WO2014053707A1

WO2014053707A1 - A part of a package

Info

Publication number: WO2014053707A1
Application number: PCT/FI2013/050962
Authority: WO
Inventors: Eija SIEKKINEN; Päivi KANGAS; Ismo Pietari
Original assignee: Upm Raflatac Oy
Priority date: 2012-10-05
Filing date: 2013-10-04
Publication date: 2014-04-10

Abstract

The invention relates to a label and to a facestock for a label comprising polyolefin, at least one inorganic coating layer adjoined to the surface of the facestock, and a printing layer against the inorganic coating layer. The invention also relates to a use of a label, to a method for producing a label, and to a combination of an item and a label.

Description

A part of a package

Field of the Invention The present invention relates to packages, and more specifically to a part of a package including graphical patterns. The invention also relates to a manufacturing and a use of a part of a package.

Background of the Invention

Packages are products enclosing or protecting items for distribution, storage, sale and use. Packages may be made of different materials, such as plastic, glass or paper. For example, plastic films may be used for packaging of food in order to keep them fresh over a longer time period. Generally packages include a part comprising graphical patterns in order to provide a visual effect and/or in order to display information about the product. Graphical patterns may be, for example, directly printed on the surface of the package, or they may be on a separate but associated label, such as an adhesive label adhered to the surface of the package. It is general practice to apply a label onto a surface of an item to provide decoration, and/or to display information about the product being sold, such as the content of the item, a trade name or logo. A label typically comprises a facestock layer and an adhesive layer for attaching the facestock to an item. The label facestock may be either a paper or plastic film or a combination of these. Plastic packages and labels are increasingly preferred.

Summary of the Invention

It is an object to provide a part of a package suitable for including graphical patterns in order to provide a visual effect and/or in order to display information about the item inside the package. Another object is to disclose a method for manufacturing a part of a package.

According to a first aspect, a label is provided. The label may include a facestock comprising polyolefin and having a first surface and a second surface, at least one inorganic coating layer adjoined to the surface of the facestock, and a printing layer against the inorganic coating layer. The inorganic layer may provide a functional layer for the printing layer. According to a second aspect, there is provided a method for producing a label including a facestock, at least one inorganic coating layer, and a printing layer. The method may comprise steps of providing a facestock, coating at least one surface of the facestock with an inorganic material, printing the inorganic layer of the facestock so as to form a printed facestock, and cutting the printed facestock so as to form a printed label.

According to a third aspect, a facestock for labels is provided. The facestock may comprise polyolefin and have a first surface and a second surface. In addition, it may comprise at least one inorganic coating layer adjoined to the surface of the facestock, and a printing layer against the inorganic coating layer. The inorganic layer may provide a functional layer for the printing layer.

According to a fourth aspect, a use of a label for labelling of an item is provided. The labelling may comprise attaching the label onto the surface of an item through an adhesive layer. Alternatively, the label may be attached by heating providing shrinking of the label. Label may also be attached during manufacturing of an item, i.e. in-mold.

According to a fifth aspect, a combination of an item and a label attached to the item is provided.

Further embodiments are presented in the dependent claims.

The facestock may comprise polypropylene at least 40 wt-%, preferably at least 70 wt-%.

The inorganic coating layer may have a surface tension of at least 38 dynes/cm, preferably at least 44 dynes/cm measured according to the standard ASTM D-2578. Thickness of the inorganic coating layer may be smaller than 500 nm, preferably smaller than 150 nm or smaller than 100 nm.

The inorganic coating layer may comprise at least one of the following: T1O2, AI2O3, SiO₂, Si₃N₄, AlSiOx, and ZnO.

The opacity of the facestock may be lower than 10%, preferably lower than 5%, or lower than 4% measured according to the standard ISO 2471 . The printing layer may comprise flexographic ink or gravure printing ink.

The label may comprise an adhesive layer against the second surface of the facestock. The adhesive layer may consist of a pressure sensitive adhesive.

The coating of the facestock with inorganic material may be a continuous atomic layer deposition process performed prior to the printing of the facestock.

The method may further comprise coating of the facestock with an adhesive layer.

Description of the Drawings

In the following, the invention will be explained with reference to the drawings, where

Fig. 1 presents an example embodiment of a package

Fig. 2 presents, in a cross sectional view, a label structure

Fig. 3 presents, in a cross sectional view, an example embodiment of a part of a package,

Fig. 4 presents, in a cross sectional view, an example embodiment of a part of a package, Fig. 5 presents, in a cross sectional view, an example embodiment of a part of a package,

Fig. 6 presents, in a cross sectional view, a multilayered inorganic coating,

Fig. 7 presents a schematic figure of a laminating process,

Fig. 8 presents an example embodiment of a continuous ALD process,

Fig. 9 presents an example embodiment of a continuous ALD process, Fig. 10 presents an example embodiment of a continuous roll-to-roll

ALD process. Detailed Description of the Invention A term "package" refers to a product enclosing or protecting items. The package may be, for example, a bottle, a box, a bag, or a wrapping film, made of glass, plastic, paper, cardboard or any combination thereof. For example, the package is made of a plastic film. Plastics in packaging include polymers, such as polyesters e.g. polyethylene terephthalate (PET), polyvinyl chloride) (PVC), polypropylene (PP) and polyethylene (PE). In this description and claims, the percentage values are percentages by weight (wt- %) unless otherwise indicated.

An example of a package 1 is shown in Fig. 1 . A part of the package refers to a part comprising graphical patterns displaying e.g. information about the product. The part of a package may be an integral part 2 of the package i.e. the graphical patterns may be directly printed on the surface 5 of the package, such as plastic film. Alternatively, the part of a package may consist of a separate associated label 3, such as an adhesive label adhered to the surface 5 of the package. The graphical patterns may be manufactured by conventional printing methods, such as gravure or flexographic processes. In order to provide high printing speeds, thin and controllable ink thickness or good colour coverage, flexographic printing is preferred. Flexographic inks may be solvent-based, water-based, or radiation curable. For example, UV curable inks may be used for flexographic printing as well as in ink-jet printers. The flexographic printing may be used in the packaging industry for the printing of flexible packages, such as plastic wrappings, corrugated board as well as adhesive label laminates. Optionally, other inks may be used, for example inks suitable for gravure, offset, electrophotography, digital, letterpress printing, screen printing, thermal transfer printing, or ink jet printing. Dynamic viscosity of inks for gravure printing may be, for example, 0.05 to 0.2 Pascal seconds and 0.05 to 0.5 Pascal seconds for flexographic printing inks. Flexographic printing is a mechanical letterpress method which is characterized by a soft and flexible printing plate. At the printing stage, the material to be printed is conveyed between the flexible printing plate and a hard backing roll, wherein printing ink is transferred by pressing to a desired location in the material to be printed. In multicolour printing, the ink layer needs to be dried (cured) after every printing unit. For example, UV curable inks may be used. UV curable printing inks are printing inks whose curing is not based on the evaporation of a solvent substance as in conventional printing inks but on a polymerization reaction by means of UV radiation and oxygen. According to their name, UV printing inks are cured by ultraviolet radiation whose wavelength is typically 180 to 380 nm. Advantages of using UV curable printing inks include the lack of a solvent, which makes it possible to reduce effluents compared with solvent-based printing inks. Also, the curing rate, formability, good resistance to chemicals and scratching, and colour saturation are examples of the advantages of the ink. With UV printing inks, the thickness of the printing ink layer is typically 0.8 to 2.5 μιτι, while it is about 0.8 to 1 μιτι for solvent-based inks. Because no mass is evaporated from UV inks after printing, it is easier to adjust the layer thickness. Because no evaporation takes place, the inks are not spread, wherein the print quality is better. Compared with conventional printing inks, radiation curable printing inks also have the advantage of a very high curing rate. The printing surfaces of UV inks are strong and glossy, which makes them a very good alternative for the printing of products susceptible to wear, such as labels.

The main components of the printing inks in mechanical printing are pigment, binder and solvent. In UV printing inks, the binder used consists of oligomers, which are often epoxy, polyester, urethane or acrylate based. Even if there are no actual solvents, functional monomers can be regarded as such in UV printing inks. The most important additive is the photoinitiator which enables the polymerization reaction. UV ink may comprise, for example, between 50 and 70% of a binder, between 10 and 30% of functional monomers, between 20 and 25% of pigment, and between 5 and 10% of additives, such as photoinitiators. Photoinitiators are compounds which contain reactive groups and react to high-energy radiation by starting the polymerization reaction. The energy of UV radiation as such is not sufficient for starting the polymerization reaction, so that the photoinitiators are a very important component in UV printing inks. The most typical photoinitiators which form free radicals contain benzophenols, acetophenols, tertiary or acrylic amines, or their derivatives. For example, 2-isopropylthioxanthone (ITX) may be used as a photoinitiator. By the energy of UV radiation, the photoinitiators of the printing ink react by producing free radicals. As a result of the reaction, the monomers and oligomers in the printing ink are combined and cross-linked to each other, forming polymer chains and simultaneously curing the printing ink to a solid film. This reaction is very fast, because it takes no longer than a few seconds, normally in some hundredth parts of seconds. The photoinitiator may start the curing reaction either by breaking into free radicals, or ions.

Solvent based inks may comprise, for example, toluene, alcohols, ketones, or glycols as a solvent. Water based inks may comprise water and alkali, alcohols and glycols as a solvent. The content of solvent may be e.g. 40 to 70%. In addition, said inks may comprise 10 to 30% of a binder, for example hydrocarbon resins and derivatives, polyamide, nitrocellulose, acrylic or styrene based polymers. The content of organic or inorganic pigments may be 5 to 40%. Further, a minor content of additives and/or may be included. A label refers to a piece of material attached to an article. The label is used to provide a visual effect and/or to designate, for example, its origin, content or use. Referring to Fig. 2, a label 3 comprises at least a face material layer 6, which refers to the top layer of the label, also called a facestock or face layer, and a printing layer 8. The label consisting of the facestock layer and the printing layer may be referred to as a printed label. The printing layer may be on the top or the reverse side of the facestock 6. In order to avoid additional protective layer(s) (overlaminate layer) on top of the printing layer, printing the reverse side of the facestock may be preferred. The face material layer 6 may be a plastic film. Alternatively, it may be paper based. The printed label may be non-adhesive, such as a shrink sleeve or in-mold label, or it may comprise an adhesive layer 16 so as to form a printed adhesive label. Thanks to the adhesive layer 16, the label can be affixed to the surface of a product. The adhesive layer may consist of a heat activated adhesive, a wet glue adhesive or a pressure sensitive adhesive (PSA). The labels consisting of PSA can be adhered to most surfaces through an adhesive layer without the use of a secondary agent, such as a solvent, or heat to strengthen the bond. The PSA forms a bond when pressure is applied onto the label at room temperature, adhering the label to the product to be labelled. The label comprising a pressure sensitive adhesive may be referred to as a pressure sensitive adhesive (PSA) label. Alternatively, the label may be attached to the article by heating which causes shrinking of the label and the attachment of the label. Label may also be attached during manufacturing of an item, i.e. in-mold.

The label structure may also comprise a release liner 10 comprising a backing material coated with a layer of a release agent, such as silicone, so as to form a printed label laminate 12. The backing material may be plastic film or paper based. The plastic film may be, for example, a polyester film, a biaxially or machine-direction oriented polypropylene film. The thickness of the plastic liner is preferably 20 to 30 microns or even less than 20 microns. Paper liners may have a thickness between 40 and 60 microns. The individual labels 3 may be cut from the label laminate structure. After the cutting, a number of individual labels may be attached to a release liner which remains continuous and uncut. Alternatively, the individual labels may be completely separate, i.e. the liner may be cut as well . The release liner protects the adhesive and is removed prior to the application of the label onto a surface of an item. Also linerless labels or non-adhesive labels, such as shrink sleeves or in-mold labels, may be provided in a continuous label web, which may be further cut to form individual labels. The label may be used for labelling of items, such as plastic or paper packages, bottles, or other containers.

With reference to Fig. 3, according to an embodiment at least a part of the package 2 consists of a plastic film 7 having a first surface and a second surface, an inorganic coating layer 14 on the first surface of the plastic film, which inorganic layer further comprises graphical patterns 8 on top of the inorganic coating layer. Alternatively, with reference to Fig. 4, graphical patterns 8 may be printed on the second surface of the plastic film 7 on top of the inorganic coating layer 14, i.e. the plastic film may be reverse side coated and printed. It is also possible that both surfaces of the plastic film 7 comprise an inorganic coating layer 14, 14' and graphical patterns 8, 8', as illustrated in Fig. 5. However, it is also possible that both surfaces of the plastic film are coated with an inorganic coating layer but only one surface comprises graphical patterns. The inorganic coating provides a functional coating layer for the plastic film to allow enhanced printability of the plastic film, such as a plastic film of hydrophobic polymers, such as polypropylene. In addition, printed layer 8' may be over coated with another inorganic coating layer 14" in order to provide a protective or barrier layer for the printing 8'. For example, the printed layer may be over laminated with a layer comprising an inorganic coating. Alternatively, the inorganic coating layer may be directly coated on top of the printed layer. It is also possible that the whole package, such as a plastic film, wrap or sleeve, contains a continuous inorganic coating layer. The plastic film may be treated prior to inorganic coating process, for example, by using flame, corona or plasma treatment in order to provide better anchorage (adhesion) of the coating layer.

The inorganic coating layer is configured to provide a functional layer, for example, in order to allow enhanced printability of the plastic film and/or better print adhesion, i.e. better adhesion of the ink. In other words, the inorganic coating layer may ease the printing of the film and improve the quality of the printed layer. The inorganic coating layer may be manufactured by using Atomic Layer Deposition (ALD) technology. ALD technology can be used for both plastic materials and papers; for example plasma assisted atomic layer deposition (PA-ALD) is suitable for low temperature applications, such as for plastic films. ALD coating may provide high quality functional layer suitable for printing. The inorganic coating layer may be composed of inorganic materials, such as metal or silicon oxides or silicon nitrides. The inorganic layer may include one or any combination of following compounds: TiO₂, AI2O3, SiO₂, Si₃N₄, AISiO_xand ZnO. According to one embodiment, the inorganic coating layer consists of only one type of compound e.g. metal oxides, such as T1O2 or AI2O3. According to another embodiment, the inorganic coating has a layered laminate structure (lamellar composite structure) consisting of several alternating layers. The alternating layers may have different compositions, i.e. the coating may include individual layers of e.g. two, three, five or more compounds listed above. For example, the inorganic coating may have a two layer structure including one layer of T1O2 and another layer of AI2O3. With reference to Fig. 6, the inorganic coating layer 14 may have a composite structure consisting of three layers. The three layer structure may include a core layer 17 having a different composition than skin layers 19, 19'. Alternatively, all three layers (core and skin layer) may have different composition. Also the thickness of the individual layers may vary.

The plastic film of a label or a package may have a monolayer structure, also called a single layer film. Alternatively, it may have a multilayer structure consisting of two or more plastic film layers, for example a core layer and at least one skin layer. A wide variety of polymers are useful in preparing the plastic film. The plastic film may include at least one homopolymer, copolymer, or it may be a polymer blend. The plastic film may comprise at least one of the following: polyolefin(s), polypropylene (PP) and polyethylene (PE). The polyethylene may be low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), or a blend thereof. Alternatively, the plastic film may be biodegradable and comprise at least one of the following polymers: polylactide (PLA), poly(hydroxyalkanoates), modified poly(saccharides) e.g. cellulose, starch, lignin, chitin. For example, the plastic film may comprise at least 40% of polypropylene (PP) homopolymer, preferably at least 50%, more preferably at least 60%, or at least 70%. Preferably, the content of homo PP is not more than 95% or not more than 90%. The content of polypropylene may be between 40 and 90% or between 50 and 80%. As an example, the film may comprise 60%, 65%, 70%, 75%, or 80% of propylene homopolymer. In addition, the film may comprise polyethylene, for example low density polyethylene (LDPE). The content of LDPE may be at least 1 % or 2%, preferably at least 3%. The content of LDPE is not more than 20% or 10%, preferably not more than 8%. For example, the LDPE content is between 1 and 20%, preferably between 3 and 10%, or between 3 and 8%. The amount of LDPE may be 3%, 4%, 5%, 6%, 7%, or 8%. LDPE is used, for example, in order to stabilize the facestock during manufacturing, thus improving the processability of the facestock. In addition, the film may comprise low molecular weight hydrocarbon resin(s) and/or styrene block copolymer(s).

The multilayer plastic film may comprise individual layers having different compositions, or alternatively all layers may have the same composition. For example, the individual layers of the multilayer plastic film may all have same composition, e.g. polyethylene. Optionally, the layers may have different compositions, e.g. one layer of polyethylene and another of polypropylene. It is also possible, that at least one layer includes a polymer blend, e.g. a blend of polyethylene and polypropylene. In a multilayer film, separate layers may also have different thicknesses. Multilayer plastic film packages may also comprise moisture and/or oxygen barrier(s), such as additional layer of polyamide (PA) or ethylene vinyl alcohol (EVOH).

In addition, the plastic film may comprise additives, such as pigments or inorganic fillers to provide, for example, a desired colour for the film. The additives may include, for example, titanium dioxide, calcium carbonate and blends thereof. The film may also comprise minor contents of other additives and/or film modifiers, e.g. an antiblocking agent, a UV stabilizer. The monolayer film may be, for example, a blown or cast film, and/or the film may be extruded. The multilayer film may be, for example, coextruded, or at least two monolayer films may be laminated together. The plastic film may be oriented monoaxially in machine direction (MD) or biaxially both in machine direction and transverse direction (TD). Thanks to the biaxial orientation, for example, the oxygen and/or water barrier properties of the film may be improved. Further, modulus/stiffness of the film may be increased, thus enhancing the control of the film during the printing process. Machine direction orientated films may be preferred, due to the higher tear resistance of the film. Alternatively, the film may be non-oriented. As an example, the film is oriented from 5 to 8 times in machine direction. Biaxially oriented film may be oriented 5 to 7 times in MD and 8 to 10 times in TD.

A plastic film may have a thickness of between 10 and 150 microns, between 15 and 120 microns, between 15 and 75 microns, or between 70 and 150 microns. For example, the plastic film may be a non-oriented polyethylene film having a thickness of between 80 and 150 microns, preferably between 80 and 1 10 microns or between 80 and 90 microns. A biaxially oriented polypropylene film (BOPP) may have a thickness of 20 to 1 10 microns, preferably 30 to 90 microns, for example, 50 microns or 60 microns. The plastic film of a label may have a total thickness smaller than 100 microns or smaller than 80 microns, preferably smaller than 60 microns. The plastic film of the label may have a thickness between 30 and 80 microns, or between 40 and 60 microns.

The plastic film comprising the inorganic layer is preferably transparent to visible light in order to provide a clear appearance of the film, which further allows the objects beneath such film to be visible through the film. A clear film is substantially transparent to visible light. The haze of the film may be less than 60%, preferably less than 50% or less than 30%, and most preferably equal to or less than 25% when measured according to the standard ASTM D1003. In addition, the haze may be at least 1 % or 10%. The haze of a clear film may be, for example, between 1 and 30%, or between 2 and 25%.

Alternatively, the plastic film may be white or opaque. White films may comprise fillers, such as T1O2. The filler may be, for example, in the core layer of the multilayer film. Alternatively, the filler may also be in other layers. Optionally, the film may be cavitated. The cavitated film may comprise, for example CaCO₃. According to an embodiment, the opacity of the plastic film is less than 10%, preferably less than 5%, and most preferably less than 4%. For example, the opacity is between 2 and 10%, preferably between 2 and 5%. According to an embodiment, the opacity of e.g. a white film may be at least 70%, at least 75%, or at least 80%, for example between 70 and 95%, or between 70 and 80%. The opacity of the film refers to the degree to which light is not allowed to travel through the film. The opacity is measured according to the standard ISO 2471 . Gloss is used as a measure of the shiny appearance of film, i.e. it is the reflection of light from the surface. The gloss of the film may be between 10 and 100%, or between 10 and 85% according to the standard DIN 67530/1 with gloss angle 60 degrees.

The plastic film may have a secant modulus 1 % value in MD between 300 and 450 MPa or between 1000 and 2500 MPa according to the standard ISO 527-3. For example, biaxially oriented polypropylene films may provide higher modulus values. A bending resistance of a biaxially oriented polypropylene film may be between 30 and 200 mN. Non-oriented polyethylene films may have a bending resistance between 35 and 65 mN. Bending resistance is measured according to the standard ISO 2493.

According to another embodiment, a part of the package consists of a separate label 3 attached to the surface of the package. With reference to Fig. 2, the label 3 comprises at least a facestock layer 6 including graphical patterns 8 (printed layer). The facestock layer may have any of the plastic film structures presented above. The label may further comprise other layers, such as an adhesive layer 16 and a release liner 10. The total label structure may also comprise other additional layers, for example tie layers, in order to improve label properties. An over-vanish or laquer layer may be used to protect the printing layer.

The inorganic layer 14 of the plastic film 6 of the label, also called a facestock layer, may be at least one side of the plastic film. Referring to Fig. 2, the inorganic coating layer of the label is preferably at the first surface of the facestock layer 6 directly contacting the printing layer 8. In other words and referring to Fig. 3, the inorganic coating layer 14 may be manufactured onto the first surface of the plastic film 7 and subsequently printed in order to achieve printed layer 8.

Referring to Fig. 7, the facestock layer 6 of the label may be coated with an inorganic layer during the label laminating process 9. The laminating process may include steps of unwinding of the backing material; siliconizing the backing material so as to form a release liner 10; coating the siliconized liner with a layer of adhesive 16 in an adhesive station 17', and laminating the adhesive coated release liner with the face material 6 so as to form an adhesive label laminate 18 from which the individual labels may be cut out. Optionally, it is possible that the adhesive is already coated to the release liner comprising silicone, i.e. the laminating process does not include the siliconizing and adhesive station for the coating of adhesive. Instead, the laminating process may include unwinding the release liner coated with an adhesive layer and activating the adhesive layer of the release liner prior to laminating step. The facestock layer 6 of the label may be coated with an inorganic layer 14 during the label laminating process, for example before the laminating nip 20 or after the laminating. If the coating is performed before the laminating nip, the coating layer may be produced on the second side of the facestock layer further contacting the adhesive layer. It is also possible that the face stock layer 6 already includes the inorganic coating layer, i.e. the facestock is not coated during the lamination process. The graphical patterns may be printed to the facestock prior to laminating process. Alternatively, the facestock layer may be printed after the lamination. It is also possible that the facestock layer of the label laminate is coated with an inorganic coating in a separate process after the laminating, for example in a pre-treatment step prior to the printing process. The individual labels may be cut out from the label laminate structure. According to one embodiment, the label may be linerless, i.e. a facestock 6 of the label 3 comprises an activatable adhesive layer. Due to the acitvatable adhesive layer there is no need for a separate release liner. Thus, the laminating step may be avoided. Thanks to the activatable adhesive, which is non-tacky prior to activation, the facestock comprising adhesive may also be continuous and wound up to a roll. According to an embodiment, an inorganic coating layer is created by using Atomic Layer Deposition (ALD) technology on at least one surface of the label or packaging material in order to enhance the printing performance of the material. The inorganic coating layer may also provide a sufficient printing ink anchorage. Thanks to the inorganic functional layer it is also possible to print hydrophobic plastic materials, such as polypropylene films. The surface suitable for printing should have a sufficiently high surface tension. A low surface tension may lead to poor retaining capability of printing ink applied to the inorganic coating layer. For example, the inorganic coating layer may have a surface tension at least 36 dynes/cm, preferably at least 38 dynes/cm or at least 44 dynes/cm measured according to the standard ASTM D-2578. The surface tension may be between 36 and 60 dynes/cm, preferably between 38 and 56 dynes/cm or between 44 and 50 dynes/cm. Thanks to the coating layer, the surface tension level may also be maintained higher than or equal to 38 dynes/cm after 50 or 120 days. Inorganic coating may also provide good immediate adhesion of the printing ink.

The inorganic coating layer may also provide a good adhesion to the part of a package, such as a plastic film or paper that is coated. Thanks to the good adhesion, peeling or delamination of the coated structure may be avoided.

The printing may include applying printing inks, primers, lacquers and overprint varnishes to the inorganic coating layer through a printing and/or coating process. The printing process may be, for example, flexography, gravure, letterpress, off-set, screen, electrophotography, digital, thermal transfer, or ink jet printing.

In an atomic layer deposition process, a substrate material, such as a plastic film, is deposited with a coating material in a controlled manner layer-by- layer, i.e. one atomic layer at a time using sequential surface reactions. In the coating of binary compounds, such as metal oxides, a reaction cycle consists of two reaction steps having different precursors, for example, TMA (trimethyl aluminium) and O3 for manufacturing a layer of AI2O3. The coating process may be of the batch type or continuous. Preferably, the coating process is a continuous roll-to-roll process, wherein a continuous web of substrate material can be coated.

According to an embodiment, the substrate material may be coated by using a molecular layer deposition (MLD) technique in order to produce hybrid organic-inorganic coatings. MLD is also based on sequential surface reactions, in which molecular fragments are deposited on the surface by using e.g. organic and inorganic precursors. The hybrid organic-inorganic coating may be, for example, alucone, also known as poly(aluminium ethylene glycol). Alucone coating is provided e.g. by sequential exposures of trimethyl aluminium (TMA) and ethylene glycol (EG).

Referring to Fig. 8, a continuous ALD process may consist of a moving substrate system 1 1 , in which the substrate material, such as a facestock of a label, is mounted on a rotating drum so that the surface of the substrate passes regions containing the precursor gases A 24 and B 24' with purge 26' and exhaust 26 regions between them to ensure that there is no intermixing of precursors. Each precursor exposure step saturates the surface with a monomolecular layer of that precursor. One rotation of the drum will produce one ALD cycle. Number of rotations of the drum may be adjusted in order to control the thickness of the coating layer. Number of rotations of the drum may be adjusted in order to control the thickness of the coating layer. For example, at a rotation speed of 500 rpm, a coating having a thickness of about 40 nm can be obtained in 1 minute. However, in this rotating drum process, the dimensions of the substrate are limited. Thus, a continuous roll- to-roll process is preferred, which enables the coating of long substrates having a length of for example 2000 m. For example, the roll-to-roll process may consist of a drum enabling the substrate web to make multiple passes through the deposition region e.g. by allowing the substrate web to take a helical path around the drum.

Fig. 9 shows a schematic presentation of an example embodiment of one module 13 in a continuous ALD process. The substrate web, such as a plastic facestock 6, will be on a continuous loop, and each pass will give one coating layer. Thicker coatings will be achieved using multiple passes of a substrate web. In Fig. 10 a schematic presentation of an example embodiment of roll-to-roll ALD process 15 is presented. The process consists of a input substrate web roll 28, an ALD coating unit consisting of several coating modules 13 and an output roll 30 consisting of a substrate having an inorganic coating layer.

For example, to produce a coating layer of a compound AB, the substrate is exposed to the precursor of A, P_A. A monolayer of PA is adsorbed on the surface and the excess material (precursor and reaction by-products) is purged away. The substrate is then exposed to the precursor of B, P_B. It reacts to form a layer AB, and any excess of PB is purged away. Then the substrate is exposed to PA again, and so on. In this way, the deposited coating is built up one layer at a time in a completely controllable manner. The thickness of the coating is proportional to the number of complete AB cycles.

As an example, one pulsing cycle of ALD process for manufacturing AI2O3 coating on the plastic web includes at least the following steps:

supplying a plastic web to the ALD coating unit;

pulsing metal precursor TMA (trimethyl aluminium) to the reaction space; reacting the TMA with the OH groups on the substrate surface;

purging the reaction chamber with inert gas (e.g. N₂) so as to release methane molecules from the surface;

pulsing non-metal precursor (counter reactant) H₂O to the reaction space so as to react with the TMA molecule fragments attached to the substrate surface;

purging the reaction chamber with inert gas (e.g. N₂) in order to remove H₂O molecules and methane molecules released from the surface reactions.

The water may be replaced in a low temperature ALD process with ozone or plasma generated oxygen radicals in order to improve process efficiency, e.g. to enable shorter process times.

The metal precursor and counter reactant for other inorganic coatings may be, for example, for SiO₂ coating, TPS (tris(tert-pentoxy)silanol) and TMA; for TiO₂ coating, TTIP (titanium tetraisopropoxide) and H₂O or TiCI₄ and H₂O, TDMAT (tetrakis(dimethylamido)titanium) and O₂ plasma or O3. Deposition temperatures may be, for example, between 30 and 180°C. For plastic films, temperatures below the melting temperature of the polymer are preferably used.

The coating layer thickness can be controlled by repeating the pulsing cycle comprising pulsing source vapors into a reactor alternately, one at a time, separated by purging or evacuation periods. In a continuous roll-to-roll process, the number of coating modules may be adjusted in order to control the coating thickness. For example, in a rotating drum a coating thickness of AI2O3 from 40 to 170 nm can be provided. Also, thinner coatings may be provided, e.g. coatings having a thickness of between 25 and 30 nm or between 10 and 15 nm.

Thanks to the atomic layer deposition, a uniform inorganic coating layer with a controlled thickness can be obtained, regardless of e.g. the shape of the substrate. The coating layer may also be pinhole-free.

The thickness of the inorganic coating layer is smaller than 500 nm, preferably smaller than 150 nm or smaller than 100 nm. The thickness may be most preferably smaller than 25 nm. For example, the thickness of the coating is at least 0.1 nm, at least 10 nm, or at least 50 nm. The thickness of the inorganic coating layer may affect the transparency and/or the opacity of the plastic film. Thus, a thin coating layer is preferred in order to provide a film having an opacity lower than 10, preferably lower than 5, and most preferably lower than 4. The thin coating layer is also preferred in order to provide a flexible functional layer which is, for example, less susceptible to cracking. The thickness of the inorganic coating layer effective for enhancing printability and/or adhesion of the printing may be, for example, between 0.1 nm and 500 nm or between 10 and 250 nm, preferably between 10 and 200 nm, or between 50 and 150 nm.

According to some embodiments, a plastic film of a package or a face stock of a label is based on polyolefin polymer(s). Preferably a label contains a face stock consisting of polyolefin film(s). The face stock may comprise at least one of the following: polypropylene (PP) film and polyethylene (PE) film. Polyolefin based face stock may have effect on environmental aspects of the labels. Polyolefin based face stock may effect on enabling environmental friendly labeling. Polyolefin based face stock may effect on enabling recycling of labeled plastic packages.

The face stock of label or the plastic film of package used in any of the embodiments may comprise polypropylene at least 40 wt. or at least 55 wt.%, or preferably at least 70 wt.% or at least 75 wt.%, or more preferably at least 85 wt.% of the total weight of polymer based materials. An amount of polypropylene may be less than 98 wt.% or less than 95 wt.%. Total content of polypropylene based polymers may be between 55 and 98 wt.% or between 55 and 95 wt.%. According to at least some embodiments, the amount of polypropylene is between 40 and 95 wt.% or between 70 and 95 wt.%. Polypropylene based face stock has effect on clarity/transparency of the label. Polypropylene based face stock may provide high transparency and "no-label look" for the label allowing the objects beneath to be seen through the face stock. Polypropylene may provide effect on haze of the faces stock. Haze of the face stock comprising 55 to 98wt.% of polypropylene is less than 25, preferably less than 10%, more preferably less than 5%, or less than 2%. Haze of the polypropylene based face stock may be for example between 0.5 and 10%, or between 1 and 5%, when measured according to standard ASTM D1003. Polypropylene may also have effect on dimensional stability of the film. Further it may have effect on stiffness of the film. Increased stiffness of the film allows thinner films to be used. Polypropylene face stock may be used in rigid bottle applications requiring excellent transparency and the 'no-label look', e.g. in beverage labeling.

Alternatively, the face stock of label or the plastic film of package used in any of the embodiments may comprise polyethylene based polymers at least 55 wt.%, or preferably at least 75 wt.%, or more preferably at least 85 wt.% of the total weight of polymer based materials. Total content of polyethylene based polymers may be between 55 and 98 wt.% or between 55 and 95 wt.%. Polyethylene may provide effect of conformability. Polyethylene based face stock may allow labeling products having complex shapes and squeezable packages. Polyethylene may also have effect on printing properties. For example, polyethylene based face stock may conform well to package contours and flex well with squeezable packaging. Polyethylene based films may be used in personal care and home care labeling. According to at least some embodiments, the plastic film or face stock comprising or consisting of polypropylene is oriented at least in one direction. Film may be monoaxially oriented in machine direction (MD), i.e. in running direction of the continuous plastic film (web). Alternatively, the film may be monoaxially oriented in cross direction (CD), i.e. in the direction perpendicular to the machine direction. Alternatively, the film may be oriented both in MD and in CD, i.e. the film may have biaxial orientation. Monoaxial orientation, also referred to as uniaxial orientation, refers to the orientation of polymer chains of the film in one direction. Orientation under uniaxial stress provides orientation of the polymer chains of the plastic film in the direction of stress provided. In other words, the polymer chains may be oriented at least partially in the direction of stretching (drawing). Machine direction stretching is normally done by means of a machine direction orienter via rolls with gradually increasing speed. The rolls are heated sufficiently to bring the film to a suitable temperature, which is normally below the melting temperature (T_m), or around the glass transition temperature (T_g) of the polymer. Biaxial orientation may be done through a tenter frame process which creates different degrees of orientation in the MD and CD directions. The films may also be oriented by using so called double bubble tubular stretching process which produces similar degrees of orientation in both the MD and TD directions. Orientation may effect on stiffness of the film. Increased stiffness of the film may allow e.g. thinner face stock to be used thus providing more cost-efficient labeling. Orientation may also provide an effect of barrier capability of the film.

According to at least some embodiments, the oriented film is further heat-set so as to provide non-shrink film having limited heat shrinking capability. Shrinkage of non-shrink film may be less than 10%, or preferably less than 5% at temperatures between 25 and 150 °C. For example, a label comprising pressure sensitive adhesive may further comprise oriented and heat-set face stock. The oriented and heat-set face stock preferably consists of oriented heat-set film(s). Alternatively, the oriented film may be shrinkable in the orientation direction of the film under exposure to external energy. Films having shrinkability are not heat-set after orientation. Film may shrink at least 15%, preferably at least 25% or more preferably at least 35% between temperature of 65 and 120 °C. According to an example, the plastic film or face stock comprising or consisting of polyethylene may be non-oriented. The non-oriented films may be manufactured by blown film extrusion technology. Alternatively, the non- oriented films may be produced by cast extrusion technology.

According to at least some embodiments, the inorganic coating layer is composed of at least one of the following metal oxide(s), silicon oxide(s) and silicon nitride(s). Preferably, the inorganic coating layer contains at least one of the following metal oxide(s) and silicon oxide(s). More preferably, the inorganic coating layer contains metal oxide(s). Metal oxide may be at least one of the following ΤΊΟ2 and AI2O3. According to an embodiment, the inorganic coating layer consists of ΤΊΟ2. According to an embodiment, the inorganic coating layer consists of AI2O3. According to at least some embodiments, the inorganic coating layer of a film comprising or consisting of polyolefin(s) includes at least one of the following: ΤΊΟ2, AI2O3, S1O2, Si3N₄, AlSiOx, and ZnO. Preferably, the inorganic coating layer consists of at least one of the following metal oxide(s) and silicon oxide(s). More preferably, the inorganic coating layer consists of at least one of the following TiO₂ and AI₂O₃.

According to an example, a non-shrinkable face stock of label is oriented at least in one direction and includes polypropylene based polymers between 55 and 98 wt.% or between 55 and 95 wt.%. The face stock film is further coated with inorganic coating layer comprising at least one of the following T1O2 and AI2O3. For example, the inorganic coating consists both T1O2 and AI2O3, preferably the coating consists of T1O2 or AI2O3. In a label structure, the face stock further comprises a printing layer against the inorganic coating layer.

According to another example, a face stock of label is non-oriented and includes polyethylene based polymers between 55 and 98 wt.% or between 55 and 95 wt.%. The face stock is further coated with inorganic coating layer comprising at least one of the following T1O2 and AI2O3. For example, the inorganic coating consists both T1O2 and AI2O3, preferably the coating consists of ΤΊΟ2 or AI2O3. In a label structure, the face stock further comprises a printing layer against the inorganic coating layer.

The embodiments described above are only example embodiments of the invention, and a person skilled in the art will readily recognize that they may be combined in various ways to generate further embodiments without deviating from the basic underlying invention.

Claims

Claims:

1 . A label including a facestock comprising polyolefin and having a first surface and a second surface;

at least one inorganic coating layer adjoined to the surface of the facestock, and a printing layer against the inorganic coating layer, wherein the inorganic layer is configured to provide a functional layer for the printing layer.

2. The label according to claim 1 , wherein the facestock comprises polypropylene at least 40 wt-%, preferably at least 70 wt-%.

3. The label according to claim 1 or 2, wherein the inorganic coating layer has a surface tension of at least 38 dynes/cm, preferably at least 44 dynes/cm measured according to the standard ASTM D-2578.

4. The label according to any of the preceding claims, wherein thickness of the inorganic coating layer is smaller than 500 nm, preferably smaller than 150 nm or smaller than 100 nm.

5. The label according to any of the preceding claims, wherein the inorganic coating layer is composed of at least one of the following metal oxide(s), silicon oxide(s) and silicon nitride(s).

6. The label according to any of the preceding claims, wherein the inorganic coating layer comprises at least one of the following: T1O2, AI2O3, S1O2, Si₃N₄, AlSiOx, and ZnO.

7. The label according to any of the preceding claims, wherein the inorganic coating layer consists of at least one of the following metal oxide(s) and silicon oxide(s).

8. The label according to any of the preceding claims, wherein the inorganic coating layer consists of at least one of the following T1O2 and AI2O3.

9. The label according to any of the preceding claims, wherein the opacity of the facestock is lower than 10%, preferably lower than 5%, or lower than 4% measured according to the standard ISO 2471 .

10. The label according to any of the preceding claims, wherein the printing layer comprises flexographic ink or gravure printing ink.

1 1 . The label according to any of the preceding claims, wherein the label comprises an adhesive layer against the second surface of the facestock.

12. The label according to claim 1 1 , wherein the adhesive layer consists of a pressure sensitive adhesive.

13. A method for producing a label including a facestock, at least one inorganic coating layer, and a printing layer, the method comprising:

providing a facestock;

coating at least one surface of the facestock with an inorganic material; printing the inorganic layer of the facestock so as to form a printed facestock; and

cutting the printed facestock so as to form a printed label.

14. The method according to claim 13, wherein the coating of the facestock with inorganic material is a continuous atomic layer deposition process performed prior to the printing of the facestock.

15. The method according to claim 13 or 14, wherein the method further comprise coating of the facestock with an adhesive layer.

16. A facestock for labels comprising polyolefin and having a first surface and a second surface;

17. The facestock according to claim 16, wherein the facestock comprises polypropylene at least 40 wt-%, preferably at least 70 wt-%.

18. The facestock according to claim 16 or 17, wherein the inorganic coating layer has a surface tension of at least 38 dynes/cm, preferably at least 44 dynes/cm measured according to the standard ASTM D-2578.

19. The facestock according to any of the claims 16 to 18, wherein thickness of the inorganic coating layer is smaller than 500 nm, preferably smaller than 150 nm or smaller than 100 nm.

20. The facestock according to any of the claims 16 to 19, wherein the inorganic coating layer is composed of at least one of the following metal oxide(s), silicon oxide(s) and silicon nitride(s).

21 .The facestock according to any of the preceding claims 16 to 20, wherein the inorganic coating layer comprises at least one of the following: T1O2, AI2O3, SiO₂, Si₃N₄, AlSiOx, and ZnO.

22. The facestock according to any of the claims 16 to 21 , wherein the inorganic coating layer consists of at least one of the following metal oxide(s) and silicon oxide(s).

23. The face stock according to any of the preceding claims 16 to 22, wherein the inorganic coating layer consists of at least one of the following T1O2

24. The facestock according to any of the preceding claims 16 to 23, wherein the opacity of the facestock is lower than 10%, preferably lower than 5%, or lower than 4% measured according to the standard ISO 2471 .

25. The facestock according to any of the preceding claims 16 to 24, wherein the printing layer comprises flexographic ink or gravure printing ink.

26. A use of a label according to any of the claims 1 to 12 for labelling of an item.

27. A combination of an item and a label attached to the item, the label including a facestock comprising polyolefin and having a first surface and a second surface, at least one inorganic coating layer adjoined to the surface of the facestock, and a printing layer against the inorganic coating layer, wherein the inorganic layer is configured to provide a functional layer for the printing layer.