An antistatic protective film and a method for manufacturing the same

Abstract

The application provides an anti-static protective film, which comprises a substrate, carbon black particles and metal fibers are contained in the substrate, the carbon black particles are uniformly distributed in the substrate and fill the gaps between the metal fibers, the length-diameter ratio L / D of the metal fibers is greater than or equal to 60, the metal fibers are aggregated on the surface of one side of the substrate to form a plurality of small protrusions, so that the surface of one side of the substrate becomes rough, and the surface roughness reaches Ra greater than or equal to 0.5 um; and a tackiness layer is uniformly arranged on the other side of the substrate opposite to the metal fibers. The application also provides a manufacturing method for manufacturing the anti-static film. The application can not only reduce the surface resistance of the protective film, but also solve the adsorption problem of the optical film after lamination.

Description

Technical Field

[0001] This invention relates to the field of optical materials technology, and more specifically, to an antistatic protective film. Background Technology

[0002] Antistatic protective film, used to cover the front and back of, for example, brightness enhancement or diffusion films, to prevent damage during storage and transportation, is a functional thin film used to protect optical films with specific optical structures. Its core functions are antistatic and anti-lamination adsorption.

[0003] Traditional antistatic protective films have the following drawbacks: A traditional antistatic protective film achieves its antistatic effect by applying an antistatic coating, but the surface is easily scratched during secondary processing, causing the antistatic effect to fail. Another traditional method for creating antistatic protective films involves adding antistatic agents and carbon black to achieve the antistatic effect. Antistatic agents include quaternary ammonium compounds, hydroxyethyl alkylamines, alkyl alcoholamine sulfates, polyol fatty acid esters, and their derivatives. The problems are that the antistatic agents are prone to precipitation, resulting in a weak antistatic effect, poor static suppression, and slow static dissipation; the antistatic effect is also unstable, dissipating over time. High addition levels of carbon black (>15wt%) are required, leading to high costs.

[0004] When optical films are stacked, they are difficult to separate due to electrostatic adsorption, and current technology cannot simultaneously solve the problems of electrostatic adsorption and stacking adsorption. The existing method to solve the stacking adsorption problem is to increase the surface roughness of the antistatic protective film by adding an extra process or modifying the die head. The surface roughness of the product produced by this method is not stable, resulting in intermittent adsorption when the films are stacked. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides an antistatic protective film and a method for manufacturing the same.

[0006] The antistatic protective film provided in this application includes a substrate containing carbon black particles and metal fibers. The carbon black particles are uniformly distributed in the substrate and fill the gaps between the metal fibers. The aspect ratio of the metal fibers is L / D > 60. The metal fibers agglomerate on one side of the substrate to form multiple tiny protrusions, making the surface of one side of the substrate rough, with a surface roughness of Ra ≥ 0.5 μm or higher.

[0007] In one embodiment, the metal fiber has a diameter of 0.3 μm to 0.6 μm and a length of 20 μm to 36 μm.

[0008] In one embodiment, the metal fiber content in the substrate is from 1 wt% to 3.5 wt%.

[0009] In one embodiment, the carbon black particles have a particle size of 50 nm to 100 nm and a specific surface area of ​​200 m² / g to 300 m² / g.

[0010] In one embodiment, the carbon black particles in the substrate are present in an amount of 0.3 wt% to 0.8 wt%.

[0011] In one embodiment, the substrate comprises polyethylene and polypropylene materials, wherein the ratio of polyethylene to polypropylene is 7:3.

[0012] In one embodiment, an adhesive layer is uniformly disposed on the side of the substrate opposite to the metal fiber; the adhesive layer is a styrene-ethylene-butene-styrene block copolymer.

[0013] In one embodiment, 1 wt% of maleic anhydride-grafted polyethylene is also added to the substrate.

[0014] In one embodiment, the metal fiber is stainless steel fiber.

[0015] This application also provides a method for manufacturing an antistatic protective film, comprising: preparing a substrate molding material; adding carbon black particles and metal fibers to the substrate molding material and mixing them evenly so that the carbon black particles and metal fibers are uniformly distributed in the substrate molding material; preparing an adhesive layer molding material; and extruding the substrate molding material and the adhesive layer molding material by two-layer co-extrusion and melt extrusion at an extrusion temperature of 190°C. During melt extrusion, a magnetic field of 0.3T-0.8T is applied to cause the fibers to concentrate and arrange on the outer surface of the protective film and form agglomerates, with a surface roughness of Ra≥0.5um or higher.

[0016] Beneficial effects:

[0017] The antistatic protective film provided in this application uses metal fibers with a higher aspect ratio (≥60). Utilizing the agglomeration caused by the excessive length of these fibers, multiple tiny protrusions are formed on the surface of the protective film, making the surface rough to a surface roughness of Ra 0.5 μm or higher. Carbon black fills the gaps between the metal fibers, stabilizing the resistance of the antistatic protective film at 10 ohms. 6 Ω-10 9 Ω can both reduce the surface resistance of the protective film and solve the adsorption problem after the optical film is stacked. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The diagram shown is a schematic diagram of the use of the antistatic protective film provided in the embodiment of this application; Figure 2 The figure shown is a cross-sectional structural diagram of an antistatic protective film provided in an embodiment of this application; Figure 3 The diagram shown is a schematic diagram of the aggregation phenomenon of metal fibers in an embodiment of this application; Figure 4 The image shown is a schematic diagram of the surface roughness structure of the antistatic protective film provided in this application under a microscope. Detailed Implementation

[0020] The embodiments of this application are described in detail below, with examples of the embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. In the description of this application, "a plurality of" means two or more, unless otherwise expressly specified.

[0021] In addition, to simplify the diagrams, some familiar structures and components will be shown in a simple schematic manner.

[0022] It should be noted that all directional indications in the embodiments of this application, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture as shown in the attached figure. If the specific posture changes, the directional indication will also change accordingly.

[0023] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit this application. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application. one

[0024] To protect optical films with specific optical microstructures on their surfaces, such as brightness enhancement films or diffusion films, embodiments of this application provide an antistatic protective film 100. (Reference) Figure 1 As shown, the antistatic protective film 100 covers the upper and lower surfaces of the protected optical film 200 during use to prevent damage to the protected optical film 200 during storage or transportation.

[0025] refer to Figures 2 to 4 As shown, the antistatic protective film 100 provided in this application includes a substrate 10, which contains carbon black particles 20 and metal fibers 30. The carbon black particles 20 are uniformly distributed in the substrate and fill the gaps between the metal fibers 30. The aspect ratio L / D of the metal fibers 30 is ≥60. The metal fibers 30 agglomerate on one side of the surface of the substrate 10 to form multiple tiny protrusions 31, making the surface of one side of the substrate 10 rough, with a surface roughness of Ra ≥0.5 μm or higher.

[0026] In this embodiment, an adhesive layer 40 is uniformly disposed on the opposite side of the substrate 10 and the metal fiber 30. The adhesive layer 40 can cover the upper and lower surfaces of the brightness enhancement film or the diffusion film, with the rough side of the substrate surface exposed. In specific applications, if the antistatic protective film 100 covers the upper and lower surfaces of the brightness enhancement film, the adhesive layer 40 contacts the prism layer of the brightness enhancement film. The surface of the adhesive layer 40 is smooth and soft, and it directly contacts the prism layer of the brightness enhancement film through weak adhesion, without damaging the surface microstructure of the brightness enhancement film. The thickness ratio of the substrate to the adhesive layer is 15:1. The substrate contains carbon black particles 20 and metal fibers 30. The carbon black particles 20 act as conductive fillers, filling the gaps between the metal fibers 30, and working synergistically with the metal fibers to adjust the resistance of the protective film, so that the surface resistance of the antistatic protective film is stabilized at 10 ohms. 6 Ω-10 9 Ω can reduce the electrostatic influence between two adjacent brightening films covered with antistatic protective film; the metal fibers 30 agglomerate on the surface of the antistatic protective film 100 to form multiple micro protrusions, making the outer surface of the substrate rough, reaching a surface roughness of Ra0.5um or higher. When the brightening film or diffusion film is stacked, the multiple micro protrusions of the antistatic protective film covering the surface of the brightening film or diffusion film contact each other, which can prevent adsorption and adhesion.

[0027] In one embodiment, the metal fiber 30 has a diameter of 0.3 μm to 0.6 μm and a length of 20 μm to 36 μm. The formation of the conductive network must satisfy percolation theory. Taking steel fiber as an example, when the aspect ratio L / D ≥ 60, the conductive percolation threshold can be reduced to ≈1.2 wt%. The fiber length is also important; fiber length < 5 μm results in low fiber overlap (resistance > 10¹³ Ω, no antistatic effect in the composite material), while fiber length > 20 μm easily leads to agglomeration. The design parameters and working mechanism of the metal fiber can be found in the table below:

[0028] In one embodiment, the content of metal fiber 30 in the substrate 10 is from 1 wt% to 3.5 wt%. If the content of metal fiber is less than 1 wt%, it will be difficult for agglomeration to form protrusions. If the content of metal fiber exceeds 3.5 wt%, it may cause the antistatic protective film to become brittle. Therefore, it is preferable that the content of metal fiber 30 in the substrate 10 is from 1 wt% to 3.5 wt%.

[0029] In one embodiment, the carbon black particles 20 have a particle size of 50 nm to 100 nm and a specific surface area of ​​200 m² / g to 300 m² / g. Since the total specific surface area of ​​carbon black particles = outer surface area (smooth surface) + inner surface area (pore surface area), a larger specific surface area and a smaller original particle size result in more particles per unit mass or volume, making it easier for them to contact each other and form a network, thus improving conductivity. In other words, using carbon black particles with a specific surface area of ​​200 m² / g to 300 m² / g achieves higher conductivity. It should be noted that if the carbon black particles are too large (e.g., >200 nm) to fill the fiber gaps, the electrostatic dissipation time will be greater than 5 seconds, leading to adsorption and adhesion of the brightening film. Conversely, if the carbon black particles are too small (e.g., <50 nm), they are prone to agglomeration, resulting in the formation of multiple black crystals during extrusion processing, affecting the properties and quality of the brightening film.

[0030] In one embodiment, the carbon black particles 20 contain 0.3 wt% to 0.8 wt% of the substrate 10. If the proportion of carbon black particles 20 is less than 0.3 wt%, the antistatic protective film may not be able to form a network of pathways, resulting in insufficient antistatic performance; if the proportion of carbon black particles 20 exceeds 0.8 wt%, the antistatic protective film may become brittle, reducing its toughness. Therefore, it is preferable that the content of carbon black particles 20 in the substrate 10 is 0.3 wt% to 0.8 wt%.

[0031] In one embodiment, the substrate 10 comprises polyethylene (PE) and polypropylene (PP) materials, wherein the ratio of polyethylene (PE) to polypropylene (PP) is 7:3.

[0032] In one embodiment, the adhesive layer 40 is a styrene-ethylene-butene-styrene block copolymer (SEBS).

[0033] In one embodiment, 1 wt% of maleic anhydride-grafted polyethylene (MAH-g-PE) is also added to the substrate 10. Maleic anhydride-grafted polyethylene improves the toughness of the antistatic protective film; if the content of metal fibers exceeds 3 wt%, it will significantly increase the brittleness of the antistatic protective film. Adding 1 wt% maleic anhydride-grafted polyethylene can improve the toughness of the maleic anhydride-grafted polyethylene and reduce its brittleness.

[0034] In one embodiment, the metal fiber 30 is stainless steel fiber, which has the advantage of being rust-resistant.

[0035] The following four examples further illustrate the substrate composition and dosage of the antistatic protective film of this application.

[0036] Example 1

[0037] Example 2

[0038] Example 3

[0039] Example 4

[0040] The performance comparison of the four examples above is shown in the table below:

[0041] As can be seen from the above comparison, the antistatic protective film provided in this application has a surface resistance that is stable at 10 times the antistatic level (static dissipation) compared to the protective films in the prior art. 6 Ω-10 9 Between Ω, roughness greater than 0.5μm, stacking peel force less than 0.5N / m², and resistance to stacking adsorption. It can be excellent. two

[0042] This application also provides a method for manufacturing an antistatic protective film, including preparing a substrate molding material, adding carbon black particles and metal fibers to the substrate molding material, mixing them evenly so that the carbon black particles and metal fibers are uniformly distributed in the substrate; preparing an adhesive layer molding material; and extruding the substrate molding material and the adhesive layer molding material by two-layer co-extrusion and melt extrusion at an extrusion temperature of 190°C. During melt extrusion, a magnetic field of 0.3T to 0.8T is applied to cause the fibers to concentrate and arrange on the outer surface of the protective film and form agglomerates, with a surface roughness of Ra≥0.5um or higher.

[0043] The antistatic protective film is produced through a two-layer co-extrusion process using a substrate molding material and an adhesive layer molding material. During melt extrusion, a magnetic field of 0.3T to 0.8T is applied to cause the metal fibers to concentrate and align on the outer surface of the antistatic protective film. During extrusion, the metal fibers in the substrate undergo directional aggregation, forming multiple tiny protrusions on the substrate surface, making the surface rough. When multiple layers of brightening films covered with the antistatic protective film are stacked, these protrusions significantly reduce the actual contact area between the films, physically eliminating interlayer adsorption. Simultaneously, these metal fibers interlock within the substrate, constructing conductive pathways. Combined with carbon black particles filling the fiber gaps, a complete conductive network is formed. The synergistic effect of these two processes constitutes a low-carbon-black, high-efficiency permanent conductive network that can stably maintain a surface resistivity of 10 ohms. 6 Ω-10 9 Within the antistatic range of Ω, it rapidly dissipates static charge, thereby achieving the effects of antistatic and anti-adhesion.

[0044] The following four examples further illustrate the manufacturing method of the antistatic protective film of this application.

[0045] Example 1 The preparation process of the protective film in this example is as follows: S1: Preparation of substrate molding material. The substrate molding material can be a mixture of PE and PP adhesive, with a PE:PP (polypropylene) mixing ratio of 7:3; S2: Add carbon black particles and stainless steel fibers to the substrate molding material and mix evenly. In specific applications, the stainless steel fibers account for 1.0 wt% and the carbon black particles account for 0.8 wt% after mixing. The substrate molding material accounts for 98.2 wt%. The stainless steel fibers have a diameter of 0.4 μm, a length of 24 μm, and an aspect ratio of L / D=60; the specific surface area of ​​the conductive carbon black is 254 m² / g. S3: Preparation of adhesive layer molding material; the adhesive layer molding material is a styrene-ethylene-butene-styrene block copolymer; S4: The extruded material is melt-extruded using a co-extrusion extruder, and a 0.5T magnetic field is applied simultaneously. In this specific application, a two-layer co-extrusion melt extrusion method is used to extrude the substrate molding material and the adhesive layer molding material. The flow ratio of the two layers is 15:1, and the extrusion temperature is 190℃. The substrate molding material contains stainless steel fibers and carbon black particles, while the adhesive layer does not contain stainless steel fibers and conductive carbon black. S5: An antistatic protective film is obtained after cooling.

[0046] Example 2: The preparation process of the protective film in this example is as follows: S1: Prepare substrate molding material, the substrate molding material is PET (polyethylene terephthalate). S2: Carbon black particles and metal fibers are added to the substrate molding material and mixed evenly. In specific applications, the mixed material contains 1.8 wt% stainless steel fiber and 0.5 wt% carbon black particles. The substrate molding material accounts for 97.7 wt%. The stainless steel fiber is 30 μm long, 0.4 μm in diameter, and has an aspect ratio of 75. The specific surface area of ​​the conductive carbon black is 254 m² / g. S3: Preparation of adhesive layer molding material; the adhesive layer molding material is a styrene-ethylene-butene-styrene block copolymer; S4: The extruded material is melt-extruded using a co-extrusion extruder, and a 0.5T magnetic field is applied simultaneously. In this specific application, a two-layer co-extrusion melt extrusion method is used to extrude the substrate molding material and the adhesive layer molding material. The flow ratio of the two layers is 15:1, and the extrusion temperature is 190℃. The substrate molding material contains stainless steel fibers and carbon black particles, while the adhesive layer does not contain stainless steel fibers and conductive carbon black. S4: An antistatic protective film is obtained after cooling.

[0047] Example 3: The preparation process of the protective film in this example is as follows: S1: Prepare the substrate molding material, which is a mixture of PE and PP adhesive, with a mixing ratio of PE (polyethylene) to PP (polypropylene) of 7:3. S2: Add carbon black particles, metal fibers, and maleic anhydride-grafted polyethylene (MAH-g-PE) to the substrate molding material and mix thoroughly. In specific applications, the mixed material comprises 3.0 wt% stainless steel fibers and 0.3 wt% carbon black particles. The substrate molding material comprises 95.7 wt%, and the maleic anhydride-grafted polyethylene (MAH-g-PE) comprises 1 wt%. The stainless steel fibers have a diameter of 0.4 μm, a length of 30 μm, and an aspect ratio of L / D = 75. The specific surface area of ​​the conductive carbon black is 254 m² / g. S3: Preparation of adhesive layer molding material; the adhesive layer molding material is a styrene-ethylene-butene-styrene block copolymer; S4: The extruded material is melt-extruded using a co-extrusion extruder, and a 0.5T magnetic field is applied simultaneously. In this specific application, a two-layer co-extrusion melt extrusion method is used to extrude the substrate molding material and the adhesive layer molding material. The flow ratio of the two layers is 15:1, and the extrusion temperature is 190℃. The substrate molding material contains stainless steel fibers and carbon black particles, while the adhesive layer does not contain stainless steel fibers and conductive carbon black. S4: An antistatic protective film is obtained after cooling.

[0048] Example 4: The preparation process of the protective film in this example is as follows: S1: Prepare the substrate molding material, which is a mixture of PE and PP adhesive, with a mixing ratio of PE (polyethylene) to PP (polypropylene) of 7:3. S2: Carbon black particles, metal fibers, and maleic anhydride-grafted polyethylene (MAH-g-PE) are added to the substrate molding material and mixed evenly. In specific applications, the mixed material contains 3.0 wt% stainless steel fibers and 0.1 wt% carbon black particles. The substrate molding material accounts for 95.9 wt%, and maleic anhydride-grafted polyethylene (MAH-g-PE) accounts for 1.0 wt%. Among the stainless steel fibers, those with an aspect ratio greater than 60 account for 2.0 wt%, and those with an aspect ratio less than 60 but greater than 30 account for 1.0 wt%. The specific surface area of ​​the conductive carbon black is 254 m² / g. S3: Preparation of adhesive layer molding material; the adhesive layer molding material is a styrene-ethylene-butene-styrene block copolymer; S4: The extruded material is melt-extruded using a co-extrusion extruder, and a 0.5T magnetic field is applied simultaneously. In this specific application, a two-layer co-extrusion melt extrusion method is used to extrude the substrate molding material and the adhesive layer molding material. The flow ratio of the two layers is 15:1, and the extrusion temperature is 190℃. The substrate molding material contains stainless steel fibers and carbon black particles, while the adhesive layer does not contain stainless steel fibers and conductive carbon black. S5: An antistatic protective film is obtained after cooling.

[0049] Performance tests were conducted on the antistatic protective films manufactured in Examples 1 to 4, as well as existing conventional protective films. Performance tests included surface resistance, roughness, and stacking adhesion tests. The stacking adhesion test involved stacking 200 A4-sized brightening films, each covered on both sides with the protective film, on a platform. After 24 hours and 48 hours, a suction cup robot was used to pick up the films one by one from above, observing whether the next film was picked up during the process. The films were then placed aside, and the number of films picked up during the entire stack was recorded and the average value was calculated. Static electricity was also tested, and the static electricity values ​​were recorded and the average value was calculated. The test results are shown in the table below:

[0050] The above comparison shows that the surface static electricity of the antistatic protective film provided in this application is much smaller than that of the protective film in the prior art, and the antistatic effect is significant. After the stacking and placement test, no film was lifted by the antistatic protective film provided in this application, which has excellent anti-stack adsorption performance compared with the protective film in the prior art.

[0051] The above specific embodiments have provided a detailed description of the technical solutions of this application. It should be understood that the application of this application is not limited to the examples described above. For those skilled in the art, improvements or modifications can be made based on the embodiments provided in this application and the above description, which is obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of this application fall within the scope of protection of the appended claims.

Claims

1. An antistatic protective film, characterized in that: The substrate includes carbon black particles and metal fibers. The carbon black particles are uniformly distributed within the substrate and fill the gaps between the metal fibers. The aspect ratio of the metal fibers is L / D≥60. The metal fibers agglomerate on one side of the substrate to form multiple tiny protrusions, making the surface of one side of the substrate rough, with a surface roughness of Ra≥0.5um or higher.

2. The antistatic protective film as described in claim 1, characterized in that: The metal fibers have a diameter of 0.3 μm to 0.6 μm and a length of 20 μm to 36 μm.

3. The antistatic protective film as described in claim 1, characterized in that: The metal fiber content in the substrate is from 1 wt% to 3.5 wt%.

4. The antistatic protective film as described in claim 1, characterized in that: The carbon black particles have a particle size of 50 nm to 100 nm and a specific surface area of ​​200 m² / g to 300 m² / g.

5. The antistatic protective film as described in claim 1, characterized in that: The carbon black particles in the substrate are present in an amount of 0.3 wt% to 0.8 wt%.

6. The antistatic protective film as described in claim 1, characterized in that: The substrate comprises polyethylene and polypropylene materials, wherein the ratio of polyethylene to polypropylene is 7:

3.

7. The antistatic protective film as described in claim 1, characterized in that: An adhesive layer is uniformly disposed on the side of the substrate opposite to the metal fiber, and the adhesive layer is a styrene-ethylene-butene-styrene block copolymer.

8. The antistatic protective film as described in claim 1, characterized in that: The substrate also contains 1 wt% maleic anhydride-grafted polyethylene.

9. The antistatic protective film as described in claim 1, characterized in that: The metal fiber is stainless steel fiber.

10. A method for manufacturing an antistatic protective film, characterized in that: A substrate molding material is prepared by adding carbon black particles and metal fibers to the substrate molding material and mixing them evenly to ensure that the carbon black particles and metal fibers are uniformly distributed in the substrate molding material. A bonding layer molding material is prepared. The substrate molding material and the bonding layer molding material are extruded by two-layer co-extrusion and melt extrusion at an extrusion temperature of 190°C. During melt extrusion, a magnetic field of 0.3T-0.8T is applied to cause the fibers to concentrate and arrange on the outer surface of the antistatic protective film and form agglomerates, with a surface roughness of Ra≥0.5um or higher.

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