JP5120963B2 - Recycling method of waste phosphor - Google Patents

Description

  The present invention relates to a method for separating and collecting phosphors used in discarded fluorescent lamps and plasma displays for each color.

  In recent years, the price of rare metals such as rare earth elements has soared. Phosphors used in plasma displays and fluorescent lamps contain a large amount of expensive rare earth elements such as Tb and Eu. Therefore, as disclosed in Non-Patent Document 1 below, a method for recovering phosphors from discarded products and separating and extracting rare earth elements by chemical treatment has been studied.

The phosphors for ordinary lamps include BAM (BaMgAl ₁₀ O ₁₇ : Eu ²⁺ ) or SCA (Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu or (Sr, Ca, Ba, Mg) ₁₀ ( PO ₄ ) ₆ C _l2 : Eu), YOX (Y ₂ O ₃ : Eu ³⁺ or YVO ₄ : Eu) as a red phosphor, and LAP (LaPO ₄ : Tb, Ce) as a green phosphor Both a three-wavelength phosphor showing white and a calcium halophosphate using a white phosphor are used. In addition, the degree of deterioration due to use and recovery of the lamp differs depending on each phosphor, and among the three-wavelength phosphors, only the blue phosphor is significantly degraded due to the change of Eu ²⁺ → Eu ³⁺ . For this reason, the collected phosphor cannot be used again for a new fluorescent lamp, and even when it is mixed with a new phosphor, the proportion that can be added is only a few percent or less. Therefore, there is a demand for a method of improving the reuse rate by separating the phosphors for each product type (for each three wavelengths, that is, for each color, or even for the same color for each composition).

  In the method of classifying phosphor types, a difference in physical properties of phosphors is generally used. First, it is conceivable to separate using the difference in specific gravity (density) of phosphors. Table 1 shows the density of each phosphor.

  In the table above, “white” means halophosphoric acid.

  As described above, it is known that the specific gravity of some of the phosphors is different, and a method of separation by centrifugation is disclosed in Patent Document 1 below. Some combinations of phosphors used in fluorescent lamps and plasma displays do not have a large difference in specific gravity even if they are different colors, and therefore cannot be separated by centrifugation. For example, for plasma displays, there is no significant difference in specific gravity between B (blue) and G (green) phosphors. Others have similar specific gravity. In order to solve this problem, Patent Document 1 discloses a method in which only a blue phosphor having a small specific gravity is separated by centrifugation, and then a red phosphor and a green phosphor are separated using a difference in surface charge. It is disclosed.

  Patent Document 2 below discloses a method for extracting and separating phosphors of each color by selecting a surfactant and a solvent composition by utilizing the fact that the zeta potentials of the phosphors are different.

JP 2004-137320 A JP 2004-262978 A

Toru Takahashi et al. Separation and recovery of rare earth elements from waste phosphor sludge by wind classification and sulfuric acid leaching method, resources and materials, Vol.117, 579-585 (2001)

  However, the method disclosed in Non-Patent Document 1 that once separates the phosphor by acid treatment has a disadvantage of high cost, and it is originally desirable to use the phosphor as it is.

  Further, in the methods disclosed in Patent Documents 1 and 2, since the phosphor after use has a binder or the like attached to the surface, the surface state is actually changed, so that it is difficult to use. In addition, there is a drawback in that the phosphors deteriorated when the blue phosphor is collected are also collected and collected.

  The present invention has been made to solve the above-described problems, and can separate and recover a specific phosphor from waste phosphor with high accuracy and efficiency, and reuse of the collected phosphor. It aims to provide a way to make it easier.

  As a result of intensive studies, the inventors have found that there is a significant difference in magnetic susceptibility among various phosphors, and invented a method for separating the various phosphors based on this difference. That is, the object of the present invention is achieved by the following means.

  That is, the waste phosphor recycling method (1) according to the present invention is a method for separating at least one phosphor from a mixture of a plurality of discarded phosphors, and using the mixture as a fluid. And a second step in which at least a part of the fluid is positioned in a magnetic field having a gradient and at least one kind of phosphor is separated by a magnetic force generated in the phosphor. It is said.

  The waste phosphor recycling method (2) according to the present invention is the same as the waste phosphor recycling method (1) described above, wherein the gradient is formed in the vertical direction, and the magnetic force acting on each of the plurality of types of phosphors. The strength of the magnetic field and the gradient is set so that the resultant force acting on at least two kinds of the phosphors in the resultant force of buoyancy and gravity is reversed.

  Further, the waste phosphor recycling method (3) according to the present invention is the above-described waste phosphor recycling method (2), among the phosphors other than the two types of phosphors in which the resultant force is reversed. The magnetic field and the strength of the gradient are set so that the resultant force acting on one type of phosphor becomes zero.

  Further, the waste phosphor recycling method (4) according to the present invention is the waste phosphor recycling method (1) to (3) described above, wherein the fluid is a liquid solvent, and the first step. Includes a third step of suspending the phosphor charged in the solvent.

  The waste phosphor recycling method (5) according to the present invention is the above-described waste phosphor recycling method (4), wherein the solvent is water containing a surfactant or an alcohol having a hydroxyl group. It is characterized by.

The waste phosphor recycling method (6) according to the present invention is the same as the waste phosphor recycling method (4) or (5) described above, wherein a plurality of types of the phosphors are LaPO ₄ : Ce as green phosphors. , Tb as a blue phosphor, BaMgAl ₁₀ O ₁₇ : Eu and (Sr, Ca, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu, the solvent has a specific gravity of 1 or more, and the second step comprises A magnetic field distribution is set so that a product of the magnetic field intensity and the gradient intensity is 34.1 T ² / m or more and less than 107 T ² / m, and a fourth step of collecting the green phosphor is included. It is characterized by that.

The waste phosphor recycling method (7) according to the present invention is the same as the waste phosphor recycling method (4) or (5) described above, wherein the plurality of types of phosphors are Zn ₂ SiO ₄ as green phosphors. : Mn containing (Y, Gd) BO ₃ : Eu as a red phosphor, the specific gravity of the solvent is 1 or more, and the product of the magnetic field intensity and the gradient intensity is 21 in the second step. The magnetic field distribution is set to be ² T ² / m or more and less than 110 T ² / m, and the product of the fifth step of collecting the red phosphor and the intensity of the magnetic field and the intensity of the gradient is 110 T ² / m. The magnetic field distribution is set so as to be less than 209 T ² / m, and the sixth step of collecting the green phosphor is included.

  Moreover, the recycling method (8) of the waste phosphor according to the present invention is the recycling method (1) to (7) of the waste phosphor described above, in the second step, in the magnetic field in the mixture. It is characterized in that the fluid in which is introduced is allowed to pass.

  Moreover, the waste phosphor recycling method (9) according to the present invention is the waste phosphor recycling method (1) to (7) described above, in the vicinity of the surface of the fluid into which the mixture has been introduced. An adsorption means capable of adsorbing the phosphor is provided, and the phosphor floating on the surface of the fluid is collected by being attached to the adsorption means.

  The waste phosphor recycling method (10) according to the present invention is the recycling method (1) to (7) of the waste phosphor, wherein the second step includes the gradient locally in the interior. A seventh step of flowing the fluid into which the mixture has been introduced, and an eighth step of collecting the fluid existing in the vicinity where the gradient is formed. It is characterized by.

  According to the recycling method of waste phosphors of the present invention, it is possible to separate specific phosphors from waste phosphors with high accuracy and efficiency, or it is possible to separate all phosphors for each color. Therefore, the collected phosphor can be easily reused.

It is sectional drawing which shows the recycling method (method 1) of the waste fluorescent substance which concerns on embodiment of this invention. It is sectional drawing which shows the recycling method (method 2) of the waste fluorescent substance which concerns on embodiment of this invention. It is sectional drawing which shows the recycling method (method 3) of the waste fluorescent substance which concerns on embodiment of this invention. It is sectional drawing which shows the recycling method (method 6) of the waste fluorescent substance which concerns on embodiment of this invention. It is sectional drawing which shows the Example (Example 1) of this invention. It is sectional drawing which shows the Example (Example 3) of this invention.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.

When a substance is placed in a magnetic field with non-uniform strength, a magnetic force is generated in the substance. The magnitude of the generated magnetic force is proportional to the product of the magnetic susceptibility (χ) of the substance, the magnitude of the magnetic flux density at the position of the substance (B), and the magnetic field gradient (grad B), which is the spatial gradient. However, if the substance is a paramagnetic substance, a magnetic force acts in the direction of increasing the magnetic flux density, and if it is a diamagnetic substance, the magnetic force acts in a direction of decreasing the magnetic flux density. Therefore, in the present invention, paying attention to the difference in magnetic susceptibility of the phosphor, the phosphor is separated according to the magnetic susceptibility.

  Specifically, Table 2 shows phosphors generally used in plasma displays and lamps and their characteristic values.

In Table 2, the magnetic susceptibility of each phosphor is expressed in unit mass (1
It is expressed as magnetization per g) (emu / g). In addition, Table 2 is an example, and even if it is the same color fluorescent substance, a composition may differ with manufacturers, and even if it is the same manufacturer, the composition of the same color fluorescent substance may differ with model numbers.

  As can be seen from Table 2, when the phosphors used in the plasma display are ZSM, YBO, and BAM, the magnetic susceptibility increases in the order of blue, green, and red. Therefore, in the present invention, a mixture of pulverized red, blue, and green phosphors collected from a discarded plasma display is put into a predetermined solvent, and this has a gradient. Place in a non-uniform magnetic field. As a result, different magnitudes of magnetic force are generated in the red, blue, and green phosphors, so that the phosphors of the respective colors can be separated.

  On the other hand, fluorescent materials for lamps include those having the same color but different magnetic susceptibility, and those having different colors having similar magnetic susceptibility, but the magnetic susceptibility differs for each phosphor type. Therefore, the phosphor mixture for lamps can be separated for each phosphor type in the same manner as described above for the phosphor mixture for plasma display.

Specifically, the following various methods are possible. In the following, the case where the mixture of phosphors for plasma display shown in Table 2 is separated will be described.

Method 1:
The mixed red, blue and green phosphors are put into a solvent (liquid) having a specific gravity smaller than those, and in a magnetic field where a magnetic field gradient exists so that the magnetic field strength is large vertically upward and small vertically downward. The solution (solvent and phosphor) is disposed (see FIG. 1). As shown to (a) of FIG. 1, the thrown-in fluorescent substance G, B, R precipitates in the downward direction in the solvent M (bottom of the container which contains the solvent) by gravity. When the solvent M in this state is arranged in a magnetic field, as shown in FIG. 1B, the red phosphor _R generates the largest upward magnetic force F _R, so the magnetic force F _R and the buoyancy F the sum F _R + F _u and _u is greater than (a value where F _R, F _u, per unit mass both F _d. hereinafter the same) than the gravity F _d, thereby floating the red phosphor R Can do. Therefore, if the substance floating on the liquid surface is collected, only the red phosphor R can be collected. In order to collect the floated substance, a known means such as a suction means (a dropper or the like) or an adsorption means (a member to which the phosphor naturally adheres) may be used.

  Then, after collecting the red phosphor R, the magnetic field and gradient are increased. As a result, the green phosphor G generates a vertically upward magnetic force larger than that of the blue phosphor B, so that the green phosphor G can be floated in the same manner as described above. Accordingly, if the substance floating on the liquid surface is collected, only the green phosphor G can be collected. Finally, if the remaining blue phosphor B is collected, three types of phosphors can be separated and collected.

Method 2:
Since many usable solvents have a specific gravity smaller than that of the phosphor, the phosphor charged in the solvent precipitates. However, when the specific gravity of the solvent is larger than that of the phosphor, the solution is placed in a magnetic field distributed so that the magnetic field strength is large vertically downward and small vertically upward (see FIG. 2). In this case, the phosphors G, B, and R float on the liquid surface of the solvent M (see (a) of FIG. 2). When the solvent M in this state is placed in a magnetic field, as shown in FIG. 2B, the red phosphor _R generates the largest downward magnetic force F _R. the sum F _R + F _d and F _d is larger than the buoyancy F _u, can be precipitated red phosphor R.

  After collecting the red phosphor R, the magnetic field and magnetic field gradient are increased. Thereby, since the vertical magnetic force larger than that of the blue phosphor B is generated in the green phosphor G, the green phosphor G can be precipitated. If the blue phosphor B remaining after the green phosphor G is collected, the three types of phosphors can be separated and collected.

Method 3:
As shown in FIG. 3, the mixed red, blue, and green phosphors G, B, and R were put into a solvent M having a specific gravity smaller than those, and the phosphors were suspended in the solvent M. In this state, the magnetic field is moved in a horizontal direction at a predetermined flow velocity v in a magnetic field distribution that is large in the vertical direction and large in the vertical direction. In FIG. 3, the solvent M in which three types of phosphors G, B, and R are suspended in the left end container is introduced into the transfer tube from the left end, and passes through the transfer tube toward the right side. The magnetic field gradient is formed within the range indicated by the symbol L in the transfer tube. In this case, among the three types of phosphors, the red phosphor R receives the largest magnetic force F _R vertically upward, and thus moves the longest distance before precipitation (see the broken line described as “R locus”). ). Since the blue phosphor B receives the smallest magnetic force F _B vertically upward, it moves the shortest distance until it settles (see the broken line described as “B locus”). And since the magnetic force which the green fluorescent substance G receives is a value between blue and red fluorescent substance B and R, it precipitates between the positions where blue and red fluorescent substance B and R precipitate. That is, the position at which the phosphor is precipitated is farther from the input end of the transfer tube in the order of blue, green, and red, and three types of phosphor can be precipitated at different positions and collected.

Method 4:
The mixed red, blue and green phosphors are put into a solvent having a higher specific gravity than that, and the phosphors are suspended in the solvent. It moves in a large magnetic field at a predetermined flow rate in a horizontal direction. In this case, among the three types of phosphors, the red phosphor receives the largest magnetic force vertically downward, so that the sum of the magnetic force acting on the red phosphor and gravity is greater than the buoyancy, and the magnetic field and If the magnitude of the gradient is set, the red phosphor can be collected by precipitation.

  Then, the solution containing the blue and green phosphors that did not precipitate was again suspended in the solvent in a magnetic field where the intensity was vertically small and the intensity was distributed greatly vertically. In one direction at a predetermined flow rate. At this time, if the magnetic field and gradient are adjusted in advance so that the sum of the magnetic force and gravity acting on the green phosphor is greater than the buoyancy, the green phosphor is precipitated and collected. can do. Finally, if a blue phosphor that floats without precipitation is collected, three types of phosphors can be separated and collected.

Method 5:
The method is the same as method 3, but the region L where the magnetic field gradient exists (see FIG. 3) is made larger so that the sum of the magnetic force and buoyancy acting on the green phosphor becomes slightly larger than gravity. Set the magnitude of the magnetic field and gradient. If the magnetic field distribution is formed in this way, the sum of the magnetic force and the buoyancy of the red phosphor is larger than the gravity, so that only the blue phosphor can be precipitated without precipitating the green and red phosphors. . Therefore, if the precipitated substance is collected, the blue phosphor can be collected.

  And the discharged | emitted liquid is collect | recovered and it passes through the inside of the magnetic field which has a gradient again. At this time, the magnitudes of the magnetic field and the gradient are set so that the sum of the magnetic force and buoyancy acting on the red phosphor is slightly larger than gravity so that the red phosphor does not precipitate. If the magnetic field distribution is formed in this way, the sum of the magnetic force and buoyancy acting on the green phosphor can be made smaller than gravity, and the green phosphor can be precipitated. If the precipitated substance is collected, the green phosphor can be collected. Finally, if the discharged liquid is collected and the red phosphor is collected, the three types of phosphors can be separated and collected.

  Although FIG. 3 shows a case where the magnetic field gradient is formed in the vertical direction, the magnetic field gradient may be formed in the horizontal direction. In order to form the magnetic field gradient in the horizontal direction, for example, the superconducting magnet may be disposed inside the transfer tube with the bore sideways.

Method 6:
As shown in FIG. 4, three types of phosphors G, B, and R are put into a vertically arranged transfer tube from one location near the inner tube wall. In the transfer tube, the solvent M moves downward, for example, by gravity. A magnet (for example, a permanent magnet) is disposed in the vicinity of the outer wall of the transfer tube (on the side facing the position where the phosphor is introduced).

  Among the three types of phosphors G, B, and R introduced near the left end in FIG. 4, the red phosphor R generates a rightward magnetic force that is greater than the other two types of phosphors B and G. The red phosphor R moves to the right while moving downward (see the broken line described as “R locus”). On the other hand, since the magnetic force generated in the blue and green phosphors B and G is relatively small, the blue and green phosphors B and G do not move almost to the right but move downward. Therefore, if the solution near the right end in FIG. 4 is collected in a container and allowed to stand still, only the red phosphor R can be recovered as a precipitate.

Thereafter, the discharged solvent M is allowed to stand still in the container, and the obtained precipitate is put into the transfer tube in the same manner as described above. At this time, the magnitudes of the magnetic field and the gradient are set in advance so that the rightward magnetic force generated in the green phosphor G moves to the vicinity of the inner wall at the right end while the green phosphor G is descending. Therefore, if the solution near the right end is collected in a container and allowed to stand still, only the green phosphor G can be recovered as a precipitate. Finally, if the blue phosphor B is collected from the discharged solution, three types of phosphors can be separated and collected.

  If all the red phosphors R cannot be collected in the first time, the process is repeated a plurality of times, and then the process of collecting the green phosphor G by resetting the magnetic field and the magnitude of the gradient is performed. Just do it.

Method 7:
When the magnetic field and the magnetic field gradient are formed in a horizontal or oblique direction, the magnetic force acts in the direction in which the magnetic field becomes stronger as the susceptibility of the phosphor increases. For example, a mixture of phosphors ZSM, YBO and BAM for plasma display. Then, YBO concentrates on the part where the magnetic field becomes strong. Therefore, if the solvent in which the phosphor is dispersed is caused to flow along a predetermined flow path and a magnetic field gradient is formed in advance by placing a magnet in the flow path, the vicinity of the magnet and the distance from the magnet are separated. By separately collecting the downstream portions, phosphors having a high magnetic susceptibility (collected from the vicinity of the magnet) and other phosphors (collected from the downstream) can be separated and recovered. The number of magnets is not limited to one and may be plural.

  In each of the above methods, it is essential to use a liquid exhibiting diamagnetism such as water or a normal organic solvent as a solvent into which the waste phosphor is charged. In order to disperse, water containing a surfactant, an organic solvent such as alcohols having a hydroxyl group and acetone are preferred, and the former water is particularly preferred because of less aggregation. As the surfactant, those that can disperse phosphor powder such as LAS and higher alcohols can be used, but considering the removal operation after separation, such as polycarboxylic acid type that does not contain sulfur, phosphorus, halogen, and ash Surfactants are particularly preferred.

  As will be described later, in order to increase the purity of the separated phosphor as a result of repeated experiments, it is desirable to disperse the phosphor powder once in a dispersion solvent and settle it by gravity in about 10 minutes to 2 hours. It has been found that the accuracy of separation decreases when a part of the powder is agglomerated.

  As a means for generating a magnetic field gradient, a known superconducting magnet, electromagnet, permanent magnet, or a ferromagnetic material (iron or the like) magnetized by an external magnetic field can be used. Superconducting magnets that can generate a strong magnetic field are particularly desirable. As for the permanent magnet, it is desirable to be a rare earth magnet (permanent magnet using a rare earth as part of the magnet material) capable of generating a strong magnetic field.

  In the rightmost column of Table 2 above, the product (B · gradB) of the magnetic field strength and the gradient magnetic field strength necessary for floating the phosphor (precipitate) thrown into water (specific gravity is 1) is shown. Table 3 is obtained by rearranging the rows of Table 2 in order of increasing B · gradB, distinguishing between the plasma display and the lamp.

Considering the case of using a solvent other than water (organic solvent, surfactant, etc.), when using a solvent having a specific gravity of 1 or more, regarding the phosphor for plasma display, B · gradB value, 21.2T ² / m or more for the red phosphor YBO, for green phosphor ZSM 110T ² / m or more, for blue phosphor BAM it is desirable that the 209T ² / m or more. That is, by setting the value of B · gradB to a value of 21.2 T ² / m or more and less than 110 T ² / m, only the precipitated red phosphor YBO can be floated. In order to separate more reliably, it is desirable to set B · gradB to a value in the range of 23 to 90 T ² / m. Further, after collecting the red phosphor, by setting B · gradB to a value of 110 T ² / m or more and less than 209 T ² / m, only the green phosphor ZSM can be floated. In order to separate more reliably, it is desirable to set B · gradB to a value in the range of 120 to 190 T ² / m.

Similarly, in the case of a fluorescent substance for a lamp, if B · gradB is appropriately set, it can be separated for each fluorescent substance type. For example, when a solvent having a specific gravity of 1 or more is used, the value of B · gradB for floating is 33.8 T ² / m or more for LAP (L) of the green phosphor and 34. 0T ² / m or more and 34.1T ² / m or more for the LAP (C). For the other colors, the smallest B · gradB is 107 T ² / m (BAM). Therefore, by setting B · gradB to a value of 34.1 T ² / m or more and less than 107 T ² / m, it is possible to float only three types of green phosphors among the precipitated phosphors. Here, 34.1 T ² / m or more is set to float all three types of green phosphors LAP (L), LAP (W), and LAP (C), and less than 107 T ² / m. This is to prevent all other phosphors from floating. In order to separate more reliably, it is desirable to set B · gradB to a value in the range of 36 to 90 T ² / m. In addition, after collecting the green phosphor, B · gradB is set to a value of 107 T ² / m or more and less than 141 T ² / m, so that only BMA (1) out of the precipitated blue phosphor is brought up. be able to. In order to separate more reliably, it is more desirable to set B · gradB to a value in the range of 115 to 130 T ² / m. Other phosphors can be separated in the same manner.

When a solvent having a specific gravity of less than 1 is used, the value of B / gradB for levitating each phosphor must be greater than the above value (when a solvent having a specific gravity of 1 or more is used). Don't be. Specifically, the specific gravity of the solvent is about 0.78 (in the case of alcohol, ethanol (specific gravity 0.786), 2-propanol (specific gravity 0.781), 1-butanol (specific gravity 0.806), etc.) ), The values corresponding to the values in the right end column of Table 2 (values of B · gradB for levitating the phosphor charged in the solvent having a specific gravity of 0.78) are 119, 22.4, and 225 from the top. , 35.7, 35.8, 35.5, 637, 904, 115, 251, 714, 629, 640, 313, 155, 816 T ² / m.

In the above, seven types of methods have been exemplified, but the present invention is not limited to these. When the magnetic field gradient is formed in the vertical direction (for example, FIGS. 1 to 3), the solvent into which the phosphor is introduced is considered in consideration of the magnitude relationship between the specific gravity of the solvent into which the phosphor is introduced and the specific gravity of each phosphor. What is necessary is just to set the magnitude | size of the magnetic field and gradient of the area | region which arrange | positions or flows. For example, in the case of a mixture of three types of phosphors, the magnetic field and the magnetic force, buoyancy, and the resultant force of gravity F ₁ , F ₂ , and F ₃ acting on each phosphor are reversed so that at least two of them are in opposite directions. What is necessary is just to set the magnitude | size of a gradient. As an example, the case where the resultant force F ₁ is opposite to the resultant forces F ₂ and F ₃ can be considered. In this case, one type of phosphor (phosphor that receives the resultant force F ₁ ) can be spatially assembled and can be easily collected. Thereafter, in order to separate the remaining two types of phosphors, the magnitude of the magnetic field and the gradient may be set so that the resultant forces F ₂ and F ₃ acting on each of them are opposite in the same manner as described above. Further, when the resultant force F ₁ is opposite to the resultant force F ₂ and the resultant force F _{3 is} almost zero, the two types of phosphors (phosphors that receive the resultant forces F _{1 and} F ₂ ) are assembled in different places. (One is precipitated and the other is levitated), and can be collected easily. The phosphor that receives the resultant force F ₃ that is substantially zero remains diffused in the solvent if it is initially diffused.

  For example, for a phosphor for a plasma display, the magnitude of the magnetic field and gradient is such that the resultant force acting on the red phosphor is vertically upward and the resultant force acting on each of the blue and green phosphors is vertically downward. Is set, the red phosphor and the blue and green phosphors can be separated. After collecting the floating red phosphor, the blue and green phosphors can be separated by setting the magnetic field and the gradient so that the resultant force acting on each of the blue and green phosphors is reversed. Can be collected.

  For the plasma display phosphor, the magnitude of the magnetic field and the gradient are such that the resultant force acting on each of the red and green phosphors is vertically upward, and the resultant force acting on the blue phosphor is vertically downward. Is set, the blue phosphor and the green and red phosphors can be separated. After collecting the precipitated blue phosphor, the green and red phosphors can be separated by adjusting the magnetic field and the gradient so that the resultant force acting on each of the green and red phosphors is reversed. Can be collected.

  For the plasma display phosphor, the resultant force acting on the red phosphor is vertically upward, the resultant force acting on the blue phosphor is vertically downward, and the resultant force acting on the green phosphor is almost zero. In addition, if the magnetic field and the magnitude of the gradient are set, the red phosphor can be levitated, the blue phosphor can be precipitated, and the green phosphor can be left diffused in the solvent. Therefore, the levitated red phosphor and the precipitated blue phosphor can be separated and collected. Each of the separation methods described above can be similarly applied to a mixture of four or more types of phosphors. That is, the present invention can also be applied to a mixture of phosphors for a lamp including four or more kinds of phosphors.

  Further, when a gradient is formed in the horizontal direction (for example, FIG. 4), the magnitude of the magnetic field and the gradient are set so that a horizontal magnetic force larger than that of other phosphors is generated in at least one type of phosphor. Should be set.

  In the above description, the case where the direction of the magnetic field gradient and the direction in which the container is arranged is mainly the vertical direction or the horizontal direction, but may be an oblique direction. Even in such a case, if the magnetic force, gravity, and buoyancy are handled as a three-dimensional vector and the position of the container wall surface is taken into consideration and the magnetic field and the gradient are set appropriately, the three types of phosphors can be separated. .

  Moreover, although the case where the fluorescent substance used with a plasma display and a fluorescent lamp was collect | recovered above was demonstrated, the application object of this invention is not limited to these. If it is a mixture in which a plurality of types of phosphors having different magnetic susceptibility are mixed in a powder form, the present invention can be applied to separate and collect the phosphors for each type.

  Moreover, although the case where the liquid solvent was used was demonstrated above, it should just be a fluid and may use gas (for example, air). For example, if the waste phosphor is finely pulverized and the mixture is sprayed toward a magnetic field gradient (with or without solvent) using air of sufficient pressure or flow rate, as described above The phosphor can be separated.

  Moreover, although the case where it isolate | separated without considering that the waste fluorescent substance deteriorated was demonstrated above, since the magnetic susceptibility of a fluorescent substance is mainly determined by rare earth ions, when a blue fluorescent substance deteriorates, a magnetic susceptibility changes. . Therefore, if magnetic field separation and centrifugation are appropriately combined, for example, it is possible to separate into red phosphor, blue phosphor, and degraded blue phosphor.

  In the above, the present invention has been described based on the specific numerical values shown in Tables 1 to 3. However, as already described, the numerical values in these tables are examples, and phosphors of the same color are used. However, the composition may differ depending on the manufacturer, and the composition of the phosphor of the same color may differ depending on the model number even if the manufacturer is the same. For example, the magnetic susceptibility of the phosphors for plasma display shown in Table 2 increases in the order of blue (BAM), green (ZSM), and red (YBO), but in a different order depending on the composition. There is also. However, the present invention can also be applied to such a case, and an appropriate separation condition may be set according to the magnetic susceptibility and density of the phosphor, the specific gravity of the solvent, and the like. Therefore, it is possible to separate phosphors of the same color from the same manufacturer for each product number.

  Hereinafter, examples will be shown to clarify the features of the present invention. In this example, as shown in FIG. 5, the phosphors were separated using the method 1 described above.

  Disperse the phosphor powder mixture containing LAP, BAM and YOX collected from the used fluorescent lamp (lamp) in water containing polycarboxylic acid surfactant, put it in a glass container, and place it under the superconducting magnet. (See FIG. 4A). The superconducting magnet used is a cylindrical toroidal coil arranged so that the cylinder axis is in the vertical direction. The magnetic field (vertical direction) is the strongest at the center of the cylinder, and from the center along the cylinder axis. A magnetic field gradient is formed so that the magnetic field decreases as it moves outward (contour lines of magnetic field strength are indicated by broken lines). As a result, LAP having a high magnetic susceptibility was levitated by the magnetic force toward the center of the superconducting magnet having a strong magnetic field, and part of the LAP adhered to the upper wall surface of the glass container (see FIG. 5B). Other phosphors BAM and YOX settled at the bottom.

At this time, in order to increase the purity of the separated phosphor, the phosphor powder in the solvent was once dispersed and then sedimented by gravity in about 10 minutes to 2 hours. At the time of LAP collection, the glass container was taken out of the superconducting magnet, LAP adhering to the upper wall surface of the glass container was collected with a spatula, and a solution near the liquid level (including LAP) was collected with a dropper. When the glass container was taken out of the superconducting magnet, LAP settled in the solution, but the lower solution was not collected, and contamination of phosphors of other colors was avoided. Further, in order to recover a large amount of LAP, surfactant-containing water was added to the remaining solution (including the phosphor), and the separation operation using a magnetic field was repeated as described above. Thereafter, the collected solution was heated to 700 ° C. to remove the surfactant, thereby recovering 56 mg of LAP having a purity of 99% or more from a mixture of 200 mg of the phosphor.

  The same as Example 1, except that the phosphor mixture was dispersed in isopropyl alcohol or normal butyl alcohol. As a result, LAP having a high magnetic susceptibility was levitated by the magnetic force in the direction of the center of the superconducting magnet having a strong magnetic field, and a part of the LAP was attached to the upper wall surface of the glass.

  In this example, as shown in FIG. 6 (a), a phosphor mixture containing LAP, BAM, and YOX recovered from a used fluorescent lamp is dispersed in water containing a surfactant, and a glass container is obtained. A rare earth permanent magnet was placed in the vicinity of the outer wall of the glass container that was placed and inclined. As a result, LAP could be concentrated in the vicinity of the side wall of the glass container on the side where the rare earth permanent magnets are arranged. The rare earth permanent magnet was a rectangular parallelepiped disk and was magnetized in the thickness direction of the disk (magnetic poles were formed on both sides in the thickness direction).

  Thereafter, as shown in FIG. 6B, the LAP could be separated from BAM and YOX and precipitated by standing the glass container vertically and separating the rare earth permanent magnet from the glass container. As a result, LAP having a purity of 99% or more could be recovered from the precipitate on the side where the rare earth permanent magnet was disposed.

  As a comparative experiment not using the present invention, a mixture of phosphor powders containing LAP, BAM, and YOX recovered from a used fluorescent lamp is dispersed in water containing a surfactant, placed in a glass container, and allowed to stand still. It was. LAP settled with a delay, and the upper part and the suspended part of the sediment were in a state of high LAP content, but most of the LAP was mixed with BAM and YOX and settled. That is, the three types of phosphors could not be separated.

  As a comparative experiment not using the present invention, a mixture of phosphors containing LAP, BAM, and YOX collected from a used fluorescent lamp was dispersed in distilled water, placed in a glass container, and inserted into the lower part of the superconducting magnet. . The phosphor slightly aggregated in distilled water and settled within 5 minutes, and separation of LAP having a high magnetic susceptibility could not be clearly observed.

G, LAP green phosphor B, BAM blue phosphor R, YOX red phosphor M solvent F _G, F _R magnetic force F _d gravity F _u buoyant

Claims (10)

A method of separating at least one phosphor from a mixture of a plurality of discarded phosphors,
A first step of charging the mixture into a fluid;
A second step of positioning at least a part of the fluid in a magnetic field having a gradient, and separating at least one kind of phosphor by a magnetic force generated in the phosphor. Method. The gradient is formed in a vertical direction;
The intensity of the magnetic field and the gradient is such that the resultant force acting on at least two types of phosphors is opposite in the resultant force of magnetic force, buoyancy and gravity acting on each of the plurality of types of phosphors. 2. The method for recycling waste phosphors according to claim 1, wherein the method is set.   The intensity of the magnetic field and the gradient are set so that the resultant force acting on one type of phosphor out of the two types of phosphors other than the two types of phosphors in which the resultant force is reversed is set to 0. The method for recycling a waste phosphor according to claim 2. The fluid is a liquid solvent;
The waste phosphor recycling method according to claim 1, wherein the first step includes a third step of suspending the phosphor charged in the solvent.   The method for recycling a waste phosphor according to claim 4, wherein the solvent is water containing a surfactant or an alcohol having a hydroxyl group. The plurality of types of phosphors include LaPO ₄ : Ce, Tb as a green phosphor and BaMgAl ₁₀ O ₁₇ : Eu and (Sr, Ca, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu as blue phosphors. ,
The solvent has a specific gravity of 1 or more,
The second step includes
5. The fourth step of collecting the green phosphor by setting a magnetic field distribution so that a product of the intensity of the magnetic field and the intensity of the gradient is 34.1 T ² / m or more and less than 107 T ² / m. Or the recycling method of the waste fluorescent substance of 5. The plurality of types of phosphors include Zn ₂ SiO ₄ : Mn as a green phosphor and (Y, Gd) BO ₃ : Eu as a red phosphor,
The solvent has a specific gravity of 1 or more,
The second step includes
A fifth step of setting the magnetic field distribution so that a product of the magnetic field intensity and the gradient intensity is 21.2 T ² / m or more and less than 110 T ² / m, and collecting the red phosphor;
Set the intensity and magnetic field distribution so that the product is less than 110T 2 / ^m or more 209T 2 / ^m between the intensity of the gradient of the magnetic field, according to claim 4 or 5 and a sixth step of collecting the green phosphor Recycling method of waste phosphor as described in 1.   The waste phosphor recycling method according to claim 1, wherein, in the second step, the fluid into which the mixture is introduced is passed through the magnetic field. An adsorbing means capable of adsorbing the phosphor is provided in the vicinity of the surface of the fluid into which the mixture is charged,
The recycling method of waste phosphors according to claim 1, wherein the phosphor floating on the surface of the fluid is collected by being attached to the adsorption means. The second step includes
A seventh step of flowing the fluid into which the mixture has been introduced along a flow path in which the gradient is locally formed;
The waste phosphor recycling method according to any one of claims 1 to 7, further comprising an eighth step of collecting the fluid existing in the vicinity where the gradient is formed.

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