Wavelength conversion device, light emitting device, and projection device

Abstract

The present invention protects a wavelength conversion device, as well as a light-emitting device and a projection device using the same. The wavelength conversion device comprises a red luminescent glass layer, an inorganic diffuse reflection layer, and a highly thermally conductive substrate stacked in sequence; the red luminescent glass layer comprises a first glass powder and a red phosphor, which are mixed and sintered to form the red luminescent glass layer; the inorganic diffuse reflection layer comprises a second glass powder and white diffuse reflection particles, which are mixed and sintered to form the inorganic diffuse reflection layer; the thermal expansion coefficient of the second glass powder is less than 4.5*10 ‑6 / K. The wavelength conversion device is entirely encapsulated in an inorganic manner, and has excellent heat resistance and thermal conductivity, a reliable structure, and good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lighting and projection, and in particular to a wavelength conversion device and a light emitting device and a projection device using the wavelength conversion device. Background Art

[0002] With the advancement of display and lighting technologies, conventional LEDs or halogen bulbs are increasingly unable to meet the high-power and high-brightness demands of displays and lighting. Using excitation light from solid-state light sources, such as laser diodes (LDs), to excite wavelength-converting materials, a method for producing visible light of various colors is gaining increasing application in lighting and display applications. This technology offers advantages such as high efficiency, low energy consumption, low cost, and long life, making it an ideal alternative to existing white light or monochromatic light sources.

[0003] In remote laser excitation phosphor technology, red phosphors suffer from severe thermal quenching, a technical bottleneck in the laser lighting and display fields. To increase the laser power density threshold of the red phosphor layer and achieve high-brightness products, red phosphor packaging has evolved from traditional silicone packaging to inorganic packaging methods such as glass and ceramics. Red phosphors are typically nitride red phosphors, which have low sintering activity. When sintering them with ceramics, it is difficult to obtain high-density, high-luminous-efficiency red luminescent ceramics. Currently, the efficiency of red luminescent ceramics is only about 60% of that of red phosphors.

[0004] In the technical route of glass encapsulation of red phosphors, in order to reduce the adverse effects of high temperature sintering on nitride red phosphors, low melting point glass is generally used to encapsulate the red phosphors. 2+ Doped (Sr,Ca)AlSiN3:Eu 2+ Red phosphors are prone to thermal decomposition above 600°C and chemically react with oxide-based glass powders at high temperatures, making it impossible to prepare efficient red luminescent glass. Therefore, a large number of researchers are looking for low-melting-point glass with a sintering temperature below 600°C. However, the thermal expansion coefficient of such low-melting-point glass powders is usually higher than 6*10 -6 / K, while the thermal expansion coefficient of the high thermal conductivity substrate that usually carries the red luminescent glass layer is smaller. For example, the thermal expansion coefficient of the aluminum nitride substrate is 4.6*10 -6 / K, the thermal expansion coefficient of the silicon nitride substrate and silicon wafer is 3*10 -6 When such a high thermal conductivity substrate is used as a carrier substrate and a red luminescent glass layer is sintered thereon, the difference in thermal expansion coefficients results in weak adhesion between the two, causing the red luminescent glass layer to easily fall off, resulting in low reliability of the resulting red wavelength conversion device. Summary of the Invention

[0005] In view of the above-mentioned defects in the prior art, the present invention provides a red wavelength conversion device with good heat resistance and thermal conductivity and high overall reliability, which is suitable for high-power excitation light.

[0006] The present invention provides a wavelength conversion device, comprising a red luminescent glass layer, an inorganic diffuse reflection layer, and a high thermal conductivity substrate stacked in sequence; the red luminescent glass layer comprises a first glass powder and a red phosphor, which are mixed and sintered to form the red luminescent glass layer; the inorganic diffuse reflection layer comprises a second glass powder and white diffuse reflection particles, which are mixed and sintered to form the inorganic diffuse reflection layer, wherein the thermal expansion coefficient of the second glass powder is less than 4.5*10 -6 / K.

[0007] In the red wavelength conversion device of the present invention, the substrate is a highly thermally conductive substrate, such as ceramic, and the reflective layer and red phosphor layer are both encapsulated in glass. The entire wavelength conversion device exhibits excellent heat resistance and thermal conductivity, capable of withstanding high excitation light power and producing high-brightness red light. Furthermore, a glass diffuse reflection layer, with a thermal expansion coefficient closer to that of the high thermal conductivity substrate, is positioned between the high thermal conductivity substrate and the red phosphor glass layer. This diffuse reflection layer diffusely reflects incident excitation and stimulated light while also improving the overall device's bonding reliability.

[0008] Preferably, the red phosphor is a nitride red phosphor, and the sintering temperature of the first glass frit is less than 500° C., more preferably less than 450° C. The first glass frit encapsulating the nitride red phosphor is a low-melting-point glass frit, which has a low sintering temperature and does not adversely affect the performance of the nitride red phosphor during the sintering process, thereby ensuring its luminous efficiency.

[0009] Preferably, the nitride red phosphor is (Sr,Ca)AlSiN3:Eu 2+ , which exists in the red luminescent glass layer in the form of rectangular crystals. Red powder (Sr,Ca)AlSiN3:Eu 2+ The crystal has three crystal planes, namely (002), (200) and (020), among which (002) has the largest area, (200) is the second largest, and (020) has the smallest area. In the red luminescent glass layer, more than half of the (Sr,Ca)AlSiN3:Eu 2+ The crystal faces the incident excitation light with the non-smallest crystal face (020), thereby improving the red powder (Sr,Ca)AlSiN3:Eu 2+ Stimulated, luminous efficiency.

[0010] Preferably, the thermal expansion coefficient of the first glass powder is less than 20*10 -6 / K, more preferably less than 10*10 -6On the premise of ensuring that the sintering temperature of the first glass frit does not adversely affect the nitride red powder, selecting the first glass frit with a small thermal expansion coefficient can further improve the reliability of the entire wavelength conversion device.

[0011] Preferably, the thermal expansion coefficient of the second glass powder is less than 3*10 -6 / K.

[0012] Preferably, the white diffuse reflective particles are one or more of titanium dioxide, aluminum oxide, yttrium oxide, zinc oxide or barium sulfate.

[0013] Preferably, the area of ​​the red phosphor on the surface of the red luminescent glass layer facing the incident excitation light is not less than 30%, so as to improve the utilization rate of the excitation light during excitation. More preferably, the red phosphor is (Sr, Ca)AlSiN3:Eu 2+ , and at the same time meet the following requirements on the surface of the red luminescent glass layer: more than half of the (Sr,Ca)AlSiN3:Eu 2+ The crystal faces the incident excitation light with the (020) crystal plane which is not the smallest in area.

[0014] Preferably, the thermal conductivity of the high thermal conductivity substrate is greater than 80 W / (m·K), and specifically, an aluminum nitride substrate, a silicon carbide substrate, a silicon nitride substrate or a single crystal silicon substrate can be selected.

[0015] The present invention also provides a light-emitting device, comprising an excitation light source and the above-mentioned wavelength conversion device.

[0016] The present invention also provides a projection device, comprising the above-mentioned light-emitting device.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] In the red wavelength conversion device of the present invention, the red luminescent layer and diffuse reflection layer are encapsulated with glass, and the substrate is a highly thermally conductive substrate such as ceramic. The entire device is completely inorganically encapsulated, resulting in excellent heat resistance and thermal conductivity, raising the threshold for withstanding laser power density, and achieving higher and more stable luminous efficiency under high-power laser excitation. Furthermore, a glass diffuse reflection layer is positioned between the highly thermally conductive substrate and the red luminescent glass layer. Its thermal expansion coefficient is closer to that of the highly thermally conductive substrate than that of the red luminescent glass layer, preventing the red luminescent glass layer from easily falling off the highly thermally conductive substrate due to the difference in thermal expansion coefficients, thereby improving the reliability of the overall wavelength conversion device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0020] Figure 1This is a schematic side structural diagram of the wavelength conversion device provided in Example 1 of the present invention.

[0021] Figure 2 (Sr,Ca)AlSiN3:Eu 2+ SEM image of the crystal structure of the phosphor.

[0022] Figure 3 for Figure 1 Schematic diagram of the surface structure of the red luminescent glass layer.

[0023] FIG4( a ) and FIG4 ( b ) are surface and side SEM images of the red light-emitting glass layer of the wavelength conversion device prepared in Example 1 of the present invention, respectively.

[0024] FIG5(a) and FIG5(b) are surface and side SEM images of the red light-emitting glass layer of the wavelength conversion device prepared in the comparative example, respectively. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] As described in the background, with the continuous development of remote laser-excited red phosphors toward higher power and higher brightness, the packaging materials for the red light-emitting layer have evolved from traditional organic silicones and resins to inorganic materials such as glass. When glass is used to encapsulate the red phosphor to form the light-emitting layer, the wavelength conversion device assembled further must not only ensure sufficient heat resistance and thermal conductivity to withstand high-power laser irradiation and stimulate the emission of high-brightness red light, but also address the issue of poor adhesion between the light-emitting glass layer and the highly thermally conductive substrate, resulting in low reliability of the overall wavelength conversion device.

[0027] See also Figure 1 , Figure 1 The figure is a side view of the wavelength conversion device 100 of the present invention. The wavelength conversion device 100 comprises a red luminescent glass layer 1, an inorganic diffuse reflection layer 2, and a highly thermally conductive substrate 3 stacked in sequence. The red luminescent glass layer 1 is formed by sintering a mixture of a first glass powder and red phosphor powder, while the inorganic diffuse reflection layer 2 is formed by sintering a second glass powder mixed with white diffuse reflection particles. The thermal expansion coefficient of the second glass powder is less than 4.5*10 -6 / K.

[0028] In practical applications, the wavelength conversion device 100 generally takes the form of a color wheel. The highly thermally conductive substrate 3 rotates at high speed driven by a motor or other driver. Incident excitation light irradiates the red luminescent glass layer 1, which excites the red phosphor to produce red fluorescence, thereby converting the wavelength of light. Compared to traditional organic light-emitting layers, the red luminescent glass layer 1 has a higher tolerance to the excitation light power. Specifically, when the excitation light excites the red phosphor to produce fluorescence, a large amount of heat is generated. The wavelength conversion device 100 of the present invention is generally inorganically packaged, capable of rapidly transferring the heat generated by the red luminescent glass layer 1 to the highly thermally conductive substrate 3 via the inorganic diffuse reflection layer 2. When the highly thermally conductive substrate 3 rotates at high speed, the heat can be rapidly transferred and diffused away. Furthermore, an inorganic diffuse reflection layer 2 is added between the red luminescent glass layer 1 and the highly thermally conductive substrate 3. Its thermal expansion coefficient is closer to that of the highly thermally conductive substrate 3 than that of the red luminescent glass layer 1, thereby improving the reliability of the wavelength conversion device 100.

[0029] In the present invention, the red phosphor in the red luminescent glass layer 1 is generally a nitride red powder, which has low thermal stability and is easily thermally decomposed above 600°C. In addition, it is easy to chemically react with the glass powder of the oxide system at high temperature. Based on this, the first glass powder in the red luminescent glass layer 1 is selected to be T f The temperature is less than 500° C., preferably less than 450° C., that is, the sintering temperature of the first glass powder must be less than 500° C., preferably less than 450° C. At this temperature, the sintered red luminescent glass layer 1 can maintain the luminous efficiency of the red nitride powder.

[0030] In a specific embodiment of the present invention, the nitride red phosphor is (Sr, Ca)AlSiN3:Eu 2+ , which exists in the red luminescent glass layer 1 as a rectangular parallelepiped crystal, and its grain structure is as follows Figure 2 As shown; red powder (Sr,Ca)AlSiN3:Eu 2+ It is an orthorhombic crystal system, and its cuboid consists of three crystal planes (002), (200) and (020) with decreasing areas. Since the crystal plane (002) has the smallest formation energy, it has the largest crystal plane area, the fewest surface defects and the highest lattice stability. Therefore, Figure 3 As shown, the red luminescent glass layer 1 faces the incident direction of the excitation light, and the red powder (Sr, Ca)AlSiN3:Eu 2+ The particles are preferably oriented in the (002) crystal plane to improve the red powder (Sr,Ca)AlSiN3:Eu 2+Stimulated, luminous efficiency; Of course, in the actual production process, there are cases where non-(002) crystal planes face the incident excitation light, such as the (200) crystal plane, or the inclined plane between (002) and (200), or even the smallest crystal plane (020) facing the incident excitation light. The most basic situation to be achieved here is that more than half of the (Sr,Ca)AlSiN3:Eu 2+ The crystal faces the incident excitation light with the non-smallest crystal face (020), which can relatively improve the red powder (Sr,Ca)AlSiN3:Eu 2+ Stimulated, luminous efficiency.

[0031] In addition, as for the proportion of the phosphor on the surface of the light-emitting layer, the area of ​​the red phosphor on the surface of the red light-emitting glass layer 1 is not less than 30%, so as to improve the utilization rate when the excitation light is irradiated. In a more preferred embodiment, the red phosphor is (Sr, Ca)AlSiN3:Eu 2+ On the surface of the red luminescent glass layer 1: more than half of the (Sr,Ca)AlSiN3:Eu 2+ The crystal faces the incident excitation light with the (020) face, which is not the smallest face. To determine the area ratio of the phosphor on the surface of the red luminescent glass layer 1, a scanning electron microscope (SEM) image of the surface of the red luminescent glass layer 1 is generally taken. The area ratio of the phosphor is calculated using image calculation software, using the characteristics of the phosphor in the SEM image, which is revealed by the different grayscale of the phosphor compared to the glass matrix.

[0032] In the wavelength conversion device 100 of one embodiment of the present invention, the second glass frit of the inorganic diffuse reflection layer 2 first needs to satisfy the requirement that the thermal expansion coefficient is lower than 4.5*10 -6 / K, preferably less than 3*10 -6 / K; This is done to ensure that the thermal expansion coefficients of the inorganic diffuse reflective layer 2 are matched as closely as possible when the slurry is applied to the highly thermally conductive substrate 3 and sintered, thereby improving the bonding stability of the device. The red luminescent glass layer 1 also has better adhesion to the inorganic diffuse reflective layer 2 than when it is fabricated directly on the highly thermally conductive substrate 3.

[0033] In addition, the two-layer structure on the high thermal conductivity substrate 3 is formed by sintering separately in sequence, so the softening point temperature of the second glass powder should be greater than the sintering temperature of the first glass powder to avoid adverse effects on the inorganic diffuse reflection layer 2 underneath when sintering the red luminescent glass layer 1.

[0034] The white diffuse reflective particles in the inorganic diffuse reflective layer 2 are selected from one or more of titanium dioxide, aluminum oxide, yttrium oxide, zinc oxide, or barium sulfate. It should be noted that the inorganic diffuse reflective layer 2 can diffuse the light spot formed on the highly thermally conductive substrate 3 by the excitation light passing through the red luminescent glass layer 1 to a certain extent, thereby improving the utilization efficiency of the red phosphor and enhancing the luminous efficiency.

[0035] In the present invention, the high thermal conductivity substrate 3 serves as a load-bearing and heat-conducting substrate and requires sufficiently high mechanical strength and thermal conductivity, with a thermal conductivity greater than 80 W / (m·K). Ceramics with high mechanical strength and good thermal conductivity are preferred as the high thermal conductivity substrate 3. Specifically, aluminum nitride substrates, silicon carbide substrates, silicon nitride substrates, or single-crystal silicon substrates can be selected.

[0036] The present invention is further described in detail below through specific examples. The following examples are only used to further illustrate the present invention and should not be construed as limiting the present invention.

[0037] Example 1

[0038] See also Figure 1 , Figure 1 FIG. 1 is a side view of the structure of the wavelength conversion device 100 according to the first embodiment. Specifically, the wavelength conversion device 100 is manufactured by the following method:

[0039] S1: Aluminum nitride ceramic is used as the high thermal conductivity substrate 3, and its thermal conductivity is greater than 80W / (m·K);

[0040] S2: Apply an inorganic slurry formed by mixing the second glass powder and white diffuse reflective particles on one surface of the aluminum nitride substrate and sinter at about 500°C to form an inorganic diffuse reflective layer 2. The second glass powder is a commercially available high borosilicate glass powder with a thermal expansion coefficient of less than 3*10 -6 / K; The white diffuse reflective particles may be one or more of titanium dioxide, aluminum oxide, yttrium oxide, zinc oxide or barium sulfate.

[0041] S3: Mix the first glass powder and (Sr,Ca)AlSiN3:Eu 2+ An inorganic slurry formed by mixing phosphors is coated on the surface of the inorganic diffuse reflection layer 2 away from the high thermal conductivity substrate 3 and sintered at about 450° C. to form a red luminescent glass layer 1 .

[0042] The first glass powder is a commercially available zinc-aluminate low-melting-point glass powder, and furthermore, its thermal expansion coefficient is less than 10*10 -6 / K. In particular, in step S3 of the first embodiment, the red luminescent glass layer slurry is applied by scraping with a tape to make the rectangular parallelepiped (Sr,Ca)AlSiN3:Eu 2+The red powder particles are evenly spread in the slurry and have a certain orientation arrangement, especially along the (002) crystal plane, there is a certain preferred orientation, such as Figure 3 Ideal conditions are shown.

[0043] As shown in Figure 4 (a) and Figure 4 (b), they are the surface and side SEM images of the red luminescent glass layer of the wavelength conversion device made in Example 1 of the present invention. In Example 1, the red luminescent glass layer was made by scraping and pressing. As can be seen from its surface Figure 4 (a), the red powder (Sr,Ca)AlSiN3:Eu 2+ The area of ​​the particles relative to the glass is high, greater than 30%; more than half of the (Sr,Ca)AlSiN3:Eu 2+ The crystal faces the incident excitation light with the (020) plane which is not the smallest in area, and has many red powder (Sr,Ca)AlSiN3:Eu 2+ The grain faces the direction of the incident excitation light with its largest (002) crystal plane; as can be seen from its side view 4(b), the red powder (Sr,Ca)AlSiN3:Eu 2+ The particles are evenly arranged and have a high density. Each red powder (Sr,Ca)AlSiN3:Eu in the red luminescent glass layer 2+ The grains are not arranged completely in parallel. Most of the cross sections of the grains in the side view are normal or oblique sections along the two smaller crystal planes (200) and (020). Corresponding to the front direction of the red luminescent glass layer, the (002) crystal plane direction is a relatively dominant orientation.

[0044] The difference between the wavelength conversion device prepared in the comparative example and the red luminescent glass layer is that the red luminescent glass layer is made by dispensing glue. As shown in Figure 5(a) and Figure 5(b), the surface and side SEM images of the red luminescent glass layer of the wavelength conversion device prepared in the comparative example are shown. As can be seen from Figure 5(a), the red powder (Sr,Ca)AlSiN3:Eu on the surface 2+ The particle area accounts for a relatively low proportion. As can be seen from Figure 5(b), the red powder (Sr,Ca)AlSiN3:Eu 2+ The particles are mainly concentrated inside the layer, with low density and no dominant orientation crystal plane.

[0045] The luminous luminance results of the wavelength conversion devices numbered 1# and 2# provided in Example 1 of the present invention and the wavelength conversion devices numbered 1# and 2# provided in the comparative example under blue excitation light are shown in Table 1 below. As can be seen from Table 1, when the color coordinates are consistent, the wavelength conversion device of Example 1 of the present invention achieves a luminous efficiency improvement of over 5% compared to the comparative example.

[0046] Table 1. Comparison of luminous lumens of wavelength conversion devices of Example 1 and Comparative Example

[0047] serial number Stable lm CIE_x CIE_y Example 1# 30.1 0.641 0.3585 Example 1 2# 30 0.6425 0.3571 Comparative Example 1# 28.4 0.6405 0.359 Comparative Example 2# 28.9 0.6412 0.3583

[0048] The present invention also provides a light-emitting device comprising an excitation light source and a wavelength conversion device 100. The wavelength conversion device 100 has the structure and functions described in the aforementioned embodiments. The light-emitting device can be used in projection and display systems, such as liquid crystal displays (LCDs) or digital light processor (DLP) projectors; lighting systems, such as automotive lighting and stage lighting; and the field of 3D display technology.

[0049] The present invention also provides a projection device, which includes the above-mentioned light-emitting device.

[0050] The above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A wavelength conversion device, characterized in that: It comprises a red luminescent glass layer, an inorganic diffuse reflection layer and a high thermal conductivity substrate stacked in sequence; The red luminescent glass layer comprises a first glass powder and a red phosphor, which are mixed and sintered to form the red luminescent glass layer; The inorganic diffuse reflection layer comprises a second glass powder and white diffuse reflection particles, which are mixed and sintered to form the inorganic diffuse reflection layer, and the thermal expansion coefficient of the second glass powder is less than 4.5*10-6 / K; The red phosphor is a nitride red phosphor, which is (Sr, Ca)AlSiN3:Eu2+ and is distributed in the red luminescent glass layer in the form of rectangular crystals; in the red luminescent glass layer, more than half of the (Sr, Ca)AlSiN3:Eu2+ crystals face the incident excitation light with a non-minimum-area crystal plane (020); The sintering temperature of the first glass powder is less than 500° C., and the thermal expansion coefficient of the first glass powder is less than 20*10-6 / K; the high thermal conductivity substrate is an aluminum nitride substrate, a silicon carbide substrate, a silicon nitride substrate or a single crystal silicon substrate.

2. The wavelength conversion device according to claim 1, wherein: The sintering temperature of the first glass powder is less than 450°C.

3. The wavelength conversion device according to claim 1 or 2, characterized in that: The thermal expansion coefficient of the first glass powder is less than 10*10-6 / K.

4. The wavelength conversion device according to claim 1, wherein: The thermal expansion coefficient of the second glass powder is less than 3*10-6 / K.

5. The wavelength conversion device according to claim 1, wherein: The white diffuse reflective particles are one or more of titanium dioxide, aluminum oxide, yttrium oxide, zinc oxide or barium sulfate.

6. The wavelength conversion device according to claim 1, wherein: On the surface of the red luminescent glass layer and in the direction facing the incident excitation light, the area of ​​the red phosphor accounts for no less than 30%.

7. The wavelength conversion device according to claim 6, wherein: The red phosphor is (Sr, Ca)AlSiN3:Eu2+, wherein on the surface of the red luminescent glass layer: more than half of the (Sr, Ca)AlSiN3:Eu2+ crystals face the incident excitation light with a non-minimum-area crystal plane (020).

8. The wavelength conversion device according to claim 1, wherein: The thermal conductivity of the high thermal conductivity substrate is greater than 80 W / (m·K).

9. A light-emitting device comprising an excitation light source and the wavelength conversion device according to any one of claims 1 to 8.

10. A projection device comprising the light emitting device according to claim 9.

Images