JPH0586613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a fluorescent film, and more particularly to a method for forming a fluorescent film on the inner surface of a bulb face of a cathode ray tube for a viewfinder used in a video camera or the like.

2. Description of the Related Art A fluorescent film on the inner surface of a valve face of a small cathode ray tube for a viewfinder used in a video camera or the like is generally formed by a precipitation method.

To form a fluorescent film using the precipitation method described above, first, an electrolytic solution such as barium acetate is supplied in a fixed amount into a bulb. Next, a phosphor suspension of water glass containing a phosphor is supplied in a fixed amount into the bulb and added to the electrolytic solution,
This electrolytic solution and the phosphor suspension are mixed in a desired ratio. At this time, the ionic electrolytic solution exhibits a cushioning effect. Then, the electrolytic solution and the phosphor suspension are mixed, and the phosphor is dispersed and precipitated. The precipitated phosphor adheres to the inner surface of the valve face, and finally a phosphor film of a desired thickness is formed on the inner surface of the valve face through a polycondensation reaction. Thereafter, the liquid remaining in the bulb is discharged, and in the next drying step, a fluorescent film is heated on the inner surface of the bulb face at a desired temperature and time to dry it and give a final finish.

The electrolytic solution used in the conventional fluorescent film forming method described above has a pH value of 7, which is the concentration of hydrogen ions.
It is a neutral barium acetate. This barium acetate is contained in the electrolytic solution at a concentration of, for example, about 300 mg. In addition, the phosphor suspension contains K ₂ O and SiO ₂
Potassium silicate (K ₂ SiO ₃ ) consisting of water (H ₂
A phosphor is added to water glass dissolved in O), and in the conventional method described above, an alkaline phosphor suspension with a pH value of about 11 is used. The above-mentioned phosphor suspension is a mixture of, for example, 1 g of phosphor and water glass in a ratio of about 0.11 to 0.44 g.

Problems to be Solved by the Invention By the way, in the conventional method for forming a fluorescent film described above, a mixed solution is prepared by mixing an electrolytic solution with a pH value of about 7 and a phosphor suspension with a pH value of about 11. was using. In this case, the liquid mixture gels and the phosphor aggregates, making it difficult for the phosphor to be evenly dispersed over the entire inner surface of the bulb face. As a result, the thickness of the phosphor film varied, making the fluorescent surface rough, and brightness and darkness sometimes occurred on the fluorescent surface during electron beam irradiation. Furthermore, barium, which is a metal component in the electrolytic solution, is a heavy metal and non-luminescent substance, and when this barium recrystallizes and adheres to the fluorescent film, it becomes non-luminescent on the fluorescent surface during electron beam irradiation. There was a problem in that black dots were formed and the quality of the fluorescent film was significantly reduced.
In particular, in the case of a cathode ray tube for viewfinder, the image on the fluorescent light emitting surface is magnified 4 to 8 times, so
The problem of non-uniformity of the fluorescent film was noticeable.

Means for Solving the Problems The present invention has been proposed in view of the above problems, and technical means for solving the problems are as follows:
In a method for forming a fluorescent film in which a fluorescent film is deposited on the inner surface of a valve face by mixing a phosphor suspension in an electrolytic solution, the electrolytic solution is made of barium acetate, acetic acid, or ammonia water adjusted to a pH of 8.5 to 9.0. This method is characterized in that the phosphor suspension is a suspension of phosphor, water glass, and caustic alkali whose pH is adjusted to 11.0 to 12.0.

Effects According to the method for forming a fluorescent film of the present invention, by using a mixed liquid with a high PH value, the mixing groove is gelled, suppressing condensation of the phosphor in the mixed liquid and dispersing the phosphor. make it good. Further, it suppresses recrystallization of non-luminescent substances, which are heavy metal components in the liquid mixture, and prevents them from adhering to the fluorescent film.

EXAMPLES An example in which the method of the present invention is applied to the formation of a fluorescent film of a cathode ray tube for viewfinder will be described below.

The fluorescent film formation of the method of the present invention by the precipitation method is performed in the first step.
Each step similar to the conventional process shown in FIGS. 4 to 4 is performed. First, as shown in FIG. 1, a bulb 1 of a cathode ray tube for viewfinder is held vertically with its face 2 facing down, and an appropriate electrolytic solution 3, which will be described later, is poured into the bulb 1 as shown in FIG. Quantitative supply by means. Next, as shown in FIG. 3, a fixed amount of phosphor suspension 5 containing phosphor 4 is supplied into bulb 1 and added to the electrolytic solution 3, and this electrolytic solution 3 and phosphor suspension 5 are combined. Mix in desired ratio. A mixed solution 6 in which this electrolytic solution 3 and the phosphor suspension 5 are mixed
The phosphor 4 contained therein is precipitated while being dispersed, and the phosphor 4 is adhered to the inner surface of the face 2 of the bulb 1, and finally a phosphor film 7 is formed on the inner surface of the face 2 by a polycondensation reaction. Thereafter, the remaining liquid in the bulb 1 is discharged, and the fluorescent film 7 is finished in the next drying process.

The feature of the method of the present invention described above is that the PH value of the mixed solution 6 is increased, and the electrolyte solution 3 of the mixed solution 6 is
An example of the composition of the phosphor suspension 5 will be described below.

First, the electrolyte solution 3 used in the method of the present invention is obtained by adding acetic acid and aqueous ammonia in a predetermined ratio to the barium acetate used in the conventional method.
When mixing the above barium acetate, acetic acid and aqueous ammonia, for 300mg/barium acetate,
0.3 to 3 c.c./acetic acid and 0.3 and 3 c.c./aqueous ammonia (containing 25%) are added, and the pH value, which is the hydrogen ion concentration at that time, is set to 8.5 to 9.0. Ideally 0.6 for 300mg/barium acetate
Preferably, cc/ of acetic acid and 0.9 cc/ of aqueous ammonia are added to set the pH value to 8.8. In addition, the permissible range for the mixing ratio of barium acetate, acetic acid, and ammonia water is specifically
50-500mg/, whereas acetic acid has 0.3-5
cc/, and ammonia water is set to 0.3 to 5 c.c./.

By adding acetic acid to barium acetate in this way, barium ions in the electrolytic solution 3 are reduced and recrystallization of barium, which is a metal component, is suppressed.
However, when acetic acid is added to the barium acetate, the PH value in the electrolytic solution 3 decreases, making it difficult for the polycondensation reaction to occur during the formation of the fluorescent film. Therefore, in order to raise the pH value of the electrolytic solution 3 to a desired value, ammonia water is added.

Next, the phosphor suspension 5 used in the method of the present invention is:
Potassium hydroxide (KOH) is added at a predetermined ratio to the water glass containing the phosphor 4 used in the conventional method. The mixing ratio of the above phosphor 4, water glass and potassium hydroxide is 0.1 to 0.4 g of water glass and 0.02 to 0.06 g per 1 g of phosphor.
of potassium hydroxide and the pH value at that time was 11.0.
Set to ~12.0. The ideal pH value of this phosphor suspension 5 is preferably 11.8. The amount of water glass added is reduced by about 10% compared to the conventional method due to the addition of potassium hydroxide. In addition, the allowable range for the mixing ratio of the phosphor 4, water glass, and potassium hydroxide is specifically 4.8 to 5.2 g of the phosphor 4.
0.5-2g of water glass and potassium hydroxide
Set to 0.1~0.3g.

By adding potassium hydroxide to the water glass containing the phosphor 4, a phosphor suspension 5 is obtained.
The PH value of the phosphor is increased to a desired value, and the dispersibility of the phosphor in the mixed liquid 6 is made good, thereby suppressing aggregation of the phosphor 4. By the way, the above-mentioned water glass is made by dissolving potassium silicate (K ₂ SiO ₃ ) in water (H ₂ O), and as mentioned above, in order to increase the pH value of the phosphor suspension 5, potassium silicate must be added. A method of increasing the amount may be considered, but in that case, Si, which is a non-luminescent substance of the heavy metal, may be easily recrystallized and non-luminescent spots may be generated on the fluorescent surface, which is not preferable. Therefore, if potassium hydroxide is added as described above, the potassium hydroxide is easily ionized, the phosphor can be easily dispersed, and the liquid can be easily drained after the phosphor film is formed.

Effects of the Invention According to the method of the present invention, since the PH value of the phosphor suspension containing the phosphor and the electrolyte solution are set high,
Aggregation of the phosphor is suppressed and the phosphor is well dispersed, so that a phosphor film with a uniform thickness can be formed, and the luminescence state of the phosphor film when irradiated with an electron beam becomes uniform. In addition, recrystallization of the metal components in the liquid mixture is suppressed, and the generation of non-light-emitting spots on the fluorescent light-emitting surface can be prevented, thereby significantly improving the quality of the fluorescent film. The above-mentioned homogenization of the fluorescent film is particularly effective in the case of a cathode ray tube for viewfinder.

[Brief explanation of the drawing]

1 to 4 are side views including partial cross sections of the valve at each step for explaining the method of the present invention. DESCRIPTION OF SYMBOLS 1... Bulb, 2... Phase, 3... Electrolyte solution, 4... Phosphor, 5... Phosphor suspension, 6...
Mixed liquid, 7... Fluorescent film.

Claims (1)

[Scope of Claims] 1. A method for forming a fluorescent film in which a fluorescent film is deposited on the inner surface of a valve face by mixing a phosphor suspension in an electrolytic solution, wherein the electrolytic solution contains acetic acid whose pH is adjusted to 8.5 to 9.0. The phosphor film is a solution consisting of barium, acetic acid, and aqueous ammonia, and the phosphor suspension is a suspension consisting of phosphor, water glass, and caustic alkali whose pH is adjusted to 11.0 to 12.0. Formation method.