Packaging adhesive film using low-energy electron beam irradiation and preparation method and application thereof

Abstract

The application provides a packaging adhesive film adopting low-energy electron beam irradiation and a preparation method and application thereof. The packaging adhesive film comprises an irradiation cross-linking buffer layer and a bonding layer. The preparation raw materials of the irradiation cross-linking buffer layer comprise 100 parts of a first EVA resin and 1-5 parts of a first additive. The preparation raw materials of the bonding layer comprise 100 parts of a second EVA resin and 1-5 parts of a second additive. The thickness of the irradiation cross-linking buffer layer is 0.05-0.35 mm. The melt index of the second EVA resin is 20-60 g / 10 min. The packaging adhesive film of the application adopts low-energy electron beam irradiation on one side of the buffer layer, realizes gradual reduction of the pre-cross-linking degree of the adhesive film from the battery side to the glass side, prevents the problem of false welding, avoids the problem that the overall pre-cross-linking degree of the irradiation cross-linking buffer layer is too large to cause hidden cracks on the battery sheet during the laminating process, and prevents the problem of poor appearance of the laminated assembly caused by poor flowability of the bonding layer.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic module technology, and relates to an encapsulating film irradiated with low-energy electron beam, its preparation method and application, specifically to an encapsulating film for a gridless cell module irradiated with low-energy electron beam, its preparation method and application. Background Technology

[0002] OBB (Out-of-Block) technology refers to eliminating the main grid in the metal electrode screen printing process and only printing fine grids, while optimizing the width and spacing of the fine grids. Solder ribbons (wires) are used to replace the main grids and bond with the fine grids to collect current and achieve cell interconnection. The introduction of OBB will have a significant impact on cost reduction and efficiency improvement. Eliminating the main grid and making the sub-grids thinner can greatly reduce the cost of silver paste consumption and result in a smaller light-shielding area, ultimately improving overall power.

[0003] OBB technology is currently in the early stages of industrialization, and various process solutions still exist in the market, mainly including SmartWire, dispensing, and welding + dispensing. The dispensing solution involves placing solder ribbons (perpendicular to the grid lines) on the front and back of the solar cell and forming a connection with adhesive. The adhesive is then cured using photopolymerization to ensure a stronger bond to the cell surface and the outside of the solder ribbons. The disadvantage of this solution is that shadows appear under the solder ribbons during EL testing, indicating insufficient adhesion between the solder ribbons and the cell. Currently, traditional photovoltaic encapsulation films on the market have high fluidity, making them prone to solder ribbon displacement during lamination, leading to incomplete connections between the solder ribbons and the cell.

[0004] Currently, there are several main methods for dispensing-type gridless cell module encapsulation:

[0005] 1) Using polyvinyl butyral resin (PVB) for encapsulation results in high material costs, high lamination temperature requirements, high process requirements, and poor moisture barrier performance.

[0006] 2) Encapsulation is carried out through a double-layer structure (pre-crosslinked layer + non-pre-crosslinked layer), which involves double-layer laying, a complicated process, and high cost;

[0007] 3) The encapsulation method uses UV curing to give the film a certain degree of pre-crosslinking. However, the encapsulation film is unstable and turns yellow after UV aging, resulting in a high rate of defects in the appearance of the laminated components.

[0008] Therefore, there is an urgent need in this field to develop an encapsulating film to solve the technical problems mentioned above, such as high material cost, high process requirements, EL instability caused by solder strip displacement and poor connection, and EL instability and yellowing of the encapsulating film during aging tests. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide an encapsulating film irradiated with low-energy electron beam, its preparation method, and its application. Specifically, it provides an encapsulating film for dispensing-type gridless solar cell modules irradiated with low-energy electron beam, its preparation method, and its application. The encapsulating film provided by the present invention has a multi-layer structure, including an irradiation crosslinking buffer layer and an adhesive layer. The encapsulating film of the present invention is co-extruded in one piece, resulting in low cost and high operability. By irradiating the buffer layer with low-energy electron beam, the pre-crosslinking degree of the encapsulating film gradually decreases from the cell side to the glass side (i.e., the pre-crosslinking degree gradually decreases from the buffer layer to the adhesive layer). This prevents the encapsulating film from having excessive fluidity, causing it to penetrate into the gap between the solder ribbon and the cell, resulting in poor soldering. It also avoids the problem of excessive overall pre-crosslinking of the irradiation crosslinking buffer layer causing microcracks in the cell during lamination. At the same time, it can prevent the appearance defects of the laminated module caused by poor fluidity of the adhesive layer.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides an encapsulating film irradiated with a low-energy electron beam, the encapsulating film comprising an irradiation crosslinking buffer layer and an adhesive layer;

[0012] The raw materials for preparing the irradiation crosslinking buffer layer include the following components by weight: 100 parts of the first EVA resin and 1 to 5 parts of the first auxiliary agent (e.g., 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.).

[0013] The raw materials for preparing the adhesive layer include the following components by weight: 100 parts of the second EVA resin and 1 to 5 parts of the second additive (e.g., 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.);

[0014] The thickness of the irradiation crosslinking buffer layer is 0.05–0.35 mm (e.g., 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, etc.);

[0015] The melt flow index of the second EVA resin at 190℃ and 2.16kg is 20-60g / 10min, for example, 20g / 10min, 25g / 10min, 30g / 10min, 35g / 10min, 40g / 10min, 45g / 10min, 50g / 10min, 55g / 10min, 60g / 10min, etc.

[0016] During use, the encapsulation film provided by this invention has the irradiation crosslinking buffer layer in direct contact with the battery cell and the adhesive layer in direct contact with the glass. By controlling the thickness of the irradiation crosslinking buffer layer within a specific range, it helps to prevent the encapsulation film from flowing too quickly and penetrating between the solder ribbon and the battery cell. By controlling the melt index of the EVA resin in the adhesive layer within a specific range, it can prevent the laminated assembly from having poor appearance.

[0017] In this invention, the encapsulating film irradiated with low-energy electron beam refers to an irradiation voltage of 100-300 keV and a dose of 20-60 kGy.

[0018] Preferably, the thickness of the adhesive layer is 0.25–0.5 mm (e.g., 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, etc.). By controlling the thickness of the adhesive layer within a specific range, the present invention helps to ensure the bonding strength between the adhesive layer and the glass, and the laminated appearance is normal.

[0019] Preferably, the melt flow index of the first EVA resin at 190°C and 2.16 kg is 2 to 30 g / 10 min, such as 2 g / 10 min, 5 g / 10 min, 8 g / 10 min, 10 g / 10 min, 13 g / 10 min, 15 g / 10 min, 18 g / 10 min, 20 g / 10 min, 23 g / 10 min, 25 g / 10 min, 28 g / 10 min, 30 g / 10 min, etc., and more preferably 2 to 25 g / 10 min.

[0020] Preferably, the VA content in the first EVA resin is 28-33%, such as 28%, 29%, 30%, 31%, 32%, 33%, etc.

[0021] Preferably, the first additive comprises the following components in parts by weight: 0.2 to 1.0 parts of crosslinking agent, 0.5 to 1.5 parts of co-crosslinking agent, 0.2 to 1.0 parts of silane coupling agent, 0.2 to 0.6 parts of tackifier, and 0.1 to 0.5 parts of light stabilizer.

[0022] Preferably, the amount of crosslinking agent in the first additive can be 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, etc.

[0023] Preferably, the amount of the crosslinking agent in the first additive can be 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.3 parts, 1.5 parts, etc.

[0024] Preferably, the amount of silane coupling agent in the first auxiliary agent can be 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, etc.

[0025] Preferably, the amount of thickener used in the first additive can be 0.2 parts, 0.4 parts, 0.6 parts, etc.

[0026] Preferably, the amount of light stabilizer in the first additive can be 0.1 parts, 0.3 parts, 0.5 parts, etc.

[0027] Preferably, the crosslinking agent comprises any one or a combination of at least two of the following: tert-butyl peroxide (TBEC), tert-amyl peroxide (TAEC), dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, or carboperoxy acid-O,O-(1,1-dimethylpropyl)-O-(2-ethylhexyl) ester.

[0028] Preferably, the co-crosslinking agent comprises any one or a combination of at least two of triallyl isocyanurate (TAIC), trimethylolpropane triacrylate (TMAIC), trimethylolpropane trimethacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), ethoxylated trimethylolpropane triacrylate (ethoxylated TMPTA), or propoxylated trimethylolpropane triacrylate (propoxylated TMPTA).

[0029] Preferably, the silane coupling agent comprises a combination of a first silane coupling agent and a second silane coupling agent.

[0030] Preferably, the content of the first silane coupling agent in the first auxiliary agent is 0.1 to 0.5 parts by weight, such as 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, etc.

[0031] Preferably, the content of the second silane coupling agent in the first auxiliary agent is 0.1 to 0.5 parts by weight, for example, 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, etc.

[0032] Preferably, the first silane coupling agent comprises any one or a combination of at least two of the following: 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, triisostearoyl titanate isopropyl, isopropyltris(dioctylpyrophosphate)titanate, isocyanate-based propyltrimethoxysilane, isocyanate-based propyltriethoxysilane, or 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

[0033] Preferably, the second silane coupling agent is a silane oligomer.

[0034] Preferably, the silane oligomer includes any one or a combination of at least two of 3-(methacryloyloxy)propyltrimethoxysilane oligomer, vinyltrimethoxysilane oligomer, or vinyltriethoxysilane oligomer.

[0035] Preferably, the tackifier comprises any one or a combination of at least two of toluene diisocyanate, isophorone diisocyanate, isophorone diisocyanate polymer, diphenylmethane diisocyanate, diphenylmethane diisocyanate polymer, hexamethylene diisocyanate, or hexamethylene diisocyanate polymer.

[0036] Preferably, the light stabilizer comprises any one or a combination of at least two of the following: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (light stabilizer 770), polysuccinate (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol), or poly-{6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-azyl]-hexyl-[4-(2,2,6,6-tetramethylpiperidinyl)-amino]}.

[0037] Preferably, the second additive comprises the following components in parts by weight: 0.2 to 1.0 parts of crosslinking agent, 0.5 to 1.5 parts of co-crosslinking agent, 0.2 to 1.0 parts of silane coupling agent, 0.1 to 0.5 parts of light stabilizer, and 0.1 to 0.5 parts of ultraviolet light absorber.

[0038] Preferably, in the second auxiliary agent, the amount of crosslinking agent can be 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, etc.

[0039] Preferably, in the second additive, the amount of the crosslinking agent can be 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.3 parts, 1.5 parts, etc.

[0040] Preferably, the amount of silane coupling agent in the second auxiliary agent can be 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, etc.

[0041] Preferably, the amount of light stabilizer in the second additive can be 0.1 parts, 0.3 parts, 0.5 parts, etc.

[0042] Preferably, the amount of ultraviolet absorber in the second auxiliary agent can be 0.1 parts, 0.3 parts, 0.5 parts, etc.

[0043] Preferably, the crosslinking agent in the second additive includes any one or a combination of at least two of the following: tert-butyl peroxide (TBEC), tert-amyl peroxide (TAEC), dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, or carboperoxy acid-O,O-(1,1-dimethylpropyl)-O-(2-ethylhexyl) ester.

[0044] Preferably, the co-crosslinking agent in the second auxiliary agent includes any one or a combination of at least two of triallyl isocyanurate (TAIC), trimethylol isocyanate (TMAIC), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), ethoxylated trimethylolpropane triacrylate (ethoxylated TMPTA), or propoxylated trimethylolpropane triacrylate (propoxylated TMPTA).

[0045] Preferably, the silane coupling agent in the second additive comprises a combination of a first silane coupling agent and a second silane coupling agent.

[0046] Preferably, the content of the first silane coupling agent in the second auxiliary agent is 0.1 to 0.5 parts by weight, for example, 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, etc.

[0047] Preferably, the content of the second silane coupling agent in the second auxiliary agent is 0.1 to 0.5 parts by weight, such as 0.1 parts by weight, 0.3 parts by weight, 0.5 parts by weight, etc.

[0048] Preferably, the first silane coupling agent in the second adjuvant comprises any one or a combination of at least two of the following: 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, triisostearoyl titanate isopropyl, isopropyltris(dioctylpyrophosphate)titanate, isocyanate-based propyltrimethoxysilane, isocyanate-based propyltriethoxysilane, or 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

[0049] Preferably, the second silane coupling agent in the second auxiliary agent is a silane oligomer.

[0050] Preferably, the silane oligomer includes any one or a combination of at least two of 3-(methacryloyloxy)propyltrimethoxysilane oligomer, vinyltrimethoxysilane oligomer, vinyltriethoxysilane oligomer, and isocyanurate-based silane oligomer.

[0051] Preferably, the ultraviolet absorber includes any one or a combination of at least two of the following: 2-hydroxy-4-n-octyloxybenzophenone, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-bis(a,a-dimethylbenzyl)phenyl)benzotriazole, 2,4-bis(2,4-xylyl)-6-(2-hydroxy-4-n-octyloxophenyl)-1,3,5-triazine, and 2,2-methylenebis[5-(1,1,3,3-tetramethylbutyl)-3-(1,3-dihydrobenzotriazole)phenol].

[0052] Preferably, the light stabilizer in the second adjuvant includes any one or a combination of at least two of the following: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (light stabilizer 770), polysuccinate (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol), or poly-{6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-azyl]-hexyl-[4-(2,2,6,6-tetramethylpiperidinyl)-amino]}.

[0053] In a second aspect, the present invention provides a method for preparing an encapsulating film as described in the first aspect, the method comprising the following steps:

[0054] The raw materials for preparing the irradiation crosslinking buffer layer and the adhesive layer are mixed in the specified amounts, co-extruded, and cast into a film. Then, the irradiation crosslinking buffer layer is subjected to electron beam irradiation pretreatment to obtain the encapsulating film.

[0055] In the electron beam irradiation pretreatment, the irradiation parameters are as follows: voltage of 100–300 keV (e.g., 100 keV, 120 keV, 140 keV, 160 keV, 180 keV, 200 keV, 220 keV, 240 keV, 260 keV, 280 keV, 300 keV, etc.), and dose of 20–60 kGy (e.g., 20 kGy, 30 kGy, 40 kGy, 50 kGy, 60 kGy, etc.).

[0056] Thirdly, the present invention provides an application of the encapsulating film as described in the first aspect in a gridless battery assembly.

[0057] Preferably, the gridless battery module includes a dispensing-type gridless battery module.

[0058] Compared with the prior art, the present invention has at least the following beneficial effects:

[0059] The encapsulation film provided by this invention adopts a special two-layer structure of irradiation crosslinking buffer layer and adhesive layer. It is co-extruded and integrally formed, which is low in cost and highly operable. The buffer layer is irradiated with a low-energy electron beam, which realizes the pre-crosslinking degree gradually decreases from the buffer layer to the adhesive layer. This can prevent the encapsulation film from having excessive fluidity and thus seeping into the gap between the solder ribbon and the battery cell, forming a poor solder joint. It can also avoid the problem of excessive pre-crosslinking of the irradiation crosslinking buffer layer causing microcracks in the battery cell during the lamination process. At the same time, it can prevent the appearance of the laminated component from being poor due to the poor fluidity of the adhesive layer. Detailed Implementation

[0060] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0061] The following is some of the raw material information for the specific embodiments of this invention:

[0062] EVA resin, melt index 6g / 10min, Sirbon UE2806;

[0063] EVA resin, melt index of 20g / 10min, Formosa Plastics 7670H;

[0064] EVA resin, melt index of 25g / 10min, Zhongke 2825;

[0065] EVA resin with a melt index of 60 g / 10 min, SK EVA42-60;

[0066] 3-(methacryloyloxy)propyltrimethoxysilane oligomer, Shandong Sico SICO-ON1743;

[0067] Hexamethylene diisocyanate polymer, Wanhua Chemical, HT-100.

[0068] Example 1

[0069] This embodiment provides an encapsulating film irradiated with a low-energy electron beam, the encapsulating film comprising an irradiation crosslinking buffer layer and an adhesive layer;

[0070] The raw materials for preparing the irradiation crosslinking buffer layer, by weight, include the following components: 100 parts of EVA resin (Sirbon UE2806), 0.5 parts of 2-ethylhexyl carbonate tert-butyl peroxide, 0.7 parts of triallyl isocyanurate, 0.8 parts of trimethylolpropane triacrylate ethoxylate, 0.2 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.3 parts of 3-(methacryloyloxy)propyltrimethoxysilane oligomer, 0.2 parts of hexamethylene diisocyanate polymer, and 0.1 parts of light stabilizer 770;

[0071] The raw materials for preparing the adhesive layer, by weight, include the following components: 100 parts of EVA resin (Zhongke 2825), 0.5 parts of 2-ethylhexyl carbonate tert-butyl peroxide, 0.7 parts of triallyl isocyanurate, 0.8 parts of trimethylolpropane triacrylate ethoxylate, 0.2 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.2 parts of isocyanate-propyltriethoxysilane, 0.2 parts of UV absorber 360, and 0.1 parts of light stabilizer 770.

[0072] The preparation method of the encapsulating film includes the following steps:

[0073] The raw materials for preparing the irradiation crosslinking buffer layer and the adhesive layer were weighed according to the weight parts and mixed evenly. They were then fed into two single-screw extruders of the co-extrusion casting machine and melt-extruded into films to prepare a double-layer co-extruded film.

[0074] The above-mentioned double-layer co-extruded film was pre-crosslinked by electron beam radiation, with the irradiated surface serving as the crosslinking buffer layer. After irradiation, the film was wound up to obtain the encapsulating film. The irradiation parameters were a voltage of 200 keV and a dose of 30 kGy. The thickness of the crosslinking buffer layer was 0.2 mm, and the thickness of the adhesive layer was 0.3 mm.

[0075] Example 2

[0076] The only difference between this embodiment and Embodiment 1 is the composition and amount of the adhesive layer, as detailed below:

[0077] The adhesive layer in this embodiment is prepared by weight of the following components: 100 parts of EVA resin (Formosa Plastics 7670H), 0.5 parts of 2-ethylhexyl carbonate tert-butyl peroxide, 0.5 parts of triallyl isocyanurate, 0.6 parts of trimethylolpropane triacrylate ethoxylate, 0.2 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.2 parts of 3-(methacryloyloxy)propyltrimethoxysilane oligomer, 0.2 parts of UV absorber 360, and 0.1 parts of light stabilizer 770.

[0078] Example 3

[0079] The only difference between this embodiment and Embodiment 1 is the composition of the adhesive layer, as detailed below:

[0080] The adhesive layer in this embodiment is prepared by weight of the following components: 100 parts of EVA resin (SK EVA42-60), 0.5 parts of 2-ethylhexyl carbonate tert-butyl peroxide, 0.7 parts of triallyl isocyanurate, 0.8 parts of trimethylolpropane triacrylate, 0.2 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.2 parts of isocyanate-propyltriethoxysilane, 0.2 parts of UV absorber 360, and 0.1 parts of light stabilizer 770.

[0081] Example 4

[0082] The only difference between this embodiment and Embodiment 1 is the irradiation parameters in the preparation method, as follows: the irradiation parameters are a voltage of 200 keV and a dose of 40 kGy.

[0083] Example 5

[0084] The only difference between this embodiment and Embodiment 1 is the irradiation parameters in the preparation method, as follows: the irradiation parameters are a voltage of 150 keV and a dose of 50 kGy.

[0085] Example 6

[0086] The only difference between this embodiment and Embodiment 1 is the thickness of the irradiation crosslinking buffer layer and the adhesive layer, as detailed below:

[0087] The thickness of the irradiation crosslinking buffer layer is 0.1 mm, and the thickness of the adhesive layer is 0.4 mm.

[0088] Example 7

[0089] The only difference between this embodiment and Embodiment 1 is the composition of the irradiated crosslinking buffer layer, as detailed below:

[0090] The raw materials for preparing the irradiation crosslinking buffer layer in this embodiment include the following components by weight: 100 parts of EVA resin (Formosa Plastics 7670H), 0.5 parts of 2-ethylhexyl carbonate tert-butyl peroxide, 0.7 parts of triallyl isocyanurate, 0.8 parts of trimethylolpropane triacrylate ethoxylate, 0.2 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.3 parts of 3-(methacryloyloxy)propyltrimethoxysilane oligomer, 0.2 parts of hexamethylene diisocyanate polymer, and 0.1 parts of light stabilizer 770.

[0091] Example 8

[0092] The only difference between this embodiment and Embodiment 1 is the composition and amount of the irradiation crosslinking buffer layer, as detailed below:

[0093] The raw materials for preparing the irradiation crosslinking buffer layer in this embodiment include the following components by weight: 100 parts of EVA resin (Zhongke 2825), 0.5 parts of 2-ethylhexyl carbonate tert-butyl peroxide, 0.7 parts of triallyl isocyanurate, 1.0 part of trimethylolpropane triacrylate, 0.2 parts of 3-methacryloyloxypropyltrimethoxysilane, 0.3 parts of 3-(methacryloyloxy)propyltrimethoxysilane oligomer, 0.2 parts of hexamethylene diisocyanate polymer, and 0.1 parts of light stabilizer 770.

[0094] Comparative Example 1

[0095] The only difference between this comparative example and Example 1 is the thickness of the irradiation crosslinking buffer layer and the adhesive layer, as detailed below:

[0096] The thickness of the irradiation crosslinking buffer layer is 0.02 mm, and the thickness of the adhesive layer is 0.3 mm.

[0097] Comparative Example 2

[0098] The only difference between this comparative example and Example 1 is the thickness of the irradiation crosslinking buffer layer and the adhesive layer, as detailed below:

[0099] The thickness of the irradiation crosslinking buffer layer is 0.4 mm, and the thickness of the adhesive layer is 0.3 mm.

[0100] Comparative Example 3

[0101] The only difference between this comparative example and Example 1 is the irradiation parameters used in the preparation method, as detailed below:

[0102] The irradiation parameters were a voltage of 400 keV and a dose of 30 kGy.

[0103] Comparative Example 4

[0104] The only difference between this comparative example and Example 1 is the irradiation parameters used in the preparation method, as detailed below:

[0105] The irradiation parameters were a voltage of 50 keV and a dose of 30 kGy.

[0106] Comparative Example 5

[0107] The only difference between this comparative example and Example 1 is that no irradiation treatment was performed.

[0108] Comparative Example 6

[0109] The only difference between this comparative example and Example 1 is that the melt index of EVA in the adhesive layer is 10 g / 10 min.

[0110] Comparative Example 7

[0111] The only difference between this comparative example and Example 1 is that the melt index of EVA in the adhesive layer is 70 g / 10 min.

[0112] Comparative Example 8

[0113] The only difference between this comparative example and Example 1 is that it only has an irradiation crosslinking buffer layer, no adhesive layer, and a single-layer structure.

[0114] The performance of the encapsulating films provided in the examples and comparative examples was tested using the following methods:

[0115] 1. Pre-crosslinking degree test:

[0116] a) Wash, dry, and weigh the stainless steel wire mesh bag, and record the weight as W1 (accurate to 0.001g).

[0117] b) Cut the encapsulating film of the present invention into small particles of less than 3mm×3mm, weigh 0.5g±0.01g of the prepared sample, put it into a stainless steel wire mesh bag to make a sample package, and weigh it as W2 (accurate to 0.001g).

[0118] c) After sealing the sample package with wire and marking it, add it to a flask. Add 1 / 2 volume of xylene solvent to the flask, attach a reflux condenser to the middle of the flask, and seal the excess opening with a rubber stopper. Heat until the xylene in the flask boils, and reflux for 5 hours at a rate of 30 drops / min.

[0119] d) After reflux, remove the sample package and place it in an oven at 140℃ for 3 hours.

[0120] e) Remove the sample package from the oven, remove the iron wire, cool it to room temperature, and weigh it as W3 (accurate to 0.001g).

[0121] f) Calculate the degree of pre-crosslinking D using the following formula:

[0122] 2. Appearance of laminated components

[0123] Place the glass into the vacuum laminator in the following order: "glass / encapsulation film of this invention / battery cell / encapsulation film of this invention / glass". At 145°C, evacuate for 5 minutes and laminate for 10 minutes. Observe the appearance for bubbles. If there are no bubbles, it is considered OK. In the encapsulation film of this invention, the adhesive layer is in contact with the glass surface and the irradiated crosslinking buffer layer is in contact with the battery surface.

[0124] 3. After lamination, EL (electroluminescence)

[0125] Place the glass into the vacuum laminator in the following order: glass / encapsulation film of this invention / battery cell / encapsulation film of this invention / glass. At 145°C, evacuate for 5 minutes and laminate for 10 minutes. Test the laminated components according to the IEC 61215 test standard. If there is no shadow on the EL, it is considered OK.

[0126] 4. TC200 Post-EL Test

[0127] The components from Test 3 were placed in a high and low temperature cycling test chamber. After passing through TC200, the components were tested for EL according to the IEC 61215 test standard. The test conditions were -40℃ to 85℃ (one cycle was not less than 5 hours) and the test time was 200 cycles. After TC200, the component power was <3% in the EL test, which was considered OK.

[0128] The performance test results are shown in Table 1.

[0129] Table 1

[0130] Pre-crosslinking degree % Component appearance EL after lamination TC200 Post-EL Test Example 1 15 OK OK OK Example 2 15 OK OK OK Example 3 13 OK OK OK Example 4 19 OK OK OK Example 5 18 OK OK OK Example 6 12 OK OK OK Example 7 14 OK OK OK Example 8 15 OK OK OK Comparative Example 1 8 OK There is a shadow There is a shadow Comparative Example 2 30 There are air bubbles and microcracks in the battery cells. OK OK Comparative Example 3 21 There are bubbles OK OK Comparative Example 4 10 OK There is a shadow There is a shadow Comparative Example 5 0 OK There is a shadow There is a shadow Comparative Example 6 18 There are bubbles OK OK Comparative Example 7 14 Parallelization of solar cells OK There is a shadow Comparative Example 8 22 There are bubbles OK OK

[0131] As can be seen from Table 1, the encapsulating films provided in the embodiments of the present invention all have good appearance, with no bubbles, no hidden cracks in the battery cells, and no shadows after lamination and after TC200.

[0132] As can be seen from Example 1, Comparative Example 1 and Comparative Example 2, if the irradiation crosslinking buffer layer is too thin, the film will have high fluidity, resulting in poor soldering between the solder ribbon and the battery cell, and the EL will have shadows after lamination; if the irradiation crosslinking buffer layer is too thick, unmelted bubbles will appear.

[0133] As can be seen from Examples 1, 3, 4 and 5, adjusting the irradiation parameters will affect the degree of pre-crosslinking. High irradiation energy will cause bubbles in the laminated component, while low irradiation energy will cause shadows on the laminated component EL.

[0134] As can be seen from Examples 1, 6, and 7, the melt index of the adhesive layer resin has a significant impact on the appearance of the laminated module. If the melt index is too low, bubbles will appear on the module during lamination; if the melt index is too high, there is a risk of cell merging during lamination.

[0135] The encapsulation film provided in Comparative Example 8 only has an irradiation crosslinking buffer layer and no adhesive layer. During lamination, the component has bubbles on its appearance.

[0136] In summary, the encapsulating film for the gridless battery module of the present invention uses low-energy electron beam irradiation on one side of the buffer layer, which achieves a gradual decrease in the pre-crosslinking degree along the buffer layer to the adhesive layer. This not only prevents the encapsulating film from having excessive fluidity and thus penetrating into the gap between the solder ribbon and the battery cell, causing poor soldering, but also avoids the overall pre-crosslinking of the irradiated crosslinking buffer layer from causing microcracks in the battery cell during the lamination process. At the same time, it also prevents the appearance problems of the laminated module caused by poor fluidity of the adhesive layer.

[0137] The applicant declares that this invention illustrates the encapsulating film irradiated with low-energy electron beams, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. An encapsulating film irradiated with a low-energy electron beam, characterized in that, The encapsulating film includes an irradiation crosslinking buffer layer and an adhesive layer; The raw materials for preparing the irradiation crosslinking buffer layer include the following components by weight: 100 parts of the first EVA resin and 1 to 5 parts of the first auxiliary agent; The first additive comprises the following components in parts by weight: 0.2 to 1.0 parts of crosslinking agent, 0.5 to 1.5 parts of co-crosslinking agent, 0.2 to 1.0 parts of silane coupling agent, 0.2 to 0.6 parts of tackifier, and 0.1 to 0.5 parts of light stabilizer; The thickness of the irradiation crosslinking buffer layer is 0.05–0.35 mm; The raw materials for preparing the adhesive layer include the following components by weight: 100 parts of the second EVA resin and 1 to 5 parts of the second additive; The melt flow index of the second EVA resin at 190°C and 2.16 kg is 20–60 g / 10 min; The second additive comprises the following components in parts by weight: 0.2 to 1.0 parts of crosslinking agent, 0.5 to 1.5 parts of co-crosslinking agent, 0.2 to 1.0 parts of silane coupling agent, 0.1 to 0.5 parts of light stabilizer, and 0.1 to 0.5 parts of ultraviolet light absorber; The encapsulating film is prepared by the following method: The raw materials for preparing the irradiation crosslinking buffer layer and the adhesive layer are mixed in the specified amounts, co-extruded, and cast into a film. Then, the irradiation crosslinking buffer layer is subjected to electron beam irradiation pretreatment to obtain the encapsulating film. In the electron beam irradiation pretreatment, the irradiation parameters are as follows: voltage of 100–300 KeV and dose of 20–60 KGy.

2. The encapsulating film according to claim 1, characterized in that, The thickness of the adhesive layer is 0.25 to 0.5 mm.

3. The encapsulating film according to claim 1, characterized in that, The melt flow index of the first EVA resin at 190°C and 2.16 kg is 2-30 g / 10 min.

4. The encapsulating film according to claim 3, characterized in that, The melt flow index of the first EVA resin at 190°C and 2.16 kg is 2-25 g / 10 min.

5. The encapsulating film according to claim 1, characterized in that, In the first EVA resin, the VA content is 28-33%.

6. The encapsulating film according to claim 1, characterized in that, The crosslinking agent in the first additive includes any one or a combination of at least two of the following: tert-butyl peroxide, tert-amyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, or carboperoxy acid-O,O-(1,1-dimethylpropyl)-O-(2-ethylhexyl) ester.

7. The encapsulating film according to claim 1, characterized in that, The co-crosslinking agent in the first additive includes any one or a combination of at least two of the following: triallyl isocyanurate, trimethylalyl isocyanate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, or propoxylated trimethylolpropane triacrylate.

8. The encapsulating film according to claim 1, characterized in that, The silane coupling agent in the first additive includes a combination of a first silane coupling agent and a second silane coupling agent.

9. The encapsulating film according to claim 8, characterized in that, In the first auxiliary agent, the content of the first silane coupling agent is 0.1 to 0.5 parts by weight.

10. The encapsulating film according to claim 8, characterized in that, In the first additive, the content of the second silane coupling agent is 0.1 to 0.5 parts by weight.

11. The encapsulating film according to claim 8, characterized in that, The first silane coupling agent comprises any one or a combination of at least two of the following: 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, triisostearoyl titanate isopropyl, isopropyltris(dioctylpyrophosphate)titanate, isocyanate-propyltrimethoxysilane, isocyanate-propyltriethoxysilane, or 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

12. The encapsulating film according to claim 8, characterized in that, The second silane coupling agent is a silane oligomer.

13. The encapsulating film according to claim 12, characterized in that, The silane oligomers include any one or a combination of at least two of 3-(methacryloyloxy)propyltrimethoxysilane oligomers, vinyltrimethoxysilane oligomers, or vinyltriethoxysilane oligomers.

14. The encapsulating film according to claim 1, characterized in that, The tackifier includes any one or a combination of at least two of toluene diisocyanate, isophorone diisocyanate, isophorone diisocyanate polymer, diphenylmethane diisocyanate, diphenylmethane diisocyanate polymer, hexamethylene diisocyanate, or hexamethylene diisocyanate polymer.

15. The encapsulating film according to claim 1, characterized in that, The light stabilizer in the first adjuvant includes any one or a combination of at least two of the following: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, polysuccinate (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester, or poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-azyl]-hexyl-[4-(2,2,6,6-tetramethylpiperidinyl)-amino]}.

16. The encapsulating film according to claim 1, characterized in that, The crosslinking agent in the second additive includes any one or a combination of at least two of the following: tert-butyl peroxide (2-ethylhexyl) carbonate, tert-amyl peroxide (2-ethylhexyl) carbonate, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, or carboperoxy acid-O,O-(1,1-dimethylpropyl)-O-(2-ethylhexyl) ester.

17. The encapsulating film according to claim 1, characterized in that, The co-crosslinking agent in the second additive includes any one or a combination of at least two of the following: triallyl isocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, or propoxylated trimethylolpropane triacrylate.

18. The encapsulating film according to claim 1, characterized in that, The silane coupling agent in the second additive includes a combination of a first silane coupling agent and a second silane coupling agent.

19. The encapsulating film according to claim 18, characterized in that, In the second auxiliary agent, the content of the first silane coupling agent is 0.1 to 0.5 parts by weight.

20. The encapsulating film according to claim 18, characterized in that, In the second auxiliary agent, the content of the second silane coupling agent is 0.1 to 0.5 parts by weight.

21. The encapsulating film according to claim 18, characterized in that, The first silane coupling agent in the second adjuvant includes any one or a combination of at least two of the following: 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, triisostearoyl titanate isopropyl, isopropyltris(dioctylpyrophosphate)titanate, isocyanate-propyltrimethoxysilane, isocyanate-propyltriethoxysilane, or 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

22. The encapsulating film according to claim 18, characterized in that, The second silane coupling agent in the second auxiliary agent is a silane oligomer.

23. The encapsulating film according to claim 22, characterized in that, The silane oligomers include any one or a combination of at least two of 3-(methacryloyloxy)propyltrimethoxysilane oligomers, vinyltrimethoxysilane oligomers, vinyltriethoxysilane oligomers, and isocyanurate-based silane oligomers.

24. The encapsulating film according to claim 1, characterized in that, The ultraviolet absorber includes any one or a combination of at least two of the following: 2-hydroxy-4-n-octyloxybenzophenone, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-bis(a,a-dimethylbenzyl)phenyl)benzotriazole, 2,4-bis(2,4-xylyl)-6-(2-hydroxy-4-n-octyloxophenyl)-1,3,5-triazine, and 2,2-methylenebis[5-(1,1,3,3-tetramethylbutyl)-3-(1,3-dihydrobenzotriazole)phenol].

25. The encapsulating film according to claim 1, characterized in that, The light stabilizer in the second adjuvant includes any one or a combination of at least two of the following: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, polysuccinate (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester, or poly-{[6-[(1,1,3,3-tetramethylbutyl)-imino]-1,3,5-triazine-2,4-diyl][2-(2,2,6,6-tetramethylpiperidinyl)-azyl]-hexyl-[4-(2,2,6,6-tetramethylpiperidinyl)-amino]}.

26. A method for preparing an encapsulating film as described in any one of claims 1-25, characterized in that, The preparation method includes the following steps: The raw materials for preparing the irradiation crosslinking buffer layer and the adhesive layer are mixed in the specified amounts, co-extruded, and cast into a film. Then, the irradiation crosslinking buffer layer is subjected to electron beam irradiation pretreatment to obtain the encapsulating film. In the electron beam irradiation pretreatment, the irradiation parameters are as follows: voltage of 100–300 KeV and dose of 20–60 KGy.

27. The application of an encapsulating film as described in any one of claims 1-25 in a gridless battery module.

28. The application according to claim 27, characterized in that, The gridless battery module includes a dispensing gridless battery module.