Method for preparing color conversion layer by compounding ultraviolet absorbent and quantum dot ink and application

Abstract

The invention belongs to the technical field of quantum dot materials, and particularly discloses a method for preparing a color conversion layer by compounding an ultraviolet absorbent and quantum dot ink and application, the color conversion layer is prepared from the quantum dot ink containing the ultraviolet absorbent or films are prepared from the quantum dot ink and the ultraviolet absorbent respectively, and the color conversion layer is prepared through superposition; the quantum dot printing ink containing the ultraviolet absorbent is obtained by adding the ultraviolet absorbent into the quantum dot printing ink composed of perovskite quantum dots CsPbX3 and an organic solvent according to the proportion of 0.01-5wt% and fully and uniformly mixing the quantum dot printing ink with the perovskite quantum dots CsPbX3 and the organic solvent. Functional molecules with ultraviolet absorption capability are compounded with quantum dot ink, so that the light stability and the heat stability of a system can be improved, ultraviolet light which is not converted by quantum dots is absorbed, and the safety and the reliability of the system are improved.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot materials technology, specifically relating to a method and application for preparing a color conversion layer by combining an ultraviolet absorber and quantum dot ink. Background Technology

[0002] In the process of upgrading display technology towards high color gamut and high brightness, the color conversion layer, as a core component, directly determines the imaging quality and lifespan of display devices. Quantum dots, due to their size-tunable fluorescence properties, have become a key material for constructing high-performance color conversion layers. Among them, inorganic halide perovskite quantum dots such as CsPbX3 (X=Cl, Br, I) exhibit irreplaceable advantages in color conversion applications such as LCD backlight modules and Mini / MicroLED displays, thanks to their near 100% photoluminescence quantum efficiency and spectral tuning capability covering the entire visible light spectrum. CsPbX3 and other inorganic halide perovskite quantum dots, with their near 100% photoluminescence quantum efficiency and spectral tuning capability covering the entire visible light spectrum, have thus become a focus of industry research and development. However, CsPbX3 quantum dots face severe challenges in practical applications of color conversion layers: First, they lack photostability. Under strong ultraviolet excitation light commonly used in display devices, halide ion migration and lattice collapse occur within hours, leading to fluorescence quenching and severely shortening the lifetime of the color conversion layer. Second, existing stability improvement schemes have limitations. Doping modification reduces quantum efficiency, ligand passivation has a short-lived effect, and although coating the surface with wide bandgap materials can improve water and oxygen resistance, the process is complex and prone to introducing defects, making it unsuitable for the large-scale preparation of quantum dot inks for color conversion layers.

[0003] In addition, existing quantum dot ink formulations generally add viscosity modifiers such as alcohol polymers to meet the rheological requirements of color conversion layer preparation processes such as inkjet printing and slot coating. These insulating additives are difficult to remove and will significantly reduce the charge transport capability of the color conversion layer film, affecting the matching of device optoelectronic performance. More importantly, traditional color conversion layers lack ultraviolet shielding design, and ultraviolet light that is not converted by quantum dots is easily leaked, which not only accelerates the degradation of quantum dots, but also poses a safety hazard to human health.

[0004] Therefore, developing a color conversion layer that combines high luminescence performance, excellent light and heat resistance, and UV shielding function has become an urgent need to break through the current technological bottleneck. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the existing technology and provide a method and application for preparing a color conversion layer by combining ultraviolet absorbers and quantum dot inks. By combining functional molecules with ultraviolet absorption capabilities with quantum dot inks, the photostability and thermal stability of the system can be improved, while simultaneously absorbing ultraviolet light that has not been converted by quantum dots, thereby improving the safety and reliability of the system.

[0006] To achieve the above objectives, one of the technical solutions of the present invention is: a method for preparing a color conversion layer by combining an ultraviolet absorber and a quantum dot ink, wherein the color conversion layer is obtained by preparing a quantum dot ink containing an ultraviolet absorber or by preparing thin films by separately preparing quantum dot ink and ultraviolet absorber and then stacking them to obtain the color conversion layer; the quantum dot ink containing an ultraviolet absorber is obtained by adding an ultraviolet absorber at a ratio of 0.01-5 wt% to a quantum dot ink composed of perovskite quantum dots CsPbX3 and an organic solvent, and mixing them thoroughly and evenly, wherein the concentration of perovskite quantum dots CsPbX3 in the quantum dot ink is 10-80 mg / ml.

[0007] Quantum dot inks containing UV absorbers can be used not only in color conversion layers but also in inkjet printing, microfluidic transport, and spin coating processes. They can form uniform quantum dot films containing UV absorbers on various substrates (such as PET films, ITO glass, and silicon wafers). The ink system of this invention has good process compatibility and is suitable for conventional LED curing, thermal curing, or photoinitiated polymerization processes. For example, in UV-excited display device applications, it can be paired with an LED curing light source with a wavelength of less than 400 nm in the UV band. The absorber strongly absorbs in the unconverted UV light band, giving the final cured quantum dot film a UV shielding function, thereby effectively preventing problems such as fluorescence decay, material yellowing, and structural degradation caused by ambient light or excitation light.

[0008] In a preferred embodiment of the present invention, the amount of ultraviolet absorber added to the quantum dot ink containing ultraviolet absorber is preferably 0.1-1 wt%.

[0009] In a preferred embodiment of the present invention, the organic solvent is one of butyl acetate, n-octanol, cyclohexanone, toluene, and xylene.

[0010] In a preferred embodiment of the present invention, the ultraviolet absorber is one or more combinations of benzotriazoles, hydroxyphenylbenzotriazoles, triazines, carboxylic acid esters, and substituted phenols.

[0011] Further preferably, the benzotriazole class includes one of UV-571, UV-328, and UV-234. Taking UV-571 as an example, its chemical name is 2-(2H-benzotriazole-2-yl)-4-methyl-6-dodecylphenol, which is in liquid state, has good compatibility with organic systems, can preferentially absorb harmful ultraviolet light and convert its energy into heat dissipation, and its absorption band covers the UV-A and UV-B regions, making it suitable for solution systems; the hydroxyphenyl benzotriazole class includes one of Tinuvin P and Tinuvin 1130, which has high absorption efficiency and good thermal stability; the triazine absorber includes one of UV-1577, which is suitable for systems requiring high transparency, with its absorption peak concentrated in 280–350 nm, and also has excellent photothermal stability; the substituted phenol class includes one of UV-0 and UV-320, which has a broad absorption capacity in the ultraviolet region, a stable structure, and is not easily migrated.

[0012] In practical applications, ultraviolet absorbers preferentially absorb ultraviolet light energy with wavelengths of 280-380 nm and convert it into heat energy for dissipation, thereby mitigating the direct destructive effect of excitation light on quantum dots. Since most of these absorbers are designed to absorb almost no light in the visible light region (400-700 nm), they do not interfere with the emission spectrum of quantum dots, thus achieving the filtering and passivation of ultraviolet excitation sources without compromising their photoluminescence properties.

[0013] In a preferred embodiment of the present invention, the specific method for obtaining the color conversion layer using quantum dot ink containing ultraviolet absorbers includes: stacking a chromium plate on a substrate, spin-coating positive photoresist, exposing it under ultraviolet light for 10-20 seconds, and then developing it in a sodium hydroxide solution; after development, etching the bare chromium plate in a cerium ammonium nitrate solution, and washing away residual photoresist with ethanol, leaving an arrayed glass pattern composed of the substrate and the remaining chromium plate; etching the arrayed glass pattern with plasma; rinsing with water and drying the surface with nitrogen after etching to obtain a patterned glass substrate with an etching depth of 2-5 μm; subsequently, misaligned bonding of PDMS, the PDMS having several microchannels, and introducing the quantum dot ink containing ultraviolet absorbers into the microchannels via a pressure injection pump; injecting air into the microchannels at the same pressure using a pressure injection pump, with an air flow rate of 10-30 rpm. The flow rate is μm / s, which allows the quantum dot ink containing UV absorbers to be blown out at the point where the microchannels and the grooves of the morphology pattern are perfectly aligned. Under stable flow drive, the quantum dot ink containing UV absorbers spreads evenly along the microchannels and fills the target area. During the preparation process, the temperature is kept constant at 25–30℃ to stabilize the solution viscosity and flow state.

[0014] More preferably, the plasma etching uses a mixture of CHF3 and Ar gas, with a CHF3 gas flow rate of 20-40 sccm, an Ar gas flow rate of 10-20 sccm, an etching time of 10-30 min, and an etching power (RF) of 200-300 W.

[0015] In a preferred embodiment of the present invention, the specific method for obtaining a color conversion layer by superimposing thin films made from quantum dot ink and ultraviolet absorber includes: filtering a quantum dot solution without ultraviolet absorber using a hydrophobic PTFE membrane to obtain quantum dot ink; printing a patterned substrate on a substrate using the quantum dot ink; mixing polystyrene, tetrahydrofuran (THF), anhydrous ethanol, and ultraviolet absorber in a ratio of (4-8) g:(80-120) ml:(10-30) ml:(0.1-0.5) g and stirring for 6-10 h to form a uniform transparent solution; and then spin-coating the printed patterned substrate at 300-500 rpm to form a uniform transparent ultraviolet protective film, thereby obtaining the color conversion layer.

[0016] More preferably, the substrate includes one of PET film, ITO glass, and silicon wafer.

[0017] To achieve the above objectives, the second technical solution of the present invention is: a color conversion layer prepared by the above-mentioned method of preparing a color conversion layer by combining ultraviolet absorber and quantum dot ink.

[0018] To achieve the above objectives, the third technical solution of the present invention is: the application of the above-mentioned color conversion layer in the fields of display, lighting, new energy, and biomedicine.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention combines functional molecules with ultraviolet absorption capabilities with quantum dot ink, which can improve the photostability and thermal stability of the system, and at the same time absorb ultraviolet light that has not been converted by quantum dots, thereby improving the safety and reliability of the system.

[0021] 2. This invention adds ultraviolet absorbers to quantum dot inks, which can significantly improve the photothermal stability of the inks without damaging the luminescent properties of quantum dots, and can also effectively absorb harmful ultraviolet light; the quantum dot inks are highly versatile and compatible with a variety of ultraviolet absorbers, preparation processes and substrates;

[0022] 3. The color conversion layer prepared by this invention has high precision and good weather resistance, and can prevent ultraviolet leakage;

[0023] 4. The color conversion layer obtained by this invention can be applied to multiple fields such as display and lighting, breaking through the industry's technical bottlenecks. Attached Figure Description

[0024] Figure 1 The structure of 2-(2H-benzotriazol-2-yl)-4-methyl-6-dodecylphenol, the UV-571 ultraviolet light absorber used in Example 1;

[0025] Figure 2 This is a diagram showing the results of using quantum dots with added UV additives to achieve a microfluidic color conversion layer in Example 1.

[0026] Figure 3 This is a schematic diagram of the structure of the transparent ultraviolet protective film in Example 2;

[0027] Figure 4 The images shown are full-color monochrome images of the transparent UV protective film in Example 2. (1) is a full-color image printed with low UV leakage RGB inkjet printing; (2) is a green array image with low UV leakage. Detailed Implementation

[0028] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0029] Example 1

[0030] Perovskite nanocrystals were prepared in two steps using a hot-injection method:

[0031] Preparation of Cs source: Mix 0.814 g Cs2CO3 (cesium carbonate), 4 ml OA (oleic acid), 40 ml ODE (octadecene), and 3 ml APTES (3-aminopropyltriethoxysilane) in a 100 ml three-necked flask; then heat under vacuum to 120 °C and keep warm for 1 h to completely remove water and oxygen from the flask; then purge with nitrogen and heat to 150 °C and keep warm for 10 min to completely dissolve Cs2CO3, obtaining a clear yellow Cs source precursor solution, which is then poured into a brown reagent bottle and stored in a refrigerator away from light. Before use, it should be heated to 120 °C.

[0032] Preparation of red perovskite nanocrystals: 40 ml ODE, 0.196 g PbBr2 (lead bromide), 0.492 g PbI2 (lead iodide), 4 ml OA, 3 ml OAm (oleylamine), and 1 ml APTES (3-aminopropyltriethoxysilane) were simultaneously added to a 100 ml three-necked flask. The flask was evacuated and heated to 120°C for 1 hour. Nitrogen gas was then introduced and the temperature was raised to 170°C. Subsequently, 3.2 ml of the Cs precursor solution obtained in step (1) was injected into the three-necked flask and reacted for 10 seconds. The three-necked flask was then immediately placed in an ice bath to cool to room temperature. The mixed solution was then centrifuged at 8000 rpm for 5 min. The precipitate was collected and dispersed in 1.6 ml xylene. After uniform dispersion, the mixture was centrifuged at 5000 rpm for 5 min. The supernatant was collected for use.

[0033] Preparation of green perovskite nanocrystals: 40 ml ODE, 0.552 g PbBr2 (lead bromide), 5.2 ml OA, and 5.2 ml OAm were added to a 100 ml three-necked flask. The mixture was heated to 120 °C and vacuum-treated to remove moisture and oxygen for 30 min. Nitrogen gas was introduced, and the mixture was heated to 180 °C and maintained for 10 min. Then, 3.2 ml of the Cs precursor solution prepared in step (1) was injected, and the three-necked flask was immediately transferred to an ice bath after 5 seconds. After cooling to room temperature, the mixture was centrifuged at 10,000 rpm for 5 min, the precipitate was collected, and dispersed in 3 ml of n-hexane. After uniform dispersion, the mixture was centrifuged at 5,000 rpm for 5 min, and the supernatant was collected.

[0034] Preparation of a perovskite nanocrystalline ink containing a UV absorber:

[0035] Take 3 ml of the supernatant obtained in the preparation of the green perovskite nanocrystals and add it to 9 ml of ethyl acetate. Centrifuge at 1000 rpm for 5 minutes and collect the precipitate. Then dissolve the precipitate in 3 ml of xylene to obtain a quantum dot solution, i.e., quantum dot ink. Dissolve 1 g of UV-571 in 3 ml of xylene solution and stir for 15 min. After stirring, add 30 μl to the above quantum dot ink and mix thoroughly to obtain perovskite nanocrystal quantum dot ink containing UV absorber. The structure of the UV-571 UV absorber 2-(2H-benzotriazol-2-yl)-4-methyl-6-dodecylphenol is as follows. Figure 1As shown, the benzotriazole ring is responsible for π-π* absorption, the substituted benzene ring is used to enhance the absorption wavelength range, and the long-chain dodecane group is used to improve the solubility of the absorbent in various solvents. When the molecule absorbs ultraviolet light, electrons transition to an excited state. The excited state has a very short lifetime, and the molecule converts energy into heat energy through a non-radiative process. Subsequently, the molecule returns to the ground state, and the structure remains unchanged. It can be seen that no permanent chemical reaction occurs during this process. This means that the process is a reversible, non-destructive, and byproduct-free physical absorption process.

[0036] During the preparation process, appropriate ligand modification or the addition of other types of additives can be performed according to specific needs and material properties. Simultaneously, the ink preparation process requires precise control of reaction conditions and proportions to ensure that the final ink performance meets expectations.

[0037] A color conversion layer was prepared using quantum dot ink containing a UV absorber: First, a chromium plate with a top-coated coating was stacked on a glass slide, positive photoresist was spin-coated, and the slide was exposed to UV light for 14 seconds, followed by development in a sodium hydroxide solution. After development, the exposed chromium plate was etched in a cerium ammonium nitrate solution, and residual photoresist was washed away with ethanol. After this step, only the glass substrate and the remaining top-coated chromium plate portion remained, forming an arrayed glass pattern. The arrayed glass pattern was etched using CHF3 / Ar plasma for 20 minutes, with a CHF3 gas flow rate of 30 sccm, an Ar gas flow rate of 15 sccm, and an etching power RF of 250 W. The surface was then rinsed with water and dried with nitrogen to obtain a patterned glass substrate with an etching depth of 3 μm. Subsequently, misaligned bonding with PDMS (PDMS containing red and green microchannels) was performed. 0.2 ml of quantum dot ink containing a UV absorber was injected into the PDMS microchannels using a pressure injection pump at 0.3 Pa. Air was then injected into the red and green microchannels at the same pressure, at a flow rate of 20 μm / s, causing the quantum dot solution at the point where the microchannels and the grooves of the morphological pattern were perfectly aligned to be blown out. Under stable flow, the ink spread uniformly along the microchannels, filling the target area. A constant temperature (e.g., 25–30 °C) was maintained during the process to stabilize the solution viscosity and flow state. After standing to allow the solvent to evaporate, quantum dot particles were deposited, as shown in the figure. Figure 2 As shown. From Figure 2 It can be seen that the quantum dot ink uniformly fills the target area in the microfluidic channel, and the resulting color conversion layer has a regular array structure. After being irradiated with ultraviolet light, the luminescence intensity is stable, proving its applicability in the field of high-precision display.

[0038] Example 2

[0039] A color conversion layer is prepared by stacking thin films made separately from quantum dot inks and ultraviolet absorbers.

[0040] (1) Preparation of quantum dot ink: The quantum dot solution obtained by dissolving and precipitating 3 ml of green perovskite nanocrystals without adding UV absorber in Example 1 above was filtered through a 22 μm hydrophobic PTFE membrane to obtain quantum dot ink;

[0041] (2) Preparation of patterned substrate (electrohydrodynamic inkjet printing): The quantum dot ink described above was applied to electrohydrodynamic inkjet printing. The printing device was an ultra-fine inkjet printer (SIJ-350), the printing substrate was ITO glass, and an ultra-fine nozzle SIJ-LN with a tip size of 5μm was used. A square wave voltage was used with an amplitude of 800V, a bias of 700V, and a frequency of 1000Hz. The printing speed and printing acceleration were set to 2 mm / s. 2 Printing temperature 25℃, relative humidity 50%;

[0042] (3) Preparation of transparent UV protective film (overlay to form color conversion layer): 6g of polystyrene, 100ml of tetrahydrofuran (THF), 20ml of anhydrous ethanol, and 0.2g of UV-571 were mixed and stirred with a rotor for 8 hours to form a homogeneous transparent solution. This solution was then spin-coated onto a printed patterned substrate at 400rpm to form a homogeneous transparent UV protective film. A schematic diagram of the structure is shown below. Figure 3 As shown, the full-color monochrome physical image is as follows: Figure 4 As shown, (1) is a low-UV-leakage RGB inkjet print full-color image, and (2) is a low-UV-leakage green array image.

[0043] Example 3

[0044] Application of the color conversion layers prepared by the two methods in Example 1 and Example 2 in displays.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a color conversion layer by a combination of an ultraviolet absorber and a quantum dot ink, characterized in that, The color conversion layer is prepared by quantum dot ink containing ultraviolet absorber or by superimposing the thin film prepared by quantum dot ink and ultraviolet absorber respectively; the quantum dot ink containing ultraviolet absorber is obtained by adding ultraviolet absorber into quantum dot ink composed of perovskite quantum dot CsPbX3 and organic solvent at a proportion of 0.01-5 wt%, and fully mixing and uniformizing, and the concentration of perovskite quantum dot CsPbX3 in the quantum dot ink is 10-80 mg / ml.

2. The method for preparing a color conversion layer using an ultraviolet absorbing agent and a quantum dot ink according to claim 1, wherein the ultraviolet absorbing agent is added to the quantum dot ink in an amount of 0.01 to 10% by weight based on the total weight of the quantum dot ink. The ultraviolet absorber is one or more combinations of benzotriazole, hydroxyphenyl benzotriazole, triazine, carboxylate and substituted phenol ultraviolet absorbers.

3. The method for preparing a color conversion layer by using an ultraviolet absorber and a quantum dot ink according to claim 2, wherein the ultraviolet absorber is added to the quantum dot ink in an amount of 0.1 to 10 wt% based on the total weight of the quantum dot ink. The benzotriazole includes one of UV-571, UV-328 and UV-234, the hydroxyphenyl benzotriazole includes one of Tinuvin P and Tinuvin 1130, the triazine absorber includes UV-1577, and the substituted phenol includes one of UV-0 and UV-320.

4. The method for preparing a color conversion layer using an ultraviolet absorbing agent and a quantum dot ink according to claim 1, wherein the ultraviolet absorbing agent is added to the quantum dot ink in an amount of 0.01 to 10 wt% based on the total weight of the quantum dot ink. The organic solvent is one of butyl acetate, n-octanol, cyclohexanone, toluene and xylene.

5. The method for preparing a color conversion layer using an ultraviolet absorbing agent and a quantum dot ink according to claim 1, wherein the ultraviolet absorbing agent is added to the quantum dot ink in an amount of 0.01 to 10 wt% based on the total weight of the quantum dot ink. The method for preparing the color conversion layer by quantum dot ink containing ultraviolet absorber includes: stacking the uniform glue chrome plate on the substrate, spin coating the positive photoresist, exposing under ultraviolet light for 10-20 s, and then developing in sodium hydroxide solution; after development, etching the exposed chrome plate in cerium ammonium nitrate solution, and washing the residual photoresist with ethanol, leaving the arrayed glass pattern composed of the substrate and the remaining uniform glue chrome plate part; plasma etching the arrayed glass pattern; after etching, rinsing with water and blowing dry the surface with nitrogen, obtaining the topographic patterned glass substrate, and the etching depth is 2-5 μm; then misregistration bonding PDMS, the PDMS is provided with a plurality of microchannels, and the quantum dot ink containing ultraviolet absorber is injected into the microchannels through a pressure syringe pump; the same pressure is used to inject air into the microchannels through a pressure syringe pump, and the air flow rate is 10-30 μm / s to blow out the quantum dot ink containing ultraviolet absorber at the position where the microchannels and the topographic patterned groove are completely aligned; under the stable flow driving, the quantum dot ink containing ultraviolet absorber spreads uniformly along the microchannels, fills the target area, and the preparation process is kept at a constant temperature of 25-30℃.

6. The method for preparing a color conversion layer by using an ultraviolet absorber and a quantum dot ink according to claim 5, wherein the ultraviolet absorber is added to the quantum dot ink in an amount of 0.1 to 10 wt% based on the total weight of the quantum dot ink. The plasma etching uses CHF3 and Ar mixed gas, the flow rate of CHF3 gas is 20-40 sccm, the flow rate of Ar gas is 10-20 sccm, the etching time is 10-30 min, and the etching power is 200-300 W.

7. The method for preparing a color conversion layer using an ultraviolet absorbing agent and a quantum dot ink according to claim 1, wherein the ultraviolet absorbing agent is added to the quantum dot ink in an amount of 0.01 to 10 wt% based on the total weight of the quantum dot ink. The method for preparing the color conversion layer by superimposing the thin films prepared by the quantum dot ink and the ultraviolet absorber respectively comprises the following steps: filtering the quantum dot solution without the ultraviolet absorber by using a hydrophobic PTFE film to obtain quantum dot ink; printing a patterned substrate on a substrate by using the quantum dot ink; mixing polystyrene, tetrahydrofuran, anhydrous ethanol and the ultraviolet absorber according to the proportion of (4-8) g:(80-120) ml:(10-30) ml:(0.1-0.5) g, and stirring for 6-10 h to form a uniform transparent solution; and then forming a uniform transparent ultraviolet protection film on the printed patterned substrate by spin coating at 300-500 rpm, so as to prepare the color conversion layer.

8. The method for preparing a color conversion layer using an ultraviolet absorbing agent and a quantum dot ink according to claim 5 or 7, wherein the ultraviolet absorbing agent is added to the quantum dot ink in an amount of 0.01 to 10% by weight based on the total weight of the quantum dot ink. The substrate comprises one of a PET film, ITO glass and a silicon wafer. 9.A color conversion layer prepared by the method for preparing the color conversion layer by compounding the ultraviolet absorber and the quantum dot ink according to any one of claims 1-8. 10.Use of the color conversion layer according to claim 9 in the fields of display, illumination, new energy and biological medicine.

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