A method for preparing a quantum dot reflective film and a reflective film

Abstract

The present invention relates to the technical field of quantum dot reflective films, and discloses a preparation method of a quantum dot reflective film and a reflective film, comprising the following steps: (1) organically ligand-modifying CsPbBr3 quantum dots with bromohexylamine to obtain modified quantum dot powder; (2) adding nylon 6 resin, modified quantum dot powder and ethanol into a reaction kettle, sealing and heating, then stopping heating and cooling to room temperature by stirring, and after separation, obtaining quantum dots wrapped with PA6; (3) blending and granulating the quantum dots wrapped with PA6 and PET, adding the obtained granulated material and PET into an auxiliary extruder after blending, adding a foaming material, titanium dioxide and PET into a main extruder, and melt-extruding to obtain a reflective film with an ABA three-layer structure, wherein the A layer contains quantum dots. By using nylon 6 resin to wrap quantum dots, the present invention improves the lifespan and temperature resistance of quantum dots, and the obtained reflective film has high brightness and color gamut, and its durability is improved.

Description

Technical Field

[0001] The invention relates to the technical field of quantum dot films, and in particular to a preparation method of a quantum dot reflective film and the reflective film. Background Art

[0002] The backlight module is an important component of the liquid crystal display panel. The general backlight module is composed of a backplane, a reflective film, a light guide plate, a diffusion film, a brightness enhancement film, and LED lamp beads. The backlight required by the general liquid crystal display panel is a combination of blue LED lamps and yellow phosphors, which produces low color purity, low color saturation and low color gamut values, so the reflective film needs to be optimized.

[0003] Metal halide perovskite quantum dots have the advantages of low processing cost, high luminous efficiency, tunable spectrum, and high color purity, and are currently a hot research topic in the field of light-emitting display. However, quantum dot materials generally have the disadvantages of insufficient temperature resistance and short lifespan. At present, the cause of quantum dot failure is often considered to be the self-exchange of organic ligands, which no longer protects the quantum dots. The quantum dots grow by themselves and eventually form larger nanocrystals. These larger nanocrystals have higher surface defects, resulting in a sharp drop in quantum efficiency. At the same time, quantum dot materials are sensitive to temperature, humidity, and oxygen. Oxygen will promote the agglomeration of small-sized CsPbBr3 quantum dots to form large-sized nanocrystals, and can also etch unstable nuclei on the surface of PQDs, resulting in more surface defects. Photoelectron spectroscopy found that under light, oxygen and CsPbBr3 undergo oxidation reactions, and oxidation products PbO are generated, which can easily lead to fluorescence quenching and inactivation, and the stability of quantum dots is poor. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a quantum dot reflective film and a reflective film. The quantum dots are wrapped with PA6 resin, which can effectively isolate water and oxygen while improving temperature resistance. The quantum dots are not completely inactivated under high temperature and high humidity conditions, and the resulting quantum dot reflective film can still maintain a good luminescence effect after aging.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a quantum dot reflective film, comprising the following steps:

[0007] (1) CsPbBr3 quantum dots are modified with organic ligands by using bromohexylamine to obtain modified quantum dot powder;

[0008] (2) Add nylon 6 resin, modified quantum dot powder and ethanol into a reactor in a ratio of 0.4-0.6 g: 10 g: 500 mL, and the total volume of the raw materials accounts for 50-80% of the volume of the reactor. After sealing, heat is increased, and then heating is stopped and cooled to room temperature by stirring. After separation, PA6-wrapped quantum dots are obtained;

[0009] (3) The PA6-wrapped quantum dots and PET are blended and granulated, and the resulting granulated material is blended with PET and added to an auxiliary extruder. The foaming material, titanium dioxide and PET are added to a main extruder and melt-extruded to obtain an ABA three-layer structure reflective film, in which layer A contains quantum dots.

[0010] The present invention encapsulates the quantum dots by PA6 resin. PA6 is a polyamide material with relatively high light transmittance and can effectively isolate water and oxygen. Therefore, it can improve the stability of the quantum dots in the reflective film without affecting the luminous efficiency of the quantum dots as much as possible. PA6 also has good temperature resistance, and thus can improve the aging resistance of the quantum dot reflective film. After aging, it can still maintain a good luminous effect, thereby improving the durability of the reflective film.

[0011] In addition, bromine-containing ligands can be used for the passivation of lead-based perovskite quantum dots. The strong electron-withdrawing ability of bromide ions can effectively passivate the B-site defects of lead halide perovskite quantum dots and curb the Pb 2+ Oxidation. And by introducing amino groups, PA6 can be easily encapsulated with quantum dots, and the hydrogen bonds between amino groups and amide groups can be used to make the encapsulation more stable and complete. At the same time, PA6 is a semi-crystalline polymer, and its crystallinity has a significant effect on transparency. During the encapsulation process, factors such as temperature, pressure and cooling rate will affect the transparency of PA6. Higher insulation temperature and faster cooling rate can help reduce crystallinity, thereby improving transparency.

[0012] Preferably, step (1) specifically comprises the following steps: adding bromohexylamine to the CsPbBr3 quantum dot solution and stirring, adding the resulting solution to ethyl acetate for precipitation, taking the supernatant and centrifuging it, adding the resulting supernatant to toluene for re-precipitation, centrifuging and drying the precipitate to obtain a modified quantum dot powder.

[0013] Preferably, the concentration of the CsPbBr3 quantum dot solution is 8×10 -6 -9×10 -6 mol / mL; the volume ratio of the CsPbBr3 quantum dot solution and bromohexylamine is 50-85:1.

[0014] Preferably, in step (2), before heating, nitrogen is introduced to replace the air in the reactor; the heating temperature is 160-180°C, the temperature is kept for 1-2 hours, and the heating rate is 1-3°C / min; the stirring speed is 500-800rpm, and the average cooling rate is 1-3°C / min.

[0015] Using ethanol as a solvent is conducive to the dispersion of modified quantum dot powders. In addition, the sealed reactor will form a high temperature and high pressure environment after heating. The melting point of nylon 6 resin is reduced in a high temperature and high pressure solvent environment, and it can be better miscible with ethanol. In the reactor, ethanol will form a saturated vapor pressure, and the ethanol vapor and liquid states will be balanced, which will further increase the pressure and promote the dissolution of nylon 6 resin. At the same time, the ethanol molecules move to form steam. Therefore, the heat preservation reaction in this state can make nylon 6 and quantum dots more dispersed. Then, by controlling the stirring speed and cooling speed during the cooling process, the stability and uniformity of the package are higher.

[0016] A faster stirring speed and cooling speed can obtain a PA6 coating with lower crystallinity. A slower speed will result in a lower light transmittance of the PA6 coating and cause quantum dots to agglomerate. However, if the speed is too fast, PA6 is not easy to be coated, and the coating effect on the surface of quantum dots is poor.

[0017] Preferably, in step (3), the mass percentage of the PA6-wrapped quantum dots in the granulated material is 1-2%.

[0018] Preferably, in step (3), the mass ratio of the granulated material to PET is 5-8%:92-95%, and the total mass percentage is 100%.

[0019] Preferably, in step (3), the mass percentages of the foaming material, titanium dioxide and PET are 5-15%: 5-15%: 70-90%, and the total mass percentage is 100%; the foaming material is poly-4-methyl-1-pentene.

[0020] In order to improve the reflectivity of the reflective film, inorganic particles (titanium dioxide) and a resin incompatible with polyester (poly-4-methyl-1-pentene) are added to polyester, which causes phase separation during the biaxial stretching process to form a large number of micropores. Each micropore can serve as a total reflection unit, and the high-density arranged total reflection units reflect light.

[0021] Preferably, in step (3), in the ABA three-layer structure, the thickness ratio of layer A, layer B and layer A is 6-8%:84-88%:6-8%, and the thickness of the upper and lower A layers is the same.

[0022] In a second aspect, the present invention further provides a reflective film obtained by the above-mentioned preparation method, wherein the reflective film is an ABA three-layer structure, wherein layer A is a polyester film containing quantum dots, and layer B is a polyester film with a microporous structure.

[0023] Preferably, in the ABA three-layer structure, the thickness ratio of the A layer, the B layer and the A layer is 6-8%:84-88%:6-8%, and the thickness of the upper and lower A layers is the same.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) PA6 has good oxygen isolation. After the quantum dots are coated with PA6, they are isolated from oxygen, which increases the life of the quantum dots and reduces the possibility of self-growth of quantum dot crystals. At the same time, PA6 has good temperature resistance. The quantum dots are not completely inactivated under high temperature and high humidity conditions, and their tolerance to ambient temperature is improved.

[0026] (2) The quantum dot reflective film has high brightness and color gamut, and can still maintain a good luminous effect after aging, and the durability of the reflective film is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the quantum dot reflective film in the present invention.

[0028] Figure 2 Schematic diagram of the structure of quantum dots wrapped in PA6 in the present invention.

[0029] The figures are marked as follows: 1. A layer; 2. PA6-wrapped quantum dots; 201. quantum dots; 202. PA6-wrapped layer; 3. B layer; 4. microporous structure; 5. titanium dioxide particles. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0031] Preparation of CsPbBr3 quantum dot solution (commercially available CsPbBr3 quantum dot solution can also be used):

[0032] (a) Weigh 0.36 g of cesium carbonate (Cs2CO3) and add it to a 50 mL three-necked flask, add 15 mL of octadecene (ODE) and 1.5 mL of oleic acid (OA), and evacuate the mixture while stirring. Heat the mixture at the same time, and stop heating after the temperature reaches 120°C. Continue evacuating the mixture for 10 min, then fill with nitrogen, continue heating to 140°C and keep warm, stirring until the Cs2CO3 is completely dissolved to form a clear and transparent solution, and keep warm to obtain a cesium oleate precursor solution.

[0033] (b) Weigh 0.2 g of lead bromide (PbBr2) and add it to a 50 mL three-necked flask, add 15 mL of octadecene (ODE), evacuate the flask while stirring, and heat it at the same time. After the temperature reaches 120°C, stop heating and continue evacuating the flask for 10 min. Then, fill with nitrogen, add 1.5 mL each of oleic acid (OA) and ammonium oleate (OAm), continue heating to 170°C, and stir until PbBr2 is completely dissolved to form a light yellow clear solution. Keep warm to obtain a lead oleate precursor solution.

[0034] (c) 1.2 mL of cesium oleate precursor solution was quickly injected into the lead oleate precursor. After reacting for 5 seconds, the solution was cooled in an ice water bath to obtain a bright green CsPbBr3 quantum dot solution with a quantum dot concentration of 8.4×10 -6 mol / mL, and the particle size of quantum dots is 10-20nm.

[0035] Example 1

[0036] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0037] (2) Weigh 10g of modified CsPbBr3 quantum dot powder, 0.5g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160°C at a heating rate of 1°C / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 2°C / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0038] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0039] like Figure 1 FIG. 1 is a schematic diagram of the structure of the quantum dot reflective film of the present invention, which includes a three-layer structure of layer A 1, layer B 3 and layer A 1. Figure 2 As shown, the A layer 1 contains PA6-wrapped quantum dots 2, which are composed of internal quantum dots 201 and a PA6 wrapping layer 202 on the outer layer of the quantum dots 201. The B layer 3 contains titanium dioxide particles 5, and a microporous structure 4 formed by adding inorganic particles and foaming materials to polyester and phase separation during biaxial stretching.

[0040] Example 2

[0041] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.35 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0042] (2) Weigh 10g of modified CsPbBr3 quantum dot powder, 0.6g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 170℃ at a heating rate of 1℃ / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 2℃ / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80℃ for 24h to obtain PA6-encapsulated quantum dots.

[0043] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0044] Example 3

[0045] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0046] (2) Weigh 10g of modified CsPbBr3 quantum dot powder, 0.5g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160°C at a heating rate of 1°C / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 3°C / min at a stirring speed of 800rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0047] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0048] Example 4

[0049] (1) At room temperature, 38.4 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4 × 10 -6 mol / mL) was added with 0.5 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 10 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 100 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0050] (2) Weigh 20g of modified CsPbBr3 quantum dot powder, 1g of PA6 resin (melt index is 26.0g / 10min), and 1000mL of ethanol into a 2L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160°C at a heating rate of 1°C / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 2°C / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0051] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 20g of PA6-wrapped quantum dot powder was blended and granulated with 980g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 6%:88%:6%.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that the quantum dots are not wrapped with PA6.

[0054] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0055] (2) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of modified CsPbBr3 quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that the quantum dots are not modified with bromohexylamine.

[0058] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 5 mL of ethyl acetate for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 min. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, and centrifuged at 10000 rpm for 10 min. The lower half of the solution containing the precipitate was taken and dried in a vacuum oven at 80 ° C for 3 days to obtain CsPbBr3 quantum dot powder.

[0059] (2) Weigh 10g of CsPbBr3 quantum dot powder, 0.5g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1.5L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160°C at a heating rate of 1°C / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 2°C / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0060] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0061] Comparative Example 3

[0062] The difference from Example 1 is that the stirring speed is 100 rpm and the cooling speed is 0.5° C. / min.

[0063] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0064] (2) Weigh 10g of modified CsPbBr3 quantum dot powder, 0.5g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1.5L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160°C at a heating rate of 1°C / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 0.5°C / min at a stirring speed of 100rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0065] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that the insulation temperature during sealing is 150° C. and the insulation time is 30 minutes.

[0068] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0069] (2) Weigh 10g of modified CsPbBr3 quantum dot powder, 0.5g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1.5L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 150°C at a heating rate of 1°C / min and keep warm for 30min. Stop heating, and gradually cool to room temperature at an average cooling rate of 2°C / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0070] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0071] Comparative Example 5

[0072] The difference from Example 1 is that the amount of PA6 added is 1 g.

[0073] (1) At room temperature, in 19.2 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 0.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 5 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 50 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0074] (2) Weigh 10g of modified CsPbBr3 quantum dot powder, 1g of PA6 resin (melt index is 26.0g / 10min), and 500mL of ethanol into a 1.5L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160°C at a heating rate of 1°C / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 2°C / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80°C for 24h to obtain PA6-encapsulated quantum dots.

[0075] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 10g of PA6-wrapped quantum dot powder was blended and granulated with 990g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melted (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melted (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0076] Comparative Example 6

[0077] The difference from Example 1 is that 50 g of PA6-wrapped quantum dot powder and 950 g of polyester (PET) particles are blended and granulated.

[0078] (1) At room temperature, 96 mL of CsPbBr3 quantum dot solution (quantum dot concentration of 8.4×10 -6 mol / mL) was added with 1.25 mL of bromohexylamine (C 11 H 22 NO2Br), stirred for 12 hours, so that bromohexylamine and the first ligand oleic acid / oleylamine were replaced. 25 mL of ethyl acetate was added for precipitation, and the insoluble matter was removed by centrifugation at 10000 rpm for 10 minutes. The supernatant was taken from the obtained solution, added to 250 mL of toluene, and precipitated again, centrifuged at 10000 rpm for 10 minutes, and the lower half of the solution containing the precipitate was taken and dried at 80 ° C in a vacuum oven for 3 days to obtain a modified CsPbBr3 quantum dot powder modified with bromohexylamine.

[0079] (2) Weigh 50g of modified CsPbBr3 quantum dot powder, 2.5g of PA6 resin (melt index is 26.0g / 10min), and 2500mL of ethanol into a 5L stainless steel reactor, and seal the reactor. Introduce nitrogen to replace the air in the reactor, then gradually increase the temperature to 160℃ at a heating rate of 1℃ / min and keep it warm for 1h. Stop heating, and gradually cool to room temperature at an average cooling rate of 2℃ / min at a stirring speed of 500rpm. Open the lid to release the pressure to obtain a suspension. The cooled suspension is subjected to solid-liquid separation, the solid is washed, and vacuum dried at 80℃ for 24h to obtain PA6-encapsulated quantum dots.

[0080] (3) The polyester (PET) particles were vacuum dried for 3 hours at a drying temperature of 150°C. After cooling, 50g of PA6-wrapped quantum dot powder was blended and granulated with 950g of polyester (PET) particles. The granulated material was vacuum dried at 80°C for 24 hours. The granulated material and 95% of the polyester (PET) particles were added to the auxiliary extruder in a mass ratio of 5% and melt blended (as layer A). The foaming material (poly-4-methyl-1-pentene), 5% titanium dioxide (average particle size of 1 μm) and 88% of the polyester (PET) particles were added to the main extruder in a mass ratio of 7% and melt blended (as layer B). The three-layer co-extrusion, melt extrusion, and then cast film and winding were performed to obtain an ABA three-layer structure reflective film with a total thickness of 100 μm. The thickness ratios of the A layer, the B layer and the A layer were 7%:86%:7%.

[0081] Performance Test:

[0082] Brightness, brightness uniformity, and color coordinates test: Take a 10.1-inch reflective film and place it in a 10.1-inch direct-lit quantum dot backlight module. Use a luminance meter (produced by Suzhou Fushida Scientific Instrument Co., Ltd., model: BM-7A) to test brightness, color coordinates, and uniformity. Brightness = sample brightness / brightness of comparison example 1*100%. The higher the brightness, the better the luminous effect. The larger the color coordinates x and y, the richer the color gamut. The higher the uniformity, the more uniform the light output of the reflective film.

[0083] In addition, the reflective film samples were aged at 60°C and 90% RH for 1000 hours, and their brightness and color coordinates were tested again. The degree of change in brightness (△brightness), color coordinates (△x, △y), and uniformity (△uniformity) before and after aging were calculated. The low degree of drift in brightness and color coordinates and the small degree of change in uniformity after aging indicate that the film material has good stability.

[0084] Table 1

[0085]

[0086] As shown in Table 1, the quantum dots in Comparative Example 1 were not wrapped with PA6, which easily led to the inactivation of quantum dots. The quantum dots in Comparative Example 2 were not modified with bromohexylamine, but were directly wrapped with PA6 resin, which resulted in a relatively poor wrapping effect and easy inactivation under an aging high temperature and high humidity environment. The stirring speed and cooling speed in the cooling process of Comparative Example 3 were too slow, which not only led to the agglomeration of quantum dots and the deterioration of the wrapping effect, but also resulted in the high crystallinity and poor transmittance of PA6, which ultimately led to the deterioration of the luminous effect, especially the poor uniformity. The temperature in the sealing and heat preservation process of Comparative Example 4 was low, and the time was too short, which resulted in the materials in the reactor not being fully compatible and dispersed, and PA6 could not be effectively wrapped on the surface of the quantum dots, which ultimately led to the easy inactivation of quantum dots. In Comparative Example 5, too much PA6 resin was added, and although quantum dots could also be wrapped, the uniformity and transmittance of the wrapping deteriorated, and the luminous effect deteriorated. In Comparative Example 6, excessive addition of PA6-encapsulated quantum dot powder during blending and granulation with PET particles will also cause the quantum dots to agglomerate easily and have poor dispersion, thereby affecting the luminescence effect and uniformity.

[0087] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a quantum dot reflective film, characterized in that: The steps include: (1) adding bromohexylamine to a CsPbBr3 quantum dot solution and stirring, adding the resulting solution to ethyl acetate for precipitation, taking the supernatant and centrifuging it, adding the resulting supernatant to toluene for reprecipitation, centrifuging and drying the precipitate to obtain a modified quantum dot powder; (2) Add nylon 6 resin, modified quantum dot powder and ethanol into the reactor in the ratio of 0.4-0.6g:10g:500mL, and the total volume of the raw materials accounts for 50-80% of the volume of the reactor. After sealing, heat to 160-180°C and keep warm for 1-2h. Then stop heating and cool to room temperature by stirring. The stirring speed is 500-800rpm and the cooling speed is 1-3°C / min. After separation, PA6-wrapped quantum dots are obtained; (3) The quantum dots wrapped in PA6 are blended with PET to form granules; the granules are blended with PET in a mass ratio of 5-8%:92-95% based on a total mass percentage of 100%, and then added to an auxiliary extruder; a foaming material, titanium dioxide and PET are added to a main extruder, wherein the foaming material is poly-4-methyl-1-pentene, and melt-extruded to obtain an ABA three-layer structure reflective film, wherein the A layer contains quantum dots.

2. The method for preparing the quantum dot reflective film according to claim 1, characterized in that: The concentration of the CsPbBr3 quantum dot solution is 8×10 -6 -9×10 -6 mol / mL.

3. The method for preparing a quantum dot reflective film according to claim 1 or 2, characterized in that: The volume ratio of the CsPbBr3 quantum dot solution to bromohexylamine is 50-85:

1.

4. The method for preparing the quantum dot reflective film according to claim 1, characterized in that: In step (2), before heating, nitrogen is introduced to replace the air in the reactor.

5. The method for preparing the quantum dot reflective film according to claim 1, characterized in that: In step (2), the heating rate is 1-3°C / min.

6. The method for preparing a quantum dot reflective film according to claim 1, characterized in that: In step (3), the mass percentage of the PA6-wrapped quantum dots in the granulated material is 1-2%.

7. The method for preparing a quantum dot reflective film according to claim 1 or 6, characterized in that: In step (3), the mass percentages of the foaming material, titanium dioxide and PET are 5-15%: 5-15%: 70-90%, and the total mass percentage is 100%.

8. The method for preparing a quantum dot reflective film according to claim 1, characterized in that: In step (3), in the ABA three-layer structure, the thickness ratio of layer A, layer B and layer A is 6-8%:84-88%:6-8%, and the thickness of the upper and lower A layers is the same.

9. A reflective film obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The reflective film is an ABA three-layer structure, wherein the A layer is a polyester film containing quantum dots, and the B layer is a polyester film with a microporous structure.

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