NL2027403B1

NL2027403B1 - Hard-coat

Info

Publication number: NL2027403B1
Application number: NL2027403A
Authority: NL
Inventors: Johannes Gerardus Maria Van Peer Cornelis
Original assignee: Nanogate Netherlands B V
Priority date: 2021-01-26
Filing date: 2021-01-26
Publication date: 2022-08-19
Also published as: WO2022164314A1

Abstract

The invention relates to a method for providing a coated polymer foil. The invention also relates to a (thermoformed) polymer foil comprising a surface coated with a UV-curable coating, obtained with or obtainable by the method according to the invention. In addition, the invention relates to an article or thermoformed article comprising the polymer foil orthe thermoformed foil of the invention.

Description

HARD-COAT

TECHNICAL FIELD The invention relates to a method for providing a (hard-)coated polymer foil that can be elongated and stretched without inducing cracks in the coating. The invention also relates to a {thermoformed) polymer foil comprising a surface coated with a UV-curable coating, obtained with or obtainable by the method according to the invention. In addition, the invention relates to an article or thermoformed article comprising the polymer foil or the thermoformed foil of the invention.

BACKGROUND Manufacturers of polymer-film comprising articles and -parts such as mobile phones, control panels, automotive applications, demand and require polymer film which meets high quality measures. An example are the stringent hardness criteria set by automotive industry. In addition, such polymer film, for example polycarbonate film, should meet high standards relating to polymer film formability, resistance to cracking of the coating upon stretching or elongation, applicability of the film in moulding processes, and relating to chemical resistance of the film surface. In addition, these hi-tech industries, e.g. automotive industry, mobile phone manufacturing, domestic control panels applications, efc., demand constant quality, robust manufacturing processes when the application of the high quality polycarbonate film is concerned, and polymer film that does not demand much attention when maintenance of previous set quality standards are considered.

Despite these demands for robust, hard, chemical resistant, easy-to-apply polymer sheets and films such as polycarbonate film, for application in car-, phone-, control panel manufacturing, efc., still currently available polycarbonate films suitable for implication in such manufacturing processes, require laborious processing steps and require the purchase and maintenance of machinery specifically mandatory to provide and maintain polymer film at the required quality with regard to e.g. hardness, chemical resistance. That is to say, currently available polycarbonate film for polymer-film comprising article manufacturing is film provided with a hard-coat that is typically UV cured in a first necessary step of providing and keeping polymer film with the required specifications (although for alternative hard-coat film, such curing can also be thermal curing), said first UV curing {or thermal curing) performed typically directly after hard-coat polycarbonate film production at the site of manufacturing of film. Then, subsequently, the hard-coat polycarbonate film is typically transferred to customers, e.g. car dashboard parts manufacturers, mobile phone casing manufacturers, control panel manufacturers, etc. Typically, the hard-coat polycarbonate film is subjected to a (thermo)forming step. Hard-coat polycarbonate films now available do require a necessary second UV curing step after the forming of the film, in order to meet the stringent industry criteria such as those set in the ASTM D1044-13 industry standard and in 40 automotive norms such as VW TL226 (VW/Porsche official test norm for automotive interior parts) and

DBL9202 (Daimler Benz official test norm for automotive interior parts). This induces the necessity to conduct crucial and additional steps as part of the manufacturing process and requires measures to handle formed film before and after the forming process with high care when avoidance of scratches, contacting film surfaces, applying pressure onto the film, efc. are concerned. Only after a cumbersome second UV curing step, requiring UV curing equipment designed and suitable for the purpose, results in a formed film which can be treated with reduced caution when damaging the surface of the formed polycarbonate film is regarded. After all, such currently available film would not meet the high quality standards if the requirement of the second UV curing step would not be obeyed. Therefore, a solution still needs to be found that allows for a less cumbersome and less critical process for applying polymer film in e.g. forming processes and moulding processes for the purpose of manufacturing polymer-film comprising articles which should resist stringent hardness tests and stringent chemical resistance tests.

International patent application WO 2018/121613 A1 (Applicant: PPG COATINGS (TIANJIN) CO., LTD. (China), relates to a high-hardness anti-steel wool UV curable coating composition comprising a high-functionality UV curable polyurethane acrylate. A method of coating a substrate with the high-hardness anti-steel UV curable coating composition and the substrate coated with the same are also provided. Typically, the coating composition of WO 2018/121613 A1 comprises butyl acetate and isobutyl acetate.

SUMMARY A first aspect of the invention relates to a method for providing a (hard-)}coated polymer foil, comprising the steps of or consisting of the steps of: (a) providing a UV-curable coating composition comprising diluent 6-prop-2-enoyloxyhexyl prop- 2-encate (HDDA), a photo-initiator, a first aliphatic multi-functional urethane acrylate oligomer and a second aliphatic multi-functional urethane acrylate oligomer, wherein the functionality of the first and second oligomer is different, and providing a polymer foil; {b) covering a surface of the polymer foil of step (a) with the UV-curable coating composition of step (a), wherein the temperature of the polymer foil is selected from the range 40°C - 95°C and the temperature of the UV-curable coating composition is selected from the range 40°C - 95°C; and (c) curing the surface of the polymer foil that is covered with UV-curable coating composition in step (b) with UV radiation, therewith providing the coated polymer foil.

Preferred is the method of the invention, wherein the coating of the coated polymer foil provided at the end of step (c) has a thickness of at least 1,0 micrometer, preferably at least 1,5 micrometer, more preferably at least 2,0 micrometer, most preferably at least 3,0 micrometer.

The invention also relates to the method of the invention, wherein the method comprises or consists of the method steps (a) — (c) and a subsequent step following step (c): {d) forming at least a part of the 40 coated polymer foil that is provided in step (©), therewith providing coated polymer foil, which is formed coated polymer foil or which comprises a part of the coated polymer foil surface area that is formed coated polymer foil, wherein the thickness of the coating of the formed coated polymer foil or of the formed part of the coated polymer foil is at least 3,0 micrometer, preferably at least 4,0 micrometer, such as 3,0 micrometer — 8,0 micrometer or 3,5 micrometer — 6,0 micrometer. Preferably, the forming is thermoforming.

Preferred is the method of the invention, wherein the method comprises or consists of the method steps (a) — (c) and a subsequent step following step (c): (d) (thermo)forming at least a part of the coated polymer foil that is provided in step (c), therewith providing coated polymer foil, which is or comprises (thermo)formed coated polymer foil comprising at least a protrusion and/or at least a recess in the (thermo)formed part of the coated polymer foil, wherein the thickness of the coating of the (thermo)formed part of the coated polymer foil defining the protrusion(s) and/or recess(es) is at least 3,0 micrometer, preferably at least 4,0 micrometer, such as 3,0 micrometer — 8,0 micrometer or 3,5 micrometer — 8,0 micrometer.

Preferred is the method of the invention, wherein the polymer foil provided in step (a) has a thickness selected from the range 0,1 millimeter — 10,0 millimeter, preferably selected from the range 0,2 millimeter — 8,0 millimeter, more preferably selected from the range 0,4 millimeter — 6,0 millimeter, most preferably selected from the range 1,0 millimeter — 4,0 millimeter, such as 2,0 millimeter — 3,0 millimeter.

Also preferred is the method of the invention, wherein the UV-curable coating composition is a solid UV-curable coating composition or a UV-curable hard-coating composition, preferably a solid UV- curable hard-coating composition.

Typically, in the method according to the invention, the UV-curable coating composition comprises: (i) a first aliphatic multi-functional urethane acrylate oligomer; (ii) a photo-initiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) optionally a second aliphatic multi-functional urethane acrylate oligomer, wherein the functionality of the first aliphatic multi-functional urethane acrylate oligomer and the second aliphatic multi-functional urethane acrylate oligomer is different; and optionally {v) a flow modifier.

Preferred is the method of the invention, wherein the UV-curable coating composition comprises: (i) a first aliphatic multi-functional urethane acrylate oligomer which is any one of an aliphatic three-functional — dodeca-functional urethane acrylate oligomer; (ii) a photo-initiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) optionally a second aliphatic multi-functional urethane acrylate oligomer which is any one of an aliphatic di-functional — dodeca-functional urethane acrylate oligomer, wherein the functionality of the first aliphatic multi-functional urethane acrylate oligomer and the second aliphatic multi-functional 40 urethane acrylate oligomer is different; and optionally;

(v) a flow modifier.

Also preferred is the method of the invention, wherein the UV-curable coating composition comprises: (i) a first aliphatic multi-functional urethane acrylate oligomer which is an aliphatic three- functional or tetra-functional urethane acrylate oligomer, preferably an aliphatic three-functional urethane acrylate oligomer; (ii) a photo-initiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) a second aliphatic multi-functional urethane acrylate oligomer which is any one of an aliphatic penta-functional — dodeca-functional urethane acrylate oligomer, preferably an aliphatic hexa- functional urethane acrylate oligomer; and optionally (v) a flow modifier.

In particular, in the method according to the invention, in step (a) the provided UV curable coating composition comprises the diluent 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA), present at 10% - 40% by weight based on the total weight of the UV curable coating composition, preferably 15% - 30% by weight, more preferably 20% - 25% by weight, such as 20% - 35% by weight.

Particularly preferred is the method according to the invention, wherein in step (a) of the method the provided UV curable coating composition comprises or consists of, based on the total weight of the UV curable coating composition: (1) 20% - 60% by weight of the first aliphatic multi-functional urethane acrylate oligomer, preferably an aliphatic tri-functional urethane acrylate oligomer; (2) 20% - 60% by weight of the second aliphatic multi-functional urethane acrylate oligomer, preferably an aliphatic hexa-functional urethane acrylate oligomer; (3) 10% - 40% by weight 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA), preferably 15% - 35% by weight, more preferably 20% - 30% by weight; (4) 0,3% — 3% by weight of the photo-initiator, preferably 0,5% - 1,5% by weight, preferably bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide; and optionally (5) 0,03% - 0,3% by weight of the flow modifier, preferably 0,05% - 0,2% by weight, preferably poly-ether-modified polydimethylsiloxane in a mixture of xylene and iso-butanol, preferably the flow modifier is present.

Even more preferred is the method according to the invention, wherein in step (a) of the method the provided UV curable coating composition comprises or consists of, based on the total weight of the UV curable coating composition: (1) 30% - 50% by weight of the first aliphatic multi-functional urethane acrylate oligomer, preferably an aliphatic tri-functional urethane acrylate oligomer, preferably 35% - 45% by weight; (2) 25% - 45% by weight of the second aliphatic multi-functional urethane acrylate oligomer, preferably an aliphatic hexa-functional urethane acrylate oligomer, preferably 30% - 40% by weight; (3) 15% - 35% by weight 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA), preferably 18% - 30% 40 by weight, more preferably 20% - 27% by weight;

(4) 0,5% — 1,5% by weight of the photo-initiator, preferably 0,7% - 1,3% by weight, preferably bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide; and (5) 0,05% - 0,3% by weight poly-ether-modified polydimethylsiloxane in a mixture of xylene and iso-butanol, preferably 0,07 - 0,13% by weight.

5 In the method according to the invention, typically in step (b) of the method the temperature of the polymer foil is selected from the range 50°C - 90°C, preferably 55°C - 85°C, more preferably 60°C - 80°C, and the temperature of the UV-curable coating composition is selected from the range 50°C - 90°C, preferably 55°C - 85°C, more preferably 60°C - 80°C.

Highly preferred is the method according to the invention, wherein the polymer foil is a polycarbonate foil. A second aspect of the invention relates to a polymer foil comprising a surface coated with a UV-curable coating or formed polymer foil, preferably thermoformed polymer foil, comprising a formed surface coated with a UV-curable coating, obtained with or obtainable by the method according to the invention wherein the polymer foil preferably is a transparent polycarbonate foil or the formed polymer foil is a transparent thermoformed polymer foil. A third aspect of the invention relates to use of the polymer foil or the formed polymer foil of the polymer foil obtained with or obtainable with the method of the invention, in the manufacturing of a formed article or of a formed object such as a thermoformed article or object, a pane such as a glass pane or sheet, and/or of a moulded article or object such as an injection-moulded article or object, preferably an article or object which comprises the polymer foil comprising a surface coated with a UV- curable coating or thermoformed polymer foil comprising a thermoformed surface coated with a UV- curable coating, which is first formed and then back moulded such as back injection-moulded. Preferred is the use according to the invention, wherein the article or object is an article or object such as a control panel and/or an article or object applied in automotive applications such as a radio panel, a control panel, a HVAC control system, or a part thereof, in telecom applications such as a housing, a keypad, an outer casing for a mobile phone. A fourth aspect of the invention relates to an article or object comprising the polymer foil comprising a surface coated with a UV-curable coating or thermoformed polymer foil comprising a thermoformed surface coated with a UV-curable coating obtained with or obtainable with the method of the invention, or provided according to the use of the invention, wherein preferably the polymer foil is a transparent polycarbonate foil or wherein the thermoformed polymer foil is a transparent thermoformed polymer foil. Preferred is an a rticle or thermoformed article of the invention, which is a laminate such as a window pane, comprising the polymer foil or the thermoformed foil, or which is an article or object applied in automotive applications such as a radio panel, a control panel, a HVAC control system, or a part thereof. 40

DEFINITIONS The term “UV curable” has its regular scientific meaning throughout the text, and here refers to the curing of a coating composition which is applied onto a surface such as a polymer sheet or polymer film, with the aid of illuminating the polymer film surface provided with the coating composition with ultraviolet radiation.

The term “hard-coat” has its regular scientific meaning throughout the text, and here refers to a coating for a polymer film such as a polycarbonate film, which coating, after curing, meets the industry hardness standard set by one or more of car manufacturers such as Volkswagen, Ford, Mercedes, such as the automotive norms such as VW TL226 (VW/Porsche official test norm for automotive interior parts) and DBL9202 (Daimler Benz official test norm for automotive interior parts} and/or the taber abrasion test (ASTM D1044-13).

The term “Hansen Solubility Parameters” has its regular scientific meeting throughout the application, and here refers to the three parameters 3D (dispersion force interactions; dispersive aspect), OP (polar force interactions; polar aspect), and 3H (hydrogen bond force interactions; hydrogen-bonding aspect) for a molecule such as a solvent molecule, as for example outlined in the paper by Steven Abbott, 29 March 2018, “Science-based formulation: the xl power of HSP for coatings compatibility issues” (reference for example accessible at the online information source: coatings. specialchem. com).

The term “solid coating” has its regular scientific meeting throughout the application, and here refers to a coating composition that essentially does not comprise solvents (is solvent-free} and that is in a solid state at room temperature (18°C - 22°C).

The term “outer surface tension” has its regular scientific meeting throughout the application, and here refers to the calculated outer fiber strain (OFS) subjected on a coating that is adhered on the outer surface of a bend layer of polymer material such as a bend film, sheet, pane, plate or foil of coated polymer material such as bend coated polycarbonate foil, expressed as st = 100r / R, wherein r is half the thickness of the layer of coated polymer material (foil, sheet, film, pane, plate, etc.) and R is the nominal bending radius to the mid of the thickness of the layer of coated polymer material.

The term “transparent” has its regular scientific meeting throughout the application, and here refers to luminous transparency of polymer material according to the ASTM standard D1003 as in force in January 2021.

The term “elongation test” has its regular scientific meeting throughout the application, and here refers to the visual inspection by eye (illumination with a fluorescence lamp) and/or by the use of a microscope (typically at 5x — 3.000x magnification such as 10x-250x magnification), of a coated polymer surface that is bend and/or elongated and/or formed such as thermoformed, such that the coating on the coated polymer surface is elongated upon the forming or bending or elongation, for the assessment of the presence of hair-like crack{s} in the elongated coating.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the 40 embodiments of the invention can operate in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

The embodiments of the invention described herein can operate in combination and cooperation, unless specified otherwise.

The various embodiments, although referred to as “preferred” or “e.g.” or “for example”, “particularly” or “in particular’ are to be construed as exemplary manners in which the invention may be implemented rather than as limiting the scope of the invention.

The term “comprising”, used in the claims, should not be interpreted as being restricted to the elements or steps listed thereafter; it does not exclude other elements or steps. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a coating comprising components A and B” should not be limited to a coating consisting only of components A and B, rather with respect to the present invention, the only enumerated components of the coating are component A and component B, and further the claim should be interpreted as including equivalents of those components.

In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element are present, unless the context clearly requires that there is one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

DETAILED DESCRIPTION It is a first goal of the present invention to provide an improved method for providing a coated polymer foil comprising a UV-curable coating, preferably a UV curable hard-coat.

It is an objective of the current invention to provide a method for providing a coated polymer foil comprising a UV-curable coating which method is accompanied by less cumbersome manufacturing requirements, for example when method steps for applying the coating is concerned and/or when the required machinery and equipment is concerned required for processing the UV curable hard-coat.

At least one of the above objectives is achieved by providing a method for providing a coated polymer film of the invention. At least a further objective is achieved by providing a polymer foil of the invention comprising a surface coated with a UV-curable coating or thermoformed polymer foil comprising a thermoformed surface coated with a UV-curable coating.

The present invention will be described with respect to particular embodiments but the invention is not limited thereto but only by the claims.

While the invention has been described in terms of several embodiments, it is contemplated that alternatives, modifications, permutations and equivalents thereof will become apparent to one having ordinary skill in the art upon reading the specification. The invention is not limited in any way to the illustrated embodiments. Changes can be made without departing from the scope which is defined by the appended claims. A first aspect of the invention relates to a method for providing a (hard-)coated polymer foil, comprising the steps of or consisting of the steps of: (a) providing a UV-curable coating composition comprising diluent 6-prop-2-enoyloxyhexyl prop- 2-enoate (HDDA), a photo-initiator, a first aliphatic multi-functional urethane acrylate oligomer and a second aliphatic multi-functional urethane acrylate oligomer, wherein the functionality of the first and second oligomer is different, and providing a polymer foil; (b) covering a surface of the polymer foil of step (a) with the UV-curable coating composition of step (a), wherein the temperature of the polymer foil is selected from the range 40°C - 95°C and the temperature of the UV-curable coating composition is selected from the range 40°C - 95°C; and (c) curing the surface of the polymer foil that is covered with UV-curable coating composition in step (b) with UV radiation, therewith providing the coated polymer foil.

Meeting the very high quality standards of the automotive industry with a coating on a polymer material such as a polycarbonate foil, film or sheet, when for example the chemical resistance, firm adhesion of the coating, resistance to tear of the coating upon elongation, hardness (e.g. successfully passing the Taber test) and resistance to crack of the coating when exposed to harsh conditions, are considered, is very hard to achieve when current common methods for adhering a coating to a surface of a polymer material are applied. Upon applying standard coating methods commonly used in the art, often perhaps the elongation test is past, but the coating fails in the adhesion water soak test; or for example cracks are not formed in a crack analysis test upon exposure to e.g. propylene-carbonate, but the chemical resistance is mediocre when the coating is contacted with acetone.

The inventors, now, established to their surprise a robust and reliable method for providing a polymer surface or at least a part thereof with a UV curable coating, e.g. a hard-coat, typically a UV curable hard coat. The UV curable hard coat or UV curable coating in general is typically a 100% solid coating (non-solvent coat). Typically, according to the invention, before adhering or imprinting the (solid) UV curable (hard) coating onto at least part of a surface area of a (film, foil or sheet of) polymer material, such as a polycarbonate foil, the UV curable (hard-)coating is provided with a diluent, typically 1,6- hexanediol di-acrylate (HDDA; PubChem CID: 25644, alternative chemical name: 13048-33-4 or hexa- methylene di-acrylate; IUPAC name: 6-prop-2-enoyloxyhexyl prop-2-enoate), providing the UV-curable coating composition suitable for application in the method of the invention. The inventors established that upon incorporating HDDA in the hard-coat UV-curable coating composition, an improved hard-coat is provided once overlaid onto a polymer surface such as a polycarbonate film, and UV cured.

Improvements are amongst other a very high hardness (as established with the Taber test) accompanied with an improved resistance to crack when the cured coating is elongated or stretched (bend, formed, thermoformed). It is now due to the current invention that (transparent) polymer film, sheet and foil such as transparent polycarbonate foil, can be provided which is provided with a hard coat and which is still formable, bendable and stretchable without introducing hair-like cracks in the coating 40 (as for example established by thermoforming the film or foil that is coated according to the method of the invention and assessing the extent of (possible) cracking by irradiating the coat surface with a fluorescence lamp).

Without wishing to be bound by any theory, the presence of the HDDA in the coating composition during the overlaying and subsequent UV curing onto the polymer material surface, allows for suitable coating compositions which have a relatively high and increased double bond number expressed as milli-equivalents per gram (meq/g) of oligomer material (used as starting material for establishing the UV cured coat), while still the resulting hard-coat passes the Taber test and is improvingly resistant to cracking. For example, a UV curable hard-coat composition comprising more than 6,0 meq double bonds per gram, but without HDDA in the composition provides for a hard-coat once applied onto an e.g. PC film, but readily cracks upon elongation of the coating; for example, the coating composition comprises 30%-45% by weight tri-functional urethane acrylate oligomer and 55%-70% by weight hexa- functional urethane acrylate oligomer based on the total weight of the solid coat (number of double bonds is 6,3 — 7,4 meq double bonds per gram of oligomers in the coat composition). When for example 20%-35% by weight HDDA is incorporated in such a solid hard-coat composition, based on the total weigh of the coating composition, the number of double bonds is still as high as about 6,0 — 7,0 meq double bonds per gram of oligomers (coating composition comprises for example 35%-45% by weight tri-functional urethane acrylate oligomer and 30%-40% by weight hexa-functional urethane acrylate oligomer based on the total weight of the solid coat), which positively contributes to providing a hard coating (high hardness; Taber test is passed), and the resistance to cracking upon elongation of the coating coated onto the surface of a polymer material is improved. Thus, the invention provides a method for providing a coated polymer surface wherein the coat is hard according to standard measures applied to assess coating hardness, and wherein still the hard coat is bendable, formable, stretchable, without introducing hair-like cracks, due to the incorporation of HDDA in the coating composition.

Discarding the HDDA according to current common practice provides a hard-coat with poorer resistance to cracking upon elongation of the hard-coat once provided onto a polymer surface, e.g. a transparent polycarbonate (PC) film. Typically, the PC film is a PC foil with a thickness of 1,5 mm — 5,0 mm such as 2,5 mm — 4,0 mm, wherein the transparent PC foil is typically made of bisphenol A as one of the building blocks (precursors; IUPAC name: 4,4'-(propane-2,2-diyl)diphenol). The inventors thus established a method for providing a hard-coated polymer film wherein the degree of cross-linking is relatively high (6 or more meq double bonds per gram oligomer starting material) in the coating composition, contributing to increased hardness of the providing coat, while still the application of bending and folding steps is suitably performed without introducing cracks in the coated surface. It is now due to the inventors that a method is provided that shifts the delicate balance between sufficient hardness of the hard-coat while still sufficient resistance to cracking of the coat is apparent upon forming or bending or stretching the hard-coat on a coated polymer foil, towards maintaining sufficient hardness (passing the Taber test) while improving the resistance to cracking, according to the method of the invention.

Without wishing to be bound by any theory, it is assumed that HDDA is penetrating the PC surface layer when the coating formulation and/or the PC surface are heated. Adding HDDA to the coating formulation improves the binding and adherence of the hard-coat to the PC upon curing, as has 40 been established in a comparative water-soak test for assessing binding of a hard-coat to a polymer surface. It is assumed that at elevated temperature, the HDDA penetrates or diffuses into the surface of the PC film: an effect referred to as ‘inter penetration layer’. The inter penetration layer is thought to contribute to binding and adherence of the coating to the PC film by the migration (or: penetration, diffusion) of the coating into the surface layer of the PC film, by enhanced mobility of the molecules (constituents) in the coating formulation during heating of the coating.

By applying the method of the invention, the inventors now made it possible to provide a polymer material such as a polycarbonate (PC) foil, that is provided with a coating, which e.g. passes the tests required for application in automotive industry. Sufficient hardness and sufficient resistance to chemical compounds and sufficient resistance to cracking upon elongation of the coat.

That is to say, when a coated polymer foil such as a coated PC foil is provided, comprising a major surface or at least part of a major surface, coated with the UV curable (hard)coat according to the method of the invention, a very toughly and firmly adhered coating is provided when the minimal thickness of the coating exceeds 1,0 micrometer. The Taber test is passed when the minimal coating thickness is applied. Such coated polymer foil meets the automotive industry requirements when for example the adhesion test in the water soak set-up is considered and when the hardness is assessed. For coating thickness of 3 micrometer or more, such as 3 — 10 micrometer, not only the hardness is sufficient (passing the Taber test), but also the chemical resistance is sufficient for passing tests such as exposure to chemicals like acetone and sun cream. Moreover, when in the method a coating thickness of at least 3 micrometer is provided, the coated polymer material such as coated transparent PC foil of 2,0-3,0 mm thickness, is suitable stretched or bend or formed such as upon thermoforming, without introducing hair-like cracks in the coating. With such coating the chemical resistance is sufficient as is assessed in the common acetone contact test.

It is part of the invention that the method also provides such a firmly adhered and hard coating onto polymer foil such as (transparent) PC foil, that even the industry standards can be met when after coating and UV curing the coated polymer foil is formed such as thermoformed. The inventors established to their surprise that when the layer of coating adhered to the foil is 3,0 micrometer or more, a very hard and inert coating on the polymer film is provided that is formable without losing resistance to cracking.

Preferred is therefore the method of the invention, wherein the method comprises or consists of the method steps (a) — (¢) and a subsequent step following step (c): (d) thermoforming at least a part of the coated polymer foil that is provided in step (c), therewith providing coated polymer foil, which is or comprises thermoformed coated polymer foil comprising at least a protrusion and/or at least a recess in the thermoformed part of the coated polymer foil, wherein the thickness of the coating of the thermoformed part of the coated polymer foil defining the protrusion(s) and/or recess(es) is at least 3,0 micrometer, preferably at least 4,0 micrometer, such as 3,0 micrometer — 8,0 micrometer or 3,5 micrometer — 6,0 micrometer.

Similarly preferred is the method of the invention, wherein the method comprises or consists of the method steps (a) — (c) and a subsequent step following step (c): {d) forming at least a part of the coated polymer foil that is provided in step (¢), therewith providing coated polymer foil, which is or formed coated polymer foil or which comprises a part that is formed coated polymer foil, wherein the thickness of the coating ofthe formed coated polymer foil or ofthe formed part of the coated polymer foil is at least 3,0 micrometer, preferably at least 4,0 micrometer, such as 3,0 micrometer — 8,0 micrometer or 3,5 micrometer — 6,0 micrometer, wherein preferably the forming is thermoforming. Thus, it is part of the invention that after UV curing the coating that is provided onto the polymer film, typically a PC foil, the UV-cured (hard-)coating on the film is subjected to a step of forming, typically under application of heat (thermofolding or thermoforming), without giving in on a series of reference quality markers, commonly assessed in automotive industry. The thermoformed coated polymer foil is a very robust and chemical resistant material when the coat, typically the hard coat, is considered. In order to achieve such a high-quality coated foil, e.g. hard-coated PC foil, the inventors established that the thickness of the coating layer that is firmly adhered to the foil surface or part thereof, after UV curing, should be at least 3,0 micrometer in the foil area of the formed sections of the coated foil surface. That is to say, after the forming, e.g. thermoforming of the coated and cured polymer foil, the thickness of the layer of adhered coating should be at least 3,0 micrometer or more, such as 3,5 micrometer — 5,5 micrometer. With a thickness of the coating layer on the foil that is or exceeds 3,0 micrometer, the coated foil can be elongated to large extend before cracking, breaking or tearing, as assessed by (non- )appearance of hair-like cracks in the coating (illuminating the elongated coat surface with a fluorescent light and/or by inspection under a microscope). In addition, in a stress test using exposure of the coated foil to propylene-carbonate according to a method known in the art, with such a minimal coating thickness on the formed parts of the foil surface, cracking of the coating is prevented. Furthermore, the inventors established that when the minimal coating thickness is achieved, after UV-curing and thermoforming, the coating remains firmly adhered onto the polymer film such as a PC foil, when the coated foil is subjected to adhesion testing by applying commonly applied water soak test. In addition, when after thermoforming of the coated polymer foil according to the method of the invention, the thickness of the coating is minimally 3,0 micrometer, typically 4,0 — 5,5 micrometer, the chemical resistance of the cured and thermoformed coating is very high when assessed in a common 10-minutes acetone exposure test known in the art. In addition, such hard-coat polymer foil such as transparent PC foil provided with UV curable hard coat according to the method of the invention, also passes harsh chemical resistance tests such as by applying sun cream onto the coated surface, even after bending or thermoforming the coated PC film.

In the method of the invention, presence of the diluent HDDA in the coating composition provides for a UV curable (hard-) coating composition suitable for application in the method of the invention for providing a coated polymer foil wherein the coating passes harsh chemical testing and intense stress testing. Due to the HDDA, the 100% solid coating (non-solvent coating) that can be applied in the method of the invention, sufficiently flows over the (part of the) foil surface upon the heating of the foil and/or the coating composition in step (b) of the method. Due to the presence of the 40 HDDA, the number of double bonds in a coating composition can be increased, when expressed in meq double bonds per gram oligomer starting material, from less than 6,0 to 6,0 or higher, such that a harder coat can be achieved, while the resistance to cracking upon (thermo)forming is improved, when compared to a similar coating composition without the HDDA incorporated and with a similar number of double bonds expressed in meq double bonds per gram oligomer starting material. See also the Examples section for example wherein coating compositions comprising aliphatic tri- and hexa- functional urethane acrylate oligomers and either or not comprising HDDA, are compared for their hardness and resistance to cracking once applied as a UV curable hard-coat on a PC foil.

As also outlined in the Examples section, the inventors tested transparent PC foil or film having a thickness of 2 mm and 3 mm, which both provided a hard-coated foil upon applying the method of the invention, which foil passed the hardness test (Taber test), passed the chemical resistance tests applied, and passed the resistance-to-cracking elongation test upon thermoforming (for the thermoforming, the minimal coating thickness was 3 micrometer, e.g. in the range 3,0 micrometer — 6,0 micrometer). As said, for achieving the desired hardness, a coating thickness provided with the method of the invention, of 1,0 — 3,0 micrometer suffices. When chemical resistance and/or resistance to hair cracking upon forming is desired for the hard-coated polymer foil, the minimal thickness for the coating provided with the method of the invention is 3,0 micrometer, such as 3,0 — 6,0 micrometer. For details on how resistance to cracking upon elongation or stretching of the coating on the polymer surface is assessed, reference is made to the Examples section.

For providing hard-coated (transparent) PC foil suitable for application in e.g. automotive industry or for manufacturing of consumer goods like mobile telephone casings, typically solvent-free solid coating compositions are applied. The inventors now improved such solid coatings by adding the diluent HDDA, for application in the method of the invention. Introducing the HDDA in the coating composition increased the number of double bonds expressed as meq double bonds per gram oligomer material comprising said double bonds (e.g. HDDA, aliphatic tri- and hexa-functional urethane acrylate oligomer), therewith increasing the number of cross-links in the coat and thus improving the hardness of the coating, while at the same time the formability is improved, expressed as a relatively harder coating while suitably formable without introducing cracks in the coat. For current hard-coat compositions known in the art, the number of double bonds present has to be at the low side of less than 6,0 meq/g, since at higher amounts of double bonds, the coated polymer material is not formable without creating hair-like cracks in the coating. Typically, applying 20% - 35% by weight HDDA in a solid coat composition provides a hard-coated polymer foil such as transparent PC foil of 1,0 — 5,0 mm 40 thickness, that is formable without cracking the coating.

Typically, in the method according to the invention, the UV-curable coating composition comprises: (i) a first aliphatic multi-functional urethane acrylate oligomer; (ii) a photo-initiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) optionally a second aliphatic multi-functional urethane acrylate oligomer, wherein the functionality of the first aliphatic multi-functional urethane acrylate oligomer and the second aliphatic multi-functional urethane acrylate oligomer is different; and optionally (v) a flow modifier.

The skilled person will understood that a solid hard-coat composition for application in the method of the invention, having a double bond content of 6,0 or higher such as 6,0 — 7,0 meq double bonds per gram oligomer material, and comprising 20% by weight HDDA based on the total mass of the solid hard-coat composition, can be provided in a range of ways. That is to say, by selecting for example a ratio for a first and second aliphatic multi-functional urethane acrylate oligomer, the number of double bond equivalents per gram oligomer can be selected at a selected amount of HDDA (number of double bonds is 8,85 meq/g HDDA, for the sake of the calculations of the number of double bonds, HDDA is seen as an oligomer with two double bonds). Typically, in the hard-coat solid coating compositions applied in the method of the invention, the amount of HDDA was 20% - 35% by weight and the aliphatic multi-functional urethane acrylate oligomer were typically selected from aliphatic tri-, hexa- and deca- functional urethane acrylate oligomers, such that the total number of double bonds exceeded 6,0 meq/g in the solid coat composition, and was typically lower than 7,0 meg/g.

Preferred is the method of the invention, wherein the UV-curable coating composition comprises: (i) a first aliphatic multi-functional urethane acrylate oligomer which is any one of an aliphatic three-functional — dodeca-functional urethane acrylate oligomer; (ii) a photo-initiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) optionally a second aliphatic multi-functional urethane acrylate oligomer which is any one of an aliphatic di-functional — dodeca-functional urethane acrylate oligomer, wherein the functionality of the first aliphatic multi-functional urethane acrylate oligomer and the second aliphatic multi-functional urethane acrylate oligomer is different; and optionally; (v) a flow modifier.

Also preferred is the method of the invention, wherein the UV-curable coating composition comprises: (i) a first aliphatic multi-functional urethane acrylate oligomer which is an aliphatic three- functional or tetra-functional urethane acrylate oligomer, preferably an aliphatic three-functional urethane acrylate oligomer; (ii) a photo-initiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA);

(iv) a second aliphatic multi-functional urethane acrylate oligomer which is any one of an aliphatic penta-functional — dodeca-functional urethane acrylate oligomer, preferably an aliphatic hexa- functional urethane acrylate oligomer; and optionally (v) a flow modifier.

As said, in the method of the invention, the solid hard-coat composition is provided with an amount expressed in weight percentage, of HDDA, and with amounts of a first aliphatic multi-functional urethane acrylate oligomer and, if present, and preferably present, a second aliphatic urethane acrylate oligomer, such that the total number of double bonds expressed as meq double bonds per gram (oligomer and HDDA, summed up) is between 6,0 and 7,0. The inventors established that in particular aliphatic tri- and hexa-functional urethane acrylate oligomers are suitable for providing the solid coating composition comprising HDDA, for application in the method of the invention, although application of urethane acrylate oligomer having different extents of functionalities can equally suitably applied in the method of the invention.

Even more preferred is the method according to the invention, wherein in step (a) of the method the provided UV curable coating composition comprises or consists of, based on the total weight of the UV curable coating composition: (1) 30% - 50% by weight of the first aliphatic multi-functional urethane acrylate oligomer, preferably an aliphatic tri-functional urethane acrylate oligomer, preferably 35% - 45% by weight; (2) 25% - 45% by weight of the second aliphatic multi-functional urethane acrylate oligomer, preferably an aliphatic hexa-functional urethane acrylate oligomer, preferably 30% - 40% by weight;

(3) 15% - 35% by weight 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA), preferably 18% - 30% by weight, more preferably 20% - 27% by weight; (4) 0,5% — 1,5% by weight of the photo-initiator, preferably 0,7% - 1,3% by weight, preferably bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide; and (5) 0,05% - 0,3% by weight poly-ether-modified polydimethylsiloxane in a mixture of xylene and iso-butanol, preferably 0,07 - 0,13% by weight.

Herewith, a coating composition is applied in the method of the invention which has a double bond content of about 6,0 — 7,0 meq double bonds per gram (oligomers + HDDA). Such coating compositions are suitable for providing a hard-coated polymer foil such as transparent PC film, that has a hardness sufficiently high to pass the industry standard hardness test (Taber test), and a resistance to chemicals that is sufficient for application of the coated polymer material in for example automotive industry and consumer goods applications, and can be formed for application in articles and objects typical for automotive industry and for consumer goods, without existence of hair-like cracks in the coating surface. Herewith, the method of the invention provides a coated polymer foil, e.g. hard-coated transparent PC foil, which as a higher hardness due to the presence of more double bond milli- equivalents per gram oligomer starting material in the coating composition, when compared to current coatings, while formability is improved when absence of cracking upon thermoforming is considered, when compared with coatings which are provided with a similar content of double bonds though without presence of HDDA in the coating composition.

In the method according to the invention, typically in step (b) of the method the temperature of the polymer foil is selected from the range 50°C - 90°C, preferably 55°C - 85°C, more preferably 60°C - 80°C, and the temperature of the UV-curable coating composition is selected from the range 50°C - 90°C, preferably 55°C - 85°C, more preferably 60°C - 80°C, wherein preferably the selected temperature for the polymer foil and the selected temperature of the UV-curable coating composition differ 30°C or less, and more preferably are the same.

For application of solid solvent-free coating compositions, adhering such solid coats onto the polymer surface requires warming up the system. That is to say, the coating composition is warmed up and/or the polymer surface is warmed up, typically, both are warmed up, for facilitating the spreading of the coating composition over the polymer surface area that is intended to be coated. The inventors established that with solid hard coats comprising the aliphatic multi-functional urethane acrylate oligomers and 20-35% by weight HDDA, viscosity of the coating composition was sufficiently lowered and spreading of the coating composition over the polymer surface was sufficiently facilitated when the polymer foil and/or the coating composition, preferably both, were heated at 50°C - 90°C, preferably 55°C - 85°C, more preferably 60°C - 80°C (polymer foil), and 50°C - 90°C, preferably 55°C - 85°C, more preferably 60°C - 80°C (UV-curable coating composition). Preferably, the polymer foil and the coating composition are heated at the same temperature, before the next step of UV curing is established.

Highly preferred is the method according to the invention, wherein the polymer foil is a polycarbonate foil. Such as PC foil is typically a transparent foil, typically with a thickness of 1,0 mm — 10,0 mm, such as 1,5 mm — 4,5 mm. For practical reasons, the upper limit for the thickness of the 40 polymer foil material is selected based on the possibility to equally and fastly heat up the polymer foil surface that is to be coated. That is to say, for polymer material with larger thickness, it requires more energy and time to heat up the polymer surface area that is to be coated compared to thinner foil. Thus, also polymer material such as PC panes, sheets, plates with a thickness exceeding 4,5 mm can be applied in the method of the invention. An aspect of the invention relates to an article or (thermo)formed article comprising the polymer foil or the thermoformed foil of the invention, i.e. provided with the method of the invention.

Since the hardness of the coating on the coated polymer foil provided with the method of the invention is so high (ie. it passes the Taber test), the coated polymer foil such as coated transparent PC foil can be applied in articles like dashboards for cars, casings for consumer goods, etc.

A second aspect of the invention relates to a polymer foil comprising a surface coated with a UV-curable coating or formed polymer foil, preferably thermoformed polymer foil, comprising a formed surface coated with a UV-curable coating, obtained with or obtainable by the method according to the invention wherein the polymer foil preferably is a transparent polycarbonate foil or the formed polymer foil is a transparent thermoformed polymer foil.

A third aspect of the invention relates to use of the polymer foil or the formed polymer foil of the polymer foil obtained with or obtainable with the method of the invention, in the manufacturing of a formed article or of a formed object such as a thermoformed article or object, a pane such as a glass pane or sheet, and/or of a moulded article or object such as an injection-moulded article or object, preferably an article or object which comprises the polymer foil comprising a surface coated with a UV- curable coating or thermoformed polymer foil comprising a thermoformed surface coated with a UV- curable coating, which is first formed and then back moulded such as back injection-moulded.

Preferred is the use according to the invention, wherein the article or object is an article or object such as a control panel and/or an article or object applied in automotive applications such as a radio panel, a control panel, a HVAC control system, or a part thereof, in telecom applications such as a housing, a keypad, an outer casing for a mobile phone.

A fourth aspect of the invention relates to an article or object comprising the polymer foil comprising a surface coated with a UV-curable coating or thermoformed polymer foil comprising a thermoformed surface coated with a UV-curable coating obtained with or obtainable with the method of the invention, or provided according to the use of the invention, wherein preferably the polymer foil is a transparent polycarbonate foil or wherein the thermoformed polymer foil is a transparent thermoformed polymer foil.

Preferred is an a rticle or thermoformed article of the invention, which is a laminate such as a window pane, comprising the polymer foil or the thermoformed foil, or which is an article or object applied in automotive applications such as a radio panel, a control panel, a HVAC control system, or a part thereof.

The invention is further illustrated by the following examples, which should not be interpreted as limiting the present invention in any way. Modifications and alternative implementations of some parts or elements or compounds are possible, and are included in the scope of protection as defined in the 40 appended claims.

EXAMPLES Example 1 Effect of presence of 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA) in a hard-coat composition comprising aliphatic multi-functional urethane acrylate oligomers on resistance to cracking of the hard- coat once applied onto a polymer foil.

The hardness of a series of UV-curable hard-coats on the surface of polycarbonate film was assessed, as well as the occurrence of hair-like cracks in the coating when the coated film was formed, under influence of the presence or absence of diluent 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA) in the hard-coat composition and therewith under influence of the number of double bonds present in the coating composition, expressed in milli-equivalents (meq) double bonds per gram of oligomers in the coating composition (Table 1).

For the test, aliphatic urethane tri-acrylate oligomer (Ebecryl 8465 UV/electron beam (EB) energy curable resin; Allnex Group), an aliphatic tri-functional urethane acrylate oligomer was mixed with hexa-functional aliphatic urethane acrylate oligomer (Ebecryl 5129 UV/EB energy curable resin; Allnex Group), an aliphatic tri-functional urethane acrylate oligomer, in various weight ratios (see Table 1, formulation 1-9) and further with HDDA were indicated (See Table 1, formulation UVFHC 100 23% comprising 23 wt% HDDA based on the total weight of the UV-curable solid hard-coat composition, and formulation UVFHC 100 30% comprising 23 wt% HDDA). The number or amount of double bonds is expressed as milli-equivalents double bonds per gram of oligomer, ie. per gram of Ebecryl 8465, Ebecryl 5128 or HDDA, or combinations thereof). For Ebecryl 8465, Ebecryl 5129 and HDDA, the number of double bonds (DB) is 2,1, 9,7 and 8,85, respectively. For the samples 1-9 and UVFHC 100 23% and UVFHC 100 30%, the number of double bonds in the hard-coat compositions is calculated based on the ratio of the Ebecryl 8465, Ebecryl 5129 and HDDA, if present, in the respective coating compositions. A suitable amount of a regular photo-initiator known and commonly applied in the art, was incorporated in the coating compositions (1% by weight or less; IRG 819 is a photo-initiator for radical polymerization of unsaturated resins upon UV light exposure, bis(2,4,6-trimethylbenzoyl)-phenyl- phosphine oxide, molecular weight 418,5 g/mol (Ciba IRGACURE 819 Photo-initiator; Ciba Specialty Chemicals, Inc.)).

Application of the coating compositions in the method of the invention was by applying the coating compositions onto transparent PC sheet or film of for example 3 mm thickness and 2 mm thickness or on Makrofol DE 1-1 polycarbonate film (Covestro, Pittsburgh, Pennsylvania, USA), an extrusion film based on Makrolon polycarbonate (Covestro). This PC film had a thickness of 0,25 mm. That is to say, for the PC sheet of 3 mm and 2 mm, a Lexan ULG1003 polycarbonate sheet was used (Sabic). For the extrusion film, a Makrofol DE 1-1 PC film was used in thickness of 0,25mm. The PC films were highly transparent and suitable for optical applications. Recommended applications for the

PC films are in automotive, labels, membrane switches, nameplates and thermoforming packaging, according to the manufacturer.

The PC films, sheets and foils applied typically are based on polymers for which bisphenol A is used as building block.

The coating compositions were applied onto the PC foil surface and the foil and the coating compositions were heated at 60°C - 80°C, followed by a UV curing step using a standard mercury wavelength H-bulb known in the art (Fusion UV 558412 H type lamp; Heraeus — Uvio (Berkshire, UK) or using a UV LED lamp known in the art (of 395 nm unit (4Pico, Sint-Oedenrode, NL). The curing speed was 0,37 m/min.). The PC films coated with the hard-coat according to the method of the invention were tested for delta haze after taber abrasion test, adhesion after ageing, formability in a Niebling HPF forming process, hardness in a pencil test and chemical resistance upon exposure to acetone.

TABLE 1. Effect of presence of 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA) in a hard-coat composition comprising aliphatic multi-functional urethane acrylate oligomers on resistance to cracking of the hard-coat once applied onto a polymer foil.

Formulation double-bond (wi%) contribution Farming EB8465 EB5129 HDDA EB 8465 | EB 5129 HDDA Total DB (3.6% OFS) : Q double 2,1 9,7 8,85 ro fe 19 9 [Is 28 1 II IMK | 2 IS 18 9 [IM IM Ie 148 IK | | 9 | 0 | 48 es fo [te 144 19 [185 IK Fw [B Be Je PB [JR Fs B me me] 7 40 _ 5,8 : 6,7 k:

’ 4 cracks co [so [so fo Jes [58 Jo [[&F [eracks | [Eso [for JE um ee | EE Pps [vo [re ews

42,35 34,85 1,1 2.9 0,9 6,3 OK 23% UVFHC 100 38,5 31,5 1,2 24

Hardness test of coats/coating — taber abrasion The hardness of the coatings tabulated in Table 1, provided with the method of the invention, is assessed in a taber abrasion test according to the ASTM D1044 standard as in force in Q4-2020 (version ASTM D1044 — 13). The hardness is compared for example to XtraForm hard-coated PC film (McDerwind Enthone). The taber abrasion is a test to determine resistance of a polymer material to abrasion.

Resistance to abrasion is defined as the ability of a material to withstand mechanical action such as rubbing, scraping, or erosion. Before subjecting coated film specimens to the taber abrasion test, the haze is measured. After subjecting the specimens to the taber abrasion test, the haze is again measured. Results of the test with a coated film or sheet are expressed by changes in % haze after the indicated number of test cycles (‘Delta haze’).

The UV curable hard-coated PC foils UVFHC 100 23% and UVFHC 100 30%, provided with the method of the invention, are presented with a lower or similar Delta haze after 100 cycles of taber abrasion in the taber abrasion test as executed according to ASTM D1044-13, when compared to coatings according to formulations 1-9. In a comparative test with the XtaForm hard-coated polycarbonate film (McDermid Enthone, Oxfordshire, UK), the test is revealing that the taber abrasion for this standard hard-coated PC film known in the art was 9,2%.

Hardness test of coats/coating — pencil test The hardness of the coatings of the invention is assessed in a pencil test according to the ASTM D3363 standard as in force in Q2-2019 (version ASTM D3363 — 5(2011)e2). Determination of the coated PC film hardness, i.e. the hardness of a coating on a substrate, involves the use of pencil leads of known hardness.

The UV curable hard-coated PC foils provided with the method of the invention are presenting with a pencil hardness similar if not equivalent or the same to the pencil hardness of the XtraForm hard- coated PC film of McDermid Enthone.

Chemical resistance test with coats/coatings The chemical resistance of the coated PC foil provided with the method of the invention, and comparative example coatings 1-9 (see Table 1) is assessed by determining the effect of exposure of a coat to liquid acetone. To this end, a coat applied onto a polymer film as a carrier of the coat, is provided with a cavity in the exposed top surface of the coat. Acetone is applied into the formed cavity and left for ten minutes at room temperature. After ten minutes, the acetone is removed and the effect of contacting the coat surface with acetone is assessed as a measure of chemical resistance of the coat.

The UV curable hard-coated PC foils UVFHC 100 23% and UVFHC 100 30% provided with the method ofthe invention expressed high chemical resistance, similar to what is observed for the PC films coated with formulations 6 and 7, since none of UVFHC 100 23% and UVFHC 100 30%as outlined in 40 the Examples section here above, is experiencing any chemical decay or effects of exposure to the acetone. That is to say, after exposure of the coated PC films according to the method of the invention to the acetone, no detectable change is apparent, there is not any slight change in color or gloss apparent, not even a slight surface etching or severe staining is apparent, and not any of pitting, cratering, swelling or erosion of coating is apparent, and in addition none of obvious and significant deterioration is observed. In contrast, for XtraForm coated PC film it was obvious that the coated surface was less stable. An opaque surface with opalescent spots was observed for the XtraForm exposed to the acetone in the chemical resistance test. No sign of damage to the UVFHC 100 23% and UVFHC 100 30% samples, is observed after exposure to the acetone.

Formability test with coatings Polycarbonate films provided with the UVFHC 100 23% and UVFHC 100 30% of the method of the invention are tested for their applicability in thermoforming applications. Comparison is made to the formability of the hard-coated PC films coated with formulations 1-9. To this end, PC films are provided with a coat UVFHC 100 23% and UVFHC 100 30% according to the method of the invention, or with the coating compositions 1-9 (Table 1), and after UV curing of the coat as here above described, the coated films are subjected to thermofolding procedures known in the art. The applied process for forming the coated PC films is the so-called “Niebling process”. Note: the XtraForm PC film requires a second UV curing step, which is not required for the coatings outlined in Table 1.

The Niebling process for the forming of plastic films The Niebling process is for the isostatic High Pressure Forming (HPF) of plastics. This “Niebling process” is applied for processing plastic films and other thin-layer materials. In brief, the Niebling process is described as follows (source: website of niebling Formtechnologie, Penzberg, DE). The heart of the Niebling process is a non-contact heating system. It comprises heating modules with individual heating elements; the temperatures of the elements are specifically adjusted. In this way a distinct temperature profile can be produced depending on the material and forming task. During this process, unlike during thermoforming, the substrate is only heated to the “glass transition temperature” (e.g.

polycarbonate: approx. 148°C), as result the material can be formed, but it is not melted. Once placed in the form, the heated material is then formed using compressed air (forming pressures up to 300 bar). The result: low material stretching and minimal position tolerances for graphic motifs (depending on material and geometry 0.3 mm). At the same time, cycle times of 10 sec. to 15 sec. are achievable. The heating system interacts with a continuously pressure profile controller.

For the PC film coated with UVFHC 100 23% and UVFHC 100 30% according to the method of the invention, and for the comparative example ‘formulation 1-9’, the formability is tested on a positive mould moulding set-up at an angle of 95° in a Niebling HPF forming process (forming temperature is 180°C).

Characteristics of applying the Niebling process of “isostatic” high pressure forming: = Low material stretching = Highest precision during the positioning of graphic motifs combined with reliable repeatability of the forming result = Retention of gloss levels, surface structures and surface feel (e.g. on matt or textured films) = Suitable for relatively large formats (up to 1,000 mm x 500 mm; forming height: up to 300 mm) and larger material thicknesses (up to 12 mm for polycarbonate) = Suitable for amongst other materials, PC = Excellently suited to the forming of films with chemically-resistant and scratch-resistant surfaces.

Elongation test — forming at elevated temperature For testing the resistance to formation of hair-like cracks in the coating on PC foil, the coated PC foils coated with the formulations of Table 1, were subjected to an outer elongation test.

That is to say, the foils were first heated for 5-10 minutes at 161-170°C in an oven and subsequently forced over a mold, ie. a pipe made of polyvinylchloride (PVC) with an outer diameter of 79 mm, therewith thermoforming the heated sheets, followed by cooling to room temperature.

The appearance and presence of cracks, e.g. hair-like cracks, in the coating at the formed and bend outer surface of the coated PC foils pointing away from the PVC pipe, was assessed by irradiating the outer surface with a fluorescence lamp.

The tested PC foils had a thickness of 2 mm or 3 mm.

The data set in Table 1 was achieved with a bisphenol A-based PC film with a thickness of 3 mm.

The tested hard-coated PC foils were bisphenaol A-based PC foils that were provided with UV curable solid hard-coat compositions as outlined in Table 1. For compositions UVFHC 100 23% and UVFHC 100 30% the coating procedure applies was according to the method of the invention.

For the formulations 1-9, a similar method was applied, though the HDDA was absent.

In the elongation test, the assessment of the appearance of hair-like cracks was assessed at constant outer fiber strain (OFS) which was the same for all coated films.

The OFS applied was 3,6%. The OFS is calculated as follows: it is assumed that after forming the PC foil does not experience any strain in the middle of the sheet of foil, when the thickness of the foil is considered (for a sheet of PC foil with a thickness of 2 mm, the middle of the sheet of foil is defined as the location in the sheet, at half the thickness of the foil, i.e. 1 mm below the surface). After thermofolding, the radius of the outer surface of the foil bend around the pipe minus the radius of the middle of the bend foil, divided by the radius of the middle of the bend foil, multiplied by 100, provides the OSF as a percentage elongation of the coating at the outer foil surface.

The results of the assessment of appearance of hair-like cracks after thermofolding and elongating the coating, are displayed in the right column of Table 1. The thickness of the coating on the formed coated film was at least 3 micrometer.

It is apparent that under influence of the presence of HDDA in the coating formulation the resistance to cracking is improved while at the same time the total number of double bonds in the coating formulation is increased, i.e. a measure for improved hardness of the coating provided. Thus, adding HDDA as a diluent to common hard-coat formulations and coating e.g. PC foil therewith, results in PC foil provided with a harder hard-coat and with better performance in the elongation test (Table 1), when the coated PC foil is provided according to the method of the invention. Example 2 A UV-curable solid hard-coat composition was prepared, referred to as Coating A: Ebecryl 8465 41,7 % (w/w) Ebecryl 5129 34,1 % (whw) HDDA 23,1% (ww) IRG 819 1% (wiw) BYK300 0,1% (w/w) IRG 819 is a photo-initiator for radical polymerization of unsaturated resins upon UV light exposure, bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide, molecular weight 418,5 g/mol (Ciba IRGACURE 819 Photo-initiator; Ciba Specialty Chemicals, Inc.); BYK300 is a solution of a poly-ether-modified polydimethylsiloxane, a silicone surface additive for solvent-borne coating systems (BYK-300, BYK- Chemie GmbH, Wesel, DE) (density (20°C) is 0.94 g/ml, non-volatile matter (10 min., 150°C) is 52%, solvents are xylene and iso-butanol in a 4(:}1 volume/volume ratio, flash point is 23°C).

The coating formulation was applied onto the surface of a PC foil with a thickness of 250 micrometer (Lexan 8080Q, high optical quality (Sabic, The Netherlands)}, using the method of the invention. A plate to plate coating configuration was applied. The PC foil is overlaid with the coating composition while in horizontal orientation relative to the horizontal. The coating formulation and the PC foil were heated at 60°C or at 80°C during contacting the surface of the PC foil with the coating composition. The hard-coat was UV cured by irradiating the coated surface with a 395-nm UV LED for about 15 seconds. The tests were performed using a sheet of float glass with the PC foil positioned thereon (size 42x30 cm?, thickness 250 micrometer), providing the master for imprinting the hard-coat composition. The imprinting was performed by using heated rollers at 60°C or at 80°C.

After UV curing, the coated PC foil was thermoformed according to the procedure outlined here above for Example 1. The elongation of the coating upon the forming was analyzed with regard to presence or absence of hair-like cracks. The thickness of the coating in the PC foil areas that were formed and that were not formed, was measured. Appearance of cracks was determined by visual inspection using a microscope and by contacting the formed coating with propylene carbonate (IUPAC name: 4-Methyl-1,3-dioxolan-2-one) and assessing whether the organic compound invaded the coating layer. Furthermore, the taber test as performed (coated PC appeared to pass the test under commonly applied test conditions). In addition, chemical resistance was assessed by contacting formed and non- formed coated PC film areas for 10 minutes with acetone.

The chemical resistance test revealed that the minimum coating thickness necessary to pass the test is 3 micrometer. That is to say, the hardness of the coating is already apparent when the thickness is 1 micrometer or more (as assessed by passing the taber test successfully). In addition, it was revealed that for an initial coating thickness of 3 micrometer or more, the coating of formed coated PC foil not only passed the chemical resistance test, but also passed the elongation test: no hair-like cracking in the areas of recesses and protrusions after formed PC foil.

The elongation was about up to 10-20% based on the initial length of a formed area of the coated foil. Thus, for arriving at a coating thickness of 3 micrometer or more after forming, the initial coating thickness should be 3,6 micrometer or more for the areas that end up in recesses or protrusions after forming. It was found that at least up to a coating thickness of 5,6 micrometer, the hardness was still at highest quality and no hair-like cracks appeared and chemical resistance was apparent, both in non-formed and formed areas of the coated PC foil. The passing of the chemical resistance test is one of the requirements demanded for application of the (formed) coated PC foil in automotive industry. In addition, the coated PC foil passed the water soak test after 1 and 2 days soaking in water (GTQ).

Moreover, when the coating was applied onto the PC foil at a temperature of 80°C, the coated PC foil passed the water soak test after 5 days of soaking (GTO; common X-hatch test after water soak according to ASTM 3359 Method A as valid in Q4-2020).

Claims

CONCLUSIONS

A method of providing a coated polymeric film comprising the steps of or consisting of the steps of: (a) providing a UV curable coating composition comprising the diluent 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA ), a photoinitiator, a first aliphatic multifunctional urethane acrylate oligomer and a second aliphatic multifunctional urethane acrylate oligomer, wherein the functionality of the first and second oligomer is different, and providing a polymer film; (b) coating a surface of the polymer film of step (a) with the UV curable coating composition of step (a), wherein the temperature of the polymer film is selected from the range of 40°C - 85°C and the temperature the UV curable coating composition is selected from the range of 40°C - 95°C; and (c) curing the surface of the polymer film coated with a UV curable coating composition in step (b) with UV radiation, thereby providing the coated polymer film.

A method according to claim 1, wherein the coating of the coated polymer film applied at the end of step (c) has a thickness of at least 1.0 micrometer, preferably at least 1.5 micrometer, more preferably at least 2.0 micrometers, most preferably at least 3.0 micrometers.

A method according to claim 1 or 2, wherein the method comprises or consists of the method steps (a) - (c) and a subsequent step following step (Cc): (d) forming at least a part of the coated polymer film provided in step (c), thereby providing coated polymer film which is molded coated polymer film or which comprises a portion of the coated polymer film surface which is molded coated polymer film, wherein the thickness of the coating of the molded coated polymer film or of the portion of the coated polymer film is at least 3.0 micrometers, preferably at least 4.0 micrometers, such as 3.0 micrometers - 8.0 micrometers or 3.5 micrometers - 6.0 micrometers, the molding preferably being thermoforming.

A method according to any one of claims 1-3, wherein the polymer film provided in step (a) has a thickness selected from the range of 0.1 millimeters - 10.0 millimeters, preferably selected from the range of 0, 2 millimeters - 8.0 millimeters, more preferably selected from the range of 0.4 millimeters - 6.0 millimeters, most preferably selected from the range of 1.0 millimeters - 4.0 millimeters, such as 2.0 millimeters - 3.0 millimeters.

A method according to any one of claims 1-4, wherein the UV curable coating composition is a solid UV curable coating composition or a UV curable hard coating composition, preferably a solid UV curable hard coating composition.

The method of any one of claims 1-5, wherein the UV curable coating composition comprises: (i) a first aliphatic multifunctional urethane acrylate oligomer; (ii) a photoinitiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) optionally a second aliphatic multifunctional urethane acrylate oligomer, wherein the functionality of the first aliphatic multifunctional urethane acrylate oligomer and the second aliphatic multifunctional urethane acrylate oligomer is different; and optionally (v) a flow modifier.

The method of any one of claims 1-6, wherein the UV curable coating composition comprises: (i) a first aliphatic multifunctional urethane acrylate oligomer which is an aliphatic trifunctional-dodeca-functional urethane acrylate oligomer; (ii) a photoinitiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) optionally a second aliphatic multifunctional urethane acrylate oligomer which is an aliphatic difunctional - dodeca-functional urethane acrylate oligomer, wherein the functionality of the first aliphatic multifunctional urethane acrylate oligomer and the second aliphatic multifunctional urethane acrylate oligomer is different; and optional; (v) a flow modifier.

A method according to any one of claims 1-7, wherein the UV curable coating composition comprises: (i) a first aliphatic multifunctional urethane acrylate oligomer which is an aliphatic trifunctional or tetrafunctional urethane acrylate oligomer, preferably an aliphatic trifunctional urethane acrylate oligomer; (ii) a photoinitiator; (iii) a diluent, preferably 6-prop-2-enoyloxyhexyl prop-2-enoate (HDDA); (iv) a second aliphatic multifunctional urethane acrylate oligomer which is an aliphatic penta-functional-dodeca-functional urethane acrylate oligomer, preferably an aliphatic hexa-functional urethane acrylate oligomer; and optionally {v) a flow modifier.

The method of any one of claims 1-8, wherein in step (a) the provided UV curable coating composition comprises the diluent 6-prop-2-enoyloxyhexylprop-2-enoate (HDDA),

present in an amount of 10% - 40% based on the total weight of the UV curable coating composition, preferably 15% - 30% by weight, more preferably 20% - 25% by weight, such as 20% - 35% by weight.

The method of any one of claims 1-9, wherein in step (a) of the method, the provided UV curable coating composition comprises or consists on a total weight basis of the UV curable coating composition: (1) 20 wt. %-60% by weight of the first aliphatic multifunctional urethane acrylate oligomer, preferably an aliphatic trifunctional urethane acrylate oligomer; (2) 20% by weight - 60% by weight of the second aliphatic multifunctional urethane acrylate oligomer, preferably an aliphatic hexafunctional urethane acrylate oligomer; (3) 10% by weight - 40% by weight of 6-prop-2-enoyloxyhexylprop-2-enoate (HDDA), preferably 15% by weight - 35% by weight, more preferably 20% by weight - 30% by weight. %; (4) 0.3 wt% - 3 wt% photoinitiator, preferably 0.5 wt. - 1.5% by weight, preferably bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide; and optionally (5) 0.03 wt% - 0.3 wt% of the feed modifier, preferably 0.05 wt% - 0.2 wt%, preferably polyether-modified polydimethylsiloxane in a mixture of xylene and isobutanol, preferably the flow modifier is present.

A method according to any one of claims 1-10, wherein in step (a) of the method, the provided UV curable coating composition comprises or consists of: (1) 30 - 50 based on the total weight of the UV curable coating composition: wt% of the first aliphatic multifunctional urethane acrylate oligomer, preferably an aliphatic trifunctional urethane acrylate oligomer, preferably 35-45 wt%; (2) 25% - 45% by weight of the second aliphatic multifunctional urethane acrylate oligomer, preferably an aliphatic hexafunctional urethane acrylate oligomer, preferably 30% - 40% by weight; (3) 15% - 35% by weight of 6-prop-2-enoyloxyhexylprop-2-encate (HDDA), preferably 18% - 30% by weight, more preferably 20% - 27% by weight; (4) 0.5%-1.5% by weight of the photoinitiator, preferably 0.7%-1.3% by weight, preferably bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; and (5) 0.05 - 0.3 wt% polyether-modified polydimethylsiloxane in a mixture of xylene and isobutanol, preferably 0.07 - 0.13 wt%.

A method according to any one of claims 1-11, wherein in step (b) of the method the temperature of the polymer film is selected from the range of 50°C - 80°C, preferably 55°C - 85°C, more preferably 80°C - 80°C, and the temperature of the UV curable coating composition is selected from the range of 50°C - 80°C, preferably 55°C - 85°C, more preferably 60°C - 80°C, wherein preferably the selected temperature for the polymer film and the selected temperature of the UV curable coating composition differ by 30°C or less, and more preferably are the same.

40

A method according to any one of claims 1-12, wherein the polymer film is a polycarbonate film or a transparent film, preferably a transparent polycarbonate film.

A polymer film comprising a surface coated with a UV curable coating or molded polymer film, preferably thermoformed polymer film, comprising a molded surface coated with a UV curable coating obtained with or obtainable by the method according to any one of the preceding claims, wherein the polymer film is preferably a transparent polycarbonate film or the formed polymer film is a transparent thermoformed polymer film.

Use of the polymer film or the molded polymer film according to claim 14 in the manufacture of a molded article or a molded object, such as a thermoformed article or object, a pane such as a glass pane or glass sheet, and/or a molded article or object such as an injection molded article or object, preferably an article or object comprising the polymer film comprising a surface coated with a UV curable coating or thermoformed polymer film comprising a thermoformed surface covered with a UV curable coating, which first molded and then re-molded as back-moulded.

Use according to claim 15, wherein the article or object is an article or object, such as a control panel and/or an article or object used in automotive applications such as a radio panel, a control panel, an HVAC control system or a part thereof, in telecom applications such as a housing, a keyboard, an outer housing for a mobile phone.

An article or object comprising the polymer film comprising a surface coated with a UV curable coating or thermoformed polymer film comprising a thermoformed surface coated with a UV curable coating according to claim 14, or provided according to claim 15 or 18, preferably wherein the polymer film has a transparent polycarbonate film or wherein the thermoformed polymer film is a transparent thermoformed polymer film.

The article or thermoformed article of claim 17, which is a laminate such as a window pane, which comprises the polymer film or the thermoformed film, or which is an article or object used in automotive applications such as a radio panel, a control panel, an HVAC control system, or part thereof.