Device capable of stain-free debonding on demand

Abstract

The present invention relates to a device comprising an electrically modifiable adhesive (A) on an electrically conductive surface (B), such as a backing or substrate. Upon application of an electric stimulus, the device allows stain-free debonding of the adhesive tape from the conductive adherend surface (S). The debonding process leaves the adherend surface undamaged, maintains the original optical and electrical properties of the substrate, thereby, permits use on sensitive adherend surfaces.

Description

[0001] tesa SE Norderstedt

[0002] DEVICE CAPABLE OF STAIN-FREE DEBONDING ON DEMAND

[0003] TECHNICAL FIELD

[0004] The present invention relates to a device comprising an electro-responsive adhesive. The device may comprise an electrically conductive surface, such as the surface of a backing, on which or in contact with which the electro-responsive adhesive is provided. The adhesive may be debonded from and bonded to a substrate, which typically is an electrically conductive substrate (also referred to as adherend), by applying a first and second stimulus, respectively. The device enables debonding, e.g. removal with significantly less force compared to normal peel-off of the adhesive from the adherend surface, upon application of an appropriate electric stimulus without leaving residues or only very small amounts of residues, thereby minimizing the risk that the adherend's surface's properties are impaired by adhesive residues.

[0005] BACKGROUND ART

[0006] Electrically debondable adhesives can change their adhesion strength when exposed to an electrical stimulus, most often a direct current (DC) voltage. They are therefore well suited for applications where the adhesive must be separated on demand from conductive surfaces, requiring minimal effort.

[0007] Electrically debondable adhesives are disclosed in several forms, including pressuresensitive, hotmelt, and structural bonding adhesives. The latter two require additional activation steps prior to their application, whereas the pressure-sensitive adhesive does not. Regardless of the adhesive form, all comprise some common components in the adhesive such as an adhesive matrix, an electrolyte component, and a crosslinker. The electrolyte is the main component that facilitates the debonding of the adhesive from the electrically conductive adherend surface when an electrical stimulus is applied. Ionic liquids dissolved in the polymer matrix are typically used as electrolytes. Plasticizers are added to it to enhance ionic conductivity, while crosslinkers or crosslinking contribute to improved cohesion strength of the adhesive. Debonding mostly occurs to the cathode side [e.g. where negative DC voltage is applied] of the adhesively bonded assembly. WO 2025 / 068404 Al, WO 2023 / 165966 Al, WO 2022 / 030565 Al, WO 2024 / 204367 Al, US 2023 / 303894 Al, US 2020 / 0002581 Al, WO 2020 / 086454 Al describe electrically debondable pressure-sensitive systems generally comprising an adhesive based on polymer matrix e.g. polyacrylates or synthetic rubbers. The compositions are typically coated onto electrically conductive backings such as metallic foils, conductive polymers, or polymeric films with conductive coatings, and can be configured as single-sided, doublesided, or transfer tapes between conductive substrates. In most cases, debonding proceeds via adhesion failure in application of an electric stimulus.

[0008] CN 119371916 describes an electrically debondable adhesive that incorporates conductive fillers (such as CNTs, graphene, or PEDOT:PSS) together with amino silane-modified electrode materials (Ag nanowires, conductive fibers, or foils). Debonding is triggered by applying a voltage, where the conductive network allows fast release while preserving good adhesion, antistatic performance, and stability under thermal and environmental stress.

[0009] WO 2023 / 175424 Al, WO 2024 / 079548 Al, EP 4 347 246 Al, EP 4 347 245 Al, and US 2024 / 263044 Al disclose electrically debondable structural adhesives comprising a matrix of polymer with epoxy functionality, thermoplastic polymer, crosslinkers, initiators and ionic liquid as electrolyte component. The adhesive is applied between two conductive surfaces activated by light or heat with pressure. On demand, debonding is achieved at the substrate or backing surface by applying usually a negative DC voltage (cathode side). The electrically conductive substrates / backings used are mainly metal / alloy foils or their oxides and conductive polymers. In structural adhesives, debonding generally occurs through adhesion or cohesion failure or mixed failure, enabling the bonded parts to be separated with reduced force.

[0010] WO 2016 / 133864 Al and EP 3199344 Bl similarly disclose reactive polyurethane hotmelt or polyamide adhesives containing 1-30 wt % inorganic or organic salts such as lithium carboxylates or sodium trifluoromethanesulfonate, and they emphasize that salts can be solids rather than ionic liquids.

[0011] WO 2013 / 135677 Al and US 2014 / 0374032 Al discloses hot-melt polyamide adhesive that can be debonded electrically. The patent requires the hot-melt adhesive to contain at least one organic or inorganic salt. The salts can be solid and may include Li, Na or K salts of aliphatic C2-C6mono- or di-carboxylic acids, aromatic mono- or di-carboxylic acids and trifluoromethanesulfonic acid. TECHNICAL PROBLEM

[0012] In view of the prior art, electrically debondable adhesives, particularly of the pressuresensitive adhesive (PSA) type, are mostly prepared using ionic liquids as the main or preferred electrolyte component. While the use of ionic liquids offers several advantages, such as non-volatility, wide temperature range applicability, and allowing debonding to occur through adhesive failure instead of cohesive failure (i.e. tearing within the adhesive layer itself). Despite all benefits, they also lead to some drawbacks, as a non-volatile residue of non-dissociated ionic liquid's layer is always found near the substrate surface after debonding of the adhesive tape [Adv. Mater. Interfaces 2022, 9, 2101447], This residue must be cleaned off for reuse of the substrate, requiring an additional cleaning step. Also, such residues may lead to impairment of the substrate surface, for example by causing corrosion, altering the surface's electrical / optical properties (e.g. causing discoloration), or increasing the surface's roughness, thereby impairing the adhesive strength if the surface is again to be used as a substrate for an adhesive.

[0013] Another issue is that ionic liquids are typically hygroscopic, easily taking up water from the air, and also tend to gradually migrate to the bonded metal surfaces. These effects can cause corrosion and unreliable debonding performance, for example, the tape may delaminate unintentionally under varying environmental conditions, or it may fail to function due to hydrolysis of the anions of ionic liquid.

[0014] In addition to some performance limitations, ionic liquids present cost and environmental concerns. The cost of ionic liquids limits their use in large-scale or cost-sensitive applications. Their persistence and poor biodegradability make disposal and sustainability also difficult.

[0015] Another point is that ionic liquids with fluorinated anions are often considered highly effective for electrically debondable adhesive systems. However, because the process usually requires relatively high bias voltages, anions such as PF6“, BF4“, or TFSI“ can start to break down, releasing toxic and corrosive gases like HF, CF4, or SO2F2. These by-products pose safety, environmental, and reliability risks, which makes fluorinated ionic liquids less suitable for use in electrically debondable adhesives.

[0016] In contrast to the above, some prior art also describes ionic-liquid-free electrically debondable systems. Debonding of these relies on joule heating, which typically results in debonding through cohesive failure and therefore leaves residues / stains on the substrate. In certain cases, the adhesive is not of the pressure-sensitive type and requires further activation before use. Further, many prior art adhesives are debondable-only, i.e. they cannot rebonded upon application of an electric stimulus after debonding, or, once debonded, can be rebonded, which may take longer recovery time and only with very limited adhesive strength as compared to the initial bonding (first bonded) strength. They are thus not reusable multiple times, which leads to improved costs and limited applicability in applications requiring debonding and rebonding.

[0017] OBJECTS OF THE INVENTION

[0018] It is therefore an object of the present invention to overcome one or more of the abovenoted drawbacks of prior adhesives.

[0019] In particular, an object of the present invention is to provide an electrically debondable and rebondable adhesive device (for example, an adhesive tape, wherein the adhesive may be pressure-sensitive) which, upon application of a corresponding first electric stimulus allows for reliable debonding while leaving no or only very little residue, thereby leaving the substrate surface substantially unchanged. The invention aims to achieve stain-free debonding, meaning that after removal of the adhesive (e.g. adhesive tape) low to no visible adhesive residues, or discolorations remain on the substrate, thereby enabling clean and damage free reuse of the bonded parts. The invention also aims to provide a device comprising a pressure sensitive adhesive without ionic liquids as electrolyte components, ensuring clean removability, for example adhesion failure comparable to ionic liquid-based systems, while leaving no visible non-volatile residue on the adherend surfaces.

[0020] The adhesive is aimed to debond on demand when an electric stimulus is applied, for example by using different DC voltages with defined time scales and polarities. After debonding, the adhesive may recover to a higher adhesive strength than in the debonded state, e.g. to the initial bond strength prior to application of any electric stimulus or close thereto, within a short time, making the system suitable for at least a few reworks cycle. Additionally or alternatively, adhesive strength can also be increased by application of a second electric stimulus, to the initial adhesive strength or higher (e.g. to the bonded state).

[0021] A further object of the present invention is to provide an adhesive composition that offers greater stability in the bonded state (for example, avoiding premature failure from the bonded surface or of the backing due to electrolyte migration). A further object of the present invention is to provide an adhesive composition with less to no toxicity hazard before and after debonding operation and is more environmentally friendly.

[0022] A further object of the invention is to provide an electrically debondable adhesive device that does not require a further cleaning operation of the adherend's surface after electrical debonding due to a first electric stimulus in order to remove residues originating from the adhesive, and which can return to a higher bonded state in short periods of time compared to initial bonded state by application of a second electric stimulus.

[0023] SUMMARY OF THE INVENTION

[0024] The present invention is based on the findings that the objects identified above can be achieved by using an aqueous electrolyte (aqueous salt solution) instead a non-aqueous system (e.g. ionic liquids or inorganic salt within an organic matrix) in the adhesive composition.

[0025] In order to achieve one or more of the above objectives, the present invention provides the following embodiments:

[0026] 1. A device comprising: an electro-responsive adhesive whose adhesive properties can be modified from a bonded state to a debonded state by a first electric stimulus, and which i) can return to the bonded state upon the passing of time, or ii) can be modified from a debonded state to a bonded state by applying a second electric stimulus, the first and second electric stimulus differing from each other. wherein the electro-responsive adhesive can be debonded from a substrate surface (ASTM stainless steel) a) without leaving residues or altering the electrical / optical properties or surface roughness of the of the substrate surface. b) leaving residues in an amount of 100 mg / m2or less. 2. The device according to embodiment 1, wherein the adhesive does not contain an ionic liquid, or contains an ionic liquid in an amount of 1% by weight or less.

[0027] 3. The device according to any one of embodiments 1 and 2, wherein the adhesive comprises 1% by weight or more of water, preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, or 5% by weight or more, but 20% by weight or less, such as 15% by weight or less.

[0028] 4. The device according to embodiment 1, 2, or 3, wherein the adhesive does not contain an ionic liquid and contains 1% by weight or more of water, preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, or 8% by weight or more.

[0029] 5. The device according to any of the preceding embodiments, which comprises one or more of an inorganic or an organic salt having melting point above 100 °C except ionic liquid, deep eutectic solvent (mixture of organic or inorganic salt as hydrogen bond acceptor and a hydrogen bond donor), an ionic surfactant, an inorganic or organic acid, an inorganic or an organic base except ionic liquid, preferably selected from the group consisting of alkali metal, earth alkali metal or ammonium halides (e.g. chlorides), sulfates, nitrates, carbonates, phosphates, alkali metal, earth alkali metal or ammonium hydroxide, hydrochloric acid, sulfuric acid, and nitric acid, and wherein preferably present in the form of an aqueous solution at a concentration of 0.1 to 10 mol / L.

[0030] 6. The device according to embodiment 1, which exhibits an initial adhesive strength of 2.5 to 15 N / cm, and after application of an electric stimulus exhibits a debonded adhesive strength of 0.1 to 2 N / cm.

[0031] 7. The device according to any one of the preceding embodiments, wherein the electric stimulus is selected from the group consisting of an alternating current (AC), an alternating voltage, a direct current (DC), a direct voltage, or a pulsed current or voltage, preferably a DC or AC current or voltage in the range of 0.5 - 230 V, more preferably a DC voltage in the range of 2 to 100 V, such as 5 to 20 V.

[0032] 8. The device, according to any one of the preceding embodiments, wherein the adhesive is present on an electrically conductive surface of a backing.

[0033] 9. The device according to any of the preceding embodiments, wherein the device is in the form of an adhesive tape, preferably selected from the group consisting of a singlesided adhesive tape, a double-sided adhesive tape, or a transfer adhesive tape. 10. The device according to any one of embodiments 8 and 9, wherein an anticorrosion adhesive layer with a thickness in the range of I to 20 ^m is present between the electrically conductive backing and the adhesive.

[0034] 11. The device according to any one of embodiments 8 to 10, wherein the backing material comprises a layer on one or both sides that is electrically conductive, preferably formed by at least one member selected from the group consisting of poly(3,4- ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), poly(3,4- ethylenedioxythiophene):p-toluenesulfonate (PEDOT :Tos), poly(3,4- propylenedioxythiophene) (ProDOT), poly(dioxythiophenes), poly(3,4-dialkylthiophenes), polyaniline (PANI), polypyrrole (PPy), poly(2,5-thienylenevinylene) (PTV), polythiophene (PTh), polythiophene derivatives, metallo-supramolecular polymers, polyacetylene (PAc), poly(p-phenylene vinylene) (PPV), polyfluorene (PF), polycarbazole (PCz), polybithiophene (PBTh), a metal foil, or an insulating polymer that has been treated to impart electrical conductivity, for example by depositing a metallic film on a polymer foil or by coating with electrically conductive materials such as carbon, aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, gold foil, silver foil, metallized PET, metallized PP, carbon ink coated film and metallized polyimide.

[0035] 12. The device according to embodiment 8 and 11, wherein the electrically conductive material forming the electrically conductive surface of the backing comprises a polymer selected from the group consisting of PEDOT, PANI, ProDOT and their derivatives, obtained from modified monomer structures including alkyl-substituted EDOT, EDOT-OH, Br-EDOT, EDOT-NH2, EDOT-COOH, optionally having a counter-ion selected from the group consisting of PSS" (poly(styrenesulfonate), Tos" (p-toluenesulfonate), CI04“ (perchlorate), BF4“ (tetrafluoroborate), PF6“ (hexafluorophosphate), OTf" (triflate), DBSA" (dodecyl benzenesulfonate), CSA" (camphorsulfonate), NO3“ (nitrate), SO42-(sulfate), HS04“ (hydrogen sulfate), TFSI" (bis(trifluoromethanesulfonyl)imide), Cl" (chloride), Br“ (bromide), I" (iodide), F" (fluoride), CF3SO3“ (trifluoromethanesulfonate), CH3SO3“ (methanesulfonate), acetate (CH3COO“), citrate, and phosphate.

[0036] 13. The device according to any one of the preceding embodiments, wherein the adhesive is selected from the group consisting of acrylic-based adhesives, urethane-based adhesives, rubber-based adhesives, vinyl-based adhesives, epoxy-based adhesives, silicone-based adhesives, and mixtures thereof, and wherein the adhesive is preferably a pressure-sensitive adhesive.

[0037] 14. The device according to any one of the preceding embodiments, wherein the adhesive is preferably an acrylic-based adhesive, more preferably an acrylic copolymer or network adhesive, prepared by polymerizing an adhesive precursor mixture comprising at least the following components a) 20 to 80 wt % of acrylate monomers (al) from the group of (meth)acrylic esters containing at least one oxygen atom; and b) 20 to 80 wt % of acrylate monomers (a2) from the group of (meth)acrylic esters and / or amides containing at least one nitrogen atom; and c) 0.0 wt % to 15 wt % of one or more electro-responsive compounds from the group of polymerizable zwitterionic monomers and / or non-polymerizable zwitterionic compounds, preferably one or more zwitterionic monomers; and d) 0.005 to 10 wt % of at least one initiator; and e) 0.0 wt % to 20 wt % of an aqueous electrolyte component; and f) 0.0 wt % to 10 wt % by weight one or more additives e.g. water-retaining additives, catalysts, corrosion inhibitors, crosslinkers, plasticizers, and tackifiers; wherein the weight fractions of the components are based on the total weight of the precursor mixture.

[0038] 15. Use of the device as defined in any of the preceding embodiments in an assembly process of electronic devices, such as computers, chips, smartphones, displays, touch panels, sensors, light sources such as LEDs or OLEDs, or other electronic devices.

[0039] Further aspects and features of the present invention will become apparent from the following description.

[0040] DETAILED DESCRIPTION OF THE INVENTION

[0041] DEFINITIONS

[0042] The "comprising" is used open-endedly and requires the presence of the recited components of features, while additional components of features are not excluded. The term, however, also encompasses the more restrictive meanings "consisting of" and "consisting essentially of", unless the context dictates otherwise. The term "consisting essentially of" requires the presence of other features or components and allows for the presence of other features or components as long as the objects of the present invention are not impaired. The expression "laterally protrude" refers in the context of the present invention to any kind of lateral protrusion of the layer or layers in question and means that the layer in question extends further, particularly in the "xy" plane and hence laterally - perpendicular to the stack direction - than does the reference layer. In place of the term "lateral protrusion", terms used in the context of the present invention include "lateral extension" or "lateral extension portion". The term "lateral" is referenced here to any direction of extent of the layer plane "xy" perpendicularly to the stack direction of the layers "z". The term is therefore independent in particular of the geometric shape of the adhesive tape in the "xy" plane, which for example may be a rectangle, as is usual for adhesive tapes (see above), or else may be a square or a circle. Minor fluctuations in the dimensions of the individual layers in the "xy" plane, resulting from the die-cutting process or similar shaping processes, are not addressed herewith, in particular since such slight projections of material, in view of the dimensions, are incapable of receiving a voltage applied thereto as planned and they do not imply any additional effort in production, thus being not brought about by means of an additional method step.

[0043] The present invention embraces all the features which are subjects of any dependent claims. Further, the present invention embraces combinations of individual features with one another, including at different preference levels. The present invention thus embraces, for example, the combination of a first feature identified as being "preferred" with a second feature identified as being, e.g., "particularly preferred". In this context, subjects identified as part of "embodiments", likewise at different preference levels, are also embraced. In other words, where the present description refers to different levels of preferences, combinations of these preferred embodiments and / or features shall also be deemed as disclosed if this combination is technically meaningful.

[0044] Whenever ranges are specified below, the upper and lower limit are included, as is any value in between.

[0045] Physical properties referred to below are generally determined at 25 °C and 1 atm pressure, unless a specific test method is indicated or the circumstances require otherwise. Properties can be determined by methods known in art or by specific test methods indicated below. In case of discrepancy, the specific test methods below prevail.

[0046] When the amount of a component of the adhesive is referred to by weight%, it refers to the value relative to the total weight of the adhesive, unless it is indicated otherwise or apparent from the circumstances. The term "conventional adhesive" is used to denote an adhesive that is not electro- responsive. Otherwise, the electro-responsive adhesive forming the essential component of the present invention may simply be referred to as "adhesive".

[0047] The term "initial bonding" or "initially bonded" refers to the adhesion strength of the adhesive measured by Test A (Peel Adhesion) outlined below without and prior to applying any electric stimulus.

[0048] The term "debonding" refers to the application of an electric stimulus that decreases the adhesive strength of the adhesive as compared to the initial adhesive strength with no electric stimulus.

[0049] The electric stimulus for modifying the adhesive to be in the debonded state may be referred to as "first" electric stimulus. An electric stimulus for modifying the adhesive to be in the bonded or rebonded state may be referred to as "second" electric stimulus. Here, the terms "first" and "second" are merely used to distinguish the electric stimuli from each other and do not imply a particular order, while they may be applied in the order first- second, or vice versa.

[0050] The term "stain-free debonding" means that when an adhesive is removed (debonded) from a substrate (adherend) surface after application of a first electric stimulus, it does not leave behind any visible residues, marks, or discoloration on the substrate, or does so in an amount of 100 mg / m2or less, based on the substrate surface where the adhesive was present. Here, the removal operation is a simple physical removal of the device. For an adhesive tape where the electro-responsive adhesive is present on a backing, this means simply peeling the tape from the adherend surface. The removal does not comprise the application of an additional treatment to the substrate surface, such as rubbing, wiping or solvent application for removing adhesive residue.

[0051] In the context of the present invention, it is acknowledged that completely stain-free debonding in the absolute chemical sense may be difficult to achieve. Nevertheless, in practical terms, stain-free debonding, understood as the removal of the adhesive tape without leaving visible or tactile residues on the substrate. So, stain-free debonding in the sense of the present invention refers to the practical removal of the adhesive without visible or tactile residues on the substrate. This is characterized by an amount of adhesive residue of 100 mg / m2or less.

[0052] The term "debonded adhesive strength" refers to the adhesion strength of the adhesive as measured by Test A (described below), after an electric stimulus (e.g. voltage) for debonding (i.e. for reducing adhesive strength) has been applied. The adhesive strength of a debonded adhesive is lower than the initial adhesive strength. A debonded adhesive strength may be in the range of 0.1 - 2 N / cm. An initial adhesive strength or re-bonded adhesive strength is higher than 2 N / cm, e.g. 2.5 N / cm or higher, by typically and preferably in the range of 2.5 to 15 N / cm.

[0053] The term "re-using" refers to the use of the adhesive again after its first debonding. Reusing may involve the application of a second electric stimulus to modify the adhesive to be in the bonded state or awaiting the return of the adhesive to the bonded state without applying a second electric stimulus after it has been modified to the debonded state by application of a first electric stimulus, and subsequent attachment of the adhesive to the substrate surface.

[0054] In the present invention, ionic conductivity may be determined by methods known in art or by Test B: Ionic Conductivity set out below. In case of discrepancy, the result obtained by Test B prevails.

[0055] The term "adhesive property" denotes any property of an adhesive that is of relevance in practice to exert the adhesive function. The adhesive property may in particular refer to the adhesive strength, determined in N / cm as determined by Test A below.

[0056] The term "electric stimulus" refers to any electric stimulus, and may thus include any voltage, duration, or frequency. The term may denote DC (Direct Current), AC (Alternating Current), VDC (Volts Direct Current), VAC (Volts Alternating Current), Pulsed DC (Pulsed Direct Current), Pulsed AC (Pulsed Alternating Current). The alternating current may have a sinusoidal waveform or may have a rectangular wave form, and the shape of the waveform is not particularly limited. In one embodiment, the electric stimulus has a voltage of 1 to 100 V, such as 1 to 50 V, 1 to 10 V, or 10 to 50 V, and may be a direct or alternating current, and preferably is a direct current. The duration of the electric stimulus is not particularly limited and may be from 0.1 to 10,000 seconds, such as from 0.5 to 1000 seconds or from 1 to 300 seconds.

[0057] The polarity of the electric stimulus, e.g. in DC form, is not particularly limited. Amongst others, polarity may be the decisive factor for an electric stimulus to increase or decrease bonding strength of an adhesive.

[0058] The term "electrically conductive" is well understood by a skilled person. A possible threshold may be defined at a conductivity of 1 S / cm or higher, 10 S / cm or higher, such as 100 S / cm or higher, e.g. 103S / cm or higher, 104S / cm or higher or 105S / cm or higher. The term "Ionic conductivity" is the measure of a material's ability to transport electric charge through the motion of ions. It is expressed as the specific conductivity (o), typically in units of siemens per centimeter (S / cm).

[0059] A pressure-sensitive adhesive or adhesive composition is understood in the invention, as is customary in the general usage, as a material which at least at room temperature is permanently tacky and also adhesive. A characteristic of a pressure-sensitive adhesive is that it can be applied by pressure to a substrate and remains adhering there, with no further definition of the pressure to be applied or the period of exposure to this pressure. In general, though in principle dependent on the precise nature of the pressure-sensitive adhesive and also on the substrate, the temperature and the atmospheric humidity, the influence of a minimal pressure of short duration, which does not go beyond gentle contact for a brief moment, is enough to achieve the adhesion effect, while in other cases a longer- term period of exposure to a higher pressure may also be necessary.

[0060] Pressure-sensitive adhesives have particular, characteristic viscoelastic properties which result in permanent tack and adhesiveness. A feature of these adhesives is that when they are mechanically deformed, there are processes of viscous flow and there is also development of elastic forces of recovery. The two processes have a certain relationship to one another in terms of their respective proportions, in dependence not only on the precise composition, the structure and the degree of crosslinking of the pressure-sensitive adhesive, but also on the rate and duration of the deformation, and on the temperature.

[0061] The proportional viscous flow is necessary for the achievement of adhesion. Only the viscous components, frequently brought about by macromolecules with relatively high mobility, permit effective wetting and effective flow onto the substrate where bonding is to take place. A high viscous flow component results in high pressure-sensitive adhesiveness (also referred to as tack or surface stickiness) and hence often also in high adhesion. Highly crosslinked systems, crystalline polymers, or polymers with glasslike solidification lack flowable components and are in general devoid of tack or possess only little tack at least.

[0062] The proportional elastic forces of recovery are necessary for the achievement of cohesion. They are brought about, for example, by very long-chain macromolecules with a high degree of coiling, and also by physically or chemically crosslinked macromolecules, and they allow the transmission of the forces that act on an adhesive bond. Description of Embodiments

[0063] The present invention provides a device, such as an adhesive tape, which possesses sufficient re-usability, i.e. which is capable of initial bonding, debonding upon application of a first electric stimulus, and re-using (e.g. re-applying the same adhesive with or without applying a second electrical stimulus for modifying the adhesive to be in the bonded state), and which therefore can be used one or more times without significantly losing its adhesive properties.

[0064] In one embodiment, the first electric stimulus is selected from the group consisting of an alternating current (AC), an alternating voltage, a direct current (DC), a direct voltage, or a pulsed current or voltage, preferably a DC or AC current or voltage in the range of 0.5 - 230 V, more preferably a DC voltage in the range of 2 to 100 V, such as 5 to 20 V. The same applies to the second electric stimulus which may have the same voltage and / or duration, but typically has an opposite polarity to the first electric stimulus.

[0065] For assessing whether a device satisfies the requirements of the present invention in relation to adhesive strength in the initial state, bonded state or rebonded state, the Test A described below is used. For testing debondability and rebondabilty upon application of a first respectively second stimulus, an electric stimulus 15 V DC for 5 minutes may be used, with opposite polarity for debonding and bonding, respectively. The adhesion strength in Test A is determined after the electric stimulus has been applied.

[0066] The device, e.g. in the form of an adhesive tape, can preferably be debonded from at least one substrate (adherend) without remnants upon application of an electric stimulus. Especially, the adhesive strength may be decreased by at least 90 % from its initial bonding strength (no voltage) or rebonded in less than 2 to 5 min after the application of DC voltage. For assessing this property, the procedure outlined in the examples section may be followed, using an ASTM steel surface as test substrate.

[0067] The device of the present invention comprises an electro-responsive adhesive whose adhesive properties can be modified from a bonded state to a debonded state by a first electric stimulus, and which i) can return to the bonded state upon the passing of time, or ii) can be modified from a debonded state to a bonded state by applying a second electric stimulus, the first and second electric stimulus differing from each other. wherein the electro-responsive adhesive can be debonded from a substrate surface (ASTM stainless steel) a) without leaving residues or altering the optical properties or surface roughness of the of the substrate surface, or b) leaving residues in an amount of 100 mg / m2or less.

[0068] In one embodiment, the criterion ii) means that the adhesive returns to an adhesive strength in the range for the bonded adhesive strength (2.5 N / cm or higher, such as 2.5 to 15 N / cm) upon storage at room temperature (25 °C) in air at 50 %RH within 24 hours or less after discontinuation of the application of the first electric stimulus, such as 12 hours or less or 6 hours or less.

[0069] Forthe first and second electric stimulus, preferred embodiments are described below. The specifics and preferred features of the first and second electric stimulus may be the same, except that typically the second electric stimulus has an opposite polarity or sometimes has higher magnitudes as compared to the first stimulus.

[0070] The requirements a) and b) are assessed on an ASTM stainless steel surface as set out in the examples section. The absence of residues can be assessed by the naked eye. The absence of alteration of the optical properties can be assessed by visual inspection or, preferably, by technical equipment, e.g. microscopy, XPS, UV-Vis and / or IR spectroscopy, comparing the surface before the bonding of the device with the device after the debonding procedure, without any additional mechanical or chemical cleaning treatment. The absence of alterations of the optical state is indicative for the fact that the surface remains unchanged and is not only free of residues but also from alterations of the surface that occur due to reaction of the substrate surface with the adhesive, e.g. oxidation or discoloration. It is thus indicative of the absence of impairments on the substrate surface due to the bonded adhesive.

[0071] Similarly, the absence of alterations of the surface roughness is indicative of a non-impaired surface state that may occur e.g. to partial dissolution of the substrate in the adhesive. The roughness can mean the arithmetic means roughness Ra, as determined by a stylus-type roughness tester. "Unaltered" means that Ra is within ± 10%, preferably ± 5%, of the Ra value before bonding of the adhesive.

[0072] For requirement (b), leaving residues in an amount of 100 mg / m2or less, this is indicative of only very few residues that go hand-in-hand with a limited risk for impairment of the substrate surface. The amount of residues may by 80 mg / m2or less, such as 60 mg / m2or less, 40 mg / m2or less, 20 mg / m2or less, or 10 mg / m2or less. Here, the area in m2is the area of the substrate to which the adhesive was bonded in the bonded state. The amount can be determined by removing the remaining adhesive with a suitable organic solvent such as acetone, diethyl ether, tetrahydrofurane, or dichloromethane, evaporating the solvent, determining the mass of residue, and dividing this mass by the area of the substrate on which the adhesive was present and from which the residue has been removed by dissolution in solvent.

[0073] The adhesive used in the device of the present invention is not particularly limited as long as it allows realizing the features described herein and set out in the claims.

[0074] The adhesive used in the device of the present invention typically does not contain an ionic liquid, in particular a low-molecular (molecular weight: 500 g / mol or less, e.g. 300 g / mol or less) ionic liquid, or contains an ionic liquid in an amount of 1% by mass or less. This is because the ionic liquid is believed to be the cause of the formation of residues after debonding. It is a key finding of the present invention that the ionic liquid, which otherwise is often necessary in order to obtain electro-responsive properties, can be replaced by an aqueous electrolyte component while simultaneously forming an electro-responsive adhesive that can achieve suitable adhesive strength in the bonded state and low adhesive strength in the debonded state. Here, an ionic liquid is defined as a compound that is exclusively formed by ions e.g. organic cation and organic or inorganic anion and that is liquid at or around room temperature (25°C) or below 100 °C.

[0075] In order to replace the ionic liquid while still forming an electro-responsive adhesive satisfying the requirements a) and / or b), the adhesive typically contains an aqueous electrolyte component. The aqueous electrolyte component is described below as component e), which is mixed with a mixture comprising the monomers (al) and (a2) forming a specific yet preferred embodiment of the present invention, yet the description given here applies independently for all adhesives present in the device of the present invention.

[0076] The adhesive thus preferably contains an aqueous electrolyte component, more preferably in an amount of 0.1% by weight or more and 20% by weight or less, based on the total weight of the adhesive. The content is preferably 0.1 wt % by weight or higher, such as 0.5 wt % by weight or higher, 1.0 wt % by weight or higher, more preferably 1.5 wt % by weight or higher, 2.0 wt % by weight or higher, 2.5 wt % by weight or higher, or 3.0 wt % by weight or higher, but is 20 wt % by weight or less. The aqueous electrolyte components comprise anions and cations, at least one of which is different from H+respectively OH’. Thus, in one embodiment the adhesive comprise one or more of an inorganic salt or an organic salt having a melting point above 100 °C, a deep eutectic solvent [mixture of organic or inorganic salt as hydrogen bond acceptor and a hydrogen bond donor], an ionic surfactant, an inorganic acid or an organic acid, or an inorganic or an organic base except ionic liquids, preferably selected from the group consisting of alkali metal, earth alkali metal or ammonium halides (e.g. chlorides), sulfates, nitrates, carbonates, phosphates, alkali metal, earth alkali metal or ammonium hydroxide, hydrochloric acid, sulfuric acid, and nitric acid, and wherein preferably the is present in the form of an aqueous solution at a concentration of 0.1 to 10 mol / L. Typical examples include aqueous alkaline solutions (pH > 7.1, e.g. 7.5 - 12.0) of the alkali metal and earth alkali metal hydroxides, such as NaOH, KOH, or LiOH, neutral (pH = 6.9 - 7.1) salt solutions like NaCI, KCI, NaSO4, or acidic (pH < 6.8, e.g. 2.0 to 6.8) solutions, such as aqueous solutions of acids such as HCI or H2SO4.

[0077] In one embodiment, salts and bases can be selected from salts and hydroxides having cations selected from the group consisting Li+, Na+, K+, Cs+, Rb+, Ag+, Cu+, Cu2+, Mg2+, NH4+, or combinations thereof; and the salts and acids may be selected from the group having anions comprising Ch, Br, I", CIO4", OH’, SCN’, AsF6’, [(CF3SO2)2N]’, [(FSO2)2N]-, CF3SO3’, CH3CO2-, [B(C2O4)2]-, [BF2(C2O4)2]-, PF6-, BF4-, [PF3(CF2CF3)3]-, C2O42’, C(CF3SO2)3-, or combinations thereof.

[0078] In one embodiment, inorganic salts can be used to prepare the aqueous electrolyte component. These salts are not particularly limited, but are preferably salts of the alkali metals, more preferably lithium. In one preferred embodiment, the salt comprises a lithium salt selected from the group consisting of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithiumtriflate (LiOTf), lithium perchlorate (LiCI04), lithium difluoro(oxalato)borate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0079] One or more of these can be used. In order to avoid corrosion and impairment of the substrate surface, the pH is preferably in the range from 6.0 - 8.0. Buffer salts can also be added to stabilize the pH, and further additives may be included to prevent corrosion or to improve stability over time. In respect of additional features, reference is made to the below description of component e), which also applies here.

[0080] If the aqueous electrolyte component is present, the adhesive will contain water. This water keeps the electrolyte in solution and prevents the formation of residues upon debonding. It is surprising that despite the presence of water, sufficiently high adhesion strength and electro-responsive properties can be obtained, as typically water-free systems were considered more useful for obtaining electro-responsive properties while maintaining suitable properties of the adhesive in use, such as sufficiently high cohesiveness allowing to obtain adhesive rather than cohesive failure at the time of debonding.

[0081] In certain embodiments, the adhesive comprises 1% by weight or more of water, preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, or 5% by weight or more, but 20% by weight or less, such as 15% by weight or less, relative to the total weight of the adhesive.

[0082] In one embodiment, the adhesive herein the adhesive does not contain an ionic liquid and contains 1% by weight or more of water, preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, or 8% by weight or more

[0083] The adhesive thus typically contains one or more ionic species that are not ionic liquids as part of the aqueous electrolyte component. These ionic species cause ionic conductivity and facilities electrolysis of water thereby enabling debonding due to gas evaluation reaction mostly because of hydrogen evaluation reaction (HER). The preferable ionic conductive of the adhesive is in the range of 1010S / cm to 10-5S / cm at 25 °C. This is sufficient to show the debonding feature of the present invention.

[0084] The electro-responsive adhesive preferably does not contain any ionic liquids, or does so in an amount of 1% by weight or less, such as 0.5% by weight or less (relative to the total weight of the adhesive). The one or more ionic species that are not ionic liquids are preferably present form in an aqueous solution, thereby forming an aqueous electrolyte.

[0085] In one embodiment, the electro-responsive adhesive used in the device of the present invention comprises one or more selected ones from acrylic adhesives, rubber-based adhesives, silicone adhesives, epoxy adhesives, polyurethane adhesives, cyanoacrylate adhesives, UV-curable adhesives and an aqueous electrolyte component consisting of salts (but not ionic liquid) or acids or bases or buffers. The adhesive may be a pressure-senstive adhesive (PSA).

[0086] In one embodiment, the adhesive, which may be a PSA, comprises an acrylic adhesive and an aqueous electrolyte component, which is preferably a solution in which one or more of alkali metal and earth alkali metal halides and / or hydroxides is dissolved, such as an aqueous NaOH or KCI solution.

[0087] It is a surprising finding of the present invention that after debonding, the adhesive, in particular the adhesive described herein made from a mixture comprising the components a) to f), recovers quickly, i.e. it regains adhesive strength back to the bonded adhesive strength, often back to the original (initial) adhesive strength prior to debonding, thereby allowing re-using the device for further bonding (rebonding) operations. In certain embodiments, the adhesive achieves an adhesive strength falling within the range of the bonded adhesive strength (2.5 to 15 N / cm) within 24 hours or less (at room temperature, i.e. 25 °C) after the end of the first electric stimulus for debonding, such as within 20 hours or less, 15 hours or less, 10 hours or less, 5 hours or less, 3 hours or less, 2 hours or less, or 1 hour or less. In this case, no second electric stimulus for increasing the debonded adhesive strength back to the bonded adhesive strength may be required.

[0088] In certain embodiments, a second electric stimulus for increasing the adhesive strength to be in the range for the bonded range may be applied or necessary. Here, the above description of the first electric stimulus applies, while typically the polarity of the second electric stimulus is the opposite to the polarity of the first electric stimulus.

[0089] In one embodiment, the electro-responsive adhesive is a PSA that is prepared by polymerizing a mixture comprising at least the following components: a) 20 wt % to 80 wt % of acrylate monomers (al) from the group of (meth)acrylic esters containing at least one oxygen atom; and b) 20 wt % to 80 wt % of acrylate monomers (a2) from the group of (meth)acrylic esters and / or amides containing at least one nitrogen atom; and c) 0.0 wt % to 15 wt % of one or more electro-responsive compounds from the group of polymerizable zwitterionic monomers and / or non-polymerizable zwitterionic compounds, preferably one or more zwitterionic monomers; and d) 0.005 wt % to 10 wt % of at least one initiator; and e) 0.0 wt % to 20 wt % of an aqueous electrolyte component; and f) 0.00 wt % to 20 wt % by weight other additives e.g. water-retaining additives, catalysts, corrosion inhibitors, crosslinkers, plasticizers and tackifier. wherein the weight fractions of the components are based on the total weight of the mixture. All weight ratios of components present in the mixture are chosen to add up to 100 wt %. However, if a solvent is present in the mixture for polymerization, the solvent is disregarded when stating the weight fractions of the components.

[0090] The PSA may be prepared a two-step process (also described in further detail below), including: (I) the provision of a mixture, including UV syrup preparation and aqueous liquid electrolyte formulation, followed by (II) polymerization, including curing by UV web polymerization or UV polymerization to obtain the adhesive composition that is employed in one embodiment of the present invention.

[0091] In one such embodiment, the PSA employed in the present invention is a pressure-sensitive adhesive polymer (random / statistical copolymer or network) containing aqueous electrolyte composition. The copolymer structure is prepared by polymerizing monomers (al) and (a2) and therefore contains units derived from these monomers also containing oxygen and optionally nitrogen atoms. The ratio of the unit containing at least one oxygen atom and the unit containing at least one nitrogen atom corresponds to the weight ratio of monomer (al) to monomer (a 2) as defined in further detail below and which is adjusted to achieve several properties such as: (a) high polarity to dissolve enough conducting salts and electro-responsive compounds, preferably zwitterionic monomers, (b) controlling the glass transition temperature (Tg) of the copolymer, and (c) making the adhesive effectively debondable. The latter cause can be explained as follows.

[0092] Without wishing to be bound by theory, it is assumed that debonding occurs by reactive dissolution of the PSA when an ionic liquid is present. This means that when e.g. a DC voltage is applied, the cation of the ionic liquid is expected to form an N-heterocyclic carbene or similar reactive species by abstracting a proton from the cations, specifically the cation of the ionic liquid containing a proton at the C2 position. This carbene species then modifies or reacts with the bonding side of the adhesive, facilitating debonding. A similar mechanism has been experimentally demonstrated for the solubilization of cellulose, proteins and polymers. It is also possible that debonding occurs by physical dissolution (no reaction) or similar processes. The latter is more likely if the C2 carbon of the cation of the ionic liquid does not have a proton. In this scenario, migration of the ionic liquid to the adhesive-adherend interface causes physical solubilization of the adhesive, resulting in debonding. Of course, both processes can occur during debonding, together with another process such as gas evolution, most probably hydrogen gas, which facilitates debonding by mechanical stress. As no ionic liquid is used in the present invention, the latter is regarded as the expected mechanism. In addition, the presence of hydroxyl anions contributes to the debonding process, since the adhesive tape contains OH“ ions which increase the local pH, promote hydrolytic cleavage of interfacial bonds, destabilize surface oxides, and, in combination with hydrogen evolution, enable reliable electro-delamination.

[0093] In one embodiment, the adhesive composition contains one or more electro-responsive compounds from the group of polymerizable zwitterionic monomers or non-polymerizable zwitterionic compounds, preferably one or more zwitterionic monomers. The one or more electro-responsive compounds are ionic species having both cation and anion in their structure, which enable the adhesive tape comprising the adhesive composition of the present invention responsive to electric fields, also after debonding faster recovery of the adhesion. More preferably, the electro-responsive compounds are zwitterionic compounds. In particular, zwitterionic compounds are molecules that contain both positive and negative charges but are overall neutral. In one embodiment, the amount of the one or more electro-responsive compounds is from 0.01 to 15 wt %, preferably from 1 wt % to 10 wt % of the adhesive composition.

[0094] As outlined above, in the above and other embodiments, the PSA further contains salts (e.g., different Na and Li salts), facilitating the adhesive composition to be ion conductive. Conducting salt aids in the solubilization of electro-responsive compounds, preferably zwitterionic monomers, and contributes to the entire adhesive becoming more electro- responsive.

[0095] In certain embodiments, the initial peel adhesion, i.e. the initial adhesive strength, as measured with Test A described hereinafter (cf. experimental section) before the application of a DC voltage source ranges from 2.5 N / cm to 15 N / cm.

[0096] In the above and other embodiments, after applying a first electric stimulus for decreasing adhesive strength, the adhesive strength in the debonded state is less than 2.5 N / cm, preferably 2.0 N / cm or less, 1.5 N / cm or less, 1.0 N / cm or less, or 0.5 N / cm or 0.1 N / cm or less.

[0097] In one embodiment, after the preparation of adhesive mass with bulk or solution or UV prepolymer methods, for example using a mixture comprising the above components a) to c) and an initiator d), the adhesive is mixed with an aqueous electrolyte component e) , and optionally with one or more selected from plasticizers, curing agents (e.g., initiators or crosslinkers) and other additives (tackifier) f) to formulate the ion conductive adhesive. The next step is to coat the adhesive on the electrically conductive layer of the backing and cure it.

[0098] In an embodiment, a UV syrup-based acrylic adhesive is mixed with one or aqueous electrolyte components and then applied to the electrically conductive layer on a backing film and UV cured to obtain an adhesive tape. This is preferable over a solvent cast method, as the curing here is polymerization that increases the anchorage of the adhesive to the electrically conductive layer as well as increasing the anchorage to the electrically conductive layer and backing film.

[0099] Below a more detailed description of the monomers that may be used in the preparation of the PSA present as electro-responsive adhesive in the device of the present invention is given. The polymer of the present invention may be a binary co- or ter-polymer comprising two main classes of monomers, categorized as low-Tgmonomers (al) and high-Tgmonomers (a2). The classification is based on the glass transition temperature (Tg) of the homopolymers of the respective monomers. Low-Tgmonomers (al) are those whose homopolymers have a Tgtypically below about 0 °C, preferably in the range of - 80 °C to 10 °C, while high-Tgmonomers (a2) are those whose homopolymers have a Tgtypically above about 50 °C, preferably in the range of 50 °C to 150 °C. Both categories include polar and non-polar monomers.

[0100] (a) Monomer (al)

[0101] In one embodiment, the PSA is prepared by polymerizing a mixture comprising monomer (al) as component a) of the mixture. The monomer (al) is an acrylate monomer from the group of the (meth)acrylic esters, preferably containing at least one oxygen atom in the alcohol moiety. In the mixture, the one monomer (al) may be contained or two or more thereof may be contained in combination. The one or more monomers(s) (al) according to the invention are present in an amount of 20 to 80 wt %, such as from 35 wt % to 72 wt %, e.g. 35 to 70 wt %, preferably 45 wt % to 68 wt %, more preferably 50 wt % to 66 wt %, based on the total weight of the mixture.

[0102] In one embodiment, the hydrocarbon part of the alcohol component in monomer (al), does not contain oxygen atoms beyond the ester functionality, such that only the two oxygen atoms of the ester group (C=O and -O-) are present. Examples include methyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, and n-heptyl acrylate.

[0103] In a preferred embodiment, the hydrocarbon part of the alcohol component in monomer (al) contains at least one additional oxygen atom, preferably at least two oxygen atoms, even more preferably 2 to 20 oxygen atoms. To the skilled person it is clear that at least one oxygen atom (or the at least two oxygen atoms) in the acrylate monomer is (are) present in addition to the two O atoms (oxygen atoms) of the ester functionality, i.e. (C=O)O. In other words, monomer (al) in total contains at least three oxygen atoms, namely the two oxygen atoms of the ester functionality and an additional oxygen atom. Preferably, monomer (al) in total contains at least four oxygen atoms, namely the two oxygen atoms of the ester functionality and two additional oxygen atoms. At least one oxygen atom (or at least two oxygen atoms) is (are) typically present in the hydrocarbon part of the alcohol component of the (meth)acrylic ester. The expression "hydrocarbon part" as used herein is the part of the ester which is introduced by an alcohol upon reaction with the carboxylic functional group of acrylic acid to form the ester. In a preferred embodiment, the monomer (al) is from the group of (meth)acrylic esters having 4 to 44 carbon atoms, preferably 7 to 44 carbon atoms, or the monomer (al) and at least one oxygen atom or at least two oxygen atoms as described above. More preferably monomer (al) is from the group of (meth)acrylic esters having 4 to 30 carbon atoms and comprising at least one oxygen atom, preferred 8 to 30 carbon atoms and at least 2 oxygen atoms.

[0104] Preferred (meth)acrylic esters contain at least one oxygen atom (or the at least two oxygen atoms in the hydrocarbon part of the alcohol component of the ester, wherein at least one non-adjacent CH2group is replaced by O. The hydrocarbon part of the alcohol component may be branched, unbranched or cyclic, saturated, or unsaturated, aliphatic or aromatic, substituted or unsubstituted, preferably it is branched or unbranched, saturated or unsaturated, and aliphatic since aromatic groups may cause color.

[0105] In a more preferred embodiment, the hydrocarbon part of the alcohol component is based on polyethylene oxide (PEO). The PEO can be linear or branched and preferably is linear. In an even more preferred embodiment, the monomer (al) is represented by the following formula (1). formula (1)

[0106] In present formula (1), R1is H or CH3, R2is H, linear or branched C^-Cig alkyl, aryl, hydroxy (CrC18) alkyl, -C(=O)CH2C(=O)CH3, -CH3or -CH2CH3, preferably CH3or CH2CH3, and n is an integer in the range from 0 to 18 or 1 to 18, preferably in the range from 0 to 15, e.g. 1 to 15, more preferably in the range from 0 to 11, such as 1 to 11 . In a preferred embodiment at least one monomer (al) used has a value of n between 0 and 11, preferably 0, 1, 2,3 or 4. Preferred are monomers that are liquid at 25 °C.

[0107] Examples of the (meth)acrylic esters include butyl acrylate (BA, n = 0, R1= H, R2= - CH2CH2CH2CH3), 2-ethylhexyl acrylate (EHA, n = 0, R1= H, R2= -CH2CH(CH2CH3)CH3), 2-(2- ethoxyethoxy)ethyl acrylate) (EEEA, also designated as EDGA, n = 2, RT= H, R2= -CH2CH3), 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate (n = 3, R1= H, R2= -CH3), diethylene glycol monomethyl ether methacrylate (n = 2, R1= CH3, R2= -CH3), 2-ethoxyethyl methacrylate (n = 1, Rx= CH3, R2= -CH2CH3), 2-methoxyethyl methacrylate (n=l, R1 =CH3, R2= -CH3) and ethylene glycol monoacetoacetate monomethacrylate (n = 1, R1= CH3, R2= - C(=O)CH2C(=O)CH3).

[0108] (b) Monomer (a2)

[0109] In one embodiment, the PSA may be prepared by polymerizing a mixture comprising monomer (a2) as component b) of the mixture. The monomer (a2) is a high Tg acrylate monomer from the group of the (meth)acrylic esters or amides, preferably, (meth)acrylic esters or amides containing at least one nitrogen atom. In the mixture, one monomer (a2) may be contained or two or more thereof may be contained in combination with monomer (al). The one or more monomer(s) (a 2) according to the invention are present in an amount of 20 wt % to 80 wt %, such as from 20 to 48 wt %, preferably 22 wt % to 38 wt %, more preferably 24 wt % to 36 wt % based on the total weight of the mixture.

[0110] In a preferred embodiment, the monomer (a 2) is from the group of (meth)acrylic esters or amides having 4 to 25 carbon atoms, more preferably 5 to 15 carbon atoms, and even more preferably 5 to 9 carbon atoms. Those ranges refer to the (meth)acrylic esters and (meth)acrylic esters amides. This achieves particularly good characteristics with regard to the object to be achieved.

[0111] The monomer (a2) is from the group of (meth)acrylic esters or amides having at least one nitrogen atom within the molecule and may have one nitrogen atom or two or more nitrogen atoms. Moreover, because the monomer (a2) has an (meth)acrylic functionality within the molecule, the monomer (a2) is a monofunctional monomer. The monomer (a2) is a component copolymerizable with the monomer (al). This achieves particularly good characteristics with regard to the object to be achieved.

[0112] If monomer (a 2) is a (meth)acrylic ester, the at least one nitrogen atom (or the at least two nitrogen atoms) is (are) typically present in the hydrocarbon part of the alcohol component of the (meth)acrylic ester, wherein at least one non-adjacent CH2group is replaced by N. The hydrocarbon part of the alcohol component may be branched, unbranched or cyclic, saturated, or unsaturated, aliphatic or aromatic, substituted or unsubstituted, preferably it is branched or unbranched, saturated or unsaturated, and aliphatic since aromatic groups may cause color.

[0113] In the present invention, by use of the monomer (a2), a proper degree of polarity can be given to the acrylic copolymer. This can provide a pressure-sensitive adhesive sheet that keeps a high adhesive force and adhesion reliability (particularly, repulsion resistance and holding power) when the sheet is bonded and can be easily peeled off from an adherend when the sheet is peeled. This achieves particularly good characteristics with regard to the object to be achieved.

[0114] In particular, with the use of the monomer (a2), a proper degree of polarity can be given to the acrylic copolymer and Tgcan be controlled.

[0115] In a preferred embodiment, the monomer (a 2) is represented by the following formula (2). formula (2)

[0116] In present formula (2), R1is H or CH3, R2or R3is -H, -CH3, -CH2OH, -CH2CH2OH, -CH3or -CH2CH3, preferably -CH3or -CH2CH3.

[0117] In a preferred embodiment the monomer (a2) is liquid at 25 °C, however, monomers that are solid at 25 °C may also be used.

[0118] Examples of the (meth)acrylamides include (meth)acrylamide, N-alkyl (meth)acrylamide, and N,N-dialkyl (meth)acrylamide. Examples of the N-alkyl (meth)acrylamide include N- methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-n-butyl (meth)acrylamide, and N- octyl acrylamide. Further, examples thereof include amino group-containing (meth)acrylamides such as dimethylaminoethyl (meth)acrylamide and diethylaminoethyl (meth)acrylamide. Next, examples of the N,N-dialkyl (meth)acrylamide include N,N- dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl) (meth)acrylamide, N,N-di(t-butyl) (meth)acrylamide, N,N-dimethyl acrylamide (R1= H, R2= -CH3R3= -CH3) and N,N-dimethyl methacrylamide (R1= CH3, R2= -CH3, R3= -CH3).

[0119] Further, examples of the (meth)acrylamides also include cyclic (meth)acrylamides having an N-acryloyl group such as (meth)acryloyl morpholine (like 4-acryloylmorpholine), (meth)acryloyl pyrrolidone, and (meth)acryloyl pyrrolidine. This achieves particularly good characteristics with regard to the object to be achieved.

[0120] Further, examples of the (meth)acrylamides also include N-dialkylaminoalkyl (meth)acrylamide monomers having an N-dialkylaminoalkyl group such as N-[3- (dimethylamino)propyl]acrylamide, N-[2-(dimethylamino)ethyl]acrylamide, N-[2- (diethylamino)ethyl]-acrylamide. This achieves particularly good characteristics with regard to the object to be achieved.

[0121] Further, examples of the (meth)acrylamides include N-hydroxylalkyl (meth)acrylamide monomers having a hydroxyalkyl group having 1 to 4 carbon atoms. Examples of the N- hydroxylalkyl (meth)acrylamide monomers having a hydroxyalkyl group having 1 to 4 carbon atoms include N-methylol (meth)acrylamide, N-(2-hydroxyethyl)acrylamide,

[0122] N-(2-hydroxyethyl)methacrylamide, N-(2-hydroxypropyl)acrylamide,

[0123] N-(2-hydroxypropyl)methacrylamide, N-(l-hydroxypropyl)acrylamide,

[0124] N-(l-hydroxypropyl)methacrylamide, N-(3-hydroxypropyl)acrylamide,

[0125] N-(3-hydroxypropyl)methacrylamide, N-(2-hydroxybutyl)acrylamide,

[0126] N-(2-hydroxybutyl)methacrylamide, N-(3-hydroxybutyl)acrylamide,

[0127] N-(3-hydroxybutyl)methacrylamide, N-(4-hydroxybutyl)acrylamide,

[0128] (c) Electro-responsive compounds:

[0129] In one embodiment, the adhesive prepared by polymerizing a mixture comprising one or more electro-responsive compounds from the group of polymerizable preferably zwitterionic monomers or non-polymerizable zwitterionic compounds as component c) of the mixture, preferably one or more zwitterionic monomers. The one or more electro- responsive compounds may be present in an amount of 0.1 wt % to 15 wt %, preferably 0.5 wt % to 10 wt %, more preferably 1 wt % to 5 wt %, based on the total weight of the mixture.

[0130] The mixture may in principle comprise any type of electro-responsive compounds from the group of polymerizable zwitterionic monomers or non-polymerizable zwitterionic compounds, preferably zwitterionic monomers, known to the skilled person.

[0131] According to preferred embodiments, the mixture of the present invention may comprise one or more zwitterionic monomers. Exemplary zwitterionic monomers may include but are not limited to monomers based on phosphobetaine, carboxybetaine, sulfobetaine, or combinations thereof. Preferably the one or more zwitterionic monomers comprise phosphobetaine monomers, carboxybetaine monomers, sulfobetaine monomers, or combinations thereof. Mixtures of different types of zwitterionic monomers may be used. The one or more zwitterionic monomers may contain acrylic functional groups. Preferably, one or more zwitterionic acrylic monomers are used in the mixture of the present invention.

[0132] According to more preferred embodiments, the one or more polymerizable electro- responsive monomers, preferably zwitterionic monomers, that may be contained in the mixture of the present invention include but not limited to:

[0133] 2-methacryloyloxyethyl phosphorylcholine;

[0134] 2-[[2-(methacryloyloxy)ethyl]dimethylammonio]acetate;

[0135] 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate;

[0136] 3-[(3-acrylamidopropyl)dimethylammonio]propanoate;

[0137] 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propane-l-sulfonate;

[0138] 4-[[2-(methacryloyloxy)ethyl]dimethylammonio]butane-l-sulfonate; 3-[[2-(acryloyloxy)ethyl]dimethylammonio]propane-l-sulfonate;

[0139] 3-[bis[2-(methacryloyloxy)ethyl](methyl)ammonio]propane-l-sulfonate;

[0140] 3-[(3-methacrylamidopropyl)dimethylammonio]propane-l-sulfonate;

[0141] 4-[(3-methacrylamidopropyl)dimethylammonio]butane-l-sulfonate.

[0142] Alternatively, the mixture of the present invention may comprise one or more non- polymerizable zwitterionic compounds. Compared to zwitterionic monomers which are polymerizable, the non-polymerizable zwitterionic compounds according to the embodiment of the present invention do not have any polymerizable group. In the present invention, the use of a polymerizable zwitterionic monomer is preferred since its distribution in the adhesive composition, obtained by polymerizing the mixture, is generally easier to achieve. However, the use of a non-polymerizable zwitterionic compound is also possible provided that it can be dissolved in the mixture of the other components prior to preparation of the adhesive composition by polymerizing this mixture. In this case, no zwitterionic monomer is necessary but the effects of the present invention may also be achieved by the non-polymerizable zwitterionic compound.

[0143] The non-polymerizable zwitterionic compounds may in principle be any type known to the skilled person. Exemplary non-polymerizable zwitterionic compounds may include but are not limited to phosphatidylcholine and non-polymerizable zwitterionic compounds based on phosphobetaine, carboxybetaine, sulfobetaine, betaine (trimethylglycine); taurine; glycine; alanine; serine; methionine; glutamine; carnosine; carnitine; histidine; lysine; arginine; hydroxyproline; proline; 3-(n-morpholino)propanesulfonic acid (mops);or combinations thereof. Preferably the one or more non-polymerizable zwitterionic compounds are selected from the group comprising a zwitterionic polymer, obtained by polymerizing phosphobetaine monomers, carboxybetaine monomers, sulfobetaine monomers, or combinations thereof; phosphatidylcholine; and betaine, such as sulfobetaine, phosphobetaine and carboxybetaine. Mixtures of different types of non-polymerizable zwitterionic compounds may be used.

[0144] (d) Initiators:

[0145] The mixture for polymerization which in one embodiment forms the basis for the adhesive comprises 0.005 to 10 wt %, preferably 0.005 to 5 wt %, more particularly 0.01 to 3 wt %, based on the total weight of the mixture, of at least one initiator as component d) of the mixture. If a mixture of two or more initiators is used, the above weight fractions are based typically on the total amount of the initiators.

[0146] The term "initiator" as used in the present disclosure refers to a compound that generate radicals or cations upon exposure to UV light and heat. The initiator used in the present invention is preferably an initiator which initiates a radical polymerization. Accordingly, the polymerization taking place in accordance with the present invention is preferably a radical polymerization.

[0147] Preferably, the initiator is a thermal initiator and / or photoinitiator, more preferably the initiator is a photoinitiator. According to a preferred embodiment, the adhesive composition is prepared by polymerizing a mixture comprising at least one, more preferably comprising at least two photoinitiators.

[0148] A thermal initiator is a compound that generates reactive species (free radicals, cations, or anions) upon exposure to heat. In the context of the present invention, the thermal initiator is not particularly limited. A photoinitiator is a compound that generates reactive species (free radicals, cations, or anions) when exposed to radiation (UV or visible). The photoinitiator typically comprises a UV initiator. Accordingly, the polymerization taking place in accordance with the present invention is preferably a UV polymerization.

[0149] The UV polymerization for syrup preparation and / or on the coated-out web may take place, for example, with the following photoinitiators, i.e. light-active initiators: 2,2-dimethoxy-2- phenylacetophenone (DMPA, 340 nm, 250 nm, Irgacure 651), 1-Hydroxy-cyclohexyl- phenyl-ketone (Irgacure 184), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (BAPO, 295 nm, 370 nm), iodonium (4-methylphenyl)[4-(2- methylpropyl)phenyl]hexafluorophosphate (242 nm), 2,2'-bithiophen-5-yl 4-N,N'- diethylaminophenyl ketone (THBP), 6,6'-(((lE,l'E)-(2,5-bis(octyloxy)-l,4- phenylene)bis(ethene-2,l-diyl))bis(4,l-phenylene))bis(l,3,5-triamine-2,4-diamine))

[0150] (400 nm). As well as the stated initiators it is possible to use other known initiators from the following classes: alpha-amino ketones, metallocenes, iodonium salts, alpha-hydroxy ketones, or phosphines. Thermal stability exists preferably up to at least 50°C.

[0151] Depending on the energy of the radicals formed on initiator scission, they may be limited to initiating the acrylate polymerization or may additionally produce crosslinking reactions as well, such as, for example, 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-l,3,5-triazine (MTT). Crosslinking of the chain is unwanted during the polymerization or syrup preparation, in order to keep the viscosities low for the coating. In the second polymerization step in the case of UV polymerization, crosslinking, photoactive crosslinkers may be added. They may also be polymerized electively into the chains. When using 2-oxo- 1,2-diphenylethyl acrylate (benzoin acrylate) or analogues thereof, polymerization in a UV tunnel at a wavelength between 300 and 400 nm produces polymers which, after the end of the polymerization in the UV tunnel, can be crosslinked briefly and intensely with UV radiation at 250 nm by activation of the benzoin acrylate units incorporated by polymerization. These crosslinkers may equally be incorporated by polymerization during a thermally initiated solution polymerization, and activated later, after drying, with UV radiation.

[0152] Benzophenone methacrylate (Visiomer 6976, 300 nm) and analogues thereof can also be used, with their known benefits and disadvantages. These initiators reduce the contamination with small molecules but require a greater time for reaction because of the biomolecular reaction. Crosslinking must take place under inert conditions.

[0153] According to preferred embodiments, a mixture of more than one initiator or multiple different initiators is used for different polymerization steps, for example, preparation of the UV syrup and final curing preferably done by UV polymerization or UV web polymerization. Preferably, a mixture of multiple initiators with different molar absorption coefficients is being used.

[0154] According to more preferred embodiments, 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651) and 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) are used. (e) Aqueous electrolyte components:

[0155] In this invention, an "aqueous electrolyte composition" means an aqueous solution where water is used as the sole or one of several solvents. In one embodiment, water form 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, e.g. 100% by mass or more, of all solvents present in the aqueous electrolyte. The remainder of the solvent may be formed by water-miscible solvents, in particular protic solvents and aprotic solvents, such as alcohols, such as methanol, ethanol, or isopropanol, ketones like acetone, and ethers like tetrahydrofuran. The use of protic solvents is preferred, as they typically provide better solvating properties for the ions present in the aqueous electrolyte composition.

[0156] It is one key finding of the present invention that the aqueous electrolyte component provides the required ionic conductivity when a voltage is applied, in the same manner as ionic liquids, yet at the same time allows a stain-free removal of the adhesive in the debonded state in the absence of ionic liquids, thereby avoiding the formation of residues that are predominantly caused by ionic liquids.

[0157] The aqueous electrolyte components comprise anions and cations, at least one of which is different from H+respectively OH’. Typical examples include alkaline solutions (pH > 7.1, e.g. 7.5 - 12.0) of the alkali metal and earth alkali metal hydroxides, such as NaOH, KOH, or LiOH, neutral (pH=6.9 - 7.1) salt solutions like NaCI, KCI, NaSO4, or acidic (pH < 6.8, e.g. 2.0 to 6.8) solutions, such as aqueous solutions of acids such as HCI or H2SO4. One or more of these can be used. In order to avoid corrosion and impairment of the substrate surface, the pH is preferably in the range from 6.0 - 8.0. Buffer salts can also be added to stabilize the pH, and further additives may be included to prevent corrosion or to improve stability over time.

[0158] Water is particularly useful as solvent because it has a high dielectric constant, is inexpensive, and is environmentally friendly. Most importantly, easy preparation procedures are possible, for example aqueous electrolytes can be prepared by dissolving the desired ionic compound (for example NaOH, KCI, or H2SO4) in deionized water to a defined molar concentration.

[0159] The aqueous electrolyte can be used on its own or mixed with other electrolyte components, and the concentration can be adjusted depending on whether higher conductivity, better stability, or easier debonding is the main requirement. The ionic strength of the aqueous electrolyte component, defined as a measure of the total concentration and charge of all ions in a solution, calculated by summing the product of each ion's concentration and the square of its charge, then dividing by two, is from 0.001 to 10 mol / L, more preferably from 0.01 to 5 mol / L, even more preferably from 0.05 to 5 mol / L, and most preferably from 0.1 to 2 mol / L or more.

[0160] The amount of the one or more aqueous electrolyte component is preferably 0.1 wt % by weight or higher, such as 0.5 wt % by weight or higher, 1.0 wt % by weight or higher, more preferably 1.5 wt % by weight or higher, 2.0 wt % by weight or higher, 2.5 wt % by weight or higher, or 3.0 wt % by weight or higher, but is 20 wt % by weight or less, preferably 15 wt % by weight or less, relative to the total weight of the mixture for forming the adhesive. These ranges apply also to the adhesive obtained therefrom, as well as to electro- responsive adhesives that are not based on the monomers a), b) and optionally c).

[0161] The concentration of the ion species (e.g. salts) in aqueous electrolyte component is in the range from about 1 pM to about 10 M, preferably from about 1 mM to about 1 M, and most preferably from about 10 mM to about 500 mM.

[0162] The aqueous electrolyte is typically prepared by dissolving one or more salts, hydroxides or acids in water.

[0163] In one embodiment, the salts and bases can be selected from salts and hydroxides having cations selected from the group consisting Li+, Na+, K+, Cs+, Rb+, Ag+, Cu+, Cu2+, Mg2+, NH4+, or combinations thereof; and the salts and acids may be selected from the group having anions comprising Cl Br, I; CIO4; OH; SCN; AsF6; [(CF3SO2)2N]; [(FSO2)2N]; CF3SO3; CH3CO2; [B(C2O4)2]-, [BF2(C2O4)2]; PF6; BF4[PF3(CF2CF3)3]; C2O42; C(CF3SO2)3; or combinations thereof.

[0164] In one embodiment, inorganic salts can be used to prepare the aqueous electrolyte component. These salts are not particularly limited, but are preferably salts of the alkali metals, more preferably lithium. In one preferred embodiment, the salt comprises a lithium salt selected from the group consisting of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithiumtriflate (LiOTf), lithium perchlorate (LiCI04), lithium difluoro(oxalato)borate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0165] In one embodiment, the inorganic salts can be selected from the group consisting of sodium chloride (NaCI), potassium chloride (KCI), sodium sulfate (Na2SO4), potassium nitrate (KNO3), sodium nitrate (NaNO3), ammonium chloride (NH4CI), ammonium nitrate (NH4NO3), magnesium sulfate (MgS04), calcium chloride (CaCI2), sodium phosphate (Na3PO4), potassium phosphate (K3PO4), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), sodium fluoride (NaF), potassium fluoride (KF), sodium acetate (CH3COONa), potassium acetate (CH3COOK), sodium bromide (NaBr), potassium bromide (KBr), potassium iodide (KI), sodium iodide (Nal), zinc sulfate (ZnS04), copper sulfate (CuS04), aluminum sulfate (AI2(SO4)3), barium chloride (BaCI2), barium nitrate (Ba(NO3)2), strontium chloride (SrCI2), Iron(ll) sulfate (FeS04), iron(lll) chloride (FeCI3), nickel sulfate (NiS04), cadmium sulfate (CdS04), chromium(lll) chloride (CrCI3).

[0166] In one embodiment, suitable organic salts are tetrabutylammonium chloride, tetraethylammonium bromide, tetramethylammonium hydroxide, benzyltrimethylammonium chloride, morpholinium chloride; tris(hydroxymethyl)aminomethane hydrochloride (tris-hcl), methylammonium chloride, dimethylammonium sulfate, glycine sodium salt, ethylenediammonium diacetate.

[0167] In one embodiment, suitable inorganic salt are sulfuric acid (H2SO4); hydrochloric acid (HCI), nitric acid (HNO3), phosphoric acid (H3PO4), boric acid (H3BO3), carbonic acid (H2CO3), hydrofluoric acid (HF), hydrobromic acid (HBr), perchloric acid (HCI04), chromic acid (H2Cr2O7), silicic acid (H2SiO3).

[0168] In one embodiment, suitable organic acids are acetic acid (CH3COOH), citric acid (C6H8O7), formic acid (HCOOH), lactic acid (C3H6O3), oxalic acid (C2H2O4), tartaric acid (C4H6O6), succinic acid (C4H6O4), benzoic acid (C7H6O2), propionic acid (C3H6O2), ascorbic acid (C6H8O6), glycolic acid (C2H4O3), malic acid (C4H6O5), glutamic acid (C5H9NO4), fumaric acid (C4H404), pyruvic acid (C3H4O3), isocitric acid (C6H8O7).

[0169] In one embodiment, suitable inorganic bases are sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH40H), calcium hydroxide (Ca(OH)2); barium hydroxide (Ba(OH)2), magnesium hydroxide (Mg(OH)2), strontium hydroxide (Sr(OH)2), aluminum hydroxide (AI(OH)3), rubidium hydroxide (RbOH), cesium hydroxide (CsOH).

[0170] In one embodiment, suitable organic bases are imidazole, pyridine; triethylamine, aniline, diethylamine, morpholine, piperidine, isoquinoline, quinuclidine, 2,6-lutidine; tetramethylguanidine; triethanolamine; tris(hydroxymethyl)aminomethane (tris base); histidine; methylamine; dimethylamine

[0171] In one embodiment, suitable buffers are phosphate buffer, acetate buffer, citrate buffer, tris-hcl buffer, borate buffer, carbonate buffer, glycine buffer, hepes buffer, mops buffer; mes buffer, pipes buffer, histidine buffer, ammonium acetate buffer, succinate buffer, tartaric acid buffer, malic acid buffer.

[0172] In one embodiment, suitable ionic surfactants are sodium dodecyl sulfate (sds), cetyltrimethylammonium bromide (ctab), dioctyl sodium sulfosuccinate (aot), sodium lauryl sulfate (sis), sodium cholate; sodium taurocholate, sodium deoxycholate, dodecylbenzene sulfonate, tetradecyltrimethylammonium chloride, sodium octyl sulfate, sodium dodecylbenzenesulfonate, tetramethylammonium dodecyl sulfate, hexadecyltrimethylammonium bromide, n-cetylpyridinium chloride, dimethyldioctadecylammonium chloride.

[0173] After the preparation of an adhesive mass by bulk or solution or UV prepolymer methods, the adhesive may be mixed with aqueous electrolyte / plasticizers / curing agents (e.g., initiators or crosslinkers) or other additives (tackifier) to formulate the ion conductive liquid adhesive also called as liquid electrolyte. The next step is to coat the ion conducive adhesive on a substrate, e.g. an electrically conductive backing, and cure it.

[0174] In a preferred embodiment, the adhesive is a UV syrup-based acrylic adhesive, mixed with aqueous electrolyte. This may be applied to a variety of substrates, e.g. to the electrically conductive coating on a primed PET backing, and then UV cured to obtain a device of the present invention, e.g. in the form of an adhesive tape. This is preferable to a solvent cast method, as the curing often is a polymerization plus crosslinking reaction (optional) that may increase the anchorage of the adhesive to the electrically conducive coating as well as increase the anchorage to a backing film.

[0175] In addition to inorganic or organic salts in water electrolyte, deep eutectic solvents (DESs) may be used as alternative electrolytes for electrically debondable adhesive systems. DESs are typically formed by mixing a hydrogen bond donor (such as urea, glycerol, sorbitol, or ethylene glycol) with a hydrogen bond acceptor (such as choline chloride, zinc chloride, or other quaternary ammonium salts) in a defined molar ratio, resulting in a eutectic mixture with a melting point significantly lower than that of the individual components. DES can act as electrolyte component as well as water retaining additives.

[0176] Some examples of deep eutectic solvents (DES) useful as the electrolyte according to the present invention, not limited thereto, are selected from the group consisting of choline chloride : urea (1:2), choline chloride : ethylene glycol (1:2), choline chloride : glycerol (1:2), choline chloride : 1,2-propanediol (1:2), choline chloride : malonic acid (1:1), choline chloride : citric acid (1:1 or 1:2), choline chloride : oxalic acid (1:1), choline chloride : lactic acid (1:1), choline chloride : acetamide (1:2), choline chloride : formamide (1:2), choline chloride : levulinic acid (1:2), choline chloride : phenol (1:2), choline chloride : sorbitol (1:1), choline chloride : ascorbic acid (1:1), choline chloride : triazole (1:2), choline chloride : thymol (1:2), choline chloride : resorcinol (1:2), choline chloride : benzoic acid (1:2), choline chloride : mandelic acid (1:2), choline chloride : 4-aminobenzoic acid (1:2), choline chloride : imidazole (1:2), choline chloride : succinic acid (1:1), choline chloride : caffeic acid (1:1), choline chloride : asparagine (1:2), choline chloride : tartaric acid (1:1), choline chloride : glucose (1:1 or 1:2), choline chloride : xylitol (1:1), betaine : urea (1:2), betaine : citric acid (1:1), betaine glycerol (1:2), tetraalkylammonium chloride urea (1:2), tetramethylammonium chloride : ethylene glycol (1:2), ethylammonium chloride : urea (1:2), ethylammonium chloride : glycerol (1:2), ethylammonium nitrate : acetamide (1:2), n,n-dimethylglycine : urea (1:2), guanidine hydrochloride : urea (1:2), zinc chloride : urea (1:4), zinc chloride : acetamide (1:2), aluminum chloride : urea (1:1.5), aluminum chloride : acetamide (1:1.5), lithium chloride acetamide (1:2), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) urea (1:2), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) : ethylene glycol (1:2), choline nitrate : urea (1:2), choline nitrate : ethylene glycol (1:2), choline acetate : urea (1:2), choline acetate : ethylene glycol (1:2), choline acetate : glycerol (1:2), choline acetate : triethylene glycol (1:2), reline, ethaline, glyceline, choline chloride-acid mixtures, metal-salt-based systems including ZnCI2 / urea, MgCI2 / urea, Mn(NO3)2-H2O, and water-in-DES formulations, amide-based systems with lithium salts including n-methyltrifluoroacetamide + LiTFSI, methyl carbamate + lithium salts, acetamide + caprolactam, and succinonitrile-based mixtures, hydrophobic DES including long-chain ammonium + fatty acids, as well as dual-salt and ternary DES electrolytes.

[0177] When incorporated into an adhesive matrix, DESs provide ionic conductivity under an applied electric field, thereby enabling debonding. Compared to conventional ionic liquids, DESs are often less costly, easier to prepare, and in many cases more environmentally benign. They also exhibit tunable viscosity and conductivity depending on the selected donor-acceptor pair and ratio, which allows adjustment of debonding performance.

[0178] By diluting a DES with water, an ADES can be prepared. The addition of water reduces viscosity, improves ionic mobility, and can enhance electrochemical stability. DESs are particularly attractive for pressure-sensitive adhesive matrices, as they can combine sufficient conductivity with lower corrosivity compared to concentrated salt solutions. Depending on the water content, DESs may also help maintain moisture in the adhesive, thus supporting long-term debonding performance. In electrically debondable systems, DESs and ADESs may promote adhesion failure similar to ionic liquids, leaving the substrate substantially free of residue. However, depending on formulation and water content, cohesive failure or partial staining may still occur. Both DES- and ADES-based electrolytes can be combined with conventional adhesive matrices (polyacrylates, synthetic rubbers) and conductive backings such as metallic foils, conductive polymers, or metallized films.

[0179] (f) Other additives:

[0180] Additional monomers:

[0181] Optionally may present one or more acrylate monomers in the adhesive that are not particularly limited and may for example be selected from the group consisting of acrylic acid, di(ethylene glycol) 2-ethylhexyl acrylate, benzyl acrylate, isobornyl acrylate, 4- hydroxybutyl acrylate (4-HBA), , 4-hydroxybutyl acrylate, methyl acrylate, methyl methacrylate, isobornyl acrylate, 2-octyl acrylate, n-heptyl acrylate, and combinations thereof. Selecting a monomer allows to tailor properties of the adhesive composition. According to particularly preferred embodiments, the one or more acrylate monomers may be selected from the group consisting of 4-hydroxybutyl acrylate, and combinations thereof. By using a hydroxy or carboxy group-containing monomer, this may serve as a solvent for additives that otherwise are not soluble in the UV syrup. If the adhesive strength needs to be increased, then monomers having more polar groups or monomers with a higher number of methylene groups as described above can be used. The one or more optional monomer(s) in the adhesive composition prepared by polymerizing the mixture with (al and a2) according to the above may preferably be present in an amount of 0 wt% to 20 wt%, preferably 1 wt% to 15 wt%, more preferably 5 wt% to 10 wt%, based on the total weight of the acrylate monomer mixture.

[0182] Crosslinkers:

[0183] In another embodiment of the invention, the adhesive composition of the present invention may be prepared by polymerizing a mixture comprising the aforementioned UV syrup further comprising a crosslinker as optional additive.

[0184] The liquid electrolyte may be crosslinked with crosslinking polyfunctional acrylates, these being molecules possessing more than one acrylate group. Suitable examples include hexanediol diacrylate (HDDA), ethoxylated trimethylolpropane triacrylate (ETPTA), 1,9- nonanediol dimethacrylate, 1,6-hexanediol dimethacrylate, di(trimethylolpropane) tetraacrylate, di(ethylene glycol) diacrylate (Di(EG)DA), bis(2-methacryloxyethyl) phosphate, di(ethylene glycol) trimethacrylate (Di(EG)DM), bisphenol A bis(2- hydroxypropyl)acrylate, ethylene glycol dimethacrylate (EGDM), dipropylene glycol diacrylate, trans-l,4-cyclohexanediol dimethacrylate, (Di(PG)DA), 1,3-glyceryl dimethacrylate, 1,10-decanediol dimethacrylate, dipropylene glycol dimethacrylate (Di(PG)DM), 1,4-diacryloylpiperazine, ethylene glycol divinyl ether (EGDVE), diethylene glycol diacrylate, diethylene glycol divinyl ether (Di(EG)DVE), diethylene glycol dimethacrylate, triethylene glycol dimethacrylate (tri (EG) DM), ethylene glycol diacrylate, dipentaerythritol pentaacrylate (DPentA), trimethylolpropane triacrylate (TMPTA), propoxylated trimethylolpropane triacrylate (PO3-TMPTA), propoxylated trimethylolpropane triacrylate (PO6-TMPTA), polyethylene glycol) diacrylate (PEDGA) and polyethylene glycol trimethacrylate.

[0185] In case all the functional groups are reacted, protic groups can also be used for crosslinking. In that case the following crosslinkers and crosslinking systems are also suitable: isocyanate crosslinkers, epoxy-based crosslinkers, melamine-based crosslinkers, peroxide-based crosslinkers, metal chelate-based crosslinkers, metal salt-based crosslinkers, carbodiimide- based crosslinkers, oxazoline-based crosslinkers, aziridine-based crosslinkers, amine-based crosslinkers or silane-based crosslinkers. A combination of different crosslinkers is likewise possible.

[0186] Where a difunctional crosslinker is used, it may be present in the adhesive composition of the present invention in an amount of 0.2 to 10 wt %, more preferably 0.5 to 3 wt %, based on 100 wt % of the polymer component. Where a trifunctional crosslinker is used, it may be present in the adhesive composition of the present invention in an amount of 0.02 to 5 wt % based on 100 wt % of the polymer component, more preferably 0.05 to 1 wt %. It is also possible, however, to use crosslinkers with higher functionality. Furthermore, a plurality of crosslinkers may be used, which in terms of their functionality may be the same or different (for example, a combination of difunctional and trifunctional crosslinkers). The amounts used ought then to be adapted advantageously.

[0187] Water-retaining additives:

[0188] The electro-responsive adhesive present in the device of the present invention may further comprise water-retaining additives. These components serve to stabilize the aqueous electrolyte within the adhesive matrix, to reduce evaporation losses, and to prevent dryingout of the water present in the electrolyte. Suitable water-retaining agents include:

[0189] (a) Polyols and related compounds: glycerol, sorbitol, ethylene glycol, propylene glycol, butylene glycol, polyethylene glycol (PEG, preferably PEG 200-600), and polypropylene glycol. (b) Hydrophilic polymers and derivatives: polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid and salts thereof (including sodium polyacrylate and potassium polyacrylate), carbomers, and cellulose derivatives including hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), and hydroxypropylcellulose (HPC).

[0190] (c) Natural and bio-based humectants: starch and modified starches, alginates such as sodium alginate and calcium alginate, chitosan, betaine, ectoine, urea, and natural polysaccharide gums.

[0191] (d) Salts and ionic additives (non-IL): sodium lactate, potassium lactate, calcium lactate, sodium acetate, potassium acetate, sodium tripolyphosphate, sodium PCA (pyrrolidone carboxylate), and other phosphate or lactate salts.

[0192] (e) Zwitterionic compounds: betaines, sulfobetaines, and carboxybetaines.

[0193] (f) Mineral-based additives: kieselguhr (diatomaceous earth), bentonite clays such as montmorillonite and hectorite, zeolites, silica gels, precipitated silica, fumed silica, calcium carbonate, and other mineral fillers capable of adsorbing or retaining water.

[0194] (g) Hybrid and specialty water-retention agents: hydrogel particles based on crosslinked polyacrylic acid, crosslinked polyethylene glycol, or acrylate-based hydrogels; functionalized silica particles (e.g., organo-silanized hydrophilic silica); organically modified diatomaceous earth; and Somarex-530.

[0195] The aqueous electrolyte may comprise a metal-organic framework (MOF) acting as a waterretaining agent, the MOF being a crystalline coordination network composed of metal ions or clusters and multidentate organic linkers, having permanent porosity and capable of reversibly adsorbing and retaining water molecules. Suitable MOFs include, without limitation, hydrolytically stable frameworks such as AI-, Zr-, Zn-, Fe-, or Cr-based MOFs (for example, MOF-303, UiO-type, MIL-type, ZIF-type, or equivalent structures), optionally functionalized to enhance water uptake or compatibility with the adhesive matrix.

[0196] Specific examples include carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol (PVA), glycerol, sorbitol, sodium polyacrylate, starch derivatives, alginates, MOF, and dextrins. By maintaining moisture, such additives ensure long-term ionic conductivity of the adhesive, thereby supporting reliable debonding behavior under applied voltage.

[0197] Depending on the application, water-retaining additives may be incorporated in amounts of about 0.1 to 20 wt % based on the total adhesive formulation. The specific type and concentration are selected to balance conductivity, adhesion, and stability without impairing optical or mechanical properties of the tape. Preferably, the amount of waterretaining additive is in the range of 0.5 to 10 wt %, and most preferably in the range of 1 to 5 wt %.

[0198] The adhesive of the present invention may further comprise electrocatalysts to facilitate water electrolysis. Suitable catalysts include, but are not limited to, noble metal catalysts such as platinum, ruthenium, or iridium; transition-metal oxides such as nickel oxide, cobalt oxide, or manganese oxide; and mixed metal hydroxides or phosphates. The presence of such catalysts reduces the overpotential for hydrogen and oxygen evolution, thereby enhancing the efficiency of the electrolysis process and improving the debonding performance.

[0199] Alloying or doping nickel with elements such as Mo, Zn, Fe, Co, or Cr can further enhance its electrochemical activity. Raney nickel, obtained by selective leaching of Ni-AI or Ni-Zn alloys, provides a highly porous surface that increases the active area. Nickel coatings on stainless steel or perforated metal plates, followed by alloy leaching, can also generate Raney-type surfaces. Substrates arranged with narrow spacing orientation support uniform current distribution and efficient removal of generated gas, which is beneficial for stable debonding.

[0200] Higher temperatures support faster electrical debonding. They improve conductivity and speed up the electrolysis reactions that generate gas at the interface. The quicker gas formation helps to lift the adhesive layer more effectively, so the bond releases faster and with less residue.

[0201] Corrosion inhibitors:

[0202] The adhesive of the present invention may further comprise corrosion inhibitors. These additives serve to protect conductive backing and the metallic substrate against electrochemical attack with or without voltage is applied. Suitable corrosion inhibitors include inorganic salts and compounds such as phosphates, borates, silicates, molybdates, or tungstates, as well as organic inhibitors such as benzotriazole derivatives, carboxylates, or amine-based inhibitors. By forming passive layers or interfering with corrosion reactions, such additives extend the service life of the adhesive system and ensure clean debonding without damage to the adherend or backing. Corrosion inhibitors may be incorporated in amounts of about 0.1 to 5 wt % based on the total adhesive formulation. The specific type and concentration are selected according to the substrate and backing materials used. Preferably, the amount is in the range of 0.1 to 3 wt %, and most preferably in the range of 0.5 to 2 wt %.

[0203] Plasticizers:

[0204] The pressure sensitive adhesive of the present invention may comprise further additives such as plasticizers, preferably in a fraction of 0 to 20 wt %, Plasticizers used may be, for example, cyclic carbonates such as ethylene carbonate (EC), vinylene carbonate (VC), propylene carbonate (PC), butylene carbonate (BC) or fluoroethylene carbonate (FEC), linear carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) or ethyl methyl carbonate (EMC), mixed carbonates, dimethylacetamide, ethyl methanesulfonate (EMS), gamma-butyrolactone, dimethyl sulfoxide, polyethylene oxide (PEO, also polyethylene glycol), PEG), "glymes" such as diglyme, triglyme, tetraglyme, ethylene glycol diacetate, ketones, or various ethers or polyethers, or mixtures thereof. Particular preference in the invention is given to the use as plasticizer based on polyethylene oxides or glymes, preferably polyethylene oxides.

[0205] Alternatively, particular preference in the invention is given to the use as plasticizer based on polyethylene oxides or glymes, preferably polypropylene oxides or block copolymer thereof, or trimethylolpropane ethoxylate.

[0206] Tackifier:

[0207] The pressure-sensitive adhesive (PSA) layer of the present invention may further comprise one or more tackifiers to adjust the adhesion balance, wetting properties, and cohesive strength of the adhesive. Tackifiers are used in PSA formulations to promote initial tack and to optimize peel and shear performance. Suitable tackifiers include, but are not limited to, pinene resins, indene resins, rosins and their disproportionated, hydrogenated, polymerized, esterified or neutralized derivatives, aliphatic and aromatic hydrocarbon resins, terpene resins, terpene-phenolic resins, and C5 to C9 hydrocarbon resins. These resins, and any combination thereof, may be selected in order to adjust adhesive properties as required, provided they are compatible with the corresponding base polymer.

[0208] The tackifier is preferably selected to be compatible with the base polymer matrix, for example acrylic copolymers or copolymers, and is incorporated in an amount sufficient to adjust the glass transition temperature (Tg) and viscoelastic behavior of the adhesive to achieve the desired adhesion profile. The proportion of tackifier in the adhesive layer is typically in the range of 0.1 to 10 wt %, preferably 0.5 to 5 wt %, based on the total solids content of the adhesive formulation.

[0209] In some embodiments, hydrogenated hydrocarbon resins or hydrogenated rosin esters are employed as they offer improved color stability, oxidation resistance, and reduced tendency for migration into adjoining layers. The choice of tackifier may also consider compatibility with ionic or electro-responsive components present in the adhesive formulation.

[0210] By the inclusion of suitable tackifiers, the PSA tape of the present invention achieves the required balance between initial tack, holding power, and clean removability after electrically stimulated debonding.

[0211] ELECTRICALLY CONDUCTIVE BACKING

[0212] In one embodiment, the device of the present invention takes the form of an adhesive tape wherein the electro-responsive adhesive is provided on a backing, which is preferably an electrically conductive backing.

[0213] A backing, constituting or forming part of a single- or double-sided tape, is not just a film to support the adhesive layer but rather an important part of the tape. This could be made from plastic, metal, textiles, and so on. A normal adhesive layer is thin, sticky, and, overall, not free-standing, like material. A backing is therefore needed to provide support, dimensional stability, strength, flexibility, and ease of handling. It acts as the carrier for the adhesive layer, protects the adhesive before application, and determines the mechanical, thermal, and electrical properties of the tape. The backing can also influence the tape's resistance to moisture, heat, chemicals, and environmental exposure.

[0214] Common backing films are polyethylene terephthalate (PET), polypropylene (PP), Polyethylene (PE), polyvinyl chloride (PVC), Polyimide (PI), cellulose acetate, Kraft paper, crepe paper, nonwoven fabric, aluminum foil, copper foil, polyester fabric, glass cloth, rayon fabric, foam (e.g., polyethylene foam, polyurethane foam), PTFE (polytetrafluoroethylene), silicone-coated paper or film, fluoropolymer films, polycarbonate (PC), nylon. Metal or metalized films are not suitable for the current invention unless it has corrosion resistance. A backing can also be made of natural fabric (cotton, linen, wool, silk, hemp, or ramie) or synthetic fabric (acrylic or spandex) or from a composite fabric (poly-cotton, cotton-spandex, or wool-acrylic). Backings films may have a thickness in the range from 5 pm to 200 pm or more.

[0215] The backing is not limited to the materials mentioned above. Its purpose is to provide sufficient mechanical strength and to enable strong anchorage to the electrically conductive layer, or to both the primer and the electrically conductive layer, to form a suitable backing.

[0216] In a preferred embodiment, backing films are polyethylene terephthalate) (PET) or etched PET and poly(propylene) (PP) films with different thicknesses, such as from 5 pm to 200 or more.

[0217] Backing films can be treated to impart electrical conductivity. Metalized backing have good electrical conductivity but suffers due to corrosion. Examples include: e.g. aluminum- coated PET (AI-PET), copper-coated PET (Cu-PET), silver-coated PET (Ag-PET), nickel-coated PET (Ni-PET), tin-coated PET (Sn-PET). Of course, also other conductive materials can be used, such as ITO-coated PET (ITO-PET), carbon coated metal foil as carbon coated stainless steel film.

[0218] An anti corrosion layer can be applied to the metalized backing to slow down corrosion. This layer could be a thin adhesive layer with corrosion inhibitor. Here, the adhesive may be a conventional adhesive, i.e. an adhesive that is not electro-responsive.

[0219] But also, it is possible to use backing with organic conducive coating such as conductive polymers: PEDOT:PSS and PEDOT:Tos are popular due to their flexibility, processability, and stability. They can be coated or polymerized on PET backing films.

[0220] Also, corrosion resistance, carbon-based materials: polymer binder-dispersed carbon black, graphite, graphene, and carbon nanotubes can be coated on prepared film. These materials conduct well, are stable, and affordable. Fine silver, copper, or nickel particles can be employed in conductive coatings. They must be safeguarded against corrosion, especially in humid or long-term voltage systems. Some systems use conductive woven or nonwoven fabrics coated or implanted with conductive fillers as the mechanical backing and conducting layer. Inks and pastes with conductive particles in a polymer matrix can be printed as thin films on various substrates. Preferred materials used in the current invention are intrinsically conductive polymers such as poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), poly(3,4- ethylenedioxythiophene):p-toluenesulfonate (PEDOT :Tos), poly(3,4-propylenedioxy- thiophene) (ProDOT), poly(dioxythiophenes), poly(3,4-dialkylthiophenes), polyaniline (PANI), polypyrrole (PPy), poly(2,5-thienylenevinylene), polythiophene, polythiophene derivatives, metallo-supramolecular polymers, polyacetylene, poly(p-phenylene vinylene), polyfluorene, polycarbazole, and polybithiophene.

[0221] As well as PEDOT, PANI, ProDOT and their derivatives e.g. obtained from modified monomer structures including alkyl-substituted EDOT, EDOT-OH, Br-EDOT, EDOT-NH2, EDOT-COOH. As the PEDOT is a composite material and needs counter anion which is not limited but could be PSS" (poly(styrenesulfonate)), Tos" (p-toluenesulfonate), CI04“ (perchlorate), BF4“ (tetrafluoroborate), PF6“ (hexafluorophosphate), OTf" (triflate), DBSA" (dodecyl benzenesulfonate), CSA" (camphorsulfonate), NO3“ (nitrate), SO42-(sulfate), HS04“ (hydrogen sulfate), TFSI" (bis(trifluoromethanesulfonyl)imide), Cl" (chloride), Br“ (bromide), I" (iodide), F" (fluoride), CF3SO3“ (trifluoromethanesulfonate), CH3SO3“ (methanesulfonate), acetate (CH3COO“), citrate, phosphate, they should have sufficient electrical conductivity.

[0222] The electrically conductive layer may be prepared on the primed backing film. The preferred materials are intrinsically conductive polymers. There are many ways to prepare the intrinsically conductive electrically conducive coating on the backing film. One is directly coating the materials (PEDOT:PSS) from aqueous or solvent dispersion, and another is coating the monomers (EDOT) and in situ polymerizing them on the backing. Also, gas-phase or UV polymerization is possible. The present invention is not limited to a particular method. Preferred is directly coating the ink or aqueous dispersion on the primer side of the backing, as it is easy and does not need any rinsing steps like the in-situ polymerization.

[0223] Another preferred material is carbon-based coating, including graphene, carbon nanotubes (CNTs), reduced graphene oxide (rGO), pyrolytic carbon, carbon paint, carbon nanofibers, graphite, amorphous carbon, carbon black, conductive carbon ink, fullerene-based coatings, carbon-loaded polymers coatings and carbon fiber coatings. These materials are often applied as thin films on primed backing layers to provide electrical conductivity in the backing. Carbon-coated surfaces can be polished to smooth them to enhance electrical conductivity. ADHEREND OR SUBSTRATE

[0224] The adherend or substrate is the target substrate of the device that shall come in contact with the electro-responsive adhesive. Together with the adherend, the device of the present invention can form a capacitor-like adhesive device. Not every adherend may be suitable for that. High electrical conductivity facilitates the formation of such a device. Some examples of adherends include copper plate / foil, stainless steel plate, aluminum plate / foil, gold-coated surfaces, silver-coated substrates, nickel plating, titanium, ITO- coated glass, carbon-coated films, graphene films, metal-coated plastics (metalized film Sn- PET or AI-PET), chromium-coated substrates, zinc-plated surfaces, tin-plated surfaces, silicon wafers with conductive coatings, and conductive carbon fiber composite substrates. From examples, it is also clear that non-conductive adherents can also be used; in this case it is generally preferred that they are coated with an electrically conductive coating, e.g. one having a higher conductivity than the underlying surface, and preferably smooth surface.

[0225] Preferred adherends of the present invention are those that have smooth surfaces with better oxidation resistance and are electrically conductive. Examples include stainless steel plates or silver-coated plastic substrates.

[0226] BRIEF DESCRIPTION OF FIGURES

[0227] Figure 1 schematically illustrates embodiments of an adhesive tape of the present invention, namely a single-layered, adhesive transfer tape comprising the electro- responsive adhesive (A).

[0228] Figure 2 schematically illustrates embodiments of an adhesive tape of the present invention, namely a single-layered, adhesive transfer tape comprising adhesive (A) with one side coated with an anticorrosion adhesive layer of (AC).

[0229] Figure 3 schematically illustrates embodiments of an adhesive tape of the present invention, namely a single-layered, single-sided adhesive tape comprising an electrically conductive backing (B) on which is disposed the electro-responsive adhesive (A).

[0230] Figure 4 schematically illustrates embodiments of an adhesive tape of the present invention, namely a single-layered, single-sided adhesive tape comprising an electrically conductive backing (B) on which is disposed the electro-responsive adhesive (A). An anticorrosion layer called (AC) is provided between the backing (B) and the electro- responsive adhesive layer (A).

[0231] Figure 5 schematically illustrates embodiments of an adhesive tape of the present invention, namely a single-layered, double-sided adhesive tape comprising two adhesive layers (A) and (C), wherein both the layers are formed from different adhesives, coated on an electrically conductive backing (B). The adhesive (C) is a conventional adhesive and may be part of a conventional adhesive transfer tape or double-sided tape, in which case a further backing and following this a further layer of conventional adhesive may be present (not shown in Figure 5).

[0232] Figure 6 schematically illustrates embodiments of an adhesive tape of the present invention, namely a single-layered, double-sided adhesive tape comprising two adhesive layers (A) and (C), wherein both the layers formed from different adhesives, coated on an electrically conductive backing (B). Between (B) and (A) there is an anticorrosion adhesive layer (AC). The adhesive (C) is a conventional adhesive and may be part of a conventional transfer or double-sided tape, in which case a further backing and following this a further layer of conventional adhesive may be present (not shown in Figure 6).

[0233] Figure 7 schematically illustrates embodiments of an adhesive device of the present invention, namely a single-layered, single-sided adhesive tape comprising of adhesive (A) and electrically conductive backing (B), laminated on an electrically conductive substrate (S). Electrically conductive substrate serves as target adherend.

[0234] DEVICE DESIGN

[0235] The device of the present invention may take any form or shape. In one embodiment, the device is or comprises an adhesive tape. In the embodiment of an adhesive tape, the device contains in addition to the adhesive (typically present in the form of an adhesive layer) at least a backing. The backing is preferably electrically conductive. This can be achieved by using a film / foil that is as such electrically conductive, such as a metal foil, by providing a conductive coating, or by blending an insulating backing material (such as a polymer, e.g. PET) with conductive particles. The adhesive tape may take any desired converted form, with adhesive tape rolls being preferred. The adhesive tape, more particularly in web form, may be produced either in the form of a roll, i.e., in the form of an Archimedean spiral rolled up onto itself, or as an adhesive strip, of the kind obtained in the form of die-cuts, for example.

[0236] The device of the present invention also includes a capacitor-like device, for example wherein an electro-responsive adhesive layer is disposed on an electrically conductive backing and / or a substrate / adherend, or wherein two electrically conductive substrates sandwich the electro-responsive adhesive, such as an electro-responsive PSA, with or without interposing elements such as additional layers.

[0237] The adhesive tape according to one embodiment of the present invention may be present in web form. A web refers to an object whose length (extent in x direction) is greater by a multiple than its width (extent in y direction), e.g., by a x:y ratio of at least 10:1, and the width is approximately, preferably exactly, the same along the entire length.

[0238] The general expression "adhesive tape" synonymously also called "adhesive strip", in the sense of the present invention encompasses all sheetlike structures, such as two- dimensionally extended films or film portions, tapes with extended length and limited width, tape portions and the like, lastly also die cuts or labels.

[0239] As well as the lengthwise extent (x direction) and widthwise extent (y direction), the adhesive tape also has a thickness (z direction), extending perpendicularly to both extents, with the widthwise extent and lengthwise extent being greater by a multiple than the thickness. The thickness is extremely similar, preferably exactly the same, over the entire two-dimensional extent of the adhesive tapes as defined by length and width. The statements apply analogously to the backing, which as an integral constituent of the adhesive tape forms a layer in x and y directions. It will be appreciated that the individual layers are disposed on top of another along the z direction.

[0240] According to preferred embodiments, the adhesive tape of the present invention is a pressure-sensitive adhesive tape. As described above, the adhesive tape of the present invention comprises different structures.

[0241] The following illustrates possible configurations of the adhesive tape of the present invention. However, there is in no way a limitation of the teachings or disclosure of the present invention as set forth herein. FIG. 1 depicts an embodiment of the device of the present invention in the form of a singlelayered, adhesive transfer tape. The adhesive tape comprises an adhesive layer formed by the adhesive (A).

[0242] FIG. 2 depicts an embodiment of the device of the present invention in the form of a singlelayered, adhesive transfer tape where one side is coated with an anticorrosion adhesive layer (AC). The adhesive tape comprises an adhesive layer formed by the adhesive (A).

[0243] FIG. 3 illustrates a single-layered, single-sided adhesive tape of the present invention. The tape comprises a backing (B) formed by a polymer film coated with electrically conducive layer with or without priming.

[0244] FIG. 4 shows a single-layer, single-sided adhesive tape according to the present invention. The tape comprises a backing (B) formed by a polymer film coated with an electrically conductive layer, with or without priming. Between the adhesive (A) and the backing (B), a very thin anticorrosive adhesive layer is provided to protect the backing (B) from corrosion.

[0245] FIG. 5 illustrates a single-layered, double-sided adhesive tape of the present invention. The tape preferably consists of electrically conductive backing (B) and one ion conductive adhesive (A) and another side conventional adhesive transfer tape (C).

[0246] FIG. 6 illustrates a single-layered, double-sided adhesive tape of the present invention. The tape preferably consists of electrically conductive backing (B) and one ion conductive adhesive (A) and other side a conventional adhesive transfer tape (C). Between the backing (B) and adhesive (A) there is an anticorrosion adhesive layer (AC) is present.

[0247] From the FIGs, it is also evident that the electrically conductive backing (B), should slightly extend beyond the adherend's surface (e.g. conductive substrates S and adhesive A) to allow space for voltage connection. However, in the case of a transfer tape where the adhesive is placed between two conductive substrates or plates, the opposite side of the plate provides enough access for voltage connection, so such protrusion is not necessary. The protrusion should not lead to any short circuiting, meaning the conductive surfaces on both sides of the ion conductive adhesive must not come into direct contact with each other. According to an embodiment of the capacitor-like adhesive device, an electro-responsive adhesive is placed between an electrically conductive coating present on a backing and an electrically conductive substrate. The adhesive strength of the tape to an electrically conducive substrate's surface can be controlled by properties of the electric stimulus, e.g. voltage polarity, voltage level, and duration of the applied voltage. For example, an electrically conductive coating of PEDOT:PSS [Poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate)] or PEDOT:Tos [Poly(3,4- ethylenedioxythiophene):p-toluenesulfonate] or carbon may be applied onto a primed PET film to prepare the backing of this embodiment of the present invention. An electro- responsive adhesive layer may then be coated on top to form a single-layered, single-sided adhesive tape. When the adhesive , which may be formed from a mixture comprising the components a) to f), is laminated onto a conductive substrate such as a steel plate (the adherend S), an adhesive device of this embodiment of the present invention is realized. Upon applying a negative DC voltage to the adherend relative to the backing, the adhesion between the adhesive tape and the adherend surface becomes weaker, allowing easy and clean removal of the adhesive tape.

[0248] In preferred embodiments, the electrically conductive coating comprises materials that exhibit adequate electrical conductivity and hydrophobicity. In one embodiment, the backing having the conductive coating may be a metalized polymer film. The coating must be resistant to corrosion in electrolyte-rich environments, should offer good weatherability, and form a strong bond with the backing. In the present invention, this layer may for example be applied onto a primed surface of a backing by either in situ polymerization of monomers of intrinsically conductive polymers or by directly coating an aqueous dispersion or viscous ink onto the primed surface.

[0249] The adhesive, as present in e.g. the adhesive tape of the invention, is not limited to particular chemistries, but the preferred system is preparation by in a two-step process (also described in further detail above), including: (i) the provision of a mixture, including UV syrup preparation and liquid electrolyte formulation with aqueous electrolyte, followed by (ii) polymerization, including curing by UV web polymerization or UV polymerization directly on the electrically conductive backing, e.g. on an electrically conductive coating on a primed backing.

[0250] According to further embodiments, the present invention also includes a device that additionally contains electrically conductive substrates or surfaces of interest where the adhesive is applied. The whole assembly is also a device in accordance with an embodiment of the present invention. In a preferred embodiment, this substrate / surface is smoother and / or more electrically conductive than the electrically conductive backing, e.g. the electrically conducive coating present on the primed backing of the adhesive tape forming one aspect of the present invention. Further, the substrate / surface may have better corrosion resistance.

[0251] In one aspect of the present invention, to ensure that the debonding does not occur at the adhesive / backing interface, an intrinsically electrically conductive hydrophobic polymer may be used either directly coated from aqueous or viscous ink of them or by in-situ polymerized from the monomer / their derivatives of them on the primed backing with a higher thickness. The primer is basically a thin adhesive layer that may work as a bridge to the coating and backing. Alternatively, nonmetallic conductive filler particles (carbon / similar kinds) may be coated on the primed backing. Finally, an ion-conductive adhesive is directly polymerized on the electrically conducive layer side of the backing to ensure enough anchorage to the backing. All these measures ensure that no debonding occurs when a negative DC voltage is applied to the backing, enabling even increase of bonding strength to the positive side and finally, without losing the ability to debond from the substrate side once the polarity is reversed. As mentioned above, in such a tape design that represents one embodiment of the present invention, the backing is preferably electrically conducive in order to provide a closed electric circuit transferring the electric stimulus to the adhesive.

[0252] PREPARATION OF DEVICE AND METHOD FOR MODIFYING THE ADHESION STRENGTH

[0253] When the device of the present invention in any form is disposed on an electrically conductive substrate, another embodiment of an adhesive device of the present invention is constructed [FIG. 7],

[0254] FIG. 7 shows an adhesive device, according to an embodiment of the invention, constructed by a single-layered, single-sided tape [FIG. 3] disposed on an electrically conductive substrate (S). In this setup, connecting the positive terminal of DC voltage source to the conductive backing (B) and the negative terminal of DC voltage source to the substrate (S) and applying a DC voltage for example 5 to 50 V for 30 s to 5 min, decreases the adhesion strength between the adhesive (A) and the conductive substrate (S), thereby achieving debonding (DB) [e.g. stain free adhesive failure] of the adhesive tape A from the conductive substrate (S) [FIG. 7], In preferred embodiments, the adhesive tape, as an embodiment of the adhesive device, can be reused multiple times for bonding, debonding, and rebonding. For instance, after debonding, the same tape can be reapplied to the substrate and bonded again. Debonding can then be triggered by applying negative potential to the substrate. The tape remains functional for a few (e.g. 5 - 10, or even more) repeated uses by simply laminating it onto an electrically conductive substrate after it regained its bonded adhesive strength (either by the lapse of time, or by applying a second electric stimulus). This cycle can be repeated without a significant loss in adhesive strength compared to the initial bonding.

[0255] METHODS, SYSTEM AND USES

[0256] As derivable from the above, the device of the present invention can be used in a method of modifying the adhesive strength of the device, the method comprising the application of one or more electric stimuli for decreasing the adhesive strength of the adhesive. Here, the one or more electric stimuli may be a DC (Direct Current), AC (Alternating Current), VDC (Volts Direct Current), VAC (Volts Alternating Current), Pulsed DC (Pulsed Direct Current), Pulsed AC (Pulsed Alternating Current), and may preferably have a DC voltage of 1 to 50 V and / or a duration of 1 second to 30 minutes. Preferably, the DC voltage or current can be supplied from a battery, a DC bench power supply, a potentiostat / galvanostat, an AC-to- DC adapter, a DC-DC converter, a USB power source or power bank, or a solar panel with a regulator.

[0257] In one embodiment, the first electric stimulus is selected from the group consisting of an alternating current (AC), an alternating voltage, a direct current (DC), a direct voltage, or a pulsed current or voltage, preferably a DC or AC current or voltage in the range of 0.5 - 230 V, more preferably a DC voltage in the range of 2 to 100 V, such as 5 to 20 V. The same applies to the second electric stimulus which may have the same voltage and / or duration, but typically has an opposite polarity to the first electric stimulus.

[0258] The present invention also relates to an adhesive system capable of modifying the adhesive strength of an adhesive, preferably a pressure-sensitive adhesive, by applying one or more electric stimuli, the adhesive system comprising a device as described above; and a controller that is configured to apply an electric stimulus to the device. The controller can control a DC power supply, RFID systems, printed batteries, capacitors, energy-harvesting circuits, and / or may also operate remotely via wireless interfaces such as Bluetooth, WiFi, or NFC. In the adhesive system, one or more electric stimuli may be applied using a controller that is operated by a user (i.e., manual operation) or are applied using a controller according to a pre-defined program (automatic operation). In one embodiment, the user or the predefined program provides electric stimuli of increasing voltage and / or duration over several cycles, for example to thereby compensate for a possible loss in the magnitude of the change of adhesion strength over several cycles.

[0259] The automatic operation may also involve further variables or conditions, e.g. the fulfilment of pre-defined criteria. Such criteria may e.g. involve conditions that are acquired by a sensor, such as temperature or humidity, or may include a security of ID check in order to avoid unauthorized usage. The security or ID check may involve identification of an individual by software means, or a password check.

[0260] In further embodiments, the present invention also relates to the use of the device, e.g. in the form of the above-described adhesive tape, for stain-free debonding applications in: (i) joining different conductive surfaces or substrates; (ii) robotics, preferably in the manufacturing of robotic gripping arms; (iii) haptic devices; (iv) applications where debonding is needed without the application of heat, light, or pressure; (v) consumer electronics; (vi) electronic packaging; (vii) microelectronics; (viii) battery mounting for EVs or cell phones with reusable functions; (ix) cell phone back cover mounting; (x) recycling applications (e.g., disassembly of products); (xi) microfabrication (e.g., transfer and positioning of small components); (xii) smart wearable electronics (e.g., health monitoring); (xiii) optoelectronics (e.g., bonding camera modules); (xiv) optical component placement; (xv) adaptive handling of soft or fragile items; (xvi) reversible gripping for testing stations; (xvii) non-mechanical holding in sterile environments; (xviii) gentle release systems for automated packaging; and (xix) printing plate mounting on printing sleeves in flexographic printing processes. The present invention provides particular benefits when the device is used in an assembly process of electronic devices, such as computers, chips, smartphones, displays, touch panels, sensors, light sources such as LEDs or OLEDs, or other electronic devices, as here residues remaining from an adhesive may lead to impaired product properties and may be particularly problematic. The transfer design of the present invention can be used in other electrochemical cell (e.g. electrochromic devices) as a PSA electrolyte. EXAMPLES

[0261] The present invention is illustrated below by a number of examples. The examples described below illustrate particularly advantageous versions of the present invention, without wishing thereby to subject the present invention to any unnecessary limitation.

[0262] RAW MATERIALS

[0263] (a) Backing films:

[0264] PET film of different thicknesses

[0265] Etched PET film

[0266] Fabric (cloth)

[0267] PP film

[0268] Sn-PET or AI-PET

[0269] (b) Electrically conductive coating materials:

[0270] PEDOT :PSS aqueous dispersion from Ossila

[0271] PEDOT:PSS ink from Sigma Aldrich

[0272] PEDOT:PSS nano particles aqueous dispersion from Sigma Aldrich

[0273] EDOT monomer with different derivatives from TCI

[0274] Aqueous carbon in k / paint [Liquiwire™] from Manchester Nanomaterials Ltd Carbon paste from Nanografi

[0275] (c) Acrylate monomers:

[0276] 2-(2-Ethoxyethoxy)ethyl acrylate (EEEA or EDGA)

[0277] N,N-Dimethylacrylamide (DMAA)

[0278] Butyl acrylate (BA)

[0279] Benzyl acrylate

[0280] Methyl acrylate (MA)

[0281] Acrylic acid (AA)

[0282] 4-Hydroxy butyl acrylate (HBA)

[0283] Hydroxy ethyl acrylate (HEA)

[0284] 2-(Methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate) (MPC) from TCI

[0285] 3-[[2-(Methacryloyloxy)ethyl]dimethylammonio]propionate (CBMA) from TCI

[0286] (d) Initiators:

[0287] 2,2-Dimethoxy-2-phenylacetophenone (Irgacure 651) from Sigma-Aldrich

[0288] 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) from Sigma-Aldrich

[0289] 2-Hydroxy-2-methylpropiophenone (Irgacure 1173) from Sigma-Aldrich (e) Ionically conducting component:

[0290] Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) from Sigma-Aldrich Lithium

[0291] Sodium chloride from Sigma-Aldrich

[0292] Lithium triflate (LiOTf), lithium triflouromethanesulfonate) from Sigma-Aldrich

[0293] Sodium hydroxide (NaOH) from Sigma-Aldrich

[0294] Potassium chloride (KCI) from Sigma-Aldrich

[0295] Lithium tetrafluoroborate (UBF4) from Sigma-Aldrich

[0296] Lithium tetrafluoroborate (UBF4) from Sigma-Aldrich

[0297] (f) Electrically conductive substrate / adherend:

[0298] ASTM steel plate

[0299] (g) Other materials):

[0300] Crosslinkers: Erisys 240, polyethylene glycol) diacrylate (PEGDA)

[0301] Oxidant: Iron(lll) p-toluenesulfonate hexahydrate from Sigma Aldrich

[0302] Butanol from Sigma Aldrich

[0303] Different types of PEGs (PEG 200, PEG 400 and similar kinds)

[0304] Different types of carbonates as ethylene carbonate (EC), vinylene carbonate (VC)

[0305] Takifier e.g. Hercolyn D

[0306] Water retaining additives e.g. carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol (PVA), glycerol, sorbitol, sodium polyacrylate, starch derivatives, dextrins.

[0307] Anticorrosion additives: benzotriazole (BTA), tolyltriazole (TTA), 2- mercaptobenzothiazole (MBT), sodium phosphate, zinc phosphate, sodium tetraborate, sodium molybdate, sodium metasilicate, ethanolamine, triethanolamine, sodium benzoate

[0308] EXPERIMENTAL EXAMPLE 1:

[0309] Example 1 demonstrates the preparation of a single-layered, single-sided adhesive tape [FIG. 3] as well as using this tape to construct an adhesive device [FIG. 7] according to the two major steps:

[0310] I. Electrically conductive backing preparation

[0311] II. Ion-conducive adhesive coating on the electrically conductive side of the backing I. Electrically conductive backing preparation: two methods were used to prepare the backing.

[0312] (1st) using PEDOT:PSS ink or aqueous dispersion or carbon ink, or metalized film or

[0313] (2nd) in-situ EDOT polymerization using iron(lll) p-toluenesulfonate hexahydrate in butanol.

[0314] For the 1stway, commercially available PEDOT :PSS or carbon ink / paste was directly applied on the already prepared primed PET or PP or etched PET film, then covered by a siliconized liner (RF02) and passed through two rubber rollers with no gap between them. This process allows the formation of a very thin layer (less than 1 micron) of ink on the primer side of the backing. Also, a strong anchorage is achieved due to the adsorption of the ink to the primer surface. After that, the whole setup was dried at 90 °C for 5 to 10 min, then another drying step for 10 min after removal of the siliconized liner (RF02). For the PEDOT:PSS or carbon ink aqueous dispersion, the coating was done using a doctor blade coater directly on the primed PET and then drying at 90 °C for 10 min. The primer here may be a corona- treated PET film or roughened PET surface, or a PET film coated with a thin adhesive layer.

[0315] In addition, electrically conductive backings such as commercially available metallized PET films were used, for example tin-coated or aluminum-coated PET. The thickness of these PET films is typically in the range of 10 to 50 pm. As these films are sensitive to corrosion, a very thin adhesive layer was applied on the tin side of the Sn-PET film to slow down the corrosion process. This layer also contained anticorrosion additives.

[0316] For the 2ndway, the EDOT solution was prepared in butanol with iron(lll) p- toluenesulfonate hexahydrate in a mole ratio of 1:2.3. The solution was coated by doctor blade on the PET or PP of different thickness and dried afterwards for 5 to 10 min at 80°C. This results in a bluish PEDOT :Tos film due to the EDOT polymerization. After that, the film was rinsed with water to remove the unreacted EDOT monomers and excess oxidant. The obtained PEDOT:Tos coated backing was air dried afterwards. The backing prepared is named as [PEDOT:PSS or PEDOT :Tos-primer-PET], which means the backing consists of either a PEDOT :PSS or PEDOT :Tos layer on top, then a primer layer in the middle, and then the bottom PET film as backing.

[0317] Finally, the obtained electrically conductive layers look blue when PEDOT:PSS orTos coated and have a surface resistance of between 15 and 4000 Q / n. The carbon ink coated film looks black with surface resistances between 50 and 1000 Q / n. However, for example tin- coated or aluminum-coated PET are in the range of 1 to 100 Q / n. II. Ion-conducive adhesive coating on the electrically conductive side of the backing : several adhesive compositions of the invention were produced with the successive steps of a) prepolymer preparation, i.e. UV syrup preparation; b) formulation of the liquid electrolyte, i.e., dissolving aqueous electrolyte, photoinitiator, and / or other monomers or additives (plasticizer) and crosslinkers into the UV syrup; and c) coating and curing of the liquid electrolyte between the conducive side of the backing e.g. [PEDOT:PSS or PEDOT:Tos-primer-PET] or [carbon-primer-PET] or Sn-PET or AI-PET and a siliconized PET liner (RF02). The curing process is related to UV polymerization. See the details below for steps a) to c).

[0318] Step a)

[0319] A mixture with a ratio wt % of 60:40 EDGA: DMAA acrylic monomer was prepared in a glass reactor. 0.0063 wt % Irgacure 651 photoinitiator was added to the mixture. The mixture was degassed under stirring with purging N2 for 30 min and then irradiated by UV light at a wavelength of 365 nm with an intensity of 0.5 mW / cm2. The mixture was kept under constant stirring and polymerization continued. The UV lamp was turned off when the reaction temperature in the glass reactor increased to AT = 26 °C. The resulting UV syrup was allowed to cool down and kept away from light. The syrups obtained had a viscosity in the range of 3500 cP to 6500 cP with a refractive index of 1.44 to 1.45.

[0320] The UV syrup from step a) was blended with other components as listed in Table 1. To prepare adhesive, the formulation includes: 80-90 wt % UV syrup from step a), 5-15 wt % of an aqueous electrolyte from NaOH or KCI, 5-10 wt % zwitterionic compound or monomers, 0.055-0.15 wt % of Irgacure 184 as the photoinitiator, 0.5-5 wt % of a plasticizer selected from such as PEG 200 or, or a carbonate-based solvent, and 0.5-2 wt % of a crosslinker.

[0321] The liquid electrolytes from step b) were coated with a layer thickness of about 50 to 150 pm between two films, e.g. [PEDOT:PSS or PEDOT:Tos-primer-PET] or [carbon-primer- PET] or Sn-PET or AL-PET and a siliconized PET liner, then UV cured. The coating was done in a way that some parts of the electrically conductive layer were kept uncoated to make electrical connection with the external DC power supply needed for debonding / rebonding operations. Upon removal of the siliconized PET liner, a single-layered, single-sided adhesive tape [comprising backing B] is provided. Curing was then achieved with irradiation from fluorescent lamps (ACTINIC) with wavelength of 350 to 400 nm (UV-A) at an intensity of 14 mW / cm2at the residence time in the irradiation tunnel being 200 to 360 seconds. This corresponds to a UV dose from 2800 to about 5000 mW.s / cm2.

[0322] The ion-conducive adhesive tape as prepared in sequence (II) is laminated to the conductive surface or substrate (e.g. ASTM steel plate) to construct an adhesive device according to an embodiment of the present invention [e.g. FIG. 7], The lamination was carried out in a manner that enables connection of the DC voltage source to the device, specifically to the electrically conductive layer of the backing and the conductive substrate. The following Table 1 shows the different adhesive tape compositions of the present invention.

[0323] Corrosion suppression on the substrate and backing

[0324] In the context of electrically debondable adhesive tapes, corrosion in backing and substrate is a known topic. The invention further considers the issue of corrosion arising from the interaction between electrolyte components and metallic surfaces. Corrosion may occur both at the adherend (substrate) and at the conductive backing, and the present invention provides measures to address both sides.

[0325] On the substrate side, corrosion was suppressed by (i) selecting substrates with inherent corrosion resistance, such as stainless steel; (ii) applying anticorrosion coatings or sacrificial anodes or corrosion-resistant plating materials or conversion coatings, for example nickel, silver based ink, tin, or palladium-nickel plating, gold, conductive polymerfilms (e.g. PEDOT, polyaniline), or carbon-based coatings (graphite, graphene, CNT), palladium-nickel alloy; chromium coating, conductive paints contain metallic flakes in a polymer binder, (iii) formulating the electrolyte with low ion conductivity 10-7to IO-9S / cm at 25 °C), (iv) incorporating corrosion inhibitors in the electrolyte and reduced corrosive potential. These measures reduce or prevent electrochemical attack under applied potential.

[0326] On the backing side, protection is achieved by the use of corrosion-resistant conductive layers or composite, such as PEDOT:PSS, carbon-based films, or noble-metal coatings. Where a metalized PET film is used (for example AI-PET or Sn-PET), a thin barrier or primer layer may be introduced between the adhesive and the metallization to shield the metal from the electrolyte. Suitable barrier layers include thin acrylate primers, silane coupling layers, or conductive polymers that provide both adhesion promotion and corrosion resistance. For the adhesive device, environmental control and process measures for preventing corrosion may include, encapsulation, wherein the tape-substrate assembly is fully enclosed in an impermeable barrier or resin to withstand harsh environments; desiccant inclusion, wherein humidity-absorbing materials are incorporated within the assembly to manage condensation, and controlled atmosphere operation, wherein the tape / substrate is deployed under low-humidity or cleanroom conditions.

[0327] The environmental control additives added in the tape are selected from the group consisting of oxygen scavengers such as sodium sulfite (Na2SO3), sodium bisulfite (NaHSO3), hydrazine (N2H4), carbohydrazide (CH6N4O), diethylhydroxylamine (DEHA), ascorbic acid (C6H8O6), ethylenediaminetetraacetic acid (EDTA), sodium dithionite (Na2S2O4), amine- based scavengers including ethanolamine, morpholine, and cyclohexylamine, and ferrous ions (Fe2+), and desiccants such as silica gel, molecular sieves, calcium chloride (CaCI2), activated alumina, clay desiccants, and phosphorus pentoxide (P2O5).

[0328] By combining (i) inherently corrosion-resistant materials, (ii) protective coatings and primers, and (iii) electrolyte formulations of reduced corrosivity, the present invention ensures durability and stable operation of the electrically debondable adhesive tape while maintaining the required electrical conductivity for the debonding process.

[0329] Table 1: Examples of adhesive tape (device) compositions used to demonstrate the stain free debonding functions of the present invention.

[0330] Examples 11 and 12 represent examples of electrically debondable PSA tapes in which the electrolyte is based on ionic liquid.

[0331] TEST METHODS

[0332] Unless otherwise indicated, all measurements were conducted at 23 °C and 50 % relative humidity. Unless indicated otherwise, moreover, the measurements of the adhesive tape were carried out with an adhesive layer with a thickness of 80 pm to 150 pm.

[0333] Test A: Peel Adhesion

[0334] A freshly prepared single-layered, single-sided adhesive tape [FIG. 1] was cut with a width of 20 mm and a length of 150 mm. The adhesive tape was applied onto a cleaned ASTM steel plate (cleaned with acetone after removing the protective film) by gentle hand pressure using a lamination squeegee, after peeling off the siliconized PET liner [FIG. 7], The other side of the adhesive tape already has backing based on PEDOT:PSS or PEDOT:Tos, or carbon ink or metal coated [tin (Sn) or Al] PET film. Then the whole setup was pressed by rolling back and forth over five times using a 4 kg roller.

[0335] The setup was then vertically hooked to the bottom holder of a tensile testing instrument (ZwickRoell Z020), and the backing was attached to the upper holder of the instrument.

[0336] For peel adhesion measurement, the backing was pulled off at an angle of 180° with a velocity of 300 mm / min. The maximum force was recorded in N / cm for a complete peel of the adhesive tape from the ASTM steel substrate. The values reported here are the average of three individual measurements.

[0337] Test B: Ionic Conductivity

[0338] The ionic conductivity, more specifically DC conductivity was measured by EIS (Electrochemical Impedance Spectroscopy) from the log-log plot of real part of the AC conductivity over an angular frequency by extrapolating the plateau region to the zerofrequency using the Dyre fit function (e.g. empirical model for frequency-dependent conductivity in disordered systems). Measurements were done by a BioLogic VMP-300 in the mode of PEIS (potentio EIS) with a constant voltage amplitude of 10 mV and a frequency range from 7 MHz to 1 Hz. A transfer tape (no backing) of circular dimension with a diameter of 18 mm was applied between two circular steel plate electrodes. The tape thickness was 80 pm to 150 pm. The ion conductivity of the samples listed in Table 1 was found to be in the range of ~ 10“7to 10“9S / cm at 25 °C.

[0339] Test C: Surface Resistance

[0340] Surface resistance was measured using a NAGY SD-510 Sheet Resistivity Meter from INNOVENT e. V. Technologieentwicklung Jena. The materials tested included PEDOT:PSS, PEDOT:Tos, carbon ink, and a tin (Sn) layer coated on a primed PET or only on a PET backing as well as ASTM steel plate before and after debonding experiments.

[0341] Test D: Color values measurement

[0342] A BYK Gardner Spectro Guide instrument was used for the color characteristics of the adhesive device within the CIELAB three-dimensional space, defined by the three color parameters £*, a*, and b*, where, L* represents the gray value (0 = black, 100 = white), a* denotes the color axis from green to red (-120 = green, +120 = red), and b* signifies the color axis from blue to yellow (- 120 = blue, + 120 = yellow). To confirm that no optical changes occurred on the ASTM steel surfaces after debonding, CIE b* value measures were carried out before and after debonding, as follows, a singlesided tape of the present invention was laminated on the ASTM steel plate, and debonding was preferred. After each experiment, the tape was removed from the ASTM steel plate and then colorimetry was performed on the ASTM plate of different region to identify the change, e.g., initial and after debonding of the tape.

[0343] EXPERIMENTAL EXAMPLE 2 - DEBONDING EXPERIMENTS

[0344] A freshly prepared single-layered, single-sided adhesive tape [FIG. 1] of 100 mm in length and 20 mm in width was laminated to an ASTM steel plate (also referred to as substrate S, FIG. 7) by removing the siliconized PET release liner. The other side of the adhesive tape already has a backing e.g., PEDOT:PSS-primer-PET or carbon-primer-PET or Sn-PET. The entire setup was then pressed by rolling it over five times back and forth using a 4 kg roller. Various experiments were carried out at different voltages, polarities, and time durations to investigate the electrically adjustable stain free debonding behavior of the adhesive tape in the adhesive device of the present invention, as summarized in Table 2 below.

[0345] For the debonding experiment, the backing (e.g. PEDOT:PSS-primer-PET or carbon-primer- PET or Sn-PET) of the adhesive (acting as the anode) was connected to the positive terminal of the DC voltage source, while the ASTM steel plate (acting as the cathode) was connected to the negative terminal of a DC voltage source [DC power supply: Kiprim DC605S], After that, a DC voltage in the range of 5 to 50 V was applied for 30 s to 5 min. Then, peel adhesion was measured following Test A, but with the DC voltage source cables disconnected from both the substrate and the backing. The bonding strength decrease of the adhesive tape with respect to the ASTM steel plate was confirmed by a decrease in peel adhesion values from its initial condition (without voltage application).

[0346] For each sample, an additional peel test was performed separately to determine the initial peel strength of the tape. All samples were allowed to have a dwelling time of 2 to 10 minutes before measuring the peel adhesion values according to test A. The results are listed as [Initial bonding (no voltage)] in Table 2.

[0347] Stain-free debonding was confirmed by adhesion failure, meaning no adhesive matrix remained on the ASTM surface. Also, by thorough visual inspection of the ASTM steel plates, which showed little to no residual adhesive component after debonding. To confirm the surface electrical and optical properties of the debonded substrate (ASTM steel plate), surface resistance, contact angle and CIE color values were measured before and after debonding. However, insignificant changes were identified before and after debonding. Therefore, to judge the difference with the present invention and ionic liquid based electrical debondable tapes, a rating system was considered as "excellent" (no visible stain, no adhesive residue, surface unchanged), "good" (almost clean, only faint trace visible at certain angles, especially at the edges, no tacky residue), "fa ir / a verage" (noticeable stain, but removable without damage), "poor" (clear adhesive residue or strong stain requiring cleaning), and "very poor" (heavy residue, visible discoloration, or surface damage after removal). Since the adhesive comprises a water-based electrolyte, a very thin water layer may sometimes appear after debonding; however, this layer is to be even beneficial by enhancing the reusability of the adhesive tape through improved wetting and bonding strength. Further, this layer quickly evaporates due to the volatility of water as compared to ionic liquids.

[0348] Table 2: Results.

[0349] In Table 2, the plus (+) and minus (-) signs next to the ASTM steel plate and the backing (Sn- PET or PEDOT:PSS-primed-PET) indicate the connection of the DC power supply terminals. For example, a minus (-) sign at the steel plate means that the negative terminal of the DC power supply was connected to the steel plate, while a plus (+) sign at the backing means that the positive terminal of the DC power supply was connected to the backing.

[0350] In our tests, the ionic-liquid-based formulation (not shown here) generally showed slightly better debonding performance than the aqueous system, with the peel force often dropping below 0.6 N / cm. Achieving a comparable reduction with some aqueous electrolyte formulation required a higher voltage and / or a longer application time.

[0351] Examples tapes can also show rebonding function with second electrical stimulus. However, the tapes with metallized backing are sometimes prone to anchorage failure if the applied DC voltage or duration is not well controlled. So far, the best rebonding performance was observed in samples with PEDOT:PSS- or carbon-ink-coated conductive backing.

[0352] Examples 1 to 10 were evaluated as "excellent" to "good" stain-free tapes. In contrast, examples 11 and 12, which employed ionic liquids as electrolyte, were rated only "fair" to "poor" due to the formation of a residue layer on the ASTM steel plate after debonding. For further qualitative analysis, this layer was collected in deuterated DMSO, and NMR measurements (1H,13C,19F) verified that it consisted mainly of undissociated ionic liquids.

Claims

CLAIMS1. A device comprising: an electro-responsive adhesive whose adhesive properties can be modified from a bonded state to a debonded state by a first electric stimulus, and which i) can return to the bonded state upon the passing of time, or ii) can be modified from a debonded state to a bonded state by applying a second electric stimulus, the first and second electric stimulus differing from each other. wherein the electro-responsive adhesive can be debonded from a substrate surface (ASTM stainless steel) a) without leaving residues or altering the electrical / optical properties or surface roughness of the of the substrate surface. a) leaving residues in an amount of 100 mg / m or less.

2. The device according to claim 1, wherein the adhesive does not contain an ionic liquid, or contains an ionic liquid in an amount of 1% by weight or less.

3. The device according to any one of claims 1 and 2, wherein the adhesive comprises 1 % by weight or more of water, preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, or 5% by weight or more, but 20% by weight or less, such as 15 % by weight or less.

4. The device according to claim 1, 2, or 3, wherein the adhesive does not contain an ionic liquid and contains 1% by weight or more of water, preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, or 8% by weight or more.

5. The device according to any of the preceding claims, which comprises one or more selected from- an inorganic or an organic salt having a melting point above 100 °C, deep eutectic solvents [mixture of organic or inorganic salt as hydrogen bond acceptor and a hydrogen bond donor], an ionic surfactant, an inorganic or organic acid,an inorganic or an organic base except ionic liquids, and which preferably comprises one or more selected from the group consisting of alkali metal, earth alkali metal or ammonium halides (e.g. chlorides), sulfates, nitrates, carbonates, phosphates, alkali metal, earth alkali metal or ammonium hydroxide or transition metal hydroxide, hydrochloric acid, sulfuric acid, and nitric acid, preferably present in the form of an aqueous solution at a concentration of 0.1 to 10 mol / L.

6. The device according to claim 1, which exhibits an initial adhesive strength of 2.5 to 15 N / cm, and after application of an electric stimulus exhibits a debonded adhesive strength of 0.1 to 2 N / cm.

7. The device according to any one of the preceding claims, wherein the electric stimulus is selected from the group consisting of an alternating current (AC), an alternating voltage, a direct current (DC), a direct voltage, or a pulsed current or voltage, preferably a DC or AC current or voltage in the range of 0.5 - 230 V, more preferably a DC voltage in the range of 2 to 100 V, such as 5 to 20 V.

8. The device according to any one of the preceding claims, wherein the adhesive is present on an electrically conductive surface of a backing.

9. The device according to any of the preceding claims, wherein the device is in the form of an adhesive tape, preferably selected from the group consisting of a single-sided adhesive tape, a double-sided adhesive tape, or a transfer adhesive tape.

10. The device according to any one of claims 8 and 9, wherein an anticorrosion adhesive layer with a thickness in the range of 1 to 20 pm is present between the electrically conductive backing and the adhesive.

11. The device according to any one of claims 8 to 10, wherein the backing material comprises a layer on one or both sides that is electrically conductive, preferably formed by at least one member selected from the group consisting of poly(3,4- ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), poly(3,4- ethylenedioxythiophene):p-toluenesulfonate (PEDOT:Tos), poly(3,4- propylenedioxythiophene) (ProDOT), poly(dioxythiophenes), poly(3,4- dialkylthiophenes), polyaniline (PANI), polypyrrole (PPy), poly(2,5-thienylenevinylene) (PTV), polythiophene (PTh), polythiophene derivatives, metallo-supramolecularpolymers, polyacetylene (PAc), poly(p-phenylene vinylene) (PPV), polyfluorene (PF), polycarbazole (PCz), polybithiophene (PBTh), a metal foil, or an insulating polymer that has been treated to impart electrical conductivity, for example by depositing a metallic film on a polymer foil or by coating with electrically conductive materials such as carbon, aluminum foil, copperfoil, nickel foil, stainless steel foil, titanium foil, gold foil, silver foil, metallized PET, metallized PP, carbon ink coated film and metallized polyimide.

12. The device according to claims 8 and 11, wherein the electrically conductive material forming the electrically conductive surface of the backing comprises a polymer selected from the group consisting of PEDOT, PANI, ProDOT and their derivatives, obtained from modified monomer structures including alkyl-substituted EDOT, EDOT- OH, Br-EDOT, EDOT-NH2, EDOT-COOH, optionally having a counter-ion selected from the group consisting of PSS“ (poly(styrenesulfonate), Tos“ (p-toluenesulfonate), CI04“ (perchlorate), BF4“ (tetrafluoroborate), PF6“ (hexafluorophosphate), OTf" (triflate), DBSA“ (dodecylbenzenesulfonate), CSA“ (camphorsulfonate), NO3“ (nitrate), SO42-(sulfate), HS04“ (hydrogen sulfate), TFSI“ (bis(trifluoromethanesulfonyl)imide), Cl" (chloride), Br“ (bromide), 1“ (iodide), F“ (fluoride), CF3SO3“ (trifluoromethanesulfonate), CH3SO3“ (methanesulfonate), acetate (CH3COO“), citrate, and phosphate.

13. The device according to any one of the preceding claims, wherein the adhesive is selected from the group consisting of acrylic-based adhesives, urethane-based adhesives, rubber-based adhesives, vinyl-based adhesives, epoxy-based adhesives, silicone-based adhesives, and mixtures thereof, and wherein the adhesive is preferably a pressure-sensitive adhesive.

14. The device according to any one of the preceding claims, wherein the adhesive is preferably an acrylic-based adhesive, more preferably an acrylic copolymer or network adhesive, prepared by polymerizing an adhesive precursor mixture comprising at least the following components a) 20 to 80 wt % of acrylate monomers (al) from the group of (meth)acrylic esters containing at least one oxygen atom; and b) 20 to 80 wt % of acrylate monomers (a 2) from the group of (meth)acrylic esters and / or amides containing at least one nitrogen atom; and c) 0.0 wt % to 15 wt % of one or more electro-responsive compounds from the group of polymerizable zwitterionic monomers and / or non-polymerizable zwitterionic compounds, preferably one or more zwitterionic monomers; and d) 0.005 to 10 wt % of at least one initiator; ande) 0.0 wt % to 20 wt % of an aqueous electrolyte component; and f) 0.0 wt % to 10 wt % by weight one or more additives e.g. water-retaining additives, catalysts, corrosion inhibitors, crosslinkers, plasticizers, and tackifiers; wherein the weight fractions of the components are based on the total weight of the precursor mixture.

15. Use of the device as defined in any of the preceding claims in an assembly process of packaging, electronic devices, such as computers, chips, smartphones, displays, touch panels, sensors, light sources such as LEDs or OLEDs, or other electronic devices.

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