Protective film and method for manufacturing same

Abstract

The invention provides a protective film and a manufacturing method thereof.The protective film adopts a flexible glass substrate with the thickness smaller than or equal to 0.5 mm. The manufacturing method comprises the following steps that etching and thinning are conducted, specifically, the glass substrate is subjected to chemical etching and thinning through etching liquid, and a protective film blank with the target thickness is obtained; screen printing of protective ink: respectively coating the protective ink on two opposite surfaces of the protective film blank; an edge treatment step: treating the protective film blank coated with the protective ink in an acidic passivation solution so as to remove microcracks on the edge of the protective film blank; an ink removing step: removing the protective ink on the protective film blank by using an ink removing agent; and a first-time polishing step: putting the original blank of the protective film subjected to ink removal into a first polishing solution for polishing treatment. According to the protective film and the manufacturing method thereof, the technological process is reasonable in design, the production yield of the protective film is effectively increased, the strength consistency of the protective film is improved, and edge microcracks and surface defects are improved.

Description

Technical Field

[0001] This application relates to the field of screen protector technology, and in particular to a screen protector and its manufacturing method. Background Technology

[0002] Traditional glass is thick, brittle, and inflexible, making it unsuitable for the needs of flexible electronic devices such as foldable screens. Ultra-thin flexible glass (UTG) is a glass material with flexibility and bendability, with a thickness of 500 micrometers or less. Unlike the traditional rigid glass used in protective films, it can be bent arbitrarily under external force without heat treatment. This material is manufactured using a special process and possesses characteristics such as ultra-thinness, wear resistance, high temperature resistance, corrosion resistance, high strength, high light transmittance, bendability, and good resilience, making it suitable for use in flexible electronic devices such as foldable screens.

[0003] In the process of developing this application, the inventors discovered that the prior art has at least the following problems: the existing UTG protective film manufacturing process is not perfect, resulting in the produced UTG protective film having problems such as poor strength consistency and easy breakage, which affects the reliability, flexibility and optical performance of the final product. Summary of the Invention

[0004] Based on this, this application provides a protective film and a method for manufacturing the same, to improve at least one of the problems existing in the prior art, such as poor process design, poor strength consistency, and easy breakage.

[0005] To achieve the above objectives, the technical solution of this application embodiment is implemented as follows: On one hand, embodiments of this application provide a method for manufacturing a protective film, wherein the protective film uses a flexible glass substrate with a thickness of 0.5 mm or less, and the manufacturing method includes the following steps: Etching and thinning step: The glass substrate is chemically etched and thinned using an etching solution to obtain a protective film blank of the target thickness; Screen printing protective ink step: Apply protective ink to both opposite surfaces of the protective film blank; Edge treatment step: The protective film blank coated with protective ink is placed in an acidic passivation solution for treatment to remove micro-cracks at the edges of the protective film blank; Ink removal step: Use an ink remover to remove the protective ink from the original protective film blank; First polishing step: The original protective film blank after ink removal is placed in the first polishing liquid for polishing treatment.

[0006] In one embodiment, the etching and thinning step is preceded by a substrate bonding step: the entire glass substrate is bonded to a rigid substrate using optical adhesive.

[0007] In one embodiment, a separation step is included before the screen printing protective ink step: peeling off the protective film blank and the liner.

[0008] In one embodiment, the ambient temperature range of the separation step is 20°C-25°C; the humidity range is 40%-60%; the separation speed is 10-30mm / s; and the peeling angle is 90°-120°.

[0009] In one embodiment, a chemical strengthening step is further included after the first polishing step: the protective film blank after the first polishing treatment is placed in molten alkali salt for ion exchange.

[0010] In one embodiment, a second polishing step is included after the chemical strengthening step: the strengthened protective film blank is placed in a second polishing liquid for polishing treatment, the pH value of the second polishing liquid is greater than the pH value of the first polishing liquid, and the first polishing liquid and the second polishing liquid are acidic polishing liquids.

[0011] In one embodiment, in the second polishing step, the polishing temperature range is 20°C-25°C; the polishing time is 30 seconds-90 seconds; and the polishing depth is no more than 2 micrometers.

[0012] In one embodiment, during the first polishing step, while polishing the protective film blank with the first polishing liquid, vibration assistance is provided by megasonic waves, the frequency range of which is 0.8-1.2MHz; the polishing time is 60-180 seconds; and the polishing depth is 2-3 micrometers.

[0013] In one embodiment, the acidic passivation solution in the edge treatment step is a mixed aqueous solution comprising hydrofluoric acid, nitric acid and a buffer, the treatment temperature is 25°C-35°C, and the treatment time is 30-90 seconds.

[0014] In one embodiment, a stacking step is included before the edge processing step: multiple protective film blanks are stacked and placed in a mounting fixture, wherein a buffer material is provided between two adjacent protective film blanks.

[0015] On the other hand, embodiments of this application provide a protective film manufactured using the manufacturing method described above.

[0016] This application has at least the following beneficial effects: The protective film and its manufacturing method provided in this application blunt the edges of the protective film blank through an edge treatment step, eliminating micro-cracks generated at the edges, improving edge strength and overall strength consistency, and also increasing the production yield of the protective film. The first polishing step can improve the smoothness of the protective film surface, which is conducive to releasing micro-stress, improving light transmittance, and further improving the overall strength consistency of the protective film. The manufacturing method provided in this application has a reasonable process flow, effectively reducing the generation of surface defects in the protective film, and improving the bending resistance and service life of the protective film. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart illustrating the manufacturing method of the protective film according to an embodiment of this application. Detailed Implementation

[0018] The technical solution of this application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the ways in which this application may be implemented. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] In the description of this application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] Please see Figure 1The protective film manufacturing method of the application embodiment uses a flexible glass substrate with a thickness of less than or equal to 0.5 mm, and the manufacturing method includes the following steps: Etching and thinning step: The glass substrate is chemically etched and thinned using an etching solution to obtain a protective film blank of the target thickness.

[0023] Specifically, for example, a hydrofluoric acid-based etching solution can be used for chemical etching to thin the glass substrate from an initial value (e.g., 0.1 mm) to a target thickness (e.g., 0.03 mm). This target thickness can be slightly thicker than the final design thickness of the protective film. For instance, if the final design thickness of the protective film (i.e., the final product thickness without considering manufacturing tolerances) is 'a', the target thickness can be designed as 'a+0.5 μm' to offset the thickness consumed in subsequent polishing processes. The hydrofluoric acid-HF concentration of the etching solution can be selected from 15% to 25%, the temperature range is controlled at 20-30℃, and the etching rate range at this temperature is 2-5 μm / min. During the thinning process, a real-time thickness monitoring system (e.g., a laser interferometer) controls the thinning endpoint. The uniformity of the thinned glass thickness can reach ±1.5 μm. With a more uniform protective film thickness, its overall strength consistency is also improved, avoiding the impact of weak local strength on the overall reliability of the protective film. In this step, if the etching rate is too fast, it can easily lead to poor thickness uniformity and surface quality; if the etching rate is too slow, it will affect efficiency. This solution, after comprehensively considering the impact of etching rate on production efficiency and surface quality, selects a suitable etching rate that ensures both sufficient production efficiency and good surface quality of the protective film. The specific composition of the etching solution is not limited, as long as its concentration range is controlled to ensure that the etching rate is neither too fast nor too slow. For example, in addition to hydrofluoric acid, the etching solution can also include hydrochloric acid, sulfuric acid, etc.

[0024] Screen printing protective ink steps: Apply protective ink to both opposite surfaces of the protective film blank.

[0025] Specifically, a fully automatic high-precision screen printing machine can be used to print UV-curable protective ink on both sides of the protective film blank. The screen printing machine uses a screen mesh of 250-400 mesh, a printing pressure of 0.2-0.4 MPa, and a high-intensity UV LED with a wavelength range of 365nm-405nm and an energy range of 800mJ / cm²-1500mJ / cm² to ensure complete ink curing and the formation of a dense protective layer on the surface of the protective film blank. Coating both sides of the protective film blank with protective ink can prevent scratches on the surface of the blank. Simultaneously, the ink printing can increase the thickness and strength to a certain extent, improving the glass sheet's resistance to breakage. The protective ink can also form a protective layer on the glass surface, preventing corrosion from acidic substances on both sides of the glass.

[0026] Edge treatment step: The protective film blank coated with protective ink is placed in an acidic passivation solution to remove micro-cracks at the edges of the protective film blank, making the edges smooth and passivated.

[0027] Specifically, the protective film blank coated with protective ink is placed in an acidic passivation solution, which is a mixed aqueous solution including hydrofluoric acid, nitric acid, and a buffer. The treatment temperature is 25℃-35℃, and the treatment time is 30-90 seconds. For example, the passivation solution may include 5%-10% by volume of hydrofluoric acid and 5%-15% by volume of nitric acid, with the remainder being a buffer. The buffer prevents the hydrofluoric acid and nitric acid from reacting too quickly with the glass; the buffer can be, for example, hydrochloric acid or sulfuric acid. This step removes the edge microcrack layer caused by cutting or other reasons, making the edges smooth and passivated, thereby increasing the edge strength by more than 30%. In the edge treatment step, the protective ink protects both sides of the protective film blank, preventing them from being corroded by acidic substances such as hydrofluoric acid, ensuring that the passivation solution only acts on the edges of the protective film blank.

[0028] Ink removal steps: Use ink remover to remove the protective ink from the original protective film.

[0029] Specifically, a specialized water-based ink remover can be used to remove the protective ink. The main component of the ink remover is an organic amine compound, with a concentration range of 8%-15%, and a treatment temperature of 50℃-70℃. This ink remover automatically removes the ink upon heating; immersing the original protective film blank in the ink remover for approximately 3-8 minutes completely dissolves the ink without producing any solid residue. This process also completes a preliminary rough cleaning step simultaneously with the ink removal. This ink removal step is simple, produces no solid residue, and eliminates the need for a rough cleaning process, thus improving production efficiency.

[0030] First polishing step: Place the original protective film blank after ink removal into the first polishing liquid for polishing treatment.

[0031] Specifically, for example, in a precision chemical etching production line, a low-concentration HF-based polishing slurry can be used in conjunction with megasonic vibration assistance. The frequency range of megasonic waves is 0.8-1.2MHz. The polishing treatment temperature is 20-25℃, and the time is 60-180 seconds. This uniformly removes a layer depth of 2-3μm from the surface, eliminating shallow scratches and pits. The surface roughness Ra can be reduced from greater than 0.1μm before the first polishing to less than 0.02μm. The HF-based polishing slurry may include, for example, 2%-5% HF by volume, 5%-10% sulfuric acid, and the remainder being additives.

[0032] To make the steps in the manufacturing process more logically connected, additional processing steps can be added, such as the following steps: Liner bonding steps: The entire glass substrate is bonded to the rigid liner using optical adhesive.

[0033] Specifically, a large sheet of glass substrate can be temporarily bonded to a rigid backing (such as borosilicate glass) using optical adhesive (OCA). The bonding pressure is 0.4-0.6 MPa, and the vacuum degree is <10 Pa to ensure no air bubbles and a smooth bond, providing support for subsequent etching and thinning steps, preventing the glass from cracking during processing, and thus improving product yield.

[0034] Etching and thinning step: The glass substrate is chemically etched and thinned using an etching solution to obtain the protective film blank.

[0035] Separation Steps: The protective film blank and the liner are peeled off under constant temperature and humidity conditions. The temperature range for these conditions is 21℃-25℃; the humidity range is 40%-60%; the separation speed is 10-30 mm / s; and the peeling angle is 90°-120°. For example, a peeling mechanism can be used to peel the protective film blank and the liner at a constant low speed and a fixed peeling angle under constant temperature conditions of 23±2℃ and constant humidity conditions of 50%±10%, avoiding stress on the protective film surface or tearing the protective film. The peeling angle refers to the angle less than 180° formed between the portion of the protective film blank that is lifted from the liner and the portion that remains adhered to the liner.

[0036] Screen printing protective ink steps: Apply protective ink to both opposite surfaces of the protective film blank.

[0037] Stacking step: After stacking multiple protective film blanks, they are placed in the insertion fixture, with buffer material between adjacent protective film blanks.

[0038] Specifically, glass sheets divided into individual protective film blanks (for example, the entire large glass substrate can be divided into individual protective film blanks by cutting, and the size of the individual protective film blanks is determined according to the screen size of the electronic product to be installed) can be stacked and placed in a fixture to facilitate subsequent batch edge processing. A buffer material (such as Teflon or silicone) is placed between two adjacent protective film blanks. The buffer material is sheet-shaped and located between two adjacent protective film blanks to separate them and prevent them from scratching each other. Specifically, the thickness of the buffer material can be 0.1~0.3mm.

[0039] Edge processing steps: Each batch of protective film blanks coated with protective ink can be placed in an acidic passivation solution for processing to make the edges smooth and passivated, while increasing the edge passivation speed and speeding up the process flow.

[0040] Ink removal process: Use ink remover to remove the protective ink from the protective film blank. A batch of protective film blanks can be soaked at a time to increase the ink removal speed.

[0041] First polishing step: Place the protective film blank after ink removal into the first polishing liquid for polishing. The first polishing process can be carried out at the same time for each batch of protective film blanks.

[0042] Chemical strengthening step: The protective film blank after the first polishing treatment is placed in molten alkali salt, so that the ions in the surface layer of the protective film blank can be exchanged with the ions in the molten alkali salt.

[0043] Specifically, a two-step chemical strengthening method can be used. First, the protective film blank is placed in a preheating furnace and preheated at 380-420℃ for 30-60 minutes. Then, it is immersed in potassium nitrate molten salt (KNO3 purity >99.9%) at 380-440℃ for ion exchange, which takes 2-4 hours. Finally, a compressive stress layer is formed on the surface of the protective film blank. The surface compressive stress (CS) of the compressive stress layer is >700MPa, and the layer depth (DOL) is >15μm, which greatly improves the bending and impact resistance of the protective film.

[0044] The second polishing step involves immersing the reinforced protective film blank in a second polishing solution. The second polishing solution has a higher pH than the first, and both are acidic. The polishing temperature is room temperature, for example, between 20℃ and 25℃, and is kept constant (meaning a temperature difference within ±2℃, ideally within ±1℃). The polishing time is 30-90 seconds, and the polishing depth is no more than 2 micrometers. Because the second polishing solution has a higher pH than the first and is acidic, it is less corrosive than the first, making it gentler.

[0045] Specifically, a milder second polishing solution is used again, with more precise temperature control (within ±0.5℃ tolerance), for 30-90 seconds to uniformly remove a 1-2μm layer depth from the surface. This step further smooths the surface of the protective film preform, releases micro-stress, further optimizes the surface roughness Ra to less than 0.015μm, and increases light transmittance by approximately 0.5%. The second polishing solution may include, for example, less than 1% HF by volume, 3%-8% nitric acid, and the remainder being a special corrosion inhibitor. The corrosion inhibitor's role is to prevent the reaction of hydrofluoric acid and nitric acid with the glass from being too rapid; the corrosion inhibitor can be, for example, hydrochloric acid or sulfuric acid. The second polishing solution in this step is milder than the first polishing solution, with a slower polishing speed and a smaller polishing depth, which can effectively improve the surface smoothness of the protective film preform, increase the light transmittance of the protective film, and also provide a smoother surface for subsequent coating processes, thereby improving the stability, durability, and optical performance of the AF film (Anti-Fingerprint Film).

[0046] Specifically, in some embodiments, the method for manufacturing the protective film includes the following steps: S1. Raw Material Inspection Steps: 100% inspection of ultra-thin glass sheets (glass substrate) is conducted. Key inspection indicators are as follows: thickness tolerance ±0.01mm, warpage less than 0.3mm, and no macroscopic defects on the surface. Laser thickness gauges and automated optical inspection (AOI) equipment are used for automatic inspection to ensure the stability of incoming materials and lay the foundation for subsequent precision processing.

[0047] S2. Liner bonding step: The inspected and qualified whole glass substrate is bonded to the rigid liner using optical adhesive.

[0048] Specifically, a large sheet of glass substrate can be temporarily bonded to a rigid backing plate (such as borosilicate glass) using optical adhesive (OCA). The bonding pressure is 0.5 MPa, and the vacuum degree is less than 10 Pa, ensuring no air bubbles and a smooth bonding.

[0049] S3. Pre-etching cleaning step: Use a multi-tank ultrasonic cleaner with deionized water and neutral detergent as the cleaning media. The ultrasonic frequency range is 40-80kHz, the temperature is 40-60℃, and the cleaning time is 3-5 minutes. This thoroughly removes organic contaminants and particles from the glass substrate surface, providing an absolutely clean surface for subsequent chemical thinning and avoiding interference with the thinning process.

[0050] S4. Etching and thinning step: The glass substrate is chemically etched and thinned using an etching solution to obtain a whole protective film blank.

[0051] Specifically, for example, a hydrofluoric acid-based etching solution can be used for chemical etching to thin the glass substrate from an initial thickness of 0.15 mm to a target thickness of 0.05 mm. The hydrofluoric acid-HF concentration of the etching solution is in the range of 20%, the temperature is controlled within the range of 25℃±2℃, and the etching rate at this temperature is 4 μm / min. During the thinning process, the thickness change is monitored in real time using a real-time laser interferometer to control the thinning endpoint.

[0052] S5. Post-etching cleaning steps: After removing the protective film blank from the etching solution, immediately place it in a high-flow overflow water rinsing tank. Immerse and rinse it in deionized water (resistivity >18MΩ·cm, i.e., pure water) at room temperature, such as 20-25℃, for 5-8 minutes. After thorough rinsing, remove residual acid from the surface of the protective film blank using high-pressure spraying to prevent over-etching and contamination. The pressure range of the high-pressure spraying is 0.5-1.0MPa, for example, 0.8MPa.

[0053] S6. Separation Step: Peel the protective film blank and the liner under constant temperature and humidity conditions. The temperature range of the constant temperature and humidity conditions is 22℃-24℃; the humidity range is 45%-55%; the separation speed is 20mm / s; and the peeling angle is 105°, 110°, or 115°.

[0054] S7. Screen printing protective ink step: Apply protective ink to both opposite surfaces of the protective film blank.

[0055] Specifically, a fully automatic high-precision screen printing machine is used to print UV-curable protective ink on both sides of the protective film blank. The screen mesh count is 300 mesh, the printing pressure is 0.3MPa, and the UV curing lamp uses a high-intensity UV LED with a wavelength range of 380nm and an energy of 1000mJ / cm² to ensure that the ink is completely cured and forms a dense protective layer.

[0056] S8. Segmentation Step: The entire protective film blank is segmented using a UV picosecond laser cutting system. The laser cutting system has a laser wavelength of 355nm, a pulse width of <10ps, a power of 8-15W, and a cutting speed of 200-500mm / s. Combined with a CCD vision positioning system, the positioning accuracy range is ±5μm, enabling direct cold cutting of the protective film contour. Specific cutting speeds can be 250mm / s, 300mm / s, 350mm / s, 400mm / s, or 450mm / s, etc.

[0057] S9. Stacking step: After stacking multiple protective film blanks, place them in the insert fixture. Buffer material is provided between adjacent protective film blanks so that each batch of protective film blanks can be processed in the subsequent edge processing step.

[0058] S10, Edge treatment step: Place the protective film blank coated with protective ink in an acidic passivation solution to make the edges smooth and passivated.

[0059] Specifically, the protective film blank is placed in an acidic passivation solution for treatment. The acidic passivation solution is a mixed aqueous solution including hydrofluoric acid, nitric acid, and a buffer. The treatment temperature is 28℃-32℃, and the treatment time is 60 seconds. For example, the passivation solution may include 8% by volume hydrofluoric acid and 12% by volume nitric acid, with the remainder being a buffer, which is hydrochloric acid.

[0060] S11. Cleaning steps before ink removal: Use an automatic inserter to insert the single protective film blank into a dedicated cleaning rack. The gap of the cleaning rack is fixed to ensure uniform cleaning in the subsequent process.

[0061] S12. Ink Removal Step: Use ink remover to remove the protective ink from the original protective film blank.

[0062] Specifically, an aqueous ink remover with organic amine compounds as its main component is used at a concentration of 12%, with a treatment temperature of 58℃-62℃ and a treatment time of 6 minutes.

[0063] S13. Inspection Steps: Perform AOI visual inspection under white or black LED backlighting to check for cracks, chipping, dirt, etc. on the surface of the protective film blank. At the same time, use a non-contact thickness sorter to classify the thickness according to a tolerance of ±2μm, monitor and manage the thickness loss of the preceding process, and improve the overall consistency of the product.

[0064] S14. First polishing step: Place the original protective film blank after ink removal into the first polishing liquid for polishing treatment.

[0065] Specifically, in a precision chemical etching production line, a low-concentration HF-based polishing slurry is used in conjunction with megasonic vibration assistance, with the megasonic frequency being 1MHz. The polishing treatment temperature is 21-24℃, and the time is 120 seconds, uniformly removing a layer depth of 2-3μm from the surface, eliminating shallow scratches and pits, and further reducing the surface roughness Ra. The HF-based polishing slurry may, for example, include 5% HF by volume, 7% sulfuric acid, and the remainder being additives.

[0066] S15. Chemical strengthening step: The protective film blank after the first polishing treatment is placed in molten alkali salt, so that the ions in the surface layer of the protective film blank can be exchanged with the ions in the molten alkali salt.

[0067] Specifically, a two-step chemical strengthening method is employed. First, the protective film blank is placed in a preheating furnace and preheated at 390-410℃ for 50 minutes. Then, it is immersed in potassium nitrate molten salt (KNO3 purity >99.9%) at a temperature of 400-420℃ for ion exchange, which lasts for 3 hours. Finally, a compressive stress layer is formed on the surface of the protective film blank.

[0068] S16. Post-strengthening cleaning steps: Immerse the chemically strengthened protective film blank directly into a hot water bath at 80-90℃ for ultrasonic vibration for 3-5 minutes at a frequency of 40kHz. This initially dissolves and removes over 99% of residual salt from the surface of the protective film blank. Then, transfer the protective film blank to a multi-stage overflow cleaning line using high-purity water (UPW, resistivity > 18.2MΩ·cm) for a final wash using mega-sonic technology to ensure complete removal of salt stains.

[0069] S17. Second polishing step: The reinforced protective film blank is placed in the second polishing liquid for polishing treatment. The pH value of the second polishing liquid is greater than that of the first polishing liquid.

[0070] Specifically, a milder second polishing solution was used again, and the process was carried out for 60 seconds under more precise temperature control (within ±0.5℃ tolerance) to uniformly remove a 1.5μm layer depth from the surface.

[0071] S18. First cleaning and drying step: Use heated high-purity deionized water (50-60℃) and isopropyl alcohol (IPA) vapor to clean and dry the surface of the protective film blank, ensuring that there are no etching residues, water stains or white spots on the surface.

[0072] S19. Coating Steps: Apply an AF anti-fingerprint coating to the surface of the protective film blank using a spray coating process to deposit a perfluoropolyether (PFPE) based AF film with a thickness of 2-5 nm. After treatment, the water droplet angle on the surface of the protective film blank can reach over 115°, and the coefficient of friction is <0.15.

[0073] S20. Cleaning and Finished Product Inspection Steps: Use a low-power plasma cleaning device (power <100W) to clean the surface of the protective film blank, or use a special solvent to gently wipe the surface of the protective film blank to remove any trace amounts of oil that may exist after coating. Perform AOI full inspection and water droplet angle test again to ensure that the appearance and coating parameters meet the standards.

[0074] S21. Second cleaning and drying step: As the final guarantee step before product delivery, the surface of the protective film blank is cleaned and dried using vapor phase cleaning or ultrapure water and IPA (steam drying system) drying process to ensure that the finished protective film meets a high standard in terms of cleanliness and dryness.

[0075] S22. Adhesive Application and Lamination Steps: In a Class 1000 clean environment, a high-precision adhesive bonding machine is used to apply AB adhesive to one side surface of the protective film blank. This side surface is the inner surface of the protective film and is used for bonding with the screen. After adhesive application, a release film is placed over the AB adhesive layer for protection, resulting in the final protective film. The adhesive application pressure range is 0.1-0.3 MPa, and the AB adhesive thickness is 25-100 μm. Air bubbles are removed by rolling with a lint-free cloth, followed by the application of the outer protective film.

[0076] This application also provides a protective film manufactured using the manufacturing method described in the above embodiments.

[0077] A bending and rubbing comparison test was conducted on the protective film manufactured using the method of the embodiments of this application and a commercially available protective film manufactured using prior art methods. The test results are shown in the table below: The test data above shows that the protective film manufactured using the method of this application has a smaller bending angle and doubles the number of bends compared to existing protective film products. The protective film manufactured using the method of this application can be effectively bent 100,000 times with a small bending radius of 1.2mm. The protective film manufactured using the method of this application was subjected to a rubbing test with a bending radius of 1.2mm and a rubbing distance of ±5mm, and no cracking was observed. For the rubbing test with a rubbing distance of ±5mm, neither the samples from this application nor the existing technology samples showed any cracking.

[0078] The protective film manufactured by the method described in this application has a high product yield and high strength. Through a combined process of "laser cutting + acidic edge passivation + two-step chemical polishing," defects on the edges and surface of the protective film are systematically eliminated, significantly improving its bending resistance and drop reliability, increasing production yield by more than 20%, and achieving a bending radius ≤1.5mm.

[0079] The protective film manufactured by the method of this application embodiment has excellent surface quality and optical properties. After chemical polishing and precision cleaning, the surface of the protective film blank achieves a mirror-like finish with Ra < 0.015 μm; it has high light transmittance, > 91%; and the AF coating effect is durable and has a smooth feel.

[0080] The protective film manufactured by the method of this application embodiment has excellent flexibility. The ultra-thin glass with a thickness of 0.03mm-0.1mm, combined with deep chemical strengthening (CS>700MPa, DOL>15μm), allows the glass to be repeatedly bent at a small radius without breaking, meeting the usage requirements of foldable screens.

[0081] The protective film manufacturing method provided in this application embodiment is fully controllable. Each process step has a clear process parameter window, online monitoring and inspection nodes, forming a closed-loop quality control to ensure high consistency and stability of product performance.

[0082] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0083] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for manufacturing a protective film, wherein the protective film uses a flexible glass substrate with a thickness of 0.5 mm or less, characterized in that, The manufacturing method includes the following steps: Etching and thinning step: The glass substrate is chemically etched and thinned using an etching solution to obtain a protective film blank of the target thickness; Screen printing protective ink step: Apply protective ink to both opposite surfaces of the protective film blank; Edge treatment step: The protective film blank coated with protective ink is placed in an acidic passivation solution for treatment to remove micro-cracks at the edges of the protective film blank; Ink removal step: Use an ink remover to remove the protective ink from the original protective film blank; First polishing step: The original protective film blank after ink removal is placed in the first polishing liquid for polishing treatment.

2. The method for manufacturing the protective film as described in claim 1, characterized in that, The etching and thinning step is preceded by a substrate bonding step: the entire glass substrate is bonded to a rigid substrate using optical adhesive.

3. The method for manufacturing the protective film as described in claim 2, characterized in that, The process includes a separation step before the screen printing protective ink step: peeling off the protective film blank and the liner.

4. The method for manufacturing the protective film as described in claim 3, characterized in that, The ambient temperature range for the separation step is 20℃-25℃; the humidity range is 40%-60%; the separation speed is 10-30mm / s; and the peeling angle is 90°-120°.

5. The method for manufacturing the protective film as described in claim 1, characterized in that, The process includes a chemical strengthening step following the first polishing step: placing the protective film blank after the first polishing treatment into a molten alkali salt for ion exchange.

6. The method for manufacturing the protective film as described in claim 5, characterized in that, The process includes a second polishing step after the chemical strengthening step: the strengthened protective film blank is placed in a second polishing liquid for polishing treatment. The pH value of the second polishing liquid is greater than that of the first polishing liquid, and both the first and second polishing liquids are acidic polishing liquids.

7. The method for manufacturing the protective film as described in claim 6, characterized in that, In the second polishing step, the polishing temperature range is 20℃-25℃; the polishing time is 30 seconds-90 seconds; and the polishing depth is no more than 2 micrometers.

8. The method for manufacturing the protective film as described in claim 1, characterized in that, In the first polishing step, while polishing the protective film blank with the first polishing liquid, vibration assistance is provided by megasonic waves, the frequency range of which is 0.8-1.2MHz; the polishing time is 60-180 seconds; and the polishing depth is 2-3 micrometers.

9. The method for manufacturing the protective film as described in claim 1, characterized in that, The acidic passivation solution in the edge treatment step is a mixed aqueous solution including hydrofluoric acid, nitric acid and buffer, with a treatment temperature of 25℃-35℃ and a treatment time of 30-90 seconds.

10. The method for manufacturing the protective film as described in claim 1, characterized in that, The process includes a stacking step before the edge processing step: multiple protective film blanks are stacked and placed in a fixture, wherein a buffer material is provided between two adjacent protective film blanks.

11. A protective film, characterized in that, It is manufactured using the manufacturing method described in any one of claims 1 to 10.

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