly onto a polyester film, wherein the thickness of the adhesive film may be 25 μm and the thickness of the polyester film may be 50 μm.

A plurality of labels may also be provided as linerless labels, i.e. without a liner. The linerless labels may be wound to form a roll RLL1(FIG. 10d). The labels100a,100bmay form a linerless labelstock STO1. The labelstock STO1may be provided as a wound roll RLL1. A first label100,100aof the roll RLL1may be separated from second label of said roll RLL1before the first first label100,100ais attached to an item IE1, ITE1a. When the linerless labelstock STO1is unwound from the roll RLL1, the adhesive layer20may be configured to separate from the wound roll RLL1without damaging the other labels of the roll RLL1. To prevent the adhesive layer20from damaging other labels on the roll RLL1, the uppermost surface SRF1of the label100may comprise a release coating91, e.g. silicone polymer applied on top of the face layer10.

Labeled Products

Referring toFIGS. 2aand 2b, the label100may be attached to an item ITE1to form a labeled item PROD1. The reflective properties of the label100may substantially match with the reflective properties of the item ITE1. Thus, the edge VE1of the label100may be less easy detect visually. In this sense, the label attached to the item may have a “vanishing edge” VE1. The label100of the labeled item PROD1may have a “vanishing edge” VE1.

Referring toFIG. 3a, the item ITE1may comprise e.g. transparent glass or plastic. The item ITE1may be e.g. a container for a beverage. The item ITE1may be e.g. a glass bottle or a plastic bottle. The item ITE1may be e.g. a transparent container made of glass. The item ITE1may be e.g. a transparent container made of PET. The refractive index of the adhesive layer may substantially match with the refractive index of items made of glass or PET.

The label100may be used e.g. for labeling a bottle, which contain beverage. The label100may be used e.g. for labeling bottles, which contain beverage.

In particular, the label100may be used for labeling recycled glass containers, e.g. glass bottles. A recycled glass bottle may have a scratched surface SRF0, and the label100may improve the visual appearance of the scratched surface SRF0.

The label100may be used e.g. for labeling a container, which contain a household chemical.

Referring toFIG. 3b, the label100may also be attached e.g. to a lacquered metallic surface. The label100may be attached e.g. to a lacquered aluminum can. The label100may hide scratches or irregularities of the metallic surface. The high gloss of the label100may even further improve the visual appearance of the reflective surface of the metallic surface.

Referring toFIG. 3c, the label100may be applied on a substantially planar surface.

Optical Properties

The label100may comprise a clear portion. The label100may comprise a clear portion to transmit illuminating light LB1through the uppermost surface SRF1to the interface SRF3between the adhesive layer20and the item ITE1.

The face layer10of the label100may comprise a clear portion. The clear portion of the face layer10may transmit illuminating light LB1through the uppermost surface SRF1to a printed region30between the face layer10and the adhesive layer20, and to transmit reflected light back from the printed region30through the uppermost surface SRF1to a viewer.

The reflective properties of the label may substantially match with the reflective properties of the item. Thus, the edge VE1of the label100may be less easy detect visually, see e.g.FIGS. 2aand 2b. In this sense, the label attached to the item may have a “vanishing edge” VE1.

The relative difference between the reflection coefficient of the uppermost surface of the label and the reflection coefficient of the exposed surface of the item may be e.g. smaller than 20%. The surface SRF0of the item ITE1may have a first reflection coefficient Rc, a labeled portion of the labeled item PROD1may have a second reflection coefficient Rtot, and the relative difference ((Rc−Rtot)/Rc) between the first reflection coefficient and the second reflection coefficient may be e.g. smaller than 20%. Consequently, the visual contrast at the edge of the label may be less easy to detect. The edge VE1of the label may be less easy to detect visually.

Thanks to the thin adhesive layer, the printed region30and/or marking MRK1may be close to the surface of the item. Consequently, the printed region30may look visually similar to a (comparative) region which would have been printed on the surface of the item. The printed region30may look visually indistinguishable from a region printed on the surface of a similar reference item.

The reflection coefficient of the interface between the adhesive layer and the face layer may be low. The uppermost surface of the label may reflect light more efficiently than the lower surfaces of the label, so as to provide a visually sharp reflection. The interface SRF2between the face layer10and the adhesive layer20may have a reflection coefficient R2, the uppermost layer SRF1of the label100may have a reflection coefficient R1, and the reflection coefficient R2of the interface SRF2may be smaller than e.g. 10% of the reflection coefficient R1of the uppermost layer SRF1. The refractive index n2of the polymeric adhesive of the layer20may be close to the refractive index n1of the face layer. The refractive index n2of the polymeric adhesive may be e.g. in the range of 80% to 98.5% of the refractive index n1of the polyester film at the wavelength of 550 nm.

In particular, the refractive index n2of the polymeric adhesive may be in the range of 90% to 98.5% of the refractive index n1of the polyester film at the wavelength of 550 nm.

High Gloss

The label may provide a high gloss surface, which may substantially match e.g. with the high gloss of a glass or aluminum surface. The labeled portion of a labeled item may even have a higher gloss and/or smoother upper surface than the bare surface of the item. The label may substantially improve the surface quality of the item.

The reflection coefficient and the gloss of the uppermost surface of the label may depend on the difference between the refractive index of the face layer and the refractive index of air. The refractive index of the face layer may be increased by stretching the face layer, in order to provide a higher gloss. The face layer may be bi-axially stretched. The refractive index n1of the stretched polyester film may be e.g. in the range of 1.55 to 1.65 at the wavelength of 550 nm. In particular, the face layer10may have been uniaxially or biaxially stretched so that the refractive index of the face layer is higher than 1.60. The label may be provided such that the uppermost surface is an interface between polyethylene terephthalate (PET) and air. The uppermost surface of the label may be implemented such that it does not comprise silicone polymer.

Reflection Coefficients

Referring toFIGS. 4aand 4b, the reflective properties of the labeled item may depend on the refractive indices of the layers of the label. n0denotes the refractive index of air AIR1. n1denotes the refractive index of the face layer10. n2denotes the refractive index of the adhesive layer20. ncdenotes the refractive index of the material MAT1of the surface of the item ITE1.

The label100may comprise a clear portion to transmit illuminating light LB0to the surface of the item ITE1and to transmit reflected light LB3from the surface of the item ITE1to the eye of a viewer.

SRF0may denote the interface between air AIR1and the bare surface of the item ITE1. SRF1may denote the interface between air AIR1and the face layer10. SRF2may denote the interface between the face layer10and the adhesive layer20. SRF3may denote the interface between the adhesive layer20and the surface of the item ITE1. The reflection coefficient R of the interface SRF0may depend on the refractive indices n0and ncaccording to the following equations:

Rsdenotes reflection coefficient for s-polarized light, Rpdenotes reflection coefficient for p-polarized light, R denotes the average of the coefficients Rsand Rp, θidenotes input angle of illuminating light, and θtoutput angle of refracted light. The direction of illuminating light may be e.g. perpendicular to the surface SRF0, and the angles θiand θtmay be equal to zero. When the input angle θiis equal to zero, the reflection coefficient Rcof the interface SRF0may be calculated according to the following equation:

Rc=(n0-nc)2(n0+nc)2(1⁢d)
When the input angle θiis equal to zero, the reflection coefficient R1of the interface SRF1may be calculated according to the following equation:

R1=(n0-n1)2(n0+n1)2(2)
When the input angle θiis equal to zero, the reflection coefficient R2of the interface SRF2may be calculated according to the following equation:

R1=(n1-n2)2(n1+n2)2(3)
When the input angle θiis equal to zero, the reflection coefficient R2of the interface SRF2may be calculated according to the following equation:

The surface of the item and the label100may be illuminated with illuminating light LB0. The interface SRF0may provide a reflected beam LBC by reflecting light of the illuminating beam LB0. The interface SRF1may provide a reflected beam LB1by reflecting light of the illuminating beam LB0. The interface SRF2may provide a reflected beam LB2by reflecting light of the illuminating beam LB0. The interface SRF3may provide a reflected beam LB3by reflecting light of the illuminating beam LB0. The printed region30may provide a reflected beam LB30by reflecting light of the illuminating beam LB0. The printed region30′ may provide a reflected beam LB30′ by reflecting light of the illuminating beam LB0. A human observer viewing a clear labeled portion detects the combined intensity of the beams LB1, LB2, LB3. Rcdenotes the reflection coefficient of the bare surface SRF0of the item ITE1. The total reflection coefficient Rtotof a clear labeled portion may be equal to the sum of the reflection coefficients of the surfaces SRF1, SRF2, and SRF3.
Rtot=R1+R2+R3(5).

To the first approximation, the total reflection coefficient Rtotof a clear labeled portion may be substantially equal to the sum of the reflection coefficients of the surfaces SRF1, SRF2, and SRF3.

To the first approximation, the visual contrast between the clear labeled portion and the bare surface of the item may be proportional to the relative difference (Rc−Rtot)/Rc.

Smoothing Effect

The label100may be arranged to make certain imperfections of the item ITE1less visible. For example, the label may provide a high quality appearance by smoothing an irregular shape of the item, and/or by hiding scratches of the surface of the item ITE1. The adhesive layer20may hide scratches of the surface of the item ITE1, and the thin face layer10may conform to the shape of the item. The face layer10may conform to the shape of the item such that the thin layer of adhesive layer20may be sufficient to hide visually detectable scratches of the surface of the item ITE1.

In case of a transparent item, the reflection coefficient R3of the interface between the adhesive layer20and the surface of the item may be low.

Referring toFIGS. 5a, and 5b, the item ITE1may have one or more curved portions REG1, one or more irregular portions REG2, and/or one or more curved irregular portions REG3. The irregular portions REG2, REG3may also be called e.g. a rough portions. The curved portion REG1may have a radius of curvature r1. The radius of curvature r1of the item ITE1may be e.g. smaller than 50 mm.

The surface roughness of the portions may be specified e.g. by providing a Ra-value, which indicates the arithmetic average of the absolute values of the profile height deviations from the mean line, recorded within an evaluation length L2. In case of the thin face layer10, the relevant evaluation length L2may be e.g. equal to 1.0 mm. h2may denote a maximum depth of a valley between two peaks within the evaluation length L2. d2(x) may denote a distance between the face layer10and the surface of the item ITE1at a position x. The average value of the distance d2may be substantially equal to the thickness of the adhesive layer20.

The thickness d10of the label100may be e.g. in the range of 10 μm to 25 μm. Thanks to the small thickness, the label100may conform to the curved shape of the item.

An average radius (r1′) of curvature of the label (100) at a portion (REG1) may be e.g. in the range of 1.001 (=(10 mm+10 μm)/10 mm) to 1.005 (=(5 mm+25 μm)/5 mm) times the average radius (r1) of curvature of said portion (REG1), in a situation where the average radius (r1) of curvature of the label (100) at said portion (REG1) is in the range of 5 mm to 10 mm, and the width of said portion (REG1) is equal to 5 mm.

Conforming to the shape of the item may ensure that the label may be firmly attached to the item even when the thickness of the adhesive layer is small. Consequently, optical reflections from the lower surface of the adhesive layer do not disturb the visual appearance of the label attached to the item. For example, more than 95% of the area of the label may be in contact with the surface of the item.

For example, an average thickness of an air gap enclosed between the adhesive layer20and the item ITE1may be lower than 0.1 μm in an area, which overlaps 95% of the area of the label100. 0.1 μm corresponds to an air gap, which is less than ¼ of the wavelength λ=550 nm. An air gap greater than 0.1 μm may cause a disturbing reflection from the interface between the air and the adhesive. An air gap greater than 0.1 μm may cause a disturbing reflection from the interface between the air and the surface of the item. An air gap greater than 0.1 μm may cause a disturbing reflection from an irregular surface of the item.

The label may smooth out irregularities and/or unevenness of the surface of the item. The adhesive may fill scratches on the surface of the item. The combination of the thin face layer and the adhesive may provide a capability to fill irregularities of a curved surface. The surface roughness value Ra of the surface of the item ITE1may be e.g. in the range of 0.5 μm to 5.0 μm. For example, average thickness of air enclosed between the adhesive layer20and the item ITE1may be lower than 0.1 μm in an area, which overlaps 95% of the area of the label100, when the surface roughness value Ra of the item ITE1is in the range of 0.5 μm to 5.0 μm.

Method for Labeling Items

Referring toFIG. 6a, a labelstock STO1may comprise a plurality of labels100carried by a release liner90. The labels100a,100b,100cmay be e.g. substantially identical.

The labels and the release liner90may be optionally wound to form a roll. The labels and the release liner may together form a labelstock STO1. The labelstock STO1may be provided as a wound roll. The labelstock STO1may be stored and/or transported as a roll. The labelstock STO1may be unwound from the roll, and the labelstock STO1may be fed to a labeling apparatus500.

Labeling Apparatus

The feeding unit FUNIT1may feed the labelstock STO1at a velocity v1to the peel plate510, and the pulling unit PUNIT1may pull the release liner90at the velocity v′1from the peel plate510. The feeding unit FUNIT1and the pulling unit PUNIT1may be arranged to cause suitable tension in the release liner90. The velocity v′1may be equal to or slightly higher than the velocity v1. The labelstock STO1may comprise the release liner90, and a plurality of labels100a,100b. The apparatus500may comprise one or more pressing members530a,530bto press the label100aagainst the surface of the item ITE1aafter the label100ahas been brought into contact with the item ITE1a. The feeding unit FUNIT1may comprise e.g. a pair of rollers521,522, and the pulling unit PUNIT1may comprise e.g. a pair of rollers523,524.

The release liner90may be bent sharply at the peel plate510so as to separate the label100afrom the release liner90. The radius of curvature of the release liner90at the edge of the peel plate510may be smaller than a predetermined value. The leading edge FE1of the label100amay be separated from the release liner90by using the peel plate510so that the adhesive layer of the label100abecomes partly exposed in the vicinity of the leading edge FE1. The leading edge FE1of the label100amay be moved in the direction SU at a velocity v1. The label100ahas also a trailing edge TE2. The direction SU may be defined by the upper surface of the peel plate510. The direction SU may denote the direction of movement of the release liner90at the upper side of the peel plate510. An actuating unit AUNIT1amay move the surface SRF0of the item ITE1ain the direction SX at a velocity vc. The actuating unit AUNIT1amay be e.g. a conveyor belt or a carousel. α0denotes an angle between the directions SX and SU. The angle α0may be called e.g. as the feeding angle or as the angle of attack. The feeding angle α0may be e.g. in the range of 10° to 30°, preferably in the range of 15° to 25°. The amount of air entrained between the label100aand the item ITE1amay be controlled by selecting the feeding angle α0. Increasing the feeding angle α0may reduce the amount of air trapped between the label100aand the item ITE1a.

During high speed labeling, the velocity vcmay be e.g. higher than 0.5 m/s. The velocity vcmay be e.g. in the range of 1 m/s to 10 m/s. The (maximum) velocity v1may be substantially equal to the velocity vc. The (maximum) velocity v1may be e.g. in the range of 90% to 110% of the velocity vc. The velocity v1may be rapidly accelerated before bringing the label100ainto contact with the item ITE1a.

The item ITE1amay be at a position x−1at a time ta,−1, before the label100acontacts the item ITE1a.

Separating Labels from Release Liner

The release liner90may be bent sharply at the peel plate510so as to separate the label100afrom the release liner90. The radius of curvature of the release liner90at the peel plate may be smaller than a predetermined value. The stiffness of the face layer10may facilitate separation of the label from the release liner, in particular when the face layer consists of stretched PET.

Stretching of the Release Liner

The labelstock STO1may have a velocity v0immediately before the entering the feeding unit FUNIT1. The pulling unit PUNIT1may be arranged to pull the release liner90such that the velocity v1is e.g. 0.5% to 3% higher than the initial velocity v0. In particular, the relative difference (v1−v0)/v0may be in the range of 1% to 2%. Consequently, the release liner90may be stretched by the pulling unit PUNIT1such that the relative elongation of the release liner90is e.g. in the range of 1% to 2%. The high dimensional stability of PET film of the label100may cause slipping of the edge of the label100awith respect to the release liner90when the release liner90is stretched. Thus, the dimensional stability of the label100and the stretching of the release liner90may together facilitate separation of the label100afrom the release liner90.

Bringing the Label into Contact with the Item

Referring toFIG. 6c, the label100amay be moved at a velocity v1in the direction SU, and the item ITE1amay be simultaneously moved in the direction SX at the velocity vcsuch that the leading edge FE1of the label100amay contact the surface SRF0of the item ITE1a. The leading edge FE1of the label100amay first contact the surface SRF0at a time ta,0. CL0denotes a contact line where the label100ameets the surface SRF0of the item ITE1a. SL0denotes a separation line where the label100ais separated from the release liner90. The item ITE1amay have a substantially circular perimeter, and the item ITE1may have an axis of symmetry AX1. The item ITE1amay have a (main) radius or curvature R1. The item ITE1amay have a diameter, which is substantially equal to two times the main radius R1.

The separation line SL0and the contact line CL0may define a reference plane REF0. TNG0denotes the tangent plane of the surface SRF0at the contact line CL0. β0denotes the angle between the reference plane REF0and the tangent plane TNG0at the time ta,0when the label100afirst contacts the surface SRF0of the item ITE1a. The orientation of the tangent plane TNG0with respect to the direction SX may depend on the relative position of the item ITE1with respect to the leading edge FE1. The orientation of the tangent plane TNG0at the time ta,0may depend on the timing of the movement of the label100a. The angle β0may be called e.g. as the relative angle or as the impact angle. The impact angle β0may depend e.g. on the feeding angle α0, on the position of the item ITE1aat the time ta,0, and on the position of the leading edge FE1at the time ta,0. The impact angle β0may be e.g. in the range of 10° to 30°, preferably in the range of 15° to 25°. Increasing the impact angle β0may reduce the amount of air trapped between the label100aand the item ITE1a. The feeding angle α0may be selected and the movement of the label100amay be timed with the movement of the item ITE1asuch that the impact angle β0at the time ta,0is in the range of 10° to 30°, preferably in the range of 15° to 25°.

The direction SU may also denote the direction of movement of the leading edge FE1of the label at the time ta,0of first contact. The direction SX may also denote the direction of movement of the surface SRF0of the item ITE1aat the point where the leading edge FE1first contacts the item ITE1a.

The method for labeling items ITE1, IT1amay comprise:separating a label100afrom a release liner90by using peel plate510,moving the surface SRF0of an item ITE1ain a first direction SX,moving the label100ain a second direction SU, andbringing a leading edge FE1of the label100ainto contact with a surface SRF0of the item ITE1such that the angle α0between the first direction SX and the second direction SU is in the range of 10° to 30°.

wherein the face layer10may comprise semi-crystalline polymeric film, the adhesive layer may consist of one or more adhesive sub-layers, a lowermost adhesive sub-layer20of said adhesive sub-layers may comprise transparent polymeric adhesive, the thickness d10of the face layer10may be in the range of 10 μm to 50 μm, the thickness d20of the adhesive layer20may be in the range of 8 μm to 25 μm, and the thickness d20of the adhesive layer20may be smaller than 95% of thickness d10of the face layer10.

The item ITE1amay be at a position x0at a time ta,0, when the label100afirst contacts the item ITE1a.

Referring toFIG. 6d, the contact line CL0may have moved farther away from the leading edge FE1after the time ta,0. A portion of the label100abetween the contact line CL0and the leading edge FE1may be adhered to the surface SRF0. Substantially the whole portion of the label100abetween the contact line CL0and the leading edge FE1may be in contact with the item ITE1a.

The trailing end TE2of the label100amay still be attached to the release layer90. A portion of the label100abetween the trailing edge TE2and the separation line SL0may still be in contact with the release liner90. The apparatus500may be arranged to cause a tension force TF0, which may control the orientation of the label100a. The tension force TF0may keep a portion of the label100asubstantially straight between the contact line CL0and the separation line SL0. The tension force TF0may keep the impact angle β0above a predetermined value, in order to reduce the amount of air trapped between the label100aand the item ITE1a. The tension force TF0may also depend on the peel force needed to separate the label100afrom the release liner90.

The item ITE1amay be at a position x1at a time ta,1, after the leading edge FE1of the label100ahas been brought into contact with the item ITE1a.

Referring toFIG. 6e, the apparatus500may comprise one or more pressing members530a,530bfor pressing the label100aagainst the item ITE1a. The pressing member530a,530bmay comprise e.g. elastic material for providing a pressing force. The elastic material may be e.g. porous elastic material. The elastic material may be e.g. foam rubber. The pressing member530amay be e.g. a sponge. The pressing member530a,530bmay be e.g. a roll coated with porous elastic material. The pressing member530a,530bmay be e.g. a brush.

A first pressing member530amay be arranged to press the label100aagainst the item ITE1asuch that the label100ahas a radius of curvature r0at the contact line CL0. The radius r0may be e.g. smaller than 20 mm, preferably smaller than 10 mm. The labeling method may comprise pressing the label ITE1aby a pressing member530asuch that a portion of the label100ais temporarily bent, wherein the radius r0of curvature of the bent portion of the label100ais smaller than 10 mm.

The first pressing member530amay meet the upper side of the label100aat an auxiliary contact line CL2. When the first pressing member530apresses the label100a, the trailing edge TE2of the label100amay still be attached to the release liner90such that the apparatus500may cause the tension force TF0for keeping a portion of the label100asubstantially straight between the separation line SL0and the auxiliary contact line CL2. The separation line SL0and the auxiliary contact line CL2may define an auxiliary reference plane REF2. The reference plane REF2and the tangent plane TNG0may define an auxiliary impact angle γ0. The auxiliary impact angle γ0may be e.g. in the range of 5° to 90°. Using a large auxiliary impact angle γ0may effectively reduce the amount of air trapped between the label100aand the item ITE1a.

The tension force TF0and/or the small radius r0may effectively reduce the amount of air trapped between the label100aand the item ITE1a. The label100atensioned by the force TF0may temporarily have a curved portion between the contact line CL1and the auxiliary contact line CL2. The curved portion may have the radius r0of curvature. The curved portion may be very stiff due to the high tensile modulus of the face layer10. The curved tensioned portion may temporarily operate as a stiff reinforcing element, which may keep the contact line CL1substantially straight. The size of an air bubble may depend on the height of a bulge formed at the contact line CL1. The size of the air bubble may be controlled by reducing the height of the bulges formed at the contact line CL1. The curved tensioned portion may reduce the size of air bubbles by effectively preventing formation of bulges in the vicinity of the contact line CL1. The curved tensioned portion may reduce the size of air bubbles by effectively preventing formation of bulges at the contact line CL1.

The item ITE1amay be at a position x2at a time ta,2, when the label100ais pressed against the item ITE1aby the pressing member530a.

Referring toFIG. 6f, the actuating unit AUNITa may be optionally arranged to rotate the item ITE1aabout an axis AX1, so that also the trailing edge TE2of the label100amay be pressed against the item ITE1aby a pressing member (e.g. the pressing member530b). Consequently, substantially the whole label100amay be brought into contact with the item ITE1a. The item ITE1amay be moved substantially in the direction SX during the rotation.

The rotation of the item ITE1amay be performed at an angular velocity ω0. The amount of air trapped between the label and the item during the rotation may be reduced by rotating the items ITE1a, ITE1bat a relatively low angular velocity ω0. The peel plate510may provide only one label at a time, whereas several items ITE1a, ITE1bmay be rotated substantially simultaneously. Consequently, even in high speed labeling, the angular velocity ω0of rotation may be arranged to be slow when compared with the translational velocity vcof the item ITE1a. In an embodiment, the rotation of the item ITE1amay be started e.g. after the leading edge FE1of the label100ahas been brought into contact with the item ITE1a.

The item ITE1amay also be rotated e.g. by squeezing the item ITE1abetween a first conveyor belt and a second conveyor belt, and by moving the first and the second conveyor belts at different velocities. In that case, the conveyor belts may operate as the actuating unit AUNIT1aand as the pressing members530a,530b.

The item ITE1amay be at a position x3at a time ta,3, when the label100ais pressed against the item ITE1aby the pressing member530b.

Referring toFIG. 6g, the labelstock STO1may comprise a plurality of labels100a,100b,100c. A second label100bmay be brought into contact with a second item ITE1bafter the trailing edge TE2of the first label100ahas been separated from the release liner90a. The second item ITE1bmay be moved e.g. by an actuator unit AUNITb.

High Speed Labeling

The apparatus500may be arranged to label items at a high rate. The apparatus500may be arranged to attach labels to more than 750 items per minute. The apparatus500may be arranged to attach labels to items at a rate, which is in the range of 750 to 1600 labels per minute. The labeling rate of the apparatus500may be higher than 15 labels/second. The average velocity of the labelstock STO1may be e.g. higher than 1 m/s.

Referring toFIG. 6h, the labelstock STO1may be sequentially accelerated and decelerated e.g. more than 15 times per second.FIG. 6hshows the velocity v1(t) of the labelstock STO1as the function of time t. The velocity v1(t) of the labelstock may be substantially equal to the velocity of the surface SRF0of a first item ITE1when a first label100ais brought into contact with the first item ITE1. The velocity v1(t) of the labelstock may be temporarily reduced after the label100ahas been fully separated from the liner90. A second item may be moved close to the peel plate510when the velocity v1(t) is low or zero. The labelstock may be accelerated again to the before the second label100bis brought into contact with the second item. The peak acceleration of the labelstock STO1during the labeling may be e.g. higher than 2000 m/s2.

ta,−1, and tb,−1may denote a time when the acceleration of the labelstock is started. ta,0and tb,0may denote a time when the label first contacts the item. At the time ta,0and tb,0, the velocity v1(t) of the labelstock may attain the velocity vcof the surface SRF0. ta,2and tb,2may denote a time when the deceleration of the labelstock is started. ta,3and ta,3may denote a time when the deceleration of the labelstock is stopped.

The item ITE1amay be at a position x−1at the time ta,−1. The item ITE1amay be at a position x0at the time ta,0. The item ITE1amay be at a position x1at the time ta,1. The item ITE1amay be at a position x2at the time ta,2. The item ITE1amay be at a position x3at the time ta,3. L01may denote the distance between the positions x0and x1. L02may denote the distance between the positions x0and x2. L03may denote the distance between the positions x0and x3.

FIG. 6ishows method steps for applying a label on the surface of an item. The steps ofFIG. 6imay be suitable for high speed labeling.

The leading edge FE1of the label100amay be separated from the release liner90by using a peel plate510(step1210).

The leading edge FE1of the label100amay be brought into contact with an item ITE1a(step1220).

The label100amay be pressed against the item ITE1aby pressing the label100awith a pressing member530a(step1230).

The trailing edge TE2of the label may be separated from the release liner (step1240).

The item ITE1amay be optionally rotated in order to press the whole area of the label100aagainst the item ITE1a(step1250). The item ITE1amay be rotated in order to press also the trailing edge TE2of the label100aagainst the item ITE1a.

Controlling the Size of Air Bubbles

Sometimes an air bubble may be trapped between the adhesive layer and the surface of the item. When that happens, the air bubble may cause residual tensile stress TF1,TF2in the face layer. The residual tensile stress TF1of the face layer10may be arranged to eliminate the air bubble BUB1by causing diffusion of air from the air bubble BUB1through the face layer10.

Also the adhesion of the adhesive layer to the surface of the item may facilitate elimination of air bubbles.

Referring toFIG. 7a, an air bubble (gas bubble) BUB1may sometimes be trapped between the label and the item. REG4may denote a region, which comprises an air bubble BUB1immediately after the label has been attached to the item ITE1. The air bubble BUB1may be located beneath a bulge of the label100. The region REG4may be vertically displaced with respect to a surrounding region. The adhesive layer20of the surrounding region may be in contact with the item ITE1. SRF3may denote an interface between the adhesive layer20and the surface of the item ITE1. SRF4may denote an interface between the adhesive layer20and air. The vertical distance between the lowermost surface of the adhesive layer20and the surface SRF0of the item ITE1may be greater than zero at the position of the air bubble BUB1. The distance between the interface SRF4and the surface SRF0of the item ITE1may be greater than zero at the position of the air bubble BUB1. The thickness of the air bubble BUB1may be e.g. greater than 0.5 μm. The adhesive layer20is not in contact with the item ITE1at the position of the air bubble BUB1.

Referring toFIG. 7b, a residual stress of the face layer10and/or adhesive wetting may be arranged to cause an overpressure in the air bubble BUB1so as to cause diffusion of air AIR1(gas) out of the bubble BUB1. The tension TF1, TF2of the stiff PET face film may create an overpressure for causing diffusion of air AIR1out of the bubble BUB1. By selecting dispensing geometry and the stiffness of the face layer10, the formation air bubbles may be minimized or prevented.

The adhesive may also cause wetting of the surface of the item so that overpressure may be generated in the bubble. The overpressure may cause diffusion of air AIR1out of the bubble BUB1. The wetting may take place at a wetting portion WP1.

The polymeric adhesive may be a pressure sensitive adhesive. The adhesion strength of the adhesive may develop as a function of time. The strength of the adhesive may increase after the label has been attached on the substrate surface. The length of the time period needed to form a suitable strength may be called as the adhesive set-up time. The adhesive set-up time may be e.g. longer than 30 minutes, longer than 1 hour, or even longer than 24 hours. The long set-up time may facilitate wetting.

The low thickness of the polyester film10may increase the rate of diffusion of air AIR1through the face layer10. The permeability of the face layer10for air may be e.g. higher than or equal to 1 cm3/m2·24 hours·100 kPa at the temperature of 25° C. The face layer10may comprise or consist of polyethylene terephthalate (PET). Using PET as the material of the face layer may provide sufficient permeability so as to control the size of air bubbles. The permeability of polyethylene terephthalate may be higher than the permeability of polyethylene naphthalate (PEN).

The face layer10may be arranged to allow diffusion or air and/or nitrogen through the face layer10. The face layer10may be filmic polyester, and the permeability of the face layer10for nitrogen may be equal to or higher than 1 cm3/m2×24 hours×100 kPa. The permeability may be determined according to standard DIN 53380.

Referring toFIG. 7c, the bubbles BUB1may be arranged to disappear after the label has been dispensed. The method of dispensing the label may comprise reducing the size of air bubbles BUB1by causing diffusion of air from the air bubble BUB1through the face layer10during at least 24 hours.

Producing the Labelstock

A labelstock STO1may be formed of a label laminate web by die-cutting labels100and stripping excess matrix material away from the release liner90, such that the labels100remain attached on the release liner90.

Referring toFIG. 8, a production chain for producing a labeled product PROD1may comprise:forming a label laminate web WEB1,forming a labelstock STO1from the label laminate web WEB1,separating a printed label100from the labelstock STO1, andattaching the printed label100to an item to provide a labeled product PROD1.

Referring toFIG. 9a, label laminate web WEB0may have an initial width w0. A plurality of printed regions30may have been formed on the face layer10by printing. A plurality of printed regions30may have been formed on the face layer10by wide web printing. The face layer10and the printed regions30may be subsequently coated with the adhesive layer20e.g. by curtain coating so as to form the label laminate web WEB0. Alternatively, the adhesive layer20may be formed on a release layer90, and the combination of the adhesive layer20and release layer90may be laminated together with the face layer10.

The label laminate web WEB0may be longitudinally cut to form a narrower label laminate web WEB1. The web WEB0may be cut e.g. along a longitudinal line CUT0. The web may have a width w1. The width w1may be smaller than the width initial width w0.

Referring toFIG. 9b, the label laminate web WEB1may comprise the face layer10, the adhesive layer20, and one or more printed regions30. The label laminate web WEB1may further comprise a release liner90. The release liner90may be coated with a release coating91. The release liner90may have a thickness d90.

Referring toFIG. 9c, individual labels100a,100bmay be cut from the web WEB1e.g. by using a die-cutting blade DIE1and a base BED0. The cutting edge of the blade DIE1may penetrate through the face layer10and through the adhesive layer20. The cutting edge of the blade DIE1may also slightly penetrate into the release liner90. Advantageously, the blade DIE1does not cut completely through the release liner90. A labelstock STO1may be formed from the web WEB1e.g. by the die-cutting.

The thickness of the d90of the release liner90may be selected to facilitate precision die-cutting. In particular, the release liner90may comprise dimensionally stable and relatively hard polyester in order to allow precision cutting. The release liner90may comprise polyester in order to allow precision cutting.

Referring toFIG. 9d, the labelstock STO1may comprise a plurality of labels100a,100b,100ccarried by a common release liner90.

FIG. 9eshows method steps for forming the labelstock STO1and labeling items with the labels of the labelstock.

In step810, the face layer may be printed to form the printed regions30. The printed regions30may comprise markings MRK1.

In step820, the printed face layer may be coated with the adhesive. The adhesive layer may comprise one or more adhesive sub-layers.

In step830, the combination of the face layer10and the adhesive layer20may be laminated with a release layer in order to form label laminate web WEB0.

In step840, one or more narrower webs WEB1may be cut from the web WEB0.

In step850, the labels may be cut e.g. by die-cutting. Labelstock STO1may be formed from the web WEB1by die-cutting.

In step870, the labels100a,100b,100cof the labelstock STO1may be attached to items, so as to provide labeled items PROD1.

Referring toFIGS. 10ato 10d, the label100or labels100a,100b,100cmay also be provided as linerless labels. The linerless labels may be supplied e.g. as a stack (i.e. a pile) or as a roll RLL1. The upper surface of the face layer10may be coated with a release coating91, so as to facilitate separation of the labels from each other. Referring toFIGS. 10cand 10d, a first label100amay be separated from a second adjacent label100be.g. by cutting or tearing the labels apart along a line CUT1.

Referring toFIG. 11a, the label laminate web may also be formed e.g. by providing a base film (step910), and coating the base film by a release coating91in order to form the release layer90(step920). The adhesive layer20may be applied on the release layer90e.g. by curtain coating (step930). The printed face layer30may be subsequently applied on top of the adhesive layer20in order to form the label laminate web WEB0, WEB1(step940). The label laminate web WEB0, WEB1may be optionally topcoated (step950). The labels100a,100b,100cmay be cut from the face layer10in step960.

Referring toFIG. 11b, the supply chain may utilize various resources for providing and using labeled items. For example, a press manufacturer may provide a printing machine for forming the printed regions30(resource1010). An ink provider may provide printing ink for forming the printed regions30(resource1020). The regions30may be formed on the face layer10by using a printing machine (resource1030). the labels100a,100bmay be cut by using die-cutting apparatus (resource1040). The labels may be attached to items by using a labeling apparatus500(resource1050). The supply chain may utilize contribution from brand owners (resource1060), contribution from distributors (resource1070). The labeled items may be delivered to end users (resource1080). The list ofFIG. 11bis non-exhaustive.

Tensile Strength

The tensile strength σ10of the polyester film may be e.g. higher than or equal to 140 MPa. The polyester film may be bi-axially oriented, and the tensile strength of the polyester film may be e.g. higher than or equal to 140 MPa in the machine direction (MD), and the tensile strength of the polyester film may be e.g. higher than or equal to 140 MPa in the cross direction (CD).

The tensile strength (σ10) of the polyester film face layer (at break) may be equal to or higher than 200 MPa. The face layer may be uniaxially or biaxially oriented. When the polyester film is bi-axially oriented, the tensile strength of the polyester film may be similar in both machine direction and cross direction higher. The face layer10may be made of a PET film. The tensile strength of the PET film (at break) may be e.g. than higher than or equal to 200 MPa in the machine direction (MD), and the tensile strength of the polyester film at break may be higher than or equal to 200 MPa in the cross direction (CD). The tensile strength of the PET film may be e.g. than higher than or equal to 220 MPa (32000 psi) in the machine direction (MD), and the tensile strength of the polyester film may be higher than or equal to 220 MPa (32000 psi) in the cross direction (CD). The tensile strength may be determined according to standard ASTM D 882.

Ultimate Elongation

The ultimate elongation of the polyester film face layer may be in the range of 65 to 190%. For example, the ultimate elongation of the polyester film face layer may be higher than or equal to 110%. The face layer may comprise or consist of bi-axially oriented PET film, wherein the elongation of the PET film may be e.g. higher than or equal to 140% in the machine direction (MD), and the elongation of the PET film may be e.g. higher than or equal to 140% in the cross direction (CD). The ultimate elongation may be determined according to standard ASTM D 882.

Degree of Crystallization

The face layer10may comprise semi-crystalline polymeric film. The degree of crystallization may have an effect on optical, mechanical, thermal and chemical properties of the polymer. The degree of crystallization of the semi-crystalline polymeric film may be in the range of 10% to 80%. The polymeric film may be oriented by uniaxial or biaxial stretching. The stretching may increase elastic modulus and/or refractive index of the face layer10.

UV Protection

In an embodiment, the face layer10may protect the printed region30from ultraviolet radiation (UV). For example, sunlight may comprise UV radiation. The UV radiation may bleach the color of the printed region30. The face layer10may optionally comprise an additive, which may absorb UV radiation. The face layer may be substantially transparent in the wavelength range of 380 nm to 760 nm, wherein the face layer may absorb UV radiation in the UV range.

The face layer10may protect the printed region30against the bleaching effect of sunlight.

Tendency to Build Up Static Charge

Filmic polyester may have a tendency to build up static electric charge. Reducing the thickness of the face layer may provide a label, which has a reduced tendency to build up static electric charge.

Adhesive Dispersion

Producing the label may comprise applying an adhesive dispersion on the face layer10or on the release layer90. The adhesive layer20may be produced by applying the adhesive dispersion on the face layer10or on the release layer90. The dispersion may have low viscosity value. The low viscosity may facilitate forming a substantially uniform thickness of the adhesive layer20. The low viscosity may facilitate forming a substantially uniform thickness of the label100. The polymeric adhesive may be applied, for example by curtain coating. The exposed surface of the adhesive may be optionally leveled e.g. by a linear smoothing bar. The thickness of the printed region may be non-negligible. The low viscosity may facilitate eliminating an elevated region, which could be caused by the thickness of the printed region30.

The viscosity of the polymeric adhesive may be equal to or less than 2000 centipoises, preferably lower than 1600 centipoises. The viscosity of the polymeric adhesive may be, for example, in the range of 1200 to 1600 centipoises, when measured with a Brookfield RVT Viscometer with #3 spindle at 20 rotations per minute (rpm) according to the manufacturer's instructions. One centipoise corresponds to one mPa×s in SI-units.

The adhesive dispersion may be applied on the semi-crystalline polymeric film such that the polymeric film does not absorb the adhesive dispersion to a significant degree.

Temperature Range

The service temperature range of the polymeric adhesive of the label100may comprise e.g. the range of −60° F. to 300° F. (−51° C. to 149° C.). The service temperature range of the polymeric adhesive may comprise e.g. the range of −40° F. to 200° F. (−40° C. to 93° C.).

The label may be applied to the item e.g. at a temperature, which is higher than or equal to 23° F. (5° C.).

For the person skilled in the art, it will be clear that modifications and variations of the labels, products and the methods according to the present invention are perceivable. The figures are schematic. The particular embodiments described above with reference to the accompanying drawings are illustrative only and not meant to limit the scope of the invention, which is defined by the appended claims.