WO2009133176A2

WO2009133176A2 - Thin layer solar module as laminated safety glass

Info

Publication number: WO2009133176A2
Application number: PCT/EP2009/055276
Authority: WO
Inventors: Bernhard Koll
Original assignee: Kuraray Europe Gmbh
Priority date: 2008-04-30
Filing date: 2009-04-30
Publication date: 2009-11-05
Also published as: WO2009133176A3; DE102008001512A1

Abstract

The invention relates to the use of softener-containing films based on polyvinyl acetals, having a tear resistance of at least 16 N/mm², for the production of thin layer photovoltaic modules.

Description

description

Thin-film solar module as laminated safety glass Technical field

The invention relates to thin-film solar modules designed as laminated safety glass using a film based on plasticizer-containing polyvinyl acetal and their use.

State of the art

Thin-film solar modules consist of a photosensitive

Semiconductor layer deposited on a substrate, e.g. a transparent plate or a flexible carrier sheet e.g. by vapor deposition, vapor deposition, sputtering or wet deposition is applied. The thus-supported semiconductor layers are then sandwiched between a glass sheet and a rigid, rear cover plate, e.g. laminated from glass or plastics using a transparent adhesive.

The transparent adhesive must completely enclose the photosensitive semiconductor layer and its electrical connection lines, be UV-stable and insensitive to moisture and be completely free of bubbles after the lamination process.

Curing resins or crosslinkable ethylene vinyl acetate (EVA) based systems are often used as transparent adhesives, as disclosed, for example, in DE 41 22 721 C1 or DE 41 28 766 A1. These adhesive systems can be set in the uncured state so low viscosity that they surround the solar cell units bubble-free. After adding a hardener or crosslinking agent, a mechanically resistant adhesive layer is obtained. A disadvantage of these adhesive systems is that aggressive substances such as acids are released during the curing process, which can destroy the photosensitive semiconductor layers, in particular thin-film modules. In addition, some casting resins tend after some years to blistering or delamination by UV radiation.

An alternative to curing adhesive systems is the use of plasticized films based on polyvinyl acetals like that the manufacture of laminated glass known polyvinyl butyral (PVB). The solar cell units are covered with one or more PVB films and bonded under elevated pressure and temperature with the desired covering materials into a laminate.

Process for the preparation of solar modules using PVB films are z. Example by DE 40 26 165 C2, DE 42 278 60 A1, DE 29 237 70 C2, DE 35 38 986 C2 or US 4,321,418 known. The use of PVB films in solar modules as composite safety glazings is e.g. in DE 20 302 045 U 1, EP 1617487 A1, and DE 35 389 86 C2. However, these documents contain no information about the mechanical, chemical and electrical properties of the PVB films used. Furthermore, the PVB film is used only for embedding the solar cell units; Safety aspects or the required properties of the PVB film are not described.

The use of PVB films in solar modules as

Bonded safety glazings is disclosed in DE 20 302 045 U1 and DE 35 389 86 C2. However, these specifications do not specify the safety properties of the composite glasses or the properties of the PVB film used.

The safety properties of a composite of glass and PVB film are known to depend on the adhesive force between the film and glass. The adhesive force should be so high that the mechanical destruction of the glass gluing the glass fragments to the film is guaranteed and sharp-edged glass fragments can not peel off. At high adhesion of the film, however, an impacting object can penetrate the laminated glass, since the PVB film hardly deforms elastically at the point of impact and only slightly contributes to the braking of the object. If the adhesion to the glass is at a lower level, the PVB film at the point of impact can be peeled off from the glass under stretching and deformed, whereby the impacting object is slowed down.

Since too low adhesion of the PVB film on the glass facilitates the detachment of glass fragments from the film and thus increases the splinter risk, one strives in practice a compromise between high and low adhesion, ie an average level of liability. This is the case in particular for composite safety plates for motor vehicles, where a high penetration resistance is important. Composite safety slices for the construction industry, especially in the case of roofing, require good splinter bonding, so that the PVB film should have a relatively high adhesion between the glass and the adhesive film.

Solar modules are increasingly being used in buildings

Facade elements or roofs used. In addition to a good photovoltaic luminous efficacy, these modules must also have comparable properties with laminated safety glazings. The solar modules described have solar cells embedded in PVB film, which, however, do not possess the safety properties of laminated safety glass.

EP 1617478 A2 describes the production of solar modules which have embedded between two PVB films solar cells. The adhesive effect of the PVB film is directly to the glass, so that the safety properties of these solar modules correspond to those of laminated safety glass.

Thin-film solar modules are not mentioned in this patent. In the case of thin-film solar modules, the adhesion of the PVB film takes place at least on one surface of the module via the solar cells and not to the glass, so that there is room for improvement here.

Technical task

The object of the present invention is therefore to

Thin-film solar modules with the properties of laminated safety glazing to provide.

Presentation of the invention

The present invention therefore relates to a photovoltaic module, comprising a laminate of a) a transparent front cover b) one or more photosensitive semiconductor layers c) at least one plasticizer-containing, based on polyvinyl acetal Foil and d) a back cover wherein the photosensitive semiconductor layers b) on the transparent

Front cover a) or the rear cover d) are applied and by at least one plasticized polyvinyl acetal based film c), which have a tensile strength according to EN ISO 527/3 of at least 16 N / mm ² , are glued together.

[0015] Plasticizer-containing films based on polyvinyl acetal which can be used according to the invention preferably have a tensile strength according to EN ISO 527/3 of 16 to 36 N / mm ² , in particular 18 to 32 N / mm ² and preferably of 20 to 30 N / mm ² .

Similarly, it must be ensured that the films have sufficient elasticity and toughness even under dynamic stress, such as the impact of a shock on the film-containing thin-film photovoltaic module. Plasticizer-containing polyvinyl acetal-based films used according to the invention therefore preferably have impact strengths of at least 1500 kJ / m ² , particularly preferably at least 1700 kJ / m ² , and in particular at least 1800 kJ / m ² or 2000 kJ / m ² . The upper limit can be a tensile impact strength of 3500 kJ / m ² . To measure the elasticity of the films under dynamic load, the impact tensile test according to DIN EN ISO 8256 (2004) is used.

Thin-film solar modules contain in particular photosensitive semiconductor layers based on amorphous or microcrystalline silicon, cadmium telluride (CdTe), CIS (copper / indium / (di) selenide) or copper / indium / gallium / sulphide / selenide (CIGS) or thin conductive layers (TCO) are chemically susceptible to corrosion, so the encapsulant must be chemically inert and free of aggressive chemical additives such as crosslinkers, crosslinkers, or primers to avoid acid traces.

Films based on polyvinyl acetals with a high alkali titre have a Reduced corrosion tendency to the photosensitive semiconductor layers or the electrical conductors used. Without being bound by the truth of this theory, the reduced tendency to corrode is possibly due to the fact that the higher basicity of the PVB film associated with an increased alkali titer neutralizes acid released by aging processes, which triggers the destruction of acid-sensitive semiconductor layers without neutralization.

The avoidance of acid traces in the production of the material is another way to reduce the tendency of the films used according to the invention to resist photosensitive semiconductor layers. Films of this type are produced by extrusion at elevated temperatures, whereby a thermal decomposition of the polymeric material or the plasticizer can occur. Furthermore, by diffused water cleavage of the residual acetate groups of the polyvinyl acetal occur, whereby acetic acid is released. In both cases, acid traces that can attack the photosensitive semiconductor layers result.

The films used according to the invention therefore preferably have a certain basicity, expressed as alkali titers, which may be above 10, preferably above 15 and in particular above 20, 30 or 40. A maximum alkali titre of 100 should not be exceeded.

The alkali titer is determined by back-titration of the film, as described below, and may be carried out by addition of basic substances, e.g. Metal salts of organic carboxylic acids having 1 to 15 carbon atoms, in particular alkali or alkaline earth metal salts such as magnesium or potassium acetate can be adjusted. The basic compound is usually used in a concentration of 0.005 to 2% by weight, in particular 0.05 to 1% by weight, based on the total mixture.

Preferably, the films used in the invention in a

Ambient humidity of 85% RH at 23 ° C a resistivity of at least 1 E + 11 ohm * cm, preferably at least 5E + 11 ohm * cm, preferably 1 E + 12 ohm * cm, preferably 5E + 12 ohm * cm, preferably 1 E + 13, preferably 5E + 13 ohm * cm, preferably 1 E + 14 ohm * cm on.

For the preparation of polyvinyl acetal polyvinyl alcohol is dissolved in water and acetalized with an aldehyde such as butyraldehyde with the addition of an acid catalyst. The precipitated polyvinyl acetal is separated, washed neutral, optionally suspended in an alkaline aqueous medium, then washed neutral again and dried.

The acid used for the acetalization must be neutralized again after the reaction. If an excess of base (eg NaOH, KOH or Mg (OH) ₂ ) is used here, the alkalititer increases and all or part of the addition of the basic substance can be dispensed with.

The polyvinyl alcohol content of the polyvinyl acetal can be adjusted by the amount of aldehyde used in the acetalization.

It is also possible to acetalize with others or more

Aldehydes having 2-10 carbon atoms (e.g., valeraldehyde).

The films based on plasticized polyvinyl acetal preferably contain uncrosslinked polyvinyl butyral (PVB), which is obtained by acetalization of polyvinyl alcohol with butyraldehyde.

The use of crosslinked polyvinyl acetals, in particular crosslinked polyvinyl butyral (PVB) is also possible. Suitable crosslinked polyvinyl acetals are e.g. in EP 1527107 B1 and WO 2004/063231 A1 (thermal self-crosslinking of polyvinyl acetals containing carboxyl groups), EP 1606325 A1 (polyvinyl acetals crosslinked with polyaldehydes) and WO 03/020776 A1 (polyvinyl acetals crosslinked with glyoxylic acid). The disclosure of these patent applications is fully incorporated by reference.

As polyvinyl alcohol terpolymers of hydrolyzed vinyl acetate / ethylene copolymers can be used in the context of the present invention. These compounds are usually hydrolyzed to more than 98 mol% and contain 1 to 10 wt. Based on ethylene units (eg type "Exceval" Kuraray Europe GmbH). As polyvinyl alcohol, hydrolyzed copolymers of vinyl acetate and at least one further ethylenically unsaturated monomer can also be used within the scope of the present invention.

The polyvinyl alcohols can be used in the context of the present invention purely or as a mixture of polyvinyl alcohols with different degree of polymerization or degree of hydrolysis.

Polyvinyl acetals still contain in addition to the acetal units

Vinyl acetate and vinyl alcohol resulting units. The polyvinyl acetals used according to the invention preferably have a polyvinyl alcohol content of less than 22% by weight, 20% by weight or 18% by weight, less than 16% by weight or 15% by weight and in particular less than 14% by weight. A polyvinyl alcohol content of 12% by weight should not be exceeded.

The polyvinyl acetate content of the invention used

Polyvinyl acetal is preferably less than 3% by weight or less than 1% by weight, more preferably less than 0.75% by weight, very preferably less than 0.5% by weight and in particular less than 0.25% by weight.

From the polyvinyl alcohol content and the residual acetate content, the degree of acetalization can be determined by calculation.

Preferably, the films have a plasticizer content of at most 40% by weight, 35% by weight, 32% by weight, 30% by weight, 28% by weight, 26% by weight, 24% by weight or 22% by weight. on, with a plasticizer content of 15 wt.% Should not be exceeded for reasons of processability of the film (each based on the total film formulation). Inventive films or photovoltaic modules may contain one or more plasticizers.

Suitable plasticizers for the films used according to the invention are one or more compounds selected from the following groups:

Esters of polyhydric aliphatic or aromatic acids, for example dialkyl adipates such as dihexyl adipate, dioctyl adipate, hexyl cyclohexyl adipate, mixtures of heptyl and nonyl adipates, diisononyl adipate, heptyl nonyl adipate and esters of adipic acid with cycloaliphatic or Etherbindungen containing ester alcohols, dialkyl sebacates such as dibutyl sebacate and esters of sebacic acid with cycloaliphatic or ether bonds containing ester alcohols, esters of phthalic acid such as butyl benzyl phthalate or bis-2-butoxyethylphthalat

Esters or ethers of polyhydric aliphatic or aromatic alcohols or oligoether glycols having one or more linear or branched aliphatic or aromatic substituents, e.g. Esters of di-, tri- or tetraglycols with linear or branched aliphatic or cycloaliphatic carboxylic acids; As examples of the latter group may serve diethylene glycol bis (2-ethylhexanoate), triethylene glycol bis (2-ethylhexanoate), tri-ethylene glycol bis (2-ethylbu-ta-no-ate) .

Tetraethylene glycol bis-n-heptanoate, triethylene glycol bis-n-heptanoate, triethylene glycol bis-n-hexanoate, tetraethylene glycol dimethyl ether and / or Dipropylenglykolbenzoat

Phosphates with aliphatic or aromatic ester alcohols, e.g. Tris (2-ethylhexyl) phosphate (TOF), triethyl phosphate, diphenyl-2-ethylhexyl phosphate, and / or tricresyl phosphate

Esters of citric acid, succinic acid and / or fumaric acid Particularly suitable as plasticizers for the films used according to the invention are one or more compounds selected from the following group: di-2-ethylhexyl sebacate (DOS), di-2-ethylhexyl adipate (DOA), dihexyl adipate (DHA ), Dibutyl sebacate (DBS), triethylene glycol bis-n-heptanoate (3G7), tetraethylene glycol bis-n-heptanoate (4G7), triethylene glycol bis-2-ethylhexanoate (3GO or 3G8) tetraethylene glycol bis-n-2 ethylhexanoate (4GO or 4G8) di-2-butoxyethyl adipate (DBEA), di-2-butoxyethoxyethyl adipate (DBEEA) di-2-butoxyethyl sebacate (DBES), di-2-ethylhexyl phthalate (DOP), di-isononyl phthalate ( DINP) triethylene glycol bis-isononanoate, triethylene glycol bis-2-propylhexanoate, tris (2-ethylhexyl) phosphate (TOF), cyclohexanedicarboxylic acid diisononyl ester (DINCH) and dipropylene glycol zoate. Plasticizers whose polarity expressed by the formula 100 × O / (C + H) is less than or equal to 9.4 are particularly suitable as plasticizers for the films used according to the invention, where O, C and H are the number of oxygen atoms. , Carbon and hydrogen atoms in each molecule. The following table shows plasticizers which can be used according to the invention and their polarity values according to the formula 100 × O / (C + H).

[0039]

Table 1

Furthermore, the ion mobility which is possibly dependent on the water content of the film and thus the specific resistance can be influenced by the addition of SiO ₂ , in particular fumed silica. The plasticizer-containing films based on polyvinyl acetal preferably contain 0.001 to 15% by weight, preferably 2 to 5% by weight, of SiO ₂ .

In a particular embodiment of the present invention, the solar module has sound insulating properties in that at least one, preferably both, of the films has soundproofing properties. Soundproofing films based on PVB are z. In EP 1 118 258 B1 or EP 387 148 B1, the disclosure of which is hereby incorporated by reference. Soundproofing foils according to EP 1 118 258 B1 increase the sound insulation of a laminated safety glass at its coincidence frequency in the range of 1,000 to 3,500 Hz by at least 2 dB, measured according to DIN EN ISO 717. Suitable sound-insulating films contain according to EP 1118258 B1:

50 to 80% by weight PVB (partially acetalized polyvinyl alcohol)

• 20 to 50 wt .-% of a plasticizer mixture containing

- 30 to 70 wt .-% - calculated as a proportion of the plasticizer mixture of one or more polyalkylene glycols of the group consisting of

Polyalkylene glycols of the general formula HO- (RO) _n -H with R = alkylene and n> 5

Derivatives of polyalkylene glycols of the general formula R ₁ -O- (R 2 -O) _n -H with R ₂ = alkylene and n> 2, in which the hydrogen of one of the two terminal hydroxyl groups of the polyalkylene glycol is linked to an organic radical R ₁ is

Derivatives of polyalkylene glycols of the general formula R ₁ -O- (R 2 -O) _n -R ₃ with R ₂ = alkylene and n> 5, in which the hydrogen of both terminal hydroxy groups of the polyalkylene glycol with an organic radical R ₁ or R _{3 is} linked.

From 70 to 30% by weight, calculated as a proportion of the plasticizer mixture, of one or more standard plasticizers, such as di-n-hexyl-adipate (DHA), and triethylene glycol-bis-n-heptanoate (3G7) or triethylene glycol bis- 2-ethylhexanoate (3G8).

The inventively usable PVB films have the

Enclosing solar cell units and their electrical connections bubble-free and non-positively; At the same time the smallest possible total thickness of the solar modules is required. For this purpose, it is expedient that under the conditions of manufacture at least one PVB film "dodges" the inserted solar cell units, that is, has a certain flowability under the laminating conditions.

Softer, i. flowable films naturally have a lower tensile strength, but are easier to work with. To obtain the desired safety properties, it is important to ensure sufficient tear resistance.

In addition to the tear strength and / or impact resistance, the adhesion of the PVB films on glass and on the solar cell units of importance. The degree of splinter bonding of PVB film in laminated safety glass is determined by the so-called Pummeltest. The performance of this test is known to the person skilled in the art or described in WO 03/033583 A1. Depending on the use, the solar modules according to the invention should have pummel values of 3 to 5 (high penetration protection) or 7 to 10 (good splinter bonding, eg in the case of overhead glazing). Preferably, a compromise of these properties is sought with Pummelwerten 5-8.

The adhesion of PVB films to glass can by the addition of adhesion regulators such. B. the disclosed in WO 03/033583 A1 alkali and / or alkaline earth metal salts of organic acids can be adjusted. Be particularly suitable potassium acetate and / or magnesium acetate have been found. In order to obtain high penetration levels it may be necessary to use PVB films without the addition of adhesion regulators such as alkali and / or alkaline earth salts.

Furthermore, the safety properties of the solar modules according to the invention are determined by the adhesion properties of the PVB films to glass. These can be described by measuring compression shear adhesion.

When measuring the film adhesion to glass surfaces, the different surface properties of flat glass must be taken into account. In the manufacture of flat glass, one side of the glass faces the tin bath and the other side the air, resulting in the tin doping of the bath side. The different sides of flat glass have a different adhesion of the PVB film due to the doping. Usually, therefore, adhesion properties of PVB films in glass laminates are measured by the film in each case has contact on the same sides of the glass sheets. The information on the compression shear adhesion to air / air or tin / tin / glass surfaces refers to appropriately constructed laminates.

The determination of the compression shear adhesion takes place according to the in

The following are described in more detail, based on those in EP 0 067 022 or DE 197 56 274 A1 mentioned methods. The other measurements are carried out according to the specified standards. All tests are carried out on glass / glass laminates with identical structure as the solar modules according to the invention, but without solar cells.

For use in solar modules according to the invention suitable PVB films preferably have a compression shear adhesion to air / air glass surfaces of 8 - 30 N / mm ² , preferably 10 - 25 N / mm ² and in particular 12 - 20 N / mm ² .

The compression shear adhesion of these films to glass surfaces with respect to the tin / tin sides of the glass is preferably 8-25 N / mm ² , preferably 10-20 N / mm ² .

The basic preparation and composition of films based on polyvinyl acetals is z. In EP 185 863 B1, EP 1 118 258 B1, WO 02/102591 A1, EP 1 118 258 B1 or EP 387 148 B1.

The thickness of the plasticized polyvinyl acetal based

Foils are usually 0.38, 0.51, 0.76, 1.14, 1.52 or 2.28 mm.

In general, in thin-film modules, the photosensitive

Semiconductor layer applied over the entire surface of the carrier i. to the edge of the carrier. Subsequently, part of the photosensitive semiconductor layer is removed again at the edge, so that for isolation purposes, a semiconductor-free edge region remains (so-called edge deletion). Due to the high resistance values of the film used according to the invention, this edge region can be very narrow, preferably below 3 cm, especially below 2 cm and in particular below 1 cm.

[0055] Films used according to the invention fill during the

Laminierprozesses the existing on the photosensitive semiconductor layers or their electrical connections cavities.

The transparent front cover is usually made of glass or PMMA. The rear cover of the photovoltaic module according to the invention may consist of glass, plastic or metal or their composites, wherein at least one of the carrier may be transparent. It is also possible to use one or both covers as Laminated glazing (ie as a laminate of at least two glass panes and at least one PVB film) or as insulating glazing with a gas gap perform. Of course, the combination of these measures is possible.

The photosensitive semiconductor layers used in the modules need not have any special properties. Mono-, polycrystalline or amorphous systems can be used.

For lamination of the laminate thus obtained, the

Those skilled in the art process with and without previous production of a pre-bond can be used.

So-called autoclave processes are carried out at an elevated pressure of about 10 to 15 bar and temperatures of 130 to 145 ° C for about 2 hours. Vacuum bag or vacuum ring method, for example, according to EP 1 235 683 B1 operate at about 200 mbar and 130 to 145 ⁰ C.

Preferably, for the preparation of the inventive

Photovoltaic modules used vacuum laminators. These consist of a heatable and evacuable chamber, in which composite glazing can be laminated within 30 - 60 minutes. Reduced pressures of 0.01 to 300 mbar and temperatures of 100 to 200 ⁰ C, in particular 130 - 160 ⁰ C have proven in practice.

Alternatively, a laminated as described above composite body between at least one pair of rollers at a temperature of 60 to 150 ° C are pressed into a module according to the invention. Systems of this type are known for the production of laminated glazing and usually have at least one heating tunnel before or after the first press shop in systems with two pressing plants.

Industrial Applicability

Furthermore, the invention relates to the use of plasticizer-containing, based on polyvinyl acetal films having a tensile strength according to EN ISO 527/3 of at least 16 N / mm ² for the production of photovoltaic modules constructed from a) a transparent front cover b) one or more photosensitive semiconductor layers c) of at least one plasticizer-containing polyvinyl acetal-based film and d) a back cover wherein the photosensitive semiconductor layers b) are applied to the transparent front cover a) or the rear cover d) and by at least one plasticizer-containing on Polyvinyl acetal based film c) are glued together.

The polyvinyl acetal-based films c) used for this purpose may have the preferred properties described.

Photovoltaic modules according to the invention can be used as a facade component,

Roofs, conservatory cover, soundproof wall, balcony or parapet or used as part of window surfaces.

measurement methods

The measurement of the volume resistivity of the film is carried out according to DIN IEC 60093 at a defined temperature and ambient humidity (23 ° C and 85% rl_F) after the film has been conditioned for at least 24 hours under these conditions. To carry out the measurement, a plate electrode type 302 132 from Fetronic GmbH and an ohmmeter ISO-Digi 5 kV from Amprobe were used. The test voltage was 2.5kV, the waiting time after application of the test voltage up to the data acquisition 60 sec. In order to ensure adequate contact between the flat plates of the measuring electrode and the film, their surface roughness R _z should not exceed 10 mm when measured according to DIN EN ISO 4287, ie, if necessary, the original surface of the PVB film before the resistance measurement by thermal embossing be smoothed.

The polyvinyl alcohol and polyvinyl alcohol acetate content of

Polyvinyl acetals were determined according to ASTM D 1396-92. The analysis of the metal ion content was carried out by atomic absorption spectroscopy (AAS).

The water or moisture content of the films is with the Karl Fischer method determined. This method can be carried out both on the unlaminated film and on a laminated photovoltaic module as a function of the distance to the edge of the film.

To determine the alkali titer, 3 to 4 grams of the plasticized polyvinyl acetal film in 100 ml of a mixture of ethanol / THF (80:20) are dissolved overnight in a magnetic stirrer. To this is added 10 ml of dilute hydrochloric acid (c = 0.01 mol / liter) and then potentiometrically potentiometric with a solution of tetrabutylammonium hydroxide (TBAH) in 2-propanol (c = 0.01 mol / liter) with a Titroprocessor against a blank titrated. The alkali titre is calculated as follows:

Alkali titre = ml HCl per 100 gr of a sample = (consumption TBAH blank - TBAH sample x 100 by weight of the sample in gr.)

The measurement of the toughness of the interlayer material under a rapid, dynamic load is carried out in the impact tensile test according to DIN EN ISO 8256 and is given in kJ / m ² . Concerning. the testing machine is referred to the ISO 13802.

The pendulum impact test is carried out in accordance with EN12600; the result is given in the classification of this standard.

The adhesion of the film to the glass is given in "punch values" in each case based on the fire or tin side of the glass.

To assess the adhesion of a PVB film is the

Compression shear test based on DE 197 56 274 A1 performed on a glass / glass laminate without solar cell. To produce the test specimens, the PVB film to be tested is placed between two flat silicate glass panes of the format 300 mm x 300 mm with a thickness of 2 mm, deaerated in a pre-composite oven with calender rolls to a glass pre-composite and then in an autoclave at a pressure of 12 bar and at a temperature of 140 ° C within a total of 90 min. pressed into a flat laminated safety glass. From the laminated safety glass thus produced, 10 samples measuring 25.4 mm × 25.4 mm are cut. These are under one Angle of 45 ° clamped in a test apparatus according to DE 197 56 274 A1, wherein the depth of the recesses is about 2/3 of the respective glass thickness. The upper half is subjected to a steadily increasing, exactly vertically downward force until it shears within the test body, ie the laminated safety glass panes to be tested.

The test parameters are as follows:

[0075]

Table 2

For each test specimen, the force exerted during shearing is linearly averaged by ten equal specimens. As far as reference is made in the following examples and the claims to the mean compression shear test value, this means this mean of 10 measurements. For the rest, reference is made to DE 197 56 274 A1.

Examples

Substrate glasses having thereon deposited, functionally contacted thin-layer cells (CIS) were laminated in the laminator method with a cover glass by PVB films of the composition given in Tables 3 and 4 and subjected to various mechanical tests. Float glass of thickness 3 mm (VSG 33.2) was used as the substrate glass and plasticized PVB with a total thickness of 0.76 was used as the film mm inserted. The quantities in Tables 3 and 4 are in wt.% Based on the sum of PVB and plasticizer. 3G8 stands for

Triethylene glycol bis-2-ethylhexanoate, DHA for dihexyl adipate and DBEA for

Di-2-butoxy-ethyl-adipate Marlophen NP6 is the trade name of Sasol

GmbH for an ethoxylated nonylphenol. It has been found that by selecting suitable

Interlayer materials i. those with a high tensile strength and / or high tensile impact strength particularly penetration resistant

Photovoltaic modules are obtained. These are as

Laminated safety glass suitable. [0080]

Table 3

1]

Table 4

Claims

claims

A photovoltaic module comprising a laminate of a) a transparent front cover b) one or more photosensitive semiconductor layers c) at least one plasticizer-containing polyvinyl acetal-based film and d) a rear cover wherein the photosensitive semiconductor layers b) on the transparent front cover a) or the back cover d) are applied and by at least one plasticized, based on polyvinyl acetal film c) are glued together, characterized in that the polyvinyl acetal based films c) have a tensile strength of at least 16 N / mm ² .

2. Photovoltaic module according to claim 1, characterized in that the polyvinyl acetal-based films c) have a tensile impact strength of at least 1500 kJ / m ² .

3. Photovoltaic module according to claim 1 or 2, characterized in that the polyvinyl acetal-based films c) in a glass / glass laminate have a compression shear adhesion to air / air glass surfaces of 8 to 30 N / mm ² .

4. Photovoltaic module according to one of claims 1 to 3, characterized in that the polyvinyl acetal based films c) have a in a glass / glass laminate a compression shear adhesion to tin / tin glass surfaces of 8 to 25 N / mm ² .

5. Photovoltaic module according to one of claims 1 to 4, characterized in that the plasticizer-containing polyvinyl acetal-based films c) have a plasticizer content of at most 40 wt.%.

6. Photovoltaic module according to one of claims 1 to 5, characterized in that the plasticized polyvinyl acetal-based films c) have an electrical contact resistance of more than 1 E11 ohm * cm in an ambient climate of 85% RH / 23 ° C.

7. Photovoltaic module according to one of claims 1 to 6 characterized in that the polyvinyl acetal has a polyvinyl acetate content of less than 3% by weight.

8. Photovoltaic module according to one of claims 1 to 7, characterized in that the polyvinyl acetal has a polyvinyl alcohol content of less than 22 wt.%.

9. Use of plasticizer-containing polyvinyl acetal-based films which have a tensile strength of at least 16 N / mm ² for the production of photovoltaic modules constructed from a) a transparent front cover b) one or more photosensitive semiconductor layers c) at least one plasticizer-containing polyvinyl acetal-based film and d) a back cover wherein the photosensitive semiconductor layers b) are applied to the transparent front cover a) or the rear cover d) and are glued together by at least one plasticized polyvinyl acetal based film c)

10. Use of the photovoltaic modules according to one of claims 1 to 8 as a facade component, roof surfaces, conservatory cover, sound insulation wall, balcony or parapet or as part of windows.