A top protection film for P-OLED panel manufacturing process and a preparation method thereof

Abstract

The application discloses a top protective film for a P-OLED panel manufacturing process, which is a three-layer composite structure and comprises a substrate layer, an adhesive layer arranged on one surface of the substrate layer, and a liner layer arranged on the side of the adhesive layer away from the substrate layer, wherein the adhesive layer is a polyurethane adhesive layer containing polysiloxane and an antistatic agent. By adopting the polyurethane adhesive containing polysiloxane and an antistatic agent and optimizing the structure and thickness of each layer, the top protective film can simultaneously achieve excellent wettability on uneven packaging surfaces during high-speed attachment, high-temperature resistance and stable fixing performance during laser cutting, and easy and clean glue-free peeling after the manufacturing process is completed, and reliable antistatic protection is provided throughout the process, so that the multiple process contradictions of protection, fixing and peeling in flexible panel manufacturing are comprehensively solved.

Description

Technical Field

[0001] This invention relates to the field of flexible display device manufacturing technology, and in particular to a top protective film for P-OLED panel manufacturing process and its preparation method. Background Technology

[0002] In the manufacturing process of flexible organic light-emitting diodes (P-OLEDs), the light-emitting elements are fabricated on a flexible substrate such as polyimide, and an encapsulation material is coated on its surface for sealing and protection. However, during subsequent process flows, processing, and transportation, the encapsulation coating is highly susceptible to exposure to foreign objects and may be subjected to external mechanical impacts, leading to damage to the underlying precision light-emitting elements. Such damage will directly manifest on the screen of the final display product, causing irreparable defects and severely affecting product yield and reliability.

[0003] To address this issue, the industry practice is to apply a temporary protective film to the panel surface. However, the flexible nature of P-OLEDs and the demanding manufacturing process place far higher comprehensive performance requirements on the protective film than usual. High adhesion and process compatibility: In high-speed automated bonding processes, the protective film must have excellent wettability to ensure that it can be quickly and completely bonded to the surface of potentially uneven packaging materials without leaving gaps and preventing foreign matter from entering; at the same time, the film itself must have extremely low curl to adapt to the high-speed and stable operation of automated equipment.

[0004] Stable processing and fixing capabilities: In the subsequent laser cutting process, the protective film must be able to firmly fix the flexible panel to prevent it from shifting during the cutting process and ensure cutting accuracy; at the same time, it must be able to withstand the instantaneous high temperature generated by the laser and have sufficient heat resistance to avoid the adhesive layer melting, failing or leaving residue.

[0005] Clean peelability: When peeling off the protective film in the final process, it is required to have appropriate and relatively low adhesion to ensure that it can be easily and cleanly peeled off from the surface of the encapsulation material without leaving any adhesive residue, damaging the panel surface, or causing the encapsulation material to scatter.

[0006] Comprehensive electrostatic protection: Throughout the entire process, the protective film needs to have stable antistatic properties to prevent static electricity from attracting dust or discharging and damaging sensitive OLED components during application and removal.

[0007] Existing common protective films (such as those based on general-purpose acrylic adhesives) cannot simultaneously meet all the above technical requirements. For example, while high adhesion facilitates fixation, it leads to difficult peeling and easy residue; lack of antistatic properties poses a risk of electrostatic damage; and insufficient heat resistance prevents laser cutting.

[0008] Therefore, there is an urgent need to develop a new type of protective film specifically for P-OLED manufacturing processes. This requires systematic innovation in dimensions such as the selection and thickness ratio of substrates and pads, and the design of the chemical composition of adhesive layers, in order to comprehensively achieve multiple goals such as excellent wettability, low curling, precise adhesion and peeling force, high heat resistance, and long-lasting antistatic properties, thereby ensuring the efficient and high-yield manufacturing of P-OLED flexible panels. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a top protective film and its preparation method for P-OLED panel manufacturing processes. This invention utilizes a polyurethane adhesive containing polysiloxane and an antistatic agent, and optimizes the structure and thickness of each layer. This achieves excellent wettability on uneven encapsulation surfaces during high-speed attachment, high-temperature resistance and stable fixation during laser cutting, and easy, clean, residue-free peeling after the process, while providing reliable antistatic protection throughout the entire process. Thus, it comprehensively resolves the multiple process contradictions of protection, fixation, and peeling in flexible panel manufacturing.

[0010] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: This invention provides a top protective film for P-OLED panel manufacturing processes, which has a three-layer composite structure, comprising: Substrate layer; An adhesive layer is disposed on one surface of the substrate layer, wherein the adhesive layer is a polyurethane adhesive layer comprising polysiloxane and an antistatic agent; A padding layer is disposed on the side of the adhesive layer away from the substrate layer.

[0011] Preferably, both the substrate layer and the liner layer are polyethylene terephthalate films.

[0012] Furthermore, the polyurethane adhesive constituting the adhesive layer is formed by reacting a polyol component with an isocyanate component, and its number average molecular weight is between 10,000 and 1,000,000.

[0013] Furthermore, in the adhesive layer, the polysiloxane content is 0.1% to 10% by weight.

[0014] Furthermore, at least one surface of the substrate layer and / or the padding layer is treated with antistatic agents; and / or, the adhesive layer contains 1% to 10% by weight of an antistatic agent.

[0015] Furthermore, the thickness of the substrate layer is 50~95μm, the thickness of the adhesive layer is 50~95μm, and the thickness of the padding layer is 50~95μm.

[0016] Furthermore, the adhesive layer has a 180° peel adhesion of 1.0~3.0 gf / in to the surface of the P-OLED panel encapsulation material.

[0017] Furthermore, the 180° peel force of the liner layer to the adhesive layer it is laminated with is 1.0~3.0 gf / in.

[0018] Furthermore, the surface resistivity of the substrate layer, the adhesive layer, and the gasket layer are all in the range of 10^5.0~10^9.0 Ω / sq.

[0019] Another aspect of the present invention provides a method for preparing the top protective film, comprising the following steps: Provide a substrate layer; On one surface of the substrate layer, a polyurethane adhesive composition comprising an antistatic agent and a polysiloxane is coated, and after drying, an adhesive layer is formed. A liner layer is provided, and the liner layer is bonded to the adhesive layer with its release surface.

[0020] The beneficial effects of this invention are as follows: This invention employs an adhesive layer with a specific composition of "a polyurethane adhesive layer containing polysiloxane and an antistatic agent," thereby synergistically and comprehensively resolving the core technological challenges faced by the protective film in P-OLED manufacturing. Specifically, this is manifested in: This process achieves a balance between excellent initial adhesion (wetting properties) and clean final peeling: the polyurethane adhesive itself has good wetting properties, and with the addition of polysiloxane, it can quickly and fully spread and adhere tightly to the uneven encapsulation material surface of the P-OLED panel, effectively preventing the intrusion of bubbles and foreign objects. Simultaneously, the adhesive layer's formulation has been optimized, allowing the adhesive layer to be easily and completely peeled off from the encapsulation surface after the process, achieving residue-free and non-damaging panel removal.

[0021] Balancing stable fixation during processing with high-temperature resistance during laser cutting: This adhesive layer provides moderate and stable bonding force, sufficient to firmly secure the flexible panel during subsequent processes such as laser cutting, preventing its displacement. More importantly, the synergistic effect of the polyurethane system and polysiloxane endows the adhesive layer with excellent heat resistance, enabling it to withstand the instantaneous high temperatures generated during laser cutting without melting or decomposing, thus ensuring cutting quality and process reliability.

[0022] It provides built-in, durable antistatic protection: by directly incorporating antistatic agents into the functional adhesive layer, the core functional layer of the protective film itself has antistatic capabilities, which can effectively dissipate the static charge generated during film application, processing and removal, and prevent electrostatic adsorption of dust or discharge from damaging sensitive OLED components. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the top protective film for the P-OLED panel manufacturing process of the present invention.

[0024] In the diagram, 1: substrate layer; 2: adhesive layer; 3: liner layer. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a top protective film for P-OLED panel manufacturing and its preparation method. The protective film has a three-layer composite structure, designed to address the multiple conflicting requirements of protective films in flexible display panel manufacturing, including high adhesion, strong adhesion, clean peeling, and comprehensive anti-static properties.

[0027] like Figure 1 As shown, the protective film includes a substrate layer 1, an adhesive layer 2, and a gasket layer 3. The adhesive layer 2 is a polyurethane adhesive layer containing a specific ratio of polysiloxane and an antistatic agent. The formulation system of this adhesive layer 2 works synergistically to achieve excellent wetting and adhesion to uneven encapsulation surfaces, high-temperature resistance and firm fixation during laser cutting, and easy, residue-free peeling after the process, while providing built-in, durable antistatic protection.

[0028] The substrate layer 1 and the padding layer 3 are preferably polyethylene terephthalate (PET) films to provide good mechanical strength, transparency, and dimensional stability. At least one surface of the substrate layer and / or the padding layer is treated with an antistatic agent.

[0029] The thickness of substrate layer 1 is 50-95 μm, the thickness of adhesive layer 2 is 50-95 μm, and the thickness of padding layer 3 is 50-95 μm. In an exemplary embodiment, the thickness of each layer can be designed as follows: substrate layer 1 is 75 μm, adhesive layer 2 is 75 μm, and padding layer 3 is 75 μm. This thickness design ensures sufficient stiffness for automated operation while maintaining flexibility suitable for flexible panel processes.

[0030] The basic composition and synthesis of polyurethane adhesives include: The polyurethane adhesive is prepared by polymerization of a polyol component and an isocyanate component, and its number average molecular weight (Mn) is preferably controlled between 10,000 and 1,000,000.

[0031] (1) Selection principles and specific examples of polyol components The chemical structure of the polyol component has a decisive influence on the wettability, heat resistance, flexibility, and peel performance of the final adhesive. To achieve the overall performance of this invention, the polyol preferably does not contain ethylene oxide (EO) groups, and in particular, polyether polyols with more than one EO group are excluded. Suitable polyols for this invention include, but are not limited to: polyester polyols, polyether polyols without EO groups, polycaprolactone polyols, polycarbonate polyols, polyacrylic acid polyols, and castor oil-based polyols. Among these, from the perspective of overall performance balance, polyester polyols, polycaprolactone polyols, and polycarbonate polyols perform better, with polyester polyols and polyether polyols without EO groups being the most preferred.

[0032] Polyester polyols: These are produced by esterification polycondensation reactions of one or more polycarboxylic acids (or anhydrides) with one or more polyols. Exemplary carboxylic acids include, but are not limited to, succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, phthalic anhydride, isophthalic acid, trimethyl adipic acid, etc. Exemplary polyols include, but are not limited to, bifunctional polyols (diols) with two hydroxyl groups, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, diethylene glycol, dipropylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, etc.; and polyfunctional polyols with three or more hydroxyl groups, such as glycerol, trimethylolpropane, pentaerythritol, etc.

[0033] Polyether polyols without EO groups: These are polyether polyols obtained by ring-opening polymerization of active hydrogen compounds with cyclic ethers other than ethylene oxide (EO), such as propylene oxide (PO), butane oxide (BO), tetrahydrofuran, etc. Active hydrogen compounds are compounds with hydroxyl groups, amines, or compounds with both hydroxyl and NH groups. Compounds with hydroxyl groups include: water, and diols (also known as glycols) (specifically, propylene glycol, 1,4-butanediol, neopentyl glycol, and butylethylenepentanediol, etc.), which are difunctional polyols with two hydroxyl groups; and trifunctional polyols with three or more hydroxyl groups, such as glycerol, trimethylpropane, and glycerol. Examples of amines include ethylenediamine, isopentanediamine, xylenediamine, and other polyamines. Examples of compounds with both hydroxyl and NH groups include N-aminoethanolamine.

[0034] For polyether polyols that do not have an EO group, oxidized alkyne adducts containing active hydrogen compounds are preferred; specific examples include trifunctional or higher polyether polyols such as polypropylene glycol (PPG), polytetrahydrofuran glycol (PTMG), and adducts of glycerol and propylene oxide.

[0035] Polycaprolactone polyols are polyols with a polyester structure, which are obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

[0036] Polycarbonate polyols: Polyols with a carbonate structure can be obtained through polycondensation of polyols and phosphorus, polycondensation of polyols and dichloroformates of deoxygenated compounds, polycondensation of polyols and diesters, and polycondensation of polyols and dicarbonates of deoxygenated compounds.

[0037] Regardless of the type of polyol chosen, it is preferable that it does not contain EO groups. Specifically, preferred types include: polyester polyols without EO groups, polyether polyols without EO groups, polycaprolactone polyols without EO groups, and polycarbonate polyols without EO groups. The number-average molecular weight (Mn) of the polyol is further preferably between 100,000 and 500,000 to achieve a better balance between adhesion properties and cohesive strength.

[0038] (2) Examples of isocyanate components Examples of polyisocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

[0039] Aromatic polyisocyanates: 1,3-phenyl diisocyanate, 4,4'-diphenyl diisocyanate (DPMDI), 1,4-phenyl diisocyanate, 1,4'-diphenylmethyl diisocyanate, 2,4-tolyl diisocyanate (2,4-TDI), 2,6-tolyl diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (MDI), 3-tetramethylsilyl diisocyanate, etc.

[0040] Aliphatic polyisocyanates: trimethyl diisocyanate, tetramethyl diisocyanate, hexamethylene diisocyanate (HDI), pentamethyl diisocyanate, 1,2-propyl diisocyanate, 2,3-butyl diisocyanate, 1,3-butyl diisocyanate, dodecyl diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate (TMHDI), etc.

[0041] Alicyclic polyisocyanates: 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate (CHDI), methyl-2,4-cyclohexane diisocyanate (HTDI), methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate) (H12MDI), etc.

[0042] Furthermore, the polyisocyanate component may also be a modified form of the aforementioned polyisocyanate, such as an adduct (TMP-adduct) formed with trimethylolpropane, a biuret, or a trimer (such as an isocyanurate ring). Considering resistance to yellowing and overall performance, aliphatic and alicyclic polyisocyanates are preferred, with aliphatic polyisocyanates being more preferred.

[0043] (3) Synthesis ratio In the synthesis of polyurethane, it is preferable to control the molar ratio (NCO / OH ratio) of hydroxyl groups (OH) in the polyol component to isocyanate groups (NCO) in the isocyanate component to be between 1.0 and 1.5. A wide variety of adhesive raw materials possess the above-mentioned characteristics. To obtain the comprehensive physical properties conforming to the characteristics of this invention, the selected polyols and isocyanates must be synthesized into resins with specific molecular weights and viscosities, and their properties can only be fully realized through a controlled polymerization process.

[0044] Specific formulation examples of polyurethane adhesive compositions: To precisely control the rheological properties, curing speed, cohesive strength, and heat resistance of the final adhesive layer, the composition can be formulated from a variety of polyurethane resins of different specifications. The following are four exemplary resins: The first polyurethane resin is synthesized based on polyester polyol and isocyanate, with a solid content of 60%~68%, a viscosity of 3000~5000cps, and solvents of toluene (45~55%), methyl ethyl ketone (MEK) (35~45%) and acetylacetone (5~15%), and a molecular weight of 300,000~500,000.

[0045] The second polyurethane resin is synthesized based on polyester polyol and isocyanate, with a solid content of 51%~59%, a viscosity of 200~2200cps, and solvents of toluene (55~65%) and ethyl acetate (EA) (35~45%), and a molecular weight of 200,000~400,000.

[0046] The third type of polyurethane resin is synthesized based on polyester polyol and isocyanate, with a solid content of 51%~59%, a viscosity of 1500~3500cps, and solvents of toluene (75~85%) and ethyl acetate (EA) (15~25%), and a molecular weight of 100,000~180,000.

[0047] The fourth type of polyurethane resin is synthesized based on polyester polyol and isocyanate, with a solid content of 16%~24%, a viscosity of 1000~3000 cps, and solvents of diethoxymethane (DEF) (25~35%) and methyl ethyl ketone (MEK) (65~75%), and a molecular weight of 130,000~150,000.

[0048] By adjusting the mixing ratio of the above resins in the adhesive composition, adhesives that meet the requirements of different process windows can be obtained. For example, the first polyurethane resin can be adjusted within the range of 16%-45%, the second polyurethane resin within the range of 16%-45%, the third polyurethane resin within the range of 0%-14%, and the fourth polyurethane resin within the range of 0%-14%. Selection and Function of Functional Additives: Polysiloxane: 0.1% to 10% by weight in the adhesive composition. The polysiloxane may contain compounds of the general formula R-(CH2)n-SiX. p (OY) 3-p The silane compound shown is an integer from 0 to 12; R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, or a substituent derived from the monovalent hydrocarbon group, or a group containing silicon and oxygen atoms, or a halogen atom. X is a hydrogen atom (H), or a monovalent hydrocarbon group having 1 to 4 carbon atoms, or a substituent derived from the monovalent hydrocarbon group, or a halogen atom. p is 0, 1, or 2. Y is an alkyl group having 1 to 12 carbon atoms, an acyl group having 1 to 12 carbon atoms, an alkenyl group (including vinyl groups) having 1 to 12 carbon atoms, a cycloalkyl group having 1 to 12 carbon atoms, a cycloalkenyl group having 1 to 12 carbon atoms, or an aryl group (such as phenyl) having 1 to 12 carbon atoms.

[0049] Polysiloxanes can significantly improve the wetting and spreading properties of adhesives on low surface energy substrates and reduce interfacial energy, thereby optimizing the cleanliness of the final peel and achieving residue-free results while ensuring sufficient adhesion during processing. Polysiloxane solutions can be prepared by mixing reactants and degassing. The solvent used in the preparation of the polysiloxane can be selected from one or more of the following substances: water, methanol, ethanol, cyclohexanone, methylcyclohexanol, acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), diethyl ketone, benzene, toluene, xylene, propylene glycol monomethyl ether acetate (PGMEA), isopropanol (IPA), and propylene glycol monomethyl ether (PGME).

[0050] Antistatic agent: 1% to 10% by weight in the adhesive composition. This additive effectively imparts long-lasting antistatic properties to the protective film.

[0051] Curing system: Add an appropriate amount of curing agent, such as organic peroxides, polyamines, or other thermosetting agents, or photoinitiators such as benzophenone, thioxanone, benzoyl peroxide, and alkyl 2-hydroxypropionic acid esters, to promote the final curing of the adhesive layer and improve its cohesive strength, heat resistance, and durability. The amount of curing agent added is, for example, 2.4% to 2.7% of the total weight.

[0052] The method for preparing the top protective film of the present invention includes the following steps: A substrate layer 1 is provided; at least one surface of the substrate layer may be selectively treated with an antistatic agent. On one surface of the substrate layer 1, a polyurethane adhesive composition comprising an antistatic agent and a polysiloxane is coated and dried to form an adhesive layer 2; wherein the drying is carried out in a hot chamber comprising at least six temperature zones with temperature gradients of 50~70℃, 70~90℃, 100~120℃, 110~130℃, 110~130℃, and 80~100℃; the working speed during the drying process is 6~10m / min.

[0053] A liner layer 3 is provided, and the liner layer 3 is laminated onto the adhesive layer 2 with its release surface. At least one surface of the liner layer may optionally be treated with an antistatic agent.

[0054] The present invention will now be described in detail through specific embodiments and comparative examples. In this embodiment, all polyurethane adhesives are applied to a PET substrate using a slot coater and dried and cured according to the six-zone temperature gradient drying conditions described above. Subsequently, a PET liner film is laminated to obtain a protective film having a substrate layer 1, an adhesive layer 2, and a liner layer 3.

[0055] Example 1 The adhesive composition, based on 100% of its total weight, comprises the following components: 16.5% first polyurethane resin, 41.0% second polyurethane resin, 12.0% third polyurethane resin, and 12.0% fourth polyurethane resin. Polysiloxane 8.0%, antistatic agent 8.0%, and curing agent 2.5%.

[0056] Preparation method: First, the first to fourth polyurethane resins were mixed at 300 rpm for 1 hour. Then, polysiloxane, antistatic agent, and curing agent were added, and the mixture was mixed a second time at 500 rpm for 1 hour to obtain a uniform adhesive composition. This composition was coated onto a PET substrate using a slot coater, dried in six zones, and then laminated with a PET liner film. The temperature gradients during the adhesive drying process were 50~70℃, 70~90℃, 100~120℃, 110~130℃, 110~130℃, and 80~100℃, respectively; the drying speed was 6~10 m / min.

[0057] Example 2 The adhesive composition comprises, by weight of 100%, the following components: 17.7% of a first polyurethane resin, 44.2% of a second polyurethane resin, 13.3% of a third polyurethane resin, 13.3% of a fourth polyurethane resin, 0.1% of a polysiloxane, 8.8% of an antistatic agent, and 2.6% of a curing agent.

[0058] Preparation method: First, the first to fourth polyurethane resins were mixed at 300 rpm for 1 hour. Then, polysiloxane, antistatic agent, and curing agent were added, and the mixture was mixed a second time at 500 rpm for 1 hour to obtain a uniform adhesive composition. The composition was coated onto a PET substrate using a slot coater, dried in six zones under the same conditions as in Example 1, and then laminated with a PET liner film.

[0059] Example 3 The adhesive composition comprises, by weight of 100%, the following components: 44.2% of a first polyurethane resin, 44.2% of a second polyurethane resin, 0.1% of a polysiloxane, 8.8% of an antistatic agent, and 2.7% of a curing agent.

[0060] Preparation method: First, the first and second polyurethane resins were mixed at 300 rpm for 1 hour. Then, polysiloxane, antistatic agent, and curing agent were added, and the mixture was mixed a second time at 500 rpm for 1 hour to obtain a uniform adhesive composition. The composition was coated onto a PET substrate using a slot coater, dried in six zones under the same conditions as in Example 1, and then laminated with a PET liner film.

[0061] Example 4 The adhesive composition comprises, by weight of 100%, the following components: 40.7% of a first polyurethane resin, 16.3% of a second polyurethane resin, 12.2% of a third polyurethane resin, 12.2% of a fourth polyurethane resin, 8.1% of a polysiloxane, 8.1% of an antistatic agent, and 2.4% of a curing agent.

[0062] Preparation method: First, the first to fourth polyurethane resins were mixed at 300 rpm for 1 hour. Then, polysiloxane, antistatic agent, and curing agent were added, and the mixture was mixed a second time at 500 rpm for 1 hour to obtain a uniform adhesive composition. The composition was coated onto a PET substrate using a slot coater, dried in six zones under the same conditions as in Example 1, and then laminated with a PET liner film.

[0063] Example 5 The difference from Example 1 is that the temperature gradients during the drying process of the six zones of the adhesive are 70~90℃, 100~120℃, 100~120℃, 110~130℃, 110~130℃, and 80~100℃, respectively.

[0064] Comparative Example In contrast, a common polyurethane adhesive with a solids content of over 50%, a molecular weight of over 40,000, and a viscosity of over 4,000 CPS was used. This adhesive is well-miscible with toluene, methyl ethyl ketone (MEK), and ethyl acetate (EA). It was applied to a PET substrate using a slotted die coater and dried under the same six-zone drying conditions as in this invention, followed by lamination with a PET liner film.

[0065] Physical property testing methods The performance of the protective film samples obtained in the examples and comparative examples was tested and evaluated as follows: (1) Surface resistance The surface resistance of each functional layer (substrate layer, adhesive layer, and backing layer) of the protective film was measured using a SIMCO ST-3 surface resistance meter according to conventional methods. A lower surface resistance value indicates better antistatic properties of the material.

[0066] (2) Optical performance (transmittance and haze) Using a transmittance / haze meter from CAS (or of equivalent precision), measure the visible light transmittance (%) and haze (%) of the protective film sample according to ASTM D1003 or equivalent standards. Read the values ​​directly.

[0067] (3) Wettability The adhesive side of the protective film sample (after removing the backing layer) is adhered to a clean standard test plate (such as frosted glass or a SUS plate with a specified roughness) with a specified surface. The time required from contact to complete adhesive spread, with no visible bubbles or unwetted areas, is visually timed. The shorter the time, the better the wetting properties.

[0068] (4) Heat resistance The protective film sample (containing the complete substrate layer, adhesive layer, and backing layer) was subjected to simulated cutting under a laser cutting head with fixed power. After cutting, the appearance changes of the adhesive layer in the cut area and heat-affected zone were visually observed, mainly assessing whether there were phenomena such as melting, flowing, discoloration, carbonization, or obvious deformation. Based on the degree to which it maintained its original state, the heat resistance appearance was rated as "excellent" (no adverse changes), "average" (slight changes but not affecting function), or "poor" (obvious flowing, melting, or other failure phenomena).

[0069] (5) Adhesion force According to ASTM D3330 test method, the protective film sample was cut to a specified width (e.g., 1 inch). After removing the backing layer, the adhesive side was adhered to a clean standard stainless steel plate (SUS 304) or a standard test plate simulating the surface of P-OLED encapsulation material at a constant speed. After standing for 30 minutes in a standard environment of 23±2℃ and 50±5%RH, a 180° peel test was performed at a peel speed of 300 mm / min. The stable average peel force was recorded in grams per inch (gf / in).

[0070] (6) Release force According to the ASTM D3330 test method, the protective film sample is cut to a specified width (e.g., 1 inch) and peeled directly at a peeling speed of 300 mm / min at a 180° angle. The force required for the padding layer to peel off from the surface of its composite adhesive layer is measured, and the stable average peel force is recorded in grams per inch (gf / in).

[0071] (7) Curled Cut the protective film sample to a specified size (e.g., 100mm × 100mm), and place it flat on a horizontal platform under standard conditions (23±2℃, 50±5%RH) to fully release stress. Measure the warp height (in mm) at all four sides or specific locations of the sample. Take the maximum or average value as the curl value of the sample. The smaller the value, the better the flatness of the film and the better its low-curl performance.

[0072] (8) Coating appearance Under standard lighting conditions, observe the macroscopic and microscopic appearance of the protective film samples (especially the adhesive coating and composite interface) with the naked eye or with the aid of a magnifying glass. Evaluate its uniformity and the presence of defects such as bubbles, foreign matter, streaks, fisheyes, and orange peel. After comprehensive judgment, the coating appearance is rated as "Excellent" (uniform, no visible defects), "Medium" (minor defects but not affecting basic use), or "Poor" (obvious defects).

[0073] The performance test results are shown in Table 1.

[0074] Table 1 Based on a comprehensive analysis of performance test data, the various embodiments provided by this invention, through differentiated formulation combinations, all achieve a balance to varying degrees regarding the multiple requirements in P-OLED panel manufacturing. Among them, Embodiment 1 demonstrates the optimal overall performance: its surface resistivity is as low as... It possesses excellent antistatic properties; wetting time is within 3 seconds, resulting in rapid adhesion; outstanding heat resistance; and an optimal balance between adhesion and release force, ensuring both firm fixation during the process and clean peeling afterward. Furthermore, it exhibits minimal curl (0.9 mm) and the highest transparency (92%). Example 3, which did not fully utilize the four resin systems, while slightly inferior in some aspects, still provided a feasible solution to meet specific requirements (such as the need for higher surface resistance). Example 4, by adjusting the component ratios, verified the significant impact of the second polyurethane content on adhesion (point force). In contrast, the comparative examples without the specific formulation system of this invention showed significant deficiencies in wettability, heat resistance, and adhesion balance. These results fully demonstrate that this invention, through precise material design and process control, successfully provides a customizable solution that effectively meets the complex demands for high-performance, multi-functional protective films in flexible display panel manufacturing.

[0075] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0076] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A top protective film for P-OLED panel manufacturing process, characterized in that, It is a three-layer composite structure, including: Substrate layer; An adhesive layer is disposed on one surface of the substrate layer, wherein the adhesive layer is a polyurethane adhesive layer comprising polysiloxane and an antistatic agent; A padding layer is disposed on the side of the adhesive layer away from the substrate layer.

2. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, Both the substrate layer and the liner layer are polyethylene terephthalate films.

3. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, The polyurethane adhesive constituting the adhesive layer is formed by reacting a polyol component with an isocyanate component, and its number average molecular weight is between 10,000 and 1,000,000.

4. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, In the adhesive layer, the polysiloxane content is 0.1% to 10% by weight.

5. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, At least one surface of the substrate layer and / or the padding layer is treated with antistatic agents; and / or, the adhesive layer contains 1% to 10% by weight of an antistatic agent.

6. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, The thickness of the substrate layer is 50~95μm, the thickness of the adhesive layer is 50~95μm, and the thickness of the padding layer is 50~95μm.

7. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, The adhesive layer has a 180° peel adhesion of 1.0~3.0 gf / in to the surface of the P-OLED panel encapsulation material.

8. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, The liner layer has a 180° peel force of 1.0~3.0 gf / in on the adhesive layer it is bonded to.

9. The top protective film for P-OLED panel manufacturing process according to claim 1, characterized in that, The surface resistivity of the substrate layer, the adhesive layer, and the padding layer are all in the range of 10^5.0~10^9.0 Ω / sq.

10. A method for preparing a top protective film as described in any one of claims 1-9, characterized in that, Includes the following steps: Provide a substrate layer; On one surface of the substrate layer, a polyurethane adhesive composition comprising an antistatic agent and a polysiloxane is coated, and after drying, an adhesive layer is formed. A liner layer is provided, and the liner layer is bonded to the adhesive layer with its release surface.

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