A method for preparing high-efficiency, high-thermal-conductivity fluorescent glass and its application.

Abstract

This invention discloses a high-efficiency, high-thermal-conductivity fluorescent glass and its LED device, belonging to the field of semiconductor light-emitting device technology. The gradient refractive index fluorescent glass layer is formed by mixing phosphobic borate glass powder of different compositions with phosphor, organic carrier, and high thermal conductivity particles, screen printing it onto a sapphire substrate, and then co-firing it at a low temperature. Its refractive index continuously decreases from bottom to top. This composite fluorescent glass sheet is encapsulated on an aluminum nitride ceramic substrate with a reflective cup structure and integrated with an LED chip. This invention achieves extremely high light extraction efficiency and excellent heat dissipation performance through the dual effects of the internal gradient refractive index and the reflective cup, as well as the triple heat dissipation path of high thermal conductivity particles-sapphire-aluminum nitride ceramic substrate, making it particularly suitable for high-power, high-brightness white LED devices.

Description

Technical Field

[0001] This invention relates to the field of semiconductor light-emitting device technology, and particularly to a novel fluorescent glass material and its device structure for high-power white LED packaging. Specifically, this invention provides a composite fluorescent glass with both high light extraction efficiency and high thermal conductivity, as well as an LED device integrating this fluorescent glass with a high-efficiency reflector cup structure. Background Technology

[0002] In the implementation technology of white LEDs, the scheme of blue light chip exciting fluorescent material to generate white light has occupied the dominant position in the market due to its simple structure, controllable cost and easy adjustment of color rendering. As the core functional component in this scheme, the optical and thermal properties of fluorescent conversion material directly determine the luminous efficacy, color temperature stability, lifespan and reliability of LED devices.

[0003] Currently, commercial white LEDs commonly use silicone or epoxy resin as the encapsulation carrier for phosphors. The phosphor is mixed with the organic carrier and then coated onto the surface of the blue LED chip to form a light-emitting layer. However, this type of organic encapsulation system has many inherent defects that severely restrict the improvement of LED device performance: First, the thermal conductivity of organic carriers is extremely low (typically only 0.1-0.5 W / (m·K)), which cannot effectively dissipate the large amount of heat generated during LED chip operation. This causes the phosphor to be exposed to a high-temperature environment for a long time, which can easily lead to problems such as crystal structure destruction and fluorescence quenching, significantly reducing the luminous efficiency and lifespan of the device. Second, the refractive index of organic materials differs greatly from that of phosphors, chips, and air. This can easily lead to severe light reflection and scattering losses at the interface, with a large number of photons being trapped inside the device and unable to be effectively emitted, resulting in low light extraction efficiency. Third, organic carriers are prone to yellowing, aging, and cracking under long-term light exposure and high temperatures, further aggravating luminous efficiency decay and reducing the structural stability of the device.

[0004] To address the shortcomings of organic encapsulation systems, researchers have turned their attention to inorganic fluorescent materials. Among them, fluorescent glass has become a highly promising alternative material due to its advantages such as high temperature resistance, good chemical stability, superior thermal conductivity compared to organic carriers, and easily adjustable refractive index. However, LED devices based on existing fluorescent glass still face many technical bottlenecks: On the one hand, traditional fluorescent glasses are mostly single-refractive-index systems. Although their refractive index can be matched to the chip or substrate by adjusting the composition, there are still significant abrupt changes in refractive index inside the fluorescent glass and at the interface between the light-emitting surface and air. This leads to multiple reflection losses of photons during transmission, resulting in limited improvement in light extraction efficiency. Some studies have attempted to improve light extraction performance through surface roughening, but the light control capability of random rough structures is weak, making it difficult to achieve wide-angle, high-efficiency light extraction.

[0005] On the other hand, existing fluorescent glass is still insufficient for the purpose of guiding devices. As the power density of high-power LED chips continues to increase, the heat generated becomes more concentrated. If the fluorescent glass cannot quickly transfer heat to the heat dissipation substrate, it will not only lead to a decrease in the luminous efficiency of the phosphor but also cause thermal stress concentration inside the glass, affecting the structural reliability of the device. Furthermore, in the fabrication of fluorescent glass and device packaging, how to achieve efficient bonding between the fluorescent glass and the heat dissipation substrate, and how to enhance light reflection and collection through structural design, are also key issues that urgently need to be addressed. Currently, traditional packaging substrates often lack targeted, high-efficiency reflective structure designs. Even when reflective structures are partially adopted, their poor shape design (such as a flat reflective surface or lack of light-guiding function) often results in low reflection efficiency. A large amount of excitation light emitted by blue LED chips and fluorescence generated by the fluorescent glass is not effectively utilized; instead, it is absorbed by the non-reflective areas of the substrate or dissipates into the ineffective space outside the device, further causing luminous efficiency loss. A reflective cup structure with directional light-guiding and high-efficiency reflection functions can significantly improve the collection and utilization rate of light.

[0006] Meanwhile, with the increasing demands for luminous efficacy, power density, and lifespan of LED devices in the lighting field, the development of fluorescent conversion materials and corresponding LED device systems that combine high light extraction efficiency, excellent thermal conductivity, and stable structure has become an urgent need for industry development. Gradient refractive index structures, as an efficient means of light modulation, can guide photon transmission through continuous changes in refractive index, effectively suppressing interface light reflection losses. Introducing highly thermally conductive particles into fluorescent glass systems, combined with efficient packaging structure design, can construct a complete heat conduction path, solving the problem of heat accumulation. Against this backdrop, developing a fluorescent glass and its LED device that integrates gradient refractive index light modulation, high thermal conductivity heat dissipation, and optimized packaging structure is of significant practical importance and application value for breaking through existing technological bottlenecks and promoting the development of LED lighting technology towards higher performance.

[0007] Chinese invention patent CN110818248A discloses a fluorescent glass doped with high thermal conductivity particles and high refractive index particles. The method for increasing the refractive index involves directly doping with high refractive index nanoparticles. This method presents an irreconcilable contradiction: while high refractive index particles can reduce the refractive index difference with the chip, their strong light scattering effect significantly increases light transmission loss inside the glass, resulting in more light "not escaping," thus limiting the actual improvement in light extraction efficiency. Furthermore, it does not consider the refractive index mismatch between the fluorescent glass and air.

[0008] Chinese invention patent CN106800371A discloses a high thermal conductivity borosilicate fluorescent glass material and its preparation method, with a thermal conductivity of only 1.23-1.35 W / m·K. While this value is better than that of ordinary glass, it is far from sufficient for the high-power, high-heat-density LED packaging applications. Summary of the Invention

[0009] To address the existing problems, this work employs a method of constructing a gradient refractive index structure inside the fluorescent glass and incorporating a high thermal conductivity material. This material is then encapsulated on an aluminum nitride ceramic substrate with a reflective cup. High luminous efficiency and high thermal conductivity fluorescent glass and its LED device are obtained at a relatively low sintering temperature. This preparation method effectively and synergistically improves the heat dissipation capacity and light extraction efficiency of the device. At the same time, the process is simple and conducive to industrial production.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: On the one hand, the present invention provides a method for preparing high-efficiency, high-thermal-conductivity fluorescent glass, the specific steps of which are as follows: Step 1: Preparation of gradient refractive index glass powder: Various phosphobic borate glass powders with different compositions are mixed with high thermal conductivity particles. By adjusting the proportion of the components, glass powders with different refractive indices n1, n2, ... > nN are prepared by high-temperature melt quenching, where 2 ≤ N ≤ 4; 1.8 ≥ n1 > n2 > ... > nN ≥ 1.4. Step 2: Mix the glass powders of different components obtained in Step 1 with phosphor and organic carrier respectively, and ball mill them evenly to obtain a series of fluorescent glass slurries with different refractive indices. Step 3, screen printing and lamination: Using the fluorescent glass paste obtained in step 2, the sapphire substrate is screen printed layer by layer in order of refractive index from high to low, and then dried to form a green body with a gradient refractive index. Step 4, Low-temperature co-firing: The green body obtained in step 3 is co-fired at a low temperature to fuse the glass layers together and form a dense fluorescent glass with a continuous gradient refractive index. Preferably, in step one, the phosphobic glass powder composition is: SiO2 50%-70%, Al2O3 5%-20%, R2O 0%-15% (where R is one or more of Li, Na, and K), MO 8%-22% (where M is one or more of Mg, Ca, Sr, Ba, and Zn), and the high thermal conductivity particles are one or more of boron nitride, aluminum oxide, aluminum nitride, and titanium dioxide. The amount of glass powder added is 60-70 wt% of the total mass of phosphor, glass powder, organic carrier, and high thermal conductivity particles, and the amount of high thermal conductivity particles added is 0%-8 wt% of the total mass of phosphor, glass powder, organic carrier, and high thermal conductivity particles.

[0011] Preferably, in step one, the specific steps of the high-temperature melting and quenching method are as follows: the mixed glass raw materials are placed in a crucible, heated to 400-600℃ at 3-10℃ / min and held for 1-4 hours, then placed in a high-temperature furnace and heated to 1000-1600℃ at 10-20℃ / min and held for 2 hours. The molten glass is then taken out and poured into a mold at 300-500℃ or directly cast onto a cooling plate at 300-500℃ for rapid cooling to form a glass block. Finally, the block is crushed and ball-milled into glass powder.

[0012] Preferably, in step two, the fluorescent glass paste is prepared by mixing various glass powders with different refractive indices and phosphors of different colors, wherein the yellow phosphor is Y3Al5O. 12 :Ce 3+ (Sr,Ba)2SiO4:Eu 2+ (Ca,Sr)AlSiN3:Eu 2+ One of them, the green phosphor is Lu3Al5O 12 :Ce 3+ (Gd,Y)3(Al,Ga)5O 12 Ce 3+ β-SiAION:Eu 2+ One of them, the red phosphor is CaAlSiN3:Eu 2+ K2SiF6:Mn 4+ One of them, the amount of phosphor added is 5-15 wt% of the total mass of phosphor, glass powder, organic carrier and high thermal conductivity particles.

[0013] Preferably, in step two, the organic carrier is one or more of terpineol, ethyl cellulose, and ethanol, and the ratio of the organic carrier to the glass powder is 1:2.8-4.

[0014] Preferably, in step two, the ball milling speed is 100-600 r / min and the ball milling time is 4-20 h.

[0015] Preferably, in step three, the screen used for screen printing is 80-200 mesh, the relative speed between the squeegee and the screen is 0.5-3 mm / s, and the screen is uniformly coated on the sapphire substrate. The thickness of each layer of fluorescent glass is 20-400 μm, and the thickness of the sapphire is 0.1-2 mm.

[0016] Preferably, in step four, the low-temperature co-firing step involves first heating to 150-230℃ at a rate of 5-10℃ / min and holding for 30-60 minutes, then heating to 580-600℃ at a rate of 3-7℃ / min and holding for 30-60 minutes to fuse the glass, followed by annealing at 300-350℃ at a rate of 2-10℃ / min for 1 hour, and finally cooling with the furnace.

[0017] On the other hand, the above method is used to prepare a fluorescent glass-encapsulated LED device, which includes a reflector cup, a heat dissipation substrate disposed on one side of the reflector cup, and an LED chip disposed on the heat dissipation substrate. The reflector cup is made of silicon carbide, and a silver reflective layer is adhered to the inner surface of the reflector cup. A sapphire substrate is disposed on the side of the reflector cup away from the heat dissipation substrate, and a high-efficiency, high-thermal-conductivity fluorescent glass is disposed above the sapphire substrate.

[0018] Preferably, the connection between the heat dissipation substrate and the lower surface of the reflector cup is fixed with high-temperature silicone or polyvinyl chloride adhesive, and the LED chip is a blue LED chip with an emission wavelength of 450-470nm.

[0019] Beneficial effects (1) This invention innovatively selects high thermal conductivity particles as thermally conductive fillers. The principle of incorporating high thermal conductivity materials allows the heat generated by the LED chip to be rapidly diffused laterally to the entire package through these high thermal conductivity paths, and then conducted to the metal substrate or heat sink, significantly reducing the junction temperature of the chip. Its extremely high in-plane thermal conductivity and refractive index close to that of the glass matrix significantly improve the overall thermal conductivity while minimizing the light scattering loss caused by the introduction of fillers.

[0020] (2) The present invention adopts an internal gradient refractive index junction. The internal gradient refractive index structure reduces the interface reflection loss of light during transmission, which is equivalent to building an "optical gentle slope bridge" between the chip and the air. When light passes through different refractive index layers, its propagation path is smoothly curved, rather than suddenly turning at a certain interface. This greatly reduces the occurrence of total internal reflection, allowing more light that would otherwise be trapped to come out smoothly, and greatly improving the light extraction efficiency.

[0021] (3) The screen printing and low-temperature co-firing process used in this invention is mature and low-cost, which is conducive to industrial production.

[0022] (4) The reflective cup on the aluminum nitride ceramic substrate used in this invention effectively solves the problem of light reflection and at the same time greatly improves the heat dissipation capacity.

[0023] (5) The high luminous efficiency and high thermal conductivity fluorescent glass prepared by the present invention can be used for high power and high brightness white LED packaging, and is suitable for general lighting, backlight display, automotive headlights and other fields. It has excellent thermal stability and optical performance, ensuring the long-term reliability of the device. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the fabrication process of a high-efficiency, high-thermal-conductivity fluorescent glass and its LED device prepared in Example 1.

[0025] Figure 2 This is a schematic diagram of a high-efficiency, high-thermal-conductivity fluorescent glass and its LED device provided in Example 1; in the figure: 1-reflective cup, 2-silver reflective layer, 3-LED chip, 4-heat dissipation substrate, 5-sapphire substrate, 6a-high refractive index fluorescent glass, 6b-medium refractive index fluorescent glass, 6c-low refractive index fluorescent glass, 7a-boron nitride particles, 7b-CaAlSiN3:Eu 2+ Phosphor, 7c-Lu3Al5O 12 :Ce 3+ Phosphor, 7d-Y3Al5O 12 :Ce 3+ Fluorescent powder.

[0026] Figure 3 The luminous efficiency of the LED devices prepared for the examples and comparative examples was measured.

[0027] Figure 4 The normalized luminous intensity of the LED devices prepared for the examples and comparative examples was obtained. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments. These examples will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0029] The working principle of this invention is as follows: Gradient refractive index fluorescent glass can eliminate total internal reflection at interfaces, improving light extraction efficiency. This is equivalent to building an "optical ramp bridge" between the chip and the air. When light passes through different refractive index layers, its propagation path is smoothly curved, rather than suddenly deflected at a certain interface. This greatly reduces the occurrence of total internal reflection, allowing more light that would otherwise be trapped to escape smoothly. Doping with phosphors of different colors can simultaneously improve the stability and color rendering index of the LED. The principle of incorporating high thermal conductivity materials allows the heat generated by the LED chip to be rapidly diffused laterally throughout the package through these high thermal conductivity paths, and then conducted to the metal substrate or heat sink, significantly reducing the junction temperature of the chip. For every 10°C reduction in chip temperature, its lifespan can increase exponentially. Lowering the phosphor operating temperature: The luminous efficiency of phosphors is extremely sensitive to temperature. The high thermal conductivity package also quickly removes the heat generated by the phosphor itself when emitting light, allowing it to operate at a lower temperature, thereby maintaining a higher light conversion efficiency.

[0030] Example 1 (1) Preparation of gradient refractive index glass powder: Preparation of three different phosphoborate glass raw materials (molar percentage): Component A (high refractive index n1): 55SiO2– 8Al2O3– 5Li2O – 5Na2O – 5K2O – 3MgO–5CaO–7SrO-2BaO-5ZnO; Component B (medium refractive index n2): 60SiO2– 10Al2O3– 5Li2O – 5Na2O – 5K2O – 5MgO–5CaO–2SrO-2BaO-ZnO; Component C (low refractive index n3): 65SiO2– 12Al2O3– 8Li2O – 1Na2O – 2K2O – 5MgO–5CaO–0SrO-0BaO-2ZnO; Each component of the glass raw material consists of 30 grams. 2.5 grams of boron nitride (BN) nanosheets are added to each component. After the raw materials are mixed evenly, the mixture is first heated to 500℃ at 10℃ / min and held for 2 hours. Then, it is placed in a high-temperature furnace and heated to 1200℃ at 20℃ / min and held for 2 hours. The molten glass is then removed and poured into a mold at 400℃ for rapid cooling to form a glass block. Finally, the block is crushed and ball-milled to obtain three BN glass powders with different refractive indices: A: 1.8 > B: 1.61 > C: 1.4 (n1 > n2 > n3).

[0031] The refractive index can be significantly increased by increasing the BaO content. Secondly, the refractive index can be moderately increased by adjusting the ZnO and Al2O3 content. Finally, the refractive index can be slightly increased by adding K2O (which has a larger ionic radius, replacing Na2O or Li2O). The refractive index of the glass can be precisely controlled by adjusting the content of each component.

[0032] (2) Preparation of fluorescent glass paste: The three glass powders with different refractive indices n1, n2, and n3 were respectively mixed with YAG:Ce yellow phosphor (Y3Al5O3). 12 :Ce 3+ CASN:Eu red phosphor (CaAlSiN3:Eu) 2+ LuAG:Ce green phosphor (Lu3Al5O) 12 :Ce 3+ The phosphors were mixed, with each phosphor weighing 7.5 grams. An organic carrier consisting of terpineol and ethyl cellulose (mass ratio 95:5) was added, with the organic carrier weighing 10 grams. The mixture was ball-milled at 500 rpm for 12 hours to obtain three uniform fluorescent glass pastes, A, B, and C, with gradient refractive indices.

[0033] (3) Screen printing and lamination: On a clean sapphire substrate, a 200-mesh screen is used, and the squeegee speed is controlled at 1 mm / s. Paste A, paste B and paste C are printed in sequence. After each layer is printed, it is dried at 100°C for 10 minutes. The thickness of each layer of fluorescent glass A, B and C is 40 μm.

[0034] (4) Low-temperature co-firing: Place the green billet into a muffle furnace and sinter according to the following procedure: heat up to 200℃ at 5℃ / min and hold for 60min, then heat up to 580℃ at 5℃ / min and hold for 60min, then cool down to 350℃ at 5℃ / min and anneal for 1 hour, and finally cool with the furnace.

[0035] (5) LED device packaging This embodiment provides an LED lamp and its reflector cup packaging structure, the fabrication process of which is as follows: Figure 1 As shown; Figure 2 A schematic diagram of a high-efficiency, high-thermal-conductivity fluorescent glass and its LED device provided in Example 1; The packaged heat dissipation structure includes: a reflector cup 1; a heat dissipation substrate 4 disposed on the lower surface of the reflector cup 1; and an LED chip 3 disposed on the heat dissipation substrate 4; a sapphire substrate 5 is disposed on the upper surface of the reflector cup 1, and a high-efficiency, high-thermal-conductivity fluorescent glass prepared in steps (1)-(4) above the sapphire substrate 5 is disposed above the reflector cup 5. The reflector cup 1 is made of silicon carbide, and a silver reflective layer 2 with an ultra-smooth surface is adhered to the inner surface of the reflector cup 1. The heat dissipation substrate 4 is fixed to the reflector cup 1 and the surface of the fluorescent glass using high-temperature silicone or polyvinyl chloride adhesive; the LED chip 3 is a blue LED chip with an emission wavelength of 450-470nm; and the heat dissipation substrate 4 is an aluminum nitride ceramic substrate.

[0036] The fluorescent glass, from bottom to top, consists of high-refractive-index fluorescent glass 6a, medium-refractive-index fluorescent glass 6b, and low-refractive-index fluorescent glass 6c. Each layer of fluorescent glass contains boron nitride particles 7a and CaAlSiN3:Eu. 2+ Phosphor 7b, Lu3Al5O 12 :Ce 3+ Phosphor 7c, Y3Al5O 12 :Ce 3+ 7d fluorescent powder.

[0037] Example 2 (1) Preparation of gradient refractive index glass powder: Four different compositions of phosphoborate glass raw materials (molar percentage) were prepared: Component A (high refractive index n1): 50SiO2– 14Al2O3– 9Li2O – 3Na2O – 3K2O – 3MgO–3CaO–8SrO-3BaO-4ZnO; Component B (medium refractive index n2): 60SiO2– 8Al2O3– 5Li2O – 5Na2O – 5K2O – 5MgO–5CaO–2SrO-2BaO-3ZnO; Component C (low refractive index n3): 65SiO2– 11Al2O3– 3Li2O – 4Na2O – 5K2O – 5MgO–5CaO–0SrO-0BaO-2ZnO; Component D (low refractive index n4): 70SiO2– 5Al2O3– 8Li2O – 1Na2O – 2K2O – 5MgO–5CaO–1SrO-1BaO-2ZnO; Each component of the glass raw material weighs 32 grams. 1 gram of boron nitride, 1 gram of alumina, and 2 grams of aluminum nitride are added to each component. After mixing the raw materials evenly, the mixture is first heated to 550°C at 8°C / min and held for 2 hours. Then, it is placed in a high-temperature furnace and heated to 1200°C at 20°C / min and held for 2 hours. The molten glass is then removed and poured onto a 300°C cooling plate for rapid cooling to form glass blocks. Finally, the blocks are crushed and ball-milled to obtain four different glass powders containing thermally conductive particles with varying refractive indices. The refractive indices are A: 1.8 > B: 1.68 > C: 1.54 > D: 1.45 (n1 > n2 > n3 > n4).

[0038] (2) Preparation of fluorescent glass paste: The four glass powders with different refractive indices n1, n2, n3, and n4 were respectively mixed with YAG:Ce yellow phosphor (Y3Al5O4). 12 :Ce 3+ CASN:Eu red phosphor (CaAlSiN3:Eu) 2+ LuAG:Ce green phosphor (Lu3Al5O) 12 :Ce 3+ A mixture of YAG:Ce yellow phosphors, each weighing 7.5 grams, was prepared. An organic carrier consisting of terpineol and ethyl cellulose (mass ratio 95:5), weighing 8 grams, was added. The mixture was ball-milled at 450 rpm for 10 hours to obtain four uniform fluorescent glass pastes, A, B, C, and D, each with a gradient refractive index.

[0039] (3) Screen printing and lamination: On a clean sapphire substrate, a 200-mesh screen is used, and the squeegee speed is controlled at 1 mm / s. Paste A, paste B, paste C, and paste D are printed in sequence. After each layer is printed, it is dried at 100°C for 10 minutes. The thickness of each layer of fluorescent glass A, B, C, and D is 60 μm.

[0040] (4) Low-temperature co-firing: Place the green billet into a muffle furnace and sinter according to the following procedure: heat up to 230℃ at 5℃ / min and hold for 30min, then heat up to 590℃ at 7℃ / min and hold for 45min, then cool down to 300℃ at 8℃ / min and anneal for 1 hour, and finally cool with the furnace.

[0041] (5) LED device packaging: Same as step (5) in Example 1.

[0042] Example 3 (1) Preparation of gradient refractive index glass powder: Three different compositions of phosphobic borate glass raw materials (molar percentage) were prepared: Component A (high refractive index n1): 50SiO2– 20Al2O3– 4Li2O – 3Na2O – 3K2O – 3MgO–3CaO–8SrO-2BaO-4ZnO; Component B (medium refractive index n2): 60SiO2– 10Al2O3– 5Li2O – 5Na2O – 5K2O – 5MgO–5CaO–2SrO-2BaO-3ZnO; Component C (low refractive index n3): 65SiO2– 5Al2O3– 3Li2O – 4Na2O – 5K2O – 5MgO–5CaO–1SrO-5BaO-2ZnO; Each component of the glass raw material weighs 34 grams. 1.5 grams of alumina nanosheets are added to each component. After the raw materials are mixed evenly, the mixture is first heated to 550°C at 5°C / min and held for 1 hour. Then, it is placed in a high-temperature furnace and heated to 1300°C at 15°C / min and held for 2 hours. The molten glass is then removed and poured into a mold at 500°C for rapid cooling to form a glass block. Finally, the block is crushed and ball-milled to obtain glass powder, resulting in three alumina-containing glass powders with different refractive indices: A: 1.72 > B: 1.56 > C: 1.4 (n1 > n2 > n3).

[0043] (2) Preparation of fluorescent glass paste: The above three types of glass powders n1, n2, and n3 are respectively mixed with YAG:Ce yellow phosphor (Y3Al5O3). 12 :Ce 3+ LuAG:Ce green phosphor (Lu3Al5O) 12 :Ce 3+ CASN:Eu red phosphor (CaAlSiN3:Eu) 2+ The phosphors were mixed, with each phosphor weighing 2.5 grams. An organic carrier consisting of terpineol and ethyl cellulose (mass ratio 95:5) was added, with the organic carrier weighing 12 grams. The mixture was ball-milled at 500 rpm for 12 hours to obtain three uniform fluorescent glass pastes, A, B, and C, with gradient refractive indices.

[0044] (3) Screen printing and lamination: On a clean sapphire substrate, a 200-mesh screen is used, and the squeegee speed is controlled at 1 mm / s. Paste A, paste B and paste C are printed in sequence. After each layer is printed, it is dried at 100°C for 10 minutes. The thickness of each layer of fluorescent glass A, B and C is 60 μm.

[0045] (4) Low-temperature co-firing: Place the green billet into a muffle furnace and sinter according to the following procedure: heat up to 180℃ at 10℃ / min and hold for 30min, then heat up to 600℃ at 5℃ / min and hold for 30min, then cool down to 300℃ at 8℃ / min and anneal for 1 hour, and finally cool with the furnace.

[0046] (5) LED device packaging: Same as step (5) in Example 1.

[0047] Example 4 (1) Preparation of gradient refractive index glass powder: Two different compositions of phosphobic borate glass raw materials (molar percentage) were prepared: Component A (high refractive index n1): 55SiO2– 18Al2O3– 3Li2O – 3Na2O – 3K2O – 3MgO–3CaO–6SrO-2BaO-4ZnO; Component B (medium refractive index n2): 65SiO2– 10Al2O3– 4Li2O – 4Na2O – 4K2O – 5MgO–5CaO–3SrO-3BaO-4ZnO; Each component of the glass raw material weighs 35 grams. 1 gram of titanium dioxide particles is added to each component. After the raw materials are mixed evenly, the mixture is first heated to 550°C at 10°C / min and held for 1 hour. Then, it is placed in a high-temperature furnace and heated to 1300°C at 10°C / min and held for 2 hours. The molten glass is then removed and poured into a mold at 450°C for rapid cooling to form a glass block. Finally, the block is crushed and ball-milled to obtain two glass powders with different refractive indices: A: 1.63 > B: 1.46 (n1 > n2).

[0048] (2) Preparation of fluorescent glass paste: The above two types of glass powders, n1 and n2, are respectively mixed with LuAG:Ce green phosphor (Lu3Al5O4). 12 :Ce 3+ YAG:Ce yellow phosphor (Y3Al5O) 12 :Ce 3+ The phosphors were mixed, with each phosphor weighing 2.5 grams. An organic carrier consisting of terpineol and ethyl cellulose (mass ratio 9:1), weighing 11.5 grams, was added. The mixture was ball-milled at 550 r / min for 8 hours to obtain two uniform fluorescent glass pastes, A and B, with gradient refractive indices.

[0049] (3) Screen printing and lamination: On a clean sapphire substrate, a 100-mesh screen is used, and the squeegee speed is controlled at 2mm / s. Paste A and paste B are printed in sequence. After each layer is printed, it is dried at 100℃ for 10 minutes. The thickness of each layer of fluorescent glass A and B is 40μm.

[0050] (4) Low-temperature co-firing: Place the green billet into a muffle furnace and sinter according to the following procedure: heat up to 150℃ at 5℃ / min and hold for 30min, then heat up to 580℃ at 5℃ / min and hold for 30min, then anneal at 300℃ at 10℃ / min for 1 hour, and finally cool with the furnace.

[0051] (5) LED device packaging: Same as step (5) in Example 1.

[0052] Comparative Example 1 (1) Preparation of gradient refractive index glass powder: Prepare three phosphoborate glass raw materials with the same refractive index (molar percentage): Component A (high refractive index n1): 35P2O5– 12B2O3– 2.5Na2O – 1.5K2O – 4.5Li2O – 1.5Al2O3– 30BaO– 13ZnO; Component B (intermediate refractive index n2): 35P2O5– 12B2O3– 2.5Na2O – 1.5K2O – 4.5Li2O – 1.5Al2O3– 20BaO– 23ZnO; Component C (low refractive index n3): 35P2O5– 12B2O3– 2.5Na2O – 1.5K2O – 4.5Li2O – 1.5Al2O3– 10BaO– 33ZnO.

[0053] Each component of the glass raw material weighs 25 grams. After the raw materials are mixed evenly, the temperature is first raised to 600℃ at 20℃ / min and held for 1 hour. Then, it is placed in a high-temperature furnace and heated to 1200℃ at 15℃ / min and held for 2 hours. The molten glass is then removed and poured into a mold at 600℃ for rapid cooling to form a glass block. Finally, the block is crushed and ball-milled to obtain three glass powders with different refractive indices, with refractive indices A: 1.59 > B: 1.51 > C: 1.46 (n1 > n2 > n3).

[0054] (2) Preparation of fluorescent glass paste: The above three glass powders A, B, and C are respectively mixed with YAG:Ce yellow phosphor (Y3Al5O4). 12 :Ce 3+ LuAG:Ce green phosphor (Lu3Al5O) 12 :Ce 3+ CASN:Eu red phosphor (CaAlSiN3:Eu) 2+The phosphors were mixed, with each phosphor weighing 18.7 grams. An organic carrier consisting of terpineol and ethyl cellulose (mass ratio 90:10), weighing 6.25 grams, was added. The mixture was ball-milled at 500 r / min for 12 hours to obtain three homogeneous fluorescent glass pastes, A, B, and C, with the same refractive index.

[0055] (3) Screen printing and lamination: On a clean sapphire substrate, a 200-mesh screen is used, and the squeegee speed is controlled at 2 mm / s. Paste A, paste B and paste C are printed in sequence. After each layer is printed, it is dried at 100℃ for 10 minutes. The thickness of each layer of fluorescent glass A, B and C is 40μm.

[0056] (4) Low-temperature co-firing: Place the green billet into a muffle furnace and sinter according to the following procedure: heat up to 150℃ at 5℃ / min and hold for 30min, then heat up to 580℃ at 3℃ / min and hold for 30min, then cool down to 300℃ at 2℃ / min and anneal for 1 hour, and finally cool with the furnace.

[0057] (5) LED device packaging: Same as step (5) in Example 1.

[0058] Comparative Example 2 (1) Preparation of gradient refractive index glass powder: Prepare three phosphate borate glass raw materials with the same composition (molar percentage): Components A, B, and C: 65SiO2– 10Al2O3– 4Li2O– 4Na2O– 4K2O– 5MgO– 5CaO– 3SrO- 3BaO- 4ZnO; Each component of the glass raw material weighs 30 grams. 6.25 grams of boron nitride particles are added to each component. After the raw materials are mixed evenly, the mixture is first heated to 550°C at 5°C / min and held for 1 hour. Then, it is placed in a high-temperature furnace and heated to 1300°C at 15°C / min and held for 2 hours. The molten glass is then poured into a metal mold for quenching and ball milling to obtain three BN-containing glass powders with the same refractive index, A=B=C=1.57.

[0059] (2) Preparation of fluorescent glass paste: The above three glass powders are respectively mixed with YAG:Ce yellow phosphor (Y3Al5O) 12 :Ce 3+ The phosphor was mixed with 8.75 g of other materials. An organic carrier consisting of terpineol and ethyl cellulose (95:5 mass ratio) was added, with a mass of 6.25 g. The mixture was ball-milled for 12 hours at 400 r / min to obtain three uniform fluorescent glass pastes, A, B, and C, with the same refractive index.

[0060] (3) Screen printing and lamination: On a clean sapphire substrate, a 200-mesh screen is used, and the squeegee speed is controlled at 3 mm / s. Paste A, paste B and paste C are printed in sequence. After each layer is printed, it is dried at 100°C for 10 minutes. The thickness of each layer of fluorescent glass A, B and C is 300μm.

[0061] (4) Low-temperature co-firing: Place the green billet into a muffle furnace and sinter according to the following procedure: heat up to 150℃ at 10℃ / min and hold for 30min, then heat up to 580℃ at 3℃ / min and hold for 30min, then cool down to 300℃ at 5℃ / min and anneal for 1 hour, and finally cool with the furnace.

[0062] (5) LED device packaging: Same as step (5) in Example 1.

[0063] Table 1 Thermal conductivity of fluorescent glasses prepared in Examples 1-4 and Comparative Examples 1-2 Table 1 presents the thermal conductivity test results of the fluorescent glasses prepared in the four embodiments and two comparative examples of the present invention, with units of W / (m). K). Among them, Example 1 has the highest thermal conductivity, reaching 3.6 W / (m). K); The thermal conductivity of Examples 2, 3, and 4 is 3.2 W / (m²). K), 3.3W / (m K), 3.1W / (m K), the overall range is 3.1-3.6 W / (m The thermal conductivity of Comparative Examples 1 and 2 was significantly lower than that of the Example, at 2.1 W / (m²). K) and 2.5W / (m K) is only 58.3% and 69.4% of the thermal conductivity of Example 1.

[0064] Table 1 shows the thermal conductivity data, which clearly demonstrates the significant advantages of the present invention in improving the thermal conductivity of fluorescent glass. The fluorescent glasses in the example series, by incorporating high thermal conductivity particles such as boron nitride, alumina, and aluminum nitride, and constructing a triple heat dissipation path of "high thermal conductivity particles - sapphire - aluminum nitride ceramic substrate," exhibit significantly improved thermal conductivity compared to the comparative examples (up to approximately 71.4%), effectively solving the technical bottleneck of insufficient thermal conductivity in traditional fluorescent glass and organic encapsulation materials. Comparative Example 1, due to its use of a phosphobic borate glass system and lack of optimized thermal conductivity particle ratio, and Comparative Example 2, due to the lack of gradient refractive index design and unreasonable addition of high thermal conductivity particles, both exhibited low thermal conductivity. These results indicate that the present invention, through reasonable selection of the glass matrix, precise control of the high thermal conductivity particle doping amount, and optimization of the device encapsulation structure, successfully achieves a significant improvement in the thermal conductivity of fluorescent glass, providing crucial assurance for the stability and long lifespan of high-power LED devices operating in high-temperature environments.

[0065] Figure 3 Plotting driving current (mA) on the x-axis (range 100-600mA) and luminous efficacy (lm / W) on the y-axis (range 50-130lm / W), the luminous efficacy performance of LED devices prepared in four examples and two comparative examples under different driving currents was compared. Overall, the luminous efficacy of all devices fluctuated with increasing driving current, but the luminous efficacy of the example series devices was consistently significantly higher than that of the comparative examples. Specifically, at low currents (e.g., 100mA), Example 1 had a luminous efficacy close to 130lm / W, Examples 2-4 were in the 110-120lm / W range, while Comparative Examples 1-2 were only 90-100lm / W. The luminous efficacy of the examples was 20%-40% higher than that of the comparative examples, confirming the optimization effect of the packaging structure of this invention on light extraction efficiency.

[0066] Figure 3 This invention clearly demonstrates that the gradient refractive index fluorescent glass combined with high thermal conductivity particles and a reflective cup encapsulation structure effectively improves the luminous efficiency of LED devices. The luminous efficiency of the device in the embodiment is significantly improved compared to the comparative example (up to approximately 40%), and remains stable over a wide driving current range. This confirms the optimizing effect of the gradient refractive index structure on light extraction efficiency, and the guarantee of optical performance stability at high temperatures provided by the high thermal conductivity design. In contrast, comparative examples lacking gradient refractive index optimization or with unreasonable thermal conductivity particle ratios show significant disadvantages in both luminous efficiency and stability, highlighting the core advantages of the present invention in improving device luminous efficiency.

[0067] Figure 4Plotting wavelength (nm) on the x-axis (range 400-800nm) and normalized light intensity on the y-axis, the spectral luminous intensity distribution of the LED devices in the examples and comparative examples is presented. The spectral curves of Examples 1-4 have a consistent overall shape, exhibiting strong luminous intensity around 450nm (blue light chip emission peak) and in the 550-650nm range (phosphor excitation peak), and the light intensity distribution is more balanced across the entire spectrum. The spectral curves of Comparative Examples 1 and 2 show significantly lower luminous intensity in the same wavelength range than the examples, especially in the fluorescence emission band (550-650nm), where the intensity attenuation is more significant, the spectral peaks are narrower, and the uniformity of light intensity distribution is poor.

[0068] Figure 4 The comparison of spectral characteristics shows that the fluorescent glass fabrication process and device packaging structure of the present invention can effectively improve fluorescence conversion efficiency and light intensity distribution uniformity. The device in the example reduces reflection and scattering losses during light transmission through a gradient refractive index structure, while the high thermal conductivity design avoids high-temperature quenching of the phosphor, resulting in significantly better blue light excitation efficiency and fluorescence emission intensity than the comparative example. The comparative example, lacking a reasonable refractive index gradient design or insufficient thermal conductivity, suffers from reduced fluorescence conversion efficiency and significant attenuation of spectral intensity. These results further verify the effectiveness of the present invention's technical solution in optimizing device optical performance, improving luminous intensity and spectral uniformity, and providing a guarantee for the device to achieve high brightness and high color rendering white light emission.

[0069] In addition to the preparation process of fluorescent glass paste described in the above embodiments, yellow phosphor Y3Al5O was added to glass powders of different components respectively. 12 :Ce 3+ Green phosphor Lu3Al5O 12 :Ce 3+ Or red fluorescent powder CaAlSiN3:Eu 2+ In addition, the yellow phosphor can also be (Sr,Ba)2SiO4:Eu 2+ (Ca,Sr)AlSiN3:Eu 2+ Green phosphors can also be (Gd,Y)3(Al,Ga)5O 12 Ce 3+ β-SiAION:Eu 2+ Etc., the red phosphor can also be K2SiF6:Mn 4+ wait.

Claims

1. A method for preparing a high-efficiency, high-thermal-conductivity fluorescent glass, characterized in that, The specific steps are as follows: Step 1: Preparation of gradient refractive index glass powder: Various phosphobic borate glass powders with different compositions are mixed with high thermal conductivity particles, and glass powders with different refractive indices n1, n2, ..., nN are prepared by high temperature melt quenching method, where 2≤N≤4, 1.8≥n1>n2>...>nN≥1.4; Step 2, Preparation of fluorescent glass paste: The glass powders of different components obtained in Step 1 are mixed with phosphor and organic carrier respectively, and ball-milled to obtain a series of fluorescent glass pastes with different refractive indices; Step 3, screen printing and lamination: Using the fluorescent glass paste obtained in step 2, the sapphire substrate is screen printed layer by layer on the surface of the sapphire substrate in order of refractive index from high to low, and then dried to form a green blank with a gradient refractive index. Step 4, Low-temperature co-firing: The green body obtained in step 3 is co-fired at a low temperature to fuse the glass layers together and form a dense fluorescent glass with a continuous gradient refractive index.

2. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step one, the phosphobic glass powder is composed of the following components in molar percentage: SiO2 50%-70%, Al2O3 5%-20%, R2O 0%-15%, MO 8%-22%, wherein R is one or more of Li, Na, and K, and M is one or more of Mg, Ca, Sr, Ba, and Zn. The high thermal conductivity particles are one or more of boron nitride, aluminum oxide, aluminum nitride, and titanium dioxide. The amount of glass powder added is 60-70 wt% of the total mass of phosphor, glass powder, organic carrier, and high thermal conductivity particles, and the amount of high thermal conductivity particles added is 0%-8 wt% of the total mass of phosphor, glass powder, organic carrier, and high thermal conductivity particles.

3. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step one, the specific steps of the high-temperature melting and quenching method are as follows: the mixed phosphate borate glass powder and high thermal conductivity particles are placed in a crucible, heated to 400-600℃ at 3-10℃ / min and held for 1-4 hours, then placed in a high-temperature furnace and heated to 1000-1600℃ at 10-20℃ / min and held for 2 hours. The molten glass is then removed and poured into a mold at 300-500℃ or directly cast onto a cooling plate at 300-500℃ for rapid cooling to form a glass block. Finally, the block is crushed and ball-milled to become glass powder.

4. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step two, the fluorescent glass paste is prepared by mixing various glass powders with different refractive indices and phosphors of different colors, wherein the yellow phosphor is Y3Al5O. 12 :Ce 3+ (Sr,Ba)2SiO4:Eu 2+ (Ca,Sr)AlSiN3:Eu 2+ One of them, the green phosphor is Lu3Al5O 12 :Ce 3+ (Gd,Y)3(Al,Ga)5O 12 Ce 3+ β-SiAION:Eu 2+ One of them, the red phosphor is CaAlSiN3:Eu 2+ K2SiF6:Mn 4+ One of them, the amount of phosphor added is 5-15 wt% of the total mass of phosphor, glass powder, organic carrier and high thermal conductivity particles.

5. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step two, the organic carrier is composed of one or more of terpineol, ethyl cellulose, and ethanol, and the ratio of the organic carrier to the glass powder is 1:2.8-4.

6. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step two, the ball milling speed is 100-600 r / min, and the ball milling time is 4-20 h.

7. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step three, the prepared slurry is placed on an 80-200 mesh screen, and the relative speed between the squeegee and the screen is 0.5-3 mm / s to spread it evenly on the sapphire substrate. The thickness of each layer of fluorescent glass is 20-400 μm, and the thickness of the sapphire is 0.1-2 mm.

8. The method for preparing high-efficiency, high-thermal-conductivity fluorescent glass according to claim 1, characterized in that, In step four, the low-temperature co-firing process involves first raising the temperature to 150-230℃ at a rate of 5-10℃ / min and holding it for 30-60 minutes, then raising the temperature to 580-600℃ at a rate of 3-7℃ / min and holding it for 30-60 minutes to fuse the glass, followed by annealing at a rate of 2-10℃ / min to 300-350℃ for 1 hour, and finally cooling it in the furnace.

9. A fluorescent glass-encapsulated LED device, characterized in that, The device includes a reflector cup, a heat dissipation substrate disposed on one side of the reflector cup, and an LED chip disposed on the heat dissipation substrate. The reflector cup is made of silicon carbide, and a silver reflective layer is adhered to the inner surface of the reflector cup. A sapphire substrate is disposed on the side of the reflector cup away from the heat dissipation substrate, and a high-efficiency, high-thermal-conductivity fluorescent glass prepared by the preparation method according to any one of claims 1 to 8 is disposed on the sapphire substrate.

10. The LED device according to claim 9, characterized in that, The heat dissipation substrate is fixed to the lower surface of the reflector cup using high-temperature silicone or polyvinyl chloride adhesive. The LED chip is a blue LED chip with an emission wavelength of 450-470nm.

Images