JP3464072B2 - Recycling treatment of recovered phosphor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating a fluorescent substance recovered in a fluorescent film forming step of a color picture tube.

[0002]

2. Description of the Related Art The fluorescent film of a color picture tube is usually blue,
The green and red phosphors are polyvinyl alcohol
Phosphor, ammonium dichromate, and other surfactants in a predetermined ratio to prepare a phosphor slurry, which is applied by spin coating to the front face of a face plate on which a black matrix has been previously formed with carbon. The phosphor slurry is coated by a suitable coating method such as a method such as UV irradiation through a shadow mask, an aperture grill or the like to cure a predetermined portion, and then development with warm water is performed in three colors. A so-called slurry coating and exposure method, which is performed on the phosphor, forms a phosphor screen of dots or stripes in a predetermined array.

By the way, the collected phosphors include those collected by shaking off the face plate in the coating step and those cleaned by developing water in the developing step. The former is
Depending on the coating method, it will be many times the coating amount of the phosphor,
Even in the latter case, it reaches 70% or more of the phosphor coating amount. Among these recovered phosphors, particularly expensive red phosphors containing rare earths are recovered and reused.

However, in the recovered phosphor, in addition to the polyvinyl slurry and ammonium dichromate, which are constituents of the phosphor slurry, a phosphor different in emission color from the recovered phosphor (red phosphor slurry) is used. Blue and green light emitting sulfide phosphors) are mixed therein, and further, carbon in the black matrix formed on the face plate is partly removed and mixed. In particular, the phosphor recovered in the developing step contains more phosphors of other colors because the unexposed portion was washed off with the developing water.

Such a recovered phosphor is usually reused by removing impurities to increase its purity. As a method of regenerating the recovered phosphor, for example, polyvinyl alcohol is used from the surface of the recovered phosphor. In order to remove it, a method of treating the recovered phosphor slurry by adding an oxidizing agent and an alkaline agent (see JP-A-3-247688), and collecting blue and green phosphors in the recovered red phosphor. In order to remove, a method of treating with an aqueous solution containing NaOH, NaClO and H ₂ O ₂ and then treating with a mineral acid (Japanese Patent Laid-Open No. 6-
No. 108047), a method of treating with a chemical solution containing a chelating agent, an oxidizing agent and an alkaline agent in order to remove copper or a copper compound adhered to the surface of the phosphor (see JP-A-3-217483). ) Etc. have been proposed.
However, in such a conventional recovery phosphor regeneration method,
Since it is necessary to carry out substantially many chemical treatment steps in a stepwise combination, the steps are complicated and dangerous.

When a red phosphor such as Y ₂ O ₂ S: Eu is treated with a mineral acid, the mineral acid reacts with the sulfide of the phosphor mixed in the red phosphor to generate hydrogen sulfide. Generated, and this reacts with Cu ²⁺ in the system to cause insoluble CuS, CuO,
A copper compound such as Cu (OH) ₂ is generated and strongly adheres to the phosphor surface. Such a copper compound is difficult to remove from the red phosphor, and adversely affects the phosphor coating film at the time of recycling.

That is, ZnS: Ag, which is a blue phosphor, is partially contained in the ZnS:
In some cases, the composition of Cu may change to generate green spots (green discoloration) in the blue pixel portion, resulting in defective color (color mixing) of the blue pixel. Further, if the recovered phosphor is directly exposed to a strong oxidant, there is a problem that the regenerated phosphor is easily deteriorated by oxidation.
The improvement was desired.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned drawbacks of the conventional method for recovering recovered phosphors, and organic substances such as polyvinyl alcohol adhered to the surface of phosphors, especially red-emitting phosphors. Also, it is possible to reliably remove unnecessary zinc compounds, copper compounds, and the like without combining stepwise chemical solution treatment steps, and to provide a method for regenerating a recovered phosphor that does not cause oxidative deterioration of the phosphor itself. The purpose is.

[0009]

The present invention is a method of regenerating a recovered phosphor, which comprises treating the phosphor recovered in the phosphor film forming step with an aqueous solution containing ozone.
In addition, it is preferable to add at least one of an alkaline agent, an oxidizing agent excluding ozone, and a chelating agent to the aqueous solution containing ozone. As the chelating agent,
It is more preferable to use ethylenediaminetetraacetic acid (EDTA) or tetraethylenepentamine (TETREN).

Next, the method for regenerating the recovered phosphor of the present invention will be described more specifically. Slurry coating, a phosphor containing impurities such as polyvinyl alcohol and chromate collected in the process of forming a fluorescent film of a cathode ray tube by an exposure method is suspended in water to form a slurry, and ozone gas is added to this. Aerate well, stir, leave still, remove supernatant, wash with water,
A dehydrated phosphor is obtained by dehydration and drying. The ozone gas used here may be directly blown into the phosphor slurry, but ozone gas-containing water generated by previously aerating ozone gas may be added to the phosphor slurry.
The above treatment with ozone gas may be repeated a plurality of times.

Incidentally, at least one of an alkaline agent, an oxidizing agent other than ozone, and a chelating agent is simultaneously added to the slurry prepared by suspending the fluorescent material in water, whereby impurities in the recovered fluorescent material are added. The removal effect can be further improved,
If an alkaline agent and an oxidizing agent are mixed together with ozone gas, the effect is significantly improved.

Examples of the alkaline agent used in the present invention include ammonia water, sodium hydroxide, potassium hydroxide, and the like, and oxidizing agents other than ozone include hydrogen peroxide, alkali periodate, and the like. You can Examples of the chelating agent include water-soluble ethylenediaminetetraacetic acid (EDTA) and tetraethylenepentamine (TETREN).

[0013]

The cured product or aggregate of polyvinyl alcohol or chromic acid is mixed in the phosphor recovered in the fluorescent film forming step. According to the treatment method of the present invention, ozone is cross-linked with polyvinyl alcohol. At the same time, they attack the molecule and the cross-linked portion with chromate ion to decompose and elute them. On the other hand, regarding copper and zinc sulfides in the recovered phosphor,
Ozone gas oxidizes to compounds such as sulfates that are soluble in the aqueous chemical solution, and is separated and removed from the recovered phosphor.

At this time, if a water-soluble chelating agent is added, the above-mentioned impurity substances can be separated and removed from the recovered fluorescent substance by both the oxidizing action of ozone and the capturing and dissolving actions of the water-soluble chelating agent. It seems to be a thing.

According to the present invention, for example, in the case of recovering and regenerating a red light emitting phosphor, a step of removing polyvinyl alcohol and the like with an alkali agent and an oxidizing agent, and zinc and zinc generated from the mixed sulfide phosphor. Mineral acid (HC
(1), H ₂ SO ₄ , HNO ₃ etc.), the contaminants of the recovered phosphor can be removed more easily than the conventional treatment method combined with the step of removing the phosphor.

Further, in the processing method of the present invention, high concentration of H
Since the phosphor is not treated with a mineral acid such as Cl, H ₂ SO ₄ , HNO ₃ or the like, it suppresses the oxidative deterioration reaction of the red phosphor such as Y ₂ O ₂ S: Eu to reduce the brightness and the yield. The decrease can be prevented.

Further, in the conventional method, in order to remove copper and copper compounds, a treatment with a mineral acid is carried out, followed by a chelating agent,
It was necessary to treat with an aqueous chemical solution containing an oxidizing agent other than an alkaline agent and ozone, but like the present invention,
If a chelating agent, an alkaline agent, and an oxidizing agent other than ozone are mixed in an aqueous solution containing ozone at the same time, there is no need for pretreatment with a mineral acid, and copper and copper compounds can be simultaneously and reliably removed.

It should be noted that the method of regenerating the recovered phosphor of the present invention can be applied not only to the phosphor itself but also to a pigmented phosphor having pigment particles adhered to its surface for improving contrast. There is no end.

[0019]

【Example】

(Example 1) Red phosphor (Y ₂ O ₂ S: Eu) 30 recovered in the developing process and coating process when forming a fluorescent film of a cathode ray tube
Put 0g in a beaker, deionized water at room temperature (25 ° C) 1
Add 000 ml, then add 3 g of ethylenediaminetetraacetic acid (EDTA) as a chelating agent (0.3% in total) and stir thoroughly, then add 5.3 ml of 8% NaOH.
(0.04% total) and 7.2 ml of 35% hydrogen peroxide (0.25% total) were added.

Next, while maintaining the suspension at room temperature (25 ° C.), ozone gas (concentration 0.1 g / l) was blown at a rate of 2 l / min from the bottom to blow O ₃ as a total amount of about 30 g as O _3. The turbid liquid was stirred for 150 minutes, and then allowed to stand for 40 minutes to settle the phosphor, and the supernatant was decanted and further washed twice with deionized water. Thereafter, this phosphor slurry was filtered, dehydrated, dried at 120 ° C., and sieved with 325 mesh to obtain a regenerated phosphor of Example 1.

Example 2 The regenerated phosphor of Example 2 was prepared in the same manner as in Example 1 except that the addition of the chelating agent ethylenediaminetetraacetic acid, NaOH and hydrogen peroxide was omitted. Got

Example 3 A regenerated phosphor of Example 3 was obtained in the same manner as in Example 1, except that the addition of ethylenediaminetetraacetic acid, which is a chelating agent, was omitted.

Comparative Example 1 300 g of the red phosphor (Y ₂ O ₂ S: Eu) recovered in the same manner as in Example 1 was placed in a beaker, 1000 ml of deionized water at 75 ° C. was added, and then 8 % NaOH (total 0.04%) and 35% hydrogen peroxide 7.2 ml (total 0.25%) were added. Next, the above suspension was stirred for 150 minutes and then allowed to stand for 40 minutes to allow the phosphor to settle, and the supernatant was decanted and washed twice with deionized water. Then, this phosphor slurry is filtered, dehydrated and dried at 120 ° C.
Sieving was performed with 25 mesh to obtain a regenerated phosphor of Comparative Example 1.

Comparative Example 2 The regenerated phosphor obtained in Comparative Example 1 was further treated with a detergent containing 1000 ml of 4.5N hydrochloric acid at 55 ° C. to obtain a regenerated phosphor of Comparative Example 2.

Comparative Example 3 The regenerated phosphor obtained in Comparative Example 2 was added with 1000 ml of deionized water at 65 ° C. to obtain 8% Na.
Treatment with 5.3 ml OH (total 0.04%), 7.2 ml 35% hydrogen peroxide (total 0.25%) and ethylenediaminetetraacetic acid (total 0.3%) as a chelating agent. Further treatment with the agent gave the regenerated phosphor of Comparative Example 3.

(Comparative Example 4) The recovered phosphors (untreated) used in Examples 1 to 3 and Comparative Examples 1 to 4 were referred to as the phosphors of Comparative Example 4 and were used as a control for comparison.

(Evaluation) For the phosphors of Examples 1 to 3 and Comparative Examples 1 to 4, the loss on ignition, the contents of zinc, copper and chromium, and the amount of yttrium eluted were measured, and the results are shown in Table 1. In addition, here, the ignition loss is 450 ° C. for each phosphor.
It is a value expressed as a percentage of the weight reduction amount after the heat treatment in step 1. The larger the value, the higher the organic substance content in each phosphor.

The contents of zinc, copper and chromium are such that each phosphor is completely dissolved in nitric acid, and zinc and chromium are IC
The values are obtained by quantitative analysis with a P emission spectrophotometer and copper with a colorimetric method using a spectrophotometer. Further, the amount of yttrium to be eluted is a value obtained by quantitatively analyzing the amount of yttrium eluted in the supernatant of the slurry in which each phosphor is suspended by an ICP emission spectrophotometer, and the larger this value is, the regeneration treatment step. Y ₂ O ₂ S: E by each chemical solution in
It shows that the elution amount of the u phosphor is large and the degree of oxidative deterioration of the phosphor itself is large.

As is clear from Table 1, the regenerated phosphor treated with the chemical solution containing ozone (Examples 1 to 1)
3) is a relative loss on ignition, zinc, copper and chromium contents compared to the phosphors (Comparative Examples 1 to 3) and the untreated phosphor (Comparative Example 4) treated by the conventional regeneration treatment method. , And the amount of dissolved yttrium is small, the content of contaminants is drastically reduced,
Further, it can be seen that the oxidative deterioration of the phosphor itself could be avoided.

[0030]

[Table 1]

[0031]

According to the present invention, by adopting the above constitution, a large number of chemical treatment steps are combined in the regenerating treatment of the phosphor recovered in the developing step and the coating step in forming the fluorescent film of the cathode ray tube. In addition to curing and agglomerating and adhering to and mixing with the phosphor, it is possible to efficiently remove impurities such as organic substances and chromium components, unwanted phosphor components and copper components, and to oxidize the phosphor itself. The phosphor can be regenerated without deterioration.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-3-217483 (JP, A) JP-A-4-23886 (JP, A) JP-A-6-108047 (JP, A) JP-A-51- 131486 (JP, A) JP 3-247688 (JP, A) JP 6-33051 (JP, A) JP 2-94287 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C09K 11/00-11/89 CA (STN)

Claims (3)

(57) [Claims] 1. A method for regenerating a recovered phosphor, which comprises treating the phosphor recovered in the phosphor film forming step with an aqueous solution containing ozone. 2. The method for regenerating a recovered phosphor according to claim 1, wherein the aqueous solution contains at least one of an alkaline agent, an oxidizing agent other than ozone, and a chelating agent. 3. The method for regenerating a recovered phosphor according to claim 2, wherein the chelating agent is ethylenediaminetetraacetic acid (EDTA) or tetraethylenepentaamine (TETREN).