Magnesium fluoride modified hollow glass bead and polaroid

Abstract

The invention belongs to the field of polaroids, and particularly relates to a magnesium fluoride modified hollow glass bead and a polaroid. The magnesium fluoride modified hollow glass bead comprises a hollow glass bead matrix, a magnesium fluoride coarse structure is compounded on the surface of the hollow glass bead matrix, and the magnesium fluoride coarse structure is magnesium fluoride particles densely distributed on the hollow glass bead matrix. According to the polaroid manufactured by using the functional coating of the magnesium fluoride modified hollow glass beads, the functions of fingerprint prevention, high wear resistance, high light transmission and light weight can be realized by using a single coating, and the comprehensive performance is excellent.

Description

Technical Field

[0001] This invention belongs to the field of polarizers, specifically relating to a magnesium fluoride modified hollow glass microsphere and a polarizer. Background Technology

[0002] Polarizing films (POLs) are an important component of display modules and play an irreplaceable role in LCD and OLED optical displays. By selectively guiding light that vibrates in a specific direction, polarizing films reduce or eliminate reflection and scattering, thereby improving image clarity and contrast.

[0003] The basic structure of a polarizer generally includes, from bottom to top, a release film, a PSA (pressure-sensitive adhesive) layer, a first TAC (cellulose triacetate) layer, a PVA (polyvinyl alcohol) layer, a second TAC layer, and a functional layer. As people's demand for consumer electronics continues to increase, different functional layers have emerged, such as anti-fingerprint functional layers and high wear-resistant functional layers.

[0004] For example, Chinese invention patent application CN116386495A, with a publication date of July 4, 2023, discloses a display device including a display panel configured to display an image; a polarizing plate disposed on the display panel; a first film disposed on the polarizing plate; a liquid crystal layer disposed on the first film; and a second film disposed on the liquid crystal layer. On the second film, functional layers such as wear-resistant, anti-pollution, UV-blocking, anti-fingerprint, and anti-glare are also disposed.

[0005] For abrasion-resistant POLs, a hard coating is typically used, such as a high-hardness acrylic polymer coating, to enhance surface abrasion resistance. The hardness of this type of hard coating is generally 3H-4H. For fingerprint-resistant POLs, a fluoropolymer layer is usually formed by surface coating. The low surface energy of fluorine materials achieves hydrophobic and oleophobic properties. However, fluoropolymers are generally more expensive and are difficult to bond chemically with inorganic substrates, making them prone to peeling off.

[0006] The aforementioned multiple functional coatings are generally achieved by stacking corresponding numbers of functional coatings, which is not only complex in process but also causes drawbacks such as light loss and heavy weight. As people pay more attention to the lightweight and multifunctionality of touch screens, there is an urgent need for a high-performance polarizer that integrates various functions while being lightweight. Summary of the Invention

[0007] The purpose of this invention is to provide magnesium fluoride modified hollow glass microspheres, which can be used as functional fillers to make cured coatings that have anti-fingerprint, high wear resistance, high light transmittance and lightweight functions, and can be applied to polarizers to improve their performance.

[0008] The second objective of this invention is to provide a polarizer that solves the problem that existing polarizers require a corresponding number of coatings to achieve fingerprint resistance and high wear resistance, which has an adverse effect on light transmittance and lightweight.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A magnesium fluoride-modified hollow glass microsphere includes a hollow glass microsphere matrix, wherein a magnesium fluoride rough structure is composited on the surface of the hollow glass microsphere matrix, and the magnesium fluoride rough structure consists of magnesium fluoride particles densely distributed on the hollow glass microsphere matrix.

[0010] This invention is pioneering. It modifies the surface of hollow glass microspheres using a roughened magnesium fluoride structure. Due to the strong electronegativity of fluoride ions, the magnesium fluoride surface is less prone to forming hydrogen bonds with water molecules or oil, thus exhibiting good hydrophobic and oleophobic properties. Simultaneously, the roughened structure formed by magnesium fluoride on the microsphere surface endows the microspheres with excellent dual-repellent properties. The lightweight nature of the hollow glass microspheres, when mixed with resin, effectively reduces the weight of the coating, achieving a lightweight design. At the same time, the high strength of the microspheres imparts excellent strength to the polarizer, exhibiting superior wear resistance and a hardness of 5-6H, a significant improvement compared to the 3-4H hardness of a single acrylic resin-cured coating.

[0011] Furthermore, the refractive index of magnesium fluoride, n≈1.38, falls between that of air (n≈1) and glass (n≈1.5). This structure creates a phase difference in reflected light, resulting in reduced reflected light and enhanced transmitted light, thus maximizing the brightness of the touchscreen display. Compared to a single hardened resin coating, the addition of the fluorinated microspheres of this invention results in less light loss, and the polarizer transmittance can reach 55%.

[0012] By adding the aforementioned magnesium fluoride-modified hollow glass microspheres to conventional resins, fingerprint resistance, high wear resistance, high light transmittance, and lightweight properties can be achieved with a single coating, thereby improving the performance of polarizers.

[0013] The aforementioned magnesium fluoride-modified hollow glass microspheres utilize inorganic fluorides to modify the hollow glass microspheres, which is lower in cost compared to commonly used fluoropolymers. Furthermore, inorganic fluorides are non-volatile, making them healthier and more in line with international environmental standards compared to the volatile nature of organic fluorides.

[0014] Preferably, the preparation method of the magnesium fluoride modified hollow glass microspheres includes the following steps: (1) surface treatment of the hollow glass microspheres using a mixed solution of NaF and acetic acid to obtain surface-treated microspheres; (2) using Mg 2+ F - The reaction occurs on the surface-treated microspheres, generating magnesium fluoride particles on the surface of the hollow glass microspheres.

[0015] More preferably, in step (2), Mg2+ F - The molar ratio is 1:(4~6); each 20g of hollow glass microspheres corresponds to the use of 0.03~0.06mol Mg. 2+ .

[0016] More preferably, in step (2), the surface-treated microbeads are mixed with a soluble magnesium salt solution with a concentration of 10-15 wt%, and then a NaF solution with a concentration of 25-35 wt% is added to carry out the reaction; the mass ratio of the surface-treated microbeads, the soluble magnesium salt solution, and the NaF solution is 20:(25-30):(25-30).

[0017] More preferably, the reaction includes stirring at room temperature for 20-30 minutes, followed by heating to 60-70°C and reacting for 1.5-2 hours.

[0018] More preferably, in the mixed solution of step (1), the mass fraction of NaF is 0.5~0.7% and the mass fraction of acetic acid is 0.5~0.7%.

[0019] More preferably, the surface treatment in step (1) includes stirring and mixing the hollow glass microspheres and the mixed solution at room temperature for 15 to 30 minutes.

[0020] A polarizer includes an anti-fingerprint and wear-resistant multifunctional coating, wherein the anti-fingerprint and wear-resistant multifunctional coating comprises a matrix resin and the aforementioned magnesium fluoride modified hollow glass microspheres distributed in the matrix resin.

[0021] The polarizer of the present invention uses a single cured coating layer to simultaneously achieve functions such as fingerprint resistance, high wear resistance, and high light transmittance. Compared with existing multi-functional coating strategies, it can simplify the process and avoid adverse effects on light transmittance and lightweight.

[0022] Preferably, the matrix resin is selected from one of acrylic resin, epoxy resin, and silicone resin.

[0023] Preferably, the polarizer uses a TAC / PVA / TAC sandwich structure, and the anti-fingerprint and wear-resistant multifunctional coating is laminated on the TAC layer. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of an existing polarizer; Figure 2 This is a schematic diagram of the polarizer structure in Example 4; Figure 3 This is a SEM image of magnesium fluoride modified hollow glass microspheres from Example 1 of the present invention. Figure 4 This is an EDS characterization image of magnesium fluoride modified hollow glass microspheres in Example 1 of the present invention; Figure 5 The results of the water droplet angle test for the polarizer in Comparative Example 1 are shown. Figure 6 The results of the water droplet angle test for the polarizer in Embodiment 4 of the present invention are shown. Detailed Implementation

[0025] (I) Preferred embodiment of the magnesium fluoride modified hollow glass microspheres of the present invention This invention achieves fluorine modification of hollow glass microspheres by forming a rough magnesium fluoride structure on the surface of the microspheres, resulting in fluorinated microspheres with hydrophobic and oleophobic properties. The innovative application of these fluorinated microspheres to a cured coating imparts higher hardness and hydrophobicity, which is highly beneficial for improving the coating's wear resistance and fingerprint resistance. Using this coating as a functional coating for polarizers allows for a balance of high wear resistance, fingerprint resistance, and lightweight design while maintaining higher light transmittance.

[0026] The structural feature of the aforementioned magnesium fluoride modified hollow glass microspheres is that a rough magnesium fluoride structure is composited on the surface of the hollow glass microspheres. This rough magnesium fluoride structure consists of numerous magnesium fluoride particles distributed like pockmarks on the surface of the hollow glass microspheres, which changes the original smooth surface of the hollow glass microspheres and endows the microspheres with new properties.

[0027] The above-mentioned magnesium fluoride modified hollow glass microspheres are prepared by the following steps: (1) Hollow glass microspheres were surface-treated using a mixed solution of NaF and acetic acid to obtain surface-treated microspheres.

[0028] A mixed solution of NaF and acetic acid can remove impurities and roughen the surface of hollow glass microspheres. NaF... - It can react with the SiO2 of hollow glass microspheres to generate water-soluble hexafluorosilicic acid, achieving the purpose of etching and roughening. Alternatively, treating the microspheres with a mixed solution of NaF and acetic acid will release H₂ due to the organic acid. + It is gentler and free of the harshness of HCl, resulting in more uniform etching of the microbeads. This avoids making the surface of the microbeads too rough or etched through, which helps to reduce the breakage rate and maintain the compressive strength of the microbeads.

[0029] Surface treatment can create pits, which facilitates the formation of magnesium fluoride that is firmly bonded to the surface of hollow glass microspheres and avoids the formation of excessively large agglomerated particles.

[0030] The NaF and acetic acid mixed solution, with both NaF and acetic acid having a mass fraction of 0.5-0.7%, is stirred and mixed with hollow glass microspheres for 15-30 minutes to achieve the desired treatment effect.

[0031] During mixing, the mass ratio of hollow glass microspheres, NaF, and acetic acid solution can be controlled at 1:(3~5). After mixing for the set time, filter out the hollow glass microspheres, wash them repeatedly with water until the pH of the washing solution is 7, and finally dry the washed hollow glass microspheres. Drying should be performed under vacuum at 90~110℃ for 2~3 hours.

[0032] (2) Utilizing Mg 2+ F - The reaction occurs on the surface-treated microspheres, generating magnesium fluoride particles on the surface of the hollow glass microspheres.

[0033] This step utilizes liquid-phase precipitation to deposit magnesium fluoride particles on the surface of the microbeads that have undergone surface treatment in step (1).

[0034] Surface-treated microspheres and a 10-15 wt% soluble magnesium salt solution can be mixed, and then a 25-35 wt% NaF solution can be added to carry out the reaction; the mass ratio of surface-treated microspheres, soluble magnesium salt solution, and NaF solution is 20:(25-30):(25-30). This method can quickly achieve homogenization of the two solutions and is beneficial for generating fine-sized magnesium fluoride particles. From a cost perspective, MgCl2 is preferred as the soluble magnesium salt.

[0035] The reaction is preferably carried out by stirring at room temperature for 20-30 minutes, followed by heating to 60-70°C and reacting for 1.5-2 hours.

[0036] After the reaction, filter out the precipitate, wash it repeatedly with water until the pH of the washing solution is 7, and finally dry it. Drying should be carried out under vacuum at 90-110℃ for 2-3 hours.

[0037] The preferred embodiments are illustrated below with reference to specific examples. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available conventional products, and the methods involved are all conventional techniques in the art.

[0038] Example 1 The magnesium fluoride modified hollow glass microspheres of this embodiment include a hollow glass microsphere matrix, on the surface of which is a magnesium fluoride rough structure, which consists of magnesium fluoride particles densely distributed on the hollow glass microsphere matrix.

[0039] The manufacturing process of the magnesium fluoride modified hollow glass microspheres is as follows: (1) Surface treatment of hollow glass microspheres Add 20g of hollow glass microspheres to a 500mL glass beaker, then add 60g of a prepared mixed solution of NaF and acetic acid, where the mass of NaF and acetic acid is 0.4g each. Stir at room temperature for 30min, filter to remove the hollow glass microspheres, and wash them 5 times with deionized water until the pH of the washing solution is around 7. Then, vacuum dry the obtained hollow glass microspheres at 100℃ for 2 hours.

[0040] (2) Preparation of fluorine-containing microbeads Add 20g of hollow glass microspheres to a 500mL glass beaker, then add 30g of a 15% MgCl2 aqueous solution and 30g of a 30% NaF aqueous solution. Stir at room temperature for 30min, then heat in a water bath at 60℃ for 1.5h. Wash with deionized water 5 times until the pH of the washing solution is around 7. Then vacuum dry the obtained hollow glass microspheres at 100℃ for 2h.

[0041] Example 2 The magnesium fluoride-modified hollow glass microspheres in this embodiment have the same structure as those in Example 1. The specific manufacturing process is as follows: (1) Surface treatment of hollow glass microspheres Add 20g of hollow glass microspheres to a 500mL glass beaker, then add 60g of a prepared mixed solution of NaF and acetic acid, where the mass of NaF and acetic acid is 0.4g each. Stir at room temperature for 30min, filter to remove the hollow glass microspheres, and wash them 5 times with deionized water until the pH of the washing solution is around 7. Then, vacuum dry the obtained hollow glass microspheres at 100℃ for 2 hours.

[0042] (2) Preparation of fluorine-containing microbeads Add 20g of hollow glass microspheres to a 500mL glass beaker, then add 30g of a 10% MgCl2 aqueous solution and 30g of a 25% NaF aqueous solution. Stir at room temperature for 30min, then heat in a water bath at 70℃ for 2h. Wash with deionized water 5 times until the pH of the washing solution is around 7. Then vacuum dry the obtained hollow glass microspheres at 100℃ for 2h.

[0043] This process, while maintaining the same degree of microbead coarsening as in Example 1, utilizes Mg... 2+ F - The concentration is low, and the coating is uneven and not dense.

[0044] Example 3 The magnesium fluoride-modified hollow glass microspheres in this embodiment have the same structure as those in Example 1. The specific manufacturing process is as follows: (1) Surface treatment of hollow glass microspheres Add 20g of hollow glass microspheres to a 500mL glass beaker, then add 60g of a prepared mixed solution of NaF and acetic acid, where the mass of NaF and acetic acid is 0.3g each. Stir at room temperature for 30min, filter to remove the hollow glass microspheres, and wash them 5 times with deionized water until the pH of the washing solution is around 7. Then, vacuum dry the obtained hollow glass microspheres at 100℃ for 2 hours.

[0045] (2) Preparation of fluorine-containing microbeads In a 500mL glass beaker, add 20g of hollow glass microspheres, then add 30g of a 10% MgCl2 aqueous solution and 30g of a 25% NaF aqueous solution. Stir at room temperature for 30min, then heat in a water bath at 60℃ for 1.5h. Wash with deionized water 5 times until the pH of the washing solution is around 7. Then vacuum dry the obtained hollow glass microspheres at 100℃ for 2h.

[0046] This process aims to minimize the loss of microbead strength by reducing the mass fraction of NaF and acetic acid. However, due to the reduction in pit sites, similar to Example 2, the coating is less and less uniform.

[0047] (II) Description of Preferred Embodiments of Polarizing Films This invention only modifies the application method of existing functional coatings such as anti-fingerprint coatings and wear-resistant coatings on polarizers, and therefore will not affect existing polarizer production lines. The functional coating can be prepared by using a resin slurry containing the aforementioned magnesium fluoride-modified hollow glass microspheres and applying it according to a specific coating method.

[0048] The resin can be selected from conventional resins such as acrylic resin, epoxy resin, and silicone resin. It is mixed with the above-mentioned magnesium fluoride modified hollow glass microspheres to prepare a resin slurry. Then, a cured coating can be formed on the substrate using ultraviolet (UV) curing film-forming technology or thermosetting film-forming technology.

[0049] The acrylic resin can be a commercially available high-abrasion-resistant polyurethane acrylate resin, such as Allnex's Ebecryl® series resins, including but not limited to Ebecryl® 2100, 2300, and 2700. The acrylic resin and magnesium fluoride-modified hollow glass microspheres are mixed uniformly at a mass ratio of 1:0.15-0.25, followed by UV curing to form a film. The UV curing process can refer to recommended requirements, such as a UV lamp power of 110W / cm (for mercury lamps), an irradiation distance of 10-20cm, a conveyor belt speed of 0.5cm / s, and a functional coating thickness generally controlled at 3-20µm.

[0050] Example 4 The polarizer in this embodiment has the following structural schematic diagram: Figure 2 As shown, the structure includes, from bottom to top, a release film, a PSA layer, a first TAC layer, a PVA layer, a second TAC layer, a functional coating, and a protective film. The functional coating consists of a base resin and magnesium fluoride-modified hollow glass microspheres dispersed in the base resin (Example 1). The protective film is made of PET material (polyethylene terephthalate).

[0051] The following explains the manufacturing method of functional coatings: The polyurethane acrylic resin and magnesium fluoride modified hollow glass microspheres from Example 1 were mixed evenly at a mass ratio of 1:0.2. The mixture was then cured with ultraviolet (UV) light to form a film. The functional coating was then applied to the surface of the second TAC layer using a coating process, with the thickness controlled to be 10 μm.

[0052] (III) Comparative Example Comparative Example 1 The polarizer in this comparative example has the following structure: Figure 1 As shown, it includes, from bottom to top, a release film, a PSA layer, a first TAC layer, a PVA layer, a second TAC layer, an HC layer (hardening layer), an AF resin layer, and a protective film.

[0053] The HC layer (hardening layer) is made of polyurethane acrylic resin (same as in Example 1), with a thickness of 3-20 μm. In this example, the thickness is 10 μm, the same as in Example 4. The AF resin layer is made of fluorinated acrylate resin, with a thickness of 5-20 nm. In this example, the thickness is set to 10 nm. The protective film is made of PET material (polyethylene terephthalate).

[0054] (iv) Experimental Examples Experimental Example 1 SEM analysis was performed on the magnesium fluoride-modified hollow glass microspheres obtained in Example 1, and the results are as follows: Figure 3 As shown.

[0055] Depend on Figure 3 It can be seen that a large number of magnesium fluoride particles are densely distributed on the surface of hollow glass microspheres. The size of the magnesium fluoride particles is in the range of (90-110) nm. The particle size distribution of magnesium fluoride particles is uniform and there is basically no agglomeration.

[0056] The magnesium fluoride-modified hollow glass microspheres obtained in Example 1 were characterized by EDS mapping, and the results are as follows: Figure 4 As shown, the substance generated on the surface of the hollow glass microspheres is magnesium fluoride particles.

[0057] Experiment Example 2 The test methods for water droplet angle, hardness, and monomer transmittance of the functional coatings in the examples and comparative examples are described below: The water droplet angle is measured using a contact angle meter. A camera is used to record the shape of the droplet on the surface and to measure the angle between the droplet and the contact line on the surface. If the droplet forms a large contact angle (usually greater than 90 degrees) on the surface, it indicates that the material surface is hydrophobic.

[0058] Hardness was tested using a pencil hardness tester, with pencils of different hardnesses ranging from 1H to 6H. The test samples were observed for scratches. For example, no scratches were found on the surface when using a 2H pencil, no scratches were found when using a 3H pencil, but scratches were found when using a 4H pencil. Therefore, the hardness grade of the coating on the test piece was 3H.

[0059] The transmittance of monomers was measured using a UV-Vis spectrophotometer with a wavelength range of 380nm-780nm.

[0060] The water droplet angle of the AF resin layer of the polarizer in Comparative Example 1 is 101°, such as Figure 5 As shown. The water droplet angle of the functional coating of the polarizer in Example 4 is 112°, as... Figure 6 As shown, the polarizer in Example 4 has a larger water droplet angle than that in Comparative Example 1, indicating better anti-fouling ability and superior fingerprint resistance.

[0061] The pencil hardness of the AF resin layer of the polarizer in Comparative Example 1 is 3H, while the pencil hardness of the functional coating of the polarizer in Example 4 is 5H. The higher hardness of the functional coating in Example 4 indicates better abrasion resistance.

[0062] The polarizer in Comparative Example 1, with its "HC layer + AF resin layer," increases the overall thickness and weight of the polarizer, making it less suitable for lightweight display module design, and its single-cell transmittance is 46%. The functional coating in Example 4 has a single-cell transmittance of 54%, with less light loss and higher single-cell transmittance.

[0063] Based on the above experiments, it can be seen that the polarizer produced by this method has higher hardness, better fingerprint resistance, higher single-cell transmittance, thinner overall design, and lighter weight compared to the existing design, demonstrating excellent overall performance.

[0064] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnesium fluoride-modified hollow glass microsphere, characterized in that, It includes a hollow glass microsphere matrix, on the surface of which is a magnesium fluoride rough structure, which consists of magnesium fluoride particles densely distributed on the hollow glass microsphere matrix.

2. The magnesium fluoride-modified hollow glass microspheres as described in claim 1, characterized in that, The preparation method of the magnesium fluoride modified hollow glass microspheres includes the following steps: (1) Hollow glass microspheres were surface-treated with a mixed solution of NaF and acetic acid to obtain surface-treated microspheres; (2) Utilizing Mg 2+ F - The reaction occurs on the surface-treated microspheres, generating magnesium fluoride particles on the surface of the hollow glass microspheres.

3. The magnesium fluoride-modified hollow glass microspheres as described in claim 2, characterized in that, In step (2), Mg 2+ F - The molar ratio is 1:(4~6); each 20g of hollow glass microspheres corresponds to the use of 0.03~0.06mol Mg. 2+ .

4. The magnesium fluoride modified hollow glass microspheres as described in claim 2, characterized in that, In step (2), the surface-treated microbeads are mixed with a soluble magnesium salt solution with a concentration of 10-15 wt%, and then a NaF solution with a concentration of 25-35 wt% is added to carry out the reaction; the mass ratio of the surface-treated microbeads, the soluble magnesium salt solution, and the NaF solution is 20:(25-30):(25-30).

5. The magnesium fluoride modified hollow glass microspheres as described in claim 2 or 4, characterized in that, The reaction consists of stirring at room temperature for 20-30 minutes, followed by heating to 60-70°C and reacting for 1.5-2 hours.

6. The magnesium fluoride-modified hollow glass microspheres as described in claim 2, characterized in that, In the mixed solution described in step (1), the mass fraction of NaF is 0.5~0.7% and the mass fraction of acetic acid is 0.5~0.7%.

7. The magnesium fluoride-modified hollow glass microspheres as described in claim 6, characterized in that, The surface treatment in step (1) includes stirring and mixing the hollow glass microspheres and the mixed solution at room temperature for 15-30 minutes.

8. A polarizer, characterized in that, The coating includes a fingerprint-resistant and wear-resistant multifunctional coating, which comprises a matrix resin and magnesium fluoride modified hollow glass microspheres as described in claim 1 distributed in the matrix resin.

9. The polarizer as described in claim 8, characterized in that, The matrix resin is selected from one of acrylic resin, epoxy resin, and silicone resin.

10. The polarizer as described in claim 8 or 9, characterized in that, The polarizer uses a TAC / PVA / TAC sandwich structure, and the anti-fingerprint and wear-resistant multifunctional coating is laminated on the TAC layer.

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