Adhesive tape, bonded component and method for electrolytically releasing bonded component

Abstract

The invention relates to an adhesive tape, an adhered component, a method for electrolytically releasing an adhered component, and the use of the adhesive tape for adhering components in electronic, motor, medical and dental devices. The adhesive tape comprises at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a reactive heat-activatable adhesive and comprises at least one electrolyte.

Description

Technical Field

[0001] This invention relates to adhesive tapes, to bonded composites, to methods for electrically debonding bonded composites, and to the use of adhesive tapes for bonding components in electronic devices, automobiles, medical devices, and dental devices. Background Technology

[0002] Double-sided pressure-sensitive adhesive tape is commonly used to bond metal parts to plastics. The resulting adhesive strength is sufficient to secure and fasten the metal parts to the plastic. The metals used are preferably steel, stainless steel, and aluminum. Examples of plastics used are PVC, ABS, PC, or blends based on these plastics. However, the demands on portable consumer electronics are constantly increasing. These products are becoming smaller, and therefore the bonding area is decreasing. These conditions are particularly problematic for metal bonding on plastics. This bonding can be achieved particularly efficiently using a heat-activated film, which, upon activation, produces exceptionally high adhesive strength.

[0003] Reactive, heat-activated adhesives can be based on different polymers and crosslinking chemicals and mechanisms.

[0004] WO 2013 / 174650 A1 discloses, for example, heat-activated adhesives based on mixtures of nitrile rubber and phenolic resin as reactive resins.

[0005] Recently, there has been a growing interest in "on-demand debonding" capabilities, driven by environmental legislation, end-customer awareness of sustainability, and increased cost pressures in production. Debonding processes are used in various scenarios, including rework, repair, recycling, and as processing aids.

[0006] Debonding technology aims to achieve cohesive splitting within the adhesive layer or detachment of the adhesive layer from the substrate. The former requires cleaning the substrate before re-bonding, while the latter does not.

[0007] However, adhesive debonding techniques that guarantee the required high and durable reliable bond strength are often relatively difficult to achieve, or their applications, such as debonding using penetrating solvents, are very time-consuming.

[0008] For example, particularly in the rework or repair of electronic devices such as smartphones and tablets, the current method primarily uses cohesive split adhesives, typically in the form of pressure-sensitive tapes, whose cohesion decreases to the point where manual cohesive separation can occur when the adhesive is heated. This results in significant rework to prepare substrate surfaces contaminated with adhesive residues for re-bonding.

[0009] In addition to thermally mediated separation methods, electro-separation methods have also been discussed. For example, EP 3031875 B1 discloses reducing the adhesive strength of acrylate adhesive compounds by applying voltage.

[0010] However, due to chemical curing, reactive thermally activated adhesives typically exhibit very high adhesion strength.

[0011] Therefore, these tape solutions are non-detachable, or cannot be detached without damaging the substrate to which they are bonded and under very high force.

[0012] Therefore, the present invention aims to provide an adhesive tape comprising at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a heat-activated adhesive, and wherein the tape can be detached from at least one substrate under a small force. Simultaneously, the adhesive strength of the tape to the substrates to be bonded should not be negatively compromised before detachment. Summary of the Invention

[0013] According to the present invention, this objective is achieved by the adhesive tape according to claim 1.

[0014] The tape according to the invention comprises an adhesive layer D, wherein the adhesive of the adhesive layer D is a reactive, heat-activated adhesive, and contains at least one electrolyte.

[0015] With the presence of the electrolyte, the adhesive layer D can be electrically detached by applying a voltage.

[0016] Surprisingly, it has been demonstrated that adhesive tapes containing at least one electrolyte and therefore containing a heat-activated reactive adhesive can be electrically detached from the bonded substrate by applying voltage in an easy and rapid manner without applying a large force, and at the same time, the adhesive strength of the tape to the substrate is not negatively impaired before detachment.

[0017] Adhesive tapes and methods for electrical re-detachment or electrical reduction of adhesive strength are known in principle in the prior art. For example, as described above, EP 3031875 B1 discloses such an electrical method. In this case, the electrically detachable adhesive formulation is an acrylate-based adhesive.

[0018] However, what was unforeseen in this case was that heat-activated adhesive tapes in film form (which have relatively high adhesive strength on various substrates) could also be electrically debonded after bonding, and this would be possible without negatively compromising the adhesive strength of the tape to the substrates to be bonded before debonding. Debonding would also be clean and easy.

[0019] In particular, unforeseen circumstances allow the relatively rigid matrix (e.g., containing rubber) in the adhesive film or tape to be electrically detachable, with the electrolyte having any compatibility with the matrix and migrating through the matrix quickly enough without negatively impairing the bond strength. Detailed Implementation

[0020] The tape of the present invention is preferably a double-sided tape. For simplicity, the tape of the present invention is also referred to as "tape" in the context of the double-sided embodiment.

[0021] This invention relates to tapes, which can exist in any desired final form, but tape rollers are preferred. Tapes, especially tapes in the form of elongated sheets, can be produced in the form of rollers, i.e., rolled up on themselves in the form of an Archimedean spiral, or produced as strips, such as in the form of blanks or diecuts.

[0022] The tape of the present invention is particularly present in the form of an elongated sheet. An elongated sheet is understood to mean an object whose length (in the x-direction) is many times greater than its width (in the y-direction), and whose width remains approximately and preferably identical throughout its length.

[0023] For the purposes of this invention, the general term "tape" and the synonymous "adhesive strip" encompasses all sheet-like structures, such as films or film portions extending in two dimensions, strips having an extended length and a finite width, strip portions, etc., and finally, die-cut pieces or labels.

[0024] In addition to its longitudinal (x-direction) and transverse (y-direction) areas, the tape also has a thickness (z-direction) perpendicular to these two areas, which is much larger than the longitudinal and transverse areas. The thickness is very substantially uniform, preferably identical within tolerances, over the entire area of ​​the tape, determined by its length and width.

[0025] The statement is made by analogy to the carrier layer that forms layers in the x and y directions as elements of an adhesive tape according to some preferred embodiments.

[0026] Understand that each layer is arranged on top of the others along the z-direction.

[0027] All statements in this specification apply to tapes according to the invention, methods for producing tapes according to the invention, bonded composites according to the invention, methods for producing bonded composites according to the invention, methods for electro-debonding composites, and uses of tapes according to the invention.

[0028] This invention also covers all features that are part of the subject matter of any dependent claim. It also covers combinations of features with each other, as well as combinations having different levels of preference. Thus, for example, the invention covers combinations of a first feature designated as "preferred" and a second feature designated as "particularly preferred." In the context of the subject matter mentioned in the "implementation" section, this also includes different levels of preference.

[0029] The adhesive of adhesive layer D is described in more detail below.

[0030] The adhesive layer D contains at least one electrolyte.

[0031] "Electrolyte" is currently understood as a compound that "dissociates into ions in a solid, liquid, or dissolved state and undergoes directional motion under the influence of an electric field," as described in the German Wikipedia entry "Elektrolyt" [electrolyte] dated January 4, 2023.

[0032] The electrolyte for the adhesive layer D is preferably selected from ionic liquids and metal salts, with ionic liquids being particularly preferred.

[0033] In particular, the tape can be easily detached by using one or more ionic liquids as electrolytes without adversely affecting the adhesive properties of the tape. Ionic liquids have the advantage of being easily and uniformly dispersed in the polymer matrix of the adhesive, and the detachment operation is faster compared to other electrolytes.

[0034] Furthermore, ionic liquids are non-volatile, especially at room temperature. They are also relatively heat-resistant, non-flammable, and chemically stable.

[0035] In the context of this invention, an ionic liquid is a salt that is liquid at room temperature (i.e., 23°C). Therefore, ionic liquids contain both anions and cations.

[0036] Therefore, ionic liquids are particularly suitable as electrolytes in the context of the separation method / method for electro-debinding of the present invention.

[0037] When a voltage is applied, anions migrate to the anode side and cations migrate to the cathode side. Not wishing to limit ourselves to this, it can be mechanistically assumed that this leads to a decrease in the adhesive strength of the adhesive layer containing the ionic liquid to at least one substrate, thereby achieving adhesive separation between the adhesive and at least one substrate.

[0038] All ionic liquids are applicable in principle to the context of this invention.

[0039] The ionic liquid used in the context of this invention comprises at least one anion and at least one cation. It is also conceivable that the ionic liquid comprises two or more types of anions and / or two or more types of cations. It is also conceivable to add two or more different ionic liquids to adhesive layer D, or for adhesive layer D to thus contain two or more different ionic liquids.

[0040] Preferably, the anions of the ionic liquid are selected from:

[0041] Br - AlCl4 - Al2Cl7 - NO3 - BF4 - PF6 - CH3COO - CF3COO - CF3CO3 - CF3SO3 - (CF3SO2)2N - (CF3SO2)3C - AsF6 - SbF6 - CF3(CF2)3SO3 - (CF3CF2SO2)2N - CF3CF2CF2COO - and (FSO2)2N - .

[0042] Surprisingly, in this way, in reactive, heat-activated adhesives, a reduction in adhesive strength is achieved by applying voltage, and thus the excellent electroremovability of the tape of the present invention is achieved. In particular, the anion achieves particularly rapid (re)removal without leaving any residue.

[0043] The anion is particularly preferably selected from (CF3SO2)2N - and (FSO2)2N - .

[0044] These anions are particularly suitable because they achieve optimal electrodegradability. In particular, re-degradation from these anions is exceptionally rapid and leaves no residue.

[0045] Preferably, the cation of the ionic liquid is selected from imidazolium-based cations, pyridinium-based cations, pyrrolidine-based cations, and ammonium-based cations.

[0046] Surprisingly, in this way, in reactive, heat-activated adhesives, a reduction in adhesive strength is achieved by applying voltage, and thus the excellent electroremovability of the tape of the present invention is achieved. In particular, the anion achieves particularly rapid (re)removal without leaving any residue.

[0047] Particularly preferred, the cation is selected from imidazolium-based cations.

[0048] These cations are particularly suitable because they achieve optimal electrodegradability. In particular, re-degradation from these cations is exceptionally rapid and leaves no residue.

[0049] Very particularly preferred, the cation is selected from 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium. Even more preferred, the cation is 1-ethyl-3-methylimidazolium.

[0050] The electrolyte for adhesive layer D is particularly preferably selected from the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI). In this way, surprisingly, in reactive, heat-activated adhesives, a reduction in adhesive strength is achieved by applying a voltage, and thus, excellent electroremovability of the tape of the present invention is achieved. In particular, the anion achieves particularly rapid (re)removal without leaving any residue.

[0051] Preferably, based on the total amount of adhesive, the first adhesive layer D contains 2% to 20% by weight, particularly preferably 5% to 18% by weight, of an electrolyte, preferably an ionic liquid.

[0052] When using such preferred or particularly preferred amounts of electrolyte, especially ionic liquid, relatively rapid electrodesorption is possible, without negatively damaging the adhesive layer before it de-adhedes from adjacent layers, especially at least one substrate.

[0053] The compound in adhesive layer D is a reactive, heat-activated adhesive.

[0054] Reactive, heat-activated adhesives (also known as "reactive adhesives") are polymer systems with functional groups that allow a chemical reaction to occur when heat is supplied, wherein the adhesive is chemically cured and thereby produces relatively high internal strength.

[0055] It may also be advantageous to design reactive adhesives in such a way that they become softer and / or more fluid at elevated temperatures in order to best conform to the bonded composite; this is particularly and preferably achieved through thermoplastic components.

[0056] High adhesive strength and thus a bonding effect are achieved due to the described chemical reaction and physical melting.

[0057] Functional groups are also referred to as reactive groups. In the context of reactive, heat-activated adhesives in this invention, these groups are particularly components of the polymer and / or other components of the adhesive, such as, in particular, resins (also referred to in this context as reactive resins) and / or crosslinking agents.

[0058] As can be inferred from the term "thermally activated," the activation that leads to the adhesive effect is accomplished by supplying heat. This means that at room temperature, more specifically at 23°C, these adhesives are not activated; that is, the mechanism leading to permanent adhesion is not triggered.

[0059] Preferably, the tape according to the invention is activated at a temperature of 110°C or higher, and preferably between 110°C and 250°C, particularly preferably between 120°C and 200°C, for its heat-activated adhesive. The term "heat-activated" preferably means activation at a temperature of 110°C or higher, and preferably between 120°C and 250°C, particularly preferably between 120°C and 200°C.

[0060] The activation duration is preferably 5 seconds to 10 minutes, and particularly preferably 5 seconds to 6 minutes.

[0061] According to a preferred embodiment of the invention, the duration is 6 to 10 minutes, particularly at an activation temperature of, for example, 120°C.

[0062] According to a further preferred embodiment of the invention, the duration is from 5 seconds to 1 minute, particularly 30 seconds, especially at an activation temperature of, for example, 180°C.

[0063] In this case, at high activation temperatures within the stated temperature range, a correspondingly short activation duration is preferably selected, while at low temperatures, a correspondingly long activation duration is selected. This also depends particularly on the desired adhesive strength.

[0064] Activation is also preferably carried out under pressure (also known as compression pressure). The compression pressure is preferably 1 to 30 bar, particularly preferably 3 to 30 bar, very preferably 5 to 30 bar, and even more preferably 5 to 15 bar, for example and especially 10 bar.

[0065] Prior to activation, so-called pre-lamination is preferably performed to achieve optimal wetting of the substrate. This is specifically and, for example, done by preheating the substrate to be bonded.

[0066] Preferably, for this purpose, the substrate to be bonded is heated to a temperature of 95 to a maximum of 120°C. The adhesive layer is applied to the respective substrate, preferably under a pressure of 2 to 6 bar for a duration of 3 to 10 seconds.

[0067] This ensures that the adhesive flows evenly onto the substrate before activation.

[0068] The reactive, heat-activated adhesives used are preferably adhesives based on a mixture of at least one nitrile rubber S1 and a reactive component, particularly a reactive resin.

[0069] The weight percentage of nitrile rubber S1 is preferably between 25% to 70% of the total composition of the reactive, heat-activated adhesive, more preferably between 30% to 60% of the total composition.

[0070] Acrylonitrile rubber S1 preferably has an acrylonitrile content of 15% to 45%. Another criterion for acrylonitrile rubber S1 is Mooney viscosity. Due to the need to ensure high flexibility and low temperature, the Mooney viscosity should preferably be below 100 (Mountie ML1+4 at 100°C; according to DIN 53523).

[0071] The proportion of reactive resin in the heat-activated adhesive is preferably between 75% by weight and 30% by weight.

[0072] The term "reactive resin" refers specifically to short- to medium-chain oligomers or polymers, particularly those with an average molecular weight up to 10,000 g / mol.

[0073] The particularly preferred groups are those found in epoxy resins. For polymeric epoxy resins, the weight-average molecular weight M of the epoxy resin is... W Preferably, it is 100 g / mol to a maximum of 10,000 g / mol.

[0074] The reactive resin is preferably selected from phenolic resin, melamine resin, terpene-phenol resin, epoxy resin and polyisocyanate.

[0075] Epoxy resins contain, for example, reaction products of bisphenol A and epichlorohydrin, epichlorohydrin, glycidyl ester, epichlorohydrin and reaction products of p-aminophenol.

[0076] The reactive resin present is more preferably at least one phenolic resin. Phenolic varnish resin and resol resin, or a combination of phenolic varnish resin and resol resin, are particularly suitable for applications with excellent applicability.

[0077] According to those skilled in the art, phenolic varnish resin is a condensation polymer of phenol and formaldehyde under acidic conditions, wherein the formaldehyde / phenol ratio is especially less than 1:1.

[0078] Amorphous phenolic resins are produced by the condensation polymerization of phenol and formaldehyde under alkaline conditions.

[0079] In a particularly preferred embodiment of the invention, the adhesive contains a combination of at least one phenolic varnish resin and at least one methyl phenolic resin. Therefore, exceptionally high cohesiveness of the adhesive layer can be achieved, and thus the adhesive strength of the tape in the composite to be bonded is further optimized.

[0080] To accelerate the reaction between the two components, a crosslinking agent and an accelerator may optionally be added to the mixture.

[0081] The crosslinking agent used is preferably HMTA (hexamethylenetetramine).

[0082] In a particularly preferred embodiment of the invention, the reactive, heat-activated adhesive of the adhesive layer D is a reactive, heat-activated adhesive based on at least one mixture of at least one nitrile rubber S1 and at least one reactive component, particularly a reactive resin, wherein the reactive component is preferably at least one reactive resin selected from: epoxy resin, melamine resin, phenolic resin such as, in particular, phenolic varnish resin and methyl phenolic resin, terpene-phenol resin and polyisocyanate, particularly preferred phenolic resin, especially phenolic varnish resin and / or methyl phenolic resin.

[0083] The adhesive layer D may further contain conventional additives, such as catalysts, more specifically zinc oxide (ZnO), fillers, pigments, and aging inhibitors.

[0084] If the adhesive comes into contact with a layer that could potentially release so-called rubber poisons such as copper, manganese(II), iron(II), cobalt, or nickel ions, it is advantageous to add at least one type of metal passivator, also known as a metal scavenger. Specific examples of these are ADK-Stab CDA-1, CDA-1H, CDA-6, and CDA-10 from Adeka, and ADK-Stab ZS-27 or ZS-90; Hostanox OSP1 from Clariant; Naugard XL-1 from SIGroup; and Irganox MD-1024 from BASF. The typical dosage is up to 0.5% by weight, based on the total weight of the adhesive.

[0085] The present invention also provides an adhesive composite comprising at least the following layers:

[0086] • First substrate A; and

[0087] • Second substrate B; and

[0088] • The tape of the present invention is disposed between substrate A and substrate B and bonds substrate A and B together.

[0089] The present invention also provides a method for electro-debinding the composite of the present invention, comprising at least the following method steps:

[0090] i.) Apply a voltage at two different points in the complex, preferably a voltage of 2 to 50 V.

[0091] Step i) of the method according to the invention applies a voltage for electro-debonding of the composite.

[0092] Voltage, especially DC voltage.

[0093] According to a preferred embodiment of the invention, the voltage is 3 to 12 V. Such a voltage can be applied, particularly by means of a battery located in the immediate vicinity of the bond (such as, particularly and for example, in mobile phones, tablets, etc.).

[0094] According to a further preferred embodiment of the invention, the voltage is 12 to 50 V. This relatively high voltage allows for particularly rapid re-disengagement; for this purpose, only a few seconds of voltage application are required.

[0095] Technicians generally know how to apply voltage without causing unwanted short circuits.

[0096] Specifically, depending on the selected voltage, the duration of voltage application in step i.) can be several seconds, more particularly 2 seconds, up to 900 seconds, and preferably up to 600 seconds.

[0097] It is also conceivable that the voltage would be applied for a period of time longer than 900 seconds, especially if the voltage is relatively low.

[0098] The method of the present invention for electro-debonding the composite of the present invention allows substrates A and B to debond from each other in a rapid and easy manner without applying excessive force.

[0099] If the layers do not separate from each other after the application of voltage without further action, the method of the present invention includes at least the following further method steps:

[0100] ii.) Apply force to adhesive layer D and / or to substrate A and / or to substrate B such that the distance between substrates A and B increases.

[0101] According to step ii.), the force that may still be required is significantly less than the adhesion strength before the voltage is applied according to step i.).

[0102] The applied voltage according to step i.) occurs at two different points on the bonded composite of the present invention. The advantageous points at which the voltage is applied depend on the construction of the tape and the bonded composite, and therefore on the properties of the individual layers bonded together and the substrates A and B.

[0103] Some preferred implementation methods are described below.

[0104] According to a preferred embodiment, the tape is a transfer tape and consists of an adhesive layer D.

[0105] In an adhesive composite comprising two substrates A and B, the tape can advantageously debond electrically again due to the fact that both substrates A and B are conductive. For this purpose, a voltage is applied to substrates A and B, causing anions to migrate towards the anode and cations towards the cathode in the adhesive blend. Not wishing to be bound by a particular theory, the inventors hypothesize the following mechanism: the applied voltage causes the migration of electrolytes in the adhesive blend layer D, more specifically, the separation of anions and cations in the ionic liquid. This results in a significant reduction in the adhesion of the adhesive blend layer D to substrate A and substrate B, and causes these layers to debond from each other.

[0106] According to a preferred embodiment of the invention, the bonded composite therefore comprises the following layers:

[0107] • First substrate A, which is conductive; and

[0108] • Second substrate B, which is conductive; and

[0109] • The tape of the present invention comprises an adhesive compound layer D and is disposed between a substrate A and a substrate B, thereby bonding the substrate A and the substrate B together.

[0110] According to a further preferred embodiment, in addition to the first adhesive layer D, the tape further comprises at least the following layers:

[0111] • Second adhesive layer C; and

[0112] • At least one conductive carrier layer T is disposed between layers D and C.

[0113] This tape can be used as a double-sided tape and is applicable to a variety of different substrates via a second adhesive compound layer C. In principle, these substrates can be the same as those in the above embodiments, wherein the tape is a transfer tape.

[0114] However, this tape can also be used particularly advantageously when only one substrate, such as substrate A, is conductive, so that substrates A and B can be debonded from each other later.

[0115] According to a preferred embodiment, xi.) only the carrier layer T or xii.) the carrier layer T and the second adhesive compound layer C are designed to be conductive.

[0116] This means that voltage can be applied to either xi) the conductive carrier layer or xii.) the second adhesive compound layer C and the conductive substrate A.

[0117] The tape is initially advantageously used as a double-sided adhesive tape for bonding, such that an electrically detachable adhesive compound layer D is attached to a conductive substrate A and a second adhesive compound layer is attached to a substrate B, which may be conductive, but does not need to be conductive.

[0118] Unwilling to be bound by a specific theory, the inventors hypothesize the following mechanism: applying voltage causes the migration of electrolytes in the adhesive blend layer D, and more specifically, the separation of anions and cations in the ionic liquid. This results in a significant reduction in the adhesion of the adhesive blend layer D to the substrate A, and causes these layers to decouple from each other.

[0119] According to a preferred embodiment of the invention, xi.) only the carrier layer is conductive. When the carrier layer protrudes laterally over at least one adhesive compound layer, a voltage can be applied to it particularly easily and preferably particularly easily.

[0120] According to a further preferred embodiment of the invention, xii.) the carrier layer and the second adhesive compound layer C are conductive. This configuration has the advantage that voltage can be applied to the adhesive compound layer C. Lateral overhangs (lateral protrusions) of the carrier layer are not required. Therefore, the tape can be produced in a simple manner, especially because layers D, T, and C can be die-cut together.

[0121] Preferably, the tape according to the above embodiment consists of three layers: D, T, and C. This is also referred to in the context of the present invention as a three-layer composite DTC.

[0122] According to a preferred embodiment of the invention, the bonded composite therefore comprises the following layers:

[0123] • First substrate A, which is conductive; and

[0124] • Second substrate B; and

[0125] • The tape of the present invention is composed of a three-layer composite DTC and bonds substrates A and B together such that the adhesive compound layer D is attached to the conductive substrate A.

[0126] According to a further preferred embodiment, in addition to the first adhesive layer D, the tape further comprises at least the following layers:

[0127] • Second adhesive layer C; and

[0128] • At least a first conductive carrier layer T, disposed between layers D and C; and

[0129] • At least one second conductive carrier layer T' is disposed on the surface of the adhesive layer D on the side opposite to the first conductive carrier layer T; and

[0130] • A third adhesive layer C' is disposed on the surface of the second conductive carrier layer T' on the side opposite to the first adhesive compound layer D.

[0131] This tape has at least a layered structure CTD-T'-C', and as a double-sided tape, it can be adapted to a variety of different substrates via adhesive compound layers C and C'.

[0132] In principle, these substrates can be the same as those in the above embodiments, wherein the tape is a transfer tape or a DTC with a three-layer structure.

[0133] However, this tape can be used particularly and advantageously so that when neither substrate A nor B is conductive, substrate A and B can be detached from each other later.

[0134] According to a preferred embodiment, xi.) only carrier layers T and T' or xii.) carrier layers T and T', as well as the second adhesive blend layer C and / or the third adhesive blend layer C', are designed to be conductive.

[0135] This means that voltage can be applied to either of the two conductive carrier layers xi.) or xii.) to at least one of the adhesive blend layers C and C', and to one or the other adhesive blend layer.

[0136] Similar to the embodiments described above, it is assumed that applying a voltage causes the migration of electrolytes in the adhesive blend layer D, and more specifically, the separation of anions and cations in the ionic liquid. This results in a significant reduction in the adhesion of the adhesive blend layer D to the conductive carrier layers T and T', and causes these layers to debond from each other.

[0137] According to a preferred embodiment of the invention, xi.) only the carrier layers T and T' are conductive. When the carrier layers T and T' protrude laterally over at least one corresponding adjacent adhesive compound layer, a voltage can be applied to them particularly easily and preferably particularly easily.

[0138] According to a further preferred embodiment of the invention, xii.) the carrier layers T and T', as well as the second and third adhesive blend layers C and C', are conductive. This configuration has the advantage that voltage can be applied to the adhesive blend layers C and C'. Lateral drape of the carrier layers T and T' is not required. Therefore, the tape can be produced in a simple manner, especially because layers C, T, D, T', and C can be die-cut together.

[0139] Preferably, the tape according to the above embodiment consists of five layers: C, T, D, T', and C'. This is also referred to in the context of the present invention as a five-layer composite CTD-T'-C'.

[0140] According to a preferred embodiment of the invention, the bonded composite therefore comprises the following layers:

[0141] • First substrate A; and

[0142] • Second substrate B; and

[0143] • The tape of the present invention is composed of a five-layer composite CTD-T'-C', which bonds substrates A and B together.

[0144] In all embodiments, the conductive substrate may be, for example, the metal casing of a mobile phone.

[0145] In all embodiments, the non-conductive substrate may be, in particular, a housing or battery or other non-conductive component such as a speaker, made of a non-conductive material such as plastic.

[0146] The present invention also provides the use of the tape of the present invention for bonding components in electronic devices, automobiles, medical devices and dental devices.

[0147] In all the above embodiments, the carrier layer T or T and T' is conductive.

[0148] These layers will be further described below. For simplicity, the term "conductive carrier layer" or simply "carrier layer" will be used. Depending on which of the above embodiments this refers to, it may refer to carrier layer T or carrier layers T and T'.

[0149] The carrier layers T and T' are independent of each other and may be the same or different from each other.

[0150] Preferably, the conductive carrier layer comprises at least one metal.

[0151] Particularly preferably, the metal is selected from copper, nickel, zinc, tin, silver, gold, aluminum, iron, chromium, and alloys of these metals. Very particularly preferably, the metal is selected from aluminum, zinc, copper, and nickel. Very preferably, aluminum is preferred.

[0152] Preferably, the conductive carrier layer has a layer thickness of 10 nm to 50 µm measured in the z-direction (i.e., the stacking direction parallel to the layer arrangement).

[0153] According to a preferred embodiment of the invention, the conductive carrier layer comprises: a) at least one metal foil, preferably aluminum foil, and / or b) at least one conductive fabric comprising at least one metal, preferably selected from copper and nickel, and / or (c) one or more sheets of at least one metal deposited by vapor deposition, preferably selected from copper and aluminum, and / or (d) at least one metal mesh, and / or (e) a foil coated with metal by vapor deposition.

[0154] In principle, it is also conceivable that layer T includes a combination of two or more of the above options.

[0155] Metal foil, such as, and preferably, aluminum foil, is known to those skilled in the art.

[0156] The metal foil, such as and preferably aluminum foil, preferably has a layer thickness of 5 to 50 μm, more preferably 10 to 30 μm, measured in the z-direction (i.e., the stacking direction parallel to the layer arrangement).

[0157] Conductive fabrics are known to those skilled in the art, particularly by the term "conductive mesh". This refers to textile fabrics, such as those made of PET (polyethylene terephthalate), coated with metals, such as copper and / or nickel, which is how the conductivity of the textile is achieved.

[0158] Those skilled in the art will also recognize that metals can be deposited directly onto surfaces as single or multiple layers, such as on the surface of the adhesive compound layer in this case.

[0159] In the context of this invention, the conductive carrier layer can be provided by depositing a metal vapor phase onto the adhesive blend layer D, adhesive blend layer C, or adhesive blend layer C'.

[0160] Furthermore, those skilled in the art are familiar with metal meshes of different sizes. Metal meshes with appropriate layer thicknesses can be produced, for example, by laying a loosely sparse cloth of appropriately fine metal wires or by die-cutting a foil with at least one appropriate layer thickness.

[0161] In the case of films coated with metal by vapor deposition, non-conductive films are specifically coated with metal by vapor deposition to make them conductive. The film material can, in principle, be any material capable of undergoing vapor deposition with metal and suitable for use as a carrier film in an adhesive tape. Materials are particularly selected from polyesters and polyolefins, and mixtures of more than one material are also conceivable. Particularly preferred polyesters are polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Particularly preferred polyolefins are polypropylene (PP) and polyethylene (PE). According to a preferred embodiment, the film material is selected from PET, PEN, PE, and PP.

[0162] Preferably, it is a PET (polyethylene terephthalate) film. This film is dimensionally stable and therefore easy to process without significant stretching or tearing. This allows for the durable application of a uniform and gapless metal layer, resulting in persistent conductivity throughout the entire film, particularly in the z-direction.

[0163] In embodiments where at least one conductive carrier layer T or at least two conductive carrier layers T and T' are present, it is preferred that the at least one adjacent adhesive compound layer protrudes laterally in at least one extending direction of the layer plane, and thus includes lateral overhangs. Voltage can then be applied to these lateral overhangs in a simple manner.

[0164] In the case of a five-layer composite, the lateral overhangs of the conductive carrier layers T and T' are spatially separated from each other in an advantageous embodiment. This makes it easier to apply a voltage to the two overhangs.

[0165] When the metal deposited by vapor deposition serves as the carrier layer, it is preferable that the carrier layer protrudes laterally in at least one extending direction of the layer plane only on an adjacent adhesive compound layer, with the corresponding other adhesive compound layer acting as a mechanical support for the metal layer. In this case, the metal layer does not actually function as a carrier. Instead, the other adhesive compound layer acts as the carrier of the metal layer. However, for simplicity, the term carrier layer is also retained for the metal layer in these embodiments. Preferably, the thickness of layer T is greater than or equal to 10 nm (nanometers), preferably 50 to 200 nm.

[0166] According to a preferred embodiment of the present invention, the conductive carrier layer T or T and T' comprises: a) at least one metal foil, preferably aluminum foil, and / or b) at least one conductive fabric comprising at least one metal, preferably selected from copper and nickel, and / or d) at least one metal mesh, and / or e) a film coated with metal by vapor deposition, and suspended in at least one extension direction over the first adhesive blend layer D and the second adhesive blend layer C or the first adhesive blend layer D and the second adhesive blend layer C and / or the first adhesive blend layer D and the third adhesive blend layer C'.

[0167] This allows voltage to be applied to the carrier layer in a simple and safe manner. Meanwhile, the tape can be produced in a relatively simple way.

[0168] According to a preferred embodiment of the present invention, the conductive carrier layer T or T and T' comprises one or more sheets of at least one vapor-deposited metal, preferably one sheet, wherein the at least one vapor-deposited metal is preferably selected from copper and aluminum.

[0169] According to a particularly preferred embodiment of the invention, the conductive carrier layer T or T and / or T' comprises e) a film coated with metal by vapor deposition, and suspended over the first adhesive layer D in at least one extending direction. In this case, the film is coated with metal by vapor deposition, particularly on one surface, and the corresponding carrier layer is attached to the first adhesive compound layer D via the metallized surface, and thus to the electrically detachable layer.

[0170] This allows voltage to be applied to the carrier layer in a simple and safe manner.

[0171] In the context of this invention, the term "lateral overhang" is understood to mean any kind of lateral protrusion of one or more layers involved, and to mean that the involved layer extends accordingly beyond the reference layer, more specifically in the "xy" plane, and therefore laterally—perpendicular to the stacking direction. In the context of this invention, the terms "lateral extension" or "lateral extension portion" are also used instead of the term "lateral protrusion."

[0172] The term “lateral” here refers to each extending direction of the layer plane “xy” perpendicular to the stacking direction “z” of the layers. Therefore, the term is particularly independent of the geometry of the tape in the “xy” plane, which can be, for example, rectangular, as is customary for tape (see above), but can also be square or circular.

[0173] The terminology does not refer to minute fluctuations in the dimensions of the individual layers in the “xy” plane caused by die-cutting processes or similar forming processes, especially since the dimensions of such minute material protrusions preclude the application of voltage to them in a planned manner.

[0174] Adhesive compound layer C or C and C' can, in principle, be based on the same compound as adhesive compound layer D; the adhesive compound of layer C or C and C' need not contain any electrolyte, but may contain it. Preferably, layer C or C and C' does not contain any electrolyte.

[0175] According to some embodiments of the three-layer composite DTC described above, the adhesive layer C is conductive.

[0176] Similarly, the adhesive compound layer C and / or adhesive compound layer C' of the five-layer composite CTD-T'-C' can be designed to be conductive.

[0177] These layers are further described below. For simplicity, the term "conductive adhesive layer" is used where appropriate. Depending on which of the above embodiments, this refers to adhesive blend layer C or adhesive blend layer C and / or C'. Furthermore, for simplicity, the expression "adhesive layer C or C and / or C" is used, which means that the corresponding layer in the described tape embodiment comprises at least three layers or at least five layers of the composite.

[0178] The adhesive compound layers C and C' are independent of each other and may be the same or different from each other.

[0179] Preferably, the conductive adhesive compound layer contains at least one metal for this purpose, such as, in particular, nickel, copper or silver, preferably in the form of conductive metal particles and / or metallized particles, more preferably metal particles.

[0180] The metallized particles are, particularly and preferably, glass or polymer particles metallized with at least one metal, resulting in the metallization of particles that were originally non-conductive to conduct electricity.

[0181] Particularly preferred, the conductive adhesive compound layer comprises conductive particles selected from nickel particles, copper particles, and silver-coated copper particles.

[0182] According to a particularly preferred embodiment, the conductive adhesive compound layer comprises nickel particles.

[0183] Preferably, based on the 100% by weight of polymer and adhesive resin present, the conductive adhesive layer contains 5% to 65% by weight, particularly preferably 20% to 40% by weight, very preferably 25% to 35% by weight of conductive particles, more particularly metal particles and / or metallized particles.

[0184] The conductive particles should preferably be no larger than or not significantly larger than the corresponding thickness of the conductive adhesive compound layer in the z-direction as measured by an optical microscope.

[0185] Preferably, the conductive particles have an average particle size of 1 to 10 μm, more preferably 1 to 6 μm, and even more preferably 3 to 5 μm, such as particularly 4 μm.

[0186] The conductive adhesive compound layer is conductive, at least in the z-direction.

[0187] However, it can also be conductive in the xy plane. If the conductive adhesive compound layer is designed to be conductive only in the z-direction, but not necessarily in the xy-direction, then in a preferred embodiment where metal, especially metal particles, are added to achieve conductivity, a smaller amount of these materials is required. This optimizes the adhesive in terms of desired conductivity, adhesion strength, flow behavior, and cost.

[0188] In the context of this invention, the layer is considered "conductive", particularly when the resistance is less than 1 ohm, as measured in the corresponding direction, and more particularly in the z-direction in this case, according to standard MIL-DTL-83528C.

[0189] The following statements apply regardless of whether the adhesive layers C or C and / or C' are designed to be conductive.

[0190] According to a preferred embodiment of the invention, adhesive layer C or C and / or C', like adhesive layer D, is a reactive, heat-activated adhesive based on at least one mixture of at least one nitrile rubber S1 and at least one reactive component, particularly a reactive resin, as described above in relation to adhesive layer D.

[0191] According to a preferred embodiment of the invention, the nitrile rubber S1 and reactive resin used in adhesive layer C or C and / or C' are the same as those used in adhesive layer D.

[0192] This makes it particularly possible to bond similar substrates (here referred to as A and B) together. Furthermore, this increases the tape's aging stability and thermal stability.

[0193] According to a further preferred embodiment of the invention, the adhesive used in adhesive layer C or C and / or C' is a different adhesive than the adhesive used in adhesive layer D.

[0194] This allows the properties of the conductive layer to be adapted particularly well to the substrate bonded via adhesive layer C or C and / or C'. Since adhesive layer C or C and / or C' preferably does not contain or must contain any electrolytes, such as ionic liquids, the composition does not need to be adapted thereto.

[0195] Preferably, the adhesive of adhesive layer D is not a pressure-sensitive adhesive, and therefore preferably not a pressure-sensitive adhesive, and adhesive layer D is therefore preferably not a pressure-sensitive adhesive layer D.

[0196] According to a preferred embodiment, the adhesive layer C or C and / or C' is also not a pressure-sensitive adhesive.

[0197] According to a further preferred embodiment of the invention, the adhesive of adhesive layer C or C and / or C' is a pressure-sensitive adhesive, and therefore adhesive layer C or C and C' is a pressure-sensitive adhesive layer.

[0198] According to the present invention, as is generally customary, pressure-sensitive adhesive compositions are currently substances that are permanently tacky and adhesive, particularly at room temperature. The pressure-sensitive adhesive formulation is characterized by its ability to be applied to a substrate under pressure and remain adhered there, without further specifying the applied pressure or the duration of exposure to that pressure. In some cases, depending on the exact properties of the pressure-sensitive adhesive formulation, temperature and humidity, and the substrate, a short-term, brief contact with minimal pressure is sufficient to achieve adhesion; in other cases, longer exposure to high pressure may be required.

[0199] Pressure-sensitive adhesive formulations possess specific, characteristic viscoelastic properties that result in durable tack and adhesive strength. Their defining feature is that, upon mechanical deformation, the outcome is a viscous flow process and the development of elastic rebound forces. These two processes are interrelated, depending not only on the exact composition, structure, and degree of cross-linking of the pressure-sensitive adhesive formulation, but also on the rate and duration of deformation and the temperature.

[0200] A viscous flow component is essential for adhesion. Only a viscous component generated by macromolecules with relatively high flowability allows for good wetting and flow to the substrate to be bonded. A high proportion of viscous flow results in high pressure-sensitive adhesive tack (also known as tackiness or surface tack), and therefore often also high adhesive strength. Highly cross-linked systems, or crystalline or glassy polymers, generally exhibit at least low pressure-sensitive adhesive tack (if any) due to the lack of free-flowing components.

[0201] Elastic resilience components are essential for achieving cohesion. For example, they are generated by very long chains and entangled macromolecules that are physically or chemically cross-linked, enabling the transmission of forces that attack the adhesive bond. They have the effect that the adhesive bond can withstand sustained stress (e.g., in the form of sustained shear stress) acting upon it to a sufficient degree over an extended period of time.

[0202] To more accurately describe and quantify the measurements of the elastic and viscous components, as well as the relationships between them, the variables of storage modulus (G') and loss modulus (G'') can be used, which can be determined by dynamic mechanical analysis (DMA, according to DIN EN ISO 6721). G' is a measure of the elastic component of the material, and G'' is a measure of the viscous component. Both parameters depend on the deformation frequency and temperature.

[0203] The parameters can be determined using a rheometer. Here, the material being examined is subjected to sinusoidal oscillating shear stress, for example, in a plate-to-plate arrangement. In the case of a shear stress-controlled device, the deformation as a function of time and the time delay of that deformation are measured relative to the onset of the shear stress. This time delay is called the phase angle δ.

[0204] The energy storage modulus G' is defined as follows:

[0205] G' = (τ / γ) • cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress vector and deformation vector).

[0206] The loss modulus G'' is defined as:

[0207] G'' = (τ / γ) • sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress vector and deformation vector).

[0208] For the purposes of this invention, if at room temperature, defined herein as at 23°C, at 10 0 Up to 10 1 Within the deformation frequency range of radians per second, G' is at least partially within 10 3 Up to 10 7 A substance is generally considered a pressure-sensitive adhesive if it falls within the range of Pa, and if G'' is also at least partially within this range. "Partially" means that at least a portion of the G' curve falls within the range of 10 Pa. 0 (inclusive) to 10 1 The range of deformation frequencies in radians per second (inclusive) (x-axis) and 10 3 (inclusive) to 10 7 The range of G' values ​​spanned by Pa (inclusive) (vertical axis) is within the window. This applies to G'' with the necessary modifications.

[0209] Preferably, the pressure-sensitive adhesive compound is prepared at 23°C for 10 minutes. 0 Up to 10 1 Within the deformation frequency range of radians / second, it has a value measured according to DIN EN ISO 6721 at 10 3 Up to 10 7Storage modulus G' and loss modulus G'' within the range of Pa.

[0210] To achieve viscoelastic properties, the monomers upon which the polymers in the pressure-sensitive adhesive formulation are based and any other components present in the formulation are specifically selected such that the pressure-sensitive adhesive formulation has a glass transition temperature (according to DIN 53765) below the service temperature (i.e., typically below room temperature (23°C)). By means of suitable cohesive strengthening measures, such as crosslinking reactions (forming bridging links between macromolecules), the temperature range in which the polymer composition exhibits pressure-sensitive adhesive properties can be expanded and / or modified. Therefore, the application range of the pressure-sensitive adhesive can be optimized by setting a balance between the flowability and cohesiveness of the formulation.

[0211] In particular, the pressure-sensitive adhesive has a glass transition temperature of ≤ 23°C as determined according to DIN 53765.

[0212] Another subject of this invention is the production of the adhesive tape of this invention.

[0213] The adhesive layer D and—depending on the implementation method—an additional adhesive are produced by known processes and formed in layer form, particularly by application.

[0214] In addition, one or more drying steps may be optionally performed.

[0215] The lamination of multiple layers on top of each other is achieved in a manner known to those skilled in the art, the layers being stacked such that this specifically provides a layer composite DTC, wherein T is arranged between D and C, or C'-T'-DTC as a double-sided tape.

[0216] The carrier layers T and T' can be provided in various ways as described above.

[0217] Therefore, it is conceivable that a) a metal foil, particularly aluminum foil, and / or b) a conductive mesh, and / or d) at least one metal mesh, and / or e) a PET film coated with metal by vapor deposition, located between the respective adhesive compound layers.

[0218] In addition, c) the metal particles can be deposited directly into the surface of the adhesive compound layer D, C, or C' via vapor deposition.

[0219] Another subject of the present invention is the production of bonded composites using the tape according to the invention.

[0220] To activate the reactive, heat-activated adhesive of the tape according to the invention, the tape is placed between the substrates to be bonded, and preferably heated under pressure, conforming to all the above statements regarding the activation of the bonding mechanism. Furthermore, pre-lamination is preferably performed, as observed above.

[0221] The tapes of the present invention are particularly double-sided tapes, wherein, depending on the embodiment, both surfaces of the adhesive layer D (transfer tape), or one surface of the first adhesive layer D and one surface of the second adhesive layer C (three-layer composite DTC), or one surface of each of the adhesive layers C and C' (five-layer composite CTD-T'-C'), can each be used for bonding to the substrate.

[0222] Advantageously, the exposed outer surface of the adhesive layer of the tape of the present invention may be provided with an anti-adhesive material, such as release paper or release film, also known as a liner. The liner may also be a material having an anti-adhesive coating on at least one side, preferably on both sides, such as a double-sided silicone-coated material. The liner, or more generally, a temporary carrier, is not part of the tape but merely an aid for production and / or its storage and / or for further processing by die-cutting. Furthermore, unlike a permanent carrier, the liner is not firmly bonded to the adhesive layer but functions as a temporary carrier, i.e., as a carrier that can be peeled off from the adhesive layer. "Permanent carrier" is also referred to as "carrier" in this application.

[0223] The thickness of each adhesive layer (in the z-direction) is preferably 10 to 225 μm, particularly preferably 15 to 150 μm, very preferably 20 to 100 μm, and even more preferably 25 to 70 μm.

[0224] In embodiments of the three-layer composite DTC and the five-layer composite CTD-T'-C', adhesive layers D and C, or D and C and D and C', have different layer thicknesses in preferred embodiments, with the thickness of adhesive layer D being, for example, less than the thickness of adhesive layers C or C and C'.

[0225] In a further preferred embodiment, layers D and C, or D, C and C', have the same layer thickness.

[0226] If the thickness of layer D is too high, it becomes uneconomical and expensive due to the electrolyte present in it.

[0227] Preferred embodiments of the invention will then be illustrated and described in more detail with reference to the accompanying drawings. In these drawings,

[0228] Figure 1 A simplified schematic cross-sectional view of the double-sided tape of the present invention is shown in a preferred embodiment; and

[0229] Figure 2 A simplified schematic cross-sectional view of the double-sided tape of the present invention is shown in a preferred embodiment; and

[0230] Figure 3 A simplified schematic cross-sectional view of the double-sided tape of the present invention is shown in a preferred embodiment; and

[0231] Figure 4 A simplified schematic cross-sectional view of the bonded composite of the present invention, in a preferred embodiment, is shown; and

[0232] Figure 5 A simplified schematic cross-sectional view of the bonded composite of the invention under applied voltage, in a preferred embodiment, is shown; and

[0233] Figure 6 A simplified schematic cross-sectional view of the bonded composite of the present invention after voltage has been applied and therefore adhesive cracking has occurred; and

[0234] Figure 7 A simplified schematic cross-sectional view of the bonded composite of the present invention, in a preferred embodiment, is shown; and

[0235] Figure 8 A simplified schematic cross-sectional view of the bonded composite of the present invention in a preferred embodiment is shown.

[0236] If available Figure 1 As seen in the image, adhesive compound layer D1 is attached to carrier layer T2 via one of its surfaces. A second adhesive compound layer C3 is disposed on the surface of carrier layer T on the side opposite to layer D.

[0237] If it is still possible Figure 1 As can be seen, the layered compound represents a double-sided tape, wherein the surface of the adhesive compound layer D and the surface of the second adhesive compound layer C can each be used for bonding.

[0238] Figure 2 A preferred embodiment of the invention is shown. In this embodiment, the conductive carrier layer T2 protrudes laterally over the adhesive blend layer D1 and the second adhesive blend layer C3 in at least one extending direction of the layer plane, such that the conductive carrier layer T2 includes a cantilever having at least one free surface 2a.

[0239] Figure 3 Another preferred embodiment of the invention is shown. In this case, the conductive carrier layer T2 protrudes laterally over the adhesive compound layer D1 in at least one extending direction of the layer plane, such that the conductive carrier layer T2 includes an overhang having a free surface 2a. Figure 3 In this process, the adhesive compound layer C3 is formed such that it also includes a hanger relative to layer D1. The carrier layer T2 is specifically a PET film coated with aluminum on one side, with the aluminum-coated side attached to layer D1.

[0240] Figure 4 A schematic illustration of the bonded composite of the present invention in a preferred embodiment is shown. (See also...) Figure 4 As can be seen, the tape is applied to the adhesive compound layer D1 on the surface of the first substrate A4, and the first substrate is conductive.

[0241] In addition, an adhesive tape is disposed on the second adhesive layer C3 on the surface of the second substrate B5.

[0242] Figure 4 Also shown by way of example, the conductive carrier layer T2 protrudes laterally over the adhesive compound layer D1 in at least one extending direction of the layer plane, such that the conductive carrier layer T includes an overhang having a free surface 2a.

[0243] A voltage can now be applied through this free surface 2a, as in Figure 5 The schematic diagram shown in the image is as follows.

[0244] Applying voltage causes the migration of electrolytes in the adhesive layer D1, and more specifically, the separation of anions and cations of the ionic liquid.

[0245] This results in a significant reduction in the adhesion of adhesive compound layer D1 to substrate A4, and causes these layers to detach from each other, as can be seen in... Figure 6 As seen in the schematic diagram.

[0246] exist Figure 7 In the preferred embodiment, another schematic illustration of the bonded composite of the present invention is shown. (See also...) Figure 7 As can be seen, the tape is applied to the adhesive compound layer C3 on the surface of the first substrate A4.

[0247] In addition, an adhesive tape is applied to the third adhesive compound layer C'7 on the surface of the second substrate B5.

[0248] Between layers C3 and C′7 is an electrically detachable adhesive compound layer D1 and two conductive carrier layers T2 and T′6, with layer D1 positioned between the carrier layers.

[0249] Figure 7Similarly, by way of example, conductive carrier layers T2 and T'6 are shown to laterally protrude from the adhesive compound layer D1 in at least one extension direction in the layer plane in each case, such that conductive carrier layer T includes an overhang having a free surface 2a, and conductive carrier layer T includes an overhang having a free surface 6a.

[0250] exist Figure 8 In, with similar Figure 7 The preferred embodiment illustrated in the diagram shows another schematic illustration of the bonded composite of the present invention. However, compared with... Figure 7 In contrast, the conductive carrier layers T2 and T'6 are suspended in different directions, resulting in the spatial separation of the resulting free surfaces 2a and 6a of these layers.

[0251] Now we can Figure 5 A similar method is used to apply voltage through these free surfaces 2a and 6a. Figure 5 In contrast to the implementation shown, voltage can be applied to surfaces 2a and 6a, meaning that neither substrate A nor B needs to be conductive.

[0252] The applied voltage causes the electrolyte to migrate in the adhesive layer D1, and more specifically, the separation of anions and cations of the ionic liquid. This results in a significant reduction in the adhesion of the adhesive mixture layer D1 to the carrier layers T2 and / or T'6, and causes these layers to decouple from each other. More specifically, detachment occurs at the layer where the negative electrode is applied.

[0253] According to Figure 8 In the case of spatially separated surfaces 2a and 6a, the application of voltage is simplified.

[0254] Figures 1 to 8 The illustrations are schematic diagrams as shown. In particular, the layer thicknesses of the individual layers D, T, and C may differ from each other. Furthermore, substrates A and B are only schematically represented as additional layers. These, of course, can have any other spatial geometry.

[0255] Several embodiments are described below to further illustrate the invention.

[0256] Test methods

[0257] Unless otherwise specified, all measurements were performed at 23°C and 50% relative humidity. Mechanical and adhesive data were determined as follows:

[0258] Molecular weight M n M w

[0259] The number-average molecular weight M reported in this document n and weight average molecular weight M wThe values ​​were determined by gel permeation chromatography (GPC). 100 µl of clarified, filtered sample (4 g / L concentration) was used for the determination. Tetrahydrofuran containing 0.1 vol% trifluoroacetic acid was used as the eluent. Measurements were performed at 25 °C. A PSS-SDV column, 5 μm, 10 μm was used as the pre-column. 3 Å, 8.0 mm 50 mm (values ​​here and below are in the following order: type, particle size, porosity, inner diameter) Length; 1 Å = 10 –10 For separation, a combination of PSS-SDV type columns was used, 5 μm, 10 m. 3 Å, 10 5 Å and 10 6 Å, each 8.0 mm 300 mm column (from Polymer Standards Service; measured by Shodex RI71 differential refractometer). Flow rate: 1.0 ml / min. Calibrate against PMMA standard (polymethyl methacrylate calibration) for polar molecules, otherwise against PS standard (polystyrene calibration).

[0260] thickness

[0261] The thickness of the adhesive compound layer can be determined by subtracting the (known or individually determineable) thickness of a section of such adhesive compound layer (defined by its length and width) applied to the liner from the thickness of a section of the same size of the liner used. The thickness of the adhesive compound layer can be determined with an accuracy of less than 1 μm using commercially available thickness measuring equipment (sensor testing equipment). If thickness fluctuations are detected, the average of measurements at no fewer than three representative points is indicated, therefore measurements are specifically avoided at creases, wrinkles, spots, etc.

[0262] As described above regarding the thickness of adhesive compound layers, the thickness of the tape (strip) or carrier can be determined in a similar manner using commercially available thickness measuring equipment (sensor testing equipment) with an accuracy of less than 1 μm deviation. If thickness fluctuations are detected, the average value of measurements at no fewer than three representative points is indicated, therefore measurements are specifically avoided at creases, wrinkles, spots, etc.

[0263] Adhesion strength

[0264] The adhesive strength of the bonded composite of the tape used for testing is determined as a parameter of the achieved adhesive quality. Therefore, in each case, the adhesive strength is quantitatively determined in a dynamic tensile shear test at 23°C and 50% relative humidity at a test speed of 10 mm / min according to DIN-EN 1465 (results expressed as N / mm² = MPa). The test specimens used are made of steel and cleaned with acetone prior to bonding. The preparation of the test specimens and the layer thickness of the tape are based on the following information.

[0265] Report the average of the three measurements.

[0266] The following embodiments of the tape according to the invention, comprising at least one adhesive layer D, are produced in the form of a transfer tape, bonded between substrates, and subsequently electrically debonded by applying voltage. The adhesive of layer D is a heat-activated adhesive, which is not a pressure-sensitive adhesive prior to activation.

[0267] According to Embodiment 1 of the present invention

[0268] The adhesive layer D is prepared as follows:

[0269] 43% by weight of Nipol 1001CG (acrylonitrile rubber) from Zeon, 40% by weight of Durez 33040 phenolic varnish resin blended with 8% HMTA (Rohm and Haas), and 10% by weight of 9610 LW methyl phenolic resin from Bakelite were prepared in a kneader as a 30% solution in methyl ethyl ketone. The kneading time was 20 hours.

[0270] Then add 7.0% by weight of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI) and mix vigorously.

[0271] The heat-activated adhesive was then applied from the solution onto the cellophane release paper and dried at 80°C for 15 minutes. After drying, the layer thickness was 30 μm.

[0272] To test the bonding strength, a transfer tape consisting of adhesive layer D was glued between two steel plates as follows:

[0273] Cut three large pieces, each approximately 15 x 25 mm², from the tape to be tested (with a release liner covering one side).

[0274] Place the steel test specimen (substrate) on a heating plate preheated to 105°C. After approximately 5 seconds of temperature control, use tweezers to apply the open side of the tape sample, which is not covered by the release paper, to the surface of the test specimen and press it smoothly with a rubber roller.

[0275] After cooling, trim off excess tape edges and remove the release paper. Place the second test specimen on a heating plate preheated to 105°C for 5 seconds and temper. Apply a coated strip (of tape on the first steel substrate) with an exact 10 mm overlap and press it onto the substrate. Then allow the pre-laminated composite to cool.

[0276] Subsequently, each activation is carried out in a hot press by heating and pressurizing.

[0277] In Embodiment 1 of the present invention, the temperature is heated to 120°C for 8 minutes under a pressure of 5 bar.

[0278] The obtained samples were stored for 24 hours at RT and 50% relative humidity (standard climate).

[0279] The adhesive strength was determined according to the above method and was 8.0 MPa.

[0280] Subsequently, the sample of Example 1 above was prepared again and its electrical removability was tested.

[0281] After bonding and activation, a voltage is applied to two steel plates, which are represented by conductive substrates A and B.

[0282] The voltage here is 48 V, and it is applied for 5 minutes.

[0283] The adhesive strength was determined according to the above method and was 3.9 MPa.

[0284] Therefore, adhesive strength can be significantly reduced by applying voltage.

[0285] Surprisingly, this allows for the provision of electrically removable, reactive, and heat-activated tapes, or tapes containing bonded composites that are heat-activated.

[0286] List of reference numerals

[0287] 1. Adhesive layer D

[0288] 2. Conductive carrier layer T

[0289] 2a Free surface of conductive carrier layer T

[0290] 3 Second adhesive layer C

[0291] 4 First substrate A

[0292] 5 Second substrate B

[0293] 6 Second conductive carrier layer T'

[0294] 6a Free surface of conductive carrier layer T'

[0295] 7 Third adhesive layer C'

Claims

1. Adhesive tape comprising at least one adhesive layer D, wherein the adhesive of the adhesive layer D is a reactive heat-activatable adhesive and contains at least one electrolyte.

2. The adhesive tape according to claim 1, wherein The electrolyte of the adhesive layer D is selected from the group consisting of ionic liquids and metal salts, wherein ionic liquids are particularly preferred.

3. The adhesive tape of claim 2, wherein The anion of the ionic liquid is selected from the group consisting of: Br - , AICI4 - , AI2CI7 - , NO3 - , BF4 - , PF6 - , CH3COO - , CF3COO - , CF3CO3 - , CF3SO3 - , (CF3SO2)2N - , (CF3SO2)3C - , AsF6 - , SbF6 - , CF3(CF2)3SO3 - , (CF3CF2SO2)2N - , CF3CF2CF2COO - , (FSO2)2N - , and particularly preferably from the group consisting of (CF3SO2)2N - and (FSO2)2N - .

4. The adhesive tape according to claim 2 or 3, characterized in that The cation of the ionic liquid is selected from the group consisting of imidazolium-based cations, pyridinium-based cations, pyrrolidinium-based cations and ammonium-based cations, and particularly preferably from the group consisting of imidazolium-based cations, wherein the cation is particularly preferably selected from the group consisting of 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, wherein the cation is very particularly preferably 1-ethyl-3-methylimidazolium.

5. Adhesive tape according to any of the preceding claims, characterised in that The electrolyte of the adhesive layer D is selected from the group consisting of the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI).

6. Adhesive tape according to any of the preceding claims, characterised in that The first adhesive layer D contains 2 to 20% by weight, preferably 5 to 18% by weight, of electrolyte, preferably ionic liquid, based on the total amount of adhesive.

7. Adhesive tape according to any of the preceding claims, characterised in that The reactive heat-activatable adhesive of the adhesive layer D is based on at least one mixture of at least one nitrile rubber S1 and at least one reactive component, in particular a reactive resin, wherein the reactive component is preferably at least one reactive resin selected from the group consisting of epoxy resins, melamine resins, phenolic resins such as in particular novolak resins and resole resins, terpene-phenol resins and polyisocyanates, particularly preferably phenolic resins, in particular novolak resins and / or resole resins.

8. The adhesive tape according to any one of claims 1 to 7, characterized in that The adhesive tape is an adhesive transfer tape and consists of the adhesive layer D.

9. The adhesive tape according to any one of claims 1 to 7, characterized in that It additionally comprises at least the following layers: • a second adhesive layer C; and • at least one electrically conductive carrier layer T arranged between the layers D and C.

10. The adhesive tape according to any one of claims 1 to 7, characterized in that It additionally comprises at least the following layers: • a second adhesive layer C; and • at least a first electrically conductive carrier layer T arranged on the surface on the side of the adhesive layer D opposite the first electrically conductive carrier layer T; and • at least one second electrically conductive carrier layer T' arranged on the surface on the side of the second carrier layer T' opposite the first adhesive layer D. and • a third adhesive layer C' arranged on the surface on the side of the second carrier layer T' opposite the first adhesive layer D.

11. The adhesive tape according to claim 9 or 10, characterized in that The electrically conductive carrier layer T or the electrically conductive first carrier layer T and the electrically conductive second carrier layer T' comprise at least one metal, wherein the metal is selected from the group consisting of copper, nickel, zinc, tin, silver, gold, aluminium, iron, chromium and alloys of these mentioned metals, wherein the electrically conductive first carrier layer T and the electrically conductive second carrier layer T' are independently of each other the same or different.

12. The adhesive tape of claim 11, wherein The electrically conductive carrier layer T or the electrically conductive first carrier layer T and the electrically conductive second carrier layer T' comprise a) at least one metal foil, preferably an aluminum foil, and / or b) at least one electrically conductive fabric comprising at least one metal, preferably selected from copper and nickel, and / or c) one or more layers of at least one metal, preferably selected from copper and aluminum, deposited by vapor deposition, and / or d) at least one metal mesh, and / or e) a foil coated with a metal by vapor deposition, wherein the electrically conductive first carrier layer T and the electrically conductive second carrier layer T' are independently of each other identical or different.

13. Bonded composite comprising at least the following layers: • a first substrate A; and • a second substrate B; and • the adhesive tape according to any one of claims 1 to 12, the adhesive tape being arranged between the substrate A and the substrate B and bonding the substrates A and B to each other.

14. Method for electrically debonding the composite according to claim 13, comprising at least the following method steps: i.) applying a voltage at two different points in the composite, the voltage preferably being 2 to 50 V.

15. Use of the adhesive tape according to any one of claims 1 to 12 for bonding components in electronic devices, motor vehicles, medical devices and dental devices.

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