A microstructured directional reflective photovoltaic backsheet and its production process

Abstract

The present invention discloses a microstructured directional reflective photovoltaic backsheet and its production process, which relates to the field of photovoltaic equipment technology and aims to solve the problem of light utilization in the blank areas of photovoltaic modules other than the solar cells. The backsheet comprises a substrate layer, an adhesive layer, and a reflective layer stacked in sequence. The substrate layer and the reflective layer are bonded by the adhesive layer, and the adhesive layer is a UV-curable adhesive layer. The adhesive layer and the reflective layer can be peeled off from each other. The reflective layer forms a microstructure with a directional reflective function on the side facing the adhesive layer. The shape of the side opposite to the reflective layer is adapted to each other, and the side of the adhesive layer facing the reflective layer forms an opposite microstructure. By compounding a reflective film on the photovoltaic backsheet, the reflective film shell plays a directional reflection role in the light at that position, and the light is re-irradiated onto the solar cell panel through reflection from the panel, thereby realizing the light in the blank areas of the photovoltaic backsheet, and more efficiently utilizing the solar energy in the blank areas.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic modules, and more particularly to a microstructured directional reflection photovoltaic back panel and a production process of the microstructured directional reflection photovoltaic back panel. Background Art

[0002] Solar energy is a green, environmentally friendly, renewable energy source. With the global population increasing and the increasing dependence on and consumption of today's dominant, non-renewable fossil fuels, concerns are growing about energy depletion and environmental pollution, creating an urgent need for the development of new, green, and renewable energy sources. Currently, single-crystalline and multicrystalline silicon photovoltaic cell modules, based on the photovoltaic principle and utilizing sunlight to generate power, are highly mature. Conventional photovoltaic modules consist, from bottom to top, of a backsheet, an encapsulating adhesive layer, a cell array, an encapsulating adhesive layer, and a front panel. Typically, the cells in the array are connected in series along the longitudinal direction of the module using tinned copper strips to conduct current and achieve module power output.

[0003] In double-glass modules or transparent backsheet modules using bifacial solar power generation technology, there is a certain gap between the cells, generally about 2mm. If the four corners of the monocrystalline silicon cell have beveled edges, a nearly octagonal blank area will be formed in the middle of the four cells. There is also a blank area around the entire cell array to the outer frame. These gaps between cells and blank areas account for approximately 3-5% of the entire module array. The sunlight that reaches these blank areas passes through the backsheet and is wasted. How to more efficiently utilize the sunlight between the cell gaps and blank areas is an ongoing research.

[0004] Currently, some companies use a glazing process to coat the gaps between cells and the corresponding blank areas around them, creating a gridded backplane. This glaze layer partially reflects sunlight, which is then reflected back onto the cells through the panel, partially utilizing the sunlight in the blank areas. However, the backplane formed by this process reflects light diffusely, which reduces the utilization rate of sunlight in the blank areas.

[0005] Therefore, a new solution needs to be proposed to solve this problem. Summary of the Invention

[0006] The purpose of the present invention is to solve the above problems and provide a production process for a microstructured directional reflective photovoltaic backsheet, which can effectively solve the problem of light utilization in the non-cell area of the photovoltaic module.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions: A production process for a microstructured directional reflective photovoltaic backsheet comprises the following steps:

[0008] Silk screen printing: A layer of UV-curable adhesive is printed on the inner side of the transparent photovoltaic backsheet through the silk screen printing process. The printing position and size correspond to the blank area on the photovoltaic backsheet.

[0009] Bonding: A side of the photovoltaic backsheet printed with UV-curable adhesive (II) is covered with a reflective film having a directional reflective function; the reflective film comprises a substrate layer, an adhesive layer, and a reflective layer stacked in sequence, the substrate layer and the reflective layer being bonded together by an adhesive layer, the adhesive layer being UV-curable adhesive layer (I), which is peelable from the reflective layer; the reflective layer side of the reflective film is bonded to the UV-curable adhesive (II).

[0010] Light curing: A UV lamp is used to irradiate the second UV curing adhesive with the reflective film through the photovoltaic backsheet to form a second UV curing adhesive layer. The second UV curing adhesive layer is bonded to the transparent photovoltaic backsheet and the reflective layer of the reflective film. The bonding strength between the second UV curing adhesive layer and the reflective layer is greater than that between the second UV curing adhesive layer and the reflective layer. After curing, the bonding strength between the second UV curing adhesive layer and the reflective layer is more than twice that between the first UV curing adhesive layer and the reflective layer.

[0011] Peeling: The base material layer of the reflective film is peeled off from the photovoltaic backboard, and the microstructure on the reflective film is copied to the second surface of the UV-curing adhesive. The reflective layer on the reflective film is retained on the photovoltaic backboard to form a directional reflective layer, thereby obtaining a photovoltaic backboard with directional reflection function.

[0012] The present invention is further configured such that a microstructure with a directional light reflection function is formed on the side of the reflective layer facing the bonding layer, the reflective layer and the opposite side of the UV-curable adhesive layer are adapted to each other in shape, and an opposite microstructure is formed on the side of the bonding layer facing the reflective layer.

[0013] The present invention is further configured such that the microstructures on the reflective film are arranged in strips obliquely at 45 degrees, each microstructure is sawtooth-shaped and includes a plurality of evenly arranged directional reflective microprotrusions; the directional reflective microprotrusions have a cross section including at least two side surfaces.

[0014] The present invention is further configured such that the surface protrusion height of the directional reflective micro-protrusions is 10-30 μm, adjacent directional reflective micro-protrusions are connected to each other to form V-shaped grooves, and the interval period is 20-80 μm.

[0015] The present invention is further configured as follows: the blank area on the photovoltaic backplane includes a blank area one between the solar cells and a blank area two around the surrounding cells; in the first blank area, the cross-section of the directional reflection micro-protrusion is an isosceles triangle, and both side surfaces are inclined planes, with an inclination angle of 30-75°; in the second blank area, the cross-section of the directional reflection micro-protrusion is a right triangle, and the two side surfaces are an inclined plane and a vertical plane, respectively, with an inclination angle of 30-75°, and the inclined plane faces the solar cell in the middle of the photovoltaic backplane.

[0016] The present invention is further configured such that the production process of the reflective film comprises the following steps:

[0017] Fabrication of the metal roller: Based on the required sunlight reflection angle of the photovoltaic backsheet, the reflection angle of the reflective film's microstructure is designed, and the metal roller is fabricated. The outer periphery of the metal roller has a microstructure that can directional reflect light.

[0018] Pretreatment: performing corona treatment on the surface of the substrate layer, and coating the surface of the corona-treated substrate layer with an adhesion promoter;

[0019] Embossing: Applying a UV-curing adhesive to the adhesion promoter surface of the substrate layer; using a metal roller with a microstructure to mold the UV-curing adhesive; and simultaneously, using a UV lamp to cure the molded position to form a UV-curing adhesive layer with a microstructure on the substrate layer;

[0020] Coating: A film is deposited on the microstructure surface of the substrate layer by vacuum deposition to form a reflective layer. The side of the reflective layer facing the substrate layer overlaps with the UV-curable adhesive layer 1, forming a microstructure with a directional reflection function for light on the reflective layer to obtain a reflective film. The reflective layer and the UV-curable adhesive layer 1 can be peeled off from each other.

[0021] The present invention is further configured such that the substrate layer is made of PET, and after corona treatment, the surface tension reaches more than 50 dynes; the adhesion promoter is a two-component solvent-based acrylic material, the adhesion promoter coating working environment temperature is 26-30°C, the humidity is 40-70% RH, the coating machine speed is 45-55m / min, and the drying tunnel temperature is 80°C-125°C-150°C-155°C-110°C respectively, and the surface coating uniformity of the substrate layer needs to be controlled during coating.

[0022] The present invention is further configured such that the UV curing adhesive is acrylic, the coating speed of the UV curing adhesive is 10-20 m / min, the coating temperature of the UV curing adhesive is 40-60°C, and the molding pressure is 1.5-5 kg / cm 2 The UV lamp used for curing is a mercury lamp or a metal halide lamp, and the curing power density is 80-200w / cm 2 .

[0023] The present invention is further configured such that, during the coating process, the coating material is aluminum, the reflective layer is an aluminum layer, the thickness of the aluminum layer is 380Å to 600Å, and the aluminum purity is greater than 99.9%; during the evaporation, the vacuum degree reaches 1×10 -2 to 1×10 -3 Pa, the aluminum plating wire feeding speed is 0.4-0.8m / min, and the aluminum plating speed is 300-400m / min.

[0024] The present invention also provides a microstructured directional reflective photovoltaic backboard, which is produced using the above-mentioned production process and includes a transparent photovoltaic backboard. A reflective layer with directional reflective function is formed on one side of the photovoltaic backboard, and the reflective layer is used to directionally reflect light toward the direction of the solar cell.

[0025] In summary, the present invention has the following beneficial effects:

[0026] By compounding a reflective film on the photovoltaic back panel, the reflective film shell can directionally reflect the light at that position, and then re-irradiate it onto the solar panel through reflection from the panel, thereby realizing the light in the blank area of the photovoltaic back panel and making more efficient use of the solar energy in the blank area.

[0027] Through the peelable microstructured directional reflective film, the base layer of the reflective film can be peeled off, leaving only the reflective layer with the directional reflective microstructure to cover the blank area of the photovoltaic backplane. The peeled base layer can be recycled, reducing the production and use costs of the reflective film and improving the production cost of the directional reflective photovoltaic backplane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a microstructured directional reflective film in Example 1 Figure 1 ;

[0029] Figure 2 A schematic diagram of the structure of a microstructured directional reflective film in Example 1 Figure 2 ;

[0030] Figure 3 A schematic diagram of the structure of a microstructured directional reflective film in Example 2 Figure 1 ;

[0031] Figure 4 A schematic diagram of the structure of a microstructured directional reflective film in Example 2 Figure 2 , to indicate the peeling state of the reflective layer;

[0032] Figure 5 This is a schematic structural diagram of a microstructure in Example 2;

[0033] Figure 6 Schematic diagram of another microstructure in Example 2;

[0034] Figure 7 This is a schematic structural diagram of the substrate layer during the rolling process in Example 2;

[0035] Figure 8 This is a schematic diagram of the structure of the photovoltaic backsheet and the reflective film bonded together in Example 3;

[0036] Figure 9 This is a schematic diagram of the structure of the photovoltaic backsheet and the reflective layer bonded together in Example 3;

[0037] Figure 10 This is a schematic structural diagram of the photovoltaic backsheet in Example 3;

[0038] Figure 11 A three-dimensional diagram of the photovoltaic backsheet in Example 3;

[0039] Figure 12 A schematic diagram of the structure of a microstructured directional reflective film in Example 4 Figure 1 ;

[0040] Figure 13 A schematic diagram of the structure of a microstructured directional reflective film in Example 4 Figure 2 , to indicate the bonding state of the reflective film and the photovoltaic back surface;

[0041] Figure 14 A schematic diagram of the structure of a microstructured directional reflective film in Example 4 Figure 3 , the state where the reflective layer is transferred to the photovoltaic backsheet;

[0042] Figure 15 This is a schematic diagram of the structure of another microstructured directional reflection film in Example 4. Figure 1 ;

[0043] Figure 16 This is a schematic diagram of the structure of another microstructured directional reflection film in Example 4. Figure 2 , to indicate the bonding state of the reflective film and the photovoltaic back surface;

[0044] Figure 17 This is a schematic diagram of the structure of another microstructured directional reflection film in Example 4. Figure 3 , the state where the reflective layer is transferred to the photovoltaic backsheet;

[0045] Figure numerals: 1. Reflective film; 11. Base material layer; 12. Reflective layer; 13. UV-curing adhesive layer 1; 14. UV-curing adhesive layer 2; 15. Back adhesive layer; 16. Release layer; 2. Microstructure; 21. Directional reflective micro-protrusions; 201. Inclined surface; 202. Arc-shaped surface; 203. Vertical surface; 3. Metal roller; 31. Adhesive roller; 4. Ultraviolet UV lamp; 5. Photovoltaic back panel; 51. Blank area; 511. Blank area 1; 512. Blank area 2. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] Example 1

[0048] This embodiment discloses a microstructured directional reflective photovoltaic backplane. By pasting a reflective film 1 on the blank areas 51 on the photovoltaic backplane 5, the reflective film can reflect sunlight in these areas. The reflected sunlight is then reflected onto the cell through the panel of the photovoltaic module, thereby realizing the utilization of sunlight in the blank areas 51 and improving the utilization efficiency of sunlight.

[0049] The reflective film 1 has microstructures 2 on it. These microstructures 2 reflect light in a directional manner, rather than diffusely, thereby ensuring consistent reflection and selectively focusing the light. By designing the angle of directional reflection, the microstructures 2 on the reflective film 1 are arranged at a directional reflection angle, enabling more efficient utilization of solar energy in the blank area 51.

[0050] The blank area 51 on the photovoltaic backsheet 5 includes a blank area 1 511 and a blank area 2 512. Figure 10 The blank area 1 511 is the gap between the cells and the center of the four cells; the blank area 2 512 is the area around the photovoltaic backsheet 5 corresponding to the cells.

[0051] like Figure 1 As shown, the reflective film 1 is a multi-layer composite structure, comprising a substrate layer 11 and a reflective layer 12. The substrate layer 11 is a PET film, and the reflective layer 12 is typically a metallic aluminum layer, which can be processed by aluminum plating. During the production process, the microstructure 2 is first embossed on the surface of the PET film, and then aluminum is plated on the microstructure 2 to form the reflective layer 12, thus forming a reflective film with microstructured directional reflection.

[0052] like Figure 2 As shown, to facilitate the attachment of the reflective film 1, a backing adhesive layer 15 and a release layer 16 are generally provided on the back side of the substrate layer 11 of the reflective film 1. The backing adhesive layer 15 is located between the release layer 16 and the substrate layer 11, and the release layer 16 can be peeled off from the backing adhesive layer 15. During use, after peeling off the release layer 16, the backing adhesive layer 15 can be directly bonded to the photovoltaic backsheet 5 to complete the attachment of the reflective film 1.

[0053] Example 2

[0054] In the reflective film 1, the reflective layer 12, i.e., the aluminum layer, is responsible for reflecting light. In the above embodiment, the reflective film 1 used on the photovoltaic backsheet 5 has a four-layer structure. The adhesive layer and the thicker PET substrate layer 11 increase the cost of the reflective film 1. Therefore, the reflective film 1 used on the photovoltaic backsheet 5 can be further optimized to produce another microstructured directional reflective film. Based on this reflective film 1, another microstructured directional reflective photovoltaic backsheet and its corresponding production process can be obtained.

[0055] This embodiment discloses a microstructured directional reflective film, such as Figure 3 As shown, the film comprises a substrate layer 11, an adhesive layer, and a reflective layer 12, which are stacked in sequence. The substrate layer 11 and the reflective layer 12 are bonded together by the adhesive layer. A microstructure 2 with a directional light-reflecting function is formed on the side of the reflective layer 12 facing the adhesive layer. The sides of the reflective layer 12 and the adhesive layer opposite each other are shaped to match each other, with the adhesive layer facing the reflective layer 12 forming an opposite microstructure 2. The directional light-reflecting microstructure 2 is located within the film's inner layer and is protected by the reflective layer 12 and adhesive layer on both sides. This maintains the surface condition of the microstructure 2, ensuring it has the desired light reflection angle and enhancing the reflection and utilization of sunlight.

[0056] The adhesive layer is a UV-curable adhesive 1, which forms a UV-curable adhesive layer 13 after curing. The UV-curable adhesive layer 13 has a strong bonding strength with the substrate layer 11, but a weak bonding strength with the reflective layer 12. The UV-curable adhesive layer 13 and the reflective layer 12 can be peeled off from each other. After peeling, the microstructure 2 on the reflective layer 12 will be exposed to the outside, playing a role in shaping reflection, such as Figure 4 The status shown.

[0057] Specifically, the microstructures 2 on the directional reflective film 1 are arranged in strips at an angle of 45 degrees. Each microstructure 2 is sawtooth-shaped and includes a plurality of evenly arranged directional reflective microprotrusions 21. The directional reflective microprotrusions 21 are generally triangular or triangular-like in shape. The directional reflective microprotrusions 21 have a cross-section including at least two side surfaces, both of which face upward, thereby reflecting light.

[0058] like Figure 5 、 6As shown in Figures 1 and 11, the surface protrusions 21 of the directional reflective film 1 have a height of 10-30 μm. Adjacent directional reflective micro-protrusions 21 are interconnected to form V-shaped grooves with a periodic interval of 20-80 μm, forming a uniformly and densely arranged microstructure 2 that effectively reflects and utilizes sunlight. Because a V-shaped groove is formed between two directional reflective micro-protrusions 21, the sides of the groove are the two side surfaces of the directional reflective micro-protrusions 21, and there is no flat bottom surface. This prevents the angle between the incident angle and the reflection angle at the bottom from being too small, which would directly reflect light, thereby ensuring that the reflected light can be effectively utilized.

[0059] The blank area 51 on the back panel is divided into two types, namely the blank area 1 511 between the cells and the blank area 2 512 around the cells. According to the different setting positions of the directional reflection film 1, there are two specifications of the directional reflection film 1. Figure 5 As shown, at the blank area 511, the directional reflective film 1 at this location can reflect light in both directions, that is, reflect light onto the nearby solar panels. Therefore, the cross-section of the directional reflective micro-protrusion 21 can be an isosceles triangle, and the angle between the two inclined surfaces 201 and the bottom surface is between 30-75 degrees. The directional reflective micro-protrusion 21 can reflect the light irradiated by this area in both directions at an angle, and then be reflected by the photovoltaic panel and illuminate the surface of the solar cell, thereby improving the utilization effect of the light. Moreover, the isosceles triangle structure can reflect light relatively evenly onto the solar cells in both directions, making the reflected light more uniform, maintaining relatively uniform illumination of the solar cells, and more efficient power generation.

[0060] like Figure 6 As shown, at blank area 2 512, the directional reflective film 1 at this location needs to reflect light only toward the middle area of the photovoltaic backsheet 5, that is, toward the direction close to the cells. Therefore, the cross-section of the directional reflective micro-protrusion 21 is a right triangle, forming only one inclined surface 201, including the inclined surface 201, the vertical surface 203, and the bottom surface. During installation, the inclined surface 201 faces the cells in the middle of the photovoltaic backsheet 5, and the angle between the inclined surface 201 and the bottom surface is maintained at 30-75°. Ideally, the inclined surface 201 will primarily reflect the light at this location toward the cells; while the vertical surface 203 remains perpendicular to the bottom surface of the right triangle. When the photovoltaic backsheet is facing the sun, the vertical surface 203 is not directly blocked by the light, and the inclined surface 201 ensures that most of the light can be reflected toward the cells.

[0061] This embodiment discloses a production process for a microstructured directional reflective film, which includes four steps: making a metal roller, pretreatment, embossing, and coating, to form the reflective film 1 .

[0062] The metal roller fabrication process involves designing the reflection angle of the microstructure 2 of the reflective film 1 based on the desired sunlight reflection angle of the photovoltaic module. Using this reflection angle as a reference, the metal roller 3 is fabricated. The outer periphery of the metal roller 3 features microstructures 2 that provide directional light reflection. Two metal rollers 3 of corresponding specifications are fabricated based on the two different specifications of the directional reflective film 1. Each film is then embossed and molded.

[0063] Pretreatment step: Pretreat one side surface of the substrate layer 11 to improve the bonding force between the substrate layer 11 and the adhesive layer, ensuring that the adhesive layer can be retained on the substrate layer 11 during the subsequent peeling process of the substrate layer 11, so that a clear microstructure 2 reflective surface is formed on the reflective layer 12.

[0064] The substrate layer 11 is made of PET. During pretreatment, the surface of the substrate layer 11 is first subjected to corona treatment. After the corona treatment, the surface tension of the substrate layer 11 on that side reaches above 50 dynes. An adhesion promoter is then applied to the corona-treated surface of the substrate layer 11 to further improve its surface adhesion.

[0065] Adhesion promoters can be made from two-component solvent-based acrylic materials, specifically those that enhance adhesion. During coating, maintain a working temperature of 26-30°C, a humidity of 40-70% RH, a coating machine speed of 45-55 m / min, and a drying oven temperature of 80-125°C, 150°C, 155°C, or 110°C. During coating, ensure strict uniformity on the surface of substrate layer 11 to avoid surface defects such as scratching, splashing, and whitening. Ensure a stable surface after coating.

[0066] Imprinting steps: Figure 7 As shown, the surface of the substrate layer 11 is embossed using a corresponding metal roller 3. The metal roller 3 and the adhesive roller 31 cooperate to apply pressure to the film surface, forming corresponding microstructures 2 on the substrate layer 11, thereby obtaining two corresponding specifications of reflective films 1. First, a UV-curable adhesive is applied to the surface of the substrate layer 11 coated with an adhesion promoter, which can be applied by spin coating or drop coating. Then, the surface of the UV-curable adhesive is embossed using the metal roller 3 having the microstructure 2. Simultaneously, an ultraviolet lamp 4 is used to irradiate and cure the embossing position, transferring the microstructure 2 on the metal roller 3 to the UV-curable adhesive layer 13, thereby forming a UV-curable adhesive layer 13 having the microstructure 2 on the substrate layer 11.

[0067] The UV-curable adhesive has the function of transferring the microstructure 2 on the metal roller 3, and the metal aluminum bonding force on the surface of the UV-curable adhesive layer 13 is weak. After subsequent aluminum plating, the aluminum layer formed on the surface has a transfer function.

[0068] Specifically, the UV curing adhesive can be acrylic. During the coating process, the coating speed of the UV curing adhesive is 10-20 m / min, the temperature of the UV curing adhesive is 40-60°C, and the molding pressure is 1.5-5 kg / cm 2 The UV lamp 4 used for curing is a mercury lamp or a metal halide lamp, and the curing power density is 80-200w / cm 2 .

[0069] Coating step: A film is deposited on one side of the microstructure 2 of the substrate layer 11 via vacuum deposition to form a coating layer, which serves as the reflective layer 12. The side of the reflective layer 12 facing the substrate layer 11 overlaps with the UV-curable adhesive layer 13, forming microstructures 2 with directional light reflection capabilities. The microstructures 2 on the UV-curable adhesive layer 1 are then reverse-molded onto the aluminum layer, resulting in the directional reflective film 1. The reflective layer 12 and UV-curable adhesive layer 13 are designed to be removable from each other.

[0070] The coating material is aluminum, and the reflective layer 12 formed by vapor deposition is an aluminum layer. The thickness of the aluminum layer is 380Å to 600Å, and the purity of aluminum is greater than 99.9%. During vapor deposition, the vacuum degree is controlled to reach 1×10 -2 to 1×10 -3 Pa; the aluminum-plated wire feeding speed is 0.4-0.8m / min, and the aluminum-plating speed is 300-400m / min.

[0071] The microstructured directional reflective film obtained by this production is used by bonding the aluminum layer of the reflective film 1 and the photovoltaic back plate 5 to each other through an adhesive. Figure 8 、 9 The state shown is achieved, and the bonding strength between the aluminum layer and the photovoltaic backsheet 5 is greater than the bonding strength between the aluminum layer and the UV-curable adhesive layer 13. Subsequently, the substrate layer 11 is peeled from the surface of the aluminum layer, separating the aluminum layer and the UV-curable adhesive layer 1. The aluminum layer, i.e., the reflective layer 12, remains on the photovoltaic backsheet 5, resulting in a photovoltaic backsheet with microstructured directional reflection.

[0072] By forming a peelable state between the substrate layer 11 and the reflective layer 12, only the reflective film 1 is bonded to the photovoltaic backboard 5, and the PET substrate layer 11 of the reflective film 1 can be recycled, saving the production cost of the reflective film 1 to a certain extent.

[0073] Example 3

[0074] This embodiment discloses a production process for a microstructured directional reflective photovoltaic backsheet, comprising four steps: silk screen printing, bonding, photocuring, and peeling. The photovoltaic backsheet 5 is a transparent backsheet. The photovoltaic backsheet 5 is bonded to the reflective layer 12 of the reflective film 1. The substrate layer 11 and UV-curable adhesive layer 13 of the reflective film 1 are peeled from the surface of the reflective layer 12. The reflective layer 12 is then directly bonded to the photovoltaic backsheet 5, resulting in a photovoltaic backsheet 5 with microstructured directional reflective properties. Furthermore, the substrate layer 11 in the reflective material is eliminated, reducing not only the thickness of the reflective material but also the ability to recycle the substrate layer 11, thereby reducing production costs.

[0075] Screen printing step: a layer of UV curing adhesive 2 is printed on the inner side of the transparent photovoltaic backsheet 1 by screen printing process, and the printing position and size correspond to the blank area 51 on the photovoltaic backsheet 5.

[0076] Bonding Step: Select the microstructured directional reflective film of the above embodiment. Before bonding, pre-cut the reflective film 1 to the corresponding shape and size. Print one side of the transparent backing with UV-curable adhesive (II) and cover the directional reflective film 1. Lay the aluminum layer of the directional reflective film 1 and the UV-curable adhesive (II) together.

[0077] Photocuring: A UV lamp 4 is used to illuminate the UV-curable adhesive layer 2 beneath the directional reflective film 1 through the transparent backplane, curing the screen-printed UV-curable adhesive layer 2 to form a UV-curable adhesive layer 2 14. This UV-curable adhesive layer 2 14 is tightly bonded to the photovoltaic backplane 5 and the aluminum layer of the directional reflective film 1. On the equipment, this photocuring step and the bonding step occur almost simultaneously. While one side is being bonded, the other side is being UV-cured, ensuring a quick and tight bond between the two and preventing deviation in the output of the bonded reflective film.

[0078] UV-curable adhesive 2 has a stronger bond with the aluminum layer. After curing, its bond with the aluminum layer is more than twice that of UV-curable adhesive 1. UV-curable adhesive 2 ensures that the reflective layer 12 can be stably bonded to the photovoltaic backsheet 5 when the substrate layer 11 is peeled off.

[0079] Peeling: The substrate layer 11 of the directional reflective film 1 is peeled from the transparent backsheet. The microstructure 2 on the directional reflective film 1 is replicated onto the second surface of the UV-curable adhesive, similar to a mold-imprinted replication process. The aluminum layer on the directional reflective film 1 is retained on the photovoltaic backsheet 5, densely covering the blank areas 51 of the photovoltaic backsheet 5, forming a directional reflective structure and obtaining a microstructured directional reflective photovoltaic backsheet 5.

[0080] The microstructured directional reflective photovoltaic backsheet is processed using the above-mentioned production process to form a three-layer composite structure comprising a photovoltaic backsheet 5, a UV-cured adhesive layer 14, and a reflective layer 12, and a microstructure 2 with directionally reflective light is formed on the outward side of the reflective layer 12. In the blank area 511 between the cells, the cross-section of the directional reflective micro-protrusion 21 is an isosceles triangle, and the angle between the two inclined surfaces 201 and the bottom surface is 30-75°. The directional reflective film 1 bonded to the blank area 511 between the cells directionally reflects light on both sides; in the blank area 512 around the cells, the cross-section of the directional reflective micro-protrusion 21 is a right triangle, comprising an inclined surface 201, a vertical surface 203, and a bottom surface. The inclined surface 201 is used to face the cell in the middle of the photovoltaic backsheet 5, and the angle between the inclined surface 201 and the bottom surface is 30-75°. The directional reflective film 1 bonded to the blank area 512 around the cells reflects light from the periphery to the inner side of the backsheet.

[0081] By directional reflection of light, the light at that location can be reflected and utilized, thereby improving the utilization efficiency of sunlight. At the same time, the base material layer 11 in the reflective film 1 is eliminated and can be recycled, which reduces the production cost of the photovoltaic backsheet 5 to a certain extent.

[0082] Example 4

[0083] This embodiment discloses a microstructured directional reflective film. Based on the second embodiment, Figure 12-17 Further details are given.

[0084] The microstructures 2 on the reflective film 1 must maintain a good surface condition, that is, the inclined surfaces 201 within the microstructures 2 must be relatively flat to avoid distortion or roughness, and to maintain the directional reflection effect on light. Because the ends of the inclined surfaces 201 within the microstructures 2 form sharp angles, both the angle between the two inclined surfaces 201 and the angle between the inclined surfaces 201 and the vertical surface 203 are relatively sharp and fragile, especially the angle between the inclined surface 201 and the vertical surface 203, where the angle is smaller.

[0085] The UV-curable adhesive layer 13 is subjected to pressure from the microstructure 2 on the surface of the metal roller 3, forming an opposing and adaptive microstructure 2. During the peeling process between the metal roller 3 and the UV-curable adhesive layer 13, the reflective film 1 separates from the metal roller 3, transitioning from circular motion to linear motion. This causes the reflective film 1 to fluctuate. Furthermore, due to the height of the microstructure 2, the microstructure 2 embossed on the UV-curable adhesive layer 13 will interfere with the microstructure 2 on the metal roller 3 during the peeling process. This, in turn, may cause a certain degree of wear on the surface of the microstructure 2 embossed on the UV-curable adhesive layer 13, particularly at the top corner of the microstructure, affecting the surface quality of the microstructure 2 embossed on the UV-curable adhesive layer 13.

[0086] To this end, the top position of the microstructure 2 of the reflective layer 12 of the reflective film 1 can be set to form a more blunt structure, such as Figure 12-17 As shown. In each microstructure 2, the end position of the inclined surface 201 is set to be an arc-shaped surface 202, and the entire direction of the arc-shaped surface 202 is close to each other in the direction of the reflective layer 12, thereby preventing the microstructure 2 on the reflective film 1 from being too sharp. At the same time, the top position of the microstructure 2 on the corresponding metal roller 3 will also form a correspondingly blunt structure, forming an inwardly curved arc surface, thereby reducing the impact on the surface of the microstructure 2 when the UV-cured adhesive layer 13 of the metal roller 3 is peeled off. Because the top of the microstructure 2 on the metal roller 3 and the top of the microstructure 2 on the UV-cured adhesive layer 13 both form a structure with a nearly rounded corner, and the height of the microstructure 2 is slightly lower than the sharp corner, the mutual interference contact between the two microstructures 2 will be reduced during the peeling process, thereby avoiding wear on the surface of the microstructure 2, and making the microstructure 2 on the reflective layer 12 smoother, forming a more stable and effective directional reflection effect.

[0087] In a single microstructure 2, the length of the curved surface 202 generally does not exceed 1 / 4 of the length of the inclined surface 201, thereby controlling the original effective reflection area of the microstructure 2 to above 75%. Combined with the reflection effect of the curved surface 202, the reflective effect of this microstructure can be maintained at approximately 90% or above. The specific utilization efficiency depends on the curvature of the curved surface and the inclination of the inclined surface. Compared with the light utilization loss caused by microstructure wear, the structure of the inclined surface combined with the curved surface can achieve more stable directional reflection efficiency.

[0088] The combination of the inclined surface 201 and the curved surface 203 can maintain the effective reflection of light by the microstructure 2 while preventing surface roughness and damage to the microstructure 2. For the two specifications of the reflective film 1, the positions of the inclined surface 201 and the curved surface 202 are also different.

[0089] like Figure 12-14 As shown, for the reflective film 1 located in the blank area 511 between the cells, a curved surface 202 is formed at the end of the inclined surface 201 of the microstructure 2. The curved surface 202 is tangent to the inclined surface 201, maintaining a smooth transition between the curved surface 202 and the inclined surface 201, and the curved surface 202 faces the side of the UV-curable adhesive layer 1. In each microstructure 2, the curved surfaces 202 at the ends of the two inclined surfaces 201 intersect to form a more obtuse angle. The two curved surfaces 202 are not tangent at the point where they connect, ensuring that the top corners of the microstructure 2 also have an inclination, tilting toward the cells on both sides, and can also reflect light in the direction of the cells, thereby utilizing the light.

[0090] like Figure 15-17 As shown, for the reflective film 1 located in the blank area 2 512 around the cell, only one inclined surface 201 is formed in the microstructure 2, and the other side is a vertical surface 203. The vertical surface 203 does not primarily participate in the reflection effect. Therefore, a curved surface 202 is formed only at the end of the inclined surface 201 on one side of the microstructure 2. The curved surface 202 is tangent to the inclined surface 201, maintaining a smooth transition between the curved surface 202 and the inclined surface 201. The vertical surface 203 intersects the curved surface 202, and at the location where the curved surface 202 intersects the vertical surface 203, its orientation is still tilted toward the cell, thereby reflecting light at that location toward the cell, thereby improving light utilization efficiency.

[0091] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A production process for a microstructured directional reflective photovoltaic backsheet, characterized in that: The steps include: Silk screen printing: a layer of ultraviolet curing adhesive is printed on the inner side of the transparent photovoltaic backsheet (5) by silk screen printing, and the position and size of the printing correspond to the blank area (51) on the photovoltaic backsheet (5); Bonding: a side of a photovoltaic backsheet (5) printed with a second ultraviolet curing adhesive is covered with a reflective film (1) having a directional reflection function; the reflective film (1) comprises a base material layer (11), an adhesive layer, and a reflective layer (12) stacked in sequence; the base material layer (11) and the reflective layer (12) are bonded together by the adhesive layer; a microstructure (2) having a directional reflection function for light is formed on the side of the reflective layer (12) facing the adhesive layer; the adhesive layer is a first ultraviolet curing adhesive layer (13); the first ultraviolet curing adhesive layer (13) and the reflective layer (12) can be peeled off from each other; one side of the reflective layer (12) of the reflective film (1) is bonded to the second ultraviolet curing adhesive; Light curing: using an ultraviolet UV lamp (4) to irradiate the second ultraviolet curing adhesive with the reflective film (1) through the photovoltaic backboard (5) to form a second ultraviolet curing adhesive layer (14), the second ultraviolet curing adhesive layer (14) is bonded to the transparent photovoltaic backboard (5) and the reflective layer (12) of the reflective film (1); the bonding force between the second ultraviolet curing adhesive and the reflective layer (12) is greater than that between the second ultraviolet curing adhesive and the reflective layer (12); after curing, the bonding force between the second ultraviolet curing adhesive layer (14) and the reflective layer (12) is more than twice the bonding force between the first ultraviolet curing adhesive layer (13) and the reflective layer (12); Peeling: The base material layer (11) of the reflective film (1) is peeled off from the photovoltaic backboard (5), the microstructure (2) on the reflective film (1) is copied to the second surface of the ultraviolet curing adhesive, and the reflective layer (12) on the reflective film (1) is retained on the photovoltaic backboard (5) to form a directional reflective layer (12), thereby obtaining a photovoltaic backboard (5) with directional reflection function.

2. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 1, characterized in that: The shapes of the side of the reflective layer (12) opposite to the UV-curable adhesive layer (13) are adapted to each other, and the side of the adhesive layer facing the reflective layer (12) is formed with an opposite microstructure (2).

3. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 2, characterized in that: The microstructures (2) on the reflective film (1) are arranged in strips obliquely at 45 degrees, each microstructure (2) is sawtooth-shaped and includes a plurality of evenly arranged directional reflective microprotrusions (21); the directional reflective microprotrusions (21) have a cross section including at least two side surfaces.

4. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 3, characterized in that: The surface protrusion height of the directional reflection micro-protrusions (21) is 10-30 μm, and adjacent directional reflection micro-protrusions (21) are connected to each other to form V-shaped grooves with an interval period of 20-80 μm.

5. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 3, characterized in that: The blank area (51) on the photovoltaic backsheet (5) includes a blank area 1 (511) between the cells and a blank area 2 (512) around the cells; at the blank area 1 (511), the cross section of the directional reflection micro-protrusion (21) is an isosceles triangle, both side surfaces are inclined planes (201), and the inclination angle of the inclined plane (201) is 30-75°; at the blank area 2 (512), the cross section of the directional reflection micro-protrusion (21) is a right triangle, the two side surfaces are the inclined plane (201) and the vertical plane (203), the inclination angle of the inclined plane (201) is 30-75°, and the inclined plane (201) faces the cell in the middle of the photovoltaic backsheet (5).

6. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 3, characterized in that: The production process of the reflective film (1) comprises the following steps: Manufacturing a metal roller: combining the angle of sunlight reflection required by the photovoltaic backsheet (5), designing the reflection angle of the microstructure (2) of the reflective film (1), and manufacturing a metal roller (3); the outer periphery of the metal roller (3) has a microstructure (2) with a function of directional reflection of light; Pretreatment: performing corona treatment on the surface of the substrate layer (11), and coating an adhesion promoter on the surface of the corona-treated substrate layer (11); Embossing: coating a UV curing adhesive on the adhesion promoter surface of the substrate layer (11); using a metal roller (3) with a microstructure (2) to mold the UV curing adhesive; and simultaneously, using an ultraviolet lamp (4) to irradiate and cure the UV curing adhesive at the molding position, thereby forming a UV curing adhesive layer (13) with the microstructure (2) on the substrate layer (11); Coating: A film is deposited on the microstructure (2) surface of the substrate layer (11) by vacuum deposition to form a reflective layer (12), and the side of the reflective layer (12) facing the substrate layer (11) overlaps with a UV-curable adhesive layer (13), forming a microstructure (2) with a directional reflection function for light on the reflective layer (12), thereby obtaining a reflective film (1).

7. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 6, characterized in that: The substrate layer (11) is made of PET, and after corona treatment, the surface tension reaches more than 50 dynes; the adhesion promoter is a two-component solvent-based acrylic material, the adhesion promoter coating working environment temperature is 26-30°C, the humidity is 40-70%RH, the coating machine speed is 45-55m / min, and the drying tunnel temperature is 80°C-125°C-150°C-155°C-110°C respectively. During coating, the surface coating uniformity of the substrate layer (11) needs to be controlled.

8. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 6, characterized in that: The UV curing adhesive is acrylic acid, the coating speed of the UV curing adhesive is 10-20 m / min, the coating temperature of the UV curing adhesive is 40-60° C., and the molding pressure is 1.5-5 kg / cm 2 The UV lamp (4) used for curing is a mercury lamp or a metal halide lamp, and the curing power density is 80-200w / cm 2 .

9. The production process of a microstructured directional reflective photovoltaic backsheet according to claim 6, characterized in that: During the coating process, the coating material is aluminum, the reflective layer (12) is an aluminum layer, the thickness of the aluminum layer is 380Å to 600Å, and the aluminum purity is greater than 99.9%; during the evaporation, the vacuum degree reaches 1×10 -2 to 1×10 -3 Pa, the aluminum plating wire feeding speed is 0.4-0.8m / min, and the aluminum plating speed is 300-400m / min.

10. A microstructured directional reflective photovoltaic backsheet, characterized in that: The production process according to any one of claims 1 to 9 is used for production, comprising a transparent photovoltaic backsheet (5), a reflective layer (12) with a directional reflection function formed on one side of the photovoltaic backsheet (5), and the reflective layer (12) is used to directionally reflect light toward the direction of the solar cell.

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