A white light LED device and a method of manufacturing the same

Abstract

This invention discloses a white LED device and its preparation method, belonging to the field of white LED lighting technology. It solves the problems of existing technologies where a single phosphor cannot emit white light, two phosphors result in low luminous efficiency of white LED lamps, and three phosphors involve complex and costly encapsulation processes. The white LED device includes an ultraviolet LED chip and a phosphor layer disposed in the optical path of the ultraviolet LED chip; the phosphor layer contains a phosphor with the chemical composition shown in formula (1), K3YSi 2‑x Hf x O7:yEu 2+ (1), where x is the mole fraction of Hf, 2-x is the mole fraction of Si, and y is the mole fraction of Eu, wherein 0.01≤x<2 and 0.001≤y≤0.1. The phosphor in the phosphor layer of the white LED device of this invention has high internal quantum efficiency, resulting in a high color rendering index for the white LED device. The color temperature is adjustable while ensuring white light emission, high internal quantum efficiency, and a high color rendering index.

Description

Technical Field

[0001] This invention relates to the field of inorganic phosphor materials technology, and in particular to a white LED device and its preparation method. Background Technology

[0002] With the continuous development of modern lighting technology, white LEDs, with their superior luminous efficacy, ultra-long lifespan, low power consumption, small size, and high reliability, have successfully replaced traditional lighting solutions such as incandescent and fluorescent lamps, becoming the absolute mainstream lighting product in the market. Their application areas have also rapidly expanded from initial indicator backlighting to various aspects such as indoor general lighting, commercial lighting, industrial lighting, automotive lighting, and display backlighting.

[0003] Currently, the mainstream technical approach for achieving commercial white LEDs is to use blue LED chips (usually based on InGaN material, with an emission wavelength of approximately 450-470nm) to excite a layer of yellow phosphor covering its surface. The most typical and widely used of these is YAG:Ce. 3+ The light-emitting principle is as follows: some of the blue light emitted by the chip mixes with the yellow light emitted after the phosphor is excited, creating the visual perception of white light in the human eye. This technical approach is popular due to its simple structure, high luminous efficiency, relatively controllable manufacturing costs, and high technological maturity. However, this "blue light + yellow light" solution has an inherent and fundamental flaw related to lighting quality: its emission spectrum severely lacks cyan light components in the 450-500nm wavelength range and deep red light components in the 600-680nm wavelength range. Cyan light is crucial for accurately reproducing the colors of objects such as water and glass, while deep red light directly affects the vibrancy of warm-colored objects such as meat, fruit, and skin. The discontinuity of the spectrum directly leads to a generally low color rendering index (CRI) for this type of lamp (usually below 80). The CRI is a key indicator of a light source's ability to reproduce the true colors of objects; the lower the Ra value, the more severe the color distortion of objects under the light.

[0004] Therefore, developing white LED devices for full-spectrum lighting based on ultraviolet LED chips is of great significance for promoting the upgrading and development of the lighting industry and advancing the application of full-spectrum lighting. Summary of the Invention

[0005] In view of the above, the present invention aims to provide a white LED device and its preparation method to at least solve one of the problems existing in the prior art: (1) the traditional blue light chip plus yellow phosphor scheme has a low color rendering index and distorted lighting color due to the lack of cyan and red light in the spectrum; (2) the preparation process of the three-color phosphor in the white LED device is complicated and costly, and cannot be widely used; (3) the single phosphor in the white LED device cannot emit white light and has low internal quantum efficiency.

[0006] The objective of this invention is mainly achieved through the following technical solutions: The first aspect of the present invention provides a white LED device, comprising: an ultraviolet LED chip and a phosphor layer disposed in the optical path of the ultraviolet LED chip; The phosphor layer comprises phosphors having the chemical composition shown in formula (1): K3YSi 2-x Hf x O7:yEu 2+ (1) Where x is the mole fraction of Hf, 2-x is the mole fraction of Si, and y is the mole fraction of Eu, and 0.01≤x<2, 0.001≤y≤0.1.

[0007] Furthermore, under the excitation of the ultraviolet LED chip, the phosphor layer emits mixed light covering the 400-850nm visible light band, forming white light.

[0008] Furthermore, the peak emission wavelength of the ultraviolet LED chip is 365-370nm.

[0009] Furthermore, the emission spectrum of the phosphor layer includes a blue light emission peak with a peak wavelength of 450-480 nm and a red light emission peak with a peak wavelength of 600-650 nm.

[0010] Furthermore, the device has a color rendering index Ra≥70 and an adjustable color temperature within the range of 2000-5000K.

[0011] Furthermore, the device has a color rendering index Ra≥89 and a color temperature that is adjustable within the range of 3900-5000K.

[0012] Furthermore, the phosphor layer is formed by mixing and curing the phosphor and the binder, wherein the mass ratio of the phosphor to the binder is 1:2-4.

[0013] A second aspect of the present invention provides a method for preparing the white LED device described in the first aspect, comprising the following steps: S1. Mix the phosphor and binder evenly to obtain a mixed colloid; S2. The mixed colloid is coated onto the ultraviolet LED chip, cured to form a phosphor layer, and then encapsulated to obtain a white LED device.

[0014] Further, in step S1, the mass ratio of the phosphor to the binder is 1:2-4.

[0015] Furthermore, the adhesive is selected from silicone and / or epoxy resin.

[0016] Furthermore, the silicone rubber is selected from at least one of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, fluorosilicone rubber, or nitrile silicone rubber; the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetramethylbiphenyl type epoxy resin, or glycidylamine type epoxy resin.

[0017] Furthermore, in step S2, the curing conditions include curing at 20-160°C for 4-10 hours.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) The white LED device of the present invention introduces phosphor with a specific composition into its phosphor layer, and regulates the Hf content in the phosphor. 4+ and Si 4+ The mole fraction of Eu regulates 2+ The phosphor alters the local crystal field environment at the lattice sites occupied by the phosphor, inducing bimodal emission of blue and red light. This bimodal emission effectively fills the cyan and red light regions of the LED lighting spectrum, resulting in good overall continuity of the emission spectrum. The device can directly emit high color rendering white light covering most of the visible light region (e.g., in Example 2, the color rendering index is as high as 90) with only a single phosphor and a color temperature of 2000-5000K. This solves the problems of complex packaging process, high cost, and uneven light color caused by multicolor phosphor mixing systems.

[0019] (2) The white LED device of the present invention contains Hf in its phosphor layer. 4+ This enhances the overall lattice rigidity of the phosphor matrix and effectively suppresses Eu. 2+ The non-radiative loss of excited-state energy results in an internal quantum efficiency of up to 83.73% for the phosphor, ensuring high luminous efficacy of the fabricated LED device. Furthermore, the preparation method employs a mature high-temperature solid-state reaction process, with readily available raw materials and a simple process, fully compatible with existing phosphor production lines. It requires no complex or demanding synthesis conditions, possessing extremely low production conversion barriers and cost advantages, facilitating large-scale production and market promotion. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 and Figure 2 The images show the XRD patterns of the phosphors prepared in Examples 1-10.

[0022] Figure 3The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 3 are shown.

[0023] Figure 4 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 4 are shown.

[0024] Figure 5 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 5 are shown.

[0025] Figure 6 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 6 are shown.

[0026] Figure 7 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 1 are shown.

[0027] Figure 8 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 2 are shown.

[0028] Figure 9 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 7 are shown.

[0029] Figure 10 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 8 are shown.

[0030] Figure 11 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 9 are shown.

[0031] Figure 12 The excitation spectrum (a) and emission spectrum (b) of the phosphor prepared in Example 10 are shown.

[0032] Figure 13 The image shows the internal quantum efficiency of the phosphor prepared in Example 3.

[0033] Figure 14 The image shows the internal quantum efficiency of the phosphor prepared in Example 4.

[0034] Figure 15 The image shows the internal quantum efficiency of the phosphor prepared in Example 5.

[0035] Figure 16 The image shows the internal quantum efficiency of the phosphor prepared in Example 6.

[0036] Figure 17 The image shows the internal quantum efficiency of the phosphor prepared in Example 1.

[0037] Figure 18The image shows the internal quantum efficiency of the phosphor prepared in Example 2.

[0038] Figure 19 The image shows the internal quantum efficiency of the phosphor prepared in Example 7.

[0039] Figure 20 The image shows the internal quantum efficiency of the phosphor prepared in Example 8.

[0040] Figure 21 The graph shows the internal quantum efficiency of the phosphor prepared in Example 9.

[0041] Figure 22 The graph shows the internal quantum efficiency of the phosphor prepared in Example 10.

[0042] Figure 23 The image shows the white LED device encapsulated with phosphor prepared in Example 3, along with its test spectrum.

[0043] Figure 24 The image shows the phosphor-encapsulated white LED device and its test spectrum obtained in Example 4.

[0044] Figure 25 The image shows a white LED device encapsulated with phosphor prepared in Example 5, along with its test spectrum.

[0045] Figure 26 The image shows the phosphor-encapsulated white LED device and its test spectrum obtained in Example 6.

[0046] Figure 27 The image shows the white LED device encapsulated with phosphor prepared in Example 1, along with its test spectrum.

[0047] Figure 28 The image shows the white LED device encapsulated with phosphor prepared in Example 2, along with its test spectrum.

[0048] Figure 29 The image shows the phosphor-encapsulated white LED device and its test spectrum obtained in Example 7.

[0049] Figure 30 The image shows the white LED device encapsulated with phosphor prepared in Example 8, along with its test spectrum.

[0050] Figure 31 The image shows the phosphor-encapsulated white LED device and its test spectrum obtained in Example 9.

[0051] Figure 32 The image shows the phosphor-encapsulated white LED device and its test spectrum obtained in Example 10.

[0052] Figure 33 Comparative Example 1 uses YAG:Ce3+ Schematic diagram and test spectrum of a white LED device packaged with phosphor and blue LED chip. Detailed Implementation

[0053] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0054] Because existing single phosphors cannot emit white light, and the reabsorption between two phosphors leads to low luminous efficiency of LED lamps, and the three phosphors have complex and costly processes, the first aspect of this invention provides a white LED device, comprising: an ultraviolet LED chip and a phosphor layer disposed in the optical path of the ultraviolet LED chip, wherein the phosphor layer contains phosphor having the chemical composition shown in formula (1): K3YSi 2-x Hf x O7:yEu 2+ (1) Where x is the mole fraction of Hf, 2-x is the mole fraction of Si, and y is the mole fraction of Eu, and 0.01≤x<2, 0.001≤y≤0.1.

[0055] In this invention, the white LED device further includes a substrate and an optical lens. The ultraviolet LED chip is fixedly disposed on the substrate, and the optical lens covers the outside of the ultraviolet LED chip and is fixed on the substrate. The optical lens and the substrate form a sealed cavity, which is filled with an inert gas. The optical lens can be made of sapphire or quartz glass.

[0056] In this invention, by utilizing Hf 4+ Partially replaces Si 4+ (By adjusting the molar fractions of the two components in the phosphor) and utilizing the significant difference in their ionic radii, strain is introduced into the crystal lattice to alter the Eu content. 2+ The local crystal field environment at the luminescent center promotes Eu 2+ Occupying two different lattice sites in the crystal lattice, the phosphor induces the simultaneous generation of blue and red light emission peaks. The emission spectrum of the phosphor can completely cover the visible light region, thereby directly achieving white light emission characteristics with a high color rendering index.

[0057] Furthermore, the inventors discovered that by adjusting the x-value, the blue / red light intensity ratio can be precisely adjusted, achieving flexible color temperature control. Simultaneously, the optimized y-value range ensures Eu... 2+ As a high-efficiency light-emitting center, it achieves excellent internal quantum efficiency (IQE), laying the material foundation for manufacturing high-performance, low-cost single-phosphor white LED devices.

[0058] According to some embodiments of the present invention, the value of x is in the range of 0.01 ≤ x < 2.

[0059] In this invention, when x>2, it means Hf 4+ Excessive content can introduce excessive lattice strain, potentially leading to crystal structure instability or even the formation of impurity phases, disrupting the main crystalline structure of the matrix, and thus significantly reducing the internal quantum efficiency. When x < 0.01, it means that Hf 4+ Insufficient content of x fails to effectively alter the local crystal field environment of the matrix lattice, resulting in a lack of blue light component in the emission spectrum. This prevents the formation of a balanced full-spectrum emission, leading to a decrease in the color rendering index and a lower color temperature of the LED device. For example, the value of x can be 0.1, 0.11, 0.12, 0.13, 0.15, 0.16, 0.18, 0.2, 0.3, or any combination of two of these values. Preferably, 0.02 ≤ x ≤ 0.3, and more preferably, 0.1 ≤ x ≤ 0.12.

[0060] In this invention, when x satisfies 0.1-0.12, Hf 4+ For Si 4+ Substitution can more effectively modulate the crystal field, making Eu 2+ The generated blue and red light emission peaks achieve an ideal intensity balance, enabling the stable preparation of white phosphors with color temperatures ranging from 2000K to 5000K. Within this range, the phosphors exhibit excellent crystallinity and high luminous efficiency, achieving an internal quantum efficiency of no less than 70%.

[0061] Furthermore, considering that when y is less than 0.001, Eu 2+ If the doping level is too low, the number of luminescent centers will be insufficient, resulting in weak luminescence intensity of the phosphor, which will be difficult to meet the brightness requirements of practical lighting applications; when y is greater than 0.1, excessively high Eu² will lead to insufficient luminescence intensity. + Doping concentration can cause concentration quenching. Excessive activator ions intensify energy transfer, leading to an increased probability of non-radiative transitions, which in turn reduces the phosphor's luminescence intensity. The inventors discovered that when 0.001 ≤ y ≤ 0.1, they can effectively avoid concentration quenching while ensuring a sufficient number of luminescent centers, thus increasing the luminescence intensity of the phosphor. 2+ Ions in K3YSi 2-x Hf x Efficient and stable luminescence is achieved in the O7 matrix. Within this preferred range of y values, Eu... 2+ Ions can uniformly replace K + / Y 3+ The lattice sites are used to achieve charge compensation and benefit from Hf 4+ Replace Si 4+The introduced lattice strain creates a reasonable energy distribution between the blue and red light emission centers, thereby synergistically achieving full visible light coverage of the emission spectrum and high internal quantum efficiency (≥70%).

[0062] For example, the value of y can be 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.06, 0.08, or 0.1, preferably 0.01-0.015.

[0063] According to some embodiments of the present invention, under ultraviolet light excitation, the emission spectrum of the phosphor includes a blue light emission peak and a red light emission peak. Specifically, the emission spectrum of the phosphor layer includes a blue light emission peak with a peak wavelength of 450-480 nm and a red light emission peak with a peak wavelength of 600-650 nm.

[0064] In this invention, when the structure of the phosphor satisfies the chemical composition shown in formula (1), and the values ​​of x and y are limited as described above, it is possible to achieve the blue and red bimodal emission characteristics of a single phosphor under ultraviolet light excitation.

[0065] According to some embodiments of the present invention, the peak emission wavelength of the ultraviolet LED chip is 365-370nm. For example, it can be 365nm, 367nm, 368nm, 369nm, or 370nm.

[0066] Furthermore, under the excitation of the ultraviolet LED chip, the phosphor layer emits mixed light covering the 400-850nm visible light band to form white light, such as 400nm, 450nm, 500nm, 550nm, 600nm, 700nm, and 800nm.

[0067] According to some specific embodiments of the present invention, the internal quantum efficiency of the phosphor in the phosphor layer can reach up to 83.73%.

[0068] According to some specific embodiments of the present invention, the color rendering index Ra of the device is ≥70, preferably ≥89, and the color temperature is adjustable in the range of 2000-5000K, preferably in the range of 3900-5000K, and more preferably in the range of 2038-4940K.

[0069] According to the present invention, the phosphor layer is formed by mixing and curing the phosphor and the binder, wherein the mass ratio of the phosphor to the binder is 1:2-4.

[0070] In this invention, the adhesive is selected from silicone rubber and / or epoxy resin, wherein the silicone rubber is selected from at least one of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, fluorosilicone rubber or nitrile silicone rubber; and the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetramethylbiphenyl type epoxy resin or glycidylamine type epoxy resin.

[0071] In this invention, the silicone and epoxy resin can be obtained commercially. For example, the silicone grade can be NFS-L-8440, ML7420AB, etc., and the epoxy resin grade can be E-600 / H-600, E-605 / H-605, ZLA-175B, etc.

[0072] According to the present invention, the phosphor in the phosphor layer can be prepared by the following preparation method: mixing a K-containing compound, a Y-containing compound, a Si-containing compound, an Hf-containing compound, and an Eu-containing compound, and then heating and sintering them under a reducing atmosphere to obtain the phosphor.

[0073] In this invention, the raw materials are mixed and sintered under a reducing atmosphere, which enables the stable trivalent europium (Eu) to be sintered. 3+ ) ions are reduced to divalent europium (Eu) 2+ (Ions) are a necessary condition for achieving efficient luminescence, ensuring the luminescent centers and high-efficiency luminescence performance in the final product.

[0074] Furthermore, this method is simple in process, has low production cost, and is well compatible with traditional phosphor production lines, making it easy to achieve mass production. It has a very promising application prospect in the field of white LED lighting.

[0075] In this invention, the mixing of K-containing compounds, Y-containing compounds, Si-containing compounds, Hf-containing compounds, and Eu-containing compounds can be carried out in an agate mortar. Specifically, the raw materials are thoroughly ground for 20-40 minutes, and then the ground raw materials are transferred to a corundum crucible and heated and sintered in a reduction tube furnace.

[0076] Furthermore, in the method, the product after heating and sintering in the reduction tube furnace is cooled to room temperature and then ground again, and then sieved (3-20µm) to obtain phosphor.

[0077] According to some embodiments of the present invention, in order to enable Eu element to achieve white light emission characteristics in a crystal matrix, it is preferable to react trivalent Eu in Eu-containing compounds under a reducing atmosphere. 3+ Reduced to divalent Eu 2+ The reducing atmosphere includes a nitrogen-hydrogen mixture, hydrogen, or carbon monoxide.

[0078] In this invention, by way of example, the nitrogen-hydrogen mixture can specifically be 1-10 vol% hydrogen + 90-99 vol% nitrogen.

[0079] According to some embodiments of the present invention, the heating rate in the reduction tube furnace is 3-10℃ / min, and sintering is carried out at 1100-1300℃ for 4-8 hours.

[0080] In this invention, the aforementioned suitable heating rate ensures stable decomposition of raw materials and release of reactive gases, avoids powder splashing, and guarantees uniform product morphology. Sintering at 1100-1300℃ for 4-8 hours ensures that the reactants can fully diffuse and react completely to form a pure phase, while allowing the grains to grow to a suitable size. This enables the stable and repeatable preparation of high-crystal quality and high-performance phosphors, avoiding impurities, defects, or decreased luminescence performance caused by improper processes.

[0081] According to some embodiments of the present invention, the K-containing compound is potassium carbonate and / or potassium hydroxide, the Y-containing compound is yttrium oxide and / or yttrium carbonate, the Si-containing compound is silicon dioxide and / or silicic acid, the Hf-containing compound is hafnium oxide and / or hafnium hydroxide, and the Eu-containing compound is europium oxide and / or europium carbonate.

[0082] According to some embodiments of the present invention, the molar ratios of the Y-containing compound (calculated as Y), the K-containing compound (calculated as K), the Si-containing compound (calculated as Si), the Hf-containing compound (calculated as Hf), and the Eu-containing compound (calculated as Eu) satisfy the following conditions: K:Y = 3:1, Hf:Y = x, and 0.01 ≤ x < 2, Si:Y = 2 - x, Eu:Y = y, and 0.001 ≤ y ≤ 0.1. This ensures that during the high-temperature solid-state reaction, each element strictly conforms to the target chemical formula K3YSi. 2-x Hf x O7:yEu 2+ To carry out a stoichiometric reaction, Hf 4+ Precise replacement of Si 4+ The lattice sites of Eu can be used to effectively regulate the crystal structure. 2+The local crystal field environment of the luminescent center induces it to simultaneously occupy two different lattice sites in the crystal lattice that emit blue and red light. This results in phosphors with high crystallinity and phase purity, achieving an ideal intensity balance between blue and red light peaks in the emission spectrum, fully covering the 400-850nm visible light region. Ultimately, a single phosphor can directly emit white light with a high color rendering index (Ra≥90) under ultraviolet chip excitation, with an internal quantum efficiency of over 83%, achieving synergistic optimization of material luminescence performance and phase stability. Preferably, the molar ratios of the Y-containing compound (calculated as Y), K-containing compound (calculated as K), Si-containing compound (calculated as Si), Hf-containing compound (calculated as Hf), and Eu-containing compound (calculated as Eu) satisfy the following conditions: K:Y=3:1, Hf:Y=x, and 0.1≤x<0.12, Si:Y=2-x, Eu:Y=y, and 0.01≤y≤0.015.

[0083] According to some preferred embodiments of the present invention, the molar ratio of the Y-containing compound (calculated as Y), the K-containing compound (calculated as K), the Si-containing compound (calculated as Si), the Hf-containing compound (calculated as Hf), and the Eu-containing compound (calculated as Eu) is 1:3:1.88-1.9:0.1-0.12:0.001-0.015.

[0084] A second aspect of the present invention provides a method for using the white LED device described in the first aspect, comprising the following steps: S1. Mix the phosphor and binder evenly to obtain a mixed colloid; S2. The mixed colloid is coated onto the ultraviolet LED chip, cured to form a phosphor layer, and then encapsulated to obtain a white LED device.

[0085] According to some embodiments of the present invention, in step S1, the mass ratio of the phosphor to the binder is 1:2-4, preferably 1:2.

[0086] Specifically, the adhesive is selected from silicone and / or epoxy resin; Specifically, the silicone rubber is selected from at least one of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, fluorosilicone rubber, or nitrile silicone rubber; the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetramethylbiphenyl type epoxy resin, or glycidylamine type epoxy resin.

[0087] Specifically, the silicone and epoxy resin can be commercially available. For example, the silicone grade can be NFS-L-8440, ML7420AB, etc., and the epoxy resin grade can be E-600 / H-600, E-605 / H-605, ZLA-175B, etc.

[0088] According to some embodiments of the present invention, the curing conditions include: curing at 20-160°C for 4-10 hours, and for better results, curing at 80-100°C for 1-2 hours, followed by curing at 140-160°C for 3-5 hours.

[0089] In this invention, the white LED device contains a phosphor with the chemical composition shown in formula (1), which can achieve a color rendering index of not less than 70 (up to 90 in Example 2), and the color temperature is adjustable in the range of 2000-5000K, preferably in the range of 3900-5000K, and more preferably in the range of 2038-4940K, so as to display warm white light or cool white light characteristics according to actual needs.

[0090] The advantages of the method of the present invention will be illustrated below through examples.

[0091] In the following examples, the crystal structure of the phosphor was tested using an X'Pert PRO X-ray diffractometer.

[0092] Excitation and emission spectra were measured using an Edinburgh (FL1000) fluorescence spectrometer.

[0093] The internal quantum efficiency of luminescence was measured using an Edinburgh (FL1000) fluorescence spectrometer.

[0094] The color rendering index and color temperature of the white LED device were tested using the Far East HAAS-2000.

[0095] The ultraviolet LED chip was purchased from Youjingxi Optoelectronics Factory on Taobao, with an emission wavelength of 365-370nm.

[0096] The silicone rubber was purchased from a Taobao store selling LED accessories for scientific research. The mass ratio of silicone rubber A to silicone rubber B is 1:4.

[0097] Example 1 S1. Potassium carbonate, yttrium oxide, silicon dioxide, hafnium dioxide, and europium oxide were added to an agate mortar in a molar ratio of 3:1:3.8:0.2:0.01 (where the molar ratio of K, Y, Si, Hf, and Eu was 3:1:1.9:0.1:0.01). The mixture was ground thoroughly for 30 minutes to obtain a mixed raw material. This mixed material was then transferred to a corundum crucible and sintered in a reducing tube furnace under a reducing atmosphere. Specifically, the temperature was increased to 1250℃ at a rate of 5℃ / min, and the sintering time was 8 hours. The reducing atmosphere was 5 vol% hydrogen + 95 vol% nitrogen. Finally, the sintered product was ground and sieved to obtain K3YSi. 1.9 Hf 0.1 O7:0.01Eu 2+ Fluorescent powder.

[0098] The phosphor was tested by XRD, as shown below. Figure 1 As shown, K3YSi 1.9 Hf 0.1 O7:0.01Eu 2+ The main XRD diffraction peaks of the phosphor are still related to K3YSi2O7:0.01Eu. 2+ To remain consistent indicates that when Hf 4+ For Si 4+ When the substitution ratio is 0.1 (x is 0.1), the crystal structure of the phosphor remains basically unchanged, but some new diffraction peaks also appear, indicating that Hf 4+ The ions successfully entered the crystal lattice and caused partial changes in the crystal structure of the K3YSi2O7 matrix.

[0099] When excited by ultraviolet light at a wavelength of 365 nm, the phosphor exhibits bimodal emission with peak wavelengths at 460 nm and 620 nm, and the emission spectrum covers the visible light band of 400-850 nm. Figure 7 It has the characteristic of emitting white light across the entire spectrum.

[0100] This phosphor also exhibits excellent luminescence properties, with a measured internal quantum efficiency of up to 82.99%. Figure 17 ); S2. The phosphor obtained in step S1 is encapsulated with a commercial 365nm ultraviolet chip to form a white light device. Specifically: weigh the silicone rubber and phosphor (the mass ratio of phosphor to silicone rubber is 1:2) and mix them evenly to obtain a mixed colloid. Coat the mixed colloid onto the ultraviolet LED chip, keep it at 90℃ for 1 hour, and then raise the temperature to 150℃ and keep it at 4 hours to ensure that the silicone rubber is fully cured. Thus, the white light LED device is encapsulated. After testing, the color rendering index of the device is as high as 89.2, and the color temperature is 4940K. Figure 27 It has a good lighting effect.

[0101] Example 2 The method is the same as in Example 1, except that the preparation method of the phosphor includes: adding potassium carbonate, yttrium oxide, silicon dioxide, hafnium dioxide, and europium oxide into an agate mortar, with a molar ratio of 3:1:3.76:0.24:0.01 (where the elemental molar ratio of K, Y, Si, Hf, and Eu is 3:1:1.88:0.12:0.01), and grinding thoroughly for 30 min to obtain a mixed raw material. The mixed raw material is then transferred to a corundum crucible and sintered in a reducing tube furnace under a reducing atmosphere. Specifically, the temperature is increased to 1250℃ at a heating rate of 5℃ / min, and the sintering time is 8 h. The reducing atmosphere is 5 vol% hydrogen + 95 vol% nitrogen. Finally, the sintered product is ground and sieved to obtain K3YSi. 1.88 Hf 0.12 O7:0.01Eu 2+ Fluorescent powder.

[0102] like Figure 8 As shown, when Hf 4+ For Si 4+ When the substitution ratio is increased to 0.12, the proportion of blue light in the emission spectrum of the phosphor in Example 2 decreases, while the proportion of red light increases, exhibiting warm white light emission characteristics. The luminescence internal quantum efficiency of this phosphor is 83.73% ( Figure 18 The phosphor was encapsulated with a 365nm ultraviolet chip to form a white light device (preparation method is the same as in Example 1). The color rendering index of the white light device is as high as 90, and the color temperature is reduced to 3900K. Figure 28 (This) exhibits a warm white light lighting effect.

[0103] Examples 3-10 Following the method of Example 1, except that the proportions of the raw materials were changed, Hf was prepared separately. 4+ For Si 4+ Phosphors with substitution ratios of 0.02, 0.04, 0.06, 0.08, 0.14, 0.16, 0.18, and 0.2, and whose chemical compositions are K3YSi, respectively. 1.98 Hf 0.02 O7:0.01Eu 2+ K3YSi 1.96 Hf 0.04 O7:0.01Eu 2+ K3YSi 1.94 Hf 0.06 O7:0.01Eu 2+ K3YSi 1.92 Hf 0.08 O7: 0.01Eu 2+ K3YSi 1.86 Hf 0.14 O7:0.01Eu2+ K3YSi 1.84 Hf 0.16 O7:0.01Eu 2+ K3YSi 1.82 Hf 0.18 O7:0.01Eu 2+ K3YSi 1.8 Hf 0.2 O7:0.01Eu 2+ .

[0104] The luminescence quantum efficiency of the above phosphor was tested, and it was fabricated into an LED device. The color rendering index and color temperature of the device were also tested. The results are shown in Table 1. Figures 3-6 Excitation and emission spectra of phosphors Figures 9-12 Excitation and emission spectra of phosphors.

[0105] Examples 11-13 Following the method of Example 1, except that the amount of europium oxide was changed, K3YSi was prepared respectively. 1.9 Hf 0.1 O7:0.002Eu 2+ K3YSi 1.9 Hf 0.1 O7:0.1Eu 2+ K3YSi 1.9 Hf 0.1 O7:0.015Eu 2+ Fluorescent powder.

[0106] Comparative Example 1 Commercial YAG:Ce 3+ Phosphors were packaged with commercial blue LED chips to prepare white LED devices, and the color rendering index and color temperature were tested. The results are shown in Table 1.

[0107] Comparative Example 2 Following the method of Example 1, except that hafnium dioxide was replaced with an equal amount of zirconium dioxide, K3YSi was prepared. 1.9 Zr 0.1 O7:0.01Eu 2+ Fluorescent powder.

[0108] The prepared K3YSi 1.9 Zr 0.1 O7:0.01Eu 2+ The phosphor was used to fabricate an LED device, which was then tested. Under ultraviolet light excitation, it only emitted orange-red light. The results are shown in Table 1.

[0109] Comparative Example 3 Following the method of Example 1, except that hafnium dioxide was not added, K3YSi2O7:0.01Eu was prepared. 2+ Phosphor. K3YSi2O7:0.01Eu 2+ When phosphors were fabricated into LED devices, the results showed that phosphors without Hf doping exhibited only orange-red light emission under ultraviolet light excitation, with no blue light emission peak. The orange-red light emission peak was located at 620 nm.

[0110] Comparative Example 4 Following the method of Example 1, except that the amount of europium oxide was changed, K3YSi was prepared. 1.9 Hf 0.1 O7:0.2Eu 2+ .

[0111] Due to Eu 2+ If the doping concentration is too high, the phosphor will experience a concentration quenching effect, resulting in no light emission.

[0112] Comparative Example 5 Following the method of Example 1, except that europium oxide was not added, K3YSi was prepared. 1.9 Hf 0.1 O7, due to K3YSi 1.9 Hf 0.1 O7 is a matrix without luminescent ions and does not emit light.

[0113] Table 1

[0114] As shown in Table 1, the K3YSi2O7 content in Comparative Example 3 is 0.01Eu. 2+ The sample only emits orange-red light, and the color temperature of the orange-red light is relatively low. With Hf 4+ As the doping ratio x increases, the proportion of blue light in the emission spectrum of the corresponding sample gradually increases. Since blue light has a higher color temperature, the color temperature of the packaged LED device also shows an increasing trend. When Hf 4+ When the doping ratio x=0.1, the blue light proportion in the emission spectrum of the sample from Example 1 reaches its maximum, and correspondingly, the LED device packaged using the sample from Example 1 also has the highest color temperature. However, with Hf 4+ As the doping ratio x further increases, the proportion of blue light in the emission spectrum of the corresponding example samples begins to gradually decrease, for example, in Example 2, Hf 4+ When the doping ratio x=0.12, the color temperature of the packaged LED device also gradually decreases to 3900K. Therefore, when Hf 4+ The doping ratio x is in the range of 0.02-0.1. As x increases, the color temperature gradually increases. 4+When the doping ratio x exceeds 0.1, the color temperature decreases with increasing x, and the color temperature increases with Hf. 4+ The doping ratio x shows a trend of first increasing and then decreasing.

[0115] Comparative Examples 2 and 3 all emit orange-red light, and their spectra do not contain any blue light components, thus they cannot form white light with a high color rendering index.

[0116] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A white LED device, characterized in that, include: Ultraviolet LED chip and phosphor layer disposed in the optical path of the ultraviolet LED chip; The phosphor layer comprises phosphors having the chemical composition shown in formula (1): K3YSi 2-x Hf x O7:yEu 2+ (1) Where x is the mole fraction of Hf, 2-x is the mole fraction of Si, and y is the mole fraction of Eu, and 0.01≤x<2, 0.001≤y≤0.

1.

2. The white LED device according to claim 1, wherein, under the excitation of the ultraviolet LED chip, the phosphor layer emits mixed light covering the 400-850nm visible light band to form white light.

3. The white LED device according to claim 1, characterized in that, The peak emission wavelength of the ultraviolet LED chip is 365-370nm.

4. The white LED device according to claim 1, characterized in that, The emission spectrum of the phosphor layer includes a blue light emission peak with a peak wavelength of 450-480 nm and a red light emission peak with a peak wavelength of 600-650 nm.

5. The white LED device according to claim 1, characterized in that, The device has a color rendering index Ra≥70 and an adjustable color temperature within the range of 2000-5000K.

6. The white LED device according to claim 1, characterized in that, The device has a color rendering index Ra≥89 and an adjustable color temperature within the range of 3900-5000K.

7. The white LED device according to claim 1, characterized in that, The phosphor layer is formed by mixing and curing the phosphor and the binder, wherein the mass ratio of the phosphor to the binder is 1:2-4.

8. A method for preparing a white LED device as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix the phosphor and binder evenly to obtain a mixed colloid; S2. The mixed colloid is coated onto the ultraviolet LED chip, cured to form a phosphor layer, and then encapsulated to obtain a white LED device.

9. The preparation method according to claim 8, characterized in that, In step S1, the mass ratio of the phosphor to the binder is 1:2-4; And / or, the adhesive is selected from silicone and / or epoxy resin; And / or, the silicone rubber is selected from at least one of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, fluorosilicone rubber or nitrile silicone rubber; the epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, tetramethylbiphenyl type epoxy resin or glycidylamine type epoxy resin.

10. The preparation method according to claim 8 or 9, characterized in that, In step S2, the curing conditions include curing at 20-160℃ for 4-10 hours.

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