High water-oxygen barrier quantum dot diffusion composite material, and preparation method and application thereof

Abstract

The application discloses a kind of high water oxygen barrier quantum dot diffusion composite material and preparation method and application, belong to optical display technical field, including the water oxygen barrier layer and quantum dot layer of alternative lamination.Its preparation method includes the following steps: water oxygen barrier layer blending granules and quantum dot layer blending granules are respectively dried, using alternative multilayer co-extrusion equipment is co-extruded, obtains the high water oxygen barrier diffusion composite material.The application also discloses the application of the high water oxygen barrier diffusion composite material in quantum dot display.The application not only simplifies the complex structure of backlight module, also realizes light diffusion, substantially improves the light, heat stability and fluorescence lifetime of quantum dot, provides new method for large-scale application of quantum dot display.The preparation method provided by the application is extrusion molding method, production process is simple, production efficiency is high, preparation process is continuous, simple, green, efficient, product batch stability is high, with wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of optical display technology, and particularly relates to a high water and oxygen barrier quantum dot diffusion composite material, its preparation method and application. Background Technology

[0002] The modern display industry began in the early 19th century, marked by the invention of the cathode ray tube (CRT) technology by German physicist Wernher von Braun in 1897. CRT monitors offered advantages such as wide color gamut, long lifespan, fast response time, and high contrast. However, due to their large size and high power consumption, CRT monitors have gradually faded from the market, finding only limited applications in specialized fields like military and aerospace. The second generation of displays was the liquid crystal display (LCD), developed by RCA in 1968. LCDs comprehensively outperformed CRT monitors in terms of contrast, power consumption, lifespan, size, and display quality. With subsequent reductions in manufacturing costs, LCDs were widely used in televisions, mobile phones, laptops, and monitors. LCDs currently boast the largest installed base and highest shipment volume in the display industry, but their narrow color gamut, backlight leakage, and long response time have hindered further applications. Third-generation displays use organic light-emitting diodes (OLEDs). Each pixel in an OLED display can be individually controlled to emit light, eliminating the need for a backlight. Compared to LCDs, OLEDs offer advantages such as high brightness, high contrast, flexibility, low response time, and low power consumption, leading to their widespread use in televisions, tablets, and mobile phones. However, their high cost, short lifespan, and decreasing yield with increasing size make OLED displays currently more suitable for mobile smart devices, hindering their complete replacement of LCDs.

[0003] To deliver clearer and more vibrant images, efforts are being made to develop various new display technologies. As a core component of displays, high-performance backlighting is crucial for enhancing display quality. Current quantum dot television (QD-TV) technology increases the NTSC color gamut from 72% to over 110% by adding a quantum dot film (QD film) to the LCD backlight. Another technological approach involves using quantum dot materials to replace the organic light-emitting materials in OLEDs to create quantum dot light-emitting diodes (QLEDs). These QLEDs have a theoretical lifespan of up to 30 years when used in display devices, but this application is currently still in the research and development stage. The quantum dot films used in current QD-TV technology still suffer from complex manufacturing processes, requiring coating, lamination, and photocuring steps, and a high price, reaching up to $100 per square meter.

[0004] Therefore, how to provide a simple and low-cost quantum dot application model to promote the further popularization of quantum dot displays is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a high water and oxygen barrier quantum dot diffusion composite material, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high water and oxygen barrier quantum dot diffusion composite material, comprising alternating layers of water and oxygen barrier layers and quantum dot layers;

[0008] The purpose of the water-oxygen barrier layer is to prevent the quantum dot material from contacting the air, thereby inhibiting the increase of surface defects caused by the shedding of surface atoms due to moisture in the air, as well as the decrease or quenching of fluorescence intensity caused by the aggregation effect of moisture; it also inhibits the decrease or quenching of fluorescence intensity caused by the oxidation of quantum dot material by oxygen in the air.

[0009] The water-oxygen barrier layer comprises the following raw materials in parts by weight:

[0010] The first matrix consists of 50-99 parts, the barrier polymer consists of 1-50 parts, and the compatibilizer consists of 0.1-5 parts.

[0011] Preferably, the upper and / or lower surfaces of the high water and oxygen barrier diffusion composite material further include a transparent matrix protective layer. This transparent protective layer can be the same transparent polymer material as the matrix polymer, or it can be a transparent polymer film such as PET or PE. It can be implemented through co-extrusion or obtained through a direct coating process. This transparent matrix protective layer can prevent scratches on the composite material during transportation or storage, ensuring the integrity of the composite material.

[0012] Preferably, the thickness of the composite material is 0.05-4 mm, more preferably 0.1-3 mm;

[0013] Preferably, the composite material has at least 4 layers, but the number of layers can be adjusted to hundreds or thousands of layers as needed.

[0014] Beneficial effects: The composite material in this invention has an alternating multilayer structure, which has the characteristic of layer-by-layer protection. That is, the outer layer protects the inner layer. Even if the fluorescence intensity of the quantum dot material in the outer or outermost layer decreases or is quenched after being affected by water and oxygen, the inner quantum dot material is not affected and can still function, thereby greatly extending the service life of the composite material.

[0015] Preferably, the thickness ratio of the water-oxygen barrier layer to the quantum dot layer is 1:1;

[0016] The quantum dot layer comprises a second matrix and quantum dots, wherein the quantum dots constitute 0.005% to 1% of the mass of the second matrix, preferably 0.01% to 0.5%.

[0017] Preferably, the barrier polymer comprises one or more of the following: ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), polyethylene terephthalate copolyester (PET), polyacrylonitrile (PAN), polyvinylidene chloride (PVDC), nylon 6 (PA6), nylon 12 (PA12), special transparent nylon (MXD6), polyvinyl alcohol (PVA), polymethyl ethylene carbonate (PPC), polyimide (PI), polychlorotrifluoroethylene (PCTFE), and polytetrafluoroethylene (PTFE).

[0018] Beneficial effects: The above-mentioned barrier polymers can improve the barrier performance of the product, mitigate the effects of moisture and oxygen on quantum dot materials, and extend the lifespan of quantum dots. Furthermore, the organic barrier phase is distributed as islands in the matrix, which can act as diffusion particles, making light more uniform and gentler as it passes through the quantum dot layer, thus improving the color gamut of the display.

[0019] Preferably, the compatibilizer includes one or more of the following: ethylene-vinyl acetate copolymer grafted maleic anhydride (EVA-g-MAH), butyl acrylate grafted maleic anhydride (ACR-g-MAH), methyl methacrylate and glycidyl methacrylate copolymer P (MMA-co-GMA), acrylonitrile-butadiene-styrene plastic grafted maleic anhydride (ABS-g-MAH), glycidyl methacrylate grafted polystyrene (PS-g-GMA), and polystyrene grafted maleic anhydride copolymer (PS-g-MAH).

[0020] Beneficial effects: The above compatibilizers can improve the interfacial compatibility between the organic barrier phase and the optical substrate, and at the same time, they can regulate the viscosity of the organic barrier phase, thereby further regulating the dispersion morphology of the organic barrier phase in the matrix.

[0021] Preferably, the quantum dot material includes carbon dots, perovskite quantum dots (ABX3), Cd-based quantum dots (CdX), Zn-group quantum dots (ZnX), and indium phosphide (InP), especially green quantum dot materials and red quantum dot materials that emit green and red light after photoexcitation.

[0022] Beneficial effects: Quantum dots have a narrow and symmetrical excitation spectrum, less stray light, and excitation colors closer to the three primary colors specified by the CIE. Displays using quantum dots can achieve a color gamut of up to 110%. When the backlight is blue light, the red and green light generated by the excitation of green and red quantum dot materials together constitute the RGB three primary colors, thus enabling the display device to display vibrant colors. Existing quantum dots suffer from poor stability. This invention protects the quantum dots through the water and oxygen barrier layer, extending their lifespan, regardless of the type of quantum dot. The reason this invention only discloses the aforementioned quantum dot materials is that blue backlights are commonly used in the display field, and red and green quantum dots can achieve the desired display effect, not that this invention can only protect red and green quantum dots.

[0023] Preferably, the first substrate and the second substrate are independently selected from one or any combination of optical grade transparent resins;

[0024] The first matrix and the second matrix can be the same transparent resin or different transparent resins. The difference in refractive index between the two matrix resins is less than 0.2, preferably less than 0.1.

[0025] The optical-grade transparent resin includes one or more of the following: polymethyl methacrylate (PMMA), polystyrene (PS), methyl methacrylate-styrene copolymer (SMMA or MS), polycarbonate (PC), polyethylene terephthalate (PET), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer (ABS), methyl methacrylate-butadiene-styrene terpolymer (MBS), poly(4-methylpentene-1) (TPX), polyethylene naphthalate (PEN), and styrene-acrylonitrile copolymer (SAN).

[0026] Beneficial effects: The above optical-grade transparent resin can ensure the transparency of the product.

[0027] More preferably, the melt viscosity of the barrier polymer is lower than the melt viscosity of the first matrix;

[0028] Beneficial Effects: Under the above conditions, orientation and deformation of the present invention only occur during the multilayer co-extrusion process. Under the action of the biaxial tensile force field during the multilayer co-extrusion process, both the melt of the first matrix and the melt of the barrier polymer will flow forward and to both sides. If the melt viscosity of the barrier polymer is greater than that of the first matrix, the deformation of the melt of the barrier polymer under the action of the biaxial tensile force field will be less than that of the first matrix, and thus it cannot be controlled into a sheet-like or fibrous structure; if the viscosities of the two are similar, the deformation is also similar, and it also cannot be controlled into a sheet-like or fibrous structure; only when the melt viscosity of the barrier polymer is less than that of the first matrix, the deformation of the barrier polymer phase is greater than that of the first matrix, and orientation deformation will occur in the direction of stress, thereby controlling it into a sheet-like or fibrous structure.

[0029] A method for preparing a high water-oxygen barrier quantum dot diffusion composite material includes the following steps:

[0030] After drying the water-oxygen barrier layer blended granules and the quantum dot layer blended granules, they were co-extruded using an alternating multilayer co-extrusion device to obtain the high water-oxygen barrier diffusion composite material.

[0031] Beneficial Effects: This invention uses a transparent polymer as a matrix and introduces an organic barrier phase into the transparent matrix resin through a simple melt processing method. This phase serves as a water and oxygen barrier layer in alternating multilayer co-extrusion. Similarly, quantum dot materials are introduced into the transparent matrix resin through a simple melt processing method, serving as the quantum dot layer in alternating multilayer co-extrusion. An A / B / A / B / A / B…A / B alternating multilayer composite material is prepared using an alternating multilayer co-extrusion device. During the multilayer co-extrusion process, the bidirectional tensile force field generated during the lamination process can regulate the morphology of the organic barrier phase, controlling its structure to a sheet-like structure. This improves the water and oxygen barrier performance of the matrix resin, preventing water and oxygen from eroding the quantum dot material, significantly improving the stability of the quantum dot material, and extending its lifespan. Simultaneously, the organic barrier phase exists in an island-like structure within the matrix, which can diffuse light, making the light more uniform and softer when passing through the quantum dot layer, thus improving the color gamut of the display. On the other hand, the bidirectional tensile force field during the stacking process can promote the dispersion of quantum dot materials, reduce the quenching effect caused by quantum dot aggregation, and also help to extend their lifespan.

[0032] Preferably, the preparation method of the water-oxygen barrier layer blended granules includes the following steps:

[0033] The first matrix and barrier polymer are dried to a moisture or other volatile content of less than 400 ppm (preferably less than 200 ppm), then mixed with a compatibilizer and granulated by a twin-screw extruder to obtain the water-oxygen barrier layer blend granules.

[0034] Beneficial Effects: This invention first dries the base resin to remove moisture and organic solvents generated during production and storage. Moisture and organic solvents degrade polymers during molding, significantly impacting the mechanical properties and transparency of the finished product. They can also introduce defects such as cracks and bubbles, affecting product quality. Therefore, drying the resin to a moisture and volatile content of 400 ppm, especially 200 ppm, results in improved mechanical and optical properties.

[0035] The purpose of this invention, which uses a twin-screw extruder for granulation, is to take advantage of the advantages of twin-screw extruders over single-screw extruders, such as thorough mixing, good heat transfer, and high melting capacity of polymers. This allows the matrix polymer, barrier phase polymer, and compatibilizer to be fully mixed, providing uniformly mixed barrier layer polymer granules for the next step of alternating multilayer co-extrusion.

[0036] Preferably, the preparation method of the quantum dot layer blend granules includes the following steps:

[0037] The second matrix is ​​dried until the moisture and / or other volatile components content is less than 400 ppm (preferably less than 200 ppm), then mixed with quantum dots and granulated by a twin-screw extruder to obtain the quantum dot layer blended granules.

[0038] Quantum dots can be directly pre-blended with a transparent matrix, or they can be dispersed in white oil or other alkanes and then pre-blended with a transparent matrix before being granulated by a twin-screw extruder.

[0039] Beneficial effects: The purpose of granulation using a twin-screw extruder in this invention is also to take advantage of its characteristics such as thorough mixing, good heat transfer, and high melting capacity of polymers, so as to achieve uniform dispersion of quantum dot materials in the matrix polymer as much as possible, which is conducive to the next step of alternating multilayer co-extrusion to produce uniformly dispersed quantum dot layer polymer granules.

[0040] Quantum dots are spherical or near-spherical semiconductor nanomaterials with dimensions ranging from 2 to 20 nm. Like conventional nanomaterials, they are difficult to achieve a monodisperse state and usually exist in an aggregated form. Therefore, they can be directly blended with the matrix material and dispersed by the torsional action of a twin-screw extruder; alternatively, the quantum dots can be pre-dispersed in white oil or other alkanes, then mixed with the matrix resin and further dispersed by a twin-screw extruder. The pre-dispersion effect of white oil or other alkanes can improve the dispersion of quantum dots.

[0041] Application of a high water and oxygen barrier quantum dot diffusion composite material in quantum dot displays.

[0042] This invention discloses a high-water-oxygen barrier quantum dot diffusion composite material, its preparation method, and its applications. This invention integrates the quantum dot film, barrier layer, and diffuser plate in a quantum display backlight module, simplifying the complex structure of the backlight module and significantly improving the optical and thermal stability and fluorescence lifetime of the quantum dots while achieving light diffusion. This provides a new method for the large-scale application of quantum dot displays. The preparation method provided by this invention is an extrusion molding method, which is simple, efficient, continuous, simple, green, and efficient, with high batch stability and broad application prospects. Attached Figure Description

[0043] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0044] Figure 1 This is a schematic diagram of the high water and oxygen barrier diffusion composite material in this invention;

[0045] Figure 2 This is a schematic diagram of the alternating multilayer co-extrusion device used in this invention;

[0046] Figure 3 Scanning electron microscope images of SMMA / EVOH composites with different EVA-g-MAH contents;

[0047] Wherein, (a) is SMMA-E 40 Scanning electron microscope image, (b) is SMMA-E 40 @E 0.5 Scanning electron microscope image, (c) is SMMA-E 40 Scanning electron microscope image of @E1, (d) is SMMA-E 40 @E 1.5 Scanning electron microscope image;

[0048] Figure 4 Scanning electron microscope (SEM) images of SMMA / EVOH composites with different EVOH contents;

[0049] Among them, (a) is 5 wt%; (b) is 10 wt%; (c) is 15 wt%; (d) is 20 wt%; (e) is 30 wt%; and (f) is 40 wt%.

[0050] Figure 5 Scanning electron microscope (SEM) images of SMMA-EVOH / SMMA-QD composites with different numbers of layers;

[0051] Among them, (a)~(d) are 2 layers; (e)~(h) are 8 layers; (i)~(l) are 32 layers; (m)~(p) are 128 layers;

[0052] Figure 6 The images show the fluorescence of the three quantum dot diffusers after ultraviolet irradiation. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] The twin-screw extruder used in this embodiment of the invention is model SHJ-20, purchased from Nanjing J&T Motor Co., Ltd.

[0056] The alternating multilayer co-extrusion apparatus structure used in the embodiments of the present invention is as follows: Figure 2 As shown, it includes a single-screw extruder 1, a single-screw extruder 2, a manifold, and a layer multiplier;

[0057] The first and second single-screw extruders are connected in parallel and connected to one end of the manifold, while the other end of the manifold is connected to the layer multiplier.

[0058] The principle of the alternating multilayer co-extrusion device used in this embodiment of the invention is as follows:

[0059] (1) The quantum dot layer and the water and oxygen barrier layer polymer melts are extruded from two single screw extruders respectively. After passing through different flow channels, they are merged into a two-layer melt at the co-extrusion die and then enter the layered stacking unit.

[0060] (2) In the layered stacking unit, the two layers of melt are first divided into two by a divider, then enter their respective flow channels, and finally merged together by a stacker, making the 2-layer melt into 4 layers, and then expanding to the initial width of the 2-layer melt. In this way, after flowing through n layered units, 2 (n+1) Composite materials with multiple layers. During the diffusion process, the melt is subjected to a two-way force of forward flow and expansion to both sides, which causes the morphology and structure of the dispersed phase to change from spherical to fibrous or sheet-like.

[0061] The torque rheometer used in this embodiment of the invention is an RM-200C torque rheometer.

[0062] The raw materials used in this invention are all obtained through conventional commercial channels. The melt flow rate of SMMA (200℃ / 5.0kg) is 1.6g / 10min, and the melt flow rate of EVOH (190℃ / 2.16kg) is 1.8g / 10min. The melt viscosity of SMMA is higher than that of EVOH. The red and green quantum dots are both CdSe (cadmium selenide) quantum dot materials.

[0063] Example 1

[0064] A method for preparing a high water-oxygen barrier quantum dot diffusion composite material includes the following steps:

[0065] (1) Dry SMMA, EVOH, and EVA-g-MAH in an oven at 80℃ for 12 hours and set aside for later use;

[0066] (2) The dried SMMA, EVOH and EVA-g-MAH were premixed in a mass ratio of 60:40:1 and then fed into a twin-screw extruder for extrusion granulation to obtain water-oxygen barrier layer blended granules, namely SMMA-EVOH layer granules.

[0067] (3) 1 kg of dried SMMA and 3.5 ml of quantum dot dispersion (3 ml of green quantum dot white oil dispersion with a concentration of 0.25 g / ml and 0.5 ml of red quantum dot white oil dispersion with a concentration of 0.25 g / ml) were premixed and fed into a twin-screw extruder for extrusion granulation to obtain quantum dot layer blended granules, namely SMMA-QD layer granules;

[0068] In steps (2) and (3), the temperatures of the three sections of the extruder are 190°C, 210°C, and 210°C, and the die temperature is 205°C.

[0069] (4) The water-oxygen barrier layer blended granules and the quantum dot layer blended granules obtained in steps (2) and (3) are respectively vacuum dried, and then... Figure 2 The alternating multilayer co-extrusion apparatus shown was used to prepare SMMA-EVOH / SMMA-QD composite materials. The specific process is as follows:

[0070] The dried SMMA-EVOH layer granules and SMMA-QD layer granules were added separately to... Figure 2 Two single-screw extruders, Extruder 1 and Extruder 2, produce SMMA-EVOH and SMMA-QD layer melts. The two melts enter a layer multiplier through a confluencer to cut and separate into layers. At the inlet of the layer multiplier, the melt is divided into two parts: one part enters the upper flow channel, and the other part enters the lower flow channel. Finally, they are stacked at the outlet of the layer multiplier to multiply the number of layers. The melt is then extruded through a die and cooled and shaped under the action of traction rollers to obtain SMMA-EVOH / SMMA-QD composite materials with 2-128 layers.

[0071] The three-stage temperatures of the single-screw extruder for the SMMA-EVOH and SMMA-QD layers are 185℃, 210℃, and 210℃, respectively, and the manifold temperature is 210℃. The single-screw extrusion speeds of the SMMA-EVOH and SMMA-QD layers are adjusted to control the thickness ratio of the SMMA layer to the SMMA-EVOH layer to be 1:1. The final thickness of the multilayer sheet is 1.3mm, which is denoted as the SMMA-EVOH / SMMA-QD composite material.

[0072] Comparative Example 1

[0073] A method for preparing SMMA sheets includes the following steps:

[0074] After drying SMMA at 80°C for 12 hours, 1 kg of dried SMMA and 3.5 ml of quantum dot dispersion (same as in Example 1) were pre-mixed and then added to a torque rheometer (RM-200C type torque rheometer). The rotor speed was set to a fixed 60 rpm, and the mixture was kneaded at 210°C for 10 minutes. The resulting sample was then molded at 185°C and 10 MPa to obtain SMMA sheets with a diameter of 50 mm and a thickness of 1 mm.

[0075] Comparative Example 2

[0076] A type of SMMA-E m @E n The method for preparing composite materials includes the following steps:

[0077] SMMA, EVOH, and EVA-g-MAH were dried at 80℃ for 12 h. The dried SMMA, EVOH, and EVA-g-MAH were then weighed according to the mass ratios shown in Table 1 and premixed with a quantum dot dispersion (3 ml of 0.25 g / ml green quantum dot white oil dispersion and 0.5 ml of 0.25 g / ml red quantum dot white oil dispersion added to 1 kg of SMMA, EVOH, and EVA-g-MAH blend). This mixture was then added to a torque rheometer for intensive mixing. The rotor speed was fixed at 60 rpm, the mixing temperature was 210℃, and the mixing time was 10 min. After mixing, the resulting sample was molded at 185℃ and 10 MPa to obtain a sheet with a diameter of 50 mm and a thickness of 1 mm, yielding SMMA-E. m @E n Composite materials.

[0078] Table 1

[0079] Sample Name SMMA EVOH EVA-g-MAH <![CDATA[SMMA-E 40 ]]> 60 40 0 <![CDATA[SMMA-E 40 @AND 0.5 ]]> 60 40 0.5 <![CDATA[SMMA-E 40 @E1]]> 60 40 1 <![CDATA[SMMA-E 40 @AND 1.5 ]]> 60 40 1.5

[0080] Note: E mE represents the content of EVOH in the barrier phase. n This represents the content of the compatibilizer EVA-g-MAH. For ternary blends, when the ratio of SMMA to EVOH is fixed and the content of EVA-g-MAH is changed, it is calculated based on a total mass of SMMA and EVOH of 100 parts.

[0081] Comparative Example 3

[0082] A type of SMMA-E m @E n The method for preparing composite materials includes the following steps:

[0083] SMMA, EVOH, and EVA-g-MAH were dried at 80℃ for 12 hours. The dried SMMA, EVOH, and EVA-g-MAH were then weighed according to the mass ratios shown in Table 2 and premixed with a quantum dot dispersion (3 ml of 0.25 g / ml green quantum dot white oil dispersion and 0.5 ml of 0.25 g / ml red quantum dot white oil dispersion added to 1 kg of the SMMA, EVOH, and EVA-g-MAH blend). This mixture was then added to a torque rheometer (RM-200C type), with the rotor speed fixed at 60 rpm, and kneaded at 210℃ for 10 minutes. The resulting sample was then molded at 185℃ and 10 MPa to obtain a sheet with a diameter of 50 mm and a thickness of 1 mm.

[0084] Table 2

[0085] Sample Name SMMA EVOH EVA-g-MAH <![CDATA[SMMA-E5@E1]]> 95 5 1 <![CDATA[SMMA-E 10 @E1]]> 90 10 1 <![CDATA[SMMA-E 15 @E1]]> 85 15 1 <![CDATA[SMMA-E 20 @E1]]> 80 20 1 <![CDATA[SMMA-E 30 @E1]]> 70 30 1 <![CDATA[SMMA-E 40 @E1]]> 60 40 1

[0086] Note: E m E represents the content of EVOH in the barrier phase. n This represents the content of the compatibilizer EVA-g-MAH.

[0087] Comparative Example 4

[0088] A method for preparing an alternating SMMA / SMMA-QD multilayer composite material includes the following steps:

[0089] (1) Before extrusion granulation, SMMA was dried in an oven at 80°C for 12 hours and then premixed with quantum dot dispersion (3 ml of green quantum dot white oil dispersion with a concentration of 0.25 g / ml and 0.5 ml of red quantum dot white oil dispersion with a concentration of 0.25 g / ml added to 1 kg SMMA). The mixture was then granulated by a twin-screw extruder to obtain quantum dot layer granules, namely SMMA-QD layer granules. The extruder temperature was 190°C, 210°C and 210°C in three sections, and the die temperature was 205°C.

[0090] (2) After vacuum drying, the obtained quantum dot layer particles are then subjected to... Figure 2The alternating multilayer co-extrusion apparatus shown prepared a 128-layer SMMA / SMMA-QD alternating multilayer material. The specific process is as follows:

[0091] Vacuum-dried SMMA and SMMA-QD granules were added to... Figure 2 The SMMA layer melt and SMMA-QD layer melt are obtained from two single-screw extruders, Extruder 1 and Extruder 2. The two melts enter the layer multiplier through a confluencer to cut and layer the melt. At the inlet of the layer multiplier, the melt is divided into two parts: one part enters the upper flow channel and the other part enters the lower flow channel. Finally, the melt is superimposed at the outlet of the layer multiplier to achieve layer multiplication. Finally, the melt is extruded through a die and cooled and shaped under the action of the traction roller to obtain a 128-layer SMMA / SMMA-QD composite material.

[0092] The three temperature sections of the single-screw extruder are 185℃, 210℃, and 210℃, respectively, and the manifold temperature is 210℃. The extrusion speeds of the single screws of extruder one and extruder two are adjusted, and the thickness ratio of the SMMA layer to the SMMA-QD layer is controlled to be 1:1. A composite material sheet with a sample width of about 30mm and a thickness of about 1.3mm is obtained.

[0093] Technical effects:

[0094] 1) Effect of compatibilizer content on the microstructure of blends

[0095] as follows Figure 3 As shown, the morphology of the EVOH phase in the SMMA continuous phase is irregular without compatibilizer, but after adding EVA-g-MAH ( Figure 3 In the SMMA system, as the content of EVA-g-MAH increases, the number of regularly shaped spherical EVOH dispersed phases gradually increases and their size decreases. When the content of EVA-g-MAH reaches 1.5 wt%, EVOH is almost entirely distributed in the SMMA system as spherical dispersed phases with a particle size of 8-15 μm. This indicates that the addition of EVA-g-MAH can effectively improve the compatibility between the SMMA and EVOH phases, making the EVOH dispersion more uniform.

[0096] 2) Effect of compatibilizer content on the light scattering properties of blends

[0097] According to ASTM D1003-61 standard, transmittance / haze was measured using a WGT-S transmittance / haze meter from Shanghai Precision Scientific Instruments Co., Ltd., with a national standard C light source having an average wavelength of 550nm. The transmittance and haze of the products obtained from SMMA and Comparative Example 2 were tested.

[0098] Table 3. Effect of compatibilizer content on the transmittance and haze of the blend

[0099] Material Light transmittance / % Haze / % SMMA 76.4 9.4 <![CDATA[SMMA-E 40 ]]> 61.8 89.9 <![CDATA[SMMA-E 40 @AND 0.5 ]]> 59.4 87.1 <![CDATA[SMMA-E 40 @E1]]> 58.1 88.8 <![CDATA[SMMA-E 40 @AND 1.5 ]]> 52.47 89.64

[0100] EVOH is dispersed in the SMMA matrix in an island-phase structure, causing multiple refractions of light as it passes through. At this point, the material already possesses good light scattering properties. Therefore, the SMMA / EVOH blend without EVA-g-MAH has a transmittance of 61.8% and a haze of 89.9%. With the addition of EVA-g-MAH, the size and quantity of the EVOH dispersed phase decrease, leading to an increase in the number of light scattering events, increased backscattering, and a decrease in transmittance.

[0101] 3) Effect of compatibilizer content on the barrier properties of blends

[0102] The barrier properties of the products obtained from SMMA and Comparative Example 2 were tested, and the testing standards are as follows:

[0103] Oxygen permeability coefficient: The oxygen permeability coefficient was determined using a VAC-V2 differential pressure gas permeameter (Jinan Langguang Electromechanical Technology Co., Ltd.) according to the standard ISO 2556-1974, "Air permeability of plastics in films and sheets under atmospheric pressure".

[0104] Water vapor transmission rate: The C306H water vapor transmission rate test system (Jinan Langguang Electromechanical Technology Co., Ltd.) was used to conduct the test in continuous mode according to ASTM F1249 standard.

[0105] Table 4. Effect of compatibilizer content on barrier performance

[0106]

[0107] As shown in Table 4, for samples with different compatibilizer contents, the barrier properties of the samples further increase with the increase of compatibilizer content. Moreover, the water vapor permeability decreases more than the oxygen barrier coefficient. When the EVA-g-MAH content is 1.5 wt%, the oxygen permeability coefficient decreases from 5.01 × 10⁻⁶. -14 cm 3 ·cm / cm 2 The pressure ·s·Pa decreased to 0.316×10 -14 cm 3 ·cm / cm 2 Water vapor permeability from 0.163 g / m³·s·Pa. 2 • Decreased to 0.0837 g / m³ over 24 hours 2 • 24h. This is because the barrier performance is greatly affected by the dispersion and size of the dispersed phase in the matrix. As the EVA-g-MAH content increases, the number of regularly shaped spherical EVOH dispersed phases increases significantly and their size decreases, thus lengthening the gas passage path and reducing its permeability coefficient.

[0108] 4) Effect of barrier phase content on barrier performance

[0109] The barrier properties of the products obtained from SMMA and Comparative Example 3 were tested using the same method as in Example 3.

[0110] Table 5. Effect of Organic Barrier Phase Content on Barrier Performance

[0111]

[0112] As shown in Table 5, when the EVOH content is below 15%, the water and oxygen barrier properties of the SMMA blend do not change significantly. However, when the EVOH content increases further, the barrier properties improve slightly. (SMMA-E) 20 The oxygen permeability and water vapor permeability of @E1 are 2.196 × 10⁻⁶. -14 cm 3 ·cm / cm 2 ·s·Pa and 1.27g / m 2 • Over 24 hours, compared to SMMA, oxygen and water vapor barriers decreased by 43% and 45%, respectively. With further increases in EVOH content, oxygen and water vapor barriers decreased significantly as EVOH content increased from 30 wt% to 40 wt%, SMMA-E 40 The oxygen permeability and water vapor permeability of @E1 are 0.4415 × 10⁻⁶. -14 cm 3 ·cm / cm 2 ·s·Pa and 0.1037g / m 2 • Over 24 hours, compared to SMMA, the levels decreased by 88% and 96%, respectively.

[0113] SMMA-E with different EVOH contents m The cross-sectional morphology of the E1 blend is as follows: Figure 4 As shown in the figure, the EVOH content has a significant impact on the phase morphology of the blend. When the mass fraction of EVOH increases from 5 wt% to 30 wt%, the EVOH is dispersed in the SMMA matrix as spherical particles, with the average particle size increasing from approximately 1.2 μm to 10.1 μm. The blend exhibits a typical island-like structure. With the EVOH content increasing to 40 wt%, the particle size of the EVOH phase increases substantially, resulting in a significant increase in its barrier properties.

[0114] 5) The effect of barrier phase content on optical performance

[0115] The transmittance and haze of the products obtained from SMMA and Comparative Example 3 were tested using the same method as in 2).

[0116] Table 6. Effect of barrier phase content on the transmittance and haze of the blend.

[0117] Material Light transmittance / % Haze / % SMMA 76.4 9.4 <![CDATA[SMMA-E5@E1]]> 71.8 72.86 <![CDATA[SMMA-E 10 @E1]]> 67.06 84.78 <![CDATA[SMMA-E 15 @E1]]> 62.66 88.14 <![CDATA[SMMA-E 20 @E1]]> 61.36 89.38 <![CDATA[SMMA-E 30 @E1]]> 59.7 90.14 <![CDATA[SMMA-E 40 @E1]]> 58.1 88.8

[0118] Table 6 shows SMMA-E m The table shows the relationship between the transmittance and haze of the @E1 blends as a function of EVOH addition. As can be seen from the table, pure SMMA has the highest transmittance of 88%. With a fixed addition of 1 wt% EVA-g-MAH, the addition of 5 wt% EVOH causes the transmittance of the blend to rapidly decrease from 88% to 71.8%, while the haze rapidly increases from 0.3% to 72.86%. When the EVOH concentration increases from 5 wt% to 15 wt%, the transmittance decreases to 62.7%, while the haze increases to 88.1%. However, when the EVOH concentration is between 15 wt% and 40 wt%, the changes in transmittance and haze are relatively small. This is because: on the one hand, as the content of the organic barrier phase increases, the total scattering cross-section of the particles increases, leading to an increase in the scattering probability and thus an increase in the total scattering angle and haze; on the other hand, as the particle size of the light diffusing agent gradually increases, forward scattering increases while scattering from other directions weakens, resulting in a decrease in haze. The combined effect of these two factors leads to relatively small changes in transmittance and haze.

[0119] 6) The effect of the number of layers on optical performance

[0120] The transmittance and haze of SMMA / SMMA-QD and SMMA-EVOH / SMMA-QD prepared by alternating multilayer co-extrusion method in Example 1 and Comparative Example 4 were tested using the same method as in Example 2), and the results are shown in Table 7.

[0121] Table 7. Transmittance and Haze of Multilayer Samples

[0122] Material Light transmittance (%) Haze (%) SMMA / SMMA-QD 128L 73.4 10.45 SMMA-EVOH / SMMA-QD 2L 59.1 75.59 SMMA-EVOH / SMMA-QD 8L 59.6 76.7 SMMA-EVOH / SMMA-QD 32L 61.7 75.37 SMMA-EVOH / SMMA-QD 128L 61.5 75.59

[0123] Note: L represents the total number of floors.

[0124] As shown in Table 7, the transmittance of the sample slightly increases with the number of layers, while the haze does not change significantly. This is because during the stretching and orientation process, the morphology of the EVOH dispersed phase changes from long fibrous to plate-like (e.g., ...) Figure 5 As shown in the figure, this increases the probability that the incident light is perpendicular to the incident long axis, resulting in a slight increase in transmittance. The changes in transmittance and haze are related to the phase morphology evolution of the EVOH phase in SMMA and the changes in the dispersion of QDs in SMMA. In the 8-layer sample, there are QDs aggregates with a size of about 200 nm, while in the 128-layer sample, the biaxial stretching effect significantly improves the aggregation of QDs, reducing the aggregate size to below 100 nm, thus increasing its transmittance and slightly reducing its haze.

[0125] 7) The effect of the number of layers on water and oxygen barrier performance

[0126] SMMA, SMMA-E20 @E1, The transmittance and haze of SMMA / SMMA-QD and SMMA-EVOH / SMMA-QD prepared by alternating multilayer co-extrusion method in Examples 1 and 4 were tested, and the testing method was the same as in 3). The results are shown in Table 8.

[0127] Table 8. Water and oxygen barrier properties of multilayer samples

[0128]

[0129]

[0130] It can be seen that, compared with SMMA without added organic barrier phase and SMMA-E with the same content of organic barrier phase, 20 Compared to @E1 composites, SMMA-EVOH / SMMA-QD alternating multilayer composites exhibit lower oxygen permeability and water vapor permeability. Furthermore, the oxygen permeability decreases further with increasing layer count. One factor is that the outer barrier layer acts as a protective layer for the inner barrier layer, reducing the impact of humidity on its oxygen barrier performance. Another factor is that during extrusion, EVOH gradually transforms from a long fibrous morphology to a sheet-like morphology that is more conducive to extending the gas permeation path. The combined effect of these two factors leads to a sharp decrease in oxygen permeability.

[0131] 8) The effect of layered structure on the fluorescence lifetime of quantum dots

[0132] Figure 6 The graph shows the light intensity changes of the alternating multilayer composite materials (SMMA / SMMA-QD 128L, SMMA-EVOH / SMMA-QD 8L, SMMA-EVOH / SMMA-QD 128L) obtained in Comparative Example 4 and the two examples 1 after being irradiated with a 365nm ultraviolet lamp for different times (test chamber temperature: 60℃, humidity: 50%RH).

[0133] Depend on Figure 6It can be seen that the light intensity of the 128-layer SMMA / SMMA-QD sample gradually decreased with the extension of irradiation time. After irradiation time exceeding 108 hours, the fluorescence was almost completely quenched. Simultaneously, a boundary line was observed between the directly irradiated part and the clamped, unirradiated part of the sample before and after irradiation. This boundary line gradually extended towards the unirradiated part with increasing aging time. At 512 hours of aging, the clamped part of the sample was also almost completely quenched. However, the 8-layer and 128-layer samples with added EVOH maintained strong fluorescence intensity even after 512 hours of irradiation, with almost no change in fluorescence intensity visible to the naked eye. This is because, with deeper irradiation, even if the outer quantum dot layer cannot be protected and fluorescence quenching occurs, the inner quantum dots are not affected, resulting in a small change in the overall fluorescence intensity of the material. When the UV aging time was 512h, the 8-layer and 128-layer samples with added EVOH showed different degrees of degradation at the edges, but the middle part remained relatively good, further demonstrating that the layer-by-layer protection of the alternating multilayer structure can significantly improve the photostability and fluorescence lifetime of QDs.

[0134] Using the time T when the fluorescence intensity is reduced by half 50 To characterize the fluorescence lifetime of quantum dots, the T128L of SMMA / SMMA-QD 128L under UV irradiation... 50 Approximately 3 hours, T of SMMA-EVOH / SMMA-QD 8L 50 At 350h, the T of SMMA-EVOH / SMMA-QD 128L increased by approximately 116 times. 50 In the 690h, it improved by more than 230 times.

[0135] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high water and oxygen barrier quantum dot diffusion composite material, characterized in that, Includes alternating layers of water and oxygen barrier and quantum dot layers; The water-oxygen barrier layer comprises the following raw materials in parts by weight: The composition consists of 60-85 parts of the first matrix, 15-40 parts of the barrier polymer, and 0.5-1.5 parts of the compatibilizer; The barrier polymer is an ethylene-vinyl alcohol copolymer; The compatibilizer is an ethylene-vinyl acetate copolymer grafted with maleic anhydride. The melt viscosity of the barrier polymer is lower than that of the first matrix; The first matrix is ​​a methyl methacrylate-styrene copolymer; The quantum dot layer comprises a second matrix and quantum dots, wherein the second matrix is ​​a methyl methacrylate-styrene copolymer; The preparation method of the high water and oxygen barrier quantum dot diffusion composite material includes the following steps: After drying the water-oxygen barrier layer blended granules and the quantum dot layer blended granules, they were co-extruded using an alternating multilayer co-extrusion device to obtain the high water-oxygen barrier diffusion composite material. During the co-extrusion process, the bidirectional tensile force field generated by the alternating layering process regulates the morphology of the organic barrier phase, transforming the organic barrier phase into a sheet-like or fibrous structure. The alternating layering is a process of doubling the number of layers, and the number of alternating layers is 32 or more.

2. The high water-oxygen barrier quantum dot diffusion composite material according to claim 1, characterized in that, The thickness of the composite material is 0.05–4 mm; The quantum dots are 0.005% to 1% of the mass of the second matrix.

3. The method for preparing a high water-oxygen barrier quantum dot diffusion composite material as described in claim 1 or 2, characterized in that, Includes the following steps: After drying the water-oxygen barrier layer blended granules and the quantum dot layer blended granules, they were co-extruded using an alternating multilayer co-extrusion device to obtain the high water-oxygen barrier diffusion composite material. During the co-extrusion process, the bidirectional tensile force field generated by the alternating layering process regulates the morphology of the organic barrier phase, transforming the organic barrier phase into a sheet-like or fibrous structure. The alternating layering is a process of doubling the number of layers, and the number of alternating layers is 32 or more.

4. The method for preparing a high water-oxygen barrier quantum dot diffusion composite material according to claim 3, characterized in that, The preparation method of the water-oxygen barrier layer blended granules includes the following steps: The first matrix is ​​dried, then mixed with a barrier polymer and a compatibilizer, and co-extruded into granules to obtain the water-oxygen barrier layer blend granules.

5. The method for preparing a high water-oxygen barrier quantum dot diffusion composite material according to claim 3, characterized in that, The preparation method of the quantum dot layer blend granules includes the following steps: The second matrix is ​​dried, then mixed with quantum dots and co-extruded to obtain the quantum dot layer blended granules.

6. The application of the high water and oxygen barrier quantum dot diffusion composite material as described in claim 1 or 2 in quantum dot displays.

Images