Method for obtaining green nitrogen oxide fluorescent material with submicron particle size

Abstract

The invention discloses a method for obtaining a green nitrogen oxide fluorescent material with a submicron particle size, and belongs to the field of fluorescent materials. The submicron particle size green nitrogen oxide fluorescent material has a chemical formula of Si < 6-z > Al < z > O < z > N < 8-z >: Eu < 2 + > (0 < z < = 4.2), the D50 median particle size is 0.9-1 [mu] m; under the excitation of 450 nm blue light, the quantum efficiency of the green nitrogen oxide fluorescent material with the submicron particle size is 60-70%. In the step of preparing the green nitrogen oxide fluorescent material with the submicron particle size, a ball milling process which can destroy the luminescent property of fluorescent material particles is not adopted, a stainless steel tube sealing fluorescent material is used, a liquid nitrogen cold quenching technology is adopted, and finally the green nitrogen oxide fluorescent material with the submicron particle size for Mini LED device packaging is obtained.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials, and more particularly to a method for obtaining green oxynitride fluorescent materials with submicron particle sizes. Background Technology

[0002] Mini LED displays, with their higher resolution, brightness, and contrast, are particularly suitable for head-mounted displays used in virtual reality (VR), augmented reality (AR), and mixed reality (MR) technologies. Traditional inorganic commercial phosphor materials (phosphors) typically have a median D50 particle size of ~10 μm. When such large-particle-size phosphors are packaged onto Mini LED chips using the same technology as traditional white LED lighting products, the number of phosphor particles encapsulated on a single Mini LED is only a few hundred, given the chip's size is on the hundreds of micrometers scale. This fluctuation in luminous performance between phosphor particles leads to variations in the Mini LED's luminous performance, ultimately resulting in a low yield rate. Therefore, to achieve the application of traditional commercial phosphor materials in Mini LED packaging, their particle size must be reduced.

[0003] Obviously, the simplest way to reduce the particle size of commercial fluorescent materials is to use mechanical ball milling. It should be noted that, as disclosed in Patent Document 1 (Liu Qingling, Jiang Kuiming, A method for preparing spherical phosphor without ball milling, CN100554364C), ball milling can easily damage the crystal form of the luminescent material, reduce its luminescent performance, and result in uneven particle size distribution and the generation of many impurities or impurity phases.

[0004] Si 6-z Al z O z N 8-z Eu 2+ (0<z≤4.2) (i.e., β-sialon:Eu) is a high-performance, chemically stable oxynitride fluorescent material that emits green light under blue light excitation. Its morphological characteristics are very distinct, unlike other near-spherical materials (such as Y3Al5O). 12 A fluorescent material containing β-Sialon:Eu (Ce), in rod form (Non-Patent Literature 1, Phosphor Deposits of β-Sialon:Eu). 2+Mixed with SnO2 Nanoparticles Fabricated by the Electrophoretic Deposition (EPD) Process, Chenning Zhang, Tetsuo Uchikoshi, Lihong Liu, Yoshio Sakka, Naoto Hirosaki, Materials, 2014, 7, 5:3623-3633, exhibiting a large length-to-diameter ratio (length-to-diameter ratio), sometimes exceeding 30. This means that when Si... 6- z Al z O z N 8-z Eu 2+ (0<z≤4.2) When using ball milling, the most likely phenomenon for this material is obviously rod fracture (along the height direction), followed by overall grinding and fragmentation. Therefore, ball milling is not suitable for Si. 6-z Al z O z N 8-z Eu 2+ The surface morphology of (0<z≤4.2) (i.e., β-sialon:Eu) is particularly severely damaged.

[0005] From the above, we can draw the following conclusions: ball milling can obtain fluorescent materials with small particle sizes, but ball milling will destroy the luminescence properties of fluorescent materials. Summary of the Invention

[0006] The purpose of this invention is to solve the aforementioned problems in the prior art and provide a method for obtaining submicron-sized green oxynitride fluorescent materials. This method does not employ mechanical ball milling, which would damage the luminescence properties of the phosphor particles, but instead uses a liquid nitrogen quenching process with commercially available Si... 6-z Al z O z N 8-z Eu 2+ Using (0<z≤4.2) (i.e., β-sialon:Eu) as raw material, a submicron-sized green oxynitride fluorescent material was obtained through liquid nitrogen quenching and stainless steel tube sealing. The chemical formula of this submicron-sized green oxynitride fluorescent material is: Si 6-z Al z O z N 8-z Eu 2+(0<z≤4.2) (i.e., β-sialon:Eu); D50 particle size is between 0.9 and 1 μm; under 450 nm blue light excitation, the quantum efficiency of the submicron-sized green oxynitride fluorescent material is 60% to 70%.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] Step (A). Load the β-sialon:Eu commercial product into a stainless steel test tube, install the stainless steel test tube onto a sealing machine, evacuate the stainless steel test tube, and then seal the stainless steel test tube with an acetylene flame to obtain a vacuum-sealed stainless steel tube containing the β-sialon:Eu commercial product.

[0009] In step (A), the sealing machine is generally used for sealing quartz tubes, but quartz tubes have poor resistance to liquid nitrogen quenching. Therefore, this invention chose stainless steel test tubes. The reason for evacuating the stainless steel test tubes is to avoid the oxidation of the internal β-sialon:Eu commercial product during heating, which would lead to a decrease in luminescence intensity.

[0010] Step (B). The stainless steel tube obtained in step (A) is heated to 750~850℃ in a muffle furnace and held at that temperature for a period of time. Then, the hot stainless steel tube is immediately removed from the muffle furnace and placed into a liquid nitrogen tank for liquid nitrogen quenching. After that, the stainless steel tube is removed from the liquid nitrogen, cut open, and the powder inside is removed, which is a submicron-sized green nitrogen oxide fluorescent material (i.e., submicron-sized β-sialon:Eu).

[0011] In step (B), a liquid nitrogen quenching process is used to directly quench the hot stainless steel tube with liquid nitrogen. Under extremely rapid cooling rates (from ~800°C to liquid nitrogen), the rod-shaped commercial Si inside the stainless steel tube... 6-z Al z O z N 8-z Eu 2+ (0<z≤4.2) (i.e., β-sialon:Eu) phosphor material undergoes brittle fracture along the diameter direction (of the rod), eventually breaking into finer submicron-sized green oxynitride phosphor material (i.e., submicron-sized β-sialon:Eu).

[0012] Preferably, in step (A), the vacuum degree is 0.01 Pa when the stainless steel test tube is evacuated.

[0013] Preferably, in step (A), the D50 particle size of the β-sialon:Eu commercial product is 15–20 μm.

[0014] Preferably, in step (B), the heating temperature is 750~850℃, and the holding time is between 10 and 20 minutes.

[0015] A second objective of this invention is to provide a light-emitting device comprising a Mini LED and a fluorescent material. The Mini LED emits light in the wavelength range of 380 nm to 480 nm and has a planar dimension of 200 μm × 200 μm. The fluorescent material comprises at least Si, prepared in the aforementioned steps. 6-z Al z O z N 8-z Eu 2+ (0<z≤4.2) (i.e., β-sialon:Eu), an inorganic fluorescent material with a submicron-sized green nitrogen oxide fluorescent material with a D50 particle size between 0.9 and 1 μm.

[0016] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0017] This invention provides a method for obtaining submicron-sized green oxynitride fluorescent materials. The chemical formula of this submicron-sized green oxynitride fluorescent material is: Si 6-z Al z O z N 8-z Eu 2+ (0<z≤4.2); D50 median particle size is between 0.9 and 1 μm; under 450 nm blue light excitation, the quantum efficiency of this submicron-sized green oxynitride phosphor is 60%–70%. In the preparation of this submicron-sized green oxynitride phosphor, the ball milling process was avoided from damaging the luminescence performance of the phosphor. The phosphor was sealed in a stainless steel tube and quenched with liquid nitrogen, ultimately yielding a submicron-sized green oxynitride phosphor for Mini LED device packaging. Attached Figure Description

[0018] Figure 1 The particle size distribution diagram is shown for the sample obtained in Comparative Example 1.

[0019] Figure 2 The emission spectrum of the sample obtained in Comparative Example 1 under 450 nm light excitation;

[0020] Figure 3 The emission spectrum of a commercial product under 450 nm light excitation;

[0021] Figure 4 The image shows the SEM image of the sample obtained in Comparative Example 1.

[0022] Figure 5SEM images of commercial products;

[0023] Figure 6 This is a particle size distribution diagram of the sample obtained in Example 1;

[0024] Figure 7 The emission spectrum of the sample obtained in Example 1 under 450 nm light excitation;

[0025] Figure 8 This is a SEM image of the sample obtained in Example 1. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. To facilitate understanding of the present invention, embodiments are listed below. Those skilled in the art should understand that the embodiments are merely for the purpose of helping to understand the present invention and should not be considered as specific limitations on the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0027] This application proposes a method for obtaining submicron-sized green oxynitride fluorescent materials, the chemical formula of which is: Si 6-z Al z O z N 8-z Eu 2+ (0<z≤4.2); D50 particle size is between 0.9 and 1 μm; under 450 nm blue light excitation, the quantum efficiency of this submicron-sized green oxynitride fluorescent material is 60% to 70%.

[0028] To obtain the above-mentioned submicron-sized green oxynitride fluorescent material, the following steps were taken:

[0029] Step (A): Fill a stainless steel test tube with the commercial β-sialon:Eu product, mount the stainless steel test tube onto a sealing machine, evacuate the stainless steel test tube, and then seal the stainless steel test tube with an acetylene flame to obtain a vacuum-sealed stainless steel tube containing the commercial β-sialon:Eu product.

[0030] Step (B): Heat the stainless steel tube obtained in step (A) to 800°C in a muffle furnace and hold it at that temperature for a period of time. Then, immediately remove the hot stainless steel tube from the muffle furnace and place it into a liquid nitrogen tank for liquid nitrogen quenching. After that, remove the stainless steel tube from the liquid nitrogen, cut it open, and take out the powder inside. This is a submicron-sized green nitrogen oxide fluorescent material (i.e., submicron-sized β-sialon:Eu).

[0031] In step (A) above, the D50 particle size of the β-sialon:Eu commercial product is 15-20 μm. In some embodiments provided by the present invention, the D50 particle size is preferably 16.72 μm.

[0032] In step (A) above, when evacuating the stainless steel test tube, the vacuum level is 0.01 Pa.

[0033] In step (B) above, the heating temperature is 750~850℃. In some embodiments provided by the present invention, the heating temperature is preferably 800℃. The heat preservation time is between 10 and 20 min. In some embodiments provided by the present invention, the heat preservation time is preferably 15 min.

[0034] After undergoing the reaction in steps (A) and (B) sequentially, a chemical formula Si is obtained. 6- z Al z O z N 8-z Eu 2+ (0<z≤4.2), a submicron-sized green oxynitride fluorescent material with a D50 particle size between 0.9 and 1 μm.

[0035] The light-emitting device comprises a Mini LED and a fluorescent material. The Mini LED emits light in the wavelength range of 380 nm to 480 nm and has a planar dimension of 200 μm × 200 μm. The fluorescent material includes at least Si, prepared in the above steps. 6-z Al z O z N 8-z Eu 2+ (0<z≤4.2), a submicron-sized green oxynitride fluorescent material with a D50 particle size between 0.9 and 1 μm.

[0036] All raw materials used in the following comparative examples and embodiments are commercially available.

[0037] Comparative Example 1

[0038] Commercial β-sialon:Eu with a D50 of 16.72 μm was ball-milled. Specifically, 10 grams of commercial β-sialon:Eu with a D50 of 16.72 μm and a mass of 60 grams of grinding balls (silicon nitride material) with a diameter of 3–8 mm were placed in a 100 ml nylon ball milling jar. The mixture was ball-milled at 1500 rpm for 24 hours. The resulting material was a green oxynitride fluorescent material prepared using a mechanical ball milling process.

[0039] The D50 of the obtained samples was tested using a laser particle size analyzer. The results showed that after prolonged mechanical ball milling, the D50 of the obtained samples decreased from the initial 16.72 μm to 2.93 μm, indicating that... Figure 1 Clearly, ball milling can indeed reduce the D50 of fluorescent materials.

[0040] The emission spectra of the obtained samples were measured using a fluorescence spectrometer under excitation with 450 nm light. Simultaneously, the emission spectra of commercial products were also measured, as shown below. Figure 2 and 3 As shown in the figure, the luminescence intensity of the sample obtained in Comparative Example 1 is lower than that of the commercial product due to the damage to the sample surface caused by ball milling. The morphology of Comparative Example 1 and the commercial product was measured using scanning electron microscopy, see [link to relevant documentation]. Figure 4 and Figure 5 Clearly, commercially available products with a rod-like shape are broken into relatively irregular shapes after ball milling.

[0041] The quantum efficiencies of Comparative Example 1 and the commercial product were tested using a quantum efficiency meter, and the values ​​were 45.2% and 78.3%, respectively. Clearly, the mechanical ball milling process significantly reduces the quantum efficiency of the commercial product. This is because the surface structure and crystallinity of the sample are disrupted after ball milling, leading to enhanced absorption between fluorescent material particles and consequently a decrease in quantum efficiency.

[0042] Example 1

[0043] Follow these steps to make it:

[0044] Step (A): β-sialon:Eu with a D50 of 16.72 μm is loaded into a stainless steel test tube. The stainless steel test tube is then mounted on a sealing machine. The stainless steel test tube is evacuated to a vacuum level of 0.01 Pa. The stainless steel test tube is then sealed with an acetylene flame to obtain a vacuum-sealed stainless steel tube containing commercial β-sialon:Eu.

[0045] Step (B): The stainless steel tube obtained in step (A) is heated to 800°C in a muffle furnace and held for 15 minutes. Then, the hot stainless steel tube is immediately removed from the muffle furnace and placed into a liquid nitrogen tank for liquid nitrogen quenching. After that, the stainless steel tube is removed from the liquid nitrogen, cut open, and the powder inside is taken out, which is a submicron-sized green nitrogen oxide fluorescent material (i.e., submicron-sized β-sialon:Eu).

[0046] The D50 of the obtained samples was tested using a laser particle size analyzer. The results showed that, using liquid nitrogen quenching technology, the D50 of the obtained samples decreased from the initial 16.72 μm to 0.95 μm. (See [link to relevant documentation]). Figure 6Clearly, using liquid nitrogen quenching technology can significantly reduce the D50 of fluorescent materials to the submicron level.

[0047] The emission spectrum of the obtained sample was measured using a fluorescence spectrometer under excitation with 450 nm light, such as... Figure 7 As shown, under the premise of using water quenching and liquid nitrogen quenching technology, since there is no obvious damage to the sample surface, the luminescence intensity of the sample obtained in Example 1 is only slightly lower than that of commercial products, but much higher than that of Comparative Example 1.

[0048] The morphology of the sample from Example 1 was measured using a scanning electron microscope. See [link to sample description]. Figure 8 Clearly, after liquid nitrogen quenching, the rod-shaped commercial product exhibited significant fracture along its height (diameter direction), resulting in a relatively regular morphology.

[0049] The quantum efficiency of Example 1 was tested using a quantum efficiency meter, and the value was 69.2%. Clearly, for the same reduction in the D50 of the fluorescent material, the quantum efficiency of the sample obtained by liquid nitrogen quenching is much higher than that of the sample obtained by ball milling. This is because ball milling damages the surface structure and crystallinity of the fluorescent material particles, increasing absorption between particles and leading to a decrease in quantum efficiency; while during liquid nitrogen quenching, the fluorescent material particles undergo brittle fracture directly, with minimal damage to the surface structure and crystallinity.

[0050] Using the method of this invention, Example 1 ultimately yielded a relatively high-performance compound with the chemical formula Si. 6- z Al z O z N 8-z Eu 2+ (0<z≤4.2, submicron-sized green oxynitride fluorescent material with D50 particle size between 0.9 and 1 μm.)

[0051] Example 2

[0052] The Si obtained in Example 1 6-z Al z O z N 8-z Eu 2+ A green oxynitride phosphor with a submicron particle size (0<z≤4.2) and a D50 particle size between 0.9 and 1 μm is encapsulated with a Mini LED with an emission wavelength of 450 nm and a planar size of 200 μm × 200 μm. The specific encapsulation process is as follows: the phosphor and epoxy resin are mixed at a mass ratio of 1:3.25, then coated onto the surface of the Mini LED, and finally cured at 150°C for 30 minutes to obtain a Mini LED device.

[0053] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0054] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0055] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for obtaining submicron-sized green oxynitride fluorescent materials, characterized in that: The chemical formula of the submicron-sized green nitrogen oxide fluorescent material is Si. 6-z Al z O z N 8-z Eu 2+ Where 0 < z ≤ 4.2; D50 particle size is between 0.9 and 1 μm; under 450 nm blue light excitation, the quantum efficiency of the submicron-sized green oxynitride fluorescent material is 60% to 70%; the method for obtaining the submicron-sized green oxynitride fluorescent material is as follows: Step (A). Load the β-sialon:Eu commercial product into a stainless steel test tube, install the stainless steel test tube on a sealing machine, evacuate the stainless steel test tube, and then seal the stainless steel test tube with an acetylene flame to obtain a vacuum-sealed stainless steel tube containing the β-sialon:Eu commercial product. Step (B). The stainless steel tube obtained in step (A) is heated in a muffle furnace and kept at that temperature for a period of time. The hot stainless steel tube is then immediately removed from the muffle furnace and placed into a liquid nitrogen tank for liquid nitrogen quenching. After that, the stainless steel tube is removed from the liquid nitrogen, cut open, and the powder inside is removed, which is the submicron-sized green nitrogen oxide fluorescent material.

2. The method for obtaining submicron-sized green oxynitride fluorescent materials as described in claim 1, characterized in that: In step (A), when the stainless steel test tube is evacuated, the vacuum level is 0.01 Pa.

3. The method for obtaining submicron-sized green oxynitride fluorescent materials as described in claim 1, characterized in that: In step (B), the heating temperature is 750~850℃.

4. The method for obtaining submicron-sized green oxynitride fluorescent materials as described in claim 1, characterized in that: In step (B), the heat preservation time is between 10 and 20 minutes.

5. The method for obtaining submicron-sized green oxynitride fluorescent materials as described in claim 1, characterized in that: The D50 particle size of the β-sialon:Eu commercial product is 15–20 μm.

6. A light-emitting device, comprising: Mini LEDs and fluorescent materials, wherein the fluorescent materials include submicron-sized green oxynitride fluorescent materials prepared by any one of claims 1 to 5.

7. The light-emitting device as described in claim 6, characterized in that: The Mini LED emits wavelengths in the range of 380 nm to 480 nm.

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