Laser illumination ceramic phosphor with adjustable emergent light spots and preparation method thereof

Abstract

The invention discloses a laser illumination ceramic phosphor with adjustable emergent light spots and a preparation method of the laser illumination ceramic phosphor. The ceramic phosphor comprises a light conversion layer and a light scattering layer covering one surface of the light conversion layer. Wherein the light scattering layer is composed of a porous silicon dioxide sublayer and a compact silicon dioxide sublayer, and the porosity of the porous silicon dioxide sublayer is larger than that of the compact silicon dioxide sublayer. The invention has the following beneficial effects: on the premise that the luminous efficiency of the fluorescent material is not reduced, the problem of non-uniform distribution of light spot color and brightness of light emitted by a laser illumination product is effectively improved, and uniform white light emission is obtained.

Description

Technical Field

[0001] The invention relates to fluorescent ceramics for laser lighting, in particular to a ceramic phosphor for laser lighting with adjustable light spot and a preparation method thereof. Background Art

[0002] As the fourth generation of lighting technology, the core technology of laser lighting is to use blue laser to excite phosphor to produce high-brightness white light, which is very useful in the fields of civil and national defense lighting due to its advantages of higher brightness and longer irradiation distance. However, as the core component of laser lighting products, when the collimated high-power blue laser is focused and irradiated to the phosphor, due to the particularity of laser energy distribution, not only is it easy to make the final mixed light from the phosphor unevenly distributed, but the phosphor is also easily damaged by high-power laser irradiation, which has become a key problem in the current application of laser lighting.

[0003] According to the principle of laser lighting, the light coming out of the surface of the phosphor consists of two parts, namely, the yellow light generated by the phosphor being excited by the blue laser and the remaining blue laser that passes through the phosphor but is not converted. The light distribution is affected by the converted light (yellow light) and the remaining laser (blue light). Therefore, by adjusting the yellow light distribution by regulating the phosphor structure, the final light spot can be affected. Through the analysis of the laser light intensity distribution and the propagation of light inside the fluorescent ceramic, the light spot of the mixed light emitted from the phosphor can be divided into the central area and the edge area. The main features are as follows: Central area: Most of the laser energy is concentrated (within the range of about ±0.1mm from the center). In the central area, a) when the power of the blue laser is very high, the number of deactivated luminescent centers in the phosphor is less than the number of blue light photons arriving, and the "light saturation" phenomenon occurs. The light intensity does not increase with the increase of the power of the excitation blue laser. Due to the large amount of remaining blue laser, the blue light brightness in the center of the light spot is extremely strong. When the "light saturation" reaches a certain level, it may even cause damage to the phosphor and prevent it from working normally, resulting in a "blue screen" phenomenon; b) when the power of the blue laser is high enough, the phosphor reaches "light saturation", and the yellow light generated by the conversion is mixed with the remaining blue laser to form a visual white light area with a relatively balanced ratio of yellow and blue light; c) when the power of the blue laser is low, most of the blue laser is converted into yellow fluorescence, making the yellow light brightness in the center of the light spot dominant.

[0004] Edge area: A small amount of laser energy is dispersed in the edge area (outside the range of about ±0.1mm from the center), and most of the blue laser light is converted into yellow fluorescence, making the yellow light brightness at the edge of the light spot extremely strong.

[0005] Based on the above analysis, the light distribution of the phosphor is in the shape of a mountain. When the power of the blue laser is high enough, the brightness in the middle is high, showing a visual white area, and the brightness at the edge gradually decreases, showing a visual yellow area, that is, the "yellow light aperture" phenomenon. This leads to uneven distribution of color and brightness of the light spot of phosphors and laser lighting products, which greatly limits the application of products.

[0006] The current public technical solutions mainly adopt the method of adding scattering particles or micropores to fluorescent materials (in glass or ceramic form), and using the scattering of light by particles to "break up" the blue laser with highly concentrated energy, so that the fluorescent body produces a more uniform light spot. Compared with fluorescent glass, fluorescent ceramics have fewer defects and better thermal conductivity and mechanical properties, and are the preferred fluorescent material for high-power laser lighting. However, the addition of scattering particles or micropores will reduce the light efficiency of fluorescent materials, which is a problem that cannot be completely reconciled in current laser lighting technology. Summary of the invention

[0007] The purpose of the present invention is to solve the problem in the prior art that the central area of ​​the ceramic phosphor light spot is "white" and the surrounding area is "yellow", and to provide a new type of ceramic phosphor for laser lighting with an adjustable light spot and a preparation method thereof, which can effectively improve the problem of uneven distribution of light spot color and brightness of laser lighting products without reducing the light efficiency of the fluorescent material, and obtain uniform white light emission.

[0008] In order to achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a ceramic phosphor for laser lighting with an adjustable light spot, comprising: a light conversion layer and a light scattering layer covering one surface of the light conversion layer; wherein the light scattering layer is composed of a porous silica sublayer and a dense silica sublayer, and the porosity of the porous silica sublayer is greater than the porosity of the dense silica sublayer.

[0009] As a preferred solution of the ceramic phosphor for laser lighting with adjustable light spot, it further comprises: a metal reflection layer covering the other surface opposite to the light conversion layer.

[0010] As a preferred solution of a ceramic phosphor for laser lighting with adjustable light spot, the porous silica sublayer contains 10-50% by area of ​​voids, and the dense silica sublayer contains 1-10% by area of ​​voids.

[0011] As a preferred solution for a ceramic phosphor for laser lighting with adjustable light spot, the thickness of the porous silicon dioxide sublayer is 50-100 nm, and the thickness of the dense silicon dioxide sublayer is 20-60 nm.

[0012] As a preferred solution of a ceramic phosphor for laser lighting with adjustable light spot, the chemical composition of the light conversion layer is (Ce x Rey Y 1-x-y )3Al5O 12 , wherein Re is one or more of Lu, Tb, Gd, and Ga, and the value ranges of x and y are: 0.005≤x≤0.05, 0<y≤0.25.

[0013] As a preferred solution for a ceramic phosphor for laser lighting with an adjustable light spot, the crystal structure of the light conversion layer is a complex phase structure of a three-dimensional uniform mixture of YAG phase and Al2O3 phase, wherein the weight proportion of the Al2O3 phase is less than 60%.

[0014] As a preferred solution for a ceramic phosphor for laser lighting with adjustable light spot, the wavelength range of the excitation light of the light conversion layer is 420-500nm, and the wavelength range of the emission light formed under the excitation of the excitation light is 450-750nm.

[0015] The present invention also provides a method for preparing a ceramic phosphor for laser lighting with an adjustable light spot, which is used to prepare the ceramic phosphor, comprising: Preparation of the light conversion layer: Preparation by hydrothermal method (Ce x Re y Y 1-x-y )3Al5O 12 Powder; (Ce x Re y Y 1-x-y )3Al5O 12 A certain amount of dispersant, epoxy resin and curing agent are added to the powder, and the mixture is stirred and dispersed to obtain a uniform aqueous slurry. The aqueous slurry is then vacuum-defoamed and tape-cast to obtain a green blank. The green blank is sintered by hot isostatic pressing to obtain the light conversion layer. The light scattering layer is prepared by immersing one surface of the light conversion layer in a coating solution containing compounds of Si and O; and drying and annealing the coated light conversion layer to obtain the light scattering layer covering one surface of the light conversion layer.

[0016] As a preferred solution of the method for preparing a ceramic phosphor for laser lighting with adjustable light spot, the metal reflective layer is prepared: the light conversion layer is coated with a metal reflective coating on the other surface thereof.

[0017] As a preferred solution for the preparation of a ceramic phosphor for laser lighting with an adjustable light spot, the light scattering layer is prepared by immersing one surface of the light conversion layer in a coating solution containing one or more of silicate, silanol and siloxane; and drying and annealing the coated light conversion layer to obtain the light scattering layer covering one surface of the light conversion layer.

[0018] Compared with the prior art, the beneficial effect of the present invention is at least that: the blue light of the LD passes through the light scattering layer composed of the porous silica sublayer and the dense silica sublayer to reach the light conversion layer, wherein a part of the blue light is converted into yellow light by the luminescent ions of the light conversion layer, and the other part of the blue light and the converted yellow light pass through the light scattering layer again to form an output white light with high light efficiency and uniform light spot. Among them, the purpose of configuring the light scattering layer is to scatter the transmitted blue light or the transmitted blue light and yellow light, and effectively improve the uneven distribution of the color and brightness of the light spot of the laser lighting product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the ceramic phosphor of the present invention.

[0020] Serial numbers in the figure: 1. light conversion layer; 2. light scattering layer; 21. porous silica sublayer; 22. dense silica sublayer 3. metal reflection layer; 4. heat sink. Implementation

[0021] The present invention is further described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0022] See also Figure 1 , the figure shows a ceramic phosphor for laser lighting with adjustable light spot. The ceramic phosphor comprises: a light conversion layer, a light scattering layer covering one surface of the light conversion layer, and a metal reflection layer covering the other surface of the light conversion layer. The light scattering layer is composed of a porous silica sublayer and a dense silica sublayer, and the porosity of the porous silica sublayer is greater than the porosity of the dense silica sublayer.

[0023] The blue light of LD passes through the light scattering layer composed of a porous silica sublayer and a dense silica sublayer to reach the light conversion layer, where part of the blue light is converted into yellow light by the luminescent ions in the light conversion layer, and the other part of the blue light and the converted yellow light pass through the light scattering layer again. Without reducing the light efficiency of the fluorescent material, the uneven distribution of the color and brightness of the light spot of the laser lighting product is effectively improved, and uniform white light emission is obtained.

[0024] Preferably, the porous silica sublayer contains 10-50 area % of voids, and the dense silica sublayer contains 1-10 area % of voids.

[0025] Preferably, the thickness of the porous silica sublayer is 50-100 nm, and the thickness of the dense silica sublayer is 20-60 nm.

[0026] Preferably, the ceramic phosphor is provided with a heat sink. Example

[0027] Use Y2O3, Gd2O3, CeO2 and Al(NO3)3•9H2O as raw materials to prepare nitrate solution, according to (Ce 0.01 G 0.20 Y 0.79 )3Al5O 12 The corresponding nitrate solutions are mixed in a stoichiometric ratio, and a powder with a particle size in the range of 50-200 nm is synthesized by a hydrothermal method at 120°C for 10 hours. A certain amount of dispersant, epoxy resin, and curing agent are added to the powder respectively, and a uniform aqueous slurry is obtained by stirring and dispersing. The aqueous slurry is then vacuum-defoamed and tape-casted to obtain a green blank; the ceramic green blank is then sintered by hot isostatic pressing to obtain the original sheet of the light-converting ceramic material.

[0028] The ceramic original sheet is precisely processed to obtain a light conversion layer with a sample thickness of 0.2mm and double-sided polishing; then, a coating solution containing silicate is immersed in one surface of the light conversion layer, and after drying and annealing, a composite fluorescent layer coated with a light scattering layer is prepared, with the first sublayer thickness of 60~80nm and the second sublayer thickness of 20~50nm; then, a reflective coating is coated on the other surface of the composite fluorescent layer, and it is welded to a metal heat dissipation base to prepare a ceramic phosphor that can be used as a device for laser lighting. Using a blue laser as a blue light excitation light source, the ceramic phosphor is a light conversion device, which can achieve uniform mixed white light for high-power laser lighting products, has significantly improved light uniformity and spot adjustability, and can meet the application field of high-power white light laser lighting. Example

[0029] Y2O3, Tb4O7, CeO2 and Al(NO3)3•9H2O were used as raw materials to prepare nitrate solution, respectively according to (Ce 0.01 Tb 0.30 Y 0.69 )3Al5O 12 The corresponding nitrate solutions are mixed in a stoichiometric ratio, and a powder with a particle size in the range of 50-200 nm is synthesized by a hydrothermal method at 120°C for 10 hours. A certain amount of dispersant, epoxy resin, and curing agent are added to the powder respectively, and a uniform aqueous slurry is obtained by stirring and dispersing. The aqueous slurry is then vacuum-defoamed and tape-casted to obtain a green blank; the ceramic green blank is then sintered by hot isostatic pressing to obtain the original sheet of the light-converting ceramic material.

[0030] The ceramic original sheet is precisely processed to obtain a light conversion layer with a sample thickness of 0.3mm and double-sided polishing; then, one surface of the light conversion layer is immersed in a coating solution containing silicate, and after drying and annealing, a composite fluorescent layer coated with a light scattering layer is prepared, with the first sublayer thickness of 70~90nm and the second sublayer thickness of 20~50nm; then, a reflective coating is coated on the other surface of the composite fluorescent layer, and it is welded to a metal heat dissipation base to prepare a ceramic phosphor that can be used as a device for laser lighting. Using a blue laser as a blue light excitation light source, the ceramic phosphor is a light conversion device, which can achieve uniform mixed white light for high-power laser lighting products, has significantly improved light uniformity and spot adjustability, and can meet the application field of high-power white light laser lighting.

[0031] The above only expresses the implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A ceramic phosphor for laser lighting with adjustable light spot, characterized in that: include: A light conversion layer and a light scattering layer covering one surface of the light conversion layer; wherein the light scattering layer is composed of a porous silica sublayer and a dense silica sublayer, and the porosity of the porous silica sublayer is greater than the porosity of the dense silica sublayer.

2. The ceramic phosphor for laser lighting with adjustable light spot according to claim 1, characterized in that: Further including: A metal reflective layer covers the other surface of the light conversion layer.

3. A ceramic phosphor for laser lighting with adjustable light spot according to claim 1 or 2, characterized in that: The porous silica sublayer contains 10-50 area % of voids, and the dense silica sublayer contains 1-10 area % of voids.

4. The ceramic phosphor for laser lighting with adjustable light spot according to claim 3, characterized in that: The thickness of the porous silica sublayer is 50-100 nm, and the thickness of the dense silica sublayer is 20-60 nm.

5. The ceramic phosphor for laser lighting with adjustable light spot according to claim 1 or 2, characterized in that: The chemical composition of the light conversion layer is (Ce x Re y Y 1-x-y )3Al5O 12 , wherein Re is one or more of Lu, Tb, Gd, and Ga, and the value ranges of x and y are: 0.005≤x≤0.05, 0<y≤0.

25.

6. The ceramic phosphor for laser lighting with adjustable light spot according to claim 4, characterized in that: The crystal structure of the light conversion layer is a three-dimensional uniformly mixed complex structure of YAG phase and Al2O3 phase, wherein the weight proportion of Al2O3 phase is less than 60%. According to the ceramic phosphor for laser lighting with adjustable light spot as claimed in claim 1, it is characterized in that the wavelength range of the excitation light of the light conversion layer is 420-500nm, and the wavelength range of the emission light formed under the excitation of the excitation light is 450-750nm.

7. A method for preparing a ceramic phosphor for laser lighting with adjustable light spot, used for preparing the ceramic phosphor according to any one of claims 1 to 6, characterized in that: include: Preparation of the light conversion layer: Preparation by hydrothermal method (Ce x Re y Y 1-x-y )3Al5O 12 Powder; (Ce x Re y Y 1-x-y )3Al5O 12 A certain amount of dispersant, epoxy resin and curing agent are added to the powder, and the mixture is stirred and dispersed to obtain a uniform aqueous slurry. The aqueous slurry is then vacuum-defoamed and tape-cast to obtain a green blank. The green blank is sintered by hot isostatic pressing to obtain the light conversion layer. The light scattering layer is prepared by immersing one surface of the light conversion layer in a coating solution containing compounds of Si and O; and drying and annealing the coated light conversion layer to obtain the light scattering layer covering one surface of the light conversion layer.

8. The method for preparing a ceramic phosphor for laser lighting with adjustable light spot according to claim 7, characterized in that: Preparation of the metal reflective layer: The light conversion layer is coated with a metal reflective coating on another surface thereof.

9. The method for preparing a ceramic phosphor for laser lighting with adjustable light spot according to claim 7, characterized in that: The light scattering layer is prepared by immersing one surface of the light conversion layer in a coating solution containing one or more of silicate, silanol and siloxane; the coated light conversion layer is dried and annealed to obtain the light scattering layer covering one surface of the light conversion layer.

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