PVA optical film casting solution with excellent stripping performance and evaluation method thereof
By using a mixture of surfactants and specific evaluation methods in the PVA optical film casting solution, the problems of poor peel performance and low evaluation efficiency of the casting solution were solved, achieving efficient and accurate peel performance evaluation and excellent film quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI WANWEI ADVANCED FUNCTIONAL MEMBRANE MATERIALS RES INST CO LTD
- Filing Date
- 2026-01-15
- Publication Date
- 2026-04-21
AI Technical Summary
In the existing technology, the poor peeling performance of the casting solution during the production of PVA optical films leads to defects such as mottled spots and diagonal lines on the film surface, and the peeling performance evaluation method is inefficient and has large errors.
By using a mixture of surfactants, including nonionic and anionic surfactants, along with polyvinyl alcohol, solvents, and plasticizers, and through specific evaluation methods simulating film-roller peeling conditions, the peeling performance of the casting solution is quantitatively evaluated.
It significantly improves the peeling properties of the casting solution, avoids film surface defects, improves the efficiency and accuracy of the evaluation method, and ensures the high transparency and mechanical properties of the film.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polarizer technology, and in particular to a PVA optical film casting solution with excellent peeling performance and its evaluation method. Background Technology
[0002] Polyvinyl alcohol (PVA) optical films are widely used in high-end display applications due to their superior properties such as high transparency and high elongation. The production of PVA optical films primarily employs a casting process, where a casting solution is extruded through an extruder and die, forming a liquid film on the surface of a casting roller. This film is then drawn and dried by a drying roller to gradually form a uniform PVA film, which is finally heat-treated to create the final product. During this process, the peeling effect of the casting solution from the casting roller directly determines the stability of film production and the optical properties of the final film.
[0003] Typically, if the peeling performance of the casting solution is poor, PVA film surfaces are prone to developing spots, diagonal lines, and other random linear defects, severely affecting film quality and thickness uniformity. Currently, the main methods for improving the peeling performance of casting solutions in production lines include improving surfactant formulations and spraying hydrophobic coatings onto the surfaces of casting rolls and drying rolls. In terms of surfactant formulation design, methods such as increasing the content of nonionic surfactants or utilizing the structural characteristics of surfactants (e.g., functional groups, chain length, branching) and electronic effects are commonly used to improve peeling performance.
[0004] Given the varying effects of different types and ratios of mixed surfactant systems on the peel performance of casting solutions, establishing efficient and accurate evaluation methods is crucial. Common peel evaluation methods mainly include observation and peel force measurement. Observation involves directly observing the peeling phenomenon of the casting solution between the casting roll and the drying roll, providing reliable results but with low efficiency. Peel force measurement measures the force required to peel the film from the substrate of the coating machine using a tensile tester. This method has large testing errors, and because the peel force value is usually small, it is difficult to distinguish the performance differences between different formulations.
[0005] To address the aforementioned issues, this patent provides a PVA casting solution with excellent peeling performance. Furthermore, it proposes a peeling performance evaluation method that combines high efficiency and accuracy to address the difficulty in evaluating peeling performance. Summary of the Invention
[0006] This invention provides a PVA optical film casting solution with excellent peeling performance and its evaluation method, which can solve the problems of defects such as film surface spots and diagonal lines caused by poor peeling performance of casting solution in the production process of PVA film in the prior art, as well as the problems of low efficiency and large error in peeling evaluation methods.
[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a PVA optical film casting solution with excellent peeling performance, comprising polyvinyl alcohol, solvent, plasticizer and surfactant; wherein the surfactant is a mixed surfactant, comprising at least one nonionic surfactant and at least one anionic surfactant.
[0008] Furthermore, the degree of polymerization of the polyvinyl alcohol is 1200-4000, and the degree of hydrolysis is 88%-99.99%.
[0009] Furthermore, the solvent is any one of deionized water, dimethyl sulfoxide, and methanol, preferably deionized water.
[0010] Furthermore, the plasticizer is one or more of ethylene glycol, propylene glycol, glycerol, and polyglycerol.
[0011] Furthermore, the content of the plasticizer is 8% to 15% of the mass of polyvinyl alcohol.
[0012] Furthermore, the nonionic surfactant includes one or more of the following: isotridecyl alcohol polyoxyethylene ether, ethylene oxide-propylene oxide block polyether, dodecyl polyoxyethylene ether, isooctanol polyoxyethylene ether, octadecylamine polyoxyethylene ether, triethylamine oleate, monoethanolamine laurate, diethanolamide oleate, decaglycerol laurate, decaglycerol caprylate, glucoside, and xylitol fatty acid ester.
[0013] Further, the anionic surfactant includes one or more of the following: sodium dodecyl sulfate, sodium lauryl ether sulfate, triethanolamine salt of fatty alcohol polyoxyethylene ether sulfate, sodium tridecyl polyoxyethylene ether sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium fatty alcohol polyoxyethylene ether carboxylate, sodium dodecylbenzene sulfonate, disodium lauryl ether sulfosuccinate, sodium fatty acid methyl ester sulfonate, sodium methyl cocoyl taurate, etc.; phosphate salts such as potassium hexadecyl phosphate, potassium fatty alcohol polyoxyethylene ether phosphate, sodium nonylphenol polyoxyethylene ether phosphate, etc.; sodium lauryl ether, sodium lauryl ether carboxylate, sodium lauroyl glutamate.
[0014] Furthermore, the content of the nonionic surfactant is NI% of the mass of polyvinyl alcohol, with a value of 0.08 ≤ NI ≤ 0.30.
[0015] Furthermore, the content of the anionic surfactant is 1% of the mass of polyvinyl alcohol, with a tolerance of 0.01 ≤ 1 ≤ 0.20%.
[0016] Furthermore, the mass ratio of the anionic surfactant to the nonionic surfactant is I / NI, where 0.04 ≤ I / NI ≤ 0.80.
[0017] Secondly, the present invention provides a method for evaluating a PVA optical film casting solution with excellent peeling performance, comprising the following steps: S1. Test preparation: Mix and dissolve polyvinyl alcohol, solvent, plasticizer and surfactant to obtain casting liquid; use steel plate as substrate, set substrate temperature and squeegee height of coating machine, and adjust squeegee height to ensure that the actual thickness of the liquid film formed after subsequent coating is 30-70μm after drying and curing. S2. Coating: After the substrate temperature stabilizes, pour the casting liquid in front of the squeegee and start coating. Start timing the moment the squeegee passes through the casting liquid. The casting liquid forms a liquid film on the substrate surface. S3. Observation and Recording: As the liquid film dries, a PVA film gradually forms. Observe the drying process. When the length of the film formation boundary line reaches more than 1 cm, record the time of film formation boundary line formation. The film formation boundary line time is... t0 represents When the film is fully and automatically peeled off, the timing stops, and the film peeling time is recorded. The film peeling time is used as... t express; S4. Calculation: Calculate the liquid film drying rate according to the formula below:
[0018] In the formula, v For liquid film drying rate, W The concentration of the casting solution. G The water content of the film. t Film formation time; S5. Characterization: After the automatically peeled film is equilibrated at 25°C and 55% humidity for 24 hours, contact angle tests are performed on the plate surface using ethylene glycol. Among them, the t0, t, v The numerical range of the contact angle, along with the value of the contact angle, serves as the evaluation criterion for the peeling performance of the casting solution.
[0019] Furthermore, in step S1, the stirring temperature is 130°C and the stirring time is 8 hours.
[0020] Further, in step S1, the concentration of the casting solution is W, 15%≤W≤35%; the temperature is 65~98℃.
[0021] Furthermore, in step S1, the temperature of the substrate is 75–110°C.
[0022] Furthermore, in step S1, the height of the scraper is 200–2000 μm.
[0023] Furthermore, in step S3, the 0s≤ t0 ≤310s, 0s≤ t ≤482s, 0s≤ t-t0≤170s.
[0024] Further, in step S4, the liquid film drying rate v Satisfies 0.14 s -1 ≤ v ≤0.47 s -1 .
[0025] Further, in step S4, the water content of the film... G The test method is as follows: The oven drying method is used, where an initial mass of m0 is dried in a forced-air drying oven to a constant weight, and the mass after drying is m1. G = (m0 - m1) / m0 100%.
[0026] Furthermore, in step S5, the contact angle is 15 to 37 degrees.
[0027] The beneficial effects of this invention are: 1. In the PVA optical film casting solution with excellent peelability described in this invention, polyvinyl alcohol serves as the core film-forming substrate. The strong hydrogen bonding of its molecular chains endows the cast film with mechanical strength and optical transparency, making it a key component ensuring the basic performance of the PVA optical film. The solvent, as a dispersion medium, can fully dissolve polyvinyl alcohol and various additives, adjusting the viscosity and flowability of the casting solution to ensure uniform film spreading during coating and avoid film surface defects caused by uneven dispersion. The plasticizer can embed between the polyvinyl alcohol molecular chains, weakening the hydrogen bonding forces between the chains, improving the flexibility and processing adaptability of the cast film, and preventing the film from becoming too brittle during drying and peeling. The mixed surfactant is composed of at least one nonionic and at least one anionic surfactant. The nonionic surfactant can effectively reduce the surface tension of the casting solution, optimize the wetting performance of the liquid film and the substrate, and reduce uneven shrinkage during the film formation process. The anionic surfactant can improve the compatibility and dispersion stability of the mixed surfactant in the PVA system, prevent the precipitation of the nonionic surfactant, and reduce the adhesion between the liquid film and the substrate by regulating the interfacial charge distribution, thus significantly improving the peeling performance of the casting solution. The synergistic effect of the two ultimately achieves the dual goals of "easy peeling and no defects" of the casting solution and "high transparency and high performance" of the optical film.
[0028] 2. By limiting the amount and ratio of nonionic and anionic surfactants, this invention can prepare a casting solution with optimal peeling performance.
[0029] 3. This invention proposes a peel performance evaluation method based on a combination of film-forming time measurement and contact angle testing in a laboratory coating machine. This method simulates the production line conditions of film-roller peeling, is simple to operate, and combines high efficiency and accuracy, providing a reliable basis for optimizing casting solution formulations. Detailed Implementation
[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.
[0031] In a first aspect, the present invention provides a PVA optical film casting solution with excellent peeling performance, wherein the PVA optical film casting solution comprises polyvinyl alcohol, solvent, plasticizer and surfactant; wherein the surfactant is a mixed surfactant, comprising at least one nonionic surfactant and at least one anionic surfactant.
[0032] In the PVA optical film casting solution with excellent peelability described in this invention, polyvinyl alcohol serves as the core film-forming substrate. The strong hydrogen bonding of its molecular chains endows the cast film with mechanical strength and optical transparency, making it a key component ensuring the basic performance of the PVA optical film. The solvent, as a dispersion medium, can fully dissolve polyvinyl alcohol and various additives, adjusting the viscosity and flowability of the casting solution to ensure uniform film spreading during coating and avoid film surface defects caused by uneven dispersion. The plasticizer can embed between the polyvinyl alcohol molecular chains, weakening the hydrogen bonding forces between them, improving the flexibility and processing adaptability of the cast film, and preventing the film from breaking due to excessive brittleness during drying and peeling. The mixed surfactant is composed of at least one nonionic and at least one anionic surfactant. The nonionic surfactant can effectively reduce the surface tension of the casting solution, optimize the wetting performance of the liquid film and the substrate, and reduce uneven shrinkage during the film formation process. The anionic surfactant can improve the compatibility and dispersion stability of the mixed surfactant in the PVA system, prevent the precipitation of the nonionic surfactant, and reduce the adhesion between the liquid film and the substrate by regulating the interfacial charge distribution, thus significantly improving the peeling performance of the casting solution. The synergistic effect of the two ultimately achieves the dual goals of "easy peeling and no defects" of the casting solution and "high transparency and high performance" of the optical film.
[0033] In some embodiments, the degree of polymerization of the polyvinyl alcohol is 1200–4000, and the degree of hydrolysis is 88%–99.99%. Excessive or insufficient polymerization will affect the processing performance of PVA and the weather resistance of the product film; insufficient hydrolysis will affect solubility and the weather resistance of the product film.
[0034] In some embodiments, the solvent is any one of deionized water, dimethyl sulfoxide, and methanol, preferably deionized water. This ensures sufficient dissolution of polyvinyl alcohol and various additives, guarantees a uniform and stable casting solution system, and can adapt to different preparation scenarios. Among them, deionized water, due to its high purity and absence of impurities, can minimize film surface defects, while also possessing advantages such as low cost, environmental friendliness, and ease of large-scale production, making it more suitable for the preparation of PVA optical films.
[0035] In some embodiments, the plasticizer is one or more of ethylene glycol, propylene glycol, glycerol, and polyglycerol. These substances all possess a polyhydroxy structure, which can efficiently embed between polyvinyl alcohol molecular chains, weakening the hydrogen bonding between molecular chains, significantly improving the flexibility and processing adaptability of the film, and effectively preventing the film from cracking due to excessive brittleness during drying, peeling, and subsequent use.
[0036] In some embodiments, the content of the plasticizer is 8% to 15% of the mass of polyvinyl alcohol. Too little plasticizer will reduce processing performance, while too much plasticizer will cause plasticizer precipitation, resulting in poor optical properties of the film.
[0037] In some embodiments, the nonionic surfactant includes one or more of the following: isotridecyl alcohol polyoxyethylene ether, ethylene oxide-propylene oxide block polyether, dodecyl polyoxyethylene ether, isooctyl alcohol polyoxyethylene ether, octadecylamine polyoxyethylene ether, triethylamine oleate, monoethanolamine laurate, diethanolamide oleate, decaglycerol laurate, decaglycerol caprylate, glucoside, and xylitol fatty acid ester. These substances possess suitable hydrophobic carbon chains and hydrophilic segments, effectively reducing the surface tension of the casting solution, optimizing the spreadability of the liquid film on the substrate, and reducing defects caused by uneven liquid film shrinkage during film formation. Simultaneously, their good compatibility avoids conflicts with other components in the system, ensuring the stability of the casting solution.
[0038] In some embodiments, the anionic surfactant includes one or more of the following: sodium dodecyl sulfate, sodium lauryl ether sulfate, triethanolamine salt of fatty alcohol polyoxyethylene ether sulfate, sodium tridecyl polyoxyethylene ether sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium fatty alcohol polyoxyethylene ether carboxylate, sodium dodecylbenzene sulfonate, disodium lauryl ether sulfosuccinate, sodium fatty acid methyl ester sulfonate, sodium methyl cocoyl taurate, etc., sulfonates, potassium hexadecyl phosphate, potassium fatty alcohol polyoxyethylene ether phosphate, sodium nonylphenol polyoxyethylene ether phosphate, etc., sodium lauryl ether, sodium lauryl ether carboxylate, sodium lauroyl glutamate, etc. These substances possess specific anionic groups and can synergistically interact with nonionic surfactants: on the one hand, they improve the dispersion stability of the mixed surfactants in the PVA system, preventing the precipitation of nonionic surfactants; on the other hand, they can regulate the interfacial charge distribution between the liquid film and the substrate, reduce interfacial adhesion, and further optimize peel performance.
[0039] In some embodiments, the content of the ionic surfactant is NI% of the mass of polyvinyl alcohol, with a range of 0.08 ≤ NI ≤ 0.30. This range ensures that it fully exerts its function of reducing surface tension and optimizing film formation: it avoids both insufficient surface tension control and uneven film spreading due to too low a content, and excessive content causing surfactant precipitation, film surface contamination, or affecting the optical properties of the film.
[0040] In some embodiments, the content of the anionic surfactant is 1% of the mass of polyvinyl alcohol, with a concentration of 0.01 ≤ 1 ≤ 0.20%. This content ensures effective synergy with the nonionic surfactant, improving system compatibility and peeling performance, while avoiding insufficient synergy due to too low a content, or excessive content leading to interfacial charge imbalance and affecting the mechanical and optical properties of the film.
[0041] In some embodiments, the mass ratio of the anionic surfactant to the nonionic surfactant is 1 / NI, where 0.04 ≤ 1 / NI ≤ 0.80. This ratio achieves optimal synergy between the two types of surfactants: the nonionic surfactant effectively reduces surface tension and optimizes film formation, while the anionic surfactant ensures stable dispersion and reduces adhesion. Simultaneously, it avoids synergistic failure caused by imbalance in the ratio, ensuring that the casting solution possesses both excellent peeling performance and film quality.
[0042] Secondly, the present invention provides a method for evaluating a PVA optical film casting solution with excellent peeling performance, comprising the following steps: S1. Test preparation: Mix and dissolve polyvinyl alcohol, solvent, plasticizer and surfactant to obtain casting liquid; use steel plate as substrate, set substrate temperature and squeegee height of coating machine, and adjust squeegee height to ensure that the actual thickness of the liquid film formed after subsequent coating is 30-70μm after drying and curing. By preparing the casting solution in advance (mixing, stirring, and cooling), the casting solution is kept stable during coating, avoiding the impact of insufficient mixing of components or temperature fluctuations on film quality. At the same time, the substrate temperature and squeegee height are precisely set, and the target film thickness (30-70 μm) is clearly defined, providing stable and suitable basic conditions for subsequent coating, drying, and peeling processes, thus avoiding deviations in peeling performance evaluation caused by improper equipment parameters from the source.
[0043] S2. Coating: After the substrate temperature stabilizes, pour the casting liquid in front of the squeegee and start coating. Start timing the moment the squeegee passes through the casting liquid. The casting liquid forms a liquid film on the substrate surface. Coating after the substrate temperature has stabilized ensures that the casting solution spreads quickly and evenly on the substrate surface to form a liquid film, reducing the problem of uneven thickness in the liquid film. At the same time, using the moment when the scraper passes through the casting solution as the timing start point can accurately capture the starting moment of the liquid film drying and peeling process, providing a unified benchmark for the accurate recording of subsequent film peeling time and improving the reliability of the evaluation data.
[0044] S3. Observation and Recording: As the liquid film dries, a PVA film gradually forms. Observe the drying process. When the length of the film formation boundary line reaches more than 1 cm, record the time of film formation boundary line formation. The film formation boundary line time is... t0 represents When the film is fully and automatically peeled off, the timing stops, and the film peeling time is recorded. The film peeling time is used as... t express; By observing the liquid film drying and film formation process, the "film formation boundary time" was recorded respectively. t0 ")" and "film formation time" t The time index can intuitively reflect the entire process of the liquid film from drying and shrinking to overcoming interfacial adhesion and finally being completely peeled off. The combination of the two time indices can comprehensively characterize the peeling start-up efficiency and overall peeling difficulty of the casting liquid, avoiding the one-sidedness of evaluation by a single time index.
[0045] S4. Calculation: Calculate the liquid film drying rate according to the formula below:
[0046] In the formula, v For liquid film drying rate, W The concentration of the casting solution. G The water content of the film. t Film formation time; The liquid film drying rate is quantified using a formula. v ), the concentration of the casting solution ( W ), film moisture content ( G ) and film formation time ( t This allows for a quantitative evaluation of the drying process; precise control of the drying rate can avoid problems such as bubbles on the film surface due to excessively fast drying and sticking to the rollers due to excessively slow drying, providing a key basis for judging whether the casting solution is suitable for the drying rhythm of industrial production.
[0047] S5. Characterization: After the automatically peeled film is equilibrated at 25°C and 55% humidity for 24 hours, contact angle tests are performed on the plate surface using ethylene glycol. Equilibrate the film in a standard environment (25℃, 55% humidity) for 24 hours to eliminate the interference of environmental factors on the film surface condition and ensure the accuracy of the contact angle test. The contact angle of the substrate surface is measured by ethylene glycol, which can directly reflect the hydrophilicity and hydrophobicity of the film surface. The hydrophilicity and hydrophobicity of the film surface are directly related to the interfacial adhesion of the substrate. Supplementing this indicator can form a multi-dimensional synergistic evaluation system with film release time and drying rate, further improving the comprehensiveness and accuracy of the evaluation of the peeling performance of the casting solution.
[0048] Among them, the t0, t, v The numerical range of the contact angle, along with the value of the contact angle, serves as the evaluation criterion for the peeling performance of the casting solution.
[0049] In some embodiments, in step S1, the stirring temperature is 130°C and the stirring time is 8 hours. This stirring condition can promote the full dissolution and uniform dispersion of components such as polyvinyl alcohol, plasticizer, and surfactant in the solvent, avoiding local agglomeration or component segregation due to uneven mixing. At the same time, the high temperature environment can weaken the hydrogen bonding between polyvinyl alcohol molecular chains, improve the compatibility of the system, and lay the foundation for the subsequent preparation of a stable casting solution.
[0050] In some embodiments, in step S1, the concentration of the casting solution is W, 15% ≤ W ≤ 35%; the temperature is 65–98°C. Limiting the concentration of the casting solution to 15%–35% balances the fluidity and film-forming properties of the casting solution, avoiding the problem of the film being too thin and easily broken due to excessively low concentration, and the problem of poor fluidity and difficulty in uniform coating due to excessively high concentration. Controlling the temperature of the casting solution to 65–98°C maintains a stable viscosity of the system, preventing the components from separating due to excessively low temperature and the solvent from evaporating too quickly due to excessively high temperature, thus ensuring the smooth progress of the coating process.
[0051] In some embodiments, in step S1, the temperature of the substrate is 75–110°C. This substrate temperature range can regulate the drying rate of the liquid film on the substrate surface. If the temperature is too high, the liquid film surface will solidify rapidly to form a "shell," making it difficult for the internal solvent to evaporate and causing blistering on the film surface. If the temperature is too low, the drying time will be too long, increasing the adhesion between the liquid film and the substrate. The temperature setting of 75–110°C can achieve uniform drying of the liquid film, balancing peeling efficiency and film quality.
[0052] In some embodiments, in step S1, the height of the doctor blade is 200–2000 μm. This doctor blade height can precisely control the initial thickness of the liquid film after coating, and after drying and curing, a target film of 30–70 μm can be stably obtained. This avoids the liquid film being too thin due to a doctor blade height that is too low, or too thick due to a doctor blade height that results in uneven drying. It provides test samples with consistent thickness for peel performance evaluation and improves the comparability of experimental data.
[0053] In some embodiments, in step S3, 0s≤ t0 ≤310s, 0s≤t ≤482s, 0s≤ t-t0 ≤170s. t0 The longer the time, the more severe the liquid film sticks to the roller, and the worse the peeling performance. t The smaller the size, the better the peeling effect. t An excessively high peel strength indicates a large peel force, which can easily lead to defects such as mottled spots and diagonal lines on the film surface.
[0054] In some embodiments, in step S4, the liquid film drying rate v Satisfies 0.14 s -1 ≤ v ≤0.47 s -1 This drying rate range is crucial for the casting solution to achieve both excellent peeling performance and film quality: a rate below 0.14... s -1 This will result in excessively long drying time and increased adhesion between the liquid film and the substrate; a rate higher than 0.47 s -1 If drying is too rapid, it can easily lead to uneven film shrinkage and cracks, while 0.14–0.47 The rate of ¹ enables stable drying and curing of the liquid film, ensuring a smooth peeling process.
[0055] In some embodiments, in step S4, the water content of the film... G The test method is as follows: The oven drying method is used, where an initial mass of m0 is dried in a forced-air drying oven to a constant weight, and the mass after drying is m1. G = (m0 - m1) / m0 100%. The moisture content was determined by drying the film to constant weight in an oven. This method can accurately quantify the residual solvent content in the film, eliminate subjective errors, and ensure that the moisture content data is true and reliable. This provides key parameter support for the subsequent accurate calculation of the liquid film drying rate, and improves the scientificity and accuracy of the drying rate evaluation.
[0056] In some embodiments, in step S5, the contact angle is 15 to 37 degrees. A contact angle below 15 degrees indicates that the film surface is too hydrophilic, has a strong adhesion to the substrate, and is difficult to peel off; a contact angle above 37 degrees indicates that the hydrophilicity is too weak, which may lead to surfactant precipitation and film surface contamination. A contact angle of 15 to 37 degrees can reduce interfacial adhesion, optimize peeling performance, and ensure the cleanliness and optical performance of the film surface.
[0057] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.
[0058] Example 1
[0059] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.4559g of surfactant. The surfactant is composed of isomeric tridecyl alcohol polyoxyethylene ether and sodium tridecyl polyoxyethylene ether sulfonate in a mass ratio of 25:1, and the plasticizer is ethylene glycol.
[0060] The evaluation method includes the following steps: S1. Test preparation: Polyvinyl alcohol, solvent, plasticizer and surfactant are mixed and stirred at 130℃ for 8 hours, and then cooled to 80℃ to obtain a 20% casting liquid. Using a steel plate as a substrate, the substrate temperature of the coating machine is set to 100℃ and the doctor blade height is set to 880μm. By adjusting the doctor blade height, it is ensured that the actual thickness of the liquid film formed after subsequent coating is 60μm after drying and curing. S2. Coating: After the substrate temperature stabilizes, pour the casting liquid in front of the squeegee and start coating. Start timing the moment the squeegee passes through the casting liquid. The casting liquid forms a liquid film on the substrate surface. S3. Observation and Recording: As the liquid film dries, a PVA film gradually forms. Observe the drying process. When the length of the film formation boundary line reaches more than 1 cm, record the time of film formation boundary line formation. The film formation boundary line time is... t0 represents When the film is fully and automatically peeled off, the timing stops, and the film peeling time is recorded. The film peeling time is used as... t express; S4. Calculation: Calculate the liquid film drying rate according to the formula below:
[0061] In the formula, v For liquid film drying rate, W The concentration of the casting solution. G The water content of the film. t Film formation time; S5. Characterization: After the automatically peeled film is equilibrated at 25°C and 55% humidity for 24 hours, contact angle tests are performed on the plate surface using ethylene glycol.
[0062] Example 2
[0063] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.5220g of surfactant. The surfactant is composed of dodecyl polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate in a mass ratio of 5:1, and the plasticizer is ethylene glycol.
[0064] The evaluation method is the same as in Example 1.
[0065] Example 3
[0066] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.609g of surfactant. The surfactant is composed of isotridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate in a mass ratio of 5:2, and the plasticizer is ethylene glycol.
[0067] The evaluation method is the same as in Example 1.
[0068] Example 4
[0069] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.785g of surfactant. The surfactant is composed of isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium carboxylate in a mass ratio of 5:4, and the plasticizer is ethylene glycol.
[0070] The evaluation method is the same as in Example 1.
[0071] Example 5
[0072] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.2262g of surfactant. The surfactant is composed of decaglycerol laurate and sodium fatty alcohol polyoxyethylene ether carboxylate in a mass ratio of 8:5, and the plasticizer is ethylene glycol.
[0073] The evaluation method is the same as in Example 1.
[0074] Example 6
[0075] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.3480g of surfactant. The surfactant is composed of isotridecyl alcohol polyoxyethylene ether and potassium hexadecyl phosphate in a mass ratio of 3:1, and the plasticizer is ethylene glycol.
[0076] The evaluation method is the same as in Example 1.
[0077] Example 7
[0078] This embodiment provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.6090g of surfactant. The surfactant is composed of octadecylamine polyoxyethylene ether and sodium fatty alcohol polyoxyethylene ether carboxylate in a mass ratio of 6:1, and the plasticizer is ethylene glycol.
[0079] The evaluation method is the same as in Example 1.
[0080] Comparative Example 1
[0081] This comparative example provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.9400g of surfactant. The surfactant is composed of isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium carboxylate in a mass ratio of 5:4, and the plasticizer is ethylene glycol.
[0082] The evaluation method is the same as in Example 1.
[0083] Comparative Example 2
[0084] This comparative example provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.7830g of surfactant. The surfactant is composed of isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium carboxylate in a mass ratio of 8:1, and the plasticizer is ethylene glycol.
[0085] The evaluation method is the same as in Example 1.
[0086] Comparative Example 3
[0087] This comparative example provides a PVA optical film casting solution with excellent peeling performance, comprising 174g of polyvinyl alcohol (polyvinyl alcohol with a degree of polymerization of 2000 and a degree of hydrolysis of 98%), 754g of deionized water, 14g of plasticizer, and 0.6960g of surfactant. The surfactant is composed of isomeric tridecyl alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium carboxylate in a mass ratio of 1:1, and the plasticizer is ethylene glycol.
[0088] The evaluation method is the same as in Example 1.
[0089] To more intuitively and clearly demonstrate the differences between the embodiments of the present invention and the comparative examples in various key performance indicators, and to facilitate understanding of the significant advantages brought by the technical solution of the present invention, the formulations of key materials of Examples 1 to 7 and Comparative Examples 1 to 3 and the test results obtained by the evaluation method of the present invention are listed in Table 1.
[0090] Table 1
[0091] To further verify the consistency between the laboratory evaluation results and actual production applications, the casting solutions of the above examples and comparative examples were tested on a production line casting machine to examine their actual peeling performance and the final product quality of the PVA optical film. The basic properties of the casting solutions of Examples 1-7 and Comparative Examples 1-3 and their corresponding product films are listed in Table 2. During the production line test, the presence of defects such as mottling and diagonal streaks on the film surface was used as the criterion for judging peeling performance (good peeling effect was marked as "○", and obvious defects were marked as "×"). The optical haze of the product film was measured using a haze meter to comprehensively evaluate the industrial application value of the casting solutions.
[0092] Table 2
[0093] As can be seen from the data in Tables 1 and 2 above, the casting solutions obtained in Examples 1 to 7 of the present invention all exhibit excellent and stable peeling processing performance and optical performance, which fully meet the design goals of the technical solution.
[0094] In Examples 1-4, the content of nonionic surfactant was constant, while the content of anionic surfactant was gradually increased from 0.01% to 0.2%. Under certain test conditions, the liquid film exhibited good peel performance, with the time to the film-forming boundary line appearing within 152-260 s and the film-forming time within 202-379 s. The automatic film-forming process showed no significant resistance, and the time interval between the film-forming time and the appearance of the boundary line was within 50-122 s. Production line testing revealed that Examples 1-4 demonstrated good peel performance and excellent optical properties. Further increasing the ionic surfactant content to 0.3%, as in Comparative Example 1, significantly prolonged the time to the appearance of the film-forming boundary line to 374 s, correspondingly extending the film-forming time to 560 s. The drying rate decreased, and the contact angle was measured at 12.1 degrees, significantly lower than the film with excellent peel performance. Furthermore, Comparative Example 1 exhibited poor peel performance and poor film surface properties during production line testing.
[0095] In Examples 5-7, with the anionic surfactant content kept constant and the nonionic surfactant content increased from 0.08% to 0.3%, the liquid film exhibited good peel performance, with the time to form a film boundary line ranging from 145 to 310 seconds and the film formation time from 145 to 482 seconds. The film formation process was normal, and the time interval between film formation and the appearance of the boundary line was within 0 to 170 seconds. During production line testing, the casting solution's processing performance and the film product's optical properties were good. Further increasing the nonionic surfactant content to 0.4%, as in Comparative Example 2, extended the liquid film formation time to 556 seconds. During testing, the casting solution's peel performance was poor, and the product film surface haze reached a high of 3.4%. It was concluded that excessive nonionic surfactant content leads to poor compatibility of the PVA solution system, affecting not only the casting solution's peel performance but also its optical properties. In addition, when the ratio of ionic to nonionic surfactants is not appropriate, it will also affect the processing performance of the casting solution. For example, in Comparative Example 3, when I / NI is 1.00, the liquid film formation time is significantly extended to 776s, and the peeling effect is poor.
[0096] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.
Claims
1. A PVA optical film casting solution with excellent peeling performance, characterized in that, It includes polyvinyl alcohol, solvent, plasticizer and surfactant; the surfactant is a mixed surfactant, including at least one nonionic surfactant and at least one anionic surfactant.
2. The PVA optical film casting solution with excellent peeling performance according to claim 1, characterized in that, The degree of polymerization of the polyvinyl alcohol is 1200–4000, and the degree of alcoholysis is 88%–99.99%. The solvent is any one of deionized water, dimethyl sulfoxide, and methanol; The plasticizer is one or more of ethylene glycol, propylene glycol, glycerol, and polyglycerol; The plasticizer content is 8% to 15% of the mass of polyvinyl alcohol.
3. The PVA optical film casting solution with excellent peeling performance according to claim 1, characterized in that, The nonionic surfactant includes one or more of the following: isotridecyl alcohol polyoxyethylene ether, ethylene oxide-propylene oxide block polyether, dodecyl polyoxyethylene ether, isooctanol polyoxyethylene ether, octadecylamine polyoxyethylene ether, triethylamine oleate, monoethanolamine laurate, diethanolamide oleate, decaglycerol laurate, decaglycerol caprylate, glucoside, and xylitol fatty acid ester.
4. The PVA optical film casting solution with excellent peeling performance according to claim 1, characterized in that, The anionic surfactant includes one or more of the following: sodium dodecyl sulfate, sodium lauryl ether sulfate, triethanolamine salt of fatty alcohol polyoxyethylene ether sulfate, sodium tridecyl polyoxyethylene ether sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium fatty alcohol polyoxyethylene ether carboxylate, sodium dodecylbenzene sulfonate, disodium lauryl ether sulfosuccinate, sodium fatty acid methyl ester sulfonate, sodium methyl cocoyl taurate, etc., sulfonates, potassium hexadecyl phosphate, potassium fatty alcohol polyoxyethylene ether phosphate, sodium nonylphenol polyoxyethylene ether phosphate, etc., sodium lauryl ether carboxylate, sodium lauroyl glutamate, etc.
5. The PVA optical film casting solution with excellent peeling performance according to claim 1, characterized in that, The content of the nonionic surfactant is NI% of the mass of polyvinyl alcohol, with a value of 0.08 ≤ NI ≤ 0.
30. The content of the anionic surfactant is 1% of the mass of polyvinyl alcohol, with a limit of 0.01 ≤ 1 ≤ 0.20%. The mass ratio of the anionic surfactant to the nonionic surfactant is I / NI, where 0.04 ≤ I / NI ≤ 0.
80.
6. A method for evaluating a PVA optical film casting solution with excellent peeling performance, characterized in that, Includes the following steps: S1. Test preparation: Mix and dissolve polyvinyl alcohol, solvent, plasticizer and surfactant to obtain casting solution; Using a steel plate as the substrate, the substrate temperature and squeegee height of the coating machine are set. By adjusting the squeegee height, it is ensured that the actual thickness of the liquid film formed after coating is 30-70 μm after drying and curing. S2. Coating: After the substrate temperature stabilizes, pour the casting liquid in front of the squeegee and start coating. Start timing the moment the squeegee passes through the casting liquid. The casting liquid forms a liquid film on the substrate surface. S3. Observation and Recording: As the liquid film dries, a PVA film gradually forms. Observe the drying process. When the length of the film formation boundary line reaches more than 1 cm, record the time of film formation boundary line formation. The film formation boundary line time is... t0 represents When the film is fully and automatically peeled off, the timing stops, and the film peeling time is recorded. The film peeling time is used as... t express; S4. Calculation: Calculate the liquid film drying rate according to the formula below: In the formula, v For liquid film drying rate, W The concentration of the casting solution. G The water content of the film. t Film formation time; S5. Characterization: After the automatically peeled film is equilibrated at 25°C and 55% humidity for 24 hours, contact angle tests are performed on the plate surface using ethylene glycol. Among them, the t0, t, v The numerical range of the contact angle, along with the value of the contact angle, serves as the evaluation criterion for the peeling performance of the casting solution.
7. The evaluation method for the PVA optical film casting solution with excellent peeling performance according to claim 6, characterized in that, In step S1, the stirring temperature is 130°C and the stirring time is 8 hours. The concentration of the casting solution is W, 15%≤W≤35%; the temperature is 65~98℃; The temperature of the substrate is 75–110°C; The height of the scraper is 200–2000 μm.
8. The evaluation method for the PVA optical film casting solution with excellent peeling performance according to claim 6, characterized in that, In step S3, 0s≤ t0 ≤310s, 0s≤ t ≤482s, 0s≤ t-t0 ≤170s.
9. The evaluation method for the PVA optical film casting solution with excellent peeling performance according to claim 6, characterized in that, In step S4, the liquid film drying rate v Satisfies 0.14 s -1 ≤ v ≤0.47 s -1 ; The moisture content of the film G The test method is as follows: The oven drying method is used, where an initial mass of m0 is dried in a forced-air drying oven to a constant weight, and the mass after drying is m1. G = (m0 - m1) / m0 100%.
10. The evaluation method for the PVA optical film casting solution with excellent peeling performance according to claim 6, characterized in that, In step S5, the contact angle is 15 to 37 degrees.