HK1053389B - Photovoltaic modules with a thermoplastic hot-melt adhesive layer and a process for their production - Google Patents

Description

Photovoltaic module with thermoplastic hot melt adhesive layer and method for producing same

Technical Field

The invention relates to photovoltaic modules with special thermoplastic adhesive layers and to a method for the production thereof.

Background

Photovoltaic modules or solar modules are understood to mean photovoltaic structural elements which generate electrical current directly from light, in particular from sunlight. Key cost-efficiency factors for the generation of solar current are the efficiency of the solar cells used, the production cost of the solar module, and the lifetime.

Conventionally, solar modules comprise a glass composite, a solar cell circuit, an embedding material, and a back side structure. The layers of the solar module must have the following functions:

the use of a front glass (top layer) protects against mechanical and weathering effects. In order to maintain the absorption losses in the spectrum in the range from 350nm to 1,150nm, it is necessary to have a very high transparency, and therefore the efficiency losses of the silicon solar cells used for the generation of the electrical current are as low as possible. Hardened low-taconite glass (3 or 4mm thick) is generally used, which has a transmission of 90 to 92% in the abovementioned spectral range.

The composite of the component is bonded using an insert material, typically an EVA (ethylene vinyl acetate) film. In a lamination operation at about 150 c, the EVA melt thus also flows into the interstices of the solar cells, the solar cells are soldered, or the solar cells are connected to one another with an electrically conductive adhesive, during which the EVA thermally crosslinks. Lamination in vacuum and under mechanical pressure prevents the formation of bubbles, which would cause refractive losses.

The backside of the module protects the solar cells and the embedding material from moisture and oxidation. The back side is also utilized for mechanical protection against scratches etc. and for insulation during assembly of the solar module. Composite films are generally used, although the structure of the back side can also be made of glass. The PVF (polyvinyl fluoride) -PET (polyethylene terephthalate) -PVF or PVF-aluminum-PVF protocol is basically employed in the composite membrane.

The so-called encapsulating materials used in the construction of solar modules (front and back sides of the module) must have excellent barrier properties, in particular against water vapor and oxygen. So that the solar cells themselves do not directly land on the corresponding contacts of the solar cells during the lamination process.

9. The photovoltaic assembly according to claim 8, wherein the adhesive is applied in the form of a bead.

10. Photovoltaic module according to claim 1, wherein in the plastic adhesive layer in C) between the top layer in a) and the solar cell, there is also a glass film with a thickness of less than 500 μm.

11. The photovoltaic assembly according to claim 1, wherein the polyurethane has a hardness of 92 on the shore a scale to 70 on the shore D scale.

12. A method for producing a photovoltaic module in which a composite comprising a cover sheet or a cover film and a plastic adhesive film, a solar cell string, and a composite comprising a film or a sheet on a back surface and a plastic adhesive film are fed to a vacuum plate laminator or a roll laminator, pressed and bonded thereto to produce a photovoltaic module, the module comprising:

A) at least one glass or impact-resistant, UV-stable, weathering-stable, transparent plastic surface layer on the front side facing the energy source, which has a low water vapor permeability,

B) at least one glass or weather-stable plastic surface layer on the rear side facing away from the energy source, which layer has a low water vapor permeability,

C) at least one plastic adhesive layer between A) and B), in which at least one or more solar cells are embedded which are electrically connected to one another,

wherein the plastic adhesive layer described in C) comprises an aliphatic thermoplastic polyurethane having a hardness of 75 Shore A to 70 Shore D and a softening temperature T determined according to the DMS-method at an E' -modulus of 2MPa_SofteningAt 90-150 ℃, the aliphatic thermoplastic polyurethane is the reaction product of: an aliphatic diisocyanate; at least one zerewitinoff-active polyol having an average of at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 600-; and at least one zerewitinoff-active polyol as a chain extender, having on average at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 60 to 500 g/mol; the molar ratio of NCO groups of the aliphatic diisocyanate to OH groups of the chain extender and the polyol is from 0.85 to 1.2.

The adhesive layer is also not sufficiently flexible.

Patent applications JP-A09-312410 and JP-A09-312408 describe the use of thermoplastic polyurethanes or elastomers as adhesive layers for solar modules. Design of solar energy component of solar energy automobileThe solar cell must be protected from mechanical vibrations. This is achieved with extremely soft TPUs, which are much softer than EVA. The bonding is performed by means of vacuum. As already mentioned above, the bonding requires long processing times. Furthermore, from the package size 2m²Vacuum laminators were no longer initially available because the escape paths of the bubbles on the edges were too long for them to escape during normal processing times and were "frozen" in the adhesive. This causes losses due to refraction. The thermoplastic polyurethanes described in JP-A09-312410 do soften during heating in a vacuum vessel, but they are not sufficient to become a liquid filling the gaps between the solar cells. Thus, a solar cell which cannot be used is produced.

Patent applications WO 99/52153 and WO 99/52154 state that solar modules are encapsulated with a composite film or composite of a polycarbonate layer and a fluoropolymer layer. These applications use EVA hot melt adhesives that are only slow to process for bonding.

Patent application DE-a 3013037 describes a solar module of symmetrical construction with PC sheets on the front and back sides, the solar cell embedding layer (adhesive layer) being characterized by a maximum E modulus of 1,000MPa, which is too stiff to tear the fragile solar cell during thermal expansion.

EVA as a hot melt adhesive must melt at about 150 ℃; the EVA then becomes a water-like liquid. If the construction of the assembly is now heavy, in this case the EVA is pressed to the side during the lamination process and the effective thickness of the adhesive layer is reduced. The crosslinking process starts at about 150 ℃ and takes 15-30 minutes. Due to the long process time, EVA can only be processed intermittently with a vacuum laminator. The EVA processing window (time dependent pressure and temperature process) is very narrow. Furthermore, EVA turns yellow under UV radiation, and in view of UV radiation, for example, cerium is doped in a glass plate above EVA as an absorber of UV [ f.j.pern, s.h.glick, solar materials and solar cells,61(2000) 153 page 188-]。

Plastic materialHas a specific silicon content of 2.10^-6K^-1) Or glass (4. 10)^-6K^-1) Obviously higher thermal expansion coefficient (50-150.10)^-6K^-1). Therefore, if the solar cell is encapsulated with plastic instead of glass, a flexible and suitable adhesive layer must be used to prevent mechanical separation of the silicon solar cell from the plastic. However, the flexibility of the adhesive layer should not be too great in order for the overall solar module composite to still have sufficient mechanical distortion stability. EVA solves the problems of different diffusion coefficients of silicon and plastic and insufficient torsional stability.

Summary of The Invention

The object of the present invention is to provide photovoltaic modules which are characterized in that they can be produced in a fast and inexpensive manner and in that they are lightweight.

This object is achieved with an optoelectronic component according to the invention.

The invention provides an optoelectronic assembly having the following structure:

A) at least one glass or impact-resistant, UV-stable, weathering-stable transparent plastic surface layer on the front side facing the energy source, which has a low water vapor permeability,

B) at least one glass or weather-stable plastic surface layer on the rear side facing away from the energy source, which layer has a low water vapor permeability,

C) at least one plastic adhesive layer between A) and B), in which at least one or more solar cells are embedded which are electrically connected to one another,

wherein the plastic adhesive layer in C) comprises an aliphatic thermoplastic polyurethane having a hardness of 75 Shore A to 70 Shore D, preferably 92 Shore A to 70 Shore D, and an E' -modulus of 2MPa, a softening temperature T_SofteningFrom 90 to 150 ℃ C (measured according to the DMS method), the aliphatic thermoplastic polyurethane is the reaction product of: an aliphatic diisocyanate; at least one kind ofZerewitinoff-active polyols having on average at least 1.8 to not more than 3.0 Zerewitinoff-active hydrogen atoms and a number average molecular weight of 600-; and at least one zerewitinoff-active polyol as a chain extender, having on average at least 1.8 to not more than 3 zerewitinoff-active hydrogen atoms and a number average molecular weight of 60 to 500 g/mol; the molar ratio of NCO groups of the aliphatic diisocyanate to the chain extender and OH groups of the polyol is from 0.85 to 1.2.

Brief Description of Drawings

Fig. 1 shows a solar module according to the invention with a cover sheet and a rear side film.

Fig. 2 shows a solar module according to the invention with a cover film and a back sheet.

Fig. 3 shows a schematic view of producing a composite of a sheet and an adhesive film.

Fig. 4 shows a schematic view of the production of a solar module using a roll laminator.

Figure 5 shows a schematic view of the production of a continuous assembly using a roll laminator.

Fig. 6 shows a schematic view of the division of a continuous assembly into standard assemblies.

Fig. 7 shows a schematic view of a foldable solar module with a film fold.

Fig. 8 shows a schematic view of a solar module electrically connected with a conductive adhesive.

Detailed Description

The present invention provides a photovoltaic module having the following structure:

A) at least one glass or impact-resistant, UV-stable, weathering-stable transparent plastic surface layer on the front side facing the energy source, which has a low water vapor permeability,

B) at least one glass or weather-stable plastic surface layer on the rear side facing away from the energy source, which layer has a low water vapor permeability,

C) at least one plastic adhesive layer between A) and B), in which at least one or more solar cells are embedded which are electrically connected to one another,

wherein the plastic adhesive layer in C) comprises an aliphatic thermoplastic polyurethane having a hardness of 75 Shore A to 70 Shore D, preferably 92 Shore A to 70 Shore D, and an E' -modulus of 2MPa, a softening temperature T_SofteningFrom 90 to 150 ℃ C (measured according to the DMS method), the aliphatic thermoplastic polyurethane is the reaction product of: an aliphatic diisocyanate; at least one zerewitinoff-active polyol having an average of at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 600-; and at least one zerewitinoff-active polyol as a chain extender, having on average at least 1.8 to not more than 3 zerewitinoff-active hydrogen atoms and a number average molecular weight of 60 to 500 g/mol; the molar ratio of NCO groups of the aliphatic diisocyanate to chain extenders and polyol OH groups is from 0.85 to 1.2, preferably from 0.9 to 1.1.

Dynamic-mechanical analysis (DMS-method)

Rectangular sheets (30 mm. times.10 mm. times.1 mm) were punched from the injection molded sheets. The test strips are subjected to very small deformations at regular intervals under constant preload (optionally depending on the stored assembly) and the force acting on the clamp is measured as a function of temperature and excitation frequency.

The applied preload serves to maintain the specimen properly tensioned at the point in time when the magnitude of deformation is negative.

Determination of the softening Point temperature T_SofteningAs the heat-resistant characteristic temperature at E' ═ 2 MPa.

DMS measurement was carried out at 1Hz and a temperature range of-150 ℃ and 200 ℃ using a SeikoDMS model 210 instrument manufactured by Seiko at a heating rate of 2 ℃/min.

The facing layer a) preferably comprises a sheet or one or more layers of films.

Layer B) preferably comprises a sheet or one or more layers of films.

The surface layer a) is preferably a film or sheet in the form of strips which are arranged on a so-called solar cell string.

The solar cells embedded in the plastic adhesive layer described in C) are preferably arranged in a solar cell string.

In order to generate the highest possible voltage for the solar cells, the solar cells are preferably soldered in series or connected to one another in series by means of a conductive adhesive layer.

When using electrically conductive adhesives, these are preferably placed directly inside the plastic adhesive layer (102, 111) [ "Kleben, grundagen-technology-anwendengen (adhesive, base-process-application), Handbuch minchener ausbildingesemini" (munich education instruction manual), axspringer press, berlin, heyd 1997], in the form of so-called adhesive beads (20), which are used in such a way that they can directly land on the corresponding contacts of the solar cells (24) during lamination and have overlapping regions (21) for connecting the solar cells in series (see fig. 8). Thus, soldering before lamination can be omitted, allowing electrical connection and encapsulation to be completed in one step.

Preferably, between the solar cells in the plastic adhesive layers described in the cover layers a) and C), there is also a glass film with a thickness of less than 500 μm.

The solar module according to the invention preferably comprises a transparent cover layer (1, 5) on the front side, an adhesive layer (2) enclosing the solar cells (4), and a back side (3, 6), which may be opaque or transparent (see fig. 1 and 2). The cap layer should have the following properties: high transparency in the range of 350nm to 1,150nm, high impact strength, stability to UV and weathering, and low water vapor permeability. The cover layers (1, 5) can be made of the following materials: glass, polycarbonate, polyester, polyvinyl chloride, fluoropolymer, thermoplastic polyurethane, or any desired combination of these materials. The cover layers (1, 5) may be made as sheets, films, or composite films. The rear side (3, 6) is stable against weathering and has a low water vapor permeability and a high electrical resistance. In addition to the materials mentioned for the front face, the rear face can also be made of polyamide, ABS or other plastics that are stable to weathering, or of metal sheets or metal foils in which an electrically insulating layer is provided. The back side (3, 6) may be made as a sheet, film, or composite film.

The adhesive layer (2) should have the following properties: the transmittance is high in 350nm-1,150nm, and the adhesive has excellent adhesion effect on silicon and aluminum contacts on the back surface of the solar cell, tin-plated front contacts, an anti-refraction layer of the solar cell, a cover material and a back material. The adhesive layer may include one or more adhesive films that may be laminated to the cover layer and/or the back surface.

The adhesive film (2) should be flexible in order to compensate for the stresses due to the difference in thermal expansion coefficients of plastic and silicon. The E modulus of the adhesive film (2) should be from more than 1MPa to less than 200MPa, preferably from more than 10MPa to less than 140MPa, the melting point being below the melting temperature of the solder connecting the solar cells, which is generally 180 ℃ to 220 ℃, or below the Vicat softening point (thermal stability) of the conductive adhesive, which is generally above 220 ℃. In addition, the adhesive film should also have a high electrical resistance, low water absorption, good resistance to UV radiation and thermal oxidation, be chemically inert, and be easy to handle without crosslinking.

In a preferred embodiment of the invention, the cover layer and the back side comprise a plastic film or sheet. The total thickness of the cover layer and the back surface is at least 2mm, preferably at least 3 mm. The solar cell is thus sufficiently protected from mechanical influences. The bond comprises at least one thermoplastic polyurethane adhesive film having a total thickness of 300-1,000 μm.

Another preferred embodiment of the invention is a solar module wherein the cover and back surfaces comprise some of the above materials with a thickness of less than 1mm and the composite material is immobilized on a suitable metal or plastic support that imparts the necessary rigidity to the overall system. The plastic support is preferably a glass fiber reinforced plastic.

Another preferred embodiment of the invention is a solar module wherein the cover layer comprises a layer of the above material having a thickness of less than 1mm and the rear side comprises a multi-layer plastic sheet to increase rigidity and significantly reduce weight.

In a further preferred embodiment of the invention, the cover layer (103) and/or the rear surface (113) comprise strips of film and sheet material having the exact dimensions of the solar cell string. The strips are fixed to the adhesive film (102 or 111) at intervals of a few millimetres to a few centimetres so that between the strings (see figure 7) there is an area where only the adhesive film, and no cover or back, can be used as, for example, a fold (131) of the film. Such solar modules may be folded and/or rolled up, for example to make them easy to transport. Such solar modules, more preferably constructed of lightweight plastic, can find application in camping areas, outdoor areas, or in other mobile applications such as mobile phones, laptops, etc.

The invention also provides a method for producing a photovoltaic module according to the invention, which is characterized in that a plate-type vacuum laminator (vacuum heat sealing machine) or a roll laminator is used for producing the photovoltaic module.

The temperature of the lamination process is preferably at least 20 ℃ and at most greater than the softening temperature T of the thermoplastic polyurethane used_SofteningThe temperature is 40 ℃ higher.

The composite comprising the cover sheet or cover film and the plastic adhesive film, the solar cell string, the composite comprising the film or sheet on the back side and the plastic adhesive film are preferably fed to a roll laminator, pressed and bonded to produce a solar module.

Roll laminators comprise at least two rolls operating in opposite directions, the two rolls rotating at a specified speed and pressing a composite of the various materials relatively at a specified temperature and pressure.

In a preferred embodiment of this method, the lamination of the cover layer (101) with the adhesive film (102) is carried out in a first step using a roll laminator (12). Such a roll laminator may be located directly downstream of the extruder from which the film is extruded. The following composites/layers are then added one on top of the other to the roll laminator (12) in the second step: a composite of a cover layer (101) and an adhesive film (102); a solar cell string (4); the back side (112) is combined with the adhesive film (111) (see fig. 4). In each case, the adhesive film of the invention is laminated or coextruded to the inside of the cap layer or back side. In the case of the cover layer or the back surface, when the thickness is more than 1mm, it is not possible to heat it by using the rolls of the roll laminator because of poor thermal conductivity. In this case, radiant heating or other forms of preheating are required in order to preheat the sheet to the corresponding temperature. The temperature of the roll laminator should be high enough to allow the adhesive film to fill all gaps between individual solar cells/solar cell strings and weld them to each other without rupture of the solar cells.

In this way, solar modules of any desired size can be produced without the occurrence of bubbles in the finished module, which can adversely affect the quality of the module.

The feeding rate of the film processed by the roll laminator is preferably 0.1m/min to 3m/min, more preferably 0.2m/min to 1 m/min.

In another preferred embodiment of the method, the solar module is produced in the form of a continuous solar module, i.e. the cover layer (10), the back side (11) and the solar cell string (14) are bonded to one another in a continuous process (see fig. 5) using a roll laminator (12). In this method, strings of soldered or adhesively connected solar cells are placed on the backside film at right angles to the lamination direction. The strings are then welded to the front and rear strings on the left and right sides, respectively, before they reach the roll, or they are connected to each other using a conductive adhesive layer using methods well known to the expert (15). Any desired length of the assembly can be so produced. After the assembly has been laminated, it can be divided into lengths, the width always corresponding to the length (17) of the battery string and the length corresponding to the width (18) of the multiple battery string. The assembly is cut along line (16) using a cutting device (see figure 6).

Aliphatic diisocyanates (A) which may be used are aliphatic and cycloaliphatic diisocyanates or mixtures of these diisocyanates (cf. the "method of organic chemistry" volume 20E "macromolecular substances from HOUBEN-WEYL, Georg Thieme Press, Stuttgart, New York, 1987, pages 1587-1593, or Justus Liebigs Annalen der Chemie, 562, pages 75-136).

By way of example, mention may be made in particular of: aliphatic diisocyanates such as ethylene diisocyanate, 1, 4-tetramethylene diisocyanate, 1, 6-hexamethylene diisocyanate, and 1, 12-dodecane diisocyanate; cycloaliphatic diisocyanates, such as isophorone diisocyanate, 1, 4-cyclohexane diisocyanate, 1-methyl-2, 4-cyclohexane diisocyanate, and 1-methyl-2, 6-cyclohexane diisocyanate, and the corresponding isomer mixtures, 4 '-dicyclohexylmethane diisocyanate, 2' -dicyclohexylmethane diisocyanate, and the corresponding isomer mixtures. Preference is given to using 1, 6-hexamethylene-diisocyanate, 1, 4-cyclohexane-diisocyanate, isophorone-diisocyanate and dicyclohexylmethane-diisocyanate, and isomer mixtures thereof. The diisocyanates listed can be used individually or in the form of mixtures with one another. They can also be used with up to 15 mol%, calculated on the total diisocyanate, of polyisocyanate, but the maximum amount of polyisocyanate added is also such that the resulting products can still be processed in the form of thermoplastics.

The zerewitinoff-active polyols (B) used according to the invention are polyols having on average at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number-average molecular weight Mn of 600-.

These polyols include, in addition to compounds comprising amino, thiol or carboxyl groups, in particular compounds containing from 2 to 3, preferably 2, hydroxyl groups, in particular compounds having a number average molecular weight Mn of 600-10,000, more preferably a number average molecular weight Mn of 600-6,000; such as polyesters, polyethers, polycarbonates, and polyester-amides containing hydroxyl groups.

Suitable polyether polyols can be prepared by reacting one or more alkylene oxides having from 2 to 4 carbon atoms in the alkylene radical with an initiator molecule containing a combination of two bonded active hydrogen atoms. Alkylene oxides which may be mentioned are, for example: ethylene oxide, 1, 2-propylene oxide, epichlorohydrin, 1, 2-butylene oxide, and 2, 3-butylene oxide. Ethylene oxide, propylene oxide, and mixtures of 1, 2-propylene oxide and ethylene oxide are preferably employed. The alkylene oxides can be used individually, alternately in succession or as mixtures. Examples of initiator molecules which can be employed are: water, amino alcohols such as N-alkyl-diethanolamine, such as N-methyl-diethanolamine, and diols such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, and 1, 6-hexanediol. Mixtures of initiator molecules may also optionally be employed. Suitable polyether alcohols are, in addition, the polymerization products of tetrahydrofuran which contain hydroxyl groups. Trifunctional polyethers in amounts of from 0 to 30% by weight, based on the difunctional polyethers, may also be used, but in such a maximum that the resulting products can still be processed in the form of thermoplastics. The substantially linear polyether diol preferably has a number average molecular weight Mn of 600-10,000, more preferably 600-6,000. They may be used alone or in admixture with one another.

Suitable polyester diols can be prepared, for example, from dicarboxylic acids having from 2 to 12 carbon atoms, preferably from 4 to 6 carbon atoms, and polyhydric alcohols. Examples of dicarboxylic acids which may be employed are: aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, and sebacic acid, or aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids can be used individually or in the form of mixtures, for example in the form of succinic, glutaric and adipic acid mixtures. For the preparation of the polyester diols, it is advantageous to optionally use, instead of the dicarboxylic acids, the corresponding dicarboxylic acid derivatives, such as carboxylic acid diesters having 1 to 4 carbon atoms in the alcohol radical, carboxylic acid anhydrides or carboxylic acid chlorides. Examples of polyols are diols having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, such as ethylene glycol, diethylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 10-decanediol, 2-dimethyl-1, 3-propanediol, or dipropylene glycol. The polyols can be used as such or in the form of mixtures with one another, depending on the desired properties. Furthermore, esters of carbonic acid with the diols mentioned, in particular with diols having 4 to 6 carbon atoms, such as 1, 4-butanediol or 1, 6-hexanediol, condensation products of omega-hydroxycarboxylic acids, such as omega-hydroxycaproic acid, or polymerization products of lactones, such as optionally substituted omega-caprolactone, are also suitable. Preference is given to using ethanediol polyadipates, 1, 4-butanediol polyadipates, ethanediol-1, 4-butanediol polyadipates, and polycaprolactones as polyesterdiols. The polyester diols have average molecular weights Mn of 600-10,000, preferably 600-6,000, and can be used individually or in the form of mixtures with one another.

Zerewitinoff-active polyols (C) are so-called chain extenders having on average 1.8 to 3.0 Zerewitinoff-active hydrogen atoms and a number-average molecular weight of 60 to 500. In addition to compounds containing amino, thiol, or carboxyl groups, these polyols are understood to mean polyols having from 2 to 3, preferably 2, hydroxyl groups.

Preferred chain extenders to be used are aliphatic diols having 2 to 14 carbon atoms such as ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 2, 3-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, diethylene glycol, dipropylene glycol, and the like. However, diesters of terephthalic acid with diols having 2 to 4 carbon atoms, such as terephthalic acid bis-ethylene glycol, or terephthalic acid bis-1, 4-butanediol, hydroquinones, such as hydroxyalkylene ethers of 1, 4-bis (. beta. -hydroxyethyl) -hydroquinone, ethoxylated bisphenols, such as 1, 4-bis (. beta. -hydroxyethyl) -bisphenol A, aliphatic diamines, such as isophorone diamine, ethylene diamine, 1, 2-propane diamine, 1, 3-propane diamine, N-methyl-propane-1, 3-diamine, or N, N' -dimethylethylene diamine, and aromatic diamines, such as 2, 4-toluylene diamine, 2, 6-toluylene diamine, 3, 5-diethyl-2, 4-toluylene diamine, or 3, 5-diethyl-2, 6-toluenediamine, or predominantly mono-, di-, tri-, or tetraalkyl-substituted 4, 4' -diaminodiphenylmethane are also suitable. More preferably, ethylene glycol, 1, 4-butanediol, 1, 6-hexanediol, 1, 4-di (. beta. -hydroxyethyl) -hydroquinone, or 1, 4-di (. beta. -hydroxyethyl) -bisphenol A is used as chain extender. In addition, small amounts of triols may also be added.

Compounds which are monofunctional with respect to isocyanates can be used as so-called chain terminators in amounts of up to 2% by weight, based on the aliphatic thermoplastic polyurethane. Suitable compounds are, for example, monoamines such as butylamine and dibutylamine, octylamine, stearylamine, N-methylstearylamine, pyrrolidine, piperidine or cyclohexylamine and monoalcohols such as butanol, 2-ethylhexanol, octanol, dodecanol, stearyl alcohol, the various pentanols, cyclohexanol and ethylene glycol monomethyl ether.

The relative amounts of compounds (C) and (B) are preferably such that the ratio of the total amount of isocyanate groups in (A) to the total amount of zerewitinoff-active hydrogen atoms in (C) and (B) is from 0.85: 1 to 1.2: 1, preferably from 0.95: 1 to 1.1: 1.

The thermoplastic polyurethane elastomers (TPU) used according to the invention may contain conventional auxiliary materials and additives as auxiliary materials and additives (D) in a maximum amount of 20% by weight, based on the total amount of TPU. Typical auxiliary materials and additives are catalysts, pigments, dyes, flameproofing agents, stabilizers against the effects of ageing and weathering, plasticizers, lubricants and mold-release agents, active mould-inhibiting and bacteria-inhibiting materials, fillers, and mixtures thereof.

Suitable catalysts are the conventional tertiary amines known from the prior art, for example triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N' -dimethylguazine, 2- (dimethylamino-ethoxy) ethanol, diazabicyclo [2, 2, 2] octane and the like, in particular organometallic compounds, for example titanic acid esters, iron compounds or tin compounds, such as tin diacetate, tin dioctoate, tin dilaurate or the dialkyltin salts of aliphatic carboxylic acids, such as dibutyltin diacetate or dibutyltin dilaurate, for example. Preferred catalysts are organometallic compounds, especially titanates, and compounds of iron and tin. The total amount of catalyst in the TPU is generally from about 0 to 5% by weight, preferably from 0 to 2% by weight, based on the total amount of TPU.

Examples of further additives are lubricants, such as fatty acid esters, their metal soaps, fatty acid amides, fatty acid ester-amides and silicone compounds, antiblocking agents, inhibitors, stabilizers against hydrolysis, light, heat and discoloration, flameproofing agents, dyes, pigments, inorganic and/or organic fillers and reinforcing agents. Reinforcing agents, particularly fibrous reinforcing materials, such as inorganic fibers and the like prepared according to the prior art, may also be added to the size. More detailed information on said auxiliary materials and additives can be found in the technical literature, for example "high polymers" in the monograph of j.h. saunders and k.c. frisch, volume XVI, Polyurethane, parts 1 and 2, published by cross-scientific publishers, 1962 and 1964; R.G-chter and H.M muller Taschenbuch fur Kunststoff-Additive [ plastics additives handbook ] (Hanser Press, Munich, 1990); or DE-A2901774.

Further additives which may be added to the TPU are thermoplastics, for example polycarbonate and acrylonitrile/butadiene/styrene terpolymers, in particular ABS. Other elastomers such as rubber, ethylene/vinyl acetate copolymers, styrene/butadiene copolymers, and other TPUs may also be employed.

Further, commercially available plasticizers suitable for addition are, for example, phosphates, phthalates, adipates, sebacates, and alkyl sulfonates.

The preparation of the TPUs can be carried out batchwise or continuously. The TPU can be prepared continuously, for example by the mixing head/mixing belt process or by the so-called extruder process. In the extruder process, for example in a multi-shaft extruder, the components (A), (B) and (C) can be metered in simultaneously, i.e.in a one-shot process, or in succession, i.e.in a prepolymer process. The present invention may employ a method of adding the prepolymer in portions from the beginning, or a method of continuously preparing the prepolymer using a part of an extruder or using a separate extruder before the prepolymer unit.

The present invention will be described in more detail with reference to examples.

Example 1

Texin is prepared by the following method^_DP7-3007 film (Industrial product from Bayer, hardness: Shore D58) extruded into Makrofol^_On the film: the vertically arranged die was fixed on an extruder having a roll unit (chill roll), which was produced by Reifenh _ user. A rubber-covered backing roll is positioned before the casting roll of the apparatus. The mold is located between the casting roll and the backing roll. To achieve very slow wind-up speeds of this "chill roll" unit, only one wind-up machine was used to wind the film composite, in order to improve Texin^_Makrofol used for melting body pair^_Adhesion of film DE 1-1 (thickness 375 μm (an industrial product of Bayer AG)), Makrofol was applied using an IR lamp before being added to the melt^_And (4) preheating the film. Texin^_The melt was pre-dried at 60 ℃ for 6 hours in a desiccator with dry air.

The following processing parameters were given:

the temperature of the die is 180 DEG C

Texin^_The material temperature of (1) 186 DEG C

The pressure in front of the die was 75bar

Rotational speed of the extruder 80rpm

The casting roll temperature was 20 deg.C

The temperature of the cooling roller is 10 DEG C

Winding speed 3m/min

The composite film produced in this way is then laminated at 160 ℃ onto the solar cell string placed in the middle thereof in a roll laminator using the hot roll process, the underlying Texin as a cover layer^_Front side, using as the back side a top Texin^_And (5) kneading. To optimize the adhesion, the composite film was preheated using an IR lamp. The feed rate of the roll laminator was 0.3 m/min. Can produce the size of 15 multiplied by 15cm in 30 seconds²The component (2).

Some solar modules (modules 4 and 5) with embedded solar cells were made without cracks and fractures.

With this production method, the efficiency of the solar cell remains unchanged.

Two different experiments were used to weathered the solar module. The efficiency before and after weathering is shown in the table.

Example 2

Using Desmopan^_88382 (manufactured by Bayer AG, hardness: 80 Shore A) was extruded as follows:

the horizontally aligned die was fixed on an extruder having a roller unit (chill roller) produced by Somatec. The chill roll was located about 5cm below the die.

To achieve a very slow wind-up speed of this "chill roll" unit, only one windup was used to wind the film. Desmopan^_At 75 deg.C in dry airPre-dried for 6 hours in the desiccator of (1).

The following processing parameters were given:

the temperature of the die is 170 DEG C

Texin^_The material temperature of (1) 177 DEG C

Pressure 27bar before the die

Rotational speed of the extruder 40rpm

The temperature of the cooling roller is 10 DEG C

Wind-up speed 1.7m/min

The film produced in this way is then used as an adhesive layer for the solar module described in fig. 1. Module (15X 15 cm)²) Is made of hardened white glass and the back is made of a composite film (Tedlar-PET-Tedlar). These solar modules were produced at 150 ℃ in 10 minutes using a vacuum laminator.

Solar modules (modules 4 and 5) with embedded solar cells were produced without cracks and fractures.

With this production method, the efficiency of the solar cell remains unchanged.

Two different experiments were used to weathered the solar module. The efficiency before and after weathering is shown in the table.

Comparative example

Comparative assemblies were produced. EVA (ethylene/vinyl acetate) is adopted to replace Texin^_DP 7-3007. The size is 15 x 15cm²The assembly of (a) was produced in 20 minutes using a vacuum laminator. The comparative assembly was also weathered (see table).

TABLE 1

Assembly	Efficiency before weathering	Efficiency after weathering in thermal cycle experiments*(IEC 61215)	Efficiency after weathering in damp Heat experiments**(IEC 61215)
				1	13.8％	13.7％	-
2	13.3％	13.5％	-
				3	13.5％	-	13.5％
4	15.2％	15.1％	-
				5	14.7％	-	14.8％
Comparison component 1	13.2％	13.3％	-
				Comparison component 1	13.9％	-	14.1％

50 cycles of-40 to +85 ℃ for about 6 hours

Standing at 80 deg.C and 85% relative humidity of air for 500 hr

In determining efficiency, the absolute error of the measurement was ± 0.3%.

The efficiency was determined according to IEC 61215.

The solar module according to the invention has the same efficiency, the same mechanical stability and stability against weathering as the comparative module (prior art). Even after weathering, the efficiency remains unchanged.

However, the production speed for producing solar modules according to the invention can be significantly faster than for comparative modules (40 times higher than for roll laminators and 2 times higher than for vacuum laminators).

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (12)

1. An optoelectronic assembly, comprising:

A) at least one glass or impact-resistant, UV-stable, weathering-stable, transparent plastic surface layer on the front side facing the energy source, which has a low water vapor permeability,

B) at least one glass or weather-stable plastic surface layer on the rear side facing away from the energy source, which layer has a low water vapor permeability,

C) at least one plastic adhesive layer between A) and B), in which at least one or more solar cells are embedded which are electrically connected to one another,

wherein the plastic adhesive layer described in C) comprises an aliphatic thermoplastic polyurethane having a hardness of 75 Shore A to 70 Shore D and a softening temperature T determined according to the DMS-method at an E' -modulus of 2MPa_SofteningAt 90-150 ℃, the aliphatic thermoplastic polyurethane is the reaction product of: an aliphatic diisocyanate; at least one zerewitinoff-active polyol having an average of at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 600-; and at least one zerewitinoff-active polyol as a chain extender, having on average at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 60 to 500 g/mol; the molar ratio of NCO groups of the aliphatic diisocyanate to OH groups of the chain extender and the polyol is from 0.85 to 1.2.

2. The photovoltaic module of claim 1, wherein the molar ratio of NCO groups of the aliphatic diisocyanate to OH groups of the chain extender and the polyol is from 0.9 to 1.1.

3. The photovoltaic module of claim 1, wherein the facing layer in a) comprises a sheet or one or more layers.

4. The photovoltaic module of claim 1, wherein the layer of B) comprises a sheet or one or more layers.

5. Photovoltaic module according to claim 1, in which the top layer in a) is a film or sheet in the form of strips arranged on a so-called solar cell string.

6. The photovoltaic module of claim 1, wherein the solar cells embedded in the plastic adhesive layer described in C) are arranged in a solar cell string.

7. The photovoltaic module of claim 6, wherein the solar cell strings are sequentially soldered or connected in series using a conductive adhesive.

8. Photovoltaic module according to claim 7, in which the electrical connections between the solar cells consist of electrically conductive adhesive, applied directly on the inside of the plastic adhesive layer described in C), so that they fall directly on the corresponding contacts of the solar cells during the lamination process.

9. The photovoltaic assembly according to claim 8, wherein the adhesive is applied in the form of a bead.

10. Photovoltaic module according to claim 1, wherein in the plastic adhesive layer in C) between the top layer in a) and the solar cell, there is also a glass film with a thickness of less than 500 μm.

11. The photovoltaic assembly according to claim 1, wherein the polyurethane has a hardness of 92 on the shore a scale to 70 on the shore D scale.

12. A method for producing a photovoltaic module in which a composite comprising a cover sheet or a cover film and a plastic adhesive film, a solar cell string, and a composite comprising a film or a sheet on a back surface and a plastic adhesive film are fed to a vacuum plate laminator or a roll laminator, pressed and bonded thereto to produce a photovoltaic module, the module comprising:

A) at least one glass or impact-resistant, UV-stable, weathering-stable, transparent plastic surface layer on the front side facing the energy source, which has a low water vapor permeability,

B) at least one glass or weather-stable plastic surface layer on the rear side facing away from the energy source, which layer has a low water vapor permeability,

C) at least one plastic adhesive layer between A) and B), in which at least one or more solar cells are embedded which are electrically connected to one another,

wherein the plastic described in C)Adhesive layer comprising an aliphatic thermoplastic polyurethane having a hardness of 75 Shore A to 70 Shore D and a softening temperature T measured according to DMS-method at an E' -modulus of 2MPa_SofteningAt 90-150 ℃, the aliphatic thermoplastic polyurethane is the reaction product of: an aliphatic diisocyanate; at least one zerewitinoff-active polyol having an average of at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 600-; and at least one zerewitinoff-active polyol as a chain extender, having on average at least 1.8 to not more than 3.0 zerewitinoff-active hydrogen atoms and a number average molecular weight of 60 to 500 g/mol; the molar ratio of NCO groups of the aliphatic diisocyanate to OH groups of the chain extender and the polyol is from 0.85 to 1.2.