Reflective wavelength conversion device and method of manufacturing the same

Abstract

The application discloses a reflective wavelength conversion device and a preparation method thereof. The reflective wavelength conversion device comprises a fluorescent layer and a heat-conducting reflective layer arranged below the fluorescent layer. The fluorescent layer is obtained by sintering fluorescent powder, glass powder and scattering particles. The fluorescent layer comprises n layers of fluorescent powder layers. The first fluorescent powder layer is close to the heat-conducting reflective layer, and the outermost layer, the nth fluorescent powder layer, is away from the heat-conducting reflective layer. 2<=n<=5. The content of fluorescent powder in the first fluorescent powder layer to the nth fluorescent powder layer increases layer by layer, and the content of scattering particles decreases layer by layer. The heat-conducting reflective layer comprises a porous alumina layer, an alumina-aluminum nitride transition layer and an aluminum nitride layer which are stacked in sequence. The porous alumina layer is arranged close to the fluorescent layer. The wavelength conversion device has high wavelength conversion efficiency, high limit blue light power resistance, good heat dissipation effect and good reliability.

Description

Technical Field

[0001] This invention relates to the field of wavelength conversion materials and devices, and more specifically, to a reflective wavelength conversion device and its preparation method. Background Technology

[0002] In the field of laser lighting and display, commonly used reflective wavelength conversion devices include silicone color wheel emission schemes and inorganic glass color wheel emission schemes. Silicone color wheel emission schemes are mainly used in power levels of 300W and below, such as laser TVs and laser micro-projectors; while inorganic glass color wheel emission schemes are mainly used in power levels above 500W, such as high-power laser engineering projectors, laser cinema projection light sources, high-power laser searchlights, and laser beam lights. The conventional structural design of these silicone or inorganic glass wavelength conversion devices consists of an upper fluorescent wavelength conversion layer, a lower fluorescent reflective layer, and a heat dissipation substrate at the bottom. In this design, the thickness of both the wavelength conversion layer and the fluorescent reflective layer is generally 100μm or more. At this thickness, the wavelength conversion layer and the fluorescent reflective layer are formed as separate films, with a significant thermal interface between them, creating interfacial thermal resistance. Furthermore, since the encapsulation materials between the wavelength conversion layer and the fluorescent reflective layer are different, and the bonding area between the fluorescent reflective layer and the heat dissipation substrate is also limited, the bonding strength between the two layers and between the fluorescent reflective layer and the heat dissipation substrate is insufficient. This leads to an increase in the thermal resistance between the layer interfaces, resulting in poor heat dissipation of the wavelength conversion device and an increased risk of thermal quenching of the wavelength conversion layer. In severe cases, if the fluorescent reflective layer and the heat dissipation substrate are not firmly bonded, the fluorescent reflective layer may detach from the surface of the heat dissipation substrate along with the wavelength conversion layer when the color wheel device rotates, causing damage to the device. Summary of the Invention

[0003] The present invention aims to overcome at least one of the defects of the prior art and provide a reflective wavelength conversion device, wherein the wavelength conversion device has high wavelength conversion efficiency, high tolerance to extreme blue light power, good heat dissipation effect, and good reliability.

[0004] Another object of the present invention is to provide a method for preparing the aforementioned reflective wavelength conversion device.

[0005] The technical solution adopted in this invention is:

[0006] A reflective wavelength conversion device includes a fluorescent layer and a thermally conductive reflective layer disposed below the fluorescent layer. The fluorescent layer is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer includes n phosphor layers, with the first phosphor layer closest to the thermally conductive reflective layer and the outermost layer furthest from the thermally conductive reflective layer being the nth phosphor layer, where 2≤n≤5. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer to the nth phosphor layer. The thermally conductive reflective layer includes a porous alumina layer, an alumina-alumina nitride transition layer, and an aluminum nitride layer stacked sequentially, with the porous alumina layer disposed close to the fluorescent layer.

[0007] The reflective wavelength conversion device described in this application features a specially designed structure for both the fluorescent layer and the thermally conductive reflective layer. The fluorescent layer comprises multiple phosphor layers, each with varying amounts of phosphor and scattering particles. The phosphor layers closer to the thermally conductive reflective layer contain less phosphor and more scattering particles, and together with the porous alumina layer, primarily reflect fluorescence. The phosphor layers further away from the thermally conductive reflective layer contain more phosphor and fewer scattering particles, and primarily provide the majority of the fluorescence. Each phosphor layer uses the same type of composition, resulting in no distinct interfaces between the fluorescent layers. Designing the thermally conductive reflective layer as a sequentially stacked structure of porous alumina layer, aluminum oxide-aluminum nitride transition layer, and aluminum nitride layer, with the porous alumina layer positioned close to the fluorescent layer, enables the thermally conductive reflective layer to possess excellent heat dissipation performance, high tolerance, and strong adhesion. This is because the refractive index difference between the air inside the porous alumina pores and the alumina gives the porous alumina layer a very high reflectivity (the refractive index of the porous medium is 1, the refractive index of alumina is 1.75, and the refractive index difference between the two is 0.75, which strongly scatters fluorescence, resulting in the porous alumina layer having a very high reflectivity). Therefore, the porous alumina layer close to the fluorescent layer plays a role in fluorescence reflection, which can replace the traditional diffuse reflection layer scheme using glass powder and diffuse reflection particles. Furthermore, due to the numerous pores at the interface between the porous alumina and the phosphor layer, the melting glass powder in the phosphor layer penetrates to a certain depth into the porous alumina layer during sintering, increasing the bonding contact area between the phosphor layer and the porous alumina layer. This results in a strong bond between the two, significantly improving the bonding strength and reducing the interfacial thermal resistance between the phosphor layer and the reflective layer. Moreover, the alumina layer has a higher thermal conductivity than traditional diffuse reflective layers composed of glass powder and diffuse reflective particles, allowing the wavelength conversion device to withstand high laser power, and the phosphor layer exhibits better resistance to thermal quenching. The aluminum nitride layer, as a thermally conductive layer, has a very high thermal conductivity and excellent heat conduction effect, enabling rapid heat transfer. The alumina-aluminum nitride transition layer, a multiphase structure of alumina and aluminum nitride, has good bonding strength with both alumina and aluminum nitride, acting as an adhesive modifier and improving the thermal stability of the wavelength conversion device. Therefore, the overall heat-conducting and reflective layer exhibits good heat dissipation, high laser power resistance, and good thermal stability.

[0008] In one embodiment, the mass ratio of the phosphor to the glass powder in the fluorescent layer is (0.1-2):1, and the mass ratio of the scattering particles to the glass powder is (0.1-1):1.

[0009] In one embodiment, the mass ratio of phosphor to glass powder in the first phosphor layer of the fluorescent layer is (0.1-0.3):1, and the mass ratio of scattering particles to glass powder is (0.7-1):1; the mass ratio of phosphor to glass powder in the nth phosphor layer of the fluorescent layer is (1-2):1, and the mass ratio of scattering particles to glass powder is (0.1-0.2):1.

[0010] In one embodiment, the scattering particles are one or a combination of aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, zinc oxide, and lithopone, with a particle size of 20-400 nm.

[0011] In one embodiment, the softening temperature of the glass powder is 500-700℃, and the glass powder is a Zn / B / Si / O system, an Al / Zn / B / O system, or a B / Si / O system, with a particle size of 1-6μm.

[0012] In one embodiment, the porous alumina layer and the alumina-alumina transition layer of the thermally conductive reflective layer are obtained by aluminum nitride oxidation. The thermally conductive reflective layer can be formed by the thermal oxidation of aluminum nitride. The porous alumina layer, the alumina-alumina transition layer, and the aluminum nitride layer of the thermally conductive reflective layer are integrated into a single design, exhibiting good adhesion and low interfacial thermal resistance. The porous alumina layer, obtained by aluminum nitride oxidation, retains its crystalline structure, allowing the wavelength conversion device to withstand higher laser power.

[0013] In one embodiment, the pore size of the porous alumina layer is 100-400 nm.

[0014] In one embodiment, the thickness of the porous alumina layer is 50–70 μm, and the thickness of the alumina-alumina nitride transition layer is 5–15 μm.

[0015] In one embodiment, the thickness of the fluorescent layer is 80–140 μm, and the thickness of the thermally conductive and reflective layer is 0.5–1 mm.

[0016] The method for fabricating the aforementioned reflective wavelength conversion device includes the following steps:

[0017] (1) Oxidation treatment of heat sink substrate: The aluminum nitride substrate is placed in an oxygen atmosphere, the oxygen partial pressure is controlled at 0.06-0.1 MPa, the heat treatment temperature is 800-900℃, and the heat treatment is held for 30-60 min to obtain an oxidized aluminum nitride substrate with a porous aluminum oxide layer on the surface and an aluminum oxide-aluminum nitride transition layer in the middle.

[0018] (2) Grinding and polishing the oxidized aluminum nitride substrate: One side of the oxidized aluminum nitride substrate is left untreated as a fluorescent reflective surface, and the remaining surfaces of the oxidized aluminum nitride substrate are ground and polished to expose the aluminum nitride layer.

[0019] (3) Preparation of fluorescent paste: Prepare fluorescent pastes of different layers according to the ratio of different fluorescent powder layers: Add glass powder, scattering particles and fluorescent powder to a mortar according to the ratio, add organic solvent, grind and stir, then stir under planetary vacuum to evenly disperse and remove bubbles, and obtain the first fluorescent powder layer fluorescent paste, ... ...

[0020] (4) Coating the first phosphor layer phosphor paste on the aluminum nitride substrate: The first phosphor layer phosphor paste is printed on the fluorescent reflective surface of the aluminum nitride substrate using a screen printing process to obtain a wet film of the first phosphor layer.

[0021] (5) Pre-drying of the wet film of the first phosphor layer: The wet film of the first phosphor layer is dried in an oven, and the pre-drying temperature is controlled at 100-120℃ and kept at the temperature for 30-60 minutes to obtain the dry film of the first phosphor layer.

[0022] (6) Coating and drying of the remaining fluorescent paste layers: Coating and drying of the remaining fluorescent paste layers in sequence, referring to the methods in steps (4) and (5);

[0023] (7) Sintering to obtain the finished product: Under air atmosphere, the aluminum nitride substrate with n phosphor layers on the surface obtained in step (6) is sintered in a high-temperature sintering furnace. The peak temperature of sintering is controlled at 750-850℃ and held for 30-90 minutes to obtain a wavelength conversion device.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The present application employs a multi-layer design for both the fluorescent layer and the thermally conductive reflective layer. The fluorescent layer contains a gradient of phosphor and scattering particle content. The phosphor layer closer to the thermally conductive reflective layer has less phosphor and more scattering particles, primarily responsible for reflecting fluorescence; the phosphor layer further away from the thermally conductive reflective layer has more phosphor and less scattering particles, responsible for providing the majority of the fluorescence. Each phosphor layer uses the same type of component, thus eliminating obvious interfaces between the resulting fluorescent layers. The thermally conductive reflective layer comprises a porous alumina layer, an alumina-alumina nitride transition layer, and an aluminum nitride layer stacked sequentially. The refractive index between the air inside the porous alumina layer and the alumina layer is... The differences between the porous alumina and phosphor layers allow the porous alumina layer to possess high reflectivity. Furthermore, the numerous pores at the interface between the porous alumina and phosphor layers allow the melting glass powder in the phosphor layer during sintering to penetrate to a certain depth into the porous alumina layer, increasing the bonding contact area between the two layers. This results in a strong bond, significantly improving adhesion strength and reducing the interfacial thermal resistance between the phosphor and reflective layers. The aluminum nitride layer, acting as a thermally conductive layer, has a very high thermal conductivity, providing excellent heat transfer. The alumina-alumina nitride transition layer, a multiphase structure of alumina and aluminum nitride, exhibits good adhesion strength to both phases, acting as an adhesive modifier and improving the thermal stability of the wavelength conversion device. The reflective wavelength conversion device boasts high wavelength conversion efficiency, high tolerance to extreme blue light power, excellent heat dissipation, and high reliability. Attached Figure Description

[0025] Figure 1 This is a simplified schematic diagram of the reflective wavelength conversion device in Example 1.

[0026] Figure 2 This is a simplified schematic diagram of the reflective wavelength conversion device in Example 2.

[0027] Figure 3 This is a simplified schematic diagram of the reflective wavelength conversion device in Example 3.

[0028] Figure 4 This is a simplified schematic diagram of the reflective wavelength conversion device in Example 4.

[0029] Figure 5 This is a simplified schematic diagram of the reflective wavelength conversion device in Example 5.

[0030] Figure 6 This is a simplified schematic diagram of the reflective wavelength conversion device in Example 6.

[0031] Figure 7 This is a simplified schematic diagram of the reflective wavelength conversion device in Comparative Example 1.

[0032] Figure 8This is a simplified schematic diagram of the reflective wavelength conversion device in Comparative Example 2.

[0033] Explanation of reference numerals in the attached figures: 1. Fluorescent layer; 11. First phosphor layer; 12. Second phosphor layer; 13. Third phosphor layer; 14. Fourth phosphor layer; 15. Fifth phosphor layer; 2. Thermally conductive and reflective layer; 21. Aluminum nitride layer; 22. Alumina-aluminum nitride transition layer; 23. Porous alumina layer. Detailed Implementation

[0034] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0035] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0036] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0037] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0038] During their research, the inventors discovered that in commercially available reflective wavelength conversion devices, when the fluorescent layer and diffuse reflection layer are bonded together, the different configurations and functions of each layer, and the fact that their thicknesses are all above 100µm, result in obvious interfaces between the layers, leading to bonding issues between the layers.

[0039] This application is made based on the findings and research of the aforementioned problems.

[0040] In one embodiment of this application, a first aspect of this application provides a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive reflective layer 2 disposed below the fluorescent layer 1. The fluorescent layer 1 is obtained by sintering phosphor, glass powder and scattering particles. The fluorescent layer includes n phosphor layers, with the first phosphor layer 11 being closer to the thermally conductive reflective layer 2, and the outermost layer away from the thermally conductive reflective layer being the nth phosphor layer, where 2≤n≤5. The phosphor content increases layer by layer from the first phosphor layer 11 to the nth phosphor layer, and the scattering particle content decreases layer by layer. The thermally conductive reflective layer 2 includes a porous alumina layer 23, an alumina-aluminum nitride transition layer 22 and an aluminum nitride layer 21 stacked sequentially, and the porous alumina layer 23 is disposed close to the fluorescent layer 1.

[0041] By designing a gradient of phosphor and scattering particle content in different phosphor layers of phosphor layer 1, the phosphor layer closer to the thermally conductive and reflective layer 2 has a lower phosphor content and a higher scattering particle content. Together with the porous alumina layer 23, it is primarily responsible for reflecting fluorescence. The phosphor layer further away from the thermally conductive and reflective layer 2 has a higher phosphor content and a lower scattering particle content, and it is primarily responsible for providing the majority of the fluorescence. Each phosphor layer uses the same type of composition, thus eliminating obvious interfaces between the phosphor layers of phosphor layer 1.

[0042] The thermally conductive reflective layer 2 is composed of a layered porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21. The porous alumina layer 23 is positioned close to the fluorescent layer 1. The porous alumina layer 23 close to the fluorescent layer 1 can replace the traditional diffuse reflective layer using glass powder and diffuse reflective particles to perform the function of fluorescence reflection. The large difference in refractive index between the air inside the porous alumina pores and the alumina enables the porous alumina layer 23 to have a very high reflectivity (the refractive index of the porous medium is 1, the refractive index of alumina is 1.75, and the refractive index difference between the two is 0.75, which is a large difference and can strongly scatter fluorescence, thus enabling the porous alumina layer 23 to have a very high reflectivity). Furthermore, due to the numerous pores at the interface between the porous alumina layer 23 and the fluorescent layer 1, the glass powder in the fluorescent layer 1 melts and penetrates to a certain depth into the porous alumina layer 23 during the sintering stage. This increases the bonding contact area between the fluorescent layer 1 and the porous alumina layer 23, resulting in a strong bond and significantly improved bonding strength. This reduces the interfacial thermal resistance between the fluorescent layer 1 and the thermally conductive and reflective layer 2. Alumina also has a higher thermal conductivity, allowing the wavelength conversion device to withstand high laser power, and the fluorescent layer 1 exhibits better resistance to thermal quenching. The aluminum nitride layer 21, as a thermally conductive layer, has a very high thermal conductivity and excellent heat conduction effect, enabling rapid heat transfer. The alumina-aluminum nitride transition layer 22 is a multiphase structure of alumina and aluminum nitride phases, exhibiting good bonding strength with both alumina and aluminum nitride, thus playing a role in adhesive modification and improving the thermal stability of the wavelength conversion device. Through the multi-layer structure design of the fluorescent layer 1 and the multi-layer structure design of the thermally conductive and reflective layer 2, the wavelength conversion device achieves high wavelength conversion efficiency, high tolerance to extreme blue light power, good heat dissipation, and high reliability.

[0043] Furthermore, considering both the cost and effectiveness of the wavelength conversion device, n is preferably 2 ≤ n ≤ 4.

[0044] In any embodiment, the mass ratio of phosphor to glass powder in the fluorescent layer 1 is (0.1-2):1, and the mass ratio of scattering particles to glass powder is (0.1-1):1. More specifically, the mass ratio of phosphor to glass powder in the first phosphor layer 11 of the fluorescent layer 1 is (0.1-0.3):1, for example, 0.1:1, 0.2:1, 0.3:1, etc.; the mass ratio of scattering particles to glass powder is (0.7-1):1, for example, 0.7:1, 0.8:1, 0.9:1, 1:1, etc. The mass ratio of phosphor to glass powder in the nth phosphor layer of the phosphor layer 1 is (1-2):1, for example, it can be 1:1, 1.5:1, 2:1, etc., preferably (1.5-2):1; the mass ratio of scattering particles to glass powder is (0.1-0.2):1, for example, it can be 0.1:1, 0.15:1, 0.2:1, preferably (0.15-0.2):1.

[0045] In any embodiment, the scattering particles are one or a combination of several selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, zinc oxide, and lithopone, with a particle size of 20-400 nm. These scattering particles have good scattering performance and light transmittance. More preferably, the particle size of the scattering particles is 50-100 nm.

[0046] In any embodiment, the softening temperature of the glass powder is 500-700℃, and the glass powder is a Zn / B / Si / O system, an Al / Zn / B / O system, or a B / Si / O system, with a particle size of 1-6μm.

[0047] Furthermore, the porous alumina layer 23 and the alumina-alumina transition layer 22 of the thermally conductive reflective layer 2 are obtained by aluminum nitride oxidation. Thus, the thermally conductive reflective layer 2 can be formed by aluminum nitride thermal oxidation, and the porous alumina layer 23, the alumina-alumina transition layer 22, and the aluminum nitride layer 21 of the thermally conductive reflective layer 2 are an integrated design with good adhesion and low interfacial thermal resistance.

[0048] More specifically, the pore size of the porous alumina layer 23 is 100-400 nm. Experiments have shown that the reflection effect is optimal when the pore size of the porous alumina layer 23 is 100-400 nm.

[0049] In any embodiment, the thickness of the porous alumina layer 23 is 50–70 μm, and the thickness of the alumina-alumina nitride transition layer 22 is 5–15 μm. The porous alumina layer 23 in this application is obtained by oxidation of aluminum nitride, and the alumina-alumina nitride transition layer 22 is obtained by incomplete oxidation of aluminum nitride. The thicknesses of the porous alumina layer 23 and the alumina-alumina nitride transition layer 22 can be controlled by adjusting the oxygen partial pressure, sintering temperature, and holding time.

[0050] In any embodiment, the thickness of the fluorescent layer 1 is 80-140 μm, for example, it can be 80 μm, 100 μm, 120 μm, 140 μm, etc., preferably 80-90 μm, and the thickness of the thermally conductive and reflective layer 2 is 0.5-1 mm, for example, it can be 0.5 mm, 0.8 mm, 1 mm, etc.

[0051] The method for fabricating the aforementioned reflective wavelength conversion device includes the following steps:

[0052] (1) Oxidation treatment of heat sink substrate: The aluminum nitride substrate is placed in an oxygen atmosphere, with the oxygen partial pressure controlled at 0.06-0.1 MPa, and the heat treatment temperature at 800-900℃ for 30-60 min, to obtain an oxidized aluminum nitride substrate with a porous aluminum oxide layer 23 on the surface and an aluminum oxide-aluminum nitride transition layer 22 in the middle. The aluminum nitride on the surface of the aluminum nitride substrate reacts with oxygen to form a porous aluminum oxide layer. In addition, the oxidation reaction of aluminum nitride with oxygen proceeds gradually from the outside to the inside of the aluminum nitride. The slightly inner aluminum nitride does not have enough time to capture oxygen, thus forming a transition layer between aluminum oxide and aluminum nitride; while the innermost aluminum nitride hardly comes into contact with oxygen, and the oxidation reaction cannot proceed, remaining as aluminum nitride material.

[0053] (2) Grinding and polishing the oxidized aluminum nitride substrate: One side of the oxidized aluminum nitride substrate is left untreated as a fluorescent reflective surface, while the remaining surfaces of the oxidized aluminum nitride substrate are ground and polished to expose the aluminum nitride layer 21. The thermal conductivity of aluminum nitride is better than that of the porous aluminum oxide layer on the surface. Grinding away the aluminum oxide layer and the transition layer between aluminum nitride and aluminum oxide to expose the aluminum nitride layer 23 can maintain the high thermal conductivity of the thermally conductive reflective layer 2.

[0054] (3) Preparation of fluorescent paste: Prepare fluorescent pastes of different layers according to the proportion of different phosphor layers: Add glass powder, scattering particles and phosphor to a mortar according to the proportion, add organic solvent (organic solvent can be terpineol, methyl acetate, ethyl acetate, etc.), grind and stir, then planetary vacuum stir to evenly disperse and remove bubbles of each component, and obtain the first phosphor layer fluorescent paste, ..., ..., ..., the nth phosphor layer fluorescent paste respectively.

[0055] (4) Coating the first phosphor layer phosphor paste on the aluminum nitride substrate: The first phosphor layer phosphor paste is printed on the fluorescent reflective surface of the aluminum nitride substrate using a screen printing process to obtain a wet film of the first phosphor layer.

[0056] (5) Pre-drying of the wet film of the first phosphor layer: The wet film of the first phosphor layer is dried in an oven, and the pre-drying temperature is controlled at 100-120℃ and kept at the temperature for 30-60 minutes to obtain the dry film of the first phosphor layer.

[0057] (6) Coating and drying of the remaining fluorescent paste layers: Coating and drying of the remaining fluorescent paste layers in sequence, referring to the methods in steps (4) and (5);

[0058] (7) Sintering to obtain the finished product: Under air atmosphere, the aluminum nitride substrate with n phosphor layers on the surface obtained in step (6) is sintered in a high-temperature sintering furnace. The peak temperature of sintering is controlled at 750-850℃ and held for 30-90 minutes to obtain a wavelength conversion device.

[0059] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application.

[0060] Example 1

[0061] like Figure 1 As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes three phosphor layers: a first phosphor layer 11 closest to the thermally conductive and reflective layer 2, and a third phosphor layer 13 furthest from the thermally conductive and reflective layer 2. A second phosphor layer 12 is disposed between the first phosphor layer 11 and the third phosphor layer 13. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer 11 to the third phosphor layer 13. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.2:1, and the mass ratio of scattering particles to glass powder is 0.8:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 0.8:1, and the mass ratio of scattering particles to glass powder is 0.5:1; in the third phosphor layer, the mass ratio of phosphor to glass powder is 1.5:1, and the mass ratio of scattering particles to glass powder is 0.15:1. The thicknesses of the first phosphor layer 11, the second phosphor layer 12, and the third phosphor layer 13 are all approximately 30 μm. The thermally conductive and reflective layer 2 comprises a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the phosphor layer 1. Specifically, the thickness of the porous alumina layer 23 is approximately 60 μm, the thickness of the alumina-alumina nitride transition layer 22 is approximately 10 μm, and the total thickness of the thermally conductive and reflective layer 2 is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0062] Specifically, in this embodiment, the scattering particles are aluminum oxide with a particle size of 50-100 nm. In other embodiments, the scattering particles may also be one or a combination of titanium oxide, zirconium oxide, magnesium oxide, zinc oxide, and lithopone, all of which have good scattering effects with a particle size of 40-200 nm.

[0063] Specifically, in this embodiment, the glass powder is a Zn / B / Si / O system with a particle size of 1-6 μm and a softening temperature of 500-700℃. In other embodiments, the glass powder may also be an Al / Zn / B / O system or a B / Si / O system.

[0064] The fabrication method of the reflective wavelength conversion device described in this embodiment includes the following steps:

[0065] (1) Oxidation treatment of heat sink substrate: A 0.8 mm thick aluminum nitride substrate is placed in an oxygen atmosphere, the oxygen partial pressure is controlled at 0.08 MPa, the heat treatment temperature is 850 °C, and the heat treatment is held for 45 min to obtain an oxidized aluminum nitride substrate with a 60 μm thick porous aluminum oxide layer 23 on the surface and a 10 μm thick aluminum oxide-aluminum nitride transition layer 22 in the middle.

[0066] (2) Grinding and polishing the oxidized aluminum nitride substrate: One side of the oxidized aluminum nitride substrate is left untreated as a fluorescent reflective surface, and the remaining surfaces of the oxidized aluminum nitride substrate are ground and polished to expose the aluminum nitride layer 21.

[0067] (3) Preparation of fluorescent paste: Fluorescent pastes of different layers are prepared according to the proportions of the first phosphor layer 11, the second phosphor layer 12 and the third phosphor layer 13 respectively: glass powder, scattering particles and phosphor are added to a mortar according to the proportion, organic solvent (terpineol) is added, and after grinding and stirring for 30 min, planetary vacuum stirring is carried out for 10 min to evenly disperse and remove bubbles, so as to obtain the first phosphor layer fluorescent paste, the second phosphor layer paste and the third phosphor layer fluorescent paste respectively.

[0068] (4) Coating the first phosphor layer phosphor paste on the aluminum nitride substrate: The first phosphor layer phosphor paste is printed on the fluorescent reflective surface of the aluminum nitride substrate using a screen printing process to obtain a wet film of the first phosphor layer.

[0069] (5) Pre-drying of the first phosphor layer wet film: The first phosphor layer wet film is dried in an oven, and the pre-drying temperature is controlled at 100-120℃. The temperature is kept for 30-60 minutes to obtain a first phosphor layer dry film with a thickness of about 30μm.

[0070] (6) Coating and drying of the remaining fluorescent paste layers: The second fluorescent paste is coated onto the first phosphor layer dry film according to the methods of steps (4) and (5), and dried to obtain the second phosphor layer dry film; the third fluorescent paste is coated onto the second phosphor layer dry film according to the methods of steps (4) and (5), and dried to obtain the third phosphor layer dry film.

[0071] (7) Sintering to obtain the finished product: Under air atmosphere, the aluminum nitride substrate with three phosphor layers on the surface obtained in step (6) is sintered in a high-temperature sintering furnace. The peak temperature of sintering is controlled at 750-850℃ and held for 30-90 minutes to obtain a wavelength conversion device.

[0072] Example 2

[0073] like Figure 2As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer 1. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes four phosphor layers: the first phosphor layer 11 is closest to the thermally conductive and reflective layer 2, and the outermost layer away from the thermally conductive and reflective layer 2 is the fourth phosphor layer 14. A second phosphor layer 12 and a third phosphor layer 13 are sequentially disposed between the first phosphor layer 11 and the fourth phosphor layer 14. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer 11 to the fourth phosphor layer 14. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.2:1, and the mass ratio of scattering particles to glass powder is 0.8:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 0.6:1, and the mass ratio of scattering particles to glass powder is 0.6:1. In the third phosphor layer 13, the mass ratio of phosphor to glass powder is 0.8:1, and the mass ratio of scattering particles to glass powder is 0.5:1. In the fourth phosphor layer 14, the mass ratio of phosphor to glass powder is 1.5:1, and the mass ratio of scattering particles to glass powder is 0.15:1. The thicknesses of the first phosphor layer 11, the second phosphor layer 12, the third phosphor layer 13, and the fourth phosphor layer 14 are 30 μm, 15 μm, 15 μm, and 30 μm, respectively. The thermally conductive and reflective layer 2 includes a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the phosphor layer 1. Specifically, the thickness of the porous alumina layer 23 is approximately 60 μm, the thickness of the alumina-alumina nitride transition layer 22 is approximately 10 μm, and the total thickness of the thermally conductive and reflective layer 2 is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0074] The only difference between Example 2 and Example 1 is the fluorescent layer 1 and its preparation method. In Example 2, the fluorescent layer 1 has four gradient-distributed phosphor layers, while in Example 1 it has three gradient-distributed phosphor layers. The preparation method of the reflective wavelength conversion device in Example 2 is the same as in Example 1, except for the different proportions, thicknesses, coating, and drying processes of the fluorescent layer 1. The preparation method of the wavelength conversion device in this example can be adapted from the preparation method of Example 1; other similarities between Example 2 and Example 1 will not be repeated here.

[0075] Example 3

[0076] like Figure 3As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes five phosphor layers. The first phosphor layer 11 is closest to the thermally conductive and reflective layer 2, and the outermost layer away from the thermally conductive and reflective layer 2 is the fifth phosphor layer 14. A second phosphor layer 12, a third phosphor layer 13, and a fourth phosphor layer 14 are sequentially disposed between the first phosphor layer 11 and the fifth phosphor layer 15. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer 11 to the fifth phosphor layer 15. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.1:1, and the mass ratio of scattering particles to glass powder is 1:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 0.3:1, and the mass ratio of scattering particles to glass powder is 0.7:1. In the third phosphor layer 13, the mass ratio of phosphor to glass powder is 0.5:1, and the mass ratio of scattering particles to glass powder is 0.5:1. In the fourth phosphor layer 14, the mass ratio of phosphor to glass powder is 0.7:1, and the mass ratio of scattering particles to glass powder is 0.3:1. In the fifth phosphor layer 15, the mass ratio of phosphor to glass powder is 2:1, and the mass ratio of scattering particles to glass powder is 0.15:1. The thicknesses of the first phosphor layer 11, the second phosphor layer 12, the third phosphor layer 13, the fourth phosphor layer 14, and the fifth phosphor layer 15 are 20 μm, 10 μm, 15 μm, 20 μm, and 20 μm, respectively. The thermally conductive and reflective layer 2 includes a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the phosphor layer 1. Specifically, the porous alumina layer has a thickness of approximately 60 μm, the alumina-alumina nitride transition layer has a thickness of approximately 10 μm, and the total thickness of the thermally conductive and reflective layer is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0077] The only difference between Example 3 and Example 1 is the fluorescent layer 1 and its preparation method. In Example 3, the fluorescent layer 1 has five gradient-distributed phosphor layers, while in Example 1 it has three gradient-distributed phosphor layers. The preparation method of the reflective wavelength conversion device in Example 3 is the same as in Example 1, except for the different proportions, thicknesses, coating, and drying processes of the fluorescent layer 1. The preparation method of the wavelength conversion device in this example can be adapted from the preparation method of Example 1; other similarities between Example 3 and Example 1 will not be repeated here.

[0078] Example 4

[0079] like Figure 4As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer 1. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes two phosphor layers: a first phosphor layer 11 closer to the thermally conductive and reflective layer 2 and a second phosphor layer 12 farther away from the thermally conductive and reflective layer 2. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.3:1, and the mass ratio of scattering particles to glass powder is 0.7:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 2:1, and the mass ratio of scattering particles to glass powder is 0.2:1. Both the first phosphor layer 11 and the second phosphor layer 12 are 40 μm. The thermally conductive and reflective layer 2 includes a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the fluorescent layer 1. Specifically, the porous alumina layer has a thickness of approximately 60 μm, the alumina-alumina nitride transition layer has a thickness of approximately 10 μm, and the total thickness of the thermally conductive and reflective layer is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0080] The only difference between Example 4 and Example 1 is the fluorescent layer and its preparation method. In Example 4, the fluorescent layer 1 has two gradient-distributed phosphor layers, while in Example 1 it has three gradient-distributed phosphor layers. The preparation method of the reflective wavelength conversion device in Example 4 is the same as in Example 1, except for the different proportions, thicknesses, coating, and drying processes of the fluorescent layer 1. The preparation method of the wavelength conversion device in this example can be adapted from the preparation method of Example 1; other similarities between Example 4 and Example 1 will not be repeated here.

[0081] Example 5

[0082] like Figure 5As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer 1. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes three phosphor layers: a first phosphor layer 11 closest to the thermally conductive and reflective layer 2, and a third phosphor layer 13 furthest from the thermally conductive and reflective layer 2. A second phosphor layer 12 is disposed between the first phosphor layer 11 and the third phosphor layer 13. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer 11 to the third phosphor layer 13. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.2:1, and the mass ratio of scattering particles to glass powder is 0.8:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 0.8:1, and the mass ratio of scattering particles to glass powder is 0.5:1; in the third phosphor layer, the mass ratio of phosphor to glass powder is 1.5:1, and the mass ratio of scattering particles to glass powder is 0.15:1. The thicknesses of the first phosphor layer 11, the second phosphor layer 12, and the third phosphor layer 13 are all approximately 30 μm. The thermally conductive and reflective layer 2 comprises a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the phosphor layer 1. Specifically, the thickness of the porous alumina layer 23 is approximately 50 μm, the thickness of the alumina-alumina nitride transition layer 22 is approximately 15 μm, and the total thickness of the thermally conductive and reflective layer 2 is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0083] The only difference between Example 5 and Example 1 is that the thickness of the porous alumina layer 23 and the alumina-alumina nitride transition layer 22 are different from those in Example 1. The thickness of the porous alumina layer 23 and the alumina-alumina nitride transition layer 22 can be adjusted by controlling the oxygen partial pressure, sintering temperature, and holding time. Specifically, the oxidation treatment of the heat sink substrate in this example is as follows: a 0.8 mm thick alumina nitride substrate is placed in an oxygen atmosphere, the oxygen partial pressure is controlled at 0.06 MPa, the heat treatment temperature is 800 °C, and the holding time is 60 min, resulting in an oxidized alumina nitride substrate with a 50 μm thick porous alumina layer 23 on the surface and a 15 μm thick alumina-alumina nitride transition layer 22 in the middle.

[0084] The remaining structure and preparation process of Example 5 are the same as those of Example 1, and will not be repeated here.

[0085] Example 6

[0086] like Figure 6As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer 1. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes three phosphor layers: a first phosphor layer 11 closest to the thermally conductive and reflective layer 2, and a third phosphor layer 13 furthest from the thermally conductive and reflective layer 2. A second phosphor layer 12 is disposed between the first phosphor layer 11 and the third phosphor layer 13. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer 11 to the third phosphor layer 13. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.2:1, and the mass ratio of scattering particles to glass powder is 0.8:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 0.8:1, and the mass ratio of scattering particles to glass powder is 0.5:1; in the third phosphor layer, the mass ratio of phosphor to glass powder is 1.5:1, and the mass ratio of scattering particles to glass powder is 0.15:1. The thicknesses of the first phosphor layer 11, the second phosphor layer 12, and the third phosphor layer 13 are all approximately 30 μm. The thermally conductive and reflective layer 2 comprises a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the phosphor layer 1. Specifically, the thickness of the porous alumina layer 23 is approximately 70 μm, the thickness of the alumina-alumina nitride transition layer 22 is approximately 5 μm, and the total thickness of the thermally conductive and reflective layer 2 is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0087] The only difference between Example 6 and Example 1 is that the thicknesses of the porous alumina layer 23 and the alumina-alumina nitride transition layer 22 are different from those in Example 1. Specifically, the oxidation treatment of the heat sink substrate in this example is as follows: a 0.8 mm thick aluminum nitride substrate is placed in an oxygen atmosphere, the oxygen partial pressure is controlled at 0.1 MPa, the heat treatment temperature is 900 °C, and the temperature is held for 30 min to obtain an oxidized aluminum nitride substrate with a 70 μm thick porous alumina layer 23 on the surface and a 5 μm thick alumina-alumina nitride transition layer 22 in the middle.

[0088] The remaining structure and preparation process of Example 6 are the same as those of Example 1, and will not be repeated here.

[0089] Comparative Example 1

[0090] like Figure 7As shown, a reflective wavelength conversion device includes a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer 1 includes three phosphor layers: a first phosphor layer 11 closest to the thermally conductive and reflective layer 2, and a third phosphor layer 13 furthest from the thermally conductive and reflective layer 2. A second phosphor layer 12 is disposed between the first phosphor layer 11 and the third phosphor layer 13. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer 11 to the third phosphor layer 13. Specifically, in the first phosphor layer 11, the mass ratio of phosphor to glass powder is 0.2:1, and the mass ratio of scattering particles to glass powder is 0.8:1. In the second phosphor layer 12, the mass ratio of phosphor to glass powder is 0.8:1, and the mass ratio of scattering particles to glass powder is 0.5:1. In the third phosphor layer, the mass ratio of phosphor to glass powder is 1.5:1, and the mass ratio of scattering particles to glass powder is 0.15:1. The thicknesses of the first phosphor layer 11, the second phosphor layer 12, and the third phosphor layer 13 are all approximately 30 μm. The thermally conductive substrate is an aluminum nitride substrate.

[0091] The fabrication process of the reflective wavelength conversion device is as follows:

[0092] (1) Preparation of fluorescent paste: Fluorescent pastes of different layers are prepared according to the proportions of the first phosphor layer 11, the second phosphor layer 12 and the third phosphor layer 13 respectively: glass powder, scattering particles and phosphor are added to a mortar according to the proportion, organic solvent (terpineol) is added, and after grinding and stirring for 30 min, planetary vacuum stirring is carried out for 10 min to evenly disperse and remove bubbles, so as to obtain the first phosphor layer fluorescent paste, the second phosphor layer paste and the third phosphor layer fluorescent paste respectively.

[0093] (2) Coating of the first phosphor layer phosphor paste on the aluminum nitride substrate: The first phosphor layer phosphor paste is printed on the surface of the aluminum nitride substrate with a thickness of 0.8 mm using a screen printing process to obtain a wet film of the first phosphor layer.

[0094] (3) Pre-drying of the first phosphor layer wet film: The first phosphor layer wet film is dried in an oven, and the pre-drying temperature is controlled at 100-120℃ and kept at the temperature for 30-60 minutes to obtain a first phosphor layer dry film with a thickness of about 30μm.

[0095] (4) Coating and drying of the remaining fluorescent paste layers: The second fluorescent paste is coated onto the first phosphor layer dry film according to the methods of steps (4) and (5), and dried to obtain the second phosphor layer dry film; the third fluorescent paste is coated onto the second phosphor layer dry film according to the methods of steps (4) and (5), and dried to obtain the third phosphor layer dry film.

[0096] (5) Sintering to obtain the finished product: Under air atmosphere, the aluminum nitride substrate with three phosphor layers on the surface obtained in step (4) is sintered in a high-temperature sintering furnace. The peak temperature of sintering is controlled at 750-850℃ and held for 30-90 minutes to obtain a wavelength conversion device.

[0097] Comparative Example 2

[0098] like Figure 8 As shown, this embodiment discloses a reflective wavelength conversion device, including a fluorescent layer 1 and a thermally conductive and reflective layer 2 disposed below the fluorescent layer. The fluorescent layer 1 is obtained by sintering phosphor, glass powder, and scattering particles. Specifically, the mass ratio of phosphor to glass powder in the fluorescent layer is 0.8:1, the mass ratio of scattering particles to glass powder is 0.5:1, and the thickness of the fluorescent layer is approximately 90 μm. The thermally conductive and reflective layer 2 includes a porous alumina layer 23, an alumina-alumina nitride transition layer 22, and an aluminum nitride layer 21 stacked sequentially, with the porous alumina layer 23 disposed close to the fluorescent layer 1. Specifically, the thickness of the porous alumina layer 23 is approximately 60 μm, the thickness of the alumina-alumina nitride transition layer 22 is approximately 10 μm, and the total thickness of the thermally conductive and reflective layer 2 is 0.8 mm. The pore size of the porous alumina layer 23 is 100-400 nm.

[0099] The method for fabricating the reflective wavelength conversion device is as follows:

[0100] (1) Oxidation treatment of heat sink substrate: A 0.8 mm thick aluminum nitride substrate is placed in an oxygen atmosphere, the oxygen partial pressure is controlled at 0.08 MPa, the heat treatment temperature is 850 °C, and the heat treatment is held for 45 min to obtain an oxidized aluminum nitride substrate with a 60 μm thick porous aluminum oxide layer 23 on the surface and a 10 μm thick aluminum oxide-aluminum nitride transition layer 22 in the middle.

[0101] (2) Grinding and polishing the oxidized aluminum nitride substrate: One side of the oxidized aluminum nitride substrate is left untreated as a fluorescent reflective surface, and the remaining surfaces of the oxidized aluminum nitride substrate are ground and polished to expose the aluminum nitride layer 21.

[0102] (3) Preparation of fluorescent paste: Add glass powder, scattering particles and fluorescent powder to a mortar according to the proportion, add organic solvent (terpineol), grind and stir for 30 minutes, then planetary vacuum stir for 10 minutes to evenly disperse and remove bubbles to obtain fluorescent paste.

[0103] (4) Coating of fluorescent paste on aluminum nitride substrate: The fluorescent paste is printed on the fluorescent reflective surface of aluminum nitride substrate using screen printing process to obtain a fluorescent powder wet film.

[0104] (5) Pre-drying of phosphor layer wet film: Dry the phosphor layer wet film in an oven, control the pre-drying temperature at 100-120℃, keep warm for 30-60min, and obtain a phosphor layer dry film with a thickness of about 90μm.

[0105] (6) Sintering to obtain the finished product: Under an air atmosphere, the aluminum nitride substrate with phosphor layer attached to the surface obtained in step (5) is sintered in a high-temperature sintering furnace. The peak temperature of sintering is controlled at 750-850℃ and held for 30-90 minutes to obtain a wavelength conversion device.

[0106] The performance of the reflective wavelength conversion devices of Examples 1 to 6, as well as Comparative Examples 1 and 2, was tested. The test items, test methods, or standards are as follows:

[0107] 1. Blue light power tolerance test: Adjust the blue light power to a low range, then continuously increase the blue light power and observe the change in luminous flux. When the luminous flux no longer increases or even decreases, record the blue light power, which is the limit value of the blue light power tolerance of the reflective wavelength conversion device. The luminous flux at the limit blue light power is the limit luminous flux.

[0108] 2. Luminous flux test: Turn on the light source and align the light outlet of the light source with the entrance of the integrating sphere so that the light completely enters the integrating sphere. Test the luminous flux of the reflective wavelength conversion device at the extreme blue light power and at a low blue light power of 30W.

[0109] 3. Aging Cycle Reliability Test: The test measures the change in luminous flux of the wavelength conversion device before and after aging under high and low temperature cycling. The maximum tolerable aging time is defined as when the luminous flux decreases to 90% of its pre-aging value. The number of cycles is calculated to assess its reliability. High and low temperature test environment: High temperature 85℃, low temperature -40℃. One cycle is 2 hours. Test results are shown in Table 1.

[0110] Table 1

[0111]

[0112] As shown in Table 1, the reflective wavelength conversion device prepared by this invention exhibits high tolerance to extreme blue light power, high luminous flux, and high luminous flux at 30W low blue light power, demonstrating good reliability. Comparing Example 1 and Comparative Example 1, it is evident that without pre-oxidation of the thermally conductive reflective layer under pre-oxygen partial pressure, the wavelength conversion device prepared has low luminous flux. Comparing Example 1 and Comparative Example 2, it is clear that without gradient treatment, the fluorescent layer easily forms an isolated interface, resulting in poor luminous efficacy and even lower reliability of the wavelength conversion device.

[0113] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A reflective wavelength conversion device, characterized in that, The system includes a fluorescent layer and a thermally conductive and reflective layer disposed below the fluorescent layer. The fluorescent layer is obtained by sintering phosphor, glass powder, and scattering particles. The fluorescent layer comprises n phosphor layers, with the first phosphor layer closest to the thermally conductive and reflective layer and the outermost phosphor layer furthest from the thermally conductive and reflective layer being the nth phosphor layer, where 2 ≤ n ≤ 5. The phosphor content increases and the scattering particle content decreases layer by layer from the first phosphor layer to the nth phosphor layer. The thermally conductive and reflective layer comprises a porous alumina layer, an alumina-alumina nitride transition layer, and an aluminum nitride layer stacked sequentially. Furthermore, the porous alumina layer is positioned close to the fluorescent layer, and the thermally conductive and reflective layer is an integrated design. When the aluminum nitride substrate is placed in an oxygen atmosphere, the aluminum nitride on the surface of the aluminum nitride substrate reacts with oxygen to generate a porous alumina layer. The oxidation reaction between aluminum nitride and oxygen proceeds gradually from the outside to the inside of the aluminum nitride. The slightly inner aluminum nitride does not have enough time to capture oxygen, thus forming a transition layer between aluminum oxide and aluminum nitride. The innermost aluminum nitride hardly comes into contact with oxygen, so the oxidation reaction cannot proceed, and it remains aluminum nitride. The mass ratio of the phosphor to the glass powder in the fluorescent layer is (0.1-2):1, and the mass ratio of the scattering particles to the glass powder is (0.1-1):

1. The mass ratio of phosphor to glass powder in the first phosphor layer of the fluorescent layer is (0.1-0.3):1, and the mass ratio of scattering particles to glass powder is (0.7-1):1; the mass ratio of phosphor to glass powder in the nth phosphor layer of the fluorescent layer is (1-2):1, and the mass ratio of scattering particles to glass powder is (0.1-0.2):

1.

2. The reflective wavelength conversion device according to claim 1, characterized in that, The scattering particles are one or a combination of aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, zinc oxide, and lithopone, with a particle size of 20-400 nm.

3. The reflective wavelength conversion device according to claim 1, characterized in that, The softening temperature of the glass powder is 500-700℃, and the glass powder is a Zn / B / Si / O system, an Al / Zn / B / O system, or a B / Si / O system, with a particle size of 1-6μm.

4. The reflective wavelength conversion device according to claim 1, characterized in that, The pore size of the porous alumina layer is 100-400 nm.

5. The reflective wavelength conversion device according to claim 1, characterized in that, The thickness of the porous alumina layer is 50–70 μm, and the thickness of the alumina-aluminum nitride transition layer is 5–15 μm.

6. The reflective wavelength conversion device according to any one of claims 1 to 5, characterized in that, The thickness of the fluorescent layer is 80–140 μm, and the thickness of the thermally conductive and reflective layer is 0.5–1 mm.

7. A method for preparing the reflective wavelength conversion device according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Oxidation treatment of heat sink substrate: The aluminum nitride substrate is placed in an oxygen atmosphere, the oxygen partial pressure is controlled at 0.06-0.1 MPa, the heat treatment temperature is 800-900℃, and the heat treatment is held for 30-60 min to obtain an oxidized aluminum nitride substrate with a porous aluminum oxide layer on the surface and an aluminum oxide-aluminum nitride transition layer in the middle. (2) Grinding and polishing the oxidized aluminum nitride substrate: One side of the oxidized aluminum nitride substrate is left untreated as a fluorescent reflective surface, and the remaining surfaces of the oxidized aluminum nitride substrate are ground and polished to expose the aluminum nitride layer. (3) Preparation of fluorescent paste: Prepare fluorescent pastes of different layers according to the ratio of different phosphor layers: Add glass powder, scattering particles and phosphor to a mortar according to the ratio, add organic solvent, grind and stir, then vacuum stir to evenly disperse and remove bubbles of each component, and obtain fluorescent pastes of the first phosphor layer to the nth phosphor layer respectively. (4) Coating the first phosphor layer phosphor paste on the aluminum nitride substrate: The first phosphor layer phosphor paste is printed on the fluorescent reflective surface of the aluminum nitride substrate using a screen printing process to obtain a wet film of the first phosphor layer. (5) Pre-drying of the first phosphor layer wet film: The first phosphor layer wet film is dried in an oven, and the pre-drying temperature is controlled at 100-120℃ for 30-60 min to obtain the first phosphor layer dry film. (6) Coating and drying of the remaining fluorescent paste layers: Coating and drying of the remaining fluorescent paste layers in sequence, referring to the methods in steps (4) and (5); (7) Sintering to obtain the finished product: Under an air atmosphere, the aluminum nitride substrate with n phosphor layers on the surface obtained in step (6) is sintered in a high-temperature sintering furnace. The peak temperature of sintering is controlled at 750-850℃ and held for 30-90 minutes to obtain a wavelength conversion device.

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