阅读说明：本技术 一种低缩率太阳能电池背板用pet基材 (PET (polyethylene terephthalate) base material for low-shrinkage solar cell backboard ) 是由 吴培服 吴迪 孙化斌 池卫 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种低缩率太阳能电池背板用PET基材,用于夹置粘接在层状复合结构的太阳能电池背板的中间,所述太阳能电池背板包括外层和内层,所述PET基材分别通过第一粘接层和第二粘接层与所述外层和内层复合成一体,其中,所述PET基材由三层共挤而成的第一聚酯层、第二聚酯层以及夹芯层构成,所述第一聚酯层和第二聚酯层采用普通PET制备而成,所述夹芯层由含有二氧化硅和碱土金属硅酸盐以及聚二甲基硅氧烷的PET制备而成。本发明的PET基材可通过低缩率的夹芯层调整控制PET基材的尺寸稳定性,以满足太阳能电池背板的技术要求,并通过两侧的第一聚酯层和第二聚酯层保持粘结性能不变,降低了成本。(The invention discloses a PET (polyethylene terephthalate) base material for a low-shrinkage solar cell backboard, which is used for being clamped and bonded in the middle of a solar cell backboard with a layered composite structure, wherein the solar cell backboard comprises an outer layer and an inner layer, the PET base material is compounded with the outer layer and the inner layer into a whole through a first bonding layer and a second bonding layer respectively, the PET base material is composed of a first polyester layer, a second polyester layer and a sandwich layer which are formed by three layers of co-extrusion, the first polyester layer and the second polyester layer are prepared from common PET, and the sandwich layer is prepared from PET containing silicon dioxide, alkaline earth metal silicate and polydimethylsiloxane. The PET substrate can adjust and control the dimensional stability of the PET substrate through the sandwich layer with low shrinkage rate so as to meet the technical requirements of the solar cell back plate, and the bonding performance is kept unchanged through the first polyester layer and the second polyester layer on the two sides, so that the cost is reduced.)

1. The PET substrate is characterized in that the PET substrate is composed of a first polyester layer, a second polyester layer and a sandwich layer, the first polyester layer and the second polyester layer are formed by three layers in a co-extrusion mode, the first polyester layer and the second polyester layer are prepared from common PET, and the sandwich layer is prepared from PET containing silicon dioxide, alkaline earth metal silicate and polydimethylsiloxane.

2. The PET substrate of claim 1 wherein the core layer has a silica content of 0.3 wt% to 1.5 wt%, an alkaline earth metal silicate content of 0.05 wt% to 0.5 wt%, and a polydimethylsiloxane content of 0.2 wt% to 1.2 wt%.

3. The PET substrate of claim 1 wherein the first and second polyester layers are each coated on their outer sides with a surface coating.

4. The PET substrate of claim 3 wherein the topcoat comprises the following components: acrylic resin, sodium dodecyl sulfate, ethanolamine surface etching agent, polyquaternium surface active bactericide, water-insoluble carbonate, melamine curing agent and propylene glycol solvent.

5. The PET substrate of claim 3 wherein the surface coating comprises 80 to 100 parts by weight of an acrylic resin, 1 to 2 parts by weight of sodium lauryl sulfate, 10 to 15 parts by weight of ethanolamine, 0.5 to 0.8 parts by weight of polyquaternium, 5 to 10 parts by weight of a water-insoluble carbonate, 1 to 2 parts by weight of melamine, and 80 to 100 parts by weight of propylene glycol.

Technical Field

The invention relates to the technical field of solar cells, in particular to accessories of a solar cell backboard, and particularly relates to a PET (polyethylene terephthalate) base material for a low-shrinkage solar cell backboard.

Background

The solar cell back plate is positioned on the back of the solar cell panel, plays a role in protecting and supporting the cell piece, and has reliable insulativity, water resistance and aging resistance.

CN 101582459 a discloses a solar cell back plate using a modified polyvinylidene fluoride alloy layer as a weather-resistant protective layer, the film comprises a first weather-resistant layer, a first bonding layer, a structure enhancement layer, a second bonding layer and a second weather-resistant layer which are bonded in sequence, wherein the first weather-resistant layer and the second weather-resistant layer are inorganic material modified polyvinylidene fluoride alloy layers, the structure enhancement layer is PET, and the first bonding layer and the second bonding layer can be one of a polyurethane adhesive layer, an acrylate adhesive layer or an epoxy adhesive layer. The solar cell back plate in the prior art is mainly of a three-layer structure, the middle of the solar cell back plate is provided with a PET (polyethylene terephthalate) base material, and a first weather-resistant layer and a second weather-resistant layer are bonded on two sides of the solar cell back plate through bonding layers. The intermediate PET substrate has good insulating properties and provides good support.

CN 103627150A discloses a polyester for solar cell back panel films, which is a PET substrate with a three-layer structure and comprises a surface layer I, a core layer and a surface layer II, wherein the core layer contains polyester chips and master batch polyester chips and contains a modified high-humidity-heat-resistance flame-retardant polyester material; the polyester film is prepared by copolymerizing purified terephthalic acid, ethylene glycol and a reactive phosphorus flame retardant.

CN 103788594A discloses a raw material formula for biaxially oriented solar back sheet polyester film and a manufacturing method thereof, wherein the formula consists of special master batch and polyethylene glycol terephthalate.

CN 101967272A discloses a method for manufacturing a polyester film for a solar cell back plate film, wherein a polyester slice adopted by the film is prepared by mixing terephthalic acid, ethylene glycol and a phosphorus compound, then esterifying and polycondensing, and the ratio of the polyester slice to a master batch polyester slice is as follows, the ratio of the polyester slice to the master batch polyester slice is 100: and 5-30 mass ratio, and mixing and drawing the film to obtain the polyester film for the solar cell back plate film.

The above prior arts all disclose PET substrates for solar cell back sheets, which mainly focus on flame retardancy and barrier properties of the PET substrates, but ignore the shrinkage properties of the solar cell back sheets.

Disclosure of Invention

The invention aims to provide a PET base material for a solar cell backboard with low shrinkage so as to reduce or avoid the problems.

In order to solve the technical problems, the invention provides a PET (polyethylene terephthalate) base material for a low-shrinkage solar cell backboard, which is used for being clamped and bonded in the middle of the solar cell backboard with a layered composite structure, wherein the solar cell backboard comprises an outer layer and an inner layer, the PET base material is compounded with the outer layer and the inner layer into a whole through a first bonding layer and a second bonding layer respectively, the PET base material is composed of a first polyester layer, a second polyester layer and a sandwich layer which are formed by three co-extrusion layers, the first polyester layer and the second polyester layer are prepared from common PET, and the sandwich layer is prepared from PET containing silicon dioxide, alkaline earth metal silicate and polydimethylsiloxane.

Preferably, in the sandwich layer, the content of the silicon dioxide is 0.3 wt% to 1.5 wt%, the content of the alkaline earth metal silicate is 0.05 wt% to 0.5 wt%, and the content of the polydimethylsiloxane is 0.2 wt% to 1.2 wt%.

Preferably, the first polyester layer and the second polyester layer are each coated on the outside with a surface coating.

Preferably, the surface coating comprises the following components: acrylic resin, sodium dodecyl sulfate, ethanolamine surface etching agent, polyquaternium surface active bactericide, water-insoluble carbonate, melamine curing agent and propylene glycol solvent.

Preferably, the surface coating layer comprises 80-100 parts by weight of acrylic resin, 1-2 parts by weight of sodium lauryl sulfate, 10-15 parts by weight of ethanolamine, 0.5-0.8 parts by weight of polyquaternium, 5-10 parts by weight of water-insoluble carbonate, 1-2 parts by weight of melamine, and 80-100 parts by weight of propylene glycol.

The invention also provides a preparation method of the surface coating of the PET substrate for the low-shrinkage solar cell back panel, the PET substrate is clamped and bonded in the middle of the solar cell back panel with the layered composite structure, the two side surfaces of the PET substrate are coated with a layer of surface coating, and the preparation method of the surface coating comprises the following steps: firstly, uniformly mixing 80-100 parts by weight of acrylic resin, 1-2 parts by weight of sodium dodecyl sulfate, 10-15 parts by weight of ethanolamine, 0.5-0.8 part by weight of polyquaternium, 5-10 parts by weight of water-insoluble carbonate, 1-2 parts by weight of melamine and 80-100 parts by weight of propylene glycol, coating the mixture on the outer surface of a polyester layer by a spin coating or spray coating mode, and curing at 70-120 ℃ for 1-2 hours to obtain a precoating layer on the outer surface of the polyester layer; then, carrying out plasma surface activation treatment on the precoat layer; then, carrying out acid cleaning on the precoat after the activation treatment; and finally, washing with water and drying to obtain the surface coating.

The PET substrate can adjust and control the dimensional stability of the PET substrate through the sandwich layer with low shrinkage rate so as to meet the technical requirements of the solar cell back plate, and the bonding performance is kept unchanged through the first polyester layer and the second polyester layer on the two sides, so that the cost is reduced.

Drawings

The drawings are only for purposes of illustrating and explaining the present invention and are not to be construed as limiting the scope of the present invention. Wherein the content of the first and second substances,

FIG. 1 shows a schematic structural view of a solar cell back sheet that can be used in the present invention;

FIG. 2 shows a schematic structural view of a PET substrate for a low shrinkage solar cell back sheet according to an embodiment of the present invention;

fig. 3 shows a schematic structural view of a PET substrate for a low shrinkage solar cell back sheet according to another embodiment of the present invention.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings. Wherein like parts are given like reference numerals.

As mentioned above, the conventional solar cell back sheet generally focuses on flame retardancy and insulation properties, and ignores the shrinkage requirement. The shrinkage rate of a common solar cell back panel is generally required to be less than or equal to 1.5%, while a common PET base material has certain dimensional stability, the shrinkage rate is generally 2-2.5%, so that the common PET base material generally cannot meet the shrinkage rate requirement of the solar cell back panel. On the other hand, reducing the shrinkage of PET by adding various additives generally reduces the adhesive properties of the PET substrate, which affects the overall performance of the solar cell backsheet of a multilayer composite structure.

Based on the defects of the prior art, the invention provides a PET substrate for a low-shrinkage solar cell back sheet, as shown in FIG. 1, which shows a structural schematic diagram of a solar cell back sheet that can be used in the invention, and shows a solar cell back sheet of a laminated composite structure, and the PET substrate 30 of the invention is used for being clamped and bonded in the middle of the solar cell back sheet of the laminated composite structure. The illustrated solar cell back sheet is a typical three-layer composite structure, and comprises an outer layer 10 and an inner layer 20, wherein a PET substrate 30 is compounded with the outer layer 10 and the inner layer 20 into a whole through a first adhesive layer 11 and a second adhesive layer 21 respectively. The inner layer 20 faces the solar cell side, and the outer layer 10 faces the outermost side, and pressure sensitive adhesive can be attached as required for adhering to a support structure such as a glass panel. In one embodiment, the thickness of the PET substrate 30 is 200-300 μm, the thickness of the inner layer 20 is 20-30 μm, the thickness of the outer layer 10 is 60-80 μm, and the thickness of each of the first adhesive layer 11 and the second adhesive layer 21 is 8-12 μm.

The solar cell back sheet shown in fig. 1 may be any type of conventional three-layer composite structure including, but not limited to, TPT, TPE, APE, etc., where T represents a fluorine-containing film, E represents an EVA film, P represents a PET film, and a represents a nylon film. For example, a common TPT structure is usually a polyvinyl fluoride/polyester/polyvinyl fluoride composite structure, a common TPE structure is usually a polyvinyl fluoride/polyester/ethylene-vinyl acetate composite structure, and a structure compounded by polyvinylidene fluoride/polyester/polyvinylidene fluoride (KPK) is also available. The middle layer of the solar cell back plate is mainly a common PET (polyethylene terephthalate) polyester film, and the outer layer of the solar cell back plate is mainly a fluorine material film such as polyvinyl fluoride and polyvinylidene fluoride. However, although the PET substrate modified with the general polyester can obtain a low shrinkage rate, the decrease in the adhesive property caused by the low shrinkage rate further deteriorates the problems of water repellency and poor adhesion between the PET polyester film and the polyvinyl fluoride film or the polyvinylidene fluoride film.

Fig. 2 shows a schematic structural diagram of a PET substrate for a low shrinkage solar cell back sheet according to an embodiment of the present invention, wherein the PET substrate 30 is composed of a first polyester layer 31, a second polyester layer 32 and a sandwich layer 33 which are co-extruded from three layers. Wherein the first polyester layer 31 is bonded to the inner layer 20 through the second bonding layer 21, and the second polyester layer 32 is bonded to the outer layer 10 through the first bonding layer 11. In one embodiment, the first polyester layer 31 has a thickness of 20 to 30 μm, the second polyester layer 32 has a thickness of 20 to 30 μm, and the core layer 33 has a thickness of 150 to 250 μm.

In order to maintain the bonding performance, in one embodiment of the present invention, the first polyester layer 31 and the second polyester layer 32 are preferably made of common PET, and the sandwich layer 33 is made of PET containing silica, alkali earth metal silicate and polydimethylsiloxane, so that the dimensional stability of the whole PET substrate 30 is controlled by adjusting the sandwich layer 33 with low shrinkage to meet the technical requirements of the solar cell back panel, and the cost can be reduced by using the first polyester layer and the second polyester layer of common PET.

The silica in the core layer 33 can improve the heat insulating property, processability and strength of the PET polyester film. The alkaline earth metal silicate, preferably magnesium silicate or calcium silicate, most preferably magnesium silicate, can reduce the increase in heat shrinkability due to the increase in the silica content of the PET polyester film. The polydimethylsiloxane can improve the dispersibility of silicon dioxide in the PET polyester, avoid agglomeration, is beneficial to reducing the addition of inorganic particles and improving the dimensional stability of the PET polyester film.

Silicon atoms of the silicon dioxide and the alkaline earth metal silicate are combined with silicon atoms of the polydimethylsiloxane, and a macromolecule at the other end of the polydimethylsiloxane can be combined with alkane of the PET polyester, so that the silicon dioxide and the alkaline earth metal silicate are uniformly dispersed and kept in the PET polyester. The alkaline earth elements in the alkaline earth metal silicate are easy to form an interactive complex with a phosphorus compound catalyst, a stabilizer, a flame retardant and the like commonly used in PET polyester, the dispersibility of silicon dioxide can be improved, the binding force of the silicon dioxide and the alkaline earth metal silicate in the PET polyester can be improved, and the improvement of the light transmittance of the PET polyester film is facilitated. In addition, as described above, the shrinkage of the PET polyester film can be reduced by adding an alkaline earth metal silicate such as magnesium silicate or calcium silicate.

It should be noted that the shrinkage of the polyester film produced by the addition of silica varies significantly, and is very advantageous for heat-shrinkable films. However, the PET polyester film used in the field of solar cells is desirable in that the shrinkage of the film is kept as low as possible. In the present invention, the combination of the silicate component and the silica improves the dispersibility, while the shrinkage of the film containing the silica is reduced by the alkaline earth metal.

In a preferred embodiment, the silica in the core layer 33 is preferably silica aerogel. The silica aerogel is a low-density silica aerogel which is porous and disordered and has a nano-scale continuous network structure, the specific surface area of the silica aerogel is much larger than that of common silica, and phosphate coupling agents and silane coupling agents (such as vinyl triethoxysilane, vinyl trimethoxysilane and vinyl tri (beta-methoxyethoxy) silane) in the prior art are more difficult to disperse than common silica. Because of its very low density, it floats easily and cannot be dispersed into the polyester. The porous structure of the aerogel can generate strong binding force through the polydimethylsiloxane, the density of the aerogel is increased, and the aerogel can be immersed into the polyester. The specific surface area of the alkaline earth metal silicate is also large, the loose and porous characteristic is similar to that of the aerogel, but the dispersibility is better, and the silicon element component of the alkaline earth metal silicate is adsorbed by the aerogel, so that the dispersibility of the aerogel can be improved, and the agglomeration is avoided.

The sandwich layer 33 added with silicon dioxide or silicon dioxide aerogel, alkaline earth metal silicate and polydimethylsiloxane has small viscosity change relative to the bulk polyester, and is favorable for keeping the stability of the parameters of the polyester film; the dosage of the anti-adhesion particles can be reduced; the processing property, tensile strength, light transmittance and flame retardant property of the polyester film are improved. In addition, the dimensional stability, the wear resistance, the high temperature resistance and the heat insulation performance of the polyester film can be improved.

In one embodiment, the core layer 33 contains 0.3 wt% to 1.5 wt% of silica, 0.05 wt% to 0.5 wt% of alkaline earth metal silicate, and 0.2 wt% to 1.2 wt% of polydimethylsiloxane. After the sandwich layer 33 is baked at 150 ℃ for half an hour, the shrinkage rates in the length direction and the width direction of the sandwich layer can be kept lower than 1.0%, the shrinkage rates in the length direction and the width direction of the PET base material 30 compounded with common PET polyester can be kept lower than 1.5% under the same conditions, and the requirements of the solar cell back plate can be met.

Fig. 3 shows a schematic structural diagram of a PET substrate for a solar cell back sheet with low shrinkage according to another embodiment of the present invention, and the PET substrate 30 of this embodiment is coated with a surface coating 35 on the outer side of the first polyester layer 31 and the second polyester layer 32, compared to the embodiment shown in fig. 2, to improve the adhesion property of the PET substrate 30. The surface coating 35 coated on the two sides of the PET substrate 30 is prepared by the same components and process, and the thickness of the surface coating 35 is 2-5 μm. Of course, it will be understood by those skilled in the art that the surface coating 35 of the present embodiment may be applied to both side surfaces of any PET substrate.

The top coat 35 comprises the following components: acrylic resin, sodium dodecyl sulfate, ethanolamine surface etching agent, polyquaternium surface active bactericide, water-insoluble carbonate, melamine curing agent and propylene glycol solvent. The ethanolamine surface etching agent can degrade and etch the outer surface of the polyester layer to a certain extent, so that the flatness of the outer surface of the polyester layer is reduced, and firm combination with the adhesive layer is favorably formed; furthermore, ethanolamine is prone to decompose during the coating curing process, which can cause the surface coating 35 to form a fluffy porous structure. The acrylic resin has hydrophilicity, and can obtain strong bonding force with the polyester layer through further emulsification of sodium dodecyl sulfate. The polyquaternium surface active bactericide can reduce the surface tension of the cured coating surface and improve the affinity of the coating and an adhesive layer, and the polyquaternium has a bactericidal function and can keep the coating in a use state for a long time. Melamine is less sensitive to moisture than other curing agents and has a better affinity for the adhesive layer. The water-insoluble carbonate can be selected from calcium carbonate or magnesium carbonate, and is required to avoid reaction with ethanolamine and dissolution in water and other water-soluble components.

In one embodiment, the surface coating 35 of the present invention comprises 80 to 100 parts by weight of acrylic resin, 1 to 2 parts by weight of sodium lauryl sulfate, 10 to 15 parts by weight of ethanolamine, 0.5 to 0.8 parts by weight of polyquaternium, 5 to 10 parts by weight of water-insoluble carbonate, 1 to 2 parts by weight of melamine, and 80 to 100 parts by weight of propylene glycol.

The surface coating 35 of the present invention can be prepared by the following steps.

Firstly, uniformly mixing 80-100 parts by weight of acrylic resin, 1-2 parts by weight of sodium dodecyl sulfate, 10-15 parts by weight of ethanolamine, 0.5-0.8 part by weight of polyquaternium, 5-10 parts by weight of water-insoluble carbonate, 1-2 parts by weight of melamine and 80-100 parts by weight of propylene glycol, coating the mixture on the outer surface of a polyester layer by a spin coating or spray coating mode, and curing at 70-120 ℃ for 1-2 hours, thereby obtaining a precoat layer on the outer surface of the polyester layer.

Thereafter, the precoat layer is subjected to a plasma surface activation treatment. After the surface activation treatment, the surface of the precoat layer forms a uniform rough surface with convex and concave parts, and the water-insoluble carbonate part can be exposed. The plasma surface activation treatment is a common treatment method in the field, and for example, the activation treatment can be carried out by oxygen, the oxygen flow is 100sccm, and the vacuum degree is 0.1-0.2mbar for 30s-60 s.

Then, the precoat layer after the activation treatment is subjected to acid washing. Preferably, the precoat layer is soaked by 6-8mol/L hydrochloric acid at 50-60 ℃ for 10-20 minutes. Through acid washing, the exposed carbonate component on the precoating layer can be partially dissolved, a porous structure can be further obtained, the surface activity of the coating is further improved, the surface tension of the coating is favorably reduced, and the affinity and the diffusibility to the adhesive are improved.

Finally, the surface coating 35 of the present invention is obtained by washing with water and drying. Washing with water for 10-20 min, and oven drying at 50-60 deg.C for 30 min.

In conclusion, the PET substrate can adjust and control the dimensional stability of the PET substrate through the sandwich layer with low shrinkage rate so as to meet the technical requirements of the solar cell back plate, and the bonding performance is kept unchanged through the first polyester layer and the second polyester layer on the two sides, so that the cost is reduced.

It should be appreciated by those of skill in the art that while the present invention has been described in terms of several embodiments, not every embodiment includes only a single embodiment. The description is given for clearness of understanding only, and it is to be understood that all matters in the embodiments are to be interpreted as including technical equivalents which are related to the embodiments and which are combined with each other to illustrate the scope of the present invention.

The above description is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations can be made by those skilled in the art without departing from the spirit and principles of the invention.