Light-curable reactive adhesive film based on (METH)acrylate-functionalised polyurethane

Abstract

The present invention relates to a light-curable, reactive, pressure-sensitive adhesive film based on an acrylate- and / or methacrylate-functionalised polyurethane, the curing of which is initiated by blue LED light or UV LED light, and which cures sufficiently slowly so that, if required, for example if non-transparent substrates are to be bonded, the parts to be bonded can be joined with a certain time delay after initiation, and which continues to cure even in the dark after bonding. High bond strengths can be achieved with the adhesive film according to the invention. The adhesive film comprises (a) at least one acrylate- and / or methacrylate-functionalised polyurethane, (b) at least one initiator, in particular a radical initiator, and (c) at least one photoredox catalyst. Reactive monomers are not required.

Description

[0001] Light-curing reactive adhesive film based on (meth)acrylate-functionalized polyurethane

[0002] Description

[0003] Technical field of the invention

[0004] The present invention relates to a light-curing, reactive, pressure-sensitive adhesive film, a process for producing the reactive adhesive film and the use of the adhesive film for bonding various materials, such as plastic, metal, glass and / or ceramic, and a composite body comprising at least two bonding surfaces which are connected to one another by the cured reactive, pressure-sensitive adhesive film.

[0005] General state of the art

[0006] Reactive adhesive films whose curing can be initiated with light, especially UV light, are well known. The reactive chemistry, or chemistry for curing such adhesive films, is based on reactive acrylic monomers that undergo radical polymerization upon initiation with (UV) light. The curing reaction is initiated with the aid of a photoinitiator, which decomposes in a photolysis reaction after absorbing (UV) light, thus forming reactive species that trigger radical polymerization. The speed of the curing reaction can be disadvantageous, particularly when non-transparent substrates are to be bonded. Once the reaction is initiated, there is usually not enough time left to join the components to be bonded. Thus, such adhesive films are only suitable for bonding (UV)-transparent substrates, since the irradiation can then occur through the components after the components have been joined.Another disadvantage of this type of adhesive film is that the polymerization does not proceed as a dark reaction.

[0007] DE 102019209513 A1 describes a reactive adhesive film based on acrylic monomers that does not exhibit these disadvantages of the prior art. A disadvantage has been found to be inadequate resistance to humid heat for many applications. EP 4159775 B1 proposes a reactive adhesive film with improved resistance to humid heat, which can achieve very high, so-called structural bond strengths.

[0008] EP 3390553 A1 proposes a method in which an adhesive tape consisting of two reacting layers A and B, separated by a barrier layer, is reacted and thus cured with the aid of a laser by removing the barrier layer through the action of the laser light. The disadvantage here is the requirement for laser light.

[0009] EP 3126402 A1 discloses a process in which a radical polymerization reaction is triggered by plasma treatment of an adhesive film containing a substance reactive toward a radical polymerization reaction and, in addition, a catalytically active substance. This process achieves a sufficiently slow curing rate. A disadvantage is that a plasma device suitable for achieving good bond strengths is not yet widely available on the market. Furthermore, the achievable bond strength results depend on parameters that are sometimes difficult to influence, such as humidity.

[0010] A disadvantage of all of the radically polymerizing reactive adhesive tapes mentioned above can be the fact that they necessarily contain acrylate or methacrylate monomers. A disadvantage is that most acrylate or methacrylate monomers have a strong and unpleasant odor. Furthermore, many acrylate or methacrylate monomers have a relatively high vapor pressure and can therefore escape prematurely from the uncured adhesive tape. The number of acrylate or methacrylate monomers that do not have these disadvantageous properties, or at least do not exhibit them very strongly, is small, which significantly limits the design possibilities for this type of adhesive tape.

[0011] Object of the present invention

[0012] The present invention is therefore based on the object of providing a light-curing, reactive, pressure-sensitive adhesive film that functions even without the use of acrylate or methacrylate monomers. Functionality here means that the adhesive film must be capable of curing, whereby the adhesive film must be able to build up both cohesive strength and sufficient adhesion to the substrate to be bonded so that a bond can be created. Curing should be able to be initiated by blue LED light or UV LED light. The adhesive film should cure sufficiently slowly so that the components to be bonded can be joined some time after initiation, so that even non-transparent components can be bonded. After initiation and joining of the components, the adhesive film should continue to cure even in the dark.

[0013] Solution to the task

[0014] This object is achieved by a light-curing, reactive, pressure-sensitive adhesive film according to the main claim, comprising (a) at least one acrylate- and / or methacrylate-functionalized polyurethane, (b) at least one initiator and (c) at least one photoredox catalyst.

[0015] Detailed description of the invention:

[0016] All statements of the description apply to the adhesive film according to the invention, the adhesive tape according to the invention, the process according to the invention for producing the adhesive film, the composite body according to the invention and the use of the adhesive film or adhesive tape according to the invention.

[0017] The invention also encompasses all features that are the subject matter of any dependent patent claims. Furthermore, the invention encompasses combinations of individual features with one another, including combinations of different degrees of preference. Thus, for example, the invention encompasses the combination of a first feature designated as "preferred" with a second feature designated as "particularly preferred." This also encompasses subject matter designated as "embodiments" with different degrees of preference. Acrylate- and / or methacrylate-functionalized polyurethane

[0018] The reactive adhesive film according to the invention comprises (a) at least one acrylate- and / or methacrylate-functionalized polyurethane.

[0019] The phrase “acrylate and / or methacrylate functionalized” means that the polyurethane can be functionalized with acrylate, methacrylate, or both acrylate and methacrylate.

[0020] The polyurethane (a) is preferably functionalized with acrylate or methacrylate. Thus, the reactive adhesive film according to the invention preferably comprises an acrylate- or methacrylate-functionalized polyurethane.

[0021] This applies to all embodiments within the scope of the present invention, unless otherwise stated.

[0022] This polyurethane is, in particular, the film-forming polymer of the reactive adhesive film according to the invention. It thus imparts its film shape to the reactive adhesive film according to the invention. The acrylate- and / or methacrylate-functionalized polyurethane remains pressure-sensitively adhesive before light curing. According to Römpp (Römpp Online 2013, document identifier RD-08-00162), pressure-sensitive adhesive films are defined as those viscoelastic adhesive films whose cured, dry film is permanently tacky and remains adhesive at room temperature. Pressure-sensitive bonding occurs immediately on almost all substrates with light contact pressure. Light contact pressure here refers to a contact pressure of greater than 0 bar exerted for a duration of greater than 0 seconds. In general, the findings on the subject of pressure-sensitive adhesion are state of the art and are comprehensively presented, for example, in "Satas, Handbook of Pressure Sensitive Adhesive Technology, Third Edition, (1999)".

[0023] Furthermore, the acrylate- and / or methacrylate-functionalized polyurethane is reactive due to the acrylate and / or methacrylate functionality. Acrylate and methacrylate groups are known to undergo radical reactions, which can be triggered, for example, by radical initiators.

[0024] In a preferred embodiment, the acrylate- and / or methacrylate-functionalized polyurethane is the chemical reaction product of a1) at least one diol and / or polyol, a2) at least one acrylate- and / or methacrylate-functionalized diol and / or polyol and a3) at least one di- and / or polyisocyanate.

[0025] Diols / polyols can, in principle, be all known doubly or polyhydroxyl-functionalized substances, in particular all polyester diol polyols, including all polycaprolactone diol polyols, all polyester carbonate diol polyols, all polyether diol polyols, and all polybutadiene diol polyols, as well as substances derived therefrom or derivatives of these substances. Also suitable are so-called chain extenders and / or crosslinkers, which here are understood to be doubly or polyhydroxyl-functionalized substances that are not poly compounds.

[0026] Polyester diolsZ polyols which can be used according to the invention are polyesters with terminally bonded hydroxyl groups.

[0027] Polyester diols have two terminally bonded hydroxyl groups, thus being difunctional. In polyester polyols, the number of terminally bonded hydroxyl groups is not clearly defined. There can be two or more hydroxyl groups per molecule. In this document, polyester polyols are understood to mean those with more than two hydroxyl groups per molecule. Polyester diol polyols usable according to the invention are generally obtained by polycondensation from diol polyols and di-polycarboxylic acids or, in the case of polycaprolactone polyols, by ring-opening polymerization from µ-caprolactone and a di- or polyfunctional starter molecule.

[0028] Polyestercarbonate diols are doubly hydroxyl-functionalized polyesters whose molecular chain also contains at least one carbonic acid ester group. They can be obtained, for example, by the polyreaction of a diol, a dicarboxylic acid, and dimethyl carbonate (DMC) or diphenyl carbonate (DPC). In polyestercarbonate polyols, the number of terminally bonded hydroxyl groups is not clearly defined. There can be two or more hydroxyl groups per molecule. In this document, polyestercarbonate polyols are understood to mean those with more than two hydroxyl groups per molecule.

[0029] Polyether diols (Z polyols) usable according to the invention are polyethers with terminally bonded hydroxyl groups. Polyether diols have two terminally bonded hydroxyl groups and are therefore difunctional. In polyether polyols, the number of terminally bonded hydroxyl groups is not clearly defined. There can be two or more hydroxyl groups per molecule. In this document, polyether polyols are understood to mean those with more than two hydroxyl groups per molecule. Polyether diols (Z polyols) usable according to the invention are primarily prepared from ethylene oxide, propylene oxide, or tetrahydrofuran by ring-opening polymerization or copolymerization using a starter molecule that determines the functionality. Polybutadiene diols are doubly hydroxyl-functionalized polybutadienes produced from butadiene in an anionic polymerization process. Well-known commercial products include the Krasol® grades from Cray Valley.

[0030] Polybutadiene polyols can contain two or more hydroxyl groups per molecule. In this document, polybutadiene polyols are defined as those with more than two hydroxyl groups per molecule. They are produced from butadiene using a radical polymerization process. Well-known commercial products include the Poly bd® grades from Cray Valley.

[0031] Examples of chain extenders are 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, propylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol or 2-ethyl-1,3-hexanediol.

[0032] Examples of crosslinkers are glycerol, trimethylolpropane or 1,2,4-butanetriol.

[0033] According to particularly advantageous embodiments of the invention, a1) is at least one diol and / or polyol selected from the group consisting of polyester diols, polyester polyols, polyester carbonate diols and polyester carbonate polyols, with polyester diols and / or polyester carbonate diols again being particularly preferred.

[0034] According to preferred embodiments of the invention, the a2) at least one acrylate- and / or methacrylate-functionalized diol and / or acrylate- and / or methacrylate-functionalized polyol is a diolic or polyolic alkyl (meth)acrylate, wherein the alkyl radical is linear or branched and the alkyl radical has three to twenty, preferably three to ten, again preferably three to six, in particular and for example three or five carbon atoms.

[0035] “Diolic alkyl (meth)acrylate” means an alkyl (meth)acrylate compound that has two hydroxyl groups on the alkyl radical.

[0036] “Polyolic alkyl (meth)acrylate” means an alkyl (meth)acrylate compound which has more than two hydroxyl groups, for example three hydroxyl groups, on the alkyl radical.

[0037] The object underlying the invention is achieved particularly well with such acrylate- and / or methacrylate-functionalized diols and / or acrylate- and / or methacrylate-functionalized polyols. According to particularly preferred embodiments of the invention, the a2) at least one acrylate- and / or methacrylate-functionalized diol and / or acrylate- and / or methacrylate-functionalized polyol is selected from the group consisting of 2,3-dihydroxypropyl acrylate (CAS No.: 10095-20-2), 2,3-dihydroxypropyl methacrylate (CAS No.: 5919-74-4), 1,3-dihydroxy-2-propanyl acrylate (CAS No.: 119051-91-1), and 3-hydroxy-2,3-bis(hydroxymethyl)propyl acrylate (CAS No.: 55919-77-2).

[0038] Again particularly preferred is a2) at least one acrylate- and / or methacrylate-functionalized diol, which in turn is very particularly preferably selected from the group consisting of 2,3-dihydroxypropyl acrylate and 2,3-dihydroxypropyl methacrylate.

[0039] Particularly preferred is a light-curing, reactive, pressure-sensitive adhesive film, wherein the at least one acrylate- and / or methacrylate-functionalized polyurethane comprises the chemical reaction product of a1) at least one diol and / or polyol, a2) 2,3-dihydroxypropyl acrylate and / or 2,3-dihydroxypropyl methacrylate and a3) at least one di- and / or poly-isocyanate.

[0040] a3) Di- and / or polyisocyanates that can be used according to the invention are all known aliphatic and / or aromatic diisocyanates and / or polyisocyanates. Diisocyanates carry two isocyanate groups per molecule, i.e., they are difunctional. Polyisocyanates carry two or more isocyanate groups per molecule. In this document, polyisocyanates are understood to mean those with more than two isocyanate groups per molecule.

[0041] Examples of suitable di- and / or polyisocyanates are 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (isophorone diisocyanate, IPDI), hexane-1,6-diisocyanate (hexamethylene diisocyanate, HDI), dicyclohexylmethane-4,4'-diisocyanate (H12MDI), tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate and / or m-tetramethylxylene diisocyanate (TMXDI), mixtures of the isocyanates mentioned or isocyanates chemically derived therefrom, for example dimerized, trimerized or polymerized types which contain, for example, urea, uretdione or isocyanurate groups.

[0042] According to advantageous embodiments, the diisocyanate hexane-1,6-diisocyanate (hexamethylene diisocyanate, HDI) is used as a3). To accelerate the reaction of the diols / polyols with the di- / polyisocyanates, one or more catalysts known to the person skilled in the art, such as tertiary amines, organobismuth or organotin compounds, to name just a few, can be used.

[0043] Bismuth and carbon-containing catalysts can be used very advantageously, preferably a bismuth carboxylate or a bismuth carboxylate derivative, in particular bismuth trisneodecanoate, CAS No.: 34364-26-6.

[0044] The catalyst concentration is adjusted to the diols / polyols and di- / polyisocyanates used. It generally ranges between 0.01 wt.% and 0.5 wt.% of the polyurethane to be produced.

[0045] The acrylate- or methacrylate-functionalized polyurethane is preferably thermoplastic.

[0046] Therefore, difunctional starting materials, i.e. diols and diisocyanates, are preferably used.

[0047] Suitable polyols are in particular triols, with higher polyols preferably being avoided.

[0048] This applies to the diols or polyols of groups a1) and a2).

[0049] When using trioien in groups a1) and a2), care should be taken to ensure that no gelation occurs during polyurethane production, i.e. that the degree of branching in relation to the length of the polymer chains produced is not so high that crosslinking occurs during polyurethane production. The degree of branching is adjusted so that no crosslinked structures form. To exclude crosslinked structures, the so-called gel point must not be exceeded. The theoretical gel point can be calculated, as known to those skilled in the art, using the gel point equation by PJ Flory or a formula derived from the Flory equation for estimating the gelation NCO / OH ratio in polyurethane formation reactions from diols and trioien with diisocyanates.

[0050] The derived formula is:

[0051] (Diol-OH) +1

[0052] (Triol-OH)

[0053] In this formula, "Diol-OH" refers to the total number of hydroxyl groups derived from diols involved in the polyurethane formation reaction. This also includes chain extenders and acrylate- and / or methacrylate-functionalized diols. "Triol-OH" refers to the total number of hydroxyl groups bound to triols involved in the polyurethane formation reaction. This also includes crosslinkers and acrylate- and / or methacrylate-functionalized triols.

[0054] The NCO / OH ratio is preferably 0.5 to 1.

[0055] The number-average hydroxyl functionality is the average number of hydroxyl groups per molecule of a polymeric diol, such as a polyester diol, or polymeric polyol, such as a polyester polyol. In this document, it is based on the number-average molecular weight of the respective diol or polyol and is calculated using the following formula: f = M n [g / mol] x OH [mmol OH / kg] / 10 6 f is the number-average mean hydroxyl functionality. M n is the number average molecular weight of the respective diol or polyol in the unit [g / mol] and OH is the hydroxyl number of the diol or polyol in the unit [mmol OH / kg].

[0056] The hydroxyl number is a measure of the content of hydroxyl groups in a diol or polyol.

[0057] The hydroxyl number is determined according to DIN 53240. According to this method, the hydroxyl number (OHN) is expressed in [mg KOH / g]. It corresponds to the amount of KOH in [mg] that is equivalent to the amount of acetic acid bound during the acetylation of 1 g of diol or polyol. To simplify formulation calculations, the hydroxyl number is converted to the unit [mmol OH / kg] in this document.

[0058] This is done according to the following formula:

[0059] OHZ [mmol OH / kg] = OHZ[mg KOH / g] x1000 / 56.1.

[0060] 56.1 is the molar mass of KOH.

[0061] If the gelation NCO / OH ratio is reached or exceeded, the formation of cross-linked structures, i.e., the onset of gelation, must be expected. The formula derived from the Flory equation provides only an approximate, but generally sufficient, indication of the NCO / OH ratio at which actual gelation occurs.

[0062] When using polyisocyanates with an isocyanate functionality of three to produce the polyurethane, similar considerations apply to avoid gelation. For this reason, the simultaneous use of triols and triisocyanates should also be avoided. Functionalities greater than three should also be avoided for this reason.

[0063] In order to achieve pressure-sensitive adhesion, the NCO / OH ratio is preferably set so that a slight deficiency of NCO groups is used, even when exclusively diols and diisocyanates are used. Preferred NCO / OH ratios in this case are in the range between 0.9 and 1.0, particularly preferably 0.9 to 0.99. If a trifunctional substance is also used, the NCO / OH ratio to be set is derived from the formula given above. The NCO / OH ratio is understood to be the ratio of the total number of all isocyanate groups used for the polyurethane formation reaction to the total number of all hydroxyl groups used for the polyurethane formation reaction, i.e. the molar ratio of isocyanate groups to hydroxyl groups, regardless of whether the molecules of the respective substances actually react completely or only partially.

[0064] To achieve pressure-sensitive adhesion, the number-average molecular weight M n of a1) at least one diol and / or polyol is preferably chosen so that it is between 400 g / mol and 6000 g / mol inclusive, preferably between 1000 g / mol and 4000 g / mol inclusive.

[0065] Furthermore, the ratio of the number of hydroxyl groups originating from a1) the at least one diol and / or polyol to the number of hydroxyl groups originating from a2) the at least one acrylate- and / or methacrylate-functionalized diol or polyol, i.e. the molar ratio of the corresponding hydroxyl groups, is preferably selected such that it is between 95 to 5 and 5 to 95, preferably between 80 to 20 and 20 to 80.

[0066] The chemical conversion to polyurethane can be carried out solvent-free—i.e., in the melt—in an organic solvent, or in an aqueous dispersion. In the latter two cases, the polyurethane is dissolved in an organic solvent or dispersed in water. To improve the dispersion of the polyurethane in water, dimethylolpropionic acid or a similarly structured substance can be used, as is known in the art.

[0067] As is also known in the prior art, the reaction to form the corresponding prepolymer can easily be conducted in such a way that only the OH groups react, while the carboxyl function remains uninvolved. Polyurethanes and their preparation are generally known to those skilled in the art.

[0068] Initiator, especially radical initiator

[0069] The adhesive film according to the invention comprises (b) at least one initiator.

[0070] As used herein, the term initiator, especially radical initiator or radical-forming substance, refers to a compound that can initiate a polymerization reaction or crosslinking reaction of the adhesive film. However, the initiator, especially radical initiator, participates only to a very small extent in the reaction and therefore does not form a polymer component that determines the properties of the bond.

[0071] In the present invention, at least one initiator, in particular a radical initiator, is added to the reactive adhesive film according to the invention. The initiator is selected such that it does not trigger a reaction in the mixture with the acrylate- and / or methacrylate-functionalized polyurethane at temperatures up to 90°C, even when the mixture is irradiated with UV or blue light. This applies as long as no photoredox catalyst or other activating substance is added to the mixture. The initiator, in particular a radical initiator, is expressly not a photoinitiator. This also applies to the use of more than one initiator, in particular a radical initiator: here, too, none of the compounds mentioned is a photoinitiator.

[0072] Free-radical initiators are preferred. Therefore, in a preferred embodiment, the light-curing, reactive, pressure-sensitive adhesive film according to the invention comprises at least one free-radical initiator as initiator (b). All free-radical initiators known in the prior art can be used. Preferred free-radical initiators are peroxides, especially hydroperoxides.

[0073] In a particularly preferred embodiment of the invention, the radical initiator is an organic peroxide, such as peroxycarboxylic acids and hydroperoxides.

[0074] Hydroperoxides are particularly preferred, in particular diisopropylbenzene hydroperoxide (CAS No. 26762-93-6). Diisopropylbenzene hydroperoxide is preferably used in the form of a 50% by weight solution of diisopropylbenzene hydroperoxide in diisopropylbenzene, available under the trade name Peroxan® IHP-50 (Pergan GmbH, Bocholt, Germany). α,α-Dimethylbenzyl hydroperoxide, also known as cumene hydroperoxide (CAS No. 80-15-9), can also be used. Furthermore, for example, p-menthane hydroperoxide (CAS No. 26762-92-5), tert-amyl hydroperoxide (CAS No. 3425-61-4), tert- -Butyl hydroperoxide (CAS No. 75-91-2) or 1,1,3,3-tetramethylbutyl hydroperoxide (CAS No. 5809-08-5) can be used.

[0075] The proportion of initiators, in particular radical initiators, is preferably in the range from 0.1 to 10% by weight, preferably 0.2 to 5% by weight, based on the total mixture of the components of the reactive adhesive film according to the invention.

[0076] In the context of the present invention, the total mixture of the components of the reactive adhesive film according to the invention represents the total amount of (a) acrylate- and / or methacrylate-functionalized polyurethanes, (b) initiators, (c) photoredox catalysts, and (d) any other optional components used, which together add up to 100 weight percent (wt. %). Solvents and water are used only for production and are not included in this analysis in the total mixture of components of the reactive adhesive film according to the invention. This also applies to solvents that may already be present in the commercially available raw materials.

[0077] Photoredox catalyst

[0078] The adhesive film according to the invention comprises (c) at least one photoredox catalyst.

[0079] As used here, the term photoredox catalyst refers to a light- or UV-sensitive compound which, when excited by light or UV light, can mediate the transfer of electrons between chemical compounds that would otherwise react more slowly or not at all. In contrast to a photoinitiator, a photoredox catalyst does not decompose into reactive fission products upon irradiation with light or UV light, but is merely put into an excited state which is generally relatively long-lasting and from which redox processes can be initiated or mediated. The photoredox catalyst preferably does not trigger any reaction in the mixture with the at least one acrylate- and / or methacrylate-functionalized polyurethane at temperatures up to 90°C, even when the mixture is irradiated with UV or blue light. This applies as long as no radical initiator or other initiating substance is added to the mixture.The photoredox catalyst is therefore not an initiator. When irradiated with UV or blue light, it merely activates the initiator, which then triggers the polymerization or crosslinking reaction. This also applies when two or more photoredox catalysts are used. Here, too, none of the photoredox catalysts is an initiator.

[0080] Photoredox catalysts known to those skilled in the art can be used as photoredox catalysts. Many of the most commonly used photoredox catalysts are polypyridyl transition metal complexes, for example, of ruthenium and iridium, such as Ru(bpm)3. 2+ (e.g. Tris(2,2'-bipyrimide)ruthenium(II) dichloride), Ru(bpz)3 2+ (e.g. Tris(2,2'-bipyrazine)ruthenium bis(hexafluorophosphate)), Ru(bpy)3 2+ , Ru(phen)3 2+ (e.g. Dichlorotris(1,10-phenanthroline)ruthenium(II) chloride), lr[dF(CF3)ppy]2(dtbbpy) +(e.g. [4,4'-ß / s(1,1-dimethylethyl)-2,2'-bipyridine- / 1, A / 1 ']bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridinyl-A / ]phenyl-C]lridium(III) hexafluorophosphate), lr(ppy)3, lr(ppy)2(dtbbpy) + (e.g. [Ir(dtbbpy)(ppy)2] [PF6]), lr(Fppy)3, or fac-lr(ppy)3(fac-tris(2-phenylpyridine)iridium(II I)). But also copper complexes, such as Cu(dap) 2+ (e.g. copper 2,9-bis(4-methoxyphenyl)-1,10-phenanthroline chloride) can be used.

[0081] According to preferred embodiments of the invention, the at least one photoredox catalyst is a transition metal complex with ruthenium as the central atom and bipyridine or a mono- or polysubstituted bipyridine derivative as the ligand. According to further preferred embodiments of the invention, the at least one photoredox catalyst is a transition metal complex with iridium as the central atom and phenylpyridine or a mono- or polysubstituted phenylpyridine derivative as the ligand.

[0082] According to a particularly preferred embodiment of the invention, the photoredox catalyst is selected from: i. [Tris(2,2'-bipyridyl)ruthenium(II)] 2+ , [Ru(bpy)3] 2+ - Formula (la): ii. Tris[2-(2,4-difluorophenyl)pyridine]iridium(lll), lr(Fppy)3; CAS No.: 387859-70-3 - Formula (lb): ill. Tris(2-phenylpyridinato)iridium(l 11), lr(ppy)3; CAS No.: 94928-86-6 - Formula (Ic):

[0083] The preferred counterion of the cation of formula (Ia) is chloride. The corresponding commercially available product contains water of crystallization. The particularly preferred embodiment of the photoredox catalyst of formula (Ia) is thus tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate (CAS No.: 50525-27-4), available from CHEMOS GmbH & Co. KG (Altdorf, Germany, http: / / www.chemos.de). The photoredox catalyst of formula (Ic) is also available from CHEMOS GmbH & Co. KG. The photoredox catalyst of formula (Ib) is available from Strem (Europe) (Bischheim, France, http: / / www.strem.com).

[0084] The proportion of the photoredox catalyst is preferably in the range of up to 1 wt.%, preferably up to 0.5 wt.%, the minimum amount advantageously being 0.01 wt.%, in each case based on the total mixture of the components of the reactive adhesive film according to the invention.

[0085] Preferably, the light-curing, reactive, pressure-sensitive adhesive film according to the invention contains no further activating, initiating or activation and initiation process-influencing components other than those mentioned in this document, in particular no photoinitiators.

[0086] Other components of the reactive adhesive film

[0087] The reactive adhesive film according to the invention may optionally contain further additives and / or auxiliaries known in the art. The proportion of the further additives and / or auxiliaries may range from 0 to 60 wt. %, preferably 0 to 40 wt. %, particularly preferably 0 to 20 wt. %, based on the total mixture of the constituents of the reactive adhesive film according to the invention. Examples of further additives and / or auxiliaries include fillers, dyes, nucleating agents, rheological additives (for example, fumed silica), blowing agents, adhesion-enhancing additives (adhesion promoters, in particular silanes and tackifier resins), compounding agents, plasticizers, and / or anti-aging, light- and UV-protective agents, for example in the form of primary and secondary antioxidants. Additives can also fulfill several functions simultaneously.

[0088] The further components of the reactive adhesive films according to the invention can also be reactive monomers or oligomers.

[0089] According to preferred embodiments of the invention, the reactive adhesive film according to the invention additionally contains reactive monomers, in particular (meth)acrylate monomers. This allows the properties of the adhesive film to be particularly well adapted to the respective requirements with a great deal of design flexibility. Advantageously, the monomers are selected so that they have the lowest possible vapor pressure, so that the object underlying the invention is still achieved as optimally as possible.

[0090] According to further preferred embodiments of the invention, the reactive adhesive film according to the invention contains no additional reactive monomers and is thus free of reactive monomers. The term "free of" in the context of the present invention also includes a certain residual amount as an impurity, so that the amount of reactive monomers in these embodiments is preferably 0 to 0.01 wt. %, but in particular 0 wt. According to these embodiments, the object underlying the invention is achieved particularly well.

[0091] Additional film-forming substances can also be components of the reactive adhesive film according to the invention, as well as polymers of monomers comprising N-vinyl compounds, as described in EP 4159775 B1.

[0092] Reactive adhesive film

[0093] The light-curing, reactive, pressure-sensitive adhesive film according to the invention is in the form of a film. As used herein, the term "adhesive film" (or adhesive layer, adhesive sheet) is intended to encompass a fully or partially applied application of the light-curing, reactive adhesive mixture, as described below. For example, a spot-like application of the adhesive that does not completely cover the substrate surface(s) to be bonded can also lead to a permanent bond within the meaning of the present invention.

[0094] The light-curing, reactive, pressure-sensitive adhesive film according to the invention comprises, in a preferred embodiment,

[0095] (a) 10 to 99 wt.% of at least one acrylate and / or methacrylate-functionalized polyurethane, and

[0096] (b) 0.1 to 10.0 wt.% of at least one initiator, and

[0097] (c) up to 1.0 wt.% of at least one photoredox catalyst, and optionally (d) 0 to 60 wt.% of further additives and / or auxiliaries, the sum of the amounts of the constituents being 100 wt.%.

[0098] Even more preferred are

[0099] (a) 50 to 99 wt.% of at least one acrylate and / or methacrylate-functionalized polyurethane, and

[0100] (b) 0.5 to 8.0 wt.% of at least one initiator, and

[0101] (c) up to 0.5 wt.% of at least one photoredox catalyst,

[0102] (d) 0 to 40 wt.% of further additives and / or auxiliaries, the sum of the amounts of the components being 100 wt.%.

[0103] Most preferred are

[0104] (a) 80 to 99 wt.% of at least one acrylate and / or methacrylate-functionalized polyurethane,

[0105] (b) 1.0 to 5.0 wt.% of at least one initiator,

[0106] (c) up to 0.2 wt.% of at least one photoredox catalyst, (d) 0 to about 20 wt.% of further additives, the sum of the amounts of the components being 100 wt.%.

[0107] In a particularly preferred embodiment of the invention, the light-curing, reactive, pressure-sensitive adhesive film according to the invention comprises a mixture of the following components:

[0108] (a) Acrylate- and / or methacrylate-functionalized polyurethane, prepared by reacting a a1 ) polyester diol with the approximate number-average molecular weight M nof 2000 g / mol or a polyester carbonate diol with an approximate number-average molecular weight of 2000 g / mol and a2) 2,3-dihydroxypropyl acrylate (CAS No.: 10095-20-2) or 2,3-dihydroxypropyl methacrylate (CAS No.: 5919-74-4) with a3) a diisocyanate, preferably hexamethylene diisocyanate or isophorone diisocyanate or dicyclohexylmethane-4,4'-diisocyanate in an NCO / OH ratio between 0.9 and 1.0,

[0109] (b) diisopropylbenzene hydroperoxide and

[0110] (c) Tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate.

[0111] A particularly preferred embodiment according to the invention contains 80 to 99 wt.% of the acrylate- and / or methacrylate-functionalized polyurethane, (b) 1.0 to 5.0 wt.% diisopropylbenzene hydroperoxide, (c) up to 0.2 wt.% Tns(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate, based on the total mixture of the components of the reactive adhesive film according to the invention.

[0112] The reactive adhesive film according to the invention generally has a layer thickness (measured with a commercially available thickness gauge, e.g., DM 2000 from Wolf Messtechnik GmbH) in the range of 20 to 200 pm, preferably 30 to 100 pm, more preferably 40 to 60 pm, and particularly preferably 50 pm. To produce greater layer thicknesses, it may be advantageous to laminate several adhesive film layers together.

[0113] In addition, the reactive adhesive film according to the invention is characterized in that it has pressure-sensitive adhesive properties before light curing, where “pressure-sensitive adhesive” is defined as stated above for polyurethane.

[0114] Furthermore, the light-curing, reactive, pressure-sensitive adhesive film according to the invention can comprise further films, foils, layers, carriers, adhesive films, pressure-sensitive adhesive films, release papers and / or release liners.

[0115] Suitable carrier materials are known to those skilled in the art. For example, permanent carriers can include films (polyester, PET, PE, PP, BOPP, PVC, polyimides), nonwovens, foams, fabrics, and / or fabric films. Temporary carriers should be provided with a release layer, which is typically made of a silicone release liner or a fluorinated release liner, or has a polyolefinic character (HDPE, LDPE).

[0116] According to preferred embodiments of the invention, the adhesive film according to the invention is used as a single-layer film, also known to the person skilled in the art as a transfer adhesive tape.

[0117] Here, too, the adhesive tape advantageously includes release paper and / or release liner for simplified storage.

[0118] According to further preferred embodiments of the invention, the reactive adhesive film (A1) according to the invention together with a further reactive adhesive film (A2) according to the invention and a film, a foil, a layer, or a carrier (B) forms a multilayer reactive, pressure-sensitive adhesive tape.

[0119] The reactive, pressure-sensitive adhesive tape of these embodiments thus comprises the layers: a light-curing, reactive, pressure-sensitive adhesive film (A1) according to the present invention; and a further light-curing, reactive, pressure-sensitive adhesive film (A2) according to the present invention; and a film, a foil, a layer, or a carrier (B) which is arranged flatly between the two reactive, pressure-sensitive adhesive films (A1) and (A2).

[0120] This results in a three-layer, reactive, pressure-sensitive adhesive tape in the layer arrangement (A1 / B / A2).

[0121] According to preferred embodiments of the invention, the adhesive tape consists of the layers A1 / B / A2.

[0122] However, the adhesive tape may also comprise further layers, such as light-curing, reactive, pressure-sensitive adhesive films of the present invention or other adhesive layers or further carrier layers.

[0123] Preferably, the film, foil, layer or carrier (B) is a polyethylene, polypropylene or polyester film, most preferably a polyester film etched with trichloroacetic acid.

[0124] Preferably, the film, foil, layer, or carrier (B) arranged between the two inventive, reactive, pressure-sensitive adhesive films (A1) and (A2) is, according to all embodiments of the adhesive tape, a polyethylene, polypropylene, or polyester film, very particularly preferably a polyester film etched with trichloroacetic acid. Such an etched polyester film with a thickness of 12 μm is available, for example, under the trade name Kemafoil® HPH 100 12p (Coveme SPA, San Lazzaro di Savena, Italy).

[0125] The adhesive tape also advantageously includes release paper and / or release liner for simplified storage.

[0126] Process for producing a reactive adhesive film

[0127] The process according to the invention comprises the following steps: i. producing the at least one acrylate- and / or methacrylate-functionalized polyurethane (a) in one or more solvents or water or solvent-free, ii. dissolving and / or finely dispersing the ingredients (a), (b) and (c) in one or more solvents or water or solvent-free with the exclusion of UV light or visible light of the wavelength by which the respective photoredox catalyst is excited, iii. mixing the dissolved or finely dispersed ingredients, iv. coating a film, a foil, a layer, a carrier, an adhesive film, a pressure-sensitive adhesive film, preferably a release paper or liner with the mixture of dissolved or finely dispersed ingredients according to step iii, v. evaporating solvent or water, unless the previous steps are carried out solvent-free or water-free, vi.Optionally, wind the reactive adhesive film into a roll. The production of the at least one acrylate- and / or methacrylate-functionalized polyurethane (a) according to step i. has already been described above and is carried out in one or more solvents or water, or solvent-free.

[0128] According to step ii, the ingredients are dissolved or finely dispersed in one or more solvents and / or water. Suitable solvents are known in the art, with preference given to solvents in which at least one of the ingredients exhibits good solubility. Acetone and methyl ethyl ketone (MEK) are particularly preferred.

[0129] As used herein, the term ingredient includes (a) the at least one acrylate- and / or methacrylate-functionalized polyurethane, (b) at least one initiator, (c) at least one photoredox catalyst, and (d) optionally the other optionally present components as indicated above.

[0130] The production of the light-curing, reactive, pressure-sensitive adhesive film according to the invention takes place at the latest from the addition of the photoredox catalyst in step ii., excluding UV light or visible light of the wavelength by which the respective photoredox catalyst is excited, in particular violet and blue light.

[0131] As a rule, and in the context of the present invention, these are preferably wavelengths of less than 500 nm, in particular 300 to 500 nm. The exclusion can generally be achieved with commercially available yellow light lamps and by covering normal light sources that have UV components and / or violet and blue light components in their wavelength spectrum with commercially available UV-protective yellow light films.

[0132] The dissolved or finely dispersed ingredients are then mixed according to step 3. using conventional mixing equipment. If necessary, the ingredients are dissolved, finely dispersed, and mixed simultaneously.

[0133] Subsequently, according to step iv, a film, foil, layer, carrier, adhesive film, pressure-sensitive adhesive film, preferably a release liner or release paper, is coated with the mixture of dissolved, finely divided ingredients. The coating is carried out using conventional techniques known in the art.

[0134] If the previous steps are not carried out solvent-free or water-free, the solvent or water is removed by evaporation after coating as per step v.

[0135] Depending on the solvents used, this is preferably done in the temperature range of 60 to 80 °C, for example.

[0136] If necessary, the reactive adhesive film can be wound into a roll in a further step vi.

[0137] For storage, the reactive adhesive film according to the invention is preferably covered with a release liner or paper.

[0138] The production of a three-layer, reactive, pressure-sensitive adhesive tape according to the invention is carried out by producing a first (A1) and a second (A2) reactive, pressure-sensitive adhesive film according to the invention, wherein the two reactive, pressure-sensitive adhesive films according to the invention are brought into contact with a film, a foil, a layer, or a carrier (B) optionally in a laminating process or by direct coating, so that a three-layer, reactive, pressure-sensitive adhesive tape in the layer arrangement (A1 / B / A2) results.

[0139] Substrates

[0140] Substrates suitable for bonding with the reactive adhesive film according to the invention include various plastics, metals, glass, and / or ceramics. The substrates to be bonded can be the same or different. They can be transparent or non-transparent.

[0141] The reactive adhesive film according to the invention is preferably used for bonding plastics, metals, and glass. Polycarbonate, polyamide, anodized aluminum, steel (e.g., stainless steel), and glass (especially surface-treated glass) are particularly preferably bonded.

[0142] The metal substrates to be bonded can generally be made of all common metals and metal alloys. Metals such as aluminum, stainless steel, steel, magnesium, zinc, nickel, brass, copper, titanium, ferrous metals, and alloys are preferred. The parts to be bonded can also be made of different metals.

[0143] Suitable plastic substrates are, for example, polycarbonate (PC), polyamide (PA), acrylonitrile-butadiene-styrene copolymers (ABS), ABS / PC blends, PMMA, glass fiber reinforced polyamides, polyvinyl chloride, polyvinylene fluoride, cellulose acetate, cycloolefin copolymers, liquid crystal polymers (LCP), polylactide, polyether ketones, polyetherimide, polyethersulfone, polymethacrylmethylimide, polymethylpentene, polyphenyl ether, polyphenylene sulfide, polyphthalamide, polyurethanes, polyvinyl acetate, styrene-acrylonitrile copolymers, polyacrylates or polymethacrylates, polyoxymethylene, acrylic ester-styrene-acrylonitrile copolymers, polyethylene, polystyrene, polypropylene and / or polyesters, such as polybutylene terephthalate (PBT) and / or polyethylene terephthalate (PET).

[0144] The substrates can be painted, printed, vapor-coated or sputtered.

[0145] In terms of their shape, the substrates to be bonded are preferably flat or two-dimensionally curved. Depending on the degree of curvature, three-dimensionally curved substrates can also be bonded with the reactive adhesive film according to the invention. The substrates to be bonded can also serve a wide variety of functions, such as housings, viewing windows, stiffening elements, etc.

[0146] It may be necessary to pretreat the surfaces of the substrates to be bonded using a physical, chemical, and / or physico-chemical process. Applying a primer or adhesion promoter composition, for example, is advantageous in this case. Corona, plasma, or flame pretreatment may also be advantageous.

[0147] The reactive adhesive film according to the invention can advantageously be used to bond components in the electronics sector, particularly smartphone and tablet components, such as touchscreens. Preferred bonding applications include the attachment of camera lenses, the bonding of flexible displays of wearables (such as fitness trackers and smartwatches), the attachment / assembly of antennas or backlight units in smartphones or tablets, FPC (flexible printed circuit) assembly or membrane lamination, and the assembly of loudspeakers. Bonding processes

[0148] The reactive adhesive film according to the invention can be used in a process for bonding two substrates, e.g. substrate 1 (e.g. polycarbonate) with another substrate 2 (e.g. metal), in order to obtain a composite body.

[0149] This method according to the invention for bonding two substrates preferably comprises the following steps:

[0150] (xi) providing a first substrate S1;

[0151] (xii) providing a second substrate S2;

[0152] (xiii) arranging the reactive adhesive film according to the invention or the reactive, pressure-sensitive adhesive tape according to the invention on substrate S1;

[0153] (xiv) Either before or after disposing the adhesive film or the adhesive tape on the substrate S1: irradiating the adhesive film or the adhesive tape with UV or blue light to form an irradiated adhesive film or an irradiated adhesive tape and to cause curing;

[0154] (xv) arranging the two substrates S1 and S2 so that they are bonded together by the irradiated adhesive film or the irradiated adhesive tape; and

[0155] (xvi) After placement: allowing the irradiated adhesive film or the irradiated adhesive tape to cure as a result of irradiation.

[0156] Alternatively, the irradiation in step (xiv) can also take place after the two substrates (xv) have been arranged or joined, in particular in the case that at least one substrate is transparent to the activating radiation.

[0157] Composite body

[0158] Furthermore, according to the invention, a composite body comprising at least two bonding surfaces is provided, in which the two bonding surfaces are connected by the cured reactive adhesive film according to the invention or by the cured reactive pressure-sensitive adhesive tape as defined above.

[0159] Product features

[0160] The reactive adhesive film according to the invention exhibits outstanding product properties that were unforeseeable even by a person skilled in the art. Depending on the photoredox catalyst used, the adhesive film can be cured with a commercially available UV-LED lamp or a blue-light LED lamp (e.g., 365 nm, 385 nm, 395 nm, 405 nm, 450 nm, and 460 nm wavelength). Surprisingly, it has been found that in many cases, either a UV-LED lamp or a blue-light LED lamp is equally suitable. A commercially available mercury vapor UV lamp may also be suitable.

[0161] Examples of suitable LED light sources for curing the reactive adhesive films according to the invention include the following products from Hönle (Dr. Hönle AG, Gilching, Germany, https: / / www.hoenle.de / ): a) LED Spot 100 HP IC 365 nm (UV LED) b) LED Spot 100 HP IC 460 nm (blue light LED)

[0162] An irradiation chamber tailored to these light sources is the LED Cube 100 IC, also from Hönle. The suitable dose is approximately in the range of 10 to 80 J / cm 2 For this purpose, a power of 30% to 90% is typically selected on the aforementioned devices. The irradiation duration is selected between 10 and 60 seconds. The distance between the light source and the reactive adhesive film according to the invention is approximately 2 to 10 cm. When using other devices with different power levels, significant deviations from the specified guideline values ​​are to be expected.

[0163] After irradiation, the adhesive film does not cure instantly. It initially remains tacky. Bonding or joining the substrates is possible within a period of at least five minutes, and depending on the photoredox catalyst used and the precise adhesive formulation, sometimes even up to 30 minutes. In other words, the adhesive film according to the invention has an open time of at least five minutes after irradiation and thus the initiation of curing. The adhesive film according to the invention cures completely within a period of approximately 24 hours after the end of irradiation. Curing occurs independently of light and thus also in the dark. Thus, even non-transparent substrates can be bonded with the adhesive film / adhesive film according to the invention.

[0164] High bond strengths can be achieved with the reactive adhesive film according to the invention. In push-out tests, values ​​of greater than 2.0 MPa can be achieved for bonds between polycarbonate test specimens (PC-PC: polycarbonate to polycarbonate), and with preferred embodiments, even values ​​of greater than 6.0 MPa (see examples). Bonds between steel, anodized aluminum, and polyamide also result in acceptable bond strengths that are significantly higher than those of non-reactive pressure-sensitive adhesives. Good results can also be achieved in mechanical shock tests. Furthermore, the adhesive films according to the invention exhibit good shock properties. The reactive adhesive films according to the invention also exhibit good storage stability, as the examples demonstrate. Furthermore, no post-curing due to crystallization processes occurs in the cured bonds, since crosslinked polyurethanes, unlike many non-crosslinked polyurethanes, do not crystallize.The bond strengths achieved after curing are therefore stable in this regard.

[0165] The fact that high bond strengths can be achieved with the reactive adhesive films according to the invention is surprising in that the adhesive films do not contain any reactive monomers. Thus, the flowable components that the skilled person assumes are necessary for adhesion development are missing. The significant cohesion buildup, which becomes apparent in comparison with the comparative examples, is also surprising given the absence of reactive monomers. The skilled person may possibly predict that the reactive adhesive films according to the invention would crosslink upon irradiation, but the significant increase in cohesive strength and the simultaneous adhesion development, both necessary for high bond strength, are surprising.

[0166] A further advantage of the reactive adhesive film according to the invention is that the density of reactive centers can be controlled by adjusting the proportion of acrylate- and / or methacrylate-functionalized diol and / or polyol in the polyurethane, without having to change the proportion of flowable components in the formulation. Thus, increasing or decreasing the proportion of reactive centers influences the viscoelastic properties of the not yet cured reactive adhesive film according to the invention less than is the case when control is achieved via the proportion of reactive monomers, which are generally liquid.

[0167] Experimental part

[0168] The following examples serve to illustrate the present invention, but should in no way be construed as limiting its scope. Table 1 lists the raw materials and materials used to produce the inventive light-curing, pressure-sensitive, reactive adhesive film, the three-layer light-curing, reactive pressure-sensitive adhesive tape, and the comparative examples, each with a trade name, manufacturer's or source's information, and the technical data relevant to this invention.

[0169] Table 1 * The hydroxyl number of the polyester carbonate diol and the polyester diol was determined according to DIN 53240. According to this method, the hydroxyl number (OHN) is expressed in [mg KOH / g]. It corresponds to the amount of KOH in [mg] that is equivalent to the amount of acetic acid bound during the acetylation of 1 g of polyol. To simplify formulation calculations, the hydroxyl number is converted to the unit [mmol OH / kg] in this document.

[0170] This is done according to the following formula: OH [mmol OH / kg] = OH [mg KOH / g] x 1000 / 56.1. 56.1 is the molar mass of KOH.

[0171] The OH and NCO numbers of the remaining diols and the diisocyanate were calculated directly from the respective molecular weights, taking into account the respective functionality.

[0172] Commercially available siliconized release liners (release films) were also used. Acetone (CAS No. 67-64-1) was used as the solvent in the examples and comparative examples.

[0173] Preparation of a solution of the acrylate- or methacrylate-functionalized polyurethane

[0174] The acrylate- or methacrylate-functionalized polyurethane was prepared by first weighing the polyester(carbonate)diol and stirring it for two hours in a conventional heatable and evacuable laboratory mixer (e.g., from PC Laborsystem) under vacuum at a temperature of 70°C. The diol was then transferred to a screw-top jar. After brief cooling, the solvent (acetone), the 2,3-dihydroxypropyl(meth)acrylate, and the catalyst (Coscat® 83) were added and stirred for 30 minutes without vacuum and without heating using a commercially available laboratory stirrer. The diisocyanate was then added and stirred until homogeneous. The chemically reacting mixture was stirred for a further 90 minutes, with the small amounts of escaping solvent being continuously replenished. To complete the reaction, the sealed screw-top jar was stored in an oven at 40°C for 7 days.

[0175] The following polyurethane solutions were prepared: PU-1 : NCO / OH ratio: 0.93

[0176] PU-2: NCO / OH ratio: 0.97

[0177] PU-3: NCO / OH ratio: 0.93 PU-4: NCO / OH ratio: 0.97

[0178] PU-5: NCO / OH ratio: 0.93

[0179] PU-6: NCO / OH ratio: 0.97 PU-7: NCO / OH ratio: 0.93

[0180] PU-8: NCO / OH ratio: 0.97

[0181] PU-9 comparison: NCO / OH ratio: 0.97 Preparation of an aqueous photoredox catalyst solution

[0182] The photoredox catalyst was used to produce the adhesive film according to the invention as a 5% by weight aqueous solution. This solution was obtained as follows:

[0183] Aqueous tris(2,2'-bipyridyl)ruthenium(l I) chloride hexahydrate solution

[0184] Under yellow light, 5 g of tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate and 95 g of deionized water were weighed into a brown screw-top jar. The jar was sealed. The tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate was completely dissolved by rolling the jar on a roller bench for 8 hours.

[0185] Example 1

[0186] Production of a reactive adhesive film according to the invention and a three-layer reactive adhesive tape according to the invention

[0187] In a brown screw-top jar, 95.78 g of the 70 wt.% polyurethane solution PU-1 and 3.40 g of Peroxan® IHP-50 (contains 50 wt.% diisopropylbenzene hydroperoxide) were weighed and mixed with a commercially available laboratory stirrer for 15 minutes at medium speed (500-1000 rpm).

[0188] All further procedures were performed under yellow light. The yellow light ceiling illumination was provided by the LT35WT5EQ / Yellow Special fluorescent lamp from NARVA Lichtquellen GmbH (NARVA Lichtquellen GmbH + Co. KG, Brand-Erbisdorf, Germany, www.narva-bel.de), which blocks wavelengths below 500 nm. To mask any residual light from other light sources, the Metolight SFLY-5 yellow film (ASMETEC GmbH, Kirchheimbolanden, Germany, www.asmetec.de), which filters out wavelengths below 470 nm, was used.

[0189] 0.82 g of the 5 wt% aqueous tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate solution was added and mixed for 5 minutes using a laboratory stirrer at medium speed. The mixture was then further mixed for 24 hours on a commercially available roller bench.

[0190] The resulting homogeneous mixture was spread three times in succession using a commercially available laboratory spreader (e.g., from SMO, Sondermaschinen Oschersleben GmbH, Oschersleben, Germany) with a doctor blade onto a siliconized polyester film (release liner), resulting in three films. The solvent was then evaporated for 15 minutes at 60 °C in a circulating air drying cabinet. The gap width during spreading was varied. It was adjusted twice so that a 50 μm thick film was obtained each time after evaporation of the solvent. In the third spreading test, the gap width was adjusted so that a 100 μm thick film was obtained after evaporation of the solvent. The resulting light-curing, reactive, pressure-sensitive, 100 μm thick adhesive film was covered with a second siliconized polyester film (release liner).Circular blanks with a diameter of 21 mm were then punched out and stored in a light-tight plastic container until testing. The tests were conducted two weeks after the blanks were produced and after six months of storage at 23°C and 50% relative humidity.

[0191] To produce a three-layer, reactive adhesive tape according to the invention, the first of the two 50 μm thick, reactive adhesive films was laminated to the trichloroacetic acid-etched polyester film Kemafoil® HPH 100 12p. This was done at room temperature, for example, using a smooth laminating roller (pressure roller) under light pressure. The second 50 μm thick, reactive adhesive film was then laminated in the same way to the other side of the trichloroacetic acid-etched polyester film. The resulting three-layer, light-curing, reactive pressure-sensitive adhesive tape was covered on both sides with a siliconized polyester film (release liner). Ring-shaped diecuts with an outer diameter of 18 mm and an inner diameter of 13 mm were then punched out. These were also stored in a light-tight plastic container until testing.Here, too, the test was carried out two weeks after production of the die-cuts and after six months of storage of the die-cuts at 23 °C and 50% relative humidity.

[0192] The percentage composition of the initial weights for the preparation of the solution / mixture of the light-curing, reactive, pressure-sensitive adhesive film as well as the percentage composition of the light-curing, reactive, pressure-sensitive adhesive film itself are listed in the following two tables: Example 1, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film Example 1, Percentage composition of the reactive adhesive film

[0193] In an analogous manner to Example 1, the inventive reactive adhesive films and the inventive three-layer reactive adhesive tapes of the further examples and comparative examples were produced.

[0194] Example 2, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film Example 2, Percentage composition of the reactive adhesive film

[0195] Example 3, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film

[0196] Example 3, Percentage composition of the reactive adhesive film

[0197] Example 4, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film Example 4, Percentage composition of the reactive adhesive film

[0198] Example 5, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film

[0199] Example 5, Percentage composition of the reactive adhesive film

[0200] Example 6, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film Example 6, Percentage composition of the reactive adhesive film

[0201] Example 7, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film

[0202] Example 7, Percentage composition of the reactive adhesive film

[0203] Example 8, Percentage composition of the solution / mixture for the preparation of the reactive adhesive film Example 8, Percentage composition of the reactive adhesive film

[0204] Comparison examples

[0205] Comparative example 1 corresponds to example 4, except that no irradiation occurs.

[0206] Percentage composition of the solution / mixture

[0207] Comparative Example 1 corresponds to Example 4, except that no irradiation is used. Percentage composition of the film Comparative Example 2, Percentage composition of the solution / mixture

[0208] Comparative example 2, percentage composition of the film

[0209] Comparative Example 3, Percentage composition of the solution / mixture

[0210] Comparative Example 3, Percentage Composition of the Film Comparative Example 4, Percentage composition of the solution / mixture

[0211] Comparative Example 4, Percentage Composition of the Film

[0212] Comparative Example 5, Percentage composition of the solution / mixture

[0213] Comparative Example 5, Percentage Composition of the Film Comparative Example 6, Percentage composition of the solution / mixture

[0214] Comparative Example 6, Percentage Composition of the Film Comparative Example 7, Percentage composition of the solution / mixture

[0215] Comparative Example 7, Percentage Composition of the Film Push-out test and mechanical shock test

[0216] The push-out test allows statements to be made about the bond strength of a double-sided adhesive product in the direction of the adhesive layer normal under continuously increasing pressure load.

[0217] The mechanical shock test allows statements to be made about the bond strength of a double-sided adhesive product in the direction of the adhesive layer normal under an undamped impact load.

[0218] Test specimens for the push-out test and the mechanical shock test

[0219] Circular plates (disks) with a diameter of 21 mm were used.

[0220] Furthermore, square perforated plates with a side length of 40 mm each were used. The hole is located centrally in the center. It is round, with a hole diameter of 9 mm each. The discs used were made of polycarbonate, anodized aluminum, and SUS steel. The square perforated plates used were made of polycarbonate, polyamide, anodized aluminum, and SUS steel.

[0221] In detail, the following test specimens were used: a) Discs:

[0222] - Plastic discs made of polycarbonate (PC) Makrolon 099, milled burr-free, 21 x 3 mm Discs made of anodized aluminum (AI), alloy 5005A, AIMgl, anodized E6 EV1, 21 x 2 mm

[0223] - Steel discs, steel grade VA1.4301 (equivalent to SUS 304), outer contour laser-cut, mirror polished on one side, 21x2 mm b) Square perforated plates:

[0224] Plastic test specimen made of polycarbonate (PC), make Makroform 099, 40x40x4 mm, plastic hole in the center, D = 9 mm

[0225] Plastic test specimen made of polyamide (PA), glass fiber reinforced, made of PA6 granulate, natural, 25% GF, Ultramid B3 WG5, 40x40x4 mm, plastic bore in the center, D = 9 mm. Test specimen made of aluminum (AI), alloy 5005A, AIMgl, anodized E6 EV1, 40x40x3 mm, aluminum bore in the center, D = 9 mm.

[0226] - Steel test specimens, steel grade VA1.4301 (equivalent to SUS 304), laser-cut inner and outer contours, mirror-polished surfaces, 40 x 40 x 3 mm, centered steel bore, diameter = 9 mm. The plastic and aluminum test specimens were purchased from Rocholl GmbH (Eschelbronn, Germany, https: / / rocholl.eu / ). The steel test specimens were supplied by Classen GmbH (Rellingen, Germany, www.classen-laser.de / ).

[0227] Sample preparation for the push-out test and the mechanical shock test A distinction is made between the single-layer, light-curing, reactive, pressure-sensitive adhesive films according to the invention, which were presented as 100 pm thick circular die-cuts (round blanks), and the three-layer, reactive adhesive tapes according to the invention, which consist of two 50 pm thick reactive films and the 12 pm thick polyester film etched with trichloroacetic acid, arranged in the middle between the two 50 pm thick reactive films, and were presented as die-cut rings.

[0228] The release liners of the die cuts were removed from one side of each die cut.

[0229] The punched pieces were each placed centrally on a test specimen blank.

[0230] The die cuts now adhered to the test specimen discs.

[0231] The remaining release paper was then removed from the die-cuts. The test specimen discs were now coated with the single-layer reactive adhesive films (discs) and the three-layer reactive adhesive tapes (rings).

[0232] Irradiation for the push-out test and the mechanical shock test

[0233] In a first series of experiments, the irradiations were carried out exclusively with UV LED light (365 nm), and in a second series, exclusively with a blue light LED (460 nm). The dose was selected as follows:

[0234] - LED Spot 100 HP IC 365 nm (UV LED): 30.0 - 34.0 J / cm 2

[0235] - LED Spot 100 HP IC 460 nm (blue light LED): 50.0 - 55.0 J / cm 2

[0236] The dose of UV and blue LED light was measured with a UV meter from Hönle (Dr. Hönle AG, Gilching, Germany, https: / / www.hoenle.de / ), the UV light with the area sensor UVA F0 (340-405 nm), the blue LED with the area sensor VIS F1 (360-550 nm).

[0237] The time interval between the end of irradiation and the joining of the test specimens was always between one and two minutes. Multiple checks were performed, and it was found that time intervals of at least five minutes or more are possible without any deterioration in bond strength.

[0238] Bonding for the push-out test and the mechanical shock test

[0239] The test specimen discs equipped with the irradiated die cuts were positioned on the perforated plate with the exposed side of the die cuts facing upwards, so that the center of the disc and the center of the hole in the perforated plate were aligned. The composite of the square perforated plate, the irradiated die cut, and the test specimen disc, held together by the adhesive strength of the die cuts, was then pressed together using a press from Howe Elektrotechnik eK (Glinde, Germany, https: / / howe-hamburg.de / ). The pressing parameters were 3 bar, 30 seconds.

[0240] After pressing, the composite was stored for three days under standard conditions of 23 °C and 50% relative humidity (RH). This resulted in a gradual curing reaction within the die-cuts and a gradually increasing adhesion between the die-cuts and the test specimens. This resulted in a bond with a gradual increase in strength over time. Push-out tests and mechanical shock tests (fresh values) were then performed.

[0241] To assess storage stability, unirradiated and unbonded die-cuts covered on both sides with release liners were stored in the dark for six months under standard conditions at 23 °C and 50% relative humidity. The die-cuts were then irradiated and bonded as described above. Push-out tests and mechanical shock tests were then performed.

[0242] The test specimens were bonded in the following combinations:

[0243] • PC blank against PC plate

[0244] • PC blank against PA plate

[0245] • Al-Ronde versus Al-Platte

[0246] • Steel blank against steel plate

[0247] The bonding surfaces were:

[0248] Circular die cuts (round blanks): 283 mm 2 (taking into account the 9 mm hole in the plates)

[0249] Ring-shaped die cuts: 122 mm 2 [Implementation] of the push-out test

[0250] Using a mandrel clamped in a tensile testing machine, pressure was applied perpendicularly to the test specimen disc through the hole in the perforated plate at a constant speed of 10 mm / min (i.e., parallel to the normal vector to the test specimen plane; centered on the hole center) until the bond loosened to such an extent that a pressure drop of 50% was recorded. The pressure acting immediately before the pressure drop is the maximum pressure Pmax. This value corresponds to the push-out values ​​[MPa] specified in the tables. All measurements were conducted in an air-conditioned room at 23 °C and 50% relative humidity (RH).

[0251] Carrying out the mechanical shock tests

[0252] The mechanical shock tests were limited to the three-layer, reactive adhesive tapes according to the invention and to irradiation with blue light. The bonded test specimens were each clamped in a specimen holder so that the composite was aligned horizontally, with the discs at the bottom and the square perforated plates at the top. The specimen holder was then centrally inserted into the designated receptacle of the device used ("DuPont Impact Tester", Cometech, TAIWAN, Model QC-641). The impact head was placed in the hole of the square perforated plate so that the circular, rounded impact geometry with a diameter of 5 mm rested centrally and flush on the bonding side of the disc.A weight (sled) with a mass of 307 g, guided by two guide rods, was dropped vertically from a height of 5 cm onto the prepared assembly consisting of the specimen holder, bonded test specimen, and impact head (measurement conditions: 23 °C, 50% relative humidity). The height of the dropping weight (h) was increased in 5 cm increments until the applied impact energy destroyed the bond due to the impact load and the disc detached from the square perforated plate. In all cases in which the bond was destroyed from a height of 5 cm, these measurements were repeated using a sled with a mass of 156 g. The energy at which the bond is destroyed corresponds to the impact energy values ​​​​given in the tables. These impact energy values, also called DuPont shock values, were calculated as follows: DuPont shock value [mJ / cm]. 2 ] = 1000*(m(slide)[kg]*9.81 [kg / m*s 2]*h[m]) / A(bonding area)[cm 2 ]

[0253] Push-out test and mechanical shock test results

[0254] For all examples (inventive and comparative examples) and all measured properties, the mean value of three individual measurements was determined.

[0255] Fracture patterns:

[0256] A = Adhesive; K = Cohesive; M = Mixed fracture

[0257] Example 1

[0258] Push-out tests

[0259] Single-layer product (round blank) Push-out tests

[0260] Three-layer product (ring) Shock tests

[0261] Three-layer product (ring)

[0262] Example 2 Push-Out Tests

[0263] Single-layer product (round blank)

[0264] Push-out tests

[0265] Three-layer product (ring) Shock tests

[0266] Three-layer product (ring)

[0267] Example 3 Push-Out Tests

[0268] Single-layer product (round blank)

[0269] Push-out tests

[0270] Three-layer product (ring) Shock tests

[0271] Three-layer product (ring)

[0272] Example 4 Push-Out Tests

[0273] Single-layer product (round blank)

[0274] Push-out tests

[0275] Three-layer product (ring) Shock tests

[0276] Three-layer product (ring)

[0277] Example 5 Push-Out Tests

[0278] Single-layer product (round blank)

[0279] Push-out tests

[0280] Three-layer product (ring) Shock tests

[0281] Three-layer product (ring)

[0282] Example 6 Push-Out Tests

[0283] Single-layer product (round blank)

[0284] Push-out tests

[0285] Three-layer product (ring) Shock tests

[0286] Three-layer product (ring)

[0287] Example 7 Push-Out Tests

[0288] Single-layer product (round blank)

[0289] Push-out tests

[0290] Three-layer product (ring) Shock tests

[0291] Three-layer product (ring)

[0292] Example 8 Push-Out Tests

[0293] Single-layer product (round blank)

[0294] Push-out tests

[0295] Three-layer product (ring) Shock tests

[0296] Three-layer product (ring) Comparison examples

[0297] Comparison example 1

[0298] Push-out tests

[0299] Single-layer product (round blank) The product did not cure. It remained tacky after bonding and subsequent storage for three days under standard conditions.

[0300] Comparative example 2 push-out tests

[0301] Single-layer product (round blank)

[0302] Storage under standard conditions: unchanged adhesive strength. Comparative Example 3

[0303] Push-out tests

[0304] Single-layer product (round blank) Storage under standard conditions: unchanged adhesive properties.

[0305] Comparison example 4

[0306] Push-out tests single-layer product (round blank)

[0307] Storage under standard conditions: unchanged adhesive strength. Comparative Example 5

[0308] Push-out tests

[0309] Single-layer product (round blank)

[0310] After exposure to UV light, the product cured instantly, making bonding impossible. After exposure to blue light, the product did not cure. It remained tacky after exposure and subsequent storage for three days under standard conditions.

[0311] Comparative example 6 Push-out tests: Single-layer product (round blank)

[0312] After UV light irradiation, the product cured instantly, making bonding impossible. After blue light irradiation, the product did not cure. It remained tacky after irradiation and subsequent 3 days of storage under standard conditions. Comparative Example 7

[0313] Push-out tests single-layer product (round blank)

[0314] After exposure to UV light, the product cured instantly, making bonding impossible. After exposure to blue light, the product did not cure. It remained tacky after exposure and subsequent storage for three days under standard conditions.

[0315] Shock tests were also conducted with three-layer products (ring) from comparative examples 1 to 7. All of the above apply analogously to the production of comparative examples 1 to 7. The results showed that none of the products cured in the comparative examples. Each of the products remained unchanged in its tackiness after bonding and subsequent storage for three days under standard conditions.

[0316] All test specimens of all comparison examples have the lowest possible shock energy value of 63 mJ / cm 2, which can be achieved with a 156 g sled weight in the test setup used (5 cm minimum drop height), was not reached. Therefore, a more precise value than < 63 mJ / cm 2 not possible as a result of the shock tests.

[0317] This applies to all test specimen substrates, i.e. PC / PC, PA / PC, Al / Al and steel / steel I.

[0318] Discussion of the results

[0319] The reactive adhesive film according to the invention can be cured with both UV LED light and blue LED light. After irradiation, it does not cure immediately, but has an open time of at least 5 minutes. It cures further in the dark, making it suitable for bonding non-transparent substrates. High bond strengths can be achieved with the reactive adhesive film according to the invention. This was particularly clearly demonstrated for polycarbonate bonds. However, bonds of aluminum, polyamide (PA), and SUS steel also exhibit bond strengths that are significantly higher than those of pressure-sensitive adhesives. Good values, which reflect the high bond strength, particularly for polycarbonate bonds, can also be achieved in the mechanical shock test. The reactive adhesive films according to the invention also exhibit good storage stability, as the examples show.

[0320] The reactive adhesive film according to the invention represents an improvement over the prior art in that it functions even without reactive monomers, meaning that no reactive monomers are necessary to achieve a bond strength that significantly exceeds the bond strength the adhesive film has when uncured, i.e., in its pressure-sensitively tacky state prior to irradiation with light. This is particularly evident in comparison with Comparative Example 1.

[0321] This is surprising, since the absence of reactive monomers eliminates the flowable components that one skilled in the art would assume are necessary for adhesion development. The significant cohesion buildup evident in comparison with the comparative examples is also surprising given the absence of reactive monomers. One skilled in the art may predict that the reactive adhesive films of the invention would crosslink upon irradiation, but the significant increase in cohesive strength and the simultaneous adhesion buildup, both necessary for high bond strength, are surprising.

[0322] Comparative Examples 2, 3, and 4 demonstrate that both the (meth)acrylate function and the initiator and photoredox catalyst are necessary components of the reactive adhesive film according to the invention. A commercially available photoinitiator does not represent an alternative as a substance that triggers the curing reaction, either as a replacement for the initiator or as a replacement for the photoredox catalyst, as Comparative Examples 5, 6, and 7 demonstrate.

Claims

Patent claims 1. A light-curing, reactive, pressure-sensitive adhesive film comprising (a) at least one acrylate and / or methacrylate functionalized polyurethane, (b) at least one initiator, and (c) at least one photoredox catalyst.

2. Light-curing, reactive, pressure-sensitive adhesive film according to claim 1, characterized in that the at least one acrylate- and / or methacrylate-functionalized polyurethane comprises the chemical reaction product of a1) at least one diol and / or polyol, a2) at least one acrylate- and / or methacrylate-functionalized diol and / or acrylate- and / or methacrylate-functionalized polyol and a3) at least one di- and / or poly-isocyanate.

3. Light-curing, reactive, pressure-sensitive adhesive film according to claim 2, characterized in that the a2) at least one acrylate- and / or methacrylate-functionalized diol and / or acrylate- and / or methacrylate-functionalized polyol is a diolic or polyolic alkyl (meth)acrylate, wherein the alkyl radical is linear or branched and the alkyl radical has three to twenty, preferably three to ten, again preferably three to six, in particular and for example three or five carbon atoms.

4. Light-curing, reactive, pressure-sensitive adhesive film according to claim 3, characterized in that a2) at least one acrylate- and / or methacrylate-functionalized diol and / or acrylate- and / or methacrylate-functionalized polyol is selected from the group consisting of 2,3-dihydroxypropyl acrylate, 2,3-dihydroxypropyl methacrylate, 1,3-dihydroxy-2-propanyl acrylate, 3-Hydroxy-2,3-bis(hydroxymethyl)propyl acrylate, wherein it is preferably selected from the group consisting of acrylate- and / or methacrylate-functionalized diols, and particularly preferably from 2,3-dihydroxypropyl acrylate and 2,3-dihydroxypropyl methacrylate.

5. Light-curing, reactive, pressure-sensitive adhesive film according to one of the preceding claims, characterized in that (a) at least one acrylate and / or methacrylate-functionalized polyurethane is a thermoplastic polyurethane.

6. Light-curing, reactive, pressure-sensitive adhesive film according to one of the preceding claims, characterized in that the at least one photoredox catalyst (c) Ruthenium as the central atom and bipyridine or a mono- or polysubstituted bipyridine derivative as ligand, or Iridium as the central atom and phenylpyridine or a mono- or polysubstituted phenylpyridine derivative as ligand.

7. Light-curing, reactive, pressure-sensitive adhesive film according to one of the preceding claims, characterized in that the at least one photoredox catalyst (c) [tris(2,2'-bipyridyl)ruthenium(II)] 2+ , tris[2-(2,4-difluorophenyl)pyridine]iridium(l II) or tris(2-phenylpyridinato)iridium(l II).

8. Light-curing, reactive, pressure-sensitive adhesive film according to one of the preceding claims, comprising (a) 10 to 99 wt.% of at least one acrylate and / or methacrylate functionalized polyurethane, (b) 0.1 to 10.0 wt.% of at least one initiator, (c) up to 1.0 wt.% of at least one photoredox catalyst.

9. Light-curing, reactive, pressure-sensitive adhesive film according to claim 8 comprising (a) 50 to 99 wt.% of at least one acrylate and / or methacrylate functionalized polyurethane, (b) 0.5 to 8.0 wt.% of at least one initiator, (c) up to 0.5 wt.% of at least one photoredox catalyst.

10. Light-curing, reactive, pressure-sensitive adhesive film according to one of the preceding claims, comprising further films, foils, layers, carriers, adhesive films, pressure-sensitive adhesive films, release papers and / or release liners.

11. A light-curing, reactive, pressure-sensitive adhesive tape comprising the layers: a light-curing, reactive, pressure-sensitive adhesive film (A1) according to any one of claims 1 to 10; and a further reactive, pressure-sensitive adhesive film (A2) according to any one of claims 1 to 10; and a film, a foil, a layer, or a carrier (B) arranged flat between the two reactive, pressure-sensitive adhesive films (A1) and (A2).

12. A process for producing a light-curing, reactive, pressure-sensitive adhesive film according to one of claims 1 to 10, characterized in that the process comprises the following steps: vii. producing the at least one acrylate- and / or methacrylate-functionalized polyurethane (a) in one or more solvents or water or solvent-free, viii. dissolving and / or finely dispersing the ingredients (a), at least one initiator (b) and at least one photoredox catalyst (c) in one or more solvents or water or solvent-free with exclusion of UV light or visible light of the wavelength by which the respective photoredox catalyst is excited, ix. mixing the dissolved or finely dispersed ingredients, x.Coating a film, foil, layer, carrier, adhesive film, pressure-sensitive adhesive film, preferably a release paper or liner, with the mixture of dissolved or finely divided ingredients according to step iii. xi. Evaporating solvent or water, unless the previous steps are carried out solvent-free or water-free. xii. Optionally, winding the reactive adhesive film into a roll.

13. Use of a light-curing, reactive, pressure-sensitive adhesive film according to one of claims 1 to 10 or of a reactive, pressure-sensitive adhesive tape according to claim 11 for producing bonds on materials selected from plastic, metal, glass and / or ceramic.

14. A composite body comprising at least two bonding surfaces which are bonded together by the cured reactive, pressure-sensitive adhesive film according to one of the preceding claims 1 to 10 or by the cured reactive, pressure-sensitive adhesive tape according to claim 11.

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