JPS6218587B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a recovery process for a pigmented phosphor for reusing the pigmented phosphor, which suppresses peeling of the pigment from the pigmented phosphor recovered from a cleaning solution containing the pigmented phosphor or a processing solution generated in a developing process. Regarding the method. Generally, the phosphor screen of a color picture tube is manufactured through the following steps. That is, (1) applying a phosphor slurry in which a predetermined phosphor is dispersed in a photosensitive binder such as a solution of polyvinyl alcohol and ammonium dichromate to the inner surface of a glass panel; (2) a process of drying this to form a coating film; (3) a process of exposing the obtained coating film to light using a predetermined exposure device through a shadow mask serving as a color selection electrode to form a latent image; (4) A process of forming phosphor stripes or phosphor dots (hereinafter collectively referred to as phosphor stripes) of a predetermined size at a desired position by performing a development process after exposure. The basic process of forming three types of phosphor stripes at positions corresponding to the openings of the shadow mask by repeating the unit process for the blue and red phosphor slurries includes () the drying process (2) described in () above; Alternatively, the phosphor screen is manufactured by adding steps (5) to (8) of recovering the phosphor from the cleaning solution or processing solution containing the phosphor produced in the developing step (4). The recovery step in parentheses was added to reduce the manufacturing cost by recovering and recycling the phosphor since the cost of phosphors, especially red-emitting phosphors containing rare earth elements, is high. Manufacturing process () to () of the above-mentioned phosphor screen
When expressed as a block diagram, it becomes as shown in Fig. 1. In FIG. 1, P means a pump for recovering a cleaning liquid or a processing liquid containing a phosphor for each unit process. Next, the manufacturing steps () to () of the phosphor screen described above will be explained with reference to FIGS. 2a to 2c, focusing on the recovery step (). Figure 2a shows green 21 due to the unit process ().
This is a cross-sectional view of the glass panel 23 on which the formation of blue 22 phosphor stripes has been completed. The coating is applied uniformly using a spin coating method. A cross section of the coated material is shown in FIG. 2b. Subsequently, the glass panel 23 in state b is placed in a drying step (2), and the slurry 2
4 is dried to become a slurry film 24'. on the other hand,
The excess slurry 24 applied to the panel skirt portion 25 is washed away by washing with water. The generated washing liquid is sent via a pump 5 to a centrifugal separator 6' in a recovery step (). If there are no defects in the dried slurry film 24', the glass panel 23 in state b is subjected to the exposure step 3 and then to the development step (4); if there is a defect, it is directly processed without going through the exposure step (3). It is placed in the developing step (4). In the development step (4), in addition to forming the phosphor stripes 26, the slurry film 2
The unexposed portion of 4' is washed away. FIG. 2c is a cross-sectional view of the glass panel 23 on which the red phosphor stripes 26 have been formed. The processing liquid in the developing step (4) is introduced into the centrifugal separator 6' via the pump 5 together with the cleaning liquid in the drying step (2). These cleaning solutions or processing solutions containing red phosphor are dehydrated and centrifuged in a centrifugal separator 6'.
Red phosphor cake 3 containing ~30% (by weight) water
The red phosphor is separated as 0. The obtained cake 30 is washed with water and purified 7, and then dehydrated again 8 to be regenerated, and the regenerated product is passed through the slurry preparation process.
(9) and used together with new phosphor 10 to prepare red phosphor slurry. That is, as shown in FIG. 3, in the purification step (7), a red phosphor cake 30 is added to a cleaning tank 31 together with pure water 32 or an aqueous solution containing a dispersant, and the tank 31 is moved by a drive motor or the like. The cleaning tank 31 is rotated at a low speed and sufficiently stirred to dissolve or suspend impurities such as the photosensitive binder, dichromate, and dust contained in the cake 30. When the stirring is finished, the rotation of the cleaning tank 31 is stopped. to precipitate the red phosphor. Next, the supernatant liquid drain valve 34 is opened to discharge the supernatant liquid containing impurity components in the cake 30, and then the water supply valve 35 is opened again to supply water to the tank 31, and the cleaning tank 31 is rotated at low speed for cleaning. , subsequent precipitation, and discharge of the supernatant liquid are repeated 2 to 4 times, and finally, with the phosphor dispersed in pure water, the discharge valve 34 is opened,
The red phosphor is passed through a 300-400 mesh filter 36 into a centrifugal separator 37, and dehydrated to obtain a purified red phosphor. Similar operations are performed for green and blue phosphors as desired, and the phosphors are purified and recovered. As mentioned above, the cleaned and purified phosphor is better in terms of the yield in the coating process (1) and the quality of the final phosphor screen compared to the one that is only separated and recovered and is not particularly cleaned and purified. You can get results. Therefore, in order to reuse the phosphor cake obtained by dehydrating the cleaning solution or treatment solution, the purification process (7) is necessary.
has become unreliable. With conventional phosphor slurries, there were no particular problems in the cleaning and purification process described above. However, recently, a method has been applied to dramatically improve the contrast of the phosphor screen by depositing a pigment having the emission color of the phosphor on the surface of the corresponding phosphor and absorbing the spectrum other than the emission color of the phosphor. ing. Specific examples of the pigments used include cobalt aluminate for blue-emitting phosphors, red iron oxide for red-emitting phosphors, and the like. Phosphors coated with pigments in this manner are generally referred to as pigmented phosphors, and although they improve the contrast of the phosphor screen, they have some technical difficulties and drawbacks in handling. That is, during the recovery step (), there is a development in which the pigment covering the phosphor is peeled off (referred to as pigment peeling). When pigment peeling occurs, not only the originally intended improvement in contrast cannot be achieved, but also the pigment peeled off from the phosphor adheres to other phosphors, causing adverse effects such as reducing their luminous efficiency. The present invention was made in order to overcome the above-mentioned drawbacks in the case of pigmented phosphors, and it is a recovery process that allows the pigmented phosphors to be washed and purified with less pigment peeling and then reused as is. The purpose is to provide a method. The present inventor succeeded in ascertaining that the cause of pigment peeling in the recovery process () was in the cleaning and purification process (7), and as a result of a detailed study of the cleaning and purification process (7), It was found that washing with water had a large effect on (7), so we conducted various research on the cleaning methods, and found that the cleaning treatment liquid had a pH of 6.
Hereinafter, it has been found that the above object can be achieved by using an aqueous solution preferably having a pH of 4 or less and treating with this aqueous solution at least once, and based on this knowledge, the present invention has been completed. Table 1 is for explaining the effects of the present invention.

[Table] That is, Table 1 shows pigmented phosphors (manufactured by Kasei Optonics Co., Ltd.) obtained by dehydrating the cleaning solution or processing solution generated in the drying step (2) and developing step (4) in the unit process (). P22−HCR2) 200g cake, pure water
800c.c. and an appropriate amount of acetic acid to adjust four different PH conditions, each in a 1 volume polyethylene bottle.
The suspended solution was stirred overnight at a low speed of 60 rpm, and the wavelength of the liquid was 520 nm.
This figure shows the results of measuring the transmittance of the light beam. Comparative Example 1 in Table 1 shows the results when pure water was used as an aqueous solution without adding acetic acid. As can be seen from Table 1, when the pH of the aqueous solution is adjusted to 6 or less, preferably about 4, there is almost no decrease in transmittance due to pigment peeling. The ability to suppress pigment peeling by lowering the pH can be explained as follows. In other words, even if the pigmented phosphor is sufficiently cured and the pigment is firmly attached to it, the pigment will adhere to it while it remains as a slurry with a neutral or slightly alkaline solution for a long time during the manufacturing process of the phosphor screen. The resin or other binder used in the process swells, and if it is washed and purified with pure water, the adhesion force will be extremely reduced. Therefore, if the first stage of the cleaning and purification process (7) is treated with an aqueous solution with a pH of 6 or less, preferably 4 or less, to strongly promote the re-hardening of the binder such as the resin, the cleaning and purification process (7) It is considered that pigment peeling is sufficiently suppressed. Hereinafter, the present invention will be explained in more detail with reference to examples. Example 1 The above-mentioned conventional cleaning and purification step (7) involves adding acetic acid to the treatment liquid (aqueous solution) when dispersing the pigmented phosphor cake in the treatment liquid in the cleaning tank 31.
The difference is that the pH was set to about 4. That is, a cake 30' of red pigmented phosphor (P22-HCR2 manufactured by Kasei Optonics Co., Ltd.) recovered from the unit process () of the cleaning tank 31 with an internal capacity of 300 ml as shown in FIG.
Kg, add pure water 120, and add an appropriate amount of acetic acid.
After forming an aqueous solution with a pH of about 4, the outlet port 38 was sealed, and the contents were stirred by rotating at a low speed of 12 rpm for 3 hours. The rotation was stopped and the phosphor 30' was allowed to precipitate for 6 hours. Next, the supernatant liquid was discharged by an inching drive, and then only 120% pure water was added, the discharge valve 34 was sealed, and the mixture was stirred again for 1 hour, and then the supernatant liquid that had been allowed to stand still was discharged. After repeating this process of adding only pure water three times,
was added and stirred for about 1 hour, then the discharge valve 34
The slurry of the phosphor obtained from the lower side is extracted from the lower side and subjected to a centrifugal dehydrator through a mesh filter 36 in the same manner as in the past, and the purified phosphor is dehydrated to complete washing. I got it. At that time, the upper water supply valve 35 was used as an air vent. Pigment peeling in the phosphor purified in this way was less than 1/8 of that in the conventional phosphor. In addition, we have improved the yield rate both in coating using a slurry of the phosphor prepared by mixing 60% of the obtained purified phosphor and 40% of a new similar type of phosphor, and on the phosphor screen as a finished tube. The quality characteristics were the same as when only the new phosphor was used. In addition, in the above explanation and examples, a pigmented red phosphor using red iron phosphor was described;
It can be similarly applied to other pigmented phosphors. Furthermore, the acid for pH adjustment is not limited to acetic acid, and known acids such as hydrochloric acid, inorganic acids such as phosphoric acid, and organic acids such as formic acid can be used. Furthermore, depending on conditions such as the structure of the equipment, throughput, degree of pigment peeling, etc., the PH range, acid treatment method, etc. may be adjusted depending on the situation, such as using a solution with a lower pH than the processing solution in the developing process at the stage of recovery. Needless to say, there are various types. As explained above, according to the method for recovering pigmented phosphors according to the present invention, peeling of pigments can be suppressed and reuse can be performed without redepositing the pigments. Excellent effects can be achieved in improving the yield of pigmented phosphors and the quality of phosphor screens, as well as reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the phosphor recovery cycle, Fig. 2 a, b, and c are cross-sectional views showing the manufacturing process of the phosphor screen, and Fig. 3 is a cross-sectional view of an example of the device used in the cleaning and purification process. It is. (Main symbols in the drawing), 30, 30': Phosphor cake, 31: Washing tank, 32: Pure water, 35: Discharge port (takeout port).

Claims (1)

[Scope of Claims] 1. A method for recovering a pigmented phosphor from a cleaning solution or a processing solution containing the pigmented phosphor produced in a phosphor screen manufacturing process using the pigmented phosphor and recycling the recovered pigment. 1. A method for recovering a pigmented phosphor, the method comprising treating the pigmented phosphor at least once with an aqueous solution having a pH of 6 or less in a washing and purification step as a regeneration treatment of the pigmented phosphor. 2. The method according to claim 1, wherein the pH of the aqueous solution is 4 or less.