A long-lasting phosphor resistant to high-alkaline solutions and its preparation method

Abstract

This application proposes a long-lasting phosphor resistant to high-alkaline solutions and a preparation method thereof. The aluminate long-lasting phosphor is coated with phosphate and then with tetraethyl orthosilicate to obtain the high-alkaline solution-resistant long-lasting phosphor. The phosphate coating is first applied, and after the phosphate and phosphor are tightly bonded, a silicon oxide composite coating is then applied. This creates a dense silicon-phosphorus oxide film that effectively resists corrosion in strong alkaline solutions. This method solves the problems of agglomeration and light decay in aluminate long-lasting phosphors and increases their service life in strong alkaline solutions.

Description

Technical Field

[0001] The present application belongs to the technical field of luminescent powders, and in particular relates to a long-lasting phosphor resistant to high-alkaline solutions and a preparation method thereof. Background Art

[0002] Long-lasting phosphors are materials that continue to emit light for minutes, hours, or even days after excitation ceases. Due to their unique optical phenomena, many long-lasting phosphors have been successfully applied in emergency lighting, in vivo bioimaging, and optical information storage. The most widely used long-lasting phosphor is SrAl2O4:Eu 2+ ,Dy 3+ It is a phosphor with bright green long afterglow (λem=510nm) first discovered by Matsuzawa et al. in 1996. 2+ 、Ce 3+ or Mn 2+ As the luminescence center, Dy 3+ 、Nd 3+ Many other aluminate, silicate, and nitride-based long-lasting phosphors doped with rare earth ions as carrier capture centers have been gradually developed, such as Sr4Al 14 O 25 :Eu 2+ ,Dy 3+ ,β-Zn3(PO4)2:Mn 2+ 、M2Si5N8:Eu 2+ ,Tm 3+ (M=Ca, Ba), etc. Current research on long-lasting phosphors focuses primarily on the luminescent center, matrix carrier, luminous brightness, and afterglow duration. There is limited research on their specific application scenarios, such as exposure to sunlight, humidity, strong acidity, and strong alkalinity. For example, the application of long-lasting phosphors in textiles and printing is largely limited by their poor alkaline resistance.

[0003] There are no reports on the alkali resistance of long-lasting phosphors in the prior art, and currently only research on improving alkali resistance in other systems is available for reference. For example, patent document CN106700662A discloses a method for preparing acid- and alkali-resistant, corrosion-resistant aluminum pigments. In an alcohol system, a long-chain silane coupling agent and a silicate ester are used as precursors, which synergistically coat the modified aluminum pigment. After washing and drying, an Al / SiO2 composite pigment with high acid and alkali resistance and high corrosion resistance is obtained. The optimal sample was stable for 48 hours in both a 0.1 mol / L hydrochloric acid solution and a sodium hydroxide solution with a pH of 12. However, this level of alkali resistance does not meet the application requirements of long-lasting phosphors, which generally need to be immersed in an alkaline solution with a pH of around 13.

[0004] Patent document CN114574191B discloses a method for producing acid- and alkali-resistant blue phosphors by coating 5-sulfosalicylic acid with barium sulfate. The method comprises the following steps: fully dissolving the raw material 5-sulfosalicylic acid in water; adding sodium hydroxide solution to the 5-sulfosalicylic acid solution, followed by sodium sulfate solution, and slowly adding barium chloride solution dropwise to produce a white precipitate; centrifuging and washing the white precipitate with deionized water in a high-speed centrifuge; drying the white precipitate and sieving it to obtain the acid- and alkali-resistant blue phosphors coated with 5-sulfosalicylic acid. This method is simple, low-cost, and environmentally friendly, and can be applied in agricultural production to convert ultraviolet light from sunlight into blue light, further improving the efficiency of crop photosynthesis. Furthermore, the coated phosphors obtained by this method are suitable for the highly alkaline pH of approximately 11, which is commonly used in pesticide applications, and the BaSO4 coating method is feasible.

[0005] However, in the solution environment of textile pigments and printing coatings, which generally have a pH of 13, Ba-based 2+ With SO4 2- The BaSO4 coating produced by the precipitation reaction is difficult to form a dense film on the phosphor surface. Therefore, the coated phosphor obtained by this method still cannot overcome the serious problems of agglomeration and light decay in this environment. Therefore, how to achieve alkali-resistant coating technology for aluminate long-lasting phosphors to achieve strong alkalinity resistance and long-lasting phosphors remains a problem that needs to be solved. Summary of the Invention

[0006] The present invention provides a long-lasting phosphor resistant to high-alkaline solutions and a preparation method thereof to solve the problems existing in the related art. The technical solution is as follows:

[0007] In the first aspect, the present invention provides a method for preparing a long-lasting phosphor resistant to high-alkaline solution, wherein the phosphor is an aluminate long-lasting phosphor with a chemical formula of Sr x Al2O4:Eu 2+ ,Dy 3+ , where 0.6≤x≤1.2;

[0008] After the phosphor is coated with phosphate, it is further coated with ethyl orthosilicate to obtain the high-alkaline solution resistant long-lasting phosphor. x Al2O4:Eu 2+ ,Dy 3+ The change of x value will affect its emission color, but has no significant effect on the alkali resistance of the phosphor. When the x value is 0.6-0.8, the emission light is blue-green, when it is 0.8-0.9, it is green, and when it is 0.9-1.2, it is yellow-green.

[0009] In one embodiment, the phosphor powder is first ground before being phosphate coated:

[0010] The powder: water: grinding ball mass ratio is 1: (1.2-1.7): (2.0-2.5), and the mixture is ball-milled for 0.5-1h, and sieved to obtain a phosphor slurry.

[0011] In one embodiment, the process of phosphate coating of phosphor is as follows:

[0012] Add phosphate to the phosphor slurry, adjust the pH to 2-3, and stir at 125-155 rpm for 4-6 hours.

[0013] In one embodiment, the phosphate is a soluble phosphate; preferably, the phosphate is disodium hydrogen phosphate and / or sodium dihydrogen phosphate.

[0014] In one embodiment, the mass of the added phosphate is 10-16% of the mass of the phosphor.

[0015] In one embodiment, the process of using ethyl orthosilicate coating is:

[0016] After the phosphate coating is completed, ethyl orthosilicate is added, and ammonia water is used to adjust the pH to 8.5-10. After the temperature reaction is completed, the mixture is cooled to room temperature to obtain a phosphor slurry coated with silicon-phosphorus oxide.

[0017] In one embodiment, after adding ethyl orthosilicate, stirring is performed for 1-2 hours, and then ammonia water is used to adjust the pH to 8.5-10.

[0018] In one embodiment, the temperature-raising reaction conditions are: raising the temperature to 70-85° C. and stirring at 180-220 rpm for 2-3 hours.

[0019] In one embodiment, after coating with ethyl orthosilicate, separation, washing, and drying are performed to obtain phosphor powder coated with silicon-phosphorus oxide; that is, phosphor powder with long afterglow resistance to high-alkaline solution.

[0020] In a second aspect, an embodiment of the present application provides a long-lasting phosphor resistant to high-alkaline solutions, which is prepared by any of the above-mentioned methods for preparing a long-lasting phosphor resistant to high-alkaline solutions.

[0021] In one embodiment, the phosphor has good fluidity after being in a strong alkaline solution with a pH of 13 for one week.

[0022] In one embodiment, the relative brightness of the phosphor is 82.0%-87.1% after being exposed to a strong alkaline solution with a pH of 13 for one week.

[0023] In one embodiment, the phosphor has a 60-minute afterglow maintenance rate change of less than 5% after being exposed to a pH=13 strong alkaline solution for one week.

[0024] The advantages or beneficial effects of the above technical solution include at least:

[0025] This application describes a method for preparing a long-lasting phosphor resistant to high-alkaline solutions. The method first coats the phosphor with phosphate, which is then tightly bonded to the phosphor. Silicon oxide is then used for a composite coating, resulting in a dense silicon-phosphorus oxide film. This sequential composite coating ensures a tightly bonded interior and a dense exterior, effectively resisting corrosion in highly alkaline solutions. This method also addresses the agglomeration and light decay issues associated with aluminate long-lasting phosphors, extending their lifespan in highly alkaline solutions.

[0026] The present invention discloses a high alkaline solution resistant long afterglow phosphor, which can be used in a strong alkaline solution. After one week in a pH=13 strong alkaline solution, the phosphor has good fluidity, a relative brightness of 82.0%-87.1%, and a 60-minute afterglow maintenance rate change of less than 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an SEM image of the silicon-phosphorus oxide-coated phosphor prepared in Example 3;

[0028] Figure 2 This is a graph showing the results of repeated parallel tests on the alkali resistance of the phosphors of Example 3 and Comparative Example 4. DETAILED DESCRIPTION

[0029] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present application. Therefore, the following description is to be considered as illustrative in nature and not restrictive.

[0030] The main luminescent component of phosphor is metal ions. Under acidic and alkaline conditions, phosphor is particularly prone to agglomeration, which affects the fluidity of the product and makes the product unusable.

[0031] Therefore, the present invention provides a method for preparing a long-lasting phosphor resistant to high-alkaline solution. The phosphor is an aluminate long-lasting phosphor with a chemical formula of Sr x Al2O4:Eu 2+ ,Dy 3+ , where 0.6≤x≤1.2;

[0032] After the phosphor is coated with phosphate, it is further coated with ethyl orthosilicate to obtain the high-alkaline solution-resistant long-afterglow phosphor.

[0033] Because phosphate film formation on the phosphor surface is slower than the hydrolysis reaction of ethyl orthosilicate, phosphate coating is performed first, followed by ethyl orthosilicate coating, to ensure the formation of a maximum -Si-OP- structural network on the phosphor particle surface. A composite coating of phosphate and silicon oxide utilizes the close adhesion of the phosphate film to the phosphor and the compactness of the silicon-phosphorus oxide film to address the agglomeration and light decay issues of aluminate long-lasting phosphors.

[0034] In one embodiment, the phosphor powder is first ground before being phosphate coated:

[0035] The powder: water: grinding ball mass ratio is 1: (1.2-1.7): (2.0-2.5), and the mixture is ball-milled for 0.5-1h, and sieved to obtain a phosphor slurry.

[0036] After ball milling, the surface energy of the phosphor increases and the surface activity is enhanced, which is conducive to the subsequent precipitation of S on the surface of the phosphate and phosphor particles. r2+ 、Al 3+ The reaction forms a phosphate film that adheres tightly to the surface. Therefore, the ball milling process before coating not only allows the particle size to be tailored to customer needs, but also increases the surface activity of the phosphor and enhances the reaction rate and adhesion strength of the subsequent coating.

[0037] In one embodiment, the sieving can be performed by selecting an appropriate sieve, and the specific sieve can be selected according to the product requirements. Preferably, the filtration is performed using a 20-60 mesh sieve to obtain phosphors with a corresponding particle size range.

[0038] In one embodiment, the process of phosphate coating of phosphor is as follows:

[0039] Add phosphate to the phosphor slurry, adjust the pH to 2-3, and stir at 125-155 rpm for 4-6 hours.

[0040] In one embodiment, hydrochloric acid is used to adjust the pH to 2-3.

[0041] Hydrochloric acid is used in the process to adjust the pH to acidic, which increases the film-forming rate of the phosphate film precipitation reaction and the degree of adhesion between the film and the surface of the phosphor particles; the lower the pH, the faster the reaction rate, but if the pH is too low, the phosphor will obviously decompose, resulting in a decrease in yield and luminescence brightness. In order to take into account the reaction speed and the luminescence performance of the phosphor, the pH is set at 2-3.

[0042] In one embodiment, the phosphate is a soluble phosphate; preferably, the phosphate is disodium hydrogen phosphate and / or sodium dihydrogen phosphate.

[0043] In one embodiment, the mass of the added phosphate is 10-16% of the mass of the phosphor.

[0044] In one embodiment, the process of using ethyl orthosilicate coating is:

[0045] After the phosphate coating is completed, ethyl orthosilicate is added, and ammonia water is used to adjust the pH to 8.5-10. After the temperature reaction is completed, the mixture is cooled to room temperature to obtain a phosphor slurry coated with silicon-phosphorus oxide.

[0046] In one embodiment, after adding ethyl orthosilicate, the mixture is stirred for 1-2 hours, and then the pH is adjusted to 8.5-10 using aqueous ammonia. The tolerance of pure phosphate membrane to strong alkali is very poor, because there are a lot of H + In a strong alkaline solution, H + Rapid detachment destroys the integrity of the phosphate film and the bonding strength with the phosphor surface. Therefore, adding TESO to form a composite film network with phosphate is a very critical step. The alkaline TESO can react with H + The slow reaction converts H + Therefore, after adding ethyl orthosilicate, stir for 1-2 hours to remove a large amount of H in the phosphate membrane. + .

[0047] Ammonia is a weak base. Using ammonia to adjust the pH to 8.5-10 allows TEOS to hydrolyze and combine with phosphate to form a dense silicon-phosphorus oxide film. Under acidic conditions, TEOS has difficulty hydrolyzing to silicon oxide, and only under alkaline conditions does TEOS undergo significant hydrolysis. Below a pH of 8, film formation is too slow, while a pH of 11 causes silicon oxide to settle too quickly, resulting in uneven film formation. Furthermore, a high pH weakens the bond between the phosphate film and the phosphor surface, reducing the product's alkali resistance.

[0048] In one embodiment, the temperature-raising reaction conditions are: raising the temperature to 70-85° C. and stirring at 180-220 rpm for 2-3 hours.

[0049] Sodium dihydrogen phosphate or disodium hydrogen phosphate slowly reacts with strontium aluminate long afterglow phosphor under acidic conditions to generate strontium dihydrogen phosphate and aluminum dihydrogen phosphate film coated on the surface of the phosphor particles; after adding ethyl acetate, the pH is adjusted to alkaline with ammonia water, and the ethyl acetate is hydrolyzed, so that strontium dihydrogen phosphate and H in the aluminum dihydrogen phosphate film are reacted. + Gradually separated, on the other hand, silicon oxide compounds and Al 3+ 、Sr 2+ 、P 5+Through oxygen bond connection, a dense [O-Sr-O-Si-OPO-Al]n network is formed to coat the phosphor, thereby improving the luminescence stability of the long-lasting phosphor in a strong alkaline solution without agglomeration.

[0050] Therefore, ethyl orthosilicate is alkaline in aqueous solution. First, ethyl orthosilicate is added to react for a period of time, and then the mildly reactive weak base ammonia water is used for alkaline adjustment. This can slowly drag out the hydrogen ions in the phosphate film, avoiding the decrease in the bonding strength between the phosphate film and the phosphor. At the same time, the ethyl orthosilicate reacts at a high temperature to generate a more dense phosphorus silicon oxide film structure network, thereby achieving the tightness of the membrane coating.

[0051] In one embodiment, after coating with ethyl orthosilicate, separation, washing, and drying are performed to obtain phosphor powder coated with silicon-phosphorus oxide; that is, phosphor powder with long afterglow resistance to high-alkaline solution.

[0052] In one embodiment, the separation step is preceded by filtration through a 300-mesh screen, followed by centrifugal dehydration. After the coating is complete, filtration through a 300-mesh screen can remove large phosphor particles that have aggregated due to poor coating. This not only makes the final product more uniform in particle size, but also further ensures the coating quality of the product.

[0053] In one embodiment, pure water is used for washing until the conductivity of the centrifuge liquid is ≤80 μS / cm.

[0054] In one embodiment, the drying is performed at 130-150° C. for 20-24 hours.

[0055] In a second aspect, an embodiment of the present application provides a long-lasting phosphor resistant to high-alkaline solutions, which is prepared by any of the above-mentioned methods for preparing a long-lasting phosphor resistant to high-alkaline solutions.

[0056] In one embodiment, the phosphor has good fluidity after being in a strong alkaline solution with a pH of 13 for one week.

[0057] In one embodiment, the relative brightness of the phosphor is 82.0%-87.1% after being exposed to a strong alkaline solution with a pH of 13 for one week.

[0058] In one embodiment, the phosphor has a 60-minute afterglow maintenance rate change of less than 5% after being exposed to a pH=13 strong alkaline solution for one week.

[0059] The following is further described with reference to specific embodiments.

[0060] Example 1

[0061] (1) The chemical formula is SrAl2O4:Eu 2+ ,Dy 3+Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill at a powder: water: grinding ball mass ratio of 1:1.2:2.0 for 1 hour, and filtered through a 20-mesh sieve to obtain a phosphor slurry;

[0062] (2) adding sodium dihydrogen phosphate (13% by weight of the phosphor mass) to the phosphor slurry, adjusting the pH to 2 with hydrochloric acid, and then stirring for 4 hours at a speed of 125 rpm to obtain a phosphate-coated phosphor slurry;

[0063] (3) adding ethyl orthosilicate having a phosphor mass concentration of 5% to the slurry obtained in step (2) while stirring, stirring for 1 hour, adding ammonia water to adjust the pH value to 9.0, increasing the stirring speed to 200 rpm, raising the temperature to 75° C., heating and stirring for 3 hours, stopping heating, cooling to room temperature, and filtering through a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide;

[0064] (4) The slurry of step (3) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 135°C and a drying time of 22h to obtain a silicon-phosphorus oxide-coated phosphor powder.

[0065] Example 2

[0066] (1) The chemical formula is SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill at a powder: water: grinding ball mass ratio of 1:1.7:2.5 for 0.5 h, and filtered through a 40-mesh sieve to obtain a phosphor slurry;

[0067] (2) adding 4% of the phosphor mass of disodium hydrogen phosphate and 9% of sodium dihydrogen phosphate to the phosphor slurry, adjusting the pH to 3 with hydrochloric acid, and then stirring for 6 hours at a speed of 130 rpm to obtain a phosphate-coated phosphor slurry;

[0068] (3) adding ethyl orthosilicate having a phosphor mass concentration of 8% to the slurry obtained in step (2) while stirring, stirring for 1 hour, adding ammonia water to adjust the pH value to 9.0, increasing the stirring speed to 180 rpm, raising the temperature to 85° C., heating and stirring for 3 hours, stopping heating, cooling to room temperature, and filtering through a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide;

[0069] (4) The slurry of step (3) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 150°C and a drying time of 20 hours to obtain a phosphor powder coated with silicon-phosphorus oxide.

[0070] Example 3

[0071] (1) The chemical formula is SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill at a powder: water: grinding ball mass ratio of 1:1.5:2.2 for 0.7 h, and filtered through a 60-mesh sieve to obtain a phosphor slurry;

[0072] (2) adding sodium dihydrogen phosphate (13% by weight of the phosphor mass) to the phosphor slurry, adjusting the pH to 2 with hydrochloric acid, and then stirring for 4 hours at a speed of 130 rpm to obtain a phosphate-coated phosphor slurry;

[0073] (3) adding 10% ethyl orthosilicate by mass to the slurry obtained in step (2) while stirring, stirring for 2 h, adding ammonia water to adjust the pH value to 9.0, increasing the stirring speed to 220 rpm, raising the temperature to 70° C., heating and stirring for 3 h, stopping heating, cooling to room temperature, and filtering through a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide;

[0074] (4) The slurry of step (3) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 135°C and a drying time of 20 hours to obtain a silicon-phosphorus oxide-coated phosphor powder.

[0075] Example 4

[0076] (1) The chemical formula is SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill at a powder: water: grinding ball mass ratio of 1:1.5:2.2 for 0.7 h, and filtered through a 60-mesh sieve to obtain a phosphor slurry;

[0077] (2) adding sodium dihydrogen phosphate (10% by weight of the phosphor) to the phosphor slurry, adjusting the pH to 2 with hydrochloric acid, and then stirring for 4 hours at a speed of 125 rpm to obtain a phosphate-coated phosphor slurry;

[0078] (3) adding ethyl orthosilicate having a phosphor mass concentration of 8% to the slurry obtained in step (2) while stirring, stirring for 1 hour, adding ammonia water to adjust the pH value to 8.5, increasing the stirring speed to 190 rpm, raising the temperature to 75° C., heating and stirring for 2 hours, stopping heating, cooling to room temperature, and filtering through a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide;

[0079] (4) The slurry of step (3) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 145°C and a drying time of 20 hours to obtain a phosphor powder coated with silicon-phosphorus oxide.

[0080] Example 5

[0081] (1) The chemical formula is SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill for 0.5 h at a powder: water: grinding ball mass ratio of 1:1.5:2.2, and filtered through a 40-mesh sieve to obtain a phosphor slurry;

[0082] (2) adding sodium dihydrogen phosphate (16% by weight of the phosphor mass) to the phosphor slurry, adjusting the pH to 2 with hydrochloric acid, and then stirring for 5 h at a speed of 155 rpm to obtain a phosphate-coated phosphor slurry;

[0083] (3) adding ethyl orthosilicate having a phosphor mass concentration of 5% to the slurry obtained in step (2) while stirring, stirring for 2 h, adding ammonia water to adjust the pH value to 10.0, increasing the stirring speed to 180 rpm, raising the temperature to 70° C., heating and stirring for 2 h, stopping heating, cooling to room temperature, and filtering through a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide;

[0084] (4) The slurry of step (3) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 150°C and a drying time of 24 hours to obtain a silicon-phosphorus oxide-coated phosphor powder.

[0085] Comparative Example 1 (1) uses the chemical formula SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill at a powder: water: grinding ball mass ratio of 1:1.5:2.2 for 0.7 h, and filtered through a 60-mesh sieve to obtain a phosphor slurry;

[0086] (2) adding sodium dihydrogen phosphate (23% by weight of the phosphor mass) to the phosphor slurry, adjusting the pH to 2 with hydrochloric acid, and then stirring for 4 hours at a speed of 130 rpm to obtain a phosphate-coated phosphor slurry;

[0087] (3) The slurry of step (2) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 135°C and a drying time of 20 hours to obtain phosphorus oxide-coated phosphor powder.

[0088] Comparative Example 2

[0089] (1) The chemical formula is SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, and ball milled in a horizontal ball mill at a powder: water: grinding ball mass ratio of 1:1.5:2.2 for 0.7 h, and filtered through a 60-mesh sieve to obtain a phosphor slurry;

[0090] (2) Adding ethyl acetate with a phosphor mass concentration of 23% to the obtained slurry while stirring, stirring for 2 hours, adding ammonia water to adjust the pH value to about 9.0, increasing the stirring speed to 220 rpm, raising the temperature to 70°C, heating and stirring for 3 hours, stopping heating, cooling to room temperature, and filtering with a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide.

[0091] (3) The slurry of step (2) is centrifuged and dehydrated, and then washed again with pure water until the conductivity of the centrifugal liquid is ≤80μS / cm, and then placed in an oven for drying at a temperature set to 135°C and a drying time of 20 hours to obtain a silicon oxide-coated phosphor powder.

[0092] Comparative Example 3

[0093] This comparative example is basically the same as Example 3, except that the ball milling process in step (1) is deleted. The modified step (1) is: selecting a material with the chemical formula SrAl2O4:Eu 2+ ,Dy 3+ Aluminate long afterglow phosphor powder was used as raw material, added at a powder:water mass ratio of 1:1.5 and stirred evenly, and filtered with a 60-mesh sieve to obtain a phosphor slurry; the other steps were the same as those in Example 3.

[0094] Comparative Example 4

[0095] This comparative example is basically the same as Example 3, except that "filtering through a 300-mesh screen" is omitted in step (3). The modified step (3) is as follows: adding ethyl acetate having a phosphor mass concentration of 10% to the slurry obtained in step (2) while stirring, stirring for 2 hours, adding ammonia water to adjust the pH value to about 9.0, increasing the stirring speed to 220 rpm, raising the temperature to 70°C, heating and stirring for 3 hours, stopping heating, and cooling to room temperature to obtain a phosphor slurry coated with silicon-phosphorus oxide; the other steps and methods are the same as those in Example 3.

[0096] Comparative Example 5

[0097] The difference between Comparative Example 5 and Example 3 is that in step (2), sodium dihydrogen phosphate (13% by weight of the phosphor mass) is added to the phosphor slurry, and then stirred for 12 hours at a speed of 130 rpm to obtain a phosphate-coated phosphor slurry. The other steps are the same as those in Example 3.

[0098] Comparative Example 6

[0099] The difference between Comparative Example 6 and Example 3 is that in step (3), ethyl orthosilicate with a phosphor mass concentration of 10% is added to the slurry obtained in step (2) while stirring, and the mixture is stirred for 2 hours. Ammonia water is added to adjust the pH value to about 7.0, the stirring speed is increased to 220 rpm, the temperature is raised to 70°C, and the mixture is heated and stirred for 3 hours. The heating is stopped, the mixture is cooled to room temperature, and the mixture is filtered through a 300-mesh sieve to obtain a phosphor slurry coated with silicon-phosphorus oxide. The other steps and methods are the same as those in Example 3.

[0100] 1. The silicon-phosphorus oxide-coated phosphor prepared in Example 3 was observed by electron scanning microscope. The SEM image is as follows: Figure 1 shown.

[0101] from Figure 1 It can be seen from the figure that the phosphor is a micron-sized sample with uniform particles.

[0102] 2. The phosphors of Examples 1-5 and Comparative Examples 1-4 were subjected to particle size analysis. The results are shown in Table 1.

[0103] Table 1 Particle size of phosphors of Examples 1-5 and Comparative Examples 1-4

[0104]

[0105] In Table 1, except for Comparative Example 4, which has a particle size D50 of 26 μm, the particle sizes D50 of the other samples are basically around 23 μm. This is related to the deletion of the screen filtration process after the coating in Comparative Example 4. Phosphors with poor coating effects tend to agglomerate to form larger particles, resulting in larger measured particle size data.

[0106] 3. The phosphors of Examples 1-5 and Comparative Examples 1-4 were immersed in a strong alkaline solution with a pH of 13 for one week. The appearance was observed and the luminescence performance change data were tested. The results are shown in Table 2.

[0107] Table 2 Changes in appearance and luminescence properties of samples after being immersed in a strong alkaline solution with pH = 13 for one week

[0108]

[0109]

[0110] In Table 2, the silicon-phosphorus oxide-coated aluminate long-lasting phosphors produced in Examples 1-5 retained over 80% of their luminance after immersion in a strong alkaline solution for one week, with their afterglow performance remaining essentially unchanged. Compared to Example 3, the alkali resistance of Comparative Examples 1-4 decreased to varying degrees. In Comparative Examples 1 and 2, the phosphors coated solely with phosphate or diethyl silicate exhibited luminance below 40% of their initial luminance after alkali immersion, with afterglow performance significantly decreasing by nearly or even exceeding 50%, and exhibited agglomeration after hydrolysis. As can be seen from the luminance and 60-minute afterglow retention, the alkali resistance of the phosphors produced in Comparative Examples 3 and 4, which eliminated the ball milling step and the post-coating sieve filtration step, respectively, decreased slightly by less than 20%. It can be seen from Comparative Examples 5 and 6 that pH has a great influence on the coating effect of phosphate and tetraethyl orthosilicate. After soaking in strong alkaline solution, agglomeration and large light decay phenomena similar to those in Comparative Examples 1 and 2 appeared.

[0111] 4. The phosphors of Example 3 and Comparative Example 4 were immersed in a strong alkaline solution of pH for one week. The alkaline resistance of the phosphors of Example 3 and Comparative Example 4 was tested in parallel. The results are as follows: Figure 2 shown.

[0112] Figure 2 The relative brightness of Example 3 ranged from a minimum of 85.3% to a maximum of 85.5%, with a difference of 0.2% and an average close to 85.4%. The relative brightness of Comparative Example 4 ranged from a minimum of 74.2% to a maximum of 83.6%, with a difference of 9.4% and an average close to 77.8%. This comparison shows that the phosphor of Example 3, obtained after coating and filtration, exhibited greater performance stability.

[0113] In summary, the present application addresses the problem of phosphors being prone to agglomeration and caking in a strong alkaline solution environment. By adopting a composite coating of phosphate and silicon oxide, the close adhesion between the phosphate film and the phosphor and the density of the silicon-phosphorus oxide film are comprehensively utilized to solve the agglomeration and light decay problems of aluminate long-afterglow phosphors, thereby improving the luminous efficiency and service life of the phosphors in a strong alkaline solution environment.

[0114] In the description of this specification, the reference terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless they are mutually inconsistent.

[0115] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0116] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should be included within the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a long-lasting phosphor, characterized in that: The phosphor is aluminate long afterglow phosphor, and its chemical formula is Sr x Al2O4:Eu 2+ ,Dy 3+ , where 0.6≤x≤1.2; After the phosphor is coated with phosphate, it is further coated with ethyl orthosilicate to obtain the long-lasting phosphor; The process of phosphor coating with phosphate is as follows: Add disodium hydrogen phosphate and / or sodium dihydrogen phosphate to the phosphor slurry, adjust the pH to 2-3, and stir at 125-155 rpm for 4-6 hours; the mass of the added phosphate should be 10-16% of the mass of the phosphor; The process of using ethyl orthosilicate coating is as follows: After the phosphate coating is completed, add ethyl orthosilicate and stir for 1-2 hours. Then, use ammonia water to adjust the pH to 8.5-10, increase the temperature to 70-85°C, and stir at 180-220 rpm for 2-3 hours. After the heating reaction is completed, cool to room temperature to obtain a phosphor slurry coated with silicon-phosphorus oxide.

2. The method for preparing a long afterglow phosphor according to claim 1, characterized in that: Before phosphate coating, the phosphor powder is ground into pulp: Ball mill the mixture for 0.5-1 h at a powder: water: grinding ball mass ratio of 1: (1.2-1.7): (2.0-2.5), and sieve to obtain a phosphor slurry.

3. The method for preparing a long afterglow phosphor according to claim 1, wherein: After being coated with ethyl orthosilicate, the phosphor powder coated with silicon-phosphorus oxide is obtained through separation, washing and drying; that is, the phosphor powder having a long afterglow coating.

4. A long afterglow phosphor, characterized in that: The phosphor is prepared by the method for preparing a long afterglow phosphor according to any one of claims 1 to 3.

5. The long-lasting phosphor according to claim 4, characterized in that: The phosphor has good fluidity after being in a pH=13 strong alkaline solution for one week; and / or, relative brightness of 82.0%-87.1%; and / or, the change in afterglow maintenance rate over 60 minutes is less than 5%.

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