A coating composition, a partially conductive insulating bifunctional backplate for back contact batteries, its preparation method and application.

Abstract

This invention, entitled "A Coating Composition, a Partially Conductive and Insulating Dual-Functional Backsheet for Back Contact Batteries, its Preparation Method, and its Application," belongs to the field of photovoltaic module encapsulation technology. The technical problem to be solved is to improve the battery's resistance to ultraviolet radiation, damp heat, and sand shedding, and to mitigate short-circuit risks. The key technical points are: a coating composition comprising: an adhesive coating, a conductive coating, and an insulating protective coating; the adhesive coating comprising: 0.3wt%-0.5wt% leveling agent, with the balance being modified polyurethane resin; the conductive coating comprising: 1wt%-2wt% adhesion promoter, 65wt%-85wt% copper paste, with the balance being an epoxy resin matrix; the insulating protective coating comprising: 0.5wt%-1wt% abrasion resistant agent, with the balance being fluorocarbon resin.

Description

Technical Field

[0001] This invention provides a coating composition, a partially conductive and insulating dual-function backsheet for back contact batteries, its preparation method, and its application, belonging to the field of photovoltaic module packaging technology. Background Technology

[0002] Back contact (BC) cells, as a core technology for high-efficiency photovoltaic cells, have the key advantage of integrating the emitter, surface field, and metal electrode on the back of the cell, with no grid lines obstructing the front. This maximizes the utilization of incident light, reduces optical losses, and achieves higher photoelectric conversion efficiency. In addition, they have a simple and neat appearance and are increasingly widely used in distributed power stations, ground power stations, and other scenarios.

[0003] The unique structure of BC cells presents significant technical challenges to module packaging, particularly the coordinated integration of the positive and negative electrode leads and insulation protection on the back of the cell. This has become a key bottleneck restricting the large-scale production, cost control, and reliability improvement of BC modules. As the core packaging component of BC modules, the backsheet primarily serves to provide insulation protection (resistance to humidity, heat, UV, and sand), structural support, and auxiliary circuit leads. Its performance directly determines the module's lifespan and operational stability. Therefore, the development of a dedicated backsheet adapted to the BC cell structure and the optimization of its manufacturing processes are crucial.

[0004] Relevant patent documents retrieved: The document, published in China (CN114038929A) on February 11, 2022, discloses a back-contact solar cell module and its manufacturing method. The module comprises a backsheet layer, a conductive layer, an insulating layer, a cell layer, and a cover plate stacked sequentially. The insulating layer has through-holes, and the conductive layer and the cell layer are electrically connected through conductors disposed within the through-holes. The key feature is that a water-blocking coating or a water-blocking film obtained by flash evaporation or screen printing is provided between the backsheet layer and the conductive layer.

[0005] The adhesive layer comprises a polymer, which is one or more of the following: ethylene-vinyl acetate, ionomer, silicone-based sealant, thermoplastic urethane, polyvinyl butyral, linear low-density polyethylene, linear high-density polyethylene, polyolefin, acrylic polymer with additives or polyurethane, and maleic anhydride-grafted terpolymer acrylic acid.

[0006] The conductor is composed of a mixture of conductive particles and resin. The conductive particles include one or more combinations of copper (Cu), silver (Ag), gold (Au), nickel (Ni), tin-lead alloy particles, tin-bismuth alloy particles, indium-tin alloy particles, indium-silver alloy particles, or tin powder particles; the resin includes rosin resin, polyimide resin, fluorocarbon resin, polyester resin, bismaleimide resin, epoxy resin, or acrylate resin.

[0007] The publication, China, CN120636892A, dated September 12, 2025, discloses a photovoltaic copper paste comprising: gradient micron-sized copper powder, nano-conductive reinforcing materials, organic binders, glass powder, reinforcing agents, and optional additives; the reinforcing agents include antioxidants, nano-interface reinforcing agents, passivating agents, and optional corrosion inhibitors; wherein the nano-interface reinforcing agents include one or more of alumina nanoparticles, antimony nanoparticles, and graphene quantum dots; and the passivating agents include benzotriazole and silane coupling agents.

[0008] Relevant non-patent literature retrieved: The journal or book title is *Coatings Industry*, and the document title is "Application Research of Transparent Fluorocarbon Coating in Solar Cell Backsheets," Volume 11, Issue 61-66, published in 2021. This document discloses that transparent backsheets are novel encapsulation materials used in bifacial power generation modules, and transparent fluorocarbon coatings are an important component. The performance of the fluorocarbon coating has a significant impact on the UV resistance and light transmittance of the transparent backsheet. This study prepared a transparent fluorocarbon coating using a two-component curing system of FEVE fluorocarbon resin and isocyanate. The effects of UV absorbers and light stabilizers in the fluorocarbon coating formulation on the UV resistance of the transparent backsheet, as well as the relationship between the particle size and dosage of inorganic particles and light transmittance, were investigated. The results show that using the preferred 5% UV absorber and 2% light stabilizer, a 10μm coating can effectively block ultraviolet rays, protecting the transparent backsheet against UV radiation exceeding 200 kWh / m². 2 Adding 5% inorganic silica particles with a particle size of 5μm can achieve a good balance between light transmittance and anti-blocking properties.

[0009] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: Existing photovoltaic copper pastes or photovoltaic coatings cannot simultaneously achieve the technical effects of low conductivity resistance, high breakdown voltage, good resistance to damp heat / UV aging, high resistance to sand shedding, and small alignment deviation. Summary of the Invention

[0010] The purpose of this invention is to provide: A coating composition, a partially conductive insulating dual-function backplate for back contact batteries, its preparation method and application, and related technologies, to solve technical problems such as improving the battery's resistance to ultraviolet radiation, damp heat, and sandfall, and avoiding short circuit risks, or combinations thereof.

[0011] Terminology Explanation: Unless otherwise defined, all technical terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the claimed subject matter pertains. Unless otherwise stated, all patents, patent inventions, and publications cited throughout this document are incorporated herein by reference in their entirety. Where multiple definitions exist for terms herein, the definitions provided in this chapter shall prevail.

[0012] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0013] The definition of the standard chemical term can be found in the reference "GB / T 31034-2024 Insulating Backsheet for Crystalline Silicon Solar Cell Modules".

[0014] Unless otherwise stated, conventional methods within the scope of the art, such as conductivity testing, shall be used.

[0015] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0016] The terms “optional / arbitrary” or “optionally / arbitrarily” mean that the event or situation described below may or may not occur, including both the occurrence and non-occurrence of the event or situation.

[0017] In a first aspect, the present invention provides: a coating composition comprising, for independent use: an adhesive coating, a conductive coating, and an insulating protective coating; The adhesive coating comprises: 0.3wt%-0.5wt% leveling agent, with the balance being modified polyurethane resin; The conductive coating comprises: 1wt%-2wt% adhesive accelerator, 65wt%-85wt% copper paste, and the balance being epoxy resin matrix; The insulating protective coating comprises: 0.5wt%-1wt% abrasion resistant agent, with the balance being fluorocarbon resin.

[0018] The leveling agent is polyether-modified polydimethylsiloxane.

[0019] The bonding accelerator is a silane coupling agent, KH-560.

[0020] The copper paste is at least one of copper paste with added antioxidant or silver-coated copper paste; the amount of antioxidant added is 0.2wt%-0.4wt% of the total mass of the copper paste, and the antioxidant is a benzotriazole compound.

[0021] The benzotriazole compounds include at least one of benzotriazole, 5-methylbenzotriazole, and carboxybenzotriazole.

[0022] The wear-resistant agent is nano-silica or nano-alumina.

[0023] In a second aspect, the present invention provides: a partially conductive and insulating dual-function backplate for a back contact battery, comprising, from bottom to top, an insulating substrate layer, an adhesive structure, a patterned conductive layer, and an insulating protective layer; The insulating substrate layer is a PET substrate; The bonding structure is a bonding coating that is applied to and cured on an insulating substrate layer, with a thickness of 5μm-10μm before curing; The patterned conductive layer is a conductive coating printed and cured on the bonding structure, with a thickness of 5μm-15μm before curing; The insulating protective layer is an insulating protective coating that is coated and cured on a patterned conductive layer, with a thickness of 20μm-50μm before curing.

[0024] The PET substrate is a PET film with a thickness of 275μm-300μm.

[0025] The PET substrate has a light transmittance of ≥85%.

[0026] The tensile strength of the PET substrate is ≥150MPa.

[0027] The conductivity resistance of the patterned conductive layer is ≤0.5Ω / m.

[0028] The light transmittance of the insulating protective layer is ≥90%.

[0029] Thirdly, the present invention provides: a method for preparing a partially conductive insulating dual-functional backplate for a back contact battery, comprising the following steps: (1) After the PET substrate is pretreated by alkali washing, water washing and drying, a bonding coating is applied locally and cured at 80℃-90℃ for 8-12 minutes to obtain substrate A; (2) Coat substrate A with conductive coating and cure at 110℃-130℃ for 25-35 min to obtain substrate B; (3) Apply an insulating protective coating to substrate B, cure at 120℃-140℃ for 20-30 minutes, and then cut and trim to obtain the final product.

[0030] The concentration of the alkaline solution used in the alkaline washing is 5wt%-10wt%.

[0031] The alkali used in the alkaline washing is sodium hydroxide.

[0032] The alkaline washing time is 10-15 minutes, and the temperature is 40-50℃.

[0033] The water washing process involves washing the water at 20℃-30℃ 3-4 times, each time for 5-8 minutes.

[0034] The drying temperature is 80℃-100℃, and the drying time is 15min-25min.

[0035] The adhesive coating is applied using screen printing, with a screen printing stencil of 200-250 mesh, a coating temperature of 70-80℃, and a coating speed of 5-10 m / min.

[0036] The conductive coating is applied using screen printing, with a screen printing stencil of 250-350 mesh and a printing speed of 5-10 m / min.

[0037] The temperature during the application of the insulating protective coating is 60℃-80℃, and the coating speed is 5m / min-12m / min.

[0038] The insulating protective coating is applied by roller coating, spraying, or screen printing.

[0039] Fourthly, the present invention provides the application of the above-described coating composition in the preparation of back contact batteries.

[0040] Fifthly, the present invention provides: a back contact battery, including the aforementioned partially conductive and insulating dual-function backplate.

[0041] The present invention has at least the following beneficial effects: 1. Compared with the prior art, the present invention achieves the integration of low resistance conductivity (≤0.5Ω / m) and high insulation protection (breakdown voltage ≥18kV / mm) through the synergistic combination of adhesive coating, conductive coating and insulating protective coating and a three-layer curing process, thus completely avoiding the risk of short circuit on the back of BC battery.

[0042] 2. According to experimental tests, the conductivity resistance of the present invention is as low as 0.3Ω / m, which is better than that of comparative examples 1-3 (0.9Ω / m-2.1Ω / m). This proves that the combination of the anti-oxidant copper paste and the epoxy resin matrix works synergistically with other layers to effectively inhibit copper oxidation and ensure long-term conductivity stability.

[0043] 3. According to experimental tests, the adhesion of the present invention remains at Grade 1 after humid heat aging, which is far superior to comparative examples 1-3. This proves that the leveling agent in the adhesive coating works synergistically with other coatings to significantly enhance interlayer bonding and avoid delamination. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the partially conductive and insulating dual-function backplate of the present invention. 1 is the insulating base material, 2 is the bonding structure, 3 is the patterned conductive layer, and 4 is the insulating protective layer. Detailed Implementation

[0045] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0046] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0047] Example 1: A coating composition Example 1 provides a coating composition comprising an adhesive coating, a conductive coating, and an insulating protective coating.

[0048] (1) Adhesive coating: Modified polyurethane adhesive coating, consisting of 0.4wt% leveling agent (polyether modified polydimethylsiloxane, Anhui Jiazhi Xinno Chemical Co., Ltd., Xinno® WE-D5411R) and the balance modified polyurethane resin (Guangdong Lankelu New Material Co., Ltd., L-8321).

[0049] (2) Conductive coating: It is composed of 1.5wt% adhesive accelerator (KH-560), 72wt% copper paste and the balance bisphenol A type epoxy resin (Dalian Qihua New Material Co., Ltd., DYD-128). The copper content of the copper paste is ≥99.5wt%, and the antioxidant is benzotriazole, accounting for 0.3wt% of the total mass of the copper paste.

[0050] (3) Insulating protective coating: A single-component fluorocarbon coating is used, consisting of 0.8wt% wear-resistant agent (nano silica, particle size 20nm) and the remainder fluorocarbon resin (Changzhou Weston Coating, WSD-1669).

[0051] Example 2: A partially conductive and insulating dual-function backplate for back contact batteries and its preparation method. Example 2 provides a partially conductive and insulating dual-function backplate for back contact batteries and its preparation method. The backplate consists of an insulating substrate layer, an adhesive structure, a patterned conductive layer, and an insulating protective layer.

[0052] like Figure 1 As shown, the partially conductive and insulating dual-function backplate for the back contact battery consists of, from bottom to top, an insulating substrate layer, an adhesive structure, a patterned conductive layer, and an insulating protective layer.

[0053] (1) Insulating substrate layer (purchased PET film, Yuxing Co., Ltd. CY25HGT48): Use finished PET film that meets industry standards (with 0.8% antistatic agent), with a thickness of 290μm, light transmittance ≥85%, and tensile strength ≥150MPa; the flatness of the purchased PET film is ≤0.1mm / m and the surface roughness is 0.05-0.1μm to ensure the stability of subsequent bonding with the adhesive structure.

[0054] (2) Adhesive structure: The adhesive coating of Example 1 is partially coated on the surface of PET film by screen printing. The area covered is the area to be printed with conductive coating later. It is completely matched with the size of the patterned conductive layer. The coating thickness is 8μm. 0.4% leveling agent added to the adhesive coating improves the coating uniformity.

[0055] (3) Patterned conductive layer: The conductive coating of Example 1 is used to prepare the conductive grid by screen printing. The conductive grid line width is 0.3 mm and the thickness is 10 μm. It is precisely matched with the BC battery busbar (deviation ≤ 0.05 mm) and the conductive resistance is ≤ 0.5 Ω / m (measured 0.3 Ω / m).

[0056] (4) Insulation protection layer: The insulation protection coating of Example 1 is used for coating. The coating thickness is 35μm (±2μm), the light transmittance is ≥90%, the UV aging resistance is 720h without yellowing or cracking, and the breakdown voltage is ≥15kV / mm (actual measurement 18kV / mm).

[0057] Opening in the insulating protective layer: size 5mm × 10mm, deviation ≤ 0.1mm.

[0058] The preparation method includes the following steps: (1) Purchased PET photovoltaic backsheet substrate (with 0.5-1% antistatic agent, 290μm) is pretreated by alkali washing, water washing and drying, and then enters the screen printing station. Using the same screen printing equipment, the adhesive coating (8μm thick before curing) is first applied locally, and then pre-cured at 85℃ for 12min to obtain substrate A.

[0059] The specific parameters for pretreatment are as follows: 8% alkali concentration, 45℃ temperature, and 12min treatment time; three washes with room temperature water, each lasting 6min; and a drying temperature of 90℃ for 20min drying time.

[0060] The bonding structure coating is achieved using a 250-mesh screen printing machine with a coating temperature of 75℃ and a coating speed of 8m / min.

[0061] (2) Replace the screen (with the same positioning mark) and prepare by screen printing. Continue to print conductive coating on the bonding structure coverage area of ​​substrate A. The conductive grid line width is 0.3 mm and the thickness before curing is 10 μm.

[0062] It is then placed in a drying oven and dried at a constant temperature of 120°C for 30 minutes to achieve simultaneous curing of the bonding structure and the patterned conductive layer, so that the two are tightly bonded together to obtain substrate B.

[0063] The patterned conductive layer printing uses a 300-mesh screen printing plate with a printing speed of 8m / min. The same plate positioning does not require recalibration, ensuring that the printing accuracy is precisely matched with the BC battery busbar.

[0064] (3) Using a continuous coating-curing integrated equipment, an insulating protective coating (thickness 35μm before curing) is applied to substrate B by roller coating. After constant temperature curing at 130℃ for 25min, an insulating protective layer is formed, and substrate C is obtained.

[0065] Insulation protective layer coating parameters: coating temperature 70℃, coating speed 8m / min, coating thickness is monitored in real time during the coating process to ensure uniform coating, no defects such as missed coating, bubbles, pinholes, etc. The coating is firmly bonded to the patterned conductive layer and PET substrate, and the coating adhesion reaches level 1 using the cross-cut adhesion test.

[0066] (4) Using an integrated laser device for “positioning and cutting”, trim the substrate C and make an opening in the insulating protective layer (size 5mm×10mm, deviation ≤0.1mm), while simultaneously trimming the edge of the back panel; finally, perform finished product inspection and packaging. Using automated online inspection equipment, simultaneously complete the inspection of insulation performance, conductivity, coating adhesion and appearance. After all indicators meet the standards, perform film packaging to obtain a dual-function back panel for back contact batteries with local conductivity and insulation.

[0067] The finished product testing indicators must meet the corresponding national standards, specifically: Insulation performance: Breakdown voltage 16kV / mm, no leakage current, in compliance with the relevant provisions of GB / T 31034-2024 "Insulating backsheet for crystalline silicon solar cell modules".

[0068] Conductivity: The conductivity resistance is 0.3Ω / m, the conductivity is uniform, there are no breaks or loose connections, and it complies with the relevant provisions of GB / T 31034-2024 "Insulating Backsheet for Crystalline Silicon Solar Cell Modules".

[0069] Coating adhesion: Tested using the cross-cut adhesion test, grade 1 (no delamination, no peeling), conforming to GB / T 9286-1998 "Cross-cut adhesion test for paints and varnishes" standard.

[0070] Appearance: No scratches, no bubbles, no damage, precise opening size, smooth edges, meeting the appearance requirements of GB / T 18911-2013 "Backsheets for Photovoltaic Modules".

[0071] Additional notes: The light transmittance and tensile strength of the PET substrate comply with GB / T 13542.2-2009 "Plastic Films for Electrical Purposes - Part 2: Polyester Films"; the UV aging resistance of the insulating protective layer complies with GB / T 16422.2-2014 "Plastics - Laboratory Light Source Exposure Test Methods - Part 2: Xenon Arc Lamps" standard.

[0072] Comparative Example 1 The only difference from Example 2 is that: The adhesion promoter in the conductive coating is replaced with 3-mercaptopropyltrimethoxysilane.

[0073] Comparative Example 2 The only difference from Example 2 is that: The leveling agent in the bonding coating was replaced with: EFKA FL 3777 fluorinated modified acrylate non-silicone leveling agent; the conductive coating consisted of 2.5 wt% bonding accelerator (KH-560), 71 wt% copper paste, and the balance bisphenol A epoxy resin (Dalian Qihua New Materials Co., Ltd., DYD-128). The copper paste was the same as in Example 1.

[0074] Comparative Example 3 The only difference from Example 2 is that: Insulating protective coating: composed of 5wt% abrasion resistant agent (nano silica, particle size 20nm) and the balance fluorocarbon resin (Changzhou Weston Coatings, WSD-1669).

[0075] The backplates prepared in Example 2 and Comparative Examples 1-3 were subjected to performance tests. The conductivity resistance was tested according to GB / T 31838.2-2020; the breakdown voltage was tested according to GB / T 1408.1-2016; the adhesion after damp heat aging was tested by placing the samples in a constant temperature and humidity test chamber at (85±2)℃ and (85±5)% relative humidity for 1000h, and the appearance was graded according to GB / T 9286-1998; the yellowing index Δb of UV aging (UV 720h) was tested according to GB / T 31034-2024; the sand shedding resistance was tested according to ASTM D968; and the alignment deviation was tested using an image measuring instrument.

[0076] The results are shown in Table 1.

[0077] Table 1

[0078] Comparative Example 1 replaced the type of adhesion promoter, Comparative Example 2 changed the type of leveling agent and the composition relationship of conductive coating, and Comparative Example 3 increased the content of abrasion resistant agent. As a result, the conductivity resistance of Comparative Examples 1-3 increased, the breakdown voltage decreased, the resistance to damp heat / UV aging decreased, the resistance to sand falling decreased, and the alignment deviation increased.

[0079] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A coating composition characterized in that, The adhesive coating, the conductive coating and the insulating protective coating are independently used; The adhesive coating comprises 0.3wt%-0.5wt% leveling agent, and the rest is modified polyurethane resin; The conductive coating comprises 1wt%-2wt% adhesion promoter, 65wt%-85wt% copper paste, and the rest is epoxy resin matrix; The insulating protective coating comprises 0.5wt%-1wt% wear-resistant agent, and the rest is fluorocarbon resin.

2. The coating composition according to claim 1, characterized in that, The leveling agent is polyether modified polydimethylsiloxane; and / or The adhesion promoter is silane coupling agent KH-560; and / or The wear-resistant agent is nano-silicon dioxide or nano-aluminum oxide.

3. The coating composition of claim 1, wherein The copper paste is at least one of copper paste added with antioxidant or silver-coated copper paste; the antioxidant is added in an amount of 0.2wt%-0.4wt% of the total mass of the copper paste, and the antioxidant is a benzotriazole compound; The benzotriazole compound comprises at least one of benzotriazole, 5-methylbenzotriazole and carboxybenzotriazole.

4. A locally conductive insulating dual function backsheet for back contact cells, characterized in that, From bottom to top, the insulating substrate layer, the adhesive structure, the patterned conductive layer and the insulating protective layer are sequentially arranged; The insulating substrate layer is a PET substrate; The adhesive structure is the adhesive coating of any one of claims 1-3 coated and cured on the insulating substrate layer, and the thickness before curing is 5μm-10μm; The patterned conductive layer is the conductive coating of any one of claims 1-3 printed and cured on the adhesive structure, and the thickness before curing is 5μm-15μm; The insulating protective layer is the insulating protective coating of any one of claims 1-3 coated and cured on the patterned conductive layer, and the thickness before curing is 20μm-50μm.

5. The locally conductive, insulating, dual function backsheet of claim 4, wherein, The PET substrate is a PET film with a thickness of 275μm-300μm, a light transmittance of ≥85% and a tensile strength of ≥150MPa; the conductive resistance of the patterned conductive layer is ≤0.5Ω / m; and the light transmittance of the insulating protective layer is ≥90%.

6. The method of making a locally conductive insulating bifunctional backsheet according to any of claims 4 or 5, characterized in that, The method comprises the following steps: (1) After the PET substrate is pretreated by alkali washing, water washing and drying, the adhesive coating of any one of claims 1-3 is coated on the substrate, the coating thickness is 5μm-10μm, and the curing is performed at 80℃-90℃ for 8min-12min to obtain a substrate A; (2) The conductive coating of any one of claims 1-3 is coated on the substrate A, the coating thickness is 5μm-15μm, and the curing is performed at 110℃-130℃ for 25min-35min to obtain a substrate B; (3) The insulating protective coating of any one of claims 1-3 is coated on the substrate B, the coating thickness is 20μm-50μm, and the curing is performed at 120℃-140℃ for 20min-30min, and then the product is obtained by cutting and trimming.

7. The preparation method according to claim 6, characterized in that, The alkali concentration of the alkali washing is 5wt%-10wt%, the alkali washing time is 10min-15min, and the alkali washing temperature is 40℃-50℃; the alkali is sodium hydroxide; the water washing is performed at 20℃-30℃ for 3-4 times, and each time is 5min-8min; and the drying temperature is 80℃-100℃, and the drying time is 15min-25min.

8. The preparation method according to claim 6, characterized in that, The adhesive coating is applied by screen printing, with a screen printing mesh count of 200-250 mesh, a coating temperature of 70℃-80℃, and a coating speed of 5m / min-10m / min. The conductive coating is applied using screen printing, with a screen printing stencil of 250-350 mesh and a printing speed of 5-10 m / min. The insulating protective coating is applied by roller coating, spraying, or screen printing. The coating temperature is 60℃-80℃, and the coating speed is 5m / min-12m / min.

9. The use of the coating composition according to any one of claims 1-3 in the preparation of a back contact battery.

10. A back contact cell characterized in that, Includes the partially conductive and insulating dual-function backplate as described in any one of claims 4 or 5, or the partially conductive and insulating dual-function backplate prepared by the preparation method described in any one of claims 6-8.

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