JP2983044B2 - Phosphor regeneration method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for regenerating a phosphor from a recovered phosphor slurry containing carbon, dichromates and polyvinyl alcohol, and particularly to a phosphor for a cathode ray tube. Related to the reproduction method.

[Prior Art] The fluorescent screen of a color cathode-ray tube generally has red, blue and green light-emitting phosphors arranged in dots or stripes and formed on the inner surface of a face plate. As the phosphors for these color cathode ray tubes, generally, a copper-activated zinc sulfide phosphor, a copper-activated gold sulfide phosphor as a green light-emitting phosphor,
A silver activated zinc sulfide based phosphor is often used as a blue light emitting phosphor, and a europium activated yttrium oxysulfide based phosphor and a europium activated yttrium oxide based phosphor are often used as a red light emitting phosphor.

As a typical method for forming the phosphor screen, there is a method called a slurry method. The slurry method refers to, for example, polyvinyl alcohol (PVA) and ammonium bichromate (A
A slurry is formed by dispersing the phosphor in a mixed aqueous solution of DC) and a surfactant, and the slurry is uniformly applied to the inner surface of a face plate for a color cathode ray tube using, for example, a spin coater to form a shadow mask. Through a process of exposing to a predetermined pattern, fixing the exposed portion of the phosphor on the face plate, and washing away the remaining phosphor slurry layer, respectively, a blue-emitting phosphor, a green-emitting phosphor, and a red-emitting phosphor This is a method of forming a phosphor screen by repeating the process on the body. In a so-called black matrix type cathode ray tube, a phosphor screen is formed by previously forming dots or stripes of a black substance such as carbon or black chrome on the inner surface of the face plate and repeating the above steps.

The amount of the phosphor washed off in the slurry method is
Since the amount of the used phosphor is 70% or more, the washed away phosphor is collected and reused. In particular, it is important to reuse an expensive phosphor containing a rare earth element such as an yttrium-based red light-emitting phosphor.

However, ADC, P
Lubricating oil such as a spin coater and a recovery machine together with phosphor slurry components such as VA, carbon that has been peeled off from the already formed phosphor screen, black substances such as black chrome, phosphors of other luminescent colors,
Contaminants such as foreign matter and dust are included. For example, in the red light-emitting phosphor slurry recovered after the last coating step of the slurry method, in addition to the slurry components such as PVA and ADC,
A small amount of contaminants such as carbon, green light-emitting phosphor, blue light-emitting phosphor, and oil are included. If such a recovered phosphor slurry is reused as it is, the PVA solidifies, the volatile oil is volatilized at the time of forming the phosphor screen, or the non-volatile oil causes application unevenness, so that the uniformity is obtained. It is difficult to form a suitable phosphor screen, and a phosphor and a black substance of another emission color are mixed, which causes inconvenience in an image. Therefore, various methods have been conventionally proposed as a method for regenerating the recovered phosphor for removing these undesired components.

For example, JP-A-47-557 discloses that an alkali solution having a pH of 12 or more and a hypohalite such as sodium hypochlorite (NaOCl) are added to the recovered phosphor slurry and heated. A method of regenerating a phosphor by separating a rare-earth phosphor from the obtained suspension and washing with water is disclosed. According to this method, since a large amount of NaOCl is used at a high alkali concentration, the surface oxidation of the phosphor is intense,
There is a disadvantage that the luminance of the regenerated phosphor is drastically reduced.

Further, in JP-A-53-17587 and JP-A-53-30486, an alkali is added to the phosphor slurry recovered in the same manner, the liquid temperature is adjusted to 60 ° C., followed by washing with water and separation. A method for recovering a phosphor is disclosed. However, in the phosphor regenerated by this method, the silica or the like coated on the phosphor surface is dissolved together with the PVA by the alkali treatment, so that the dispersibility of the phosphor in the phosphor slurry and the dispersibility of the phosphor on the face plate are reduced. Adhesive strength is reduced.

Further, in JP-A-53-18489, by subjecting the phosphor to an alkali treatment, baking the phosphor at 200 to 400 ° C., and reattaching silica lost by dissolution or peeling, washing with water and separating. A method for regenerating a phosphor is disclosed. Phosphors regenerated in this manner have significantly improved adhesion loss but poor dispersibility.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and a phosphor capable of forming a uniform phosphor screen that has good luminance and dispersibility, excellent coating characteristics, and excellent coating properties. An object of the present invention is to provide a method for regenerating the obtained phosphor.

[Means for Solving the Problems] A method for regenerating a phosphor of the present invention is a method for regenerating a phosphor from a recovered phosphor slurry containing carbon, dichromates and polyvinyl alcohol, and comprises the following three steps: It is characterized by including.

The first step involves carbon, bichromates, and
A decomposition treatment step of separating the phosphor from the collected phosphor slurry containing contaminants such as PVA, and the second step is an oxide or oxide formed on the phosphor surface by the oxidizing agent used in the decomposition step. An acid treatment step for removing sulfides and improving the phosphor surface, and a third step is a surface treatment step for improving the dispersibility, coating characteristics, and the like of the phosphor.

In the decomposition treatment step, an alkali is added to the recovered phosphor slurry (after adding water and heating) to prepare a warm phosphor suspension having an alkali concentration of 0.5N or less in the slurry. , 1.0 to 2 with respect to the dry solid content in the recovered phosphor slurry
It is characterized by adding 0.0% by weight of an oxidizing agent.

The phosphor slurry is preferably heated to 70 ° C. or higher. This is to make the PVA, ADC and the like fixed to the recovered phosphor flexible.

The alkali, NaOH, KOH, LiOH, NH 4 OH, K 2 CO 3
And Na ₂ CO _{3 and the} like. The amount of alkali added is preferably 1.0% by weight or more, more preferably 2.0% by weight or more, based on the dry solid content in the phosphor slurry.

The amount of dry solid components excluding the phosphor in the phosphor slurry usually ranges from 1 to 20% by weight. Therefore, if the amount of the alkali added is less than 2.0% by weight, it is difficult to sufficiently decompose the contaminants in the phosphor slurry. . Further, when the alkali concentration exceeds 0.5 N, the oxidizing action when the oxidizing agent is added after the alkali treatment is too strong, so that the luminance and the coating characteristics tend to decrease.

If the amount of the oxidizing agent is less than 1.0% by weight, it is difficult to sufficiently remove PVA or the like coated on the phosphor surface from the phosphor. If the content is 20.0% by weight or more, the oxidizing action is too strong, and a large amount of oxide is generated on the phosphor surface, so that the luminance and coating characteristics are reduced. This amount is preferably 3 to 10% by weight.

As oxidizing agents, C ₃ H ₃ N ₃ O ₃ , C ₃ Cl ₂ NaN ₃ O ₃ and C ₃ Cl ₃ N ₃
O ₃ etc. can be used. Particularly, C ₃ H ₃ N ₃ O ₃ (isocyanuric acid) is preferable. It is effective to use chlorinated isocyanuric acid (C ₃ Cl ₂ NaN ₃ O ₃ , C ₃ Cl ₃ N ₃ O ₃ ) particularly for those containing a large amount of PVA or ADC. However, it is desirable not to use C ₃ Cl ₂ NaN ₃ O ₃ and C ₃ Cl ₃ N ₃ O ₃ when regenerating a zinc sulfide-based phosphor. Because C ₃ Cl ₂ NaN ₃ O ₃ and C ₃ Cl ₃
This is because N ₃ O ₃ has a strong oxidizing power to the phosphor, so that it significantly dissolves the zinc sulfide-based phosphor, thereby lowering the luminance of the zinc sulfide phosphor. On the other hand, when the zinc sulfide based phosphor is mixed in the recovered rare earth phosphor slurry, it is effective to use C ₃ Cl ₃ N ₃ O ₃ to suppress the light emission. Also, when an oxidizing agent other than isocyanuric acid is added in an amount of 10% by weight or more, the luminance of the recovered phosphor is significantly reduced.

In the acid treatment step, the phosphor is separated from the decomposition-treated suspension, washed with water, and then further added with an acid to adjust the pH to 3.0 to 5.0.

Examples of the acid include dilute sulfuric acid, dilute hydrochloric acid, and concentrated acetic acid, and it is particularly preferable to use concentrated acetic acid.

When regenerating a zinc sulfide phosphor, the pH of the suspension
If it is less than 3.0, the zinc sulfide-based phosphor dissolves violently, causing a decrease in luminance. On the other hand, when regenerating a rare earth phosphor mixed with a zinc sulfide-based phosphor, it is desirable to adjust the pH to 3.0 to 4.0 in order to dissolve the zinc sulfide-based phosphor.

The surface treatment step is preferably a water-soluble compound containing at least one element selected from the group consisting of Zn, Al and an alkaline earth metal in a suspension containing the phosphor, which is preferably sufficiently acid-washed and then thoroughly washed with water, and Colloidal silica having a particle size of 50 nm or less, at least one coating compound selected from the group consisting of alumina sol and titania sol is added, and the pH is adjusted.
This is a step of coating the surface of the phosphor with the coprecipitated compound by adjusting it to 6.5 to 7.5. Alternatively, after adding a water-soluble monomer such as acrylic acid or methacrylic acid to the above-mentioned suspension, a polymerization initiator such as ammonium persulfate is added, so that polyacrylic acid or polymethacrylic acid is added to the phosphor surface. May be applied. In addition to the above steps, a step of attaching silica, which is generally used when manufacturing a new phosphor, can be applied.

In the surface treatment step, the amount of the compound coated on the phosphor surface, for example, colloidal silica, is preferably in the range of about 0.005 to 1.5 parts by weight, and more preferably about 0.
It is preferable to adjust the addition amount so as to be 01 to 0.5 parts by weight. If the addition amount is less than 0.005 parts by weight, the adhesion of the regenerated phosphor to the face plate tends to be insufficient, and if it exceeds 1.5 parts by weight, the dispersibility tends to deteriorate, so that a uniform phosphor screen is obtained. Difficult to get. The amount of the water-soluble metal compound is such that the amount of the metal ion is
About 0.003 to 0.5% by weight, preferably about
It is preferably 0.01 to 0.1 part by weight. This metal compound includes zinc sulfate, zinc nitrate, aluminum sulfate,
Aluminum nitrate, calcium nitrate, magnesium nitrate, strontium nitrate and the like can be used.

As colloidal silica, commercially available Ludox AM (manufactured by DuPont), Snowtex BK, Snowtex AM (manufactured by Nissan Chemical), alumina sol 520
(Manufactured by Nissan Chemical Industries, Ltd.) and titania sol can be used. Further, commercially available ultrafine powder of silica and titania having a particle size of 50 nm or less, for example, titanium dioxide P25 (manufactured by Aerosil) can be used. When using this ultrafine powder, suspend the ultrafine powder in water in advance, and adjust the pH of the suspension.
Must be adjusted to 10 or more, and milled to form a colloid or sol. However, if the particle size exceeds 50 nm, the dispersibility of the phosphor deteriorates. Therefore, a particle size of 50 nm or less is selected.

Further, when the phosphor to be regenerated is a phosphor with a pigment, a part of the pigment is peeled off in the first decomposition step, so that at least one binder selected from the group consisting of gelatin and urea resin emulsion is preferably used. By adding a pigment, a surface treatment step for supplementing the peeled pigment can be performed. In addition, a pigment can be attached using a commonly used organic binder.

The amount of the binder is usually about 30 to
50% by weight. As the binder to be used, gelatin or a urea resin emulsion may be used alone or in combination. When these are used as a mixture, it is preferable to use the gelatin and the urea resin in a weight ratio of 1: 1 to 10: 1. The weight ratio in this range is preferable because the pigment is firmly attached to the phosphor and the dispersibility of the phosphor is improved.

The pigment is mainly attached to improve the contrast of the screen, and as such a pigment, a pigment having the same color as the emission color of the phosphor is usually used. Ultramarine and cobalt blue are used for titanium green and blue light emitting phosphors, and red iron oxide (yellow) and yellow iron oxide are used for red light emitting phosphors.

Further, depending on the type of the recovered phosphor, there is a recovered slurry in which the dispersibility of the phosphor is insufficient when performing the above three steps, due to the extremely strong cohesion of the phosphors. Normally, by using an isocyanuric acid-based oxidizing agent in the decomposition treatment step, sufficient dispersibility can be obtained. However, if desired, a dispersion step using a bead mill or a ball mill can be performed. This dispersing step is usually carried out by carrying out an acid treatment step and then transferring the phosphor together with water to a mixer tank containing balls or beads and stirring for about 30 minutes. This step is particularly effective for those having a strong cohesive force of the recovered phosphor or those to which a lump of PVA which is difficult to decompose is attached.

[Function] According to the method of the present invention, first, in the decomposition treatment step, the phosphor slurry is heated to, for example, 70 ° C. or more, so that the PVA, ADC, and the like coated on the collected phosphor surface are softened. can do. Next, the phosphor is dispersed by adding an alkali, and the softened PVA, ADC, and the like are easily dissolved in the warm alkali suspension. Further, the carbon contained between the phosphors is completely released in the suspension by the dispersion of the phosphors, and floats in the alkaline suspension because its specific gravity is smaller than that of the phosphors. Furthermore, by adding an oxidizing agent, PVA, A softened by alkali
DC and the like can be peeled off. In particular, an isocyanuric acid-based oxidizing agent is very easy to handle because it is in a powder form, and has an effect of peeling off solid PVA attached to the phosphor because of its high oxidizing power. Thereafter, an oxide treatment or an sulfide generated on the phosphor surface by the oxidizing agent can be removed by an acid treatment step, or another light emitting component can be removed in the recovery of the rare earth phosphor slurry. Furthermore, the dispersibility and coating characteristics of the phosphor can be improved by a surface treatment step thereafter.

(Example) Hereinafter, an example is shown and the present invention is explained concretely.

Example 1 Pretreatment Step First, 300 ion-exchanged water (hereinafter, referred to as water) is put into a tank, and a recovered blue light-emitting phosphor ZnS: Ag, Al having PVA, ADC, and the like fixed to the tank (200 kg in dry weight). Was added while crushing. Further, water was added to prepare a total of 500 phosphor suspensions and stirred for 30 minutes.

Next, while stirring the suspension, the bottom valve of the tank was opened to flow out of the tank, and the suspension was passed through a nylon 300 mesh sieve to remove foreign substances and dust, and stored in another tank.

Decomposition Treatment Step Water was further added to the phosphor suspension contained in another tank to make the total amount 600. While stirring the phosphor suspension, 5 kg of NaOH was added as an alkali, and the temperature of the solution was adjusted to 75 ° C. by blowing heated steam. To this phosphor suspension, 15 kg of isocyanuric acid (C ₃ H ₃ N ₃ O ₃ ) was added as an oxidizing agent, and 1. while keeping the liquid temperature at 75 ° C.
Stir for 5 hours. After completion of the stirring, the phosphor suspension was left to settle the phosphor. After the phosphor has sufficiently settled,
The side valve connected to the side of the tank was opened, and the supernatant solution containing the dissolved PVA, ADC and the like was discharged.

Further water was added to the remaining phosphor suspension to bring the total volume to 80.
The mixture was stirred at 0, stirred for 10 minutes, the phosphor suspension was left to sediment the phosphor, the side valve was opened, and the supernatant was discharged to wash the phosphor with water. further,
The water washing operation was repeated several times until the pH value of the phosphor suspension reached around 7.

Water was added to the obtained phosphor suspension to make the total amount 500, and the bottom valve of the tank was opened with stirring, and the phosphor suspension was passed through a 300-mesh sieve, so that it was not dissolved by alkali, PVA and A separated from phosphor with oxidizing agent
DC was removed. The suspension thus wet-sieved was placed in another tank.

Weak acid treatment step Water was added to the contained phosphor suspension to make the total volume 600, and concentrated acetic acid was added dropwise while stirring to adjust the pH value of the phosphor suspension to 4.2. This phosphor suspension was stirred for 5 minutes and then left to sediment the phosphor. Thereafter, the same washing operation was performed several times until the pH value became around 7 in the same manner as in the above-mentioned decomposition treatment step, and this suspension was stored in another tank.

Surface treatment step Water is added to the obtained phosphor suspension to make the total amount 600, and 20 wt% of colloidal silica (Ludox AM, manufactured by DuPont) having a particle size of about 20 nm is added to the phosphor suspension while stirring.
Was added to aqueous dispersion 1 and 1.2 wt% aqueous zinc sulfate solution, and the pH was adjusted to 7.4 by adding aqueous ammonia, followed by stirring for 10 minutes to attach silica to the phosphor surface.
After that, the phosphor suspension is left to sediment the phosphor,
Water washing operation was performed several times until the pH value reached around 7 in the same manner as in the acid treatment step to obtain a phosphor suspension of the regenerated phosphor.

Storage Water was added to the obtained phosphor suspension, and the suspension was stored in another tank with stirring, and the regenerated phosphor was stored in a state containing water.

A part of this phosphor suspension was taken, filtered and dried, and the relative luminance of the regenerated phosphor obtained when the emission luminance of the new phosphor was set to 100 was measured. Also PV at normal rate
A, ADC and a surfactant were added to form a regenerated phosphor slurry, and the coating properties were examined. The coating characteristics are as follows: the volume average diameter (Dm) of the phosphor in the phosphor slurry;
After the centrifugation of the ml at 1000 rpm for 15 minutes, the sedimentation volume of the phosphor was measured to evaluate the dispersibility of the phosphor. Table 1 shows the results. Dm is preferably as close to new as possible, and the smaller the sedimentation volume, the better the dispersibility of the phosphor.

 Further, the adhesive strength of the phosphor was evaluated as follows.

After the phosphor slurry is applied to the face plate and dried, a filter having a variable transmittance is provided between the exposure light source and the shadow mask when exposing the phosphor screen with a stripe-shaped shadow mask. The stripe width of the phosphor screen formed when exposed with a filter with a transmittance of 100%
The thickness is set to 180 μm, and the light transmittance of the filter is gradually reduced to reduce the exposure amount. As the exposure amount is reduced, the stripe width of the phosphor screen becomes narrower, and finally striping of the stripe occurs. Therefore, the width of the stripe when the stripe started to peel was evaluated as the adhesive strength of the phosphor. That is, it can be considered that the smaller the stripe width at which peeling starts, the stronger the adhesive force.

Comparative Example 1 As Comparative Example 1, a phosphor was obtained by performing only the same pretreatment step as in Example 1 and the same decomposition treatment step as in Example 1 except that 10 kg of Na ₂ S ₂ O ₈ was added as an oxidizing agent. Was regenerated and the measurement was performed in the same manner. Table 1 shows the results.

Comparative Example 2 As Comparative Example 2, a phosphor was regenerated by performing the same surface treatment step as in Example 1 after the same treatment step as in Comparative Example 1, and the measurement was performed in the same manner. The result is
It is shown in the table.

Example 2 Pretreatment Step A pretreatment was performed in the same manner as in Example 1 except that a green phosphor of ZnS: Cu, Au, Al having a dry weight of 200 kg was used as the recovered phosphor.

Decomposition treatment step A decomposition treatment step was performed in the same manner as in Example 1 except that 12 kg of chlorinated isocyanuric acid was added as an oxidizing agent.

Acid treatment step The acid treatment step was performed in the same manner as in Example 1.

Surface treatment step To the obtained phosphor suspension, an aqueous solution of aluminum nitrate 6.5 containing 2.0% by weight of aluminum and 1 kg of the colloidal silica used in Example 1 were added, and the pH of the suspension was adjusted to 6.5 with aqueous ammonia. By adjusting, they were attached to the surface of the phosphor. Thereafter, a washing operation was performed in the same manner as in Example 1 to obtain a phosphor suspension of the regenerated phosphor.

Storage In the same manner as in Example 1, the regenerated phosphor was stored.

The same measurement as in Example 1 was performed using the obtained regenerated phosphor. Table 1 shows the results.

Comparative Example 3 As Comparative Example 3, a phosphor was obtained by performing only the same pretreatment step as in Example 2 and the same decomposition treatment step as in Example 2 except that 10% of 30% H ₂ O ₂ was added as an oxidizing agent. Was regenerated and the measurement was performed in the same manner. Table 1 shows the results.

Comparative Example 4 As Comparative Example 4, a phosphor was regenerated by performing a surface treatment step similar to that of Example 2 after a treatment step similar to that of Comparative Example 3, and measurement was performed in the same manner. The result is
It is shown in the table.

Example 3 Pretreatment A pretreatment was performed in the same manner as in Example 1 except that a 200 kg by dry weight of Y ₂ O ₂ S: Eu, Sm red light emitting phosphor was used as the recovered phosphor.

Decomposition process Tolchlorisocyanuric acid (C ₃ Cl ₃ N
_A decomposition treatment step was performed in the same manner as in Example 1 except that 10 kg of ₃ O ₃ ) was added.

Acid Treatment Step Water was added to the obtained phosphor suspension to make the total amount 600, and heated steam was blown into the suspension to promote the reaction while stirring the suspension, and the liquid temperature was set to 70 ° C. Dilute hydrochloric acid was added to the phosphor suspension to adjust the pH to 4.0, and the mixture was stirred for 30 minutes while maintaining the liquid temperature at 70 ° C.

After stirring, the phosphor suspension was left to sediment the phosphor. Thereafter, a washing operation was performed in the same manner as in Example 1.

Surface treatment step Water was added to the obtained phosphor suspension to make the total amount 600, and 5% by weight of polymethacrylic acid 1 and 100 g of ammonium persulfate were added with stirring. Heated steam was blown into this phosphor suspension to warm the liquid temperature to 70 ° C. and stirred for 1 hour. After stirring, the phosphor suspension was left to stand, the phosphor was allowed to settle, and a washing operation was performed in the same manner as in Example 1 to obtain a phosphor suspension of a regenerated phosphor.

Storage The regenerated phosphor was stored in the same manner as in Example 1.

The same measurement as in Example 1 was performed using the obtained regenerated phosphor. Table 1 shows the results.

Comparative Example 5 As Comparative Example 5, a phosphor was prepared by performing only the same pretreatment step as in Example 3 and the same decomposition treatment step as in Example 3 except that 30% H ₂ O ₂ 10 was added as an oxidizing agent. The sample was regenerated and the measurement was performed in the same manner. Table 1 shows the results.

Comparative Example 6 As Comparative Example 6, a phosphor was regenerated by performing the same surface treatment step as in Example 3 after the same treatment step as in Comparative Example 5, and the measurement was performed in the same manner. The result is
It is shown in the table.

Example 4 Pretreatment Step As a recovered phosphor, a phosphor slurry containing 200 kg of a pigmented red light-emitting phosphor Y ₂ O ₂ S: Eu, Sm to which 0.3% of Fe ₂ O ₃ (Bengara) is attached, and 700 ppm of a ZnS-based phosphor. A pretreatment was performed in the same manner as in Example 1 except for using.

Decomposition treatment step The decomposition treatment step was performed in the same manner as in Example 1.

Acid treatment step An acid treatment step was performed in the same manner as in Example 3.

Surface treatment (pigment adhesion) step A part of the phosphor suspension of the washed phosphor is separated, filtered, dried, and the reflectance of the obtained regenerated phosphor and the reflectance of a new phosphor are measured. Measurements and comparison showed that about 40% of the attached pigment was exfoliated or dissolved.

Then, water was added to the phosphor suspension to reduce the total amount to 600.
With stirring, 240 g of Fe ₂ O ₃ , 60 g of gelatin and 25 g of a urea resin emulsion were added, acetic acid was added to adjust the pH to 5, and the mixture was stirred for 30 minutes. After stirring, a water washing operation was performed in the same manner as in Example 1.

Storage While stirring the obtained phosphor suspension, open the valve at the bottom of the tank, pass this phosphor suspension through a Nutsche funnel covered with a filter cloth, and filter to remove water sufficiently. It was taken out and dried with a dryer at 120 ° C. to obtain a phosphor with a pigment, which was stored.

The measurement was carried out in the same manner as in Example 1 using the obtained phosphor with pigment. Table 1 shows the results.

Comparative Example 7 As Comparative Example 7, the phosphor was regenerated by performing only the pretreatment and decomposition treatment steps in the same manner as in Example 4, and the measurement was performed in the same manner. Table 1 shows the results.

Comparative Example 8 As Comparative Example 8, a phosphor was regenerated by performing a surface treatment step similar to that of Example 4 after a treatment step similar to that of Comparative Example 7, and measurement was performed in the same manner. The result is
It is shown in the table.

Example 5 Pretreatment Step A pretreatment was performed in the same manner as in Example 1 except that a 200 kg by dry weight Y ₂ O ₂ S: Eu red light emitting phosphor was used as the recovered phosphor. The recovered phosphor was solidified in PVA and ADC, and was in a solid state rather than a slurry state.

Decomposition treatment step The decomposition treatment step was performed in the same manner as in Example 1.

Acid treatment step An acid treatment step was performed in the same manner as in Example 3.

Dispersion Step After the obtained phosphor suspension was washed with water in the same manner as in Example 1, the suspension was transferred to a mixer mill containing beads and stirred for 30 minutes. After the stirring, the lower valve of the mixer mill was opened to separate the phosphor suspension from the beads. This suspension was then placed in another tank.

Surface treatment step A surface treatment step was performed in the same manner as in Example 3.

Storage The regenerated phosphor was filtered, dried and stored in the same manner as in Example 4.

The measurement was performed in the same manner as in Example 1 using the obtained regenerated phosphor. Table 1 shows the results.

Comparative Example 9 As Comparative Example 9, fluorescence was obtained by performing only the same decomposition treatment step as in Example 5 except that the same pretreatment step as in Example 5 and the addition of 10 NaOCl (effective chlorine amount 12%) as an oxidizing agent were performed. The body was regenerated and measurements were made in a similar manner. Table 1 shows the results.

Comparative Example 10 As Comparative Example 10, the phosphor was regenerated by performing the same surface treatment steps as in Example 5 after the same treatment steps as in Comparative Example 9, and the measurement was performed in the same manner. The result is
It is shown in the table.

As is clear from the table, Examples 1 to 5 have relative luminance, Dm
Values, sedimentation volume and adhesive strength are all good, but without acid treatment and surface treatment step (Comparative Examples 1, 3, 5, 7,
In 9), the Dm value and the sedimentation volume are particularly increased, and the adhesive strength is extremely poor.

When the acid treatment is not performed (Comparative Examples 2, 4, 6, 8, 10),
Since the surface treatment substance is attached to the phosphor, it is possible to obtain a recycled phosphor that is almost new. However, by performing the acid treatment step as in Examples 1 to 9, oxides or sulfides on the phosphor surface are removed, and the surface condition of the phosphor is improved. As a result, a sufficient effect of the attached surface treatment substance can be obtained, and a phosphor having good dispersibility and coating properties can be obtained. Especially, what we did not expect,
With respect to the adhesive strength, coating properties superior to those of a new phosphor could be achieved.

[Effects of the Invention] As described above, according to the method of the present invention, carbon, bichromates and
It is possible to efficiently separate only the phosphor from the phosphor slurry containing PVA and to minimize the oxides generated on the surface, and it is possible to minimize the amount of oxides or It is possible to effectively remove sulfides and improve the condition of the phosphor surface. Third
The dispersibility and coating characteristics of the phosphor can be improved in the surface treatment step. In particular, by using an isocyanuric acid-based oxidizing agent in the first decomposition treatment step, it is possible to decompose and remove even solid PVA strongly adhered to the phosphor. For this reason, the dispersibility of the phosphor is greatly improved. Furthermore, since the isocyanuric acid-based oxidizing agent is in a powder form, it can be easily handled, hardly splatters on a human body like a liquid, and can be safely operated. If the conventional oxidizing agent is added in an amount of 10% by weight or more based on the dry solid content of the recovered slurry, the brightness of the recovered phosphor is significantly reduced. However, the brightness decreases even if 20% by weight of the isocyanuric oxidizing agent is added. Can not be seen.

As described above, according to the method of the present invention, there is provided a method for regenerating a recovered phosphor, in which a phosphor having good luminance and dispersibility, excellent coating properties, and capable of forming a uniform phosphor screen is obtained. You.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoichi Bando 491-100 Kaminakacho Oka, Anan City, Tokushima Prefecture Inside Nichia Chemical Industry Co., Ltd. A Chemical Industry Co., Ltd. (58) Fields surveyed (Int. Cl. ⁶ , DB name) C09K 11/00-11/89

Claims (6)

(57) [Claims] 1. A method for regenerating a phosphor from a recovered phosphor slurry containing carbon, dichromates and polyvinyl alcohol, comprising: (a) adding an alkali to the recovered phosphor slurry;
A warm phosphor suspension having an alkali concentration of 0.5 N or less in the slurry was prepared, and C ₃ H ₃ N ₃ O ₃ and C ₃ Cl ₂ NaN ₃ O ₃ were added to the suspension.
And at least one selected from the group consisting of C ₃ Cl ₃ N ₃ O ₃
The oxidizing agent is added to the suspension at 1.0-2
A decomposition treatment step of adding 0.0% by weight; and (b) an acid treatment of separating the phosphor from the suspension, adding an acid to the suspension obtained by adding water, and adjusting the pH to 3.0 to 5.0. And (c) a surface treatment step of treating the surface of the phosphor separated from the suspension. 2. The method according to claim 1, wherein the amount of the alkali added is 1.0% by weight or more based on the dry solid content of the phosphor slurry. 3. The surface treatment step is a step of adding at least one adhesive and a pigment selected from the group consisting of gelatin and urea emulsion to the acid-treated phosphor suspension. The method according to claim 1, wherein 4. The surface treatment step comprises the steps of: adding a water-soluble compound containing at least one element selected from the group consisting of Zn, Al and an alkaline earth metal to the acid-treated phosphor suspension; The method according to claim 1, wherein at least one selected from the group consisting of colloidal silica, alumina sol, and titania sol having a size of 50 nm or less is added to adjust the pH to 6.5 to 7.5. 5. The surface treatment step comprises adding acrylic acid or methacrylic acid to the acid-treated phosphor suspension,
The method according to claim 1, wherein the step of coating the phosphor surface with polyacrylic acid or polymethacrylic acid by adding a polymerization initiator. 6. The method according to claim 1, further comprising a dispersion step of dispersing the phosphor in a ball mill or a bead mill after the acid treatment step.