Adhesive tape for encapsulating an organic electronic arrangement

Abstract

Translucent multiphase adhesive comprising at least one continuous phase and dispersed domains, the at least one continuous phase having a refractive index of more than 1.45 and a permeation rate for water vapor of less than 100 g/m.sup.2, and the disperse domains being present in a size range of 0.1 m to 50 m and being included in a weight fraction of not more than 10 wt % in the adhesive, characterized in that the disperse domains are polymeric in nature and have a water vapor permeation rate of less than 100 g/m.sup.2d and a refractive index of less than 1.45.

Claims

1. A translucent multiphase adhesive comprising at least one continuous phase as well as dispersely distributed domains, the at least one continuous phase comprising: a refractive index of more than 1.45 and a water vapor permeation rate of less than 100 g/m.sup.2, and the disperse domains have an average diameter in a size range from 0.1 m to 50 m, are present in a weight fraction of not more than 10 wt % in the adhesive, and wherein the disperse domains are polymeric in nature, have a WVTR of less than 100 g/m.sup.2d, and have a refractive index of less than 1.45.

2. The adhesive according to claim 1, further wherein, the average diameter (d50) of the polymeric disperse domains is in a size range between 0.1 m and 50 m.

3. The adhesive according to claim 1, further wherein, the weight fraction of the dispersely distributed polymeric domains in the adhesive is more than 1 wt %, more particularly between 1 and 5 wt % when the refractive index of the domains is below 1.40, and more particularly between 5 and 10 wt % when the refractive index of the domains is 1.45.

4. The adhesive according to claim 1, further wherein, the polymeric disperse domains have a refractive index of less than 1.41, preferably of less than 1.37.

5. The adhesive according to claim 1, further wherein, the continuous phase in the visible light of the spectrum (wavelength range from 400 nm to 800 nm) exhibits a transmittance of more than 70% and/or a haze of less than 5.0%, preferably less than 2.5%.

6. The adhesive according to claim 1, further wherein, the adhesive at a layer thickness of 50 m has a water vapor permeation rate of less than 50 g/(m.sup.2.Math.d) and/or an oxygen transmission rate of less than 5000 g/(m.sup.2.Math.d.Math.bar).

7. The adhesive according to claim 1, further wherein, the adhesive in a layer 50 m thick is a light-scattering adhesive having a light transmittance of more than 70% and a haze of more than 10%.

8. The adhesive according to claim 1, further wherein, the adhesive has only one continuous phase and only one disperse phase.

9. The adhesive according to claim 1, further wherein, the polymer of the disperse polymeric domains comprises fluorine, preferably in that the polymeric domains are present in the form of fluorine-containing microcrystalline waxes.

10. The adhesive according to claim 1, further wherein, the adhesive consists of a continuous phase containing an adhesive, and a dispersed phase containing a distributed particulate filler.

11. The adhesive according to claim 10, wherein, the filler is present in the form of particles in a particle size distribution wherein not more than 1 vol % of the filler exceeds the average layer thickness of the layer of adhesive.

12. The adhesive according to claim 10, wherein, the continuous phase of adhesive is a pressure-sensitive adhesive or is an activatable adhesive, more particularly a pressure-sensitive adhesive.

13. The adhesive according to claim 1, wherein, the adhesive is a pressure-sensitive adhesive or is an activatable adhesive, more particularly a pressure-sensitive adhesive.

14. The adhesive according to claim 1, further wherein, the adhesive comprises at least one getter material which is adapted to sorb at least one permeable substance.

15. The adhesive according to claim 14, further wherein, the amount of getter material in the adhesive is not more than 10 wt %, preferably not more than 5 wt %, and at the same time is at least 0.01 wt %, preferably at least 0.05 wt %.

16. The adhesive according to claim 14, further wherein, the getter material is in nanoscale form, more particularly such that the extent in at least one dimension is not more than 500 nm, preferably not more than 200 nm, very preferably not more than 100 nm.

17. The adhesive according to claim 1, further wherein, the refractive indices of the continuous phase and of the disperse domains differ by more than 0.8, preferably more than 0.12, and very preferably more than 0.16.

18. An adhesive tape comprising a layer of an adhesive according to claim 1.

19. The adhesive tape according to claim 17, wherein the adhesive tape comprises a layer of the adhesive and additionally comprises at least one further layer selected from: an adhesive, a carrier material and a liner.

20. The adhesive tape according to claim 18, wherein, the carrier material is a polymeric carrier material.

21. The adhesive tape according to claim 19, wherein, the carrier material comprises at least one in organic barrier layer.

22. A method for protecting an organic electrical arrangement disposed on a substrate, in which a cover is applied to the electronic arrangement in such a way that the electronic arrangement is at least partly covered by the cover, and the cover is adhesively bonded at least over part of the area to the substrate and/or to the electronic arrangement, where the adhesive bond includes at least one layer of an adhesive according to claim 1.

23. The method according to claim 21, further wherein the layer of adhesive is a layer of an adhesive tape.

24. The method according to claim 21, further wherein, the cover is adhesively bonded by first applying a layer of the adhesive, optionally as part of a double-sided adhesive tape comprising further layers, and, thereafter, applying a liner to the substrate and/or the electronic arrangement.

25. The method according to claim 24, further wherein the layer of adhesive and the liner are applied jointly to the substrate and/or the electronic arrangement.

26. The method according to claim 21, further wherein, the liner completely covers the electronic arrangement.

27. The method according to claim 21, further wherein, in addition to the electronic arrangement, a region of the substrate near the electronic arrangement is also at least partly covered by the liner.

28. The method according to claim 21, further wherein, the layer of adhesive completely covers the electronic arrangement.

29. A translucent multiphase adhesive comprising at least one continuous phase as well as dispersely distributed domains, the at least one continuous phase comprising: a refractive index of more than 1.45 and a water vapor permeation rate of less than 100 g/m.sup.2, and the disperse domains have an average diameter in a size range from 0.1 m to 50 m, and also are present in a weight fraction of not more than 10 wt % in the adhesive, wherein, the disperse domains are selected from the group consisting of: poly(hexafluoropropylene oxide); poly(tetrafluoroethylene-co-hexafluoropropylene); fluorinated ethylene propylene; poly(pentadecafluorooctyl acrylate); poly(tetrafluoro-3-(heptafluoropropoxy)propyl acrylate); poly(tetrafluoro-3-(pentafluoroethoxy)propyl acrylate); poly(tetrafluoroethylene); tetrafluoroethylene hexafluoropropylene vinylidene fluoride; poly(undecafluorohexyl acrylate); perfluoroalkoxy; ethylene tetrafluoroethylene; poly(nonafluoropentyl acrylate); poly(tetrafluoro-3-(trifluoromethoxy)propyl acrylate); poly(pentafluorovinyl propionate); poly(heptafluorobutyl acrylate); poly(trifluorovinyl acetate); poly(octafluoropentyl acrylate;) poly(methyl 3,3,3-trifluoropropyl siloxane); poly(pentafluoropropyl acrylate); poly(2-heptafluorobutoxy)ethyl acrylate); poly(chlorotrifluoroethylene); poly(2,2,3,4,4-hexafluorobutyl acrylate); poly(trifluoroethyl acrylate); poly(2-(1,1,2,2-tetrafluoroethoxy)ethyl acrylate); poly(trifluoroisopropyl methacrylate); poly(2,2,2-trifluoro-1-methylethyl methacrylate); poly(2-trifluoroethoxyethyl acrylate); poly(vinylidene fluoride); ethylene chlorotrifluoroethylene; poly(trifluoroethyl methacrylate); and, poly(isobutyl methacrylate).

30. A translucent multiphase adhesive comprising at least one continuous phase as well as dispersely distributed domains, the at least one continuous phase comprising: a refractive index of more than 1.45 and a water vapor permeation rate of less than 100 g/m.sup.2, and the disperse domains have an average diameter in a size range from 0.1 m to 50 m, and also are present in a weight fraction of not more than 10 wt % in the adhesive, wherein: the disperse domains are selected from the group consisting of: poly(hexafluoropropylene oxide) (PHFPO), fluorinated ethylene propylene polymer (FEP), poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene hexafluoropropylene vinylidene fluoride) (THV), perfluoroalkoxy polymer (PFA), poly(ethylene tetrafluoroethylene) (ETFE), poly(chlorotrifluoroethylene) (PCTFE), poly(vinylidene fluoride) (PVDF), and, poly(ethylene chlorotrifluoroethylene) (ECTFE), as well as co-polymers and terpolymers thereof.

Description

(1) Further details, features and advantages of the present invention are elucidated in more detail below with reference to preferred exemplary embodiments. In the drawing

(2) FIG. 1 shows an (opto)electronic arrangement according to the prior art, in a diagrammatic representation,

(3) FIG. 2 shows a first (opto)electronic arrangement of the invention, in diagrammatic representation, and

(4) FIG. 3 shows a second (opto)electronic arrangement of the invention, in diagrammatic representation.

(5) FIG. 4 shows a further (opto)electronic arrangement of the invention, in diagrammatic representation, as utilized in a test for determining the lifetime of an electronic construction.

(6) FIG. 1 shows a first embodiment of an organic electronic arrangement 1 according to the prior art. This arrangement 1 has a substrate 2 on which an electronic structure 3 is arranged. The substrate 2 itself is designed as a barrier for permeates, and thus forms part of the encapsulation of the electronic structure 3. Disposed above the electronic structure 3, in the present case also at a distance from it, is a further liner 4 designed as a barrier.

(7) In order to encapsulate the electronic structure 3 to the side as well, and at the same time to join the liner 4 to the electronic arrangement 1 in its remaining part, an adhesive 5 runs round adjacent to the electronic structure 3 on the substrate 2. It is unimportant here whether the adhesive has been joined first to the substrate 2 or first to the liner 4. The adhesive 5 joins the liner 4 to the substrate 2. As a result of an appropriately thick embodiment, moreover, the adhesive 5 allows the liner 4 to be distanced from the electronic structure 3.

(8) The adhesive 5 is a prior-art adhesive, in other words an adhesive with a high permeation barrier, which may also have been filled to a high fraction with getter material. The transparency of the adhesive is not relevant in this construction.

(9) An adhesive transfer tape would presently be provided in the form of a diecut, which on account of its delicate geometry would be more difficult to handle than an adhesive transfer tape applied substantially over the full area.

(10) FIG. 2 shows an inventive embodiment of an (opto)electronic arrangement 1. Shown, again, is an electronic structure 3 which is disposed on a substrate 2 and is encapsulated by the substrate 2 from below. Above and to the side of the electronic structure, the inventive adhesive for example in the embodiment is now arranged as an adhesive transfer tape 6 over the full area. Accordingly, the electronic structure 3 is encapsulated fully from above by the adhesive transfer tape 6. A liner 4 is then applied to the adhesive transfer tape 6. The adhesive transfer tape 6 is one based on the inventive adhesive transfer tape as described above in general form and specified in more detail hereinafter in exemplary embodiments. In the version shown, the adhesive transfer tape consists only of a layer of an inventive adhesive.

(11) In contrast to the preceding embodiment, the liner 4 is not mandatorily required to meet the high barrier requirements, since with a full-area covering of the electronic arrangement by the adhesive transfer tape, the barrier is provided by the adhesive already. The liner 4 may merely take on, for example, a mechanical protection function, or alternatively it may additionally be provided as a permeation barrier.

(12) FIG. 3 shows an alternative embodiment of an (opto)electronic arrangement 1. In contrast to the preceding embodiments, there are now two adhesive transfer tapes 6a, b, which in the present case are identical in form, but which may also be different. The first adhesive transfer tape 6a is arranged on the full area of the substrate 2. The electronic structure 3 is provided on the adhesive transfer tape 6a, and is fixed by the adhesive transfer tape 6a. The assembly of adhesive transfer tape 6a and electronic structure 3 is then covered over its full area with the further adhesive transfer tape 6b, meaning that the electronic structure 3 is encapsulated from all sides by the adhesive transfer tapes 6a, b. Provided above the adhesive transfer tape 6b, in turn, is the liner 4.

(13) In this embodiment, neither the substrate 2 nor the liner 4 need therefore mandatorily have barrier properties. They may, however, nevertheless be provided, in order to further restrict the permeation of permeates to the electronic structure 3.

(14) In relation to FIGS. 2 and 3, in particular, it is noted that in the present case these are diagrammatic representations. From the representations it is in particular not apparent that the adhesive transfer tape, here and preferably and in each case, has a homogeneous layer thickness. At the transition to the electronic structure, therefore, there is not a sharp edge, as it appears in the representation, but instead the transition is fluid and it is possible instead for small unfilled or gas-filled regions to remain. If desired, however, there may also be conformation to the substrate, particularly when application is carried out under vacuum and/or an autoclave step follows. Moreover, the adhesive is compressed to different extents locally, and so, as a result of flow processes, there may be a certain compensation of the difference in height of the edge structures. The dimensions shown are also not to scale, but instead serve rather only for more effective representation. In particular, the electronic structure itself is generally of relatively flat design (often less than 1 m thick).

(15) Even direct contact of the adhesive with the electronic construction is not mandatory. It is also possible for other layers to be arranged in between, such as a thin-layer encapsulation of the electronic construction, or barrier films, for example.

(16) The thickness of the adhesive transfer tape may span all customary thicknesses, in other words, approximately, from 1 m up to 3000 m. A thickness of between 25 and 100 m is preferred, since, within this range, bond strength and handling properties are particularly positive. A further preferred range is a thickness of 3 to 25 m, since in this range the amount of substances permeating through the bondline can be minimized solely by the small cross-sectional area of the bondline in an encapsulation application.

(17) To produce an adhesive transfer tape of the invention, the carrier of the adhesive tape, or the liner, is coated or printed on one side with the adhesive of the invention, from solution or dispersion or in 100% form (as a melt, for example), or the tape is produced by (co)extrusion. An alternative form of production is by transfer of a layer of adhesive of the invention by lamination to a carrier material or a liner. The layer of adhesive may be crosslinked by heat or high-energy radiation.

(18) This operation preferably takes place in an environment in which the specific permeate is present only in a low concentration or almost not at all. An example that may be given is a relative atmospheric humidity of less than 30%, preferably of less than 15%.

(19) To optimize the properties it is possible for the adhesive employed to be blended with one or more additives such as tackifiers (resins), plasticizers, fillers, pigments, UV absorbers, light stabilizers, aging inhibitors, crosslinking agents, crosslinking promoters or elastomers.

(20) The amount of a layer of adhesive may be within the limits of the amount customary in the adhesive tape sector, that is about from 1 to 3000 g/m.sup.2. It is preferably 1 to 120 g/m.sup.2, preferably 10 to 100 g/m.sup.2, where amount means the amount after any removal of water or solvent that may be carried out.

Test Methods

(21) The measurements are carried out under test conditions of 231 C. and 505% relative humidity.

Measurement of Haze and of Transmittance

(22) The HAZE value describes the fraction of transmitted light which is scattered forward at large angles by the irradiated sample. The HAZE value hence quantifies the opaque properties of a layer that disrupt clear sight through.

(23) The transmittance and the haze of the adhesive are determined in analogy to ASTM D1003-11 (Procedure A (Byk Haze-gard Dual hazemeter), standard illuminant D65) at room temperature on the adhesive in a layer 50 m thick. No correction is made for interfacial reflection losses.

(24) Since for thin adhesive transfer tapes, correct application in the measuring instrument is important in order not to falsify the result, an auxiliary carrier was used. The carrier used was a PC film from GE Plastics (Lexan 8010 film, thickness 125 m).

(25) This carrier met all of the criteria (smooth, planar surface, very low haze, high transmittance, high homogeneity) in order for the adhesive tape specimens to be mounted in a planar manner on the measuring channel.

(26) The measurements were performed on crosslinked adhesive tapes.

Measurement of Refractive Index

(27) The refractive index is determined in a method based on ISO 489 (method A, measuring wavelength 589 nm) at a temperature of 20 C. and a relative humidity of 50%. Shaped articles were produced from the particles by means of pressure and temperature. The contact fluid used in the measurement was cinnamon oil.

Measurement of Water Vapor Permeation Rate WVTR

(28) The WVTR is in this case at 38 C. and 90% relative humidity in accordance with ASTM F-1249. A duplicate determination is carried out in each case, and an average formed. The value reported is standardized for a thickness of 50 m/is based on the particular thickness of the test specimen measured.

(29) For the measurements, the adhesive transfer tapes were bonded to a highly permeable polysulfone membrane (available from Sartorius) which itself makes no contribution to the permeation barrier. The measurements were conducted on crosslinked adhesive tapes.

Lifetime Test

(30) As a measure for determining the lifetime of an electronic construction, a calcium test was employed. This test is shown in FIG. 4. It involves depositing a thin layer of calcium 23, measuring 1010 mm.sup.2, under reduced pressure onto a glass plate 21, and then storing the assembly under a nitrogen atmosphere. The thickness of the calcium layer 23 is approximately 100 nm. The calcium layer 23 is encapsulated using an adhesive tape (2323 mm.sup.2) with the adhesive 22 under test and with a thin glass sheet 24 (30 m, from Schott) as carrier material. For stabilization, the thin glass sheet was laminated with a PET film 26 that was 100 m thick, using an adhesive transfer tape 25 that was 50 m thick, the tape comprising a pressure-sensitive acrylate adhesive of high optical transparency. The adhesive 22 is applied to the glass plate 21 in such a way that the adhesive 22 covers the calcium mirror 23 with a margin of 6.5 mm (A-A) remaining all round. Because of the impervious glass carrier 24, the permeation ascertained is only that through the PSA or along the interfaces.

(31) The test is based on the reaction of calcium with water vapor and oxygen, as described by, for example, A. G. Erlat et al. in 47.sup.th Annual Technical Conference ProceedingsSociety of Vacuum Coaters, 2004, pages 654 to 659, and by M. E. Gross et al. in 46.sup.th Annual Technical Conference ProceedingsSociety of Vacuum Coaters, 2003, pages 89 to 92. The light transmittance of the calcium layer is monitored in the test, and increases as a result of the conversion to calcium hydroxide and calcium oxide. In the case of the test construction described, this increase takes place starting from the margin, and so the visible area of the calcium mirror goes down. The time taken for the absorption of light by the calcium mirror to halve is termed the lifetime. The method captures not only the degradation of the surface of the calcium mirror from the margin and on the surface, as a result of local degradation, but also the uniform reduction in the layer thickness of the calcium mirror as a result of full-area degradation.

(32) Measurement conditions selected were 60 C. and 90% relative humidity. The specimens were bonded over the full area, without bubbles, with a 50 m thickness of the PSA layer. The measurements were carried out on crosslinked adhesive tapes. The result (in h) was obtained as the average value from three individual measurements.

(33) From the time taken for the calcium mirror to break down completely, moreover, a water vapor permeation rate (Carbon atoms-WVTR) is calculated. This is done by multiplying the mass of the vapor-applied calcium by a factor of 0.9 (mass ratio H.sub.2O/Carbon atoms for the conversion reaction of metallic calcium to transparent calcium hydroxide) in order to determine the mass of the water vapor that has entered by permeation. This is then related to the permeation cross section (peripheral length of the test construction x thickness of adhesive) and also to the time taken for the calcium mirror to break down completely. The computed measurement is also divided by the width of the all-round edge (in mm) and thereby standardized to a permeation distance of 1 mm. The Carbon atoms-WVTR is reported in g/m.sup.2*d.

Measurement of MMAP and DACP

(34) MMAP is the mixed methylcyclohexane-aniline cloud point, determined using a modified ASTM C 611 method. Methylcyclohexane is employed for the heptane used in the standard test procedure. The method uses resin/aniline/methylcyclohexane in a ratio of 1/2/1 (5 g/10 ml/5 ml), and the cloud point is determined by cooling a heated clear mixture of the three components until complete clouding just ensues.

(35) The DACP is the diacetone cloud point, and is determined by cooling a heated solution of 5 g of resin, 5 g of xylene and 5 g of diacetone alcohol to the point at which the solution turns cloudy.

Measurement of Peel Adhesion

(36) The peel adhesions on glass were determined in a method similar to ISO 29862 (method 3) at 23 C. and 50% relative humidity, with a peel speed of 30 mm/min and a peel angle of 180. The reinforcing film used was an etched PET film having a thickness of 36 m, as obtainable from Coveme (Italy). The measurement strip was bonded in this case by means of a rolling machine at a temperature of 23 C. The adhesive tapes were peeled off immediately after application. The measurement (in N/cm) was the average from three individual measurements.

Softening Temperature

(37) The softening temperature of copolymers, hard blocks and soft blocks, and uncured reactive resins is determined calorimetrically by way of Differential Scanning calorimetry (DSC) according to DIN 53765:1994-03. Heating curves run with a heating rate of 10 K/min. The specimens are measured in Al crucibles with perforated lids under a nitrogen atmosphere. The heating curve evaluated is the second heating curve. Amorphous substances give glass transition temperatures, while (semi)crystalline substances give melting temperatures. A glass transition can be seen as a step in the thermogram. The glass transition temperature is evaluated as the middle point of this step. A melting temperature can be seen as a peak in the thermogram. The melting temperature recorded is the temperature at which the greatest heat change occurs.

Molecular Weight

(38) The molecular weight determinations of the weight-average molecular weights M.sub.w and of the number-average molecular weights M.sub.n took place by means of gel permeation chromatography (GPC). The eluent used was THF (tetrahydrofuran) with 0.1 vol % of trifluoroacetic acid. The measurement was made at 25 C. The pre-column used was PSS-SDV, 5, 10.sup.3 , ID 8.0 mm50 mm. For the separation, the columns used were PSS-SDV, 5, 10.sup.3 and also 10.sup.5 and 106 each with ID 8.0 mm300 mm. The sample concentration was 4 g/I, the flow rate 1.0 ml per minute Measurement took place against polystyrene standards.

Elongation at Break

(39) The elongation at break is determined in accordance with ISO 29864 (method A, 20 mm test strip width) at 23 C. and 50% relative humidity. The test is carried out on adhesive specimens 500 m thick.

EXAMPLES

(40) In the text below, the invention will be elucidated in more detail by examples, but without wishing to restrict the invention to these examples.

(41) Adhesive

(42) Unless otherwise indicated, all quantities in the examples below are percentages by weight or parts by weight based on the overall composition without photoinitiator. The amount of photoinitiator is based on the amount of epoxy resin used.

(43) Activatable Pressure-Sensitive Adhesive:

(44) TABLE-US-00003 33.4 SibStar 62 M SiBS (polystyrene-block-polyisobutylene parts block copolymer) from Kaneka with 20 wt % block polystyrene content 33.3 Uvacure 1500 cycloaliphatic diepoxide from Cytec, parts viscosity at 23 C. about 300 mPas 33.3 Escorez 5300 a fully hydrogenated hydrocarbon resin from parts Exxon ring and ball softening 105 C., DACP = 71, MMAP = 72 1 part Triarylsulfonium cationic photoinitiator from Sigma-Aldrich hexafluoro- The photoinitiator has an absorption antimonate maximum in the 320 nm to 360 nm range and took the form of a 50 wt % strength solution in propylene carbonate

(45) For the activatable pressure-sensitive adhesive used as adhesive in the examples, the polymer basis selected was a polystyrene-block-polyisobutylene block copolymer from Kaneka. The fraction of styrene in the polymer as a whole is 20 wt %. The molar mass is 60 000 g/mol. The glass transition temperature of the polystyrene blocks is 100 C. and that of the polyisobutylene blocks is 60 C.

(46) The tackifying resin selected was Escorez 5300, a fully hydrogenated hydrocarbon resin from Exxon.

(47) The active resin selected was Uvacure 1500 from Dow, a cycloaliphatic diepoxide (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate). The glass transition temperature of Uvacure 1500 is 53 C.

(48) These raw materials were dissolved at room temperature in a mixture of toluene (300 parts), acetone (150 parts), and special-boiling-point spirit 60/95 (550 parts), to give a 50 wt % solution.

(49) When all of the solid constituents had fully dissolved, the fillers were added. Homogeneous distribution in the adhesive was achieved by using a high-speed laboratory stirrer having a dispersing disk. The weighed-out particles (5% of the solids content of the adhesive) were added in portions to the adhesive already being stirred. Following full addition, the composition was dispersed for 30 minutes. In order to comminute agglomerated solids still present subsequently, the composition was worked on by means of an Ultra-Turrax (from IKA) for a further 5 minutes.

(50) The solution of the photoinitiator was then added.

(51) For the production of adhesive transfer tapes, the adhesives were applied from solution to a conventional siliconized PET liner (Silphan S50 M374 from Siliconature) by means of a laboratory coater. Drying took place initially with 10-minute room-temperature storage, followed by a period of a further 10 minutes in a drying oven at 120 C. Immediately after drying, the layers of adhesive were lined with a further siliconized PET liner (Silphan S50 M371). The thickness of the adhesive layer after drying was 50 m in each case.

(52) For different tests, the adhesive tapes after application were cured in the test construction using UV light (UV dose: sum of UV-A+B+C, determined using the Power Puck from EIT, of 2000 mJ/cm.sup.2). This was done using a laboratory UV irradiation unit from Eltosch with a medium-pressure mercury lamp. Following UV irradiation, the respective construction was after-crosslinked in a drying cabinet at 80 C. for 30 minutes. Fillers used were as follows (table 3):

(53) TABLE-US-00004 Particle Refractive size d50 index Filler Description [m] (23 C.) F1 Ceridust micronized, low molecular 4 1.35 9202 F mass polytetrafluoroethylene (PTFE) from Clariant F2 Ceridust PTFE modified PE wax from 5 1.39 3920 F Clariant F3 Tospearl 3120 micronized silicone resin 12 1.40 from Momentive F4 Ceridust 2051 micronized hydrocarbon wax 7 1.51 from Clariant F5 Spheromers PMMA beads from 15 1.49 CA15-1 Microbeads AS F6 Mowital polyvinyl butyral from 50 1.48 B60HH Kuraray with a polyvinyl alcohol content of 14 wt % and a polyvinyl acetate content of 2.5 wt % F7 Syloid ED2 amorphous silica from 4 1.44* Grace F8 AEROSIL fumed silica hydrophobized 0.016 1.44* R972 with dimethyldichlorosilane, (primary) from Evonik *literature value (at about 20-30 C.) Fillers F3 to F8 result in noninventive examples (comparative examples C1-C6).

(54) Table 4 presents the adhesives produced, which were subsequently processed to form adhesive transfer tapes. Additionally shown are the values found for haze and transmittance.

(55) For example B3, in addition to the filler, vinyltrimethoxysilane (VTMS) was added as a molecularly dispersible getter.

(56) TABLE-US-00005 Fraction of filler Haze Transmittance Filler [wt %] [%] [%] B1 F1 Ceridust 9202 F 5 56.9 90.6 B2 F2 Ceridust 3920 F 5 21.5 92.4 B3 F1 Ceridust 9202 F 5 54.8 91.2 VTMS 5 B4 F1 Ceridust 9202 F 1 16.57 92 B5 F1 Ceridust 9202 F 2.5 35.73 91.3 B6 F1 Ceridust 9202 F 10 80.43 89.17 C1 F4 Ceridust 2051 5 9.7 92.9 C2 F5 Spheromers CA15-1 5 13.7 92.6 C3 F6 Mowital B60HH 5 6.9 92.4 C4 F7 Syliod ED2 5 28.8 92.6 C5 F8 AEROSIL R972 5 2.3 92.5 C6 F3 Tospearl 3120 5 20.1 92.9 C7 none 0 0.61 93.2

(57) The experiments show that surprisingly, below a refractive index of 1.45 (examples B1-B6 and also comparative examples C4 and C6), for a given filler content, a substantially greater haze is obtained with a transmittance barely increased relative to the unfilled adhesive (C5). This effect is particularly strong for a refractive index of less than 1.41 (B2, C6), and especially strong for a refractive index of less than 1.37 (B1, B3, B4-B6).

(58) The refractive index of the crosslinked adhesive was determined as being 1.53. it is also apparent from this that a difference in the refractive index of more than 0.08, more particularly of more than 0.12, and very preferably of more than 0.16 is beneficial to a high translucency. One preferred embodiment of the adhesive therefore has domains whose refractive index is more than 0.8, more particularly more than 0.12, and very preferably more than 0.16 below that of the continuous phase.

(59) Example B3 shows that a molecularly dispersible getter material does not influence the translucency. A getter material of this kind is therefore preferred.

(60) Furthermore, the bond strength of the uncrosslinked adhesive transfer tapes was determined. Table 5 presents the results:

(61) TABLE-US-00006 Peel adhesion on glass [N/cm] Example crosslinked adhesive B1 4.9 C7 6.4

(62) It follows from this that the addition of polymeric fillers reduces the peel adhesion only slightly. For the use of the adhesive for encapsulating an optoelectronic construction, the remaining peel adhesion is completely sufficient.

(63) The following permeation rates were ascertained (standardized to a thickness of 50 m):

(64) TABLE-US-00007 Example WVTR [g/m.sup.2 d] B1 8.4 B2 8.0 C4 12.9 C6 20.2 C7 7.9

(65) The comparison of the permeation rate of examples B1 and B2 with the unfilled adhesive (C7) shows only a slight change, explainable by the water repellency properties of the fluorine-containing filler. The silicone-based filler F3 in C6 has a very high WVTR, as known for silicones. There is therefore a marked deterioration in the WVTR of the adhesive. Silicones, therefore, are not suitable for the application, and fluorine-containing polymers are preferred.

(66) The inorganic filler in C4, while not itself water vapor permeable, does increase the polarity in the adhesive, and so the WVTR goes up. This shows one disadvantage of polar inorganic fillers.

(67) Furthermore, the lifetime test was carried out. Permeation rates determined were as follows (table 6):

(68) TABLE-US-00008 Example Ca-WVTR [g/m.sup.2 d] B1 0.38 B3 0.24 C7 0.30

(69) The permeation rates determined in the calcium test likewise show that the barrier properties are impaired only slightly (B1 vs. C7) as a result of adding the fluorine-containing polymer. The further addition of a getter material (B3) leads to significantly improved permeation properties.