JPH0412751B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a phosphor that can be suitably used in the production of television cathode ray tubes. [Prior Art] A television cathode ray tube has the structure shown in FIGS. 3 and 4, for example, and the phosphor screen is generally formed by forming three colors on the inner surface of a face plate 11 provided with a black matrix 13. Phosphor picture element R
(red), G (green), and B (blue), and then filming treatment to make the surfaces of the phosphors R, G, and B uniform and smooth in order to increase the reflective effect of the metal back 12. After that, for example, aluminum is vapor deposited to provide the metal back 12, and finally, the filming material other than the phosphor portion is burned. However, in the series of operations for creating the phosphor screen as described above, for example, a part of the blue picture element B (for example, the shaded area 4 in Fig. 4) was contaminated with a very small amount of Cu, and the original color was lost. A color change occurs, for example, from blue luminescence to green luminescence. In other words, troubles such as green spots appearing in the blue picture element B and poor coloring of the blue picture element often occur during the manufacture of cathode ray tubes. The green discoloration of this blue picture element is due to the trace amount of Cu mixed in with the blue phosphor.
This is thought to be due to a compositional change from ZnS:Ag to ZnS:Cu or ZnS:Cu:Ag. Therefore, when we investigated the causes of such Cu contamination, we found that Cu powder, Cu
External factors such as compounds, etc., and the phosphor itself
This is thought to be an internal factor that brings the source of Cu contamination. Further investigation into the source of contamination of blue phosphor reveals that
In addition to blue pixels, there are also quite a few cases of green pixels and red pixels. Among these, green-emitting phosphors include, for example, ZnS:
It has a composition of Cu and Al, and there is a possibility that Cu compounds may adhere to the surface of the phosphor. On the other hand, red-emitting phosphors have a composition of Y ₂ O ₂ S:Eu, for example, and do not contain Cu, but because the materials are expensive, they are often collected and recycled for reuse. Sometimes,
During recovery, the blue-emitting phosphor, green-emitting phosphor, and Cu mixed in during the manufacture of cathode ray tubes are mixed together and processed, and due to the specifications of the recycling process, Cu in particular becomes precipitates such as CuS and becomes the red-emitting phosphor. It often sticks to surfaces and remains. In fact, the incidence of color defects in blue picture elements is not very high due to Cu contamination alone due to internal and external factors, but color defects may occur due to the filming process when forming the phosphor screen. increase
That is, when the filming liquid contains an organic acid such as acrylic acid, these acids ionize Cu powder or Cu compounds and promote the diffusion of Cu ⁺⁺ . This Cu ⁺⁺ penetrates into the blue pixel area, for example, and is removed in the next combustion process.
Generates green spots with compositions of ZnS:Cu and ZuC:Cu,Ag. [Problems to be Solved by the Invention] The present invention aims to eliminate contamination of phosphors caused by internal and external factors, which has been a problem in the past, and in particular contamination by Cu ions and the like that induce discoloration of phosphors. It has been done. [Means for Solving the Problems] The phosphor of the present invention, which was discovered as a means to solve the above-mentioned conventional problems, is characterized by having a cation exchanger attached to its surface. be. More specifically, the phosphor of the present invention is at least one member of the group consisting of a zinc sulfide phosphor containing at least one of silver and copper as an activator and a yttrium oxysulfide phosphor containing europium as an activator. This is a surface-treated phosphor characterized in that a cation exchanger is attached to the surface of the phosphor via a binder. [Description of structure and action] The cation exchanger used in the present invention is, for example, an organic substance having a cation exchange group such as a carboxylic acid group (-COOH) or a sulfonic acid group (-SO ₃ H) in its structure. , inorganic substances that can exchange, adsorb, or absorb cations in their structures. Specific examples of organic cation exchangers include polyvinyl alcohol, polyacrylic, polyamide, polyphenol, polystyrene, and cellulose polymers with sulfonic acid groups (-
Examples include cation exchange resins having cation exchange groups such as SO ₃ H) and carboxylic acid groups (-COOH); and chelating ion exchange resins having the ability to form chelates with metal ions. In addition, in the case of this chelate resin, unlike ordinary ion exchange reactions, it has a high selective adsorption property for metal ions, and those with iminodiacetic acid type coordination groups introduce copper ions (Cu ²⁺ ).
There are also some that selectively adsorb and are more effective for the purpose of the present invention. Examples of the inorganic cation exchanger include inorganic substances having cation exchange ability such as zeolite and zeolite. As a specific method for attaching a cation exchanger to the surface of a phosphor, for example, as shown in FIG. Ion exchanger 3
It is particularly effective to deposit the phosphor evenly and uniformly over the entire surface of the phosphor. For example, one method is to create fine ion-exchange resins and ion-exchange fibers and attach them to the surface of the phosphor via a binder as shown in Figure 1. There is a method using a substance that has a carboxyl group (-COOH), for example, alginic acid. Specifically, when water-soluble sodium alginate is used as the cation exchanger, it is not possible to form a stable film simply by dipping the phosphor in a solution. First, the first layer on the surface of the phosphor has adhesion to the phosphor, and it is necessary to make sodium alginate insoluble. Colloidal alumina AlOOH is suitable as such a binder. In the above case, in the coating layer of the sodium alginate solution, the hydrogen atoms of the carboxyl group (-COOH) are in contact with the colloidal alumina.
It is replaced by Al ions and forms an insolubilized film.
In this case, when reacted with excess Al, free ion exchange groups, which should exchange contaminants such as Cu ions on the outside of the sodium alginate solution coating layer, are released.
Since COOH is used up, it is important to limit the amount of Al replacement to the amount necessary for film formation. Furthermore, if the film is simply treated with alkali after the film forming reaction, the carboxyl groups in the outermost shell can release Al and become capable of adsorbing metals. Another method is to attach phosphate ions instead of colloidal alumina, then add metal cations (Mg ⁺⁺ , Ca ⁺⁺ , Zn ⁺⁺ , Al ⁺⁺ , Ba ⁺⁺ etc.), A binder layer of metal phosphate is formed, and when an aqueous solution of water-soluble sodium alginate is added to this, divalent or trivalent metal ions such as Al attached to the surface of the phosphor or in the phosphor are added. reacts with contaminants such as Cu ions to form an insoluble and stable ion exchange protective film such as aluminum alginate. In this way, by attaching a cation exchanger to the surface of the phosphor, considering the case of internal factors of phosphor contamination, trace amounts of Cu metal that are difficult to remove during the phosphor manufacturing process (including the regeneration process) can be removed. , Cu compound,
If Cu ions are present, they can be exchange-adsorbed and chemically inactivated, and contamination of other phosphors can also be prevented. Furthermore, in the case of contaminants caused by external factors, they can be similarly exchanged and adsorbed to chemically inactivate them, thereby preventing them from diffusing into the interior of the phosphor. Simply using microcapsules as a pollution prevention membrane
A film that is dense enough to suppress the diffusion of Cu ⁺⁺ ions cannot be created, and no significant effect can be obtained. [Example] Hereinafter, the present invention will be explained in more detail by showing specific examples. Example 1 100 g of a phosphor prepared by adding 20 ppm of Cu in the form of CuS to a green-emitting phosphor (ZnS: Cu, Al) synthesized under appropriate conditions and forcibly contaminating it was added to 400 ml of pure water.
While stirring, add 50 ppm of colloidal alumina to the phosphor, stir for 30 minutes, add 300 ppm of sodium alginate aqueous solution as sodium alginate, stir for 30 minutes, and PH with NH ₄ OH.
After adjusting the temperature to 8 to 9 and stirring for 10 minutes, dehydrate and dry. The color change resistance of the thus treated green-emitting phosphor of the present invention to the blue-emitting phosphor was investigated in the following manner in comparison with the untreated green-emitting phosphor that had not undergone the above-mentioned treatment. . Each panel is coated with a green solid film and both untreated phosphors, exposed to light on the entire surface, then a blue solid film is overcoated on each panel and exposed on the entire surface, and then a filming liquid (acrylic emulsion) is applied.
Bake each panel thus made at 450°C for 30 minutes. For evaluation of discoloration, the number of green luminescent spots generated on the blue surface of the top coat was counted, and the average number of spots on the two coated panels was determined. The results are shown in Table 1.

[Table] The discolored spots had a diameter of about 0.2 mm to 1 mm. Example 2 A red light-emitting phosphor (Y ₂ O ₂ S: Eu) recovered from developer waste, etc. was regenerated under appropriate conditions and treated in the same manner as in Example 1, with the addition amount of sodium alginate being changed. The same panel as in Example 1 was obtained except that the phosphor of the present invention was changed and the undercoat was changed to a red solid film, and the characteristics of discoloration on the blue surface were investigated. The results are shown in Figure 2. Example 3 Blue-emitting phosphor ZuS synthesized under appropriate conditions:
Suspend 100g of Ag in 400ml of pure water and stir
Add 1 ml of 10wt% H ₄ P ₂ O ₇ and stir for 30 minutes.
Add 15 ml of a 10 wt% aqueous solution of Al ₂ (SO ₄ ) ₃ , stir for 30 minutes, leave to stand, remove the supernatant, wash with pure water, dehydrate, suspend in 400 ml of pure water again, and stir while stirring.
300 ppm of sodium alginate was added and the treatment was then carried out in the same manner as in Example 1 to obtain a treated phosphor. The evaluation of this phosphor was performed by first coating a panel with a red-emitting phosphor that was forcibly contaminated by adding 20 ppm of Cu in the form of CuS, and using either the previously mentioned treated phosphor or the untreated blue-emitting phosphor that had not undergone the above treatment. A phosphor was overcoated and the same procedure as in Example 1 was carried out. As a result, the phosphor of the present invention had high resistance to contamination from the red-emitting phosphor that was forcibly contaminated with Cu ⁺⁺ , but the untreated phosphor without the cation exchanger attached The phosphors were contaminated with Cu ⁺⁺ and had a high degree of discoloration. Example 4 Blue-emitting phosphor ZuS synthesized under appropriate conditions:
Suspend 100g of Ag in 400ml of pure water and add 100ppm of colloidal alumina to the phosphor while stirring.
After stirring for 30 minutes, convert the sodium alginate aqueous solution into sodium alginate based on the fluorescent weight.
After adding 400ppm and stirring for 30 minutes, adjust the pH to 8~ with NH ₄ OH.
After adjusting the temperature to 9 and stirring for 10 minutes, dehydrate and dry. The effect of color fastness of the thus prepared phosphor of the present invention was examined in the following manner. For panels primed with a red-emitting phosphor that has been forcibly contaminated (addition of 20 ppm Cu in the form of CuS) and overcoated with a blue-emitting phosphor of the present invention, and for comparison with an untreated blue-emitting phosphor, The number of discolored samples was examined in the same manner as in Example 1. Second result
Shown in the table.

[Table] Example 5 100 g of a blue-emitting phosphor (ZuS:Ag) synthesized under known conditions was suspended in 400 ml of pure water, and a 10 wt% aqueous solution of pyrophosphoric acid (H ₄ P ₂ O ₇ ) was added while stirring. After stirring for 30 minutes, add 15 ml of a 10 wt% solution of aluminum sulfate [Al ₂ (SO ₄ ) ₃ ] and stir for 30 minutes. Next, after standing for 30 minutes, the supernatant liquid is removed, and the remainder is washed with pure water, filtered, and dehydrated. Resuspend the filtered and dehydrated cake in 400ml of pure water,
While stirring, add 1.6 ml of PVA (polyvinyl alcohol) solution (5% solution) and apply it to the phosphor.
Stir for 30 minutes after addition in an amount of 800 ppm. Next, add 400ml of aminoacetaldehyde.
Stir for 30 minutes to convert PVA into aminoacetal and harden and fix the modified PVA film on the surface of the phosphor. Furthermore, after adding 200 ppm of tannic acid and stirring for 20 minutes, the zinc sulfate solution was converted to zinc by weight.
By adding an amount equivalent to 1000 ppm and leaving it to stand after stirring for 20 minutes, the modified PVA, which is a phosphor surface coating, is formed.
Tannic acid metal chelate is generated on the membrane surface layer. After removing the supernatant liquid, the dehydrated cake obtained by washing with water, filtration and dehydration was dried at 110°C, and further dried at 300°C.
By classifying with a mesh nylon sieve, a phosphor having a PVA base layer on the surface and an ion exchanger bonded to metal tannate (Zn) chelate was obtained as a passed through material. The resistance to discoloration of this phosphor was evaluated using the method described in Example 3, and the results shown in Table 3 below were obtained. From the table, it is clear that the number of discolourations occurring in the phosphor of the present invention is clearly smaller than that of the untreated phosphor and the phosphor treated with a base treatment for fixing the PVA layer (aluminum phosphate adhesion treatment). I understand.

〔Effect of the invention〕

As explained above, according to the present invention, Cu ⁺⁺
It is possible to prevent the phosphor from being contaminated by contaminants such as, for example, to suppress the defective changes in blue picture elements that often occur in the conventional cathode ray tube manufacturing process, and to reduce the incidence of discoloration.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining one configuration example of the phosphor of the present invention. FIG. 2 is a curve diagram showing the discoloration prevention effect of the phosphor of the present invention produced in Examples. FIG. 3 is a cross-sectional view of a television cathode ray tube fluorescent screen. FIG. 4 is a perspective view of the television cathode ray tube fluorescent screen seen from the face plate side. DESCRIPTION OF SYMBOLS 1... Phosphor, 2... Binder layer, 3... Cation exchanger layer, 11... Face plate, 1
2...Metal back, R...Red picture element, G...
Green picture element, B... Blue picture element.

Claims (1)

[Scope of Claims] 1. A phosphor that is at least one member of the group consisting of a zinc sulfide phosphor containing at least one of silver and copper as an activator and a yttrium oxysulfide phosphor containing europium as an activator. A surface-treated phosphor characterized by having a cation exchanger attached to the surface via a binder. 2. The surface-treated phosphor according to claim 1, wherein the binder is at least one of colloidal alumina and metal phosphate.