Adhesive tape containing getter material

Abstract

The aim of the invention is to effectively protect a flat adhesive compound from permeates originating from the surroundings as well as from permeates trapped during lamination, winding, stacking or other processing steps. For this purpose, the adhesive tape comprises at least the following layers in the indicated order: a first outer adhesive compound layer A, a layer B, which contains at least one inorganic getter material, and a second outer adhesive compound layer C. The invention also relates to the use of said adhesive tape as an encapsulation material.

Claims

1. An adhesive tape comprising the layers A, B and C in the order stated, wherein: layer A is a first outer layer of adhesive, layer B is a continuous layer comprising at least 95 wt %, based on a total weight of the layer B, of at least one inorganic getter material, and layer C is a second outer layer of adhesive wherein the getter material in its application form has a minimum permeate uptake capacity for water and/or oxygen of 1% of its own weight, and wherein the inorganic getter material is selected form the group consisting of calcium sulfate, calcium chloride, calcium oxide, fumed silicas, zeolites, and a mixture of two or more of the above substances.

2. The adhesive tape of claim 1, wherein at least one of the layers A and C consists of a pressure sensitive adhesive.

3. The adhesive tape of claim 2, wherein the getter material is present in particulate form in the layer B.

4. The adhesive tape of claim 1, wherein the getter material is present in particulate form in the layer B.

5. The adhesive tape of claim 1 which comprises, in addition to the layers A, B, and C, a carrier layer which does not comprise any getter material and is disposed between the layers A and C.

6. The adhesive tape of claim 1, wherein layer B comprises at least 99 wt %, based on a total weight of the layer B, of the at least one inorganic getter material.

7. The adhesive tape of claim 1, wherein layer A and layer C both consist of pressure sensitive adhesives.

8. An adhesive tape comprising the layers A, B and C in the order stated, wherein: layer A is a first outer layer of adhesive, layer B is a continuous layer comprising at least 95 wt %, based on a total weight of the layer B, of at least one inorganic getter material, and layer C is a second outer layer of adhesive wherein layer A and layer C layers each consist of the same adhesive.

9. An adhesive tape comprising the layers A, B and C in the order stated, wherein: layer A is a first outer layer of adhesive, layer B is a continuous layer comprising at least 95 wt %, based on a total weight of the layer B, of at least one inorganic getter material, and layer C is a second outer layer of adhesive, and wherein the layer A and the layer C each have a water vapor permeation rate of less than 50 g/(m.sup.2*d), said water vapor permeation rates being measured based on an adhesive thickness of 50 m, measured at 38 C. and 90% relative humidity in accordance with the American Society for Testing and Materials (ASTM) F-12249 test.

10. An adhesive tape comprising the layers A, B and C in the order stated, wherein: layer A is a first outer layer of adhesive, layer B is a continuous layer comprising at least 95 wt %, based on a total weight of the layer B, of at least one inorganic getter material, and layer C is a second outer layer of adhesive, and wherein the adhesive tape further comprises, in addition to the layers A, B, and C, at least one carrier layer and at least one barrier layer against one or more permeates, the barrier layer and the carrier layer being in direct contact with one another and disposed between the layers A and C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a continuous layer 20 of inorganic getter material in between them.

(2) FIG. 2 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a perforated layer 21 of inorganic getter material in between them.

(3) FIG. 3 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a perforated layer 22 of inorganic getter material in between them, with the adhesives penetrating the layer of getter material and at least partly surrounding it.

(4) FIG. 4 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a layer 23 of particulate inorganic getter material in between them.

(5) FIG. 5 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a layer 23 of particulate inorganic getter material in between them, with the adhesives penetrating the layer of getter material and at least partly surrounding it.

(6) FIG. 6 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a layer 24 of particulate inorganic getter material in between them, the getter material being embedded in a stretched polymer matrix. The matrix material does not fully wet the getter particles (not shown explicitly in the figure), but only partly if at all. The resulting porosity therefore allows the permeates to easily reach the surface of the getter material.

(7) FIG. 7 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a layer 25 of particulate inorganic getter material in between them, the getter material being embedded loosely in a sheetlike textile structure.

(8) FIG. 8 likewise shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a layer 25 of particulate inorganic getter material in between them, the getter material being embedded loosely in a sheetlike textile structure.

(9) FIG. 9 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also two continuous layers 20, 21 of inorganic getter material in between them, the layers 20 and 21 being applied each on one side of a continuous carrier material 30.

(10) FIG. 10 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also two continuous layers 20, 21 of inorganic getter material in between them, the layers 20 and 21 being applied each on one side of a perforated carrier material 31.

(11) FIG. 11 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a layer 24 of particulate inorganic getter material in between them, the getter material being embedded in a stretched polymer matrix and the adhesives being lined with release liners 40, 41.

(12) FIG. 12 shows an adhesive tape which consists of two layers 10, 11 of adhesive and also a continuous layer 20 of inorganic getter material in between them and also an inorganic barrier layer 50, the layer 20 being applied on one side and the inorganic barrier layer 50 being applied on the other side of a continuous carrier material 30.

(13) A further subject of the invention is a process for producing an adhesive tape of the invention, said process comprising the following steps: providing a first layer A of adhesive; applying a layer B comprising at least one inorganic getter material to the layer A, by coating or laminating, for example; covering the free side of the layer B with a further layer C of adhesive, by coating or laminating, for example.

(14) An alternative embodiment of the process for producing an adhesive tape of the invention comprises the following steps: providing an auxiliary carrier, as for example an abhesive liner, an abhesive web or roll; applying a layer B comprising at least one inorganic getter material; covering the layer B with a first layer A of adhesive, by means of coating or laminating, for example; detaching the assembly from the auxiliary carrier and covering the exposed surface with a second layer C of adhesive, by coating or laminating, for example.

(15) The processes of the invention take place preferably within an environment in which the specific permeate is present only at a low concentration or essentially not at all. For the case of water (vapor) as permeate, an example might be a relative atmospheric humidity of less than 30%, preferably less than 15%.

(16) A further subject of the invention is the use of calcium and/or calcium oxide to indicate the permeate content of an adhesive and/or of an adhesive tape. With increasing binding of water, accordingly, calcium oxide changes its color from white to transparent. Metallic calcium as well, with increasing uptake of water, loses its metallically opaque appearance and becomes increasingly transparent. So as long as getter material can still be seen in the visual appearance of the unspent state, this may be taken as an indication that as yet no permeate, or at most little permeate, has diffused into the adhesive that is to be protected.

(17) A further subject of the invention is the use of an adhesive tape of the invention as encapsulation material, more particularly for the protection of electronic arrangements, foods and/or drugs. An adhesive tape of the invention is outstandingly suitable for encapsulating an electronic arrangement with respect to permeates, by the application of the adhesive tape to and/or around those regions of the electronic arrangement that are to be encapsulated. Besides the optoelectronic arrangements already mentioned, use is similarly advantageously possible in other electronic arrangements such as electrochemical cells, e.g., fuel cells or electrolysis cells, and/or batteries. In the region of packaging as well, especially the packaging of foods or drug packaging, adhesive tapes of the invention are highly suitable.

(18) Encapsulation in the present context refers not only to complete enclosure of the region to be encapsulated, but even just regional application of an adhesive tape of the invention to those regions to be encapsulated of an electronic arrangement in particular, as for example a single-sided covering or encasing of an electronic structure.

(19) In principle, two modes of encapsulation can be carried out with adhesive tapes. Either the adhesive tape is diecut or cut to shape beforehand, and bonded only around the regions that are to be encapsulated, or it is bonded over the full area of the regions to be encapsulated. An advantage of the second variant is the greater ease of handling and the often better protection.

EXAMPLES

(20) Various adhesive tapes filled with getter material were produced. They were laminated from various layers by means of a laboratory roll laminator in a controlled-climate chamber at 23 C. and a relative atmospheric humidity of 50%.

(21) Layers of Adhesive:

(22) To produce layers of adhesive, different adhesives were applied from solution to a conventional liner of type SILPHAN S75 M371 (silicone coated PET) from Siliconature, using a laboratory coating device, and were dried. The thickness of the layer of adhesive after drying was 12 m in each case. Drying took place in each case at 120 C. for 30 minutes in a laboratory drying cabinet. The indication of parts in the listing below denotes parts by weight.

(23) TABLE-US-00001 K1: Pressure sensitive adhesive 100 parts Tuftec SBBS with 30 wt % block polystyrene P 1500 content, from Asahi. The SBBS contains about 68 wt % diblock content. 100 parts Escorez Hydrogenated HC resin with a softening 5600 point of 100 C., from Exxon 25 parts Ondina White oil composed of paraffinic and 917 naphthenic fractions, from Shell The solvent used was a mixture of toluene and acetone in a ratio of 2:1

(24) TABLE-US-00002 K2: Hotmelt adhesive 100 parts Kraton FG 1924 Maleic anhydride-modified SEBS with 13 wt % block polystyrene content, 36 wt % diblock, and 1 wt % maleic acid from Kraton 25 parts Escorez 5600 Hydrogenated HC resin with a softening point of 100 C., from Exxon 1 part Aluminum acetylacetonate The solvent used was a mixture of toluene and acetone in a ratio of 2:1

(25) TABLE-US-00003 K3: Radiation-activatable hotmelt adhesive 25 parts Epiclon Bisphenol A and bisphenol F-based 835 LV epoxy resin from DIC, Japan, molecular weight M.sub.w about 350 g/mol 25 parts Epicote Bisphenol-based epoxy resin from 1001 Mitsubishi Chemical Company, Japan, molecular weight M.sub.w about 900 g/mol 50 parts YP-70 Bisphenol A and bisphenol F-based phenoxy resin from Nippon Steel Chemical Group, Japan, molecular weight M.sub.w about 55 000 g/mol 1.5 parts Irgacure lodonium salt-based UV 250 photoinitiator from BASF (iodonium, (4-methylphenyl) [4-(2-methylpropyl)phenyl]-, hexafluorophosphate(1-)) The solvent used was methyl ethyl ketone.

(26) TABLE-US-00004 K4: Heat-activatable adhesive 90 parts Ultramid 1C Copolyamide 6/66/136 from BASF with a viscosity number in 96% strength sulfuric acid according to ISO 307 of 122 ml/g 10 parts EPR 166 Bisphenol-based epoxy resin from Bakelite, epoxide number of 184 20 parts PEG 2000 Polyethylene glycol with average molar mass of 2000 20 parts Foralyn 5040 Tackifier resin from Eastman The adhesive was produced in an operation as set out in DE 102006047739 A1 with ethanol as solvent.

(27) The layers of adhesive were stored at 23 C. and 50% relative atmospheric humidity for 72 hours (conditioning A). The water content of the layers of adhesive was determined in each case prior to combination with the getter material.

(28) Measurement of Water Content

(29) The water content was determined in accordance with DIN 53715 (Karl-Fischer titration). The measurement was made on a Karl-Fischer coulometer 851 in conjunction with an oven sampler (oven temperature 140 C.). A triple determination was carried out with an initial mass of around 0.3 g in each case. The water content reported is the arithmetic mean of the measurements.

(30) Measurement of Water Vapor Permeation Rate

(31) The WVTR is measured at 38 C. and 90% relative atmospheric humidity in accordance with ASTM F-1249 and is standardized for a thickness of 50 m.

(32) TABLE-US-00005 Water Water content vapor Layer [ppm] permeation of conditioning rate adhesive A [g/m.sup.2 d] K1 853 37 K2 551 22 K3 3216 32 K4 16400 220

(33) In addition, specimens of the layer of adhesive 1 were also dried for only 5 minutes at 120 C. The residual solvent content remaining was determined immediately after drying.

(34) Determination of Residual Solvent Content:

(35) The residual solvent content of the adhesives was determined by means of headspace gas chromatography. A sample with an area of about 12.5 cm.sup.2 was cut from the swatch specimen, adhered to a metal wire spiral, and transferred to a headspace sample vial measuring around 22 ml.

(36) The samples were measured using a Dani GC 86.10 gas chromatograph with Quma QHS-S40 autosampler. The samples were conditioned in the instrument at 120 C. for 1 hour. Detection took place using a flame ionization detector (FID). The peaks in the GC were quantified against external standards.

(37) TABLE-US-00006 Residual solvent Layer content [mg/m.sup.2] of (based on 25 m adhesive layer thickness) K1 102 (5 min drying)
Production of Matrices Comprising Getter Material:
Matrix Layer with Incompletely Embedded Getter Material (Getter Material Partly Surrounded by Matrix Material)

(38) The polypropylene polymers Inspire D 404.01 and 7C06 from Dow were mixed in a ratio of 1:1 and extruded. The mixture is identified below as PP matrix. The film was produced in a layer on a twin-screw extrusion unit from Coperion (d=25 mm, L/d=37) with flange-connected flat die, followed by a chill roll station. The getter material was supplied by means of a side feeder after the melting and homogenizing of the polymer components in an amount of 30 wt %.

(39) The die temperature was 235 C., the chill roll temperature 85 C. After cooling, the film was clamped into a simultaneous laboratory stretching frame and stretched simultaneously in an oven at a temperature of 150 C. in two directions at right angles to one another within the film plane. The stretching ratio in both directions was about 1:7. The film had a final thickness of about 30 m.

(40) The film produced was tested for its water vapor permeability at 38 C. and 90% relative atmospheric humidity in accordance with ASTM F-1249. For a measurement area of 10 cm.sup.2, values above the upper limit of the instrument, of 1000 g/m.sup.2, were obtained, enabling the conclusion that pores have formed around the getter particles as intended.

(41) Matrix Layer with Embedded Getter Material (Getter Material Surrounded by Matrix Material)

(42) As a further example, the film extruded as above was pressed in a Lauffer vacuum press at a temperature of 230 C. to give a film having a weight per unit area of 30 g/m.sup.2.

(43) The film produced was measured for its water vapor permeability at 38 C. and 90% relative atmospheric humidity in accordance with ASTM F-1249. After the establishment of the equilibrium state (saturation of the getter material beforehand), a water vapor permeability of 43 g/m.sup.2d was found. As expected, therefore, the getter material was completely surrounded by the matrix material.

(44) Immediately after their production, the getter-filled carrier layers were welded into vacuum-treated pouches of a permeation-impervious film laminate (polyester film/aluminum foil/sealing adhesive film), stored under a nitrogen atmosphere in a glovebox, and not removed until immediately before use.

(45) Getter Materials Used:

(46) TABLE-US-00007 Designation Description Trade name Supplier G1 Calcium Calcium oxide Sigma- oxide nanopowder Aldrich G2 Lithium Lithium chloride Sigma- chloride anhydrous Aldrich G3 Calcium High-purity Osnabruegge calcium granules G4 Barium High-purity Osnabruegge barium granules G5 Zeolite 13X Molecular Sieves, Sigma- 13X powder Aldrich
Production of Adhesive Tapes:

(47) The adhesive tapes were produced in a dry environment at 23 C. and approximately 20% relative humidity.

(48) Adhesive tapes with the powder-form getter materials G1, G2, and G5 were produced by using a screen to scatter a quantity of approximately 2 g/m.sup.2 to one side of a layer of adhesive. The second layer of adhesive was then laminated onto the scattered side, by means of a laboratory laminating device, at the temperature reported in each case below.

(49) As a comparative example, the same amount of getter material was dispersed into the dissolved adhesive, which had been freed beforehand from water using zeolite beads from Sigma-Aldrich, and the adhesive was coated out and dried as described above. Here a layer of adhesive with a thickness of 25 m was produced.

(50) For adhesive tapes with the metallic getter materials, the metal was applied by vapor deposition, producing in each case a getter material layer thickness of approximately 300 nm.

(51) In one instance, one side of the layer of adhesive was vapor-coated, and the vapor-coated side was then laminated to the second layer of adhesive.

(52) In the other instance, a carrier film was vapor-coated with the getter material. This carrier film was laminated on both sides to one layer of adhesive in each case, as indicated above.

(53) The carrier film used was a polyester film having a thickness of approximately 12 m and a coating of an inorganic barrier layer approximately 40 nm thick (GX-P-F from Toppan Printing, hereinafter called barrier PET), with the getter material layer being applied on the side of the polyester film opposite from the inorganic barrier layer.

(54) For adhesive tapes with a matrix layer comprising the getter material, the matrix layer was laminated on both sides with the layer of adhesive indicated in each case.

(55) Table 1 shows an overview of the adhesive tapes produced containing getter material:

(56) TABLE-US-00008 TABLE 1 Getter material-filled adhesive tapes Laminating Adhe- Carrier Getter Matrix Adhe- temperature sive 1 material material material sive 2 [ C.] Example 1 K1 G1 K1 60 2 K1 G2 K1 3 K1 G3 K1 4 K1 G4 K1 5 K1 G1 PP K1 6 K1 G2 PP K1 7 K1 barrier- G3 K1 PET 8 K2 G1 K2 120 9 K2 G2 K2 10 K2 G3 K2 11 K2 G4 K2 12 K2 G1 PP K2 13 K2 G2 PP K2 14 K2 barrier- G3 K2 PET 15 K3 G1 K3 100 16 K3 G2 K3 17 K3 G3 K3 18 K3 G4 K3 19 K3 G1 PP K3 20 K3 G2 PP K3 21 K3 barrier- G3 K3 PET 22 K4 G1 K4 100 23 K4 G2 K4 24 K4 G3 K4 25 K4 G4 K4 26 K4 G1 PP K4 27 K4 G2 PP K4 28 K4 barrier- G3 K4 PET 29 K1* G5 K1* 60 30 K1 G1 PP K1 60 31 K1 G2 PP K1 60 Compar- ative examples C1 G1 K1 C2 G2 K1 C3 G5 K1* *brief drying, with residual solvent

(57) For Examples 1, 2, 5, 6 and 29-31 and also for Comparative Examples C1-3, the bond strengths to steel were determined in analogy to ISO 29862 (method 3) at 23 C. and 50% relative atmospheric humidity with a take-off speed of 300 mm/min and a peel angle of 180. The reinforcing film used was an etched PET film with a thickness of 50 m, as available from Coveme (Italy).

(58) The measuring strip here was bonded at a temperature of 60 C. using a laboratory laminator. Table 2 shows the results.

(59) For further investigation, adhesive tape sections measuring about 100100 mm.sup.2 were lined on both sides with a permeation-impervious liner of type Alu I 38 UV1 from Mondi, including an aluminum foil carrier. Lamination took place at a temperature of 100 C. in order to allow close conformation of the liner. The liner therefore prevents water permeating from the adhesive tape into the glovebox during storage.

(60) The specimens were stored in the glovebox under the stated conditions for a period of 14 days.

(61) Finally, the water content and/or toluene content of the adhesive in the specimens was ascertained. Samples here were taken from the middle of the specimen area, in order to avoid edge effects. Getter, carrier or matrix materials present were not removed. The assumption is that regeneration of the getter and hence release of permeates takes place only at significantly higher temperatures than those used for measurement. The results are summarized in Table 2:

(62) TABLE-US-00009 TABLE 2 Testing of the drying of the layers of adhesive and their adhesive properties Water Bond content strength Example [ppm] [N/cm] 1 480 6.1 2 215 6.0 3 459 4 632 5 104 6.5 6 87 6.5 7 734 8 320 9 80 10 306 11 421 12 108 13 84 14 489 15 2200 16 550 17 2103 18 2894 19 244 20 195 21 3364 22 28667 23 3757 24 27703 25 33663 26 1670 27 835 28 34096 31 207 6.5 (28d: 122) 32 186 6.5 (28d: 106) C1 384 5.5 C2 96 4.6 Residual solvent content Example [mg/m.sup.2] 29 76 5.9 C3 69 6.0

(63) The results show that drying of the adhesive is achieved in the case of the adhesive tapes of the invention. In comparison to adhesive tapes of the prior art (C1-C3), the adhesive tapes of the invention (Examples 1, 2, 29, 5, 6) achieve similar drying efficiency, but without having the disadvantages of the comparative examples in terms of bonding properties. Accordingly, the comparative specimens C1 and C2 produced in accordance with the prior art have lower bond strengths owing to the getter materials dispersed in the adhesive.

(64) These conclusions also apply equivalently with regard to the removal of residual solvents (Example 29 and Comparative Example C3).

(65) When Examples 5 and 6 are compared with Examples 31 and 32, the advantage of a particulate getter material only partly surrounded by matrix material (Examples 5 and 6) relative to a substantially completely surrounded particulate getter material (Examples 31 and 32) becomes apparent: after a storage time of 14 days, Examples 5 and 6 exhibit a much lower water content than Examples 31 and 32. The latter were subsequently stored for a further 14 days, after which their water content was at a similarly low level to that of Examples 5 and 6. The drying was therefore quicker in the case of constructions according to the invention, with particulate getter material only partly surrounded by matrix material.

(66) It is advantageous, furthermore, if the carrier material itself exhibits a high barrier with respect to the permeate (Examples 7, 14, 21 and 28) since in that case the getter capacity can be adapted to the amount of permeate to be actually taken up. In the experiments, the water content found was higher overall than in the complementary examples without a carrier film (3, 10, 17 and 24), permitting the conclusion that only the layer of adhesive in contact with the getter layer was freed from permeate. It would also be possible, therefore, to reduce the getter content in the design of such adhesive tapes.