DE10358264A1 - Production of pressure-sensitive adhesive foil with rastered adhesive area, e.g. for reversible use, involves local selective cure of adhesion on base and removal of uncured areas - Google Patents

Abstract

Production of a pressure-sensitive adhesive (PSA) foil with rastered adhesive area comprises local selective cure of a layer of PSA on a base and then removing the uncured areas, so that the cured areas remain on the base. An independent claim is also included for adhesive foil produced by this process.

Description

The Application relates to a process for producing a pressure-sensitive adhesive film with structured adhesive surface as well Adhesive films produced by such a method.

microstructured surfaces be for PSA tapes more and more interesting, because here specifically adhesive properties can be influenced.

An already very old example is market-standard sticky notes. For such temporary bonds are z. B. screen-applied adhesives. This is an example in which structuring reduces the bond area and thus achieves adhesive force depression with respect to the substrates. Such structuring of a PSA, for example, the writings reveal DE 33 46 100 A1 and US 3,857,731 ,

A another method of structuring make microphase-separated Block copolymers there, such as. As polyacrylates with polystyrene or Polymethacrylatendblöcken. Due to the microphase separation, hard blocks are formed here, which are in a soft pressure sensitive matrix and not tacky domains represent. Due to this physical crosslinking, the PSAs reach high shear strengths.

A another possibility represents the selective UV crosslinking of polyacrylates. Here are Polyacrylates with attached to the main polymer chain UV photoinitiators targeted by a UV mask irradiated with UV light and in certain Networked segments. By segmenting in hard and soft domains become the adhesive properties especially with regard to the internal cohesion increased.

Out Nature, on the other hand, is aware of liability processes that are at its best Structuring based. An example here are gecko feet. Geckos have excellent adhesion with their feet, caused by very finely branched Hair. So far, it has not succeeded in such a fine structure build up in the adhesive film area. The above methods provide no possibility to do this since with these methods no pressure-sensitive adhesives with fine tube structures can be built.

task The invention is therefore to offer a method which a corresponding production of microstructured pressure-sensitive adhesive films or bands allows in which the pressure-sensitive adhesive is in particular perpendicular in the form of tube on the carrier material stands and forms a knobbed structure, so that the corresponding Adhesive film has pressure-sensitive adhesive properties.

Is solved the task surprisingly and unpredictable by a procedure as defined in the main claim is described. The dependent claims relate to improvements of the method according to the invention. Another Claim relates to a pressure-sensitive adhesive film, as obtained by the method according to the invention available is.

Accordingly the invention relates to a process for producing a pressure-sensitive adhesive film, characterized by local crosslinking of a layer of a pressure-sensitive adhesive on a carrier material and subsequently Removal of the PSA in the non-crosslinked areas, wherein the crosslinked areas as pressure-sensitive adhesive elements on the carrier material remain.

The local cross-linking of the film is caused in particular by that the crosslinking is caused by actinic radiation, wherein certain areas of the PSA layer for the radiation not or only partially accessible especially by giving these areas a locally structured Cover, in particular a mask, a grid, a textured Foil (which for actinic radiation locally dependent permeable to varying degrees is) or the like, is covered.

The Shape of the pressure-sensitive adhesive elements is essentially through the cover and the type of irradiation (eg perpendicularly incident rays) generated. In principle, all forms of pressure-sensitive adhesive elements, for. As those in Kalottenform conceivable. Adhesive adhesive elements are advantageous, the at any choice of the face substantially perpendicular on the pressure-sensitive adhesive surface standing sidewalls exhibit.

Advantageously, the adhesive elements located on the pressure-sensitive adhesive film form a substantially cylindrical shape. In a first embodiment of the invention, the pressure-sensitive adhesive elements have a flat end face. In a second advantageous embodiment of the invention, the end faces of the pressure-sensitive adhesive elements have a concave, that is still curved inside, end face; in particular caused by a volume contraction of the crosslinked areas during deprotection and / or crosslinking.

is the first applied PSA layer on the substrate applied the same thickness, so arise preferably adhesive elements of identical height. The faces these pressure-sensitive adhesive elements are thus essentially in an escape, representing a plane-parallel plane to the support surface (the term "substantially" is used herein) there the faces the pressure-sensitive adhesive elements need not necessarily be planar). It but may be advantageous in terms of the use of the pressure-sensitive adhesive film be, the PSA layer in different areas of the carrier material apply different thickness and thus on the produced pressure-sensitive adhesive film To produce pressure-sensitive adhesive elements of different heights. The faces of the pressure-sensitive adhesive elements are then essentially in a non-planned imaginary area.

• • zunächst eine Haftklebemasse, welche ein Polymer enthält, das mit funktionellen Gruppen (G1) funktionalisiert ist, welche – zunächst geschützt vorliegen, – in der Lage sind, thermisch eine Vernetzung der Haftklebemasse hervorzurufen oder zu unterstützen, – säurekatalytisch entschützt werden können, mit Photokationenerzeugern vermischt auf ein Trägermaterial beschichtet wird,
• • die Haftklebemassenschicht lokal selektiv mit UV-Licht bestrahlt wird,
• • die Haftklebemassenschicht anschließend selektiv vernetzt wird und
• • anschließend die nicht-vernetzten Bereiche der Haftklebemassenschicht entfernt werden.

Advantageously, the inventive method is carried out in such a way that

• First, a pressure-sensitive adhesive which contains a polymer which is functionalized with functional groups (G1) which - initially protected, - are capable of thermally causing or supporting crosslinking of the PSA, - can be deprotected by acid catalysis, with photo-cation generators is coated on a carrier material mixed,
• The layer of PSA is locally selectively irradiated with UV light,
• The PSA layer is then selectively cross-linked and
• • then remove the non-crosslinked areas of the PSA layer.

The Removing the non-crosslinked areas of the PSA layer happens preferably by dissolving the PSA by means a suitable solvent. Suitable solvents to the solution of non-networked Polyacrylates are known to the person skilled in the art and can be used in the prior art be easily removed.

When solvent can advantageous z. Ketones such as acetone and butanone, aromatic compounds such as Toluene and xylene, heterocycles, such as tetrahydrofuran, aliphatic Compounds such as boiling-point benzene, alcohols, such as ethanol, isopropanol, Propanol and butanol can be used.

Of the Term foils is overarching for flat structures meant all kinds and thus includes two-dimensional area (z. B. roll goods, bale goods) and elongated (eg adhesive tapes) structures. Likewise, two-dimensionally limited structures are included (eg labels).

When functional group G1 are in a preferred procedure Used hydroxy groups.

When Protecting groups within the meaning of the invention can be those skilled in the art for such Use known protection groups (see for example Protective Groups in Organic Synthesis, by Peter G. M. Wuts, Theodora W. Greene, Wiley-Interscience; 3nd edition (May 15, 1999). Very the protection is advantageous over tert-butoxycarbonyl protecting groups (BOC groups).

Especially Advantageous to do before by the UV and thermal Crosslinking reaction additional Crosslinking substances to the polymer mixture to be crosslinked. Suitable crosslinker substances in this sense are difunctional or polyfunctional Isocyanates or difunctional or polyfunctional epoxides. Be used can but here also all other bi- or multi-functional, familiar to the expert Compounds capable of crosslinking poly (meth) acrylates.

• a) 85–99,8 Gew.-% (bezogen auf die Polymermischung) eines Polyacrylatcopolymers auf Basis folgender Monomerbausteine: a1) eines oder mehrerer Acrylsäureester und/oder Methacrylsäureester der folgenden Formel CH₂ = CH(R¹)(COOR²), wobei R² = H oder CH₃ und R² eine Alkylkette mit 1–20 C-Atomen ist, zu 65–99 Gew.-%, bezogen auf a), a2) ggf. eines oder mehrerer olefinisch ungesättigter Monomere mit weiteren funktionellen Gruppen (G2), zu 0–15 Gew.-%, bezogen auf a), a3) eines oder mehrerer Acrylate und/oder Methacrylate, deren Alkoholkomponente tert.-Butoxycarbonyl- (BOC-) und/oder Hydroxy-Gruppen enthält, zu 1–20 Gew.-%, bezogen auf a),
• b) 0,1–10 Gew.%, insbesondere 0,5–1 Gew.-% (bezogen auf die Polymermischung) eines oder mehrerer Photokationenerzeuger,
• c) 0,1–5 Gew.-%, insbesondere 0,5–1 Gew.-% (bezogen auf die Polymermischung) eines oder mehrerer bifunktioneller oder multifunktioneller Vernetzer, insbesondere Isocyanate oder Epoxide,

eingesetzt wird.The process according to the invention is very preferably carried out by using as the pressure-sensitive adhesive a mixture of

• a) 85-99.8 wt .-% (based on the polymer mixture) of a polyacrylate copolymer based on the following monomer units: a1) one or more acrylic acid esters and / or methacrylic acid esters of the following formula CH ₂ = CH (R ¹ ) (COOR ² ), where R ² = H or CH ₃ and R ^{2 is} an alkyl chain having 1-20 C atoms, to 65-99 wt .-%, based on a), a2) optionally one or more olefinically unsaturated monomers having further functional groups (G2), to 0-15% by weight, based on a), a3) one or more acrylates and / or methacrylates whose alcohol component contains tert-butoxycarbonyl (BOC) and / or hydroxyl groups, to 1-20% by weight, based on a),
• b) 0.1-10% by weight, in particular 0.5-1% by weight (based on the polymer mixture), of one or more photocation generators,
• c) 0.1-5% by weight, in particular 0.5-1% by weight (based on the polymer mixture) of one or more bifunctional or multifunctional crosslinking agents, in particular isocyanates or epoxides,

is used.

there be supra by the definition of the state of the polymer in the Pressure-sensitive adhesive described. In particular, this means in terms of to the component a3) that first Acrylates and / or methacrylates, their alcohol component hydroxy groups contains can be polymerized and the protective function is introduced into the polymer, or alternatively the already provided with the protective function acrylates and / or Methacrylates according to the component of the polymerization process can be subjected. A combination of both procedures is possible. All Variants lead to a polymer in which according to the above Definition of the alcohol component of component a3) by BOC protective groups protected Having hydroxy groups.

In a very preferred procedure for a1) acrylic and methacrylic acid esters with alkyl groups consisting of 4 to 14 carbon atoms, preferably 4 to 9 C atoms, used.

specific Examples without limiting themselves by this list 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 their branched Isomers, such as. For example, isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Isooctyl acrylate, isooctyl methacrylate.

Further are advantageously used compound classes in the sense of a1) monofunctional acrylates or methacrylates of bridged cycloalkyl alcohols, consisting of at least 6 C atoms. The cycloalkyl alcohols can also be substituted, for. By C1-6 alkyl groups, halogens or cyano groups. specific Examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyladamantyl acrylate.

in the Meaning of the optional component a2) may advantageously be used monomers which are polar groups such as carboxyl, sulfonic and phosphonic acid, hydroxy-lactam and lactone, N-substituted amide, N-substituted amine, carbamate, epoxy, Thiol, ether, alkoxy. Cyan or similar wear.

moderate basic monomers a2) are z. B. N, N-dialkyl substituted amides, such as N, N-dimethylacrylamide, N, N-dimethylmethylmethacrylamide, N-tert-butylacrylamide, N-vinylpyrrolidone, N-vinyllactam, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, Diethylaminoethyl methacrylate, diethylaminoethyl acrylate, N-methylolmethacrylamide, N- (buthoxymethyl) methacrylamide, N-methylolacrylamide, N- (ethoxymethyl) acrylamide, N-isopropylacrylamide, but this list is not exhaustive.

Further preferred examples of a2) 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, tetrahydrofufuryl acrylate, β-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, wherein this list also not final to understand.

In Another very preferred interpretation as monomers a2) Vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, vinyl compounds used with aromatic rings and heterocycles in α-position. Here too are not exclusive some examples: vinyl acetate, vinyl formamide, vinyl pyridine, Ethyl vinyl ether, vinyl chloride, vinylidene chloride and acrylonitrile.

In a further preferred embodiment, monomers a2) which have a high static glass transition temperature are added to the described comonomers of group a1). As components own aromatic vinyl compounds, such as. As styrene, wherein preferably the aromatic nuclei consist of C ₄ to C ₁₈ and may also contain heteroatoms. Particularly preferable examples are 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, Ben cyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, t-butylphenyl acrylate, t-butylphenyl methacrylate, 4-biphenyl acrylate and methacrylate, 2-naphthyl acrylate and methacrylate and mixtures of those monomers, although this list is not exhaustive.

In order to obtain a desired glass transition temperature T _{G, A of} the polymers of T _{G, A} ≥ -30 ° C, very preferably ≥ -10 ° C, most preferably ≥ + 20 ° C, the monomers are advantageously selected in accordance with the above and the quantitative Composition of the monomer mixture advantageously chosen such that the desired T _{G, A} value for the polymer results according to the Fox equation (G1) (see TG Fox, Bull. Am. Phys Soc., 1 (1956) 123).

Here n represents the number of runs via the monomers used, w _n the mass fraction of the respective monomer n (wt .-%) and T _{G, n} the respective glass transition temperature of the homopolymer of the respective monomers n in K.

The acrylate PSA usable in the context of this invention advantageous over Conventional free-radical polymerizations produced. For the radical extending polymerizations are preferred initiator systems used in addition contain further radical initiators for the polymerization, in particular thermally decomposing radical-forming azo or peroxo initiators. In principle, however, all acrylates customary to the person skilled in the art are customary Initiators. The production of C-centered radicals is in Houben Weyl, Methods of Organic Chemistry, Vol. E 19a, pp. 60-147. These methods are preferably applied by analogy.

Examples of radical sources are peroxides, hydroperoxides and azo compounds, as some non-exclusive examples of typical free-radical initiators may be mentioned potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, azodiisoic acid butyronitrile, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate, benzpinacol. In a very preferred embodiment, the free-radical initiator used is 1,1'-azobis (cyclohexanecarbonitrile) (Vazo 88 ^™ from DuPont) or azodisobutyronitrile (AIBN).

The average molecular weights _M.sub.w of the PSAs formed in the free-radical polymerization are very preferably selected such that they are in the range from 200,000 to 4,000,000 g / mol; PSAs having average molecular weights _M.sub.w of 600,000 to 800,000 g / mol are produced especially for further use as hotmelt PSAs. The determination of the average molecular weight is carried out by size exclusion chromatography (GPC) or matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS).

The Polymerization may be in bulk, in the presence of one or more organic solvent, in Presence of water or in mixtures of organic solvents and water performed become. The aim is the amount of solvent used as low as possible to keep. Suitable organic solvents are pure alkanes (eg, hexane, heptane, octane, isooctane), aromatic hydrocarbons (eg benzene, toluene, xylene), esters (eg ethyl acetate, acetate, propyl, butyl or hexyl esters), 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 offset to ensure that this Reaction mixture during 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, Hydroxyetherderivaten, amino alcohols, ketones and the like, as well as derivatives and mixtures thereof.

The Polymerization time is - depending on Sales and temperature - between 4 and 72 hours. The higher the reaction temperature selected can be, that is, The higher the thermal stability the reaction mixture is, the lower the reaction time chosen become.

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

As photocation generator (also in the sense of component b) iodonium compounds are preferably used, which release strong Lewis acid under UV irradiation. A particularly preferred compound and is commercially available Triacrylsulfoniumhexafluorophosphat (Cyracure UVI-6990 ^® c of Messrs. Union Carbide). Further suitable photocation generators are given in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. In addition, Carroy et al., Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints "Oldring (ed.), 1994, SITA, London.

to Further development can be mixed with the polyacrylate PSA resins. As zuzusetzende Tackifying resins are all previously known and known in the art The adhesive resins described in the literature can be used. Mentioned the pinene, indene and rosin resins whose disproportionated, hydrogenated, polymerized, esterified derivatives and salts, aliphatic and aromatic hydrocarbon resins, terpene resins and terpene phenolic resins and C5, C9 and other hydrocarbon resins. Any combinations this and other resins can be used to control the properties of the resulting adhesive to set as desired. In general, all with the appropriate polyacrylate compatible (soluble) Resins, in particular, reference is made to all aliphatic, aromatic, alkylaromatic hydrocarbon resins, hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins, functional Hydrocarbon resins and natural resins. On the presentation of the State of knowledge in the "Handbook of Pressure Sensitive Adhesive Technology "by Donatas Satas (van Nostrand, 1989) be explicit pointed.

Farther can optionally plasticizers (plasticizers), fillers (eg fibers, carbon black, zinc oxide, Titanium dioxide, chalk, solid or hollow glass spheres, microspheres other materials, silica, Silicates), nucleating agents, blowing agents, Compounding agents and / or anti-aging agents, e.g. B. in shape from primary and secondary Antioxidants or be added in the form of sunscreens.

When support material the adhesive films, for example for adhesive tapes, can be the usual and familiar to the expert Use materials such as films (polyester, PET, PE, PP, BOPP, PVC). This list should not be final be.

to Coating the polymers described above as hotmelt systems or from solution the carrier coated. It may be advantageous or necessary, the solvent to remove from the PSA. Here, in principle, all the expert known methods are used. A very preferred method is the concentration over a single or twin screw extruder. The twin-screw extruder can be the same or in opposite directions operate. The solvent or water is preferred over distilled off several vacuum stages. In addition, depending on the distillation temperature of the solvent heated counter. The residual solvent shares are preferably <1%, more preferably <0.5% and very preferably <0.2%. The hotmelt is processed from the melt. Then it will be over one melt die or an extrusion die coated, where appropriate, the adhesive film is stretched to to achieve the optimum coating thickness.

For anchoring the pressure-sensitive adhesive on the carrier It may be beneficial if the carrier material before coating treated with corona, flame or plasma. For the atmospheric plasma treatment are suitable for. B. devices the company Plasmatreat.

Farther can it for the process and for the Anchoring advantageous if a chemical anchoring z. B. over a primer takes place.

The general reaction principle for the crosslinking reaction controlled by introduction of BOC protective groups is shown below:
The crosslinking of the polymer mixture is carried out by two successive reactions. In the first step, a BOC-functionalized polymer is prepared. A relatively simple way to do this is given by a polymer-analogous reaction, ie by a reaction on the macromolecules, which modifies the chemical composition, but does not significantly change the degree of polymerization. At this stage, occurring due to the production process reactions attack the protected hydroxide groups not.

The polymer now containing BOC groups is then recovered by an acid catalyzed reaction deprotected, wherein the BOC groups are converted to the free hydroxy group:

These Reaction is for example in the photoresist technique (photoresists: photosensitive, film-forming materials (photoresists), the solubility changes due to exposure or irradiation; at negative working Photoresists, this is done by crosslinking or photopolymerization) used for the production of chip structures. The for this Process required acid is due to the UV irradiation of a blended photocation initiator prepared.

• a) Reaktion mit Isocyanaten als Vernetzer
• b) Reaktion mit Epoxiden als Vernetzer

In the second step, the hydroxy functions are used for the reaction with a crosslinker. Generally one can distinguish between two reactions:

• a) reaction with isocyanates as crosslinker
• b) reaction with epoxides as crosslinkers

The Reaction with isocyanates proceeds without acidity at elevated temperatures.

On the other hand extends the reaction with the epoxides only under acid catalysis. Again, here is the supply of thermal energy necessary.

If you transfer now these reaction sequences on the for needed the inventive method PSAs, so must at least the base polymers contain BOC functions. Hydroxy groups containing polymers which, for example, conventionally via a free radical polymerization can be made then reacted in a polymer-analogous reaction with BOC anhydride, making the BOC-protected polymers receives. Alternatively, it is possible to the BOC groups over already protected incorporating monomers present in the polymer. In this case will be for the polymerization advantageously BOC-protected acrylate or methacrylate monomers used for the polymerization.

Both the base polymers and the polymers provided with the BOC groups are characterized by a low viscosity. The flow viscosity of the uncrosslinked BOC-containing PSAs is re relatively low, as there are hardly any polar comonomers that could form pronounced hydrogen bonds. At this stage, therefore, the polymer composition has a very good processability in the hotmelt process.

To the processing and addition of UV cation initiators as well Diisocyanates or diepoxides or multifunctional isocyanates or multifunctional epoxides as Vernetzerreagentien the component mixture subsequently as hotmelt pressure sensitive adhesive z. B. over a coating nozzle on a carrier coated (for example PET film).

to Improving anchorage can be beneficial to that support material is pretreated. here we can all appropriate measures to increase the surface tension be used, such. As corona, flame, plasma or the chemical oxidation or etching. Furthermore you can also be used primers that have a chemical Venetzungspotential have. here we can again compounds with the following reactive groups are used: Carboxylic acids, Isocyanates, epoxides, amines, carbodiimides, aziridines, amides, aminoamides and hydroxides.

to UV crosslinking is achieved by short-term ultraviolet irradiation in a wavelength range of 200 to 400 nm, depending on the UV photocagen generator used, irradiated, in particular using mercury high pressure or medium pressure lamps at a power of 80 to 240 W / cm. The irradiation intensity becomes the respective quantum yield of the UV photogenerator and the adapted to be achieved degree of networking. Too large amounts of cations can do this to lead, that the resolution of the photolithographic process is reduced by the cations diffuse into unirradiated segments.

By the UV irradiation selectively takes place the reaction (R1), due of the photocagen generator, an acid is formed which is linked to the BOC group reacts to the free hydroxyl function. This reaction is included Temperatures> 100 ° C. As optimum For example, a range between 120 and 140 ° C is preferred. With the thermal Release of the hydroxy reaction are now available for the multifunctional crosslinkers reactive groups available, So that the Reactions (R2a) or (R2b) proceed: The isocyanates react in selective areas at these temperatures directly with the resulting Hydroxy functions and crosslink the pressure-sensitive adhesive on the support, so that selectively cross-linked segments arise in these areas. The for the crosslinking with the multifunctional epoxides required protons are present by the acid generated by the photocation initiator. Therefore, runs also the crosslinking with the multifunctional epoxides in situ.

in the Meaning of the inventive method, it is advantageous if particularly high Vernetzungsgrade be achieved in the segments. In a preferred Design, the degree of crosslinking is above 80%, more preferably above 90%, and highly preferred at above 95%.

By crosslinking with isocyanates form amide groups which linking the polymer chains. By linking the solubility decreases. The crosslinked polymer segments are no longer soluble. In one of the networking following process step, the soluble segments are dissolved and thus from the support material away. The resolved Mass can be used again. The crosslinked, non-soluble segments remain as pressure-sensitive adhesive elements on the carrier material. After the partial dissolution process the "nub structure" remains on the carrier material back, which then advantageous from the residual solvent by the introduction of heat is released.

The selective irradiation is preferably achieved through a shadow mask, the for the radiation only locally continuous is, or alternatively by an embossed film, which is an inhomogeneous Thickness and / or density and therefore zones with high permeability for ultraviolet Radiation next to those with poorer or no UV transmission has.

In the 1 the irradiation of the acrylate composition ( 2 ) through a shadow mask ( 1 ), wherein the acrylate composition ( 2 ) on the support ( 3 ) ( 1a ). The initially polar groups of the acrylate composition ( 1 ) have been converted into nonpolar groups by introduction of BOC protecting groups according to the main claim; by UV light ( 4 ) and at high temperatures (> 80 ° C), these are converted back into polar acrylic acid groups. The ultraviolet rays ( 4 ), the mask ( 1 ) only in the area of the holes ( 11 ), so that, after irradiation, those in the second part ( 1b ) of the figure shows:

Polar (deprotected) groups can only be found in certain areas ( 21 ) of the acrylate composition ( 2 ), next to these are other areas ( 22 ), in which there are still only nonpolar, protected by BOC groups functions.

If the acrylic PSA is now heated, it is only in the polar areas ( 21 ) by hydrogen interactions between the polar groups to a crosslinking reaction, so that the then crosslinked areas ( 23 ), while the non-polar (non-crosslinked) regions ( 24 ) have a lower viscosity ( 1c ).

Another effect is the release of isobutene gas and carbon dioxide at the cross-linking sites. This reaction reduces the molecular weight of the crosslinked regions ( 23 ) of the PSA ( 2 ) and one observes a volume contraction ( 231 ). The layer thickness of the acrylic PSA ( 2 ) at the irradiated sites ( 23 ) lower; this changes the surface topography of the PSA ( 2 ).

Subsequently, with solvent, the uncrosslinked areas ( 24 ), whereby the networked areas ( 23 ) as pressure-sensitive adhesive elements on the carrier material ( 3 ) remain. There remains a kind of "nub structure".

2 (a) and 2 B) show by way of example cutouts of two embodiments of pressure-sensitive adhesive films produced by the process according to the invention, in each case with the carrier ( 3 ), on which the pressure-sensitive adhesive elements ( 23 ) (networked segments). The two embodiments differ in the diameter of the pressure-sensitive adhesive elements and their distance from one another. The position number ( 231 ) refers to the volume contraction on the "summit" of the pressure-sensitive adhesive elements.

In the two illustrated embodiments, the pressure-sensitive adhesive elements ( 231 ) in a substantially cylindrical shape.

In a preferred embodiment of the invention, the pressure-sensitive adhesive elements ( 23 ) a height of greater than 10 microns, more preferably greater than 25 microns and most preferably greater than 100 microns. In principle, there are no upward restrictions by the inventive method. However, practice has shown that the maximum height should be limited to about 1 mm since otherwise the pressure-sensitive adhesive elements will become too unstable. In a further embodiment of the invention, the diameter of the pressure-sensitive adhesive elements ( 23 ) preferably less than 10 mm, very preferably less than 2 mm, most preferably less than 20 μm. The limit of the diameter down is determined by the wavelength of the incoming UV light. In a very preferred for the inventive method design pressure-sensitive adhesive elements ( 23 ) made with the minimum possible diameter.

Furthermore, the distance between the pressure-sensitive adhesive elements can be varied. In general, the distance in a preferred design should be as low as possible. At the top, in a particular embodiment, the limits are given by the coating width. Preferably, the maximum distance is less than 10 cm, more preferably less than 1 cm. The minimum distance between the pressure-sensitive adhesive elements ( 23 ) is again given by the wavelength of the incoming UV light. A preferred minimum distance is less than 1 mm, very preferably less than 200 μm. The invention can be implemented particularly well if the number of pressure-sensitive adhesive elements ( 23 ) is maximum.

Examples

The The following exemplary experiments are intended to illustrate the invention without that by the choice of the examples given will unnecessarily limit the invention should.

Test Methods:

to Examination of the samples served the following test methods:

180 ° bond strength test (test A)

One 20 mm wide strip one on a polyester or siliconized Release paper coated acrylic PSA was applied to steel plates, which previously washed twice with acetone and once with isopropanol were upset.

Of the Pressure-sensitive adhesive tape was applied twice with a 2 kg weight to the substrate pressed. The tape was subsequently immediately at a speed of 30 mm / min and at a 180 ° angle from Subtracted substrate. All measurements were taken at room temperature air-conditioned conditions.

The Measurement results are given in N / cm and are averaged out of three Measurements.

sample preparation

in the The following will be the preparation the starting polymers described.

The polymers studied were prepared conventionally via a free radical polymerization according to the following examples; the average molecular weight M _{w of} the polymer was about 800,000 g / mol. Hydroxyl group-containing polymers were reacted in a polymer-analogous reaction with BOC anhydride. As a second component, a UV cation generator was added to 0.1-15 parts by weight. As a third component, the multifunctional (containing at least two isocyanate or epoxide functions) isocyanates or epoxides were added to 0.1 to 5 parts by weight.

These Component mixture was then used as hot melt pressure sensitive adhesive z. B. over a coating nozzle on a carrier (For example, polyester film or BOPP film) in the form of a layer coated and selectively with UV light (for example Hg low pressure lamp or emission emitter) through a shadow mask. Then it became the pressure-sensitive adhesive tape thus prepared by a solvent bath guided (For example, toluene or acetone) and then dried again.

introduction of protection

HEMA

Hydroxyethylmethacrylat

HPA

Hydroxypropylacrylat

4-HS

4-Hydroxystyrol

For the introduction of BOC groups into the base polymers, the following monomers were conventionally incorporated into the polymer by free radical polymerization:

HEMA

hydroxyethyl methacrylate

HPA

hydroxypropyl acrylate

4-HS

4-hydroxystyrene

example 1

One for radical Polymerizations Conventional 2 L glass reactor was mixed with 40 g HEMA, 80 g of methyl acrylate, 280 g of butyl acrylate, and 300 g of acetone / isopropanol (97: 3) filled. After 45 minutes Passage of nitrogen gas with stirring, the reactor was on Heated to 58 ° C and 0.4 g of AIBN [2,2'-azobis (2-methylbutyronitrile)] added. Subsequently became the outer heating bath at 75 ° C heated and the reaction is carried out constantly at this outside temperature. To 4 and 6 h was diluted with 150 g of acetone / isopropanol mixture. To 48 h reaction time, the polymerization was stopped and on Room temperature cooled.

Example 2

It The procedure was analogous to Example 1. The polymerization was 40 g HPA, 80 g methyl acrylate, 80 g isobornyl acrylate and 200 g 2-ethylhexyl acrylate used. The solvent amounts were retained.

Example 3

It The procedure was analogous to Example 1. The polymerization was 200 g 4-hydroxystyrene, 150 g 2-ethylhexyl acrylate and 60 g methyl acrylate used. The solvent amounts were retained.

Subsequently were the polymers 1-3 protected in a polymer-analogous reaction. Suitable for the reaction Di-tert-butyl dicarbonate with catalytic amounts of N, N-dimethylaminopyridine or the reaction with chloroformic acid tert-butyl ester with preceding Deprotonation by sodium hydride.

a) polymer-analogous reaction with di-tert-butyl dicarbonate

The Polymers from Examples 1-3 (100 g each) were dissolved in an acetone / toluene mixture (500 ml) and stirred 1.2 equivalents Di-tert-butyl dicarbonate (based on the number of hydroxyl groups), solved in 150 ml of toluene. After 24 h, the reaction was stopped and the solvents removed in a vacuum.

b) Polymer-analogous reaction with chloroformic acid tert-butyl ester

The Polymers from Examples 1-3 (200 g each) were dried in vacuo and then in 500 ml of toluene dissolved. While stirring and under argon atmosphere became 1 equivalent NaH (based on the number of hydroxy groups) added. To 60 minutes of reaction time, 1.5 equivalents of tert-butyl chloroformate were added dropwise and the reaction was for 24 h at 80 ° C heated. After cooling to Room temperature was added aqueous ammonium chloride solution, extracted the organic phase several times with aqueous solution and dried the polymer at 60 ° C for 24 H.

c) reaction of the monomers with di-tert-butyl dicarbonate

The Monomers HEMA, HPA or 4-HS were dissolved in THF and added with stirring 1.2 equivalents of di-tert-butyl dicarbonate (based on the number of hydroxyl groups). After 24 h the reaction was stopped and the solvent removed in vacuo. The BOC-protected Products were purified by distillation.

By the implementation changed the comonomer composition is not, only the hydroxy groups were protected by BOC groups. The resulting protected Compounds are hereinafter referred to as 1-BOC (from Example 1 and BOC), 2-BOC (from example 2 and BOC) and 3-BOC (from Example 3 and BOC).

alternative Examples 1-BOC to 3-BOC can be obtained by the polymerization BOC-protected monomers produce:

Networking the samples

All Samples were selectively irradiated with a steel shadow mask. As a shadow mask were screen masks with 50% passage and a mesh size of 60 μm used.

Example 1va

100 of the adhesive composition 1-BOC g (50% solution) was mixed with 2 g Triacrylsulfoniumhexafluorophosphat (Cyracure UVI-6990 ^® (Union Carbide]; mixed 50% solution) and 5 g of aromatic polyisocyanate (Desmodur L75 ^® [BAYER AG]). After homogenization (removal of the solvent), the adhesive was spread on a 25 micron thick Saran-primed PET film (layer thickness Saranprimer: 2 microns), irradiated for 60 seconds with UV light through the shadow mask and heated at 140 ° C for 15 minutes. For UV irradiation, a xenon chloride radiator (VIB 308 Bulb (FUSION) was used.) Subsequently, the pressure-sensitive adhesive tape was placed in toluene for 30 minutes and then dried at 120 ° C. for 10 minutes.

Example 2va

100 of the adhesive g of 2-BOC (50% in solution) were mixed with 2 g Triacrylsulfoniumhexafluorophosphat; mixed and 5 g of aromatic polyisocyanate (Desmodur L75 ^® [BAYER AG]) (Cyracure UVI-6990 ^® [UNION CARBIDE] 50% solution). After homogenization (removal of the solvent), the adhesive was spread on a 25 micron thick Saran-primed PET film (layer thickness Saranprimer: 2 microns), irradiated for 60 seconds with UV light through the shadow mask and heated at 140 ° C for 15 minutes. For UV irradiation, a xenon chloride emitter (VIB 308 Bulb [FUSION]) was used. Subsequently, the pressure-sensitive adhesive tape was placed in toluene for 30 minutes and then dried at 120 ° C for 10 minutes.

Example 3va

100 of the adhesive g of 3-BOC (50% in solution) were mixed with 2 g Triacrylsulfoniumhexafluorophosphat; mixed and 5 g of aromatic polyisocyanate (Desmodur L75 ^® [BAYER AG]) (Cyracure UVI-6990 ^® [UNION CARBIDE] 50% solution). After homogenization (removal of the solvent), the adhesive was spread on a 25 micron thick Saran-primed PET film (layer thickness Saranprimer: 2 microns), irradiated for 60 seconds with UV light through the shadow mask and heated at 140 ° C for 15 minutes. For UV irradiation, a xenon chloride emitter (VIB 308 Bulb [FUSION]) was used. Subsequently, the pressure-sensitive adhesive tape was placed in toluene for 30 minutes and then dried at 120 ° C for 10 minutes.

Example 1vb

100 of the adhesive composition 1-BOC g (50% in solution) were mixed with 2 g Triacrylsulfoniumhexafluorophosphat; mixed and 1 g bisepoxidiertem bisphenol A (Rutapox 164 ^® [BAKELITE AG]) (Cyracure UVI-6990 ^® [UNION CARBIDE] 50% solution) , After homogenization (removal of the solvent), the adhesive was extruded onto a 25 μm thick Saran-primed PET film (layer thickness Saranprimer: 2 μm) irradiated for 60 seconds with UV light irradiated through the shadow mask and tempered at 140 ° C for 15 minutes. The xenon chloride radiator (VIB 308 Bulb [FUSION]) was used for UV irradiation. Subsequently, the pressure-sensitive adhesive tape was placed in toluene for 30 minutes and then dried at 120 ° C for 10 minutes.

Results

To check the adhesive properties of the inventive method The microstructured pressure-sensitive adhesive tapes produced became the instant adhesive power determined on steel. The measured values are listed in Table 1.

The Measurements prove that all examples have tacky properties and thus can be used as pressure-sensitive adhesive tapes. Farther decreed the pressure-sensitive adhesives over their structure a very soft peel. The pressure-sensitive adhesives are therefore excellent for suitable for reversible applications. In addition, can be surprising with this method Pressure-sensitive adhesive dots on the carrier generate their height is larger as her diameter. This is a clear advantage over the conventional screen printing technique. Furthermore, the pressure-sensitive adhesive points chemically on the carrier tied, so that there is a very good anchorage here. Here in There is another advantage of this method over the Screen printing technology.

Claims (6)

Process for producing a pressure-sensitive adhesive film with rastered adhesive surface, characterized by locally selective crosslinking of a layer of a Pressure-sensitive adhesive on a carrier material and subsequently Removal of the PSA in the non-crosslinked areas, so that the crosslinked areas act as pressure-sensitive adhesive elements on the substrate remain. Method according to claim 1, characterized in that that • first one A pressure-sensitive adhesive which contains a polymer having functional groups (G1) which is functionalized - initially protected, - in the Able to thermally cause crosslinking of the PSA or to support, - acid catalysis deprotected can be  With Photocatalyst generators are coated on a carrier material, • the PSA layer locally selectively irradiated with UV light, • the PSA layer subsequently is selectively crosslinked and • then the non-crosslinked areas of the PSA are removed. Method according to claim 2, characterized in that that as functional groups (G1) hydroxy groups are contained, which by BOC groups Protected (tert-butoxycarbonyl) protected. Method according to at least one of the preceding Claims, characterized in that the length and width dimensions the pressure-sensitive adhesive elements and / or the distances between the pressure-sensitive adhesive elements the pressure-sensitive adhesive film in the micrometer range or smaller. Method according to at least one of the preceding claims, characterized in that the PSA is a mixture of a) 85-99.8 wt .-% (based on the polymer mixture) of a polyacrylate copolymer based on a1) one or more acrylic acid esters and / or methacrylic acid esters the following formula CH ₂ = CH (R ¹ ) (COOR ² ), where R ² = H or CH ₃ and R ^{2 is} an alkyl chain having 1-20 C atoms, to 65-99 wt .-%, based on a), a2) optionally one or more olefinically unsaturated monomers having further functional groups (G2), to 0-15 wt .-%, based on a), a3) of one or more acrylates and / or methacrylates whose alcohol component contains tert-butoxycarbonyl (BOC) and / or hydroxyl groups, to 1 -20% by weight, based on a), b) 0.1-10% by weight, in particular 0.5-1% by weight (based on the polymer mixture), of one or more photocation generators, c) 0.1- 5 wt .-%, in particular 0.5-1 wt .-% (based on the polymer mixture) of one or more bifunctional or multifunctional crosslinking agents, in particular isocyanates or epoxides, is used. Pressure-sensitive adhesive film, obtainable by a process according to one of the preceding claims.