Preparation method of quantum dot composite material, display device

Abstract

The present disclosure provides a preparation method of quantum dot composite material and a display device. The preparation method of quantum dot composite material comprises: S1, melting and co-extruding a second hydrophobic resin and a hydrophilic resin in a weight ratio of 100:(3-25), and an optional compatibilizer at a first temperature to obtain a hydrophilic modified master batch; S2, mixing a first hydrophobic resin and a quantum dot material to obtain a quantum dot master batch; and S3, melting and co-extruding the hydrophilic modified master batch as a first layer material and the quantum dot master batch as a second layer material at a second temperature to obtain a plate-shaped quantum dot composite material.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of quantum dot composite materials, and in particular, to a preparation method of quantum dot composite material and a display device. BACKGROUND

[0002] As a new generation of luminescent material, quantum dots have great application prospects in the field of display backlight technology due to their high luminescent efficiency, adjustable luminescent peak position, and narrow half-peak width. The quality of the backlight of a display product directly determines important parameters such as the brightness, uniformity, color step, and saturation of the display screen. The use of quantum dot technology greatly improves the color gamut performance of display products, makes the screen colors more vivid, and effectively reduces power consumption and heat generation. However, quantum dot materials are sensitive to water, and under the conditions of moisture and light, they will have problems such as efficiency reduction and luminescent peak position shift. The current mainstream technology is to encapsulate quantum dots in a matrix with water blocking capability. However, the encapsulation matrix still has certain water permeability, and under the condition of long-term light exposure, with the continuous infiltration of trace moisture, quantum dots will inevitably gradually fail. SUMMARY

[0003] The purpose of the present disclosure is to provide a preparation method of quantum dot composite material, comprising: S1, melt co-extruding a second hydrophobic resin and a hydrophilic resin in a weight ratio of 100:(3-25), and an optional compatibilizer at a first temperature to obtain a hydrophilically modified master batch; S2, mixing a first hydrophobic resin and quantum dot material to obtain a quantum dot master batch; S3, melt co-extruding the above-mentioned hydrophilically modified master batch as the first layer material and the above-mentioned quantum dot master batch as the second layer material at a second temperature to obtain a plate-shaped quantum dot composite material.

[0004] Further, the above-mentioned S1 further comprises mixing the above-mentioned hydrophilically modified master batch with an auxiliary agent, and the auxiliary agent comprises one or more of a diffusing agent, an antioxidant, and a light stabilizer.

[0005] Further, the range of the above-mentioned first temperature is 180-260℃, and the range of the above-mentioned second temperature is 190-240℃.

[0006] Further, the weight ratio of the above-mentioned second hydrophobic resin to the above-mentioned compatibilizer is 100:(0-20).

[0007] Further, the particle size of the above-mentioned hydrophilically modified master batch is 2-5mm.

[0008] Further, the above-mentioned hydrophilic resin is selected from one or more of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyamide, polyethylene glycol, polyacrylamide, polyacrylic acid, and sulfonated polystyrene.

[0009] Further, the compatibilizer is selected from one or more of a copolymer of the hydrophilic resin and the second hydrophobic resin, a copolymer of the second hydrophobic resin monomer and maleic anhydride, a copolymer of the second hydrophobic resin monomer and glycidyl methacrylate, and a copolymer of the second hydrophobic resin monomer and isocyanate.

[0010] Further, the first hydrophobic resin and the second hydrophobic resin are independently selected from one or more of polystyrene, polypropylene, cyclic olefin copolymer, and polymethyl methacrylate, and preferably the first hydrophobic resin and the second hydrophobic resin are of the same type.

[0011] Further, in S1, the melt co-extrusion is performed by an extruder, and the screw rotation speed of the extruder is 100-500 rpm.

[0012] Further, one or more of the first hydrophobic resin, the second hydrophobic resin, and the hydrophilic resin is a resin master batch obtained by pre-pelletization.

[0013] The present disclosure also provides a display device comprising the quantum dot composite material prepared by any of the above preparation methods.

[0014] By using the technical solution provided by the present disclosure, the hydrophilic resin and the hydrophilic resin are first melt co-extruded and pelletized at a certain feeding ratio, and then the obtained hydrophilic modified master batch and the quantum dot master batch are second melt co-extruded and pelletized. Since the phase morphology of the blend is closely related to the processing history and component ratio, the hydrophilic modified region containing the dispersed phase of the hydrophilic resin and the hydrophobic region containing the quantum dot material are formed in the quantum dot composite material. The water in the system tends to accumulate in the hydrophilic modified region due to the chemical potential difference between the hydrophilic modified region and the hydrophobic region, so as to reduce the influence of the water penetrating into the composite material on the quantum dots in the hydrophobic region. Further, the adverse effects of the water penetrating into the composite material on the quantum dots can be effectively inhibited, and the service time and aging resistance of the quantum dot composite material are prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0015] The drawings accompanying the specification of the present disclosure serve to provide a further understanding of the present disclosure, and the illustrative embodiments of the present disclosure and their descriptions serve to explain the present disclosure, and do not constitute improper limitations on the present disclosure. In the drawings:

[0016] Figure 1 A TEM image of the water absorption functional layer of the quantum dot composite plate material of Example 1 of the present disclosure is shown.

[0017] Figure 2 A TEM image of the water absorption functional layer of the quantum dot composite plate material of Example 3 of the present disclosure is shown.

[0018] Figure 3 A TEM image of the water-absorbing functional layer of the quantum dot composite panel of Example 4 of the present disclosure is shown.

[0019] Figure 4 A TEM image of the water-absorbing functional layer of the quantum dot composite panel of Example 5 of the present disclosure is shown.

[0020] Figure 5 A TEM image of the surface layer of the quantum dot composite panel of Comparative Example 2 of the present disclosure is shown.

[0021] Figure 6 A TEM image of the surface layer of the quantum dot composite panel of Comparative Example 3 of the present disclosure is shown.

[0022] Figure 7 A comparison of the peeling of the quantum dot composite panels of Example 1 and Comparative Example 3 is shown.

[0023] Figure 8 Changes in quantum efficiency of the quantum dot composite panels of Examples 1-5 and Comparative Examples 1-2 after high-temperature and high-humidity aging are shown. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed description is merely illustrative in nature and is intended to provide further description of the disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0025] It should be noted that the terms "first", "second", and the like, used in the description and the claims of this disclosure are used to distinguish similar objects, and are not necessarily used to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged, where appropriate, to describe the embodiments of the disclosure described herein. In addition, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a list of steps or units is not necessarily limited to those steps or units clearly identified, but can include other steps or units not clearly identified or inherent to such processes, methods, products, or apparatus.

[0026] As introduced in the background, the existing base body with water barrier capability still has certain water permeability, which is mainly related to the principle of water barrier of the base body: through the strong force between polymer molecules, the molecules are tightly packed to form a continuous phase of water barrier polymer, so that water is not easy to penetrate, but there are still gaps between the tightly packed polymer molecules, and water molecules will continue to penetrate into the material from these gaps, causing the quantum dots to gradually lose effectiveness. Although the resin with good barrier performance (which must form a continuous phase) can greatly reduce the water permeability, but the substrate material of the resin base body (such as polyamide, polyvinyl alcohol, PET, etc.) is usually poor in compatibility with common optical products, so the mechanical properties (especially impact resistance and peel resistance) of the high-barrier resin material forming a continuous phase will be greatly reduced, resulting in deterioration of product quality. In addition, the inventors of the present disclosure found that the resin structure with good barrier performance usually contains amide, imide, hydroxyl, ether and other polar structures, which will quench quantum dots during melt processing, so it is not suitable for direct processing with quantum dots.

[0027] On the other hand, if a hydrophilic resin is directly set as a protective layer outside the quantum dot layer, there will be a problem that the hydrophilic resin (for example, PVA) has poor compatibility with the substrate of the quantum dot layer and a huge difference in physical properties, so that the protective layer cannot be attached to the surface of the substrate without increasing the adhesion layer; and poor processability, not suitable for melt co-extrusion which is a simple and economical preparation method, coating is complicated and high cost; in addition, it is also easy to absorb water and deform to cause warping, which seriously affects the use of the plate.

[0028] In one aspect of the present disclosure, a preparation method of a quantum dot composite material is provided, comprising: S1, melt co-extruding a second hydrophobic resin and a hydrophilic resin in a weight ratio of 100:(3-25), and an optional compatibilizer at a first temperature to obtain a hydrophilically modified master batch; S2, mixing a first hydrophobic resin and a quantum dot material to obtain a quantum dot master batch; and S3, melt co-extruding the hydrophilically modified master batch as a first layer material and the quantum dot master batch as a second layer material at a second temperature to obtain a plate-shaped quantum dot composite material.

[0029] The preparation method of the present disclosure first melt co-extrudes and granulates the hydrophobic resin and the hydrophilic resin at a certain feeding ratio in the first melt co-extrusion and granulation, and then melt co-extrudes and plates the obtained hydrophilic modified master batch and quantum dot master batch in the second melt co-extrusion and plate making. Since the phase morphology of the blend is closely related to the processing history and component ratio, the hydrophilic modified region containing the dispersed phase of the hydrophilic resin and the hydrophobic region containing the quantum dot material are formed in the quantum dot composite material. The chemical potential difference between the hydrophilic modified region and the hydrophobic region in the system causes the water infiltrating into the composite material to tend to accumulate in the hydrophilic modified region, thereby reducing the influence of the water infiltrating into the composite material on the quantum dots in the hydrophobic region. Further, the adverse effects of the water infiltrating into the composite material on the quantum dots can be effectively inhibited, and the service time and aging resistance of the quantum dot composite material can be prolonged.

[0030] It should be noted that the order of S1 and S2 has no priority. The "optional compatibilizer" should be understood as: S1, melt co-extruding the second hydrophobic resin, the hydrophilic resin and the compatibilizer at the first temperature to obtain the hydrophilic modified master batch; or S1, melt co-extruding the second hydrophobic resin and the hydrophilic resin at the first temperature to obtain the hydrophilic modified master batch.

[0031] In some embodiments, S1 further comprises mixing the hydrophilic modified master batch with an additive, the additive comprising one or more of a diffusing agent, an antioxidant, and a light stabilizer.

[0032] In some embodiments, the antioxidant comprises one or more of dibutylhydroxytoluene, t-butylhydroquinone, dilauryl thiodipropionate, tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, n-octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, tris[2,4-di-tert-butylphenyl]phosphite, 4,4'-thiobis(6-tert-butyl-3-methylphenol), isooctanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol diphosphite dioctadecyl ester, and triethylene glycol bis-β-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionate.

[0033] In some embodiments, the light stabilizer comprises one or more of decanedioic acid bis-2,2,6,6-tetramethylpiperidinyl ester, succinic acid polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2-hydroxy-5-methyl-phenyl)-2H-benzotriazole, 2-hydroxy-4-n-octyloxybenzophenone, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol, and 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol.

[0034] In some embodiments, the diffusing agent comprises at least one of titanium white, glass fiber, nano-silica, silicone resin, and glass microbead.

[0035] In some embodiments, the first temperature ranges from 180-260°C and the second temperature ranges from 190-240°C. The high temperature helps to achieve uniform dispersion of the hydrophilic resin in the second hydrophobic resin.

[0036] In some embodiments, the weight ratio of the second hydrophobic resin to the hydrophilic resin is 100:(5-20).

[0037] In some embodiments, the weight ratio of the second hydrophobic resin to the compatibilizer is 100:(0-20).

[0038] In some embodiments, the particle size of the hydrophilic-modified masterbatch is 2-5 mm. Controlling the particle size of the hydrophilic-modified masterbatch helps to achieve uniform dispersion of the hydrophilic resin in the second hydrophobic resin.

[0039] In some embodiments, the hydrophilic resin can be selected from one or more of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyamide, polyethylene glycol, polyacrylamide, polyacrylic acid, sulfonated polystyrene.

[0040] In some embodiments, the compatibilizer can be selected from one or more of a copolymer of the hydrophilic resin and the second hydrophobic resin, a copolymer of the second hydrophobic resin monomer and maleic anhydride, a copolymer of the second hydrophobic resin monomer and glycidyl methacrylate, a copolymer of the second hydrophobic resin monomer and isocyanate.

[0041] In some embodiments, the first hydrophobic resin and the second hydrophobic resin are independently selected from one or more of polystyrene, polypropylene, cyclic olefin copolymer, polymethyl methacrylate.

[0042] In some embodiments, the first hydrophobic resin and the second hydrophobic resin can be the same species.

[0043] In some embodiments, in S1, the melt co-extrusion is performed by an extruder, and the screw rotation speed of the extruder is 100-500 rpm. Controlling the screw rotation speed of the extruder can facilitate the uniform dispersion of the hydrophilic resin in the second hydrophobic resin.

[0044] In addition, increasing the cooling rate during the extrusion drawing after the melt blending can also facilitate the uniform dispersion of the hydrophilic resin in the second hydrophobic resin. For example, an air cooler can be introduced in the step of extrusion drawing to increase the cooling rate. The means that can facilitate the uniform dispersion of the hydrophilic resin in the second hydrophobic resin are not limited to the above-mentioned enumeration.

[0045] In some embodiments, one or more of the first hydrophobic resin, the second hydrophobic resin, and the hydrophilic resin can be a resin master batch obtained by pre-pelletization. The first hydrophobic resin, the second hydrophobic resin, and the hydrophilic resin can be used after being pre-pelletized or directly used. The resin master batch can improve its dispersibility during processing.

[0046] In another aspect of the present disclosure, a quantum dot composite material is provided, which comprises a quantum dot layer and a water absorption functional layer covering the surface of the quantum dot layer, the quantum dot layer comprising a continuous phase of a first hydrophobic resin and quantum dot material dispersed in the continuous phase of the first hydrophobic resin, and the water absorption functional layer comprising a continuous phase of a second hydrophobic resin and a plurality of dispersed phases dispersed in the continuous phase of the second hydrophobic resin, at least part of the materials of the plurality of dispersed phases comprising a hydrophilic resin.

[0047] The technical solution provided by the present disclosure facilitates the construction of a hydrophilic modification zone (i.e., the water absorption functional layer) containing a dispersed phase of a hydrophilic resin and a hydrophobic zone (i.e., the quantum dot layer) containing quantum dot material in the quantum dot composite material, and utilizes the chemical potential difference between the hydrophilic modification zone and the hydrophobic zone in the system to make the water infiltrating into the composite material tend to accumulate in the hydrophilic modification zone, thereby reducing the influence of the water infiltrating into the composite material on the quantum dots in the hydrophobic zone. In turn, the adverse effects of the water infiltrating into the composite material on the quantum dots can be effectively inhibited, and the service time and aging resistance of the quantum dot composite material can be prolonged.

[0048] In order to minimize the adverse effects of the water infiltrating into the composite material on the quantum dot material, it is preferred that the water absorption functional layer does not comprise quantum dot material having a light conversion function.

[0049] In some embodiments, the size of the dispersed phase is 0.01-10 μm. Preferably, the size of the dispersed phase is not more than 4 μm, or not more than 3 μm, or not more than 2 μm, or not more than 1 μm. The smaller the size of the dispersed phase indicates that the hydrophilic resin is more finely and uniformly dispersed in the second hydrophobic resin, which is helpful to improve the water absorption capacity of the water absorption functional layer. In some embodiments, the size of each dispersed phase is not exactly the same. In some embodiments, the size distribution of the dispersed phase is 1±0.8 μm.

[0050] In some embodiments, the hydrophilic resin can be selected from one or more of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyamide, polyethylene glycol, polyacrylamide, polyacrylic acid, sulfonated polystyrene.

[0051] In some embodiments, the water absorption functional layer further comprises a compatibilizer, which can be selected from one or more of a copolymer of the hydrophilic resin and a second hydrophobic resin, a copolymer of monomers of the second hydrophobic resin and maleic anhydride, a copolymer of monomers of the second hydrophobic resin and glycidyl methacrylate, a copolymer of monomers of the second hydrophobic resin and isocyanate. The compatibilizer helps to improve the compatibility of the hydrophilic resin and the second hydrophobic resin, facilitating the uniform dispersion of the hydrophilic resin.

[0052] In some embodiments, the weight ratio of the second hydrophobic resin to the hydrophilic resin is 100:(3-25).

[0053] In some embodiments, the weight ratio of the second hydrophobic resin to the hydrophilic resin is 100:(3-10), or 100:(10-15), or 100:(15-20), or 100:(20-25).

[0054] In some embodiments, the quantum dot layer and the water absorption functional layer independently further comprise one or more of a diffusing agent, an antioxidant, a light stabilizer. When the water absorption functional layer comprises a diffusing agent, an antioxidant, a light stabilizer, etc. auxiliary agent, the auxiliary agent can exist in the same dispersed phase with the hydrophilic resin, or can independently form a dispersed phase dispersed in the second hydrophobic resin.

[0055] In some embodiments, the first hydrophobic resin and the second hydrophobic resin are independently selected from one or more of polystyrene, polypropylene, cyclic olefin copolymer, polymethyl methacrylate.

[0056] In some embodiments, the first hydrophobic resin and the second hydrophobic resin can be the same kind.

[0057] In some embodiments, the thickness of the quantum dot layer is 0.1-1mm, and the thickness of the water absorption functional layer is 0.3-2mm.

[0058] In some embodiments, the quantum dot composite material is a plate structure, and at least one of the upper and lower surfaces of the quantum dot layer is covered with a water absorption functional layer. In some embodiments, the total thickness of the quantum dot composite material is 0.5-3 mm, and the thickness ratio of each water absorption functional layer to the quantum dot layer is independently selected from 1:1-1:10. The thickness of each layer of the plate structure can be determined by electron microscope EDX element analysis of the plate section, determining the hydrophilic / hydrophobic layer boundary according to the element distribution boundary, and then determining the thickness of each layer. For a plate structure formed by three-layer co-extrusion, the thickness ratio can also be converted according to the width of the three-layer co-extrusion die and the flow rate of the solution.

[0059] In some embodiments, the refractive index of the second hydrophobic resin and the hydrophilic resin differs by 0.02 or more. By utilizing the difference in refractive index between the hydrophilic resin and the second hydrophobic resin, the water absorption functional layer achieves a certain degree of scattering effect, which can reduce the amount of commonly used diffusing agent.

[0060] The quantum dot material involved in the present disclosure can be a II-VI compound, a IV-VI compound, a I-III-VI compound, a II-III-VI compound, a I-II-IV-VI compound, or a III-V compound. The above-mentioned II-VI compound can further include a III metal. The above-mentioned III-V compound can further include a II metal (e.g., InZnP). The above-mentioned quantum dot material can be a core-shell structure or an alloy structure. And the above-mentioned quantum dot material does not include carbon quantum dots or silicon quantum dots.

[0061] In yet another aspect of the present disclosure, a display device is provided, which includes the quantum dot composite material prepared by any of the above-mentioned preparation methods. Since the quantum dot composite material of the present disclosure has good aging resistance, the display device containing it also has a longer service life.

[0062] The quantum dot composite material, the preparation method of the quantum dot composite material, and the display device provided by the present application will be further illustrated below in combination with examples and comparative examples.

[0063] Example 1

[0064] (1) Put 100 parts of polystyrene resin (calculated by weight parts, the same below), 10 parts of polyamide resin master batch, and 3 parts of compatibilizer into an extruder, set the temperatures of the one-zone, two-zone, three-zone, four-zone, and five-zone dies to 230℃, 250℃, 250℃, 250℃, 250℃, and 260℃, respectively, and set the screw rotation speed to 400 rpm, to perform melt blending, extrusion traction, and granulation drying, thereby preparing a first hydrophilic modified master batch with an average particle size of about 3 mm.

[0065] (2) First hydrophilic modified master batch 100 parts, antioxidant 0.2 parts, light stabilizer 0.2 parts are uniformly stirred and mixed to obtain a second hydrophilic modified master batch.

[0066] (3) Polystyrene resin 100 parts, CdSe quantum dot pre-dispersion master batch 10 parts, diffusing agent 1 part, antioxidant 0.2 parts, light stabilizer 0.2 parts are uniformly stirred and mixed to prepare a quantum dot master batch. The CdSe quantum dot pre-dispersion master batch (same below) is obtained by melt co-extrusion and cooling and cutting of CdSe quantum dots and polystyrene resin, and the particle size is about 2-6 mm.

[0067] (4) The extruder zone 1, zone 2, zone 3, zone 4, zone 5 head temperature is set to 190℃, 210℃, 210℃, 210℃, 210℃, 220℃, respectively, and the screw rotation speed is 400 rpm. The second hydrophilic modified master batch is used as the material of the upper and lower two layers, and the quantum dot master batch is used as the material of the middle layer to carry out three-layer plate melt co-extrusion. Through traction stretching, cooling and shaping, and cutting, a quantum dot composite board is prepared, and the thickness of the upper and lower water absorption functional layers of the quantum dot composite board is controlled to be 0.3 mm, and the thickness of the middle quantum dot layer is 1.2 mm.

[0068] The surface layer of the water absorption functional layer of the quantum dot composite board is observed by transmission electron microscope, and the TEM photo obtained is as shown in Figure 1 It can be seen that a large number of dispersed phases formed by polyamide resin are uniformly dispersed in the polystyrene continuous phase, and the polystyrene continuous phase and the polyamide dispersed phase together present a sea-island structure (the continuous phase is "sea" and the dispersed phase is "island"). The size distribution of the dispersed phase is in the range of about 0.05-0.5 μm.

[0069] Example 2

[0070] The difference between this embodiment and Example 1 is that the CdSe quantum dot pre-dispersion master batch in step (3) is 20 parts. In step (4), the thickness of the upper and lower water absorption functional layers of the quantum dot composite board is controlled to be 0.6 mm, and the thickness of the middle quantum dot layer is 0.6 mm.

[0071] Example 3

[0072] The difference between this embodiment and Example 1 is that the polyamide resin master batch in step (1) is 5 parts, and the compatibilizer is 1 part. The thickness of the water absorption functional layer and the quantum dot layer of the prepared quantum dot composite board is unchanged.

[0073] The surface layer of the water absorption functional layer of the quantum dot composite board is observed by transmission electron microscope, and the TEM photo obtained is as shown in Figure 2It can be seen that a large number of island-shaped polyamide resin dispersed phases are uniformly dispersed in the polystyrene continuous phase, and the polyamide dispersed phase morphology is similar to that of Example 1, only the amount is less than that of Example 1, and the size of the dispersed phase is about 0.05-0.5 μm.

[0074] Example 4

[0075] The difference between this example and Example 1 is that 10 parts of the polyamide resin master batch in step (1) is replaced by 20 parts, and no compatibilizer is used.

[0076] The surface layer of the water absorption functional layer of the quantum dot composite board is observed by transmission electron microscopy, and the TEM photos obtained are as shown in Figure 3 The polyamide resin forms island-shaped dispersed phases with a size of about 1-4 μm, and the size of the dispersed phase is significantly larger than that of Examples 1 and 3.

[0077] Example 5

[0078] The difference between this example and Example 1 is that 10 parts of the polyamide resin master batch in step (1) is replaced by 10 parts of polyethylene glycol resin.

[0079] The surface layer of the water absorption functional layer of the quantum dot composite board is observed by transmission electron microscopy, and the TEM photos obtained are as shown in Figure 4 The polyethylene glycol resin forms island-shaped dispersed phases with a size of about 0.5-2 μm in the polystyrene continuous phase matrix.

[0080] Example 6

[0081] The difference between this example and Example 1 is that 10 parts of the polyamide resin master batch in step (1) is replaced by 10 parts of polyvinyl alcohol resin.

[0082] Example 7

[0083] The difference between this example and Example 1 is that 10 parts of the polyamide resin master batch in step (1) is replaced by 10 parts of ethylene-vinyl alcohol copolymer resin.

[0084] Example 8

[0085] The difference between this example and Example 1 is that 10 parts of the polyamide resin master batch in step (1) is replaced by 10 parts of polyacrylamide resin.

[0086] Example 9

[0087] The difference between this example and Example 1 is that 10 parts of the polyamide resin master batch in step (1) is replaced by 10 parts of polyacrylic acid resin.

[0088] Example 10

[0089] The difference between this example and Example 1 is that 10 parts of the sulfonated polystyrene resin in step (1) is replaced by 10 parts of the polyamide resin.

[0090] Example 11

[0091] The difference between this example and Example 1 is that 100 parts of the polystyrene resin in step (1) is replaced by 100 parts of the polypropylene resin.

[0092] Example 12

[0093] The difference between this example and Example 1 is that 100 parts of the polystyrene resin in step (1) is replaced by 100 parts of the cyclic olefin copolymer.

[0094] Example 13

[0095] The difference between this example and Example 1 is that 100 parts of the polystyrene resin in step (1) is replaced by 100 parts of the polymethyl methacrylate resin.

[0096] Comparative Example 1

[0097] (1) 100 parts of the polystyrene resin, 0.5 parts of the diffusing agent, 0.2 parts of the antioxidant, and 0.2 parts of the light stabilizer are uniformly stirred and mixed to obtain a mixed material.

[0098] (2) 100 parts of the polystyrene resin, 10 parts of the CdSe quantum dot pre-dispersed master batch, 1 part of the diffusing agent, 0.2 parts of the antioxidant, and 0.2 parts of the light stabilizer are uniformly stirred and mixed to obtain a quantum dot master batch.

[0099] (3) The extruder zone 1, zone 2, zone 3, zone 4, and zone 5 are set to 190℃, 210℃, 210℃, 210℃, 210℃, and 220℃, respectively, and the screw rotation speed is 400 rpm. The mixed material obtained in step (1) is used as the material of the upper and lower layers, and the quantum dot master batch is used as the material of the middle layer for three-layer plate melt co-extrusion. Through traction stretching, cooling and shaping, and cutting, a quantum dot composite plate is prepared, and the thickness of the upper and lower layers of the quantum dot composite plate is controlled to be 0.3 mm, and the thickness of the middle quantum dot layer is 1.2 mm.

[0100] Comparative Example 2

[0101] The difference between this example and Example 1 is that 100 parts of the polystyrene resin, 20 parts of the polyamide resin, 0.5 parts of the diffusing agent, 0.2 parts of the antioxidant, and 0.2 parts of the light stabilizer are uniformly stirred and mixed to obtain a mixed material.

[0102] The surface layer of the quantum dot composite plate is observed by transmission electron microscopy, and the TEM photograph obtained is as shown in Figure 5The TEM photograph of the surface layer of the quantum dot composite sheet is shown in FIG. 3. It can be seen that, in step (1), when the polystyrene resin and the polyamide resin are simply mixed without undergoing melt co-extrusion granulation, and the content of the polyamide resin exceeds the range of the preparation method of the present disclosure, the polyamide resin is distributed in the polystyrene resin matrix in the form of an ellipse with poor size uniformity, and the size of most of the dispersed phase is above 5 μm.

[0103] Comparative Example 3

[0104] The difference between the present comparative example and Comparative Example 2 is that, in step (1), the amount of the polyamide resin is 50 parts.

[0105] The surface layer of the quantum dot composite sheet was observed by transmission electron microscopy, and the TEM photograph obtained is shown in FIG. 3. It can be seen that, in step (1), when the polystyrene resin and the polyamide resin are simply mixed without undergoing melt co-extrusion granulation, and the content of the polyamide resin exceeds the range of the preparation method of the present disclosure, the polyamide resin is distributed in the polystyrene resin matrix in the form of an ellipse with poor size uniformity, and the size of most of the dispersed phase is above 5 μm. Figure 6 It can be seen that, in step (1), when the polystyrene resin and the polyamide resin are simply mixed without undergoing melt co-extrusion granulation, and the content of the polyamide resin exceeds the range of the preparation method of the present disclosure, the polyamide resin is distributed in the polystyrene resin matrix in the form of an ellipse with poor size uniformity, and the size of most of the dispersed phase is above 5 μm. Figure 6 The polyamide resin forms a continuous phase, and the polyamide resin and the polystyrene resin form a heterogeneous blend (i.e., two kinds of materials showing two kinds of contrasts, and each kind of material is dispersed with the other kind of material). The polyamide resin forming a continuous phase should theoretically have both hydrophilicity and good barrier properties, but when it forms a continuous phase, the physical properties of the hydrophilic surface layer and the quantum dot layer of the composite sheet have significantly changed, and the surface layer is prone to natural peeling (as shown in FIG. 2), at this time, the three-layer structure of the composite sheet cannot be maintained, and lacks practical application value. Figure 7

[0106] It should be noted that the sample slices of the quantum dot composite sheets of the examples and comparative examples of the present disclosure for transmission electron microscopy testing were prepared at -50°C, and then observed at room temperature by transmission electron microscopy. Due to the change in environmental temperature and the difference in shrinkage rate of different resin materials, partial slices may appear local warping and show the brightness of the substrate, so in the TEM photograph, an elliptical or crescent-shaped bright part close to the edge of the hydrophilic resin can be seen.

[0107] Figure 8 The high-temperature high-humidity light aging results (aging conditions: 40°C, humidity 85% RH, blue light irradiation 8 mW / cm 2 ) of the quantum dot composite sheets prepared in Examples 1-5 and Comparative Examples 1-2 are shown in FIG. 4. It can be seen that, in step (1), when the polystyrene resin and the polyamide resin are simply mixed without undergoing melt co-extrusion granulation, and the content of the polyamide resin exceeds the range of the preparation method of the present disclosure, the polyamide resin is distributed in the polystyrene resin matrix in the form of an ellipse with poor size uniformity, and the size of most of the dispersed phase is above 5 μm. Figure 8 ​The quantum efficiency change trend of the quantum dots can be seen that the quantum dot of the comparative example 1 (without surface hydrophilic modification) board decays relatively rapidly, and the quantum efficiency decays to below 90% within 72h, and continues to rapidly decrease with the growth of the aging time. The aging performance of the comparative example 2 board is similar to that of the comparative example 1, and since the hydrophilic polyamide resin cannot be uniformly dispersed during simple blending, the hydrophilic modification effect is poor, and it is difficult to show the effect. The quantum efficiency decay rate of the quantum dot composite board of the examples 1-5 is lower than that of the comparative examples 1 and 2.

[0108] Compared with example 3, example 2 has better aging resistance effect, and can maintain the efficiency higher than 90% within 600h of aging due to the higher content of the hydrophilic polyamide resin (10 parts) and the larger thickness of the water absorption functional layer (0.6mm); example 1 has slightly worse aging resistance effect than example 2 due to the high content of the hydrophilic polyamide resin (10 parts) and the moderate thickness of the water absorption functional layer (0.3mm). The aging resistance effect of example 3 is further reduced than examples 1 and 2 due to the lower content of the hydrophilic polyamide resin (5 parts) and the moderate thickness of the hydrophilic surface layer (0.3mm), but the overall performance of example 3 is still better than that of the comparative example 1 without hydrophilic modification. Example 4 increases the content of the hydrophilic resin and does not use a compatibilizer, which causes the polyamide resin to tend to fuse into a larger dispersed phase during processing, rather than forming a uniform and fine small-size dispersed phase, thereby reducing the hydrophilic modification effect. Therefore, compared with examples 1-3, the quantum efficiency of the board of example 4 decays relatively rapidly, and cannot maintain the efficiency higher than 90% after the aging time exceeds 100h. Example 5 uses polyethylene glycol with stronger hydrophilicity as the hydrophilic resin, and still can achieve micron to sub-micron dispersion under the processing conditions. The quantum efficiency decay performance of the board of example 5 shows the aging resistance performance similar to that of example 2, which indicates that different types of hydrophilic resins also have a clear positive effect under the implementation scheme.

[0109] In summary, the construction of the hydrophilic modification zone in the quantum dot composite material and the distribution of the quantum dot material in the hydrophobic zone indeed help to reduce the adverse effects of water on the stability of the quantum dots during the aging process; in addition, when the hydrophilic modification zone is constructed by controlling the blending means, it is also crucial to ensure the uniform dispersion of the hydrophilic modification material in the hydrophobic continuous phase.

[0110] The above only describes the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a quantum dot composite material, characterized in that, include: S1, a second hydrophobic resin and a hydrophilic resin are melt-blended at a weight ratio of 100:(3-25) at a first temperature, followed by extrusion, granulation, and drying. The first temperature ranges from 180 to 260 °C, to obtain a hydrophilic modified masterbatch. The particle size of the hydrophilic modified masterbatch is 2-5 mm. The hydrophilic resin is selected from one or more of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyamide, polyethylene glycol, polyacrylamide, polyacrylic acid, and sulfonated polystyrene. S2, a first hydrophobic resin is mixed with a quantum dot material to obtain a quantum dot masterbatch. The first hydrophobic resin and the second hydrophobic resin are independently selected from one or more of polystyrene, polypropylene, and cyclic olefin copolymers. S3, the hydrophilic modified masterbatch is used as the first layer material, and the quantum dot masterbatch is used as the second layer material. The mixture is melt-co-extruded at a second temperature, which ranges from 190 to 240 °C, to obtain a plate-shaped quantum dot composite material.

2. The preparation method according to claim 1, characterized in that, The S1 further includes: mixing the hydrophilic modified masterbatch with an auxiliary agent, wherein the auxiliary agent includes one or more of a dispersant, an antioxidant, and a light stabilizer.

3. The preparation method according to claim 1, characterized in that, S1 is: the second hydrophobic resin and the hydrophilic resin are melt-blended at the first temperature with a weight ratio of 100:(3-25) and a compatibilizer, followed by extrusion traction, granulation and drying to obtain the hydrophilic modified masterbatch.

4. The preparation method according to claim 3, characterized in that, The weight ratio of the second hydrophobic resin to the compatibilizer is 100:(1-20).

5. The preparation method according to claim 3, characterized in that, The compatibilizer is selected from one or more of the following: a copolymer of the hydrophilic resin and the second hydrophobic resin; a copolymer of the monomer of the second hydrophobic resin and maleic anhydride; a copolymer of the monomer of the second hydrophobic resin and glycidyl methacrylate; and a copolymer of the monomer of the second hydrophobic resin and isocyanate.

6. The preparation method according to claim 1, characterized in that, The first hydrophobic resin is of the same type as the second hydrophobic resin.

7. The preparation method according to claim 1, characterized in that, In step S1, the melt blending is carried out by an extruder, and the screw speed of the extruder is 100-500 rpm.

8. The preparation method according to claim 1, characterized in that, One or more of the first hydrophobic resin, the second hydrophobic resin, and the hydrophilic resin are resin masterbatches obtained by pre-granulation.

9. A display device, characterized in that, This includes quantum dot composite materials prepared by the preparation method according to any one of claims 1-8.

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