PRESSURE SENSITIVE ADHESIVE ELECTROLYTE

Abstract

A pressure sensitive adhesive polymer electrolyte having a peel adhesion by test A of more than 1 N/cm and an ionic conductivity by test B of more than 10.sup.−6 (ohm*cm).sup.−1, prepared by polymerizing: 5-60 wt % of acrylate monomer from the group of the (meth)acrylic esters having 4-15 carbon atoms, which as a homopolymer would have a T.sub.g by test C of less than −30° C., 10-80 wt % of acrylate monomer from the group of the (meth)acrylic esters having 4-25 carbon atoms and containing at least one heteroatom, which as a homopolymer would have a T.sub.g by test C of less than 100° C., 0.05-10 wt % of initiator, 2-13 wt % of conducting salt, optionally plasticizer, and optionally solvent, which after the polymerization is typically removed at least partly,
where optionally one or more of the components are added at least proportionally only during or after the polymerization.

Claims

1. Pressure sensitive adhesive polymer electrolyte having a peel adhesion by test A of more than 1 N/cm and an ionic conductivity by test B of more than 10.sup.−6 (ohm*cm).sup.−1, prepared by polymerizing a mixture comprising at least the following components: a. 5-60 wt % of acrylate monomer selected from the group consisting of (meth)acrylic esters having 4-15 carbon atoms, which as a homopolymer would have a T.sub.g by test C of less than −30° C., b. 10-80 wt % of acrylate monomer selected from the group consisting of (meth)acrylic esters having 4-25 carbon atoms and containing at least one heteroatom, which as a homopolymer would have a T.sub.g by test C of less than 100° C., c. 0.05-10 wt % of initiator, d. 2-13 wt % of conducting salt, e. optionally plasticizer, f. and optionally solvent, where optionally one or more of the components are added at least proportionally only during or after the polymerization.

2. Pressure sensitive adhesive polymer electrolyte according to claim 1, wherein the initiator is a thermal initiator and/or a photoinitiator.

3. Pressure sensitive adhesive polymer electrolyte according to claim 1, wherein the polymerization is a UV polymerization.

4. Pressure sensitive adhesive polymer electrolyte according to claim 1, wherein the mixture further comprises crosslinker.

5. Pressure sensitive adhesive polymer electrolyte according to claim 1, characterized by a haze by test D of less than 10%.

6. Pressure sensitive adhesive polymer electrolyte claim 1, characterized by a transmission by test E of more than 75%.

7. Pressure sensitive adhesive polymer electrolyte claim 1, characterized by a colour parameter b* by test F of −6<b*<6.

8. Pressure sensitive adhesive polymer electrolyte claim 1, characterized by a colour parameter a* by test F of −6<a*<6.

9. Pressure sensitive adhesive polymer electrolyte claim 1, characterized by a heat resistance by test G of more than 60° C.

10. Pressure sensitive adhesive polymer electrolyte claim 1, characterized by a holding power by test H of more than 10 min.

11. Pressure-sensitive adhesive tape comprising at least one layer of a pressure sensitive adhesive polymer electrolyte according to claim 1, where the pressure-sensitive adhesive tape is optionally double-sidedly adhesive and optionally is an adhesive transfer tape.

12. Roll of product comprising (a) a roll core and (b) in web form, a pressure-sensitive adhesive tape according to claim 11, with the pressure-sensitive adhesive tape being wound in multiple plies in the form of an Archimedean spiral on the roll core.

13. Method of using the pressure sensitive adhesive polymer electrolyte according to claim 1 or an adhesive tape comprising said pressure sensitive adhesive polymer electrolyte in an electrochromic glazing system or a battery.

14. Electrochromic system comprising a first half-cell A and a second half-cell B, with the two half-cells A and B being joined to one another over the full area or a partial area by way of a pressure sensitive adhesive polymer electrolyte according to claim 1 or an adhesive tape comprising said pressure sensitive adhesive polymer electrolyte.

15. Method for producing an electrochromic system, comprising joining a first half-cell A and a second half-cell B to one another to form an electrochromic system by lamination of a pressure sensitive adhesive polymer electrolyte according to claim 1 or an adhesive tape comprising said pressure sensitive adhesive polymer electrolyte.

Description

EXAMPLES

[0117] Raw materials used in the examples were as follows:

[0118] (a) Acrylate monomers: [0119] 2-ethylhexyl acrylate (EHA) from BASF, which in homopolymerized form has a T.sub.g by test C of −50° C. [0120] 2-(2-ethoxyethoxy)ethyl acrylate from Polysciences, which in homopolymerized form has a T.sub.g by test C of −70° C. [0121] 2-cyanoethyl acrylate (2-CEA, Bimax name BX-2-CEA) from Bimax Speciality Polymers, which in homopolymerized form has a T.sub.g by test C of 4° C. [0122] Glycidyl methacrylate from Mitsubishi Gas Chemical Company, which in homopolymerized form has a T.sub.g by test C of 41° C.

[0123] (b) Thermal initiators: [0124] Vazo 67™: 2,2′-azobis(2-methylbutyronitrile) from DuPont

[0125] (c) Photoinitiators: [0126] Benzoin ethyl ether from Sigma-Aldrich [0127] Lauroyl peroxide (LPO) (C.sub.24H.sub.46O.sub.4) from Sigma-Aldrich, also suitable as a thermal initiator

[0128] (d) Radical scavenger: [0129] Perkadox 16™: Bis(4-tert-butylcyclohexyl) peroxydicarbonate from Akzo Nobel

[0130] (e) Crosslinkers: [0131] Hexanediol diacrylate (HDDA) from Polysciences [0132] Trimethylolpropane trimethacrylate (TMPTMA) (C.sub.16H.sub.26O.sub.6) from Polysciences [0133] 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MTT) from TCI Deutschland GmbH

[0134] (f) Conducting salts: [0135] Lithium hexafluorophosphate (LiPF.sub.6) from Sigma-Aldrich [0136] Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) from Sigma-Aldrich [0137] Lithium tetrafluoroborate (LiTFB) from Sigma-Aldrich

[0138] (g) Solvents: [0139] Diethyl ether from Sigma-Aldrich, boiling point (1013 mbar): 35° C. [0140] Ethyl acetate from Sigma-Aldrich, boiling point (1013 mbar): 77° C.

[0141] (h) Plasticizers: [0142] Ethylene carbonate (EC) from Sigma-Aldrich, boiling point (1013 mbar): no boiling point, instead decomposition at 248° C. (i.e. decomposition temperature=248° C.) [0143] Diethyl carbonate (DEC) from Sigma-Aldrich, boiling point (1013 mbar): 126 to 128° C. [0144] Ethyl methyl carbonate (EMC) from Sigma-Aldrich, boiling point (1013 mbar): 107° C.

[0145] (i) Additives: [0146] Acetylcysteine (chain transfer agent) from Sigma-Aldrich [0147] Zinc chloride (catalyst) from Sigma-Aldrich

[0148] Example 1 below shows the preparation of a pressure sensitive adhesive polyelectrolyte of the invention by means of solution polymerization. Disregarding solvents, the components used bring the total to 100 wt %.

Example 1—Solution Polymerization

[0149] A cyanoethyl acrylate-based, pressure sensitive adhesive polymer of the invention was prepared by charging a glass reactor having a capacity of 2 L with 302 g of a mixture of 3.53 wt % of glycidyl methacrylate, 35.29 wt % of 2-cyanoethyl acrylate and 31.76 wt % of 2-ethylhexyl acrylate, 0.47 wt % of acetylcysteine, 10.59 wt % of EC and 10.59 wt % of DEC in 300 g of ethyl acetate. After degassing of the reaction solution, with passage of nitrogen through the solution for 45 minutes with stirring, the solution was heated to a temperature of 58° C. and 0.2 g (0.05 wt %) of 2,2′-azobis(2-methylbutyronitrile) (Vazo 67™ from DuPont) was added as radical initiator. Following the addition the reaction solution was heated to a temperature of 75° C. and the polymerization reaction was carried out at this temperature. One hour after the beginning of the reaction, the reaction mixture was admixed with a further 0.2 g (0.05 wt %) of 2,2′-azobis(2-methylbutyronitrile). Four hours after the beginning of the reaction, the reaction mixture was diluted with 100 g of ethyl acetate. A further 100 g of ethyl acetate were added after a further four hours (in other words eight hours after the beginning of the reaction). To reduce the residual radical initiator remaining in the reaction mixture, the reaction mixture was admixed, eight and ten hours after the beginning of the reaction, with in each case 0.6 g (0.14 wt %) of bis-(4-tert-butylcyclohexanyl) peroxydicarbonate (Perkadox 16™ from Akzo Nobel). Twenty four hours after the beginning of the reaction, the polymerization reaction was ended by cooling of the reaction mixture to room temperature (23° C.). To produce an adhesive from the resulting polymer, the reaction product was blended with 15 g of a 10 wt % strength solution of zinc chloride in diethyl ether, corresponding to 0.35 wt % of zinc chloride. In addition 7.06 wt % of LiTFSI were added as conducting salt, and the mixture was coated out using a comma bar on a release film (dry thickness: 30 μm) and dried (40 m tunnel with eight drying zones at 30, 40, 40, 60, 90, 120, 120 and 20° C. and a belt speed of 15 m/min.). A small part of the plasticizer (EC or DEC) evaporates in the dryer, with more than 80 wt % of the plasticizers still being present after drying.

[0150] The examples below show the preparation of a pressure sensitive adhesive polyelectrolyte of the invention by means of UV polymerization (Examples 2 to 9) and also of a comparative electrolyte likewise produced by UV polymerization (Comparative example 10).

Examples 2 to 9—UV Polymerization

[0151] The electrolytes of the invention, polymerized preferably without solvent, were produced with the successive steps of a) prepolymer preparation, i.e. syrup preparation, b) formulation of the prepolymer, i.e. incorporation of the prepolymer or syrup into the final mixture, and c) coating and curing the final mixture, with curing relating to the polymerization or crosslinking. All quantity figures are based on the final formulation after process steps a) and b). See the details below:

Example 2

[0152] The individual steps in the preparation of the pressure sensitive adhesive polymer electrolyte are described below with reference to Example 2, including the respective quantities:

[0153] Step a) A mixture of 25 wt % of 2-ethylhexyl acrylate (2-EHA), 35 wt % of 2-(2-ethoxyethoxy)ethyl acrylate and 0.2 wt % of benzoin ethyl ether was irradiated in a stirred tank reactor with a Philips Actinic BL TL-D 15 W/10 1SL/25 UV lamp (UV-A radiation 350-400 nm, distance from the surface of the reaction mixture: 20 cm) to a conversion of 10% as monitored with a ReactIR 702L TEMCT from Mettler Toledo. During the reaction the reaction temperature was held at 20° C. The reaction was ended when the target conversion was reached, by shutting off the lamp and blowing in oxygen.

[0154] Step b) The reaction mixture from step a) (“syrup”) was mixed with 29.55 wt % of 2-cyanoethyl acrylate (2-CEA), a further 0.1 wt % of benzoin ethyl ether, 0.15 wt % of 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MTT) and 10 wt % of lithium hexafluorophosphate.

[0155] Step c) A layer 30 μm thick was applied by nozzle coating to a siliconized liner (75 μm PET) and lined with a second 75 μm PET liner. With exclusion of oxygen, the mixture was irradiated between the two liners using the same UV-A radiation as for preparation of the syrup. Curing was performed with a dose of 80 mWs/cm.sup.2 by means of 56 Philips Actinic BL TL-D 15 W/10 1SL/25 lamps, with the residence time in the irradiation tunnel being 3.5 minutes, i.e. 210 seconds.

Examples 3 to 9

[0156] The pressure sensitive adhesive polyelectrolytes of Examples 3 to 9 were prepared as described above for the polyelectrolyte from Example 2, with the nature and amount of the components used being varied as specified in Table 1 (the components add up to 100 wt % in each case). Where used, plasticizers (EC, DEC) are still completely in the product after curing.

Comparative Example 10—UV Polymerization

[0157] The electrolyte from comparative example 10 was also prepared by UV polymerization. In this case, however, a prepolymerization step a) was omitted. In a step b), the components trimethylolpropane trimethacrylate (TMPTMA), lauroyl peroxide, lithium hexafluorophosphate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate were mixed, and in step c) a layer 30 μm thick was applied to a siliconized liner (75 μm PET) and lined with a second 75 μm PET liner. With exclusion of oxygen, the mixture was irradiated between the two liners using UV-A radiation. The curing was performed with a dose of 80 mWs/cm.sup.2 by means of 56 Philips Actinic BL TL-D 15 W/10 1SL/25 lamps, the residence time in the irradiation tunnel being 3.5 minutes, i.e. 210 seconds (instead of the irradiation, curing may also take place thermally at 80° C. for 1800 seconds). The nature and amount of the components are likewise specified in Table 1.

TABLE-US-00001 TABLE 1 Components in preparing the polymer electrolytes and curing conditions. Dose (time) in Example Components step a) Added components step b) step c) 2 25 wt % 2-EHA, 35 wt % 2-(2- 31.55 wt % 2-CEA, 0.1 wt % 80 mWs/cm.sup.2 ethoxyethoxy)ethyl acrylate, benzoin ethyl ether, (210 s) 0.2 wt % benzoin ethyl ether 0.15 wt % MTT, 8 wt % LiPF.sub.6 3 20 wt % 2-EHA, 30 wt % 2-(2- 19.55 wt % 2-CEA, 0.1 wt % 80 mWs/cm.sup.2 ethoxyethoxy)ethyl acrylate, benzoin ethyl ether, (210 s) 0.2 wt % benzoin ethyl ether 0.15 wt % MTT, 10 wt % LiPF.sub.6, 10 wt % EC, 10 wt % DEC 4 25 wt % 2-EHA, 35 wt % 2-(2- 31.7 wt % 2-CEA, 0.1 wt % 80 mWs/cm.sup.2 ethoxyethoxy)ethyl acrylate, benzoin ethyl ether, (210 s) 0.2 wt % benzoin ethyl ether 8 wt % LiPF.sub.6 5 20 wt % 2-EHA, 30 wt % 2-(2- 19.7 wt % 2-CEA, 0.1 wt% 80 mWs/cm.sup.2 ethoxyethoxy)ethyl acrylate, benzoin ethyl ether, (210 s) 0.2 wt % benzoin ethyl ether 10 wt % LiPF.sub.6, 10 wt % EC, 10 wt % DEC 6 54.55 wt % 2-EHA, 40 wt % 2- 0.1 wt % benzoin ethyl 80 mWs/cm.sup.2 (2-ethoxyethoxy)ethyl acrylate, ether, 0.15 wt % MTT, (210 s) 0.2 wt % benzoin ethyl ether 5 wt % LiPF.sub.6 7 25 wt % 2-EHA, 35 wt % 2-(2- 31.55 wt % 2-CEA, 80 mWs/cm.sup.2 ethoxyethoxy)ethyl acrylate, 0.1 wt % benzoin ethyl (210 s) 0.2 wt % benzoin ethyl ether ether, 0.15 wt % MTT, 8 wt % LiTFSI 8 25 wt % 2-EHA, 35 wt %, 2-(2- 31.55 wt % 2-CEA, 0.1 wt % 80 mWs/cm.sup.2 ethoxyethoxy)ethyl acrylate, benzoin ethyl ether, (210 s) 0.2 wt % benzoin ethyl ether 0.15 wt % MTT, 8 wt % LiTFB 9 18.15 wt % 2-EHA, 30 wt % 2- 19.55 wt % 2-CEA, 0.1 wt % 80 mWs/cm.sup.2 (2-ethoxyethoxy)ethyl acrylate, benzoin ethyl ether, (210 s) 0.2 wt % benzoin ethyl ether 2 wt % HDDA, 10 wt % LiPF.sub.6, 10 wt % EC, 10 wt % DEC 10 No prepolymerization 2 wt % TMPTMA, 80 mWs/cm.sup.2 1 wt % LPO, 97 wt % 1 M (210 s) (or LiPF.sub.6 in EC:EMC:DEC 80° C. (1800 s)) (weight ratio 1:1:1)

[0158] Results and Discussion:

[0159] Table 2 shows the profile of properties of the polymer electrolytes prepared in Examples 1 to 10. Reported in each case are the ionic conductivity, the glass transition temperature (T.sub.g), the peel adhesion (PA) on steel, the holding power (HP), the heat resistance (Shear Adhesion Failure Temperature, SAFT), the haze, the transmission and the colour parameters b* as determined in the test methods section.

TABLE-US-00002 TABLE 2 Profile of properties of the polymer electrolytes. Ionic PA Trans- Ex- conductivity T.sub.g steel HP SAFT Haze mission ample [S/cm] [° C.] [N/cm] [min.] [° C.] [%] [%] b* 1 1.5*10.sup.−5 −28 4.5 10000 >200 2.0 98 2.6 2 8.8*10.sup.−5 −45 4.2 10000 >200 1.1 98 1.5 3 2.3*10.sup.−3 −52 3.9 8668 135 1.3 98 1.1 4 1.2*10.sup.−4 −53 4.6 9567 161 1.1 99 1.2 5 4.2*10.sup.−3 −51 3.6 4571 144 1.4 98 0.7 6 9.2*10.sup.−6 −65 3.1 2554 112 1.3 97 1.2 7 2.9*10.sup.−5 −45 3.8 10000 192 1.3 98 1.8 8 1.3*10.sup.−5 −45 3.4 10000 >200 1.5 98 1.1 9 7.3*10.sup.−3 −51 2.4 10000 138 1.1 98 0.7 10 1.1*10.sup.−2 27 0.1 n.a. n.a. 14.7 95 2.1

[0160] Example 2 shows a transparent polymer electrolyte which is able to accommodate a high fraction of conducting salt. As a result of the high polarity of more than 30 wt % polymerized 2-CEA, the solubility is high, and because of the addition in the second polymerization step on the already shaped sheet, gelling does not disrupt the optical effects. There is therefore no need for regulating additions such as RAFT regulators, for example. Because of the impurities in the raw materials, 2-CEA has a strong tendency towards gelling, and can be used only at low concentrations in the procedures normally employed. Example 3 additionally contains low molecular mass plasticizers. In spite of this the cohesion, at 8668 minutes, is still within a satisfactory range. The plasticizer fraction is beneficial to the ionic mobility, and the conductivity rises.

[0161] Example 4 shows that even without the addition of the branched crosslinker MTT it is possible to obtain sufficient cohesion with a high fraction of 2-CEA used, particularly if no further regulators are employed. There again the ionic conductivity is somewhat better than when using MTT. Example 5, however, has a low cohesion if polymerization takes place without the branching crosslinker, with a high plasticizer fraction and with a relatively small amount of 2-CEA.

[0162] Example 6 has a high fraction of apolar 2-EHA employed and correspondingly is not able to dissolve very much conducting salt. The ionic conductivity is therefore low.

[0163] Examples 7 and 8 use the conducting salts LiTSFI and LiTFB, in which case the conductivity still adopts a sufficient value, but below that of the LiPF.sub.6.

[0164] Example 9 shows that good cohesion and conductivity values are still achievable, in spite of the higher plasticizer fraction, with the crosslinking monomer HDDA. Particularly noteworthy is the low b* value.

[0165] Example 10 shows an electrolyte which does have a high conductivity, but has low dimensional stability and peel adhesion. Owing to a lack of cohesion, it is not possible to measure either the holding power or the SAFT test, since the sample failed as early as during hanging prior to measurement. Moreover, the polymer network was not compatible with the conducting salt and plasticizer, so producing an uneven porous structure which exhibited a very high haze of 14.7%. Haze values of such levels are not tolerable for optically transparency cells such as electrochromic systems, for example.

Test Methods

[0166] Unless otherwise indicated, all measurements were conducted at 23° C. and 50% relative humidity. Unless indicated otherwise, moreover, the measurements of the pressure sensitive adhesive polymer electrolyte were carried out on a polymer electrolyte layer with a thickness of 30 μm; in other words, the results for the pressure sensitive adhesive polymer electrolyte typically relate to a layer thickness of 30 μm.

[0167] The mechanical and technical adhesive data were ascertained as follows:

Test A—Peel Adhesion

[0168] The peel adhesion of the samples in the form of an adhesive tape 30 μm thick on a glass substrate (peel strength) was determined with a method based on PSTC 1. A strip of the sheetlike element with a width of 2 cm was applied to a glass plate so that only one free end section of the strip was not in contact with the surface of the glass plate. The region of the adhesive strip in contact with the glass substrate was pressed onto the glass substrate in a defined way by a triple rollover using a roller having a mass of 2 kg, with each rollover comprising two pressure-exerting roller passes each in opposite travel directions. The temporary liner was subsequently removed by hand.

[0169] For the peel adhesion measurement itself, the glass plate with the sheetlike element thus mounted was fastened so as to be stationary. The sheetlike element was affixed by its free end to a tensile testing machine, and 10 min after bonding (for measurement of the instantaneous peel adhesion) it was pulled off using the tensile testing machine with a peel angle of 180° at a travel velocity of 300 mm/min. The maximum force at which there was still no parting of the bond observed corresponds to the peel adhesion on the substrate in question and is reported in N/cm. The measurement value (in N/cm) was obtained as the average from three individual measurements.

Test B—Ionic Conductivity

[0170] The ionic conductivity for lithium ions was measured by EIS (Electrochemical Impedance Spectroscopy), by calculating the ionic conductivity from the Nyquist Plot Fit of a matching equivalent circuit diagram. Measurement took place using a Metrohm Autolab PGSTAT204 with FRA32M module, with an attached Autolab Microcell HC apparatus with top-mounted TSC battery cell. A sample with a diameter of 10 mm was applied between the electrodes. The sample thickness was measured beforehand with a Wolf DM2010 thickness gauge for the purpose of calculating the cell constant. The measurement was made at a frequency of 100 kHz to 0.1 Hz with an AC voltage of 10 mV RMS. Analysis was carried out using the NOVA2 software. The measuring temperature was 25° C.

Test C—Glass Transition Temperature T.SUB.g

[0171] Glass transition points—referred to synonymously as glass transition temperatures—are reported as the result of measurements made by Dynamic Scanning Calorimetry (DSC) in accordance with DIN 53 765, especially section 7.1 and 8.1, but with uniform heating and cooling rates of 10 K/min in all heating and cooling steps (compare DIN 53 765; section 7.1; note 1). The initial sample mass was 20 mg.

Test D—Haze

[0172] The haze value describes the fraction of transmitted light which is scattered forward at large angles by the transirradiated sample. The haze value therefore quantifies material defects in the surface or the structure that disrupt a clear transmitted view. For sample preparation, a 30 μm adhesive transfer tape of the pressure sensitive adhesive sample was applied without bubbles to a polycarbonate film (125 μm Lexan 8010 with freshly uncovered surfaces; the haze of this film alone is 0.09%). The method for measuring the haze value is described in the standard ASTM D 1003. The standard requires the measurement of four transmission measurements. For each transmission measurement, the degree of light transmission is calculated. The four degrees of transmission are converted to give the percentage haze value. The haze value is measured using a Hazegard Plus from Byk-Gardner GmbH. The samples were transirradiated vertically and the transmitted light was measured photoelectrically in an integrating sphere (Ulbricht sphere). The spectral sensitivity is adapted to the CIE standard spectral value function Y under standard illuminant C.

Test E—Transmission

[0173] For sample preparation, a 30 μm adhesive transfer tape of the pressure sensitive adhesive sample was applied without bubbles to a polycarbonate film (125 μm Lexan 8010 with freshly uncovered surfaces; the haze of this film alone is 0.09%). The values for transmission and haze were measured on a Hazegard Plus from Byk-Gardner. The samples were transirradiated vertically and the transmitted light was measured photoelectrically in an integrating sphere (Ulbricht sphere). The spectral sensitivity is adapted to the CIE standard spectral value function Y under standard illuminant C. The transmission was measured in the wavelength length from 190 to 900 nm using a Uvikon 923 from Biotek Kontron. The absolute transmission is reported as the value at 550 nm in %. Prior to the measurement, an empty channel measurement was carried out over the entire wavelength range.

Test F—Colour Characteristics

[0174] The procedure was as per DIN EN ISO 11664, and the colour characteristics were investigated in the CIELAB three-dimensional space formed by the three colour parameters L*, a* and b*. This was done using a BYK Gardner Spectro Guide instrument, equipped with a D/65° lamp. Within the CIELAB system, L* indicates the grey value (0=black, 100=white), a* the colour axis from green to red (−120=green, +120=red) and b* the colour axis from blue to yellow (−120=blue, +120=yellow). The positive value range for b* therefore indicates, for example, the intensity of the yellow colour component. The reference used was a white ceramic tile having a b* of +1.05. This tile also served as a sample holder, onto which the adhesive layer under test was laminated. Colourimetry for the adhesive under test, i.e. the pressure sensitive adhesive sample, took place on the pure layer of adhesive in each case, with a layer thickness of 30 μm unless otherwise indicated. The values reported in the specification for L*, a* and b* of the layer of adhesive have already been processed to remove the values of the substrate tile. For example, b* of the layer of adhesive as reported in the specification is the difference between the colour value determined for the adhesive film specimen applied to the substrate tile, and the colour value determined for the pure substrate tile.

Test G—Shear Adhesion Failure Temperature (SAFT), Heat Resistance

[0175] This test serves for accelerated testing of the shear strength of adhesive tapes under temperature load. An adhesive tape (length about 50 mm, width 10 mm) cut from the respective sample specimen, i.e. from a pressure sensitive adhesive sample with a layer thickness of 30 μm, was adhered to a steel test plate cleaned with acetone, so that the steel plate protruded to the right and left beyond the adhesive tape and so that the adhesive tape protruded beyond the test plate at the upper edge by 2 mm. The bond area of the sample in terms of height×width=13 mm×10 mm. The bond site was then fixed by rolling a 2 kg steel roller over it six times at a velocity of 10 m/min. The adhesive tape was reinforced flush with a stable adhesive strip which served as a support for the travel sensor. The sample was hung up vertically by means of the test plate.

[0176] The sample specimen for measurement was loaded at the bottom end with a weight of 50 g. The steel test plate with the bonded test specimen was heated, beginning at 25° C. at a rate of 9° C. per minute, to the final temperature of 200° C. The slip travel of the specimen (“SAFT shear travel”) was measured by means of the travel sensor as a function of temperature and time. The maximum slip travel is set at 1000 μm; if exceeded, the test is discontinued.

Test H—Holding Power

[0177] A strip of the respective sample specimen (adhesive tape in the form of a layer of the pressure sensitive adhesive sample having a thickness of 30 μm) 13 mm wide was applied to a steel plate. The steel plates were washed four times with acetone beforehand and left to lie in the air for at least one minute and not more than ten minutes. The area of application was 20 mm×13 mm (length×width). The adhesive tape was subsequently pressed onto the steel support four times using a roller having a weight of 2 kg. A 1 kg weight was affixed on the adhesive tape. The holding power times measured are reported in minutes and correspond to the average from three measurements. The measurements were carried out in a heating cabinet at 40° C. The experiment was discontinued in each case after a maximum duration of 10 000 min.

Test 1—Electrochemical Stability

[0178] For determining the electrochemical stability, i.e. the oxidative stability, the linear sweep voltametry (LSV) against a platinum counter-electrode with a sweep of 1 mV/s was used. A range from −0.1 V to 6.5 V against Li/Li.sup.+ was measured, with platinum being used as the working electrode in the anodic range and copper as the working electrode in the cathodic range. In the plot of the current density [mA/cm.sup.2] against the potential with respect to Li/Li.sup.+[V], the stability window was defined for a maximum deviation in current density by 0.25 mA/cm.sup.2. Measurement took place using a Metrohm Autolab PGSTAT204, with analysis using the NOVA2 software.

Test J—Relative Permittivity ε.SUB.r

[0179] The relative permittivity was measured at a temperature of 23° C. in a plate capacitor with variable measuring slot, the electrode plates of said capacitor having a diameter of 60 mm. For the measurement, a sample of uniform thickness was introduced as a dielectric into the measuring slot without air inclusion and was contacted, over its whole area and without interstices, with the two electrode plates. The resulting distance between the electrode plates (which ought ideally to be identical to the thickness of the sample under test) is determined by means of a slide gauge. In addition, a blank measurement was carried out with the electrode plates at an identical distance apart, for which the material under test was removed, meaning that, for the blank measurement, air was used as a dielectric of known permittivity. For both the actual measurement and the blank measurement, the capacitance of the measurement setup for a measurement frequency of 1 kHz was determined using an LCR instrument (Type: GWInstec LCR 821). The relative permittivity of the sample material was determined in a comparison of the two capacitances found; the calculation took place in accordance with conventional determination methods of the kind specified in standard ASTM D150, for example.