Gradient refractive index fluorescent glass structure and preparation method thereof

Abstract

The invention relates to a gradient refractive index fluorescent glass structure and a preparation method thereof, and belongs to the technical field of fluorescent glass. The structure comprises substrate glass and a fluorescent glass coating located on the upper surface of the substrate glass, and the substrate glass has gradient refractive indexes from large to small from the bottom to the upper surface of the substrate glass. The method comprises the following steps: preparing substrate glass, and carrying out gradient crystallization on the substrate glass through laser treatment to prepare substrate glass with a gradient refractive index; the laser is femtosecond laser, the laser wavelength is 800 to 1000 nm, the pulse width is 200 to 800 fs, the pulse frequency is 1 to 10 kHz, the scanning rate is 100 to 500 mm / s, and the repetition frequency is 5 to 10 times; and then preparing fluorescent glass coating slurry, and coating the fluorescent glass coating slurry on the upper surface of the substrate glass with the gradient refractive index for sintering and molding. Layered structures with different refractive indexes are formed through laser processing, it is ensured that continuous refractive index changes are achieved in the whole glass body, and therefore the optical performance is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent glass, and particularly relates to a gradient refractive index fluorescent glass structure and a preparation method thereof. Background Art

[0002] In recent years, due to the continuous maturity and wide application of LED technology, the market of fluorescence conversion materials has been continuously expanding. Fluorescent glass has become the first choice of fluorescence conversion materials due to its good thermal stability and high thermal conductivity. However, there are still deficiencies in the preparation process and optical properties of fluorescent glass, and it is difficult to simultaneously meet high luminous flux and high light extraction efficiency, which restricts the development of high-power lighting sources.

[0003] One of the factors affecting the light extraction efficiency of LEDs is the packaging structure. Since there is a large difference in the refractive index (n) of the LED chip, fluorescent glass, and air, the critical angle of light extraction is small and the Fresnel reflection loss is large, ultimately resulting in a decrease in light extraction efficiency. Therefore, it is necessary to change the packaging structure of the LED to improve the light extraction efficiency.

[0004] To improve the light extraction efficiency, the packaging structure with a gradient refractive index is the most commonly used method at present. Glasses with different refractive indices are stacked and bonded between the glass layers with an adhesive to prepare a glass structure with a gradient refractive index. However, the long-term operation of high-power LEDs will cause the bonding layer to age and crack, seriously affecting the service life of the LEDs. At present, screen printing technology is applied to prepare fluorescent glass with a gradient refractive index. Different refractive index glasses are prepared by adding different regulators, and then mixed with fluorescent powder to form fluorescent glass slurries with different refractive indices; the fluorescent glass slurries with different refractive indices are coated on a glass substrate by screen printing technology and then sintered to form fluorescent glass with a gradient refractive index. However, it is difficult to control the thickness of different fluorescent glass layers by screen printing technology, and there will be certain gaps between the fluorescent glass layers, which also affects the light extraction efficiency of the LEDs. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention proposes a gradient refractive index fluorescent glass structure, which forms a layered structure with different refractive indices through laser treatment to ensure continuous refractive index change throughout the glass body, thereby significantly improving the optical performance.

[0006] It adopts the following technical solutions: A gradient refractive index fluorescent glass structure, comprising a substrate glass and a fluorescent glass coating on the upper surface of the substrate glass, wherein the substrate glass has a gradient refractive index decreasing from the bottom to its upper surface.

[0007] Further, the mass ratio of each component of the substrate glass is 50-70% SiO 2, 10 - 30% Al 2 O 3 , 10 - 30% MgO, 0 - 5% R 2 O, 0 - 5% CaF 2 , where R 2 O is one or more of Na 2 O, K 2 O, Li 2 O.

[0008] Furthermore, the substrate glass is successively divided into a bottom region, a middle region, and a surface region from the bottom to its upper surface. Among them, the refractive index of the surface region is 1.55, the refractive index of the middle region is 1.55 - 1.75, and the refractive index of the bottom region is 1.8 - 1.9.

[0009] Furthermore, the slurry of the fluorescent glass coating includes glass powder, yellow yttrium garnet structure phosphor, as well as solvent and binder; The mass ratio of the glass powder to the yellow yttrium garnet structure phosphor is 9:1, the mass ratio of the solvent to the binder is 8.5:1.5, where the solvent is ethanol or terpineol, and the binder is cellulose and its derivatives; the total mass ratio of the glass powder and the phosphor to the total mass of the solvent and the binder is 1:1; The mass ratio of each component of the glass powder is: 40 - 60% P 2 O 5 , 20 - 40% ZnO, 5 - 10% B 2 O 3 , 0 - 10% Al 2 O 3 , 0 - 10% RO, 0 - 10% R 2 O, where RO is one or more of CaO, BaO, MgO, and R 2 O is one or more of Na 2 O, K 2 O, Li 2 O.

[0010] Furthermore, the refractive index of the fluorescent glass coating is 1.5 - 1.55.

[0011] This application also provides a preparation method of a gradient refractive index fluorescent glass structure, including the following steps: S1. Prepare a substrate glass with a gradient refractive index: Prepare the substrate glass; perform laser treatment on the substrate glass to make it gradient crystallized, and obtain a substrate glass with a gradient refractive index; Among them, the laser is a femtosecond laser with a laser wavelength of 800 - 1000 nm, a pulse width of 200 - 800 fs, a pulse frequency of 1 kHz - 10 kHz, a scanning rate of 100 - 500 mm / s, and a repetition times of 5 - 10 times to achieve crystal structures in different regions and form a predetermined refractive index gradient; S2. Prepare the fluorescent glass coating slurry; S3. Prepare the gradient refractive index fluorescent glass: Coat the fluorescent glass coating slurry onto the upper surface of the substrate glass with a gradient refractive index through screen printing technology, and then sinter it into shape.

[0012] Furthermore, in step S1, the preparation of the substrate glass includes: Prepare the base glass: Weigh the glass raw materials and mix them evenly to obtain a batch; heat the batch to 1600 °C at a rate of 5 °C / min and hold for 60 min, then pour it into a graphite mold for shaping, anneal at 600 °C for 60 min, and then cool down with the furnace; Prepare the substrate glass: Cut the base glass to 10×10×1 mm by wire cutting, and then polish and clean the surface.

[0013] Furthermore, in step S2, the preparation of the fluorescent glass coating slurry includes: Weigh the glass raw materials and mix them evenly to obtain a batch; Heat the batch to 1500 °C at a rate of 5 °C / min and hold for 60 min, then pour it into water for water quenching; Grind the obtained glass to 200 - 300 mesh to obtain glass powder; Weigh 90% glass powder and 10% yellow yttrium garnet structure fluorescent powder according to the mass ratio, and then add a mixed solution of a solvent and a binder with a mass ratio of 8.5:1.5 to obtain the fluorescent glass coating slurry.

[0014] Furthermore, the main crystal phase of the crystallized substrate glass after laser treatment is cordierite.

[0015] The beneficial effects of the present invention compared with the prior art are: 1. The present invention uses a Mg - Al - Si system as the substrate glass, and adding CaF 2 On the one hand, it can increase the refractive index of the substrate glass (>1.8); on the other hand, it can be used as a nucleating agent to precipitate the cordierite structure. The refractive index of cordierite is about 1.5. Precipitating the cordierite structure in the substrate glass can adjust the refractive index of the substrate glass. At the same time, the precipitated cordierite can be used as a luminescent matrix phase to achieve red light emission with a main emission peak at 600 nm to adjust the color temperature.

[0016] 2. By utilizing the fact that the energy of the laser decreases from the upper surface of the glass downward, the number of crystals is regulated to decrease from the upper surface of the glass downward, thereby preparing a substrate glass with a gradient refractive index, which can effectively avoid the voids existing before the traditional gradient refractive index fluorescent glass layer and reduce the large total reflection and Fresnel reflection of light caused by air, thereby enhancing the light extraction efficiency. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of forming a gradient refractive index by laser treating the substrate glass; Figure 2 It is a schematic diagram of total reflection at the interface of the gradient refractive index fluorescent glass prepared in the embodiment of the present invention; Figure 3 It is a schematic diagram of total reflection at the interface of the gradient refractive index fluorescent glass prepared in the comparative example of the present invention.

[0018] Description of the reference numerals: 1. Substrate glass; 2. Fluorescent glass coating. Detailed Embodiment

[0019] To make the present invention clearer and more understandable, the following further describes a gradient refractive index fluorescent glass structure and its preparation method according to the present invention with reference to the drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] A gradient refractive index fluorescent glass structure includes a substrate glass 1 and a fluorescent glass coating 2 on the upper surface of the substrate glass 1. Among them, the substrate glass 1 has a gradient refractive index that decreases from the bottom to its upper surface.

[0021] In this embodiment, the mass ratios of the components of the substrate glass 1 are 50 - 70% SiO 2 , 10 - 30% Al 2 O 3 , 10 - 30% MgO, 0 - 5% R 2 O, 0 - 5% CaF 2 , where R 2 O is one or more of Na 2 O, K 2 O, Li 2 O.

[0022] The substrate glass 1 is sequentially divided into a bottom region, a middle region, and a surface region from the bottom to its upper surface. Correspondingly, the refractive index of the surface region is 1.55, the refractive index of the middle region is 1.55 - 1.75, and the refractive index of the bottom region is 1.8 - 1.9.

[0023] The slurry of the fluorescent glass coating 2 includes glass powder, yellow yttrium garnet structure fluorescent powder, as well as a solvent and a binder; The mass ratio of the glass powder to the yellow yttrium garnet structure phosphor is 9:1, and the mass ratio of the solvent to the binder is 8.5:1.5. The solvent is ethanol or terpineol, and the binder is cellulose and its derivatives; the total mass ratio of the glass powder and the phosphor to the total mass of the solvent and the binder is 1:1; The mass ratio of each component of the glass powder is: 40-60% P 2 O 5 、20-40% ZnO, 5-10% B 2 O 3 、0-10%Al 2 O 3 、0-10% RO, 0-10% R 2 O, where RO is one or more of CaO, BaO, and MgO, and R 2 O is one or more of Na 2 O, K 2 O, Li 2 O.

[0024] The refractive index of the sintered fluorescent glass coating 2 is 1.5-1.55.

[0025] A preparation method of a gradient refractive index fluorescent glass structure provided by the present application includes the following steps: S1. Prepare a substrate glass with a gradient refractive index: Obtain the substrate glass; 1. Obtain the base glass: The mass ratio of each component of the substrate glass is 50-70% SiO 2 、10-30%Al 2 O 3 、10-30% MgO, 0-5% R 2 O, 0-5% CaF 2 , where R 2 O is one or more of Na 2 O, K 2 O, Li 2 O. In this embodiment, the mass percentages of each component of the substrate glass are 60% SiO 2 、20% Al 2 O 3 、15% MgO, 2% Na 2 O, 3% CaF 2 . Accurately weigh the raw materials, mix them evenly in a mortar to obtain a batch mixture.

[0026] Then heat the batch mixture to 1600 °C at a rate of 5 °C / min and hold for 60 min, then pour it into a graphite mold for molding, and anneal at 600 °C for 60 min, and then cool with the furnace to obtain the base glass.

[0027] 2. Obtain the substrate glass: Cut the obtained base glass into 10×10×1 mm by wire cutting, and then polish and clean the surface to obtain the substrate glass with a refractive index of 1.85.

[0028] Obtain the substrate glass with a gradient refractive index; As Figure 1 shown, perform laser treatment on the substrate glass, and the laser is incident from the upper surface of the substrate glass downward. Here, the laser wavelength is 800 nm, the pulse width is 300 fs, the pulse frequency is 2 kHz, the scanning rate is 100 mm / s, and the number of repetitions is 5 times to obtain the substrate glass 1 with a gradient refractive index, where the surface area (laser treatment surface) n = 1.55, the middle area n = 1.55 - 1.75, and the bottom area n = 1.85. The main crystal phase of the substrate glass after laser treatment is cordierite.

[0029] S2. Prepare the fluorescent glass coating slurry: 1. The mass ratios of the components of the glass powder in the fluorescent glass coating slurry are: 40 - 60% P 2 O 5 、20 - 40% ZnO、5 - 10% B 2 O 3 、0 - 10% Al 2 O 3 、0 - 10% RO、0 - 10% R 2 O, where RO is one or more of CaO, BaO, and MgO, and R 2 O is one or more of Na 2 O, K 2 O, and Li 2 O. In this embodiment, the mass percentages of the glass powder components of the fluorescent glass coating are 45% P 2 O 5 、20% ZnO、10% B 2 O 3 、5% Al 2 O 3 、5% CaO、5% MgO、5% Na 2 O、5% K 2 O. Accurately weigh the raw materials and mix them evenly in a mortar to obtain the batch mixture.

[0030] 2. Heat the batch mixture to 1500 °C at a rate of 5 °C / min and hold for 60 min, and then pour it into water for water quenching.

[0031] 3. Grind the obtained glass to 200 - 300 mesh to obtain the glass powder.

[0032] 4. Mix the glass powder and the yellow yttrium garnet structure phosphor (mass ratio 9:1) evenly, and then add the mixed solution of the solvent and the binder to prepare a fluorescent glass layer slurry with a refractive index of 1.5. Herein, the solvent is ethanol or terpineol, the binder is cellulose and its derivatives, and the mass ratio of the solvent to the binder is 8.5:1.5. For example, the solvent and the binder are a mixed solution of ethanol and ethyl cellulose (mass ratio 8.5:1.5) (wherein, the total mass of the glass powder and the phosphor is in a ratio of 1:1 to the total mass of ethanol and ethyl cellulose).

[0033] S3. Prepare the gradient refractive index fluorescent glass: Coat the fluorescent glass layer slurry onto the substrate glass by screen printing technology, then heat it to 700 °C at a rate of 5 °C / min and sinter for 60 min, and then cool it with the furnace to obtain the gradient refractive index fluorescent glass.

[0034] Comparative example A method for preparing a fluorescent glass structure provided in the comparative example of this application does not adopt a laser treatment method. Specifically, it includes the following steps: S1. Prepare the substrate glass: 1. Prepare the base glass: The mass percentages of the components of the substrate glass are 60% SiO 2 、20% Al 2 O 3 、15% MgO, 2% Na 2 O, 3% CaF 2 , accurately weigh the raw materials, mix them evenly in a mortar to obtain a batch mixture.

[0035] Then heat the batch mixture to 1600 °C at a rate of 5 °C / min, hold for 60 min, pour it into a graphite mold for molding, and anneal at 600 °C for 60 min, and then cool it with the furnace to obtain the base glass.

[0036] 2. Prepare the substrate glass: Cut the obtained base glass to 10×10×1 mm by wire cutting, and then polish and clean the surface to obtain a substrate glass with a refractive index of 1.85.

[0037] S2. Prepare the fluorescent glass coating slurry: 1. The mass percentages of the glass powder components of the fluorescent glass layer are 45% P 2 O 5 、20% ZnO, 10% B 2 O 3 、5% Al 2 O 3 、5% CaO, 5% MgO, 5% Na 2 O, 5% K2 O, accurately weigh the raw materials, mix them evenly in a mortar to obtain a batch mixture.

[0038] 2. Heat the batch mixture at a rate of 5 °C / min to 1500 °C and hold for 60 min, then pour it into water for water quenching.

[0039] 3. Grind the obtained glass to 200 - 300 mesh to obtain glass powder.

[0040] 4. Mix the glass powder evenly with yellow yttrium garnet - structured phosphor (mass ratio 9:1), then add a mixed solution of ethanol and ethyl cellulose (mass ratio 8.5:1.5) (where the total mass of the glass powder and phosphor is in a ratio of 1:1 to the total mass of ethanol and ethyl cellulose) to obtain a fluorescent glass layer slurry with a refractive index of 1.5.

[0041] S3. Prepare gradient - refractive - index fluorescent glass: Coat the fluorescent glass layer slurry onto the substrate glass by screen - printing technology, then heat it at a rate of 5 °C / min to 700 °C and sinter for 60 min, and then cool it in the furnace to obtain the gradient - refractive - index fluorescent glass.

[0042] Through the comparison of the fluorescent glasses obtained from the examples and comparative examples, Figure 2 is a schematic diagram of total internal reflection at the interface of the gradient - refractive - index fluorescent glass prepared in the example. Since the refractive index gradually decreases from the LED chip to the encapsulation material, the total internal reflection at the interface is small, and the light - emitting efficiency increases. Figure 3 is a schematic diagram of total internal reflection at the interface of the fluorescent glass prepared in the comparative example. The large refractive - index difference causes total internal reflection at the interface, resulting in a decrease in the light - emitting efficiency.

[0043] Generally speaking, in this application, a system with Mg - Al - Si as the substrate glass is first used, and CaF 2 is added as a refractive - index regulator and nucleating agent; then the substrate glass is subjected to laser treatment, and by controlling the number of local crystallizations, different refractive indices are obtained, so that the glass substrate forms a predetermined gradient refractive index; afterwards, the fluorescent glass coating is coated on the substrate glass through screen - printing technology and low - temperature sintering technology to obtain the gradient - refractive - index fluorescent glass. In the present invention, by laser - treating the substrate glass, using the energy of the laser to decrease from the glass surface downwards, the number of crystallizations is regulated to decrease from the glass surface downwards, forming a layered structure with different refractive indices, ensuring a continuous refractive - index change throughout the glass body. On the one hand, it can reduce the total internal reflection and Fresnel reflection of light caused by too large a refractive - index difference at the encapsulation interface; on the other hand, compared with traditional gradient - refractive - index fluorescent glasses, it can avoid the existence of voids between each layer of fluorescent glass, which affects the light - emitting efficiency.

[0044] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And these obvious changes or modifications derived from the essence of the present invention still fall within the protection scope of the present invention.

Claims

1. A gradient refractive index fluorescent glass structure, comprising a substrate glass (1) and a fluorescent glass coating (2) located on the upper surface of the substrate glass (1), characterized in that: The substrate glass (1) has a gradient refractive index from large to small from the bottom to the upper surface.

2. The gradient refractive index fluorescent glass structure according to claim 1, characterized in that: The mass ratio of the components of the substrate glass (1) is 50-70% SiO2, 10-30% Al2O3, 10-30% MgO, 0-5% R2O, and 0-5% CaF2, wherein R2O is one or more of Na2O, K2O, and Li2O.

3. The gradient refractive index fluorescent glass structure according to claim 1, characterized in that: The substrate glass (1) is divided into a bottom region, a middle region and a surface region from the bottom to the upper surface thereof, wherein the refractive index of the surface region is 1.55, the refractive index of the middle region is 1.55-1.75, and the refractive index of the bottom region is 1.8-1.

9.

4. The gradient refractive index fluorescent glass structure according to claim 1, characterized in that: The slurry of the fluorescent glass coating (2) comprises glass powder, yellow yttrium garnet structure fluorescent powder, solvent and binder; The mass ratio of the glass powder and the yellow yttrium garnet structure phosphor is 9:1, the mass ratio of the solvent and the binder is 8.5:1.5, wherein the solvent is ethanol or pine alcohol, and the binder is cellulose and its derivatives; the total mass ratio of the glass powder and the phosphor to the total mass ratio of the solvent and the binder is 1:1; The mass ratio of each component of the glass powder is: 40-60% P2O5, 20-40% ZnO, 5-10% B2O3, 0-10% Al2O3, 0-10% RO, 0-10% R2O, wherein RO is one or more of CaO, BaO, MgO, and R2O is one or more of Na2O, K2O, and Li2O.

5. The gradient refractive index fluorescent glass structure according to claim 1, characterized in that: The refractive index of the fluorescent glass coating (2) is 1.5-1.

55.

6. The method for preparing a gradient refractive index fluorescent glass structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Preparation of substrate glass with gradient refractive index: Producing substrate glass; performing laser treatment on the substrate glass to make it gradient crystallized, thereby producing substrate glass with a gradient refractive index; Wherein, the laser is a femtosecond laser with a laser wavelength of 800-1000 nm, a pulse width of 200-800 fs, a pulse frequency of 1kHz-10 kHz, a scanning rate of 100-500 mm / s, and a repetition number of 5-10 times, so as to realize the crystal structure of different regions and form a predetermined refractive index gradient; S2, preparing fluorescent glass coating slurry; S3. Preparation of gradient refractive index fluorescent glass: The fluorescent glass coating slurry is coated onto the upper surface of the substrate glass with a gradient refractive index by screen printing technology, and then sintered into shape.

7. The method for preparing a gradient refractive index fluorescent glass structure according to claim 6, characterized in that: In step S1, the preparation of the substrate glass includes: Prepare basic glass: weigh glass raw materials and mix them evenly to prepare batch material; heat the batch material to 1600°C at 5°C / min and keep it at that temperature for 60 min, then pour it into a graphite mold for molding, and anneal it at 600°C for 60 min, and then cool it with the furnace; The substrate glass was prepared by cutting the base glass into pieces of 10×10×1 mm by wire cutting, and then the surface was polished and cleaned.

8. The method for preparing a gradient refractive index fluorescent glass structure according to claim 6, characterized in that: In step S2, preparing the fluorescent glass coating slurry comprises: Weigh glass raw materials and mix them evenly to obtain a batch material; The batch was heated to 1500 °C at 5 °C / min and kept at this temperature for 60 min, then poured into water for water quenching; Grinding the obtained glass to 200-300 mesh to obtain glass powder; 90% of glass powder and 10% of yellow yttrium garnet structure phosphor are weighed and mixed according to the mass ratio, and then a mixed solution of a solvent and a binder in a mass ratio of 8.5:1.5 is added to prepare a fluorescent glass coating slurry.

9. The method for preparing a gradient refractive index fluorescent glass structure according to claim 6, characterized in that: The main crystal phase of the substrate glass crystal after laser treatment is cordierite.

Images