Gradient polarizer protective film and preparation method and application thereof

Abstract

The invention relates to a gradient polarizer protective film and a preparation method and application thereof, and belongs to the technical field of optical devices. The gradient polarizer protective film sequentially comprises a base material layer, a strong conductive layer, a low conductive main body layer and a weak conductive layer from bottom to top, the colloid raw materials of the strong conductive layer comprise a polymerizable antistatic monomer, a nano ion conductor, a block copolymerization modifier, a cross-linking auxiliary agent, a photoinitiator and an acrylic acid pre-polymerization solution; the colloid raw materials of the low-conductivity main body layer comprise a polymerizable antistatic monomer, a cross-linking auxiliary agent, a photoinitiator and an acrylic acid pre-polymerized solution; and the colloid raw materials of the weak conductive layer comprise a cross-linking auxiliary agent, a photoinitiator and an acrylic acid pre-polymerized solution. According to the gradient polarizer protective film, stripping interface charges can be quickly dissipated along the gradient conductive layer, the film tearing voltage is remarkably reduced, antistatic groups do not migrate or separate out, and the aims of long-term antistatic stability are achieved while high light transmittance and excellent adhesive force are kept are achieved.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and in particular to a gradient polarizer protective film, its preparation method, and its application. Background Technology

[0002] Polarizing film protective films are widely used in the manufacturing and packaging of optical devices such as liquid crystal displays (LCDs), organic light-emitting diode displays (OLEDs), and touch modules to prevent contamination or scratches on the polarizing film surface. Polarizing film protective films are typically composed of a PET substrate and acrylic pressure-sensitive adhesive (PSA) or polyurethane (PU). Acrylic PSA is widely used due to its superior transparency and adhesion. However, in downstream applications, there is a rapid tear-off process between the polarizing film and the protective film (i.e., "fast tear"), with tear speeds potentially exceeding 20 m / min. During this process, a large amount of static charge is generated instantly upon separation of the protective film from the polarizing film. The accumulation of this static charge can lead to an instantaneous tear voltage of hundreds of volts (V). This can cause electrostatic discharge (ESD) damage to the display panel driver integrated circuits or sensors, or the charge can easily attract dust, causing bubbles or "shadow" defects. Furthermore, the antistatic properties may degrade after long-term storage, causing the tear voltage to rise again.

[0003] Therefore, the industry has attempted to improve the quick-tear static electricity problem by adding antistatic agents or surface conductive layers to pressure-sensitive adhesive systems, but some limitations still exist. Patent CN 119775946 A discloses a low-tear-film voltage polyurethane protective film and its preparation method, mentioning the addition of antistatic agents (such as those stabilizing the surface resistance to 10) to polyurethane (PU) pressure-sensitive adhesives. 8 ~10¹ 0The method uses an antistatic agent with an internally added antistatic PET layer and a polyurethane antistatic adhesive layer to reduce the electrostatic voltage during film removal. However, relying solely on the internally added antistatic agent can lead to its migration to the surface or interface, resulting in haze or shadows over time. Furthermore, the migration of the antistatic agent is enhanced under high temperature and humidity conditions, leading to large resistivity fluctuations. Patent CN119931519A discloses a high-temperature resistant antistatic protective film for polarizers and its preparation method. This method uses a mixed adhesive of high-temperature resistant acrylate polymer and antistatic agent, combined with a release film structure, to reduce voltage accumulation during film removal. However, in this method, the peel force of the protective film is reduced, and the adhesive layer has a homogeneous structure, resulting in no effective dissipation path for interfacial charge at the moment of film removal, leading to a high voltage peak. Patent WO2008120465A1 discloses polyester films for antistatic films, surface protective films, and surface protection of optical components. These films involve coating one surface of the polyester film with a coating containing an antistatic polymer compound to provide antistatic properties. However, coating a substrate with an antistatic coating typically leads to increased substrate haze. Furthermore, most of these studies focus on the structure or tearing method of the protective film, while innovation in material systems targeting "rapid dissipation of charge at the tear-off interface" and "low tear-off voltage" remains insufficient. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a gradient polarizer protective film, its preparation method, and its application. The gradient conductive low-tear pressure-sensitive adhesive of this invention introduces polymerizable antistatic monomers into acrylic PSA and constructs a conductive gradient structure along the thickness direction. This allows the charge at the peel interface to dissipate rapidly along the gradient conductive layer, significantly reducing the peel voltage. Furthermore, the antistatic groups do not migrate or precipitate, achieving the goal of maintaining high light transmittance and excellent adhesion while possessing long-term antistatic stability.

[0005] This invention is achieved through the following technical solution:

[0006] The first objective of this invention is to provide a gradient polarizer protective film, wherein the gradient polarizer protective film comprises, from bottom to top, a substrate layer, a highly conductive layer, a low-conductivity main layer, and a weakly conductive layer;

[0007] By weight, the colloidal raw material of the strong conductive layer includes 4-10 parts polymerizable antistatic monomer, 0.4-1.5 parts nano-ionic conductor, 1-5 parts block copolymer modifier, 0.1-0.5 parts crosslinking aid, 0.1-0.5 parts photoinitiator and 100 parts acrylic prepolymer liquid;

[0008] The colloidal raw material of the low conductivity host layer includes 1-5 parts polymerizable antistatic monomer, 0.1-0.5 parts crosslinking aid, 0.1-0.5 parts photoinitiator and 100 parts acrylic prepolymer liquid;

[0009] The colloidal raw material of the weakly conductive layer includes 0.1-0.5 parts of crosslinking aid, 0.1-0.5 parts of photoinitiator, and 100 parts of acrylic acid prepolymer;

[0010] The raw materials of the acrylic prepolymer include 90-120 parts solvent, 85-110 parts main monomer, 0.05-0.5 parts free radical initiator, 0.1-1 parts crosslinking aid and 0.1-0.5 parts photoinitiator; the main monomer includes one or more of n-butyl acrylate (BA), 2-ethylhexyl acrylate (EHA) and methyl methacrylate (MMA).

[0011] In one embodiment of the present invention, the substrate layer is a PET base film, selected from at least one of the following: Toray Industries, DuPont, Jiangsu Sidike, and Sichuan Dongcai Company.

[0012] And / or, the thickness of the substrate layer is 38 μm to 75 μm, specifically 38 μm, 50 μm, and 75 μm;

[0013] And / or, the thickness of the strongly conductive layer is 8~12 μm;

[0014] And / or, the thickness of the low conductivity host layer is 9~15 μm;

[0015] And / or, the thickness of the weakly conductive layer is 5~8 μm.

[0016] In one embodiment of the present invention, the polymerizable antistatic monomer is selected from monomers containing quaternary ammonium salts or zwitterionic groups, specifically one or more of sulfobetaine methacrylate, [2-(methacryloyloxy)ethyl]trimethylammonium salt, quaternary ammonium carboxylate inner salt, and imidazoline metal salt.

[0017] In one embodiment of the present invention, the nano-ionic conductor is a conductive microparticle containing Li⁺ or SiO₂, such as NASICON-type Li⁺ nanoparticles. 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP), garnet-type nanoparticles Li 6.4 La3Zr 1.4 Ta 0.6 O 12 (LLZTO), polymer-ceramic composite microparticles MXene-mSiO2, etc.

[0018] In one embodiment of the present invention, the block copolymer modifier is selected from polyquaternary ammonium salt block copolymers; the polyquaternary ammonium salt block copolymer is selected from at least one of polyether-polysiloxane quaternary ammonium salt block copolymers and quaternary ammonium salt-fluorosilicone acrylate block copolymers.

[0019] In one embodiment of the present invention, the crosslinking aid is selected from isocyanate acrylate or trimethylolpropane triacrylate.

[0020] In one embodiment of the present invention, the photoinitiator is selected from one or more of DAROCUR 1173, IRGACURE 184 and TPO.

[0021] In one embodiment of the present invention, the solvent is selected from one or more of toluene, ethyl acetate, and butanone;

[0022] And / or, the free radical initiator is selected from one or more of azobisisobutyronitrile (AIBN), dimethyl azobisisobutyrate, and azobisisovalerate.

[0023] The second objective of this invention is to provide a method for preparing the aforementioned gradient polarizer protective film, comprising the following steps:

[0024] (1) Preparation of acrylic acid prepolymer solution;

[0025] (2) A polymerizable antistatic monomer, nano-ionic conductor, block copolymer modifier, crosslinking aid, photoinitiator and acrylic acid prepolymer liquid are mixed to obtain a highly conductive layer colloid;

[0026] (3) Mix polymerizable antistatic monomer, crosslinking aid, photoinitiator and acrylic prepolymer to obtain a low conductivity host layer colloid;

[0027] (4) Mix polymerizable antistatic monomer, crosslinking aid, photoinitiator and acrylic prepolymer to obtain a weakly conductive layer colloid;

[0028] (5) Coating a strong conductive layer colloid onto the substrate layer and baking it to obtain a strong conductive layer; then coating a low conductive base layer colloid and baking it to obtain a low conductive base layer; finally coating a weak conductive layer colloid and baking it to obtain a weak conductive layer; after UV curing and molding, it is aged to obtain a gradient polarizer protective film.

[0029] A third objective of this invention is to provide the application of the aforementioned gradient polarizer protective film in the fabrication of optical devices.

[0030] This invention introduces polymerizable antistatic monomers in the bottom and middle layers to provide stable, non-migrating ionic sites to attract charges, and adds nano-ionic conductors to establish rapid ion migration channels. Combined with the conductivity gradient in the thickness direction, it makes it easier for interfacial charges to be "absorbed" into the interior and dissipated. Without affecting transparency, it significantly reduces the tear-off voltage and improves long-term stability, making it suitable for the industrial production of polarizer protective films and optical display devices.

[0031] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0032] (1) Low tear film voltage: This invention utilizes antistatic monomers to attract the charge generated on the surface during the tear film process, guides the interface charge to be transferred to the adhesive layer in an orderly and rapid manner through a gradient conductive structure, and establishes a fast charge dissipation channel by the nano-ion conductor added to the bottom layer, thereby reducing the tear film voltage by more than 80%.

[0033] (2) Antistatic stability: The antistatic monomers are covalently bonded and added in large quantities to the bottom layer to form ion sites that are not easy to migrate to the surface. They will not migrate or precipitate to the surface in large quantities in high temperature and high humidity environments.

[0034] (3) Resistant to damp heat and low residue: Antistatic monomers and nano-ionic conductors are covered in the bottom layer, which are not easy to migrate and precipitate to the surface during damp heat aging. The cross-linking network is stable, and the performance is almost unchanged after 240 h at 65℃ / 95%RH.

[0035] (4) Suitable for high-speed production lines: It maintains low voltage and stable adhesion even under automatic film tearing conditions of 6 m / min. Attached Figure Description

[0036] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0037] Figure 1 This is a schematic diagram of the structure of the gradient polarizer protective film of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0040] The transparent PET base film was a 38μm transparent PET film (P51) purchased from Jiangsu Sidike New Material Technology Co., Ltd.

[0041] n-Butyl acrylate (BA) was purchased from Jinan Century Tongda Chemical Co., Ltd.

[0042] 2-Ethylhexyl acrylate (EHA) was purchased from Wuhan Yuqing Jiaheng Pharmaceutical Co., Ltd.

[0043] Methyl methacrylate (MMA) was purchased from Shandong Yanshuo Chemical Co., Ltd.

[0044] The initiator azobisisobutyronitrile (AIBN) was purchased from Jinan Century Tongda Chemical Co., Ltd.

[0045] The polymerizable antistatic monomer [2-(methacryloyloxy)ethyltrimethylammonium chloride] was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0046] Li nano-ion conductor 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP) was purchased from Guangdong Tusheng Technology Co., Ltd.

[0047] The block copolymer modifier, polyether-polysiloxane quaternary ammonium salt block copolymer, was purchased from Yantai Debon Technology Co., Ltd.

[0048] Example 1

[0049] This embodiment provides a method for preparing a protective film for a gradient polarizer, the specific steps of which are as follows:

[0050] 1. Preparation of acrylic acid prepolymer solution:

[0051] Add 60 parts of solvent (ethyl acetate / toluene = 1:1, mass ratio) to a reaction vessel, set the temperature to 70-75℃, stir at 300 rpm for 5 min, then add 10 parts of BA monomer, 3 parts of EHA monomer, 3 parts of MMA monomer and 0.20 parts of AIBN, and stir at 70℃ for 15 min; then raise the temperature to 75℃, and add another 60 parts of BA monomer, 12 parts of EHA monomer, 12 parts of MMA monomer, and 40 parts of solvent (ethyl acetate / toluene = 1:1) in two portions over 2 hours. After the addition is complete, raise the temperature to 80℃ and maintain the temperature for 120 min. When the viscosity of the system reaches 600-650 mPa·s (about 2 h), cool it to 70℃, add 0.5 parts of TMPTA and 0.3 parts of Irgacure 184, stir for 15 minutes to mix evenly; continue to keep it at 75℃ for 60 minutes, then cool it to ≤40℃, adjust the solid content to 50±1 wt%, and the viscosity to 950-1000 mPa·s (25℃). Filter it through a 400-mesh filter cloth to obtain a transparent prepolymer.

[0052] 2. Preparation of gradient conductive structural adhesive:

[0053] (1) Preparation of the bottom strongly conductive layer colloid: 6 parts of polymerizable antistatic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride and nano-ionic conductor Li 1.3 Al 0.3 Ti 1.7One part of (PO4)3 (LATP), two parts of polyether-polysiloxane quaternary ammonium salt block copolymer, 0.3 parts of TMPTA, and 0.3 parts of Irgacure 184 were added to 100 parts of acrylic prepolymer solution and mixed at room temperature (25°C) for 30 min at a speed of 300 rpm / min to obtain a bottom strongly conductive layer colloid.

[0054] (2) Preparation of low conductivity intermediate layer colloid: 2 parts of polymerizable antistatic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride, 0.3 parts of TMPTA and 0.3 parts of Irgacure 184 were added to 100 parts of acrylic acid prepolymer solution and mixed at room temperature (25°C) for 30 min at a speed of 300 rpm / min to obtain the low conductivity intermediate layer colloid.

[0055] (3) Preparation of surface weak conductive layer colloid: 100 parts of acrylic prepolymer solution without adding antistatic components, only 0.3 parts of TMPTA and 0.3 parts of Irgacure 184 are added and mixed at room temperature (25℃) for 30 min at a speed of 300 rpm / min to obtain surface weak conductive layer colloid.

[0056] 3. Stepwise gradient coating of polarizer protective film:

[0057] First, a highly conductive bottom layer colloid is coated onto a 38 μm transparent PET base film and baked in an oven at 60℃ for 1 min, then at 90℃ for 2 min, resulting in a dry adhesive thickness of 8 μm. Next, a low-conductivity intermediate layer colloid is coated and baked at 80℃ for 2 min, resulting in a dry adhesive thickness of 10 μm. Finally, a weakly conductive top layer colloid is coated and baked in an oven at 70℃ for 1 min, resulting in a dry adhesive thickness of 7 μm. Then, a 365nm UV lamp with an energy of 200 mJ / cm² is used for UV curing, followed by aging at 80℃ for 30 min, resulting in a total dry adhesive thickness of 25 μm to ensure sufficient cross-linking.

[0058] Example 2

[0059] This embodiment provides a method for preparing a gradient polarizer protective film, similar to Embodiment 1, except that no nano-ionic conductors are added in the preparation of the underlying strongly conductive colloid. The specific steps are as follows:

[0060] 1. Preparation of acrylic acid prepolymer solution:

[0061] Add 60 parts of solvent (ethyl acetate / toluene = 1:1, mass ratio) to a reaction vessel, set the temperature to 70-75℃, stir at 300 rpm for 5 min, then add 10 parts of BA monomer, 3 parts of EHA monomer, 3 parts of MMA monomer and 0.20 parts of AIBN, and stir at 70℃ for 15 min; then raise the temperature to 75℃, and add another 60 parts of BA monomer, 12 parts of EHA monomer, 12 parts of MMA monomer, and 40 parts of solvent (ethyl acetate / toluene = 1:1) in two portions over 2 hours. After the addition is complete, raise the temperature to 80℃ and maintain the temperature for 120 min. When the viscosity of the system reaches 600-650 mPa·s (about 2 h), cool it to 70℃, add 0.5 parts of TMPTA and 0.3 parts of Irgacure 184, stir for 15 minutes to mix evenly; continue to keep it at 75℃ for 60 minutes, then cool it to ≤40℃, adjust the solid content to 50±1 wt%, and the viscosity to 950-1000 mPa·s (25℃). Filter it through a 400-mesh filter cloth to obtain a transparent prepolymer.

[0062] 2. Preparation of gradient electrical structural adhesive:

[0063] (1) Preparation of the bottom strong conductive layer colloid: 6 parts of polymerizable antistatic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride, 2 parts of polyether-polysiloxane quaternary ammonium salt block copolymer, 0.3 parts of TMPTA and 0.3 parts of Irgacure 184 were added to 100 parts of acrylic prepolymer liquid and mixed at room temperature (25°C) for 30 min at a speed of 300 rpm / min.

[0064] (2) Preparation of low conductivity intermediate layer colloid: 2 parts of polymerizable antistatic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride, 0.3 parts of TMPTA and 0.3 parts of Irgacure 184 were added to 100 parts of acrylic acid prepolymer solution and mixed at room temperature (25°C) for 30 min at a speed of 300 rpm / min.

[0065] (3) Preparation of surface weak conductive layer colloid: 100 parts of acrylic prepolymer solution without adding antistatic components, only 0.3 parts of TMPTA and 0.3 parts of Irgacure 184 are added and mixed at room temperature (25℃) for 30 min at a speed of 300 rpm / min.

[0066] 3. Apply polarizer protective film:

[0067] A highly conductive colloid was coated onto a 38 μm transparent PET base film and baked at 60℃ for 1 min, then at 90℃ for 2 min, resulting in a dry adhesive thickness of 8 μm. A low-conductivity intermediate layer colloid was then coated and baked at 80℃ for 2 min, resulting in a dry adhesive thickness of 10 μm. Finally, a weakly conductive surface layer colloid was coated and baked at 70℃ for 1 min, resulting in a dry adhesive thickness of 7 μm. The film was then cured using a 365 nm UV lamp with an energy of 200 mJ / cm², and further cured at 80℃ for 30 min to ensure complete cross-linking.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a gradient polarizer protective film, similar to Example 1, except that: the intermediate low-conductivity main layer is removed, and a high-conductivity layer is directly thickened to replace the intermediate low-conductivity layer; the specific steps are as follows:

[0070] 1. Preparation of acrylic acid prepolymer solution:

[0071] Add 60 parts of solvent (ethyl acetate / toluene = 1:1, mass ratio) to a reaction vessel, set the temperature to 70-75℃, stir at 300 rpm for 5 min, then add 10 parts of BA monomer, 3 parts of EHA monomer, 3 parts of MMA monomer and 0.20 parts of AIBN, and stir at 70℃ for 15 min; then raise the temperature to 75℃, and add another 60 parts of BA monomer, 12 parts of EHA monomer, 12 parts of MMA monomer, and 40 parts of solvent (ethyl acetate / toluene = 1:1) in two portions over 2 hours. After the addition is complete, raise the temperature to 80℃ and maintain the temperature for 120 min. When the system viscosity reaches 600-650 mPa·s (approximately 2 h), cool to 70℃, add 0.5 parts TMPTA and 0.3 parts Irgacure 184, and stir for 15 minutes to mix thoroughly; continue to maintain the temperature at 75℃ for 60 minutes, then cool to ≤40℃, adjust the solid content to 50±1 wt%, and the viscosity to 950-1000 mPa·s (25℃). Filter through a 400-mesh filter cloth to obtain a transparent prepolymer liquid.

[0072] 2. Preparation of gradient conductive structural adhesive:

[0073] (1) Preparation of a single-layer highly conductive colloid: 6 parts of polymerizable antistatic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride and nano-ionic conductor Li 1.3 Al 0.3 Ti 1.71 part of (PO4)3 (LATP), 2 parts of block copolymer polyether-polysiloxane quaternary ammonium salt block copolymer, 0.3 parts of TMPTA, and 0.3 parts of Irgacure 184 were added to 100 parts of acrylic prepolymer solution and mixed at room temperature (25°C) for 30 min at a speed of 300 rpm / min.

[0074] (2) Preparation of surface weak conductive layer colloid: 100 parts of acrylic prepolymer solution without adding antistatic components, only 0.3 parts of TMPTA and 0.3 parts of Irgacure 184 are added and mixed at room temperature (25℃) for 30 min at a speed of 300 rpm / min.

[0075] 3. Apply polarizer protective film:

[0076] First, a highly conductive colloid is coated onto a 38 μm transparent PET base film and baked in an oven at 60℃ for 1 min, then at 90℃ for 2 min, resulting in a dry adhesive thickness of 18 μm. Next, a weakly conductive colloid is coated onto the surface and baked in an oven at 70℃ for 1 min, resulting in a dry adhesive thickness of 7 μm. Then, a 365 nm UV lamp with an energy of 200 mJ / cm² is used for UV curing. After curing, the film is aged at 80℃ for 30 min, resulting in a total dry adhesive thickness of 25 μm, ensuring sufficient cross-linking.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing a gradient polarizer protective film, similar to Example 1, except that: the intermediate low-conductivity layer and the surface weak-conductivity layer are removed, and the strong-conductivity layer is directly thickened to replace the intermediate and surface layers. The specific steps are as follows:

[0079] 1. Preparation of acrylic acid presol:

[0080] Add 60 parts of solvent (ethyl acetate / toluene = 1:1) to the reaction vessel, set the temperature to 70-75℃, stir at 200-300 rpm for 5 min, then add 10 parts of BA monomer, 3 parts of EHA monomer, 3 parts of MMA monomer and 0.20 parts of AIBN, and stir at 72-78℃ for 10-15 min; then raise the temperature to 75-80℃, and add another 60 parts of BA monomer, 12 parts of EHA monomer, 12 parts of MMA monomer, and 40 parts of solvent in 2-3 portions over 1.5-2.5 hours. After the addition is complete, raise the temperature to 75-80℃ and maintain the temperature for 120 min. When the viscosity of the system reaches 500-700 mPa·s (about 2 h), cool it to 70℃, add 0.5 parts of TMPTA and 0.3 parts of Irgacure 184, stir for 15 minutes to mix evenly; continue to keep it at 75-80℃ for 60-90 minutes, then cool it to ≤40℃, adjust the solid content to 50±1 wt%, and the viscosity to 800-1200 mPa·s (25℃). Filter it through a 400-mesh filter cloth to obtain a transparent prepolymer.

[0081] 2. Preparation of single-layer conductive structural adhesive:

[0082] (1) Preparation of a single-layer highly conductive colloid: 6 parts of polymerizable antistatic monomer 2-(methacryloyloxy)ethyltrimethylammonium chloride and nano-ionic conductor Li 1.3 Al 0.3 Ti 1.7 1 part of (PO4)3 (LATP), 2 parts of block copolymer polyether-polysiloxane quaternary ammonium salt block copolymer, 0.3 parts of TMPTA, and 0.3 parts of Irgacure 184 were added to 100 parts of acrylic prepolymer solution and mixed at room temperature (25°C) for 30 min at a speed of 300 rpm / min.

[0083] 3. Apply polarizer protective film:

[0084] A single layer of highly conductive colloid was coated onto a 38 μm transparent PET base film and baked in an oven at 60℃ for 1 min and then at 90℃ for 2 min, resulting in a dry colloid thickness of 25 μm. After UV curing, the film was cured at 80℃ for 30 min to ensure full cross-linking.

[0085] Performance testing

[0086] The following performance tests were performed on the above embodiments and comparative examples:

[0087] 1. Film tearing voltage test: Tested using an FMX-004 electrostatic voltage tester;

[0088] 2. Transmittance and haze testing: A Sanenshi haze and transmittance meter, model: YS6002-M benchtop transmittance and color haze meter, was used.

[0089] 3. Surface resistance test: Tested according to the method of standard ASTM D-257;

[0090] 4. Adhesion test: Cut the protective film into 1-inch pieces, stick them to a standard steel plate, let it stand for 20 minutes, and then peel it off at a speed of 300 cm / min.

[0091] 5. Shadow test: After the protective film has been aged by damp heat, observe it under a strong light to see if there are uneven haze shadows on the surface.

[0092] The test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As shown in Table 1, the sample from Example 1, under the peel test conditions of 6 m / min and 180° peeling, had a peak instantaneous peel voltage of only about 84 V, which is about 83% lower than that of the traditional system (>500 V). This is mainly due to the gradient conductive structure containing antistatic monomers guiding the rapid transfer of interfacial charge to the intermediate and bottom layers. The nano-ionic conductors added to the bottom layer establish a rapid charge dissipation channel, allowing the static charge generated during the rapid peeling process to be quickly dissipated. In addition, the antistatic monomers are covalently bonded and added to the bottom layer, forming ionic sites that are not easily migrated to the surface. They do not migrate or precipitate to the surface in large quantities in high temperature and high humidity environments. After aging for 240 hours under humid heat conditions of 65℃ / 95%RH, the resistance and adhesion of the sample showed almost no change, and no haze or residue was observed.

[0096] In Example 2, the gradient conductive structure was still used, and the excellent tear-off voltage performance was maintained. The instantaneous peak value of the tear-off voltage was only about 135 V. However, the nano-ionic conductor was removed. Although the charge could be attracted to the adhesive layer by the gradient conductive structure, the instantaneous peak value of the tear-off voltage was 135 V, which was significantly higher than that of Example 1 due to the reduction of conductive channels.

[0097] Comparative Example 1 removed the intermediate low-conductivity layer and directly replaced it with a highly conductive layer. Due to the absence of the intermediate transition conductive layer, charges were rapidly attracted and accumulated on the surface of the highly conductive layer, slowing down the dissipation rate and causing the peeling voltage to increase slightly to 149V. However, because the highly conductive layer contained a high proportion of antistatic monomers, the overall optical transmittance decreased to below 90%, and the haze also increased significantly to 2.36%. During the aging process, antistatic monomers and nano-ions were slightly precipitated, resulting in slight haze on the surface. Similarly, Comparative Example 2 directly coated a single layer of highly conductive layer. The surface charge could not achieve gradient transfer and accumulated in large quantities on the surface, competing for nano-ion channels. This resulted in a peak instantaneous voltage of 297V, an overall optical transmittance of below 88.7%, and a haze increase to 3.23%. Furthermore, the precipitation of antistatic monomers and nano-ion conductors caused haze and even slight residue.

[0098] This demonstrates that the gradient conductive structure can effectively suppress static electricity accumulation under high-speed stripping conditions while maintaining excellent optical and durability properties.

[0099] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A gradient polarizing plate protective film, characterized by, The gradient polarizer protective film comprises, from bottom to top, a substrate layer, a strong conductive layer, a low conductive main body layer and a weak conductive layer. The colloidal raw material of the strong conductive layer comprises, by weight, 4-10 parts of polymerizable antistatic monomer, 0.4-1.5 parts of nano ionic conductor, 1-5 parts of block copolymer modifier, 0.1-0.5 parts of crosslinking aid, 0.1-0.5 parts of photoinitiator and 100 parts of acrylic prepolymer liquid. The colloidal raw material of the low conductive main body layer comprises 1-5 parts of polymerizable antistatic monomer, 0.1-0.5 parts of crosslinking aid, 0.1-0.5 parts of photoinitiator and 100 parts of acrylic prepolymer liquid. The colloidal raw material of the weak conductive layer comprises 0.1-0.5 parts of crosslinking aid, 0.1-0.5 parts of photoinitiator and 100 parts of acrylic prepolymer liquid.

2. The protective film for a gradient polarizing plate according to claim 1, wherein The substrate layer is a PET base film. The thickness of the substrate layer is 38 μm~75 μm. The thickness of the strong conductive layer is 8~12 μm. The thickness of the low conductive main body layer is 9~15 μm. The thickness of the weak conductive layer is 5~8 μm.

3. The protective film for a gradient polarizing plate according to claim 1, wherein The polymerizable antistatic monomer is selected from one or more of a monomer containing quaternary ammonium salt or a monomer containing zwitterionic group; the polymerizable antistatic monomer is selected from one or more of sulfobetaine methacrylate, [2-(methacryloyloxy)ethyl] trimethylammonium salt, quaternary ammonium carboxylic acid inner salt and imidazoline metal salt.

4. The protective film for a gradient polarizing plate according to claim 1, wherein The nano ionic conductor is a conductor microparticle containing Li⁺ or SiO2.

5. The protective film for a gradient polarizing plate according to claim 1, wherein The block copolymer modifier is a polyquaternary ammonium salt block copolymer; the polyquaternary ammonium salt block copolymer is selected from one or more of polyether-polysiloxane quaternary ammonium salt block copolymer and quaternary ammonium salt-fluorosilicone acrylate block copolymer.

6. The gradient polarizer protection film according to claim 1, wherein The crosslinking aid is selected from isocyanate acrylate or trimethylolpropane triacrylate.

7. The gradient polarizer protection film according to claim 1, wherein The photoinitiator is selected from one or more of DAROCUR1173, IRGACURE 184 and TPO.

8. The gradient polarizer protection film according to claim 1, wherein The raw material of the acrylic prepolymer liquid comprises 90-120 parts of solvent, 85-110 parts of main monomer, 0.05-0.5 parts of free radical initiator, 0.1-1 parts of crosslinking aid and 0.1-0.5 parts of photoinitiator; the main monomer comprises one or more of n-butyl acrylate, 2-ethylhexyl acrylate and methyl methacrylate.

9. The method of producing a protective film for a gradient polarizing plate according to claims 1 to 8, characterized in that, The method comprises the following steps: (1) preparing an acrylic prepolymer liquid; (2) mixing the polymerizable antistatic monomer, nano ionic conductor, block copolymer modifier, crosslinking aid, photoinitiator and acrylic prepolymer liquid to obtain a strong conductive layer colloid; (3) mixing the polymerizable antistatic monomer, crosslinking aid, photoinitiator and acrylic prepolymer liquid to obtain a low conductive main body layer colloid; (4) mixing the polymerizable antistatic monomer, crosslinking aid, photoinitiator and acrylic prepolymer liquid to obtain a weak conductive layer colloid; (5) coating the strong conductive layer colloid on the substrate layer, baking to obtain a strong conductive layer; then coating the low conductive main body layer colloid, baking to obtain a low conductive main body layer; finally coating the weak conductive layer colloid, baking to obtain a weak conductive layer; after UV curing and forming, aging to obtain a gradient polarizer protective film.

10. Use of the gradient polarizing plate protective film according to claims 1 to 8 for the production of optical devices.

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