KR20050084414A - Self-adhesive article with at least one layer of a thermally-conducting adhesive mass and method for production thereof - Google Patents

Abstract

In a method for production of a self-adhesive article a thermally- conducting adhesive mass containing acrylate is coated on a support in a hot-melt coating method with stretching or orientation such that an anisotropic thermally-conducting layer with a back-shrinkage of at least 3 % measured on the free adhesive mass film is generated. Stampings for use in the electrical and electronic industries can be produced from said material.

Description

Self-adhesive products having at least one layer of thermally conductive adhesive mass and methods for making the same. {SELF-ADHESIVE ARTICLE WITH AT LEAST ONE LAYER OF A THERMALLY-CONDUCTING ADHESIVE MASS AND METHOD FOR PRODUCTION THEREOF}

The present invention is not limited to the general characteristics but is described below through examples and experiments.

The following test methods are used to examine the samples:

Gel Permeation Chromatography GPC (Test A)

Average molecular weight M _W and polydispersity PD are determined by gel permeation chromatography. The eluent used is THF containing 0.1 vol% trifluoroacetic acid. Measure at 25 ° C. The preliminary column used is PSS-SDV 5μ, 10 ³ mm ³ , ID 8.0mm x 50mm. Columns PSS-SDV, 5μ, 10 ³ and also 10 ⁵ and 10 ⁶ with IDs of 8.0 mm × 300 mm respectively. Sample concentration is 4 g / l and flow rate is 1.0 ml per minute. Measure against PMMA standard.

Shrinkage Restoration Measurement (Test B)

Strips of at least 30 mm in width and 20 cm in length are cut parallel to the coating of the hot melt. Laminating together the four strips to the respective application rate of 100g / m ² and to obtain a layer thickness comparable to each other, laminating the eight strips from 50g / m ^2. The specimens obtained in this way are then cut to exactly 20 mm in width and over-adhered with a space of 15 cm at each end with a paper strip. The prepared test specimens are therefore suspended vertically at RT and the change in length is monitored over time until no further shrinkage of the sample can be observed. Report the initial length reduced by the final value as% contractile recovery relative to the initial length.

To measure orientation after a long time, the coated and oriented PSAs are stored in swatch form for a long time and then analyzed.

Measurement of contact resistance (test C)

Electrical conductivity is measured by the 4-wire method through electrical contact resistance. For investigation, measurements are made on aluminum and copper. In each case, a 50 μm thick PSA film is bonded to the solid copper plate. Prior to measurement, the plate is roughened with sandpaper and washed with ethanol. The bonded foil is a copper foil. The measurement area is 2.54 x 2.54 cm.

180 ° bond strength test (test D)

A 20 mm wide strip of acrylate PSA coated with polyester or siliconized release paper is applied to the steel plate. Depending on the direction and withdrawal, specimens of longitudinal or transverse axes are bonded to the steel plate. The PSA strip is pressed twice on the substrate using a weight of 2 kg. Immediately afterwards, the adhesive tape is peeled off at 30 mm / min and 180 ° angles. The steel plate is washed twice with acetone and once with isopropanol. The measurement results are reported in N / cm and are the average of three measurements. All measurements are performed at room temperature under controlled climatic conditions.

Electrically Conductive Material Used:

Silver coated nickel particles:

Diameter from 20 to 40 μm, commercially available from Potter Industries

Nickel particles:

Diameters greater than 10 μm, commercially available from Novamet, Inc.

Sample manufacturing

Polymer 1

A 200 L reactor for free radical polymerization is 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 nitrogen gas was passed through the reactor for 45 minutes with stirring, the reactor was heated to 58 ° C. and 40 g of 2,2′-azoisobutyronitrile (AIBN) was added. The external heat bath is then heated to 75 ° C. and the reaction is carried out constantly at this external temperature. After 1 hour of reaction time, 40 g of AIBN is further added. After 5 and 10 hours, dilute 15 kg of acetone / isopropanol (95: 5) 15 kg at each time point. After 6 and 8 hours, 100 g of each dicyclohexyl peroxydicarbonate (Perkadox 16 ^R , Akzo Nobel) in a solution of 800 g of acetone is added. After 24 hours the reaction is terminated and the batch is cooled to room temperature. As a result of measuring the molecular weight by Test A, M _W is 754,000 g / mol and polydispersity M _W / M _n is 5.3.

Polymer 2

A conventional 200 L reactor is 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) for free radical polymerization. After nitrogen gas was passed through the reactor for 45 minutes with stirring, the reactor was heated to 58 ° C. and 40 g of 2,2′-azoisobutyronitrile (AIBN) was added. The external heat bath is then heated to 75 ° C. and the reaction is carried out constantly at this external temperature. After 1 hour of reaction time, 40 g of AIBN is further added. After 5 and 10 hours, dilute 15 kg of acetone / isopropanol (95: 5) 15 kg at each time point. After 6 and 8 hours, 100 g of each dicyclohexyl peroxydicarbonate (Perkadox 16 ^R , Akzo Nobel) in a solution of 800 g of acetone is added. After 24 hours the reaction is terminated and the batch is cooled to room temperature. As a result of measuring the molecular weight by Test A, M _W is 812,000 g / mol and polydispersity M _W / M _n is 5.8.

Example 1:

Polymer 1 is mixed with 20% by weight silver coated nickel particles based on the polymer fraction.

Example 2:

Polymer 1 is mixed with 30% by weight silver coated nickel particles based on the polymer fraction.

Example 3:

Polymer 2 is mixed with 20 weight percent nickel particles based on the polymer fraction.

Example 4:

Polymer 2 is mixed with 30 weight percent nickel particles based on the polymer fraction.

i) preparation of specimens for measuring shrinkage resilience;

PSA in solution is concentrated on a Bersdorff concentrated extruder at an output of about 40 kg / h at a temperature of about 115 ° C. After concentration, the remaining solvent fraction is less than 0.5% by weight. The composition is then coated onto a 12 μm PET film previously coated with 1.5 g / m ² of silicone (polydimethylsiloxane) at a defined coating temperature (composition temperature) and web speed of 10 m / min, with a die gap of 300 μm. The composition is applied through a hanger extrusion die and the width of the coating is 33 cm. For a coating rate of 100 g / m ² (approximately 100 μm thick), the draw ratio is set to 3: 1 and for a coating rate of 50 g / m ² (approximately 50 μm thick), the withdrawal ratio is 6: Set to 1.

The siliconized PET film is passed over a co-rotating steel roller cooled to 5 ° C. Thus, at the point of contact between the PSA film and the PET film, the PSA film is immediately cooled. The application rate is 50 or 100 g / m ² . In the inline process, after about 5 m of web section, the PSA tape is then crosslinked with an electron beam.

For electron beam irradiation, crosslinking is performed using a device from Electron Crosslinking AB, Halmstad, Sweden. The coated PSA tape is guided through the accelerator window of the accelerator onto a cooling roll which is present as a standard form. Within their irradiation zone, atmospheric oxygen is replaced with pure nitrogen. The web speed is in each case 10 m / min. Irradiate under an acceleration voltage of 200 kV.

To determine shrinkage resilience, test B is performed.

In order to measure the electrical conductivity, test C is performed. Bond strength is measured according to test D.

result

In a first step, two polymers are prepared having an average molecular weight M _W of about 800,000 g / mol. Examples 1 to 4 of the present invention were carried out using the PSA. As the electrically conductive material, nickel particles were selected on the one hand and silver coated nickel particles on the other.

In a first analysis, the degree of orientation of each PSA was measured. Therefore, the shrinkage recovery in the glass film in the following paragraph was measured according to test method B. The measured values are summarized in Table 1.

Consideration of Shrinkage Restoration Value Measured on Glass Films (Test B) Example Shrinkage Restoration in Glass Films (Test B) One 65% 2 70% 3 62% 4 69%

All examples in Table 1 show obvious elasticity. A further precondition for the PSA of the present invention is electrical conductivity. Thus, in the following, the electrical conductivity of each example was measured according to test method C. The measured values are summarized in Table 2.

Consideration of electrical resistance measured according to test C Example Ω electrical resistivity (test C) One <0.75 2 <0.5 3 <0.75 4 <0.5

All electrical resistivity was measured for a layer thickness of 50 μm. All materials had lower electrical resistance and thus higher electrical conductivity. By increasing the electrical conductivity addition to 30% by weight, the electrical resistance was further lowered further to less than 0.5 kPa.

In order to confirm the adhesive properties, the bond strength to the steel was further measured. The layer thickness of PSA for these measurements is 50 μm. The measured values are shown in Table 3.

Consideration of bonding strength measured according to test D Example Bond strength for steel of [N / cm] (test D) One 2.9 2 2.5 3 3.2 4 2.7

The values shown in Table 3 make it clear that Examples 1 to 4 have pressure sensitive adhesive properties. The amount of addition can also control the bond strength. High fractions of filler material lower the bond strength.

The present invention relates to a process for producing a pressure sensitive adhesive article having at least one layer of a heat conducting pressure sensitive adhesive (PSA) mass and in particular to pressure sensitive adhesives obtainable in this way for adhesive bonding in particular in the field of electrical and electronic components. It is about a product.

In the computerized era, electrically conductive PSAs are being used more and more to couple electrodes or electromagnetic components. The purpose is to maintain electrical conductivity and avoid the onset of electrical discharge.

Generally, for these applications, electrically conductive acrylate PSA tapes are used. Electrical conductivity can be achieved in two different ways. On the one hand the conductive film or fabric is used and on the other hand the PSA is deformed by the electrically conductive component so that it becomes electrically conductive itself.

Examples of electrically conductive media are described, for example, in US Pat. Nos. 5,939,190 and 6,235,385 and in the patent documents cited herein.

Electrically conductive acrylate PSAs have been known for a long time. Thus, US Pat. No. 4,113,981 describes how electrical conductivity can be achieved by adding metal powder or SiC powder. Depending on the degree of filling, the conductivity may vary. In addition, when the mass is included between two electrodes, only the electrical conductivity in the z direction is obtained by limiting to 30%.

In US Pat. No. 5,300,340, silverized glass beads and metal beads are mixed with PSA. The diameter of these beads is at least exactly the same size as the layer thickness of the PSA. Electrical conductivity is thus induced by bringing the conductive beads into direct contact with the conductive material (eg, electrode) to be bonded.

US Pat. No. 5,620,795 and US Pat. No. 6,126,865 use polyacrylates of comonomer compositions defined as electrically conductive acrylate PSAs. The comonomer composition of polyacrylates is selected such that the highly nonpolar resin is compatible with the polyacrylate, and thus can use an electrically conductive PSA to realize a high bond strength on the nonpolar surface.

However, as a result of miniaturization in the electronic / computer industry, the requirements placed on electrically conductive PSAs are becoming more stringent. The electrical components to be joined are more compact in size and in many cases only a diecut can still be used for the joining. In addition, the space of the circuit is continually decreasing and therefore the electrically conductive PSA needs to possess very low flow action in the specific direction (for the next electrically conductive component).

It is an object of the present invention, in particular, to provide electrically conductive pressure sensitive adhesives for the electrical and electronic industries, in which the disadvantages in the prior art have been avoided, in particular the swelling or outflow of the pressure sensitive adhesive to the outside at the bonding edges. This was definitely avoided.

This object has been surprisingly achieved and in a manner unexpected to those skilled in the art, with carriers having at least 3% shrinkage recovery by means of means of anisotropy (including temporary carriers in which the pressure-sensitive adhesive can be removed again). An oriented pressure sensitive adhesive having a coating on the phase is obtained and an associated pressure sensitive adhesive product is obtained in this manner. New development steps of the invention are characterized in the dependent claims.

The achievement of the object of the present invention is to provide an electrical or electronic component having at least one layer of an electrically conductive pressure sensitive adhesive, ie a pressure sensitive adhesive based on polyacrylate and / or polymethacrylate in the absence or presence of additional comonomers. A method of making a pressure sensitive adhesive article for bonding, wherein a layer that is at least anisotropic in terms of one property is produced from the electrically conductive pressure sensitive adhesive in the coating process by stretching, drawing or pressing in the coating process and the layer The silver possesses at least 3% shrinkage resiliency, as measured by shrinkage resiliency measurements in accordance with Test B on a film liberated at the end of the layer in at least one direction along the plane of the layer.

Anisotropy means that one or more properties of the pressure-sensitive adhesive in one spatial direction in the PSA layer are different from the same properties in one or more other directions, in other words, the anisotropic property is directional and not uniform in the material.

The pressure sensitive adhesive preferably possesses a known orientation, such as a deflecting direction, in the polymer structure.

The coating process can be, for example, a hot melt roll coating process, a melt die coating process or an extrusion coating process.

In another aspect of the invention, the coating process is a conventional coating process from a solution and for example here the stretching is followed by stretching or withdrawing onto a carrier layer which is preferably stretchable.

The electrically conductive pressure sensitive adhesive may be coated by a coating process on one or both sides of a sheet or tape carrier, which may be a transfer tape or release liner.

Pressure sensitive adhesives that can be used according to the invention

According to the present invention, elastic pressure sensitive adhesives or else anisotropically oriented or simply "oriented" pressure sensitive adhesives are used. Anisotropically oriented PSAs possess a tendency to revert to their initial state as a result of their 'entropy-elastic' action after stretching in a given direction. As the electrically conductive PSA having elasticity, it is preferable to use (meth) acrylate PSA.

Preferred in the present invention are pressure-sensitive adhesives obtainable by free radical addition polymerization, wherein

Pressure-sensitive adhesives based on at least 50% by weight of at least one acrylic monomer from the compound group of formula:

Wherein R ₁ is H or CH ₃ and the radical R ₂ is H or CH ₃ or is selected from the group consisting of branched or unbranched saturated alkyl groups of 2 to 30 carbon atoms.

The average molecular weight M _W of a pressure-sensitive adhesive is 200,000 g / mol or more.

The pressure sensitive adhesive applied to the carrier has a biased orientation, which can be measured by test B via shrinkage resilience in the glass film, which is at least 3%.

Contains an effective fraction of one or more electrically conductive components.

The monomer is preferably selected so that the obtained polymer can be used as PSA at room temperature or elevated temperature, and in particular, the obtained polymer is described in "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989). Selected to possess pressure sensitive adhesive properties.

In a further aspect of the invention, the comonomer composition is selected such that the PSA can be used as a thermally activatable PSA.

Polymers which are preferably used as elastically electrically conductive PSAs are preferably of the formula CH ₂ = CH (R ₁ ) (COOR ₂ ) where R ₁ is H or CH ₃ and R ₂ is alkyl having 1 to 20 carbon atoms Chain or H), by polymerization of a monomer mixture consisting of acrylic esters and / or methacrylic esters and / or free acids.

The polyacrylate molar mass M _W is preferably used in an amount of at least 200,000 g / mol.

In one highly preferred method, acrylic or methacrylic monomers are used and consist of acrylic and methacrylic esters having alkyl groups of 4 to 14 carbon atoms, preferably 4 to 9 carbon atoms. Without being limited to a specific enumeration, certain examples are methyl acrylate, 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 branched isomers such as iso Butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate and isooctyl methacrylate. A further class of compounds that can be used are monofunctional acrylates and / or methacrylates of bridged cycloalkyl alcohols consisting of at least 6 carbon atoms. Cycloalkyl alcohols may also be substituted, for example, by C 1-6 alkyl groups, halogen atoms or cyano groups. Specific examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyladamantyl acrylate.

In one process, such as carboxyl radicals, sulfonic and phosphonic acids, hydroxyl radicals, lactams and lactones, N-substituted amides, N-substituted amines, carbamates, epoxies, thiols, alkoxy or cyano radicals, ethers and the like Monomers having polar groups are used.

Suitable basic monomers are, for example, N, N-dialkyl-substituted amides such as N, N-dimethylacrylamide, N, N-dimethylmethylmethacrylamide, N-tert-butylacrylamide , N-vinylpyrrolidine, N-vinyllactam, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, N-methylol methacrylate, N -(Butoxymethyl) methacrylamide, N-methylolacrylamide, N- (ethoxymethyl) acrylamide, N-isopropylacrylamide and this enumeration is not limiting.

Further 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, vinylacetic acid, tetrahydrofurfuryl acrylate, β-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconic acid and dimethylacrylic acid, the enumeration of which is not limiting. .

In one further very preferred procedure, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides and vinyl compounds having aromatic rings and heterocycles in the α-position are used as monomers. Here, non-exclusively mention may be made, for example, of vinyl acetate, vinylformamide, vinylpyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride and acrylonitrile.

Moreover, in further procedures, photoinitiators having copolymerizable double bonds are used. Suitable photoinitiators include Norish I and II photoinitiators. For example, benzoin acrylate and acrylated benzophenone (manufactured by UCB (Ebecryl P 36 ^R )). In principle, it is possible to copolymerize any photoinitiator known to the person skilled in the art and capable of crosslinking the polymer by free radical mechanisms under UV irradiation. A review of possible photoinitiators that can be functional with double bonds is described in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentais and Applications", Hanser-Verlag, Munich 1995. For further supplementation see Carroy et al. in "Chemistry and Technology of UV and EB Formulations for Coatings, Inks and Paints", Oldring (ed.), 1994, SITA, London.

In another preferred procedure, the comonomers described are mixed with monomers having a high electrostatic glass transition temperature. Suitable components are styrenes which comprise aromatic vinyl compounds and for example the aromatic nucleus consists mainly of C ₄ to C ₁₈ units and may also 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-biphenylyl acrylate, 4-biphenylyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate and these monomers And mixtures thereof are not limiting.

In addition, the composition of the PSA of the present invention allows the PSA to have shrinkage restorability and the shrinkage restorability is measured by test B (measurement of shrinkage restorability in glass film) and is at least 3%. For preferred power generation, PSAs having a shrinkage recovery of at least 30% and very preferably at least 50% are used.

In addition, the configuration of the PSA of the present invention is the addition of an electrically conductive compound. Thus, in one preferred version, an electrically conductive filler material is used. Such materials include metal particles, metal powders, metal beads, metal fabrics without being limited by this enumeration, and the metals used are, for example, nickel, gold, silver, iron, lead, tin, zinc, stainless steel , Bronze and copper, or copper particles coated with nickel, nickel particles, polymer beads or particles, or glass microbeads. In addition, lead / tin alloys of different compositions are available, for example as supplied by Sherrit Gordon, Ltd.

In a further aspect of the invention, electrically conductive polymers such as polythiophene, substituted polythiophene, polyethylenedioxythiophene, polyaniline, substituted polyaniline, polyparaphenylene, substituted polyparaphenylene, polypyrrole , Substituted polypyrrole, polyacetylene, substituted polyacetylene, polyphenyl sulfide, substituted polyphenyl sulfide, polyfuran, substituted polyfuran, polyalkylfluorene, substituted polyalkylfluorene and mixtures of the aforementioned polymers Is added. To enhance the conductivity, what is called a dopant may be added. Here, various metal salts or Lewis acids or electrophiles can be used. Non-limiting examples are p-toluenesulfonic acid or camphorsulfonic acid. Additional electrically conductive polymers include polyvinylbenzyltrimethylammonium chloride and similar compounds, which are described in US Pat. No. 5,061,294.

In a further preferred embodiment of the invention, the diameter of the electrically conductive filler is lower than the layer thickness of the PSA. In one preferred embodiment, a dispersant from ORMECON is used. Depending on the dopant and chemical composition, the electrically conductive polymer added has a conductivity of 1 to 500 S / cm.

In further embodiments, the electrically conductive material used may be a carbon compound, such as, for example, C-60. It is also possible to improve electrical conductivity by targeted doping with these compounds. However, moreover, it is also possible to use the hygroscopic salts described in US Pat. No. 4,973,338 as the electrically conductive material.

The electrically conductive material is added up to 50% by weight based on poly (meth) acrylate. In a preferred embodiment, the fraction is 30% by weight based on poly (meth) acrylate. The fraction is chosen according to the desired electrical conductivity to be achieved. However, the fraction should not exceed the amount such that the PSA loses the pressure-sensitive adhesive properties.

The resin can be mixed with PSA for further development. As the adhesive resin to be added, any present adhesive resin and a resin described in the literature can be used without exception. Representatives that may be mentioned are pinene resins, indene resins and rosines, these disproportionated, hydrogenated, polymerized and esterified derivatives and salts, aliphatic and aromatic hydrocarbon resins, terpene resins and terpene-phenol resins and also C5, C9 and other hydrocarbon resins. Any desired combinations of these and additional resins can be used to adjust the properties of the adhesive obtained according to the requirements. Generally speaking, any resin that is compatible (soluble) with the unknown polyacrylate may be used, in particular all aliphatic, aromatic and alkylaromatic hydrocarbon resins, single monomeric basic hydrocarbon resins, hydrogenated hydrocarbon resins, functional hydrocarbons Resins and natural resins may be mentioned. In particular, mention may be made of those described in "Handbook of Pressurre Sensitive Adhesive Technology" by Donates Satas (Van Nostrand, 1989).

Additionally, optionally, plasticizers, additional fillers (e.g. fibers, carbon black, zinc oxide, chalk, solid or hollow glass beads, microbeads made of other materials, silica, silicates), nucleating agents, swelling agents, admixtures and And / or aging inhibitors may be added, for example, in the form of primary and secondary antioxidants or in the form of light stabilizers.

In addition, crosslinkers and crosslinking accelerators may be mixed. Examples of crosslinkers suitable for electron beam crosslinking and UV crosslinking include difunctional or polyfunctional acrylates, difunctional or polyfunctional isocyanates (including blocked forms) and difunctional or multifunctional epoxides.

For any crosslinking with UV light, a UV absorbing photoinitiator can be added to the PSA. Useful photoinitiators which are used very effectively are benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, substituted acetophenones such as 2,2-diethoxyacetophenone [Ciba Geigy ^R ) Marketed as Irgacure 651 ^R from], 2,2-dimethoxy-2-phenyl-1-phenylethanone, dimethoxyhydroxyacetophenone, substituted α-ketol, for example 2-methoxy-2- Hydroxypropiophenone, aromatic sulfonyl chlorides such as 2-naphthylsulfonyl chloride and photoactive oximes such as 1-phenyl-1,2-propanedione 2- (O-ethoxycarbonyl) oxime to be.

The photoinitiators described above and other photoinitiators that may be used and also other photoinitiators of Norrish I or Norish II type may contain the following radicals: benzophenone, acetophenone, benzyl, benzoin, hydroxyalkylphenone, phenyl cyclo Hexyl ketone, anthraquinone, trimethylbenzoylphosphine oxide, methylthiophenylmorpholine ketone, aminoketone, azobenzoin, thioxanthone, hexaarylbisimidazole, triazine or fluorenone, each of these radicals being one additional Substituted by one or more halogen atoms and / or one or more alkyloxy groups and / or one or more amino groups or hydroxy groups. Representative considerations are described in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. For further details see Carroy et al. in "Chemistry and Technology of UV and EB Formulations for Coatings, Inks and Paints", Oldring (ed.), 1994, SITA, London.

Manufacturing Process for PSA of the Invention

For polymerization, the obtained polymers can be used in particular as PSAs at room temperature or at elevated temperatures, in particular in the handbook of Pressure Sensitive Adhesive Technology by Donatas Satas (van Nostrand, New York 1989). The monomers are selected to have pressure sensitive adhesive properties.

In order to achieve that the preferred polymer glass transition temperature T _g is 25 ° C. or lower for PSA, the monomers are selected in this manner as mentioned above and Fox formula (E1) [TGFox, Bull. Am. Phys, Soc. It is highly desirable to select monomer mixtures of advantageous composition in a quantitative manner in such a way as to obtain the desired T _g for the polymer according to 1 (1956) 123:

In the equation, n means the serial number of the monomer used, w _n is the mass fraction for each monomer n (% by weight) and T _{g, n} is the glass transition temperature of each homopolymer of monomer n at K Indicates.

It is advantageous to carry out conventional free radical polymerization to prepare poly (meth) acrylate PSAs. For polymerizations that proceed with free radicals, preference is given to using initiator systems containing further free radical initiators for polymerization, in particular free radical forming azo or peroxo initiators which are thermally decomposed. In principle, however, all conventional initiators familiar to those skilled in the art for acrylates are suitable. The production of C-concentrated radicals is described in Houben Weyl, Methoden der Organischen Chemie, Vol. E 19a, pp. 60-147. These methods are similarly used in the first place. Examples of free radical sources are peroxides, hydroperoxides, and azo compounds; Some non-limiting examples of typical free radical photoinitiators that may be mentioned herein include potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, azodiiso Butyronitrile, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate and benzpinacol. In one very preferred version, the free radical initiator used is 1,1′-azobis (cyclohexanecarbonitrile) (DuPont Vazo 88 ^™ ) or azodiisobutyronitrile (AIBN).

The electrically conductive material may be mixed into the monomer before polymerization and / or after the end of polymerization.

The average molecular weight M _w of the PSAs formed in the free radical polymerization is very preferably chosen such that their range is from 200,000 to 4000,000 g / mol and is especially averaged for further use as an electrically conductive hot melt PSA with elasticity. PSAs having a molecular weight M _{W of} from 400,000 to 1,400,000 g / mol are preferred. Average molecular weight is determined by matrix assisted laser desorption / ionization coupled with size exclusion chromatography (GPC) or mass spectrometry (MALDI-MS).

The polymerization can be carried out in the absence of solvent, in the presence of one or more organic solvents, in the presence of water or in the presence of a mixture of organic solvents and water. The aim is to minimize the amount of solvent used. Suitable organic solvents include straight chain alkanes (e.g. hexane, heptane, octane, isooctane), aromatic hydrocarbons (e.g. benzene, toluene, xylene), esters (e.g. ethyl, propyl, butyl or hexyl acetate), Halogenated hydrocarbons (eg chlorobenzene), alkanols (eg methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether) and ethers (eg diethyl ether, dibutyl ether) or mixtures thereof to be. Water-miscible or hydrophilic co-solvents are added to the aqueous polymerization reaction to ensure that the reaction mixture is in the form of a homogeneous phase during monomer conversion. Auxiliary solvents that may be used with the advantages of the present invention are aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidines, N-alkylpyrrolidinones, N-alkylpyrrolidones, polyethylene glycols, polypropylene glycols, amides, carboxylic acids And salts, esters, organic sulfides, sulfoxides, sulfones, alcohol derivatives, hydroxy ether derivatives, amino alcohols, ketones and the like and also derivatives and mixtures thereof.

Depending on the conversion and temperature the polymerization time is from 2 to 72 hours. The higher the reaction temperature that can be selected, ie the higher the thermal stability of the reaction mixture, the shorter the selected reaction time can be.

With regard to the polymerization initiation, heat introduction is essential for the thermal decomposition initiator. For these initiators, polymerization can be initiated by heating to 50-160 ° C., depending on the type of initiator.

For this preparation, it may also be advantageous to polymerize the acrylate PSA without solvent. Particularly suitable techniques for use in this case are those polymerization techniques. The polymerization is initiated by UV light, but low enough to have a conversion of about 10-30%. The resulting polymer syrup can then be bonded, for example, to a film (in the simplest case ice cube) and subsequently polymerized in water with a high conversion. These pellets can be used continuously as acrylic hot melt adhesives and it is particularly preferred to use film materials compatible with polyacrylates for melting operations. For this production method, a thermally conductive material can be added before or after polymerization.

Another advantageous manufacturing method for poly (meth) acrylate PSAs is anionic polymerization. In this case, the reaction medium used preferably comprises an inert solvent such as aliphatic and cycloaliphatic hydrocarbons, for example or else aromatic hydrocarbons.

In this case the biopolymer is generally represented by the structure P _L (A) -Me, where Me is a group I metal, for example lithium, sodium or potassium and P _L (A) is a polymer that grows from acrylic monomers. to be. The molar mass of the polymer during manufacture is controlled by the ratio of initiator concentration and monomer concentration. Examples of suitable polymerization initiators include, but are not limited to, n-propyllithium, n-butyllithium, secondary-butyllithium, 2-naphthylithium, cyclohexyllithium and octylithium. In addition, initiators based on samarium complexes are known for the polymerization of acrylates (Macromolecules, 1995, 28, 7886) and can be used herein.

It is furthermore possible to use difunctional initiators such as 1,1,4,4-tetraphenyl-1,4-dirithiobutane or 1,1,4,4-tetraphenyl-1,4-dithioisobutane. Can be. Co-initiators can also be used. Suitable co-initiators include lithium halides, alkali metal alkoxides and alkylaluminum compounds. In one very preferred version, the ligand and co-initiator allow acrylic monomers such as n-butyl acrylate and 2-ethylhexyl acrylate to be directly polymerized and produced in the polymer by transesterification with the corresponding alcohol. It is chosen so that it is not necessary.

Suitable methods for preparing polyacrylate PSAs with narrow molecular weight distributions also include controlled free radical polymerization methods. In this case, preference is given to using the control reagents of the formulas (I) and (II) below for the polymerization.

In the above formula,

R and R ¹ are independently selected or identical to each other,

Branched and unbranched C ₁ to C ₁₈ alkyl radicals, C ₃ to C ₁₈ alkenyl radicals; Alkynyl radicals of C ₃ to C ₁₈ ;

Alkoxy radicals of C ₁ to C ₁₈ ;

C ₁ to C ₁₈ alkyl radicals substituted by one or more OH groups or halogen atoms or silyl ethers; C ₃ to C ₁₈ alkynyl radicals; C ₃ to C ₁₈ alkenyl radicals;

C ₂ to C ₁₈ heteroalkyl radicals having at least one oxygen atom and / or one NR ^* group in the carbon chain, wherein R ^* is any radical (in particular an organic radical);

C ₁ -C ₁₈ alkyl radicals substituted by one or more ester groups, amine groups, carbonate groups, cyano groups, isocyano groups and / or epoxy groups and / or sulfur; C ₃ -C ₁₈ alkynyl radicals, C ₃ to C ₁₈ alkenyl radicals,

C ₃ -C ₁₂ cycloalkyl radicals;

-C ₆ -C ₁₈ aryl or benzyl radicals;

-Hydrogen.

Modulating reagents of type I preferably consist of the following further restricted compounds:

Halogen atoms herein are preferably F, Cl, Br or I, more preferably Cl and Br. Very suitable alkyl, alkenyl and alkynyl radicals in the various substituents include both linear and branched.

Examples of alkyl radicals having 1 to 18 carbon atoms include 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 radicals having 3 to 18 carbon atoms include 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 and hydroxyhexyl.

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

An example of a suitable C ₂ -C ₁₈ heteroalkyl radical having at least one oxygen atom in the carbon chain is —CH ₂ —CH ₂ —O—CH ₂ —CH ₃ .

Examples of C ₃ -C ₁₂ cycloalkyl radicals include cyclopropyl, cyclopentyl, cyclohexyl and trimethylcyclohexyl.

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

Listed above only provide examples for each group of compounds and are not claimed as complete.

Other compounds that can be used as modulating reagents include the compounds of formulas III and IV below.

In the above formula,

R ² may be selected from the groups described above for these radicals independently of R and R ¹ .

In the case of the conventional 'RAFT' process, the polymerization is generally carried out with low conversion in order to have a very narrow molecular weight distribution (WO 98/01478 A1). However, as a result of low conversion, these polymers have a high fraction of residual monomers adversely affecting the technical adhesive properties, the residual monomers contaminating solvent recycles in the concentrating operation and the corresponding self-adhesive tapes exhibit very high outgassing behavior. Cannot be used as PSA and in particular cannot be used as hot melt PSA. In order to overcome the disadvantages of low conversion, in one particularly preferred procedure the polymerization is initiated two or more times.

As a further controlled free radical polymerization method, nitroxide-controlled polymerization can be carried out. For free radical stabilization in a preferred procedure, nitoroxide of the formula Va or Vb is used.

In the above formula,

R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ mean independently of the following compounds or atoms:

i) halides, for example chlorine, bromine or iodine,

ii) linear, branched, cyclic and heterocyclic hydrocarbons having 1 to 20 carbon atoms which may be saturated, unsaturated or aromatic,

iii) ester-COOR ¹¹ , alkoxide-OR ¹² and / or phosphonate-PO (OR ¹³ ) ₂ , wherein R ¹¹ , R ¹² or R ¹³ means radicals from group ii).

The compounds of formula Va or Vb may also be attached to any type of polymer chain (primarily such that at least one of the radicals mentioned above constitutes a polymer chain of this type) and thus may be used for the synthesis of polyacrylate PSAs. .

More preferred are modulators for the polymerization of the following types of compounds:

2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-carbamoyl-PROXYL, 2,2-dimethyl-4,5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-hydroxyimine-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-piperidinyl Prison,

N-tert-butyl 1-phenyl-2-methylpropyl nitroxide,

N-tert-butyl 1- (2-naphthyl) -2-methylpropyl nitroxide,

N-tert-butyl 1-diethylphosphono-2,2-dimethylpropyl nitroxide,

N-tert-butyl 1-dibenzylphosphono-2,2-dimethylpropyl nitroxide,

N- (1-phenyl-2-methylpropyl) 1-diethylphosphono-1-methylethyl nitroxide,

Di-t-butyl nitroxide,

Diphenyl nitroxide,

T-butyl t-amyl nitroxide.

A series of further polymerization methods according to another method by which PSA can be prepared can be selected in the prior art:

U.S. Patent 4,581,429 A describes controlled growth free radical polymerization using a compound of the formula R'R''NOY, wherein Y is a free radical species capable of polymerizing unsaturated monomers. have. In general, however, the reaction has a low conversion rate. A particular problem is the polymerization of acrylates which occur only in very low yields and molar masses. WO 98/13392 A1 describes open chain alkoxyamine compounds with symmetrical substitution patterns. EP 735 052 A1 describes a method for producing thermoplastic elastomers having a narrow molar mass distribution. WO 96/24620 A1 describes polymerization processes in which highly specific free radical compounds, such as phosphorus containing nitroxides based on imidazolidine, are used. WO 98/44008 A1 describes specific nitroxyls based on morpholine, piperazine and piperazinedione. DE 199 49 352 A1 describes heterocyclic alkoxyamines as regulators in controlled growth free radical polymerization. Corresponding further development of alkoxyamines or the development of corresponding free nitroxides improve the efficacy for preparing polyacrylates. Hawker, paper to the National Meeting of the American Chemical Society, Spring 1997; Husemann, paper to the IUPAC World-Polymer Meeting 1998, Gold Coast.

As a further controlled polymerization method, atomic transfer radical polymerization (ATRP) can be advantageously used for synthesizing polyacrylate PSA, in which case as an initiator of a mono or difunctional secondary or tertiary halide And Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au (EP 0 824 111 A1; EP 826 698 A1; EP 824 110 A1; EP 841 346 A1) as initiators for halide extraction. The complexes of EP 850 957 A1) may be mentioned. Various possibilities of ATRP are further described in US Pat. No. 5,945,491 A, US Pat. No. 5,854,364 A and US Pat. No. 5,789,487 A.

Orientation, Coating Process, Treatment of Carrier Material with Electrically Conductive PSA

To prepare the oriented PSA, the polymer described above is preferably coated as a hot melt system (ie from the melt). For this production method, therefore, it is necessary to remove the solvent from the PSA. In principle, any technique known to those skilled in the art can be used. One very preferred technique is to concentrate using a single screw or twin screw extruder. The twin screw extruder can be operated with either co-rotating or counter-rotating. The solvent or water is preferably distilled through two or more vacuum steps. Moreover, reverse heating is carried out depending on the distillation temperature of the solvent. The residual solvent fraction is preferably less than 1%, more preferably less than 0.5% and very preferably less than 0.2%. The hot melt is further processed from the melt.

Orientation in the PSA is created during coating through the coating process. Different coating techniques can be used for coating as hot melt and also for orientation. In one version, the electrically conductive PSA is coated by a roll coating process and the orientation is created by drawing out. Various roll coating techniques are described in "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989). In another version, the orientation is achieved by coating through the melt die. The contact process and the non-contact process can be distinguished herein. Here, the orientation of the electrically conductive PSA is produced on the one hand by die design in the coating die or else by post-employment withdrawal operation from the die. The draw rate can be adjusted by, for example, the width of the die gap. Withdrawal occurs whenever the layer thickness of the PSA film on the carrier material to be coated is less than the width of the die gap.

In another preferred method, this orientation is achieved by extrusion coating. Extrusion coating is preferably carried out using an extrusion die. The extrusion die used has the advantages of one of three categories: T-die, fishtail die and coated hanger die. Each type differs in the design of their flow channels. The shape of the extrusion die can also create specific orientations in the hot melt PSA. In addition, similar to the melt die coating, orientation can also be obtained by drawing the PSA tape film after emergence from the die.

In order to produce oriented (meth) acrylate PSAs, it is particularly desirable to perform coating onto the carrier using a coat hanger die, in particular in such a way that the polymer layer is formed on the carrier while moving the die relative to the carrier. Do. The elapsed time between coating and crosslinking is advantageously small. In one process the crosslinking is carried out after less than 60 minutes, more preferably less than 3 minutes and in very preferred processes less than 5 seconds in the inline process.

The carrier material treated with the electrically conductive PSA may be a single sided or double sided adhesive tape.

In one very preferred version, a transfer tape is produced. Examples of suitable carrier materials include films with all siliconized or fluorinated release effects. Film materials that may be mentioned herein include, for example, BOPP, MOPP, PET, PVC, PU, PE, PE / EVA, EPDM, PP and PE. Moreover, for the transfer tape, it is also possible to use release papers (glass paper, kraft paper, polyolefin coated paper).

If the carrier material remains in the PSA (eg in the form of a carrier film), it is also preferred to use a carrier material that possesses a high degree of electrical conductivity. For this case, for example, metal or metallized films or metal doped films can be used.

Particularly preferred films consist of, but are not limited to, aluminum, copper, stainless steel, or metal alloys. In another embodiment, the polymerizable carrier material is selected from PE, PP, polyimide, PET, PVC, PU or nylon and is provided on one or both sides with a metal layer. Metals that can be used include, for example, aluminum, chromium, nickel, copper, nickel alloys, silver, gold or mixtures thereof. In one preferred technique, these metals are applied to films with very low layer thicknesses by the sputtering method.

However, metalized fabric carrier materials may additionally be used. An example of this is reported in US Pat. No. 5,939,190.

The best orientation effect is obtained by depositing onto the cooling surface. As a result, during coating the carrier material must be cooled directly by the roll. The roll may be cooled by the liquid film / contact film or by the cooling gas on the outside or inside. Cooling gas may also be used to cool the PSA emerging from the sheath die. In one preferred procedure the roll is wetted with the contact medium and then placed between the roll and the carrier material.

For this procedure, both melt and extrusion dies can be used. In one very preferred procedure, the roll is cooled to room temperature and in an extremely preferred procedure it is cooled to a temperature below 10 ° C. The roll must also rotate.

In a further procedure as part of the production process, moreover, a roll is used to crosslink the oriented PSA.

UV crosslinking is influenced by irradiation with shortwave ultraviolet light with a wavelength range of 200 nm to 400 nm, in particular using a high pressure or medium pressure mercury lamp at an output of 80 to 240 W / cm, depending on the UV photoinitiator used. The irradiation intensity is adjusted to the respective quantum yield of the UV light initiator, the degree of crosslinking to be performed and the degree of orientation.

Moreover, in one preferred version, electron beams can be used to crosslink the electrically conductive and oriented PSAs. Typical irradiation devices that can be used include linear cathode systems, scanner systems, and fragmented cathode systems, where an electron beam accelerator is involved. A broad description of the prior art and the most important process factors are described in Skelhorne, Electron Beam Processing, in Chemistry and Technology of UV and EB formulation for Coatings, Inks and Paints, Vol. 1, 1991, SITA, London. Typical accelerator voltages are located in the range of 50 kV to 500 kV, preferably in the range of 80 kV to 300 kV. The scattering capacity used is in the range of 5 to 150 kGy, in particular in the range of 20 to 100 kGy. It is also possible to use two crosslinking methods, or other methods that allow high energy irradiation.

In a further preferred manufacturing method, the electrically conductive and oriented PSAs are coated onto a roll provided with a contact medium. As a result of the contact medium, the PSA can be cooled very quickly. Advantageously, it is subsequently laminated onto the carrier material. In addition, as a contact medium, a material having a capacity to contact between the PSA and the roll surface, in particular, a material filling the space between the carrier material and the roll surface (not flat at the roll surface, for example, a bubble) Can be used. To carry out this technique, a rotary cold roll is coated with a contact medium. In one preferred procedure, the selected contact medium is a liquid, for example water.

Examples of suitable additives for water as the contact medium include alkyl alcohols such as ethanol, propanol, butanol and hexanol and are not limited in selecting alcohol as a result of these examples. Also particularly advantageous are long chain alcohols, polyglycols, ketones, amines, carboxylates, sulfonates and the like. Many of these compounds lower surface tension or increase conductivity.

Lowering the surface tension can also be achieved by adding small amounts of nonionic and / or anionic and / or cationic surfactants to the contact medium. The simplest way to achieve this is to use a commercially available washing composition or soap solution as the contact medium, preferably at a concentration of several g / l in water. In particular, suitable compounds are special surfactants which can be used even at low concentrations. Examples thereof include sulfonium surfactants (eg β-di (hydroxylalkyl) sulfonium salts) and also for example nonylphenylsulfonic acid ammonium salts or block copolymers, in particular diblocks. In particular, mention may be made of surfactants in the prior art (Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2000 Electronic Release, Wiley-VCH, Weinheim 2000).

As the contact medium, the above-mentioned liquids can be used alone or in combination with each other in each case even without addition of water. In order to improve the properties of the contact medium (e.g., to increase shear resistance or to reduce the delivery to the inner surface of the surfactant, etc., to improve the cleaning power for the final product), to enhance salts, gels and similar viscosities Additives may also be advantageously added to the contact medium and / or to the adjuvant used. In addition, the roll may have a surface of the structure that is macroscopically soft or low level. It has been found that the rolls have a surface structure, in particular surface roughness. This allows the wetting by the contact medium to be improved. In particular, the coating process is particularly well carried out when the roll is preferably adjustable in the range of -30 ° C to 200 ° C, very preferably in the range of 5 ° C to 25 ° C. The contact medium is preferably applied to the rolls. A second roll that absorbs the contact medium can be used for the continuous wetting of the coating rolls. However, it can also be applied, for example by spraying, without contact.

For variations of the manufacturing method in which the rolls are used simultaneously with, for example, an electron beam, it is common to use a milled metal roll that absorbs incident electrons and the X-rays formed in the process.

To prevent corrosion, rolls are generally covered with a protective coating. The coating is preferably selected such that it is effectively wetted by the contact medium. In general, the surface is conductive. However, it may also be more advantageous to coat it with one or more coatings of insulators or semiconductor materials.

When a liquid is used as the contact medium, one obvious procedure is that a second roll having a wettable or advantageously adsorbing surface must be run through a bath containing the contact medium and the roll is then wetted with the contact medium. Or is impregnated therein and applied to the film of the contact medium by contact with the roll.

In one preferred process, the PSA is coated directly on the contact medium roll and crosslinked. For this purpose, the methods and apparatus described for UV crosslinking and EB crosslinking can then be used. After crosslinking, the electrically conductive and oriented PSAs are then transferred to the carrier material. Carrier materials already mentioned can be used.

The orientation characteristic in the electrically conductive PSA depends on the coating process. The orientation can be controlled, for example, by the die temperature and the coating temperature and also by the molecular weight of the polymer.

The degree of orientation is freely adjustable through the die gap width. The thicker the PSA film extruded from the coating die, the greater the extent that the adhesive is drawn out to the relatively thin PSA film on the carrier material. The drawing operation can be freely adjusted by the freely adjustable die width as well as by the decreasing web speed of the carrier material.

The orientation of the adhesive mass can further be measured by means of infrared dichroism or X-ray dispersion with a polarimeter. In many cases, the orientation in acrylate PSA is known to be maintained for only a few days in an uncrosslinked state. During non-operation or storage, the system slows down and loses its preferential direction. As a result of crosslinking after coating, the effect can be significantly enhanced. Relaxation of the oriented polymer chain is concentrated towards zero and the oriented PSA can be stored for a very long time without losing its preferential orientation.

In one preferred method, the degree of orientation is determined by measuring shrinkage recoverability in the glass film (see Test B).

In addition to the described method, orientation can also be produced after coating. In this case, a stretchable carrier material is then preferably used and then the PSA is withdrawn during stretching. In this case, it is also usually possible to use PSA coated from solution or water. In one preferred procedure, this extracted PSA is then crosslinked by actinic radiation.

Usage

The invention further provides for the use of electrically conductive and oriented PSAs for joining components in the electrical and electronics industries. In one preferred embodiment, the PSA of the present invention is used as a transfer tape. In this case, the release paper is removed to bond the electrically conductive material. If the very adjacent conductor tracks are coupled in parallel, the joining direction is chosen such that the electrically conductive PSA of the present invention possesses elasticity in the direction of the next parallel conductor track. In this way, short circuits can be avoided because the PSAs do not leak in a single direction compared to conventional electrically conductive PSAs.

A further advantage is the electrically conductive PSA diecut, which is particularly suitable for joining very small electrical parts which are easy during manufacture and are very stable three-dimensionally during bonding and therefore very effectively. A further advantage of electrically conductive and oriented PSAs is that they are reversible. As a result of the orientation, the PSA of the present invention can be stretched in the oriented direction, which in turn reduces the bond strength and tack. By this means, the electrically conductive material can be bonded to the PSA of the present invention and again separated from each other. In a further embodiment, the PSAs of the present invention possess anisotropic electrically conductive properties. As a result of the orientation of the polymer chains, the electrically conductive filler material desorbs in one preferred direction and loses contact with each other. As a result of this process, the electrical conductivity in the orientation direction is lowered such that the PSA and also the corresponding PSA tapes also have anisotropic electrical conductivity.

Claims (16)

A method of making a pressure sensitive adhesive article having one or more layers of electrically conductive pressure sensitive adhesive, wherein one layer of the electrically conductive pressure sensitive adhesive is at least anisotropic in terms of one property, and in coating process by stretching, drawing or pressing. And wherein said layer has at least 3% shrinkage recovery in terms of the longitudinal direction of the layer measured on the glass pressure-sensitive adhesive film in at least one direction along the plane of the layer. The method of claim 1, wherein the coating process is a hot melt roll coating process, a melt die coating process, or an extrusion coating process. The method of claim 1 wherein the coating process is a conventional coating process with subsequent stretching or withdrawal on a stretchable carrier. The method according to claim 1, wherein the electrically conductive pressure sensitive adhesive is coated on one or both sides of the sheet or tape carrier. The method of claim 4 wherein the carrier is a transfer tape, a release liner or an electrically conductive carrier material. The method according to claim 1, wherein the pressure sensitive adhesive used is based on polyacrylates and / or polymethacrylates. The method of claim 6, wherein the pressure sensitive adhesive is based on at least 50% by weight of at least one acrylic monomer from a compound group of formula: wherein the pressure sensitive adhesive has an average molecular weight M _W of at least 200,000 g / mol. In the above formula, R ₁ is H or CH ₃ , The radical R ₂ is selected from the group consisting of H or CH ₃ or branched or unbranched saturated alkyl groups having 2 to 30 carbon atoms. The crosslinking agent, in particular the difunctional or polyfunctional acrylate and / or methacrylate, the difunctional or polyfunctional isocyanate or the difunctional or polyfunctional epoxide, is pressure sensitive. Added to the adhesive. 10. The method of claim 8, wherein the pressure sensitive adhesive is preferably photochemically crosslinked immediately after or during the hot melt coating. The metal particles, metal powders, metal beads, metal fibers, or nickel coated following particles according to claim 1, in which the electrically conductive material, in particular the metal is in particular nickel, gold, silver, and copper. : A process characterized in that copper particles, nickel particles, polymer beads, polymer particles or glass microbeads, or hollow glass microbeads are mixed in a pressure sensitive adhesive. 11. A method according to claim 10, characterized in that the electrically conductive material is mixed in an amount of up to 200% by weight, preferably 5 to 50% by weight, more preferably 10 to 40% by weight, based on the weight of the pressure sensitive adhesive. Way. The method according to any one of claims 1 to 11, wherein the electrical conductivity of the pressure sensitive adhesive is 1 to 500 S / cm. The method of claim 1, wherein the electrical conductivity is anisotropic and is lower along the plate located in the pressure sensitive adhesive layer than across the plane of the layer, and 2S in the transverse direction along the plate of the layer. / cm or more. The pressure sensitive adhesive according to claim 1, wherein the pressure sensitive adhesive further comprises additional substances or additives, for example aging inhibitors, light stabilizers, ozone protecting agents, fatty acids, plasticizers, nucleating agents, swelling agents, accelerators. And / or fillers. A pressure-sensitive adhesive article obtainable by the method according to claim 1, in particular for joining two electrical parts. The pressure sensitive adhesive article of claim 15 in the form of a die cut.