DE102014222723A1 - Process for the indirect plasma treatment of release layers - Google Patents

Abstract

The present invention relates to a method for the indirect plasma treatment of a release layer, comprising the steps of: introducing a plasma gas into a discharge space; Exciting the plasma gas into a plasma state by discharge; Blowing out the plasma gas in a plasma state from the discharge space; and exposing the release layer to the plasma gas in a plasma state after purging the plasma gas from the discharge space. The invention further relates to release layers obtainable by this process; Release liner comprising a carrier and such a release layer; and adhesive tapes comprising the release liner according to the invention and at least one adhesive.

Description

Technical field of the invention

The present invention relates to a process for the indirect plasma treatment of a release layer, comprising the steps of (i) introducing a plasma gas into a discharge space; (ii) exciting the plasma gas into a plasma state by discharge; (iii) blowing out the plasma gas in a plasma state from the discharge space; and (iv) exposing the release layer to the plasma gas in a plasma state after purging the plasma gas from the discharge space, wherein the purging of the plasma gas in a plasma state from the discharge space is preferably by a plasma gas flow. The present invention further relates to release layers obtainable by the method described herein, as well as release liners comprising a support and the release layer. Also described are adhesive tapes comprising the release liner described herein and an adhesive.

General state of the art

Adhesive tapes are often wound into a roll in the form of an Archimedean spiral at the end of the manufacturing process. For this purpose, the adhesive is covered before winding the adhesive tape with a release liner (also referred to as release or covering). Release liners are also used for covering flat goods such as labels. In the case of double-sided adhesive tapes, release liners can be adjusted in such a way that one side of the adhesive tape is first exposed during the unwinding of the tape. This is possible if the release values between the respective release layer and the adhesive on the individual sides of the double-sided adhesive tape differ from one another.

The release liners used are paper or film carriers which are provided with a release layer in order to reduce the adhesion tendency of adhering products to these surfaces (release-effective function). The release agents used are various substances, such as silicones, fluorinated silicones, fluorinated alkanes and polyolefins, silicone copolymers, carbamates, waxes or mixtures thereof. Silicones have largely prevailed over the last few years due to their good processability and advantageous release properties. Due to the large number of different compositions, silicones can also be used to adjust the release values of release liners. The level of the respective peel force of a pressure-sensitive adhesive of a silicone-based release liner is usually adjusted by silicone resins and in particular by so-called MQ resins. A good overview of silicone resins and especially MQ resins offers Satas, Handbook of Pressure Sensitive Adhesive Technology, 3rd Edition, p. 664 , The different peel forces of the individual release layers compared to an adhesive are the result of different MQ resin fractions in the respective release composition.

Although it is possible with the MQ resins to specifically adjust the release forces of a release liner and in particular the release forces of the release liner from the individual sides of a double-sided adhesive tape, a specific silicone composition must be selected for each desired release force coated on a carrier and cured. This makes it necessary to use and also stockpile multiple release liners with different MQ resin contents when there is a need for different release properties. Due to the large variety of different adhesive composition such storage is hardly feasible. Furthermore, the use of many different coating compositions can lead to increased waste material, since the individual coating compositions can not be permanently stored. Instead, the particular coating composition must be prepared just prior to application.

In addition, it is known that the use of MQ resins can change the release force profile of silicone-coated release liners. The separation force profile is the dependence of the release force on the withdrawal speed of the release liner from the adhesive. Typically, the force required to remove a release liner from an adhesive increases (or decreases) in the range of low take-off speeds (from 0 to, for example, 20 m / min) with increasing take-off speed before a release force sets in which is only slightly lower than the take-off force depends. Whether the release force increases in the range of low take-off speeds (increasing profile) or decreases (sloping profile) depends on the content of MQ resin in the formulation. For high resin contents, sloping profiles are often observed and for low resin contents frequently rising profiles.

If the proportion of MQ resins in the silicone composition of the release coating is increased in order to increase the separation forces of the release liner compared to a specific adhesive, it can come in the separation force profile to a reversal of the separation force curve. Thus, the profile of the release force profile in silicone resin-containing formulations is difficult to predict, especially in the range of low take-off speeds. For example, it has been observed that in the low pull-off rate range of 0-20 m / min, the release values are high in the case of a high MQ resin concentration and decrease with increasing drawdown, although the release values are low at low draw speeds in the case of low MQ resin or resin free formulations and usually increase slightly with increasing take-off speed.

The use of MQ resins in silicone-based release coatings is therefore not always ideal for the specific adjustment of certain release forces.

Also known from the prior art is the corona treatment of silicone-coated carrier materials. However, such known from the prior art materials are not release liners that could be used for strong pressure-sensitive acrylate adhesives with high bond strengths on steel. Because the effect achieved by a classical, direct corona treatment leads to such a strong interaction between the above-mentioned strongly adhesive adhesives and the corona-treated surface that such a treated substrate is no longer suitable as a release material.

Object of the present invention

It is an object of the present invention to address the drawbacks of the prior art and to provide an improved physical process by means of which the release values of release liners can be adjusted in a simple manner, even for strongly tacky products, without it there is a significant change in the profile of the release force profile compared with an untreated liner (reference liner) or an excessive interaction between the corona-treated surface and the adhesive due to over-treatment.

Summary of the present invention

• – Einbringen eines Plasmagases in einen Entladungsraum;
• – Anregen des Plasmagases in einen Plasmazustand durch Entladung;
• – Ausblasen des Plasmagases in einem Plasmazustand aus dem Entladungsraum; und
• – Aussetzen der Release-Schicht dem Plasmagas in einem Plasmazustand nach dem Ausblasen des Plasmagases aus dem Entladungsraum.

The present invention addresses this problem and the problems of the prior art by providing a physical process for the indirect plasma treatment of a release layer, comprising the steps:

• - introducing a plasma gas into a discharge space;
• - exciting the plasma gas into a plasma state by discharge;
• - Blowing the plasma gas in a plasma state from the discharge space; and
• Exposing the release layer to the plasma gas in a plasma state after blowing out the plasma gas from the discharge space.

Surprisingly, it has been shown that the indirect plasma treatment in relation to the standard plasma treatment has a very low efficiency, which can be reduced by suitable measures again. As a result, the indirect plasma treatment is particularly suitable for the generation of low treatment effects.

In a preferred embodiment of the invention, the blowing out of the plasma gas takes place in a plasma state from the discharge space by a plasma gas flow. Particularly preferably, the plasma gas is excited into a plasma state via an electrical high voltage having a frequency of 2000 to 100,000 Hz, wherein the high voltage is switched on and off with a switching frequency of 30 to 5000 Hz.

The present invention further relates to a release layer obtainable by the process according to the invention; Release liner, comprising a support and the release layer obtainable by the process according to the invention; and an adhesive tape comprising the release liner and an adhesive in contact with the release liner release layer.

In the method of indirect plasma treatment of a release layer described herein, a plasma gas is excited with a high voltage electrical discharge. For this purpose, an electrode or an electrode system by a high-frequency generator with an AC voltage of about 5-50 kV, and a frequency between 2 and 100 kHz, preferably supplied between 18-100 kHz.

The high-voltage discharge occurs in a discharge space between an electrode system lying at a high electrical potential (also referred to below as the electrode system) and a counterelectrode, which is usually at ground potential. In the present case, the discharge space is understood to be the region between the electrode system and the counterelectrode. Here, either the electrode system or the counter electrode is coated with a high-voltage resistant insulator. As an insulator is preferably a layer of silicone rubber, ceramic or glass in question. Alternatively, both the electrode system and the counter electrode can be coated with such a high-voltage resistant insulator.

The inventive method for indirect plasma treatment is preferably carried out at atmospheric pressure. By "atmospheric pressure", the present invention means a pressure of 0.5 to 2 times the ambient pressure, preferably 0.75 to 1.5 times, more preferably 0.9 to 1.2 times the ambient pressure. In the case of a plasma treatment in which the individual steps of the method according to the invention are carried out at said pressures, the present invention also speaks of indirect "atmospheric pressure plasma treatment", which is also referred to herein as indirect "corona treatment".

In the treatment of the release layer according to the invention, the plasma gas is blown out of the discharge space after being excited, in order to expose a release layer to the plasma gas in a plasma state.

The blowing out takes place in this case preferably by a stream of the plasma gas. According to the plasma gas is thus preferably first passed into the discharge space between the electrode system and the counter electrode, excited in a plasma state and then led out in a plasma state from the discharge space. In this case, the introduction of the plasma gas into the electrode space and the carrying out of the plasma gas after the excitation into a plasma state from the electrode space are preferably carried out continuously.

The electrons emerging from the electrode experience a high acceleration in the electric field between the electrode system and the counter electrode. It is assumed that portions of the energy in collisions are delivered to the molecules of the plasma gas, in the case of air as a plasma gas so mainly to oxygen and nitrogen molecules. In the case of air, this leads to a dissociation or ionization of mainly oxygen and nitrogen molecules.

When the plasma gas is excited into a plasma state by discharge (also called "corona discharge" in the case of atmospheric pressure plasma treatment), a plurality of arcs are generated. If the electrode or the counterelectrode has a dielectric coating at ground potential, the discharge gap consisting of the arcs is limited by this dielectric coating. The corona discharge, which arises when the plasma gas is excited into a plasma state by discharge, is therefore also referred to as a barrier discharge.

In order to obtain a uniform treatment effect over the entire width of the release layer to be treated, it is expedient to blow the plasma gas out of the discharge space such that the entire width of the release layer to be treated is exposed to the plasma gas in a plasma state. For this purpose, the plasma gas in a plasma state is passed out of the discharge space through an opening, for example through a slot, the opening preferably extending over the entire width of the release layer to be treated. An opening extending across the width of the surface to be treated has the advantage that a uniform treatment over the entire width of the surface can be ensured.

Depending on the size of the opening, preferably the slot, the intensity of the treatment effect can also be varied. This has the background that a relatively small exit orifice, compared to a relatively large exit orifice, results in a high local concentration of plasma gas in a plasma state. The intensity of the treatment effect can also be controlled by the distance between the outlet opening of the plasma gas in a plasma state from the discharge space and the surface of the release layer to be treated. Preferably, the distance between the outlet opening and the release layer to be treated is about 1-10 mm.

By adjusting the generator power, it is possible to adjust the intensity of the treatment effect depending on the web speed such that the release layer to be treated Dose of 0.01 to more than 100 W · min / m2 can be suspended. For the purposes of the present invention, web speed is understood to mean the speed at which the release layer to be treated is passed through the plasma gas blown out of the discharge space. The web speed may be zero or may be in a range of greater than zero to 500 m / min and more. Typically, a facility for handling a release layer is designed so that it is not the rate-limiting factor in an overall facility. By a targeted adjustment of the distance between the outlet opening and the surface on the one hand and by adjusting the size and nature of the outlet opening, wherein z. B. only a selectable partial flow reaches the release layer, and the gas flow amount on the other hand, it is possible to reduce the intensity of the treatment effect to a fraction of the treatment effect over a direct plasma / corona treatment at the same dose, so that any small treatment effects can be realized ,

In a preferred embodiment, the release layer applied, for example, to a support can be guided through the treatment zone without a counter-roller on the back of the support, so that the side of the release layer facing the discharge opening of the discharge space is treated. The treatment effect is much lower than when a guide of the carrier on a counter-roller through the treatment room, which is contrary to a desired low treatment effect. However, a release layer also experiences a treatment on the side of the carrier facing away from the discharge opening of the discharge space, but this treatment is always significantly lower than the release layer facing the discharge opening of the discharge space.

In a further preferred embodiment of the invention, the release layer applied, for example, to a carrier can be guided over a roller so that the release layer facing the outlet opening of the discharge space is treated.

Air between the roller and the carrier can also cause an undesirable treatment effect on the back of the carrier. In order to suppress unwanted treatment of the back of the carrier, it may be useful to avoid introduced by the web movement and roller rotation drag air between the material to be treated and the roller. For this purpose, the air before between the roller and the carrier, by means of a pressure roller, an air nozzle, by electrostatic application, for. B. by means of a charging electrode R130 Fa. Eltex, or another measure be pressed out.

In a preferred embodiment of the invention, the plasma gas is excited into a plasma state via an electrical high voltage having a frequency of 2000 to 100,000 Hz, wherein the high voltage is switched on and off with a switching frequency of 30 to 5000 Hz. In principle, the invention strives for uniform treatment effects over the entire electrode width of the corona or plasma system. For a uniform discharge across the width of the electrodes in the case of a pulsed excitation of the plasma gas, a relatively high minimum electrical power P _{min is} required. This means that at a certain web speed under normal conditions, a certain minimum treatment effect can not be undercut. This minimum electrical power is typically one-fifth to one-tenth of the maximum useful generator power for a particular electrode design. On the one hand, this means that the possible power range of the generator can not be exploited due to the necessary minimum power for the electrodes, and the web speed can only be varied by a factor of 5-10 in the case of the requirement for a constant treatment effect. On the other hand, the treatment effect in the case of release layers despite the indirect plasma treatment in a continuous plasma discharges sometimes at low web speeds without the measures described above at the exit slit to reduce the treatment effect is still so pronounced that even at the lowest possible treatment strength separation forces against strongly pressure-sensitive adhesives For example, strongly tacky acrylate adhesives are achieved which make it difficult to use the treated surface as a release layer with particularly low release forces for such an adhesive, in particular if a larger speed range is to be covered.

In other words, it is difficult with a conventional, ie unpulsed plasma treatment to produce release layers with particularly low release values in a range of 2 to 100 cN / cm against strongly pressure-sensitive adhesives a constant required release value at low speeds and over a wide speed range receive. If, for example, the speed is increased by a factor of 25 from 5 m / min to 125 m / min, the power of the corona generator must also change by a factor for a constant treatment dose. Normal unpulsed treatment stations can only cover a factor of 5 to 10 in the power range. Often there is also the requirement that Even with a stop on the train no over- and no sub-treatments are created, whereby the required performance range is once again significantly extended to very small performances.

This aspect of the invention is based on the finding that the limit for the minimum treatment effect can be reduced by pulses (rapid periodic switching on and off) of the high-frequency discharge, preferably by pulsing the corona discharge. In this case, an electrical power P is set equal to or above the minimum power of the plasma unit P _min during the switch-on, so that during this time a homogeneous discharge, preferably a homogeneous corona discharge, is ensured across the width of the electrodes. Pulses can be used to reduce the minimum effective electrical power for uniform treatment across the web width to less than 1% of the minimum electrical power without pulses. In the non-pulsed state, the power in a treatment station can be varied by a factor of 5-10 for sensible use. With the combination of pulsing and normal power setting, the effective power can be varied by a factor of about 500. A safe ignition over the entire web width occurs at each pulse, as long as the power during the on-time is at least as large as the minimum power P _min for a uniform treatment across the web width.

The effective electric power P _{effective of} a pulsed discharge is given by the ratio of the turn-on t ₁ to the repetition time T and the power P during the turn-on time.

For a set power of P = P _min during the on-time, an effective power of:

In a preferred embodiment of the invention, the repetition time T is varied at a fixed switch-on time t ₁ for setting the effective power. Alternatively, the repetition time T can be varied at a fixed switch-on time t ₁ . In another embodiment of the invention, both the on time and the reheat time are varied simultaneously.

In a particularly preferred embodiment of the invention, the discharge, ie the excitation of the plasma gas into a plasma state, is pulse width modulated. In the case of pulse width modulation ("PWM"), the on-time t _{1 is changed} at a fixed recovery time T for the variation of the effective power. The switch-on time t ₁ is preferably 0.002 to 33 ms.

By pulsing, d. H. the rapid periodic switching on and off of the discharge makes it possible to increase the treatment dose, ie. H. To choose the energy incident on a square meter of treated surface particularly low and yet to ensure a homogeneous treatment over the entire electrode width.

D:

Behandlungsdosis in W·min/m²

P_effektiv:

effektive Generatorleistung in W

v:

Maschinengeschwindigkeit in m/min, mit der die zu behandelnde Oberfläche durch die Plasmaatmosphäre bewegt wird, wobei diese Plasmaatmosphäre durch das Ausblasen des Plasmagases aus dem Entladungsraum erzeugt wird

b:

Elektrodenbreite in m

The calculation of the treatment dose is carried out according to the formula (1).

D:

Treatment dose in W / min / m ²

P _effective :

effective generator power in W

v:

Machine speed in m / min, with which the surface to be treated is moved through the plasma atmosphere, this plasma atmosphere is generated by the blowing out of the plasma gas from the discharge space

b:

Electrode width in m

By selectively adjusting the power of the dose can be adjusted at a certain engine speed such that the resulting dose D of the target dose D corresponds _to. P _soll = P _effective = D _soll * v

The pulsing of the high-frequency discharge takes place according to the invention with a switching frequency of 30 to 5000 Hz. This ensures that the release layer can be exposed to a dose of 0.01-6 W · min / m ² . In a preferred embodiment of the invention, the dose to which the release layer is exposed in the method according to the invention is 0.01-6, preferably 0.01-3 W · min / m ² .

By adjusting the treatment dose to the range mentioned, the separation behavior of the release layers described herein can be adjusted in a targeted manner, without reversing the course of the release force profile in the region of low take-off speeds. The release force of the treated release layer with respect to a particular adhesive surface increases with increasing treatment dose. Furthermore, the inventive method allows the treatment of release layers with a plasma discharge such that the treated release layers are also suitable as release materials against strongly adhesive surfaces such as acrylate-based PSAs. In particular, the method according to the invention allows the provision of release layers whose release forces are in the range from 2 to 100 cN / cm in relation to strongly adhesive adhesives.

By exciting the plasma gas into a plasma state by discharge, an atmosphere (also referred to herein generally as a "plasma atmosphere" and, in the case of corona treatment, a "corona atmosphere") is formed which is suitable for plasma treatment of the release layer. By the indirect plasma treatment, preferably by an indirect plasma treatment, in which the high-frequency corona discharge is switched on and off selectively, d. H. by the pulsed excitation of the plasma gas, the inventive method allows a particularly gentle yet uniform treatment of the release layer. Such a gentle treatment with a comparatively low treatment effect would not be possible in the case of an unpulsed conventional plasma treatment and would not allow the provision of release layers with particularly low separation forces.

In a preferred embodiment of the invention, the plasma gas consists of nitrogen, carbon dioxide, argon, helium, air or a mixture of two or more of these gases. In a further embodiment of the invention, the plasma gas may further contain hydrogen.

In a likewise preferred embodiment of the invention, the release layer is applied to a carrier. Preferably, the carrier is over the entire surface, d. H. covering and not only selectively covered by the release layer, so that the thickness of the release layer is preferably in a range of 0.05-5 microns.

In a further embodiment of the invention, the release layer contains at least one silicone, at least one fluorinated silicone, at least one fluorinated or partially fluorinated alkane or polyolefin, at least one silicone copolymer, at least one carbamate, at least one wax, or mixtures of two or more of the mentioned substances. The release layer is particularly preferably silicone-based. For the purposes of the present invention, "silicone-based" means that the release layer comprises at least one silicone-based polymer (hereinafter also referred to as "base polymer"). The base polymers used are polysiloxanes, preferably functionalized and unfunctionalized polydimethylsiloxanes.

Preferably, the composition underlying the release layer contains up to 80 parts by weight, more preferably up to 40 parts by weight of a silicone resin, based on 100 parts by weight of silicone resin and base polymer. Suitable silicone resins are known resins, preferably MQ resins. Suitable resins are described D. Statas in: Handbook of Pressure Sensitive Adhesive Technology, 3rd Edition, page 664 , Commercially available examples of particularly preferred resins are RCA 395 from Bluestar Silicones, Syl- ^Off® SL 40 from Dow Corning, and ^CRA® 17 from Wacker Silicones. In a further embodiment of the invention, the composition underlying the release layer is free of silicone resins.

The release layer to be treated by the method according to the invention can be based on solvent-containing and / or solvent-free systems. A "solvent-containing system" means that the system in question is applied as an actual solvent-containing system, after which, however, usually only a maximum of traces of the solvent in the release layer are present after thermally initiated drying and crosslinking. The skilled person nevertheless speaks of a "solvent-containing system" and thus characterizes the special properties of such a solvent-based release layer.

The composition on which the release layer is based can be radiation-crosslinking (UV or electron beam), condensation-curing or addition-crosslinking. The composition which forms the release layer to be treated is preferably addition-curing.

The composition underlying the release layer is preferably a crosslinkable silicone system. These include mixtures of crosslinking catalysts, so-called thermally curable condensation or addition-crosslinking polysiloxanes and crosslinking component. For condensation-crosslinking silicone systems, tin compounds such as dibutyltin diacetate are frequently included in the composition as crosslinking catalysts.

• • ein alkenyliertes Polydiorganosiloxan (insbesondere lineare und verzweigte Polymere mit endständigen und nichtendständigen Alkenylgruppen),
• • ein Polyorganowasserstoffsiloxan-Vernetzungsmittel sowie
• • einen Hydrosilylierungskatalysator.

The composition underlying the release layer is particularly preferably an addition-crosslinking silicone system. Silicone-based release coatings on addition-curing basis can be cured by hydrosilylation. These release agents usually comprise the following components:

• An alkenylated polydiorganosiloxane (especially linear and branched polymers containing terminal and non-terminal alkenyl groups),
• A polyorganohydrogensiloxane crosslinking agent as well
• • a hydrosilylation catalyst.

As catalysts for addition-crosslinking silicone systems (hydrosilylation catalysts), for example, platinum or platinum compounds, such as, for example, the Karstedt catalyst (a Pt (0) complex compound) have prevailed. Alternatively, rhodium compounds can be used.

Furthermore, it is also possible to use photoactive catalysts, so-called photoinitiators, in combination with UV-curable cationically crosslinking siloxanes based on epoxide and / or vinyl ethers or UV-curable free-radical crosslinking siloxanes, such as acrylate-modified siloxanes. Likewise, the use of electron beam curable silicones (eg silicone acrylates) is possible. Corresponding systems may also contain other additives, such as stabilizers or leveling agents, depending on the intended use.

Also useful are compositions in which the crosslinking reaction between organopolysiloxanes having hydrocarbyl substituted with mercapto groups bonded directly to the silicon atoms and organopolysiloxanes having vinyl groups bonded directly to the silicon atoms is in the presence of a photosensitizer. Such masses are used for example in the US 4,725,630 A1 described.

When using the example in the DE 33 16 166 C1 The organopolysiloxane compositions containing epoxy groups substituted hydrocarbon radicals directly bonded to the silicon atoms are induced by the release of a catalytic amount of acid which is obtained by photo-decomposition of added onium salt catalysts. Other cationic-mechanism-curable organopolysiloxane compositions are materials having, for example, propenyloxysiloxane end groups.

In addition to the base polymer and a possible silicone resin, in the composition on which the release layer to be treated according to the invention is based, further constituents such as anchoring aids; organic and / or inorganic pigments; Fillers such as carbon black and organic and / or inorganic particles (eg polymethyl methacrylate (PMMA), barium sulfate or titanium oxide (TiO ₂ )); and organic and / or inorganic antistatics such as ionic polyelectrolytes, organic salts, ionic liquids, metal powders (eg silver powder), graphite and carbon nanotubes.

In a preferred embodiment of the invention, the composition on which the release layer to be treated according to the invention is based, in each case independently 0 to 5 parts by weight of one or more anchoring aids, one or more pigments, one or more fillers, and one or more antistatic agents, respectively based on 100 parts by weight of base polymer and silicone resin.

The inventive method is suitable for targeted adjustment of the release forces of release liners. In this case, the indirect plasma treatment as described herein allows an increase in the separation forces, without significantly changing the separation force profile, ie the profile of the release force as a function of the withdrawal speed, the (untreated) release layer. In this respect, the method according to the invention allows the provision of release liners in which the absolute release force values can be set without significant change in the release force profile as a function of the dose. By the term "setting the absolute release force values without substantially changing the release force profile" is meant that the shape of the diagram does not change significantly when the release forces (Y-axis) are applied against the withdrawal speed (X-axis). Instead, the profile shifts only in its absolute values (Y-axis) as a function of the treatment dose. However, the shape of the separation force profile, ie the shape of the curve itself, remains essentially unchanged. Obtaining the release force profile over different treatment doses is a significant advantage of the method according to the invention. Because of this, starting from a surface to be treated in a simple way release layers with different degrees of separation behavior can be produced against one and the same adhesive. The release force profiles of the different release layers are still preserved. Overlapping the release forces of different release layers can thus be avoided both at low and at high take-off speeds. This has the advantage that in the case of double-sided adhesive tapes, even with only a slight difference in the release values, selective removal of exactly the release liner with the lower release force from the adhesive is possible without having to rely on different silicone compositions. Especially in the field of highly automated processes errors are thus avoided, since an identical or at least similar separation force profile ensures a safe and uniform difference in the separation forces between the two release layers and the adhesive over all take-off speeds. In addition, another advantage of maintaining known release force profiles is that adhesives can be transferred from a liner to a substrate, for example, without changing the process speed process parameters such. As pressure forces to readjust.

Against this background, the present invention also relates to release layers, which are obtainable by the process according to the invention, and release liners, comprising a support and a release layer.

In a preferred embodiment of the invention, this support is selected from the group consisting of polyethylene terephthalate (PET), polybutylene, polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC) and paper. Particularly preferred supports are glassine papers, clay-coated papers, Kraft papers, machine-grade papers and polyolefin-coated papers, and biaxially stretched PET, mono- and biaxially drawn PP, cast PP (extruded PP), HDPE and LDPE. Examples of suitable carriers which are provided with a release layer and are particularly suitable for treatment with the process according to the invention are siliconised glassine papers from Mondi (G-Liner), siliconized polyolefin-coated papers from Loparex (Polyslik ^TM ), siliconized PET films from Siliconature (SILPHAN S), siliconized mono- and biaxially stretched PP films, as well as cast aluminum films from Siliconature (SILPROP S, SILPROP M, SILPROP K) and siliconized HDPE and LDPE films from the company Mondi.

In a further aspect, the present invention relates to adhesive tapes comprising a release liner whose release layer has been treated by the method described herein. In the case of these adhesive tapes, at least one side of the adhesive of the adhesive tape is in contact with the release layer obtainable by the process according to the invention.

In a particularly preferred embodiment, the present invention relates to adhesive tapes in which the adhesive which is in contact with the release liner of the invention comprises an acrylate-based adhesive, preferably an acrylate-based adhesive having a bond strength to steel of 1-20, particularly preferably of 5 Is -15 N / cm. In an exemplary embodiment of the invention, the coating weight of the adhesive is 50 g / m 2. The adhesive forces on steel mentioned herein are determined as follows: A 2 cm wide and 25 cm longer strip of the adhesive tape is glued to the test plate by rolling it twice five times with a winding speed of 10 m / min using a 4 kg roller. The test plate is clamped in the lower clamping jaw of the tensile testing machine (BZ2.5 / TN1S Zwick) and the adhesive tape is stretched over its free end by means of a tensile testing machine (BZ2.5 / TN1S Zwick) at a peeling angle of 180 ° at a speed of 300 mm / min deducted. The necessary force is determined. The measurement results are averaged over three measurements and normalized to the width of the strip in N / cm. The test plates are polished steel plates (material no. 1.4301, DIN EN 10088-2 , Surface 2R) with the surface roughness Ra = 80-130 nm).

In a further, likewise preferred embodiment of the invention, the adhesive which is in contact with the release liner of the release liner of the adhesive tape described herein has a maximum proportion of acrylic acid and methacrylic acid (hereinafter also "(meth) acrylic acid content") 5, preferably 3, more preferably 1 weight percent, based on the total composition of the adhesive. By this is meant that the proportion of acrylic acid and methacrylic acid units in the adhesive composition together does not exceed said values. The term "acrylic acid and methacrylic acid units" includes both copolymerized acrylic acid and methacrylic acid within possible (sticky) sticky polymers of the adhesive as well as a possible (residual) monomer content of acrylic acid and methacrylic acid in the composition. In other words, the proportion of polymerized acrylic acid and methacrylic acid units and possible residual monomers in its sum does not exceed the maximum proportions mentioned.

Experimental part

The following exemplary experiments are intended to further illustrate the invention without unnecessarily limiting the invention by the choice of examples given.

Examples 1-8

D:

Coronadosis in W min/m²

P:

Generatorleistung in W

v:

Maschinengeschwindigkeit in m/min

b:

Elektrodenbreite in m

A double-sided siliconized PE-coated glassine release paper with a width of 330 mm was applied to a plasma system from VITO for indirect plasma treatment in which the discharge is produced between two electrodes arranged above the silicon layer of the release paper to be treated Plasma gas exposed in a plasma state. For this purpose, the flow of the plasma gas was adjusted so that the plasma gas (nitrogen with a residual oxygen content of 5 ppm) after being excited in a plasma state from the discharge space in the direction of the arranged under the electrodes release paper is pressed. Here, the release paper was moved at a web speed of 12 m / min to 100 m / min relative to the exit port of the plasma gas in a plasma state. The power of the corona system was set to 1000 watts for this indirect treatment. The gap between the housing with the electrodes and the release paper was 6 or 8 mm. The calculation of the treatment dose is carried out according to the formula (1). D = P / (v * b) (1)

D:

Coronadosis in W min / m ²

P:

Generator power in W

v:

Machine speed in m / min

b:

Electrode width in m

The release force of the pretreated release papers is determined by bonding with three test strips each 20 mm wide. The test strips used are test tapes with the product numbers tesa 7475 and tesa 7476. Tesa 7475 is an adhesive tape with a PET film as a carrier, on which an acrylate compound is applied (adhesion to steel 12.5 N / cm). Tesa 7476 is an adhesive tape with a fabric tape as a support on which a natural rubber adhesive is applied (bond strength to steel 8 N / cm). The samples are stored for 24 hours at 70 ° C for tesa 7475 and at 40 ° C for tesa 7476 under a weight load of the bond of 2 N / cm 2 before the measurement. After storage, the test strips are cut to a length of 220 mm and stored for two hours under test conditions. For the measurement, the upper test strip of the bond is placed in the upper jaw of a tensile tester as shown in AFERA 4001 is used, clamped. The lower test strip is clamped in the lower jaw. The jaw distance is 50 mm. The measurement is made at a speed of 300 mm / min, with which the jaws are moved apart. The mean value, determined over a distance of 100 mm, from three measurements of the force required for the separation of the bond corresponds to the release force. The measurements are carried out at a test climate of 23 ± 1 ° C and 50 ± 5% rel. Humidity carried out. The measured release force of the indirect corona treated release paper is shown in Table 1. Table 1: Release force against acrylic adhesive tape tesa 7475 and natural rubber adhesive tape tesa 7476. Example No. Dose [W min / m ² ] Gap setting [mm] Release force tesa 7475 [cN / cm] Release force tesa 7476 [cN / cm] 0 Reference. 0 6 5 18 1 16.7 6 11 22 2 33 6 15 23 3 67 6 25 27 4 139 6 54 34 5 16.7 8th 9 21 6 33 8th 15 23 7 67 8th 24 26 8th 139 8th 53 31

Examples 9-12

A double-sided siliconized glassine release paper with a width of 300 mm was applied to a corona system from VITO for indirect plasma treatment (plasma line), in which the discharge is produced between two electrodes arranged above the silicon layer of the release paper to be treated, a plasma gas Exposed to plasma state. For this purpose, the flow of the plasma gas was adjusted so that the plasma gas (nitrogen with a residual oxygen content of 5 ppm) after being excited in a plasma state from the discharge space in the direction of the arranged under the electrodes release paper is pressed. Here, the release paper was moved at a web speed of 25 m / min to 200 m / min relative to the exit port of the plasma gas in a plasma state. The power of the corona system was set to 1000 watts for this indirect treatment. The gap between the housing with the electrodes and the release paper was 4 mm. The calculation of the treatment dose is carried out according to the formula (1). The measurement of the separation forces was carried out as described for Examples 1-8. The measured separation forces are listed in Table 2. Table 2: Release force against acrylic adhesive tape tesa 7475 Example No. Dose [Wmin / m2] Release force tesa 7475 [cN / cm] 0 Ref. 0 6 1 8.3 7 2 16.7 16 3 33 34

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4725630 A1 [0050]
• DE 3316166 C1 [0051]

Cited non-patent literature

• Satas, Handbook of Pressure Sensitive Adhesive Technology, 3rd Edition, p. 664 [0003]
• D. Statas in: Handbook of Pressure Sensitive Adhesive Technology, 3rd Edition, page 664 [0043]
• DIN EN 10088-2 [0058]
• AFERA 4001 [0062]

Claims (20)

Process for the indirect plasma treatment of a release layer, comprising the steps: - introducing a plasma gas into a discharge space; - exciting the plasma gas into a plasma state by discharge; - Blowing the plasma gas in a plasma state from the discharge space; and Exposing the release layer to the plasma gas in a plasma state after blowing out the plasma gas from the discharge space. The method of claim 1, wherein the blowing out of the plasma gas takes place in a plasma state from the discharge space by a plasma gas flow. Method according to one of claims 1 or 2, wherein the exciting of the plasma gas is in a plasma state via a high voltage electrical with a frequency of 2000 to 100,000 Hz and the high voltage with a switching frequency of 30 to 5000 Hz on and off. A method according to any one of the preceding claims, wherein the plasma gas comprises nitrogen, carbon dioxide, argon, helium, air or mixtures thereof. Method according to one of the preceding claims, wherein the exciting of the plasma gas is pulse width modulated. Method according to one of the preceding claims, wherein the exciting of the plasma gas is pulsed at a variable repetition time and a fixed on-time or pulsed at variable repetition and variable on-time. Method according to one of the preceding claims, wherein the release layer is exposed to a dose of 0.01 to 60 W · min / m2. Method according to one of the preceding claims, wherein the release layer is applied to a carrier and covers the carrier over the entire surface. The method of claim 8, wherein during the step of exposing the release layer to the plasma gas in a plasma state after the plasma gas has been blown out of the discharge space via a counter roll through the plasma gas blown out of the discharge space. The method of claim 8, wherein the carrier without counter-roller and without a support is passed through the blown out of the discharge space plasma gas. Method according to one of the preceding claims, wherein the release layer is exposed only to a part of the blown out of the discharge space plasma gas. Method according to one of the preceding claims, wherein the release layer at least one silicone, at least one fluorinated silicone, at least one silicone copolymer, at least one carbamate, at least one fluorinated, partially fluorinated or unfluorinated alkane or polyolefin, at least one wax or mixtures of two or contains more of the substances mentioned. Method according to one of the preceding claims, wherein the composition underlying the release layer contains at least one silicone-based polymer. The method of claim 13, wherein the release layer underlying composition contains up to 80 parts by weight of a silicone resin, based on 100 parts by weight of silicone resin and silicone-based polymer. Release layer obtainable by the process according to any one of claims 1-14. Release liner comprising a carrier and a release layer according to claim 15. The release liner of claim 16, wherein the backing is selected from the group consisting of biaxially oriented polyethylene terephthalate, polybutylene, polypropylene, polyethylene, monoaxially stretched polypropylene, biaxially oriented polypropylene, PVC, cast PP, and paper. Adhesive tape comprising a release liner according to one of Claims 16 or 17 and at least one adhesive. Adhesive tape according to claim 18, wherein the at least one adhesive is in contact with the release layer of the release liner and / or with the release liner facing away from the release liner. An adhesive tape according to claim 19, wherein the at least one adhesive is in contact with the release liner release liner and does not exceed a maximum (meth) acrylic acid content of 5, preferably 3, more preferably 1 weight percent, based on the total composition of at least an adhesive that is in contact with the release liner Release Layer.