WO2013056952A1

WO2013056952A1 - Method for encapsulating an electronic assembly

Info

Publication number: WO2013056952A1
Application number: PCT/EP2012/068937
Authority: WO
Inventors: Thorsten Krawinkel
Original assignee: Tesa Se
Priority date: 2011-10-21
Filing date: 2012-09-26
Publication date: 2013-04-25
Also published as: DE102011085038A1; TW201333141A

Abstract

The invention relates to a method for encapsulating an electronic assembly against permeants, wherein an adhesive tape surface element is provided and applied to the regions to be encapsulated, wherein the adhesive tape surface element comprises at least one layer of an adhesive mass which can be bonded by means of actinic radiation, characterized in that the adhesive tape surface element is bonded in a first bonding step before application only in sub-regions by means of actinic radiation, the adhesive tape surface element is then applied, and the adhesive tap surface element is bonded by means of actinic radiation in another bonding step in a different region from the sub-regions of the first bonding step.

Description

description

Method for encapsulating an electronic device

The invention relates to a method for encapsulating an electronic device against permeants, in which an adhesive tape surface element is provided and applied to the areas to be encapsulated, wherein the adhesive tape surface element comprises at least one layer of an adhesive crosslinkable by means of actinic radiation. (Opto) Electronic devices are increasingly used in commercial products or are about to be launched. Such arrangements include inorganic or organic electronic structures, such as organic, organometallic or polymeric semiconductors or combinations thereof. These arrangements and products are rigid or flexible depending on the desired application, whereby there is an increasing demand for flexible arrangements. The production of such arrangements is effected, for example, by printing processes such as high-pressure, intaglio, screen printing, planographic printing or so-called "non-impact printing" such as thermal transfer printing, ink jet printing or digital printing, but vacuum methods such as chemical vapor deposition (CVD), physical vapor are also frequently used Deposition (PVD), plasma enhanced chemical or physical deposition (PECVD), sputtering, (plasma) etching or vapor deposition, the patterning is usually done by masks.

Electrophoretic or electrochromic structures or displays, organic or polymeric light-emitting diodes (OLEDs or PLEDs) in display and display devices or as illumination, electroluminescent lamps, light-emitting electrochemical devices may be mentioned as examples of (commercial) electronic applications which are already interesting in their market potential Cells (LEECs), organic solar cells, preferably dye or polymer solar cells, inorganic solar cells, preferably thin-film solar cells, in particular based on silicon, germanium, copper, Indium and / or selenium, organic field effect transistors, organic switching elements, organic optical amplifiers, organic laser diodes, organic or inorganic sensors or organically or inorganic based RFID transponder listed. As a technical challenge for the realization of a sufficient life and function of (opto) electronic arrangements in the field of inorganic and / or organic (opto) electronics, especially in the field of organic (opto) electronics, is a protection of the contained therein To see components in front of permeants. Permeants can be a variety of low molecular weight organic or inorganic compounds, especially water vapor and oxygen.

A variety of (opto) electronic arrangements in the field of inorganic and / or organic (opto) electronics, especially when using organic raw materials, is sensitive to both water vapor and oxygen, for many arrangements, the penetration of water vapor as larger problem is classified. Therefore, encapsulation protection is required during the lifetime of the electronic device, otherwise performance will degrade over the period of use. Thus, for example, by an oxidation of the components such as in light-emitting devices such as electroluminescent lamps (EL lamps) or organic light-emitting diodes (OLED), the luminosity, in electrophoretic displays (EP displays) the contrast or in solar cells, the efficiency within a very short time drastically reduce.

In inorganic and / or organic (opto) electronics, in particular in organic (opto) electronics, there is a particular need for flexible adhesive solutions which represent a permeation barrier for permeants, such as oxygen and / or water vapor. In addition, there are a variety of other requirements for such (opto) electronic arrangements. The flexible adhesive solutions should therefore not only achieve good adhesion between two substrates, but additionally meet properties such as high shear strength and peel strength, chemical resistance, aging resistance, high transparency, easy processability and high flexibility and flexibility.

A common approach in the art is therefore to allow the electronic assembly between two water vapor and oxygen impermeable substrates lay. This is followed by a seal at the edges. For inflexible structures, glass or metal substrates are used which offer a high permeation barrier but are very susceptible to mechanical stress. Furthermore, these substrates cause a relatively large thickness of the entire assembly. In the case of metal substrates, there is also no transparency. For flexible arrangements, however, surface substrates, such as transparent or non-transparent films, are used, which can be multi-layered. Here, both combinations of different polymers, as well as inorganic or organic layers can be used. The use of such surface substrates allows a flexible, extremely thin structure. In this case, a wide variety of substrates, such as films, fabrics, nonwovens and papers or combinations thereof are possible for the various applications.

In order to achieve the best possible sealing, special barrier adhesives are used. A good adhesive for the sealing of (opto) electronic components has a low permeability to oxygen and in particular to water vapor, has sufficient adhesion to the assembly and can flow well on this. Reduced infiltration on the assembly can reduce interfacial barrier action by incomplete wetting of the assembly surface and residual pores, allowing lateral entry of oxygen and water vapor regardless of adhesive properties. Only if the contact between mass and substrate is continuous, the mass properties are the determining factor for the barrier effect of the adhesive.

To characterize the barrier effect, the oxygen transmission rate OTR (Oxygen Transmission Rate) and the water vapor transmission rate WVTR (Water Vapor Transmission Rate) are usually specified. The respective rate indicates the area- and time-related flow of oxygen or water vapor through a film under specific conditions of temperature and partial pressure and possibly other measurement conditions such as relative humidity. The lower these values are, the better the respective material is suitable for encapsulation. The specification of the permeation is based not only on the values for WVTR or OTR but always includes an indication of the mean Path length of the permeation, such as the thickness of the material, or a normalization to a certain path length.

The permeability P is a measure of the permeability of a body to gases and / or liquids. A low P value indicates a good barrier effect. The permeability P is a specific value for a defined material and a defined permeant under steady state conditions at a given permeation path length, partial pressure and temperature. The permeability P is the product of diffusion term D and solubility term S: P = D ^* S

The solubility term S in the present case describes the affinity of the barrier adhesive to the permeant. For example, in the case of water vapor, a small value for S of hydrophobic materials is achieved. The diffusion term D is a measure of the mobility of the permeant in the barrier material and is directly dependent on properties such as molecular mobility or free volume. Often relatively low values are achieved for strongly cross-linked or highly crystalline D materials. However, highly crystalline materials tend to be less transparent and greater crosslinking results in less flexibility. The permeability P usually increases with an increase in molecular mobility, such as when the temperature is increased or the glass transition point is exceeded.

Approaches to increase the barrier effect of an adhesive must consider the two parameters D and S, in particular with regard to the influence on the permeability of water vapor and oxygen. In addition to these chemical properties, effects of physical influences on the permeability must also be considered, in particular the mean permeation path length and interfacial properties (flow behavior of the adhesive, adhesion). The ideal barrier adhesive has low D values and S values with very good adhesion to the substrate.

A low solubility term S is usually insufficient to achieve good barrier properties. A classic example of this is in particular siloxane elastomers. The materials are extremely hydrophobic (small solubility term), but have a comparatively low barrier to water vapor and oxygen due to their freely rotatable Si-O bond (large diffusion term). For a good barrier effect So, a good balance between solubility term S and diffusion term D is necessary. However, this consideration only relates to the volume barrier properties of the material. In addition, a high interfacial barrier is required for effective encapsulation of sensitive functional elements, which is influenced by the wetting / flow behavior of the material on the bonding substrate.

For this purpose, liquid adhesives and adhesives based on epoxides have hitherto been used (W098 / 21287 A1, US 4,051, 195 A, US 4,552,604 A). These have a low diffusion term D due to strong cross-linking. Their main application is edge bonding of rigid arrangements, but also moderately flexible arrangements. Curing takes place thermally or by means of UV radiation. A full-surface bonding is hardly possible due to the shrinkage caused by the curing, as it comes to tensions between adhesive and substrate during curing, which in turn can lead to delamination.

The use of these liquid adhesives has a number of disadvantages. For example, low-molecular-weight components (VOCs) can damage the delicate electronic structures of the device and make it difficult to handle production. The adhesive must be applied consuming each individual component of the arrangement. The purchase of expensive dispensers and fixators is necessary to ensure accurate positioning. The type of application also prevents a rapid continuous process and also by the subsequently required lamination step, the achievement of a defined layer thickness and bond width can be made difficult within narrow limits by the low viscosity.

Furthermore, such highly crosslinked adhesives have only a low degree of flexibility after curing. The use of thermal-crosslinking systems is limited in the low temperature range or in 2-component systems by the pot life, ie the processing time until a gelling has taken place. In the high temperature range and in particular in the case of long reaction times, the sensitive (opto) electronic structures again limit the usability of such systems - the maximum applicable temperatures for (opto) electronic structures are often 60 ° C., since pre-damage can already occur from this temperature , In particular, flexible arrangements which contain organic electronics and are encapsulated with transparent polymer films or composites of polymer films and inorganic layers have narrow limits here. This also applies to laminating under high pressure. In order to achieve an improved durability, a waiver of a temperature-stressing step and lamination under lower pressure is advantageous here.

As an alternative to the thermally curable liquid adhesives, radiation-curing adhesives are also frequently used in the meantime (US 2004/0225025 A1). The use of radiation-curing adhesives avoids a long-lasting heat load on the electronic device. Other above-mentioned disadvantages of liquid adhesives such as VOC, shrinkage, delamination and low flexibility also remain.

In particular, if the (opto) electronic arrangements are to be flexible, it is important that the adhesive used is not too rigid and brittle. Therefore, especially pressure-sensitive adhesives and heat activated, bondable adhesive films are suitable for such bonding. In order to flow well on the substrate, but at the same time to achieve a high bond strength, the adhesives should first be as soft as possible, but then be crosslinked. As crosslinking mechanisms, depending on the chemical basis of the adhesive, it is possible to carry out temperature curing and / or radiation curing. While the temperature cure is quite slow, radiation hardening can be initiated within a few seconds. Therefore, radiation curing, in particular UV curing, are particularly preferred in continuous production processes.

US 2006/0100299 A1 discloses a UV-curable pressure-sensitive adhesive tape for encapsulating an electronic device. The pressure-sensitive adhesive tape has an adhesive based on a combination of a polymer having a softening point in the sense of US 2006/0100299 A1 of greater than 60 ° C., a polymerizable epoxy resin having a softening point in the sense of US 2006/0100299 A1 of below 30 ° C. and a photoinitiator on. The polymers may be polyurethane, polyisobutylene, polyacrylonitrile, polyvinylidene chloride, poly (meth) acrylate or polyester, but especially a polyacrylate. Furthermore, adhesive resins, plasticizers or fillers are included. In principle, two types of encapsulation can be carried out with adhesive tapes. Either the adhesive tape is first punched out and glued only around the areas to be encapsulated, or it is glued over the entire area to be encapsulated areas. An advantage of the second variant is the easier handling and often better protection. However, problems arise from the requirement for crosslinkability of the adhesive: For the crosslinking, the presence of reactive components is required. However, such components could react with, and thereby destroy, sensitive areas (eg, organic matter) of the (opto) electronic device. On the other hand, sensitive components of the (opto) electronic arrangement are exposed to UV radiation when the adhesive tape is applied in the uncrosslinked state and then irradiated for bonding to the (opto) electronic arrangement for crosslinking.

In the first case, consideration is given to the use of an intermediate layer between the organic layers and the adhesive. However, this is undesirable because it entails additional costs on the one hand, because on the other hand it is difficult to position such layers in exactly the right place, which complicates the encapsulation process, and since such an additional layer could also adversely affect the transparency of the cover , The object of the invention is therefore to avoid such processes in the encapsulation of electronic devices using adhesive tapes, which are able to damage the electronic device. It is advantageous if in particular the damage by aggressive components of the adhesive of the adhesive tapes and / or the direct and indirect damage by actinic radiation - in particular by UV radiation - is avoided. In the context of this document, the damage caused directly by the radiation is termed direct damage, as indirect damage the damage which is caused by secondary processes of the radiation as well as the damage resulting from products of such subsequent processes, for example by fragments or radicals formed by radiation.

This object could be achieved by an encapsulation method using adhesive tapes, in which the damage-prone areas of the electronic arrangements are largely removed from both the influence of damaging components from the adhesive tape and the influence of harmful radiation. Accordingly, the invention relates to a method for encapsulating an electronic device against permeant, in which an adhesive tape surface element is provided and is applied to the areas to be encapsulated, wherein the adhesive tape surface element comprises at least one layer of an adhesive crosslinkable by means of actinic radiation. According to the invention, the adhesive tape surface element is crosslinked prior to application in a first crosslinking step only in some areas by means of actinic radiation, the adhesive tape surface element then applied to the areas to be encapsulated and the adhesive tape surface element after application in a further crosslinking step in a part of the areas of the first cross-linking step, that is to say cross-linked in a different-sized area by means of actinic radiation. This differently sized area preferably represents essentially the negative of the areas irradiated in the first step, that is to say it is crosslinked in the areas by means of actinic radiation which were not crosslinked in the first crosslinking step.

The term "electronic arrangement" in the sense of the inventive teaching also includes optoelectronic arrangements By way of example, without wishing to be limited thereby, the arrangements mentioned at the outset may be mentioned.

Actinic radiation is such in particular high-energy radiation, which - if appropriate using suitable crosslinker substances - are able to initiate crosslinking reactions of the adhesive. Actinic radiation is understood to be, for example, electron radiation (ESH), visible light (for example violet light) and in particular UV light. In a particularly preferred procedure, the crosslinking is therefore initiated in the first crosslinking step and / or in the further crosslinking step by UV radiation.

The terms "first crosslinking step" and "further crosslinking step" relate only to designate their sequence in the process according to the invention, without wishing to exclude linguistically that before, between and / or after these crosslinking steps other crosslinking reactions and / or further process steps could take place , As adhesive crosslinkable by means of actinic radiation it is possible to use outstandingly a pressure-sensitive adhesive or a heat-activated adhesive composition. Particularly preferred are UV-crosslinkable PSAs or UV-crosslinkable heat activated adhesives, ie adhesives whose crosslinking can be initiated by irradiation with UV light.

The encapsulation of the electronic device involves the application of a protective layer or protective film to the areas to be encapsulated. The protective layer can be applied as a separate component by means of an adhesive tape, or it can be applied as an integrated component of an adhesive tape, for example in the form of the carrier of an adhesive tape, another, additionally present adhesive tape layer or such that a single-layer adhesive tape (adhesive layer) itself Includes protection functions. As a protective layer or protective film can be used in particular those materials which are provided with a permeation barrier for the corresponding permeants, in particular for oxygen and / or hydrogen. In particular for bonding such protective layers or protective films, single-layer adhesive tapes, which are formed only from the corresponding adhesive layer, are suitable. Double-sided adhesive tapes which have two outer adhesive layers can also be used for bonding such protective layers or protective films.

The adhesive layer (s) and / or the carrier layer (s) may have additional protective effect against permeants.

In a preferred embodiment of the inventive method for encapsulating an electronic device against permeants, the protective layer and the adhesive may be provided as part of an adhesive tape. This type of administration allows a particularly simple and uniform application.

Adhesive tape surface elements are flat adhesive tape sections, diecuts or other prefabricated pieces, regardless of their shape (adhesive tape surface elements can be regularly - for example, round, rectangular or square, or irregular, they can be full-area or frame-shaped) , It is particularly advantageous to use full-surface adhesive tape surface elements that exceed the extent of the areas to be encapsulated in such a way that a sufficient bond can be achieved on the underlying substrate surface outside the areas to be encapsulated.

In one embodiment, the general term "adhesive tape" comprises a carrier material which is provided on one or both sides with an adhesive The carrier material comprises all flat structures, for example films or film sections expanded in two dimensions, tapes with extended length and limited width, A wide variety of substrates, such as films, fabrics, nonwovens and papers, can be combined with the adhesives for various applications In the case of a transfer adhesive tape, the adhesive is applied between flexible liners which have been provided with a release layer and / or have anti-adhesive properties before application, for which a liner is first regularly removed, the adhesive applied and then the second The pressure-sensitive adhesive can thus be used directly for bonding two surfaces in (opto) electronic arrangements.

But there are also tapes possible in which not two liners but with a single double-sided separating equipped liner is used. The adhesive tape web is then covered on its upper side with one side of a double-sidedly separated liner, its lower side covered with the back of the double-sidedly equipped liner, in particular an adjacent turn on a bale or a roll.

In the present case, polymer films, film composites or films or film composites provided with organic and / or inorganic layers are preferably used as the carrier material of an adhesive tape. Such films / film composites can consist of all common plastics used for film production, but are not to be mentioned as examples by way of non-limiting example:

Polyethylene, polypropylene - in particular the oriented polypropylene (OPP) produced by mono- or biaxial stretching, cyclic olefin copolymers (COC), polyvinyl chloride (PVC), polyesters - in particular polyethylene terephthalate (PET) and Polyethylene naphthalate (PEN), ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), polyamide (PA), polyethersulfone (PES) or polyimide (PI). The support may also be combined with organic or inorganic coatings or layers. This can be done by conventional methods such as painting, printing, evaporation, sputtering, co-extrusion or lamination. By way of example, but not by way of limitation, oxides or nitrides of silicon and of aluminum, indium-tin oxide (ITO) or sol-gel coatings may be mentioned here.

Particularly preferred are these films / film composites, in particular the polymer films provided with a Permeationsbarriere for oxygen and water vapor, the permeation barrier exceeds the requirements for the packaging area (WVTR <10 ^"1 g / (m ² d); OTR <10 ^{" 1} cm ³ / (m ² d bar)). The determination of the permeability to oxygen (OTR) and water vapor (WVTR) is carried out according to DIN 53380 Part 3 or ASTM F-1249. The oxygen permeability is measured at 23 ° C and a relative humidity of 50%. The water vapor permeability is determined at 37.5 ° C and a relative humidity of 90%. The results are normalized to a film thickness of 50 μm.

In addition, in a preferred embodiment, the films / film composites may be made transparent, so that the overall structure of such an adhesive article is transparent. "Transparency" means an average transmission in the visible range of light of at least 75%, preferably higher than 90%.

The process according to the invention comprises at least two crosslinking steps, namely at least the first crosslinking step and at least the further crosslinking step. In each of these two crosslinking steps, only partial areas of the adhesive tape surface elements are crosslinked. This partial crosslinking can be achieved in particular by covering the respective non-crosslinkable adhesive tape area with a mask. According to the invention, the process can thus be carried out in such a way that the adhesive tape in the first crosslinking step in the areas in which no crosslinking should take place in this first crosslinking step, with a actinic radiation, in particular UV radiation, covering the shielding mask, and / or such that the adhesive tape in the further crosslinking step in the areas in which no crosslinking is to take place in this further crosslinking step - especially in the areas that were already cross-linked in the first crosslinking step - with one of the actinic radiation , in particular the UV radiation, shielding mask covers. Typically, after further crosslinking, the entire tape portion has been exposed to radiation at least once.

Between the first and the further crosslinking step, the partially crosslinked adhesive tape is applied to the (opto) electronic arrangement. In a particularly preferred method procedure, the procedure is such that the shielding mask used in the further method step has at least such shape and / or dimensions that, when placed on the applied adhesive tape, it covers such areas of the underlying (opto) electronic arrangement-in particular completely , which are sensitive to reactive components in the adhesive and / or actinic radiation, in particular UV radiation, so can be directly or indirectly damaged by actinic radiation.

The subject matter of the method according to the invention is an at least two-stage crosslinking, in particular using two masks. Very preferably, the adhesive tape is first crosslinked by means of actinic radiation, preferably by means of UV radiation, in particular at the points which subsequently with the reactive components of the adhesive and / or actinic before bonding, ie before application to the areas to be encapsulated Radiation sensitive areas (for example, organic layers) come into contact. For this purpose, a mask is preferably used whose openings are adapted to the corresponding areas to be protected in particular (ie the sensitive areas), so that after application of this mask, the adhesive tape is crosslinked only at the points where this is desired in the first crosslinking step.

In a subsequent step, the adhesive tape is glued to the substrate to be encapsulated so that the cross-linked areas lie exactly over the sensitive areas. Since the reactive components have already reacted off in the crosslinking reaction at these crosslinked adhesive tape sites, the (opto) electronic arrangement can no longer be damaged thereby. The area of the crosslinked sites may also be larger than the area of the sensitive areas. This allows a safer Arrangement of the adhesive tape over the sensitive areas, taking into account any tolerances in the registration accuracy in the lamination process.

If the actual protective layer is not already integrated in the adhesive tape, it is now placed on the adhesive tape and glued to it. This can be effected in pressure-sensitive adhesive tapes due to the inherent tackiness of the adhesive tape and heat-activated adhesive tapes by supplying heat (thermal energy). Since the adhesive tape is still soft in the non-crosslinked area, it can still flow well onto the protective layer, so that effective bonding is possible.

In a subsequent - the further - crosslinking step, a second mask is now applied which leaves the non-crosslinked regions of the adhesive tape accessible to radiation and covers the already crosslinked regions, thereby covering in particular the sensitive regions of the (opto) electronic application. The crosslinking is in turn initiated with actinic radiation, preferably with UV radiation, wherein the sensitive regions of the (opto) electronic device are protected from the radiation by the mask.

The process according to the invention can be operated continuously. An exemplary process procedure for this provides that (at least) two irradiation units (for example one or both UV emitters) are provided, of which one is responsible for the initiation of the first crosslinking step and the other for the crosslinking of the further crosslinking step. Before each irradiation unit, a mask is mounted in such a way that, according to its function, it corresponds in each case to the statements made above. The irradiation units can be operated with different or the same intensity and / or radiation characteristics.

The adhesive tape surface elements can now be isolated - for example, applied to a quasi-Endlosträger, such as a roll - one after the other (or in groups) placed under the first irradiation unit, there are partially cross-linked by the mask, then each on the likewise to be encapsulated (opto ) are applied to electronic arrangements, which may also be isolated on a guide in particular, wherein the respective provided with the adhesive tape surface element (opto) electronic arrangement is sequentially (or in groups) under the second irradiation unit and through the corresponding mask there the further crosslinking step is carried out. Preference is given to using an adhesive, preferably comprising pressure-sensitive adhesive

(a) at least one copolymer containing at least isobutylene or butylene as a comonomer type and at least one comonomer type which - considered as a hypothetical homopolymer - has a softening temperature of greater than 40 ° C,

(b) at least one kind of at least partially hydrogenated tackifier resin,

(C) at least one type of reactive resin having a softening temperature of less than 40 ° C, preferably less than 20 ° C. In the case of amorphous substances, the softening temperature corresponds to the glass transition temperature; in the case of (semi) crystalline substances, the softening temperature corresponds to the melting temperature.

In the field of adhesives, PSAs are characterized in particular by their permanent tackiness and flexibility. A material that exhibits permanent tack must have a suitable combination of adhesive and cohesive properties at all times. For good adhesion properties,

To adjust pressure-sensitive adhesives so that an optimal balance of adhesive and cohesive properties exists.

The adhesive is preferably a pressure-sensitive adhesive, ie a viscoelastic composition which remains permanently tacky and adhesive at room temperature in a dry state.

The bonding takes place by light pressure immediately on almost all substrates.

According to an advantageous embodiment, the one or more copolymers are random, alternating, block, star and / or graft copolymers having a molecular weight M _w

(Weight average) of 300,000 g / mol or smaller, preferably 200,000 g / mol or smaller.

Smaller molecular weights are preferred because of their better processability.

More preferably, the one or more copolymers are block, star and / or

Graft copolymers comprising at least one grade of a first polymer block ("soft block") having a softening temperature of less than -20 ° C and at least one grade of a second polymer block ("hard block") having a softening temperature greater than +40 ° C.

The soft block is preferably constructed nonpolar and preferably contains butylene or isobutylene as Homopolymerblock or copolymer block, the latter preferably with itself or with each other or copolymerized with other particularly preferred nonpolar comonomers. As non-polar comonomers, for example (partially) hydrogenated polybutadiene, (partially) hydrogenated polyisoprene and / or polyolefins are suitable. The hard block is preferably composed of styrene, styrene derivatives and / or other aromatic or (cyclo) aliphatic hydrocarbon monomers.

In a particularly advantageous embodiment, the described preferred soft and hard blocks are realized simultaneously in the copolymer (s).

It is advantageous if the at least one block copolymer is a triblock copolymer composed of two terminal hard blocks and one medium soft block. Diblock copolymers are also well suited as are mixtures of tri- and diblock copolymers.

The adhesive according to the invention contains at least one kind of at least partially hydrogenated tackifier resin, advantageously those which are compatible with the copolymer or, if a copolymer of hard and soft blocks is used, are mainly compatible with the soft block (soft resins).

It is advantageous if this adhesive resin has a Klebharzerweichungstemperatur greater than 25 ° C.

Examples of suitable resins in the PSA are non-hydrogenated, partially or completely hydrogenated rosin-based rosin derivatives, hydrogenated polymers of dicyclopentadiene, non-hydrogenated, partially, selectively or completely hydrogenated hydrocarbon resins based on C ₅ , C ₅ / C ₉ or C ₉ monomer streams, polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene, hydrogenated polymers of preferably pure C ₈ and C ₉ aromatics are used. The aforementioned adhesive resins can be used both alone and in admixture

Both solid and liquid resins can be used at room temperature. In order to ensure high aging and UV stability, hydrogenated resins having a degree of hydrogenation of at least 90%, preferably of at least 95%, are preferred. Furthermore, non-polar resins with a DACP value (diacetone alcohol cloud point) above 30 ° C. and a MMAP value (mixed methylcyclohexane aniline point) of greater than 50 ° C., in particular with a DACP value above 37 ° C. and a MMAP value greater than 60 ° C preferred. The DACP value and the MMAP value each indicate the solubility in a particular solvent. By selecting these areas, a particularly high permeation barrier, in particular against water vapor, is achieved.

The preferred adhesive further contains at least one type of reactive resin for the radiation-chemical optionally and thermal crosslinking with a softening temperature of less than 20 ° C. These are preferably based on aliphatic or cycloaliphatic components.

The reactive resins are, above all, cyclic ethers, in particular epoxides, ie compounds which carry at least one oxirane group, or oxetanes. It is also excellent to use acrylate and methacrylate resins as reactive resins. This performance serves only as an example for under the influence of radiation reactive substances.

The adhesive resin softening point is carried out according to the relevant method known as Ring and Ball, which is standardized according to ASTM E28.

To determine the Klebharzerweichungstemperatur comes a ring-ball machine

HRB 754 from Herzog is used. Resin samples are first finely ground.

The resulting powder is placed in a brass cylinder with bottom opening

(Inner diameter at the upper part of the cylinder 20 mm, diameter of the bottom opening of the cylinder 16 mm, height of the cylinder 6 mm) filled and on a

Hot table melted. The filling amount is chosen so that the resin after the

Melting the cylinder fully filled without supernatant.

The resulting specimen, including the cylinder, is inserted in the sample holder of the HRB 754. Glycerol is used to fill the tempering bath, provided that the adhesive resin softening temperature is between 50 ° C and 150 ° C. At lower Klebharzerweichungstemperaturen can also be used with a water bath. The test balls have a diameter of 9.5 mm and weigh 3.5 g. In accordance with the HRB 754 procedure, the ball is placed above the specimen in the temperature control bath and deposited on the specimen. 25 mm below the cylinder bottom there is a catch plate, 2 mm above this a light barrier. During the measuring process, the temperature is increased at 5 ° C / min. In the temperature range of the adhesive resin softening temperature, the ball begins to move through the bottom opening of the cylinder until it eventually stops on the catch plate. In this position, it is detected by the photocell and registered at this time, the temperature of the bath. There is a double determination. The adhesive resin softening temperature is the average of the two individual measurements.

The softening temperature of copolymers, hard and soft blocks and uncured reactive resins is determined calorimetrically by differential scanning calorimetry (DSC) according to DIN 53765: 1994-03. Heating curves run at a heating rate of 10 K / min. The samples are measured in AI crucibles with perforated lid and nitrogen atmosphere. The second heating curve is evaluated. In the case of amorphous materials, glass transition temperatures occur; in the case of (semi) crystalline materials, melting temperatures. A glass transition is recognizable as a step in the thermogram. The glass transition temperature is evaluated as the center of this stage. A melting temperature can be recognized as a peak in the thermogram. The melting temperature is the temperature at which the highest heat of reaction occurs. The adhesive composition further preferably contains at least one type of UV initiator, in particular a UV initiator for the cationic or radical curing of the reactive resins. Advantageous are photoinitiators which have an absorption at less than 350 nm and advantageously at greater than 250 nm. Among the initiators of cationic UV curing, triarylsulfonium hexafluoroantimonates, borates and phosphates, and diaryliodonium hexafluoroantimonates, borates and phosphates are preferred, with the anions usually being perfluorinated or having perfluoroaryl substituents. Tris (trifluoromethylsulfonyl) methides are also suitable as anions.

Suitable representatives of photoinitiators for radical curing are type I photoinitiators, that is to say so-called α-splitters such as benzoin and acetophenone derivatives, benzil ketals or acylphosphine oxides, type II photoinitiators, that is to say so-called hydrogen abstractors such as benzophenone derivatives and some quinones, diketones and thioxanthones. Furthermore, triazine derivatives can be used to initiate radical reactions. Advantageous photoinitiators of type I include, for example, benzoin, benzoin ethers such as, for example, benzoin methyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutyl ether, methylolbenzoin derivatives such as methylolbenzoinpropyl ether, 4-benzoyl-1,3-dioxolane and its derivatives, benzil ketal. Derivatives such as 2,2-dimethoxy-2-phenylacetophenone or 2-benzoyl-2-phenyl-1,3-dioxolane, α, α-dialkoxyacetophenones such as α, α-dimethoxyacetophenone and α, α-diethoxyacetophenone, α-hydroxyalkylphenones such as 1 - Hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone and 2-hydroxy-2-methyl-1- (4-iso-propylphenyl) -propanone, 4- (2-hydroxyethoxy) -phenyl-2-hydroxy-2- methyl-2-propanone and its derivatives, α-aminoalkylphenones such as 2-methyl-1 - [4- (methylthio) -phenyl] -2-morpholinopropan-2-one and 2-benzyl-2-dimethylamino-1 - (4- morpholinophenyl) -butan-1-one, acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and ethyl-2,4,6-trimethylbenzoylphenylphosphinate and O. Acyl-a-oximinoketones. Advantageous photoinitiators of type II include, for example, benzophenone and its derivatives such as 2,4,6-trimethylbenzophenone or 4,4'-bis (dimethylamino) benzophenone, thioxanthone and its derivatives such as 2-iso-propylthioxanthone and 2,4-diethylthioxanthone , Xanthone and its derivatives and anthraquinone and its derivatives.

Type II photoinitiators are used particularly advantageously in combination with nitrogen-containing coinitiators, the so-called amine synergists. For the purposes of this invention, preference is given to using tertiary amines. Furthermore, hydrogen atom donors are advantageously used in combination with type II photoinitiators. Examples include substrates containing amino groups. Examples of amine synergists are methyldiethanolamine, triethanolamine, ethyl 4- (dimethylamino) benzoate, 2-n-butoxyethyl 4- (dimethylamino) benzoate, 2-ethylhexyl-4- (dimethylamino) benzoate, 2-

(Dimethylaminophenyl) ethanone and unsaturated and thus copolymerizable tertiary amines, (meth) acrylated amines, unsaturated amine-modified oligomers and polymers based on polyester or polyether and amine-modified (meth) acrylates.

It is also possible to use polymerizable type I and / or type II photoinitiators. For the purposes of these inventions, it is also possible to use any desired combinations of different types of type I and / or type II photoinitiators.

Low color and low odor photoinitiators are favored.

The adhesive may be added to customary additives such as anti-aging agents (antiozonants, antioxidants, light stabilizers, etc.).

As additives to the adhesive are typically used:

Plasticizers such as plasticizer oils or low molecular weight liquid polymers such as low molecular weight

polybutenes

• primary antioxidants such as sterically hindered phenols

• secondary antioxidants such as phosphites or thioethers

· Process stabilizers such as C radical scavenger

• Sunscreens such as UV absorbers or hindered amines

• processing aids

• Net additives

· Bonding agent

• End block booster resins and / or

Optionally further polymers of preferably elastomeric nature; correspondingly useful elastomers include, but are not limited to, those based on pure hydrocarbons, for example, unsaturated polydienes such as natural or synthetically produced polyisoprene or polybutadiene, chemically substantially saturated elastomers such as saturated ethylene-propylene copolymers, α-olefin copolymers, polyisobutylene, butyl rubber, ethylene Propylene rubber, as well as chemically functionalized hydrocarbons such as halogen-containing, acrylate-containing, allyl or vinyl ether-containing polyolefins

Further suitable and advantageously recognized elastomers are disclosed in EP 1 743 928 A1. The additives or additives are not mandatory, the adhesive also works without these are added individually or in any combination.

Inventive methods can also be used advantageously in combination with other UV-curable adhesive systems. Examples of further adhesive systems are disclosed in US 2006/100299 A1, EP 1 418 912 A1 and US 2009/026934 A1. The skilled worker is further known, the list of said adhesive systems is not to be understood as exclusive. Since the electronic structures (opto) electronic arrangements are often susceptible to UV radiation, it has been found to be particularly advantageous if the adhesive is formed UV blocking. In the present case, the term "UV-blocking" denotes an average transmittance of not more than 20%, preferably not more than 10%, more preferably not more than 1% in the corresponding wavelength range. UVA radiation) is UV-blocking, preferably in the wavelength range from 280 nm to 400 nm (UVA and UVB radiation), more preferably in the wavelength range from 190 nm to 400 nm (UVA, UVB and UVC radiation).

The UV-blocking effect is advantageous when using the sensitive and encapsulated functional element-containing end product in directly incident daylight. UV curing occurs at higher intensities and is not significantly affected by the UV blockers.

The UV-blocking effect of the adhesive can be achieved in particular by adding UV blockers or suitable fillers to the PSA. Suitable UV blockers are, for example, HALS (Hinder Armine Light Stabilizer) such as Tinuvin from BASF or benzimidazole derivatives. Particularly suitable as the filler is titanium dioxide, in particular nanoscale titanium dioxide, since this allows transparency to be maintained in the visible range. Aromatic constituents in the adhesive, for example in the elastomers (in particular incorporated styrene or other aromatic monomers) or in the reactive resins, show advantageous UV-blocking effect. The UV blockers are not mandatory, the adhesive also works without these are added.

Nanosized and / or transparent fillers are preferably used as fillers of the adhesive. A filler is referred to herein as nanoscale if it has a maximum extent of about 100 nm, preferably of about 10 nm, in at least one dimension. Particular preference is given to using mass-transparent fillers with a platelet-shaped crystallite structure and a high aspect ratio with homogeneous distribution. The fillers with a platelet-like crystallite structure and aspect ratios well above 100 generally only have a thickness of a few nm, but the length or the width of the crystallites can be up to a few μm. Such fillers are also referred to as nanoparticles. The particulate configuration of the fillers with small dimensions is also particularly advantageous for a transparent design of the PSA. By building labyrinth-like structures using the previously described fillers in the adhesive matrix, the diffusion path of, for example, oxygen and water vapor is extended such that its permeation through the adhesive layer is reduced. For better dispersibility of these fillers in the binder matrix, these fillers can be superficially modified with organic compounds. The use of such fillers per se is known, for example, from US 2007/0135552 A1 and WO 02/026908 A1.

In a further advantageous embodiment, fillers which can interact with oxygen and / or water vapor in a particular manner are also used. In the (opto) electronic arrangement penetrating oxygen or water vapor is then bound to these fillers chemically or physically. These fillers are also referred to as getter, scavenger, desiccant or absorber. Such fillers include, by way of example but not limitation, oxidizable metals, halides, salts, silicates, oxides, hydroxides, sulfates, sulfites, carbonates of metals and transition metals, perchlorates and activated carbon, including its Modifications. Examples are cobalt chloride, calcium chloride, calcium bromide, lithium chloride, zinc chloride, zinc bromide, silica (silica gel), alumina (activated aluminum), calcium sulfate, copper sulfate, sodium dithionite, sodium carbonate, magnesium carbonate, titanium dioxide, bentonite, montmorillonite, diatomaceous earth, zeolites and oxides of (Erd ) Alkali metals, such as barium oxide, calcium oxide, iron oxide and Magesiumoxid or carbon nanotubes. Furthermore, it is also possible to use organic absorbers, such as, for example, polyolefin copolymers, polyamide copolymers, PET copolyesters or other absorbers based on hybrid polymers, which are mostly used in combination with catalysts such as, for example, cobalt. Further organic absorbers are, for example, slightly crosslinked polyacrylic acid, ascorbates, glucose, gallic acid or unsaturated fats and oils.

If desired, the proportion of filler should not be too low in order to achieve the best possible effectiveness with regard to the barrier effect. The proportion is preferably at least 5 wt .-%, more preferably at least 10 wt .-% and most preferably at least 15 wt .-%. Typically, the highest possible proportion of fillers is used without excessively reducing the adhesive forces of the adhesive or impairing other properties. Depending on the filler type, filler contents of greater than 40% by weight to a maximum of 70% by weight can be achieved.

Furthermore, the finest possible distribution and the highest possible surface area of the fillers are advantageous. This allows a higher efficiency and a higher loading capacity and is achieved in particular with nanoscale fillers.

The fillers are not mandatory, the adhesive also works without these are added individually or in any combination.

Claims

claims

Method for encapsulating an electronic device against permeants, in which an adhesive tape surface element is provided and applied to the areas to be encapsulated,

wherein the adhesive tape surface element comprises at least one layer of an actinic radiation-crosslinkable adhesive,

characterized in that

the adhesive tape surface element is crosslinked before application in a first crosslinking step only in some areas by means of actinic radiation, the adhesive tape surface element is then applied,

the adhesive tape surface element is crosslinked by means of actinic radiation after application in a further crosslinking step in a region which differs from the partial regions of the first crosslinking step.

Method according to claim 1, characterized in that

which differs from the sub-areas of the first networking step

Area is the area that was not networked in the first cross-linking step.

Method according to one of the preceding claims, characterized in that

the adhesive is a pressure-sensitive adhesive or a heat-activated adhesive composition.

Method according to one of the preceding claims, characterized in that

the adhesive is a UV-crosslinkable adhesive.

A method according to claim 4, characterized in that

the crosslinking in the first crosslinking step and / or in the further

Crosslinking step is initiated by UV radiation.

Method according to one of the preceding claims, characterized in that the adhesive tape in the first cross-linking step in the areas in which no cross-linking is to take place in this cross-linking step, is covered with a mask which shields the corresponding actinic radiation.

Method according to one of the preceding claims, characterized in that

the adhesive tape in the further crosslinking step in the areas which were already crosslinked in the first crosslinking step, is covered with a mask which shields the corresponding actinic radiation.

Method according to one of the preceding claims, characterized in that

the shielding mask used in the further method step has at least such dimensions that it covers indirect or directly sensitive areas of the electrical arrangement against UV radiation.