CN105278225A - Wavelength conversion device, manufacture method thereof, correlative light-emitting device, and projection system - Google Patents

Abstract

The invention discloses a wavelength conversion device and its preparation method, a related light-emitting device and a projection system. The wavelength conversion device comprises: a light-emitting layer, a diffuse reflection layer and a ceramic substrate stacked in sequence; the light-emitting layer contains fluorescent powder and a first glass Powder, wherein the fluorescent powder accounts for 14.1% to 38.7% by volume of the light-emitting layer; the diffuse reflection layer contains white scattering particles and the first glass powder, wherein the volume fraction of white scattering particles to the diffuse reflection layer is 22.0% to 62.9% ; The linear expansion coefficient of the ceramic substrate is greater than that of the first glass powder, and smaller than that of the fluorescent powder and white scattering particles. By adjusting the volume fraction of phosphor powder in the light-emitting layer and the volume fraction of white scattering particles in the diffuse reflection layer, the light-emitting layer and the diffuse reflection layer have sufficiently high luminous efficiency and reflectivity, respectively, and have small internal thermal resistance and interface. Thermal resistance, so as to achieve the beneficial effect of obtaining stable and high-efficiency outgoing light.

Description

Wavelength conversion device and its preparation method, related light emitting device and projection device

technical field

The invention relates to the field of display and illumination, in particular to a wavelength conversion device and a preparation method thereof, a related light-emitting device and a projection device.

Background technique

With the development of display and lighting technology, the original LED or halogen bulb as a light source is increasingly unable to meet the high power and high brightness requirements of display and lighting. Visible light of various colors can be obtained by using excitation light emitted by a solid-state light source such as LD (Laser Diode, laser diode) to excite wavelength conversion materials, and this technology is increasingly used in lighting and display. This technology has the advantages of high efficiency, low energy consumption, low cost, and long life, and is an ideal alternative to existing white or monochromatic light sources.

In the prior art, the light source of laser excitation wavelength conversion material, in order to improve the light utilization rate, mostly adopts reflective type—the light passes through the phosphor sheet (ie, the light-emitting layer) and then enters the reflector (ie, the reflective layer and the substrate), and is then absorbed Reflected back to the phosphor sheet to ensure that the light exits in the same direction and avoid light loss due to the scattering effect of the phosphor sheet. However, with the gradual increase of the excitation light power and its power density, the high temperature resistance performance of the wavelength conversion device (including the reflective layer and the reflective layer) is becoming more and more difficult to meet people's needs. On the one hand, the metal reflective film used as the reflective layer is prone to oxidation at high temperatures, resulting in a decrease in its reflectivity; on the other hand, the silica gel used to encapsulate the phosphor can only work at 200°C for a long time, when the temperature rises to 250°C , the silica gel will quickly deteriorate, resulting in a decrease in its light transmittance.

For the reflective layer, in order to prevent the metal reflective layer from being oxidized at high temperature, some researchers have attempted to prepare some stable inorganic scattering materials as the reflective layer, which can withstand higher temperatures without chemical reaction. As for the silica gel used to bond phosphors and inorganic scattering materials, some researchers have proposed to use glass materials instead, which have good light transmittance and high softening point temperature.

However, it has been found in practical applications that this wavelength conversion device, which uses inorganic scattering materials as the reflective layer and glass materials as the bonding agent between phosphor powder and inorganic scattering materials, can remain stable under high-power laser irradiation, but its Poor heat dissipation and low luminous efficiency.

Contents of the invention

In view of the above technical problems, the present invention provides a wavelength conversion device, the content and linear expansion coefficient of each component of the wavelength conversion device satisfy a certain relationship, and can meet the requirements of stable and high luminous efficiency under the irradiation of a high-power light source. shoot light.

The invention provides a wavelength conversion device, comprising: a luminescent layer, a diffuse reflection layer and a ceramic substrate stacked in sequence; the luminescent layer contains fluorescent powder and a first glass powder, wherein the volume fraction of the fluorescent powder in the luminescent layer is 14.1% ~38.7%; the diffuse reflection layer contains white scattering particles and the first glass frit, wherein the volume fraction of white scattering particles in the diffuse reflection layer is 22.0% to 62.9%; the linear expansion coefficient of the ceramic substrate is greater than that of the first glass frit coefficient; the linear expansion coefficient of the ceramic substrate is smaller than that of the fluorescent powder; the linear expansion coefficient of the ceramic substrate is smaller than that of the white scattering particles.

Preferably, the volume fraction of phosphor powder in the light-emitting layer is 29.1%-38.7%.

Preferably, the linear expansion coefficient of the ceramic substrate is 4.0×10 ^-6 /K˜6.0×10 ^-6 /K, and the thermal conductivity of the ceramic substrate is greater than or equal to 80 W/mK.

Preferably, the ceramic substrate is one of an aluminum nitride substrate and a silicon carbide substrate.

Preferably, an interface bonding layer is also included, located between the ceramic substrate and the diffuse reflection layer.

Preferably, the interface bonding layer is an aluminum oxide layer.

Preferably, the ceramic substrate is an aluminum nitride substrate, and the aluminum oxide layer is obtained by oxidizing the surface of the aluminum nitride substrate.

Preferably, the interface bonding layer is a glass bonding layer, and the glass bonding layer contains the first glass frit.

Preferably, the interface bonding layer is a silver-glass bonding layer, and the silver-glass bonding layer contains silver and a second glass powder, and the melting point of the second glass powder is lower than that of the first glass powder.

Preferably, the surface of the ceramic substrate is etched.

Preferably, the first glass powder is borosilicate glass, the molar percentage of boron oxide in the first glass powder is 10%-19%, and the molar percentage of silicon oxide is 70%-90%.

Preferably, the first glass powder is a combination of at least two of silicate glass powder, borosilicate glass powder, borophosphate glass powder and zinc phosphate glass powder.

Preferably, the white scattering particles are one or a combination of aluminum oxide, magnesium oxide, boron nitride, yttrium oxide, zinc oxide, titanium oxide and zirconium oxide.

Preferably, the reflectance of the diffuse reflection layer to visible light is greater than 90%.

Preferably, the structural formula of the phosphor is (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O ₁₂ :Ce or (Ca _1-ab Sr _a Ba _b )AlSiN ₃ :Eu, where 0≤a ≤1, 0≤b≤1, Ln is a lanthanide element.

Preferably, there is a continuous transition layer between the light emitting layer and the diffuse reflection layer.

The present invention also provides a method for preparing the above-mentioned wavelength conversion device, comprising the following steps:

Step 1: providing a ceramic substrate;

Step 2: Mix the white scattering particles, the first glass powder and the organic carrier to prepare a diffuse reflection layer slurry, cover the diffuse reflection layer slurry on the treated surface of the ceramic substrate, and prepare a diffuse reflection layer green sheet, white The volume fraction of the scattering particles in the total volume of the white scattering particles and the first glass powder is 22.0% to 62.9%; the linear expansion coefficient of the white scattering particles is greater than that of the ceramic substrate; the linear expansion coefficient of the first glass powder is smaller than that of the ceramic substrate coefficient of linear expansion;

Step 3: Mix the phosphor powder, the first glass powder and the organic carrier to prepare the luminescent layer slurry, and cover the luminescent layer slurry on the diffuse reflection layer green sheet to obtain the luminescent layer green sheet. The phosphor powder accounts for the phosphor powder and the first The volume fraction of the total volume of the glass powder is 14.1% to 38.7%; the linear expansion coefficient of the phosphor powder is greater than that of the ceramic substrate;

Step 4: co-sintering the light-emitting layer green sheet, the diffuse reflection layer green sheet, and the ceramic substrate to obtain a wavelength conversion device.

Preferably, step 1 includes: performing oxidation treatment on the surface of the ceramic substrate to form an oxide layer, or performing corrosion treatment on the surface of the ceramic substrate, or first oxidation treatment on the surface of the ceramic substrate and then etching treatment, or first etching treatment on the surface of the ceramic substrate and then oxidation treatment deal with.

The present invention also provides a light-emitting device, which includes an excitation light source and any one of the above-mentioned wavelength conversion devices.

The present invention also provides a projection device, including the above-mentioned light emitting device.

Compared with the prior art, the present invention includes the following beneficial effects:

In the present invention, by regulating the volume fraction of the fluorescent powder in the luminescent layer and the volume fraction of the white scattering particles in the diffuse reflection layer to be in a certain appropriate range, the synergy and complementary advantages of the two are realized, so that the luminescent layer and the diffuse reflection layer The layers have sufficiently high luminous efficiency and reflectivity, and at the same time, since the amount of the first glass frit in the present invention is sufficient to wrap the fluorescent powder and the white scattering particles, the inside of the luminescent layer and the diffuse reflection layer have relatively small porosity, thereby Internal thermal resistance reduces; On the other hand, because the coefficient of linear expansion of ceramic substrate is greater than that of glass frit and less than the coefficient of linear expansion of fluorescent powder and white scattering particle, under the composition ratio of luminescent layer and diffuse reflection layer of the present invention , the coefficient of linear expansion of the ceramic substrate is close to the average coefficient of linear expansion of the light-emitting layer and the diffuse reflection layer, so that when the wavelength conversion device of the present invention is prepared and used, the materials on both sides of the contact surface of the ceramic substrate and the diffuse reflection layer will not be affected by expansion. Or shrink to produce excessive relative displacement, so that the ceramic substrate and the diffuse reflection layer are firmly combined and have a small interface thermal resistance.

In summary, the technical solution of the present invention satisfies a certain relationship between the content of each layer component and the linear expansion coefficient in the wavelength conversion device, so that the luminous efficiency of the wavelength conversion device is high, and the internal thermal resistance and interface thermal resistance are both reduced. Therefore, the beneficial effect of obtaining stable and high-luminous-efficiency outgoing light is achieved.

Description of drawings

FIG. 1 is a schematic structural view of Embodiment 1 of the wavelength conversion device of the present invention;

FIG. 2 is a schematic structural diagram of Embodiment 2 of the wavelength conversion device of the present invention;

FIG. 3 is a schematic structural diagram of Embodiment 3 of the wavelength conversion device of the present invention.

detailed description

Embodiments of the present invention will be described in detail below with reference to the drawings and implementation methods. For clarity of description, "upper" and "lower" described below all refer to upper and lower in the drawings.

Embodiment one

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of Embodiment 1 of the wavelength conversion device of the present invention. As shown in the figure, the wavelength conversion device 100 includes a light emitting layer 110 , a diffuse reflection layer 120 and a ceramic substrate 130 . Wherein the light emitting layer 110 is a sintered body comprising phosphor powder and the first glass powder, and the diffuse reflection layer 120 is a sintered body comprising white scattering particles and the first glass powder.

After the excitation light emitted by the excitation light source is incident on the light-emitting layer 110, the phosphor powder is excited to emit the subject light. After the excited light and the unexcited excitation light pass through the light-emitting layer 110, they are incident on the diffuse reflection layer 120, and then are reflected back to the light-emitting layer 110, wherein the excited light and part of the unexcited excitation light pass through the light-emitting layer 110 and exit, The rest of the excitation light is converted by the light-emitting layer 110 into the accepted light. The total incident light of the wavelength conversion device 100 is the excitation light, and the total output light is the stimulated light and part of the unexcited excitation light.

When the wavelength conversion device 100 performs light wavelength conversion, the heat generated mainly includes: the heat released by the conversion of the excitation light into the subject light in the light-emitting layer 110, the heat generated by the reflection of the excitation light and the subject light in the diffuse reflection layer 120 (The diffuse reflective layer cannot achieve 100% reflectivity), the heat generated by the propagation of the excitation light and the received light in the light emitting layer 110 and the diffuse reflective layer 120 . The heat propagation path of the wavelength conversion device 100 is mainly from the fluorescent powder to the first glass powder in the light-emitting layer 110, then to the first glass powder and white scattering particles in the diffuse reflection layer 120, and then through the diffuse reflection layer 120. The first glass frit in contact with the ceramic substrate 130 reaches the ceramic substrate 130 and is emitted. It can be seen that the heat dissipation of the wavelength conversion device 100, in addition to being affected by the thermal conductivity of the components of each component, mainly depends on the density of the light emitting layer 110, the density of the diffuse reflection layer 120, and the density of the diffuse reflection layer 120 and ceramics. The degree of interfacial bonding of the substrate 130 .

In this embodiment, the light emitting layer 110 is composed of phosphor powder and the first glass powder, wherein the volume fraction of the phosphor powder in the light emitting layer 110 is 14.1%-38.7%.

In this embodiment, the light-emitting layer 110 is formed by mixing and sintering phosphor powder, first glass powder and organic carrier, wherein the organic carrier is removed during the sintering process, and the first glass powder is softened and forms a continuous body during the sintering process. It is filled between the phosphor particles and wraps the phosphor into layers. Since phosphor powder is the main body of wavelength conversion in the light emitting layer 110 , the amount of phosphor powder determines the amount of light that can be converted by the wavelength conversion device. In the case of a certain amount of fluorescent powder, if the proportion of fluorescent powder in the light-emitting layer 110 is too small, the thickness of the light-emitting layer 110 is too large, resulting in a large thermal resistance of the light-emitting layer 110 along the direction of heat propagation; on the other hand, if the fluorescent powder If the proportion of the light-emitting layer 110 is too large, the amount of the first glass powder is not enough to wrap each phosphor particle, so that the phosphor particles are adjacent to each other and form pores. The existence of this hole not only increases the heat of the light-emitting layer 110 itself. resistance, and also increases the thermal resistance of the interface between the phosphor particles and the first glass frit, so that the thermal conductivity of the light-emitting layer 110 is reduced. Through experiments in this embodiment, it is obtained that when the volume fraction of the phosphor powder in the luminescent layer 110 is 14.1% to 38.7%, both luminous performance and thermal conductivity can be taken into account; and when the volume fraction of the phosphor powder in the luminescent layer 110 is 29.1% to 38.7%. , the light-emitting and heat-dissipating properties of the light-emitting layer 110 are more excellent.

Phosphor absorbs light with a shorter peak wavelength and emits light with a longer peak wavelength. Specifically, the phosphor can be selected from a garnet-based phosphor material (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O that absorbs blue light with a peak wavelength of 420nm to 470nm and emits light with a peak wavelength of 500nm to 600nm. ₁₂ : Ce (0≤a≤1,0≤b≤1), you can also choose to absorb blue light with a peak wavelength of 420nm~470nm and emit a nitride phosphor with a peak wavelength of 600nm~660nm (Ca _1-ab Sr _a Ba _b ) AlSiN ₃ :Eu (0≤a≤1,0≤b≤1), wherein Ln is a lanthanide element. The average linear expansion coefficient of this type of phosphor is approximately 7×10 ^-6 /K˜9×10 ^-6 /K.

The first glass powder is used to bond the fluorescent powder, and as a medium for light and heat to propagate in the luminescent layer 110, silicate glass powder, borosilicate glass powder, borophosphate glass powder, zinc phosphate glass can be selected powder etc. In this embodiment, borosilicate glass frit with high light transmittance and high temperature resistance is preferred, and its light transmittance exceeds 90%. The average coefficient of linear expansion of this type of glass frit is approximately 3×10 ^-6 /K～3.5×10 ^-6 /K. In this embodiment, the molar percentage of boron oxide in the first glass frit is 10%-19%, and the molar percentage of silicon oxide in the first glass frit is 70%-90%.

In addition, the first glass powder can be a single type of glass powder, or a combination of two or more glass powders. In the present invention, water glass and glass frit may also be selected as the adhesive to replace the first glass powder, which will not be repeated here.

In this embodiment, the diffuse reflection layer 120 is composed of white scattering particles and the first glass frit, wherein the volume fraction of the white scattering particles in the diffuse reflection layer 120 is 22.0% to 62.9%, and the reflectance of the diffuse reflection layer 120 to visible light is greater than 90%.

Unlike specular reflection, which only has one reflection, in the reflection process in this embodiment, the light is reflected multiple times by the white scattering particles, and as the number of reflections increases, the light loss also increases, and this part of the lost light is converted into heat, thereby This adversely affects the heat dissipation of the wavelength conversion device. When the proportion of white scattering particles in the diffuse reflection layer 120 is too small, the white scattering particles are sparsely distributed on the cross section of the diffuse reflection layer parallel to its incident plane, and the light will continue to propagate to the inside of the diffuse reflection layer until it is reflected. In order to make the reflectance of the diffuse reflection layer 120 higher than 90%, the diffuse reflection layer 120 needs to have a sufficiently large thickness. The increase in the light propagation distance will lead to an increase in the number of times the light is reflected during the process from the incident and diffuse reflection layers to the exit, that is, the heat generated increases. On the other hand, when the proportion of the white scattering particles in the diffuse reflection layer 120 is too large, the amount of the first glass powder is not enough to wrap each white scattering particle, so that the white scattering particles are adjacent to each other and form pores. Existence not only increases the thermal resistance of the diffuse reflection layer 120 itself, but also increases the thermal resistance of the interface between the white scattering particles and the first glass frit, thereby reducing the thermal conductivity of the diffuse reflection layer 120 . Through experiments in this embodiment, it is obtained that when the volume fraction of the white scattering particles in the diffuse reflection layer 120 is 22.0% to 62.9%, both reflective performance and thermal conductivity performance can be taken into account.

After the light is incident on the diffuse reflection layer 120 , it is reflected by the white scattering particles and then exits toward the light emitting layer 110 . The white scattering particles either have a high reflectivity for visible light, or have a high refractive index and use the total reflection property of light to reflect. In this embodiment, since the temperature of the wavelength conversion device 100 in the working state is relatively high, the white scattering particles are selected from aluminum oxide, magnesium oxide, yttrium oxide, boron nitride, zinc oxide, and titanium oxide with good chemical stability and temperature stability. Or powder of zirconia, these materials can keep stable near the softening point temperature of glass powder.

The glass powder in the diffuse reflection layer 120 is preferably the same glass powder as the first glass powder in the luminous layer 110. This composition can ensure a firmer bond between the diffuse reflection layer 120 and the luminescent layer 110, and it can withstand thermal expansion and contraction. There will be no voids due to the difference in thermal expansion coefficient between the two. Of course, the glass frit in the diffuse reflection layer 120 can also be chosen to be different from that of the light emitting layer 110.

In this embodiment, the ceramic substrate 130 conducts and dissipates the heat generated by the light emitting layer 110 and the diffuse reflection layer 120 . The ceramic substrate needs to have good thermal conductivity, and its thermal conductivity is greater than or equal to 80W/mK. The ceramic substrate 130 in this embodiment is an aluminum nitride substrate, and silicon carbide or similar materials can also be selected as the substrate material.

In addition to the thermal conductivity of the ceramic substrate 130 itself, the interface thermal resistance generated by the contact between the ceramic substrate 130 and the diffuse reflection layer 120 is an important part of the heat dissipation of the wavelength conversion device. Since the diffuse reflective layer 120 is formed by coating the ceramic substrate 130 with a slurry mixed with glass powder and white scattering particles and sintered at high temperature, if the thermal expansion coefficient of the diffuse reflective layer 120 is too different from that of the ceramic substrate 130, the diffuse reflective layer will be cooled at high temperature. During the process, relatively large thermal stress will be generated, resulting in diffuse micro-cracks, and more seriously, shedding, resulting in increased thermal resistance between the ceramic substrate 130 and the diffuse reflection layer 120 .

Since the components of each layer are different, and these different components have different average linear expansion coefficients, when the wavelength conversion device is heated and cooled, the deformation of the diffuse reflection layer 120 is different from that of the ceramic substrate 130, resulting in a Voids are generated, which in turn leads to an increase in the thermal resistance of the interface, which has an adverse effect on the heat dissipation of the wavelength conversion device.

Since the linear expansion coefficients of the white scattering particles and the phosphor powder are greater than that of the first glass powder, according to the calculation method of the thermal expansion coefficient of the composite material, the average linear expansion coefficient of the light-emitting layer 110 is between that of the phosphor powder and the first glass powder. coefficients, the average linear expansion coefficient of the diffuse reflection layer 120 is between the linear expansion coefficients of the white scattering particles and the first glass frit, that is, the linear expansion coefficient of the ceramic substrate is greater than that of the first glass frit and smaller than that of the fluorescent Linear expansion coefficient of powder and white scattering particles. Therefore, choosing the ceramic substrate so that its thermal expansion coefficient is close to the average linear expansion coefficient of the light emitting layer 110 and the diffuse reflection layer 120 can minimize the large interface thermal resistance caused by the mismatch of thermal expansion coefficients. In this embodiment, the aluminum nitride substrate with a linear expansion coefficient of 4×10 ^-6 /K to 6×10 ^-6 /K can not only ensure the thermal conductivity and mechanical strength of the substrate, but also ensure that it will not be used during manufacture or use. In the process, a large interface thermal resistance is generated due to the mismatch of the thermal expansion coefficient of the diffuse reflection layer.

The preparation method of the wavelength conversion device 100 in the first embodiment is as follows:

Step 1: providing a ceramic substrate 130;

Step 2: mix the white scattering particles, the first glass powder and the organic carrier to prepare a slurry for the diffuse reflection layer, and cover the slurry on the treated surface of the ceramic substrate 130 to prepare a green sheet for the diffuse reflection layer. The first glass frit in the green sheet does not soften and deform;

Step 3: mixing the fluorescent powder, the first glass powder and the organic carrier to prepare a light-emitting layer slurry, and covering the slurry on the diffuse reflection layer green sheet to obtain a light-emitting layer green sheet;

Step 4: co-sintering the lamination of the light-emitting layer green sheet, the diffuse reflection layer green sheet and the ceramic substrate to obtain a wavelength conversion device.

In step 2, the diffuse reflective layer green sheet is not sintered, the first glass powder has not undergone a softening process, and only part of the organic carrier is removed by low-temperature baking, so the diffuse reflective layer green sheet does not form a dense and continuous surface structure . In Step 4, the light-emitting layer green sheet, the diffuse reflection layer green sheet and the ceramic substrate are sintered together, wherein the first glass powder on both sides of the contact surface between the light-emitting layer green sheet and the diffuse reflection layer green sheet has increased fluidity near its softening point , the glass powder is bonded to each other to form a continuous body, so that a continuous transition layer is formed between the luminous layer and the diffuse reflection layer. The continuous transition layer has no obvious phase interface, so the interface thermal resistance between the luminescent layer and the diffuse reflection layer is very small , so that the heat transfer performance is good.

In the above preparation steps, the organic carrier is used to uniformly mix the fluorescent powder with the first glass powder or the white scattering particles with the first glass powder, and can choose silicone oil, ethanol, ethylene glycol, xylene, etc. of various systems such as phenyl, methyl, etc. , ethyl cellulose, terpineol, butyl carbitol, PVA, PVB, PAA, PEG in one or more mixtures. The organic carrier can promote the uniform mixing of glass powder and phosphor powder or white scattering particles, most of which are decomposed during the sintering process, but a very small part may remain in the wavelength conversion device.

In the wavelength conversion device manufactured according to a specific implementation of this example, the volume fraction of phosphor powder in the light-emitting layer 110 is 29.1%, and the volume fraction of white scattering particles in the diffuse reflection layer 120 is 49.2%. Under excitation light irradiation, the measured initial luminous intensity of the wavelength conversion device 100 is 2875.6lm. After 2 minutes of irradiation, it is measured that the luminous intensity of the wavelength conversion device 100 has dropped by 6.3%. The luminous intensity and attenuation degree can be The application of the wavelength conversion device 100 in a light emitting device is satisfied.

In more comparative examples, without changing the volume fraction of the phosphor powder in the light-emitting layer 110, only changing the volume fraction of the white scattering particles in the diffuse reflection layer 120, and measuring the initial luminous intensity of the wavelength conversion device 100 under the irradiation of laser light And the luminous intensity after two minutes of irradiation, the comparison results shown in Table 1 are obtained. Wherein, when the volume fraction of white scattering particles in the diffuse reflection layer 120 is 22.0%, the initial luminous intensity is 2855.1lm, and decays by 5.8% after two minutes; when the volume fraction of white scattering particles in the diffuse reflection layer 120 is 53.0%, the starting intensity The initial luminous intensity is 2963.3lm, which decays by 7.3% after two minutes; when the volume fraction of white scattering particles in the diffuse reflection layer 120 is 62.9%, the initial luminous intensity is 2980.4lm, and decays by 6.9% after two minutes; the white scattering particles When the volume fraction of the diffuse reflection layer 120 is 69.3%, the initial luminous intensity is 2923.8lm, and the attenuation is 66.0% after two minutes. Under this ratio, the heat dissipation effect is very poor, which affects the normal use of the wavelength conversion device 100 . When the volume fraction of phosphor powder in the light-emitting layer 110 is taken as other values between 14.1% and 38.7% other than 29.1%, similar conclusions can still be obtained by changing the volume fraction of white scattering particles in the diffuse reflection layer.

Table 1 Effects of different volume fractions of white scattering particles on the luminous intensity and stability of the device

It can be seen that when the volume fraction of white scattering particles is small, the light loss of the wavelength conversion device is large, resulting in low luminous intensity; and when the volume fraction of white scattering particles is large, the thermal resistance of the diffuse reflection layer increases, resulting in its The heat cannot be dissipated, so that the working temperature of the phosphor increases and the light conversion efficiency decreases.

In other comparative examples of this embodiment, the diffuse reflection layer 120 of the wavelength conversion device contains white scattering particles with a volume fraction of 49.2%. The initial luminous intensity of the wavelength conversion device 100 and the luminous intensity after two minutes of irradiation were measured, and the results shown in Table 2 were obtained. Wherein, when the volume fraction of the phosphor powder in the light-emitting layer 110 is 14.1%, the initial luminous intensity is 2544.5lm, and decays by 5.4% after two minutes. When the volume fraction of layer 110 is 19.0%, the initial luminous intensity is 2593.4lm, which decays by 5.6% after two minutes; 6.9% attenuation after 1 minute; when the volume fraction of the phosphor powder in the luminescent layer 110 is 37.0%, the initial luminous intensity is 2877.0lm, and decays 8.4% after two minutes; when the volume fraction of the phosphor powder in the luminescent layer 110 is 38.7%, The initial luminous intensity is 2882.6lm, which decays by 9.8% after two minutes.

When the volume fraction of white scattering particles is taken as other values between 22.0% and 62.9% other than 49.2%, similar conclusions can still be obtained by changing the volume fraction of phosphor powder in the light-emitting layer.

Table 2 Effect of different phosphor volume fractions on luminous intensity and stability

It can be seen that when the phosphor powder volume fraction is small, the light-emitting layer 110 absorbs and converts less excitation light, resulting in low luminous intensity of the wavelength conversion device 100; and when the phosphor powder volume fraction is large, although the wavelength conversion device 100 has The initial luminous intensity increases, but the internal pores of the luminescent layer increase, resulting in an increase in its thermal resistance, resulting in the inability to dissipate the heat generated by the phosphor, which increases the operating temperature of the phosphor and reduces the light conversion efficiency.

However, in other series of experiments, such as taking the volume fraction of phosphor powder as 52% (exceeding from 14.1% to 38.7%), and changing the volume fraction of white scattering particles, it was found that the wavelength conversion device either had low luminous intensity, or the luminous intensity decayed quickly ; Similarly, take the white scattering particles at 72% (exceeding 22.0% ~ 62.9%) unchanged, and change the volume fraction of the phosphor, it is found that the luminous intensity of the wavelength conversion device decays quickly.

After the above series of experiments, it is concluded that the volume fraction of the white scattering particles in the diffuse reflection layer and the phosphor powder in the light-emitting layer must be within a certain range, and the two must meet the ratio requirements at the same time to ensure high reflectivity and luminous efficiency. , and has lower thermal resistance. In this embodiment, the volume fraction of white scattering particles in the diffuse reflection layer is 22.0% to 62.9%, and the volume fraction of phosphor powder in the light emitting layer is 14.1% to 38.7%. The wavelength conversion device has stable and high luminous efficiency outgoing light. In order to further increase the luminous intensity of the wavelength conversion device, the volume fraction of the fluorescent powder in the luminescent layer is preferably 29.1%-38.7%.

Embodiment two

Please refer to FIG. 2 . FIG. 2 is a schematic structural diagram of Embodiment 2 of the wavelength conversion device of the present invention. As shown in the figure, the wavelength conversion device 200 includes a light-emitting layer 210 , a diffuse reflection layer 220 and a ceramic substrate 230 . Different from Embodiment 1, in this embodiment, the wavelength conversion device 200 also includes an interface bonding layer 231 .

In this embodiment, the ceramic substrate 230 is an aluminum nitride substrate, the interface bonding layer 231 is an alumina layer, and the alumina layer 231 is formed on the surface of the aluminum nitride substrate 230 and is a part of the ceramic substrate 230 .

The preparation method of the wavelength conversion device 200 in this embodiment is as follows:

Step 1: providing an aluminum nitride substrate 230, and performing surface densification treatment on the aluminum nitride substrate 230, specifically including heating the aluminum nitride substrate 230 at 800-1000° C. for 0.5-2 hours to obtain an aluminum oxide layer 231;

Step 2: mixing the white scattering particles, the first glass powder and the organic carrier to prepare a slurry for the diffuse reflection layer, covering the slurry on the treated surface of the aluminum nitride substrate 230 to prepare a green sheet for the diffuse reflection layer, The first glass frit in the green sheet of the diffuse reflection layer is not softened and deformed;

Step 3: mixing the fluorescent powder, the first glass powder and the organic carrier to prepare a light-emitting layer slurry, and covering the slurry on the diffuse reflection layer green sheet to obtain a light-emitting layer green sheet;

Step 4: co-sintering the lamination of the light-emitting layer green sheet, the diffuse reflection layer green sheet and the aluminum nitride substrate to obtain a wavelength conversion device.

Since a loose oxide layer is easily formed on the surface of aluminum nitride, the actual contact area when the diffuse reflection layer is combined with the ceramic substrate is not large enough, and has an adverse effect on heat transfer from the diffuse reflection layer to the ceramic substrate. Therefore, in this embodiment, the surface of the ceramic substrate 230 is treated, and a dense aluminum oxide layer 231 is formed on the surface of the aluminum nitride substrate 230 through high-temperature oxidation treatment, so that the ceramic substrate 230 and the diffuse reflection layer 220 are closely connected through the aluminum oxide layer 231. catch. The aluminum oxide layer 231 has a thickness of 0.1 μm˜100 μm, and this thickness will not cause significant changes in the thermal resistance of the wavelength conversion device 200 .

In addition, the loose layer on the surface of the aluminum nitride substrate 230 can also be removed by acid etching, that is, step 1 in the preparation method of this embodiment is replaced by immersing the aluminum nitride substrate 231 in an acid solution for corrosion. This treatment process can remove the loose oxide structure on the surface of aluminum nitride.

In other embodiments, the surface oxidation treatment and the surface corrosion treatment may also be combined, oxidation treatment first and then corrosion treatment, or corrosion treatment first and then oxidation treatment.

Embodiment three

Please refer to FIG. 3 . FIG. 3 is a schematic structural diagram of Embodiment 3 of the wavelength conversion device of the present invention. As shown in the figure, the wavelength conversion device 300 includes a light emitting layer 310 , a diffuse reflection layer 320 , a ceramic substrate 330 and an interface bonding layer 340 . Different from the second embodiment, in this embodiment, the interface bonding layer 340 is a layer structure independent of the ceramic substrate 330 .

In this embodiment, the interface bonding layer 340 is a glass bonding layer, and the glass bonding layer includes the same first glass frit as that in the diffuse reflection layer 320 .

Due to the problem of the preparation process, when the diffuse reflection layer 320 is fired on the ceramic substrate 330 , there may be white scattering particles in direct contact with the ceramic substrate 330 . Since the white scattering particles do not undergo a softening and reshaping process like glass powder, their contact area with the ceramic substrate 330 is small, and voids are generated around them, resulting in large interface thermal resistance. Therefore, in this embodiment, the glass bonding layer 340 is added on the surface of the ceramic substrate 330 to prevent white scattering particles from contacting the ceramic substrate. Of course, in the present invention, a glass frit different from the first glass frit can also be selected as the glass bonding layer 340 .

In a modified embodiment of this embodiment, the interface bonding layer 340 is a silver glass bonding layer, and the silver glass bonding layer includes nano silver particles and a second glass frit. Nano-silver particles are dispersed in the silver-glass adhesive layer 340, which increases the thermal conductivity of the silver-glass adhesive layer 340, making it have better thermal conductivity than the glass adhesive layer. Wherein, the softening point of the second glass powder is lower than that of the first glass powder in the diffuse reflection layer 320 . On the one hand, the softening point of the second glass powder is low, which ensures that the nano-silver will not be oxidized due to excessive temperature during the sintering process; on the other hand, the softening point of the second glass powder is lower than that of the first glass powder, so that During the sintering process, its fluidity is stronger than that of the diffuse reflection layer, and it can better fill the pores in the ceramic substrate 330 and the diffuse reflection layer 320 . In addition, the silver glass bonding layer 340 is relatively thin, so that the layer structure of the wavelength conversion device will not be damaged due to the strong fluidity of the second glass frit during the sintering process.

The preparation method of the wavelength conversion device 300 in this embodiment is as follows:

Step 1: providing an aluminum nitride substrate 330, performing a surface densification treatment on the aluminum nitride substrate 330, and covering the surface of the aluminum nitride substrate 330 with an interface bonding layer;

Step 2: mixing the white scattering particles, the first glass powder and the organic carrier to prepare a slurry for the diffuse reflection layer, covering the slurry on the treated surface of the aluminum nitride substrate 330 to prepare a green sheet for the diffuse reflection layer, The first glass frit in the green sheet of the diffuse reflection layer is not softened and deformed;

Step 3: mixing the fluorescent powder, the first glass powder and the organic carrier to prepare a light-emitting layer slurry, and covering the slurry on the diffuse reflection layer green sheet to obtain a light-emitting layer green sheet;

Step 4: co-sintering the lamination of the light-emitting layer green sheet, the diffuse reflection layer green sheet and the aluminum nitride substrate to obtain a wavelength conversion device.

Wherein, the interface bonding layer in step 1 may be the first glass frit bonding layer or the silver glass bonding layer.

The present invention also provides a light-emitting device, which includes an excitation light source and a wavelength conversion device, wherein the wavelength conversion device may have the structures and functions of the above-mentioned embodiments. The light-emitting device can be applied to projection and display systems, such as liquid crystal display (LCD, Liquid Crystal Display) or digital light path processor (DLP, Digital Light Processor) projectors; it can also be applied to lighting systems, such as automotive lighting; it can also be applied to 3D display in the technical field. The present invention also provides a projection system, which includes a light emitting device and a projection device, wherein the light emitting device may have the structure and function of the above light emitting device.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (20)

1. A wavelength conversion device, characterized in that, comprising: A light-emitting layer, a diffuse reflection layer and a ceramic substrate stacked in sequence; The luminescent layer includes phosphor powder and a first glass powder, wherein the volume fraction of the phosphor powder in the luminescent layer is 14.1% to 38.7%; The diffuse reflection layer includes white scattering particles and first glass frit, wherein the volume fraction of the white scattering particles in the diffuse reflection layer is 22.0% to 62.9%; The coefficient of linear expansion of the ceramic substrate is greater than the coefficient of linear expansion of the first glass frit; The coefficient of linear expansion of the ceramic substrate is smaller than the coefficient of linear expansion of the phosphor; The coefficient of linear expansion of the ceramic substrate is smaller than that of the white scattering particles. 2 . The wavelength conversion device according to claim 1 , wherein the volume fraction of the fluorescent powder in the light-emitting layer is 29.1%-38.7%. 3. The wavelength conversion device according to claim 1, wherein the coefficient of linear expansion of the ceramic substrate is 4.0×10 ^-6 /K to 6.0×10 ^-6 /K, and the thermal conductivity of the ceramic substrate is greater than Equal to 80W/mK. 4. The wavelength conversion device according to claim 1, wherein the ceramic substrate is one of an aluminum nitride substrate and a silicon carbide substrate. 5. The wavelength conversion device according to claim 1, further comprising an interface bonding layer located between the ceramic substrate and the diffuse reflection layer. 6. The wavelength conversion device according to claim 5, wherein the interface bonding layer is an aluminum oxide layer. 7. The wavelength conversion device according to claim 6, wherein the ceramic substrate is an aluminum nitride substrate, and the aluminum oxide layer is obtained by oxidation treatment of the surface of the aluminum nitride substrate. 8 . The wavelength conversion device according to claim 5 , wherein the interface bonding layer is a glass bonding layer, and the glass bonding layer includes a first glass frit. 9. The wavelength conversion device according to claim 5, wherein the interface bonding layer is a silver glass bonding layer, and the silver glass bonding layer comprises silver and a second glass powder, and the second glass powder has a melting point lower than that of the first glass frit. 10. The wavelength conversion device according to claim 1 or 4, characterized in that, the surface of the ceramic substrate is an etched surface. 11. The wavelength conversion device according to claim 1, characterized in that, the first glass powder is borosilicate glass, and the molar percentage of boron oxide in the first glass powder is 10% to 19%, and the oxidized The molar percentage of silicon is 70%-90%. 12. The wavelength conversion device according to claim 1, wherein the first glass powder is at least one of silicate glass powder, borosilicate glass powder, borophosphate glass powder, and zinc phosphate glass powder. A combination of the two. 13. The wavelength conversion device according to claim 1, wherein the white scattering particles are one or more of aluminum oxide, magnesium oxide, boron nitride, yttrium oxide, zinc oxide, titanium oxide, and zirconium oxide. combination of species. 14. The wavelength conversion device according to claim 1, wherein the reflectance of the diffuse reflection layer to visible light is greater than 90%. 15. The wavelength conversion device according to claim 1, characterized in that, the structural formula of the fluorescent powder is (Y _1-a Ln _a ) ₃ (Al _1-b Ga _b ) ₅ O ₁₂ :Ce or (Ca _{1 -ab} Sr _a Ba _b ) AlSiN ₃ :Eu, wherein 0≤a≤1, 0≤b≤1, and Ln is a lanthanide element. 16. The wavelength conversion device according to claim 1, wherein a continuous transition layer is formed between the light-emitting layer and the diffuse reflection layer. 17. A method for preparing a wavelength conversion device, comprising the steps of: Step 1: providing a ceramic substrate; Step 2: mixing the white scattering particles, the first glass powder and an organic vehicle to prepare a diffuse reflection layer slurry, and covering the diffuse reflection layer slurry on the treated surface of the ceramic substrate to obtain a diffuse reflection layer In the green sheet, the volume fraction of the white scattering particles accounting for the total volume of the white scattering particles and the first glass frit is 22.0% to 62.9%; the linear expansion coefficient of the white scattering particles is greater than that of the ceramic substrate; The coefficient of linear expansion of the first glass frit is smaller than the coefficient of linear expansion of the ceramic substrate; Step 3: Mix the fluorescent powder, the first glass powder and the organic carrier to prepare a luminescent layer slurry, and cover the luminescent layer slurry on the diffuse reflection layer green sheet to obtain a luminescent layer green sheet. The volume fraction of the total volume of the powder and the first glass powder is 14.1% to 38.7%; the coefficient of linear expansion of the fluorescent powder is greater than that of the ceramic substrate; Step 4: co-sintering the light-emitting layer green sheet, the diffuse reflection layer green sheet and the ceramic substrate to obtain a wavelength conversion device. 18. The method for preparing a wavelength conversion device according to claim 17, wherein the first step comprises: performing oxidation treatment on the surface of the ceramic substrate to form an oxide layer, or performing corrosion treatment on the surface of the ceramic substrate , or the surface of the ceramic substrate is oxidized first and then corroded, or the surface of the ceramic substrate is corroded and then oxidized. 19. A light emitting device, comprising an excitation light source and the wavelength conversion device according to any one of claims 1-16. 20. A projection device comprising the light emitting device according to claim 19.