Coatings and primers

Abstract

A method for coating a substrate comprising at least one chemical group is provided by contacting the substrate surface with a compound comprising at least one carbon-carbon double bond or a mixture of a first monomer M1 and a second monomer M2. Then, a reaction is initiated by the reaction of the photoactive group and the carbon-carbon double bond by subjecting at least a portion of the formed complex to actinic radiation, wherein the wavelength of the actinic radiation is suitable for being absorbed by the photoactive group, to form a covalent bond. The method is largely resistant to inhibition by impurities in the substrate surface. Greater uniformity of the elastic modulus of the entire substrate and the added layer can be achieved. When an additional topcoat is applied, the resulting surface has high hardness, and the scratch resistance is improved. When a top sheet is applied, the abrasion resistance is improved.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to coatings or primers. If desired, additional coatings, i.e. topcoats, can be applied over the coating. Thin coatings are made by contacting the surface of a substrate with a compound or mixture, and then initiating a reaction that forms covalent bonds by irradiating the photoreactive groups on the surface of the substrate or the reactive chemical groups in the liquid mixture that react with the photoreactive chemical groups on the surface. BACKGROUND

[0002] In many industrial processes, it is desirable to attach a dried thin film with residual reactive groups to a substrate. This film is used at a later stage to attach a coating to the first substrate or to glue another object such as a film to the first substrate.

[0003] In the polymer film industry, rollers are used to tension the film web, and the rollers are in contact with both surfaces of the film, so there is a risk of contamination of the rollers with liquid, partially liquid or very sticky films, and an increased risk of transferring dust and other unwanted surface defects. In other cases, it is desirable to activate a surface at one site and use the activated surface at another site, and transport between the two sites is easier if the surface of the activated substrate is dry.

[0004] According to the state of the art, the standard method to ensure interlayer adhesion in multi-layer UV cured coating systems is to deliberately undercure the first layer of paint. The next layer of paint then reacts with the undercured top of the previous layer, which ensures good adhesion. In acrylate systems, undercuring is typically via oxygen inhibition, which tends to leave a thin, less reactive layer on the top of the layer of paint. Once the next layer is applied, the oxygen has no effect and the oxygen inhibited layer reacts with the bottom of the subsequent layer, resulting in perfect interlayer adhesion. If carefully performed during manufacturing, it is possible to dry the film to touch and have a sufficient amount of residual reactive groups to obtain good adhesion to the next layer.

[0005] In very thin coating layers, the oxygen inhibition method is impractical because it is difficult to control the bulk polymerization to form the film while leaving a sub-micron portion of the oxygen inhibited because atmospheric oxygen diffusion typically affects the top 1-3 microns of the coating

[0006] JP 5568311 discloses nanoparticles adhered to a substrate via polymerizable groups on the nanoparticles. The nanoparticles can be in the form of an additive to a monomer mixture, or in the form of an emulsion or solution, and are attached to the substrate using actinic radiation. The nanoparticles so attached can be used as is, or as adhesion promoters for subsequent layers.

[0007] US 7,455,891 discloses a method for attaching a thin primer layer to a corona, plasma or flame activated surface. The primer is in the form of a solution, emulsion or suspension and is dried prior to the use of actinic radiation to react the primer with the surface using electromagnetic waves. The primer can form the final coating or as a base for a second coating layer to form the final surface.

[0008] JP 2006510774 discloses a method for adhering a film to a corona, low temperature plasma, flame or high radiation treated organic or inorganic surface using a primer comprising an initiator or initiator monomer blend in the form of a melt, suspension, solution or emulsion. The method involves a first heating step and optionally a step of using actinic radiation to form an adherent layer. A further coating layer is applied and reacted with the primer layer to form a final article.

[0009] US 6,733,847 discloses a method for attaching a thin primer layer to a corona, plasma or flame activated surface. The primer comprises a monomer having a hydrogen donating group and an ethylenically unsaturated group. The layer spontaneously adheres to the surface via the hydrogen donating group. The layer can then be reacted with a coating composition capable of reacting with the ethylenically unsaturated group to form a final coated object.

[0010] JP 2014063762 discloses an organosilicon aqueous dispersion primer formulation for a polymer resin surface with actinic photocuring.

[0011] US 4,495,020 discloses a primer composition containing isocyanate to provide a surface suitable for gluing a polyester plastic article to other or the same type of plastic article.

[0012] US 9,692,412 discloses a coating formulation for plastic and transparent inorganic substrates, wherein the coating formulation contains a polyacrylate, a diisocyanate, a polyether polyol and a compound containing a photopolymerizable group and a hydroxyl group.

[0013] US 2003 / 01502767 discloses a primer composition comprising a polymer reacted with, for example, maleic anhydride.

[0014] EP 0574352 discloses a method for modifying the surface characteristics of a preformed polymeric substrate by graft polymerization on the substrate to impart altered properties thereto, which comprises: placing the polymeric substrate in a plasma to form free radicals on the substrate; contacting the substrate having free radicals with oxygen to form hydroperoxy groups on the surface of the substrate; and graft polymerizing an ethylenically unsaturated monomer and a crosslinking agent onto the surface of the polymeric substrate.

[0015] US 2017 / 0290955 discloses a medical device for implantation into a body, the medical device comprising: a polymeric substrate; and a layer of poly(vinylpyrrolidone-alt-maleic anhydride) formed on a surface of the polymeric substrate, wherein the polymer chains of poly(vinylpyrrolidone-alt-maleic anhydride) are entangled with the polymeric substrate to form a smooth, hydrophilic layer.

[0016] US 6,582,754 discloses a method for coating a material surface, comprising the steps of: (a) covalently bonding to the material surface a compound comprising an ethylenically unsaturated double bond; (b) polymerizing monomers comprising reactive or cross-linkable groups on the surface and thereby providing a primary polymer coating comprising reactive or cross-linkable groups, (c) in the case of monomers comprising reactive groups in step (b), reacting the reactive groups of the primary coating with a further compound comprising an ethylenically unsaturated double bond and graft-polymerizing a hydrophilic monomer and optionally a co-monomer having cross-linkable groups onto the primary coating obtained according to step (b), and (d) in the case of cross-linkable groups being present in step (b) or (c), initiating cross-linking of said groups.

[0017] CN 104945983 and CN 104945985 disclose monofunctional methacrylates forming a polymer chain with maleic anhydride. In a first step a polyanhydride is formed which is reacted with an epoxy resin in a subsequent step. Thereby, the anhydride is reacted to a polyanhydride. Since monofunctional methacrylates are used, no cross-linking network is formed. In the introduction, it is disclosed that first an acrylic resin with anhydride side groups is synthesized, which is then subjected to a modified epoxy resin, the epoxy-modified acrylic resin is prepared by preparing a one-component epoxy-modified acrylic coating with excellent adhesion, good hardness and gloss.

[0018] US 2019 / 263072 discloses a method for bonding composite substrates, wherein a curable surface treatment layer is applied to a curable composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured, but the surface treatment layer remains partially cured. The surface treatment layer can be a resin film or a release layer consisting of a fabric impregnated with a resin. If a release layer is used, the release layer is peeled off after co-curing, leaving a residual film of the partially cured resin. A subsequent dry physical surface treatment, such as plasma, is carried out to physically modify the surface of the surface treatment layer. After the dry physical surface treatment, the composite substrate is provided with a chemically active bondable surface that adherently bonds with another composite substrate to form a covalently bonded structure.

[0019] US 5,254,395 discloses a coating system which forms a highly abrasion resistant, chemically resistant, impact resistant protective finish on a substrate. The coating system is based on the use of two different properties but excellent adhesion to each other of the coatings. The outermost or surface coating layer is a highly crosslinked hard polymer which adheres to an underlying base coating layer of a compatible softer polymer. The outer hard polymer preferably comprises a highly crosslinked acrylic copolymer derived from at least 40 wt% of a multifunctional aliphatic acrylate monomer having three or more functional groups, while the underlying softer polymer preferably comprises a crosslinked aliphatic urethane acrylate copolymer and a multifunctional aliphatic acrylate monomer having three or more functional groups.

[0020] GB 2107723 discloses a method for treating a substrate which can be cured by exposure to actinic radiation, the method comprising preparing a solution comprising water, 0.1-75 wt% of acrylic acid and 0.01-5 wt% of a suitable surfactant, depositing a layer of the solution on the substrate, and exposing the treated substrate to actinic radiation.

[0021] US 8,227,050 discloses a UV-curable coating composition comprising one or more monomers, one or more multifunctional oligomers, one or more pigments, one or more photoinitiators, and a volatile organic solvent.

[0022] WO 2012 / 042059 discloses a method for manufacturing a thiol-ene polymer article comprising the steps of a) reacting a compound comprising at least two thiol groups and a compound comprising at least two carbon-carbon double bonds in a non-stoichiometric ratio to obtain a first intermediate article, wherein the first intermediate article comprises at least one unreacted group selected from unreacted thiol groups and unreacted carbon-carbon double bonds, and b) contacting the first intermediate article with a second article, wherein the surface of the second article at least partially comprises reactive groups, and reacting at least a portion of the unreacted groups on the first intermediate article with chemical groups on the second article to obtain covalent bonds and form a final article.

[0023] WO 2019 / 185302 discloses a primer formulation for melamine, wherein the complex formed between a secondary amine and a carbon-carbon double bond is observed to be initiated by actinic radiation. The invention is useful for coatings when a sufficient amount of actinic radiation can penetrate a liquid layer to produce a sufficient amount of covalent bonds between a substrate and a coating.

[0024] It is desirable to also be able to provide coatings on substrates other than those containing secondary amines. Thermosetting substrates containing secondary amines have high elastic moduli, for example, melamine-formaldehyde, with an elastic modulus exceeding approximately 7 GPa. On the other hand, the additive layers in WO2019 / 185302 have relatively low elastic moduli, and it is desirable to provide substrates and associated coating techniques where the difference in elastic modulus between the substrate and the applied layer (one or more layers) is low.

[0025] For primers based on existing technology, curing must be adjusted to leave a sufficient number of reactive groups when the primer has been applied. A method less sensitive to curing conditions, and particularly less sensitive to over-curing, is desired.

[0026] One problem with the prior art is that certain impurities in the substrate or intentionally added compounds such as antioxidants can act as inhibitors, making the reaction with conventional photoinitiators to form a film impossible or at least hindered.

[0027] Another problem in the prior art is to provide a primer that can be cured to a dry state, i.e., dry to the touch, to simplify the treatment before applying and curing subsequent coatings. Summary of the Invention

[0028] The purpose of this invention is to eliminate at least some of the disadvantages of the prior art and to provide improved coatings and / or primers.

[0029] In a first aspect, a method for coating a substrate is provided, the method comprising the following sequential steps:

[0030] a) Providing a substrate comprising at least one chemical group selected from the group consisting of aromatic rings, sulfur, and peroxides, wherein at least a portion of the at least one chemical group is located on the surface of the substrate.

[0031] b) Contact at least a portion of the substrate surface with one of the following:

[0032] i) A compound containing at least one carbon-carbon double bond, wherein the compound optionally contains a chemical group capable of abstracting hydrogen, and

[0033] ii) A mixture comprising a first monomer M1 and a second monomer M2, wherein the monomers are capable of undergoing polymerization to form a copolymer covalently bonded to a substrate, wherein at least one of the ratios r1 and r2 is less than 0.45, and wherein k 11 and k 22 One is at least 10 times larger than the other, except when it comes to k. 11 and k 22 When the condition does not apply, r1 = r2 = 0, where r1 = k 11 / k 12and r2=k 22 / k 21 ,

[0034] wherein k 11 is the rate constant of the propagation reaction of the addition of monomer M1 to the growing copolymer chain ~M1*,

[0035] wherein k 12 is the rate constant of the propagation reaction of the addition of monomer M2 to the growing copolymer chain ~M1*,

[0036] wherein k 21 is the rate constant of the propagation reaction of the addition of monomer M1 to the growing copolymer chain ~M2*,

[0037] wherein k 22 is the rate constant of the propagation reaction of the addition of monomer M2 to the growing copolymer chain ~M2*,

[0038] c) initiating the reaction with actinic radiation to form covalent bonds by reaction of the at least one chemical group at the surface of the substrate with i) the compound or ii) the monomers M1 and M2, thereby forming i) the polymer or ii) the copolymer covalently bound to the surface of the substrate,

[0039] d) applying at least one of the coating and the sheet on the surface of the substrate, and

[0040] e) curing the at least one coating.

[0041] In a second aspect, a substrate coated according to the above described method is provided.

[0042] The present application is very suitable for applications where an improved adhesion to various substrates is desired.

[0043] In addition, especially when a top coating is added on the coating, the resulting surface has a high hardness and the scratch resistance is improved. When a thermoplastic sheet or film is added, for example, then the abrasion resistance is improved.

[0044] In comparison to the prior art, the modulus of elasticity of the substrate according to the present application is better matched with the modulus of elasticity of the applied layer(s) (one or more). For example, a substrate comprising PP or PET according to the present application has a modulus of elasticity below 3 GPa, which is better matched with the modulus of elasticity of an added layer (one or more) comprising acrylate. Thereby, using the present application a weakening layer with a very different modulus of elasticity can be avoided.

[0045] In addition, it is an advantage that the primer can be cured to a non-tacky or non-damp state, after which a topcoat or subsequent coating is applied and cured.

[0046] The method according to the present application is less sensitive to curing conditions and in particular to very high doses of actinic radiation. The reaction method according to the present application provides for a stop of the reaction after step c) by the initial composition and any remaining excess groups are essentially insensitive to overcuring within reasonable limits, ensuring a sufficient amount of remaining reactive groups for reaction with the second layer in a later subsequent step.

[0047] The method is suitable for actinic radiation curing under inert conditions, for example in a nitrogen atmosphere. Due to the absence of oxygen inhibition, the method is less sensitive to overcuring of the top surface compared to current primer formulations.

[0048] The method according to the present application is less sensitive to aging due to the low homopolymerization rate of the excess reactive groups after curing and the glassy barrier impedes diffusion thereby additionally reducing homopolymerization. DETAILED DESCRIPTION

[0049] Before the present application is disclosed and described, it is to be understood that this application is not limited to the particular configurations, method steps, substrates, and materials disclosed herein as such configurations, method steps, substrates, and materials can vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present application is limited only by the appended claims and equivalents thereof.

[0050] It must be noted that as used herein and in the appended claims, the singular form "a", "an", and "the" include plural reference unless the context clearly dictates otherwise.

[0051] As used herein and unless otherwise indicated, any term and scientific term used herein is intended to have the meaning commonly understood by one of ordinary skill in the art to which this application pertains.

[0052] As used herein, (meth)acrylate is a generic term encompassing both acrylate and methacrylate.

[0053] As used herein, photo-reactive group means a chemical group that is essentially chemically inert under the relevant conditions and becomes a reactive chemical group when exposed to actinic radiation. Typically, but not always, the actinic radiation is ultraviolet light.

[0054] As used herein, abstracting hydrogen is removing a hydrogen atom from a molecule. Thus, a chemical group capable of abstracting hydrogen is a chemical group capable of removing a hydrogen atom.

[0055] Unless otherwise indicated, all percentages and ratios are calculated on a weight basis throughout the specification and claims. For example, the ratio r is calculated based on the number of chemical groups and not on a weight basis.

[0056] In a first aspect, a method for coating a substrate is provided, the method comprising the following sequential steps:

[0057] a) Providing a substrate comprising at least one chemical group selected from the group consisting of aromatic rings, sulfur, and peroxides, wherein at least a portion of the at least one chemical group is located on the surface of the substrate.

[0058] b) Contact at least a portion of the substrate surface with one of the following:

[0059] i) A compound containing at least one carbon-carbon double bond, wherein the compound optionally contains a chemical group capable of abstracting hydrogen, and

[0060] ii) A mixture comprising a first monomer M1 and a second monomer M2, wherein the monomers are capable of undergoing polymerization to form a copolymer covalently bonded to a substrate, wherein at least one of the ratios r1 and r2 is less than 0.45, and wherein k 11 and k 22 One is at least 10 times larger than the other, except when it comes to k. 11 and k 22 When the condition does not apply, r1 = r2 = 0, where r1 = k 11 / k 12 And r2 = k 22 / k 21 ,

[0061] Where k 11 The growth rate constant for the growth reaction of monomer M1 added to the growing copolymer chain ~M1* is given by [the value of M1].

[0062] Where k 12 The growth rate constant for the growth reaction of adding monomer M2 to the growing copolymer chain ~M1* is given.

[0063] Where k 21 The growth rate constant for the growth reaction of monomer M1 added to the growing copolymer chain ~M2* is given.

[0064] Where k 22 The growth rate constant for the growth reaction of adding monomer M2 to the growing copolymer chain ~M2* is given.

[0065] c) A reaction initiated by photochemical radiation to form a covalent bond to the substrate surface by reacting at least one chemical group at the surface of the substrate with the i) compound or ii) monomers M1 and M2, thereby forming the i) polymer or ii) copolymer covalently bonded to the substrate surface.

[0066] d) Applying at least one of the coating and sheet to the surface of the substrate, and

[0067] e) curing the at least one coating.

[0068] Consider two different monomers M1 and M2. If we consider growing copolymer chains ~M1* and ~M2* where monomers M1 and M2 are added to one end of the polymer chain, we have the following reactions:

[0069]

[0070] then r1 and r2 are defined as r1 = k 11 / k 12 and r2 = k 22 / k 21 where k 11 , k 12 , k 21 and k 22 are the growth rate constants for the above growth reactions. r1 is interpreted as the reactivity of ~M1* with M1 versus ~M1* with M2. r2 is interpreted as the reactivity of ~M2* with M2 versus ~M2* with M1. The growing polymer chain is a copolymer with M1 or M2 at one end. At least a portion of the copolymer is covalently bonded to the substrate surface. In one embodiment, the copolymer that is not covalently bonded to the surface is washed away after the reaction. The ratios r, r1 and r2 are different ratios.

[0071] At least one of r1 and r2 is less than 0.45. Either r1 is less than 0.45, or r2 is less than 0.45, or both r1 and r2 are less than 0.45. In one embodiment, at least one of r1 and r2 is less than 0.1. In one embodiment, at least one of r1 and r2 is less than 0.05. In one embodiment, one of r1 and r2 is zero or close to zero. In one embodiment, both r1 and r2 are zero or close to zero. The ratios indicate that homopolymerization is suppressed in one of the reactions.

[0072] With respect to the rate constants k 11 and k 22 , one is at least 10 times larger than the other, 10*k 11 ≤ k 22 or 10*k 22 ≤ k 11 This makes the rate of homopolymerization in one of the reactions much faster than the rate of homopolymerization in the other reaction. This parameter selection allows for the application and curing of a coating in different steps. After the first curing, there will be reactive groups left for the second curing reaction. When r1 = r2 = 0, there will be alternating copolymer with no homopolymerization, and then with respect to k 22 and k 11The condition does not apply when both r1 and r2 are substantially 0 such that r1 ~ r2 ~ 0. It is also applicable when both r1 and r2 are lower than 0.05.

[0073] For mixtures with low k 22 and r1 > r2, M2 will be the remaining group that reacts later, even if there is an excess of M1.

[0074] The term monomer should be interpreted as polymerizable unit, thus encompassing both monomers and polymerizable oligomers. Thereby, it is possible to carry out reactions with polymerized oligomers.

[0075] In one embodiment, the substrate surface is contacted with a mixture comprising a first monomer M1 and a second monomer M2 in step b). In one embodiment, the first monomer M1 and the second monomer M2 are one of the following options

[0076] i) acrylate and maleate,

[0077] ii) acrylate and vinyl ether,

[0078] iii) methacrylate and vinyl ether,

[0079] iv) acrylate and allyl ether,

[0080] v) methacrylate and maleate,

[0081] vi) methacrylate and maleimide,

[0082] vii) acrylate and maleimide

[0083] viii) vinyl ether and maleate, and

[0084] ix) styrene and maleate.

[0085] The first monomer M1 and the second monomer M2 are selected from one of the options i) to ix). The options i) to ix) contain two different groups for each option and the first and second monomers are chosen such that one of each is present. In one embodiment, the first monomer M1 and the second monomer M2 are acrylate and maleate. In another embodiment, the first monomer M1 and the second monomer M2 are acrylate and vinyl ether. In another embodiment, the first monomer M1 and the second monomer M2 are methacrylate and vinyl ether. In another embodiment, the first monomer M1 and the second monomer M2 are acrylate and allyl ether. In another embodiment, the first monomer M1 and the second monomer M2 are methacrylate and maleate. In another embodiment, the first monomer M1 and the second monomer M2 are methacrylate and maleimide. In another embodiment, the first monomer M1 and the second monomer M2 are acrylate and maleimide. In another embodiment, the first monomer M1 and the second monomer M2 are vinyl ether and maleate. In another embodiment, the first monomer M1 and the second monomer M2 are styrene and maleate. Thereby, the first monomer M1 and the second monomer M2 can be pairs of the above mentioned choices.

[0086] The above mentioned pairs of monomers fulfill the requirement regarding the ability to perform a polymerization reaction to form a copolymer covalently bonded to the substrate. The above mentioned pairs of monomers also fulfill the requirement that at least one of the ratios r1 and r2 is less than 0.45 and additionally k 11 and k 22 is at least 10 times larger than the other. Thereby, the above mentioned list of pairs of monomers can replace the above mentioned general requirements for the monomers.

[0087] The method comprises the step of d) applying at least one of the coating and the sheet on the surface of the substrate. Either a liquid coating can be applied which is then preferably cured or a sheet or film can be applied. Thereby, in step d) one of the group of a liquid coating, a sheet and a film is applied.

[0088] The method comprises the subsequent step e) of curing the at least one coating or sheet applied in step d). Such a step e) is performed after step d). If the coating is the final coating, it can also be referred to as a topcoat. In particular, when a top coating is added on the coating, the resulting surface has a high hardness and the scratch resistance is improved. If the outermost layer is an applied film, the abrasion resistance can be improved. In one embodiment, a second coating is applied after step c). If no further coating is applied, the second coating can be referred to as a topcoat. When using the method of the present invention, the properties of the resulting finished coated substrate are significantly improved. In one embodiment, at least one further coating is applied after step c). Thereby, in one embodiment, the coating is used as a primer. The coating can also be used as a single coating or as a topcoat on another coating.

[0089] In one embodiment, the second layer applied in step d) is a thermoplastic sheet material such as a thermoplastic sheet. When added, design elements such as a relief structure are enabled. When added, wear resistance is greatly improved.

[0090] In one embodiment, the sheet material comprises polypropylene and / or polyethylene or other polymeric material, which has the advantage of being transparent to actinic radiation, capable of initiating surface reactions of photoactive groups, located on a surface remote from the light, in contact with a liquid comprising carbon-carbon double bonds. Thereby, the applied sheet material is fixed to the surface by curing with actinic radiation, which is applied through the applied sheet material and reaches the interface between the applied sheet material and the substrate surface.

[0091] In another embodiment, the thermoplastic sheet material comprising PET is activated by irradiation on at least one surface, after which the sheet material is contacted with the treated substrate in step d), wherein the irradiated surface of the sheet material faces downwards towards the substrate. This procedure is necessary because PET is typically opaque to the relevant wavelengths.

[0092] In one embodiment, an acrylate-based coating is applied as at least one further coating, i.e. a second coating.

[0093] In one embodiment, the method additionally comprises a step of removing at least a portion of i) the compound or ii) the mixture which has not reacted to form a covalent bond after step c). Excess molecules as well as other optional additives can be removed by washing or other suitable means.

[0094] For example, polyolefins, aromatic group-containing polymers, ether-containing polymers and sulfur-containing polymers which are surface activated by corona, plasma or flame can all be successfully coated. The adhesion of the subsequent topcoat is greatly improved. In one embodiment, the substrate comprises at least one selected from the group consisting of polyolefins, aromatic group-containing polymers, ether group-containing polymers and sulfur-containing polymers. In one embodiment, the surface is treated with at least one selected from the group consisting of corona treatment, plasma treatment and flame treatment prior to step b).

[0095] There are many different substrates which can be used in the present application. In one embodiment, the substrate comprises at least one selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polyphenylene oxide (PPO), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), polystyrene (PS), polyether ether ketone (PEEK) and polycarbonate (PC).

[0096] In one embodiment, an electron withdrawing group is present in the vicinity of at least one carbon-carbon double bond in the compound. In one embodiment, an electron withdrawing group is present on both sides of at least one carbon-carbon double bond in the compound. When a compound comprising at least one thiol group is present, the electron withdrawing group has the advantage of giving a faster reaction.

[0097] In one embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 are dissolved in at least one solvent before being brought into contact with the surface of the substrate. In an alternative embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 are not dissolved or diluted in a solvent before being brought into contact with the surface of the substrate. In the latter embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 are used in pure form. Also in the latter embodiment, additional additives can be added to i) the compound or ii) the first monomer M1 and the second monomer M2. In one embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 are not dissolved or diluted in a solvent, it is possible to select i) the compound or ii) the first monomer M1 and the second monomer M2 with a low viscosity, so that it can be roll-coated in an effective manner in a suitable thickness.

[0098] In one embodiment, the surface of the substrate is additionally contacted with at least one compound comprising at least one thiol group in step b). In one embodiment, the ratio (r) between the number of thiol groups and the number of carbon-carbon double bonds in step b) fulfils 0.05 < r < 20. In another embodiment, the ratio r fulfils 0.2 < r < 5. In alternative embodiments, the ratio r fulfils one of 0.3 < r < 0.9 and 1.1 < r < 3, thus the latter embodiment requires a deviation from the stoichiometry between thiol groups and carbon-carbon bonds. The advantage of adding thiols is that the surface can be dried, thus making the surface of the substrate dry after step c). The substrate is then easier to handle and additional coatings can be applied later in step d). (The ratio r is different from the ratios r1 and r2).

[0099] In one embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 that are brought into contact with the surface of the substrate in step b) are pure substances, and in alternative embodiments of step b) the surface of the substrate is contacted with a formulation comprising i) the compound or ii) the first monomer M1 and the second monomer M2. Such formulations can also comprise additional compounds, additives and solvents.

[0100] In one embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 are inkjetted on the surface in step b). In one embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 are contacted with at least a part of the surface of the substrate by inkjetting in step b). In addition, or alternatively, other known application methods can be used, such as roll coating, anilox, spraying and dipping, etc.

[0101] In one embodiment, the first monomer M1 is an acrylate, and wherein r1 is lower than 10. This embodiment also applies if the second monomer M2 is an acrylate. This will improve the bonding with acrylates.

[0102] In one embodiment, one of r1 and r2 is larger than 0.1. This will facilitate film formation.

[0103] In one embodiment, k 11 and one of k 22 is lower than 3000 l / (mol s). This will reduce the tendency to overcure. Such mixtures are difficult to overcure. The growth constant is measured with the rotating sector method.

[0104] In one embodiment, a Norrish Type II photoinitiator is contacted with the surface of the substrate in step b). In one embodiment, an additional substance such as a Norrish Type II photoinitiator is added together with i) the compound or ii) the first monomer M1 and the second monomer M2 in step b). In an alternative embodiment, they are added separately before and / or after i) the compound or ii) the mixture is contacted with the surface of the substrate. In one embodiment, the photoinitiator is in the mixture of step b). In one embodiment, the Norrish Type II photoinitiator is in the mixture of step b).

[0105] Hydrogen abstraction based photoinitiators can also be referred to as Norrish Type II photoinitiators. The photo-excited carbonyl compound is the hydrogen abstractor which is considered to be the Norrish Type II photoinitiator. Suitable carbonyl compounds for use as Norrish Type II photoinitiators include aromatic ketones and quinones, such as benzophenone, ketone sulfones, thioxanthones, 1,2-diketones, anthraquinones, fluorenone, xanthone, phenylacetophenone derivatives, benzoin ethers, benzyl ketals, phenylglyoxalic acid esters, mono- and bis-acyl phosphines. In one embodiment, the Norrish Type II initiator is an initiator selected from the group consisting of benzophenone, thioxanthone, 1,2-diketone and anthraquinone. Suitable Norrish Type II initiators are disclosed by CRIVELLO J.V. et al. in "Volume III: Photoinitiators for Free Radical Cationic & Anionic Photopolymerization", 2ndEdition, edited by BRADLEY G., London, United Kingdom, John Wiley & Sons Ltd, 1998, pages 287-294, which is incorporated herein by reference in its entirety.

[0106] In one embodiment, the Norrish Type II photoinitiator is present in the formulation to be added in step b) in an amount of 0.1 to 15 wt.-%, based on the weight of the photosensitive composition in contact with the surface of the substrate.

[0107] In one embodiment, the contacting in step b) is performed by applying a layer having a thickness in the interval of 0.2-20 pm. Application techniques known to the skilled person can be used to apply i) the compound or ii) the first monomer M1 and the second monomer M2 and further components in step b).

[0108] In one embodiment, all components to be added in step b) are provided in a single formulation. This simplifies the addition process. Then, all compounds and additional substances are applied in one mixture.

[0109] In one embodiment, i) the compound or ii) the first monomer M1 and the second monomer M2 to be applied in step b) are provided in an acidic mixture. For certain applications, the acidity improves the shelf life. In one embodiment, the formulation is acidic and comprises a Norrish Type II photoinitiator in addition to i) the compound or ii) the first monomer M1 and the second monomer M2. The low pH in the acidic formulation improves the shelf life of the Norrish Type II photoinitiator. The combination of a Norrish Type II photoinitiator and an acidic pH is particularly suitable for improving the shelf life of the formulation to be added in step b).

[0110] In one embodiment, the irradiation is carried out by UV radiation. Many photoreactive groups become reactive by UV irradiation of suitable energy.

[0111] In one embodiment, the surface in step b) is contacted with i) the compound or ii) the first monomer M1 and the second monomer M2 in a pattern. This provides the possibility to partially treat the substrate surface in a desired pattern. It is thus possible to form a pattern by applying i) the compound or ii) the first monomer M1 and the second monomer M2 in a desired pattern.

[0112] In one embodiment, the irradiation is carried out in a pattern. This provides the additional possibility to surface modify the substrate surface in a desired pattern. The irradiation in a pattern is carried out by known methods, such as applying a mask or irradiation with a laser. It is thus possible to form a pattern on the substrate by irradiating only the parts where the photoactive groups of the surface are located.

[0113] In one embodiment, the thickness of the applied layer comprising i) the compound or ii) the first monomer M1 and the second monomer M2 and the absorbance of the applied layer at the wavelength of the actinic radiation are adjusted so that the reaction is still initiated in step c). The person skilled in the art is able to adjust the thickness of the applied layer and the absorbance of the applied formulation so that sufficient irradiation reaches the substrate surface when the layer is applied after the description of the studies. The absorbance is adjusted by adjusting the concentration(s) of the components in the formulation that absorb the actinic radiation at the relevant wavelength. The Beer-Lambert law can help the skilled person in this respect.

[0114] In one embodiment, at least step c) is carried out in an inert atmosphere. In another embodiment, steps b) and c) are carried out in an inert atmosphere. In another embodiment, steps b), c) and d) are carried out in an inert atmosphere. In another embodiment, steps b), c), d) and e) are carried out in an inert atmosphere. In another embodiment, steps a), b), c), d) and e) are carried out in an inert atmosphere. In one embodiment, the inert atmosphere comprises 98 wt% or more, preferably 99 wt% or more, more preferably 99.5 wt% or more of an inert gas. Alternatively, the inert atmosphere comprises 95 wt% or more of an inert gas. In one embodiment, the inert atmosphere comprises 2 wt% or less of oxygen, preferably 1 wt% or less of oxygen, more preferably 0.5 wt% or less of oxygen. In one embodiment, the inert gas comprises nitrogen. The use of an inert atmosphere makes the method less sensitive to overcuring of the top surface due to the absence of oxygen inhibition.

[0115] In a second aspect, a substrate coated according to the above method is provided.

[0116] The substrate contains molecules that are peroxides and or sulfur and or aromatic groups that are accessible at the surface. A compound containing at least one C=C double bond is added to the substrate. Alternatively, a first monomer M1 and a second monomer M2 are added to the substrate.

[0117] One very important feature is that the reaction is initiated by direct irradiation of the chemical groups at the surface of the substrate. The chemical groups at the surface of the substrate directly absorb energy from the actinic radiation. Such chemical groups can also be called photoreactive groups. In the case of peroxides, depending on the molecular structure of the surface-bonded peroxide, the peroxide cleaves into a surface-bonded alkoxy radical and a free hydroxyl radical or alkoxy radical.

[0118] The substituted benzene group is excited with UV to form a triplet or singlet state. The excited state is able to react with the carbon-carbon double bond in a number of ways.

[0119] a) The triplet state of the substituted benzene ring (terephthalate in the case of PET) formed with UV radiation of a certain minimum energy forms a diradical structure on the benzene ring in the presence of a hydrogen donor. These radicals are able to form a covalent bond with the carbon-carbon double bond or they form a peroxyl radical in the presence of atmospheric oxygen, which after hydrogen abstraction forms a peroxide that cleaves under UV light to form an alkoxy radical that is able to react with the carbon-carbon double bond to form a covalent bond.

[0120] b) In some cases, a radical anion is formed, which can react with the electron-deficient carbon-carbon double bond by an anionic addition reaction.

[0121] Although in some embodiments a photoinitiator is added, a photoinitiator is not required. In fact, the addition of a photoinitiator is often not suitable because it can absorb the actinic radiation that is then not available to initiate the reaction. Generally only a small amount of UV absorbing compounds such as photoinitiators is tolerated. The amount of photoinitiator that is generally used to initiate various reactions is generally too high. In one embodiment, no photoinitiator is added. In one embodiment, there is no photoinitiator or another compound that absorbs actinic radiation at all. In some conditions, an amount of certain photoinitiators can be tolerated and used. Such conditions include:

[0122] a) The wavelength at which the chemical groups at the surface of the substrate absorb energy is sufficiently different from the wavelength at which the photoinitiator absorbs light.

[0123] b) The application layer containing the photoinitiator is very thin so that there is anyway a sufficient amount of radiation reaching the chemical groups at the surface of the substrate and / or the application layer containing the photoinitiator is diluted so that there is anyway a sufficient amount of radiation reaching the chemical groups at the surface of the substrate.

[0124] The above conditions can also be combined with an increase in the intensity and / or dose of the actinic radiation.

[0125] The primer coating according to the prior art is usually applied in a layer ranging between 10-30 microns and is designed to form a film with a minimum amount of UV dose. The UV dose below 370 nm reaching the bottom of the layer is always very small. According to the prior art, the adhesion of such films is either by surface energy matching or via a secondary spontaneous reaction between the hydroxyl groups present after the corona treatment and the isocyanate groups in the primer.

[0126] The actinic radiation is required to reach the substrate surface through a layer of applied solution because of the chemical groups at the substrate surface. In comparable prior art, photoinitiators or other UV blocking compounds are used in similar systems, which makes this approach impossible to use or impossible to observe in most systems because no or too little actinic radiation reaches the surface. The inventors believe that this is the reason why this effect has not been observed before.

[0127] The result of the reaction is the formation of covalent bonds. Covalent bonds can be verified by the fact that the film cannot be removed by boiling the substrate and film in water for 2 hours, for example. A removed film indicates the absence of covalent bonds. A film that is still adhering after boiling in water for several hours (2 hours) can indicate the presence of covalent bonds and / or the presence of entanglements of polymer chains, i.e. an IPN-like structure. Thus, a removed film ensures the absence of covalent bonds. However, a film that is still adhering after boiling in water for several hours can indicate covalent bonds or alternatively entanglements of polymer chains. Thus, in order to ensure the presence of covalent bonds in case the film is still adhering, it is necessary to control for entanglements of polymer chains, i.e. an IPN-like structure.

[0128] Covalent bonding can be distinguished from adhesion from an IPN-like morphology by cross-sectioning the coated substrate and examining the interface between the substrate and the coating. In case of adhesion mainly by covalent bonds, the surface structure of the substrate will remain essentially intact, whereas in case of an IPN-like morphology, there will be a transition zone between the coating and the substrate that is different from the original substrate surface structure, which is detected via spectroscopic measurements (e.g. IR or Raman microscopy), SEM, optical microscopy or similar methods. When adhesion from an IPN-like morphology has been ruled out, then it can be concluded that covalent bonds are present.

[0129] In general, the content of any photoinitiator or other absorbing compound does not have to be so high as to initiate a reaction of the chemical groups at the surface of the substrate. Thus, in one embodiment, the photoinitiator is present in an amount that does not prevent the initiation of a reaction to form covalent bonds by the reaction of cleaved chemical groups and carbon-carbon double bonds at the surface of the substrate.

[0130] Generally, the film formation by consumption of the double bonds should not be too fast so that the amount of actinic radiation is not sufficient to allow the formation of covalent bonds between the carbon-carbon double bonds and the photoreactive groups before the carbon-carbon double bonds are consumed or diffusion to the surface is hindered by the high viscosity of the evolving network.

[0131] If necessary, the delayed gelation in the thiol-ene, where the viscosity remains essentially constant before the gel point, is suitable to counteract this effect, because the diffusion of the carbon-carbon double bonds is fast until the late stages of film formation. Moreover, the non-initiating ability of the thiol-ene is advantageous, because very little actinic radiation is absorbed at the effective wavelength, allowing most of the actinic radiation to reach the photoreactive groups on the surface. Therefore, these are additional advantages of adding a compound comprising at least one thiol group.

[0132] The actinic radiation, typically UV radiation, should reach the surface of the substrate where the photosensitive groups are located. This can be achieved by irradiating the surface. In one embodiment, this can be achieved by irradiating through the substrate, provided that the substrate is transparent and / or very thin at the relevant wavelength. The solution comprising the compound comprising at least one C=C double bond should not absorb too much actinic radiation. The product of the thickness of the applied solution and the absorption at the relevant wavelength should not be too high so that enough actinic radiation can reach the surface of the substrate where the photosensitive groups are located. Higher absorption of radiation in such a solution can be compensated to some extent by a thinner applied solution.

[0133] The same principle of at least an effective amount of actinic radiation reaching the groups at the surface also applies to the coating solution and / or the sheet applied in step d). In such embodiments, the light path passes through the coating solution or the sheet before reaching the opposite surface of the thermoplastic sheet. In the case of thermoplastic sheets according to the prior art, the UV-active glue is designed to react very fast to form a solid polymer, where essentially all carbon-carbon double bonds are consumed within such a short time frame that no covalent bonding via activation of the photoreactive groups on the surface of the thermoplastic sheet facing the applied primer by actinic radiation can be observed. This explains why this effect has not been noticed before.

[0134] The following table gives examples of suitable monomer pairs M1 and M2 suitable for use together in the present application.

[0135] M1 [M2] r 1(计算) ]]> r 2(计算) ]]> k 11 (l / (mol s)) k 22 (l / (mol s)) acrylate maleate 22.2 0.04 11000-18000 low acrylate vinyl ether 5.7 0 11000-18000 low methacrylate vinyl ether 16 0 700-2200 low acrylate allyl ether 0.91 0 1100-18000 low methacrylate maleate 13.6 0.04 700-2200 low methacrylate maleimide 20.2 0.03 700-2200 low vinyl ether maleate 0.01 0.11 low low styrene maleate 4.19 0.01 100-350 low

[0136] The values of r1 and r2 are calculated using the Alfrey Price Q-e scheme, where r1 = (Q1 / Q2)exp[-el(el-e2)] and r2 = (Q2 / Q1)exp[-e2(e2-el)]. In case of no detailed study of the actual copolymerization, the published values of Q and e for the monomer pairs can be used to estimate r1 and r2.k11 and k 22 Taken from the literature.

[0137] For k 22 , the term "low" in the table means a value that is much lower, i.e. more than 10 times lower, than k 11 . This does not apply for the case where both r1 and r2 are very close to zero. Very close to zero is interpreted as lower than 0.05.

[0138] functional group Q e acrylate 0.92 0.75 methacrylate 0.57 0.3 vinyl ether 0.03 -1.49 allyl ether 0.079 -2.65 styrene 1 -0.8 maleate 0.053 1.08 fumarate 0.24 2.26 maleimide 0.035 1.013

[0139] Both maleates and fumarates are present in unsaturated polyesters and are thus covered by the present invention, although the kinetic constants are slightly different from each other.

[0140] K 11 is the propagation rate constant for M1 homopolymerization and k 22 is the propagation rate constant for M2 homopolymerization, as described in more detail above.

[0141] It is to be understood that the present application is not limited to the particular embodiments illustrated herein. These embodiments are provided for illustrative purposes only and are not intended to limit the scope of the present application, which is defined only by the appended claims and their equivalents.

[0142] example

[0143] Example 1 (Bo-PET)

[0144] Bo-PET (biaxially stretched polyethylene terephthalate) film was cut into pieces and used as a substrate. The pieces were wiped clean with IPA (isopropyl alcohol). A thin layer of either pure hexanediol diacrylate (HDDA) or a commercially available UV-curing acrylate based topcoat from Bona AB (UE1664) containing a photoinitiator was applied as a primer on the PET film in a layer of about 1 pm thick (1 g / sqm). The PET film with the primer layer was put into a curing device containing a conveyor belt and stationary medium pressure mercury lamps emitting UVA, UVB, UVC and UVV light. Different UV doses were tested.

[0145] The surface properties of the primer layer after exposure to UV were tested directly using gloved fingers and a spatula to determine if the primer layer had cured. If the gloved fingers or spatula left a mark in the primer layer, the surface was determined to be "wet". If the gloved fingers or spatula left no mark in the primer layer, the surface was determined to be "dry". If a portion of the surface was dry, while other portions were wet, or very faint marks were observable, the surface was determined to be "almost dry". If the surface touched by the gloved fingers was tacky, the surface was determined to be "tacky". These results are presented under "Surface Properties" in the table below.

[0146] Subsequently, a thicker layer of UV-cured acrylate-based topcoat from Bonas AB (UE1664) was applied on top of the primer layer using a 22 pm rod applicator, and given a UV dose of 1.4 J / cm2(UVA) in the same curing device, which resulted in full curing and drying of the layers. 2

[0147] The adhesion of the coated layer to the substrate was tested using a standard tape test ("Crosshatch Test") according to the Crosshatch Test described in ISO 2409. Briefly, cuts were made through the coating to the substrate in a square pattern, with 25 areas each approximately 1 mm 2 The tape was pressed on the coating and quickly pulled off. The resulting damage was assessed by evaluating the amount of coating that had been removed by the tape, with CH=0 being the best adhesion (no coating removed) and CH=5 being the worst adhesion (all or almost all coating removed).

[0148] For reference, no primer layer was applied on the PET film prior to applying, curing and testing a 22 pm thick UV-cured acrylate-based topcoat in the same manner as described above.

[0149] The results are presented in the table below.

[0150] sample number primer UV (mJ / cm2 UVA) surface properties crosshatch #1 HDDA 700 moist CH=0 #2 HDDA 1400 almost dry CH=0 #3 UE1664 700 almost dry CH=0 #4 UE1664 1400 dry CH=5 #5 none - - CH=3-4

[0151] The results in the table above show that by using a thin primer layer of either pure HDDA or the UV-cured acrylate topcoat UE1664, which activates the surface of the substrate upon exposure to UV light, the adhesion is significantly improved compared to the reference case (#5). However, when the thin UE1664 is cured to dryness, the interlayer adhesion between the primer layer and the thick topcoat fails, and thus the Crosshatch Test fails. This demonstrates the difficulty in obtaining a dry primer layer, which is required in some applications, while still maintaining the interlayer adhesion to the subsequently applied coated layer.

[0152] Example 2 (PET)

[0153] ​Another experiment was performed following exactly the same procedure as described above, but using a 2 mm thick PET (polyethylene terephthalate) sheet purchased from Nordbergs Tekniska AB as substrate.

[0154]

[0155]

[0156] A thin layer of HDDA primer gave excellent results on the PET sheet using a grid method before topcoat. No surface

[0157] Example 3 (BoPET, thicker HDDA)

[0158] Another experiment was performed using the same method and substrate as in example 1, but instead of applying a 1 pm layer of primer, a layer of HDDA of about 14 pm thickness was applied. In this case, the uncured HDDA on the PET substrate was wiped off before the topcoat was applied.

[0159] sample number primer UV (mJ / cm2 UVA) surface properties crosshatch #8 14 μm HDDA 440 moist CH=0 #9 14 μm HDDA 1400 moist CH=0 #10 none - - CH=3-4

[0160] Example 4 (off-stoichiometric acrylate on boPET)

[0161] Another experiment was performed using the same method and substrate as in example 1 using either a formulation of 70 wt% HDDA (1,6-hexanediol diacrylate) and 30 wt% PETMA (pentaerythritol-tetramercaptoacetate) (formulation “A”), or a formulation of 69.75 wt% HDDA, 29.75 wt% PETMA and 0.5 wt% ITX (formulation “B”), where ITX is a Norrish type II photoinitiator, as primer. Both formulations have a thiol / acrylate ratio of about 0.5, and thus the acrylate functionality is about 100% off-stoichiometric with respect to the thiol functionality. The primer layer was applied as before in a layer of about 1 pm thickness (1 g / sqm).

[0162] The coatings were tested for adhesion to the substrate using a grid method test.

[0163] Some of the samples were then submerged in boiling water for 2 hours, dried and retested using the grid method test.

[0164]

[0165] The above results show that even when dried, both formulations A and B passed the grid method test, i.e. the interlayer adhesion did not fail. Furthermore, even after boiling for 2 hours, the adhesion of the test samples was not affected.

[0166] Example 5 (PP)

[0167] Two different types of polypropylene (PP) substrates were used as substrates: i) unprocessed PP sheets of different colors (“homogenous PP”) and ii) filled PP films of different colors (“filled PP”), none of which were coated.

[0168] The substrates were wiped clean with IPA and subjected to a corona treatment using a hand-held laboratory corona treater (Model BD-20 from Electro-technic products inc.) with the electrode at 30 cm 2 The electrode was moved over the large substrate at a distance of 5-10 mm in 30 seconds.

[0169] The primer formulations used were “Formulation A” and “Formulation B”, both of which are described in the examples above, as well as a formulation consisting of the monomer SR9020 from Sartomer with 3% of ITX Norrish Type II photoinitiator (referred to as Formulation “C”).

[0170] A thin primer layer was applied on the substrates as described above in approximately 1 pm thick layers (1 g / m 2 ) of primer. The substrates and primer were then exposed to the same “Hg” mercury curing device as described in Example 1, but in one case the primer layer was instead exposed to a 365 nm UV LED exposure device (3000 mJ / cm2at 365 nm, 30 mW / cm 2 ) at 365 nm). After exposure, the surface properties of the primer were checked using gloved fingers and a spatula as described in Example 1. The same topcoat as in Example 1 was then applied with a 22 pm rod applicator and cured in the Hg mercury curing device using a dose of 1400 mJ / cm 2 (UVA) as described in Example 1.

[0171] As a reference, no primer layer was applied on the corona treated substrates before the application and curing of a 22 pm thick UV-cured acrylate based topcoat as in Example 1.

[0172] The evaluation was done with the Crosshatch test as described in Example 1.

[0173] Some of the samples were subsequently submerged in boiling water for 2 hours, dried and retested with the Crosshatch test.

[0174]

[0175]

[0176] Note that on the dark substrate of filled PP (#26), the 22 pm UE1664 topcoat layer did not cure at all.

[0177] Example 6 (PE)

[0178] In another experiment, the exact same method as in Example 4 (IPA wipe, corona treatment, primer application, UV, topcoat application and UV) was used, but on an unprocessed polyethylene (PE) surface of quality “PE 1000 Natural” purchased from Nordberg Technology.

[0179]

[0180] Example 7 (off-stoichiometric variant)

[0181] As before, filled PP (dark) was used as substrate.

[0182] A formulation consisting of a variant of Formulation A (HDDA and PETMA) was used as primer layer, wherein different amounts of off-stoichiometry were calculated as the ratio of thiol groups to acrylate groups.

[0183] The PP substrate was first wiped clean with IPA and subsequently treated with corona (exactly as described in Example 5).

[0184] Then, the primer formulation was immediately applied to a thickness of approximately 1 pm thick layer (1 g / sqm) and exposed to UV mercury lamps (same procedure as in Example 1) with a dose of 2x700 mJ / cm2as measured in UVA. After each 700 mJ / cm2(UVA) pass, the surface was tested with gloved fingers and a spatula to determine the surface properties as described in Example 1. Thereafter, a layer of UV acrylate topcoat UE1664 of approximately 22 pm (22 g / sqm) thick was applied using a bar applicator and cured by exposure to 1400 mJ / cm2as measured in UVA.

[0185] Finally, the adhesion of the coating was tested using the crosshatch method test as described in Example 1.

[0186]

[0187] Example 8 (double bonds)

[0188] In this example, the following substrates were used: filled PP (dark), BoPET and PE (all described previously).

[0189] Monomer DVE-3 (triethylene glycol divinyl ether) or TAOE (tetra(allyloxy)ethane) was used as primer layer.

[0190] The filled PP (dark) substrates were corona treated exactly as described in example 5. The BoPET and PE substrates were not corona treated.

[0191] A primer layer was applied to a thickness of approximately 1 pm (1 g / sqm) and UV cured using a Hg mercury lamp (2x 700 mJ / cm2as measured in UVA) as before. Thereafter, a UV acrylate UE1664 layer of approximately 22 pm thickness was applied and UV cured (1400 mJ / cm2as measured in UVA).

[0192] Finally, the adhesion of the coating was tested using the crosshatch method test as described above.

[0193] sample number substrate primer layer crosshatch #35 PP filled (dark) DVE-3 CH=3-4 #36 PP filled (dark) TAOE CH=2 #37 BoPET DVE-3 CH=0 #38 BoPET TAOE CH=1 #39 PET DVE-3 CH=0 #40 PET none CH=0

[0194] Example 9

[0195] Several different materials were used as substrates. The materials used were: “BoPET film”, clear Bo-PET (biaxially oriented polyethylene terephthalate) film; “PET film”, clear PET (polyethylene terephthalate) film (0.1 mm thick) purchased from Nordby Technology; “PET 2mm”, 2 mm thick white PET (polyethylene terephthalate) sheet purchased from Nordby Technology, “Filled PP”, opaque and glossy filled PP sheet purchased from Direktlaminat AB; “PE film”, polyethylene (PE) film (0.25 mm thick) purchased from Nordby Technology; “PE 6mm”, 6 mm thick unprocessed PE (polyethylene) sheet (quality “PE 1000 natural”) purchased from Nordby Technology; “PMMA 2mm”, 2 mm thick clear PMMA (poly(methyl methacrylate)) sheet purchased from Nordby Technology; and “Acrylate”, cured acrylate surface.

[0196] The cured “Acrylate” surface was prepared by applying a 1 pm thick layer of M1814 from Mercene Labs to a grey melamine board purchased from Direktlaminat AB, UV curing in a medium pressure mercury lamp at 600 mJ / cm 2 (UVA), applying a 12 pm UV cured acrylate base finish (UE1664) from Bonas AB, and UV curing in a medium pressure mercury lamp at 1400 mJ / cm 2 (UVA), which fully cured and dried the layers.

[0197] All of the above materials were cut into pieces and used as substrates. The pieces were wiped clean with a piece of dry cotton paper.

[0198] Two different primer formulations were prepared: "Formulation X", which used 49.4 wt% Ebecryl 2221 (hexafunctional aromatic urethane acrylate oligomer) from Allnex Belgium SA / NV, 49.4 wt% Rapi-Cure DVE-3 (triethylene glycol divinyl ether) and 1.6 wt% Speedcure-2 ITX (a Norrish Type II photoinitiator of the thioxanthone family, 2-isopropylthioxanthone) from Lambson Limited; and "Formulation Y", which used 48.8 wt% Trimethylolpropane Diallyl Ether 90, purchased from Perstorp Specialty Chemicals AB, 48.8 wt% Ebecryl 2221 and 2.4 wt% Speedcure-2 ITX from Lambson Limited.

[0199] All substrates made of PE or PP (i.e. "Filled PP", "PE Film" and "PE 6mm") were corona treated using a hand-held laboratory corona treater (Model BD-20 from Etes-Technik GmbH) with the electrode at 30 cm 2 The large substrates were moved over a distance of 5-10 mm in 30 seconds.

[0200] A thin layer of either "Formulation X" or "Formulation Y" was applied as a primer on the substrates in a layer of approximately 1 pm thick (1 g / sqm). The substrates with the primer layer were put into a curing device, which contains a conveyor belt and fixed medium pressure mercury lamps emitting UVA, UVB, UVC and UVV light, and there exposed to a total dose of 600 mJ / cm 2 (UVA).

[0201] The surface properties of the primer layer after exposure to UV were tested directly using gloved fingers and a spatula to determine whether the primer layer had cured. If the gloved fingers or spatula left a trace in the primer layer, the surface was determined to be "wet". If the gloved fingers or spatula did not leave any trace in the primer layer, the surface was determined to be "dry". If part of the surface was dry, while other parts were wet, or very faint traces were observable, the surface was determined to be "almost dry". These results are presented under "Surface properties" in the table below.

[0202] Subsequently, a thicker layer of UV-cured acrylate-based topcoat from Bona AB (UE1664) was applied on top of the primer layer using a 22 pm rod applicator, and given a UV dose of 1.4 J / cm2in the same curing device, which resulted in full curing and drying of the layers. 2 (UVA) of 1.4 J / cm2, which resulted in full curing and drying of the layers.

[0203] The adhesion of the coated layers to the substrate was tested using a standard tape test (“Crosshatch Test”) according to the Crosshatch Test described in ISO 2409. Briefly, cuts were made through the coating to the substrate in a square pattern, with 25 areas each approximately 1 mm 2 The tape was pressed on the coating and quickly pulled down. The resulting damage was assessed by evaluating the amount of coating that had been removed by the tape, with CH=0 being the best adhesion (no coating removed) and CH=5 being the worst adhesion (all or almost all coating removed).

[0204] For reference, no primer layer was applied on the substrate before applying, curing and testing a 22 pm thick UV-cured acrylate-based topcoat in the same way as described above.

[0205] The results are presented in the table below.

[0206]

[0207]

[0208] The results in the table above show the potential of curing a dry or almost dry film on various polymer substrates, and the film in turn provides improved adhesion to both the substrate and the subsequent topcoat.

[0209] Example 10, different monomer pairs

[0210] The following monomers and oligomers were used: AIPE (unsaturated polyester where the unsaturation comes from the co-reaction of maleic anhydride with a polyfunctional alcohol, Sir Industriale, Italy), Styrene (Sigma Aldrich), Rapi-Cure DVE-3 (triethylene glycol divinyl ether) "DVE3", SR350D (trimethylolpropane triacrylate, Arkema), APE (pentaerythritol allyl ether, Perstorp chemicals), BMI 1500 (difunctional maleimide, Caplinq) "BMI", Ebecryl 2221 (polyfunctional acrylate from Chimex) "Eb2221", SR 9020 (trifunctional acrylate, Sartomer) SR238 (HDDA, hexanediol diacrylate, Arkema). These monomers and oligomers were used to make ten different monomer mixtures, mixed in the weight ratios according to the table below. To all ten monomer mixtures was added 2.4wt% Speedcure-2 ITX (photoinitiator) from Lambson Limited, resulting in ten corresponding formulations.

[0211]

[0212] All percentages are by weight.

[0213] The above formulations were applied at 1 g / m 2 of thickness on a 50 pm thick PET film from Mitsubishi, cured according to the table below, where N indicates the number of passes per pass under a lamp of 135 mJ / cm 2 (UVA). After assessing the state of cure, where AD+ (abbreviation for "Almost Dry +" indicates the state before the film is completely dry, according to the explanation regarding dryness assessment in previous examples). The samples were coated with UT 7710 (Bonar Acrylic Finishes) using a 22 micron rod. The topcoat was cured using the same equipment as in previous examples, with 1.2 J / cm 2 (UVA) as measured in UVA.

[0214] The results are presented in the table below. All exposure amounts written as "mJ" in the table refer to "mJ / cm2(UVA)".

[0215]

[0216]

[0217] The examples show the applicability of the present invention to several monomer pairs, all of which are characterized by a very large process window with respect to UV exposure, and very good adhesion to PET foil. Formulations 8, 9 and 10, consisting of acrylate oligomer and acrylate monomer with photoinitiator, produced poor adhesion between topcoat and substrate when the formulation was cured to almost dry state, showing the detrimental effect of high homopolymerization rate of reactive groups for interlayer adhesion to topcoat when a dry film is required during manufacturing.

[0218] Example 11

[0219] The cured and dried formulation X film on a 50 pm thick PET film from Toray, prepared according to example 9, was stored in the dark at room temperature for 5 months. The acrylate topcoat was applied and cured according to example 9.

[0220] The results are presented in the table below.

[0221] substrate surface crosshatch Toray PET Formulation X, dry, stored 5 months 0 Toray PET no primer 5

[0222] The above examples show that the reactivity to the acrylate topcoat remains unchanged after long storage at room temperature.

[0223] Example 12

[0224] To test the effect of UV dose on the primer, in particular the effect of UV dose (high dose) on adhesion to the next coating layer, several different UV doses were tested.

[0225] A 2 mm thick white PET (polyethylene terephthalate) sheet “PET 2 mm” from Nordberg Technology was cut into smaller pieces and used as substrate. The pieces were wiped clean with a piece of dry cotton paper.

[0226] The primer formulation used was “Formulation X”, containing 49.4 wt% Ebecryl 2221 from Cytec Industries, 49.4 wt% Rapi-Cure DVE-3 from Sartomer and 1.6 wt% Speedcure-2 ITX from Lambson Limited.

[0227] A thin layer of “Formulation X” was applied as primer on the substrate in a layer of about 1 pm thick (1 g / sqm). The substrate with the primer layer was put into a curing device, which contains a conveyor belt and stationary medium pressure mercury lamps emitting UVA, UVB, UVC and UVV light, and exposed there to different UV doses as presented in the table below.

[0228] The surface properties of the primer layer after exposure to UV were tested directly using gloved fingers and a spatula to determine if the primer layer had cured. If the gloved fingers or spatula left a mark in the primer layer, the surface was determined to be "wet". If the gloved fingers or spatula left no mark in the primer layer, the surface was determined to be "dry". If a portion of the surface was dry, while other portions were wet, or very faint marks were observable, the surface was determined to be "almost dry". These results are presented under "Surface Properties" in the table below.

[0229] Subsequently, a thicker layer of UV-cured acrylate-based topcoat (UE1664) from Bona AB was applied on top of the primer layer using a 22 pm rod applicator, and given a UV dose of 1.4 J / cm2(UVA) in the same curing device, which resulted in full curing and drying of the layers. 2 (UVA) in the same curing device, which resulted in full curing and drying of the layers.

[0230] The adhesion of the coated layer to the substrate was tested using a standard tape test ("Crosshatch Test") according to the Crosshatch Test described in ISO 2409. Briefly, cuts were made through the coating to the substrate in a square pattern, with 25 areas each approximately 1 mm 2 The tape was pressed onto the coating and quickly pulled off. The resulting damage was assessed by evaluating the amount of coating that had been removed by the tape, with CH=0 being the best adhesion (no coating removed), and CH=5 being the worst adhesion (all or almost all coating removed).

[0231] For reference, no primer layer was applied on the substrate before applying, curing and testing a 22 pm thick UV-cured acrylate-based topcoat in the same manner as described above.

[0232] The results are presented in the table below.

[0233]

[0234]

[0235] The results in the table above show that the primer can form a film, and can withstand a large excess of UV, beyond film formation, and still provide good adhesion to the topcoat.

[0236] Example 13, several different substrates

[0237] Several different common plastics were used as substrates, the following were obtained from Norbergs Tekniska AB:

[0238] PPO (polyphenylene oxide) mass "gray blue 6 mm", ABS (acrylonitrile butadiene styrene copolymer) mass "white 2 mm", PVC-XT (extruded polyvinyl chloride) mass "gray 1 mm", HIPS (high impact polystyrene) mass "white 2 mm", PEEK (polyether ether ketone) mass "natural calendered 2 mm", PMMA (polymethyl methacrylate) "clear transparent 4 mm", and PC (polycarbonate) mass "clear transparent 1 mm".

[0239] A PS (polystyrene) sample was cut from the lid of a 150 mm diameter polystyrene petri dish obtained from VWR.

[0240] An acrylate surface was prepared by applying a 12 μm thick layer of UT7710 (Bona Acrylate Finish) onto a substrate that had good adhesion to UT7710 and curing with a dose of 1.4 mJ / cm 2 (UVA) from a fixed medium pressure mercury lamp.

[0241] The formulation Y was applied in a layer of approximately 1 μm thick (1 g / m 2 ) using a previously wiped substrate with lint-free paper, but without other cleaning or surface activation.

[0242] The substrate with the primer layer was cured using an apparatus comprising a conveyor belt and a fixed medium pressure mercury lamp emitting UVA, UVB, UVC and UVV light. The substrate with the primer layer was passed through the curing apparatus multiple times, each time exposing the primer and substrate to 135 mJ / cm 2 (UVA). After each pass (passes 1-6), the surface properties of the primer were evaluated using gloved fingers and a spatula in the same manner as described in the above examples.

[0243] In the following table, "W" is an abbreviation for "wet", "AD" is an abbreviation for "almost dry", "D" is an abbreviation for "dry", and "AD+" is an abbreviation for "almost dry + dry", i.e. a state in between "almost dry" and "dry".

[0244] After 6 passes or 810 mJ / cm 2 (UVA), all samples were dry or almost dry, UT7710 (Bona Acrylate Finish) was applied using a 22 micron rod, cured at 1.4 J / cm 2 (UVA), and the crosshatch method was evaluated. Another set of samples received a double dose (1620 mJ / cm 2The substrates were treated and tested with the grid method. As a reference, the substrates were coated with UT 7710 without pre-treatment with formulation Y, called "no primer" in the table below. The experiments with double UV dose and the reference without primer (Y pre-treatment) had exactly the same topcoat, which was applied in the same way.

[0245] The results are presented in the table below. All exposure amounts written as "mJ" in the table refer to "mJ / cm2(UVA)".

[0246]

[0247] This example shows good results on several plastic types without the need for abrasive, solvent or corona pre-treatment. It shows the ability to withstand overexposure on most substrate types. The evolution of dryness also illustrates a very wide processing window, both tolerating overexposure and insufficient exposure, as the AD state is already compatible with many industrial processes.

[0248] Example 14

[0249] To test the influence of the UV dose on the primer, in particular the influence of the UV dose on the adhesion of the substrate and the next coating layer, several different UV doses were tested.

[0250] 1 mm thick clear PC (polycarbonate) sheets from Nordberg Technology were cut into smaller pieces and used as substrates. The pieces were wiped clean with a dry cotton paper.

[0251] The primer formulation used was "Formulation X" containing 49.4 wt% Ebecryl 2221 from CVC Specialty Chemicals, 49.4 wt% Rapi-Cure DVE-3 and 1.6 wt% Speedcure-2 ITX from Lambson Limited.

[0252] A thin layer of "Formulation X" was applied as primer on the substrates in a layer of about 1 pm thick (1 g / sqm). The substrates with the primer layer were put in a curing device containing a conveyor belt and fixed medium pressure mercury lamps emitting UVA, UVB, UVC and UVV light and exposed there to different UV doses as presented in the table below.

[0253] The surface properties of the primer layer after exposure to UV were tested directly using gloved fingers and a spatula to determine if the primer layer had cured. If the gloved fingers or spatula left a mark in the primer layer, the surface was determined to be "wet". If the gloved fingers or spatula did not leave any mark in the primer layer, the surface was determined to be "dry". If a portion of the surface was dry, while other portions were wet, or very faint marks were observable, the surface was determined to be "almost dry". These results are presented under "Surface Properties" in the table below.

[0254] Subsequently, a thicker layer of UV-cured acrylate-based topcoat from Bonas AB (UE1664) was applied on top of the primer layer using a 22 pm rod applicator, and given a UV dose of 1.4 J / cm2(UVA) in the same curing device, which resulted in full curing and drying of the layers. 2

[0255] The adhesion of the coated layer to the substrate was tested using a standard tape test ("Crosshatch Test") according to the Crosshatch Test described in ISO 2409. Briefly, cuts were made through the coating to the substrate in a square pattern, with 25 areas each approximately 1 mm 2 The tape was pressed on the coating and quickly pulled off. The resulting damage was assessed by evaluating the amount of coating that had been removed by the tape, with CH=0 being the best adhesion (no coating removed) and CH=5 being the worst adhesion (all or almost all coating removed).

[0256] For reference, no primer layer was applied on the substrate before applying, curing and testing a 22 pm thick UV-cured acrylate-based topcoat in the same manner as described above.

[0257] The results are presented in the table below.

[0258]

[0259] The results in the table above show that the primer performs well over a wide range of UV doses.

[0260] Example 15

[0261] To test the concept of the primer under inert conditions, a sealed box Addixx Inert Box (Model IB-K162504SR-UF quartz window, Addixx Specialities, Biiidingen, Germany) was used. The Addixx Inert Box is equipped with one quartz window on the top lid in order to UV irradiate its content and with two valves in order to purge atmospheric gases with inert gas.

[0262] ​Chemical nitrogen (ultra-clean nitrogen, <5 ppm O2 and humidity, from Linde Industrigaser, Sweden) was connected to the Addixx inert box and downstream from this inert box to another sealed box in which an oxygen detector (Greisinger GMH3692 oxygen detector with sensor GGO381) was placed.

[0263] A primer formulation "Formulation Z" was prepared containing 50 wt% Ebecryl 2221 from Cytec Industries and 50 wt% Rapi-Cure DVE-3 (triethylene glycol divinyl ether). A thin layer of Formulation Z was applied on a 50 pm thick PET film from Toyobo in a layer of approximately 1 pm thick (1 g / sqm). The PET film with the primer layer was put into the Addixx inert box, purged with nitrogen for several minutes until the reading of the oxygen detector was <0.5% (<5000 ppm), after which the valve was closed. Then, the nitrogen-filled Addixx inert box containing the primed PET film was placed in a curing device, which comprised a conveyor belt and stationary medium pressure mercury lamps emitting UVA, UVB, UVC and UVV light. Different UV doses were tested.

[0264] The surface properties of the primer layer after exposure to UV were tested directly using gloved fingers and a spatula to determine whether the primer layer had cured. If the gloved fingers or spatula left a trace in the primer layer, the surface was determined to be "wet". If the gloved fingers or spatula did not leave any trace in the primer layer, the surface was determined to be "dry". If part of the surface was dry, while other parts were wet, or very faint traces were observable, the surface was determined to be "almost dry". If the surface touched with the gloved fingers was sticky, the surface was determined to be "sticky". These results are presented under "Surface properties" in the table below.

[0265] Subsequently, a thicker layer of a UV-cured acrylate-based topcoat (UT7710) from Bona AB was applied on top of the primer layer using a 22 pm rod applicator, and a UV dose of 1.4 J / cm2(UVA) was given in the same curing device under atmospheric conditions, which resulted in full curing and drying of the layers. 2 (UVA) was given in the same curing device under atmospheric conditions, which resulted in full curing and drying of the layers.

[0266] The adhesion of the coating layer to the substrate was tested using a standard tape test ("Crosshatch test") according to the Crosshatch test described in ISO 2409. Briefly, cuts were made through the coating to the substrate in a square pattern, where 25 areas were each approximately 1 mm 2The tape was pressed onto the coating and quickly pulled down. The resulting damage was assessed by evaluating the amount of coating that had been removed by the tape, where CH=0 is the best adhesion (no coating removed) and CH=5 is the worst adhesion (all or almost all of the coating removed).

[0267] For reference, no primer layer was applied to the PET film prior to applying, curing and testing a 22 pm thick UV-cured acrylate-based topcoat in the same manner as described above.

[0268] The results are presented in the table below.

[0269]

[0270]

[0271] The results in the table above show that the primer performs well under inert conditions and over a wide range of UV doses.

Claims

1. A method for coating a substrate, the method comprising the following sequential steps: a) Providing a substrate comprising at least one chemical group selected from the group consisting of aromatic rings, sulfur, and peroxides, wherein at least a portion of said at least one chemical group is located on the surface of the substrate. b) Contacting at least a portion of the surface of the substrate with one of the following: i) A compound containing at least one carbon-carbon double bond, wherein the compound optionally contains a chemical group capable of abstracting hydrogen, and ii) A mixture comprising a first monomer M1 and a second monomer M2, wherein the monomers are capable of undergoing polymerization to form a copolymer covalently bonded to the substrate, wherein at least one of the ratios r1 and r2 is less than 0.45, and wherein k 11 and k 22 One is at least 10 times larger than the other, except when it comes to k. 11 and k 22 When the aforementioned conditions do not apply, r1=r2=0, where r1 =k 11 / k 12 And r2 = k 22 / k 21 , Where k 11 The growth rate constant is the growth rate constant for the growth reaction in which monomer M1 is added to the growing copolymer chain ~M1*. Where k 12 The growth rate constant is the growth rate constant for the growth reaction in which monomer M2 is added to the growing copolymer chain ~M1*. Where k 21 The growth rate constant is the growth rate constant for the growth reaction in which monomer M1 is added to the growing copolymer chain ~M2*. Where k 22 The growth rate constant is the growth rate constant for the growth reaction in which monomer M2 is added to the growing copolymer chain ~M2*. And wherein the first monomer M1 and the second monomer M2 are one of the following options. i) M1 is an acrylate and M2 is a maleate ester. ii) M1 is an acrylate and M2 is a vinyl ether. iii) M1 is a methacrylate and M2 is a vinyl ether. iv) M1 is an acrylate and M2 is an allyl ether. v) M1 is a methacrylate and M2 is a maleate ester. vi) M1 is methacrylate and M2 is maleimide. vii) M1 is an acrylate and M2 is a maleimide. viii) M1 is a vinyl ether and M2 is a maleate ester, and ix) M1 is styrene and M2 is maleate. c) A reaction initiated by photochemical radiation to form covalent bonds by the reaction of at least one chemical group at the surface of the substrate with the compound of i) or the monomers M1 and M2 of ii), thereby forming a polymer of i) or a copolymer of ii) covalently bonded to the surface of the substrate. d) Applying at least one of the coating and sheet to the surface of the substrate, and e) Curing the at least one coating.

2. The method of claim 1, wherein the method further comprises, after step c), removing at least a portion of the compound i) or the mixture ii) that has not yet reacted to form a covalent bond.

3. The method according to any one of claims 1-2, wherein the substrate comprises at least one selected from the group consisting of polyolefins, polymers containing aromatic groups, polymers containing ether groups, and sulfur-containing polymers.

4. The method according to any one of claims 1-2, wherein the substrate comprises at least one selected from the group consisting of: polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), poly(p-phenylene ether) (PPO), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), polystyrene (PS), polyether ether ketone (PEEK), and polycarbonate (PC).

5. The method according to any one of claims 1-2, wherein the surface is treated with at least one selected from the group consisting of corona treatment, plasma treatment and flame treatment prior to step b).

6. The method according to any one of claims 1-2, wherein an electron-withdrawing group is present near the at least one carbon-carbon double bond in the compound.

7. The method according to any one of claims 1-2, wherein electron-withdrawing groups are present on both sides of the at least one carbon-carbon double bond in the compound.

8. The method according to any one of claims 1-2, wherein i) the compound or ii) the mixture is dissolved in at least one solvent before contacting the substrate surface.

9. The method according to any one of claims 1-2, wherein i) the compound or ii) the mixture is not dissolved or diluted in a solvent before contacting the substrate surface.

10. The method according to any one of claims 1-2, wherein the substrate surface in step b) is further contacted with at least one compound comprising at least one thiol group.

11. The method of claim 10, wherein the ratio (r) between the number of thiol groups and the number of carbon-carbon double bonds in step b) satisfies 0.05 ≤ r ≤ 20.

12. The method of claim 10, wherein the ratio (r) between the number of thiol groups and the number of carbon-carbon double bonds in step b) satisfies 0.2 ≤ r ≤ 5.

13. The method of claim 10, wherein the ratio (r) between the number of thiol groups and the number of carbon-carbon double bonds in step b) satisfies one of 0.3 ≤ r ≤ 0.9 and 1.1 ≤ r ≤ 3.

14. The method according to any one of claims 1-2, wherein in step b), the Norish type II photoinitiator is in contact with the surface of the substrate.

15. The method according to any one of claims 1-2, wherein the contact in step b) is performed by applying a layer with a thickness in the range of 0.2-20 μm.

16. The method according to any one of claims 1-2, wherein the compound i) or the mixture ii) to be applied in step b) is provided as an acidic mixture.

17. The method according to any one of claims 1-2, wherein all components to be added in step b) are provided in a single formulation.

18. The method of claim 17, wherein the formulation is acidic and comprises, in addition to the compound, a Norish type II photoinitiator.

19. The method of claim 17, wherein the thickness of the application layer comprising i) the compound or ii) the mixture and the absorbance of the application layer at the wavelength of the photochemical radiation are adjusted such that the reaction is still initiated in step c).

20. The method according to any one of claims 1-2, wherein the irradiation is performed by UV radiation.

21. The method according to any one of claims 1-2, wherein the surface in step b) is in patterned contact with the compound.

22. The method according to any one of claims 1-2, wherein the irradiation is performed in a pattern.

23. The method according to any one of claims 1-2, wherein the compound in step b) contacts at least a portion of the substrate surface by inkjet printing.

24. The method according to any one of claims 1-2, wherein at least step c) is carried out in an inert atmosphere.

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