DE10259549A1 - PSA article with at least one layer of an electrically conductive PSA and process for its production - Google Patents

Abstract

In a method for producing a pressure-sensitive adhesive article, an electrically conductive acrylate-containing pressure-sensitive adhesive is coated on a carrier by stretching or stretching within a hotmelt coating process in such a way that an anisotropic electrically conductive layer with a shrinkback of at least 3%, measured on the free pressure-sensitive adhesive film, is produced. Die cuts can advantageously be made from the material for the electrical and electronics industry.

Description

The invention relates to a method for the production of a pressure sensitive adhesive article which has at least one layer from a thermally conductive Has PSA, and a PSA article obtainable in this way, especially for Bonding in the field of electrical and electronic components.

In the age of computerization become electrically conductive PSAs more and more for bonding electrodes or electromagnetic components used. The goal is the electrical conductivity and to avoid electrical flashovers.

Usually for this Applications electrically conductive acrylic PSA used. The electrical conductivity can by two different Methods can be achieved. On the one hand, conductive foils or fabrics are used, on the other hand, the PSA is made up of electrically conductive components modified and thus electrically conductive itself.

Examples of electrically conductive carrier materials are, for example, in US 5,939,190 and 6,235,385 as well as the patents cited there.

Electrically conductive acrylic PSAs have also been known for a long time. So in US 4,113,981 described that electrical conductivity can be achieved by adding metal powder or SiC powder. The conductivity can be varied by the degree of filling. Furthermore, if the mass is enclosed between two electrodes, an electrical conductivity is only achieved in the z direction by limiting it to 30%.

In US 5,300,340 silver-plated glass beads and metal beads are mixed into a PSA. The diameter of these beads is at least as large as the layer thickness of the PSA. The electrical conductivity is thus achieved through the direct contact of the conductive beads with the conductive substances to be bonded (e.g. electrodes).

In US 5,620,795 and US 6,126,865 Polyacrylates of a certain comonomer composition are used as electrically conductive acrylic PSAs. The comonomer composition of the polyacrylates is chosen such that very non-polar resins are compatible with the polyacrylate and thus high adhesive strengths can be achieved on non-polar surfaces with the electrically conductive PSA.

By miniaturization in the Electronics / computer industry are however increasingly demanding requirements for electrical conductive PSAs provided. The electrical components to be glued are always in their size smaller, so often only die cuts can be used for gluing. Farther the distance between the circuits decreases continuously, so that electrically conductive PSAs required are in a certain direction (to the next electrically conductive component) a very low flow behavior have.

The object of the invention is therefore electrically conductive PSAs, especially for to provide the electrical and electronics industries where the disadvantages in the prior art are avoided and in particular a swelling or flowing out of the PSA at the edge reliable bonding is avoided.

The task is solved surprisingly and for the person skilled in the art in an unpredictable manner by means of a method, with the help of anisotropic, oriented PSAs with a shrinkback of at least 3% coated on a support (if necessary also a temporary one Carrier, from which the PSA can be removed) are, as well as by the associated pressure sensitive adhesive articles obtainable in this way. Further developments of the invention are characterized in the subclaims.

The solution of the invention task encompasses a method for producing a pressure sensitive adhesive article for bonding of electrical or electronic parts, the at least one Layer of an electrically conductive pressure sensitive adhesive, i.e. a PSA based on polyacrylates and / or polymethacrylates with optionally further comonomers, wherein in one Coating processes by stretching, stretching or compressing at least one in terms of a property of anisotropic layer made of the electrically conductive PSA is generated, one in at least one direction along the layer plane shrinkback of at least 3% regarding the linear expansion the layer, measured with a shrinkback measurement after test B on free film.

Anisotropy means that at least a property of the PSA in a spatial direction within the layer of the PSA of the same property distinguishes in at least one other direction; i.e. anisotropic Properties are vectorial and not uniform within the material.

The PSA preferably has an orientation as known as such, i.e. a preferred direction within the polymer structure.

The coating process can, for example a "hot melt" or hot melt roll coating process, a melt nozzle coating process or an extrusion coating process.

In an alternative embodiment In the invention, the coating method is conventional Coating process, for example from solution, in which subsequently the coating is stretched or stretched, preferably on an elastic strap.

The electrically conductive PSA can be coated on one or both sides with the coating process leaf or ribbon-shaped carrier can also be coated using a transfer tape or a release liner can be.

Can be used according to the invention PSAs

According to the invention, PSAs are with a resilience or anisotropically oriented or simply "oriented" PSAs are also used. anisotropic oriented PSAs have a tendency to look for one Extension in a given direction through the 'entropy-elastic behavior' to the initial state move back.

As electrically conductive PSAs with a resilience preferably (meth) acrylic PSAs used.

• – die Haftklebemasse zu mindestens 50 Gew.-% auf zumindest einem acrylischen Monomer aus der Gruppe der Verbindungen der folgenden allgemeinen Formel basiert:
  
  wobei R₁ = H oder CH₃ ist und der Rest R₂ = H oder CH₃ ist oder gewählt wird aus der Gruppe der verzweigten oder unverzweigten, gesättigten Alkylgruppen mit 2 – 30 Kohlenstoffatomen.
• – das mittlere Molekulargewicht M_W der Haftklebemasse mindestens 200.000 g/mol beträgt,
• – die auf einen Träger aufgetragene Haftklebemasse eine Vorzugsrichtung besitzt, die nach Test B über den Rückschrumpf im freien Film bestimmt werden kann und zumindest größer 3 % liegt.
• – die einen effektiven Anteil zumindest einer elektrisch leitfähigen Komponente enthält

For the purposes of the invention, preference is given to a PSA which can be obtained by radical polymerization, where

• At least 50% by weight of the PSA is based on at least one acrylic monomer from the group of the compounds of the following general formula:
  
  where R ₁ = H or CH ₃ and the radical R ₂ = H or CH ₃ or is selected from the group of branched or unbranched, saturated alkyl groups having 2 to 30 carbon atoms.
• The average molecular weight M _{W of} the PSA is at least 200,000 g / mol,
• - The PSA applied to a carrier has a preferred direction which can be determined according to test B via the shrinkback in the free film and is at least greater than 3%.
• - Which contains an effective proportion of at least one electrically conductive component

The monomers are preferably chosen such that the resulting ones Polymers at room temperature or higher temperatures than PSAs can be used in particular such that the resulting polymers pressure-sensitive adhesive properties accordingly of the “Handbook of Pressure Sensitive Adhesive Technology "by Donatas Satas (van Nostrand, New York 1989).

In another inventive Interpretation, the comonomer composition is chosen such that the PSAs are heat-activatable PSAs let insert.

The polymers, which are preferably used as electrically conductive PSAs with a resilience, can preferably be obtained by polymerizing a monomer mixture which consists of acrylic acid esters and / or methacrylic acid esters and / or their free acids with the formula CH ₂ = C (R ₁ ) (COOR ₂ ), where R ₁ = N or CH ₃ and R _{2 is} an alkyl chain with 1 - 20 C atoms or H.

The molecular weights M _{W of} the polyacrylates used are preferably M _W ≥ 200,000 g / mol.

In a very preferred way Acrylic or methacrylic monomers used, which consist of acrylic and methacrylic acid esters with alkyl groups consist of 4 to 14 carbon atoms, preferably 4 to 9 carbon atoms. Specific examples without going through this enumeration restrict wanting are 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, e.g. isobutyl, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate.

Other connection classes to be used are monofunctional acrylates or methacrylates of bridged cycloalkyl alcohols, consisting of at least 6 carbon atoms. The cycloalkyl alcohols can also be substituted, e.g. by C-1-6 alkyl groups, halogen atoms or cyano groups. Specific examples are cyclohexyl methacrylates, Isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyladamantylacrylate.

In one approach, monomers used, the polar groups such as carboxyl residues, sulfonic and phosphonic acid, hydroxy residues, Lactam and lactone, N-substituted amide, N-substituted amine, carbamate, Wear epoxy, thiol, alkoxy, cyan radicals, ether or the like.

Moderate basic monomers are e.g. N, N-dialkyl substituted amides such as e.g. N, N-dimethylacrylamide, N, N-dimethylmethyl methacrylamide, N-tert-butylacrylamide, N-vinylpyrrolidone, N-vinyllactam, dimethylaminoethyl methacrylate, Dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, N-methylol methacrylamide, N- (buthoxymethyl) methacrylamide, N-methylolacrylamide, N- (ethoxymethyl) acrylamide, N-isopropylacrylamide, although this list is not exhaustive.

Other preferred examples are Hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, Hydroxypropyl methacrylate, allyl alcohol, maleic anhydride, itaconic anhydride, Itaconic acid, glyceridyl methacrylate, Phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, cyanoethyl methacrylate, cyanoethyl acrylate, Glyceryl methacrylate, 6-hydroxyhexyl methacrylate, vinyl acetic acid, tetrahydrofufurylacrlyat, β-acryloyloxypropionic acid, trichloracrylic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, where this list not concluding is.

In another very preferred one Procedure as monomers are vinyl esters, vinyl ethers, vinyl halides, Vinylidene halides, vinyl compounds with aromatic cycles and Heterocycles in the α-position used. Here, too, a few examples are not exclusively mentioned: Vinyl acetate, vinyl formamide, vinyl pyridine, ethyl vinyl ether, vinyl chloride, Vinylidene chloride and acrylonitrile.

In a further procedure, photoinitiators with a copolymerizable double bond are also used. Norrish I and II photoinitiators are suitable as photoinitiators. Examples are, for example, benzoin acrylate and an acrylated benzophenone from UCB (Ebecryl P 36 ^® ). In principle, all photoinitiators known to the person skilled in the art can be copolymerized which can crosslink the polymer via a radical mechanism under UV radiation. An overview of possible usable photoinitiators that can be functionalized with a double bond is given in Fouassier: "Photoinititation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. In addition, Carroy et al. In "Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints ", Oldring (ed.), 1994, SITA, London.

In a further preferred procedure, monomers are added to the comonomers described which have a high static glass transition temperature. Aromatic vinyl compounds, such as, for example, styrene, are suitable as components, the aromatic nuclei preferably consisting of C ₄ to C _{18 building} blocks and also being able to contain heteroatoms. Particularly preferred examples are 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 acrylate and 2-methacrylate, and methacrylate and methacrylate and mixtures of those monomers, this list is not exhaustive.

It is also part of the inventive PSA that the PSA has a shrinkback, wherein the shrinkback over a Determination according to test B (shrinkback measurement in free film) is at least 3%. In preferred developments PSAs are used in which the shrinkback is at least 30%, very preferably at least 50%.

It is also part of the inventive PSA an addition of an electrically conductive connection. In a Preferred design are therefore electrically conductive filling materials used. Such materials include, without being limited by this list, metal particles, Metal powder, metal balls, metal fibers, the metals being e.g. Nickel, gold, silver, iron, lead, tin, zinc, stainless steel, bronze and copper or nickel coatings on copper particles, on nickel particles, used on polymer balls or particles or glass microspheres become. Still useful are e.g. also lead / tin alloys with different compositions, such as by Sherrit Gordon, Ltd. Tobe offered.

In a further embodiment of the invention, electrically conductive polymers can be added, such as polythiophene, subsituierte polythiophenes, Polyethylendioxythiophene, polyaniline, substiutierte polyaniline, polyparaphenylene, substituted polyparaphenylene, polypyrrole, substituted polypyrroles, polyacetylenes, substituted polyacetylenes, polyphenylene, substituted polyphenylene, polyfurans, substituted polyfurans Polyalkylfluorene, substituted polyalkylfluorenes and mixtures of the above-mentioned polymers. So-called dopants can be added to improve conductivity. Various metal salts or Lewis acid or electrophiles can be used here. Examples which do not claim to be complete are p-toluenesulfonic acid or camphorsulfonic acid. Further electrically conductive polymers include polyvinylbenzyltrimethylammonium chloride and similar compounds which are described in US 5,061,294 were quoted.

In a further preferred interpretation the invention is the diameter of the electrically conductive fillers less than the layer thickness of the PSA. In a preferred one Dispersions from ORMECON are used. The added electrically conductive Depending on the dopant and chemical composition, polymers have a conductivity between 1 and 500 S / cm.

In a further configuration, carbon compounds, such as C-60, can be added as electrically conductive materials. With these compounds as well, an improved electrical conductivity can be achieved by targeted doping. Furthermore, hygroscopic salts can also be used as electrically conductive substances US 4,973,338 to be discribed.

Electrically conductive substances are used up added to 50% by weight based on the poly (meth) acrylate. In a preferred interpretation is the proportion 30% by weight based on the poly (meth) acrylate. The amount will be according to the desired electrical conductivity to be achieved. The share should, however don't exceed a lot so that the pressure sensitive adhesive loses the adhesive properties.

For further development, the inventive PSAs can be admixed with resins. As to be added tackifying resins are, without exception, all known and in adhesive resins described in the literature can be used. Be mentioned representative of the pinene, indene and rosin resins, their disproportionate, hydrogenated, polymerized, esterified derivatives and salts, the aliphatic and aromatic hydrocarbon resins, terpene resins and terpene phenolic resins as well as C5, C9 and other hydrocarbon resins. Any combinations this and other resins can used to improve the properties of the resulting adhesive set as desired. In general, all can be with the appropriate polyacrylate compatible (soluble) Use resins, in particular reference is made to all aliphatic, aromatic, alkyl aromatic hydrocarbon resins, hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins, functional Hydrocarbon resins and natural resins. On the representation of the State of knowledge in the “Handbook of Pressure Sensitive Adhesive Technology "by Donatas Satas (van Nostrand, 1989) be express pointed.

Furthermore, plasticizers (plasticizers), other fillers (such as fibers, soot, Zinc oxide, chalk, solid or hollow glass spheres, microspheres from others Materials, silica, Silicates), nucleating agents, blowing agents, Compounding agents and / or anti-aging agents, e.g. in shape from primary and secondary Antioxidants or added in the form of light stabilizers.

In addition, crosslinkers and promoters can be added for networking. Suitable crosslinkers for electron beam crosslinking and UV crosslinking are, for example, bi- or multifunctional acrylates, bi- or multifunctional isocyanates (also in blocked form) or bi- or multifunctional epoxies.

For an optional crosslinking with UV light, UV-absorbing photoinitiators can be added to the polyacrylate PSAs. Useful photoinitiators that are very easy to use are benzoin ethers, such as. As benzoin methyl ether and benzoin isopropyl ether, substituted acetophenones, such as. B. 2,2-Diethoxyacetophenone (available as Irgacure 651 ^® from Ciba Geigy ^® ), 2,2-dimethoxy-2-phenyl-1-phenylethanone, dimethoxyhydroxyacetophenone, substituted α-ketols, such as. B. 2-methoxy-2-hydroxypropiophenone, aromatic sulfonyl chlorides, such as. B. 2-naphthyl sulfonyl chloride, and photoactive oximes such. B. 1-phenyl-1,2-propanedione-2- (O-ethoxycarbonyl) oxime.

The above mentioned and other usable ones Photoinitiators and others of the Norrish I or Norrish II type can contain the following residues: benzophenone, acetophenone, benzil, Benzoin, hydroxyalkylphenone, phenylcyclohexylketone, anthraquinone, Trimethylbenzoylphosphine oxide, methylthiophenylmorpholine ketone, Aminoketone, azobenzoin, thioxanthone, hexarylbisimidazole, triazine, or fluorenone, each of these residues additionally with one or more Halogen atoms and / or one or more alkyloxy groups and / or one or more amino groups or hydroxy groups substituted can be. A representative overview is from Fouassier: "Photoinititation, Photopolymerization and Photocuring: Fundamentals and Applications ", Hanser-Verlag, Munich 1995, given. additional Carroy et al. in "Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints ", Oldring (ed.), 1994, SITA, London.

manufacturing for the inventive PSAs

For the polymerization, the monomers are chosen such that the resulting polymers can be used as pressure-sensitive adhesives at room temperature or higher temperatures, in particular such that the resulting polymers have pressure-sensitive adhesive properties in accordance with the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989) To achieve a preferred glass transition temperature T _{G of} the polymers of T _G 25 25 ° C. for PSAs, the monomers are very preferably selected in accordance with what has been said above and the quantitative composition of the monomer mixture is advantageously chosen such that Equation (G1) (cf. TG Fox, Bull. Am. Phys. Soc. 1 (1956) 123) gives the desired T _G value for the polymer.

Herein n represents the running number of the monomers used, w _n the mass fraction of the respective monomer n (% by weight) and T _{G, n} the respective glass transition temperature of the homopolymer from the respective monomers n in K.

For the production of the poly (meth) acrylate PSAs conventional radical polymerizations are advantageous carried out. For the radical polymerizations are preferred initiator systems used that additionally contain further radical initiators for the polymerization, in particular thermally decaying radical-forming azo or peroxo initiators. in principle however, all are suitable for acrylates usual to the expert Initiators. The production of C-centered radicals is in progress Weyl, Methods of Organic Chemistry, Vol. E 19a, pp. 60-147. These methods are preferably used in analogy.

Examples of radical sources are peroxides, hydroperoxides and azo compounds, and some non-exclusive examples of typical radical initiators are potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, azodiisoic acid butyronitrile, cyclohexyl peroxyloctyl peroxyl peroxyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetraperyl tetra peroxo In a very preferred embodiment, 1,1'-azo-bis- (cyclohexanecarbonitrile) (Vazo 88 ^™ from DuPont) or azodisobutyronitrile (AIBN) is used as the radical initiator.

The electrically conductive materials can the monomers before the polymerization and / or after completion of the Polymerization can be added.

The average molecular weights M _W of the PSAs formed in the radical polymerization are very preferably chosen such that they are in a range from 200,000 to 4,000,000 g / mol; PSAs with average molecular weights M _W of 400,000 to 1,400,000 g / mol are produced specifically for further use as electrically conductive hotmelt PSAs with resilience. The average molecular weight is determined by size exclusion chromatography (GPC) or matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS).

The polymerization can be carried out in bulk, in the presence of one or more organic solvents, in the presence of Water or in mixtures of organic solvents and water can be carried out. The aim is to minimize the amount of solvent used as possible to keep. Suitable organic solvents are pure alkanes (e.g. hexane, heptane, octane, isooctane), aromatic hydrocarbons (e.g. benzene, toluene, xylene), esters (e.g. ethyl acetate, propyl acetate, butyl or hexyl ester), halogenated hydrocarbons (e.g. Chlorobenzene), alkanols (e.g. methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether) and ethers (e.g. diethyl ether, dibutyl ether) or mixtures thereof. The aqueous polymerization reactions can with a water-miscible or hydrophilic cosolvent be relocated to ensure that this Reaction mixture during of the monomer conversion is in the form of a homogeneous phase. Advantageous usable cosolvents for the present invention are chosen from the following group, consisting of aliphatic alcohols, Glycols, ethers, glycol ethers, pyrrolidines, N-alkylpyrrolidinones, N-alkylpyrrolidones, Polyethylene glycols, polypropylene glycols, amides, carboxylic acids and Salts thereof, esters, organosulfides, sulfoxides, sulfones, alcohol derivatives, hydroxy ether derivatives, Amino alcohols, ketones and the like, as well as derivatives and mixtures from that.

The polymerization time is - depending on Turnover and temperature - between 2 and 72 hours. The higher the reaction temperature chosen can be, that is, The higher thermal stability of the reaction mixture, the shorter the reaction time chosen become.

To initiate the polymerization is for the thermally decaying initiators the entry of heat essential. The polymerization can for the thermally decomposing initiators by heating to 50 to 160 ° C, depending on Initiator type.

For the production can also be advantageous, the acrylic PSAs polymerize in bulk. Here, the prepolymerization use. The polymerization is initiated with UV light, however only led to a low turnover of approx. 10 - 30%. Then you can this polymer syrup e.g. are sealed in foils (in the simplest Ice cube case) and then polymerized through in water to a high conversion. This Pellets can then be used as an acrylic hot melt adhesive, being used for the melting process particularly preferred foil materials are used that with are compatible with polyacrylate. This preparation method can also be used the thermally conductive Material additives before or add after the polymerization.

Another advantageous manufacturing process for the Anionic polymerization is poly (meth) acrylate PSAs. Inert solvents are preferred as the reaction medium used, e.g. aliphatic and cycloaliphatic hydrocarbons, or also aromatic hydrocarbons.

The living polymer in this case is generally represented by the structure P _L (A) -Me, where Me is a Group I metal such as lithium, sodium or potassium, and P _L (A) is a growing polymer of the acrylate monomers , The molar mass of the polymer to be produced is controlled by the ratio of initiator concentration to monomer concentration. Suitable polymerization initiators are, for. B. n-propyllithium, n-butyllithium, sec-butyllithium, 2-naphthyllithium, cyclohexyllithium or octyllithi um, whereby this list does not claim to be complete. Initiators based on samarium complexes for the polymerization of acrylates are also known (Macromolecules, 1995, 28, 7886) and can be used here.

Furthermore, difunctional ones can also be used Use initiators, such as 1,1,4,4-tetraphenyl-1,4-dilithiobutane or 1,1,4,4-tetraphenyl-1,4-dilithioisobutane. Leave coinitiators get involved too. Suitable coinitiators include Lithium halides, alkali metal alkoxides or alkyl aluminum compounds. The ligands and coinitiators are in a very preferred version chosen so that acrylate monomers, such as. n-Butyl acrylate and 2-ethylhexyl acrylate, directly polymerized can be and not in the polymer by transesterification with the corresponding one Alcohol must be generated.

worin R und R¹ unabhängig voneinander gewählt oder gleich sind

• – verzweigte und unverzweigte C₁- bis C₁₈-Alkylreste; C₃- bis C₁₈-Alkenylreste; C₃-bis C₁₈-Alkinylreste;
• – C₁- bis C₁₈-Alkxoyreste
• – durch zumindest eine OH-Gruppe oder ein Halogenatom oder einen Silylether substituierte C₁- bis C₁₈-Alkylreste; C₃- bis C₁₈-Alkenylreste; C₃- bis C₁₈-Alkinylreste;
• – C₂-C₁₈-Hetero-Alkylreste mit mindestens einem O-Atom und/oder einer NR*-Gruppe in der Kohlenstoffkette, wobei R* ein beliebiger (insbesondere organischer) Rest sein kann,
• – mit zumindest einer Estergruppe, Amingruppe, Carbonatgruppe, Cyanogruppe, Isocyanogruppe und/oder Epoxidgruppe und/oder mit Schwefel substituierte C₁-C₁₈-Alkylreste, C₃-C₁₈-Alkenylreste, C₃-C₁₈-Alkinylreste;
• – C₃-C₁₂-Cycloalkylreste
• – C₆-C₁₈- Aryl- oder Benzylreste
• – Wasserstoff

darstellen.Controlled radical polymerization methods are also suitable for the production of polyacrylate PSAs with a narrow molecular weight distribution. A control reagent of the general formula is then preferably used for the polymerization:

wherein R and R ^{1 are} independently selected or the same

• - branched and unbranched C ₁ - to C ₁₈ -alkyl radicals; C ₃ to C ₁₈ alkenyl radicals; C _{3 to} C ₁₈ alkynyl radicals;
• C ₁ to C ₁₈ alkoxy residues
• - C ₁ - to C ₁₈ -alkyl radicals substituted by at least one OH group or a halogen atom or a silyl ether; C ₃ to C ₁₈ alkenyl radicals; C ₃ to C ₁₈ alkynyl radicals;
• C ₂ -C ₁₈ heteroalkyl radicals having at least one O atom and / or one NR * group in the carbon chain, where R * can be any (in particular organic) radical,
• - With at least one ester group, amine group, carbonate group, cyano group, isocyano group and / or epoxy group and / or sulfur-substituted C ₁ -C ₁₈ alkyl groups, C ₃ -C ₁₈ alkenyl groups, C ₃ -C ₁₈ alkynyl groups;
• - C ₃ -C ₁₂ cycloalkyl radicals
• - C ₆ -C ₁₈ aryl or benzyl radicals
• - hydrogen

represent.

Control reagents of type (I) preferably consist of the following further restricted compounds:
Halogen atoms are preferably F, Cl, Br or I, more preferably Cl and Br. Both linear and branched chains are outstandingly suitable as alkyl, alkenyl and alkynyl radicals in the various substituents.

Examples of alkyl radicals which 1 to Contain 18 carbon atoms, are methyl, ethyl, propyl, isopropyl, Butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl, undecyl, tridecyl, tetradecyl, Hexadecyl and octadecyl.

Examples of alkenyl residues with 3 to 18 Carbon atoms are propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, isododecenyl and Oleyl.

Examples of alkynyl having 3 to 18 carbon atoms are propynyl, 2-butynyl, 3-butynyl, n-2-octynyl and n-2-octadecynyl.

Examples of hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl or hydroxyhexyl.

Examples of halogen-substituted alkyl radicals are dichlorobutyl, monobromobutyl or trichlorohexyl.

A suitable C ₂ -C ₁₈ heteroalkyl radical with at least one O atom in the carbon chain is, for example, -CH ₂ -CH ₂ -O-CH ₂ -CH ₃ .

Cyclopropyl, cyclopentyl, cyclohexyl or trimethylcyclohexyl are used, for example, as C ₃ -C ₁₂ cycloalkyl radicals.

Examples of C ₆ -C ₁₈ aryl radicals are phenyl, naphthyl, benzyl, 4-tert-butylbenzyl or other substituted phenyl, such as, for example, ethyl, toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene or bromotoluene.

The above listings serve just as examples of the respective connection groups and have no claim to Completeness.

wobei R² ebenfalls unabhängig von R und R¹ aus der oben aufgeführten Gruppe für diese Reste gewählt werden kann.Compounds of the following types can also be used as control reagents

where R ^{2 can} also be selected independently of R and R ¹ from the group listed above for these radicals.

The conventional 'RAFT process' mostly only up to low sales polymerized (WO 98/01478 A1) to narrow molecular weight distributions to realize. The low sales make these polymers but not as PSAs and especially not as hotmelt PSAs use because the high proportion of residual monomers the adhesive Properties adversely affected, the residual monomers contaminate the solvent recyclate in the concentration process and the corresponding self-adhesive tapes have a very high outgassing behavior would show. This disadvantage low sales in a particularly preferred procedure, the Polymerization initiated several times.

wobei R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰ unabhängig voneinander folgende Verbindungen oder Atome bedeuten:

• i) Halogenide, wie z.B. Chlor, Brom oder Iod
• ii) lineare, verzweigte, cyclische und heterocyclische Kohlenwasserstoffe mit 1 bis 20 Kohlenstoffatomen, die gesättigt, ungesättigt oder aromatisch sein können,
• iii) Ester -COOR¹¹, Alkoxide -OR¹² und/oder Phosphonate -PO(OR¹³)₂,

wobei R¹¹, R¹² oder R¹³ für Reste aus der Gruppe ü) stehen.As a further controlled radical polymerization method, nitroxide-controlled polymerizations can be carried out. For radical stabilization, nitroxides of type (Va) or (Vb) are used in a favorable procedure:

where R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ independently of one another denote the following compounds or atoms:

• i) halides, such as chlorine, bromine or iodine
• ii) linear, branched, cyclic and heterocyclic hydrocarbons with 1 to 20 carbon atoms, which can be saturated, unsaturated or aromatic,
• iii) esters -COOR ¹¹ , alkoxides -OR ¹² and / or phosphonates -PO (OR ¹³ ) ₂ ,

where R ¹¹ , R ¹² or R ^{13 are} radicals from the group ü).

Connections of (Va) or (Vb) can also bound to polymer chains of any kind (primarily in the sense that at least one of the above-mentioned residues represents such a polymer chain) and thus be used to build up polyacrylate PSAs.

• – 2,2,5,5-Tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-Carbamoyl-PROXYL, 2,2-dimethyl-4,5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-Hydroxylimine-PROXYL, 3-Aminomethyl-PROXYL, 3-Methoxy-PROXYL, 3-t-Butyl-PROXYL, 3,4-Di-t-butyl-PROXYL
• – 2,2,6,6-Tetramethyl-1-piperidinyloxy pyrrolidinyloxyl (TEMPO), 4-Benzoyloxy-TEMPO, 4-Methoxy-TEMPO, 4-Chloro-TEMPO, 4-Hydroxy-TEMPO, 4-Oxo-TEMPO, 4-Amino-TEMPO, 2,2,6,6,-Tetraethyl-1-piperidinyloxyl, 2,2,6-Trimethyl-6-ethyl-1-piperidinyloxyl
• – N-tert.-Butyl-1-phenyl-2-methyl propyl Nitroxid
• – N-tert.-Butyl-1-(2-naphtyl)-2-methyl propyl Nitroxid
• – N-tert.-Butyl-1-diethylphosphono-2,2-dimethyl propyl Nitroxid
• – N-tert.-Butyl-1-dibenzylphosphono-2,2-dimethyl propyl Nitroxid
• – N-(1-Phenyl-2-methyl propyl)-1-diethylphosphono-1-methyl ethyl Nitroxid
• – Di-t-Butylnitroxid
• – Diphenylnitroxid
• – t-Butyi-t-amyl Nitroxid

Controlled regulators for the polymerization of compounds of the type:

• - 2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-carbamoyl-PROXYL, 2,2-dimethyl-4,5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-hydroxylimine-PROXYL, 3-aminomethyl-PROXYL, 3-methoxy-PROXYL, 3-t-butyl-PROXYL, 3,4-di-t-butyl-PROXYL
• - 2,2,6,6-tetramethyl-1-piperidinyloxy pyrrolidinyloxyl (TEMPO), 4-benzoyloxy-TEMPO, 4-methoxy-TEMPO, 4-chloro-TEMPO, 4-hydroxy-TEMPO, 4-oxo-TEMPO, 4 -Amino-TEMPO, 2,2,6,6, -Tetraethyl-1-piperidinyloxyl, 2,2,6-trimethyl-6-ethyl-1-piperidinyloxyl
• - N-tert-butyl-1-phenyl-2-methyl propyl nitroxide
• - N-tert-Butyl-1- (2-naphthyl) -2-methyl propyl nitroxide
• - N-tert-Butyl-1-diethylphosphono-2,2-dimethyl propyl nitroxide
• - N-tert-butyl-1-dibenzylphosphono-2,2-dimethyl propyl nitroxide
• - N- (1-phenyl-2-methyl propyl) -1-diethylphosphono-1-methyl ethyl nitroxide
• - Di-t-butyl nitroxide
• - Diphenyl nitroxide
• - t-Butyi-t-amyl nitroxide

A number of other polymerization methods, according to which the PSAs in an alternative way can be produced by walking, can be selected from the prior art:
US 4,581,429 A discloses a controlled radical polymerization process which uses as initiator a compound of the formula R'R "NOY, in which Y is a free radical species which can polymerize unsaturated monomers. However, the reactions generally have low conversions. The polymerization of Acrylates which only run in very low yields and molar masses WO 98/13392 A1 describes open-chain alkoxyamine compounds which have a symmetrical substitution pattern. EP 735 052 A1 discloses a process for producing thermoplastic elastomers with narrow molar mass distributions. WO 96/24620 A1 describes a polymerization process in which very special radical compounds such as. B. phosphorus-containing nitroxides based on imidazolidine can be used. WO 98/44008 A1 discloses special nitroxyls based on morpholines, piperazinones and piperazine dions. DE 199 49 352 A1 describes heterocyclic alkoxyamines as regulators in controlled radical polymerizations. Corresponding further developments of the alkoxyamines and the corresponding free nitroxides improve the efficiency for the production of polyacrylates (Hawker, contribution to the General Meeting of the American Chemical Society, spring 1997; Husemann, contribution to the IUPAC World-Polymer Meeting 1998, Gold Coast).

Atom Transfer Radical Polymerization (ATRP) can advantageously be used as a further controlled polymerization method for the synthesis of the polyacrylate PSAs, preferably monofunctional or difunctional secondary or tertiary halides as initiators and for the abstraction of the (r) halide (s) Cu, Ni, , Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au complexes ( EP 0 824 111 A1 ; EP 826 698 A1 ; EP 824 110 A1 ; EP 841 346 A1 ; EP 850 957 A1 ) are used. The different possibilities of the ATRP are also in the scriptures US 5,945,491 A . US 5,854,364 A and US 5,789,487 A described.

Orientation coating process, equipment of the carrier material with the electrically conductive PSA

For the production of oriented The above-described polymers are preferred for PSAs coated as hot melt systems (i.e. from the melt). For the manufacturing process it may therefore be necessary to remove the solvent from the PSA to remove. Here you can in principle all methods known to the person skilled in the art can be used. A very preferred method is the concentration over a Single or twin screw extruders. The twin screw extruder can same or opposite operate. The solvent or water is preferred over distilled several vacuum stages. In addition, depending on the distillation temperature of the solvent against heated. The residual solvent content are preferably <1 %, more preferably <0.5 % and very preferably <0.2 %. The hot melt is processed from the melt.

The orientation within the PSA will during of the coating produced by the coating process. For coating As a hot melt and thus also for orientation, different coating processes can be used be used. In one embodiment, the electrically conductive PSAs are applied over a Roll coating process coated and orientation by stretching generated. Different roll coating processes are in the “Handbook of Pressure Sensitive Adhesive Technology "by Donatas Satas (van Nostrand, New York 1989). In another version, the orientation by coating over a melting nozzle reached. Here you can choose between the contact and the contactless procedure be distinguished. The orientation of the electrically conductive PSA can be done here by the nozzle design inside the coating nozzle generated or in turn by a stretching process after the nozzle exit. The orientation is freely adjustable. The stretch ratio can e.g. by the width of the nozzle gap to be controlled. Stretching always occurs when the layer thickness of the PSA film on the substrate to be coated is less than the width of the nozzle gap.

In another preferred method orientation is achieved through the extrusion coating. The extrusion coating is preferably carried out with an extrusion die. The extrusion dies used can advantageously come from one of the three following categories: T-nozzle, fish-tail nozzle and bracket nozzle. The individual types differ in the shape of their flow channel. By the shape of the extrusion die can also have an orientation within the hot melt pressure sensitive adhesive be generated. Furthermore, here - in analogy to the melting nozzle coating - also an orientation after the nozzle exit can be achieved by stretching the PSA film.

To produce oriented (meth) acrylate PSAs, it is particularly preferred to coat an ironing nozzle on a carrier, in such a way that a polymer layer is formed on the carrier by a relative movement from nozzle to carrier. The time between the coating and the crosslinking is advantageously short. In a preferred procedure, crosslinking takes place after less than 60 minutes, in a more preferred procedure after less than 3 minutes, in one extremely preferred In-line procedure after less than 5 seconds.

The one with an electrically conductive PSA equipped support material it can be a single or double-sided tape.

In a very preferred embodiment Transfer tapes made. Suitable carrier materials are e.g. all siliconized or fluorinated films with a release effect. BOPP, MOPP, PET, Called PVC, PUR, PE, PE / EVA, EPDM, PP and PE. Furthermore, for transfer tapes also release papers (glassine papers, kraft papers, polyolefinic coated papers).

For the case that the backing material remains in the PSA (e.g. in the form of a carrier film) preferably a carrier material used, which also has a high electrical conductivity has. For can this case e.g. Metal or metallized foils or metal-doped foils be used.

Particularly preferred foils are without this enumeration right to completeness has, made of aluminum, copper, stainless steel, or metal alloys. In Another design uses a polymeric carrier material, e.g. PE. PP, Polyimide, PET, PVC, PUR or nylon selected and with a metal layer provided on one or two sides. As metals e.g. Aluminum, Chrome, nickel, copper, nickel alloys, copper alloys, silver, Use gold or mixtures of these. In a preferred one These metals are made using the sputtering technique on the technique Films applied with very thin layers.

Furthermore, metallized fabrics can also be used as carrier materials. Examples of this are, for example, in US 5,939,190 called.

The best orientation effects are achieved by placing them on a cold surface. Therefore, that should support material through a roller during the coating directly cooled become. The cooling the roller can pass through a liquid film / contact film from the outside or from the inside or through a cooling Gas. The cooling Gas can also be used to control the amount emerging from the coating nozzle Cool the PSA. In a preferred procedure, the roller is coated with a contact medium wetted, which is then between the roller and the carrier material located. Preferred embodiments for the Implementation of such a technique is described below.

For this method can use both a melt die and an extrusion die become. In a very preferred way, the roller at room temperature, in an extremely preferred Procedure cooled to temperatures below 10 ° C. The roller should also rotate.

In another way This manufacturing process also turns the roller into a network of the oriented ones PSA used.

For UV crosslinking, short-wave is used ultraviolet radiation in a wavelength range from 200 to 400 nm, depending on the UV photoinitiator used, irradiated, in particular using high pressure or medium pressure mercury lamps with a power of 80 to 240 W / cm. The radiation intensity is the respective quantum yield of the UV photoinitiator, the one to be set Degree of networking and the degree adapted to the orientation.

It is also possible to use the electrically conductive and to crosslink oriented PSAs with electron beams. Typical radiation devices that can be used are Linear cathode systems, scanner systems or segment cathode systems, if it is an electron beam accelerator. A detailed one Description of the state of the art and the main process parameters can be found at Skelhorne, Electron Beam Processing, in Chemistry and Technology of UV and EB formulation for Coatings, Inks and Paints, Vol. 1, 1991, SITA, London. The typical acceleration voltages are in the range between 50 kV and 500 kV, preferably 80 kV and 300 kV. The spreading cans used range from 5 to 150 kGy, especially between 20 and 100 kGy.

You can also use both networking methods be applied or other procedures involving high energy radiation enable.

In another preferred manufacturing process become the electrically conductive and oriented PSAs on one with a contact medium provided roller coated. The contact medium can in turn the PSA can be cooled very quickly. Will be beneficial then later on the carrier material concealed.

Can also be used as a contact medium a material can also be used which is capable of making contact to produce between the PSA and the roller surface, in particular a material covering the cavities between carrier material and roller surface (for example unevenness in the roller surface, bubbles). to Implementation of this technique is a rotating chill roll with a contact medium coated. In a preferred procedure, the contact medium is a liquid selected such as. Water.

For water as the contact medium, for example, alkyl alcohols such as ethanol, propanol, butanol, hexanol are suitable as additives, without wishing to restrict the choice of alcohols by these examples. Long-chain alcohols, polyglycols, ketones, amines, carboxylates, sulfonates and the like are also very advantageous. Many of these compounds lower or increase surface tension the conductivity.

A lowering of the surface tension can also by adding small amounts of nonionic and / or anionic and / or cationic surfactants to the contact medium can be achieved. In the simplest case, this can be done commercially dish soap or soap solutions use, preferably in a concentration of a few g / l in water as a contact medium. Special surfactants, which are particularly suitable can also be used at low concentrations. For that be for example sulfonium surfactants (e.g. β-di (hydroxyalkyl) sulfonium salt), furthermore, for example, ethoxylated nonylphenylsulfonic acid ammonium salts or block copolymers, especially diblocks. Here in particular referred to the state of the art under "surfactants" in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2000 Electronic Release, Wiley-VCH, Weinheim 2000.

They can be used as contact media aforementioned liquids even without the addition of water individually or in combination can be used together. To improve the properties of the contact medium (e.g. to increase shear resistance, decrease the transfer of surfactants or the like on the liner surface and thus improved cleaning options of the final product) the contact medium and / or the additives used advantageous salts, gels and the like viscosity-increasing Additives are added. Furthermore, the roller can be macroscopic smooth or have a slightly textured surface. It has proven, if it has a surface structure, especially roughening the surface. The wetting through the This can improve the contact medium.

The coating process runs particularly well from when the roller can be tempered, preferably in one area from –30 C to 200 ° C, very particularly preferably from 5 ° C. up to 25 ° C.

The contact medium is preferred be applied to the roller. A second roller, which takes up the contact medium for the continuous wetting of the coating roller be used. But it is also possible that it is applied without contact, for example by spraying.

For the variant of the manufacturing process by the roller simultaneously for use e.g. is used with electron beams usually a grounded metal roller that holds the electrons and the resulting X-rays absorbed used.

To prevent corrosion is the roller usually covered with a protective layer. This is preferably selected so that she is well wetted by the contact medium. Generally the surface is conductive. It can also be cheaper be them with one or more layers of insulating or to coat semiconducting material.

For the case of a liquid as a contact medium, you can proceed in an excellent manner if a second roller, advantageously with a wettable or absorbent surface a bath with the contact medium is running, is wetted or soaked with the contact medium and by touching the roller applies or spreads a film of this contact medium.

In a preferred way the pressure sensitive adhesive is directly on the one provided with the contact medium Roll coated and cross-linked. Again, the described ones can be used for this Methods and systems used for UV crosslinking and ES crosslinking become. After networking, the electrically conductive and Transfer oriented PSA onto a carrier material. It can the carrier materials already cited be used.

The degree of orientation within the electrically conductive PSAs depend on the coating process. The Orientation can e.g. through the nozzle and coating temperature as well controlled by the molecular weight of the polymer.

The degree of orientation is through the nozzle gap width freely adjustable. The thicker the PSA film, the out the coating nozzle forced out becomes the stronger can apply the adhesive to a thinner PSA film on the backing material be stretched. This stretching process can be set in addition to the freely adjustable die width also due to the web speed of the decreasing carrier material can be freely set.

Measuring the orientation of the Adhesive can continue with a polarimeter, with infrared dichroism or with X-ray scattering respectively. It is known that the Orientation in acrylic PSAs in the uncrosslinked state in many cases only remains for a few days. The system relaxes in the Rest or storage time and loses its preferred direction. By Crosslinking after coating can have this effect significantly reinforced become. The relaxation of the oriented polymer chains converges towards zero, and the oriented PSAs can be used without Loss of their preferred direction over a very large period be stored.

In a preferred method the measure of Orientation by measuring the shrinkback in the free film (see Test B) determined.

In addition to the described methods, the orientation can also be generated after the coating. A stretchable carrier material is then preferably used here, in which case the PSA is also stretched when expanded. In this case, conventional solutions or water can also be used Use layered PSAs. In a preferred procedure, this stretched PSA is in turn crosslinked with actinic radiation.

use

The invention further relates to the use of the electrically conductive and oriented PSAs for gluing components in the electrical and electronics industry. In a preferred embodiment the inventive PSAs are used as transfer tapes. In this case, the gluing of electrically conductive substances the release paper removed. In parallel, very narrow interconnects glued, the direction of gluing is chosen such that the inventive electrically conductive PSA a resilience towards Next has parallel conductor track. In this way, short circuits can be avoided because the PSA is electrical compared to conventional conductive PSAs do not flow out in this direction.

Another advantage is electrical conductive sticky die-cuts which are particularly easy to produce and also during the bond are very dimensionally stable and therefore very effective are suitable for bonding very small electrical parts. On Another advantage of the electrically conductive and oriented PSAs lies in the reversibility. The inventive PSAs can be oriented stretch in the oriented direction, which in turn leads to a decrease of tack and tack. About this Way can be glued with the inventive pressure sensitive adhesive electrically conductive Separate substances again.

In another embodiment the inventive PSA has anisotropic electrically conductive properties. The orientation of the polymer chains makes the electrically conductive filling materials pulled apart in a preferred direction and lose contact to each other. Through this process the electrical conductivity reduced in the direction of orientation so that the PSAs and thus the corresponding PSA tapes are also anisotropic electrical conductivities exhibit.

The invention is without restriction explained to the general public through examples and experiments.

The samples were examined following test methods applied:

Gel Permeation Chromatography GPC (Test A)

The average molecular weight M _W and the polydispersity PD were determined by gel permeation chromatography. THF with 0.1% by volume of trifluoroacetic acid was used as the eluent. The measurement was carried out at 25 ° C. PSS-SDV, 5 μ, 10 ³ Å, ID 8.0 mm × 50 mm was used as the guard column. The columns PSS-SDV, 5 μ, 10 ³ and 10 ⁵ and 10 ⁶ , each with an ID of 8.0 mm × 300 mm, were used for the separation. The sample concentration was 4 g / l, the flow rate 1.0 ml per minute. It was measured against PMMA standards.

Measurement of the shrinkback (Test B)

Strips of at least 30 mm wide and 20 cm long were cut parallel to the coating direction of the hot melt. For bulk applications at 100 g / m ² , 4 strips were laminated one above the other, at 50 g / m ² 8 strips were laminated one above the other in order to obtain comparable layer thicknesses. The body obtained in this way was then cut to a width of exactly 20 mm and pasted with paper strips at the respective ends at a distance of 15 cm. The test specimen prepared in this way was then suspended vertically at RT and the change in length was followed over time until no further shrinkage of the sample could be determined. The initial length reduced by the final value was then given as a shrinkback in percent based on the initial length.

For the measurement of orientation after a long time was coated and oriented PSAs over a longer period of time as a cloth sample stored and then analyzed.

Contact resistance measurement (Test C)

The electrical conductivity is measured via the electrical contact resistance using the 4-wire method. For the investigation, measurements were made against aluminum and against copper. A 50 μm thick PSA film was bonded to a solid copper plate. The plates were made before the Mes solution built up with sandpaper and cleaned with ethanol. A copper foil was glued as a foil. The measuring area was 2.54 × 2.54 cm.

180 ° adhesive strength test (test D)

A 20 mm wide strip of one on a polyester or siliconized release paper coated acrylic PSA was applied to steel plates. It was - depending on the direction and stretching - longitudinal or Cross pattern glued to the steel plate. The pressure sensitive tape was pressed twice onto the substrate with a 2 kg weight. The Masking tape was then used immediately at 30 mm / min and at a 180 ° angle subtracted from the substrate. The steel plates were washed twice with acetone and washed once with isopropanol. The measurement results are in N / cm and are averaged from three measurements. All measurements were carried out at room temperature under air-conditioned conditions.

Electrically conductive materials used:
Silver-coated nickel particles:
20-40 μm diameter available from Potter Industries.
Nickel particles:
Diameters greater than 10 μm available from Novamet, Inc.

manufacturing of the samples

Polymer 1

A conventional 200 L reactor for radical polymerizations was charged with 2400 g of acrylamide, 64 kg of 2-ethylhexyl acrylate, 6.4 kg of N-isopropylacrylamide and 53.3 kg of acetone / isopropanol (95: 5). After passing through with nitrogen gas for 45 minutes while stirring, the reactor was heated to 58 ° C. and 40 g of 2,2'-azoisobutyronitrile (AIBN) were added. The outer heating bath was then heated to 75 ° C. and the reaction was carried out constantly at this outside temperature. After a reaction time of 1 h, 40 g of AIBN were again added. After 5 h and 10 h, each was diluted with 15 kg of acetone / isopropanol (95: 5). After 6 and 8 h 100 g of dicyclohexyl peroxydicarbonate (Perkadox ^® 16, Fa. Akzo Nobel) were each dissolved in 800 g of acetone was added respectively. The reaction was stopped after a reaction time of 24 h and cooled to room temperature. The determination of the molecular weight according to Test A gave an M _W = 754,000 g / mol with a polydispersity M _W / M _n = 5.3.

Polymer 2

A 200 L reactor conventional for radical polymerizations was charged with 1200 g of acrylamide, 74 kg of 2-ethylhexyl acrylate, 4.8 kg of N-isopropylacrylamide and 53.3 kg of acetone / isopropanol (95: 5). After passing through with nitrogen gas for 45 minutes while stirring, the reactor was heated to 58 ° C. and 40 g of 2,2'-azoisobutyronitrile (AIBN) were added. The outer heating bath was then heated to 75 ° C. and the reaction was carried out constantly at this outside temperature. After a reaction time of 1 h, 40 g of AIBN were again added. After 5 h and 10 h, each was diluted with 15 kg of acetone / isopropanol (95: 5). After 6 and 8 h 100 g of dicyclohexyl peroxydicarbonate (Perkadox ^® 16, Fa. Akzo Nobel) were each dissolved in 800 g of acetone was added respectively. The reaction was stopped after a reaction time of 24 h and cooled to room temperature.

The determination of the molecular weight according to Test A gave an M _W = 812,000 g / mol with a polydispersity M _W / M _n = 5.8.

Example 1:

Polymer 1 was silver coated with 20% by weight Nickel particles mixed based on the polymer content.

Example 2:

Polymer 1 was silver coated with 30% by weight Nickel particles mixed based on the polymer content.

Example 3:

Polymer 2 was with 20 wt .-% nickel particles blended based on the polymer content.

Example 4:

Polymer 2 was with 30 wt .-% nickel particles blended based on the polymer content.

i) Pattern production for Determination of the shrinkback

The PSAs in solution were concentrated on a Bersdorff concentration extruder with a throughput of approx. 40 kg / h at a temperature of approx. 115 ° C. The residual solvent content after the concentration was less than 0.5% by weight. Then, through a bracket extrusion die with a die gap of 300 μm and a coating width of 33 cm at a specific coating temperature (melt temperature) at a web speed of 10 m / min, onto a 12 μm layer coated with 1.5 g / m ² silicone (polydimethylsiloxane) PET film coated. With a mass application of 100 g / m ² (approx. 100 μm thick PSA layer), a stretching ratio of 3: 1 was set, with a mass application of 50 g / m ² (approx. 50 μm thick PSA layer) a stretching ratio of 6: 1 was set ,

The siliconized PET film is passed over a co-rotating steel roller cooled to 5 ° C. At the point of contact of the PSA film on the PET film, the PSA film is thus cooled down immediately. The mass application was 50 or 100 g / m ² . In the in-line process, the pressure-sensitive adhesive tape is then crosslinked with electron beams after a path of approximately 5 m.

For the electron radiation was crosslinked with a device from Electron Crosslinking AB, Halmstad, Sweden. The coated PSA tape was about a standard cooling roller passed under the accelerator's Lenard window. there was in the radiation zone of atmospheric oxygen by purging with displaced pure nitrogen. The web speed was 10 m / min in each case. It was with a Accelerating voltage of 200 kV shines through.

To determine the shrinkback Test B was carried out.

To determine the electrical conductivity Test C was carried out. The adhesive strength was determined according to test D.

results

In a first step, two polymers with an average molecular weight M _W of approximately 800,000 g / mol were produced. Examples 1-4 according to the invention were produced with these PSAs. Nickel particles and silver-coated nickel particles were selected as the electrically conductive materials.

In a first investigation the degree of orientation of the individual PSAs was determined. Therefore, the shrinkback was in the following according to test method B. determined in free film. The measured values are in Table 1 summarized.

Table 1. Overview of shrinkback values determined in the free film (test B).

All examples in Table 1 point a pronounced one Resilience. Another requirement for the inventive pressure sensitive adhesive is electrical conductivity. Therefore, the electrical conductivity was determined according to test method C. of the individual examples. The determined values are in Table 2 summarized.

Table 2: Overview of the electrical resistance determined according to test C.

All electrical resistances were with a layer thickness of 50 μm determined. The materials had all low electrical resistances and thus a high electrical conductivity. By increasing the electrically conductive additions to 30 w%, the electrical resistance was again significantly reduced to <0.5 Ω.

To check the technical adhesive properties, the adhesive strength on steel was also determined. For these measurements too, the layer thickness of the PSA was 50 μm. The measured values are listed in Table 3: Table 3: Overview of the bond strengths determined according to Test D

The values shown in Table 3 make it clear that Examples 1-4 have pressure-sensitive properties. By the amounts of the additive leaves also control the adhesive force. Through high proportions of the filling material the adhesive strength drops.

Claims (16)

A method for producing a pressure-sensitive adhesive article which has at least one layer of an electrically conductive pressure-sensitive adhesive, characterized in that in a coating process by stretching, stretching or compressing an at least one property anisotropic with respect to one property is produced from the electrically conductive pressure-sensitive adhesive, which is in at least one direction has a shrinkback of at least 3% along the layer plane with respect to the longitudinal expansion of the layer, measured on the free PSA film. A method according to claim 1, characterized in that the coating process is a hot melt roll coating process, a melt nozzle coating process or is an extrusion coating process. A method according to claim 1, characterized in that the coating process is a conventional coating process with subsequent Stretching or stretching on a stretchable support. Method according to one of claims 1 to 3, characterized in that that the electrically conductive PSA coated on one or both sides on a sheet or ribbon-shaped support becomes. A method according to claim 4, characterized in that the carrier a transfer ribbon, a release liner or an electrically conductive carrier material is. Method according to one of claims 1 to 5, characterized in that that as a pressure-sensitive adhesive one based on polyacrylate and / or polymethacrylate is used. A method according to claim 6, characterized in that the PSA at least 50 wt .-% on at least one acrylic monomer from the group of compounds of the following general based formula:

where R ₁ = H or CH ₃ and the radical R ₂ = H or CH ₃ or is selected from the group of branched or unbranched, saturated alkyl groups having 2 to 30 carbon atoms and the average molecular weight M _{W of} the PSA at least 200,000 g / mol is. Method according to one of claims 1 to 6, characterized in that that crosslinking agents have been added to the PSA, especially bi- or multifunctional acrylates and / or methacrylates, bi- or multifunctional isocyanates or bi- or multifunctional epoxies. A method according to claim 8, characterized in that the PSA immediately after or during the hot melt coating is crosslinked, preferably photochemically. Method according to one of claims 1 to 9, characterized in that that the pressure sensitive adhesive is mixed with electrically conductive materials are, in particular metal particles, metal powder, metal balls, metal fibers, where as metals in particular nickel, gold, silver and copper or the following nickel-coated particles, namely copper particles, nickel particles, Polymer balls, polymer particles or glass microspheres or glass microspheres. A method according to claim 10, characterized in that the electrically conductive Materials in a proportion up to 200 wt .-%, preferably between 5 and 50% by weight, more preferably between 10 and 40% by weight, based on the weight of the PSA. Method according to one of claims 1 to 11, characterized in that that electrical conductivity the PSA is between 1 and 500 S / cm. Method according to one of claims 1 to 12, characterized in that that electrical conductivity is anisotropic and longitudinal a level lying in the pressure-sensitive adhesive layer is less than transverse to the layer level, at least in the direction transverse to the layer level Is 2 S / cm. Method according to one of claims 1 to 13, characterized in that that the PSA has other substances or additives, such as anti-aging agents, Light stabilizers, antiozonants, fatty acids, plasticizers, nucleating agents, blowing agents, Accelerators and / or fillers contains. Pressure sensitive adhesive articles, in particular for bonding two electrical ones Parts, available with a method according to one of claims 1 to 14. Pressure sensitive adhesive article according to claim 15 in the form of a Stamped product.