BARRIER ADHESIVE MASS WITH POLYMER GETTER MATERIAL

Abstract

The invention relates to a barrier adhesive mass having high breakthrough times for water and also providing a good adhesive performance. This is achieved by a barrier adhesive mass comprising at least one elastomer and at least one reactive resin, and is characterised in that the barrier adhesive mass comprises at least one polymer G containing at least two functions suitable for constructing a polymer, as well as at least two hydrolysable silyl groups. The invention also relates to an adhesive tape comprising a barrier adhesive mass according to the invention, and to the use of an adhesive mass of this type for sealing electronic assemblies.

Claims

1. A barrier adhesive compound, comprising at least one elastomer and at least one reactive resin, wherein; the barrier adhesive compound comprises at least one polymer G, containing at least two functional groups capable of building a polymer and at least two hydrolyzable silyl groups.

2. The barrier adhesive compound of claim 1, wherein the at least one polymer G has a polyacrylate backbone.

3. The barrier adhesive compound of claim 1, wherein the functional groups capable of building a polymer are selected independently of one another, and are selected from the group consisting of: vinyl groups, (meth)acrylate groups, hydroxy groups, amino groups, isocyanate groups, cyclic ether groups, and epoxy groups.

4. The barrier adhesive compound of claim 1, wherein the functional groups capable of building a polymer are selected independently from one another, and are selected from: (meth)acrylate groups and epoxy groups.

5. The barrier adhesive compound of claim 1, wherein the functional groups capable of building a polymer comprise epoxycycloalkyl groups.

6. The barrier adhesive compound claim 1, wherein the hydrolyzable silyl groups correspond to formula (I)
Si(OR.sup.1).sub.xR.sup.2.sub.3-x(I), in which: R.sup.1 is a methyl and/or an ethyl residue; and, R.sup.2 is an alkyl and/or an aryl residue; and, x=1 to 3.

7. The barrier adhesive compound of claim 6, wherein each R.sup.1 is an ethyl residue.

8. The barrier adhesive compound of claim 6, wherein x=2 or 3.

9. The barrier adhesive compound of claim 1, wherein the at least one elastomer is a vinyl aromatic block copolymer.

10. The barrier adhesive compound of claim 1, wherein the at least one reactive resin contains cyclic ether groups.

11. The barrier adhesive of claim 1 which contains 15-80% wt. of a reactive resin based on the total weight of the barrier adhesive compound.

12. The barrier adhesive compound of claim 1, wherein the barrier adhesive compound is a pressure-sensitive adhesive compound.

13. An adhesive tape, comprising a barrier adhesive compound of claim 12.

14. A method of sealing of electronic devices comprising the step of: applying the barrier adhesive compound of claim 1 to a surface of the electronic device.

Description

EXAMPLES

Measurement Methods

Determination of Penetration Time

Accelerated Life Test

[0094] A calcium test was conducted as a measure of determination of the useful life of an electronic structure. This is shown in FIG. 1. For this purpose, a 10?10 mm.sup.2 large, thin calcium layer 23 was deposited in a vacuum on a glass plate 21 and then stored in a nitrogen atmosphere. The thickness of the calcium layer 23 was approximately 100 nm. For encapsulation of the calcium layer 23, an adhesive tape (23?23 mm.sup.2) with the adhesive compound to be tested 22 and a thin glass sheet 24 (35 ?m, manufactured by Schott) was used as a carrier material. For stabilization, the thin glass sheet was laminated with a 100 ?m thick PET film 26 by means of a 50 ?m thick transfer adhesive tape 25 from a highly optically transparent acrylate pressure-sensitive adhesive compound. The adhesive compound 22 was applied to the glass plate 21 in such a way that the adhesive compound 22 covered the calcium level 23 with an edge protruding on all sides measuring 6.5 mm (A-A). Because of the opaque glass carrier 24, only the permeation through the pressure-sensitive adhesive or along the interfaces was determined.

[0095] The test is based on the reaction of calcium with water vapour and oxygen, as described for example by A. G. Erlat et al. in 47th Annual Technical Conference ProceedingsSociety of Vacuum Coaters, 2004, pp. 654 to 659, and M. E. Gross et al. in 46th Annual Technical Conference ProceedingsSociety of Vacuum Coaters, 2003, pp. 89 to 92. In this case, the optical transmission of the calcium layer, which increases with the conversion into calcium hydroxide and calcium oxide, is monitored. This conversion took place in the test structure described beginning from the edge, so that the visible surface of the calcium level decreased. The time required for reducing the light absorption of the calcium level by half is referred to as useful life. This method allowed determination of both the reduction in the area of the calcium level beginning from the edge and the local decrease in the area, as well as the homogeneous decrease in the layer thickness of the calcium level by full-surface degradation.

[0096] 60? C. and 90% relative humidity were selected as measurement conditions. The sample was bonded over the entire area and blister-free with a layer thickness of the pressure-sensitive adhesive compound of 50 ?m. The reduction in the Ca level was followed by means of transmission measurements. The penetration time is defined as the time required by moisture to cross the distance to the Ca. During this time, the transmission of the Ca level changes only marginally.

Adhesive Compound Layers

Starting Materials Used:

[0097]

TABLE-US-00001 Sibstar 62M SiBS (polystyrene-block-polyisobutylene-block copolymer, M = 60.000 g/mol) manufactured by Kaneka with 20 wt. % block polystyrene content. The glass transition temperature of the polystyrene block was 100? C. and that of the polyisobutylene block was ?60? C. The SiBS had a diblock content of 36 wt. %. Uvacure 1500 Cycloaliphatic diepoxide manufactured by Cytec Escorez 5300 Fully hydrated hydrocarbon resin manufactured by Exxon (ring and ball 105? C., DACP = 71, MMAP = 72) 3-Glycidoxypropyltri- Epoxy-modified trimethoxysilane methoxysilane (CAS: 2530-83-8) Shin-Etsu X12-981S Polymeric getter with triethoxysilyl and epoxy side groups, epoxy equivalent = 290 g/mol, ratio (number of groups) epoxy/ethoxysilyl = 3 Triarylsulfonium Cationic photoinitiator from Sigma-Aldrich hexafluoroantimonate The photoinitiator shows an absorptions maximum in the range of 320 nm to 360 nm and was in the form of a 50 wt. % solution in propylene carbonate

Example 1

[0098] For the production of adhesive compound layers, various adhesive compounds were applied from a solution to a conventional liner (siliconized polyester film) by means of a laboratory application device and dried. The adhesive compound layer thickness after drying was 50?5 ?m. Drying was carried out in each case first at RT for 10 minutes and then for 10 minutes at 120? C. in a laboratory drying cabinet. The respective dried adhesive compound layers were immediately laminated with a second liner (siliconized polyester film with low separating force) on the open side.

[0099] Sibstar 62M, Escorez 5300, Uvacure 1500, and the silyl functional polymeric getter (see Table 1 for parts by weight) were dissolved in a mixture of toluene (300 g), acetone (150 g), and special boiling point solvent 60/95 (550 g), giving rise to a 50 wt. % solution. After this, triarylsulfonium hexafluoroantimonate was added to the solution as a photoinitiator.

[0100] By means of a doctor blade method, the formulation was coated from solution onto a siliconized PET liner and dried at 120? C. for 15 min. The amount of the compound applied was 50 g/m.sup.2. The sample was covered with a further layer of a PET layer that was also siliconized but separated more easily.

[0101] The sample was sluiced into a glove box. A portion of the sample was laminated in a blister-free manner with a rubber application roller onto a Ca-vapour-plated glass substrate. This was covered with the second PET liner, and a layer of a thin sheet glass was laminated onto it. After this, curing was carried out through the covering glass by UV irradiation (dose: 80 mJ/cm.sup.2; lamp type: non-doped mercury lamp). This sample was used for the accelerated life test.

TABLE-US-00002 TABLE 1 Compositions Example: K1 K2 K3 K4 V1 V2 V3 V4 V5 wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. % SiBStar 62M 35.5 34.7 33.6 31.7 37.5 35.5 34.7 33.6 31.7 Uvacure 1500 24 23.5 22.7 21.5 25 24 23.5 22.7 21.5 Shin-Etsu X12-981S 5 7 10 15 0 0 0 0 0 3-Glycidoxypropyl- 0 0 0 0 0 5 7 10 15 trimethoxysilane Escorez 5300 35.4 34.7 33.6 31.7 37.4 35.4 34.7 33.6 31.7 Triarylsulfonium 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 hexafluoroantimonate

[0102] The water penetration times in the Ca test are shown in Table 2:

TABLE-US-00003 TABLE 2 Penetration times in climate testing 60? C./90% rH) 5% Getter 7% Getter pene- pene- 10% Getter 15% Getter tration tration penetration penetration Name time (h) time (h) time (h) time (h) K1-K4 (getter X12- 1250 1400 1450 1550 981S) V2-V5 (getter (3- 1050 1175 980 720 glycidyloxypropyl) trimethoxysilane))

[0103] The penetration times for pressure-sensitive adhesives with the polymeric multifunctional getter according to the invention are significantly improved compared to low-molecular trimethoxysilanes (V2-V5). This is surprising, because the low-molecular weight getter contains a larger number of hydrolyzable groups per mass unit. Presumably, this is attributable to the fact that the groups of the getter according to invention that are capable of polymerization are involved in the reaction during the curing step, and the network density is therefore not reduced as in the case of low-molecular getter.