CN102618287B - Method for preparing yellowgreen fluorescent powder for light-emitting diodes (LEDs) - Google Patents

Abstract

The invention discloses a method for preparing yellow-green fluorescent powder for LEDs , which belongs to the field of preparation of luminescent materials. The method includes steps: batching, mixing, firing, crushing, cleaning, drying, and sieving and packaging. Features: a pre-processing step is added before the batching step. The pre-processing step includes sieving the matrix material, activating the dehumidification and compounding of the flux to form a compound flux. The mixing method is to put the dehumidified activator and compound flux into the three-dimensional motion mixer and mix them, and then introduce the premix and the sieved matrix material into the mixture. Mixing in the machine; crushing is to screen the fired material by a vibrating sieve, and then screened by an ultrasonic grading sieve, and then introduced into a jet mill for crushing; cleaning is to clean and classify the powder to be cleaned; The powder is classified into the particle size of the finished product, and the yellow-green phosphor powder for LED is obtained after packaging . Advantages: It is guaranteed that the obtained yellow-green phosphor has very ideal primary and secondary characteristics.

Description

Preparation method of yellow-green fluorescent powder for LED

technical field

The invention belongs to the technical field of luminescent material preparation, and in particular relates to a preparation method of yellow-green fluorescent powder for LEDs.

Background technique

Because white light LED has the characteristics of energy saving, environmental protection, long service life, low working voltage and fast response speed, and can basically meet all human requirements for artificial light sources, it is widely used in indoor, especially outdoor (also called outdoor) lighting. Backlights for outdoor lighting such as landscape lighting, traffic lights, car lights, advertisements and display screens are the fourth generation of light sources after fluorescent lamps and HID lamps.

At present, there are three main ways to realize white LEDs: one is to apply yellow phosphor (mainly YAG: Ce) on the blue chip, and mix blue light and fluorescence to form white light; the other is to combine red, green and blue Three colors of chips are combined and packaged, and the light emitted by the chip is directly mixed into white light; the third is to use the near-ultraviolet light chip to excite phosphors of red, green, and blue colors to mix into white light. Among these three methods, the latter two methods are difficult to be widely used due to the relatively complicated circuits and/or the lack of suitable phosphors or chips, while the first method is currently used due to its simple circuit structure and relatively cheap cost. White LED lighting dominates.

The technical information about the preparation method of the yellow fluorescent powder for LED is widely found in published Chinese and foreign patent documents, such as CN1482208A, CN101126024A (high temperature solid phase method); CN1664063A, CN101249978A (sol-gel method); CN101113333A, CN101012376A (precipitation method); CN1398817A (combustion method); CN1052745C (microwave method); CN1775904A, CN1597841A (gas phase method); US6614179B1 (high temperature solid phase method).

Furthermore, representative public documents such as the "synthesis method of phosphor powder for white light LED" recommended by publication number CN101760196, the "yellow phosphor powder and its preparation method" provided by CN101914381A, the "preparation method of yellow phosphor powder" introduced by CN101948693A, CN101962547A discloses "a yellow phosphor for white LEDs and its co-preparation method" and CN102234511A discloses "a method for preparing yellow phosphors for white LEDs", and so on.

The typical literature introduction of the preparation method of yellow-green fluorescent powder for LED is as "a kind of yellow-green fluorescent powder material and preparation method" published by Chinese patent application publication number CN102352242A, "a kind of fluorescent powder material and its preparation" introduced by publication number CN1927996A Method and white LED electric light source", CN1919854A provides "compound, phosphor composition containing it and light-emitting device" and CN101824321A discloses "a phosphor powder for white LED based on blue light excitation and its preparation method", etc. .

Whether it is yellow phosphor powder for LED or yellow-green phosphor powder for LED, the preparation methods are basically the same, that is, the steps involved are: batching, mixing, firing (sintering), crushing (customarily called crushing or Ball milling), cleaning, drying and sieving to obtain yellow or yellow-green fluorescent powder for LED.

As known in the industry, red-visible up-conversion materials can be divided into three categories according to the composition of the matrix: one is halogen-containing compounds; the other is sulfide and oxide; the third is activators (mainly rare earth elements). The choice of the matrix depends on the phonon energy. Generally, the greater the phonon energy of the matrix, the stronger the non-radiative relaxation (also called transition) of rare earth ions, and the lower the upconversion rate. Therefore, in the preparation of luminescent A material with a lower phonon cut-off energy can be selected as a material to obtain a higher upconversion luminous efficiency (for details, please refer to P123-126, Volume 21, Issue 2, "Journal of China Rare Earth Society").

The matrix materials of phosphors mainly include aluminate phosphors represented by Al ₂ O ₃ ; borate phosphors represented by B ₂ O ₃ ; and silicate phosphors represented by SiO ₂ . Aluminate phosphors represented by Al ₂ O ₃ are commonly used.

The preparation method of yellow-green fluorescent powder for LEDs in the prior art has the disadvantages of the following two aspects: one, due to the host material (Al ₂ O ₃ , Lu ₂ O ₃ and Ga ₂ O ₃ ), the activator (CeO ₂ ) and the flux H ₃ BO ₃ lack pre-treatment measures, so it is difficult to select the required phosphor powder with relatively close particle size specifications, and the luminous intensity and luminous performance are poor. Because the manufacturer of yellow-green phosphor powder for LEDs purchased from commercial channels and shown in Figure 1 as one of the main matrix materials, Al ₂ O ₃ only roughly meets the requirements of D ₅₀ (Note: D ₅₀ is also called the median diameter or median particle size, and D ₅₀ is used to represent the average particle size of the powder), more specifically, since the Al ₂ O ₃ matrix material has both alumina with a particle size of about 5.2 μm and a particle size of Alumina with a particle size of 1-3μm, and alumina with a particle size of 9-15μm, so the particle size distribution range is wide, so it is difficult to choose a relatively close particle size specification to prepare the required phosphor, which eventually leads to high temperature solidification. In the phase reaction, a large difference in the grain size of the crystal lattice occurs. And because the amount of rare earth activator materials such as CeO ₂ in the entire formula is relatively small relative to the matrix materials (Al ₂ O ₃ , Lu ₂ O ₃ and Ga ₂ O ₃ ), and the rare earth materials are easy to absorb moisture , often ignore the moisture content, that is, do not dehumidify, so in the high-temperature solid-state reaction process of the phosphor powder, the amount of rare earth materials is insufficient, resulting in defects in the crystal lattice of the product generated by the reaction, thus affecting the luminous intensity of the phosphor powder. Have a certain impact. Also because the flux plays an important role in the whole process of ion diffusion and formation of a luminescent matrix with a complete lattice, which not only affects the grain distribution and luminous efficiency of the phosphor, but also affects the hardness of the sintered block. If the hardness is too large, the crystal morphology will be destroyed in the subsequent treatment, which will affect the generation performance of the phosphor; secondly, in the mixing step, the matrix materials (Al ₂ O ₃ , Lu ₂ O ₃ and Ga ₂ O ₃ ) activator (CeO ₂ ) and flux (H ₃ BO ₃ ) are mixed in a rotating container or in a stirring shaft-type stirring container, and each stirring container can only do circular motion , so it can only be obtained by prolonging the mixing time (usually about 40 hours) to obtain a relatively uniform degree. However, due to the long-time mixing and the fact that various raw materials are dry powders, under long-term movement, the powders rub against each other and generate heat, which increases the viscosity, and static electricity is generated during the friction process, causing agglomeration , the mixture obtained by this mixing method is shown in Figure 2, which is a scanning electron microscope (SEM) figure, as can be seen from Figure 2, even after mixing for about forty hours, the mixing effect is still It is unsatisfactory, and the lack of mixing effect will cause the activation material and fluxing material which account for a small proportion in the formula to not be uniformly dispersed around the matrix material. The grains with more grains grow larger, and the opposite side is small, and the lattice with a little more active material distribution around the matrix material grows completely, and the lattice defects on the opposite side are serious. Due to these drawbacks, the obtained yellow phosphor powder shown in Figure 3 lacks uniform particle size distribution and inconsistent lattice morphology, which ultimately leads to poor primary and secondary properties of the phosphor (primary properties: absorption spectrum, Excitation spectrum, emission spectrum, quantum efficiency and luminous efficiency, etc.; secondary characteristics: dispersion, stability and light decay characteristics); third, as shown in Figure 4, due to the usual Therefore, in the process of friction between powder and ball milling media such as agate balls, glass balls and/or corundum balls, although large particles are broken, small particle size powders are also ground finer , so according to the well-known theory in the industry, when the particle size of the powder is less than 1 μm, it almost no longer has the effect of luminescence, which leads to the excessively wide particle size of the powder and more invalid luminescent particles. If airflow crushing is purely used, although the degree of damage to the crystal lattice is significantly lower than that of ball milling, due to the lack of disintegration of the agglomerated particles before the airflow crushing, the impact of the powder itself is quite different, resulting in the force Inhomogeneous, so the lack of ball milling will also occur; Fourth, as shown in Figure 5, since the crushed powder (dry powder) is usually introduced into a container with a stirrer in the cleaning step and stirred, it will be removed after standing for clarification. Water, and repeated several times, so it is objectively difficult to remove ultrafine powder and large particle size powder in this process, resulting in too wide particle size distribution, because ultrafine powder (particle size ≤ 1 μm) does not have luminous efficacy; its Fifth, since the cleaned and dried powder is only sieved through a 100-250 mesh sieve before being packaged, there is a phenomenon of coexistence of fine particle size and large particle size powder in the yellow-green phosphor, see Figure 6 for details .

In view of the above prior art, it is necessary to improve it. For this reason, the applicant has made positive and beneficial repeated attempts, and the technical solution to be introduced below is produced under this background.

Contents of the invention

The task of the present invention is to provide a kind of matrix material that helps to select the relative concentration of particle size distribution in a targeted manner so as to meet the requirements of preparing fluorescent powder with good primary and secondary characteristics, and is beneficial to control the water content of the activator and reduce the cost. In order to ensure that the phosphor powder has an ideal lattice morphology, it can improve the luminous intensity and thermal stability, it is beneficial to improve the uniformity of the crystal grain distribution of the phosphor powder, so as to improve the luminous efficiency and facilitate the improvement of matrix materials, activators and fluxes. The mixing effect of the three ensures uniform particle size distribution of the produced powder, complete crystal lattice morphology, and a method for preparing yellow-green phosphors for LEDs that is good at discarding invalid luminescent particles and controlling the particle distribution range.

The task of the present invention is accomplished like this, a kind of preparation method of yellow-green fluorescent powder for LED, the steps that this method comprises are batching, mixing, firing, crushing, cleaning, drying and sieving packaging successively, wherein, The batching is to weigh the matrix material, the activator and the flux according to the mass percentage, and it is characterized in that: a pre-processing step is added before the batching step, and the pre-processing step includes the matrix Material sieving, dehumidification of the activator and compounding of the flux into a composite flux, the mixing is to first put the dehumidified activator and composite flux into a three-dimensional motion mixer for mixing, And control the mixing time and the spindle speed of the three-dimensional motion mixer to obtain the premix, then introduce the premix and the sieved matrix material into the three-dimensional motion mixer for mixing, and control the mixing time and control of the three-dimensional motion mixer The main shaft speed of the three-dimensional motion mixer is used to obtain the material to be fired; the crushing is to screen the fired powder obtained in the firing step first by a vibrating screen, then by an ultrasonic grading screen, and then introduce a jet mill for crushing , to obtain the powder to be cleaned, and control the inlet pressure and outlet pressure of the jet mill; the cleaning is to introduce the powder to be cleaned into the cleaning, sedimentation and classification device for cleaning and classification, and obtain the classified drying Powder: the sieving is to classify the powder obtained in the drying step through an airflow grading sieve, and obtain the yellow-green fluorescent powder for LEDs after the packaging step.

In a specific embodiment of the present invention, the sieving of the matrix material is to sieve the matrix material into three grades with a particle size of 1-4.4 μm, 4.5-6.5 μm and 6.6-10 μm by means of an air-flow type grading sieve; The dehumidification of the activator is to put the activator into an oven for baking, and control the baking temperature and baking time, as well as control the moisture content of the activator.

In another specific embodiment of the present invention, the control of the mixing time of the three-dimensional motion mixer is to control the mixing time to 3-4h, and the control of the spindle speed of the three-dimensional motion mixer is to control the spindle speed to 8-12r/min; the mixing time of the three-dimensional motion mixer is controlled to be 10-20h, and the spindle speed of the three-dimensional motion mixer is controlled to be 12-18r/min.

In yet another specific embodiment of the present invention, the matrix material is a mixture of Al ₂ O ₃ , Lu ₂ O ₃ and Ga ₂ O ₃ ; the activator is CeO ₂ ; the composite auxiliary The flux is a combination of H ₃ BO ₃ , BaF ₂ , AlF ₂ and SrF ₂ .

In yet another specific embodiment of the present invention, the control of the baking temperature is to control the temperature to 100-120°C, the control of the baking time is to control the time to 60-240min, and the control of the activator The water content is to control the water content to 0.05-0.5%.

In yet another specific embodiment of the present invention, the mass percent of Al ₂ O ₃ is 13-25%, the mass percent of Lu ₂ O ₃ is 60-72.5%, and the Ga ₂ The mass percentage of O ₃ is 2-14%, the mass percentage of CeO ₂ is 0.3-5.8%; the mass percentage of the composition composed of H ₃ BO ₃ , BaF ₂ , AlF ₂ and SrF ₂ is 0.18-7.18%, wherein: the mass percentage of _H3BO3 is 7-25%, the mass percentage of _BaF2 is 25-48 _% , and the mass percentage of _AlF2 is 25-41% , the mass percent of the SrF ₂ is 4-25%.

In a more specific embodiment of the present invention, the mesh number of the vibrating sieve is 200-250 mesh; the mesh number of the ultrasonic grading sieve is 300-500 mesh, and the pulverization by the jet mill is The powder with a _D50 particle size of 10-20 μm sieved by an ultrasonic grading sieve is pulverized into a powder with a _D50 particle size of 7-8 μm. The pressure is controlled at 0.8-1.2MPa, and the outlet pressure is controlled at 0.4-0.8MPa.

In a further specific embodiment of the present invention, the cleaning, sedimentation and classification device includes a stirring container with a stirrer; a first extraction mechanism, a second extraction mechanism and a third extraction mechanism, the first extraction mechanism It includes a first timing control valve, a first extraction pump, a first storage tank and a first pipeline, the first timing control valve and the first extraction pump are sequentially connected in the middle of the first pipeline, and one end of the first pipeline is connected to the The upper part of the stirring container in the height direction is connected, and the other end of the first pipeline extends into the first storage tank, wherein the first timing control valve is located between the stirring container and the first extraction pump, and the second extraction mechanism includes a second Two timing control valves, the second extraction pump, the second storage tank and the second pipeline, the second timing control valve and the second extraction pump are connected in the middle of the second pipeline in turn, and one end of the second pipeline is connected to the stirring container The middle part of the height direction is connected, and the other end of the second pipeline extends into the second storage tank, wherein the second timing control valve is located between the stirring container and the second extraction pump, and the third extraction mechanism includes a third timing The control valve, the third extraction pump, the third storage tank and the third pipeline, the second timing control valve and the second extraction pump are connected in the middle of the third pipeline in sequence, and the height of one end of the third pipeline and the stirring container The lower part of the direction is connected, and the other end of the third pipeline extends into the third storage tank, wherein the third timing control valve is located between the stirring container and the third extraction pump.

In yet another specific embodiment of the present invention, the particle size classification of the finished product through the airflow classification sieve is to sieve the powder obtained in the drying step to obtain a particle size distribution range of D ₁₀ =3-5 μm , D ₅₀ =7-8 μm and D ₉₀ =10-12 μm finished powder.

In the technical solution provided by the present invention, since the matrix material is screened before mixing, the matrix material with a relatively concentrated particle size distribution can be selected and put into the subsequent mixing step to be mixed together with the activator and flux to meet the requirements of the preparation. The particle size distribution of the powder is uniform and the crystal lattice morphology is complete, which finally enables the phosphor to have excellent primary and secondary characteristics; due to the dehumidification of the activator, the moisture content of the activator is effectively controlled to ensure that the phosphor has ideal crystal lattice morphology and improve luminous efficiency and thermal stability (light decay rate), so that the brightness of the phosphor powder is increased by 5-10%, and the light decay rate is reduced by 10-20%; It is formulated as a composite flux, so that the firing temperature can be reduced in the subsequent firing steps, and the firing temperature is reduced from 1550-1650°C in the prior art to 1400-1500°C, which not only prolongs the service life of the firing furnace, It also embodies energy saving. In addition, it can effectively control the hardness of the fired powder, improve the lattice damage caused by the excessive hardness of the powder during the post-processing of the powder, improve the uniformity of the grain distribution of the phosphor, and improve the The luminous efficiency of phosphor powder; since the premix obtained by mixing the activator and the flux is mixed with the matrix material, and the three-dimensional motion mixing method is used for mixing, the ideal mixing effect can be obtained, and the powder particle size The distribution is uniform, the crystal lattice morphology is complete, and because the invalid luminescent particles are discarded and the distribution range of the particles is controlled, it is fully guaranteed that the obtained yellow-green phosphor has very ideal primary and secondary characteristics.

Description of drawings

Fig. 1 is a scanning electron microscope image of a matrix material Al ₂ O ₃ purchased from commercial channels.

Fig. 2 is a scanning electron microscope image of a mixture of matrix material, activator and flux in the prior art.

FIG. 3 is a scanning electron micrograph of a yellow-green phosphor in the prior art.

Fig. 4 is a particle distribution diagram of phosphor screen powder obtained after ball milling in the prior art.

FIG. 5 is a distribution diagram of phosphor particles after washing in the prior art.

Fig. 6 is a scanning electron micrograph of the dried powder sieved through a 100-250 mesh sieve in the prior art.

Fig. 7 is a scanning electron micrograph of the matrix material Al ₂ O ₃ sieved by an air-flow classifying sieve according to the method of the present invention.

Fig. 8 is a scanning electron micrograph of the mixture obtained by first mixing the rare earth activator and flux with the aid of a three-dimensional motion mixer, and then mixing the matrix material with the three-dimensional motion mixer in the method of the present invention.

Fig. 9 is a distribution diagram of phosphor particles obtained after crushing by the method of the present invention.

Fig. 10 is a distribution diagram of phosphor particles after cleaning by the method of the present invention.

Fig. 11 is a schematic diagram of the cleaning, sedimentation and classification device used in the method of the present invention.

Fig. 12 is a scanning electron micrograph of the yellow-green powder obtained by classifying the dried powder according to the method of the present invention.

Detailed ways

Example 1:

See Figures 7 through 12.

The preparation method of yellow-green fluorescent powder for LED comprises the following steps: batching, mixing, firing, crushing, cleaning, drying and sieving, wherein: the batching is to weigh the matrix material and the activator according to the mass percentage And take the flux, the matrix material is the mixture of Al ₂ O ₃ , Lu ₂ O ₃ and Ga ₂ O ₃ , wherein the mass percentage of Al ₂ O ₃ (which has been sieved) is 25%, and the mass percentage of Lu ₂ O ₃ The percentage is 60%, the mass percentage of Ga ₂ O ₃ is 2.2%, the activator is CeO ₂ , the mass percentage of CeO ₂ is 5.8%, and the flux is a combination of H ₃ BO ₃ , BaF ₂ , AlF ₂ and SrF ₂ material, namely composite flux, the mass percent of the composite flux is 7%, wherein: the mass percent of H ₃ BO ₃ in the composite flux is 25%, the mass percent of BaF ₂ is 46%, the mass percent of AlF ₂ The mass percentage is 25%, and the mass percentage of SrF ₂ is 4%. As the technical gist of the technical solution provided by the present invention, the Al ₂ O ₃ of the aforementioned matrix material, the activator CeO ₂ and the flux agent are composed of H ₃ BO ₃ , BaF 2 , AlF _{2 and} SrF ₂ before entering the batching. Pre-treatment of the composite flux, that is to say, adding a pre-treatment step before the batching step, specifically: Al ₂ O ₃ is sieved into a particle size of 1-4.4 μm, 4.5-6.5 μm and 6.6-10μm three grades (4.5-6.5μm grade is used in this embodiment), for the preparation of yellow phosphors with different requirements, one of the three grades of Al ₂ O ₃ is selected from the three grades, and the air flow The particle size uniformity of Al ₂ O ₃ sieved by a type grading sieve can be shown in Figure 7; the activator, namely CeO ₂ , is sent to the oven for dehumidification. 0.2% activator; first put the flux, which is the composition of H ₃ BO ₃ , BaF ₂ , AlF ₂ and SrF ₂ , that is, the composite flux and the activator CeO ₂ into the three-dimensional motion mixer for mixing , the three-dimensional kinematic mixer is preferably but not limited to the model SYH-200 multi-directional kinematic mixing tank produced by Shenzhen Yuanda Machinery Co., Ltd., Guangdong Province, China, and the mixing time is 3h. The spindle speed of this multi-directional kinematic mixing tank is 10r/min to obtain the premix, and then mix the premix with the aforementioned matrix material Al ₂ O ₃ with a sieve particle size grade of 4.5-6.5 μm, and Lu ₂ O ₃ and Ga ₂ O ₃ which are also used as matrix materials Drop into the three-dimensional motion mixer and mix for 20h, the spindle speed of the three-dimensional motion mixer is controlled to be 15r/min. In the present embodiment, the three-dimensional motion mixer is preferably selected without limitation and is also provided by Shenzhen Yuanda Machinery Co., Ltd., Guangdong Province, China. The model produced by the Co., Ltd. is SYH-800 multi-directional motion mixing tank, and the particle size of the material to be fired is shown in Figure 8.

The SYH-200 and SYH-800 multi-directional motion mixing tanks mentioned in this embodiment are supported by the passive main shaft and the universal joint for three-dimensional movement in the directions of X, Y and Z axes. The movement is also a revolution movement, so that the materials in the mixing tank are diffused and sheared from time to time, which greatly enhances the mixing effect of the materials. Due to the three-dimensional movement of the mixing tank, it overcomes the use of rotating containers or The influence of centrifugal force produced by the stirring shaft type stirring container reduces the specific gravity segregation of the material, thereby ensuring the mixing effect. It fully embodies the technical effect claimed by the applicant in the column of technical effect.

The calcined powder obtained by the firing step is first introduced into a vibrating sieve with a mesh number of 200, that is, a mechanical vibrating sieve, and then screened by an ultrasonic grading sieve (also called an ultrasonic vibrating grading sieve). The mesh of the ultrasonic grading sieve is 500 mesh. The particle size of the powder is controlled to be 10-20 μm, and then introduced into a jet mill for pulverization. The jet mill is preferably but not limited to the GTM-400 pulverizer produced by Pioneer Machinery Co., Ltd., Changshu City, Jiangsu Province, China. The jet mill is a ceramic-lined flat mill, so that the D50 particle size of the powder is controlled to 7-8μm. The air inlet and outlet pressures of the jet mill are 0.8MPa and 0.4MPa respectively. The powder, that is, the phosphor particle is schematically shown in FIG. 9 .

Utilize the cleaning, sedimentation and classification device of Fig. 11 to clean the aforementioned powder to be cleaned after being pulverized by the jet mill, the applicant firstly describes the structure of the cleaning, sedimentation and classification device, including a stirring container 1 with an agitator 11; a first Extraction mechanism 2, a second extraction mechanism 3 and a third extraction mechanism 4, the first extraction mechanism 2 includes a first timing control valve 21, a first extraction pump 22, a first storage tank 23 and a first pipeline 24, The first timing control valve 21 and the first extraction pump 22 are sequentially connected to the middle part of the first pipeline 24, and one end of the first pipeline 24 is connected with the upper part of the height direction of the stirring vessel 1, while the other end of the first pipeline 24 Extending into the first storage tank 23, wherein the first timing control valve 21 is located between the stirring container 1 and the first extraction pump 22, the second extraction mechanism 3 includes a second timing control valve 31, a second extraction pump 32, The second storage tank 33 and the second pipeline 34, the second timing control valve 31 and the second extraction pump 32 are connected in the middle part of the second pipeline 34 successively, and one end of the second pipeline 34 is in the height direction of the stirring container 1 and the other end of the second pipeline 34 extends into the second bucket 33, wherein the second timing control valve 31 is located between the stirring container 1 and the second extraction pump 32, and the third extraction mechanism 4 includes The third timing control valve 41, the third extraction pump 42, the third storage tank 43 and the third pipeline 44, the second timing control valve 41 and the second extraction pump 42 are connected in the middle of the third pipeline 44 in sequence, One end of the three pipelines 44 is connected to the lower part of the height direction of the stirring vessel 1, and the other end of the third pipeline 44 extends into the third bucket 43, wherein the third timing control valve 41 is located between the stirring vessel 1 and the first mixing vessel. Between the three extraction pumps 32 . The applicant describes the method or process of cleaning the powder to be cleaned: introduce the powder to be cleaned into the stirring container 1, and introduce deionized water (the ratio of adding 4 liters of deionized water per kilogram of fluorescent powder) to start stirring 11, the rotating speed of the agitator is 15-20r/min, after the agitator is stirred for 25-35min, the first timing control valve 21 of the first extraction mechanism 2 is opened in sequence, the first extraction pump 22 works, and the stirring container The slurry solution in the upper part of 1 is introduced into the first material tank 23 through the first pipeline 24, and then the second timing control valve 31 of the second extraction mechanism 3 is opened, and the second extraction pump 32 works, and the stirring container 1 The slurry solution located in the middle is introduced into the second storage tank 33 through the second pipeline 34, and then the third timing control valve 41 of the third extraction mechanism 4 is opened, the third extraction pump 42 works, and the mixture in the stirring container 1 The slurry solution at the lower part is introduced into the third storage tank 43 through the third pipeline 44 . Then, the powder slurry in the first, second, and third storage tanks 23, 33, and 43 are respectively introduced into the centrifuge to dry, and the obtained powder to be dried, that is, the distribution of phosphor particles after cleaning, is shown in Fig. 10 shown. This step is based on the principle that different powder particle sizes have different settling velocities. The slurry extracted by the first extraction mechanism 2, that is, the slurry located on the upper part of the stirring container 1, is due to the ultra-fine particle size of the powder and the inclusion of impurities generated during the cleaning process. Therefore, it is usually discarded, and the powder extracted by the second extraction mechanism 3 is the normal powder (finished powder), while the lower layer, that is, the powder extracted by the third extraction mechanism 4 has a large particle size and needs to be re-extracted. Use after processing. Accordingly, the particle distribution of phosphor powder shown in FIG. 10 is for the powder extracted by the second extraction mechanism 3 and dried by centrifugal drying.

The graded powder to be dried obtained after the above cleaning is dried according to the same process in the prior art, and is packaged after sieving. However, as a technical point of the present invention: the powder obtained in the drying step is passed through an airflow classification sieve Carry out particle size classification of the finished product, and separate D ₁₀ = 3-5 μm, D ₅₀ = 7-8 μm and D ₉₀ = 10-12 μm to obtain a high-quality powder with a highly concentrated particle size distribution, that is to say, the particle size classification of the finished product through an air-flow classification sieve The obtained yellow-green powder to be packaged has a uniform particle size, no agglomeration phenomenon between particles and a complete crystal lattice, as shown in FIG. 12 .

The yellow-green fluorescent powder for LEDs obtained in this embodiment has the advantage of narrow particle size distribution. Compared with the yellow-green fluorescent powder in the prior art, through analysis and testing: the brightness is increased by 3-5%, and the particle size uniformity is increased by 30%. As mentioned above, the lattice defects are reduced by about 30%, so that the light decay and color drift of the phosphor powder can be reduced, and the thermal stability can be improved.

Example 2:

Only change the mass percent of sieved _{Al2O3 to} 13%, change _the mass percent of _Lu2O3 to 72.5%, _{change the mass percent of Ga2O3 to} 14%, change the mass percent of _CeO2 is 0.3%, change the mass percentage of the composite flux consisting of H ₃ BO ₃ , BaF ₂ and AlF ₂ to 0.2%, wherein: the mass percentage of H ₃ BO ₃ is changed to 8%, the mass percentage of BaF _{2 The} percentage is changed to 40%, the mass percent of _AlF2 is changed to 41%, the mass percent of _{SrF2 is} changed to 11% _; 100°C and 240min, the water content of CeO ₂ is 0.07%; the mixing time of the composite flux and the activator is changed to 4h, and the spindle speed of the three-dimensional motion mixer, that is, the spindle speed of the multi-directional motion mixing tank is changed to 8r/min , the mixing time of the premix and the matrix material with a particle size of 6.6-10 μm, that is, Al ₂ O ₃ and Lu ₂ O ₃ and Ca ₂ O ₃ as the matrix material, was changed to 10 hours, and the spindle speed of the three-dimensional motion mixer was changed to It is 18r/min; change the mesh number of the vibrating screen to 250 mesh, change the mesh number of the ultrasonic grading screen to 300 mesh, and change the air inlet and outlet pressure of the jet mill to 1.2MPa and 0.8MPa respectively, and the rest are the same Description of Example 1.

Example 3:

Only change the mass percent of sieved _{Al2O3 to} 20%, change the mass _percent of _Lu2O3 to 65%, change the mass percent of _Ga2O3 to 8%, _change the mass percent of _CeO2 is 2.5%, change the mass percentage of the composite flux consisting of H ₃ BO ₃ , BaF ₂ and AlF ₂ to 4.5%, wherein: the mass percentage of H ₃ BO ₃ is changed to 10%, the mass percentage of BaF ₂ The percentage is changed to 35%, the mass percent of _AlF2 is changed _to 30%, the mass percent of _{SrF2 is} changed to 25% _; 110°C and 70min, the water content of _CeO2 is 0.5%; the mixing time of the composite flux and the activator is changed to 3.5h, and the spindle speed of the three-dimensional motion mixer, that is, the spindle speed of the multi-directional motion mixing tank is changed to 12r /min, the mixing time of the premix and the matrix material with a particle size of 1-4.4μm, that is, Al ₂ O ₃ and Lu ₂ O ₃ and Ca ₂ O ₃ that are also used as matrix materials, is changed to 15h, and the three-dimensional motion mixer Change the spindle speed to 13r/min; change the mesh number of the vibrating screen to 220 mesh, change the mesh number of the ultrasonic grading screen to 400 mesh, and change the air inlet and outlet pressures of the jet mill to 1MPa and 0.6MPa respectively. Same as the description of embodiment 1.

Claims (8)

1. A kind of LED preparation method of yellow-green fluorescence powder, the step that the method comprises is followed successively by batching, batch mixing, burn till, broken, clean, oven dry and the packing of sieving, wherein, described batching is for to take by weighing substrate material by mass percent, take by weighing activator and take by weighing fusing assistant, it is characterized in that: before described batching step, have additional the pre-process step, this pre-process step comprises described substrate material screening, be re-dubbed compound fusing assistant to described activator dehumidifying with to described fusing assistant, described batch mixing is will drop in the three-dimensional motion mixer with compound fusing assistant through the activator of dehumidifying first to mix, and the speed of mainshaft of control mixing time and control three-dimensional motion mixer, obtain Preblend, again Preblend is introduced in the three-dimensional motion mixing tank jointly with the substrate material of screening and mixed, and the speed of mainshaft of the mixing time of control three-dimensional motion mixing tank and control three-dimensional motion mixing tank obtains material to be burnt till; Described fragmentation be with by described burn till that step obtains burn till powder first by the vibratory screening apparatus screening, again by the screening of ultrasonic wave sizing screen, then introduce micronizer mill and pulverize, obtain powder to be cleaned, and the intake pressure of control micronizer mill and go out atmospheric pressure; Described cleaning is described powder to be cleaned to be introduced to clean in the classification of sedimentation device clean and classification, obtains the powder to be dried of classification; Described sieving is that the powder that will be obtained by baking step carries out the product grading classification by the air classification sieve, behind packaging step, obtain LED yellow-green fluorescence powder, described cleaning classification of sedimentation device comprises a stirred vessel with agitator (11) (1); One first drawing mechanism (2), one second drawing mechanism (3) and one the 3rd drawing mechanism (4), the first drawing mechanism (2) comprises the first timing control valve (21), the first extraction pump (22), the first bucket (23) and the first pipeline (24), the first timing control valve (21) and the first extraction pump (22) are connected to the middle part of the first pipeline (24) in turn, one end of the first pipeline (24) is connected with the top of the short transverse of stirred vessel (1), and the other end of the first pipeline (24) is stretched in the first bucket (23), wherein, the first timing control valve (21) is positioned between stirred vessel (1) and the first extraction pump (22), the second drawing mechanism (3) comprises the second timing control valve (31), the second extraction pump (32), the second bucket (33) and the second pipeline (34), the second timing control valve (31) and the second extraction pump (32) are connected to the middle part of the second pipeline (34) in turn, one end of the second pipeline (34) is connected with the middle part of the short transverse of stirred vessel (1), and the other end of the second pipeline (34) is stretched in the second bucket (33), wherein, the second timing control valve (31) is positioned between stirred vessel (1) and the second extraction pump (32), the 3rd drawing mechanism (4) comprises the 3rd timing control valve (41), the 3rd extraction pump (42), the 3rd bucket (43) and the 3rd pipeline (44), the second timing control valve (41) and the second extraction pump (42) are connected to the middle part of the 3rd pipeline (44) in turn, one end of the 3rd pipeline (44) is connected with the bottom of the short transverse of stirred vessel (1), and the other end of the 3rd pipeline (44) is stretched in the 3rd bucket (43), wherein, the 3rd timing control valve (41) is positioned between stirred vessel (1) and the 3rd extraction pump (32).

2. LED according to claim 1 is characterized in that with the preparation method of yellow-green fluorescence powder described substrate material screening is to adopt airflow classification to be sieved into the Three Estate that particle diameter is 1-4.4 μ m, 4.5-6.5 μ m and 6.6-10 substrate material; Described dehumidifying is activator to be inserted in the baking oven cure to activator, and controls stoving temperature and cure the time, and the water ratio of control activator.

3. The LED according to claim 1 preparation method of yellow-green fluorescence powder, the mixing time that it is characterized in that described control three-dimensional motion mixer is that mixing time is controlled to be 3-4h, and the speed of mainshaft of described control three-dimensional motion mixer is that the speed of mainshaft is controlled to be 8-12r/min; The mixing time of described control three-dimensional motion mixing tank is controlled to be 10-20h, and the speed of mainshaft of described control three-dimensional motion mixing tank is that the speed of mainshaft is controlled to be 12-18r/min.

4. LED according to claim 1 is characterized in that with the preparation method of yellow-green fluorescence powder described substrate material is Al ₂ O ₃ , Lu ₂ O ₃ And Ga ₂ O ₃ Mixture; Described activator is CeO ₂ Described compound fusing assistant is H ₃ BO ₃ , BaF ₂ , AlF ₃ And SrF ₂ Composition.

5. The LED according to claim 2 preparation method of yellow-green fluorescence powder, it is characterized in that described control stoving temperature is that temperature is controlled to be 100-120 ℃, the described control time of curing is that the time is controlled to be 60-240min, and the water ratio of described control activator is to be 0.05-0.5% with moisture control.

6. LED according to claim 4 is characterized in that described Al with the preparation method of yellow-green fluorescence powder ₂ O ₃ Mass percent be 13-25%, described Lu ₂ O ₃ Mass percent be 60-72.5%, described Ga ₂ O ₃ Mass percent be 2-14%, described CeO ₂ Mass percent be 0.3-5.8%; Described by H ₃ BO ₃ , BaF ₂ , AlF ₃ And SrF ₂ The mass percent of the composition that consists of is 0.18-7.18%, wherein: described H ₃ BO ₃ Mass percent be 7-25%, described BaF ₂ Mass percent be 25-48%, described AlF ₃ Mass percent be 25-41%, described SrF ₂ Mass percent be 4-25%.

7. The LED according to claim 1 preparation method of yellow-green fluorescence powder, the order number that it is characterized in that described vibratory screening apparatus is the 200-250 order; The order number of described ultrasonic wave sizing screen is the 300-500 order, and it is the D that gets by the ultrasonic wave classification sieve that described micronizer mill is pulverized ₅₀ Particle diameter is that the powder of 10-20 μ m is crushed to D ₅₀ Particle diameter is the powder of 7-8 μ m, and the intake pressure of described control micronizer mill is that intake pressure is controlled to be 0.8-1.2MPa with going out atmospheric pressure, and the pressure-controlling of will giving vent to anger is 0.4-0.8MPa.

8. LED according to claim 1 is with the preparation method of yellow-green fluorescence powder, it is characterized in that described to carry out the product grading classification by the air classification sieve be the powder that described baking step obtains to be divided to sift out particle size distribution range be D ₁₀ =3-5 μ m, D ₅₀ =7-8 μ m and D ₉₀ The finished product powder of=10-12 μ m

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