An optical composite film with ultrahigh haze, high light transmittance and high strength and a preparation method thereof

Abstract

This invention discloses an optical composite film with ultra-high haze, high transmittance, and high strength, and its preparation method, relating to the field of flexible optical materials. The optical composite film with ultra-high haze, high transmittance, and high strength is prepared by impregnating high-porosity paper in a water-soluble polymer solution and then removing the solvent; the mass ratio of the water-soluble polymer to the high-porosity paper in the water-soluble polymer solution is (0.43–3.82):1, and the high-porosity paper is filter paper or Xuan paper. The haze value of this optical composite film with high haze, high transmittance, and high strength is between 78.75% and 95.15%, the maximum total transmittance is 84.76%, and the tensile strength is as high as 93.62 MPa, making it applicable to flexible optical devices or LED lighting.

Description

Technical Field

[0001] This invention belongs to the field of flexible optical materials, specifically relating to an optical composite film with ultra-high haze, high transmittance and high strength and its preparation method. Background Technology

[0002] High-transmittance optically transparent materials are essential components of optical devices, widely used in lenses, automotive glass, lighting devices, displays, and solar cells. Typically, conventional optical materials prioritize high transmittance and low haze for better clarity. For example, acrylic glass possesses excellent plasticity and extremely high transmittance (up to 92%), while exhibiting very low haze (≤2%), allowing incident light to pass primarily as direct rays. Currently, in most LED lighting systems, to achieve wider and more uniform coverage of the emitted light, point light sources need to be transformed into surface light sources, requiring more diffused light. Optical materials with high transmittance and high haze can effectively meet this requirement. On one hand, high transmittance allows incident light to pass through the optical material as much as possible, minimizing energy loss; on the other hand, high haze allows the emitted light to exit as diffused light, resulting in more uniform and softer light, providing a more comfortable lighting environment. Furthermore, highly transparent and high-haze materials can be used in light management coatings and substrates for solar panels, significantly improving photoelectric conversion efficiency. This is because one reason for energy conversion efficiency loss in solar cells is the significant amount of light reflected at the active layer interface, failing to be coupled by the active layer. High-transmittance and high-haze materials, through wide-angle scattering and absorption, greatly enhance light absorption efficiency and the coupling length between the solar cell and incident light. In addition, high-transmittance and high-haze materials have important applications in areas such as anti-glare and privacy protection.

[0003] Traditional high-haze materials can be created by introducing microstructures on the material surface or by introducing scattering particles within the material. Commonly used scattering particles include SiO2 particles, metal nanoparticles, metal nanowires, and polymer nanospheres. However, these introduced scattering particles tend to aggregate within the material, failing to disperse uniformly and thus affecting the material's optical properties. With the development of flexible wearable devices, optical materials that simultaneously possess high transmittance, high haze, good mechanical properties, environmental friendliness, and low cost are attracting increasing attention. Summary of the Invention

[0004] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide an optical composite film with high haze, high transmittance and high strength and a method for preparing the same.

[0005] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0006] The first aspect of the present invention provides an optical composite film with ultra-high haze, high light transmittance and high strength, which is prepared by impregnating high-porosity paper in a water-soluble polymer solution and removing the solvent; the mass ratio of water-soluble polymer to high-porosity paper in the water-soluble polymer solution is (0.43~3.82):1, and the high-porosity paper is filter paper or Xuan paper.

[0007] According to the above-mentioned optical composite film with ultra-high haze, high light transmittance and high strength, preferably, the water-soluble polymer is at least one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol with a relative molecular weight of 2000 to 8000, and polyethylene oxide.

[0008] According to the aforementioned optical composite film with ultra-high haze, high light transmittance and high strength, preferably, the mass fraction of the water-soluble polymer solution is 1% to 3%.

[0009] According to the above-mentioned optical composite film with ultra-high haze, high light transmittance and high strength, preferably, the degree of alcoholysis of the polyvinyl alcohol is 88-99% and the relative molecular weight is 75,000-114,000; the relative molecular weight of the polyvinylpyrrolidone is 40,000-1,300,000.

[0010] According to the aforementioned optical composite film with ultra-high haze, high light transmittance and high strength, preferably, the relative molecular weight of the polyethylene oxide is 100,000 to 1,000,000.

[0011] According to the aforementioned optical composite film with ultra-high haze, high light transmittance, and high strength, preferably, the mass ratio of the water-soluble polymer to the high-porosity paper is (0.43–3.82):1. Further, when the high-porosity paper is filter paper, the mass ratio of the water-soluble polymer to the filter paper is (0.43–2.33):1, and when the high-porosity paper is Xuan paper, the mass ratio of the water-soluble polymer to the Xuan paper is (0.70–3.82):1.

[0012] According to the above-mentioned optical composite film with ultra-high haze, high light transmittance and high strength, preferably, the water-soluble polymer solution also includes a plasticizer, and the mass ratio of the plasticizer to the high-porosity paper is (0.33~1.64):1.

[0013] According to the aforementioned optical composite film with ultra-high haze, high light transmittance, and high strength, preferably, the mass ratio of the plasticizer to the high-porosity paper is (0.33-1.64):1. Further, when the high-porosity paper is filter paper, the mass ratio of the plasticizer to the filter paper is (0.33-1):1, and when the high-porosity paper is Xuan paper, the mass ratio of the plasticizer to the Xuan paper is (0.55-1.64):1.

[0014] According to the above-mentioned optical composite film with ultra-high haze, high light transmittance and high strength, preferably, the plasticizer is at least one of glycerol, 1,3-butanediol, polyethylene glycol 200 (polyethylene glycol with a relative molecular weight of 200), polyethylene glycol 300 (polyethylene glycol with a relative molecular weight of 300), and polyethylene glycol 400 (polyethylene glycol with a relative molecular weight of 400).

[0015] The second aspect of the present invention also provides a method for preparing an optical composite film with ultra-high haze, high light transmittance and high strength. The preparation method is as follows: high-porosity paper is impregnated in a water-soluble polymer solution, and after impregnation, the solvent is slowly evaporated to obtain an optical composite film with ultra-high haze, ultra-high light transmittance and high strength.

[0016] According to the above-described method for preparing an optical composite film with ultra-high haze, high transmittance, and high strength, preferably, the water-soluble polymer solution is a pure solution of the water-soluble polymer or a mixed solution of the water-soluble polymer and a plasticizer.

[0017] According to the above-mentioned method for preparing an optical composite film with ultra-high haze, high transmittance and high strength, preferably, after defoaming the water-soluble polymer solution, the high-porosity paper is then impregnated into the water-soluble polymer solution.

[0018] According to the above preparation method, preferably, the evaporation temperature is 30-45°C.

[0019] The third aspect of the present invention also provides the application of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength in flexible optical devices or LED lighting lamps.

[0020] Compared with the prior art, the positive and beneficial effects achieved by this invention are as follows:

[0021] (1) The preparation method of the optical composite film with ultra-high haze, high transmittance and high strength of the present invention, on the one hand, causes the high porosity paper to swell through the wetting of the solution. The water-soluble polymer will fill the swollen high porosity paper and its internal pores. By using the method of slow evaporation of solvent, the solvent with a large difference in refractive index from the high porosity paper is removed. The incident light can pass through the optical composite film with ultra-high haze, high transmittance and high strength better and undergo a scattering effect. On the other hand, it can also improve the strength of the optical composite film with ultra-high haze, high transmittance and high strength. The optical composite film of this invention features ultra-high haze, high transmittance, and high strength. The haze value is between 78.75% and 95.15%, the total transmittance is as high as 84.76%, and the tensile strength is as high as 93.62 MPa. The total transmittance of the optical composite film of this invention has actually reached 85%, which is close to the theoretical limit. This indicates that the light energy loss is minimal, and it solves the technical problem of light energy loss under the conditions of high transmittance and low haze in traditional polymer films.

[0022] (2) The present invention uses high porosity paper as the load matrix. High porosity paper has the characteristics of high porosity and low density, which can fully impregnate the water-soluble polymer inside the high porosity paper, achieve good interfacial compatibility, and make an optical composite film with ultra-high haze, high light transmittance and high strength.

[0023] (3) A small number of bubbles will be generated during the preparation of the optical composite film. The residual bubbles will change the light path of the incident light in the optical composite film with ultra-high haze, high transmittance and high strength, and affect its transmittance. Therefore, the preparation method of the optical composite film with ultra-high haze, high transmittance and high strength of the present invention needs to adopt a defoaming process to remove bubbles.

[0024] (4) The present invention employs a slow solvent evaporation method, which not only helps to improve the fusion between the polymer and the substrate, but also preserves the fiber texture on the substrate surface, maintains its surface roughness, and further improves the haze of the composite film. In addition, this method can control the optical properties of both sides of the composite film by adjusting the surface roughness of the solution film-forming container.

[0025] (5) In the process of preparing the optical composite film, the present invention also adds a plasticizer. The plasticizer can form hydrogen bonds with the hydroxyl groups on the molecular chain of the water-soluble polymer, thereby reducing the probability of forming hydrogen bonds between water-soluble polymers and destroying the crystallinity of the water-soluble polymer. Without reducing the haze and transmittance of the optical composite film, it can significantly improve the toughness and impact resistance of the optical composite film with ultra-high haze, high transmittance and high strength, and broaden its application range.

[0026] (6) The water-soluble polymer used in this invention has good water solubility, film-forming properties, transparency, biocompatibility, mechanical properties and safety and non-toxicity, and will not pollute the environment, which meets the requirements of environmental protection.

[0027] (7) The method for preparing the optical composite film with ultra-high haze, high transmittance and high strength of the present invention is simple and easy to implement, requires no expensive equipment, has a wide range of raw material sources, and is low in cost, which is conducive to the industrial transformation of the technology. Attached Figure Description

[0028] Figure 1 Photographs of untreated qualitative filter paper and the sample prepared in Example 9;

[0029] Figure 2 Photographs of the optical properties of the polyester film and the sample prepared in Example 9;

[0030] Figure 3 Tensile strength versus strain curves for untreated qualitative filter paper (a), sample (b) prepared in Example 7, sample (c) prepared in Example 8, and sample (d) prepared in Example 1. Detailed Implementation

[0031] The present invention will be further illustrated by specific embodiments below, but this does not limit the scope of the invention.

[0032] (I) Experiments with different types of polymers:

[0033] To investigate the effects of different types of water-soluble polymers on the haze, total transmittance, scattered light, and parallel light of optical composite films with ultra-high haze, high transmittance, and high strength, the inventors conducted the following experiments. Some experimental parameters and results are shown in Table 1.

[0034] Example 1:

[0035] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a polyvinyl alcohol 1788 solution (relative molecular weight 75000, degree of alcoholysis 88%) and then removing the solvent. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0036] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 40.0g of polyvinyl alcohol 1788 (relative molecular weight 75000) solution (mass fraction 2%) is vacuum defoamed for 5 min and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (80g / m²) is applied. 2An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol 1788 solution. After impregnation, the film was removed and placed horizontally in a 30°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0037] Example 2:

[0038] Example 2 is basically the same as Example 1, except that the water-soluble polymer is polyvinyl alcohol 1799 (relative molecular weight 75000, degree of alcoholysis 99%).

[0039] Example 3:

[0040] Example 3 is basically the same as Example 1, except that the water-soluble polymer is polyethylene glycol (relative molecular weight 6000, degree of alcoholysis 88%).

[0041] Example 4:

[0042] Example 4 is basically the same as Example 1, except that the water-soluble polymer is polyvinylpyrrolidone (relative molecular weight 1,300,000).

[0043] Example 5:

[0044] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a solution of polyvinylpyrrolidone (relative molecular weight 1,300,000) and then removing the solvent. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0045] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 42g of polyvinylpyrrolidone (relative molecular weight 1300000) solution (mass fraction 3%) is vacuum defoamed for 5 min and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (80g / m²) is applied. 2 An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol pyrrolidone solution. After impregnation, the film was removed and placed horizontally in a 30°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0046] Example 6:

[0047] The content of Example 6 is basically the same as that of Example 5, except that the water-soluble polymer is polyethylene glycol (relative molecular weight 2000, degree of alcoholysis 88%).

[0048] The haze, total transmittance, scattered light, and parallel light of the samples prepared in Examples 1-6 were measured under the following conditions: a Shimadzu UV-3150 ultraviolet spectrophotometer with an integrating sphere was used, according to the national standard GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics". The haze (H%) and total transmittance (T%) of the prepared film materials were measured and calculated respectively. t %), scattered light (T) d %) and parallel light (T) p (%), the test results are shown in Table 1.

[0049] Table 1. Effects of different polymer types on the optical properties of optical composite films.

[0050]

[0051] As shown in Table 1, the qualitative filter paper has coarse fibers with numerous pores. Air has a refractive index of 1, while cellulose has a refractive index of 1.6. This significant difference in refractive index causes a substantial change in the direction of incident light within the fibers, preventing much of the incident light from penetrating the paper surface, resulting in high haze and low transmittance. When an aqueous solution of polyvinyl alcohol (PVA) is added, the good interfacial compatibility between PVA and cellulose allows the solution to swell the filter paper fibers. Simultaneously, the water-soluble PVA fills the swollen fibers and their internal pores. Since PVA has a refractive index of 1.5 and water has a refractive index of 1.33, the slow evaporation of water allows for better scattering and transmission of incident light within the filter paper, improving the transmittance of the optical composite film with ultra-high haze, high transmittance, and high strength. Comparing untreated qualitative filter paper with Example 1, it is evident that adding polyvinyl alcohol 1788 significantly improves the total transmittance and scattered light while reducing the parallel light value without decreasing the sample haze. Comparing Example 1 with Example 2, it is evident that, with the same degree of polymerization and relative molecular weight of polyvinyl alcohol, the degree of alcoholysis of polyvinyl alcohol has almost no effect on the optical properties of the optical composite film. Comparing Example 1 with Example 3, it is evident that for polyvinyl alcohol 1788, a higher relative molecular weight results in better wettability with paper fibers, thus the sample haze is slightly lower than that of polyethylene glycol, but the total transmittance is higher; in particular, the sample prepared in Example 1 has a total transmittance as high as 8... 1.98%, indicating high light transmittance; comparing Examples 5 and 6, it can be seen that, under the same mass fraction and amount of water-soluble polymer, the optical properties of the optical composite film prepared by different polymer types are also different. Compared with Example 5, the haze of the sample prepared in Example 6 increased by 16.03% and the total light transmittance decreased by 0.73%. However, due to the low melting point of low molecular weight polyethylene glycol and its weak bonding force with fibers, it is easy to fall off, resulting in poor applicability; as shown in Table 1, the optical composite film with ultra-high haze, high light transmittance and high strength obtained by treating qualitative filter paper with polyvinyl alcohol with a relative molecular weight of 75000 has the best optical performance.

[0052] (II) Experiments with different amounts of water-soluble polymer added:

[0053] To investigate the effects of different amounts of polyvinyl alcohol added on the haze, total transmittance, scattered light, and parallel light of an optical composite film with ultra-high haze, high transmittance, and high strength, the inventors conducted the following experiments: Examples 1, 4, 5, 7, and 8. The specific details of Examples 7 and 8 are as follows. The experimental results are shown in Table 2.

[0054] Example 7:

[0055] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a polyvinyl alcohol 1788 solution (relative molecular weight 75000, degree of alcoholysis 88%) and then removing the solvent. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0056] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 23.0g of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) solution (mass fraction 1%) is vacuum defoamed for 5 minutes and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (basis weight 80g / m²) is applied. 2 An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol 1788 solution. After impregnation, the film was removed and placed horizontally in a 30°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0057] Example 8:

[0058] The content of Example 2 is basically the same as that of Example 1, except that: 54.0g of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) solution (mass fraction 1%) was vacuum defoamed for 5min and dried at 40℃.

[0059] Table 2 Effect of different amounts of water-soluble polymer added on the optical properties of optical composite films

[0060]

[0061] As shown in Table 2, with the continuous increase of polyvinyl alcohol 1788 addition, the haze of the prepared optical composite film continuously decreases, while the total transmittance, scattered light, and parallel light continuously increase. When the amount of polyvinyl alcohol 1788 added is 0.8g, the total transmittance of the prepared optical composite film reaches 81.98%, which is close to the limit value. With the continuous increase of polyvinylpyrrolidone addition, the optical performance of the prepared optical composite film decreases in terms of haze. Therefore, polyvinyl alcohol 1788 is preferably the water-soluble polymer for preparing the optical composite film.

[0062] (III) Experiments with different plasticizers:

[0063] To investigate the effects of different plasticizers on the haze, total transmittance, scattered light, parallel light, tensile strength, and elongation at break of optical composite films with ultra-high haze, ultra-high transmittance, and high strength, the inventors conducted the following experiments, namely Example 1, Example 9, and Example 10. The specific contents of Example 9 and Example 10 are as follows, and the experimental results are shown in Table 3.

[0064] Example 9:

[0065] An optical composite film with ultra-high haze, ultra-high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a mixed solution of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) and glycerol, followed by solvent removal. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0066] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 40g of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) solution (mass fraction 2%) and 0.54g of glycerol are mixed evenly, vacuum degassing for 5min, and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (basis weight 80g / m²) is applied. 2 An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol 1788 solution. After impregnation, the film was removed and placed horizontally in a 35°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0067] Example 10:

[0068] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a mixed solution of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) and polyethylene glycol 400, followed by solvent removal. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0069] The preparation method of the aforementioned optical composite film with ultra-high haze, high transmittance, and high strength comprises the following steps: 40g of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) solution (mass fraction 2%) and 0.54g of polyethylene glycol 400 are mixed evenly, vacuum degassing for 5 minutes, and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (80g / m²) is applied. 2 An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol 1788 solution. After impregnation, the film was removed and placed horizontally in a 35°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0070] Table 3. Effects of different plasticizers on the properties of optical composite films

[0071]

[0072] As shown in Table 3, the addition of plasticizer increases the number of hydroxyl groups per unit volume, which can more effectively reduce the interaction forces between water-soluble polymers and disrupt the crystallinity of water-soluble polymers, thereby improving the flexibility of the composite film as much as possible while meeting mechanical strength requirements. Comparing Example 1 with Example 9 or Example 10, it is evident that the optical properties of the optical composite film prepared by treating high-porosity paper with glycerol or polyethylene glycol 400 remain almost unchanged, while the tensile strength and elongation at break change significantly. Compared with the sample prepared in Example 1, the tensile strength of the sample prepared in Example 9 decreased by 67.7%, while the elongation at break increased significantly by 2.45 times; compared with the sample prepared in Example 1, the tensile strength of the sample prepared in Example 10 decreased by 68.9%, while the elongation at break increased significantly by 3.31 times. Therefore, the addition of plasticizer can adjust the flexibility and impact resistance of the optical composite film without affecting its optical properties of ultra-high haze, high transmittance, and high strength, thus broadening its applications.

[0073] (IV) Experiments with different amounts of plasticizer added:

[0074] To investigate the effects of different glycerol addition amounts on the haze, total transmittance, scattered light, parallel light, tensile strength, and elongation at break of an optical composite film with ultra-high haze, high transmittance, and high strength, the inventors conducted the following experiments: Examples 1, 11, 12, and 9, with corresponding glycerol addition amounts of 0g, 0.18g, 0.27g, and 0.54g, respectively. The experimental results are shown in Table 4.

[0075] Example 11:

[0076] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a mixed solution of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) and glycerol, followed by solvent removal. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0077] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 40g of polyvinyl alcohol 1788 (relative molecular weight 75000) solution (mass fraction 2%) and 0.18g of glycerol are mixed evenly, vacuum degassing is performed for 5 minutes, and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (80g / m²) is applied. 2 An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol 1788 solution. After impregnation, the film was removed and placed horizontally in a 35°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0078] Example 12:

[0079] The content of Example 12 is basically the same as that of Example 11, except that the amount of glycerol added is 0.27g.

[0080] Table 4. Effects of different glycerol addition amounts on the properties of optical composite films.

[0081]

[0082] As shown in Table 4, with the continuous increase of glycerol addition, the haze of the optical composite film gradually decreased, the light transmittance slowly increased, and the tensile strength continuously decreased while the elongation at break continuously increased. Compared with the untreated qualitative filter paper, the addition of polyvinyl alcohol 1788 in Example 1, with its strictly linear and regular structure and high mechanical strength, significantly increased the tensile strength of the sample prepared in Example 1 by 4.1 times, while reducing the elongation at break by 30.2%. Therefore, the tensile strength and elongation at break of the optical composite film can be controlled by adjusting the amount of plasticizer added, thereby improving its flexibility and impact resistance and broadening its application in flexible optical devices.

[0083] (V) Experiments with paper of different porosities:

[0084] To investigate the effects of different high-porosity papers on the haze, total transmittance, scattered light, and parallel light of an optical composite film with ultra-high haze, high transmittance, and high strength, the inventors conducted the following experiments, namely Examples 13 and 14, with qualitative filter paper and Xuan paper as the corresponding high-porosity papers, respectively. The experimental results are shown in Table 5.

[0085] Example 13:

[0086] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating qualitative filter paper in a mixed solution of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) and glycerol, followed by solvent removal. The qualitative filter paper (0.54 g, basis weight 80 g / m³) is untreated. 2 (Approximately 165 μm thick).

[0087] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 42g of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) solution (mass fraction 3%) and 0.18g of glycerol are mixed evenly, vacuum degassing for 5min, and then transferred to a polytetrafluoroethylene evaporating dish. Then, 0.54g of qualitative filter paper (basis weight 80g / m²) is applied. 2An optical composite film with a thickness of approximately 165 μm was impregnated in a polyvinyl alcohol 1788 solution. After impregnation, the film was removed and placed horizontally in a 30°C constant temperature oven for 48 hours. After the moisture was slowly evaporated, an optical composite film with ultra-high haze, high light transmittance, and high strength was obtained.

[0088] Example 14:

[0089] An optical composite film with ultra-high haze, high light transmittance, and high strength is prepared by impregnating Xuan paper in a mixed solution of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) and glycerol, followed by solvent removal. The untreated Xuan paper (basis weight 49 g / m²) is used. 2 ).

[0090] The preparation method of the above-mentioned optical composite film with ultra-high haze, high transmittance and high strength is as follows: 42g of polyvinyl alcohol 1788 (relative molecular weight 75000, degree of alcoholysis 88%) solution (mass fraction 3%) and 0.18g of glycerol are mixed evenly, vacuum degassing for 5 minutes, and then transferred to a polytetrafluoroethylene evaporating dish. Then, Xuan paper (49g / m²) is added... 2 The film is impregnated in a polyvinyl alcohol 1788 solution. After impregnation, it is taken out and placed horizontally in a 30°C constant temperature oven for 48 hours. After the moisture is slowly evaporated, an optical composite film with ultra-high haze, high light transmittance and high strength is obtained.

[0091] Table 5. Effects of paper with different high porosity on the optical properties of optical composite films.

[0092]

[0093] As shown in Table 5, the haze values ​​of Examples 13 and 14 are 85.65% and 84.57%, respectively. While maintaining high haze, their total light transmittance is increased to 84.30% and 81.99%, respectively. The fibers in the qualitative filter paper are finer and more uniform than those in Xuan paper, resulting in higher total light transmittance. This indicates that the optical composite film prepared by impregnating qualitative filter paper in a water-soluble polymer solution has better optical properties, exhibiting high haze, high light transmittance, and high strength.

[0094] Performance testing of the optical composite film with high haze, high transmittance, and high strength according to this invention:

[0095] (1) Optical performance testing of optical composite films with high haze, high transmittance and high strength

[0096] Taking the sample prepared in Example 9 of this invention as an example, the optical properties of the optical composite film of this invention, which has high haze, high transmittance, and high strength, were tested. Meanwhile, to compare with the sample prepared in Example 9, the inventors also conducted experiments on untreated qualitative filter paper. The test methods are as follows, and the results are as follows. Figure 1 and Figure 2 As shown.

[0097] The testing method is as follows: Figure 1 In the image, A and B are photographs of untreated qualitative filter paper and the sample prepared in Example 9 placed on the same mesh material, respectively. Figure 2 In the images, 2A and 2B are photographs of the sample prepared in Example 9, taken close to the pattern and 3 cm away from the pattern surface, respectively; 2C and 2D are photographs of the polyester film (polyethylene terephthalate, haze: 10.3%, total transmittance: 90.16%), taken close to the pattern and 3 cm away from the pattern surface, respectively; 2E and 2F are photographs of the scattering of the polyester film and the optical composite film with ultra-high haze, high transmittance and high intensity on the panel, respectively, when a laser pointer (wavelength 650nm, spot size 1×2mm) is irradiated at a distance of 10 cm from the polyester film and the sample prepared in Example 9.

[0098] Depend on Figure 1 It is evident that the texture information of the covering mesh material cannot be clearly seen through untreated qualitative filter paper, while the texture information of the covering mesh material can be clearly seen through the sample prepared in Example 9. Compared with untreated qualitative filter paper, the transparency and transmittance of the sample prepared in Example 9 are significantly improved. Therefore, the preparation method of the optical composite film with ultra-high haze, high transmittance and high strength of the present invention can significantly improve the transmittance of qualitative filter paper (Haze: 98.60%, Tt: 26.16%), while maintaining ultra-high haze (85.64%).

[0099] Depend on Figure 2 It can be seen that, through Figure 2 Compared to 2B, due to the high haze characteristics of the optical composite film with ultra-high haze, high transmittance, and high strength, it has a strong scattering effect on incident light. The scattering effect intensifies with increasing distance. Compared to 2A, in 2B, the detailed information of the covered pattern is no longer visible through the sample prepared in Example 9. Figure 2 Compared to 2D, due to the high light transmittance and low haze of polyester film, it has almost no scattering effect on incident light. The scattering effect does not change with increasing distance. Therefore, as seen from 2C and 2D, the clarity of the pattern is not significantly related to its distance from the polyester film. Figure 2 B and Figure 2Compared to 2D, this invention combines the high haze characteristics of an optical composite film with ultra-high haze, high transmittance, and high strength, and the low haze characteristics of a polyester film. Figure 2 The pattern clarity of the sample prepared in Example 9 in B was significantly reduced. Figure 2 As can be seen from E, since the polyester film has almost no scattering effect on the incident laser, when the laser irradiates the polyester film at a distance of 10cm, a laser beam with clear edges and a small area of ​​halo around it is formed on the panel behind the polyester film. As can be seen from 2F, since the optical composite film with ultra-high haze, high transmittance and high intensity has a strong scattering effect on the incident laser, when the laser irradiates the sample prepared in Example 9 at a distance of 10cm, a large-sized (30mm in diameter) light spot is formed on the panel behind the sample prepared in Example 9.

[0100] (2) Mechanical strength test of optical composite film with ultra-high haze, high transmittance and high strength

[0101] Taking the samples from Examples 1, 7, and 8 of this invention as examples, the tensile strength and strain of the optical composite film of this invention, which possesses ultra-high haze, high light transmittance, and high strength, were tested. Simultaneously, for comparison with the samples from Examples 1, 7, and 8 of this invention, untreated qualitative filter paper was also tested. The test methods are as follows, and the test results are as follows. Figure 3 As shown.

[0102] The test method is as follows: Shimadzu universal tensile testing machine (SHIMADZUAGS-100N) was used, the tensile rate was 1 mm / min, and the test sample was a dumbbell-shaped specimen with a width of 4 mm.

[0103] Depend on Figure 3 As can be seen, in this invention, high-porosity paper is impregnated in a water-soluble polymer solution. The water-soluble polymer enters the high-porosity paper fibers and their internal pores. Due to the large number of polar groups (hydroxyl groups) in the water-soluble polymer (such as polyvinyl alcohol), and the entanglement between polymer segments and the strong hydrogen bonding between the segments and the paper fibers, the tensile strength and modulus of the composite film are significantly improved. The maximum tensile strength of the untreated qualitative filter paper is only 18.41 MPa (a), while the maximum tensile strengths of the samples prepared in Examples 7 (b), 8 (c), and 1 (d) are 50.21 MPa, 67.34 MPa, and 93.62 MPa, respectively. Compared with the untreated qualitative filter paper, as the content of water-soluble polymer in the optical composite film with high haze, high transmittance, and high strength increases, the tensile strength of the optical composite film increases by 2.73, 3.66, and 5.09 times, respectively.

[0104] The above embodiments are specific implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any other combination, change, modification, substitution, or simplification that does not exceed the design concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing an optical composite film with ultra-high haze, high transmittance, and high strength, characterized in that, The preparation method is as follows: high porosity paper is impregnated in a water-soluble polymer solution with a mass fraction of 1% to 3%. After impregnation, the solvent is slowly evaporated to obtain an optical composite film with ultra-high haze, ultra-high light transmittance and high strength. The mass ratio of the water-soluble polymer to the high-porosity paper in the water-soluble polymer solution is (0.43-3.82):

1. The water-soluble polymer is at least one of polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol with a relative molecular weight of 2000-8000, and polyethylene oxide. The high-porosity paper is filter paper or Xuan paper. The water-soluble polymer solution also contains a plasticizer, and the mass ratio of the plasticizer to the high-porosity paper is (0.33–1.64):

1.

2. The preparation method according to claim 1, characterized in that, The degree of alcoholysis of the polyvinyl alcohol is 88-99%, and the relative molecular weight is 75,000-114,000; the relative molecular weight of the polyvinylpyrrolidone is 40,000-1,300,000.

3. The preparation method according to claim 1, characterized in that, The plasticizer is at least one of glycerol, 1,3-butanediol, polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400.

4. The preparation method according to claim 1, characterized in that, After defoaming the water-soluble polymer solution, the high-porosity paper is then impregnated in the water-soluble polymer solution.

5. The application of the optical composite film with ultra-high haze, high transmittance and high strength prepared by any of the preparation methods described in claims 1-4 in flexible optical devices or LED lighting lamps.

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