Flexible heated area element

The subject of the invention is therefore, as has been said, a flat element with a first self-adhesive side surface and a second self-adhesive side surface, the flat element having a series of layers consisting of a heating layer, a contact layer and an adhesive layer, where the adhesive layer contacts the first side surface of the contact layer and is connected to it in an electrically conductive manner, p WHO wherein the heating layer and the contact layer are in contact directly with each other and wherein the layer of adhesive is in contact with the second side surface of the contact layer and touching it directly, and wherein the heating layer consists of nagrzewalnej internally of the first adhesive adhesive which is made in a PTC thermistor that heats up when electricity flows, while the adhesive layer consists of a second adhesive adhesive, wherein the first self-adhesive and second self-adhesive are self-adhesive pressure masses which at room temperature ensure a permanent adhesive connection to the substrate and where the contact layer is at least mostly in the form of a flat-stretched, intermittent contact element.

[23] Thanks to the flat, intermittent form of the contact element, this element has elastic properties, and thus exhibits increased resistance to destructive stress. In this case, the contact element gains elasticity in a direction parallel to the direction of the main extension (plane of the main extension), so that the contact element, in the event of a force perpendicular to the main direction of extension, is movable elastic and does not tear under the influence of the resulting mechanical stress. At the same time, thanks to at least the most flat form of the contact element, it is guaranteed that the cross-section of the contact surface between the electrically conductive and the heating layer is large enough to provide heating on a large surface, and thus guarantee the most important functions of the element.

[24] The flat element of the invention does not therefore require the use of a carrier foil that would reduce its flexibility. Surprisingly, it turns out here that the flat element of the invention has a higher adhesive strength than the corresponding prior art constructions. In this way, this particularly flexible shape also meets the criterion of protection against the formation of debris without additional support film. In addition, when using this type of flat element, it is possible to obtain an adhesive connection showing a thickness, which is also only possible with unheated double-sided adhesive tapes, which makes it possible to reduce the thickness of the entire structure.

[25] In addition, it is advantageous if the flat element, in addition to exhibiting the above-mentioned properties, is shaped in such a way that all partial areas of the intermittent contact element are electrically conductive to each other through the intermittent (discontinuous) contact element. In this way, the contact element is constructed as the only electrode (pole) of the heating layer, so that the current can penetrate through the entire contact surface (contact surface) of the contact element with the heating layer, exhibiting the properties of a PTC thermistor, and thus affect the heating of the full surface of the flat element. In this way, it is possible to obtain high heating power on a maximum surface in a large area. The second contact (contact) of the heating layer (second electrode or second pole) takes place through an additional contact element, which is provided outside the flat element, for example, it can be a well-conductive metal layer placed on the first substrate, or a metal layer located on the second ground.

[26] Instead of creating the above-mentioned embodiment, it may also be advantageous if the intermittent contact element has at least two partial areas that are not electrically connected to each other by the intermittent contact element. Due to this kind of partial areas, which can be shaped, for example, as a large number of individual sections, it is possible to realize in the contact element both electrical contacts (contacts) (electrodes or poles) necessary to ensure the heating operation of the heating layer, so that it is possible to dispense with from additional electrically conductive layers outside the flat element, thus, the final assembly of a flat element on glued substrates is greatly facilitated. In addition, it is also possible to apply different voltages to individual partial sections of a flat element, for example in order to create a voltage gradient on this surface and to adapt the heating power individually to the respective requirements.

[27] In addition to the features described above for one or more embodiments, it is advantageous if the intermittent contact element has grooves (grooves) whose main direction of stretching extends at least in the majority in one of the spatial dimensions, the preferred direction. In this way, it is possible to achieve a very high degree of flexibility of the flat element in one direction with minimal violation of the mechanical stability and cross-section of the electrical (contact) surface. This may be particularly desirable if the flat element is to be mounted on the surface in the form of a cylindrical mantle, which is strongly bent in one direction, while showing a small radius of curvature.

[28] In addition, it may be advantageous if the intermittent contact element exhibits a branched comb structure or has a finger structure. This type of shape allows optimal use of almost the entire surface of the flat element for heat generation with only small recesses, without exerting a major adverse effect on mechanical properties, or without strong voltage drops throughout the entire layer. In the case of the comb structure and the finger structure, individual forks or fingers move away from the main band. The main band here may have a larger cross-section than the forks or fingers themselves, or may have the same cross-section. The difference between the comb and finger structure is that the branching elements in the comb structure are arranged on one side of the main band, and in the case of the finger structure they are arranged (branching) on ​​both sides. Both structures can have both single and multiple branches and at the same time both regular and irregular arrangements, and can be used both for shaping the contact element as a single electrode, as well as for shaping the contact element in the form of several electrodes in the contact layer.

[29] In the first self-adhesive mass, it is advantageous if, in addition to the properties of one or more of the embodiments described above, it also includes an electrically conductive filler. In a particularly simple and inexpensive way, it is possible to obtain an adhesive with PTC thermistor properties, which for many applications provides sufficiently high heating power. It is particularly advantageous here if the electrically conductive filler is selected from the group consisting of graphite, carbon nanoparticles and carbon black, in particular conductive carbon black. The advantage of this type of composition is the fact that the fillers have a very good connection with the polymer matrix, so that this type of adhesive mass has a very high consistency, and thus provides a very high mechanical load capacity.

[30] In terms of the thermistor PTC properties of the first pressure-sensitive adhesive, it is especially advantageous if the first pressure-sensitive adhesive has partially crystalline polymers or even partially crystalline block copolymers, in particular in an amount exceeding 30% by weight in the first pressure-sensitive adhesive. amount exceeding 50% by weight. This configuration provides the advantage that in this way adhesive masses can be used as the first self-adhesive, which in addition to good technical properties associated with gluing, have a high degree of conductivity and at the same time so strongly developed PTC thermistor properties that they can significantly reduce current, thus preventing overheating effectively.

[31] In addition, for these types of embodiments it has proved to be advantageous if the electrically conductive filler is present in the first self-adhesive mass in an amount of 1% to 60% by weight, preferably 5% to 30% by weight, since in this way it is possible to produce adhesive masses, which on the one hand ensure sufficiently high conductivity (allowing at all current to flow through the adhesive), and at the same time they show a sufficiently low degree of conduction (so that the resistor does not generate too much heat as a result of the voltage drop), so that they can be used generally as heating masses with PTC thermistor properties, on the other hand they have a high proportion adhesive, which also ensures high adhesive strength.

[32] In addition to the features of one or more of the above-described embodiments, it has proved to be advantageous if the first pressure-sensitive adhesive and the second pressure-sensitive adhesive are pressurized masses. These types of systems allow for particularly easy gluing, where no additional steps are necessary in the gluing process, such as heating of flat elements, thanks to which such self-adhesive masses can also be used on glued substrates showing strongly irregular geometry or sensitive to high temperatures .

[33] In particular, masses based at least partly on at least one acrylic monomer with the general formula CH2 = C (R¹) (COOR²), where R¹ is selected from the group consisting of H and CH3 and R² is selected from the group consisting of H and saturated or unsaturated, unbranched or branched, substituted or unsubstituted C1 to C30 acrylic residues, in particular if the pressure-activated adhesive pressure based on at least one acrylic monomer with the general formula CH2 = C (R¹) (COOR^2'), where R¹ is selected from the group consisting of H and CH3 and R^2' is selected from the group consisting of H and saturated or unsaturated, unbranched or branched, substituted or unsubstituted C2 to C20 acrylic residues, and is also based on at least one comonomer polymerized with this acrylic monomer, which is selected in particular from the group consisting of vinyl compounds functional groups, maleic anhydride, styrene, styrene compounds, vinyl acetate, acrylamides or photoinitiators functionalized by double bonds. Instead, the pressure-sensitive adhesive mass can also contain at least partly a natural rubber mass and / or a synthetic rubber mass and a silicone adhesive mass. These types of pressure-sensitive adhesive masses have the advantage of allowing control of the technical properties associated with gluing a flat element, and thus their intentional adaptation to the specific features to be exhibited by the target adhesive connection, for example taking into account the specific substrate or conditions environment.

[34] In addition to the features of one or more of the embodiments described above, it has proved to be advantageous if the composition of the first pressure-sensitive adhesive is identical to the composition of the second pressure-sensitive adhesive. In this way, it is very easy to realize an internally heated flat element with particularly high heating power. Instead, it may also be useful if the composition of the first adhesive compound differs from the composition of the second adhesive compound, which makes it possible in particular that two adhesive substrates with different properties can be glued together, e.g. a polar glass surface with a non-polar one polymeric surface, e.g. with a polyolefinic surface.

[35] In addition to the features of one or more of the above-described embodiments, it has proved to be advantageous if the flat element on the surface of the heating layer side facing away from the intermittent contact element also has a third layer of adhesive. In this way, the technical properties associated with the gluing of the first self-adhesive mass are made independent of the self-adhesive properties of the side surfaces of the flat element. In this way, it is possible to achieve a particularly high degree of stability of the adhesive connection, because the adhesive masses on the adhesive side surfaces of the flat element can be individually adapted to the respective adhesive substrate and at the same time the heating layer is adjusted to ensure a good connection with the contact element, which is particularly important if the material of the contact element surface is significantly different from the material, of which the surface of the adhesive substrate is made, for example in the case of a metal contact element and polyolefin adhesive substrate.

[36] In the case of a flat element, in addition to the features of one or more of the embodiments described above, the heating layer may have a thickness less than 1 mm, preferably a thickness in the range from 10 μm to 400 μm, particularly preferably in the range between 20 μm and 200 um. This type of heating layer design ensures optimal properties, because the heating layer on the one hand is thick enough to achieve sufficiently high heating power, and on the other hand thin enough to guarantee fast heat conduction in the heating layer and good mechanical properties, i.e. good flexibility and consistency material.

[37] It is also advantageous if the flat element, in addition to the features mentioned above, has one flexible, solid support. This allows for a very stable flat element with a high degree of flexibility. Instead, the flat element can also be made without a support. This is particularly advantageous in cases where it is necessary to provide particularly high flexibility and / or a small installation depth of a flat element.

[38] In terms of ease of use, it has proved to be very useful if the flat element, in addition to the features mentioned above, in one or more of the versions described above on the first self-adhesive and adhesive side surface and / or on the second self-adhesive and adhesive side surface has a temporary support. This solution allows to avoid undesired sticking during production, storage and gluing process, and thus allows to simplify the course of these process stages.

[39] According to a further aspect of the present invention, glued bonding consisting of a glued substrate and one of the above-mentioned flat elements is proposed. Previously glued anastomoses have the disadvantage that it is not possible to glue them reliably to bent surfaces (surfaces with curvature), because as a result of the stiffness of a one-sided flat element glued in this anastomosis it is possible to detach the anastomosis from this type of bent surface. This disadvantage was eliminated by using a flat element according to the invention. This is particularly advantageous if the glued anastomosis is an anastomosis consisting of at least one double-sided self-adhesive adhesive flat element and if the substrate to be glued is a transparent glass or a mirror, because in this type of systems due to the high tare weight of the substrate to be bonded, it is particularly problematic for the adhesive substrate to detach from the holder and the subsequent damage to the substrate as a result of this process.

[40] In addition, the present invention proposes the use of the flat element described above for gluing glued substrates in the automotive industry, in particular its use for heating the glued assembly described above. If the glued bonding of the type known to be glued on a glued surface with a curved surface is internally heated, then the glue will soften when the glue mass warms up, and thus the consistency of the glue will decrease. Due to the high inherent stiffness of the flat elements used so far, this may cause the softened adhesive mass to separate, so that the glued bonding will detach from the glued substrate. This disadvantage was eliminated by using the flat element according to the invention for heating the glued anastomosis.

[41] In addition, according to the invention it is also possible to use in which such a flat element is glued to the human or animal body, for example to release a hermetically sealed active substance to the skin or to the upper surface of the fur, for example in a topically active form or a transdermal patch. The flat element has at least one active substance which is released as a result of heat, or whose release is promoted as a result of high temperature. In this way, time and quantitatively controlled release of relevant active substances can easily be triggered.

[42] Finally, the present invention provides a method for producing a flat element, comprising the steps of forming a first adhesive layer, applying the intermittent contact element directly to the surface of the first adhesive layer, and applying the second adhesive layer to the surface of the intermittent contact element. In previous methods, the contact element was always applied to a solid support, which only allowed to obtain thick flat elements, which usually have little flexibility. As a result of applying the contact element directly to the surface of the adhesive, it is possible with a small technological effort to obtain flat elements of small thickness, without the need to apply the contact element separately on the support (permanent or temporary), which contributes to the simplification of production technology.

[43] The individual preferred embodiments may, unless otherwise stated, be combined in any manner to provide the previously described and other preferred operations; these properties are therefore considered separately as well as in combination with those contained in the independent claims.

[44] In order to approximate the invention, it has been described in a general way below - some representative examples of individual components of partial aspects of the invention have been explained and described, which can be combined almost freely, depending on the properties we want to achieve. In general, the present invention relates to a flat element with a first adhesive pressure sensitive side surface and a second pressure adhesive pressure side surface. Flat elements within the meaning of this patent application are, in particular, all commonly used and suitable elements, with a predominantly flat shape. They allow the surface to stick and can have a variety of forms, in particular they can be flexible - as an adhesive film, adhesive tape, self-adhesive label or self-adhesive embossed pad.

[45] This flat element is self-adhesive on its first surface and on its second surface. Here, the first and second surfaces correspond to both surfaces of the flat element arranged parallel to the direction of its main extension, i.e. in the upper and lower sides.

[46] The term self-adhesive within the meaning of this patent application is in particular the surface on which it is placed at least locally, but preferably over the entire surface, an adhesive mass. Adhesive masses mean, without exception, all adhesive masses based on pressure-sensitive adhesive masses and / or thermally activated (hot melt) adhesive masses, i.e. adhesive masses that, by themselves, provide a permanent adhesive connection to the substrate (substrate, substrate) adhesive or glued). "Based" or "based" or "based" means in this patent letter that the technical adhesive properties of this adhesive system are determined at least to a large extent by the basic properties of this adhesive or adhesive components (the so-called base polymer) ), which is of course not excluded, that these properties may be additionally affected by the use of modified auxiliary substances or additives or further polymeric adhesive masses in the gluing system.

[47] Adhesives activated by pressure are defined as such types of adhesive, which at room temperature even at relatively low pressure ensure permanent adhesion to the ground. In contrast, thermally activated (hot melting) adhesive masses are those adhesive masses that only at elevated temperatures allow permanent adhesion to the substrate, while the resulting adhesive bond is also preserved after subsequent adhesion to room temperature. Stickiness (possibility of sticking) of thermally activated (hot melting) adhesive masses is based on their adhesive (adhesive) properties.

[48] ​​Adhesion is usually referred to as a physical effect that causes the two phases to be joined together to hold each other on their boundary surfaces by intermolecular interaction. Adhesion, or stickiness, hereby determines the adhesion of the adhesive to the surface of the substrate and is a decisive factor in the initial tack (so-called "tack") and adhesive strength. To be able to influence the adhesion of the adhesive in a targeted manner, softeners and resins that increase the adhesive strength (so-called binders) are often added to the adhesive.

[49] Coherence or cohesion is usually defined as a physical effect which, as a consequence, causes internal fusion of a substance or a mixture of substances as a result of intramolecular and / or intermolecular interactions. Therefore, the cohesion forces have an impact on the stickiness and plasticity of the adhesive mass, which can be defined as viscosity and shear strength time. To deliberately increase the coherence of adhesive masses, they are often subjected to additional crosslinking, for this purpose reactive components (and thus crosslinkable) or other chemical cross-linking agents are added to the adhesive and / or the adhesive is subjected to subsequent treatment actinic radiation (rich in energy).

[50] The technical properties associated with gluing pressure-sensitive self-adhesive mass are primarily determined by the ratio of adhesive and cohesive properties. For example, in some applications, it is important that the adhesive materials used have high consistency - cohesion - and thus have very high internal consistency, while for other applications, in particular, high adhesion (stickiness) is important.

[51] According to the invention, the flat element has a series of layers arranged in a certain order. The sequence of layers is defined in particular the arrangement of individual layers in space in a direction perpendicular to the main direction of their stretching (in the form of a stack), which are in contact with each other and between which there are no additional layers. Layer is defined in particular as a flat arrangement of the system with uniform functionality, whose spatial dimensions are much smaller than in the other two directions in space, which determine the main direction of extension. Such a layer may be compact or intermittent and may consist of one material or several different materials - especially if this contributes to the uniform functionality of the layer. This layer may have the same thickness throughout the plane, or it may have different thicknesses. In addition, such a layer may also have more than one functionality.

[52] The contact layer between the heating layer and the adhesive layer is placed in the layer of object of the invention. The contact layer is any well-conductive layer with which a voltage can be applied and / or an electric current can be led through the heating layer; the contact layer thus fulfills the role of connecting external electric power cables to the flat element (contact electrode role). A heating layer is any layer made to heat a flat element. An adhesive layer is defined as any compound containing adhesive and adapted for the connection of a flat element with an adhesive substrate.

[53] Consequently, the heating layer is in contact with the first side surface of the contact layer (i.e. the top and bottom of the contact layer) so that both layers contact each other directly. In addition, the heating layer is electrically connected to the first side surface of the contact layer. The connection is referred to as electrically conductive, in particular if the total resistance of the connection, which consists of the resistance of the connected partial sections and the contact resistance of the connection, is about the same value as the total resistance of other electrically conductive areas and contacts (contacts).

[54] In addition, the second side surface of the contact layer (corresponding to the second side surface, i.e. the bottom or top side of the contact layer) contacts the adhesive layer and directly touches it. The adhesive layer here consists of a second adhesive layer. All customary and suitable pressure-sensitive adhesive masses can be used as self-adhesive adhesives.

[55] In accordance with the invention, the heating layer also consists of an internally heated first layer of pressure-sensitive adhesive. Also, all customary and suitable pressure-sensitive adhesive masses can be used as the first pressure-sensitive adhesive. An internally heated layer can be any layer that can be spontaneously heated under the action of an electric current, which means that this layer without the use of additional elements or components is able to produce heat when the electric current flows through it or after applying voltage to the layer , but it is irrelevant whether the current or voltage is AC or AC, or DC or DC. In addition, the first self-adhesive mass is made in the form of a PTC thermistor that heats up when electric current flows through it.

[56] An important element of the invention in the contact layer is also at least mostly a surface-stretched, intermittent contact element. A contact element is, in particular, an element made of electrically conductive material, the structure of which is entirely electrically conductive at least in a partial area. "At least mostly surface-stretched" means that the partial areas of which the contact layer consists are layered flat, with individual partial areas also projecting from this flat arrangement.

[57] The contact layer is an electrically conductive connection between the heating layer and a source of current or voltage. The contact layer can be made as one of the two electrode connections (poles) of the heating layer, or it can include both electrode connections.

If the contact layer forms only one of the two electrode connections of the heating layer, for the electrical layer to be able to flow through the heating layer, heating it, a second electrode connection is required. This second electrode connection can be made inside the flat element of the invention - for example in the form of an additional, second flexible contact layer - or be provided on one of two adhesive substrates, for example as a metal layer on the glass surface (e.g. as silver mirror glass).

[58] According to the invention, the contact layer is not closed over the entire surface but is interrupted, so that grooves (recesses) exist on this discontinuous layer, also extending in a direction perpendicular to the main direction of stretching of the layer. Consequently, this layer is not compact over the entire surface, but has recesses that can pass through the entire layer (through holes) or can be limited to only part of the layer (troughs, for example to reduce the thickness of the contact layer locally). The cavities can take on various forms, for example be regular or irregular, have a uniform or variable width, have straight, beveled or curved walls and the like. In addition, the recesses may extend over the contact layer in different directions, and may also have a particularly preferred direction, so that the contact layer exhibits particularly high elasticity in the direction of elongation perpendicular to this preferred direction.

[59] In terms of the specific embodiment of these recesses, the contact element may have a different form, for example a broken surface, or a wrinkled or branched wire structure, and the like, for example, a single or multiple branched comb or finger structure. Further suitable contact elements are, for example, broken metal foils, uniform mesh gratings, wire grates, metal networks or electrically conductive nonwovens. Also, non-metallic conductors such as metal oxides (e.g., indium tin oxide) or internally conductive polymers can be used in accordance with the invention. In order to improve the flexibility of the flat element, at least one contact layer preferably has a mean or maximum thickness of less than 50 μm, preferably less than 20 μm and even less than 10 μm.

[60] The electrically conductive areas of the contact element may be connected to each other in a electrically conductive manner (all areas or only part of the areas) or may be in the form of a single area of ​​the contact element which is not connected to other areas by the contact element in a conductive manner. Alternatively, part of the areas may also be electrically connected to each other, and the other part may be separate. This, of course, does not exclude a conductive connection via the heating layer, which is even required according to the invention.

[61] In particular, it is provided that the contact element comprises two non-electrically conductive areas which are made as two lead wires for the electrodes (poles) of the heating layer. If the entire contact element is entirely electrically conductive, then it is used as one of the two poles of the heating layer, with the current flowing mainly in a direction perpendicular to the main extension, and in the arrangement where the contact element is two electrode connections, in addition to orthogonal current flow, instead of it there is a lateral current flow perpendicular to the main extension.

[62] As a first pressure-sensitive adhesive in the heating layer, all pressure-sensitive pressure-sensitive adhesive, which conducts electricity flowing through this pressure-sensitive adhesive without decomposition, can in principle be used. Preferably, heat is generated in this self-adhesive heating layer spontaneously as a result of a voltage drop that occurs due to electrical resistance, but it is also possible to achieve heating based on other effects, such as by using another electrothermal converter or an electrically initiated exothermic chemical reaction . According to the invention, such flat elements can be used once or more times; also the heat generation process can be carried out one or more times. Such a heating layer may have a perpendicular to the main stretch (average) thickness less than 1 mm, preferably a thickness in the range from 10 μm to 400 μm, particularly preferably in the range between 20 μm and 200 μm. In the preferred case of using the layer as an electric heating element, it may exhibit sufficient electrical resistance on the one hand to ensure heating of the layer, and on the other hand low enough to ensure current flow through the layer.

[63] According to the invention, this heating layer must exhibit the characteristics of a PTC thermistor and must therefore have a positive temperature coefficient, and hence the PTC effect. Preferably, such a layer is shaped in such a way in terms of positive temperature coefficient and resistance that for a given operating voltage and operating current, the heat generation in the heating layer is limited by the PTC effect, so that this layer automatically regulates heat generation and in particular does not exceed the set maximum value temperature. It thus avoids overheating of the flat element.

[64] The first self-adhesive mass is preferably a pressure-sensitive self-adhesive mass comprising at least one electrically conductive filler as electrically conductive material. As an electrically conductive filler, an addition to the self-adhesive compound is considered, electrically conductive alone (i.e. without self-adhesive compound), or only after mixing with the self-adhesive adhesive compound.

[65] In principle, all suitable fillers compatible with the first self-adhesive mass can be used as fillers. In particular, fillers selected from the group consisting of graphite and carbon black, in particular conductive carbon black (e.g. Printex®XEder from Degussa), and any combination of these ingredients are used here. Additionally, or instead of them, other carbon-based fillers, in particular nanoscale fillers, i.e. with stretching dimensions not exceeding 500 nm, preferably below 200 nm and even below nm, for example carbon nanoparticles such as nanotubes can be advantageously used carbon (e.g. Carbon Nanotubes from Ahwahnee or concentrates with high content of carbon nanofillers (masterbatches) from Hyperion Catalysis), carbon nanofibers, fullerenes and the like.

[66] Preferably, the filler is used in an amount such that the proportion of the filler in the first self-adhesive mass is high enough to ensure adequate electrical conductivity in the first self-adhesive mass, and on the other hand, small enough to only slightly affect the mechanical properties of the first mass adhesive. The combination of various fillers of this type may also be advantageous, thus allowing adequate resistance to sudden temperature changes to be achieved with a sufficiently low degree of filling, in particular in the case of a combination of carbon nanotubes with carbon black or graphite.

[67] In addition, fillers may have a modified surface. In this way, it is possible to purposefully influence the individual properties of the adhesive - for example, to improve the dispersion of carbon nanotubes or soot in the adhesive. In order to increase the PTC effect, the surface of electrically conductive fillers, e.g. soot particles, can be completely or partially coated with metals such as nickel, silver or gold, silanes or formamides.

[68] Conductivity and thus also achievable temperature and heating rate depend, among others, on the degree of filling of the electrically conductive filler, i.e. its weight share in the self-adhesive mass. By increasing the degree of filling, a higher degree of conductivity and possibly higher temperatures can be achieved. In this way, the effect of the electric heating effect of the first self-adhesive mass can be determined by means of the degree of filling. The degree of filling is preferably between 1 and 60% by weight. It is very preferably in the range from 5 to 30% by weight of filler. The electrical conductivity, and hence the heat of the first adhesive compound, also depend on their base polymer.

[69] In order to obtain the first adhesive mass with PTC thermistor properties, electrically conductive fillers may be added to the monomers of the first adhesive mass before polymerization and / or together with the polymers only after polymerization. The preferentially electrically conductive filler is added after polymerization to the molten base polymer of the first self-adhesive adhesive.

[70] In particular, if the first self-adhesive mass is applied to the flat object of the invention as a hot melt gluing system, the electrically conductive filler is preferably placed directly in the molten mass. It is desirable to homogeneously disintegrate in the sense according to the present invention. The homogeneous distribution of the filler in the first self-adhesive mass is preferably achieved by combining the ingredients in twin screw extruders, continuous molding kneaders (e.g. Buss kneading machines) or planetary extruders. The advantage of this process is the fact that the production process is only briefly contaminated with a separate filler and that solvents are avoided.

[71] In general, all polymers with suitable adhesive properties, having a PTC effect and behaving as thermistors with a positive temperature coefficient can be used as the first self-adhesive in the heating layer. The occurrence and intensity of the PTC effect depends on the shape of the network, for example whether the filler itself is in the form of an agglomerate or not. The PTC effect can be supported, among others, by orientations implemented during the production process inside the polymer components of the first self-adhesive adhesive mass, for example by introducing anisotropy in terms of physical properties and / or in the direction of the macromolecules in it.

[72] If a self-adhesive mass with an electrically conductive filler is used as the PTC thermistor system, then it has proved beneficial to use multi-phase systems, in particular those in which at least one phase, in the temperature range in which the PTC effect occurs as a result of heating it expands by volume, which, according to generally accepted scientific explanations, is at least partly responsible for the behavior of the system as a PTC thermistor (see J. Meyer in Polymer Engineering and Science, 13 (1973), pp. 462-468). Self-adhesive masses based on polymers or polymer blends (polymer blends) in which one or more fillers are present besides electrically conductive filler are also referred to as multiphase.

[73] The use of self-adhesive adhesives containing partially crystalline polymers has proved to be particularly advantageous here. Both single- and multi-phase systems, both homo- and polymers, in particular partially crystalline block polymers, can be used as partially crystalline polymers. The partially crystalline polymers can be part of the base polymer themselves or additive. Crystalline partial regions of this type of partially crystalline polymers exhibit stronger calf expansion than their amorphous regions when the polymer matrix is ​​softened.

[74] Preferably, the pressure-activated pressure sensitive adhesive contains at least 30% by weight of partially crystalline polymers in the heating layer, even better the proportion of partially crystalline polymers in the pressure-sensitive adhesive mass is at least 50%. Adhesive masses lose their proportion as the proportion of partially crystalline forms loses their sticky properties, so that when using pressure-sensitive adhesive masses, the proportion of partially crystalline polymers must be kept lower than for thermally activated (thermofusible) adhesive masses this high enough stickiness.

[75] Partially crystalline polymers in which the crystallization degree is above 20% or even above 40% is preferred in the pressure-activated pressure sensitive adhesive used as the first pressure-sensitive adhesive. The degree of crystallinity is determined by means of dynamic scanning calorimetry (Differential Scanning Calorimetry; DSC).

[76] Particularly preferably as block copolymers, styrene block polymers are used, such as SBS (styrene-butadiene-styrene block copolymers), SIS (styrene-isoprene-styrene block copolymers), SEBS (styrene-ethylene-butylene-styrene block copolymers) or SEPS (styrene ethylene propylene styrene block copolymers).

[77] The addition of polymeric or inorganic fillers is also preferred, which, when heated, by melting, support the PTC effect. These can be, for example, polyolefin waxes with a high proportion of crystal structures or ionic liquids (low melting metal salts). By selecting the appropriate melting temperature of the fillers, you can also adjust the temperature at which the PTC thermistor properties will occur (PTC effect).

[78] According to the invention, both pressure-sensitive adhesive masses are pressure-activated adhesive.

[79] As pressure-sensitive adhesive masses, in principle, all pressure-sensitive adhesive systems with suitable adhesive properties can be used, i.e. pressure-sensitive adhesive systems. The monomers used to manufacture pressure-sensitive adhesive masses are selected in particular in such a way that the polymers obtained at room temperature or at higher temperatures can be used as pressure-sensitive adhesive masses.

[80] Sticky under pressure within the meaning of the present invention is an adhesive which, according to "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989), shows adhesive properties (pressure activated adhesion).

[81] To achieve the preferred adhesive masses activated by the glass transition temperature pressure Tg <25 ° C, the monomers are usually chosen in such a way and the quantitative composition of the monomer mix is ​​selected in such a way that they behave analogously to the equation presented by Fox (cf. TG Fox, Bull. Am. Phys. Soc. 1 (1956) 123), so that the desired value of the glass transition temperature Tg of the resulting polymer results from the equation

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[82] In this equation, n represents here the current number for the monomers used, n in the mass share of the specified monomer n (in weight%), and TG, n the melting point (glass transition) of the homopolymer on transition from monomer n to K. For example, pressure-sensitive adhesive masses based on acrylates and / or methacrylates, natural rubbers and / or synthetic rubbers can be used as pressure-sensitive adhesive masses activated by pressure on the first pressure-sensitive adhesive mass and / or the second pressure-sensitive adhesive mass.

[83] Thus, pressure-sensitive adhesive masses based on acrylic acid and / or methacrylic acid and / or on the basis of esters of the abovementioned compounds or based on hydrated natural or synthetic rubbers may be used, as they are particularly resistant to aging and they are resistant to frequent heating processes of the flat element of the invention.

[84] Acrylate adhesive masses, obtained for example by radical polymerization, which are at least partly based on at least one acrylic monomer of the general formula CH2 = C (R¹) (COOR²), where R¹ is equal to H or is the residue CH3 and R² is equal to H or is selected from the group of saturated, unbranched or branched, substituted or unsubstituted C1 to C30 acrylic residues. At least one acrylic monomer should have a mass fraction of at least 50% by weight in the pressure-sensitive adhesive mass.

[85] In accordance with further preferred embodiments, polymers which (a1) are at least partly based on at least one acrylic monomer of the general formula CH2 = C (R¹) (COOR^2'), where R¹ is equal to H or is the residue CH3 and R^2' is selected from the group of saturated, unbranched or branched, substituted or unsubstituted C2 to C20 acrylic residues.

(a2) are based at least in part on a comonomer polymerized with at least one acrylic monomer selected in particular from the group consisting of functional vinyl compounds, maleic anhydride, styrene, styrene compound, vinyl acetate, double bond functionalized acrylamides and photoinitiators.

[86] Preferably, at least one acrylic monomer (a1) has a mass fraction of 65% to 100% by weight, and at least one comonomer (a2) has a mass fraction of 0% by weight to 35% by weight in an adhesive mass.

[87] In addition, the average molecular weight Mw (average weight) of the pressure-sensitive adhesive at 800,000 g / mol has proved to be advantageous, in particular in terms of obtaining the desired mechanical properties of the pressure-activated adhesive.

[88] At least one pressure-sensitive adhesive may, according to one further embodiment, also include or based on natural or synthetic rubber. In order to obtain the self-adhesive adhesive mass from natural rubber, the natural rubber was ground until the desired molecular weight was obtained, after which an electrically conductive filler was added.

[89] As a special embodiment, partially crystalline polymers such as EVA (ethylene vinyl acetate) or polyolefins may also be used as self-adhesive adhesives or added to them. In particular, when the first self-adhesive adhesive is used, this type of adhesive systems provide additional support for the PTC effect due to the increase in the volume of the crystalline phase when the melting point of the crystals is exceeded.

[90] In the preferred version, acrylic or methacrylic monomers with the general formula CH2 = C (R¹) (COOR^2"), including esters of acrylic and methacrylic acid, the R group^2" is selected from the group of saturated, branched or unbranched, substituted or unsubstituted C4 to C14 alkyl residues, in particular C4 to C9 alkyl residues.

Specific examples are, without being limited to the list below, methacrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate , n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate and their branched isomers such as, for example, isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate or isooctyl acrylate.

[91] Further classes of compounds that can be used are monofunctional acrylates or methacrylates of the general formula CH2 = C (R¹) (COOR²'"), with the rest of R²'' is selected from the group of bridged or non-bridged cycloalkyl residues with at least 6 C atoms. Cycloalkyl residues can also be substituted, for example, C1 to C6 alkyl groups, halogen atoms or cyano groups. Specific examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyl adamantyl acrylate.

[92] In a preferential procedure, acrylic monomers and / or comonomers having one or more substituents are used, in particular polar substituents, for example carboxyl groups, sulfonic acid, phosphonic acid, hydroxyl, lactam, lactone, N-substituted amide groups, substituted N amino groups, carbamate, epoxy, thiol, alkoxy, cyano, halide and ether groups.

[93] Very preferably monomers selected from the following group can be used as acrylic monomer (a1): substituted or unsubstituted compounds including methacrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-acrylate -nonyl, lauryl acrylate, stearyl acrylate, behenyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyl adamantyl acrylate.

[94] Moderately basic comonomers (a2) such as, for example, single or double N-alkyl substituted amides, in particular acrylamides, are also suitable. Specific examples are, for example, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N- (tert-octyl) acrylamide, N-vinylpyrrolidone, lactam-N-vinyl, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethylacrylate -methyl, N-methyl methacrylamide, N- (butoxymethyl) methacrylamide, N- (ethoxymethyl) acrylamide, N-isopropyl acrylamide, this list is not final.

[95] Further preferred examples of (a2) comonomers are hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, maleic anhydride, itaconic acid anhydride, itaconic acid, glyceride methacrylate, phenoxyethyl acrylate methacrylate, , 2-butoxyethyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, glyceryl methacrylate, 6-hydroxyhexyl methacrylate, vinyl acetic acid, tetrahydrofurfuryl acrylate, beta-acryloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, this list is not exhaustive or definitive.

[96] The extended preferred method of acting as comonomers (a2) may be vinyl compounds, in particular vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, a vinyl compound with cyclic aromatics and heterocyclic compounds in the alpha position, wherein as examples, not closing the list and not claiming to be the only ones, one can mention vinyl acetate, vinylformamide, vinylpyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride, styrene and acrylonitrile.

[97] Particularly preferably as the above-mentioned at least one comonomer (a2) a photoinitiator with a copolymerized double bond may be used, selected in particular in the group consisting of Norrish type I photoinitiators or Norrish type II photoinitiators, benzoin acrylates or acrylated benzophenones.

[98] In a further preferred procedure, in addition to the comonomers (a2) described above, additional monomers with a high glass transition temperature are used. Vinyl aromatics, such as styrene, are suitable as such monomers, preferably the aromatic cores are composed of C4 to C18 modules and may also contain heteroatoms. Particularly preferred examples are, for example, 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, t-butylphenyl acrylate, t-butylphenyl methacrylate 4-biphenyl and 4-biphenyl methacrylate, 2-naphthyl acrylate and 2-naphthyl methacrylate, and mixtures of these monomers, this list is not complete or final.

[99] Preferably, the self-adhesive adhesives used to make flat elements are additionally crosslinked, with a high level of crosslinking being sought, as they further enhance the PTC effect (cf. EP 0 311 142 A1 sowie. US 4 775 778 A) and therefore are particularly suitable for the first self-adhesive. The cross-linking process allows to eliminate or mitigate the effects of the NTC (Negative Temperature Coefficient) effect, which until now could be observed at temperatures below the melting point of the first self-adhesive adhesive.

[100] According to a preferred embodiment of the invention, the base polymer of the first pressure-sensitive adhesive preferably has a degree of crosslinking corresponding to at least a gelation value of 35%, in particular higher than 60%. The gelation value in the present invention is the ratio of base polymer fractions soluble in a suitable solvent (e.g. toluene or xylene) to the sum of soluble fractions and insoluble fractions of the base polymer.

[101] A high degree of crosslinking can be obtained as part of the crosslinking step implemented using electron radiation. Typical devices that can be used for irradiation are linear cathode systems, scanning systems (contact testing) or segment cathode systems when it comes to electron radiation accelerators. A comprehensive description of the state of the art and the most important technological parameters in this area can be found in Skelhorne in: "Electron Beam Processing, in Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints", Vol. 1, 1991, SITA, London. Typical accelerating voltages are between 50 kV and 500 kV, preferably between 80 kV and 300 kV. Typical radiation doses used are in the range between 5 kGy and 150 kGy, in particular between 20 kGy and 100 kGy. It is also possible to use other technologies that allow irradiation with high energy.

[102] In addition, according to the invention, the degree of crosslinking can be a variant for electrical conductivity, and hence thermal heating. By increasing the dose of electron radiation interacting during the crosslinking reaction (and consequently also increasing the degree of crosslinking), it is possible to increase the electrical conductivity so that with a constant current flow through the heating layer of the flat element, the achieved temperature of the self-adhesive mass increases. In the same way, the PTC thermistor properties of the first pressure-sensitive adhesive can be controlled by the degree of crosslinking.

[103] In order to reduce the radiation dose necessary to carry out the crosslinking reaction, additional crosslinking agents and / or crosslinking promoters, in particular those which can be thermally excited by electron radiation, can be admixed to the pressure-sensitive adhesive. Suitable crosslinking agents for electron radiation crosslinking are, for example, bifunctional or polyfunctional acrylates or methacrylates, triallyl cyanurates and triallyl isocyanurates. Preferably, bifunctional or polyfunctional epoxides, hydroxides, isocyanates or silanes are used as heat activated crosslinkers.

[104] The adhesive may contain natural additional recipe ingredients and / or additives, such as auxiliary substances, pigments, rheological additives, additives to improve adhesion, softeners (plasticizers), resins, elastomers, anti-aging agents (antioxidants), agents sun protection agents, UV absorbers and other auxiliaries and additives, such as desiccants (e.g. zeolites - molecular sieves or calcium oxide), fluidizers and flow agents, wetting agents such as surface-active agents or catalysts and heat-conducting fillers, fillers or heat-storage additives which are released by heat or whose release is accelerated by the action of heat.

[105] All finely ground additives, such as chalk, magnesium carbonate, zinc carbonate, kaolin, barium sulfate, titanium dioxide or calcium oxide can be used as excipients. Further examples are talc, mica, silica, silicates or zinc oxide. It is naturally possible to also use mixtures of the abovementioned substances.

[106] The pigments used may be organic or inorganic. It is possible to use all types of organic or inorganic color pigments, for example white pigments or titanium dioxide, to increase resistance to light and UV radiation or metal pigments.

[107] Examples of rheological additives are pyrogenic silicas, layered silicates (for example bentonites), high molecular weight polyamide powder or castor oil derivative powder.

[108] Additives to increase adhesion can be, for example, substances selected from the group of polyamides, epoxides or silanes.

[109] Examples of emollients used to improve sticky properties are phthalic acid esters, trimellitic acid esters, phosphoric acid esters, adipic acid esters and esters of other acyclic dicarbonic acids, fatty acid esters, hydroxy acid esters, phenol alkylsulfonic acid esters, aliphatic, cycloaliphatic and aromatic mineral oils, hydrocarbons, liquid and semi-solid rubbers (e.g. nitrile or polyisoprene rubbers), butene and / or isobutene composed of liquid or semi-solid polymers, acrylic acid esters, polyvinyl ether, liquid and soft resins based on raw materials that also form a basis for sticky resins , lanolin and other waxes, silicones and polymeric softeners, e.g. polyester or polyurethanes.

[110] Additives released under the influence of heat, or the release of which is supported by the influence of increased temperature, are such systems containing an active substance which is released under the influence of heat, so that controlled release of this active substance is possible. Any substance which can be used as an active substance, for example a dye, a medical or cosmetic active substance, as well as an igniter (initiating explosive) can be used here as the active substance. The action can be implemented, for example, by the release of the substance (e.g. in the case of a locally active substance) or by thermal activation, e.g. as a result of a thermally initiated chemical reaction (e.g. molecular rearrangement, crosslinking or decomposition) or during a thermally activated physical process (e.g. adsorption / desorption or phase transition). The additive released as a result of heat can be, for example, a locally active medical substance, hermetically sealed in a fusible matrix.

[111] The formulation of the adhesive with additional ingredients, for example auxiliaries and softeners, also corresponds to the current state of the art.

[112] To optimize the adhesive and technical properties, resins may be added to the self-adhesive adhesives of the invention. All resins known so far and described in the literature can be used as stickiness resins (resins that increase adhesive strength). Examples include pinene, indene and rosin resins, their hydrated, disproportionated, polymerized and esterified derivatives and salts, aliphatic and aromatic hydrocarbon resins, terpene resins and terpene phenol resins as well as C5 and C9 resins and other hydrocarbon resins. Any combination of these and further resins can be used intentionally to set the properties of the resulting adhesive mass as required. In general, it is possible to use all compatible (soluble) resins compatible with the appropriate polymer base, in particular aliphatic, aromatic, alkylaromatic hydrocarbon resins based on pure monomers, hydrated hydrocarbon resins, functional hydrocarbon resins and natural resins. In the preferential version, resins are used that do not reduce electrical conductivity and heatability, also for a long period.

[113] Another advantageous version of the flat element can be obtained by adding heat-storage filler to at least one of the layers. The term heat storage filler in the present invention is understood to mean any filler with a high heat capacity, in particular with a heat capacity exceeding 0.7 J / gK. As a result of the thermal buffer action of these substances during heating, an even course during heating can be achieved and uniform heat dissipation after the end of the active heat production process. Fillers with a high heat capacity that can be advantageously used include, for example, aluminum, beryllium, boron, calcium, iron, graphite, potassium, copper, magnesium, phosphorus or compounds of the abovementioned substances, in particular alumina and aluminum chloride, carbonate calcium, calcium chloride, copper sulfate, magnetite, hematite, magnesium carbonate and magnesium chloride, phosphorus chloride or phosphorus oxide (these substances may also have additional functions in a flat element, such as potassium or phosphorus can be used as igniters).

[114] It is advantageous if at least one layer of the adhesive has a high thermal conductivity, in particular at least 0.5 W / m * K, and very preferably above 1 W / m * K. This can be achieved by adding heat-conducting fillers, in particular by adding fillers with electrically insulating but easily heat-conducting properties, such as boron nitride or alumina, because they do not have a negative effect on electrical conductivity due to the latter. However, it is also possible to use electrically conductive fillers with high thermal conductivity, for example silver, aluminum or copper. Due to pressure-sensitive adhesive masses, the energy required to melt the thermally activated (hot melt) adhesive can be better transferred, which ensures shorter cycle times when applying the flat object of the invention to the substrate to be glued.

[115] According to the invention, the composition of the first pressure-sensitive adhesive can be identical to, or may differ from, the composition of the second pressure-sensitive adhesive.

[116] In addition to the heating layer, contact layer and adhesive layer, the inventive flat element may also have additional layers. And so it is possible that the flat element will contain additional layers of adhesive, for example, if a third layer of pressure-sensitive adhesive is provided on the side facing away from the intermittent (discontinuous) contact of the heating layer. This adhesive can be any suitable pressure-sensitive adhesive, for example pressure-sensitive adhesive with one of the base adhesives previously described.

[117] In a further preferred embodiment, at least one layer of the heatable flat element is equipped with a mechanism that, when the flat element is first heated, increases the consistency in the first self-adhesive mass, the second self-adhesive mass and / or possibly in the third self-adhesive mass. This can be achieved, for example, by increasing the crosslinking density as a result of thermally initiated additional crosslinking, which can be achieved in particular by (internal) heating of the flat element by itself. Preferably, such a flat element is therefore used in such a way that first glueing is made with at least one glued substrate, followed by the first heating, during which the curing of the adhesive connection is achieved.

[118] Usually a flat element is not equipped with a support, which allows maximum flexibility of the whole flat element. In addition, a flexible solid support may also be provided in the flat element. This carrier can be used to optimize general mechanical properties, such as the flat element's puncture resistance. All suitable carrier materials, such as films made of metal and / or plastics, textile flat elements (e.g. fabrics, knitted fabrics, inserts, nonwovens) or combinations of such materials can be used as such solid supports. Also these solid supports can be continuous (full) over the entire surface, or intermittent (discontinuous). If a solid support of this type is provided, it is necessary according to the invention that it is not in contact with the contact element at all times, but that it is placed on one layer of adhesive.

[119] It is preferred that, in addition to high flexibility, the solid support also has a high thermal conductivity, in particular a thermal conductivity of at least 0.5 W / m * K and even above 1 W / m * K. Polymers filled with thermally conductive fillers, such as boron nitride or alumina, are particularly preferred materials. Such solid supports usually have a thickness below 50 μm, preferably below 25 μm, so as not to reduce the overall flexibility of the entire structure.

[120] In a particularly preferred embodiment, the solid support is in the form of a polymer foam, since in this way the flexibility of the entire flat element is not significantly reduced.

[121] In addition, a flat element on its first side adhesive surface and / or the second side adhesive surface may be provided with a temporary support. All sheathing materials with release properties can be used as such temporary supports, such as interleaving paper or a web - technological liner - which at least partially covers one of the external adhesive masses. As a covering material, for example, all siliconized or fluorinated films can be used to facilitate unwinding and separation, which can be removed without leaving any residue. The material of the films can be, for example, PP (polypropylene), BOPP (biaxially oriented polypropylene), MOPP (uniaxially oriented polypropylene), PET (polyethylene terephthalate), PVC (polyvinyl chloride), PUR (polyurethane), PE (polyethylene) , PE / EVA (polyethylene / ethylene vinyl acetate copolymers) and EPDM (ethylene-propylene diene terpolymers). In addition, it is also possible to use interleaving papers, such as pellets, strong paper or papers with a polyolefin coating.

[122] Protective materials are particularly preferably used which, by themselves, have a high thermal conductivity of at least 0.5 W / m * K or even higher than 1 W / m * K. Polymers filled with thermally conductive fillers, such as boron nitride or alumina, are particularly preferred materials.

[123] The flat element thus includes at least one layer in which heat can be generated, this layer being sticky under pressure, at least one further adhesive layer under pressure and between these layers - a discontinuous electrically conductive layer constituting at least one electrode (one pole) of the contact layer. It is important here that the contact element is not applied to the support layer, but that it is placed directly between the heating layer and the adhesive layer.

[124] In order to produce flat elements according to the invention, all known and applicable methods can be used without exception. For example, polymer adhesive layers under pressure or thermally activated (hot melt) adhesive layers in the object of the invention can be produced by means of the production methods of polymer flat elements usually used according to the prior art. These include, for example, extrusion of flat films, extrusion of blown films, application by calenders (roller applicators), coating from a solution, suspension, or from a monomeric or pre-polymeric pre-polymer phase.

[125] To make a flat element, usually one of the two self-adhesive masses is applied flat in the form of a layer, for example on a solid support or on a production support - the so-called technological liner or web of material - which during the process or at the end of the production at the latest will be separated again from the flat element. A contact element is then applied to this pressure-sensitive adhesive. After applying the contact element, a second pressure-sensitive adhesive is applied to the exposed side surface of the contact element.

[126] It is naturally possible to obtain the flat element according to the invention also by means of a different production technology, for example in such a way that the contact element is first applied to the technological liner, then it is connected to the self-adhesive adhesive mass, then the technological liner is removed from of the contact element, after which a second self-adhesive mass is applied to the lateral surface of the contact element that is now exposed.

[127] For applying the contact element to one of the self-adhesive adhesives or possibly to a technological liner, all known technologies can be used, e.g. application (e.g. printing) of conductive varnishes, pastes or inks, transfer of sheets, films or layers (e.g. composed of metal) by hot stamping, hot welding, laminating or laminating, or discontinuous application of polymer mixtures and conductive fillers (e.g. polymer mixtures with carbon black), in which case the contact element must have a conductivity of at least one factor higher than the internally heated first adhesive.

[128] In a simple version of this type of technology, the first self-adhesive heat sealant is in contact with an electrically conductive metal mesh. In the preferred version, metals are used which corrode for a long time or only slightly. In very preferred versions, for example, copper or aluminum is used, but it is also possible to make contact with silver or gold.

[129] In a preferred embodiment, the metal can be separated directly on the pressure-sensitive adhesive, for example by means of electroplating technology or by vaporization, by means of laser technology, it is also possible to laminate a continuous or intermittent layer by transferring it from a technological liner.

[130] When using a conductive varnish, ink, printing ink, internally conductive polymer or a blend of polymers with conductive substances, printing technologies, in particular screen printing, are preferred, since in this way particularly easy, variable and reproducible application of discontinuous contact layers is possible. The printout can be done with a solution, from a suspension or from a molten mass.

[131] In the production of the flat element of the invention, it may be particularly advantageous to carry out this process in accordance with a technology in which the first adhesive layer consisting of one of two self-adhesive masses is first produced (e.g. by applying the adhesive mass to a technological liner) and which then is applied to the upper side of the layer thus obtained by an intermittent contact element, this can also be done using a clamping force, after which a second adhesive layer consisting of a second self-adhesive mass is applied to the surface of the intermittent contact in the last stage.

[132] In accordance with the invention, flat elements are used to connect two substrates together, or to connect two different partial areas in only one adhesive substrate. Because the flat element has adhesive properties on both sides, it is also prepared to provide an adhesive connection between the surfaces of two substrates to be glued. In particular, the flat element is used for gluing glued substrates in the automotive industry and is used, for example, in cars, buses, rail vehicles, ships or aircraft.

[133] The flat element according to the invention can be a component of an adhesive bond. According to this letter, an adhesive bond is an bond obtained by sticking, consisting of a flat element and at least one adhesive substrate, which is glued to the first self-adhesive side surface, or also to the second self-adhesive side surface of the flat element either directly or through additional components. Preferably, the mirror glass is used as the adhesive substrate, in particular the rear side of the mirror glass, or in the case of a transparent flat element it is a transparent glass, for example on a display screen, or a vehicle windshield. Accordingly, the flat element forming the subject of the invention is used for heating this type of glued joint.

[134] Thus, the flat element according to the invention can be used as a mirror heating (external and internal mirror), in a heated inner liner (mounting, sound insulation, heating), for heating windscreen washer fluid or for freezing protection, for heating the tank ( in particular diesel vehicles), for heating fuel pipes (at the same time as a mounting), for heating de-icing systems (de-icing of bearing surfaces, possibly together with mounting functions), in the steering wheel heating, for heating the heating air (additional heating when the engine is cold) or for heating the intake air (combustion air). The above list is purely exemplary and the possibilities of using a flat element are not limited to the specific examples listed above.

[135] In addition, it is possible to list a number of additional applications, for example (without being limited to these examples), to prevent the formation of condensation or dew on surfaces (e.g. mirrors in the bathroom, for fixing and heating, as a laminated anti-settling layer dew e.g. for use in the bathroom, as a heated adhesive film for tiles, on prescription or sun glasses or in a case for glasses), in seat heating (e.g. in cars, with integrated application combining seat heating and occupancy sensor for airbags), on benches at stops, on seats in sports stadiums, in gastronomy outside buildings and in toilet seats, in quilts or electric mats, in plate heaters (e.g. for food and dishes, but also in high-mountain ovens or cooking machines, in particular when using solar cells), in shoe heaters (especially as an insert), in band heating (pipelines, boilers, etc.), for heating rooms (on example in wall or floor heating or as folding tent heating), in heating water beds, as the so-called Thermobox for maintaining the temperature of the housing interior or in electronics, for example in combination with a Peltier cell in HiFi equipment to guarantee a constant temperature), for motorcycles (for example as steering wheel or seat heating), as greenhouse heating (for example as large area radiant or convection heating or as small area local heating directly on plants, e.g. . as root heating), for functionally heated wardrobes (e.g. in motorcyclist clothing or winter clothing), for heating and possibly for attaching display systems (e.g. LCD, OLED and electrophoretic displays, e.g. as freezing protection to camera displays or external monitors or clocks on church towers or for defrosting them), for heating external switches (e.g. as a defrosting installation for surfaces or roof gutters), in hatcheries (e.g. for young animals, for hatching eggs or in neonatal incubators), in medical therapy (e.g. in warming therapy, as warming patches and for use in transdermal therapeutic systems and for the administration of drugs through the skin (so-called transdermal drug delivery) or as igniters.

[136] According to the self-adhesive adhesive used, the flat element is attached only by pressure to the surface to be glued.

[137] Other advantages and possible applications arise from the embodiments, which will be described in more detail below based on the attached drawings. In fig. 1 in the upper part schematically a longitudinal section is shown through the flat element of the invention with a dashed contact element with a comb structure, in which all partial areas are connected to each other by a dashed contact element in an electrically conductive manner, in the central part a horizontal section is schematically shown through the upper flat element, and in the lower part the longitudinal section is schematically shown through the flat element according to the invention after it has been glued to the upper substrate and the lower substrate together with the auxiliary electrode;

Fig. 2 in the upper part schematically shows a longitudinal section through a flat element according to the invention with a dashed contact element with a double comb structure in which the two partial areas are not connected electrically through the intermittent contact element, while the lower part is a schematic representation of the horizontal section through the upper flat element;

Fig. 3 schematically shows a longitudinal section through a flat element according to the invention with a dashed contact element with a double comb structure and a solid support as a glued substrate;

Fig. 4 schematically shows a longitudinal section through a flat element according to the invention with a dashed contact element with a double comb structure and a third adhesive compound;

Fig. 5 schematically shows a longitudinal section through a flat element according to the invention protected by a temporary support;

Fig. 6 shows the measurement data curve, which graphically shows the active resistance determined for different temperatures of the flat element according to the invention (example 1);

Fig. 7 shows the measurement data curve, which graphically shows the active resistance determined for different temperatures of another flat element according to the invention (example 2);

Fig. 8 shows the measurement data curve, which graphically shows the active resistance of a flat element available for sale in various temperatures (example 1);

Fig. 9 schematically shows a longitudinal section through measuring structures for determining elasticity (resistance to sudden temperature changes) and filling joints.

Fig. 10 shows a bar diagram with measurement data from tests to determine resistance to sudden changes in temperature for various flat elements.

[138] Each of the flat elements described for example has a heatable first adhesive 10, a contact element 20 and a second adhesive 30.

[139] Fig. 1 shows a flat element according to the invention with a first pressure-sensitive adhesive 10, a contact element 20 and a second pressure-sensitive adhesive 30. The flat element is not provided here with a stabilizing supporting foil that reduces flexibility. Here, the first pressure-sensitive adhesive 10 and the second pressure-sensitive adhesive 30 are sticky here. In the area of ​​the first pressure-sensitive adhesive mass 10, heat is generated as a heating layer. The contact element 20 acts as a discontinuous, electrically conductive layer sandwiched between the adhesive layers, allowing the first adhesive mass 10 to contact.

[140] The contact element 20 here shows a comb structure with a uniform cross-section in which the fingers branch in the upper region on the same side of the main band as the fingers in the lower region. As can be seen in the central part of Fig. 1, all partial areas of the contact element 20 are connected together as a whole - so that it can act in the layer as the only contact electrode (pole) for the internally heatable first adhesive mass (which is represented by the freely selectable "-" or " + "). In connection with adhesive substrates 40, an additional contact electrode as an external auxiliary electrode 21 is therefore necessary so that current can flow through the first layer of adhesive. This external contact (auxiliary) electrode is in this example placed on the upper side of the bottom adhesive substrate 40 as a thin metal layer. With the interaction of the contact element 20 and the external auxiliary electrode 21, current can flow through the first pressure-sensitive adhesive, which runs mostly perpendicular to the surface tension of the first pressure-sensitive adhesive (and thus in the z direction).

[141] Fig. 2 shows another flat element according to the invention with a first self-adhesive 10, a contact element 20 and a second self-adhesive 30. Here too, the first self-adhesive 10 and the second self-adhesive 30 are sticky under pressure or thermally activated. In the area of ​​the first pressure-sensitive adhesive mass 10, heat is generated as a heating layer. The contact element 20 functions as a discontinuous, electrically conductive layer sandwiched between the adhesive layers, allowing the first adhesive mass 10 to contact.

[142] Also here, the contact element exhibits a comb structure with an even cross-section. As can be seen at the bottom of Fig. 2, the upper partial area of ​​the contact element 20 and the lower partial area of ​​the contact element 20 are not, however, connected together in such a way that each of these two partial areas can act as a contact electrode for the internally heatable first self-adhesive adhesive and therefore the contact element contains both contact electrodes (represented by means of freely chosen "+" and "-" symbols), so that it is not necessary to use an external auxiliary electrode. With the interaction of the two partial areas of the contact element 20, current can flow through the first pressure-sensitive adhesive, which runs mostly in the direction of the surface stretching of the first pressure-sensitive adhesive (and thus in the xy direction) and only slightly perpendicular to it.

[143] The flat element shown in fig. 3 is identical to the flat element shown in fig. 2 both in terms of shape and location of the first pressure-sensitive adhesive 10 of the contact element 20 and the second pressure-sensitive adhesive 30. In contrast to the construction shown in fig. 2 the flat element shown in fig. 3 has, however, a durable carrier 16, which is positioned as (upper) substrate glued on the second adhesive 30.

[144] The flat element in Fig. 4 according to the invention is identical to the flat element shown in Fig. 2 in both shape and location of the first pressure-sensitive adhesive 10 of the contact element 20 and the second pressure-sensitive adhesive 30. In contrast to the flat element shown in fig. 2 the flat element shown in fig. 4 however, it has a third self-adhesive adhesive 30 on the underside of the first pressure-sensitive adhesive 10, which allows a flat element to stick better to the substrate to be glued. Because the contact element 20 in this example includes both contact electrodes of the first adhesive, the third adhesive can be chosen freely - as in the example shown in figure 4 - in the same way as the second adhesive 30.

[145] The flat element shown in Fig. 5 is identical to the flat element shown in Fig. 2 in terms of the shape and location of the contact element 20 and the second adhesive 30, the difference is that the mass self-adhesive adhesive is an internally heat-adhesive adhesive mass activated by pressure 11. To protect the pressure sensitive adhesive activated by pressure 11 against unintentional sticking in the event of accidental contact, the pressure sensitive adhesive from the outside of the flat element is at the bottom - at least partly covered by the temporary carrier 24.

[146] The invention has been further described by means of individual example selected experiments, without however being limited to their scope by such and no other selection of tests.

[147] The following test methods were used to characterize the flat element according to the invention:

[148] Determination of the adhesive strength (bonding) of self-adhesive pressure-sensitive adhesive masses activated by pressure (test A) was carried out in a peel test on a steel plate at an angle of 180⁰ at a tear-off speed of 300 mm / min according to ASTM D 3330-04. All measurements were carried out at room temperature (23 ° C) and in an air-conditioned environment (with relative humidity of 50%).

[149] The determination of the adhesive strength (bonding) of the thermally activated heat-sealing adhesive masses (test B) was carried out in the peeling force test T (test B). To this end, a 200 μm thick thermally activated (hot melt) adhesive test strip was applied in a vacuum atmosphere to a polyester film without surface treatment (Mitsubishi H) using a heating press at a temperature of 140 ° C. A 20 mm wide strip was cut from the combined system obtained in this way and subjected to conditioning for 24 hours in room ambient conditions. Then the heating foil was removed at room temperature in an air-conditioned atmosphere from the polyester carrier, while the force needed to perform this operation was measured. In this process, neither the hot melt adhesive nor the polyester film were supported or attached, which resulted in tearing it off in the form of the letter T. The measurement results are given in N / cm and are the average of three measurements.

[150] Determination of electric heat (test C) was carried out for a flat element by measuring the temperature increase after applying the voltage. The temperature was measured using a Pt100 thermal sensor. The flat element according to the invention and the comparative example were applied to the glass plate by adhesive pressure. A voltage of 12.8 V was applied to the flexible heating element using a transformer. After 600 seconds, the temperature was measured directly on the surface of the glass plate. The measurement results are given in ° C.

[151] As part of this test, the extent of the PTC effect was determined on identical test samples; for this purpose, the time course of the matching temperatures after the power supply was recorded. The temperature measurement was carried out in the manner described above. Then the current and voltage time course was recorded, thanks to which it was possible to calculate the resistance changes according to Ohm's law.

[152] As examples of the flat elements according to the invention, flat elements were made with pressure-sensitive adhesive activated as the first pressure-sensitive adhesive.

[153] In order to obtain an internally heatable pressure-sensitive adhesive mass, similarly to EP 04 712 016, a pressure-sensitive adhesive base mass consisting of comonomers in proportions of 44.5% by weight of 2-ethylhexyl acrylate , 44.5% by weight n-butyl acrylate, 8% by weight methacrylate and 3% by weight acrylic acid. By determining the relative molar mass, the average relative molar mass Mw was obtained at 650,000 g / mol with a Mw / Mn polydispersity of 7.0. The base pressure-sensitive adhesive obtained in this way was mixed in a solution with 40 wt. graphite (Timcal Timrex KS 6) and then applied with a spatula (for application) to siliconized pellet interleaving paper (Laufenberg company). After a drying time of 10 minutes at 120 ° C, the thickness of the pressure-sensitive adhesive layer thus obtained was 100 μm.

[154] Next, this self-adhesive adhesive mass activated by pressure was cross-linked with electron radiation. Electron radiation was emitted by a device from Electron Crosslinking AB, Halmstad, from Sweden. The adhesive tape applied with a layer of pressure-sensitive adhesive activated by pressure was passed through the provided, standard cooling roller under the accelerator Lenard window. In the irradiation zone, the oxygen in the air was displaced by flushing with pure nitrogen. The belt speed was 10 m / min here. The dose of electron radiation was 50 kGy at an accelerating voltage of 180 kV for Example 1.

[155] For internally heat-activated (hot-melt) adhesive mass (comparative experiments), ethylene vinyl acetate copolymer (EVA) Escorene Ultra FL 00728 (ExxonMobil) with a 28% wt content of vinyl acetate was used as the base heat-activated adhesive. . In this heat-activated base adhesive, a Haake Rheomix measuring kneader at 140 ° C and a rotational speed of 120 min-1 with 14% by weight of conductive carbon black (Printex XE2; Degussa) was mixed with the mass for 45 minutes. The thickness of the polymer blend obtained in this way was carried out by means of a vacuum press

200 um.

Example in accordance with the invention [156] In example 1, the Fig. 2 construction using the above-described self-adhesive self-adhesive mass activated by a pressure of 100 μm as the first self-adhesive mass, the first base self-adhesive mass activated by the pressure of a 75 μm mass as the second self-adhesive mass and cut from copper foil 0 , 03 mm, comb-shaped two-piece contact element, 1.5 mm apart. The heatable surface was 180 cm².

Comparative examples [157] The comparative example uses the one presented in fig. 2 construction using the above-described thermally activated (heat-melting) 150 mm thick adhesive as the first self-adhesive adhesive, the first self-adhesive base adhesive activated by 75 μm pressure as the second self-adhesive adhesive and cut from copper foil 0.03 mm, a comb-shaped two-piece contact element, 1.5 mm apart. The conductive bands of the contact element were applied at a temperature of 140 ° C on a thermally activated adhesive. The heatable surface was 180 cm².

[158] In comparative example B the structure shown in Fig. 9 b) was made (without substrate 40 and glass plate 41) with the previously described internally heatable hot melt adhesive 9 with a thickness of 150 μm and with the above-described self-adhesive base adhesive 22 with a thickness of 75 μm. Conductive bands (ribbons) were obtained by using a conductive silver lacquer, which was applied directly to a thermally activated (hot melt) heat-sealing adhesive. This construction can be compared directly with comparative examples in terms of functionality in gluing and heating.

[159] In example 1, a commercially available PTC heating element was used, used in the exterior mirrors of Porsche cars.

[160] In Comparative Example 2, the structure shown in Fig. 9 a) was made (without substrate 40 and glass plate 41) with the previously described internally heatable hot melt adhesive 9 with a thickness of 150 μm and with the above-described pressure-sensitive adhesive base 22 with a thickness of 75 μm. This design 10 differs from Comparative Example B only by the use of a flexible conductive plate made of 30 μm thick copper conduction paths applied to 75 μm thick polyester film to ensure contact between the hot melt adhesive mass, so that a comparison of the properties of both samples can illustratively show advantages of the flat element without support, as a special embodiment of the invention in relation to the embodiment of the flat element with a solid support.

[161] The adhesive strength (bonding) was determined for the pressure-sensitive adhesive base described above according to test A:

Self-adhesive base adhesive activated by pressure: 7.4 N / cm

Heat-adhesive self-adhesive mass activated by pressure: 6.3 N / cm [162] The results of this test show that after adding an electrically conductive filler to the base self-adhesive pressure mass activated by pressure, its adhesive properties are still maintained.

[163] The peel force (breaking strength) was determined for the previously described hot melt adhesive mass and the previously heated hot melt adhesive mass according to test B:

Base hot melt adhesive: 4.5 N / cm

Heated hot melt adhesive material: 3.1 N / cm [164] The results of this study show that after adding an electrically conductive filler to the base hot melt adhesive its adhesive properties under thermal activation conditions are still maintained.

[165] Heat resistance and PTC effect were determined in both Example 1 and Comparative Example A as well as in Comparative Example 1 according to Test C. The flat elements reached the following temperatures in these tests:

Example 1:

Comparative Example A Comparative Example 1:

° C 64 ° C ° C [166] The test results show that the flat elements according to the invention achieve a heating power corresponding to the heating power of the car mirror heating systems currently available on the market.

[167] Calculated on the basis of the instantaneous current and the corresponding instantaneous voltage, the general resistance of the flat element is shown in Fig. 6 and Fig. 8 depending on the temperature. The form of the curve obtained there informs about the PTC effect in the heating layers. Fig. 6 shows the results for Example 1, Fig. 7 the results for Comparative Example A, and Fig. 8 the results for Comparative Example 1. When comparing the measurement data curves obtained in this way, it can be seen that the PTC effect for the flat elements according to the invention is even stronger than in the commercial comparative example.

[168] The exemplary experiments described above prove the excellent suitability of the flexible flat elements according to the invention to obtain a stable, heated adhesive connection.