PU protective film

Abstract

The utility model discloses a PU (Polyurethane) protective film, which comprises a PET (Polyethylene Terephthalate) base material layer (1) and a PU adhesive layer (2), the surface of the PU adhesive layer (2) is coated with an adhesion enhancement layer (3), the surface of the adhesion enhancement layer (3) is coated with a surface hydrophobic layer (4), and the thickness of the adhesion enhancement layer (3) is 1-3 microns; and the thickness of the surface hydrophobic layer (4) is 0.5-1 [mu] m. According to the PU protective film disclosed by the utility model, through a composite structure of the adhesion enhancement layer, the surface hydrophobic layer and the chemical modification layer, the adhesion of dust and oil stain is effectively prevented, the cleanliness is improved, meanwhile, the excellent adhesion force of the PU adhesive layer is kept, and compared with the prior art, the PU protective film shows stronger antifouling property and operability.

Description

TECHNICAL FIELD

[0001] The utility model relates to a PU protective film. BACKGROUND

[0002] PU protective film is a functional protective film made of transparent PET film as base material, single-sided coated with polyurethane glue, and the glue surface is attached with release film. It has the characteristics of high light transmittance, high weather resistance, low adhesion and easy to tear, no residual glue, high temperature resistance, etc. PU protective film is generally used to provide protection in the production process of liquid crystal panel, or to protect ITO and glass panel from damage during transportation, and is suitable for the protection of touch screen devices such as smart phones, tablet computers, etc. PU protective film plays an important role in the field of electronic product protection due to its unique performance and wide application field.

[0003] CN 114369418 B discloses a PU protective film for display screen process, which focuses on the improvement of the polyurethane pressure-sensitive adhesive layer of the PU protective film. Through modification of the polyurethane, the prepared protective film has good cohesion and high peeling strength, low adhesive creep, no residue, good exhaust performance, no overflow during laser cutting, etc. At the same time, the surface resistivity is effectively reduced, and the anti-aging and anti-static effects are more excellent.

[0004] CN 111732925 B discloses a modified PU adhesive and a modified PU adhesive protective film with excellent weather resistance, which also focuses on the modification of PU adhesive. The prepared PU adhesive protective film has no residue, no fogging, and no circle printing on the surface of the glass when attached to the vehicle glass, and has good exhaust performance, small peeling force, and easy peeling on the glass surface.

[0005] Although the above-mentioned PU protective film has many advantages, it also has some disadvantages. For example, although good performance can be obtained by modifying the PU adhesive, such as easy attachment, no residue, etc., the PU adhesive layer has adhesion, which can easily adsorb dust and oil stains, thereby reducing the performance of the PU protective film. The common solution is to add an antistatic agent to the base material or PU adhesive layer to reduce the adsorption of dust by static electricity. However, it is difficult to effectively prevent oil stains with an antistatic agent, and once dust or oil stains are attached, it is difficult to remove them from the surface of the PU adhesive layer. If the surface energy of the PU adhesive layer is reduced to facilitate cleaning, the adhesion of the PU adhesive layer will also be reduced. SUMMARY

[0006] The technical problem to be solved by the utility model is to provide a PU protective film to reduce or avoid the problems mentioned above.

[0007] To solve the above-mentioned technical problems, this utility model proposes a PU protective film, including a PET substrate layer and a PU adhesive layer, wherein an adhesion enhancement layer is coated on the surface of the PU adhesive layer, and a surface hydrophobic layer is coated on the surface of the adhesion enhancement layer, wherein the thickness of the adhesion enhancement layer is 1-3μm; and the thickness of the surface hydrophobic layer is 0.5-1μm.

[0008] Preferably, the thickness of the PET substrate layer is 50μm-100μm; and the thickness of the PU adhesive layer is 25μm-50μm.

[0009] The PU protective film of this invention, through a composite structure of an adhesion enhancement layer, a surface hydrophobic layer, and chemical modification, not only effectively prevents the adhesion of dust and oil stains and improves cleanliness, but also maintains the excellent adhesion of the PU adhesive layer. Compared with the prior art, it exhibits stronger anti-fouling properties and operability. Attached Figure Description

[0010] The accompanying drawings are intended only to illustrate and explain this application and do not limit the scope of this utility model.

[0011] Figure 1 The diagram shown is a structural schematic of a PU protective film according to a specific embodiment of the present invention. Detailed Implementation

[0012] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, specific embodiments are now described with reference to the accompanying drawings. Identical components are denoted by the same reference numerals.

[0013] like Figure 1 As shown, in order to solve the problems mentioned in the background art, this utility model designs and proposes an improved PU protective film, including a PET substrate layer 1 and a PU adhesive layer 2. Unlike the prior art, this utility model coats an adhesion enhancement layer 3 on the surface of the existing PU adhesive layer 2, and coats a surface hydrophobic layer 4 on the surface of the adhesion enhancement layer 3.

[0014] The basic concept of this utility model is that by first coating a specially designed adhesion enhancement layer 3 on the PU adhesive layer 2, this material can form a good bond with both the PU adhesive layer 2 and the subsequently coated surface hydrophobic layer 4; at the same time, the surface hydrophobic layer 4 is designed to effectively reduce the adhesion of dust and dirt while still maintaining high adhesion.

[0015] In one embodiment, the thickness of the PET substrate layer 1 is preferably 50-100 μιη, which can ensure good transparency and high mechanical strength. The thickness of the PU adhesive layer 2 is preferably 25-50 μιη, which can provide appropriate adhesion, flexibility and protection. The thickness of the adhesion enhancement layer 3 is preferably 1-3 μιη, too thin adhesion enhancement layer can not provide sufficient adhesion; too thick adhesion enhancement layer can affect the flexibility of the overall film, and increase the complexity of the coating. The thickness of the surface hydrophobic layer 4 is preferably 0.5-1 μιη, which can provide effective hydrophobicity without affecting the adhesion of the PU adhesive layer. In summary, the thickness of each layer can ensure the balance of the performance of each layer, while ensuring good hydrophobicity, adhesion and stain resistance.

[0016] In another embodiment, the adhesion enhancement layer 3 is prepared from the following components by weight: polyurethane acrylate (PUA) 50-70 parts by weight, low molecular weight epoxy resin 20-30 parts by weight, 3-aminopropyl triethoxysilane (APTES) 5-10 parts by weight, difluorophenyl ester 2-5 parts by weight, isopropyl alcohol 5-15 parts by weight.

[0017] Specifically, polyurethane acrylate (PUA) as the core component of the adhesion enhancement layer 3 provides excellent flexibility and adhesion. Preferably, the molecular weight of PUA is in the range of 5000-20000 g / mol. For example, BASF Joncryl 500 can be used; or Desmodur E 10 or Desmodur N100 of Covestro, Germany can be used.

[0018] Low molecular weight epoxy resin is used to improve the interfacial bonding force between the coating and the substrate. Preferably, the molecular weight is in the range of 350-600 g / mol, for example, EPIKOTE Resin 828 of BASF can be used, or Araldite GY 2855 of Huntsman, USA can be used, or D.E.R.331 of Dow Chemical can be used.

[0019] 3-aminopropyl triethoxysilane (APTES) is used to improve the interfacial bonding force between the coating and the substrate. For example, A3648 of Sigma-Aldrich of Merck can be used; or Dynasylan AMEO of Evonik can be used.

[0020] Difluorophenyl ester is used to improve the flexibility of the adhesion enhancement layer and reduce the brittleness of the coating. For example, Merck's Sigma-Aldrich F10727 can be used; or T3139 from TCI Chemicals can be used.

[0021] Isopropyl alcohol is used as a solvent to adjust the viscosity of the coating for easy application. Industrial-grade raw materials can be selected.

[0022] Further, the adhesion enhancement layer 3 can be prepared by the following steps.

[0023] Specifically, the adhesion enhancement layer 3 is prepared by the mixing step of the adhesion coating, the coating step of the adhesion coating, and the curing step of the adhesion enhancement layer.

[0024] The mixing step of the adhesion coating includes: first, adding isopropyl alcohol as a solvent base to adjust the viscosity in a stirring container. Then, polyurethane acrylate (PUA) and epoxy resin are added to the solvent according to the ratio, and a stirrer is used to stir evenly to ensure that the resin is fully dissolved. Then, 3-aminopropyl triethoxysilane (APTES) and difluorophenyl ester are added and continue to stir until completely dissolved. APTES will promote the bonding force between the resin and the substrate, and difluorophenyl ester will improve the flexibility of the coating. Finally, after mixing, the room temperature is stirred for 30-60 minutes to ensure that all components are uniformly mixed, and to avoid excessive temperature causing the solvent to volatilize too quickly.

[0025] The coating step of the adhesion coating includes: using a spraying device to spray the adhesion coating onto the surface of the PUA layer at 40-50°C, the sprayed coating thickness is 1-3μm, and the spraying speed is 20-30cm / s.

[0026] The curing step of the adhesion enhancement layer includes: after coating, naturally volatilize in the air for 10-15 minutes. The coated substrate is placed in an oven for pre-baking to remove residual solvent, the pre-baking temperature is 60-70°C, and the pre-baking time is 10-15 minutes. After pre-baking the coating, further heat curing treatment is carried out, the heat curing temperature is 70-80°C, and the curing time is 30-60 minutes. After curing is completed, the coated substrate is taken out and naturally cooled to room temperature, and strong impact or pressure should be avoided during the cooling process to avoid affecting the quality of the coating. In order to ensure the quality, after the preparation is completed, the hardness of the coating is checked using a Shore A hardness tester to ensure that the hardness is between 40-60A.

[0027] In yet another embodiment, the surface hydrophobic layer 4 is prepared from the following components in the following weight parts: fluoroalkylsilane 6-10 parts by weight, polydimethylsiloxane (PDMS) 25-35 parts by weight, polyvinyl acetal (PVA) 30-40 parts by weight, isopropyl alcohol 10-20 parts by weight, and methyl triethoxysilane (MPTES) 5-8 parts by weight.

[0028] The fluoroalkylsilane can form a hydrophobic film on the surface, greatly reducing the surface energy and preventing the adhesion of oil stains and dust. For example, Sigma-Aldrich 306063 from Merck or Sigma-Aldrich can be used. Alternatively, a perfluoroalkylsilane product from Dow Chemical can be used.

[0029] The polydimethylsiloxane (PDMS) is used to provide additional surface hydrophobicity, while enhancing the mechanical strength and weather resistance of the coating. The polydimethylsiloxane (PDMS) can be selected from DOWSIL 550 Fluid from Dow Corning, or GP-1500 from Gelest, USA.

[0030] The polyvinyl acetal (PVA) is used to improve the hydrophobicity and adhesion of the coating. When PVA and fluoroalkylsilane are crosslinked, the chemical stability of the surface coating can be effectively increased. For example, ZTC-108 or ZTC-178 from Hangzhou Zhongtai PVA can be used, or PVA-1788 or PVA-117 from Jiangsu Lianhai Biology can be used.

[0031] Isopropyl alcohol is used as a solvent to adjust the concentration and flowability of the coating, ensuring uniform coating of the coating. Industrial-grade raw materials can be selected.

[0032] Methyl triethoxysilane (MPTES) is used to enhance the stability and anti-pollution ability of the hydrophobic layer, while maintaining good surface affinity. For example, MPTES 448312 from Merck or Sigma-Aldrich can be used, or Silquest A-187 from Momentive can be used.

[0033] Further, the surface hydrophobic layer 4 can be prepared by the following steps.

[0034] Specifically, the surface hydrophobic layer 4 is prepared by a mixing step of hydrophobic coating, a coating step of hydrophobic coating, and a curing step of hydrophobic coating.

[0035] The mixing step of the hydrophobic coating includes: first, a desired amount of polyvinyl acetal (PVA) is added to isopropyl alcohol, and a magnetic stirrer is used to stir until it is completely dissolved. If the PVA is difficult to dissolve, it can be slightly heated during stirring, but the temperature should not exceed 50°C to prevent degradation of the PVA. Stir until the PVA is completely dissolved and a uniform solution is formed. Then, methyl triethoxysilane (MPTES) is added to the PVA solution and stirring is continued to ensure that the MPTES is completely dispersed. After that, fluoralkylsilane is added and stirring is continued to ensure that the two silanes are thoroughly mixed. The mixed solution is set aside to ensure that it is stable and uniform after stirring is completed. Then, polydimethylsiloxane (PDMS) is added to the solution and stirring is continued with the stirrer to ensure that the PDMS is thoroughly mixed with the silane components. Finally, the mixed coating is left to stand for 15-30 minutes to remove air bubbles and ensure that the coating is more uniform, avoiding bubbles or uneven layers during application.

[0036] The coating step of the hydrophobic coating includes: before coating, ensure that the surface of the adhesion enhancement layer 3 is clean, dry, and free of oil. Isopropyl alcohol or ethanol can be used to clean the surface. The hydrophobic coating is evenly sprayed onto the surface of the adhesion enhancement layer 3 through a spraying device to ensure that the coating is uniform and free of air bubbles.

[0037] The curing step of the hydrophobic coating includes: placing the coating in a dry environment at 20-30°C for 1-2 hours. Then, curing at 60-80°C for 30-60 minutes to promote cross-linking reactions and ensure the stability and weather resistance of the coating.

[0038] Further, after the surface hydrophobic layer 4 is cured and formed, the surface hydrophobic layer 4 can be chemically modified by a chemical modifier mainly composed of MPTES (methyl triethoxysilane). The purpose is to strengthen the bonding force between the surface hydrophobic layer and the adhesion enhancement layer and the substrate (PU glue layer).

[0039] MPTES (methyl triethoxysilane) as a crosslinking agent can react with the substrate or adhesion enhancement layer through siloxane bonds on the surface of the coating. The ethoxy groups of MPTES react with water or other active functional groups to form Si-O-Si bonds, making the surface hydrophobic layer more stable and improving the adhesion to the adhesion enhancement layer. Silane crosslinking not only improves the chemical resistance and weather resistance of the coating, but also enhances the adhesion of the coating, ensuring strong bonding between different layers. Through siloxane crosslinking of MPTES, not only the adhesion between the coating and other layers can be enhanced, but also the surface hydrophobicity can be improved. The silane crosslinking agent has low surface energy characteristics, and after modification, it can further increase the contact angle of the coating, forming an effective hydrophobic surface to prevent the attachment of water, oil or other pollutants. Through chemical modification, the surface of the hydrophobic layer presents a more uniform chemical structure, thereby improving its hydrophobicity. Through chemical modification of the surface hydrophobic layer, the microstructure of the coating can also be controlled, and the surface roughness can be adjusted through crosslinking reaction to make the surface more self-cleaning and reduce the attachment of pollutants.

[0040] Further, the chemical modifier is composed of the following raw materials by weight: MPTES (methyl triethoxysilane) 5-8 parts by weight, isopropanol 5-10 parts by weight, deionized water 0.5-1 parts by weight.

[0041] Specifically, the chemical modifier can be prepared by the following steps: accurately weighed methyl triethoxysilane is added to isopropanol and deionized water and stirred to form a uniform solution. The water in the solution reacts with MPTES to form silanol groups (Si-OH), preparing for crosslinking reaction. The stirring time is 30-60 minutes to ensure that MPTES is fully hydrolyzed, and the silanol groups generated by the hydrolysis reaction will provide activity for the subsequent crosslinking reaction.

[0042] The specific steps of chemical modification treatment are as follows: using roll coating method, the prepared chemical modifier is extruded (the pressure should be controlled between 0.1-0.2 MPa) on the already solidified surface hydrophobic layer 4, to ensure that the modification solution can fully penetrate and react with the surface. The amount of chemical modifier is 5-10% of the total weight of the surface hydrophobic layer. Then, at room temperature, the reaction is carried out for 10-30 minutes, so that the ethoxy groups of MPTES form Si-O-Si crosslinking network with the functional groups (such as fluorinated alkyl silane, PVA, etc.) in the surface hydrophobic layer. After crosslinking reaction, the coated substrate is placed at 60-80°C for curing for 30-60 minutes to ensure complete crosslinking reaction. After curing is completed, the substrate is taken out and allowed to cool naturally to room temperature. At this time, the surface hydrophobic layer has been enhanced in adhesion to the lower layer through the later chemical modification, while still maintaining good hydrophobicity.

[0043] Example 1

[0044] Adhesion enhancement layer (thickness 1 μm): polyurethane acrylate (PUA): 70 parts; epoxy resin: 20 parts; APTES: 5 parts; difluorophenyl ester: 2 parts; isopropyl alcohol: 10 parts.

[0045] Surface hydrophobic layer (thickness 0.5 μm): fluoroalkylsilane: 6 parts; polydimethylsiloxane (PDMS): 25 parts; PVA: 30 parts; isopropyl alcohol: 10 parts; MPTES: 5 parts.

[0046] Chemical modifier: MPTES: 5 parts; isopropyl alcohol: 5 parts; deionized water: 0.5 parts. The amount of chemical modifier is 5% of the total weight of the surface hydrophobic layer.

[0047] Performance parameters: contact angle: 105°; surface energy: about 26 mN / m; adhesion: 5.1 N / cm; stain resistance: good oil stain cleanability, better water-based stain cleanability.

[0048] Example 2

[0049] Adhesion enhancement layer (thickness 2 μm): polyurethane acrylate (PUA): 60 parts; epoxy resin: 30 parts; APTES: 5 parts; difluorophenyl ester: 2 parts; isopropyl alcohol: 10 parts.

[0050] Surface hydrophobic layer (thickness 1 μm): fluoroalkylsilane: 10 parts; polydimethylsiloxane (PDMS): 30 parts; PVA: 30 parts; isopropyl alcohol: 15 parts; MPTES: 5 parts.

[0051] Chemical modifier: MPTES: 8 parts; isopropyl alcohol: 10 parts; deionized water: 1 part. The amount of chemical modifier is 6% of the total weight of the surface hydrophobic layer.

[0052] Performance parameters: contact angle: 115°; surface energy: about 20 mN / m; adhesion: 5.3 N / cm; stain resistance: very strong oil stain resistance, almost no dust adhesion, excellent cleanability

[0053] Example 3

[0054] Adhesion enhancement layer (thickness 1.5 μm): polyurethane acrylate (PUA): 50 parts; epoxy resin: 30 parts; APTES: 5 parts; difluorophenyl ester: 3 parts; isopropyl alcohol: 12 parts.

[0055] Surface hydrophobic layer (thickness 0.8 μm): fluoroalkylsilane: 8 parts; polydimethylsiloxane (PDMS): 25 parts; PVA: 35 parts; isopropyl alcohol: 12 parts; MPTES: 6 parts.

[0056] Chemical modifiers: MPTES: 7 parts; isopropanol: 8 parts; deionized water: 0.8 parts. The amount of chemical modifiers used is 7% of the total weight of the surface hydrophobic layer.

[0057] Performance parameters: Contact angle: 108°; Surface energy: approximately 24 mN / m; Adhesion: 5.4 N / cm; Stain resistance: Good oil stain cleaning ability, adaptable to various environments.

[0058] Example 4

[0059] Adhesion reinforcement layer (thickness 2.5μm): polyurethane acrylate (PUA): 65 parts; epoxy resin: 25 parts; APTES: 6 parts; difluorophenyl ester: 2 parts; isopropanol: 8 parts.

[0060] Surface hydrophobic layer (thickness 0.7 μm): fluoroalkyl silane: 7 parts; polydimethylsiloxane (PDMS): 27 parts; PVA: 32 parts; isopropanol: 13 parts; MPTES: 8 parts.

[0061] Chemical modifiers: MPTES: 6 parts; isopropanol: 9 parts; deionized water: 0.9 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0062] Performance parameters: Contact angle: 110°; Surface energy: approximately 22 mN / m; Adhesion: 5.2 N / cm; Stain resistance: Extremely strong resistance to oil and dust, keeping it clean for a long time.

[0063] Example 5

[0064] Adhesion reinforcement layer (thickness 3μm): polyurethane acrylate (PUA): 60 parts; epoxy resin: 20 parts; APTES: 6 parts; difluorophenyl ester: 2 parts; isopropanol: 12 parts.

[0065] Surface hydrophobic layer (thickness 0.6 μm): fluoroalkyl silane: 6 parts; polydimethylsiloxane (PDMS): 30 parts; PVA: 33 parts; isopropanol: 14 parts; MPTES: 6 parts.

[0066] Chemical modifiers: MPTES: 7 parts; isopropanol: 7 parts; deionized water: 0.7 parts. The amount of chemical modifiers used is 9% of the total weight of the surface hydrophobic layer.

[0067] Performance parameters: Contact angle: 103°; Surface energy: approximately 28 mN / m; Adhesion: 5.1 N / cm; Stain resistance: Good cleaning properties against oil and dust.

[0068] Example 6

[0069] Adhesion reinforcement layer (thickness 1.2μm): polyurethane acrylate (PUA): 65 parts; epoxy resin: 25 parts; APTES: 7 parts; difluorophenyl ester: 3 parts; isopropanol: 12 parts.

[0070] Surface hydrophobic layer (thickness 0.9 μm): fluoroalkyl silane: 9 parts; polydimethylsiloxane (PDMS): 28 parts; PVA: 32 parts; isopropanol: 12 parts; MPTES: 6 parts.

[0071] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 10% of the total weight of the surface hydrophobic layer.

[0072] Performance parameters: Contact angle: 107°; Surface energy: approximately 25 mN / m; Adhesion: 5.3 N / cm; Stain resistance: Resistant to oil, dust and water stains, with excellent cleaning properties.

[0073] Comparative Example 1 (surface hydrophobic layer omitted, no chemical modification performed)

[0074] Adhesion reinforcement layer (thickness 1.5μm): polyurethane acrylate (PUA): 70 parts; epoxy resin: 20 parts; APTES: 5 parts; difluorophenyl ester: 2 parts; isopropanol: 10 parts.

[0075] Surface hydrophobic layer: omitted

[0076] Performance parameters: Contact angle: 85°; Surface energy: approximately 40 mN / m; Adhesion: 5.5 N / cm; Stain resistance: The surface easily absorbs oil and dust.

[0077] Analysis: By omitting the surface hydrophobic layer, the hydrophobicity of the protective film decreases significantly, making it prone to attracting dust and oil, resulting in poor cleanability. Compared to Example 1, it exhibits poor hydrophobicity and stain resistance, and cannot effectively reduce surface adhesion.

[0078] Comparative Example 2 (Adhesion reinforcement layer omitted)

[0079] Adhesion reinforcement layer: omitted

[0080] Surface hydrophobic layer (thickness 0.8 μm): fluoroalkyl silane: 8 parts; polydimethylsiloxane (PDMS): 30 parts; PVA: 32 parts; isopropanol: 12 parts; MPTES: 6 parts.

[0081] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0082] Performance parameters: Contact angle: 100°; Surface energy: approximately 30 mN / m; Adhesion: 3.0 N / cm; Stain resistance: poor, with low ability to clean oil and dust.

[0083] Analysis: Omitting the adhesion reinforcement layer significantly reduces the bonding force between the PU adhesive layer and the surface hydrophobic layer, resulting in decreased adhesion and poor film stability. Furthermore, the surface hydrophobic layer is less effective than in Example 1, leading to poorer cleanliness.

[0084] Comparative Example 3 (MPTES crosslinking agent omitted)

[0085] Adhesion reinforcement layer (1 μm thickness): polyurethane acrylate (PUA): 65 parts; epoxy resin: 25 parts; APTES: 6 parts; difluorophenyl ester: 2 parts; isopropanol: 12 parts.

[0086] Surface hydrophobic layer (thickness 0.5 μm): fluoroalkyl silane: 7 parts; polydimethylsiloxane (PDMS): 27 parts; PVA: 32 parts; isopropanol: 12 parts.

[0087] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0088] Performance parameters: Contact angle: 95°; Surface energy: approximately 27 mN / m; Adhesion: 4.8 N / cm; Stain resistance: Good oil stain cleaning ability and strong dust adhesion.

[0089] Analysis: By omitting the MPTES crosslinking agent, the chemical modification of the film layer is insufficient, the performance of the surface hydrophobic layer is reduced, resulting in a lower contact angle and poorer stain resistance than in Example 1.

[0090] Comparative Example 4 (Reduced fluoroalkylsilane content)

[0091] Adhesion reinforcement layer (thickness 2.5μm): polyurethane acrylate (PUA): 60 parts; epoxy resin: 30 parts; APTES: 6 parts; difluorophenyl ester: 3 parts; isopropanol: 12 parts.

[0092] Surface hydrophobic layer (thickness 0.9 μm): fluoroalkyl silane: 5 parts; polydimethylsiloxane (PDMS): 28 parts; PVA: 32 parts; isopropanol: 14 parts; MPTES: 6 parts.

[0093] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0094] Performance parameters: Contact angle: 95°; Surface energy: approximately 35 mN / m; Adhesion: 5.3 N / cm; Stain resistance: poor, oil stains adhere quite noticeably.

[0095] Analysis: Reducing the content of fluoroalkylsilanes significantly decreased hydrophobicity, and the contact angle and stain resistance were not as good as in Example 1. Insufficient hydrophobicity resulted in more noticeable oil adhesion.

[0096] Comparative Example 5 (reduced polydimethylsiloxane content)

[0097] Adhesion reinforcement layer (thickness 3μm): polyurethane acrylate (PUA): 60 parts; epoxy resin: 25 parts; APTES: 5 parts; difluorophenyl ester: 3 parts; isopropanol: 12 parts.

[0098] Surface hydrophobic layer (thickness 0.6 μm): fluoroalkyl silane: 8 parts; polydimethylsiloxane (PDMS): 22 parts; PVA: 35 parts; isopropanol: 12 parts; MPTES: 6 parts.

[0099] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0100] Performance parameters: Contact angle: 98°; Surface energy: approximately 30 mN / m; Adhesion: 5.2 N / cm; Stain resistance: Strong oil stain adhesion on the surface.

[0101] Analysis: Reducing the content of polydimethylsiloxane slightly decreases the surface hydrophobicity, significantly increases oil adhesion, and results in poor cleanability.

[0102] Comparative Example 6 (excessive isopropanol content)

[0103] Adhesion reinforcement layer (thickness 1.2μm): polyurethane acrylate (PUA): 65 parts; epoxy resin: 25 parts; APTES: 7 parts; difluorophenyl ester: 3 parts; isopropanol: 18 parts.

[0104] Surface hydrophobic layer (thickness 0.7 μm): fluoroalkyl silane: 7 parts; polydimethylsiloxane (PDMS): 27 parts; PVA: 32 parts; isopropanol: 15 parts; MPTES: 6 parts.

[0105] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0106] Performance parameters: Contact angle: 100°; Surface energy: approximately 28 mN / m; Adhesion: 5.0 N / cm; Stain resistance: moderate oil stain cleaning ability, surface easily attracts dust.

[0107] Analysis: Excessive isopropanol content may lead to volatility issues in the coating, affecting its uniformity and adhesion, resulting in a film performance inferior to that of Example 1.

[0108] Comparative Example 7 (higher difluorophenyl ester content)

[0109] Adhesion reinforcement layer (thickness 2μm): polyurethane acrylate (PUA): 60 parts; epoxy resin: 25 parts; APTES: 5 parts; difluorophenyl ester: 5 parts; isopropanol: 10 parts.

[0110] Surface hydrophobic layer (thickness 0.5 μm): fluoroalkyl silane: 7 parts; polydimethylsiloxane (PDMS): 28 parts; PVA: 30 parts; isopropanol: 12 parts; MPTES: 6 parts.

[0111] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0112] Performance parameters: Contact angle: 102°; Surface energy: approximately 32 mN / m; Adhesion force: 5.4 N / cm.

[0113] Comparative Example 8 (reduced PVA content and increased isopropanol content)

[0114] Adhesion reinforcement layer (thickness 2μm): polyurethane acrylate (PUA): 60 parts; epoxy resin: 30 parts; APTES: 6 parts; difluorophenyl ester: 3 parts; isopropanol: 12 parts.

[0115] Surface hydrophobic layer (thickness 0.6 μm): fluoroalkyl silane: 7 parts; polydimethylsiloxane (PDMS): 30 parts; PVA: 20 parts; isopropanol: 15 parts; MPTES: 6 parts.

[0116] Chemical modifiers: MPTES: 5 parts; isopropanol: 8 parts; deionized water: 0.5 parts. The amount of chemical modifiers used is 8% of the total weight of the surface hydrophobic layer.

[0117] Performance parameters: Contact angle: 95°. Due to the further reduction of PVA, hydrophobicity decreases slightly, resulting in a relatively low contact angle. Surface energy: Approximately 36 mN / m. The surface energy is relatively increased, resulting in lower hydrophobicity. Adhesion: 5.2 N / cm. Adhesion has decreased slightly but remains at a high level and has not caused significant impact. Stain resistance: Poor oil stain removal; difficult to clean, and prone to surface dust adhesion.

[0118] Comparative Example 9 (Ordinary PU Protective Film)

[0119] Ordinary PU protective films lack an adhesion enhancement layer and a surface hydrophobic layer, resulting in relatively poor performance parameters, specifically in terms of adhesion, hydrophobicity, stain resistance, and weather resistance.

[0120] Performance parameters: Contact angle: 70-90°; Surface energy: 38-45 mN / m; Adhesion: 4.0-5.5 N / cm; Stain resistance: Due to the lack of a hydrophobic surface layer, its stain resistance is poor. Oil, dust, fingerprints, and other contaminants easily adhere to the membrane surface, making cleaning difficult. The membrane surface is easily contaminated, leading to a decline in optical performance and affecting the user experience.

[0121] Based on the embodiments, comparative examples, and performance comparisons with ordinary PU protective films, this utility model has significant improvements and outstanding advantages, specifically as follows: By adding a surface hydrophobic layer (composed of fluoroalkyl silane and polydimethylsiloxane, etc.) to the PU adhesive layer, the contact angle of the film surface reaches over 100°, significantly improving the hydrophobicity of the film and reducing the adsorption of moisture, oil, and dust. The optimized composition of the surface hydrophobic layer gives the film surface excellent waterproof and stain-resistant properties, avoiding the shortcomings of conventional PU protective films that easily attract fingerprints, oil, and dust.

[0122] The adhesion enhancement layer (using PUA, epoxy resin, APTES, etc.) strengthens the adhesion of the PU adhesive layer and solves the problem of residue left by ordinary PU protective films. The coated adhesion enhancement layer forms a good bond with the PU adhesive layer and the subsequent hydrophobic surface layer, thereby ensuring the stability and workability of the film.

[0123] Chemical modification (such as MPTES) further enhances the adhesion between the membrane surface and the substrate, while maintaining the membrane's tearability and stability.

[0124] This invention effectively improves the weather resistance of the membrane through a dual design of an adhesion enhancement layer and a surface hydrophobic layer, reducing aging, yellowing, and physical degradation under ultraviolet radiation. Treating the surface hydrophobic layer with chemical modifiers such as MPTES not only improves the membrane's chemical stability but also enhances its adaptability to high temperatures, ultraviolet radiation, and environmental changes. Ordinary PU protective films lack an additional protective layer, making them prone to yellowing and aging under ultraviolet radiation, resulting in poor weather resistance and a limited lifespan.

[0125] This invention improves the scratch resistance of the membrane through the design of an adhesion enhancement layer and a surface hydrophobic layer. In particular, the use of epoxy resin and polydimethylsiloxane enhances the hardness and abrasion resistance of the coating, making the membrane more resistant to external scratches and friction, protecting the equipment surface from damage. Ordinary PU protective films have poor scratch resistance; the PU adhesive layer lacks an additional reinforcing coating, making it susceptible to scratches or wear during use, affecting the membrane's appearance and protective effect.

[0126] In summary, this invention employs an innovative composite structure consisting of an adhesion enhancement layer, a hydrophobic surface layer, and chemical modification, overcoming the shortcomings of traditional PU protective films in terms of adhesion and hydrophobicity, thus offering greater flexibility and application possibilities. Through this composite structure, it effectively prevents the adhesion of dust and oil, improving cleanliness, while maintaining the excellent adhesion of the PU adhesive layer. Compared to existing technologies, it exhibits stronger anti-fouling properties and greater operability.

[0127] By comparing the embodiments with the comparative examples, it can be clearly seen that the solution proposed by this utility model has significant advantages in multiple performance indicators, demonstrating its superior performance and broad application potential.

[0128] Those skilled in the art should understand that although the present invention has been described with reference to multiple embodiments, not every embodiment contains only one independent technical solution. This description is provided merely for clarity; those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of the present invention.

[0129] The above description is merely an illustrative embodiment of this utility model and is not intended to limit the scope of this utility model. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this utility model should fall within the protection scope of this utility model.

Claims

1. A PU protective film, comprising a PET substrate layer (1) and a PU adhesive layer (2), characterized in that, The surface of the PU adhesive layer (2) is coated with an adhesion enhancement layer (3), and a surface hydrophobic layer (4) is coated on the surface of the adhesion enhancement layer (3). The thickness of the adhesion enhancement layer (3) is 1-3 μm, and the thickness of the surface hydrophobic layer (4) is 0.5-1 μm.

2. The PU protective film as described in claim 1, characterized in that, The thickness of the PET substrate layer (1) is 50μm-100μm; the thickness of the PU adhesive layer (2) is 25μm-50μm.

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